Plasma concentrations of trimethylamine-N-oxide, choline and betaine in patients with moderate to advanced chronic kidney disease and their relation to cardiovascular and renal outcomes

Objectives Trimethylamine N-oxide (TMAO) is a gut bacteria mediated liver metabolite of dietary betaine, choline, and carnitine which is excreted by glomerular filtration. We studied whether TMAO is associated with cardiovascular disease (CVD) in patients with chronic kidney disease (CKD). Methods Among 478 patients with CKD stage G2 (n = 104), G3a (n = 163), G3b (n = 123), and G4 (n = 88), we studied the association between fasting plasma concentrations of TMAO, choline or betaine at baseline and kidney function, prevalent CVD and future renal outcomes during a mean follow-up of 5.1 years. Results Decreased glomerular filtration rate was associated with higher plasma concentrations of TMAO, choline and betaine. Baseline concentrations of TMAO were higher in participants with preexisting CVD compared to those without CVD (8.4 [10.1] vs. 7.8 [8.0] μmol/L; p = 0.047), but the difference was not significant after adjusting for confounders. During the follow up, 147 participants experienced CVD or died and 144 reached the predefined renal endpoint. In the adjusted regression analyses, TMAO or choline concentrations in the upper three quartiles (versus the lowest quartile) were not associated with any of the study clinical endpoints. In contrast, the adjusted hazard ratio of plasma betaine in the highest quartile versus the lowest quartile was 2.14 (1.32, 3.47) for the CVD endpoint and 1.64 (1.00, 2.67) for the renal endpoint. Conclusions Elevated plasma TMAO concentrations were explained by impaired kidney function. Elevated plasma concentrations of betaine, but not that of TMAO or choline predicted adverse outcomes. TMAO might not be an appropriate target to reduce CVD or renal outcomes in patients with preexisting CKD.