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The pathogenesis of non-alcoholic steatohepatitis (NASH) is still unclear and the prevention of the development of hepatocellular carcinoma (HCC) has not been established. We established an atherogenic and high-fat diet mouse model that develops hepatic steatosis, inflammation, fibrosis, and liver tumors at a high frequency. Using two NASH-HCC mouse models, we showed that peretinoin, an acyclic retinoid, significantly improved liver histology and reduced the incidence of liver tumors. Interestingly, we found that peretinoin induced autophagy in the liver of mice, which was characterized by the increased co-localized expression of microtubule-associated protein light chain 3B-II and lysosome-associated membrane protein 2, and increased autophagosome formation and autophagy flux in the liver. These findings were confirmed using primary mouse hepatocytes. Among representative autophagy pathways, the autophagy related (Atg) 5-Atg12-Atg16L1 pathway was impaired; especially, Atg16L1 was repressed at both the mRNA and protein level. Decreased Atg16L1 mRNA expression was also found in the liver of patients with NASH according to disease progression. Promoter analysis revealed that peretinoin activated the promoter of Atg16L1 by increasing the expression of CCAAT/enhancer-binding-protein-alpha. Interestingly, Atg16L1 overexpression in HepG2 cells inhibited palmitate-induced NF-kB activation and interleukin-6-induced STAT3 activation. We showed that Atg16L1 induced the de-phosphorylation of Gp130, a receptor subunit of interleukin-6 family cytokines, which subsequently repressed phosphorylated-STAT3 (Tyr705) levels, and this process might be independent of autophagy function. Thus, peretinoin prevents the progression of NASH and the development of HCC through activating the autophagy pathway by increased Atg16L1 expression, which is an essential regulator of autophagy and anti-inflammatory proteins.

// Kai Takegoshi 1 , Masao Honda 1, 2 , Hikari Okada 1 , Riuta Takabatake 1 , Naoto Matsuzawa-Nagata 3 , Jean S. Campbell 4 , Masashi Nishikawa 1 , Tetsuro Shimakami 1 , Takayoshi Shirasaki 1 , Yoshio Sakai 1 , Taro Yamashita 1 , Toshinari Takamura 3 , Takuji Tanaka 5 , Shuichi Kaneko 1, 3 1 Department of Gastroenterology, Kanazawa University Graduate School of Medicine, Kanazawa, Japan 2 Department of Advanced Medical Technology, Kanazawa University Graduate School of Health Medicine, Kanazawa, Japan 3 Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medicine, Kanazawa, Japan 4 Department of Pathology, University of Washington School of Medicine, Seattle, WA, USA 5 The Tohkai Cytopathology Institute: Cancer Research and Prevention, Gifu, Japan Correspondence to: Masao Honda, email: mhonda@m-kanazawa.jp Keywords: branched-chain amino acids, nonalcoholic steatohepatitis, mammalian target of rapamycin complex 1, hepatocellular carcinoma, transforming growth factor β1 Received: May 12, 2016 Accepted: December 27, 2016 Published: February 13, 2017 ABSTRACT Oral supplementation with branched-chain amino acids (BCAA; leucine, isoleucine, and valine) in patients with liver cirrhosis potentially suppresses the incidence of hepatocellular carcinoma (HCC) and improves event-free survival. However, the detailed mechanisms of BCAA action have not been fully elucidated. BCAA were administered to atherogenic and high-fat (Ath+HF) diet-induced nonalcoholic steatohepatitis (NASH) model mice. Liver histology, tumor incidence, and gene expression profiles were evaluated. Ath+HF diet mice developed hepatic tumors at a high frequency at 68 weeks. BCAA supplementation significantly improved hepatic steatosis, inflammation, fibrosis, and tumors in Ath+HF mice at 68 weeks. GeneChip analysis demonstrated the significant resolution of pro-fibrotic gene expression by BCAA supplementation. The anti-fibrotic effect of BCAA was confirmed further using platelet-derived growth factor C transgenic mice, which develop hepatic fibrosis and tumors. In vitro, BCAA restored the transforming growth factor (TGF)-β1-stimulated expression of pro-fibrotic genes in hepatic stellate cells (HSC). In hepatocytes, BCAA restored TGF-β1-induced apoptosis, lipogenesis, and Wnt/β-Catenin signaling, and inhibited the transformation of WB-F344 rat liver epithelial stem-like cells. BCAA repressed the promoter activity of TGFβ1R1 by inhibiting the expression of the transcription factor NFY and histone acetyltransferase p300. Interestingly, the inhibitory effect of BCAA on TGF-β1 signaling was mTORC1 activity-dependent, suggesting the presence of negative feedback regulation from mTORC1 to TGF-β1 signaling. Thus, BCAA induce an anti-fibrotic effect in HSC, prevent apoptosis in hepatocytes, and decrease the incidence of HCC; therefore, BCAA supplementation would be beneficial for patients with advanced liver fibrosis with a high risk of HCC.

医薬保健研究域保健学系, Differentially regulated microRNA (miRNA) are associated with hepatic fibrosis; however, their potential usefulness for blocking hepatic fibrosis has not been exploited fully. We examined the expression of miRNA in the liver of a transgenic mouse model in which platelet-derived growth factor C (PDGF-C) is overexpressed (Pdgf-c Tg), resulting in hepatic fibrosis and steatosis and the eventual development of hepatocellular carcinoma (HCC). Robust induction of miR-214 correlated with fibrogenesis in the liver of Pdgf-c Tg mice, atherogenic high-fat diet-induced NASH mice, and patients with chronic hepatitis B or C. Pdgf-c Tg mice were injected with locked nucleic acid (LNA)-antimiR-214 via the tail vein using Invivofectamine 2.0 and the degree of hepatic fibrosis and tumor incidence were evaluated. Pdgf-c Tg mice treated with LNA-antimiR-214 showed a marked reduction in fibrosis and tumor incidence compared with saline or LNA-miR-control-injected control mice. In vitro, LNA-antimiR-214 significantly ameliorated TGF-β1-induced pro-fibrotic gene expression in Lx-2 cells. MiR-214 targets a negative regulator of EGFR signaling, Mig-6. Mimic-miR-214 decreased the expression of Mig-6 and increased the levels of EGF-mediated p-EGFR (Y1173 and Y845) and p-Met (Tyr1234/1235) in Huh-7 cells. Conversely, LNA-antimiR-214 repressed the expression of these genes. In conclusion, miR-214 appears to participate in the development of hepatic fibrosis by modulating the EGFR and TGF-β signaling pathways. LNA-antimiR-214 is a potential therapy for the prevention of hepatic fibrosis. MiR-214 appears to participate in the development of hepatic fibrosis by modulating EGFR and TGF-β signaling pathways. LNA-anti-miR-214 may be a potentially therapy in the prevention of hepatic fibrosis. © 2015 Japanese Cancer Association.