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

摘要： 房颤(房颤)是多因素和获得性因素，如肥胖、酗酒和心力衰竭。 在其发病机制中起重要作用。此外，尽管使用了抗凝剂来预防左房血栓形成， 房颤患者仍有发生缺血性中风或抗凝并发症的风险。我们无法 利用可用的工具管理房颤强调了寻找新的靶向治疗途径的迫切需要 其潜在的机制。在过去的几年里，肠道微生物群被认为与动脉粥样硬化有关 肠道微生物群将饮食中的胆碱分解为三甲胺(TMA)引起的疾病 肝脏由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)，并与 动脉粥样硬化性疾病：(I)通过启动和激活NOD、LRR-来增加内皮细胞炎症 和含比林结构域3(NLRP3)的炎症体通过产生线粒体活性氧 (Ii)通过调节白色脂肪组织来增加肥胖，以及(Iii)通过以下方式促进血栓形成 激活血小板。在动物模型中，NLRP3炎症小体与房颤的发病机制有关。 肥胖是房颤的主要危险因素，TMAO促进血栓形成可能增加房颤患者的 对中风易感性。我们收集的初步数据表明：(I)TMAO独立 TMAO与房颤的发生和流行有关(Ii)TMAO可使NLRP3炎症小体在心房样诱导中启动 多能干细胞来源的心肌细胞(a-ICM)，(Iii)TMAO钝化体外心房动作电位 和(Iv)TMAO降低小鼠心脏的静息电位和 缩短a-ICM的动作电位时程，降低动作电位的峰值。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房颤的发病。 心肌细胞，从而促进房颤。在这个项目中，我们建议研究潜在的机制 TMAO和肠道微生物群与房颤的关系。目标1将研究肠道微生物群的作用 房颤易感性。我们将首先用广谱抗生素抑制整个肠道微生物区系，使用AF 易感小鼠进食和停用胆碱饮食，并监测房颤的进展。然后我们将使用一条路径 特异性抑制剂氟甲基胆碱(FMC)证明胆碱对TMAO的代谢是特异性的 推广房颤。在最后一组研究中，我们将通过排泄物来确认肠道微生物区系在房颤中的作用 移植以确定房颤的易感性是否是一种可传播的特征。第二个目标是调查 TMAO促进房颤的机制。第一个分目标将探索NLRP3炎症小体在 TMAO增加了房颤、纤维化和左房血栓的易感性。第二个子目标将探索 TMAO在小鼠心房电生理功能障碍中的作用 人造心脏组织。总之，这些研究可能会将饮食、肠道微生物群和房颤联系在一起。

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.