Vitamin D receptor polymorphisms and susceptibility to Parkinson’s disease and Alzheimer’s disease: a meta-analysis

Neuroplasticity-related effects of vitamin D relevant to its neuroprotective effects: A narrative review

The pathophysiology of a wide range of central nervous system (CNS) disorders, such as neurodegenerative and psychiatric diseases, has been associated with impairment of neurogenic and synaptogenic processes. Therefore, pharmacological and/or nutritional strategies based on the stimulation and/or restoration of these processes may have beneficial effects against diseases in which these processes are impaired. In this context, vitamin D has emerged as a promising neuroprotective compound. Due to its pleiotropic properties, it can interact with multiple molecular targets and thereby affect different cell types, including neurons and glial cells. This neurosteroid contributes to CNS homeostasis by non-genomic and genomic mechanisms through its interaction with vitamin D receptors (VDRs). Among several properties of this vitamin, its role in neuronal proliferation and differentiation as well as in synaptic plasticity has received attention. Considering this background, this narrative review aims to highlight the neuroplasticity-related mechanisms of vitamin D that may be associated with its neuroprotective effects.

Correlation between vitamin D metabolic pathway-related gene polymorphisms and cardiovascular disease

Vitamin D plays important roles in various physiological processes such as cardiovascular health, calcium balance regulation, bone health, immune system support, neurological function regulation, muscle function maintenance, and anti-inflammatory effects. Therefore, maintaining its adequate levels is essential for overall health. Genetic polymorphisms in vitamin D metabolic pathways have become a key factor affecting the susceptibility and progression of cardiovascular disease (CVD). This article reviews the relationship between gene polymorphisms in vitamin D metabolic pathways and vitamin D levels or CVD. It is emphasized that the polymorphisms of key genes such as GC, VDR, CYP2R1, CYP24A1 and CYP27B1 are related to the pathogenesis of CVD. These polymorphisms can regulate serum levels of vitamin D, thereby affecting the susceptibility, comorbidities and clinical manifestations of CVD. Despite the progress made, there are still inconsistencies and gaps in the literature. Thus, it is necessary to conduct large-scale, multicenter studies to verify these findings and deepen our understanding of the intricate interactions between gene polymorphisms in vitamin D metabolic pathways and CVD.

Associations of vitamin D receptor polymorphisms with risk of Alzheimer's disease, Parkinson's disease, and mild cognitive impairment: a systematic review and meta-analysis

Vitamin D is a lipid soluble steroid hormone, which plays a critical role in the calcium homeostasis, neuronal development, cellular differentiation, and growth by binding to vitamin D receptor (VDR). Associations between VDR gene polymorphism and Alzheimer's disease (AD), Parkinson's disease (PD), and mild cognitive impairment (MCI) risk has been investigated extensively, but the results remain ambiguous. The aim of this study was to comprehensively assess the correlations between four VDR polymorphisms (FokI, BsmI, TaqI, and ApaI) and susceptibility to AD, PD, and MCI. Crude odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to determine the relationship of interest. Pooled analyses suggested that the ApaI polymorphism decreased the overall AD risk, and the TaqI increased the overall PD susceptibility. In addition, the BsmI and ApaI polymorphisms were significantly correlated with the overall MCI risk. Stratified analysis by ethnicity further showed that the TaqI and ApaI genotypes reduced the AD predisposition among Caucasians, while the TaqI polymorphism enhanced the PD risk among Asians. Intriguingly, carriers with the BB genotype significantly decreased the MCI risk in Asian descents, and the ApaI variant elevated the predisposition to MCI in Caucasians and Asians. Further studies are need to identify the role of VDR polymorphisms in AD, PD, and MCI susceptibility.

The Impact of Vitamin D on Neuropsychiatric Disorders

Vitamin D is a fat-soluble vitamin that has multiple biological effects on the body. Recent findings have also linked vitamin D deficiency to a range of neuropsychiatric disorders. The aim of this review article is to provide insight into the metabolism of vitamin D and its effect on the body, especially on the brain, and to recognize the role of vitamin D in some neuropsychiatric disorders. Vitamin D is well-known as a neuroactive steroid that modulates brain functions and development. There is strong evidence to show that optimal vitamin D levels are important to protect against neuropsychiatric disorders. Vitamin D has also been proposed to alter neurotransmitter pathways in the central nervous system. Abnormalities in these neurotransmitters have been implicated in various neuropsychiatric diseases, such as schizophrenia, Parkinson's disease, and depression. Vitamin D also has some reported neurosteroid-like actions, including regulation of calcium homeostasis, clearance of amyloid-peptide, and antioxidant and anti-inflammatory effects, as well as possible protection against the neurodegenerative mechanisms associated with Alzheimer's disease and autism. Vitamin D is an important modulator of brain development and has many functions in the brain. Several studies found that vitamin D has a protective role in neuropsychiatric disorders, and its supplementation decreases the development of these disorders and lowers their symptoms. Therefore, evidence shows that early intervention to maintain vitamin D concentrations at sufficiently high levels is crucial to slow, prevent, or improve neurocognitive decline.

Significance of the Vitamin D Receptor on Crosstalk with Nuclear Receptors and Regulation of Enzymes and Transporters

The vitamin D receptor (VDR), in addition to other nuclear receptors, the pregnane X receptor (PXR) and constitutive androstane receptor (CAR), is involved in the regulation of enzymes, transporters and receptors, and therefore intimately affects drug disposition, tissue health, and the handling of endogenous and exogenous compounds. This review examines the role of 1α,25-dihydroxyvitamin D₃ or calcitriol, the natural VDR ligand, on activation of the VDR and its crosstalk with other nuclear receptors towards the regulation of enzymes and transporters, notably many of the cytochrome P450s including CYP3A4 and sulfotransferase 2A1 (SULT2A1) as well as cholesterol 7α-hydroxylase (CYP7A1). Moreover, the VDR upregulates the intestinal channel, TRPV6, for calcium absorption, LDL receptor-related protein 1 (LRP1) and receptor for advanced glycation end products (RAGE) in brain for β-amyloid peptide efflux and influx, the sodium phosphate transporters (NaP_i), the apical sodium-dependent bile acid transporter (ASBT) and organic solute transporters (OSTα-OSTβ) for bile acid absorption and efflux, respectively, the renal organic anion transporter 3 (OAT3) and several of the ATP-binding cassette protein transporters-the multidrug resistance protein 1 (MDR1) and the multidrug resistance-associated proteins (MRPs). Hence, the role of the VDR is increasingly being recognized for its therapeutic potential and pharmacologic activity, giving rise to drug-drug interactions (DDI). Therapeutically, ligand-activated VDR shows anti-inflammatory effects towards the suppression of inflammatory mediators, improves cognition by upregulating amyloid-beta (Aβ) peptide clearance in brain, and maintains phosphate, calcium, and parathyroid hormone (PTH) balance and kidney function and bone health, demonstrating the crucial roles of the VDR in disease progression and treatment of diseases.

Gut feelings: the microbiota-gut-brain axis on steroids

The intricate connection between central and enteric nervous systems is well established with emerging evidence linking gut microbiota function as a significant new contributor to gut-brain axis signaling. Several microbial signals contribute to altered gut-brain communications, with steroids representing an important biological class that impacts central and enteric nervous system function. Neuroactive steroids contribute pathologically to neurological disorders, including dementia and depression, by modulating the activity of neuroreceptors. However, limited information is available on the influence of neuroactive steroids on the enteric nervous system and gastrointestinal function. In this review, we outline how steroids can modulate enteric nervous system function by focusing on their influence on different receptors that are present in the intestine in health and disease. We also highlight the potential role of the gut microbiota in modulating neuroactive steroid signaling along the gut-brain axis.

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.

Vitamin D Receptor Gene Polymorphisms and Risk of Alzheimer Disease and Mild Cognitive Impairment: A Systematic Review and Meta-Analysis

The results from epidemiologic studies suggest that vitamin D receptor (VDR) gene polymorphisms are potentially associated with Alzheimer disease (AD) and mild cognitive impairment (MCI), but this association has yet to be confirmed. Here, we conducted a meta-analysis based on a larger sample size to clarify the contribution of VDR gene polymorphisms to MCI and AD susceptibility. The PubMed, Embase, Cochrane Library, and China National Knowledge Infrastructure databases were searched to obtain studies published before 30 October, 2020. The case group includes MCI and AD patients, and the matched controls were without any cognitive complaints. ORs and 95% CIs were used to assess the strength of the association. Ten case-control studies with 3573 participants and 4 loci of ApaI rs7975232, BsmI rs1544410, FokI rs10735810, and TaqI rs731236 were included in the meta-analysis. The global assessment indicated an association between the BsmI polymorphism and increased odds of MCI in the allelic model (b compared with B; OR: 1.77; 95% CI: 1.24, 2.54), the dominant model (bb + Bb compared with BB; OR: 2.04; 95% CI: 1.32, 3.16), and the heterozygote model (Bb compared with BB; OR: 1.97; 95% CI: 1.26, 3.09). In contrast, the ApaI polymorphism was protective against MCI in all models. The dominant model (tt + Tt compared with TT; OR: 1.44; 95% CI: 1.17, 1.79) and the homozygous model (tt compared with TT; OR: 1.43; 95% CI: 1.02, 2.00) revealed an association between the TaqI polymorphism of the VDR gene and increased odds of AD, particularly for Caucasian subjects. Egger's linear regression test found no publication bias. This meta-analysis indicated that VDR ApaI and BsmI, and TaqI gene polymorphisms may be important predictors of MCI and AD, respectively, with population discrepancies. More research is needed to further confirm these associations, especially considering gene-gene interactions, gene-environment interactions, and other confounding factors.

Association of Vitamin D Receptor Polymorphisms with Amyloid-β Transporters Expression and Risk of Mild Cognitive Impairment in a Chilean Cohort

Background: Amyloid-β peptide (Aβ) deposition in Alzheimer’s disease (AD) is due to an imbalance in its production/clearance rate. Aβ is transported across the blood-brain barrier by LRP1 and P-gp as efflux transporters and RAGE as influx transporter. Vitamin D deficit and polymorphisms of the vitamin D receptor (VDR) gene are associated with high prevalence of mild cognitive impairment (MCI) and AD. Further, vitamin D promotes the expression of LRP1 and P-gp in AD-animal model brains. Objective: To associate VDR polymorphisms Apa I (rs7975232), Taq I (rs731236), and Fok I (rs2228570) with the risk of developing MCI in a Chilean population, and to evaluate the relationship of these polymorphisms to the expression of VDR and Aβ-transporters in peripheral blood mononuclear cells (PBMCs). Methods: VDR polymorphisms Apa I, Taq I, and Fok I were determined in 128 healthy controls (HC) and 66 MCI patients. mRNA levels of VDR and Aβ-transporters were evaluated in subgroups by qPCR. Results: Alleles A of Apa I and C of Taq I were associated with a lower risk of MCI. HC with the Apa I AA genotype had higher mRNA levels of P-gp and LRP1, while the expression of VDR and RAGE were higher in MCI patients and HC. For Fok I, the TC genotype was associated with lower expression levels of Aβ-transporters in both groups. Conclusion: We propose that the response to vitamin D treatment will depend on VDR polymorphisms, being more efficient in carriers of protective alleles of Apa I polymorphism.

Association of Vitamin D Receptor Gene Polymorphisms with Serum Vitamin D Levels in a Greek Rural Population (Velestino Study)

BACKGROUND/AIM

An alarming increase in vitamin D deficiency even in sunny regions highlights the need for a better understanding of the genetic background of the vitamin D endocrine system and the molecular mechanisms of gene polymorphisms of the vitamin D receptor (VDR). In this study, the serum levels of 25(OH)D3 were correlated with common VDR polymorphisms (ApaI, BsmI, FokI, and TaqI) in 98 subjects of a Greek homogeneous rural population.

METHODS

25(OH)D3 concentration was measured by ultra-HPLC, and the VDR gene polymorphisms were identified by quantitative real-time PCR followed by amplicon high-resolution melting analysis.

RESULTS

Subjects carrying either the B BsmI (OR: 0.52, 95% CI: 0.27-0.99) or t TaqI (OR: 2.06, 95%: 1.06-3.99) allele presented twice the risk for developing vitamin D deficiency compared to the reference allele. Moreover, subjects carrying 1, 2, or all 3 of these genotypes (BB/Bb, Tt/tt, and FF) demonstrated 2-fold (OR: 2.04, 95% CI: 0.42-9.92), 3.6-fold (OR: 3.62, 95% CI: 1.07-12.2), and 7-fold (OR: 6.92, 95% CI: 1.68-28.5) increased risk for low 25(OH)D3 levels, respectively.

CONCLUSIONS

Our findings reveal a cumulative effect of specific VDR gene polymorphisms that may regulate vitamin D concentrations explaining, in part, the paradox of vitamin D deficiency in sunny regions, with important implications for precision medicine.

Vitamin D Receptor Polymorphisms in Sex-Frailty Paradox

The “male-female health-survival paradox” evidences that the survival advantage observed in women is linked to higher rates of disability and poor health status compared to men, a phenomenon also called the “sex-frailty paradox”. The depletion of vitamin D seems to play a role in the fragilization of old persons, and genetic polymorphisms of the vitamin D receptor (VDR) gene seem to be involved in regulating the vitamin D pathway. This study correlated the VDR gene polymorphisms (FokI, ApaI, BsmiI, and TaqI) with frailty, computed by frailty index (FI), in 202 persons (127 women and 75 men, aged from 60 to 116 years), aiming to capture the involvement of vitamin D in the sex-frailty paradox. The results showed slightly higher FI (p = 0.05), lower levels of 25(OH)D (p = 0.04), and higher levels of parathyroid hormone PTH (p = 0.002) and phosphorus (p < 0.001) in women than in men. Interestingly, the ApaI minor allele (Aa + aa) showed a significant positive association with FI (p = 0.03) and a negative association with inorganic phosphorus values (p = 0.04) compared to AA genotype only in women, regardless of age. The exact mechanism and the causal role that, in old women, links ApaI polymorphism with frailty are still unclear. However, we could speculate that a specific genetic profiling, other than 25(OH)D levels, play a role in the sex-frailty paradox.

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.

Vitamin D Deficiency and Autism Spectrum Disorder

Vitamin D is a neurosteroid hormone crucially involved in neurodevelopment. Neural cell proliferation, neurotransmission, oxidative stress and immune function represent the main mechanisms mediated by vitamin D in the Central Nervous System. Therefore, its deficiency during pregnancy and early childhood may significantly impact on a developing brain, leading to possible adverse neuropsychological outcomes including Autism Spectrum Disorder (ASD). Significant vitamin D deficiency is described within children affected by ASD and in pregnant mothers whose offspring will later develop ASD, suggesting a possible role of the hormone as a contributing risk factor in the etiopathogenesis of ASD. We reviewed the actual literature on the potential contributing role of prenatal and early postnatal vitamin D deficiency in ASD etiopathogenesis, at both genetic and environmental levels, and the possible effect of vitamin D supplementation in autistic children. Conflicting but promising results emerged on the topic. Further Randomized Controlled Trials studies carried out during pregnancy and early infancy are necessary for better understanding the possible contribution of vitamin D deficiency in the etiopathogenesis of autism and the potential efficacy of the hormone supplementation in the improvement of ASD core symptoms.

Vitamin D Receptor Polymorphisms Associated with Autism Spectrum Disorder

Vitamin D is endowed with a number of biological properties, including down-regulation of inflammation, and might contribute to the pathogenesis of autism spectrum disorders (ASD). Vitamin D binds to the vitamin D Receptor (VDR); the biological activity of the ensuing complex depends on VDR FokI, BsmI, ApaI, and TaqI gene polymorphisms. We evaluated such Single Nucletoide Polymorphismsm (SNPs) in a cohort of 100 Italian families with ASD children. FokI genotype distribution was skewed in ASD children compared with their healthy sibs (P_c = 0.03 2 df) and to a group of 170 Italian healthy women (HC) (P_c = 0.04 2 df). FokI genotype and allelic distribution skewing were also observed in mothers of ASD children compared to HC (P_c = 0.04 2 df). Both Transmission Disequilibrium Test for single loci and haplotype analysis distribution revealed a major FokI (C) allele-mediated protective effect, which was more frequently transmitted (73%) than not transmitted to healthy sibs (P = 0.02). A protective FokI-, BsmI-, ApaI-, and TaqI (CCAG) haplotype was more frequently carried by healthy sibs than by ASD children (P = 1 × 10^-4 ; OR: 0.1, 95% CI: 0.03-0.4) too. Finally, a strong gene-dose association of FokI (T) allele with both higher Childhood Autism Rating Scale score (P_c = 0.01) and, particularly, with hyperactivity behavior (P_c = 0.006) emerged in ASD children. Because the protein produced by the FokI (T) allele is transcriptionally less active than that produced by the FokI (C) allele, the reduced biological activity of the vitamin D/VDR complex prevalent in ASD could favor ASD- and maternal immune activation- associated inflammation. Vitamin D supplementation might be useful in preventative and rehabilitation protocols for ASD. Autism Res 2020, 13: 680-690. © 2020 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Vitamin D deficiency and Vitamin D receptor (VDR) polymorphisms are associated with structural and functional brain abnormalities and behavioral disorders. We analyzed the association of VDR gene polymorphisms in a cohort of 100 Italian families with ASD children. A strong correlation between one of the VDR polymorphisms and hyperactivity behavior was evidenced in ASD children. In healthy mothers, the same VDR polymorphism was also correlated with an increased risk of giving birth to children with ASD.

The Correlation Between Vitamin D Receptor (VDR) Gene Polymorphisms and Autism: A Meta-analysis

Vitamin D receptor (VDR) polymorphisms are risk factors for autism. We performed a systematic meta-analysis to explore the relationship between VDR gene polymorphisms and autism. A literature review of articles from Pubmed, Embase, the Cochrane Library, and Springer was conducted up to January 28, 2019. The association between SNPs and autism was calculated using pooled odd ratios (ORs) and 95% confidence intervals (CIs). Additionally, tests for heterogeneity, publication bias, and sensitivity were conducted. Six eligible studies with a total of 2001 participants (1045 cases and 956 controls) were included. Meta-analysis indicated that the "C" allele of the rs731236 gene, including C vs. T (OR = 1.3254, 95% CI = 1.0897-1.6122), CC vs. TT (OR = 2.0871, 95% CI = 1.3395-3.2519), and CC vs. TT + CT (OR = 1.9610, 95% CI = 1.2985-2.9615), might be a risk factor for autism. Moreover, the "G" allele of rs7975232 (G vs. T: OR = 0.8228, 95% CI = 0.6814-0.9934) was associated with a protective effect against the development of autism. No significant differences were found in the allele frequencies of rs11568820, rs1544410, and rs2228570 in the cases and controls. This meta-analysis revealed that both VDR rs731236 and rs7975232 were significantly associated with autism, whereas VDR rs11568820, rs1544410, and rs2228570 might not be correlated with the incidence of autism.

Blood biomarkers with Parkinson's disease clusters and prognosis: The oxford discovery cohort

Background

Predicting prognosis in Parkinson's disease (PD) has important implications for individual prognostication and clinical trials design and targeting novel treatments. Blood biomarkers could help in this endeavor.

Methods

We identified 4 blood biomarkers that might predict prognosis: apolipoprotein A1, C‐reactive protein, uric acid and vitamin D. These biomarkers were measured in baseline serum from 624 Parkinson's disease subjects (median disease duration, 1.0 years; interquartile range, 0.5–2.0) from the Oxford Discovery prospective cohort. We compared these biomarkers against PD subtypes derived from clinical features in the baseline cohort using data‐driven approaches. We used multilevel models with MDS‐UPDRS parts I, II, and III and Montreal Cognitive Assessment as outcomes to test whether the biomarkers predicted subsequent progression in motor and nonmotor domains. We compared the biomarkers against age of PD onset and age at diagnosis. The q value, a false‐discovery rate alternative to P values, was calculated as an adjustment for multiple comparisons.

Results

Apolipoprotein A1 and C‐reactive protein levels differed across our PD subtypes, with severe motor disease phenotype, poor psychological well‐being, and poor sleep subtype having reduced apolipoprotein A1 and higher C‐reactive protein levels. Reduced apolipoprotein A1, higher C‐reactive protein, and reduced vitamin D were associated with worse baseline activities of daily living (MDS‐UPDRS II).

Conclusion

Baseline clinical subtyping identified a pro‐inflammatory biomarker profile significantly associated with a severe motor/nonmotor disease phenotype, lending biological validity to subtyping approaches. No blood biomarker predicted motor or nonmotor prognosis. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Association between vitamin D receptor gene FokI and TaqI variants with autism spectrum disorder predisposition in Iranian population

BACKGROUND AND AIM

Autism spectrum disorder (ASD) is one of the neurodevelopmental and cognitive conditions that involves 1 in 160 children around the world. Several studies showed that there is a relationship between vitamin D receptor (VDR) gene polymorphisms with the neurodevelopmental behavioral disorders. In the current study, we aimed to highlight the association of VDR gene polymorphisms (FokI and TaqI) with the risk of autism in Birjand population.

MATERIAL AND METHODS

In this case-control study eighty-one patients recognized with ASD and one hundred-eight healthy controls were recruited to the study from 2017 to 2018. Genotyping was carried out by polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP) technique for all subjects.

RESULTS

Calculated odds ratio and P-value for the alleles of VDR gene FokI and TaqI variants between autistic patients and controls did not show a significant difference (P > 0.05). However, calculated homozygous recessive (tt) for TaqI polymorphism was statistically significant (P = 0.015) in control group and there was also statistically meaningful difference in both case and control groups in ft haplotype (P = 0.04).

CONCLUSION

These results provide preliminary evidence that genetic variants of the VDR gene (FokI and TaqI) might have a possible reduced risk of ASD occurrence in children. The additional examination is needed to acquire more decisive and precise results in this area.

Vitamin D basis of Alzheimer's disease: from genetics to biomarkers

Alzheimer's disease (AD) is a progressive neurodegenerative disorder seen mostly in the elderly population. While to date AD research has focused on either neurochemical disruptions, genetic studies, or the pathological hallmarks, little has been done to establish a novel approach that would encompass all three aspects, one that would overcome the current barriers in AD research and determine the cause of AD and, eventually, discover a treatment. Meanwhile, there have been strong indications in recent years that vitamin D, a secosteroid hormone, and its receptors are fundamentally involved in neurodegenerative mechanisms. Observational studies have pointed to vitamin D deficiency as a genetic risk factor for AD, Parkinson's disease (PD), vascular dementia, and multiple sclerosis (MS), as well as other neurological disorders, brought about by alterations in genes involved in metabolism, transportation, and actions of vitamin D. Molecular studies have demonstrated that vitamin D treatments prevent amyloid production while also increasing its clearance from the brain in AD. Finally, recent vitamin D intervention studies have reported significant improvement in cognitive performance in subjects with senile dementia, mild cognitive impairment, and AD. This review aims to describe how a vitamin D research strategy, fully integrating all aspects of present-day AD research, would elucidate the genetic, molecular, and biochemical background of the disease.

Molecular evidence of role of vitamin D deficiency in various extraskeletal diseases

BACKGROUND

Role of vitamin D is not only limited to skeletal system but various other systems of the body, such as immune system, endocrine system, and cardiopulmonary system.

MATERIALS AND METHODS

It is supported by the confirmations of systems-wide expression of vitamin D receptor (VDR), endocrinal effect of calcitriol, and its role in immune responses.

RESULTS

Expression of VDR in various systems, immunoregulatory and hormonal response of vitamin D and deficiency of vitamin D may establish various pathologies in the body.

CONCLUSION

This review provides molecular evidence of relation of vitamin D with extra skeletal.

Higher Vitamin D Levels Are Associated with Better Attentional Functions: Data from the NorCog Register

OBJECTIVES

The aim of this cross-sectional study was to evaluate which cognitive domains are mostly affected in persons with vitamin D insufficiency or deficiency, defined as 25(OH)D < 50 nmol/l and < 25 nmol/l, respectively.

METHODS

Data were collected from the Norwegian register for persons assessed for cognitive symptoms (NorCog). 580 persons aged ≥ 65 years were included. The following cognitive and neuropsychiatric tests were used: Mini Mental State Examination, Norwegian Revised Version (MMSE-NR), the Clock Drawing test, the Trail Making Test A and B, the 10-word memory test and the figure copying test from CERAD - immediate and delayed recall, The Controlled Oral Word Association Test -FAS and Boston Naming test. Neuropsychiatric symptoms were assessed by Neuropsychiatric Inventory-Questionnaire and Cornell Scale for Depression in Dementia.

RESULTS

Vitamin D-insufficiency was found in approx. 30 % of the study cohort. After adjustment for relevant covariates, higher serum 25(OH)D levels were associated with higher score on MMSE-NR (p=0.032) and 10-word Memory Test, immediate recall (p=0.038), as well as faster execution of Trail Making Test A and B (p=0.038 and p=0.021, respectively). Other tests were not significantly associated with 25(OH)D levels.

CONCLUSION

Higher vitamin D levels appear to be associated with better cognition, especially in areas of executive function and mental flexibility.

Amyloid Beta 1-42 Alters the Expression of miRNAs in Cortical Neurons

Recently, Aβ1-42 was demonstrated to have the potential to translocate into the nucleus and to be involved in the transcriptional regulation of certain neurodegeneration-related genes. This data raises the question of whether Aβ-induced neurodegeneration might include the expression of miRNAs. Thus, our aim in this study was to investigate the effects of Aβ1-42 on certain miRNAs which are related with vitamin D metabolism, neuronal differentiation, development, and memory. This question was investigated in primary cortical neurons that were treated with 10 μM Aβ and/or 10^-8 M 1,25-dihydroxyvitamin D3 at different time points by expression analysis of let-7a-5p, miR-26b-5p, miR-27b-3p, miR-31a-5p, miR-125b-5p, and miR-192-5p with qRT-PCR. Our data indicate that amyloid pathology has effects on the expression of miRNAs. Furthermore, some of these miRNAs simultaneously regulate the proteins or the enzymes involved in neuronal metabolism. The experimental setup that we used and the data we acquired supply valuable information about the miRNAs that play a part in the Aβ pathology and suggested Aβ as a counterpart of vitamin D at the crossroads of neuronal differentiation, development, and memory.

BsmI polymorphism in the vitamin D receptor gene is associated with 25-hydroxy vitamin D levels in individuals with cognitive decline

ABSTRACT Elderly people are at a high risk of developing vitamin D (VitD) deficiency due to both decreased intake and cutaneous synthesis. Most of the biological actions of VitD are mediated by the vitamin D receptor (VDR), which is present in neurons and glial cells of the hippocampus, and in the cortex and subcortical nuclei, essential areas for cognition. It is known that VDR gene polymorphisms may decrease the VDR affinity for VitD. Objective: The present study aimed to investigate the influence of VitD levels on cognitive decline in patients with dementia due to Alzheimer's disease (AD, n = 32) and mild cognitive impairment (MCI, n = 15) compared to cognitively healthy elderly (n = 24). We also evaluated the association of VDR gene polymorphisms with cognitive disturbance. Methods: Four polymorphisms on the VDR gene were studied, namely, BsmI, ApaI, FokI and TaqI, by polymerase chain reaction-restriction fragment length polymorphism. Serum levels of 25-hydroxy vitamin D (25(OH)D) were determined by high performance liquid chromatography. Results: No significant difference in 25(OH)D levels or genotypic/allelic frequencies was observed between the groups. Deficiency of 25(OH)D was more frequently observed in women. The AA/AG genotypes of the BsmI polymorphism was associated with sufficient 25(OH)D levels, while the GG genotype of this same polymorphism was associated to insufficient levels in the cognitively-impaired group (individuals with AD or MCI). Conclusions: The data obtained do not confirm the relationship between reductions of VitD levels, polymorphisms in the VDR gene, and altered cognitive function in this sample. However, the data indicate that BsmI polymorphism in the VDR gene is associated with the VitD levels in individuals with cognitive decline.

Neuro-nutrients as anti-alzheimer's disease agents: A critical review

Alzheimer's disease (AD) is characterized by a massive neuronal death causing memory loss, cognitive impairment and behavioral alteration that ultimately lead to dementia and death. AD is a multi-factorial pathology controlled by molecular events such as oxidative stress, protein aggregation, mitochondrial dysfunction and neuro inflammation. Nowadays, there is no efficient disease-modifying treatment for AD and epidemiological studies have suggested that diet and nutrition have a significant impact on the development of this disorder. Indeed, some nutrients can protect all kind of cells, including neurons. As prevention is better than cure, life style improvement, with a special emphasis on diet, should seriously be considered as an anti-AD track and intake of nutrients promoting neuronal health is the need of the hour. Diets rich in unsaturated fatty acids, polyphenols and vitamins have been shown to protect against AD, whereas saturated fatty acids-containing diets deprived of polyphenols promote the development of the disease. Thus, Mediterranean diets, mainly composed of fruits, vegetables and omega-3 fatty acids, stand as valuable, mild and preventive anti-AD agents. This review focuses on our current knowledge in the field and how one can fight this devastating neurodegenerative disorder through the simple proper modification of our life style.

Health Risks of Hypovitaminosis D: A Review of New Molecular Insights

Hypovitaminosis D has become a pandemic, being observed in all ethnicities and age groups worldwide. Environmental factors, such as increased air pollution and reduced ultraviolet B (UVB) irradiation, as well as lifestyle factors, i.e., decreased outdoor activities and/or poor intake of vitamin D-rich food, are likely involved in the etiology of a dramatic reduction of vitamin D circulating levels. The insufficiency/deficiency of vitamin D has long been known for its association with osteoporosis and rickets. However, in the last few decades it has become a serious public health concern since it has been shown to be independently associated with various chronic pathological conditions such as cancer, coronary heart disease, neurological diseases, type II diabetes, autoimmune diseases, depression, with various inflammatory disorders, and with increased risk for all-cause mortality in the general population. Prevention strategies for these disorders have recently involved supplementation with either vitamin D2 or vitamin D3 or their analogs at required daily doses and tolerable upper-limit levels. This review will focus on the emerging evidence about non-classical biological functions of vitamin D in various disorders.

Polymorphisms in Vitamin D Receptor Genes in Association with Childhood Autism Spectrum Disorder

Both genetic and environmental factors have been implicated in the etiology of autism spectrum disorder (ASD). This case-control study aimed to determine the association of single-nucleotide polymorphisms (SNPs) rs731276 (TaqI), rs1568820 (Cdx2), rs1544410 (BsmI), and rs2228570 (FokI) in the vitamin D receptor (VDR) gene with susceptibility of childhood ASD and severity of the disease. A total of 201 children with ASD and 200 healthy controls from the Han Chinese population were recruited. SNP genotyping was carried out by TaqMan probe-based real-time PCR using genomic DNA extracted from blood cells. Among four examined SNPs, only the CT genotype (odds ratio (OR) = 1.96, 95% confidence interval (CI) = 1.05-3.68, P = 0.0351) and the C allele (OR = 1.88, 95% CI = 1.02-3.46, P = 0.0416) of the rs731276 were significantly associated with increased risks of childhood ASD. None of the SNPs were associated with severity of childhood ASD. Our results reveal that certain polymorphisms in the VDR gene are a risk factor related to childhood ASD in the Han Chinese population.

Vitamin D and Neurological Diseases: An Endocrine View

Vitamin D system comprises hormone precursors, active metabolites, carriers, enzymes, and receptors involved in genomic and non-genomic effects. In addition to classical bone-related effects, this system has also been shown to activate multiple molecular mediators and elicit many physiological functions. In vitro and in vivo studies have, in fact, increasingly focused on the "non-calcemic" actions of vitamin D, which are associated with the maintenance of glucose homeostasis, cardiovascular morbidity, autoimmunity, inflammation, and cancer. In parallel, growing evidence has recognized that a multimodal association links vitamin D system to brain development, functions and diseases. With vitamin D deficiency reaching epidemic proportions worldwide, there is now concern that optimal levels of vitamin D in the bloodstream are also necessary to preserve the neurological development and protect the adult brain. The aim of this review is to highlight the relationship between vitamin D and neurological diseases.

Vitamin D and the brain: Genomic and non-genomic actions

1,25(OH)2D3 (vitamin D) is well-recognized as a neurosteroid that modulates multiple brain functions. A growing body of evidence indicates that vitamin D plays a pivotal role in brain development, neurotransmission, neuroprotection and immunomodulation. However, the precise molecular mechanisms by which vitamin D exerts these functions in the brain are still unclear. Vitamin D signalling occurs via the vitamin D receptor (VDR), a zinc-finger protein in the nuclear receptor superfamily. Like other nuclear steroids, vitamin D has both genomic and non-genomic actions. The transcriptional activity of vitamin D occurs via the nuclear VDR. Its faster, non-genomic actions can occur when the VDR is distributed outside the nucleus. The VDR is present in the developing and adult brain where it mediates the effects of vitamin D on brain development and function. The purpose of this review is to summarise the in vitro and in vivo work that has been conducted to characterise the genomic and non-genomic actions of vitamin D in the brain. Additionally we link these processes to functional neurochemical and behavioural outcomes. Elucidation of the precise molecular mechanisms underpinning vitamin D signalling in the brain may prove useful in understanding the role this steroid plays in brain ontogeny and function.

Vitamin D in the Parkinson Associated Risk Syndrome (PARS) study

BACKGROUND

Lower vitamin D levels have been associated with manifest Parkinson's disease, prompting the hypothesis that vitamin D insufficiency or deficiency may increase risk for PD.

OBJECTIVES

To evaluate vitamin D levels in a population at risk for developing PD.

METHODS

Plasma vitamin D levels were measured in the Parkinson Associated Risk Syndrome Study, a cohort of asymptomatic individuals, some of whom are at high risk for PD. Vitamin D levels were compared between subjects at high risk for PD (hyposmia and dopamine transporter scan deficit) versus all others and examined for correlations with dopaminergic system integrity.

RESULTS

Mean vitamin D levels did not differ between groups, with a level of 27.8 ng/mL (standard deviation = 12.0) in the high-risk group versus 24.7 ng/mL (standard deviation = 9.0) in all others (P = 0.09). Vitamin D levels did not associate with putaminal dopamine transporter uptake.

CONCLUSIONS

Our data from the asymptomatic Parkinson Associated Risk Syndrome cohort do not support the hypothesis that chronic vitamin D insufficiency threatens dopaminergic system integrity, contributing to PD pathogenesis. © 2017 International Parkinson and Movement Disorder Society.

Association of UV radiation with Parkinson disease incidence: A nationwide French ecologic study

BACKGROUND

Vitamin D is thought to contribute to brain health, but it is unclear whether low vitamin D levels are associated with increased incidence of Parkinson's disease (PD). Using ultraviolet B (UV-B) as a surrogate for vitamin D levels, we conducted a nationwide ecologic study in France in order to examine the association of UV-B with PD incidence.

METHODS

We used French national drug claims databases to identify PD cases using a validated algorithm. UV-B data from the solar radiation database were derived from satellite images. We estimated PD incidence (2010-2012) at the canton level (small administrative French unit) and used multilevel Poisson regression to examine its association with UV-B (2005 annual average), after adjustment for age, sex, deprivation index, density of neurologists, smoking, proportion of agricultural land, and vitamin D supplementation.

RESULTS

Analyses are based on 69,010 incident PD patients. The association between UV-B and PD incidence was quadratic (P<0.001) and modified by age (P<0.001). Below 70y, incidence was higher in the bottom quintile (relative risk, RR_Q1:45-49y=1.18, 95% CI=1.08-1.29) compared with the middle UV-B quintile, and lower in the top quintile (RR_Q5:45-49y=0.85 [0.77-0.94]). An opposite pattern was observed in older subjects (RR_Q1:85-89y=0.92 [0.89-0.96]; RR_Q5:85-89y=1.06 [1.02-1.11]). Analysis based on continuous UV-B yielded similar conclusions.

CONCLUSIONS

In this nationwide study, there was an age-dependent quadratic association between UV-B and PD incidence. This study suggests that reasonable UV-B exposure is associated with lower PD risk in younger persons and that future studies should examine dose-response relations and take age into account.

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.

The Impact of Vitamin E and Other Fat-Soluble Vitamins on Alzheimer´s Disease

Alzheimer’s disease (AD) is the most common cause of dementia in the elderly population, currently affecting 46 million people worldwide. Histopathologically, the disease is characterized by the occurrence of extracellular amyloid plaques composed of aggregated amyloid-β (Aβ) peptides and intracellular neurofibrillary tangles containing the microtubule-associated protein tau. Aβ peptides are derived from the sequential processing of the amyloid precursor protein (APP) by enzymes called secretases, which are strongly influenced by the lipid environment. Several vitamins have been reported to be reduced in the plasma/serum of AD-affected individuals indicating they have an impact on AD pathogenesis. In this review we focus on vitamin E and the other lipophilic vitamins A, D, and K, and summarize the current knowledge about their status in AD patients, their impact on cognitive functions and AD risk, as well as their influence on the molecular mechanisms of AD. The vitamins might affect the generation and clearance of Aβ both by direct effects and indirectly by altering the cellular lipid homeostasis. Additionally, vitamins A, D, E, and K are reported to influence further mechanisms discussed to be involved in AD pathogenesis, e.g., Aβ-aggregation, Aβ-induced neurotoxicity, oxidative stress, and inflammatory processes, as summarized in this article.

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.

1,25-Dihydroxyvitamin D and Klotho: A Tale of Two Renal Hormones Coming of Age

1,25-Dihydroxyvitamin D3 (1,25D) is the renal metabolite of vitamin D that signals through binding to the nuclear vitamin D receptor (VDR). The ligand-receptor complex transcriptionally regulates genes encoding factors stimulating calcium and phosphate absorption plus bone remodeling, maintaining a skeleton with reduced risk of age-related osteoporotic fractures. 1,25D/VDR signaling exerts feedback control of Ca/PO4 via regulation of FGF23, klotho, and CYP24A1 to prevent age-related, ectopic calcification, fibrosis, and associated pathologies. Vitamin D also elicits xenobiotic detoxification, oxidative stress reduction, neuroprotective functions, antimicrobial defense, immunoregulation, anti-inflammatory/anticancer actions, and cardiovascular benefits. Many of the healthspan advantages conferred by 1,25D are promulgated by its induction of klotho, a renal hormone that is an anti-aging enzyme/coreceptor that protects against skin atrophy, osteopenia, hyperphosphatemia, endothelial dysfunction, cognitive defects, neurodegenerative disorders, and impaired hearing. In addition to the high-affinity 1,25D hormone, low-affinity nutritional VDR ligands including curcumin, polyunsaturated fatty acids, and anthocyanidins initiate VDR signaling, whereas the longevity principles resveratrol and SIRT1 potentiate VDR signaling. 1,25D exerts actions against neural excitotoxicity and induces serotonin mood elevation to support cognitive function and prosocial behavior. Together, 1,25D and klotho maintain the molecular signaling systems that promote growth (p21), development (Wnt), antioxidation (Nrf2/FOXO), and homeostasis (FGF23) in tissues crucial for normal physiology, while simultaneously guarding against malignancy and degeneration. Therefore, liganded-VDR modulates the expression of a "fountain of youth" array of genes, with the klotho target emerging as a major player in the facilitation of health span by delaying the chronic diseases of aging.

Gene expression and functional annotation of human choroid plexus epithelium failure in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most common form of dementia. AD has a multifactorial disease etiology and is currently untreatable. Multiple genes and molecular mechanisms have been implicated in AD, including ß-amyloid deposition in the brain, neurofibrillary tangle accumulation of hyper-phosphorylated Tau, synaptic failure, oxidative stress and inflammation. Relatively little is known about the role of the blood-brain barriers, especially the blood-cerebrospinal fluid barrier (BCSFB), in AD. The BCSFB is involved in cerebrospinal fluid (CSF) production, maintenance of brain homeostasis and neurodegenerative disorders.

RESULTS

Using an Agilent platform with common reference design, we performed a large scale gene expression analysis and functional annotation of the Choroid Plexus Epithelium (CPE), which forms the BCSFB. We obtained 2 groups of freshly frozen Choroid Plexus (CP) of 7 human donor brains each, with and without AD: Braak stages (0-1) and (5-6). We cut CP cryo-sections and isolated RNA from cresyl-violet stained, laser dissected CPE cells. Gene expression results were analysed with T-tests (R) and the knowledge-database Ingenuity. We found statistically significantly altered gene expression data sets, biological functions, canonical pathways, molecular networks and functionalities in AD-affected CPE. We observed specific cellular changes due to increased oxidative stress, such as the unfolded protein response, E1F2 and NRF2 signalling and the protein ubiquitin pathway. Most likely, the AD-affected BCSFB barrier becomes more permeable due to downregulation of CLDN5. Finally, our data also predicted down regulation of the glutathione mediated detoxification pathway and the urea cycle in the AD CPE, which suggest that the CPE sink action may be impaired. Remarkably, the expression of a number of genes known to be involved in AD, such as APP, PSEN1, PSEN2, TTR and CLU is moderate to high and remains stable in both healthy and affected CPE. Literature labelling of our new functional molecular networks confirmed multiple previous (molecular) observations in the AD literature and revealed many new ones.

CONCLUSIONS

We conclude that CPE failure in AD exists. Combining our data with those of the literature, we propose the following chronological and overlapping chain of events: increased Aß burden on CPE; increased oxidative stress in CPE; despite continuous high expression of TTR: decreased capability of CPE to process amyloid; (pro-) inflammatory and growth factor signalling by CPE; intracellular ubiquitin involvement, remodelling of CPE tight junctions and, finally, cellular atrophy. Our data corroborates the hypothesis that increased BCSFB permeability, especially loss of selective CLDN5-mediated paracellular transport, altered CSF production and CPE sink action, as well as loss of CPE mediated macrophage recruitment contribute to the pathogenesis of AD.

Evidence for the Importance of Vitamin D Status in Neurologic Conditions

OPINION STATEMENT

Vitamin D status has been proposed as relevant to many neurological disorders. Data suggest that vitamin D may be important for the development of the nervous system, and it also plays a role in neuroimmunology and neuroprotection. Lower levels of circulating 25-hydroxyvitamin D have been linked with increased risk of multiple sclerosis (MS) and Alzheimer's disease (AD). While people with amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), and stroke have lower vitamin D levels than those without the diseases, it is unclear if this is because hypovitaminosis D contributes to disease risk or is a consequence of immobility and other factors caused by the disease. Lower levels of vitamin D have been associated with worse prognosis in MS, PD, ALS, and stroke, while no longitudinal studies have been performed to evaluate such an association in AD. Small pilot trials have been performed to evaluate vitamin D supplementation for some of these diseases, but there have been no phase III studies to support vitamin D supplementation in these patient populations; further, ideal levels of 25-hydroxyvitamin D are not known. Thus, while some expert panels or individuals have suggested routine testing and supplementation for patients with these neurological conditions, it is our opinion that there are currently insufficient data to support high-dose vitamin D supplementation to specifically treat or prevent these conditions.

Association between Vitamin D Receptor Gene Polymorphisms with Childhood Temporal Lobe Epilepsy

Vitamin D (VD) is implicated in multiple aspects of human physiology and vitamin D receptor (VDR) polymorphisms are associated with a variety of neuropsychiatric disorders. Although VD deficiency is highly prevalent in epilepsy patients and converging evidence indicates a role for VD in the development of epilepsy, no data is available on the possible relationship between epilepsy and genetic variations of VDR. In this study, 150 controls and 82 patients with temporal lobe epilepsy (TLE) were genotyped for five common VDR polymorphisms (Cdx-2, FokI, BsmI, ApaI and TaqI) by the polymerase chain reaction-ligase detection reaction method. Our results revealed that the frequency of FokI AC genotype was significantly higher in the control group than in the patients (p = 0.003, OR = 0.39, 95% CI = 0.21–0.73), whereas the AA genotype of ApaI SNP was more frequent in patients than in controls (p = 0.018, OR = 2.92, 95% CI = 1.2–7.1). However, no statistically significant association was found between Cdx-2, BsmI and TaqI polymorphisms and epilepsy. Additionally, in haplotype analysis, we found the haplotype GAT (BsmI/ApaI/TaqI) conferred significantly increased risk for developing TLE (p = 0.039, OR = 1.62, 95% CI = 1.02–2.56). As far as we know, these results firstly underline the importance of VDR polymorphisms for the genetic susceptibility to epilepsy.

Vitamin D and Alzheimer's Disease: Neurocognition to Therapeutics

Alzheimer's disease (AD), the major cause of dementia worldwide, is characterized by progressive loss of memory and cognition. The sporadic form of AD accounts for nearly 90% of the patients developing this disease. The last century has witnessed significant research to identify various mechanisms and risk factors contributing to the complex etiopathogenesis of AD by analyzing postmortem AD brains and experimenting with animal and cell culture based models. However, the treatment strategies, as of now, are only symptomatic. Accumulating evidences suggested a significant association between vitamin D deficiency, dementia, and AD. This review encompasses the beneficial role of vitamin D in neurocognition and optimal brain health along with epidemiological evidence of the high prevalence of hypovitaminosis D among aged and AD population. Moreover, disrupted signaling, altered utilization of vitamin D, and polymorphisms of several related genes including vitamin D receptor (VDR) also predispose to AD or AD-like neurodegeneration. This review explores the relationship between this gene-environmental influence and long term vitamin D deficiency as a risk factor for development of sporadic AD along with the role and rationale of therapeutic trials with vitamin D. It is, therefore, urgently warranted to further establish the role of this potentially neuroprotective vitamin in preventing and halting progressive neurodegeneration in AD patients.

Vitamin D receptor gene polymorphisms and Parkinson's disease in a population with high ultraviolet radiation exposure

INTRODUCTION

A high prevalence of vitamin D deficiency has been reported in Parkinson's disease (PD). Epidemiologic studies examining variability in genes involved in vitamin D metabolism have not taken into account level of exposure to ultraviolet radiation (UVR). We examined whether exposure to UVR (as a surrogate for vitamin D levels) and variations in the vitamin D receptor gene (VDR) are associated with PD.

METHODS

Within a geographical information system (GIS) we linked participants' geocoded residential address data to ground level UV data to estimate historical exposure to UVR. Six SNPs in VDR were genotyped in non-Hispanic Caucasian subjects.

RESULTS

Average lifetime UVR exposure levels were >5000 Wh/m(2), which was higher than levels for populations in previous studies, and UVR exposure did not differ between cases and controls. Homozygotes for the rs731236 TT (major allele) genotype had a 31% lower risk of PD risk (OR=0.69; 95% CI=0.49, 0.98; p=0.04 for TT vs. TC+CC). The rs7975232 GG (minor allele) genotype was also associated with decreased risk of PD (OR=0.63; 95% CI=0.42, 0.93; p=0.02 for GG vs. TG+TT). The association between PD risk and a third locus, rs1544410 (BsmI), was not statistically significant after adjustment for covariates, although there was a trend for lower risk with the GG genotype.

CONCLUSIONS

This study provides initial evidence that VDR polymorphisms may modulate risk of PD in a population highly exposed to UVR throughout lifetime.