Relationship Between Hepcidin, Interluken-6, And Ferritin In Division-I Cross-country Runners Over A Competitive Season

Abstract

Iron deficiency, which can be assessed by the iron storage protein ferritin (fer) can negatively affect athletic performance. We have previously observed that Division 1 cross country (XC) runners have fer levels that are at the low end of normal ranges despite being iron supplemented. The hormone hepcidin and the cytokine/myokine interleukin-6 (IL6) can both influence iron regulation but have not been evaluated in this population. PURPOSE: The purpose of this study was to determine how hepcidin and IL6 change over a season in DI XC runners and determine whether changes in these parameters were related to changes in fer, hemoglobin concentration (Hb) or hematocrit (Hct). METHODS: 45 athletes (25 female, 20 male) were recruited from the University of Colorado DI XC team in the fall of 2017. Fasted blood samples were collected in October (before NCAA XC championships), January, and March (during the outdoor track season). Blood samples were analyzed for Hb, Hct, fer, IL6 and hepcidin. All runners were provided with oral iron supplements from a certified nutritionist during this period. RESULTS: All biomarkers remained stable across the season except Hb, which was significantly higher in March. In males vs. females, there were no differences in hepcidin (24 ± 11 vs. 21 ± 11 ng/ml; p > 0.05) or IL6 (16 ± 21 vs. 12 ± 24 pg/mL; p > 0.05). When compared to females, males had higher fer (64 ± 33 vs 47 ± 24 ng/mL; p < 0.05), Hct (48 ± 2 vs 44 ± 3 %; p < 0.001), and Hb (16.3 ± 0.7 vs 14.8 ± 0.8 g/dl; p < 0.01). After controlling for sex, there was a positive relationship between hepcidin and fer (r = 0.47, p < 0.01); 20% of the variability in fer was explained by hepcidin and 51% was explained by individual variability. There were no relationships between IL6 and hepcidin or IL6 and fer. CONCLUSION: Despite a consistent iron supplementation regime, hepcidin, IL6 and fer do not seem to systematically change across a season in collegiate runners. As expected, hepcidin and fer were positively related, but there were no relationships between IL6 and other measured parameters. Although fer was at the low end of normal for both men and women, all other parameters were normal at all time points, suggesting that the normal range of fer for endurance athletes may be lower than the general population.