Effects of glucagon-like peptide 1 analogs in combination with insulin on myocardial infarct size in rats with type 2 diabetes mellitus

AIM: To evaluate the effects of glucagon-like peptide-1 analogs (GLP-1a) combined with insulin on myocardial ischemia-reperfusion injury in diabetic rats. METHODS: Type 2 diabetes mellitus (T2DM) was induced in male Wistar rats with streptozotocin (65 mg/kg) and verified using an oral glucose tolerance test. After anesthesia, the left coronary artery was occluded for 40 min followed by 80 min reperfusion. Blood glucose level was measured during surgery. Rats were randomized into six groups as follows: (1) control rats; (2) insulin (0.1 U/kg) treated rats prior to ischemia; (3) insulin (0.1 U/kg) treated rats at reperfusion; (4) GLP-1a (140 mg/kg) treated rats prior to ischemia; (5) GLP-1a (140 mg/kg) treated rats at reperfusion; and (6) rats treated with GLP-1a (140 mg/kg) prior to ischemia plus insulin (0.1 U/kg) at reperfusion. Myocardial area at risk and infarct size was measured planimetrically using Evans blue and triphenyltetrazolium chloride staining, respectively. RESULTS: There was no significant difference in the myocardial area at risk among groups. Insulin treatment before ischemia resulted in a significant increase in infarct size (34.7% ± 3.4% vs 18.6% ± 3.1% in the control rats, P < 0.05). Post-ischemic administration of insulin or GLP-1a had no effect on infarct size. However, pre-ischemic administration of GLP-1a reduced infarct size to 12% ± 2.2% (P < 0.05). The maximal infarct size reduction was observed in the group treated with GLP-1a prior to ischemia and insulin at reperfusion (8% ± 1.6%, P < 0.05 vs the control and GLP-1a alone treated groups). CONCLUSION: GLP-1a pre-administration results in myocardial infarct size reduction in rats with T2DM. These effects are maximal in rats treated with GLP-1a pre-ischemia plus insulin at reperfusion.