Endocrine Abstracts

Background: Type 2 DM is a disease caused by both insulin resistance and an insulin secretory defect.

Reports suggest that vitamin D supplementation improves insulin resistance and pancreatic beta-cell function, however, there is paucity of data on vitamin D and glycaemia among type 2 diabetes mellitus in Nigeria.

Objective: To determine the effect of vitamin D supplementation on insulin resistance and pancreatic beta-cell function in type 2 DM subjects.

Methods: A single-blind prospective randomized placebo controlled trial, involving type 2 DM participants attending the Diabetes clinic of the Lagos University Teaching Hospital. The study participants consisted of 42 T2DM participants with poor glycaemic control and vitamin D deficiency selected following a prior cross sectional study on 114 type 2 DM participants for determination of vitamin D status and glycaemia. These participants were randomized into two equal groups of treatment and a placebo arms.

Levels of serum vitamin D, fasting glucose, HbA1c, calcium, albumin, phosphate, serum insulin, creatinine and alanine transaminase were determined. Vitamin D₃ supplements (3000 IU daily) were given to the participants in the treatment arm and placebo given to the placebo arm. Insulin resistance and pancreatic beta-cell function were determined at baseline and after 12 weeks of vitamin D₃ supplementation.

Results: There was a reduction from baseline in the mean insulin resistance level in both the treatment and placebo groups. However, this reduction was only statistically significant in the Treatment group (P<0.01). The proportion of subjects with improvement in insulin resistance status (HOMA-IR<2) was significantly higher in the treatment arm, P<0.05.

There was a reduction in the mean insulin secretory capacity in the treatment group (Z=−0.402; P=0.29) while it increased in the placebo group (Z=−0.72; P=0.18). This difference was however, not statistically significant.

Conclusion: Vitamin D₃ supplementation results in a reduction in insulin resistance but no effect on pancreatic beta-cell function in T2DM.