Osteocalcin is negatively associated with C-reactive protein and positively associated with systolic blood pressure in Chinese women

Background: Inflammation exacerbates age-related diseases such as osteoporosis, type 2 diabetes and atherosclerosis. Osteocalcin (OCN), a bone formation marker, can suppress inflammation to improve bone and glucose metabolism. Increase in osteoblast activity is also associated with vascular calcification, which in turn contributes to vascular stiffness and elevated systolic blood pressure (SBP). Aim: To investigate the association of OCN with the inflammation marker C-reactive protein (CRP) and with SBP. Methods: The study subjects comprised 160 women (age 21–81 years) with normal glucose tolerance (NGT) and normal blood pressure (NBP). Serum OCN, fasting plasma glucose, and 2 h post-challenge glucose levels during oral glucose tolerance test, fasting insulin, glycated hemoglobin A1c (HbA1c), hepatic and renal functions, electrolytes, CRP, SBP and diastolic pressure were measured. Results: Serum OCN was negatively associated with CRP (r=–0.107, P=0.001) and positively associated with SBP after adjustment for confounding factors (r=0.23, P=0.003). Age (r=0.094, P=0.005), body mass index (r=–0.498, P=0.005) and SBP (r=0.132, P=0.029) were the major determinants of the variations of OCN (adjusted R2 = 0.608, P=0.01). When SBP was used as a dependent variable, age (β =0.344, P=0.001), body weight (r=0.303, P=0.001), fasting plasma glucose OCN (r=0.209, P=0.049), entered the regression model (adjusted R2 = 0.420, P=0.028). Compared with the lowest SBP group, there was an increase in OCN between the groups (P=0.001), and the highest OCN levels were observed in subjects in the highest SBP group, even when multiple confounders were adjusted (P=0.015). Conclusions: The bone formation marker, serum OCN, was negatively associated with CRP and positively associated with SBP in NGT and NBP women. Whether the increased OCN level in NGT and NBP subjects is an early marker predicting the subtle rise in blood pressure and the risk of occurrence of hypertension requires further study.