A cross-sectional study of osteocalcin and body fat measures among obese adolescents


  • Disclosure: The authors have nothing to disclose.

  • Funding agencies: Dr. Lenders received support from the Joel and Barbara Alpert Endowment for the Children of the City, the NIH grant MO1-RR00533 (Boston University School of Medicine, Michael F. Holick). We are very thankful for the contribution of Howard Bauchner in the review of the manuscript with support from his 5 K24 HD042489. The GPRN is funded by the Elizabeth Glaser Pediatric Research Foundation (EGPRF), a program of the Elizabeth Glaser Pediatric AIDS Foundation. The study was funded by the EGPRF and the NIH/NCRR (Stanford University: grant number MO1-RR00070; Baylor College of Medicine: grant number MO1-RR00188; University of California, San Francisco: UCSF-CTSI grant number UL-RR024131-01; University of California, Los Angeles: grant number MO1-RR00865; Harvard Medical School: Children's Hospital Boston grant number MO1-RR02172).


Osteocalcin (OCN), a marker of osteoblast activity, has been implicated in the regulation of energy metabolism by the skeleton and thus may affect body fat measures.


To examine the relationships of OCN to body fat measures and whether they vary according to markers of energy and vitamin D metabolism.

Design and Methods:

Data were obtained from 58 obese adolescents aged 13-17.9 years (38 females, 8 black or African-American). Total fat mass (FM) [dual X-ray absorptiometry (DXA)] and visceral adipose tissue (VAT) [computerized axial tomography (CT)] were calculated. Blood tests included leptin, OCN, 25-hydroxyvitamin D [25(OH)D], parathyroid hormone (PTH), thyroid function tests, and triglycerides. Markers of glucose metabolism were obtained from fasting and OGTT samples.

Results and Conclusions:

Adolescents with 25(OH)D <20 ng mL−1 were considered deficient (n = 17/58); none had high PTH (PTH ≥ 65 pg mL−1). OCN was associated with lower VAT (−84.27 ± 33.89 mm2) and BMI (−0.10 ± 0.05 kg m−2), not FM (P = 0.597) in a core model including age, sex, race, geographic latitude, summer, height z-score, and tanner stage. Adding 25(OH)D deficiency and PTH attenuated the inverse association of OCN to VAT. There was a significant interaction of OCN and 25(OH)D deficiency on FM (0.37 ± 0.18 kg, P = 0.041) and BMI (0.28 ± 0.10 kg m−2, P = 0.007) in this adjusted model, which was further explained by leptin. Adding A1C to the core model modified the relationship of OCN to VAT (−93.08 ± 35.05 mm2, P = 0.011), which was further explained by HOMA-IR. In summary, these findings provide initial evidence for a relationship between OCN and body fat measures that is dependent on energy metabolism and vitamin D status among obese adolescents.