ApaI, BsmI, FokI, and TaqI Polymorphisms in the Vitamin D Receptor Gene and Parkinson's Disease

Immunomodulatory actions of vitamin D in various immune-related disorders: a comprehensive review

For many years, vitamin D has been acknowledged for its role in maintaining calcium and phosphate balance. However, in recent years, research has assessed its immunomodulatory role and come up with conflicting conclusions. Because the vitamin D receptor is expressed in a variety of immune cell types, study into the precise role of this molecule in diseases, notably autoimmune disorders, has been made possible. The physiologically activated version of vitamin D also promotes a tolerogenic immunological condition in addition to modulating innate and acquired immune cell responses. According to a number of recent studies, this important micronutrient plays a complex role in numerous biochemical pathways in the immune system and disorders that are associated with them. Research in this field is still relatively new, and some studies claim that patients with severe autoimmune illnesses frequently have vitamin D deficiencies or insufficiencies. This review seeks to clarify the most recent research on vitamin D's immune system-related roles, including the pathophysiology of major disorders.

Vitamin D: A Potential Mitigation Tool for the Endemic Stage of the COVID-19 Pandemic?

The impact of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic and associated development of clinical symptoms of COVID-19 have presented an enormous global impact on our health care systems, public health and economy. To date several observational epidemiological studies consistently found that vitamin D deficiency, measured as low levels of circulating 25-hydroxyvitamin D, is associated with cardiovascular diseases, diabetes, certain cancers, autoimmune diseases and many infectious diseases, including acute respiratory infections. Since vitamin D is not merely immunosuppressive but also acts as an immunomodulator in tolerance and homeostasis, many experts have considered a role of vitamin D in the prevalence and severity of immune mediated inflammatory diseases, such as SARS-CoV-2, adding to the evidence of the importance of vitamin D in the immune response against viral respiratory infections and reinforcing the need for targeted vitamin D supplementation, with a focus on high-risk populations and a high-dose supplementation treatment for COVID-19 hospitalized patients. The expected transition to endemicity of SARS-CoV-2 even further corroborates as a potential of vitamin D as an potential mitigation tool for the prevention of COVID-19. The aim of this paper is to analyse the current evidence regarding vitamin D and present a hypothesis of its potential role in the current COVID-19 pandemic and in the future as a potential preventive measurement in public health.

Genetic Variability of the Vitamin D Receptor Affects Susceptibility to Parkinson’s Disease and Dopaminergic Treatment Adverse Events

Vitamin D is a lipid-soluble molecule and an important transcriptional regulator in many tissues and organs, including the brain. Its role has been demonstrated also in Parkinson’s disease (PD) pathogenesis. Vitamin D receptor (VDR) is responsible for the initiation of vitamin D signaling cascade. The aim of this study was to assess the associations of VDR genetic variability with PD risk and different PD-related phenotypes. We genotyped 231 well characterized PD patients and 161 healthy blood donors for six VDR single nucleotide polymorphisms, namely rs739837, rs4516035, rs11568820, rs731236, rs2228570, and rs1544410. We observed that VDR rs2228570 is associated with PD risk (p < 0.001). Additionally, we observed associations of specific VDR genotypes with adverse events of dopaminergic treatment. VDR rs1544410 (GG vs. GA + AA: p = 0.005; GG vs. GA: p = 0.009) was associated with the occurrence of visual hallucinations and VDR rs739837 (TT vs. GG: p = 0.036), rs731236 (TT vs. TC + CC: p = 0.011; TT vs. TC: p = 0.028; TT vs. CC: p = 0.035), and rs1544410 (GG vs. GA: p = 0.014) with the occurrence of orthostatic hypotension. We believe that the reported study may support personalized approach to PD treatment, especially in terms of monitoring vitamin D level and vitamin D supplementation in patients with high risk VDR genotypes.

Association of vitamin D receptor gene TaqI polymorphism with Alzheimer's disease in a Southeastern European Caucasian population

The role of vitamin D in Alzheimer's Disease (AD) has been studied over the past years. The results from numerous studies have indicated that the molecular pathways involved in the development of AD are closely related to the molecular pathways of the mechanisms of action of vitamin D. However, only a limited number of studies have described the key role of vitamin D receptor (VDR) in the regulation of the functions of vitamin D and the potential effect of single nucleotide polymorphisms (SNPs) of the VDR gene. Thus, the aim of the present study was to investigate the VDR TaqI polymorphism in relation to AD in a Southeastern European Caucasian (SEC) cohort. Further, the present study aimed to compare the results obtained with those of other AD populations. For this purpose, blood samples from 90 confirmed patients with AD [median age, 74 years; median mini-mental state examination (MMSE) score of 21; median frontal assessment battery (FAB) score of 10] and 103 healthy controls (median age, 57 years) were analyzed to determine the genotypes of TaqI (rs731236) using quantitative PCR. The frequencies (%) of the TaqI TT, TC and CC genotypes in the controls/patients were 34/48.9, 47.6/41.1 and 18.4/10.0, respectively. Statistically significant differences were observed for the TaqI C allele [odds ratio (OR). 0.54; 95% confidence interval (CI), 0.30-0.96; P=0.035], the TaqI TT genotype (OR, 1.86; 95% CI, 1.04-3.32; P=0.035) and the TaqI CC genotype (OR, 0.119; 95% CI, 0.014-0.995; P=0.032,) in relation to the MMSE score <21 in the patient's group. The TaqI TT allele was found to increase the risk of developing AD by 1.86-fold in the SEC population, while the TaqI C allele may act protectively, with a 46% lower risk of developing the disease. Patients with the TaqI CC genotype were found to have an 88% less likelihood of developing severe cognitive impairment based on the MMSE score. On the whole, the present study did not confirm the results of previous studies on the VDR TaqI C allele in patients with AD.

Vitamin D receptor gene polymorphisms and idiopathic Parkinson disease: an Egyptian study

Background

Accumulating data have suggested that vitamin D receptor (VDR) gene is a pretender gene for vulnerability to Parkinson disease (PD). This study aimed to assess the relationship of VDR gene polymorphisms (FokI and ApaI) with PD. Fifty patients suffering from PD and 50 age- and sex-matched healthy controls were included. Unified Parkinson Disease Rating Scale (UPDRS) was done to assess disease severity. Genetic testing for VDR gene single nucleotide polymorphisms (FokI and ApaI) was done using real time polymerase chain reaction (PCR) technique.

Results

Concerning frequency of genes and alleles for vitamin D receptor gene polymorphisms (FokI and ApaI), no statistically significant difference was found between PD patients and controls. AC genotype was associated with younger age and younger age at onset of disease compared to CC and AA genotypes of ApaI gene polymorphisms. CC genotype was significantly positively correlated with fatigue and urine incontinence. VDR gene polymorphisms were not found to be independent predictors for severity of PD after adjustment for possible confounders.

Conclusion

VDR gene polymorphisms are related to the clinical manifestations rather than etiology or severity of idiopathic PD.

VDR Gene Polymorphisms and Cluster Headache Susceptibility: Case-Control Study in a Southeastern European Caucasian Population

Cluster headache (CH) is a severe primary headache disorder with a genetic component, as indicated by family and twin studies. Diurnal and seasonal rhythmicity are key features of the disease and might be related to vitamin D, as low vitamin D levels have been observed in patients with cluster headache. In addition, the vitamin D receptor (VDR) occurs in brain areas and particularly in the hypothalamus. The aim of the present case-control study was to investigate the association of cluster headache susceptibility and clinical phenotypes with the VDR gene polymorphisms FokI, BsmI and TaqI in a Southeastern European Caucasian population. DNA was extracted from 131 unrelated CH patients and 282 non-headache controls and genotyped using real-time PCR (melting curve analysis). Linkage disequilibrium (LD) analysis confirmed that BsmI and TaqI, both located in the 3'UTR of the VDR gene, are in strong LD. Genotype and allele frequency distribution analysis of the VDR FokI, BsmI, and TaqI polymorphisms showed no statistically significant difference between cases and controls, whereas haplotype analysis indicated that the TAC haplotype might be associated with decreased cluster headache susceptibility. Intra-patient analysis according to diverse clinical phenotypes showed an association of the BsmI GG and TaqI TT genotypes with more frequent occurrence of CH attacks in this cohort. Therefore, a possible association was observed between VDR gene polymorphisms BsmI and TaqI or a linked locus and susceptibility for cluster headache development and altered clinical phenotypes in the Southeastern European Caucasian study population. Further large-scale replication studies are needed to validate these findings.

The VDR FokI (rs2228570) polymorphism is involved in Parkinson's disease

The etiology of Parkinson's disease (PD) is presumably multifactorial and likely involves interactions between genetic and environmental factors, as well as mitochondrial dysfunction, oxidative stress and inflammation. Among environmental factors, Vitamin D was reported to associate with the risk of PD. Vitamin D activity is mediated by its binding to the vitamin D Receptor (VDR), a transcriptional factor for almost 3% of human genes. We genotyped for ApaI, BsmI, TaqI, FokI and rs1989969 VDR single nucleotide polymorphisms (SNPs) a cohort of 406 PD and 800 healthy controls (HC) and found a strong association between the FokI (rs2228570) VDR SNP and PD. Thus, the TT genotype and the T allele resulted associated with PD in the overall analyzed PD population. Gender-based stratification of data indicated that results were maintained for FokI TT genotype and T allele in male PD patients, whereas the FokI T allele alone was confirmed as a risk factor for PD in females. Co-segregation analyses indicated the TaqI ApaI FokI rs1989969 GCTG as a "risk" haplotype for PD. In a subgroup of patients and controls neural Vitamin D and VDR concentration was analyzed in extravesicles (NDEVs) isolated from peripheral blood: no differences emerged between PD and HC. NDEVs results will need to be validated in ampler cohort but we can speculate that, if at neuronal level the amounts of Vitamin D and of VDR are comparable, than the bioavailability of vitamin D and the efficacy of the vitamin D/VDR axis is differentially modulated in PD by VDR SNPs.

The relationships of vitamin D, vitamin D receptor gene polymorphisms, and vitamin D supplementation with Parkinson's disease

In recent years, many studies have investigated the correlations between Parkinson's disease (PD) and vitamin D status, but the conclusion remains elusive. The present review focuses on the associations between PD and serum vitamin D levels by reviewing studies on the associations of PD with serum vitamin D levels and vitamin D receptor (VDR) gene polymorphisms from PubMed, Web of Science, Cochrane Library, and Embase databases. We found that PD patients have lower vitamin D levels than healthy controls and that the vitamin D concentrations are negatively correlated with PD risk and severity. Furthermore, higher vitamin D concentrations are linked to better cognitive function and mood in PD patients. Findings on the relationship between VDR gene polymorphisms and the risk of PD are inconsistent, but the FokI (C/T) polymorphism is significantly linked with PD. The occurrence of FokI (C/T) gene polymorphism may influence the risk, severity, and cognitive ability of PD patients, while also possibly influencing the effect of Vitamin D3 supplementation in PD patients. In view of the neuroprotective effects of vitamin D and the close association between vitamin D and dopaminergic neurotransmission, interventional prospective studies on vitamin D supplementation in PD patients should be conducted in the future.

A Review of the Relationship Between Vitamin D and Parkinson Disease Symptoms

Vitamin D is a fat-soluble secosteroid that exerts its effects by binding to the vitamin D receptor (VDR), through which it directly and indirectly modulates the expression of hundreds to thousands of genes. While originally known for its role in regulating calcium homeostasis and metabolism, vitamin D is now associated with many other health conditions, including Parkinson's disease (PD). A high prevalence of vitamin D deficiency has been noted in PD for at least the past two decades. These findings, along with the discovery that the VDR and 1α-hydroxylase, the enzyme that converts vitamin D to its active form, are highly expressed in the substantia nigra, led to the hypothesis that inadequate levels of circulating vitamin D may lead to dysfunction or cell death within the substantia nigra. Studies investigating the relationship between vitamin D status and PD, however, have been inconsistent. Two prospective studies examined the association between mid-life vitamin D levels and risk of PD and produced conflicting results-one demonstrated an increased risk for PD with lower mid-life vitamin D levels, and the other showed no association between vitamin D and PD risk. One of the most consistent findings in the literature is the inverse association between serum vitamin D level and motor symptom severity in cross-sectional studies. While these data suggest that vitamin D may modify the disease, another likely explanation is confounding due to limited mobility. Fall risk has been associated with vitamin D in PD, but more study is needed to determine if supplementation decreases falls, which has been demonstrated in the general population. The association between vitamin D and non-motor symptoms is less clear. There is some evidence that vitamin D is associated with verbal fluency and verbal memory in PD. Studies in PD have also shown associations between vitamin D status and mood, orthostatic hypotension and olfactory impairment in PD. While more research is needed, given the numerous potential benefits and limited risks, vitamin D level assessment in PD patients and supplementation for those with deficiency and insufficiency seems justified.

Association between vitamin D receptor polymorphisms and susceptibility to Parkinson's disease: An updated meta-analysis

The relationships between vitamin D receptor (VDR) gene polymorphisms, particularly ApaI, BsmI, FokI, and TaqI, and Parkinson's disease (PD) has received increasing attention in the research community. However, as the results yielded by this increased research have hitherto conflicted, we performed an updated meta-analysis of reports on the relationships between VDR polymorphisms and PD published before October 2019 that we collected from the PUBMED, EMBASE, EBSCO, China National Knowledge Infrastructure (CNKI), and Wanfang databases. The ten articles that met our screening criteria included 2782 patients and 3194 healthy controls. All the data that we received were analyzed with Stata 12.0 statistical software. The odds ratio (OR) and 95 % confidence intervals (CIs) were used to determine the relationship between VDR gene diversity and PD. While we did not find a significant correlation between the ApaI, BsmI, and TaqI polymorphisms and the risk of PD in any of the considered genetic models, we found a clear association between the FokI polymorphism and susceptibility to PD (C vs. T: OR = 1.246, 95 % CI: 1.101-1.411, P = 0; CC vs. TT: OR = 1.630, 95 % CI: 1.243-2.139, P = 0; CT vs. TT: OR = 1.382, 95 % CI: 1.059-1.804, P = 0.017; CC + CT vs. TT: OR = 1.491, 95 % CI: 1.159-1.919,P = 0.002; CC vs. CT + TT: OR = 1.261, 95 % CI: 1.062-1.496, P = 0.008). Our subgroup analysis performed according to ethnicity revealed that FokI increased the risk of PD in Asian populations (C vs. T: OR = 1.261, 95 % CI: 1.080-1.472, P = 0.003; CC vs. TT: OR = 1.664, 95 % CI: 1.189-2.330, P = 0.003; CT vs.TT: OR = 1.387, 95 % CI: 1.000-1.925, P = 0.05; CC + CT vs. TT: OR = 1.497, 95 % CI: 1.098-2.042, P = 0.011; CC vs. CT + TT: OR = 1.285, 95 % CI: 1.036-1.593, P = 0.022). Overall, the gene polymorphism of FokI only increases the risk of PD among Asian populations. Given the limited sample size of this study, the findings should be carefully explained.

Genetic, environmental and biomarker considerations delineating the regulatory effects of vitamin D on central nervous system function

Studies show that vitamin D (vit-D) (25(OH)D), the bioactive metabolite (1,25(OH)2D3) and vit-D receptors (vit-D receptor; protein disulphide isomerase, family A member 3) are expressed throughout the brain, particularly in regions pivotal to learning and memory. This has led to the paradigm that avoiding vit-D deficiency is important to preserve cognitive function. However, presently, it is not clear if the common clinical measure of serum 25(OH)D serves as a robust surrogate marker for central nervous system (CNS) homeostasis or function. Indeed, recent studies report CNS biosynthesis of endogenous 25(OH)D, the CNS expression of the CYP group of enzymes which catalyse conversion to 1,25(OH)2D3 and thereafter, deactivation. Moreover, in the periphery, there is significant ethnic/genetic heterogeneity in vit-D conversion to 1,25(OH)2D3 and there is a paucity of studies which have actually investigated vit-D kinetics across the cerebrovasculature. Compared with peripheral organs, the CNS also has differential expression of receptors that trigger cellular response to 1,25(OH)2D3 metabolites. To holistically consider the putative association of peripheral (blood) abundance of 25(OH)D on cognitive function, herein, we have reviewed population and genetic studies, pre-clinical and clinical intervention studies and moreover have considered potential confounders of vit-D analysis.

Effect of Vitamin D in HN9.10e Embryonic Hippocampal Cells and in Hippocampus from MPTP-Induced Parkinson's Disease Mouse Model

It has long been proven that neurogenesis continues in the adult brains of mammals in the dentatus gyrus of the hippocampus due to the presence of neural stem cells. Although a large number of studies have been carried out to highlight the localization of vitamin D receptor in hippocampus, the expression of vitamin D receptor in neurogenic dentatus gyrus of hippocampus in Parkinson's disease (PD) and the molecular mechanisms triggered by vitamin D underlying the production of differentiated neurons from embryonic cells remain unknown. Thus, we performed a preclinical in vivo study by inducing PD in mice with MPTP and showed a reduction of glial fibrillary acidic protein (GFAP) and vitamin D receptor in the dentatus gyrus of hippocampus. Then, we performed an in vitro study by inducing embryonic hippocampal cell differentiation with vitamin D. Interestingly, vitamin D stimulates the expression of its receptor. Vitamin D receptor is a transcription factor that probably is responsible for the upregulation of microtubule associated protein 2 and neurofilament heavy polypeptide genes. The latter increases heavy neurofilament protein expression, essential for neurofilament growth. Notably N-cadherin, implicated in activity for dendritic outgrowth, is upregulated by vitamin D.

Nuclear receptor gene polymorphisms and warfarin dose requirements in the Quebec Warfarin Cohort

Warfarin is primarily metabolized by cytochrome 2C9, encoded by gene CYP2C9. Here, we investigated whether variants in nuclear receptor genes which regulate the expression of CYP2C9 are associated with warfarin response. We used data from 906 warfarin users from the Quebec Warfarin Cohort (QWC) and tested the association of warfarin dose requirement at 3 months following the initiation of therapy in nine nuclear receptor genes: NR1I3, NR1I2, NR3C1, ESR1, GATA4, RXRA, VDR, CEBPA, and HNF4A. Three correlated SNPs in the VDR gene (rs4760658, rs11168292, and rs11168293) were associated with dose requirements of warfarin (P = 2.68 × 10^-5, P = 5.81 × 10^-4, and P = 5.94 × 10^-4, respectively). Required doses of warfarin were the highest for homozygotes of the minor allele at the VDR variants (P < 0.0026). Variants in the VDR gene were associated with the variability in response to warfarin, emphasizing the possible clinical relevance of nuclear receptor gene variants on the inter-individual variability in drug metabolism.

Association of vitamin D receptor BsmI, TaqI, FokI, and ApaI polymorphisms with susceptibility of chronic periodontitis: A systematic review and meta-analysis based on 38 case -control studies

BACKGROUND

There has been increasing interest in the study of the association between Vitamin D receptor (VDR) gene polymorphisms and risk of chronic periodontitis. However, the results remain inconclusive. To better understand the roles of VDR polymorphisms (BsmI, TaqI, FokI, and ApaI) in chronic periodontitis susceptibility, we conducted this systematic review and meta-analysis.

MATERIALS AND METHODS

The PubMed, Google Scholar, and Web of Science database were systemically searched to determine all the eligible studies about VDR polymorphisms and risk of chronic periodontitis up to April 2017. Odds ratio (OR) and 95% confidence interval (CI) were used to evaluate the associations between VDR polymorphisms and chronic periodontitis risk. All the statistical analyses were performed by Comprehensive Meta-Analysis. All P values were two-tailed with a significant level at 0.05.

RESULTS

Finally, a total of 38 case-control studies in 19 publications were identified which met our inclusion criteria. There are ten studies with 866 chronic periodontitis cases and 786 controls for BsmI, 16 studies with 1570 chronic periodontitis cases and 1676 controls for TaqI, five studies with 374 chronic periodontitis cases and 382 controls for FokI, and seven studies with 632 chronic periodontitis cases and 604 controls for ApaI. Overall, no significant association was observed between VDR gene BsmI, TaqI, FokI, and ApaI polymorphisms and risk of chronic periodontitis in any genetic model. Subgroup analysis stratified by ethnicity suggested a significant association between BsmI polymorphism and chronic periodontitis risk in the Caucasian subgroup under allele model (A vs. G: OR = 1.747, 95% CI = 1.099-2.778, P = 0.018). Further, no significant associations were observed when stratified by Hardy-Weinberg equilibrium status for BsmI, TaqI, and ApaI.

CONCLUSION

Our results suggest that BsmI, TaqI, FokI, and ApaI polymorphisms in the VDR gene might not be associated with risk of chronic periodontitis in overall population.

Vitamin D receptor gene polymorphisms and cognitive decline in Parkinson's disease

We and others have suggested that vitamin D receptor gene (VDR) polymorphisms influence susceptibility for Parkinson's disease (PD), Alzheimer's disease (AD), mild cognitive impairment (MCI) or overall cognitive functioning. Here we examine VDR polymorphisms and cognitive decline in patients with PD. Non-Hispanic Caucasian PD patients (n=190) in the Parkinson Environment Gene (PEG) study were successfully genotyped for seven VDR polymorphisms. Cognitive function was assessed with the Mini-Mental State Exam (MMSE) at baseline and at a maximum of three follow-up exams. Using repeated-measures regression we assessed associations between VDR SNP genotypes and change in MMSE longitudinally. PD cases were on average 67.4years old at diagnosis and were followed for an average of 7.1years into disease. Each additional copy of the FokI A allele was associated with a 0.115 decrease in the total MMSE score per year of follow-up (β=-0.115, SE(β)=0.05, p=0.03) after adjusting for age, sex, education and PD duration. The effect on MMSE by the FokI A allele was comparable in absolute magnitude to the effect for disease duration in years prior to first interview (β=-0.129 per year, SE(β)=0.08, p=0.13), and years of education (β=0.118 per year, SE(β)=0.03, p<0.001). When LD/LED use and PD subtype were added to the model, the effect of the FokI A allele on total MMSE score was magnified (β=-0.141, SE(β)=0.05, p=0.005). Results point to Fokl, a functional VDR polymorphism, as being associated with cognitive decline in PD. Future studies examining the contributions of the vitamin D metabolic pathway to cognitive dysfunction in PD are needed.

Advances in understanding genomic markers and pharmacogenetics of Parkinson's disease

INTRODUCTION

The inheritance pattern of Parkinson's disease (PD) is likely multifactorial (owing to the interplay of genetic predisposition and environmental factors). Many pharmacogenetic studies have tried to establish a possible role of candidate genes in PD risk. Several studies have focused on the influence of genes in the response to antiparkinsonian drugs and in the risk of developing side-effects of these drugs.

AREAS COVERED

This review presents an overview of current knowledge, with particular emphasis on the most recent advances, both in case-control association studies on the role of candidate genes in the risk for PD as well as pharmacogenetic studies on the role of genes in the development of side effects of antiparkinsonian drugs. The most reliable results should be derived from meta-analyses of case-control association studies on candidate genes involving large series of PD patients and controls, and from genome-wide association studies (GWAS).

EXPERT OPINION

Prospective studies of large samples involving several genes with a detailed history of exposure to environmental factors in the same cohort of subjects, should be useful to clarify the role of genes in the risk for PD. The results of studies on the role of genes in the development of side-effects of antiparkinsonian drugs should, at this stage, only be considered preliminary.