Post-exercise serum hepcidin levels were unaffected by hypoxic exposure during prolonged exercise sessions

Iron Status and Physical Performance in Athletes

Iron is an important mineral in the body, essential for muscle function and oxygen transport. Adequate levels of iron in the blood are necessary for athletes, as iron-deficiency anemia can reduce physical performance. Several studies have investigated iron status and supplementation in iron-deficient athletes, and determined how physical strain can change iron balance and markers related to iron status. The question of how to influence and optimize iron status, as well as other markers that can affect iron metabolism, has been less thoroughly investigated. Therefore, the aim of this review is to take a closer look at the importance of iron values, iron markers, and factors that can change iron metabolism for physical performance and the extent to which physical performance can be influenced in a positive or negative way. A systematic search of the PubMed database was performed, with the use of « iron» or «iron deficiency» or «hemoglobin» AND «athletes» AND «athletic performance» as a strategy of the search. After the search, 11 articles were included in the review after the application of inclusion and exclusion criteria. Major findings include that iron supplementation had the best effect in athletes with the lowest iron status, and effects on physical performance were mostly achieved in those who were originally in a deficit. Iron supplementation could be beneficial for optimal erythropoietic response during altitude training, even in athletes with normal iron stores at baseline, but should be performed with caution. Alteration of the hepcidin response can affect the use of existing iron stores for erythropoiesis. Energy intake, and the amount of carbohydrates available, may have an impact on the post-exercise hepcidin response. Optimal vitamin D and B12 levels can possibly contribute to improved iron status and, hence, the avoidance of anemia.

Impact of Exercise in Hypoxia on Inflammatory Cytokines in Adults: A Systematic Review and Meta-analysis

BACKGROUND

Both acute exercise and environmental hypoxia may elevate inflammatory cytokines, but the inflammatory response in the hypoxic exercise is remaining unknown.

OBJECTIVE

We performed this systematic review and meta-analysis to examine the effect of exercise in hypoxia on inflammatory cytokines, including IL-6, TNF-α and IL-10.

METHODS

PubMed, Scopus and Web of Science were searched to identify the original articles that compared the effect of exercise in hypoxia with normoxia on IL-6, TNF-α and IL-10 changes, published up to March 2023. Standardized mean differences and 95% confidence intervals (CIs) were calculated using a random effect model to (1) determine the effect of exercise in hypoxia, (2) determine the effect of exercise in normoxia and (3) compare the effect of exercise in hypoxia with normoxia on IL-6, TNF-α and IL-10 responses.

RESULTS

Twenty-three studies involving 243 healthy, trained and athlete subjects with a mean age range from 19.8 to 41.0 years were included in our meta-analysis. On comparing exercise in hypoxia with normoxia, no differences were found in the response of IL-6 [0.17 (95% CI - 0.08 to 0.43), p = 0.17] and TNF-α [0.17 (95% CI - 0.10 to 0.46), p = 0.21] between the conditions. Exercise in hypoxia significantly increased IL-10 concentration [0.60 (95% CI 0.17 to 1.03), p = 0.006] compared with normoxia. In addition, exercise during both hypoxia and normoxia increased IL-6 and IL-10, whereas TNF-α was increased only in hypoxic exercise condition.

CONCLUSION

Overall, exercise in both hypoxia and normoxia increased inflammatory cytokines; however, hypoxic exercise may lead to a greater inflammatory response in adults.

Hepcidin response to three consecutive days of endurance training in hypoxia

PURPOSE

The purpose of this study was to determine the effects of 3 consecutive days of endurance training in hypoxia on hepcidin responses.

METHOD

Nine active healthy males completed two trials, consisting of 3 consecutive days of endurance training in either hypoxia [fraction of inspired oxygen (F_iO₂): 14.5%) or normoxia (F_iO₂: 20.9%). On days 1-3, participants performed one 90 min session of endurance training per day, consisting of high-intensity endurance interval exercise [10 × 4 min of pedaling at 80% of maximal oxygen uptake ([Formula: see text]O_2max) with 2 min of active rest at 30% of [Formula: see text]O_2max] followed by 30 min of continuous exercise at 60% of [Formula: see text]O_2max. Venous blood samples were collected prior to exercise each day during the experimental period (days 1-4) to determine serum hepcidin, iron, ferritin, haptoglobin, and ketone body concentrations.

RESULT

Serum iron (p < 0.0001), ferritin (p = 0.005) and ketone body (p < 0.0001) concentrations increased significantly in both trials on days 2-4 compared with day 1, with no significant differences between trials. No significant changes in serum haptoglobin concentrations were observed throughout the experimental period in either trial. Serum hepcidin concentrations also increased significantly on days 2-4 compared with day 1 in both trials (p = 0.004), with no significant differences observed between trials.

CONCLUSION

3 consecutive days of endurance training in hypoxia did not affect hepcidin concentrations compared with endurance training in normoxia.

Association of Serum Hepcidin Levels with Aerobic and Resistance Exercise: A Systematic Review

BACKGROUND

Prevalence of iron deficiency is commonly reported among athletic population groups. It impairs physical performance due to insufficient oxygen delivery to target organs and low energy production. This is due to the high demand of exercise on oxygen delivery for systemic metabolism by the erythrocytes in the blood. Hepcidin, the key regulator of iron homeostasis, decreases to facilitate iron efflux into the circulation during enhanced erythropoiesis. However, acute anaemia of exercise is caused by increased hepcidin expression that is induced by stress and inflammatory signal. The study aimed to systematically review changes in serum hepcidin levels during resistance and aerobic exercise programmes.

METHODS

A systemic literature search from 2010 to April 2020 across seven databases comprised of Cochrane library, PubMed, Web of Science, Scopus, Embase, MEDLINE, and OpenGrey. The primary outcome was increased or decreased serum hepcidin from baseline after the exercise activity. Risks of bias were evaluated by using the National Institutes of Health (NIH) for quality assessment of before and after different exercise programmes.

RESULTS

Overall, twenty-three studies met the inclusion criteria. Out of the 23 studies, 16 studies reported significantly exercise-induced serum hepcidin elevation. Of the 17 studies that evaluated serum interleukin (IL)-6 levels, 14 studies showed significant exercise-induced serum IL-6 elevation. Changes in exercise-induced serum hepcidin and IL-6 levels were similar in both resistance and endurance exercise. Significant correlations were observed between post-exercise hepcidin and baseline ferritin levels (r = 0.69, p < 0.05) and between post-exercise hepcidin and post-exercise IL-6 (r = 0.625, p < 0.05).

CONCLUSION

Resistance and endurance training showed significant increase in serum hepcidin and IL-6 levels in response to exercise. Baseline ferritin and post-exercise IL-6 elevation are key determining factors in the augmentation of hepcidin response to exercise.

Hemolysis Is Responsible for Elevation of Serum Iron Concentration After Regular Exercises in Judo Athletes

Serum iron concentration increases in marathon athletes after running due to mechanical destruction of red blood cells (hemolysis). This study was performed to examine whether serum iron concentration increases after regular Judo exercise, and if so, whether such post-exercise iron increase is caused by hemolysis. We examined biochemical parameters related to red blood cell and iron metabolism in 16 male competitive Judo athletes before and after traditional exercise training composed of basic movements and freestyle matchup. The parameters were adjusted for changes in plasma volume based on simultaneously measured albumin concentration. The red blood cell count, hemoglobin concentration, and hematocrit levels decreased significantly, by 6.0-8.4%, after Judo exercise. The serum iron concentration and transferrin saturation increased significantly, from 87 ± 34 μg/dL to 98 ± 29 μg/dL and from 27.1 ± 9.7% to 31.2 ± 9.0%, respectively. Furthermore, the serum free hemoglobin level increased by 33.9% (p < 0.05), and haptoglobin concentration decreased by 19.2% (p < 0.001). A significant negative correlation was observed between Δ haptoglobin concentration and Δ serum iron concentration (r = - 0.551, p = 0.027). The results of this study indicate that serum iron concentration increases significantly after Judo exercise due to hemolysis.

Partial sleep deprivation after an acute exercise session does not augment hepcidin levels the following day

The purpose of the present study was to determine the effects of partial sleep deprivation (PSD) after an exercise session in the evening on the endurance exercise-induced hepcidin response the following morning. Ten recreationally trained males participated under two different conditions. Each condition consisted of 2 consecutive days of training (days 1 and 2). On day 1, participants ran for 60 min at 75% of maximal oxygen uptake ( V ˙ O2max ) followed by 100 drop jumps. Sleep duration at night was manipulated, with a normal length of sleep (CON condition, 23:00-07:00 hr) or a shortened length of sleep (PSD condition). On the morning of day 2, the participants ran for 60 min at 65% of V ˙ O2max . Sleep duration was significantly shorter under the PSD condition (141.2 ± 13.3 min) than under the CON condition (469.0 ± 2.3 min, p < .0001). Serum hepcidin, plasma interleukin (IL)-6, serum haptoglobin, iron, and myoglobin levels did not differ significantly between the conditions (p > .05) on the morning (before exercise) of day 2. Additionally, the 3-hr postexercise levels for the hematological variables were not significantly different between the two conditions (p > .05). In conclusion, the present study demonstrated that a single night of PSD after an exercise session in the evening did not affect baseline serum hepcidin level the following morning. Moreover, a 60 min run the following morning increased serum hepcidin and plasma IL-6 levels significantly, but the exercise-induced elevations were not affected by PSD.

No effect of supplemented heat stress during an acute endurance exercise session in hypoxia on hepcidin regulation

Hepcidin is a novel factor for iron deficiency in athletes, which is suggested to be regulated by interleukin-6 (IL-6) or erythropoietin (EPO).

PURPOSE

The purpose of the present study was to compare endurance exercise-induced hepcidin elevation among "normoxia", "hypoxia" and "combined heat and hypoxia".

METHODS

Twelve males (21.5 ± 0.3 years, 168.1 ± 1.2 cm, 63.6 ± 2.0 kg) participated in the present study. They performed 60 min of cycling at 60% of [Formula: see text] in either "heat and hypoxia" (HHYP; F_iO₂ 14.5%, 32 °C), "hypoxia" (HYP; F_iO₂ 14.5%, 23 °C) or "normoxia" (NOR; F_iO₂ 20.9%, 23 °C). After completing the exercise, participants remained in the prescribed conditions for 3 h post-exercise. Blood samples were collected before, immediately and 3 h after exercise.

RESULTS

Plasma IL-6 level significantly increased immediately after exercise (P < 0.05), with no significant difference among the trials. A significant elevation in serum EPO was observed 3 h after exercise in hypoxic trials (HHYP and HYP, P < 0.05), with no significant difference between HHYP and HYP. Serum hepcidin level increased 3 h after exercise in all trials (NOR, before 18.3 ± 3.9 and post180 31.2 ± 6.3 ng/mL; HYP, before 13.5 ± 2.5 and post180 23.3 ± 3.6 ng/mL, HHYP; before 15.8 ± 3.3 and post180 31.4 ± 5.3 ng/mL, P < 0.05). However, there was no significant difference among the trials during post-exercise.

CONCLUSION

Endurance exercise in "combined heat and hypoxia" did not exacerbate exercise-induced hepcidin elevation compared with the same exercise in "hypoxia" or "normoxia".