Impact of the Association Between PNPLA3 Genetic Variation and Dietary Intake on the Risk of Significant Fibrosis in Patients With NAFLD

PNPLA3 gene variation modulates diet-induced improvement in liver lipid content in type 2 diabetes

BACKGROUND&AIMS

Lifestyle-induced weight reduction remains crucial for managing type 2 diabetes and steatotic liver disease, but its effectiveness varies. We postulated that the G allele in the rs738409 single nucleotide polymorphism within patatin-like phospholipase domain-containing protein 3 (PNPLA3), which associates with metabolic dysfunction-associated steatotic liver disease, also modulates diet-related metabolic effects.

METHODS

Participants with type 2 diabetes were randomized to 8-week hypocaloric diets (energy intake: -1,256 kJ/d of, <30 kcal% fat): high in cereal fiber and coffee excluding red meat (HF-RM + C; n = 16), or low in cereal fiber, devoid of coffee, but high in red meat (LF + RM-C; n = 15). Whole-body insulin sensitivity (M value) was assessed using [2H]glucose and hyperinsulinemic-normoglycemic clamps, hepatic lipid content (HCL) and body fat volumes by magnetic resonance spectroscopy/imaging before and after intervention.

RESULTS

Despite comparable weight loss, HCL decreased more in non-carriers (-65 %) than in G-allele carriers (-36 %) upon HF-RM + C diet (both p < 0.05 vs baseline and between groups), but only among non-carriers (-46 %, p < 0.05 vs baseline) upon LF + RM-C. Upon HF-RM + C diet, increase in insulin sensitivity was not different between carriers (+27 % p = 0.051 from baseline) and non-carriers (+21 %, p = 0.032 from baseline), p > 0.05 for between-group comparison. Upon LF + RM-C diet, both groups equally improved their whole-body insulin sensitivity (+42 % for non-carriers and +37 % for carriers, p < 0.05 vs baseline). Upon HF-RM + C diet, non-carriers decreased circulating interleukin-18 from baseline by -31 %, whereas, upon LF + RM-C diet, non-carriers decreased circulating anti-inflammatory interleukin-1 receptor antagonist levels by 14 % (both p < 0.05 vs baseline).

CONCLUSIONS

Humans with the PNPLA3 G-allele show modified dietary-induced effects on steatotic liver disease in type 2 diabetes despite body weight reduction. Registration at Clinicaltrials.gov, Identifier number: NCT01409330.

Clinical associations of portal-based disease in MASLD: proposal of a new histological scoring system

Portal inflammation (PI) and ductular reaction (DR) in metabolic dysfunction-associated steatotic liver disease (MASLD) have shown associations with disease severity. We developed a histologic categorization of these features to correlate with known features of MASLD. This study proposes a scoring schema for PI, PP and DR, and relates them to histologic and clinical features in children and adults. This expanded scoring system was developed to identify clinically relevant categories and defined criteria for scoring biopsies. In adults (N:483), more severe PI, PP, and DR were associated with older age (p ≤ 0.002), and PP and DR were associated with increased alkaline phosphatase (ALP) (p ≤ 0.003), GGT (p ≤ 0.001), and total bilirubin (p ≤ 0.01). More severe PI, PP, and DR were associated with higher NAFLD activity score (NAS), fibrosis stage, and diagnosis of metabolic dysfunction-associated steatohepatitis (MASH) (p ≤ 0.05). In children (N:151), PP and DR were associated with younger age (p ≤ 0.0001), and elevated AST, ALT, and ALP (p ≤ 0.05). More severe PI, PP, and DR were associated with advanced fibrosis stage, and PP and DR were associated with diagnosis of borderline or definite MASH in children (p ≤ 0.05). From multivariable ordinal logistic regression analysis, a higher fibrosis stage was independently associated with more severe PI in both adults and children. Interobserver agreement was substantial for PI, PP and DR. The proposed scoring system demonstrated reproducibility and associations between more severe portal-based disease and advanced liver histology, age, and elevated liver enzymes in adults and children. Evaluation of portal disease could provide insight into therapeutic response and disease progression.

PNPLA3 rs738409, environmental factors and liver-related mortality in the US population

BACKGROUND & AIMS

Little is known about the interplay between patatin-like phospholipase domain-containing protein 3 (PNPLA3 rs738409 C>G), environmental factors, and the risk of liver-related death.

METHODS

A total of 4,361 adults were selected from NHANES III, 1991-1994. All participants were linked to the National Death Index until 2019 (mean follow-up: 23.2 years). Liver-related death was the study outcome. Associations of PNPLA3, diet, light alcohol intake, smoking, and BMI (kg/m2) with liver-related death were examined using competing risk regression models.

RESULTS

The PNPLA3 G-allele was significantly associated with liver-related death (adjusted subhazard ratio [adj.sHR] 2.9, 95% CI 1.4-5.8). Light alcohol intake (adj.sHR 2.2, 95% CI 1.1-4.5), top quartiles of monounsaturated fat (adj.sHR 0.43, 95% CI 0.12-0.99) and cholesterol (adj.sHR 2.6, 95% CI 1.00-8.8), coffee intake ≥3 cups/day (adj.sHR 0.05, 95% CI 0.06-0.10), former/current smoking (adj.sHR 1.8, 95% CI 1.2-2.6), BMI (adj.sHR 1.1, 95% CI 1.03-1.2), and healthy eating index (adj.sHR 0.96, 95% CI 0.93-0.98) were associated with liver-related death. Joint effects between PNPLA3 and environmental factors showed that the risk of liver-related death was significantly increased in carriers of the G-allele with light alcohol intake (adj.sHR 3.7), higher consumption (top quartile) of cholesterol (adj.sHR 4.1), former (adj.sHR 4.3) or current (adj.sHR 3.5) smoking, or BMI ≥30 (adj.sHR 4.0) kg/m2. The effects of the G-allele on the risk of LRD were significantly attenuated in those with top quartile consumption of monounsaturated fat (adj.sHR 0.5) or coffee intake ≥3 cups/day (adj.sHR 0.09). Healthy eating index was inversely associated with liver-related death across all PNPLA3 genotypes (adj.sHR 0.94, 0.96, and 0.97 for CC, CG, and GG, respectively).

CONCLUSIONS

PNPLA3 is associated with liver-related death and this relationship is significantly modified by anthropometric and environmental factors.

IMPACT AND IMPLICATIONS

Light alcohol intake, dietary factors (healthy eating index, monounsaturated fat, cholesterol), coffee intake, smoking status, and BMI are independently associated with the risk of liver-related death. The increased inherited risk of liver-related death associated with PNPLA3 rs738409 appears to be attenuated by healthy eating index, monounsaturated fat, and coffee intake, and exacerbated by light alcohol intake, smoking, and BMI. Reducing harmful environmental exposures and increasing healthy eating habits may help mitigate the risk of liver-specific mortality even in those with high genetic risk.

Impact of PNPLA3 in Lean Individuals and in Cryptogenic Steatotic Liver Disease

BACKGROUND

Although metabolic dysfunction-associated steatotic liver disease (MASLD) is strongly associated with obesity, around 20% of individuals with hepatic steatosis may nonetheless have normal body mass index, a condition often referred to as lean nonalcoholic fatty liver disease (NAFLD). Under the new nomenclature and definition of MASLD, lean NAFLD can be further divided into lean MASLD (when there is one or more cardiometabolic risk factors) and cryptogenic steatotic liver disease (when there is no cardiometabolic risk factor).

RESULTS

Current studies suggest that the at-risk PNPLA3 rs738409 variant is more common among individuals with lean NAFLD than their overweight and obese counterparts. However, even in this group, cardiometabolic risk factors are often required for the development of hepatic steatosis and liver injury. In the general population, PNPLA3 gene polymorphism is associated with an increased risk of MASLD, more severe liver histology (i.e., the presence of steatohepatitis and fibrosis) and future development of hepatocellular carcinoma and cirrhotic complications. Emerging data also suggest that individuals carrying the PNPLA3 GG genotype might have a greater reduction in hepatic steatosis and liver enzymes with lifestyle intervention and metabolic treatments, such as glucagon-like peptide-1 receptor agonists.

CONCLUSION

Studies have not specifically examined the impact of PNPLA3 in lean individuals.

Human genetics of metabolic dysfunction-associated steatotic liver disease: from variants to cause to precision treatment

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by increased hepatic steatosis with cardiometabolic disease and is a leading cause of advanced liver disease. We review here the genetic basis of MASLD. The genetic variants most consistently associated with hepatic steatosis implicate genes involved in lipoprotein input or output, glucose metabolism, adiposity/fat distribution, insulin resistance, or mitochondrial/ER biology. The distinct mechanisms by which these variants promote hepatic steatosis result in distinct effects on cardiometabolic disease that may be best suited to precision medicine. Recent work on gene-environment interactions has shown that genetic risk is not fixed and may be exacerbated or attenuated by modifiable (diet, exercise, alcohol intake) and nonmodifiable environmental risk factors. Some steatosis-associated variants, notably those in patatin-like phospholipase domain-containing 3 (PNPLA3) and transmembrane 6 superfamily member 2 (TM6SF2), are associated with risk of developing adverse liver-related outcomes and provide information beyond clinical risk stratification tools, especially in individuals at intermediate to high risk for disease. Future work to better characterize disease heterogeneity by combining genetics with clinical risk factors to holistically predict risk and develop therapies based on genetic risk is required.

Assessment of dietary, genetic and metabolic factors in South Indian adolescents with metabolic dysfunction-associated steatotic liver disease: a case-control study protocol

INTRODUCTION

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a leading cause of liver disease among adolescents. The objectives of this study are to investigate the associations of dietary, genetic and metabolic factors with MASLD in South Indian adolescents.

METHODS AND ANALYSIS

The study will employ a case-control study design. We will recruit 280 adolescents (140 cases and 140 controls) from hospital and school settings. The hospital setting will be the paediatric gastroenterology outpatient department (OPD) at the study institution and the school setting will be selected urban schools from Ernakulam, Kerala. At the hospital, cases and controls will be selected from the patients who are attending the paediatric gastroenterology OPD with complaints of generalised abdominal pain or constipation with no other significant medical complaints or use of medications. A sensitisation programme on MASLD for parents of adolescents will be conducted in schools. All consenting parents along with their adolescent wards will be invited for study participation. Cases will be defined as adolescents having evidence of hepatic steatosis in ultrasound and meeting any one of the paediatric cardiometabolic criteria for MASLD. Those who fail to satisfy this criteria will be defined as controls. All participants will undergo nutritional and physical activity assessments using validated questionnaires along with blood sampling for biochemical analysis and genetic testing. We will examine the associations between MASLD and dietary parameters using Pearson's χ2 tests after stratifying dietary variables into categorical groups. Logistic regression will be used to assess the impact of dietary parameters and single-nucleotide polymorphisms (SNPs) on the risk of MASLD.

ETHICS AND DISSEMINATION

Ethics approval was obtained from the Ethics Committee of Amrita School of Medicine, Kochi. Informed consent will be obtained from participants and their legal guardians before enrolment. The study findings will provide valuable insights into the evolution of MASLD among adolescents in South India.

Global Epidemiological Impact of PNPLA3 I148M on Liver Disease

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) has increased exponentially over the past three decades, in parallel with the global rise in obesity and type 2 diabetes. It is currently the most common cause of liver-related morbidity and mortality. Although obesity has been identified as a key factor in the increased prevalence of MASLD, individual differences in susceptibility are significantly influenced by genetic factors. PNPLA3 I148M (rs738409 C>G) is the variant with the greatest impact on the risk of developing progressive MASLD and likely other forms of steatotic liver disease. This variant is prevalent across the globe, with the risk allele (G) frequency exhibiting considerable variation. Here, we review the contribution of PNPLA3 I148M to global burden and regional differences in MASLD prevalence, focusing on recent evidence emerging from population-based sequencing studies and prevalence assessments. We calculated the population attributable fraction (PAF) as a means of quantifying the impact of the variant on MASLD. Furthermore, we employ quantitative trait locus (QTL) analysis to ascertain the associations between rs738409 and a range of phenotypic traits. This analysis suggests that these QTLs may underpin pleiotropic effects on extrahepatic traits. Finally, we outline potential avenues for further research and identify key areas for investigation in future studies.

Total choline intake, liver fibrosis and the progression of metabolic dysfunction-associated steatotic liver disease: Results from 2017 to 2020 NHANES

OBJECTIVES

This study investigated the cross-sectional relationships of total choline intake with the prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) and its progression to liver fibrosis.

STUDY DESIGN

The study used data on total choline intake, hepatic steatosis, and liver fibrosis from the cross-sectional 2017-2020 National Health and Nutrition Examination Survey, including 24-h dietary recalls and liver ultrasound elastography (FibroScan®).

MAIN OUTCOME MEASURES

Steatosis was defined as a controlled attenuation parameter score ≥ 285dB/m. Fibrosis was defined as median liver stiffness ≥8 kPa. Complex survey-adjusted regression models were used in all analyses. Effect modification by sex, race, and cardiometabolic risk factors was investigated.

RESULT

Total choline intake was not associated with MASLD status (n = 5687; odds ratio per 100 mg/d [95 % confidence interval]: 0.96 [0.85,1.09]; P = 0.55). However, among people with MASLD, a higher total choline intake was associated with higher odds of fibrosis (n = 2019; 1.15 [1.01,1.30]; P = 0.03). This association was observed in men (P-interaction = 0.1; 1.23 [1.02,1.48]; P = 0.03), but not in women (1.05 [0.88,1.24]; P = 1.0). Choline intake also tended to be positively associated with fibrosis in people with MASLD who were overweight or had central obesity (P-interaction = 0.02; 1.15 [1.00,1.34]; P = 0.06).

CONCLUSIONS

Overall, no significant association was observed between total choline intake and the prevalence of MASLD. However, in people with MASLD, a higher choline intake was associated with higher odds of developing liver fibrosis. This association appeared to differ by sex and cardiometabolic risk factors.

The role of dietary modification in the prevention and management of metabolic dysfunction-associated fatty liver disease: An international multidisciplinary expert consensus

Metabolic dysfunction-associated fatty liver disease (MAFLD) or metabolic dysfunction-associated steatotic liver disease (MASLD), has become the leading cause of chronic liver disease worldwide. Optimal dietary intervention strategies for MAFLD are not standardized. This study aimed to achieve consensus on prevention of MAFLD through dietary modification. A multidisciplinary panel of 55 international experts, including specialists in hepatology, gastroenterology, dietetics, endocrinology and other medical specialties from six continents collaborated in a Delphi-based consensus development process. The consensus statements covered aspects ranging from epidemiology to mechanisms, management, and dietary recommendations for MAFLD. The recommended dietary strategies emphasize adherence to a balanced diet with controlled energy intake and personalized nutritional interventions, such as calorie restriction, high-protein, or low-carbohydrate diets. Specific dietary advice encouraged increasing the consumption of whole grains, plant-based proteins, fish, seafood, low-fat or fat-free dairy products, liquid plant oils, and deeply colored fruits and vegetables. Concurrently, it advised reducing the intake of red and processed meats, saturated and trans fats, ultra-processed foods, added sugars, and alcohol. Additionally, maintaining the Mediterranean or DASH diet, minimizing sedentary behavior, and engaging in regular physical activity are recommended. These consensus statements lay the foundation for customized dietary guidelines and proposing avenues for further research on nutrition and MAFLD.

Genetics of Metabolic Dysfunction-associated Steatotic Liver Disease: The State of the Art Update

Recent advances in the genetics of metabolic dysfunction-associated steatotic liver disease (MASLD) are gradually revealing the mechanisms underlying the heterogeneity of the disease and have shown promising results in patient stratification. Genetic characterization of the disease has been rapidly developed using genome-wide association studies, exome-wide association studies, phenome-wide association studies, and whole exome sequencing. These advances have been powered by the increase in computational power, the development of new analytical algorithms, including some based on artificial intelligence, and the recruitment of large and well-phenotyped cohorts. This review presents an update on genetic studies that emphasize new biological insights from next-generation sequencing approaches. Additionally, we discuss innovative methods for discovering new genetic loci for MASLD, including rare variants. To comprehensively manage MASLD, it is important to stratify risks. Therefore, we present an update on phenome-wide association study associations, including extreme phenotypes. Additionally, we discuss whether polygenic risk scores and targeted sequencing are ready for clinical use. With particular focus on precision medicine, we introduce concepts such as the interplay between genetics and the environment in modulating genetic risk with lifestyle or standard therapies. A special chapter is dedicated to gene-based therapeutics. The limitations of approved pharmacological approaches are discussed, and the potential of gene-related mechanisms in therapeutic development is reviewed, including the decision to perform genetic testing in patients with MASLD.

PNPLA3 rs738409, age, diabetes, sex, and advanced fibrosis jointly contribute to the risk of major adverse liver outcomes in metabolic dysfunction-associated steatotic liver disease

BACKGROUND AND AIMS

The patatin-like phospholipase domain-containing protein 3 ( PNPLA3 ) rs738409 variant is associated with steatotic liver disease and its progression. We examined the association between PNPLA3 and the development of major adverse liver outcomes (MALOs) and how nonmodifiable and modifiable conditions modify this relationship.

APPROACH AND RESULTS

A total of 2075 adults with biopsy-confirmed metabolic dysfunction-associated steatotic liver disease (MASLD) were enrolled in the metabolic dysfunction-associated steatohepatitis Clinical Research Network (MASH CRN) studies and followed prospectively until death, transplant, or withdrawal of consent. One hundred four MALOs were recorded during an average of 4.3 years. PNPLA3 G-allele (Adj. sub-hazard ratio (sHR): 1.4, 95% CI: 1.07-1.8), advanced fibrosis (AF) (Adj. sHR: 7.8, 95% CI: 4.4-13.8), age >60 years (Adj. sHR: 2.9, 95% CI: 1.3-6.8), and type 2 diabetes mellitus (Adj. sHR: 2.8, 95% CI: 1.8-4.2) were associated with MALO. Among participants with AF, those carrying the G-allele displayed the highest cumulative incidence of MALO (85%) versus noncarriers (53%), p =0.03, and p -value for interaction <0.01. The strength of the association between PNPLA3 and MALO was statistically significantly greater among older than 60 years (sHR: 2.1, 95% CI: 1.5-2.8), women (sHR: 1.4, 95% CI: 1.1-1.9), and those with AF (sHR: 1.9, 95% CI: 1.5-2.4) or type 2 diabetes mellitus (sHR: 2.1, 95% CI: 1.5-2.8) as compared with their counterparts, p -value for interaction between PNPLA3 and each factor<0.01.

CONCLUSIONS

The deleterious effects of PNPLA3 rs738409 on the risk of MALO are significantly worsened by AF, age, type 2 diabetes mellitus, and sex.

Gut microbes, diet, and genetics as drivers of metabolic liver disease: a narrative review outlining implications for precision medicine

Metabolic dysfunction-associated steatotic liver disease (MASLD) is rapidly increasing in prevalence, impacting over a third of the global population. The advanced form of MASLD, Metabolic dysfunction-associated steatohepatitis (MASH), is on track to become the number one indication for liver transplant. FDA-approved pharmacological agents are limited for MASH, despite over 400 ongoing clinical trials, with only a single drug (resmetirom) currently on the market. This is likely due to the heterogeneous nature of disease pathophysiology, which involves interactions between highly individualized genetic and environmental factors. To apply precision medicine approaches that overcome interpersonal variability, in-depth insights into interactions between genetics, nutrition, and the gut microbiome are needed, given that each have emerged as dynamic contributors to MASLD and MASH pathogenesis. Here, we discuss the associations and molecular underpinnings of several of these factors individually and outline their interactions in the context of both patient-based studies and preclinical animal model systems. Finally, we highlight gaps in knowledge that will require further investigation to aid in successfully implementing precision medicine to prevent and alleviate MASLD and MASH.

The future backbone of nutritional science: integrating public health priorities with system-oriented precision nutrition

Adopting policies that promote health for the entire biosphere (One Health) requires human societies to transition towards a more sustainable food supply as well as to deepen the understanding of the metabolic and health effects of evolving food habits. At the same time, life sciences are experiencing rapid and groundbreaking technological developments, in particular in laboratory analytics and biocomputing, placing nutrition research in an unprecedented position to produce knowledge that can be translated into practice in line with One Health policies. In this dynamic context, nutrition research needs to be strategically organised to respond to these societal expectations. One key element of this strategy is to integrate precision nutrition into epidemiological research. This position article therefore reviews the recent developments in nutrition research and proposes how they could be integrated into cohort studies, with a focus on the Swiss research landscape specifically.

Genetic risk accentuates dietary effects on hepatic steatosis, inflammation and fibrosis in a population-based cohort

BACKGROUND & AIMS

Steatotic liver disease (SLD), characterized by elevated liver fat content (LFC), is influenced by genetics and diet. However, whether diet has a differential effect based on genetic risk is not well-characterized. We aimed to determine how genetic factors interact with diet to affect SLD in a large national biobank.

METHODS

We included UK Biobank participants with dietary intake measured by 24-hour recall and genotyping. The primary predictors were dietary pattern, PNPLA3-rs738409-G, TM6SF2-rs58542926-T, a 16-variant hepatic steatosis polygenic risk score (PRS), and gene-environment interactions. The primary outcome was LFC, and secondary outcomes were iron-controlled T1 time (cT1, a measure of liver inflammation and fibrosis) and liver-related events/mortality.

RESULTS

A total of 21,619 participants met inclusion criteria. In non-interaction models, Mediterranean diet and intake of fruit/vegetables/legumes and fish associated with lower LFC, while higher red/processed meat intake and all genetic predictors associated with higher LFC. In interaction models, all genetic predictors interacted with Mediterranean diet and fruit/vegetable/legume intake, while the steatosis PRS interacted with fish intake and the TM6SF2 genotype interacted with red/processed meat intake, to affect LFC. Dietary effects on LFC were up to 3.8-fold higher in PNPLA3-rs738409-GG vs. -CC individuals, and 1.4-3.0-fold higher in the top vs. bottom quartile of the steatosis PRS. Gene-diet interactions were stronger in participants with vs. without overweight. The steatosis PRS interacted with Mediterranean diet and fruit/vegetable/legume intake to affect cT1 and most dietary and genetic predictors associated with risk of liver-related events or mortality by age 70.

CONCLUSIONS

Effects of diet on LFC and cT1 were markedly accentuated in patients at increased genetic risk for SLD, implying dietary interventions may be more impactful in these populations.

IMPACT AND IMPLICATIONS

Genetic variants and diet both influence risk of hepatic steatosis, inflammation/fibrosis, and hepatic decompensation; however, how gene-diet interactions influence these outcomes has previously not been comprehensively characterized. We investigated this topic in the community-based UK Biobank and found that genetic risk and dietary quality interacted to influence hepatic steatosis and inflammation/fibrosis on liver MRI, so that the effects of diet were greater in people at elevated genetic risk. These results are relevant for patients and medical providers because they show that genetic risk is not fixed (i.e. modifiable factors can mitigate or exacerbate this risk) and realistic dietary changes may result in meaningful improvement in liver steatosis and inflammation/fibrosis. As genotyping becomes more routinely used in clinical practice, patients identified to be at high baseline genetic risk may benefit even more from intensive dietary counseling than those at lower risk, though future prospective studies are required.

Non-Hispanic Black Persons With Nonalcoholic Fatty Liver Disease Have Lower Rates of Advanced Fibrosis, Cirrhosis, and Liver-Related Events Even After Controlling for Clinical Risk Factors and PNPLA3 Genotype

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) is less frequent in non-Hispanic persons (NHB), but there are knowledge gaps in our understanding of disease severity and outcomes of NAFLD in NHB. We compared liver histology and clinical outcomes of NAFLD in non-Hispanic Black persons (NHB) and non-Hispanic White persons (NHW).

METHODS

We compared liver histology and outcomes of 109 NHB and 1,910 NHW adults with biopsy-proven NAFLD participating in the Nonalcoholic Steatohepatitis Clinical Research Network observational studies. The relationship between self-reported NHB race/ethnicity and advanced fibrosis was assessed through multivariable logistic regression after controlling for clinical covariates and PNPLA3 genotype.

RESULTS

NHB and NHW with NAFLD had similar NAFLD activity scores (NAS, 4.4 vs 4.3, P = 0.87) and proportions with definite metabolic dysfunction-associated steatohepatitis (59% vs 58%, P = 1.0), but NHB had significantly lower rates of advanced fibrosis (22% vs 34%, P = 0.01) or cirrhosis (4.6% vs 12.1%, P = 0.010). Compared with NHW, NHB had significantly lower frequency of advanced fibrosis (Odds Ratio: 0.48, 95% Confidence Interval: 27-0.86, P = 0.01). In a comparison between 24 NHB and 655 NHW with advanced fibrosis, the NAS (5.6 vs 4.9, P = 0.01) and lobular inflammation grade (2.2 vs 1.7, P < 0.002) were significantly higher among NHB with advanced fibrosis. One NHB and 23 NHW died during follow-up (0.30 vs 0.28 per 100 person-year follow-up). Seven and zero liver-related deaths occurred in NHW and NHB with NAFLD, respectively.

DISCUSSION

The risk of advanced fibrosis in NHB with NAFLD is significantly lower, after controlling for clinical risk factors and PNPLA3 genotype. Although their risk of advanced fibrosis was low, NHB with NAFLD and advanced fibrosis had higher NAS and lobular inflammation, indicating a difference in their relationship between necroinflammation and fibrosis.

PNPLA3 is a triglyceride lipase that mobilizes polyunsaturated fatty acids to facilitate hepatic secretion of large-sized very low-density lipoprotein

The I148M variant of PNPLA3 is closely associated with hepatic steatosis. Recent evidence indicates that the I148M mutant functions as an inhibitor of PNPLA2/ATGL-mediated lipolysis, leaving the role of wild-type PNPLA3 undefined. Despite showing a triglyceride hydrolase activity in vitro, PNPLA3 has yet to be established as a lipase in vivo. Here, we show that PNPLA3 preferentially hydrolyzes polyunsaturated triglycerides, mobilizing polyunsaturated fatty acids for phospholipid desaturation and enhancing hepatic secretion of triglyceride-rich lipoproteins. Under lipogenic conditions, mice with liver-specific knockout or acute knockdown of PNPLA3 exhibit aggravated liver steatosis and reduced plasma VLDL-triglyceride levels. Similarly, I148M-knockin mice show decreased hepatic triglyceride secretion during lipogenic stimulation. Our results highlight a specific context whereby the wild-type PNPLA3 facilitates the balance between hepatic triglyceride storage and secretion, and suggest the potential contribution of a loss-of-function by the I148M variant to the development of fatty liver disease in humans.

High red meat consumption among PNPLA3 polymorphism carriers is associated with NAFLD in a multi-center cross-sectional study

BACKGROUND & AIM

Patatin-like phospholipase domain-containing 3 gene (PNPLA3) polymorphism has been implicated in susceptibility to non-alcoholic fatty liver disease (NAFLD), with evidence for potential interaction with nutrition. However, the combination of meat consumption with genetic polymorphism has not been tested. Therefore, this study aims to test the association between the joint presence of PNPLA3 rs738409 G-allele with high meat consumption and NAFLD in populations with diverse meat consumption.

METHODS

A cross-sectional study among Israeli screening and Brazilian primary healthcare populations. Food consumption was assessed by a food-frequency questionnaire. PNPLA3 polymorphism was defined as homozygous (GG) or heterozygous (GC). Inconclusive/probable NAFLD was defined as a fatty liver index (FLI) ≥ 30 and probable NAFLD as FLI ≥ 60.

RESULTS

The sample included 511 subjects from the screening and primary healthcare populations (n = 213 and n = 298, respectively). Genetic polymorphism (homozygous GG or heterozygous GC) combined with high consumption of total meat, red and/or processed meat, unprocessed red meat, and processed meat was associated with the highest odds for inconclusive/probable NAFLD (OR = 2.75, 95%CI 1.27-5.97, p = 0.011; OR = 3.24, 1.43-7.34, p = 0.005; OR = 2.92, 1.32-6.47, p = 0.008; OR = 3.16, 1.46-6.83, p = 0.003, respectively), adjusting for age, gender, BMI, alcohol consumption, carbohydrate, and saturated fat intake. In addition, genetic polymorphism combined with high processed meat consumption was associated with the highest odds for probable NAFLD (OR = 2.40, 95%CI 1.04-5.56, p = 0.040).

CONCLUSIONS

High red meat intake may confer a greater risk for NAFLD among PNPLA3 polymorphism carriers. Prospective studies are needed to confirm these findings and consider minimizing red and processed meat consumption among PNPLA3 polymorphism carriers.

Associations of arsenic exposure and arsenic metabolism with the risk of non-alcoholic fatty liver disease

Growing evidences supported that arsenic exposure contributes to non-alcoholic fatty liver disease (NAFLD) risk, but findings were still inconsistent. Additionally, once absorbed, arsenic is methylated into monomethyl and dimethyl arsenicals. However, no studies investigated the association of arsenic metabolism with NAFLD. Our objectives were to evaluate the associations of arsenic exposure and arsenic metabolism with NAFLD prevalence. We conducted a case-control study with 1790 participants derived from Dongfeng-Tongji cohort and measured arsenic species (arsenite, arsenate, monomethylarsonate [MMA], dimethylarsinate [DMA], and arsenobetaine) in urine. Arsenic exposure (∑As) was defined as the sum of inorganic arsenic (iAs), MMA, and DMA. Arsenic metabolism was evaluated as the proportions of inorganic-related species (iAs%, MMA%, and DMA%) and methylation efficiency ratios (primary methylation index [PMI], secondary methylation index [SMI]). NAFLD was diagnosed by liver ultrasound. Logistic regression was used to evaluate the associations. The median of ∑As was 13.24 μg/g creatinine. The ∑As showed positive and nonlinear association with moderate/severe NAFLD (OR: per log-SD = 1.33, 95% CI: [1.03,1.71]; Pfor nonlinearity = 0.021). The iAs% (OR: per SD = 1.16, 95% CI: [1.03,1.30]) and SMI (OR: per log-SD = 1.16, 95% CI: [1.03,1.31]) showed positive while MMA% (OR: per SD = 0.80, 95% CI: [0.70,0.91]) and PMI (OR: per log-SD = 0.86, 95% CI: [0.77,0.96]) showed inverse associations with NAFLD. Moreover, the ORs (95% CI) of NAFLD for each 5% increase in iAs% was 1.36 (1.17,1.58) when MMA% decreased and 1.07 (1.01,1.13) when DMA% decreased; and for each 5% increase in MMA%, it was 0.74 (0.63,0.86) and 0.79 (0.69,0.91) when iAs% and DMA% decreased, respectively. The results suggest that inorganic arsenic exposure is positively associated with NAFLD risk and arsenic methylation efficiency plays a role in the NAFLD. The findings provide clues to explore potential interventions for the prevention of NAFLD. Prospective studies are needed to validate our findings.

NAFLD Fibrosis Progression and Type 2 Diabetes: The Hepatic-Metabolic Interplay

The bidirectional relationship between type 2 diabetes and (non-alcoholic fatty liver disease) NAFLD is indicated by the higher prevalence and worse disease course of one condition in the presence of the other, but also by apparent beneficial effects observed in one, when the other is improved. This is partly explained by their belonging to a multisystemic disease that includes components of the metabolic syndrome and shared pathogenetic mechanisms. Throughout the progression of NAFLD to more advanced stages, complex systemic and local metabolic derangements are involved. During fibrogenesis, a significant metabolic reprogramming occurs in the hepatic stellate cells, hepatocytes, and immune cells, engaging carbohydrate and lipid pathways to support the high-energy-requiring processes. The natural history of NAFLD evolves in a variable and dynamic manner, probably due to the interaction of a variable number of modifiable (diet, physical exercise, microbiota composition, etc.) and non-modifiable (genetics, age, ethnicity, etc.) risk factors that may intervene concomitantly, or subsequently/intermittently in time. This may influence the risk (and rate) of fibrosis progression/regression. The recognition and control of the factors that determine a rapid progression of fibrosis (or its regression) are critical, as the fibrosis stages are associated with the risk of liver-related and all-cause mortality.

The sulfur microbial diet and risk of nonalcoholic fatty liver disease: a prospective gene-diet study from the UK Biobank

BACKGROUND

The gut microbiota is closely related to liver diseases. The dietary pattern associated with sulfur-metabolizing bacteria in stool has been found to influence intestinal health.

OBJECTIVE

We aimed to investigate whether consuming the sulfur microbial diet is associated with nonalcoholic fatty liver disease (NAFLD).

METHODS

We included 143,918 participants of European descent from the UK Biobank. Information on serving sizes used per diet component was recorded by an online 24-h dietary assessment tool (Oxford WebQ). The total sulfur microbial diet score was constructed by summing the product of β-coefficients and corresponding serving sizes. NAFLD was ascertained using hospital inpatient and death records. Cox proportional hazard models were used to estimate the adjusted hazard ratio (HR) and 95% confidence interval (CI). Mediation analyses were used to investigate underlying mediators including body mass index, waist circumference, glucose, triglyceride, urate, and C-reactive protein. A polygenic risk score for NAFLD was constructed and stratified to assess whether the association is modified by genetic predisposition.

RESULTS

After a median follow-up of 11.7 y (interquartile range: 11.3-12.5 y), we documented 1540 incident cases of NAFLD. After adjustment for covariates, we observed an overall J-shaped relationship between the sulfur microbial diet and risk of NAFLD. Those in the highest quartile of sulfur microbial diet score had a 46% increased risk of NAFLD [HRQ4vsQ1 (95% CI): 1.46 (1.26, 1.69)]. We also found that this association is partly mediated by metabolic disorders and systemic inflammation. In addition, the positive association was stronger among individuals at higher genetic risk for NAFLD (Pinteraction = 0.044).

CONCLUSIONS

The sulfur microbial diet had adverse associations with incident NAFLD, particularly in those at a higher genetic risk. Our study may provide evidence on the role of sulfur-metabolizing bacteria in the diet-NAFLD association.

Association of liver fibrosis with extrahepatic cancer in steatotic liver disease patients with PNPLA3 I148M GG genotype

The impacts of patatin-like phospholipase domain-containing protein 3 (PNPLA3) I148M-rs738409, methylenetetrahydrofolate reductase (MTHFR) Ala222Val-rs1801133, and aldehyde dehydrogenase 2 (ALDH2) Glu504Lys-rs671 on the outcomes of Taiwanese patients with steatotic liver disease (SLD) have remained elusive. An 8-year prospective cohort study of patients with (n = 546) and without (n = 580) SLD (controls) was undertaken in a Taiwanese tertiary care center. The 546 SLD patients comprised 306 (56.0%) men and 240 (44.0%) women with mean ages of 53.3 and 56.4 years, respectively. Compared with the controls, SLD patients had an increased frequency of the PNPLA3 I148M-rs738409 GG genotype (25.5 vs. 5.9%, p = 0.001). Among the SLD patients, 236 (43.1%) suffered cardiovascular events, 52 (9.5%) showed extrahepatic cancers, 13 (2.38%) experienced hepatic events, including hepatocellular carcinoma (n = 3, 0.5%) and liver cirrhosis (n = 8, 1.47%), and none died. The Fibrosis-4 (FIB-4) scores were associated with extrahepatic cancer (hazard ratio [HR] 1.325; 95% confidence interval [CI], 1.038-1.691) and cirrhosis development (HR 1.532; 95% CI, 1.055-2.224), and the PNPLA3 I148M-rs738409 G allele (β = 0.158, 95% CI, 0.054-0.325) was associated with the FIB-4 score. Stratified analyses showed that the impact of the FIB-4 score on extrahepatic cancer development was evident only in SLD patients with the PNPLA3 I148M-rs738409 GG genotype (HR 1.543; 95% CI, 1.195-1.993) and not in patients with the GC or CC genotype. Moreover, the ALDH2 Glu504Lys-rs671 G allele had a dose-dependent effect on alcoholism, and the MTHFR and ALDH2 genotypes were not significantly associated with SLD patient outcomes. In conclusion, special vigilance should be exercised for emerging extrahepatic cancer in SLD patients with the PNPLA3 I148M-rs738409 GG genotype and high FIB-4 scores.

Lifestyle interventions in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a dynamic chronic liver disease that develops in close association with metabolic irregularities. Between 2016 and 2019, the global prevalence among adults was reported as 38% and among children and adolescents it was about 10%. NAFLD can be progressive and is associated with increased mortality from cardiovascular disease, extrahepatic cancers and liver complications. Despite these numerous adverse outcomes, no pharmacological treatments currently exist to treat nonalcoholic steatohepatitis, the progressive form of NAFLD. Therefore, the main treatment is the pursuit of a healthy lifestyle for both children and adults, which includes a diet rich in fruits, nuts, seeds, whole grains, fish and chicken and avoiding overconsumption of ultra-processed food, red meat, sugar-sweetened beverages and foods cooked at high heat. Physical activity at a level where one can talk but not sing is also recommended, including leisure-time activities and structured exercise. Avoidance of smoking and alcohol is also recommended. Policy-makers, community and school leaders need to work together to make their environments healthy by developing walkable and safe spaces with food stores stocked with culturally appropriate and healthy food items at affordable prices as well as providing age-appropriate and safe play areas in both schools and neighbourhoods.

A nutrigenetic precision approach for the management of non-alcoholic fatty liver disease

BACKGROUND & AIMS

The Patatin-like phospholipase domain-containing 3 (PNPLA3) rs738409 single nucleotide polymorphism (SNP) is one of the major genetic determinant of non-alcoholic fatty liver disease (NAFLD) and is strongly regulated by changes in energy balance and dietary factors. We aimed to investigate the association between the PNPLA3 rs738409 SNP, nutrient intake and NAFLD severity.

METHOD

PNPLA3-rs738409 SNP was genotyped in 181 patients with NAFLD who completed the EPIC Food Frequency Questionnaire. Liver steatosis was evaluated by Controlled Attenuation Parameter (CAP) (Fibroscan®530, Echosens). According to the established cut-off, a CAP value ≥ 300 dB/m was used to identify severe steatosis (S3). An independent group of 46 biopsy-proven NAFLD subjects was used as validation cohort.

RESULTS

Overall, median age was 53 years (range 44; 62) and 60.2% of patients were male. Most subjects (56.3%) had S3 and showed increased liver stiffness (p < 0.001), AST (p = 0.003) and ALT levels (p < 0.001) compared to those with CAP<300 dB/m. At logistic regression analyses we found that the interaction between carbohydrates intake and the carriers of the PNPLA3 G risk allele was significantly associated with S3 (p = 0.001). The same result was confirmed in the validation cohort, were the interaction between high carbohydrate intake (48%) and PNPLA3 SNP was significantly associated with steatosis ≥33% (p = 0.038).

CONCLUSION

The intake of greater than or equal to 48% carbohydrate in NAFLD patients carriers of the CG/GG allele of PNPLA3 rs738409 may increase the risk of significant steatosis.

Substrate-Specific Function of PNPLA3 Facilitates Hepatic VLDL-Triglyceride Secretion During Stimulated Lipogenesis

The I148M variant of PNPLA3 is strongly linked to hepatic steatosis. Evidence suggests a gain-of-function role for the I148M mutant as an ATGL inhibitor, leaving the physiological relevance of wild-type PNPLA3 undefined. Here we show that PNPLA3 selectively degrades triglycerides (TGs) enriched in polyunsaturated fatty acids (PUFAs) independently of ATGL in cultured cells and mice. Lipidomics and metabolite tracing analyses demonstrated that PNPLA3 mobilizes PUFAs from intracellular TGs for phospholipid desaturation, supporting hepatic secretion of TG-rich lipoproteins. Consequently, mice with liver-specific knockout or acute knockdown of PNPLA3 both exhibited aggravated liver steatosis and concomitant decreases in plasma VLDL-TG, phenotypes that manifest only under lipogenic conditions. I148M-knockin mice similarly displayed impaired hepatic TG secretion during lipogenic stimulation. Our results highlight a specific context whereby PNPLA3 facilitates the balance between hepatic TG storage and secretion and suggest the potential contributions of I148M variant loss-of-function to the development of hepatic steatosis in humans.

Summary Statement

We define the physiological role of wild type PNPLA3 in maintaining hepatic VLDL-TG secretion.

A TNFα/Miz1-positive feedback loop inhibits mitophagy in hepatocytes and propagates non-alcoholic steatohepatitis

BACKGROUND & AIMS

Non-alcoholic steatohepatitis (NASH) is a chronic inflammatory disease that can further progress to cirrhosis and hepatocellular carcinoma. However, the key molecular mechanisms behind this process have not been clarified.

METHODS

We analyzed human NASH and normal liver tissue samples by RNA-sequencing and liquid chromatography-mass spectrometry, identifying hepatocyte cytosolic protein Myc-interacting zinc-finger protein 1 (Miz1) as a potential target in NASH progression. We established a Western diet+fructose-induced NASH model in hepatocyte-specific Miz1 knockout and adeno-associated virus type 8-overexpressing mice. Human NASH liver organoids were used to confirm the mechanism, and immunoprecipitation and mass spectrometry were used to detect proteins that could interact with Miz1.

RESULTS

We demonstrate that Miz1 is reduced in hepatocytes in human NASH. Miz1 is shown to bind to peroxiredoxin 6 (PRDX6), retaining it in the cytosol, blocking its interaction with mitochondrial Parkin at Cys431, and inhibiting Parkin-mediated mitophagy. In NASH livers, loss of hepatocyte Miz1 results in PRDX6-mediated inhibition of mitophagy, increased dysfunctional mitochondria in hepatocytes, and production of proinflammatory cytokines, including TNFα, by hepatic macrophages. Crucially, the increased production of TNFα results in a further reduction in hepatocyte Miz1 by E3-ubiquitination. This produces a positive feedback loop of TNFα-mediated hepatocyte Miz1 degradation, resulting in PRDX6-mediated inhibition of hepatocyte mitophagy, with the accumulation of dysfunctional mitochondria in hepatocytes and increased macrophage TNFα production.

CONCLUSIONS

Our study identified hepatocyte Miz1 as a suppressor of NASH progression via its role in mitophagy; we also identified a positive feedback loop by which TNFα production induces degradation of cytosolic Miz1, which inhibits mitophagy and thus leads to increased macrophage TNFα production. Interruption of this positive feedback loop could be a strategy to inhibit the progression of NASH.

IMPACT AND IMPLICATIONS

Non-alcoholic steatohepatitis (NASH) is a chronic inflammatory disease that can further develop into cirrhosis and hepatocellular carcinoma. However, the key molecular mechanism of this process has not been fully clarified. Herein, we identified a positive feedback loop of macrophage TNFα-mediated hepatocyte Miz1 degradation, resulting in PRDX6-mediated inhibition of hepatocyte mitophagy, aggravation of mitochondrial damage and increased macrophage TNFα production. Our findings not only provide mechanistic insight into NASH progression but also provide potential therapeutic targets for patients with NASH. Our human NASH liver organoid culture is therefore a useful platform for exploring treatment strategies for NASH development.

The Role of Choline, Soy Isoflavones, and Probiotics as Adjuvant Treatments in the Prevention and Management of NAFLD in Postmenopausal Women

Nonalcoholic fatty liver disease (NAFLD) is a prevalent condition among postmenopausal women that can lead to severe liver dysfunction and increased mortality. In recent years, research has focused on identifying potential lifestyle dietary interventions that may prevent or treat NAFLD in this population. Due to the complex and multifactorial nature of NAFLD in postmenopausal women, the disease can present as different subtypes, with varying levels of clinical presentation and variable treatment responses. By recognizing the significant heterogeneity of NAFLD in postmenopausal women, it may be possible to identify specific subsets of individuals who may benefit from targeted nutritional interventions. The purpose of this review was to examine the current evidence supporting the role of three specific nutritional factors-choline, soy isoflavones, and probiotics-as potential nutritional adjuvants in the prevention and treatment of NAFLD in postmenopausal women. There is promising evidence supporting the potential benefits of these nutritional factors for NAFLD prevention and treatment, particularly in postmenopausal women, and further research is warranted to confirm their effectiveness in alleviating hepatic steatosis in this population.

Type 2 Diabetes Mellitus, Non-Alcoholic Fatty Liver Disease, and Metabolic Repercussions: The Vicious Cycle and Its Interplay with Inflammation

The prevalence of metabolic-related disorders, such as non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (DM2), has been increasing. Therefore, developing improved methods for the prevention, treatment, and detection of these two conditions is also necessary. In this study, our primary focus was on examining the role of chronic inflammation as a potential link in the pathogenesis of these diseases and their interconnections. A comprehensive search of the PubMed database using keywords such as "non-alcoholic fatty liver disease", "type 2 diabetes mellitus", "chronic inflammation", "pathogenesis", and "progression" yielded 177 relevant papers for our analysis. The findings of our study revealed intricate relationships between the pathogenesis of NAFLD and DM2, emphasizing the crucial role of inflammatory processes. These connections involve various molecular functions, including altered signaling pathways, patterns of gene methylation, the expression of related peptides, and up- and downregulation of several genes. Our study is a foundational platform for future research into the intricate relationship between NAFLD and DM2, allowing for a better understanding of the underlying mechanisms and the potential for introducing new treatment standards.

Clinical characteristics and management of patients with nonalcoholic steatohepatitis in a real-world setting: analysis of the Ipsos NASH therapy monitor database

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is the more severe, inflammatory type of nonalcoholic fatty liver disease (NAFLD). NASH, a leading indication for liver transplantation, is growing in prevalence. The extent of liver fibrosis, ranging from fibrosis stage (FS) of none (F0) to cirrhosis (F4), is a strong predictor of health outcomes. There is little information on patient demographics and clinical characteristics by fibrosis stage and NASH treatment outside of academic medical centers.

METHODS

We conducted a cross-sectional observational study using Ipsos' syndicated NASH Therapy Monitor database, consisting of medical chart audits provided by sampled NASH-treating physicians in the United States in 2016 (n = 174) and 2017 (n = 164). Data was collected online.

RESULTS

Of 2,366 patients reported on by participating physicians and included in the analysis, 68% had FS F0-F2, 21% had bridging fibrosis (F3), and 9% had cirrhosis (F4). Common comorbidities were type 2 diabetes (56%), hyperlipidemia (44%), hypertension (46%), and obesity (42%). Patients with more advanced fibrosis scores (F3-F4) had higher comorbidity rates than patients with F0-F2. Commonly used diagnostic tests included ultrasound (80%), liver biopsy (78%), AST/ALT ratio (43%), NAFLD fibrosis score (25%), transient elastography (23%), NAFLD liver fat score (22%), and Fatty Liver Index (19%). Most commonly prescribed medications were vitamin E (53%), statins (51%), metformin (47%), angiotensin converting enzyme inhibitors (28%), and beta blockers (22%). Medications were commonly prescribed for reasons other than their known effects.

CONCLUSION

Physicians in this study, drawn from a spectrum of practice settings, relied on ultrasound and liver biopsy for diagnosis and vitamin E, statins, and metformin for pharmacological treatment of NASH. These findings imply poor adherence to guidelines in the diagnosis and management of NAFLD and NASH. Nonalcoholic steatohepatitis (NASH) is a liver disease caused by excess fat in the liver which can lead to liver inflammation and scarring (fibrosis), ranging from stage F0 (no scarring) to F4 (advanced scarring). The stage of liver scarring can predict the likelihood of future health problems, including liver failure and liver cancer. However, we do not fully understand how patient characteristics may vary at different stages of liver scarring. We looked at medical information from physicians treating patients diagnosed with NASH to understand how patient characteristics might differ based on the severity of their liver scarring. The majority (68%) of patients were stage F0-F2, with 30% having advanced scarring (F3-F4). In addition to NASH, many patients also had type 2 diabetes, high cholesterol, high blood pressure, and obesity. Patients with more advanced scarring (F3-F4) were more likely to have these diseases than patients with less severe disease (F0-F2). Diagnosis of NASH by participating physicians was based on tests including imaging (ultrasound, CT scan, MRI), liver biopsy, blood tests, and whether patients had other conditions that would put them at risk for NASH. The medications that the doctors prescribed most often to their patients included vitamin E and drugs to treat high cholesterol, high blood pressure, or diabetes. Medications were frequently prescribed for reasons other than their known effects. By understanding how patient characteristics vary by stages of liver scarring and how NASH is currently managed may help guide the evaluation and treatment of NASH when NASH-specific therapies become available.

Eating, diet, and nutrition for the treatment of non-alcoholic fatty liver disease

Nutrition and dietary interventions are a central component in the pathophysiology, but also a cornerstone in the management of patients with non-alcoholic fatty liver disease (NAFLD). Summarizing our rapidly advancing understanding of how our diet influences our metabolism and focusing on specific effects on the liver, we provide a comprehensive overview of dietary concepts to counteract the increasing burden of NAFLD. Specifically, we emphasize the importance of dietary calorie restriction independently of the macronutrient composition together with adherence to a Mediterranean diet low in added fructose and processed meat that seems to exert favorable effects beyond calorie restriction. Also, we discuss intermittent fasting as a type of diet specifically tailored to decrease liver fat content and increase ketogenesis, awaiting future study results in NAFLD. Finally, personalized dietary recommendations could be powerful tools to increase the effectiveness of dietary interventions in patients with NAFLD considering the genetic background and the microbiome, among others.

Genetics in non-alcoholic fatty liver disease: The role of risk alleles through the lens of immune response

The knowledge on the genetic component of non-alcoholic fatty liver disease (NAFLD) has grown exponentially over the last 10 to 15 years. This review summarizes the current evidence and the latest developments in the genetics of NAFLD and non-alcoholic steatohepatitis (NASH) from the immune system's perspective. Activation of innate and or adaptive immune response is an essential driver of NAFLD disease severity and progression. Lipid and immune pathways are crucial in the pathophysiology of NAFLD and NASH. Here, we highlight novel applications of genomic techniques, including single-cell sequencing and the genetics of gene expression, to elucidate the potential involvement of NAFLD/NASH-risk alleles in modulating immune system cells. Together, our focus is to provide an overview of the potential involvement of the NAFLD/NASH-related risk variants in mediating the immune-driven liver disease severity and diverse systemic pleiotropic effects.

Nutritional Genomics in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a common chronic condition associated with genetic and environmental factors in which fat abnormally accumulates in the liver. NAFLD is epidemiologically associated with obesity, type 2 diabetes, and dyslipidemia. Environmental factors, such as physical inactivity and an unbalanced diet, interact with genetic factors, such as epigenetic mechanisms and polymorphisms for the genesis and development of the condition. Different genetic polymorphisms seem to be involved in this context, including variants in PNPLA3, TM6SF2, PEMT, and CHDH genes, playing a role in the disease's susceptibility, development, and severity. From carbohydrate intake and weight loss to omega-3 supplementation and caloric restriction, different dietary and nutritional factors appear to be involved in controlling the onset and progression of NAFLD conditions influencing metabolism, gene, and protein expression. The polygenic risk score represents a sum of trait-associated alleles carried by an individual and seems to be associated with NAFLD outcomes depending on the dietary context. Understanding the exact extent to which lifestyle interventions and genetic predispositions can play a role in the prevention and management of NAFLD can be crucial for the establishment of a personalized and integrative approach to patients.

What do we know about nutrient-based strategies targeting molecular mechanisms associated with obesity-related fatty liver disease?

Obesity is a risk factor for developing nonalcoholic fatty liver disease (NAFLD), and the associated molecular mechanisms could be targeted with nutrient-based strategies. Therefore, it is necessary to review the current mechanisms to propose further treatments. Obesity facilitates the onset of insulin resistance, lipidic abnormalities, hepatic fat accumulation, lipid peroxidation, mitochondrial dysfunction, excessive reactive oxygen species (ROS) production, and inflammation, all related to further steatosis progression and fibrosis. Microbiota alterations can also influence liver disease by the translocation of pathogenic bacteria, energy extraction from short chain fatty acids (SCFAs), intestinal suppression of the expression of fasting-induced adipose factor (FIAF), reduction of bile acids, and altered choline metabolism. There are also genetic polymorphisms in metabolic proteins that predispose to a higher risk of liver diseases, such as those found in the patatin-like phospholipase domain-containing 3 (PNPLA3), transmembrane 6 superfamily member 2 (TM6SF2), membrane-bound O-acyltransferase domain-containing 7 (MBOAT7) or also known as lysophosphatidylinositol acyltransferase 1 (LPIAT1), transmembrane channel-like 4 genes (TMC4), fat mass and obesity-associated protein (FTO), the b Klotho (KLB) and carboxylesterase (CES1). No clear dietary guidelines target all mechanisms related to NAFLD development and progression. However, energy and carbohydrate intake restriction, regular physical exercise, supplementation of antioxidants, and restoration of gut microbiota seem to have beneficial effects on the new proposed features of NAFLD.

Interaction between the PNPLA3 Gene and Nutritional Factors on NAFLD Development: The Korean Genome and Epidemiology Study

Genetic and nutritional factors contribute to the development of non-alcoholic fatty liver disease (NAFLD); however, gene-diet interactions in NAFLD development are poorly understood. In this case-control study, a large dataset from the Korean Genome and Epidemiology Study cohort (n = 72,299) comprising genomic data, medical records, social history, and dietary data was used. We investigated the interactions between the PNPLA3 rs738409 genotype and nutritional factors and their possible effect on the risk of NAFLD development in 2950 patients with NAFLD and 12,907 controls. In the PNPLA3 risk allele group, high protein, fat, sodium, phosphorus, niacin, and vitamin B6 intakes were associated with a decreased risk of NAFLD. In the non-risk allele group, only high fat intake was associated with a decreased risk of NAFLD. Among these nutrients, high sodium intake had a significant protective interaction with the PNPLA3 genotype against NAFLD (p = 0.002). Among salty foods, only kimchi had a significant protective effect against the PNPLA3 genotype (p = 0.012). Thus, the PNPLA3 genotype is differentially associated with nutritional factors. In particular, it interacts with kimchi, a fermented vegetable dish. Therefore, fermented vegetables may serve as a tailored therapeutic food for people with the PNPLA3 risk allele.

Multi-Omics Nutritional Approaches Targeting Metabolic-Associated Fatty Liver Disease

Currently, metabolic-associated fatty liver disease (MAFLD) is a leading global cause of chronic liver disease, and is expected to become one of the most common indications of liver transplantation. MAFLD is associated with obesity, involving multiple mechanisms such as alterations in lipid metabolism, insulin resistance, hyperinflammation, mitochondrial dysfunction, cell apoptosis, oxidative stress, and extracellular matrix formation. However, the onset and progression of MAFLD is variable among individuals, being influenced by intrinsic (personal) and external environmental factors. In this context, sequence structural variants across the human genome, epigenetic phenomena (i.e., DNA methylation, histone modifications, and long non-coding RNAs) affecting gene expression, gut microbiota dysbiosis, and metabolomics/lipidomic fingerprints may account for differences in MAFLD outcomes through interactions with nutritional features. This knowledge may contribute to gaining a deeper understanding of the molecular and physiological processes underlying MAFLD pathogenesis and phenotype heterogeneity, as well as facilitating the identification of biomarkers of disease progression and therapeutic targets for the implementation of tailored nutritional strategies. This comprehensive literature review highlights the potential of nutrigenetic, nutriepigenetic, nutrimetagenomic, nutritranscriptomics, and nutrimetabolomic approaches for the prevention and management of MAFLD in humans through the lens of precision nutrition.

One size does not fit all; practical, personal tailoring of the diet to NAFLD patients

Different dietary regimens for weight loss have developed over the years. Since the most evidenced treatment for non-alcoholic fatty liver disease (NAFLD) is weight reduction, it is not surprising that more diets targeting obesity are also utilized for NAFLD treatment. However, beyond the desired weight loss effects, one should not ignore the dietary composition of each diet, which may not necessarily be healthy or safe over the long term for hepatic and extrahepatic outcomes, especially cardiometabolic outcomes. Some of these diets are rich in saturated fat and red meat, are very strict, and require close medical supervision. Some may also be very difficult to adhere to for long periods, thus reducing the patient's motivation. The evidence for a direct benefit to NAFLD by restrictive diets such as very-low-carb, ketogenic, very-low-calorie diets, and intermittent fasting is scarce, and the long-term safety has not been tested. Nowadays, the approach is that the diet should be tailored to the patient's cultural and personal preferences. There is strong evidence for the independent protective association of NAFLD with a diet based on healthy eating patterns of minimally-processed foods, low in sugar and saturated fat, high in polyphenols, and healthy types of fats. This leads to the conclusion that a Mediterranean diet should serve as a basis that can be restructured into other kinds of diets. This review will elaborate on the different diets and their role in NAFLD. It will provide a practical guide to tailor the diet to the patients without compromising its composition and safety.

Methionine cycle in nonalcoholic fatty liver disease and its potential applications

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.

Metabolic dysfunction-associated fatty liver disease: advances in genetic and epigenetic implications

PURPOSE OF REVIEW

Fatty liver associated with metabolic dysfunction, also known under the acronym NAFLD (nonalcoholic fatty liver disease) is the leading global cause of chronic liver disease. In this review, we address the state of research on genetics and epigenetics of NAFLD with focus on key discoveries and conceptual advances over the past 2 years.

RECENT FINDINGS

The analysis of NAFLD-associated genetic variant effects on the whole-transcriptome, including quantitative trait loci (QTL) associated with gene expression (eQTL) or splicing (sQTL) may explain pleiotropic effects. Functional experiments on NAFLD-epigenetics, including profiling of liver chromatin accessibility quantitative trait loci (caQTL) show co-localization with numerous genome-wide association study signals linked to metabolic and cardiovascular traits. Novel studies provide insights into the modulation of the hepatic transcriptome and epigenome by tissue microbiotas. Genetic variation of components of the liver cellular respirasome may result in broad cellular and metabolic effects. Mitochondrial noncoding RNAs may regulate liver inflammation and fibrogenesis. RNA modifications as N6-methyladenosine may explain sex-specific differences in liver gene transcription linked to lipid traits.

SUMMARY

The latest developments in the field of NAFLD-genomics can be leveraged for identifying novel disease mechanisms and therapeutic targets that may prevent the morbidity and mortality associated with disease progression.

VIDEO ABSTRACT

http://links.lww.com/COL/A23.

Nonalcoholic Fatty Liver Disease in Children

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. It represents a spectrum of disease from simple hepatic steatosis to steatohepatitis that may develop into progressive hepatic fibrosis and even cirrhosis. NAFLD is the most rapidly increasing indication for liver transplantation in adults. In children, the incidence of NAFLD has also increased over the past decade. Although the majority of children with NAFLD are overweight or obese, there is an increasing subset of children with normal body mass index with so-called lean NAFLD. NAFLD in children is associated with several extrahepatic manifestations, including hyperlipidemia, insulin resistance, and obstructive sleep apnea. The pathogenesis of NAFLD in children involves a multifactorial interaction among genetics, in utero exposures, early childhood exposures, and ongoing nutritional exposures. Although there are some similarities between pediatric NAFLD and adult NAFLD, liver biopsies in children show histologic differences between the two. The current standard-of-care treatment of NAFLD in children is lifestyle change to decrease caloric intake and increase physical activity. There are no medications currently approved for the treatment of NAFLD in children. This article aims to summarize the current understanding of pediatric NAFLD and future directions for intervention and therapeutic aims.

Diet and exercise in NAFLD/NASH: Beyond the obvious

Lifestyle represents the most relevant factor for non-alcoholic fatty liver disease (NAFLD) as the hepatic manifestation of the metabolic syndrome. Although a tremendous body of clinical and preclinical data on the effectiveness of dietary and lifestyle interventions exist, the complexity of this topic makes firm and evidence-based clinical recommendations for nutrition and exercise in NAFLD difficult. The aim of this review is to guide readers through the labyrinth of recent scientific findings on diet and exercise in NAFLD and non-alcoholic steatohepatitis (NASH), summarizing "obvious" findings in a holistic manner and simultaneously highlighting stimulating aspects of clinical and translational research "beyond the obvious". Specifically, the importance of calorie restriction regardless of dietary composition and evidence from low-carbohydrate diets to target the incidence and severity of NAFLD are discussed. The aspect of ketogenesis-potentially achieved via intermittent calorie restriction-seems to be a central aspect of these diets warranting further investigation. Interactions of diet and exercise with the gut microbiota and the individual genetic background need to be comprehensively understood in order to develop personalized dietary concepts and exercise strategies for patients with NAFLD/NASH.

The Protection Conferred by HSD17B13 rs72613567 Polymorphism on Risk of Steatohepatitis and Fibrosis May Be Limited to Selected Subgroups of Patients With NAFLD

INTRODUCTION

Our study aimed to explore how PNPLA3 rs738409 or phenotypic risk factors may moderate the relationship between HSD17B13 rs72613567 and risk of steatohepatitis and fibrosis.

METHODS

This analysis consisted of 1,153 non-Hispanic whites with biopsy-proven nonalcoholic fatty liver disease enrolled in the nonalcoholic steatohepatitis Clinical Research Network studies. Nonalcoholic fatty liver disease severity was determined by liver histology scored centrally according to the nonalcoholic steatohepatitis Clinical Research Network criteria. Moderation and logistic regression analyses were performed to identify the influence of moderators (PNPLA3 rs738409, age, sex, body mass index, and diabetes) on the relationship between HSD17B13 rs72613567 and risk of steatohepatitis and fibrosis.

RESULTS

HSD17B13 rs72613567 genotype frequency was as follows: (-/-), 64%; (-/A), 30%; (A/A), 6%. Moderation analysis showed that the protective effect of HSD17B13 rs72613567 A-allele on risk of steatohepatitis remained only significant among patients with PNPLA3 rs738409 genotype CC (β coeff: -0.19, P = 0.019), women (β coeff: -0.18, P < 0.001), patients of age ≥ 45 years (β coeff: -0.18, P < 0.001), patients with body mass index ≥ 35 kg/m2 (β coeff: -0.17, P < 0.001), and patients with diabetes (β coeff: -0.18, P = 0.020). Among women, the protective effect of HSD17B131 rs72613567 A-allele on risk of steatohepatitis was stronger in those aged ≥ 51 years. Logistic regression-based sensitivity analysis including various important subgroups confirmed our observations.

DISCUSSION

The protection conferred by HSD17B13 rs72613567 A-allele on risk of steatohepatitis and fibrosis may be limited to selected subgroups of individuals who are aged ≥ 45 years, women and have class ≥ 2 obesity or diabetes, and those with PNPLA3 rs738409 CC genotype.