The Role of Vitamin D in Neuroprotection in Multiple Sclerosis: An Update

Multiple sclerosis (MS) is a complex neurological condition that involves both inflammatory demyelinating and neurodegenerative components. MS research and treatments have traditionally focused on immunomodulation, with less investigation of neuroprotection, and this holds true for the role of vitamin D in MS. Researchers have already established that vitamin D plays an anti-inflammatory role in modulating the immune system in MS. More recently, researchers have begun investigating the potential neuroprotective role of vitamin D in MS. The active form of vitamin D, 1,25(OH)₂D₃, has a range of neuroprotective properties, which may be important in remyelination and/or the prevention of demyelination. The most notable finding relevant to MS is that 1,25(OH)₂D₃ promotes stem cell proliferation and drives the differentiation of neural stem cells into oligodendrocytes, which carry out remyelination. In addition, 1,25(OH)₂D₃ counteracts neurodegeneration and oxidative stress by suppressing the activation of reactive astrocytes and M1 microglia. 1,25(OH)₂D₃ also promotes the expression of various neuroprotective factors, including neurotrophins and antioxidant enzymes. 1,25(OH)₂D₃ decreases blood-brain barrier permeability, reducing leukocyte recruitment into the central nervous system. These neuroprotective effects, stimulated by 1,25(OH)₂D₃, all enhance neuronal survival. This review summarizes and connects the current evidence supporting the vitamin D-mediated mechanisms of action for neuroprotection in MS.

The protective role of interaction between vitamin D, sex hormones and calcium in multiple sclerosis

Multiple sclerosis (MS) is a neurological disorder that causes disability and paralysis, especially among young adults. Although interactions of several factors, such as viral infections, autoimmunity, genetic and environmental factors, performance a role in the beginning and progression of the disease, the exact cause of MS is unknown to date. Different immune cells such as Th1 and Th17 play an impressive role in the immunopathogenesis of MS, while, regulatory cells such as Th2 and Treg diminish the severity of the illness. Sex hormones have a vital role in many autoimmune disorders, including multiple sclerosis. Testosterone, estrogen and progesterone have various roles in the progress of MS, which higher prevalence of disease in women and more severe in men reveals the importance of sex hormones' role in this disease. Vitamin D after chemical changes in the body, as an active hormone called calcitriol, plays an important role in regulating immune responses and improves MS by modulating the immune system. The optimum level of calcium in the body with vitamin D modulates immune responses and calcium as an essential ion in the body plays a key role in the treatment of autoimmune diseases. The interaction between vitamin D and sex hormones has protective and therapeutic effects against MS and functional synergy between estrogen and calcitriol occurs in disease recovery. Moreover, vitamin D and calcium interact with each other to regulate the immune system and shift them to anti-inflammatory responses.

ApaI, BsmI and TaqI VDR gene polymorphisms in association with multiple sclerosis in Slovaks

OBJECTIVE

Vitamin D acts through vitamin D receptor (VDR) and has promising beneficial effects in the development and progression of multiple sclerosis (MS). The purpose of our study was to investigate the possible association of the VDR gene polymorphisms ApaI, BsmI and TaqI with the MS susceptibility and with the rate of disease disability progression in the Central European Slovak population.

METHODS

The allele and genotype variants of ApaI, TaqI and BsmI VDR gene polymorphisms were analysed in 270 clinically diagnosed MS patients and 303 healthy controls. Genotyping was performed by polymerase chain reaction and restriction analysis. Patients were stratified by the rate of disease disability progression using MSSS scores.

RESULTS

By logistic regression analysis, we revealed that genotype BB (AA) of BsmI VDR gene polymorphism is decreasing the risk of MS (BB (AA) vs Bb (AG) + bb (GG); OR = 0.59, 95% CI = 0.39-0.90, plog = 0.014). We did not identify any association of ApaI and TaqI polymorphisms neither with MS development nor with the disease progression.

DISCUSSION

We showed for the first time that BsmI genotype BB (AA) is associated with the decreased susceptibility to MS in Slovak population. We propose the BsmI gene polymorphism to be one of the important genetic markers in evaluation of the risk of MS. However, our data suggest that VDR gene polymorphisms ApaI, BsmI and TaqI are not useful in the prediction of disease disability progression rate in MS in Slovaks.