High levels of trimethylamine N-oxide increase risk of coronary heart disease

Long-term increases in the gut-microbial metabolite trimethylamine N-oxide (TMAO) appear to heighten the risk of coronary heart disease (CHD), reveals a study.

Moreover, a repeated assessment of TMAO over 10 years can improve the identification of individuals who are at increased risk of CHD, according to the authors.

A total of 760 healthy women at baseline were recruited in this prospective nested cohort study. Plasma TMAO levels were measured both at the first (1989 to 1990) and the second (2000 to 2002) blood collections. The authors then calculated the 10-year changes (Δ) in TMAO. Finally, they identified incident cases of CHD (n=380) after the second blood collection through 2016 and matched these to controls (n=380).

Regardless of TMAO levels at baseline, 10-year increases in TMAO from the first to the second blood collection resulted in a significant increase in the risk of CHD (relative risk [RR] in the top tertile, 1.58, 95 percent confidence interval [CI], 1.05–2.38; RR per 1-SD increase, 1.33, 95 percent CI, 1.06–1.67). Participants with increased TMAO levels (the top tertile) at both time points, compared with those with consistently low TMAO levels, had the highest risk of CHD (RR, 1.79, 95 percent CI, 1.08–2.96).

In addition, unhealthy dietary patterns, as assessed by the Alternate Healthy Eating Index), bolstered the association between ΔTMAO and CHD risk, which was attenuated, not surprisingly, by healthy dietary patterns (p_interaction=0.008).

“Diet may modify the associations of ΔTMAO with CHD risk,” the authors said.