Role of PI3K/Akt signal pathway in gensenoside Rb1 pretreatment-induced attenuation of myocardial ischemia-reperfusion injury in diabetic rats

Objective To investigatc the role of phosphatidylinositol 3-kinase (PI3K)/protein-serine-threonine kinases (Akt) signal pathway in ginsenoside Rb1 pretreatment-induced attenuation of myocardial ischemiareperfusion (I/R) injury in diabetic rats.Methods Male SD rats weighing 250-300 g were used in this study.Diabetes mellitus was induced by intraperitoneal streptozotocin and confirmed by fasting blood glucose ≥ 16.7mmol/L.Eight weeks after diabetes mellitus was induced,48 rats were randomly divided into 4 groups ( n =12each):group myocardial I/R (group I/R); group ginsenoside Rb1 (group R); group ginsenoside Rb1 + wortmannin (PI3K inhibitor) (group RW) and group wortmannin (group W).Myocardial I/R was induced by occlusion of anterior descending branch of left coronary artery for 30 min followed by 120 min reperfusion.Ginsenoside Rb1 40 mg/kg was injected iv at 10 min before ischemia in groups R and RW,while in groups RW and W wortmannin 15 μg/kg was injected iv at 20 min before ischemia.Arterial blood samples were collected at the end of 120 min reperfusion for determination of creatine kinase (CK) and lactate dehydrogenase (LDH) activities.The rats were then sacrificed.The infarct size was measured by tetrazolium method.Myocardial apoptosis was detected by TUNEL and apoptotic index (the number of apoptotic myocardial cells/the total number of myocardial cells) was calculated.The expression of Akt and phosphorylated Akt (p-Akt) was determined by Western blotting.Results Ginsenoside Rb1 pretreatment significantly reduced the infarct size,myocardial cell apoptotic index and serum CK and LDH activities and up-regulated p-Akt expression in group R as compared with group I/R.The protective effects of ginsenoside Rbl against myocardial I/R injury were significantly attenuated by wortmannin pretreatment in group RW compared with group R.Conclusion PI3K/Akt signal pathway is involved in the protective effects of ginsenoside Rb1 against myocardial I/R injury in diabetic rats. Key words: 1-Phosphatidylinositol 3-kinase;  Protein-serine-threonine kinases;  GINSENOSIDE; Myocardial reperfusion injury;  Diabetes mellitus