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

项目摘要/摘要 对低血糖的防御是生存的关键，在临床意义上尤其重要。 设置胰岛素诱导的低血糖。胰岛素诱导的低血糖在1型和晚期患者中普遍存在 2型糖尿病，并与广泛的负面影响有关，包括工作减少 生产力和生活质量，减少对强化胰岛素疗法的坚持或建议， 事故和其他疾病的发生率增加，有时甚至死亡。在身体发育的同时 预防或纠正糖尿病患者低血糖的高度集成防御系统 由于过度胰岛素引起的反复低血糖，这些反调节防御措施是 妥协，导致低血糖的恶性循环，通常是低血糖 意识不清(低血糖相关的自主神经衰竭；HAF)源于被废除的 交感神经-肾上腺臂的逆调节反应。Ghrelin生物学的几个方面表明Ghrelin 可能参与胰岛素诱导的低血糖的逆调节反应：1)Ghrelin分泌 由低糖和交感肾上腺激活直接刺激；2)随后升高的Ghrelin在其 处理许多影响葡萄糖处理的潜在下游靶点，包括相互作用 使用几种传统的反调节反应荷尔蒙。然而，虽然生长激素对血液的调节 葡萄糖和血糖都是在限制卡路里的情况下进行评估的， Ghrelin系统在胰岛素诱导的低血糖的逆调节反应中的作用还不完全。 通过实验评估，例如通过在没有胰岛素刺激的小鼠中重新产生胰岛素诱导的低血糖或HAAF。 完整的胃促生长素系统。在这里，我们将测试Ghrelin扮演着关键的、保护性的、反调节角色的概念 人体对胰岛素诱导的低血糖的反应。特别是，我们将分离出 胰岛素与低血糖对生长激素分泌的影响通过胰岛素团注诱导的低血糖测试， 缺乏胰岛素受体的小鼠的高胰岛素-低血糖钳夹和Ghrelin分泌的体外研究 选择性地在ghrelin-KO小鼠的ghrelin细胞和连翘苷-降糖钳中。我们将决定 AgRP和SF1神经元中GHSRs在反调节反应中的需求和充分性 利用Cre-lox转基因小鼠和化学遗传学技术。此外，我们还将确定ghrelin是否缺失 通过评估Ghrelin对野生型小鼠低血糖的反应来增加对HAAF的易感性 HAAF和缺乏Ghrelin的小鼠反复低血糖后的总体反调节反应。 我们针对Ghrelin系统的独一无二的重组小鼠模型工具箱，我们团队在 研究Ghrelin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 小鼠的葡萄糖钳夹将使我们不仅可以获得重要的和新的见解，而且还可以对抗低血糖。 HAAF的调节和发育，还包括Ghrelin细胞生理和Ghrelin的作用。

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.