Liver fibrogenesis in non-alcoholic steatohepatitis

Liver fibrosis pathologies and potentials of RNA based therapeutics modalities

Liver fibrosis (LF) occurs when the liver tissue responds to injury or inflammation by producing excessive amounts of scar tissue, known as the extracellular matrix. This buildup stiffens the liver tissue, hinders blood flow, and ultimately impairs liver function. Various factors can trigger this process, including bloodborne pathogens, genetic predisposition, alcohol abuse, non-steroidal anti-inflammatory drugs, non-alcoholic steatohepatitis, and non-alcoholic fatty liver disease. While some existing small-molecule therapies offer limited benefits, there is a pressing need for more effective treatments that can truly cure LF. RNA therapeutics have emerged as a promising approach, as they can potentially downregulate cytokine levels in cells responsible for liver fibrosis. Researchers are actively exploring various RNA-based therapeutics, such as mRNA, siRNA, miRNA, lncRNA, and oligonucleotides, to assess their efficacy in animal models. Furthermore, targeted drug delivery systems hold immense potential in this field. By utilizing lipid nanoparticles, exosomes, nanocomplexes, micelles, and polymeric nanoparticles, researchers aim to deliver therapeutic agents directly to specific biomarkers or cytokines within the fibrotic liver, increasing their effectiveness and reducing side effects. In conclusion, this review highlights the complex nature of liver fibrosis, its underlying causes, and the promising potential of RNA-based therapeutics and targeted delivery systems. Continued research in these areas could lead to the development of more effective and personalized treatment options for LF patients.

Association between frailty and hepatic fibrosis in NAFLD among middle-aged and older adults: results from NHANES 2017-2020

Background

Although previous studies found that frailty is prevalent in NAFLD patients with advanced liver fibrosis and cirrhosis, studies examining the relationship are spare.

Aim

Our study aspires to investigate the potential correlation between the Frailty Index (FI) and hepatic fibrosis among middle-aged and older adults with NAFLD.

Methods

Data from the 2017-2020.03 National Health and Nutrition Examination Survey (NHANES) were utilized for this study, with a final of 2,383 participants aged 50 years and older included. The quantification of frailty was executed employing a 49-item frailty index. The recognition of hepatic steatosis and fibrosis was accomplished through the utilization of the controlling attenuation parameter (CAP) and transient elastography (TE). The relationship between the FI and hepatic fibrosis were investigated employing univariable and multivariable-adjusted logistic regression analyses. A subgroup analysis was conducted, dividing the subjects based on gender, Body Mass Index (BMI), and the presence of hyperlipidemia.

Results

The findings demonstrated a positive correlation between the FI and significant hepatic fibrosis in NAFLD, even after using multivariate logistic regression models adjusting for potential confounding factors (OR = 1.022, 95% CI, 1.004-1.041) and in tertiles (Q3vs Q1: OR = 2.004, 95% CI, 1.162-3.455). In the subgroup analysis, the correlation was more statistically significant in male (OR = 1.046, 95% CI, 1.022-1.071), under/normal weight (OR = 1.077, 95% CI, 1.009-1.150), overweight (OR = 1.040, 95% CI, 1.010-1.071), and subjects without hyperlipidemia (OR = 1.054, 95% CI, 1.012-1.097). The area under the Receiver Operating Characteristic (ROC) curve for the FI in assessing the existence of substantial fibrosis in NAFLD was 0.612 (95% CI, 0.596-0.628).

Conclusion

This study demonstrated a positive correlation between significant hepatic fibrosis and frailty, particularly among males aged 50 years and older, who were non-obese and did not have hyperlipidemia with NAFLD. Additional studies are required to further validate these findings.

CETP-derived Peptide Seq-1, the Key Component of HB-ATV-8 Vaccine Prevents Stress Responses, and Promotes Downregulation of Pro-Fibrotic Genes in Hepatocytes and Stellate Cells

BACKGROUND

The nasal vaccine HB-ATV-8 has emerged as a promising approach for NAFLD (non-alcoholic fatty liver disease) and atherosclerosis prevention. HB-ATV-8 contains peptide seq-1 derived from the carboxy-end of the Cholesteryl Ester Transfer Protein (CETP), shown to reduce liver fibrosis, inflammation, and atherosclerotic plaque formation in animal models. Beyond the fact that this vaccine induces B-cell lymphocytes to code for antibodies against the seq-1 sequence, inhibiting CETP's cholesterol transfer activity, we have hypothesized that beyond the modulation of CETP activity carried out by neutralizing antibodies, the observed molecular effects may also correspond to the direct action of peptide seq-1 on diverse cellular systems and molecular features involved in the development of liver fibrosis.

METHODS

The HepG2 hepatoma-derived cell line was employed to establish an in vitro steatosis model. To obtain a conditioned cell medium to be used with hepatic stellate cell (HSC) cultures, HepG2 cells were exposed to fatty acids or fatty acids plus peptide seq-1, and the culture medium was collected. Gene regulation of COL1A1, ACTA2, TGF-β, and the expression of proteins COL1A1, MMP-2, and TIMP-2 were studied.

AIM

To establish an in vitro steatosis model employing HepG2 cells that mimics molecular processes observed in vivo during the onset of liver fibrosis. To evaluate the effect of peptide Seq-1 on lipid accumulation and pro-fibrotic responses. To study the effect of Seq-1-treated steatotic HepG2 cell supernatants on lipid accumulation, oxidative stress, and pro-fibrotic responses in HSC.

RESULTS AND CONCLUSION

Peptide seq-1-treated HepG2 cells show a downregulation of COLIA1, ACTA2, and TGF-β genes, and a decreased expression of proteins such as COL1A1, MMP-2, and TIMP-2, associated with the remodeling of extracellular matrix components. The same results are observed when HSCs are incubated with peptide Seq-1-treated steatotic HepG2 cell supernatants. The present study consolidates the nasal vaccine HB-ATV-8 as a new prospect in the treatment of NASH directly associated with the development of cardiovascular disease.

Cyanotoxins Increase Cytotoxicity and Promote Nonalcoholic Fatty Liver Disease Progression by Enhancing Cell Steatosis

Freshwater prokaryotic cyanobacteria within harmful algal blooms produce cyanotoxins which are considered major pollutants in the aquatic system. Direct exposure to cyanotoxins through inhalation, skin contact, or ingestion of contaminated drinking water can target the liver and may cause hepatotoxicity. In the current study, we investigated the effect of low concentrations of cyanotoxins on cytotoxicity, inflammation, modulation of unfolded protein response (UPR), steatosis, and fibrosis signaling in human hepatocytes and liver cell models. Exposure to low concentrations of microcystin-LR (MC-LR), microcystin-RR (MC-RR), nodularin (NOD), and cylindrospermopsin (CYN) in human bipotent progenitor cell line HepaRG and hepatocellular carcinoma (HCC) cell lines HepG2 and SK-Hep1 resulted in increased cell toxicity. MC-LR, NOD, and CYN differentially regulated inflammatory signaling, activated UPR signaling and lipogenic gene expression, and induced cellular steatosis and fibrotic signaling in HCC cells. MC-LR, NOD, and CYN also regulated AKT/mTOR signaling and inhibited autophagy. Chronic exposure to MC-LR, NOD, and CYN upregulated the expression of lipogenic and fibrosis biomarkers. Moreover, RNA sequencing (RNA seq) data suggested that exposure of human hepatocytes, HepaRG, and HCC HepG2 cells to MC-LR and CYN modulated expression levels of several genes that regulate non-alcoholic fatty liver disease (NAFLD). Our data suggest that low concentrations of cyanotoxins can cause hepatotoxicity and cell steatosis and promote NAFLD progression.

Extracellular volume fraction obtained by dual-energy CT depicting the etiological differences of liver fibrosis

PURPOSE

To assess etiological differences in extracellular volume fraction (ECV) and evaluate its influence on staging performance.

METHODS

A total of 166 patients with normal liver (n = 14) and chronic liver disease related to viral hepatitis (n = 71), alcohol (n = 44), and nonalcoholic steatohepatitis (NASH) (n = 37) underwent dual-energy CT (DECT) of the liver (5-min equilibrium-phase images) between January 2020 and July 2022. The iodine densities of the parenchyma and aorta were measured and ECV was calculated. Comparisons of ECV between each etiology and METAVIR fibrosis stage were statistically analyzed (p < 0.05).

RESULTS

ECV in each etiology and all patients significantly increased with higher fibrosis stage (p < 0.001) and showed a strong or moderate correlation with fibrosis stage (Spearman's ρ; all patients, 0.701; viral hepatitis, 0.638; alcoholic, 0.885; NASH, 0.791). In stages F2-F4, ECV in alcoholic liver disease was significantly larger than those for viral hepatitis and NASH (p < 0.05); however, no significant difference in stage F1 was found among the three etiologies. The cutoff values and areas under the receiver operating characteristic curve (AUC-ROCs) for discriminating fibrosis stage (≥ F1- ≥ F4) were higher for alcohol (cutoff values and AUC-ROC; 20.1% and 0.708 for ≥ F1, 23.8% and 0.990 for ≥ F2, 24.3% and 0.968 for ≥ F3, and 26.6% and 0.961 for ≥ F4, respectively) compared with those for the others.

CONCLUSION

ECV in alcoholic liver disease is higher than that in other etiologies in the advanced stages of fibrosis, and etiological differences in ECV affect the staging performance of fibrosis.

Per- and polyfluoroalkyl substances activate UPR pathway, induce steatosis and fibrosis in liver cells

Per- and polyfluoroalkyl substances (PFAS), which include perfluorooctanoic acid (PFOA), heptafluorobutyric acid (HFBA), and perfluorotetradecanoic acid (PFTA), are commonly occurring organic pollutants. Exposure to PFAS affects the immune system, thyroid and kidney function, lipid metabolism, and insulin signaling and is also involved in the development of fatty liver disease and cancer. The molecular mechanisms by which PFAS cause fatty liver disease are not understood in detail. In the current study, we investigated the effect of low physiologically relevant concentrations of PFOA, HFBA, and PFTA on cell survival, steatosis, and fibrogenic signaling in liver cell models. Exposure of PFOA and HFBA (10 to 1000 nM) specifically promoted cell survival in HepaRG and HepG2 cells. PFAS increased the expression of TNFα and IL6 inflammatory markers, increased endogenous reactive oxygen species (ROS) production, and activated unfolded protein response (UPR). Furthermore, PFAS enhanced cell steatosis and fibrosis in HepaRG and HepG2 cells which were accompanied by upregulation of steatosis (SCD1, ACC, SRBP1, and FASN), and fibrosis (TIMP2, p21, TGFβ) biomarkers expression, respectively. RNA-seq data suggested that chronic exposures to PFOA modulated the expression of fatty acid/lipid metabolic genes that are involved in the development of NFALD and fatty liver disease. Collectively our data suggest that acute/chronic physiologically relevant concentrations of PFAS enhance liver cell steatosis and fibrosis by the activation of the UPR pathway and by modulation of NFALD-related gene expression.

Liver Fibrosis in Non-alcoholic Fatty Liver Disease: From Liver Biopsy to Non-invasive Biomarkers in Diagnosis and Treatment

An increasing percentage of people have or are at risk to develop non-alcoholic fatty liver disease (NAFLD) worldwide. NAFLD comprises different stadia going from isolated steatosis to non-alcoholic steatohepatitis (NASH). NASH is a chronic state of liver inflammation that leads to the transformation of hepatic stellate cells to myofibroblasts. These cells produce extra-cellular matrix that results in liver fibrosis. In a normal situation, fibrogenesis is a wound healing process that preserves tissue integrity. However, sustained and progressive fibrosis can become pathogenic. This process takes many years and is often asymptomatic. Therefore, patients usually present themselves with end-stage liver disease e.g., liver cirrhosis, decompensated liver disease or even hepatocellular carcinoma. Fibrosis has also been identified as the most important predictor of prognosis in patients with NAFLD. Currently, only a minority of patients with liver fibrosis are identified to be at risk and hence referred for treatment. This is not only because the disease is largely asymptomatic, but also due to the fact that currently liver biopsy is still the golden standard for accurate detection of liver fibrosis. However, performing a liver biopsy harbors some risks and requires resources and expertise, hence is not applicable in every clinical setting and is unsuitable for screening. Consequently, different non-invasive diagnostic tools, mainly based on analysis of blood or other specimens or based on imaging have been developed or are in development. In this review, we will first give an overview of the pathogenic mechanisms of the evolution from isolated steatosis to fibrosis. This serves as the basis for the subsequent discussion of the current and future diagnostic biomarkers and anti-fibrotic drugs.

The PPAR α/γ Agonist Saroglitazar Improves Insulin Resistance and Steatohepatitis in a Diet Induced Animal Model of Nonalcoholic Fatty Liver Disease

Insulin resistance and hepatic lipid accumulation constitute the metabolic underpinning of nonalcoholic steatohepatitis (NASH). We tested the hypothesis that saroglitazar, a PPAR α/γ agonist would improve NASH in the diet-induced animal model of NAFLD. Mice received chow diet and normal water (CDNW) or high fat western diet and ad lib sugar water (WDSW). After 12 weeks, WDSW fed mice were randomized to receive (1) WDSW alone, (2) WDSW + vehicle, (3) WDSW + pioglitazone or (4) WDSW + saroglitazar for an additional 12 weeks. Compared to mice on WDSW and vehicle controls, mice receiving WDSW + saroglitazar had lower weight, lower HOMA-IR, triglycerides, total cholesterol, and ALT. Saroglitazar improved steatosis, lobular inflammation, hepatocellular ballooning and fibrosis stage. NASH resolved in all mice receiving saroglitazar. These effects were at par with or superior to pioglitazone. Molecular analyses confirmed target engagement and reduced oxidative stress, unfolded protein response and fibrogenic signaling. Transcriptomic analysis further confirmed increased PPAR-target expression and an anti-inflammatory effect with saroglitazar. Lipidomic analyses demonstrated that saroglitazar also reduced triglycerides, diglycerides, sphingomyelins and ceramides. These preclinical data provide a strong rationale for developing saroglitazar for the treatment of NASH in humans.

FGF21: An Emerging Therapeutic Target for Non-Alcoholic Steatohepatitis and Related Metabolic Diseases

The rising global prevalence of obesity, metabolic syndrome, and type 2 diabetes has driven a sharp increase in non-alcoholic fatty liver disease (NAFLD), characterized by excessive fat accumulation in the liver. Approximately one-sixth of the NAFLD population progresses to non-alcoholic steatohepatitis (NASH) with liver inflammation, hepatocyte injury and cell death, liver fibrosis and cirrhosis. NASH is one of the leading causes of liver transplant, and an increasingly common cause of hepatocellular carcinoma (HCC), underscoring the need for intervention. The complex pathophysiology of NASH, and a predicted prevalence of 3-5% of the adult population worldwide, has prompted drug development programs aimed at multiple targets across all stages of the disease. Currently, there are no approved therapeutics. Liver-related morbidity and mortality are highest in more advanced fibrotic NASH, which has led to an early focus on anti-fibrotic approaches to prevent progression to cirrhosis and HCC. Due to limited clinical efficacy, anti-fibrotic approaches have been superseded by mechanisms that target the underlying driver of NASH pathogenesis, namely steatosis, which drives hepatocyte injury and downstream inflammation and fibrosis. Among this wave of therapeutic mechanisms targeting the underlying pathogenesis of NASH, the hormone fibroblast growth factor 21 (FGF21) holds considerable promise; it decreases liver fat and hepatocyte injury while suppressing inflammation and fibrosis across multiple preclinical studies. In this review, we summarize preclinical and clinical data from studies with FGF21 and FGF21 analogs, in the context of the pathophysiology of NASH and underlying metabolic diseases.

Isorhamnetin Alleviates Steatosis and Fibrosis in Mice with Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is the most severe and progressive form of nonalcoholic fatty liver disease (NAFLD), which can lead to life-threatening conditions, however, there is still no approved drug for the treatment of NASH. In this study we used human-like NASH mouse model and treated orally with isorhamnetin at a dose of 50 mg/kg to analyze the effect of isorhamnetin on the progression of NASH. NASH-induced mice represented severe steatosis with inflammation, and fibrosis in liver accompanied with high level of liver injury markers in serum. Isorhamnetin treatment reduced intrahepatic lipid accumulation and TG content by inhibiting de novo lipogenic pathway in NASH-induced mice. Consistent with this, isorhamnetin-treated NASH mice showed improved liver injury markers, reduced collagen deposition as well as decreased gene expression of fibrogenic markers. Taken together, here we showed for the first time that synthesized isorhamnetin alleviates pathologic features of NASH and thus can potentially contribute to NASH drug development.

Non-alcoholic fatty liver disease, liver fibrosis score and cognitive function in middle-aged adults: The Framingham Study

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is common and has been recently related to brain health. We aimed to assess the relationships of NAFLD and its severity, using the NAFLD fibrosis score (NFS), with cognitive performance.

METHODS

Framingham study Offspring and 3rd generation participants were included if they attended exams 9 (2002-2008) and 2 (2008-2011), respectively, were free of dementia and stroke, and did not have excessive alcohol intake. Between 2008 and 2011, participants underwent Multi-detector computed tomography scans of the abdomen to determine NAFLD diagnosis and the NFS was used to categorize the severity of fibrosis. Cross-sectional relationships of NAFLD and the NFS with cognitive testing of memory, abstract reasoning, visual perception, attention and executive function were assessed, while adjusting for multiple cardiometabolic variables including visceral adipose tissue, diabetes and insulin resistance.

RESULTS

Of the 1287 participants (mean age = 61±12 years, 48% men), 378 (29%) had NAFLD. The presence of NAFLD was not associated with cognitive function. However, among those with NAFLD (mean age = 61±12 years; 58% men), high compared to low risk of advanced fibrosis was associated with poorer performance on similarities (β = -2.22 ± 0.83; P = 0.009) and trail-making B minus A (β = -0.11 ± 0.05; P = 0.028), independently of potential confounders.

CONCLUSIONS

Participants with high risk of advanced fibrosis may have poorer cognitive function compared to those with low risk, particularly in executive function and abstract reasoning. Future findings are necessary to evaluate the value of the NFS as a biomarker that predicts cognitive impairment and dementia and to explore the role of hepatic fibrosis in brain health.

Combined effects of ambient particulate matter exposure and a high-fat diet on oxidative stress and steatohepatitis in mice

BACKGROUND

Chronic exposure to ambient particulate matter with aerodynamic diameters < 2.5 (PM2.5) induces oxidative injury and liver pathogenesis. The present study assessed the effect and mechanism of long-term, real-world airborne particulate matter (PM) exposure on oxidative stress and hepatic steatosis in the context of a standard chow diet (STD) and a high-fat diet (HFD); the study further explored whether a combination of PM exposure and HFD treatment exacerbates the adverse effects in mice.

METHODS

C57BL/6J mice fed with STD or HFD (41.26% kcal fat) were exposed to PM or filtered air (FA) for 5 months. Lipid metabolism, oxidative stress and liver pathogenesis were evaluated. Real-time PCR and western blotting were performed to determine gene expression and molecular signal transduction in liver.

RESULTS

Chronic airborne PM exposure impaired oxidative homeostasis, caused inflammation and induced hepatic steatosis in mice. Further investigation found that exposure to real-world PM increased the expression of hepatic Nrf2 and Nrf2-regulated antioxidant enzyme gene. The increased protein expression of the sterol regulatory element binding protein-1c (SREBP-1c) and fatty acid synthase (FAS) in the liver were also observed in PM-exposed groups. Furthermore, the combination of PM exposure and HFD treatment caused a synergistic effect on the changes of lipid accumulation oxidative stress, inflammation in the mouse liver.

CONCLUSIONS

Through in vivo study, we reveal that the combination of real-world ambient PM exposure and HFD treatment aggravates hepatic lipid metabolism disorders, inflammation and oxidative stress. PM exposure may accelerate the progression to non-alcoholic steatohepatitis by regulating SREBP-1c/FAS regulatory axis.

Combination effects of airborne particulate matter exposure and high-fat diet on hepatic fibrosis through regulating the ROS-endoplasmic reticulum stress-TGFβ/SMADs axis in mice

BACKGROUND

Hepatic fibrosis, characterized by an excessive accumulation of extracellular matrix, is associated with toxic substance exposure, chronic infections, mechanical injury, airborne fine particulate matter (PM_2.5) exposure and metabolic disease. This study aimed to investigate the effect and mechanism of long-term, real-world airborne particulate matter (PM) exposure on hepatic fibrosis and further explored whether combination treatment of PM exposure and high-fat diet (HFD) aggravate the adverse effects in mice.

METHODS AND RESULTS

Six-week-old male C57BL/6J mice fed with either a standard chow diet (STD) or an HFD were treated with either filtered air (FA) or PM for 18 weeks. Metabolic parameters, histological examination, gene expression analysis, and Western blot analysis were utilized to measure the effect and mechanism of PM exposure on hepatic fibrosis and to further analyze the synergistic effect of HFD. Subchronic airborne PM exposure induces hepatic fibrosis in mice, and combination treatment of PM exposure and HFD accelerate the adverse effect. Meanwhile, subchronic exposure to real-world PM increased the level of hepatic ROS, and the expression of endoplasmic reticulum (ER) stress markers (GRP78 and CHOP), p-SMAD2 and p-SMAD3, as well as up-regulated TGFβ and collagen 1 in liver tissues. Furthermore, PM exposure and HFD displayed the synergistic effects on these changes in liver.

CONCLUSION

Our findings indicate that airborne PM exposure aggravates HFD -induced hepatic fibrosis. The ROS-ER stress-TGFβ/SMADs regulatory axis mediates the effects of airborne PM exposure on accelerating hepatic fibrosis.

Nanoparticles for the treatment of liver fibrosis

Chronic liver diseases represent a global health problem due to their high prevalence worldwide and the limited available curative treatment options. They can result from various causes, both infectious and noninfectious diseases. The application of nanoparticle (NP) systems has emerged as a rapidly evolving area of interest for the safe delivery of various drugs and nucleic acids for chronic liver diseases. This review presents the pathogenesis, diagnosis and the emerging nanoparticulate systems used in the treatment of chronic liver diseases caused by liver fibrosis. Activated hepatic stellate cell (HSC) is considered to be the main mechanism for liver fibrosis. Ultrasonography and magnetic resonance imaging techniques are widely used noninvasive diagnostic methods for hepatic fibrosis. A variety of nanoparticulate systems are mainly focused on targeting HSC in the treatment of hepatic fibrosis. As early liver fibrosis is reversible by current NP therapy, it is being studied in preclinical as well as clinical trials. Among various nanoparticulate systems, inorganic NPs, liposomes and nanomicelles have been widely studied due to their distinct properties to deliver drugs as well as other therapeutic moieties. Liposomal NPs in clinical trials is considered to be a milestone in the treatment of hepatic fibrosis. Currently, NP therapy for liver fibrosis is updating fast, and hopefully, it can be the future remedy for liver fibrosis.

Mechanisms of hepatic stellate cell activation

Hepatic fibrosis is a dynamic process characterized by the net accumulation of extracellular matrix resulting from chronic liver injury of any aetiology, including viral infection, alcoholic liver disease and NASH. Activation of hepatic stellate cells (HSCs) - transdifferentiation of quiescent, vitamin-A-storing cells into proliferative, fibrogenic myofibroblasts - is now well established as a central driver of fibrosis in experimental and human liver injury. Yet, the continued discovery of novel pathways and mediators, including autophagy, endoplasmic reticulum stress, oxidative stress, retinol and cholesterol metabolism, epigenetics and receptor-mediated signals, reveals the complexity of HSC activation. Extracellular signals from resident and inflammatory cells including macrophages, hepatocytes, liver sinusoidal endothelial cells, natural killer cells, natural killer T cells, platelets and B cells further modulate HSC activation. Finally, pathways of HSC clearance have been greatly clarified, and include apoptosis, senescence and reversion to an inactivated state. Collectively, these findings reinforce the remarkable complexity and plasticity of HSC activation, and underscore the value of clarifying its regulation in hopes of advancing the development of novel diagnostics and therapies for liver disease.

Activation of Insulin-PI3K/Akt-p70S6K Pathway in Hepatic Stellate Cells Contributes to Fibrosis in Nonalcoholic Steatohepatitis

BACKGROUND AND AIMS

Hyperinsulinemia and insulin resistance are hallmark features of nonalcoholic fatty liver disease and steatohepatitis (NASH). It remains unclear whether and how insulin contributes to the development of fibrosis in NASH. In this study, we explored insulin signaling in the regulation of hepatic stellate cell (HSC) activation and the progression of NASH-fibrosis.

METHODS

Phosphorylation of Akt and p70S6K were examined in primary HSC and in a rat model of NASH-fibrosis induced by high-fat and high-cholesterol diet for 24 weeks. HSC activation was analyzed for the changes in cell morphology, intracellular lipid droplets, expression of α-SMA and cell proliferation. The serum markers and histology for NASH-fibrosis were also characterized in animals.

RESULTS

Insulin enhanced the expression of smooth muscle actin-α in quiescent but not in activated HSC in culture. Insulin-mediated activation of the PI3K/Akt-p70S6K pathway was involved in the regulation of profibrogenic effects of insulin. Although insulin did not stimulate HSC proliferation directly, the insulin-PI3K/Akt-p70S6K pathway was necessary for serum-enhanced cell proliferation during initial HSC activation. In a rat model of NASH-fibrosis induced by high-fat and high-cholesterol diet, hyperinsulinemia is associated with the activation of p70S6K and enhanced fibrosis.

CONCLUSION

The insulin-PI3K/Akt-p70S6K pathway plays an important role in the early activation of HSC. The profibrogenic effect of insulin is dependent on the activation stage of HSC. Dysregulation of the insulin pathway likely correlates with the development of fibrosis in NASH, suggesting a potentially novel antifibrotic target of inhibiting insulin signaling in HSC.

Nonalcoholic steatohepatitis-related hepatocellular carcinoma: is there a role for the androgen receptor pathway?

The epidemic of insulin resistance, obesity, and metabolic syndrome has led to the emergence of nonalcoholic steatohepatitis (NASH) as the most common cause of liver disease in the US. Patients with NASH are at an increased risk for hepatic disease-related morbidity and death, and chronic inflammation in NASH patients can lead to hepatocellular carcinoma (HCC). The prevalence of HCC is higher in males than in females, and genetic studies have identified androgen and androgen receptors (ARs) as partially responsible for the gender disparity in the development of liver disease and HCC. Although many factors are known to play important roles in the progression of inflammation in NASH patients, the role of androgen and AR in the progression of NASH to HCC has been understudied. This review summarizes the evidence for a potential role of androgen and the AR pathway in the development of NASH-related HCC and in the treatment of HCC. It has been proposed that AR plays a role in the progression of HCC: inhibitory roles in early stages of hepatocarcinogenesis and tumor-promoting roles in advanced stages. AR can be activated by several pathways, even in the absence of androgen. While AR has been explored as a potential therapeutic target in HCC, several clinical trials have failed to demonstrate a clinical benefit of antiandrogen drugs in HCC. This review discusses the potential reason for these observations and discuss the potential future trials design in this important setting.

Review article: emerging anti-fibrotic therapies in the treatment of non-alcoholic steatohepatitis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) can lead to non-alcoholic steatohepatitis (NASH) and cirrhosis. Fibrosis predicts worse outcomes and mortality. New treatments targeting fibrosis are being investigated to reverse disease progression.

AIM

To review the new pipeline therapeutic agents targeting fibrosis in NASH patients, with particular focus on clinical trials in which reversing fibrosis and portal hypertension are the primary outcomes.

METHODS

The literature was searched in PubMed between January 2000 and January 2016 using search terms non-alcoholic fatty liver disease and NASH, with filters of 'English language'. We focused on fibrosis improvement as the key outcome. We also searched the ClinicalTrials.gov for promising agents that target fibrosis in NASH patients.

RESULTS

Significant advances have been made on approaches targeting fibrosis in NASH patients. Many therapeutic agents are already in development, some of which have shown promising results in preclinical and phase I studies. Novel therapies have entered phase II and III studies targeting fibrosis reversal and/or improvement in portal hypertension. Innovative studies have also started looking into combining these agents, aiming at different mechanisms to maximise therapeutic outcomes. We found five clinical trials in phase II and one in phase III focusing on fibrosis in NASH patients as key outcomes. One of the phase II trials is using combination therapy to target fibrosis.

CONCLUSIONS

Ongoing research studies are already investigating new pathways aimed at reversing fibrosis in NASH patients. Novel therapeutic agents are in development and are expected to offer unique options to NASH patients with advanced fibrosis.

The Therapeutic Promise of Mesenchymal Stem Cells for Liver Restoration

Hepatocyte transplantation aims to provide a functional substitution of liver tissue lost due to trauma or toxins. Chronic liver diseases are associated with inflammation, deterioration of tissue homeostasis, and deprivation of metabolic capacity. Recent advances in liver biology have focused on the pro-regenerative features of mesenchymal stem cells (MSCs). We argue that MSCs represent an attractive therapeutic option to treat liver disease. Indeed, their pleiotropic actions include the modulation of immune reactions, the stimulation of cell proliferation, and the attenuation of cell death responses. These characteristics are highly warranted add-ons to their capacity for hepatocyte differentiation. Undoubtedly, the elucidation of the regenerative mechanisms of MSCs in different liver diseases will promote their versatile and disease-specific therapeutic use.

Insulin Resistance but Not Visceral Adiposity Index Is Associated with Liver Fibrosis in Nondiabetic Subjects with Nonalcoholic Fatty Liver Disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is associated with obesity, type 2 diabetes mellitus, and dyslipidemia. It is well known that the presence of visceral fat increases the risk for metabolic complications of obesity, especially NAFLD. The visceral adiposity index (VAI), a novel marker of visceral fat dysfunction, shows a strong association with insulin resistance and also cardiovascular and cerebrovascular events. However, there is conflicting data regarding the association between VAI and NAFLD. Our aim was to assess the relationship between VAI, insulin resistance, adipocytokines, and liver histology, in nondiabetic subjects with NAFLD.

METHODS

A total of 215 male patients with biopsy-proven NAFLD were included. Among this group, serum levels of adiponectin, tumor necrosis factor-α (TNF-α, interleukin-6 (IL-6), and high-sensitivity C-reactive protein (hsCRP) were measured in 101 patients whose blood samples were available.

RESULTS

High gamma-glutamyl transferase (GGT), high total cholesterol (TC), high triglycerides (TGs), low high-density lipoprotein cholesterol (HDL-C), and presence of metabolic syndrome were significantly associated with higher VAI, although only higher GGT and TC were independent factors on multiple linear regression analysis. On the other hand, no significant association was found between VAI and adiponectin, TNF-α, IL-6, and hsCRP levels. The multivariate analysis of variables in patients with (n=124) and without (n=91) fibrosis showed that only higher homeostasis model assessment of insulin resistance value was independently associated with liver fibrosis.

CONCLUSIONS

Our findings suggest that VAI is not related to the severity of hepatic inflammation or fibrosis in nondiabetic patients with NAFLD. The lack of association between the adipocytokines and VAI also implies that the VAI may not be a significant indictor of the adipocyte functions.

Fibrogenesis and Carcinogenesis in Nonalcoholic Steatohepatitis (NASH): Involvement of Matrix Metalloproteinases (MMPs) and Tissue Inhibitors of Metalloproteinase (TIMPs)

Nonalcoholic steatohepatitis (NASH) is emerging worldwide because life-styles have changed to include much over-eating and less physical activity. The clinical and pathophysiological features of NASH are very different from those of HBV- and HCV-chronic liver diseases. The prognosis of NASH is worse among those with nonalcoholic fatty liver diseases (NAFLD), and some NASH patients show HCC with or without cirrhosis. In the present review we discuss fibrogenesis and the relationship between fibrosis and HCC occurrence in NASH to clarify the role of MMPs and TIMPs in both mechanisms. Previously we proposed MMP and TIMP expression in the multi-step occurrence of HCC from the literature based on viral-derived HCC. We introduce again these expressions during hepatocarcinogenesis and compare them to those in NASH-derived HCC, although the relationship with hepatic stem/progenitor cells (HPCs) invasion remains unknown. Signal transduction of MMPs and TIMPs is also discussed because it is valuable for the prevention and treatment of NASH and NASH-derived HCC.

Cellular and molecular mechanisms in the pathogenesis of liver fibrosis: An update

There have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying liver fibrogenesis. Recent data indicate that the termination of fibrogenic processes and the restoration of deficient fibrolytic pathways may allow the reversal of advanced fibrosis and even cirrhosis. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in liver fibrosis. Activation of hepatic stellate cells (HSCs) remains a central event in fibrosis, complemented by other sources of matrix-producing cells, including portal fibroblasts, fibrocytes and bone marrow-derived myofibroblasts. These cells converge in a complex interaction with neighboring cells to provoke scarring in response to persistent injury. Defining the interaction of different cell types, revealing the effects of cytokines on these cells and characterizing the regulatory mechanisms that control gene expression in activated HSCs will enable the discovery of new therapeutic targets. Moreover, the characterization of different pathways associated with different etiologies aid in the development of disease-specific therapies. This article outlines recent advances regarding the cellular and molecular mechanisms involved in liver fibrosis that may be translated into future therapies. The pathogenesis of liver fibrosis associated with alcoholic liver disease, non-alcoholic fatty liver disease and viral hepatitis are also discussed to emphasize the various mechanisms involved in liver fibrosis.

Primary hepatocellular carcinoma and metabolic syndrome: An update

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy. The incidence of hepatocellular carcinoma has increased dramatically by 80% over the past two decades in the United States. Numerous basic science and clinical studies have documented a strong association between hepatocellular carcinoma and the metabolic syndrome. These studies have documented that, in most patients, non-alcoholic fatty liver disease is the hepatic manifestation of the metabolic syndrome, which may progress to hepatocellular carcinoma through the cirrhotic process. However, minority of patients with non-alcoholic fatty liver disease may progress to hepatocellular carcinoma without cirrhosis. This review summarizes the current literature of the link between hepatocellular carcinoma and metabolic syndrome with special emphasis on various components of the metabolic syndrome including risk of association with obesity, diabetes mellitus, hyperlipidemia, and hypertension. Current understanding of pathophysiology, clinical features, treatments, outcomes, and surveillance of hepatocellular carcinoma in the background of metabolic syndrome and non-alcoholic fatty liver disease is reviewed. With the current epidemic of metabolic syndrome, the number of patients with non-alcoholic fatty liver disease is increasing. Subsequently, it is expected that the incidence and prevalence of HCC will also increase. It is very important for the scientific community to shed more light on the pathogenesis of HCC with metabolic syndrome, both with and without cirrhosis. At the same time it is also important to quantify the risk of hepatocellular carcinoma associated with the metabolic syndrome in a prospective setting and develop surveillance recommendations for detection of hepatocellular carcinoma in patients with metabolic syndrome.