Low serum osteocalcin levels are associated with diabetes mellitus in glucocorticoid treated patients.

Abstract

Osteocalcin (OC) is involved in the regulation of glucose homeostasis. Glucocorticoid (GC) treatment is associated with impaired osteoblast function, decreased OC levels, and the development and/or worsening of pre-existing diabetes mellitus (DM). Whether decreased OC levels in GC-treated subjects contribute to DM is not well known. The aim of this study was to analyse whether OC levels in GC-treated patients are associated with the presence of DM. One hundred twenty-seven patients (aged 61.5 ± 17.9years) on GC treatment were included. GC dose, treatment duration, presence of DM and bone formation (OC, bone ALP, PINP) and resorption markers (urinary NTX, serum CTX) were analysed. The cut-offs of each bone turnover marker (BTM) for the presence of DM were evaluated and optimised with the Youden index and included in the logistic regression analysis. Among the patients, 17.3% presented DM. No differences were observed in GC dose or duration or the presence of fractures. Diabetics showed lower levels of OC (7.57 ± 1.01 vs. 11.56 ± 1; p < 0.001), PINP (21.48 ± 1.01 vs. 28.39 ± 1; p = 0.0048), NTX (24.91 ± 1.01 vs. 31.7 ± 1; p = 0.036) and CTX (0.2 ± 1.01 vs. 0.3 ± 1; p = 0.0016). The discriminating BTM cut-offs for DM presence were < 9.25ng/mL for OC, < 24ng/mL for PINP, < 27.5nMol/mM for NTX and < 0.25ng/mL for CTX. In a multivariate logistic regression model adjusted for GC dose, BMI, age and the above four BTMs, only OC remained independently associated with DM presence. Thus, in a model adjusted for GC dose, BMI and age, OC was significantly associated with DM (OR: 6.1; 95%CI 1.87-19.89; p = 0.001). Decreased OC levels in GC-treated patients are associated with increased odds of DM, and only OC was independently associated with DM in a model including four BTMs.