Genome-wide association study identifies variants associated with histologic features of nonalcoholic Fatty liver disease

Genome-wide association analysis to search for new loci associated with stroke risk in Northwestern Chinese population

BACKGROUND AND PURPOSE

Genetic factors play an important role in the pathogenesis of stroke(S). This study aimed to screen the loci associated with S risk in northwestern Chinese population by genome-wide association analysis (GWAS).

METHODS

A total of 1394 subjects, including 682 S patients and 692 controls, were enrolled in this study. SPSS 25.0 software was used for statistical analysis, and the independent sample t-test as well as Chi-square test were used to analyze the differences in age and gender between the case and control groups. The Precision Medicine Diversity Array (PMDA) genotyping chip was used in this study. The genotyping platform was the Gene Titan multi-channel instrument, and the Axiom Analysis Suite 6.0 software was used for the data analyzing. Besides, the LASSO analysis, SNP-SNP and GO/KEGG analysis were conducted to analyze the association between significant loci and S risk.

RESULTS

A total of 30 SNPs were found to be associated with the S risk based on additive model (p < 5 × 10-8). After the LASSO screening, 22 SNPs showed the diagnostic value in S. The SNPs interaction analysis further screened the SNP-SNP interaction groups associated with the S risk(p < 0.05). Finally, the GO/KEGG analysis discovered the suggestive significance loci could be involved in the S development mainly by immune-related functions and pathways.

CONCLUSION

This study discovered 30 S related SNPs and analyzed the potential pathways associated with genes located on the 30 SNPs, which were beneficial for enriching the genetic mechanism analysis of S in northwestern Chinese population.

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.

Crosstalk in extrahepatic and hepatic system in NAFLD/NASH

Non-alcoholic fatty liver disease (NAFLD) has emerged as the most prevalent chronic liver disease globally. Non-alcoholic steatohepatitis (NASH) represents an extremely progressive form of NAFLD, which, without timely intervention, may progress to cirrhosis or hepatocellular carcinoma. Presently, a definitive comprehension of the pathogenesis of NAFLD/NASH eludes us, and pharmacological interventions targeting NASH specifically remain constrained. The aetiology of NAFLD encompasses a myriad of external factors including environmental influences, dietary habits and gender disparities. More significantly, inter-organ and cellular interactions within the human body play a role in the development or regression of the disease. In this review, we categorize the influences affecting NAFLD both intra- and extrahepatically, elaborating meticulously on the mechanisms governing the onset and progression of NAFLD/NASH. This exploration delves into progress in aetiology and promising therapeutic targets. As a metabolic disorder, the development of NAFLD involves complexities related to nutrient metabolism, liver-gut axis interactions and insulin resistance, among other regulatory functions of extraneous organs. It further encompasses intra-hepatic interactions among hepatic cells, Kupffer cells (KCs) and hepatic stellate cells (HSCs). A comprehensive understanding of the pathogenesis of NAFLD/NASH from a macroscopic standpoint is instrumental in the formulation of future therapies for NASH.

Serum proteome signatures associated with liver steatosis in adolescents with obesity

PURPOSE

Childhood obesity, a pressing global health issue, significantly increases the risk of metabolic complications, including metabolic dysfunction associated with steatotic liver disease (MASLD). Accurate non-invasive tests for early detection and screening of steatosis are crucial. In this study, we explored the serum proteome, identifying proteins as potential biomarkers for inclusion in non-invasive steatosis diagnosis tests.

METHODS

Fifty-nine obese adolescents underwent ultrasonography to assess steatosis. Serum samples were collected and analyzed by targeted proteomics with the Proximity Extension Assay technology. Clinical and biochemical parameters were evaluated, and correlations among them, the individuated markers, and steatosis were performed. Receiver operating characteristic (ROC) curves were used to determine the steatosis diagnostic performance of the identified candidates, the fatty liver index (FLI), and their combination in a logistic regression model.

RESULTS

Significant differences were observed between subjects with and without steatosis in various clinical and biochemical parameters. Gender-related differences in the serum proteome were also noted. Five circulating proteins, including Cathepsin O (CTSO), Cadherin 2 (CDH2), and Prolyl endopeptidase (FAP), were identified as biomarkers for steatosis. CDH2, CTSO, Leukocyte Immunoglobulin Like Receptor A5 (LILRA5), BMI, waist circumference, HOMA-IR, and FLI, among others, significantly correlated with the steatosis degree. CDH2, FAP, and LDL combined in a logit model achieved a diagnostic performance with an AUC of 0.91 (95% CI 0.75-0.97, 100% sensitivity, 84% specificity).

CONCLUSIONS

CDH2 and FAP combined with other clinical parameters, represent useful tools for accurate diagnosis of fatty liver, emphasizing the importance of integrating novel markers into diagnostic algorithms for MASLD.

Differential Effects of Genetic Polymorphism on Comorbid Disease in Metabolic Dysfunction-Associated Steatotic Liver Disease

BACKGROUND & AIMS

PNPLA3 rs738409, TM6SF2 rs58542926, and HSD17B13 rs72613567 have been associated with an increased risk of liver-related events (LREs) in patients with metabolic dysfunction-associated steatotic liver disease (MASLD). In this study, we investigated the combined effects of these variants on LREs.

METHODS

The longitudinal multicenter cohort study enrolled 1178 patients with biopsy-proven MASLD. We calculated the genetic risk of hepatic fibrosis and LRE according to the impact of these variants.

RESULTS

Patients with genetic fibrosis scores of 2, 3, and 4 or 5 were at greater risk than patients with scores of 0 or 1, with odds ratios of 2.45 (95% CI, 1.27-4.74), 2.14 (95% CI, 1.17-3.94), and 2.54 (95% CI, 1.35-4.77), respectively. Multivariate analysis revealed that PNPLA3 and TM6SF2, but not HSD17B13, were associated significantly with LRE development. The hazard ratio of the genetic high-risk group for LRE was 1.91 (95% CI, 1.20-3.04). The higher risk of LRE development in the genetic high-risk group also was seen in patients with F ≥ 3 or Fibrosis-4 index > 2.67. The hazard ratios of the genetic high-risk group for LRE were greater in patients without obesity, without diabetes, and of younger age compared with patients with obesity, with diabetes, or of older age, respectively.

CONCLUSIONS

This combination of MASLD-related genetic variants is useful for predicting LREs in Japanese patients with MASLD. The genetic risk according to these variants is useful for LRE risk assessment, especially in patients without metabolic risk factors or in younger patients in Japan.

Review article: Hepatic steatosis and its associations with acute and chronic liver diseases

BACKGROUND

Hepatic steatosis is a common finding in liver histopathology and the hallmark of metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease (NAFLD), whose global prevalence is rising.

AIMS

To review the histopathology of hepatic steatosis and its mechanisms of development and to identify common and rare disease associations.

METHODS

We reviewed literature on the basic science of lipid droplet (LD) biology and clinical research on acute and chronic liver diseases associated with hepatic steatosis using the PubMed database.

RESULTS

A variety of genetic and environmental factors contribute to the development of chronic hepatic steatosis or steatotic liver disease, which typically appears macrovesicular. Microvesicular steatosis is associated with acute mitochondrial dysfunction and liver failure. Fat metabolic processes in hepatocytes whose dysregulation leads to the development of steatosis include secretion of lipoprotein particles, uptake of remnant lipoprotein particles or free fatty acids from blood, de novo lipogenesis, oxidation of fatty acids, lipolysis and lipophagy. Hepatic insulin resistance is a key feature of MASLD. Seipin is a polyfunctional protein that facilitates LD biogenesis. Assembly of hepatitis C virus takes place on LD surfaces. LDs make important, functional contact with the endoplasmic reticulum and other organelles.

CONCLUSIONS

Diverse liver pathologies are associated with hepatic steatosis, with MASLD being the most important contributor. The biogenesis and dynamics of LDs in hepatocytes are complex and warrant further investigation. Organellar interfaces permit co-regulation of lipid metabolism to match generation of potentially toxic lipid species with their LD depot storage.

Clinical and genetic risk factors for progressive fibrosis in metabolic dysfunction-associated steatotic liver disease

BACKGROUND

Fibrosis-4 (FIB4) is a recommended noninvasive test to assess hepatic fibrosis among patients with metabolic dysfunction-associated steatotic liver disease (MASLD). Here, we used FIB4 trajectory over time (ie, "slope" of FIB4) as a surrogate marker of liver fibrosis progression and examined if FIB4 slope is associated with clinical and genetic factors among individuals with clinically defined MASLD within the Million Veteran Program Cohort.

METHODS

In this retrospective cohort study, FIB4 slopes were estimated through linear regression for participants with clinically defined MASLD and FIB4 <2.67 at baseline. FIB4 slope was correlated with demographic parameters and clinical outcomes using logistic regression and Cox proportional hazard models. FIB4 slope as a quantitative phenotype was used in a genome-wide association analysis in ancestry-specific analysis and multiancestry meta-analysis using METAL.

RESULTS

FIB4 slopes, generated from 98,361 subjects with MASLD (16,045 African, 74,320 European, and 7996 Hispanic), showed significant associations with sex, ancestry, and cardiometabolic risk factors (p < 0.05). FIB4 slopes also correlated strongly with hepatic outcomes and were independently associated with time to cirrhosis. Five genetic loci showed genome-wide significant associations (p < 5 × 10-8) with FIB4 slope among European ancestry subjects, including 2 known (PNPLA3 and TM6SF2) and 3 novel loci (TERT 5.1 × 10-11; LINC01088, 3.9 × 10-8; and MRC1, 2.9 × 10-9).

CONCLUSIONS

Linear trajectories of FIB4 correlated significantly with time to progression to cirrhosis, with liver-related outcomes among individuals with MASLD and with known and novel genetic loci. FIB4 slope may be useful as a surrogate measure of fibrosis progression.

Identification of key markers for the stages of nonalcoholic fatty liver disease: An integrated bioinformatics analysis and experimental validation

BACKGROUND

The identification of biomarkers for the early diagnosis of nonalcoholic fatty liver disease (NAFLD) is urgently needed. Here, we aimed to identify NAFLD biomarkers in the early stages of steatosis (SS) and nonalcoholic steatohepatitis (NASH) based on differential gene expression from bioinformatics data.

METHODS

A meta-analysis was performed from transcriptomic databases retrieved from public repositories containing data from biopsies of patients at various stages of NAFLD development. The status of the selected molecules was validated in the serum of patients with NAFLD by ELISA.

RESULTS

We identified 121 differentially expressed genes (DEGs) associated with SS and 402 associated with NASH. Gene Ontology (GO) enrichment revealed that the altered genes were primarily associated with dysfunction of primary cellular processes, and pathway analyses were mainly related to cholesterol metabolism. We identified ACSS2, PCSK9, and CYP7A1 as candidate biomarkers for SS and ANGPTL3, CD36, CYP51A1, FASN, FAS, FDFT1, and LSS as candidate biomarkers for NASH.

CONCLUSIONS

By experimental validation of bioinformatics data from patients with NAFLD, we identified promising biomarkers for detecting SS and NASH that might be useful for screening and diagnosing early NAFLD stages in humans.

Genetic Associations with Placental Proteins in Maternal Serum Identify Biomarkers for Hypertension in Pregnancy

Background

Preeclampsia is a complex syndrome that accounts for considerable maternal and perinatal morbidity and mortality. Despite its prevalence, no effective disease-modifying therapies are available. Maternal serum placenta-derived proteins have been in longstanding use as markers of risk for aneuploidy and placental dysfunction, but whether they have a causal contribution to preeclampsia is unknown.

Objective

We aimed to investigate the genetic regulation of serum placental proteins in early pregnancy and their potential causal links with preeclampsia and gestational hypertension.

Study design

This study used a nested case-control design with nulliparous women enrolled in the nuMoM2b study from eight clinical sites across the United States between 2010 and 2013. The first- and second-trimester serum samples were collected, and nine proteins were measured, including vascular endothelial growth factor (VEGF), placental growth factor, endoglin, soluble fms-like tyrosine kinase-1 (sFlt-1), a disintegrin and metalloproteinase domain-containing protein 12 (ADAM-12), pregnancy-associated plasma protein A, free beta-human chorionic gonadotropin, inhibin A, and alpha-fetoprotein. This study used genome-wide association studies to discern genetic influences on these protein levels, treating proteins as outcomes. Furthermore, Mendelian randomization was used to evaluate the causal effects of these proteins on preeclampsia and gestational hypertension, and their further causal relationship with long-term hypertension, treating proteins as exposures.

Results

A total of 2,352 participants were analyzed. We discovered significant associations between the pregnancy zone protein locus and concentrations of ADAM-12 (rs6487735, P= 3.03×10 -22 ), as well as between the vascular endothelial growth factor A locus and concentrations of both VEGF (rs6921438, P= 7.94×10 -30 ) and sFlt-1 (rs4349809, P= 2.89×10 -12 ). Our Mendelian randomization analyses suggested a potential causal association between first-trimester ADAM-12 levels and gestational hypertension (odds ratio=0.78, P= 8.6×10 -4 ). We also found evidence for a potential causal effect of preeclampsia (odds ratio=1.75, P =8.3×10 -3 ) and gestational hypertension (odds ratio=1.84, P =4.7×10 -3 ) during the index pregnancy on the onset of hypertension 2-7 years later. The additional mediation analysis indicated that the impact of ADAM-12 on postpartum hypertension could be explained in part by its indirect effect through gestational hypertension (mediated effect=-0.15, P= 0.03).

Conclusions

Our study discovered significant genetic associations with placental proteins ADAM-12, VEGF, and sFlt-1, offering insights into their regulation during pregnancy. Mendelian randomization analyses demonstrated evidence of potential causal relationships between the serum levels of placental proteins, particularly ADAM-12, and gestational hypertension, potentially informing future prevention and treatment investigations.

The Role of PNPLA3_rs738409 Gene Variant, Lifestyle Factors, and Bioactive Compounds in Nonalcoholic Fatty Liver Disease: A Population-Based and Molecular Approach towards Healthy Nutrition

This study aimed to investigate the impact of a common non-synonymous gene variant (C>G, rs738409) in patatin-like phospholipase domain-containing 3 (PNPLA3), leading to the substitution of isoleucine with methionine at position 148 (PNPLA3-I148M), on susceptibility to nonalcoholic fatty liver disease (NAFLD) and explore potential therapeutic nutritional strategies targeting PNPLA3. It contributed to understanding sustainable dietary practices for managing NAFLD, recently referred to as metabolic-dysfunction-associated fatty liver. NAFLD had been diagnosed by ultrasound in a metropolitan hospital-based cohort comprising 58,701 middle-aged and older Korean individuals, identifying 2089 NAFLD patients. The interaction between PNPLA3 and lifestyle factors was investigated. In silico analyses, including virtual screening, molecular docking, and molecular dynamics simulations, were conducted to identify bioactive compounds from foods targeting PNPLA3(I148M). Subsequent cellular experiments involved treating oleic acid (OA)-exposed HepG2 cells with selected bioactive compounds, both in the absence and presence of compound C (AMPK inhibitor), targeting PNPLA3 expression. Carriers of the risk allele PNPLA3_rs738409G showed an increased association with NAFLD risk, particularly with adherence to a plant-based diet, avoidance of a Western-style diet, and smoking. Delphinidin 3-caffeoyl-glucoside, pyranocyanin A, delta-viniferin, kaempferol-7-glucoside, and petunidin 3-rutinoside emerged as potential binders to the active site residues of PNPLA3, exhibiting a reduction in binding energy. These compounds demonstrated a dose-dependent reduction in intracellular triglyceride and lipid peroxide levels in HepG2 cells, while pretreatment with compound C showed the opposite trend. Kaempferol-7-glucoside and petunidin-3-rutinoside showed potential as inhibitors of PNPLA3 expression by enhancing AMPK activity, ultimately reducing intrahepatic lipogenesis. In conclusion, there is potential for plant-based diets and specific bioactive compounds to promote sustainable dietary practices to mitigate NAFLD risk, especially in individuals with genetic predispositions.

The Role of Nuclear Receptors in the Pathogenesis and Treatment of Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a global health burden closely linked to insulin resistance, obesity, and type 2 diabetes. The complex pathophysiology of NAFLD involves multiple cellular pathways and molecular factors. Nuclear receptors (NRs) have emerged as crucial regulators of lipid metabolism and inflammation in NAFLD, offering potential therapeutic targets for NAFLD. Targeting PPARs and FXRs has shown promise in ameliorating NAFLD symptoms and halting disease progression. However, further investigation is needed to address side effects and personalize therapy approaches. This review summarizes the current understanding of the involvement of NRs in the pathogenesis of NAFLD and explores their therapeutic potential. We discuss the role of several NRs in modulating lipid homeostasis in the liver, including peroxisome proliferator-activated receptors (PPARs), liver X receptors (LXRs), farnesoid X receptors (FXRs), REV-ERB, hepatocyte nuclear factor 4α (HNF4α), constitutive androstane receptor (CAR) and pregnane X receptor (PXR).The expanding knowledge of NRs in NAFLD offers new avenues for targeted therapies, necessitating exploration of novel treatment strategies and optimization of existing approaches to combat this increasingly prevalent disease.

A cross-disorder study to identify causal relationships, shared genetic variants, and genes across 21 digestive disorders

Digestive disorders are a significant contributor to the global burden of disease and seriously affect human quality of life. Research has already confirmed the presence of pleiotropic genetic loci among digestive disorders, and studies have explored shared genetic factors among pan-cancers, including various malignant digestive disorders. However, most cross-phenotype studies within the digestive tract system have been limited to a few traits, with no systematic coverage of common benign and malignant digestive disorders. Here, we analyzed data from the UK Biobank to investigate 21 digestive disorders, exploring the genetic correlations and causal relationships between diseases, as well as the common genetic factors and potential biological pathways driving these relationships. Our findings confirmed the extensive genetic correlation and causal relationship between digestive disorders, providing important insights into the genetic etiology, causality, disease prevention, and clinical treatment of diseases.

Histological findings and NAFLD/NASH Status in liver biopsies of patients subjected to bariatric surgery

Objective

To investigate nonalcoholic fatty liver disease (NAFLD), nonalcoholic steatohepatitis (NASH) and hepatic fibrosis in biopsies of people with obesity who underwent bariatric surgery and examine the possible association of different variables with a diagnosis of NAFLD and NASH.

Materials and methods

Epidemiological, clinical and laboratory data from 574 individuals with obesity of both genders seen by the same physician between 2003 and 2009 who had a liver biopsy during bariatric surgery were examined.

Results

Of the 437 patients included, 39.8% had some degree of liver fibrosis, 95% had a histologic diagnosis of NAFLD, and the risk factors were age ≥ 28 years and Homeostatic Model Assessment (HOMA) ≥ 2.5 (p = 0.001 and p = 0.016, respectively). In the NAFLD group, NASH was present in 26% of patients and the associated factors were aspartate aminotransferase and alanine aminotransferase index (AST/ALT) > 1, high-density lipoprotein cholesterol (HDL-c) < 40 mg/dL, total cholesterol (TC) ≥ 200 mg/dL, gamma-glutamyl transferase (GGT) > 38 U/L and triglycerides (TG) levels > 150 mg/dL. The independent risk factors were low HDL-c, elevated AST/ALT and high TG.

Conclusion

The variables associated with a diagnosis of NAFLD were HOMA ≥ 2.5 and age ≥ 28 years. NASH was associated with low HDL-c, high TG and AST/ALT ≤ 1.

The greater impact of PNPLA3 polymorphism on liver-related events in Japanese non-alcoholic fatty liver disease patients: A multicentre cohort study

BACKGROUND & AIMS

PNPLA3 rs738409 has been associated with an increased risk of liver-related events in patients with non-alcoholic fatty liver disease (NAFLD). In this study, we investigated the epidemiology of NAFLD and the impact of PNPLA3 on prognosis in Japan.

METHODS

A longitudinal multicentre cohort study, the JAGUAR study, includes 1550 patients with biopsy-proven NAFLD in Japan. We performed genetic testing and evaluated outcomes from this cohort. Liver-related events were defined as hepatocellular carcinoma (HCC) and decompensated liver cirrhosis events.

RESULTS

During follow-up (median [range], 7.1 [1.0-24.0] years), 80 patients developed HCC, 104 developed liver-related events, and 59 died of any cause. The 5-year rate of liver-related events for each single-nucleotide polymorphism was 0.5% for CC, 3.8% for CG, and 5.8% for GG. Liver-related deaths were the most common (n = 28); only three deaths were due to cardiovascular disease. Multivariate analysis identified carriage of PNPLA3 CG/GG (hazard ratio [HR] 16.04, p = .006) and FIB-4 index >2.67 (HR 10.70, p < .01) as predictors of liver-related event development. No HCC or liver-related death was found among patients with PNPLA3 CC. There was a significantly increased risk of HCC, liver-related events, and mortality for CG/GG versus CC, but no difference between the CG and GG genotypes.

CONCLUSIONS

In Japanese individuals, the main cause of death from NAFLD is liver-related death. The greater risk of liver-related events incurred by PNPLA3 G allele was shown in Japan. Risk stratification for NAFLD in Japan is best accomplished by integrating PNPLA3 with the FIB-4 index.

Genome-wide association meta-analysis identifies 17 loci associated with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is common and partially heritable and has no effective treatments. We carried out a genome-wide association study (GWAS) meta-analysis of imaging (n = 66,814) and diagnostic code (3,584 cases versus 621,081 controls) measured NAFLD across diverse ancestries. We identified NAFLD-associated variants at torsin family 1 member B (TOR1B), fat mass and obesity associated (FTO), cordon-bleu WH2 repeat protein like 1 (COBLL1)/growth factor receptor-bound protein 14 (GRB14), insulin receptor (INSR), sterol regulatory element-binding transcription factor 1 (SREBF1) and patatin-like phospholipase domain-containing protein 2 (PNPLA2), as well as validated NAFLD-associated variants at patatin-like phospholipase domain-containing protein 3 (PNPLA3), transmembrane 6 superfamily 2 (TM6SF2), apolipoprotein E (APOE), glucokinase regulator (GCKR), tribbles homolog 1 (TRIB1), glycerol-3-phosphate acyltransferase (GPAM), mitochondrial amidoxime-reducing component 1 (MARC1), microsomal triglyceride transfer protein large subunit (MTTP), alcohol dehydrogenase 1B (ADH1B), transmembrane channel like 4 (TMC4)/membrane-bound O-acyltransferase domain containing 7 (MBOAT7) and receptor-type tyrosine-protein phosphatase δ (PTPRD). Implicated genes highlight mitochondrial, cholesterol and de novo lipogenesis as causally contributing to NAFLD predisposition. Phenome-wide association study (PheWAS) analyses suggest at least seven subtypes of NAFLD. Individuals in the top 10% and 1% of genetic risk have a 2.5-fold to 6-fold increased risk of NAFLD, cirrhosis and hepatocellular carcinoma. These genetic variants identify subtypes of NAFLD, improve estimates of disease risk and can guide the development of targeted therapeutics.

Nonalcoholic Fatty Liver Disease in Lean/Nonobese and Obese Individuals: A Comprehensive Review on Prevalence, Pathogenesis, Clinical Outcomes, and Treatment

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide, with an estimated prevalence of 25% globally. NAFLD is closely associated with metabolic syndrome, which are both becoming increasingly more common with increasing rates of insulin resistance, dyslipidemia, and hypertension. Although NAFLD is strongly associated with obesity, lean or nonobese NAFLD is a relatively new phenotype and occurs in patients without increased waist circumference and with or without visceral fat. Currently, there is limited literature comparing and illustrating the differences between lean/nonobese and obese NAFLD patients with regard to risk factors, pathophysiology, and clinical outcomes. In this review, we aim to define and further delineate different phenotypes of NAFLD and present a comprehensive review on the prevalence, incidence, risk factors, genetic predisposition, and pathophysiology. Furthermore, we discuss and compare the clinical outcomes, such as insulin resistance, dyslipidemia, hypertension, coronary artery disease, mortality, and progression to nonalcoholic steatohepatitis, among lean/nonobese and obese NAFLD patients. Finally, we summarize the most up to date current management of NAFLD, including lifestyle interventions, pharmacologic therapies, and surgical options.

Abdominal obesity and alcohol use modify the impact of genetic risk for incident advanced liver disease in the general population

BACKGROUND & AIMS

Genetic variants, abdominal obesity and alcohol use are risk factors for incident liver disease (ILD). We aimed to study whether variants either alone or when aggregated into genetic risk scores (GRSs) associate with ILD, and whether waist-hip ratio (WHR) or alcohol use interacts with this risk.

METHODS

Our study included 33 770 persons (mean age 50 years, 47% men) who participated in health-examination surveys (FINRISK 1992-2012 or Health 2000) with data on alcohol use, WHR and 63 genotypes associated with liver disease. Data were linked with national health registers for liver-related outcomes (hospitalizations, malignancies and death). Exclusions were baseline clinical liver disease. Mean follow-up time was 12.2 years. Cox regression analyses between variants and ILD were adjusted for age, sex and BMI.

RESULTS

Variants in PNPLA3, IFNL4, TM6SF2, FDFT1, PPP1R3B, SERPINA1 and HSD17B13 were associated with ILD. GRSs calculated from these variants were not associated with WHR or alcohol use, but were exponentially associated with ILD (up to 25-fold higher risk in high versus low score). The risk of ILD in individuals with high GRS and high WHR or alcohol use compared with those with none of these risk factors was increased by up to 90-fold. GRSs provided new prognostic information particularly in individuals with high WHR.

CONCLUSIONS

The effect of multiple genetic variants on the risk of ILD is potentiated by abdominal obesity and alcohol use. Simple GRSs may help to identify individuals with adverse lifestyle who are at a particularly high risk of ILD.

Comparative Analysis of Global Hepatic Gene Expression in Adolescents and Adults with Non-alcoholic Fatty Liver Disease

Introduction

To gain insights into the mechanisms underlying distinct nonalcoholic fatty liver disease (NAFLD) histological phenotypes between children and adults, we compared hepatic gene expression profiles associated with NAFLD phenotypes between the two age groups.

Methods

Histological characteristics of intra-operative liver biopsies from adolescents and adults undergoing bariatric surgery were assessed by the same pathologist using the non-alcoholic steatohepatitis (NASH) Clinical Research Network scoring system. Hepatic gene expression was measured by microarray analysis. Transcriptomic signatures of histological phenotypes between the two groups were compared, with significance defined as p-value <0.05 and a fold change >1.5.

Results

In 67 adolescents and 76 adults, distribution of histological phenotypes was: not-NAFLD (controls) 51% vs 39%, NAFL 39% vs 37%, and NASH 10% vs 24%, respectively. There were 279 differentially expressed genes in adolescents and 213 in adults with NAFLD vs controls. In adolescents, transcriptomes for NAFL vs controls, and borderline vs definite NASH were undifferentiable, whereas in adults, NAFL and borderline NASH demonstrated a transcriptomic gradient between controls and definite NASH. When applied to adolescents, significant adult genes discriminated borderline and definite NASH from control and NAFL, but the majority of significant pediatric genes were not portable to adults. Genes associated with NASH in adolescents and adults showed some ontological consistency but notable differences.

Conclusions

There is some similarity but major differences in the transcriptomic profiles associated with NAFLD between adolescents and adults with severe obesity. These data suggest different mechanisms contribute to the pathogenesis of NAFLD severity at different stages in life.

The genetic background shapes the susceptibility to mitochondrial dysfunction and NASH progression

Non-alcoholic steatohepatitis (NASH) is a global health concern without treatment. The challenge in finding effective therapies is due to the lack of good mouse models and the complexity of the disease, characterized by gene-environment interactions. We tested the susceptibility of seven mouse strains to develop NASH. The severity of the clinical phenotypes observed varied widely across strains. PWK/PhJ mice were the most prone to develop hepatic inflammation and the only strain to progress to NASH with extensive fibrosis, while CAST/EiJ mice were completely resistant. Levels of mitochondrial transcripts and proteins as well as mitochondrial function were robustly reduced specifically in the liver of PWK/PhJ mice, suggesting a central role of mitochondrial dysfunction in NASH progression. Importantly, the NASH gene expression profile of PWK/PhJ mice had the highest overlap with the human NASH signature. Our study exposes the limitations of using a single mouse genetic background in metabolic studies and describes a novel NASH mouse model with features of the human NASH.

Non-alcoholic fatty liver disease: Definition and subtypes

Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases worldwide, with a global prevalence of approximately 30%. However, the prevalence of NAFLD has been variously reported depending on the comorbidities. The rising prevalence of obesity in both the adult and pediatric populations is projected to consequently continue increasing NAFLD prevalence. It is a major cause of chronic liver disease worldwide, including cirrhosis and hepatocellular carcinoma (HCC). NAFLD has a variety of clinical phenotypes and heterogeneity due to the complexity of pathogenesis and clinical conditions of its occurrence, resulting in various clinical prognoses. In this article, we briefly described the basic definition of NAFLD and classified the subtypes based on current knowledge in this field.

Lung- and liver-dominant phenotypes of Korean eight constitution medicine have different profiles of genotype associated with each organ function

Eight Constitution Medicine (ECM), a ramification of traditional Korean medicine, has categorized people into eight constitutions. The main criteria of classification are inherited differences or predominance in the functions of organs, such as the liver or lung, diagnosed through ECM-specific pulse patterns. This study investigated the association between single nucleotide polymorphism (SNP) genotypes and ECM phenotypes and explored candidate genetic makeups responsible for each constitution using a genome-wide association study (GWAS). Sixty-three healthy volunteers, who were either categorized as the Hepatonia (HEP, n = 32) or Pulmotonia (PUL, n = 31) constitution, were enrolled. HEP and PUL are two contrasting ECM types representing the dominant liver and lung phenotypes, respectively. SNPs were analyzed from the oral mucosa DNA using a commercially available microarray chip that can identify 820,000 SNPs. We conducted GWAS using logistic regression analysis and additive mode genotypes and constructed phylogenetic trees using the SNPhylo program with 8 SNPs specific for the liver phenotype and 15 SNPs for the lung phenotype. Although genome-wide significant SNPs were not found, the phylogenetic tree showed a clear difference between the two constitutions. This is the first observation suggesting genetic involvement in the ECM and can be extended to all ECM constitutions.

A multiancestry genome-wide association study of unexplained chronic ALT elevation as a proxy for nonalcoholic fatty liver disease with histological and radiological validation

Nonalcoholic fatty liver disease (NAFLD) is a growing cause of chronic liver disease. Using a proxy NAFLD definition of chronic elevation of alanine aminotransferase (cALT) levels without other liver diseases, we performed a multiancestry genome-wide association study (GWAS) in the Million Veteran Program (MVP) including 90,408 cALT cases and 128,187 controls. Seventy-seven loci exceeded genome-wide significance, including 25 without prior NAFLD or alanine aminotransferase associations, with one additional locus identified in European American-only and two in African American-only analyses (P < 5 × 10-8). External replication in histology-defined NAFLD cohorts (7,397 cases and 56,785 controls) or radiologic imaging cohorts (n = 44,289) replicated 17 single-nucleotide polymorphisms (SNPs) (P < 6.5 × 10-4), of which 9 were new (TRIB1, PPARG, MTTP, SERPINA1, FTO, IL1RN, COBLL1, APOH and IFI30). Pleiotropy analysis showed that 61 of 77 multiancestry and all 17 replicated SNPs were jointly associated with metabolic and/or inflammatory traits, revealing a complex model of genetic architecture. Our approach integrating cALT, histology and imaging reveals new insights into genetic liability to NAFLD.

Research progress on the relationship between TM6SF2 rs58542926 polymorphism and non-alcoholic fatty liver disease

INTRODUCTION

nonalcoholic fatty liver disease is a common liver disease with a global average prevalence of about 25%. In addition to the incidence of NAFLD being related to obesity, diabetes, hyperlipidemia, etc., genetic factors also have an important impact on the incidence of NAFLD.

AREAS COVERED

Current experimental results and clinical studies show that the transmembrane 6 superfamily member 2 (TM6SF2) gene plays an important role in the pathogenesis of NAFLD. The research on genetic polymorphism of TM6SF2 gene mainly focuses on rs58542926 locus (rs58542926 c.449 C > T, p. Glu167Lys, E167K). The Mutations of this site might increase the risk of NAFLD in carriers.

EXPERT OPINION

The mutation of this site causes the disorder of triglyceride metabolism in the liver, which leads to the deposition of a large amount of lipids in the liver, and further induces the incidence of NAFLD. With the study of the mechanism of TM6SF2 gene polymorphism in the pathogenesis of NAFLD, it is helpful to understand the molecular mechanism of the pathogenesis of NAFLD, which has a great value for the treatment of NAFLD.

Genome-Wide Association Study of NAFLD Using Electronic Health Records

Genome-wide association studies (GWAS) have identified several risk loci for nonalcoholic fatty liver disease (NAFLD). Previous studies have largely relied on small sample sizes and have assessed quantitative traits. We performed a case-control GWAS in the UK Biobank using recorded diagnosis of NAFLD based on diagnostic codes recommended in recent consensus guidelines. We performed a GWAS of 4,761 cases of NAFLD and 373,227 healthy controls without evidence of NAFLD. Sensitivity analyses were performed excluding other co-existing hepatic pathology, adjusting for body mass index (BMI) and adjusting for alcohol intake. A total of 9,723,654 variants were assessed by logistic regression adjusted for age, sex, genetic principal components, and genotyping batch. We performed a GWAS meta-analysis using available summary association statistics. Six risk loci were identified (P < 5*10-8 ) (apolipoprotein E [APOE], patatin-like phospholipase domain containing 3 [PNPLA3, transmembrane 6 superfamily member 2 [TM6SF2], glucokinase regulator [GCKR], mitochondrial amidoxime reducing component 1 [MARC1], and tribbles pseudokinase 1 [TRIB1]). All loci retained significance in sensitivity analyses without co-existent hepatic pathology and after adjustment for BMI. PNPLA3 and TM6SF2 remained significant after adjustment for alcohol (alcohol intake was known in only 158,388 individuals), with others demonstrating consistent direction and magnitude of effect. All six loci were significant on meta-analysis. Rs429358 (P = 2.17*10-11 ) is a missense variant within the APOE gene determining ϵ4 versus ϵ2/ϵ3 alleles. The ϵ4 allele of APOE offered protection against NAFLD (odds ratio for heterozygotes 0.84 [95% confidence interval 0.78-0.90] and homozygotes 0.64 [0.50-0.79]). Conclusion: This GWAS replicates six known NAFLD-susceptibility loci and confirms that the ϵ4 allele of APOE is associated with protection against NAFLD. The results are consistent with published GWAS using histological and radiological measures of NAFLD, confirming that NAFLD identified through diagnostic codes from consensus guidelines is a valid alternative to more invasive and costly approaches.

Identification of 90 NAFLD GWAS loci and establishment of NAFLD PRS and causal role of NAFLD in coronary artery disease

The prevalence of non-alcoholic fatty liver disease (NAFLD), now also known as metabolic dysfunction-associated fatty liver disease (MAFLD), is rapidly increasing worldwide due to the ongoing obesity epidemic. However, currently the NALFD diagnosis requires non-readily available imaging technologies or liver biopsy, which has drastically limited the sample sizes of NAFLD studies and hampered the discovery of its genetic component. Here we utilized the large UK Biobank (UKB) to accurately estimate the NAFLD status in UKB based on common serum traits and anthropometric measures. Scoring all individuals in UKB for NAFLD risk resulted in 28,396 NAFLD cases and 108,652 healthy individuals at a >90% confidence level. Using this imputed NAFLD status to perform the largest NAFLD genome-wide association study (GWAS) to date, we identified 94 independent (R² < 0.2) NAFLD GWAS loci, of which 90 have not been identified before; built a polygenic risk score (PRS) model to predict the genetic risk of NAFLD; and used the GWAS variants of imputed NAFLD for a tissue-aware Mendelian randomization analysis that discovered a significant causal effect of NAFLD on coronary artery disease (CAD). In summary, we accurately estimated the NAFLD status in UKB using common serum traits and anthropometric measures, which empowered us to identify 90 GWAS NAFLD loci, build NAFLD PRS, and discover a significant causal effect of NAFLD on CAD.

Understanding the Role of the Gut Microbiome and Microbial Metabolites in Non-Alcoholic Fatty Liver Disease: Current Evidence and Perspectives

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. NAFLD begins as a relatively benign hepatic steatosis which can evolve to non-alcoholic steatohepatitis (NASH); the risk of cirrhosis and hepatocellular carcinoma (HCC) increases when fibrosis is present. NAFLD represents a complex process implicating numerous factors—genetic, metabolic, and dietary—intertwined in a multi-hit etiopathogenetic model. Recent data have highlighted the role of gut dysbiosis, which may render the bowel more permeable, leading to increased free fatty acid absorption, bacterial migration, and a parallel release of toxic bacterial products, lipopolysaccharide (LPS), and proinflammatory cytokines that initiate and sustain inflammation. Although gut dysbiosis is present in each disease stage, there is currently no single microbial signature to distinguish or predict which patients will evolve from NAFLD to NASH and HCC. Using 16S rRNA sequencing, the majority of patients with NAFLD/NASH exhibit increased numbers of Bacteroidetes and differences in the presence of Firmicutes, resulting in a decreased F/B ratio in most studies. They also present an increased proportion of species belonging to Clostridium, Anaerobacter, Streptococcus, Escherichia, and Lactobacillus, whereas Oscillibacter, Flavonifaractor, Odoribacter, and Alistipes spp. are less prominent. In comparison to healthy controls, patients with NASH show a higher abundance of Proteobacteria, Enterobacteriaceae, and Escherichia spp., while Faecalibacterium prausnitzii and Akkermansia muciniphila are diminished. Children with NAFLD/NASH have a decreased proportion of Oscillospira spp. accompanied by an elevated proportion of Dorea, Blautia, Prevotella copri, and Ruminococcus spp. Gut microbiota composition may vary between population groups and different stages of NAFLD, making any conclusive or causative claims about gut microbiota profiles in NAFLD patients challenging. Moreover, various metabolites may be involved in the pathogenesis of NAFLD, such as short-chain fatty acids, lipopolysaccharide, bile acids, choline and trimethylamine-N-oxide, and ammonia. In this review, we summarize the role of the gut microbiome and metabolites in NAFLD pathogenesis, and we discuss potential preventive and therapeutic interventions related to the gut microbiome, such as the administration of probiotics, prebiotics, synbiotics, antibiotics, and bacteriophages, as well as the contribution of bariatric surgery and fecal microbiota transplantation in the therapeutic armamentarium against NAFLD. Larger and longer-term prospective studies, including well-defined cohorts as well as a multi-omics approach, are required to better identify the associations between the gut microbiome, microbial metabolites, and NAFLD occurrence and progression.

Variations in TM6SF2, PCSK9 and PCSK7 genes and risk of hepatic steatosis after liver transplantation: a cross-sectional study

Background

Genetic abnormalities might have important role in pathogenesis of hepatic steatosis after liver transplantation. We aimed to investigate association between genetic variations in transmembrane 6 superfamily member 2 (TM6SF2) rs58542926, proprotein convertase subtilisin/kexin type 9 (PCSK9) rs505151 and proprotein convertase subtilisin/kexin type 7 (PCSK7) rs2277287 with hepatic steatosis in liver transplant recipients.

Methods

In a cross-sectional study, adult (> 18 years) liver transplant recipients who were referred for their routine post-transplant follow-up between June 2018 and September 2018 were included in the study. Hepatic steatosis in transplant recipients was assessed by controlled attenuation parameter (CAP). Polymerase chain reaction-restriction fragment length polymorphism (PCR–RFLP) was used to study TM6SF2 rs58542926, PCSK7 rs2277287 and PCSK9 rs505151 genotypes.

Results

107 liver transplant recipients were included. There was no association between different genotypes of PCSK9 rs505151 and PCSK7 rs2277287 with hepatic steatosis in liver transplant recipients (P value > 0.05). The presence of TT genotype of TM6SF2 rs58542926 was higher in patients with hepatic steatosis measured by CAP after liver transplantation. In patients with moderate and severe hepatic steatosis (grade 2 and 3 steatosis), AG + GG genotypes of PCSK9 rs505151 were more prevalent than AA genotype (OR 8.667; 95% CI 1.841–40.879; P value = 0.004) compared to patients with mild steatosis (grade 1). In multivariate regression model, AG + GG genotypes of PCSK9 rs505151 were associated with moderate and severe steatosis in liver transplant recipients (OR 5.747; 95% CI 1.086–30.303; P value = 0.040).

Conclusions

Genetic variations in TM6SF2 rs58542926 and PCSK9 rs505151 might be associated with hepatic steatosis in liver transplant recipients.

Hepatokine Pregnancy Zone Protein Governs the Diet-Induced Thermogenesis Through Activating Brown Adipose Tissue

Intermittent fasting (IF), as a dietary intervention for weight loss, takes effects primarily through increasing energy expenditure. However, whether inter-organ systems play a key role in IF remains unclear. Here, a novel hepatokine, pregnancy zone protein (PZP) is identified, which has significant induction during the refeeding stage of IF. Further, loss of function studies and protein therapeutic experiment in mice revealed that PZP promotes diet-induced thermogenesis through activating brown adipose tissue (BAT). Mechanistically, circulating PZP can bind to cell surface glucose-regulated protein of 78 kDa (GRP78) to promote uncoupling protein 1 (UCP1) expression via a p38 MAPK-ATF2 signaling pathway in BAT. These studies illuminate a systemic regulation in which the IF promotes BAT thermogenesis through the endocrinal system and provide a novel potential target for treating obesity and related disorders.

PNPLA3, TM6SF2, and MBOAT7 Influence on Nutraceutical Therapy Response for Non-alcoholic Fatty Liver Disease: A Randomized Controlled Trial

Introduction: PNPLA3, TM6SF2, and MBOAT7 genes play a crucial role in non-alcoholic fatty liver disease (NAFLD) development and worsening. However, few data are available on their treatment response influence. The aim of this trial is to explore the effect derived from silybin-phospholipids complex (303 mg of silybin-phospholipids complex, 10 μg of vitamin D, and 15 mg of vitamin E twice a day for 6 months) oral administration in NAFLD patients carrying PNPLA3-rs738409, TM6SF2-rs58542926, or MBOAT7-rs641738 genetic variants. Materials and Methods: In all, 92 biopsy-proven NAFLD patients were grouped in 30 NAFLD wild type controls, 30 wild type treated patients, and 32 mutated treated ones. We assessed glycemia (FPG), insulinemia, HOMA-IR, aspartate and alanine aminotransferases (AST, ALT), C-reactive protein (CRP), thiobarbituric acid reactive substance (TBARS), stiffness, controlled attenuation parameter (CAP), dietary daily intake, and physical activity at baseline and end of treatment. Results: The wild-type treated group showed a significant improvement of FPG, insulinemia, HOMA-IR, ALT, CRP, and TBARS (p < 0.05), whereas no improvements were recorded in the other two study groups. NAFLD wild type treated patients showed higher possibilities of useful therapeutic outcome (p < 0.01), obtained from the prescribed therapeutic regimen, independently from age, sex, comorbidities, medications, CAP, and stiffness in comparison to the mutated group. Discussion: The assessed mutations are independently associated with no response to a silybin-based therapeutic regimen and could be considered as useful predictive markers in this context. Clinical Trial Registry Number: www.ClinicalTrials.gov, identifier: NCT04640324.

Association of Genetic Risk Score With NAFLD in An Ethnically Diverse Cohort

Most genetic studies of nonalcoholic fatty liver disease (NAFLD) have been conducted in Whites. In this large and ethnically diverse cohort, we assessed the transportability of previously identified genetic variants for NAFLD, built a genetic risk score (GRS), and examined its association with NAFLD risk in multiple ethnic groups. Thirty previously identified genome-wide association studies (GWAS) variants (P < 5 × 10-8 ) and 17 other variants associated with NAFLD were examined in a nested case-control study of NAFLD (1,448 cases/8,444 controls) in this multi-ethnic cohort study. We then built a GRS using 11 independent single-nucleotide polymorphisms from these prior studies and examined its association with NAFLD by cirrhosis status across multiple ethnic groups. Of the 30 GWAS SNPs, 20 (67%) were replicated (P < 0.05) in the pooled multi-ethnic population. The highest percentage of replication was seen in Latinos (43%), followed by Japanese Americans (37%), Whites (17%), and Native Hawaiians and African Americans (≤10%). Several genetic variants, including those in PNPLA3 (patatin-like phospholipase domain containing 3), HSD17B13 (hydroxysteroid 17-beta dehydrogenase 13), TM6SF2 (transmembrane 6 superfamily member 2), GATAD2A (GATA zinc finger domain containing 2A), GCKR (glucokinase regulator), SUGP1 (SURP and G-patch domain containing 1), MBOAT7 (membrane bound O-acyltransferase domain containing 7), TRIB1 (tribbles pseudokinase 1), SAMM50 (sorting and assembly machinery component), and ERLIN1 (ER lipid raft associated 1)-CHUK (component of inhibitor of nuclear factor kappa B kinase complex)-CWF19L1 (CWF19 like cell cycle control factor 1) gene cluster, were replicated in at least two ethnic groups. An 11-SNP weighted GRS was associated with NAFLD risk in the multi-ethnic population (odds ratio [OR] per SD increase = 1.41; 95% confidence interval [CI] = 1.32-1.50), as well as in each ethnic group (OR ranged from 1.30 in African Americans to 1.52 in Latinos). The GRS-NAFLD association was stronger for NAFLD with cirrhosis (OR = 1.67; 95% CI = 1.46-1.92) compared to NAFLD without cirrhosis (OR = 1.37; 95% CI = 1.28-1.46) (P heterogeneity = 0.003). Conclusion: In this ethnically diverse cohort, we replicated several key genetic variants for NAFLD and showed the utility of GRS based on the risk alleles for NAFLD risk stratification in multiple ethnic groups.

Genome-wide association study of liver enzyme elevation in rheumatoid arthritis patients starting methotrexate

Aim: To identify novel genetic variants predisposing to elevation of Alanine aminotransferase (ALT) in rheumatoid arthritis (RA) patients after initiation of methotrexate (MTX) treatment. Patients & methods: We performed genome-wide association studies in 198 RA patients starting MTX. Outcomes were maximum level of ALT and ALT >1.5-times the upper level of normal within the first 6 months of treatment. Results: RAVER2 (rs72675408) was significantly associated with maximum level of ALT (p = 4.36 × 10^-8). This variant is in linkage disequilibrium with rs72675451, which is associated with differential expression of JAK1 and RAVER2. Conclusion: We found an association between ALT elevation and genetic variants that may regulate the expression of JAK1 and RAVER2. JAK1 encodes a janus kinase involved in the pathogenesis of RA.

Role of Cholesterol-Associated Steatohepatitis in the Development of NASH

The rising prevalence of nonalcoholic fatty liver disease (NAFLD) and NAFLD-related cirrhosis in the United States and globally highlights the need to better understand the mechanisms causing progression of hepatic steatosis to fibrosing steatohepatitis and cirrhosis in a small proportion of patients with NAFLD. Accumulating evidence suggests that lipotoxicity mediated by hepatic free cholesterol (FC) overload is a mechanistic driver for necroinflammation and fibrosis, characteristic of nonalcoholic steatohepatitis (NASH), in many animal models and also in some patients with NASH. Diet, lifestyle, obesity, key genetic polymorphisms, and hyperinsulinemia secondary to insulin resistance are pivotal drivers leading to aberrant cholesterol signaling, which leads to accumulation of FC within hepatocytes. FC overload in hepatocytes can lead to ER stress, mitochondrial dysfunction, development of toxic oxysterols, and cholesterol crystallization in lipid droplets, which in turn lead to hepatocyte apoptosis, necrosis, or pyroptosis. Activation of Kupffer cells and hepatic stellate cells by hepatocyte signaling and cholesterol loading contributes to this inflammation and leads to hepatic fibrosis. Cholesterol accumulation in hepatocytes can be readily prevented or reversed by statins. Observational studies suggest that use of statins in NASH not only decreases the substantially increased cardiovascular risk, but may ameliorate liver pathology. Conclusion: Hepatic FC loading may result in cholesterol-associated steatohepatitis and play an important role in the development and progression of NASH. Statins appear to provide significant benefit in preventing progression to NASH and NASH-cirrhosis. Randomized controlled trials are needed to demonstrate whether statins or statin/ezetimibe combination can effectively reverse steatohepatitis and liver fibrosis in patients with NASH.

Large Rab GTPases: Novel Membrane Trafficking Regulators with a Calcium Sensor and Functional Domains

Rab GTPases are major coordinators of intracellular membrane trafficking, including vesicle transport, membrane fission, tethering, docking, and fusion events. Rab GTPases are roughly divided into two groups: conventional “small” Rab GTPases and atypical “large” Rab GTPases that have been recently reported. Some members of large Rab GTPases in mammals include Rab44, Rab45/RASEF, and Rab46. The genes of these large Rab GTPases commonly encode an amino-terminal EF-hand domain, coiled-coil domain, and the carboxyl-terminal Rab GTPase domain. A common feature of large Rab GTPases is that they express several isoforms in cells. For instance, Rab44’s two isoforms have similar functions, but exhibit differential localization. The long form of Rab45 (Rab45-L) is abundantly distributed in epithelial cells. The short form of Rab45 (Rab45-S) is predominantly present in the testes. Both Rab46 (CRACR2A-L) and the short isoform lacking the Rab domain (CRACR2A-S) are expressed in T cells, whereas Rab46 is only distributed in endothelial cells. Although evidence regarding the function of large Rab GTPases has been accumulating recently, there are only a limited number of studies. Here, we report the recent findings on the large Rab GTPase family concerning their function in membrane trafficking, cell differentiation, related diseases, and knockout mouse phenotypes.

Allele-specific variation at APOE increases nonalcoholic fatty liver disease and obesity but decreases risk of Alzheimer's disease and myocardial infarction

Nonalcoholic fatty liver disease (NAFLD) is a leading cause of chronic liver disease and is highly correlated with metabolic disease. NAFLD results from environmental exposures acting on a susceptible polygenic background. This study performed the largest multiethnic investigation of exonic variation associated with NAFLD and correlated metabolic traits and diseases. An exome array meta-analysis was carried out among eight multiethnic population-based cohorts (n = 16 492) with computed tomography (CT) measured hepatic steatosis. A fixed effects meta-analysis identified five exome-wide significant loci (P < 5.30 × 10-7); including a novel signal near TOMM40/APOE. Joint analysis of TOMM40/APOE variants revealed the TOMM40 signal was attributed to APOE rs429358-T; APOE rs7412 was not associated with liver attenuation. Moreover, rs429358-T was associated with higher serum alanine aminotransferase, liver steatosis, cirrhosis, triglycerides and obesity; as well as, lower cholesterol and decreased risk of myocardial infarction and Alzheimer's disease (AD) in phenome-wide association analyses in the Michigan Genomics Initiative, United Kingdom Biobank and/or public datasets. These results implicate APOE in imaging-based identification of NAFLD. This association may or may not translate to nonalcoholic steatohepatitis; however, these results indicate a significant association with advanced liver disease and hepatic cirrhosis. These findings highlight allelic heterogeneity at the APOE locus and demonstrate an inverse link between NAFLD and AD at the exome level in the largest analysis to date.

Diagnosis and management of secondary causes of steatohepatitis

The term non-alcoholic fatty liver disease (NAFLD) was originally coined to describe hepatic fat deposition as part of the metabolic syndrome. However, a variety of rare hereditary liver and metabolic diseases, intestinal diseases, endocrine disorders and drugs may underlie, mimic, or aggravate NAFLD. In contrast to primary NAFLD, therapeutic interventions are available for many secondary causes of NAFLD. Accordingly, secondary causes of fatty liver disease should be considered during the diagnostic workup of patients with fatty liver disease, and treatment of the underlying disease should be started to halt disease progression. Common genetic variants in several genes involved in lipid handling and metabolism modulate the risk of progression from steatosis to fibrosis, cirrhosis and hepatocellular carcinoma development in NAFLD, alcohol-related liver disease and viral hepatitis. Hence, we speculate that genotyping of common risk variants for liver disease progression may be equally useful to gauge the likelihood of developing advanced liver disease in patients with secondary fatty liver disease.

Therapeutic pipeline in nonalcoholic steatohepatitis

Our understanding of nonalcoholic fatty liver disease pathophysiology continues to advance rapidly. Accordingly, the field has moved from describing the clinical phenotype through the presence of nonalcoholic steatohepatitis (NASH) and degree of fibrosis to deep phenotyping with a description of associated comorbidities, genetic polymorphisms and environmental influences that could be associated with disease progression. These insights have fuelled a robust therapeutic pipeline across a variety of new targets to resolve steatohepatitis or reverse fibrosis, or both. Additionally, some of these therapies have beneficial effects that extend beyond the liver, such as effects on glycaemic control, lipid profile and weight loss. In addition, emerging therapies for NASH cirrhosis would have to demonstrate either reversal of fibrosis with associated reduction in portal hypertension or at least delay the progression with eventual decrease in liver-related outcomes. For non-cirrhotic NASH, it is the expectation that reversal of fibrosis by one stage or resolution of NASH with no worsening in fibrosis will need to be accompanied by overall survival benefits. In this Review, we summarize NASH therapies that have progressed to phase II and beyond. We also discuss some of the potential clinical challenges with the use of these new therapies when approved.

Nutrigenetic Interactions Might Modulate the Antioxidant and Anti-Inflammatory Status in Mastiha-Supplemented Patients With NAFLD

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease with no therapeutic consensus. Oxidation and inflammation are hallmarks in the progression of this complex disease, which also involves interactions between the genetic background and the environment. Mastiha is a natural nutritional supplement known to possess antioxidant and anti-inflammatory properties. This study investigated how a 6-month Mastiha supplementation (2.1 g/day) could impact the antioxidant and inflammatory status of patients with NAFLD, and whether genetic variants significantly mediate these effects. We recruited 98 patients with obesity (BMI ≥ 30 kg/m²) and NAFLD and randomly allocated them to either the Mastiha or the placebo group for 6 months. The anti-oxidative and inflammatory status was assessed at baseline and post-treatment. Genome-wide genetic data was also obtained from all participants, to investigate gene-by-Mastiha interactions. NAFLD patients with severe obesity (BMI > 35kg/m²) taking the Mastiha had significantly higher total antioxidant status (TAS) compared to the corresponding placebo group (P value=0.008). We did not observe any other significant change in the investigated biomarkers as a result of Mastiha supplementation alone. We identified several novel gene-by-Mastiha interaction associations with levels of cytokines and antioxidant biomarkers. Some of the identified genetic loci are implicated in the pathological pathways of NAFLD, including the lanosterol synthase gene (LSS) associated with glutathione peroxidase activity (Gpx) levels, the mitochondrial pyruvate carrier-1 gene (MPC1) and the sphingolipid transporter-1 gene (SPNS1) associated with hemoglobin levels, the transforming growth factor‐beta‐induced gene (TGFBI) and the micro-RNA 129-1 (MIR129-1) associated with IL-6 and the granzyme B gene (GZMB) associated with IL-10 levels. Within the MAST4HEALTH randomized clinical trial (NCT03135873, www.clinicaltrials.gov) Mastiha supplementation improved the TAS levels among NAFLD patients with severe obesity. We identified several novel genome-wide significant nutrigenetic interactions, influencing the antioxidant and inflammatory status in NAFLD.

The Effect of Genetic Polymorphism in Response to Body Weight Reduction in Japanese Patients with Nonalcoholic Fatty Liver Disease

BACKGROUND

weight loss as a result of lifestyle intervention is effective when treating non-alcoholic fatty liver disease (NAFLD). We estimated the effects of PNPLA3 rs738409 and HSD17B13 rs6834314 variants in response to diet therapy in Japanese patients with NAFLD.

METHODS

we analyzed the correlation between the change in liver stiffness and change in body weight in 140 patients administered diet therapy for 1-year, according to PNPLA3 and HSD17B13 genotypes.

RESULTS

the bodyweight (BW) reduction rate was greater in patients with the PNPLA3 genotype CC than CG and GG (p = 0.035). Change in liver stiffness measurement (LSM) was significantly associated with a change in BW in PNPLA3 CG/GG (r = 0.279/0.381), but not in PNPLA3 CC (p = 0.187). Change in LSM was correlated with change in BW only in patients with HSD17B13 AG/GG (r = 0.425), but not the AA genotype (p = 0.069). A multivariate analysis identified that a change in LSM was correlated with a change in BW in carriers of HSD17B13 AG/GG (B = 3.043, p = 0.032), but not HSD17B13 AA. The change in LSM of patients with a BW reduction of more than 7% (0.50) was significantly greater than that of patients with a BW reduction of less than 7% (0.83) (p = 0.038).

CONCLUSIONS

in Japanese patients with NAFLD, HSD17B13 rs6834314 polymorphism is associated with the change in LSM by lifestyle intervention. The approach, including genetic assessments, may contribute to the establishment of appropriate therapeutic strategies to treat NAFLD.

Sex and Menopause Modify the Effect of Single Nucleotide Polymorphism Genotypes on Fibrosis in NAFLD

The development of fibrosis in nonalcoholic fatty liver disease (NAFLD) is influenced by genetics, sex, and menopausal status, but whether genetic susceptibility to fibrosis is influenced by sex and reproductive status is unclear. Our aim was to identify metabolism-related single nucleotide polymorphisms (SNPs), whose effect on NAFLD fibrosis is significantly modified by sex and menopausal status. We performed a cross-sectional, proof-of-concept study of 616 patients in the Duke NAFLD Clinical Database and Biorepository. The primary outcome was nonalcoholic steatohepatitis-Clinical Research Network (NASH-CRN) fibrosis stage. Menopause status was self-reported; age 51 years was used as a surrogate for menopause in patients with missing menopause data. The Metabochip was used to obtain 98,359 SNP genotypes in known metabolic pathway genes for each patient. We used additive genetic models to characterize sex and menopause-specific effects of SNP genotypes on NAFLD fibrosis stage. In the main effects analysis, none of the SNPs were associated with fibrosis at P < 0.05 after correcting for multiple comparisons. Twenty-five SNPs significantly interacted with sex/menopause to affect fibrosis stage (interaction P < 0.0001). After removal of loci in linkage disequilibrium, 10 independent loci were identified. Six were in the following genes: KCNIP4 (potassium voltage-gated channel interacting protein 4), PSORS1C1 (psoriasis susceptibility 1 candidate 1), KLHL8 (Kelch-like family member 8), GLRA1 (glycine receptor alpha 1), NOTCH2 (notch receptor 2), and PRKCH (protein kinase C eta), and four SNPs were intergenic. In stratified models, four SNPs were significant in premenopausal and postmenopausal women, three only in postmenopausal women, two in men and postmenopausal women, and one only in premenopausal women. Conclusion: We identified 10 loci with a significant sex/menopause interaction with respect to fibrosis. None of these SNPs were significant in all sex/menopause groups, suggesting modulation of genetic susceptibility to fibrosis by sex and menopause status. Future studies of genetic predictors of NAFLD progression should account for sex and menopause.

Exploring a Region on Chromosome 8p23.1 Displaying Positive Selection Signals in Brazilian Admixed Populations: Additional Insights Into Predisposition to Obesity and Related Disorders

We recently reported a deviation of local ancestry on the chromosome (ch) 8p23.1, which led to positive selection signals in a Brazilian population sample. The deviation suggested that the genetic variability of candidate genes located on ch 8p23.1 may have been evolutionarily advantageous in the early stages of the admixture process. In the present work, we aim to extend the previous work by studying additional Brazilian admixed individuals and examining DNA sequencing data from the ch 8p23.1 candidate region. Thus, we inferred the local ancestry of 125 exomes from individuals born in five towns within the Southeast region of Brazil (São Paulo, Campinas, Barretos, and Ribeirão Preto located in the state of São Paulo and Belo Horizonte, the capital of the state of Minas Gerais), and compared to data from two public Brazilian reference genomic databases, BIPMed and ABraOM, and with information from the 1000 Genomes Project phase 3 and gnomAD databases. Our results revealed that ancestry is similar among individuals born in the five Brazilian towns assessed; however, an increased proportion of sub-Saharan African ancestry was observed in individuals from Belo Horizonte. In addition, individuals from the five towns considered, as well as those from the ABRAOM dataset, had the same overrepresentation of Native-American ancestry on the ch 8p23.1 locus that was previously reported for the BIPMed reference sample. Sequencing analysis of ch 8p23.1 revealed the presence of 442 non-synonymous variants, including frameshift, inframe deletion, start loss, stop gain, stop loss, and splicing site variants, which occurred in 24 genes. Among these genes, 13 were associated with obesity, type II diabetes, lipid levels, and waist circumference (PRAG1, MFHAS1, PPP1R3B, TNKS, MSRA, PRSS55, RP1L1, PINX1, MTMR9, FAM167A, BLK, GATA4, and CTSB). These results strengthen the hypothesis that a set of variants located on ch 8p23.1 that result from positive selection during early admixture events may influence obesity-related disease predisposition in admixed individuals of the Brazilian population. Furthermore, we present evidence that the exploration of local ancestry deviation in admixed individuals may provide information with the potential to be translated into health care improvement.

Individualized Polygenic Risk Score Identifies NASH in the Eastern Asia Region: A Derivation and Validation Study

INTRODUCTION

Strong evidence indicates that multiple genetic and environmental risk factors play a role in the pathogenesis of nonalcoholic steatohepatitis (NASH). We aimed to develop and validate a novel nomogram, incorporating both genetic and clinical factors, for predicting NASH.

METHODS

A total of 1,070 Asian individuals with biopsy-confirmed nonalcoholic fatty liver disease (NAFLD) from 2 countries (China and South Korea) were recruited. The histological spectrum of NAFLD was classified according to the NASH clinical research network scoring system. The nomogram was developed in the Chinese training set (n = 402), and then, it was validated in both the Chinese internal validation set (n = 136) and the external Korean validation cohort (n = 532), respectively.

RESULTS

Sex, metabolic syndrome, insulin resistance, serum aspartate aminotransferase levels, and PNPLA3 (rs738409) and HSD17B13 (rs72613567) genetic variants were strongly associated with NASH. Based on their regression coefficients, we developed a nomogram with good discriminatory ability (area under the receiver operating characteristic curve: 0.81, 95% confidence interval [CI] 0.77-0.85) and good calibration (Hosmer-Lemeshow test, P = 0.794) for identifying NASH. In the 2 validation cohorts, the nomogram showed high area under the receiver operating characteristic curves (internal validation set: 0.80, 95% CI 0.72-0.88; external validation cohort: 0.76, 95% CI 0.72-0.80) and good calibration.

DISCUSSION

Our newly developed and externally validated nomogram, incorporating both genetic and clinical risk factors, may be conveniently used to predict NASH. Further validation studies in other ethnic groups are warranted to confirm its diagnostic utility to identify NASH, among patients with biopsy-proven NAFLD.

The Role of Diagnostic Biomarkers, Omics Strategies, and Single-Cell Sequencing for Nonalcoholic Fatty Liver Disease in Severely Obese Patients

Liver disease due to metabolic dysfunction constitute a worldwide growing health issue. Severe obesity is a particularly strong risk factor for non-alcoholic fatty liver disease, which affects up to 93% of these patients. Current diagnostic markers focus on the detection of advanced fibrosis as the major predictor of liver-related morbidity and mortality. The most accurate diagnostic tools use elastography to measure liver stiffness, with diagnostic accuracies similar in normal-weight and severely obese patients. The effectiveness of elastography tools are however hampered by limitations to equipment and measurement quality in patients with very large abdominal circumference and subcutaneous fat. Blood-based biomarkers are therefore attractive, but those available to date have only moderate diagnostic accuracy. Ongoing technological advances in omics technologies such as genomics, transcriptomics, and proteomics hold great promise for discovery of biomarkers and increased pathophysiological understanding of non-alcoholic liver disease and steatohepatitis. Very recent developments have allowed for single-cell sequencing and cell-type resolution of gene expression and function. In the near future, we will therefore likely see a multitude of breakthrough biomarkers, developed from a deepened understanding of the biological function of individual cell types in the healthy and injured liver.

Hypermethylation of the PZP gene is associated with hepatocellular carcinoma cell proliferation, invasion and migration

Pregnancy zone protein (PZP), a member of the proteinase inhibitor I39 (‐2‐macroglobulin) family of proteins, is involved in the initiation and development of various tumors. The gene encoding PZP is hypermethylated and expressed at low levels in hepatocellular carcinoma (HCC) tissue and cells, but the function of PZP in HCC cells remains unclear. Here, we analyzed DNA methylation and mRNA expression of HCC in The Cancer Genome Atlas Liver Hepatocellular Carcinoma dataset. We identified 10 methylation‐driven genes, of which PZP was significantly hypermethylated and poorly expressed in tumor tissue. We confirmed that PZP is highly methylated and poorly expressed in HCC cell lines via quantitative real‐time PCR experiment and methylation‐specific PCR. Furthermore, PZP markedly inhibited the proliferation, invasion and migration of HCC cells. These findings may provide a basis for exploring novel therapeutic targets for HCC.

Exome-wide scan identifies significant association of rs4788084 in IL27 promoter with increase in hepatic fat content among Indians

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a global epidemic that often progresses to liver cirrhosis and hepatocellular carcinoma. In contrast to most world populations where NAFLD is mostly prevalent among obese, NAFLD among Indians and generally among South and South-East Asians is unique and highly prevalent among individuals who are lean. Genetics of NAFLD in Indian populations is understudied. In this study, we have used an exome-wide approach to identify genetic determinants of hepatic fat content (HFC) in India.

METHODS

HFC was measured in 244 participants using Proton magnetic resonance spectroscopy (H1-MRS). Quantitative trait loci (QTL) mapping was done exome-wide, to identify SNPs associated with HFC. The effects of the interaction between adiposity and QTLs on HFC were studied using a regression model. Association of the significant loci with disease severity was studied in 146 NAFLD patients among 244 participants, who underwent liver biopsy.

RESULTS

Our study identified 4 significantly associated SNPs (rs738409 and rs2281135 (PNPLA3), rs3761472 (SAMM50), rs17513722 (FAM161A) and rs4788084), with HFC after adjusting for the effects of covariates (p-value < 0.0005). rs738409, rs2281135 (PNPLA3), and rs3761472 (SAMM50) were associated with hepatocyte ballooning, lobular and portal inflammation and non-alcoholic steatohepatitis (NASH) (p-value < 0.05). rs4788048 is an eQTL for IL27 and SULT1A2 genes, both of which are highly expressed in healthy livers and are likely to be involved in NAFLD pathogenesis.

CONCLUSIONS

Our study identified the novel association of rs4788084 with HFC, which regulates the expression of IL-27, an immune regulatory gene. We further showed that adiposity affected the HFC, irrespective of the genetic predisposition.

Identifying Shared Risk Genes between Nonalcoholic Fatty Liver Disease and Metabolic Traits by Cross-Trait Association Analysis

Nonalcoholic fatty liver disease (NAFLD) generally co-occurs with metabolic disorders, but it is unclear which genes have a pleiotripic effect on NAFLD and metabolic traits. We performed a large-scale cross-trait association analysis to identify the overlapping genes between NAFLD and nine metabolic traits. Among all the metabolic traits, we found that obesity and type II diabetes are associated with NAFLD. Then, a multitrait association analysis among NAFLD, obesity and type II diabetes was conducted to improve the overall statistical power. We identified 792 significant variants by a cross-trait meta-analysis involving 100 pleiotripic genes. Moreover, we detected another two common genes by a genome-wide gene test. The results from the pathway enrichment analysis show that the 102 shared risk genes are enriched in cancer, diabetes, insulin secretion, and other related pathways. This study can help us understand the molecular mechanisms underlying comorbid NAFLD and metabolic disorders.

Genetic and epigenetic disease modifiers: non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD)

Inter-individual and inter-ethnic differences and difference in the severity and progression of liver disease among patients with non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) suggests the involvement of genetic and epigenetic factors in their pathogenesis. This article reviews the genetic and epigenetic modifiers in patients with NAFLD and ALD. Evidence regarding the genetic and epigenetic disease modifiers of NAFLD and ALD was reviewed by searching the available literature. Both genome wide association studies (GWAS) and candidate gene studies pertaining to the pathogenesis in both diseases were included. Clinical implications of the available information are also discussed. Several studies have shown association of both NAFLD and ALD with I148M PNPLA3 variant. In addition to the higher prevalence of hepatic steatosis, the I148M PNPLA3 variant is also associated with severity of liver disease and risk of hepatocellular carcinoma (HCC). TM6SF2 is the other genetic variant shown to be significantly associated with hepatic steatosis and cirrhosis in patients with NAFLD and ALD. The Membrane bound O-acyltransferase domain-containing 7 (MBOAT7) genetic variant is also associated with both NAFLD and ALD. In addition to these mutations, several variants related to the genes involved in glucose metabolism, insulin resistance, lipid metabolism, oxidative stress, inflammatory pathways, fibrosis have also been shown to be the disease modifiers in patients with NAFLD and ALD. Epigenetics involving several micro RNAs and DNA methylation could also modify the disease course in NAFLD and ALD. In conclusion the available literature suggests that genetics and epigenetics are involved in the pathogenesis of NAFLD and ALD which may affect the disease prevalence, severity and response to treatment in these patients.

Liver Fibrosis in Non-alcoholic Fatty Liver Disease: From Liver Biopsy to Non-invasive Biomarkers in Diagnosis and Treatment

An increasing percentage of people have or are at risk to develop non-alcoholic fatty liver disease (NAFLD) worldwide. NAFLD comprises different stadia going from isolated steatosis to non-alcoholic steatohepatitis (NASH). NASH is a chronic state of liver inflammation that leads to the transformation of hepatic stellate cells to myofibroblasts. These cells produce extra-cellular matrix that results in liver fibrosis. In a normal situation, fibrogenesis is a wound healing process that preserves tissue integrity. However, sustained and progressive fibrosis can become pathogenic. This process takes many years and is often asymptomatic. Therefore, patients usually present themselves with end-stage liver disease e.g., liver cirrhosis, decompensated liver disease or even hepatocellular carcinoma. Fibrosis has also been identified as the most important predictor of prognosis in patients with NAFLD. Currently, only a minority of patients with liver fibrosis are identified to be at risk and hence referred for treatment. This is not only because the disease is largely asymptomatic, but also due to the fact that currently liver biopsy is still the golden standard for accurate detection of liver fibrosis. However, performing a liver biopsy harbors some risks and requires resources and expertise, hence is not applicable in every clinical setting and is unsuitable for screening. Consequently, different non-invasive diagnostic tools, mainly based on analysis of blood or other specimens or based on imaging have been developed or are in development. In this review, we will first give an overview of the pathogenic mechanisms of the evolution from isolated steatosis to fibrosis. This serves as the basis for the subsequent discussion of the current and future diagnostic biomarkers and anti-fibrotic drugs.

Validation of genetic variants associated with metabolic dysfunction-associated fatty liver disease in an ethnic Chinese population

BACKGROUND

Genetic factors play an important role in the pathogenesis and development of metabolic dysfunction-associated fatty liver disease (MAFLD).

AIM

To study the association of single nucleotide polymorphisms (SNPs), previously identified in Western populations, with the risk of MAFLD in a Singapore Chinese population and their interactions with environmental and medical risk factors.

METHODS

A retrospective case-control study was conducted with 72 MAFLD cases and 72 controls with no hepatic steatosis on computed tomography, magnetic resonance imaging, or controlled attenuation parameter score. Subjects were recruited from two tertiary hospitals. Genetic alleles such as NCAN, GCKR, LYPLAL1, PNPLA3, PPP1R3B, FDFT1, COL13A1, EFCAB4B, PZP, and TM6SF2 were genotyped using the TaqMan^® Predesigned SNP Genotyping Assay.

RESULTS

Weight and body mass index (BMI) were 1.2-times higher in patients (70.6 kg, 95% confidence interval [CI]: 57.1-84.1 vs 60.8 kg, 95%CI: 48.5-73.1, P < 0.001 and 26.9 kg, 95%CI: 23-40.8 vs 23.3 kg 95%CI: 19-27.6, P < 0.001 respectively). The prevalence of diabetes mellitus in patients was 40.3% and 20.8% in controls (P = 0.011). Patients had higher mean triglycerides than controls (P < 0.001). PNPLA3 GG was more likely to be associated with MAFLD (43.4% CC vs 69.7% GG, P = 0.017, and 44.8% CG vs 69.7% GG, P = 0.022). In multivariable analysis, hypertriglyceridemia (odds ratio [OR]: 2.04 95%CI: 1.3-3.1, P = 0.001), BMI (OR: 1.2 95%CI: 1.1-1.4, P < 0.001) and PNPLA3 GG (OR: 3.4 95%CI: 1.3-9.2, P = 0.014) were associated with MAFLD (area under the receiver operating characteristic curve of 0.823).

CONCLUSION

Among the Chinese population of Singapore, PNPLA3 homozygous GG allele is a strong predictor of MAFLD, whereas LYPLAL1, GCKR, FDFT1, COL13A1, PZP, and TM6SF2 are not significantly associated. Hypertriglyceridemia, high BMI, and PNPLA3 GG are independent predictors of MAFLD.