Carboxylation of osteocalcin affects its association with metabolic parameters in healthy children

OBJECTIVE Osteocalcin (OC), a bone-derived protein, was recently shown to regulate metabolic pathways in mice. Undercarboxylated OC (ucOC), but not carboxylated OC (cOC), increases adiponectin and insulin secretion. It is unclear if carboxylation of OC affects its association with metabolic parameters in humans. RESEARCH DESIGN AND METHODS The associations between ucOC, cOC, total and high-molecular-weight (HMW) adiponectin, and insulin secretion (homeostasis model assessment [HOMA]-beta) were investigated in a population-based sample of healthy prepubertal children (n = 103; 49 boys and 54 girls). RESULTS Weight-dependent associations were observed between the different forms of OC and metabolic parameters. Higher cOC was related to lower HMW adiponectin (with a stronger association in leaner children; P < 0.001). Higher ucOC-to-cOC ratio was associated with higher HOMA-beta (P < 0.01) in leaner children and associated with higher HMW adiponectin (P < 0.001) in heavier children. CONCLUSIONS In a weight-dependent manner, cOC and the proportion of ucOC are differentially related to HMW adiponectin and insulin secretion in healthy children.