The effects of vitamin D receptor silencing on the expression of LVSCC-A1C and LVSCC-A1D and the release of NGF in cortical neurons

Tremendous Fidelity of Vitamin D3 in Age-related Neurological Disorders

Vitamin D3 (VD) is a secosteroid hormone and shows a pleiotropic effect in brain-related disorders where it regulates redox imbalance, inflammation, apoptosis, energy production, and growth factor synthesis. Vitamin D3's active metabolic form, 1,25-dihydroxy Vitamin D3 (1,25(OH)2D3 or calcitriol), is a known regulator of several genes involved in neuroplasticity, neuroprotection, neurotropism, and neuroinflammation. Multiple studies suggest that VD deficiency can be proposed as a risk factor for the development of several age-related neurological disorders. The evidence for low serum levels of 25-hydroxy Vitamin D3 (25(OH)D3 or calcidiol), the major circulating form of VD, is associated with an increased risk of Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), dementia, and cognitive impairment. Despite decades of evidence on low VD association with neurological disorders, the precise molecular mechanism behind its beneficial effect remains controversial. Here, we will be delving into the neurobiological importance of VD and discuss its benefits in different neuropsychiatric disorders. The focus will be on AD, PD, and HD as they share some common clinical, pathological, and epidemiological features. The central focus will be on the different attributes of VD in the aspect of its anti-oxidative, anti-inflammatory, anti-apoptotic, anti-cholinesterase activity, and psychotropic effect in different neurodegenerative diseases.

A Novel and Robust Protocol for Differentiation of SH-SY5Y Neuroblastoma Cells into Neuron Like Cells

Introduction

Human neuroblastoma cell line SH-SY5Y is a frequently used experimental cellular model in a variety of neuropsychiatric and neurodegenerative disorders. It is crucial to use a culture protocol that supports the fully differentiation of SH-SY5Y into neuron-like phenotype for the consistency of the results with neurons in vivo. However, a standardized neuronal differentiation protocol for SH-SY5Y cells still does not exist. Numerous differentiation methods have been proposed in the literature, yet SH-SY5Y cells with stronger neuronal characteristics and a more favorable environment for these differentiated cells are required in order to best representation of neurons. Therefore, in the study, we aimed to establish a more successful differentiation protocol for SH-SY5Y cells based on the primary neuron culture technique, which neuronal maturation is very well defined.

Methods

In the study, we rearranged previous SH-SY5Y differentiation protocols, combined them with our primary neuron culture protocol and created a robust and reproducible protocol for differentiation of SH-SY5Y.

Results

Our proposed "retinoic acid+brain-derived neurotrophic factor (RA+BDNF)-induced 7 days differentiation (conalbumin- on day 4) protocol provided well developed neurites, adequate expression and localization of neuronal and synaptic markers resembling mature neurons.

Conclusion

The differentiation protocol we present can enable researchers to obtain satisfactory and properly differentiated SH-SY5Y cells in each independent experiment, achieving the closest possible in vivo results.

Molecular mechanisms reconstruction from single-cell multi-omics data with HuMMuS

MOTIVATION

The molecular identity of a cell results from a complex interplay between heterogeneous molecular layers. Recent advances in single-cell sequencing technologies have opened the possibility to measure such molecular layers of regulation.

RESULTS

Here, we present HuMMuS, a new method for inferring regulatory mechanisms from single-cell multi-omics data. Differently from the state-of-the-art, HuMMuS captures cooperation between biological macromolecules and can easily include additional layers of molecular regulation. We benchmarked HuMMuS with respect to the state-of-the-art on both paired and unpaired multi-omics datasets. Our results proved the improvements provided by HuMMuS in terms of transcription factor (TF) targets, TF binding motifs and regulatory regions prediction. Finally, once applied to snmC-seq, scATAC-seq and scRNA-seq data from mouse brain cortex, HuMMuS enabled to accurately cluster scRNA profiles and to identify potential driver TFs.

AVAILABILITY AND IMPLEMENTATION

HuMMuS is available at https://github.com/cantinilab/HuMMuS.

Role of Calcitriol and Vitamin D Receptor (VDR) Gene Polymorphisms in Alzheimer's Disease

Alzheimer's disease (AD) is characterized by amyloid beta (Aβ) buildup and neuronal degeneration. An association between low serum vitamin D levels and an increased risk of AD has been reported in several epidemiological studies. Calcitriol (1,25-dihydroxycholecalciferol) is the active form of vitamin D, and is generated in the kidney and many other tissues/organs, including the brain. It is a steroid hormone that regulates important functions like calcium/phosphorous levels, bone mineralization, and immunomodulation, indicating its broader systemic significance. In addition, calcitriol confers neuroprotection by mitigating oxidative stress and neuroinflammation, promoting the clearance of Aβ, myelin formation, neurogenesis, neurotransmission, and autophagy. The receptors to which calcitriol binds (vitamin D receptors; VDRs) to exert its effects are distributed over many organs and tissues, representing other significant roles of calcitriol beyond sustaining bone health. The biological effects of calcitriol are manifested through genomic (classical) and non-genomic actions through different pathways. The first is a slow genomic effect involving nuclear VDR directly affecting gene transcription. The association of AD with VDR gene polymorphisms relies on the changes in vitamin D consumption, which lowers VDR expression, protein stability, and binding affinity. It leads to the altered expression of genes involved in the neuroprotective effects of calcitriol. This review summarizes the neuroprotective mechanism of calcitriol and the role of VDR polymorphisms in AD, and might help develop potential therapeutic strategies and markers for AD in the future.

Impact of micronutrients and nutraceuticals on cognitive function and performance in Alzheimer's disease

Alzheimer's disease (AD) is a major global health problem today and is the most common form of dementia. AD is characterized by the formation of β-amyloid (Aβ) plaques and neurofibrillary clusters, leading to decreased brain acetylcholine levels in the brain. Another mechanism underlying the pathogenesis of AD is the abnormal phosphorylation of tau protein that accumulates at the level of neurofibrillary aggregates, and the areas most affected by this pathological process are usually the cholinergic neurons in cortical, subcortical, and hippocampal areas. These effects result in decreased cognitive function, brain atrophy, and neuronal death. Malnutrition and weight loss are the most frequent manifestations of AD, and these are also associated with greater cognitive decline. Several studies have confirmed that a balanced low-calorie diet and proper nutritional intake may be considered important factors in counteracting or slowing the progression of AD, whereas a high-fat or hypercholesterolemic diet predisposes to an increased risk of developing AD. Especially, fruits, vegetables, antioxidants, vitamins, polyunsaturated fatty acids, and micronutrients supplementation exert positive effects on aging-related changes in the brain due to their antioxidant, anti-inflammatory, and radical scavenging properties. The purpose of this review is to summarize some possible nutritional factors that may contribute to the progression or prevention of AD, understand the role that nutrition plays in the formation of Aβ plaques typical of this neurodegenerative disease, to identify some potential therapeutic strategies that may involve some natural compounds, in delaying the progression of the disease.

Nutritional Support System (NSS) as a New Therapeutic Strategy for Cerebral Palsy

Cerebral palsy (CP) is part of a group of nonprogressive motor disorders. The disease affects movement and posture and constitutes the most frequent cause of motor disability in childhood. CP is characterized by spasticity, reflecting lesions in the pyramidal pathway. Treatment is currently focused on physical rehabilitation, and the annual progression of the disease is 2-3%. About 60% of these patients present severe degrees of malnutrition associated with dysphagia, gastrointestinal abnormalities, malabsorption, increased metabolism, and depression. These alterations promote sarcopenia functional dependence and affect the quality of life and delay the evolution of motor skills. Currently, there is evidence that the supplementation of several nutrients, dietary correction, and probiotics can improve neurological response by stimulating neuroplasticity, neuroregeneration, neurogenesis, and myelination. This therapeutic strategy could shorten the response period to treatment and increase both gross and fine motor skills. The interaction of nutrients and functional foods integrating a Nutritional Support System (NSS) has shown greater efficiency in neurological stimulation than when nutrients are supplied separately. The most studied elements in the neurological response are glutamine, arginine, zinc, selenium, cholecalciferol, nicotinic acid, thiamine, pyridoxine, folate, cobalamin, Spirulina, omega-3 fatty acids, ascorbic acid, glycine, tryptophan, and probiotics. The NSS represents a therapeutic alternative that will restore neurological function in patients with spasticity and pyramidal pathway lesions, both characteristics of patients with CP.

Molecular Regulation of the CNS by Vitamin D

Vitamin D is a lipid-soluble vitamin that can be found in some foods. It is also produced endogenously (in the presence of ultraviolet light), transported through the blood to the targets organs and this is the reason to consider vitamin D as a hormone. It is known that vitamin D has genomic and non-genomic effects. This review is focused mainly on the vitamin D receptors, the importance of vitamin D as a neuromodulator, the role of vitamin D in the pathophysiology of devastating neurological disorders such as Alzheimer's disease, multiple sclerosis, amyotrophic lateral sclerosis, Parkinson's disease and the benefit of vitamin D and its derivates in alleviating these disorders.

Maternal vitamin D status and attention deficit hyperactivity disorder (ADHD), an under diagnosed risk factor; A review

Vitamin D is important to mediate several brain processes such as proliferation, apoptosis, and neurotransmission in early stages of life. Vitamin D deficiency during critical periods of development can lead to persistent brain alterations. Vitamin D homeostasis during pregnancy is affected by two factors which includes an increase in mother’s calcitriol levels and an increase in mother’s Vitamin D Binding protein concentrations. Attention deficient hyperactivity disorder (ADHD) is an outcome of a complicated interaction between genetic, environmental, and developmental traits, and genetic factors cover about 80% of the cases. The efficiency of the immune system can be altered by a deficiency of Vitamin D in maternal body and maternal stress during gestation such as perinatal depression. Studies have proved that during gestation if there is a deficiency of vitamin D in maternal body, it can influence the brain development of the fetus and can also alter the synthesis of the brain-derived neurotropic factor. The current manuscript has been compiled to elaborate different factors which are associated with ADHD particularly focusing on the relationship of vitamin D deficiency in mothers. References material was selected from NCBI (PUBMED), Science direct, Google scholar, Publons etc. Using the terms ADHD, Vitamin D and Maternal nutritional status. Although, controversial relationship was found between the deficiency of Vitamin D level in pregnant women and development of ADHD in children but more controlled trials are required for future direction as well as to rule out other associated causes.

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.

25(OH)Vitamin D and autism spectrum disorder: genetic overlap and causality

OBJECTIVE

To identify whether there exists a genetic correlation and causal relationship between 25(OH)D and autism spectrum disorder (ASD).

METHODS

Based on large-scale genome-wide association studies, a series of genetic approaches were adopted to obtain summary statistics. Using linkage disequilibrium score regression, we assessed the shared polygenic structure between traits and performed pleiotropic analysis under composite null hypothesis (PLACO) to identify pleiotropic loci between complex traits. A bidirectional Mendelian randomization (MR) analysis was applied to investigate whether there is a causal relationship between 25(OH)D and ASD.

RESULTS

The linkage disequilibrium score regression (LDSC) showed a negative genetic correlation between 25(OH)D and ASD (rg = - 0.227, P < 0.05), and PLACO analysis identified 20 independent pleiotropic loci matched to 24 pleiotropic genes, of which the function reveals an underlying mechanism on 25(OH)D and ASD. In Mendelian randomization analysis, the inverse variance-weighted (IVW) method with OR = 0.941 (0.796, 1.112) and p < 0.474 did not show a causal relationship between 25(OH)D and ASD, while, in the reverse Mendelian randomization analysis, IVW method showed OR = 1.042 (0.930, 1.169), indicating no causal relationship either.

CONCLUSION

This study provides evidence for a shared genetic overlap between 25(OH)D and ASD. Bidirectional MR analysis also did not show a definite causal relationship between 25(OH)D and ASD.

Molecular insights into the pathogenic impact of vitamin D deficiency in neurological disorders

Neurological disorders are the major cause of disability, leading to a decrease in quality of life by impairing cognitive, sensorimotor, and motor functioning. Several factors have been proposed in the pathogenesis of neurobehavioral changes, including nutritional, environmental, and genetic predisposition. Vitamin D (VD) is an environmental and nutritional factor that is widely distributed in the central nervous system's subcortical grey matter, neurons of the substantia nigra, hippocampus, thalamus, and hypothalamus. It is implicated in the regulation of several brain functions by preserving neuronal structures. It is a hormone rather than a nutritional vitamin that exerts a regulatory role in the pathophysiology of several neurological disorders, including Alzheimer's disease, Parkinson's disease, epilepsy, and multiple sclerosis. A growing body of epidemiological evidence suggests that VD is critical in neuronal development and shows neuroprotective effects by influencing the production and release of neurotrophins, antioxidants, immunomodulatory, regulation of intracellular calcium balance, and direct effect on the growth and differentiation of nerve cells. This review provides up-to-date and comprehensive information on vitamin D deficiency, risk factors, and clinical and preclinical evidence on its relationship with neurological disorders. Furthermore, this review provides mechanistic insight into the implications of vitamin D and its deficiency on the pathogenesis of neurological disorders. Thus, an understanding of the crucial role of vitamin D in the neurobiology of neurodegenerative disorders can assist in the better management of vitamin D-deficient individuals.

Vitamin D receptor regulates transcription of mitochondrial DNA and directly interacts with mitochondrial DNA and TFAM

Vitamin D receptor (VDR) is an essential transcription factor (TF) synthesized in different cell types. We hypothesized that VDR might also act as a mitochondrial TF. We conducted the experiments in primary cortical neurons, PC12, HEK293T, SH-SY5Y cell lines, human peripheral blood mononuclear cells (PBMC) and human brain. We showed that vitamin D/VDR affects the expression of mitochondrial DNA (mtDNA) encoded oxidative phosphorylation (OXPHOS) subunits. We observed the co-localization of VDR with mitochondria and the mtDNA with confocal microscopy. mtDNA-chromatin-immunoprecipitation and electrophoretic mobility shift assays indicated that VDR was able to bind to the mtDNA D-loop site in several locations, with a consensus sequence 'MMHKCA'. We also reported the possible interaction between VDR and mitochondrial transcription factor A (TFAM) and their binding sites located in close proximity in mtDNA. Consequently, our results showed for the first time that VDR was able to bind and regulate mtDNA transcription and interact with TFAM even in the human brain. These results not only revealed a novel function of VDR, but also showed that VDR is indispensable for energy demanded cells.

Perinatal depression and serum vitamin D status: A cross-sectional study in urban China

BACKGROUND

Although vitamin D has been found to be associated with perinatal depression, the results are inconsistent. The aim of this cross-sectional study was to examine the association between vitamin D and PND in Chinese pregnant women and lactating women.

METHODS

A total of 1773 participants were included, including 907 lactating women and 866 pregnant women. The Edinburgh Postnatal Depression Scale (EPDS) was used to screen for PND, and those with scores ≥13 were considered to have PND. Serum 25-hydroxyvitamin D concentrations were assessed with high-performance liquid chromatography.

RESULTS

The prevalence of postpartum depression (PPD) and antenatal depression (AD) were 15.9 % and 9.8 %, respectively. Compared with individuals with sufficient vitamin D, those with vitamin D deficiency were associated with a higher prevalence of PPD in lactating women (OR = 1.71, 95%CI: 1.01-2.88, p = 0.044). The serum 25(OH)D of lactating women was inversely associated with the scores of the factor "depressive mood" of the EPDS (ORper 5 ng/mL = -0.10, 95%CI: -0.19 to -0.01, p = 0.032). No significant association between serum 25-hydroxyvitamin D and AD was observed.

LIMITATIONS

First, this study is a cross-sectional design, which can only determine associations but not causality. Secondly, this study only included participants from urban areas. Thirdly, there are still some possible confounding factors that have not been considered.

CONCLUSION

In conclusion, this study suggested a significant association between vitamin D status and PPD; however, the association between vitamin D status and AD was not significant.

Vitamin D, a Secosteroid Hormone and Its Multifunctional Receptor, Vitamin D Receptor, in Alzheimer's Type Neurodegeneration

Vitamin D is a secosteroid hormone exerting neurosteroid-like properties. Its well-known nuclear hormone receptor, and recently proposed as a mitochondrial transcription factor, vitamin D receptor, acts for its primary functions. The second receptor is an endoplasmic reticulum protein, protein disulfide isomerase A3 (PDIA3), suggested to act as a rapid response. Vitamin D has effects on various systems, particularly through calcium metabolism. Among them, the nervous system has an important place in the context of our subject. Recent studies have shown that vitamin D and its receptors have numerous effects on the nervous system. Neurodegeneration is a long-term process. Throughout a human life span, so is vitamin D deficiency. Our previous studies and others have suggested that the out-come of long-term vitamin D deficiency (hypovitaminosis D or inefficient utilization of vitamin D), may lead neurons to be vulnerable to aging and neurodegeneration. We suggest that keeping vitamin D levels at adequate levels at all stages of life, considering new approaches such as agonists that can activate vitamin D receptors, and utilizing other derivatives produced in the synthesis process with UVB are crucial when considering vitamin D-based intervention studies. Given most aspects of vitamin D, this review outlines how vitamin D and its receptors work and are involved in neurodegeneration, emphasizing Alzheimer's disease.

Vitamin D and neurodegenerative diseases

Neurodegenerative diseases, featured by progressive loss of structure or function of neurons, are considered incurable at present. Movement disorders like tremor and postural instability, cognitive or behavioral disorders such as memory impairment are the most common symptoms of them and the growing patient population of neurodegenerative diseases poses a serious threat to public health and a burden on economic development. Hence, it is vital to prevent the occurrence of the diseases and delay their progress. Vitamin D can be transformed into a hormone in vivo with both genomic and non-genomic actions, exerting diverse physiological effects. Cumulative evidence indicates that vitamin D can ameliorate neurodegeneration by regulating pertinent molecules and signaling pathways including maintaining Ca2+ homeostasis, reducing oxidative stress, inhibiting inflammation, suppressing the formation and aggregation of the pathogenic protein, etc. This review updates discoveries of molecular mechanisms underlying biological functions of vitamin D in neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, multiple sclerosis, and vascular dementia. Clinical trials investigating the influence of vitamin D supplementation in patients with neurodegenerative diseases are also summarized. The synthesized information will probably provoke an enhanced understanding of the neuroprotective roles of vitamin D in the nervous system and provide therapeutic options for patients with neurodegenerative diseases in the future.

Therapeutic and mechanistic intervention of vitamin D in neuropsychiatric disorders

Vitamin D deficiency is believed to affect between 35 and 55% of the world's population, making it a hidden pandemic. In addition to its role in bone and calcium homeostasis, vitamin D has also been linked in preclinical and clinical research to brain function. These outcomes have also been used for a variety of neuropsychiatric and neurodevelopmental problems. Nevertheless, these individuals are more prone to develop signs of cognitive decline. This review will emphasize the association between vitamin D and neuropsychiatric illnesses such as autism, schizophrenia, depression, and Attention Deficit Hyperactivity Disorder (ADHD). While numerous research show vitamin D's essential role in cognitive function in neuropsychiatric illnesses, it is too early to propose its effect on cognitive symptoms with certainty. It is necessary to conduct additional research into the associations between vitamin D deficiency and cognitive abnormalities, particularly those found in autism, schizophrenia, depression, and ADHD, to develop initiatives that address the pressing need for novel and effective preventative therapeutic strategies.

Vitamin D and the Central Nervous System: Causative and Preventative Mechanisms in Brain Disorders

Twenty of the last one hundred years of vitamin D research have involved investigations of the brain as a target organ for this hormone. Our group was one of the first to investigate brain outcomes resulting from primarily restricting dietary vitamin D during brain development. With the advent of new molecular and neurochemical techniques in neuroscience, there has been increasing interest in the potential neuroprotective actions of vitamin D in response to a variety of adverse exposures and how this hormone could affect brain development and function. Rather than provide an exhaustive summary of this data and a listing of neurological or psychiatric conditions that vitamin D deficiency has been associated with, here, we provide an update on the actions of this vitamin in the brain and cellular processes vitamin D may be targeting in psychiatry and neurology.

The Mediation Effect of Peripheral Biomarkers of Calcium Metabolism and Chronotypes in Bipolar Disorder Psychopathology

Calcium (Ca++) metabolism may be impaired in several psychiatric diseases. We hypothesize that calcium imbalance might also correlate with a specific chronotype and could be recognized as a marker of illness severity in bipolar disorder (BD). We aimed to (1) identify the association between calcium imbalance and a specific chronotype in a cohort of BD patients, and (2) test the mediation role of high parathyroid hormone (PTH) levels towards a specific chronotype and illness severity in BD patients. Patients’ socio-demographic and clinical characteristics were collected with an ad-hoc schedule. We administered the Hamilton Depression Rating Scale (HAM-D), the Hamilton Rating Scale for Anxiety (HAM-A), the Young Mania Rating Scale (YMRS), and the Morningness Eveningness Questionnaire (MEQ). 100 patients affected by BD were recruited. The Kruskal-Wallis test showed a significant difference between the three MEQ groups in PTH levels (p < 0.001) and vitamin D levels (p = 0.048) but not in Ca++ levels (p = 0.426). Dwass-Steel-Critchlow-Fligner Pairwise analyses performed concerning three MEQ groups revealed significantly higher scores on PTH levels in MEQ-E subjects compared to MEQ-M and MEQ-I (in both cases, p < 0.001). No differences emerged between calcium levels among the three chronotypes. The mediation analysis has shown that elevated PTH levels are directly influenced by more severe HAM-A, HAM-D, and YMRS scores. MEQ-E could be a marker related to BD and predispose to various factors influencing mood symptoms. The combination of vitamin D therapy in MEQ-E may help to improve prognosis in this subtype of patients affected by BD.

Association of vitamin D receptor gene haplotypes with late‑onset Alzheimer's disease in a Southeastern European Caucasian population

Vitamin D receptor (VDR) gene single nucleotide polymorphisms (SNPs) have been investigated over the past years with the aim of identifying any association with the development of Alzheimer's disease (AD). However, information regarding the potential association of VDR SNP haplotypes with AD is limited. The aim of the present study was to provide additional knowledge on the effects of VDR haplotypes on the development of late-onset AD in a cohort of Southeastern European Caucasians (SECs). The study sample included 78 patients with late-onset AD and 103 healthy subjects as the control group. VDR SNPs that were analyzed were TaqI (rs731236), BsmI (rs1544410) and FokI (rs2228570). The CAC (TaqI, BsmI and FokI) haplotype was found to be associated with a 53% lower risk of developing the disease (OR, 0.47; 95% CI, 0.23-0.96; P=0.04) and the TAC (TaqI, BsmI and FokI) haplotype was associated with an ~6-fold greater risk of developing AD (OR, 6.19; 95% CI, 1.91-20.13; P=0.0028). Female subjects carrying the TAC haplotype had a ~9-fold greater risk of developing AD in comparison to female control subjects (OR, 9.27; 95% CI, 1.86-46.28; P<0.05). The TaqI and BsmI polymorphisms were in high linkage disequilibrium (D'=0.9717, r=0.8467) and produced a haplotype with a statistically significant different frequency between the control and AD group. The TA (TaqI and BsmI) haplotype was associated with an ~8-fold greater risk of developing AD (OR, 8.27; 95% CI, 2.70-25.28; P<0.05). Female TA carriers had an ~14-fold greater risk of developing the disease in comparison to female control subjects (OR, 13.93; 95% CI, 2.95-65.87; P<0.05). On the whole, the present study demonstrates that in the SEC population, TAC and TA are risk haplotypes for AD, while the CAC haplotype may act protectively. SEC women carrying the TAC or TA haplotype are at a greater risk of developing AD, thus suggesting that women are markedly affected by the poor utilization of vitamin D induced by the VDR haplotype.

Vitamin D as a Risk Factor for Multiple Sclerosis: Immunoregulatory or Neuroprotective?

Vitamin D insufficiency during childhood has been linked to the development of multiple sclerosis (MS), typically an adult-onset inflammatory demyelinating disease of the central nervous system (CNS). Since vitamin D was known to have immunoregulatory properties on both innate and adaptive immunity, it was hypothesized that low vitamin D resulted in aberrant immune responses and the development of MS. However, vitamin D receptors are present on many cell types, including neurons, oligodendrocytes, astrocytes and microglia, and vitamin D has profound effects on development and function of the CNS. This leads to the possibility that low vitamin D may alter the CNS in a manner that makes it vulnerable to inflammation and the development of MS. This review analysis the role of vitamin D in the immune and nervous system, and how vitamin D insufficiency in children may contribute to the development of MS.

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.

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 and the Risks of Depression and Anxiety: An Observational Analysis and Genome-Wide Environment Interaction Study

Previous studies have suggested that vitamin D (VD) was associated with psychiatric diseases, but efforts to elucidate the functional relevance of VD with depression and anxiety from genetic perspective have been limited. Based on the UK Biobank cohort, we first calculated polygenic risk score (PRS) for VD from genome-wide association study (GWAS) data of VD. Linear and logistic regression analysis were conducted to evaluate the associations of VD traits with depression and anxiety traits, respectively. Then, using individual genotype and phenotype data from the UK Biobank, genome-wide environment interaction studies (GWEIS) were performed to identify the potential effects of gene × VD interactions on the risks of depression and anxiety traits. In the UK Biobank cohort, we observed significant associations of blood VD level with depression and anxiety traits, as well as significant associations of VD PRS and depression and anxiety traits. GWEIS identified multiple candidate loci, such as rs114086183 (p = 4.11 × 10⁻⁸, LRRTM4) for self-reported depression status and rs149760119 (p = 3.88 × 10⁻⁸, GNB5) for self-reported anxiety status. Our study results suggested that VD was negatively associated with depression and anxiety. GWEIS identified multiple candidate genes interacting with VD, providing novel clues for understanding the biological mechanism potential associations between VD and psychiatric disorders.

Protein disulfide isomerase A3 might be involved in the regulation of 24-dehydrocholesterol reductase via vitamin D equilibrium in primary cortical neurons

Vitamin D is a secosteroid hormone mediating its functions via vitamin D receptor (VDR) and an endoplasmic reticulum chaperone, protein disulfide isomerase A3 (PDIA3). From a physiological perspective, there is also a well-established association of cholesterol and vitamin D synthesis, since both share a common metabolic substrate, 7 dehydrocholesterol (7-DHC). Yet, the potential basic pathways, of the biological interplay of DHCR24 and vitamin D equilibrium, on neuronal level, are yet to be determined. In this study, we aimed to investigate the relation between vitamin D pathways and DHCR24 in primary cortical neuron cultures. The neocortex of Sprague-Dawley rat embryos (E16) was used for the preparation of primary cortical neuron cultures. DHCR24 mRNA and protein expression levels were determined by qRT-PCR, Western blotting, and immunofluorescent labeling in 1,25-dihydroxyvitamin D3-treated or VDR/PDIA3-silenced primary cortical neurons. The mRNA expression of DHCR24 was significantly decreased in the cortical neurons treated with 10-8M 1,25-dihydroxyvitamin D3 (p<0.001). In parallel with the mRNA results, DHCR24 protein expression in cortical neurons treated with 10-8M 1,25-dihydroxyvitamin D3 was also significantly lower than untreated neurons (p<0.05). These data were also confirmed with immunofluorescent labeling and fluorescence intensity measurements of DHCR24 (p<0.001). Finally, DHCR24 mRNA expression level was significantly increased in PDIA3 siRNA-treated neurons (p<0.05). Similar to the mRNA results, the DHCR24 protein expression of PDIA3 siRNA-treated neurons was also statistically higher than the other groups (p<0.05). Results of this mechanistic experimental basic study demonstrate that DHCR24 mRNA expression and protein concentrations attenuated in response to vitamin D treatment. Furthermore, we observed that PDIA3 might be involved in this modulatory effect. Our findings indicate a complex interaction of DHCR24 and vitamin D equilibrium, through the involvement of PDIA3 and vitamin D in the modulation of cholesterol metabolism in neuronal cells, requiring future studies on the field.

Co-treatment of vitamin D supplementation with enriched environment improves synaptic plasticity and spatial learning and memory in aged rats

RATIONALE AND OBJECTIVE

Environmental enrichment (EE) has been shown in old rats to improve learning and memory. Vitamin D (VitD) has also been shown to modulate age-related, cognitive dysfunction. As both EE and VitD could work to improve cognition via enhancement of neurotrophic factors, their effects might occlude one another. Therefore, a clinically relevant question is whether noted cognition-promoting effects of EE and VitD can co-occur.

METHODS

Aged rats were housed for 6 weeks in one of three housing conditions: environmentally enriched (EE), socially enriched (SE), or standard condition (SC). Further, a 4th group was co-treated with VitD supplementation (400 IU kg^-1 daily, 6 weeks) under EE conditions (EE + VitD).

RESULTS

Treatment with VitD and EE housing were associated with higher score on measures of learning and memory and exhibited lower anxiety scores compared to EE alone, SE or SC as assayed in the elevated plus maze, Morris water maze, passive avoidance, and open field tasks. Additionally, in the EE + VitD group, mRNA expression levels of NGF, TrkA, BDNF, Nrf2, and IGF-1 were significantly higher compared to expression seen in the EE group. Furthermore, field potential recordings showed that EE + VitD resulted in a greater enhancement of hippocampal LTP and neuronal excitability when compared to EE alone.

CONCLUSIONS

These findings demonstrate that in aged rats exposure to EE and VitD results in effects on hippocampal cognitive dysfunction and molecular mechanisms which are greater than effects of EE alone, suggesting potential for synergistic therapeutic effects for management of age-related cognitive decline.

Altered Transcriptional Profile of Mitochondrial DNA-Encoded OXPHOS Subunits, Mitochondria Quality Control Genes, and Intracellular ATP Levels in Blood Samples of Patients with Parkinson's Disease

Mitochondrial dysfunctions are significant contributors to neurodegeneration. One result or a cause of mitochondrial dysfunction might be the disruption of mtDNA transcription. Limited data indicated an altered expression of mtDNA encoded transcripts in Alzheimer's disease (AD) or Parkinson's disease (PD). The number of mitochondria is high in cells with a high energy demand, such as muscle or nerve cells. AD or PD involves increased risk of cardiomyopathy, suggesting that mitochondrial dysfunction might be systemic. If it is systemic, we should observe it in different cell types. Given that, we wanted to investigate any disruption in the regulation of mtDNA encoded gene expression in addition to PINK1, PARKIN, and ATP levels in peripheral blood samples of PD cases who are affected by a neurodegenerative disorder that is very well known by its mitochondrial aspects. Our results showed for the first time that: 1) age of onset > 50 PD sporadic (PDS) cases: mtDNA transcription and quality control genes were affected; 2) age of onset <50 PDS cases: only mtDNA transcription was affected; and 3) PD cases with familial background: only quality control genes were affected. mtDNA copy number was not a confounder. Intracellular ATP levels of PD case subgroups were significantly higher than those of healthy subjects. We suggest that a systemic dysregulation of transcription of mtDNA or mitochondrial quality control genes might result in the development of a sporadic form of the disease. Additionally, ATP elevation might be an independent compensatory and response mechanism. Hyperactive cells in AD and PD require further investigation.

DHCR7 rs12785878 T>C Polymorphism Is Associated With an Increased Risk of Early Onset of Alzheimer's Disease in Chinese Population

Background: Vitamin D insufficiency has been considered a risk factor for Alzheimer's disease (AD) in several studies. Recently, four single-nucleotide polymorphisms (SNPs) to be genome-wide significant for 25-hydroxyvitamin D [25(OH)D] were identified to have an association with the risk of AD. These include GC rs2282679 A>C, CYP2R1 rs10741657 T>C, DHCR7 rs12785878 T>C, and CYP24A1 rs6013897 T>A. However, the association between these polymorphisms and AD susceptibility in the Chinese population remains unclear.

Methods: A case-control cohort study was conducted in 676 AD patients (mean age at onset was 69.52 ± 10.90 years, male: 39.2%) and 551 healthy controls (mean age was 67.73 ± 6.02 years, male: 44.8%). Genotyping was determined by PCR and SNaPshot sequencing. To determine whether the four SNPs account for risks in AD in Chinese population, multivariate logistic regression models were performed. Stratified analysis was performed based on gender and age of onset of AD, separately. Statistical significance was set at 0.0125 (0.05/4) based on Bonferroni correction.

Findings:DHCR7 rs12785878 T>C was found to be significantly associated with an increased risk of early-onset Alzheimer's disease (EOAD) (n = 300, risk allele C, adjusted OR = 1.542, adjusted 95% CI = 1.176–2.023, p = 0.002). There was no statistical significance of the other three SNPs between the two groups.

Interpretation: Our results suggested that DHCR7 rs12785878 T>C might be associated with an increased risk of EOAD in the Chinese population, while other polymorphisms related to vitamin D insufficiency might not be. However, due to the limited data in this study, replication studies in a larger sample are required.

Antidepressant Actions of Ketamine: Potential Role of L-Type Calcium Channels

Recently, the United States Food and Drug Administration approved esketamine, the S-enantiomer of ketamine, as a fast-acting therapeutic drug for treatment-resistant depression. Although ketamine is known as an N-methyl-d-aspartate (NMDA) receptor antagonist, the underlying mechanisms of how it elicits an antidepressant effect, specifically at subanesthetic doses, are not clear and remain an advancing field of research interest. On the other hand, high-dose (more than the anesthetic dose) ketamine-induced neurotoxicity in animal models has been reported. There has been progress in understanding the potential pathways involved in ketamine-induced antidepressant effects, some of which include NMDA-receptor antagonism, modulation of voltage-gated calcium channels, and brain-derived neurotrophic factor (BDNF) signaling. Often these pathways have been shown to be linked. Voltage-gated L-type calcium channels have been shown to mediate the rapid-acting antidepressant effects of ketamine, especially involving induction of BDNF synthesis downstream, while BDNF deficiency decreases the expression of L-type calcium channels. This review focuses on the reported studies linking ketamine's rapid-acting antidepressant actions to L-type calcium channels with an objective to present a perspective on the importance of the modulation of intracellular calcium in mediating the effects of subanesthetic (antidepressant) versus high-dose ketamine (anesthetic and potential neurotoxicant), the latter having the ability to reduce intracellular calcium by blocking the calcium-permeable NMDA receptors, which is implicated in potential neurotoxicity.

Vitamin D and Neurotrophin Levels and Their Impact on the Symptoms of Schizophrenia

INTRODUCTION

Vitamin D is involved in brain development and functioning, as well as in regulation of neurotrophic factors. Changes in the expression of those factors are possibly responsible for morphologic abnormalities and symptoms in patients suffering from schizophrenia.

OBJECTIVE

The main goal of this research was to investigate the interrelationship between vitamin D, nerve growth factors (NGF, brain-derived neurotrophic factor [BDNF], and neuregulin-1 [NRG1]), and schizophrenia symptom domains.

METHODS

This research included 97 inpatients diagnosed with schizophrenia. Schizophrenia symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS). Blood samples were taken in order to analyze concentrations of vitamin D, BDNF, NRG1, and NGF growth factors. The obtained results were used in a multiple regression analysis.

RESULTS

The vitamin D concentration positively affected the concentration of NRG1 (F = 8.583, p = 0.005) but not the concentration of other investigated growth factors (BDNF and NGF). The clinical characteristics and symptom domains of schizophrenia seemed to be unaffected by the concentrations of vitamin D, BDNF, and NGF, while the NRG1 concentration significantly affected positive symptom domains of schizophrenia (F = 4.927, p = 0.030).

CONCLUSION

The vitamin D concentration positively affected NRG1 levels but not schizophrenia symptomatology as measured by PANSS. The as-sociation between the two could be intermediated via NRG1.

Vitamin D and schizophrenia: 20 years on

Many epidemiological studies have highlighted the link between vitamin D deficiency and schizophrenia. In particular, two prominent studies report an association between neonatal vitamin D deficiency and an increased risk of schizophrenia. In parallel, much has been learnt about the role of vitamin D in the developing central nervous system over the last two decades. Studies in rodent models of developmental vitamin D (DVD)-deficiency describe how brain development is altered leading to a range of neurobiological and behavioral phenotypes of interest to schizophrenia. While glutamate and gamma aminobutyric acid (GABA) systems have been little investigated in these models, alterations in developing dopamine systems are frequently reported. There have been far more studies reporting patients with schizophrenia have an increased risk of vitamin D deficiency compared to well controls. Here we have conducted a systematic review and meta-analysis that basically confirms this association and extends this to first-episode psychosis. However, patients with schizophrenia also have poorer general health, poorer diets, are frequently less active and also have an increased risk of other medical conditions, all factors which reduce circulating vitamin D levels. Therefore, we would urge caution in any causal interpretation of this association. We also summarize the inconsistent results from existing vitamin D supplementation trials in patients with schizophrenia. In respect to animal models of adult vitamin D deficiency, such exposures produce subtle neurochemical alterations and effects on cognition but do not appear to produce behavioral phenotypes of relevance to schizophrenia. We conclude, the hypothesis that vitamin D deficiency during early life may increase the risk of schizophrenia remains plausible and warrants ongoing research.

PGC-1α reduces Amyloid-β deposition in Alzheimer's disease: Effect of increased VDR expression

Amyloid-β (Aβ) is the core component of amyloid plaques of Alzheimer's disease (AD). Recent evidence has confirmed that Aβ triggers neurodegeneration by dramatically suppressing vitamin D receptor (VDR) expression. Thus far, the onset mechanisms and means of preventing AD are largely unknown. Perioxisome proliferator-activated receptor-γ coactivator (PGC-1α), as a transcriptional coactivator of VDR could protect cells against oxidative stress. Thus, upregulation of PGC-1α is a candidate therapeutic strategy for AD. To investigate the effect of PGC-1α in AD, and to illuminate the precise involvement of VDR in the neuroprotective strategy, the varies of molecular of PGC-1α and VDR were studied in APP/PS-1 double transgenic (2xTg-AD) mice at 6 months of age, significant reduction in the expression of PGC-1α and VDR was found in their hippocampus and the cortex. Besides, a specific mouse line, Dlx5/6-Cre:PGC-1α^fl/fl in which the PGC-1α deficiency was limited to the hippocampus and the cortex, was used to study the target intervention of PGC-1α, decreased expression of VDR and increased oxidative damage were observed in AD-related brain regions by PGC-1α deficiency. To explore the function and therapeutic strategy of PGC-1α in AD, an adeno-associated virus (AAV) was used to induce PGC-1α overexpressed in the hippocampus of 2xTg-AD mice. Overexpressed PGC-1α results in a remarkable increase in the levels of VDR associated with a significant reduction in the expression of Aβ plaques and of 8-oxo-dG in 2xTg-AD mice. These data may have ramifications for neuroprotective strategies targeting overexpression of PGC-1α in Alzheimer's disease.

Vitamin D: Brain and Behavior

It has been 20 years since we first proposed vitamin D as a "possible" neurosteroid.^{( 1 )} Our work over the last two decades, particularly results from our cellular and animal models, has confirmed the numerous ways in which vitamin D differentiates the developing brain. As a result, vitamin D can now confidently take its place among all other steroids known to regulate brain development.^{( 2 )} Others have concentrated on the possible neuroprotective functions of vitamin D in adult brains. Here these data are integrated, and possible mechanisms outlined for the various roles vitamin D appears to play in both developing and mature brains and how such actions shape behavior. There is now also good evidence linking gestational and/or neonatal vitamin D deficiency with an increased risk of neurodevelopmental disorders, such as schizophrenia and autism, and adult vitamin D deficiency with certain degenerative conditions. In this mini-review, the focus is on what we have learned over these past 20 years regarding the genomic and nongenomic actions of vitamin D in shaping brain development, neurophysiology, and behavior in animal models. © 2020 The Author. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Low Levels of LRRK2 Gene Expression are Associated with LRRK2 SNPs and Contribute to Parkinson's Disease Progression

Parkinson's disease (PD) is a chronic neurodegenerative disease that has relatively slow progression with motor symptoms. Leucine-rich repeat kinase 2 (LRRK2) gene mutations and polymorphisms are suggested to be associated with PD. In this study, we aimed to investigate the association between single-nucleotide polymorphisms (SNPs) of the LRRK2 gene, namely, rs11176013, rs10878371, rs11835105, and PD. Genotypes of 132 PD cases and 133 healthy individuals were determined by qRT-PCR. Haplotype analysis was performed. Additionally, LRRK2 mRNA expression levels were determined in 83 PD cases and 55 healthy subjects. The relationship between LRRK2 mRNA levels, the target SNPs, and clinical data was also investigated. Our results indicated that the "GG" genotype and "G" allele of rs11176013 and the "CC" genotype and "C" allele of rs10878371 were more frequent in cases. The "GCG" haplotype was significantly more frequent in cases. LRRK2 mRNA expression levels in patients were significantly lower than those in healthy individuals. The patients with the "CC" genotype for rs10878371 and the "GG" genotype for rs11176013 had decreased LRRK2 mRNA levels. We found that the rs11176013 "GG" genotype and the rs10878371 "CC" genotype were less frequently seen in cases with akinetic rigid or combined akinetic rigid and tremor-dominant initial symptoms. Consequently, our results demonstrate that the rs11176013 and rs10878371 polymorphisms are associated with PD in a Turkish cohort, and moreover, these results suggest that these polymorphisms may affect the expression of the LRRK2 gene and disease progression and thus play a role in the pathogenesis of PD.

Noteworthy idiosyncrasies of 1α,25-dihydroxyvitamin D3 kinetics for extrapolation from mouse to man: Commentary

Calcitriol or 1,25-dihydroxyvitamin D₃ [1,25(OH)₂ D₃ ] is the active ligand of the vitamin D receptor (VDR) that plays a vital role in health and disease. Vitamin D is converted to the relatively inactive metabolite, 25-hydroxyvitamin D₃ [25(OH)D₃ ], by CYP27A1 and CYP2R1 in the liver, then to 1,25(OH)₂ D₃ by a specific, mitochondrial enzyme, CYP27B1 (1α-hydroxylase) that is present primarily in the kidney. The degradation of both metabolites is mostly carried out by the more ubiquitous mitochondrial enzyme, CYP24A1. Despite the fact that calcitriol inhibits its formation and degradation, allometric scaling revealed strong interspecies correlation of the net calcitriol clearance (CL estimated from dose/AUC_∞ ), production rate (PR), and basal, plasma calcitriol concentration with body weight (BW). PBPK-PD (physiologically based pharmacokinetic-pharmacodynamic) modeling confirmed the dynamic interactions between calcitriol and Cyp27b1/Cyp24a1 on the decrease in the PR and increase in CL in mice. Close scrutiny of the literature revealed that basal levels of calcitriol had not been taken into consideration for estimating the correct AUC_∞ and CL after exogenous calcitriol dosing in both animals and humans, leading to an overestimation of AUC_∞ and underestimation of the plasma CL. In humans, CL was decreased in chronic kidney disease but increased in cancer. Collectively, careful pharmacokinetic data analysis and improved definition are achieved with PBPK-PD modeling, which embellishes the complexity of dose, enzyme regulation, and disease conditions. Allometric scaling and PBPK-PD modeling were applied successfully to extend the PBPK model to predict calcitriol kinetics in cancer patients.

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.

The Influence of Vitamin D on Neurodegeneration and Neurological Disorders: A Rationale for its Physio-pathological Actions

Vitamin D is a steroid hormone implicated in the regulation of neuronal integrity and many brain functions. Its influence, as a nutrient and a hormone, on the physiopathology of the most common neurodegenerative diseases is continuously emphasized by new studies. This review addresses what is currently known about the action of vitamin D on the nervous system and neurodegenerative diseases such as Multiple Sclerosis, Alzheimer's disease, Parkinson's disease and Amyotrophic Lateral Sclerosis. Further vitamin D research is necessary to understand how the action of this "neuroactive" steroid can help to optimize the prevention and treatment of several neurological diseases.

Effects of Vitamin D Use on Outcomes of Psychotic Symptoms in Alzheimer Disease Patients

OBJECTIVE

To identify medications that may prevent psychosis in patients with Alzheimer disease (AD).

METHODS

The authors compared the frequency of medication usage among patients with AD with or without psychosis symptoms (AD + P versus AD - P). The authors also conducted survival analysis on time to psychosis for patients with AD to identify drugs with beneficial effects. The authors further explored the potential molecular mechanisms of identified drugs by gene-signature analysis. Specifically, the gene expression profiles induced by the identified drug(s) were collected to derive a list of most perturbed genes. These genes were further analyzed by the associations of their genetic variations with AD or psychosis-related phenotypes.

RESULTS

Vitamin D was used more often in AD - P patients than in AD + P patients. Vitamin D was also significantly associated with delayed time to psychosis. AD and/or psychosis-related genes were enriched in the list of genes most perturbed by vitamin D, specifically genes involved in the regulation of calcium signaling downstream of the vitamin D receptor.

CONCLUSION

Vitamin D was associated with delayed onset of psychotic symptoms in patients with AD. Its mechanisms of action provide a novel direction for development of drugs to prevent or treat psychosis in AD. In addition, genetic variations in vitamin D-regulated genes may provide a biomarker signature to identify a subpopulation of patients who can benefit from vitamin D treatment.

Vitamin D deficiency and androgen excess result eutrophic remodeling and reduced myogenic adaptation in small cerebral arterioles in female rats

Vitamin D (vitD) insufficiency affects 1 billion people worldwide. Androgen excess (AE) occurs in 8% of fertile females. There are few data about the combined effect of vitD deficiency and AE on the early biomechanical changes of cerebral arterioles in fertile-aged female. Forty-six adolescent female Wistar rats (21-28 day-old, weighing 90-110 g) were grouped randomly in four groups: vitD supplemented groups with and without transdermal testosterone (T) treatment, as well as vitD deficient groups also with and without transdermal T (n = 11 or 12, in all cases). After 8 weeks of treatment, anterior cerebral arterioles (in vivo diameter of 90-130 µm) were obtained and cylindrical segments were examined by pressure arteriography. Myogenic tone, tangential stress and incremental elastic moduli were computed and statistically analyzed. Elastic density was studied on resorcin-fuchsin-stained histological section. VitD deficiency with T treatment resulted in significantly lower inner radii and higher wall thickness values with reduced tangential stress and increased elastic fiber density. VitD deficiency reduced myogenic tone at higher intraluminar pressures (>110 mmHg). Our conclusion is that plasma vitD level is an important factor in the control of myogenic tone in cerebral resistance arteries. AE and vitD deficiency acting parallel induce remodeling of their wall.

Focus on 1,25-Dihydroxyvitamin D3 in the Peripheral Nervous System

In this review, we draw attention to the roles of calcitriol (1,25-dihydroxyvitamin D3) in the trophicity of the peripheral nervous system. Calcitriol has long been known to be crucial in phosphocalcium homeostasis. However, recent discoveries concerning its involvement in the immune system, anti-cancer defenses, and central nervous system development suggest a more pleiotropic role than previously thought. Several studies have highlighted the impact of calcitriol deficiency as a promoting factor of various central neurological diseases, such as multiple sclerosis, amyotrophic lateral sclerosis, Parkinson's disease, and Alzheimer's disease. Based on these findings and recent publications, a greater role for calcitriol may be envisioned in the peripheral nervous system. Indeed, calcitriol is involved in myelination, axonal homogeneity of peripheral nerves, and neuronal-cell differentiation. This may have useful clinical consequences, as calcitriol supplementation may be a simple means to avoid the onset and/or development of peripheral nervous-system disorders.

Molecular basis of vitamin D action in neurodegeneration: the story of a team perspective

Vitamin D, a secosteroid hormone, has, over the years, mainly been known for its classic role in the maintenance of calcium homeostasis of the human body. However, there is increasing understanding that vitamin D contributes to the regulation of Ca²⁺ homeostasis, especially via voltage-gated calcium channels, in another major organ that uses calcium, the brain. Almost 30 years ago, the role of dysregulation in the aging brain and in Alzheimer's disease (AD) gave rise to the Ca²⁺ hypothesis of brain aging and dementia. We thus made calcium homeostasis the starting point of our studies, proposing the notion that the consequences of long-term deficiency and/or inefficient utilization of vitamin D may cause the disruption of calcium homeostasis in neurons, this creating a vulnerability of neurons to aging and neurodegeneration. In this mini-review, we aim to describe the potential of vitamin D (cholecalciferol) as a neurosteroid based on our findings and conclusions.

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.

Vitamin D in Synaptic Plasticity, Cognitive Function, and Neuropsychiatric Illness

Over a billion people worldwide are affected by vitamin D deficiency. Although vitamin D deficiency is associated with impaired cognition, the mechanisms mediating this link are poorly understood. The extracellular matrix (ECM) has now emerged as an important participant of synaptic plasticity and a new hypothesis is that vitamin D may interact with aggregates of the ECM, perineuronal nets (PNNs), to regulate brain plasticity. Dysregulation of PNNs caused by vitamin D deficiency may contribute to the presentation of cognitive deficits. Understanding the molecular mechanisms underpinning the role of vitamin D in brain plasticity and cognition could help identify ways to treat cognitive symptoms in schizophrenia and other neuropsychiatric conditions.

Adult vitamin D deficiency disrupts hippocampal-dependent learning and structural brain connectivity in BALB/c mice

Converging evidence from human and animal studies support an association between vitamin D deficiency and cognitive impairment. Previous studies have shown that hippocampal volume is reduced in adults with vitamin D deficiency as well as in a range of disorders, such as schizophrenia. The aim of the current study was to examine the effect of adult vitamin D (AVD) deficiency on hippocampal-dependent spatial learning, and hippocampal volume and connectivity in healthy adult mice. Ten-week-old male BALB/c mice were fed a control (vitamin D 1500 IU/kg) or vitamin D-depleted (vitamin D 0 IU/kg) diet for a minimum of 10 weeks. The mice were then tested for hippocampal-dependent spatial learning using active place avoidance (APA) and on tests of muscle and motor coordination (rotarod and grip strength). The mice were perfused and brains collected to acquire ex vivo structural and diffusion-weighted images using a 16.4 T MRI scanner. We also performed immunohistochemistry to quantify perineuronal nets (PNNs) and parvalbumin (PV) interneurons in various brain regions. AVD-deficient mice had a lower latency to enter the shock zone on APA, compared to control mice, suggesting impaired hippocampal-dependent spatial learning. There were no differences in rotarod or grip strength, indicating that AVD deficiency did not have an impact on muscle or motor coordination. AVD deficiency did not have an impact on hippocampal volume. However, AVD-deficient mice displayed a disrupted network centred on the right hippocampus with abnormal connectomes among 29 nodes. We found a reduction in PNN positive cells, but no change in PV, centred on the hippocampus. Our results provide compelling evidence to show that AVD deficiency in otherwise healthy adult mice may play a key role in hippocampal-dependent learning and memory formation. We suggest that the spatial learning deficits could be due to the disruption of right hippocampal structural connectivity.

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.

Vitamin D protects dopaminergic neurons against neuroinflammation and oxidative stress in hemiparkinsonian rats

BACKGROUND

The deficiency in 1α, 25-dihydroxyvitamin D3 (VD3) seems to increase the risk for neurodegenerative pathologies, including Parkinson's disease (PD). The majority of its actions are mediated by the transcription factor, VD3 receptor (VD3R).

METHODS

The neuroprotective effects of VD3 were investigated on a PD model. Male Wistar rats were divided into the following groups: sham-operated (SO), 6-OHDA-lesioned (non-treated), and 6-OHDA-lesioned and treated with VD3 (7 days before the lesion, pre-treatment or for 14 days after the 6-OHDA striatal lesion, post-treatment). Afterwards, the animals were subjected to behavioral tests and euthanized for striatal neurochemical and immunohistochemical assays. The data were analyzed by ANOVA and the Tukey test and considered significant for p < 0.05.

RESULTS

We showed that pre- or post-treatments with VD3 reversed behavioral changes and improved the decreased DA contents of the 6-OHDA group. In addition, VD3 reduced the oxidative stress, increased (TH and DAT), and reduced (TNF-alpha) immunostainings in the lesioned striata. While significant decreases in VD3R immunoreactivity were observed after the 6-OHDA lesion, these changes were blocked after VD3 pre- or post-treatments. We showed that VD3 offers neuroprotection, decreasing behavioral changes, DA depletion, and oxidative stress. In addition, it reverses partially or completely TH, DAT, TNF-alpha, and VD3R decreases of immunoreactivities in the non-treated 6-OHDA group.

CONCLUSIONS

Taken together, VD3 effects could result from its anti-inflammatory and antioxidant actions and from its actions on VD3R. These findings should stimulate translational research towards the VD3 potential for prevention or treatment of neurodegenerative diseases, as PD.