Osteocalcin, adipokines and their associations with glucose metabolism in type 1 diabetes

To determine osteocalcin (OC) and adipokines in type 1 diabetes (T1D) and healthy controls, and to explore possible associations between glucose and bone metabolism, body composition and adipokines. Serum levels of total OC, undercarboxylated (UC-OC), leptin, adiponectin, and other parameters of glucose and bone metabolism were measured in 128 patients with T1D (mean duration 21.2years) and in 77 healthy controls, matched for gender, age, and body mass index (BMI). Partial correlations (adjusted for age and gender) with parameters of body composition (BMI, fat body mass [derived from bone mineral density scans]), glycaemic control (hemoglobin A1c (HbA1c), daily insulin dose in T1D), skeletal homeostasis (osteoprotegerin (OPG), receptor activator of NF-κB ligand (RANKL), all measured in serum), and serum insulin-like growth factor 1 (IGF-1) were also examined. Independent predictors of total and UC-OC were then explored. Total OC was lower in males with T1D (16.3±6.4 vs. 22.2±9.9ng/ml; p=0.001), whereas UC-OC did not show group differences. Adiponectin was higher in T1D patients, both for males and females (8.9±6.6 vs. 5.7±2.5μg/ml; p=0.004 and 13.8±6.4 vs. 8.8±4.0μg/ml; p<0.001). IGF-1 was lower only in females with T1D (146.6±68.8 vs. 203.0±74.4ng/ml; p<0.001). BMI and fat body mass were similar in T1D and controls. In T1D patients, total OC was inversely correlated with BMI and HbA1c, and UC-OC inversely correlated with HbA1c. In T1D patients, leptin positively correlated with BMI, fat body mass and daily insulin dose, while adiponectin inversely correlated with BMI and daily insulin dose. Multivariate regression modelling showed that determinants of higher total OC levels were male gender (p=0.04, ß-coefficient=2.865) and lower HbA1c (p=0.04, ß-coefficient=-0.117), whereas determinants of UC-OC levels were T1D (p=0.016, ß-coefficient=2.015), higher IGF-1 (p=0.004, ß-coefficient=0.011) and lower HbA1c (p=0.011, ß-coefficient=- 0.061). Total OC and UC-OC are associated with good glycaemic control in T1D, with gender-specific differences for total-OC. The association of leptin and adiponectin with glycaemic control, as observed in controls, does not seem to be a feature in T1D, although both adipokines appear to be related to the insulin demand. This article is part of a Special Issue entitled "Bone and diabetes".