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通过强化胰岛素治疗逆转；然而，一个主要的障碍是低血糖的发展。低血糖的不良影响主要涉及脑功能，特别是认知功能。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。本实验将探讨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。在此基础上，我们想评估短链和中链脂肪酸在低血糖状态下支持脑代谢的能力。我们对糖尿病动物和正常动物的既往反复低血糖发作对代谢率和血脑屏障对替代燃料乳酸、醋酸盐和辛酸盐的吸收的影响感兴趣。在糖尿病和低血糖的啮齿动物模型中，这些底物对脑氧化能力的各自贡献尚未得到充分表征。在我们的第一个目标中，我们将通过体内磁共振光谱来解决这个问题，我们将研究反复低血糖对醋酸盐和辛烷酸代谢通量率的影响，以及在神经元和星形细胞室中相关的谷氨酸/谷氨酰胺循环。我们将在第二个目标中研究正常和糖尿病大鼠的反复低血糖是否会诱导血脑屏障对乳酸、醋酸和辛烷类替代底物的摄取增加。增加单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western blot测定单羧酸转运蛋白1、2和4的mRNA和蛋白水平，我们将能够回答这个问题。替代燃料、底物利用的变化和代谢的增加是否确实能够在低血糖状态下维持正常的大脑活动，将在目标3的功能分析中进行测试，使用EEC和MR光谱寻找高能磷酸盐。这项提议的长期目标是更好地理解低血糖期间大脑内替代燃料的运输和代谢的变化，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引起的损伤。

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.