Gut Microbiota–Derived Trimethylamine N-Oxide Contributes to Abdominal Aortic Aneurysm Through Inflammatory and Apoptotic Mechanisms

Abstract

Background: Large-scale human and mechanistic mouse studies indicate a strong relationship between the microbiome-dependent metabolite trimethylamine N-oxide (TMAO) and several cardiometabolic diseases. This study aims to investigate the role of TMAO in the pathogenesis of abdominal aortic aneurysm (AAA) and target its parent microbes as a potential pharmacological intervention. Methods: TMAO and choline metabolites were examined in plasma samples, with associated clinical data, from 2 independent patient cohorts (N=2129 total). Mice were fed a high-choline diet and underwent 2 murine AAA models, angiotensin II infusion in low-density lipoprotein receptor–deficient ( Ldlr −/− ) mice or topical porcine pancreatic elastase in C57BL/6J mice. Gut microbial production of TMAO was inhibited through broad-spectrum antibiotics, targeted inhibition of the gut microbial choline TMA lyase (CutC/D) with fluoromethylcholine, or the use of mice genetically deficient in flavin monooxygenase 3 ( Fmo3 −/− ). Finally, RNA sequencing of in vitro human vascular smooth muscle cells and in vivo mouse aortas was used to investigate how TMAO affects AAA. Results: Elevated TMAO was associated with increased AAA incidence and growth in both patient cohorts studied. Dietary choline supplementation augmented plasma TMAO and aortic diameter in both mouse models of AAA, which was suppressed with poorly absorbed oral broad-spectrum antibiotics. Treatment with fluoromethylcholine ablated TMAO production, attenuated choline-augmented aneurysm initiation, and halted progression of an established aneurysm model. In addition, Fmo3 −/− mice had reduced plasma TMAO and aortic diameters and were protected from AAA rupture compared with wild-type mice. RNA sequencing and functional analyses revealed choline supplementation in mice or TMAO treatment of human vascular smooth muscle cells–augmented gene pathways associated with the endoplasmic reticulum stress response, specifically the endoplasmic reticulum stress kinase PERK. Conclusions: These results define a role for gut microbiota–generated TMAO in AAA formation through upregulation of endoplasmic reticulum stress–related pathways in the aortic wall. In addition, inhibition of microbiome-derived TMAO may serve as a novel therapeutic approach for AAA treatment where none currently exist.

Innate immunity of vascular smooth muscle cells contributes to two-wave inflammation in atherosclerosis, twin-peak inflammation in aortic aneurysms and trans-differentiation potential into 25 cell types

“…In IL-17-treated VSMCs, NFKBID and NFKBIZ were upregulated ( Figure 9D ). As shown in Figures 14A, 14B , upregulated genes from innate immune genes, cytokines and chemokines, plasma membrane proteins, nuclear membrane proteins, nucleoli proteins, nucleoplasm proteins, TFs, oxidative stress cell death genes, necrotic cell death genes, pyroptosis cell death genes, efferocytosis genes, and fibrosis genes were downregulated in 5 master gene-deficient transcriptomic datasets including inflammatory TFs AHR –/– dataset ( 62 , 122 – 124 ), nuclear factor-kB (NF-kB) –/– with and without LPS stimulation dataset ( 125 – 127 ), superoxide-generating NADPH oxidase heavy chain subunit (NOX2) –/– dataset ( 23 , 37 , 128 , 129 ), endoplasmic reticulum (ER) stress ( 130 ) inducer) stimulation dataset, eukaryotic translation initiation factor 2 alpha kinase 3 (PRKR-like endoplasmic reticulum kinase, PERK –/– ( 7 , 131 )) and PERK –/– with tunicamycin (inhibitor of the UDP-N-acetylglucosamine-dolichol phosphate N-acetylglucosamine-1-phosphate transferase) dataset, trained immunity (innate immune memory)-promoting histone lysine methyltransferase SET7 –/– dataset ( 132 , 133 ) and were upregulated in antioxidant TF NRF2 –/– transcriptomic datasets ( 11 ), respectively. Our analysis showed that AhR and PERK deficiency had the most significant downregulation of innate immune genes, cytokines and chemokines, oxidative stress cell death genes, and nuclear stress genes ( Figure 14A ).…”

Letter by Teng et al Regarding Article, “Gut Microbiota–Derived Trimethylamine N-Oxide Contributes to Abdominal Aortic Aneurysm Through Inflammatory and Apoptotic Mechanisms”

“…We congratulate Benson et al 1 on the recent publication of their article in Circulation. The authors comprehensively reported that the disruption of the metaorganismal production of trimethylamine N-oxide (TMAO) by targeting either the gut microbiome or the liver enzyme flavin-containing monooxygenase 3 (FMO3) of the host organism decreases circulating TMAO and protects mice from abdominal aortic aneurysm development in 2 independent mouse models.…”

The Role of Gut and Oral Microbiota in the Formation and Rupture of Intracranial Aneurysms: A Literature Review

“…In recent years, there has been a growing interest in the role of the microbiome in cardiovascular and cerebrovascular diseases [ 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. The “microbiome” encompasses all microorganisms residing in or on various parts of the human body, which includes bacteria, fungi, and viruses (and all of their genes).…”

“…More recently, attention has turned to the intestinal microbiome’s role in this process, with certain dietary components, such as carnitine from red meat and phosphatidylcholine from egg yolk, being metabolized by gut bacteria into trimethylamine, eventually converted in the liver into trimethylamine n-oxide (TMAO), which has been established as a risk factor for atherosclerosis [ 25 , 26 ]. For aortic aneurysms there is growing evidence about a potential role of the gut microbiome in formation and rupture [ 21 , 27 , 28 , 29 ]. For example, it was shown that patients with Campylobacter gracilis or Fusobacterium in their gut microbiome had a significantly higher incidence of aortic aneurysm-related events [ 27 ].…”