Exploration Of Hydration Practices And Prolonged Endurance Exercise Effects On Plasma Apelin Concentration

Abstract

Reduced circulating concentrations of the endogenous peptide apelin is implicated in many negative health conditions, and apelin administration can reverse sarcopenia processes. While acute and chronic exercise elicits greater circulating apelin concentrations, little attention has been given to apelin’s water regulatory roles (i.e., AVP opposition) and manipulation by water intake to enhance human health. PURPOSE: We investigated the impact of hydration status and process on plasma apelin following prolonged endurance exercise and after a subsequent water challenge. METHODS: Twenty-two male cyclists (age median=54y and range=29-72y) completed a 161km event (mean=26°C, 76%RH; maximum=30°C, 93%RH; mean finish time = 372 ± 93min). Participants were interviewed for dietary intake in the morning and during the ride. Hydration biomarkers included body mass change (BMΔ), urine specific gravity (Usg) and color (Ucol), plasma osmolality (Posm) and copeptin (Pcop), and apelin (Pap), which were collected before (PRE), immediately after the ride (POST), and 1h following a 650mL water bolus (POST1h). RESULTS: Pap paradoxically decreased after exercise (PRE = 1.19 ± 0.29, POST = 1.02 ± 0.27 ng/mL; p = 0.04). It is plausible that hypohydration at POST (according to -1.96% BMΔ and Pcop, Usg, Ucol (p < 0.05), but not Posm (p = 0.31)) masked any drive of acute exercise to increase Pap, or that prolonged endurance exercise differentially affects Pap, although POST and POST1h Pap did not correlate with finish time (p = 0.76 and 0.31, respectively). Interestingly, the water bolus did not alter Pap concentrations versus POST (POST1h = 1.0 ± 0.29 ng/mL; p = 0.66). POST Pap correlated with PRE Posm (r = -0.47), and POST1h Pap with PRE Ucol (r = -0.46; both p < 0.05), suggesting baseline hydration might alter Pap responses. Despite previous reports, Pap was not significantly correlated with age at any time point (p = 0.36 to 0.73) perhaps due to chronic exercise practices of these cyclists. CONCLUSIONS: This real-world scenario demonstrated complex relationships among plasma apelin, exercise, and hydration. Our data suggests insufficient baseline hydration might mitigate the acute exercise-induced Pap elevation. As an increasingly valuable modulator of chronic health, further research should address complexities of Pap responses.