西格列汀对2型糖尿病大鼠胰岛素分泌的影响

Effect of sitagliptin on insulin secretion in rats with type 2 diabetes mellitus

目的探讨西格列汀对2型糖尿病(T2DM)大鼠胰岛素分泌的影响。方法SD大鼠60只随机分为三组,每组20只。正常对照组采用基础饲料喂养,模型对照组和西格列汀组采用高糖、高脂饲料喂养。喂养8周后,模型对照组和西格列汀组予腹腔注射链脲佐菌素40 mg/kg建立T2DM大鼠模型。西格列汀组予西格列汀30 mg·kg^(-1)·d^(-1)连续灌胃治疗4周,正常对照组和模型对照组予等容量生理盐水灌胃。比较各组大鼠TC、TG、FBG、FIns水平和HOMA-IR;免疫组化染色观察大鼠胰岛素的分泌情况;实时荧光定量PCR法检测大鼠胰腺组织胰高血糖素样肽1受体(GLP-1R)、环磷酸腺苷(cAMP)、蛋白激酶A(PKA)、cAMP反应元件结合蛋白(CREB)、胰十二指肠同源盒1(PDX-1)和胰岛素mRNA表达;Western blot法检测大鼠GLP-1R、cAMP、PKA、磷酸化PKA、CREB、磷酸化CREB、PDX-1和胰岛素蛋白表达。结果与正常对照组相比,模型对照组TC、TG、FBG、FIns水平和HOMA-IR升高,胰岛素阳性表达面积减少,GLP-1R、cAMP、PKA、CREB、PDX-1和胰岛素mRNA表达下调,GLP-1R、cAMP、磷酸化PKA、磷酸化CREB、PDX-1和胰岛素蛋白表达下调(P<0.01)。与模型对照组相比,西格列汀组TC、TG、FBG、FIns水平和HOMA-IR降低,胰岛素阳性表达面积增加,GLP-1R、cAMP、PKA、CREB、PDX-1和胰岛素mRNA表达上调,GLP-1R、cAMP、磷酸化PKA、磷酸化CREB、PDX-1和胰岛素蛋白表达上调(P<0.05或P<0.01)。结论西格列汀能改善T2DM大鼠分泌胰岛素,其机制可能与上调GLP-1R/cAMP信号通路有关。

Objective To explore the effect of sitagliptin on insulin secretion in the rats with type 2 diabetes mellitus(T2DM).Methods Sixty SD rats were equally randomized into three groups.The rats in group C were fed with basic diet,while which in groups of A and B were fed with high sugar and high fat diet for 8 weeks.The T2DM rat model in groups of A and B was established by intraperitoneal injection of streptozotocin 40 mg/kg.Then group A was treated with sitagliptin 30 mg·kg^(-1)·d^(-1)by gavage for 4 weeks,while groups of B and C were given equal volume of normal saline by gavage.The levels of TC,TG,FBG,FIns and HOMA-IR were compared among three groups.Immunohistochemical staining was used to observe the secretion of insulin in rats.The mRNA expressions of glucagon-like peptide-1 receptor(GLP-1R),cyclic adenosine monophosphate(cAMP),protein kinase A(PKA),cAMP-response element binding protein(CREB),pancreaticoduodenal homeobox 1(PDX-1)and insulin in pancreas tissues of rats were detected by real-time fluorescent quantitative PCR.The protein expressions of GLP-1R,cAMP,PKA,p-PKA,CREB,p-CREB,PDX-1,and insulin in pancreas tissues of rats were detected by Western blot.Results Compared with group C,the levels of TC,TG,FBG,FIns and HOMA-IR were increased,the positive area of insulin was decreased,the mRNA expressions of GLP-1R,cAMP,PKA,CREB,PDX-1,insulin and the protein expressions of GLP-1R,cAMP,p-PKA,p-CREB,PDX-1,insulin were down-regulated in group B(P<0.01).Compared with group B,the levels of TC,TG,FBG,FIns and HOMA-IR were decreased,the positive area of insulin was increased,and the mRNA expressions of GLP-1R,cAMP,PKA,CREB,PDX-1,insulin and the protein expressions of GLP-1R,cAMP,p-PKA,p-CREB,PDX-1,insulin were up-regulated in group A(P<0.05 or P<0.01).ConclusionSitagliptin treatment is able to improve the secretion of insulin in T2DM rats,which may be related to the up-regulation of GLP-1R/cAMP signal pathway.