Determinants of fibrosis progression and regression in NASH

Animal Models of Fibrosis in Nonalcoholic Steatohepatitis: Do They Reflect Human Disease?

Nonalcoholic steatohepatitis (NASH) is one of the most common chronic liver diseases in the world, yet no pharmacotherapies are available. The lack of translational animal models is a major barrier impeding elucidation of disease mechanisms and drug development. Multiple preclinical models of NASH have been proposed and can broadly be characterized as diet-induced, deficiency-induced, toxin-induced, genetically induced, or a combination of these. However, very few models develop advanced fibrosis while still reflecting human disease etiology or pathology, which is problematic since fibrosis stage is considered the best prognostic marker in patients and an important endpoint in clinical trials of NASH. While mice and rats predominate the NASH research, several other species have emerged as promising models. This review critically evaluates animal models of NASH, focusing on their ability to develop advanced fibrosis while maintaining their relevance to the human condition.

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) for the management of nonalcoholic fatty liver disease (NAFLD): A systematic review

There are no licensed drugs for nonalcoholic fatty liver disease (NAFLD), and there is a lack of consensus on the best outcome measures for controlled trials. This systematic review aimed to evaluate the efficacy of GLP-1 RAs in the management of NAFLD, the degree of heterogeneity in trial design and the robustness of conclusions drawn from these clinical trials. We searched publication databases and clinical trial registries through 2 November 2019 for clinical trials with NAFLD. We evaluated improvements in histological findings, noninvasive markers of hepatic steatosis, inflammation, and fibrosis, insulin resistance and anthropometric measures. Our final analysis included 24 clinical trials, comprising 6313 participants with a mean duration of 37 weeks. Four clinical trials, including RCT (n = 1), single-arm studies (n = 2) and case series studies (n = 1), used biopsy-confirmed liver histological change as their end-points. The remaining studies (n = 20) used surrogate end-points. GLP-1 RAs were effective for the improvement in hepatic inflammation, hepatic steatosis and fibrosis. More importantly, GLP-1 RAs showed promise in improving the histological features of NASH. In addition, 8 ongoing trials were identified. In this systematic review of published and ongoing clinical trials of the efficacy of GLP-1RAs for NAFLD, we found that GLP-1 RAs are effective for hepatic steatosis and inflammation, with the potential to reverse fibrosis. Further prospective studies of sufficient duration using histological end-points are needed to fully assess the efficacy of GLP-1 RAs in the management of NAFLD.

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.

Non-alcoholic fatty liver disease: A major challenge in type 2 diabetes mellitus (Review)

Non-alcoholic fatty liver disease (NAFLD) has a high prevalence in type 2 diabetes mellitus (T2DM) patients, being one of the disorders with a relevant global burden. Cross-sectional studies have shown that patients with T2DM and NAFLD have a higher prevalence of liver fibrosis, compared with the general population. Patients with non-alcoholic steatohepatitis (NASH) and T2DM have an increased mortality and morbidity, therefore they generate substantial health care costs. NASH worsens chronic diabetes complications, and T2DM aggravate the NASH progression to fibrosis, cirrhosis, and even hepatocellular carcinoma (HCC). The objectives in NAFLD and NASH therapy are to reduce disease activity, to slow down progression of fibrosis, and to lower the risk factors. Unfortunately, there are no specific validated pharmacological therapies. Several trials have demonstrated that anti-diabetic agents such as thiazolidindiones, sodium-glucose co-transporter inhibitors, glucagon like peptide-1 receptor analogs, or dipeptidyl peptidase-4 inhibitors might have complimentary benefits for patients with NAFLD. Some of the effect on reducing steatosis and fibrosis is explained by the weight loss these treatments produce. A goal in standard care is developing screening tools, early and non-invasive diagnosis methods, studying the pleiotropic effects of drugs, together with newer therapeutic agents, which can target mutual pathogenic mechanisms for diabetes and liver disease.

Update to the Society of Radiologists in Ultrasound Liver Elastography Consensus Statement

This multidisciplinary update of the Society of Radiologists in Ultrasound consensus statement on liver elastography incorporates the large volume of new information available in the literature since the initial publication. The recommended procedure for acquiring stiffness measurements is reviewed. There has been substantial improvement in the acoustic radiation force impulse (ARFI) technology-most notably the addition of a quality assessment of the shear wave propagation. Due to the efforts of the Quantitative Imaging Biomarkers Alliance, or QIBA, the variability of liver stiffness measurements between systems had decreased. There are now effective treatments for hepatitis B and hepatitis C, and follow-up after effective treatment should be based on the use of the delta change of the value obtained at viral eradication or suppression. Because the detection of compensated advanced chronic liver disease (cACLD) is very important, the new guidelines are made based on the probability of cACLD for given stiffness values. The panel recommends a vendor-neutral rule of four for interpretation for ARFI techniques. This new method simplifies interpretation of liver stiffness results and is more clinically relevant.

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.

Non-invasive diagnosis of non-alcoholic steatohepatitis and advanced fibrosis in Japan: A targeted literature review

Despite the invasive nature of liver biopsy, it remains the current standard for diagnosing non-alcoholic steatohepatitis (NASH) and fibrosis staging. Given the rising prevalence of non-alcoholic fatty liver disease (NAFLD) in Japan, there is a need for reliable non-invasive tests to accurately and efficiently identify NASH and advanced (F3/F4) fibrosis. A review of published works from English and Japanese sources was undertaken in PubMed, Embase, and Ichushi Web to identify studies reporting diagnostic characteristics of NITs in biopsy-proven Japanese NAFLD/NASH patients including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the receiver operating characteristic curve. The performance of non-invasive tests for two diagnostic questions were assessed, namely: (i) identifying NASH cases among NAFLD; and (ii) distinguishing advanced fibrosis (F3-4) from milder fibrosis (F0-2). Twenty-five studies reported outcomes for serum biomarkers, imaging, scoring systems, and novel complex techniques (based on multivariable regression models) for both diagnostic questions. Serum biomarkers were the most commonly assessed method for NASH identification, whereas scoring systems and imaging techniques were most commonly studied for fibrosis staging. In general, tests for NASH identification showed higher PPVs than NPVs, suggesting their usefulness in identifying probable NASH cases. The reverse was observed for fibrosis staging, with higher NPVs than PPVs, suggesting their use in excluding patients at low risk of F3/F4 disease rather than identifying definite F3/F4 fibrosis. In Japanese studies, simple scoring systems and imaging techniques showed particular usefulness in prediction of fibrosis staging, and combinations of serum biomarkers showed diagnostic potential for NASH screening.

Metabolic inflammation as an instigator of fibrosis during non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive storage of fatty acids in the form of triglycerides in hepatocytes. It is most prevalent in western countries and includes a wide range of clinical and histopathological findings, namely from simple steatosis to steatohepatitis and fibrosis, which may lead to cirrhosis and hepatocellular cancer. The key event for the transition from steatosis to fibrosis is the activation of quiescent hepatic stellate cells (qHSC) and their differentiation to myofibroblasts. Pattern recognition receptors (PRRs), expressed by a plethora of immune cells, serve as essential components of the innate immune system whose function is to stimulate phagocytosis and mediate inflammation upon binding to them of various molecules released from damaged, apoptotic and necrotic cells. The activation of PRRs on hepatocytes, Kupffer cells, the resident macrophages of the liver, and other immune cells results in the production of proinflammatory cytokines and chemokines, as well as profibrotic factors in the liver microenvironment leading to qHSC activation and subsequent fibrogenesis. Thus, elucidation of the inflammatory pathways associated with the pathogenesis and progression of NAFLD may lead to a better understanding of its pathophysiology and new therapeutic approaches.

Metabolic Inflammation-A Role for Hepatic Inflammatory Pathways as Drivers of Comorbidities in Nonalcoholic Fatty Liver Disease?

Nonalcoholic fatty liver disease (NAFLD) is a global and growing health concern. Emerging evidence points toward metabolic inflammation as a key process in the fatty liver that contributes to multiorgan morbidity. Key extrahepatic comorbidities that are influenced by NAFLD are type 2 diabetes, cardiovascular disease, and impaired neurocognitive function. Importantly, the presence of nonalcoholic steatohepatitis and advanced hepatic fibrosis increase the risk for systemic comorbidity in NAFLD. Although the precise nature of the crosstalk between the liver and other organs has not yet been fully elucidated, there is emerging evidence that metabolic inflammation-in part, emanating from the fatty liver-is the engine that drives cellular dysfunction, cell death, and deleterious remodeling within various body tissues. This review describes several inflammatory pathways and mediators that have been implicated as links between NAFLD and type 2 diabetes, cardiovascular disease, and neurocognitive decline.

One-Carbon Metabolism in Fatty Liver Disease and Fibrosis: One-Carbon to Rule Them All

Nonalcoholic fatty liver disease (NAFLD) is a term used to characterize a range of disease states that involve the accumulation of fat in the liver but are not associated with excessive alcohol consumption. NAFLD is a prevalent disease that can progress to organ damage like liver cirrhosis and hepatocellular carcinoma. Many animal models have demonstrated that one-carbon metabolism is strongly associated with NAFLD. Phosphatidylcholine is an important phospholipid that affects hepatic lipid homeostasis and de novo synthesis of this phospholipid is associated with NAFLD. However, one-carbon metabolism serves to support all cellular methylation reactions and catabolism of methionine, serine, glycine, choline, betaine, tryptophan, and histidine. Several different pathways within one-carbon metabolism that play important roles in regulating energy metabolism and immune function have received less attention in the study of fatty liver disease and fibrosis. This review examines what we have learned about hepatic lipid metabolism and liver damage from the study of one-carbon metabolism thus far and highlights unexplored opportunities for future research.

Systematic Literature Review and Critical Appraisal of Health Economic Models Used in Cost-Effectiveness Analyses in Non-Alcoholic Steatohepatitis: Potential for Improvements

BACKGROUND

Non-alcoholic steatohepatitis (NASH) is a severe, typically progressive form of non-alcoholic fatty liver disease (NAFLD). The global prevalence of NASH is increasing, driven partly by the global increase in obesity and type 2 diabetes mellitus (T2DM), such that NASH is now a leading cause of cirrhosis. There is currently an unmet clinical need for efficacious and cost-effective treatments for NASH; no pharmacologic agents have an approved indication for NASH.

OBJECTIVE

Our objective was to summarise and critically appraise published health economic models of NASH, to evaluate their quality and suitability for use in the assessment of novel treatments for NASH, and to identify knowledge gaps, challenges and opportunities for future modelling.

METHODS

A systematic literature review was performed using the MEDLINE, Embase, Cochrane Library and EconLit databases to identify published health economic analyses in patients with NAFLD or NASH. Supplementary hand searches of grey literature were also performed. Articles published up to November 2019 were included in the review. Quality assessment of identified studies was also performed.

RESULTS

A total of 19 articles comprising 16 unique models including either NAFLD as a whole or NASH alone were included in the review. Structurally, most models had a state-transition component; in terms of health states, two different approaches to early disease states were used, modelling either progression through fibrosis stages or NAFLD/NASH-specific health states. Conditions that frequently co-exist with NASH, such as obesity, T2DM and cardiovascular disease were not captured in models identified here. Late-stage complications such as cirrhosis, decompensated cirrhosis and hepatocellular carcinoma were consistently included, but input data (e.g. costs, utilities and transition probabilities) for late-stage complications were frequently sourced from other liver disease areas. The quality of included studies was heterogenous, and only a small proportion of studies reported internal and external validation processes.

CONCLUSION

The health economic models identified in this review are associated with limitations primarily driven by a lack of NASH-specific data. Identified models also largely overlooked the intricate association between NASH and other conditions, including obesity and T2DM, and did not capture the increased risk of cardiovascular events associated with NASH. High-quality, transparent, validated health economic models of NASH will be required to evaluate the cost effectiveness of treatments currently in development, particularly compounds that may target other non-hepatic outcomes.

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.

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.

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.

Collagen biology and non-invasive biomarkers of liver fibrosis

There is an unmet need for high-quality liquid biomarkers that can safely and reproducibly predict the stage of fibrosis and the outcomes of chronic liver disease (CLD). The requirement for such markers has intensified because of the high global prevalence of diseases such as non-alcoholic fatty liver disease (NAFLD). In particular, there is a need for diagnostic and prognostic tools, as well as predictive biomarkers that reflect the efficacy of interventions, as described by the BEST criteria (Biomarkers, EndpointS, and other Tools Resource). This review covers the various liver collagens, their functional role in tissue homeostasis and delineates the common nomenclature for biomarkers based on BEST criteria. It addresses the common confounders affecting serological biomarkers, and describes defined collagen epitope biomarkers that originate from the dynamic processes of extracellular matrix (ECM) remodelling during liver injury.

Serum soluble sialic acid-binding immunoglobulin-like lectin-7 concentration as an indicator of liver macrophage activation and advanced fibrosis in patients with non-alcoholic fatty liver disease

AIM

Non-alcoholic fatty liver disease (NAFLD) is a leading cause of liver disease worldwide. Because liver fibrosis is associated with the long-term prognosis of patients with NAFLD, there is an urgent need for non-invasive markers of liver fibrosis. Sialic acid-binding immunoglobulin-like lectin-7 (Siglec-7) is an immunomodulatory molecule expressed on various immune cells, including macrophages, which plays a key role in liver inflammation and fibrosis in NAFLD. We aimed to determine whether serum levels of soluble Siglec-7 (sSiglec-7) could have utility at a marker of fibrosis in this patient population.

METHODS

We examined serum samples from 93 NAFLD patients and 19 healthy donors for macrophage-associated protein, including sSiglec-7, soluble CD163, and YKL-40, and examined their correlation with liver fibrosis scores, tissue elastography, and histological findings. Independent factors associated with advanced fibrosis were analyzed using a logistic regression model and a decision tree. To clarify the source of sSiglec-7, we examined its expression in liver tissue-derived macrophages and cultured monocyte-derived macrophages.

RESULTS

Serum sSiglec-7 levels were significantly higher in NAFLD patients compared with healthy donors, and correlated positively with sCD163 and YKL-40 levels. Serum sSiglec-7 was an independent diagnostic marker with high specificity (96.3%) for advanced fibrosis (F3 and F4) in NAFLD patients. Siglec-7 was mainly expressed on CCR2⁺ macrophages in the liver, and sSiglec-7 production by monocyte-derived macrophages in vitro was increased after stimulation by pro-inflammatory factors.

CONCLUSIONS

Elevated serum sSiglec-7 could serve as an independent marker with high specificity for advanced liver fibrosis in patients with NAFLD.

The acute effect of metabolic cofactor supplementation: a potential therapeutic strategy against non-alcoholic fatty liver disease

The prevalence of non-alcoholic fatty liver disease (NAFLD) continues to increase dramatically, and there is no approved medication for its treatment. Recently, we predicted the underlying molecular mechanisms involved in the progression of NAFLD using network analysis and identified metabolic cofactors that might be beneficial as supplements to decrease human liver fat. Here, we first assessed the tolerability of the combined metabolic cofactors including l-serine, N-acetyl-l-cysteine (NAC), nicotinamide riboside (NR), and l-carnitine by performing a 7-day rat toxicology study. Second, we performed a human calibration study by supplementing combined metabolic cofactors and a control study to study the kinetics of these metabolites in the plasma of healthy subjects with and without supplementation. We measured clinical parameters and observed no immediate side effects. Next, we generated plasma metabolomics and inflammatory protein markers data to reveal the acute changes associated with the supplementation of the metabolic cofactors. We also integrated metabolomics data using personalized genome-scale metabolic modeling and observed that such supplementation significantly affects the global human lipid, amino acid, and antioxidant metabolism. Finally, we predicted blood concentrations of these compounds during daily long-term supplementation by generating an ordinary differential equation model and liver concentrations of serine by generating a pharmacokinetic model and finally adjusted the doses of individual metabolic cofactors for future human clinical trials.

Pathophysiological-based treatments of complications of cirrhosis

Detailed knowledge and understanding of the pathophysiological mechanisms and changes in hepatic and splanchnic function leading to the development of haemodynamic changes and portal hypertension in patients with cirrhosis are essential since it guides the search for targets to ameliorate liver-related abnormalities. Recent research has focused on the gut-liver axis, changes in intestinal permeability, translocation of bacterial products, and inflammation as important drivers of haemodynamic alterations and thereby targets for treatment. Additionally, treatment strategies should focus on microbiotic modulation, antiangiogenics, anti-inflammatory strategies, and modulation of bile acid metabolism. This paper aims to review contemporary pathophysiological-based treatment principles of the major complications of cirrhosis and portal hypertension and future targets for treatment.

Extracellular Vesicles in NAFLD/ALD: From Pathobiology to Therapy

In recent years, knowledge on the biology and pathobiology of extracellular vesicles (EVs) has exploded. EVs are submicron membrane-bound structures secreted from different cell types containing a wide variety of bioactive molecules (e.g., proteins, lipids, and nucleic acids (coding and non-coding RNA) and mitochondrial DNA). EVs have important functions in cell-to-cell communication and are found in a wide variety of tissues and body fluids. Better delineation of EV structures and advances in the isolation and characterization of their cargo have allowed the diagnostic and therapeutic implications of these particles to be explored. In the field of liver diseases, EVs are emerging as key players in the pathogenesis of both nonalcoholic liver disease (NAFLD) and alcoholic liver disease (ALD), the most prevalent liver diseases worldwide, and their complications, including development of hepatocellular carcinoma. In these diseases, stressed/damaged hepatocytes release large quantities of EVs that contribute to the occurrence of inflammation, fibrogenesis, and angiogenesis, which are key pathobiological processes in liver disease progression. Moreover, the specific molecular signatures of released EVs in biofluids have allowed EVs to be considered as promising candidates to serve as disease biomarkers. Additionally, different experimental studies have shown that EVs may have potential for therapeutic use as a liver-specific delivery method of different agents, taking advantage of their hepatocellular uptake through interactions with specific receptors. In this review, we focused on the most recent findings concerning the role of EVs as new structures mediating autocrine and paracrine intercellular communication in both ALD and NAFLD, as well as their potential use as biomarkers of disease severity and progression. Emerging therapeutic applications of EVs in these liver diseases were also examined, along with the potential for successful transition from bench to clinic.

Disruption of hepatic one-carbon metabolism impairs mitochondrial function and enhances macrophage activity in methionine-choline-deficient mice

One-carbon metabolism is a collection of metabolic cycles that supports methylation and provides one-carbon bound folates for the de novo synthesis of purine and thymidine nucleotides. The methylation of phosphatidylethanolamine to form choline has been extensively studied in the context of fatty liver disease. However, the role of one-carbon metabolism in supporting nucleotide synthesis during liver damage has not been addressed. The objective of this study is to determine how the disruption of one-carbon metabolism influences nucleotide metabolism in the liver after dietary methionine and choline restriction. Mice (n=8) were fed a methionine-choline-deficient or control diet for 3 weeks. We treated mice with the compound alloxazine (0.5 mg/kg), a known adenosine receptor antagonist, every second day during the final week of feeding to probe the function of adenosine signaling during liver damage. We found that concentrations of several hepatic nucleotides were significantly lower in methionine- and choline-deficient mice vs. controls (adenine: 13.9±0.7 vs. 10.1±0.6, guanine: 1.8±0.1 vs. 1.4±0.1, thymidine: 0.0122±0.0027 vs. 0.0059±0.0027 nmol/mg dry tissue). Treatment of alloxazine caused a specific decrease in thymidine nucleotides, decrease in mitochondrial content in the liver and exacerbation of steatohepatitis as shown by the increased hepatic lipid content and altered macrophage morphology. This study demonstrates a role for one-carbon metabolism in supporting de novo nucleotide synthesis and mitochondrial function during liver damage.

Evaluation of the histological variability of core and wedge biopsies in nonalcoholic fatty liver disease in bariatric surgical patients

BACKGROUND

Liver biopsy remains the gold standard for characterizing and evaluating treatment response in nonalcoholic fatty liver disease (NAFLD). Liver heterogeneity and sampling variability can affect the reliability of results. This study aimed to compare histological variability of intraoperative wedge and core liver biopsies from different lobes in bariatric patients, to better inform surgeons on biopsy method and guide interpretation of results.

METHODS

We prospectively recruited bariatric surgical patients. Intraoperative core biopsies were taken from the left and right lobe, with a wedge biopsy taken from the left. All biopsies were graded by a specialist liver pathologist, blinded to clinical details and biopsy site. Concordance of histological findings between sites was evaluated.

RESULTS

There were 91 participants (72.2% female), mean age 46.8 ± 12.0 years, body mass index 45.9 ± 9.4 kg/m². There was no significant pattern for up- or down-grading disease dependent on biopsy technique. Moderate to strong agreement was seen in the presence of NAFLD and nonalcoholic steatohepatitis (NASH, κ = 0.609-0.865, p < 0.001) between biopsy sites. Individual components (steatosis, inflammation, ballooning) showed weaker agreement (κ = 0.386-0.656, p < 0.01). Fibrosis showed particularly poor agreement (κ = 0.223-0.496, p < 0.01). Detection of pathology improved with a combination of biopsy techniques, compared to a single biopsy method.

CONCLUSION

Overall diagnosis of NAFLD or NASH shows good agreement between biopsy sites, but individual components, particularly fibrosis stage, vary significantly. Clinicians should consider biopsies from varied sites, to better assess liver disease severity. These data have important implications in fibrosis assessment of NAFLD and are relevant in the interpretation of histological efficacy of investigational pharmacotherapies.

TRIAL REGISTRATION

ACTRN12615000875505 (Australian Clinical Trials Register).

Activation of BK Channels Prevents Hepatic Stellate Cell Activation and Liver Fibrosis Through the Suppression of TGFβ1/SMAD3 and JAK/STAT3 Profibrotic Signaling Pathways

Large-conductance and Ca²⁺-activated K⁺ (BK) channels are expressed in human hepatic stellate cells (HSCs), where they have roles in normal hepatic microcirculation, as well as in portal hypertension in liver cirrhosis through the regulation of contractility in activated HSCs. Nevertheless, whether BK channel activity exerts protective effects against aberrant HSC activation and hepatic fibrosis is unknown. Here, we report that BK channels are expressed in activated primary rat HSCs as well as in a human HSC line. Moreover, whole-cell K⁺ currents recorded from activated HSCs were markedly increased by exposure to rottlerin, a BK channel-specific activator, but were inhibited by treatment with the BK channel-specific inhibitor, paxilline, suggesting that BK channels are functional in activated HSCs. Overexpression but not downregulation of the BK channel pore-forming alpha subunit, KCNMA1, led to reduced migration and collagen expression in activated HSCs. Consistently, rottlerin treatment suppressed the fibrogenic cell function both in vitro and in CCl₄-induced liver fibrosis in vivo. Microarray and pathway analysis, combined with a luciferase reporter assay and western blotting, further showed that rottlerin treatment led to a significant downregulation of the profibrotic TGFβ1/SMAD3 and JAK/STAT3 signaling pathways, both in vitro and in vivo. Our findings not only link BK channel function to profibrotic signaling pathways, but also provide evidence that BK channel activation represents a promising therapeutic strategy for the treatment of liver fibrosis.

The role of the sphingolipid pathway in liver fibrosis: an emerging new potential target for novel therapies

Sphingolipids (SL) are a family of bioactive lipids and a major cellular membrane structural component. SLs include three main compounds: ceramide (Cer), sphingosine (Sp), and sphingosine-1-phosphate (S-1P), all of which have emerging roles in biological functions in cells, especially in the liver. They are under investigation in various liver diseases, including cirrhosis and end-stage liver disease. In this review, we provide an overview on the role of SLs in liver pathobiology and focus on their potential role in the development of hepatic fibrosis. We describe recent evidence and suggest SLs are a promising potential therapeutic target for the treatment of liver disease and fibrosis.

Hepatocyte Injury and Hepatic Stem Cell Niche in the Progression of Non-Alcoholic Steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease characterized by lipid accumulation in hepatocytes in the absence of excessive alcohol consumption. The global prevalence of NAFLD is constantly increasing. NAFLD is a disease spectrum comprising distinct stages with different prognoses. Non-alcoholic steatohepatitis (NASH) is a progressive condition, characterized by liver inflammation and hepatocyte ballooning, with or without fibrosis. The natural history of NAFLD is negatively influenced by NASH onset and by the progression towards advanced fibrosis. Pathogenetic mechanisms and cellular interactions leading to NASH and fibrosis involve hepatocytes, liver macrophages, myofibroblast cell subpopulations, and the resident progenitor cell niche. These cells are implied in the regenerative trajectories following liver injury, and impairment or perturbation of these mechanisms could lead to NASH and fibrosis. Recent evidence underlines the contribution of extra-hepatic organs/tissues (e.g., gut, adipose tissue) in influencing NASH development by interacting with hepatic cells through various molecular pathways. The present review aims to summarize the role of hepatic parenchymal and non-parenchymal cells, their mutual influence, and the possible interactions with extra-hepatic tissues and organs in the pathogenesis of NAFLD.

Lipoatrophy-Associated Insulin Resistance and Hepatic Steatosis are Attenuated by Intake of Diet Rich in Omega 3 Fatty Acids

SCOPE

Glucose homeostasis and progression of nonalcoholic fatty liver disease (NAFLD) and hepatomegaly in severe lipoatrophic mice and their modulation by intake of a diet rich in omega 3 (n-3) fatty acids (HFO) are evaluated.

METHODS AND RESULTS

Severe lipoatrophic mice induced by PPAR-γ deletion exclusively in adipocytes (A-PPARγ KO) and littermate controls (A-PPARγ WT) are evaluated for glucose homeostasis and liver mass, proteomics, lipidomics, inflammation, and fibrosis. Lipoatrophic mice are heavier than controls, severely glucose intolerant, and hyperinsulinemic, and develop NAFLD characterized by increased liver glycogen, triacylglycerol, and diacylglycerol contents, mitotic index, apoptosis, inflammation, steatosis score, fibrosis, and fatty acid synthase (FAS) content and activity. Lipoatrophic mice also display liver enrichment with monounsaturated in detriment of polyunsaturated fatty acids including n-3 fatty acids, and increased content of cardiolipin, a tetracyl phospholipid exclusively found at the mitochondria inner membrane. Administration of a high-fat diet rich in n-3 fatty acids (HFO) to lipoatrophic mice enriches liver with n-3 fatty acids, reduces hepatic steatosis, FAS content and activity, apoptosis, inflammation, and improves glucose homeostasis.

CONCLUSION

Diet enrichment with n-3 fatty acids improves glucose homeostasis and reduces liver steatosis and inflammation without affecting hepatomegaly in severe lipoatrophic mice.

Adaptive immunity: an emerging player in the progression of NAFLD

In the past decade, nonalcoholic fatty liver disease (NAFLD) has become a leading cause of chronic liver disease and cirrhosis, as well as an important risk factor for hepatocellular carcinoma (HCC). NAFLD encompasses a spectrum of liver lesions, including simple steatosis, steatohepatitis and fibrosis. Although steatosis is often harmless, the lobular inflammation that characterizes nonalcoholic steatohepatitis (NASH) is considered a driving force in the progression of NAFLD. The current view is that innate immune mechanisms represent a key element in supporting hepatic inflammation in NASH. However, increasing evidence points to the role of adaptive immunity as an additional factor promoting liver inflammation. This Review discusses data regarding the role of B cells and T cells in sustaining the progression of NASH to fibrosis and HCC, along with the findings that antigens originating from oxidative stress act as a trigger for immune responses. We also highlight the mechanisms affecting liver immune tolerance in the setting of steatohepatitis that favour lymphocyte activation. Finally, we analyse emerging evidence concerning the possible application of immune modulating treatments in NASH therapy.

Nonalcoholic Steatohepatitis Is Associated With Liver-Related Outcomes and All-Cause Mortality in Chronic Hepatitis B

BACKGROUND AND AIMS

Chronic hepatitis B (CHB) and nonalcoholic fatty liver disease are increasingly observed together in clinical practice, and development of nonalcoholic steatohepatitis (NASH) represents another leading cause of liver-related morbidity and mortality. Our aims were to determine whether biopsy-proven NASH impacts clinical outcomes in CHB patients and assess prognostic risk factors.

APPROACH AND RESULTS

CHB patients attending two tertiary centers in North America and Europe over 13 years with available clinical and biopsy data were included. Patients were categorized as no-NASH or probable/definite NASH based on standardized histological assessment. Clinical events (death, decompensation, transplant, and hepatoma) were evaluated, and Kaplan-Meier survival estimates and Cox proportional hazards regression were used to analyze the incidence of events. There were 1,089 CHB patients, classified as no-NASH (n = 904, 83%) or NASH (n = 185, 17%), with 52 (6%) versus 27 (15%) experiencing outcome events during follow-up, respectively. In the multivariable analysis adjusting for age, sex, hepatitis B e antigen serostatus, and diabetes, the presence of NASH and concomitant advanced fibrosis (AF) was significantly associated with clinical outcomes (hazard ratio [95% confidence interval], 4.8 [2.6-9.0], P < 0.01) when compared to absence of NASH and AF (reference). NASH and AF were associated with a greater risk of outcomes compared to AF (P = 0.01) or NASH alone (P < 0.01). Of the three histological determinants of NASH, ballooning and inflammation, but not steatosis, were independently associated with clinical outcomes (P < 0.05) in place of NASH. NASH was significantly associated with increased risk of hepatocellular carcinoma and death (P < 0.01) but not decompensation (P = 0.33).

CONCLUSIONS

In our large combined tertiary center cohort, patients with concomitant NASH and CHB had more AF and shorter time to development of liver-related outcomes or death compared to patients with CHB alone. Among patients with AF, superimposed NASH predicted poorer clinical outcomes.

Investigating fibrosis and inflammation in an ex vivo NASH murine model

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease, characterized by excess fat accumulation (steatosis). Nonalcoholic steatohepatitis (NASH) develops in 15-20% of NAFLD patients and frequently progresses to liver fibrosis and cirrhosis. We aimed to develop an ex vivo model of inflammation and fibrosis in steatotic murine precision-cut liver slices (PCLS). NASH was induced in C57Bl/6 mice on an amylin and choline-deficient l-amino acid-defined (CDAA) diet. PCLS were prepared from steatohepatitic (sPCLS) and control (cPCLS) livers and cultured for 48 h with LPS, TGFβ1, or elafibranor. Additionally, C57Bl/6 mice were placed on CDAA diet for 12 wk to receive elafibranor or vehicle from weeks 7 to 12. Effects were assessed by transcriptome analysis and procollagen Iα1 protein production. The diets induced features of human NASH. Upon culture, all PCLS showed an increased gene expression of fibrosis- and inflammation-related markers but decreased lipid metabolism markers. LPS and TGFβ1 affected sPCLS more pronouncedly than cPCLS. TGFβ1 increased procollagen Iα1 solely in cPCLS. Elafibranor ameliorated fibrosis and inflammation in vivo but not ex vivo, where it only increased the expression of genes modulated by PPARα. sPCLS culture induced inflammation-, fibrosis-, and lipid metabolism-related transcripts, explained by spontaneous activation. sPCLS remained responsive to proinflammatory and profibrotic stimuli on gene expression. We consider that PCLS represent a useful tool to reproducibly study NASH progression. sPCLS can be used to evaluate potential treatments for NASH, as demonstrated in our elafibranor study, and serves as a model to bridge results from rodent studies to the human system.NEW & NOTEWORTHY This study showed that nonalcoholic steatohepatitis can be studied ex vivo in precision-cut liver slices obtained from murine diet-induced fatty livers. Liver slices develop a spontaneous inflammatory and fibrogenic response during culture that can be augmented with specific modulators. Additionally, the model can be used to test the efficacy of pharmaceutical compounds (as shown in this investigation with elafibranor) and could be a tool for preclinical assessment of potential therapies.

Natural History of Nonalcoholic Fatty Liver Disease: Implications for Clinical Practice and an Individualized Approach

Nonalcoholic fatty liver disease (NAFLD) is becoming the most prevalent liver disease worldwide, associated with epidemics of overweight and resulting metabolic syndrome (MetS). Around 20-30% of patients with NAFLD develop progressive liver fibrosis, which is the most important predictor of liver-related and overall morbidity and mortality. In contrast to classical understanding, no significant association has been demonstrated between the inflammatory component of NAFLD, i.e., nonalcoholic steatohepatitis (NASH), and the adverse clinical outcomes. Older age (>50 years) and presence of type 2 diabetes mellitus, in addition to some genetic variants, are most consistently reported indicators of increased risk of having liver fibrosis. However, critical driving force for the progression of fibrosis and risk factors for this have still not been fully elucidated. Apart from the genetic profile, gut dysbiosis, weight gain, worsening of insulin resistance, and worsening of liver steatosis represent candidate factors associated with unfavourable development of liver disease. Cardiovascular events, extrahepatic malignancies, and liver-related deaths are the leading causes of mortality in NAFLD. As patients with advanced fibrosis are under highest risk of adverse clinical outcomes, efforts should be made to recognize individuals under risk and rule out the presence of this stage of fibrosis, preferably by using simple noninvasive tools. This process should start at the primary care level by using validated biochemical tests, followed by direct serum tests for fibrosis or elastography in the remaining patients. Patients with advanced fibrosis should be referred to hepatologists for aggressive lifestyle modification and correction of the components of MetS, and cirrhotic patients should be screened for hepatocellular carcinoma and oesophageal varices.

Ataxia telangiectasia mutated pathway disruption affects hepatic DNA and tissue damage in nonalcoholic fatty liver disease

To overcome the rising burdens of nonalcoholic fatty liver disease, mechanistic linkages in mitochondrial dysfunction, inflammation and hepatic injury are critical. As ataxia telangiectasia mutated (ATM) gene oversees DNA integrity and mitochondrial homeostasis, we analyzed mRNAs and total proteins or phosphoproteins related to ATM gene by arrays in subjects with healthy liver, fatty liver or nonalcoholic steatohepatitis. Functional genomics approaches were used to query DNA damage or cell growth events. The effects of fatty acid-induced toxicity in mitochondrial health, DNA integrity and cell proliferation were validated in HuH-7 cells, including by inhibiting ATM kinase activity or knckdown of its mRNA. In fatty livers, DNA damage and ATM pathway activation was observed. During induced steatosis in HuH-7 cells, lowering of ATM activity produced mitochondrial dysregulation, DNA damage and cell growth inhibition. In livers undergoing steatohepatitis, ATM was depleted with increased hepatic DNA damage and growth-arrest due to cell cycle checkpoint activations. Moreover, molecular signatures of oncogenesis were associated with upstream mechanistic networks directing cell metabolism, inflammation or growth that were either activated (in fatty liver) or inactivated (in steatohepatitis). To compensate for hepatic growth arrest, preoncogenic oval cell populations expressing connexin-43 and/or albumin emerged. These oval cells avoided DNA damage and proliferated actively. We concluded that ATM is a major contributor to the onset and progression of nonalcoholic fatty liver disease. Therefore, specific markers for ATM pathway dysregulation will allow prospective segregation of cohorts for disease susceptibility and progression from steatosis to steatohepatitis. This will offer superior design and evaluation parameters for clinical trials. Restoration of ATM activity with targeted therapies should be appropriate for nonalcoholic fatty liver disease.

The Effect of Moderate Weight Loss on a Non-Invasive Biomarker of Liver Fibrosis: A Randomised Controlled Trial

BACKGROUND

Referral to weight loss programmes is the only effective treatment for non-alcoholic fatty liver disease (NAFLD). Clinicians should advise weight loss and screen for liver fibrosis using the Enhanced Liver Fibrosis (ELF) score.

AIM

To examine if the ELF score changes with weight loss.

DESIGN AND SETTING

Randomised controlled trial (ISRCTN85485463) in UK primary care during 2007-2008.

METHOD

Adults with a BMI of 27-35 kg/m2 and ≥1 risk factor for obesity-related disease were randomised to attend a community weight loss programme (n = 45) or receive usual weight loss advice from a practice nurse (n = 28). Weight and the ELF score were measured at baseline and 1 year. Analysis of covariance examined mean changes in the ELF score between groups and its relationship with weight loss.

RESULTS

Mean (SD) BMI was 31.10 kg/m2 (2.55) with evidence of moderate levels of liver fibrosis at baseline (mean ELF score: 8.93 [0.99]). There was no evidence that the community weight loss programme reduced the ELF score compared with usual care (difference +0.13 points, 95% CI: -0.25 to 0.52) despite greater weight loss (difference: -2.66 kg, 95% CI: -5.02 to -0.30). Mean weight loss in the whole cohort was 7.8% (5.9). There was no evidence of an association between weight change and change in ELF; the coefficient for a 5% weight loss was -0.15 (95% CI: -0.30 to 0.0002).

CONCLUSION

We found no evidence that the ELF score changed meaningfully following moderate weight loss. Clinicians should not use the ELF score to measure improvements in NAFLD fibrosis following weight loss programmes.

Evasion of apoptosis by myofibroblasts: a hallmark of fibrotic diseases

Organ fibrosis is a lethal outcome of autoimmune rheumatic diseases such as systemic sclerosis. Myofibroblasts are scar-forming cells that are ultimately responsible for the excessive synthesis, deposition and remodelling of extracellular matrix proteins in fibrosis. Advances have been made in our understanding of the mechanisms that keep myofibroblasts in an activated state and control myofibroblast functions. However, the mechanisms that help myofibroblasts to persist in fibrotic tissues remain poorly understood. Myofibroblasts evade apoptosis by activating molecular mechanisms in response to pro-survival biomechanical and growth factor signals from the fibrotic microenvironment, which can ultimately lead to the acquisition of a senescent phenotype. Growing evidence suggests that myofibroblasts and senescent myofibroblasts, rather than being resistant to apoptosis, are actually primed for apoptosis owing to concomitant activation of cell death signalling pathways; these cells are poised to apoptose when survival pathways are inhibited. This knowledge of apoptotic priming has paved the way for new therapies that trigger apoptosis in myofibroblasts by blocking pro-survival mechanisms, target senescent myofibroblast for apoptosis or promote the reprogramming of myofibroblasts into scar-resolving cells. These novel strategies are not only poised to prevent progressive tissue scarring, but also have the potential to reverse established fibrosis and to regenerate chronically injured tissues.

Comparison of murine steatohepatitis models identifies a dietary intervention with robust fibrosis, ductular reaction, and rapid progression to cirrhosis and cancer

Progressive fibrosis, functional liver failure, and cancer are the central liver-related outcomes of nonalcoholic steatohepatitis (NASH) but notoriously difficult to achieve in mouse models. We performed a direct, quantitative comparison of hepatic fibrosis progression in well-defined methionine- and choline-deficient (MCD) and choline-deficient, amino-acid defined (CDAA) diets with increasing fat content (10-60% by calories) in C57Bl/6J and BALB/cAnNCrl mice. In C57Bl/6J mice, MCD feeding resulted in moderate fibrosis at week 8 (up to twofold increase in total hepatic collagen content) and progressive weight loss irrespective of dietary fat. In contrast, CDAA-fed mice did not lose weight and developed progressive fibrosis starting from week 4. High dietary fat in the CDAA diet model induced the lipid metabolism genes for sterol regulatory element-binding protein and stearoyl-CoA desaturase-2 and increased ductular reaction and fibrosis in a dose-dependent manner. Longitudinal analysis of CDAA with 60% fat (HF-CDAA) feeding revealed pronounced ductular reaction and perisinusoidal bridging fibrosis, with a sevenfold increase of hepatic collagen at week 12, which showed limited spontaneous reversibility. At 24 wk, HF-CDAA mice developed signs of cirrhosis with pan-lobular "chicken wire" fibrosis, 10-fold hydroxyproline increase, regenerative nodules, portal hypertension and elevated serum bilirubin and ammonia levels; 80% of mice (8/10) developed multiple glypican-3- and/or glutamine synthetase-positive hepatocellular carcinomas (HCC). High-fat (60%) supplementation of MCD in C57Bl/6J or feeding the HF-CDAA diet fibrosis-prone BALB/cAnNCrl strain failed to result in increased fibrosis. In conclusion, HF-CDAA feeding in C57Bl/6J mice was identified as an optimal model of steatohepatitis with robust fibrosis and ductular proliferations that progress to cirrhosis and HCC within 24 wk. This robust model will aid the testing of interventions and drugs for severe NASH.NEW & NOTEWORTHY Via quantitative comparison of several dietary models, we report HF-CDAA feeding in C57Bl/6 mice as an excellent model recapitulating several key aspects of fibrotic NASH: 1) robust, poorly reversible liver fibrosis, 2) prominent ductular reaction, and 3) progression to cirrhosis, portal hypertension, and liver cancer within 24 wk. High fat dose-dependently activates SREBP2/SCD2 genes and drives liver fibrosis in e HF-CDAA model. These features qualify the model as a robust and practical tool to study mechanisms and novel treatments addressing severe human NASH.

Hepatocyte TNF Receptor-Associated Factor 6 Aggravates Hepatic Inflammation and Fibrosis by Promoting Lysine 6-Linked Polyubiquitination of Apoptosis Signal-Regulating Kinase 1

Activation of apoptosis signal-regulating kinase 1 (ASK1) is a key driving force of the progression of nonalcoholic steatohepatitis (NASH) and represents an attractive therapeutic target for NASH treatment. However, the molecular and cellular mechanisms underlying ASK1 activation in the pathogenesis of NASH remain incompletely understood. In this study, our data unequivocally indicated that hyperactivated ASK1 in hepatocytes is a potent inducer of hepatic stellate cell (HSC) activation by promoting the production of hepatocyte-derived factors. Our previous serial studies have shown that the ubiquitination system plays a key role in regulating ASK1 activity during NASH progression. Here, we further demonstrated that tumor necrosis factor receptor-associated factor 6 (TRAF6) promotes lysine 6 (Lys6)-linked polyubiquitination and subsequent activation of ASK1 to trigger the release of robust proinflammatory and profibrotic factors in hepatocytes, which, in turn, drive HSC activation and hepatic fibrosis. Consistent with the in vitro findings, diet-induced liver inflammation and fibrosis were substantially attenuated in Traf6^+/- mice, whereas hepatic TRAF6 overexpression exacerbated these abnormalities. Mechanistically, Lys6-linked ubiquitination of ASK1 by TRAF6 facilitates the dissociation of thioredoxin from ASK1 and N-terminal dimerization of ASK1, resulting in the boosted activation of ASK1-c-Jun N-terminal kinase 1/2 (JNK1/2)-mitogen-activated protein kinase 14(p38) signaling cascade in hepatocytes. Conclusion: These results suggest that Lys6-linked polyubiquitination of ASK1 by TRAF6 represents a mechanism underlying ASK1 activation in hepatocytes and a key driving force of proinflammatory and profibrogenic responses in NASH. Thus, inhibiting Lys6-linked polyubiquitination of ASK1 may serve as a potential therapeutic target for NASH treatment.

Biophysical Control of Bile Duct Epithelial Morphogenesis in Natural and Synthetic Scaffolds

The integration of bile duct epithelial cells (cholangiocytes) in artificial liver culture systems is important in order to generate more physiologically relevant liver models. Understanding the role of the cellular microenvironment on differentiation, physiology, and organogenesis of cholangiocytes into functional biliary tubes is essential for the development of new liver therapies, notably in the field of cholangiophaties. In this study, we investigated the role of natural or synthetic scaffolds on cholangiocytes cyst growth, lumen formation and polarization. We demonstrated that cholangiocyte cyst formation efficiency can be similar between natural and synthetic matrices provided that the mechanical properties of the hydrogels are matched. When using synthetic matrices, we also tried to understand the impact of elasticity, matrix metalloprotease-mediated degradation and integrin ligand density on cyst morphogenesis. We demonstrated that hydrogel stiffness regulates cyst formation. We found that controlling integrin ligand density was key in the establishment of large polarized cysts of cholangiocytes. The mechanism of lumen formation was found to rely on cell self-organization and proliferation. The formed cholangiocyte organoids showed a good MDR1 (multi drug resistance protein) transport activity. Our study highlights the advantages of fully synthetic scaffold as a tool to develop bile duct models.

Imaging Fibrogenesis in a Diet-Induced Model of Nonalcoholic Steatohepatitis (NASH)

Purpose

Liver fibrosis is the hallmark of chronic nonalcoholic steatohepatitis (NASH) and is characterised by the excessive deposition of extracellular matrix proteins. Early detection and accurate staging of liver fibrosis is critically important for patient management. One of the earliest pathological markers in NASH is the activation of hepatic stellate cells (HSCs) which may be exploited as a marker of fibrogenesis. Activated HSCs secreting factors such as integrin α_vβ₃ propagate fibrosis. The purpose of the current study was to assess the utility of the integrin α_vβ₃ imaging agent [¹⁸F]FtRGD for the early detection of fibrosis in a diet-induced model of NASH longitudinally using PET imaging.

Procedures

Mice were fed with either standard chow diet (SD), high-fat diet (HFD), or a choline-deficient, L-amino acid-defined high-fat fibrogenic diet (CDAHFD) to mimic the clinical pathology of liver disease and followed longitudinally for 10 weeks to assess the development of liver fibrosis using [¹⁸F]FtRGD positron emission tomography (PET) imaging. Standard blood biochemistry, histological measures, and qPCR were used to quantify integrin α_vβ₃, smooth muscle actin, and collagen types 1 and 6 to assess the extent of NASH pathology and accurately stage liver fibrosis.

Results

The CDAHFD fibrogenic diet predictably developed hepatic inflammation and steatosis over the 10 weeks studied with little NASH pathology detected in high fat diet-treated animals. Stage 1 fibrosis was detected early by histology at day 21 and progressed to stage 2 by day 35 and stage 3 by day 56 in mice fed with CDAHFD diet only. Noninvasive imaging with [¹⁸F]FtRGD correlated well with integrin α_vβ₃ and was able to distinguish early mild stage 2 fibrosis in CDAHFD animals compared with standard chow diet-fed animals at day 35. When compared with high fat diet-fed animals, [¹⁸F]FtRGD was only able to distinguish later moderate stage 2 fibrosis in CDAHFD animals at day 49.

Conclusions

The diet-induced progression of liver fibrosis was confirmed using histology and correlated well with the mRNA of integrin α_vβ₃ and extracellular matrix protein expression. [¹⁸F]FtRGD showed very good correlation between liver uptake and integrin α_vβ₃ expression and similar detection sensitivity to the current clinical gold standard modalities for staging of liver fibrosis.

Dietary wheat amylase trypsin inhibitors promote features of murine non-alcoholic fatty liver disease

We previously demonstrated that a common dietary protein component, wheat amylase trypsin inhibitors (ATI), stimulate intestinal macrophages and dendritic cells via toll like receptor 4. Activation of these intestinal myeloid cells elicits an inflammatory signal that is propagated to mesenteric lymph nodes, and that can facilitate extraintestinal inflammation. Mice were fed a well-defined high fat diet, with (HFD/ATI) or without (HFD) nutritionally irrelevant amounts of ATI. Mice on HFD/ATI developed only mild signs of intestinal inflammation and myeloid cell activation but displayed significantly higher serum triglycerides and transaminases compared to mice on HFD alone. Moreover, they showed increased visceral and liver fat, and a higher insulin resistance. ATI feeding promoted liver and adipose tissue inflammation, with M1-type macrophage polarization and infiltration, and enhanced liver fibrogenesis. Gluten, the major protein component of wheat, did not induce these pathologies. Therefore, wheat ATI ingestion in minute quantities comparable to human daily wheat consumption exacerbated features of the metabolic syndrome and non-alcoholic steatohepatitis, despite its irrelevant caloric value.

Antifibrotic effects of specific siRNA targeting connective tissue growth factor delivered by polyethyleneimine‑functionalized magnetic iron oxide nanoparticles on LX‑2 cells

Connective tissue growth factor (CTGF) is a possible key determinant of progressive fibrosis. Nanotechnology has been considered as a potential tool for developing novel drug delivery systems for various diseases, including liver fibrosis. The present study aimed to investigate the potential antifibrotic activity of CTGF small interfering RNA (siRNA) mediated by polyethyleneimine (PEI)-functionalized magnetic iron oxide (Fe₃O₄) nanoparticles (NPs) in LX-2 cells. PEI-Fe₃O₄/siRNA complexes were synthesized to facilitate siRNA delivery and were transfected into LX-2 cells. Laser confocal microscopy was employed to investigate the cell uptake of PEI-Fe₃O₄/siRNA complexes. Reverse transcription-quantitative PCR (RT-qPCR) and western blotting were used to verify the effect of gene silencing. The results showed that siRNA-loaded PEI-Fe₃O₄ exhibited low cytotoxicity. The transfection efficiency of PEI-Fe₃O₄/siRNA reached 73.8%, and RT-qPCR and western blotting demonstrated effective gene silencing. These results indicated that CTGF siRNA delivered by PEI-Fe₃O₄ NPs significantly reduces CTGF expression and collagen production in activated LX-2 cells, providing a basis for future in vivo studies.

A Functional Role of GAS6/TAM in Nonalcoholic Steatohepatitis Progression Implicates AXL as Therapeutic Target

BACKGROUND AND AIMS

GAS6 signaling, through the TAM receptor tyrosine kinases AXL and MERTK, participates in chronic liver pathologies. Here, we addressed GAS6/TAM involvement in Non-Alcoholic SteatoHepatitis (NASH) development.

METHODS

GAS6/TAM signaling was analyzed in cultured primary hepatocytes, hepatic stellate cells (HSC) and Kupffer cells (KCs). Axl^-/-, Mertk^-/- and wild-type C57BL/6 mice were fed with Chow, High Fat Choline-Deficient Methionine-Restricted (HFD) or methionine-choline-deficient (MCD) diet. HSC activation, liver inflammation and cytokine/chemokine production were measured by qPCR, mRNA Array analysis, western blotting and ELISA. GAS6, soluble AXL (sAXL) and MERTK (sMERTK) levels were analyzed in control individuals, steatotic and NASH patients.

RESULTS

In primary mouse cultures, GAS6 or MERTK activation protected primary hepatocytes against lipid toxicity via AKT/STAT-3 signaling, while bemcentinib (small molecule AXL inhibitor BGB324) blocked AXL-induced fibrogenesis in primary HSCs and cytokine production in LPS-treated KCs. Accordingly; bemcentinib diminished liver inflammation and fibrosis in MCD- and HFD-fed mice. Upregulation of AXL and ADAM10/ADAM17 metalloproteinases increased sAXL in HFD-fed mice. Transcriptome profiling revealed major reduction in fibrotic- and inflammatory-related genes in HFD-fed mice after bemcentinib administration. HFD-fed Mertk^-/- mice exhibited enhanced NASH, while Axl^-/- mice were partially protected. In human serum, sAXL levels augmented even at initial stages, whereas GAS6 and sMERTK increased only in cirrhotic NASH patients. In agreement, sAXL increased in HFD-fed mice before fibrosis establishment, while bemcentinib prevented liver fibrosis/inflammation in early NASH.

CONCLUSION

AXL signaling, increased in NASH patients, promotes fibrosis in HSCs and inflammation in KCs, while GAS6 protects cultured hepatocytes against lipotoxicity via MERTK. Bemcentinib, by blocking AXL signaling and increasing GAS6 levels, reduces experimental NASH, revealing AXL as an effective therapeutic target for clinical practice.

Type 2 diabetes mellitus: A risk factor for progression of liver fibrosis in middle-aged patients with non-alcoholic fatty liver disease

BACKGROUND AND AIM

The severity of liver fibrosis is strongly associated with prognosis in patients with non-alcoholic fatty liver disease (NAFLD). We evaluated clinical risk factors for progression of liver fibrosis in patients with NAFLD.

METHODS

This study included 1562 middle-aged (36-64 years) patients with NAFLD and less severe liver fibrosis (fibrosis-4 index < 1.3).

RESULTS

During follow-up, 186 patients progressed to advanced fibrosis (fibrosis-4 index > 2.67). The 3-, 5-, 7-, and 10-year cumulative incidence of progression to advanced fibrosis was 4.4%, 6.7%, 11.0%, and 16.7%, respectively. In the univariate analysis, age, albumin concentration, and type 2 diabetes mellitus (T2DM) were significantly associated with progression to advanced fibrosis. Multivariate analysis with adjustment for age, smoking, body mass index, albumin, estimated glomerular filtration rate, dyslipidemia, T2DM, and steatosis showed that age ≥ 50 years (hazard ratio [HR], 2.121; 95% confidence interval [CI], 1.462-3.076; P < 0.001), albumin concentration < 4.2 g/dL (HR, 1.802; 95% CI, 1.285-2.528; P < 0.001), and the presence of T2DM (HR, 1.879; 95% CI, 1.401-2.520; P < 0.001) were independently associated with progression to advanced fibrosis. Conversely, degree of steatosis was not associated with progression to advanced fibrosis. The respective 3-, 5-, 7-, and 10-year cumulative incidence of progression to advanced fibrosis was 3.6%, 5.0%, 8.2%, and 12.9% in patients without T2DM (n = 1077) and 6.1%, 10.4%, 16.7%, and 24.0% in patients with T2DM (n = 485) (P < 0.001).

CONCLUSIONS

Type 2 diabetes mellitus is associated with progression to advanced liver fibrosis in middle-aged NAFLD patients, even those with less severe liver fibrosis.

PI3K inhibition reduces murine and human liver fibrogenesis in precision-cut liver slices

BACKGROUND

Liver fibrosis results from continuous inflammation and injury. Despite its high prevalence worldwide, no approved antifibrotic therapies exist. Omipalisib is a selective inhibitor of the PI3K/mTOR pathway that controls nutrient metabolism, growth and proliferation. It has shown antifibrotic properties in vitro. While clinical trials for idiopathic pulmonary fibrosis have been initiated, an in-depth preclinical evaluation is lacking. We evaluated omipalisib's effects on fibrogenesis using the ex vivo model of murine and human precision-cut tissue slices (PCTS).

METHODS

Murine and human liver and jejunum PCTS were incubated with omipalisib up to 10 μM for 48 h. PI3K pathway activation was assessed through protein kinase B (Akt) phosphorylation and antifibrotic efficacy was determined via a spectrum of fibrosis markers at the transcriptional and translational level.

RESULTS

During incubation of PCTS the PI3K pathway was activated and incubation with omipalisib prevented Akt phosphorylation (IC50 = 20 and 1.5 nM for mouse and human, respectively). Viability of mouse and human liver PCTS was compromised only at the high concentration of 10 and 1-5 μM, respectively. However, viability of jejunum PCTS decreased with 0.1 (mouse) and 0.01 μM (human). Spontaneously increased fibrosis related genes and proteins were significantly and similarly suppressed in mouse and in human liver PCTS.

CONCLUSIONS

Omipalisib has antifibrotic properties in ex vivo mouse and human liver PCTS, but higher concentrations showed toxicity in jejunum PCTS. While the PI3K/mTOR pathway appears to be a promising target for the treatment of liver fibrosis, PCTS revealed likely side effects in the intestine at higher doses.

Effect of Weight Reduction on Histological Activity and Fibrosis of Lean Nonalcoholic Steatohepatitis Patient

BACKGROUND AND OBJECTIVES

Weight reduction has evidenced benefit on attenuation of histological activity and fibrosis of nonalcoholic steatohepatitis (NASH), but there is scarcity of data for lean NASH subgroup. We have designed this study to compare the effects of weight reduction on histological activity and fibrosis of lean and non-lean NASH.

METHODS

We have included 20 lean and 20 non-lean histologically proven NASH patients. BMI < 25 kg/m2 was defined as non-lean. Informed consent was taken from each subject. All methods were carried out in accordance with the Declaration of Helsinki. Moderate exercise along with dietary restriction was advised for both groups for weight reduction. After 1 year, 16 non-lean and 15 lean had completed second liver biopsy.

RESULTS

Age, sex, alanine transaminase (ALT), aspartate aminotransferase (AST), gamma-glutamyltrasferase (GGT), Homeostasis model assessment insulin resistance (HOMA-IR), triglyceride and high density lipoprotein (HDL) was similar in both groups. Steatosis, ballooning, lobular inflammation, nonalcoholic fatty liver disease activity score (NAS) and fibrosis was similar in the two groups. In lean/non-lean group, any amount of weight reduction, ≥ 5% weight reduction and ≥ 7% weight reduction was found in respectively 8/11, 5/6 and 2/6 patients. In both lean and non-lean groups, weight reduction of any amount was associated with significant reduction of steatosis, ballooning and NAS, except lobular inflammation and fibrosis. In both groups, weight reduction of ≥ 5% was associated with significant reduction in NAS only. However, significant improvement in NAS was noted with ≥ 7% weight reduction in non-lean group only.

CONCLUSION

Smaller amount of weight reduction had the good benefit of improvement in all the segments of histological activity in both lean and non-lean NASH.

Deletion of organic cation transporter Oct3 promotes hepatic fibrosis via upregulation of TGFβ

Organic cation transporters (OCT) are responsible for the intracellular uptake and detoxification of a broad spectrum of endogenous and exogenous substrates. OCTs are downregulated in cholestasis, fibrosis, and hepatocellular carcinoma, but the underlying molecular mechanisms and downstream effects of OCT deletion are unknown. Oct3-knockout (Oct3^-/-; FVB.Slc22a3^tm10pb) and wild-type (WT; FVB) mice were subject to escalating doses of carbon tetrachloride (CCl₄) or thioacetamide (TAA) for 6 wk to induce advanced parenchymal liver fibrosis. Secondary biliary fibrosis was generated by bile duct ligation. Liver fibrosis was assessed by hydroxyproline determination, quantitative Sirius red morphometry, and quantitative real-time PCR for fibrosis and inflammation-related genes. Ductular reaction was assessed by bile duct count per field of view in hematoxylin and eosin staining. General gene expression analyses were performed in liver tissue from untreated Oct3^-/- and WT mice. Finally, primary murine hepatocytes were treated with the nonselective OCT inhibitor quinine, and transforming growth factor-β1 (Tgfβ1) protein expression was quantified by quantitative real-time PCR and Western blot. Oct3^-/- mice developed significantly more fibrosis after bile duct ligation and CCl₄ treatment compared with WT mice. Ductular reaction was enhanced in the long-term model. Concomitantly, Oct1 mRNA expression was downregulated during cholestatic and chemically (TAA and CCl₄) induced fibrogenesis. The downregulation of Oct1 mRNA in fibrotic liver tissue reversed within 4 wk after TAA cessation. Gene expression analysis by next-generation sequencing revealed an enrichment of Tgfβ1 target genes in Oct3^-/- mice. Tgfβ1 mRNA expression was significantly upregulated after chemically induced fibrosis (P < 0.001) in Oct3^-/- compared with WT mice. Accordingly, in primary murine hepatocytes functional inhibition of OCT led to an upregulation of Tgfβ1 mRNA expression. Loss of Oct3 promotes fibrogenesis by affecting Tgfβ-mediated homeostasis in mice with chronic biliary and parenchymal liver damage and fibrosis.NEW & NOTEWORTHY We show for the first time that organic cation transporter 3 (Oct3) is not only downregulated in fibrosis but loss of Oct3 also leads to an upregulation of transforming growth factor-β contributing to fibrosis progression.