Trimethylsulfonium: a promising new biomarker for hydrogen sulfide?

Hydrogen sulfide is a toxic gas but is naturally produced in human tissues and is referred to as the “third gaseous signaling molecule”. Little is known about the metabolic pathways of hydrogen sulfide and its endogenous natural production in humans. Thiosulfate is the currently used biomarker for hydrogen sulfide but its utility has been shown to be limited to exposure to high levels of inhaled hydrogen sulfide rather than probing low levels of environmental exposure or as a biomarker for the endogenously produced third gaseous signaling molecule. We recently identified a new metabolite in human urine, trimethylsulfonium. In the present review, we discuss the little information known about trimethylsulfonium production in humans, its potential to serve as a biomarker for hydrogen sulfide, and its utility as a biomarker under various settings.