PKC在软脂酸诱导的肝细胞胰岛素抵抗信号转导中的作用

Effects of PKC on signal transduction in palmitate-induced hepatic insulin resistance

目的探讨蛋白激酶PKC在软脂酸(PA)诱导的肝细胞胰岛素抵抗中的作用。方法将DMEM培养基中含0.25mmol/L的软脂酸(PA组)与HepG2细胞共同培养24h,并设立正常对照组(Control组)。加入PKC抑制剂chelerythrine chloride(CC),胰岛素刺激后分光光度酶偶联速率法测定胞内糖异生限速酶磷酸烯醇式丙酮酸羧激酶(PEPCK)活性,Western blot测定胞内胰岛素受体底物2(IRS-2)蛋白水平。结果PA组与Control组相比,基础及胰岛素刺激的PEPCK活性升高(P<0.05);加入CC与否,Control组IRS-2蛋白水平存在明显差异(P<0.05),PA组中却无明显变化(P>0.05),而PEPCK活性在Control组、PA组均无明显改变(P>0.05)。结论细胞胰岛素抵抗时,糖异生的关键酶活性以及胰岛素信号通路的信号蛋白异常改变,胰岛素信号转导PKC通路可能存在传导障碍。

Objective To study effects of PKC on signal transduction in palmitate （PA）-induced hepatic insulin resistance （IR）. Methods HepG2 cells were incubated in DMEM medium with 0. 25 mmol/L PA for 24 h, normal groups were taken as controls. Phosphoenolpyruvate carboxykinase （PEPCK） activity and protein level of insulin receptor substrate （IRS）-2 in cell lysates were measured by spectrophotometric enzyme-coupling rate method and Western blot analysis respectively after cells stimulated by insulin. The changes of PEPCK activity and protein level of IRS-2 were evaluated with or without PKC inhibitor chelerythrine chloride （CC）. Results In PA groups, Basal and insulin-stimulated PEPCK activity in PA group were significantly higher than those in control group （ P 〈 0. 05 ）. Before and after CC intervention, protein level of IRS-2 was parallel in PA groups （P 〉 0. 05 ） , and it was disparity in control groups （P 〈 0. 05 ）, however, insulin - stimulated PEPCK activity had no significant difference in both groups （P 〉 0. 05 ）. Conclusions The abnormal changes in PEPCK activity and ectopic expression of IRS-2 protein are determined in IR hepatic cells. The occurence of hepatic IR might be attributed partly to the defects of PKC pathway of insulin signaling.