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

Abstract

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 µM, 12–15 µM) and the precursor for endogenous hydrogen sulfide production cystine (47 µM, 44–50 µM). There was no correlation between 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.