Nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease affecting approximately 25% of the global population. Although a majority of NAFLD patients will never experience liver-related symptoms it is estimated that 5-10% will develop cirrhosis-related complications with risk of death or need for liver transplantation. NAFLD is closely associated with cardiovascular disease and components of the metabolic syndrome. However, NAFLD is not uncommon in lean individuals and may in these subjects represent a different entity with separate pathophysiological mechanisms involved implying a higher risk for development of end-stage liver disease. There is considerable fluctuation in the histopathological course of NAFLD that may partly be attributed to lifestyle factors and dietary composition. Nutrients such as fructose, monounsaturated fatty acids, and trans-fatty acids may aggravate NAFLD. Presence of type 2 diabetes mellitus seems to be the most important clinical predictor of liver-related morbidity and mortality in NAFLD. Apart from severity of the metabolic syndrome, genetic polymorphisms and environmental factors, such as moderate alcohol consumption, may explain the variation in histopathological and clinical outcome among NAFLD patients.

Nonalcoholic fatty liver disease (NAFLD) is rapidly becoming the most common cause of chronic liver disease worldwide. This is primarily driven by the global epidemic of obesity and diabetes as well as the aging of the general population. Most of the epidemiology data of NAFLD for North America are published from studies originating in the United States (U.S.). The overall prevalence of NAFLD in the U.S. is estimated to be 24%. Hispanic Americans have a higher prevalence of NAFLD, whereas African Americans have a lower prevalence of NAFLD. The exact contributions of genetic and environmental factors on these differences in the prevalence rates have not been determined. From the spectrum of NAFLD, patients with non-alcoholic steatohepatitis (NASH) are at the highest risk of progression to cirrhosis and hepatocellular carcinoma (HCC). The most recent data regarding the progression of NASH suggest a complex pattern of progression and regression of fibrosis. Factors influencing the progression and regression of NASH have not been fully described. More research is needed to better understand NAFLD in Mexico and Canada.

Although controversial, male sex has been considered a risk factor for NAFLD. Furthermore, the prevalence of NAFLD in men is 2 times higher than in women.33
The issues of ethnicity and its impact on NAFLD have evolved over the years. In fact, initial reports suggested that compared to non‐Hispanic whites, Hispanic individuals have a significantly higher prevalence of NAFLD, whereas non‐Hispanic blacks have a significantly lower prevalence of NAFLD.39 Although the prevalence of NAFLD among American‐Indian and Alaskan‐Native populations seem to be lower (0.6%‐2.2%), these rates need to be confirmed.31 It is intriguing that most of the recent data suggest that the ethnic differences reported for NAFLD may be explained by the genetic variation related to the patatin‐like phospholipase domain‐containing protein 3 (PNPLA‐3) gene.40
In summary, the incidence of NAFLD varies across the world, ranging from 28.01 per 1,000 person‐years (95% CI, 19.34‐40.57) to 52.34 per 1,000 person‐years (95% CI, 28.31‐96.77).
Natural History and Outcomes of NAFLD
Over the past two decades, studies have reported the natural history of patients with NAFLD.1 There is growing evidence that patients with histological NASH, especially those with some degree of fibrosis, are at higher risk for adverse outcomes such as cirrhosis and liver‐related mortality.1 These studies have also shown the following:

Age, sex, and ethnicity: The prevalence of NAFLD may vary according to age, sex, and ethnicity.31 In fact, both the prevalence of NAFLD and stage of liver disease appear to increase with age.34
Table 3 -
Risk Factors Associated With NAFLD
Common Conditions With Established Association
Other Conditions Associated With NAFLD
aThe Adult Treatment Panel III clinical definition of MetS requires the presence of three or more of the following features: (1) waist circumference greater than 102 cm in men or greater than 88 cm in women; (2) TG level 150 mg/dL or greater; (3) HDL cholesterol level less than 40 mg/dL in men and less than 50 mg/dL in women; (4) systolic blood pressure 130 mm Hg or greater or diastolic pressure 85 mm Hg or greater; and (5) fasting plasma glucose level 110 mg/dL or greater.287
Although controversial, male sex has been considered a risk factor for NAFLD. Furthermore, the prevalence of NAFLD in men is 2 times higher than in women.33
The issues of ethnicity and its impact on NAFLD have evolved over the years. In fact, initial reports suggested that compared to non‐Hispanic whites, Hispanic individuals have a significantly higher prevalence of NAFLD, whereas non‐Hispanic blacks have a significantly lower prevalence of NAFLD.39 Although the prevalence of NAFLD among American‐Indian and Alaskan‐Native populations seem to be lower (0.6%‐2.2%), these rates need to be confirmed.31 It is intriguing that most of the recent data suggest that the ethnic differences reported for NAFLD may be explained by the genetic variation related to the patatin‐like phospholipase domain‐containing protein 3 (PNPLA‐3) gene.40

The worldwide obesity epidemic over the last 20 years has led to a dramatic increase in the prevalence of non-alcoholic fatty liver disease, the hepatic manifestation of the metabolic syndrome. Estimates of prevalence vary depending on the population studied and the methods used to assess hepatic fat content, but are commonly quoted as between 10 and 30% of the adults in the Western hemisphere. Fatty liver develops when fatty acid uptake and synthesis in the liver exceeds fatty acid oxidation and export as TAG. Studies of pathogenesis point to insulin resistance, lipotoxicity, oxidative stress and chronic inflammation being central to the development and progression of the disease. A proportion of individuals with fatty liver develop progressive disease, though large prospective longitudinal studies are lacking. Nevertheless, fatty liver is associated with increased all-cause and liver-related mortality compared with the general population. Management of fatty liver centres around lifestyle and dietary measures to induce controlled and sustained weight loss. Management of cardiovascular risk factors aims to reduce mortality, while certain dietary interventions have been shown to reduce steatosis and inflammation. Specific pharmacological treatments also show promise, but their use is not widespread. A multi-system and multi-disciplinary approach to the management of this disorder is proposed.

Non-alcoholic fatty liver disease (NAFLD) is associated with the growing incidence of metabolic syndrome. Diet is an important contributor to the pathogenesis of NAFLD. In this review, we focused on recent publications reporting on the effect of macro- and micronutrients on development and progression of NAFLD. In general, saturated fat and fructose seem to stimulate hepatic lipid accumulation and progression into NASH, whereas unsaturated fat, choline, antioxidants, and high-protein diets rich in isoflavones seem to have a more preventive effect. Knowledge of the underlying mechanisms by which diet affects NAFLD is expanding, not in the least due to innovative techniques, such as genomics tools that provide detailed comprehensive information on a large high-throughput scale. Although most nutrients seem to interfere with the balance between hepatic de novo lipogenesis (endogenous synthesis of fatty acids) and lipid oxidation (burning fat for energy), there are also indications that diet can trigger or prevent hepatic lipid accumulation by influencing the interaction between liver, gut, and adipose tissue. This review now gives a current detailed overview of diet-mediated mechanisms underlying NAFLD development and progression and summarizes recent results of genomics (transcriptomics, proteomics and metabolomics) studies that contribute to improved staging, monitoring and understanding of NAFLD pathophysiology.

Nonalcoholic fatty liver disease (NAFLD) is the most frequent liver disease worldwide, and is commonly associated with the metabolic syndrome. Secular trends in the prevalence of these diseases may be associated with the increased fructose consumption observed in the Western diet. NAFLD is characterized by two steps of liver injury: intrahepatic lipid accumulation (hepatic steatosis), and inflammatory progression to nonalcoholic steatohepatitis (NASH) (the 'two-hit' theory). In the first 'hit', hepatic metabolism of fructose promotes de novo lipogenesis and intrahepatic lipid, inhibition of mitochondrial beta-oxidation of long-chain fatty acids, triglyceride formation and steatosis, hepatic and skeletal muscle insulin resistance, and hyperglycemia. In the second 'hit', owing to the molecular instability of its five-membered furanose ring, fructose promotes protein fructosylation and formation of reactive oxygen species (ROS), which require quenching by hepatic antioxidants. Many patients with NASH also have micronutrient deficiencies and do not have enough antioxidant capacity to prevent synthesis of ROS, resulting in necroinflammation. We postulate that excessive dietary fructose consumption may underlie the development of NAFLD and the metabolic syndrome. Furthermore, we postulate that NAFLD and alcoholic fatty liver disease share the same pathogenesis.

Background: The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing in parallel with obesity and type 2 diabetes.

Aim: To review the global epidemiology of

Nafld Methods: We retrieved articles from PubMed using search terms of NAFLD, epidemiology, prevalence, incidence, and comorbidities.

Results: Over 250 articles were reviewed. In 2016, the global NAFLD prevalence was 25%; this increased to >30% in 2019. Prevalence in Asia, Latin America and Middle East-North Africa (MENA) was 30.8%, 34.5% and 42.6%, respectively. Prevalence increased with age. Although prevalence was higher in men, prevalence in post-menopausal women was similar. NAFLD prevalence was higher in certain subpopulations, especially among the obese and those with metabolic syndrome (MS). However, the prevalence of lean NAFLD was 11.2%. The global prevalence of non-alcoholic steatohepatitis (NASH) is estimated between 2% and 6% in the general population. Approximately 7% of patients with NAFLD have advanced fibrosis; rates were between 21% and 50% among patients with NASH. Overall mortality related to NAFLD was 15-20 per 1000 person-years, and increased substantially in patients with NASH, especially in those with components of MS. Recent data suggest mortality/morbidity from NAFLD is increasing globally but NAFLD awareness remains low among patients and healthcare providers.

Conclusions: NAFLD poses a global public health problem with a very high disease burden in Asia, MENA and Latin America. Research is needed to better quantify the full impact of NAFLD and to develop strategies to improve awareness and risk stratification.

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most common chronic liver disease worldwide with a reported prevalence ranging 20-30% depending on the studied populations. The high prevalence of NAFLD is probably due to the contemporary epidemics of obesity, unhealthy dietary pattern, and sedentary lifestyle. NAFLD patients are at increased risk of cardiovascular and liver related mortality. The cornerstone of any treatment regimen for patients with NAFLD is lifestyle modification focused on weight loss, exercise, and improving insulin sensitivity. The purpose of this review is to outline the effect of diet and lifestyle factors on developing NAFLD.

Non-alcoholic fatty liver disease (NAFLD) is associated with the growing incidence of metabolic syndrome. Diet is an important contributor to the pathogenesis of NAFLD. In this review, we focused on recent publications reporting on the effect of macro- and micronutrients on development and progression of NAFLD. In general, saturated fat and fructose seem to stimulate hepatic lipid accumulation and progression into NASH, whereas unsaturated fat, choline, antioxidants, and high-protein diets rich in isoflavones seem to have a more preventive effect. Knowledge of the underlying mechanisms by which diet affects NAFLD is expanding, not in the least due to innovative techniques, such as genomics tools that provide detailed comprehensive information on a large high-throughput scale. Although most nutrients seem to interfere with the balance between hepatic de novo lipogenesis (endogenous synthesis of fatty acids) and lipid oxidation (burning fat for energy), there are also indications that diet can trigger or prevent hepatic lipid accumulation by influencing the interaction between liver, gut, and adipose tissue. This review now gives a current detailed overview of diet-mediated mechanisms underlying NAFLD development and progression and summarizes recent results of genomics (transcriptomics, proteomics and metabolomics) studies that contribute to improved staging, monitoring and understanding of NAFLD pathophysiology.

Nonalcoholic fatty liver disease (NAFLD) is the most frequent liver disease worldwide, and is commonly associated with the metabolic syndrome. Secular trends in the prevalence of these diseases may be associated with the increased fructose consumption observed in the Western diet. NAFLD is characterized by two steps of liver injury: intrahepatic lipid accumulation (hepatic steatosis), and inflammatory progression to nonalcoholic steatohepatitis (NASH) (the 'two-hit' theory). In the first 'hit', hepatic metabolism of fructose promotes de novo lipogenesis and intrahepatic lipid, inhibition of mitochondrial beta-oxidation of long-chain fatty acids, triglyceride formation and steatosis, hepatic and skeletal muscle insulin resistance, and hyperglycemia. In the second 'hit', owing to the molecular instability of its five-membered furanose ring, fructose promotes protein fructosylation and formation of reactive oxygen species (ROS), which require quenching by hepatic antioxidants. Many patients with NASH also have micronutrient deficiencies and do not have enough antioxidant capacity to prevent synthesis of ROS, resulting in necroinflammation. We postulate that excessive dietary fructose consumption may underlie the development of NAFLD and the metabolic syndrome. Furthermore, we postulate that NAFLD and alcoholic fatty liver disease share the same pathogenesis.

The global prevalence of nonalcoholic fatty liver disease (NAFLD) has dramatically increased in parallel with the epidemic of obesity. Controversy has emerged around dietary guidelines recommending low-fat-high-carbohydrate diets and the roles of dietary macronutrients in the pathogenesis of metabolic disease. In this Review, the topical questions of whether and how dietary fats and carbohydrates, including free sugars, differentially influence the accumulation of liver fat (specifically, intrahepatic triglyceride (IHTG) content) are addressed. Focusing on evidence from humans, we examine data from stable isotope studies elucidating how macronutrients regulate IHTG synthesis and disposal, alter pools of bioactive lipids and influence insulin sensitivity. In addition, we review cross-sectional studies on dietary habits of patients with NAFLD and randomized controlled trials on the effects of altering dietary macronutrients on IHTG. Perhaps surprisingly, evidence to date shows no differential effects between free sugars, with both glucose and fructose increasing IHTG in the context of excess energy. Moreover, saturated fat raises IHTG more than polyunsaturated or monounsaturated fats, with adverse effects on insulin sensitivity, which are probably mediated in part by increased ceramide synthesis. Taken together, the data support the use of diets that have a reduced content of free sugars, refined carbohydrates and saturated fat in the treatment of NAFLD.

Nonalcoholic fatty liver disease (NAFLD) is rapidly becoming the most common cause of chronic liver disease worldwide. This is primarily driven by the global epidemic of obesity and diabetes as well as the aging of the general population. Most of the epidemiology data of NAFLD for North America are published from studies originating in the United States (U.S.). The overall prevalence of NAFLD in the U.S. is estimated to be 24%. Hispanic Americans have a higher prevalence of NAFLD, whereas African Americans have a lower prevalence of NAFLD. The exact contributions of genetic and environmental factors on these differences in the prevalence rates have not been determined. From the spectrum of NAFLD, patients with non-alcoholic steatohepatitis (NASH) are at the highest risk of progression to cirrhosis and hepatocellular carcinoma (HCC). The most recent data regarding the progression of NASH suggest a complex pattern of progression and regression of fibrosis. Factors influencing the progression and regression of NASH have not been fully described. More research is needed to better understand NAFLD in Mexico and Canada.

Although controversial, male sex has been considered a risk factor for NAFLD. Furthermore, the prevalence of NAFLD in men is 2 times higher than in women.33
The issues of ethnicity and its impact on NAFLD have evolved over the years. In fact, initial reports suggested that compared to non‐Hispanic whites, Hispanic individuals have a significantly higher prevalence of NAFLD, whereas non‐Hispanic blacks have a significantly lower prevalence of NAFLD.39 Although the prevalence of NAFLD among American‐Indian and Alaskan‐Native populations seem to be lower (0.6%‐2.2%), these rates need to be confirmed.31 It is intriguing that most of the recent data suggest that the ethnic differences reported for NAFLD may be explained by the genetic variation related to the patatin‐like phospholipase domain‐containing protein 3 (PNPLA‐3) gene.40
In summary, the incidence of NAFLD varies across the world, ranging from 28.01 per 1,000 person‐years (95% CI, 19.34‐40.57) to 52.34 per 1,000 person‐years (95% CI, 28.31‐96.77).
Natural History and Outcomes of NAFLD
Over the past two decades, studies have reported the natural history of patients with NAFLD.1 There is growing evidence that patients with histological NASH, especially those with some degree of fibrosis, are at higher risk for adverse outcomes such as cirrhosis and liver‐related mortality.1 These studies have also shown the following:

Non-alcoholic fatty liver disease (NAFLD) has rapidly become the most common liver disease globally and is currently estimated to affect 38% of the global population. Only a minority of patients with NAFLD will progress to cirrhosis or hepatocellular carcinoma, but from this vast population the total number of patients who are at risk of such severe outcomes is increasing. Worryingly, individuals are increasingly being affected by NAFLD at an earlier age, meaning there is more time for them to develop severe complications. With considerable changes in dietary composition and urbanisation, alongside the growth in obesity and type 2 diabetes in the global population, in particular in developing countries, the global proportion of persons affected by NAFLD is projected to increase further. Yet, there are large geographical discrepancies in the prevalence rates of NAFLD and its inflammatory component non-alcoholic steatohepatitis (NASH). Such differences are partly related to differing socio-economic milieus, but also to genetic predisposition. In this narrative review, we discuss recent changes in the epidemiology of NAFLD and NASH from regional and global perspectives, as well as in special populations. We also discuss the potential consequences of these changes on hepatic and extrahepatic events.

Purpose Of Review: Choline is an essential nutrient and the liver is a central organ responsible for choline metabolism. Hepatosteatosis and liver cell death occur when humans are deprived of choline. In the last few years, there have been significant advances in our understanding of the mechanisms that influence choline requirements in humans and in our understanding of choline's effects on liver function. These advances are useful in elucidating why nonalcoholic fatty liver disease (NAFLD) occurs and progresses sometimes to hepatocarcinogenesis.

Recent Findings: Humans eating low-choline diets develop fatty liver and liver damage. This dietary requirement for choline is modulated by estrogen and by single-nucleotide polymorphisms in specific genes of choline and folate metabolism. The spectrum of choline's effects on liver range from steatosis to development of hepatocarcinomas, and several mechanisms for these effects have been identified. They include abnormal phospholipid synthesis, defects in lipoprotein secretion, oxidative damage caused by mitochondrial dysfunction, and endoplasmic reticulum stress. Furthermore, the hepatic steatosis phenotype can be characterized more fully via metabolomic signatures and is influenced by the gut microbiome. Importantly, the intricate connection between liver function, one-carbon metabolism, and energy metabolism is just beginning to be elucidated.

Summary: Choline influences liver function, and the dietary requirement for this nutrient varies depending on an individual's genotype and estrogen status. Understanding these individual differences is important for gastroenterologists seeking to understand why some individuals develop NAFLD and others do not, and why some patients tolerate total parenteral nutrition and others develop liver dysfunction.

Industrialized society-caused dysregular human behaviors and activities such as overworking, excessive dietary intake, and sleep deprivation lead to perturbations in the metabolism and the development of metabolic syndrome. Non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disease worldwide, affects around 30% and 25% of people in Western and Asian countries, respectively, which leads to numerous medical costs annually. Insulin resistance is the major hallmark of NAFLD and is crucial in the pathogenesis and for the progression from NAFLD to non-alcoholic steatohepatitis (NASH). Excessive dietary intake of saturated fats and carbohydrate-enriched foods contributes to both insulin resistance and NAFLD. Once NAFLD is established, insulin resistance can promote the progression to the more severe state of liver endangerment like NASH. Here, we review current and potential studies for understanding the complexity between insulin-regulated glycolytic and lipogenic homeostasis and the underlying causes of NAFLD. We discuss how disruption of the insulin signal is associated with various metabolic disorders of glucoses and lipids that constitute both the metabolic syndrome and NAFLD.

Nonalcoholic fatty liver disease (NAFLD) is the most frequent liver disease worldwide, and is commonly associated with the metabolic syndrome. Secular trends in the prevalence of these diseases may be associated with the increased fructose consumption observed in the Western diet. NAFLD is characterized by two steps of liver injury: intrahepatic lipid accumulation (hepatic steatosis), and inflammatory progression to nonalcoholic steatohepatitis (NASH) (the 'two-hit' theory). In the first 'hit', hepatic metabolism of fructose promotes de novo lipogenesis and intrahepatic lipid, inhibition of mitochondrial beta-oxidation of long-chain fatty acids, triglyceride formation and steatosis, hepatic and skeletal muscle insulin resistance, and hyperglycemia. In the second 'hit', owing to the molecular instability of its five-membered furanose ring, fructose promotes protein fructosylation and formation of reactive oxygen species (ROS), which require quenching by hepatic antioxidants. Many patients with NASH also have micronutrient deficiencies and do not have enough antioxidant capacity to prevent synthesis of ROS, resulting in necroinflammation. We postulate that excessive dietary fructose consumption may underlie the development of NAFLD and the metabolic syndrome. Furthermore, we postulate that NAFLD and alcoholic fatty liver disease share the same pathogenesis.

A central issue in the understanding of the pathogenesis of nonalcoholic fatty liver disease is the problem of the underlying mechanisms which are not fully understood. In the setting of excessive central adiposity, insulin resistance is the major underlying cause of fat accumulation in hepatocytes. Because of the difficulties with human trials, several animal models have been developed for this purpose mainly characterized as follows: genetically disturbed or murine fatty liver, methionine-choline deficient diet fed or murine steatohepatitis, and high-fat or sucrose diet fed models. Although these animal models have provided useful information, none of them accurately reflect genetic, metabolic and biochemical characteristics of the human disease.

Background: Whether there is an association between dietary choline intake and non-alcoholic fatty liver disease (NAFLD) in American adults remains unclear.

Methods: Data came from the National Health and Nutrition Examination Survey 2017-2018. Choline intake was defined by the mean amounts of two 24 h dietary recalls, and choline intake was categorized into three groups according to the quartiles: inadequate (P). Hepatic steatosis was assessed with FibroScan, in which VCTE was employed with controlled attenuation to derive the controlled attenuation parameter (CAP), and NAFLD was defined as a CAP score ≥285 dB/m. Multivariable linear regression was performed to assess the linear relationship between choline intake and CAP. Multivariable logistics regression models were conducted to assess the association between choline intake status and NAFLD in the final sample and subgroup analysis was then performed in men and women.

Results: The amount of dietary choline was inversely associated with CAP score (β = -0.262, 95%

Ci: -0.280, -0.245). Compared to inadequate choline intake, optimal choline intake was related to a lower risk of NAFLD (

Or: 0.705, 95%

Ci: 0.704-0.706) in the final sample. Subgroup analysis by gender revealed that the highest choline intake status was associated with a lower risk of NAFLD both in females (

Or: 0.764, 95%

Ci: 0.762-0.766), and males (

Or: 0.955, 95%

Ci: 0.953-0.958) when compared to the lowest choline intake.

Conclusions: With the latest NHANES data, we found that higher dietary choline was associated with a lower risk of NAFLD in American adults, and such a relationship exists in both females and males.

Fatty liver is a complex disease often accompanying metabolic syndrome and Type 2 diabetes mellitus (T2DM). Hepatosteatosis may have roots in multiple metabolic abnormalities. However, metabolic dysfunction in the 1-carbon cycle (1CC), which produces the methyl donor S-adenosylmethionine (SAM) and phosphatidylcholine (PC), induces hepatic lipogenesis in model systems. Human diseases where 1CC or PC synthesis is disrupted, such as alcoholism, congenital lipodystrophy, or cystic fibrosis, often present with fatty liver. Given that the 1CC is clearly linked to this disease, it is critical to understand how the individual metabolites drive mechanisms increasing stored hepatic lipids. In this review, I summarize evidence that ties the 1CC to fatty liver disease along with data proposing mechanisms for increased lipogenesis or decreased lipid export by phosphatidylcholine.

Purpose Of Review: Choline is an essential nutrient and the liver is a central organ responsible for choline metabolism. Hepatosteatosis and liver cell death occur when humans are deprived of choline. In the last few years, there have been significant advances in our understanding of the mechanisms that influence choline requirements in humans and in our understanding of choline's effects on liver function. These advances are useful in elucidating why nonalcoholic fatty liver disease (NAFLD) occurs and progresses sometimes to hepatocarcinogenesis.

Recent Findings: Humans eating low-choline diets develop fatty liver and liver damage. This dietary requirement for choline is modulated by estrogen and by single-nucleotide polymorphisms in specific genes of choline and folate metabolism. The spectrum of choline's effects on liver range from steatosis to development of hepatocarcinomas, and several mechanisms for these effects have been identified. They include abnormal phospholipid synthesis, defects in lipoprotein secretion, oxidative damage caused by mitochondrial dysfunction, and endoplasmic reticulum stress. Furthermore, the hepatic steatosis phenotype can be characterized more fully via metabolomic signatures and is influenced by the gut microbiome. Importantly, the intricate connection between liver function, one-carbon metabolism, and energy metabolism is just beginning to be elucidated.

Summary: Choline influences liver function, and the dietary requirement for this nutrient varies depending on an individual's genotype and estrogen status. Understanding these individual differences is important for gastroenterologists seeking to understand why some individuals develop NAFLD and others do not, and why some patients tolerate total parenteral nutrition and others develop liver dysfunction.

Carbohydrates with high glycaemic index are proposed to promote the development of obesity, insulin resistance and fatty liver, but the mechanism by which this occurs remains unknown. High serum glucose concentrations are known to induce the polyol pathway and increase fructose generation in the liver. Here we show that this hepatic, endogenously produced fructose causes systemic metabolic changes. We demonstrate that mice unable to metabolize fructose are protected from an increase in energy intake and body weight, visceral obesity, fatty liver, elevated insulin levels and hyperleptinaemia after exposure to 10% glucose for 14 weeks. In normal mice, glucose consumption is accompanied by aldose reductase and polyol pathway activation in steatotic areas. In this regard, we show that aldose reductase-deficient mice are protected against glucose-induced fatty liver. We conclude that endogenous fructose generation and metabolism in the liver represents an important mechanism by which glucose promotes the development of metabolic syndrome.

The global prevalence of nonalcoholic fatty liver disease (NAFLD) has dramatically increased in parallel with the epidemic of obesity. Controversy has emerged around dietary guidelines recommending low-fat-high-carbohydrate diets and the roles of dietary macronutrients in the pathogenesis of metabolic disease. In this Review, the topical questions of whether and how dietary fats and carbohydrates, including free sugars, differentially influence the accumulation of liver fat (specifically, intrahepatic triglyceride (IHTG) content) are addressed. Focusing on evidence from humans, we examine data from stable isotope studies elucidating how macronutrients regulate IHTG synthesis and disposal, alter pools of bioactive lipids and influence insulin sensitivity. In addition, we review cross-sectional studies on dietary habits of patients with NAFLD and randomized controlled trials on the effects of altering dietary macronutrients on IHTG. Perhaps surprisingly, evidence to date shows no differential effects between free sugars, with both glucose and fructose increasing IHTG in the context of excess energy. Moreover, saturated fat raises IHTG more than polyunsaturated or monounsaturated fats, with adverse effects on insulin sensitivity, which are probably mediated in part by increased ceramide synthesis. Taken together, the data support the use of diets that have a reduced content of free sugars, refined carbohydrates and saturated fat in the treatment of NAFLD.

The relationship between metabolic derangements and fatty liver development are undeniable, since more than 75% of patients with type 2 diabetes mellitus present with fatty liver. There is also significant epidemiological association between insulin resistance (IR) and metabolic (dysfunction)-associated fatty liver disease (MAFLD). For little more than 2 years, the nomenclature of fatty liver of non-alcoholic origin has been intended to change to MAFLD by multiple groups. While a myriad of reasons for which MAFLD is thought to be of metabolic origin could be exposed, the bottom line relies on the role of IR as an initiator and perpetuator of this disease. There is a reciprocal role in MAFLD development and IR as well as serum glucose concentrations, where increased circulating glucose and insulin result in increased lipogenesis by sterol regulatory element-binding protein-1c induced lipogenic enzyme stimulation; therefore, increased endogenous production of triglycerides. The same effect is achieved through impaired suppression of adipose tissue (AT) lipolysis in insulin-resistant states, increasing fatty acid influx into the liver. The complementary reciprocal situation occurs when liver steatosis alters hepatokine secretion, modifying fatty acid metabolism as well as IR in a variety of tissues, including skeletal muscle, AT, and the liver. The aim of this review is to discuss the importance of IR and AT interactions in metabolic altered states as perhaps the most important factor in MAFLD pathogenesis.

A central issue in the understanding of the pathogenesis of nonalcoholic fatty liver disease is the problem of the underlying mechanisms which are not fully understood. In the setting of excessive central adiposity, insulin resistance is the major underlying cause of fat accumulation in hepatocytes. Because of the difficulties with human trials, several animal models have been developed for this purpose mainly characterized as follows: genetically disturbed or murine fatty liver, methionine-choline deficient diet fed or murine steatohepatitis, and high-fat or sucrose diet fed models. Although these animal models have provided useful information, none of them accurately reflect genetic, metabolic and biochemical characteristics of the human disease.

Cholesterol synthesis in the endoplasmic reticulum requires electron input at multiple steps and utilizes both NADH and NADPH as the electron source. Four enzymes catalyzing five steps in the pathway require electron input: squalene monooxygenase, lanosterol demethylase, sterol 4α-methyl oxidase, and sterol C5-desaturase. The electron-donor proteins for these enzymes include cytochrome P450 reductase and the cytochrome b5 pathway. Here I review the evidence for electron donor protein requirements with these enzymes, the evidence for additional electron donor pathways, and the effect of deletion of these redox enzymes on cholesterol and lipid metabolism.

Epidemiological studies link fructose consumption with metabolic disease, an association attributable in part to fructose-mediated lipogenesis. The mechanisms governing fructose-induced lipogenesis and disease remain debated. Acutely, fructose increases de novo lipogenesis through the efficient and uninhibited action of ketohexokinase and aldolase B which yields substrates for fatty-acid synthesis. Chronic fructose consumption further enhances the capacity for hepatic fructose metabolism by activating several key transcription factors (i.e., SREBP1c and ChREBP) which augment the expression of lipogenic enzymes, increasing lipogenesis and further compounding hypertriglyceridemia and hepatic steatosis. Hepatic insulin resistance develops from diacylglycerol-PKCɛ-mediated impairment of insulin signaling and possibly additional mechanisms. Initiatives that decrease fructose consumption and therapies that block fructose-mediated lipogenesis will be necessary to avert future metabolic pandemics.

Epidemiologic and animal studies implicate overconsumption of fructose in the development of nonalcoholic fatty liver disease, but the molecular mechanisms underlying fructose-induced chronic liver diseases remain largely unknown. Here, we have presented evidence supporting the essential function of the lipogenic transcription factor carbohydrate response element-binding protein (ChREBP) in mediating adaptive responses to fructose and protecting against fructose-induced hepatotoxicity. In WT mice, a high-fructose diet (HFrD) activated hepatic lipogenesis in a ChREBP-dependent manner; however, in Chrebp-KO mice, a HFrD induced steatohepatitis. In Chrebp-KO mouse livers, a HFrD reduced levels of molecular chaperones and activated the C/EBP homologous protein-dependent (CHOP-dependent) unfolded protein response, whereas administration of a chemical chaperone or Chop shRNA rescued liver injury. Elevated expression levels of cholesterol biosynthesis genes in HFrD-fed Chrebp-KO livers were paralleled by an increased nuclear abundance of sterol regulatory element-binding protein 2 (SREBP2). Atorvastatin-mediated inhibition of hepatic cholesterol biosynthesis or depletion of hepatic Srebp2 reversed fructose-induced liver injury in Chrebp-KO mice. Mechanistically, we determined that ChREBP binds to nuclear SREBP2 to promote its ubiquitination and destabilization in cultured cells. Therefore, our findings demonstrate that ChREBP provides hepatoprotection against a HFrD by preventing overactivation of cholesterol biosynthesis and the subsequent CHOP-mediated, proapoptotic unfolded protein response. Our findings also identified a role for ChREBP in regulating SREBP2-dependent cholesterol metabolism.

Context: There is an ongoing debate about whether and how fructose is involved in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). A recent experimental study showed an increased intrahepatic triglyceride (IHTG) content in mice deficient for aldolase B (aldo B-/-), the enzyme that converts fructose-1-phosphate to triose phosphates.

Objective: To translate these experimental findings to the human situation.

Design: Case-control study.

Setting: Outpatient clinic for inborn errors of metabolism.

Patients Or Other Participants: Patients with hereditary fructose intolerance, a rare inborn error of metabolism caused by a defect in aldolase B (n = 15), and healthy persons matched for age, sex, and body mass index (BMI) (n =15).

Main Outcome Measure: IHTG content, assessed by proton magnetic resonance spectroscopy.

Results: IHTG content was higher in aldo B-/- patients than controls (2.5% vs 0.6%; P = 0.001) on a background of lean body mass (median BMI, 20.4 and 21.8 kg/m2, respectively). Glucose excursions during an oral glucose load were higher in aldo B-/- patients (P = 0.043). Hypoglycosylated transferrin, a surrogate marker for hepatic fructose-1-phosphate concentrations, was more abundant in aldo B-/- patients than in controls (P < 0.001). Finally, plasma β-hydroxybutyrate, a biomarker of hepatic β-oxidation, was lower in aldo B-/- patients than controls (P = 0.009).

Conclusions: This study extends previous experimental findings by demonstrating that aldolase B deficiency also results in IHTG accumulation in humans. It suggests that the accumulation of fructose-1-phosphate and impairment of β-oxidation are involved in the pathogenesis.

Context: There is an ongoing debate about whether and how fructose is involved in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). A recent experimental study showed an increased intrahepatic triglyceride (IHTG) content in mice deficient for aldolase B (aldo B-/-), the enzyme that converts fructose-1-phosphate to triose phosphates.

Objective: To translate these experimental findings to the human situation.

Design: Case-control study.

Setting: Outpatient clinic for inborn errors of metabolism.

Patients Or Other Participants: Patients with hereditary fructose intolerance, a rare inborn error of metabolism caused by a defect in aldolase B (n = 15), and healthy persons matched for age, sex, and body mass index (BMI) (n =15).

Main Outcome Measure: IHTG content, assessed by proton magnetic resonance spectroscopy.

Results: IHTG content was higher in aldo B-/- patients than controls (2.5% vs 0.6%; P = 0.001) on a background of lean body mass (median BMI, 20.4 and 21.8 kg/m2, respectively). Glucose excursions during an oral glucose load were higher in aldo B-/- patients (P = 0.043). Hypoglycosylated transferrin, a surrogate marker for hepatic fructose-1-phosphate concentrations, was more abundant in aldo B-/- patients than in controls (P < 0.001). Finally, plasma β-hydroxybutyrate, a biomarker of hepatic β-oxidation, was lower in aldo B-/- patients than controls (P = 0.009).

Conclusions: This study extends previous experimental findings by demonstrating that aldolase B deficiency also results in IHTG accumulation in humans. It suggests that the accumulation of fructose-1-phosphate and impairment of β-oxidation are involved in the pathogenesis.

Epidemiological studies link fructose consumption with metabolic disease, an association attributable in part to fructose-mediated lipogenesis. The mechanisms governing fructose-induced lipogenesis and disease remain debated. Acutely, fructose increases de novo lipogenesis through the efficient and uninhibited action of ketohexokinase and aldolase B which yields substrates for fatty-acid synthesis. Chronic fructose consumption further enhances the capacity for hepatic fructose metabolism by activating several key transcription factors (i.e., SREBP1c and ChREBP) which augment the expression of lipogenic enzymes, increasing lipogenesis and further compounding hypertriglyceridemia and hepatic steatosis. Hepatic insulin resistance develops from diacylglycerol-PKCɛ-mediated impairment of insulin signaling and possibly additional mechanisms. Initiatives that decrease fructose consumption and therapies that block fructose-mediated lipogenesis will be necessary to avert future metabolic pandemics.

Despite the existence of numerous studies supporting a pathological link between fructose consumption and the development of the metabolic syndrome and its sequelae, such as non-alcoholic fatty liver disease (NAFLD), this link remains a contentious issue. With this article, we shed a light on the impact of sugar/fructose intake on hepatic de novo lipogenesis (DNL), an outcome parameter known to be dysregulated in subjects with type 2 diabetes and/or NAFLD. In this review, we present findings from human intervention studies using physiological doses of sugar as well as mechanistic animal studies. There is evidence from both human and animal studies that fructose is a more potent inducer of hepatic lipogenesis than glucose. This is most likely due to the liver's prominent physiological role in fructose metabolism, which may be disrupted under pathological conditions by increased hepatic expression of fructolytic and lipogenic enzymes. Increased DNL may not only contribute to ectopic fat deposition (i.e. in the liver), but it may also impair several metabolic processes through DNL-related fatty acids (e.g. beta-cell function, insulin secretion, or insulin sensitivity).

Overconsumption of high-fat diet (HFD) and sugar-sweetened beverages are risk factors for developing obesity, insulin resistance, and fatty liver disease. Here we have dissected mechanisms underlying this association using mice fed either chow or HFD with or without fructose- or glucose-supplemented water. In chow-fed mice, there was no major physiological difference between fructose and glucose supplementation. On the other hand, mice on HFD supplemented with fructose developed more pronounced obesity, glucose intolerance, and hepatomegaly as compared to glucose-supplemented HFD mice, despite similar caloric intake. Fructose and glucose supplementation also had distinct effects on expression of the lipogenic transcription factors ChREBP and SREBP1c. While both sugars increased ChREBP-β, fructose supplementation uniquely increased SREBP1c and downstream fatty acid synthesis genes, resulting in reduced liver insulin signaling. In contrast, glucose enhanced total ChREBP expression and triglyceride synthesis but was associated with improved hepatic insulin signaling. Metabolomic and RNA sequence analysis confirmed dichotomous effects of fructose and glucose supplementation on liver metabolism in spite of inducing similar hepatic lipid accumulation. Ketohexokinase, the first enzyme of fructose metabolism, was increased in fructose-fed mice and in obese humans with steatohepatitis. Knockdown of ketohexokinase in liver improved hepatic steatosis and glucose tolerance in fructose-supplemented mice. Thus, fructose is a component of dietary sugar that is distinctively associated with poor metabolic outcomes, whereas increased glucose intake may be protective.

Epidemiologic and animal studies implicate overconsumption of fructose in the development of nonalcoholic fatty liver disease, but the molecular mechanisms underlying fructose-induced chronic liver diseases remain largely unknown. Here, we have presented evidence supporting the essential function of the lipogenic transcription factor carbohydrate response element-binding protein (ChREBP) in mediating adaptive responses to fructose and protecting against fructose-induced hepatotoxicity. In WT mice, a high-fructose diet (HFrD) activated hepatic lipogenesis in a ChREBP-dependent manner; however, in Chrebp-KO mice, a HFrD induced steatohepatitis. In Chrebp-KO mouse livers, a HFrD reduced levels of molecular chaperones and activated the C/EBP homologous protein-dependent (CHOP-dependent) unfolded protein response, whereas administration of a chemical chaperone or Chop shRNA rescued liver injury. Elevated expression levels of cholesterol biosynthesis genes in HFrD-fed Chrebp-KO livers were paralleled by an increased nuclear abundance of sterol regulatory element-binding protein 2 (SREBP2). Atorvastatin-mediated inhibition of hepatic cholesterol biosynthesis or depletion of hepatic Srebp2 reversed fructose-induced liver injury in Chrebp-KO mice. Mechanistically, we determined that ChREBP binds to nuclear SREBP2 to promote its ubiquitination and destabilization in cultured cells. Therefore, our findings demonstrate that ChREBP provides hepatoprotection against a HFrD by preventing overactivation of cholesterol biosynthesis and the subsequent CHOP-mediated, proapoptotic unfolded protein response. Our findings also identified a role for ChREBP in regulating SREBP2-dependent cholesterol metabolism.

Several mechanisms whereby insulin resistance could cause an alteration in lipid metabolism have been described. Hyperinsulinemia is known to enhance hepatic synthesis of very-low-density lipoprotein (VLDL) and thus may directly contribute to the increased plasma triglyceride and LDL cholesterol levels.79 Resistance to the action of insulin on lipoprotein lipase in peripheral tissues also may contribute to elevated triglyceride and LDL cholesterol levels.80,81 It has been suggested that insulin resistance may be responsible for the reduced levels of HDL cholesterol observed in type 2 diabetes patients and that despite enhanced HDL cholesterol synthesis, the plasma HDL cholesterol concentration was significantly reduced in patients with type 2 diabetes compared with control subjects. This decrease in plasma HDL cholesterol was entirely accounted for by an increase in the rate of apolipoprotein A1/HDL cholesterol degradation, which exceeded the enhanced rate of its synthesis.82
Thus, from current knowledge, it is reasonable to suggest that weight control and lifestyle modification could alter the prevalence of the syndrome of insulin resistance and improve the risk profiles for cardiovascular disease as children make the transition toward adolescence and young adulthood.

Epidemiological studies link fructose consumption with metabolic disease, an association attributable in part to fructose-mediated lipogenesis. The mechanisms governing fructose-induced lipogenesis and disease remain debated. Acutely, fructose increases de novo lipogenesis through the efficient and uninhibited action of ketohexokinase and aldolase B which yields substrates for fatty-acid synthesis. Chronic fructose consumption further enhances the capacity for hepatic fructose metabolism by activating several key transcription factors (i.e., SREBP1c and ChREBP) which augment the expression of lipogenic enzymes, increasing lipogenesis and further compounding hypertriglyceridemia and hepatic steatosis. Hepatic insulin resistance develops from diacylglycerol-PKCɛ-mediated impairment of insulin signaling and possibly additional mechanisms. Initiatives that decrease fructose consumption and therapies that block fructose-mediated lipogenesis will be necessary to avert future metabolic pandemics.

Background: Dietary high fructose (HFr) is a known metabolic disruptor contributing to development of obesity and diabetes in Western societies. Initial molecular changes from exposure to HFr on liver metabolism may be essential to understand the perturbations leading to insulin resistance and abnormalities in lipid and carbohydrate metabolism. We studied vervet monkeys (Clorocebus aethiops sabaeus) fed a HFr (n=5) or chow diet (n=5) for 6 weeks, and obtained clinical measures of liver function, blood insulin, cholesterol and triglycerides. In addition, we performed untargeted global transcriptomics, proteomics, and metabolomics analyses on liver biopsies to determine the molecular impact of a HFr diet on coordinated pathways and networks that differed by diet.

Results: We show that integration of omics data sets improved statistical significance for some pathways and networks, and decreased significance for others, suggesting that multiple omics datasets enhance confidence in relevant pathway and network identification. Specifically, we found that sirtuin signaling and a peroxisome proliferator activated receptor alpha (PPARA) regulatory network were significantly altered in hepatic response to HFr. Integration of metabolomics and miRNAs data further strengthened our findings.

Conclusions: Our integrated analysis of three types of omics data with pathway and regulatory network analysis demonstrates the usefulness of this approach for discovery of molecular networks central to a biological response. In addition, metabolites aspartic acid and docosahexaenoic acid (DHA), protein ATG3, and genes ATG7, and HMGCS2 link sirtuin signaling and the PPARA network suggesting molecular mechanisms for altered hepatic gluconeogenesis from consumption of a HFr diet.

High-fructose intake in healthy men is associated with characteristics of metabolic syndrome. Extensive knowledge exists about the differences between hepatic fructose and glucose metabolism and fructose-specific mechanisms favoring the development of metabolic disturbances. Nevertheless, the causal relationship between fructose consumption and metabolic alterations is still debated. Multiple effects of fructose on hepatic metabolism are attributed to the fact that the liver represents the major sink of fructose. Fructose, as a lipogenic substrate and potent inducer of lipogenic enzyme expression, enhances fatty acid synthesis. Consequently, increased hepatic diacylglycerols (DAG) are thought to directly interfere with insulin signaling. However, independently of this effect, fructose may also counteract insulin-mediated effects on liver metabolism by a range of mechanisms. It may drive gluconeogenesis not only as a gluconeogenic substrate, but also as a potent inducer of carbohydrate responsive element binding protein (ChREBP), which induces the expression of lipogenic enzymes as well as gluconeogenic enzymes. It remains a challenge to determine the relative contributions of the impact of fructose on hepatic transcriptome, proteome and allosterome changes and consequently on the regulation of plasma glucose metabolism/homeostasis. Mathematical models exist modeling hepatic glucose metabolism. Future models should not only consider the hepatic adjustments of enzyme abundances and activities in response to changing plasma glucose and insulin/glucagon concentrations, but also to varying fructose concentrations for defining the role of fructose in the hepatic control of plasma glucose homeostasis.

Epidemiological studies link fructose consumption with metabolic disease, an association attributable in part to fructose-mediated lipogenesis. The mechanisms governing fructose-induced lipogenesis and disease remain debated. Acutely, fructose increases de novo lipogenesis through the efficient and uninhibited action of ketohexokinase and aldolase B which yields substrates for fatty-acid synthesis. Chronic fructose consumption further enhances the capacity for hepatic fructose metabolism by activating several key transcription factors (i.e., SREBP1c and ChREBP) which augment the expression of lipogenic enzymes, increasing lipogenesis and further compounding hypertriglyceridemia and hepatic steatosis. Hepatic insulin resistance develops from diacylglycerol-PKCɛ-mediated impairment of insulin signaling and possibly additional mechanisms. Initiatives that decrease fructose consumption and therapies that block fructose-mediated lipogenesis will be necessary to avert future metabolic pandemics.

Excessive caloric intake in a form of high-fat diet (HFD) was long thought to be the major risk factor for development of obesity and its complications, such as fatty liver disease and insulin resistance. Recently, there has been a paradigm shift and more attention is attributed to the effects of sugar-sweetened beverages (SSBs) as one of the culprits of the obesity epidemic. In this review, we present the data invoking fructose intake with development of hepatic insulin resistance in human studies and discuss the pathways by which fructose impairs hepatic insulin action in experimental animal models. First, we described well-characterized pathways by which fructose metabolism indirectly leads to hepatic insulin resistance. These include unequivocal effects of fructose to promote de novo lipogenesis (DNL), impair fatty acid oxidation (FAO), induce endoplasmic reticulum (ER) stress and trigger hepatic inflammation. Additionally, we entertained the hypothesis that fructose can directly impede insulin signaling in the liver. This appears to be mediated by reduced insulin receptor and insulin receptor substrate 2 (IRS2) expression, increased protein-tyrosine phosphatase 1B (PTP1b) activity, whereas knockdown of ketohexokinase (KHK), the rate-limiting enzyme of fructose metabolism, increased insulin sensitivity. In summary, dietary fructose intake strongly promotes hepatic insulin resistance complex interplay of several metabolic pathways, at least some of which are independent of increased weight gain and caloric intake. The current evidence shows that the fructose, but not glucose, component of dietary sugar drives metabolic complications and contradicts the notion that fructose is merely a source of palatable calories that leads to increased weight gain and insulin resistance.

Despite the existence of numerous studies supporting a pathological link between fructose consumption and the development of the metabolic syndrome and its sequelae, such as non-alcoholic fatty liver disease (NAFLD), this link remains a contentious issue. With this article, we shed a light on the impact of sugar/fructose intake on hepatic de novo lipogenesis (DNL), an outcome parameter known to be dysregulated in subjects with type 2 diabetes and/or NAFLD. In this review, we present findings from human intervention studies using physiological doses of sugar as well as mechanistic animal studies. There is evidence from both human and animal studies that fructose is a more potent inducer of hepatic lipogenesis than glucose. This is most likely due to the liver's prominent physiological role in fructose metabolism, which may be disrupted under pathological conditions by increased hepatic expression of fructolytic and lipogenic enzymes. Increased DNL may not only contribute to ectopic fat deposition (i.e. in the liver), but it may also impair several metabolic processes through DNL-related fatty acids (e.g. beta-cell function, insulin secretion, or insulin sensitivity).

Overconsumption of high-fat diet (HFD) and sugar-sweetened beverages are risk factors for developing obesity, insulin resistance, and fatty liver disease. Here we have dissected mechanisms underlying this association using mice fed either chow or HFD with or without fructose- or glucose-supplemented water. In chow-fed mice, there was no major physiological difference between fructose and glucose supplementation. On the other hand, mice on HFD supplemented with fructose developed more pronounced obesity, glucose intolerance, and hepatomegaly as compared to glucose-supplemented HFD mice, despite similar caloric intake. Fructose and glucose supplementation also had distinct effects on expression of the lipogenic transcription factors ChREBP and SREBP1c. While both sugars increased ChREBP-β, fructose supplementation uniquely increased SREBP1c and downstream fatty acid synthesis genes, resulting in reduced liver insulin signaling. In contrast, glucose enhanced total ChREBP expression and triglyceride synthesis but was associated with improved hepatic insulin signaling. Metabolomic and RNA sequence analysis confirmed dichotomous effects of fructose and glucose supplementation on liver metabolism in spite of inducing similar hepatic lipid accumulation. Ketohexokinase, the first enzyme of fructose metabolism, was increased in fructose-fed mice and in obese humans with steatohepatitis. Knockdown of ketohexokinase in liver improved hepatic steatosis and glucose tolerance in fructose-supplemented mice. Thus, fructose is a component of dietary sugar that is distinctively associated with poor metabolic outcomes, whereas increased glucose intake may be protective.

Epidemiological studies link fructose consumption with metabolic disease, an association attributable in part to fructose-mediated lipogenesis. The mechanisms governing fructose-induced lipogenesis and disease remain debated. Acutely, fructose increases de novo lipogenesis through the efficient and uninhibited action of ketohexokinase and aldolase B which yields substrates for fatty-acid synthesis. Chronic fructose consumption further enhances the capacity for hepatic fructose metabolism by activating several key transcription factors (i.e., SREBP1c and ChREBP) which augment the expression of lipogenic enzymes, increasing lipogenesis and further compounding hypertriglyceridemia and hepatic steatosis. Hepatic insulin resistance develops from diacylglycerol-PKCɛ-mediated impairment of insulin signaling and possibly additional mechanisms. Initiatives that decrease fructose consumption and therapies that block fructose-mediated lipogenesis will be necessary to avert future metabolic pandemics.

Excessive caloric intake in a form of high-fat diet (HFD) was long thought to be the major risk factor for development of obesity and its complications, such as fatty liver disease and insulin resistance. Recently, there has been a paradigm shift and more attention is attributed to the effects of sugar-sweetened beverages (SSBs) as one of the culprits of the obesity epidemic. In this review, we present the data invoking fructose intake with development of hepatic insulin resistance in human studies and discuss the pathways by which fructose impairs hepatic insulin action in experimental animal models. First, we described well-characterized pathways by which fructose metabolism indirectly leads to hepatic insulin resistance. These include unequivocal effects of fructose to promote de novo lipogenesis (DNL), impair fatty acid oxidation (FAO), induce endoplasmic reticulum (ER) stress and trigger hepatic inflammation. Additionally, we entertained the hypothesis that fructose can directly impede insulin signaling in the liver. This appears to be mediated by reduced insulin receptor and insulin receptor substrate 2 (IRS2) expression, increased protein-tyrosine phosphatase 1B (PTP1b) activity, whereas knockdown of ketohexokinase (KHK), the rate-limiting enzyme of fructose metabolism, increased insulin sensitivity. In summary, dietary fructose intake strongly promotes hepatic insulin resistance complex interplay of several metabolic pathways, at least some of which are independent of increased weight gain and caloric intake. The current evidence shows that the fructose, but not glucose, component of dietary sugar drives metabolic complications and contradicts the notion that fructose is merely a source of palatable calories that leads to increased weight gain and insulin resistance.

Obese, insulin-resistant states are characterized by a paradoxical pathogenic condition in which the liver appears to be selectively insulin resistant. Specifically, insulin fails to suppress glucose production, yet successfully stimulates de novo lipogenesis. The mechanisms underlying this dysregulation remain controversial. Here, we hypothesized that carbohydrate-responsive element-binding protein (ChREBP), a transcriptional activator of glycolytic and lipogenic genes, plays a central role in this paradox. Administration of fructose increased hepatic hexose-phosphate levels, activated ChREBP, and caused glucose intolerance, hyperinsulinemia, hypertriglyceridemia, and hepatic steatosis in mice. Activation of ChREBP was required for the increased expression of glycolytic and lipogenic genes as well as glucose-6-phosphatase (G6pc) that was associated with the effects of fructose administration. We found that fructose-induced G6PC activity is a major determinant of hepatic glucose production and reduces hepatic glucose-6-phosphate levels to complete a homeostatic loop. Moreover, fructose activated ChREBP and induced G6pc in the absence of Foxo1a, indicating that carbohydrate-induced activation of ChREBP and G6PC dominates over the suppressive effects of insulin to enhance glucose production. This ChREBP/G6PC signaling axis is conserved in humans. Together, these findings support a carbohydrate-mediated, ChREBP-driven mechanism that contributes to hepatic insulin resistance.

BACKGROUND &

Aims: Folate and cobalamin are methyl donors needed for the synthesis of methionine, which is the precursor of S-adenosylmethionine, the substrate of methylation in epigenetic, and epigenomic pathways. Methyl donor deficiency produces liver steatosis and predisposes to metabolic syndrome. Whether impaired fatty acid oxidation contributes to this steatosis remains unknown.

Methods: We evaluated the consequences of methyl donor deficient diet in liver of pups from dams subjected to deficiency during gestation and lactation.

Results: The deprived rats had microvesicular steatosis, with increased triglycerides, decreased methionine synthase activity, S-adenosylmethionine, and S-adenosylmethionine/S-adenosylhomocysteine ratio. We observed no change in apoptosis markers, oxidant and reticulum stresses, and carnityl-palmitoyl transferase 1 activity, and a decreased expression of SREBP-1c. Impaired beta-oxidation of fatty acids and carnitine deficit were the predominant changes, with decreased free and total carnitines, increased C14:1/C16 acylcarnitine ratio, decrease of oxidation rate of palmitoyl-CoA and palmitoyl-L-carnitine and decrease of expression of novel organic cation transporter 1, acylCoA-dehydrogenase and trifunctional enzyme subunit alpha and decreased activity of complexes I and II. These changes were related to lower protein expression of ER-α, ERR-α and HNF-4α, and hypomethylation of PGC-1α co-activator that reduced its binding with PPAR-α, ERR-α, and HNF-4α.

Conclusions: The liver steatosis resulted predominantly from hypomethylation of PGC1-α, decreased binding with its partners and subsequent impaired mitochondrial fatty acid oxidation. This link between methyl donor deficiency and epigenomic deregulations of energy metabolism opens new insights into the pathogenesis of fatty liver disease, in particular, in relation to the fetal programming hypothesis.

BACKGROUND &

Aims: Nutrients influence non-alcoholic fatty liver disease. Essential fatty acids deficiency promotes various syndromes, including hepatic steatosis, through increased de novo lipogenesis. The mechanisms underlying such increased lipogenic response remain unidentified.

Methods: We used wild type mice and mice lacking Liver X Receptors to perform a nutrigenomic study that aimed at examining the role of these transcription factors.

Results: We showed that, in the absence of Liver X Receptors, essential fatty acids deficiency does not promote steatosis. Consistent with this, Liver X Receptors are required for the elevated expression of genes involved in lipogenesis in response to essential fatty acids deficiency.

Conclusions: This work identifies, for the first time, the central role of Liver X Receptors in steatosis induced by essential fatty acids deficiency.

Fatty liver is a highly heterogenous condition driven by various pathogenic factors in addition to the severity of steatosis. Protein insufficiency has been causally linked to fatty liver with incompletely defined mechanisms. Here we report that fatty liver is a sulfur amino acid insufficient state that promotes metabolic inflexibility via limiting coenzyme A availability. We demonstrate that the nutrient-sensing transcriptional factor EB synergistically stimulates lysosome proteolysis and methionine adenosyltransferase to increase cysteine pool that drives the production of coenzyme A and glutathione, which support metabolic adaptation and antioxidant defense during increased lipid influx. Intriguingly, mice consuming an isocaloric protein-deficient Western diet exhibit selective hepatic cysteine, coenzyme A and glutathione deficiency and acylcarnitine accumulation, which are reversed by cystine supplementation without normalizing dietary protein intake. These findings support a pathogenic link of dysregulated sulfur amino acid metabolism to metabolic inflexibility that underlies both overnutrition and protein malnutrition-associated fatty liver development.

BACKGROUND &

Aims: Folate and cobalamin are methyl donors needed for the synthesis of methionine, which is the precursor of S-adenosylmethionine, the substrate of methylation in epigenetic, and epigenomic pathways. Methyl donor deficiency produces liver steatosis and predisposes to metabolic syndrome. Whether impaired fatty acid oxidation contributes to this steatosis remains unknown.

Methods: We evaluated the consequences of methyl donor deficient diet in liver of pups from dams subjected to deficiency during gestation and lactation.

Results: The deprived rats had microvesicular steatosis, with increased triglycerides, decreased methionine synthase activity, S-adenosylmethionine, and S-adenosylmethionine/S-adenosylhomocysteine ratio. We observed no change in apoptosis markers, oxidant and reticulum stresses, and carnityl-palmitoyl transferase 1 activity, and a decreased expression of SREBP-1c. Impaired beta-oxidation of fatty acids and carnitine deficit were the predominant changes, with decreased free and total carnitines, increased C14:1/C16 acylcarnitine ratio, decrease of oxidation rate of palmitoyl-CoA and palmitoyl-L-carnitine and decrease of expression of novel organic cation transporter 1, acylCoA-dehydrogenase and trifunctional enzyme subunit alpha and decreased activity of complexes I and II. These changes were related to lower protein expression of ER-α, ERR-α and HNF-4α, and hypomethylation of PGC-1α co-activator that reduced its binding with PPAR-α, ERR-α, and HNF-4α.

Conclusions: The liver steatosis resulted predominantly from hypomethylation of PGC1-α, decreased binding with its partners and subsequent impaired mitochondrial fatty acid oxidation. This link between methyl donor deficiency and epigenomic deregulations of energy metabolism opens new insights into the pathogenesis of fatty liver disease, in particular, in relation to the fetal programming hypothesis.

BACKGROUND &

Aims: Nutrients influence non-alcoholic fatty liver disease. Essential fatty acids deficiency promotes various syndromes, including hepatic steatosis, through increased de novo lipogenesis. The mechanisms underlying such increased lipogenic response remain unidentified.

Methods: We used wild type mice and mice lacking Liver X Receptors to perform a nutrigenomic study that aimed at examining the role of these transcription factors.

Results: We showed that, in the absence of Liver X Receptors, essential fatty acids deficiency does not promote steatosis. Consistent with this, Liver X Receptors are required for the elevated expression of genes involved in lipogenesis in response to essential fatty acids deficiency.

Conclusions: This work identifies, for the first time, the central role of Liver X Receptors in steatosis induced by essential fatty acids deficiency.

Fatty liver is a highly heterogenous condition driven by various pathogenic factors in addition to the severity of steatosis. Protein insufficiency has been causally linked to fatty liver with incompletely defined mechanisms. Here we report that fatty liver is a sulfur amino acid insufficient state that promotes metabolic inflexibility via limiting coenzyme A availability. We demonstrate that the nutrient-sensing transcriptional factor EB synergistically stimulates lysosome proteolysis and methionine adenosyltransferase to increase cysteine pool that drives the production of coenzyme A and glutathione, which support metabolic adaptation and antioxidant defense during increased lipid influx. Intriguingly, mice consuming an isocaloric protein-deficient Western diet exhibit selective hepatic cysteine, coenzyme A and glutathione deficiency and acylcarnitine accumulation, which are reversed by cystine supplementation without normalizing dietary protein intake. These findings support a pathogenic link of dysregulated sulfur amino acid metabolism to metabolic inflexibility that underlies both overnutrition and protein malnutrition-associated fatty liver development.

Scope: A compromised nutritional status in methyl-group donors may provoke several molecular alterations triggering the development of nonalcoholic fatty liver disease (NAFLD) in humans and experimental animals. In this study, we investigated a role and the underlying molecular mechanisms of methionine metabolic pathway malfunctions in the pathogenesis of NAFLD.

Methods And Results: We fed female Swiss albino mice a control (methionine-adequate) diet and two experimental (methionine-deficient or methionine-supplemented) diets for 10 weeks, and the levels of one-carbon metabolites, expression of one-carbon and lipid metabolism genes in the livers were evaluated. We demonstrate that both experimental diets increased hepatic levels of S-adenosyl-l-homocysteine and homocysteine, altered expression of one-carbon and lipid metabolism genes, and caused lipid accumulation, especially in mice fed the methionine-deficient diet. Markers of oxidative and ER stress response were also elevated in the livers of mice fed either diet.

Conclusion: Our findings indicate that both dietary methionine deficiency and methionine supplementation can induce molecular abnormalities in the liver associated with the development of NAFLD, including deregulation in lipid and one-carbon metabolic pathways, and induction of oxidative and ER stress. These pathophysiological events may ultimately lead to lipid accumulation in the livers, triggering the development of NAFLD.

Recently, the protective effects of a methionine-rich diet on hepatic oxidative stress and fibrosis have been suggested but not adequately studied. We, therefore, hypothesized that L-methionine supplementation would ameliorate the progression of hepatic injury in a diet-induced non-alcoholic steatohepatitis (NASH) model and aimed to investigate the underlying mechanism. NASH was developed in male Sprague Dawley rats by feeding them with a high-fat-fructose diet (HFFrD) for 10 weeks. The results demonstrated that L-methionine supplementation to NASH rats for 16 weeks improved the glycemic, lipid, and liver function profiles in NASH rats. Histological analysis of liver tissue revealed a remarkable improvement in the three classical lesions of

Nash: steatosis, inflammation, and ballooning. Besides, L-methionine supplementation ameliorated the HFFrD-induced enhanced lipogenesis and lipid peroxidation. An anti-inflammatory effect of L-methionine was also observed through the inhibition of the release of proinflammatory cytokines. Furthermore, the hepatic SIRT1/AMPK signaling pathway was associated with the beneficial effects of L-methionine. This study demonstrates that L-methionine supplementation in HFFrD-fed rats improves their liver pathology regulation of lipogenesis, inflammation, and the SIRT1/AMPK pathway, thus encouraging its clinical evaluation for the treatment of NASH.

BACKGROUND &

Aims: A holistic insight on the relationship between obesity and metabolic dysfunction-associated fatty liver disease is an unmet clinical need. Omics investigations can be used to investigate the multifaceted role of altered mitochondrial pathways to promote nonalcoholic steatohepatitis, a major risk factor for liver disease-associated death. There are no specific treatments but remission via surgery might offer an opportunity to examine the signaling processes that govern the complex spectrum of chronic liver diseases observed in extreme obesity. We aim to assess the emerging relationship between metabolism, methylation and liver disease.

Methods: We tailed the flow of information, before and after steatohepatitis remission, from biochemical, histological, and multi-omics analyses in liver biopsies from patients with extreme obesity and successful bariatric surgery. Functional studies were performed in HepG2 cells and primary hepatocytes.

Results: The reversal of hepatic mitochondrial dysfunction and the control of oxidative stress and inflammatory responses revealed the regulatory role of mitogen-activated protein kinases. The reversible metabolic rearrangements leading to steatohepatitis increased the glutaminolysis-induced production of α-ketoglutarate and the hyperactivation of mammalian target of rapamycin complex 1. These changes were crucial for the adenosine monophosphate-activated protein kinase/mammalian target of rapamycin-driven pathways that modulated hepatocyte survival by coordinating apoptosis and autophagy. The signaling activity of α-ketoglutarate and the associated metabolites also affected methylation-related epigenomic remodeling enzymes. Integrative analysis of hepatic transcriptome signatures and differentially methylated genomic regions distinguished patients with and without steatohepatitis.

Conclusion: We provide evidence supporting the multifaceted potential of the increased glutaminolysis-induced α-ketoglutarate production and the mammalian target of rapamycin complex 1 dysregulation as a conceivable source of the inefficient adaptive responses leading to steatohepatitis.

Lay Summary: Steatohepatitis is a frequent and threatening complication of extreme obesity without specific treatment. Omics technologies can be used to identify therapeutic targets. We highlight increased glutaminolysis-induced α-ketoglutarate production as a potential source of signals promoting and exacerbating steatohepatitis.

Convincing evidence links aberrant B-vitamin dependent hepatic methionine metabolism to the pathogenesis of alcoholic liver disease (ALD). This review focuses on the essential roles of folate and vitamins B6 and B12 in hepatic methionine metabolism, the causes of their deficiencies among chronic alcoholic persons, and how their deficiencies together with chronic alcohol exposure impact on aberrant methionine metabolism in the pathogenesis of ALD. Folate is the dietary transmethylation donor for the production of S-adenosylmethionine (SAM), which is the substrate for all methyltransferases that regulate gene expressions in pathways of liver injury, as well as a regulator of the transsulfuration pathway that is essential for production of glutathione (GSH), the principal antioxidant for defense against oxidative liver injury. Vitamin B12 regulates transmethylation reactions for SAM production and vitamin B6 regulates transsulfuration reactions for GSH production. Folate deficiency accelerates the experimental development of ALD in ethanol-fed animals while reducing liver SAM levels with resultant abnormal gene expression and decreased production of antioxidant GSH. Through its effects on folate metabolism, reduced SAM also impairs nucleotide balance with resultant increased DNA strand breaks, oxidation, hepatocellular apoptosis, and risk of carcinogenesis. The review encompasses referenced studies on mechanisms for perturbations of methionine metabolism in ALD, evidence for altered gene expressions and their epigenetic regulation in the pathogenesis of ALD, and clinical studies on potential prevention and treatment of ALD by correction of methionine metabolism with SAM.

12.1 Mechanism of Action Vitamin B 12 can be converted to coenzyme B 12 in tissues, and as such is essential for conversion of methylmalonate to succinate and synthesis of methionine from homocysteine, a reaction which also requires folate. In the absence of coenzyme B 12 , tetrahydrofolate cannot be regenerated from its inactive storage form, 5-methyltetrahydrofolate, and a functional folate deficiency occurs. Vitamin B 12 also may be involved in maintaining sulfhydryl (SH) groups in the reduced form required by many SH-activated enzyme systems. Through these reactions, vitamin B 12 is associated with fat and carbohydrate metabolism and protein synthesis.

BACKGROUND &

Aims: Nutrients influence non-alcoholic fatty liver disease. Essential fatty acids deficiency promotes various syndromes, including hepatic steatosis, through increased de novo lipogenesis. The mechanisms underlying such increased lipogenic response remain unidentified.

Methods: We used wild type mice and mice lacking Liver X Receptors to perform a nutrigenomic study that aimed at examining the role of these transcription factors.

Results: We showed that, in the absence of Liver X Receptors, essential fatty acids deficiency does not promote steatosis. Consistent with this, Liver X Receptors are required for the elevated expression of genes involved in lipogenesis in response to essential fatty acids deficiency.

Conclusions: This work identifies, for the first time, the central role of Liver X Receptors in steatosis induced by essential fatty acids deficiency.

Scope: A compromised nutritional status in methyl-group donors may provoke several molecular alterations triggering the development of nonalcoholic fatty liver disease (NAFLD) in humans and experimental animals. In this study, we investigated a role and the underlying molecular mechanisms of methionine metabolic pathway malfunctions in the pathogenesis of NAFLD.

Methods And Results: We fed female Swiss albino mice a control (methionine-adequate) diet and two experimental (methionine-deficient or methionine-supplemented) diets for 10 weeks, and the levels of one-carbon metabolites, expression of one-carbon and lipid metabolism genes in the livers were evaluated. We demonstrate that both experimental diets increased hepatic levels of S-adenosyl-l-homocysteine and homocysteine, altered expression of one-carbon and lipid metabolism genes, and caused lipid accumulation, especially in mice fed the methionine-deficient diet. Markers of oxidative and ER stress response were also elevated in the livers of mice fed either diet.

Conclusion: Our findings indicate that both dietary methionine deficiency and methionine supplementation can induce molecular abnormalities in the liver associated with the development of NAFLD, including deregulation in lipid and one-carbon metabolic pathways, and induction of oxidative and ER stress. These pathophysiological events may ultimately lead to lipid accumulation in the livers, triggering the development of NAFLD.

As one of the bicyclic metabolic pathways of one-carbon metabolism, methionine metabolism is the pivot linking the folate cycle to the transsulfuration pathway. In addition to being a precursor for glutathione synthesis, and the principal methyl donor for nucleic acid, phospholipid, histone, biogenic amine, and protein methylation, methionine metabolites can participate in polyamine synthesis. Methionine metabolism disorder can aggravate the damage in the pathological state of a disease. In the occurrence and development of chronic liver diseases (CLDs), changes in various components involved in methionine metabolism can affect the pathological state through various mechanisms. A methionine-deficient diet is commonly used for building CLD models. The conversion of key enzymes of methionine metabolism methionine adenosyltransferase (MAT) 1 A and MAT2A/MAT2B is closely related to fibrosis and hepatocellular carcinoma. In vivo and in vitro experiments have shown that by intervening related enzymes or downstream metabolites to interfere with methionine metabolism, the liver injuries could be reduced. Recently, methionine supplementation has gradually attracted the attention of many clinical researchers. Most researchers agree that adequate methionine supplementation can help reduce liver damage. Retrospective analysis of recently conducted relevant studies is of profound significance. This paper reviews the latest achievements related to methionine metabolism and CLD, from molecular mechanisms to clinical research, and provides some insights into the future direction of basic and clinical research.

Administration of amino acid solutions to a patient with hepatic insufficiency may result in plasma amino acid imbalances, hyperammonemia, prerenal azotemia, stupor and coma. Hyperammonemia is of special significance in infants as its occurrence in the syndrome caused by genetic metabolic defects is sometimes associated, although not necessarily in a causal relationship, with mental retardation. This reaction appears to be dose related and is more likely to develop during prolonged therapy. It is essential that blood ammonia be measured frequently in infants. The mechanisms of this reaction are not clearly defined but may involve genetic defects and immature or subclinically impaired liver function. Conservative doses of amino acids should be given, dictated by the nutritional status of the patient. Should symptoms of hyperammonemia develop, amino acid administration should be discontinued and the patient’s clinical status reevaluated.

Recently, the protective effects of a methionine-rich diet on hepatic oxidative stress and fibrosis have been suggested but not adequately studied. We, therefore, hypothesized that L-methionine supplementation would ameliorate the progression of hepatic injury in a diet-induced non-alcoholic steatohepatitis (NASH) model and aimed to investigate the underlying mechanism. NASH was developed in male Sprague Dawley rats by feeding them with a high-fat-fructose diet (HFFrD) for 10 weeks. The results demonstrated that L-methionine supplementation to NASH rats for 16 weeks improved the glycemic, lipid, and liver function profiles in NASH rats. Histological analysis of liver tissue revealed a remarkable improvement in the three classical lesions of

Nash: steatosis, inflammation, and ballooning. Besides, L-methionine supplementation ameliorated the HFFrD-induced enhanced lipogenesis and lipid peroxidation. An anti-inflammatory effect of L-methionine was also observed through the inhibition of the release of proinflammatory cytokines. Furthermore, the hepatic SIRT1/AMPK signaling pathway was associated with the beneficial effects of L-methionine. This study demonstrates that L-methionine supplementation in HFFrD-fed rats improves their liver pathology regulation of lipogenesis, inflammation, and the SIRT1/AMPK pathway, thus encouraging its clinical evaluation for the treatment of NASH.

Nonalcoholic fatty liver disease (NAFLD) is a spectrum of chronic liver conditions that are characterized by steatosis, inflammation, fibrosis, and liver injury. The global prevalence of NAFLD is rapidly increasing in proportion to the rising incidence of obesity and type 2 diabetes. Because NAFLD is a multifaceted disorder with many underlying metabolic abnormalities, currently, there is no pharmacological agent that is therapeutically approved for the treatment of this disease. Folate is a water-soluble B vitamin that plays an essential role in one-carbon transfer reactions involved in nucleic acid biosynthesis, methylation reactions, and sulfur-containing amino acid metabolism. The liver is the primary organ responsible for storage and metabolism of folates. Low serum folate levels have been observed in patients with obesity and diabetes. It has been reported that a low level of endogenous folates in rodents perturbs folate-dependent one-carbon metabolism, and may be associated with development of metabolic diseases such as NAFLD. This review highlights the biological role of folate in the progression of NAFLD and its associated metabolic complications including obesity and type 2 diabetes. Understanding the role of folate in metabolic disease may position this vitamin as a potential therapeutic for NAFLD.

12.1 Mechanism of Action Vitamin B 12 can be converted to coenzyme B 12 in tissues, and as such is essential for conversion of methylmalonate to succinate and synthesis of methionine from homocysteine, a reaction which also requires folate. In the absence of coenzyme B 12 , tetrahydrofolate cannot be regenerated from its inactive storage form, 5-methyltetrahydrofolate, and a functional folate deficiency occurs. Vitamin B 12 also may be involved in maintaining sulfhydryl (SH) groups in the reduced form required by many SH-activated enzyme systems. Through these reactions, vitamin B 12 is associated with fat and carbohydrate metabolism and protein synthesis.

12.1 Mechanism of Action Vitamin B 12 can be converted to coenzyme B 12 in tissues, and as such is essential for conversion of methylmalonate to succinate and synthesis of methionine from homocysteine, a reaction which also requires folate. In the absence of coenzyme B 12, tetrahydrofolate cannot be regenerated from its inactive storage form, 5-methyltetrahydrofolate, and a functional folate deficiency occurs. Vitamin B 12 also may be involved in maintaining sulfhydryl (SH) groups in the reduced form required by many SH-activated enzyme systems. Through these reactions, vitamin B 12 is associated with fat and carbohydrate metabolism and protein synthesis.

Convincing evidence links aberrant B-vitamin dependent hepatic methionine metabolism to the pathogenesis of alcoholic liver disease (ALD). This review focuses on the essential roles of folate and vitamins B6 and B12 in hepatic methionine metabolism, the causes of their deficiencies among chronic alcoholic persons, and how their deficiencies together with chronic alcohol exposure impact on aberrant methionine metabolism in the pathogenesis of ALD. Folate is the dietary transmethylation donor for the production of S-adenosylmethionine (SAM), which is the substrate for all methyltransferases that regulate gene expressions in pathways of liver injury, as well as a regulator of the transsulfuration pathway that is essential for production of glutathione (GSH), the principal antioxidant for defense against oxidative liver injury. Vitamin B12 regulates transmethylation reactions for SAM production and vitamin B6 regulates transsulfuration reactions for GSH production. Folate deficiency accelerates the experimental development of ALD in ethanol-fed animals while reducing liver SAM levels with resultant abnormal gene expression and decreased production of antioxidant GSH. Through its effects on folate metabolism, reduced SAM also impairs nucleotide balance with resultant increased DNA strand breaks, oxidation, hepatocellular apoptosis, and risk of carcinogenesis. The review encompasses referenced studies on mechanisms for perturbations of methionine metabolism in ALD, evidence for altered gene expressions and their epigenetic regulation in the pathogenesis of ALD, and clinical studies on potential prevention and treatment of ALD by correction of methionine metabolism with SAM.

Non-alcoholic fatty liver disease (NAFLD) is the most frequent chronic liver disease without effective therapy. Selenium, as an essential trace element for humans, is notable for its antioxidant properties. The previous study shows that selenium levels in NAFLD patients are lower than normal ones. Selenium supplementation can effectively alleviate metabolic disorders by relieving anti-oxidative stress and anti-inflammatory regulation. However, the correlation between selenium and NAFLD has not been fully clarified. Herein, we review the current studies on selenium in regulating the different stages of NAFLD and summarize relevant clinical trials to highlight the potential roles of selenium in NAFLD treatment.

BACKGROUND &

Aims: Nutrients influence non-alcoholic fatty liver disease. Essential fatty acids deficiency promotes various syndromes, including hepatic steatosis, through increased de novo lipogenesis. The mechanisms underlying such increased lipogenic response remain unidentified.

Methods: We used wild type mice and mice lacking Liver X Receptors to perform a nutrigenomic study that aimed at examining the role of these transcription factors.

Results: We showed that, in the absence of Liver X Receptors, essential fatty acids deficiency does not promote steatosis. Consistent with this, Liver X Receptors are required for the elevated expression of genes involved in lipogenesis in response to essential fatty acids deficiency.

Conclusions: This work identifies, for the first time, the central role of Liver X Receptors in steatosis induced by essential fatty acids deficiency.

As a chronic metabolic disease affecting epidemic proportions worldwide, the pathogenesis of Nonalcoholic Fatty Liver Disease (NAFLD) is not clear yet. There is also a lack of precise biomarkers and specific medicine for the diagnosis and treatment of NAFLD. Methionine metabolic cycle, which is critical for the maintaining of cellular methylation and redox state, is involved in the pathophysiology of NAFLD. However, the molecular basis and mechanism of methionine metabolism in NAFLD are not completely understood. Here, we mainly focus on specific enzymes that participates in methionine cycle, to reveal their interconnections with NAFLD, in order to recognize the pathogenesis of NAFLD from a new angle and at the same time, explore the clinical characteristics and therapeutic strategies.

Scope: A compromised nutritional status in methyl-group donors may provoke several molecular alterations triggering the development of nonalcoholic fatty liver disease (NAFLD) in humans and experimental animals. In this study, we investigated a role and the underlying molecular mechanisms of methionine metabolic pathway malfunctions in the pathogenesis of NAFLD.

Methods And Results: We fed female Swiss albino mice a control (methionine-adequate) diet and two experimental (methionine-deficient or methionine-supplemented) diets for 10 weeks, and the levels of one-carbon metabolites, expression of one-carbon and lipid metabolism genes in the livers were evaluated. We demonstrate that both experimental diets increased hepatic levels of S-adenosyl-l-homocysteine and homocysteine, altered expression of one-carbon and lipid metabolism genes, and caused lipid accumulation, especially in mice fed the methionine-deficient diet. Markers of oxidative and ER stress response were also elevated in the livers of mice fed either diet.

Conclusion: Our findings indicate that both dietary methionine deficiency and methionine supplementation can induce molecular abnormalities in the liver associated with the development of NAFLD, including deregulation in lipid and one-carbon metabolic pathways, and induction of oxidative and ER stress. These pathophysiological events may ultimately lead to lipid accumulation in the livers, triggering the development of NAFLD.

Convincing evidence links aberrant B-vitamin dependent hepatic methionine metabolism to the pathogenesis of alcoholic liver disease (ALD). This review focuses on the essential roles of folate and vitamins B6 and B12 in hepatic methionine metabolism, the causes of their deficiencies among chronic alcoholic persons, and how their deficiencies together with chronic alcohol exposure impact on aberrant methionine metabolism in the pathogenesis of ALD. Folate is the dietary transmethylation donor for the production of S-adenosylmethionine (SAM), which is the substrate for all methyltransferases that regulate gene expressions in pathways of liver injury, as well as a regulator of the transsulfuration pathway that is essential for production of glutathione (GSH), the principal antioxidant for defense against oxidative liver injury. Vitamin B12 regulates transmethylation reactions for SAM production and vitamin B6 regulates transsulfuration reactions for GSH production. Folate deficiency accelerates the experimental development of ALD in ethanol-fed animals while reducing liver SAM levels with resultant abnormal gene expression and decreased production of antioxidant GSH. Through its effects on folate metabolism, reduced SAM also impairs nucleotide balance with resultant increased DNA strand breaks, oxidation, hepatocellular apoptosis, and risk of carcinogenesis. The review encompasses referenced studies on mechanisms for perturbations of methionine metabolism in ALD, evidence for altered gene expressions and their epigenetic regulation in the pathogenesis of ALD, and clinical studies on potential prevention and treatment of ALD by correction of methionine metabolism with SAM.

BACKGROUND &

Aims: Folate and cobalamin are methyl donors needed for the synthesis of methionine, which is the precursor of S-adenosylmethionine, the substrate of methylation in epigenetic, and epigenomic pathways. Methyl donor deficiency produces liver steatosis and predisposes to metabolic syndrome. Whether impaired fatty acid oxidation contributes to this steatosis remains unknown.

Methods: We evaluated the consequences of methyl donor deficient diet in liver of pups from dams subjected to deficiency during gestation and lactation.

Results: The deprived rats had microvesicular steatosis, with increased triglycerides, decreased methionine synthase activity, S-adenosylmethionine, and S-adenosylmethionine/S-adenosylhomocysteine ratio. We observed no change in apoptosis markers, oxidant and reticulum stresses, and carnityl-palmitoyl transferase 1 activity, and a decreased expression of SREBP-1c. Impaired beta-oxidation of fatty acids and carnitine deficit were the predominant changes, with decreased free and total carnitines, increased C14:1/C16 acylcarnitine ratio, decrease of oxidation rate of palmitoyl-CoA and palmitoyl-L-carnitine and decrease of expression of novel organic cation transporter 1, acylCoA-dehydrogenase and trifunctional enzyme subunit alpha and decreased activity of complexes I and II. These changes were related to lower protein expression of ER-α, ERR-α and HNF-4α, and hypomethylation of PGC-1α co-activator that reduced its binding with PPAR-α, ERR-α, and HNF-4α.

Conclusions: The liver steatosis resulted predominantly from hypomethylation of PGC1-α, decreased binding with its partners and subsequent impaired mitochondrial fatty acid oxidation. This link between methyl donor deficiency and epigenomic deregulations of energy metabolism opens new insights into the pathogenesis of fatty liver disease, in particular, in relation to the fetal programming hypothesis.

Background: As a central organ of energy metabolism, the liver is closely related to selenium for its normal function and disease development. However, the underlying roles of mitochondrial energy metabolism and mitophagy in liver fibrosis associated with selenium remain unclear.

Methods: 28 rats were randomly divided into normal, low-selenium, nano-selenium supplement-1, and supplement-2 groups for a 12-week intervention. We observed pathological and ultrastructural changes in the liver and analyzed the effects of selenium deficiency and nano-selenium supplementation on liver metabolic activities and crucial proteins expression of mammalian target of the rapamycin (mTOR) signaling pathway.

Results: Selenium deficiency caused liver pathological damage and fibrosis with the occurrence of mitophagy by disrupting normal metabolic activities; meanwhile, the mTOR signaling pathway was up-regulated to enhance mitophagy to clear damaged mitochondria. Furthermore, nano-selenium supplements could reduce the severity of pathological damage and fibrosis in livers and maintain normal energy metabolic activity. With the increased concentrations of nano-selenium supplement, swelling mitochondria and mitophagy gradually decreased, accompanied by the higher expression of mTOR and phosphorylation-modified mTOR proteins and lower expression of unc-51 like autophagy activating kinase 1 (ULK1) and phosphorylation-modified ULK1 proteins.

Conclusions: Mitophagy regulated by the mTOR signaling pathway plays a dual protective role on low-selenium inducing liver fibrosis and nano-selenium supplements preventing liver fibrosis. Mitochondrial energy metabolism plays an important role in these processes as well.

Selenium (Se) intake disequilibrium is associated with many human diseases (e.g., Keshan disease and type 2 diabetes). To understand the mechanism of Se deficiency-induced hepatic pathogenesis, a pure line pig model was established by feeding a diet with either 0.07 mg/kg Se or 0.3 mg/kg Se for 16 weeks. The hepatic metabolome, lipidome, global proteome, and whole transcriptome were analyzed. Se deficiency causes a redox imbalance via regulation of selenoproteins at both the mRNA and protein level, and blocks the glutathione anti-oxidant system along with enhanced glutathione synthesis and catabolism. The Warburg effect was observed by enhanced activation of the glycolysis and phosphate pentose pathways. The tricarboxylic acid cycle was dysfunctional since the preliminary metabolites decreased and shifted from using glycolysis origin substrates to a glutamine catabolism-preferred metabolic mode. The reprogrammed central carbon metabolism induced widely restrained lipid synthesis. In addition, a Se deficiency initiated inflammation by activating the NF-κB pathway through multiple mechanisms. These results identified the potential metabolic vulnerability of the liver in response to a Se deficiency-induced redox imbalance and possible therapeutic or intervention targets.

BACKGROUND &

Aims: Nutrients influence non-alcoholic fatty liver disease. Essential fatty acids deficiency promotes various syndromes, including hepatic steatosis, through increased de novo lipogenesis. The mechanisms underlying such increased lipogenic response remain unidentified.

Methods: We used wild type mice and mice lacking Liver X Receptors to perform a nutrigenomic study that aimed at examining the role of these transcription factors.

Results: We showed that, in the absence of Liver X Receptors, essential fatty acids deficiency does not promote steatosis. Consistent with this, Liver X Receptors are required for the elevated expression of genes involved in lipogenesis in response to essential fatty acids deficiency.

Conclusions: This work identifies, for the first time, the central role of Liver X Receptors in steatosis induced by essential fatty acids deficiency.

As a chronic metabolic disease affecting epidemic proportions worldwide, the pathogenesis of Nonalcoholic Fatty Liver Disease (NAFLD) is not clear yet. There is also a lack of precise biomarkers and specific medicine for the diagnosis and treatment of NAFLD. Methionine metabolic cycle, which is critical for the maintaining of cellular methylation and redox state, is involved in the pathophysiology of NAFLD. However, the molecular basis and mechanism of methionine metabolism in NAFLD are not completely understood. Here, we mainly focus on specific enzymes that participates in methionine cycle, to reveal their interconnections with NAFLD, in order to recognize the pathogenesis of NAFLD from a new angle and at the same time, explore the clinical characteristics and therapeutic strategies.

Fatty liver is a highly heterogenous condition driven by various pathogenic factors in addition to the severity of steatosis. Protein insufficiency has been causally linked to fatty liver with incompletely defined mechanisms. Here we report that fatty liver is a sulfur amino acid insufficient state that promotes metabolic inflexibility via limiting coenzyme A availability. We demonstrate that the nutrient-sensing transcriptional factor EB synergistically stimulates lysosome proteolysis and methionine adenosyltransferase to increase cysteine pool that drives the production of coenzyme A and glutathione, which support metabolic adaptation and antioxidant defense during increased lipid influx. Intriguingly, mice consuming an isocaloric protein-deficient Western diet exhibit selective hepatic cysteine, coenzyme A and glutathione deficiency and acylcarnitine accumulation, which are reversed by cystine supplementation without normalizing dietary protein intake. These findings support a pathogenic link of dysregulated sulfur amino acid metabolism to metabolic inflexibility that underlies both overnutrition and protein malnutrition-associated fatty liver development.

As a chronic metabolic disease affecting epidemic proportions worldwide, the pathogenesis of Nonalcoholic Fatty Liver Disease (NAFLD) is not clear yet. There is also a lack of precise biomarkers and specific medicine for the diagnosis and treatment of NAFLD. Methionine metabolic cycle, which is critical for the maintaining of cellular methylation and redox state, is involved in the pathophysiology of NAFLD. However, the molecular basis and mechanism of methionine metabolism in NAFLD are not completely understood. Here, we mainly focus on specific enzymes that participates in methionine cycle, to reveal their interconnections with NAFLD, in order to recognize the pathogenesis of NAFLD from a new angle and at the same time, explore the clinical characteristics and therapeutic strategies.

Nonalcoholic fatty liver disease (NAFLD) is a spectrum of chronic liver conditions that are characterized by steatosis, inflammation, fibrosis, and liver injury. The global prevalence of NAFLD is rapidly increasing in proportion to the rising incidence of obesity and type 2 diabetes. Because NAFLD is a multifaceted disorder with many underlying metabolic abnormalities, currently, there is no pharmacological agent that is therapeutically approved for the treatment of this disease. Folate is a water-soluble B vitamin that plays an essential role in one-carbon transfer reactions involved in nucleic acid biosynthesis, methylation reactions, and sulfur-containing amino acid metabolism. The liver is the primary organ responsible for storage and metabolism of folates. Low serum folate levels have been observed in patients with obesity and diabetes. It has been reported that a low level of endogenous folates in rodents perturbs folate-dependent one-carbon metabolism, and may be associated with development of metabolic diseases such as NAFLD. This review highlights the biological role of folate in the progression of NAFLD and its associated metabolic complications including obesity and type 2 diabetes. Understanding the role of folate in metabolic disease may position this vitamin as a potential therapeutic for NAFLD.

12.1 Mechanism of Action Vitamin B 12 can be converted to coenzyme B 12 in tissues, and as such is essential for conversion of methylmalonate to succinate and synthesis of methionine from homocysteine, a reaction which also requires folate. In the absence of coenzyme B 12 , tetrahydrofolate cannot be regenerated from its inactive storage form, 5-methyltetrahydrofolate, and a functional folate deficiency occurs. Vitamin B 12 also may be involved in maintaining sulfhydryl (SH) groups in the reduced form required by many SH-activated enzyme systems. Through these reactions, vitamin B 12 is associated with fat and carbohydrate metabolism and protein synthesis.

Oxidative stress (OxS) is considered a major factor in the pathophysiology of inflammatory chronic liver diseases, including non-alcoholic liver disease (NAFLD). Chronic impairment of lipid metabolism is closely related to alterations of the oxidant/antioxidant balance, which affect metabolism-related organelles, leading to cellular lipotoxicity, lipid peroxidation, chronic endoplasmic reticulum (ER) stress, and mitochondrial dysfunction. Increased OxS also triggers hepatocytes stress pathways, leading to inflammation and fibrogenesis, contributing to the progression of non-alcoholic steatohepatitis (NASH). The antioxidant response, regulated by the Nrf2/ARE pathway, is a key component in this process and counteracts oxidative stress-induced damage, contributing to the restoration of normal lipid metabolism. Therefore, modulation of the antioxidant response emerges as an interesting target to prevent NAFLD development and progression. This review highlights the link between disturbed lipid metabolism and oxidative stress in the context of NAFLD. In addition, emerging potential therapies based on antioxidant effects and their likely molecular targets are discussed.

Selenium (Se) intake disequilibrium is associated with many human diseases (e.g., Keshan disease and type 2 diabetes). To understand the mechanism of Se deficiency-induced hepatic pathogenesis, a pure line pig model was established by feeding a diet with either 0.07 mg/kg Se or 0.3 mg/kg Se for 16 weeks. The hepatic metabolome, lipidome, global proteome, and whole transcriptome were analyzed. Se deficiency causes a redox imbalance via regulation of selenoproteins at both the mRNA and protein level, and blocks the glutathione anti-oxidant system along with enhanced glutathione synthesis and catabolism. The Warburg effect was observed by enhanced activation of the glycolysis and phosphate pentose pathways. The tricarboxylic acid cycle was dysfunctional since the preliminary metabolites decreased and shifted from using glycolysis origin substrates to a glutamine catabolism-preferred metabolic mode. The reprogrammed central carbon metabolism induced widely restrained lipid synthesis. In addition, a Se deficiency initiated inflammation by activating the NF-κB pathway through multiple mechanisms. These results identified the potential metabolic vulnerability of the liver in response to a Se deficiency-induced redox imbalance and possible therapeutic or intervention targets.

BACKGROUND &

Aims: Nutrients influence non-alcoholic fatty liver disease. Essential fatty acids deficiency promotes various syndromes, including hepatic steatosis, through increased de novo lipogenesis. The mechanisms underlying such increased lipogenic response remain unidentified.

Methods: We used wild type mice and mice lacking Liver X Receptors to perform a nutrigenomic study that aimed at examining the role of these transcription factors.

Results: We showed that, in the absence of Liver X Receptors, essential fatty acids deficiency does not promote steatosis. Consistent with this, Liver X Receptors are required for the elevated expression of genes involved in lipogenesis in response to essential fatty acids deficiency.

Conclusions: This work identifies, for the first time, the central role of Liver X Receptors in steatosis induced by essential fatty acids deficiency.

Fatty liver is a complex disease often accompanying metabolic syndrome and Type 2 diabetes mellitus (T2DM). Hepatosteatosis may have roots in multiple metabolic abnormalities. However, metabolic dysfunction in the 1-carbon cycle (1CC), which produces the methyl donor S-adenosylmethionine (SAM) and phosphatidylcholine (PC), induces hepatic lipogenesis in model systems. Human diseases where 1CC or PC synthesis is disrupted, such as alcoholism, congenital lipodystrophy, or cystic fibrosis, often present with fatty liver. Given that the 1CC is clearly linked to this disease, it is critical to understand how the individual metabolites drive mechanisms increasing stored hepatic lipids. In this review, I summarize evidence that ties the 1CC to fatty liver disease along with data proposing mechanisms for increased lipogenesis or decreased lipid export by phosphatidylcholine.

Fatty liver is a highly heterogenous condition driven by various pathogenic factors in addition to the severity of steatosis. Protein insufficiency has been causally linked to fatty liver with incompletely defined mechanisms. Here we report that fatty liver is a sulfur amino acid insufficient state that promotes metabolic inflexibility via limiting coenzyme A availability. We demonstrate that the nutrient-sensing transcriptional factor EB synergistically stimulates lysosome proteolysis and methionine adenosyltransferase to increase cysteine pool that drives the production of coenzyme A and glutathione, which support metabolic adaptation and antioxidant defense during increased lipid influx. Intriguingly, mice consuming an isocaloric protein-deficient Western diet exhibit selective hepatic cysteine, coenzyme A and glutathione deficiency and acylcarnitine accumulation, which are reversed by cystine supplementation without normalizing dietary protein intake. These findings support a pathogenic link of dysregulated sulfur amino acid metabolism to metabolic inflexibility that underlies both overnutrition and protein malnutrition-associated fatty liver development.

As one of the bicyclic metabolic pathways of one-carbon metabolism, methionine metabolism is the pivot linking the folate cycle to the transsulfuration pathway. In addition to being a precursor for glutathione synthesis, and the principal methyl donor for nucleic acid, phospholipid, histone, biogenic amine, and protein methylation, methionine metabolites can participate in polyamine synthesis. Methionine metabolism disorder can aggravate the damage in the pathological state of a disease. In the occurrence and development of chronic liver diseases (CLDs), changes in various components involved in methionine metabolism can affect the pathological state through various mechanisms. A methionine-deficient diet is commonly used for building CLD models. The conversion of key enzymes of methionine metabolism methionine adenosyltransferase (MAT) 1 A and MAT2A/MAT2B is closely related to fibrosis and hepatocellular carcinoma. In vivo and in vitro experiments have shown that by intervening related enzymes or downstream metabolites to interfere with methionine metabolism, the liver injuries could be reduced. Recently, methionine supplementation has gradually attracted the attention of many clinical researchers. Most researchers agree that adequate methionine supplementation can help reduce liver damage. Retrospective analysis of recently conducted relevant studies is of profound significance. This paper reviews the latest achievements related to methionine metabolism and CLD, from molecular mechanisms to clinical research, and provides some insights into the future direction of basic and clinical research.

BACKGROUND &

Aims: A holistic insight on the relationship between obesity and metabolic dysfunction-associated fatty liver disease is an unmet clinical need. Omics investigations can be used to investigate the multifaceted role of altered mitochondrial pathways to promote nonalcoholic steatohepatitis, a major risk factor for liver disease-associated death. There are no specific treatments but remission via surgery might offer an opportunity to examine the signaling processes that govern the complex spectrum of chronic liver diseases observed in extreme obesity. We aim to assess the emerging relationship between metabolism, methylation and liver disease.

Methods: We tailed the flow of information, before and after steatohepatitis remission, from biochemical, histological, and multi-omics analyses in liver biopsies from patients with extreme obesity and successful bariatric surgery. Functional studies were performed in HepG2 cells and primary hepatocytes.

Results: The reversal of hepatic mitochondrial dysfunction and the control of oxidative stress and inflammatory responses revealed the regulatory role of mitogen-activated protein kinases. The reversible metabolic rearrangements leading to steatohepatitis increased the glutaminolysis-induced production of α-ketoglutarate and the hyperactivation of mammalian target of rapamycin complex 1. These changes were crucial for the adenosine monophosphate-activated protein kinase/mammalian target of rapamycin-driven pathways that modulated hepatocyte survival by coordinating apoptosis and autophagy. The signaling activity of α-ketoglutarate and the associated metabolites also affected methylation-related epigenomic remodeling enzymes. Integrative analysis of hepatic transcriptome signatures and differentially methylated genomic regions distinguished patients with and without steatohepatitis.

Conclusion: We provide evidence supporting the multifaceted potential of the increased glutaminolysis-induced α-ketoglutarate production and the mammalian target of rapamycin complex 1 dysregulation as a conceivable source of the inefficient adaptive responses leading to steatohepatitis.

Lay Summary: Steatohepatitis is a frequent and threatening complication of extreme obesity without specific treatment. Omics technologies can be used to identify therapeutic targets. We highlight increased glutaminolysis-induced α-ketoglutarate production as a potential source of signals promoting and exacerbating steatohepatitis.

Methionine is an essential sulfur-containing amino acid that is metabolized mainly in the liver, where it is converted to S-adenosylmethionine (SAM) by methionine adenosyltransferase. Importantly, SAM is a metabolically pleiotropic molecule that participates in three types of biochemical reactions; transmethylation, transsulfuration (which results in the transfer of sulfur from methionine to serine to form cysteine), and amino propylation (to synthesize polyamines). Critical roles of SAM in the liver have been extensively studied using transgenic animals with chronically reduced or increased hepatic SAM levels. Interestingly, both models with abnormal hepatic SAM concentrations develop liver disease suggesting that SAM homeostasis plays a pivotal role in liver disease. The transsulfuration pathway is connected to the production of glutathione (GSH), which has potent antioxidant capacity in the liver. Accumulating data show that GSH depletion renders the liver vulnerable to oxidative stress and prone to progression of liver disease. In this review, we highlight the importance of homeostasis in the metabolism of sulfur-containing amino acids with a particular focus on the transsulfuration pathway which could be a promising therapeutic target in liver injury.

Scope: A compromised nutritional status in methyl-group donors may provoke several molecular alterations triggering the development of nonalcoholic fatty liver disease (NAFLD) in humans and experimental animals. In this study, we investigated a role and the underlying molecular mechanisms of methionine metabolic pathway malfunctions in the pathogenesis of NAFLD.

Methods And Results: We fed female Swiss albino mice a control (methionine-adequate) diet and two experimental (methionine-deficient or methionine-supplemented) diets for 10 weeks, and the levels of one-carbon metabolites, expression of one-carbon and lipid metabolism genes in the livers were evaluated. We demonstrate that both experimental diets increased hepatic levels of S-adenosyl-l-homocysteine and homocysteine, altered expression of one-carbon and lipid metabolism genes, and caused lipid accumulation, especially in mice fed the methionine-deficient diet. Markers of oxidative and ER stress response were also elevated in the livers of mice fed either diet.

Conclusion: Our findings indicate that both dietary methionine deficiency and methionine supplementation can induce molecular abnormalities in the liver associated with the development of NAFLD, including deregulation in lipid and one-carbon metabolic pathways, and induction of oxidative and ER stress. These pathophysiological events may ultimately lead to lipid accumulation in the livers, triggering the development of NAFLD.

BACKGROUND &

Aims: Folate and cobalamin are methyl donors needed for the synthesis of methionine, which is the precursor of S-adenosylmethionine, the substrate of methylation in epigenetic, and epigenomic pathways. Methyl donor deficiency produces liver steatosis and predisposes to metabolic syndrome. Whether impaired fatty acid oxidation contributes to this steatosis remains unknown.

Methods: We evaluated the consequences of methyl donor deficient diet in liver of pups from dams subjected to deficiency during gestation and lactation.

Results: The deprived rats had microvesicular steatosis, with increased triglycerides, decreased methionine synthase activity, S-adenosylmethionine, and S-adenosylmethionine/S-adenosylhomocysteine ratio. We observed no change in apoptosis markers, oxidant and reticulum stresses, and carnityl-palmitoyl transferase 1 activity, and a decreased expression of SREBP-1c. Impaired beta-oxidation of fatty acids and carnitine deficit were the predominant changes, with decreased free and total carnitines, increased C14:1/C16 acylcarnitine ratio, decrease of oxidation rate of palmitoyl-CoA and palmitoyl-L-carnitine and decrease of expression of novel organic cation transporter 1, acylCoA-dehydrogenase and trifunctional enzyme subunit alpha and decreased activity of complexes I and II. These changes were related to lower protein expression of ER-α, ERR-α and HNF-4α, and hypomethylation of PGC-1α co-activator that reduced its binding with PPAR-α, ERR-α, and HNF-4α.

Conclusions: The liver steatosis resulted predominantly from hypomethylation of PGC1-α, decreased binding with its partners and subsequent impaired mitochondrial fatty acid oxidation. This link between methyl donor deficiency and epigenomic deregulations of energy metabolism opens new insights into the pathogenesis of fatty liver disease, in particular, in relation to the fetal programming hypothesis.

Fatty liver is a highly heterogenous condition driven by various pathogenic factors in addition to the severity of steatosis. Protein insufficiency has been causally linked to fatty liver with incompletely defined mechanisms. Here we report that fatty liver is a sulfur amino acid insufficient state that promotes metabolic inflexibility via limiting coenzyme A availability. We demonstrate that the nutrient-sensing transcriptional factor EB synergistically stimulates lysosome proteolysis and methionine adenosyltransferase to increase cysteine pool that drives the production of coenzyme A and glutathione, which support metabolic adaptation and antioxidant defense during increased lipid influx. Intriguingly, mice consuming an isocaloric protein-deficient Western diet exhibit selective hepatic cysteine, coenzyme A and glutathione deficiency and acylcarnitine accumulation, which are reversed by cystine supplementation without normalizing dietary protein intake. These findings support a pathogenic link of dysregulated sulfur amino acid metabolism to metabolic inflexibility that underlies both overnutrition and protein malnutrition-associated fatty liver development.

Methionine is an essential sulfur-containing amino acid that is metabolized mainly in the liver, where it is converted to S-adenosylmethionine (SAM) by methionine adenosyltransferase. Importantly, SAM is a metabolically pleiotropic molecule that participates in three types of biochemical reactions; transmethylation, transsulfuration (which results in the transfer of sulfur from methionine to serine to form cysteine), and amino propylation (to synthesize polyamines). Critical roles of SAM in the liver have been extensively studied using transgenic animals with chronically reduced or increased hepatic SAM levels. Interestingly, both models with abnormal hepatic SAM concentrations develop liver disease suggesting that SAM homeostasis plays a pivotal role in liver disease. The transsulfuration pathway is connected to the production of glutathione (GSH), which has potent antioxidant capacity in the liver. Accumulating data show that GSH depletion renders the liver vulnerable to oxidative stress and prone to progression of liver disease. In this review, we highlight the importance of homeostasis in the metabolism of sulfur-containing amino acids with a particular focus on the transsulfuration pathway which could be a promising therapeutic target in liver injury.

Fatty liver is a highly heterogenous condition driven by various pathogenic factors in addition to the severity of steatosis. Protein insufficiency has been causally linked to fatty liver with incompletely defined mechanisms. Here we report that fatty liver is a sulfur amino acid insufficient state that promotes metabolic inflexibility via limiting coenzyme A availability. We demonstrate that the nutrient-sensing transcriptional factor EB synergistically stimulates lysosome proteolysis and methionine adenosyltransferase to increase cysteine pool that drives the production of coenzyme A and glutathione, which support metabolic adaptation and antioxidant defense during increased lipid influx. Intriguingly, mice consuming an isocaloric protein-deficient Western diet exhibit selective hepatic cysteine, coenzyme A and glutathione deficiency and acylcarnitine accumulation, which are reversed by cystine supplementation without normalizing dietary protein intake. These findings support a pathogenic link of dysregulated sulfur amino acid metabolism to metabolic inflexibility that underlies both overnutrition and protein malnutrition-associated fatty liver development.

BACKGROUND &

Aims: Systemic inflammation and organ failure(s) are the hallmarks of acute-on-chronic liver failure (ACLF), yet their pathogenesis remains uncertain. Herein, we aimed to assess the role of amino acids in these processes in patients with ACLF.

Methods: The blood metabolomic database of the CANONIC study (comprising 137 metabolites, with 43% related to amino acids) - obtained in 181 patients with ACLF and 650 with acute decompensation without ACLF (AD) - was reanalyzed with a focus on amino acids, in particular 9 modules of co-regulated metabolites. We also compared blood metabolite levels between ACLF and AD.

Results: The main findings in ACLF were: i) Metabolite modules were increased in parallel with increased levels of markers of systemic inflammation and oxidative stress. ii) Seventy percent of proteinogenic amino acids were present and most were increased. iii) A metabolic network, comprising the amino acids aspartate, glutamate, the serine-glycine one-carbon metabolism (folate cycle), and methionine cycle, was activated, suggesting increased purine and pyrimidine nucleotide synthesis. iv) Cystathionine, L-cystine, glutamate and pyroglutamate, which are involved in the transsulfuration pathway (a methionine cycle branch) were increased, consistent with increased synthesis of the antioxidant glutathione. v) Intermediates of the catabolism of 5 out of the 6 ketogenic amino acids were increased. vi) The levels of spermidine (a polyamine inducer of autophagy with anti-inflammatory effects) were decreased.

Conclusions: In ACLF, blood amino acids fueled protein and nucleotide synthesis required for the intense systemic inflammatory response. Ketogenic amino acids were extensively catabolized to produce energy substrates in peripheral organs, an effect that was insufficient because organs failed. Finally, the decrease in spermidine levels may cause a defect in autophagy contributing to the proinflammatory phenotype in ACLF.

Lay Summary: Systemic inflammation and organ failures are hallmarks of acute-on-chronic liver failure (ACLF). Herein, we aimed to characterize the role of amino acids in these processes. The blood metabolome of patients with acutely decompensated cirrhosis, and particularly those with ACLF, reveals evidence of intense skeletal muscle catabolism. Importantly, amino acids (along with glucose), are used for intense anabolic, energy-consuming metabolism in patients with ACLF, presumably to support de novo nucleotide and protein synthesis in the activated innate immune system.

URSODEOXYCHOLIC ACID, OMEGA‐3 FATTY ACIDS, AND MISCELLANEOUS AGENTS
Several studies180 have investigated ursodeoxycholic acid (UDCA; conventional and high doses) to improve aminotransferases and steatosis in patients with NAFLD and liver histology in patients with NASH. All but one study203 have been proof‐of‐concept studies with small numbers of participants and/or surrogate endpoints. Notably, a single, large, multicenter RCT convincingly showed that UDCA offers no histological benefit over placebo in patients with NASH.203 Omega‐3 fatty acids, currently approved in the United States to treat hypertriglyceridemia, have been investigated to treat NAFLD both in animal models and in humans.205 In a review of the published literature in 2010, Masterton et al.206 found experimental evidence to support the use of omega‐3 fatty acids in patients with NAFLD to improve liver disease, but the interpretation of human studies was limited by small sample size and methodological flaws. However, two recently reported studies failed to show convincing therapeutic benefit for omega‐3 fatty acids in patients with NAFLD or NASH.207 More than a dozen other miscellaneous agents have been investigated in small, proof‐of‐concept studies, and their detailed evaluation is beyond the scope of this guidance.
32. UCDA is not recommended for the treatment of NAFLD or NASH.
33. Omega‐3 fatty acids should not be used as a specific treatment of NAFLD or NASH, but they may be considered to treat hypertriglyceridemia in patients with NAFLD.
Alcohol Use in Patients With NAFLD and NASH
Heavy alcohol consumption is a risk factor for CLD and should be avoided by patients with NAFLD and NASH. NIAAA defines heavy or at‐risk drinking as more than four standard drinks on any day or more than 14 drinks per week in men or more than three drinks on any day or seven drinks per week in women.209 Although several cross‐sectional studies210 have suggested a beneficial effect of light alcohol consumption (on average, less than one drink per day) on the presence (defined either biochemically or by imaging) and severity of NAFLD, a recent metaregression analysis of 42,059 participants combined from six studies raised the possibility of potential confounding caused by lower BMI among those who are moderate drinkers.217 There are no longitudinal studies reporting the effect of ongoing alcohol consumption on disease severity or natural history of NAFLD or NASH. The effects of light drinking on the cardiovascular system and cancer risks, if any, have not been investigated in individuals with NAFLD.

This randomized controlled trial investigated the safety and efficacy of MF4637, a high concentrate omega-3 fatty acid preparation, in correcting the omega-3 fatty acid nutritional deficiency in non-alcoholic fatty liver disease (NAFLD). The primary end point of the study was set as the change of red blood cell (RBC) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) by MF4637. Whether the omega-3 concentrate could lower liver fat was evaluated in a subset of patients. Furthermore, 176 subjects with NAFLD were randomized to receive the omega-3 concentrate ( = 87) or placebo ( = 89) for 24 weeks, in addition to following standard-of-care dietary guidelines. The omega-3 index, omega-6: omega-3 fatty acid ratio and quantitative measurements of RBC EPA and DHA were determined at baseline and study completion. Magnetic resonance imaging of liver fat was conducted in a subset of patients. Administration of high concentrate omega-3 for 24 weeks significantly increased the omega-3 index and absolute values of RBC EPA and DHA, and decreased the RBC omega-6: omega-3 fatty acid ratio ( < 0.0001). A significant reduction in liver fat content was reported in both groups.

(1) Aim: Non-alcoholic fatty liver disease (NAFLD) is a prevalent disease worldwide. Omega-3 polyunsaturated fatty acids (n-3 PUFAs) bear anti-inflammatory action and can ameliorate hyperlipidemia. We wish to appraise the effects of n-3 PUFAs supplement on NAFLD. (2) Methods: We searched CENTRAL, Embase, and MEDLINE on 29 March 2020 for randomized control trials (RCTs) on the effects of n-3 PUFAs supplementation in treating NAFLD. The Cochrane Collaboration's tool was used to assess the risk of bias of included RCTs. (3) Results: We included 22 RCTs with 1366 participants. The risk of bias of included RCTs was generally low or unclear. n-3 PUFAs supplementation significantly reduced liver fat compared with placebo (pooled risk ratio 1.52; 95% confidence interval (CI) 1.09 to 2.13). n-3 PUFAs supplementation also significantly improved the levels of triglyceride, total cholesterol, high-density lipoprotein, and body-mass index, with pooled mean difference and 95% CI being -28.57 (-40.81 to -16.33), -7.82 (-14.86 to -0.79), 3.55 (1.38 to 5.73), and -0.46 (-0.84 to -0.08), respectively. (4) Conclusions: The current evidence supports the effects of n-3 PUFAs supplementation in improving fatty liver. n-3 PUFAs supplementation may also improve blood lipid levels and obesity.

12.1 Mechanism of Action The mechanism of action of Omega-3-Acid Ethyl Ester (omega-3-acid ethyl esters) is not completely understood. Potential mechanisms of action include inhibition of acyl-CoA:1,2-diacylglycerol acyltransferase, increased mitochondrial and peroxisomal β-oxidation in the liver, decreased lipogenesis in the liver, and increased plasma lipoprotein lipase activity. Omega-3-Acid Ethyl Ester (omega-3-acid ethyl esters) may reduce the synthesis of TG in the liver because EPA and DHA are poor substrates for the enzymes responsible for TG synthesis, and EPA and DHA inhibit esterification of other fatty acids.

12.1 Mechanism of Action The mechanism of action of omega-3-acid ethyl esters is not completely understood. Potential mechanisms of action include inhibition of acyl-CoA:1,2-diacylglycerol acyltransferase, increased mitochondrial and peroxisomal β-oxidation in the liver, decreased lipogenesis in the liver, and increased plasma lipoprotein lipase activity. Omega-3-acid ethyl esters may reduce the synthesis of triglycerides in the liver because EPA and DHA are poor substrates for the enzymes responsible for TG synthesis, and EPA and DHA inhibit esterification of other fatty acids.

Betaine has previously been demonstrated to protect the liver against alcohol‑induced fat accumulation. However, the mechanism through which betaine affects alcohol‑induced hepatic lipid metabolic disorders has not been extensively studied. The present study aimed to investigate the effect of betaine on alcoholic simple fatty liver and hepatic lipid metabolism disorders. A total of 36 rats were randomly divided into control, ethanol and ethanol + betaine groups. Liver function, morphological alterations, lipid content and tumor necrosis factor (TNF)‑α levels were determined. Hepatic expression levels of diacylglycerol acyltransferase (DGAT) 1, DGAT2, sterol regulatory element binding protein (SREBP)‑1c, SREBP‑2, fatty acid synthase (FAS), 3‑hydroxy‑3‑methyl‑glutaryl (HMG)‑CoA reductase, peroxisome proliferator-activated receptor λ coactivator (PGC)‑1α, adiponectin receptor (AdipoR) 1 and AdipoR2 were quantified. Serum and adipose tissue adiponectin levels were assessed using an enzyme‑linked immunoassay. The results demonstrated that alcohol‑induced ultramicrostructural alterations in hepatocytes, including the presence of lipid droplets and swollen mitochondria, were attenuated by betaine. Hepatic triglyceride, free fatty acid, total cholesterol and cholesterol ester contents and the expression of DGAT1, DGAT2, SREBP‑1c, SREBP‑2, FAS and HMG‑CoA reductase were increased following ethanol consumption, however were maintained at control levels following betaine supplementation. Alcohol‑induced decreases in hepatic PGC‑1α mRNA levels and serum and adipose tissue adiponectin concentrations were prevented by betaine. The downregulation of hepatic AdipoR1 which resulted from alcohol exposure was partially attenuated by betaine. No significant differences in liver function, TNF‑α, phospholipid and AdipoR2 levels were observed among the control, ethanol and ethanol + betaine groups. Overall, these results indicated that betaine attenuated the alcoholic simple fatty liver by improving hepatic lipid metabolism via suppression of DGAT1, DGAT2, SREBP‑1c, FAS, SREBP‑2 and HMG‑CoA reductase and upregulation of PGC‑1α.

The liver plays a critical role in lipid metabolism. Hepatic dysfunction is not only the direct cause of fatty liver disease, but the main risk factor for obesity, diabetes, and other metabolic diseases. So far, therapeutic strategies against fatty liver disease are very limited. Betaine is a methyl donor. Current studies reported that the intake of betaine decreases body fat and is beneficial for treatment of fatty liver disease and metabolic syndrome. However, the underlying mechanisms remain largely unknown. In this study, to investigate the role of betaine on hepatic lipid metabolism and explore the underlying mechanism, HepG2 cells were cultured with fatty acids and betaine. The data indicated that betaine inhibited hepatic fat accumulation and promoted mitochondrial content and activity, suggesting that betaine is involved in the regulation of lipid and energy metabolism. Gene expression analysis implied that betaine inhibits fatty acid synthesis, but stimulates fatty acid oxidation and lipid secretion. Further, to study the mechanism of betaine, FTO (RNA demethylase) and its mutant (loss of demethylase activity) were used. The results showed that FTO blocked the ability of betaine to regulate lipid metabolism and mitochondrial content, but the FTO mutant had no effect, suggesting that betaine influences RNA methylation. This work links betaine administration with mitochondrial activity and RNA methylation, and provides a potential target for the development of new therapeutic strategies for the treatment of fatty liver disease.

Purpose: Nonalcoholic fatty liver disease (NAFLD) is currently the leading cause of chronic liver disease in developing countries. The pathogenesis is complex, and there is currently no effective treatment. Betaine is an essential intermediate in choline catabolism and an important component of the methionine cycle. Betaine deficiency is associated with NAFLD severity, and its mechanism needs to be further elaborated.

Methods: In this study, an NAFLD mouse model was established by feeding ApoE mice a high-fat diet. The effects of betaine on NAFLD were investigated, including its mechanism.

Results: In this study, after treatment with betaine, blood lipid levels and liver damage were significantly decreased in the NAFLD mouse model. The fat infiltration of the liver tissues of high-fat diet (HFD)-fed mice after betaine administration was significantly improved. Betaine treatment significantly upregulated AMP-activated protein kinase (AMPK), fibroblast growth factor 10 (FGF10), and adipose triglyceride lipase (ATGL) protein levels both in vivo and in vitro and suppressed lipid metabolism-related genes. Furthermore, the overexpression of FGF10 increased the protein level of AMPK and decreased lipid accumulation in HepG2 cells.

Conclusion: Taken together, the data strongly suggest that betaine significantly prevents high-fat diet-induced NAFLD through the FGF10/AMPK signaling pathway in ApoE mice.

The increasing prevalence of non-alcoholic fatty liver disease (NAFLD) poses a growing challenge in terms of its prevention and treatment. The 'multiple hits' hypothesis of multiple insults, such as dietary fat intake, lipogenesis, insulin resistance, oxidative stress, mitochondrial dysfunction, gut dysbiosis and hepatic inflammation, can provide a more accurate explanation of the pathogenesis of NAFLD. Betaine plays important roles in regulating the genes associated with NAFLD through anti-inflammatory effects, increased free fatty oxidation, anti-lipogenic effects and improved insulin resistance and mitochondrial function; however, the mechanism of betaine remains elusive.

Betaine, a methyl donor, plays a crucial role in lipid metabolism. Previous studies have shown that appropriate betaine supplementation in a high-fat diet reduces triglycerides (TG) of serum and hepatopancreas in fish. However, the underlying mechanism remains unclear. This study examined whether betaine can enhance the secretion of very low-density lipoprotein (VLDL) and sought to identify the specific mechanisms through which this enhancement occurs. A lipid accumulation model was established in gibel carp and L8824 cells using a high-fat diet and oleic acid, respectively. Different doses of betaine (1, 4, and 16 g/kg in the diet; 400 μmol in cell culture) were administered, and measurements were taken for lipid deposition, gene expression of HNF4α, MTTP, and ApoB, as well as the regulation of Mttp and Apob promoters by HNF4α. The results showed that betaine supplementation mitigated lipid droplet accumulation, TG levels, and VLDL production induced by the high-fat diet in gibel carp hepatopancreas and L8824 cells. Moreover, betaine not only increased VLDL content in the cell culture supernatant but also reversed the inhibitory effects of the high-fat diet on protein expression of MTTP, ApoB, and HNF4α in both gibel carp hepatopancreas and L8824 cells. Additionally, HNF4α exhibits transactivating activity on the promoter of Mttp in gibel carp. These findings suggest that betaine supplementation exerts its effects through the HNF4α/MTTP/ApoB pathway, promoting the assembly and secretion of VLDL and effectively reducing lipid accumulation in the hepatopancreas of farmed gibel carp fed a high-fat diet.

Betaine, a common methyl donor whose methylation is involved in the biosynthesis of carnitine and phospholipids in animals, serves as food and animal feed additive. The present study used liquid chromatography-mass spectrometry (LC-MS) to analyze the liver protein profile of mice on a high fat (HF) diet to investigate the mechanism by which betaine affects hepatic metabolism. Although betaine supplementation had no significant effect on body weight, a total of 103 differentially expressed proteins were identified between HF diet + 1% betaine group (HFB) and HF diet group by LC-MS (fold change > 2, p < 0.05). The addition of 1% betaine had a significant enhancement of the expression of enzymes related to fatty acid oxidation metabolism, such as hydroxyacyl-Coenzyme A dehydrogenase (HADHA), enoyl Coenzyme A hydratase 1 (ECHS1) (p < 0.05) etc., and the expression of apolipoprotein A-II (APOA2) protein was significantly reduced (p < 0.01). Meanwhile, the protein expression of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and succinate-CoA ligase (SUCLG1) were highly significant (p < 0.01). Pathway enrichment using the Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed that the functions of differential proteins involved fatty acid catabolism, carbohydrate metabolism, tricarboxylic acid cycle (TCA) and peroxisome proliferator-activated receptor alpha (PPARα) signaling pathway. Protein−protein interaction (PPI) analysis discovered that acetyl-Coenzyme A acetyltransferase 1 (ACAT1), HADHA and ECHS1 were central hubs of hepatic proteomic changes in the HFB group of mice. Betaine alleviates hepatic lipid accumulation by enhancing fatty acid oxidation and accelerating the TCA cycle and glycolytic process in the liver of mice on an HF diet.

Liver diseases related complications represent a significant source of morbidity and mortality worldwide, creating a substantial economic burden. Oxidative stress, excessive inflammation, and dysregulated energy metabolism significantly contributed to liver diseases. Therefore, discovery of novel therapeutic drugs for the treatment of liver diseases are urgently required. Licorice is one of the most commonly used herbal drugs in Traditional Chinese Medicine for the treatment of liver diseases and drug-induced liver injury (DILI). Various bioactive components have been isolated and identified from the licorice, including glycyrrhizin, glycyrrhetinic acid, liquiritigenin, Isoliquiritigenin, licochalcone A, and glycycoumarin. Emerging evidence suggested that these natural products relieved liver diseases and prevented DILI through multi-targeting therapeutic mechanisms, including anti-steatosis, anti-oxidative stress, anti-inflammation, immunoregulation, anti-fibrosis, anti-cancer, and drug-drug interactions. In the current review, we summarized the recent progress in the research of hepatoprotective and toxic effects of different licorice-derived bioactive ingredients and also highlighted the potency of these compounds as promising therapeutic options for the treatment of liver diseases and DILI. We also outlined the networks of underlying molecular signaling pathways. Further pharmacology and toxicology research will contribute to the development of natural products in licorice and their derivatives as medicines with alluring prospect in the clinical application.

12.2 Pharmacodynamics Betaine Anhydrous for Oral Solution was observed to lower plasma homocysteine concentrations in three types of homocystinuria, including CBS deficiency; MTHFR deficiency; and cbl defect. Patients have taken Betaine Anhydrous for Oral Solution for many years without evidence of tolerance. There has been no demonstrated correlation between Betaine concentrations and homocysteine concentrations. In CBS-deficient patients, large increases in methionine concentrations over baseline have been observed. Betaine Anhydrous for Oral Solution has also been demonstrated to increase low plasma methionine and S- adenosylmethionine (SAM) concentrations in patients with MTHFR deficiency and cbl defect.

The liver plays a critical role in lipid metabolism. Hepatic dysfunction is not only the direct cause of fatty liver disease, but the main risk factor for obesity, diabetes, and other metabolic diseases. So far, therapeutic strategies against fatty liver disease are very limited. Betaine is a methyl donor. Current studies reported that the intake of betaine decreases body fat and is beneficial for treatment of fatty liver disease and metabolic syndrome. However, the underlying mechanisms remain largely unknown. In this study, to investigate the role of betaine on hepatic lipid metabolism and explore the underlying mechanism, HepG2 cells were cultured with fatty acids and betaine. The data indicated that betaine inhibited hepatic fat accumulation and promoted mitochondrial content and activity, suggesting that betaine is involved in the regulation of lipid and energy metabolism. Gene expression analysis implied that betaine inhibits fatty acid synthesis, but stimulates fatty acid oxidation and lipid secretion. Further, to study the mechanism of betaine, FTO (RNA demethylase) and its mutant (loss of demethylase activity) were used. The results showed that FTO blocked the ability of betaine to regulate lipid metabolism and mitochondrial content, but the FTO mutant had no effect, suggesting that betaine influences RNA methylation. This work links betaine administration with mitochondrial activity and RNA methylation, and provides a potential target for the development of new therapeutic strategies for the treatment of fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive fat deposition in the liver, which is often associated with disrupted iron homeostasis. Betaine has been reported to be hepatoprotective, yet whether and how betaine ameliorates high-fat diet-induced disruption of hepatic lipid and iron homeostasis remains elusive. In this study, mice were fed either standard (CON) or high-fat diet (HFD) for 9 weeks to establish a NAFLD model. Mice raised on HF diet were then assigned randomly to HF and HFB groups, HFB group being supplemented with 1% (/) of betaine in the drinking water for 13 weeks. Betaine supplementation significantly alleviated excessive hepatic lipid deposition and restored hepatic iron content. Betaine partly yet significantly reversed HFD-induced dysregulation of lipogenic genes such as PRARγ and CD36, as well as the iron-metabolic genes including FPN and HAMP that encodes hepcidin. Similar mitigation effects of betaine were observed for BMP2 and BMP6, the up-stream regulators of hepcidin expression. Betaine significantly rectified disrupted expression of methyl transfer gene, including BHMT, GNMT and DNMT1. Moreover, HFD-modified CpG methylation on the promoter of PRARγ and HAMP genes was significantly reversed by betaine supplementation. These results indicate that betaine alleviates HFD-induced disruption of hepatic lipid and iron metabolism, which is associated with modification of CpG methylation on promoter of lipogenic and iron-metabolic genes.

All patients who developed cerebral edema had homocystinuria due to CBS deficiency and had severe elevation in plasma methionine concentrations (range 1,000 to 3,000 microM). As cerebral edema has also been reported in patients with hypermethioninemia, secondary hypermethioninemia due to betaine therapy has been postulated as a possible mechanism of action [see Warnings and Precautions (5.1)]. Other adverse reactions include: anorexia, agitation, depression, irritability, personality disorder, sleep disturbed, dental disorders, diarrhea, glossitis, nausea, stomach discomfort, vomiting, hair loss, hives, skin odor abnormalities, and urinary incontinence.

Unlabelled: Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease and affects millions of people worldwide. Despite the increasing prevalence of NAFLD, the exact molecular/cellular mechanisms remain obscure and effective therapeutic strategies are still limited. It is well-accepted that free fatty acid (FFA)-induced lipotoxicity plays a pivotal role in the pathogenesis of NAFLD. Inhibition of FFA-associated hepatic toxicity represents a potential therapeutic strategy. Glycyrrhizin (GL), the major bioactive component of licorice root extract, has a variety of pharmacological properties including anti-inflammatory, antioxidant, and immune-modulating activities. GL has been used to treat hepatitis to reduce liver inflammation and hepatic injury; however, the mechanism underlying the antihepatic injury property of GL is still poorly understood. In this report, we provide evidence that 18 beta-glycyrrhetinic acid (GA), the biologically active metabolite of GL, prevented FFA-induced lipid accumulation and cell apoptosis in in vitro HepG2 (human liver cell line) NAFLD models. GA also prevented high fat diet (HFD)-induced hepatic lipotoxicity and liver injury in in vivo rat NAFLD models. GA was found to stabilize lysosomal membranes, inhibit cathepsin B expression and enzyme activity, inhibit mitochondrial cytochrome c release, and reduce FFA-induced oxidative stress. These characteristics may represent major cellular mechanisms, which account for its protective effects on FFA/HFD-induced hepatic lipotoxicity.

Conclusion: GA significantly reduced FFA/HFD-induced hepatic lipotoxicity by stabilizing the integrity of lysosomes and mitochondria and inhibiting cathepsin B expression and enzyme activity.

Liver diseases and their related complications endanger the health of millions of people worldwide. The prevention and treatment of liver diseases are still serious challenges both in China and globally. With the improvement of living standards, the prevalence of metabolic liver diseases, including non-alcoholic fatty liver disease and alcoholic liver disease, has increased at an alarming rate, resulting in more cases of end-stage liver disease. Therefore, the discovery of novel therapeutic drugs for the treatment of liver diseases is urgently needed. Glycyrrhizin (GL), a triterpene glycoside from the roots of licorice plants, possesses a wide range of pharmacological and biological activities. Currently, GL preparations (GLPs) have certain advantages in the treatment of liver diseases, with good clinical effects and fewer adverse reactions, and have shown broad application prospects through multitargeting therapeutic mechanisms, including antisteatotic, anti-oxidative stress, anti-inflammatory, immunoregulatory, antifibrotic, anticancer, and drug interaction activities. This review summarizes the currently known biological activities of GLPs and their medical applications in the treatment of liver diseases, and highlights the potential of these preparations as promising therapeutic options and their alluring prospects for the treatment of liver diseases.

This study provides the scientific basis for the anti-inflammatory effects of licorice extract in a t-BHP (tert-butyl hydrogen peroxide)-induced liver damage model and the effects of its ingredients, glycyrrhizic acid (GA), liquiritin (LQ) and liquiritigenin (LG), in a lipopolysaccharide (LPS)-stimulated microglial cell model. The GA, LQ and LG inhibited the LPS-stimulated elevation of pro-inflammatory mediators, such as inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta and interleukin (IL)-6 in BV2 (mouse brain microglia) cells. Furthermore, licorice extract inhibited the expression levels of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) in the livers of t-BHP-treated mice models. This result suggested that mechanistic-based evidence substantiating the traditional claims of licorice extract and its three bioactive components can be applied for the treatment of inflammation-related disorders, such as oxidative liver damage and inflammation diseases.

Nonalcoholic steatohepatitis (NASH) is the progressive stage of nonalcoholic fatty liver disease that may ultimately lead to cirrhosis and liver cancer, and there are few therapeutic options for its treatment. Glycyrrhizin (GL), extracted from the traditional Chinese medicine liquorice, has potent hepatoprotective effects in both preclinical animal models and in humans. However, little is currently known about its effects and mechanisms in treating NASH. To explore the effects of GL on NASH, GL or its active metabolite glycyrrhetinic acid (GA) was administered to mice treated with a methionine- and choline-deficient (MCD) diet-induced NASH model, and histologic and biochemical analyses were used to measure the degree of lipid disruption, liver inflammation, and fibrosis. GL significantly improved MCD diet-induced hepatic steatosis, inflammation, and fibrosis and inhibited activation of the NLR family pyrin domain-containing 3 (NLRP3) inflammasome. GL significantly attenuated serum bile acid accumulation in MCD diet-fed mice partially by restoring inflammation-mediated hepatic farnesoid X receptor inhibition. In Raw 264.7 macrophage cells, both GL and GA inhibited deoxycholic acid-induced NLRP3 inflammasome-associated inflammation. Notably, both intraperitoneal injection of GL's active metabolite GA and oral administration of GL prevented NASH in mice, indicating that GL may attenuate NASH via its active metabolite GA. These results reveal that GL, via restoration of bile acid homeostasis and inhibition of inflammatory injury, can be a therapeutic option for treatment of NASH.

Nonalcoholic fatty liver disease (NAFLD) is associated with low testosterone levels in serum. The aim of this study was to evaluate the effect of apple vinegar on fertility indices in a rat model of NAFLD. To study this effect, 32 adult male rats were divided into four groups: A-normal diet, B-high-fat diet (HFD), C-apple vinegar and D-HFD plus apple vinegar. At the end of the week 22, the Lee index, serum lipid profiles, liver enzymes, glucose and total antioxidant levels (TAC) in serum were determined. In addition, liver and testis tissue homogenate, histopathology, serum testosterone and sperm parameters were measured and HOMA-IR calculated. Significant reduction in Lee index, serum triglyceride, cholesterol, liver enzymes and glucose levels was observed in vinegar treated group compared with HFD group. Vinegar lowered insulin resistance compared with HFD (p < 0.01). Steatosis in hepatocytes reduced from 56% in HFD group to 20% in group D (p < 0.05). Vinegar caused a significant increase in serum testosterone, improvement in sperm parameters and a reduced germ cell apoptosis (p < 0.05). There was an insignificant increase in TAC levels in the serum and homogenate tissue of liver and testis compared with HFD. This study reports apple vinegar has beneficial effects on male rat fertility indices in an in vivo model of NAFLD.

Red delicious apples were used to produce natural apple cider with and without inclusion of maceration. Traditional surface and industrial submersion methods were then applied to make vinegar from apple ciders. Apple cider vinegar samples produced with inclusion of maceration in the surface method had the highest total phenolic content, chlorogenic acid, ORAC, and TEAC levels. Cholesterol and apple vinegar samples were administered using oral gavage to all groups of rats except the control group. Apple cider vinegars, regardless of the production method, decreased triglyceride and VLDL levels in all groups when compared to animals on high-cholesterol diets without vinegar supplementation. Apple cider vinegars increased total cholesterol and HDL and LDL cholesterol levels and decreased liver function tests when compared to animals on a high-cholesterol diet without vinegar supplementation. A high-cholesterol diet resulted in hepatic steatosis. VSBM and VSB groups significantly decreased steatosis.

Acetic acid has been proposed to improve lifestyle-related diseases, including hyperlipidemia and hyperglycemia. This study compared the hypoglycemic and hypolipogenic effects of acetic acid vinegar (AV, contains only 4% acetic acid) and -fermented grain vinegar (MV) containing various bioactive compounds in 3T3L1 cells and C57BL/KsJ- mice (DB). The DB were divided randomly into three treatment groups containing nine mice each; DB-, AV-, and MV-groups were orally administered 1 mL/kg/day of distilled water, acetic acid vinegar, and vinegar, respectively, for 8 weeks. Exposure to AV and MV inhibited the adipogenic differentiation of 3T3L1 preadipocytes and lipid accumulation during differentiation. Oral administration of AV or MV to the mice resulted in a marked reduction in the body weight, liver weight, and hepatic triglyceride content compared to the control DB-group. Moreover, treatment with AV and MV clearly increased the expression of cyclic adenosine monophosphate (cAMP) and AMP-activated protein kinase (AMPK) and suppressed the expression of fatty acid synthetase in liver tissues of DB. Significantly, lower levels of fasting blood glucose, insulin, leptin, and the glycosylated hemoglobin (HbA1c) as well as higher levels of the skeletal muscle GLUT4 expression were obtained in the AV- or MV-groups than levels determined in the control DB-group ( < .05). Although MV has the potential to be a natural alternative treatment for obesity-associated type 2 diabetes, this study suggests that acetic acid is the central ingredient in MV responsible for the hypoglycemic and hypolipogenic effects in the DB mice.

Obesity is a worldwide epidemic characterized by excessive fat accumulation, associated with multiple comorbidities and complications. Emerging evidence points to gut microbiome as a driving force in the pathogenesis of obesity. Vinegar intake, a traditional remedy source of exogenous acetate, has been shown to improve glycemic control and to have anti-obesity effects. New functional foods may be developed by supplementing traditional food with probiotics. is a suitable choice because of its resistance to high temperatures. To analyze the possible synergic effect of Vinegar and against the metabolic alterations induced by a high fat diet (HFD), we fed twelve-week-old C57BL/6 mice with HFD for 5 weeks after 2 weeks of acclimation on a normal diet. Then, food intake, body weight, blood biochemical parameters, histology and liver inflammatory markers were analyzed. Although vinegar drink, either alone or supplemented with , reduced food intake, attenuated body weight gain and enhanced glucose tolerance, only the supplemented drink improved the lipid serum profile and prevented hepatic HFD-induced overexpression of CD36, IL-1β, IL-6, LXR and SREBP, thus reducing lipid deposition in the liver. The beneficial properties of the -supplemented vinegar appear to be mediated by a reduction in insulin and leptin circulating levels.

The main objective of this study is to determine the effects of apple vinegar on the metabolic changes caused by hypercaloric diet in Wistar rats. Apple vinegar was first analyzed to find out the total acidity, the polyphenolic and flavonoid contents, the total antioxidant capacity, and the free radical scavenging activity. study on adult male and female Wistar rats was conducted by administering a drink containing either 10% D-glucose or water (control) for five weeks. Apple vinegar is administered daily by gavage (2 mL/kg) to rats fed D-glucose for 5 weeks. The results showed that the polyphenolic content in apple vinegar was 148.02 ± 10.16 mg GAE/100 mL, flavonoid content was 22.93 ± 0.73 QE/100 mL, and total antioxidant capacity was 13.4 ± 0.47 mg AAE/100 mL. Free radical IC apple vinegar scavenging activity (DPPH) was 0.74 ± 0.154 L/mL. The total acidity was (3.24 ± 0.02 mg AAE/100 mL). The treatment during five weeks with D-glucose leads to increased plasma glucose, lipid profile, hepatic enzyme levels, urea, and creatinine. Simultaneous treatment with apple vinegar improves the parameters studied. These results clearly show that the daily consumption of vinegar can reduce the rise in blood sugar and lipid profile induced by hypercaloric diet in rats. Therefore, the use of apple vinegar would have a very beneficial effect in the prevention of metabolic disorders caused by high-caloric food.

Vinegars are one of only a few acidic condiments throughout the world. Vinegars can mainly be considered grain vinegars and fruit vinegars, according to the raw materials used. Both grain vinegars and fruit vinegars, which are fermented by traditional methods, possess a variety of physiological functions, such as antibacteria, anti-infection, antioxidation, blood glucose control, lipid metabolism regulation, weight loss, and anticancer activities. The antibacteria and anti-infection abilities of vinegars are mainly due to the presence of organic acids, polyphenols, and melanoidins. The polyphenols and melanoidins also provide the antioxidant abilities of vinegars, which are produced from the raw materials and fermentation processes, respectively. The blood glucose control, lipid metabolism regulation, and weight loss capabilities from vinegars are mainly due to acetic acid. Besides caffeoylsophorose (inhibits disaccharidase) and ligustrazine (improves blood circulation), other functional ingredients present in vinegars provide certain health benefits as well. Regarding anticancer activities, several grain vinegars strongly inhibit the growth of some cancer cells in vivo or in vitro, but related functional ingredients remain largely unknown, except tryptophol in Japanese black soybean vinegar. Considering the discovering of various functional ingredients and clarifying their mechanisms, some vinegars could be functional foods or even medicines, depending on a number of proofs that demonstrate these constituents can cure chronic diseases such as diabetes or cardiovascular problems.

To investigate the etiopathogenesis of fatty liver hemorrhagic syndrome (FLHS) and the protective effects of soybean lecithin against FLHS in laying hens, 135 healthy 300-day-old Hyline laying hens were randomly divided into groups: control (group 1), diseased (group 2), and protected (group 3). Each group contained 45 layers with 3 replicates. The birds in these 3 groups were fed a control diet, a high-energy/low-protein (HELP) diet or the HELP diet supplemented with 3% soybean lecithin instead of maize. The fat percent in the liver was calculated. Histopathological changes in the liver were determined by staining, and the mRNA expression levels of apolipoproteinA I (apoA I) and apolipoprotein B100 (apoB100) in the liver were determined by RT-PCR. The results showed that the fat percent in the liver of group 2 was much higher (P < 0.01) than that of group 1 and group 2 on d 30 and 60. The histology of the liver in group 2 on d 30 and 60 displayed various degrees of liver lesions, while the hepatocytes showed a normal structure in group 3 with mild microvesicular steatosis in the liver cell on d 30 and 60. The mRNA expression levels of apoA I and apoB100 in the livers were variable throughout the experiment. The expression level of apoA I in group 2 significantly decreased on d 60 (P < 0.05); the expression level of apoB100 slightly increased on d 30 in group 2, while it sharply decreased on d 60. Compared to group 1, the expression level of apoB100 showed no significant difference in group 3 (P < 0.05). This study indicated that FLHS induced pathological changes and abnormal expression of apoA I and apoB100 in the livers of laying hens and that soybean lecithin alleviated these abnormal changes.

The aim of this experiment was to investigate the effect of soy lecithin on serum-related indicators and liver health in laying hens under the influence of high-fat diets. 180 peak laying hens at 40 weeks of age were randomly assigned to one of the four diets using a 2 × 2 factorial and fed for 5 weeks. The results showed that compared to the low-fat group, the high-fat group had lower egg production ( < 0.05) and higher average daily feed intake and feed-to-egg ratio ( < 0.05). At the 21 day, the serum levels of triglyceride (TC) and superoxide dismutase (SOD) were higher ( < 0.05), high-density lipoproteins cholesterol (HDL-C) levels were lower ( < 0.01), catalase (CAT) activity was lower ( < 0.05), TC and malondialdehyde (MDA) levels in liver were higher ( < 0.01) and SOD activity in liver was lower ( < 0.05) in layers supplemented with soy lecithin. CAT activity in serum was increased ( < 0.01) and total antioxidant capacity (T-AOC) activity in the liver was decreased ( < 0.05) after increasing the dietary fat concentration. The addition of soy lecithin and the increase in dietary fat concentration had a highly significant interaction on serum CAT activity and liver TC content in layers ( < 0.01). At the 35 day, the serum alanine aminotransferase (ALT) activity was higher ( < 0.01), serum glutathione peroxidase (GSH-Px) and CAT activity were higher ( < 0.05), and serum triglyceride (TG) content and total T-AOC capacity activity were lower ( < 0.05) in layers supplemented with soy lecithin. Increasing dietary fat concentration decreased alanine aminotransferase (ALT), aspartate aminotransferase (AST) and GSH-Px activity in serum ( < 0.05). However, it increased TG and MDA content in liver ( < 0.05), and highly decreased SOD content in liver ( < 0.01) in layers. The addition of soy lecithin and increasing dietary fat concentration had a highly significant reciprocal effect on serum ALT viability and CAT viability ( < 0.01) and liver TG and MDA content and SOD viability ( < 0.05) in layers. In conclusion, feeding high-fat diets will adversely affect the laying performance of laying hens, while long-term addition of lecithin can improve the blood lipids and liver lipids of laying hens, enhance the antioxidant capacity of the liver, and maintain liver health.

Vegetable lecithins, widely used in the food industry as emulsifiers, are a mixture of naturally occurring lipids containing more than 50% of phospholipids (PL). PL exert numerous important physiological effects. Their amphiphilic nature notably enables them to stabilise endogenous lipid droplets, conferring them an important role in lipoprotein transport, functionality and metabolism. In addition, beneficial effects of dietary lecithin on metabolic disorders have been reported since the 1990s. This review attempts to summarize the effects of various vegetable lecithins on lipid and lipoprotein metabolism, as well as their potential application in the treatment of dyslipidemia associated with metabolic disorders. Despite controversial data concerning the impact of vegetable lecithins on lipid digestion and intestinal absorption, the beneficial effect of lecithin supplementation on plasma and hepatic lipoprotein and cholesterol levels is unequivocal. This is especially true in hyperlipidemic patients. Furthermore, the immense compositional diversity of vegetable lecithins endows them with a vast range of biochemical and biological properties, which remain to be explored in detail. Data on the effects of vegetable lecithins alternative to soybean, both as supplements and as ingredients in different foods, is undoubtedly lacking. Given the exponential demand for vegetable products alternative to those of animal origin, it is of primordial importance that future research is undertaken in order to elucidate the mechanisms by which individual fatty acids and PL from various vegetable lecithins modulate lipid metabolism. The extent to which they may influence parameters associated with metabolic disorders, such as intestinal integrity, low-grade inflammation and gut microbiota must also be assessed.

Purpose Of Review: An increasing number of studies in experimental animals suggest that dietary phospholipids might be of benefit in the treatment of fatty liver disease. This raises the possibility that synthetic or naturally occurring phospholipid isolates could be used as hepatoprotective nutraceuticals or functional foods. The aim of the present article is to review published data describing the beneficial effects of dietary phospholipids on hepatic lipid metabolism and their potential to affect atherosclerosis and cardiovascular disease.

Recent Findings: Consistent results have been obtained supporting the concept that phospholipid from various sources (i.e., soybean, safflower, egg and fish roe) can reduce liver lipid levels. The primary site of action for this effect appears to be in the intestinal lumen, where dietary phospholipids are able to interfere with neutral sterol absorption. Results have also been obtained suggesting that dietary phospholipids can stimulate bile acid and cholesterol secretion. Additional work suggests that dietary phospholipids can have a beneficial effect on plasma lipid and lipoprotein levels.

Summary: The concept of using naturally occurring compounds such as phospholipid to treat or prevent hepatic steatosis is very attractive. Controlled human trials are, however, required to verify the efficacy of this approach. It is also important that additional research be conducted to determine the extent to which certain phospholipids have the ability to increase plasma HDL levels and potentially affect the onset or development of cardiovascular disease.

Dietary lecithin can stimulate bile formation and biliary lipid secretion, particularly cholesterol output in bile. Studies also suggested that the lecithin-rich diet might modify hepatic cholesterol homeostasis and lipoprotein metabolism. Therefore, we examined hepatic activities of 3-hydroxy-3 methylglutaryl coenzyme A reductase "HMG -CoA reductase", cholesterol 7 alpha-hydroxylase and acyl-Co

A: cholesterol acyltransferase "ACAT" as well as plasma lipids and lipoprotein composition in rats fed diets enriched with 20% of soybean lecithin during 14 days. We also evaluated the content of hepatic canalicular membrane proteins involved in lipid transport to the bile (all P-glycoproteins as detected by the C 219 antibody and the sister of P-glycoprotein "spgp" or bile acid export pump) by Western blotting. As predicted, lecithin diet modified hepatic cholesterol homeostasis. The activity of hepatic HMG-CoA reductase and cholesterol 7 alpha-hydroxylase was enhanced by 30 and 12% respectively, while microsomal ACAT activity showed a dramatic decrease of 75%. As previously reported from ACAT inhibition, the plasma level and size of very low-density lipoprotein (VLDL) were significantly decreased and bile acid pool size and biliary lipid output were significantly increased. The canalicular membrane content of lipid transporters was not significantly affected by dietary lecithin. The current data on inhibition of ACAT activity and related metabolic effects by lecithin mimic the previously reported effects following drug-induced inhibition of ACAT activity, suggesting potential beneficial effects of dietary lecithin supplementation in vascular disease.

Purpose Of Review: An increasing number of studies in experimental animals suggest that dietary phospholipids might be of benefit in the treatment of fatty liver disease. This raises the possibility that synthetic or naturally occurring phospholipid isolates could be used as hepatoprotective nutraceuticals or functional foods. The aim of the present article is to review published data describing the beneficial effects of dietary phospholipids on hepatic lipid metabolism and their potential to affect atherosclerosis and cardiovascular disease.

Recent Findings: Consistent results have been obtained supporting the concept that phospholipid from various sources (i.e., soybean, safflower, egg and fish roe) can reduce liver lipid levels. The primary site of action for this effect appears to be in the intestinal lumen, where dietary phospholipids are able to interfere with neutral sterol absorption. Results have also been obtained suggesting that dietary phospholipids can stimulate bile acid and cholesterol secretion. Additional work suggests that dietary phospholipids can have a beneficial effect on plasma lipid and lipoprotein levels.

Summary: The concept of using naturally occurring compounds such as phospholipid to treat or prevent hepatic steatosis is very attractive. Controlled human trials are, however, required to verify the efficacy of this approach. It is also important that additional research be conducted to determine the extent to which certain phospholipids have the ability to increase plasma HDL levels and potentially affect the onset or development of cardiovascular disease.

Vegetable lecithins, widely used in the food industry as emulsifiers, are a mixture of naturally occurring lipids containing more than 50% of phospholipids (PL). PL exert numerous important physiological effects. Their amphiphilic nature notably enables them to stabilise endogenous lipid droplets, conferring them an important role in lipoprotein transport, functionality and metabolism. In addition, beneficial effects of dietary lecithin on metabolic disorders have been reported since the 1990s. This review attempts to summarize the effects of various vegetable lecithins on lipid and lipoprotein metabolism, as well as their potential application in the treatment of dyslipidemia associated with metabolic disorders. Despite controversial data concerning the impact of vegetable lecithins on lipid digestion and intestinal absorption, the beneficial effect of lecithin supplementation on plasma and hepatic lipoprotein and cholesterol levels is unequivocal. This is especially true in hyperlipidemic patients. Furthermore, the immense compositional diversity of vegetable lecithins endows them with a vast range of biochemical and biological properties, which remain to be explored in detail. Data on the effects of vegetable lecithins alternative to soybean, both as supplements and as ingredients in different foods, is undoubtedly lacking. Given the exponential demand for vegetable products alternative to those of animal origin, it is of primordial importance that future research is undertaken in order to elucidate the mechanisms by which individual fatty acids and PL from various vegetable lecithins modulate lipid metabolism. The extent to which they may influence parameters associated with metabolic disorders, such as intestinal integrity, low-grade inflammation and gut microbiota must also be assessed.

Dietary lecithin can stimulate bile formation and biliary lipid secretion, particularly cholesterol output in bile. Studies also suggested that the lecithin-rich diet might modify hepatic cholesterol homeostasis and lipoprotein metabolism. Therefore, we examined hepatic activities of 3-hydroxy-3 methylglutaryl coenzyme A reductase "HMG -CoA reductase", cholesterol 7 alpha-hydroxylase and acyl-Co

A: cholesterol acyltransferase "ACAT" as well as plasma lipids and lipoprotein composition in rats fed diets enriched with 20% of soybean lecithin during 14 days. We also evaluated the content of hepatic canalicular membrane proteins involved in lipid transport to the bile (all P-glycoproteins as detected by the C 219 antibody and the sister of P-glycoprotein "spgp" or bile acid export pump) by Western blotting. As predicted, lecithin diet modified hepatic cholesterol homeostasis. The activity of hepatic HMG-CoA reductase and cholesterol 7 alpha-hydroxylase was enhanced by 30 and 12% respectively, while microsomal ACAT activity showed a dramatic decrease of 75%. As previously reported from ACAT inhibition, the plasma level and size of very low-density lipoprotein (VLDL) were significantly decreased and bile acid pool size and biliary lipid output were significantly increased. The canalicular membrane content of lipid transporters was not significantly affected by dietary lecithin. The current data on inhibition of ACAT activity and related metabolic effects by lecithin mimic the previously reported effects following drug-induced inhibition of ACAT activity, suggesting potential beneficial effects of dietary lecithin supplementation in vascular disease.

Epidemiological studies identify meat as a major source of choline; however, the most comprehensive reference for food choline content, the United States Department of Agriculture (USDA) database for dietary choline, does not include values for meats of importance in some regions. In this work, the total choline and choline-containing moieties of 20 samples of meat were analyzed by LC-MS/MS; 16 samples analyzed are absent from the USDA database and 4 samples included for comparison. Average total choline for one serving (75 g) was 50 ± 12 mg, which was 82.6% ± 5.5% phosphatidylcholine. There was general agreement between total choline levels in the meats analyzed in this work and USDA values. A strong negative correlation (r = -0.777, p < 0.001) between total choline and fat content was found. This research added choline composition data to a food group that is a major source of choline and ultimately this data will assist in obtaining more accurate estimates of dietary choline.

Choline is an essential nutrient with critical roles in several biological processes including neuronal development, cell signaling, nerve impulse transmission, and lipid transport and metabolism. The National Cancer Institute method was used to assess usual intakes of choline from foods according to data for participants enrolled in the National Health and Nutrition Examination Survey 2009-2014 datasets and pregnant women in the 2005-2014 datasets. Suboptimal intakes of choline are present across many gender and life-stage subpopulations, as well as pregnant women in the U.S. Only 8.03 ± 0.56% of adults and 8.51 ± 2.89% pregnant women meet the AI for choline. Children 2-3 years were the most likely to meet their gender and life-stage specific AI, followed by children 4-8 years. Adults 19+ years who consume eggs were more likely to meet their gender and life-stage AI as compared to non-consumers (57.3 ± 1.45% and 2.43 ± 0.28%). Consumers of eggs had almost double the usual intake of choline as compared to non-consumers (525 ± 5.17 mg/d and 294 ± 1.98; < 0.0001). Protein food (meat, poultry and seafood) consumption also increased usual choline intakes compared to non-consumers (345 ± 2.21 mg/day and 235 ± 8.81; < 0.0001) to a lesser degree, but did not result in substantial increases in the percent of individuals meeting the AI. No subpopulation exceeded the UL for choline. This research illustrates that it is extremely difficult to achieve the AI for choline without consuming eggs or taking a dietary supplement.

The objective of this study is to assess the usual intake and food sources of choline in a group of Romanian kindergarten children. A cross-sectional study was performed among 71 children aged 4-6 years from four kindergartens from Cluj-Napoca, Romania. Dietary intake data were collected by means of three-day food records. The mean (SD) daily intake of choline was 215 (32) mg/day, 22.5% of the participants fulfilling the adequate intake (AI) for children 4-6 years of age of 250 mg of choline per day. The main food sources were meat (mainly poultry), eggs, grains, cereals, and baked products (mainly bread), and dairy products (mainly milk). The results of the logistic regression analyses show that an appropriate consumption of choline/day was statistically significantly associated with the consumption of at least one egg per three days (OR = 7.5, < 0.05), a minimum of two portions of milk or dairy products per day (500 mL milk or yoghurt, or 60 g of cheese/day) (OR = 4.4, < 0.05), and at least one portion of meat/day (90 g/day) (OR = 14.4, < 0.05). The results underline the need for future surveys in this field, as well as actions to encourage an appropriate diet for children, including an appropriate content of choline.

Background: The importance of adequate choline intake during pregnancy has been well documented, but low intake is common. Total choline intake, main food sources of choline, as well as associations between choline intake and egg and dairy consumption were determined in a sample of pregnant women attending the high-risk antenatal clinic at a regional hospital in Bloemfontein, South Africa.

Methods: A cross-sectional study design was used. Trained fieldworkers collected dietary intake data using a validated quantified food frequency questionnaire (QFFQ), after which all food items were matched to foods in the USDA Database for the Choline Content of Common Foods (Release 2) to quantify choline intake. Logistic regression with backward selection (p < 0.05) was used to determine whether egg and dairy consumption were independently associated with a choline intake below the adequate intake (AI) level.

Results: The median daily intake of choline was 275 mg (interquartile range 185 mg - 387 mg) (N = 681). Most participants (84.7%) consumed less than the AI of 450 mg/day for choline. Meat and meat products, cereals, eggs and dairy contributed mostly to choline intake. Food items that contributed most to choline intake included full-cream milk, maize porridge, brown bread, deep-fried potatoes and deep-fried dough (vetkoek). A choline intake below the AI was significantly associated with lower egg and dairy intakes (p < 0.0001 and p = 0.0002 respectively).

Conclusion: Most pregnant women in the current study had choline intakes below the AI. It is recommended that public health messaging targeted at pregnant women promote the consumption of foods that can significantly contribute to choline intake, such as eggs and dairy.

Choline is an essential nutrient with critical roles in several biological processes including neuronal development, cell signaling, nerve impulse transmission, and lipid transport and metabolism. The National Cancer Institute method was used to assess usual intakes of choline from foods according to data for participants enrolled in the National Health and Nutrition Examination Survey 2009-2014 datasets and pregnant women in the 2005-2014 datasets. Suboptimal intakes of choline are present across many gender and life-stage subpopulations, as well as pregnant women in the U.S. Only 8.03 ± 0.56% of adults and 8.51 ± 2.89% pregnant women meet the AI for choline. Children 2-3 years were the most likely to meet their gender and life-stage specific AI, followed by children 4-8 years. Adults 19+ years who consume eggs were more likely to meet their gender and life-stage AI as compared to non-consumers (57.3 ± 1.45% and 2.43 ± 0.28%). Consumers of eggs had almost double the usual intake of choline as compared to non-consumers (525 ± 5.17 mg/d and 294 ± 1.98; < 0.0001). Protein food (meat, poultry and seafood) consumption also increased usual choline intakes compared to non-consumers (345 ± 2.21 mg/day and 235 ± 8.81; < 0.0001) to a lesser degree, but did not result in substantial increases in the percent of individuals meeting the AI. No subpopulation exceeded the UL for choline. This research illustrates that it is extremely difficult to achieve the AI for choline without consuming eggs or taking a dietary supplement.

Choline was officially recognized as an essential nutrient by the Institute of Medicine (IOM) in 1998. There is significant variation in the dietary requirement for choline that can be explained by common genetic polymorphisms. Because of its wide-ranging roles in human metabolism, from cell structure to neurotransmitter synthesis, choline-deficiency is now thought to have an impact on diseases such as liver disease, atherosclerosis, and, possibly, neurological disorders. Choline is found in a wide variety of foods. Eggs and meats are rich sources of choline in the North American diet, providing up to 430 milligrams per 100 grams. Mean choline intakes for older children, men, women, and pregnant women are far below the adequate intake level established by the IOM. Given the importance of choline in a wide range of critical functions in the human body, coupled with less-than-optimal intakes among the population, dietary guidance should be developed to encourage the intake of choline-rich foods.

Epidemiological studies identify meat as a major source of choline; however, the most comprehensive reference for food choline content, the United States Department of Agriculture (USDA) database for dietary choline, does not include values for meats of importance in some regions. In this work, the total choline and choline-containing moieties of 20 samples of meat were analyzed by LC-MS/MS; 16 samples analyzed are absent from the USDA database and 4 samples included for comparison. Average total choline for one serving (75 g) was 50 ± 12 mg, which was 82.6% ± 5.5% phosphatidylcholine. There was general agreement between total choline levels in the meats analyzed in this work and USDA values. A strong negative correlation (r = -0.777, p < 0.001) between total choline and fat content was found. This research added choline composition data to a food group that is a major source of choline and ultimately this data will assist in obtaining more accurate estimates of dietary choline.

Choline is an essential nutrient with critical roles in several biological processes including neuronal development, cell signaling, nerve impulse transmission, and lipid transport and metabolism. The National Cancer Institute method was used to assess usual intakes of choline from foods according to data for participants enrolled in the National Health and Nutrition Examination Survey 2009-2014 datasets and pregnant women in the 2005-2014 datasets. Suboptimal intakes of choline are present across many gender and life-stage subpopulations, as well as pregnant women in the U.S. Only 8.03 ± 0.56% of adults and 8.51 ± 2.89% pregnant women meet the AI for choline. Children 2-3 years were the most likely to meet their gender and life-stage specific AI, followed by children 4-8 years. Adults 19+ years who consume eggs were more likely to meet their gender and life-stage AI as compared to non-consumers (57.3 ± 1.45% and 2.43 ± 0.28%). Consumers of eggs had almost double the usual intake of choline as compared to non-consumers (525 ± 5.17 mg/d and 294 ± 1.98; < 0.0001). Protein food (meat, poultry and seafood) consumption also increased usual choline intakes compared to non-consumers (345 ± 2.21 mg/day and 235 ± 8.81; < 0.0001) to a lesser degree, but did not result in substantial increases in the percent of individuals meeting the AI. No subpopulation exceeded the UL for choline. This research illustrates that it is extremely difficult to achieve the AI for choline without consuming eggs or taking a dietary supplement.

Choline was officially recognized as an essential nutrient by the Institute of Medicine (IOM) in 1998. There is significant variation in the dietary requirement for choline that can be explained by common genetic polymorphisms. Because of its wide-ranging roles in human metabolism, from cell structure to neurotransmitter synthesis, choline-deficiency is now thought to have an impact on diseases such as liver disease, atherosclerosis, and, possibly, neurological disorders. Choline is found in a wide variety of foods. Eggs and meats are rich sources of choline in the North American diet, providing up to 430 milligrams per 100 grams. Mean choline intakes for older children, men, women, and pregnant women are far below the adequate intake level established by the IOM. Given the importance of choline in a wide range of critical functions in the human body, coupled with less-than-optimal intakes among the population, dietary guidance should be developed to encourage the intake of choline-rich foods.

Lean and extralean meats, poultry, and fish: Beneficial sources of protein and magnesium. Only lean or extralean meats should be selected; visible fats should be trimmed away; meat should be broiled, roasted, or poached; and skin should be removed from poultry. Although the 2015 US Dietary Guidelines Advisory Committee reported that dietary cholesterol was no longer a nutrient of concern, for some individuals (eg, those with elevated LDL-C), reduced intake of egg yolks (180 mg cholesterol per yolk) may be appropriate. Two egg whites have the same protein content as 1 oz meat.
Fats and oils: The AHA/ACC diet recommends avoiding trans fats and limiting SFAs to <6% of total calories. Polyunsaturated and monounsaturated fatty acids should be substituted for SFAs and trans fat. An upper limit on total fat was not set, but total energy intake should support weight-control efforts. The DASH diet has smaller serving sizes for higher-fat foods from the fats and oils group. For instance, 1 tablespoon of regular salad dressing is 1 serving, and 2 tablespoons of low-fat dressing is 1 serving. Examples include soft margarine, vegetable oil (canola, corn, olive, soybean, safflower), low-fat mayonnaise, and light salad dressing. Caution is needed to avoid sources with added salt or sugar.

Choline is a vitamin-like essential nutrient, important throughout one's lifespan. Therefore, choline salts are added to infant formula, supplements and functional foods. However, if choline is present in a natural form, e.g. bound to phospholipids, it may be more efficiently absorbed. The study's aim was to evaluate if choline uptake is improved after consumption of an egg yolk phospholipid drink, containing 3 g of phospholipid bound choline, compared to a control drink with 3 g of choline bitartrate. We performed a randomized, double blind, cross-over trial with 18 participants. Plasma choline, betaine and dimethylglycine concentrations were determined before and up to six hours after consumption of the drinks. The plasma choline response, as determined by the incremental area under the curve, was four times higher after consumption of the egg yolk phospholipid drink compared with the control drink ( 0.01). Similar outcomes were also observed for choline's main metabolites, betaine ( 0.01) and dimethylglycine ( 0.01). Consumption of natural choline from egg yolk phospholipids improved choline absorption compared to consumption of chemically produced choline bitartrate. This information is of relevance for the food industry, instead of adding choline-salts, adding choline from egg yolk phospholipids can improve choline uptake and positively impact health.

Vitamins are essential components of enzyme systems involved in normal growth and function. The quantitative estimation of the proportion of dietary vitamins, that is in a form available for utilization by the human body, is limited and fragmentary. This review provides the current state of knowledge on the bioavailability of thirteen vitamins and choline, to evaluate whether there are differences in vitamin bioavailability when human foods are sourced from animals or plants. The bioavailability of naturally occurring choline, vitamin D, vitamin E, and vitamin K in food awaits further studies. Animal-sourced foods are the almost exclusive natural sources of dietary vitamin B-12 (65% bioavailable) and preformed vitamin A retinol (74% bioavailable), and contain highly bioavailable biotin (89%), folate (67%), niacin (67%), pantothenic acid (80%), riboflavin (61%), thiamin (82%), and vitamin B-6 (83%). Plant-based foods are the main natural sources of vitamin C (76% bioavailable), provitamin A carotenoid β-carotene (15.6% bioavailable), riboflavin (65% bioavailable), thiamin (81% bioavailable), and vitamin K (16.5% bioavailable). The overview of studies showed that in general, vitamins in foods originating from animals are more bioavailable than vitamins in foods sourced from plants.

In this comprehensive review, we examine the main preclinical and clinical investigations assessing the effects of different forms of choline supplementation currently available, including choline alfoscerate (CHNOP), also known as alpha-glycerophosphocholine (α-GPC, or GPC), choline bitartrate, lecithin, and citicoline, which are cholinergic compounds and precursors of acetylcholine. Extensively used as food supplements, they have been shown to represent an effective strategy for boosting memory and enhancing cognitive function.

Choline is a vitamin-like essential nutrient, important throughout one's lifespan. Therefore, choline salts are added to infant formula, supplements and functional foods. However, if choline is present in a natural form, e.g. bound to phospholipids, it may be more efficiently absorbed. The study's aim was to evaluate if choline uptake is improved after consumption of an egg yolk phospholipid drink, containing 3 g of phospholipid bound choline, compared to a control drink with 3 g of choline bitartrate. We performed a randomized, double blind, cross-over trial with 18 participants. Plasma choline, betaine and dimethylglycine concentrations were determined before and up to six hours after consumption of the drinks. The plasma choline response, as determined by the incremental area under the curve, was four times higher after consumption of the egg yolk phospholipid drink compared with the control drink ( 0.01). Similar outcomes were also observed for choline's main metabolites, betaine ( 0.01) and dimethylglycine ( 0.01). Consumption of natural choline from egg yolk phospholipids improved choline absorption compared to consumption of chemically produced choline bitartrate. This information is of relevance for the food industry, instead of adding choline-salts, adding choline from egg yolk phospholipids can improve choline uptake and positively impact health.

Forty-five women (35-45 year) were randomly assigned to three iron (Fe) absorption sub-studies, which measured the effects of dietary animal proteins on the absorption of heme Fe. Study 1 was focused on heme, red blood cell concentrate (RBCC), hemoglobin (Hb), RBCC+beef meat; study 2 on heme, heme+fish, chicken, and beef; and study 3 on heme and heme+purified animal protein (casein, collagen, albumin). Study 1: the bioavailability of heme Fe from Hb was similar to heme only (∼13.0%). RBCC (25.0%) and RBCC+beef (21.3%) were found to be increased 2- and 1.6-fold, respectively, when compared with heme alone (p<0.05). Study 2: the bioavailability from heme alone (10.3%) was reduced (p<0.05) when it was blended with fish (7.1%) and chicken (4.9%), however it was unaffected by beef. Study 3: casein, collagen, and albumin did not affect the bioavailability of Fe. Proteins from animal source foods and their digestion products did not enhance heme Fe absorption.

Epidemiological studies identify meat as a major source of choline; however, the most comprehensive reference for food choline content, the United States Department of Agriculture (USDA) database for dietary choline, does not include values for meats of importance in some regions. In this work, the total choline and choline-containing moieties of 20 samples of meat were analyzed by LC-MS/MS; 16 samples analyzed are absent from the USDA database and 4 samples included for comparison. Average total choline for one serving (75 g) was 50 ± 12 mg, which was 82.6% ± 5.5% phosphatidylcholine. There was general agreement between total choline levels in the meats analyzed in this work and USDA values. A strong negative correlation (r = -0.777, p < 0.001) between total choline and fat content was found. This research added choline composition data to a food group that is a major source of choline and ultimately this data will assist in obtaining more accurate estimates of dietary choline.