Hypothalmic glucose sensing and hypoglycemic counterregulation

描述(申请人提供)：这是一位新的研究人员提出的RO1申请。该项目的总体目标是确定受损的低血糖反调节的组成部分，以及确定和测试潜在的治疗干预新靶点。1型和晚期2型糖尿病患者的常见表现是葡萄糖感觉受损、低血糖意识不清和反调节受损。这些病理过程加剧了胰岛素诱导的低血糖发作的频率和严重程度，使低血糖成为糖尿病血糖控制的限速步骤。这一应用的初步结果表明，胰岛素除了显著降低血糖水平外，还在大脑中具有重要的直接作用，独立地调节葡萄糖感觉和交感肾上腺对低血糖的反应。这项建议的总体假设是，调节中枢神经系统下丘脑的胰岛素敏感治疗靶点可以改善实验动物对低血糖的认知和反调节反应。利用局部下丘脑RT-PCR技术确定关键基因和下丘脑基因表达的组合模式，将有助于识别下丘脑葡萄糖感知受损和反调节受损动物模型的分子病理学。本研究的具体目的是：(1)剖析胰岛素在中枢神经系统(CNS)调节低血糖反调节反应中的潜在作用；(2)确定胰岛素可能通过调节葡萄糖转运体和/或葡糖激酶调节下丘脑葡萄糖感受的机制，并将这些胰岛素调节的葡萄糖感觉神经元的变化与低血糖条件下神经元的功能活动联系起来；(3)在中枢胰岛素作用增强或降低的模型中，探讨胰岛素在急性低血糖改变认知功能中的作用，并区分认知和反调节反应；以及(4)利用RT-PCR技术研究胰岛素诱导的复发性低血糖所致的下丘脑局部基因的表达模式，并将基因表达的变化与葡萄糖感觉受损和低血糖反调节受损相关联。

DESCRIPTION (provided by applicant): This is a RO1 application by a new investigator. The overall goal of this project is to identify components of impaired hypoglycemic counterregulation as well as to identify and test potential new targets for therapeutic intervention. Common findings in patients with type 1 and advanced type 2 diabetes are impaired glucose sensing, hypoglycemia unawareness and impaired counterregulation. These pathological processes exacerbate the frequency and severity of insulin-induced hypoglycemic episodes making hypoglycemia the rate limiting step in the glycemic management of diabetes. Preliminary results in this application demonstrate that insulin, in addition to acutely lowering blood glucose levels, has a major direct effect in the brain to independently modulate both glucose sensing and the sympathoadrenal response to hypoglycemia. The overall hypothesis in this proposal is that modulation of insulin-sensitive therapeutic targets in the hypothalamus of the central nervous system can improve the cognitive and counterregulatory responses to hypoglycemia in experimental animals. The use of a regional hypothalamic RT-PCR technique to identify key genes and combined patterns of hypothalamic gene expression will help to identify molecular pathology in animal models of impaired hypothalamic glucose sensing and impaired counterregulation. The specific aims to be addressed in this research proposal are to: (1) dissect the potential role of insulin action in the central nervous system (CNS) in regulating the counterregulatory response to hypoglycemia; (2) determine the mechanisms by which insulin may regulate hypothalamic glucose sensing via regulation of glucose transporters and/or glucokinase and correlate these insulin-modulated changes in glucose sensing neurons with neuronal functional activity under conditions of hypoglycemia; (3) explore the role of insulin in altering cognitive function during acute hypoglycemia in models of increased or decreased CNS insulin action and differentiate the cognitive from the counterregulatory responses; and (4) examine the pattern of regional hypothalamic gene expression uniquely attributable to insulin-induced recurrent hypoglycemia with the use of RT-PCR and correlate alterations in gene expression with impaired glucose sensing and impaired hypoglycemic counterregulation.