Poster Presentation 29th Australian and New Zealand Bone and Mineral Society Annual Scientific Meeting 2019

Osteocalcin and its forms across the lifespan in adult men (#117)

Cassandra Smith 1 2 , Sarah Voisin 1 , Ahmed Al Saedi 2 3 , Steven Phu 2 3 , Tara Brennan-Speranza 4 , Lewan Parker 5 , Nir Eynon 1 , Danielle Hiam 1 , Xu Yan 1 , David Scott 2 6 , Lauren C Blekkenhorst 7 8 , Joshua R Lewis 7 8 , Ego Seman 9 , Elizabeth Byrnes 10 , Leon Flicker 8 11 , Gustavo Duque 2 3 , Bu B Yeap 8 12 , Itamar Levinger 1 2 3
  1. Institute for Health and Sport (iHeS), Victoria University, Melbourne, VIC, Australia
  2. Australian Institute for Musculoskeletal Sciences (AIMSS), University of Melbourne, Melbourne, VIC, Australia
  3. Department of Medicine- Western Health, University of Melbourne, Melbourne, VIC, Australia
  4. Department of Physiology and Bosch Institute for Medical Research, University of Sydney, Sydney, NSW, Australia
  5. Institute for Physical Activity and Nutrition (IPAN), Deakin University, Melbourne, VIC, Australia
  6. School of Clinical Sciences at Monash Health, Monash University, Melbourne, VIC, Australia
  7. School of Medical and Health Sciences, Edith Cowan University, Perth, Western Australia, Australia
  8. Medical School, University of Western Australia, Perth, WA, Australia
  9. University of Melbourne and the Department of Endocrinology, University of Melbourne, Melbourne, VIC, Australia
  10. Department of Biochemistry, Queen Elizabeth II Medical Centre, Perth, Western Australia, Australia
  11. Western Australian Centre for Health & Ageing, University of Western Australia, Perth, WA, Australia
  12. Department of Endocrinology and Diabetes, Fiona Stanley Hospital, Perth, WA, Australia

Background: Osteocalcin (OC), an osteoblast-specific secreted protein expressed by mature osteoblasts is used in clinical practice and in research as a marker of bone turnover. OC, has two major forms carboxylated (cOC) and undercarboxylated (ucOC) and each form has a different biological function including bone remodelling and glucose metabolism. Reference ranges for cOC and ucOC across the adult lifespan are not clear and current reference intervals for ucOC are limited to older men. Given the different physiological roles of cOC and ucOC, development of reference ranges of the total OC (tOC) and different forms may help to identify people who are at risk for future bone or metabolic conditions.

Methods: Blood was collected in the morning after an overnight fast from 236 community dwelling men (18 to 92 years old). Participants did not have a history of diabetes,  antiresorptive, warfarin or glucocorticoid use. Serum was analysed for tOC and the ucOC fraction using the hydroxyapatite binding method. cOC, ucOC/OC and cOC/OC ratios were calculated. Reference intervals were established by polynomial quantile regression analysis.

Results: The normal range for our reference population of young men (≤30 years), was: tOC 17.9-56.8 ng/mL, ucOC 7.1- 22.0 ng/mL, cOC 8.51-40.3 ng/mL (mean and 95% CI). Aging had a significant effect on tOC, ucOC and cOC which reflected a “U” shape pattern. The ucOC/OC ratio increases with increasing age while cOC/OC ratio decreases with age. Body mass index (BMI) explained 4% of the variance in the ratios, while age explained  31% of the variance.

Conclusions: We have defined reference ranges for the OC-forms across the adult male lifespan and demonstrated OC-ratios better reflect the effects of aging on OC-forms.