Nonalcoholic fatty liver disease and portal hypertension

Nonalcoholic fatty liver disease (NAFLD) is a substantial and growing problem worldwide and has become the second most common indication for liver transplantation as it may progress to cirrhosis and develop complications from portal hypertension primarily caused by advanced fibrosis and erratic tissue remodeling. However, elevated portal venous pressure has also been detected in experimental models of fatty liver and in human NAFLD when fibrosis is far less advanced and cirrhosis is absent. Early increases in intrahepatic vascular resistance may contribute to the progression of liver disease. Specific pathophenotypes linked to the development of portal hypertension in NAFLD include hepatocellular lipid accumulation and ballooning injury, capillarization of liver sinusoidal endothelial cells, enhanced contractility of hepatic stellate cells, activation of Kupffer cells and pro-inflammatory pathways, adhesion and entrapment of recruited leukocytes, microthrombosis, angiogenesis and perisinusoidal fibrosis. These pathological events are amplified in NAFLD by concomitant visceral obesity, insulin resistance, type 2 diabetes and dysbiosis, promoting aberrant interactions with adipose tissue, skeletal muscle and gut microbiota. Measurement of the hepatic venous pressure gradient by retrograde insertion of a balloon-tipped central vein catheter is the current reference method for predicting outcomes of cirrhosis associated with clinically significant portal hypertension and guiding interventions. This invasive technique is rarely considered in the absence of cirrhosis where currently available clinical, imaging and laboratory correlates of portal hypertension may not reflect early changes in liver hemodynamics. Availability of less invasive but sufficiently sensitive methods for the assessment of portal venous pressure in NAFLD remains therefore an unmet need. Recent efforts to develop new biomarkers and endoscopy-based approaches such as endoscopic ultrasound-guided measurement of portal pressure gradient may help achieve this goal. In addition, cellular and molecular targets are being identified to guide emerging therapies in the prevention and management of portal hypertension.

Current and Future Treatments in the Fight Against Non-Alcoholic Fatty Liver Disease

Obesity is recognised as a risk factor for many types of cancers, in particular hepatocellular carcinoma (HCC). A critical factor in the development of HCC from non-alcoholic fatty liver disease (NAFLD) is the presence of non-alcoholic steatohepatitis (NASH). Therapies aimed at NASH to reduce the risk of HCC are sparse and largely unsuccessful. Lifestyle modifications such as diet and regular exercise have poor adherence. Moreover, current pharmacological treatments such as pioglitazone and vitamin E have limited effects on fibrosis, a key risk factor in HCC progression. As NAFLD is becoming more prevalent in developed countries due to rising rates of obesity, a need for directed treatment is imperative. Numerous novel therapies including PPAR agonists, anti-fibrotic therapies and agents targeting inflammation, oxidative stress and the gut-liver axis are currently in development, with the aim of targeting key processes in the progression of NASH and HCC. Here, we critically evaluate literature on the aetiology of NAFLD-related HCC, and explore the potential treatment options for NASH and HCC.

Bile acid modulators for the treatment of nonalcoholic steatohepatitis (NASH)

INTRODUCTION

Nonalcoholic steatohepatitis (NASH) is a progressive form of nonalcoholic fatty liver disease (NAFLD) for which therapy is suboptimal. The farnesoid-X-receptor (FXR) and the G protein bile acid receptor (GPBAR)1 are two bile acid-activated receptors that exert regulatory effects on lipid, glucose, energy, and immune homeostasis. GPBAR1 and FXR ligands have shown efficacy in reversing steatohepatitis and fibrosis in preclinical models of NASH.

AREA COVERED

This article evaluates the efficacy and pitfalls of GPBAR1 and FXR-based therapies in the treatment of NASH. While there are no GPBAR1 agonist in clinical development, several FXR ligands have completed phase 2 and phase 3 trials in NASH. EDP305, tropifexor, cilofexor, nidufexor, TERN.101, Px-104, EYP001, MET409. Individual FXR agonists have shown variable efficacy in reversing liver steatohepatitis and fibrosis. Class-related, dose-dependent side effects: pruritus, increased plasma levels of cholesterol and LDLc, and reduction of HDL have been reported.

EXPERT OPINION

Efficacy of FXR agonists as stand-alone therapy is limited by dose-related side effects. Efficacy of combining an FXR agonist with statins, CCR2, and ACC inhibitors is currently investigated. Identification of patient subsets would allow development of patients tailored therapy using a combination of drugs acting on different molecular mechanisms.

Epidemiology: Pathogenesis, and Diagnostic Strategy of Diabetic Liver Disease in Japan

Type 2 diabetes (T2D) is closely associated with nonalcoholic fatty liver disease (NAFLD). Nonalcoholic steatohepatitis (NASH), a severe form of NAFLD, can lead to cirrhosis, hepatocellular carcinoma (HCC), and hepatic decompensation. Patients with T2D have twice the risk of HCC incidence compared with those without T2D. Because the hepatic fibrosis grade is the main determinant of mortality in patients with NAFLD, identifying patients with advanced fibrosis using non-invasive tests (NITs) or imaging modalities is crucial. Globally, the fibrosis-4 index (FIB-4 index), NAFLD fibrosis score, and enhanced liver fibrosis test have been established to evaluate hepatic fibrosis. Two-step algorithms using FIB-4 index as first triaging tool are globally accepted. It remains unknown which kinds of NITs or elastography are best as the second step tool. In Japan, type IV collagen 7s or the CA-fibrosis index (comprising type IV collagen 7s and aspartate aminotransferase (AST)) is believed to precisely predict advanced fibrosis in NAFLD. Patients with NAFLD who have high non-invasive test results should be screened for HCC or esophageal varices. Risk factors of rapid fibrosis progression in NAFLD includes age, severe obesity, presence of T2D, menopause in women, and a patatin-like phospholipase domain containing the 3 GG genotype. Patients with NAFLD who have these risk factors should be intensively treated with lifestyle modification or pharmacotherapies for preventing liver-related mortality.

Current and emerging pharmacotherapeutic interventions for the treatment of liver fibrosis

INTRODUCTION

Chronic liver disease is due to various causes of persistent liver damage and will eventually lead to the development of liver fibrosis. If no treatment is initiated, this condition may progress to cirrhosis and hepatocellular carcinoma. Current treatments comprise the elimination of the cause of injury, such as by lifestyle changes, alcohol abstinence, and antiviral agents. However, such etiology-driven therapy is often insufficient in patients with late-stage fibrosis/cirrhosis, therefore maintaining the need for efficient antifibrotic pharmacotherapeutic interventions.

AREAS COVERED

The authors discuss the recent advances in the development of antifibrotic drugs, which target various pathways of the fibrogenesis process, including cell death, inflammation, gut-liver axis, and myofibroblast activation. Due to the significant burden of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), various agents which specifically target metabolic pathways and their related receptors/ligands have been developed. For some of them, e.g., obeticholic acid, advanced stage clinical trials indicate antifibrotic efficacy in NAFLD and NASH.

EXPERT OPINION

Significant advances have been made in the development of novel antifibrotic pharmacotherapeutics. The authors expect that the development of combinatorial therapies, which combine compounds that target various pathways of fibrosis progression, will have a major impact as future etiology-independent therapies.

Serum Mac-2 Binding Protein Levels Associate with Metabolic Parameters and Predict Liver Fibrosis Progression in Subjects with Fatty Liver Disease: A 7-Year Longitudinal Study

Background: Mac-2 binding protein (M2BP) is a highly glycosylated secreted glycoprotein that is involved in immune defense and regulation. Our cross-sectional studies indicated that serum M2BP was a useful liver fibrosis biomarker for nonalcoholic fatty liver disease (NAFLD). In this study, we conducted a 7-year longitudinal study to investigate the significance of serum M2BP levels (baseline and at 7-year follow-up) and their relationships with other metabolic parameters of fatty liver disease. Methods: We enrolled 715 study subjects (521 male and 194 female) during health examinations. Study subjects received blood sampling tests and abdominal ultrasound tests at baseline and follow-up. Results: Univariate analyses demonstrated that serum M2BP levels were significantly correlated with various parameters related to metabolic risk (body mass index (BMI), systolic blood pressure, triglyceride, high density lipoprotein (HDL)-cholesterol) and metabolic syndrome diseases (obesity, hypertension, dyslipidemia, diabetes mellitus, fatty liver (FL)). Multiple logistic regression analyses demonstrated that BMI and FL were independent determinants for serum M2BP levels. Baseline serum M2BP levels were significant independent determinants for changes in platelet count, Fibrosis-4 (FIB4) index, and NAFLD fibrosis score. Higher serum M2BP levels (>1.80 μg/mL) strongly correlated with changes in the FIB4-index. Conclusions: The results of this study suggest that changes in serum M2BP levels reflect changes in specific metabolic disease-related parameters, and baseline serum M2BP levels could predict changes in liver fibrosis.

How effective are nonalcoholic fatty liver disease models for drug discovery?

The spectrum of nonalcoholic fatty liver disease (NAFLD) ranges from simple steatosis to nonalcoholic steatohepatitis (NASH) with hepatic fibrosis up to liver cirrhosis and hepatocellular carcinoma, displaying a global health problem with no effective therapy yet. Multiple preclinical models reflecting different aspects of the disease helped to identify a variety of different targets over the last years. However, some recent clinical trials have revealed a lack of translatability, emphasizing the need for more effective preclinical research. In this editorial, we discuss different NAFLD mouse models as well as emerging ex vivo and in vitro models that have been used in drug discovery and dissect the translational challenges that have to be considered in drug development.

Lipoprotein A, combined with alanine aminotransferase and aspartate aminotransferase, contributes to predicting the occurrence of NASH: a cross-sectional study

Background

Nonalcoholic steatohepatitis (NASH) progresses from simple nonalcoholic fatty liver (NAFL) and has a poor prognosis. Abnormal lipid metabolism is closely related to the occurrence and development of nonalcoholic fatty liver disease (NAFLD). This study aimed to study the relationships between serum lipid metabolites and NASH, and to improve the early diagnosis of NASH.

Methods

This study included 86 NAFLD patients (23 NASH and 63 NAFL), and 81 unaffected individuals as controls from West China Hospital between October 2018 and May 2019. With lipid metabolites as the focus of the study, the differences in lipid metabolites were compared between the control group, NAFL patients, and NASH patients. Logistic regression analysis was used to examine the risk factors of NASH. Finally, receiver operating characteristic curve (ROC curve) was used to analyze the efficacy of the metabolites in NASH prediction.

Results

The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lipoprotein A (LPA) increased with the severity of NAFLD. In NAFLD patients, LPA (OR:1.61; 95%CI: 1.03–2.52) was a potential risk factor for NASH, and ROC analysis showed that the combination of LPA, ALT, and AST had a greater predictive efficiency for NASH.

Conclusions

Abnormal apolipoprotein/lipoprotein is closely related to lipid metabolism disorder in patients with NAFLD. In NAFL, the combination of LPA, ALT, and AST contributes to predicting the occurrence of NASH. LPA may be a potential biomarker and therapeutic target for diagnosing and treating NASH.

Liver fibrogenesis: un update on established and emerging basic concepts

Liver fibrogenesis is defined as a dynamic and highly integrated process occurring during chronic injury to liver parenchyma that can result in excess deposition of extracellular matrix (ECM) components (i.e., liver fibrosis). Liver fibrogenesis, together with chronic inflammatory response, is then primarily involved in the progression of chronic liver diseases (CLD) irrespective of the specific etiology. In the present review we will first offer a synthetic and updated overview of major basic concepts in relation to the role of myofibroblasts (MFs), macrophages and other hepatic cell populations involved in CLD to then offer an overview of established and emerging issues and mechanisms that have been proposed to favor and/or promote CLD progression. A special focus will be dedicated to selected issues that include emerging features in the field of cholangiopathies, the emerging role of genetic and epigenetic factors as well as of hypoxia, hypoxia-inducible factors (HIFs) and related mediators.

LncPRYP4-3 serves as a novel diagnostic biomarker for dissecting subtypes of metabolic associated fatty liver disease by targeting RPS4Y2

Longitudinal studies have improved current diagnostics and management of metabolic associated fatty liver disease (MAFLD) patients by liver biopsy and therapeutic intervention, yet the deficiency of biomarker spectrum for dissecting subtypes largely hinders the symptomatic treatment. We originally enriched serum from peripheral blood of 618 healthy donors (HD) and 580 MAFLD (400 NAFL, 180 NASH) patients according to multiple clinicopathological indicators. Microarray profiling and qRT-PCR were conducted to identify lncRNAs as candidate biomarkers of MAFLD. Then, we analyzed the matching score of the indicated lncRNA with CAP or MAFLD-associated pathological parameters as well. Additionally, we took advantage of interaction network together with gene expression profiling analysis to further explore the underlying target genes of the identified lncRNA. Herein, we found CAP in nearly all of the NAFL (399/400) and NASH (179/180) patients was higher than that in the HDs (611/618). The differentially expressed lncRNAs were involved in multiple metabolic or immunologic processes by regulating MAFLD-associated pathways. Of them, serum lncPRYP4-3 was identified as a novel candidate biomarker of MAFLD, which was further confirmed by correlation analysis with clinical indicators. Thereafter, we deduced PRS4Y2 was a candidate target of lncPRYP4-3 and mediated the dysfunction in NAFL and NASH patients. Serum lncPRYP4-3 served as a novel biomarker of MAFLD and helped distinguish the subtypes and benefit precise intervention therapy. Our findings also provided overwhelming new evidence for the alteration in biological processes and gene ontology in MAFLD patients.

Predicting and elucidating the etiology of fatty liver disease: A machine learning modeling and validation study in the IMI DIRECT cohorts

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is highly prevalent and causes serious health complications in individuals with and without type 2 diabetes (T2D). Early diagnosis of NAFLD is important, as this can help prevent irreversible damage to the liver and, ultimately, hepatocellular carcinomas. We sought to expand etiological understanding and develop a diagnostic tool for NAFLD using machine learning.

METHODS AND FINDINGS

We utilized the baseline data from IMI DIRECT, a multicenter prospective cohort study of 3,029 European-ancestry adults recently diagnosed with T2D (n = 795) or at high risk of developing the disease (n = 2,234). Multi-omics (genetic, transcriptomic, proteomic, and metabolomic) and clinical (liver enzymes and other serological biomarkers, anthropometry, measures of beta-cell function, insulin sensitivity, and lifestyle) data comprised the key input variables. The models were trained on MRI-image-derived liver fat content (<5% or ≥5%) available for 1,514 participants. We applied LASSO (least absolute shrinkage and selection operator) to select features from the different layers of omics data and random forest analysis to develop the models. The prediction models included clinical and omics variables separately or in combination. A model including all omics and clinical variables yielded a cross-validated receiver operating characteristic area under the curve (ROCAUC) of 0.84 (95% CI 0.82, 0.86; p < 0.001), which compared with a ROCAUC of 0.82 (95% CI 0.81, 0.83; p < 0.001) for a model including 9 clinically accessible variables. The IMI DIRECT prediction models outperformed existing noninvasive NAFLD prediction tools. One limitation is that these analyses were performed in adults of European ancestry residing in northern Europe, and it is unknown how well these findings will translate to people of other ancestries and exposed to environmental risk factors that differ from those of the present cohort. Another key limitation of this study is that the prediction was done on a binary outcome of liver fat quantity (<5% or ≥5%) rather than a continuous one.

CONCLUSIONS

In this study, we developed several models with different combinations of clinical and omics data and identified biological features that appear to be associated with liver fat accumulation. In general, the clinical variables showed better prediction ability than the complex omics variables. However, the combination of omics and clinical variables yielded the highest accuracy. We have incorporated the developed clinical models into a web interface (see: https://www.predictliverfat.org/) and made it available to the community.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03814915.

What's in a name? Renaming 'NAFLD' to 'MAFLD'

In medicine, language matters and the words used to name and describe a disease can have a profound impact on patients and their families. Over the last two decades, many criticisms have been voiced about the nomenclature and definition of non-alcoholic fatty liver disease (NAFLD) in regards not only to the prominent role that alcohol plays in the definition but also on the negative impacts of the nomenclature including trivialization, stigmatization and less consideration of the disease in health policy. Recently, a consensus of international experts proposed that the disease acronym be changed from NAFLD to metabolic (dysfunction) associated fatty liver disease or 'MAFLD'. This change goes far beyond a mere semantic revision and may be the first step that catalyses the process to better conceptualize the disease for health promotion, patient orientation, case identification, ongoing clinical trials and for health services delivery. Here we review the history of, and definitions of MAFLD in the context of advancing our understanding of the pathogenesis of the disease. We also address the reasons, signals, promises, challenges and the way going forward from the name change from various stakeholder perspectives.

Update on NAFLD genetics: From new variants to the clinic

Non-alcoholic fatty liver disease (NAFLD) is the leading cause of liver diseases in high-income countries and the burden of NAFLD is increasing at an alarming rate. The risk of developing NAFLD and related complications is highly variable among individuals and is determined by environmental and genetic factors. Genome-wide association studies have uncovered robust and reproducible associations between variations in genes such as PNPLA3, TM6SF2, MBOAT7, GCKR, HSD17B13 and the natural history of NAFLD. These findings have provided compelling new insights into the biology of NAFLD and highlighted potentially attractive pharmaceutical targets. More recently the development of polygenic risk scores, which have shown promising results for the clinical risk prediction of other complex traits (such as cardiovascular disease and breast cancer), have provided new impetus for the clinical validation of genetic variants in NAFLD risk stratification. Herein, we review current knowledge on the genetic architecture of NAFLD, including gene-environment interactions, and discuss the implications for disease pathobiology, drug discovery and risk prediction. We particularly focus on the potential clinical translation of recent genetic advances, discussing methodological hurdles that must be overcome before these discoveries can be implemented in everyday practice.

Review article: the emerging role of genetics in precision medicine for patients with non-alcoholic steatohepatitis

BACKGROUND

Non-alcoholic steatohepatitis (NASH) is a severe form of non-alcoholic fatty liver disease (NAFLD) characterised by liver fat accumulation, inflammation and progressive fibrosis. Emerging data indicate that genetic susceptibility increases risks of NAFLD, NASH and NASH-related cirrhosis.

AIMS

To review NASH genetics and discuss the potential for precision medicine approaches to treatment.

METHOD

PubMed search and inclusion of relevant literature.

RESULTS

Single-nucleotide polymorphisms in PNPLA3, TM6SF2, GCKR, MBOAT7 and HSD17B13 are clearly associated with NASH development or progression. These genetic variants are common and have moderate-to-large effect sizes for development of NAFLD, NASH and hepatocellular carcinoma (HCC). The genes play roles in lipid remodelling in lipid droplets, hepatic very low-density lipoprotein (VLDL) secretion and de novo lipogenesis. The PNPLA3 I148M variant (rs738409) has large effects, with approximately twofold increased odds of NAFLD and threefold increased odds of NASH and HCC per allele. Obesity interacts with PNPLA3 I148M to elevate liver fat content and increase rates of NASH. Although the isoleucine-to-methionine substitution at amino acid position 148 of the PNPLA3 enzyme inactivates its lipid remodelling activity, the effect of PNPLA3 I148M results from trans-repression of another lipase (ATGL/PNPLA2) by sequestration of a shared cofactor (CGI-58/ABHD5), leading to decreased hepatic lipolysis and VLDL secretion. In homozygous Pnpla3 I148M knock-in rodent models of NAFLD, targeted PNPLA3 mRNA knockdown reduces hepatic steatosis, inflammation and fibrosis.

CONCLUSION

The emerging genetic and molecular understanding of NASH paves the way for novel interventions, including precision medicines that can modulate the activity of specific genes associated with NASH.

The STAT4 and not the IFNL3 variant is associated with hepatitis B virus clearance in a population from the Khyber Pakhtunkhwa region of Pakistan

BACKGROUND AND STUDY AIMS

Host genetic modifiers of the risk and persistence of hepatitis B virus (HBV) infection in the Pakistani population have not been clearly elucidated. Recently, two genome-wide association studies described that STAT4 and IFNL3 variants are associated with different aspects of the course of HBV infection. However, the roles of these variants in the persistence of HBV infection have not been investigated in the HBV-infected population of Pakistan. Therefore, we examined the roles of the STAT4 and IFNL3 variants in a chronic HBV-infected population from the Khyber Pakhtunkhwa (KPK) region of Pakistan.

PATIENTS AND METHODS

STAT4 rs7574865 and IFNL3 rs12979860 genotyping were performed in 297 subjects (240 infected with HBV and 57 controls). Statistical analyses were performed using the chi-squared test, Student's t-test, Hardy-Weinberg equilibrium tests and logistic regression models.

RESULTS

Among the 297 subjects, compared with the IFNL3 rs12979860 genotype [odds ratio (OR) = 0.7, 95% confidence interval (CI) = 0.39-1.29, p = 0.2), the STAT4 rs7574865 genotype was independently associated with the risk of developing chronic HBV infection [OR = 1.9, 95% CI = 1.09-3.50, p = 0.02].

CONCLUSION

The STAT4 rs7574865 and not the IFNL3 rs12979860 variant is associated with persistence of HBV infection in a Pakistani population from the KPK region.

Prevalence and risk factors of fatty liver in Portuguese adults

BACKGROUND

Prevalence of fatty liver (FL) and nonalcoholic fatty liver disease (NAFLD) depends mainly on obesity, diabetes and genetic factors. FL and NAFLD prevalence was evaluated in Portuguese adult population and correlated with several risk factors and related mortality data, within the same period.

MATERIALS AND METHODS

A cross-sectional, population-based multicenter study, voluntary and randomly selected in 834 Portuguese adults (18-79 years). Participants were evaluated after 12-hour fasting. Anthropometric data, past history including alcohol consumption, and associated diseases were registered. Blood samples were collected for biochemical testing. Dietary intake was evaluated using a semi-quantitative food frequency questionnaire. Presence of FL was evaluated using ultrasound, and NAFLD was diagnosed after exclusion of other causes for liver disease.

RESULTS

Adjusted prevalence of FL and NAFLD was 37.8% and 17.0%, respectively. FL individuals were older, more frequently males, with increased probability of having obesity, diabetes or harmful alcohol consumption (HAC). NAFLD individuals were also older, but had a similar sex distribution and an increased probability of obesity and diabetes. In both groups, no differences were found regarding dietary pattern or physical activity. During the same time period, nonalcoholic steatohepatitis (NASH) liver-related deaths in Portugal were 0.105/100 000, while alcohol-related liver disease mortality was 6.790/100 000.

CONCLUSION

The large spectrum of FL was present in more than one third of the population, although only less than half could be classified as NAFLD. Other significant risk factors, such as HAC, are probably implicated in FL, explaining the low NASH-related mortality compared with the high alcohol-related mortality during the same time period.

Unraveling the Epigenetic Basis of Liver Development, Regeneration and Disease

A wealth of studies over several decades has revealed an epigenetic prepattern that determines the competence of cellular differentiation in the developing liver. More recently, studies focused on the impact of epigenetic factors during liver regeneration suggest that an epigenetic code in the quiescent liver may establish its regenerative potential. We review work on the pioneer factors and other chromatin remodelers that impact the gene expression patterns instructing hepatocyte and biliary cell specification and differentiation, along with the requirement of epigenetic regulatory factors for hepatic outgrowth. We then explore recent studies involving the role of epigenetic regulators, Arid1a and Uhrf1, in efficient activation of proregenerative genes during liver regeneration, thus highlighting the epigenetic mechanisms of liver disease and tumor development.

The Role of Insulin Resistance and Diabetes in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) consists of the entire spectrum of fatty liver disease in patients without significant alcohol consumption, ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH) to cirrhosis, with NASH recently shown as an important cause of hepatocellular carcinoma (HCC). There is a close relationship between insulin resistance (IR) and NAFLD, with a five-fold higher prevalence of NAFLD in patients with type 2 diabetes (T2DM) compared to that in patients without T2DM. IR is involved in the progression of disease conditions such as steatosis and NASH, as well as hepatic fibrosis progression. The mechanisms underlying these processes involve genetic factors, hepatic fat accumulation, alterations in energy metabolism, and inflammatory signals derived from various cell types including immune cells. In NASH-associated fibrosis, the principal cell type responsible for extracellular matrix production is the hepatic stellate cell (HSC). HSC activation by IR involves “direct” and “indirect” pathways. This review will describe the molecular mechanisms of inflammation and hepatic fibrosis in IR, the relationship between T2DM and hepatic fibrosis, and the relationship between T2DM and HCC in patients with NAFLD.

Oxidative Stress Management in Chronic Liver Diseases and Hepatocellular Carcinoma

Chronic viral hepatitis B and C and non-alcoholic fatty liver disease (NAFLD) have been widely acknowledged to be the leading causes of liver cirrhosis and hepatocellular carcinoma. As anti-viral treatment progresses, the impact of NAFLD is increasing. NAFLD can coexist with chronic viral hepatitis and exacerbate its progression. Oxidative stress has been recognized as a chronic liver disease progression-related and cancer-initiating stress response. However, there are still many unresolved issues concerning oxidative stress, such as the correlation between the natural history of the disease and promising treatment protocols. Recent findings indicate that oxidative stress is also an anti-cancer response that is necessary to kill cancer cells. Oxidative stress might therefore be a cancer-initiating response that should be down regulated in the pre-cancerous stage in patients with risk factors for cancer, while it is an anti-cancer cell response that should not be down regulated in the post-cancerous stage, especially in patients using anti-cancer agents. Antioxidant nutrients should be administered carefully according to the patients’ disease status. In this review, we will highlight these paradoxical effects of oxidative stress in chronic liver diseases, pre- and post-carcinogenesis.

Histological grading evaluation of non-alcoholic fatty liver disease after bariatric surgery: a retrospective and longitudinal observational cohort study

Non-alcoholic fatty liver disease (NAFLD) is a chronic disease with several degrees of histological features which may progress to cirrhosis. Obesity is an important risk factor and although NAFLD has no specific pharmacological treatment, bariatric surgery has been associated with NAFLD regression in severely obese patients. However, few longitudinal histological studies support this finding. Therefore, firstly, a retrospective study was performed including clinical and histological data of 895 obese patients who underwent bariatric surgery. In addition, histological analyses of 30 patient’s liver biopsies were evaluated at two timepoints (T1 and T2). The retrospective analysis of the total number of patients revealed that the average body mass index (BMI) was 35.91 ± 2.81 kg/m². The liver biopsies during bariatric surgery showed that 53.52% did not present NAFLD, 30.16% had NASH, 15.98% isolated steatosis and 0.34% liver cirrhosis. The median BMI of the longitudinal cohort decreased from 37.9 ± 2.21 kg/m² at the time of bariatric surgery (T1) to 25.69 ± 3.79 kg/m² after 21 ± 22 months after the procedure (T2). The prevalence of NAFLD in T1 was 50%, and 16.67% in T2. The histological area of collagen fiber was lower in T2 compared to T1 (p = 0.0152) in the majority of patients, which was also illustrated by immunohistochemistry for Kupffer cell and myofibroblast formation markers. These findings confirmed the NAFLD regression after bariatric surgery and, for the first time, showed the amelioration of these features using more accurate histopathological techniques.

Prevalence and Profile of Nonalcoholic Fatty Liver Disease in Lean Adults: Systematic Review and Meta-Analysis

Data on prevalence and profile of nonalcoholic fatty liver disease (NAFLD) among individuals who are lean (normal body mass index) is unclear. Published data from studies comparing lean with obese NAFLD or with healthy subjects on prevalence, comorbidities, liver chemistry and histology, and metabolic/inflammatory markers were analyzed. Data were reported as odds ratio and 95% confidence interval for categorical variables and difference of means for continuous variables. Analysis of 53 studies on 65,029 subjects with NAFLD (38,084 lean) and 249,544 healthy subjects showed a prevalence of lean NAFLD at 11.2% in the general population. Among individuals with NAFLD, the prevalence of lean NAFLD was 25.3%. Lean NAFLD versus healthy subjects had higher odds for abnormalities on metabolic profile, including metabolic syndrome and its components, renal and liver function, and patatin‐like phospholipase domain‐containing protein 3 (PNPLA3) G allele; and inflammatory profile, including uric acid and C‐reactive protein. The abnormalities were less severe among lean versus obese NAFLD on metabolic syndrome with its components, renal and liver chemistry, liver stiffness measurement, PNPLA3 and transmembrane 6 superfamily member 2 polymorphisms, and uric acid levels as markers of inflammation. Lean NAFLD had less severe histologic findings, including hepatocyte ballooning, lobular inflammation, NAFLD activity score, and fibrosis stage. Limited data also showed worse outcomes between obese versus lean NAFLD. Conclusion: Lean NAFLD is a distinct entity with metabolic, biochemical, and inflammatory abnormalities compared to healthy subjects and a more favorable profile, including liver histology of steatohepatitis and fibrosis stage, compared to obese NAFLD. We suggest that prospective multicenter studies examine long‐term hepatic and extrahepatic outcomes in individuals with lean NAFLD.

Hepatic lipid droplet homeostasis and fatty liver disease

In cells, lipids are stored in lipid droplets, dynamic organelles that adapt their size, abundance, lipid and protein composition and organelle interactions to metabolic changes. Lipid droplet accumulation in the liver is the hallmark of non-alcoholic fatty liver disease (NAFLD). Due to the prevalence of obesity, the strongest risk factor for steatosis, NAFLD and its associated complications are currently affecting more than 1 billion people worldwide. Here, we review how triglyceride and phospholipid homeostasis are regulated in hepatocytes and how imbalances between lipid storage, degradation and lipoprotein secretion lead to NAFLD. We discuss how organelle interactions are altered in NAFLD and provide insights how NAFLD progression is associated with changes in hepatocellular signaling and organ-crosstalk. Finally, we highlight unsolved questions in hepatic LD and lipoprotein biology and give an outlook on therapeutic options counteracting hepatic lipid accumulation.

Molecular Mechanisms Regulating Obesity-Associated Hepatocellular Carcinoma

Obesity is a global, intractable issue, altering inflammatory and stress response pathways, and promoting tissue adiposity and tumorigenesis. Visceral fat accumulation is correlated with primary tumor recurrence, poor prognosis and chemotherapeutic resistance. Accumulating evidence highlights a close association between obesity and an increased incidence of hepatocellular carcinoma (HCC). Obesity drives HCC, and obesity-associated tumorigenesis develops via nonalcoholic fatty liver (NAFL), progressing to nonalcoholic steatohepatitis (NASH) and ultimately to HCC. The better molecular elucidation and proteogenomic characterization of obesity-associated HCC might eventually open up potential therapeutic avenues. The mechanisms relating obesity and HCC are correlated with adipose tissue remodeling, alteration in the gut microbiome, genetic factors, ER stress, oxidative stress and epigenetic changes. During obesity-related hepatocarcinogenesis, adipokine secretion is dysregulated and the nuclear factor erythroid 2 related factor 1 (Nrf-1), nuclear factor kappa B (NF-κB), mammalian target of rapamycin (mTOR), phosphatidylinositol-3-kinase (PI3K)/phosphatase and tensin homolog (PTEN)/Akt, and Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathways are activated. This review captures the present trends allied with the molecular mechanisms involved in obesity-associated hepatic tumorigenesis, showcasing next generation molecular therapeutic strategies and their mechanisms for the successful treatment of HCC.

Validation of PNPLA3 polymorphisms as risk factor for NAFLD and liver fibrosis in an admixed population

INTRODUCTION AND AIM

Studies have shown that two polymorphisms were associated with steatosis and progression of non-alcoholic fatty liver disease (NAFLD) in different populations: the Patatin-like Phospholipase Domain Containing 3 (PNPLA3) and Transmembrane 6 Superfamily Member 2 (TM6SF2). However, the frequency and significance of these polymorphisms in an admixed population, i.e., Brazilian, is unknown. Therefore, we aimed to evaluate them in healthy subjects in comparison to patients with NAFLD.

MATERIAL AND METHODS

This was a multicenter cross-sectional study in 248 patients with biopsy-proven NAFLD and in 134 healthy controls from two tertiary centers in Brazil. PNPLA3 (rs738409 c.444C>G) and TM6SF2 (rs58542926 c.449C>T) polymorphisms were evaluated.

RESULTS

In controls, the frequencies of PNPLA3 CC and CG+GG were 49.25% and 50.74%, respectively; in NAFLD patients, this was 31.05% and 68.88% (p=0.0044, 95% CI 1.037-2.977). PNPLA3 GG subjects had an increased risk (3.29-fold) of having NAFLD when compared to CC subjects (p=0.0044, 95% CI 1.504-7.225). In patients with nonalcoholic steatohepatitis (NASH), PNPLA3 GG compared to CC was associated with higher AST levels [38.4±25.3 versus 36.7±40.1IU/L, p=0.0395)] and with the presence of liver fibrosis (≥F2 fibrosis, p=0.0272). TM6SF2 polymorphisms were not in Hardy-Weinberg equilibrium in our NAFLD group precluding further analysis.

CONCLUSION

We demonstrated for the first time that PNPLA3 CG+GG increase the risk of NAFLD among Brazilian subjects. Moreover, PNPLA3 GG was associated with liver enzyme elevation and fibrosis in NASH patients.

Bax inhibitor-1 deficiency leads to obesity by increasing Ca2+-dependent insulin secretion

Abstract

Transmembrane BAX inhibitor motif containing 6 (TMBIM6), also known as Bax inhibitor-1, is an evolutionarily conserved protein involved in endoplasmic reticulum (ER) function. TMBIM6 is an ER Ca²⁺ leak channel and its deficiency enhances susceptibility to ER stress due to inhibition of the ER stress sensor IRE1α. It was previously shown that TMBIM6 overexpression improves glucose metabolism and that TMBIM6 knockout mice develop obesity. We here examined the metabolic alterations underlying the obese phenotype and subjected TMBIM6 knockout mice to indirect calorimetry and euglycemic-hyperinsulinemic tests with stable isotope dilution to gauge tissue-specific insulin sensitivity. This demonstrated no changes in heat production, food intake, activity or hepatic and peripheral insulin sensitivity. TMBIM6 knockout mice, however, featured a higher glucose-stimulated insulin secretion in vivo as assessed by the hyperglycemic clamp test and hepatic steatosis. This coincided with profound changes in glucose-mediated Ca²⁺ regulation in isolated pancreatic β cells and increased levels of IRE1α levels but no differences in downstream effects of IRE1α like increased Xbp1 mRNA splicing or Ire1-dependent decay of insulin mRNA in the pancreas. We therefore conclude that lack of TMBIM6 does not affect insulin sensitivity but leads to hyperinsulinemia, which serves to explain the weight gain. TMBIM6-mediated metabolic alterations are mainly caused by its role as a Ca²⁺ release channel in the ER.

Key messages

TMBIM6^−/− leads to obesity and hepatic steatosis.

Food intake and energy expenditure are not changed in TMBIM6^−/− mice.

No changes in insulin resistance in TMBIM6^−/− mice.

Increased insulin secretion caused by altered calcium dynamics in β cells.

Diet induces hepatocyte protection in fatty liver disease via modulation of PTEN signaling

Fatty liver disease (FLD) is characterized by accumulation of excess fat in the liver. The underlying molecular mechanism associated with the progression of the disease has been in elusive. Hepatocellular demise due to increased oxidative stress resulting in an inflammatory response may be a key feature in FLD. Recent advances in molecular biology have led to an improved understanding of the molecular pathogenesis, suggesting a critical association between the PI3K/AKT/PTEN signaling pathway and FLD. In particular, PTEN has been associated with regulating the pathogenesis of hepatocyte degeneration. Given the function of mitochondria in reactive oxygen species (ROS) generation and the initiation of oxidative stress, the mitochondrial antioxidant network is of interest. It is vital to balance the activity of intracellular key molecules to maintain a healthy liver. Consequently, onset of FLD may be delayed using dietary protective agents that alter PTEN signaling and reduce ROS levels. The advancement of research on dietary regulation with a focus on modulatory roles in ROS generation and PTEN associated signaling is summarized in the current study, supporting further preventive and therapeutic exploration.

PNPLA3 I148M gene variant and chronic kidney disease in type 2 diabetic patients with NAFLD: Clinical and experimental findings

BACKGROUND AND AIMS

Emerging evidence suggests an association between patatin-like phospholipase domain-containing protein-3 (PNPLA3) rs738409 (I148M protein variant) and risk of chronic kidney disease (CKD), but the mechanisms underpinning this association are poorly understood.

METHODS

We studied 157 patients with type 2 diabetes (T2DM) who underwent ultrasonography and vibration-controlled transient elastography for diagnosing nonalcoholic fatty liver disease (NAFLD). CKD was defined as estimated glomerular filtration rate (e-GFR) <60 mL/min/1.73 m² and/or abnormal albuminuria. We surveyed PNPLA3 mRNA expression in human tissues, using the liver as a positive control, and also measured PNPLA3 mRNA and protein expression levels in human cell lines represented in the kidney and the liver.

RESULTS

In all, 112 patients had NAFLD and 43 had CKD. Patients homozygous for the I148M variant (n = 11) had lower e-GFR levels (60.6 ± 11.7 vs 77.8 ± 15.9 vs 83.5 ± 16.5 mL/min/1.73 m² , P = .0001) and higher prevalence of CKD (63.6% vs 24.2% vs 25.0%, P = .028), compared to those with I/M (n = 66) and I/I (n = 80) PNPLA3 genotype. The association of I148M homozygosity with lower e-GFR levels (P < .0001) and higher risk of CKD (adjusted-odds ratio 6.65; 95% CI 1.65-26.8, P = .008) was independent of liver disease severity (as detected by liver stiffness ≥7kPa) and other risk factors. PNPLA3 mRNA expression was greatest in liver and renal cortex, and podocytes showed high PNPLA3 mRNA and protein levels, comparable to that of hepatocytes and hepatic stellate cells respectively.

CONCLUSIONS

The PNPLA3 I148M variant was associated with CKD, independently of common renal risk factors and severity of NAFLD PNPLA3 expression levels were particularly high in renal podocytes.

MAFLD: A Consensus-Driven Proposed Nomenclature for Metabolic Associated Fatty Liver Disease

Fatty liver associated with metabolic dysfunction is common, affects a quarter of the population, and has no approved drug therapy. Although pharmacotherapies are in development, response rates appear modest. The heterogeneous pathogenesis of metabolic fatty liver diseases and inaccuracies in terminology and definitions necessitate a reappraisal of nomenclature to inform clinical trial design and drug development. A group of experts sought to integrate current understanding of patient heterogeneity captured under the acronym nonalcoholic fatty liver disease (NAFLD) and provide suggestions on terminology that more accurately reflects pathogenesis and can help in patient stratification for management. Experts reached consensus that NAFLD does not reflect current knowledge, and metabolic (dysfunction) associated fatty liver disease "MAFLD" was suggested as a more appropriate overarching term. This opens the door for efforts from the research community to update the nomenclature and subphenotype the disease to accelerate the translational path to new treatments.

ARRB1 inhibits non-alcoholic steatohepatitis progression by promoting GDF15 maturation

BACKGROUND & AIMS

Non-alcoholic steatohepatitis (NASH) is associated with the dysregulation of lipid metabolism and hepatic inflammation. The causal mechanism underlying NASH is not fully elucidated. This study investigated the role of β-Arrestin1 (ARRB1) in the progression of NASH.

METHODS

Liver tissue from patients with NASH and controls were obtained to evaluate ARRB1 expression. NASH models were established in Arrb1-knockout and wild-type mice fed either a high-fat diet (HFD) for 26 weeks or a methionine/choline-deficient (MCD) diet for 6 weeks.

RESULTS

ARRB1 expression was reduced in liver samples from patients with NASH. Reduced Arrb1 levels were also detected in murine NASH models. Arrb1 deficiency accelerated steatohepatitis development in HFD-/MCD-fed mice (accompanied by the upregulation of lipogenic genes and downregulation of β-oxidative genes). Intriguingly, ARRB1 was found to interact with growth differentiation factor 15 (GDF15) and facilitated the transportation of GDF15 precursor (pro-GDF15) to the Golgi apparatus for cleavage and maturation. Treatment with recombinant GDF15 ablated the lipid accumulation in the presence of Arrb1 deletion both in vitro and in vivo. Re-expression of Arrb1 in the NASH models ameliorated the liver disease, and this effect was greater in the presence of pro-GDF15 overexpression. By contrast, the effect of pro-GDF15 overexpression alone was impaired in Arrb1-deficient mice. In addition, the severity of liver disease in patients with NASH was negatively correlated with ARRB1 expression.

CONCLUSION

ARRB1 acts as a vital regulator in the development of NASH by facilitating the translocation of GDF15 to the Golgi apparatus and its subsequent maturation. Thus, ARRB1 is a potential therapeutic target for the treatment of NASH.

LAY SUMMARY

Non-alcoholic steatohepatitis (NASH) is associated with the progressive dysfunction of lipid metabolism and a consequent inflammatory response. Decreased ARRB1 is observed in patients with NASH and murine NASH models. Re-expression of Arrb1 in the murine NASH model ameliorated liver disease, an effect which was more pronounced in the presence of pro-GDF15 overexpression, highlighting a promising strategy for NASH therapy.

Non-obese patients with nonalcoholic fatty liver disease may use a lower liver stiffness cut-off to assess fibrosis stages

OBJECTIVE

We aimed to estimate the optimal cut-off values of liver stiffness measurement (LSM) for diagnosing and staging fibrosis in non-obese and obese patients with nonalcoholic fatty liver disease (NAFLD).

METHODS

NAFLD patients diagnosed by liver biopsy according to the Nonalcoholic Steatohepatitis Clinical Research Network scoring system were enrolled in this study. Non-obesity was defined as a body mass index (BMI) less than 25 kg/m² . LSM was performed by experienced physicians within 2 weeks before or after liver biopsy.

RESULTS

A total of 158 patients were included. Average BMI of the non-obese (n = 68) and obese (n = 90) groups was 23.2 ± 1.6 and 27.9 ± 2.5 kg/m² , respectively. After adjusted for age, fibrosis stage, steatosis grade and type 2 diabetes mellitus, the obese group had a LSM of 3.522 kPa higher than the non-obese patients (P = 0.003). LSM values of the non-obese patients had a lower trend when stratified by fibrosis stage, especially in cirrhosis (F4; P = 0.021). Applying separate cut-off values for patients with NAFLD in individual fibrosis stage, 5.8 vs 7.5 kPa (≥ F1), 7.6 vs 8.5 kPa (≥ F2), 9.1 vs 11.2 kPa (≥ F3), and 12.5 vs 14.3 kPa (F4), improved their diagnostic odds ratios compared with overall cut-off values. In the non-obese NAFLD group, using a separate cut-off avoided underestimating 9.1% of patients with cirrhosis.

CONCLUSIONS

Non-obese NAFLD group had lower LSM than the obese group. Different cut-off values should be used to measure liver fibrosis stage in non-obese and obese NAFLD patients.

Toward Genetic Prediction of Nonalcoholic Fatty Liver Disease Trajectories: PNPLA3 and Beyond

Nonalcoholic fatty liver disease (NAFLD) is on the verge of becoming the leading cause of liver disease. NAFLD develops at the interface between environmental factors and inherited predisposition. Genome-wide association studies, followed by exome-wide analyses, led to identification of genetic risk variants (eg, PNPLA3, TM6SF2, and SERPINA1) and key pathways involved in fatty liver disease pathobiology. Functional studies improved our understanding of these genetic factors and the molecular mechanisms underlying the trajectories from fat accumulation to fibrosis, cirrhosis, and cancer over time. Here, we summarize key NAFLD risk genes and illustrate their interactions in a 3-dimensional "risk space." Although NAFLD genomics sometimes appears to be "lost in translation," we envision clinical utility in trial design, outcome prediction, and NAFLD surveillance.

Macrophages in metabolic associated fatty liver disease

Metabolic associated fatty liver disease (MAFLD), formerly named non-alcoholic fatty liver disease is the most common liver disorder in many countries. The inflammatory subtype termed steatohepatitis is a driver of disease progression to cirrhosis, hepatocellular carcinoma, liver transplantation, and death, but also to extrahepatic complications including cardiovascular disease, diabetes and chronic kidney disease. The plasticity of macrophages in response to various environmental cues and the fact that they can orchestrate cross talk between different cellular players during disease development and progression render them an ideal target for drug development. This report reviews recent advances in our understanding of macrophage biology during the entire spectrum of MAFLD including steatosis, inflammation, fibrosis, and hepatocellular carcinoma, as well as for the extra-hepatic manifestations of MAFLD. We discuss the underlying molecular mechanisms of macrophage activation and polarization as well as cross talk with other cell types such as hepatocytes, hepatic stellate cells, and adipose tissue. We conclude with a discussion on the potential translational implications and challenges for macrophage based therapeutics for MAFLD.

Possible Relevance of PNPLA3 and TLL1 Gene Polymorphisms to the Efficacy of PEG-IFN Therapy for HBV-Infected Patients

Lifestyle changes have led to an increase in the number of patients with nonalcoholic fatty liver disease (NAFLD). However, the effects of NAFLD-associated single-nucleotide gene polymorphisms (SNPs) in HBV-infected patients have not been adequately investigated. Methods: We investigated the association of the NAFLD-related SNPs patatin-like phospholipase domain-containing protein 3 (PNPLA3; rs738409), transmembrane 6 superfamily member 2 (TM6SF2; rs58542926), 17-beta hydroxysteroid dehydrogenase 13 (HSD17B13; rs72613567, rs6834314 and rs62305723), membrane-bound O-acyltransferase domain containing 7 (MBOAT7; rs641738) and glucokinase regulatory protein (GCKR; rs1260326) with the presence of histologically proven hepatic steatosis (HS) in HBV-infected patients (n = 224). We also investigated tolloid-like 1 (TLL1) SNP (rs17047200), which has been reported to be involved in the disease progression in Japanese NAFLD patients, and evaluated the association of HS and various SNPs with the treatment efficacy of pegylated-interferon (PEG-IFN) monotherapy following nucleotide/nucleoside (NA) treatment (NA/PEG-IFN sequential therapy; n = 64). Among NAFLD-associated SNPs evaluated, only the PNPLA3 SNP was significantly associated with the presence of hepatic steatosis in a total of 224 HBV-infected patients (P = 1.0 × 10⁻⁴). Regarding the sequential therapy, PNPLA3 SNP and TLL1 SNP were related to the treatment efficacy, and patients without minor alleles of these SNPs showed favorable results with a high virologic response and significant reduction in their HBsAg titer. A multivariate analysis showed that HBeAg positivity (odds ratio 5.810, p = 0.016) and the absence of a risk allele in PNPLA3 and TLL1 SNPs (odds ratio 8.664, p = 0.0042) were significantly associated with treatment efficacy. The PNPLA3 SNP might be associated with the presence of HS, and the combination of the PNPLA3 and TLL1 SNPs might be related to the efficacy of PEG-IFN monotherapy following NA treatment.

The Molecular and Mechanistic Insights Based on Gut-Liver Axis: Nutritional Target for Non-Alcoholic Fatty Liver Disease (NAFLD) Improvement

Non-alcoholic fatty liver disease (NAFLD) is recognized as the most frequent classification of liver disease around the globe. Along with the sequencing technologies, gut microbiota has been regarded as a vital factor for the maintenance of human and animal health and the mediation of multiple diseases. The modulation of gut microbiota as a mechanism affecting the pathogenesis of NAFLD is becoming a growing area of concern. Recent advances in the communication between gut and hepatic tissue pave novel ways to better explain the molecular mechanisms regarding the pathological physiology of NAFLD. In this review, we recapitulate the current knowledge of the mechanisms correlated with the development and progression of NAFLD regulated by the gut microbiome and gut-liver axis, which may provide crucial therapeutic strategies for NAFLD. These mechanisms predominantly involve: (1) the alteration in gut microbiome profile; (2) the effects of components and metabolites from gut bacteria (e.g., lipopolysaccharides (LPS), trimethylamine-N-oxide (TMAO), and N,N,N-trimethyl-5-aminovaleric acid (TMAVA)); and (3) the impairment of intestinal barrier function and bile acid homeostasis. In particular, the prevention and therapy of NAFLD assisted by nutritional strategies are highlighted, including probiotics, functional oligosaccharides, dietary fibers, ω-3 polyunsaturated fatty acids, functional amino acids (L-tryptophan and L-glutamine), carotenoids, and polyphenols, based on the targets excavated from the gut-liver axis.

Characterization of the variability in the extent of nonalcoholic fatty liver induced by a high-fat diet in the genetically diverse Collaborative Cross mouse model

Interindividual variability and sexual dimorphisms in the development of nonalcoholic fatty liver disease (NAFLD) are still poorly understood. In the present study, male and female strains of Collaborative Cross (CC) mice were fed a high-fat and high-sucrose (HF/HS) diet or a control diet for 12 weeks to investigate interindividual- and sex-specific variations in the development of NAFLD. The severity of liver steatosis varied between sexes and individual strains and was accompanied by an elevation of serum markers of insulin resistance, including increases in total cholesterol, low-density lipoproteins, high-density lipoproteins, phospholipids, and glucose. The development of NAFLD was associated with overexpression of the critical fatty acid uptake and de novo lipogenesis genes Pparg, Mogat1, Cd36, Acaab1, Fabp2, and Gdf15 in male and female mice. The expression of Pparg, Mogat1, and Cd36 was positively correlated with liver triglycerides in male mice, and Mogat1 and Cd36 expression were positively correlated with liver triglycerides in female mice. Our results indicate the value of CC mice in combination with HF/HS diet-induced alterations as an approach to study the susceptibility and interindividual variabilities in the pathogenesis of nonalcoholic fatty liver and early nonalcoholic steatohepatitis at the population level, uncovering of susceptible and resistant cohorts, and identifying sex-specific molecular determinants of disease susceptibility.

Noninvasive Diagnosis of NAFLD and NASH

The aim of this review is to outline emerging biomarkers that can serve as early diagnostic tools to identify patients with nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) and, among them, the subgroup of best candidates for clinical trials on emerging compounds. Regarding possible predictors of NAFLD, a number of studies evaluated a combination of serum biomarkers either available in routine practice (or investigational) or proprietary and expensive. So far, magnetic resonance imaging-derived proton density fat fraction (MRI-PDFF) appears to be the most accurate for fatty liver diagnosis. In clinical practice, the main question is how to diagnose NASH early. There are new promising biomarkers that can help in diagnosing early stages of NASH, yet they include variables not routinely tested. In the setting of NASH, most studies confirm that, in spite of several well-known limitations, transient elastography or point shear wave elastography can help in enriching the pool of patients that should be screened for investigational treatments. Newer multiomics biomarkers including those focusing on microbiota can be useful but require methods to be standardized and implemented. To date, one biomarker alone is not able to non- or minimally invasively identify patients with NASH and mild to moderate fibrosis.

The Controversial Role of Human Gut Lachnospiraceae

The complex polymicrobial composition of human gut microbiota plays a key role in health and disease. Lachnospiraceae belong to the core of gut microbiota, colonizing the intestinal lumen from birth and increasing, in terms of species richness and their relative abundances during the host's life. Although, members of Lachnospiraceae are among the main producers of short-chain fatty acids, different taxa of Lachnospiraceae are also associated with different intra- and extraintestinal diseases. Their impact on the host physiology is often inconsistent across different studies. Here, we discuss changes in Lachnospiraceae abundances according to health and disease. With the aim of harnessing Lachnospiraceae to promote human health, we also analyze how nutrients from the host diet can influence their growth and how their metabolites can, in turn, influence host physiology.

Retinoic acid induced 16 deficiency exacerbates high-fat diet-induced steatohepatitis in mice

Non-alcoholic fatty liver disease (NAFLD) associated with obesity may progress to non-alcoholic steatohepatitis, cirrhosis and hepatocellular carcinoma (HCC). Retinoic acid induced 16 (RAI16) plays an important role in cell apoptosis and is also a potential marker for HCC. Here we aimed to test the effect of RAI16 deficiency on liver pathology in high-fat diet (HFD) fed mice. Wild type (WT) and RAI16 knockout (RAI16-/-) C57BL/6 mice were fed with HFD or chow for up to 12 months. With consumption of HFD diet, RAI16-/- mice on HFD developed much more excess fatty liver within 4 months than WT mice on HFD. The expressions of fatty acid synthesis associated molecules Ppar-γ, Srebp-1c and Fas were further increased in RAI16-/- mice compared with WT mice on HFD. Macrophage infiltration related molecules Mcp-1 and F4/80 and pro-inflammatory factor Lcn2 were significantly increased in RAI16-/- mice compared with WT mice on HFD. Conclusively, RAI16 deficiency exacerbated HFD-induced liver injury, associated with increased inflammation. These findings indicate that RAI16 plays an important role in HFD-induced liver pathology and might be considered as a target for treatment of NAFLD. SIGNIFICANCE: 1. RAI16-/- mice on HFD developed much more excess fatty liver. 2. RAI16-/- mice showed more macrophage infiltration and proinflammation.

Fatty liver diseases, mechanisms, and potential therapeutic plant medicines

The liver is an important metabolic organ and controls lipid, glucose and energy metabolism. Dysruption of hepatic lipid metabolism is often associated with fatty liver diseases, including nonalcoholic fatty liver disease (NAFLD), alcoholic fatty liver diseases (AFLD) and hyperlipidemia. Recent studies have uncovered the contribution of hormones, transcription factors, and inflammatory cytokines to the pathogenesis of dyslipidemia and fatty liver diseases. Moreover, a significant amount of effort has been put to examine the mechanisms underlying the potential therapeutic effects of many natural plant products on fatty liver diseases and metabolic diseases. We review the current understanding of insulin, thyroid hormone and inflammatory cytokines in regulating hepatic lipid metabolism, focusing on several essential transcription regulators, such as Sirtuins (SIRTs), Forkhead box O (FoxO), Sterol-regulatory element-binding proteins (SREBPs). We also discuss a few representative natural products with promising thereapeutic effects on fatty liver disease and dyslipidemia.

PTPROt aggravates inflammation by enhancing NF-κB activation in liver macrophages during nonalcoholic steatohepatitis

Rationale: Inflammation plays a crucial role in the progression of nonalcoholic steatohepatitis (NASH). Protein tyrosine phosphatase receptor type O truncated isoform (PTPROt) is an integral membrane protein that has been identified in osteoclasts, macrophages, and B lymphocytes. However, its relationship between inflammation and NASH is largely unknown. Herein, we aimed to study the function of PTPROt in NASH progression.

Methods: We established a NASH mouse model in wild-type (WT), PTPRO knockout mice by western diet (WD) and methionine-choline-deficient diet (MCD). In addition, MCD-induced NASH model was established in BMT mice. Moreover, we determined the expression of PTPROt in liver macrophages in human subjects without steatosis, with simple steatosis, and with NASH to confirm the relationship between PTPROt and NASH. In vitro assays were also performed to study the molecular role of PTPROt in NASH progression.

Results: Human samples and animal model results illustrated that PTPROt is increased in liver macrophages during NASH progression and is positively correlated with the degree of NASH. Our animal model also showed that PTPROt in liver macrophages can enhance the activation of the NF-κB signaling pathway, which induces the transcription of genes involved in the inflammatory response. Moreover, PTPROt promotes the transcription of pro-oxidant genes and inhibits antioxidant and protective genes via increased activation of the NF-κB signaling pathway, thereby causing an increased level of reactive oxygen species (ROS) and damaged mitochondria. This triggers the NLRP3-IL1β axis and causes a heightened inflammatory response. Notably, PTPROt partially limits inflammation and ROS production by promoting mitophagy, which participates in a negative feedback loop in this model.

Conclusions: Our data strongly indicate that PTPROt plays a dual role in inflammation via the NF-κB signaling pathway in liver macrophages during NASH. Further studies are required to explore therapeutic strategies and prevention of this common liver disease through PTPROt.

Liver Fibrosis: Mechanistic Concepts and Therapeutic Perspectives

Liver fibrosis due to viral or metabolic chronic liver diseases is a major challenge of global health. Correlating with liver disease progression, fibrosis is a key factor for liver disease outcome and risk of hepatocellular carcinoma (HCC). Despite different mechanism of primary liver injury and disease-specific cell responses, the progression of fibrotic liver disease follows shared patterns across the main liver disease etiologies. Scientific discoveries within the last decade have transformed the understanding of the mechanisms of liver fibrosis. Removal or elimination of the causative agent such as control or cure of viral infection has shown that liver fibrosis is reversible. However, reversal often occurs too slowly or too infrequent to avoid life-threatening complications particularly in advanced fibrosis. Thus, there is a huge unmet medical need for anti-fibrotic therapies to prevent liver disease progression and HCC development. However, while many anti-fibrotic candidate agents have shown robust effects in experimental animal models, their anti-fibrotic effects in clinical trials have been limited or absent. Thus, no approved therapy exists for liver fibrosis. In this review we summarize cellular drivers and molecular mechanisms of fibrogenesis in chronic liver diseases and discuss their impact for the development of urgently needed anti-fibrotic therapies.

NAFLD as a driver of chronic kidney disease

Non-alcoholic fatty liver disease (NAFLD) and chronic kidney disease (CKD) are worldwide public health problems, affecting up to 25-30% (NAFLD), and up to 10-15% (CKD) of the general population. Recently, it has also been established that there is a strong association between NAFLD and CKD, regardless of the presence of potential confounding diseases such as obesity, hypertension and type 2 diabetes. Since NAFLD and CKD are both common diseases that often occur alongside other metabolic conditions, such as type 2 diabetes or metabolic syndrome, elucidating the relative impact of NAFLD on the risk of incident CKD presents a substantial challenge for investigators working in this research field. A growing body of epidemiological evidence suggests that NAFLD is an independent risk factor for CKD and recent evidence also suggests that associated factors such as metabolic syndrome, dysbiosis, unhealthy diets, platelet activation and processes associated with ageing could also contribute mechanisms linking NAFLD and CKD. This narrative review provides an overview of the literature on: a) the evidence for an association and causal link between NAFLD and CKD and b) the underlying mechanisms by which NAFLD (and factors strongly linked with NAFLD) may increase the risk of developing CKD.

Assessment of Genetic Aspects of Non-alcoholic Fatty Liver and Premature Cardiovascular Events

Recent evidence has demonstrated a strong interplay and multifaceted relationship between non-alcoholic fatty liver disease (NAFLD) and cardiovascular disease (CVD). CVD is the major cause of death in patients with NAFLD. NAFLD also has strong associations with diabetes and metabolic syndrome. In this comprehensive review, we aimed to overview the primary environmental and genetic risk factors of NAFLD, and CVD and also focus on the genetic aspects of these two disorders. NAFLD and CVD are both heterogeneous diseases with common genetic and molecular pathways. We have searched for the latest published articles regarding this matter and tried to provide an overview of recent insights into the genetic aspects of NAFLD and CVD. The common genetic and molecular pathways involved in NAFLD and CVD are insulin resistance (IR), subclinical inflammation, oxidative stress, and atherogenic dyslipidemia. According to an investigation, the exact associations between genomic characteristics of NAFLD and CVD and casual relationships are not fully determined. Different gene polymorphisms have been identified as the genetic components of the NAFLDCVD association. Some of the most documented ones of these gene polymorphisms are patatin-like phospholipase domain-containing protein 3 (PNPLA3), transmembrane 6 superfamily member 2 (TM6SF2), hydroxysteroid 17-beta dehydrogenase 13 (HSD17B13), adiponectin-encoding gene (ADIPOQ), apolipoprotein C3 (APOC3), peroxisome proliferator-activated receptors (PPAR), leptin receptor (LEPR), sterol regulatory element-binding proteins (SREBP), tumor necrosis factor-alpha (TNF-α), microsomal triglyceride transfer protein (MTTP), manganese superoxide dismutase (MnSOD), membrane-bound O-acyltransferase domain-containing 7 (MBOAT7), and mutation in DYRK1B that substitutes cysteine for arginine at position 102 in kinase-like domain. Further cohort studies with a significant sample size using advanced genomic assessments and next-generation sequencing techniques are needed to shed more light on genetic associations between NAFLD and CVD.