Membrane Bound O-acyltransferase Domain Containing 7 Research Articles

A Cell Specific Effect of MBOAT7 MAFLD-risk Variant on Immune Cells.

Disease risk variants are likely to affect gene expression in a context- and cell-type specific manner. The membrane bound O-acyltransferase domain containing 7 (MBOAT7) rs8736 metabolic-dysfunction-associated fatty liver disease (MAFLD)-risk variant was recently reported to be a negative regulator of toll-like receptors (TLRs) signalling in macrophages. Whether this effect is generic or cell-type specific in immune cells is unknown. We investigated the impact of modulating TLR signaling on MBOAT7 expression in peripheral blood mononuclear cells (PBMCs). We also examined whether the rs8736 polymorphism in MBOAT7 regulates this effect. Furthermore, we measured the allele-specific expression of MBOAT7 in various immune cell populations under both unstimulated and stimulated conditions. We show that MBOAT7 is down-regulated by TLRs in PBMCs. This effect is modulated by the MBOAT7 rs8736 polymorphism. Additionally, we provide evidence that MBOAT7 acts primarily as a modulator of TLR signalling in mononuclear phagocytes. Our results highlight the importance of studying Genome-Wide Association Studies (GWAS) signals in the specific cell types in which alterations of gene expression are found.

The Intersection of Genetic Factors, Aberrant Nutrient Metabolism and Oxidative Stress in the Progression of Cardiometabolic Disease.

Cardiometabolic disease (CMD), which encompasses metabolic-associated fatty liver disease (MAFLD), chronic kidney disease (CKD) and cardiovascular disease (CVD), has been increasing considerably in the past 50 years. CMD is a complex disease that can be influenced by genetics and environmental factors such as diet. With the increased reliance on processed foods containing saturated fats, fructose and cholesterol, a mechanistic understanding of how these molecules cause metabolic disease is required. A major pathway by which excessive nutrients contribute to CMD is through oxidative stress. In this review, we discuss how oxidative stress can drive CMD and the role of aberrant nutrient metabolism and genetic risk factors and how they potentially interact to promote progression of MAFLD, CVD and CKD. This review will focus on genetic mutations that are known to alter nutrient metabolism. We discuss the major genetic risk factors for MAFLD, which include Patatin-like phospholipase domain-containing protein 3 (PNPLA3), Membrane Bound O-Acyltransferase Domain Containing 7 (MBOAT7) and Transmembrane 6 Superfamily Member 2 (TM6SF2). In addition, mutations that prevent nutrient uptake cause hypercholesterolemia that contributes to CVD. We also discuss the mechanisms by which MAFLD, CKD and CVD are mutually associated with one another. In addition, some of the genetic risk factors which are associated with MAFLD and CVD are also associated with CKD, while some genetic risk factors seem to dissociate one disease from the other. Through a better understanding of the causative effect of genetic mutations in CMD and how aberrant nutrient metabolism intersects with our genetics, novel therapies and precision approaches can be developed for treating CMD.

MBOAT7 expression is associated with disease progression in COVID-19 patients

Background and aimThe emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in late 2019 caused a pandemic of acute respiratory disease, named coronavirus disease 2019 (COVID-19). COVID-19 became one of the most challenging health emergencies, hence the necessity to find different prognostic factors for disease progression, and severity. Membrane bound O-acyltransferase domain containing 7 (MBOAT7) demonstrates anti-inflammatory effects through acting as a fine-tune regulator of the amount of cellular free arachidonic acid. We aimed in this study to evaluate MBOAT7 expression in COVID-19 patients and to correlate it with disease severity and outcomes.MethodsThis case-control study included 56 patients with confirmed SARS-CoV-2 diagnosis and 28 control subjects. Patients were further classified into moderate (n = 28) and severe (n = 28) cases. MBOAT7, tumor necrosis factor-α (TNF-α), and interleukin-1ß (IL-1ß) mRNA levels were evaluated in peripheral blood mononuclear cells (PBMC) samples isolated from patients and control subjects by real time quantitative polymerase chain reaction (RT-qPCR). In addition, circulating MBOAT7 protein levels were assayed by enzyme-linked immunosorbent assay (ELISA).ResultsSignificant lower levels of circulating MBOAT7 mRNA and protein were observed in COVID-19 patients compared to control subjects with severe COVID-19 cases showing significant lower levels compared to moderate cases. Moreover, severe cases showed a significant upregulation of TNF-α and IL-1ß mRNA. MBOAT7 mRNA and protein levels were significantly correlated with inflammatory markers (TNF-α, IL-1ß, C-reactive protein (CRP), and ferritin), liver enzymes, severity, and oxygen saturation levels.ConclusionCOVID-19 is associated with downregulation of MBAOT7, which correlates with disease severity.

Association of GCKR and MBOAT7 genetic polymorphisms with non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is one of the most important causes of chronic liver disease (CLD) in both Western and Asian populations. There is wide inter-individual variability in the occurrence of NAFLD and progression to non-alcoholic steatohepatitis (NASH) even after correcting environmental factors, and its true explanation can be provided by heritability. Two such genetic variations, the glucokinase regulator (GCKR) and membrane bound O-acyltransferase domain containing 7 (MBOAT7) genes, in NAFLD patients were studied in the Indian population. A cross sectional analytical study was conducted in the Department of Gastroenterology at a tertiary care centre. In total 100 subjects in the age range of 18-65 years were included in the study; 50 were patients with NAFLD including fatty liver, NASH and NASH related cirrhosis, and 50 were healthy subjects (No NAFLD). The polymorphisms rs780094 and rs1260326 for GCKR and rs641738 for MBOAT7 were determined using PCR followed by the PCR-RFLP. GCKR rs780094 minor allele A was more common in NAFLD patients (p = 0.00001). Within the spectrum of NAFLD, the A allele was present frequently among cirrhotics as compared to NASH and fatty liver (p = 0.00001). Morbidly obese individuals showed significant association with the homozygous A allele (p = 0.028). These results were not seen with GCKR rs1260326 across all alleles. In MBOAT7 (rs641738) the frequency of the minor allele T for NAFLD was 84% vs. 80% in healthy subjects (p = 0.79). The association of the T allele among the spectrum of NAFLD was not statistically significant (p = 0.79). GCKR genetic variant rs780094 was found to be significantly associated with NAFLD. The MBOAT7 (rs641738) genetic variant was not found to be significantly associated with NAFLD.

Gene Variants Implicated in Steatotic Liver Disease: Opportunities for Diagnostics and Therapeutics.

Non-alcoholic fatty liver disease (NAFLD) describes a steatotic (or fatty) liver occurring as a consequence of a combination of metabolic, environmental, and genetic factors, in the absence of significant alcohol consumption and other liver diseases. NAFLD is a spectrum of conditions. Steatosis in the absence of inflammation is relatively benign, but the disease can progress into more severe forms like non-alcoholic steatohepatitis (NASH), liver cirrhosis, and hepatocellular carcinoma. NAFLD onset and progression are complex, as it is affected by many risk factors. The interaction between genetic predisposition and other factors partially explains the large variability of NAFLD phenotype and natural history. Numerous genes and variants have been identified through large-scale genome-wide association studies (GWAS) that are associated with NAFLD and one or more subtypes of the disease. Among them, the largest effect size and most consistent association have been patatin-like phospholipase domain-containing protein 3 (PNPLA3), transmembrane 6 superfamily member 2 (TM6SF2), and membrane-bound O-acyltransferase domain containing 7 (MBOAT7) genes. Extensive in vitro and in vivo studies have been conducted on these variants to validate these associations. The focus of this review is to highlight the genetics underpinning the molecular mechanisms driving the onset and progression of NAFLD and how they could potentially be used to improve genetic-based diagnostic testing of the disease and develop personalized, targeted therapeutics.

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.

MTARC1 and HSD17B13 Variants Have Protective Effects on Non-Alcoholic Fatty Liver Disease in Patients Undergoing Bariatric Surgery

The severity of hepatic steatosis is modulated by genetic variants, such as patatin-like phospholipase domain containing 3 (PNPLA3) rs738409, transmembrane 6 superfamily member 2 (TM6SF2) rs58542926, and membrane-bound O-acyltransferase domain containing 7 (MBOAT7) rs641738. Recently, mitochondrial amidoxime reducing component 1 (MTARC1) rs2642438 and hydroxysteroid 17-beta dehydrogenase 13 (HSD17B13) rs72613567 polymorphisms were shown to have protective effects on liver diseases. Here, we evaluate these variants in patients undergoing bariatric surgery. A total of 165 patients who underwent laparoscopic sleeve gastrectomy and intraoperative liver biopsies and 314 controls were prospectively recruited. Genotyping was performed using TaqMan assays. Overall, 70.3% of operated patients presented with hepatic steatosis. NASH (non-alcoholic steatohepatitis) was detected in 28.5% of patients; none had cirrhosis. The increment of liver fibrosis stage was associated with decreasing frequency of the MTARC1 minor allele (p = 0.03). In multivariate analysis MTARC1 was an independent protective factor against fibrosis ≥ 1b (OR = 0.52, p = 0.03) and ≥ 1c (OR = 0.51, p = 0.04). The PNPLA3 risk allele was associated with increased hepatic steatosis, fibrosis, and NASH (OR = 2.22, p = 0.04). The HSD17B13 polymorphism was protective against liver injury as reflected by lower AST (p = 0.04) and ALT (p = 0.03) activities. The TM6SF2 polymorphism was associated with increased ALT (p = 0.04). In conclusion, hepatic steatosis is common among patients scheduled for bariatric surgery, but the MTARC1 and HSD17B13 polymorphisms lower liver injury in these individuals.

A metabolic associated fatty liver disease risk variant in MBOAT7 regulates toll like receptor induced outcomes

The breakdown of toll-like receptor (TLR) tolerance results in tissue damage, and hyperactivation of the TLRs and subsequent inflammatory consequences have been implicated as risk factors for more severe forms of disease and poor outcomes from various diseases including COVID-19 and metabolic (dysfunction) associated fatty liver disease (MAFLD). Here we provide evidence that membrane bound O-acyltransferase domain containing 7 (MBOAT7) is a negative regulator of TLR signalling. MBOAT7 deficiency in macrophages as observed in patients with MAFLD and in COVID-19, alters membrane phospholipid composition. We demonstrate that this is associated with a redistribution of arachidonic acid toward proinflammatory eicosanoids, induction of endoplasmic reticulum stress, mitochondrial dysfunction, and remodelling of the accessible inflammatory-related chromatin landscape culminating in macrophage inflammatory responses to TLRs. Activation of MBOAT7 reverses these effects. These outcomes are further modulated by the MBOAT7 rs8736 (T) MAFLD risk variant. Our findings suggest that MBOAT7 can potentially be explored as a therapeutic target for diseases associated with dysregulation of the TLR signalling cascade.

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

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

Profiling of cell-free DNA methylation and histone signatures in pediatric NAFLD: A pilot study.

Nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease in children and adolescents, increasing the risk of its progression toward nonalcoholic steatohepatitis (NASH), cirrhosis, and cancer. There is an urgent need for noninvasive early diagnostic and prognostic tools such as epigenetic marks (epimarks), which would replace liver biopsy in the future. We used plasma samples from 67 children with biopsy-proven NAFLD, and as controls we used samples from 20 children negative for steatosis by ultrasound. All patients were genotyped for patatin-like phospholipase domain containing 3 (PNPLA3), transmembrane 6 superfamily member 2 (TM6SF2), membrane bound O-acyltransferase domain containing 7 (MBOAT7), and klotho-β (KLB) gene variants, and data on anthropometric and biochemical parameters were collected. Furthermore, plasma cell-free DNA (cfDNA) methylation was quantified using a commercially available kit, and ImageStream(X) was used for the detection of free circulating histone complexes and variants. We found a significant enrichment of the levels of histone macroH2A1.2 in the plasma of children with NAFLD compared to controls, and a strong correlation between cfDNA methylation levels and NASH. Receiver operating characteristic curve analysis demonstrated that combination of cfDNA methylation, PNPLA3 rs738409 variant, coupled with either high-density lipoprotein cholesterol or alanine aminotransferase levels can strongly predict the progression of pediatric NAFLD to NASH with area under the curve >0.87. Conclusion: Our pilot study combined epimarks and genetic and metabolic markers for a robust risk assessment of NAFLD development and progression in children, offering a promising noninvasive tool for the consistent diagnosis and prognosis of pediatric NAFLD. Further studies are necessary to identify their pathogenic origin and function.

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

IntroductionWe aimed to confirm the association between some single nucleotide polymorphisms (SNPs) and metabolic dysfunction‐associated fatty liver disease (MAFLD) in western China.MethodsA 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.ResultsThe 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.ConclusionsIn 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.

MBOAT7 rs641738 variant in metabolic-dysfunction-associated fatty liver disease and cardiovascular risk.

Although metabolic-dysfunction-associated fatty liver disease (MAFLD) is associated with an increased cardiovascular risk, MAFLD predisposing genetic variants were not steadily related to cardiovascular events. Therefore, we aimed to assess whether membrane-bound O-acyltransferase domain-containing 7 (MBOAT7) rs641738 variant is associated with an increased cardiovascular risk in in MAFLD patients. We conducted an observational cross-sectional study including 77 subjects (38 MAFLD patients, 39 controls), between January-September 2020 using hepatic ultrasonography and SteatoTestTM to assess hepatic steatosis. Echocardiographic and Doppler ultrasound parameters were evaluated. Genomic DNA was extracted and rs641738 SNP was genotyped using TaqMan assays. The rs641738 variant was not significantly associated with MAFLD, with a p-value of 0.803, 0.5265, 0.9535, and 0.5751 for codominant, dominant, recessive, and overdominant genotypes, respectively. The rs641738 variant overdominant genotype significantly predicted atherosclerotic cardiovascular disease (ASCVD) risk algorithm in univariate analysis (-4.3 [95% CI -8.55 - -0.55, p-value= 0.048]), but lost significance after multivariate analysis (-3.98 [95% CI -7.9 - -0.05, p-value= 0.053]). The rs641738 variant recessive genotype significantly predicted ActiTest in univariate analysis (0.0963 [95% CI 0.0244 - 0.1681, p-value= 0.009]), but lost significance after multivariate analysis (0.0828 [95% CI -0.016 - 0.1816, p-value= 0.105]). No significant association was observed between rs641738 variant and MAFLD in the studied population. The rs641738 variant was found to predict ASCVD risk score and ActiTest in univariate linear regression analysis. However, the significance of both associations was lost after performing multivariate analysis.

Improvement of liver fibrosis, but not steatosis, after HCV eradication as assessment by MR-based imaging: Role of metabolic derangement and host genetic variants.

Significant liver fibrosis regression occurs after hepatitis C virus (HCV) therapy. However, the impact of direct-acting antivirals (DAAs) on steatosis is less clear. This study was aimed at evaluating serial fibrosis and steatosis alterations in patients with HCV genotype 1, who achieved sustained virological response (SVR). We enrolled 55 HCV mono-infected and 28 HCV/HIV co-infected patients receiving elbasvir/grazoprevir from a clinical trial. Fibrosis and steatosis were assessed at baseline, follow-up week-24 (FUw24) and week-72 (FUw72) by magnetic resonance elastography (MRE) and proton density fat fraction (PDFF), respectively. Patatin-like phospholipase domain-containing protein 3 (PNPLA3) rs738409, transmembrane six superfamily member 2 (TM6SF2) rs58542926 and membrane bound O-acyltransferase domain-containing 7 (MBOAT7) rs641738 polymorphisms were determined by allelic discrimination. Overall, mean MRE decreased significantly from baseline to FUw24 and FUw72. At FUw72, patients with baseline F2-F4 had higher rate of ≥30% MRE decline compared with individuals with baseline F0-F1 (30.2%vs.3.3%, P = 0.004). In multivariate analysis, significant fibrosis was associated with MRE reduction. The prevalence of steatosis (PDFF≥5.2%) at baseline was 21.7%. Compared to baseline, there were 17 (20.5%) patients with decreased PDFF values at FUw72 (<30%), while 23 (27.7%) patients had increased PDFF values (≥30%). Regarding the overall cohort, mean PDFF significantly increased from baseline to FUw72, and displayed positive correlation with body mass index (BMI) alteration. In multivariate analysis, the presence of diabetes, PNPLA3 CG+GG genotypes and increased BMI at FUw72 were significantly associated with progressive steatosis after SVR. Other genetic variants were not related to fibrosis and steatosis alteration. This study concluded that HCV eradication was associated with fibrosis improvement. However, progressive steatosis was observed in a proportion of patients, particularly among individuals with metabolic derangement and PNPLA3 variants. The combined clinical parameters and host genetic factors might allow a better individualized strategy in this sub-group of patients to alleviate progressive steatosis after HCV cure.

Evaluation of the association of a variant in PNPLA3 and TM6SF2 with fibrosis progression in patients with chronic hepatitis C infection after eradication: A retrospective study.

The relationship of single nucleotide polymorphisms (SNPs) in patatin-like phospholipase domain containing 3 (PNPLA3) rs738409, transmembrane 6 superfamily member 2 (TM6SF2) rs58542926, and membrane bound O-acyltransferase domain containing 7 (MBOAT7) rs641738 with outcomes in patients with hepatitis C infection (HCV) is unclear. This study aimed to evaluate the association of PNPLA3, TM6SF2, and MBOAT7 with the baseline fibrosis stage and progression of liver fibrosis after HCV eradication with direct antiviral agents (DAAs). A total of 171 patients who received the DAAs at the Peking University First Hospital between June 2015 and June 2020 were included in the retrospective cohort. Transient elastography was used to determine liver stiffness measurements (LSMs) at the baseline, the end of treatment (EOT), 24weeks after treatment (W24), and the last follow-up (LFU) visit. We used the QIAamp Blood Mini Kit (Qiagen) for whole blood genomic DNA extraction and polymerase chain reaction for PNPLA3, TM6SF2, and MBOAT7 amplification of the target gene. The PNPLA3 rs738409 SNP was associated with the baseline fibrosis stage in multivariate logistic regression analysis adjusted for other factors, and the adjusted odds ratio (OR) for advanced fibrosis (≥F3) at baseline was 2.52 (95% confidence interval[CI]=1.096-5.794, p=0.03). The G and GG alleles were predictive of advanced fibrosis (OR=1.98, 95% CI=1.021-4.196, p=0.015; OR=3.12, 95% CI=1.572-6.536, p=0.005). Similarly, the OR of TM6SF2 rs58542926 at baseline was 2.608 (95% CI=1.081-6.29, p=0.033). T and TT alleles were predictive of advanced fibrosis (OR=2.3, 95% CI=1.005-5.98, p=0.007; OR=3.05, 95% CI=1.32-6.87, p=0.001). After adjustment, the MBOAT7 rs641738 T plus TT alleles were not independently associated with the baseline fibrosis stage (95% CI=0.707-2.959, p=0.312). At the EOT, there were 35 patients and 136 patients in the fibrosis improvement and fibrosis non-improvement group, respectively. Logistic regression analysis showed that the G allele in PNPLA3 rs738409 was associated with fibrosis progression (OR=2.47, 95% CI=1.125-5.89, p=0.003). The GG alleles were predictive of fibrosis progression (OR=2.95, 95% CI=1.35-6.35, p=0.005). Similarly, the ORs of the T and TT alleles in TM6SF2 rs58542926 for fibrosis progression were 1.82 and 2.21, respectively (95% CI=1.006-5.373, p=0.045; 95% CI=1.18-5.75, p=0.01). At the W24 visit, we found that there was an association between the G allele in PNPLA3 rs738409 and fibrosis progression (OR=2.218, 95% CI=1.095-5.631, p=0.015). Moreover, GG alleles were also predictive for fibrosis progression (OR=2.558, 95% CI=1.252-5.15, p=0.008). Similarly, the OR of T allele and TT alleles in TM6SF2 rs58542926 for fibrosis progression was 2.056 and 2.652 (95% CI=1.013-5.592, p=0.038; 95% CI=1.25-5.956, p=0.015). For additional affirmation, we surveyed fibrosis progression utilizing the Cox proportional hazards model. G and GG alleles in PNPLA3 rs738409 were associated with an increased risk of progression to advanced fibrosis in multivariate model (hazard ratio [HR]1.566, 95% CI=1.02-2.575, p=0.017; and HR2.109, 95% CI=1.36-3.271, p=0.001, respectively). Besides, T and TT alleles in TM6SF2 rs58542926 were associated with an increased risk of progression to advanced fibrosis in multivariate model (HR=1.322, 95% CI=1.003-1.857, p=0.045; and HR=1.855, 95% CI=1.35-2.765, p=0.006, respectively). In contrast, rs641738 in MBOAT7 did not show a significant trend in the univariate and multivariate models. The PNPLA3 CG/GG SNP at rs738409 and TM6SF2 CT/TT SNP at rs58542926 were associated with the baseline fibrosis stage and fibrosis progression after HCV eradication with DAAs.

Metabolic Syndrome but Not Fatty Liver-Associated Genetic Variants Correlates with Glomerular Renal Function Decline in Patients with Non-Alcoholic Fatty Liver Disease.

The association between non-alcoholic fatty liver disease (NAFLD) and chronic kidney disease (CKD) has been extensively demonstrated. Recent studies have focused attention on the role of patatin-like phospholipase domain-containing 3 (PNPLA3) rs738409 polymorphism in the association between NAFLD and CKD in non-metabolic adults and children, but the genetic impact on NAFLD-CKD association is still a matter of debate. The aim of the study was to investigate the impact of PNPLA3, transmembrane 6 superfamily member 2 (TM6SF2), membrane-bound O-acyltransferase domain containing 7 (MBOAT7) and glucokinase regulatory protein (GCKR) gene variants rather than metabolic syndrome features on renal function in a large population of NAFLD patients. The present study is a post hoc analysis of the Plinio Study (ClinicalTrials.gov: NCT04036357). PNPLA3, TM6SF2, MBOAT7 and GCKR genes were analyzed by using real-time PCR with TaqMan probes. Glomerular filtration rate (GFR) was estimated with CKD-EPI. We analyzed 538 NAFLD; 47.2% had GFR < 90 mL/min/1.73 m2 while 5.9% had GFR < 60 mL/min/1.73 m2. The distribution of genotypes was superimposable according to GFR cut-offs. Results from the multivariable regression model did not show any correlation between genotypes and renal function. Conversely, metabolic syndrome was highly associated with GFR < 90 mL/min/1.73 m2 (odds ratio (OR): 1.58 [1.10–2.28]) and arterial hypertension with GFR < 60 mL/min/1.73 m2 (OR: 1.50 [1.05–2.14]). In conclusion, the association between NAFLD and CKD might be related to the shared metabolic risk factors rather than the genetic NAFLD background.

Expression of Membrane Bound O-Acyltransferase Domain Containing 7 after Myocardial Infarction and its Role in Lipid Metabolism in vitro.

Background: Previous microarray analysis on peripheral blood leukocytes from three patients with acute myocardial infarction (AMI) showed that elevated expression of membrane bound o-acyltransferase domain containing 7(MBOAT7) relative to control. To further verify these findings, we investigated more patients and explored the possible mechanisms in vitro.Objective: To study alterations in MBOAT7 expression in leukocytes after AMI, and to explore the relationship between MBOAT7 and lipid metabolism pathways in hepatocytes in vitro.Methods: Ninety patients with AMI and 90 controls were recruited from the Han population in Northeast China. RT-fluorescent PCR was used to measure MBOAT7 mRNA levels. MBOAT7 interference and overexpression vectors were constructed and transfected into L-02 hepatocytes and expression was examined by RT-qPCR and western blotting. The expression of SCAP, LDLR, HMGCR, ACAT1, ABCA1, SREBP1, ACC, FAS, SCD, and PPARγ in the lipid metabolism pathway were investigated by RT-qPCR. Triglyceride and cholesterol levels were measured by ELISA.Results: It was found that MBOAT7 mRNA levels were elevated in the leukocytes of patients with AMI. Hepatocytes were successfully transfected, shown by attenuated MBOAT7 mRNA levels in the silenced group (0.41±0.04 vs 1.01±0.07 for control, P=0.0019 <0.01) and raised levels in the overexpressing cells (23.29±0.39 vs 1.00±0.06 for control, P <0.0001). These results were confirmed by western blotting. Expression of the lipid metabolism-related genes was altered in response to MBOAT7 expression. Triglyceride levels increased after MBOAT7 silencing (118.40 ± 2.26 vs 70.54 ± 0.25 for control, P<0.0001), as did those of cholesterol (628.30 ± 8.89 vs 544.70 ± 11.04, P = 0.0041) but were not altered on MBOAT7 overexpression.Conclusion: MBOAT7 did not affect the metabolism of triglycerides in hepatocytes through fatty acid synthesis and decomposition pathways. The MBOAT7 level in the peripheral blood can be used as a marker for acute myocardial infarction but cannot be used as a single therapeutic target to regulate lipid metabolism.

Genetics Is of the Essence to Face NAFLD.

Nonalcoholic fatty liver disease (NAFLD) is the commonest cause of chronic liver disease worldwide. It is closely related to obesity, insulin resistance (IR) and dyslipidemia so much so it is considered the hepatic manifestation of the Metabolic Syndrome. The NAFLD spectrum extends from simple steatosis to nonalcoholic steatohepatitis (NASH), a clinical condition which may progress up to fibrosis, cirrhosis and hepatocellular carcinoma (HCC). NAFLD is a complex disease whose pathogenesis is shaped by both environmental and genetic factors. In the last two decades, several heritable modifications in genes influencing hepatic lipid remodeling, and mitochondrial oxidative status have been emerged as predictors of progressive hepatic damage. Among them, the patatin-like phospholipase domain-containing 3 (PNPLA3) p.I148M, the Transmembrane 6 superfamily member 2 (TM6SF2) p.E167K and the rs641738 membrane bound-o-acyltransferase domain-containing 7 (MBOAT7) polymorphisms are considered the most robust modifiers of NAFLD. However, a forefront frontier in the study of NAFLD heritability is to postulate score-based strategy, building polygenic risk scores (PRS), which aggregate the most relevant genetic determinants of NAFLD and biochemical parameters, with the purpose to foresee patients with greater risk of severe NAFLD, guaranteeing the most highly predictive value, the best diagnostic accuracy and the more precise individualized therapy.

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.

MBOAT7-TMC4 rs641738 Is Not Associated With the Risk of Hepatocellular Carcinoma or Persistent Hepatitis B Infection

ObjectiveA hot genetic variant, rs641738 within the membrane-bound O-acyltransferase domain containing 7(MBOAT7) and transmembrane channel-like 4 (TMC4), was recently reported to be associated with several liver diseases. However, the results remain controversial. Therefore, this study aimed to explore the role of MBOAT7-TMC4 rs641738 in the risk of hepatocellular carcinoma (HCC) and persistent hepatitis B virus (HBV) infection.MethodsWe first conducted a case-control study that included 779 HCC cases and 1412 cancer-free controls. Controls consisted of 678 persistent HBV carriers and 734 spontaneously recovered subjects. The gene variant rs641738 was genotyped using the MassARRAY platform. The results were analyzed in five genetic models using multivariate logistic regression analyses. Next, we performed a systematic review and meta-analysis to further explore the role of this variant in HCC risk.ResultsThe results suggested no association between MBOAT7-TMC4 rs641738 and HCC risk in most genetic models (all P > 0.05). Although a marginally significant association was observed in TT vs. CC (P = 0.037) and the recessive models (P = 0.044). The meta-analysis of 2135 HCC cases and 4388 controls supported that this variant was not related to HCC risk, even in the TT vs. CC and recessive models. We also determined that this variant did not influence persistent HBV infection.ConclusionOur work highlights that MBOAT7-TMC4 rs641738 is not associated with the risk of HCC or persistent HBV infection. This study provides some clues to identify the “truth” of potential disease-related genetic factors in the post-genome era.

Role of candidate gene variants in modulating the risk and severity of alcoholic hepatitis

Alcoholic hepatitis (AH) is a severe and life-threatening alcohol-associated liver disease. Only a minority of heavy drinkers acquires AH and severity varies among affected individuals, suggesting a genetic basis for the susceptibility to and severity of AH. A cohort consisting of 211 patients with AH and 176 heavy drinking controls was genotyped for five variants in five candidate genes that have been associated with chronic liver diseases: rs738409 in patatin-like phospholipase domain-containing protein 3 (PNPLA3), rs72613567 in hydroxysteroid 17-beta dehydrogenase 13 (HSD17B13), rs58542926 in transmembrane 6 superfamily member 2 (TM6SF2), rs641738 in membrane bound O-acyltransferase domain containing 7 (MBOAT7), and a copy number variant in the haptoglobin (HP) gene. We tested the effects of individual variants and the combined/interacting effects of variants on AH risk and severity. We found significant associations between AH risk and the risk alleles of rs738409 (p=0.0081) and HP (p=0.0371), but not rs72613567 (p=0.3132), rs58542926 (p=0.2180), or rs641738 (p=0.7630), after adjusting for patient's age and sex. A multiple regression model indicated that PNPLA3 rs738409:G [OR=1.59 (95% CI: 1.15-2.22), p=0.0055] and HP*2 [OR=1.38 (95% CI: 1.04-1.82), p=0.0245], when combined and adjusted for age and sex also had a large influence on AH risk among heavy drinkers. In the entire cohort, variants in PNPLA3 and HP were associated with increased total bilirubin and Model for End-stage Liver Disease (MELD) score, both measures of AH severity. The HSD17B13 rs72613567:AA allele was not found to reduce risk of AH in patients carrying the G allele of PNPLA3 rs738409 (p=0.0921). PNPLA3 and HP genetic variants increase AH risk and are associated with total bilirubin and MELD score, surrogates of AH severity.