Vitamin D and Parkinson's disease.

Parkinson's disease (PD) is the second most common form of neurodegeneration among the elderly population. PD is clinically characterized by tremors, rigidity, slowness of movement, and postural imbalance. Interestingly, a significant association has been demonstrated between PD and low levels of vitamin D in the serum, and vitamin D supplement appears to have a beneficial clinical effect on PD. Genetic studies have provided the opportunity to determine which proteins link vitamin D to PD pathology, e.g., Nurr1 gene, toll-like receptor, gene related to lipid disorders, vascular endothelial factor, tyrosine hydroxylase, and angiogenin. Vitamin D also exerts its effects on cancer through nongenomic factors, e.g., bacillus Calmette-Guerin vaccination, interleukin-10, Wntβ-catenin signaling pathways, mitogen-activated protein kinase pathways, and the reduced form of the nicotinamide adenine dinucleotide phosphate. In conclusion, vitamin D might have a beneficial role in PD. Calcitriol is best used for PD because it is the active form of the vitamin D(3) metabolite and modulates inflammatory cytokine expression. Further investigation with calcitriol in PD is needed.