Indian ASD probands with 25(OH)D and vitamin D binding protein deficiency exhibited higher severity

The severity of autism spectrum disorder (ASD) shows wide variations, though the reason remains unclear. Vitamin D (VitD) deficiency is considered a risk factor for ASD and its supplementation was reported to reduce symptom severity. Since VitD, either synthesized in the skin or absorbed from the food, is transported to the liver by the vitamin D binding protein (DBP), we have analyzed DBP genetic polymorphisms [rs7041 (A/C), rs4588 (G/T), and rs3755967 (C/T)] affecting DBP function [Case = 411; Control = 397], levels of plasma 25(OH)D and DBP [Case = 25; Control = 26], and DBP mRNA expression [Case = 74; Control = 44] in a group of Indo-Caucasoid ASD probands and neurotypical subjects. ASD probands with rs7041'CC', rs4588 'TT', and rs3755967 'TT' genotypes exhibited higher scores for a few traits. Scores for Imitation and Listening response were also higher in the presence of the "A-T" haplotype (rs7041-rs4588). Plasma 25(OH)D and DBP levels as well as DBP mRNA expressions were significantly lower in the ASD probands as compared to the neurotypical subjects. We infer that DBP deficiency, in the presence of risk genetic variants, could be one of the reasons for the reported 25(OH)D deficiency of the ASD probands.