Influence of Trimethylamine N-Oxide on Platelet Activation.

Microbiome-derived trimethylamine N-oxide (TMAO) has been associated with platelet hyperreactivity and subsequent atherogenesis. Whether physiological TMAO-levels influence platelet-derived lipid mediators remains unknown. Little is known about pre-analytic factors potentially influencing TMAO concentrations. We aimed at developing a quantitative LC-MS/MS method to investigate in-vivo and in-vitro pre-analytical factors in TMAO analysis to properly assess the proposed activating effect of TMAO on platelets. TMAO, betaine, carnitine, and choline were analyzed by HILIC-ESI-MS/MS within 6 min total run time. Method validation included investigation of reproducibility, recovery, sensitivity, and in-vitro pre-analytical factors. A 24-h monitoring experiment was performed, evaluating in-vivo pre-analytical factors like daytime or diet. Finally, the effects of different TMAO concentrations on platelet activation and corresponding alterations of platelet-derived eicosanoid release were analyzed. The method showed high reproducibility (CVs ≤ 5.3%), good recovery rates (96-98%), and negligible in-vitro pre-analytical effects. The influence of in-vivo pre-analytical factors on TMAO levels was not observable within the applied experimental conditions. We did not find any correlation between TMAO levels and platelet activation at physiological TMAO concentrations, whereas platelet-derived eicosanoids presented activation of the cyclooxygenase and lipoxygenase pathways. In contrast to previously published results, we did not find any indications regarding diet dependency or circadian rhythmicity of TMAO levels. Our results do not support the hypothesis that TMAO increases platelet responsiveness via the release of lipid-mediators.

Association of plasma trimethylamine N-oxide levels with atherosclerotic cardiovascular disease and factors of the metabolic syndrome.

BACKGROUND AND AIMS: The association of plasma trimethylamine N-oxide (TMAO) with atherosclerotic cardiovascular disease (ASCVD), diabetes mellitus (DM) and its determinants, as well as the role of TMAO as a predictor for short and long-term mortality, is still under discussion. We investigated associations between four plasma metabolites of the TMAO pathway and different clinical manifestations of atherosclerosis, diabetes determinants, and risk of short and long-term mortality in patients with stable ASCVD, acute myocardial infarction (AMI), cardiogenic shock (CS), and DM in three independent cohorts. METHODS: TMAO and its dietary precursors were simultaneously quantified by liquid chromatography-tandem mass spectrometry in a total of 2655 participants of the German Leipzig Research Center for Civilization Diseases (LIFE)-Heart study, LIFE-Adult study, and the European Culprit Lesion Only PCI versus Multivessel PCI in Cardiogenic Shock (CULPRIT-SHOCK) multicenter trial. Associations with ASCVD manifestations, metabolic syndrome, 30-day mortality of patients with AMI and CS, and long-term mortality of subjects with suspected coronary artery disease (CAD) were analyzed. RESULTS: TMAO plasma levels were not independently associated with stable ASCVD. Elevated TMAO plasma concentrations were independently associated with obesity (odds ratio, 1.23; p < 0.01) and DM (odds ratio, 1.37; p < 0.001) in LIFE-Heart. The latter association was confirmed in LIFE-Adult. We found no association of TMAO plasma levels with short-term mortality in patients with AMI and CS. However, TMAO plasma levels were independent predictors of long-term mortality in patients with suspected CAD (hazard ratio, 1.24; p < 0.05). CONCLUSIONS: Potential proatherogenic mechanisms of TMAO seem to have no short-term effect in AMI. Presented associations with diabetes mellitus and obesity suggest that TMAO might have a functional role in metabolic syndrome.