Iron Supplementation During 3 Consecutive Days Of Endurance Training Augmented Hepcidin Concentration

Abstract

PURPOSE: Several physiological mechanisms have been proposed to explain impaired iron status, such as gastrointestinal bleeding, hemolysis, lack of iron in dietary diet and losses in sweat. However, detailed mechanisms underlying exercise-induced iron deficiency among athletes remain unclear. Hepcidin, the 25-amino acid peptide hormone, is a key mediator of iron homeostasis and it may represent another mechanism for iron deficiency in response to exercise training.The present study was designed to investigate impact of consecutive days of strenuous endurance training on hepcidin concentration. The influence of iron supplementation during training period was also determined. METHODS: Fourteen male endurance athletes (long distance runners, triathletes) participated (mean ± standard error, age: 19-22 yrs ; height: 1.68 ± 0.01m ; body mass: 57.3 ± 1.6 kg; maximal oxygen uptake (VO2max): 59.6 ± 0.8 ml/kg/min). Subjects were randomly assigned to either an iron treatment group (Fe group, n=7) or a placebo group (CON group, n=7). All subjects completed 3 consecutive days of endurance training, consisting of two bouts of 75 min of treadmill running at 75 % of VO2max, separated with 3h of rest between bouts. In the Fe group, 12 mg of iron was provided using flavor drink twice a day (24 mg/day), whereas the subjects in the CON group took the same flavor drink without iron. Venous blood samples were collected in early morning on days1-4 and 3h after second bout of exercise on day1. Serum hepcidin, ferritin, iron, myoglobin and plasma IL-6 concentrations were evaluated. RESULTS: The Fe and CON groups showed acute elevations of serum hepcidin, myoglobin and plasma IL-6 concentrations 3h after exercise (P < 0.05 vs. baseline). After 3 days of training period (day4), serum hepcidin concentration was significantly higher in Fe group than in CON group (11.0 ± 2.5 ng/mL vs. 5.9 ± 1.6 ng/mL, P < 0.05). Moreover, serum iron concentration was decreased only in Fe group on day 4 (91.3 ± 13.5 in the Fe group vs. 129.7 ± 7.4 μg/dL in the CON group). CONCLUSIONS: Three consecutive days of endurance training increased hepcidin concentration at baseline when the iron was supplemented.