淫羊藿苷减轻高糖诱导的C2C12肌管细胞胰岛素抵抗

Icariin attenuates high glucose-induced insulin resistance in C2C12 myotubes

目的:探讨淫羊藿苷对高糖诱导的C2C12肌管细胞胰岛素抵抗的影响及其可能的机制。方法:高糖(25 mmol/L葡萄糖)诱导C2C12肌管细胞胰岛素抵抗,并观察淫羊藿苷在高糖条件下对Akt T308磷酸化、葡萄糖转运蛋白4(GLUT4)膜转位及葡萄糖摄取的影响。Western blot法检测蛋白和磷酸化蛋白的表达,比色法测定细胞葡萄糖摄取,小干扰RNA敲减p38 MAPK的表达。结果:(1)淫羊藿苷改善高糖对胰岛素刺激的Akt T308磷酸化的不利影响,显著升高Akt T308磷酸化水平,具体表现为,以25、50和75μmol/L的淫羊藿苷处理细胞24 h,可见淫羊藿苷以剂量依赖方式提高Akt T308磷酸化(P<0.05或P<0.01);而以50μmol/L的淫羊藿苷处理细胞12、24和36 h,可见淫羊藿苷以时间依赖方式提高Akt T308磷酸化(P<0.05或P<0.01)。此外,淫羊藿苷处理(50μmol/L,24 h)显著提高GLUT4在质膜上的表达和细胞对葡萄糖的摄取(P<0.01);(2)高糖作用下,淫羊藿苷可显著提高p38 MAPK蛋白的磷酸化水平(P<0.01);(3)高糖作用下,采用特异性抑制剂或基因沉默方法抑制p38 MAPK活性或蛋白表达可显著降低淫羊藿苷对胰岛素刺激的Akt T308磷酸化(P<0.01)、GLUT4质膜转位(P<0.01)及细胞对葡萄糖摄取的调节作用(P<0.05)。结论:淫羊藿苷通过刺激p38 MAPK磷酸化减轻高糖诱导的C2C12肌管细胞胰岛素抵抗。

AIM:To observe the potential effects of icariin on high glucose-induced insulin resistance in C2C12 myotubes and to investigate its underlying mechanisms.METHODS:The insulin resistance model was induced by high glucose(25 mmol/L)in the C2C12 myotubes.The effects of icariin on Akt phosphorylation at T308,glucose transporter 4(GLUT4)membrane translocation,and glucose uptake were investigated in high glucose-treated C2C12 myotubes.The protein levels of phosphorylated proteins were determined by Western blot.The glucose uptake was measured by colorimetric method.The small interfering RNA(siRNA)was used to knockdown the expression of p38 MAPK.RESULTS:Icariin significantly increased insulin-stimulated Akt T308 phosphorylation in C2C12 myotubes treated with high glucose.Treatment with icariin at 25,50 and 75μmol/L for 24 h increased Akt T308 phosphorylation in a dose-dependent manner(P<0.05 or P<0.01).Treatment with icariin at 50μmol/L for 12,24 and 36 h increased Akt T308 phosphorylation in a time-dependent manner(P<0.05 or P<0.01).In addition,treatment with icariin at 50μmol/L for 24 h significantly enhanced the expression of GLUT4 on plasma membrane(P<0.01)and 2-deoxyglucose(2-DG)uptake(P<0.01).Treatment with icariin recovered high glucose-reduced p38 MAPK phosphorylation(P<0.01).Pharmacological or genetic inhibition of p38 MAPK abolished the protective impacts of icariin on insulin-stimulated Akt T308 phosphorylation(P<0.01),GLUT4 plasma membrane translocation(P<0.01),and 2-DG uptake under high glucose condition(P<0.05).CONCLUSION:Icariin attenuates high glucose-induced insulin resistance in C2C12 myotubes by activating p38 MAPK.