Reactive oxygen species induce HNF-4α expression via the ASK1-CREB pathway, promoting ChREBP expression and lipogenesis in hepatocytes

초록

Aims: The production of reactive oxygen species (ROS) increases with aging and is associated with liver diseases. ChREBP is involved in lipogenic gene expression in hepatocytes, and we hypothesized that increases in ROS production would induce liver metabolic diseases via regulation of ChREBP expression. Main methods: Mechanism studies were conducted using H2O2 induced HepG2 cells and primary hepatocytes from old mouse. Key findings: We detected increases in ChREBP expression, lipogenic gene (FAS and SCD1) expression, and intracellular triglyceride (TG) levels in H2O2-treated HepG2 cells, which were inhibited by ChREBP knockdown. ChREBP expression and intracellular TG levels were higher in primary hepatocytes from old mice than in those of young mice. Compared with old wild-type mice, intracellular TG levels were significantly reduced in primary hepatocytes from old ChREBP knockout mice. Furthermore, H2O2 stimulation was found to induce HNF-4 alpha expression in HepG2 cells and this expression was higher in primary hepatocytes from old mice. ChIP-qPCR assays indicated that binding of HNF-4 alpha to ChREBP promoter was significantly increased by H2O2 treatment in HepG2 cells. Further study revealed that H2O2-promoted increases in ChREBP expression and intracellular TG levels were significantly inhibited by HNF-4 alpha knockdown. H2O2 treatment also significantly increased ASK1 expression, whereas ASK1 knockdown inhibited H2O2-induced HNF-4 alpha expression. Significance: Collectively, our data indicate that an increase in ROS production can induce HNF-4 alpha expression via the ASK1 pathway and subsequently enhances the expression of ChREBP, thereby contributing to lipogenesis. This pathway may be involved in the elevated liver lipid levels associated with aging and oxidative stress.

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