Osteocalcin: pathophysiological links and clinical considerations in orthogeriatric patients with and without diabetes mellitus

Aims: To investigate the relationship between osteocalcin (OC), an osteoblast-specific protein, clinical characteristics and outcomes in orthogeriatric patients with and without type 2 diabetes mellitus (DM). Methods: Data from 206 older (>60 years) patients with DM (mean age 77.0 8.8 years, 60.2% women) and 450 patients without DM (mean age 78.1 10.2 years, 72.6% women) admitted to the orthopaedic unit of our hospital in 20122014 were used. Total OC, procollagen 1N-terminal propeptide (P1NP), C-terminal telopeptide of type 1 collagen (CTX) were measured by immunoassay. Correlations between OC, clinical and laboratory variables were explored. Results: In DM and non-DM groups the mean values of OC were similar (6.30 4.67 vs. 5.99 3.83 lg/L, p = 0.379) and not associated with presence of hip or any fracture; on multivariate logistic regression the independent correlates of OC were P1NP and CTX (positive) and GFR (negative). No significant differences in mean OC concentrations were observed when the DM patients were analysed by glycaemic control (HbA1c levels) or type of treatment regiments. In both groups, there was a strong positive association between OC and prolonged (>20 days) length of hospital stay (LOS, r = 0.779, p < 0.001, and r = 0.763, p < 0.001, respectively) and a negative association with the peak CRP levels (r = 0.229, p = 0.001, and r = 0.136, p = 0.004). In DM patients OC also significantly correlated with the total LOS (r = 0.143, p = 0.042) and in-hospital mortality (r = 0.156, p = 0.025). Conclusions: In orthogeriatric patients total OC is not associated with type 2 DM, HbA1c levels and fractures, but may predict prolonged LOS, high post-operative inflammatory response and in-hospital mortality for DM patients.