血管紧张素Ⅱ受体阻滞剂对糖尿病大鼠胰岛功能和纤维化的影响及其作用机制

The Influence of Ang Ⅱ Receptor Blocker on the Pancreatic Islet Function and Fibrosis in Diabetic Rats and Its Mechanism

目的探讨血管紧张素Ⅱ受体阻滞剂(氯沙坦)对链脲佐菌素诱导的糖尿病大鼠胰岛功能、胰岛纤维化的影响及机制。方法Wistar雄性大鼠以高脂高热量饲料喂养,配合小剂量链脲佐菌素腹腔注射建立糖尿病大鼠模型,随机分为糖尿病对照组和氯沙坦干预组,同时设立正常对照组。氯沙坦干预组用氯沙坦30mg/(kg·d)灌胃。检测各组大鼠的血糖、血清胰岛素,计算胰岛素抵抗指数。实验结束后取胰腺组织,HE染色观察形态学变化,分别用免疫组化法和实时荧光定量PCR技术检测胰岛组织转化生长因子-β1(TGF-β1)、Smad7、纤维化的I型胶原(Collagen I)的蛋白和mRNA表达。结果糖尿病对照组与正常对照组相比,血糖增高,血胰岛素水平降低,胰岛素抵抗指数增高,并有明显的体重减轻,差异有统计学意义(P<0.05);氯沙坦干预组与糖尿病对照组相比,除体重无明显变化外,血糖、胰岛素及胰岛素抵抗指数均有明显改善(P<0.05)。HE染色结果显示:糖尿病对照组的胰岛结构紊乱,出现纤维化;氯沙坦干预组胰岛形态结构有所恢复,纤维化减轻,但未完全恢复正常。免疫组化结果显示:糖尿病对照组TGF-β1及Collagen I蛋白表达较正常对照组增加(P<0.05),Smad7蛋白表达较正常对照组减少(P<0.05);氯沙坦干预组TGF-β1及Collagen I蛋白表达较糖尿病对照组减少(P<0.05),Smad7蛋白表达增加(P<0.05)。实时荧光定量PCR结果显示:糖尿病对照组TGF-β1及Collagen I mRNA表达较正常对照组增加,Smad7mRNA表达较正常对照组减少(P<0.05);氯沙坦干预组TGF-β1及Collagen I mRNA表达较糖尿病对照组减少,Smad7mRNA表达增加(P<0.05)。结论血管紧张素Ⅱ受体阻滞剂氯沙坦能够改善糖尿病大鼠胰岛纤维化,保护胰岛功能,发挥抗糖尿病效应,其作用可能是通过调节TGF-β1/Smads信号转导途径,进而降低Collagen I的表达来实现的。

Objective To investigate the effects and mechanism of the type 1 receptor blocker of AngⅡ（losartan）on pancreatic islet function and fibrosis in rat model of streptozotocin（STZ）-induced diabetes mellitus（DM）.Methods Twenty-six male wistar rats were randomly divided into 3 groups：normal control group fed by standard laboratory diet,DM control group fed by high-fat diet and injected with STZ,and losartan group receiving injection of STZ followed by Losartan treatment.Body weight,blood glucose levels,fasting serum insulin levels,and homeostasis model assessment of insulin resistance（HOMA-IR）were measured.The pancreas was collected for histological examination.The levels of transforming growth factor（TGF）-β1,Smad 7 and collagen I protein and gene expression in pancreatic tissue were measured by immunohistochemistry and real time polymerase chain reaction（PCR）.Results Compared to normal control group,body weight and serum insulin levels were significantly decreased,blood glucose and HOMA-IR significantly increased in DM control group（all P〈0.05）.Compared to DM control group,there were significant improvements in every index except body weight in losartan group（all P〈0.05）.Hemalum-Eosin（HE）staining analysis showed that pancreaticβcells in DM control group were irregularly arranged,and pancreatic fiber tissues increased in amount.In contrast,the lesion of islet tissue in losartan group was alleviated,but not restored to the normal level.The expressions of TGF-β1 and collagen I protein and mRNA were increased,Smad 7 decreased in DM control group compared to normal control group.The DM-associated elevation of TGF-β1 and collagen I and reduction of Smad7 were significantly reversed in losartan group（all P〈0.05）.Conclusion Losartan can improve pancreatic islet function and alleviate islet fibrosis,which may be related to TGF-β1 down-regulation and Smad 7 up-regulation that reduce the level of collagen I through signal transduction pathway of TGF-β1/Smads.