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通过吡啶还毒素磷酸盐（PLP）作为关键反应的辅助作用在人类单碳（1C）代谢中起关键作用同生的同工型和同型半胱氨酸分解代谢的转硫途径的酶。该应用要求支持扩展GRANT DK072398的目标1（维生素B6对单碳代谢的影响），该目标探讨了人类甘氨酸代谢及其维生素B6依赖性的定量表征。我们最近按照我们资助的赠款中所述，完全完成了最初计划的AIM 1协议。该方案涉及[1,2-13c2]甘氨酸作为研究甘氨酸动力学，甘氨酸到丝氨酸互转换，甘氨酸裂解动力学的主要示踪剂的稳定同位素输注，以及甘氨酸裂解动力学以及甘良作为碳供体在单碳纤维中的碳供体的作用（均为碳纤维化的生物）的作用（contectection contplemin and conterplomin and conterplomin and depe nisted vortamin contered contered contered retainmin bymin bb6双标记的甘氨酸示踪剂具有这项研究的许多属性。该方法的一个关键方面是测定呼吸样品中13CO2的演变，这表明甘氨酸脱羧过程（主要通过GCS）。但是，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位置（例如，通过10型甲基四氢叶酸脱氢酶）从C-2位置产生13CO2。阐明此问题的拟议输液协议将在我们完成的AIM 1研究中使用，但标记的甘氨酸注入的甘氨酸将是[1-13c]甘氨酸（即仅在羧基上标记）。受试者（n = 6，维生素B6足够）将从完成AIM 1研究的同一个人中招募。在此过程中，呼吸13CO2的产生将特别反映甘氨酸脱羧。在新研究中，将在双标记的甘氨酸（以前的AIM 1研究）与羧基标记的甘氨酸的甘氨酸（先前的AIM 1研究）之间的13CO2产生进行比较。高原13CO2生产中的这些示踪剂与13CO2生产曲线下的区域之间的任何差异都将反映出AIM 1中甘氨酸C-2碳的次级13CO2生产的程度。因此，我们将能够充分考虑甘氨酸是脱羧酸苯基脱甲基化与甘氨酸C-2脱离的单蛋白的氧化的程度脱氢酶。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这些途径的慢性疾病与营养/代谢扰动之间联系的能力。公共卫生相关性：单碳代谢是生物化学过程的收集，其中人体合成核苷酸，RNA和DNA的构件以及包括代谢和遗传调节至关重要的甲基包括甲基的一碳单位。慢性病的风险在内，包括血块，中风和某些形式的心脏病与单碳代谢的营养或遗传变化有关。拟议的研究将扩展我们以前的研究，所有这些都具有提高我们对这些代谢过程速率的理解及其对营养和遗传变量的反应的主要目标。