Vitamin D and multiple sclerosis: an update

Vitamin D deficiency in relation with the systemic and central inflammation during multiple sclerosis

Background

During the last decade, vitamin D (VitD) has become a topic of interest in immune regulation, especially in multiple sclerosis (MS) disease. Amongst the wide range of effects reported for this vitamin on the immune system, a regulatory role on cytokines production has been described. Our aim is to analyze the status of VitD and its correlation with the circulating inflammation and the intrathecal humoral response during MS.

Methods

We analyzed samples of 318 individuals: 108 MS patients and 210 controls. Determination of 25-(OH) VitD3 level in serum was made using electrochemiluminescence method. Circulating inflammatory cytokines (IL-6, IL-8, IL-10, TNF-a, IL12p70 and IL-1b) were investigated using Cytometer Bead Array Technology. The central humoral response was characterized using CSF isofocusing test and IgG Index calculation.

Results

As expected, mean value of VitD was significantly lower in MS group (26 nmol/L) than in control group (34.75 nmol/L) (p=0.002), with a severe deficiency in 67% of MS patients. Mean value of VitD was significantly lower in MS female patients. Regarding cytokines, mean value of TNFa was significantly higher in MS patients with oligoclonal bands of IgG in the CSF. IL6 was positively correlated with IgG level in serum of MS patients.

Conclusions

Our results support the association of VitD deficiency with MS, especially in female patients of our region. However, the vitamin level seems to not correlate with inflammatory cytokines nor with disability. Interestingly, TNFa and IL6 levels were correlated with the intrathecal synthesis of IgG and the circulating IgG level, respectively.

Low vitamin D status is associated with inflammatory response in older patients with cerebral small vessel disease

OBJECTIVES

This study aimed to determine the association of the NF-κB inflammatory signaling pathway with vitamin D status in older cerebral small vessel disease (SVD) patients.

METHODS

We measured serum 25(OH)D, pro-and anti-inflammatory cytokines, and mRNA levels of the vitamin D-activating enzyme, CYP27B1, as well as NF-kB, COX-2, the chemokine-CCL2, IL-1β, IL-6, TNF-α, TGF-β, and IL-10, in cerebral SVD patients aged ≥60 years presenting with vascular dementia and age and gender-matched healthy controls.

RESULTS

Low vitamin D status (insufficiency: serum 25(OH)D 12-20 ng/ml; deficiency: ≤12 ng/ml) was more prevalent among patients compared to controls. The mRNA levels of NF-kB, COX-2, CCL2, IL-1β, and IL-6, and serum levels of pro-inflammatory cytokines (IL-1α, IL-1β, IL-6, and TNF-α) were significantly higher in cases compared to controls. There was a significant correlation between CYP27B1 and NF-kB, COX-2, CCL2, and IL-1β gene expression. Serum IL-1α, IL-1β, and IL-6 concentrations and the expression of CCL-2, NF-kB2, and NF-kB3 genes were higher in vitamin D-deficient subjects compared to vitamin D-sufficient subjects. There was a significant negative correlation between serum 25(OH)D and IL-1α, IL-6, and TNF-α, and a positive correlation between 25(OH)D and IL-10.

CONCLUSION

Low vitamin D is associated with an inflammatory response via NF-kB signaling, which could play a role in the etio-pathogenesis of SVD. Further large-scale studies are required to validate our findings.

Multiple sclerosis: Motor dysfunction

Multiple sclerosis is a chronic neurological disease characterized by inflammation and degeneration within the central nervous system. Over the course of the disease, most MS patients successively accumulate inflammatory lesions, axonal damage, and diffuse CNS pathology, along with an increasing degree of motor disability. While the pharmacological approach to MS targets inflammation to decrease relapse rates and relieve symptoms, disease-modifying therapy and immunosuppressive medications may not prevent the accumulation of pathology in most patients leading to long-term motor disability. This has been met with recent interest in promoting plasticity-guided concepts, enhanced by neurophysiological and neuroimaging approaches to address the preservation of motor function.

The rs4759314 SNP within Hotair lncRNA is associated with risk of multiple sclerosis

Recent studies have demonstrated the role of long non-coding RNAs (lncRNAs) in the pathophysiology of autoimmune disorders such as multiple sclerosis (MS). Among these transcripts is HOX transcript antisense intergenic RNA (HOTAIR) whose contribution in MS has been verified both in animal models and in human studies. In the current study, we genotyped three single nucleotide polymorphisms (SNPs) with this lncRNA (rs12826786, rs1899663 and rs4759314) in 403 Iranian MS patients and 420 healthy subjects. After correction of P values for multiple comparisons, the rs4759314 SNP was associated with risk of MS in allelic model (OR (95% CI)= 1.34 (1.08-1.67), adjusted P value=0.02). The other SNPs were not associated with risk of MS in any inheritance model. The C G A haplotype (rs12826786, rs1899663 and rs4759314, respectively) was less prevalent in cases compared with controls (OR (95% CI)= 0.73 (0.59-0.90), adjusted P value=0.03). The T G A haplotype was more common among cases compared with controls (OR (95% CI)= 1.58 (1.20-2.08), adjusted P value=0.01). Taken together, HOTAIR might be regarded as a risk locus for MS in Iranian population.

Menopause-Associated Lipid Metabolic Disorders and Foods Beneficial for Postmenopausal Women

Menopause is clinically diagnosed as a condition when a woman has not menstruated for one year. During the menopausal transition period, there is an emergence of various lipid metabolic disorders due to hormonal changes, such as decreased levels of estrogens and increased levels of circulating androgens; these may lead to the development of metabolic syndromes including cardiovascular diseases and type 2 diabetes. Dysregulation of lipid metabolism affects the body fat mass, fat-free mass, fatty acid metabolism, and various aspects of energy metabolism, such as basal metabolic ratio, adiposity, and obesity. Moreover, menopause is also associated with alterations in the levels of various lipids circulating in the blood, such as lipoproteins, apolipoproteins, low-density lipoproteins (LDLs), high-density lipoproteins (HDL) and triacylglycerol (TG). Alterations in lipid metabolism and excessive adipose tissue play a key role in the synthesis of excess fatty acids, adipocytokines, proinflammatory cytokines, and reactive oxygen species, which cause lipid peroxidation and result in the development of insulin resistance, abdominal adiposity, and dyslipidemia. This review discusses dietary recommendations and beneficial compounds, such as vitamin D, omega-3 fatty acids, antioxidants, phytochemicals—and their food sources—to aid the management of abnormal lipid metabolism in postmenopausal women.

Comorbidities in multiple sclerosis-a plea for interdisciplinary collaboration to improve the quality of life of MS patients

The negative influence of comorbidities on the quality of life of people with multiple sclerosis is evident and the problem is increasingly acknowledged by numerous international studies in long-term care. One therapeutic option would be an add-on therapy with vitamin D (VD), with the aim of achieving a therapeutically effective dose. The individually required VD dose must be tested, since the response to a certain dose is subject to variations between individuals. A possible toxicity with increased 1.25(OH)D3 (active VD metabolite) is largely prevented by increased activity of 24-hydroxylase (CYP24A1). Monitoring of serum VD levels as well as serum calcium and phosphate levels (optional Ca excretion in 24-hour urine, Ca creatinine ratio in urine) provides safety and is necessary because possible mutations on the (catabolic) CYP24A1 gene can lead to a partial or total loss of 24-hydroxylase activity and provoke hypercalcemia/hyperphosphatemia. The main therapeutic objective is to maintain functional and social independence by using drugs with a high safety profile. The prevention and optimal management of comorbidities can influence the quality of life of patients with MS (PwMS) when included in patient care. Adequate measures can reduce the burden of MS only if the risk of comorbidity is reduced through targeted monitoring, early detection and diagnosis. Such a strategy will contribute to influencing the premature mortality of patients with MS. If VD is recognized as a "multipurpose steroid hormone", it could also be used to maintain cognitive function and prevent premature possible dementia, especially as there is evidence that VD deficiency correlates with brain atrophy (hippocampus). At present, MS therapy is still a balancing act between therapeutically efficient action and the management of unexpected side effects, with VD add-on therapy being almost unproblematic and most likely to be accepted by PwMS.

A novel comprehensive paradigm for the etiopathogenesis of multiple sclerosis: therapeutic approaches and future perspectives on its treatment

It is well recognized that variation in the geographical distribution of prevalence of multiple sclerosis (MS) exists: increasing the latitude its prevalence increases as well, but the underlying causes of such dissimilarity still remained elusive as of today. Currently, the most accredited hypothesis is that the closer to the equator the more pronounced is the amount of sunlight which, in turn, increases the production of vitamin D. Cholecalciferol is indeed deficient in MS patients, but this factor does not explain by itself the etiopathogenesis of the disease. In the present study, to search for a pattern and provide a model of the disease's etiology consistent with this regional factor, as well with its changing ethnic, sex-ratio, lifestyle variations and the other unexplained aspects of MS, an extensive analysis of peer-reviewed literature and data was conducted. The arisen hypothesis was that, increasing the latitude, the factor that varies and can have the stronger effect on the human organism, is the continuous and ever-increasing diversity of the natural light-dark cycle. The consequent effort of the suprachiasmatic nucleus to entrain the organism's circadian rhythm affects the hypothalamic-pituitary-adrenal axis resulting in desynchronizing the central and peripheral circadian clocks and pathologizing the immunitary system. To verify such hypothesis, a theoretical framework of the etiopathogenesis, coherent with the gathered literature, was conceived and a demonstration to corroborate it was eventually devised and performed. The results underscored that people living in countries subjected to a further circadian disruptive factor, as daylight saving time, have a 6.35 times higher prevalence of MS than States placed on their same latitude that do not observe it, thus strongly supporting the hypothesis. As further reinforcement of the conclusions, it is worth mentioning that the levels of polyamines rise abruptly in autoimmune diseases. Moreover, among their numerous roles, these polycations participate to the regulation of the circadian clock so their sudden variation might disrupt it. Following these interesting findings, new perspectives in therapies are, therefore, proposed.

Sunshine, Sea, and Season of Birth: MS Incidence in Wales

Maternal sun exposure in gestation and throughout the lifetime is necessary for vitamin D synthesis, and living near the sea is a population level index of seafood consumption. The aim of this study was to estimate the incidence rate of multiple sclerosis (MS) in Wales and examine its association with sun exposure, coastal living, and latitude. The study used a database of MS hospital visits and admissions in Wales between 2002 and 2013. For the 1,909 lower layer super output areas (LSOAs) in Wales, coastal status, population, longitude/latitude, and average sunshine hours per day were obtained. Age-specific and age-standardised MS incidence were calculated and modelled using Poisson regression. The distribution of births by month was compared between MS cases and the combined England and Wales population. There were 3,557 new MS cases between 2002 and 2013, with an average annual incidence of 8.14 (95% CI: 7.69–8.59) among males and 12.97 (95% CI: 12.44–13.50) among females per 100,000 population. The female-to-male ratio was 1.86:1. For both sexes combined, the average annual incidence rate was 9.10 (95% CI: 8.80–9.40). All figures are age-standardized to the 1976 European standard population. Compared to the combined England and Wales population, more people with MS were born in April, observed-to-expected ratio: 1.21 (95% CI: 1.08–1.36). MS incidence varied directly with latitude and inversely with sunshine hours. Proximity to the coast was associated with lower MS incidence only in easterly areas. This study shows that MS incidence rate in Wales is comparable to the rate in Scotland and is associated with environmental factors that probably represent levels of vitamin D.

Association between levels of vitamin D and inflammatory markers in healthy women

Background

No one can deny that the biological importance of vitamin D is much beyond its classical role in bone metabolism. Several recent publications have highlighted its potential role in the functioning of the immune system. The overall objective of this study was to look into possible correlations between levels of vitamin D and inflammatory markers in sera of healthy adult women. These markers included proinflammatory cytokines (interleukin [IL]-1β, IL-6, IL-8, IL-17, interferon [IFN]-γ, and tumor necrosis factor [TNF]-α), anti-inflammatory cytokines (IL-4, IL-10, and IL-13), as well as C-reactive protein (CRP) as a general indicator of inflammation.

Methods

Venous blood samples were collected from 118 healthy adult women and serum levels of vitamin D, CRP, proinflammatory cytokines (IL-1β, IL-6, IL-8, IL-17, IFN-γ, and TNF-α), and anti-inflammatory cytokines (IL-4, IL-10, and IL-13) were measured.

Results

There were no significant direct correlations between serum levels of vitamin D and any of the inflammatory markers measured. However, subjects with deficient levels of vitamin D and high CRP produced significantly higher levels of the proinflammatory cytokines (TNF-α and IL-8) as compared to subjects with low CRP levels with nondeficient and deficient levels of vitamin D. Further, the anti-inflammatory/proinflammatory ratios suggest a role of vitamin D in maintaining an anti-inflammatory environment at low levels of CRP, an association that is weaker at high CRP levels in subjects with subclinical inflammatory situations.

Conclusion

These data point to a possible role of vitamin D as a contributing factor in balancing cytokines toward an anti-inflammatory role in inflammatory situations.

Molecular Biology and Clinical Mitigation of Cancer Treatment-Induced Neuropathy

Disruption of microtubule function is the antitumor mechanism of several classes of drugs used to treat cancer today. However, the significant beneficial effect on tumor outcomes is frequently counterbalanced by neurotoxic complications. Despite an abundance of scientific data, our under-standing of the biological mechanisms underlying this toxic reaction remains unclear, further hindering attempts to identify and develop effective preventive strategies. The primary goals of this review are to: (1) provide insight regarding the biology of the microtubule, (2) analyze the molecular and biochemical pathways that may be involved in the development of neurotoxicity, and (3) propose a unifying concept linking drug-induced neuropathy, microtubule dysfunction, and vitamin D.

Regulation of Dendritic Cell Function by Vitamin D

Studies over the last two decades have revealed profound immunomodulatory aspects of vitamin D on various aspects of the immune system. This review will provide an overview of Vitamin D metabolism, a description of dendritic cell subsets, and highlight recent advances on the effects of vitamin D on dendritic cell function, maturation, cytokine production and antigen presentation. The active form of vitamin D, 1,25(OH)₂D₃, has important immunoregulatory and anti-inflammatory effects. Specifically, the 1,25(OH)₂D₃-Vitamin D₃ complex can affect the maturation and migration of many dendritic cell subsets, conferring a special immunoregulatory role as well as tolerogenic properties affecting cytokine and chemokine production. Furthermore, there have been many recent studies demonstrating the effects of Vitamin D on allergic disease and autoimmunity. A clear understanding of the effects of the various forms of Vitamin D will provide new opportunities to improve human health.

Circadian rhythm of serum 25 (OH) vitamin D, calcium and phosphorus levels in the treatment and management of type-2 diabetic patients

The circadian time structure of serum 25 (OH) vitamin D (25-OHD), calcium (Ca) and phosphorus (P) may prove to be helpful in prevention, efficacy and management of diabetes mellitus. Ten newly diagnosed patients with type-2 diabetes mellitus (6 men and 4 women), 30-65 years of age, and 10 age-matched clinically healthy volunteers (7 men and 3 women) were synchronized for one week with diurnal activity from about 06:00 to about 22:00 and nocturnal rest. Breakfast was served around 08:00, lunch around 13:30 and dinner around 20:00. Drugs/nutraceuticals known to affect the vitamin D-calcium metabolism and status were not taken. Blood samples were collected at 6-h intervals for 24 h under standardized, 24-h synchronized conditions. Serum 25-OHD, Ca, P, Ca-P product and Ca-P ratio were determined. A marked circadian variation was demonstrated for 25-OHD in healthy volunteers (p = 0.030) and of borderline statistical significance in the diabetic patients (p = 0.083) by population-mean cosinor analysis. Similarly, healthy volunteers showed borderline significance for serum Ca, P and Ca-P ratio. The circadian acrophase of Ca occurred later in the patients as compared to healthy controls. Mapping the circadian rhythm (an important component of the broader time structure or chronome, which includes a.o., trends with age and extra-circadian components) of vitamin D and calcium is needed for exploring their role as markers in the treatment and management of diabetic patients.

Vitamin D and the brain: key questions for future research

Over the last decade a convergent body of evidence has emerged from epidemiology, animal experiments and clinical trials which links low vitamin D status with a range of adverse neuropsychiatric outcomes. This research demonstrates that the timing of exposure to low vitamin D influences the nature of brain phenotypes, as exposures during gestation versus adulthood result in different phenotypes. With respect to early life exposures, there is robust evidence from rodent experiments indicating that transient developmental vitamin D (DVD) deficiency is associated with changes in brain structure, neurochemistry, gene and protein expression and behavior. In particular, DVD deficiency is associated with alterations in the dopaminergic neurotransmitter systems. In contrast, recently published animal experiments indicate that adult vitamin D (AVD) deficiency is associated with more subtle neurochemical and behavioral phenotypes. This paper explores key issues that need to be addressed in future research. There is a need to define the timing and duration of the 'critical window' during which low vitamin D status is associated with differential and adverse brain outcomes. We discuss the role for 'two-hit hypotheses', which propose that adult vitamin D deficiency leaves the brain more vulnerable to secondary adverse exposures, and thus may exacerbate disease progression. Finally, we explore the evidence implicating a role for vitamin D in rapid, non-genomic mechanisms that may involve L-type calcium channels and brain function. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.

Vitamin D deficiency predisposes to adherent-invasive Escherichia coli-induced barrier dysfunction and experimental colonic injury

BACKGROUND

Adherent-invasive Escherichia coli (AIEC) colonization has been strongly implicated in the pathogenesis of Crohn's disease. Environmental triggers such as vitamin D deficiency have emerged as key factors in the pathogenesis of inflammatory bowel diseases. The aim of this study was to investigate the effects of 1,25(OH)2D3 on AIEC infection-induced changes in vivo and in vitro.

METHODS

Barrier function was assessed in polarized epithelial Caco-2-bbe cells grown in medium with or without vitamin D and challenged with AIEC strain LF82. Weaned C57BL/6 mice were fed either a vitamin D-sufficient or -deficient diet for 5 weeks and then infected with AIEC, in the absence and presence of low-dose dextran sodium sulphate. Disease severity was assessed by histological analysis and in vivo intestinal permeability assay. Presence of invasive bacteria was assessed by transmission electron microscopy.

RESULTS

Caco-2-bbe cells incubated with 1,25(OH)2D3 were protected against AIEC-induced disruption of transepithelial electrical resistance and tight-junction protein redistribution. Vitamin D-deficient C57BL/6 mice given a course of 2% dextran sodium sulphate exhibited pronounced epithelial barrier dysfunction, were more susceptible to AIEC colonization, and showed exacerbated colonic injury. Transmission electron microscopy of colonic tissue from infected mice demonstrated invasion of AIEC and fecal microbiome analysis revealed shifts in microbial communities.

CONCLUSIONS

These data show that vitamin D is able to mitigate the deleterious effects of AIEC on the intestinal mucosa, by maintaining intestinal epithelial barrier homeostasis and preserving tight-junction architecture. This study highlights the association between vitamin D status, dysbiosis, and Crohn's disease.

Serum 25(OH) Vitamin D levels is not associated with disability in multiple sclerosis patients: A case-control study

BACKGROUND

It seems that serum vitamin D levels are one of the potential environmental factors affecting the severity of multiple sclerosis (MS). In this study, we aim to evaluate vitamin D levels in MS patients and healthy subjects and assess the relationship between vitamin D level and disability.

METHODS

In this case-control study, 168 rapid relapsing MS patients and 168 matched healthy controls were randomly included in this study. Demographic characteristics and serum vitamin D levels for patients and controls, as well as expanded disability status scale (EDSS), duration of disease and diagnostic lag for patients were evaluated. We followed up patients for 6 months and relapses were recorded.

RESULTS

The mean serum vitamin D levels were 19.16 ± 17.37 inpatients and 25.39 ± 19.67 in controls (P = 0.560). The mean serum vitamin D levels were 12.65 ± 13.3 in patients with relapses and 22.08 ± 18.22 in patients without any relapses (P < 0.001). There was no significant correlation between EDSS score and serum vitamin D levels (r = -0.08, P = 0.280). There was a significant positive correlation between EDSS score and disease duration (r = 0.52, P < 0.001).

CONCLUSION

In conclusion, vitamin D level in patients with MS was significantly lower than the healthy subjects, but no significant relationship was found between vitamin D levels and disability. Our findings did not suggest a protective role for serum vitamin D levels against disability.

Effect of vitamin D3 supplementation on TNF-α serum level and disease activity index in Iranian IBD patients

AIM

The aim of the study was to assess the effectiveness of vitamin D3 [1, 25(OH)2D3] treatment in IBD with regard to tumor necrosis factor-alpha (TNF-α) serum level and clinical disease activity index (CDAI).

BACKGROUND

Vitamin D has immune-regulatory functions in experimental inflammatory bowel disease (IBD) and vitamin D deficiency is common in IBD patients.

PATIENTS AND METHODS

This was a randomized clinical trial on 108 IBD patients with serum 25-OHD levels less than 30ng/ml, which divided into vitamin D and control groups. Vitamin D group received 50000 IU vitamin D3 for 12 weeks. Before and after the study, TNF-α and 25-OHD serum levels were measured by ELISA method. Data were analyzed using paired t-test, chi-square test and Spearman correlation coefficient. P-values ​​less than 0.05 were considered statistically significant.

RESULTS

Before the intervention no significant difference was found between baseline characteristics and TNF-α serum level of two groups. After intervention TNF-α serum level reduced but this reduction was not statistically significant (p= 0.07, 95% CI: -0.45 to 8.14). The mean serum 25-OHD level of vitamin D increased from 15.54 to 67.89, which was statistically significant (p= 0.00, 95% CI: -61.40 to -43.30). TNF-α level was also associated significantly with CDAI before (Spearman's rho: 0.3, p<0.0001) and after (Spearman's rho: 0.27, P=0.01) intervention.

CONCLUSION

Oral supplementation vitamin D3 significantly increased serum vitamin D levels and insignificantly reduced serum TNF-α level. More studies with larger samples would be beneficial to assess vitamin D3 supplementation efficient effect in IBD.

Vitamin D as a novel therapy in inflammatory bowel disease: new hope or false dawn?

There is increasing scientific interest in the field of vitamin D research, moving the focus beyond bone health to other disease processes. Low circulating vitamin D levels have been reported as a risk factor for several pathophysiologically divergent diseases, including cancers, diabetes, CVD, multiple sclerosis and inflammatory diseases, including rheumatoid arthritis and inflammatory bowel disease (IBD). But, therein, remains the challenge: can any single nutrient contribute to multiple complex disease mechanisms and, ultimately, have therapeutic potential? The aim of this review is to critically evaluate several strands of scientific evidence surrounding vitamin D and inflammation, primarily focusing on IBD. Epidemiological studies suggest an increased incidence of IBD and rheumatoid arthritis in countries of more northern latitudes, mirroring sunlight patterns. A considerable body of evidence supports the anti-inflammatory effects of vitamin D, at least in animal models of IBD. Although it is accepted that suboptimal vitamin D status is common in IBD, some studies suggest that this associates with more severe disease. With regard to treatment, the data are only beginning to emerge from randomised controlled trials to suggest that people with IBD may remain in remission longer when treated with oral vitamin D. In conclusion, several strands of evidence suggest that vitamin D may modify the immune response in IBD. There is a continued need for large well-designed clinical trials and mechanistic studies to determine if, and how, this emerging promise translates into tangible clinical benefits for people with chronic debilitating diseases such as IBD.

Impaired T cell activation and cytokine production by calcitriol-primed human B cells

The biologically active form of vitamin D3 , 1, 25-dihydroxyvitamin D3 (calcitriol), is a potent modulator of the immune response. We have shown previously that calcitriol modulates the immunoglobulin response in vitro and in vivo in mice and humans. To analyse the underlying molecular mechanisms we studied whether calcitriol-primed B cells modulate T cell activation and function. Human B cells were stimulated with anti-CD40 and interleukin (IL)-4 in the presence of increasing concentrations of calcitriol. After removal of calcitriol, primed B cells were co-cultured with autologous CD4(+) T cells; the B cell phenotype T cell activation and their consecutive cytokine production were also assessed. Naive T cells co-cultured with calcitriol-primed naive B cells showed a reduced expansion, nuclear factor of activated T cells, cytoplasmic 2 (NFATc2) expression and cytokine production upon restimulation. CD86 expression on B cells after calcitriol priming was identified as an underlying mechanism, as T cell activation and expansion was rescued by activating anti-CD28 antibodies. Our data indicate that calcitriol-primed B cells display an impaired capacity to activate T cells. Taken together, we identified a novel B cell-dependent vitamin D immune regulatory mechanism, namely by decreased co-stimulation of calcitriol-primed B cells.

Oral vitamin D increases the frequencies of CD38+ human B cells and ameliorates IL-17-producing T cells

Vitamin D deficiency (serum 25-hydroxyvitamin D < 50 nm) has been associated with the onset of immunological diseases including atopic dermatitis (AD), cutaneous or systemic lupus erythematosus and allergic asthma. In this study, we assessed whether oral vitamin D (cholecalciferol) supplementation leads to a systemic modulation of the phenotype of circulating lymphocyte populations and whether a defined serum 25-hydroxyvitamin D (25(OH)D) concentration can be related to the effects on lymphocytes. Cholecalciferol was administered in a dose-escalation setting to vitamin D-deficient individuals from 2000 up to 8000 IU daily for 12 weeks. Individuals without cholecalciferol intake served as controls. Peripheral B cells and T cells were examined by multicolour flow cytometric analysis. The mean serum 25(OH)D concentrations increased upon cholecalciferol intake up to 159 ± 28.7 nm, and remained low in the control group 30.0 ± 12.5 nm. Following cholecalciferol intake, the frequencies of circulating CD38 expressing B cells were significantly increased and IFN-γ+ , and/or IL-17+ CD4+ T helper cells were decreased. These data were identified to correlate with the serum 25(OH)D levels by applying two different analysis approaches (ROC and a nonlinear regression analysis). Our data indicate that increasing 25(OH)D serum concentrations are associated with an increased expression of CD38 on B cells and a decreased T-cell-dependent proinflammatory cytokine production. The therapeutical role of our findings in systemic immunological diseases should be explored in the future by further controlled clinical studies.

Association between reduced plasma 25-hydroxy vitamin D and increased risk of cancer in patients with inflammatory bowel diseases

BACKGROUND & AIMS

Vitamin D deficiency is common among patients with inflammatory bowel diseases (IBD) (Crohn's disease or ulcerative colitis). The effects of low plasma 25-hydroxy vitamin D (25[OH]D) on outcomes other than bone health are understudied in patients with IBD. We examined the association between plasma level of 25(OH)D and risk of cancers in patients with IBD.

METHODS

From a multi-institutional cohort of patients with IBD, we identified those with at least 1 measurement of plasma 25(OH)D. The primary outcome was development of any cancer. We examined the association between plasma 25(OH)D and risk of specific subtypes of cancer, adjusting for potential confounders in a multivariate regression model.

RESULTS

We analyzed data from 2809 patients with IBD and a median plasma level of 25(OH)D of 26 ng/mL. Nearly one-third had deficient levels of vitamin D (<20 ng/mL). During a median follow-up period of 11 years, 196 patients (7%) developed cancer, excluding nonmelanoma skin cancer (41 cases of colorectal cancer). Patients with vitamin D deficiency had an increased risk of cancer (adjusted odds ratio, 1.82; 95% confidence interval, 1.25-2.65) compared with those with sufficient levels. Each 1-ng/mL increase in plasma 25(OH)D was associated with an 8% reduction in risk of colorectal cancer (odds ratio, 0.92; 95% confidence interval, 0.88-0.96). A weaker inverse association was also identified for lung cancer.

CONCLUSIONS

In a large multi-institutional IBD cohort, a low plasma level of 25(OH)D was associated with an increased risk of cancer, especially colorectal cancer.

Vitamin D deficiency promotes epithelial barrier dysfunction and intestinal inflammation

BACKGROUND

Vitamin D, an important modulator of the immune system, has been shown to protect mucosal barrier homeostasis. This study investigates the effects of vitamin D deficiency on infection-induced changes in intestinal epithelial barrier function in vitro and on Citrobacter rodentium-induced colitis in mice.

METHODS

Polarized epithelial Caco2-bbe cells were grown in medium with or without vitamin D and challenged with enterohemorrhagic Escherichia coli O157:H7. Barrier function and tight junction protein expression were assessed. Weaned C57BL/6 mice were fed either a vitamin D-sufficient or vitamin D-deficient diet and then infected with C. rodentium. Disease severity was assessed by histological analysis, intestinal permeability assay, measurement of inflammatory cytokine levels, and microbiome analysis.

RESULTS

1,25(OH)2D3 altered E. coli O157:H7-induced reductions in transepithelial electrical resistance (P < .01), decreased permeability (P < .05), and preserved barrier integrity. Vitamin D-deficient mice challenged with C. rodentium demonstrated increased colonic hyperplasia and epithelial barrier dysfunction (P < .0001 and P < .05, respectively). Vitamin D deficiency resulted in an altered composition of the fecal microbiome both in the absence and presence of C. rodentium infection.

CONCLUSIONS

This study demonstrates that vitamin D is an important mediator of intestinal epithelial defenses against infectious agents. Vitamin D deficiency predisposes to more-severe intestinal injury in an infectious model of colitis.

25-Hydroxyvitamin D: analysis and clinical application

25-Hydroxyvitamin D (25-OHD) is one of the most popular tests requested by clinicians nowadays because in addition to bone diseases, many non-skeletal disorders have been suggested to be linked to vitamin D deficiency or insufficiency. Methodologies used in clinical laboratories include competitive vitamin D protein binding assays (CPBA), immunoassays, high performance liquid chromatography (HPLC), and liquid chromatography-tandem mass spectrometry (LC-MS/MS). In this review article, we introduce the basic metabolism and physiology of vitamin D, key issues in the methods for 25-OHD measurement currently used in most clinical laboratories, and clinical applications of 25-OHD testing. We conclude that although the methodologies for 25-OHD testing have improved significantly, considerable bias between different methods and laboratories still exists. Therefore, standardization of the method is critical. The optimal 25-OHD levels should be determined based on the standardized method. Also, more studies are needed to further determine the relationship between vitamin D deficiency or insufficiency and non-skeletal diseases as well as daily vitamin D dose requirement for reducing the risk of non-skeletal diseases.

Hypovitaminosis d in patients with type 2 diabetes mellitus: a relation to disease control and complications

Aims. This study aims at assessing the relationship between 25 (OH) vitamin D (25-OHD) levels and microvascular complications in patients with type 2 diabetes mellitus (DM2). Methods. 136 patients (59 ± 11 years) with DM2 (disease duration 8.6 ± 7 years) participated in this cross-sectional study. Anthropometric data, HbA1c, 25-OHD levels, serum creatinine, and urine microalbumin/creatinine ratio were collected. Dilated retinal exam was performed, and diabetic neuropathy was assessed using the United Kingdom Screening Score. Results. Serum 25-OHD correlated negatively with HbA1c (r = -0.20,  P = 0.049). Mean 25-OHD levels were lower in subjects with diabetic retinopathy compared to those without retinopathy (12.3 ± 5.5 versus 21.8 ± 13.7, P < 0.001) and lower in subjects with diabetic neuropathy compared to those without neuropathy (16.4 ± 10.4 versus 23.5 ± 14.5, P = 0.004). After adjustment for BMI, diabetes duration, and smoking, 25-OHD was an independent predictor of HbA1c ( β   -0.14; P = 0.03). After adjustment for HbA1c, age, smoking, BMI and disease duration, 25-OHD were independent predictors for diabetic retinopathy: OR 2.8 [95% CI 2.1-8.0] and neuropathy: OR 4.5 [95% CI 1.6-12] for vitamin D < 20 versus vitamin D ≥ 20 ng/mL. Conclusion. Low serum 25-OHD level was an independent predictor of HbA1c, diabetic neuropathy, and diabetic retinopathy in patients with DM2.

Update on therapeutic options for multiple sclerosis

Multiple sclerosis (MS) is one of the most common neurologic disorders that affects young people. The disorder has long been associated with clinical relapses and a disabling course. However, there has been a rapid expansion in the available treatment options for MS, and new insights into existing therapies, as decades of research has begun to produce tangible treatment results leading to newly approved an emerging therapies.

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.

Is serum vitamin D levels associated with disability in patients with newly diagnosed multiple sclerosis?

BACKGROUND

Although the precise etiology of multiple sclerosis (MS) is unknown, it seems that both genetic and environmental factors are important. Recent studies suggest that low serum vitamin D levels are important environmental factor in MS. The aim of this study was to compare the serum levels of vitamin D between MS patients and healthy subjects, and to determine its association with disability in MS patients.

METHODS

In this cross-sectional study, a total of 52 patients with MS were randomly recruited and matched for age and sex with 52 healthy subjects. Demographic characteristics and serum vitamin D levels for both groups, as well as duration of disease Expanded Disability Status Scale (EDSS) for MS patients were evaluated. Statistical analysis was performed by independent samples t-test and multiple linear regression analysis.

RESULTS

The mean serum vitamin D levels were 26.5 ± 16.3 ng/ml in MS patients vs. 37.1 ±19.7 in healthy subjects (P = 0.003). A linear regression analysis showed no significant association between vitamin D levels and EDSS score of patients with MS (P = 0.345), after adjusting for the covariates.

CONCLUSION

Our findings did not suggest a protective association for serum vitamin D levels against disability in MS patients.

Availability of 25-hydroxyvitamin D(3) to APCs controls the balance between regulatory and inflammatory T cell responses

1,25-Dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], the active form of vitamin D, exerts potent effects on several tissues including cells of the immune system, where it affects T cell activation, differentiation and migration. The circulating, inactive form of vitamin D, 25(OH)D(3), is generally used as an indication of vitamin D status. However, use of this precursor depends on its uptake by cells and subsequent conversion by the enzyme 25(OH)D(3)-1α-hydroxylase (CYP27B1) into active 1,25(OH)(2)D(3). Using human T cells, we show in this study that addition of inactive 25(OH)D(3) is sufficient to alter T cell responses only when dendritic cells (DCs) are present. Mechanistically, CYP27B1 is induced in DCs upon maturation with LPS or upon T cell contact, resulting in the generation and release of 1,25(OH)(2)D(3), which subsequently affects T cell responses. In most tissues, vitamin D binding protein acts as a carrier to enhance the use of vitamin D. However, we show that vitamin D binding protein modulates T cell responses by restricting the availability of inactive 25(OH)D(3) to DC. These data indicate that the level of free 25(OH)D(3) available to DCs determines the inflammatory/regulatory balance of ensuing T cell responses.

Vitamin D, invariant natural killer T-cells and experimental autoimmune disease

Vitamin D is an important regulator of the immune system in general and multiple sclerosis in particular. Experimentally (i), invariant natural killer T (iNKT) cells have been shown to be important suppressors of autoimmune diseases such as experimental autoimmune encephalomyelitis (EAE; an animal model of multiple sclerosis). Conversely, in experimental allergic asthma iNKT cells are required for disease induction and are therefore pathogenic. The active form of vitamin D (calcitriol) suppresses EAE. The development of EAE symptoms is accelerated in vitamin D deficiency. Interestingly experimental asthma is less severe in vitamin D deficiency although there is no effect of calcitriol on disease severity. The data suggest that an important target of vitamin D in EAE and asthma are the iNKT cells. Vitamin D and/or vitamin D receptor deficiency results in the impaired development of iNKT cells. Vitamin D is critical very early during development of the immune system. Low levels of vitamin D in utero resulted in significantly reduced numbers of iNKT cells that failed to recover when calcitriol was used to supplement neonatal or adult mice. The data suggest that one of the consequences of early vitamin D deficiency is a reduction in the numbers of iNKT cells that develop. The iNKT cells are required for the beneficial effects of calcitriol in EAE. The important role of vitamin D on iNKT cells could impact the development of human immune-mediated diseases including multiple sclerosis and asthma.

Vitamin D, invariant natural killer T-cells and experimental autoimmune disease

Vitamin D is an important regulator of the immune system in general and multiple sclerosis in particular. Experimentally (i), invariant natural killer T (iNKT) cells have been shown to be important suppressors of autoimmune diseases such as experimental autoimmune encephalomyelitis (EAE; an animal model of multiple sclerosis). Conversely, in experimental allergic asthma iNKT cells are required for disease induction and are therefore pathogenic. The active form of vitamin D (calcitriol) suppresses EAE. The development of EAE symptoms is accelerated in vitamin D deficiency. Interestingly experimental asthma is less severe in vitamin D deficiency although there is no effect of calcitriol on disease severity. The data suggest that an important target of vitamin D in EAE and asthma are the iNKT cells. Vitamin D and/or vitamin D receptor deficiency results in the impaired development of iNKT cells. Vitamin D is critical very early during development of the immune system. Low levels of vitamin D in utero resulted in significantly reduced numbers of iNKT cells that failed to recover when calcitriol was used to supplement neonatal or adult mice. The data suggest that one of the consequences of early vitamin D deficiency is a reduction in the numbers of iNKT cells that develop. The iNKT cells are required for the beneficial effects of calcitriol in EAE. The important role of vitamin D on iNKT cells could impact the development of human immune-mediated diseases including multiple sclerosis and asthma.

Vitamin D, multiple sclerosis and inflammatory bowel disease

It has now been more than 20years since the vitamin D receptor was identified in cells of the immune system. The immune system has now been established as an important target of vitamin D. Vitamin D receptor knockout and vitamin D deficient mice have a surplus of effector T cells that have been implicated in the pathology of multiple sclerosis (MS) and inflammatory bowel disease (IBD). The active form of vitamin D directly and indirectly suppresses the function of these pathogenic T cells while inducing several regulatory T cells that suppress MS and IBD development. There is reason to believe that vitamin D could be an environmental factor that may play a role in the development of these immune mediated diseases in the clinic but at present there has not been a causal relationship established. Nonetheless, current evidence suggests that improving vitamin D status and/or using vitamin D receptor agonists may be useful in MS and IBD.

Is multiple sclerosis an autoimmune disease?

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) with varied clinical presentations and heterogeneous histopathological features. The underlying immunological abnormalities in MS lead to various neurological and autoimmune manifestations. There is strong evidence that MS is, at least in part, an immune-mediated disease. There is less evidence that MS is a classical autoimmune disease, even though many authors state this in the description of the disease. We show the evidence that both supports and refutes the autoimmune hypothesis. In addition, we present an alternate hypothesis based on virus infection to explain the pathogenesis of MS.

Multiple sclerosis is not a disease of the immune system

Multiple sclerosis is a complex neurodegenerative disease, thought to arise through autoimmunity against antigens of the central nervous system. The autoimmunity hypothesis fails to explain why genetic and environmental risk factors linked to the disease in one population tend to be unimportant in other populations. Despite great advances in documenting the cell and molecular mechanisms underlying MS pathophysiology, the autoimmunity framework has also been unable to develop a comprehensive explanation of the etiology of the disease. I propose a new framework for understanding MS as a dysfunction of the metabolism of lipids. Specifically, the homeostasis of lipid metabolism collapses during acute-phase inflammatory response triggered by a pathogen, trauma, or stress, starting a feedback loop of increased oxidative stress, inflammatory response, and proliferation of cytoxic foam cells that cross the blood brain barrier and both catabolize myelin and prevent remyelination. Understanding MS as a chronic metabolic disorder illuminates four aspects of disease onset and progression: 1) its pathophysiology; 2) genetic susceptibility; 3) environmental and pathogen triggers; and 4) the skewed sex ratio of patients. It also suggests new avenues for treatment.

Evidence for the role of B cells and immunoglobulins in the pathogenesis of multiple sclerosis

The pathogenesis of multiple sclerosis (MS) remains elusive. Recent reports advocate greater involvement of B cells and immunoglobulins in the initiation and propagation of MS lesions at different stages of their ontogeny. The key role of B cells and immunoglobulins in pathogenesis was initially identified by studies in which patients whose fulminant attacks of demyelination did not respond to steroids experienced remarkable functional improvement following plasma exchange. The positive response to Rituximab in Phase II clinical trials of relapsing-remitting MS confirms the role of B cells. The critical question is how B cells contribute to MS. In this paper, we discuss both the deleterious and the beneficial roles of B cells and immunoglobulins in MS lesions. We provide alternative hypotheses to explain both damaging and protective antibody responses.

The vitamin D receptor gene is associated with Alzheimer's disease

Vitamin D may have a role in brain function. Low levels have been frequently associated with cognitive decline and may contribute to diseases of the nervous system. The vitamin D receptor (VDR) is widely expressed in human brain. Vitamin D appears to be neuroprotective and may regulate inflammation in the brain. We examined two VDR polymorphisms, Apa1 and Taq1. We used DNA from 255 Alzheimer's disease (AD) cases and 260 cognitively screened elderly controls from the longitudinal cohort of the Oxford Project to Investigate Memory and Ageing (OPTIMA). The presence of each of the linked alleles, Apa1 T and Taq1 G, was associated with the risk of AD, particularly in people <75 years old: odds ratios ≥3.0 and p≤0.005. We also found preliminary evidence of interactions associated with AD between these polymorphisms and two other genes involved in the regulation of inflammation, interleukin-10 (IL10) and dopamine β-hydroxylase (DBH): synergy factors ≥3.4, uncorrected p<0.05. These associations are biologically plausible and are consistent with a role for vitamin D in AD. Nevertheless, we consider this to be a hypothesis-generating study, which needs to be replicated in a larger dataset.

Demographic, genetic, and environmental factors that modify disease course

As with susceptibility to disease, it is likely that multiple factors interact to influence the phenotype of multiple sclerosis and long-term disease outcomes. Such factors may include genetic factors, socioeconomic status, comorbid diseases, and health behaviors, as well as environmental exposures. An improved understanding of the influence of these factors on disease course may reap several benefits, such as improved prognostication, allowing us to tailor disease management with respect to intensity of disease-modifying therapies and changes in specific health behaviors, in the broad context of coexisting health issues. Such information can facilitate appropriately adjusted comparisons within and between populations. Elucidation of these factors will require careful study of well-characterized populations in which the roles of multiple factors are considered simultaneously.

Epstein-Barr and other viral mimicry of autoantigens, myelin and vitamin D-related proteins and of EIF2B, the cause of vanishing white matter disease: massive mimicry of multiple sclerosis relevant proteins by the Synechococcus phage

The Epstein-Barr virus expresses proteins containing numerous short consensi (identical pentapeptides at least, or longer gapped consensi) that are identical to those in 16 multiple sclerosis autoantigens or in the products of multiple sclerosis susceptibility genes. Other viruses implicated in multiple sclerosis also display such mimicry and the Synechococcus phage was identified as a novel and major contributor to this phenomenon. Cyanobacteria hosts of Synechococcus phage favor temperate climes, in line with multiple sclerosis distribution, and bacterial and phage ecology accords closely with multiple sclerosis epidemiology. Bovine, ovine or canine viral proteins were also identified as autoantigen homologues, in line with epidemiological data linking multiple sclerosis to cattle density, sheep contact and dog ownership. Viral proteins align with known autoantigens, other myelin and vitamin D-related proteins and the translation initiation factor EIF2B, which is implicated in vanishing white matter disease. These data suggest that the autoantigens in multiple sclerosis, which causes demyelination in animal models, may be generated by antibodies raised to viral protein homologues. Multiple autoantibodies may cause multiple sclerosis via protein knockdown and immune activation. Their selective removal may be of clinical benefit as already suggested by promising results using plasmapheresis or immunoadsorption in certain multiple sclerosis patients.

Role of vitamin D in immune responses and autoimmune diseases, with emphasis on its role in multiple sclerosis

Vitamin D is a seco-steroid involved in calcium and phosphorus metabolism, and bone formation and mineralization, through binding to a specific nuclear receptor, vitamin D receptor (VDR). Besides its well-established functions on bone health, multiple lines of evidence have indicated the immunomodulatory roles of vitamin D. Vitamin D can affect both innate and adaptive immunity, and prevent autoimmune responses efficiently. Vitamin D regulates the immune responses by suppressing T cell proliferation and modulating macrophage functions. Epidemiological studies have shown that vitamin D deficiency is associated with multiple diseases such as rickets and cancer. Moreover, associations between vitamin D and autoimmune diseases have been confirmed in multiple sclerosis (MS), rheumatoid arthritis (RA), etc. The present review mainly summarized the recent findings on the immunomodulatory role of vitamin D in various disorders, with special focus on its role in MS, an autoimmune disease of the nervous system.

Genetic predictors of 25-hydroxyvitamin D levels and risk of multiple sclerosis

Risk of multiple sclerosis (MS) decreases with increasing plasma levels of 25-hydroxyvitamin D [25(OH)D]. If this association reflected a protective effect of vitamin D, MS risk should be lower among individuals carrying genetic variants that predict high 25(OH)D levels. The aim of the study was to determine whether individuals with genotypes predicting higher 25(OH)D levels have decreased MS risk. Logistic regression was used to assess the association between single nucleotide polymorphisms (SNPs) associated with 25(OH)D levels and MS risk in 1,655 cases and 6,349 controls. Analyses were further stratified by HLA-DR15 status, assessed by genotyping a single SNP strongly correlated with the HLA DRB1 1501 risk haplotype, and complemented by considering a SNP near CYP27B1. SNPs in GC were predictors of 25(OH)D levels, but not MS risk, in either HLA-DR15 negative or HLA-DR15 positive individuals. In contrast, there was a suggestion of a difference in the effect of a CYP2R1 allele dependent on HLA-DR15 genotype. The 'A' allele of CYP2R1 rs10741657 was associated with increased 25(OH)D levels and a non-significant reduced MS risk among HLA-DR15 negative (OR = 0.89, 95% CI: 0.79, 1.01) that was not apparent in HLA-DR15 positive individuals. The 'C' allele of CYP27B1 rs703842 was inversely associated with MS risk; this association appeared stronger among HLA-DR15 negative (OR = 0.79, 95% CI: 0.69, 0.90) compared to HLA-DR15 positive individuals (OR = 0.91, 95% CI: 0.80, 1.04). This preliminary finding suggests the possibility that the putative beneficial effect of vitamin D on MS risk maybe attenuated in individuals carrying the HLA-DR15 MS risk allele.

Vitamin D in health and disease: current perspectives

Despite the numerous reports of the association of vitamin D with a spectrum of development, disease treatment and health maintenance, vitamin D deficiency is common. Originating in part from the diet but with a key source resulting from transformation by exposure to sunshine, a great deal of the population suffers from vitamin D deficiency especially during winter months. It is linked to the treatment and pathogenesis and/or progression of several disorders including cancer, hypertension, multiple sclerosis, rheumatoid arthritis, osteoporosis, muscle weakness and diabetes. This widespread deficiency of Vitamin D merits consideration of widespread policies including increasing awareness among the public and healthcare professionals.

Assessing vitamin D status: pitfalls for the unwary

The use of vitamin D testing has grown rapidly in the recent times as a result of increased interest in the role of vitamin D in health. Although the generally accepted measure of vitamin D status is circulating 25(OH)D concentration, there is little consensus on which assay method should be used. Commonly used assays include competitive protein-binding assay, RIA, enzyme immunoassay, chemiluminescence immunoassays, HPLC, and LC-MS/MS, each with its own advantages and disadvantages. However, there is significant interassay and interlaboratory variability in measurements. Our simulation of the published data showed that using a deficiency cut-point of 50 nmol/L, 57% of samples assessed using a chemiluminescence immunoassay were classified as deficient compared with 41% of samples assessed using LC-MS/MS; a 20% misclassification rate. Similar rates of misclassification were seen at 75 nmol/L. This has implications for clinical practice and decision limits for vitamin D supplementation, suggesting that cut-points should be assay specific rather than universal and that greater harmonization between laboratories is required. Newer assays using alternative biological samples to determine the circulating 25(OH)D have been proposed and advances in the genetics of vitamin D and the role of vitamin D-binding protein may improve future assay accuracy.

Why do T cells express the vitamin D receptor?

Vitamin D is an important regulator of immune function. T cells express the vitamin D receptor (VDR) and have been shown to be direct and indirect vitamin D targets. Why should T cells be responsive to vitamin D? The data suggest that expression of the VDR is required for the development of two cell types, NKT cells and CD8αα T cells, which inhibit autoimmunity. In addition, effector T cell cytokine production is regulated by vitamin D. Available evidence suggests that NKT and CD8αα T cells express the VDR as part of the selection process to protect against the generation of autoimmunity, particularly in the gut.