Adaptations of CNS Metabolism to Hypoglycemia in Diabetes

描述（由申请人提供）：糖尿病的长期并发症可以通过强化胰岛素治疗逆转;然而，一个主要障碍是低血糖的发展。低血糖的不良影响主要涉及脑功能，特别是认知。我们的目标是更好地了解中枢神经系统低血糖的后果，以及它如何影响糖尿病患者和强化胰岛素治疗下的正常脑代谢。本提案中描述的实验将解决低血糖期间脑能量底物利用的基本机制。我们小组从1型糖尿病患者中获得的初步数据表明，在低血糖期间，葡萄糖以外的燃料的摄取和代谢增加。基于此，我们想评估短链和中链脂肪酸在低血糖情况下支持脑代谢的能力。我们感兴趣的是在糖尿病和正常动物的代谢率和血脑屏障摄取的替代燃料乳酸盐，乙酸盐和辛酸盐的前期复发性低血糖发作的影响。这些底物在啮齿动物糖尿病和低血糖模型中对脑氧化能力的各自贡献尚未完全表征。我们将在我们的第一个目标，通过MR波谱在体内，在那里我们将看看反复低血糖对代谢通量率的乙酸和辛酸和相关的谷氨酸/谷氨酰胺循环在神经元和星形胶质细胞的影响。在我们的第二个目标，我们将调查是否在正常和糖尿病大鼠反复低血糖诱导增加血脑屏障摄取的替代底物乳酸，乙酸和辛酸。增加一元羧酸转运的潜在潜在分子机制可能是转运蛋白的上调。通过原位杂交和蛋白质印迹法测定单羧酸转运蛋白1、2和4的mRNA和蛋白质水平，我们将能够回答这个问题。替代燃料、底物利用率的变化和代谢的增加是否确实能够在低血糖症下维持正常的脑活动，将在目标三中使用EEC进行功能测定以及通过MR光谱法寻找高能磷酸盐进行测试。该提案的长期目标是更好地了解低血糖期间大脑内发生的替代燃料的运输和代谢变化，以及糖尿病和强化胰岛素治疗如何影响这一过程。这将为开发新的治疗方法提供基础，这些方法可用于临床实践，以保护大脑免受低血糖诱导的损伤。

DESCRIPTION (provided by applicant): Long term complications of diabetes can be reversed by intensive insulin therapy; however a major obstacle is the development of hypoglycemia. The adverse effects of hypoglycemia predominantly involve brain function, particularly cognition. Our goal is to better understand the consequences of CNS hypoglycemia and how it affects normal brain metabolism in diabetes and under intensive insulin treatment. The experiments described in this proposal are going to address the fundamental mechanisms underlying brain energy substrate utilization during hypoglycemia. Preliminary data our group has generated from type 1 diabetic patients suggests that during hypoglycemia uptake and metabolism of fuels other than glucose are increased. Based on this we want to assess the ability of short and medium chain fatty acids to support brain metabolism under hypoglycemia. We are interested in the effect of antecedent recurrent hypoglycemic episodes in diabetic and normal animals on rates of metabolism and blood brain barrier uptake of the alternate fuels lactate, acetate and octanoate. The respective contribution of these substrates to brain oxidative capacity in rodent models of diabetes and hypoglycemia has not yet been fully characterized. We are going to address this question in our first aim via MR spectroscopy in vivo, where we will look at the influence of recurrent hypoglycemia on metabolic flux rates of acetate and octanoid and associated glutamate/ glutamine cycling in the neuronal and astrocytic compartments. We will investigate in our second aim whether recurrent hypoglycemia in normal and diabetic rats induces an increase in blood brain barrier uptake of the alternate substrates lactate, acetate and octanoid. A potential underlying molecular mechanism to increased monocarboxylic acid transport could be the upregulation of transporter proteins. By measuring the mRNA and protein levels of monocarboxylic acid transporters 1, 2 and 4 by in situ hybridization and western blot we will be able to answer this question. Whether alternate fuels, changes in substrate utilization and increased metabolism are indeed able to sustain normal brain activity under hypoglycemia will be tested in aim three in a functional assay using EEC as well as by MR spectroscopy looking for high-energy phosphates. The long term goal of this proposal is to better understand the changes to transport and metabolism of alternate fuels that occur within the brain during hypoglycemia and how diabetes and intensive insulin treatment affect this process. This will provide the basis for the development of novel therapeutic approaches that could be used in clinical practice to protect the brain from hypoglycemia-induced injury.