Protective role of 1,25(OH)2 vitamin D3 in the mucosal injury and epithelial barrier disruption in DSS-induced acute colitis in mice

Autophagy inhibitor 3-methyladenine mitigates the severity of colitis in aged mice by inhibiting autophagy

BACKGROUND

The elderly ulcerative colitis (UC) patients pose unique challenges due to their comorbidities, diminished functional capacity, and heightened risk of treatment-related complications. Thus, finding a safe and effective treatment for this age group is crucial.

AIM

This study investigates the role of autophagy in the pathogenesis of UC in young and elderly patients, and explores the therapeutic potential and mechanisms of autophagy modulators in aged mice with dextran sulfate sodium (DSS)-induced colitis.

METHODS

Colonic biopsies were collected from young and old UC patients as well as comparable healthy subjects. Young (6-8 weeks) and aged (56 weeks) C57BL/6 mice were treated with DSS to induce acute colitis model. The autophagy inhibitor 3-methyladenine was administered intraperitoneally to aged DSS-induced mice. The autophagy activity was detected by the protein expressions of LC3B-II, p62 and ATG5 by western blot and immunohistochemistry. The levels of TNF -α, IL-6, CCL4, CXCL12 and CD86 were measured by qRT-PCR. The transcriptional activity of NF-κB was measured by electrophoretic mobility shift assay (EMSA).

RESULTS

Increased autophagy activity was observed in aged DSS-induced mice. Treatment with 3-methyladenine suppressed autophagy in intestinal epithelial cells (IECs) and alleviated colitis severity. Additionally, 3-methyladenine reduced macrophage recruitment, decreased IL-6 levels, and inhibited NF-κB signaling, thereby mitigating inflammation.

CONCLUSION

Significant differences in autophagy activity were identified between young and aged DSS-induced mice. These findings underscore the potential therapeutic benefits of autophagy inhibition in elderly UC patients.

Disrupted mitochondrial morphology and function exacerbate inflammation in elderly-onset ulcerative colitis

BACKGROUND

The characteristics of ulcerative colitis (UC) in the elderly are quite different from the young population. Mitochondrial injury is a key mechanism regulating both aging and inflammation. This study aims to reveal the role of mitochondrial damage in the pathogenesis of adult- and elderly-onset UC.

METHODS

RNA-sequencing of colonic mucosa from adult- and elderly-onset UC patients was performed. Mitochondria-related differentially expressive genes (mDEGs) and immune cell infiltration analysis were identified and performed in colonic tissues from UC patients. Mice aged 6-8 weeks and 20-24 months were administered 2% dextran sodium sulphate (DSS) for 7 days to induce colitis. Mitochondrial morphological changes and ATP levels were evaluated in the colons of mice. Mechanistically, we explored the association of key mDEG with reactive oxygen species (ROS), oxygen consumption rates, NLRP3/IL-1β pathway in HCT116 cell line.

RESULTS

Thirty mDEGs were identified between adult- and elderly-onset UC, which were related primarily to mitochondrial respiratory function and also had significant correlation with different infiltrates of immune cells. Compared with young colitis mice, DSS-induced colitis in the aged mice exhibited more severe inflammation, damaged mitochondrial structure and lower ATP levels in colonic tissues. ALDH1L1 was identified as a hub DEG through protein-protein interaction networks of RNA-seq, which was downregulated in UC patients or colitis mice versus healthy controls. In tumor necrosis factor-alpha-stimulated HCT116 cells, mitochondrial ROS, NLRP3 and IL-1β expression increased less and mitochondrial respiration had an upregulated trend after knocking down ALDH1L1.

CONCLUSION

There are significant differences in mitochondrial structure, ATP production and mitochondria-related gene expression between adult- and elderly-onset UC, which have a potential link with cytokine pathways and immune microenvironment. The more prominent mitochondrial injury may be a key factor for more severe inflammatory response and poorer outcome in elderly-onset UC.

Effects of Vitamin D Supplementation on Serum 25-Hydroxy Cholecalciferol in Inflammatory Bowel Diseases: A Meta-Analysis of Randomized Clinical Trials

Background

Earlier studies about the influence of vitamin D (Vit D) supplementation on patients with inflammatory bowel disease (IBD) reported inconsistent results. Current comprehensive systematic review and meta-analysis was conducted to assess the effect of Vit D supplementation on clinical and subclinical factors in patients with IBD.

Methods

PubMed, Scopus, and Web of Science databases were searched for relevant randomized controlled trials (RCTs) on the effect of Vit D supplementation in IBD patients, published up to March 2023. Data were analyzed by the random-effect model. Heterogeneity was assessed by Cochran's Q test and I-square (I 2) statistic. The mean differences (MDs) were calculated as the summary effect size.

Results

We included nine related articles, and our findings indicated that vitamin D administration increased serum vitamin D levels compared to placebo (weighted mean difference (WMD): 12.08; 95% confidence interval (95% CI): 9.06, 15.09; I 2 = 97.01%; P < 0.001) in IBD patients. However, it had no significant influence on disease activity (standardized mean difference (SMD): 0.27; 95% CI: -0.42, 0.95; I2 = 91.7%; P < 0.001) or serum levels of C-reactive protein (CRP) (WMD: -1.42; 95% CI: -3.90, 1.06; I2 = 41.9%; P = 0.262).

Conclusions

Current meta-analysis showed a significant effect of Vit D supplementation on increasing serum cholecalciferol. However, no significant effects of Vit D supplementation on the disease activity and serum levels of CRP were seen. Further studies are needed to expand current knowledge in this issue and found a significant increment in serum 25-hydroxy cholecalciferol concentrations following Vit D supplementation in IBD patients.

Effects of vitamin D deficiency on chronic alcoholic liver injury

Vitamin D deficiency (VDD) has been found among alcoholics. However, little is known about the effect of VDD on alcoholic liver disease and the molecular mechanisms remain unclear. The aim of the current study was to evaluate whether vitamin D was deficient among patients with alcoholic fatty liver disease (AFLD) and the effect of VDD on chronic alcoholic liver injury and possible molecular mechanisms in mice. Our results found that lower 25-hydroxyvitamin D [25(OH)D] concentrations in patients with AFLD. And further analysis found that 25(OH)D is a protective factor in patients with AFLD. Mice experiments indicated that VDD can alter the composition of gut microbiota, down-regulate the protein levels of intestinal tight junction protein Occludin and E-cadherin, up-regulate the expression of inflammatory cytokines (tnf-α, il-1β, il-6, il-8, ccl2, il-10) in liver and colon tissue. And further exacerbated the protein levels of p65,P-IκB,P-p65 in alcoholic liver injury mice. In conclusion, VDD aggravates chronic alcoholic liver injury by activating NF-κB signaling pathway.

A New Strategy for Dietary Nutrition to Improve Intestinal Homeostasis in Diarrheal Irritable Bowel Syndrome: A Perspective on Intestinal Flora and Intestinal Epithelial Interaction

BACKGROUND AND OBJECTIVES

Although a reasonable diet is essential for promoting human health, precise nutritional regulation presents a challenge for different physiological conditions. Irritable Bowel Syndrome (IBS) is characterized by recurrent abdominal pain and abnormal bowel habits, and diarrheal IBS (IBS-D) is the most common, seriously affecting patients' quality of life. Therefore, the implementation of precise nutritional interventions for IBS-D has become an urgent challenge in the fields of nutrition and food science. IBS-D intestinal homeostatic imbalance involves intestinal flora disorganization and impaired intestinal epithelial barrier function. A familiar interaction is evident between intestinal flora and intestinal epithelial cells (IECs), which together maintain intestinal homeostasis and health. Dietary patterns, such as the Mediterranean diet, have been shown to regulate gut flora, which in turn improves the body's health by influencing the immune system, the hormonal system, and other metabolic pathways.

METHODS

This review summarized the relationship between intestinal flora, IECs, and IBS-D. It analyzed the mechanism behind IBS-D intestinal homeostatic imbalance by examining the interactions between intestinal flora and IECs, and proposed a precise dietary nutrient intervention strategy.

RESULTS AND CONCLUSION

This increases the understanding of the IBS-D-targeted regulation pathways and provides guidance for designing related nutritional intervention strategies.

Dietary therapies for adult and pediatric inflammatory bowel disease

Diet is an environmental exposure implicated in the development of inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC). Dietary therapy is also a tool for management of these conditions. Nutrition therapy for IBD has been shown to reduce intestinal inflammation, promote healing, and alleviate symptoms, as well as improve patients' nutrition status. Although the mechanisms of action of most nutrition therapies for IBD are not well understood, the diets are theorized to eliminate triggers for gut dysbiosis and mucosal immune dysfunction associated with the typical Western diet. Exclusive enteral nutrition and the Crohn's disease exclusion diet are increasingly being used as the primary treatment modality for the induction of remission and/or maintenance therapy in children, and in some adults, with CD. Several other diets, such as the Mediterranean diet, anti-inflammatory diet for IBD, and diets excluding gluten, FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols), lactose, or other compounds, may be helpful in symptom management in both CD and UC, though evidence for biochemical efficacy is limited. In this review, we discuss the role of diet components in IBD pathogenesis and examine diets currently used in the management of children and adults with IBD. We also address practical, psychosocial, and cultural considerations for dietary therapy across diverse populations.

Panaxynol improves crypt and mucosal architecture, suppresses colitis-enriched microbes, and alters the immune response to mitigate colitis

Ulcerative colitis (UC) is an idiopathic inflammatory disease of the large intestine, which impacts millions worldwide. Current interventions aimed at treating UC symptoms can have off-target effects, invoking the need for alternatives that may provide similar benefits with less unintended consequences. This study builds on our initial data, which showed that panaxynol-a novel, potent, bioavailable compound found in American ginseng-can suppress disease severity in murine colitis. Here we explore the underlying mechanisms by which panaxynol improves both chronic and acute murine colitis. Fourteen-week-old C57BL/6 female mice were either given three rounds of dextran sulfate sodium (DSS) in drinking water to induce chronic colitis or one round to induce acute colitis. Vehicle or panaxynol (2.5 mg/kg) was administered via oral gavage three times per week for the study duration. Consistent with our previous findings, panaxynol significantly (P < 0.05) improved the disease activity index and endoscopic scores in both models. Using the acute model to examine potential mechanisms, we show that panaxynol significantly (P < 0.05) reduced DSS-induced crypt distortion, goblet cell loss, and mucus loss in the colon. 16S Sequencing revealed panaxynol altered microbial composition to suppress colitis-enriched genera (i.e., Enterococcus, Eubacterium, and Ruminococcus). In addition, panaxynol significantly (P < 0.05) suppressed macrophages and induced regulatory T-cells in the colonic lamina propria. The beneficial effects of panaxynol on mucosal and crypt architecture, combined with its microbial and immune-mediated effects, provide insight into the mechanisms by which panaxynol suppresses murine colitis. Overall, this data is promising for the use of panaxynol to improve colitis in the clinic.NEW & NOTEWORTHY In the current study, we report that panaxynol ameliorates chemically induced murine colitis by improving colonic crypt and mucosal architecture, suppressing colitis-enriched microbes, reducing macrophages, and promoting the differentiation of regulatory T-cells in the colonic lamina propria. This study suggests that this novel natural compound may serve as a safe and effective treatment option for colitis patients.

GSK343 modulates macrophage M2 polarization through the EZH2/MST1/YAP1 signaling axis to mitigate neurological damage induced by hypercalcemia in CKD mice

Chronic kidney disease (CKD) often culminates in hypercalcemia, instigating severe neurological injuries that are not yet fully understood. This study unveils a mechanism, where GSK343 ameliorates CKD-induced neural damage in mice by modulating macrophage polarization through the EZH2/MST1/YAP1 signaling axis. Specifically, GSK343 downregulated the expression of histone methyltransferase EZH2 and upregulated MST1, which suppressed YAP1, promoting M2 macrophage polarization and thereby, alleviating neural injury in hypercalcemia arising from renal failure. This molecular pathway introduced herein not only sheds light on the cellular machinations behind CKD-induced neurological harm but also paves the way for potential therapeutic interventions targeting the identified axis, especially considering the M2 macrophage polarization as a potential strategy to mitigate hypercalcemia-induced neural injuries.

Vitamin D and celiac disease

Celiac disease (CD) is an immune-mediated condition affecting the small intestine. Its reported global prevalence falls within the range of 0.7% to 1.4%. Notably, historically, higher rates, reaching 1% in Western Ireland, have been documented. Recent research has even revealed prevalence rates as elevated as 2% in northern Europe. These findings underscore the urgency for swift and cost-effective diagnosis, especially in individuals identified through screening efforts. At present, the diagnosis of CD relies on a multifaceted approach involving positive serological markers such as IgA anti-tissue transglutaminase (anti-TTG) and anti-endomysial antibodies (anti-EMA). These serological findings are assessed in conjunction with classical histological alterations, as outlined in the Marsh classification. CD is an inflammatory condition triggered by the consumption of gluten, resulting from intricate interactions between genetic, immunological, and environmental factors. CD is linked to malabsorption, leading to nutritional deficiencies. Individuals with CD are required to adhere to a gluten-free diet, which itself can lead to nutrient deficiencies. One such deficiency includes vitamin D, and there is substantial experimental evidence supporting the notion of a bidirectional relationship between CD and vitamin D status. A low level of vitamin D has a detrimental impact on the clinical course of the disease. Here we summarize the key characteristics of CD and explore the prominent roles of vitamin D in individuals with CD.

Taurine Regulates the Expression of Interleukin -17/10 and Intestinal Flora and Protects the Liver and Intestinal Mucosa in a Nonalcoholic Fatty Liver Disease Rat Model

Purpose

To investigate the intestinal inflammatory response and the abundance of intestinal bacteria in rats with high-fat diet (HFD)-induced nonalcoholic fatty liver disease (NAFLD) and assess the intervention effects of taurine (TAU).

Methods

Forty male Sprague-Dawley rats were randomly divided into five groups: group I, normal diet and normal saline gavage; group II, normal diet and TAU gavage; group III, HFD and normal saline gavage; group IV, HFD and TAU gavage (from the 1st week); group V, HFD and TAU gavage (from the 10th week). At the end of the 16th week, all the animals were sacrificed. Body weight, liver weight, liver function, and serum lipid levels were measured. The histopathologies of the liver and ileum were observed. The mRNA and protein expression levels of interleukin 17 (IL-17) and IL-10 in the ileum were detected by reverse transcription quantitative polymerase chain reaction (qPCR) and immunohistochemistry. Three types of bacteria were detected in intestinal feces using the 16S rDNA qPCR method.

Results

The ileal IL-17 level in group III was significantly higher than those in the other four groups (P < 0.01). The ileal IL-10 mRNA levels in group IV was significantly higher than those in groups III and V (P < 0.05), and IL-10 protein MOD levels in group III was significantly lower than those in the other four groups (P < 0.01). The numbers of Lactobacillus in group III were significantly lower than those in the other four groups (P < 0.01 or P < 0.05). The numbers of Bifidobacteria in groups IV and V were significantly increased compared with that in group III (P < 0.05).

Conclusion

TAU may down-regulate the expression of IL-17, up-regulate the expression of IL-10 and regulate the intestinal flora, and alleviate the liver and intestinal damage in rats with HFD-induced NAFLD.

Caffeic acid 3,4-dihydroxyphenethyl ester prevents colorectal cancer through inhibition of multiple cancer-promoting signal pathways in 1,2-Dimethylhydrazine/dextran sodium sulphate mouse model

OBJECTIVE

To elucidate the potential feature and mechanism of the caffeic acid 3,4-dihydroxyphenethyl ester (CADPE) molecule, which can prevent colorectal cancer (CRC) in the 1,2-Dimethylhydrazine (DMH)/dextran sodium sulphate (DSS)-induced mouse model.

METHODS

Institute of cancer research (ICR) male mice were injected with 20 mg/kg DMH for a week. After that, 2% DSS was administered in the drinking water for another 7 d. The CADPE treatment was given to the DMH/DSS induced male mice at three different periods until their sacrifice. Histopathological examination was used for observing the CRC development at colonic mucosa. Immunohistochemistry (IHC), blood cells smearing and crypt damage scoring methods were used for investigating the anti-inflammation feature of CADPE related to CRC. The reversing targets searching method was applied with artificial intelligence (AI), computer-aided drug designing (CADD) and Ingenuity Pathway Analysis (IPA) techniques for predicting the potential targets and mechanism of CADPE highly related to CRC.

RESULTS

The data indicated that CADPE inhibited CRC tumor development in the colitis-associated DMH/DSS induced mouse model after giving the early treatment. CADPE also impeded the acute inflammation by decreasing the infiltration of neutrophils significantly during the initial stage of CRC development. Finally, our data showed that CADPE prevented CRC by blocking active sites of three pivotal protein targets including epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK) and mammalian target of rapamycin (mTOR) in two major cancer development pathways.

CONCLUSIONS

CADPE effectively prevented CRC at early stage of tumor germination in the DMH/DSS mouse model highly likely due to its anti-acute inflammation characteristic and the ability of blocking EGFR, ERK and mTOR activities in two highly related CRC developing pathways.

Co-administration of 1,25-dihydroxyvitamin D3 and infliximab improves colitis in mice by modulating Treg differentiation

Objectives

The combination of TNF-α inhibitors and vitamin D in colitis remains to be elucidated. In the present study, we revealed the benefit of infliximab (IFX) and vitamin D in a mouse model of Ulcerative colitis (UC).

Materials and Methods

A dextran sulfate sodium-induced colitis model was used. The therapeutic effect of the combination was evaluated by symptom and histopathology analysis. The synergistic mechanism was explored by detecting the regulatory effect of the combined therapy on Regulatory T cell (Treg) differentiation.

Results

IFX and 1,25-dihydroxyvitamin D3 (VitD3) synergistically prevented the development of colitis by improving clinical signs, pathological and hematological manifestation, and inhibiting intestinal inflammation (decreasing TNF-α, IL-1β, and IL-6). Co-administration of IFX (2.5 mg/kg) with VitD3 or IFX (5.0 mg/kg) with VitD3 was more effective than administration of IFX (2.5 mg/kg, 5.0 mg/kg). There was no difference in therapeutic effect between IFX (5.0 mg/kg) and VitD3+ IFX (2.5 mg/kg) groups or between the VitD3+IFX (5.0 mg/kg) and VitD3+ Azathioprine (AZA) groups. VitD3 or combination therapy showed more powerful regulation of splenetic Treg differentiation and IL-10 production than IFX alone. Moreover, VitD3 alone or in combination induced higher levels of Foxp3 and IL-10 than IFX in colon tissue. In ulcerative colitis patients, serum VitD3 levels positively correlated with Treg levels.

Conclusion

VitD3 and IFX synergistically inhibit colitis based on their powerful regulation of Treg differentiation. VitD3 combined with IFX is an alternative therapy for patients who are intolerant to standard doses of IFX or combination of IFX and AZA.

An efficient co-delivery system based on multilayer structural nanoparticles for programmed sequential release of resveratrol and vitamin D3 to combat dextran sodium sulfate-induced colitis in mice

Multilayer structural nanoparticles (MSNPs) fabricated by layer-by-layer self-assembly were used for the co-encapsulation of resveratrol (Res) and vitamin D3 (Vd). Res and Vd co-encapsulated MSNPs (Res-Vd-MSNPs) were evaluated by appearance, morphology, particle size, ζ potential and encapsulation efficiency (EE). The results showed that Res-Vd-MSNPs were spherical in shape with a particle size of 625.4 nm and a surface charge of +26.1 mV. The EE of Res and Vd was as high as 93.6 % and 90.8 %, respectively. Res-Vd-MSNPs exhibited better stability and lower degradation rate in simulated gastric fluid, allowing the programmed sequential release of Vd and Res in simulated intestinal fluid and simulated colonic fluid, which was also confirmed by in vivo fluorescence imaging of mice. In addition, Res-Vd-MSNPs effectively alleviated the clinical symptoms of dextran sulfate sodium salt (DSS)-induced colitis in mice, including weight loss, diarrhea and fecal bleeding, and it especially exerted a preventive effect on DSS-induced colon tissue damage and colon shortening. Furthermore, Res-Vd-MSNPs suppressed the expression of anti-inflammatory cytokines such as TNF-α, IL-1β and IL-6 and ameliorated DSS-induced oxidative damage, decreased colonic myeloperoxidase (MPO) and nitric oxide (NO) activities and elevated glutathione (GSH) level in DSS-treated mice. This study illustrated that MSNPs were potential carriers for developing the co-delivery system for the synergistic prevention and treatment of ulcerative colitis.

Disease pathogenesis and barrier functions regulated by group 3 innate lymphoid cells

The mucosal surface is in constant contact with foreign antigens and is regulated by unique mechanisms that are different from immune responses in the peripheral organs. For the last several decades, only adaptive immune cells such as helper T (Th) cells, Th1, Th2, or Th17 were targeted to study a wide variety of immune responses in the mucosal tissues. However, since their discovery, innate lymphoid cells (ILCs) have been attracting attention as a unique subset of immune cells that provide border defense with various functions and tissue specificity. ILCs are classified into different groups based on cell differentiation and functions. Group 3 innate lymphoid cells (ILC3s) are particularly in close proximity to mucosal surfaces and therefore have the opportunity to be exposed to a variety of bacteria including pathogenic bacteria. In recent years, studies have also provided much evidence that ILC3s contribute to disease pathogenesis as well as the defense of mucosal surfaces by rapidly responding to pathogens and coordinating other immune cells. As the counterpart of helper T cells, ILC3s together with other ILC subsets establish the immune balance between adaptive and innate immunity in protecting us from invasion or encounter with non-self-antigens for maintaining a complex homeostasis. In this review, we summarize recent advances in our understanding of ILCs, with a particular focus on the function of ILC3s in their involvement in bacterial infection and disease pathogenesis.

Intestinal Membrane Function in Inflammatory Bowel Disease

Inflammatory bowel disease is a set of chronic inflammatory diseases that mainly develop in the gastrointestinal mucosa, including ulcerative colitis and Crohn's disease. Gastrointestinal membrane permeability is an important factor influencing the pharmacological effects of pharmaceuticals administered orally for treating inflammatory bowel disease and other diseases. Understanding the presence or absence of changes in pharmacokinetic properties under a disease state facilitates effective pharmacotherapy. In this paper, we reviewed the gastrointestinal membrane function in ulcerative colitis and Crohn's disease from the perspective of in vitro membrane permeability and electrophysiological parameters. Information on in vivo permeability in humans is summarized. We also overviewed the inflammatory bowel disease research using gut-on-a-chip, in which some advances have recently been achieved. It is expected that these findings will be exploited for the development of therapeutic drugs for inflammatory bowel disease and the optimization of treatment options and regimens.

Gut microbiota in pre-clinical rheumatoid arthritis: From pathogenesis to preventing progression

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by progressive polyarthritis that leads to cartilage and bone damage. Pre-clinical RA is a prolonged state before clinical arthritis and RA develop, in which autoantibodies (antibodies against citrullinated proteins, rheumatoid factors) can be present due to the breakdown of immunologic self-tolerance. As early treatment initiation before the onset of polyarthritis may achieve sustained remission, optimize clinical outcomes, and even prevent RA progression, the pre-clinical RA stage is showing the prospect to be the window of opportunity for RA treatment. Growing evidence has shown the role of the gut microbiota in inducing systemic inflammation and polyarthritis via multiple mechanisms, which may involve molecular mimicry, impaired intestinal barrier function, gut microbiota-derived metabolites mediated immune regulation, modulation of the gut microbiota's effect on immune cells, intestinal epithelial cells autophagy, and the interaction between the microbiome and human leukocyte antigen alleles as well as microRNAs. Since gut microbiota alterations in pre-clinical RA have been reported, potential therapies for modifying the gut microbiota in pre-clinical RA, including natural products, antibiotic therapy, fecal microbiota transplantation, probiotics, microRNAs therapy, vitamin D supplementation, autophagy inducer-based treatment, prebiotics, and diet, holds great promise for the successful treatment and even prevention of RA via altering ongoing inflammation. In this review, we summarized current studies that include pathogenesis of gut microbiota in RA progression and promising therapeutic strategies to provide novel ideas for the management of pre-clinical RA and possibly preventing arthritis progression.

1,25(OH)2D3 alleviates oxidative stress and inflammation through up-regulating HMGCS2 in DSS-induced colitis

BACKGROUND

Previous study found that supplements with active vitamin D3 alleviated experimental colitis. The objective of this study was to investigate the possible role of 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), a ketone synthase, on vitamin D3 protecting against experimental colitis.

METHODS

HMGCS2 and vitamin D receptor (VDR) were measured in UC patients. The effects of vitamin D deficiency (VDD) and exogenous 1,25(OH)2D3 supplementation on experimental colitis were investigated in dextran sulfate sodium (DSS)-treated mice. DSS-induced oxidative stress and inflammation were analyzed in HT-29 cells. HMGCS2 was detected in 1,25(OH)2D3-pretreated HT-29 cells and mouse intestines. HMGCS2 was silenced to investigate the role of HMGCS2 in 1,25(OH)2D3 protecting against experimental colitis.

RESULTS

Intestinal HMGCS2 downregulation was positively correlated with VDR reduction in UC patients. The in vivo experiments showed that VDD exacerbated DSS-induced colitis. By contrast, 1,25(OH)2D3 supplementation ameliorated DSS-induced colon damage, oxidative stress and inflammation. HMGCS2 was up-regulated after 1,25(OH)2D3 supplementation both in vivo and in vitro. Transfection with HMGCS2-siRNA inhibited antioxidant and anti-inflammatory effects of 1,25(OH)2D3 in DSS-treated HT-29 cells.

CONCLUSION

1,25(OH)2D3 supplementation up-regulates HMGCS2, which is responsible for 1,25(OH)2D3-mediated protection against oxidative stress and inflammation in DSS-induced colitis. These findings provide a potential therapeutic strategy for alleviating colitis-associated oxidative stress and inflammation.

Vitamin D Attenuates Ulcerative Colitis by Inhibiting ACSL4-Mediated Ferroptosis

BACKGROUND

With environmental and lifestyle changes, recent epidemiological studies have shown that the prevalence of Ulcerative Colitis (UC) is on the rise, while treatment options are limited. There is an urgent need to explore the underlying mechanisms of vitamin D (VD) as an effective treatment.

METHODS

Dextran sulfate sodium-induced mice and lipopolysaccharide-induced HCT116 cells were used to establish the classic UC models in vivo and in vitro, respectively. Typical symbols of inflammation (IL-6, COX-2), oxidative stress (MDA, MPO, GSH), and ferroptosis (ACSL4, GPX4, SLC7A11, and Iron) were analyzed by Western blot, Immunohistochemistry, RT-PCR, and relative assay kits. The inflammation factors and oxidative stress injury of cells transfected with ACSL4+/+ plasmids were tested by Western blot, MDA, and MPO methods.

RESULTS

Vitamin D attenuated the levels of COX-2, IL-6, Iron, MDA, and MPO and improved SOD1 and GSH contents in DSS + VD and LPS + VD groups, compared with model groups. Ferrostatin-1 (Fer-1) could relieve the levels of COX-2, IL-6, Iron, MDA, and MPO while increasing the contents of SOD1 and GSH in DSS + Fer-1 and LPS + Fer-1 compared to model groups. VD downregulated the expression of ACSL4 and upregulated GPX4 in tissues and cells. After transfected with ACSL4+/+ plasmids, we found VD's role of downregulating inflammation and oxidative stress was relieved.

CONCLUSIONS

Vitamin D can relieve UC by inhibiting ferroptosis both in mice and in cells through the negative regulation of ACSL4, providing new insight into the therapeutic function of VD on UC.

Compromised NHE8 Expression Is Responsible for Vitamin D-Deficiency Induced Intestinal Barrier Dysfunction

Objectives: Vitamin D (VitD) and Vitamin D receptor (VDR) are suggested to play protective roles in the intestinal barrier in ulcerative colitis (UC). However, the underlying mechanisms remain elusive. Evidence demonstrates that Na+/H+ exchanger isoform 8 (NHE8, SLC9A8) is essential in maintaining intestinal homeostasis, regarded as a promising target for UC therapy. Thus, this study aims to investigate the effects of VitD/VDR on NHE8 in intestinal protection. Methods: VitD-deficient mice, VDR-/- mice and NHE8-/- mice were employed in this study. Colitis mice were established by supplementing DSS-containing water. Caco-2 cells and 3D-enteroids were used for in vitro studies. VDR siRNA (siVDR), VDR over-expression plasmid (pVDR), TNF-α and NF-κb p65 inhibitor QNZ were used for mechanical studies. The expression of interested proteins was detected by multiple techniques. Results: In colitis mice, paricalcitol upregulated NHE8 expression was accompanied by restoring colonic mucosal injury. In VitD-deficient and VDR-/- colitis mice, NHE8 expression was compromised with more serious mucosal damage. Noteworthily, paricalcitol could not prevent intestinal barrier dysfunction and histological destruction in NHE8-/- mice. In Caco-2 cells and enteroids, siVDR downregulated NHE8 expression, further promoted TNF-α-induced NHE8 downregulation and stimulated TNF-α-induced NF-κb p65 phosphorylation. Conversely, QNZ blocked TNF-α-induced NHE8 downregulation in the absence or presence of siVDR. Conclusions: Our study indicates depressed NHE8 expression is responsible for VitD-deficient-induced colitis aggravation. These findings provide novel insights into the molecular mechanisms of VitD/VDR in intestine protection in UC.

Consumption of honey ameliorates lipopolysaccharide-induced intestinal barrier dysfunction via upregulation of tight junction proteins

PURPOSE

The leaky gut barrier is an important factor leading to various inflammatory gastrointestinal disorders. The nutritional value of honey and variety of its health benefits have long been recognized. This study was undertaken to assess the role of Indian mustard honey in preventing lipopolysaccharide (LPS)-induced intestinal barrier dysfunction using a combination of in vitro and in vivo experimental model systems.

METHODS

LPS was used to induce intestinal barrier damage in a trans-well model of Caco-2 cells (1 µg/ml) and in Swiss albino mice (5 mg/kg body weight). Gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS) were used to analyse sugar and phenolic components in honey samples. The Caco-2 cell monolayer integrity was evaluated by transepithelial electrical resistance (TEER) and paracellular permeability assays. The histopathology of intestinal tissue was analysed by haematoxylin and eosin dual staining. The quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to quantify the transcription of genes. The protein expression was analysed by immunofluorescence, western blot and ELISA-based techniques.

RESULTS

The in vitro data showed that honey prevented LPS-induced intestinal barrier dysfunction dose dependently as was measured by TEER and paracellular flux of FITC-dextran dye. Further, the in vivo data showed a prophylactic effect of orally administered honey as it prevented the loss of intestinal barrier integrity and villus structure. The cellular localization and expression of tight junction (TJ) proteins were upregulated along with downregulation of pro-inflammatory cytokines in response to the administration of honey with LPS.

CONCLUSIONS

The findings of this study suggest a propitious role of honey in the maintenance of TJ protein integrity, thereby preventing LPS-induced intestinal barrier disintegration.

Developmental vitamin D-deficiency produces autism-relevant behaviours and gut-health associated alterations in a rat model

Developmental vitamin D (DVD)-deficiency is an epidemiologically established risk factor for autism. Emerging studies also highlight the involvement of gut microbiome/gut physiology in autism. The current study aims to examine the effect of DVD-deficiency on a broad range of autism-relevant behavioural phenotypes and gut health. Vitamin D deficient rat dams exhibited altered maternal care, DVD-deficient pups showed increased ultrasonic vocalizations and as adolescents, social behaviour impairments and increased repetitive self-grooming behaviour. There were significant impacts of DVD-deficiency on gut health demonstrated by alterations to the microbiome, decreased villi length and increased ileal propionate levels. Overall, our animal model of this epidemiologically validated risk exposure for autism shows an expanded range of autism-related behavioural phenotypes and now alterations in gut microbiome that correlate with social behavioural deficits raising the possibility that DVD-deficiency induced ASD-like behaviours are due to alterations in gut health.

Vitamin D3/VDR inhibits inflammation through NF-κB pathway accompanied by resisting apoptosis and inducing autophagy in abalone Haliotis discus hannai

Vitamin D3 is believed to be a contributing factor to innate immunity. Vitamin D receptor (VDR) has a positive effect on inhibiting nuclear factor κB (NF-κB)-mediated inflammation. The underlying molecular mechanisms remain unclear, particularly in mollusks. Consequently, this study will investigate the process of vitamin D3/VDR regulating NF-κB pathway and further explore their functions on inflammation, autophagy, and apoptosis in abalone Haliotis discus hannai. Results showed that knockdown of VDR by using siRNA and dsRNA of VDR in vitro and in vivo led to more intense response of NF-κB signaling to lipopolysaccharide and higher level of apoptosis and autophagy. In addition, 1,25(OH)2D3 stimulation after VDR silencing could partially alleviate apoptosis and induce autophagy. Overexpression of VDR restricted the K48-polyubiquitin chain-dependent inhibitor of κB (IκB) ubiquitination and apoptosis-associated speck-like protein containing CARD (ASC) oligomerization. Besides, VDR silencing resulted in increase of ASC speck formation. In further mechanistic studies, we showed that VDR can directly bind to IκB and IKK1 in vitro and in vivo. In the feeding trial, H&E staining, TUNEL, and electron microscope results showed that vitamin D3 deficiency (0 IU/kg) could recruit more basophilic cells and increase more TUNEL-positive apoptotic cells and lipid droplets (LDs) than vitamin D3 supplement (1000 IU/kg and 5000 IU/kg). In summary, abalone VDR plays a negative regulator role in NF-κB-mediated inflammation via interacting with IκB and inhibiting ubiquitin-dependent degradation of IκB. Vitamin D3 in combination with VDR is essential to establish a delicate balance between autophagy and apoptosis in response to inflammation.

The Role of Vitamin D in Health and Disease: A Narrative Review on the Mechanisms Linking Vitamin D with Disease and the Effects of Supplementation

Vitamin D insufficiency or deficiency (VDD) is a very prevalent condition in the general population. Vitamin D is necessary for optimal bone mineralization, but apart from the bone effects, preclinical and observational studies have suggested that vitamin D may have pleiotropic actions, whereas VDD has been linked to several diseases and higher all-cause mortality. Thus, supplementing vitamin D has been considered a safe and inexpensive approach to generate better health outcomes-and especially so in frail populations. Whereas it is generally accepted that prescribing of vitamin D in VDD subjects has demonstrable health benefits, most randomized clinical trials, although with design constraints, assessing the effects of vitamin D supplementation on a variety of diseases have failed to demonstrate any positive effects of vitamin D supplementation. In this narrative review, we first describe mechanisms through which vitamin D may exert an important role in the pathophysiology of the discussed disorder, and then provide studies that have addressed the impact of VDD and of vitamin D supplementation on each disorder, focusing especially on randomized clinical trials and meta-analyses. Despite there already being vast literature on the pleiotropic actions of vitamin D, future research approaches that consider and circumvent the inherent difficulties in studying the effects of vitamin D supplementation on health outcomes are needed to assess the potential beneficial effects of vitamin D. The evaluation of the whole vitamin D endocrine system, rather than only of 25-hydroxyvitamin D levels before and after treatment, use of adequate and physiologic vitamin D dosing, grouping based on the achieved vitamin D levels rather than the amount of vitamin D supplementation subjects may receive, and sufficiently long follow-up are some of the aspects that need to be carefully considered in future studies.

The synergistic effect of Levilactobacillus brevis IBRC-M10790 and vitamin D3 on Helicobacter pylori-induced inflammation

Background

Owing to the emergence and spread of multidrug resistance mechanisms in Helicobacter pylori, achieving a successful eradication has become exceedingly difficult. Thus, this study for the first time determines the effect of a combination of vitamin D3 and probiotic on the pathogenesis and treatment of H. pylori.

Methods

We established an in vitro experimental system using AGS human gastric carcinoma cells and explored the synergistic effect of Levilactobacillus brevis IBRC-M10790 and vitamin D3 on H. pylori. Live and pasteurized L. brevis, L. brevis-derived membrane vesicles (MVs), and L. brevis cell-free supernatant (CFS), as well as their combination with vitamin D3 were used during this study. We assessed the anti-inflammatory and anti-oxidative effects of these combinations using RT-qPCR and ELISA, respectively. We further performed an adhesion assay to evaluate the influence of L. brevis and vitamin D3 on the adherence rate of H. pylori to AGS cells.

Results

Our results demonstrated that L. brevis and vitamin D3 possess anti-inflammatory and anti-oxidative effects against H. pylori infection in AGS cells. The combination of vitamin D3 with the probiotic strain (particularly live L. brevis and its CFS) can more efficiently reduce the expression of pro-inflammatory cytokines IL-6, IL-8, IFN-γ, and TNF-α in the AGS cells. Moreover, vitamin D3 and L. brevis exhibited an additive impact preserving the integrity of the epithelial barrier by increasing the expression of the tight junction protein ZO-1. Furthermore, this combination can potentially reduce H. pylori adherence to AGS cells.

Conclusions

This study indicates the advantage of combining vitamin D3 and probiotic to attenuate H. pylori-induced inflammation and oxidative stress. Consequently, probiotic and vitamin D3 co-supplementation can be considered as a novel therapeutic approach to manage and prevent H. pylori infection.

The multiphasic TNF-α-induced compromise of Calu-3 airway epithelial barrier function

Purpose: Airway epithelial barrier leak and the involvement of proinflammatory cytokines play a key role in a variety of diseases. This study evaluates barrier compromise by the inflammatory mediator Tumor Necrosis Factor-α (TNF-α) in the human airway epithelial Calu-3 model. Methods: We examined the effects of TNF-α on barrier function in Calu-3 cell layers using Transepithelial Electrical Resistance (TER) and transepithelial diffusion of radiolabeled probe molecules. Western immunoblot analyses of tight junctional (TJ) proteins in detergent soluble fractions were performed. Results: TNF-α dramatically reduced TER and increased paracellular permeability of both 14C-D-mannitol and the larger 5 kDa probe, 14C-inulin. A time course of the effects shows two separate actions on barrier function. An initial compromise of barrier function occurs 2-4 hours after TNF-α exposure, followed by complete recovery of barrier function by 24 hrs. Beginning 48 hrs. post-exposure, a second more sustained barrier compromise ensues, in which leakiness persists through 144 hrs. There were no changes in TJ proteins observed at 3 hrs. post exposure, but significant increases in claudins-2, -3, -4, and -5, as well as a decrease in occludin were seen at 72 hrs. post TNF-α exposure. Both the 2-4 hr. and the 72 hr. TNF-α induced leaks are shown to be mediated by the ERK signaling pathway. Conclusion: TNF-α induced a multiphasic transepithelial leak in Calu-3 cell layers that was shown to be ERK mediated, as well as involve changes in the TJ complex. The micronutrients, retinoic acid and calcitriol, were effective at reducing this barrier compromise caused by TNF-α. The significance of these results for airway disease and for COVID-19 specifically are discussed.

Tobacco Alkaloid Assessment in a DSS-Induced Colitis Mouse Model with a Fully Humanized Immune System

Inflammatory bowel disease (IBD) refers to chronic intestinal immune-mediated diseases including two main disease manifestations: ulcerative colitis (UC) and Crohn’s disease (CD). Epidemiological, clinical, and preclinical evidence has highlighted the potential anti-inflammatory properties of naturally occurring alkaloids. In the present study, we investigated the potential anti-inflammatory activities of the tobacco alkaloids nicotine and anatabine in a dextran sulfate sodium (DSS)-induced UC mouse model with a fully humanized immune system. Our results show that nicotine significantly reduced all acute colitis symptoms and improved colitis-specific endpoints, including histopathologically assessed colon inflammation, tissue damage, and mononuclear cell infiltration. The tobacco alkaloid anatabine showed similar effectiveness trends, although they were generally weaker or not significant. Gene expression analysis in the context of biological network models of IBD further pinpointed a possible mechanism by which nicotine attenuated DSS-induced colitis in humanized mice. The current study enables further investigation of possible molecular mechanisms by which tobacco alkaloids attenuate UC symptoms.

Proteomic Analysis Reveals Changes in Tight Junctions in the Small Intestinal Epithelium of Mice Fed a High-Fat Diet

The impact of a high-fat diet (HFD) on intestinal permeability has been well established. When bacteria and their metabolites from the intestinal tract flow into the portal vein, inflammation in the liver is triggered. However, the exact mechanism behind the development of a leaky gut caused by an HFD is unclear. In this study, we investigated the mechanism underlying the leaky gut related to an HFD. C57BL/6J mice were fed an HFD or control diet for 24 weeks, and their small intestine epithelial cells (IECs) were analyzed using deep quantitative proteomics. A significant increase in fat accumulation in the liver and a trend toward increased intestinal permeability were observed in the HFD group compared to the control group. Proteomics analysis of the upper small intestine epithelial cells identified 3684 proteins, of which 1032 were differentially expressed proteins (DEPs). Functional analysis of DEPs showed significant enrichment of proteins related to endocytosis, protein transport, and tight junctions (TJ). Expression of Cldn7 was inversely correlated with intestinal barrier function and strongly correlated with that of Epcam. This study will make important foundational contributions by providing a comprehensive depiction of protein expression in IECs affected by HFD, including an indication that the Epcam/Cldn7 complex plays a role in leaky gut.

Therapeutic and Prophylactic Role of Vitamin D and Curcumin in Acetic Acid-Induced Acute Ulcerative Colitis Model

Ulcerative Colitis (UC) is a disease that negatively affects quality of life and is associated with sustained oxidative stress, inflammation and intestinal permeability. Vitamin D and Curcumin; It has pharmacological properties beneficial to health, including antioxidant and anti-inflammatory properties. Our study investigates the role of Vitamin D and Curcumin in acetic acid-induced acute colitis model. To investigate the effect of Vitamin D and Curcumin, Wistar-albino rats were given 0.4 mcg/kg Vitamin D (Post-Vit D, Pre-Vit D) and 200 mg/kg Curcumin (Post-Cur, Pre-Cur) for 7 days and acetic acid was injected into all rats except the control group. Our results; colon tissue TNF-α, IL-1β, IL-6, IFN-γ and MPO levels were found significantly higher and Occludin levels were found significantly lower in the colitis group compared to the control group (p < 0.05). TNF-α and IFN-γ levels decreased and Occludin levels increased in colon tissue of Post-Vit D group compared to colitis group (p < 0.05). IL-1β, IL-6 and IFN-γ levels were decreased in colon tissue of Post-Cur and Pre-Cur groups (p < 0.05). MPO levels in colon tissue decreased in all treatment groups (p < 0.05). Vitamin D and Curcumin treatment significantly reduced inflammation and restored the normal histoarchitecture of the colon. From the present study findings, we can conclude that Vitamin D and Curcumin protect the colon from acetic acid toxicity with their antioxidant and anti-inflammatory potential.

Vitamin D and Microbiome: Molecular Interaction in Inflammatory Bowel Disease Pathogenesis

Studies of systemic autoimmune diseases point to characteristic microbial patterns in various diseases, including inflammatory bowel disease (IBD). Autoimmune diseases, and IBD in particular, show a predisposition to vitamin D deficiency, leading to alterations in the microbiome and disruption of intestinal epithelial barrier integrity. In this review, we examine the role of the gut microbiome in IBD and discuss how vitamin D-vitamin D receptor (VDR)-associated molecular signaling pathways contribute to the development and progression of IBD through their effects on gut barrier function, the microbial community, and immune system function. The present data demonstrate that vitamin D promotes the proper function of the innate immune system by acting as an immunomodulator, exerting anti-inflammatory effects, and critically contributing to the maintenance of gut barrier integrity and modulation of the gut microbiota, mechanisms that may influence the IBD development and progression. VDR regulates the biological effects of vitamin D and is related to environmental, genetic, immunologic, and microbial aspects of IBD. Vitamin D influences the distribution of the fecal microbiota, with high vitamin D levels associated with increased levels of beneficial bacterial species and lower levels of pathogenic bacteria. Understanding the cellular functions of vitamin D-VDR signaling in intestinal epithelial cells may pave the way for the development of new treatment strategies for the therapeutic armamentarium of IBD in the near future.

The interaction between obesity and visceral hypersensitivity

Obesity has been a worldwide problem associated with numerous chronic diseases such as cardiovascular disease, type 2 diabetes, and metabolic disorders. It may also play a role in visceral hypersensitivity, contributing to irritable bowel syndrome. (i) Adipose tissue secretes various inflammatory mediators, causing intestinal hyperpermeability and nerve endings activation. (ii) Obesity and gastrointestinal microbiota could affect each other, and microbial metabolites can increase sensitivity of the colon. (iii) Vitamin D deficiency contributes to both fat accumulation and disruption of the intestinal mucosal barrier. (iv) Brain-gut axis may be another bridge from obesity to visceral hypersensitivity.

Vitamin D Receptor Mediates Attenuating Effect of Lithocholic Acid on Dextran Sulfate Sodium Induced Colitis in Mice

Bile acids are major components of bile; they emulsify dietary lipids for efficient digestion and absorption and act as signaling molecules that activate nuclear and membrane receptors. The vitamin D receptor (VDR) is a receptor for the active form of vitamin D and lithocholic acid (LCA), a secondary bile acid produced by the intestinal microflora. Unlike other bile acids that enter the enterohepatic circulation, LCA is poorly absorbed in the intestine. Although vitamin D signaling regulates various physiological functions, including calcium metabolism and inflammation/immunity, LCA signaling remains largely unknown. In this study, we investigated the effect of the oral administration of LCA on colitis in a mouse model using dextran sulfate sodium (DSS). Oral LCA decreased the disease activity of colitis in the early phase, which is a phenotype associated with the suppression of histological injury, such as inflammatory cell infiltration and goblet cell loss. These protective effects of LCA were abolished in VDR-deleted mice. LCA decreased the expression of inflammatory cytokine genes, but this effect was at least partly observed in VDR-deleted mice. The pharmacological effect of LCA on colitis was not associated with hypercalcemia, an adverse effect induced by vitamin D compounds. Therefore, LCA suppresses DSS-induced intestinal injury in its action as a VDR ligand.

Effect of prepartum source and amount of vitamin D supplementation on lactation performance of dairy cows

The objectives of this experiment were to determine the effects of supplementing 25-hydroxyvitamin D₃ (calcidiol, CAL) compared with vitamin D₃ (cholecalciferol, CHOL) at 1 or 3 mg/d in late gestation on production outcomes of dairy cows. One hundred thirty-three parous and 44 nulliparous pregnant Holstein cows were enrolled in the experiment. Cows were blocked by parity and previous lactation milk yield (parous) or genetic merit (nulliparous) and assigned randomly to receive 1 or 3 mg/d of CAL or CHOL in a 2 × 2 factorial arrangement of treatments (CAL1, CAL3, CHOL1, and CHOL3). Treatments were provided to individual cows as a top-dress to the prepartum diet from 250 d in gestation until parturition. The prepartum diet had a dietary cation-anion difference of -128 mEq/kg of dry matter. Production and disease were evaluated for the first 42 d in milk, and reproduction was evaluated to 300 d in milk. Incidence of postpartum diseases did not differ among treatments. Feeding CAL compared with CHOL increased yields of colostrum and colostrum fat, protein, and total solids, resulting in an increased amount of net energy for lactation secreted as colostrum (CHOL = 7.0 vs. CAL = 9.0 ± 0.7 Mcal). An interaction between source and amount was observed for milk yield: CAL3 increased milk yield compared with CHOL3 (CHOL3 = 34.1 vs. CAL3 = 38.7 ± 1.4 kg/d) but milk yield did not differ between CAL1 and CHOL1 (CHOL1 = 36.9 vs. CAL1 = 36.4 ± 1.4 kg/d). Concentrations of serum calcidiol on day of calving and average serum Ca from d 2 to 11 postpartum were positively associated with milk yield in the first 42 d in milk. Interactions between source and amount of vitamin D were also observed for pregnancy after first AI: the percentage of cows receiving CHOL1 and CAL3 that became pregnant was smaller than that of cows receiving CHOL3 and CAL1. However, pregnancy per AI and pregnancy by 300 d in milk did not differ among treatments. Overall, CAL3 increased milk yield compared with CHOL3, whereas in cows fed 1 mg/d (CAL1 and CHOL1), the source of vitamin D generally had no effect. The effect of CAL3 may be explained in part by serum CAL concentrations and postpartum serum Ca, which were associated with milk yield.

Comparison of the anti-inflammatory effects of vitamin E and vitamin D on a rat model of dextran sulfate sodium-induced ulcerative colitis

The present study aimed to compare the clinical effects of vitamin E and vitamin D on a rat model of dextran sulfate sodium (DSS)-induced ulcerative colitis (UC), and to elucidate the underlying mechanisms associated with changes in the levels of cytokines. After successful establishment of the rat model of DSS-induced UC, prednisolone (1 mg/kg), vitamin D (50 ng) and vitamin E (6, 30 and 150 IU/kg) were orally administered for 1 week. The pharmacodynamics were evaluated by a daily combination of clinical observation (CO) scores, histopathological evaluations and assessment of molecular markers of inflammation. Administration of vitamin D, vitamin E (30 and 150 IU/kg), prednisolone, and the combination of vitamin D and vitamin E resulted in a decrease in CO scores. The severity of inflammation of the colon was markedly alleviated in the treatment groups compared with that in the untreated DSS group according to the results of histopathological examination; however, they showed different inhibitory effects on the levels of some cytokines. In conclusion, the present results indicated that oral administration of vitamin E could promote recovery of DSS-induced UC by the inhibition of proinflammatory cytokines, and that its underlying mechanism may differ from that of vitamin D and glucocorticoid drugs.

Serum 25-Hydroxyvitamin D and Cancer Risk: A Systematic Review of Mendelian Randomization Studies

Epidemiological studies suggest that higher serum 25-hydroxyvitamin D is associated with lower risk for several cancers, including breast, prostate, colorectal, and lung cancers. To mitigate confounding, genetic instrumental variables (IVs) have been used to estimate causal associations between 25-hydroxivtamin D and cancer risk via Mendelian randomization (MR). We provide a systematic review of 31 MR studies concerning 25-hydroxyvitamin D and cancer incidence and mortality identified from biomedical databases. MR analyses were conducted almost exclusively in European-ancestry populations and identified no statistically significant associations between higher genetically predicted 25-hydroxyvitamin D and lower risk for total cancer or colorectal, breast, prostate, lung, or pancreatic cancers. In recent studies including ≥80 genetic IVs for 25-hydroxyvitamin D, null associations were reported for total cancer (odds ratio [95% confidence interval] per 1-standard deviation increase: 0.98 [0.93-1.04]), breast (1.00 [0.98-1.02]), colorectal (0.97 [0.88-1.07]), prostate (0.99 [0.98-1.01]), and lung cancer (1.00 [0.93-1.03]). A protective association was observed for ovarian cancer in the Ovarian Cancer Association Consortium (0.78 [0.63-0.96] per 20 nmol/L increase, p-trend = 0.03), but not in the UK Biobank (1.10 [0.80-1.51]). Null associations were reported for other tumor sites (bladder, endometrium, uterus, esophagus, oral cavity and pharynx, kidney, liver, thyroid, or neural cells). An inconsistent protective association for cancer-specific mortality was also observed. Results from MR analyses do not support causal associations between 25-hydroxyvitamin D and risk for cancer incidence or mortality. Studies including non-White populations may be valuable to understand low 25-hydroxyvitamin D as a modifiable risk factor in populations with a higher risk of common cancers, including African ancestry individuals.

Vitamin A- and D-Deficient Diets Disrupt Intestinal Antimicrobial Peptide Defense Involving Wnt and STAT5 Signaling Pathways in Mice

Vitamin A and D deficiencies are associated with immune modulatory effects and intestinal barrier impairment. However, the underlying mechanisms remain unclear. C57BL/6J mice were fed either a diet lacking in vitamin A (VAd), vitamin D (VDd) or a control diet (CD) for 12 weeks. Gut barrier function, antimicrobial peptide (AMP) defense and regulatory pathways were assessed. VAd mice compared to CD mice showed a reduced villus length in the ileum (p < 0.01) and decreased crypt depth in the colon (p < 0.05). In both VAd- and VDd-fed mice, ileal α-defensin 5 (p < 0.05/p < 0.0001 for VAd/VDd) and lysozyme protein levels (p < 0.001/p < 0.0001) were decreased. Moreover, mRNA expression of lysozyme (p < 0.05/p < 0.05) and total cryptdins (p < 0.001/p < 0.01) were reduced compared to controls. Furthermore, matrix metalloproteinase-7 (Mmp7) mRNA (p < 0.0001/p < 0.001) as well as components of the Wnt signaling pathway were decreased. VAd- and VDd-fed mice, compared to control mice, exhibited increased expression of pro-inflammatory markers and β-defensins in the colon. Organoid cell culture confirmed that vitamins A and D regulate AMP expression, likely through the Jak/STAT5 signaling pathway. In conclusion, our data show that vitamin A and D regulate intestinal antimicrobial peptide defense through Wnt and STAT5 signaling pathways.

The association between vitamin D status and inflammatory bowel disease among children and adolescents: A systematic review and meta-analysis

Aim

Vitamin D deficiency is very common among children with IBD. Since there are conflicting results regarding the association of vitamin D with IBD, we conducted this systematic review to confirm the association of vitamin D with IBD.

Methods

We conducted a systematic search in Scopus, Cochrane Library, Web of Science, PubMed, and Google Scholar to find relevant studies. Articles with cross-sectional and case-control designs that reported the association between vitamin D and IBD among children were included.

Results

Eventually, 9 studies (with 16 effect sizes) reported the mean and SD or the median and the interquartile range of serum vitamin D levels in both subjects with IBD and control subjects. The random effects meta-analysis revealed that subjects with IBD had -1.159 ng/ml (95% CI: -2.783, 0.464) lower serum vitamin D concentrations compared with their healthy counterparts, but this difference was not significant. A total of 14 studies (with 18 effect sizes) with 2,602 participants provided information for the prevalence of vitamin D deficiency or insufficiency in patients with IBD as 44% (95% CI: 0.34-0.54) with significant heterogeneity noted among studies (p < 0.001; I² = 97.31%).

Conclusion

This systematic and meta-analysis study revealed that vitamin D deficiency was associated with IBD. Longitudinal studies should be conducted in the future to confirm our findings. Large randomized controlled trials assessing the doses of supplementation of vitamin D would provide a better understanding of the association between vitamin D and IBD.

The Pivotal Role of Aryl Hydrocarbon Receptor-Regulated Tight Junction Proteins and Innate Immunity on the Synergistic Effects of Postbiotic Butyrate and Active Vitamin D3 to Defense against Microbial Invasion in Salmonella Colitis

Our recent report illustrated the unitedly advantageous effects of postbiotic butyrate on active vitamin D3 (VD3)-orchestrated innate immunity in Salmonella colitis. There is growing awareness that aryl hydrocarbon receptor (AhR) can regulate intestinal immunity and barrier function, through modulating cecal inflammation and junction proteins expression. Hence, we researched the participation of AhR-regulated tight junction functions on the united effects of butyrate and VD3 on intestinal defense to Salmonella infection. Salmonella colitis model were elicited by oral gavage with 1 × 10⁸ CFU of a S. typhimurium wild-type strain SL1344 in C57BL/6 mice. Before and after the colitis generation, mice were fed with butyrate and/or VD3 by oral gavage in the absence or presence of intraperitoneal injection of AhR inhibitor for 4 and 7 days, respectively. We observed that butyrate and VD3 could concert together to reduce the invasion of Salmonella in colitis mice by enhancing cecal cytokines and antimicrobial peptides expression and reducing zonulin and claudin-2 protein expressions in mucosal stain, compared to single treatment, which were counteracted by AhR inhibitor. It implies that AhR is involved in the united effects of butyrate and VD3 on the intestinal defense to Salmonella infection in colitis mice. This study discloses the promising alternative therapy of combining postbiotic and VD3 for invasive Salmonellosis and the pivotal role of AhR pathway.

The role of vitamin D receptor gene polymorphism in the development of necrotizing enterocolitis

BACKGROUND

Vitamin D and its receptor (VDR) effects on the gastrointestinal system are among its most critical multisystemic effects.

METHODS

This study aimed to reveal that VDR gene polymorphisms may constitute a risk factor for necrotizing enterocolitis (NEC). VDR Fok1-Bsm1-Apa single-nucleotide polymorphisms were analyzed in the NEC group (n = 74) and the control group (n = 147). Among 1112 babies at and below 36 weeks of gestational age who were hospitalized between January 2013 and December 2016 with a diagnosis of prematurity, 74 of a total of 148 patients who developed NEC during follow-up (NEC group) were included in the study. When NEC was diagnosed according to clinical and radiological findings and staged using Modified Bell criteria, 9 (12.1%) of 74 babies were stage 1A, 13 (17.5%) stage 1B, and 5 (6.7%) stage 2A, 33 (44.5%) stage 2B, 7 (9.4%) stage 3A, 7 (9.4%) stage 3B. Of 964 babies who did not develop NEC during follow-up, 147 were included as the control group in the study. Genotyping of VDR polymorphisms was assayed by real-time PCR. From 221 premature babies in the NEC and control groups, 2 ml peripheral blood was taken appropriately and meticulously into an EDTA tube. DNA was isolated from these blood samples. DNA amplification was performed using a thermal cycler (Applied Biosystems GeneAmp PCR System 9600).

RESULTS

When the two groups were compared in terms of the prevalence of VDR Fok1 C/T genotype, it was found that TT genotype increased the risk of NEC by 2.697 times, and there was a significant relationship between TT genotype and the risk of NEC (p = 0.041). Multivariable logistic regression analysis was performed in terms of gestational age, birth weight, VDR gene polymorphism data between NEC and the control group. According to the analysis results, TT polymorphism, increased the risk of disease 4.5 times (p = 0.033).

CONCLUSION

Fok 1 C > T polymorphism in the VDR gene plays a role in the development of NEC. Identifying the risk groups by detecting gene polymorphisms that cause increased susceptibility to NEC may assist in the follow-up of these patients and in making early treatment decisions for them.

IMPACT

In this study examining the non-bone effects of the genetic differences in vitamin D metabolism in premature babies, Fok 1 polymorphism has been observed to be an essential risk factor for NEC. This is the first study in our country that has investigated the relationship between VDR gene polymorphism and necrotizing enterocolitis among the Turkish population. Identifying the risk groups by detecting gene polymorphisms that cause increased susceptibility to NEC may assist in the monitoring of these patients and in making early treatment decisions for them.

Associations between serum vitamin D biomarkers and tumor expression of Ki67, p53, and COX-2 in colorectal cancer cases from the Southern Community Cohort Study

Higher 25-hydroxyvitamin D is associated with lower colorectal cancer (CRC) risk, with limited data from African Americans (AAs), who have greater risk for CRC and 25-hydroxyvitamin D deficiency. In a predominantly AA sample of CRC cases from the Southern Community Cohort Study (SCCS), we report associations between vitamin D biomarkers and tumor expression of proteins implicated in vitamin D's anti-tumorigenic pathways (e.g. proliferation and inflammation) and CRC prognosis. SCCS participants with incident CRC were identified via state cancer registries. Serum 25-hydroxyvitamin D and vitamin D binding protein (VDBP) were measured at enrollment. 'Free' 25-hydroxyvitamin D was calculated via standard equation. Cellular Ki67, p53, and COX-2 were measured from tumor samples and categorized using literature-defined cut-points related to survival. Generalized linear models were used to measure associations between vitamin D exposures, tumor biomarkers, and stage. In total, 104 cases (40-79 years) were analyzed. 25-hydroxyvitamin D was not associated with high Ki67 (odds ratio (OR) per 1-standard deviation (SD) increase [95% confidence interval] 1.35[0.86-2.11]), p53 (0.75[0.47-1.20]), or COX-2 expression (1.25[0.78-2.01]), or metastatic disease (1.04[0.59-1.81]). Mean biomarker expression was unrelated to 25-hydroxyvitamin D (p-trend ≥.09). Null associations were observed for VDBP and free 25-hydroxyvitamin D. In AAs (n = 70), higher VDBP was associated with lower odds of high Ki67 expression (0.53[0.28-0.98], p-trend =.04). In conclusion, we observed no associations between 25-hydroxyvitamin D and prognostic marker expression in CRC. An inverse association between VDBP and tumor Ki67 in AAs is consistent with reports showing relationships with reduced CRC mortality.

Possible Impact of Vitamin D Status and Supplementation on SARS-CoV-2 Infection Risk and COVID-19 Symptoms in a Cohort of Patients with Inflammatory Bowel Disease

The coronavirus disease (COVID-19) pandemic represents a global health challenge, particularly considering concomitant diseases. Patients with inflammatory bowel diseases (IBD) can be considered a population at risk. On the other hand, the risk of developing IBD and COVID-19 have both been described as modulated by vitamin D (VD) levels. In this work, a cohort of 106 adult patients affected by IBD was prospectively enrolled, during the second wave of the pandemic in Italy. In these patients, VD plasma levels, demographic, and clinical characteristics were tested for a correlation/an association with the risk of infection with SARS-CoV-2 in the study period (anti-spike IgG positivity) and the severity of COVID-19 symptoms. By multivariate logistic regression analysis, VD supplementation (Odds Ratio; OR 0.116, p = 0.002), therapy with monoclonal antibodies (OR 0.227, p = 0.007), and the use of mesalazine (OR 2.968, p = 0.046) were found to be independent predictors of SARS-CoV-2 positivity. Moreover, hypertension was associated with severe disease (p = 0.019), while a VD level higher than 30 ng/mL (p = 0.031, OR 0.078) was associated with asymptomatic infection. No interplay between IBD activity and COVID-19 risk of infection or symptoms was observed. These results confirm the importance of VD levels in defining the risk of COVID-19 and give encouraging data about the safety of maintaining immunomodulatory treatments for IBD during the COVID-19 pandemic.

Vitamin D3 and Lactobacillus rhamnosus GG/p40 Synergize to Protect Mice From Colitis by Promoting Vitamin D Receptor Expression and Epithelial Proliferation

BACKGROUND

While vitamin D (VitD) levels are negatively correlated with inflammatory bowel disease (IBD) activity, VitD supplementation does not reduce IBD severity. The probiotic Lactobacillus rhamnosus GG (LGG), which secretes p40, can upregulate colonic VitD receptor (VDR) expression. We therefore evaluated synergy between VitD3 and LGG/p40 in the treatment of mouse colitis.

METHODS

A dextran sulfate sodium (DSS) colitis model was established in Vdr+/+ and Vdr-/- mice, and mice were treated with VitD3, LGG, or p40 alone or in combination for 7 to 14 days. Colitis severity was assessed by weight loss, disease activity index (DAI), colon length, histology, and inflammatory cytokine expression together with VDR expression, proliferation, and apoptosis. In vitro, VDR expression and cell viability were assessed in HCT116 cells after stimulation with p40.

RESULTS

Total and nuclear VDR protein expression were lower in DSS-treated Vdr+/+ mice compared with control mice (P < .05). Compared with the DSS group, VitD3 + LGG alleviated colitis as assessed by significantly improved DAI and histological scores, increased colon length, decreased colonic Tnf, and increased Il10 expression together with increased colonic VDR gene and protein expression and increased Ki-67 proliferation index (P < .05). In Vdr-/- mice, VitD3 + LGG had no effect on DSS colitis. In Vdr+/+ mice, VitD3 + p40 also reduced colitis severity according to clinicopathological and immunological metrics and increased VDR expression and epithelial proliferation (P < .05). In HCT116 cells, p40 stimulation increased VDR protein expression and viability (P < .05).

CONCLUSIONS

VitD3 and LGG/p40 synergistically improve the severity of colitis by increasing colonic VDR expression and promoting colonic epithelial proliferation.

Vitamin D impacts on the intestinal health, immune status and metabolism in turbot (Scophthalmus maximus L.)

Vitamin D (VD) plays a vital role in various physiological processes in addition to its classic functions on maintaining the balance of Ca and P metabolism. However, there still are gaps to understand in depth the issues on the precise requirement, metabolic processes and physiological functions of VD in fish. In this study, we investigated the effects of VD on the growth, intestinal health, host immunity and metabolism in turbot (Scophthalmus maximus L.), one important commercial carnivorous fish in aquaculture, through the supplementation of different doses of dietary VD3 (0, 200, 400, 800 and 1600 μg VD3/kg diet). According to our results, the optimal VD3 level in the feed for turbot growth was estimated to be around 400 IU/kg, whereas VD3 deficiency or overdose in diets induced the intestinal inflammation, lowered the diversity of gut microbiota and impaired the host resistance to bacterial infection in turbot. Moreover, the level of 1α,25(OH)2D3, the active metabolite of VD3, reached a peak value in the turbot serum in the 400 μg group, although the concentrations of Ca and phosphate in the turbot were stable in all groups. Finally, the deficiency of dietary VD3 disturbed the nutritional metabolism in turbot, especially the metabolism of lipids and glucose. In conclusion, this study evaluated the optimal dose of dietary VD3 for turbot and provided the evidence that VD has a significant impact on intestinal health, host immunity and nutritional metabolism in fish, which deepened our understanding on the physiological functions and metabolism of VD3 in fish.

Role of Vitamin D in Celiac Disease and Inflammatory Bowel Diseases

Vitamin D (VD) is a pro-hormone that has long been known as a key regulator of calcium homeostasis and bone health in both children and adults. In recent years, studies have shown that VD may exert many extra-skeletal functions, mainly through a relevant modulation of the innate and adaptive immune system. This has suggested that VD could play a fundamental role in conditioning development, clinical course, and treatment of several autoimmune disorders, including celiac disease (CD) and inflammatory bowel diseases (IBDs). The main aim of this review is to evaluate the relationships between VD, CD, and IBDs. Literature analysis showed a potential impact of VD on CD and IBDs can be reasonably assumed based on the well-documented in vitro and in vivo VD activities on the gastrointestinal tract and the immune system. The evidence that VD can preserve intestinal mucosa from chemical and immunological damage and that VD modulation of the immune system functions can contrast the mechanisms that lead to the intestinal modifications characteristic of gastrointestinal autoimmune diseases has suggested that VD could play a role in controlling both the development and the course of CD and IBDs. Administration of VD in already diagnosed CD and IBD cases has not always significantly modified disease course. However, despite these relevant problems, most of the experts recommend monitoring of VD levels in patients with CD and IBDs and administration of supplements in patients with hypovitaminosis.

Vitamin D as a Nutri-Epigenetic Factor in Autoimmunity-A Review of Current Research and Reports on Vitamin D Deficiency in Autoimmune Diseases

Epigenetics is a series of alterations regulating gene expression without disrupting the DNA sequence of bases. These regulatory mechanisms can result in embryogenesis, cellular differentiation, X-chromosome inactivation, and DNA-protein interactions. The main epigenetic mechanisms considered to play a major role in both health and disease are DNA methylation, histone modifications, and profiling of non-coding RNA. When the fragile balance between these simultaneously occurring phenomena is disrupted, the risk of pathology increases. Thus, the factors that determine proper epigenetic modeling are defined and those with disruptive influence are sought. Several such factors with proven negative effects have already been described. Diet and nutritional substances have recently been one of the most interesting targets of exploration for epigenetic modeling in disease states, including autoimmunity. The preventive role of proper nutrition and maintaining sufficient vitamin D concentration in maternal blood during pregnancy, as well as in the early years of life, is emphasized. Opportunities are also being investigated for affecting the course of the disease by exploring nutriepigenetics. The authors aim to review the literature presenting vitamin D as one of the important nutrients potentially modeling the course of disease in selected autoimmune disorders.

The Crosstalk between Vitamin D and Pediatric Digestive Disorders

Vitamin D is a cyclopentane polyhydrophenanthrene compound involved mainly in bone health and calcium metabolism but also autophagy, modulation of the gut microbiota, cell proliferation, immune functions and intestinal barrier integrity. The sources of vitamin D include sunlight, diet and vitamin D supplements. Vitamin D3, the most effective vitamin D isoform is produced in the human epidermis as a result of sunlight exposure. Vitamin D undergoes two hydroxylation reactions in the liver and kidney to reach its active form, 1,25-dihydroxyvitamin D. Recent studies highlighted a complex spectrum of roles regarding the wellbeing of the gastrointestinal tract. Based on its antimicrobial effect, it was recently indicated that vitamin D supplementation in addition to standard eradication therapy might enhance H. pylori eradication rates. Moreover, it was suggested that low levels of vitamin D might also be involved in the acquisition of H. pylori infection. In terms of celiac disease, the negative effects of vitamin D deficiency might begin even during intrauterine life in the setting of maternal deficiency. Moreover, vitamin D is strongly related to the integrity of the gut barrier, which represents the core of the pathophysiology of celiac disease onset, in addition to being correlated with the histological findings of disease severity. The relationship between vitamin D and cystic fibrosis is supported by the involvement of this micronutrient in preserving lung function by clearing airway inflammation and preventing pathogen airway colonization. Moreover, this micronutrient might exert anticatabolic effects in CF patients. Inflammatory bowel disease patients also experience major benefits if they have a sufficient level of circulating vitamin D, proving its involvement in both induction and remission in these patients. The findings regarding the relationship between vitamin D, food allergies, diarrhea and constipation remain controversial, but vitamin D levels should be monitored in these patients in order to avoid hypo- and hypervitaminosis. Further studies are required to fill the remaining gaps in term of the complex impact of vitamin D on gastrointestinal homeostasis.

Genomic analysis of 1,25-dihydroxyvitamin D3 action in mouse intestine reveals compartment and segment-specific gene regulatory effects

1,25-dihydroxyvitamin D (VD) regulates intestinal calcium absorption in the small intestine (SI) and also reduces risk of colonic inflammation and cancer. However, the intestine compartment-specific target genes of VD signaling are unknown. Here, we examined VD action across three functional compartments of the intestine using RNA-seq to measure VD-induced changes in gene expression and Chromatin Immunoprecipitation with next generation sequencing to measure vitamin D receptor (VDR) genomic binding. We found that VD regulated the expression of 55 shared transcripts in the SI crypt, SI villi, and in the colon, including Cyp24a1, S100g, Trpv6, and Slc30a10. Other VD-regulated transcripts were unique to the SI crypt (162 up, 210 down), villi (199 up, 63 down), or colon (102 up, 28 down), but this did not correlate with mRNA levels of the VDR. Furthermore, bioinformatic analysis identified unique VD-regulated biological functions in each compartment. VDR-binding sites were found in 70% of upregulated genes from the colon and SI villi but were less common in upregulated genes from the SI crypt and among downregulated genes, suggesting some transcript-level VD effects are likely indirect. Consistent with this, we show that VD regulated the expression of other transcription factors and their downstream targets. Finally, we demonstrate that compartment-specific VD-mediated gene expression was associated with compartment-specific VDR-binding sites (<30% of targets) and enrichment of intestinal transcription factor-binding motifs within VDR-binding peaks. Taken together, our data reveal unique spatial patterns of VD action in the intestine and suggest novel mechanisms that could account for compartment-specific functions of this hormone.

Maternal VD3 supplementation during gestation improves intestinal health and microbial composition of weaning piglets

Vitamin D₃ (VD₃) has been reported to improve the reproductive performance of sows. This study was conducted to investigate the long-term effect of maternal VD₃ supplementation during gestation on the intestinal health of piglets. Twenty-three Landrace × Yorkshire gilts were randomly allocated into two groups to receive one of the following two diets during gestation: basal diet (CON group, 800 IU VD₃ per kg diet, n = 12) and VD₃ supplemented diet (VD₃ group, 2000 IU VD₃ per kg diet, n = 11). All sows were then fed with the same diet during lactation. Results showed that maternal VD₃ supplementation during lactation tended to decrease (p = 0.08) the body weight loss of sows during lactation compared to the CON group. Besides, the relative length and weight of the small intestine (SI) and the villus height of the duodenum and ileum in weaning piglets were much higher (p < 0.05) in the VD₃ group than those in the CON group, though their body weight was not changed. Meanwhile, maternal VD₃ supplementation significantly upregulated the expression levels of IGF-1, IGF-2R, VDR, GLUT-2 and CAT1 in the duodenum (p < 0.05), and increased the expression levels of IGF-1, IGF-1R, IGF-2R, VDR, Occludin, ZO-1, MUC2, PEPT1 and CAT1 (p < 0.05) in the jejunum of suckling piglets compared with the CON group. Besides, the concentration of SigA in the jejunum of suckling piglets was higher (p < 0.05) in the VD₃ group than that in the CON group. In addition, maternal VD₃ supplementation significantly increased the contents of short chain fatty acids and the relative abundance of Lactobacillus and Faecalibacterium (p < 0.05) in the feces of weaning piglets compared to the CON group. Moreover, the relative abundance of unidentified_Lachnospiraceae in the feces of weaning piglets tended to be higher (p = 0.05), while that of unidentified_Spirochaetaceae was lower (p < 0.05) in the VD₃ group than those in the CON group. Taken together, maternal VD₃ supplementation during gestation could improve the intestinal function and microbiota in suckling piglets.

Vitamin D Receptor-Dependent Protective Effect of Moderate Hypoxia in a Mouse Colitis Model

Although hypoxia is important for maintaining the intestinal barrier, its effect on the barrier during acute colitis and the underlying mechanisms are not fully understood. To explore the influence of hypoxia in dextran sulfate sodium (DSS)-induced colitis mice and the role of hypoxia-inducible factor (HIF) and vitamin D receptor (VDR) in the process. Colitis mice were subjected to hypoxia to detect intestinal barrier function changes. And the mechanisms were explored in vitro. First, compared with colitis mice without hypoxia stimulation, those with hypoxia stimulation showed significantly decreased pathological damage and improved permeability of the intestinal barrier. The expression of tight junction proteins (occludin, ZO-1), HIF-1α as well as VDR was up-regulated in colitis mice with hypoxia stimulation. However, in VDR gene knockout (KO)colitis mice, hypoxia treatment showed no protective effect, suggesting the VDR dependency of this effect. Similarly although hypoxia stimulation could enhance the single-layer epithelial transmembrane electrical resistance in DLD-1 and NCM460 cells, these effects disappeared in VDR-knockdown cells. Furthermore, over-expression of HIF-1α in DLD-1 and NCM460 increased the expression of VDR, whereas HIF-1α-knockdown reduced the VDR expression directly. Chromatin immunoprecipitation and luciferase assays confirmed that HIF-1α can bind to the promoter region of the VDR gene under hypoxia. Finally, compared with their wild-type siblings, VDR-KO mice showed reduced abundance of anaerobic bacteria and SCFA-producing bacteria. Hypoxia was protective against DSS-induced colitis, and VDR is instrumental in it. Furthermore, HIF-1α-VDR mediates the effect of hypoxia on the barrier function. Moreover, intestinal flora may be an important link between hypoxia and VDR.