RESUMO
Insulin resistance plays a major role in type 2 diabetes and obesity. In this disorder, lipid accumulation is accompanied by increased TNF-alpha expression in the muscle. The aims of this study were to evaluate the effects of tumor necrosis factor-a [TNF-alpha] gene knockdown on key elements of insulin signaling pathway [IRS-1 and. Akt] and insulin resistance in C2C12 muscle cells in the presence and absence of palmitate. To knockdown protein expression of TNF-alpha, the C2C12 cells were transfected with the shRNA containing antisense sequence of murine TNF-alpha gene. The analysis of TNF-alpha protein expression and phosphorylation and protein levels of IRS-1 and Akt were subsequently detected by western blot. In TNF-alpha knockdown cells, the protein expression level of TNF-alpha was reduced by 58%. Under treatment with palmitate, insulin stimulated phosphorylation of IRS-1 [Tyr632] and Akt [Ser473] in knockdown cells was increased 1.7 and 2.6 fold, respectively, compared to the controls. Our findings showed that decreasing the TNF-alpha protein level can enhance the activity of the important elements of insulin signaling pathway [IRS-1 and Akt], leading to the improvement of insulin resistance in myotubes, data suggesting that TNF-alpha may potentially be a therapeutic target for fatty acid induced insulin resistance observed in type 2 diabetes and metabolic syndrome