THE RELATIONSHIP BETWEEN THE DISTRIBUTION OF BODY FAT AND THE LEVEL OF OSTEOCALCIN IN CHINESE ADOLESCENTS

Objective: Current studies on body fat distribution and bone metabolism in adolescents are very limited. This study aimed to examine the relationship between the body fat distribution and serum osteocalcin levels in adolescents. Design and method: A total of 1068 subjects (564 boys,52.8%) aged 12–18 years from Ningxia were randomly selected through a stratified cluster sampling. Serum osteocalcin levels were measured by ELISA. An automatic bioelectric impedance analysis (BIA) was used to measure body compositions, which included body fat mass(BFM),trunk fat mass(TFM),limbs fat mass(LFM),visceral fat level(VFL). Results: In the total population, serum osteocalcin levels were negatively correlated with BFM, TFM, LFM, and fat mass percentage (FMP) (r = -0.076, -0.066, -0.094 and -0.117, respectively, all P < 0.05); Serum osteocalcin levels were positively correlated with limb fat mass percentage (LFMP) (r = 0.167, P < 0.001). Logistic regression analysis showed that the odds ratios (ORs) of FMP in the third and second quintiles suggesting high levels of osteocalcin is 0.28 (95% confidence interval [CI],0.13—0.57) and 0.44(95% CI, 0.25—0.76) compared with the lowest quartile level among total population, respectively. Additionally, the corresponding ORs for high levels of osteocalcin were 0.2 (95%CI, 0.05–0.72) in the fourth quantile of FMP,0.21 (95%CI, 0.08–0.55) in the third quantile of FMP and 0.45(95% CI, 0.25–0.82) in the second quantile of FMP in boys, respectively. Compared with the reference subgroup, the fourth quantile level of LFMP could better predict high osteocalcin levels between boys and girls, and the ORs were 7.46 (95%CI, 2.79—19.96) and 2.60(95%CI: 1.36—4.96), respectively. Conclusions: FMP have a negative impact on bone resorption in in Chinese adolescents, especially in boys. However, LFMP has a protective effect on bone metabolism between Chinese boys and girls.