Alterations in Circulating Levels of Vitamin D Binding Protein, Total and Bioavailability of Vitamin D in Diabetes Retinopathy Patients

Abstract AimsThe aims of this study were to investigate the association between circulating levels of vitamin D binding protein (VDBP) and its genotypes and diabetic retinopathy risk.MethodsIn this study, 154 patients with type 2 diabetes mellitus; 62 with diabetic retinopathy (DR) and 92 without DR/and or diabetic nephropathy (DN), were recruited. Circulating levels of 25-hydroxyvitamin D3 and VDBP levels were measured in the patients. The genotype and phenotype of VDBP were evaluated based on two common VDBP variations; rs7041 and rs4588.ResultsSerum levels of VDBP were significantly lower in patients with DR than in patients without DR/and or DN (Ln-VDBP (μg/ml): 6.14±0.92 vs. 6.73±1.45, p = 0.001) even after adjustment for age, sex, body mass index, disease duration, eGFR, HbA1C, and serum levels of 25(OH)D. The distribution of VDBP phenotypes and genotypes in the two studied groups were nearly the same, and the distribution was similar to that of the general population.Conclusions In this study, we found out the association between lower levels of VDBP and risk of DR. However, the precise mechanism linking these two remains unknown. Further and more in-depth research to find out the underlying causes of the relationship is needed.