Vitamin D deficiency and genetic polymorphisms of Vitamin D-associated genes in Parkinson's Disease

Parkinson’s Disease (PD) and vitamin D share a unique link as Vitamin D deficiency (VDD) prevails in PD. Thus, an in-depth understanding of Vitamin D biology in PD might be crucial for therapeutic strategies emphasizing Vitamin D. Specifically, explicating the effect of VDD and genetic polymorphisms of vitamin D-associated genes in PD, like VDR (Vitamin D Receptor) or GC (Vitamin D Binding Protein), may aid the process along with polymorphisms of Vitamin D metabolizing genes (e.g., CYP2R1, CYP27A1) in PD. Literature review of single nucleotide polymorphisms (SNPs) related to Vitamin D levels [GC (GC1-rs7041, GC2-rs4588), CYP2R1, CYP24A1, CYP27B1] and Vitamin D function [VDR (FokI - rs2228570, ApaI - rs7976091, BsmI-rs1544410, TaqI-rs731236)] was conducted to explore their relationship with PD severity globally. Furthermore, the DisGeNET database was utilized to explore the gene-disease associations in PD, and STRING alongside Cytoscape was utilized to identify critical genes associated with PD. VDR-FokI polymorphism was reported to be significantly associated with PD in Hungarian, Chinese, and Japanese populations, whereas VDR-ApaI polymorphism was found to affect PD in the Iranian population. However, VDR-TaqI and BsmI polymorphisms had no significant association with PD severity. Conversely, GC1 polymorphisms reportedly affected Vitamin D levels without influencing the disease severity. CYP2R1 (excluding rs1993116) was also reportedly linked to clinical manifestations of PD. Genetic polymorphisms might cause VDD despite enough sunlight exposure and vitamin D-rich food intake, enhancing inflammation, and thereby influencing PD pathophysiology. Knowledge of the polymorphisms associated with vitamin D appears promising for developing new therapeutic strategies against PD.