桑叶提取物调控 IRS-1/PI3K/GLUT4 通路影响 2 型糖尿病胰岛素抵抗机制研究

目的:提取桑叶中的黄酮类及多酚类物质,观察其对2型糖尿病(T2DM)模型大鼠降血糖及改善胰岛素抵抗(IR)的作用,并探讨其分子机制。方法:取雄性SD大鼠,分为正常组、模型组、二甲双胍组、桑叶提取物组,除正常组以外建立T2DM模型,灌胃干预4周,观察药物对模型大鼠一般情况、生化指标、骨骼肌病理等的影响。测定胰岛素受体底物-1 (IRS-1)、磷脂酰肌醇3-激酶(PI3K)中的p85α、葡萄糖转运体-4 (GLUT4)在骨骼肌组织中的信使核糖核酸(mRNA)及蛋白表达水平。结果:与正常组比较,模型组空腹血糖(FBG)、IR稳态模型指数(HOMA-IR)、血清胰岛素、总胆固醇、甘油三酯、低密度脂蛋白水平升高(P<0.05);IRS-1、PI3K p85α、GLUT4的mRNA及蛋白表达明显下降(P<0.05)。与模型组比较,桑叶提取物组FBG、HOMA-IR、总胆固醇、甘油三酯、低密度脂蛋白水平下降(P<0.05);IRS-1、PI3K p85α、GLUT4的mRNA及蛋白表达明显升高(P<0.05);二甲双胍组FBG有所下降,但差异无统计学意义,血清胰岛素及HOMA-IR指数、高密度脂蛋白、甘油三酯水平无明显差异,总胆固醇、低密度脂蛋白水平降低(P<0.05),IRS-1、PI3K p85α、GLUT4的mRNA及蛋白表达有所上升但差异无统计学意义。此外,免疫组化分析显示,与模型组比较,桑叶提取物组表现为IRS-1强染色。结论:桑叶提取物可以降低T2DM大鼠体质量、血糖水平及总胆固醇、甘油三酯、低密度脂蛋白水平从而改善IR,且这种降血糖、降血脂作用是通过IRS-1/PI3K/GLUT4信号通路来完成的。

Study on the Effect of Mulberry Leaves Extract Regulating IRS-1/PI3K/GLUT4 Pathway on the Insulin Resistance Mechanism in Type 2 Diabetes Mellitus

Objective:To extract the flavonoids and polyphenol substances from mulberry leaves,observe its effect on reducing blood sugar and improving insulin resistance(IR) in type 2 diabetes mellitus(T2DM) model rats and study its molecular mechanism. Methods:Selected the male SD rats and divided them into the normal group,the model group,the metformin group and the mulberry leaves extract group. Established the T2DM model in addition to the normal group, gave the intervention of gastric perfusion for four weeks and observed the effect of drugs on general conditions,biochemical indexes and skeletal muscular pathology in model rats. Determined the mRNA and protein expression levels of insulin receptor substrates-1(IRS-1), p85α of phosphoinositide 3-kinase(PI3K) and glucose transporter 4(GLUT4) in the skeletal muscle tissue. Results: Compared with the normal group, the levels of the fasting plasma glucose(FBG), homeostasis model of assessment for insulin resistence index(HOMA-IR),serum insulin,total cholesterol,triglyceride and low density lipoprotein in the model group were increased(P < 0.05);the mRNA and protein expressions in IRS-1, PI3K p85α and GLUT4 were obviously decreased(P < 0.05). Compared with the model group, the levels of FBG, HOMA-IR, total cholesterol,triglyceride and low density lipoprotein in the mulberry leaves extract group were decreased(P < 0.05);the mRNA and protein expressions in IRS-1, PI3Kp85α and GLUT4 were obviously increased(P < 0.05);the FBG in the metformin group was decreased but the difference was no significant, there was no significant difference being found in the levels of serum insulin, HOMA-IR indexes, high density lipoprotein and triglyceride and the levels of total cholesterol and low density lipoprotein were decreased(P < 0.05);the mRNA and protein expressions in IRS-1,PI3K p85α and GLUT4 were increased but there was no significant difference. In addition, immunohistochemical analysis showed that when compared with the model group, the mulberry leaves extract group was presented as IRS-1 strong coloring. Conclusion: Mulberry leaves extract can reduce the body mass, blood glucose levels and the levels of total cholesterol, triglyceride and low density lipoprotein in T2DM rats to improve IR,and the effect of lowering blood sugar and blood lipid is completed through IRS-1/PI3K/GLUT4 signal pathway.