Identification of a Single Nucleotide Polymorphism of Vitamin D Receptor (VDR) and Vitamin D Binding Protein (VDBP) Gene and Its Dysregulated Pathway Through VDR-VDBP Interaction Network Analysis in Vitamin D-Deficient Infertile Females.

INTRODUCTION: The prevalence of female infertility in Pakistan is currently estimated at 22%, and emerging research suggests that vitamin D (VD) deficiency (VDD) may play a significant role in influencing female fertility. The focus of this study was to investigate the single nucleotide polymorphism (SNP) patterns within the VD binding protein (VDBP). The study aimed to explore dysregulated pathways and gene enrichment through an interaction network analysis, specifically focusing on the interplay between the VD receptor (VDR) and VDBP in females experiencing unexplained infertility (UI) coupled with VDD.

METHODS: A cross-sectional study was conducted on VD-deficient, fertile, and UI female subjects. VDBP and VDR were assessed by enzyme-linked immunoassay and genotyping performed. FunRich (version 3.1.3; https://funrich.org/index.html) was employed for analysis of the identified proteins: VDR and VDBP and with their mapped gene datasets, gene enrichment, and protein-protein interaction (PPI) network.

RESULTS: The mean VD and VDR values of infertile females were significantly lower than those of fertile females. VDBP in infertile females (median (IQR)): 296.05 (232.58-420.23)) was lower than that of fertile females (469.9 (269.57-875.55), (p=0.01)). On sequence analysis, a mutation rs 4588 SNP (Thr 436 Lys) was found in exon 11 of the VDBP gene of UI females, but no mutation in exons 8 and 9 of the VDR gene, with some insignificant intronic variants, was observed. The proteins such as plasma membrane estrogen receptor signaling pathway (p < 0.001), VDR, SMAD3, NCOR1, CREBBP, NCOA1, STAT1, GRB2, PPP2CA, TP53, and NCOA2 were enriched after biological pathway grouping when VDR was made the focused gene and directly interacting with VDBP.

CONCLUSION: The females with UI exhibited significantly low VD, VDBP, and VDR. The plasma membrane estrogen receptor signaling pathway was enriched in VDD infertile females.