The Protective Effect And Mechanism Of Metformin On Myocardial Ischemia Reperfusion Injury

Part ?:Study on cardioprotective effect of metformin on ischemia reperfusion injury in ratsObjective:To investigate the cardioprotective effect of metformin on ischemia reperfusion injury in rats.Methods:The animal models of myocardial ischemia-reperfusion injury were established and they were divided into three groups:the sham group,the group of myocardial ischemia-reperfusion injury and the metformin treatment group.The data were detected and recorded after 30 min of ischemia and 2 hours during reperfusion.The myocardial infarct size was measured by myocardial staining among groups.The pathological changes of myocardium were observed by HE staining.The serum CK-MB and cTNI levels in each group were detected by automated biochemical analyzer.The serum SOD activity was detected by the method of WST-1.The serum LDH activity was detected by the method of micro-enzyme linked immunosorbent assay.The serum levels of TNF-aand IL-6 were detected by the ELISA method.The serum MDA level was detected by the TBA method.The cardiac function of rats were evaluated by P-V conduit monitoring system.Results:The pathological changes of myocardial morphology were observed by HE staining.The myocardial structure of the sham group was intact,the myocardial fibers were arranged regularly.There was no obvious inflammatory cells and red cells infiltration in myocardial tissue.In the group of myocardial ischemia-reperfusion injury,the myocardial fibers were disordered,the cells were degenerated and necrotic,interstitial edema,myolysis was obvious,and large inflammatory cells infiltrated in the myocardial tissue.In the group of metformin treatment,the myocardial fibers were arranged a little disorder.And there was a few of inflammatory cells and red cells infiltration in myocardial tissue.The myocardial structure destruction of the metformin treatment group was significantly reduced compared with those in the group of myocardial ischemia-reperfusion injury.The results of TTC staining showed that there was no myocardial infarchtin in the sham group.Compared with the group of myocardial ischemia-reperfusion injury,the size of myocardial infarchtin from the metformin treatment group was obviously reduced,and there was significantly statistical difference(P<0.05).Compared with those in the sham group,the levels of CK-MB,TNI,TNF-a,IL-6,LDH and MDA were increased and SOD activity was decreased in the group of myocardial ischemia-reperfusion injury.And there was significantly statistical difference(P<0.05).Compared with those in the group of myocardial ischemia-reperfusion injury,the levels of CK-MB,TNI,TNF-?.IL-6,LDH and MDA were decreased and SOD activity was increased in the metformin treatment group.And there was significantly statistical difference(P<0.05).Compared with those in the sham group,the indexes of PRSW and EF in the group of myocardial ischemia-reperfusion injury were significantly decreased at 1 week and 4 weeks time points.Compared with those in the group of myocardial ischemia-reperfusion injury,PRSW and EF indexes in the metformin treatment group were significantly increased.And there was significantly statistical difference(P<0.05).Conclusions:Metformin could reduce myocardial responses to injury,inflammatory response and oxidative stress response of myocardial ischemia-reperfusion injury and improve the cardiac function in rats.Part ?:Study on effect of metformin on apotosis of myocardial cells during hypoxia/reoxygenation injuryObjective:To investigate the effect and underlying mechanism of metformin on myocardial cell apoptosis induced by myocardial ischemia-reperfusion injury in rats.Methods:Forty suckling Wistar rats were selected,and the hearts were removed under aseptic condition.Rat myocardial cells were primarily cultured to establish hypoxia/reoxygenation injury(H/R)models of myocardial cells in vitro and the models were randomly classfied into four groups:blank control group,metformin group,H/R group and metformin+H/R group.The apoptotic rate of primary rat myocardial cells in each group was tested with the terminal deoxynucleotidyl transferase dUTP nick end labeling(TUNEL)assay.The cell counting kit-8(CCK-8)assay was utilized to measure the viability of primary rat myocardial cells in each group.The relative expression of HIF-la mRNA of primary rat myocardial cells in each group was assessed by using real-time PCR.The relative expression of Bcl-2 and Bax protein of primary rat myocardial cells in each group was tested by using Western Blot assay.Results:As compared with the blank control group,the apoptotic rate of primary rat myocardial cells in the H/R group was significantly increased(P<0.001)and the cell viability was obviously reduced(P<0.001).When compared with hypoxia and reoxygenation culture,metformin pretreatment significantly reduced the apoptotic rate of myocardial cells(P<0.001)and promoted cell survival in rats(P<0.001).Meanwhile,real-time PCR results showed that the relative expression of HIF-la mRNA was significantly decreased in the metformin+H/R group.Western Blot results showed that the relative expression of Bcl-2 protein was significantly increased and relative expression of Bax protein was significantly decreased in the metformin+H/R group,with statistical differences.Conclusion:Metformin can reduce the apoptosis of rat myocardial cells following ischemia-reperfusion injury.The underlying mechanism may be associated with an improvement in cell viability,suppression in HIF-la expression,increase in the apoptosis inhibitor Bcl-2e expression and decrease in the Bax expression.Part ?:Effects of metformin on autophagyofmyocardial cellsin rats with myocardium injury of ischemia reperfusionObjective:To investigate the effect of metformin on autophagy of myocardial cells in rats with myocardium injury of ischemia reperfusion.Methods:The SD rats were used to establish rat models with myocardium injury of ischemia reperfusion induced by ligation of the left anterior descending coronary artery and then randomly divided into the following 3 groups:the sham group,the control group treated with normal saline by intragastric administration,the treatment group treated with metformin by intragastric administration,and Echocardiography was performed at 4,8,and 12 weeks.The autophagy rate of myocardial cells were observed in each group by transmission electron microscopy respectively;the levelsof protein Cathepsin D and Beclin-1 expression were detected by western blotting.Results:Echocardiography showed reduced systolic function at 4 weeks after modeling.At 12 weeks after metformin intervention,significantly higher left ventricular ejection fraction(LVEF)was observed in the treatment group compared to the control group(P<0.05);but there were no statistical difference for the left ventricular posterior wall thickness(LVPWT)in end-systole,the interventricular septal thickness(IVST)in end-systole,the left ventricular posterior wall thickness(LVPWT)in end-diastole and in the interventricular septal thickness(IVST)in end-diastole among groups.The autophagy rate of myocardial cells was significantly lower in the treatment group versus the control group(P<0.05).Compared to the sham group,the levels of proteins Beclin-1 and Cathepsin D expression significantly increased in the control group(P<0.05),but decreased markedly in the treatment group(P<0.05).Conclusion:Reductions in the autophagy of myocardial cells and improvements in the cardiac functions of rats with myocardium injury of ischemia reperfusion by metformin may be attributable to regulation of the levels of proteinsBeclin-1 and Cathepsin D expression.Part ?:Study on cardioprotective effect of metformin on injury after PCI in patients with acute myocardial infarctionObjective:To explore the effect of t metformin on injury after percutaneous transluminal coronary intervention(PCI)in patients with acute myocardial infarction and its underlying mechanisms.Methods:Eighty cases of diabetes patients with acute myocardial infarction who had been hospitalized in our hospital from January 2016 to March 2018 were recruited in this study and underwent PCI immediately.The enrolled patients were divided into the observation group(n=40)and the control group(n=40)according to whether taking orally metformin.In addition to usual care,the patients in the control group did not received metformin before acute myocardial infarction,while those in the observation group received metformin treatment before acute myocardial infarction.All the patients were treated for 1 month.The two groups were compared in the treatment effect of angina pectoris after PCI,changes in serum inflammatory factors,angina frequency and duration,ECG ST-T segment improvement effect,cardiac function,and the rate of adverse events.Results:The overall response rate of angina pectoris after PCI was 92.5%in the observation group,which was substantially higher than 72.5%in the control group(P<0.05).At the end of the treatment,IL-6 and TNF-a levels in the observation group were remarkably lower than those in the control group(both P<0.05);the angina frequency and duration in the observation group were also significantly lower than those in the control group,and the differences were statistically significant between the two groups.The ECG ST-T segment improvement rate in the observation group was significantly higher than those in the control group and there were significant differences between two groups.Additionally,the left ventricular ejection fraction(LVEF)in the observation group was significantly higher than that in the control group(P<0.05),but the left ventricular end-diastolic diameter(LVDD)was significantly smaller(P<0.05).No significant between-group difference was seen in the rate of overall adverse events.Conclusion:The metformin treatment was effective in treating injury response to PCI for patients with acute myocardial infarction,leading to fewer adverse events.This might be associated with improved cardiac function,and lower IL-6 and TNF-a expression levels.