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

Comprehensive Strategy for Identifying Extracellular Vesicle Surface Proteins as Biomarkers for Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a liver disorder that has become a global health concern due to its increasing prevalence. There is a need for reliable biomarkers to aid in the diagnosis and prognosis of NAFLD. Extracellular vesicles (EVs) are promising candidates in biomarker discovery, as they carry proteins that reflect the pathophysiological state of the liver. In this review, we developed a list of EV proteins that could be used as diagnostic biomarkers for NAFLD. We employed a multi-step strategy that involved reviewing and comparing various sources of information. Firstly, we reviewed papers that have studied EVs proteins as biomarkers in NAFLD and papers that have studied circulating proteins as biomarkers in NAFLD. To further identify potential candidates, we utilized the EV database Vesiclepedia.org to qualify each protein. Finally, we consulted the Human Protein Atlas to search for candidates' localization, focusing on membrane proteins. By integrating these sources of information, we developed a comprehensive list of potential EVs membrane protein biomarkers that could aid in diagnosing and monitoring NAFLD. In conclusion, our multi-step strategy for identifying EV-based protein biomarkers for NAFLD provides a comprehensive approach that can also be applied to other diseases. The protein candidates identified through this approach could have significant implications for the development of non-invasive diagnostic tests for NAFLD and improve the management and treatment of this prevalent liver disorder.

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

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

Nonalcoholic steatohepatitis-associated hepatocarcinogenesis in mice fed a modified choline-deficient, methionine-lowered, L-amino acid-defined diet and the role of signal changes

Nonalcoholic steatohepatitis (NASH) can progress to cirrhosis and even hepatocellular carcinoma (HCC). The incidence of NASH-associated HCC is increasing, posing a serious public health threat. Unfortunately, the underlying pathological mechanisms, including the possible differences between neoplastic and non-neoplastic lesions, remain largely unknown. Previously, we reported a dietary mouse NASH model with a choline-deficient, methionine-lowered, L-amino-acid-defined, high-fat diet containing shortening without trans fatty acids (CDAA-HF-T[-]), which rapidly induces fibrosis and proliferative lesions in the liver. This study aimed to develop a mouse CDAA-HF-T(-) model capable of assessing NASH-associated hepatocarcinogenesis and identifying key signaling factors involved in its underlying mechanisms. Multiple large masses, histopathologically hepatocellular adenomas and carcinomas, and hemangiosarcomas were detected in the liver samples of mice fed CDAA-HF-T(-) for 52 or 63 weeks, along with highly advanced fibrosis and numerous foamy, phagocytic macrophages in the adjacent nontumoral area. Multiple metastatic nodules were found in the lungs of one of the animals, and lymphoid clusters were found in all CDAA-HF-T(-) group mice. In the Ingenuity Pathways Analysis of RNA expression data, the CDAA-HF-T(-) feeding revealed common signal changes in nontumoral and tumoral liver tissues, including increased IL-8 and RhoGTPases signaling and decreased lipid metabolism. Meanwhile, macrophage inflammatory protein 2 (MIP-2) expression levels were upregulated in nontumoral liver tissue from the end of Week 13 of CDAA-HF-T(-) feeding to the end of Week 63. On the other hand, MIP-2 was expressed on macrophages in non-tumor areas and hepatocytes in tumor areas. Therefore, the CDAA-HF-T(-) mouse model is useful for assessing NASH and NASH-associated hepatocarcinogenesis, and IL-8 signaling plays important roles in NASH-associated carcinogenesis and cirrhosis, but it may also play different roles in nontumoral liver tissue and tumorigenesis.

The impact of transmembrane 6 superfamily 2 (TM6SF2) rs58542926 on liver-related events in patients with advanced chronic liver disease

BACKGROUND & AIMS

Genetic factors such as the transmembrane 6 superfamily 2 (TM6SF2) rs58542926 single nucleotide variant(SNV) modulate the susceptibility for (advanced) chronic liver disease ([A]CLD). However, the impact of this variant in patients who have already progressed to ACLD is unknown.

METHODS

The association between TM6SF2-rs58542926 genotype and liver-related events was evaluated in 938 ACLD patients undergoing hepatic venous pressure gradient (HVPG) measurement.

RESULTS

Mean HVPG was 15±7 mmHg and mean UNOS MELD (2016) 11±5 points. Viral hepatitis (n = 495, 53%) was the most common cause of ACLD, followed by alcohol-related (ARLD; n = 342, 37%) and non-alcoholic fatty liver disease (NAFLD; n = 101, 11%). While 754 (80%) patients harboured the TM6SF2 wild-type (C/C), 174 (19%) and 10 (1%) patients had one or two T-alleles. At baseline, patients with at least one TM6SF2 T-allele had more pronounced portal hypertension (HVPG: 16±7 vs. 15±7 mmHg; p = 0.031), higher gamma-glutamyl transferase levels (123 [63-229] vs. 97 [55-174] UxL-1; p = 0.002), and more commonly hepatocellular carcinoma (17% vs. 12%; p = 0.049). Harbouring the TM6SF2 T-allele was associated with the composite endpoint hepatic decompensation/liver transplantation/liver-related death (SHR: 1.44 [95%CI: 1.14-1.83]; p = 0.003). This was confirmed in multivariable competing risk regression analyses that were adjusted for severity of portal hypertension and hepatic dysfunction at baseline.

CONCLUSION

The TM6SF2 variant modulates liver disease progression beyond the development of ACLD, as it modifies the risks of hepatic decompensation and liver-related death, independently of baseline liver disease severity.

The efficacy of L-carnitine in patients with nonalcoholic steatohepatitis and concomitant obesity

BACKGROUND

In light of the high prevalence of nonalcoholic fatty liver disease and obesity, treatment options for nonalcoholic steatohepatitis are of particular interest. The purpose of the study is to assess the efficacy of L-carnitine and its effects on the functional state of the liver, as well as on lipid and carbohydrate metabolism in patients with nonalcoholic steatohepatitis and concomitant obesity.

METHODS

People in the control group followed a hypocaloric diet and received 1 tablet of simvastatin 20 mg once a day and 2 capsules of essential phospholipids 600 mg three times a day for 90 days. People in the experimental group followed a hypocaloric diet and received 1 tablet of simvastatin 20 mg once a day and L-carnitine 10 mL orally two times a day for 90 days.

RESULTS

L-carnitine normalized the blood lipid profile of subjects, as demonstrated by a significant decrease in the blood levels of total cholesterol, triglycerides, low-density lipoproteins, atherogenic index, and insulin resistance. The use of L-carnitine in patients with nonalcoholic steatohepatitis and concomitant obesity contributes to the steady reduction of the main clinical and biochemical symptoms of nonalcoholic steatohepatitis.

CONCLUSIONS

L-carnitine produces positive effects on the blood lipid profile and carbohydrate metabolism.

Remnant cholesterol has a non-linear association with non-alcoholic fatty liver disease

OBJECTIVE

We intend to look at the link between remnant cholesterol (RC) and nonalcoholic fatty liver disease (NAFLD). We hypothesis there may be a positive and nonlinear relationship between RC and NAFLD.

METHODS

The information for this investigation was obtained from the National Health and Nutrition Examination Survey 2017-2020 database. The RC value was obtained by subtracting the sum of high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) from the total cholesterol (TC) level. NAFLD diagnosis was based on ultrasonography results.

RESULTS

The analysis included 3370 participants and observed a positive relationship between RC and NAFLD, after adjusting for confounders. A non-linear association between RC and NAFLD was also identified in the research, with an inflection point of 0.96 mmol/l. The effect sizes of 3.88 (2.43 to 6.2) and 0.59 (0.21 to 1.71) were determined on the left and right sides of the inflection point, respectively. In subgroup analysis, we identified age (P for interaction = 0.0309) and waist circumference (P for interaction = 0.0071) as interaction factors.

CONCLUSIONS

Elevated RC levels were found to be linked to NAFLD, even after controlling for traditional risk factors. Moreover, non-linear pattern in the relationship between RC and NAFLD was also identified.

Lipid droplet biogenesis and functions in health and disease

Ubiquitous yet unique, lipid droplets are intracellular organelles that are increasingly being recognized for their versatility beyond energy storage. Advances uncovering the intricacies of their biogenesis and the diversity of their physiological and pathological roles have yielded new insights into lipid droplet biology. Despite these insights, the mechanisms governing the biogenesis and functions of lipid droplets remain incompletely understood. Moreover, the causal relationship between the biogenesis and function of lipid droplets and human diseases is poorly resolved. Here, we provide an update on the current understanding of the biogenesis and functions of lipid droplets in health and disease, highlighting a key role for lipid droplet biogenesis in alleviating cellular stresses. We also discuss therapeutic strategies of targeting lipid droplet biogenesis, growth or degradation that could be applied in the future to common diseases, such as cancer, hepatic steatosis and viral infection.

Precision Medicine in Fatty Liver Disease/Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease, and is related to fatal and non-fatal liver, metabolic, and cardiovascular complications. Its non-invasive diagnosis and effective treatment remain an unmet clinical need. NAFLD is a heterogeneous disease that is most commonly present in the context of metabolic syndrome and obesity, but not uncommonly, may also be present without metabolic abnormalities and in subjects with normal body mass index. Therefore, a more specific pathophysiology-based subcategorization of fatty liver disease (FLD) is needed to better understand, diagnose, and treat patients with FLD. A precision medicine approach for FLD is expected to improve patient care, decrease long-term disease outcomes, and develop better-targeted, more effective treatments. We present herein a precision medicine approach for FLD based on our recently proposed subcategorization, which includes the metabolic-associated FLD (MAFLD) (i.e., obesity-associated FLD (OAFLD), sarcopenia-associated FLD (SAFLD, and lipodystrophy-associated FLD (LAFLD)), genetics-associated FLD (GAFLD), FLD of multiple/unknown causes (XAFLD), and combined causes of FLD (CAFLD) as well as advanced stage fibrotic FLD (FAFLD) and end-stage FLD (ESFLD) subcategories. These and other related advances, as a whole, are expected to enable not only improved patient care, quality of life, and long-term disease outcomes, but also a considerable reduction in healthcare system costs associated with FLD, along with more options for better-targeted, more effective treatments in the near future.

From Non-Alcoholic Fatty Liver to Hepatocellular Carcinoma: A Story of (Mal)Adapted Mitochondria

Non-alcoholic fatty liver disease (NAFLD) is a global pandemic affecting 25% of the world's population and is a serious health and economic concern worldwide. NAFLD is mainly the result of unhealthy dietary habits combined with sedentary lifestyle, although some genetic contributions to NAFLD have been documented. NAFLD is characterized by the excessive accumulation of triglycerides (TGs) in hepatocytes and encompasses a spectrum of chronic liver abnormalities, ranging from simple steatosis (NAFL) to steatohepatitis (NASH), significant liver fibrosis, cirrhosis, and hepatocellular carcinoma. Although the molecular mechanisms that cause the progression of steatosis to severe liver damage are not fully understood, metabolic-dysfunction-associated fatty liver disease is strong evidence that mitochondrial dysfunction plays a significant role in the development and progression of NAFLD. Mitochondria are highly dynamic organelles that undergo functional and structural adaptations to meet the metabolic requirements of the cell. Alterations in nutrient availability or cellular energy needs can modify mitochondria formation through biogenesis or the opposite processes of fission and fusion and fragmentation. In NAFL, simple steatosis can be seen as an adaptive response to storing lipotoxic free fatty acids (FFAs) as inert TGs due to chronic perturbation in lipid metabolism and lipotoxic insults. However, when liver hepatocytes' adaptive mechanisms are overburdened, lipotoxicity occurs, contributing to reactive oxygen species (ROS) formation, mitochondrial dysfunction, and endoplasmic reticulum (ER) stress. Impaired mitochondrial fatty acid oxidation, reduction in mitochondrial quality, and disrupted mitochondrial function are associated with a decrease in the energy levels and impaired redox balance and negatively affect mitochondria hepatocyte tolerance towards damaging hits. However, the sequence of events underlying mitochondrial failure from steatosis to hepatocarcinoma is still yet to be fully clarified. This review provides an overview of our understanding of mitochondrial adaptation in initial NAFLD stages and highlights how hepatic mitochondrial dysfunction and heterogeneity contribute to disease pathophysiology progression, from steatosis to hepatocellular carcinoma. Improving our understanding of different aspects of hepatocytes' mitochondrial physiology in the context of disease development and progression is crucial to improving diagnosis, management, and therapy of NAFLD/NASH.

Genetic Polymorphisms and Diversity in Nonalcoholic Fatty Liver Disease (NAFLD): A Mini Review

Nonalcoholic fatty liver disease (NAFLD) is a common liver disease with a wide spectrum of liver conditions ranging from hepatic steatosis to nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma. The prevalence of NAFLD varies across populations, and different ethnicities have specific risks for the disease. NAFLD is a multi-factorial disease where the genetics, metabolic, and environmental factors interplay and modulate the disease's development and progression. Several genetic polymorphisms have been identified and are associated with the disease risk. This mini-review discussed the NAFLD's genetic polymorphisms and focusing on the differences in the findings between the populations (diversity), including of those reports that did not show any significant association. The challenges of genetic diversity are also summarized. Understanding the genetic contribution of NAFLD will allow for better diagnosis and management explicitly tailored for the various populations.

Non-alcoholic fatty liver disease establishment and progression: genetics and epigenetics as relevant modulators of the pathology

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) results from metabolic dysfunctions that affect more than one-third of the world population. Over the last decades, scientific investigations have clarified many details on the pathology establishment and development; however, effective therapeutics approaches are still evasive. In addition, studies demonstrated that NAFLD establishment and progression are related to several etiologies. Recently, genetics and epigenetics backgrounds have emerged as relevant elements to the pathology onset, and, hence, deserve deep investigation to clarify molecular details on NAFLD signaling, which may be correlated with population behavior. Thus, to minimize the global problem, public health and public policies should take advantage of studies on NAFLD over the next following decades.

METHODS

In this context, we have performed a selective literature review focusing on biochemistry of lipid metabolism, genetics, epigenetics, and the ethnicity as strong elements that drive NAFLD establishment.

RESULTS

Considering the etiological agents that acts on NAFLD development and progression, the genetics and the epigenetics emerged as relevant factors. Genetics acts as a powerful element in the establishment and progression of the NAFLD. Over the last decades, details concerning genes and their polymorphisms, as well as epigenetics, have been considered relevant elements in the systems biology of diseases, and their effects on NAFLD should be considered in-depth, as well as the ethnicity, clarifying whether people are susceptible to liver diseases. Moreover, the endemicity and social problems of hepatic disfunction are far to be solved, which require a combined effort of various sectors of society.

CONCLUSION

Hence, the elements presented and discussed in this short review demonstrated their relevance to the physiological control of NAFLD, opening perspectives for research to develop new strategy to treat fatty liver diseases.

The protective roles of augmenter of liver regeneration in hepatocytes in the non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) occurs in 25% of the global population and manifests as lipid deposition, hepatocyte injury, activation of Kupffer and stellate cells, and steatohepatitis. Predominantly expressed in hepatocytes, the augmenter of liver regeneration (ALR) is a key factor in liver regulation that can alleviate fatty liver disease and protect the liver from abnormal liver lipid metabolism. ALR has three isoforms (15-, 21-, and 23-kDa), amongst which 23-kDa ALR is the most extensively studied. The 23-kDa ALR isoform is a sulfhydryl oxidase that resides primarily in the mitochondrial intermembrane space (IMS), whereby it protects the liver against various types of injury. In this review, we describe the role of ALR in regulating hepatocytes in the context of NAFLD. We also discuss questions about ALR that remain to be explored in the future. In conclusion, ALR appears to be a promising therapeutic target for treating NAFLD.

RISK FACTORS FOR HEPATOCELLULAR CARCINOMA IN PATIENTS WITH NON-ALCOHOLIC FATTY LIVER DISEASE

Non-alcoholic fatty liver disease is growing in worldwide prevalence and thus, is expected to have a higher number of NAFLD-related hepatocellular carcinoma (HCC) in the following years. This review describes the risk factors associated with HCC in NAFLD-patients. The presence of liver cirrhosis is the preponderant one. Male gender, PNPLA3 variants, diabetes, and obesity also appear to predispose to the development of HCC, even in non-cirrhotic subjects. Thus far, intensive lifestyle modifications, including glycemic control, and obesity treatment, are effective therapies for NAFLD/ non-alcoholic steatohepatitis and, therefore, probably, also for HCC. Some drugs that aimed at decreasing inflammatory activity and fibrosis, as well as obesity, were studied. Other data have suggested the possibility of HCC chemoprevention. So far, however, there is no definitive evidence for the routine utilization of these drugs. We hope, in the future, to be able to profile patients at higher risk of NAFLD-HCC and outline strategies for early diagnosis and prevention.

The TM6SF2 variant as a risk factor for hepatocellular carcinoma development in chronic liver disease patients

Introduction

Hepatocellular carcinoma (HCC) is one of the most prevalent cancers worldwide. A non-synonymous single nucleotide polymorphism (SNP) of the transmembrane 6 superfamily member 2 (TM6SF2) gene is associated with non-alcoholic fatty liver disease. SNPs of the TM6SF2 gene play an important role in the pathogenesis of HCC in alcoholic cirrhosis, but there are limited data regarding other possible etiologies. We aimed to evaluate the role of the rs58542926 polymorphism in the development of HCC in Egyptian chronic liver disease (CLD) patients.

Material and methods

A total of 120 participants, including 40 HCC patients, 40 CLD patients, and 40 healthy controls, were selected. Real-time polymerase chain reaction (RT-PCR) was used to detect the TM6SF2 rs58542926 polymorphism.

Results

There were no significant differences among the three studied groups regarding age (p = 0.06) and gender (p = 0.75). Frequencies of the CT, TT, CT + TT genotypes and the T allele were significantly higher in HCC patients than in the CLD and control groups (p < 0.001, p = 0.005, and p < 0.001, respectively). CLD patients with the CT genotype had a significantly increased risk of HCC development (OR = 4.67, 95% CI: 1.67-12.90). Patients with the TT genotype had a significantly increased risk of HCC (OR = 9.33, 95% CI: 1.72-50.61). Moreover, the T allele was correlated with an increased risk of HCC (OR = 5.44, 95% CI: 2.09-14.17) compared to the C allele.

Conclusions

The TM6SF2 rs58542926 genotype is associated with an increased risk of HCC in the Egyptian population.

Association of metabolic dysfunction-associated fatty liver disease with kidney disease

Non-alcoholic fatty liver disease (NAFLD) is characterized by the accumulation of fat in more than 5% of hepatocytes in the absence of excessive alcohol consumption and other secondary causes of hepatic steatosis. In 2020, the more inclusive term metabolic (dysfunction)-associated fatty liver disease (MAFLD) - defined by broader diagnostic criteria - was proposed to replace the term NAFLD. The new terminology and revised definition better emphasize the pathogenic role of metabolic dysfunction and uses a set of definitive, inclusive criteria for diagnosis. Diagnosis of MAFLD is based on evidence of hepatic steatosis (as assessed by liver biopsy, imaging techniques or blood biomarkers and scores) in persons who are overweight or obese and have type 2 diabetes mellitus or metabolic dysregulation, regardless of the coexistence of other liver diseases or excessive alcohol consumption. The known association between NAFLD and chronic kidney disease (CKD) and our understanding that CKD can occur as a consequence of metabolic dysfunction suggests that individuals with MAFLD - who by definition have fatty liver and metabolic comorbidities - are at increased risk of CKD. In this Perspective article, we discuss the clinical associations between MAFLD and CKD, the pathophysiological mechanisms by which MAFLD may increase the risk of CKD and the potential drug treatments that may benefit both conditions.

Non-alcoholic Fatty Liver Disease and Depression: Evidence for Genotype × Environment Interaction in Mexican Americans

This study examines the impact of G × E interaction effects on non-alcoholic fatty liver disease (NAFLD) among Mexican Americans in the Rio Grande Valley (RGV) of South Texas. We examined potential G × E interaction using variance components models and likelihood-based statistical inference in the phenotypic expression of NAFLD, including hepatic steatosis and hepatic fibrosis (identified using vibration controlled transient elastography and controlled attenuation parameter measured by the FibroScan Device). We screened for depression using the Beck Depression Inventory-II (BDI-II). We identified significant G × E interactions for hepatic fibrosis × BDI-II. These findings provide evidence that genetic factors interact with depression to influence the expression of hepatic fibrosis.