Vitamin D3Confers Protection from Autoimmune Encephalomyelitis Only in Female Mice

Vitamin D levels and risk of multiple sclerosis in patients with clinically isolated syndromes

Background:

Growing evidence suggests that vitamin D deficiency may be one of the most important environmental factors for the development of multiple sclerosis (MS).

Objectives:

The objectives of this paper are to evaluate serum 25-hydroxyvitamin D (25(OH)D) levels in patients with clinically isolated syndromes (CIS) and to examine whether they are related to MS risk.

Methods:

This is a retrospective study of 100 CIS patients hospitalized from 2000 to 2009 at San Raffaele Hospital, Milan, Italy. We evaluated baseline 25(OH)D level as well as clinical, brain magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) data.

Results:

A total of 52% of CIS patients had vitamin D deficiency (25(OH)D < 50 nmol/l). During follow-up (median: 7.17 years), 55 patients developed clinically definite MS (CDMS). Patients with very low (< 10th percentile) and low (< 25th percentile) 25(OH)D levels were particularly at risk of CDMS (HRs (95% CIs): 2.12 (0.91–4.96) and 1.61 (0.85–3.03), respectively), while no further reduction in the HRs of disease was observed at high levels of 25(OH)D. This association was even stronger after adjustment for additional risk factors for CDMS development (HRs (95% CIs) for 25(OH)D levels < 10th and 25th percentiles: 3.34 (1.32–8.45) and 2.04 (0.96–4.36), respectively).

Conclusion:

Low serum vitamin D is associated with increased MS risk in patients with CIS.

Sex and gender issues in multiple sclerosis

Multiple sclerosis (MS) is universally found to be more prevalent in women than men. This has led to extensive studies of differences in the immune system or nervous system between women and men, which might be caused by the effects of gonadal hormones, genetic differences, and different environmental exposures and modern lifestyle in men and women. We review the effects of sex and gender from a genetic, immunological and clinical point of view. We discuss the effects of sex on the clinical expression of MS and responses to therapy, as well as issues concerning pregnancy.

The current state of play of rodent models to study the role of vitamin D in UV-induced immunomodulation

Ultraviolet radiation (UVR) from sunlight is immunomodulatory and the main source of vitamin D for humans. Vitamin D can also regulate adaptive immunity, through mechanisms that involve the induction or activation of regulatory T cells. Similar mechanisms have also been proposed for the induction of regulatory T cells after skin exposure to UVR. Here we discuss the converging and diverging immunoregulatory pathways of UVR and vitamin D, including the molecular pathways for regulatory T cell induction, non-genomic pathways regulated by vitamin D, antimicrobial peptides, skin integrity and potential interactions between vitamin D and other UVR-induced mediators. We then discuss possible in vivo approaches that could be used to demonstrate a direct (or otherwise) role for vitamin D in mediating the immunosuppressive effects of UVR such as the use of dietary vitamin D restriction to induce vitamin D deficiency, gene knockout mice or drugs to block enzymes of vitamin D metabolism. We end with discussion of the epigenetic effects of vitamin D and UVR for immunosuppression.

Serum levels of 25-hydroxy vitamin D in normal Biozzi and C57BL/6 mice and during the course of chronic relapsing experimental autoimmune encephalomyelitis (CR EAE)

OBJECTIVE AND DESIGN

The aim of the study was to examine possible variations in the levels of 25-hydroxy vitamin D [25-(OH)D] in sera from normal Biozzi and C57BL/6 mice and during the course of chronic relapsing experimental autoimmune encephalomyelitis (CR EAE).

MATERIAL

Serum concentrations of 25-(OH)D were measured in normal male and female Biozzi and C57BL/6 mice, at 3-4 weeks old and 8-10 weeks old, with a minimum of six animals/group. Levels of the vitamin were also determined in CR EAE-inoculated mice, and controls, during the course of the disease using a minimum of six animals/treatment.

METHODS

Cardiac blood was collected from the groups of normal, control and CR EAE-sensitised mice and sera prepared, by centrifugation of clotted samples, and assayed for 25-(OH)D levels by chemiluminescence assay.

RESULTS

Normal male and female Biozzi and C57BL/6 mice had significantly higher levels of 25-(OH)D at 8-10 weeks old compared to concentrations at 3-4 weeks of age (P < 0.005). Also, levels of the vitamin were significantly raised in C57BL/6 male and female mice compared to values in samples from corresponding Biozzi mice. In addition, the amounts of 25-(OH)D in sera from female Biozzi and C57BL/6 mice were significantly increased compared to strain and aged-matched male mice. The CR EAE mice with acute stage disease had significantly higher 25-(OH)D levels compared to controls (P < 0.005). Vitamin concentrations fell to within controls values with the progression of CR EAE.

CONCLUSIONS

Our preliminary studies have revealed marked differences between the amounts of 25-(OH)D in sera from Biozzi and C57BL/6 mice together with clear gender bias. The investigations also show significant, but selective changes, in levels of the vitamin during the course of CR EAE that are not always associated with the neurological disease state.

Sexual disparities in the incidence and course of MS

Multiple sclerosis (MS) affects three times more women than men and this ratio appears to be increasing. However male patients experience increased disease progression, brain atrophy, and cognitive impairment. Gonadal hormones may modulate these sex differences. For example, female puberty heralds an increased risk of MS, and during pregnancy disease activity is milder, with an increased risk of postpartum relapses. Gonadal hormones likely have complex and inflammatory and neuroprotective effects, and may interact with other disease modulators, such as vitamin D. Sex differences in the heritability of disease susceptibility genes implicate a role for epigenetic modification. Many questions remain, including the impact of sex on treatment response and epigenetic changes, and the modulatory potential of hormonal treatments. This article summarizes what is known about sexual dimorphism in MS onset and course, as well as potential interactions between sex and other factors influencing MS pathogenesis, incidence and severity.

Expression of vitamin D receptor and metabolizing enzymes in multiple sclerosis-affected brain tissue

Vitamin D deficiency has been implicated as a risk factor for multiple sclerosis (MS), but how vitamin D metabolism affects MS pathophysiology is not understood. We studied the expression of vitamin D receptor (VDR) and related enzymes, including 1,25(OH)(2)D-24-hydroxylase (24-OHase; CYP24A1) and 25(OH)D-1α-hydroxylase (CYP27B1), in CNS tissues of 39 MS patients and 20 controls and in primary human glial cells in vitro. In control and MS normal-appearing white matter (NAWM), nuclear VDR immunostaining was observed in oligodendrocyte-like cells, human leukocyte antigen (HLA)-positive microglia, and glial fibrillary acidic protein-positive astrocytes. There was a 2-fold increase in VDR transcripts in MS NAWM versus control white matter (p = 0.03). In chronic active MS lesions, HLA-positive microglia/macrophages showed nuclear VDR staining; astrocytes showed nuclear and cytoplasmic VDR staining. Staining for 24-OHase was restricted to astrocytes.VDR and CYP27B1 mRNA expressions were increased in active MS lesions versus NAWM (p < 0.01, p = 0.04, respectively). In primary human astrocytes in vitro, the active form of vitamin D, 1,25(OH)(2)D(3), induced upregulation of VDR and CYP24A1. Tumor necrosis factor and interferon-γ upregulated CYP27B1 mRNA in primary human microglia and astrocytes. Increased VDR expression in MS NAWM and inflammatory cytokine-induced amplified expression of VDR and CYP27B1 in chronic active MS lesions suggest increased sensitivity to vitamin D in NAWM and a possible endogenous role for vitamin D metabolism in the suppression of active MS lesions.

Low vitamin D levels increase anemia risk in Korean women

BACKGROUND

We assessed the impact of vitamin D on hemoglobin levels in Korean adults, considering gender and menopausal status.

METHODS

We analyzed 2528 men and 3258 women divided into quartiles of vitamin D from the Fifth Korean National Health and Nutrition Examination Survey 2010. Anemia was defined as a hemoglobin level of <13 g/dl in men and <12 g/dl in women.

RESULTS

Pre- and post-menopausal women in the lowest 25-hydroxyvitamin D group were at an increased risk of anemia, after adjusting for confounding factors (OR (95% CI); Premenopausal: Q1 (≥18.45 ng/ml), 1; Q2 (14.69-18.44 ng/ml), 1.120 (0.745, 1.683); Q3 (11.93-14.68 ng/ml), 1.427 (0.963, 2.116); and Q4 (≤11.92 ng/ml), 1.821 (1.240, 2.673); P=0.009; and Post: Q1 (≥22.04 ng/ml), 1; Q2 (16.92-22.03 ng/ml), 1.106 (0.697, 1.756); Q3 (13.37-16.91 ng/ml), 1.167 (0.740, 1.839); and Q4 (≤13.36 ng/ml), 1.583 (1.026, 2.447); P=0.038). In addition, pre- and post-menopausal women in the lower 25-hydroxyvitamin D group were at a higher risk of iron deficient anemia and anemia of inflammation. However, post-menopausal women did not show a higher risk of anemia with CKD (P=0.470). Men with the lowest 25-hydroxyvitamin D levels did not show a higher risk of anemia (P=0.528).

CONCLUSIONS

Vitamin D-deficient Korean women had a higher risk of anemia.

Contribution of vitamin D insufficiency to the pathogenesis of multiple sclerosis

The contribution of vitamin D insufficiency to the pathogenesis of multiple sclerosis (MS) is reviewed. Among the multiple recently discovered actions of vitamin D, an immunomodulatory role has been documented in experimental autoimmune encephalomyelitis and in humans. This action in the peripheral immune system is currently the main known mechanism through which vitamin D might influence MS, but other types of actions could be involved within the central nervous system. Furthermore, vitamin D insufficiency is widespread in temperate countries and in patients with MS at the earliest stages of the disease, suggesting that the deleterious effects related to vitamin D insufficiency may be exerted in these patients. In fact, many genetic and environmental risk factors appear to interact and contribute to MS. In genetics, several human leukocyte antigen (HLA) alleles (more particularly HLA-DRB1*1501) could favour the disease whereas some others could be protective. Some of the genes involved in vitamin D metabolism (e.g. CYP27B1) also play a significant role. Furthermore, three environmental risk factors have been identified: past Epstein-Barr virus infection, vitamin D insufficiency and cigarette smoking. Interactions between genetic and environmental risk or protective factors may occur during the mother's pregnancy and could continue during childhood and adolescence and until the disease is triggered in adulthood, therefore possibly modulating the MS risk throughout the first decades of life. Furthermore, some clinical findings already strongly suggest that vitamin D status influences the relapse rate and radiological lesions in patients with MS, although the results of adequately powered randomized clinical trials using vitamin D supplementation have not yet been reported. While awaiting these incontrovertible results, which might be long in coming, patients with MS who are currently in vitamin D insufficiency should be supplemented, at least for their general health status, using moderate doses of the vitamin.

Vitamin D(3) at 50x AI attenuates the decline in paw grip endurance, but not disease outcomes, in the G93A mouse model of ALS, and is toxic in females

BACKGROUND

We previously demonstrated that dietary vitamin D(3) at 10x the adequate intake (AI) attenuates the decline in functional capacity in the G93A mouse model of ALS. We hypothesized that higher doses would elicit more robust changes in functional and disease outcomes.

OBJECTIVE

To determine the effects of dietary vitamin D(3) at 50xAI on functional outcomes (motor performance, paw grip endurance) and disease severity (clinical score), as well as disease onset, disease progression and lifespan in the transgenic G93A mouse model of ALS.

METHODS

Starting at age 25 d, 100 G93A mice (55 M, 45 F) were provided ad libitum with either an adequate (AI; 1 IU D(3)/g feed) or high (HiD; 50 IU D(3)/g feed) vitamin D(3) diet.

RESULTS

HiD females consumed 9% less food corrected for body weight vs. AI females (P = 0.010). HiD mice had a 12% greater paw grip endurance over time between age 60-141 d (P = 0.015), and a 37% greater score during disease progression (P = 0.042) vs. AI mice. Although HiD females had a non-significant 31% greater CS prior to disease onset vs. AI females, they exhibited a significant 20% greater paw grip endurance AUC (P = 0.020) when corrected for clinical score.

CONCLUSION

Dietary D(3) supplementation at 50x the adequate intake attenuated the decline in paw grip endurance, but did not influence age at disease onset, hindlimb paralysis or endpoint in the transgenic G93A mouse model of ALS. Furthermore, females may have reached the threshold for vitamin D(3) toxicity as evidence by reduced food intake and greater disease severity prior to disease onset.

Can we prevent or treat multiple sclerosis by individualised vitamin D supply?

Apart from its principal role in bone metabolism and calcium homeostasis, vitamin D has been attributed additional effects including an immunomodulatory, anti-inflammatory, and possibly even neuroprotective capacity which implicates a possible role of vitamin D in autoimmune diseases like multiple sclerosis (MS). Indeed, several lines of evidence including epidemiologic, preclinical, and clinical data suggest that reduced vitamin D levels and/or dysregulation of vitamin D homeostasis is a risk factor for the development of multiple sclerosis on the one hand, and that vitamin D serum levels are inversely associated with disease activity and progression on the other hand. However, these data are not undisputable, and many questions regarding the preventive and therapeutic capacity of vitamin D in multiple sclerosis remain to be answered. In particular, available clinical data derived from interventional trials using vitamin D supplementation as a therapeutic approach in MS are inconclusive and partly contradictory. In this review, we summarise and critically evaluate the existing data on the possible link between vitamin D and multiple sclerosis in light of the crucial question whether optimization of vitamin D status may impact the risk and/or the course of multiple sclerosis.

Pathogenesis of pediatric multiple sclerosis

Onset of multiple sclerosis in childhood occurs in 3-5% of patients. There is limited, but growing knowledge about the underlying pathobiology of pediatric MS. It is crucial to better understand this area in order to address central questions in the field: 1) Can pediatric multiple sclerosis inform us about factors related to disease initiation and propagation? 2) What are the biomarkers of disease course in pediatric multiple sclerosis; 3) Does pediatric multiple sclerosis pathogenesis differ from adult-onset multiple sclerosis; 4) How can we optimize treatment in pediatric demyelinating diseases? 5) Can pediatric multiple sclerosis provide insights into the environmental risk factors for multiple sclerosis in general? Here we review the current knowledge of the pathogenesis of multiple sclerosis in children, and address the five questions raised above.

Acute erythemal ultraviolet radiation causes systemic immunosuppression in the absence of increased 25-hydroxyvitamin D3 levels in male mice

Vitamin D is synthesised by ultraviolet (UV) irradiation of skin and is hypothesized to be a direct mediator of the immunosuppression that occurs following UV radiation (UVR) exposure. Both UVR and vitamin D drive immune responses towards tolerance by ultimately increasing the suppressive activities of regulatory T cells. To examine a role for UVR-induced vitamin D, vitamin D₃-deficient mice were established by dietary vitamin D₃ restriction. In comparison to vitamin D₃-replete mice, vitamin D₃-deficient mice had significantly reduced serum levels of 25-hydroxyvitamin D₃ (25(OH)D₃, <20 nmol.L⁻¹) and 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃, <20 pmol.L⁻¹). Following either acute erythemal UVR, or chronic sub-erythemal UVR (8 exposures over 4 weeks) treatment, serum 25(OH)D₃ levels significantly increased in vitamin D₃-deficient female but not male mice. To determine if UVR-induced vitamin D was a mediator of UVR-induced systemic immunosuppression, responses were measured in mice that were able (female) or unable (male) to increase systemic levels of 25(OH)D₃ after UVR. Erythemal UVR (≥4 kJ/m²) suppressed contact hypersensitivity responses (T helper type-1 or -17), aspects of allergic airway disease (T helper type-2) and also the in vivo priming capacity of bone marrow-derived dendritic cells to a similar degree in female and male vitamin D₃-deficient mice. Thus, in male mice, UVR-induced 25(OH)D₃ is not essential for mediating the immunosuppressive effects of erythemal UVR.

The Ifng gene is essential for Vdr gene expression and vitamin D₃-mediated reduction of the pathogenic T cell burden in the central nervous system in experimental autoimmune encephalomyelitis, a multiple sclerosis model

Compelling evidence suggests that vitamin D3 insufficiency may contribute causally to multiple sclerosis (MS) risk. Experimental autoimmune encephalomyelitis (EAE) research firmly supports this hypothesis. Vitamin D3 supports 1,25-dihydroxyvitamin D3 (1,25-[OH]2D3) synthesis in the CNS, initiating biological processes that reduce pathogenic CD4+ T cell longevity. MS is prevalent in Sardinia despite high ambient UV irradiation, challenging the vitamin D-MS hypothesis. Sardinian MS patients frequently carry a low Ifng expresser allele, suggesting that inadequate IFN-γ may undermine vitamin D3-mediated inhibition of demyelinating disease. Testing this hypothesis, we found vitamin D3 failed to inhibit EAE in female Ifng knockout (GKO) mice, unlike wild-type mice. The two strains did not differ in Cyp27b1 and Cyp24a1 gene expression, implying equivalent vitamin D3 metabolism in the CNS. The 1,25-(OH)2D3 inhibited EAE in both strains, but 2-fold more 1,25-(OH)2D3 was needed in GKO mice, causing hypercalcemic toxicity. Unexpectedly, GKO mice had very low Vdr gene expression in the CNS. Injecting IFN-γ intracranially into adult mice did not increase Vdr gene expression. Correlating with low Vdr expression, GKO mice had more numerous pathogenic Th1 and Th17 cells in the CNS, and 1,25-(OH)2D3 reduced these cells in GKO and wild-type mice without altering Foxp3+ regulatory T cells. Thus, the Ifng gene was needed for CNS Vdr gene expression and vitamin D3-dependent mechanisms that inhibit EAE. Individuals with inadequate Ifng expression may have increased MS risk despite high ambient UV irradiation because of low Vdr gene expression and a high encephalitogenic T cell burden in the CNS.

Vitamin D and multiple sclerosis: review of a possible association

There has been growing interest in determining environmental risk factors that may play a role in the development or progression of multiple sclerosis (MS). Epidemiological evidence and data from human and animal studies have shown an association between low serum vitamin D levels and an increased incidence of MS and that supplementation with vitamin D may protect against MS development and/or disease relapses. The most appropriate vitamin D dosage for patients with MS is unclear, but investigator shave proposed that serum vitamin D concentrations between 75 and 100 nmol/L (30-40 ng/mL) are optimal to achieve favor able clinical outcomes. Vitamin D supplemented in doses up to 3000 International Units (IU) daily may be necessary to achieve these levels in many patients, and doses of 500 to 800 IU daily appear to be necessary to maintain desired serum vitamin D levels.Short-term supplementation with doses up to 40 000 IU daily has been found to be safe. However, larger and longer clinical studies are needed to assess whether a true relationship exists between serum vitamin D concentrations and MS and to determine a safe and effective amount of vitamin D supplementation.

Interference with RhoA-ROCK signaling mechanism in autoreactive CD4+ T cells enhances the bioavailability of 1,25-dihydroxyvitamin D3 in experimental autoimmune encephalomyelitis

Vitamin D deficiency is a major risk factor for central nervous system (CNS) demyelinating diseases including multiple sclerosis (MS) and its animal model, that of experimental autoimmune encephalomyelitis (EAE). Both vitamin D(3) and 1, 25-dihydroxyviatmin-D(3) (calcitriol) had beneficial effects in EAE/MS. However, the exact cause of vitamin D deficiency in EAE/MS is not clear. Previously, we documented that lovastatin (LOV) provides protection in EAE animals via inhibition of RhoA-ROCK signaling. Herein, we demonstrate that LOV prevents the lowering of circulating 25-hydroxyvitamin-D(3) and 1,25-dihydroxyviatmin-D(3) levels including 1,25-dihydroxyviatmin-D(3) levels in the peripheral lymphoid organs and CNS of treated EAE animals. These effects of LOV were attributed to enhanced expression of vitamin D synthesizing enzyme (1α-hydroxylase) in kidney and the CNS, with corresponding reduction of vitamin D catabolizing enzyme (24-hydorxylase) expression in the CNS of EAE animals via inhibition of RhoA-ROCK signaling. Ex vivo and in vitro studies established that autoreactive Th1/Th17 cells had higher expression of 24-hydroxylase than Th2/T regulatory cells, that was reverted by LOV or ROCK inhibitor. Interestingly, LOV-mediated regulation of vitamin D metabolism had improved vitamin D(3) efficacy to confer protection in EAE animals and that was ascribed to the LOV- and calcitriol-induced immunomodulatory synergy. Together, these data provide evidence that interfering with RhoA-ROCK signaling in autoreactive Th1/Th17 cells can improve vitamin D(3) efficacy in clinical trials of MS and related neurodegenerative disorders.

25-Hydroxyvitamin D depletion does not exacerbate MPTP-induced dopamine neuron damage in mice

Recent clinical evidence supports a link between 25-hydroxyvitamin D insufficiency (serum 25-hydroxyvitamin D [25(OH)D] levels <30 ng/mL) and Parkinson's disease. To investigate the effect of 25(OH)D depletion on neuronal susceptibility to toxic insult, we induced a state of 25(OH)D deficiency in mice and then challenged them with the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We found there was no significant difference between control and 25(OH)D-deficient animals in striatal dopamine levels or dopamine transporter and tyrosine hydroxylase expression after lesioning with MPTP. Additionally, we found no difference in tyrosine hydroxylase expression in the substantia nigra pars compacta. Our data suggest that reducing 25(OH)D serum levels in mice has no effect on the vulnerability of nigral dopaminergic neurons in vivo in this model system of parkinsonism.

Vitamin D and multiple sclerosis: epidemiology, immunology, and genetics

PURPOSE OF REVIEW

This review provides a brief update of new research findings on the role of vitamin D in multiple sclerosis (MS).

RECENT FINDINGS

Evidence continues to accumulate supporting a protective role for vitamin D in MS risk and progression. Notable recent findings are that high 25-hydroxyvitamin D [25(OH)D] at the time of a first demyelinating event predicts a lower MS risk and a decreased risk of MS among offspring whose mothers had high predicted 25(OH)D levels. While a small vitamin D intervention study did not find an association between vitamin D and MS progression, this study had little statistical power, and larger trials will be needed to assess the therapeutic potential of vitamin D. Recent immunological studies also show modulation of the immune system by vitamin D that may be favorable for preventing or slowing the progression of MS. The demonstration that rare variants in CYP27B1, which encodes the enzyme that converts vitamin D to its active form, are strongly associated with MS risk supports a causal role of vitamin D deficiency as a risk factor for MS.

SUMMARY

Research on the nature of the association between vitamin D and MS risk and progression continues to progress; however, additional research on the timing and dose-response relationship will be crucial for designing future prevention and treatment trials.

Intrathecal levels of vitamin D and IgG in multiple sclerosis

BACKGROUND

Intrathecal synthesis of IgG is a hallmark of multiple sclerosis (MS). Vitamin D may modulate B-cell function and dampen the synthesis of IgG.

OBJECTIVE

To investigate the relation between vitamin D levels in cerebrospinal fluid and serum and intrathecal synthesis of IgG.

METHODS

25-hydroxyvitamin D (25(OH)D) and IgG were assessed in cerebrospinal fluid and serum in 40 patients with MS.

RESULTS

There was no significant correlation between the IgG index and 25(OH)D levels in cerebrospinal fluid or serum. The levels of 25(OH)D in cerebrospinal fluid and serum did not differ between patients with and without intrathecal synthesis of IgG. There was a non-significant trend towards a positive correlation between the concentrations of 25(OH)D and IgG in the cerebrospinal fluid, but not in serum.

CONCLUSION

Physiological variation in vitamin D does not exert a major impact on intrathecal synthesis of IgG in MS.

Dietary vitamin D3 supplementation at 10× the adequate intake improves functional capacity in the G93A transgenic mouse model of ALS, a pilot study

BACKGROUND

Vitamin D has antioxidant, anti-inflammatory, and neuroprotective properties, and may mitigate amyotrophic lateral sclerosis (ALS) pathology.

AIMS

To determine the effects of dietary vitamin D(3) (D(3)) at 10-fold the adequate intake (AI) on functional and disease outcomes and lifespan in the transgenic G93A mouse model of ALS.

METHODS

Starting at age 40 days, 32 G93A mice (21 M, 11 F) were provided ad libitum with either an adequate (AI; 1 IU/g feed) or high (HiD; 10 IU/g feed) D(3) diet. Differences were considered significant at P≤ 0.10, as this was a pilot study.

RESULTS

For paw grip endurance, HiD mice had a 7% greater score between 60-133 d versus AI mice (P= 0.074). For motor performance, HiD mice had a 22% greater score between 60-133 days (P= 0.074) versus AI mice due to changes observed in male mice, where HiD males had a 33% greater score (P= 0.064) versus AI males. There were no significant diet differences in disease onset, disease progression, or lifespan.

CONCLUSION

Although disease outcomes were not affected, D(3) supplementation at 10-fold the AI improved paw grip endurance and motor performance in the transgenic G93A mouse model of ALS, specifically in males.

Sex-related factors in multiple sclerosis susceptibility and progression

The pathogenesis of multiple sclerosis (MS) involves complex interactions between genetic susceptibility and environmental triggers. Clinical observations suggest that the study of sex differences might provide important insight into mechanisms of pathogenesis and progression of the disease in patients. MS occurs more frequently in women than in men, indicating that sex-related factors have an effect on an individual's susceptibility to developing the condition. These factors include hormonal, genetic and environmental influences, as well as gene-environment interactions and epigenetic mechanisms. Interestingly, women do not have a poorer prognosis than men with MS despite a higher incidence of the disease and more-robust immune responses, which suggests a mechanism of resilience. Furthermore, the state of pregnancy has a substantial effect on disease activity, characterized by a reduction in relapse rates during the third trimester but an increased relapse rate in the postpartum period. However, pregnancy has little effect on long-term disability in women with MS. The unravelling of the mechanisms underlying these clinical observations in the laboratory and application of the results to the clinical setting is a unique and potentially fruitful strategy to develop novel therapeutic approaches for MS.

Contribution of GPR30 for 1,25 dihydroxyvitamin D₃ protection in EAE

Previous studies have demonstrated that vitamin D3-mediated protection in EAE occurs only in females and is dependent on the presence of diestrus levels of 17β-estradiol (E2). To evaluate the role of estrogen receptors in vitamin D3 treatment of EAE, we compared disease severity, CNS histopathology and immunological responses in vehicle and calcitrol (1,25 dihydroxyvitamin D₃) treated WT C57BL/6 mice vs. GPR30 membrane estrogen receptor (MER) knockout mice with MOG-35-55 peptide-induced EAE. Our results demonstrated that vitamin D₃-mediated prevention of clinical signs, CNS cellular lesions and demyelination observed in WT mice was abrogated in GPR30-KO mice with EAE. Regulatory effects of vitamin D₃ treatment that were MER dependent included increased levels of IL-10 and IL-6 secreted by MOG peptide-reactive splenocytes and increased expression of CCL5, CCR1 & CCR3 in spleen tissue. These results demonstrate for the first time that the MER is a key contributor to the E2-dependent effects of vitamin D₃-mediated protection in EAE.

An update on vitamin D and human immunity

In the last 5 years, there has been a remarkable change in our understanding of the health benefits of vitamin D. The classical actions of vitamin D as a determinant of mineral metabolism and rachitic bone disease have been expanded to include a broader role in skeletal homoeostasis and prevalent bone disorders such as osteoporosis. However, it is the nonskeletal function of vitamin D that has attracted most attention. Although pluripotent responses to vitamin D have been recognized for many years, our new perspective on nonclassical vitamin D function stems from two more recent concepts. The first is that impaired, vitamin D status is common to many populations across the globe. This has prompted studies to explore the health impact of suboptimal circulating levels of vitamin D, with association studies linking vitamin D 'insufficiency' to several chronic health problems including autoimmune and cardiovascular disease, hypertension and common cancers. In support of a broader role for vitamin D in human health, studies in vitro and using animal models have highlighted immunomodulatory and anticancer effects of vitamin D that appear to depend on localized activation of vitamin D. The conclusion from these reports is that many nonclassical actions of vitamin D are independent of conventional vitamin D endocrinology and are therefore more sensitive to variations in vitamin D status. The current review summarizes these developments, with specific reference to the newly identified effects of vitamin D on the immune system, but also highlights the challenges in translating these observations to clinical practice.

Influence of dietary components on regulatory T cells

Common dietary components including vitamins A and D, omega-3 and probiotics are now widely accepted to be essential to protect against many diseases with an inflammatory nature. On the other hand, high-fat diets are documented to exert multiple deleterious effects, including fatty liver diseases. Here we discuss the effect of dietary components on regulatory T cell (Treg) homeostasis, a central element of the immune system to prevent chronic tissue inflammation. Accordingly, evidence on the impact of dietary components on diseases in which Tregs play an influential role will be discussed. We will review chronic tissue-specific autoimmune and inflammatory conditions such as inflammatory bowel disease, type 1 diabetes mellitus, multiple sclerosis, rheumatoid arthritis and allergies among chronic diseases where dietary factors could have a direct influence via modulation of Tregs homeostasis and functions.

Genetics of experimental allergic encephalomyelitis supports the role of T helper cells in multiple sclerosis pathogenesis

OBJECTIVE

The major histocompatibility complex (MHC) is the primary genetic contributor to multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE), but multiple additional interacting loci are required for genetic susceptibility. The identity of most of these non-MHC genes is unknown. In this report, we identify genes within evolutionarily conserved genetic pathways leading to MS and EAE.

METHODS

To identify non-MHC binary and quantitative trait loci (BTL/QTL) important in the pathogenesis of EAE, we generated phenotype-selected congenic mice using EAE-resistant B10.S and EAE-susceptible SJL mice. We hypothesized that genes linked to EAE BTL/QTL and MS-GWAS can be identified if they belong to common evolutionarily conserved pathways, which can be identified with a bioinformatic approach using Ingenuity software.

RESULTS

Many known BTL/QTL were retained and linked to susceptibility during phenotype selection, the most significant being a region on chromosome 17 distal to H2 (Eae5). We show in pathway analysis that T helper (T(H))-cell differentiation genes are critical for both diseases. Bioinformatic analyses predicted that Eae5 is important in CD4 T-effector and/or Foxp3(+) T-regulatory cells (Tregs), and we found that B10.S-Eae5(SJL) congenic mice have significantly greater numbers of lymph node CD4 and Tregs than B10.S mice.

INTERPRETATION

These results support the polygenic model of MS/EAE, whereby MHC and multiple minor loci are required for full susceptibility, and confirm a critical genetic dependence on CD4 T(H)-cell differentiation and function in the pathogenesis of both diseases.

Vitamin D3 deficiency differentially affects functional and disease outcomes in the G93A mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neuromuscular disease characterized by motor neuron death in the central nervous system. Vitamin D supplementation increases antioxidant activity, reduces inflammation and improves motor neuron survival. We have previously demonstrated that vitamin D(3) supplementation at 10× the adequate intake improves functional outcomes in a mouse model of ALS.

OBJECTIVE

To determine whether vitamin D deficiency influences functional and disease outcomes in a mouse model of ALS.

METHODS

At age 25 d, 102 G93A mice (56 M, 46 F) were divided into two vitamin D(3) groups: 1) adequate (AI; 1 IU D(3)/g feed) and 2) deficient (DEF; 0.025 IU D(3)/g feed). At age 113 d, tibialis anterior (TA), quadriceps (quads) and brain were harvested from 42 mice (22 M and 20 F), whereas the remaining 60 mice (34 M and 26 F) were followed to endpoint.

RESULTS

During disease progression, DEF mice had 25% (P=0.022) lower paw grip endurance AUC and 19% (P=0.017) lower motor performance AUC vs. AI mice. Prior to disease onset (CS 2), DEF mice had 36% (P=0.016) lower clinical score (CS) vs. AI mice. DEF mice reached CS 2 six days later vs. AI mice (P=0.004), confirmed by a logrank test which revealed that DEF mice reached CS 2 at a 43% slower rate vs. AI mice (HR= .57; 95% CI: 0.38, 1.74; P=0.002). Body weight-adjusted TA (AI: r=0.662, P=0.001; DEF: r=0.622, P=0.006) and quads (AI: r=0.661, P=0.001; DEF: r=0.768; P<0.001) weights were strongly correlated with age at CS 2.

CONCLUSION

Vitamin D(3) deficiency improves early disease severity and delays disease onset, but reduces performance in functional outcomes following disease onset, in the high-copy G93A mouse.

Vitamin D sensitive EBNA-1 specific T cells in the cerebrospinal fluid of patients with multiple sclerosis

The pathogenesis of multiple sclerosis (MS) may involve intrathecal Epstein-Barr virus nuclear antigen-1 (EBNA-1) specific T cells susceptible to modulation by vitamin D. We established EBNA-1 reactive T cell lines from the cerebrospinal fluid (CSF) and blood of three MS patients and cloned EBNA-1 specific CD4+ T cells from two of these. T cell clones from CSF and blood displayed Th1 or Th17 phenotypes and were restricted by HLA-DR molecules, in one patient encoded by the DRB1*0403 or DRB1*1501 haplotypes. 1,25-dihydroxyvitamin D inhibited proliferation and suppressed secretion of IFN-γ and IL-17, irrespective of T cell origin and HLA restriction.

XVI European Charcot Foundation lecture: nutrition and environment: can MS be prevented?

Multiple sclerosis (MS) is a relatively common debilitating neurologic disease that affects people in early adulthood. While the characteristic pathology of MS has been well described, the etiology of the disease is not well understood, despite decades of research and the identification of strong genetic and environmental candidates for susceptibility. A question central to all diseases, but posed specifically for MS at the XVI European Charcot Foundation Lecture, was 'Can MS be prevented?' To address this question, we have evaluated the available data regarding nutritional and environmental factors that may be related to MS susceptibility and suggest the extent to which a potential intervention may reduce disease burden. It is our opinion that intervention, particularly supplementation with vitamin D, could have a dramatic impact on disease prevalence. Understanding that any intervention or behavioral modification will surely act in the context of genetic susceptibility and unidentified stochastic events, it is likely that not all MS is 'preventable'. Epidemiologic observation has provided key insights into environmental and nutritional factors that may alter one's susceptibility to MS, however, there are still many questions in unraveling the etiology of this complex disease.

Vitamin D in the healthy and inflamed central nervous system: access and function

High exposure to vitamin D may protect against development and progression of multiple sclerosis (MS), possibly through the immunomodulatory properties of its biologically active metabolite 1,25-dihydroxyvitamin D. So far, most studies on the possible mechanisms for vitamin D involvement in MS have focused on immune modulation outside the central nervous system (CNS). However, vitamin D may also interfere with the pathophysiology of MS within the CNS. In this review, the potential presence and functions of vitamin D in the inflamed and healthy CNS are explored. We discuss that vitamin D, vitamin D binding protein (DBP), the vitamin D receptor (VDR) and enzymes needed for metabolism (CYP27B1) are present in the CNS. Both VDR and CYP27B1 are expressed on a variety of cells, including neurons, glial cells, and invading lymphocytes. Additionally, vitamin D has been postulated to play a modulating role in several key-processes in MS pathophysiology, including inflammation, demyelination, axonal damage, and remyelination. We conclude that a local role of vitamin D in the inflamed CNS is likely and potentially relevant to MS. Future studies should further characterize the impact of vitamin D on the local disease process of MS in the CNS.

Vitamin D and immune function: an overview

Immunomodulatory actions of vitamin D have been recognised for over a quarter of a century, but it is only in the last few years that the significance of this to normal human physiology has become apparent. Two key factors have underpinned this revised perspective. Firstly, there are increasing data linking vitamin insufficiency with prevalent immune disorders. Improved awareness of low circulating levels of precursor 25-hydroxyvitamin D in populations across the globe has prompted epidemiological investigations of health problems associated with vitamin D insufficiency. Prominent among these are autoimmune diseases such as multiple sclerosis, type 1 diabetes and Crohn's disease, but more recent studies indicate that infections such as tuberculosis may also be linked to low 25-hydroxyvitamin D levels. The second factor expanding the link between vitamin D and the immune system is our improved knowledge of the mechanisms that facilitate this association. It is now clear that cells from the immune system contain all the machinery needed to convert 25-hydroxyvitamin D to active 1,25-dihydroxyvitamin D, and for subsequent responses to 1,25-dihydroxyvitamin D. Mechanisms such as this are important for promoting antimicrobial responses to pathogens in macrophages, and for regulating the maturation of antigen-presenting dendritic cells. The latter may be a key pathway by which vitamin D controls T-lymphocyte (T-cell) function. However, T-cells also exhibit direct responses to 1,25-dihydroxyvitamin D, notably the development of suppressor regulatory T-cells. Collectively these observations suggest that vitamin D is a key factor linking innate and adaptive immunity, and both of these functions may be compromised under conditions of vitamin D insufficiency.

Vitamin D: evidence for its role as a prognostic factor in multiple sclerosis

Vitamin D insufficiency has been shown to be associated with increased susceptibility to multiple sclerosis (MS), but until recently, it was unclear if vitamin D status also influences the prognosis of the disease. In experimental autoimmune encephalomyelitis, a mouse model of MS, the administration of vitamin D reduces the severity of the disease. Initial reports in MS of inverse associations between vitamin D levels and disability or relapse rate were encouraging, but the cross-sectional or retrospective study designs limited their interpretability. More recently, studies of pediatric-onset and adult MS have demonstrated that among those with established MS, those with lower vitamin D levels are at higher risk for subsequent relapse. These observational data provide strong support for randomized controlled trials of vitamin D supplementation in MS.

Vitamin D-mediated immune regulation in multiple sclerosis

Although Vitamin D is best known as a modulator of calcium homeostasis, it also has immune modulating potential. A protective effect of Vitamin D on Multiple Sclerosis (MS) is supported by the reduced risk associated with sun exposure and use of Vitamin D supplements. Moreover, high circulating levels of Vitamin D have been associated with lower risk of MS. To gain more insight into putative regulatory mechanisms of Vitamin D in MS pathogenesis, we studied 132 Hispanic patients with clinically definite MS, 58 with relapsing remitting MS (RR MS) during remission, 34 RR MS patients during relapse, and 40 primary progressive MS cases (PP MS). Sixty healthy individuals matched with respect to place of residence, race/ethnicity, age and gender served as controls. Levels of 25(OH) Vitamin D and 1,25(OH)(2) Vitamin D, measured by ELISA were significantly lower in RR MS patients than in controls. In addition, levels in patients suffering relapses were lower than during remissions. By contrast, PP MS patients showed similar values to controls. Proliferation of both freshly isolated CD4+ T cells and MBP-specific T cells was significantly inhibited by 1,25(OH)(2) Vitamin D. Moreover, activated Vitamin D enhanced the development of IL-10 producing cells, and reduced the number of IL-6 and IL-17 secreting cells. Notably, VDR expression was induced by 1,25(OH)(2) Vitamin D in both activated and resting cells. Interestingly, T cells were able to metabolize 25(OH) Vitamin D into biologically active 1,25(OH)(2) Vitamin D, since T cells express 1α-hydroxylase constitutively. Finally, 1,25(OH)(2) Vitamin D also increased the expression and biological activity of IDO, triggering significant increase in the number of CD4+CD25+ T regulatory cells. Collectively, these findings suggest that 1,25(OH)(2) VitaminD plays an important role in T cell homeostasis during the course of MS, suggesting correction of its deficiency may be useful during treatment of the disease.

Regulation of Mycobacterium-specific mononuclear cell responses by 25-hydroxyvitamin D3

The active vitamin D metabolite, 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), has been shown to be an important regulator of innate and adaptive immune function. In addition, synthesis of 1,25(OH)(2)D(3) from 25-hydroxyvitamin D(3) (25(OH)D(3)) by the enzyme 1α-hydroxylase in monocytes upon activation by TLR signaling has been found to regulate innate immune responses of monocytes in an intracrine fashion. In this study we wanted to determine what cells expressed 1α-hydroxylase in stimulated peripheral blood mononuclear cell (PBMC) cultures and if conversion of 25(OH)D(3) to 1,25(OH)(2)D(3) in PBMC cultures regulated antigen-specific immune responses. Initially, we found that stimulation of PBMCs from animals vaccinated with Mycobacterium bovis (M. bovis) BCG with purified protein derivative of M. bovis (M. bovis PPD) induced 1α-hydroxylase gene expression and that treatment with a physiological concentration of 25(OH)D(3) down-regulated IFN-γ and IL-17F gene expression. Next, we stimulated PBMCs from M. bovis BCG-vaccinated and non-vaccinated cattle with M. bovis PPD and sorted them by FACS according to surface markers for monocytes/macrophages (CD14), B cells (IgM), and T cells (CD3). Sorting the PBMCs revealed that 1α-hydroxylase expression was induced in the monocytes and B cells, but not in the T cells. Furthermore, treatment of stimulated PBMCs with 25(OH)D(3) down-regulated antigen-specific IFN-γ and IL-17F responses in the T cells, even though 1α-hydroxylase expression was not induced in the T cells. Based on evidence of no T cell 1α-hydroxylase we hypothesize that activated monocytes and B cells synthesize 1,25(OH)(2)D(3) and that 1,25(OH)(2)D(3) down-regulates antigen-specific expression of IFN-γ and IL-17F in T cells in a paracrine fashion.

Predominance of Th2 polarization by vitamin D through a STAT6-dependent mechanism

Background

Vitamin D has several reported immunomodulatory properties including the reduced generation of pro-inflammatory CD4+ T helper 1 (Th1) cells and the increase in levels of the anti-inflammatory Th2 subset. Less clear has been the impact of vitamin D on the pro-inflammatory Th17 subset, and whether and how vitamin D may preferentially drive the polarization of one of the T helper subsets.

Methods

Using human peripheral blood-derived mononuclear cells and mouse splenocytes and lymph node cells in culture, we examined whether and how vitamin D preferentially skews T cells towards the Th1, Th2 or Th17 subsets. Mice afflicted with the multiple sclerosis-like condition, experimental autoimmune encephalomyelitis (EAE), were examined in vivo for the relevance of the tissue culture-derived results.

Results

We report that the biologically active form of vitamin D, 1,25-dihydroxyvitamin D3 {1,25(OH)2D3}, consistently generates human and murine Th2 cells in culture, frequently leaving unchanged the levels of Th1/Th17 cytokines. As a result, the ratio of Th2 to Th1 and Th17 is increased by 1,25(OH)2D3. The upregulation of Th2 to Th1 or Th17 subsets by 1,25(OH)2D3 is enabled by an increase of the GATA-3 transcription factor, which itself is promoted upstream by an elevation of the STAT6 transcription factor. In mice, the alleviation of EAE severity by 1,25(OH)2D3 is accompanied by elevation of levels of GATA-3 and STAT6. Significantly, the efficacy of 1,25(OH)2D3 in ameliorating EAE is completely lost in mice genetically deficient for STAT6, which was accompanied by the inability of 1,25(OH)2D3 to raise GATA-3 in STAT6 null lymphocytes.

Conclusions

These results of vitamin D promoting a Th2 shift through upstream GATA-3 and STAT6 transcription factors shed mechanistic understanding on the utility of vitamin D in MS.

Vitamin D deficiency reduces the benefits of progesterone treatment after brain injury in aged rats

Administration of the neurosteroid progesterone (PROG) has been shown to be beneficial in a number of brain injury models and in two recent clinical trials. Given widespread vitamin D deficiency and increasing traumatic brain injuries (TBIs) in the elderly, we investigated the interaction of vitamin D deficiency and PROG with cortical contusion injury in aged rats. Vitamin D deficient (VitD-deficient) animals showed elevated inflammatory proteins (TNFα, IL-1β, IL-6, NFκB p65) in the brain even without injury. VitD-deficient rats with TBI, whether given PROG or vehicle, showed increased inflammation and greater open-field behavioral deficits compared to VitD-normal animals. Although PROG was beneficial in injured VitD-normal animals, in VitD-deficient subjects neurosteroid treatment conferred no improvement over vehicle. A supplemental dose of 1,25-dihydroxyvitamin D(3) (VDH) given with the first PROG treatment dramatically improved results in VitD-deficient rats, but treatment with VDH alone did not. Our results suggest that VitD-deficiency can increase baseline brain inflammation, exacerbate the effects of TBI, and attenuate the benefits of PROG treatment; these effects may be reversed if the deficiency is corrected.

1,25-Dihydroxyvitamin D3 acts directly on the T lymphocyte vitamin D receptor to inhibit experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an incurable autoimmune neurodegenerative disease. Environmental factors may be key to MS prevention and treatment. MS prevalence and severity decrease with increasing sunlight exposure and vitamin D(3) supplies, supporting our hypothesis that the sunlight-dependent hormone, 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2) D(3) ), inhibits autoimmune T-cell responses in MS. Moreover, 1,25-(OH)(2) D(3) inhibits and reverses experimental autoimmune encephalomyelitis (EAE), an MS model. Here, we investigated whether 1,25-(OH)(2) D(3) inhibits EAE via the vitamin D receptor (VDR) in T lymphocytes. Using bone marrow chimeric mice with a disrupted VDR only in radio-sensitive hematopoietic cells or radio-resistant non-hematopoietic cells, we found that hematopoietic cell VDR function was necessary for 1,25-(OH)(2) D(3) to inhibit EAE. Furthermore, conditional targeting experiments showed that VDR function in T cells was necessary. Neither 1,25-(OH)(2) D(3) nor T-cell-specific VDR targeting influenced CD4(+) Foxp3(+) T-cell proportions in the periphery or the CNS in these studies. These data support a model wherein 1,25-(OH)(2) D(3) acts directly on pathogenic CD4(+) T cells to inhibit EAE.

Vitamin D as a T-cell modulator in multiple sclerosis

Vitamin D is a potent immune modulator, keeping the T-cell compartment in a more tolerogenic state. Multiple sclerosis (MS), a disease in which an autoreactive T-cell response contributes to inflammation in the central nervous system, has been associated with vitamin D deficiency. The effects of vitamin D on the immune system are believed to be an important driver of this association. In this chapter, we elaborate on vitamin D as a modulator of the T-cell response. This discussion will be placed in the perspective of MS as a T-cell-mediated disease and in the perspective of the numerous association studies on vitamin D deficiency and multiple health outcomes. We conclude that there is a firm experimental and epidemiological basis supporting the model of vitamin D as a physiological immune modulator, on which intervention studies assessing clinical and immunological outcome measures should be designed.

Increasing incidence of multiple sclerosis in women in Northern Finland

Background: The geographical distribution of multiple sclerosis (MS) means that prevalence rates increase with latitude north or south of the equator. Temporally, a tendency for increased incidences of MS has been observed over the past two decades.

Objectives: Since epidemiological studies of MS in areas close to the Arctic Circle are rare, we evaluated the incidence and prevalence of MS in Northern Ostrobothnia by means of a retrospective cohort study covering the period 1992–2007.

Methods: Patients with a definite clinical diagnosis of MS based on the Poser criteria and the early McDonald criteria of 2001 were identified in the region of Northern Ostrobothnia (population 386,972) and the incidence was calculated at 1-year time intervals, both overall and by gender.

Results: The overall prevalence was 103/100,000 (95% CI, 93–113), with a female/male ratio of 2.17. The mean overall incidence was 6.3/100,000 (95% CI, 5.2–7.2). The incidence shows a tendency to increase over the 16-year period due to a pronounced rise in the female incidence.

Conclusions: Our results show a high prevalence of MS in Northern Ostrobothnia and a disproportional increase in the female MS incidence. These recent epidemiological features may be associated with environmental risk factors such as a vitamin D deficit, low life-long UV radiation and the high-latitude geographical location.

Gender differences in 1,25 dihydroxyvitamin D3 immunomodulatory effects in multiple sclerosis patients and healthy subjects

Vitamin D(3) is best known as a calcium homeostasis modulator; however, it also has immune-modulating potential. In this study, we demonstrated that immunomodulatory effects of vitamin D(3) are significantly stronger in females than in males in multiple sclerosis patients, as well as in healthy subjects. Inhibition of self-reactive T cell proliferation and reduction in IFN-γ- and IL-17-secreting cell numbers were considerably greater in females. Furthermore, the increase in IL-10-secreting and CD4(+)CD25(+)FoxP3(+) regulatory T cell numbers were also greater in females. In parallel with these findings, female subjects had fewer CYP24A1 transcripts encoding the 1,25-dihydroxyvitamin D(3)-inactivating enzyme, as well as greater binding and internalization of vitamin D(3)-binding protein, a transporter for vitamin D(3) and its metabolites. These gender-based disparities lead to the accumulation of vitamin D(3) and its metabolites in target cells from female subjects and result in a more potent anti-inflammatory effect. Interestingly, 17-β estradiol reproduced these effects on self-reactive T cells and macrophages from male subjects, suggesting a functional synergy between 1,25-dihydroxyvitamin D(3) and 17-β estradiol, mediated through estrogen receptor α. Collectively, these results demonstrate estrogen-promoted differences in vitamin D(3) metabolism, suggesting a greater protective effect of vitamin D(3)-based therapeutic strategies in women.

Is hypovitaminosis D one of the environmental risk factors for multiple sclerosis?

The role of hypovitaminosis D as a possible risk factor for multiple sclerosis is reviewed. First, it is emphasized that hypovitaminosis D could be only one of the risk factors for multiple sclerosis and that numerous other environmental and genetic risk factors appear to interact and combine to trigger the disease. Secondly, the classical physiological notions about vitamin D have recently been challenged and the main new findings are summarized. This vitamin could have an important immunological role involving a number of organs and pathologies, including autoimmune diseases and multiple sclerosis. Furthermore, human requirements for this vitamin are much higher than previously thought, and in medium- or high-latitude countries, they might not be met in the majority of the general population due to a lack of sunshine and an increasingly urbanized lifestyle. Thereafter, the different types of studies that have helped to implicate hypovitaminosis D as a risk factor for multiple sclerosis are reviewed. In experimental autoimmune encephalomyelitis, vitamin D has been shown to play a significant immunological role. Diverse epidemiological studies suggest that a direct chain of causality exists in the general population between latitude, exposure to the sun, vitamin D status and the risk of multiple sclerosis. New epidemiological analyses from France support the existence of this chain of links. Recently reported immunological findings in patients with multiple sclerosis have consistently shown that vitamin D significantly influences regulatory T lymphocyte cells, whose role is well known in the pathogenesis of the disease. Lastly, in a number of studies on serum levels of vitamin D in multiple sclerosis, an insufficiency was observed in the great majority of patients, including at the earliest stages of the disease. The questionable specificity and significance of such results is detailed here. Based on a final global analysis of the cumulative significance of these different types of findings, it would appear likely that hypovitaminosis D is one of the risk factors for multiple sclerosis.

Vitamin D and the intracrinology of innate immunity

An immunomodulatory role for vitamin D was first proposed more than 25 years ago, based on two salient observations. Firstly it was shown that monocytes/macrophages from patients with the granulomatous disease sarcoidosis constitutively synthesize the active form of vitamin D, 1,25-dihydroxyvitamin D (1,25(OH)(2)D) from precursor 25-hydroxyvitamin D (25OHD). Secondly, the receptor for 1,25(OH)(2)D (vitamin D receptor, VDR) is detectable in activated, proliferating lymphocytes. These observations suggested a mechanism whereby 1,25(OH)(2)D produced by monocytes could act upon adjacent T-cells or B-cells, but the impact of such a system on normal immune regulation was uncertain. Indeed, it is only in recent years that a much clearer picture of the role of vitamin D as a determinant of immune responsiveness has emerged. Two new concepts have prompted this change. Firstly studies of innate immunity have shown that intracrine induction of antimicrobial activity by vitamin D is a pivotal component of monocyte/macrophage response to infection. Secondly, it is now clear that sub-optimal vitamin D status is a common feature of many populations throughout the world, with the potential to compromise monocyte/macrophage metabolism of 25OHD and subsequent actions of 1,25(OH)(2)D. The current review details these new developments with specific reference to the metabolic and signaling mechanisms associated with innate immune regulation by vitamin D and implications for human disease.

Vitamin D and multiple sclerosis

The hypothesis that adequate vitamin D nutrition can contribute to the prevention of multiple sclerosis (MS) was originally proposed to explain the geographical distribution of MS, but only recently has the relation between various measures of vitamin D (eg, sun exposure, dietary sources, and serum concentrations of 25-hydroxyvitamin D) and risk of developing MS been rigorously investigated. Overall, the results of these studies support a protective effect of vitamin D, but there are uncertainties and many unanswered questions, including how vitamin D exerts a protective effect, how genetic variations modify the effect, and whether vitamin D can influence the course of MS progression.