| Autor: |
Ryan BJ; Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States., Barney DE Jr; Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States.; Oak Ridge Institute for Science and Education, Belcamp, Maryland, United States., McNiff JL; Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States.; Combat Feeding Division, United States Army Combat Capabilities Development Command (DEVCOM), Natick, Massachusetts, United States., Drummer DJ; Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States.; Oak Ridge Institute for Science and Education, Belcamp, Maryland, United States., Howard EE; Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States., Gwin JA; Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States., Carrigan CT; Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States., Murphy NE; Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States., Wilson MA; Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States., Pasiakos SM; Office of Dietary Supplements, United States Department of Health and Human Services, National Institutes of Health, Bethesda, Maryland, United States., McClung JP; Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States., Margolis LM; Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States. |
| Abstrakt: |
Strenuous physical training increases total blood volume (BV) through expansion of plasma volume (PV) and red cell volume (RCV). In contrast, exogenous erythropoietin (EPO) treatment increases RCV but decreases PV, rendering BV stable or slightly decreased. This study aimed to determine the combined effects of strenuous training and EPO treatment on BV and markers of systemic and muscle iron homeostasis. In this longitudinal study, eight healthy nonanemic males were treated with EPO (50 IU/kg body mass, three times per week, sc) across 28 days of strenuous training (4 days/wk, exercise energy expenditures of 1,334 ± 24 kcal/day) while consuming a controlled, energy-balanced diet providing 39 ± 4 mg/day iron. Before (PRE) and after (POST) intervention, BV compartments were measured using carbon monoxide rebreathing, and markers of iron homeostasis were assessed in blood and skeletal muscle (vastus lateralis). Training + EPO increased ( P < 0.01) RCV (13 ± 6%) and BV (5 ± 4%), whereas PV remained unchanged ( P = 0.86). The expansion of RCV was accompanied by a large decrease in whole body iron stores, as indicated by decreased ( P < 0.01) ferritin (-77 ± 10%) and hepcidin (-49 ± 23%) concentrations in plasma. Training + EPO decreased ( P < 0.01) muscle protein abundance of ferritin (-25 ± 20%) and increased ( P < 0.05) transferrin receptor (47 ± 56%). These novel findings illustrate that strenuous training combined with EPO results in both increased total oxygen-carrying capacity and hypervolemia in young healthy males. The decrease in plasma and muscle ferritin suggests that the marked upregulation of erythropoiesis alters systemic and tissue iron homeostasis, resulting in a decline in whole body and skeletal muscle iron stores. NEW & NOTEWORTHY Strenuous exercise training combined with erythropoietin (EPO) treatment increases blood volume, driven exclusively by red cell volume expansion. This hematological adaptation results in increased total oxygen-carrying capacity and hypervolemia. The marked upregulation of erythropoiesis with training + EPO reduces whole body iron stores and circulating hepcidin concentrations. The finding that the abundance of ferritin in muscle decreased after training + EPO suggests that muscle may release iron to support red blood cell production. |
