An NMR-Based Approach to Identify Urinary Metabolites Associated with Acute Physical Exercise and Cardiorespiratory Fitness in Healthy Humans—Results of the KarMeN Study

Abstract

Knowledge on metabolites distinguishing the metabolic response to acute physical exercise between fit and less fit individuals could clarify mechanisms and metabolic pathways contributing to the beneficial adaptations to exercise. By analyzing data from the cross-sectional KarMeN (Karlsruhe Metabolomics and Nutrition) study, we characterized the acute effects of a standardized exercise tolerance test on urinary metabolites of 255 healthy women and men. In a second step, we aimed to detect a urinary metabolite pattern associated with the cardiorespiratory fitness (CRF), which was determined by measuring the peak oxygen uptake (VO2peak) during incremental exercise. Spot urine samples were collected pre- and post-exercise and 47 urinary metabolites were identified by nuclear magnetic resonance (NMR) spectroscopy. While the univariate analysis of pre-to-post-exercise differences revealed significant alterations in 37 urinary metabolites, principal component analysis (PCA) did not show a clear separation of the pre- and post-exercise urine samples. Moreover, both bivariate correlation and multiple linear regression analyses revealed only weak relationships between the VO2peak and single urinary metabolites or urinary metabolic pattern, when adjusting for covariates like age, sex, menopausal status, and lean body mass (LBM). Taken as a whole, our results show that several urinary metabolites (e.g., lactate, pyruvate, alanine, and acetate) reflect acute exercise-induced alterations in the human metabolism. However, as neither pre- and post-exercise levels nor the fold changes of urinary metabolites substantially accounted for the variation of the covariate-adjusted VO2peak, our results furthermore indicate that the urinary metabolites identified in this study do not allow to draw conclusions on the individual’s physical fitness status. Studies investigating the relationship between the human metabolome and functional variables like the CRF should adjust for confounders like age, sex, menopausal status, and LBM.

Sex-Specific Relationship between the Cardiorespiratory Fitness and Plasma Metabolite Patterns in Healthy Humans—Results of the KarMeN Study

“…Contrary to a previous attempt to explain the variability of CRF in the KarMeN population based on urinary metabolites [ 65 ], we were now able to identify sets of plasma metabolites that, together with clinical and phenotypical variables, contributed to a relatively good explanation of the VO 2peak in both sexes, after adjusting for age and menopausal status. In all approaches, the FM (%) entered the models as the first variable, already explaining 33.5% (females) or 42.3% (males) of the confounder-adjusted VO 2peak .…”

“…As a measure of PF, CRF was assessed by a standardized incremental exercise test on a bicycle ergometer (Ergobike medical, Daum, Fürth, Germany). All participants started pedaling at 25 Watts and the workload was then augmented by 25 Watt every 2 min until individual exhaustion, as previously described [ 65 , 67 ]. The respiratory gas exchange was measured breath-by-breath by using a cardiopulmonary exercise testing system (MetaMax 3B, Cortex, Leipzig, Germany).…”

Metabolomics and Lipidomics: Expanding the Molecular Landscape of Exercise Biology

“…It has been suggested that the urinary metabolome can be considered complementary to the blood metabolome, since urine contains numerous end-products derived from food and drug metabolism [ 50 ]. Recent publications support the utility of urine analysis to reflect metabolomic changes following acute exercise, as analysis of urine permits confirmation of well-appreciated exercise-induced changes in metabolites related to several pathways including glycolysis (e.g., pyruvate and lactate), TCA cycle (e.g., citrate and succinate) and amino acid metabolism (e.g., alanine, taurine) [ 82 , 83 , 84 , 85 , 86 ]. In one of the earliest urinary metabolomic papers published, Kistner et al reported that within 15–30 min following an incremental cycling test, significant increases in urinary carnitine and novel urinary exercise-responsive metabolites could be observed; notably including increases in leucine derivatives methylsuccinate and 3-hydroxyisovalerate, and valine derivative 3-aminoisobutyrate.…”

“…In one of the earliest urinary metabolomic papers published, Kistner et al reported that within 15–30 min following an incremental cycling test, significant increases in urinary carnitine and novel urinary exercise-responsive metabolites could be observed; notably including increases in leucine derivatives methylsuccinate and 3-hydroxyisovalerate, and valine derivative 3-aminoisobutyrate. Increased urinary levels of these derivatives indicate branched-chain amino acid (BCAA) degradation and excretion in urine following exhaustive exercise [ 82 ]. However, an often-reported downside of metabolomic analyses in urine is that metabolite concentrations are highly influenced by hydration status and thus require normalization for water content.…”

The Metabolic Signature of Cardiorespiratory Fitness: A Systematic Review

“…Included studies were published between 2012 and 2021 (Table 1 and ESM). Fifteen studies included both female and male participants [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48], and seven studies investigated male participants only [49][50][51][52][53][54][55]. One study examined adolescents [38], and the remaining 21 studies enrolled only adults (defined as participants aged > 18 years).…”