Determination of methylmercury metabolism and elimination status in humans

人体甲基汞代谢和消除状态的测定

• 批准号: 8969362
• 负责人: MATTHEW D RAND
• 金额: $ 23.03万
• 依托单位: UNIVERSITY OF ROCHESTER
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2017-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8969362
• 关键词: Affect; Alkylmercury lyase; Antibiotics; Bacteria; Biological; Biological Markers; Consumption; Correlation Studies; DNA; Diet; Dietary Factors; Dose; Enzymes; Epidemiology; Feces; Fishes; Future; Genes; Genetic; Goals; Hair; Health; Human; Human Microbiome; Human body; Individual; Intestines; Investigation; Ions; Measures; Mediating; Mercury; Metabolic; Metabolism; Methods; Methylation; Methylmercury Compounds; Modeling; Nutrient; Operon; Organ; Outcome; Oxidoreductase; Persons; Plasmids; Population; Population Study; Predisposition; Relative (related person); Resistance; Risk; Rodent; Rodent Model; Role; Sampling; Seafood; Testing; Toxic Environmental Substances; Toxic effect; Tuna; Variant; Work; analytical method; base; enzyme activity; experience; feeding; human subject; improved; microbiome; nutrition related genetics; public health relevance; trait

 DESCRIPTION (provided by applicant): Methylmercury (MeHg) is a persistent environmental toxin that accumulates in fish and seafood. Understanding the risks of MeHg versus the benefits of essential nutrients in a fish diet is a priority human health issue. Toxicity of MeHg is dictate by its slow rate elimination rate, which is known to be highly variable from person to person. Methods to quantify MeHg elimination in people are grossly underdeveloped. Furthermore, the mechanisms of MeHg metabolism that are required for its elimination are not fully understood. Our objectives are two-fold: 1) to establish non-invasive methods to quantify the variable trait of MeHg metabolism and elimination in individual people consuming a normal fish diet and 2) to validate the putative role for intestinal bacterial enzymes in de-methylation of MeHg which facilitates its elimination. Our long-term goal is to use this method to investigate genetic and dietary factors that affect MeHg metabolism. We will work with a model first established in rodent models whereby de-methylation of MeHg by bacteria in the gut is a rate-limiting step in its elimination. However, the role of gut bacteria in MeHg de-methylation and elimination in humans remains to be characterized. A number of bacterial species in the human microbiome harbor Hg-detoxifying genes contained in the mer locus. Of particular importance to our hypothesis are the merB (organomercurial lyase) and merA (mercury reductase) genes, which carry out reductive de-methylation of MeHg. Our working hypotheses are that: 1) elimination of MeHg from the human body is dictated by the rate-limiting step of MeHg de-methylation and 2) the majority of MeHg de-methylation in humans occurs in the gut via bacterial mercury de-toxifying enzymes. With these hypotheses we predict differences in MeHg elimination rate between individuals will correspond with the abundance and activity of the merB and merA genes in the gut microbiome. In this study we will evaluate outcomes in human subjects fed meals of tuna with naturally occurring levels of MeHg. In Aim 1, we will determine the correlation of MeHg elimination rate with MeHg de-methylation status in human subjects subsequent to fish meal consumption. MeHg elimination rate will be determined by longitudinal Hg analysis of hair samples. MeHg de-methylation status will be determined as the percent Hgi in feces. In Aim 2, we will determine the influence of the abundance and activity of bacterial merB and merA on MeHg elimination rate and MeHg de-methylation status. We will investigate fecal samples of subjects receiving tuna meals for the abundance and diversity of merB and merA DNA and as well as the specific enzyme activity of merB and merA variants. Statistical correlations of merB and merA abundance and activity with MeHg elimination rate and with de-methylation status in feces will be determined. We anticipate the findings from this study will yield an invaluable method to identify individuals with a "fast" or "slow" MeHg metabolism, and furthermore resolve a potential mechanism for altering MeHg metabolism via changes to the gut bacterial composition.

 描述（由申请人提供）：甲基汞（MeHg）是一种持久性环境毒素，在鱼类和海鲜中积累。了解鱼类食物中甲基汞的风险与基本营养素的益处是人类健康的一个优先问题。甲基汞的毒性取决于其缓慢的消除速率，众所周知，这是因人而异的。对人体内消除甲基汞进行量化的方法还远远不够。此外，消除甲基汞所需的甲基汞代谢机制尚未完全了解。我们的目标是双重的：1）建立非侵入性的方法来量化的变量性状的 食用正常鱼类饮食的个体的甲基汞代谢和消除; 2）验证肠道细菌酶在促进甲基汞消除的甲基汞去甲基化过程中的假定作用。我们的长期目标是使用这种方法来调查影响甲基汞代谢的遗传和饮食因素。我们将首先在啮齿动物模型中建立一个模型，其中肠道细菌对甲基汞的去甲基化是其消除的限速步骤。然而，肠道细菌在人体甲基汞去甲基化和消除过程中的作用仍有待确定。人类微生物组中的许多细菌物种在mer基因座中含有汞解毒基因。对我们的假设特别重要的是merB（有机汞裂解酶）和merA（汞还原酶）基因，它们对甲基汞进行还原性去甲基化。我们的工作假设是：1）甲基汞从人体中的消除是由甲基汞去甲基化的限速步骤决定的，2）人体中的大部分甲基汞去甲基化通过细菌汞去甲基化酶发生在肠道中。通过这些假设，我们预测个体之间甲基汞消除率的差异将与肠道微生物组中merB和merA基因的丰度和活性相对应。在这项研究中，我们将评估人类受试者食用含有自然存在的甲基汞水平的金枪鱼餐的结果。在目标1中，我们将确定人类受试者食用鱼粉后甲基汞消除率与甲基汞去甲基化状态的相关性。甲基汞的消除率将通过对头发样本进行纵向汞分析来确定。甲基汞的去甲基化状态将以粪便中汞的百分比来确定。在目标2中，我们将确定细菌merB和merA的丰度和活性对甲基汞消除率和甲基汞去甲基化状态的影响。我们将研究接受金枪鱼餐的受试者的粪便样本中merB和merA DNA的丰度和多样性，以及merB和merA变体的特异性酶活性。将确定merB和merA丰度和活性与甲基汞消除率和粪便中去甲基化状态的统计相关性。我们预计，这项研究的结果将产生一个宝贵的方法，以确定个人的“快速”或“缓慢”的甲基汞代谢，并进一步解决了一个潜在的机制，通过改变肠道细菌组成改变甲基汞代谢。