Vitamin D and Its Analogues Decrease Amyloid-β (Aβ) Formation and Increase Aβ-Degradation

The associations of serum vitamin D status and vitamin D supplements use with all-cause dementia, Alzheimer's disease, and vascular dementia: a UK Biobank based prospective cohort study

BACKGROUND

Prior studies on vitamin D and dementia outcomes yielded mixed results and had several important limitations.

OBJECTIVES

We aimed to assess the associations of both serum vitamin D status and supplementation with all-cause dementia, Alzheimer's disease (AD), and vascular dementia (VD) incidence.

METHODS

With a prospective cohort study design, we comprehensively assessed the associations of vitamin D and multivitamin supplementation, as well as vitamin D deficiency {25-hydroxyvitamin D [25(OH)D] <30 nmol/L}, and insufficiency [25(OH)D 30 to <50 nmol/L], with the 14-year incidence of all-cause dementia, AD, and VD in 269,229 participants, aged 55 to 69, from the UK Biobank.

RESULTS

Although 5.0% reported regular vitamin D use and 19.8% reported multivitamin use, the majority of participants exhibited either vitamin D deficiency (18.3%) or insufficiency (34.0%). However, vitamin D deficiency was less prevalent among users of vitamin D (6.9%) or multivitamin preparations (9.5%) than among nonusers (21.5%). Adjusted Cox regression models demonstrated 19% to 25% increased risk of all 3 dementia outcomes for those with vitamin D deficiency [hazard ratio (HR) 95% confidence interval (CI)]: 1.25 (1.16, 1.34) for all-cause dementia; 1.19 (1.07-1.31) for AD; 1.24 (1.08-1.43) for VD] and 10% to 15% increased risk of those with vitamin D insufficiency [HR (95% CI): 1.11 (1.05, 1.18) for all-cause dementia; 1.10 (1.02-1.19) for AD; 1.15 (1.03-1.29) for VD]. Regular users of vitamin D and multivitamins had 17% and 14% lower risk of AD [HR (95% CI): 0.83 (0.71, 0.98)] and VD [HR (95% CI): 0.86 (0.75, 0.98)] incidence, respectively.

CONCLUSIONS

Although our findings indicate the potential benefits of vitamin D supplementation for dementia prevention, randomized controlled trials are essential for definitive evidence.

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.

A bidirectional link between sulfatide and Alzheimer's disease

Reduced sulfatide level is found in Alzheimer's disease (AD) patients. Here, we demonstrate that amyloid precursor protein (APP) processing regulates sulfatide synthesis and vice versa. Different cell culture models and transgenic mice models devoid of APP processing or in particular the APP intracellular domain (AICD) reveal that AICD decreases Gal3st1/CST expression and subsequently sulfatide synthesis. In return, sulfatide supplementation decreases Aβ generation by reducing β-secretase (BACE1) and γ-secretase processing of APP. Increased BACE1 lysosomal degradation leads to reduced BACE1 protein level in endosomes. Reduced γ-secretase activity is caused by a direct effect on γ-secretase activity and reduced amounts of γ-secretase components in lipid rafts. Similar changes were observed by analyzing cells and mice brain samples deficient of arylsulfatase A responsible for sulfatide degradation or knocked down in Gal3st1/CST. In line with these findings, addition of sulfatides to brain homogenates of AD patients resulted in reduced γ-secretase activity. Human brain APP level shows a significant negative correlation with GAL3ST1/CST expression underlining the in vivo relevance of sulfatide homeostasis in AD.

A Combinational Therapy for Preventing and Delaying the Onset of Alzheimer's Disease: A Focus on Probiotic and Vitamin Co-Supplementation

Alzheimer's disease is a progressive neurodegenerative disorder with a complex etiology, and effective interventions to prevent or delay its onset remain a global health challenge. In recent years, there has been growing interest in the potential role of probiotic and vitamin supplementation as complementary strategies for Alzheimer's disease prevention. This review paper explores the current scientific literature on the use of probiotics and vitamins, particularly vitamin A, D, E, K, and B-complex vitamins, in the context of Alzheimer's disease prevention and management. We delve into the mechanisms through which probiotics may modulate gut-brain interactions and neuroinflammation while vitamins play crucial roles in neuronal health and cognitive function. The paper also examines the collective impact of this combinational therapy on reducing the risk factors associated with Alzheimer's disease, such as oxidative stress, inflammation, and gut dysbiosis. By providing a comprehensive overview of the existing evidence and potential mechanisms, this review aims to shed light on the promise of probiotic and vitamin co-supplementation as a multifaceted approach to combat Alzheimer's disease, offering insights into possible avenues for future research and clinical application.

Drug repurposing for neurodegenerative diseases using Zebrafish behavioral profiles

Drug repurposing can accelerate drug development while reducing the cost and risk of toxicity typically associated with de novo drug design. Several disorders lacking pharmacological solutions and exhibiting poor results in clinical trials - such as Alzheimer's disease (AD) - could benefit from a cost-effective approach to finding new therapeutics. We previously developed a neural network model, Z-LaP Tracker, capable of quantifying behaviors in zebrafish larvae relevant to cognitive function, including activity, reactivity, swimming patterns, and optomotor response in the presence of visual and acoustic stimuli. Using this model, we performed a high-throughput screening of FDA-approved drugs to identify compounds that affect zebrafish larval behavior in a manner consistent with the distinct behavior induced by calcineurin inhibitors. Cyclosporine (CsA) and other calcineurin inhibitors have garnered interest for their potential role in the prevention of AD. We generated behavioral profiles suitable for cluster analysis, through which we identified 64 candidate therapeutics for neurodegenerative disorders.

What is known about the effects of vitamin D in neuropsychiatric lupus?

Systemic lupus erythematosus (SLE) is an autoimmune disease that can affect several organs and systems. The central and/or peripheral nervous system can suffer from complications known as neuropsychiatric lupus (NPSLE). Studies have associated the manifestations of SLE or NPSLE with vitamin D deficiency. It has been shown that hypovitaminosis D can lead to cognition deficits and cerebral hypoperfusion in patients with NPSLE. In this review article, we will address the main features related to vitamin D supplementation or serum vitamin D levels with neuropsychiatric manifestations, either in patients or in animal models of NPSLE.

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 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.

Association between Low Vitamin D Status, Serotonin, and Clinico-Biobehavioral Parameters in Alzheimer's Disease

INTRODUCTION

Studies suggest a role of vitamin D in the progression and symptomatology of Alzheimer's disease (AD), with few in vitro studies pointing to effects on serotonergic and amyloidogenic turnover. However, limited data exist in AD patients on the potential association with cognition and behavioral and psychological signs and symptoms of dementia (BPSD). In this retrospective cross-sectional study, we, therefore, explored potential correlations of serum 25-hydroxyvitamin D3 (25(OH)D3) concentrations, indicative of vitamin D status, with serum serotonin (5-hydroxytryptamine, 5-HT) levels, cognitive/BPSD scorings, and cerebrospinal fluid (CSF) biomarker levels.

METHODS

Frozen serum samples of 25 well-characterized AD subjects as part of a previous BPSD cohort were analyzed, of which 15 had a neuropathologically confirmed diagnosis. Serum 25(OH)D3 levels were analyzed by means of LC-MS/MS, whereas 5-HT concentrations were quantified by competitive ELISA.

RESULTS

Among AD patients, vitamin D deficiency was highly prevalent, defined as levels below 50 nmol/L. Regression analyses, adjusted for age, gender, and psychotropic medications, revealed that serum 25(OH)D3 and 5-HT levels were positively associated (p = 0.012). Furthermore, serum 25(OH)D3 concentrations correlated inversely with CSF amyloid-beta (Aβ1-42) levels (p = 0.006), and serum 5-HT levels correlated positively with aggressiveness (p = 0.001), frontal behavior (p = 0.001), depression (p = 0.004), and partly with cognitive performance (p < 0.005). Lastly, AD patients on cholinesterase inhibitors had higher serum 25(OH)D3 (p = 0.030) and lower serum 5-HT (p = 0.012) levels.

CONCLUSIONS

The molecular associations between low vitamin D status, serum 5-HT, and CSF Aβ1-42 levels are highly remarkable, warranting further mechanistic and intervention studies to disclose potential involvement in the clinico-biobehavioral pathophysiology of AD.

Vitamin D alleviates cognitive dysfunction and brain damage induced by copper sulfate intake in experimental rats: focus on its combination with donepezil

This study aimed to demonstrate the potential benefits of donepezil (DPZ) and vitamin D (Vit D) in combination to counteract the neurodegenerative disorders induced by CuSO4 intake in experimental rats. Neurodegeneration (Alzheimer-like) was induced in twenty-four male Wistar albino rats by CuSO4 supplement to drinking water (10 mg/L) for 14 weeks. AD rats were divided into four groups: untreated AD group (Cu-AD) and three treated AD groups; orally treated for 4 weeks with either DPZ (10 mg/kg/day), Vit D (500 IU/kg/day), or DPZ + Vit D starting from the 10th week of CuSO4 intake. Another six rats were used as normal control (NC) group. The hippocampal tissue content of β-amyloid precursor protein cleaving enzyme 1 (BACE1), phosphorylated Tau (p-tau), clusterin (CLU), tumor necrosis factor-α (TNF-α), caspase-9 (CAS-9), Bax, and Bcl-2 and the cortical content of acetylcholine (Ach), acetylcholinesterase (AChE), total antioxidant capacity (TAC), and malondialdehyde (MDA) were measured. Cognitive function tests (Y-maze) and histopathology studies (hematoxylin and eosin and Congo red stains) and immunohistochemistry for neurofilament. Vit D supplementation alleviated CuSO4-induced memory deficits including significant reduction hippocampal BACE1, p-tau, CLU, CAS-9, Bax, and TNF-α and cortical AChE and MDA. Vit D remarkably increased cortical Ach, TAC, and hippocampal Bcl-2. It also improved neurobehavioral and histological abnormalities. The effects attained by Vit D treatment were better than those attained by DPZ. Furthermore, Vit D boosted the therapeutic potential of DPZ in almost all AD associated behavioral and pathological changes. Vit D is suggested as a potential therapy to retard neurodegeneration.

Neuroimmunological Effect of Vitamin D on Neuropsychiatric Long COVID Syndrome: A Review

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the coronavirus disease 2019 (COVID-19). COVID-19 is now recognized as a multiorgan disease with a broad spectrum of manifestations. A substantial proportion of individuals who have recovered from COVID-19 are experiencing persistent, prolonged, and often incapacitating sequelae, collectively referred to as long COVID. To date, definitive diagnostic criteria for long COVID diagnosis remain elusive. An emerging public health threat is neuropsychiatric long COVID, encompassing a broad range of manifestations, such as sleep disturbance, anxiety, depression, brain fog, and fatigue. Although the precise mechanisms underlying the neuropsychiatric complications of long COVID are presently not fully elucidated, neural cytolytic effects, neuroinflammation, cerebral microvascular compromise, breakdown of the blood-brain barrier (BBB), thrombosis, hypoxia, neurotransmitter dysregulation, and provoked neurodegeneration are pathophysiologically linked to long-term neuropsychiatric consequences, in addition to systemic hyperinflammation and maladaptation of the renin-angiotensin-aldosterone system. Vitamin D, a fat-soluble secosteroid, is a potent immunomodulatory hormone with potential beneficial effects on anti-inflammatory responses, neuroprotection, monoamine neurotransmission, BBB integrity, vasculometabolic functions, gut microbiota, and telomere stability in different phases of SARS-CoV-2 infection, acting through both genomic and nongenomic pathways. Here, we provide an up-to-date review of the potential mechanisms and pathophysiology of neuropsychiatric long COVID syndrome and the plausible neurological contributions of vitamin D in mitigating the effects of long COVID.

Alzheimer's Disease Treatment: The Search for a Breakthrough

As the search for modalities to cure Alzheimer's disease (AD) has made slow progress, research has now turned to innovative pathways involving neural and peripheral inflammation and neuro-regeneration. Widely used AD treatments provide only symptomatic relief without changing the disease course. The recently FDA-approved anti-amyloid drugs, aducanumab and lecanemab, have demonstrated unclear real-world efficacy with a substantial side effect profile. Interest is growing in targeting the early stages of AD before irreversible pathologic changes so that cognitive function and neuronal viability can be preserved. Neuroinflammation is a fundamental feature of AD that involves complex relationships among cerebral immune cells and pro-inflammatory cytokines, which could be altered pharmacologically by AD therapy. Here, we provide an overview of the manipulations attempted in pre-clinical experiments. These include inhibition of microglial receptors, attenuation of inflammation and enhancement of toxin-clearing autophagy. In addition, modulation of the microbiome-brain-gut axis, dietary changes, and increased mental and physical exercise are under evaluation as ways to optimize brain health. As the scientific and medical communities work together, new solutions may be on the horizon to slow or halt AD progression.

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 and Its Analogues: From Differences in Molecular Mechanisms to Potential Benefits of Adapted Use in the Treatment of Alzheimer’s Disease

Lifestyle habits and insufficient sunlight exposure lead to a high prevalence of vitamin D hypovitaminosis, especially in the elderly. Recent studies suggest that in central Europe more than 50% of people over 60 years are not sufficiently supplied with vitamin D. Since vitamin D hypovitaminosis is associated with many diseases, such as Alzheimer’s disease (AD), vitamin D supplementation seems to be particularly useful for this vulnerable age population. Importantly, in addition to vitamin D, several analogues are known and used for different medical purposes. These vitamin D analogues differ not only in their pharmacokinetics and binding affinity to the vitamin D receptor, but also in their potential side effects. Here, we discuss these aspects, especially those of the commonly used vitamin D analogues alfacalcidol, paricalcitol, doxercalciferol, tacalcitol, calcipotriol, and eldecalcitol. In addition to their pleiotropic effects on mechanisms relevant to AD, potential effects of vitamin D analogues on comorbidities common in the context of geriatric diseases are summarized. AD is defined as a complex neurodegenerative disease of the central nervous system and is commonly represented in the elderly population. It is usually caused by extracellular accumulation of amyloidogenic plaques, consisting of amyloid (Aβ) peptides. Furthermore, the formation of intracellular neurofibrillary tangles involving hyperphosphorylated tau proteins contributes to the pathology of AD. In conclusion, this review emphasizes the importance of an adequate vitamin D supply and discusses the specifics of administering various vitamin D analogues compared with vitamin D in geriatric patients, especially those suffering from AD.

Selective vitamins as potential options for dietary therapeutic interventions: In silico and In vitro insights from mutant C terminal fragment of FGA

We have used an integrated computational approach to explore the role of vitamin C and vitamin D in preventing aggregation of Fibrinogen A alpha-chain (FGA^cter) protein responsible for renal amyloidosis. We modelled structures of E524K / E526K mutants of FGA^cter protein and examined the potential interactions of these mutants with vitamin C and vitamin D3. Interaction of these vitamins at the amyloidogenic site may prevent the intermolecular interaction required for amyloid formation. The binding free energy values of vitamin C and vitamin D3 for E524K FGA^cter and E526K FGA^cter are - 67.12 ± 30.46 kJ/mole and - 79.45 ± 26.12 kJ/mol, respectively. Experimental studies using Congo red absorption, aggregation index studies and AFM imaging show encouraging results. The AFM images of E526K FGA^cter contained more extensive and higher protofibril aggregates, whereas, in the presence of vitamin D3, small monomeric and oligomeric aggregates were observed. Overall, the works provide interesting results about vitamin C and D role in preventing renal amyloidosis.

The Pathological Effects of Circulating Hydrophobic Bile Acids in Alzheimer's Disease

Recent clinical studies have revealed that the serum levels of toxic hydrophobic bile acids (deoxy cholic acid, lithocholic acid [LCA], and glycoursodeoxycholic acid) are significantly higher in patients with Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) when compared to control subjects. The elevated serum bile acids may be the result of hepatic peroxisomal dysfunction. Circulating hydrophobic bile acids are able to disrupt the blood-brain barrier and promote the formation of amyloid-β plaques through enhancing the oxidation of docosahexaenoic acid. Hydrophobic bile acid may find their ways into the neurons via the apical sodium-dependent bile acid transporter. It has been shown that hydrophobic bile acids impose their pathological effects by activating farnesoid X receptor and suppressing bile acid synthesis in the brain, blocking NMDA receptors, lowering brain oxysterol levels, and interfering with 17β-estradiol actions such as LCA by binding to E2 receptors (molecular modelling data exclusive to this paper). Hydrophobic bile acids may interfere with the sonic hedgehog signaling through alteration of cell membrane rafts and reducing brain 24(S)-hydroxycholesterol. This article will 1) analyze the pathological roles of circulating hydrophobic bile acids in the brain, 2) propose therapeutic approaches, and 3) conclude that consideration be given to reducing/monitoring toxic bile acid levels in patients with AD or aMCI, prior/in combination with other treatments.

The Vitamin D Receptor as a Potential Target for the Treatment of Age-Related Neurodegenerative Diseases Such as Alzheimer's and Parkinson's Diseases: A Narrative Review

The vitamin D receptor (VDR) belongs to the nuclear receptor superfamily of transcription factors. The VDR is expressed in diverse brain regions and has been implicated in the neuroprotective, antiaging, prosurvival, and anti-inflammatory action of vitamin D. Accordingly, a relationship between vitamin D insufficiency and susceptibility to neurodegenerative diseases has been suggested. However, due to the multitargeted mechanisms of vitamin D and its often overlapping genomic and nongenomic effects, the role of the VDR in brain pathologies remains obscure. In this narrative review, we present progress in deciphering the molecular mechanism of nuclear VDR-mediated vitamin D effects on prosurvival and anti-inflammatory signaling pathway activity within the central nervous system. In line with the concept of the neurovascular unit in pathomechanisms of neurodegenerative diseases, a discussion of the role of the VDR in regulating the immune and vascular brain systems is also included. Next, we discuss the results of preclinical and clinical studies evaluating the significance of vitamin D status and the efficacy of vitamin D supplementation in the treatment of Parkinson's and Alzheimer's diseases, emphasizing the possible role of the VDR in these phenomena. Finally, the associations of some VDR polymorphisms with higher risks and severity of these neurodegenerative disorders are briefly summarized.

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 Potential of Natural Compounds in Neurodegenerative Diseases: Insights from Clinical Trials

Neurodegenerative diseases are caused by the gradual loss of neurons' function. These neurological illnesses remain incurable, and current medicines only alleviate the symptoms. Given the social and economic burden caused by the rising frequency of neurodegenerative diseases, there is an urgent need for the development of appropriate therapeutics. Natural compounds are gaining popularity as alternatives to synthetic drugs due to their neuroprotective properties and higher biocompatibility. While natural compounds' therapeutic effects for neurodegenerative disease treatment have been investigated in numerous in vitro and in vivo studies, only few have moved to clinical trials. This article provides the first systematic review of the clinical trials evaluating natural compounds' safety and efficacy for the treatment of the five most prevalent neurodegenerative disorders: Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis, and Huntington's disease.

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 D3 supplementation ameliorates cognitive impairment and alters neurodegenerative and inflammatory markers in scopolamine induced rat model

A multifaceted approach can be effective for the treatment of dementia including the most common form, Alzheimer's disease (AD). However, currently, it involves only symptomatic treatment with cholinergic drugs. Beneficial effects of high Vitamin D₃ levels or its intake in the prevention and treatment of cognitive disorders have been reported. Thus, the present study examined the preventive effect of Vitamin D₃ (Calcitriol) supplementation on cognitive impairment and evaluated its impact on the accumulation or degradation of Aβ plaques. A single intraperitoneal injection of scopolamine was used to induce cognitive impairment in rats. Treatment of Vitamin D₃ was provided for 21 days after the injection. Various behavioral parameters like learning, spatial memory and exploratory behavior, biochemical alterations in the brain homogenate and histology of the hippocampus were investigated. Our results indicated that scopolamine-induced rats depicted cognitive deficits with high Aβ levels and hyperphosphorylated tau proteins in the brain tissue, while Vitamin D supplementation could significantly improve the cognitive status and lower these protein levels. These results were supported by the histopathological and immunohistochemical staining of the hippocampal brain region. Furthermore, mechanistic analysis depicted that Vitamin D supplementation improved the Aβ protein clearance by increasing the neprilysin levels. It also reduced the accumulation of Aβ plaques by lowering neuroinflammation as well as oxidative stress. The present findings indicate that Vitamin D₃ supplementation can ameliorate cognitive deficits and thereby delay AD progression by increasing Aβ plaque degradation, reducing inflammation and oxidative stress.

Interdisciplinary Approaches to Deal with Alzheimer's Disease-From Bench to Bedside: What Feasible Options Do Already Exist Today?

Alzheimer's disease is one of the most common neurodegenerative diseases in the western population. The incidence of this disease increases with age. Rising life expectancy and the resulting increase in the ratio of elderly in the population are likely to exacerbate socioeconomic problems. Alzheimer's disease is a multifactorial disease. In addition to amyloidogenic processing leading to plaques, and tau pathology, but also other molecular causes such as oxidative stress or inflammation play a crucial role. We summarize the molecular mechanisms leading to Alzheimer's disease and which potential interventions are known to interfere with these mechanisms, focusing on nutritional approaches and physical activity but also the beneficial effects of cognition-oriented treatments with a focus on language and communication. Interestingly, recent findings also suggest a causal link between oral conditions, such as periodontitis or edentulism, and Alzheimer's disease, raising the question of whether dental intervention in Alzheimer's patients can be beneficial as well. Unfortunately, all previous single-domain interventions have been shown to have limited benefit to patients. However, the latest studies indicate that combining these efforts into multidomain approaches may have increased preventive or therapeutic potential. Therefore, as another emphasis in this review, we provide an overview of current literature dealing with studies combining the above-mentioned approaches and discuss potential advantages compared to monotherapies. Considering current literature and intervention options, we also propose a multidomain interdisciplinary approach for the treatment of Alzheimer's disease patients that synergistically links the individual approaches. In conclusion, this review highlights the need to combine different approaches in an interdisciplinary manner, to address the future challenges of Alzheimer's disease.

Changes in Metabolic Parameters in Patients with Diabetic Kidney Disease Depending on the Status of D3

BACKGROUND

Type 2 diabetes is a metabolic disease characterized by hyperglycemia as a result of insulin resistance and decreased insulin secretion. A relatively large number of patients with this type of diabetes have abdominal obesity, which also affects insulin resistance development. Chronic hyperglycemia can lead to damage and dysfunction of various organs, and a striking example is diabetic nephropathy. Diabetic nephropathy is a specific kind of kidney damage that occurs due to complications of diabetes and is accompanied by the formation of diffuse or nodular glomerulosclerosis, which can lead to terminal renal failure and requires immediate substitution through renal therapy or renal transplantation. Diabetic nephropathy is diagnosed with albuminuria and a decrease in the rate of glomerular filtration.

METHODS

This review was based on a literature search for the most important evidence of vitamin D as a possible method of prevention for obesity, type 2 diabetes, and diabetic nephropathy. Collected published articles were summarized according to their overall themes.

RESULTS

In this review, we considered vitamin D as a possible method of treatment for type 2 diabetes, as well as its complications, including diabetic nephropathy.

CONCLUSION

Studies show that vitamin D inhibits the renin-angiotensin-aldosterone system, resulting in improved renal function in diabetic nephropathy. Vitamin D also has antiinflammatory, antiproliferative, and anti-metastatic effects, which improve endothelial function.

Vitamin D Mitigates Hyperglycemia-Induced Cognition Decline in Danio rerio (Zebrafish) through the Activation of Antioxidant Mechanisms

Hyperglycemia contributes to the development of cognition impairment and related disorders, induces oxidative stress in neuronal cells; thereby, impairs normal signaling mechanisms involved in cognition processes. Studies have shown a significant decrease in the vitamin D in individuals with hyperglycemia and cognition impairment. But whether supplementing vitamin D has any beneficiary impact on mitigating hyperglycemia-induced cognition impairment is unknown. We have first tested the impact of hyperglycemia on the induction of cognition deficiency in a zebrafish model. Next, the molecular mechanisms related to oxidative stress, which are deregulated in hyperglycemic zebrafish brains, have been explored. Subsequently, the impact of supplementing the water with vitamin D and a known activator of nuclear factor erythroid-2 related factor 2 (Nrf2) i.e., sulforaphane (SFN) on learning and memory functions were assessed. We showed a significant increase in the oxidative stress in the brain tissue of zebrafish residing in hyperglycemic water (111 mM glucose). Addition of vitamin D and SFN increased Nrf2, but differentially modulated its target genes (NQO1, SOD, GPx etc) activity in zebrafish and neuronal cell lines thereby improved the hyperglycemia-induced decline of cognition impairment. Mechanistically, vitamin D binds to the Keap1 protein; thereby, interfering with its binding to Nrf2, which leads to the activation of antioxidant mechanisms in the cells. In summary, reducing the oxidative stress through vitamin D treatment is a possible option for controlling the cognition impairment in diabetic population, but studies testing this possibility in clinical trials are currently needed.

Vitamin B12 Attenuates Changes in Phospholipid Levels Related to Oxidative Stress in SH-SY5Y Cells

Oxidative stress is closely linked to Alzheimer’s disease (AD), and is detected peripherally as well as in AD-vulnerable brain regions. Oxidative stress results from an imbalance between the generation and degradation of reactive oxidative species (ROS), leading to the oxidation of proteins, nucleic acids, and lipids. Extensive lipid changes have been found in post mortem AD brain tissue; these changes include the levels of total phospholipids, sphingomyelin, and ceramide, as well as plasmalogens, which are highly susceptible to oxidation because of their vinyl ether bond at the sn-1 position of the glycerol-backbone. Several lines of evidence indicate that a deficiency in the neurotropic vitamin B12 is linked with AD. In the present study, treatment of the neuroblastoma cell line SH-SY5Y with vitamin B12 resulted in elevated levels of phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, and plasmalogens. Vitamin B12 also protected plasmalogens from hydrogen peroxide (H₂O₂)-induced oxidative stress due to an elevated expression of the ROS-degrading enzymes superoxide-dismutase (SOD) and catalase (CAT). Furthermore, vitamin B12 elevates plasmalogen synthesis by increasing the expression of alkylglycerone phosphate synthase (AGPS) and choline phosphotransferase 1 (CHPT1) in SH-SY5Y cells exposed to H₂O₂-induced oxidative stress.

Associations Between Intrathecal Levels of Vitamin D, Cytokines, and Core Biomarkers of Alzheimer’s Disease: A Cross-Sectional Study

Background: Several studies have examined association between vitamin D levels in serum and cognition, but little is known of vitamin D levels in cerebrospinal fluid (CSF) and association with Alzheimer’s disease (AD). Objective: In this cross-sectional, explorative study we investigated possible associations of vitamin D in CSF with biomarkers for AD, amyloid-β, tau protein/phosphorylated tau protein in CSF, and with the cytokines IL-6, IL-8, and TNF-α in CSF in patients with cognitive impairment and cognitively healthy controls. Methods: We included 100 outpatients ≥65 years referred for assessment of cognitive impairment and 76 age- and sex-matched cognitively healthy controls. Levels of 25-hydroxyvitamin D (25(OH)D), amyloid-β, tau protein and phosphorylated tau protein, as well as IL-6, IL-8, and TNF-α, were analyzed in CSF in both groups. Results: Higher levels of 25(OH)D in CSF in all groups together were associated with lower levels of tau protein (p = 0.01) and phosphorylated tau protein (p = 0.005). We found no association between 25(OH)D levels in CSF and pathological levels of amyloid-β in CSF nor levels of IL-6 or TNF-α in CSF. Higher levels of 25(OH)D in CSF were associated with higher levels of IL-8 in CSF (p = 0.002). However, vitamin D explained only 6% of variance in IL-8. There was no significant difference between the patient groups and the control group regarding the association between 25(OH)D in CSF and any of the three cytokines in CSF. Conclusion: Participants with higher CSF levels of 25(OH)D exhibited reduced CSF levels of tau protein and phosphorylated tau protein.

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.

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.

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.

Mechanistic Link between Vitamin B12 and Alzheimer’s Disease

Alzheimer’s disease (AD) is the most common form of dementia in the elderly population, affecting over 55 million people worldwide. Histopathological hallmarks of this multifactorial disease are an increased plaque burden and tangles in the brains of affected individuals. Several lines of evidence indicate that B12 hypovitaminosis is linked to AD. In this review, the biochemical pathways involved in AD that are affected by vitamin B12, focusing on APP processing, Aβ fibrillization, Aβ-induced oxidative damage as well as tau hyperphosphorylation and tau aggregation, are summarized. Besides the mechanistic link, an overview of clinical studies utilizing vitamin B supplementation are given, and a potential link between diseases and medication resulting in a reduced vitamin B12 level and AD are discussed. Besides the disease-mediated B12 hypovitaminosis, the reduction in vitamin B12 levels caused by an increasing change in dietary preferences has been gaining in relevance. In particular, vegetarian and vegan diets are associated with vitamin B12 deficiency, and therefore might have potential implications for AD. In conclusion, our review emphasizes the important role of vitamin B12 in AD, which is particularly important, as even in industrialized countries a large proportion of the population might not be sufficiently supplied with vitamin B12.

Association of serum 25-hydroxyvitamin D concentrations with risk of dementia among individuals with type 2 diabetes: A cohort study in the UK Biobank

BACKGROUND

Several epidemiological studies have suggested that vitamin D status is associated with risk of dementia in general populations. However, due to the synergistic effect between diabetic pathology and neuroinflammation, and the prothrombotic profile in patients with diabetes, whether vitamin D is associated with risk of dementia among patients with diabetes is unclear. This study aimed to investigate the associations of circulating vitamin D levels with risks of all-cause dementia, Alzheimer disease (AD), and vascular dementia (VD) among adults with type 2 diabetes (T2D).

METHODS AND FINDINGS

This study included 13,486 individuals (≥60 years) with T2D and free of dementia at recruitment (2006-2010) from the UK Biobank study. Serum 25-hydroxyvitamin D (25[OH]D) concentrations were measured using the chemiluminescent immunoassay method at recruitment. Serum 25(OH)D ≥ 75 nmol/L was considered sufficient, according to the Endocrine Society Clinical Practice Guidelines. Incidence of all-cause dementia, AD, and VD cases was ascertained using electronic health records (EHRs). Each participant's person-years at risk were calculated from the date of recruitment to the date that dementia was reported, date of death, date of loss to follow-up, or 28 February 2018, whichever occurred first. Among the 13,486 individuals with T2D (mean age, 64.6 years; men, 64.3%), 38.3% had vitamin D ≥ 50 nmol/L and only 9.1% had vitamin D ≥ 75 nmol/L. During a mean follow-up of 8.5 years, we observed 283 cases of all-cause dementia, including 101 AD and 97 VD cases. Restricted cubic spline analysis demonstrated a nonlinear relationship between serum 25(OH)D and risk of all-cause dementia (Pnonlinearity < 0.001) and VD (Pnonlinearity = 0.007), and the nonlinear association reached borderline significance for AD (Pnonlinearity = 0.06), with a threshold at around a serum 25(OH)D value of 50 nmol/L for all the outcomes. Higher serum levels of 25(OH)D were significantly associated with a lower risk of all-cause dementia, AD, and VD. The multivariate hazard ratios and 95% confidence intervals for participants who had serum 25(OH)D ≥ 50 nmol/L, compared with those who were severely deficient (25[OH]D < 25 nmol/L), were 0.41 (0.29-0.60) for all-cause dementia (Ptrend < 0.001), 0.50 (0.27-0.92) for AD (Ptrend = 0.06), and 0.41 (0.22-0.77) for VD (Ptrend = 0.01). The main limitation of the current analysis was the potential underreporting of dementia cases, as the cases were identified via EHRs.

CONCLUSIONS

In this study, we observed that higher concentrations of serum 25(OH)D were significantly associated with a lower risk of all-cause dementia, AD, and VD among individuals with T2D. Our findings, if confirmed by replication, may have relevance for dementia prevention strategies that target improving or maintaining serum vitamin D concentrations among patients with T2D.

Serum Vitamin D as a Marker of Impaired Information Processing Speed and Early Disability in Multiple Sclerosis Patients

Slowed information processing speed (IPS) is the hallmark and first cognitive domain to be altered in multiple sclerosis (MS) patients. Insufficient serum vitamin D was previously associated with disease development, relapses, and progression, but little is reported on cognition. However, vitamin D and cognitive impairment (CI) in other neurodegenerative diseases have already been linked. We explored the possible correlation between vitamin D and IPS at diagnosis and early disability at last follow-up in 81 MS patients. At diagnosis, we collected vitamin D levels and performed a Symbol Digit Modalities Test (SDMT). Raw scores were adjusted for age, gender, and educational level. Early disability was evaluated with MS severity score (MSSS) and age-related MSSS (ARMSS). A total of 71 patients (86.58%) showed hypovitaminosis D (19.71 ± 8.76 ng/mL) and 18 patients (21.95%) had CI. Patients with CI showed severe hypovitaminosis D (p = 0.004). No patients with sufficient vitamin D levels had CI. We found a positive correlation between vitamin D levels at diagnosis and (1) SDMT raw and z-score that persisted after correction for sunlight exposure and MRI baseline characteristics, and (2) EDSS, MSSS, and ARMSS after a mean 2 year follow-up. Low vitamin D levels may affect both cognition and early disability in newly diagnosed MS patients.

Impact of Vitamin D3 Deficiency on Phosphatidylcholine-/Ethanolamine, Plasmalogen-, Lyso-Phosphatidylcholine-/Ethanolamine, Carnitine- and Triacyl Glyceride-Homeostasis in Neuroblastoma Cells and Murine Brain

Vitamin D₃ hypovitaminosis is associated with several neurological diseases such as Alzheimer's disease, Parkinson's disease or multiple sclerosis but also with other diseases such as cancer, diabetes or diseases linked to inflammatory processes. Importantly, in all of these diseases lipids have at least a disease modifying effect. Besides its well-known property to modulate gene-expression via the VDR-receptor, less is known if vitamin D hypovitaminosis influences lipid homeostasis and if these potential changes contribute to the pathology of the diseases themselves. Therefore, we analyzed mouse brain with a mild vitamin D hypovitaminosis via a targeted shotgun lipidomic approach, including phosphatidylcholine, plasmalogens, lyso-phosphatidylcholine, (acyl-/acetyl-) carnitines and triglycerides. Alterations were compared with neuroblastoma cells cultivated in the presence and with decreased levels of vitamin D. Both in cell culture and in vivo, decreased vitamin D level resulted in changed lipid levels. While triglycerides were decreased, carnitines were increased under vitamin D hypovitaminosis suggesting an impact of vitamin D on energy metabolism. Additionally, lyso-phosphatidylcholines in particular saturated phosphatidylcholine (e.g., PC aa 48:0) and plasmalogen species (e.g., PC ae 42:0) tended to be increased. Our results suggest that vitamin D hypovitaminosis not only may affect gene expression but also may directly influence cellular lipid homeostasis and affect lipid turnover in disease states that are known for vitamin D hypovitaminosis.

Inflammatory Cascade in Alzheimer's Disease Pathogenesis: A Review of Experimental Findings

Alzheimer’s disease (AD) is the leading cause of dementia worldwide. Most AD patients develop the disease in late life, named late onset AD (LOAD). Currently, the most recognized explanation for AD pathology is the amyloid cascade hypothesis. It is assumed that amyloid beta (Aβ) aggregation and deposition are critical pathogenic processes in AD, leading to the formation of amyloid plaques, as well as neurofibrillary tangles, neuronal cell death, synaptic degeneration, and dementia. In LOAD, the causes of Aβ accumulation and neuronal loss are not completely clear. Importantly, the blood–brain barrier (BBB) disruption seems to present an essential role in the induction of neuroinflammation and consequent AD development. In addition, we propose that the systemic inflammation triggered by conditions like metabolic diseases or infections are causative factors of BBB disruption, coexistent inflammatory cascade and, ultimately, the neurodegeneration observed in AD. In this regard, the use of anti-inflammatory molecules could be an interesting strategy to treat, delay or even halt AD onset and progression. Herein, we review the inflammatory cascade and underlying mechanisms involved in AD pathogenesis and revise the anti-inflammatory effects of compounds as emerging therapeutic drugs against AD.

Cognitive Dysfunction in Systemic Lupus Erythematosus: Immunopathology, Clinical Manifestations, Neuroimaging and Management

Cognitive dysfunction (CD) is a common yet often clinically subtle manifestation that considerably impacts the health-related quality of life in patients with systemic lupus erythaematosus (SLE). Given the inconsistencies in CD assessment and challenges in its attribution to SLE, the reported prevalence of CD differs widely, ranging from 3 to 88%. The clinical presentation of CD in SLE is non-specific and may manifest concurrently with overt neuropsychiatric illness such as psychosis or mood disorders or as isolated impairment of attention, working memory, executive dysfunction or processing speed. Despite the lack of standardized and sensitive neuropsychological tests and validated diagnostic biomarkers of CD in SLE, significant progress has been made in identifying pathogenic neural pathways and neuroimaging. Furthermore, several autoantibodies, cytokines, pro-inflammatory mediators and metabolic factors have been implicated in the pathogenesis of CD in SLE. Abrogation of the integrity of the blood-brain barrier (BBB) and ensuing autoantibody-mediated neurotoxicity, complement and microglial activation remains the widely accepted mechanism of SLE-related CD. Although several functional neuroimaging modalities have consistently demonstrated abnormalities that correlate with CD in SLE patients, a consensus remains to be reached as to their clinical utility in diagnosing CD. Given the multifactorial aetiology of CD, a multi-domain interventional approach that addresses the risk factors and disease mechanisms of CD in a concurrent fashion is the favourable therapeutic direction. While cognitive rehabilitation and exercise training remain important, specific pharmacological agents that target microglial activation and maintain the BBB integrity are potential candidates for the treatment of SLE-related CD.

A Fundamental Role for Oxidants and Intracellular Calcium Signals in Alzheimer's Pathogenesis-And How a Comprehensive Antioxidant Strategy May Aid Prevention of This Disorder

Oxidative stress and increased cytoplasmic calcium are key mediators of the detrimental effects on neuronal function and survival in Alzheimer's disease (AD). Pathways whereby these perturbations arise, and then prevent dendritic spine formation, promote tau hyperphosphorylation, further amplify amyloid β generation, and induce neuronal apoptosis, are described. A comprehensive program of nutraceutical supplementation, comprised of the NADPH oxidase inhibitor phycocyanobilin, phase two inducers, the mitochondrial antioxidant astaxanthin, and the glutathione precursor N-acetylcysteine, may have important potential for antagonizing the toxic effects of amyloid β on neurons and thereby aiding prevention of AD. Moreover, nutraceutical antioxidant strategies may oppose the adverse impact of amyloid β oligomers on astrocyte clearance of glutamate, and on the ability of brain capillaries to export amyloid β monomers/oligomers from the brain. Antioxidants, docosahexaenoic acid (DHA), and vitamin D, have potential for suppressing microglial production of interleukin-1β, which potentiates the neurotoxicity of amyloid β. Epidemiology suggests that a health-promoting lifestyle, incorporating a prudent diet, regular vigorous exercise, and other feasible measures, can cut the high risk for AD among the elderly by up to 60%. Conceivably, complementing such lifestyle measures with long-term adherence to the sort of nutraceutical regimen outlined here may drive down risk for AD even further.

Kidney function and dementia risk in community-dwelling older adults: the Shanghai Aging Study

BACKGROUND

Association between kidney dysfunction and dementia has been studied in western cohorts, but with inconsistent conclusions which may be due to the different measurements of kidney function. We aim to verify the hypothesis that lower levels of kidney function would be associated with increased risk of incident dementia in Chinese elderly.

METHODS

One thousand four hundred twelve dementia-free participants aged 60 years or older from the Shanghai Aging Study were enrolled and followed up for 5.3 years on average. Glomerular filtration rate (GFR) was calculated by using combined creatinine-cystatin C CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation. Diagnoses of incident dementia and Alzheimer's disease (AD) were established using DSM-IV and NINCDS-ADRDA criteria based on medical, neurological, and neuropsychological examinations to each participant. Cox proportional regression was used to analyze the association of baseline GFR_crcys levels with incident dementia/AD, adjusting age, gender, education years, APOE-ε4, diabetes, hypertension, baseline Mini-Mental State Examination score, and proteinuria.

RESULTS

A total of 113 (8%) and 84 (7%) participants developed dementia and AD. Comparing to participants with high GFR_crcys (≥ 80 ml/min/1.73 m²), participants with low (< 67 ml/min/1.73 m²) and moderate GFR_crcys (67 ≤ GFR < 80 ml/min/1.73 m²) had increased risk of incident dementia with hazard ratios (HRs) of 1.87 (95% CI 1.02-3.44) and 2.19 (95% CI 1.21-3.95) after adjustment for confounders, respectively. Low (HR = 2.27 [95%CI 1.10-4.68]) and moderate (HR = 2.14 [95% CI 1.04-4.40]) GFR_crcys at baseline was also independently associated with incident AD after adjustments when comparing to high GFR_crcys. The significant association between GFR_crcys and dementia risk was observed in female but not in male participants.

CONCLUSIONS

GFR_crcys may be considered as a marker of an individual's vulnerability to the increased risk of cognitive decline.

Role of nutraceuticals in cognition during aging and related disorders

Cognitive abilities are compromised with advancing age posing a great risk for the development of dementia and other related brain disorders. Genetic susceptibility as well as environmental exposures determine the fate of cognitive aging and its transition to pathological states. Emerging epidemiological and observational studies have revealed the importance of lifestyle factors including dietary patterns and nutritional intake in the maintenance of cognitive health and reducing the risk of neurodegenerative disorders. In this context, nutraceutical interventions have gained considerable attention in preventing age-related cognitive deficits and counteracting pathological processes. Nutraceuticals include dietary plants and derivatives, food supplements and processed foods with nutritional and pharmaceutical values. The present review highlights the importance of nutraceuticals in attenuating cognitive aging and its progression to dementia, with specific emphasis on chemical constituents, neurocognitive properties and mechanism of action.

Vitamin D deficiency exacerbates Alzheimer-like pathologies by reducing antioxidant capacity

Vitamin D (VD) deficiency is prevalent among aging people and Alzheimer's disease (AD) patients. However, the roles of VD deficiency in the pathology of AD remain largely unexplored. In this study, APP/PS1 mice were fed a VD-deficient diet for 13 weeks to evaluate the effects of VD deficiency on the learning and memory functions and the neuropathological characteristics of the mice. Our study revealed that VD deficiency accelerated cognitive impairment in the APP/PS1 mice. Mechanistic studies revealed that VD deficiency promoted glial activation and increased inflammatory factor secretion. Furthermore, VD deficiency increased the production and deposition of Aβ by elevating the expression levels of amyloid precursor protein (APP) and β-site APP cleavage enzyme 1 (BACE1). In addition, VD deficiency increased the phosphorylation of Tau at Thr181, Thr205 and Ser396 by increasing the activities of cyclin-dependent kinase 5 (CDK5) and glycogen synthase kinase 3α/β (GSK3α/β) and promoted synaptic dystrophy and neuronal loss. All these effects of VD deficiency may be ascribed to enhanced oxidative stress via the downregulation of superoxide dismutase 1 (SOD1), glutathione peroxidase 4 (GPx4) and cystine/glutamate exchanger (xCT). Taken together, our data suggest that VD deficiency exacerbates Alzheimer-like pathologies via promoting inflammatory stress, increasing Aβ production and elevating Tau phosphorylation by decreasing antioxidant capacity in the brains of APP/PS1 mice. Hence, rescuing the VD status of AD patients should be taken into consideration during the treatment of AD.

Vitamin D and Glaucoma: A Critical Review of the Literature

Primary open-angle glaucoma is a progressive optic neuropathy which can lead to irreversible blindness if untreated. A number of studies have been published suggesting a correlation between the level of serum vitamin D3 and glaucoma or intraocular pressure (IOP). The latter is known to be a major risk factor for glaucoma and is the main target of glaucoma treatment. We give a critical review of the literature, exploring what is known about this matter. While some studies report an inverse association between serum vitamin D3 and IOP, others do not confirm this finding. Similar divergent conclusions came from studies regarding the association between serum vitamin D3 and the presence or severity of glaucoma. The effect of vitamin D3 on IOP decrease has been attributed to both aqueous humor production and trabecular meshwork outflow pathway increase. Vitamin D3 has been shown to play a major role in reducing inflammation, modulating the immune response, and decreasing angiogenesis in the eye and in other organs. It has been suggested that, through its neuroprotective effect, vitamin D3 could be a protective factor for glaucoma and that vitamin D3 deficiency could explain glaucoma occurrence or severity in some patients. Other neurodegenerative diseases such as Alzheimer’s disease and multiple sclerosis have been similarly related to vitamin D3 deficiency. 1α,25(OH)2 vitamin D3 (calcitriol) supplementation has been shown to be beneficial for lowering IOP in monkeys. Although the studies highlighted in this review show interesting results, their limitations underscore the need for both population-based studies and larger randomized controlled trial with vitamin D3 supplementation. The specific role of vitamin D3 in the pathology of glaucoma remains to be elucidated, together with the possible therapeutic benefit of vitamin D3 supplementation.

Myogenic, genomic and non-genomic influences of the vitamin D axis in skeletal muscle

Despite vitamin D-deficiency clinically presenting with myopathy, muscle weakness and atrophy, the mechanisms by which vitamin D exerts its homeostatic effects upon skeletal muscle remain to be fully established. Recent studies have shown that the receptor by which 1α,25-dihydroxyvitamin D₃ (1,25[OH]₂ D₃ ) exerts its biological actions (ie, the vitamin D receptor, VDR) elicits both genomic and non-genomic effects upon skeletal muscle. The controversy surrounding skeletal muscle VDR mRNA/protein expression in post-natal muscle has been allayed by myriad recent studies, while dynamic expression of VDR throughout myogenesis, and association of higher VDR levels during muscle regeneration/immature muscle cells, suggests a role in myogenesis and perhaps an enrichment of VDR in satellite cells. Accordingly, in vitro studies have demonstrated 1,25(OH)₂ D₃ is anti-proliferative in myoblasts, yet pro-differentiation in latter stages of myogenesis. These effects involve modulation of gene expression (VDR as a transcriptional co-activator controls ~3% of the genome) and post-genomic intracellular signalling for example, via c-Src and alterations to intramuscular calcium homeostasis and proteostasis. The aim of this review is to consider the biomolecular role for the vitamin D/VDR axis in myogenesis, while also exploring global evidence for genomic and non-genomic mechanisms of action for 1,25(OH)₂ D₃ /VDR.

Low Vitamin D Levels and Risk of Incident Delirium in 351,000 Older UK Biobank Participants

BACKGROUND/OBJECTIVES

Delirium is common in older adults, especially following hospitalization. Because low vitamin D levels may be associated with increased delirium risk, we aimed to determine the prognostic value of blood vitamin D levels, extending our previous genetic analyses of this relationship.

DESIGN

Prospective cohort analysis.

SETTING

Community-based cohort study of adults from 22 cities across the United Kingdom (the UK Biobank).

PARTICIPANTS

Adults aged 60 and older by the end of follow-up in the linked hospital inpatient admissions data, up to 14 years after baseline (n = 351,320).

MEASUREMENTS

At baseline, serum vitamin D (25-OH-D) levels were measured. We used time-to-event models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between vitamin D deficiency and incident hospital-diagnosed delirium, adjusted for age, sex, assessment month, assessment center, and ethnicity. We performed Mendelian randomization genetic analysis in European participants to further investigate vitamin D and delirium risk.

RESULTS

A total of 3,634 (1.03%) participants had at least one incident hospital-diagnosed delirium episode. Vitamin D deficiency (<25 nmol/L) predicted a large incidence in delirium (HR = 2.49; 95% CI = 2.24-2.76; P = 3*10^-68 , compared with >50 nmol/L). Increased risk was not limited to the deficient group: insufficient levels (25-50 nmol/L) were also at increased risk (HR = 1.38; 95% CI = 1.28-1.49; P = 4*10^-18 ). The association was independent of calcium levels, hospital-diagnosed fractures, dementia, and other relevant cofactors. In genetic analysis, participants carrying more vitamin D-increasing variants had a reduced likelihood of incident delirium diagnosis (HR = .80 per standard deviation increase in genetically instrumented vitamin D: .73-.87; P = 2*10^-7 ).

CONCLUSION

Progressively lower vitamin D levels predicted increased risks of incident hospital-diagnosed delirium, and genetic evidence supports a shared causal pathway. Because low vitamin D levels are simple to detect and inexpensive and safe to correct, an intervention trial to confirm these results is urgently needed.

Vitamins: a nutritional intervention to modulate the Alzheimer's disease progression

Background: Alzheimer's disease is known as one of the fastest growing lethal diseases worldwide where we have limited and undesired ways for regulating its pathological progress. Now-a-days, nutritional compounds have been using to treat several brain disorders and one of them; vitamins were strongly reported to combat cognition and memory deterioration in neurodegenerative diseases including Alzheimer's disease. Objective: Here, the author tried to find the precise physiological roles, status, and worth of vitamins in the brain and how exactly these nutrients modulate progression of Alzheimer's disease. Results & Discussion: After a comprehensive and systematic literature review, the author reports that vitamins have various targets in Alzheimer's disease pathogenesis by which they act to avert the neuronal dysfunction in the disease. Several Alzheimer's disease-associated neurological deficits have reported regulating by vitamin intake but the beneficial effects identified mostly in combinatorial and long-term studies. Conclusion: In this way, the author suggests that it might be better to test vitamins with other components over single vitamin approach for a compatible and synergistic effect as well as using a combination of vitamin with other compounds can target multiple pathways. This strategy may help in deteriorating memory dysfunction and cognition impairment in Alzheimer's disease pathophysiology.Abbreviations: APOE: apolipoprotein E; APP: amyloid precursor protein; ATP: adenosine triphosphate; Aβ- β-amyloid; cGMP: cyclic guanine monophosphate; CNS: central nervous system; DNA: deoxyribonucleic acid; IU: international units; RA: retinoic acid; RAR: retinoic acid receptor; RNA: ribonucleic acid; ROS: reactive oxygen species; tHcy: total homocysteine; α: alpha; β: beta; γ: gama; ε: epsilon; g: gram; µ: micron; mg: milligram; ⬆: increased,⬇: decreased.

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

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

On the Etiopathogenesis and Pathophysiology of Alzheimer's Disease: A Comprehensive Theoretical Review

Alzheimers' disease (AD) is the most common cause of dementia, with an estimated 5 million new cases occurring annually. Among the elderly, AD shortens life expectancy, results in disability, decreases quality of life, and ultimately, leads to institutionalization. Despite extensive research in the last few decades, its heterogeneous pathophysiology and etiopathogenesis have made it difficult to develop an effective treatment and prevention strategy. Aging is the biggest risk factor for AD and evidence suggest that the total number of older people in the population is going to increase astronomically in the next decades. Also, there is evidence that air pollution and increasing income inequality may result in higher incidence and prevalence of AD. This makes the need for a comprehensive understanding of the etiopathogenesis and pathophysiology of the disease extremely critical. In this paper, a quintuple framework of thyroid dysfunction, vitamin D deficiency, sex hormones, and mitochondria dysfunction and oxidative stress are used to provide a comprehensive description of AD etiopathogenesis and pathophysiology. The individual role of each factor, their synergistic and genetic interactions, as well as the limitations of the framework are discussed.

The impact of capsaicinoids on APP processing in Alzheimer's disease in SH-SY5Y cells

The vanilloid capsaicin is a widely consumed spice, known for its burning and "hot" sensation through activation of TRPV1 ion-channels, but also known to decrease oxidative stress, inflammation and influence tau-pathology. Beside these positive effects, little is known about its effects on amyloid-precursor-protein (APP) processing leading to amyloid-β (Aβ), the major component of senile plaques. Treatment of neuroblastoma cells with capsaicinoids (24 hours, 10 µM) resulted in enhanced Aβ-production and reduced Aβ-degradation, leading to increased Aβ-levels. In detailed analysis of the amyloidogenic-pathway, both BACE1 gene-expression as well as protein-levels were found to be elevated, leading to increased β-secretase-activity. Additionally, γ-secretase gene-expression as well as activity was enhanced, accompanied by a shift of presenilin from non-raft to raft membrane-domains where amyloidogenic processing takes place. Furthermore, impaired Aβ-degradation in presence of capsaicinoids is dependent on the insulin-degrading-enzyme, one of the major Aβ-degrading-enzymes. Regarding Aβ-homeostasis, no differences were found between the major capsaicinoids, capsaicin and dihydrocapsaicin, and a mixture of naturally derived capsaicinoids; effects on Ca²⁺-homeostasis were ruled out. Our results show that in respect to Alzheimer's disease, besides the known positive effects of capsaicinoids, pro-amyloidogenic properties also exist, enhancing Aβ-levels, likely restricting the potential use of capsaicinoids as therapeutic substances in Alzheimer's disease.

Vitamins D3 and D2 have marked but different global effects on gene expression in a rat oligodendrocyte precursor cell line

Background

Vitamin D deficiency increases the risk of developing multiple sclerosis (MS) but it is unclear whether vitamin D supplementation improves the clinical course of MS, and there is uncertainty about the dose and form of vitamin D (D2 or D3) to be used. The mechanisms underlying the effects of vitamin D in MS are not clear. Vitamin D3 increases the rate of differentiation of primary oligodendrocyte precursor cells (OPCs), suggesting that it might help remyelination in addition to modulating the immune response. Here we analyzed the transcriptome of differentiating rat CG4 OPCs treated with vitamin D2 or with vitamin D3 at 24 h and 72 h following onset of differentiation.

Methods

Gene expression in differentiating CG4 cells in response to vitamin D2 or D3 was quantified using Agilent DNA microarrays (n = 4 replicates), and the transcriptome data were processed and analysed using the R software environment. Differential expression between the experimental conditions was determined using LIMMA, applying the Benjamini and Hochberg multiple testing correction to p-values, and significant genes were grouped into co-expression clusters by hierarchical clustering. The functional significance of gene groups was explored by pathway enrichment analysis using the clusterProfiler package.

Results

Differentiation alone changed the expression of about 10% of the genes at 72 h compared to 24 h. Vitamin D2 and D3 exerted different effects on gene expression, with D3 influencing 1272 genes and D2 574 at 24 h. The expression of the vast majority of these genes was either not changed in differentiating cells not exposed to vitamin D or followed the same trajectory as the latter. D3-repressed genes were enriched for Gene Ontology (GO) categories including transcription factors and the Notch pathway, while D3-induced genes were enriched for the Ras pathway.

Conclusions

This study shows that vitamin D3, compared with D2, changes the expression of a larger number of genes in OLs. Identification of genes affected by D3 in OLs should help to identify mechanisms mediating its action in MS.

Active form of vitamin D analogue mitigates neurodegenerative changes in Alzheimer's disease in rats by targeting Keap1/Nrf2 and MAPK-38p/ERK signaling pathways

BACKGROUND

The nuclear factor erythroid2-related factor2 (Nrf2), a chief transcriptional regulator of antioxidant response element (ARE), is considered a promising target for the prevention of Alzheimer's disease (AD). Vitamin D has been recognized to have a crucial role in improving AD cognitive functions. The present study was conducted to evaluate the effects of active vitamin D analogue, Maxacalcitol, on Keap1-Nrf2 signaling pathway in experimental Alzheimer's disease in rats.

MATERIALS AND METHODS

The study was conducted on thirty female white albino rats divided equally into 3 groups: control group, Alzheimer group induced by Lipopolysaccharide and Alzheimer group treated with active vitamin D3 analogue, Maxacalcitol. The following parameters were assessed in rat brain tissues: Gene expression of Nrf2, Keap1 and MAF by RT-PCR, protein levels of phosphorylated MAPK-38p and ERK1/2 by Western Blot Technique, estimation of HO-1, Amyloid β, p-Tau levels and serum levels of TNFα, IL-10 and total 25-hydroxyvitamin D, serum calcium levels, GSH and MDA levels were also estimated in addition to cognitive function tests and histo-pathological examination of rat brain tissues.

RESULTS

In Alzheimer group, there was a significant deficit in cognition along with down-regulation of gene expression of Nrf2 and the protein levels of its downstream antioxidant effectors (HO-1 and GSH) with increased levels of the lipid peroxidation biomarker MDA. Also, there was increased neuro-inflammation as evidenced by increased levels of TNFα and decreased levels of IL-10. Moreover, there were increased amyloid β load and enhanced levels of phosphorylation of MAPK-38 and ERK1/2 leading to hyperphosphorylation of Tau protein. In addition, there were decreased serum levels of both total 25-hydroxyvitamin D and calcium. Treatment with vitamin D3 analogue, Maxacalcitol significantly improved cognitive dysfunction and histopathological picture of the brains of Alzheimer rats. Also, Vitamin D analogue significantly increased expression of Nrf2 and its downstream effectors (HO-1 and GSH), improved serum levels of total 25-hydroxyvitamin D and calcium, decreased neuro-inflammation and Amyloid β load as well as hyperphosphorylation of MAPK-38, ERK1/2 and tau proteins were also observed. Therefore, these data suggest that vitamin D analogue, Maxacalcitol could be used as a therapeutic agent in treatment of Alzheimer disease.