Endocrine Abstracts

Introduction: The osteoblast derived bone formation marker osteocalcin has been reported to decrease adipose tissue in mice. In elderly men, osteocalcin was reported to correlate inversely with fat mass.

Aim: To examine the relationship between osteocalcin and regional fat depots.

Method: The Odense Androgen Study is a population-based, cross-sectional study of 779 randomly selected men aged 20–29 years. Total, central, upper extremity, and lower extremity fat mass (TFM, CFM, UEFM, and LEFM) was assessed by DXA. Abdominal subcutaneous, thigh subcutaneous, visceral, and thigh intramuscular adipose tissue (abdSAT, thiSAT, VAT, and IMAT) was assessed by MRI. Osteocalcin, bone-specific alkaline phosphatase (bsALP), carboxy-terminal telopeptide of type 1 collagen (1CTP), insulin, glucose, and lipids, were analyzed in serum samples drawn in fasting state between 0800 and 1000 h Blood pressure was recorded.

Results: Osteocalcin correlated negatively with TFM (R=−0.18, P<0001), CFM (R=−0.21, P<0.0001), UEFM (R=−0.18, P<0.0001), LEFM (R=−0.12, P=0.001), abdSAT (R=−0.18, P=0.0003), VAT (R=−0.27, P<0.00001), and IMAT (R=−0.16, P=0.001). No correlations were observed between the fat parameters and the other bone markers despite highly significant correlations between osteocalcin and bsALP (R=0.40, P<10⁹) and 1CTP (R=0.41, P<10⁹). Osteocalcin decreased from age 20 to 29 years (R=−0.40, P<10⁹), while CFM (R=0.14, P=0.0001), abdSAT (R=0.12, P=0.02), VAT (R=0.25, P<0.0001), and IMAT (R=0.11, P=0.03) increased significantly. Osteocalcin correlated negatively with total cholesterol (R=−0.09, P=0.01), LDL-cholesterol (R=−0.09, P=0.009) and diastolic blood pressure (R=−0.07, P=0.046).

Conclusion: In cross-sectional analyses, osteocalcin was the only bone marker that correlated with adiposity: osteocalcin correlated inversely with all fat parameters, except thiSAT. The age-related decline of osteocalcin was accompanied by an increase in deep adipose tissues (VAT rather than abdSAT, IMAT rather than thiSAT). High blood pressure and dyslipidemia was associated with low osteocalcin levels. Our data support the hypothesis that osteocalcin is negatively associated with adiposity in humans.