Non-classical mechanisms of transcriptional regulation by the vitamin D receptor: insights into calcium homeostasis, immune system regulation and cancer chemoprevention

Vitamin D and human health: evidence from Mendelian randomization studies

We summarized the current evidence on vitamin D and major health outcomes from Mendelian randomization (MR) studies. PubMed and Embase were searched for original MR studies on vitamin D in relation to any health outcome from inception to September 1, 2022. Nonlinear MR findings were excluded due to concerns about the validity of the statistical methods used. A meta-analysis was preformed to synthesize study-specific estimates after excluding overlapping samples, where applicable. The methodological quality of the included studies was evaluated according to the STROBE-MR checklist. A total of 133 MR publications were eligible for inclusion in the analyses. The causal association between vitamin D status and 275 individual outcomes was examined. Linear MR analyses showed genetically high 25-hydroxyvitamin D (25(OH)D) concentrations were associated with reduced risk of multiple sclerosis incidence and relapse, non-infectious uveitis and scleritis, psoriasis, femur fracture, leg fracture, amyotrophic lateral sclerosis, anorexia nervosa, delirium, heart failure, ovarian cancer, non-alcoholic fatty liver disease, dyslipidemia, and bacterial pneumonia, but increased risk of Behçet's disease, Graves' disease, kidney stone disease, fracture of radium/ulna, basal cell carcinoma, and overall cataracts. Stratified analyses showed that the inverse association between genetically predisposed 25(OH)D concentrations and multiple sclerosis risk was significant and consistent regardless of the genetic instruments GIs selected. However, the associations with most of the other outcomes were only pronounced when using genetic variants not limited to those in the vitamin D pathway as GIs. The methodological quality of the included MR studies was substantially heterogeneous. Current evidence from linear MR studies strongly supports a causal role of vitamin D in the development of multiple sclerosis. Suggestive support for a number of other health conditions could help prioritize conditions where vitamin D may be beneficial or harmful.

Age-Dependent Effect of Calcitriol on Mouse Regulatory T and B Lymphocytes

The hormonally active vitamin D3 metabolite, calcitriol, functions as an important modulator of the immune system. We assumed that calcitriol exerts different effects on immune cells and cytokine production, depending on the age of the animal; therefore, we analyzed its effects on regulatory T lymphocytes and regulatory B lymphocytes in healthy young and old female C57Bl/6/Foxp3GFP mice. In the lymph nodes of young mice, calcitriol decreased the percentage of Tregs, including tTregs and pTregs, and the expression of GITR, CD103, and CD101; however, calcitriol increased the level of IL-35 in adipose tissue. In the case of aged mice, calcitriol decreased the percentages of tTregs and CD19+ cells in lymph nodes and the level of osteopontin in the plasma. Additionally, increases in the levels of IgG and the lowest levels of IFN-γ, IL-10, and IL-35 were observed in the adipose tissue of aged mice. This study showed that calcitriol treatment had different effects, mainly on Treg phenotypes and cytokine secretion, in young and old female mice; it seemed that calcitriol enhanced the immunosuppressive properties of the lymphatic organs and adipose tissue of healthy young mice but not of healthy aged mice, where the opposite effects were observed.

Association Between Vitamin D Deficiency and Testosterone Levels in Adult Males: A Systematic Review

Vitamin D deficiency and its potential impact on testosterone levels have been subjects of scientific interest. This systematic review aims to evaluate the association between vitamin D deficiency and testosterone levels in adult males and examine the effects of vitamin D supplementation on testosterone. A comprehensive literature search was conducted in accordance with the PRISMA guidelines across PubMed, Google Scholar, and ScienceDirect. The inclusion criteria involved studies published in English between 2013 and 2023, which investigated the correlation between vitamin D and testosterone levels in adult males. The process of data extraction and synthesis encompassed various aspects, including study characteristics, participant demographics, measurement methods, and outcomes pertaining to the association. The initial search resulted in a pool of 354,235 articles. Through the application of relevant filters and the review of titles and abstracts, 48 articles were chosen for further assessment. Out of these, eight studies fulfilled the inclusion criteria and were ultimately incorporated into the final review. The included studies consisted of four cross-sectional studies, three randomized controlled trials (RCTs), and one analysis utilizing Mendelian randomization. The results showed heterogeneity among the studies, as some reported a positive correlation between vitamin D levels and testosterone, while others did not find a significant association. The effects of vitamin D supplementation on testosterone levels were inconclusive, with limited evidence of significant changes in total testosterone. However, potential influences on sex hormone-binding globulin and free testosterone levels were observed. To establish more definitive evidence regarding the impact of vitamin D on testosterone levels, there is a need for further well-designed, long-term RCTs that encompass diverse populations.

Effects of aerobic training and vitamin D supplementation on glycemic indices and adipose tissue gene expression in type 2 diabetic rats

Type 2 diabetes mellitus (T2DM) is a progressive metabolic disorder mainly caused by overweight and obesity that accumulates pro-inflammatory factors in adipose tissue. Studies have confirmed the efficacy of exercise and vitamin D supplementation in preventing, controlling, and treating diabetes. While, reduced physical activity and vitamin D deficiency are related to increased adiposity, blood glucose level, insulin concentration, and insulin resistance. This study purposed to investigate the effect of 8-week aerobic training with vitamin D supplementation on the expression of AMPK, PGC-1α, and UCP-1 genes expression in the visceral adipose tissue of obese rats with T2DM. In this experimental study, fifty male Wistar rats were divided into 5 groups (n = 10): aerobic training and vitamin D supplementation (AT + Vit D), aerobic training (5 days/week for 8 weeks; AT), vitamin D supplementation (Vit D), diabetic control (C) and NC (Non-Diabetic Control). AT + Vit D and AT groups practiced an 8-week aerobic training, 5 days a week. Vit D and AT + Vit D groups receive 5000 IU of vitamin D by injection once a week while AT and C received sesame oil. After blood sampling, visceral fat was taken to measure AMPK, PGC-1α, and UCP1 gene expression. Data were statistically analyzed by One-way ANOVA and paired sample t-test at a significance level of p < 0.05. Based on our results BW, BMI, WC, visceral fat, insulin, glucose, and HOMA-IR were significantly lower in the AT + Vit D, AT, and Vit D groups compared with the C group (p < 0.01). Furthermore, AT + Vit D, AT, and Vit D upregulated AMPK, PGC-1α, and UCP1 gene expression compared to the C. Based on the results compared to AT and Vit D, AT + Vit D significantly upregulated AMPK (p = 0.004; p = 0.001), PGC-1α (p = 0.010; p = 0.001), and UCP1 (p = 0.032; p = 0.001) gene expression, respectively. Also, AT induced more significant upregulations in the AMPK (p = 0.001), PGC-1α (p = 0.001), and UCP1 gene expression (p = 0.001) than Vit D. Vitamin D supplementation enhanced the beneficial effects of aerobic training on BW, BMI, WC, visceral fat, insulin, glucose, and HOMA-IR in diabetic rats. We also observed that separate AT or Vit D upregulated the gene expression of AMPK, PGC-1α, and UCP1 however, combined AT + Vit D upregulated AMPK, PGC-1α, and UCP1 more significantly. These results suggested that combining aerobic training and vitamin D supplementation exerted incremental effects on the gene expressions related to adipose tissue in animal models of diabetes.

Vitamin D Deficiency and Gingival Enlargement: A Case Report

The occurrence of vitamin D insufficiency is rising constantly, and most pediatric patients are below the required levels. Individuals with vitamin D deficiency are more susceptible to inflammatory diseases because it reduces their immunity. The role of vitamin D deficiency in gingival enlargement has been reported in the literature. In this case report, we are describing a case in which a vitamin D supplement has resolved the gingival enlargement significantly without any invasive procedure. A 12-year-old boy reported a chief complaint of swollen gums in the upper and lower front teeth region. On clinical examination, there was minor surface plaque and calculus along with the formation of pseudopockets, but there was no clinical attachment loss. The patient has been advised to undergo laboratory tests for a complete blood profile, including a vitamin assessment. The patient reported after two and a half months with a gingivectomy on the first quadrant at a private clinic. They reported back to us because they didn't want the same trauma from surgery again and wanted a more conservative treatment option. So, on the basis of the reassessment of reports, vitamin D deficiency was confirmed, and treatment was started with 60,000 thousand I/U of vitamin D supplement weekly and advised for sunlight exposure with minimal clothing. There was a significant decrease in enlargement observed after the six-month follow-up period. Vitamin D supplements can be a more conservative treatment option for gingival enlargement of unknown etiology.

Do Vitamin D receptor gene polymorphisms affect bone mass density in men?: A meta-analysis of observational studies

The signs of aging in humans can often be detected through a decrease in bone mass density (BMD). The decrease in BMD as a risk of osteoporosis is often only seen in women, but not in men, even though men also have a risk of osteoporosis which can affect their well-being. We conducted study searches through databases such as PubMed, EBSCO, ProQuest, Willey Online, Science Direct, and SAGE. We performed analysis on four types of Vitamin D receptor polymorphisms: BsmI, ApaI, FokI, and TaqI from 14 potential studies involving men. We found that several genetic analysis models of BsmI and FokI significantly affected BMD in men: BB vs bb in whole body BMD (SMD = 0.43, 95% CI = [0.12-0.75], p = 0.0008, BB vs Bb in whole body BMD (SMD = -1.38, 95% CI = [-1.87 to 0.88], p < 0.00001), and FF+Ff vs ff spine BMD (SMD = 0.59, 95% CI = 0.13-1.05], p = 0.001), even after adjusting for comorbidities as confounding variables. The present meta-analysis showed that BsmI and FokI polymorphisms of the VDR gene were correlated with decreased BMD in men which may contribute to the aging process and well-being.

Ligand-Independent Actions of the Vitamin D Receptor: More Questions Than Answers

Our predominant understanding of the actions of vitamin D involve binding of its ligand, 1,25(OH)D, to the vitamin D receptor (VDR), which for its genomic actions binds to discrete regions of its target genes called vitamin D response elements. However, chromatin immunoprecipitation‐sequencing (ChIP‐seq) studies have observed that the VDR can bind to many sites in the genome without its ligand. The number of such sites and how much they coincide with sites that also bind the liganded VDR vary from cell to cell, with the keratinocyte from the skin having the greatest overlap and the intestinal epithelial cell having the least. What is the purpose of the unliganded VDR? In this review, I will focus on two clear examples in which the unliganded VDR plays a role. The best example is that of hair follicle cycling. Hair follicle cycling does not need 1,25(OH)₂D, and Vdr lacking the ability to bind 1,25(OH)₂D can restore hair follicle cycling in mice otherwise lacking Vdr. This is not true for other functions of VDR such as intestinal calcium transport. Tumor formation in the skin after UVB radiation or the application of chemical carcinogens also appears to be at least partially independent of 1,25(OH)₂D in that Vdr null mice develop such tumors after these challenges, but mice lacking Cyp27b1, the enzyme producing 1,25(OH)₂D, do not. Examples in other tissues emerge when studies comparing Vdr null and Cyp27b1 null mice are compared, demonstrating a more severe phenotype with respect to bone mineral homeostasis in the Cyp27b1 null mouse, suggesting a repressor function for VDR. This review will examine potential mechanisms for these ligand‐independent actions of VDR, but as the title indicates, there are more questions than answers with respect to this role of VDR. © 2021 The Author. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Vitamin D and Breast Cancer: Mechanistic Update

The presence of the vitamin D receptor (VDR) in mammary gland and breast cancer has long been recognized, and multiple preclinical studies have demonstrated that its ligand, 1,25-dihydroxyvitamin D (1,25D), modulates normal mammary gland development and inhibits growth of breast tumors in animal models. Vitamin D deficiency is common in breast cancer patients, and some evidence suggests that low vitamin D status enhances the risk for disease development or progression. Although many 1,25D-responsive targets in normal mammary cells and in breast cancers have been identified, validation of specific targets that regulate cell cycle, apoptosis, autophagy, and differentiation, particularly in vivo, has been challenging. Model systems of carcinogenesis have provided evidence that both VDR expression and 1,25D actions change with transformation, but clinical data regarding vitamin D responsiveness of established tumors is limited and inconclusive. Because breast cancer is heterogeneous, the relevant VDR targets and potential sensitivity to vitamin D repletion or supplementation will likely differ between patient populations. Detailed analysis of VDR actions in specific molecular subtypes of the disease will be necessary to clarify the conflicting data. Genomic, proteomic, and metabolomic analyses of in vitro and in vivo model systems are also warranted to comprehensively understand the network of vitamin D-regulated pathways in the context of breast cancer heterogeneity. This review provides an update on recent studies spanning the spectrum of mechanistic (cell/molecular), preclinical (animal models), and translational work on the role of vitamin D in breast cancer. © 2021 The Author. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Vitamin D receptor (VDR) expression in different molecular subtypes of canine mammary carcinoma

BACKGROUND

The molecular-based classification of canine mammary carcinomas (CMCs) has been the focus of much current research. Both in canines and humans, the triple-negative (TN) molecular subtype of mammary cancer is defined by a lack of expression of progesterone receptor (PR), oestrogen receptor (ER) and HER2. It has a poor prognosis; no effective targeted therapy is available. Vitamin D displays anticarcinogenic properties, and the expression of its receptor (VDR) has been found in different molecular subtypes, being about 30-40 % of TN breast cancer (TNBC) positive to it. We assessed the VDR expression in the different molecular subtypes of 58 CMCs from 45 female dogs using an immunohistochemical panel for the molecular classification of included: PR, ER, HER2, cytokeratin (CK) 5, CK14, and Ki67. In addition, we studied the relationship among the molecular subtypes of CMCs and clinicopathologic parameters.

RESULTS

Investigation showed VDR positivity in 45.0 % of the triple-negative CMCs (TNCMCs), 27.3 % of luminal B and 19.0 % of luminal A. Luminal A was the most molecular subtype represented of the total tumours (36.2 %), followed of TNCMCs (34.5 %), luminal B (20.7 %) and HER2-overexpression (10.3 %). Both HER2-overexpression and TNCMC subtypes were positively related to lymphatic invasion (P = 0.028), simple histologic subtype (P = 0.007), a higher histological grade (P = 0.045) and a trend to higher proliferation index (P = 0.09).

CONCLUSIONS

The highest VDR expression was observed in TNCMC, being almost half of them (45 %) positive to this receptor. VDR expression was absent in HER2-overexpression tumours and low in luminal A and B molecular subtypes.

Vitamin D-regulated Gene Expression Profiles: Species-specificity and Cell-specific Effects on Metabolism and Immunity

Vitamin D has pleiotropic physiological actions including immune system regulation, in addition to its classical role in calcium homeostasis. Hormonal 1,25-dihydroxyvitamin D (1,25D) signals through the nuclear vitamin D receptor, and large-scale expression profiling has provided numerous insights into its diverse physiological roles. To obtain a comprehensive picture of vitamin D signaling, we analyzed raw data from 94 (80 human, 14 mouse) expression profiles of genes regulated by 1,25D or its analogs. This identified several thousand distinct genes directly or indirectly up- or downregulated in a highly cell-specific manner in human cells using a 1.5-fold cut-off. There was significant overlap of biological processes regulated in human and mouse but minimal intersection between genes regulated in each species. Disease ontology clustering confirmed roles for 1,25D in immune homeostasis in several human cell types, and analysis of canonical pathways revealed novel and cell-specific roles of vitamin D in innate immunity. This included cell-specific regulation of several components of Nucleotide-binding Oligomerization Domain-like (NOD-like) pattern recognition receptor signaling, and metabolic events controlling innate immune responses. Notably, 1,25D selectively enhanced catabolism of branched-chain amino acids (BCAAs) in monocytic cells. BCAA levels regulate the major metabolic kinase mammalian Target of Rapamycin (mTOR), and pretreatment with 1,25D suppressed BCAA-dependent activation of mTOR signaling. Furthermore, ablation of BCAT1 expression in monocytic cells blocked 1,25D-induced increases in autophagy marker LAMP1. In conclusion, the data generated represents a powerful tool to further understand the diverse physiological roles of vitamin D signaling and provides multiple insights into mechanisms of innate immune regulation by 1,25D.

Effects of Vitamin D Receptor, Cytochrome P450 3A, and Cytochrome P450 Oxidoreductase Genetic Polymorphisms on the Pharmacokinetics of Remimazolam in Healthy Chinese Volunteers

Remimazolam is a new ultra-short-acting benzodiazepine used to induce and maintain anesthesia and procedural sedation. Its compound structure is similar to midazolam's. Midazolam metabolism might be affected by vitamin D receptor (VDR), cytochrome P450 3A, and cytochrome P450 oxidoreductase genetic polymorphisms. This study investigated the effects of VDR, cytochrome P450 3A, and cytochrome P450 oxidoreductase genetic polymorphisms on the pharmacokinetics of remimazolam in healthy Chinese volunteers after a single intravenous injection of remimazolam besylate. Blood samples were collected from subjects (n = 62) at scheduled time intervals before and after injection. High-performance liquid chromatography-tandem mass spectrometry was used to quantify plasma remimazolam and RF7054 (its inactive carboxylic acid metabolite) concentrations. The relationship between plasma remimazolam concentration, pharmacokinetic parameters, and polymorphic alleles was assessed for each subject. The rs4516035 allele affected the elimination half-life of RF7054 (P = .043), while the rs1544410 allele affected the dose-normalized maximum observed plasma concentration (C_max /D) of remimazolam (P = .025) in 46 volunteers. Results showed that VDR genetic polymorphisms might affect the pharmacokinetics of remimazolam in the Chinese population.

Vitamin D in the prevention of exacerbations of asthma in preschoolers (DIVA): protocol for a multicentre randomised placebo-controlled triple-blind trial

INTRODUCTION

Preschoolers have the highest rate of emergency visits and hospitalisations for asthma exacerbations of all age groups, with most triggered by upper respiratory tract infections (URTIs) and occurring in the fall or winter. Vitamin D insufficiency is highly prevalent in Canadian preschoolers with recurrent asthma exacerbations, particularly in winter. It is associated with more URTIs and, in patients with asthma, more oral corticosteroid (OCS) use. Although evidence suggests that vitamin D supplements significantly decrease URTIs and asthma exacerbations requiring OCS, there is insufficient data in preschoolers. This study aims to determine the impact of vitamin D₃ supplementation on exacerbations requiring OCS, in preschoolers with recurrent URTI-induced asthma exacerbations.

METHODS AND ANALYSIS

This is a phase III, randomised, triple-blind, placebo-controlled, parallel-group multicentre trial of vitamin D₃ supplementation in children aged 1-5 years, with asthma triggered by URTIs and a recent history of frequent URTIs and OCS use. Children (n=865) will be recruited in the fall and early winter and followed for 7 months. They will be randomised to either the (1) intervention: two oral boluses of 100 000 international unit (IU) vitamin D₃ (3.5 months apart) with 400 IU vitamin D₃ daily; or (2) control: identical placebo boluses with daily placebo. The primary outcome is the number of exacerbations requiring OCS per child, documented by medical and pharmacy records. Secondary outcomes include number of laboratory-confirmed viral URTIs, exacerbation duration and severity, parent functional status, healthcare use, treatment deintensification, cost and safety.

ETHICS AND DISSEMINATION

This study has received ethical approval from all sites. Results will be disseminated via international conferences and manuscripts targeting paediatricians and respirologists, and to families of asthmatic children via our Quebec parents-partners outreach programme. If proven effective, findings may markedly influence the management of URTI-induced asthma in high-morbidity preschoolers and could be directly implemented into practice with an update to clinical guidelines.

TRIAL REGISTRATION NUMBER

NCT03365687.

Relationship between Serum Vitamin D and Calcium Levels and Vitamin D Receptor Gene Polymorphisms in Colorectal Cancer

Background

Many epidemiological studies have shown that vitamin D deficiency is associated with various types of human cancers. The biological action of vitamin D and its metabolites is mediated by the transcription factor vitamin D receptor (VDR). The VDR gene is highly expressed in the colon and is involved in many biological functions. The aim of the current study was to assess the relationship between serum vitamin D metabolite and calcium levels with VDR polymorphisms in normal and colorectal cancer (CRC) patients.

Methods

Fifty Saudi CRC patients and fifty controls were enrolled in the study. The levels of total vitamin D, 25(OH)D₃, and calcium were measured in serum.

Results

The homozygous genotype (aa) of the ApaI VDR polymorphism (rs7975232) was found to correlate with total serum vitamin D levels of CRC patients, while the heterozygous (Tt) TaqI VDR polymorphism (rs731236) was associated with serum calcium levels. In contrast, the BsmI and FokI VDR polymorphisms (rs1544410 and rs2228570, resp.) did not affect the serum levels of total vitamin D, 25-hydroxyvitamin D₃, and calcium.

Conclusion

Appropriate vitamin D levels were shown to be important in preventing the onset of CRC.

Apolipoprotein M could inhibit growth and metastasis of SMMC7721 cells via vitamin D receptor signaling

Objective: Hepatocellular carcinoma (HCC) is one of the most common malignant tumors with high mortality-to-incidence ratios. Apolipoprotein M (ApoM), a member of the apolipoprotein family, is mainly synthesized in the liver, whereas its role in HCC has not been elucidated. Here, we examined the effect of ApoM on the biological behavior of HCC cells and the possible mechanisms. Methods: We used CRISPR/Cas9 technology to knock out ApoM in SMMC7721 cells. Differentially expressed genes before and after ApoM knockout (KO) were analyzed by GeneChip microarrays and confirmed by qRT-PCR. Cell assays of proliferation, apoptosis, migration and invasion were performed in SMMC7721 cells, and the expression of epithelial-mesenchymal transition (EMT) markers was performed by western blot. And we performed functional recovery experiments by overexpressing vitamin D receptor (VDR) in SMMC7721. Results: The ApoM-KO SMMC7721 cell line was successfully constructed using the CRISPR/Cas9 technology. Our results showed that silencing ApoM suppressed apoptosis and promoted proliferation, migration, invasion and EMT of SMMC7721 cells. The microarray data revealed that a total of 1,868 differentially expressed genes were identified, including VDR. The qRT-PCR and western blot verification results demonstrated that knocking out ApoM could significantly reduce the expression of VDR. The functional recovery experiments indicated that VDR overexpression could offset the inhibition of cell apoptosis and the promotion of cell proliferation, migration, invasion and EMT caused by knocking out ApoM in SMMC7721 cells. Conclusion: ApoM could function as a tumor suppressor to inhibit the growth and metastasis of SMMC7721 cells via VDR signaling in HCC.

Activation of the vitamin D receptor transcription factor stimulates the growth of definitive erythroid progenitors

The pathways that regulate the growth of erythroid progenitors are incompletely understood. In a computational analysis of gene expression changes during erythroid ontogeny, the vitamin D receptor (Vdr) nuclear hormone receptor transcription factor gene was identified in fetal and adult stages, but not at the embryonic stage of development. Vdr was expressed in definitive erythroid (EryD) progenitors and was downregulated during their maturation. Activation of Vdr signaling by the vitamin D3 agonist calcitriol increased the outgrowth of EryD colonies from fetal liver and adult bone marrow, maintained progenitor potential, and delayed erythroid maturation, as revealed by clonogenic assays, suspension culture, cell surface phenotype, and gene expression analyses. The early (cKit⁺CD71^lo/neg), but not the late (cKit⁺CD71^hi), EryD progenitor subset of Lin^negcKit⁺ cells was responsive to calcitriol. Culture of cKit⁺CD71^lo/neg progenitors in the presence of both vitamin D3 and glucocorticoid receptor ligands resulted in an increase in proliferation that was at least additive compared with either ligand alone. Lentivirus shRNA-mediated knockdown of Vdr expression abrogated the stimulation of early erythroid progenitor growth by calcitriol. These findings suggest that Vdr has a cell-intrinsic function in early erythroid progenitors. Targeting of downstream components of the Vdr signaling pathway may lead to new approaches for the expansion of erythroid progenitors ex vivo.

Vitamin D Supplementation in Mechanically Ventilated Patients in the Medical Intensive Care Unit

BACKGROUND

The utility of vitamin D (VITD) supplementation during critical illness and whether it may alter outcomes, including mortality and ventilator-free days, is unclear. We performed a retrospective cohort study in a generalizable population to investigate this question.

METHODS

We included all mechanically ventilated adults admitted to the medical intensive care unit (ICU) service at a tertiary center from 2009 to 2012 who were in the ICU for at least 72 hours. Patients were grouped as having received or not received VITD at any time during the first 7 days of their ICU stay, and we adjusted for the following covariates with multivariable analyses: simplified acute physiology score, age, gender, admission diagnosis, race/ethnicity, admission season, admission day of the week, and VITD supplementation prior to admission.

RESULTS

Among the 610 included patients, 281 received VITD, and 329 did not. There were no differences in outcomes between these groups. However, we did find significantly more ventilator-free days (21.0±2.6 [adjusted mean days±standard error] vs 17.6±2.4, P=0.04) and ICU-free days (18.5±2.5 vs 16.3±2.3, P=0.03) in patients who were taking VITD prior to admission (n=91) vs those who were not (n=519). No patients who were taking VITD before admission died vs 34.5% of those who were not (estimated odds ratio=4.9×10^-7 , 95% CI=3.1×10^-7 to 7.5×10^-7 , P<0.0001).

CONCLUSION

These results suggest that VITD supplementation during critical illness may not provide benefit and that further research investigating potential supplementation in ambulatory patients at high risk of ICU admission (eg, severe underlying chronic disease) is warranted.

Vitamin D protects against diabetic nephropathy: Evidence-based effectiveness and mechanism

Vitamin D has been suggested to harbor multiple biological activities, among them the potential of vitamin D in the protection of diabetic nephropathy (DN) has attracted special attention. Both animal studies and clinical trials have documented an inverse correlation between low vitamin D levels and DN risk, and supplementation with vitamin D or its active derivatives has been demonstrated to improve endothelial cell injury, reduce proteinuria, attenuate renal fibrosis, and resultantly retard DN progression. Vitamin D exerts its pharmacological effects primarily via vitamin D receptor, whose activation inhibits the renin-angiotensin system, a key culprit for DN under hyperglycemia. The anti-DN benefit of vitamin D can be enhanced when administrated in combination with angiotensin converting enzyme inhibitors or angiotensin II receptor blockers. Mechanistic studies reveal that pathways relevant to inflammation participate in the pathogenesis of DN, however, consumption of vitamin D-related products negatively regulates inflammatory response at multiple levels, indicated by inhibiting macrophage infiltration, nuclear factor-kappa B (NF-κB) activation, and production of such inflammatory mediators as transforming growth factor-β(TGF-β), monocyte chemoattractant protein 1(MCP-1), and regulated upon activation normal T cell expressed and secreted protein(RANTES). The robust anti-inflammatory property of vitamin D-related products allows them with a promising renoprotective therapeutic option for DN. This review summarizes new advances in our understanding of vitamin D-related products in the DN management.

Vitamin D Deficiency as It Relates to Oral Immunity and Chronic Periodontitis

The biologically active form of vitamin D, 1,25 dihydroxyvitamin D (1,25(OH)2D) and its receptor, the vitamin D receptor (VDR), play roles in maintaining oral immunity and the integrity of the periodontium. Results of observational cross-sectional clinical studies investigating the association between vitamin D serum level and the incidence and severity of chronic periodontitis indicate that, perhaps owing to the immunomodulatory, anti-inflammatory, and antibacterial properties of 1,25(OH)2 D/VDR signalling, a sufficient serum level of vitamin D is necessary for the maintenance of periodontal health. In cases of established chronic periodontitis, vitamin D supplementation is associated with reduction in the severity of periodontitis. As cross-sectional studies provide only weak evidence for any causal association and therefore are of questionable value, either longitudinal cohort studies, case controlled studies, or randomized control trials are needed to determine whether or not deficiency of vitamin D is a risk factor for chronic periodontitis, and whether or not vitamin D supplementation adjunctive to standard periodontal treatment is in any way beneficial. In this article, we discuss the relationship between vitamin D, oral immunity and periodontal disease and review the rationale for using vitamin D supplementation to help maintain periodontal health and as an adjunct to standard periodontal treatment.

Calcitriol and Its Analogs Establish the Immunosuppressive Microenvironment That Drives Metastasis in 4T1 Mouse Mammary Gland Cancer

In our previous study, calcitriol and its analogs PRI-2191 and PRI-2205 stimulated 4T1 mouse mammary gland cancer metastasis. Therefore, we aimed to analyze the inflammatory response in 4T1-bearing mice treated with these compounds. Gene expression analysis of the splenocytes and regional lymph nodes demonstrated prevalence of the T helper lymphocytes (Th2) response with an increased activity of regulatory T (Treg) lymphocytes in mice treated with these compounds. We also observed an increased number of mature granulocytes and B lymphocytes and a decreased number of TCD4⁺, TCD4⁺CD25⁺, and TCD8⁺, as well as natural killer (NK) CD335⁺, cells in the blood of mice treated with calcitriol and its analogs. Among the splenocytes, we observed a significant decrease in NK CD335⁺ cells and an increase in TCD8⁺ cells. Calcitriol and its analogs decreased the levels of interleukin (IL)-1β and IL-10 and increased the level of interferon gamma (IFN-γ) in the plasma. In the tumor tissue, they caused an increase in the level of IL-10. Gene expression analysis of lung tissue demonstrated an increased level of osteopontin (Spp1) and transforming growth factor β (TGF-β) mRNA. The expression of Spp1 was also elevated in lymph nodes. Calcitriol and its analogs caused prevalence of tumor-conducive changes in the immune system of 4T1 tumor-bearing mice, despite the induction of some tumor-disadvantageous effects.

The Biological Activities of Vitamin D and Its Receptor in Relation to Calcium and Bone Homeostasis, Cancer, Immune and Cardiovascular Systems, Skin Biology, and Oral Health

Vitamin D plays an important role in calcium homeostasis and bone metabolism, with the capacity to modulate innate and adaptive immune function, cardiovascular function, and proliferation and differentiation of both normal and malignant keratinocytes. 1,25(OH)2D, the biologically active form of vitamin D, exerts most of its functions through the almost universally distributed nuclear vitamin D receptor (VDR). Upon stimulation by 1,25(OH)2D, VDR forms a heterodimer with the retinoid X receptor (RXR). In turn, VDR/RXR binds to DNA sequences termed vitamin D response elements in target genes, regulating gene transcription. In order to exert its biological effects, VDR signalling interacts with other intracellular signalling pathways. In some cases 1,25(OH)2D exerts its biological effects without regulating either gene expression or protein synthesis. Although the regulatory role of vitamin D in many biological processes is well documented, there is not enough evidence to support the therapeutic use of vitamin D supplementation in the prevention or treatment of infectious, immunoinflammatory, or hyperproliferative disorders. In this review we highlight the effects of 1,25(OH)2D on bone and calcium homeostasis, on cancer, and refer to its effects on the cardiovascular and immune systems.

Vitamin D-deficiency induces eosinophil spontaneous activation

Eosinophils (Eo) play a critical role in immunity and immune inflammation. The maintenance of Eo homeostasis is not fully understood yet. Vitamin D (VitD) is involved in the regulation of a large number of biochemical reactions. This study tests a hypothesis that VitD receptor (VDR) contributes to the homeostasis of Eos. In this study, EoL-1 cells (an Eo cell line) were cultured in the presence or absence of calcitriol. The Eo-mediators, including major basic protein (MBP), Eo peroxidase (EPX), Eo cationic protein (ECP) and Eo-derived neurotoxin (EDN), were assessed in the culture supernatant and in EoL-1 cells. We observed that, in a VitD deficient environment, EoL-1 cells produced high levels of the Eo-mediators, including MBP, EPX, ECP and EDN, which could be suppressed by the addition of calcitriol to the culture. EoL-1 cells expressed VitD receptor (VDR), which was up regulated by exposure to calcitriol. VDR formed complexes with the transcription factors of the Eo-mediators, which prevented the transcription factors to bind to the promoters of the Eo-mediators, and therefore prevented the Eo-mediated gene transcription. The Eo spontaneous activation was also found in the intestinal mucosa of VDR-deficient mice, in which the intestinal epithelial barrier dysfunction was observed. In conclusion, VDR contributes to the maintenance of the homeostasis of Eos by regulating the gene transcription of the Eo mediators. The VDR-deficiency is one of the causative factors inducing Eo spontaneous activation. This phenomenon may be taken into account in the management of the Eo-related diseases.

Vitamin D signaling in intestinal innate immunity and homeostasis

The lumen of the gut hosts a plethora of microorganisms that participate in food assimilation, inactivation of harmful particles and in vitamin synthesis. On the other hand, enteric flora, a number of food antigens, and toxins are capable of triggering immune responses causing inflammation, which, when unresolved, may lead to chronic conditions such as inflammatory bowel disease (IBD). It is important, therefore, to contain the gut bacteria within the lumen, control microbial load and composition, as well as ensure adequate innate and adaptive immune responses to pathogenic threats. There is growing evidence that vitamin D signaling has impacts on all these aspects of intestinal physiology, contributing to healthy enteric homeostasis. VD was first discovered as the curative agent for nutritional rickets, and its classical actions are associated with calcium absorption and bone health. However, vitamin D exhibits a number of extra-skeletal effects, particularly in innate immunity. Notably, it stimulates production of pattern recognition receptors, anti-microbial peptides, and cytokines, which are at the forefront of innate immune responses. They play a role in sensing the microbiota, in preventing excessive bacterial overgrowth, and complement the actions of vitamin D signaling in enhancing intestinal barrier function. Vitamin D also favours tolerogenic rather than inflammogenic T cell differentiation and function. Compromised innate immune function and overactive adaptive immunity, as well as defective intestinal barrier function, have been associated with IBD. Importantly, observational and intervention studies support a beneficial role of vitamin D supplementation in patients with Crohn's disease, a form of IBD. This review summarizes the effects of vitamin D signaling on barrier integrity and innate and adaptive immunity in the gut, as well as on microbial load and composition. Collectively, studies to date reveal that vitamin D signaling has widespread effects on gut homeostasis, and provide a mechanistic basis for potential therapeutic benefit of vitamin D supplementation in IBD.

A vitamin D receptor agonist converts CD4+ T cells to Foxp3+ regulatory T cells in patients with ulcerative colitis

One of the pathological features of ulcerative colitis (UC) is the dysfunction of immune regulatory T cells (Treg cells); the pathogenesis is unclear and needs to be further investigated. Vitamin D has immune regulatory functions. This study tests a hypothesis that vitamin D receptor (VDR) regulates Treg cell differentiation. Peripheral blood samples were collected from UC patients and healthy subjects. The correlation between VDR expression and T helper (Th)2 cell differentiation in peripheral CD4⁺ T cells was analyzed. We observed that the expression of VDR was lower, the expression of interleukin (IL)-4 was higher, in peripheral CD4⁺ T cells of UC patients than that in healthy controls. Naive CD4⁺ T cells from VDR deficient mice were prone to differentiating into Th2 cells, which could be adjusted by the presence of VDR agonists. The Th2 polarization status in the peripheral CD4⁺ T cells of UC patients could be converted to regulatory T cells in the culture in the presence of VDR agonists. In conclusion, the peripheral Th2 cells in UC patients can be converted to regulatory T cells by VDR agonists in the culture. The results suggest that administration of VDR agonists at proper dosages may improve the immunity of UC patients.

The Role of Vitamin D in the Immune System as a Pro-survival Molecule

PURPOSE

Vitamin D is a fascinating and attractive molecule that has gained particular attention in medicine in recent years. Its immunomodulatory and anti-inflammatory potential might resemble the activity of many nature-derived molecules (eg, flavonoids), but its role in biology was selected during a long evolutionary pathway to dampen the damaging effect of cell stress response and of the immune reaction. In this sense, this molecule can be considered an ancient hormone that serves, in its primary role, as a pro-survival agent. The goal of this review was to elucidate this topic.

METHODS

The article reviews current literature on the field, focusing on issues regarding the role of vitamin D in immunity.

FINDINGS

Vitamin D participates in the survival machinery used by the cell, and in particular it plays a major role in synchronizing calcium oscillatory signaling to allow cell autophagy or apoptosis during a stress response.

IMPLICATIONS

Vitamin D should be better highlighted in its molecular action and vitamin D receptor genomics to conceive a more suited therapeutic supplementation protocol in clinics.

Species-specific regulation of innate immunity by vitamin D signaling

While many global mechanisms of innate immune responses to pathogen threat are conserved over a vast range of species, the details of those responses and their regulation appear to be highly species-specific. An array of studies over recent years has revealed that hormonal vitamin D is an important regulator of innate immunity. In humans, the hormone-bound VDR directly induces the transcription of genes encoding antimicrobial peptides (AMPs), pattern recognition receptors and key cytokines implicated in innate immune responses. We find that the vitamin D response elements (VDREs) in a number of these human genes are highly conserved in a range of primates, but not present in rodent genes. Consistent with this, VDR target genes encoding AMPs human beta-defensin 2 (HBD2) and cathelicidin (CAMP) and the pattern recognition receptor NOD2 are induced by 1,25(OH)₂D in human cells of epithelial or myeloid origin but not similarly regulated in mouse cells. In addition, while conditioned media from human epithelial cells treated with 1,25(OH)₂D produced antimicrobial activity against E. coli and the lung pathogen Pseudomonas aeruginosa, no such activity was detected in conditioned media from comparable 1,25(OH)₂D-treated mouse epithelial cells. Given that other work has provided evidence that 1,25(OH)₂D does control innate immune responses in mouse models of disease, we discuss the species-specific similarities and differences in 1,25(OH)₂D-regulated innate immunity.

Protective links between vitamin D, inflammatory bowel disease and colon cancer

Vitamin D deficiency has been associated with a wide range of diseases and multiple forms of cancer including breast, colon, and prostate cancers. Relatively recent work has demonstrated vitamin D to be critical in immune function and therefore important in inflammatory diseases such as inflammatory bowel disease (IBD). Because vitamin D deficiency or insufficiency is increasingly prevalent around the world, with an estimated 30%-50% of children and adults at risk for vitamin D deficiency worldwide, it could have a significant impact on IBD. Epidemiologic studies suggest that low serum vitamin D levels are a risk factor for IBD and colon cancer, and vitamin D supplementation is associated with decreased colitis disease activity and/or alleviated symptoms. Patients diagnosed with IBD have a higher incidence of colorectal cancer than the general population, which supports the notion that inflammation plays a key role in cancer development and underscores the importance of understanding how vitamin D influences inflammation and its cancer-promoting effects. In addition to human epidemiological data, studies utilizing mouse models of colitis have shown that vitamin D is beneficial in preventing or ameliorating inflammation and clinical disease. The precise role of vitamin D on colitis is unknown; however, vitamin D regulates immune cell trafficking and differentiation, gut barrier function and antimicrobial peptide synthesis, all of which may be protective from IBD and colon cancer. Here we focus on effects of vitamin D on inflammation and inflammation-associated colon cancer and discuss the potential use of vitamin D for protection and treatment of IBD and colon cancer.

Calcitriol inhibits bleomycin-induced early pulmonary inflammatory response and epithelial-mesenchymal transition in mice

Early pulmonary inflammation and epithelial-mesenchymal transition (EMT) play important roles during lung fibrosis. Increasing evidence demonstrates that calcitriol, the active form of vitamin D3, has anti-inflammatory activities. The aim of this study was to investigate the effects of calcitriol on bleomycin (BLM)-induced early pulmonary inflammation and subsequent EMT. Mice were intratracheally injected with BLM (3.0mg/kg). In three calcitriol+BLM groups, mice were intraperitoneal (i.p.) injected with different doses of calcitriol (0.2, 1.0 or 5.0 μg/kg) daily, beginning at 48 h before BLM injection. Twenty-four hours, seven and fourteen days after BLM injection, pulmonary inflammation and EMT were evaluated. As expected, BLM-induced infiltration of inflammatory cells in the lungs was attenuated by calcitriol. BLM-induced pulmonary inflammatory cytokines were repressed by calcitriol. Moreover, BLM-induced nuclear translocation of nuclear factor kappa B (NF-κB) p65 was blocked by calcitriol. In addition, BLM-induced phosphorylation of pulmonary p38 MAPK and protein kinase B (Akt) was inhibited by calcitriol. Further analysis showed that BLM-induced α-smooth muscle actin (α-SMA), a marker for EMT in the lungs, was significantly attenuated by calcitriol. BLM-induced transforming growth factor-beta 1 (TGF-β1) up-regulation and Smad phosphorylation were attenuated by calcitriol. In conclusion, calcitriol inhibits BLM-induced early pulmonary inflammation and subsequent EMT.

The hormone-bound vitamin D receptor enhances the FBW7-dependent turnover of NF-κB subunits

Signaling by hormonal vitamin D, 1,25-dihydroxyvitamin D (1,25D) has attracted increasing interest because of its non-classical actions, particularly its putative anticancer properties and its role in controlling immune system function. Notably, the hormone-bound vitamin D receptor (VDR) suppresses signaling by pro-inflammatory NF-κB transcription factors, although the underlying mechanisms have remained elusive. Recently, the VDR was shown to enhance the turnover of the oncogenic transcription factor cMYC mediated by the E3 ligase and tumor suppressor FBW7. As FBW7 also controls the turnover of the p100 (NF-κB2) subunit of the family, we determined whether the 1,25D enhanced FBW7-dependent turnover of NF-κB subunits p100, p105 (NF-κB1) and p65 (RELA). Protein levels of all three subunits declined markedly in the presence of 1,25D in multiple cell lines in the absence of substantial changes in mRNA expression. The VDR coimmunoprecipitated with all three subunits, and 1,25D treatment accelerated subunit turnover in cycloheximide-treated cells. Importantly, we observed an association of FBW7 with p105 and p65, as well as p100, and knockdown of FBW7 eliminated 1,25D-dependent subunit turnover. Moreover, expression of NF-κB target genes was elevated in FBW7-depleted cells. These results reveal that 1,25D signaling suppresses NF-κB function by enhancing FBW7-dependent subunit turnover.

Vitamin D is significantly associated with total testosterone and sex hormone-binding globulin in Malaysian men

OBJECTIVE

Cross-sectional studies in the Caucasian population have shown a significant relationship between vitamin D and testosterone levels, but data in the Asian population are limited. This study aimed to determine the association between vitamin D and testosterone levels in Malaysian men.

METHODS

Chinese and Malay men (n = 382) aged 20 years or above residing in the Klang Valley, Malaysia were recruited. Their fasting blood was collected for serum testosterone, sex hormone-binding globulin (SHBG) and 25-hydroxyvitamin D (25(OH)D) assays. Relationship between 25(OH)D and testosterone levels was analyzed using multiple regression analysis. Testosterone and SHBG levels among subjects with different vitamin D status were compared using univariate analysis. Confounders such as age, ethnicity and body mass index (BMI) were adjusted.

RESULTS

25(OH)D was significantly and positively associated with total testosterone and SHBG levels before and after adjustment for age and ethnicity (p < 0.05). Only association with SHBG remained significant after further adjustment for BMI (p < 0.05). Total testosterone and SHBG values displayed an increasing trend from subjects with vitamin D deficiency to those with optimal level (p < 0.05). The trend was attenuated after adjustment for BMI (p > 0.05).

CONCLUSION

25(OH)D is significantly associated with total testosterone and SHBG in Malaysian men but this association is BMI-dependent.

Insights into genetic and epigenetic determinants with impact on vitamin d signaling and cancer association studies: the case of thyroid cancer

Vitamin D is a key regulator of calcium metabolism and has been implicated as a cancer preventive agent. However, clinical studies have revealed conflicting results on its cancer preventive properties, attributed in part to multiple metabolic and regulatory factors susceptible to affect individual responses to exogenous vitamin D. Vitamin D is obtained from dietary sources and sun exposure, which depends on numerous parameters such as skin type, latitude, and lifestyle factors. Focusing on thyroid cancer (TC), we document that genetic and epigenetic determinants can greatly impact individual response to vitamin D and may outweigh the classical clinical correlative studies that focus on sun exposure/dietary intake factors. In particular, genetic determinants innate to host intrinsic metabolic pathways such as highly polymorphic cytochromes P450s responsible for the metabolic activation of vitamin D are expressed in many organs, including the thyroid gland and can impact vitamin D interaction with its nuclear receptor (VDR) in thyroid tissue. Moreover, downstream regulatory pathways in vitamin D signaling as well as VDR are also subject to wide genetic variability among human populations as shown by genome-wide studies. These genetic variations in multiple components of vitamin D pathways are critical determinants for the revaluation of the potential preventive and anticancer properties of vitamin D in TC.

Fundamentals of vitamin D hormone-regulated gene expression

Initial research focused upon several known genetic targets provided early insight into the mechanism of action of the vitamin D hormone (1,25-dihydroxyvitamin D3 (1,25(OH)2D3)). Recently, however, a series of technical advances involving the coupling of chromatin immunoprecipitation (ChIP) to unbiased methodologies that initially involved tiled DNA microarrays (ChIP-chip analysis) and now Next Generation DNA Sequencing techniques (ChIP-seq analysis) has opened new avenues of research into the mechanisms through which 1,25(OH)2D3 regulates gene expression. In this review, we summarize briefly the results of this early work and then focus on more recent studies in which ChIP-chip and ChIP-seq analyses have been used to explore the mechanisms of 1,25(OH)2D3 action on a genome-wide scale providing specific target genes as examples. The results of this work have advanced our understanding of the mechanisms involved at both genetic and epigenetic levels and have revealed a series of new principles through which the vitamin D hormone functions to control the expression of genes. This article is part of a Special Issue entitled '16th Vitamin D Workshop'.

Modeling vitamin D actions in triple negative/basal-like breast cancer

Breast cancer is a heterogeneous disease with six molecularly defined subtypes, the most aggressive of which are triple negative breast cancers that lack expression of estrogen receptor (ER) and progesterone receptor (PR) and do not exhibit amplification of the growth factor receptor HER2. Triple negative breast cancers often exhibit basal-like gene signatures and are enriched for CD44+ cancer stem cells. In this report we have characterized the molecular actions of the VDR in a model of triple negative breast cancer. Estrogen independent, invasive mammary tumor cell lines established from wild-type (WT) and VDR knockout (VDRKO) mice were used to demonstrate that VDR is necessary for 1,25-dihydroxyvitamin D3 (1,25D) mediated anti-cancer actions in vitro and to identify novel targets of this receptor. Western blotting confirmed differential VDR expression and demonstrated the lack of ER, PR and Her2 in these cell lines. Re-introduction of human VDR (hVDR) into VDRKO cells restored the anti-proliferative actions of 1,25D. Genomic profiling demonstrated that 1,25D failed to alter gene expression in KO240 cells whereas major changes were observed in WT145 cells and in KO clones stably expressing hVDR (KO(hVDR) cells). With a 2-fold cutoff, 117 transcripts in WT145 cells and 197 transcripts in the KO(hVDR) clones were significantly altered by 1,25D. Thirty-five genes were found to be commonly regulated by 1,25D in all VDR-positive cell lines. Of these, we identified a cohort of four genes (Plau, Hbegf, Postn, Has2) that are known to drive breast cancer invasion and metastasis whose expression was markedly down regulated by 1,25D. These data support a model whereby 1,25D coordinately suppresses multiple proteins that are required for survival of triple-negative/basal-like breast cancer cells. Since studies have demonstrated a high prevalence of vitamin D deficiency in women with basal-like breast cancer, correction of vitamin D deficiency in these women represents a reasonable, but as yet untested, strategy to delay recurrence and extend survival. This article is part of a Special Issue entitled '16th Vitamin D Workshop'.