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OBJECTIVES: To develop a mouse model of non-alcoholic fatty liver disease (NAFLD) that replicates the characteristic of the disease in humans, including development of obesity, dysbiosis, fibrosis and liver tumors. METHODS: Agouti yellow (Ay) mice, which have hyperphagia, were fed a Western diet (WD) (42% kcal from fat, 341 g/Kg sucrose, and 0.2% cholesterol) and a drinking solution containing fructose and glucose equivalent to 42 g/L of high fructose corn syrup (HFCS). Wild-type mice fed a low-fat diet (LFD) (10% kcal from fat) served as lean controls. After 16 weeks of diet treatment, tissues were collected and analyzed. Obesity was evaluated via body weight and body composition. NAFLD was evaluated by histology and confirmed by liver lipid quantification, plasma ALT and AST levels, expression of inflammation-related genes, and fibrosis-specific staining. Gene expression profile was evaluated by RNAseq. Gut microbiota dysbiosis was evaluated by 16S rRNA metagenomics. RESULTS: Ay mice fed the Western diet and HFCS for 16 weeks developed obesity and NAFLD. Histological evaluation determined that the mice developed non-alcoholic steatohepatitis (NASH) with steatosis, liver injury, inflammation, and fibrosis. This was confirmed by the following analyses: In these mice, steatosis, quantified by liver TAG content, increased 4X when compared to lean controls. Liver injury, assessed by measuring plasma ALT and AST, increased 11X and 4X, respectively. Inflammation, evaluated by liver mRNA expression of Tnf and CCl2, increased 6X and 12X, respectively. Fibrosis, quantified morphometrically, increased 2.5X. Gene expression profiling showed increases in inflammation- and fibrosis-related pathways, similar to NASH in humans. In addition, these mice developed gut microbiota dysbiosis, with increased Bacteroidetes and Proteobacteria and decreased Firmicutes, as reported in NASH in humans. Finally, 60% of the Ay mice developed liver tumors when fed the WD + HFCS diet for one year. CONCLUSIONS: Ay mice fed a Western diet and HFCS developed obesity, gut microbiota dysbiosis, and NASH, including fibrosis and tumors, replicating the characteristics of NASH in humans. We present this as a new model for studying NASH physiopathology and testing new therapies. FUNDING SOURCES: NIH CUNY.

Summary Nonalcoholic steatohepatitis (NASH) is a leading cause of liver disease worldwide. However, the molecular basis of how benign steatosis progresses to NASH is incompletely understood, which has limited the identification of therapeutic targets. Here we show that the transcription regulator TAZ (WWTR1) is markedly higher in hepatocytes in human and murine NASH liver than in normal or steatotic liver. Most importantly, silencing of hepatocyte TAZ in murine models of NASH prevented or reversed hepatic inflammation, hepatocyte death, and fibrosis, but not steatosis. Moreover, hepatocyte-targeted expression of TAZ in a model of steatosis promoted NASH features, including fibrosis. In vitro and in vivo mechanistic studies revealed that a key mechanism linking hepatocyte TAZ to NASH fibrosis is TAZ/TEA domain (TEAD)-mediated induction of Indian hedgehog (Ihh), a secretory factor that activates fibrogenic genes in hepatic stellate cells. In summary, TAZ represents a previously unrecognized factor that contributes to the critical process of steatosis-to-NASH progression.

Fibrosis and cancer represent two major complications of chronic liver disease. MicroRNAs have been implicated in the development of fibrosis and cancer, thus constituting potential therapeutic targets. Here, we investigated the role of miR-21, a microRNA that has been implicated in the development of fibrosis in multiple organs and also been suggested to act as "oncomir". Accordingly, miR-21 was the microRNA that showed the strongest upregulation in activated hepatic stellate cells (HSC) in multiple models of fibrogenesis, with an 8- to 24-fold induction compared to quiescent HSC. However, miR-21 antisense inhibition did not suppress the activation of murine or human HSC in culture or in liver slices. Moreover, antisense inhibition or genetic deletion of miR-21 in two independently generated knockout mice did not alter HSC activation or liver fibrosis in models of toxic and biliary liver injury. Despite a strong upregulation of miR-21 in injury-associated hepatocellular carcinoma and in cholangiocarcinoma, miR-21 deletion or antisense inhibition did not reduce the development of liver tumors. As inhibition of the most upregulated microRNA did not affect HSC activation, liver fibrosis and fibrosis-associated liver cancer, we additionally tested the role of microRNAs in HSC by HSC-specific Dicer deletion. Although Dicer deletion decreased microRNA expression in HSC and altered the expression of select genes, it only exerted negligible effects on HSC activation and liver fibrosis. In conclusion, genetic and pharmacologic manipulation of miR-21 does not inhibit the development of liver fibrosis and liver cancer. Moreover, suppression of microRNA synthesis does not significantly affect HSC phenotype and activation. This article is protected by copyright. All rights reserved.

Although short-term incubation of hepatocytes with oleic acid (OA) stimulates secretion of apolipoprotein B100 (apoB100), exposure to higher doses of OA for longer periods inhibits secretion in association with induction of endoplasmic reticulum (ER) stress. Palmitic acid (PA) induces ER stress, but its effects on apoB100 secretion are unclear. Docosahexaenoic acid (DHA) inhibits apoB100 secretion, but its effects on ER stress have not been studied. We compared the effects of each of these fatty acids on ER stress and apoB100 secretion in McArdle RH7777 (McA) cells: OA and PA induced ER stress and inhibited apoB100 secretion at higher doses; PA was more potent because it also increased the synthesis of ceramide. DHA did not induce ER stress but was the most potent inhibitor of apoB100 secretion, acting via stimulation of autophagy. These unique effects of each fatty acid were confirmed when they were infused into C57BL6J mice. Our results suggest that when both increased hepatic secretion of VLDL apoB100 and hepatic steatosis coexist, reducing ER stress might alleviate hepatic steatosis but at the expense of increased VLDL secretion. In contrast, increasing autophagy might reduce VLDL secretion without causing steatosis.

Hepatocellular carcinoma (HCC) is the sixth most common cancer worldwide, and the third leading cause of cancer mortality. The great majority of patients are not eligible for curative therapies, and therapeutic approaches for advanced disease show only limited efficacy. Difficulties to treat HCC are due to the heterogenous genetic alterations of HCC, profound alterations in the hepatic microenvironment, and incomplete understanding of HCC biology. Mouse models of HCC will be helpful to improve our understanding of HCC biology, the contributions of the specific pathways and genetic alterations to carcinogenesis. In addition, mouse models of HCC may contribute to elucidate the role of the tumor microenvironment, and serve as models for preclinical studies. As no single mouse model is appropriate to study all of the above, we discuss key features and limitations of commonly used models. Furthermore, we provide detailed protocols for select models, in which HCC is induced genetically, chemically or by transplantation of tumor cells.

Objective Chemokines are known to play an important role in the pathophysiology of alcoholic hepatitis (AH), a form of acute-on-chronic liver injury frequently mediated by gut derived lipopolysaccharide (LPS). In our study, we hypothesise that chemokine CCL20, one of the most upregulated chemokines in patients with AH, is implicated in the pathogenesis of AH by mediating LPS induced liver injury. Design CCL20 gene expression and serum levels and their correlation with disease severity were assessed in patients with AH. Cellular sources of CCL20 and its biological effects were evaluated in vitro and in vivo in chronic, acute and acute-on-chronic experimental models of carbon tetrachloride and LPS induced liver injury. RNA interference technology was used to knockdown CCL20 in vivo. Results CCL20 hepatic and serum levels were increased in patients with AH and correlated with the degree of fibrosis, portal hypertension, endotoxaemia, disease severity scores and short term mortality. Moreover, CCL20 expression was increased in animal models of liver injury and particularly under acute-on-chronic conditions. Macrophages and hepatic stellate cells (HSCs) were identified as the main CCL20 producing cell types. Silencing CCL20 in vivo reduced LPS induced aspartate aminotransferase and lactate dehydrogenase serum levels and hepatic proinflammatory and profibrogenic genes. CCL20 induced proinflammatory and profibrogenic effects in cultured primary HSCs. Conclusions Our results suggest that CCL20 upregulation is strongly associated with LPS and may not only represent a new potential biomarker to predict outcome in patients with AH but also an important mediator linking hepatic inflammation, injury and fibrosis in AH.

SummaryIncreased translocation of intestinal bacteria is a hallmark of chronic liver disease and contributes to hepatic inflammation and fibrosis. Here we tested the hypothesis that the intestinal microbiota and Toll-like receptors (TLRs) promote hepatocellular carcinoma (HCC), a long-term consequence of chronic liver injury, inflammation, and fibrosis. Hepatocarcinogenesis in chronically injured livers depended on the intestinal microbiota and TLR4 activation in non-bone-marrow-derived resident liver cells. TLR4 and the intestinal microbiota were not required for HCC initiation but for HCC promotion, mediating increased proliferation, expression of the hepatomitogen epiregulin, and prevention of apoptosis. Gut sterilization restricted to late stages of hepatocarcinogenesis reduced HCC, suggesting that the intestinal microbiota and TLR4 represent therapeutic targets for HCC prevention in advanced liver disease.