Role of Ghrelin in the Counter-Regulatory Response to Insulin-Induced Hypoglycemia

项目概要/摘要 对低血糖的防御对于生存是至关重要的，并且在临床上显著的低血糖中是特别重要的。 胰岛素引起的低血糖。胰岛素诱导的低血糖在1型和晚期糖尿病患者中普遍存在。 2型糖尿病，并与广泛的负面影响，包括减少工作 生产力和生活质量，对强化胰岛素方案的依从性或建议降低， 事故和其他疾病的发生率增加，偶尔死亡。当身体发育的时候 一种高度整合的防御系统，用于预防或纠正糖尿病患者的低血糖 由于过度胰岛素化而经历反复低血糖，这些反调节防御是 损害，导致低血糖的恶性循环， 无意识（低血糖相关的自主神经功能衰竭; HAAF）源于废除 交感肾上腺臂的反调节反应。生长激素释放肽生物学的几个方面表明，生长激素释放肽 可能参与对胰岛素诱导的低血糖的反调节反应：1）生长激素释放肽分泌是 直接由低葡萄糖和交感肾上腺激活刺激; 2）随后升高的ghrelin具有其 处置许多影响葡萄糖处理的潜在下游靶点，包括相互作用 几种传统的反调节反应激素。然而，虽然生长激素调节血液 葡萄糖和血糖已经在诸如热量限制、 胃饥饿素系统对胰岛素诱导的低血糖的反调节反应尚未完全 通过实验评估，例如通过在小鼠中重新产生胰岛素诱导的低血糖或HAAF，而没有胰岛素诱导的低血糖。 完整的胃饥饿素系统在这里，我们将测试的概念，胃饥饿素发挥关键，保护，反调节作用 对胰岛素引起的低血糖的反应。特别是，我们将分离的直接影响， 通过进行胰岛素推注诱导的低血糖试验， 高胰岛素-低血糖钳夹和缺乏胰岛素受体小鼠的离体生长素释放肽分泌研究 选择性地在ghrelin细胞和根皮苷-降血糖钳在ghrelin-KO小鼠。我们将确定 AgRP神经元或SF 1神经元GHSRs在反调节反应中的需要和充分性 使用Cre-lox转基因小鼠和化学遗传学技术。同时，我们将确定生长激素释放肽缺失 通过评估生长激素释放肽对野生型小鼠低血糖的反应， 缺乏ghrelin的小鼠反复低血糖后HAAF和总体反调节反应 我们独一无二的针对生长激素释放肽系统的重组小鼠模型工具箱，我们的团队在 研究生长激素释放肽的作用和分泌，以及我们在葡萄糖代谢方面的专业知识，包括执行 小鼠的葡萄糖钳将使我们获得重要和新颖的见解，不仅是低血糖的反- 调节和HAAF的发展，而且还有ghrelin细胞生理学和ghrelin作用。

PROJECT SUMMARY/ABSTRACT Defense against hypoglycemia is critical for survival, and is of particular importance in the clinically-significant setting of insulin-induced hypoglycemia. Insulin-induced hypoglycemia is prevalent in Type 1 and advanced Type 2 diabetes mellitus, and is associated with a far-ranging negative impact, including reduced work productivity and quality of life, decreased adherence to or recommendations for intensive insulin regimens, increased incidence of accidents and other morbidities, and occasionally death. While the body has developed a highly integrated defense system with which to prevent or correct hypoglycemia, in diabetes patients experiencing recurrent hypoglycemia due to over-insulinization, these counter-regulatory defenses are compromised, contributing to what can become a vicious cycle of hypoglycemia and often hypoglycemia unawareness (hypoglycemia-associated autonomic failure; HAAF) stemming from an abrogated sympathoadrenal arm of the counter-regulatory response. Several facets of ghrelin biology suggest that ghrelin may participate in the counter-regulatory response to insulin-induced hypoglycemia: 1) ghrelin secretion is directly stimulated by low glucose and sympathoadrenal activation; 2) the ensuing raised ghrelin has at its disposal many potential downstream targets with which to influence glucose handling, including interactions with several traditional counter-regulatory response hormones. However, while ghrelin regulation of blood glucose and by blood glucose have been evaluated in contexts such as caloric restriction, the overall role of the ghrelin system in the counter-regulatory response to insulin-induced hypoglycemia has not been fully assessed experimentally, for instance by re-creating insulin-induced hypoglycemia or HAAF in mice without an intact ghrelin system. Here, we will test the concept that ghrelin plays a key, protective, counter-regulatory role in the body’s response to insulin-induced hypoglycemia. In particular, we will dissociate the direct effects of insulin versus hypoglycemia on ghrelin secretion by performing insulin bolus-induced hypoglycemia tests, hyperinsulinemic-hypoglycemic clamps, and ex vivo ghrelin secretion studies in mice lacking insulin receptors selectively in ghrelin cells and phloridzin-hypoglycemic clamps in ghrelin-KO mice. We will determine requirement and sufficiency for GHSRs in AgRP neurons or SF1 neurons on the counter-regulatory response using Cre-lox transgenic mice and chemogenetic technology. Also, we will determine if ghrelin deletion increases susceptibility to HAAF by assessing the ghrelin response to hypoglycemia in wild-type mice with HAAF and the overall counter-regulatory response following recurrent hypoglycemia in mice lacking ghrelin. Our one-of-a-kind toolbox of recombinant mouse models targeting the ghrelin system, our team’s expertise in studying both ghrelin action and secretion, and our expertise in glucose metabolism including performing glucose clamps in mice will allow us to gain important and novel insights into not only hypoglycemia counter- regulation and the development of HAAF, but also ghrelin cell physiology and ghrelin action.