Increased cerebral ischemic injury by repeated hypoglycemic episodes in diabetes

描述(申请人提供)：该项目的长期目标是通过降低糖尿病患者脑缺血的严重程度和发生率来改善糖尿病患者的神经健康。脑缺血和心脏病是糖尿病最严重的并发症，占糖尿病患者死亡率的84%以上。脑缺血的流行病学研究表明，糖尿病既增加了脑缺血的发病风险，又加剧了脑缺血的后果。高血糖是致病因素之一。在临床研究中，强化抗糖尿病治疗能够延缓糖尿病继发性并发症的发生和进展。糖尿病强化治疗的主要副作用是低血糖。一些报告描述了接受强化治疗的1型和2型糖尿病患者的低血糖发作。使用链脲佐菌素糖尿病大鼠，我们观察到反复低血糖(RH)使胰岛素治疗的糖尿病(ITD)大鼠的大脑对全脑缺血更加敏感，并导致更大的脑损伤。目前，我们建议研究RH增加ITD缺血损伤的机制。在初步研究中，我们观察到RH后ITD大鼠海马区缺血内细胞外pH下降增强，葡萄糖转运蛋白1和3水平升高。我们假设，在胰岛素治疗的糖尿病脑中，RH后葡萄糖转运体水平的增加会导致缺血内酸中毒的增加，从而使大脑对脑缺血诱导的损伤增强敏感。本研究拟验证以下特定目标以检验中心假设：1)确定RH如何增加ITD大鼠的脑缺血损伤；2)确定RH暴露的ITD大鼠脑缺血内pH下降增加脑缺血损伤的机制；以及3)确定RH增加ITD大鼠海马区GLUT1和GLUT3水平的机制。我们期望这些研究能够深入了解RH增加糖尿病患者缺血性损害的机制。了解这一机制将有助于改善脑缺血后的预后。

DESCRIPTION (provided by applicant): The long-term goal of this project is to improve neurological health of diabetics by decreasing the severity and incidence of cerebral ischemia in diabetics. Cerebral ischemia and heart disease are the most serious complications of diabetes, accounting for more than 84% of the mortality among diabetics. Epidemiological studies of cerebral ischemia suggest that diabetes increases both the risk of incidence and exacerbates the consequences of cerebral ischemia. Hyperglycemia is one of the contributing factors. In clinical studies, intensive anti-diabetic therapy was able to delay the onset and slow the progression of secondary complications of diabetes. The major side-effect of intensive diabetic therapy is hypoglycemia. Several reports described hypoglycemic episodes in type 1 and type 2 diabetics receiving intensive therapy. Using the streptozotocin-diabetic rat, we observed that recurrent hypoglycemia (RH) renders the insulin-treated diabetic (ITD) rat brain more sensitive to global cerebral ischemia and results in greater brain damage. Presently, we are proposing to investigate the mechanism by which RH increases ischemic damage in ITD. In preliminary studies we observed that the intra-ischemic extracellular pH drop was enhanced, and the levels of glucose transporters (GLUTs) 1 and 3 were increased in the hippocampus of ITD rats subjected to RH. We hypothesize that in the insulin-treated diabetic brain, increased glucose transporter levels following RH lead to increased intra-ischemic acidosis, sensitizing the brain towards the enhancement of cerebral ischemia-induced damage. The following specific objectives are proposed to test the central hypothesis: 1) To determine how RH increases cerebral ischemic damage in ITD rats; 2) To determine the mechanism by which the larger intra-ischemic pH drop in RH-exposed ITD rats increases cerebral ischemic damage; and 3) To determine the mechanism by which RH increases GLUT1 and GLUT3 levels in the hippocampus of ITD rats. We expect these studies to provide insight into the mechanism by which RH increases ischemic damage in diabetics. Understanding this mechanism will help improve outcome following cerebral ischemia.