Biological Mechanisms through which TMAO Promotes Atherosclerosis

项目摘要 心血管疾病（CVD）仍然是美国死亡的主要原因，但传统的危险因素， 如血脂水平升高和高血压，占CVD风险的不到50%。我们有 最近确定了动脉粥样硬化的一种新机制，其中代谢物三甲胺N-氧化物（TMAO） 来源于肠道微生物组和肝脏介导的饮食胆碱和L-肉碱代谢， 在小鼠中与主动脉病变形成相关，并与人类CVD风险升高相关。我们的数据进一步 表明TMAO水平通过饮食基质和宿主之间复杂的相互作用来调节 肝脏和其他器官系统中的遗传因素。然而，调节TMAO的生物学途径， 肝脏生产水平以及这些因素是否与饮食胆碱或L-肉碱相互作用， 动脉粥样硬化是未知的。此外，关于生物学方面的许多问题仍然没有答案。 TMAO促进动脉粥样硬化形成的机制以及TMAO与CVD之间的关系是否 在人类中代表着因果关系。本文提出的综合战略直接解决这些问题 知识上的重大差距。在具体目标1中，我们将确定潜在的亲- 使用我们最近创建的转基因小鼠模型， 缺乏含黄素单加氧酶3（Fmo 3），这是负责肝脏TMAO的主要酶 生产将在上下文中全面表征Fmo 3缺失小鼠的主动脉病变发展 高胆固醇饮食我们还将使用药理学和遗传扰动策略， 小鼠模型，以确定TMAO是否在体内促进炎症过程， 通过NF-κ B B途径介导血管壁的损伤。在具体目标2中，我们将使用比较系统 遗传学策略，> 41，000名受试者和一组约100个近交系小鼠品系，以确定遗传因素 通过主效应和/或基因-饮食相互作用影响血浆TMAO水平。的结果予以 同线性映射研究将用于在> 500，000名受试者中进行计算机模拟和孟德尔随机化分析 建立TMAO和CVD风险之间的因果关系。总的来说，拟议的研究 1）阐明TMAO促进动脉粥样硬化的炎症机制的潜力; 2） 确定一种新的和临床上重要的CVD风险因素的遗传决定因素，并提供一种 更好地了解基因和饮食因素之间的相互作用如何介导血浆TMAO的变化 水平和CVD风险; 3）提供遗传证据表明TMAO和CVD之间的关系是因果关系。 总之，我们的研究结果将支持靶向TMAO是一种新的治疗方法的观点 可能独立于已知生物学途径和风险因素降低CVD风险的策略。

PROJECT SUMMARY Cardiovascular disease (CVD) remains the leading cause of death in the US but traditional risk factors, such as elevated lipid levels and hypertension, account for less than 50% of the risk for CVD. We have recently identified a novel mechanism for atherosclerosis where trimethylamine N-oxide (TMAO), a metabolite derived from gut microbiome and hepatic-mediated metabolism of dietary choline and L-carnitine, increases aortic lesion formation in mice and is associated with elevated risk of CVD in humans. Our data further indicate that TMAO levels are regulated through complex interactions between dietary substrates and host genetic factors in the liver and other organ systems. However, the biological pathways that regulate TMAO at the level of hepatic production and whether these factors interact with dietary choline or L-carnitine to affect atherosclerosis are not known. Furthermore, many questions remain unanswered with respect to the biological mechanisms by which TMAO promotes atherogenesis and whether the association between TMAO and CVD in humans represents a causal relationship. The integrative strategies proposed herein directly address these critical gaps in knowledge. In Specific Aim 1, we will determine the biological mechanisms underlying the pro- atherogenic properties of TMAO using a genetically modified mouse model that we recently created for deficiency of flavin-containing monooxygenase 3 (Fmo3), the major enzyme responsible for hepatic TMAO production. Fmo3 null mice will be comprehensively characterized for aortic lesion development in the context of a atherogenic high choline diet. We will also use pharmacological and genetic perturbations strategies in mouse models to determine in vivo whether the inflammatory processes TMAO promotes at the level of the vessel wall are mediated through the NF-B pathway. In Specific Aim 2, we will use comparative systems genetics strategies with >41,000 subjects and a panel of ~100 inbred mouse strains to identify genetic factors influencing plasma TMAO levels through main effects and/or gene-dietary interactions. The results of these synteny mapping studies will be used for in silico and Mendelian randomization analyses in >500,000 subjects to establish a causal relationship between TMAO and risk of CVD. In combination, the proposed studies have the potential to 1) elucidate the inflammatory mechanisms through which TMAO promotes atherosclerosis; 2) identify the genetic determinants of a novel and clinically important risk factor for CVD as well as provide a better understanding of how interactions between genes and dietary factors mediate changes in plasma TMAO levels and CVD risk; and 3) provide genetic evidence that the relationship between TMAO and CVD is causal. Taken together, results from our studies would support the notion that targeting TMAO is a novel therapeutic strategy that may decrease CVD risk independent of known biological pathways and risk factors.