肌肽对1型糖尿病大鼠心脏的保护作用

Protective role of carnosine on cardiac dysfunction in type 1 diabetes mellitus rat model

目的:探讨肌肽(CAR)对1型糖尿病(T1DM)大鼠心功能的影响及保护机制。方法:采用链脲佐菌素(STZ)单次腹腔注射的方法制作大鼠1型糖尿病模型。将40只雄性SD大鼠随机分为正常对照(C)组,肌肽对照(C+CAR)组,糖尿病模型(DM)组和糖尿病CAR治疗(DM+CAR)组,每组10只。12周后处死大鼠,颈总动脉插管测定心功能;酶联免疫吸附法测定左心室肌超氧化物歧化酶(SOD)活性和丙二醛(MDA)含量;real-time PCR法检测肿瘤坏死因子α(TNF-α)、白细胞介素1β(IL-1β)和IL-6的mRNA表达;免疫荧光法检测缝隙连接蛋白43(Cx43)的分布;Western blot法检测Cx43及蛋白激酶C(PKC)各亚型的蛋白表达。结果:与C组相比,DM组大鼠左心室舒张末压(LVEDP)升高,左心室内压最大上升和下降速率(±dp/dt_(max))降低(P <0. 01);左心室肌组织SOD活性降低,MDA含量升高(P <0. 01);TNF-α、IL-1β和IL-6的mRNA表达水平升高(P <0. 01);Cx43分布紊乱;磷酸化Cx43和PKCε蛋白水平升高(P <0. 01)。与DM组相比,DM+CAR组的LVEDP降低,±dp/dt升高(P <0. 01);左心室肌组织的SOD活性升高,MDA含量降低(P <0. 05);TNF-α、IL-1β和IL-6的mRNA表达水平降低(P <0. 01);Cx43分布好转;磷酸化的Cx43及PKCε蛋白水平降低(P <0. 01)。结论:肌肽治疗能改善1型糖尿病大鼠心功能障碍,其机制可能与降低左心室氧化应激和炎症反应,通过PKCε抑制Cx43磷酸化,并改善其分布有关。

AIM:To explore the effects of carnosine(CAR)on cardiac dysfunction in type 1 diabetic mellitus rats and the underlying mechanism.METHODS:The SD rats were randomly divided into 4 groups:control(C)group,control+carnosine(C+CAR)group,diabetes mellitus(DM)group and diabetes mellitus+carnosine(DM+CAR)group(n=10).The rats were sacrificed after 12 weeks.The cardiac function was assessed by ventricular cannulation.The activity of superoxide dismutase(SOD)and the content of malondialdehyde(MDA)were assessed by ELISA.The mRNA levels of tumor necrosis factorα(TNF-α),interleukin-1β(IL-1β)and IL-6 were measured by real-time PCR.The distribution of connexin 43(Cx43)was examined by immunofluorescence.The protein levels of Cx43 and protein kinase C(PKC)were determined by Western blot.RESULTS:Compared with the C group,the left ventricular end diastolic pressure(LVEDP)was increased whereas the left ventricular pressure maximum rise/fall velocity(±d p/d t max)was decreased in the DM group(P<0.01).The activity of SOD decreased while the MDA increased in the left ventricular tissues(P<0.01).The mRNA levels of TNF-α,IL-1βand IL-6 were increased(P<0.01).The Cx43 distribution was irregular.The protein levels of phosphorylated Cx43 and PKCεwere elevated(P<0.01).Compared with the DM group,the cardiac function of LVEDP and±d p/d t max in DM+CAR group was ameliorated(P<0.01),with increased SOD activity and decreased MDA content(P<0.05).The mRNA levels of TNF-α,IL-1βand IL-6 were reduced(P<0.01).The Cx43 distribution was improved and the protein levels of phosphorylated Cx43 and PKCεwere decreased(P<0.01).CONCLUSION:CAR treatment can improve the cardiac function by its anti-oxidative and anti-inflammation effects and suppression of Cx43 abnormalities through PKCεin DM rats.