Leptin promotes methionine adenosyltransferase 2A expression in hepatic stellate cells by the downregulation of E2F-4 via the β-catenin pathway

Most obese patients develop hyperleptinaemia. Leptin, mainly produced by adipocytes, demonstrates a promotional role in liver fibrosis. Hepatic stellate cell (HSC) activation, a key step in liver fibrogenesis, requires global reprogramming of gene expression. The remodeling of DNA methylation is a mechanism of the epigenetic regulation of gene expression. The biosynthesis of S-adenosylmethionine, a principle biological methyl donor, is catalyzed by methionine adenosyltransferase (MAT) such as MATII which has been shown to promote HSC activation in vitro. This study was mainly aimed to determine the effect of leptin on MAT2A expression (the catalytic subunit of MATII) in HSCs. Results showed that MAT2A knockdown reduced leptin-induced HSC activation and liver fibrosis in the leptin-deficient mouse model. Leptin promoted MAT2A expression in HSCs and increased MAT2A promoter activity. The axis of the beta-catenin pathway/E2F-4 mediated the effect of leptin on MAT2A expression. Leptin-induced beta-catenin signaling reduced E2F-4 expression and thus abated E2F-4 binding to MAT2A promoter at a site around -2779 bp, leading to an increase in the MAT2A promoter activity. These data might shed more light on the mechanisms responsible for liver fibrogenesis in obese patients with hyperleptinaemia.