Relationships of serum leptin levels with biochemical markers of bone turnover and with growth factors in normal weight and overweight children.

OBJECTIVE

To examine the hypothesis of an influence of leptin on growth factors and on biochemical markers of bone turnover of prepubertal overweight children.

DESIGN AND METHODS

395 prepubertal children, 6-13 years of age, were selected and the relationships between circulating serum levels of leptin and insulin-like growth factor I (IGF-I), insulin growth factor binding protein-3 (IGFBP-3) and some biochemical markers of bone turnover (osteocalcin, OC; carboxyterminal propeptide of type I procollagen, PICP, and carboxyterminal propeptide of type I collagen, ICTP) were analyzed. The subjects were subdivided into normal weight (NW, n = 163) and weight excess (WE, n = 232) subjects.

RESULTS AND CONCLUSIONS

Significant differences between the two groups were found for leptin (p < 0.01), IGF-I (p < 0.01) and IGFBP-3 (p < 0.01), with higher values in WEs, and for OC (p < 0.01) with higher values in NWs. A significant reduction of leptin (p < 0.01) and IGFBP-3 (p < 0.01) serum values and an increase of those of OC (p < 0.01) and PICP (p < 0.05), but not of ICTP, were registered in 103 WEs who showed a drop in weight excess during a weight-excess reduction program. No variations were observed in 26 non-responsive subjects. In a multivariate analysis in which leptin, corrected by BMI and sex, was the independent variable, a significant negative correlation was found with PICP (beta = -0.235, p < 0.01), IGF-I (beta = -0.180, p < 0.01) and height velocity (beta = -0.155, p < 0.01). There was no correlation with OC, ICTP and IGFBP-3. The results demonstrate that nutritional status and leptin levels are involved in the regulation of growth factors and biochemical markers of bone formation.