Effect of tyrosol on myocardial ischemia-reperfusion injury in diabetic rats and the role of SIRT1/AMPK/eNOS signaling pathway

Objective To evaluate the effect of tyrosol on myocardial ischemia-reperfusion (I/R) injury in diabetic rats and the role of silent mating-type information regulation 1 (SIRT1)/adenosine monophosphate-activated protein kinase (AMPK)/endothelial nitric oxide synthase (eNOS) signaling pathway. Methods SPF healthy adult male Sprague-Dawley rats, weighing 200-220 g, were intraperitoneally injected with streptozotocin 60 mg/kg to establish the model of diabetes mellitus.Fifty-six diabetic rats were divided into 4 groups (n=14 each) using a random number table method: sham operation group (S group), myocardial I/R group(I/R group), myocardial I/R plus tyrosol group (I/R+ T group), and myocardial I/R plus tyrosol plus SIRT1 inhibitor EX527 group (I/R+ T+ E group). In I/R+ T and I/R+ T+ E groups, tyrosol 20 mg·kg-1·d-1 was given by gavage for 45 consecutive days, and the equal volume of normal saline was given in the other two groups.In I/R+ T+ E group, EX527 5 mg·kg-1·d-1 was intraperitoneally injected for 3 consecutive days before ischemia, and EX527 5 mg/kg was intraperitoneally injected at 20 min before reperfusion.Myocardial I/R was induced by ligation of the left anterior descending branch of coronary artery for 30 min followed by 2-h reperfusion.The myocardial infarct volume was measured by TTC staining.The levels of creatine kinase-MB (CK-MB), lactic dehydrogenase (LDH) and 5-F2t-isoprostane in serum and superoxide dismutase (SOD) in myocardial tissues were detected by enzyme-linked immunosorbent assay.The expression of SIRT1, AMPK, phosphorylated AMPK (p-AMPK), eNOS and p-eNOS was detected by Western blot. Results Compared with S group, the levels of serum CK-MB, LDH and 15-F2t-Isoprostane and myocardial infarction volume were significantly increased, the SOD activity was decreased, and the SIRT1 expression was down-regulated in I/R group, and the levels of serum CK-MB, LDH and 15-F2t-Isoprostane and myocardial infarction volume were significantly increased, the SOD activity was decreased, the SIRT1 expression was down-regulated, and the expression of p-AMPK and p-eNOS was up-regulated in I/R+ T and I/R+ T+ E groups (P 0.05). Compared with I/R+ T group, the levels of CK-MB, LDH and 15-F2t-isoprostane in serum and myocardial infarct volume were significantly increased, the SOD activity was increased, and the expression of SIRT1, p-AMPK and p-eNOS was down-regulated in I/R+ T+ E group (P<0.05). Conclusion Tyrosol can mitigate myocardial I/R injury, and the mechanism may be related to activating SIRT1/AMPK/eNOS signaling pathway and inhibiting oxidative stress response in diabetic rats. Key words: Antioxidants; Diabetes mellitus; Myocardial reperfusion injury; Sirtuin 1; Protein-serine-threonine kinases; Nitric oxide synthase