Influence of prolonged physical exercise on the erythropoietin concentration in blood

Physical exercise improved the hematological effect of vitamin D in type 2 diabetes mellitus-induced nephrotoxicity in rats

Introduction

Globally, one of the major causes of renal dysfunction is diabetes mellitus (DM), and diabetic-induced nephrotoxicity has been linked with anemia. Presently, numerous antidiabetic drugs have been designed for the management of this disorder but they possess their undesirable effects such as anemia and acute kidney injury. Hence, we explore the use of vitamin D with or without exercise for the management of DM-induced renal dysfunction.

Methods

Thirty-six (36) Wistar rats were randomly separated into six (6) groups: control (vehicle treated), diabetes untreated (HFD + STZ), diabetes + vitamin D (HFD + STZ + vitamin D), diabetes + exercise (HFD + STZ + exercise), diabetes + vitamin D + exercise (HFD + STZ + vitamin D+ exercise), diabetes + metformin (HFD + STZ + metformin).

Results

Vitamin D with or without exercise significantly reduced T2DM-induced hyperglycemia. Also, a decrease in T2DM-induced increase in urea, creatinine, lactate dehydrogenase, lactate, cholesterol, and triglyceride and a rise in DM-associated reduction in high-density lipoprotein. These events were associated with a significant increase in red blood cells, hematocrit value, hemoglobin, erythropoietin, and a decrease in white blood cell count. Furthermore, vitamin D with or without exercise reversed T2DM-induced increase in pro-oxidant and pro-inflammatory markers. This observed oxido-inflammatory response was associated with a significant increase in xanthine oxidase activities and uric acid concentration. Interestingly, better recovery rates from DM-associated hematological imbalance were discovered in rats co-treated with vitamin D and exercise.

Conclusion

Our findings revealed that exercise enhanced the hematological effect of vitamin D in HFD + STZ-induced T2DM animals.

Ketone monoester plus high-dose glucose supplementation before exercise does not affect immediate post-exercise erythropoietin concentrations versus glucose alone

The objective of this study was to examine the effect of consuming ketone monoester plus a high dose of carbohydrate from glucose (KE + CHO) on the change in erythropoietin (EPO) concentrations during load carriage exercise compared with carbohydrate (CHO) alone. Using a randomized, crossover design, 12 males consumed KE + CHO (573 mg KE/kg body mass, 110 g glucose) or CHO (110 g glucose) 30 min before 4 miles of self-paced treadmill exercise (KE + CHO:51 ± 13%, CHO: 52 ± 12% V̇O2peak) wearing a weighted vest (30% body mass; 25 ± 3 kg). Blood samples for analysis were obtained under resting fasted conditions before (Baseline) consuming the KE + CHO or CHO supplement and immediately after exercise (Post). βHB increased (p < 0.05) from Baseline to Post in KE + CHO, with no change in CHO. Glucose and glycerol increased (p < 0.05) from Baseline to Post in CHO, with no effect of time in KE + CHO. Insulin and lactate increased (p < 0.05) from Baseline to Post independent of treatment. EPO increased (p < 0.05) from Baseline to Post in KE + CHO and CHO with no difference between treatments. Although KE + CHO altered βHB, glucose, and glycerol concentrations, results from this study suggest that KE + CHO supplementation before load carriage exercise does not enhance immediate post-exercise increases in EPO compared with CHO alone.

Hematological Adaptations to Post-Exercise Sauna Bathing With No Fluid Intake: A Randomized Cross-Over Study

Purpose: Sauna bathing is recommended to improve the sports training process, yet empirical evidence confirming its effectiveness is still inconclusive. We examined the effects of post-exercise sauna bathing on hematological adaptations and exercise capacity in healthy men. Methods: Thirteen physical education students participated in randomized cross-over study: two, 4-week interventions, with 10-week washout. The interventions involved 3 times per week 60-min stationary cycling either with 30-min of post-exercise sauna bathing (89 ± 3°C, 10 ± 2% RH) or without; no fluid was ingested during both exercise and sauna sessions. Before and after both interventions, participants were tested for total hemoglobin mass (tHb-mass), intravascular volumes, erythropoietin, ferritin, red blood cell parameters with reticulocyte fractions, along with maximal/peak and submaximal variables in a graded exercise test (GXT). Results: Regardless of intervention type, tHb-mass increased (p = .014) whereas ferritin concentration decreased (p = .027); however, changes in tHb-mass were within the range of typical error (<1.8%). Absolute and relative values of maximal power and power at gas exchange threshold, as well as peak oxygen uptake (all p < .010), also increased irrespective of intervention type. Conclusions: The use of post-exercise sauna bathing with fluid intake restrictions does not provide any additional benefits in tested variables over endurance training alone. Thus, further evidence is required before recommendations to utilize this post-exercise conditioning strategy are deemed valid.

Role of Distinct Fat Depots in Metabolic Regulation and Pathological Implications

People suffering from obesity and associated metabolic disorders including diabetes are increasing exponentially around the world. Adipose tissue (AT) distribution and alteration in their biochemical properties play a major role in the pathogenesis of these diseases. Emerging evidence suggests that AT heterogeneity and depot-specific physiological changes are vital in the development of insulin resistance in peripheral tissues like muscle and liver. Classically, AT depots are classified into white adipose tissue (WAT) and brown adipose tissue (BAT); WAT is the site of fatty acid storage, while BAT is a dedicated organ of metabolic heat production. The discovery of beige adipocyte clusters in WAT depots indicates AT heterogeneity has a more central role than hither to ascribed. Therefore, we have discussed in detail the current state of understanding on cellular and molecular origin of different AT depots and their relevance toward physiological metabolic homeostasis. A major focus is to highlight the correlation between altered WAT distribution in the body and metabolic pathogenesis in animal models and humans. We have also underscored the disparity in the molecular (including signaling) changes in various WAT tissues during diabetic pathogenesis. Exercise-mediated beneficial alteration in WAT physiology/distribution that protects against metabolic disorders is evolving. Here we have discussed the depot-specific biochemical adjustments induced by different forms of exercise. A detailed understanding of the molecular details of inter-organ crosstalk via substrate utilization/storage and signaling through chemokines provide strategies to target selected WAT depots to pharmacologically mimic the benefits of exercise countering metabolic diseases including diabetes.

The effects of normoxic endurance exercise on erythropoietin (EPO) production and the impact of selective β1 and non-selective β1 + β2 adrenergic receptor blockade

PURPOSE

Habitual endurance exercise results in increased erythropoiesis, which is primarily controlled by erythropoietin (EPO), yet studies demonstrating upregulation of EPO via a single bout of endurance exercise have been equivocal. This study compares the acute EPO response to 30 min of high versus 90 min of moderate-intensity endurance exercise and whether that response can be upregulated via selective adrenergic receptor blockade.

METHODS

Using a counterbalanced, cross-over design, fifteen participants (age 28 ± 8) completed two bouts of running (30-min, high intensity vs 90-min, moderate intensity) matched for overall training stress. A separate cohort of fourteen participants (age 31 ± 6) completed three bouts of 30-min high-intensity cycling after ingesting the preferential β₁-adrenergic receptor (AR) antagonist bisoprolol, the non-preferential β₁ + β₂ antagonist nadolol or placebo. Venous blood was collected before, during, and after exercise, and serum EPO levels were determined by ELISA.

RESULTS

No detectable EPO response was observed during or after high intensity running, however, in the moderate-intensity trial EPO was significantly elevated at both during-exercise timepoints (+ 6.8% ± 2.3% at 15 min and + 8.7% ± 2.2% at 60 min). No significant change in EPO was observed post-cycling or between the trials involving βAR blockade.

CONCLUSION

Neither training mode (running or cycling), nor beta-blockade significantly influenced the EPO response to 30 min of high-intensity exercise, however, 90 min of moderate-intensity running elevated EPO during exercise, returning to baseline immediately post-exercise. Identifying the optimal mode, duration and intensity required to evoke an EPO response to exercise may help tailor exercise prescriptions designed to maximize EPO response for both performance and clinical applications.

Marathon Run-induced Changes in the Erythropoietin-Erythroferrone-Hepcidin Axis are Iron Dependent

Alterations in iron metabolism after physical activity are manifested through the rise of blood hepcidin (Hpc) levels. However, in many athletes, no changes in Hpc levels are observed after exercise despite the presence of inflammation. The missing links could be erythropoietin (EPO) and erythroferrone (ERFE), which down-regulate Hpc biosynthesis. EPO, ERFE and Hpc biosynthesis is modified by serum iron through transferrin receptor 2. Consequently, we investigated whether marathon-induced changes in EPO, ERFE and Hpc levels are blood iron-dependent. Twenty-nine healthy male marathon runners were analyzed. Serum iron, ferritin, transferrin, EPO, ERFE and Hpc levels were assessed before, immediately after, and 9 ± 2 days after the marathon. The runners whose serum Hpc decreased after the marathon (n = 15), showed a significant increase in ERFE levels. In athletes whose serum iron levels were below 105 µg/day (n = 15), serum EPO (p = 0.00) and ERFE levels (p = 0.00) increased with no changes in Hpc concentration. However, in athletes with low serum iron, no changes in EPO levels were observed when serum ferritin exceeded 70 ng/mL (n = 7). Conversely, an increase in ERFE levels was observed in marathoners with low serum iron, independently of serum ferritin (n = 7). This indicates modulation of blood iron may affect exercise-induced changes in the EPO/ERFE/Hpc axis. Further study is needed to fully understand the physiological meaning of the interdependence between iron and the EPO/ERFE/Hpc axis.

Reduction of hemoglobin, not iron, inhibited maturation of red blood cells in male rats exposed to high intensity endurance exercises

The existence of sports anemia, induced by strenuous or long-term exercise and characterized by decreases of red blood cells (RBCs), hemoglobin and iron content, remains to be doubtful. To observe the effects of endurance exercise on RBCs and explain the underlying reason, we designed this study by observing RBCs parameters and iron metabolism in 8-weeks training rats and effects of iron supplement or protein supplement on RBCs. Results showed that erythrocyte counts, hematocrit, mean corpuscular volume and hemoglobin content decreased while RBC distribution width increased in exercised rats at later stage during 8 weeks training. But the contents of serum iron and ferritin decreased only at 1-week and 2-week and returned to normal at 4-week and 8-week. Same as iron content, apparent iron absorption rate was declined at early stage but restored to normal level at 8-week, as well as serum adrenaline, cortisol and insulin levels. Instead, the contents of total protein and albumin in serum were decreased at later stage during 8-weeks training. Furthermore, we observed that protein supplement ameliorated RBCs parameters in rats exposed to 8 weeks swimming exercise, but iron supplement had no effects on RBCs, though it obviously increased iron content of serum and the liver. Based on these results, we drew a conclusion that transient changes of iron metabolism, which may be induced by stress hormone changes, was not the reason for RBCs decrease in endurance exercises but hemoglobin reduction, induced by defects in protein supplement, impeded development of RBCs.

Interrelationships between changes in erythropoietin, plasma volume, haemoglobin concentration, and total haemoglobin mass in endurance athletes

Interrelationships between physiological changes (Δ) in erythropoietin (EPO), plasma volume (PV), haemoglobin concentration ([Hb]), and total haemoglobin mass (tHb-mass) were examined in cyclists who trained in different altitudes. Regardless of differences in pattern of changes observed in three training locations, ΔEPO was correlated positively with ΔPV, negatively with Δ[Hb], and trivially with ΔtHb-mass. Δ[Hb] was negatively correlated with ΔPV. In the pooled data the Spearman's rank correlation coefficients were as follows: r = 0.783, P < 0.001; r = -0.704, P < 0.001; r = 0.136, P > 0.05; r = -0.813, P < 0.001, respectively. The obtained results have shown that EPO does not only regulate [Hb] by erythropoiesis stimulation but also by PV modulation, which probably aims at keeping proper level of arterial oxygen content for oxygen delivery to tissues.

Comprehensive overview of hemoglobin mass and blood volume in elite athletes across a wide range of different sporting disciplines

BACKGROUND

The aim of the study was to compare total hemoglobin mass (tHb-mass) and blood volume (BV) across elite athletes with different sporting specializations.

METHODS

The study enrolled 222 members of Russian national teams from 12 different sporting disciplines and non-Olympic sports. The athletes were tested in the middle of a competitive season for tHb-mass, BV, plasma volume (PV), hemoglobin concentration (Hb), and hematocrit level (Hct) determination. tHb-mass measurements were performed using CO- rebreathing technique, alongside Hb and Hct (capillary blood).

RESULTS

In elite endurance athletes both male and female values for tHb-mass, BV and PV, were significantly higher compared to anaerobic, technical sports and untrained subjects. The highest values of relative tHb-mass across all 15 groups were found in cross-country skiers (15.1±0.1 g/kg) and cyclists (15.0±0.5 g/kg). In the anaerobic group the highest value of tHb-mass was within the short-track group - i.e. 12.9±0.5 g/kg which was significantly lower than in cycling. In all aerobic groups, anaerobic and breath-hold divers we found significant difference in relative tHb-mass compared to untrained subjects. The difference between relative tHb-mass in the cycling group and untrained subjects was 31.3%, 17% for short track, 30.1% for handball and 33.5% for motor sport. For the largest group (biathlon) we performed correlation analysis for males and females with competitive performance and found relationship in both groups (P<0.05).

CONCLUSIONS

The study clearly demonstrates the difference between endurance and non-endurance athletes in tHb-mass for elite males and females athletes and its importance in competitive aerobic performance.

Biology of VO2 max: looking under the physiology lamp

In this review, we argue that several key features of maximal oxygen uptake (VO₂ max) should underpin discussions about the biological and reductionist determinants of its interindividual variability: (i) training-induced increases in VO₂ max are largely facilitated by expansion of red blood cell volume and an associated improvement in stroke volume, which also adapts independent of changes in red blood cell volume. These general concepts are also informed by cross-sectional studies in athletes that have very high values for VO₂ max. Therefore, (ii) variations in VO₂ max improvements with exercise training are also likely related to variations in these physiological determinants. (iii) All previously untrained individuals will respond to endurance exercise training in terms of improvements in VO₂ max provided the stimulus exceeds a certain volume and/or intensity. Thus, genetic analysis and/or reductionist studies performed to understand or predict such variations might focus specifically on DNA variants or other molecular phenomena of relevance to these physiological pathways.

Erythropoiesis with endurance training: dynamics and mechanisms

The purpose of the present study was to characterize the progression of red blood cell volume (RBCV) expansion and potential volumetric and endocrine regulators of erythropoiesis during endurance training (ET). Nine healthy, untrained volunteers (age = 27 ± 4 yr) underwent supervised ET consisting of 3–4 × 60 min cycle ergometry sessions per week for 8 wk. Plasma volume (PV), RBCV, and overnight fasting hematological markers were determined before and at weeks 2, 4, and 8 of ET. In addition, plasma erythropoietin (EPO), cortisol, copeptin, and proatrial natriuretic peptide concentrations were measured during a 3-h morning period at baseline and postexercise at weeks 1 and 8. PV increased from baseline (2,405 ± 335 ml) at weeks 2, 4, and 8 (+374 ± 194, +505 ± 156, and +341 ± 160 ml, respectively, P < 0.001). Increases in RBCV from baseline (1,737 ± 442 ml) were manifested at week 4 (+109 ± 114 ml, P = 0.030) and week 8 (+205 ± 109 ml, P = 0.001). Overnight fasting plasma EPO concentration increased from baseline (11.3 ± 4.8 mIU/ml) at week 2 (+2.5 ± 2.8 mIU·ml−1, P = 0.027) and returned to baseline concentration at weeks 4 and 8. Higher 3-h-postexercise EPO concentration was observed at week 1 (11.6 mIU/ml) compared with week 8 (8.4 ± 3.9 mIU/ml, P = 0.009) and baseline (9.0 ± 4.2 mIU/ml, P = 0.019). Linear relationships between EPO concentration and hematocrit (β = −56.2, P < 0.001) and cortisol (β = 0.037, P < 0.001) were detected throughout the ET intervention. In conclusion, ET leads to mild, transient increases in circulating EPO concentration, concurring with early PV expansion and lowered hematocrit, preceding gradual RBCV enhancement.

Haematological rather than skeletal muscle adaptations contribute to the increase in peak oxygen uptake induced by moderate endurance training

It remains unclear whether improvements in peak oxygen uptake (V̇(O2peak)) following endurance training (ET) are primarily determined by central and/or peripheral adaptations. Herein, we tested the hypothesis that the improvement in V̇(O2peak) following 6 weeks of ET is mainly determined by haematological rather than skeletal muscle adaptations. Sixteen untrained healthy male volunteers (age = 25 ± 4 years, V̇(O2peak) = 3.5 ± 0.5 l min(-1)) underwent supervised ET (6 weeks, 3-4 sessions per week). V̇(O2peak), peak cardiac output (Q̇(peak)), haemoglobin mass (Hb(mass)) and blood volumes were assessed prior to and following ET. Skeletal muscle biopsies were analysed for mitochondrial volume density (Mito(VD)), capillarity, fibre types and respiratory capacity (OXPHOS). After the post-ET assessment, red blood cell volume (RBCV) was re-established at the pre-ET level by phlebotomy and V̇(O2peak) and Q̇(peak) were measured again. We speculated that the contribution of skeletal muscle adaptations to the ET-induced increase in V̇(O2peak) would be revealed when controlling for haematological adaptations. V̇(O2peak) and Q̇(peak) were increased (P < 0.05) following ET (9 ± 8 and 7 ± 6%, respectively) and decreased (P < 0.05) after phlebotomy (-7 ± 7 and -10 ± 7%). RBCV, plasma volume and Hb(mass) all increased (P < 0.05) after ET (8 ± 4, 4 ± 6 and 6 ± 5%). As for skeletal muscle adaptations, capillary-to-fibre ratio and total Mito(VD) increased (P < 0.05) following ET (18 ± 16 and 43 ± 30%), but OXPHOS remained unaltered. Through stepwise multiple regression analysis, Q̇(peak), RBCV and Hb(mass) were found to be independent predictors of V̇(O2peak). In conclusion, the improvement in V̇(O2peak) following 6 weeks of ET is primarily attributed to increases in Q̇(peak) and oxygen-carrying capacity of blood in untrained healthy young subjects.

Assessment of hematological profiles of adult male athletes from two different air pollutant zones of West Bengal, India

Health effects from air pollution are severe concern of today's world. The study was undertaken to assess the effects of air pollution on hematological profiles of trained and untrained males of West Bengal. The sample consisted of 60 sprinters, 60 footballers, and 120 untrained males, subdivided into two groups from two zones, namely, Tollygunge and Sonarpur. Suspended particulate matter (SPM), respirable particulate matter (RPM), oxides of sulfur (SOx), and oxides of nitrogen (NOx) of ambient air were monitored for both zones. Height and weight of all the subjects were measured. Venous blood sample was drawn from the cubital vein, and the red blood cell count (TC), packed cell volume (PCV), hemoglobin (Hb) concentration, mean corpuscular volume (MCV), and mean corpuscular hemoglobin concentration (MCHC) were determined by standard methods. Results revealed that SPM, RPM, SOx, and NOx concentrations were significantly higher in the Tollygunge area than Sonarpur. TC, PCV, and Hb concentration of untrained males were significantly higher than footballers in both regions but no significant difference were observed when compared with sprinters, except the Hb concentration in the Tollygunge zone. On the other hand, all hematological parameters of both trained and untrained males were significantly higher in the Sonarpur area than Tollygunge. It was concluded that environmental air pollutants might influence hematological profile adversely both in trained and sedentary males. However, further investigation in this area is needed.

Cluster of erythrocyte band 3: a potential molecular target of exhaustive exercise-induced dysfunction of erythrocyte deformability

The aim of this study is to explore the effect of exhaustive exercise on erythrocyte band 3 (SLC4A1; EB3). The association between the alterations of EB3 and red blood cell (RBC) deformability induced by exercise-induced dysfunction has been investigated. Rats were divided among 2 groups: (i) control (C), and (ii) exercise exhausted (E). RBC deformability was investigated in the rats in the exhaustive exercise and control groups. Erythrocytes from the control and exercise-exhausted groups were evaluated for the expression of erythrocyte band 3 through immunoblotting and immunofluorescence studies. Exhaustive exercise led to significant increments in the levels of clustering of erythrocyte band 3 along with the conjugation of membrane proteins to form high-molecular-weight complexes (P < 0.05). Under shear stresses, RBC deformability was found to decline significantly in the exhaustive exercise groups compared with the control group. These data suggest that the RBC dysfunction observed during exercise-induced oxidative stress could be associated with alterations in the structure and function of erythrocyte band 3, which in turn leads to dysfunction in the rheological properties of RBCs. These results provide further insight into erythrocyte damage induced by exhaustive exercise.

Acute normobaric hyperoxia transiently attenuates plasma erythropoietin concentration in healthy males: evidence against the 'normobaric oxygen paradox' theory

AIM

The purpose of the present study was to evaluate the 'normobaric oxygen paradox' theory by investigating the effect of a 2-h normobaric O(2) exposure on the concentration of plasma erythropoietin (EPO).

METHODS

Ten healthy males were studied twice in a single-blinded counterbalanced crossover study protocol. On one occasion they breathed air (NOR) and on the other 100% normobaric O(2) (HYPER). Blood samples were collected Pre, Mid and Post exposure; and thereafter, 3, 5, 8, 24, 32, 48, 72 and 96 h, and 1 and 2 weeks after the exposure to determine EPO concentration.

RESULTS

The concentration of plasma erythropoietin increased markedly 8 and 32 h after the NOR exposure (approx. 58% and approx. 52%, respectively, P ≤ 0.05) as a consequence of its natural diurnal variation. Conversely, the O(2) breathing was followed by approx. 36% decrement of EPO 3 h after the exposure (P ≤ 0.05). Moreover, EPO concentration was significantly lower in HYPER than in the NOR condition 3, 5 and 8 h after the breathing intervention (P ≤ 0.05).

CONCLUSION

In contrast to the 'normobaric oxygen paradox' theory, the present results indicate that a short period of normobaric O(2) breathing does not increase the EPO concentration in aerobically fit healthy males. Increased O(2) tension suppresses the EPO concentration 3 and 5 h after the exposure; thereafter EPO seems to change in a manner consistent with natural diurnal variation.

Erythropoietin promotes deleterious cardiovascular effects and mortality risk in a rat model of chronic sports doping

Athletes who abuse recombinant human erythropoietin (rhEPO) consider only the benefit to performance and usually ignore the potential short and long-term liabilities. Elevated haematocrit and dehydratation associated with intense exercise may reveal undetected cardiovascular risk, but the mechanisms underlying it remain to be fully explained. This study aimed to evaluate the cardiovascular effects of rhEPO in rats under chronic aerobic exercise. A ten week protocol was performed in four male Wistar rat groups: control--sedentary; rhEPO--50 IU kg(-1), 3 times/wk; exercised (EX)--swimming for 1 h, 3 times/wk; EX + rhEPO. One rat of the EX + rhEPO group suffered a sudden death episode during the week 8. rhEPO in trained rats promoted erythrocyte count increase, hypertension, heart hypertrophy, sympathetic and serotonergic overactivation. The suddenly died rat's tissues presented brain with vascular congestion; left ventricular hypertrophy, together with a "cardiac-liver", suggesting the hypothesis of heart failure as cause of sudden death. In conclusion, rhEPO doping in rats under chronic exercise promotes not only the expected RBC count increment, suggesting hyperviscosity, but also other serious deleterious cardiovascular and thromboembolic modifications, including mortality risk, which might be known and assumed by all sports authorities, including athletes and their physicians.

Activation of the erythropoietin receptor in human skeletal muscle

OBJECTIVE

Erythropoietin receptor (EPOR) expression in non-hematological tissues has been shown to be activated by locally produced and/or systemically delivered EPO. Improved oxygen homeostasis, a well-established consequence of EPOR activation, is very important for human skeletal muscle performance. In the present study we investigate whether human skeletal muscle fibers and satellite cells express EPOR and if it is activated by exercise.

DESIGN AND METHODS

Ten healthy males performed 65 min of cycle exercise. Biopsies were obtained from the vastus lateralis muscle and femoral arterio-venous differences in EPO concentrations were estimated.

RESULTS

The EPOR protein was localized in areas corresponding to the sarcolemma and capillaries. Laser dissection identified EPOR mRNA expression in muscle fibers. Also, EPOR mRNA and protein were both detected in human skeletal muscle satellite cells. In the initial part of the exercise bout there was a release of EPO from the exercising leg to the circulation, possibly corresponding to an increased bioavailability of EPO. After exercise, EPOR mRNA and EPOR-associated JAK2 phosphorylation were increased.

CONCLUSIONS

Interaction with JAK2 is required for EPOR signaling and the increase found in phosphorylation is therefore closely linked to the activation of EPOR. The receptor activation by acute exercise suggests that signaling through EPOR is involved in exercise-induced skeletal muscle adaptation, thus extending the biological role of EPO into the skeletal muscle.

Effects of various training modalities on blood volume

It is controversially discussed whether soccer games should be played at moderate (2001-3000 m) and high altitudes (3001-5500 m) or should be restricted to near sea level and low altitude (501-2000 m) conditions. Athletes living at altitude are assumed to have a performance advantage compared with lowlanders. One advantage of altitude adaptation concerns the expansion of total hemoglobin mass (tHb-mass), which is strongly related to endurance performance at sea level. Cross-sectional studies show that elite athletes posses approximately 35% higher tHb-mass than the normal population, which is further elevated by 14% in athletes native to altitude of 2600 m. Although the impact of this huge tHb-mass expansion on performance is not yet investigated for altitude conditions, lowland athletes seek for possibilities to increase tHb-mass to similar levels. At sea level tHb-mass is only moderately influenced by training and depends more on genetic predisposition. Altitude training in contrast, using either the conventional altitude training or the live high-train low (>14 h/day in hypoxia) protocol for 3-4 weeks above 2500 m leads to mean increases in tHb-mass of 6.5%. This increase is, however, not sufficient to close the gap in tHb-mass to elite athletes native to altitude, which may be in advantage when tHb-mass has the same strong influence on aerobic performance at altitude as it has on sea level.

Drugs in sport: a scientist-athlete's perspective: from ambition to neurochemistry

This article, by the United Kingdom's last Olympic Marathon Medal winner, Charlie Spedding, and his brother, the pharmacologist, Michael Spedding, covers the difficulties posed by the availability of powerful drugs to ameliorate athletic performance, from an athlete's perspective, particularly in view of the fact that performances are becoming highly optimised with less margin for further physiological improvement. The authors have had long athletic careers and argue that doping not only devalues performance but sport, and exercise, as a whole. Furthermore, the neurotrophic and metabolic changes involved in exercise and training, which can be modified by drugs, are central to health and reflect a part of the epidemic in obesity.

Erythropoietin regulations in humans under different environmental and experimental conditions

In the adult human, the kidney is the main organ for the production and release of erythropoietin (EPO). EPO is stimulating erythropoiesis by increasing the proliferation, differentiation and maturation of the erythroid precursors. In the last decades, enormous efforts were made in the purification, molecular encoding and description of the EPO gene. This led to an incredible increase in the understanding of the EPO-feedback-regulation loop at a molecular level, especially the oxygen-dependent EPO gene expression, a key function in the regulation loop. However, studies in humans at a systemic level are still very scanty. Therefore, it is the purpose of the present review to report on the main recent investigations on EPO production and release in humans under different environmental and experimental conditions, including: (i) studies on EPO circadian, monthly and even annual variations, (ii) studies in connection with short-, medium- and long-term exercise at sea-level which will be followed (iii) by studies performed at moderate and high altitude.

Changes in erythropoiesis, iron metabolism and oxidative stress after half-marathon

OBJECTIVE

In marathon runners changes in red blood cell count, haematocrit and haemoglobin in relation to haemodilution have been reported. Moreover, it has been hypothesized that strenuous exercise induces oxidant stress through several different mechanisms. This study investigated the haematological variables, iron status and oxidative indices before, immediately and 48 h after a race in 8 healthy trained males aged 33-44 years running a 21-km marathon in 79 +/- 3 min.

METHODS

The haematological parameters were determined by standard procedures. Erythropoietin and soluble-transferrin receptor were evaluated immunoenzymatically. Nontransferrin-bound iron (NTBI) was assayed by high-performance liquid chromatography after nitrilotriacetic acid chelation. Malonyldialdehyde (MDA) concentration was assayed colorimetrically.

RESULTS

The total number of reticulocytes rose significantly after the run with a significant increase in the high-RNA-content fraction (14 +/- 5, p < 0.0006). Erythropoietin rose by 26% (15.0 +/- 2.8 mU/ml, p < 0.004) and by 25% (14.9 +/- 2.13 mU/ml, p < 0.02) immediately and 48 h after the race, respectively. Serum iron and serum ferritin remained unchanged but NTBI and serum MDA increased significantly immediately after running (1.16 +/- 0.40 mmol/l, p < 0.0008; 0.76 +/- 0.16 mmol/l, p < 0.0001). Significant positive correlations at any time between MDA and polymorphonuclear neutrophils (p = 0.0005), MDA and NTBI (p = 0.0018), polymorphonuclear neutrophils and NTBI (p = 0.0008) and between lactate dehydrogenase and NTBI (p = 0.0212) were observed.

CONCLUSIONS

The erythropoietic changes observed in marathon runners are the results of several interacting mechanisms that involve either the haemopoietic system per se or erythrocyte haemolysis and oxidative stress.

Erythropoietin and renin as biological markers in critically ill patients

Introduction

During sepsis the endocrine, immune and nervous systems elaborate a multitude of biological responses. Little is known regarding the mechanisms responsible for the final circulating erythropoietin (EPO) and renin levels in septic shock. The aim of the present study was to assess the role of EPO and renin as biological markers in patients with septic shock.

Methods

A total of 44 critically ill patients with septic shock were evaluated.

Results

Nonsurvivors had significantly higher serum EPO levels than did survivors on admission (median [minimum–maximum]; 61 [10–602] versus 20 [5–369]). A negative relationship between serum EPO and blood haemoglobin concentrations was observed in the survivor group (r = -0.61; P < 0.001). In contrast, in the nonsurvivors the serum EPO concentration was independent of the blood haemoglobin concentration. Furthermore, we observed significant relationships between EPO concentration and lactate (r = 0.5; P < 0.001), arterial oxygen tension/fractional inspired oxygen ratio (r = -0.41; P < 0.005), arterial pH (r = -0.58; P < 0.001) and renin concentration (r = 0.42; P < 0.005). With regard to renin concentration, significant correlations with lactate (r = 0.52; P < 0.001) and arterial pH (r = -0.33; P < 0.05) were observed.

Conclusion

Our findings show that EPO and renin concentrations increased in patients admitted to the intensive care unit with septic shock. Renin may be a significant mediator of EPO upregulation in patients with septic shock. Further studies regarding the regulation of EPO expression are clearly warranted.

Erythropoietin

This article summarizes recent advances in understanding the production and action of the hormone erythropoietin (Epo) with respect to high altitude physiology and sports medicine. Hypoxia is the main stimulus for Epo gene expression. An O2-labile protein (hypoxia-inducible factor 1, HIF-1) has been identified that is hydroxylated and degraded under normoxic conditions but active in hypoxia, where it enhances Epo gene transcription resulting in elevated hemoglobin levels and O2 capacity of the blood. The stimulation of Epo production at lowered arterial O2 tension can be maladaptive, if erythrocytosis develops such as seen in high altitude habitants. Within physiological limits the aerobic power increases in parallel with blood O2 capacity. Therefore, some elite athletes have misused recombinant human Epo (rhEpo), which is a beneficial anti-anemic drug in clinical practice. Indirect and direct methods to detect rhEpo doping have been recently developed.

Pharmacokinetics/pharmacodynamics of recombinant human erythropoietins in doping control

The purpose of this paper is: (i) to compare recombinant human erythropoietin (rHuEPO) pharmacokinetics in athletes and healthy individuals; and (ii) to report pharmacokinetic/pharmacodynamic (PK/PD) studies performed in athletes. Effect parameters in PK/PD studies included: (i) red blood cell variables (haematocrit, reticulocyte count); and (ii) markers of iron metabolism (serum soluble transferrin receptors [sTfR], ferritin [fr] and sTfR : fr ratio). To understand the choice of these markers, we first performed a brief review of the pharmacological effects of rHuEPO. Few studies have been conducted in healthy individuals and there are minimal references concerning pharmacokinetics in athletes. A 'flip-flop' phenomenon was noted after subcutaneous administration. The pharmacokinetics appeared linear from 50-1000 U/kg, but this linearity was not observed at the lowest dose of 10 U/kg. A negative-feedback loop of endogenous erythropoietin production occurred at the end of treatment. The half-life of the terminal part of the curves seemed to be slightly higher in athletes (36-42 vs 32 hours) than in untrained individuals and total clearance tended to be greater (17.5 vs 6.5 mL/h/kg). In conclusion, more investigations are needed to better understand the relationship between rHuEPO administration and changes in haematological and iron-metabolism parameters in athletes, particularly after chronic low-dose administration of rHuEPO.

Red blood cell variables in highly trained pubescent athletes: a comparative analysis

BACKGROUND

A suboptimal haematological status has often been recorded in athletes involved in intensive physical activity. There have even been reports of "sports anaemia" associated with intensive physical exercise. However, studies on the effect of different types of exercise practiced over a long period of time on the red blood cell variables in pubescent athletes are very few.

AIM

To assess the basic red blood cell variables in highly trained pubescent athletes from different sports and to compare the results with those for a control untrained group. Sex related differences in these variables were also assessed.

METHODS

876 highly trained athletes (559 boys and 317 girls) were included in the study. Their mean (SEM) age, weight, and duration of training were: 14.01 (0.06) years, 56.24 (0.52) kg, and 3.52 (0.07) years respectively. The control group consisted of 357 untrained subjects (171 boys and 186 girls) with mean (SEM) age and weight of 14.58 (0.09) years and 57.75 (0.67) kg. The group of athletes was divided into seven subgroups according to the sport practiced: athletics (105), swimming (107), rowing (230), wrestling (225), weight lifting (47), various team sports (92), and other sports (67). Venous blood samples were drawn from the cubital vein, and the red blood cell count, packed cell volume, haemoglobin concentration, and mean corpuscular volume were measured. Statistical indices were computed for each group and for each variable, and analysis of variance factorial analysis was performed to evaluate the statistical significance of the differences detected.

RESULTS

The highly trained group was found to have lower red blood cell count, packed cell volume, and haemoglobin concentration (p<0.001) than the control untrained group (4.61 (0.01) x 10(12)/l v 4.75 (0.02) x 10(12)/l, 0.389 (0.001) v 0.404 (0.002) l/l, and 133.01 (0.38) v 139.9 (0.62) g/l respectively). These variables were lower for the boys of the trained group than for the boys of the control group (p<0.001), and similarly for the girls (p<0.001). The lowest red blood cell count, packed cell volume, and haemoglobin concentration were measured in blood samples from the boys of the swimming subgroup (4.54 (0.06) x 10(12)/l, 0.386 (0.006) l/l, and 129.38 (1.80) g/l respectively) and the rowing subgroup (4.66 (0.03) x 10(12)/l, 0.400 (0.003) l/l, and 136.21 (0.94) respectively). The same distribution was found for the girls: lowest in the rowing subgroup (4.32 (0.04) x 10(12)/l, 0.314 (0.003) l/l, and 124.27 (0.93) g/l) and the swimming subgroup (4.40 (0.05) x 10(12)/l, 0.375 (0.005) l/l, and 125.90 (1.30) g/l). No differences were found in the mean corpuscular volume.

CONCLUSIONS

Continuous (more than one year) high intensity sports training (twice a day/five days a week) results in a decrease in the basic red blood cell variables in pubescent boys and girls, this being most pronounced in the submaximal sports.

Increase in immune activation, vascular endothelial growth factor and erythropoietin after an ultramarathon run at moderate altitude

The present study was performed to investigate the effects of exhaustive long lasting exercise at moderate altitude on the time course of serum immunomodulatory peptides, vascular endothelial growth factor (VEGF) and serum erythropoietin (EPO). Thirteen well trained runners participated at the Swiss Alpine Marathon of Davos (distance 67 km, altitude difference 2300 m). Interleukin-6 was significantly elevated in the first 2h after the run. In contrast, tumor necrosis factor-alpha and both soluble tumor necrosis factor-a receptors I and II were increased after exercise termination and showed sustained serum concentrations the following days. Neopterin, a serum marker for the activation of the cellular immune system, was increased until day two after the run. Immediately after the run VEGF was significantly elevated and further increased 2.4-fold until day five post exercise (p = 0.005). EPO was also increased after exercise but reached its maximum 2 h after the run (2-fold increase; p = 0.004) and decreased thereafter. The main findings of our study are that prolonged strenuous exercise at moderate altitude induced a significant long lasting increase in serum VEGF and EPO which was accompanied by an activation of the immune system.

Erythropoietin concentration and arterial haemoglobin saturation with supramaximal exercise

The aim of this study was to determine if the hypoxaemic stimulus generated by intense exercise results in the physiological response of increased erythropoietin production. Twenty athletes exercised for 3 min at 109 +/- 2.8% (mean +/- s) maximal oxygen consumption. Estimated oxyhaemoglobin saturation was measured by reflective probe pulse oximetry (Nellcor N200) and was validated against arterial oxyhaemoglobin saturation by CO-oximetry in eight athletes. Serum erythropoietin concentrations-as measured using the INCSTAR Epo-Trac radioimmunoassay-increased significantly by 28 +/- 9% at 24 h post-exercise in 11 participants, who also had an arterial oxyhaemoglobin saturation < or = 91% (P < 0.05). Decreased ferritin levels and increased reticulocyte counts were observed at 96 h post-exercise. However, no significant changes in erythropoietin levels were observed in nine non-desaturating athletes and eight non-exercise controls. Good agreement was shown between arterial oxyhaemoglobin saturation and percent estimated oxyhaemoglobin saturation (limits of agreement = -3.9 to 3.7%). In conclusion, short supramaximal exercise can induce both hypoxaemia and increased erythropoietin levels in well-trained individuals. The decline of arterial hypoxaemia levels below 91% during exercise appears to be necessary for the exercise-induced elevation of serum erythropoietin levels. Furthermore, reflective probe pulse oximetry was found to be a valid predictor of percent arterial oxyhaemoglobin saturation during supramaximal exercise when percent estimated oxyhaemoglobin saturation > or = 86%.

Effects of acute exercise on plasma erythropoietin levels in trained runners

PURPOSE

The purpose of this study was to investigate further the influence of exercise on erythropoietin.

METHODS

We observed the effects of high intensity running on plasma erythropoietin concentration in competitive distance runners. A repeated measures design was used to compare the responses of intermittent high intensity (HIGH) exercise to continuous moderate intensity (MOD) exercise and rest (REST). The HIGH treatment consisted of 60 min of exercise alternating 5 min of running at approximately 90% of VO2max with 5 min of brisk walking. The MOD treatment consisted of a continuous 60-min run on the treadmill at 60% of VO2max. Blood samples were collected immediately before the exercise (PRE), immediately following the exercise (POST), and 4 (heart rate (4HR), 12 (12HR), 24 (24HR), and 48 (48HR)) h following the exercise. The variables examined included plasma erythropoietin concentration ([EPO]), hemoglobin (Hb) concentration ([Hb]), hematocrit (Hct), red blood cell count (RBC), and mean corpuscular volume (MCV).

RESULTS

ANOVA revealed the expected treatment-by-time interaction for Hct and [Hb] suggesting a hemodilution at 24 and 48 h postexercise for the MOD and HIGH treatments. However, no significant treatment-by-time interactions were observed for [EPO], RBC, or MCV.

CONCLUSION

These results indicate that intermittent high intensity exercise does not have a significant effect on [EPO] in trained distance runners.

Preanalytical factors and the measurement of cytokines in human subjects

Cytokines are widely measured in research. However, cytokine analyses are influenced by a myriad of factors. For instance, a delay in the separation of plasma from cells may lead to a 50% decrease in the concentration of tumor necrosis factor in plasma. Another example is the secretion of interleukin-1 beta in women which can be twice as high during the follicular phase as in the luteal phase. The factors influencing the outcome of these tests can be divided into in vivo preanalytical factors (e.g., aging, chronobiological rhythms, diet, etc), in vitro preanalytical factors (e.g., specimen collection, equipment, transport, storage, etc), and analytical factors. To improve the value of the cytokine tests, factors strongly influencing the results have to be controlled. This can be done by using standardized assays and specimen collection procedures. In general, sufficient attention is not given to the preanalytical factors, especially in the measurement of cytokines. This article reviews the preanalytical factors which may influence the outcome of these tests in human subjects.

Erythropoietin in 29 men during and after prolonged physical stress combined with food and fluid deprivation

The study investigated the influence of prolonged physical stress during survival training with food and fluid deprivation on the serum concentrations of erythropoietin (EPO). A group of 29 male subjects [mean age 22.2 (SD 2.8) years, height 1.78 (SD 0.06) m, and body mass (m(b)) 73.5 (SD 8.6) kg] were studied for 5 days of multifactorial stress including restricted water intake (11 H2O. day(-1)) and food intake (628 kJ. day(-1)) combined with physical exercise (estimated energy expenditure approximately 24000 kJ.day(-1)) and sleep deprivation (20 h within 5 days). Blood samples were taken before (T1), after 72 h (T2) and 120 h (T3) of physical stress, and after 48 h, (T4) and 72 h (T5) of recovery. The samples were analysed for EPO, and concentrations of serum iron (Fe), haptoglobin (Hapto), transferrin (Trans), ferritin (Fer), haemoglobin (Hb) and packed cell volume (PCV). The m(b) had decreased by 6.77 kg at T3 (P <0.01) and 0.68 kg at T5. The EPO and Hapto decreased during the survival training (P <0.01) and increased during the recovery period (P <0.01). The Fe increased during the survival training (P <0.01) and remained above the control concentrations during recovery (P <0.01). The Hapto decreased during the survival training (P <0.01) and remained below control concentration at T4 and T5 (P <0.01). The Trans decreased continuously over the week (P <0.01). The Fer increased during the survival training (P <0.01) and returned to control concentration at T5. The Hb increased from T1 to T2 (P <0.01) and had decreased significantly at T5 (P <0.01). The PCV increased from T1 to T2 (P <0.01) and remained below control levels afterwards (P <0.01). From our study it was concluded that, in humans, prolonged physical stress with food and fluid deprivation induces a marked EPO decrease, which is followed by a rapid increase during recovery to restore the reduced O2 transport capacity.

Application of a modified INCSTAR Epo-trac 125/RIA for measurement of serum erythropoietin concentration in elite athletes

OBJECTIVES

To evaluate the analytical performance of a radioimmunoassay for measurement of erythropoietin.

DESIGN AND METHODS

The INCSTAR Epo-trac 125I radioimmunoassay was examined for applications requiring sensitivity and precision within the normal range.

RESULTS

Sensitivity was improved by increasing sample volume to 300 microL. Minimal detectable concentration was determined at 5.3 U/L, %CV ranged from 4.8-5.8 and 13.3-6.4 for intra- and inter-assay imprecision, respectively. Accuracy was maximized by controlling for lipemic and hemolyzed samples and ensuring serum was separated from the clot within 1 h of collection. Values demonstrated good correlation to the Diagnostic Systems Laboratory RIA-kit.

CONCLUSIONS

With sample volume increased to 300 microL and control of sample preparation, the INCSTAR Epo-trac 125/RIA showed improved precision. Assay sensitivity at lower values allows resolution of changes in erythropoietin within the normal reference range. Age was not found to influence erythropoietin concentration. Within 10 days sojourn at moderate altitude an increase in circulating erythropoietin and reticulocytosis was observed in swimmers.

An early effect of acute plasma volume expansion in humans on serum erythropoietin concentration

The effect of acute plasma volume change in humans on serum erythropoietin [EPO]s, plasma active renin [REN] and plasma aldosterone [ALDO] concentrations was examined. Plasma volume (PV) expansion was induced by intravenous infusion of 150 ml (30g) of plasma albumin and 500 ml of physiological saline. The [EPO]s decreased by 14.3% (corrected values for PV expansion) and remained decreased for 5 h. The [REN] was decreased by more than 25% during the day of the experiment and [ALDO] by more than 60%. Only a weak positive correlation was found between [EPO]s and [REN] (r = 0.35; P < 0.05) but a lack of correlation between changes in PV and [EPO]s as well as between [EPO]s and [ALDO] was seen. We postulated that in healthy men an acute PV expansion by 10% to 17.5% would not appear to promote stimulation of EPO synthesis for at least 11 h. Since a weak positive correlation was observed between [EPO]s and [REN] and a lack of correlation between [EPO]s and [ALDO], it would seem that there is no direct link between [REN] and [ALDO] and erythropoietin synthesis in healthy subjects.

Hypoxia and training-induced adaptation of hormonal responses to exercise in humans

To establish whether or not hypoxia influences the training-induced adaptation of hormonal responses to exercise, 21 healthy, untrained subjects (2) years, mean (SE)] were studied in three groups before and after 5 weeks' training (cycle ergometer, 45 min.day-1, 5 days.week-1). Group 1 trained at sea level at 70% maximal oxygen uptake (VO2max), group 2 in a hypobaric chamber at a simulated altitude of 2500 m at 70% of altitude VO2max, and group 3 at a simulated altitude of 2500 m at the same absolute work rate as group 1. Arterial blood was sampled before, during and at the end of exhaustive cycling at sea level (85% of pretraining VO2max). VO2max increased by 12 (2)% with no significant difference between groups, whereas endurance improved most in group 1 (P < 0.05). Training-induced changes in response to exercise of noradrenaline, adrenaline, growth hormone, beta-endorphin, glucagon, and insulin were similar in the three groups. Concentrations of erythropoietin and 2,3-diphosphoglycerate at rest did not change over the training period. In conclusion, within 5 weeks of training, no further adaptation of hormonal exercise responses takes place if intensity is increased above 70% VO2max. Furthermore, hypoxia per se does not add to the training-induced hormonal responses to exercise.

Diurnal variations of serum erythropoietin in trained and untrained subjects

The diurnal variations of serum-erythropoietin concentration ([s-EPO]) were investigated in six physically trained (T) and eight untrained (UT) men. The T subjects had a higher mean maximal oxygen uptake than UT subjects [75.7 (SEM 1.6) ml.min-1.kg-1 versus 48.3 (SEM 1.4) ml.min-1.kg-1, P < 0.0001] and a lower mean body mass index [BMI, 21.7 (SEM 0.7) kg.m-2 versus 24.4 (SEM 0.6) kg.m-2, P = 0.02]. Each subject was followed individually for 24 h as they performed their normal daily activities. Venous blood samples were collected from awakening (0 min) until the end of the 24-h period (1440 min). Both T and UT had a nadir of [s-EPO] 120 min after awakening [10.0 (SEM 0.3) U.l-1 versus 11.5 (SEM 2.1) U.l-1, P > 0.05]. The UT and T increased their [s-EPO] to peak values at 960 min and 960-1200 min, respectively (ANOVA P = 0.03) after awakening [UT: 18.4 (SEM 2.8) U.l-1; T: 16.2 (SEM 2.5) U.l-1, P > 0.05]. The mean 24-h [s-EPO] were 14.5 (SEM 1.0) U.l-1 and 14.9 (SEM 0.9) U.l-1 in T and UT, respectively (P > 0.05). The individual mean 24-h [s-EPO] were not correlated to body mass, BMI or maximal oxygen uptaken. Significant diurnal variations in [s-EPO] occurred in these healthy subjects irrespective of their levels of physical activity.

The effect of short and long duration exercise on serum erythropoietin concentrations

The effects of short and long duration exercise on serum erythropoietin concentrations [EPO]s were studied in seven male cross-country skiers of national team standard and eight male marathon runners, respectively. The short duration exercise was performed as 60 min of cycling at an intensity of 80%-95% of maximal heart rate. Arterial blood oxygen saturations monitored by pulse-oximetry remained unchanged throughout exercise. The partial pressure of O2 at which haemoglobin was half-saturated with O2 calculated from forearm venous blood gas tension and blood O2 saturation, and the erythrocyte 2,3-diphosphoglycerate did not change significantly during the exercise. Blood lactate concentrations were increased at the end of exercise [from 1.3 (SEM 0.1) to 3.6 (SEM 0.3) mmol.l-1]. The [EPO]s determined (by enzyme-linked immunosorbent assay) pre-exercise, 5 min, 6 h, 19 h, and 30 h after the exercise were unchanged [from 16.1 (SEM 2.6) to 19.1 (SEM 3.2), 17.9 (SEM 3.0), 17.0 (SEM 2.5), and 18.6 (SEM 2.9) U.l-1, respectively]. The [EPO]s were not correlated to the earlier parameters. The long duration exercise consisted of habitual training, a 3 week break from training followed by 2 and 4 weeks of re-training. The [EPO]s, body fat (BF), and serum free-testosterone concentrations determined at the end of each period remained unchanged. The maximal oxygen uptakes were decreased after the break from training and increased during retraining (P = 0.04). Body mass (mb) increased after the break in training (P = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)