Sclerostin and bone mass in pubertal girls: different associations between athletes and non-athletes.

Background: Rhythmic gymnasts (RG) start their heavy trainings already at early age and despite of low body fat mass, their bone parameters are higher than in untrained controls (UC). The specific role of sclerostin and preadipocyte factor-1 (Pref-1), which are the negative regulators of bone mass by inhibiting bone formation, is not well understood in puberty. The aims of the study were to compare sclerostin and Pref-1 between RG and UC, and to evaluate relationships of sclerostin and Pref-1 with bone mass.

Methods: Study involved 32 RG and 32 UC girls aged 10-12 years. Bone mass and body composition were measured by dual-energy X-ray absorptiometry, and plasma sclerostin and Pref-1 concentrations were assessed from fasting blood samples.

Results: Sclerostin was higher (P<0.0001) in RG (24.2±8.8 pmol/L) compared with UC (14.7±10.0 pmol/L¹), while Pref-1 was similar between the groups. In RG, sclerostin was positively correlated with lumbar spine (LS) (r=0.44; P=0.012) and femoral neck (FN) (r=0.37; P=0.039) bone mineral content (BMC), whereas in UC, sclerostin was inversely associated with LS (r=-0.37; P=0.039) and FN (r=-0.35; P=0.048) BMC. In RG, sclerostin remained positively correlated with LS BMC independent of confounding factors (r=0.60; P=0.001). Pref-1 was not correlated with any bone mass values in both groups.

Conclusions: Early pubertal RG girls have higher plasma sclerostin levels compared UC. Sclerostin has differential associations with bone mass in RG compared to UC.