Vitamin D Binding Protein Isoforms and Vitamin D Levels in Diabetes Patients

Abstract

Vitamin D binding protein (DBP) is the primary transport protein for the multiple forms of vitamin D in the body. Variations in the structure of DBP can affect the binding affinity with vitamin D, which can result in a vitamin D deficiency. Vitamin D deficiency is seen in various autoimmune disorders such as rheumatoid arthritis, systemic lupus erythematosus, and diabetes mellitus type 1 (DM1). The increasing prevalence of autoimmune disorders highlights the importance of identifying possible associations with deficient vitamin D serum levels. The objective of this research was to examine the relationship between the serum concentration of 25-hydroxyvitamin D and the concentration of the specific DBP isoforms in diabetic individuals. Vitamin D concentrations were measured using an EIA method, DBP concentrations were measured using an ELISA test, and the likely DBP isoform was determined using SNP TaqMan® analysis. Diabetic participants were compared to control participants. Allele frequencies were consistent with the standard European Ancestry reference population. A Mann Whitney U test revealed no significant difference among the DBP isoform values between the diabetic group and control population. Linear regression showed no correlation between DBP levels and vitamin D levels (R²=0.3402). There was no observed dosage effect in individuals having one or two copies of the mutant allele to the levels of DBP and vitamin D. DBP isoforms and concentrations of DBP had no effect on vitamin D concentrations in our DM1 testing population.

ABBREVIATIONS: DBP - Vitamin D binding protein, DM1 - Diabetes mellitus type 1