Packed-Nanofiber Solid-Phase Extraction Coupled with High-Performance Liquid Chromatography Fluorescence for Determining Gut Microbiota-Host Cometabolites and Indoleamines in Human Urine

Exercise reduces the risk of inflammatory diseases by modulating different tissue and cell types, including those within the gastrointestinal tract. Obtaining a more comprehensive understanding of pathophysiology requires monitoring of dynamic changes in cometabolites. This study aimed to develop a method for determining gut microbiota-host cometabolites and indoleamines in human urine. Four key gut microbiota-host cometabolites were chromatographically separated by isocratic elution, with a running time of 10 min. The linearity of this method was confirmed over different concentration ranges: 1.0-400 ng/mL for melatonin (MEL), indole-3-propionic acid (3-IPA), indole (IND), and skatole (SKT). This method was extremely sensitive and stable and hence could be successfully applied to characterize the changes in gut microbiota-host cometabolites in human before- and after-running urine. The concentrations of MEL, 3-IPA, IND, and SKT in after-running urine were 84.0 +/- 9.69, 25.9 +/- 3.39, 343.7 +/- 36.8, and 14.6 +/- 1.36 ng/mL, respectively. Moreover, the concentrations in before-running urine were 54.2 +/- 5.10, 14.4 +/- 1.30, 250.8 +/- 14.1, and 9.43 +/- 1.07 ng/mL, respectively, which showed significantly less difference in concentrations (p < 0.05) in before- than after-running urine. Overall, the established method could simultaneously monitor gut microbiota-host cometabolites and hence can be further applied to clinical and comprehensive pathophysiological studies.