Genes and Nutrition: Dietary Choline, the Gut Microbiota, and Atrial Fibrillation

摘要： 心房颤动（AF）是多因素和后天因素造成的，例如肥胖、酗酒和心力衰竭， 有助于其发病机制。此外，尽管使用抗凝剂来预防左心房血栓形成， 房颤患者仍面临缺血性中风或抗凝并发症的风险。我们无能为力 使用可用工具管理 AF 强调迫切需要寻找针对目标的新治疗途径 其根本机制。在过去的几年里，肠道微生物群与动脉粥样硬化有关 肠道微生物群将膳食胆碱分解代谢为三甲胺 (TMA)，而三甲胺在体内进一步氧化，从而导致疾病 肝脏通过黄素单加氧酶转化为三甲胺 N-氧化物 (TMAO)。血浆TMAO水平升高 独立预测主要不良心血管事件（MACE），并在机制上与 动脉粥样硬化疾病通过 (i) 通过启动和激活 NOD-、LRR- 增加内皮炎症 和包含吡啶结构域 3 (NLRP3) 的炎症小体，通过线粒体活性氧的产生 种，（ii）通过调节白色脂肪组织增加肥胖，以及（iii）通过以下方式增强血栓形成 激活血小板。 NLRP3 炎症小体与动物模型中 AF 的发病机制有关， 肥胖是房颤的主要危险因素，TMAO增强血栓形成可能会增加房颤患者的血栓形成 中风的易感性。我们已经收集了初步数据，证明 (i)TMAO 独立 与普遍和偶发的 AF 相关，(ii)TMAO 可能在心房样诱导的 NLRP3 炎性体中启动 多能干细胞衍生的心肌细胞 (a-iCM)，(iii) TMAO 减弱离体心房动作电位 小鼠心脏以肠道微生物群依赖的方式，并且 (iv) TMAO 降低静息电位并 缩短 a-iCMS 中动作电位的持续时间并降低其峰值幅度。这些数据表明 TMAO 可能通过引起代谢和电生理功能障碍参与 AF 的发病机制。 心肌细胞，从而促进 AF。在这个项目中，我们建议研究潜在的机制 TMAO 和肠道微生物组与 AF 的关联。目标 1 将研究肠道微生物组的作用 AF 易感性。我们将首先使用 AF 使用广谱抗生素抑制整个肠道微生物群 敏感小鼠接受或不接受胆碱饮食并监测 AF 的进展。然后我们将使用一条路径 特异性抑制剂氟甲基胆碱 (FMC)，以证明胆碱代谢为 TMAO 是特异性的 促进 AF。在最后一组研究中，我们将通过粪便检测来确认肠道微生物群在 AF 中的作用。 移植以确定房颤易感性是否是一种传染性特征。第二个目标将调查 TMAO 促进 AF 的机制。第一个子目标将探讨 NLRP3 炎性体在 TMAO 促进房颤、纤维化和左心房血栓形成的易感性。第二个子目标将探讨 TMAO 在离体小鼠心房研究和心房引起电生理功能障碍中的作用 工程心脏组织。这些研究可能将饮食、肠道微生物组和房颤联系起来。

Summary: Atrial fibrillation (AF) is multifactorial and acquired factors, such as obesity, alcohol abuse, and heart failure, contribute to its pathogenesis. Moreover, despite the use of anticoagulants to prevent left atrial thrombosis, patients with AF are still at risk for ischemic stroke or the complications of anticoagulation. Our inability to manage AF with available tools emphasizes the critical need to search for novel treatment pathways that target its underlying mechanisms. Over the past several years the gut microbiome has been linked to atherosclerotic disease by gut microbiota catabolism of dietary choline to trimethylamine (TMA) which is further oxidized in the liver by flavin monooxygenase to trimethylamine N-oxide (TMAO). Elevated plasma TMAO levels independently predict major adverse cardiovascular events (MACE) and have been mechanistically linked to atherosclerotic disease by (i) increasing endothelial inflammation by priming and activating the NOD-, LRR- and pyrin domain-containing 3 (NLRP3) inflammasome by the production of mitochondrial reactive oxygen species, (ii) increasing adiposity by regulating white adipose tissue, and (iii) enhancing thrombosis by activating platelets. The NLRP3 inflammasome has been linked to the pathogenesis of AF in animal models, obesity is a major risk factor for AF, and enhancement of thrombosis by TMAO may increase AF patients’ susceptibility to stroke. We have gathered preliminary data demonstrating that (i)TMAO independently associates with prevalent and incident AF, (ii)TMAO may prime the NLRP3 inflammasome in atrial-like induced pluripotent stem cell-derived cardiomyocytes (a-iCMs), (iii) TMAO blunts the atrial action potential in ex vivo mouse hearts in a gut microbiota dependent manner, and (iv) TMAO reduces the resting potential and shortens the duration and decreases the peak amplitude of the action potential in a-iCMS. These data suggest TMAO may be involved in the pathogenesis of AF by causing metabolic and electrophysiological dysfunction in cardiomyocytes, thereby promoting AF. In this project, we propose to investigate the mechanisms underlying the association of TMAO and the gut microbiome with AF. Aim 1 will investigate the role of the gut microbiome in AF susceptibility. We will first suppress the entire gut microbiota with broad spectrum antibiotics using AF susceptible mice on and off a choline diet and monitor for the progression of AF. We then will use a pathway specific inhibitor, fluoromethylcholine (FMC), to demonstrate that choline metabolism to TMAO is specifically promoting AF. In a final set of studies, we will confirm the role of the gut microbiota in AF by performing fecal transplants to determine if susceptibility to AF is a transmissible trait. The second aim will investigate mechanisms by which TMAO promote AF. The first subaim will explore the role of the NLRP3 inflammasome in the TMAO-promoted susceptibility to AF, fibrosis, and left atrial thrombosis. The second sub aim will explore the role of TMAO in causing electrophysiological dysfunction in ex vivo mouse atrial studies and in atrial engineered heart tissue. Together these studies may link together the diet, the gut microbiome, and AF.