Affiliation:
1. From the Second Department of Internal Medicine, Sapporo Medical University School of Medicine, Sapporo, Japan.
Abstract
OBJECTIVE
Alteration in endoplasmic reticulum (ER) stress in diabetic hearts and its effect on cytoprotective signaling are unclear. Here, we examine the hypothesis that ER stress in diabetic hearts impairs phospho–glycogen synthase kinase (GSK)-3β–mediated suppression of mitochondrial permeability transition pore (mPTP) opening, compromising myocardial response to cytoprotective signaling.
RESEARCH DESIGN AND METHODS
A rat model of type 2 diabetes (OLETF) and its control (LETO) were treated with tauroursodeoxycholic acid (TUDCA) (100 mg · kg−1 · day−1 for 7 days), an ER stress modulator. Infarction was induced by 20-min coronary occlusion and 2-h reperfusion.
RESULTS
Levels of ER chaperones (GRP78 and GRP94) in the myocardium and level of nonphoshopho–GSK-3β in the mitochondria were significantly higher in OLETF than in LETO rats. TUDCA normalized levels of GRP78 and GRP94 and mitochondrial GSK-3β in OLETF rats. Administration of erythropoietin (EPO) induced phosphorylation of Akt and GSK-3β and reduced infarct size (% risk area) from 47.4 ± 5.2% to 23.9 ± 3.5% in LETO hearts. However, neither phosphorylation of Akt and GSK-3β nor infarct size limitation was induced by EPO in OLETF rats. The threshold for mPTP opening was significantly lower in mitochondria from EPO-treated OLETF rats than in those from EPO-treated LETO rats. TUDCA restored responses of GSK-3β, mPTP opening threshold, and infarct size to EPO receptor activation in OLETF rats. There was a significant correlation between mPTP opening threshold and phospho–GSK-3β–to–total GSK-3β ratio in the mitochondrial fraction.
CONCLUSIONS
Disruption of protective signals leading to GSK-3β phosphorylation and increase in mitochondrial GSK-3β are dual mechanisms by which increased ER stress inhibits EPO-induced suppression of mPTP opening and cardioprotection in diabetic hearts.
Publisher
American Diabetes Association
Subject
Endocrinology, Diabetes and Metabolism,Internal Medicine
Cited by
113 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献