Endocrine Abstracts

Introduction: Vitamin D insufficiency is common in subjects with type 2 diabetes. Observational studies suggest that vitamin D plays a role in the pathogenesis of type 2 diabetes. However, results of intervention studies have been inconsistent. We investigated the effects of improving vitamin D status on insulin sensitivity and inflammatory markers in type 2 diabetic patients with vitamin D insufficiency.

Methods: A double blind, randomized, placebo controlled, intervention study was conducted. Sixteen patients with type 2 diabetes and vitamin D insufficiency (≤50 nmol/l) were recruited. Eight patients were randomized to supplementation with cholecalciferol for 12 weeks (11 200 IU (280 μg) daily for 2 weeks followed by 5600 IU (140 μg) daily for 10 weeks), and eight patients received identical placebo tablets for 12 weeks. To assess insulin sensitivity the hyperinsulinemic euglycemic clamp method was used. DEXA scan, 24-h-ambulatory blood pressure monitoring (ABPM) and fasting blood samples were performed at baseline and at the end of the 12 weeks intervention.

Results: Serum levels of 25(OH)vitamin D and 1,25(OH)₂vitamin D after 12 weeks increased significantly from baseline values in the intervention group (P=0.01 and P=0.004). Serum 25OHD concentrations increased from 31.0±4.9 nmol/l at baseline to 104.9±19.0 nmol/l in the intervention group, whereas a decrease from 34.8±3.8 to 32.1±3.4 nmol/l was observed in the placebo group. The change in serum 25OHD concentrations between the two groups differed significantly (P=0.02). However no significant changes in insulin sensitivity (M-value), inflammation, blood pressure, lipid profile, or HbA1c were found.

Conclusions: Significant improvement in vitamin D status after 12 weeks treatment with colecalciferol does not reduce insulin resistance, blood pressure, inflammation or glycosylated haemoglobin in patients with established type 2 diabetes.

Grey circles = Placebo, black = Vitamin D. Δ Vitamin D vs. Δ placebo: P=0.431 Blue line = Mean value Vitamin D, Red line = Mean value Placebo.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.