Decrease in age-related tau hyperphosphorylation and cognitive improvement following vitamin D supplementation are associated with modulation of brain energy metabolism and redox state

Effects of patent foramen ovale in migraine: a metabolomics-based study

Patent foramen ovale (PFO), a cardiac anatomical anomaly inducing abnormal haemodynamics, leads to a paradoxical bypass of the pulmonary circulation. PFO closure might alleviate migraines; however, clinical evidence and basic experiments for the relationship are lacking. To explore the effect of PFO on migraine, 371 migraineurs finishing blood tests and contrast transthoracic echocardiography for the detection of PFO were prospectively included. Multivariate regression analysis revealed that PFO was independently associated with aura, and lower cystatin-C (cys-C) and calcium levels. Among them, patients with PFO who underwent percutaneous PFO closure were continuously followed up 1 year after the operation. The intensity of migraine was significantly relieved and the levels of cys-C and calcium increased after PFO closure. Untargeted and targeted metabolomics of plasma from migraineurs before and after PFO closure revealed that 5-HT and glutathione (GSH) metabolites were differentially expressed after PFO closure. The differential metabolites were then validated in the plasma and brain tissues of PFO mouse models by LC-MS/MS analysis. Desorption electrospray ionization mass imaging demonstrated that these metabolic alterations occurred mainly in the posterior cerebral cortex. Collectively, aura, cys-C and calcium could be biomarkers of migraineurs with PFO. PFO might have an impact on the posterior head associated with the regulation of 5-HT and GSH. PFO closure might relieve migraine by improving 5-HT clearance metabolism and ameliorating redox reactions. Our results may provide evidence for an indication of PFO closure in migraine and support the related potential mechanism. KEY POINTS: Aura, and levels of cystatin-C and calcium are biomarkers of migraineurs with a patent foramen ovale (PFO). The clearance of pulmonary metabolism of 5-HT and deoxygenated blood might be the reason for the improvement of migraine symptoms in patients with PFO. The posterior region of the brain is the main area responsible for PFO-induced migraine.

The effects of supplementation of vitamin D to the egg-yolk extender on cryopreservation of ram semen

OBJECTIVES

This study aimed to examine the effects of supplementation of vitamin D to the egg-yolk extender on characteristics of frozen-thawed ram semen.

METHODS

Semen samples obtained from adult rams were pooled and divided into five equal volumes. It was reconstituted with extenders containing different concentrations of vitamin D: 0 (control), 12.5 (VITD 12.5), 25 (VITD 25), 50 (VITD 50), and 100 ng/mL (VITD 100), and then they were frozen. Sperm motility parameters, plasma membrane functional integrity, acrosomal integrity, DNA fragmentation, and mitochondrial membrane potential of the groups were evaluated after sperm thawing.

RESULTS

Total motility and progressive motility were higher in VITD 50 than in all other groups (p < 0.05). Higher sperm straightness, linearity, and wooble were higher in VITD 50 than in the control group (p < 0.05). A similar pattern of VITD 50 was observed for plasma membrane integrity and mitochondrial membrane potential (p > 0.05).

CONCLUSIONS

In the study, it was observed that adding vitamin D to the extender had a beneficial effect on ram spermatological parameters. In addition, it was concluded that the use of the 50 ng/mL vitamin D in the extender provided more effective protection than the other doses.

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.

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.

Bioenergetic Impairment in the Neuro-Glia-Vascular Unit: An Emerging Physiopathology during Aging

An emerging concept termed the "neuro-glia-vascular unit" (NGVU) has been established in recent years to understand the complicated mechanism of multicellular interactions among vascular cells, glial cells, and neurons. It has been proverbially reported that the NGVU is significantly associated with neurodegenerative disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). Physiological aging is an inevitable progression associated with oxidative damage, bioenergetic alterations, mitochondrial dysfunction, and neuroinflammation, which is partially similar to the pathology of AD. Thus, senescence is regarded as the background for the development of neurodegenerative diseases. With the exacerbation of global aging, senescence is an increasingly serious problem in the medical field. In this review, the coupling of each component, including neurons, glial cells, and vascular cells, in the NGVU is described in detail. Then, various mechanisms of age-dependent impairment in each part of the NGVU are discussed. Moreover, the potential bioenergetic alterations between different cell types in the NGVU are highlighted, which seems to be an emerging physiopathology associated with the aged brain. Bioenergetic intervention in the NGVU may be a new direction for studies on delaying or diminishing aging in the future.

Navigating Alzheimer's Disease via Chronic Stress: The Role of Glucocorticoids

Alzheimer's disease (AD) is a chronic intensifying incurable progressive disease leading to neurological deterioration manifested as impairment of memory and executive brain functioning affecting the physical ability like intellectual brilliance, common sense in patients. The recent therapeutic approach in Alzheimer's disease is only the symptomatic relief further emerging the need for therapeutic strategies to be targeted in managing the underlying silent killing progression of dreaded pathology. Therefore, the current research direction is focused on identifying the molecular mechanisms leading to the evolution of the understanding of the neuropathology of Alzheimer's disease. The resultant saturation in the area of current targets (amyloid β, τ Protein, oxidative stress etc.) has led the scientific community to rethink of the mechanistic neurodegenerative pathways and reprogram the current research directions. Although, the role of stress has been recognized for many years and contributing to the development of cognitive impairment, the area of stress has got the much-needed impetus recently and is being recognized as a modifiable menace for AD. Stress is an unavoidable human experience that can be resolved and normalized but chronic activation of stress pathways unsettle the physiological status. Chronic stress mediated activation of neuroendocrine stimulation is generally linked to a high risk of developing AD. Chronic stress-driven physiological dysregulation and hypercortisolemia intermingle at the neuronal level and leads to functional (hypometabolism, excitotoxicity, inflammation) and anatomical remodeling of the brain architecture (senile plaques, τ tangles, hippocampal atrophy, retraction of spines) ending with severe cognitive deterioration. The present review is an effort to collect the most pertinent evidence that support chronic stress as a realistic and modifiable therapeutic earmark for AD and to advocate glucocorticoid receptors as therapeutic interventions.

The Molecular Mechanisms by Which Vitamin D Prevents Insulin Resistance and Associated Disorders

Numerous studies have shown that vitamin D deficiency is very common in modern societies and is perceived as an important risk factor in the development of insulin resistance and related diseases such as obesity and type 2 diabetes (T2DM). While it is generally accepted that vitamin D is a regulator of bone homeostasis, its ability to counteract insulin resistance is subject to debate. The goal of this communication is to review the molecular mechanism by which vitamin D reduces insulin resistance and related complications. The university library, PUBMED, and Google Scholar were searched to find relevant studies to be summarized in this review article. Insulin resistance is accompanied by chronic hyperglycaemia and inflammation. Recent studies have shown that vitamin D exhibits indirect antioxidative properties and participates in the maintenance of normal resting ROS level. Appealingly, vitamin D reduces inflammation and regulates Ca²⁺ level in many cell types. Therefore, the beneficial actions of vitamin D include diminished insulin resistance which is observed as an improvement of glucose and lipid metabolism in insulin-sensitive tissues.

Comparison of Serum Free and Bioavailable 25-Hydroxyvitamin D Levels in Alzheimer's Disease and Healthy Control Patients

OBJECTIVE

Many studies have investigated lower 25-hydroxyvitamin D (25[OH]D) levels in patients with Alzheimer's disease (AD) compared with those in control patients. In the present study, we aimed to evaluate serum free and bioavailable 25(OH)D levels in patients with AD and in healthy control patients.

METHODS

The AD group consisted of 85 patients aged >60 years who were diagnosed with possible AD according to National Institute on Aging-Alzheimer's Association criteria and 85 healthy control patients. Serum levels of total 1,25-dihydroxyvitamin D, total 25(OH)D, vitamin D binding protein (VDBP), parathormone, calcium, phosphorus and albumin, free 25(OH)D, bioavailable 25(OH)D, and the bioavailable 25(OH)D/total 25(OH)D ratio were compared in both groups.

RESULTS

Total 25(OH)D, free 25(OH)D, bioavailable 25(OH)D, and the bioavailable 25(OH)D/total 25(OH)D ratio were significantly lower (P <.001, P <.001, P <.001, P <.05, respectively) in the AD group, whereas the VDBP level was significantly higher (P <.05) in the AD than in the control group.

CONCLUSION

Free and bioavailable 25(OH)D detected at lower levels in patients with AD limit the target central effects of 25(OH)D; this result suggests that reduced levels of the active free form of vitamin D may be a risk factor for AD and dementia.

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.

Exercise enhances the effectiveness of vitamin D therapy in rats with Alzheimer's disease: emphasis on oxidative stress and inflammation

Alzheimer's disease (AD) is characterized by gradual loss of memory and cognitive functions which can affect anyone. Authors declared that there is a link between vitamin D and brain function. It has been proven that vitamin D plays an important role in improving AD cognitive functions. Researchers have found that exercise has many beneficial effects on humans. In addition to cardioprotection, it has been demonstrated that exercise provides an effective improvement in different brain functions. So in our study, we aimed to evaluate the effect of each of vitamin D and/ or exercise on AD and if they could be used as a potential line for treating AD. This study was conducted on fifty female white albino rats divided equally into 5 groups: control group, Alzheimer group induced by Lipopolysaccharide, Alzheimer group treated with vitamin D, Alzheimer group treated with exercise and Alzheimer group treated with both vitamin D and exercise. The following parameters were assessed in rat brain tissues: acetylcholine esterase (AChE) activity, levels of amyloid β 42 and tau proteins, dopamine brain neurotransmitter, BDNF and NGF by ELISA. Serum levels of IL-6 and IL-10 were assessed by ELISA. MDA, GSH and vitamin D levels were also estimated in addition to cognitive function tests and histopathological examination of rat brain tissues. In Alzheimer group, there was a significant increase in the proinflammatory cytokine IL-6, the lipid peroxidation marker MDA, amyloid β and tau proteins^, levels. In addition to a significant increase in time consumed in T-maze test. Alzheimer group also showed a significant decrease in the anti-inflammatory cytokine IL-10, the anti-oxidative stress biomarker GSH, the neurotransmitters AChE and dopamine, and the growth factors BDNF and NGF as well as serum vitamin D levels. Treatment with either vitamin D or exercise significantly improved cognitive dysfunction and the histopathological picture of the brains of Alzheimer's rats with the best results in combined vitamin D and exercise treated group. The treated groups, especially combined vitamin D and exercise group, showed a significant decrease in IL-6, MDA, amyloid β and tau proteins levels, but on the other hand they showed a significant increase in IL-10, GSH, AChE, dopamine, BDNF and NGF. These data suggest that combined vitamin D and exercise could be considered as a potential and effective line for treating AD.

Analysis of Association between Vitamin D Deficiency and Insulin Resistance

Recent evidence revealed extra skeleton activity of vitamin D, including prevention from cardiometabolic diseases and cancer development as well as anti-inflammatory properties. It is worth noting that vitamin D deficiency is very common and may be associated with the pathogenesis of insulin-resistance-related diseases, including obesity and diabetes. This review aims to provide molecular mechanisms showing how vitamin D deficiency may be involved in the insulin resistance formation. The PUBMED database and published reference lists were searched to find studies published between 1980 and 2019. It was identified that molecular action of vitamin D is involved in maintaining the normal resting levels of ROS and Ca2+, not only in pancreatic β-cells, but also in insulin responsive tissues. Both genomic and non-genomic action of vitamin D is directed towards insulin signaling. Thereby, vitamin D reduces the extent of pathologies associated with insulin resistance such as oxidative stress and inflammation. More recently, it was also shown that vitamin D prevents epigenetic alterations associated with insulin resistance and diabetes. In conclusion, vitamin D deficiency is one of the factors accelerating insulin resistance formation. The results of basic and clinical research support beneficial action of vitamin D in the reduction of insulin resistance and related pathologies.

Vitamin D in Neurological Diseases: A Rationale for a Pathogenic Impact

It is widely known that vitamin D receptors have been found in neurons and glial cells, and their highest expression is in the hippocampus, hypothalamus, thalamus and subcortical grey nuclei, and substantia nigra. Vitamin D helps the regulation of neurotrophin, neural differentiation, and maturation, through the control operation of growing factors synthesis (i.e., neural growth factor [NGF] and glial cell line-derived growth factor (GDNF), the trafficking of the septohippocampal pathway, and the control of the synthesis process of different neuromodulators (such as acetylcholine [Ach], dopamine [DA], and gamma-aminobutyric [GABA]). Based on these assumptions, we have written this review to summarize the potential role of vitamin D in neurological pathologies. This work could be titanic and the results might have been very fuzzy and even incoherent had we not conjectured to taper our first intentions and devoted our interests towards three mainstreams, demyelinating pathologies, vascular syndromes, and neurodegeneration. As a result of the lack of useful therapeutic options, apart from the disease-modifying strategies, the role of different risk factors should be investigated in neurology, as their correction may lead to the improvement of the cerebral conditions. We have explored the relationships between the gene-environmental influence and long-term vitamin D deficiency, as a risk factor for the development of different types of neurological disorders, along with the role and the rationale of therapeutic trials with vitamin D implementation.

Vitamin D, Cognition and Alzheimer's Disease: The Therapeutic Benefit is in the D-Tails

Since its discovery during the epidemic of rickets in the early 1920s, the physiological effects of vitamin D on calcium/phosphorus homeostasis have been thoroughly studied. Along with the understanding of its actions on skeletal diseases and advances in cellular and molecular biology, this misnamed vitamin has gained attention as a potential player in a growing number of physiological processes and a variety of diseases. During the last 25 years, vitamin D has emerged as a serious candidate in nervous system development and function and a therapeutic tool in a number of neurological pathologies. More recently, experimental and pre-clinical data suggest a link between vitamin D status and cognitive function. Human studies strongly support a correlation between low levels of circulating 25-hydroxyvitamin D (25(OH)D) and cognitive impairment or dementia in aging populations. In parallel, animal studies show that supplementation with vitamin D is protective against biological processes associated with Alzheimer’s disease (AD) and enhances learning and memory performance in various animal models of aging and AD. These experimental observations support multiple mechanisms by which vitamin D can act against neurodegenerative processes. However, clinical interventional studies are disappointing and fail to associate increased 25(OH)D levels with improved cognitive outcomes. This review collects the current available data from both animal and human studies and discusses the considerations that future studies examining the effects of vitamin D status on neurocognitive function might consider.

Vitamin D3 attenuates cognitive deficits and neuroinflammatory responses in ICV-STZ induced sporadic Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by intracellular neurofibrillary tangles and extracellular Aβ deposition. Growing experimental evidence indicate diverse biological effects of vitamin D₃ including antioxidant, neuroprotective, anti-inflammatory and cardiovascular benefits. However, the underlying neuroprotective mechanism of vitamin D₃ is still largely elusive. Therefore, the present study was aimed to investigate the neuroprotective effects of vitamin D₃ on ICV-STZ induced sporadic AD. Our study demonstrated that vitamin D3 pretreatment significantly improved spatial learning and memory functions and effectively mitigated ICV-STZ mediated neuronal oxidative stress, mitochondrial aberrations and improved cholinergic functions. Moreover, vitamin D₃ attenuated hippocampal neuroinflammatory response and reduced neuronal death in cortex and hippocampus. Our findings indicated that prophylactic vitamin D₃ supplementation ameliorated ICV-STZ mediated neurobehavioral alterations, oxidative stress and neuroinflammation thereby improving cholinergic functions and reversed degenerative changes in brain. Thus, our study further provides evidence for its therapeutic supplementation for various neurodegenerative disorders including AD.

Role of Vitamin D in Amyloid clearance via LRP-1 upregulation in Alzheimer's disease: A potential therapeutic target?

Amyloid beta (Aβ) deposition is considered to be one of the primary reason to trigger Alzheimer's disease (AD). Literature clearly suggests decline in Aβ clearance to be accountable for progression of late onset AD as compared to augmented Aβ production. There may be several pathways for Aβ clearance out of which one of the major pathway is the vascular-mediated removal of Aβ from the brain across the blood-brain barrier (BBB) via efflux pumps or receptors. Among Aβ scavenger receptors, low density lipoprotein receptor related protein (LRP-1) has been most extensively studied. LRP-1, is highly expressed in neurons and located on abluminal side of the brain capillaries whose expression decreases in AD patients which give rise to increased cerebral Aβ deposition. Recent evidences reveal that post 1,25-(OH)₂D₃ treatment, LRP1 expression increases significantly for both in-vivo and in-vitro studies, since Vitamin D receptors (VDR) are broadly expressed in brain. Biological actions of Vitamin D are mediated via its nuclear hormone receptor vitamin D receptor (VDR) and is found to regulate many genes. Several lines of evidence suggest that VDR deficiency/inhibition can be a potential risk factor for AD and sufficient Vitamin D supplementation is beneficial to prevent AD onset/pathology or slow down the progression of disease. The present review establishes a strong correlation between Vitamin D and LRP-1 and their possible involvement in Aβ clearance and thereby emerging as new therapeutic target.

Vitamin D deficiency and diabetes

Vitamin D deficiency has been linked to the onset of diabetes. This review summarizes the role of Vitamin D in maintaining the normal release of insulin by the pancreatic beta cells (β-cells). Diabetes is initiated by the onset of insulin resistance. The β-cells can overcome this resistance by releasing more insulin, thus preventing hyperglycaemia. However, as this hyperactivity increases, the β-cells experience excessive Ca2+ and reactive oxygen species (ROS) signalling that results in cell death and the onset of diabetes. Vitamin D deficiency contributes to both the initial insulin resistance and the subsequent onset of diabetes caused by β-cell death. Vitamin D acts to reduce inflammation, which is a major process in inducing insulin resistance. Vitamin D maintains the normal resting levels of both Ca2+ and ROS that are elevated in the β-cells during diabetes. Vitamin D also has a very significant role in maintaining the epigenome. Epigenetic alterations are a feature of diabetes by which many diabetes-related genes are inactivated by hypermethylation. Vitamin D acts to prevent such hypermethylation by increasing the expression of the DNA demethylases that prevent hypermethylation of multiple gene promoter regions of many diabetes-related genes. What is remarkable is just how many cellular processes are maintained by Vitamin D. When Vitamin D is deficient, many of these processes begin to decline and this sets the stage for the onset of diseases such as diabetes.

Pleiotropic protective effects of Vitamin D against high fat diet-induced metabolic syndrome in rats: One for all

Several lines of evidence point to the association of vitamin D deficiency with the different components of metabolic syndrome. Yet, the effect of vitamin D supplementation on metabolic syndrome is not clearly elucidated. Herein, we tested the hypothesis that administration of vitamin D, either alone or in combination of metformin can improve metabolic and structural derangements associated with metabolic syndrome. Fifty wistar rats were randomly assigned to serve either as normal control (10 rats) or metabolic syndrome rats, by feeding them with a standard or a high fat diet (HFD), respectively. Metabolic syndrome rats were further assigned to receive either vehicle, Metformin (100mg/Kg orally), vitamin D (6ng/Kg SC.) or both, daily for 8 weeks. Body weight, blood pressure, serum glucose, insulin, insulin resistance, lipid profile, oxidative stress, serum uric acid and Ca⁺² were assessed at the end of the study. Histopathological examination of hepatic, renal and cardiac tissues were also performed. Treatment with vitamin D was associated with a significant improvement of the key features of metabolic syndrome namely obesity, hypertension and dyslipidaemia with a neutral effect on Ca⁺² level. When combined with metformin, most of the other metabolic abnormalities were ameliorated. Furthermore, a significant attenuation of the associated hepatic steatosis was observed with vitamin D as well as vitamin D/metformin combination. In conclusion, vitamin D can improve hypertension, metabolic and structural abnormalities induced by HFD, and it provides additional benefits when combined with metformin. Therefore, vitamin D could represent a feasible therapeutic option for prevention of metabolic syndrome.

Evaluation of cognitive subdomains, 25-hydroxyvitamin D, and 1,25-dihydroxyvitamin D in the European Male Ageing Study

PURPOSE

Although lower levels of vitamin D have been related to poor cognitive functioning and dementia in older adults, evidence from longitudinal investigations is inconsistent. The objective of this study was to determine whether 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)₂D] levels are associated with specified measures of cognitive decline in ageing men.

METHODS

The European Male Ageing Study (EMAS) followed 3369 men aged 40-79 over 4.4 years. 25(OH)D levels at baseline were measured by radioimmunoassay, and 1,25(OH)₂D levels were obtained with liquid chromatography-tandem mass spectrometry. Visuoconstructional abilities, visual memory, and processing speed at baseline and follow-up were assessed using the Rey-Osterrieth Complex Figure Test (ROCF), Camden Topographical Recognition Memory (CTRM), and the Digit Symbol Substitution Test (DSST).

RESULTS

Following attritions, a total of 2430 men with a mean (SD) age of 59.0 (10.6) were included in the analyses. At baseline, the mean 25(OH)D concentration was 64.6 (31.5) nmol/l, and mean 1,25(OH)₂D level was 59.6 (16.6) pmol/l. In age-adjusted linear regression models, high 25(OH)D concentrations were associated with a smaller decline in the DSST (β = 0.007, p = 0.020). Men with low 25(OH)D levels (<50 nmol/l) showed a greater decline in the CTRM compared to men with higher (≥75 nmol/l) levels (β = -0.41, p = 0.035). However, these associations disappeared after adjusting for confounders such as depressive symptoms, BMI, and comorbidities. There was no indication of a relationship between 1,25(OH)₂D and decline in cognitive subdomains.

CONCLUSION

We found no evidence for an independent association between 25(OH)D or 1,25(OH)₂D levels and visuoconstructional abilities, visual memory, or processing speed over on average 4.4 years in this sample of middle-aged and elderly European men.

Vitamin D interacts with Esr1 and Igf1 to regulate molecular pathways relevant to Alzheimer's disease

Background

Increasing evidence suggests a potential therapeutic benefit of vitamin D supplementation against Alzheimer’s disease (AD). Although studies have shown improvements in cognitive performance and decreases in markers of the pathology after chronic treatment, the mechanisms by which vitamin D acts on brain cells are multiple and remain to be thoroughly studied. We analyzed the molecular changes observed after 5 months of vitamin D3 supplementation in the brains of transgenic 5xFAD (Tg) mice, a recognized mouse model of AD, and their wild type (Wt) littermates. We first performed a kinematic behavioural examination at 4, 6 and 8 months of age (M4, M6 and M8) followed by a histologic assessment of AD markers. We then performed a comparative transcriptomic analysis of mRNA regulation in the neocortex and hippocampus of 9 months old (M9) female mice.

Results

Transcriptomic analysis of the hippocampus and neocortex of both Wt and Tg mice at M9, following 5 months of vitamin D3 treatment, reveals a large panel of dysregulated pathways related to i) immune and inflammatory response, ii) neurotransmitter activity, iii) endothelial and vascular processes and iv) hormonal alterations. The differentially expressed genes are not all direct targets of the vitamin D-VDR pathway and it appears that vitamin D action engages in the crosstalk with estrogen and insulin signaling. The misexpression of the large number of genes observed in this study translates into improved learning and memory performance and a decrease in amyloid plaques and astrogliosis in Tg animals.

Conclusions

This study underlies the multiplicity of action of this potent neurosteroid in an aging and AD-like brain. The classical and non-classical actions of vitamin D3 can act in an additive and possibly synergistic manner to induce neuroprotective activities in a context-specific way.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-016-0087-2) contains supplementary material, which is available to authorized users.

Vitamin D: a custodian of cell signalling stability in health and disease

There is increasing evidence that a deficiency in vitamin D contributes to many human diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), hypertension and cardiovascular disease. The ability of vitamin D to maintain healthy cells seems to depend on its role as a guardian of phenotypic stability particularly with regard to the reactive oxygen species (ROS) and Ca2+ signalling systems. Vitamin D maintains the expression of those signalling components responsible for stabilizing the low-resting state of these two signalling pathways. This vitamin D signalling stability hypothesis proposes that vitamin D, working in conjunction with klotho and Nrf2 (nuclear factor-erythroid-2-related factor 2), acts as a custodian to maintain the normal function of the ROS and Ca2+ signalling pathways. A decline in vitamin D levels will lead to an erosion of this signalling stability and may account for why so many of the major diseases in man, which have been linked to vitamin D deficiency, are associated with a dysregulation in both ROS and Ca2+ signalling.

Vitamin D and Alzheimer's Disease: Neurocognition to Therapeutics

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

Vitamin D cell signalling in health and disease

Vitamin D deficiency has been linked to many human diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), hypertension and cardiovascular disease. A Vitamin D phenotypic stability hypothesis, which is developed in this review, attempts to describe how this vital hormone acts to maintain healthy cellular functions. This role of Vitamin D as a guardian of phenotypic stability seems to depend on its ability to maintain the redox and Ca(2+) signalling systems. It is argued that its primary action is to maintain the expression of those signalling components responsible for stabilizing the low resting state of these two signalling pathways. This phenotypic stability role is facilitated through the ability of vitamin D to increase the expression of both Nrf2 and the anti-ageing protein Klotho, which are also major regulators of Ca(2+) and redox signalling. A decline in Vitamin D levels will lead to a decline in the stability of this regulatory signalling network and may account for why so many of the major diseases in man, which have been linked to vitamin D deficiency, are associated with a dysregulation in both ROS and Ca(2+) signalling.

Inhibition of PMCA activity by tau as a function of aging and Alzheimer's neuropathology

Ca2+-ATPases are plasma membrane and intracellular membrane transporters that use the energy of ATP hydrolysis to pump cytosolic Ca2+ out of the cell (PMCA) or into internal stores. These pumps are the main high-affinity Ca2+ systems involved in the maintenance of intracellular free Ca2+ at the properly low level in eukaryotic cells. The failure of neurons to keep optimal intracellular Ca2+ concentrations is a common feature of neurodegeneration by aging and aging-linked neuropathologies, such as Alzheimer's disease (AD). This disease is characterized by the accumulation of β-amyloid senile plaques and neurofibrillary tangles of tau, a protein that plays a key role in axonal transport. Here we show a novel inhibition of PMCA activity by tau which is concentration-dependent. The extent of inhibition significantly decreases with aging in mice and control human brain membranes, but inhibition profiles were similar in AD-affected brain membrane preparations, independently of age. No significant changes in PMCA expression and localization with aging or neuropathology were found. These results point out a link between Ca2+-transporters, aging and neurodegeneration mediated by tau protein.

Vitamin D and cognition in older adults: an update of recent findings

PURPOSE OF REVIEW

Ageing is a generally known risk factor for cognitive decline and dementia. Underlying mechanisms are expected to be multifactorial, but the exact causes are still elusive. This article reviews the potential role of vitamin D in brain function by presenting an overview of recently published mechanistic, rodent as well as human studies.

RECENT FINDINGS

There is emerging evidence that suggests a beneficial role for vitamin D in brain physiology, for instance by the promotion of neurotransmission, neurogenesis, synaptogenesis, amyloid clearance and the prevention of neuronal death. In addition, several observational studies have shown associations between higher serum vitamin D concentrations and better cognitive performance. To date, imaging studies and randomized controlled trials are scarce, but these studies are expected to fulfil a crucial role towards a better understanding on vitamin D-mediated brain processes in the future.

SUMMARY

Despite accumulating evidence supporting a role of vitamin D in brain function, only a handful of human trials have been performed. Consequently, the question whether the association between vitamin D, cognitive decline and dementia is causal cannot be sufficiently answered yet.