Non-invasive tool for monitoring biomarker profiles in sweat to promote physical activity in older adults

Background: Sweat analysis has gained increasing attention due to its constitution with diverse biomolecules, offering a non-invasive alternative to invasive procedures such as blood sampling or cerebrospinal fluid (CSF) collection. This method offers a more accessible and convenient approach to monitoring physiological responses. Tryptophan is an essential amino acid that undergoes catabolism through the kynurenine pathway to generate various metabolites. These metabolites play important roles in regulating mood, energy levels, and overall well-being, and their concentrations in sweat may reflect physiological responses to exercise and metabolic activity. However, the change in metabolite concentrations, particularly in sweat, remains limited.

Purpose: This study aims to develop a method for sweat collection and analysis using High-Performance Liquid Chromatography (HPLC) to investigate the sweat content of tryptophan (TRP) and its metabolites in older adults.

Method: The HPLC conditions were optimized with standard TRP and metabolite solutions. Sweat samples from ninety adults (45-90 years old) were collected, and the TRP and its metabolites were analyzed using HPLC coupled with UV-vis and fluorescence detectors.

Results: The optimized conditions have a retention time of under 10 minutes and linear responses of R2 > 0.99. TRP and its metabolites from sweat were detectable in the concentrations range of 130-8,000 fmol/ µg sodium, 25-200 fmol/ µg sodium, and 0.5-70 pmol/µg sodium for TRP, kynurenine, and 3-hydroxy anthranilic acid, respectively. Notably, TRP decreased, while kynurenine, increased with age.

Conclusion: The HPLC technique provides a simple, fast, and sensitive method for quantifying sweat content. Incorporating tryptophan metabolite analysis into the sweat profile may facilitate the development of personalized exercise to motivate physical performance in older populations.

Practical implications: Implementation of this method has the potential to promote physical activity among older adults, resulting in healthier aging and improved overall well-being.

Funding: Mahidol University