Progression Of Nonalcoholic Steatohepatitis Research Articles

The methyltransferase METTL3 negatively regulates nonalcoholic steatohepatitis (NASH) progression

Nonalcoholic steatohepatitis (NASH) is a key step in the progression of nonalcoholic fatty liver (NAFL) to cirrhosis. However, the molecular mechanisms of the NAFL-to-NASH transition are largely unknown. Here, we identify methyltransferase like 3 (METTL3) as a key negative regulator of NASH pathogenesis. Hepatocyte-specific deletion of Mettl3 drives NAFL-to-NASH progression by increasing CD36-mediated hepatic free fatty acid uptake and CCL2-induced inflammation, which is due to increased chromatin accessibility in the promoter region of Cd36 and Ccl2. Antibody blockade of CD36 and CCL2 ameliorates NASH progression in hepatic Mettl3 knockout mice. Hepatic overexpression of Mettl3 protects against NASH progression by inhibiting the expression of CD36 and CCL2. Mechanistically, METTL3 directly binds to the promoters of the Cd36 and Ccl2 genes and recruits HDAC1/2 to induce deacetylation of H3K9 and H3K27 in their promoters, thus suppressing Cd36 and Ccl2 transcription. Furthermore, METTL3 is translocated from the nucleus to the cytosol in NASH, which is associated with CDK9-mediated phosphorylation of METTL3. Our data reveal a mechanism by which METTL3 negatively regulates hepatic Cd36 and Ccl2 gene transcription via a histone modification pathway for protection against NASH progression.

Dual role of neutrophils in modulating liver injury and fibrosis during development and resolution of diet-induced murine steatohepatitis

Inflammatory changes in the liver represent a key feature of non-alcoholic steatohepatitis (NASH), the progressive form of non-alcoholic fatty liver disease (NAFLD). Innate immune activation including hepatic neutrophilic infiltration acts as an important inflammatory trigger as well as a potential mediator of inflammation resolution. In this study, we dissected the effects of neutrophil depletion via anti-lymphocyte antigen 6 complex locus G6D (Ly6G) antibodies administration during ongoing high fat-fructose-cholesterol (FFC) diet-induced murine NASH and during inflammation resolution by switching into a low-fat control diet. During NASH progression, protective effects were shown as HSC activation, cell infiltration and activation of pro-inflammatory macrophages were ameliorated. Furthermore, these changes were contrasted with the effects observed when neutrophil depletion was performed during the resolution phase. Impaired resolving mechanisms, such as a failure to balance the pro and anti-inflammatory cytokines ratio, deficient macrophage phenotypic switch into a pro-restorative profile, and defective repair and remodeling processes were observed when neutrophils were depleted in this scenario. This study described phase-dependent contrasting roles of neutrophils as triggers and pro-resolutive mediators of liver injury and fibrosis associated with diet-induced NASH in mice. These findings have important translational implications at the time of designing NASH therapeutic strategies.

Non-alcoholic steatohepatitis and risk of hepatocellular carcinoma.

The emergence of non-alcoholic fatty liver disease (NAFLD) as the leading chronic liver disease worldwide raises some concerns. In particular, NAFLD is closely tied to sedentary lifestyle habits and associated with other metabolic diseases, such as obesity and diabetes. At the end of the disease spectrum, non-alcoholic steatohepatitis (NASH) may progress to cirrhosis and hepatocellular carcinoma (HCC), representing a serious health problem to modern society. Recently, an increasing number of HCC cases originating from this progressive disease spectrum have been identified, with different levels of severity and complications. Updating the current guidelines by placing a bigger focus on this emerging cause and highlighting some of its unique features is necessary. Since, the drivers of the disease are complex and multifactorial, in order to improve future outcomes, having a better understanding of NASH progression into HCC may be helpful. The risks that can promote disease progression and currently available management strategies employed to monitor and treat NASH-related HCC make up the bulk of this review.

Hyperlipidemia May Synergize with Hypomethylation in Establishing Trained Immunity and Promoting Inflammation in NASH and NAFLD.

We performed a panoramic analysis on both human nonalcoholic steatohepatitis (NASH) microarray data and microarray/RNA-seq data from various mouse models of nonalcoholic fatty liver disease NASH/NAFLD with total 4249 genes examined and made the following findings: (i) human NASH and NAFLD mouse models upregulate both cytokines and chemokines; (ii) pathway analysis indicated that human NASH can be classified into metabolic and immune NASH; methionine- and choline-deficient (MCD)+high-fat diet (HFD), glycine N-methyltransferase deficient (GNMT-KO), methionine adenosyltransferase 1A deficient (MAT1A-KO), and HFCD (high-fat-cholesterol diet) can be classified into inflammatory, SAM accumulation, cholesterol/mevalonate, and LXR/RXR-fatty acid β-oxidation NAFLD, respectively; (iii) canonical and noncanonical inflammasomes play differential roles in the pathogenesis of NASH/NAFLD; (iv) trained immunity (TI) enzymes are significantly upregulated in NASH/NAFLD; HFCD upregulates TI enzymes more than cytokines, chemokines, and inflammasome regulators; (v) the MCD+HFD is a model with the upregulation of proinflammatory cytokines and canonical and noncanonical inflammasomes; however, the HFCD is a model with upregulation of TI enzymes and lipid peroxidation enzymes; and (vi) caspase-11 and caspase-1 act as upstream master regulators, which partially upregulate the expressions of cytokines, chemokines, canonical and noncanonical inflammasome pathway regulators, TI enzymes, and lipid peroxidation enzymes. Our findings provide novel insights on the synergies between hyperlipidemia and hypomethylation in establishing TI and promoting inflammation in NASH and NAFLD progression and novel targets for future therapeutic interventions for NASH and NAFLD, metabolic diseases, transplantation, and cancers.

GPR40 agonist inhibits NLRP3 inflammasome activation via modulation of nuclear factor-κB and sarco/endoplasmic reticulum Ca2+-ATPase

The NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome is a multi-protein intracellular complex that activates proinflammatory cytokines, including interleukin (IL)-1β and IL-18. Inflammasome activation is related to metabolic inflammation, such as the progression of non-alcoholic steatohepatitis. Fasiglifam (TAK875), a selective G-protein coupled receptor 40 (GPR40) agonist with high affinity, significantly improves glucose-dependent insulin secretion and weight gain without hypoglycemia. Interestingly, we found that two GPR40 agonists, TAK875 and AMG1638, suppressed activation of the NLRP3 inflammasome in bone marrow-derived macrophages (BMDMs). TAK875 inhibited inflammasome activation by blocking formation of apoptosis-associated speck-like protein containing a CARD (ASC), an inflammasome component. TAK875 also suppressed NLRP3 inflammasome-induced pyroptosis of BMDMs. Moreover, nuclear factor-kappa B (NF-κB)-dependent priming of the NLRP3 inflammasome was partially inhibited by TAK875 and AMG1638. The intracellular Ca2+ increase caused by ATP, nigericin (pore-forming toxin), or endoplasmic reticulum stress activates the NLRP3 inflammasome. Pre-exposure of BMDMs to TAK875 suppressed the ATP-induced intracellular Ca2+ increase, which was reversed by thapsigargin, a sarco/endoplasmic reticulum Ca2+-ATPase inhibitor. Oral administration of mice with TAK875 suppressed the increase in serum IL-1β in mice treated with lipopolysaccharide/D-galactosamine in vivo. These findings indicate that the free fatty acid-sensing GPR40 plays a key role in the NLRP3 inflammasome pathway.

An RNAi therapeutic targeting hepatic DGAT2 in a genetically obese mouse model of nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a severe liver disorder characterized by triglyceride accumulation, severe inflammation, and fibrosis. With the recent increase in prevalence, NASH is now the leading cause of liver transplant, with no approved therapeutics available. Although the exact molecular mechanism of NASH progression is not well understood, a widely held hypothesis is that fat accumulation is the primary driver of the disease. Therefore, diacylglycerol O-acyltransferase 2 (DGAT2), a key enzyme in triglyceride synthesis, has been explored as a NASH target. RNAi-based therapeutics is revolutionizing the treatment of liver diseases, with recent chemical advances supporting long-term gene silencing with single subcutaneous administration. Here, we identified a hyper-functional, fully chemically stabilized GalNAc-conjugated small interfering RNA (siRNA) targeting DGAT2 (Dgat2-1473) that, upon injection, elicits up to 3months of DGAT2 silencing (>80%-90%, p< 0.0001) in wild-type and NSG-PiZ "humanized" mice. Using an obesity-driven mouse model of NASH (ob/ob-GAN), Dgat2-1473 administration prevents and reverses triglyceride accumulation (>85%, p< 0.0001) without increased accumulation of diglycerides, resulting in significant improvement of the fatty liver phenotype. However, surprisingly, the reduction in liver fat did not translate into a similar impact on inflammation and fibrosis. Thus, while Dgat2-1473 is a practical, long-lasting silencing agent for potential therapeutic attenuation of liver steatosis, combinatorial targeting of a second pathway may be necessary for therapeutic efficacy against NASH.

Immune cell-mediated features of non-alcoholic steatohepatitis.

Non-alcoholic fatty liver disease (NAFLD) includes a range of hepatic manifestations, starting with liver steatosis and potentially evolving towards non-alcoholic steatohepatitis (NASH), cirrhosis or even hepatocellular carcinoma. NAFLD is a major health burden, and its incidence is increasing worldwide. Although it is primarily a disease of disturbed metabolism, NAFLD involves several immune cell-mediated inflammatory processes, particularly when reaching the stage of NASH, at which point inflammation becomes integral to the progression of the disease. The hepatic immune cell landscape is diverse at steady state and it further evolves during NASH with direct consequences for disease severity. In this Review, we discuss current concepts related to the role of immune cells in the onset and progression of NASH. A better understanding of the mechanisms by which immune cells contribute to NASH pathogenesis should aid the design of innovative drugs to target NASH, for which current therapeutic options are limited.

Utility of Metabolomic Biomarkers to Identify Nonalcoholic Fatty Liver Disease in Liver Transplant Recipients.

Background.Nonalcoholic fatty liver disease (NAFLD) is a rising indication for liver transplantation (LT). Identification of NAFLD recurrence and those at risk for more progressive disease after LT remains elusive as the diagnosis requires biopsy, which is invasive and impractical for serial monitoring. We therefore aimed to identify metabolites in the blood associated with recurrent NAFLD that could potentially be used for detection and monitoring.Methods.This cross-sectional pilot study included 37 LT recipients who underwent simultaneous liver biopsy and plasma collection for metabolomic analysis. Metabolic profiles were compared between patients with recurrent NAFLD, normal liver (negative control), and acute rejection (rejection control).Results.Univariate analysis revealed 14 metabolites that were significantly altered in patients with recurrence of NAFLD compared with negative controls and 19 compared with rejection controls (P < 0.05). In addition, metabolomic profiling identified 16 metabolites that distinguished nonalcoholic fatty liver versus nonalcoholic steatohepatitis. Metabolite class trends among patients with recurrent NAFLD following LT were consistent with prior metabolomics data in patients with NAFLD in the non-LT setting.Conclusions.In conclusion, we identified candidate metabolites that could be used in the clinical setting to noninvasively identify recurrent NAFLD and differentiate NAFL from the more progressive nonalcoholic steatohepatitis. Further investigation with a larger sample size is warranted to validate these results.

Effect of exercise and diet intervention in NAFLD and NASH via GAB2 methylation

BackgroundNonalcoholic fatty liver disease (NAFLD) is a disorder that extends from simple hepatic steatosis to nonalcoholic steatohepatitis (NASH), which is effectively alleviated by lifestyle intervention. Nevertheless, DNA methylation mechanism underling the effect of environmental factors on NAFLD and NASH is still obscure. The aim of this study was to investigate the effect of exercise and diet intervention in NAFLD and NASH via DNA methylation of GAB2.MethodsMethylation of genomic DNA in human NAFLD was quantified using Infinium Methylation EPIC BeadChip assay after exercise (Ex), low carbohydrate diet (LCD) and exercise plus low carbohydrate diet (ELCD) intervention. The output Idat files were processed using ChAMP package. False discovery rate on genome-wide analysis of DNA methylation (q < 0.05), and cytosine-guanine dinucleotides (CpGs) which are located in promoters were used for subsequent analysis (|Δβ|≥ 0.1). K-means clustering was used to cluster differentially methylated genes according to 3D genome information from Human embryonic stem cell. To quantify DNA methylation and mRNA expression of GRB2 associated binding protein 2 (GAB2) in NASH mice after Ex, low fat diet (LFD) and exercise plus low fat diet (ELFD), MassARRAY EpiTYPER and quantitative reverse transcription polymerase chain reaction were used.ResultsBoth LCD and ELCD intervention on human NAFLD can induce same DNA methylation alterations at critical genes in blood, e.g., GAB2, which was also validated in liver and adipose of NASH mice after LFD and ELFD intervention. Moreover, methylation of CpG units (i.e., CpG_10.11.12) inversely correlated with mRNA expression GAB2 in adipose tissue of NASH mice after ELFD intervention.ConclusionsWe highlighted the susceptibility of DNA methylation in GAB2 to ELFD intervention, through which exercise and diet can protect against the progression of NAFLD and NASH on the genome level, and demonstrated that the DNA methylation variation in blood could mirror epigenetic signatures in target tissues of important biological function, i.e., liver and adipose tissue.Trialregistration International Standard Randomized Controlled Trial Number Register (ISRCTN42622771)

Dextran Sulfate Sodium Salt-Induced Colitis Aggravates Gut Microbiota Dysbiosis and Liver Injury in Mice With Non-alcoholic Steatohepatitis.

Objective: Inflammatory bowel disease (IBD) is characterized by gut microbiota dysbiosis, which is also frequently observed in patients with non-alcoholic fatty liver disease. Whether gut microbiota dysbiosis in IBD patients promotes the development of non-alcoholic steatohepatitis (NASH) remains unclear. We aimed to explore the role of gut microbiota dysbiosis in the development of NASH in mice with dextran sulfate sodium salt (DSS) induced colitis.Design: Dextran sulfate sodium salt was used to induce colitis, and high fat (HF), in combination with a high-fructose diet, was used to induce NASH in C57BL/6J male mice. Mice were treated with (1%) DSS to induce colitis in cycles, and each cycle consisted of 7 days of DSS administration followed by a 10-day interval. The cycles were repeated throughout the experimental period of 19 weeks. Pathological alterations in colitis and NASH were validated by hematoxylin and eosin (H&E), oil red O, Sirius red staining, and immunofluorescence. Gut microbiota was examined by 16S rRNA sequencing, and gene expression profiles of hepatic non-parenchymal cells (NPCs) were detected by RNA sequencing.Results: Dextran sulfate sodium salt administration enhanced the disruption of the gut–vascular barrier and aggravated hepatic inflammation and fibrosis in mice with NASH. DSS-induced colitis was accompanied by gut microbiota dysbiosis, characterized by alteration in the core microbiota composition. Compared with the HF group, the abundance of p_Proteobacteria and g_Bacteroides increased, while that of f_S24-7 decreased in the DSS + HF mice. Specifically, gut microbiota dysbiosis was characterized by enrichment of lipopolysaccharide producing bacteria and decreased abundance of short-chain fatty acid-producing bacteria. Gene expression analysis of liver NPCs indicated that compared with the HF group, genes related to both inflammatory response and angiocrine signaling were altered in the DSS + HF group. The expression levels of inflammation-related and vascular development genes correlated significantly with the abundance of p_Proteobacteria, g_Bacteroides, or f_S24-7 in the gut microbiota, implying that gut microbiota dysbiosis induced by DSS might aggravate hepatic inflammation and fibrosis by altering the gene expression in NPCs.Conclusion: Dextran sulfate sodium salt-induced colitis may promote the progression of liver inflammation and fibrosis by inducing microbiota dysbiosis, which triggers an inflammatory response and disrupts angiocrine signaling in liver NPCs. The abundance of gut microbiota was associated with expression levels of inflammation-related genes in liver NPCs and may serve as a potential marker for the progression of NASH.

Low-dose LPS promotes progress of non-alcoholic steatohepatitis by up-regulating TLR4 in macrophages

Low-dose LPS promotes progress of non-alcoholic steatohepatitis by up-regulating TLR4 in macrophages

Endotoxins and Non-Alcoholic Fatty Liver Disease.

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. It occurs with a prevalence of up to 25%, of which 10–20% cases progress to nonalcoholic steatohepatitis (NASH), cirrhosis, and liver cancer. The histopathology of NASH is characterized by neutrophilic infiltration, and endotoxins from gram-negative rods have been postulated as a contributing factor. Elevations in endotoxin levels in the blood can be classified as intestinal and hepatic factors. In recent years, leaky gut syndrome, which is characterized by impaired intestinal barrier function, has become a significant issue. A leaky gut may prompt intestinal bacteria dysbiosis and increase the amount of endotoxin that enters the liver from the portal vein. These contribute to persistent chronic inflammation and progressive liver damage. In addition, hepatic factors suggest that liver damage can be induced by low-dose endotoxins, which does not occur in healthy individuals. In particular, increased expression of CD14, an endotoxin co-receptor in the liver, may result in leptin-induced endotoxin hyper-responsiveness in obese individuals. Thus, elevated blood endotoxin levels contribute to the progression of NASH. The current therapeutic targets for NASH treat steatosis and liver inflammation and fibrosis. While many clinical trials are underway, no studies have been performed on therapeutic agents that target the intestinal barrier. Recently, a randomized placebo-controlled trial examined the role of the intestinal barrier in patients with NAFLD. To our knowledge, this study was the first of its kind and study suggested that the intestinal barrier may be a novel target in the future treatment of NAFLD.

Emerging Roles of T Cells in the Pathogenesis of Nonalcoholic Steatohepatitis and Hepatocellular Carcinoma.

Nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease worldwide. A significant proportion of patients with NAFLD develop a progressive inflammatory condition termed nonalcoholic steatohepatitis (NASH), which may eventually advance to cirrhosis and hepatocellular carcinoma (HCC). NASH is characterized by steatosis, hepatocyte ballooning, and lobular inflammation. Heightened immune cell infiltration is a hallmark of NASH, yet the mechanisms whereby hepatic inflammation occurs in NASH and how it contributes to disease initiation and progression remain incompletely understood. Emerging evidence indicates that intrahepatic T cell immune mechanisms play an integral role in the pathogenesis of NASH and its transition to HCC. In this review, we summarize the current knowledge regarding the T cell-mediated mechanisms of inflammation in NASH. We highlight recent preclinical and human studies implicating various subsets of conventional and innate-like T cells in the onset and progression of NASH and HCC. Finally, we discuss the potential therapeutic strategies targeting T cell-mediated responses for the treatment of NASH.

Genetics, Immunity and Nutrition Boost the Switching from NASH to HCC.

Nonalcoholic fatty liver disease (NAFLD) is the leading contributor to the global burden of chronic liver diseases. The phenotypic umbrella of NAFLD spans from simple and reversible steatosis to nonalcoholic steatohepatitis (NASH), which may worsen into cirrhosis and hepatocellular carcinoma (HCC). Notwithstanding, HCC may develop also in the absence of advanced fibrosis, causing a delayed time in diagnosis as a consequence of the lack of HCC screening in these patients. The precise event cascade that may precipitate NASH into HCC is intricate and it entails diverse triggers, encompassing exaggerated immune response, endoplasmic reticulum (ER) and oxidative stress, organelle derangement and DNA aberrancies. All these events may be accelerated by both genetic and environmental factors. On one side, common and rare inherited variations that affect hepatic lipid remodeling, immune microenvironment and cell survival may boost the switching from steatohepatitis to liver cancer, on the other, diet-induced dysbiosis as well as nutritional and behavioral habits may furtherly precipitate tumor onset. Therefore, dietary and lifestyle interventions aimed to restore patients’ health contribute to counteract NASH progression towards HCC. Even more, the combination of therapeutic strategies with dietary advice may maximize benefits, with the pursuit to improve liver function and prolong survival.

Hepatic CDP-diacylglycerol synthase 2 deficiency causes mitochondrial dysfunction and promotes rapid progression of NASH and fibrosis

Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of pathologies, ranging from steatosis to nonalcoholic steatohepatitis (NASH). The factors promoting the progression of steatosis to NASH are still unclear. Recent studies suggest that mitochondrial lipid composition is critical in NASH development. Here, we showed that CDP-DAG synthase 2 (Cds2) was downregulated in genetic or diet-induced NAFLD mouse models. Liver-specific deficiency of Cds2 provoked hepatic steatosis, inflammation and fibrosis in five-week-old mice. CDS2 is enriched in mitochondria-associated membranes (MAMs), and hepatic Cds2 deficiency impaired mitochondrial function and decreased mitochondrial PE levels. Overexpression of phosphatidylserine decarboxylase (PISD) alleviated the NASH-like phenotype in Cds2f/f;AlbCre mice and abnormal mitochondrial morphology and function caused by CDS2 deficiency in hepatocytes. Additionally, dietary supplementation with an agonist of peroxisome proliferator-activated receptor alpha (PPARα) attenuated mitochondrial defects and ameliorated the NASH-like phenotype in Cds2f/f;AlbCre mice. Finally, Cds2 overexpression protected against high-fat diet-induced hepatic steatosis and obesity. Thus, Cds2 modulates mitochondrial function and NASH development.

Hepatocyte glutathione S-transferase mu 2 prevents non-alcoholic steatohepatitis by suppressing ASK1 signaling

Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease worldwide. The advanced stage of NAFLD, non-alcoholic steatohepatitis (NASH), has been recognized as a leading cause of end-stage liver injury for which there are no FDA-approved therapeutic options. Glutathione S-transferase Mu 2 (GSTM2) is a phase II detoxification enzyme. However, the roles of GSTM2 in NASH have not been elucidated. Multiple RNA-seq analyses were used to identify hepatic GSTM2 expression in NASH. Invitro and invivo gain- or loss-of-function approaches were used to investigate the role and molecular mechanism of GSTM2 in NASH. We identified GSTM2 as a sensitive responder and effective suppressor of NASH progression. GSTM2 was significantly downregulated during NASH progression. Hepatocyte GSTM2 deficiency markedly aggravated insulin resistance, hepatic steatosis, inflammation and fibrosis induced by a high-fat diet and a high-fat/high-cholesterol diet. Mechanistically, GSTM2 sustained MAPK pathway signaling by directly interacting with apoptosis signal-regulating kinase 1 (ASK1). GSTM2 directly bound to the N-terminal region of ASK1 and inhibited ASK1 N-terminal dimerization to subsequently repress ASK1 phosphorylation and the activation of its downstream JNK/p38 signaling pathway under conditions of metabolic dysfunction. These data demonstrated that hepatocyte GSTM2 is an endogenous suppressor that protects against NASH progression by blocking ASK1 N-terminal dimerization and phosphorylation. Activating GSTM2 holds promise as a therapeutic strategy for NASH. IIT-2021-277. New therapeutic strategies for non-alcoholic steatohepatitis are urgently needed. We identified that the protein GSTM2 exerts a protective effect in response to metabolic stress. Therapies that aim to increase the activity of GSTM2 could hold promise for the treatment of non-alcoholic steatohepatitis.

Sparcl1 promotes nonalcoholic steatohepatitis progression in mice through upregulation of CCL2.

Nonalcoholic fatty liver disease (NAFLD) represents a spectrum of chronic liver disease ranging from simple steatosis (NAFL) to nonalcoholic steatohepatitis (NASH). However, the molecular mechanisms of NASH progression remain incompletely understood. White adipose tissue (WAT) has emerged as an important endocrine organ and contributes not only to the initial stage of NAFLD, but also to its severity. In the current study, through transcriptomic analysis we identified increased expression of Sparcl1, a secreted glycoprotein, in the WAT from NASH mice. Plasma Sparcl1 levels were similarly elevated and positively correlated with hepatic pathological features in NASH patients. Functional studies showed that both chronic injection of recombinant Sparcl1 protein and overexpression of Sparcl1 exaggerated hepatic inflammation and liver injury in mice. In contrast, genetic ablation of Sparcl1, knockdown of Sparcl1 in WAT, and treatment with a Sparcl1-neutralizing antibody dramatically alleviated diet-induced NASH pathogenesis. Mechanistically, Sparcl1 promoted the expression of C-C motif chemokine ligand 2 (CCL2) in hepatocytes through binding to Toll-like receptor 4 (TLR4) and activation of the NF-κB/p65 signaling pathway. Genetically or pharmacologically blocking the CCL2/CCR2 pathway attenuated the hepatic inflammatory response evoked by Sparcl1. Thus, our results demonstrated an important role for Sparcl1 in NASH progression, suggesting a potential target for therapeutic intervention.

Targeting adipose tissue to tackle NASH: SPARCL1 as an emerging player.

Nonalcoholic steatohepatitis (NASH) is a leading cause of chronic liver disease, affecting 1.5%-6.5% of the world population. Currently, there are no FDA-approved drugs to treat this disease. Accumulating evidence suggests that metabolically hazardous visceral fat contributes to NASH progression by releasing fatty acids and proinflammatory mediators. Therefore, targeting adipose tissue to reduce adipose inflammation may provide an effective strategy to treat NASH. Another strategy is to target specific inflammatory mediators that are produced by adipose tissue and contribute to NASH progression. In this issue of the JCI, Liu, Xiang, et al. demonstrate that secreted protein acidic and rich in cysteine-like protein 1 (SPARCL1) was highly upregulated in adipose tissue and played a role in exacerbating NASH progression in a mouse model of NASH. Thus, inhibition of SPARCL1 may provide another attractive strategy to tackle NASH.

Hepatocyte-Specific Deletion of HIF2α Prevents NASH-Related Liver Carcinogenesis by Decreasing Cancer Cell Proliferation.

Background & AimsHypoxia and hypoxia-inducible factors (HIFs) are involved in chronic liver disease progression. We previously showed that hepatocyte HIF-2α activation contributed significantly to nonalcoholic fatty liver disease progression in experimental animals and human patients. In this study, using an appropriate genetic murine model, we mechanistically investigated the involvement of hepatocyte HIF-2α in experimental nonalcoholic steatohepatitis (NASH)-related carcinogenesis.MethodsThe role of HIF-2α was investigated by morphologic, cellular, and molecular biology approaches in the following: (1) mice carrying hepatocyte-specific deletion of HIF-2α (HIF-2α-/- mice) undergoing a NASH-related protocol of hepatocarcinogenesis; (2) HepG2 cells stably transfected to overexpress HIF-2α; and (3) liver specimens from NASH patients with hepatocellular carcinoma.ResultsMice carrying hepatocyte-specific deletion of HIF-2α (hHIF-2α-/-) showed a significant decrease in the volume and number of liver tumors compared with wild-type littermates. These effects did not involve HIF-1α changes and were associated with a decrease of cell proliferation markers proliferating cell nuclear antigen and Ki67. In both human and rodent nonalcoholic fatty liver disease–related tumors, HIF-2α levels were strictly associated with hepatocyte production of SerpinB3, a mediator previously shown to stimulate liver cancer cell proliferation through the Hippo/Yes-associated protein (YAP)/c-Myc pathway. Consistently, we observed positive correlations between the transcripts of HIF-2α, YAP, and c-Myc in individual hepatocellular carcinoma tumor masses, while HIF-2α deletion down-modulated c-Myc and YAP expression without affecting extracellular signal-regulated kinase 1/2, c-Jun N-terminal kinase, and AKT-dependent signaling. In vitro data confirmed that HIF-2α overexpression induced HepG2 cell proliferation through YAP-mediated mechanisms.ConclusionsThese results indicate that the activation of HIF-2α in hepatocytes has a critical role in liver carcinogenesis during NASH progression, suggesting that HIF-2α–blocking agents may serve as novel putative therapeutic tools.

Astaxanthin Prevents Diet-Induced NASH Progression by Shaping Intrahepatic Immunity.

Dietary change leads to a precipitous increase in non-alcoholic fatty liver disease (NAFLD) from simple steatosis to the advanced form of non-alcoholic steatohepatitis (NASH), affecting approximately 25% of the global population. Although significant efforts greatly advance progress in clarifying the pathogenesis of NAFLD and identifying therapeutic targets, no therapeutic agent has been approved. Astaxanthin (ASTN), a natural antioxidant product, exerts an anti-inflammation and anti-fibrotic effect in mice induced with carbon tetrachloride (CCl4) and bile duct ligation (BDL); thus, we proposed to further investigate the potential effect of ASTN on a diet-induced mouse NASH and liver fibrosis, as well as the underlying cellular and molecular mechanisms. By treating pre-development of NASH in mice induced with a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD), we have demonstrated that oral administration ASTN preventively ameliorated NASH development and liver fibrosis by modulating the hepatic immune response, liver inflammation, and oxidative stress. Specifically, ASTN treatment led to the reduction in liver infiltration of monocyte-derived macrophages, hepatic stellate cell (HSC) activation, oxidative stress response, and hepatocyte death, accompanied by the decreased hepatic gene expression of proinflammatory cytokines such as TNF-α, TGF-β1, and IL-1β. In vitro studies also demonstrated that ASTN significantly inhibited the expression of proinflammatory cytokines and chemokine CCL2 in macrophages in response to lipopolysaccharide (LPS) stimulation. Overall, in vivo and in vitro studies suggest that ASTN functions as a promising therapeutic agent to suppress NASH and liver fibrosis via modulating intrahepatic immunity.