A time-course investigation of the human urinary excretion of the hydrogen sulfide biomarker trimethylsulfonium

Hydrogen sulfide is a toxic gas but also recognized as an endogenously produced metabolite in humans playing key roles. We previously identified trimethylsulfonium, which can be a methylation product of hydrogen sulfide but the stability in the production of trimethylsulfonium has not been investigated. In the present work, the intra-and inter-individual variability in the excretion of trimethylsulfonium over 2 months in a group of healthy volunteers was investigated. Urinary levels of trimethylsulfonium (mean: 56 nM, 95% CI: 48-68 nM) were > 100-fold lower than the conventional hydrogen sulfide biomarker thiosulfate (13 mu M, 12-15 mu M) and the pre-cursor for endogenous hydrogen sulfide production cystine (47 mu M, 44-50 mu M). There was no correlation be-tween urinary trimethylsulfonium and thiosulfate. Higher intra-individual variability in the excretion of trimethylsulfonium (generally 2-8 fold) than that for cystine (generally 2-3 fold) was found. Trimethylsulfonium displayed significant inter-individual variability with two concentration clusters at 117 nM (97-141) and 27 nM (22-34). In conclusion, the observed inter-and intra-individual variability must be considered when using urinary trimethylsulfonium as a biomarker.