Effect of vitamin D on cognitive function and white matter hyperintensity in patients with mild Alzheimer's disease

Executive function impairment is associated with low serum vitamin D levels in children with epilepsy

PURPOSE

Executive function (EF) impairment and vitamin D deficiency are common clinical features among children with epilepsy (CWE). Recently, vitamin D has become a potential modification factor that affects cognitive status in individuals with neurological disorders. In this study, we investigated the association between EF status and vitamin D levels in patients with CWE.

METHODS

In total, 79 CWE patients and 39 healthy controls (HCs) were recruited in this study. Each participant's EF was assessed using the Behavior Rating Inventory of Executive Function-Parent form (Brief-P), and the serum level of 25-OH vitamin D was measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

Compared with those in the HC group, the CWE group had higher T scores of Brief-P scale, including global executive composite (GEC) (51.01(45.12, 60.69) vs. 44.08(39.24, 49.96), p＜0.001), behavioral regulation index (BRI) (51.29(45.67, 59.13) vs. 45.67(40.06, 51.29), p＜0.001), metacognition index (MI) (51.83(46.77, 59.43) vs. 46.13(40.44, 51.83), p＜0.001), and lower serum vitamin D (14.85(10.24,23.2) vs. 22.5(16.91,30), p＜0.001) levels. After adjustment for covariates, multivariate linear regression models suggested that for every 1 ng/ml increase in vitamin D, the GEC, BRI, and MI would decrease by 0.52 (Coeff = -0.48; 95 % CI = -0.69, -0.26; p = 0.000), 0.45 (Coeff = -0.45; 95 % CI = -0.69, -0.20; p = 0.000), and 0.47 (Coeff = -0.45; 95 % CI = -0.67, -0.22; p = 0.000), respectively.

CONCLUSION

There may be an association between decreased vitamin D levels and EF impairment in CWE. Future research should consider longitudinal variations in EF related to improving vitamin D deficiency.

Vitamin D Reduces GABA-Positive Astrocytes in the 5xFAD Mouse Model of Alzheimer's Disease

Background

Vitamin D has neuroprotective and immunomodulating functions that may impact glial cell function in the brain. Previously, we reported molecular and behavioral changes caused by deficiency and supplementation of vitamin D in an Alzheimer's disease (AD) mouse model. Recent studies have highlighted reactive astrocytes as a new therapeutic target for AD treatment. However, the mechanisms underlying the therapeutic effects of vitamin D on the glial cells of AD remain unclear.

Objective

To investigate the potential association between vitamin D deficiency/supplementation and the pathological progression of AD, including amyloid-β (Aβ) pathology and reactive astrogliosis.

Methods

Transgenic hemizygous 5XFAD male mice were subjected to different dietary interventions and intraperitoneal vitamin D injections to examine the effects of vitamin D deficiency and supplementation on AD. Brain tissue was then analyzed using immunohistochemistry for Aβ plaques, microglia, and astrocytes, with quantifications performed via ImageJ software.

Results

Our results demonstrated that vitamin D deficiency exacerbated Aβ plaque formation and increased GABA-positive reactive astrocytes in AD model mice, while vitamin D supplementation ameliorated these effects, leading to a reduction in Aβ plaques and GABA-positive astrocytes.

Conclusions

Our findings highlight the significant impact of vitamin D status on Aβ pathology and reactive astrogliosis, underscoring its potential role in the prevention and treatment of AD. This study provides the first in vivo evidence of the association between vitamin D and reactive astrogliosis in AD model mice, indicating the potential for targeting vitamin D levels as a novel therapeutic approach for AD.

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 deficit is associated with accelerated brain aging in the general population

Vitamin D deficiency has been associated with reduced neurocognitive functioning and the neurodegenerative processes. However, existing evidence on brain structural correlates of vitamin D deficiency is controversial. We sought to investigate associations of vitamin D levels with imaging patterns of brain aging. In addition, we investigated whether low vitamin D levels were associated with gray matter volumes, whole brain volumes and hippocampus volumes. Structural MRI data and vitamin D levels were obtained in 1,865 subjects from the general population. Linear regressions were applied to investigate the association of vitamin D levels and vitamin D deficiency with imaging derived brain age, total brain, gray matter and hippocampal volumes. Different sets of covariates were included. Vitamin D deficiency was significantly associated with increased brain age. Also, linear vitamin D levels were significantly associated with total brain and gray matter volumes, while no significant association with hippocampal volume was found. Further interaction analyses showed that this association was only significant for male subjects. Our results support previous findings suggesting that vitamin D-deficient individuals have an accelerated brain aging. In addition, associations between vitamin D levels and total brain/ gray matter volumes suggest neuroprotective effects of vitamin D on the brain.

Vitamin D and brain health: an observational and Mendelian randomization study

BACKGROUND

Higher vitamin D status has been suggested to have beneficial effects on the brain.

OBJECTIVES

To investigate the association between 25-hydroxyvitamin D [25(OH)D], neuroimaging features, and the risk of dementia and stroke.

METHODS

We used prospective data from the UK Biobank (37-73 y at baseline) to examine the association between 25(OH)D concentrations with neuroimaging outcomes (N = 33,523) and the risk of dementia and stroke (N = 427,690; 3414 and 5339 incident cases, respectively). Observational analyses were adjusted for age, sex, ethnicity, month, center, and socioeconomic, lifestyle, sun behavior, and illness-related factors. Nonlinear Mendelian randomization (MR) analyses were used to test for underlying causality for neuroimaging outcomes (N = 23,901) and dementia and stroke (N = 294,514; 2399 and 3760 cases, respectively).

RESULTS

Associations between 25(OH)D and total, gray matter, white matter, and hippocampal volumes were nonlinear, with lower volumes both for low and high concentrations (adjusted P-nonlinear ≤ 0.04). 25(OH)D had an inverse association with white matter hyperintensity volume [per 10 nmol/L 25(OH)D; adjusted β: -6.1; 95% CI: -11.5, -7.0]. Vitamin D deficiency was associated with an increased risk of dementia and stroke, with the strongest associations for those with 25(OH)D <25 nmol/L (compared with 50-75.9 nmol/L; adjusted HR: 1.79; 95% CI: 1.57, 2.04 and HR: 1.40; 95% CI: 1.26, 1.56, respectively). Nonlinear MR analyses confirmed the threshold effect of 25(OH)D on dementia, with the risk predicted to be 54% (95% CI: 1.21, 1.96) higher for participants at 25 nmol/L compared with 50 nmol/L. 25(OH)D was not associated with neuroimaging outcomes or the risk of stroke in MR analyses. Potential impact fraction suggests 17% (95% CI: 7.22, 30.58) of dementia could be prevented by increasing 25(OH)D to 50 nmol/L.

CONCLUSIONS

Low vitamin D status was associated with neuroimaging outcomes and the risks of dementia and stroke even after extensive covariate adjustment. MR analyses support a causal effect of vitamin D deficiency on dementia but not on stroke risk.

The Role of Vitamin D in Alzheimer’s Disease: A Transcriptional Regulator of Amyloidopathy and Gliopathy

Alzheimer’s disease (AD) is characterized by amyloid-beta (Aβ) accumulation and cognitive mental decline. Epidemiological studies have suggested an association between low serum vitamin D levels and an increased risk of AD. Vitamin D regulates gene expression via the vitamin D receptor, a nuclear ligand-dependent transcription factor. However, the molecular mechanism underlying the pathogenic and therapeutic effects of vitamin D on AD is not fully understood yet. To better understand how vitamin D regulates the expression of genes related to AD pathology, first, we induced vitamin D deficiency in 5xFAD mice by providing a vitamin-D-deficient diet and observed the changes in the mRNA level of genes related to Aβ processing, which resulted in an increase in the Aβ load in the brain. The vitamin D-deficient diet also suppressed the expression of genes for microglial Aβ phagocytosis. Interestingly, vitamin D deficiency in the early stage of AD resulted in earlier memory impairment. In addition, we administered vitamin D intraperitoneally to 5xFAD mice with a normal diet and found lower Aβ levels with the suppressed expression of genes for Aβ generation and observed improved memory function, which may be potentially associated with reduced MAO-B expression. These findings strongly suggest the role of vitamin D as a crucial disease-modifying factor that may modulate the amyloid pathology with regard to reducing AD symptoms.

Correlation between serum 25(OH)D and cognitive impairment in Parkinson's disease

This study aimed to investigate the relationship between serum 25(OH)D and cognitive impairment in patients with Parkinson's disease (PD), hoping to provide possible ideas for the diagnosis and prevention of PD with cognitive impairment. Vitamin D is a neurosteroid with neurotrophic and neuroprotective functions, playing an important role in PD and its progression. In the present study, serum 25(OH)D levels were significantly decreased in PD patients (45.86 ± 14.81 nmol/L)compared to healthy controls(56.54 ± 14.00 nmol/L) (P < 0.001), and significant differences were also observed in PD patients with normal cognition (PD-NC), PD patients with mild cognitive impairment (PD-MCI)and PD patients with dementia (PDD)(P < 0.05). Moreover, there was a positive correlation between serum 25(OH)D levels and Montreal cognitive assessment(MoCA) scores (r = 0.489,P < 0.001).The increased serum 25(OH)D was an independent protective factor of cognitive impairment in PD (OR = 0. 949, P = 0.005), and the sensitivity, specificity, and AUC under the ROC curve area of serum 25(OH)D were 53.3%, 86.5%, and 0.713, respectively. These findings support the relationship between cognitive impairment and Vitamin D in PD patients. Serum 25(OH)D may be a useful biomarker for diagnosing cognitive impairment in patients with PD.

Impact of 25-Hydroxy Vitamin D on White Matter Hyperintensity in Elderly Patients: A Systematic Review and Meta-Analysis

Some studies show that low serum vitamin D levels are associated with white matter hyperintensity (WMH), while other studies report no association. This meta-analysis aimed to investigate the presence of an association between serum 25-hydroxy vitamin D [25(OH)D] levels and WMH. PubMed, Embase, the Cochrane Library, CNKI, WANFANG, and VIP were searched for available papers published up to December 2020. The outcomes were the odds ratios (ORs) with 95% confidence intervals (CIs) for the association between different vitamin D statuses and WMH. All meta-analyses were performed using a random-effects model. Five studies (4393 patients) were included. Compared with sufficient 25(OH)D levels, 25(OH)D deficiency was not associated with WMH (OR = 1.67, 95%CI: 0.92–3.04; I² = 70.2%, P_{heterogeneity} = 0.009), nor was 25(OH)D insufficiency (OR = 1.21, 95%CI: 0.89–1.65; I² = 48.1%, P_{heterogeneity} = 0.103). A decrease of 25 nmol/L in 25(OH)D levels was associated with WMH (OR = 1.83, 95%CI: 1.34-2.49; I² = 0%, P_{heterogeneity}= 0.512). The sensitivity analyses showed that the results were robust. 25(OH)D deficiency and insufficiency are not associated with WMH. A decrease of 25 nmol/L in 25(OH)D levels was associated with WMH, but this result will have to be confirmed. Prospective trials, both cross-sectional and longitudinal, are necessary to examine the association between 25(OH)D levels and WMH.

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

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

The Role of Vitamin D as a Biomarker in Alzheimer's Disease

Vitamin D and cognition is a popular association, which led to a remarkable body of literature data in the past 50 years. The brain can synthesize, catabolize, and receive Vitamin D, which has been proved to regulate many cellular processes in neurons and microglia. Vitamin D helps synaptic plasticity and neurotransmission in dopaminergic neural circuits and exerts anti-inflammatory and neuroprotective activities within the brain by reducing the synthesis of pro-inflammatory cytokines and the oxidative stress load. Further, Vitamin D action in the brain has been related to the clearance of amyloid plaques, which represent a feature of Alzheimer Disease (AD), by the immune cell. Based on these considerations, many studies have investigated the role of circulating Vitamin D levels in patients affected by a cognitive decline to assess Vitamin D’s eventual role as a biomarker or a risk factor in AD. An association between low Vitamin D levels and the onset and progression of AD has been reported, and some interventional studies to evaluate the role of Vitamin D in preventing AD onset have been performed. However, many pitfalls affected the studies available, including substantial discrepancies in the methods used and the lack of standardized data. Despite many studies, it remains unclear whether Vitamin D can have a role in cognitive decline and AD. This narrative review aims to answer two key questions: whether Vitamin D can be used as a reliable tool for diagnosing, predicting prognosis and response to treatment in AD patients, and whether it is a modifiable risk factor for preventing AD onset.

Vitamins in Alzheimer's Disease-Review of the Latest Reports

Alzheimer's disease (AD) is the most common form of dementia, and the aging of the population means that the number of cases is successively increasing. The cause of the disease has not been established, but it is suggested that many factors affect it, including nutritional aspects. As part of the work, the PubMed database has been searched, beginning from 2005, for terms related to key nutritional aspects. A diet rich in antioxidant vitamins can improve the cognitive functions of patients. Thanks to an adequate intake of B vitamins, homocysteine levels are reduced, which indirectly protects against the development of the disease. A properly balanced diet, as well as the use of appropriate supplementation, can contribute to improving the clinical condition of patients with AD.

Low 25OH Vitamin D Blood Levels Are Independently Associated With Higher Amyotrophic Lateral Sclerosis Severity Scores: Results From a Prospective Study

Background: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive degeneration of upper and lower motor neurons. Prognosis is highly variable, ranging from few months to more than 30 years. 25OH vitamin D (25OH VD) blood levels have been associated with worse prognosis of ALS, but these results remain in dispute. We addressed this controversy with a prospective study and multivariate analysis to study the influence of known clinical prognostic factors of the disease and 25OH VD levels on Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) severity score (ALS-SS), as defined by the monthly rate of decline of ALSFRS-R score, to identify the factors most closely linked to the risk of worsening of the disease.

Results:This prospective cohort of ALS patients recruited 127 individuals, and 105 of them met inclusion criteria. Mean age of onset was 62.2 ± 12.1 years, 32% of subjects had bulbar onset, and gender ratio was 1.44 (male/female). Mean 25OH VD level was 26.8 ± 10.8 ng/ml and was similar between males and females. Patients with 25OH VD levels <15 ng/ml had significantly higher ALS-SS at inclusion (ALS-SSi) than those with normal levels (>30 ng/ml), p = 0.011. The study of ALS-SS as calculated at the end of follow-up (ALS-SSe) was not found correlated to initial 25OH VD levels (r = −0.19; p = 0.084). Univariate analysis showed that ALS-SSe correlated with 25OH VD levels, ALS duration at inclusion, slow vital capacity (SVC) at inclusion, and SVC loss. Multivariate model showed that 25OH VD levels were independently associated with ALS-SSe: r = −0.0125, p = 0.033. Log rank test with Kaplan–Meier curves did not show significant differences of survival between the groups defined by 25OH VD levels: <15, >15 and <30, and > 30 ng/ml, p = 0.88.

Conclusions: This prospective study in ALS patients confirmed previous retrospective results: ALS-SSi is significantly higher in patients with severe VD deficiency. For the first time, multivariate analysis showed that 25OH VD level was an independent prognostic factor correlated to ALS-SSe, suggesting that discrepancies between previous works could be due to confounders. It would be important that the present work be replicated in larger samples to confirm the present findings.