Abstract
Objective: The purpose of this study was to compare the relative metabolic profile of human biofluids before, during, and after strenuous endurance exercise.
Method: Urine, blood, and sweat samples were collected from eleven healthy endurance trained cyclists at the beginning of, during, and immediately after a two hour cycle ergometer ride at 65% VO2peak. The exercised-induced metabolic changes in the sampled biofluids were followed using nuclear magnetic resonance (NMR) spectra recorded on a 700 MHz NMR spectrometer. Within the biofluids, group separation was accomplished based on relative changes in the distribution of metabolites based on their concentrations using a combination of principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA) and orthogonal partial least squares discriminant analysis (OPLS-DA). Specific metabolites in the NMR spectra could be identified from their characteristic peak positions.
Results: Urine profiles showed significant pre- vs post-exercise differences based on relative metabolite concentration changes. The significant contributors to this difference were creatinine and acetoacetate, which increased following exercise, and glycine, citrate and alanine which decreased. The differences seen in blood plasma were almost exclusively due to the substantial changes in glucose and lactate levels. The most novel of the biofluids, sweat, interestingly showed pre-, mid-, and post- exercise differences due to significant increases in lactate and to a lesser extent, changes in pyruvate and glycerol. In several instances plasma and sweat showed contrasting metabolite concentration changes across the exercise regimen.
Conclusion: The metabolic profile (metabolome) of plasma, sweat, and urine all show significant, yet differing responses to strenuous endurance exercise.