MONOCARBOXYLIC ACIDS AND AMINO ACIDS IN BRAIN METABOLISM AND TRAFFICKING

项目二的研究提出了这样一个假设，即它对 大脑保持生产和利用的适当平衡 乳酸盐，因为这种一元羧酸是这两种酶关键底物 发育中的大脑和成熟的大脑。乳酸转运受损，或 酮体进入大脑可能会限制这些关键底物的使用， 能量和神经递质的生物合成 苯丙酮尿症（PKU）和枫尿症。相反， 脑脊液和/或脑中乳酸盐浓度升高 组织是利氏病的一个突出特征， 患有精神发育迟滞有证据表明，氨基酸和 一元羧酸代谢是密切和动态的 相互关联大量的乳酸盐，特别是在 小脑，由谷氨酸和谷氨酰胺通过TCA代谢形成 通过苹果酸酶循环转化为丙酮酸。具体来说，标签 前体和13/C-NMR将用于确定相对重要性 谷氨酸和谷氨酰胺作为乳酸的前体 在星形胶质细胞和神经元中产生。乳酸的相对贡献 和酮体对皮质神经元中神经递质生物合成的影响， 小脑颗粒细胞，以及PAHenu 2小鼠（具有相同的 人类PKU突变）。神经胶质/神经元运输 PKU小鼠脑中底物的浓度将使用[1- 13 C]葡萄糖和[2-/13 C]乙酸盐。抑制TCA循环活性， 氟柠檬酸盐将被用作Leigh病的模型。如果 在脑乳酸的情况下， 酸中毒是由氨基酸合成，通过调节乳酸的产生， 这种生物合成途径需要不同的治疗策略 而不是通过糖酵解产生。

Studies in Project II address the hypothesis that it is crucial for the brain to maintain the proper balance of production and utilization of lactate since this monocarboxylic acid is a key substrate in both developing brain and mature brain. Impairment in transport of lactate or ketone bodies into brain may limit the use of these key substrates for energy and neurotransmitter biosynthesis in developing brain in Phenylketonuria (PKU) and Maple Syrup Urine Disease. Conversely, an elevated concentration of lactate in cerebrospinal fluid and/or brain tissue is a prominent feature in Leigh's disease, a condition associated with mental retardation. There is evidence that amino acid and monocarboxylic acid metabolism are intimately and dynamically interconnected. A substantial portion of lactate, particularly in the cerebellum, is formed from glutamate and glutamine metabolized via the TCA cycle an converted to pyruvate via malic enzyme. Specifically, labeled precursors and 13/C-NMR will be used to determine the relative importance of the amino acids glutamate and glutamine as precursors for lactate production in astrocytes and neurons. The relative contribution of lactate and ketone bodies to neurotransmitter biosynthesis in cortical neurons, cerebellar granule cells, and in the PAHenu2 mouse (which has the same mutation of humans with PKU) will be determine. Glial/neuronal trafficking of substrates in the PKU mouse brain will be evaluated using [1- 13C]glucose and [2-/13C]acetate. Inhibition of TCA cycle activity with fluorocitrate will be used as a model for Leigh's disease. If a significant portion of the lactate in conditions with cerebral lactic acidosis is synthesize from amino acids, modulating lactate production by this biosynthetic pathway would require different therapeutic strategies than if it was produced via glycolysis.