TNF Alpha-Induced SOX2 Expression Promotes Hepatic Steatois in Diet-Induced Obesity Model

Abstract

Diet-induced obesity can cause metabolic or inflammatory damage on liver. Nonalcoholic fatty liver disease (NAFLD) begins with the fat accumulation in hepatocyte, but can lead to hepatocellular carcinoma (HCC). Sex-determining region Y-box 2 (SOX2) is a critical transcription factor involving regeneration and pluripotency. The expression level of Sox2 is correlated with progression of HCC, and anti-inflammatory effects of Sox2 in mesenchymal stem cells have been found. However, the expression of Sox2 by inflammatory cytokines in hepatocyte in NAFLD or the role of SOX2 in fat accumulation has been rarely reported. Here, we found that high-fat diet feeding, with or without high fructose in drinking water, significantly upregulated SOX2 in the livers of mice. In vitro, treatment with free fatty acids (FFAs) and fructose increased SOX2 expression in FL83B cells compared with the vehicle-treated group. Furthermore, overexpression or knockdown of SOX2 in FL83B cells promoted or suppressed, respectively, triglyceride synthesis and lipid accumulation after FFAs stimulation. The expression levels of several lipogenesis-related molecules were found to be altered by SOX2 expression. In addition, among several cytokines, only the treatment of tumor necrosis factor-alpha (TNFα) increased the SOX2 expression compared with the vehicle-treated control. Further, upregulation of (TNFα) by FFA/fructose was observed, and TNFα and FFA/fructose induced SOX2 expression was abolished by pretreatment of a TNFα inhibitor. Collectively, our findings suggest that TNFα-SOX2 signaling pathway in hepatocyte may be one of targets for early prevention of the development of NAFLD.