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.

我们假设支链氨基酸 (BCAA) 水平升高 它们的 α-酮酸 (BCKA) 不仅扰乱氨基酸运输， 还会影响大脑能量代谢，破坏平衡 细胞间运输，并通过参与的酶改变流量 氨基酸神经递质合成。最终，这种扰动可能 对神经发育有深远影响，导致智力低下。 我们实验室最近的四项发现支持了这一假设：1) α-酮异己酸 (α-KIC) 水平升高，通过引入 微透析刺激体内谷氨酸和谷氨酰胺的氧化， 改变细胞的能量状态并降低可用性 谷氨酸用于神经递质功能； 2）我们已经证明了 完整的大脑表明谷氨酸和谷氨酰胺的氧化代谢是 与海马区谷氨酰胺氧化速率区分开 大约是谷氨酸氧化速率的 5 倍； 3）升高 通过微透析引入亮氨酸和 α-KIC 水平 大鼠脑间隙增加 2-4 倍 大中性氨基酸 (LNAA) 的间质浓度和 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 的细胞内反应明显不同。 拟议的研究将：1）结合两种既定的方法，即 微透析和特异性细胞消融，以确定效果 BCAA 和 BCKA 对特定细胞类型氧化代谢的影响 不同的大脑区域； 2)测定BCAA和BCKA对氨基的影响 消融特定的组织后，酸交换到组织液中 神经毒性化合物对脑细胞的影响； 3）表征运输 LNAA 神经元细胞； 4) 表征 LNAA 和 BCKA 对 完整大鼠大脑和培养物中的谷氨酸/谷氨酰胺代谢 已知细胞类型的脑细胞。包含人类星形胶质细胞，正常和 三体 21，应该提供有关病因学的有价值的信息 由于先天性新陈代谢缺陷而导致的智力低下 染色体异常，将为临床提供指导 针对这些条件的方法。