Elevated Serum Trimethylamine N-Oxide Levels Are Associated with Mortality in Male Patients on Peritoneal Dialysis

Background: Elevated levels of serum trimethylamine N-oxide (TMAO) have been previously linked to adverse cardiovascular (CV) and all-cause mortality in hemodialysis patients. However, the clinical significance of serum TMAO levels in patients treated with peritoneal dialysis (PD) is unclear. Methods: A total of 1,032 PD patients with stored serum samples at baseline were enrolled in this prospective study. Serum concentrations of TMAO were quantified by ultra-performance liquid chromatography-tandem mass spectrometry. Cox proportional hazards and competing-risk regression models were performed to examine the association of TMAO levels with all-cause and CV mortality. Results: The median level of serum TMAO in our study population was 34.5 (interquartile range (IQR), 19.8–61.0) μM. During a median follow-up of 63.7 months (IQR, 43.9–87.2), 245 (24%) patients died, with 129 (53%) deaths resulting from CV disease. In the entire cohort, we observed an association between elevated serum TMAO levels and all-cause mortality (adjusted subdistributional hazard ratio [SHR], 1.22; 95% confidence interval [95% CI], 1.01–1.48; p = 0.039) but not CV mortality. Further analysis revealed such association differed by sex; the elevation of serum TMAO levels was independently associated with increased risk of both all-cause (SHR, 1.37; 95% CI, 1.07–1.76; p = 0.013) and CV mortality (SHR, 1.41; 95% CI, 1.02–1.94; p = 0.038) in men but not in women. Conclusions: Higher serum TMAO levels were independently associated with all-cause and CV mortality in male patients treated with PD.