CNS Mechanisms of Acute Hypoglycemia-Associate Autonomic Failure

描述（由申请人提供）： 摘要低血糖相关性自主神经功能衰竭（HAAF）是一种与1型和2型糖尿病相关的综合征，由短时间内多次低血糖（低血糖）发作引起。其特征在于对血糖下降症状的感知和神经内分泌反调节反应（CRR）（一种激素和神经反应，包括交感肾上腺激活和肾上腺素（EPI）释放;下丘脑/垂体/肾上腺（HPA）轴激活和肾上腺糖皮质激素释放;以及胰高血糖素（GLU）释放）受损。这些反应中最关键的是GLU和EPI的释放，以及随后在几分钟内刺激肝脏葡萄糖的释放。在糖尿病个体中，GLU反应在疾病状态早期丧失，因此糖尿病个体严重依赖于EPI释放以获得低血糖的CRR。在过去的十年中，我们一直在研究在HAAF的（非糖尿病）啮齿动物模型中在CRR的介导中起关键作用的大脑部位。我们的实验室和其他实验室已经确定了脑干、内侧下丘脑和边缘前脑中的神经细胞群，它们相互联系并有助于CRR。然而，关于糖尿病大脑对低血糖挑战的激活或反应的信息很少。我们现在建议在急性糖尿病模型中系统地评估CRR的关键神经元素，长期目标是确定受损反应的组成部分作为治疗干预的潜在目标。使用链脲佐菌素（STZ）-糖尿病大鼠模型和高胰岛素低血糖钳夹方法，我们将测量神经激活（cFos，pCREB和pERK 1/2表达）在整个大脑中对单次（SH）或第三次（复发性，RH）低血糖的反应。我们还将筛选脊髓和肾上腺，即，从大脑激活肾上腺的途径。我们将确定大脑葡萄糖敏感部位对局部神经葡萄糖减少刺激的反应性。最后，我们将评估肾上腺素能药物舍曲林（SERT）对糖尿病大鼠低血糖CRR的影响，因为我们已经观察到用该药物治疗的非糖尿病大鼠的EPI反应增强。因此，拟定研究将实现在糖尿病动物模型中评价神经性血糖减少症和低血糖症的感知和反应的短期总体目标。 公共卫生相关性： 美国1型和2型糖尿病的患病率和发病率，其他“西方化”国家和新兴国家的艾滋病发病率很高，在过去十年中，美国的艾滋病发病率一直在上升，目前CDC估计总人口中每千人有7.5人。此外，1型和2型糖尿病在退伍军人中的发病率很高：目前，据估计，在退伍军人管理局接受医疗护理的男性中有16%患有糖尿病。糖尿病是一种昂贵的疾病，从各个角度来看，包括并发症的医疗费用，以及患者和护理人员在患者生活中的心理困扰。在VA人员支持和VA服务方面，对血糖控制不良导致一种或多种糖尿病慢性并发症的患者的护理是昂贵的和时间密集的。强化胰岛素治疗的目标是延迟、预防或降低长期并发症的严重程度，理论上仍然是最好的治疗方案。然而，最近的报告显示，在接受强化治疗的糖尿病患者人群中，死亡率增加，但未发现心血管获益，这突出表明需要将低血糖作为糖尿病并发症加以解决。对低血糖的反应（以及低血糖频繁发作时发生的失败反应）显然源于脑功能的改变，因此了解糖尿病动物或人类对低血糖反应的脑机制至关重要。我们研究了在非糖尿病动物模型中，关键脑区对低血糖反应的活动。我们现在建议在糖尿病动物模型中研究大脑激活，其基本原理是识别易受低血糖影响的大脑区域，以及识别它们在低血糖生化反应受损中的作用，是辅助治疗的第一个关键步骤，以预防与糖尿病强化胰岛素治疗相关的低血糖。

DESCRIPTION (provided by applicant): Abstract Hypoglycemia-associated autonomic failure, or HAAF, is a syndrome associated with type1 and type2 diabetes that results from the experience of multiple episodes of low blood sugar (hypoglycemia) within a short timeframe. It is characterized by impairment of both the sensing of symptoms of falling blood glucose and the neuroendocrine counterregulatory response (CRR), a hormonal and neural response that includes sympathoadrenal activation and epinephrine (EPI) release; activation of the hypothalamic/pituitary/adrenal (HPA) axis and release of adrenal glucocorticoids; and glucagon (GLU) release. Most critical of these responses are the GLU and EPI release, and consequent stimulation of hepatic glucose release within minutes. In the diabetic individual, the GLU response is lost early in the disease state, and thus diabetic individuals are critically dependent upon EPI release for the CRR to hypoglycemia. For the past ten years, we have been studying brain sites that play a critical role in the mediation of the CRR in a (non-diabetic) rodent model of HAAF. Our lab and others have identified neural cell groups in the brainstem, medial hypothalamus, and limbic forebrain that are linked to each other and contribute to the CRR. However, there is very little information available about the activation or response of the diabetic brain to a hypoglycemic challenge. We now propose to systematically evaluate the key neural elements of the CRR in a model of acute diabetes, with the long-term objective of determining the components of impaired responding as potential targets for therapeutic intervention. Using a streptozotocin (STZ)-diabetic rat model and hyperinsulinemic hypoglycemic clamp methodology, we will measure neural activation (cFos, pCREB, and pERK1/2 expression) in response to a single (SH) or a third (recurrent, RH) bout of hypoglycemia throughout the brain. We will also screen the spinal cord and adrenal gland, i.e., the pathway of activation of the adrenal gland from the brain. We will determine the responsivity of brain glucose-sensing sites to a localized neuroglucopenic stimulus. Finally, we will evaluate the effect of the serotonergic agent sertraline (SERT) on the hypoglycemia CRR in diabetic rats, as we have observed enhanced EPI responding in non-diabetic rats treated with this agent. The proposed studies will thus achieve the short-term overall objective of evaluating the sensing of, and response to, neuroglucopenia and hypoglycemia in an animal model of diabetes. PUBLIC HEALTH RELEVANCE: The prevalence and incidence of both type1 and type2 diabetes in the U.S., other "Westernized", and emerging countries is high, and has been increasing in the U.S. for the past decade, with current CDC estimates of 7.5 individuals per thousand in the population overall. Further, both type1 and type2 diabetes are prevalent at a high rate in the veteran population: Currently, it is estimated that 16% of men receiving medical care at the VA have diabetes. Diabetes is a costly disease from every perspective, including medical costs for complications, and psychological distress for both the patient and the care-givers in the patient's life. Care of patients in which poor blood sugar control has resulted in one or more of the chronic complications of diabetes is costly and time- intensive in terms of VA staff support and VA services. The goal of intensified insulin therapy to delay, prevent, or decrease the severity, of long-term complications is still, theoretically, the best treatment regimen available. However, the recent report of increased mortality, with no identified cardiovascular benefit, in a population of intensively-treated diabetic individuals highlights the need to address hypoglycemia as a diabetic complication. The response to hypoglycemia (and the failed response which occurs with frequent episodes of hypoglycemia) is clearly rooted in altered brain function, thus understanding the brain mechanisms underlying the response to hypoglycemia in diabetic animals or humans is critical. We have studied the activity of key brain regions in response to hypoglycemia in a non-diabetic animal model. We are now proposing to study brain activation in an animal model of diabetes, with the rationale that identifying brain regions that are vulnerable to hypoglycemia, as well as identification of their role in an impaired biochemical response to hypoglycemia, is the first critical step to ancillary therapies to prevent hypoglycemia in association with intensive insulin therapy in diabetes.