Abstract 105: Increased Circulating Trimethylamine N-oxide (TMAO) Augments the Incidence of Abdominal Aortic Aneurysm in Low Penetrant C57BL/6J Mice

Abstract

Background: The gut microbiota is a metabolically active endocrine organ critical to the maintenance of cardiovascular health. Dietary sources of choline are metabolized by microbial enzymes to form trimethylamine (TMA). Metabolism by the host hepatic enzyme flavin-containing monooxygenase 3 (FMO3) converts TMA to the pro-inflammatory molecule trimethylamine N-oxide (TMAO). Human clinical trials have correlated high levels of circulating TMAO to an increased risk of cardiometabolic diseases. However, this meta-organismal pathway has not been evaluated in the context of abdominal aortic aneurysm (AAA). The objective of this study was to determine the effects of a high choline diet on the development of AAA. Methods: C57BL/6J male (n=20) and female (n=20) mice were fed either a standard chow control diet (n = 10 each sex) or a choline-rich diet (1%; n = 10 each sex) for 5 weeks. After 1 week of diet, basal abdominal ultrasounds were performed and angiotensin II (AngII; 1,000 ng/kg/min) was infused for 28 days via implantation of osmotic minipumps. Termination ultrasounds were performed on day 27 and mice were sacrificed on day 28. Aortas were harvested for evaluation of aneurysm progression and plasma was analyzed for the metabolites TMA, TMAO, and choline. To determine whether TMAO was elevated in human patients with AAA, plasma samples from participants with fast growing AAAs (n = 85), slow growing AAAs (n = 84), and normal (non-aneurysmal) aortas (n = 115) were analyzed for plasma TMAO levels via liquid chromatography tandem mass spectrometry (LC-MS/MS). Results: Administration of a choline-rich diet augmented the incidence (P < 0.02) and aortic diameter (P < 0.001) of AAAs in both male and female mice versus placebo-fed mice. Plasma levels of TMA, TMAO, and choline were significantly elevated in choline-fed mice versus normal chow (P < 0.05). Importantly, circulating levels of plasma TMAO were significantly elevated in a step-wise fashion with the rate of aneurysm growth versus non-aneurysmal control patients (fast growing > slow growing > normal patients; P < 0.001). Conclusions: Our results indicate increases in circulating TMAO augments the growth status of aneurysms in human patients and the incidence of AAA in a low penetrant C57BL/6J mouse model.