Association between Serum Total Osteocalcin Level and Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

Studies on the association between serum total osteocalcin level and type 2 diabetes mellitus (T2DM) had reported controversial results. The aim of this study was to comprehensively assess this association through a meta-analysis. Eligible articles were identified in electronic databases from their inception through May 1, 2015. To assess the relationship between serum total osteocalcin and T2DM, a meta-analysis was performed to determine whether total osteocalcin differed obviously between individuals with and without T2DM, and whether serum total osteocalcin level was associated with the risk of T2DM. The standardized mean difference (SMD) and their 95% confidence intervals (95% CIs) for total osteocalcin between individuals with and without T2DM, and pooled odds ratios (ORs) and their 95% CI for the T2DM risk were calculated by meta-analysis. Twenty-four papers fulfilled the inclusion criteria. From the pooled data, the total osteocalcin level was significantly lower among T2DM patients than controls (SMD: - 2.87; 95% CI-3.76 to - 1.98; p<0.00001), and high total osteocalcin level was significantly and independently associated with decreased risk of T2DM (OR=0.70, 95% CI 0.56-0.88; p=0.002). There was no evidence for publication bias. Serum total osteocalcin level is significantly lower in T2DM patients than controls, and total osteocalcin is inversely associated with the development of T2DM.