Osteocalcin as a marker of metabolic risk in healthy postmenopausal women

Objective: Several studies have reported the role of osteocalcin on glucose and fat metabolism. In this study, we analyzed the relationship between the concentration of osteocalcin and metabolic risk factors in healthy postmenopausal women. Methods: Cross-sectional analyses of 54 postmenopausal women aged 56 +/- 3.5 years were conducted. We recorded clinical and biochemical data of metabolic risk including fasting plasma glucose (FPG) level and evaluated the relationship between serum osteocalcin and bone formation markers. Results: Serum osteocalcin concentration was negatively correlated with FPG (beta = -0.328, P = 0.035). When osteocalcin levels were divided into tertiles, we found significant differences in FPG between the highest and the lowest tertiles (84 +/- 11 vs 98 +/- 30 mg/dL, respectively; P = 0.029). We found significantly lower osteocalcin levels in women with impaired fasting glucose levels than in those with normoglycemia (10.7 +/- 6.1 vs 17.1 +/- 7.4 ng/mL, respectively; P = 0.006). We also found lower concentrations of osteocalcin in obese women versus nonobese women (14.4 +/- 8.8 vs 17.3 +/- 6.2 ng/mL; P = 0.034) and women with increased low-density lipoprotein cholesterol levels versus those with low LDL-c levels (14.1 +/- 5.4 vs 18.9 +/- 9.1 ng/mL; P = 0.045). A concentration of 13.5 ng/mL or lower showed a sensitivity of 85.7% and a specificity of 63.8% to detect increased risk for diabetes (FPG >= 100 mg/dL). In contrast, serum levels of bone alkaline phosphatase did not correlate with any variable. Conclusions: In this population, there is a consistent association between osteocalcin and markers of metabolic syndrome. We suggest potential usefulness of serum osteocalcin as a predictor for increased risk of diabetes in postmenopausal women.