1,25-Dihydroxyvitamin D modulates L-type voltage-gated calcium channels in a subset of neurons in the developing mouse prefrontal cortex

Vitamin D: The crucial neuroprotective factor for nerve cells

Vitamin D is well known for its role in regulating the absorption and utilization of calcium and phosphorus as well as bone formation, and a growing number of studies have shown that vitamin D also has important roles in the nervous system, such as maintaining neurological homeostasis and protecting normal brain function, and that neurons and glial cells may be the targets of these effects. Most reviews of vitamin D's effects on the nervous system have focused on its overall effects, without distinguishing the contributors to these effects. In this review, we mainly focus on the cells of the central nervous system, summarizing the effects of vitamin D on them and the related pathways. With this review, we hope to elucidate the role of vitamin D in the nervous system at the cellular level and provide new insights into the prevention and treatment of neurodegenerative diseases in the direction of neuroprotection, myelin regeneration, and so on.

Vitamins, minerals and their maternal levels' role in brain development: An updated literature-review

One's neurobehavioural and mental health are built during the exact and complex process of brain development. It is thought that fetal development is where neuropsychiatric disorders first emerged. Behavioural patterns can change as a result of neuropsychiatric illnesses. The incidence is rising quickly; nevertheless, providing exceptional care remains a significant challenge for families and healthcare systems. It has been demonstrated that one of the main factors causing the transmission of these diseases is maternal exposure. Through physiologic pathways, maternal health and intrauterine exposures can affect brain development. Our attention has been focused on epigenetic factors, particularly in the gestational environment, which may be responsible for human neurodegenerative diseases since our main mental development occurs during the nine months of intrauterine life. After thoroughly searching numerous databases, this study examined the effect of fat-soluble vitamins, water-soluble vitamins, and minerals and their maternal-level effect on brain development.

Vitamin D Deficiency Does Not Affect Cognition and Neurogenesis in Adult C57Bl/6 Mice

Vitamin D deficiency is a global problem. Vitamin D, the vitamin D receptor, and its enzymes are found throughout neuronal, ependymal, and glial cells in the brain and are implicated in certain processes and mechanisms in the brain. To investigate the processes affected by vitamin D deficiency in adults, we studied vitamin D deficient, control, and supplemented diets over 6 weeks in male and female C57Bl/6 mice. The effect of the vitamin D diets on proliferation in the neurogenic niches, changes in glial cells, as well as on memory, locomotion, and anxiety-like behavior, was investigated. Six weeks on a deficient diet was adequate time to reach deficiency. However, vitamin D deficiency and supplementation did not affect proliferation, neurogenesis, or astrocyte changes, and this was reflected on behavioral measures. Supplementation only affected microglia in the dentate gyrus of female mice. Indicating that vitamin D deficiency and supplementation do not affect these processes over a 6-week period.

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.

Neuro-Restorative Effect of Nimodipine and Calcitriol in 1-Methyl 4-Phenyl 1,2,3,6 Tetrahydropyridine-Induced Zebrafish Parkinson's Disease Model

OBJECTIVE

Parkinson's disease (PD) is one of the most prevalent neurodegenerative diseases, characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta. The treatment of PD aims to alleviate motor symptoms by replacing the reduced endogenous dopamine. Currently, there are no disease-modifying agents for the treatment of PD. Zebrafish (Danio rerio) have emerged as an effective tool for new drug discovery and screening in the age of translational research. The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is known to cause a similar loss of dopaminergic neurons in the human midbrain, with corresponding Parkinsonian symptoms. L-type calcium channels (LTCCs) have been implicated in the generation of mitochondrial oxidative stress, which underlies the pathogenesis of PD. Therefore, we investigated the neuro-restorative effect of LTCC inhibition in an MPTP-induced zebrafish PD model and suggested a possible drug candidate that might modify the progression of PD.

METHODS

All experiments were conducted using a line of transgenic zebrafish, Tg(dat:EGFP), in which green fluorescent protein (GFP) is expressed in dopaminergic neurons. The experimental groups were exposed to 500 μmol MPTP from 1 to 3 days post fertilization (dpf). The drug candidates : levodopa 1 mmol, nifedipine 10 μmol, nimodipine 3.5 μmol, diethylstilbestrol 0.3 μmol, luteolin 100 μmol, and calcitriol 0.25 μmol were exposed from 3 to 5 dpf. Locomotor activity was assessed by automated tracking and dopaminergic neurons were visualized in vivo by confocal microscopy.

RESULTS

Levodopa, nimodipine, diethylstilbestrol, and calcitriol had significant positive effects on the restoration of motor behavior, which was damaged by MPTP. Nimodipine and calcitriol have significant positive effects on the restoration of dopaminergic neurons, which were reduced by MPTP. Through locomotor analysis and dopaminergic neuron quantification, we identified the neuro-restorative effects of nimodipine and calcitriol in zebrafish MPTP-induced PD model.

CONCLUSION

The present study identified the neuro-restorative effects of nimodipine and calcitriol in an MPTP-induced zebrafish model of PD. They restored dopaminergic neurons which were damaged due to the effects of MPTP and normalized the locomotor activity. LTCCs have potential pathological roles in neurodevelopmental and neurodegenerative disorders. Zebrafish are highly amenable to high-throughput drug screening and might, therefore, be a useful tool to work towards the identification of diseasemodifying treatment for PD. Further studies including zebrafish genetic models to elucidate the mechanism of action of the diseasemodifying candidate by investigating Ca2+ influx and mitochondrial function in dopaminergic neurons, are needed to reveal the pathogenesis of PD and develop disease-modifying treatments for PD.

Vitamin D attenuates monosodium glutamate-induced behavioural anomalies, metabolic dysregulation, cholinergic impairment, oxidative stress, and astrogliosis in rats

BACKGROUND

Monosodium glutamate (MSG) is a commonly used flavor enhancer that has raised concerns due to its potential adverse effects on various organs. This study explored the neuroprotective potential of Vitamin D, a beneficial micronutrient, in mitigating MSG-induced neurotoxicity.

MATERIALS AND METHODS

Adult male Wistar rats were categorized into five groups: control (2 ml/kg PBS orally for 30 days), MSG (40 mg/kg orally for 30 days), VIT-D (oral cholecalciferol; 500 IU/kg for 30 days), MSG+VIT-D (MSG for 30 days followed by VIT-D for another 30 days), and VIT-D/MSG (concurrent VIT-D and MSG for 30 days). The rats underwent neurobehavioral, histochemical, and biochemical analyses following the treatments.

RESULTS

MSG treatment caused a decline in both long and short-term memory, along with reduced exploratory and anxiogenic behavior, mitigated by vitamin D treatment. MSG exposure also induced impaired behavior, dyslipidemia, oxidative stress, lipid peroxidation, altered cholinergic transmission, and increased chromatolysis and neuroinflammation in the frontal cortex, hippocampus, and cerebellum.

CONCLUSIONS

VIT-D demonstrated a mitigating effect on MSG-induced adverse outcomes, highlighting its potential to attenuate neurodegenerative cascades. This investigation contributes to understanding MSG-associated neurotoxicity and suggests vitamin D as a valuable and potential intervention for neuroprotection.

Genomic and non-genomic action of vitamin D on ion channels - Targeting mitochondria

Recent studies revealed that mitochondria are not only a place of vitamin D3 metabolism but also direct or indirect targets of its activities. This review summarizes current knowledge on the regulation of ion channels from plasma and mitochondrial membranes by the active form of vitamin D3 (1,25(OH)2D3). 1,25(OH)2D3, is a naturally occurring hormone with pleiotropic activities; implicated in the modulation of cell differentiation, and proliferation and in the prevention of various diseases, including cancer. Many experimental data indicate that 1,25(OH)2D3 deficiency induces ionic remodeling and 1,25(OH)2D3 regulates the activity of multiple ion channels. There are two main theories on how 1,25(OH)2D3 can modify the function of ion channels. First, describes the involvement of genomic pathways of response to 1,25(OH)2D3 in the regulation of the expression of the genes encoding channels, their auxiliary subunits, or additional regulators. Interestingly, intracellular ion channels, like mitochondrial, are encoded by the same genes as plasma membrane channels. Therefore, the comprehensive genomic regulation of the channels from these two different cellular compartments we analyzed using a bioinformatic approach. The second theory explores non-genomic pathways of vitamin D3 activities. It was shown, that 1,25(OH)2D3 indirectly regulates enzymes that impact ion channels, change membrane physical properties, or directly bind to channel proteins. In this article, the involvement of genomic and non-genomic pathways regulated by 1,25(OH)2D3 in the modulation of the levels and activity of plasma membrane and mitochondrial ion channels was investigated by an extensive review of the literature and analysis of the transcriptomic data using bioinformatics.

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.

Genome-wide Association Analysis of Schizophrenia and Vitamin D Levels Shows Shared Genetic Architecture and Identifies Novel Risk Loci

Low vitamin D (vitD) levels have been consistently reported in schizophrenia (SCZ) suggesting a role in the etiopathology. However, little is known about the role of underlying shared genetic mechanisms. We applied a conditional/conjunctional false discovery rate approach (FDR) on large, nonoverlapping genome-wide association studies for SCZ (N cases = 53 386, N controls = 77 258) and vitD serum concentration (N = 417 580) to evaluate shared common genetic variants. The identified genomic loci were characterized using functional analyses and biological repositories. We observed cross-trait SNP enrichment in SCZ conditioned on vitD and vice versa, demonstrating shared genetic architecture. Applying the conjunctional FDR approach, we identified 72 loci jointly associated with SCZ and vitD at conjunctional FDR < 0.05. Among the 72 shared loci, 40 loci have not previously been reported for vitD, and 9 were novel for SCZ. Further, 64% had discordant effects on SCZ-risk and vitD levels. A mixture of shared variants with concordant and discordant effects with a predominance of discordant effects was in line with weak negative genetic correlation (rg = -0.085). Our results displayed shared genetic architecture between SCZ and vitD with mixed effect directions, suggesting overlapping biological pathways. Shared genetic variants with complex overlapping mechanisms may contribute to the coexistence of SCZ and vitD deficiency and influence the clinical picture.

The Synaptic and Circuit Functions of Vitamin D in Neurodevelopment Disorders

Vitamin D deficiency/insufficiency is a public health issue around the world. According to epidemiological studies, low vitamin D levels have been associated with an increased risk of some neurodevelopmental disorders, including autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD). Animal models reveal that vitamin D has a variety of impacts on the synapses and circuits in the brain. A lack of vitamin D affects the expression of synaptic proteins, as well as the synthesis and metabolism of various neurotransmitters. Depending on where vitamin D receptors (VDRs) are expressed, vitamin D may also regulate certain neuronal circuits through the endocannabinoid signaling, mTOR pathway and oxytocin signaling. While inconsistently, some data suggest that vitamin D supplementation may be able to reduce the core symptoms of ASD and ADHD. This review emphasizes vitamin D's role in the synaptic and circuit mechanisms of neurodevelopmental disorders including ASD and ADHD. Future application of vitamin D in these disorders will depend on both basic research and clinical studies, in order to make the transition from the bench to the bedside.

Gated Calcium Ion Channel and Mutation Mechanisms in Multidrug-Resistant Tuberculosis

A wide spectrum of Gram-positive/Gram-negative bacteria has been found resistant to a wide spectrum of antibiotics in the United States of America during the past decade. Drug-resistant tuberculosis is not yet a major threat in North/South America, Europe, and the Middle East. However, the migration of populations in times of drought, famine, and hostilities may increase the global reach of this ancient pathogen. Given an increased spread from China and India to African countries, drug-resistant Mycobacterium tuberculosis has become an emerging topic of concern for Europe and North America. Due to the dangers associated with the spread of pathogens among different populations, the World Health Organization continues to expand healthcare advisories for therapeutic approaches for both stationary and migrating populations. As much of the literature focuses on endemic to pandemic viruses, we remain concerned that other treatable communicable diseases may be ignored. One such disease is multidrug-resistant tuberculosis. We focus on molecular mechanisms that this pathogen relies upon for the development of multidrug resistance via gene mutation and the evolutionary development of new enzyme and calcium channels.

Recording plasticity in neuronal activity in the rodent intrinsic cardiac nervous system using calcium imaging techniques

The intrinsic cardiac nervous system (ICNS) is composed of interconnected clusters of neurons called ganglionated plexi (GP) which play a major role in controlling heart rate and rhythm. The function of these neurons is particularly important due to their involvement in cardiac arrhythmias such as atrial fibrillation (AF), and previous work has shown that plasticity in GP neural networks could underpin aberrant activity patterns that drive AF. As research in this field increases, developing new techniques to visualize the complex interactions and plasticity in this GP network is essential. In this study we have developed a calcium imaging method enabling the simultaneous recording of plasticity in neuronal activity from multiple neurons in intact atrial GP networks. Calcium imaging was performed with Cal-520 AM labeling in aged spontaneously hypertensive rats (SHRs), which display both spontaneous and induced AF, and age-matched Wistar Kyoto (WKY) controls to determine the relationship between chronic hypertension, arrhythmia and GP calcium dynamics. Our data show that SHR GPs have significantly larger calcium responses to cholinergic stimulation compared to WKY controls, as determined by both higher amplitude and longer duration calcium responses. Responses were significantly but not fully blocked by hexamethonium, indicating multiple cholinergic receptor subtypes are involved in the calcium response. Given that SHRs are susceptible to cardiac arrhythmias, our data provide evidence for a potential link between arrhythmia and plasticity in calcium dynamics that occur not only in cardiomyocytes but also in the GP neurons of the heart.

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.

Developmental exposure to vitamin D deficiency and subsequent risk of schizophrenia

Over the last half century, a body of convergent evidence has accumulated linking disruption of early brain development with an increased risk of mental disorders, including schizophrenia. The orderly cascade of brain development may be disrupted by exposure to suboptimal concentrations of a range of biological substrates and micronutrients. We hypothesized that those exposed to vitamin D deficiency during early life, have an increased risk of neurodevelopmental disorders, including schizophrenia. The hypothesis was based on the link between an increased risk of schizophrenia in (a) those born in winter and spring, when vitamin D deficiency is more prevalent, and (b) the offspring of dark-skinned migrants living in cold climates, who have a markedly increased risk of vitamin D deficiency. In this review, we summarize evidence from analytic epidemiology related to this hypothesis. Two case-control studies based on Danish neonatal dried blood spots have found that neonatal vitamin deficiency is associated with an increased risk of schizophrenia. However, recent genetic analyses have also suggested that common variants linked to schizophrenia may lead to lower vitamin D concentrations (possibly mediated via reduced outdoor activity). We summarize limitations of the current evidence and outline suggestions that can guide future research. Based on currently available data, there is insufficient evidence to support public health recommendations related to this topic. However, we cannot reject the hypothesis that the provision of vitamin D supplementation to pregnant women and/or offspring in groups vulnerable to vitamin D deficiency may subsequently reduce the incidence of schizophrenia in the offspring.

Paraventricular Vitamin D Receptors Are Required for Glucose Tolerance in Males but Not Females

When delivered directly into the brain, vitamin D, can improve glucose levels in male mice. Additionally, the loss of the vitamin D receptor (VDR) in male mice's paraventricular hypothalamus (PVH) results in impaired glucose tolerance. Data in humans shows that low vitamin D levels are detrimental to glucose homeostasis, an effect that may be more prominent in men. However, it is unknown if vitamin D action in the brain is required for normal glucose regulation in female mice. This study shows that in both viral and genetic models, male mice with obesity and PVH VDR loss have impaired glucose tolerance while female mice are unaffected. Weights were unaltered in both sexes by PVH VDR loss. Additionally, PVH VDR loss did not cause any glucose abnormalities in either sex when the mice were on a chow diet. Utilizing electrophysiology studies, we show PVH VDR loss resulted in decreased baseline firing frequency and resting membrane potential in males, but not females. Additionally, male mice with PVH VDR loss had impaired miniature excitatory postsynaptic currents (mEPSC), while females were unaffected. Interestingly, the PVH neurons of both sexes were activated by exogenous vitamin D (1,25-dihydroxyvitamin D3), an effect dependent upon the VDR. Thus, there is sexual dimorphism, for the actions of the PVH VDR on glucose regulation. PVH VDRs are necessary for normal glucose homeostasis in males but not females and this may be secondary to actions of the VDR on neuronal activity.

Effect of Vitamin D Supplementation on Outcomes in People With Early Psychosis: The DFEND Randomized Clinical Trial

IMPORTANCE

People with psychotic disorders have an increased risk of vitamin D deficiency, which is evident during first-episode psychosis (FEP) and associated with unfavorable mental and physical health outcomes.

OBJECTIVE

To examine whether vitamin D supplementation contributes to improved clinical outcomes in FEP.

DESIGN, SETTING, AND PARTICIPANTS

This multisite, double-blind, placebo-controlled, parallel-group randomized clinical trial from the UK examined adults 18 to 65 years of age within 3 years of a first presentation with a functional psychotic disorder who had no contraindication to vitamin D supplementation. A total of 2136 patients were assessed for eligibility, 835 were approached, 686 declined participation or were excluded, 149 were randomized, and 104 were followed up at 6 months. The study recruited participants from January 19, 2016, to June 14, 2019, with the final follow-up (after the last dose) completed on December 20, 2019.

INTERVENTIONS

Monthly augmentation with 120 000 IU of cholecalciferol or placebo.

MAIN OUTCOMES AND MEASURES

The primary outcome measure was total Positive and Negative Syndrome Scale (PANSS) score at 6 months. Secondary outcomes included total PANSS score at 3 months; PANSS positive, negative, and general psychopathology subscale scores at 3 and 6 months; Global Assessment of Function scores (for symptoms and disability); Calgary Depression Scale score, waist circumference, body mass index, and glycated hemoglobin, total cholesterol, C-reactive protein, and vitamin D concentrations at 6 months; and a planned sensitivity analysis in those with insufficient vitamin D levels at baseline.

RESULTS

A total of 149 participants (mean [SD] age, 28.1 (8.5) years; 89 [59.7%] male; 65 [43.6%] Black or of other minoritized racial and ethnic group; 84 [56.4%] White [British, Irish, or of other White ethnicity]) were randomized. No differences were observed in the intention-to-treat analysis in the primary outcome, total PANSS score at 6 months (mean difference, 3.57; 95% CI, -1.11 to 8.25; P = .13), or the secondary outcomes at 3 and 6 months (PANSS positive subscore: mean difference, -0.98; 95% CI, -2.23 to 0.27 at 3 months; mean difference, 0.68; 95% CI, -0.69 to 1.99 at 6 months; PANSS negative subscore: mean difference, 0.68; 95% CI, -1.39 to 2.76 at 3 months; mean difference, 1.56; 95% CI, -0.31 to 3.44 at 6 months; and general psychopathology subscore: mean difference, -2.09; 95% CI, -4.36 to 0.18 at 3 months; mean difference, 1.31; 95% CI, -1.42 to 4.05 at 6 months). There also were no significant differences in the Global Assessment of Function symptom score (mean difference, 0.02; 95% CI, -4.60 to 4.94); Global Assessment of Function disability score (mean difference, -0.01; 95% CI, -5.25 to 5.23), or Calgary Depression Scale score (mean difference, -0.39; 95% CI, -2.05 to 1.26) at 6 months. Vitamin D levels were very low in the study group, especially in Black participants and those who identified as another minoritized racial and ethnic group, 57 of 61 (93.4%) of whom had insufficient vitamin D. The treatment was safe and led to a significant increase in 25-hydroxyvitamin D concentrations.

CONCLUSIONS AND RELEVANCE

In this randomized clinical trial, no association was found between vitamin D supplementation and mental health or metabolic outcomes at 6 months. Because so few patients with FEP were vitamin D replete, the results of this study suggest that this group would benefit from active consideration in future population health strategies.

TRIAL REGISTRATION

isrctn.org Identifier: ISRCTN12424842.

Vitamin D in the time of the coronavirus (COVID-19) pandemic - a clinical review from a public health and public mental health perspective

Individuals with serious mental disorders (SMD) may have a higher risk of vitamin D (VIT-D) deficiency. They also experience higher mortality because of coronavirus disease 2019 (COVID-19) infection. Therefore, we have conducted a comprehensive review to examine the significance of VIT-D for public health and public mental health during the ongoing COVID-19 pandemic. This review had three specific aims, from a global perspective to (a) create a profile of VIT-D and review the epidemiology of VIT-D deficiency, (b) explore VIT-D deficiency as risk factor for SMD and COVID-19 infections and (c) examine the effectiveness of VIT-D supplementation for both conditions. We found that, in terms of SMD, the evidence from laboratory and observational studies points towards some association between VIT-D deficiency and depression or schizophrenia. Mendelian randomisation studies, however, suggest no, or reverse, causality. The evidence from intervention studies is conflicting. Concerning COVID-19 infection, on proof of principle, VIT-D could provide a plausible defence against the infection itself and against an adverse clinical course. But data from observational studies and the first preliminary intervention studies remain conflicting, with stronger evidence that VIT-D may mitigate the clinical course of COVID-19 infection rather than the risk of infection in the first place. From a public health and public mental health point of view, based on the currently limited knowledge, for individuals with SMD, the benefits of VIT-D optimisation through supplementation seem to outweigh the risks. VIT-D supplementation, however, should not substitute for vaccination or medical care for COVID-19 infection.

Defining vitamin D receptor expression in the brain using a novel VDRCre mouse

Vitamin D action has been linked to several diseases regulated by the brain including obesity, diabetes, autism, and Parkinson's. However, the location of the vitamin D receptor (VDR) in the brain is not clear due to conflicting reports. We found that two antibodies previously published as specific in peripheral tissues are not specific in the brain. We thus created a new knockin mouse with cre recombinase expression under the control of the endogenous VDR promoter (VDR^Cre ). We demonstrated that the cre activity in the VDR^Cre mouse brain (as reported by a cre-dependent tdTomato expression) is highly overlapping with endogenous VDR mRNAs. These VDR-expressing cells were enriched in multiple brain regions including the cortex, amygdala, caudate putamen, and hypothalamus among others. In the hypothalamus, VDR partially colocalized with vasopressin, oxytocin, estrogen receptor-α, and β-endorphin to various degrees. We further functionally validated our model by demonstrating that the endogenous VDR agonist 1,25-dihydroxyvitamin D activated all tested tdTomato⁺ neurons in the paraventricular hypothalamus but had no effect on neurons without tdTomato fluorescence. Thus, we have generated a new mouse tool that allows us to visualize VDR-expressing cells and to characterize their functions.

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.

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.

Vitamin D actions in neurons require the PI3K pathway for both enhancing insulin signaling and rapid depolarizing effects

Despite correlations between low vitamin D levels and diabetes incidence/severity, supplementation with vitamin D has not been widely effective in improving glucose parameters. This may be due to a lack of knowledge regarding how low vitamin D levels physiologically affect glucose homeostasis. We have previously shown that the brain may be a critical area for vitamin d-mediated action on peripheral glucose levels. However, the mechanisms for how vitamin D acts in the brain are unknown. We utilized a multimodal approach to determine the mechanisms by which vitamin D may act in the brain. We first performed an unbiased search (RNA-sequencing) for pathways affected by vitamin D. Vitamin D (125-dihydroxyvitamin D3; 1,25D3) delivered directly into the third ventricle of obese animals differentially regulated multiple pathways, including the insulin signaling pathway. The insulin signaling pathway includes PI3K, which is important in the brain for glucose regulation. Since others have shown that vitamin D acts through the PI3K pathway in non-neuronal cells (muscle and bone), we hypothesized that vitamin D may act in neurons through a PI3K-dependent pathway. In a hypothalamic cell-culture model (GT1-7 cells), we demonstrate that 1,25D3 increased phosphorylation of Akt in the presence of insulin. However, this was blocked with pre-treatment of wortmannin, a PI3K inhibitor. 1,25D3 increased gene transcription of several genes within the PI3K pathway, including Irs2 and p85, without affecting expression of InsR or Akt. Since we had previously shown that 1,25D3 has significant effects on neuronal function, we also tested if the PI3K pathway could mediate rapid actions of vitamin D. We found that 1,25D3 increased the firing frequency of neurons through a PI3K-dependent mechanism. Collectively, these data support that vitamin D enhances insulin signaling and neuronal excitability through PI3K dependent processes which involve both transcriptional and membrane-initiated signaling events.

Neonatal vitamin D status and risk of childhood epilepsy

OBJECTIVE

Epilepsy is a nervous system abnormality that may be caused by unknown exposures during fetal development. Studies have shown neuroprotective effects of early exposure to vitamin D in other neurological disorders, and seasonal variation in birth of children with epilepsy. We aimed to investigate if neonatal 25(OH)D₃ was associated with risk of childhood epilepsy.

METHODS

This case-cohort study compared neonatal 25(OH)D₃ levels from children with epilepsy (n = 403) and a random selected cohort of controls (n = 1163), assessing the hazard of first epilepsy diagnosis between 1 and 4 years of age from a weighted Cox proportional hazard model. Analyses were adjusted for parental education, maternal age, maternal epilepsy, maternal ethnicity, and gestational age, and additionally for season of birth and smoking during pregnancy.

RESULTS

The mean (standard deviation [SD]) of neonatal 25(OH)D₃ levels were 30.8(19.6) nmol/L among cases and 28.5(19.4) nmol/L among the cohort. The hazard ratio (HR) of epilepsy was in a dose-response pattern higher among children from the highest neonatal 25(OH)D₃ quintiles (P-trend = .004). Results were unchanged after including season of birth in the analysis, where a significantly higher HR of epilepsy was observed among children in the two highest quintiles compared to children in the lowest quintile (Q4: HR_adj  1.62, 95% CI 1.07-2.47 and Q5: HR_adj  1.86, 95% CI 1.21-2.86).

SIGNIFICANCE

In this study, the risk of childhood epilepsy increased with neonatal 25(OH)D₃ categories in a dose-response pattern, suggesting an association between a high neonatal 25(OH)D₃ and the risk of childhood epilepsy. Considering that adjusting for season of birth strengthened the results, we conclude that maternal intake of vitamin D, and not vitamin D from sun exposure, was the vitamin D source associated with epilepsy. Although we cannot, in the present study, control for compounds in the diet like pollutants or heavy metals, which may correlate with dietary vitamin D, future studies investigating fetal origin of epilepsy should focus on compounds correlating with vitamin D.

Pathogenesis and management of Brugada syndrome in schizophrenia: A scoping review

CONTEXT

Excess cardiovascular morbidity and an increased prevalence of sudden cardiac death (SCD) contributes to premature mortality in schizophrenia. Brugada syndrome (BrS) is an important but underrecognized cause of SCD. It is more commonly seen in schizophrenia than in general population controls.

METHODS

We conducted a scoping review to describe the pathogenesis of BrS in schizophrenia and to identify the psychotropic medications that increase the risk of unmasking BrS and associated ventricular arrhythmias resulting in SCD.

FINDINGS

Schizophrenia and BrS share similar calcium channel abnormalities, which may result in aberrant myocardial conductivity. It remains uncertain if there is a genetic pre-disposition for BrS in a subset of patients with schizophrenia. However, the unmasking of Brugada ECG patterns with the use of certain antipsychotics and antidepressants increases the risk of precipitating SCD, independent of QT prolongation.

CONCLUSIONS AND FUTURE DIRECTIONS

Specific cardiology assessment and interventions may be required for the congenital or unmasked Brugada ECG pattern in schizophrenia. The current long-term standard of care for BrS is an implantable cardioverter defibrillator (ICD), but post-implantation psychological effects must be considered. Careful use of antipsychotic and other psychotropic medications is necessary to minimize proarrhythmic effects due to impact on cardiac sodium and calcium ion channels. When prescribing such drugs to patients with schizophrenia, clinicians should be mindful of the potentially fatal unmasking of Brugada ECG patterns and how to manage it. We present recommendations for psychiatrists managing this patient population.