TMAO as a biomarker of cardiovascular events: a systematic review and meta-analysis

Background: Unmasking the residual cardiovascular risk is a major research challenge in the attempt to reduce cardiovascular disease (CVD) morbidity and mortality. Mounting evidence suggests that a high circulating level of trimethylamine N-oxide is a new potential CVD risk factor. We performed a systematic review of the published studies to clarify the association between circulating high levels of TMAO and cardiovascular events. Methods: Studies evaluating the association between TMAO and CVD events were searched by electronic databases up to December 2018. Pooled results were expressed as risk ratio (RR) with 95% pertinent confidence interval (CI). Results: Three studies for a total of 923 patients at high/very high CVD risk were included in our analysis. Overall, a high TMAO level was associated with both major adverse cardiovascular events (RR = 2.05; 95% CI 1.61–2.61) and all-cause mortality (RR = 3.42; 95% CI 2.27–5.15). Conclusions: Our findings support a role of high TMAO levels in predicting CVD events. High levels of TMAO may be a new CVD risk factor, potentially useful to better plan personalized CVD prevention strategies.