Characterization of sweat induced with pilocarpine, physical exercise, and collected passively by metabolomic analysis

Background/purpose: The elimination of the pain associated with needle picking is a strong motivation for the development of clinical non-invasive diagnostic methods. Sweat has been described as an alternative biological sample that may have a direct relation to the plasma composition. Materials and methods: In this study, analysis of sweat of human volunteers obtained by induction with pilocarpine is compared with sweat samples obtained by physical exercise and by passive collection along 7hours. The sweat samples have been analyzed by 1H nuclear magnetic resonance spectroscopy. Results: A range of 34 different metabolites has been detected in sweat samples, including lactate, several amino acids, pyroglutamate, and urocanate. Most of the metabolites identified were quantified. The majority of the amino acids detected in sweat seem to have origin in the epidermis surface. No significant differences in sweat samples from female and male were observed by 1H NMR metabolomic analysis. Conclusions: Principal component analysis (PCA) shows that both physical exercise and pilocarpine methods seem to be equally reproducible methods in terms of sweat metabolite composition presenting better repeatability than natural sweat collection. Nevertheless, this difference is mainly originated from amino acids with origin from the skin surface.