Sclerostin as a novel marker of bone turnover in athletes

Abstract

Sclerostin is a protein secreted by osteocytes that acts as an inhibitor of bone formation. It has been shown that physical activity affects sclerostin concentration and thus bone remodelling. The aim of the study was to evaluate serum concentrations of sclerostin, selected bone turnover markers (PTH, P1NP), 25(OH)D3 and the intake of calcium and vitamin D in physically active versus sedentary men. A total of 59 healthy men aged 17-37 were enrolled in the study (43 athletes and 16 non-athletes). The mean sclerostin concentration in the group of athletes (A) was significantly higher than in non-athletes (NA) (35.3±8.9 vs 28.0±5.6 pmol·l-1, p= 0.004). A compared with NA had higher concentrations of P1NP (145.6±77.5 vs 61.2±22.3 ng·ml-1, p= <0.0001) and 25(OH)D3 (16.9±8.4 vs 10.3±4.3 ng·ml-1, p= 0.004) and lower concentrations of PTH (25.8±8.3 vs 38.2±11.5 pg·ml-1, p= <0.0001). Vitamin D deficiency was found in 77% of A and 100% of NA. A and NA had similar daily energy intake. They did not differ as to the intake of calcium and vitamin D. We observed a negative correlation between the serum concentrations of sclerostin and calcium in the studied subjects. Our results suggest that regular, long-lasting physical training may be associated with higher concentration of sclerostin. It seems that increased sclerostin is not related to other bone turnover markers (PTH, P1NP).

Effects of physical activity on sclerostin concentrations

“…Gombos et al [6] found that sclerostin levels increased in a similar group of women as in our study, who underwent a program of walking exercise or resistance exercise, compared to a control group. Similar results were presented by Zagrodna et al [39] who reported that male athletes had significantly higher sclerostin levels than age-matched sedentary men. Also, Lombardi et al [40] investigating sclerostin concentrations in elite athletes, found higher sclerostin levels in males participating in weight-bearing disciplines than in those who participated in nonweight-bearing sports.…”

Hormonal responses following eccentric exercise in humans

“…The purpose of this study was therefore to examine the eccentric exercise-induced responses of hormones 8 as well as secreted proteins that are exercise-regulated and have been associated with skeletal muscle regeneration and adaptation, [18][19][20] i.e. GH, insulin-like growth factor binding protein-3 (IGFBP-3), cortisol, prolactin, thyroid-stimulating hormone (TSH), free thyroxine (fT4), irisin, follistatin and sclerostin.…”

“…Indeed, some of these hormones have aroused particular interest because of their potential role in exercise-induced muscle adaptations. [19][20][21][22][23][24] In particular, irisin is a hormone predominantly expressed in human muscle 25,26 and is required for the exercise-induced conversion of white adipose tissue to brown. 18,25 In addition, follistatin is an antagonist of myostatin, the negative regulator of muscle regeneration, 27 while sclerostin is a mechanical loading-regulated protein whose serum levels have been shown to be affected by physical exercise.…”

“…18,25 In addition, follistatin is an antagonist of myostatin, the negative regulator of muscle regeneration, 27 while sclerostin is a mechanical loading-regulated protein whose serum levels have been shown to be affected by physical exercise. 20,28 We monitored the serum changes of the aforementioned hormones and muscle-associated secreted proteins for several days after the completion of an eccentric exercise protocol in humans, posing the hypothesis that their circulating levels would be changed during the recovery period following exercise-induced muscle damage, thus suggesting their potential role as mediators of muscle regeneration and adaptation after the damaging exercise.…”

“…12,44,45 Lastly, we explored the potential responses of sclerostin, which is secreted by osteocytes and acts as an inhibitor of bone formation and whose serum levels appear to be affected by physical exercise. 20,28 In particular, 8 wk of exercise training resulted in significantly decreased serum levels of sclerostin; however, there are no reports in the literature regarding the acute effects of muscle mechanical overloading and damage on circulating levels of this secreted factor. Interestingly, in this study we observed a gradual decrease of circulating sclerostin up to 48 hrs after the single bout of eccentric exercise, before increasing (though without reaching significance) at 120 hrs post exercise, accompanied by its strong positive correlations with GH responses.…”