Interrelationship between glucose metabolism and undercarboxylated osteocalcin: a cross-sectional study in a community-dwelling population.

OBJECTIVE Undercarboxylated osteocalcin (ucOC) produced from the bone was recently found to play a regulatory role in the insulin and adiponectin secretion. We performed a cross-sectional study to investigate the relationship between ucOC and diabetes mellitus (DM). METHODS We included 1,870 subjects aged over 50 from participants of a health examination. According to the current medication and past history, 605 subjects had hypertension (HT), 316 had dyslipidemia (DL), and 182 had type 2 DM. Fasting blood samples were collected to measure concentrations of ucOC and the bone turnover marker, tartrate-resistant acid phosphatase 5b (TRACP5b) by ELISA. RESULTS The serum ucOC level was significantly lower in DM(+) than DM(-) in both men and women. In a logistic regression analysis, a low level of ucOC was significantly associated with the presence of DM in both men and women after adjusting for age, BMI, serum creatinine, triglyceride, and TRACP5b. Multiple regression analysis showed a negative association of ucOC with HbA1c and fasting plasma glucose, and a positive association with the insulin level. In contrast, no association was found between TRACP5b and the indices above, suggesting that the effect of ucOC on the insulin secretion and the glycemic status was independent of bone turnover. CONCLUSIONS The present cross-sectional study showed a significant association between ucOC and glucose metabolism after correction with bone turnover in a community-dwelling population both in men and women, indicating that ucOC may play an important role in the pathogenesis of DM through the pathways independent of bone metabolism.