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）作为关键反应的辅酶的基本功能在人体一碳（1C）代谢中发挥关键作用，包括由线粒体甘氨酸裂解系统（GCS）、线粒体和细胞溶质丝氨酸羟甲基转移酶（SHMT）亚型以及高半胱氨酸催化剂转硫途径的酶催化的那些反应。本申请请求支持扩展资助DK 072398（维生素B6对一碳代谢的影响）的目标1，该目标1涉及人体甘氨酸代谢及其维生素B6依赖性的定量表征。我们最近完成了最初计划的目标1协议，完全符合我们资助的赠款。该方案涉及以[1，2 - 13 C2]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-丝氨酸互变、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消耗前后进行检查）。双标记的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确定呼吸样本中13 CO2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13 CO2的产生主要来自甘氨酸13 C-羧基，并且13 CO2的产生来自C-2位（例如，通过10-甲酰四氢叶酸脱氢酶）是可忽略的。用于澄清该问题的拟定输注方案与我们已完成的Aim 1研究中使用的方案相同，但输注的标记甘氨酸将是[1- 13 C]甘氨酸（即，仅在羧基上标记）。受试者（n=6，维生素B6充足）将从完成目标1研究的相同个体中招募。在该过程中，呼吸13 CO2的产生将具体反映甘氨酸脱羧。将使用双标记甘氨酸（先前的目标1研究）与新研究中的羧基标记甘氨酸对每例受试者的13 CO2产生进行比较。这些示踪剂在平台13 CO2生产和13 CO2生产曲线下的面积之间的任何差异将反映目标1中甘氨酸的C-2碳的次级13 CO2生产的程度。因此，我们将能够充分说明甘氨酸脱羧的程度与甘氨酸C-2衍生的一碳单元通过反应如10-甲酰四氢叶酸脱氢酶的氧化。总体而言，这些研究将产生新的信息来源和处置的甘氨酸衍生碳进入人体一碳代谢。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。公共卫生关系：一碳代谢是生物化学过程的集合，其中身体合成核苷酸，RNA和DNA的构建模块，以及一碳单元，包括在代谢和遗传调节中至关重要的甲基。慢性疾病的风险，包括血栓、中风和某些形式的心脏病，都与一碳代谢中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，所有这些研究的主要目标都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。