Novel role of the vitamin D receptor in maintaining the integrity of the intestinal mucosal barrier

Role of vitamin D on gut microbiota in cystic fibrosis

This review explores the potential for vitamin D to favorably alter the gut microbiota, given emerging evidence of the role of vitamin D in controlling mucosal inflammation in the gut. It will focus on cystic fibrosis (CF) patients, a population with both vitamin D deficiency due to gut malabsorption and an altered gut microbiota composition. Recent evidence shows that vitamin D acts to maintain the integrity of the gut mucosal barrier by enhancement of intercellular junctions that control mucosal permeability and reduction of pro-inflammatory cytokines such as IL-8. In addition, vitamin D receptor-mediated signaling has been shown to inhibit inflammation-induced apoptosis of intestinal epithelial cells. As a result of these effects on the intestinal mucosa, maintenance of sufficient vitamin D status may be essential for the development of a healthy gut microbiota, particularly in conditions defined by chronic mucosal inflammation such as CF. We hypothesize here that high dose vitamin D may be used to favorably manipulate the aberrant mucosa seen in patients with CF. This may result in improved clinical outcomes in association with a low inflammatory environment that allows beneficial bacteria to outcompete opportunistic pathogens. Current evidence is sparse but encouraging, and additional evidence is needed to establish vitamin D as a therapeutic approach for gut microbiota modification.

Influence of Microbiota on Intestinal Immune System in Ulcerative Colitis and Its Intervention

Ulcerative colitis (UC) is an inflammatory bowel disease (IBD) with chronic and recurrent characteristics caused by multiple reasons. Although the pathogenic factors have not been clarified yet, recent studies have demonstrated that intestinal microbiota plays a major role in UC, especially in the immune system. This review focuses on the description of several major microbiota communities that affect UC and their interactions with the host. In this review, eight kinds of microbiota that are highly related to IBD, including Faecalibacterium prausnitzii, Clostridium clusters IV and XIVa, Bacteroides, Roseburia species, Eubacterium rectale, Escherichia coli, Fusobacterium, and Candida albicans are demonstrated on the changes in amount and roles in the onset and progression of IBD. In addition, potential therapeutic targets for UC involved in the regulation of microbiota, including NLRPs, vitamin D receptor as well as secreted proteins, are discussed in this review.

Vitamin D Axis in Inflammatory Bowel Diseases: Role, Current Uses and Future Perspectives

Increasing evidence supports the concept that the vitamin D axis possesses immunoregulatory functions, with vitamin D receptor (VDR) status representing the major determinant of vitamin D’s pleiotropic effects. Vitamin D promotes the production of anti-microbial peptides, including β-defensins and cathelicidins, the shift towards Th2 immune responses, and regulates autophagy and epithelial barrier integrity. Impairment of vitamin D-mediated pathways are associated with chronic inflammatory conditions, including inflammatory bowel diseases (IBD). Interestingly, inhibition of vitamin D pathways results in dysbiosis of the gut microbiome, which has mechanistically been implicated in the development of IBD. Herein, we explore the role of the vitamin D axis in immune-mediated diseases, with particular emphasis on its interplay with the gut microbiome in the pathogenesis of IBD. The potential clinical implications and therapeutic relevance of this interaction will also be discussed, including optimizing VDR function, both with vitamin D analogues and probiotics, which may represent a complementary approach to current IBD treatments.

Anti-inflammatory effect of glucose-lysine Maillard reaction products on intestinal inflammation model in vivo

Inflammatory bowel diseases (IBDs) are chronic disorders that are characterized by intestinal epithelial inflammation and injury. Currently, the most employed therapies are antibiotics and anti-inflammatory drugs; however, the side effects limit long-term effectiveness. We evaluated the impact of glucose-lysine Maillard reaction products (Glc-Lys MRPs) on colitis, induced in rats by an administration of 5% dextran sulfate sodium (DSS) in drinking water. Glc-Lys MRPs ameliorate DSS-induced colitis, as determined by a decrease in disease index activity, colon weight/length ratio, nitric oxide levels in serum, recovery of body weight loss, colon length and serum lysozyme levels. Furthermore, Glc-Lys MRPs increase the glutathione content and the activity of glutathione peroxidase, superoxide dismutase and catalase, and inhibit lipid peroxidation and myeloperoxidase activity in colon tissues. In particular, Glc-Lys MRPs suppress the mRNA level of the inflammatory cytokines and nuclear factor-κB in colon tissues. This study suggests the potential of Glc-Lys MRPs in preventing or treating IBDs.

The endocrine vitamin D system in the gut

The active vitamin D metabolite 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) has important regulatory actions in the gut through endocrine and probably also intracrine, autocrine and paracrine mechanisms. By activating the vitamin D receptor (VDR), which is expressed at a high level in the small intestine and colon, 1,25(OH)₂D₃ regulates numerous genes that control gut physiology and homeostasis. 1,25(OH)₂D₃ is a major responsible for epithelial barrier function and calcium and phosphate absorption, and the host's defense against pathogens and the inflammatory response by several types of secretory and immune cells. Moreover, recent data suggest that 1,25(OH)₂D₃ has a regulatory effect on the gut microbiota and stromal fibroblasts. Many studies have linked vitamin D deficiency to inflammatory bowel diseases (ulcerative colitis and Crohn's disease) and to an increased risk of colorectal cancer, and the possible use of VDR agonists to prevent or treat these diseases is receiving increasing interest.

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.

High-dose vitamin D3 supplementation decreases the number of colonic CD103+ dendritic cells in healthy subjects

PURPOSE

Vitamin D may induce tolerance in the intestinal immune system and has been shown to regulate the phenotype of tolerogenic intestinal dendritic cells (DCs) in vitro. It is unknown whether vitamin D supplementation affects human intestinal DCs in vivo, and we aimed to investigate the tolerability and effect on intestinal CD103⁺DCs of high-dose vitamin D₃ treatment in healthy subjects.

METHODS

Ten healthy subjects received a total of 480,000 IU oral vitamin D₃ over 15 days and colonic biopsies were obtained before and after intervention by endoscopy. Lamina propria mononuclear cells (LPMCs) were isolated from the biopsies, stained with DC surface markers and analysed with flow cytometry. Snap-frozen biopsies were analysed with qPCR for DC and regulatory T cell-related genes.

RESULTS

No hypercalcemia or other adverse events occurred in the test subjects. Vitamin D decreased the number of CD103⁺ DCs among LPMCs (p = 0.006). Furthermore, vitamin D induced mRNA expression of TGF-β (p = 0.048), TNF-α (p = 0.006) and PD-L1 (p = 0.02) and tended to induce IL-10 expression (p = 0.06). Multivariate factor analysis discriminated between pre- and post-vitamin D supplementation with a combined increased qPCR expression of PD1, PD-L1, TGF-β, IL-10, CD80, CD86, FOXP3, NFATc2 and cathelicidin.

CONCLUSION

High-dose vitamin D supplementation is well tolerated by healthy subjects and has a direct effect on the CD103⁺ DCs, local cytokine and surface marker mRNA expression in the colonic mucosa, suggestive of a shift towards a more tolerogenic milieu.

Vitamin D insufficiency in the first 6 months of infancy and challenge-proven IgE-mediated food allergy at 1 year of age: a case-cohort study

BACKGROUND

Ecological evidence suggests vitamin D insufficiency (VDI) due to lower ambient ultraviolet radiation (UVR) exposure may be a risk factor for IgE-mediated food allergy. However, there are no studies relating directly measured VDI during early infancy to subsequent challenge-proven food allergy.

OBJECTIVE

To prospectively investigate the association between VDI during infancy and challenge-proven food allergy at 1 year.

METHODS

In a birth cohort (n = 1074), we used a case-cohort design to compare 25-hydroxyvitamin D₃ (25(OH)D₃ ) levels among infants with food allergy vs a random subcohort (n = 274). The primary exposures were VDI (25(OH)D₃ <50 nM) at birth and 6 months of age. Ambient UVR and time in the sun were combined to estimate UVR exposure dose. IgE-mediated food allergy status at 1 year was determined by formal challenge. Binomial regression was used to examine associations between VDI, UVR exposure dose and food allergy and investigate potential confounding.

RESULTS

Within the random subcohort, VDI was present in 45% (105/233) of newborns and 24% (55/227) of infants at 6 months. Food allergy prevalence at 1 year was 7.7% (61/786), and 6.5% (53/808) were egg-allergic. There was no evidence of an association between VDI at either birth (aRR 1.25, 95% CI 0.70-2.22) or 6 months (aRR 0.93, 95% CI 0.41-2.14) and food allergy at 1 year.

CONCLUSIONS

There was no evidence that VDI during the first 6 months of infancy is a risk factor for food allergy at 1 year of age. These findings primarily relate to egg allergy, and larger studies are required.

Extraskeletal actions of vitamin D

The vitamin D receptor (VDR) is found in nearly all, if not all, cells in the body. The enzyme that produces the active metabolite of vitamin D and ligand for VDR, namely CYP27B1, likewise is widely expressed in many cells of the body. These observations indicate that the role of vitamin D is not limited to regulation of bone and mineral homeostasis, as important as that is. Rather, the study of its extraskeletal actions has become the major driving force behind the significant increase in research articles on vitamin D published over the past several decades. A great deal of information has accumulated from cell culture studies, in vivo animal studies, and clinical association studies that confirms that extraskeletal effects of vitamin D are truly widespread and substantial. However, randomized, placebo-controlled clinical trials, when done, have by and large not produced the benefits anticipated by the in vitro cell culture and in vivo animal studies. In this review, I will examine the role of vitamin D signaling in a number of extraskeletal tissues and assess the success of translating these findings into treatments of human diseases affecting those extracellular tissues.

Nutrition meets the microbiome: micronutrients and the microbiota

There is increasing evidence that food is an important factor that influences and shapes the composition and configuration of the gut microbiota. Most studies have focused on macronutrients (fat, carbohydrate, protein) in particular and their effects on the gut microbiota. Although the microbiota can synthesize different water-soluble vitamins, the effects of vitamins synthesized within the microbiota on systemic vitamin status are unclear. Few studies exist on the shuttling of vitamins between the microbiota and intestine and the impact of luminal vitamins on the microbiota. Studying the interactions between vitamins and the microbiota may help to understand the effects of vitamins on the barrier function and immune system of the intestinal tract. Furthermore, understanding the impact of malnutrition, particularly low micronutrient supply, on microbiota development, composition, and metabolism may help in implementing new strategies to overcome the deleterious effects of malnutrition on child development. This article reviews data on the synthesis of different micronutrients and their effects on the human microbiota, and further discusses the consequences of malnutrition on microbiota composition.

Modulation of inflammatory and immune responses by vitamin D

Vitamin D (VitD) is a prohormone most noted for the regulation of calcium and phosphate levels in circulation, and thus of bone metabolism. Inflammatory and immune cells not only convert inactive VitD metabolites into calcitriol, the active form of VitD, but also express the nuclear receptor of VitD that modulates differentiation, activation and proliferation of these cells. In vitro, calcitriol upregulates different anti-inflammatory pathways and downregulates molecules that activate immune and inflammatory cells. Administration of VitD has beneficial effects in a number of experimental models of autoimmune disease. Epidemiologic studies have indicated that VitD insufficiency is frequently associated with immune disorders and infectious diseases, exacerbated by increasing evidence of suboptimal VitD status in populations worldwide. To date, however, most interventional studies in human inflammatory and immune diseases with VitD supplementation have proven to be inconclusive. One of the reasons could be that the main VitD metabolite measured in these studies was the 25-hydroxyVitD (25OHD) rather than its active form calcitriol. Although our knowledge of calcitriol as modulator of immune and inflammatory reactions has dramatically increased in the past decades, further in vivo and clinical studies are needed to confirm the potential benefits of VitD in the control of immune and inflammatory conditions.

Vitamin D/VDR, Probiotics, and Gastrointestinal Diseases

Vitamin D is an important factor in regulating inflammation, immune responses, and carcinoma inhibition via action of its receptor, vitamin D receptor (VDR). Recent studies have demonstrated the role of vitamin D/VDR in regulating host-bacterial interactions. Probiotics are beneficial bacteria with the power of supporting or favoring life on the host. In the current review, we will discuss the recent progress on the roles of vitamin D/VDR in gut microbiome and inflammation. We will summarize evidence of probiotics in modulating vitamin D/VDR and balancing gut microbiota in health and gastrointestinal diseases. Moreover, we will review the clinical application of probiotics in prevention and therapy of IBD or colon cancer. Despite of the gains, there remain several barriers to advocate broad use of probiotics in clinical therapy. We will also discuss the limits and future direction in scientific understanding of probiotics, vitamin D/VDR, and host responses.

Vitamin D Receptor Level in Biopsy Specimen of Patients with Ulcerative Colitis: Results from a Center in Western Anatolia

BACKGROUND

Ulcerative colitis (UC) is a chronic, inflammatory bowel diseases characterized by uncontrolled inflammatory condition of the colon and rectal mucosa marked by recurrent periods of remission and exacerbation. Vitamin D receptor (VDR) is a member of the steroid receptor family that mediates the effects of vitamin D by regulating transcription of multiple cellular genes. We aimed to evaluate vitamin d receptor level in biopsy specimen of patients with UC in this study.

METHODS

VDR levels were retrospectively studied in colon biopsy specimens of UC patients. The Spearman's rho correlation analysis, The Kolmogorov-Smirnov, Mann Whitney U, and chi-square tests were used for statistical analysis. The p values below 0.05 were considered statistically significant.

RESULTS

Study included 112 UC patients (65 male and 47 female) and 30 controls (19 female and 11 male) who had normal results in biopsy examinations carried out due to various reasons. VDR levels of UC patients were statistically lower than control subjects, and was not associated with duration of the disease and place of involvement.

CONCLUSIONS

VDR is an important receptor in the pathogenesis of UC, and optimizing vitamin D levels could have a therapeutic role in UC.

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.

Maternal/neonatal vitamin D deficiency: a new risk factor for necrotizing enterocolitis in preterm infants?

OBJECTIVE

The objective of the study was to investigate the possible association between maternal/neonatal 25-hydroxy vitamin D (25-OHD) levels and development of necrotizing enterocolitis (NEC).

STUDY DESIGN

One hundred and forty-five preterm infants ⩽36 weeks of gestation were enrolled. 25-OHD levels were determined in maternal/neonatal blood samples that were obtained at the time of admission to the neonatal intensive care unit.

RESULTS

Of the 145 enrolled patients, 26 (18%) developed NEC. Maternal/neonatal 25-OHD levels in the NEC group were significantly lower than those of the no-NEC group (P=0.001 and 0.004, respectively). In univariate logistic regression analysis, both maternal/neonatal vitamin D levels were a significant predictor of NEC (odds ratio (OR): 0.92 and 0.89; P<0.001 and P<0.005, respectively). However, multivariate logistic regression analysis revealed that only maternal vitamin D level was a significant predictor of NEC (OR: 0.86, P<0.0009).

CONCLUSION

This is the first study to propose a possible association between maternal/neonatal 25-OHD levels and subsequent development of NEC in preterm infants.

Vitamin D Receptor-Dependent Signaling Protects Mice From Dextran Sulfate Sodium-Induced Colitis

Low vitamin D status potentiates experimental colitis, but the vitamin D-responsive cell in colitis has not been defined. We hypothesized that vitamin D has distinct roles in colonic epithelial cells and in nonepithelial cells during colitis. We tested this hypothesis by using mice with vitamin D receptor (VDR) deletion from colon epithelial cells (CEC-VDRKO) or nonintestinal epithelial cells (NEC-VDRKO). Eight-week-old mice were treated with 1.35% dextran sulfate sodium (DSS) for 5 days and then euthanized 2 or 10 days after removal of DSS. DSS induced body weight loss and increased disease activity index and spleen size. This response was increased in NEC-VDRKO mice but not CEC-VDRKO mice. DSS-induced colon epithelial damage and immune cell infiltration scores were increased in both mouse models. Although the epithelium healed between 2 and 10 days after DSS administration in control and CEC-VDRKO mice, epithelial damage remained high in NEC-VDRKO mice 10 days after removal of DSS, indicating delayed epithelial healing. Gene expression levels for the proinflammatory, M1 macrophage (Mɸ) cytokines tumor necrosis factor-α, nitric oxide synthase 2, and interleukin-1β were significantly elevated in the colon of NEC-VDRKO mice at day 10. In vitro experiments in murine peritoneal Mɸs demonstrated that 1,25 dihydroxyvitamin D directly inhibited M1 polarization, facilitated M2 polarization, and regulated Mɸ phenotype switching toward the M2 and away from the M1 phenotype. Our data revealed unique protective roles for vitamin D signaling during colitis in the colon epithelium as well as nonepithelial cells in the colon microenvironment (i.e., modulation of Mɸ biology).

Vitamin D treatment modulates immune activation in cystic fibrosis

Persistent inflammatory response in cystic fibrosis (CF) airways is believed to play a central role in the progression of lung damage. Anti-inflammatory treatment may slow lung disease progression, but adverse side effects have limited its use. Vitamin D has immunoregulatory properties. We randomized 16 CF patients to receive vitamin D2, vitamin D3 or to serve as controls, and investigated the effect of vitamin D supplementation on soluble immunological parameters, myeloid dendritic cells (mDCs) and T cell activation. Three months of vitamin D treatment were followed by two washout months. Vitamin D status at baseline was correlated negatively with haptoglobin, erythrocyte sedimentation rate and immunoglobulin A concentration. Total vitamin D dose per kg bodyweight correlated with the down-modulation of the co-stimulatory receptor CD86 on mDCs. Vitamin D treatment was associated with reduced CD279 (PD-1) expression on CD4⁺ and CD8⁺ T cells, as well as decreased frequency of CD8⁺ T cells co-expressing the activation markers CD38 and human leucocyte antigen D-related (HLA-DR) in a dose-dependent manner. There was a trend towards decreased mucosal-associated invariant T cells (MAIT) cell frequency in patients receiving vitamin D and free serum 25-hydroxyvitamin D (free-s25OHD) correlated positively with CD38 expression by these cells. At the end of intervention, the change in free-s25OHD was correlated negatively with the change in CD279 (PD-1) expression on MAIT cells. Collectively, these data indicate that vitamin D has robust pleiotropic immunomodulatory effects in CF. Larger studies are needed to explore the immunomodulatory treatment potential of vitamin D in CF in more detail.

Leaky Gut As a Danger Signal for Autoimmune Diseases

The intestinal epithelial lining, together with factors secreted from it, forms a barrier that separates the host from the environment. In pathologic conditions, the permeability of the epithelial lining may be compromised allowing the passage of toxins, antigens, and bacteria in the lumen to enter the blood stream creating a “leaky gut.” In individuals with a genetic predisposition, a leaky gut may allow environmental factors to enter the body and trigger the initiation and development of autoimmune disease. Growing evidence shows that the gut microbiota is important in supporting the epithelial barrier and therefore plays a key role in the regulation of environmental factors that enter the body. Several recent reports have shown that probiotics can reverse the leaky gut by enhancing the production of tight junction proteins; however, additional and longer term studies are still required. Conversely, pathogenic bacteria that can facilitate a leaky gut and induce autoimmune symptoms can be ameliorated with the use of antibiotic treatment. Therefore, it is hypothesized that modulating the gut microbiota can serve as a potential method for regulating intestinal permeability and may help to alter the course of autoimmune diseases in susceptible individuals.

Vitamin D3 induces vitamin D receptor and HDAC11 binding to relieve the promoter of the tight junction proteins

Intestinal epithelial barrier dysfunction and vitamin D (VitD)-deficiency play a critical role in a large number of diseases. The histone deacetylases (HDAC) are associated with a large number of immune diseases. This study tests a hypothesis that the interaction between VitD and HDAC is associated with the regulation of epithelial barrier functions. In this study, human intestinal epithelial cell line, T84 cells, was cultured into monolayers to be used as a model to test the epithelial barrier functions. We observed that in a VitD-deficient environment, the T84 monolayer barrier function was compromised. Exposure to calcitriol (the active form of VitD3) in the culture increased the expression of VitD receptor (VDR) in T84 cells. In a VitD-sufficient environment, VDR formed a complex with histone deacetylase-11 (HDAC11); the complex was markedly decreased in a VitD-deficient environment. We also observed that significantly more binding of HDAC11 to the promoter of the tight junction proteins inhibit the gene transcription activities of these loci in the VitD-deficient environment, which were abolished by the presence of calcitriol in the culture. In conclusion, the interaction between VDR and HDAC11 plays a crucial role in the maintenance of the epithelial barrier integrity.

Gut microbiota interactions with the immunomodulatory role of vitamin D in normal individuals

BACKGROUND

Due to immunomodulatory properties, vitamin D status has been implicated in several diseases beyond the skeletal disorders. There is evidence that its deficiency deteriorates the gut barrier favoring translocation of endotoxins into the circulation and systemic inflammation. Few studies investigated whether the relationship between vitamin D status and metabolic disorders would be mediated by the gut microbiota composition.

OBJECTIVE

We examined the association between vitamin D intake and circulating levels of 25(OH)D with gut microbiota composition, inflammatory markers and biochemical profile in healthy individuals.

METHODS

In this cross-sectional analysis, 150 young healthy adults were stratified into tertiles of intake and concentrations of vitamin D and their clinical and inflammatory profiles were compared. The DESeq2 was used for comparisons of microbiota composition and the log2 fold changes (log2FC) represented the comparison against the reference level. The association between 25(OH)D and fecal microbiota (16S rRNA sequencing, V4 region) was tested by multiple linear regression.

RESULTS

Vitamin D intake was associated with its concentration (r=0.220, p=0.008). There were no significant differences in clinical and inflammatory variables across tertiles of intake. However, lipopolysaccharides increased with the reduction of 25(OH)D (p-trend <0.05). Prevotella was more abundant (log2FC 1.67, p<0.01), while Haemophilus and Veillonella were less abundant (log2FC -2.92 and -1.46, p<0.01, respectively) in the subset with the highest vitamin D intake (reference) than that observed in the other subset (first plus second tertiles). PCR (r=-0.170, p=0.039), E-selectin (r=-0.220, p=0.007) and abundances of Coprococcus (r=-0.215, p=0.008) and Bifdobacterium (r=-0.269, p=0.001) were inversely correlated with 25(OH)D. After adjusting for age, sex, season and BMI, 25(OH)D maintained inversely associated with Coprococcus (β=-9.414, p=0.045) and Bifdobacterium (β=-1.881, p=0.051), but significance disappeared following the addition of inflammatory markers in the regression models.

CONCLUSION

The role of vitamin D in the maintenance of immune homeostasis seems to occur in part by interacting with the gut microbiota. The attenuation of association of bacterial genera by inflammatory markers suggests that inflammation participate in part in the relationship between the gut microbiota and vitamin D concentration. Studies with appropriate design are necessary to address hypothesis raised in the current study.

The effect of polymeric formula on enterocyte differentiation

Exclusive enteral nutrition is established as an initial therapy to induce remission in active Crohn's disease (CD), especially in children, but the mechanisms of action of this therapy are yet to be fully defined. Intestinal alkaline phosphatase (IAP), a recognised marker of enterocyte differentiation, is implicated in the innate gut immune response to enteric pathogens. Using the Caco-2 human adenocarcinoma cell line, this study showed that the incubation of human cells with a polymeric formula (PF) resulted in a dose-dependent increase in the expression of IAP on the cell surface. While further investigation is required to determine the pathway(s) involved, this finding suggests that cell surface-associated IAP may be an aspect of the gut's innate immune response to pathogenic bacteria that is strengthened by PF in the setting of CD.

Experimental study on 1,25(OH)2 D3 amelioration of oral lichen planus through regulating NF-κB signaling pathway

OBJECTIVE

To explore the protective function of vitamin D (VD)/vitamin D receptor (VDR) on the development of oral lichen planus (OLP) and elaborate the underling mechanism of it.

METHODS

H&E staining, myeloid peroxidase (MPO) assays, quantitative PCR (qPCR), Western blotting, and Elisa were used to test the human biopsies and serum. QPCR, Western blotting, Elisa, and siRNA transfection were also performed in LPS-induced keratinocytes to observe the functions of vitamin D and VDR.

RESULTS

The lack of VDR in the diseased biopsies from OLP patients was associated with activated helper T-cell type 1 (Th1)-driven inflammatory response. Importantly, the status of serum 25-hydroxyvitamin D of OLP patients was reduced consistently. In a cultured cell model, 1,25(OH)₂ D₃ could downregulate excessive production of pro-inflammatory factors induced by lipopolysaccharide (LPS) in keratinocyte HaCat cells. Mechanistically, even though LPS-induced cytokines in keratinocytes were inhibited both by nuclear factor-κB (NF-κB) inhibitor and by activator protein 1 (AP-1) inhibitor, VDR-dependent 1,25(OH)₂ D₃ blocked the activation of phosphorylated-NF-κB p65 rather than c-Jun/c-Fos in the presence of LPS stimulation.

CONCLUSION

These results suggest that 1,25(OH)₂ D₃ plays an anti-inflammatory role in OLP by mediating NF-κB signaling pathway but not AP-1 signaling pathway with a VDR-dependent manner, predicting vitamin D supplement may be a potential strategy for the OLP management.

Molecular pathways driving disease-specific alterations of intestinal epithelial cells

Due to the fact that chronic inflammation as well as tumorigenesis in the gut is crucially impacted by the fate of intestinal epithelial cells, our article provides a comprehensive overview of the composition, function, regulation and homeostasis of the gut epithelium. In particular, we focus on those aspects which were found to be altered in the context of inflammatory bowel diseases or colorectal cancer and also discuss potential molecular targets for a disease-specific therapeutic intervention.

Computational methods using genome-wide association studies to predict radiotherapy complications and to identify correlative molecular processes

The biological cause of clinically observed variability of normal tissue damage following radiotherapy is poorly understood. We hypothesized that machine/statistical learning methods using single nucleotide polymorphism (SNP)-based genome-wide association studies (GWAS) would identify groups of patients of differing complication risk, and furthermore could be used to identify key biological sources of variability. We developed a novel learning algorithm, called pre-conditioned random forest regression (PRFR), to construct polygenic risk models using hundreds of SNPs, thereby capturing genomic features that confer small differential risk. Predictive models were trained and validated on a cohort of 368 prostate cancer patients for two post-radiotherapy clinical endpoints: late rectal bleeding and erectile dysfunction. The proposed method results in better predictive performance compared with existing computational methods. Gene ontology enrichment analysis and protein-protein interaction network analysis are used to identify key biological processes and proteins that were plausible based on other published studies. In conclusion, we confirm that novel machine learning methods can produce large predictive models (hundreds of SNPs), yielding clinically useful risk stratification models, as well as identifying important underlying biological processes in the radiation damage and tissue repair process. The methods are generally applicable to GWAS data and are not specific to radiotherapy endpoints.

Diet as a Trigger or Therapy for Inflammatory Bowel Diseases

The most common question asked by patients with inflammatory bowel disease (IBD) is, "Doctor, what should I eat?" Findings from epidemiology studies have indicated that diets high in animal fat and low in fruits and vegetables are the most common pattern associated with an increased risk of IBD. Low levels of vitamin D also appear to be a risk factor for IBD. In murine models, diets high in fat, especially saturated animal fats, also increase inflammation, whereas supplementation with omega 3 long-chain fatty acids protect against intestinal inflammation. Unfortunately, omega 3 supplements have not been shown to decrease the risk of relapse in patients with Crohn's disease. Dietary intervention studies have shown that enteral therapy, with defined formula diets, helps children with Crohn's disease and reduces inflammation and dysbiosis. Although fiber supplements have not been shown definitively to benefit patients with IBD, soluble fiber is the best way to generate short-chain fatty acids such as butyrate, which has anti-inflammatory effects. Addition of vitamin D and curcumin has been shown to increase the efficacy of IBD therapy. There is compelling evidence from animal models that emulsifiers in processed foods increase risk for IBD. We discuss current knowledge about popular diets, including the specific carbohydrate diet and diet low in fermentable oligo-, di-, and monosaccharides and polyols. We present findings from clinical and basic science studies to help gastroenterologists navigate diet as it relates to the management of IBD.

Mucosal Ecological Network of Epithelium and Immune Cells for Gut Homeostasis and Tissue Healing

The intestinal epithelial barrier includes columnar epithelial, Paneth, goblet, enteroendocrine, and tuft cells as well as other cell populations, all of which contribute properties essential for gastrointestinal homeostasis. The intestinal mucosa is covered by mucin, which contains antimicrobial peptides and secretory IgA and prevents luminal bacteria, fungi, and viruses from stimulating intestinal immune responses. Conversely, the transport of luminal microorganisms-mediated by M, dendritic, and goblet cells-into intestinal tissues facilitates the harmonization of active and quiescent mucosal immune responses. The bacterial population within gut-associated lymphoid tissues creates the intratissue cohabitations for harmonized mucosal immunity. Intermolecular and intercellular communication among epithelial, immune, and mesenchymal cells creates an environment conducive for epithelial regeneration and mucosal healing. This review summarizes the so-called intestinal mucosal ecological network-the complex but vital molecular and cellular interactions of epithelial mesenchymal cells, immune cells, and commensal microbiota that achieve intestinal homeostasis, regeneration, and healing.

Nutrition and IBD: Malnutrition and/or Sarcopenia? A Practical Guide

Malnutrition is a major complication of inflammatory bowel disease (IBD). This mini review is focusing on main determinants of malnutrition in IBD, the most important components of malnutrition, including lean mass loss and sarcopenia, as an emerging problem. Each one of these components needs to be well considered in a correct nutritional evaluation of an IBD patient in order to build a correct multidisciplinary approach. The review is then focusing on possible instrumental and clinical armamentarium for the nutritional evaluation.

Vitamin D receptor is a novel transcriptional regulator for Axin1

BACKGROUND

Axin1 is a scaffold protein in the β-catenin destruction complex, which, if disrupted, contributes to pathogenesis of various human diseases, including colorectal carcinogenesis and inflammatory bowel diseases (IBD). We have previously demonstrated that Salmonella infection promotes the degradation and plasma sequestration of Axin1, leading to bacterial invasiveness and inflammatory responses. Vitamin D and the vitamin D receptor (VDR) appear to be important regulators of IBD and colon cancer. Although VDR and Axin1 are all involved in intestinal inflammation, it remains unclear whether these processes are related or function independently. In the current study, we hypothesize that VDR is an important regulator for the maintenance of physiological level of Axin1.

METHODS

Using the intestinal epithelial conditional VDR knockout mouse model (VDR^ΔIEC) and cultured cell lines, influences of VDR status on the expression of Axin1 was evaluated by Western blots and real-time PCR. Loss- and gain-of-function assays were used to investigate the regulation of VDR on Axin1 at the transcriptional and translational levels. Cells were treated with cycloheximide or actinomycin for molecular mechanistic studies. Candidate genomic VDR binding sites for Axin1 were tested by chromatin immunoprecipitation (ChIP) assay. Physical interactions among VDR, Axin1, and β-catenin were tested by immunoprecipitation. Cellular localization of Axin1 with different VDR status was determined by fractionation and immunohistochemistry.

RESULTS

We found that VDR deletion led to lower protein and mRNA levels of Axin1, whereas knockdown of Axin1 did not change the expression level of VDR protein. Immunoprecipitation data did not support physical interaction between VDR and Axin1. The VDR regulation of Axin1 was through a VDR genomic binding site for Axin1 gene on the regulatory region. Fractionation data showed that cytosolic Axin1 was significantly reduced due to VDR deletion, leaving the nuclear fraction unchanged. In ileum, Axin1 was distributed in the cytosol of apical epithelium and crypts.

CONCLUSION

VDR is important for the maintenance of physiological level of Axin1. The discovery of Axin1 as a VDR target gene provides novel and fundamental insights into the interactions between the VDR and β-catenin signaling pathways.

Vitamin D differentially regulates Salmonella-induced intestine epithelial autophagy and interleukin-1β expression

AIM

To investigate the effects of active vitamin D3 on autophagy and interleukin (IL)-1β expression in Salmonella-infected intestinal epithelial cells (IECs).

METHODS

Caco-2 cells, NOD2 siRNA-, Atg16L1 siRNA- or vitamin D receptor (VDR) siRNA-transfected Caco-2 cells were pretreated with 1,25-dihydroxyvitamin D3 (1,25D3), and then infected by wild-type S. typhimurium strain SL1344. The conversion of LC3-I to LC3-II was detected by Western blot analysis and LC3⁺ autophagosome was analyzed by immunofluorescence. Caco-2 cells or VDR siRNA-transfected cells were pretreated with 1,25D3, and then infected by SL1344. Membrane protein and total RNA were analyzed by Western blot and RT-PCR for VDR and Atg16L1 protein and mRNA expression, respectively. Atg16L1 siRNA-transfected Caco-2 cells were pretreated by 1,25D3 and then infected with SL1344. Total RNA was analyzed by RT-PCR for IL-1β mRNA expression.

RESULTS

The active form of vitamin D, 1,25D3, showed enhanced VDR-mediated Atg16L1 mRNA expression, membranous Atg16L1 protein expression leading to enhanced autophagic LC3II protein expression and LC3 punctae in Salmonella-infected Caco-2 cells which was counteracted by Atg16L1 and VDR siRNA, but Atg16L1 mediated suppression of IL-1β expression. Thus, active vitamin D may enhance autophagy but suppress inflammatory IL-1β expression in Salmonella-infected IECs.

CONCLUSION

Active vitamin D might enhance autophagic clearance of Salmonella infection, while modulation of inflammatory responses prevents the host from detrimental effects of overwhelming inflammation.

The Role of Vitamin D in Allergic Diseases in Children

The role of vitamin D in calcium and phosphate homeostasis is well known; however, in addition to traditional functions, vitamin D modulates a variety of processes, and evidence shows that it has an important role in different allergic diseases such as asthma, atopic dermatitis, and food allergy. Vitamin D acts by binding to the vitamin D receptor, which is present in a variety of tissues; for this reason it is considered a hormone. One of the most important functions is to modulate the immune system response, both innate and adaptive, by suppressing Th2-type response and increasing natural killer cells. Recent studies show that higher serum levels of 25-hydroxyvitamin D were associated with a reduced risk for asthma exacerbations and hospitalization. Other experimental data suggest that vitamin D can potentially increase the therapeutic response to glucocorticoid and potentially be used as an add-on treatment in steroid-resistant asthmatic patients. However, vitamin D stimulates the production and regulation of skin antimicrobial peptides, such as cathelicidins, which have both direct antimicrobial activity and induced host cellular response by triggering cytokine release. Recent evidence suggests that low blood vitamin D level is a risk factor for food allergy; vitamin D deficiency predisposes to gastrointestinal infections, which may promote the development of food allergy. In conclusion, several data suggest that serum 25-hydroxyvitamin D levels are often insufficient in children with asthma, atopic dermatitis, and food allergy. Further clinical trials are needed to provide conclusive evidence and to identify the effects of vitamin D in allergic diseases.

Translating nutritional immunology into drug development for inflammatory bowel disease

PURPOSE OF REVIEW

To highlight recent advances in the understanding of nutritional immunology and in the development of novel therapeutics for inflammatory bowel disease (IBD).

RECENT FINDINGS

We highlight the variety of factors that contribute to the interaction of the immune system and nutrition including the microbiome and the nervous system stimulation of the gut. We describe the potential for therapeutic development in IBD. Further, we review the cellular metabolic effects on immune activation and promising therapeutic targets. Finally, we show how the progression of understanding the role of lanthionine synthetase C-like 2 has encompassed both nutritional and therapeutic advances and led to the development of novel oral small molecule therapeutics for IBD.

SUMMARY

Nutritional immunology and drug development research centered around immunoregulatory pathways can provide safer and more effective drugs while accelerating the path to cures.

Effect of Long Noncoding RNA H19 Overexpression on Intestinal Barrier Function and Its Potential Role in the Pathogenesis of Ulcerative Colitis

BACKGROUND

Recently, long noncoding RNA (lncRNA) H19 has been reported to be related with VDR signaling and the development of inflammatory diseases including osteoarthritis. The aim of this study was to investigate the correlation between the expression level of H19 and VDR in ulcerative colitis (UC) tissues and to investigate the effect of H19 overexpression on intestinal epithelial barrier function.

METHODS

The expression level of H19, miR-675-5p, and VDR in UC tissues and paired normal tissues collected from 12 patients with UC was investigated by quantitative real-time polymerase chain reaction. Caco-2 monolayers were used to test the effect of H19 and miR-675-5p overexpression on the intestinal epithelial barrier function and the status of tight junction proteins and VDR. Luciferase assay was used to validate the target site of miR-675-5p in the 3'UTR of VDR mRNA.

RESULTS

The expression of H19 was found to be negatively correlated with the expression of VDR in UC tissues (r = 0.5369, P < 0.05). The expression of miR-675-5p was also found to be negatively correlated with the expression of VDR in UC tissues (r = 0.5233, P < 0.01). H19 overexpression increased Caco-2 monolayer permeability and decreased the expression of tight junction proteins and VDR, which was significantly attenuated by cotransfection with miR-675-5p inhibitors. The 3'UTR of VDR mRNA was validated to be one of the direct targets of miR-675-5p.

CONCLUSIONS

This study reveals the destructive effect of H19 overexpression on intestinal epithelial barrier function and suggests a potential role of H19 in the development of UC. In addition, H19 overexpression may be one of the mechanisms underlying the decreased expression of VDR in UC tissues and the interaction between H19 and VDR signaling may provide potential therapeutic targets for UC.

Role of vitamin D3 combined to alginates in preventing acid and oxidative injury in cultured gastric epithelial cells

Background

Gastric diseases are a worldwide problem in modern society, as reported in the USA, in the range of 0.5–2 episodes/year/person and an incidence of 5–100 episodes/1000/week according to seasons and age. There is convincing evidence that oxidative stress is involved in the pathogenesis of acute gastric injury. Acid secreted from gastric parietal cells determines mucosal injuries which in turn cause inflammation and oxidative stress. Consequent inflammation produces free radicals by mitochondria thus causing lipid peroxidation, oxidative and acidic stress, which can lead to cell apoptosis. Vitamin D_3, the active form of vitamin D, may counteract intracellular cell death and improve epithelial regeneration.

Methods

This study was planned to assess whether vitamin D₃ is a protective factor against acid injury and oxidative stress in gastric epithelial cells. Primary epithelial cells and GTL-16 cells have been used to test the effects of Grisù® alone or in combination with vitamin D₃ during oxidative stress or high acid exposition measuring cell viability, ROS production, cellular adhesion time along with apoptotic, autophagic and survival pathways. The combined effect of Grisù® and vitamin D₃ was found more effective in counteracting the negative consequences of oxidative stress and acidity conditions than some other gastroprotective agents, such as Maalox® or Gaviscon®.

Results

In case of oxidative stress or acidity condition the stimulation with Grisù® alone caused an improvement of cell viability and a reduction of ROS production on epithelial gastric cells. In addition, the adhesion time of the cells was improved. All these effects were increased by the presence of vitamin D₃. Similar data were also observed in primary gastric epithelial cells confirming the results obtained in GTL-16 cells.

Conclusions

These results suggest that Grisù® in combination with vitamin D₃ may exert a gastroprotective effect to maintain or restore the integrity of gastric epithelium through an antioxidant pathway, inhibiting apoptosis and activating survival kinases. Moreover, the combination of Grisù® and vitamin D₃ improves cell viability and decreases ROS production compared to other gastroprotective agents combined with vitamin D₃. All these data were validated using primary cells isolated from gastric tissue.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-016-0543-z) contains supplementary material, which is available to authorized users.

Maternal vitamin D beneficially programs metabolic, gut and bone health of mouse male offspring in an obesogenic environment

BACKGROUND/OBJECTIVES

Vitamin D is an anti-inflammatory nutrient and a determinant of bone health. Some prospective studies suggest that maternal vitamin D status is positively associated with offspring bone mass. We found that serum concentrations of lipopolysaccharide (LPS), an inflammatory molecule related to adiposity, insulin resistance and bone resorption, is lower in healthy mouse offspring exposed to high dietary vitamin D during pregnancy and lactation. LPS reaches the circulation via the gut. This study investigated whether maternal vitamin D programs metabolic, gut and bone health of male offspring in an obesogenic environment.

METHODS

C57BL/6J dams received an AIN-93G diet with high (H) or low (L) vitamin D during pregnancy and lactation. At weaning, offspring remained on their dam's vitamin D level (LL or HH) or were switched (LH or HL) and fed a high fat (44.2%) and sucrose (19.8%) diet. Glucose response, adiposity, systemic inflammation (LPS, cytokines), intestinal permeability and mass, strength and microarchitecture of trabecular and cortical bone were assessed in 7-month-old male offsprings.

RESULTS

Higher maternal dietary vitamin D resulted in lower intestinal permeability (fecal albumin, P=0.010) and benefited trabecular but not cortical bone structure at the distal femur (higher trabecular number, P=0.022; less trabecular separation, P=0.015) and lumbar vertebra 2 (bone volume/total volume%, P=0.049). Higher maternal and offspring vitamin D resulted in lower fasting glucose (HH versus LL, P=0.039) and serum LPS concentrations (dam diet, P=0.011; pup diet, P=0.002). Higher offspring vitamin D resulted in lower epididymal fat pad relative weight (P=0.006). The serum concentrations of IL-6 and TNF-α did not differ among groups.

CONCLUSIONS

Maternal dietary vitamin D beneficially programs intestinal permeability and systemic LPS concentration, which is accompanied by stronger trabecular bone in an obesogenic environment. Thus, the gut may mediate vitamin D effects. Moreover, optimizing vitamin D in early life may be critical for later health.

Effect of vitamin D on gastrointestinal symptoms and health-related quality of life in irritable bowel syndrome patients: a randomized double-blind clinical trial

BACKGROUND

Low-grade mucosal inflammation and immune activation are involved in the pathogenesis of irritable bowel syndrome (IBS). Furthermore, IBS symptoms are associated with a significantly higher prevalence of psychological distress, which in itself results into an impaired quality of life (QoL). Vitamin D could ameliorate the symptoms of patients suffering from IBS through its beneficial effects on psychological factors and inflammation.

METHODS

A total of 90 IBS patients participated in this double-blind, randomized, placebo-controlled study. Participants were randomly selected to receive either 50 000 IU vitamin D3 or a placebo fortnightly for a period of 6 months. Patients reported their IBS symptoms at the baseline and monthly during intervention periods. The IBS severity score system (IBSSS) and IBS-specific QoL questionnaires were used at the baseline and postintervention.

KEY RESULTS

Over the 6-month intervention period, a significantly greater improvement in IBS symptoms such as abdominal pain and distention, flatulence, rumbling, and overall gastrointestinal (GI) symptoms (except dissatisfaction with bowel habits) was observed in the patients receiving vitamin D as compared to the placebo group. The IBSSS and the IBS-QoL scores in the vitamin D group significantly improved compared to the placebo group postintervention (mean IBSSS score change: -53.82 ± 23.3 vs -16.85 ± 25.01, p < 0.001, respectively; mean IBS-QoL score change: 14.26 ± 3 vs 11 ± 2.34, p < 0.001, respectively).

CONCLUSIONS & INFERENCES

Vitamin D seems to be an effective and safe option to improve QoL and symptoms of IBS. ClinicalTrials.gov (NCT02579902).

The Role of Interleukin-1 in Inflammatory and Malignant Human Skin Diseases and the Rationale for Targeting Interleukin-1 Alpha

Inflammation plays a major role in the induction and progression of several skin diseases. Overexpression of the major epidermal proinflammatory cytokines interleukin (IL) 1 alpha (IL-1α) and 1 beta (IL-1β) is positively correlated with symptom exacerbation and disease progression in psoriasis, atopic dermatitis, neutrophilic dermatoses, skin phototoxicity, and skin cancer. IL-1β and the interleukin-1 receptor I (IL-1RI) have been used as a therapeutic target for some autoinflammatory skin diseases; yet, their system-wide effects limit their clinical usage. Based on the local effects of extracellular IL-1α and its precursor, pro-IL-1α, we hypothesize that this isoform is a promising drug target for the treatment and prevention of many skin diseases. This review provides an overview on IL-1α and IL-β functions, and their contribution to inflammatory and malignant skin diseases. We also discuss the current treatment regimens, and ongoing clinical trials, demonstrating the potential of targeting IL-1α, and not IL-1β, as a more effective strategy to prevent or treat the onset and progression of various skin diseases.

Abdominal tuberculosis: Diagnosis and demographics, a 10-year retrospective review from a single centre

AIM: To review all cases of abdominal tuberculosis (ATB) for demographic details, diagnostic work up and evidence of vitamin D deficiency.

METHODS: This was a retrospective analysis of all patients diagnosed with ATB from June 2003 to August 2013 at St George’s Hospital, London. Demographic data was available from the local tuberculosis database. Further clinical information was collected from electronic patient records, including radiology, endoscopy, microbiology, histology, biochemistry and serology. Patients were classified as either confirmed ATB [if mycobacteria tuberculosis (MTB) was cultured from abdominal site] or presumed ATB (if suggestive findings or high clinical suspicion). Subtypes of ATB were classified as tuberculosis (TB) peritonitis, luminal TB, solid organ TB or from a combination of sites.

RESULTS: There were a total of 65 cases identified in this time period, with a mean of 6.5 cases per year (range 4-9). Mean age 42 years, 49.2% females. Fifty-two point three percent were South Asian, 38.5% African. Forty-nine point two percent had gastrointestinal endoscopy, 30.8% paracentesis and 24.6% surgery in order to obtain samples. Forty-seven point seven percent were defined as confirmed ATB with positive culture of MTB from abdominal sites, the rest were treated as presumed ATB. Twenty-four point six percent had co-existing sputum culture positive for MTB, and 30.8% had an abnormal chest X-ray. Subtypes of ATB: 35.4% had TB peritonitis; 27.7% luminal TB; 3.1% solid organ TB; and 33.8% TB at a combination of abdominal sites. Thirteen point nine percent were human immunodeficiency virus positive, all with CD4 count less than 300 cells/μL. Seventy point five percent had severe vitamin D deficiency, and 25% were vitamin D deficient.

CONCLUSION: ATB mainly affects young South Asian and African patients, with difficulties in confirming diagnosis despite a range of non-invasive and invasive diagnostic tests.

Oxygen metabolism and barrier regulation in the intestinal mucosa

Mucosal surfaces are lined by epithelial cells and provide an important barrier to the flux of antigens from the outside. This barrier is provided at a number of levels, including epithelial junctional complexes, mucus production, and mucosa-derived antimicrobials. Tissue metabolism is central to the maintenance of homeostasis in the mucosa. In the intestine, for example, baseline pO2 levels are uniquely low due to counter-current blood flow and the presence of large numbers of bacteria. As such, hypoxia and HIF signaling predominates normal intestinal metabolism and barrier regulation during both homeostasis and active inflammation. Contributing factors that elicit important adaptive responses within the mucosa include the transcriptional regulation of tight junction proteins, metabolic regulation of barrier components, and changes in autophagic flux. Here, we review recent literature around the topic of hypoxia and barrier function in health and during disease.

Co-Administration of Soy Isoflavones and Vitamin D in Management of Irritable Bowel Disease

BACKGROUND AND AIMS

The substantial characteristics of Irritable Bowel Syndrome (IBS) are associated with estrogens in women. Both soy isoflavones and vitamin D can modulate estrogen receptors in the colonic smooth muscles. The aim of this study was to investigate the effects of soy isoflavones, vitamin D and their probable interactions in women with IBS.

METHODS

In a factorial blinded randomized clinical trial, 100 women with IBS (age:18-75yr, were randomly assigned in 4 arms to receive either placebo of vitamin D and placebo of soy isoflavones (P+P), or placebo of vitamin D and soy isoflavones (P+S), or vitamin D and placebo of soy isoflavones (D+P), or vitamin D and soy isoflavones (D+S) for 6 weeks. Dosage of soy isoflavone was 2 capsules of 20 mg soy isoflavones per day, and dosage of vitamin D was one pearl of 50'000 IU biweekly. The clinical outcomes were IBS symptoms severity scores (IBS-SSS), disease- specific quality of life (IBS-QOL) and total score (IBS-TS) that evaluated at weeks 0, 6, and 10, and compared to each other.

RESULTS

IBS-TS improved significantly in both S+P and D+P groups (p- value = 0.004, 0.015). The interaction effect of soy isoflavones and vitamin D on IBS-TS was significant (p<0.05). The interaction effect of soy isoflavones with vitamin D and the main effect of vitamin D on IBS-SSS were not statistically significant, whereas IBS-SSS decreased significantly in S+P and D+P groups (p-value = 0.001, 0.047 respectively).

CONCLUSION

Our results indicate that co-administration of soy isoflavones with vitamin D did not improve the IBS- SSS and IBS- QOL; however, it improved the IBS-TS.

TRIAL REGISTRATION

Clinical Trials.gov NCT02026518.

Serum 25-hydroxyvitamin D concentration is inversely associated with mucosal inflammation in patients with ulcerative colitis

BACKGROUND

Vitamin D exerts anti-inflammatory actions both in vitro and in murine models of colitis. In previous studies, we demonstrated that vitamin D protects against the development of colitis by maintaining the integrity of the intestinal mucosal barrier.

OBJECTIVE

We sought to evaluate whether deficient serum 25 hydroxyvitamin D [25(OH)D] concentrations are associated with increased mucosal inflammation, a loss of epithelial junctional proteins, and an increase in mucosal inflammatory cytokines in patients with ulcerative colitis (UC).

DESIGN

We prospectively enrolled 230 subjects with UC. Serum 25(OH)D concentrations were compared with the Mayo endoscopic score, the total Mayo score, and histologic activity. Colonic mucosal expression concentrations of vitamin D receptor (VDR), E-cadherin, zonula occluden 1 (ZO-1), occludin, claudin-2, tumor necrosis factor α (TNF-α), and interleukin 8 (IL-8) were compared between dichotomous groups with low or high serum 25(OH)D concentrations.

RESULTS

The mean serum 25(OH)D concentration was 21.8 ng/mL. Subjects stratified by concentrations included 12.6% ≥30 ng/mL, 45.6% ≥20 to <30 ng/mL, 37.4% ≥10 to <20 ng/mL, and 4.4% <10 ng/mL. There was an inverse association between serum 25(OH)D concentrations and mucosal inflammation as assessed by the Mayo endoscopy score (P = 0.01), disease activity as indicated by the total Mayo score (P = 0.001), and histologic activity (P = 0.02). A serum 25(OH)D concentration <20 ng/mL was associated with decreased mucosal transcript and protein expression concentrations of VDR, E-cadherin, and occludin as well as decreased protein expression of ZO-1, whereas TNF-α and IL-8 mucosal transcript expression concentrations were increased.

CONCLUSIONS

In UC patients, serum 25(OH)D concentration is inversely correlated with mucosal inflammation and disease activity. These results, coupled with the findings that serum 25(OH)D concentrations correlate with the mucosal expression of VDR as well as epithelial junction proteins and inversely with proinflammatory cytokines, suggest that vitamin D deficiency may contribute to UC inflammation by disrupting epithelial barrier function.

Clinical significance of serum 25OHD level in patients with Crohn's disease

AIM: To detect serum 25OHD levels in patients with Crohn's disease, and to analyze the relationship between serum 25OHD level and clinical parameters of Crohn's disease.

METHODS: Forty-five outpatients or inpatients with Crohn's disease (CD group) and 40 normal controls (NC group) were included in the study. Serum 25OHD levels were measured in all subjects by electrochemiluminescence. Correlation analysis was performed to identify the association between serum 25OHD levels and clinical indices of Crohn's disease. Afterwards, we analyzed the influence of related clinical indices on the level of serum 25OHD.

RESULTS: Serum 25OHD level was significantly lower in the CD group than in the NC group (12.17 ng/mL ± 6.12 ng/mL vs 19.56 ng/mL ± 5.69 ng/mL, P < 0.05, t = 5.738). The detection rate of 25OHD deficiency was significantly higher in the CD group than that of the NC group (86.7% vs 62.5%, P < 0.05, χ² = 6.649). Serum 25OHD level was correlated with BMI (P < 0.05, r = 0.508), CRP (P < 0.05, r = -0.713), ESR (P < 0.05, r = -0.389), duration of exposure to sunshine < 30 min/d (P < 0.05, r = 0.362), active disease (P < 0.05, r = 0.384) and use of remicade (P < 0.05, r = 0.475). Serum 25OHD level was significantly lower in patients with Crohn's disease whose duration of exposure to sunshine was < 30 min/d than in those with a duration of exposure to sunshine > 30 min/d (10.33 ng/mL ± 5.75 ng/mL vs 14.47 ng/mL ± 5.91 ng/mL, P < 0.05, t = 2.371), in patients who did not use remicade than in those who used remicade (8.51 ng/mL ± 3.95 ng/mL vs 14.19 ng/mL ± 6.21 ng/mL, P < 0.05, t = 3.302), and in patients with active disease than in those with an inactive stage (9.36 ng/mL ± 4.43 ng/mL vs 14.05 ng/mL ± 6.44 ng/mL, P < 0.05, t = 2.693).

CONCLUSION: Patients with Crohn's disease have significantly lower serum 25OHD level than healthy people. Disease activity, duration of exposure to sunshine and use of remicade can affect serum 25OHD levels in patients with Crohn's disease.

The Relationship between Vitamin D Status and Allergic Diseases in New Zealand Preschool Children

Recent research on vitamin D in young children has expanded from bone development to exploring immunomodulatory effects. Our aim was to investigate the relationship of vitamin D status and allergic diseases in preschool-aged children in New Zealand. Dried capillary blood spots were collected from 1329 children during late-winter to early-spring for 25(OH)D measurement by LC-MS/MS. Caregivers completed a questionnaire about their child's recent medical history. Analysis was by multivariable logistic regression. Mean 25(OH)D concentration was 52(SD19) nmol/L, with 7% of children <25 nmol/L and 49% <50 nmol/L. Children with 25(OH)D concentrations ≥75 nmol/L (n = 29) had a two-fold increased risk for parent-report of doctor-diagnosed food allergy compared to children with 25(OH)D 50-74.9 nmol/L (OR = 2.21, 1.33-3.68, p = 0.002). No associations were present between 25(OH)D concentration and presence of parent-reported eczema, allergic rhinoconjunctivitis or atopic asthma. Vitamin D deficiency was not associated with several allergic diseases in these New Zealand preschool children. In contrast, high 25(OH)D concentrations were associated with a two-fold increased risk of parental-report food allergy. This increase supports further research into the association between vitamin D status and allergic disease in preschool children.

Optimal vitamin D plasma levels are associated with lower bacterial DNA translocation in HIV/hepatitis c virus coinfected patients

OBJECTIVE

Vitamin D has been linked to the immune response modulation and the integrity of the intestinal mucosal barrier. Therefore, vitamin D might be involved in bacterial translocation related to HIV infection. Our major aim was to analyze the association between plasma levels of 25-hydroxy-vitamin D [25(OH)D] and bacterial 16S ribosomal DNA (bactDNA) in 120 HIV/hepatitis c virus (HCV) coinfected patients.

DESIGN

Cross-sectional study.

METHODS

Plasma 25(OH)D levels were quantified by enzyme immunoassay. The vitamin D status was defined as deficient (<25 nmol/l), insufficient (25-74 nmol/l), and optimal (≥75 nmol/l) plasma levels. Plasma bactDNA levels were measured by quantitative real-time PCR. For bactDNA levels the cutoffs used were as follows: low [<p25th (46 copies/μl)], moderate [p25th to p50th (78 copies/μl)], high [p50th to p75th (159 copies/μl)], and very high (>p75th).

RESULTS

Eighteen (15%) patients had 25(OH)D deficiency, 93 (77.5%) had insufficiency and nine (7.5%) had 25(OH)D optimal values. The bactDNA levels were lower in patients with 25(OH)D at least 75 nmol/l [37 copies/μl] than in patients with 25(OH)D insufficiency [84.2 copies/μl; P = 0.042]. Conversely, low bactDNA levels (<p25th) were found in 66.7% of patients with 25(OH)D optimal levels, whereas bactDNA levels above p25th were found only in 11.1% of them (P = 0.029). The plasma 25(OH)D not less than 75 nmol/l was associated with low bactDNA levels (<p25th) [adjusted OR = 8.13 (95% confidence interval = 1.82; 36.67); P = 0.006)]. The patients with optimal vitamin D status [25(OH)D ≥75 nmol/l] had lower plasma levels of CCL7 (P = 0.047) and basic fibroblast growth factor (P = 0.042).

CONCLUSION

The optimal vitamin D status was associated with low bacterial translocation and inflammation in HIV/HCV coinfected patients.

Flavonoids in Inflammatory Bowel Disease: A Review

Inflammatory bowel disease (IBD) is characterized by chronic inflammation of the intestine that compromises the patients’ life quality and requires sustained pharmacological and surgical treatments. Since their etiology is not completely understood, non-fully-efficient drugs have been developed and those that have shown effectiveness are not devoid of quite important adverse effects that impair their long-term use. In this regard, a growing body of evidence confirms the health benefits of flavonoids. Flavonoids are compounds with low molecular weight that are widely distributed throughout the vegetable kingdom, including in edible plants. They may be of great utility in conditions of acute or chronic intestinal inflammation through different mechanisms including protection against oxidative stress, and preservation of epithelial barrier function and immunomodulatory properties in the gut. In this review we have revised the main flavonoid classes that have been assessed in different experimental models of colitis as well as the proposed mechanisms that support their beneficial effects.

Serum vitamin D and colonic vitamin D receptor in inflammatory bowel disease

AIM: To determine serum vitamin D levels and colonic vitamin D receptor (VDR) expression in inflammatory bowel disease (IBD) and non-IBD patients and correlate these with histopathology.

METHODS: Puerto Rican IBD (n = 10) and non-IBD (n = 10) patients ≥ 21 years old scheduled for colonoscopy were recruited. Each patient completed a questionnaire and provided a serum sample and a colonic biopsy of normal-appearing mucosa. For IBD patients, an additional biopsy was collected from visually diseased mucosa. Serum vitamin D levels were measured by ultra-performance liquid chromatography and mass spectrometry. Hematoxylin and eosin stained tissue sections from colonic biopsies were classified histologically as normal or colitis (active/inactive), and scored for the degree of inflammation present (0-3, inactive/absent to severe). Tissue sections from colonic biopsies were also stained by immunohistochemistry for VDR, for which representative diagnostic areas were photographed and scored for staining intensity using a 4-point scale.

RESULTS: The IBD cohort was significantly younger (40.40 ± 5.27, P < 0.05) than the non-IBD cohort (56.70 ± 1.64) with a higher prevalence of vitamin D deficiency (40% vs 20%, respectively) and insufficiency (70% vs 50%, respectively). Histologic inflammation was significantly higher in visually diseased mucosa from IBD patients (1.95 ± 0.25) than in normal-appearing mucosa from control patients (0.25 ± 0.08, P < 0.01) and from IBD patients (0.65 ± 0.36, P < 0.05) and correlated inversely with VDR expression in visually diseased colonic tissue from IBD patients (r = -0.44, P < 0.05) and from IBD patients with Crohn’s disease (r = -0.69, P < 0.05), but not in normal-appearing colonic tissue from control patients or IBD patients. Control and IBD patient serum vitamin D levels correlated positively with VDR expression in normal colon from control and IBD patients (r = 0.38, P < 0.05) and with patient age (r = 0.54, P < 0.01).

CONCLUSION: Levels of serum vitamin D correlate positively with colonic VDR expression in visually normal mucosa whereas inflammation correlates negatively with colonic VDR expression in visually diseased mucosa in Puerto Rican patients.

Effect of vitamin D supplementation on inflammation: protocol for a systematic review

INTRODUCTION

The extraskeletal role of vitamin D is being increasingly recognised. This has important clinical implications, as vitamin D deficiency has reached epidemic proportions worldwide. Vitamin D has proposed anti-inflammatory properties, yet the role of vitamin D supplementation in reducing inflammation remains largely unknown. The purpose of this review is to investigate the impact of vitamin D supplementation on inflammation, and to identify relevant knowledge gaps in the field.

METHODS AND ANALYSIS

Medline, CINAHL, EMBASE and All EBM will be systematically searched for randomised controlled trials (RCTs) and systematic reviews of RCTs, comparing vitamin D supplementation with placebo, usual care or other pharmacological or non-pharmacological interventions. One reviewer will assess articles for eligibility according to prespecified selection criteria, after which 2 independent reviewers will perform data extraction and quality appraisal. Meta-analyses will be conducted where appropriate.

ETHICS AND DISSEMINATION

Formal ethical approval is not required as no primary data is collected. This systematic review will identify potential clinical implications of vitamin D deficiency and supplementation, and will be disseminated through a peer-reviewed publication and at conference meetings, to inform future research on the efficacy of vitamin D supplementation for inflammation and inflammatory diseases.

PROSPERO REGISTRATION NUMBER

CRD42016037104.

Lack of Vitamin D Receptor Causes Dysbiosis and Changes the Functions of the Murine Intestinal Microbiome

PURPOSE

The microbiome modulates numerous aspects of human physiology and is a crucial factor in the development of various human diseases. Vitamin D deficiency and downregulation of the vitamin D receptor (VDR) are also associated with the pathogenesis of diseases such as inflammatory bowel disease, cancers, obesity, diabetes, and asthma. VDR is a nuclear receptor that regulates the expression of antimicrobial peptides and autophagy regulator ATG16L1. Vitamin D may promote a balanced intestinal microbiome and improve glucose homeostasis in diabetes. However, how VDR regulates microbiome is not well known. In the current study, we hypothesize that VDR status regulates the composition and functions of the intestinal bacterial community.

METHODS

Fecal and cecal stool samples were harvested from Vdr knockout (Vdr(-/-)) and wild-type mice for bacterial DNA and then sequenced with 454 pyrosequencing. The sequences were denoised and clustered into operational taxonomic units, then queried against the National Center for Biotechnology Information database. Metagenomics were analyzed, and the abundances of genes involved in metabolic pathways were compared by reference to the Kyoto Encyclopedia of Genes and Genomes and Clusters of Orthologous Groups databases.

FINDINGS

In the Vdr(-/-) mice, Lactobacillus was depleted in the fecal stool, whereas Clostridium and Bacteroides were enriched. Bacterial taxa along the Sphingobacteria-to-Sphingobacteriaceae lineage were enriched, but no genera reached statistical significance. In the cecal stool, Alistipes and Odoribacter were depleted, and Eggerthella was enriched. Notably, all of the taxa upstream of Eggerthella remained unchanged. A comparison of Vdr(-/-) and wild-type samples revealed 40 (26 enriched, 14 depleted) and 72 (41 enriched, 31 depleted) functional modules that were significantly altered in the cecal and fecal microbiomes, respectively (both, P < 0.05), due to the loss of Vdr. In addition to phylogenetic differences in gut microbiome with different intestinal origins, we identify several important pathways, such as nucleotide-binding oligomerization domain-like receptor, affected by Vdr status, including amino acid, carbohydrate, and fatty acid synthesis and metabolism, detoxification, infections, signal transduction, and cancer and other diseases.

IMPLICATIONS

Our study fills knowledge gaps by having investigated the microbial profile affected by VDR. Insights from our findings can be exploited to develop novel strategies to treat or prevent various diseases by restoring VDR function and healthy microbe-host interactions.

1,25-dihydroxyvitamin D3 inhibits corneal wound healing in an ex-vivo mouse model

PURPOSE

Impaired healing of corneal injuries can result in ulceration and complete loss of vision, especially in the elderly. Such patients frequently also exhibit vitamin D insufficiency. 1,25-dihydroxyvitamin D3 is the active vitamin D metabolite. As it affects cell proliferation and inflammation, we herein aimed at elucidating its influence on corneal wound healing after alkali burn by using in vitro and ex vivo techniques.

METHODS

mRNA abundance in human corneal epithelial cells in response to vitamin D3 was determined by RT-PCR. Corneal re-epithelialization after alkaline burn was analyzed using enucleated mouse eyes and fluorescein staining.

RESULTS

Human corneal epithelial cells (HCEC) expressed the vitamin D receptor (VDR) and retinoid x receptor (RXR) and were responsive to 1,25- dihydroxyvitamin D3, as shown by induction of the 1,25- dihydroxyvitamin D3 responsive gene cyp-24A1 and slightly reduced abundance of IL-6 mRNA. However, no effect on cell vitality and migration was observed. In contrast, re-epithelialization of mouse corneas ex vivo was dose dependently inhibited by 1,25- dihydroxyvitamin D3.

CONCLUSIONS

These data indicate that topically applied 1,25- dihydroxyvitamin D3 does not seem to be suitable for therapy of corneal lesions.