Vitamin B6 Effects on One-Carbon Metabolism

维生素 B6 对一碳代谢的影响

• 批准号: 7470266
• 负责人: JESSE F. GREGORY
• 金额: $ 6.3万
• 依托单位: UNIVERSITY OF FLORIDA
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-15 至 2010-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7470266
• 关键词: Accounting; Address; Adult; Area; Biochemical Process; Blood Clot; Blood coagulation; Breath Tests; Carbon; Carbon Dioxide; Catabolism; Chronic Disease; Coenzymes; Collection; DNA; Decarboxylation; Dependence; Enzymes; Evolution; Formyltetrahydrofolate dehydrogenase; Funding; Generations; Genetic; Glycine; Glycine Hydroxymethyltransferase; Grant; Heart Diseases; Homocysteine; Homocystine; Human; Individual; Infusion procedures; Kinetics; Label; Link; Metabolic; Metabolism; Methods; Mitochondria; Mutation; Nucleotides; Nutritional; Pathway interactions; Play; Positioning Attribute; Procedures; Process; Production; Protein Isoforms; Protocols documentation; Public Health; Pyridoxal Phosphate; RNA; Rate; Reaction; Recruitment Activity; Regulation; Request for Applications; Research; Risk; Role; Sampling; Serine; Source; Stroke; Tracer; Vitamin B6; carboxyl group; glycine cleavage system; improved; methyl group; novel; oxidation; response

DESCRIPTION (provided by applicant): Vitamin B6 plays a critical role in human one-carbon (1C) metabolism through the essential function of pyridoxal phosphate (PLP) as coenzyme for key reactions including those catalyzed by the mitochondrial glycine cleavage system (GCS), mitochondrial and cytosolic serine hydroxymethyltransferase (SHMT) isoforms, and the enzymes of the transsulfuration pathway of homocysteine catabolism. This application requests support to extend Aim 1 of grant DK072398 (Vitamin B6 Effects on One-Carbon Metabolism), which addresses the quantitative characterization of human glycine metabolism and its vitamin B6-dependence. We recently completed the originally planned Aim 1 protocol exactly as described in our funded grant. This protocol involved a stable isotopic infusion with [1,2-13C2]glycine as the primary tracer to investigate glycine kinetics, glycine-to-serine interconversion, glycine cleavage kinetics, and the role of glycine as a carbon donor in one-carbon metabolism (examined before and after controlled vitamin B6 depletion). The doubly-labeled glycine tracer has many attributes for this study. A key aspect of the method is the determination of the evolution of 13CO2 in breath samples, indicative of glycine decarboxylation processes (primarily via the GCS). However, we cannot be assured that the generation of 13CO2 is primarily from the glycine13C-carboxyl group and that 13CO2 generation from the C-2 position (e.g., via 10-formyltetrahydrofolate dehydrogenase) is negligible. The proposed infusion protocol to clarify this issue will be identical that used in our completed Aim 1 study with the exception that the labeled glycine infused will be [1-13C]glycine (i.e., labeled only on the carboxyl group). Subjects (n=6, vitamin B6 adequate) will be recruited from the same individuals who completed the Aim 1 study. In this procedure, the generation of breath 13CO2 specifically will reflect glycine decarboxylation. Comparisons will be made of 13CO2 production in each subject between doubly-labeled glycine (previous Aim 1 study) versus carboxyl labeled glycine in the new study using. Any difference between these tracers in plateau 13CO2 production and the areas under the 13CO2 production curves of will reflect the extent of secondary 13CO2 production from the C-2 carbon of glycine in Aim 1. Thus, we will be able to account fully for the extent by which glycine is decarboxylated versus the oxidation of glycine C-2 derived one-carbon units via reactions such as 10-formyltetrahydrofolate dehydrogenase. Overall, these studies will yield novel information regarding the sources and disposition of glycine-derived carbons entering human one-carbon metabolism. This information will, thus, enhance our ability to evaluate linkages between chronic disease and nutritional/metabolic perturbations of these pathways. PUBLIC HEALTH RELEVANCE: One-carbon metabolism is the collection of biochemical processes in which the body synthesizes nucleotides, the building blocks of RNA and DNA, and one-carbon units including methyl groups that are vital in metabolism and genetic regulation. Risk of chronic disease including blood clots, stroke and some forms of heart disease are linked to nutritional or genetic changes in one-carbon metabolism. The proposed research will extend our previous studies, all of which have the major objective of improving our understanding of the rates of these metabolic processes and their response to nutritional and genetic variables.

描述（由申请人提供）：维生素 B6 通过磷酸吡哆醛 (PLP) 作为关键反应（包括由线粒体甘氨酸裂解系统 (GCS)、线粒体和胞质丝氨酸羟甲基转移酶 (SHMT) 催化的反应）的辅酶的基本功能，在人体一碳 (1C) 代谢中发挥关键作用 同种型，以及同型半胱氨酸分解代谢的转硫途径的酶。本申请请求支持扩展拨款 DK072398 的目标 1（维生素 B6 对一碳代谢的影响），该目标解决人类甘氨酸代谢及其维生素 B6 依赖性的定量特征。我们最近完全按照我们资助的赠款中的描述完成了最初计划的 Aim 1 协议。该方案涉及以 [1,2-13C2] 甘氨酸作为主要示踪剂的稳定同位素输注，以研究甘氨酸动力学、甘氨酸与丝氨酸的相互转化、甘氨酸裂解动力学以及甘氨酸作为碳供体在一碳代谢中的作用（在受控维生素 B6 消耗之前和之后进行检查）。双标记甘氨酸示踪剂对于本研究具有许多属性。该方法的一个关键方面是测定呼吸样品中 13CO2 的演变，表明甘氨酸脱羧过程（主要通过 GCS）。然而，我们不能保证 13CO2 的产生主要来自甘氨酸 13C-羧基，并且从 C-2 位（例如，通过 10-甲酰四氢叶酸脱氢酶）产生的 13CO2 可以忽略不计。为澄清这一问题而提出的输注方案与我们已完成的目标 1 研究中使用的方案相同，但输注的标记甘氨酸将是 [1-13C] 甘氨酸（即仅在羧基上进行标记）。受试者（n=6，维生素 B6 充足）将从完成 Aim 1 研究的同一个人中招募。在此过程中，呼吸 13CO2 的产生将具体反映甘氨酸脱羧作用。将比较每个受试者双标记甘氨酸（之前的目标 1 研究）与新研究中使用的羧基标记甘氨酸之间的 13CO2 产生。这些示踪剂在平台 13CO2 产量和 13CO2 产量曲线下面积之间的任何差异都将反映目标 1 中甘氨酸 C-2 碳二次 13CO2 产量的程度。因此，我们将能够充分说明甘氨酸脱羧的程度与通过 10-甲酰四氢叶酸等反应对甘氨酸 C-2 衍生的一碳单元进行氧化的程度 脱氢酶。总体而言，这些研究将产生有关进入人类一碳代谢的甘氨酸衍生碳的来源和处置的新信息。因此，这些信息将增强我们评估慢性疾病与这些途径的营养/代谢扰动之间联系的能力。公共健康相关性：一碳代谢是身体合成核苷酸（RNA 和 DNA 的组成部分）以及包括甲基在内的一碳单位的生化过程的集合，这些单位对新陈代谢和遗传调控至关重要。血栓、中风和某些形式的心脏病等慢性疾病的风险与一碳代谢的营养或遗传变化有关。拟议的研究将扩展我们之前的研究，所有这些研究的主要目标是提高我们对这些代谢过程的速率及其对营养和遗传变量的反应的理解。