Vitamin D and glycemic control in diabetes mellitus type 2

Objectives: The extraskeletal effects of vitamin D have attracted considerable interest. Vitamin D deficiency appears to be related to the development of diabetes mellitus type 2 and the metabolic syndrome. Vitamin D may affect glucose homeostasis, vitamin D levels having been found to be inversely related to glycosylated hemoglobin levels in gestational diabetes mellitus. In addition, vitamin D appears to protect from the development of gestational diabetes mellitus. The aim was to study levels of 25-hydroxy vitamin D-3 [25(OH)D-3] and the relationship between 25(OH)D-3 levels and glycemic control in patients with diabetes mellitus type 2. Methods: Glycosylated hemoglobin (HbA1(c)) and 25(OH) D3 levels were measured in a group of 120 diabetes mellitus type 2 patients. The same measurements were performed in a group of 120 control subjects of the same age and sex. 25(OH)D-3 was measured by radioimmunoassay and glycosylated hemoglobin (HbA1(c)) was measured by high-performance liquid chromatography. Results: 25(OH)D-3 levels were lower in the diabetes mellitus type 2 patients than in the control group, being 19.26 +/- 0.95 ng/ml and 25.49 +/- 1.02 ng/ml, in the patient and control groups, respectively (p < 0.001, Student's t-test). 25( OH) D-3 levels were found to be inversely associated with HbA1c levels in the diabetic patients (p = 0.008, r(2) = 0.058, linear regression). 25(OH) D-3 levels were found to be inversely associated with HbA1c when the patient and control groups were analysed together (p < 0.001, r(2) = 0.086). Conclusions: Vitamin D levels appeared to be lower in diabetes mellitus type 2 patients than in the control group, vitamin D levels being related to glycemic control in diabetes mellitus type 2. These findings may have therapeutic implications as cautious vitamin D supplementation may improve glycemic control in diabetes mellitus type 2.