Apelin as a Potential Regulator of Peak Athletic Performance

Apelin, as a cardiokine/myokine, is emerging as an important regulator of cardiac and skeletal muscle homeostasis. Loss of apelin signaling results in premature cardiac aging and sarcopenia. However, the contribution of apelin to peak athletic performance remains largely elusive. In this paper, we assessed the impact of maximal cardiorespiratory exercise testing on the plasma apelin levels of 58 male professional soccer players. Circulating apelin-13 and apelin-36, on average, increased transiently after a single bout of treadmill exercise; however, apelin responses (Δapelin = peak - baseline values) showed a striking interindividual variability. Baseline apelin-13 levels were inversely correlated with those of Δapelin-13 and Δapelin-36. Δapelin-13 showed a positive correlation with the maximal metabolic equivalent, relative maximal O₂ consumption, and peak circulatory power, whereas such an association in the case of Δapelin-36 could not be detected. In conclusion, we observed a pronounced individual-to-individual variation in exercise-induced changes in the plasma levels of apelin-13 and apelin-36. Since changes in plasma apelin-13 levels correlated with the indicators of physical performance, whole-body oxygen consumption and pumping capability of the heart, apelin, as a novel exerkine, may be a determinant of peak athletic performance.

Adrenal, Gonadal and Peripherally Steroid Changes in Response to Extreme Physical Stress for Characterizing Load Capacity in Athletes

Athletes are often exposed to extreme physical stress during training or competitions. The consequent activation of the hypothalamus–hypophysis–adrenal (HPA) axis results in intensified steroid hormone production in the adrenal cortex. We determined the impact of an acute extreme physical stress on adrenal and gonadal steroidogenesis in healthy male professional athletes (n = 40). The subjects underwent an extreme physical load test until total voluntary fatigue between 14:00 and 18:00 when the hormone levels are relatively stable. Blood was taken before the start (baseline), at the peak load (peak), and 30 min following completion of the exercise (recovery). The vital parameters, lactate levels, and blood levels of the 14 steroid hormones were recorded. The multivariate statistical analysis of the results revealed that all monitored hormone levels increased upon stress. Significant changes in steroid concentrations were detected at peak versus baseline, peak versus recovery, and at baseline versus recovery. The mineralocorticoid (including aldosterone and corticosterone), glucocorticoid (11-deoxycortisol and cortisol), and androgen (androstenedione, dehydroepiandrosterone, and dehydroepiandrosterone sulfate) pathways, as well as gonadal testosterone synthesis are activated simultaneously under extreme physical load. The profiling of adrenal and gonadal steroid biosynthesis in athletes may help the characterization of their loading capacity.