The Effects And Mechanisms Of SelS Gene Silencing On Palmitate-induced Insulin Resistance In HepG2 Hepatocytes

The epidemic of type 2 diabetes with impaired glucose tolerance is one of the main causes of morbidity and mortality worldwide, insulin resistance is known as a major risk factor for type 2 diabetes. Studies show that selenium has a two-sided effect on human health, low and high selenium intake both increase the incidence of type 2 diabetes. Selenoprotein S(SelS) is a glucose-regulated protein, which has a close connection with type 2 diabetes. Elevated FFAs derived from adipocytes have been suggested to contribute to insulin resistance, the link between increased circulating FFAs and insulin resistance might be ectopic lipid accumulation and inflammation. Thus, studies of the relationship between SelS gene expression and insulin resistance may provide some information for the prevention and treatment of type 2 diabetes.In this paper, HepG2 cells were treated with 0.25 mM palmitate for 24 h, then insulin for 15 min, to explore the effects of SelS gene silencing on gluconeogenesis, glycogen synthesis and the insulin signaling pathway. We also studied the relationship between SelS gene silencingand the AMPK activity.RNA interference, real-time fluorescent quantitative PCR, Western Blotting, glycogen colorimetric assay, spectrophotometry were used to explore the effects of SelS gene silencing on palmitate-induced glucose metabolism and the underlying mechanism. The results showed that SelS siRNA decreased gluconeogenesis gene expression remarkably, increased the Akt, FOXO1 and IRS-1 phosphorylation, and reduced the phosphorylation of JNK, while there was no notable changes in glycogen content. These data suggested that SelS gene silencing can enhance insulin sensitivity. Meanwhile the phosphorylation of AMPK increased largely, indicating that AMPK was activated. With the treatment of AMPK inhibitor Compound C, the diminished gluconeogenesis gene expression increased inversely, exacerbating insulin resistance. It suggested that SelS siRNA can inhibit gluconeogenesis gene expression through activating AMPK. Our experimental results demonstrate that SelS gene silencing ameliorates insulin resistance induced by palmitate in the HepG2 cells through the activation of AMPK, finally promoting the transduction of insulin signal pathway and glucose metabolism.