Bone Abstracts

Introduction: Obesity is the direct cause of a number of immediate problems during childhood. Among them the high prevalence of fractures and joint problems in obese children was observed. Leptin may influence the development and bone remodeling in children, but this phenomenon is not well understood. Therefore, we studied the relationships between leptin and bone turnover markers, growth factors and anthropometric parameters in obese children.

Description of methods: We determined in 55 obese (z-score BMI >2) and 50 non-obese (z-score BMI <−1+1>) children aged 5–10 years serum leptin, soluble leptin receptor, bone alkaline phosphatase (BALP), osteocalcin (OC), collagen type I crosslinked C-telopeptide (CTX-I), IGF-1 (insulin-like growth factor-1) and IGFBPs (insulin-like growth-factor binding proteins) using immunoenzymatic methods. Body composition and total bone mineral density were measured by dual-energy X-ray absorptiometry.

Results: Between studied groups, differences in profile of bone formation markers were found. The level of OC was lower by about 20% (P<0.01) but activity of BALP was higher by about 20% (P<0.001) in patients than in healthy non-obese subjects. The positive correlations were found between BALP and leptin (P<0.01), IGF-1 (P<0.01), IGFBP-3 (P<0.05) and BMI (P<0.001). Moreover, BALP correlated negatively with leptin receptor and IGFBP-1 (P<0.05). OC correlated significantly only with IGFBP-1. No significant relations between CTX-I and fat tissue parameters as well as body composition were found.

Conclusions: We demonstrated that obesity during prepubertal period is associated with increased whole-body bone mass, alternation in the leptin/leptin receptor ratio, the growth hormone axis and bone metabolism. Further studies concerning lifestyle modification in these children elucidate the influence of weight-loss therapy on bone metabolism.