Quercetin: A Phytoestrogen Attenuate GSK-3β Inhibitors Induced Delayed Cardioprotection in Diabetic Rat Heart

Abstract

Background and Objective: Glycogen synthase kinase (GSK-3β) play central role in Ischemic Pre Conditioning (IPC) mediated early as well as late effect of cardioprotection. The signaling pathway of IPC gets diminished during diabetes mellitus. The present study was designed to investigate the whether GSK-3β inhibitors, administered 24 h before the ischemia, would exert the cardioprotection in diabetic rat. Methods: Diabetes Mellitus (DM) was induced by single administration of streptozotocin (STZ) (50 mg kgG 1 , i.p.). Rat heart was isolated and mounted on Langendroff's apparatus and subjected to 30 min of ischaemia followed by 120 min of reperfusion. Myocardial infarct size was estimated by triphenyltetrazolium chloride (TTC) staining, lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB) were measured for the extent of myocardial damage. Results: Administration of GSK-3β inhibitors, SB 216763 (SB, 0.6 mg kgG 1 , i.p.) and indirubin-3 monooxime (IND, 0.4 mg kgG 1 , i.p.), 24 h before, not 12 h before the isolation of heart, significantly attenuated I/R-induced infarct size, release of LDH and CK-MB, as compared to vehicle treated group. However, this observed cardioprotection was significantly attenuated by administration of quercetin (4 mg kgG 1 , i.p) an inhibitor of heat shock protein 72 (HSP-72) 1h before the treatment of either drugs. Conclusion: Administration of GSK-3β inhibitors 24 h before the ischemic insult produces the cardioprotection in diabetic rat heart which may be mediated through HSP-72, since it was significantly attenuated by pretreatment with quercetin.