Effects of altitude and recombinant human erythropoietin on iron metabolism: a randomized controlled trial

Strenuous training combined with erythropoietin induces red cell volume expansion-mediated hypervolemia and alters systemic and skeletal muscle iron homeostasis

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.

Iron deficiency and supplementation in heart failure

Non-anaemic iron deficiency (NAID) is a strategic target in cardiovascular medicine because of its association with a range of adverse effects in various conditions. Endeavours to tackle NAID in heart failure have yielded mixed results, exposing knowledge gaps in how best to define 'iron deficiency' and the handling of iron therapies by the body. To address these gaps, we harness the latest understanding of the mechanisms of iron homeostasis outside the erythron and integrate clinical and preclinical lines of evidence. The emerging picture is that current definitions of iron deficiency do not assimilate the multiple influences at play in patients with heart failure and, consequently, fail to identify those with a truly unmet need for iron. Additionally, current iron supplementation therapies benefit only certain patients with heart failure, reflecting differences in the nature of the unmet need for iron and the modifying effects of anaemia and inflammation on the handling of iron therapies by the body. Building on these insights, we identify untapped opportunities in the management of NAID, including the refinement of current approaches and the development of novel strategies. Lessons learned from NAID in cardiovascular disease could ultimately translate into benefits for patients with other chronic conditions such as chronic kidney disease, chronic obstructive pulmonary disease and cancer.

Indirect biomarkers of blood doping: A systematic review

The detection of blood doping represents a current major issue in sports and an ongoing challenge for antidoping research. Initially focusing on direct detection methods to identify a banned substance or its metabolites, the antidoping effort has been progressively complemented by indirect approaches. The longitudinal and individual monitoring of specific biomarkers aims to identify nonphysiological variations that may be related to doping practices. From this perspective, the identification of markers sensitive to erythropoiesis alteration is key in the screening of blood doping. The current Athlete Biological Passport implemented since 2009 is composed of 14 variables (including two primary markers, i.e., hemoglobin concentration and OFF score) for the hematological module to be used for indirect detection of blood doping. Nevertheless, research has continually proposed and investigated new markers sensitive to an alteration of the erythropoietic cascade and specific to blood doping. If multiple early markers have been identified (at the transcriptomic level) or developed directly in a diagnostics' kit (at a proteomic level), other target variables at the end of the erythropoietic process (linked with the red blood cell functions) may strengthen the hematological module in the future. Therefore, this review aims to provide a global systematic overview of the biomarkers considered to date in the indirect investigation of blood doping.

Contemporary blood doping-Performance, mechanism, and detection

Blood doping is prohibited for athletes but has been a well-described practice within endurance sports throughout the years. With improved direct and indirect detection methods, the practice has allegedly moved towards micro-dosing, that is, reducing the blood doping regime amplitude. This narrative review evaluates whether blood doping, specifically recombinant human erythropoietin (rhEpo) treatment and blood transfusions are performance-enhancing, the responsible mechanism as well as detection possibilities with a special emphasis on micro-dosing. In general, studies evaluating micro-doses of blood doping are limited. However, in randomized, double-blinded, placebo-controlled trials, three studies find that infusing as little as 130 ml red blood cells or injecting 9 IU × kg bw-1 rhEpo three times per week for 4 weeks improve endurance performance ~4%-6%. The responsible mechanism for a performance-enhancing effect following rhEpo or blood transfusions appear to be increased O2 -carrying capacity, which is accompanied by an increased muscular O2 extraction and likely increased blood flow to the working muscles, enabling the ability to sustain a higher exercise intensity for a given period. Blood doping in micro-doses challenges indirect detection by the Athlete Biological Passport, albeit it can identify ~20%-60% of the individuals depending on the sample timing. However, novel biomarkers are emerging, and some may provide additive value for detection of micro blood doping such as the immature reticulocytes or the iron regulatory hormones hepcidin and erythroferrone. Future studies should attempt to validate these biomarkers for implementation in real-world anti-doping efforts and continue the biomarker discovery.

The anaemia treatment journey of CKD patients: from epoetins to hypoxia-inducible factor-prolyl hydroxylase inhibitors

The discovery and development of erythropoiesis-stimulating agents was a journey lasting more than a century, leading to the cloning and approval of recombinant human erythropoietin (rHuEpo). This was an impressive clinical advance, providing the possibility of correcting the symptoms associated with anaemia in chronic kidney disease. Associated iron use was needed to produce new haemoglobin-containing blood red cells. Partial anaemia correction became the standard of care since trials aiming for near-normal haemoglobin levels showed a higher risk of adverse cardiovascular events. Hoping to reduce the cardiovascular risks, a new category of drugs was developed and tested. Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) are small molecules than can be formulated into orally active pills. They simulate reduced tissue oxygen pressure, thus stimulating the production of endogenous erythropoietin (Epo) by the kidneys and liver. Clinical trials with these compounds demonstrated that HIF-PHIs are at least as effective as rHuEpo in treating or correcting anaemia in non-dialysis and dialysis patients. Trials with HIF-PHIs did not demonstrate superiority in safety outcomes and in some trials, outcomes were worse. There was also a focus on oral delivery, a possible beneficial iron-sparing effect and the ability to overcome Epo resistance in inflamed patients. A negative effect is possible iron depletion, which may explain adverse outcomes.

Microdoses of Recombinant Human Erythropoietin Enhance Time Trial Performance in Trained Males and Females

PURPOSE

We investigated the effects of recombinant human erythropoietin (rHuEPO) administration on exercise endurance, maximal aerobic performance, and total hemoglobin mass (tHb). We hypothesized that frequent, small intravenous injections of epoetin β would increase time trial performance, peak oxygen uptake (V̇O 2peak ), and tHb in both males and females.

METHODS

We included 48 healthy, recreational to trained males ( n = 24, mean ± SD V̇O 2peak = 55 ± 5 mL O 2 ·kg -1 ⋅min -1 ) and females ( n = 24; V̇O 2peak of 46 ± 4 mL O 2 ·kg -1 ⋅min -1 ) in a counterbalanced, double-blind, randomized, placebo-controlled study design stratified by sex. Time trial performance, V̇O 2peak , and tHb were determined before and after intravenous injections of either rHuEPO (9 IU·kg bw -1 epoetin β) or saline (0.9% NaCl) three times weekly for 4 wk.

RESULTS

A time-treatment effect ( P < 0.05) existed for time trial performance. Within the rHuEPO group, mean power output increased by 4.1% ± 4.2% ( P < 0.001). Likewise, a time-treatment effect ( P < 0.001) existed for V̇O 2peak , where the rHuEPO group improved V̇O 2peak and peak aerobic power by 4.2% ± 6.1% ( P < 0.001) and 2.9% ± 4.0% ( P < 0.01), respectively. A time-treatment effect ( P < 0.001) existed for tHb, where the rHuEPO group increased tHb by 6.7% ± 3.4% ( P < 0.001). A main effect of "sex" alone was also evident ( P < 0.001), but no sex-specific interactions were found. No changes were observed in the placebo group for mean power output, V̇O 2peak , peak aerobic power, or tHb.

CONCLUSIONS

Microdoses with intravenous rHuEPO provide a sufficient erythropoietic stimuli to augment tHb and enhance aerobic-dominated performance in both trained males and females.

Does Hypoxia and Stress Erythropoiesis Compromise Cardiac Function in Healthy Adults? A Randomized Trial

OBJECTIVES

To investigate whether recombinant human erythropoietin (rHuEPO) injections during an altitude training camp impact heart function.

METHODS

Thirty (12 women) moderately trained subjects stayed at 2320 m altitude for 4 weeks while training. Subjects were randomized to placebo (isotonic saline) or rHuEPO (20 IU/kg body weight) i.v. injections. Transthoracic echocardiography imaging was acquired 3 days after arrival to altitude and prior to the first placebo or rHuEPO injection as well as one day after the last rHuEPO injection three weeks later.

RESULTS

rHuEPO did not alter cardiovascular morphology parameters, systolic or diastolic function. In the placebo group, altitude exposure improved left ventricle (LV) systolic function due to an increased twist angle but rHuEPO had no additional effects. Pulmonary arterial systolic pressure was unaffected in either group. Notably, rHuEPO hampered LV untwist rate without affecting LV early filling.

CONCLUSION

rHuEPO provided during mild altitude exposure does not cause any major effects on heart function. The observed alteration in LV untwist induced by rHuEPO is unlikely to have a meaningful clinical effect. Trial Registration Registered on www.

CLINICALTRIALS

gov (NCT04227665).

Tracking immature reticulocyte proteins for improved detection of recombinant human erythropoietin (rhEPO) abuse

Athletes abuse recombinant human erythropoietin (rhEPO) and erythropoiesis stimulating agents to increase hemoglobin mass and improve performance. To evade detection, athletes have developed sophisticated blood doping regimens, which often include rhEPO micro-dosing. Detection of these methods requires biomarkers with increased sensitivity and a sample matrix that is more amenable to frequent testing in the field. We have developed a method to measure two immature reticulocyte proteins, CD71 and ferrochelatase (FECH), and one total erythrocyte protein, Band 3, in dried blood spots (DBS). This method was tested in response to rhEPO administration after low doses, 40 IU/kg, micro-doses, 900 IU, or saline injection in 20 healthy subjects. During administration of low-dose rhEPO, the mean CD71/Band 3 and FECH/Band 3 ratio increased by 412 ± 197% and 250 ± 44%, respectively. The mean response for the current biomarker, RET%, increased by 195 ± 35%. During administration of rhEPO micro-doses, CD71/Band 3 increased to 127 ± 25% on day 35 and 139 ± 36% on day 39, while no increase was observed in RET%. After rhEPO administration, during the washout phase, mean values decreased to a minimum of 64 ± 4% and 64 ± 11% for CD71/Band 3 and RET%, respectively. However, CD71/Band 3 remained below 75% of baseline for at least 4 weeks after rhEPO injection, while RET% returned to baseline levels. The results demonstrate that immature reticulocyte proteins have a larger response to rhEPO administration than the current biomarker, RET%, and can be monitored in the DBS matrix.