Bone metabolism and glucose control in children and adolescents with T1DM

Objectives: Experimental studies suggested that undercarboxylated osteocalcin (GluOC) is directly related to insulin sensitivity and secretion. Aim of the present study was to evaluate whether in type 1diabetic children and adolescents the glycemic control is influenced by the bone metabolism. Methods: We studied 79 DMT1 patients (45 male), age 14(7) years, disease duration 59(49) months, HbA1c 7.8(1.2)%, insulin requirement 0.8(0.3) U/kg/day; 12 patients were treated with CSII and 57 with MDI. In all patients we measured: height (H), weight, waist circumference (WC), L2-L4 spine and total bodyBMD(evaluated by DXA), serum levels of calcium, phosphate, magnesium, alkaline phosphatase, PTH, 25-OH-D, undercarboxylated (GluOC) and carboxylated osteocalcin (GlaOC). Data are reported as median (IQR). Mann–Whitney, simple and multiple regressions were used for statistical analysis. Results: We divided our patients according to the metabolic control in two groups: Group A (good control – HbA1c ≤7.5%) and Group B (poor control – HbA1c >7.5%). Group B showed significantly lower levels of 25-hydroxy vitamin D (23.6 ng/ml (12.6) vs. 18.6 ng/ml (13.2); p < 0.01). Alkaline phosphatase resulted inversely correlated to GluOC adjusted for age (p < 0.05) and to GluOC/GlaOC ratio (p < 0.01). L2-L4 (p < 0.0001) and total body (p < 0.0002) BMD ZScore were both highly directly correlated to SDS-BMI.WC/H ratio resulted directly correlated to GluOC/GlaOC ratio (p < 0.01) and inversely correlated to GlaOC adjusted for age (p < 0.01). Conclusion: Our results support the hypothesis of a favorable effect of vitamin D on insulin/glucose balance in children and adolescents with T1DM, with no evidence of significant effect of exogenous insulin and metabolic control on osteocalcin levels and bone density. Furthermore our study confirms inverse correlation between osteocalcin and visceral fat, previously reported both in mice and humans.