Prevalence of the TM6SF2 variant and non-alcoholic fatty liver disease in Chinese

Unraveling Mechanisms of Genetic Risks in Metabolic Dysfunction-Associated Steatotic Liver Diseases: A Pathway to Precision Medicine

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a growing global health problem, affecting ∼1 billion people. This condition is well established to have a heritable component with strong familial clustering. With the extraordinary breakthroughs in genetic research techniques coupled with their application to large-scale biobanks, the field of genetics in MASLD has expanded rapidly. In this review, we summarize evidence regarding genetic predisposition to MASLD drawn from family and twin studies. Significantly, we delve into detailed genetic variations associated with diverse pathogenic mechanisms driving MASLD. We highlight the interplay between these genetic variants and their connections with metabolic factors, the gut microbiome, and metabolites, which collectively influence MASLD progression. These discoveries are paving the way for precise medicine, including noninvasive diagnostics and therapies. The promising landscape of novel genetically informed drug targets such as RNA interference is explored. Many of these therapies are currently under clinical validation, raising hopes for more effective MASLD treatment.

Intestinal TM6SF2 protects against metabolic dysfunction-associated steatohepatitis through the gut-liver axis

Transmembrane-6 superfamily member 2 (TM6SF2) regulates hepatic fat metabolism and is associated with metabolic dysfunction-associated steatohepatitis (MASH). TM6SF2 genetic variants are associated with steatotic liver disease. The pathogenesis of MASH involves genetic factors and gut microbiota alteration, yet the role of host-microbe interactions in MASH development remains unclear. Here, we discover that mice with intestinal epithelial cell-specific knockout of Tm6sf2 (Tm6sf2ΔIEC) develop MASH, accompanied by impaired intestinal barrier and microbial dysbiosis. Transplanting stools from Tm6sf2ΔIEC mice induces steatohepatitis in germ-free recipient mice, whereas MASH is alleviated in Tm6sf2ΔIEC mice co-housed with wild-type mice. Mechanistically, Tm6sf2-deficient intestinal cells secrete more free fatty acids by interacting with fatty acid-binding protein 5 to induce intestinal barrier dysfunction, enrichment of pathobionts, and elevation of lysophosphatidic acid (LPA) levels. LPA is translocated from the gut to the liver, contributing to lipid accumulation and inflammation. Pharmacological inhibition of the LPA receptor suppresses MASH in both Tm6sf2ΔIEC and wild-type mice. Hence, modulating microbiota or blocking the LPA receptor is a potential therapeutic strategy in TM6SF2 deficiency-induced MASH.

Interaction Between PNPLA3 and SIRT5 Genetic Variants in Association with Liver Fibrosis Severity in Patients with Metabolic Dysfunction-Associated Steatotic Liver Disease

BACKGROUND/OBJECTIVES

This study evaluated the association between polymorphisms in the PNPLA3, TM6SF2, HSD17B13, and SIRT5 genes and the severity of fibrosis and steatosis in metabolic dysfunction-associated steatotic liver disease (MASLD).

METHODS

Fibrosis and steatosis were assessed by MRE and MRI-PDFF, respectively. The polymorphisms were determined by allelic discrimination in blood samples.

RESULTS

204 patients aged 57.0 ± 13.5 years were included. Sixty-two (30.4%) patients had significant fibrosis (≥F2). Among F2-F4 fibrosis, the PNPLA3 rs738409 GG genotype was significantly higher than the CC + CG genotypes (44.9% vs. 21.4%, p = 0.001). The SIRT5 rs12216101 GG vs. TT + TG genotypes also exhibited a similar trend (64.3% vs. 27.9%, p = 0.012). In multivariate analysis, the PNPLA3 GG genotype (OR = 3.48, 95%CI: 1.50-8.06; p = 0.004) and SIRT5 rs12216101 GG genotype (OR = 5.43, 95%CI: 1.32-22.33; p = 0.019) were independently associated with F2-F4 fibrosis. Additionally, the proportion of patients with F2-F4 fibrosis significantly increased with the number of combined risk genotypes. Among S2-S3 steatosis, the prevalence of HSD17B13 AG + GG genotypes was higher than that of the AA genotype (37.5% vs. 23.9%, p = 0.048) and independently associated with moderate/severe steatosis in multivariate analysis (OR = 2.26, 95%CI: 1.14-4.49; p = 0.020).

CONCLUSIONS

Our data indicate that the PNPLA3 and SIRT5 polymorphisms were independently and additively linked to significant fibrosis, while the HSD17B13 polymorphism was associated with increased steatosis in Thai populations. These data might emphasize the importance of genetic variants in progressive MASLD.

Gut microbiota in MAFLD: therapeutic and diagnostic implications

Metabolic dysfunction-associated fatty liver disease (MAFLD), formerly known as nonalcoholic fatty liver disease, is becoming a significant contributor to chronic liver disease globally, surpassing other etiologies, such as viral hepatitis. Prevention and early treatment strategies to curb its growing prevalence are urgently required. Recent evidence suggests that targeting the gut microbiota may help treat and alleviate disease progression in patients with MAFLD. This review aims to explore the complex relationship between MAFLD and the gut microbiota in relation to disease pathogenesis. Additionally, it delves into the therapeutic strategies targeting the gut microbiota, such as diet, exercise, antibiotics, probiotics, synbiotics, glucagon-like peptide-1 receptor agonists, and fecal microbiota transplantation, and discusses novel biomarkers, such as microbiota-derived testing and liquid biopsy, for their diagnostic and staging potential. Overall, the review emphasizes the urgent need for preventive and therapeutic strategies to address the devastating consequences of MAFLD at both individual and societal levels and recognizes that further exploration of the gut microbiota may open avenues for managing MAFLD effectively in the future.

Genetic and metabolic aspects of non-alcoholic fatty liver disease (NAFLD) pathogenicity

Background

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease showing a rising prevalence globally. Genetic predisposition plays a key role in the development and progression of the disease pathogenicity.

Main body

This paper summarizes genetic associations based on their influence on several metabolic aspects such as lipid metabolism, glucose metabolism, hepatic iron accumulation and cholesterol metabolism toward the NAFLD pathogenicity. Furthermore, we present variations in some epigenetic characters and the microRNA profile with regard to NAFLD.

Conclusion

As reported in many studies, the PNPLA3 rs738409 variant seems to be significantly associated with NAFLD susceptibility. Other gene variants like TM6SF2 rs58542926, MBOAT7 rs641738 and GCKR variants also appear to be more prevalent among NAFLD patients. We believe these genetic variants may provide insights into new trends in developing noninvasive biomarkers and identify their suitability in clinical practice in the future.

Graphical abstract

Genetic Predictors of Comorbid Course of COVID-19 and MAFLD: A Comprehensive Analysis

Metabolic-associated fatty liver disease (MAFLD) and its potential impact on the severity of COVID-19 have gained significant attention during the pandemic. This review aimed to explore the genetic determinants associated with MAFLD, previously recognized as non-alcoholic fatty liver disease (NAFLD), and their potential influence on COVID-19 outcomes. Various genetic polymorphisms, including PNPLA3 (rs738409), GCKR (rs780094), TM6SF2 (rs58542926), and LYPLAL1 (rs12137855), have been investigated in relation to MAFLD susceptibility and progression. Genome-wide association studies and meta-analyses have revealed associations between these genetic variants and MAFLD risk, as well as their effects on lipid metabolism, glucose regulation, and liver function. Furthermore, emerging evidence suggests a possible connection between these MAFLD-associated polymorphisms and the severity of COVID-19. Studies exploring the association between indicated genetic variants and COVID-19 outcomes have shown conflicting results. Some studies observed a potential protective effect of certain variants against severe COVID-19, while others reported no significant associations. This review highlights the importance of understanding the genetic determinants of MAFLD and its potential implications for COVID-19 outcomes. Further research is needed to elucidate the precise mechanisms linking these genetic variants to disease severity and to develop gene profiling tools for the early prediction of COVID-19 outcomes. If confirmed as determinants of disease severity, these genetic polymorphisms could aid in the identification of high-risk individuals and in improving the management of COVID-19.

TM6SF2 reduces lipid accumulation in vascular smooth muscle cells by inhibiting LOX-1 and CD36 expression

TM6SF2, predominantly expressed in the liver and intestine, is closely associated with lipid metabolism. We have demonstrated the presence of TM6SF2 in VSMCs within human atherosclerotic plaques. Subsequent functional studies were conducted to investigate its role in lipid uptake and accumulation in human vascular smooth muscle cells (HAVSMCs) using siRNA knockdown and overexpression techniques. Our results showed that TM6SF2 reduced lipid accumulation in oxLDL-stimulated VSMCs, likely through the regulation of lectin-like oxLDL receptor 1 (LOX-1) and scavenger receptor cluster of differentiation 36 (CD36) expression. We concluded that TM6SF2 plays a role in HAVSMC lipid metabolism with opposing effects on cellular lipid droplet content by downregulation of LOX-1 and CD36 expression.

Genetic Markers Predisposing to Nonalcoholic Steatohepatitis

The growing prevalence of nonalcoholic fatty liver disease (NAFLD) has sparked interest in understanding genetics and epigenetics associated with the development and progression of the disease. A better understanding of the genetic factors related to progression will be beneficial in the risk stratification of patients. These genetic markers can also serve as potential therapeutic targets in the future. In this review, we focus on the genetic markers associated with the progression and severity of NAFLD.

Direct activation of the fibroblast growth factor-21 pathway in overweight and obese cats

Introduction

Feline obesity is common, afflicting ~25-40% of domestic cats. Obese cats are predisposed to many metabolic dyscrasias, such as insulin resistance, altered blood lipids, and feline hepatic lipidosis. Fibroblast Growth Factor-21 (FGF21) is an endocrine hormone that mediates the fat-liver axis, and in humans and animals, FGF21 can ameliorate insulin resistance, non-alcoholic fatty liver disease, and obesity. Activation of the FGF21 pathway may have therapeutic benefits for obese cats.

Methods

In this preliminary cross-sectional study, ad libitum fed, purpose-bred, male-neutered, 6-year-old, obese and overweight cats were administered either 10 mg/kg/day of an FGF21 mimetic (FGF21; n = 4) or saline (control; n = 3) for 14 days. Body weight, food, and water intake were quantified daily during and 2 weeks following treatment. Changes in metabolic and liver parameters, intrahepatic triglyceride content, liver elasticity, and gut microbiota were evaluated.

Results

Treatment with FGF21 resulted in significant weight loss (~5.93%) compared to control and a trend toward decreased intrahepatic triglyceride content. Cats treated with FGF21 had decreased serum alkaline phosphatase. No significant changes were noted in liver elasticity, serum, liver, or metabolic parameters, or gut microbiome composition.

Discussion

In obese and overweight cats, activation of the FGF21 pathway can safely induce weight loss with trends to improve liver lipid content. This exploratory study is the first to evaluate the FGF21 pathway in cats. Manipulation of the FGF21 pathway has promising potential as a therapeutic for feline obesity. Further studies are needed to see if FGF21-pathway manipulation can be therapeutic for feline hepatic lipidosis.

Molecular Screening via Sanger Sequencing of the Genetic Variants in Non-Alcoholic Fatty Liver Disease Subjects in the Saudi Population: A Hospital-Based Study

Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases, along with steatosis and non-alcoholic steatohepatitis (NASH), and is associated with cirrhosis and hepatocellular carcinoma. Candidate gene and genome-wide association studies have validated the relationships between NAFLD, NASH, PNPLA3, TM6SF2, and HFE. The present study utilized five polymorphisms in three genes: PNPLA3 (I148M and K434E) TM6SF2 (E167K), and HFE (H63D and C282Y), based on undocumented case−control studies in the Saudi Arabian population. A total of 95 patients with NAFLD and 78 non-NAFLD subjects were recruited. Genomic DNA was isolated, and polymerase chain reaction and Sanger sequencing were performed using specific primers for the I148M, K434E, E167K, H63D, and C282Y. NAFLD subjects were older when compared to controls and showed the significant association (p = 0.0001). Non-significant association was found between gender (p = 0.26). However, both weight and BMI were found to be associated. Hardy−Weinberg equilibrium analysis confirmed that H63D, I148M, and K434E polymorphisms were associated. Genotype analysis showed only K434E variant was associated with NAFLD and non-NAFLD (OR-2.16; 95% CI: 1.08−4.31; p = 0.02). However, other polymorphisms performed with NAFLD and NASH were not associated (p > 0.05), and similar analysis was found when ANOVA was performed (p > 0.05). In conclusion, we confirmed that K434E polymorphism showed a positive association in the Saudi population.

Genetic variants associated with metabolic dysfunction-associated fatty liver disease in western China

INTRODUCTION

We aimed to confirm the association between some single nucleotide polymorphisms (SNPs) and metabolic dysfunction-associated fatty liver disease (MAFLD) in western China.

METHODS

A total of 286 cases and 250 healthy controls were enrolled in our study. All samples were genotyped for patatin-like phospholipase domain containing 3 (PNPLA3) rs738409, transmembrane 6 superfamily member 2 (TM6SF2) rs58542926, membrane-bound O-acyltransferase domain containing 7 (MBOAT7) rs641738, glucokinase regulator (GCKR) rs1260326 and rs780094, and GATA zinc finger domain containing 2A (GATAD2A) rs4808199. Using logistic regression analysis, we evaluated the association between MAFLD and each SNP under different models. Multiple linear regression was used to find the association between SNPs and laboratory characteristics. Multifactor dimensionality reduction was applied to test SNP-SNP interactions.

RESULTS

The recessive model and additive model of PNPLA3 rs738409 variant were related to MAFLD (odds ratio [OR] = 1.791 and 1.377, respectively, p = 0.038 and 0.027, respectively). However, after Benjamini-Hochberg adjustment for multiple tests, all associations were no longer statistically significant. PNPLA3 rs738409 correlated with AST levels. GCKR rs780094 and rs1260326 negatively correlated with serum glucose but positively correlated with triglycerides in MAFLD. Based on MDR analysis, the best single-locus and multilocus models for MAFLD risk were rs738409 and six-locus models, respectively.

CONCLUSIONS

In the Han population in western China, no association was found between these SNPs and the risk of MAFLD. PNPLA3 rs738409 was associated with aspartate aminotransferase levels in MAFLD patients. GCKR variants were associated with increased triglyceride levels and reduced serum fasting glucose in patients with MAFLD.

TM6SF2: A Novel Genetic Player in Nonalcoholic Fatty Liver and Cardiovascular Disease

Transmembrane 6 superfamily member 2 (TM6SF2) is located on chromosome 19 (19p12) and encodes for a protein of undetermined function. Genetic studies have reported the association between a nonsynonymous variant in TM6SF2 (E167K, rs58542926) with hepatic triglyceride content and its impact on the cardiovascular system. Clinical and epidemiological studies have confirmed the role of TM6SF2 in the development of nonalcoholic fatty liver disease (NAFLD). Recently, TM6SF2 was also shown to play an important role in promoting hepatic fibrosis and hepatocellular cancer in mouse models. This review aims to capture the physiological role of TM6SF2 in the regulation of lipid metabolism and its involvement in cardiometabolic diseases.

Asian perspective on NAFLD-associated HCC

Recent data suggest that non-alcoholic fatty liver disease (NAFLD) has become a major public health problem in Asia, with an updated population prevalence of 34%. In parallel, NAFLD-associated hepatocellular carcinoma (HCC) is also on the rise. In this review, we describe the changing epidemiology of HCC in Asia over the past 30 years. While traditional risk factors for HCC (older age, male sex and metabolic factors) are also important in Asia, the PNPLA3 gene polymorphism is particularly prevalent in East Asia and may increase the risk of HCC. NAFLD among non-obese individuals is also commonly described in Asia. Because NAFLD is often undiagnosed, few patients receive HCC surveillance, and the target surveillance population beyond patients with cirrhosis remains poorly defined. As a result, NAFLD-associated HCC is often diagnosed at an advanced stage, rendering curative treatment impossible. Finally, despite around 20-30 years of universal vaccination, chronic HBV infection remains prevalent in Asia, and emerging evidence highlights the importance of metabolic factors and concomitant hepatic steatosis on HCC development in infected patients. Future studies should explore the role of metabolic treatments in HCC prevention among patients with hepatic steatosis and concomitant liver diseases.

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.

TM6SF2 rs58542926 is related to hepatic steatosis, fibrosis and serum lipids both in adults and children: A meta-analysis

BACKGROUND AND AIMS

Findings about the associations between transmembrane 6 superfamily member 2 (TM6SF2) rs58542926 and nonalcoholic fatty liver disease have not been consistently replicated, particularly in steatosis and fibrosis. The present study aimed to investigate the associations between the rs58542926T allele and the spectrum of NAFLD and its related metabolic phenotypes.

METHODS

Systematic literature research was performed to analyse the associations between rs58542926 and the spectrum of NAFLD and its related metabolic phenotypes. A random effects meta-analysis with a dominant genetic model was applied.

RESULTS

Data from 123,800 individuals across 44 studies were included in the current meta-analysis.rs58542926 T allele was associated with an increased risk of NAFLD in both adults (OR=1.62; 95% CI: 1.40, 1.86) and children (OR=2.87; 95% CI: 1.85, 4.46). Children had a stronger association with NAFLD (P=0.01). rs58542926 T allele was also positively associated with steatosis progression (mean difference=0.22; 95% CI: 0.05, 0.39) and fibrosis stage (OR=1.50; 95% CI: 1.20, 1.88) in adults. The TM6SF2 rs58542926 T allele was positively associated with ALT in both adults and children (both P<0.01) and only with higher AST in adults (P<0.01). The rs58542926 T allele was negatively associated with serum total cholesterol (TC), low-density lipoprotein (LDL), and triglycerides (TGs) in both adults and children (all P<0.01).The serum level of TG was much lower in adults than in children (P<0.01).

CONCLUSION

TM6SF2 rs58542926 is involved in the entire spectrum of NAFLD and its related metabolic phenotype, and differences in serum lipid levels were observed between adults and children.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42021288163.

Liver-Specific Deletion of Mouse Tm6sf2 Promotes Steatosis, Fibrosis, and Hepatocellular Cancer

BACKGROUND AND AIMS

Human transmembrane 6 superfamily 2 (TM6SF2) variant rs58542926 is associated with NAFLD and HCC. However, conflicting reports in germline Tm6sf2 knockout mice suggest no change or decreased very low density lipoprotein (VLDL) secretion and either unchanged or increased hepatic steatosis, with no increased fibrosis. We generated liver-specific Tm6Sf2 knockout mice (Tm6 LKO) to study VLDL secretion and the impact on development and progression of NAFLD.

APPROACH AND RESULTS

Two independent lines of Tm6 LKO mice exhibited spontaneous hepatic steatosis. Targeted lipidomic analyses showed increased triglyceride species whose distribution and abundance phenocopied findings in mice with liver-specific deletion of microsomal triglyceride transfer protein. The VLDL triglyceride secretion was reduced with small, underlipidated particles and unchanged or increased apolipoprotein B. Liver-specific adeno-associated viral, serotype 8 (AAV8) rescue using either wild-type or mutant E167K-Tm6 reduced hepatic steatosis and improved VLDL secretion. The Tm6 LKO mice fed a high milk-fat diet for 3 weeks exhibited increased steatosis and fibrosis, and those phenotypes were further exacerbated when mice were fed fibrogenic, high fat/fructose diets for 20 weeks. In two models of HCC, either neonatal mice injected with streptozotocin (NASH/STAM) and high-fat fed or with diethylnitrosamine injection plus fibrogenic diet feeding, Tm6 LKO mice exhibited increased steatosis, greater tumor burden, and increased tumor area versus Tm6 flox controls. Additionally, diethylnitrosamine-injected and fibrogenic diet-fed Tm6 LKO mice administered wild-type Tm6 or E167K-mutant Tm6 AAV8 revealed significant tumor attenuation, with tumor burden inversely correlated with Tm6 protein levels.

CONCLUSIONS

Liver-specific Tm6sf2 deletion impairs VLDL secretion, promoting hepatic steatosis, fibrosis, and accelerated development of HCC, which was mitigated with AAV8- mediated rescue.

NAFLD and renal function in children: is there a genetic link?

Introduction: Over the past decades, a large amount of both adult and pediatric data has shown relationship between Nonalcoholic Fatty Liver Disease (NAFLD) and chronic kidney disease (CKD), resulting in an overall increased cardiometabolic burden. In view of the remarkable role of the genetic background in the NAFLD pathophysiology, a potential influence of the major NAFLD polymorphisms (e.g. the I148M variant of the Patatin-like phospholipase containing domain 3 (PNPLA3) gene, the E167K allele of the Transmembrane 6 superfamily member 2 (TM6SF2), the hydroxysteroid 17-beta dehydrogenase 13 (HSD17B13), and the Membrane bound O-acyltransferase domain containing 7-transmembrane channel-like 4 (MBOAT7-TMC4) genes) on renal function has been supposed. A shared metabolic and proinflammatory pathogenesis has been hypothesized, but the exact mechanism is still unknown.Areas covered: We provide a comprehensive review of the potential genetic link between NAFLD and CKD in children. Convincing both adult and pediatric evidence supports this association, but there is some dispute especially in childhood.Expert opinion: Evidence supporting a potential genetic link between NAFLD and CKD represents an intriguing aspect with a major clinical implication because of its putative role in improving strategy programs to counteract the higher cardiometabolic risk of these patients.

Lean NAFLD: an underrecognized and challenging disorder in medicine

Classically, Non-Alcoholic Fatty Liver Disease (NAFLD) has been thought to be driven by excessive weight gain and obesity. The overall greater awareness of this disorder has led to its recognition in patients with normal body mass index (BMI). Ongoing research has helped to better understand potential causes of Lean NAFLD, the risks for more advanced disease, and potential therapies. Here we review the recent literature on prevalence, risk factors, severity of disease, and potential therapeutic interventions.

Lean Americans With Nonalcoholic Fatty Liver Disease Have Lower Rates of Cirrhosis and Comorbid Diseases

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is typically associated with obesity. Little is known about the prevalence of cirrhosis in patients with NAFLD and a normal body mass index (BMI).

METHODS

We determined prevalence of cirrhosis, cardiovascular disease (CVD), and metabolic abnormalities among participants in all BMI categories in the TARGET-NASH study. A total of 3386 patients with NAFLD were enrolled from August 2016 through March 2019. The odds ratios of cirrhosis, CVD, and metabolic abnormalities were estimated by age and race, adjusting for sex and center type.

RESULTS

Based on standard BMI cutoff values, 12.8% of study subjects were lean, 27.1% were overweight, 26.5% had class 1 obesity, and 33.7% had class 2 or 3 obesity. Asians accounted for 48.7% of lean participants, and proportions decreased as BMI categories increased (P < .0001). Lower proportions of lean participants had cirrhosis (22.6% vs 40.2% of non-lean participants), CVD history (9.0% vs 14.8% of nonlean participants), diabetes (32.6% vs 53.5% of non-lean participants), hypertension (47.8% vs 67.4% of non-lean participants), or dyslipidemia (54.0% vs 64.1% of non-lean participants). Asian participants had a lower prevalence of cirrhosis, history of CVD, cardiovascular events, and diabetes compared with non-Asians, independent of BMI category. After we adjusted for age, sex, and center type and site, the odds of NAFLD-associated cirrhosis in Asians who were lean was almost half the odds of NAFLD-associated cirrhosis in non-Asians who were lean (odds ratio, 0.47; 95% CI, 0.29-0.77).

CONCLUSIONS

More than 10% participants in a cohort of persons with NAFLD in the United States are lean; Asians account for almost half of the lean persons with NAFLD. Lean participants had a lower prevalence of cirrhosis, CVD, and metabolic abnormalities than non-lean persons with NAFLD. Asian participants had a significantly lower prevalence of cirrhosis, CVD, and metabolic abnormalities than non-Asians in all BMI categories. ClinicalTrials.gov, Number: NCT02815891.

A Sequential Algorithm Combining ADAPT and Liver Stiffness Can Stage Metabolic-Associated Fatty Liver Disease in Hospital-Based and Primary Care Patients

INTRODUCTION

Metabolic-associated fatty liver disease is common, with fibrosis the major determinant of adverse outcomes. Population-based screening tools with high diagnostic accuracy for the staging of fibrosis are lacking.

METHODS

Three independent cohorts, 2 with both liver biopsy and liver stiffness measurements (LSMs, n = 254 and 65) and a population sample (n = 713), were studied. The performance of a recently developed noninvasive algorithm (ADAPT [age, diabetes, PRO-C3 and platelets panel]) as well as aspartate aminotransferase-to-platelet ratio index, fibrosis-4, nonalcoholic fatty liver disease fibrosis score, and LSM was used to stage patients for significant (≥F2) and advanced (≥F3) fibrosis.

RESULTS

In the hospital-based cohorts, the N-terminal propeptide of type 3 collagen (Pro-C3) increased with fibrosis stage (P < 0.0001) and independently associated with advanced fibrosis (odds ratio = 1.091, 95% confidence interval [CI]: 1.053-1.113, P = 0.0001). ADAPT showed areas under the receiver operating characteristics curve of 0.831 (95% CI: 0.779-0.875) in the derivation and 0.879 (95% CI: 0.774-0.946) in the validation cohort for advanced fibrosis. This was superior to the existing fibrosis scores, aspartate aminotransferase-to-platelet ratio index, fibrosis-4, BARD (BMI, aspartate aminotransferase to alanine aminotransferase ratio [AAR], diabetes), and nonalcoholic fatty liver disease fibrosis score in most comparisons and comparable with LSM. Serial use of ADAPT and LSM had diagnostic accuracy of 92.5%, with 98% and 100% negative predictive value in the derivation and validation cohorts, respectively. In the population cohort, PRO-C3 associated with advanced fibrosis (P = 0.04), while ADAPT had a negative predictive value of 98% for excluding advanced fibrosis.

DISCUSSION

PRO-C3 and ADAPT reliably exclude advanced fibrosis in low-risk populations. The serial combination of ADAPT with LSM has high diagnostic accuracy with a low requirement for liver biopsy. The proposed algorithm would help stratify those who need biopsies and narrow down those patients who would need to be referred to specialty clinics.

Association of LDLR rs1433099 with the Risk of NAFLD and CVD in Chinese Han Population

BACKGROUND AND AIMS

Recent genome-wide association studies have shown that low-density lipoprotein receptor (LDLR) rs1433099 polymorphism is associated with cardiovascular disease (CVD) risk in many countries. However, the association of LDLR rs1433099 with CVD in China has not been reported yet. There are no studies on LDLR rs1433099 and non-alcoholic fatty liver disease (NAFLD) as well. The purpose of this study was to investigate whether LDLR rs1433099 is related to CVD or NAFLD in the Chinese population.

METHODS

LDLR rs1433099 polymorphism was genotyped in 507 individuals, including 140 healthy controls, 79 NAFLD patients, 185 CVD patients, and 103 patients with NAFLD combined with CVD. The expression of LDLR was tested by the sequence detection system, and clinical parameters were assessed by biochemical tests and physical examination.

RESULTS

The genotype distribution of LDLR rs1433099 was not statistically different among the NAFLD group, the CVD group, the combined group, and the healthy control group (p>0.05). There was no significant correlation of LDLR rs1433099 genotypic distribution or allele frequency and the risk of NAFLD, CVD or NAFLD combined with CVD (p>0.05). In the CVD group, T allele carriers had higher alkaline phosphatase and gamma-glutamyl transpeptidase than non-carriers (p<0.05).

CONCLUSIONS

Our study demonstrated that the LDLR rs1433099 polymorphism is not a risk factor of NAFLD. The LDLR rs1433099 polymorphism may increase the risk of CVD through a mechanism involving alkaline phosphatase and gamma-glutamyl transpeptidase.

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.

FTO Polymorphisms are Associated with Metabolic Dysfunction-Associated Fatty Liver Disease (MAFLD) Susceptibility in the Older Chinese Han Population

Background

As fat and obesity play a vital role in the pathophysiology of metabolic dysfunction-associated fatty liver disease (MAFLD), this study aims to investigate the association between the fat mass and obesity-associated gene (FTO) and MAFLD.

Methods

Six SNPs (rs6499640, rs1421085, rs8050136, rs3751812, rs9939609 and rs9930506) within FTO were genotyped for 741 MAFLD patients (median age, 69.98; interquartile range, 66.55–75.93) and 825 healthy people (median age, 69.94; interquartile range, 66.39–75.64). Allele and genotype frequencies, pairwise linkage disequilibrium (LD) and haplotype analysis were calculated.

Results

BMI, waist circumference, systolic blood pressure, diastolic blood pressure, fasting plasma glucose, triglyceride, alanine transaminase, glutamyl transpeptidase and the prevalence of diabetes were found to be higher in the MAFLD individuals comparing to the control ones (P < 0.05). For rs1421085, the C allele frequency was remarkably higher in MAFLD after Bonferroni correction (OR [95% CI] =1.353 [1.095–1.671]; P_corr =0.030), and a significantly different genotype result was observed in log-additive model (OR [95% CI] =1.369 [1.108–1.691]; P_corr =0.024). For rs8050136, significantly increased A allele frequency was observed in MAFLD (OR [95% CI] =1.371 [1.109–1.695]; P_corr =0.024), and A-allele carriers showed increased MAFLD risk (OR [95% CI] =1.393 [1.103–1.759]; P_corr =0.030). For rs3751812, the T allele frequency was remarkably higher in MAFLD (OR [95% CI] =1.369 [1.108–1.691]; P_corr =0.024), and T-allele carriers demonstrated high MAFLD risk (OR [95% CI] =1.392 [1.103–1.756]; P_corr =0.030). For rs9939609, A allele frequency was also remarkably high in MAFLD (OR [95% CI] =1.369 [1.108–1.691]; P_corr =0.024), and A-allele carriers were more susceptible to MAFLD (OR [95% CI] =[1.103–1.756]; P_corr =0.030). A strong LD was found among rs1421085, rs8050136, rs3751812 and rs9939609 (r² >0.8), and individuals with C-A-T-A haplotype had an elevated MAFLD risk (P =0.005).

Conclusion

The case-control study indicated that C variant of rs1421085, A variant of rs8050136, T variant of rs3751812 and A variant of rs9939609 are associated with elevated MAFLD risk in the older Chinese Han population.

Genome-Wide Association Study of Liver Fat: The Multiethnic Cohort Adiposity Phenotype Study

The global rise in fatty liver is a major public health problem. Thus, it is critical to identify both global and population-specific genetic variants associated with liver fat. We conducted a genome-wide association study (GWAS) of percent liver fat and nonalcoholic fatty liver disease (NAFLD) assessed by magnetic resonance imaging in 1,709 participants from the population-based Multiethnic Cohort Adiposity Phenotype Study. Our participants comprised older adults of five U.S. racial/ethnic groups: African Americans (n = 277), Japanese Americans (n = 424), Latinos (n = 348), Native Hawaiians (n = 274), and European Americans (n = 386). The established missense risk variant rs738409 located in patatin-like phospholipase domain containing 3 (PNPLA3) at 22q13 was confirmed to be associated with percent liver fat (P = 3.52 × 10-15) but more strongly in women than men (P heterogeneity = 0.002). Its frequency correlated with the prevalence of NAFLD across the five ethnic/racial groups. Rs738409 was also associated with homeostasis model assessment of insulin resistance (HOMA-IR) (beta = 0.028; P = 0.009) and circulating levels of insulin (beta = 0.022; P = 0.020) and alanine aminotransferase (beta = 0.016; P = 0.030). A novel association of percent liver fat with rs77249491 (located at 6q13 between limb region 1 domain containing 1 [LMBRD1] and collagen type XIX alpha 1 chain [COL19A1] (P = 1.42 × 10-8) was also observed. Rs7724941 was associated with HOMA-IR (beta = 0.12; P = 0.0005), insulin (beta = 0.11; P = 0.0003), triglycerides (beta = 0.059; P = 0.01), high-density lipoprotein (beta = -0.046; P = 0.04), and sex hormone binding globulin (beta = -0.084; P = 0.0012). This variant was present in Japanese Americans (minor allele frequency [MAF], 8%) and Native Hawaiians (MAF, 2%). Conclusion: We replicated the PNPLA3 rs738409 association in a multiethnic population and identified a novel liver fat risk variant in Japanese Americans and Native Hawaiians. GWASes of percent liver fat in East Asian and Oceanic populations are needed to replicate the rs77249491 association.

Association between nonalcoholic fatty liver disease and extrahepatic cancers: a systematic review and meta-analysis

BACKGROUND

NAFLD is tightly associated with various diseases such as diabetes, cardiovascular disease, kidney disease, and cancer. Previous studies had investigated the association between NAFLD and various extrahepatic cancers, but the available data to date is not conclusive. The aim of this study was to investigate the association between NAFLD and various extrahepatic cancers comprehensively.

METHODS

Searches were conducted of various electronic databases (PubMed, EMBASE, Medline, and the Cochrane Library) to identify observational studies published between 1996 and January 2020 which investigated the association between NAFLD and extrahepatic cancers. The pooled OR/HR/IRR of the association between NAFLD and various extrahepatic cancers were analyzed.

RESULTS

A total of 26 studies were included to investigate the association between NAFLD and various extrahepatic cancers. As the results shown, the pooled OR values of the risk of colorectal cancer and adenomas in patients with NAFLD were 1.72 (95%CI: 1.40-2.11) and 1.37 (95%CI: 1.29-1.46), respectively. The pooled OR values of the risk of intrahepatic cholangiocarcinoma and extrahepatic cholangiocarcinoma in patients with NAFLD were 2.46 (95%CI: 1.77-3.44) and 2.24 (95%CI: 1.58-3.17), respectively. The pooled OR value of the risk of breast cancer in patients with NAFLD was 1.69 (95%CI: 1.44-1.99). In addition, NAFLD was also tightly associatied with the risk of gastric cancer, pancreatic cancer, prostate cancer, and esophageal cancer.

CONCLUSIONS

NAFLD could significantly increase the development risk of colorectal adenomas and cancer, intrahepatic and extrahepatic cholangiocarcinoma, breast, gastric, pancreatic, prostate, and esophageal cancer. NAFLD could be considered as one of the influencing factors during the clinical diagnosis and treatment for the extrahepatic cancers.

Interaction of TM6SF2 E167K and PNPLA3 I148M variants in NAFLD in northeast China

INTRODUCTION AND AIM

This study aimed to confirm the association of the transmembrane 6 superfamily member 2 (TM6SF2) E167K variant with non-alcoholic fatty liver disease (NAFLD) and the degree of steatosis, as well as the additive effect of body mass index (BMI) or the patatin-like phospholipase domain-containing protein 3 (PNPLA3) I148M and TM6SF2 E167K variants in NAFLD.

MATERIALS AND METHODS

A total of 158 NAFLD patients and 158 matched controls were recruited. Steatosis was classified as mild, moderate and severe by FibroScan. Associations between the TM6SF2 E167K variant and NAFLD as well as clinical parameters were evaluated.

RESULTS

Although the frequency of the T allele was low in the Chinese population (MAF=7.4%), there was still a significant association between the E167K variant and NAFLD (odds ratio=3.379, 95% confidence interval: 1.500-7.612, P=0.003). In particular, the TM6SF2 genotype was also associated with the degree of steatosis (P=0.023). The TM6SF2 variant was associated with increased alanine aminotransferase (ALT) but no other clinical parameters, such as aspartate aminotransferase (AST), alkaline phosphatase (ALP) and lipids. Notably, we also found that an additive effect of the TM6SF2 E167K and PNPLA3 I148M variants in NAFLD. Furthermore, we did not identify an association between the TM6SF2 E167K variant and NAFLD in the non-obese population.

CONCLUSION

The TM6SF2 E167K variant was associated with NAFLD in northeast China, and there was an interaction between the PNPLA3 I148M and TMS6F2 E167K variants in NAFLD.

MiR-30b-5p regulates the lipid metabolism by targeting PPARGC1A in Huh-7 cell line

BACKGROUND

MiRNAs are a group of multifunctional non-coding RNAs which play an important role in the various physiological processes including the development of NAFLD. Recent studies have shown that miR-30b-5p tightly associated with the abnormal lipid metabolism in patients with NAFLD, but the detailed mechanism of miR-30b-5p in the lipid metabolism was remain unclear. The aim of this study was to investigate the effect of miR-30b-5p on the lipid metabolism in hepatocellular carcinoma Huh-7 cells.

MATERIAL AND METHODS

The correlation of intracellular fat content with the expression of miR-30b-5p in Huh-7 cells and HepG2 cells was investigated by treated cells with different concentrations of FFAs. The effect of miR-30b-5p on the lipid deposition in Huh-7 cells was tested by oil red O staining and TG concentrations measurement. qRT-PCR and western blot were used to investigate the lipid metabolism-related genes PPAR-α, SREBP-1, and GULT1 in miR-30b-5p overexpressed or inhibited Huh-7 cells. Target genes of miR-30b-5p were predicted using starBase, miRDB, and TargetScan databases and verified by qRT-PCR and western blot.

RESULTS

The expression of miR-30b-5p was significant decreased in the FFAs treated Huh-7 cells and HepG2 cells. Overexpressing miR-30b-5p in Huh-7 cells decreased the number and size of lipid droplets and intracellular TG concentrations in Huh-7 cells. Expression of fatty acid oxidation related gene PPAR-α was increased and expression of lipid synthesis related gene SREBP-1 was decreased in the miR-30b-5p overexpressed Huh-7 cells. In addition, miR-30b-5p regulates the intracellular lipid metabolism by targeting PPARGC1A.

CONCLUSIONS

Overexpression of miR-30b-5p could reduce the intracellular fat deposition in Huh-7 cells, and miR-30b-5p might regulate the intracellular lipid metabolism by targeting the PPARGC1A in Huh-7 cells.

Genetic Risk Factors and Disease Modifiers of Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease is strongly associated with obesity and the metabolic syndrome, but genetic factors also contribute to disease susceptibility. Human genetic studies have identified several common genetic variants contributing to nonalcoholic fatty liver disease initiation and progression. These findings have provided new insights into the pathogenesis of nonalcoholic fatty liver disease and opened up new avenues for the development of therapeutic interventions. In this review, we summarize the current state of knowledge about the genetic determinants of nonalcoholic fatty liver disease, focusing on the most robustly validated genetic risk factors and on recently discovered modifiers of disease progression.

Association of TM6SF2 rs58542926 gene polymorphism with the risk of non-alcoholic fatty liver disease and colorectal adenoma in Chinese Han population

Background

Genetic factors affect the risk of non-alcoholic fatty liver disease (NAFLD) and colorectal adenoma (CRA) importantly. Transmembrane protein 6 superfamily member 2 (TM6SF2) rs58542926 is a significant genetic susceptibility site for NAFLD. The relationships of TM6SF2 rs58542926 with the risk of NAFLD and CRA in Chinese Han population were unclear. The aim of this study was to investigate the association of TM6SF2 rs58542926 with the risk of NAFLD and CRA, and the effect of CRA on TM6SF2 rs58542926 carried NAFLD patients.

Results

A total of 839 Chinese Han population were included in this retrospective study. TM6SF2 rs58542926 polymorphism was genotyped in B-type ultrasonography proven NAFLD patients with or without CRA, CRA patients and healthy controls, using polymerase chain reaction. Serum lipid profiles were determined using biochemical methods. Statistical analyses were performed using SPSS statistical software, version 16.0 for mac. There was a significant difference in the distribution of genotype and allele of TM6SF2 rs58542926 in NAFLD and NAFLD&CRA patients compared to controls. The CT + TT genotypes were tightly associated with the risk of NAFLD and NAFLD&CRA. TM6SF2 rs58542926 T allele promotes the abnormal regulation of lipids metabolism and liver injury in NAFLD patients and NAFLD&CRA patients. CRA aggravates the clinical performance of NAFLD in T allele carriers.

Conclusions

We demonstrated the significant association between TM6SF2 rs58542926 polymorphism and the risk of NAFLD and NAFLD&CRA in a Chinese Han population. The TM6SF2 rs58542926 T allele promotes the abnormal regulation of lipid profiles and liver injury in NAFLD patients, NAFLD&CRA patients, and overall subjects.

Genetic polymorphisms associated with nonalcoholic fatty liver disease in Uyghur population: a case-control study and meta-analysis

Background

Polymorphisms have been identified to predispose to NAFLD. Here, we accessed the seven polymorphisms of rs1260326, rs780094 in GCKR, rs2954021 near TRIB1, rs2228603 in NCAN, rs58542926 in TM6SF2, rs12137855 near LYPLAL1, and rs10883437 near CPN1 on NAFLD susceptibility in the Uygur population.

Material and methods

We collected 620 samples (317 NAFLD and 303 controls) for this case-control study. Meta-analysis was performed using Stata Software.

Results

Our data detected that the rs1260326 (T vs. C: OR = 1.27, 95% CI = 1.01–1.59) and rs780094 (T vs. C: OR = 1.30, 95% CI = 1.04–1.63) were significantly associated with the susceptibility to NAFLD in Uygur population. The rs1260326 and rs780094 T/T genotype are significantly associated with soda, egg, and soybean intakes in the consumption group with twice or more in a week. Furthermore, a significant haplotype effect of rs1260326/T- rs780094/T was found (OR = 1.29, 95% CI: 1.03–1.62) compared with CC haplotype. An additional meta-analysis using 4352 cases and 10,168 controls established that rs780094 (OR = 1.21, 95%CI: 1.14–1.28) is significantly associated with NAFLD. Finally, among the 4 case-control studies on rs1260326, including 712 NAFLD and 658 controls, significant associations were found in Asian, liver biopsy, adult and pediatric groups.

Conclusion

Collectively, both our case-control study and meta-analysis confirm a significant association between rs780094 and NAFLD. Additionally, our results suggest Asian-specific, liver biopsy-specific, adult-specific and pediatric-specific associations between the rs1260326 and NAFLD. Moreover, the rs1260326 and rs780094 T/T genotype are significantly associated with food habits, such as soda, egg, and soybean.

Electronic supplementary material

The online version of this article (10.1186/s12944-018-0877-3) contains supplementary material, which is available to authorized users.

Magnitude of Nonalcoholic Fatty Liver Disease: Eastern Perspective

Nonalcoholic fatty liver disease (NAFLD) is currently the most common chronic liver disease worldwide, affecting a quarter of the global adult population. Nonalcoholic steatohepatitis, the more active form of NAFLD with active hepatic necroinflammation and faster fibrosis progression, has become one of the leading indications for liver transplantation and an important cause of hepatocellular carcinoma in Western countries. Epidemiological studies suggest that NAFLD is almost equally prevalent in Asia as in the West, but severe liver complications appear to be less common. In this article, we review the epidemiology, clinical characteristics, risk factors and clinical outcomes of NAFLD in Asia. We highlight the issue of NAFLD in the nonobese population and discuss whether it is a unique phenomenon in Asia. Because of the rapidly changing epidemiology and natural history, future studies should continue to monitor the magnitude of NAFLD in Asia and define the best policy to control this new epidemic.

Genetic and Epigenetic Modifiers of Alcoholic Liver Disease

Alcoholic liver disease (ALD), a disorder caused by excessive alcohol consumption is a global health issue. More than two billion people consume alcohol in the world and about 75 million are classified as having alcohol disorders. ALD embraces a wide spectrum of hepatic lesions including steatosis, alcoholic steatohepatitis (ASH), fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). ALD is a complex disease where environmental, genetic, and epigenetic factors contribute to its pathogenesis and progression. The severity of alcohol-induced liver disease depends on the amount, method of usage and duration of alcohol consumption as well as on age, gender, presence of obesity, and genetic susceptibility. Genome-wide association studies and candidate gene studies have identified genetic modifiers of ALD that can be exploited as non-invasive biomarkers, but which do not completely explain the phenotypic variability. Indeed, ALD development and progression is also modulated by epigenetic factors. The premise of this review is to discuss the role of genetic variants and epigenetic modifications, with particular attention being paid to microRNAs, as pathogenic markers, risk predictors, and therapeutic targets in ALD.

Promoting genetics in non-alcoholic fatty liver disease: Combined risk score through polymorphisms and clinical variables

Non-alcoholic fatty liver disease (NAFLD) has a prevalence of approximately 30% in western countries, and is emerging as the first cause of liver cirrhosis and hepatocellular carcinoma (HCC). Therefore, risk stratification emerges as fundamental in order to optimize human and economic resources, and genetics displays intrinsic characteristics suitable to fulfill this task. According to the available data, heritability estimates for hepatic fat content range from 20% to 70%, and an almost 80% of shared heritability has been found between hepatic fat content and fibrosis. The rs738409 single nucleotide polymorphism (SNP) in patatin-like phospholipase domain-containing protein 3 gene and the rs58542926 SNP in transmembrane 6 superfamily member 2 gene have been robustly associated with NAFLD and with its progression, but promising results have been obtained with many other SNPs. Moreover, there has been proof of the additive role of the different SNPs in determining liver damage, and there have been preliminary experiences in which risk scores created through a few genetic variants, alone or in combination with clinical variables, were associated with a strongly potentiated risk of NAFLD, non-alcoholic steatohepatitis (NASH), NASH fibrosis or NAFLD-HCC. However, to date, clinical translation of genetics in the field of NAFLD has been poor or absent. Fortunately, the research we have done seems to have placed us on the right path: We should rely on longitudinal rather than on cross-sectional studies; we should focus on relevant outcomes rather than on simple liver fat accumulation; and we should put together the genetic and clinical information. The hope is that combined genetic/clinical scores, derived from longitudinal studies and built on a few strong genetic variants and relevant clinical variables, will reach a significant predictive power, such as to have clinical utility for risk stratification at the single patient level and even to esteem the impact of intervention on the risk of disease-related outcomes. Well-structured future studies would demonstrate if this vision can become a reality.

The Genetics of Clinical Liver Diseases: Insight into the TM6SF2 E167K Variant

The transmembrane 6 superfamily member 2 (TM6SF2) gene E167K variant (rs58542926) was identified by exome-wide association study as a nonsynonymous single nucleotide polymorphism associated with nonalcoholic fatty liver disease. The TM6SF2 E167K variant features a C-to-T substitution at nucleotide 499, encoding a glutamate with lysine change at codon 167 (E167K). TM6SF2 is markedly expressed in the liver, small intestine and kidney, and has been proposed as an important risk factor for diseases associated with lipid metabolism. Subsequently, multifunctional studies of the TM6SF2 E167K variant have been carried out in a spectrum of liver diseases, such as nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, fibrosis, cirrhosis, and viral hepatitis. This review summarizes the research status of the TM6SF2 E167K variant in different liver diseases and specific populations, and discusses the potential mechanisms of the TM6SF2 E167K variant's role in the progression of various liver diseases.

New insights into genetic predisposition and novel therapeutic targets for nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease in the United States affecting 80-100 million Americans. NAFLD encompasses a spectrum of diseases ranging from excess liver fat (nonalcoholic fatty liver or NAFL), to necro-inflammation (nonalcoholic steatohepatitis or NASH), to fibrosis/ cirrhosis, and malignant transformation (hepatocellular carcinoma). Susceptibility to NAFLD is highly variable and it remains unclear why some patients with NAFLD exhibit NASH, whereas patients with known risk factors have NAFL only. The reasons for this variability can be a partially attributed to differences in genetic background. In the last decade, there have been multiple genome wide association studies, which have enriched our understanding of the genetic basis of NAFLD. The I148M PNPLA3 (patatin-like phospholipase domain-containing protein 3) variant has been identified as the major common genetic determinant of NAFLD. Variants with moderate effect size like TM6SF2, MBOAT7 and GCKR have also been shown to have a significant contribution. New research has uncovered major pathways leading to disease development and progression; therefore, multiple medications are being developed and tested for the treatment of advanced NAFLD. These agents target metabolic mechanisms as well as inflammation and fibrosis pathways. Several randomized clinical trials (RCTs) are evaluating the efficacy of these novel agents on histological improvement of disease severity and decreasing liver-related outcomes. FDA-approved medications for NASH and NASH-related fibrosis are expected by 2020.

Genetics of alcoholic liver disease and non-alcoholic steatohepatitis

Alcohol-related liver disease (ARLD) and non-alcoholic fatty liver disease (NAFLD) are leading causes of chronic liver disease globally. Both ARLD and NAFLD are multifactorial and refer to a spectrum of disease severity, ranging from steatosis through steatohepatitis to fibrosis and cirrhosis. Both diseases exhibit substantial inter-patient variation in long-term outcomes and are best considered complex disease traits where genetic and environmental factors interact to mediate disease severity and progression. Here, we briefly review the current literature describing the best validated genetic modifiers that influence severity of these liver conditions, including variants of the genes PNPLA3, TM6SF2 and MBOAT7, which have also been implicated in lipid dysregulation.

Lack of evidence supporting a role of TMC4-rs641738 missense variant-MBOAT7- intergenic downstream variant-in the Susceptibility to Nonalcoholic Fatty Liver Disease

Current knowledge on the genetic basis of nonalcoholic fatty liver disease (NAFLD) suggests that variants contributing not only to the disease predisposition but histological severity as well are located in genes that regulate lipid metabolism. We explored the role of rs641738 C/T located in TMC4 (transmembrane channel-like 4) exon 1 (p.Gly17Glu) and 500 bases- downstream of MBOAT7 gene (TMC4/MBOAT7), in the genetic risk for developing NAFLD in a case-control study. Our sample included 634 individuals (372 patients with NAFLD diagnosed by liver biopsy and 262 control subjects); genotyping was performed by a Taqman assay. Genotype frequencies in controls (CC: 84, CT: 137, TT: 41) and patients (CC: 134, CT: 178, TT: 60) were in Hardy-Weinberg equilibrium; minor allele frequency 40.8%. Our sample had 84–99% power if an additive genetic model is assumed for estimated odds ratios of 1.3–1.5, respectively. We found no evidence of association between rs641738 and either NAFLD (Cochran-Armitage test for trend, p = 0.529) or the disease severity (p = 0.61). Low levels of MBOAT7 protein expression were found in the liver of patients with NAFLD, which were unrelated to the rs641738 genotypes. In conclusion, the role of rs641738 in the pathogenesis of NAFLD is inconclusive.

New trends on obesity and NAFLD in Asia

Traditionally, obesity and its related diseases have been considered a problem in Western countries. However, in the past two decades, urbanisation in many Asian countries has led to a sedentary lifestyle and overnutrition, setting the stage for the epidemic of obesity. This article reviews the epidemiological trend of obesity in Asia, with special emphasis on the emerging condition of non-alcoholic fatty liver disease (NAFLD). Currently, the population prevalence of NAFLD in Asia is around 25%, like many Western countries. While hepatocellular carcinoma and end-stage liver disease secondary to NAFLD remain uncommon, a rising trend has emerged. Around 8-19% of Asians with body mass indexes less than 25kg/m2 are also found to have NAFLD, a condition often described as "lean" or "non-obese" NAFLD. Although this condition is generally less severe than that in more obese patients, steatohepatitis and fibrotic disease are well recognized. Central adiposity, insulin resistance and weight gain are major risk factors, and genetic predisposition, such as the PNPLA3 polymorphism appears to be more important in the development of NAFLD in the non-obese population. Lifestyle modification remains the cornerstone of management for obesity and NAFLD, but few patients can achieve adequate weight reduction and even fewer can maintain the weight in the long run. While pharmacological agents have entered phase III development for steatohepatitis, Asian patients are under-represented in most drug trials. Future studies should define the optimal management of obesity and NAFLD in Asia.

Significant positive association of endotoxemia with histological severity in 237 patients with non-alcoholic fatty liver disease

BACKGROUND

Patients with nonalcoholic steatohepatitis (NASH) have gut dysbiosis and intestinal bacterial overgrowth.

AIM

To test the hypothesis that endotoxemia is associated with the histological severity of nonalcoholic fatty liver disease (NAFLD) and determine factors associated with endotoxemia.

METHODS

The endotoxemia markers lipopolysaccharide-binding protein (LBP) and endotoxin levels were measured in 237 NAFLD patients 1 day before liver biopsy. Biomarkers of liver injury and transient elastography were performed as additional markers of disease severity.

RESULTS

A total of 114/237 (48%) patients had NASH and 80/237 (34%) had F2-4 fibrosis. LBP was correlated with lobular inflammation (P=.001), while both LBP (P=.0004) and endotoxin levels (P=0.008) were correlated with fibrosis. LBP was also correlated with cytokeratin-18 fragments (P=.002) and aspartate aminotransferase-to-alanine aminotransferase ratio (P=.006), and both LBP (P=.019) and endotoxin (P=.006) were correlated with liver stiffness measurement by transient elastography. LBP was increased in patients with NASH (15.3±4.6 vs 13.8±3.3 μg/mL; P=.005) and F2-4 fibrosis (15.4±4.4 vs 14.0±3.7 μg/mL; P=.008). Interestingly, patients harbouring the TM6SF2 rs58542926 T allele that predispose to NAFLD/NASH had higher LBP level. By multivariate analysis, gender, higher body mass index and glycated haemoglobin, and TM6SF2 variants were independent factors associated with increased LBP level.

CONCLUSIONS

Endotoxemia is positively associated with NASH and significant fibrosis. The association between TM6SF2 and endotoxemia warrants further investigations. The findings may shed light on the pathogenesis of NASH and inform a novel treatment target.

Relationships between Genetic Variations of PNPLA3, TM6SF2 and Histological Features of Nonalcoholic Fatty Liver Disease in Japan

Background/Aims

It is important to determine the noninvasive parameters of histological features in nonalcoholic fatty liver disease (NAFLD). The aim of this study was to investigate the value of genetic variations as surrogate markers of histological features.

Methods

The parameters that affected the histological features of NAFLD were investigated in 211 Japanese patients with biopsy-proven NAFLD. The relationships between genetic variations in PNPLA3 rs738409 or TM6SF2 rs58542926 and histological features were analyzed. Furthermore, the impact of genetic variations that affected the pathological criteria for the diagnosis of nonalcoholic steatohepatitis (NASH) (Matteoni classification and NAFLD activity score) was evaluated.

Results

The fibrosis stage of PNPLA3 GG was significantly more progressive than that of CG by multiple comparisons. Multivariate analysis identified PNPLA3 genotypes as predictors of fibrosis of stage 2 or more, but the impact tended to decrease at stage 3 or greater. There were no significant differences among the histological features of the three genotypes of TM6SF2. PNPLA3 genotypes partly affected the definition of NASH by the NAFLD activity score, but TM6SF2 genotypes did not affect the definition of NASH.

Conclusions

In Japanese patients with biopsy-proven NAFLD, PNPLA3 genotypes may partly affect histological features, including stage of fibrosis, but the TM6SF2 genotype does not affect histological features.

Effect of traditional Chinese medicine formula Sinisan on chronic restraint stress-induced nonalcoholic fatty liver disease: a rat study

Background

Nonalcoholic fatty liver disease (NAFLD) represents one of the most common forms of liver disease worldwide, and it is always regarded as a consequence of a sedentary, food-abundant lifestyle, sitting for an extended time, and a low physical activity level, which often coincide with chronic and long-lasting psychological stress. A Chinese medicine Sinisan (SNS) may be a potential formula for treating this kind of disease.

Methods

In this study, a long-term chronic restraint stress protocol was used to investigate the mechanism underlying stress-induced NALFD. To investigate the effect of SNS treatment on stress-induced NAFLD, we measured the liver and serum values of total cholesterol (TC), triglyceride (TG), liver free fatty acids (FFA), low-density lipoprotein, superoxide dismutase, tumor necrosis factor-α, malondialdehyde, interleukin (IL)-6, and serum values of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase. Results are shown as a mean ± standard deviation. Significant differences between the groups were evaluated using the Student t-test. For multiple comparisons, one-way analysis of variance (ANOVA) was used. If the results of ANOVA indicated significant differences, post hoc analysis was performed with the Tukey test or Dunnett test, and p < 0.05 was considered statistically significant.

Results

Long-term chronic stress led to steatosis and non-alcoholic steatohepatitis. Additionally, SNS treatment significantly increased body weight gain (p < 0.01) and sucrose preference (p < 0.001), and it reduced the liver values of TC, TG, and FFA (p < 0.05). SNS also reduced the serum values of AST and ALT (p < 0.001), and the liver value of IL-6 (p < 0.01).

Conclusions

This study’s results demonstrate that psychological stress may be a significant risk factor of NAFLD. Furthermore, the traditional Chinese medicine formula SNS may have some beneficial effect in antagonizing psychological stress and stress-related NAFLD.

Genetic predisposition in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease whose prevalence has reached global epidemic proportions. Although the disease is relatively benign in the early stages, when severe clinical forms, including nonalcoholic steatohepatitis (NASH), cirrhosis and even hepatocellular carcinoma, occur, they result in worsening the long-term prognosis. A growing body of evidence indicates that NAFLD develops from a complex process in which many factors, including genetic susceptibility and environmental insults, are involved. In this review, we focused on the genetic component of NAFLD, with special emphasis on the role of genetics in the disease pathogenesis and natural history. Insights into the topic of the genetic susceptibility in lean individuals with NAFLD and the potential use of genetic tests in identifying individuals at risk are also discussed.

Hepatitis B and concomitant hepatic steatosis

Hepatic steatosis is becoming more common in Asia with prevalence becoming as common as Western countries. Concomitant Hepatitis B and hepatic steatosis is increasingly encountered in clinical practice. The interaction between the two concomitant conditions at both molecular level and clinical outcome remains to be explored. The present review is aimed at summarizing the existing literature on the complex interaction of the two-concomitant disease.

Diverse impacts of the rs58542926 E167K variant in TM6SF2 on viral and metabolic liver disease phenotypes

A genome-wide exome association study has identified the transmembrane 6 superfamily member 2 (TM6SF2) rs58542926 variant encoding an E167K substitution as a genetic determinant of hepatic steatosis in nonalcoholic fatty liver disease (NAFLD). The roles of this variant across a spectrum of liver diseases and pathologies and on serum lipids comparing viral hepatitis to NAFLD and viral load in chronic viral hepatitis, as well as its intrahepatic molecular signature, have not been well characterized. We undertook detailed analyses in 3260 subjects with viral and nonviral liver diseases and in healthy controls. Serum inflammatory markers and hepatic expression of TM6SF2 and genes regulating lipid metabolism were assessed in a subset with chronic hepatitis C (CHC). The rs58542926 T allele was more prevalent in 502 NAFLD patients than controls (P = 0.02) but not different in cohorts with CHC (n = 2023) and chronic hepatitis B (n = 507). The T allele was associated with alterations in serum lipids and hepatic steatosis in all diseases and with reduced hepatic TM6SF2 and microsomal triglyceride transfer protein expression. Interestingly, the substitution was associated with reduced CHC viral load but increased hepatitis B virus DNA. The rs58542926 T allele had no effect on inflammation, impacted ≥F2 fibrosis in CHC and NAFLD assessed cross-sectionally (odds ratio = 1.39, 95% confidence interval 1.04-1.87, and odds ratio = 1.62, 95% confidence interval 1.03-2.52, respectively; P < 0.03 for both), but had no effect on fibrosis progression in 1174 patients with CHC and a known duration of infection.

CONCLUSION

The TM6SF2 E167K substitution promotes steatosis and lipid abnormalities in part by altering TM6SF2 and microsomal triglyceride transfer protein expression and differentially impacts CHC and chronic hepatitis B viral load, while effects on fibrosis are marginal. (Hepatology 2016;64:34-46).

Meta-analysis of the influence of TM6SF2 E167K variant on Plasma Concentration of Aminotransferases across different Populations and Diverse Liver Phenotypes

A nonsynonymous E167K (rs58542926 C/T) variant in TM6SF2 gene was recently associated with nonalcoholic fatty liver disease (NAFLD). We explored the association between E167K and plasma concentrations of alanine (ALT) and aspartate (AST) aminotransferases through a meta-analysis. We also estimated the strength of the effect across diverse liver phenotypes, including NAFLD and chronic viral hepatitis; fourteen studies were included. We found that ALT (p = 3.2 × 10⁻⁶, n = 94,414) and AST (p = 0007, n = 93,809) levels were significantly associated with rs58542926 in NAFLD. By contrast, rs58542926 was not associated with either ALT (p = 0.24, n = 4187) or AST (p = 0.17, n = 2678) levels in four studies on chronic hepatitis. In conclusion, the results of the pooled estimates in patients with NAFLD showed that carriers of the T allele (EK + KK), when compared with homozygous subjects for the C allele (EE genotype) have increased levels of aminotransferases; however, this increase represents –2.5 (9.8%) and 1.2 (5%) IU/L of ALT and AST respectively, which is fairly small compared with the large effect of PNPLA3- rs738409-G allele that is associated with a –28% increase in serum ALT.

Genetic Factors That Affect Risk of Alcoholic and Nonalcoholic Fatty Liver Disease

Genome-wide association studies and candidate gene studies have informed our understanding of factors contributing to the well-recognized interindividual variation in the progression and outcomes of alcoholic liver disease and nonalcoholic fatty liver disease. We discuss the mounting evidence for shared modifiers and common pathophysiological processes that contribute to development of both diseases. We discuss the functions of proteins encoded by risk variants of genes including patatin-like phospholipase domain-containing 3 and transmembrane 6 superfamily member 2, as well as epigenetic factors that contribute to the pathogenesis of alcoholic liver disease and nonalcoholic fatty liver disease. We also discuss important areas of future genetic research and their potential to affect clinical management of patients.