Lower serum osteocalcin is associated with more severe metabolic syndrome in elderly men from the MINOS cohort

Background: Bone has emerged as an endocrine organ regulating energy metabolism through secretion of osteocalcin. In epidemiological studies, presence of metabolic syndrome (MetS) was associated with lower osteocalcin level. Objectives: We evaluated whether osteocalcin level was associated with MetS severity in men and whether it was more strongly associated with MetS compared with N-terminal propeptide of type I procollagen (PINP), bone-specific alkaline phosphatase (BAP), and C-terminal telopeptide of type I collagen (bCTX). Methods: We included 798 men aged 51-85 years for total osteocalcin measurement. Number of MetS criteria was used to define severity. We used polytomous logistic regression to assess the relationship between MetS severity and osteocalcin level. Results: Thirty percent of men had MetS. In patients with MetS, the higher the number of MetS traits were present, the lower was the average osteocalcin level (0-2 criteria: 551 men: 19.5 +/- 6.7 ng/ml, three criteria: 155 men: 19.3 +/- 7.4 ng/ml, four criteria: 72 men: 17.3 +/- 5.7 ng/ml, and five criteria: 20 men: 15.0 +/- 5.1 ng/ml; P for trend=0.002). In the polytomous logistic regression model, an increase in osteocalcin level of 10 ng/ml was associated with lower prevalence of severe MetS: three criteria (odds ratio (OR) =0.93 (0.70-1.24)), four criteria (ORZ=0.54 (0.34-0.84)), and five criteria (ORZ0.28 (0.10-0.82)) in comparison with no MetS (P for trend=0.008). After adjustment, using stepwise analysis of the polytomous logistic regression model, we observed that osteocalcin, age, and apparent free testosterone entered in the model but not other bone markers (PINP, bCTX, and BAP). Conclusion: In older Caucasian men, total osteocalcin level was associated with MetS severity. Osteocalcin was more strongly associated with MetS severity than other bone turnover markers.