Brain Insulin Action Regulates Hypothalamic Glucose Sensing

脑胰岛素作用调节下丘脑葡萄糖感应

• 批准号: 7912978
• 负责人: Kelly A Diggs-Andrews
• 金额: $ 1.36万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7912978
• 关键词: Address; Biological Assay; Blood Glucose; Brain; Coma; Diabetes Mellitus; FOS gene; Genetic; Glucokinase; Glucose; Glucose Transporter; Goals; Hypoglycemia; Hypothalamic structure; Individual; Insulin; Insulin-Dependent Diabetes Mellitus; Link; Measures; Mediating; Methods; Mus; National Institute of Diabetes and Digestive and Kidney Diseases; Neuraxis; Neurons; Proteins; Radioisotopes; Regulation; Research; Risk; Role; Seizures; Site; Techniques; biological adaptation to stress; blood glucose regulation; combat; design; diabetic patient; experience; fighting; glucose sensor; glucose uptake; insight; insulin signaling; mouse model; non-diabetic; prevent; response; type I diabetic

DESCRIPTION (provided by applicant): Episodes of severe low blood sugar (hypoglycemia) are a major problem for Type 1 diabetic patients. Normally, the brain senses hypoglycemia and triggers a "fight-or-flight" stress response to rapidly increase blood sugar and prevent a seizure or coma. Unfortunately, people with Type 1 diabetes do not detect low blood glucose as well as non-diabetic individuals and their ability to defend against it is severely impaired. Therefore, they are at a greater risk of experiencing severe hypoglycemic episodes. Hypoglycemia is the limiting step in the treatment of diabetes and precludes against the benefits linked to intensive glucose control. Due to these consequences, a major research initiative of the NIDDK is to prevent or reduce hypoglycemia in Type 1 diabetics, specifically by defining the "mechanisms and modulators" of brain glucose sensing. This proposal is designed to study the role and mechanism by which insulin regulates brain glucose sensing. Key evidence suggests that insulin acts in the brain to regulate glucose homeostasis, CNS glucose sensing, and the counterregulatory response (CRR) to hypoglycemia, but the site and method of CNS insulin action are still unknown. This study will 1) investigate whether insulin acts on hypothalamic neurons to regulate brain glucose sensing and 2) determine how insulin regulates glucose sensing by evaluating its effects on key glucose sensors and CNS glucose uptake. First, taking advantage of a genetic mouse model that lacks CNS insulin action (NIRKO mouse), this study will assess whether CNS insulin action regulates the brain's ability to detect and respond to hypoglycemia. The CRR and neuronal activation in response to hypoglycemia will be measured via hypoglycemic clamp studies and c-fos immunostaining. Further, to clarify a mechanism of CNS insulin action, this study will also assess whether insulin regulates key glucose sensors and/or CNS glucose uptake. Glucose sensing proteins, including glucose transporters (GLUTs) and glucokinase (GK), will be assayed for altered expression in the NIRKO mouse via standard immunohistochemical techniques. Similarly, to detect changes in brain glucose uptake, regional brain glucose utilization will be evaluated using a radioisotope assay. Overall, this study will provide new insights into insulin's role in regulating CNS glucose sensing and the hypoglycemic counterregulatory response. Because intensive insulin therapy increases the risk of severe hypoglycemia (low blood glucose episode), hypoglycemia impedes tight glucose management in diabetic patients. Therefore, understanding how the brain regulates the stress response to hypoglycemia is critical to devise therapies to combat hypoglycemia.

描述（由申请人提供）：严重低血糖（低血糖）发作是1型糖尿病患者的主要问题。正常情况下，大脑会感知到低血糖，并触发“战斗或逃跑”的应激反应，以迅速增加血糖，防止癫痫发作或昏迷。不幸的是，1型糖尿病患者不能像非糖尿病患者那样检测到低血糖，他们抵御低血糖的能力严重受损。因此，他们经历严重低血糖发作的风险更大。低血糖是糖尿病治疗中的限制性步骤，并排除了与强化血糖控制相关的益处。由于这些后果，NIDDK的主要研究计划是预防或减少1型糖尿病患者的低血糖，特别是通过定义大脑葡萄糖感知的“机制和调节剂”。本研究旨在研究胰岛素对脑葡萄糖感知的调节作用及其机制。关键证据表明，胰岛素在大脑中调节葡萄糖稳态、CNS葡萄糖感知和对低血糖的反调节反应（CRR），但CNS胰岛素作用的部位和方法仍不清楚。本研究将1）研究胰岛素是否作用于下丘脑神经元以调节脑葡萄糖感知，2）通过评估胰岛素对关键葡萄糖感受器和CNS葡萄糖摄取的影响来确定胰岛素如何调节葡萄糖感知。首先，利用缺乏CNS胰岛素作用的遗传小鼠模型（NIRKO小鼠），本研究将评估CNS胰岛素作用是否调节大脑检测和响应低血糖的能力。将通过低血糖钳夹研究和c-fos免疫染色测量低血糖反应的CRR和神经元激活。此外，为了阐明CNS胰岛素作用的机制，本研究还将评估胰岛素是否调节关键葡萄糖传感器和/或CNS葡萄糖摄取。将通过标准免疫组织化学技术测定葡萄糖敏感蛋白（包括葡萄糖转运蛋白（GLUT）和葡萄糖激酶（GK））在NIRKO小鼠中的表达变化。同样，为了检测脑葡萄糖摄取的变化，将使用放射性同位素测定评价局部脑葡萄糖利用。总之，这项研究将提供新的见解，胰岛素的作用，调节中枢神经系统葡萄糖传感和低血糖的反调节反应。由于强化胰岛素治疗增加了严重低血糖（低血糖发作）的风险，因此低血糖阻碍了糖尿病患者的严格血糖管理。因此，了解大脑如何调节对低血糖的应激反应对于设计治疗低血糖至关重要。