Alterations of systemic and muscle iron metabolism in human subjects treated with low-dose recombinant erythropoietin

Abstract

The high iron demand associated with enhanced erythropoiesis during high-altitude hypoxia leads to skeletal muscle iron mobilization and decrease in myoglobin protein levels. To investigate the effect of enhanced erythropoiesis on systemic and muscle iron metabolism under nonhypoxic conditions, 8 healthy volunteers were treated with recombinant erythropoietin (rhEpo) for 1 month. As expected, the treatment efficiently increased erythropoiesis and stimulated bone marrow iron use. It was also associated with a prompt and considerable decrease in urinary hepcidin and a slight transient increase in GDF-15. The increased iron use and reduced hepcidin levels suggested increased iron mobilization, but the treatment was associated with increased muscle iron and L ferritin levels. The muscle expression of transferrin receptor and ferroportin was upregulated by rhEpo administration, whereas no appreciable change in myoglobin levels was observed, which suggests unaltered muscle oxygen homeostasis. In conclusion, under rhEpo stimulation, the changes in the expression of muscle iron proteins indicate the occurrence of skeletal muscle iron accumulation despite the remarkable hepcidin suppression that may be mediated by several factors, such as rhEpo or decreased transferrin saturation or both. (Blood. 2009; 113:6707-6715)

Cell-specific regulation of Ferroportin transcription following experimentally-induced acute anemia in mice

“…However we cannot rule out the possibility that other stimuli induced by bleeding may concur to regulate FPN expression. Among these, erythropoietin (EPO) has been shown to induce FPN expression in Caco2 cells [25] and in humans erythropoietin administration affects FPN expression in muscle [26] and in peritoneal exudates macrophages [27]. However, the administration of recombinant human EPO to mice did not affect FPN expression in the duodenum [28].…”

Setup for human sera MALDI profiling: The case of rhEPO treatment

“…The time course of plasma EPO levels (Supporting Information Fig. 5S) monitored as described previously [42], increased up to three times in plasma after 6 days of treatment; accordingly, a similar increment was expected in serum and thus we focused our attention on samples at day 0 (control samples) and at day 6, in which EPO reached the maximal concentration. Both columns, Hu7 and Hu14, were adopted to verify the effects on the dynamic range of samples treated with rhEPO, whereas DHAP was the matrix of choice.…”

“…EPO levels were assessed by enzymelinked immunoabsorbent assay (ELISA) kit (R&D Systems, Minneapolis, MN, USA). Sera and plasma were obtained as described previously [42].…”

“…Serum samples were collected from ten healthy young male volunteers, carefully selected, and well-char- acterized subjects. Characteristics of the subjects have been described previously [42]. By profiling these samples, we expected to detect the differences related to changes induced by increased erythropoiesis, hematocrit, hemoglobin, and iron mobilization, and to propose a new method for monitoring rhEPO treatment that could be useful for both clinical purposes and antidoping tests.…”

“…For this reason, rhEPO is on the list of prohibited substances of International Olympic Committee (IOC) and World Anti-Doping Agency (WADA) [41]. In a previous study on male volunteers [42], rhEPO administration effectively increased erythropoiesis, hematocrit, hemoglobin, and iron mobilization; therefore, a number of changes in serum profile are expected. Due to the short half-life, detection of rhEPO is associated to its assumption modality and available tests can reveal only chronic and/or massive assumption [43]; hence, the development of tests for monitoring rhEPO and proteins or peptides associated to its intake remains of great interest both for clinical purposes and for antidoping in sport practice.…”