FOLATE DEFICIENCY AND ONE-CARBON METABOLISM

叶酸缺乏和一碳代谢

• 批准号: 3248135
• 负责人: CONRAD WAGNER
• 金额: $ 12.44万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-08-01 至 1998-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3248135
• 关键词: DNA methylation; S adenosylmethionine; cell type; creatine; folate deficiency; gene expression; homocysteine; immunocytochemistry; laboratory rat; methyl group; methylation; methyltransferase; nutrition related tag; pancreas; pathogenic diet; phospholipids; tissue /cell culture

The broad objective of this proposal is to determine whether a deficiency of folate, which is needed for the de novo synthesis of methyl groups, causes similar metabolic consequences as a deficiency of preformed methyl groups. Diets that contain no methionine and choline cause spontaneous liver cancer. Ethionine, an analogue of methionine that interferes with methylation, is a carcinogen, but when injected to choline deficient mice, ethionine rapidly causes acute pancreatitis. One explanation for the effects of methyl deficiency has been the decreased ratio of S- adenosylmethionine (SAM) to S-adenosylhomocysteine (SAH) that results. A wide variety of cellular methylation reactions are inhibited when the ratio of SAM/SAH is decreased, including the methylation of DNA which controls gene expression in eukaryotes. It has been shown by the P.I. that folate deficiency produces a decrease in the SAM/SAH ratio, in liver and pancreas, which is as great as that caused by methyl group deficiency. This SAM/SAH ratio is regulated by the enzyme, glycine N- methyltransferase (GNMT), which contains tightly bound folate. Immunohistochemical studies have shown that GNMT is concentrated in the exocrine pancreas. A high concentration of GNMT implies that methylation and folate are particularly important for certain cell types. These aspects are investigated in the specific aims which are: 1. To investigate whether folate deficiency affects pancreatic secretion in vivo, in situ and in tissue culture using the AR42J cell line. 2. To investigate whether folate deficiency affects the methylation of small molecules (creatine, phospholipids) and macromolecules (DNA). 3. To extend the immunohistochemical localization of GNMT to a variety of tissues. 4. To develop an immunohistochemical method for detecting folate within tissues. Immunohistochemical localization of folate will be modeled after the method used by the neurochemists for the localization of brain neurotransmitters. Rapid folate deficiency will be produced in rats by feeding the amino defined diet of Walzem and Clifford. Undermethylation of DNA will be evaluated by the ability to enzymatically incorporate additional methyl groups, by an altered expression of poly A+ RNA, and by an altered response of DNA to restriction endonucleases. Undermethylation of DNA in folate deficiency can affect gene expression. The ability to estimate folate levels of specific cells within tissues may provide a means of looking for localized folate deficiency as a cause of pre-neoplastic lesions in smokers and oral-contraceptive users.

该提案的广泛目标是确定是否缺乏 叶酸，这是从头合成甲基所需的 导致类似的代谢后果与预先形成的甲基缺乏 组。 不含蛋氨酸和胆碱的饮食会自发 肝癌。 乙他，一种蛋氨酸的类似物 甲基化是一种致癌物，但注射到胆碱不足时 小鼠，乙酸氨酸迅速引起急性胰腺炎。 一种解释 甲基缺乏的作用是S-的降低比率降低 腺苷硫氨氨酸（SAM）到S-腺基质类生态半胱氨酸（SAH）。 当 SAM/SAH的比率降低了，包括DNA的甲基化 控制真核生物中的基因表达。 P.I. 叶酸缺乏会在肝脏中降低SAM/SAH比率 和胰腺，与甲基引起的胰腺一样大 不足。 该SAM/SAH比受酶，甘氨酸N-的调节 甲基转移酶（GNMT），其中包含紧密结合的叶酸。 免疫组织化学研究表明，GNMT集中在 外分泌胰腺。 高浓度的GNMT意味着甲基化 叶酸对于某些细胞类型尤其重要。 这些 在特定目的中研究了各个方面： 1。研究叶酸缺乏是否影响胰腺分泌 使用AR42J细胞系，体内，原位和组织培养。 2。研究叶酸缺乏是否影响 小分子（肌酸，磷脂）和大分子（DNA）。 3。将GNMT的免疫组织化学定位扩展到一种品种 组织。 4。开发一种用于检测叶酸的免疫组织化学方法 组织。 叶酸的免疫组织化学定位将在 神经化学家使用的方法用于大脑的定位 神经递质。 大鼠会产生快速的叶酸缺乏 为Walzem和Clifford的氨基定义的饮食喂食。 甲基化不足 DNA的DNA将通过酶合并的能力来评估 其他甲基，通过Poly A+ RNA的表达改变，并且 通过DNA对限制性核酸内切酶的反应改变。 叶酸缺乏症中DNA的甲基化不足会影响基因表达。 估计组织中特定细胞水平的能力 可以提供一种将局部叶酸缺乏作为原因的方法 吸烟者和口服征服用户中的肿瘤前病变。