Relationship Between Nonalcoholic Fatty Liver Disease Susceptibility Genes and Coronary Artery Disease

Diabetes as a risk factor for MASH progression

Non-alcoholic (now: metabolic) steatohepatitis (MASH) is the progressive inflammatory form of metabolic dysfunction-associated steatotic liver disease (MASLD), which often coexists and mutually interacts with type 2 diabetes (T2D), resulting in worse hepatic and cardiovascular outcomes. Understanding the intricate mechanisms of diabetes-related MASH progression is crucial for effective therapeutic strategies. This review delineates the multifaceted pathways involved in this interplay and explores potential therapeutic implications. The synergy between adipose tissue, gut microbiota, and hepatic alterations plays a pivotal role in disease progression. Adipose tissue dysfunction, particularly in the visceral depot, coupled with dysbiosis in the gut microbiota, exacerbates hepatic injury and insulin resistance. Hepatic lipid accumulation, oxidative stress, and endoplasmic reticulum stress further potentiate inflammation and fibrosis, contributing to disease severity. Dietary modification with weight reduction and exercise prove crucial in managing T2D-related MASH. Additionally, various well-known but also novel anti-hyperglycemic medications exhibit potential in reducing liver lipid content and, in some cases, improving MASH histology. Therapies targeting incretin receptors show promise in managing T2D-related MASH, while thyroid hormone receptor-β agonism has proven effective as a treatment of MASH and fibrosis.

Metabolic dysfunction-associated steatotic liver disease and atherosclerosis

PURPOSE OF REVIEW

To update information about the relationship between metabolic dysfunction-associated steatotic liver disease (MASLD) and atherosclerosis. This review emphasizes the potential mechanisms linking MASLD with atherosclerosis and the possible causal relationships between these conditions.

RECENT FINDINGS

An increased risk of cardiovascular disease is related to MASLD. Several molecular, cellular, and metabolic mechanisms have been described to explain the development of atherothrombosis in MASLD patients. These include atherogenic dyslipidemia, low-grade vascular inflammation, endothelial dysfunction, foam cell formation, proliferation of vascular smooth muscle cells, insulin resistance, gut microbiota dysbiosis, activation of renin-angiotensin and sympathetic nervous systems, hypercoagulability, and decreased fibrinolysis. Also, there is recent evidence suggesting an association between genetically driven liver fat and coronary heart disease mediated by the causal effect of apoB-containing lipoproteins. Several meta-analyses and systematic reviews have reported a strong association between MASLD and cardiovascular outcomes. MASLD is an important and independent risk factor for atherosclerosis development. Multiple mechanisms may be involved in this association. Further research is required to establish a causal association between MASLD and atherosclerosis.

Type 1 diabetes mellitus and non-alcoholic fatty liver disease: a two-sample Mendelian randomization study

Background

NAFLD (Nonalcoholic fatty liver disease) is becoming an increasingly common cause of chronic liver disease. Metabolic dysfunction, overweight/obesity, and diabetes are thought to be closely associated with increased NAFLD risk. However, few studies have focused on the mechanisms of NAFLD occurrence in T1DM.

Methods

We conducted a two-sample Mendelian randomization (MR) analysis to assess the causal association between T1DM and NAFLD with/without complications, such as coma, renal complications, ketoacidosis, neurological complications, and ophthalmic complications. Multiple Mendelian randomization methods, such as the inverse variance weighted (IVW) method, weighted median method, and MR-Egger test were performed to evaluate the causal association of T1DM and NAFLD using genome-wide association study summary data from different consortia, such as Finngen and UK biobank.

Results

We selected 37 SNPs strongly associated with NAFLD/LFC (at a significance level of p < 5 × 10-8) as instrumental variables from the Finnish database based on the T1DM phenotype (8,967 cases and 308,373 controls). We also selected 14/16 SNPs based on with or without complications. The results suggest that the genetic susceptibility of T1DM does not increase the risk of NAFLD (OR=1.005 [0.99, 1.02], IVW p=0.516, MR Egger p=0.344, Weighted median p=0.959, Weighted mode p=0.791), regardless of whether complications are present. A slight causal effect of T1DM without complications on LFC was observed (OR=1.025 [1.00, 1.03], MR Egger p=0.045). However, none of the causal relationships were significant in the IVW (p=0.317), Weighted median (p=0.076), and Weighted mode (p=0.163) methods.

Conclusion

Our study did not find conclusive evidence for a causal association between T1DM and NAFLD, although clinical observations indicate increasing abnormal transaminase prevalence and NAFLD progression in T1DM patients.

The relationship between genetic liver fat and coronary heart disease is explained by apoB-containing lipoproteins

BACKGROUND

The relationship between genetically-driven liver fat and coronary heart disease (CHD) remains unclear. ApoB-containing lipoproteins are known causal factors for CHD and may explain this relationship.

METHODS AND RESULTS

We conducted a genome-wide association study (GWAS) in the UK Biobank to identify genetic variants associated with liver fat. We then investigated the effects that these genetic variants had on both apoB-containing lipoproteins and CHD. Using Mendelian Randomization (MR) analyses, we examined if the relationship between genetically-driven liver fat and CHD could be attributed to its effect on apoB-containing lipoproteins. We found 25 independent liver-fat associated single-nucleotide polymorphisms (SNPs) with differing effects on lipoprotein metabolism. The SNPs were classified into three groups/clusters. The first cluster (N = 3 SNPs) displayed lipoprotein-raising effects. The second cluster (N = 12 SNPs) displayed neutral effects on lipoproteins and the third cluster (N = 10 SNPs) displayed lipoprotein-lowering effects. For every 1% higher liver fat, the first cluster showed an increased risk of CHD (OR = 1.157 [95% CI: 1.108-1.208]). The second cluster showed a non-significant effect on CHD (OR = 0.988 [95% CI: 0.965-1.012], whereas the third cluster showed a protective effect of increased liver fat on CHD (OR = 0.942 [95% CI: 0.897-0.989]). When adjusting for apoB, the risk for CHD became null.

CONCLUSIONS

Here, we identify 25 liver-fat associated SNPs. We find that SNPs that increase, decrease or have neutral effects on apoB-containing lipoproteins show increased, decreased or neutral effects on CHD, respectively. Therefore, the relationship between genetically-driven liver fat and CHD is mediated by the causal effect of apoB.

Association between non-alcoholic fatty liver disease and coronary artery disease outcomes: A systematic review and meta-analysis

OBJECTIVES

To evaluate the association between non-alcoholic fatty liver disease (NAFLD) and cardiovascular outcomes, including angina, coronary artery disease (CAD), coronary artery calcification (CAC), myocardial infarction (MI), and calcified coronary plaques.

METHODS

A comprehensive search of databases, including PubMed, EMBASE, and Cochrane Library, was conducted up to January 2023. Studies were included investigating the relationship between NAFLD and cardiovascular outcomes in adult populations. Exclusion criteria were studies on animals, pediatric populations, and those not published in English. Two reviewers assessed the risk of bias in the included studies using the Newcastle-Ottawa Scale. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using random-effects models.

RESULTS

The meta-analysis included 32 studies with a total of 5,610,990 participants. NAFLD demonstrated significant associations with increased risks of angina (Relative Risk (RR): 1.45, 95% CI: 1.17, 1.79), CAD (RR: 1.21, 95% CI: 1.07, 1.38), CAC >0 (RR: 1.39, 95% CI: 1.15, 1.69), and calcified coronary plaques (RR: 1.55, 95% CI: 1.05, 2.27). However, no significant association was found between NAFLD and CAC >100 (RR: 1.16, 95% CI: 0.97, 1.38) or MI (RR: 1.70, 95% CI: 0.16, 18.32).

CONCLUSION

The meta-analysis demonstrated a significant association between NAFLD and cardiovascular outcomes independent of conventional cardiovascular disease (CVD) risk factors. These findings emphasize the importance of prevention, early detection, and proper management of NAFLD.

Metabolic dysfunction-associated steatotic liver disease and the heart

The prevalence and severity of metabolic dysfunction-associated steatotic liver disease (MASLD) are increasing. Physicians who treat patients with MASLD may acknowledge the strong coincidence with cardiometabolic disease, including atherosclerotic cardiovascular disease (asCVD). This raises questions on co-occurrence, causality, and the need for screening and multidisciplinary care for MASLD in patients with asCVD, and vice versa. Here, we review the interrelations of MASLD and heart disease and formulate answers to these matters. Epidemiological studies scoring proxies for atherosclerosis and actual cardiovascular events indicate increased atherosclerosis in patients with MASLD, yet no increased risk of asCVD mortality. MASLD and asCVD share common drivers: obesity, insulin resistance and type 2 diabetes mellitus (T2DM), smoking, hypertension, and sleep apnea syndrome. In addition, Mendelian randomization studies support that MASLD may cause atherosclerosis through mixed hyperlipidemia, while such evidence is lacking for liver-derived procoagulant factors. In the more advanced fibrotic stages, MASLD may contribute to heart failure with preserved ejection fraction by reduced filling of the right ventricle, which may induce fatigue upon exertion, often mentioned by patients with MASLD. Some evidence points to an association between MASLD and cardiac arrhythmias. Regarding treatment and given the strong co-occurrence of MASLD and asCVD, pharmacotherapy in development for advanced stages of MASLD would ideally also reduce cardiovascular events, as has been demonstrated for T2DM treatments. Given the common drivers, potential causal factors and especially given the increased rate of cardiovascular events, comprehensive cardiometabolic risk management is warranted in patients with MASLD, preferably in a multidisciplinary approach.

NAFLD: An Emerging Causal Factor for Cardiovascular Disease

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease worldwide that poses a significant threat to human health. Cardiovascular disease (CVD) is the leading cause of mortality in NAFLD patients. NAFLD and CVD share risk factors such as obesity, insulin resistance, and type 2 diabetes. However, whether NAFLD is a causal risk factor for CVD remains a matter of debate. This review summarizes the evidence from prospective clinical and Mendelian randomization studies that underscore the potential causal relationship between NAFLD and CVD. The mechanisms of NAFLD contributing to the development of CVD and the necessity of addressing CVD risk while managing NAFLD in clinical practice are also discussed.

MBOAT7 in liver and extrahepatic diseases

MBOAT7 is a protein anchored to endomembranes by several transmembrane domains. It has a catalytic dyad involved in remodelling of phosphatidylinositol with polyunsaturated fatty acids. Genetic variants in the MBOAT7 gene have been associated with the entire spectrum of non-alcoholic fatty liver (NAFLD), recently redefined as metabolic dysfunction-associated fatty liver disease (MAFLD) and, lately, steatotic liver disease (SLD), and to an increasing number of extrahepatic conditions. In this review, we will (a) elucidate the molecular mechanisms by which MBOAT7 loss-of-function predisposes to MAFLD and neurodevelopmental disorders and (b) discuss the growing number of genetic studies linking MBOAT7 to hepatic and extrahepatic diseases. MBOAT7 complete loss of function causes severe changes in brain development resulting in several neurological manifestations. Lower MBOAT7 hepatic expression at both the mRNA and protein levels, due to missense nucleotide polymorphisms (SNPs) in the locus containing the MBOAT7 gene, affects specifically metabolic and viral diseases in the liver from simple steatosis to hepatocellular carcinoma, and potentially COVID-19 disease. This body of evidence shows that phosphatidylinositol remodelling is a key factor for human health.

Cardiovascular Implications of Metabolic Dysfunction-Associated Fatty Liver Disease

Both nonalcoholic fatty liver disease (NAFLD) and metabolic dysfunction-associated fatty liver disease (MAFLD) have been associated with incident cardiovascular disease (CVD), independent of confounders. Causality has recently been inferred by Mendelian randomization studies. Although these findings have contributed to current guidelines that recommend screening for and treatment of cardiovascular risk factors, it not yet clear how to position NAFLD/MAFLD in cardiovascular risk estimation scores and, consequently, which treatment targets should be used. This review aims to provide practical tools as well as suggestions for further research in order to effectively prevent CVD events in patients with NAFLD/MAFLD.

MBOAT7 rs641738 (C>T) is associated with NAFLD progression in men and decreased ASCVD risk in elder Chinese population

Background and aim

The MBOAT7 rs641738 (C>T) variant has demonstrated an association with non-alcoholic fatty liver disease (NAFLD) in both adult and pediatric patients, while few studies have been conducted in elderly populations. Hence, a case-control study was undertaken to assess their correlation in elderly residents in a Beijing community.

Materials and methods

A total of 1,287 participants were included. Medical history, abdominal ultrasound, and laboratory tests were recorded. Liver fat content and fibrosis stage were detected by Fibroscan. Genotyping of genomic DNA was performed using the 96.96 genotyping integrated fluidics circuit.

Results

Of the recruited subjects, 638 subjects (56.60%) had NAFLD, and 398 subjects (35.28%) had atherosclerotic cardiovascular disease (ASCVD). T allele carriage was associated with higher ALT (p=0.005) and significant fibrosis in male NAFLD patients (p=0.005) compared to CC genotype. TT genotype was associated with reduced risk of metabolic syndrome (OR=0.589, 95%CI: 0.114-0.683, p=0.005) and type 2 diabetes (OR=0.804, 95%CI: 0.277-0.296, p=0.048) in NAFLD population when compared to the CC genotype. In addition, TT genotype was also associated with reduced risk of ASCVD (OR=0.570, 95%CI:0.340-0.953, p=0.032) and less obesity (OR=0.545, 95%CI: 0.346-0.856, p=0.008) in the whole population.

Conclusion

MBOAT7 rs641738 (C>T) variant was associated with fibrosis in male NAFLD patients. The variant also reduced risk of metabolic traits and type 2 diabetes in NAFLD and ASCVD risk in Chinese elders.

Relationship between NAFLD and coronary artery disease: A Mendelian randomization study

BACKGROUND AND AIMS

There is an ongoing debate on whether NAFLD is an active contributor or an innocent bystander in the pathogenesis of coronary artery disease (CAD). The aim of the present study was to assess the causal relationship between NAFLD and CAD.

APPROACH AND RESULTS

We performed two-sample Mendelian randomization (MR) analyses using summary-level data to assess the association between genetically predicted NAFLD (i.e., chronically elevated serum alanine aminotransferase levels [cALT], imaging-based and biopsy-confirmed NAFLD) and risk of CAD. Analyses were repeated after exclusion of NAFLD susceptibility genes that are associated with impaired VLDL secretion.Inverse-variance weighted MR analyses showed a statistically significant association between genetically predicted cALT and risk of CAD (OR: 1.116, 95% CI: 1.039, 1.199), but not for the other NAFLD-related traits (OR: 1.046, 95% CI: 0.764, 1.433 and OR: 1.014, 95% CI: 0.968, 1.062 for imaging-based and biopsy-confirmed NAFLD, respectively). MR-Egger regression revealed a statistically significant intercept, indicative of directional pleiotropy, for all traits. Repeat analyses after exclusion of genes associated with impaired VLDL secretion showed consistent associations between genetically predicted NAFLD and CAD for all traits (i.e., cALT [OR: 1.203, 95% CI: 1.113, 1.300]), imaging-based (OR: 2.149, 95% CI: 1.276, 3.620) and biopsy-confirmed NAFLD (OR: 1.113, 95% CI: 1.041, 1.189), which persisted when more stringent biopsy-confirmed NAFLD criteria were used (OR: 1.154, 95% CI: 1.043, 1.278) or when more stringent MR methods were applied. MR-Egger regression did not show a statistically significant intercept.

CONCLUSION

The two-sample MR analyses showed a robust association between genetically predicted NAFLD and CAD after exclusion of genetic variants that are implicated in impaired VLDL secretion.

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

Introduction

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.

Methods

We conducted an observational cross-sectional study including 77 subjects (38 MAFLD patients, 39 controls), between January-September 2020 using hepatic ultrasonography and SteatoTest^TM to assess hepatic steatosis. Echocardiographic and Doppler ultrasound parameters were evaluated. Genomic DNA was extracted and rs641738 SNP was genotyped using TaqMan assays.

Results

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]).

Conclusion

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.

FIB-4 Index and Neutrophil-to-Lymphocyte-Ratio as Death Predictor in Coronary Artery Disease Patients

Nonalcoholic fatty liver disease (NAFLD)-associated liver fibrosis is likely related to coronary artery disease (CAD) by the mediation of systemic inflammation. This study aimed at evaluating the predictive value of neutrophil-to-lymphocyte-ratio (NLR) and fibrosis-4 index (FIB-4), indices of inflammation and fibrosis, respectively, on CAD mortality. Data from 1460 CAD patients (1151 males, age: 68 ± 10 years, mean ± SD) were retrospectively analyzed. Over a median follow-up of 26 months (interquartile range (IQR) 12−45), 94 deaths were recorded. Kaplan−Meier survival analysis revealed worse outcomes in patients with elevation of one or both biomarkers (FIB-4 > 3.25 or/and NLR > 2.04, log-rank p-value < 0.001). In multivariate Cox regression analysis, the elevation of one biomarker (NLR or FIB-4) still confers a significant independent risk for mortality (hazard ratio (HR) = 1.7, 95% confidence interval (95% CI): 1.1−2.7, p = 0.023), whereas an increase in both biomarkers confers a risk corresponding to HR = 3.5 (95% CI: 1.6−7.8, p = 0.002). Categorization of patients with elevated FIB-4/NLR could provide valuable information for risk stratification and reduction of residual risk in CAD patients.

Association between de novo lipogenesis susceptibility genes and coronary artery disease

BACKGROUND AND AIMS

Coronary artery disease (CAD) is the principal cause of death in individuals with non-alcoholic fatty liver disease (NAFLD). The aim of this study was to use genetic epidemiology to study the association between de novo lipogenesis (DNL), one of the major pathways leading to NAFLD, and CAD risk.

METHODS AND RESULTS

DNL susceptibility genes were used as instruments and selected using three approaches: 1) genes that are associated with both high serum triglycerides and low sex hormone-binding globulin, both downstream consequences of DNL (unbiased approach), 2) genes that have a known role in DNL (biased approach), and 3) genes that have been associated with serum fatty acids, used as a proxy of DNL. Gene-CAD effect estimates were retrieved from the meta-analysis of CARDIoGRAM and the UK Biobank (∼76014 cases and ∼264785 controls). Effect estimates were clustered using a fixed-effects meta-analysis. Twenty-two DNL susceptibility genes were identified by the unbiased approach, nine genes by the biased approach and seven genes were associated with plasma fatty acids. Clustering of genes selected in the unbiased and biased approach showed a statistically significant association with CAD (OR:1.016, 95%CI:1.012; 1.020 and OR:1.013, 95%CI:1.007; 1.020, respectively), while clustering of fatty acid genes did not (OR:1.004, 95%CI:0.996-1.011). Subsequent exclusion of potential influential outliers did reveal a statistically significant association (OR:1.009, 95%CI:1.000; 1.018).

CONCLUSIONS

DNL susceptibility genes are associated with an increased risk of CAD. These findings suggest that DNL may be involved in the pathogenesis of CAD and favor further development of strategies that target NAFLD through DNL.

Dissecting causal relationships between nonalcoholic fatty liver disease proxied by chronically elevated alanine transaminase levels and 34 extrahepatic diseases

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is prevalent worldwide and is associated with the risk of many extrahepatic diseases. However, whether NAFLD is a risk marker or a common cause of extrahepatic diseases is unclear.

METHODS

We searched PubMed to identify NAFLD-related extrahepatic diseases. Genetic instrumental variables (IVs) for NAFLD surrogated by chronically elevated alanine transaminase levels and eligible extrahepatic diseases were retrieved from the corresponding genome-wide association analysis. We proposed a procedure for Mendelian randomization (MR) analysis and performed validation analyses to dissect the association between NAFLD and extrahepatic diseases. The Bonferroni method was used to correct the bias of multiple testing.

RESULTS

In total, 34 extrahepatic diseases were included and 54 SNPs were used as IVs for NAFLD. The MR analysis gave a robust and significant (or suggestive) estimate for the association between NAFLD and 9 extrahepatic diseases: type 2 diabetes (odds ratio [OR] = 1.182, 95 % confidence interval [CI] 1.125-1.243, P = 5.40 × 10^-11), cholelithiasis (OR = 1.171, 95%CI 1.083-1.266, P = 7.47 × 10^-5), diabetic hypoglycemia (OR = 1.170, 95%CI 1.071-1.279, P = 5.14 × 10^-4), myocardial infarction (OR = 1.122, 95%CI 1.057-1.190, P = 1.46 × 10^-4), hypertension (OR = 1.060, 95%CI 1.029-1.093, P = 1.18 × 10^-4), coronary artery disease (OR = 1.052, 95%CI 1.010-1.097, P = 1.58 × 10^-2), heart failure (OR = 1.047, 95%CI 1.006-1.090, P = 2.44 × 10^-2), dementia (OR = 0.881, 95%CI 0.806-0.962, P = 5.01 × 10^-3), and pancreatic cancer (OR = 0.802, 95%CI 0.654-0.983, P = 3.32 × 10^-2). Validation analyses using IVs from biopsy-confirmed and imaging-determined NAFLD reported similar results to the main analysis. For the remaining 25 outcomes, no significant or definitive association was yielded in MR analysis.

CONCLUSIONS

Genetic evidence suggests putative causal relationships between NAFLD and a set of extrahepatic diseases, indicating that NAFLD deserves high priority in clinical practice.

Fructose 1-phosphate, an evolutionary signaling molecule of abundancy

Evidence is accumulating that specifically fructose exerts adverse cardiometabolic effects in humans. Recent experimental studies have shown that fructose not only serves as a substrate for, among others, intrahepatic lipid formation, but also has a signaling function. It is postulated that fructose 1-phosphate (F1-P) has evolved as a signaling molecule of abundancy that stimulates nutrient absorption, lipid storage, and reproduction. Such a role would provide an explanation for why fructose contributes to the pathogenesis of evolutionary mismatch diseases, including nonalcoholic fatty liver disease (NAFLD), cardiovascular disease, polycystic ovary syndrome (PCOS), and colorectal cancer, in the current era of nutritional abundance. It is anticipated that reducing F1-P, by either pharmacological inhibition of ketohexokinase (KHK) or societal measures, will mitigate the risk of these diseases.

Membrane-bound O-acyltransferase 7 (MBOAT7)-driven phosphatidylinositol remodeling in advanced liver disease

Advanced liver diseases account for approximately 2 million deaths annually worldwide. Roughly, half of liver disease-associated deaths arise from complications of cirrhosis and the other half driven by viral hepatitis and hepatocellular carcinoma. Unfortunately, the development of therapeutic strategies to treat subjects with advanced liver disease has been hampered by a lack of mechanistic understanding of liver disease progression and a lack of human-relevant animal models. An important advance has been made within the past several years, as several genome-wide association studies have discovered that an SNP near the gene encoding membrane-bound O-acyltransferase 7 (MBOAT7) is associated with severe liver diseases. This common MBOAT7 variant (rs641738, C>T), which reduces MBOAT7 expression, confers increased susceptibility to nonalcoholic fatty liver disease, alcohol-associated liver disease, and liver fibrosis in patients chronically infected with viral hepatitis. Recent studies in mice also show that Mboat7 loss of function can promote hepatic steatosis, inflammation, and fibrosis, causally linking this phosphatidylinositol remodeling enzyme to liver health in both rodents and humans. Herein, we review recent insights into the mechanisms by which MBOAT7-driven phosphatidylinositol remodeling influences liver disease progression and discuss how rapid progress in this area could inform drug discovery moving forward.

Causal relationship between polycystic ovary syndrome and coronary artery disease: A Mendelian randomisation study

OBJECTIVE

Polycystic ovary syndrome (PCOS) has been associated with an increased risk of coronary artery disease (CAD). However, it remains uncertain whether this increased risk is the result of PCOS per se or, alternatively, is explained by obesity, a common feature of PCOS. The aim of this study was to assess the causal association between PCOS and CAD and the role of obesity herein.

DESIGN AND METHODS

We conducted two-sample Mendelian randomisation analyses in large-scale, female-specific datasets to study the association between genetically predicted (1) risk of PCOS and risk of CAD, (2) body mass index (BMI) and risk of PCOS and (3) BMI and risk of CAD. Primary analyses were conducted with the inverse-variance weighted (IVW) method. Simple median, penalized weighted median and contamination mixture analyses were performed to assess the robustness of the outcomes.

RESULTS

IVW analyses did not show a statistically significant association between PCOS and CAD (odds ratio [OR]: 0.99, 95% confidence interval [CI]: 0.89, 1.11). In contrast, genetically predicted BMI was statistically significantly associated with an increased odds of PCOS (OR: 3.21, 95% CI: 2.26, 4.56) and CAD (OR: 1.38, 95% CI: 1.14, 1.67). Similar results were obtained when secondary analyses were performed.

CONCLUSION

These sex-specific analyses show that the genetically predicted risk of PCOS is not associated with the risk of CAD. Instead, the genetically predicted risk of obesity (and its downstream metabolic effects) is the common denominator of both PCOS and CAD risk.

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

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

Machine Learning Approach to Classify Cardiovascular Disease in Patients With Nonalcoholic Fatty Liver Disease in the UK Biobank Cohort

Background Nonalcoholic fatty liver disease (NAFLD) is the most prevalent liver disease worldwide. Cardiovascular disease (CVD) is the leading cause of mortality among patients with NAFLD. The aim of our study was to develop a machine learning algorithm integrating clinical, lifestyle, and genetic risk factors to identify CVD in patients with NAFLD. Methods and Results We created a cohort of patients with NAFLD from the UK Biobank, diagnosed according to proton density fat fraction from magnetic resonance imaging data sets. A total of 400 patients with NAFLD with subclinical atherosclerosis or clinical CVD, defined by disease codes, constituted cases and 446 NAFLD cases with no CVD constituted controls. We evaluated 7 different supervised machine learning approaches on clinical, lifestyle, and genetic variables for identifying CVD in patients with NAFLD. The most significant clinical and lifestyle variables observed by the predictive modeling were age (59 years [54.00-63.00 years]), hypertension (145 mm Hg [134.0-156.0 mm Hg] and 85 mm Hg [79.00-93.00 mm Hg]), waist circumference (98 cm [95.00-105.00 cm]), and sedentary lifestyle, defined as time spent watching TV >4 h/d. In the genetic data, single-nucleotide polymorphisms in IL16 and ANKLE1 gene were most significant. Our proposed ensemble-based integrative machine learning model achieved an area under the curve of 0.849 using the random forest modeling for CVD prediction. Conclusions We propose a machine learning algorithm that identifies CVD in patients with NAFLD through integration of significant clinical, lifestyle, and genetic risk factors. These patients with NAFLD at higher risk of CVD should be flagged for screening and aggressive treatment of their cardiometabolic risk factors to prevent cardiovascular morbidity and mortality.

Association of NAFLD with cardiovascular disease and all-cause mortality: a large-scale prospective cohort study based on UK Biobank

Objective

Nonalcoholic fatty liver disease (NAFLD) is considered as the hepatic manifestation of metabolic syndrome, sharing the similar cardiometabolic risk factors with cardiovascular disease (CVD). Whether NAFLD by itself is associated with increased cardiovascular events and death remain an issue to debate. This study aimed to further investigate the association between NAFLD and adverse CVD outcomes.

Methods

Participants were followed up until the end of 2020 in current analysis. NAFLD is defined using fatty liver index (FLI). Cox proportional hazard model was used to analyze the association between NAFLD and all-cause mortality, major adverse cardiovascular events (MACEs), CVD mortality, fatal/nonfatal acute myocardial infarction (AMI), and fatal/nonfatal stroke. C-index was calculated to evaluate the model enhancement when adding NAFLD factor.

Results

After screening the data of 502,492 participants in the original cohort, 215,245 eligible participants were included in this study for MACEs outcome. Compared with non-NAFLD participants, the multivariable adjusted hazard ratios of NAFLD group was 1.25 (1.14-1.36) for MACEs; 1.14 (1.08-1.20) for all-cause mortality; 1.61(1.42-1.82) for CVD mortality; 1.58(1.19-2.11) for AMI mortality; and 1.18 (0.85-1.64) for stroke mortality. When adding FLI, C-index of NAFLD model improved for all-cause mortality, MACEs, and CVD mortality compared with that in the traditional CVD risk factor model.

Conclusion

NAFLD is an independent risk factor for all-cause mortality and adverse CVD outcomes. Based on the traditional CVD risk factor model, additionally screening NAFLD could improve the prediction efficiency for adverse CVD outcomes.

Research progress, challenges and perspectives on PNPLA3 and its variants in Liver Diseases

The human patatin-like phospholipase domain-containing 3 gene (PNPLA3) is highly expressed in liver and adipose tissue and encodes a transmembrane polypeptide chain containing 481 amino acids. The I148M variant of PNPLA3 is a single nucleotide polymorphism, which is related to a variety of liver and cardiovascular diseases and their complications (such as non-alcoholic fatty liver disease, liver fibrosis, coronary artery disease). This review mainly describes the pathophysiological effects of PNPLA3 and its variants, and their roles in the progression of liver disease and its complications.

Metabolic-associated Fatty Liver Disease as Assessed by the Fatty Liver Index Among Migrant and Non-migrant Ghanaian Populations

BACKGROUND AND AIMS

Metabolic-associated fatty liver disease (MAFLD) is driven by high caloric intake and sedentary lifestyle. Migration towards high income countries may induce these driving factors; yet, the influence of such on the prevalence of MAFLD is clearly understudied. Here, we investigated the Fatty Liver Index (FLI), a proxy of steatosis in MAFLD, after migration of Ghanaian subjects.

METHODS

Cross-sectional data of 5282 rural, urban and migrant participants from the Research on Obesity and Diabetes among African Migrants (also known as RODAM) study were analyzed with logistic regression for geographical differences in FLI and associations with type 2 diabetes mellitus (T2DM), waist-to-hip ratio, and 10-year predicted risk of atherosclerotic cardiovascular disease (ASCVD).

RESULTS

Both FLI and the proportion with an FLI indicative of MAFLD steatosis (FLI ≥60) were higher in migrants compared with non-migrants. Prevalence of elevated FLI (FLI ≥60) in non-migrant males was 4.2% compared to 28.9% in migrants. For females, a similar gradient was observed, from 13.6% to 36.6% respectively. Compared to rural residents, the odds for a FLI ≥60 were higher in migrants living in urban Europe (odds ratio [OR] 9.02, 95% confidence interval [CI]: 5.02-16.20 for men, and 4.00, 95% CI: 3.00-5.34 for women). Compared to controls, the ORs for FLI ≥60 were 2.43 (95% CI: 1.73-3.41) for male T2DM cases and 2.02 (95% CI: 1.52-2.69) for female T2DM cases. One-unit higher FLI was associated with an elevated (≥7.5%) 10-year ASCVD risk (OR: 1.051, 95% CI: 1.041-1.062 for men, and 1.020, 95% CI: 1.015-1.026 for women).

CONCLUSIONS

FLI as a proxy for MAFLD increased stepwise in Ghanaians from rural areas, through urban areas, to Europe. Our results clearly warrant awareness for MAFLD in migrant population as well as confirmation with imaging modalities.

Relationship between AGT rs2493132 polymorphism and the risk of coronary artery disease in patients with NAFLD in the Chinese Han population

Objective

To investigate the relationship between angiotensin (AGT) rs2493132 gene polymorphism and the risk of developing non-alcoholic fatty liver disease (NAFLD) and coronary artery disease (CAD) in the Chinese Han population.

Methods

Polymerase chain reaction was performed to determine AGT genotypes. Anthropometric and clinical data were investigated and statistically analyzed in the clinical laboratory department of Qingdao Municipal Hospital.

Results

The AGT rs2493132 CT + TT genotype was an important risk factor for CAD in patients with NAFLD and NAFLD + CAD in healthy controls. The AGT rs2493132 T allele increased the risk of NAFLD + CAD in healthy controls. The AGT rs2493132 CT + TT genotype and T allele also significantly increased the risk of CAD in patients with NAFLD after adjustments for age, sex, and body mass index. In addition, AGT rs2493132 T allele carriers showed higher total cholesterol (TC) and low-density lipoprotein (LDL) levels compared with non-carriers.

Conclusions

The AGT rs2493132 CT + TT genotype and T allele significantly increased the risk of developing CAD in patients with NAFLD in the Chinese Han population. The AGT rs2493132 T allele was associated with increased serum TC and LDL levels.

Mitochondrial Lipid Homeostasis at the Crossroads of Liver and Heart Diseases

The prevalence of NAFLD (non-alcoholic fatty liver disease) is a rapidly increasing problem, affecting a huge population around the globe. However, CVDs (cardiovascular diseases) are the most common cause of mortality in NAFLD patients. Atherogenic dyslipidemia, characterized by plasma hypertriglyceridemia, increased small dense LDL (low-density lipoprotein) particles, and decreased HDL-C (high-density lipoprotein cholesterol) levels, is often observed in NAFLD patients. In this review, we summarize recent genetic evidence, proving the diverse nature of metabolic pathways involved in NAFLD pathogenesis. Analysis of available genetic data suggests that the altered operation of fatty-acid β-oxidation in liver mitochondria is the key process, connecting NAFLD-mediated dyslipidemia and elevated CVD risk. In addition, we discuss several NAFLD-associated genes with documented anti-atherosclerotic or cardioprotective effects, and current pharmaceutical strategies focused on both NAFLD treatment and reduction of CVD risk.

Bile acids profile, histopathological indices and genetic variants for non-alcoholic fatty liver disease progression

OBJECTIVE

Metabolomic studies suggest plasma levels of bile acids (BAs) are elevated amongst subjects with non-alcoholic fatty liver disease (NAFLD) compared to healthy controls. However, it remains unclear whether or not specific BAs are associated with the clinically relevant transition from nonalcoholic fatty liver (i.e. simple steatosis) to non-alcoholic steatohepatitis (NASH), or enhanced progression of hepatic fibrosis, or genetic determinants of NAFLD/NASH.

METHODS

Among sequential subjects (n=102) undergoing diagnostic liver biopsy, we examined the associations of a broad panel of BAs with distinct histopathological features of NAFLD, the presence of NASH, and their associations with genetic variants linked to NAFLD and NASH.

RESULTS

Plasma BA alterations were observed through the entire spectrum of NAFLD, with several glycine conjugated forms of the BAs demonstrating significant associations with higher grades of inflammation and fibrosis. Plasma 7-Keto-DCA levels showed the strongest associations with advanced stages of hepatic fibrosis [odds ratio(95% confidence interval)], 4.2(1.2-16.4), NASH 24.5(4.1-473), and ballooning 18.7(4.8-91.9). Plasma 7-Keto-LCA levels were associated with NASH 9.4(1.5-185) and ballooning 5.9(1.4-28.8). Genetic variants at several NAFLD/NASH loci were nominally associated with increased levels of 7-Keto- and glycine-conjugated forms of BAs, and the NAFLD risk allele at the TRIB1 locus showed strong tendency toward increased plasma levels of GCA (p=0.02) and GUDCA (p=0.009).

CONCLUSIONS

Circulating bile acid levels are associated with histopathological and genetic determinants of the transition from simple hepatic steatosis into NASH. Further studies exploring the potential involvement of bile acid metabolism in the development and/or progression of distinct histopathological features of NASH are warranted.

The PNPLA3-I148M Variant Confers an Antiatherogenic Lipid Profile in Insulin-resistant Patients

CONTEXT

The I148M (rs738409-G) variant in PNPLA3 increases liver fat content but may be protective against cardiovascular disease. Insulin resistance (IR) amplifies the effect of PNPLA3-I148M on liver fat.

OBJECTIVE

To study whether PNPLA3-I148M confers an antihyperlipidemic effect in insulin-resistant patients.

DESIGN

Cross-sectional study comparing the impact of PNPLA3-I148M on plasma lipids and lipoproteins in 2 cohorts, both divided into groups based on rs738409-G allele carrier status and median HOMA-IR.

SETTING

Tertiary referral center.

PATIENTS

A total of 298 obese patients who underwent a liver biopsy during bariatric surgery (bariatric cohort: age 49 ± 9 years, body mass index [BMI] 43.2 ± 6.8 kg/m2), and 345 less obese volunteers in whom liver fat was measured by proton magnetic resonance spectroscopy (nonbariatric cohort: age 45 ± 14 years, BMI 29.7 ± 5.7 kg/m2).

MAIN OUTCOME MEASURES

Nuclear magnetic resonance profiling of plasma lipids, lipoprotein particle subclasses and their composition.

RESULTS

In both cohorts, individuals carrying the PNPLA3-I148M variant had significantly higher liver fat content than noncarriers. In insulin-resistant and homozygous carriers, PNPLA3-I148M exerted a distinct antihyperlipidemic effect with decreased very-low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) particles and their constituents, and increased high-density lipoprotein particles and their constituents, compared with noncarriers. VLDL particles were smaller and LDL particles larger in PNPLA3-I148M carriers. These changes were geometrically opposite to those due to IR. PNPLA3-I148M did not have a measurable effect in patients with lower IR, and its effect was smaller albeit still significant in the less obese than in the obese cohort.

CONCLUSIONS

PNPLA3-I148M confers an antiatherogenic plasma lipid profile particularly in insulin-resistant individuals.

rs641738C>T near MBOAT7 is associated with liver fat, ALT and fibrosis in NAFLD: A meta-analysis

BACKGROUND & AIMS

A common genetic variant near MBOAT7 (rs641738C>T) has been previously associated with hepatic fat and advanced histology in NAFLD; however, these findings have not been consistently replicated in the literature. We aimed to establish whether rs641738C>T is a risk factor across the spectrum of NAFLD and to characterise its role in the regulation of related metabolic phenotypes through a meta-analysis.

METHODS

We performed a meta-analysis of studies with data on the association between rs641738C>T genotype and liver fat, NAFLD histology, and serum alanine aminotransferase (ALT), lipids or insulin. These included directly genotyped studies and population-level data from genome-wide association studies (GWAS). We performed a random effects meta-analysis using recessive, additive and dominant genetic models.

RESULTS

Data from 1,066,175 participants (9,688 with liver biopsies) across 42 studies were included in the meta-analysis. rs641738C>T was associated with higher liver fat on CT/MRI (+0.03 standard deviations [95% CI 0.02-0.05], pz = 4.8×10-5) and diagnosis of NAFLD (odds ratio [OR] 1.17 [95% CI 1.05-1.3], pz = 0.003) in Caucasian adults. The variant was also positively associated with presence of advanced fibrosis (OR 1.22 [95% CI 1.03-1.45], pz = 0.021) in Caucasian adults using a recessive model of inheritance (CC + CT vs. TT). Meta-analysis of data from previous GWAS found the variant to be associated with higher ALT (pz = 0.002) and lower serum triglycerides (pz = 1.5×10-4). rs641738C>T was not associated with fasting insulin and no effect was observed in children with NAFLD.

CONCLUSIONS

Our study validates rs641738C>T near MBOAT7 as a risk factor for the presence and severity of NAFLD in individuals of European descent.

LAY SUMMARY

Fatty liver disease is a common condition where fat builds up in the liver, which can cause liver inflammation and scarring (including 'cirrhosis'). It is closely linked to obesity and diabetes, but some genes are also thought to be important. We did this study to see whether one specific change ('variant') in one gene ('MBOAT7') was linked to fatty liver disease. We took data from over 40 published studies and found that this variant near MBOAT7 is linked to more severe fatty liver disease. This means that drugs designed to work on MBOAT7 could be useful for treating fatty liver disease.

Dysregulated lipid metabolism links NAFLD to cardiovascular disease

Background

Non-alcoholic fatty liver disease (NAFLD) is rapidly becoming a global health problem. Cardiovascular diseases (CVD) are the most common cause of mortality in NAFLD patients. NAFLD and CVD share several common risk factors including obesity, insulin resistance, and type 2 diabetes (T2D). Atherogenic dyslipidemia, characterized by plasma hypertriglyceridemia, increased small dense low-density lipoprotein (LDL) particles, and decreased high-density lipoprotein cholesterol (HDL-C) levels, is often observed in NAFLD patients.

Scope of review

In this review, we highlight recent epidemiological studies evaluating the link between NAFLD and CVD risk. We further focus on recent mechanistic insights into the links between NAFLD and altered lipoprotein metabolism. We also discuss current therapeutic strategies for NAFLD and their potential impact on NAFLD-associated CVD risk.

Major conclusions

Alterations in hepatic lipid and lipoprotein metabolism are major contributing factors to the increased CVD risk in NAFLD patients, and many promising NASH therapies in development also improve dyslipidemia in clinical trials.

Genetic predisposition in metabolic-dysfunction-associated fatty liver disease and cardiovascular outcomes-Systematic review

BACKGROUND

Despite the demonstrated increased cardiovascular (CV) risk associated with metabolic-dysfunction-associated fatty liver disease (MAFLD), genetic variants predisposing to MAFLD were not constantly associated with CV events. Recently, rs641738C > T near membrane-bound O-acyltransferase domain-containing 7 (MBOAT7) has been studied in MAFLD and CV outcomes. Therefore, we aimed to evaluate the association between rs641738C > T in the presence and severity of hepatic steatosis, fibrosis, biochemical markers and progression to hepatocellular carcinoma (HCC), in addition to CV outcomes in MAFLD.

MATERIALS AND METHODS

An electronic search on PubMed, Embase and Cochrane Library for articles published till 23 March 2020 was systematically performed. Articles were screened, and data extracted from eligible studies by two reviewers independently.

RESULTS

Studies conducted on adults with MAFLD involving European, Hispanic and African American populations evaluating rs641738 reported reduced hepatic expression of MBOAT7, increased hepatic fat content, severity of MAFLD, susceptibility to develop NASH, advanced fibrosis and HCC in adults. However, most articles involving Asian individuals contradicted these findings. Studies involving obese children associated rs641738 with increased plasma alanine aminotransferase (ALT) levels, while its association with MAFLD remains inconsistent. The rs641738 variant was assessed as a MAFLD susceptibility gene in coronary artery disease (CAD) reporting neutral effects.

CONCLUSIONS

Despite inconclusive results in Asian populations, rs641738C > T near MBOAT7 is associated with increased hepatic fat, MAFLD severity, susceptibility to develop NASH, advanced fibrosis and HCC in adults from Caucasian, Hispanic and African American ethnicities with MAFLD, as well as elevated ALT levels in children, while exerting neutral effects in CAD.

Association between PNPLA3 rs738409 G variant and MRI cerebrovascular disease biomarkers

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) has been associated with greater cerebral white matter hyperintensity (WMH) volume and microbleeds. The adiponutrin (PNPLA3) rs738409 G variant, a robust NAFLD susceptibility variant, has been variably associated with carotid atherosclerosis. We hypothesized that this variant is associated with WMH volume, microbleeds, covert brain infarction (CBI), and small perivascular spaces.

METHODS

We performed a cross-sectional analysis of the Northern Manhattan Study-MRI Substudy. The associations between the rs738409 G variant allele and outcomes were assessed using linear regression for WMH volume, logistic regression for microbleeds and CBI, and Poisson regression for small perivascular spaces. Models were adjusted for age, sex, principal components, diabetes, and body mass index.

RESULTS

We included 1063 Northern Manhattan Study participants who had brain MRI and genotype data available (mean age 70 ± 9 years, 61% women). The G allele frequency was 24%. The prevalence of any microbleeds and CBI were 8% and 18%, respectively. The median WMH volume and small perivascular space count score were 7.7 mL and 6, respectively. GG homozygosity, but not heterozygosity, was associated with WMH volume (β = 0.27; 95% CI, 0.03, 0.51) compared to non-carriers. Having at least one G allele was associated with the presence of microbleeds (Odds ratio, 1.78; 95% CI, 1.02, 3.12); the association was attenuated in other models. No associations were observed for CBI and small perivascular spaces.

CONCLUSION

The PNPLA3 rs738409 G allele was associated with greater WMH volume, and inconsistent associations with microbleeds were seen.

Defects in High Density Lipoprotein metabolism and hepatic steatosis in mice with liver-specific ablation of Hepatocyte Nuclear Factor 4A

BACKGROUND

Aberrant concentration, structure and functionality of High Density Lipoprotein (HDL) are associated with many prevalent diseases, including cardiovascular disease and non-alcoholic fatty liver disease (NAFLD). Mice with liver-specific ablation of Hnf4α (H4LivKO) present steatosis and dyslipidemia by mechanisms that are not completely understood. The aim of this study was to explore the role of liver HNF4A in HDL metabolism and the development of steatosis.

METHODS AND RESULTS

Serum and tissue samples were obtained from 6-weeks old H4LivKO mice and their littermate controls. Liver and serum lipids were measured and HDL structure and functionality were assessed. Global gene expression changes in the liver were analyzed by expression arrays, validations were performed by RT-qPCR and DNA-protein interactions were studied by chromatin immunoprecipitation (ChIP). H4LivKO mice presented liver steatosis, increased liver triglyceride content and decreased concentration of serum total cholesterol, HDL cholesterol, triglycerides, phospholipids and cholesteryl esters. Most classes of phospholipids showed significant changes in species ratio and sphingosine-1-phosphate (S1P) levels were reduced. H4LivKO serum was enriched in the smaller, denser HDL particles, devoid of APOA2 and APOM apolipoproteins, exhibiting decreased activity of paraoxonase-1 but retaining macrophage cholesterol efflux capacity and phospho-AKT activation in endothelial cells. Global gene expression analysis revealed the association of liver HNF4A with known and novel regulators of HDL metabolism as well as NAFLD-susceptibility genes.

CONCLUSIONS

HNF4A ablation in mouse liver causes hepatic steatosis, perturbations in HDL structure and function and significant global changes in gene expression. This study reveals new targets of HNF4A involved in HDL metabolism and the development of steatosis and enriches our knowledge on HDL functionality in NAFLD.

Independent and joint correlation of PNPLA3 I148M and TM6SF2 E167K variants with the risk of coronary heart disease in patients with non-alcoholic fatty liver disease

Background

CHD is reported to be the primary cause of death in patients with NAFLD. Genetic susceptibility genes contribute to the developmental risk of NAFLD or CHD. Whether the genetic factors could affect the risk of CHD in NAFLD patients is not clear. The aim of this study was to investigate the association of PNPLA3 I148M and TM6SF2 E167K variants with the risk of CHD in NAFLD patients in Chinese Han population.

Patients and methods

PNPLA3 I148M and TM6SF2 E167K variants were genotyped in a cohort of 189 patients with NAFLD and CHD, as well as 242 patients with NAFLD and 242 healthy controls by gene sequencing. Additionally, serum lipids profiles were determined by standard clinical laboratory methods.

Results

The minor allele frequency of PNPLA3 I148M and TM6SF2 E167K were 0.39 and 0.06 in this cohort, respectively. The distributions of PNPLA3 I148M genotypes and alleles were significant different in NAFLD group vs controls and in NAFLD+CHD group vs NAFLD group (all P <  0.05). NAFLD patients who carry the CG + GG genotype suffered the relative lower risk of CHD than CC genotype carriers (OR = 0.6, 95%CI: 0.40–0.90, P = 0.01). In addition, PNPLA3 I148M and TM6SF2 E167K possess the joint correlation with the decreased risk of CHD in NAFLD patients with the increased number of risk alleles. Besides, PNPLA3 I148M and TM6SF2 E167K variants associated with the decreased serum lipid levels in overall series.

Conclusions

There was a joint protective correlation of PNPLA3 I148M and TM6SF2 E167K variants with the developmental risk of CHD in NAFLD patients. PNPLA3 I148M and TM6SF2 E167K variants might correlated with the decreased risk of CHD in NAFLD patients by associated with the reduced serum lipid levels.

Fatty liver, cardiometabolic disease and mortality

PURPOSE OF REVIEW

We discuss the findings of the most recent metanalyses on the association between nonalcoholic fatty liver disease (NAFLD), cardiometabolic disease and mortality.

RECENT FINDINGS

Recent metanalyses have shown that NAFLD is associated with incident type 2 diabetes mellitus (T2DM) and incident cardiovascular disease (CVD). Nonalcoholic steatohepatitis, which can be diagnosed by liver biopsy only in tertiary care centers, is often associated with liver fibrosis, which has been shown by metanalyses to increase both cardiovascular and liver-related mortality. Hyperlipidemia, lipotoxicity and impaired insulin secretion are among the possible mechanisms underlying the association of NAFLD with T2DM and CVD. Metanalyses of the association between NAFLD and mortality in the general population, where risk stratification cannot be performed on the basis of liver biopsy, have given contradictory results.

SUMMARY

To establish conclusively whether NAFLD adds to known prognostic factors of death in the general population will require a shared operational definition of NAFLD, purposefully designed cohort studies, and the use of clinically relevant measures of effect size.

Non-alcoholic fatty liver disease and cardiovascular disease: assessing the evidence for causality

Non-alcoholic fatty liver disease (NAFLD) is highly prevalent among individuals with type 2 diabetes. Although epidemiological studies have shown that NAFLD is associated with cardiovascular disease (CVD), it remains unknown whether NAFLD is an active contributor or an innocent bystander. Plasma lipids, low-grade inflammation, impaired fibrinolysis and hepatokines are potential mediators of the relationship between NAFLD and CVD. The Mendelian randomisation approach can help to make causal inferences. Studies that used common variants in PNPLA3, TM6SF2 and GCKR as instruments to investigate the relationship between NAFLD and coronary artery disease (CAD) have reported contrasting results. Variants in PNPLA3 and TM6SF2 were found to protect against CAD, whereas variants in GCKR were positively associated with CAD. Since all three genes have been associated with non-alcoholic steatohepatitis, the second stage of NAFLD, the question of whether low-grade inflammation is an important mediator of the relationship between NAFLD and CAD arises. In contrast, the differential effects of these genes on plasma lipids (i.e. lipid-lowering for PNPLA3 and TM6SF2, and lipid-raising for GCKR) strongly suggest that plasma lipids account for their differential effects on CAD risk. This concept has recently been confirmed in an extended set of 12 NAFLD susceptibility genes. From these studies it appears that plasma lipids are an important mediator between NAFLD and CVD risk. These findings have important clinical implications, particularly for the design of anti-NAFLD drugs that also affect lipid metabolism.

Genetics of Non-Alcoholic Fatty Liver and Cardiovascular Disease: Implications for Therapy?

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide. The most common cause of mortality in NAFLD is cardiovascular disease (CVD), and a key of focus in drug development is to discover therapies that target both liver injury and CVD risk. NAFLD and CVD are complex disease spectra with complex heritability patterns. Nevertheless, genome wide association studies and meta-analyses of these have identified genetic loci that are associated with increased risk of relevant pathological features of disease or clinical endpoints. This review focuses on the genetic risk loci identified in the NAFLD spectrum and asks whether any of these are also risk factors for CVD. Surprisingly, given the shared co-morbidities and risk factors, little robust evidence exists that NAFLD and CVD share genetic risk. Despite this, therapeutic intervention that targets both liver disease and CVD remains an important clinical need and a major focus for pharmaceutical development.

Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is considered the hepatic manifestation of the metabolic syndrome (MetS) and comprises one of the largest health threats of the twenty-first century. In this chapter, we review the current state of knowledge of NAFLD and underline the striking similarities with atherosclerosis. We first describe current epidemiological data showing the staggering increase of NAFLD numbers and its related clinical and economic costs. We then provide an overview of pathophysiological hepatic processes in NAFLD and highlight the systemic aspects of NAFLD that point toward metabolic crosstalk between organs as an important cause of metabolic disease. Finally, we end by highlighting the currently investigated therapeutic approaches for NAFLD, which also show strong similarities with a range of treatment options for atherosclerosis.

NAFLD and Atherosclerosis: Two Sides of the Same Dysmetabolic Coin?

The prevalence of non-alcoholic fatty liver disease (NAFLD) is strongly increasing and may put patients at increased risk for atherosclerotic cardiovascular disease (asCVD). Both disease phenotypes often co-occur, in the case of obesity, insulin resistance, diabetes mellitus type 2, and the metabolic syndrome. We explore the pathogenesis of NAFLD, the epidemiology of asCVD in NAFLD patients, shared drivers of both phenotypes, and factors caused by NAFLD that contribute to asCVD. Genetic studies support that NAFLD may drive asCVD through mixed hyperlipidemia. Next, we discuss the prospects of lifestyle improvement and pharmacological treatment of NAFLD for asCVD risk reduction. Finally, we point out that earlier identification of patients with NAFLD should be pursued by increasing awareness of the association of these two phenotypes and collaboration between the involved physicians.