The Effect Of Glucagon-like Peptide-1Receptor Agonist On The Expression Of Bcl-2、Bax In The Myocardial Tissue Of Diabetic Rats

Objective:Diabetes mellitus (DM) is a group of clinical syndrome that caused by multiple factors and featured by chronical hyperglycemia. It can lead to multi-system damage.Cardiovascular disease was one of the major diabetic complication,the study of diabetic angiocardiopathy mainly focus on macroangiopathy.In recent years study confirmed diabetic cardiomyopathy(DCM) was caused by diabetic microangiopathy complication.Myocardial cell apoptosis is one of the main pathological changes of DCM. Bax and Bcl-2are the more apoptosis related gene in the present research,they site with mitochondrial for regulating apoptosis,and the ratio of Bcl-2/Bax commonly used to measure the level of apoptosis. Exenatide(EX),a new drug that remedy diabetes mellitus,is the agonist of glucagon-like peptide-1(GLP-1) receptor,which was synthesized recently.Functions of exenatide mainly mediated by glucagon-like peptide-1receptor(GLP-1R). Recent studies have found that exenatide can protect myocardium from injury,but the specific mechanism of protection is still unclear.The aim of this study is to observe the changes of myocardial pathological structure and detect the changes of Bcl-2、Bax mRNA and protein level,calculate the ratio of Bcl-2/Bax in DM rats myocardial in exenatide intervention so as to investigate whether exenatide has a protective effect on DM myocardial cell apoptosis.Methods:36clean grade inbred male Wistar rats were reared in single cage with standard feed in specific pathogen-free conditions.Fed adaptability1Week after select10of them randomly as normal group(N group),feed with normal animal feeds.Others with fatty feed and sugary stuff and8weeks later,26rats were injected with30mg streptozocin/kg BW via the tail vein.N group rats was injected with equal buffer solution.Blood samples were taken from canthus veins for glucose test in72hours.The glucose levels of experiment group rats were more than16.7mmol/L,drinked water>40ml/d,urine glucose positive(++～++++).DM rats modelled successfully which were randomly divided into exenatide intervention group(EX group)(n=11)and DM group(n=11).EX group was administered with exenatide (1.0nmol·kg-1) by subcutaneous injection daily,N group and DM group were subcutaneous injected by physiological saline in the same amount.After12weeks,there were10rats left in each group,record body weight of the rats,these three group rats were killed by the femoral artery bleeding,and taken blood to detect biochemical indicators.Some myocardial of left ventricle was obtained and fixated with10%formalin and some myocardial tissue was fixated with liquid nitrogen and obtained at-80℃:①Observed the structural changes of myocardial tissue by HE staining;②Detected the expression of of Bcl-2、Bax mRNA and the ratio of Bcl-2/Bax in DM rats myocardial by Real-time quantitative PCR;③Detected the expression of Bcl-2、Bax protein and the ratio of Bcl-2/Bax by Western Blotting and calculated relative expression with GAPDH as internal control.Results:①HE staining:N group had normal myocardial structure.While the myocardial tissue structure of DM group was disordered, myocardial cells hypertrophy and proliferation, karyopyknosis,intercellular circumscription unclear, myocardial fibers severe edema and fracture,myocardial interstitial fibrosis,the changes of the above presents the early-phase change of DCM;Myocardial damages in EX group were alleviated,but it didn’t recover to normal level.②Compared with N group,the expression of Bax mRNA and protein in DM group increased obviously,while the expression of Bcl-2mRNA and protein and the ratio of Bcl-2/Bax decreased obviously (P<0.01), the difference was statistically significant; compared with DM group, the expression of Bax mRNA and protein in EX group decreased obviously, the expression of Bcl-2mRNA and protein and the ratio of Bcl-2/Bax increased obviously (P<0.01),the difference was statistically significant.Conclusions:①Compared with N group rats,the expression of Bax in DM rats myocardium increased obviously, Bcl-2and the ratio of Bcl-2/Bax decreased obviously, suggesting that myocardial cell apoptosis may play a role in the pathogenesis of diabetes myocardial injury.②The pathological changes of myocardium in EX group were slighter than DM group.The expression of Bcl-2and the ratio of Bcl-2/Bax in intervention group increased obviously,suggesting that exenatide can alleviate DM myocardial injury probably by reducing myocardial cells apotosis.