津力达对胰岛素抵抗大鼠肝脏PI3K/AKT信号通路的影响

目的:探讨津力达改善大鼠胰岛素敏感性的分子作用机制。方法:48只SD大鼠随机分为正常组和高脂饮食组,分别予以普通饲料及高脂饲料喂养。喂养后6周后行高胰岛素-正葡萄糖钳夹实验,鉴定胰岛素抵抗大鼠造模成功。随后将高脂喂养组分为5组,分别为模型组、津力达低、中、高剂量组(0.75,1.5,3.0 g·kg-1)和二甲双胍组(0.2 g·kg-1)。药物干预8周后行钳夹实验和ip葡萄糖耐量实验,并留取大鼠血清,测定空腹血糖(FBG),空腹胰岛素(FINS),糖化血红蛋白(Hb A1c),葡萄糖输注率(GIR),甘油三酯(TG),总胆固醇(TC),高密度脂蛋白胆固醇(HDL-C),低密度脂蛋白胆固醇(LDLC),极低密度脂蛋白胆固醇(VLDL-C)水平;并留取大鼠肝脏标本,RT-PCR检测肝脏胰岛素受体(INSR),胰岛素受体底物-1(IRS-1),蛋白激酶B(AKT),磷脂酰肌醇3激酶(PI3K)和葡萄糖转运蛋白2(GLUT2)的mRNA表达水平,Western blot检测IRS-1和AKT的总蛋白及磷酸化蛋白表达水平,并计算p-AKT/AKT和p-IRS-1/IRS-1。结果:与正常组比较,模型组FBG,FINS,Hb A1c,TC及VLDL-C水平明显升高(P0.05),INSR,IRS-1,PI3K,AKT和GLUT2 mRNA表达下降,HDL-C,GIR含量明显降低(P0.05),p-IRS-1/IRS-1明显升高,p-AKT/AKT明显降低(P0.05);与模型组比较,津力达干预后,大鼠葡萄糖输注率明显升高,FBG,FINS,Hb A1c,TG,TC,LDL-C及VLDL-C水平明显降低(P0.05),对HDL-C无明显影响,津力达明显上调肝脏INS,IRS-1,AKT和GLUT2 mRNA表达(P0.05),升高GIR含量,对PI3K无显著影响;津力达干预组p-IRS-1/IRS-1明显降低,p-AKT/AKT明显升高(P0.05)。结论:津力达可改善胰岛素抵抗,纠正糖脂代谢紊乱,可能与上调PI3K/AKT信号通路有关。

Effect of Jinlida on PI3K/AKT Signal Pathway in Liver Tissue of Insulin Resistant Rats

Objective: To investigate the molecular mechanisms of Jinlida on ameliorating insulin sensitivity in insulin resistant rats. Method: Fourty-eight SD rats were randomly divided into 2 groups: the control group (normal diet) and the high-fat-diet group (high-fat diet). After 6 weeks of high-fat diet, the insulin resistant model in rats was tested by the euglycemic hyperinsulinemic clamp. Then the high-fat-diet rats were randomly subdivided into 5 groups: the high-fat group (HF), the low-, middle- and high-dose Jinlida groups (0.75, 1.5,3.0 g·kg^-1) and the metformin group (0.2 g·kg^-1). After 8 weeks of treatment, hyperinsulin-euglycemic clamp and intraperitoneal glucose tolerance test were performed to evaluate the whole-body insulin sensitivity. Blood samples were collected and fasting blood glucose (FBG), fasting plasma insulin (FINS), glycosylated hemoglobin (HbA1c), total cholesterol (TC), triglycerides (TG), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C) and very low density lipoprotein cholesterol (VLDL-C) were tested. The mRNA expressions of insulin signaling pathway molecules such as insulin receptor (INSR), insulin receptor substrate-1 (IRS-1), phosphatidylinositol3 kinase (PI3K), protein kinase (AKT) and glucose transporter (GLUT2) were investigated by quantitative RT-PCR. The protein expressions of phosphorylation and total IRS-1, AKT were determined by Western blot. The phosphorylated Akt/total Akt (p-Akt/Akt) and phosphorylated IRS-1/total IRS-1(p-IRS-1/IRS-1) were evaluated. Result: Compared with the control group, glucose infusion rate (GIR) decreased, levels of FBG, FINS, HbA1c, TG, TC,LDL-C and VLDL-C increased, level of HDL-C decreased, mRNA expressions of INS, IRS-1, AKT and GLUT2 decreased in the HF group (P<0.05). Compared with the HF group, GIR decreased, levels of FBG, FINS, HbA1c, TG, TC and VLDL-C increased, mRNA expressions of INS, IRS-1, AKT and GLUT2 increased, the ratio of p-IRS-1/IRS-1 decreased, the ratio of p-AKT/AKT increased in the Ji Lida groups (P<0.05). However, there was no significant effect on the level of HDL-C and expression of PI3K in the Ji Lida groups. Conclusion: Jinlida could effectively reduce the insulin resistance and improve the glucose and lipid metabolic disorder in high-fat-diet rats. The possible molecular mechanism might be related to inhibiting the PI3K/AKT signaling pathway.