An independent positive relationship between the serum total osteocalcin level and fat-free mass in healthy premenopausal women.

Context: It is widely reported that osteocalcin is negatively associated with fat mass. However, there are few reports describing its correlation with fat-free mass, particularly in women.

Objectives: The objective of the current study was to investigate the possible relationship between osteocalcin and fat-free mass in healthy, nonobese women.

Design And Setting: This study was performed in a tertiary university teaching hospital.

Subjects: A total of 504 healthy women aged 20-75 years were enrolled.

Main Outcome Measures: Body composition was measured using a bioelectronics impedance analyzer. The serum concentrations of total osteocalcin, estradiol, leptin, osteoprotegerin, the receptor activator of nuclear factor-κB ligand, IGF-I, fasting plasma glucose, and urinary N-terminal telopeptide of type I collagen were tested. The bone mineral densities (BMDs) at the lumbar spine and proximal femoral neck were measured by dual-energy X-ray absorptiometry.

Results: The serum total osteocalcin level had a significant positive association with fat-free mass (r = 0.168, P = .007) after adjusting for age, fat mass, menopausal status, estradiol, fasting glucose, leptin, osteoprotegerin, receptor activator of nuclear factor-κB ligand, IGF-I, N-terminal telopeptide of type I collagen, BMDs, and waist and hip circumference. Analysis in pre- and postmenopausal women demonstrated that this association was only present in premenopausal women (r = 0.190, P = .005). The multiple stepwise regression analysis revealed that hip circumference, femoral neck-BMD, fat mass, leptin, osteocalcin, and age are the contributors to the changes in fat-free mass in premenopausal women (adjusted R(2) = 0.521, P < .001).

Conclusion: The serum level of total osteocalcin was positively associated with fat-free mass independent of age, fat mass, leptin, and other confounders in premenopausal women.