LARGE NEUTRAL AMINO ACIDS--TRANSPORT AND EFFECTS ON OXIDATIVE BRAIN METABOLISM

大分子中性氨基酸——转运及其对脑氧化代谢的影响

• 批准号: 6301883
• 负责人: H. Ronald Zielke
• 金额: $ 17.82万
• 依托单位: UNIVERSITY OF MARYLAND BALTIMORE
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-05-01 至 2001-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6301883
• 关键词: aerobiosis; aminoacid transport; astrocytes; bioenergetics; brain metabolism; branched chain aminoacid; catecholamines; cerebellum; corpus striatum; enzyme activity; gamma aminobutyrate; glutamate dehydrogenase; glutamates; glutamine; granule cell; human tissue; intracellular transport; ketoacid; laboratory rat; membrane transport proteins; microdialysis; neurons; nitrogen metabolism; serotonin; tissue /cell culture

We hypothesize that elevated levels of branched chain amino acids (BCAA) and their alpha-keto acids (BCKA) perturb not only amino acid transport, but also affect brain energy metabolism, disrupt the equilibrium of intercellular trafficking, and alter flux through enzymes involved in amino acid neurotransmitter synthesis. Ultimately such perturbations may have profound effects on neurodevelopment leading to mental retardation. Four recent findings from our laboratory support this hypothesis: 1) elevated levels of alpha-ketoisocaproate (alpha-KIC) introduced via microdialysis stimulate the in vivo oxidation of glutamate and glutamine, altering the energy states of the cells and decreasing the availability of glutamate for neurotransmitter function; 2) we have demonstrated in the intact brain that the oxidative metabolism of glutamate and glutamine is compartmentalized with glutamine oxidation rates in the hippocampus being approximately 5-fold greater than glutamate oxidation rates; 3) elevated levels of leucine and alpha-KIC, introduced via microdialysis to the interstitial space of rat brain, result in a 2-4 fold increase in the interstitial concentrations of large neutral amino acids (LNAA) and glutamine and 4) cultured rat cortical neurons and astrocytes have a pronounced different intracellular response to exogenous BCAA and BCKA. The proposed studies will: 1) combine two established methodologies, i.e., microdialysis and specific cellular ablation, to determine the effect of BCAA and BCKA on the oxidative metabolism by specific cell types in different brain regions; 2) determine the effect of BCAA and BCKA on amino acid exchanges into the interstitial fluid following ablation of specific types of brain cells by neurotoxic compounds; 3) characterize transport of LNAA by neuronal cells; 4) characterize the effect of LNAA and BCKA on glutamate/glutamine metabolism in the intact rat brain and in culture brain cells of know cell type. Inclusion of human astrocytes, normal and trisomic 21, should provide valuable information about the etiology of mental retardation resulting from in born errors of metabolism and chromosomal abnormalities and will provide guidelines for clinical approaches to these conditions.

我们假设分支链氨基酸水平升高（BCAA） 他们的α-酮酸（BCKA）不仅氨基酸转运，而且 但也影响大脑能量代谢，破坏 细胞间贩运，并通过涉及的酶改变通量 氨基酸神经递质合成。最终这样的扰动可能 对神经发育有深远的影响，导致智力低下。 我们实验室的四个最新发现支持这一假设：1） 通过 微透析刺激谷氨酸和谷氨酰胺的体内氧化， 改变细胞的能量状态并降低可用性 神经递质功能的谷氨酸； 2）我们在 完整的大脑，谷氨酸和谷氨酰胺的氧化代谢是 用谷氨酰胺氧化速率在海马的隔离 大约比谷氨酸氧化速率大约5倍； 3）高架 通过微透析引入的亮氨酸和α-KIC水平 大鼠大脑的间质空间，导致2-4倍的增加 大型中性氨基酸（LNAA）和 谷氨酰胺和4）培养的大鼠皮质神经元和星形胶质细胞具有 对外源性BCAA和BCKA的明显不同细胞内反应。 拟议的研究将：1）结合两种既定方法，即 微透析和特定的细胞消融，以确定 BCAA和BCKA在特定细胞类型的氧化代谢上 不同的大脑区域； 2）确定BCAA和BCKA对氨基的影响 特异性后，酸交换到间质液中 神经毒性化合物的脑细胞类型； 3）表征运输的 神经元细胞的LNAA； 4）表征LNAA和BCKA对 完整大鼠脑和培养物中的谷氨酸/谷氨酰胺代谢 知识细胞类型的脑细胞。包括人类星形胶质细胞，正常和 Trisomic 21应提供有关病因的宝贵信息 由代谢的出生错误和 染色体异常，将为临床提供指南 解决这些条件的方法。