Baseline osteocalcin levels and incident diabetes in a 3-year prospective study of high-risk individuals

Abstract

Aim: Experimental evidence suggests that osteocalcin is a key messenger that affects both adipocytes and insulin-producing β cells. Epidemiological cross-sectional studies have shown a negative association between plasma levels of osteocalcin and glucose. For this reason, the hypothesis that lower baseline osteocalcin plasma levels are associated with diabetes was prospectively tested.

Methods: The study population consisted of individuals at high risk for type 2 diabetes who were screened for participation in the Greek arm of a European type 2 diabetes prevention study (the DE-PLAN study). All participants were free of diabetes at baseline and underwent a second evaluation 3 years later. Diabetes status was defined according to an oral glucose tolerance test.

Results: A total of 307 subjects were included in the present analysis. The population, including 154 men (50.3%), was middle-aged (54.4 ± 10.2 years) and overweight (BMI: 29.5 ± 4.9 kg/m(2)). At baseline, mean total plasma osteocalcin was lower in those with impaired fasting glucose and/or impaired glucose tolerance compared with those with normal glucose tolerance (6.0 ± 3.1 ng/mL vs. 7.3 ± 4.0 ng/mL, respectively; P = 0.01). After 3 years, 36 subjects had developed diabetes. In the prospective evaluation, there was no association between baseline osteocalcin levels and diabetes (OR: 1.04 per 1 ng/mL, 95% CI: 0.93-1.15; P = 0.49) on multivariable logistic regression analysis, nor was there any correlation with changes in plasma glucose after 3 years (r = 0.09, P = 0.38).

Conclusion: Our prospective results show that lower levels of circulating osteocalcin do not predict future diabetes development and, in contrast to most cross-sectional published data so far, suggest that this molecule may not be playing a major role in glucose homoeostasis in humans.

Keywords: Bone density; Osteocalcin; Type 2 diabetes.