Metabolomics of arsenic based on speciation studies

Biomedical research on arsenic can be divided into three steps, i.e., speciation of the entirety of arsenic in a biological system (metallome), examination of the metabolism of arsenic based on the speciation of metallome (metabolomics), and examination of the metallomics underlying the mechanism that triggers biological/physiological/toxicological effects based on the metabolomics. In the present communication, the metabolic pathway for inorganic arsenic, a known human carcinogen, was explained based on current results of speciation. In addition to the consecutive reduction and oxidative methylation reactions converting inorganic arsenicals to the major urinary metabolite dimethylarsinic acid, the role of the conjugation reaction involving glutathione resulting in excretion from the liver was discussed. Furthermore, sulfur-containing arsenicals (thioarsenicals) identified as new metabolites in the livers of rats were characterized chemically and metabolically.