Alternative routes of gut microbial methylamine metabolism that may limit trimethylamine N-oxide, a trigger for atherosclerosis.

肠道微生物甲胺代谢的替代途径可能会限制三甲胺 N-氧化物（动脉粥样硬化的触发因素）。

基本信息

批准号：
9908066
负责人：
JOSEPH Adrian KRZYCKI
金额：
$ 39.84万
依托单位：
OHIO STATE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2016
资助国家：
美国
起止时间：
2016-05-01 至 2022-12-31
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): Cardiovascular disease is the leading cause of mortality in the United States. Evidence is accumulating that certain human intestinal microbes contribute to atherosclerosis leading to cardiovascular disease, thereby increasing the risk of heart attack, stroke, and death. Gut microbes convert quaternary amines (QAs), e.g. carnitine, butyrobetaine, choline, and glycine betaine, to trimethylamine (TMA). TMA enters the bloodstream and once converted by liver flavoproteins to trimethylamine-N-oxide (TMAO), can trigger macrophage mediated vascular lipid deposition. Serum TMAO levels accordingly correlate with atherosclerosis and the above catastrophic health events. TMA production by QA lyases or reductases has long been considered the sole route of microbial QA degradation under the anaerobic conditions prevalent in the gut; but recent evidence reveals a more complex microbial ecology of QAs. Intestinal isolates have been shown to catabolically remove the N-methyl groups of QAs during growth; and the demethylated QA products do not generate TMA. The central hypothesis of this work is that QA demethylation might serve to moderate microbial TMA production in the human intestine, providing a mechanism for homeostasis or therapeutic control of TMAO levels; and thereby a means to decrease the risk of cardiovascular disease. There is a critical need for identification of enzymes mediating demethylation of QAs, the organisms in which they operate, and their prevalence in the human gut. The working hypothesis for the mechanism of QA demethylation is that members of the MttB superfamily, one of which is known to demethylate glycine betaine, use a range of QA substrates. QA demethylating microbes contain multiple MttB proteins. An example is the human intestinal symbiont Eubacterium limosum that demethylates all QAs known to serve as TMA precursor in the gut, and produces increased levels of MttB family members during growth by QA demethylation. The specific aims of this project period are independent yet synergistic. Proteomics coupled to biochemical methods will identify and characterize key proteins that mediate catabolic demethylation of QAs by E. limosum. The knowledge gained will fuel ongoing ecological examination of human gut microbiota with focus on QA demethylation. Enrichment cultures for isolation will be made from human fecal samples for novel trophic groups of QA demethylating microbes, as well those consuming QA demethylation products. A metagenomic examination with deep sequencing of gut microbiota DNA from human fecal samples will allow statistical enumeration of genes whose products generate TMA from QAs versus those whose products demethylate QAs and avoid TMA generation. The results will be correlated with urine levels of QA metabolites. The overall outcomes of this project period will uncover a general mechanism by which many QAs are demethylated in the gut, and provide an initial test of the hypothesis that the interaction of QA degrading microbes in the gut may provide a means to control levels of TMA, and thereby the proatherogenic compound TMAO.

描述（由申请人提供）：越来越多的证据表明，某些人类肠道微生物会导致动脉粥样硬化，从而导致心血管疾病，从而增加心脏病发作、中风和死亡的风险。微生物将季胺 (QA)，例如肉碱、丁甜菜碱、胆碱和甘氨酸甜菜碱转化为三甲胺 (TMA)。进入血液，一旦被肝脏黄素蛋白转化为三甲胺-N-氧化物 (TMAO)，就会触发巨噬细胞介导的血管脂质沉积，因此与动脉粥样硬化和 QA 裂解酶或还原酶产生的上述灾难性健康事件相关。被认为是肠道中普遍存在的厌氧条件下微生物 QA 降解的唯一途径；但最近的证据揭示了更复杂的微生物生态学；肠道分离株已被证明可以在生长过程中分解代谢去除 QA 的 N-甲基基团；并且去甲基化的 QA 产物不会产生 TMA。人类肠道，提供一种TMAO水平的稳态或治疗控制机制；以及一种降低心血管疾病风险的方法。迫切需要鉴定介导的酶。 QAs 的去甲基化、它们发挥作用的生物体以及它们在人类肠道中的普遍性 QA 去甲基化机制的工作假设是 MttB 超家族的成员（其中之一已知可以使甘氨酸甜菜碱去甲基化）使用一系列的酶。 QA 底物。QA 去甲基化微生物含有多种 MttB 蛋白，其中一个例子是人类肠道共生体 Limosum，它可以使所有已知的 QA 去甲基化，作为 TMA。该项目期间的具体目标是独立但协同的蛋白质组学与生化方法相结合，将鉴定和表征 E 介导 QA 分解代谢去甲基化的关键蛋白质。所获得的知识将推动对人类肠道微生物群的持续生态检查，重点是从人类粪便样本中制备用于分离的 QA 富集培养物。对 QA 去甲基化微生物的营养群体，以及那些消耗 QA 去甲基化产品的微生物进行宏基因组学检查，对人类粪便样本中的肠道微生物群 DNA 进行深度测序，将可以统计计算其产物从 QA 中产生 TMA 的基因，以及其产物使 QA 去甲基化并避免 TMA 的基因。结果将与尿液中 QA 代谢物的水平相关，该项目期间的总体结果将揭示许多 QA 在体内去甲基化的一般机制。肠道中 QA 降解微生物的相互作用可能提供了一种控制 TMA 水平的方法，从而控制促动脉粥样硬化化合物 TMAO 的水平，并对该假设进行了初步检验。