No effect of supplemented heat stress during an acute endurance exercise session in hypoxia on hepcidin regulation

Abstract

Hepcidin is a novel factor for iron deficiency in athletes, which is suggested to be regulated by interleukin-6 (IL-6) or erythropoietin (EPO).

Purpose: The purpose of the present study was to compare endurance exercise-induced hepcidin elevation among "normoxia", "hypoxia" and "combined heat and hypoxia".

Methods: Twelve males (21.5 ± 0.3 years, 168.1 ± 1.2 cm, 63.6 ± 2.0 kg) participated in the present study. They performed 60 min of cycling at 60% of [Formula: see text] in either "heat and hypoxia" (HHYP; F_iO₂ 14.5%, 32 °C), "hypoxia" (HYP; F_iO₂ 14.5%, 23 °C) or "normoxia" (NOR; F_iO₂ 20.9%, 23 °C). After completing the exercise, participants remained in the prescribed conditions for 3 h post-exercise. Blood samples were collected before, immediately and 3 h after exercise.

Results: Plasma IL-6 level significantly increased immediately after exercise (P < 0.05), with no significant difference among the trials. A significant elevation in serum EPO was observed 3 h after exercise in hypoxic trials (HHYP and HYP, P < 0.05), with no significant difference between HHYP and HYP. Serum hepcidin level increased 3 h after exercise in all trials (NOR, before 18.3 ± 3.9 and post180 31.2 ± 6.3 ng/mL; HYP, before 13.5 ± 2.5 and post180 23.3 ± 3.6 ng/mL, HHYP; before 15.8 ± 3.3 and post180 31.4 ± 5.3 ng/mL, P < 0.05). However, there was no significant difference among the trials during post-exercise.

Conclusion: Endurance exercise in "combined heat and hypoxia" did not exacerbate exercise-induced hepcidin elevation compared with the same exercise in "hypoxia" or "normoxia".

Keywords: Erythropoietin; Heat; Hepcidin; Hypoxia; Interleukin-6.