Protective effects of sitagliptin on myocardial injury and cardiac function in an ischemia/reperfusion rat model

The purpose of this study is to investigate the effects and the underlying mechanisms of sitagliptin pretreatment on myocardial injury and cardiac function in myocardial ischemia/reperfusion (I/R) rat model. The rat model of myocardial I/R was constructed by coronary occlusion. Rats were pretreated with sitagliptin (300 mg/kg/day) for 2 weeks, and then subjected to 30 min ischemia and 2h reperfusion. The release of lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB), cardiac function and cardiomyocyte apoptosis were evaluated. The levels of malondialdehyde (MDA), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in heart and glucagon-like peptide-1 (GLP-1) level in plasma were measured. Western blot analysis was performed to detect the target proteins of sitagliptin. Our results showed that sitagliptin pretreatment decreased LDH and CK-MB release, and MDA level in I/R rats. More importantly, we revealed for the first time that sitagliptin pretreatment decreased cardiomyocyte apoptosis while increased the levels of GSH-Px and SOD in heart. Sitagliptin also increased GLP-1 level and enhanced cardiac function in I/R rats. Furthermore, sitagliptin pretreatment up-regulated Akt(serine473) and Bad(serine136) phosphorylation, reduced the ratio of Bax/Bcl-2, and decreased expression levels of cleaved caspase-3 and caspase-3. Interestingly, the above observed effects of sitagliptin were all abolished when co-administered with GLP-1 receptor antagonist exendin-(9-39) or PI3K inhibitor LY294002. Taken together, our data indicate that sitagliptin pretreatment could reduce myocardial injury and improve cardiac function in I/R rats by reducing apoptosis and oxidative damage. The underlying mechanism might be the activation of PI3K/Akt signaling pathway by GLP-1/GLP-1 receptor.