Vitamin D receptor negatively regulates bacterial-stimulated NF-kappaB activity in intestine

Vitamin D and Metabolic Dysfunction-Associated Fatty Liver Disease (MAFLD): An Update

Non-alcoholic fatty liver disease (NAFLD) is the first cause of chronic liver disease worldwide; it ranges from simple steatosis to steatohepatitis (NASH) and, potentially, cirrhosis and hepatocarcinoma. NAFLD is also an independent risk factor for type 2 diabetes, cardiovascular diseases, and mortality. As it is largely associated with insulin resistance and related disorders, NAFLD has been recently re-named as Metabolic dysfunction-Associated Fatty Liver Disease (MAFLD). At present, there are no approved pharmacological treatments for this condition. Vitamin D is a molecule with extensive anti-fibrotic, anti-inflammatory, and insulin-sensitizing properties, which have been proven also in hepatic cells and is involved in immune-metabolic pathways within the gut–adipose tissue–liver axis. Epidemiological data support a relationship hypovitaminosis D and the presence of NAFLD and steatohepatitis (NASH); however, results from vitamin D supplementation trials on liver outcomes are controversial. This narrative review provides an overview of the latest evidence on pathophysiological pathways connecting vitamin D to NAFLD, with emphasis on the effects of vitamin D treatment in MAFLD by a nonsystematic literature review of PubMed published clinical trials. This article conforms to the Scale for Assessment of Narrative Review Articles (SANRA) guidelines. Evidence so far available supports the hypothesis of potential benefits of vitamin D supplementation in selected populations of NAFLD patients, as those with shorter disease duration and mild to moderate liver damage.

Does Serum Vitamin D Level Affect COVID-19 Infection and Its Severity?-A Case-Control Study

BACKGROUND

As effective medication to treat COVID-19 is currently unavailable, preventive remedies may be particularly important.

OBJECTIVE

To examine the relationship between serum 25-hydroxy vitamin D (25(OH)D) level and COVID-19 infection, its severity, and its clinical case characteristics.

METHODS

This case-control study compared serum 25(OH)D levels and rates of vitamin D deficiency (VDD) between 80 healthy controls and 62 patients diagnosed with COVID-19 and admitted to Guangxi People's Hospital, China, 2/16/2020-3/16/2020. Cases were categorized into asymptomatic, mild/moderate, and severe/critical disease. Logistic regression analysis was conducted to examine the associations between 25(OH)D level, or VDD, and case status/severity of COVID-19 while controlling for demographics and comorbidities. A threshold level of vitamin D for conveying COVID-19 risk was estimated.

RESULTS

Severe/critical COVID-19 cases were significantly older and had higher percentages of comorbidity (renal failure) compared to mild cases. The serum 25(OH)D concentration in COVID-19 patient was much lower than that in healthy control. And 25(OH)D level was the lowest in severe/critical cases, compared with mild cases. In further, significantly higher rates of VDD were found in COVID-19 cases (41.9%) compared to healthy controls (11.1%). And VDD was the greatest in severe/critical cases (80%), compared with mild cases (36%). These statistically significant associations remained even after controlling for demographics and comorbidities. A potential threshold of 25(OH)D (41.19 nmol/L) to protect against COVID-19 was identified.

CONCLUSION

Elderly and people with comorbidities were susceptible to severe COVID-19 infection. VDD was a risk factor for COVID-19, especially for severe/critical cases. While further confirmation is needed, vitamin D supplementation may have prevention or treatment potential for COVID-19 disease.

Mucosal vitamin D signaling in inflammatory bowel disease

Epidemiological studies have identified vitamin D (25(OH)D) deficiency to be highly prevalent among patients with inflammatory bowel disease (IBD), and low serum levels correlate with a higher disease activity and a more complicated disease course. The link to IBD pathogenesis has been subject of investigations, primarily due to the distinct immunological functions of vitamin D signaling, including anti-inflammatory and anti-fibrotic actions. Vitamin D is a pleiotropic hormone that executes its actions on cells through the vitamin D receptor (VDR). A leaky gut, i.e. an insufficient intestinal epithelial barrier, is thought to be central for the pathogenesis of IBD, and emerging data support the concept that vitamin D/VDR signaling in intestinal epithelial cells (IECs) has an important role in controlling barrier integrity. Here we review the latest evidence on how vitamin D promotes the interplay between IECs, the gut microbiome, and immune cells and thereby regulate the intestinal immune response. On the cellular level, vitamin D signaling regulates tight junctional complexes, apoptosis, and autophagy, leading to increased epithelial barrier integrity, and promotes expression of antimicrobial peptides as part of its immunomodulating functions. Further, intestinal VDR expression is inversely correlated with the severity of inflammation in patients with IBD, which might compromise the positive effects of vitamin D signaling in patients with flaring disease. Efforts to reveal the role of vitamin D in the pathophysiology of IBD will pave the road for the invention of more rational treatment strategies of this debilitating disease in the future.

Inhibition of Histone Deacetylation by MS-275 Alleviates Colitis by Activating the Vitamin D Receptor

BACKGROUND

Ulcerative colitis [UC] is a common chronic inflammatory bowel disease without curative treatment.

METHODS

We conducted gene set enrichment analysis to explore potential therapeutic agents for UC. Human colon tissue samples were collected to test H3 acetylation in UC. Both in vivo and in vitro colitis models were constructed to verify the role and mechanism of H3 acetylation modification in UC. Intestine-specific vitamin D receptor [VDR]-/- mice and VD [vitamin D]-deficient diet-fed mice were used to explore downstream molecular mechanisms accordingly.

RESULTS

According to the Connectivity Map database, MS-275 [class I histone deacetylase inhibitor] was the top-ranked agent, indicating the potential importance of histone acetylation in the pathogenesis of UC. We then found that histone H3 acetylation was significantly lower in the colon epithelium of UC patients and negatively associated with disease severity. MS-275 treatment inhibited histone H3 deacetylation, subsequently attenuating nuclear factor kappa B [NF-κB]-induced inflammation, reducing cellular apoptosis, maintaining epithelial barrier function, and thereby reducing colitis activity in a mouse model of colitis. We also identified VDR as be a downstream effector of MS-275. The curative effect of MS-275 on colitis was abolished in VDR-/- mice and in VD-deficient diet-fed mice and VDR directly targeted p65. In UC patients, histone H3 acetylation, VDR and zonulin-1 expression showed similar downregulation patterns and were negatively associated with disease severity.

CONCLUSIONS

We demonstrate that MS-275 inhibits histone deacetylation and alleviates colitis by ameliorating inflammation, reducing apoptosis, and maintaining intestinal epithelial barrier via VDR, providing new strategies for UC treatment.

Lactic Acid Bacteria Isolated From Korean Kimchi Activate the Vitamin D Receptor-autophagy Signaling Pathways

BACKGROUND

Probiotic lactic acid bacteria (LAB) have been used in the anti-inflammation and anti-infection process of various diseases, including inflammatory bowel disease (IBD). Vitamin D receptor (VDR) plays an essential role in pathogenesis of IBD and infectious diseases. Previous studies have demonstrated that the human VDR gene is a key host factor to shape gut microbiome. Furthermore, intestinal epithelial VDR conditional knockout (VDRΔIEC) leads to dysbiosis. Low expressions of VDR is associated with impaired autophagy, accompanied by a reduction of ATG16L1 and LC3B. The purpose of this study is to investigate probiotic effects and mechanism in modulating the VDR-autophagy pathways.

METHODS

Five LAB strains were isolated from Korean kimchi. Conditional medium (CM) from these strains was used to treat a human cell line HCT116 or intestinal organoids to measure the expression of VDR and autophagy. Mouse embryonic fibroblast (MEF) cells with or without VDR were used to investigate the dependence on the VDR signaling. To test the role of LAB in anti-inflammation, VDR+/+ organoids were treated with 121-CM before infection with Salmonella enterica serovar Enteritidis. In vivo, the role of LAB in regulating VDR-autophagy signaling was examined using LAB 121-CM orally administrated to VDRLoxp and VDRΔIEC mice.

RESULTS

The LAB-CM-treated groups showed higher mRNA expression of VDR and its target genes cathelicidin compared with the control group. LAB treatment also enhanced expressions of Beclin-1 and ATG16L1 and changed the ratio of LC3B I and II, indicating the activation of autophagic responses. Furthermore, 121-CM treatment before Salmonella enterica serovar Enteritidis infection dramatically increased VDR and ATG16L1 and inhibited the inflammation. Administration of 121-CM to VDRLoxp and VDRΔIEC mice for 12 and 24 hours resulted in an increase of VDR and LC3B II:I ratio. Furthermore, we identified that probiotic proteins P40 and P75 in the LAB-CM contributed to the anti-inflammatory function by increasing VDR.

CONCLUSIONS

Probiotic LAB exert anti-inflammation activity and induces autophagy. These effects depend on the VDR expression. Our data highlight the beneficial effects of these 5 LAB strains isolated from food in anti-infection and anti-inflammation.

Artesunate interacts with the vitamin D receptor to reverse sepsis-induced immunosuppression in a mouse model via enhancing autophagy

BACKGROUND AND PURPOSE

Immunosuppression is the predominant cause of mortality for sepsis because of failure to eradicate pathogens. No effective and specific drugs capable of reversing immunosuppression are clinically available. Evidences implicate the involvement of the vitamin D receptor (NR1I1) in sepsis-induced immunosuppression. The anti-malarial artesunate was investigated to determine action on sepsis-induced immunosuppression.

EXPERIMENTAL APPROACH

The effect of artesunate on sepsis-induced immunosuppression was investigated in mice and human and mice cell lines. Bioinformatics predicted vitamin D receptor as a candidate target for artesunate, which was then identified using PCR and immunoblotting. Vdr, Atg16l1 and NF-κB p65 were modified to investigate artesunate 's effect on pro-inflammatory cytokines release, bacterial clearance and autophagy activities in sepsis-induced immunosuppression.

KEY RESULTS

Artesunate significantly reduced the mortality of caecal ligation and puncture (CLP)-induced sepsis immunosuppression mice challenged with Pseudomonas aeruginosa and enhanced pro-inflammatory cytokine release and bacterial clearance to reverse sepsis-induced immunosuppression in vivo and in vitro. Mechanistically, artesunate interacted with vitamin D receptor, inhibiting its nuclear translocation, which influenced ATG16L1 transcription and subsequent autophagy activity. Artesunate inhibited the physical interaction between vitamin D receptor and NF-κB p65 in LPS-tolerant macrophages and then promoted the nuclear translocation of NF-κB p65, which activated the transcription of NF-κB p65 target genes such as pro-inflammatory cytokines.

CONCLUSION AND IMPLICATIONS

Our findings provide evidence that artesunate interacted with vitamin D receptor to reverse sepsis-induced immunosuppression in an autophagy and NF-κB-dependent manner, highlighting a novel approach for sepsis treatment and drug repurposing of artesunate has a bidirectional immunomodulator.

Vitamin D and the Host-Gut Microbiome: A Brief Overview

There is a growing body of evidence for the effects of vitamin D on intestinal host-microbiome interactions related to gut dysbiosis and bowel inflammation. This brief review highlights the potential links between vitamin D and gut health, emphasizing the role of vitamin D in microbiological and immunological mechanisms of inflammatory bowel diseases. A comprehensive literature search was carried out in PubMed and Google Scholar using combinations of keywords "vitamin D," "intestines," "gut microflora," "bowel inflammation". Only articles published in English and related to the study topic are included in the review. We discuss how vitamin D (a) modulates intestinal microbiome function, (b) controls antimicrobial peptide expression, and (c) has a protective effect on epithelial barriers in the gut mucosa. Vitamin D and its nuclear receptor (VDR) regulate intestinal barrier integrity, and control innate and adaptive immunity in the gut. Metabolites from the gut microbiota may also regulate expression of VDR, while vitamin D may influence the gut microbiota and exert anti-inflammatory and immune-modulating effects. The underlying mechanism of vitamin D in the pathogenesis of bowel diseases is not fully understood, but maintaining an optimal vitamin D status appears to be beneficial for gut health. Future studies will shed light on the molecular mechanisms through which vitamin D and VDR interactions affect intestinal mucosal immunity, pathogen invasion, symbiont colonization, and antimicrobial peptide expression.

Vitamin D status and vitamin D receptor genotypes in celiac disease: a meta-analysis

BACKGROUND

There have been various articles reporting relationship between Vitamin D (VitD) and celiac disease (CeD), but results remain controversial. This study aimed to conduct a meta-analysis to systematically review and quantify the relationship between VitD and CeD. Moreover, difference in Vitamin D Receptor (VDR) genotypes between CeD patients and controls was also analyzed.

METHODS

Articles published until July 20, 2019 in the PubMed, MEDLINE, and EMBASE databases were searched. According to the inclusion and exclusion criteria, relevant statistical data were collated and extracted, which were finally analyzed by STATA15.1.

RESULTS

27 articles and 28 sets of data were included. It showed that average 25(OH)D level in CeD patients was 8.36 nmol/L lower than controls (Weighted Mean Difference (WMD) = -8.36, 95% CI = [-14.63, -2.09] nmol/L). After gluten-free diet treatment, we found that average 25(OH)D level in treated patients was 15.6 nmol/L higher than untreated patients (WMD = 15.6, 95% CI = [5.96, 25.23] nmol/L). In addition, 25(OH)D level in treated patients was close to healthy controls (WMD = -2.82, 95% CI = [-6.45, 0.73] nmol/L). However, genetic polymorphism analysis showed that there is no difference in VDR genotypes between CeD and control.

CONCLUSIONS

CeD had decreased serum 25(OH)D levels, which returned to normal after treatment, suggesting that VitD may play a role in the development of CeD. The directionality of this association cannot be confirmed from cross-sectional studies. Demonstration of a causal role of VitD deficiency in CeD development in future studies could have important therapeutic implications.

Vitamin D and intestinal homeostasis: Barrier, microbiota, and immune modulation

Vitamin D plays a pivotal role in intestinal homeostasis. Vitamin D can impact the function of virtually every cell in the gut by binding to its intracellular receptor (VDR) and subsequently transcribing relevant genes. In the lumen, the mucus layer and the underlying epithelium serve to keep resident microbiota at bay. Vitamin D ensures an appropriate level of antimicrobial peptides in the mucus and maintains epithelial integrity by reinforcing intercellular junctions. Should bacteria penetrate the epithelial layer and enter the interstitium, immune sentinel cells (e.g. macrophages, dendritic cells, and innate lymphoid cells) elicit inflammation and trigger the adaptive immune response by activating Th1/Th17 cells. Vitamin D/VDR signaling in these cells ensures clearance of the bacteria. Subsequently, vitamin D also quiets the adaptive immune system by suppressing the Th1/Th17 cells and favoring Treg cells. The importance of vitamin D/VDR signaling in intestinal homeostasis is evidenced by the development of a chronic inflammatory state (e.g. IBD) when this signaling system is disrupted.

Vitamin D Receptor Protects Against Dysbiosis and Tumorigenesis via the JAK/STAT Pathway in Intestine

BACKGROUND & AIMS

Vitamin D exerts regulatory roles via vitamin D receptor (VDR) in mucosal immunity, host defense, and inflammation involving host factors and microbiome. Human Vdr gene variation shapes the microbiome and VDR deletion leads to dysbiosis. Low VDR expression and diminished vitamin D/VDR signaling are observed in colon cancer. Nevertheless, how intestinal epithelial VDR is involved in tumorigenesis through gut microbiota remains unknown. We hypothesized that intestinal VDR protects mice against dysbiosis via modulating the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway in tumorigenesis.

METHODS

To test our hypothesis, we used an azoxymethane/dextran sulfate sodium-induced cancer model in intestinal VDR conditional knockout (VDR^ΔIEC) mice, cell cultures, stem cell-derived colonoids, and human colon cancer samples.

RESULTS

VDR^ΔIEC mice have higher numbers of tumors, with the location shifted from the distal to proximal colon. Fecal microbiota analysis showed that VDR deletion leads to a bacterial profile shift from normal to susceptible carcinogenesis. We found enhanced bacterial staining in mouse and human tumors. Microbial metabolites from VDR^ΔIEC mice showed increased secondary bile acids, consistent with observations in human CRC. We further identified that VDR protein bound to the Jak2 promoter, suggesting that VDR transcriptionally regulated Jak2. The JAK/STAT pathway is critical in intestinal and microbial homeostasis. Fecal samples from VDR^ΔIEC mice activate the STAT3 signaling in human and mouse organoids. Lack of VDR led to hyperfunction of Jak2 in response to intestinal dysbiosis. A JAK/STAT inhibitor abolished the microbiome-induced activation of STAT3.

CONCLUSIONS

We provide insights into the mechanism of VDR dysfunction leading to dysbiosis and tumorigenesis. It indicates a new target: microbiome and VDR for the prevention of cancer.

Vitamin D3 modulates yellow catfish (Pelteobagrus fulvidraco) immune function in vivo and in vitro and this involves the vitamin D3/VDR-type I interferon axis

Vitamin D₃ (VD₃) has been shown to regulate immune function in mammals. 1,25-dihydroxyvitamin (1,25(OH)₂D₃) is the active form of vitamin D₃, which is also known as calcitriol. The current study investigated the immunomodulatory effects of 1,25(OH)₂D₃ on the innate immune response of yellow catfish (Pelteobagrus fulvidraco) after in vivo and in vitro immune challenge. The in vivo results showed that increasing dietary vitamin D₃ decreased mortality, enhanced the immune protective rate, and increased serum lysozyme, catalase and SOD activities in yellow catfish infected with Edwardsiella Ictaluri (p < 0.05). The in vitro results showed that 1,25(OH)₂D₃ (0, 1, 10, 100, 200 pM) dose-dependently attenuated the rate of apoptosis and production or reactive oxygen species and increased the phagocytic activity of head kidney macrophages stimulated with 10 mg/L lipopolysaccharide (LPS) and 100 mg/L of Poly(I:C) (p < 0.05). Real-time quantitative PCR results showed that increasing dietary vitamin D₃ content in vivo and increasing the level of 1,25(OH)₂D₃in vitro partially regulated the expression of VD₃/VDR-type I interferon axis genes (vdr, irf-3, ifn-a, jak1, stat1, ifi56 and ifp35) after immune challenge. These results indicated that vitamin D₃ content helped yellow catfish to resist oxidative stress and inflammation caused by immune challenge, and immunomodulation involved the VD₃/VDR-type I interferon action axis.

The impact of maternal and early life malnutrition on health: a diet-microbe perspective

BACKGROUND

Early-life malnutrition may have long-lasting effects on microbe-host interactions that affect health and disease susceptibility later in life. Diet quality and quantity in conjunction with toxin and pathogen exposure are key contributors to microbe-host physiology and malnutrition. Consequently, it is important to consider both diet- and microbe-induced pathologies as well as their interactions underlying malnutrition.

MAIN BODY

Gastrointestinal immunity and digestive function are vital to maintain a symbiotic relationship between the host and microbiota. Childhood malnutrition can be impacted by numerous factors including gestational malnutrition, early life antibiotic use, psychological stress, food allergy, hygiene, and exposure to other chemicals and pollutants. These factors can contribute to reoccurring environmental enteropathy, a condition characterized by the expansion of commensal pathobionts and environmental pathogens. Reoccurring intestinal dysfunction, particularly during the critical window of development, may be a consequence of diet-microbe interactions and may lead to life-long immune and metabolic programming and increased disease risk. We provide an overview of the some key factors implicated in the progression of malnutrition (protein, fat, carbohydrate, iron, vitamin D, and vitamin B12) and discuss the microbiota during early life that may contribute health risk later in life.

CONCLUSION

Identifying key microbe-host interactions, particularly those associated with diet and malnutrition requires well-controlled dietary studies. Furthering our understanding of diet-microbe-host interactions will help to provide better strategies during gestation and early life to promote health later in life.

Effects of an Omega-3 and Vitamin D Supplement on Fatty Acids and Vitamin D Serum Levels in Double-Blinded, Randomized, Controlled Trials in Healthy and Crohn's Disease Populations

Two trials separately measured the bioavailability and impact on inflammation of a supplement taken daily containing 510 mg Docosahexaenoic acid (DHA), 344 mg Eicosapentaenoic acid (EPA), and 1000 IU of vitamin D (25-hydroxyvitamin D; 25(OH)D), for healthy and Crohn’s disease (CD) populations. Both trials were double blinded, randomized, placebo-controlled with cross-over. Participants were randomly allocated to groups A (placebo then supplement) or B (supplement then placebo). Both included a washout. Fatty acid (N-3 PUFAs) and vitamin D serum levels, plasma C-reactive protein (CRP), and stool calprotectin were measured before and after each treatment period. Outcome measures were analyzed using generalized linear mixed models, including terms for treatment, period, and a treatment-by-period interaction. The supplement significantly increased serum levels in healthy and CD groups for EPA (p < 0.001 and p < 0.001, respectively), Docosapentaenoic acid (p < 0.001 and 0.005), DHA (p < 0.001 and 0.006), the omega-3 index (p < 0.001 and 0.001), and (vitamin D (p < 0.001 and 0.027). CRP and calprotectin measures showed no evidence of a treatment effect on inflammation; however, model estimation was imprecise for both outcomes, hence further research is required to elucidate potential inflammation effects. The nutrient supplement increased serum levels of key N-3 PUFAs and vitamin D in both populations, showing the preparation was readily bioavailable.

Salmonella Enteritidis Effector AvrA Suppresses Autophagy by Reducing Beclin-1 Protein

Autophagy is a cellular process to clear pathogens. Salmonella enterica serovar Enteritidis (S.E) has emerged as one of the most important food-borne pathogens. However, major studies still focus on Salmonella enterica serovar Typhimurium. Here, we reported that AvrA, a S. Enteritidis effector, inhibited autophagy to promote bacterial survival in the host. We found that AvrA regulates the conversion of LC3 I into LC3 II and the enrichment of lysosomes. Beclin-1, a key molecular regulator of autophagy, was decreased after AvrA expressed strain colonization. In S.E-AvrA--infected cells, we found the increases of protein levels of p-JNK and p-c-Jun and the transcription level of AP-1. AvrA-reduction of Beclin-1 protein expression is through the JNK pathway. The JNK inhibitor abolished the AvrA-reduced Beclin-1 protein expression. Moreover, we identified that the AvrA mutation C186A abolished its regulation of Beclin-1 expression. In addition AvrA protein was found interacted with Beclin-1. In organoids and infected mice, we explored the physiologically related effects and mechanism of AvrA in reducing Beclin-1 through the JNK pathway, thus attenuating autophagic responses. This finding not only indicates an important role of S. Enteritidis effector in reducing host protein as a strategy to suppress autophagy, but also suggests manipulating autophagy as a new strategy to treat infectious diseases.

A simple and sensitive method to detect vitamin D receptor expression in various disease models using stool samples

Vitamin D receptor (VDR) executes the main biological functions of its ligand vitamin D. VDR/vitamin D plays critical roles in regulating host immunity, maintaining barrier functions, and shaping gut microbiome. Reduction of intestinal VDR has been reported in various diseases, including inflammatory diseases and colon cancer. However, it is always challenging to get biopsies to test the pathologic changes of VDR in intestine. In the current study, we reported a simple and sensitive quantitative PCR (qPCR) method to detect reduction of intestinal VDR using fecal samples. We validated this method in several experimental models, such as colitis, bacterial infection, and aging. We further correlated the qPCR data of VDR with the protein level of VDR in colon or serum 25 (OH)D₃ in mice with different VDR status (VDR^+/+, VDR^+/-, and VDR^−/−). Our data indicate that the qPCR method to test VDR using fecal samples could detect the expression level of intestinal VDR in various diseases. Our study highlights the feasibility, sensitivity, and simplicity of a molecular method to study the status of VDR as a biomarker.

Regulation of bile acid metabolism-related signaling pathways by gut microbiota in diseases

Over the past decade, there has been increasing attention on the interaction between microbiota and bile acid metabolism. Bile acids are not only involved in the metabolism of nutrients, but are also important in signal transduction for the regulation of host physiological activities. Microbial-regulated bile acid metabolism has been proven to affect many diseases, but there have not been many studies of disease regulation by microbial receptor signaling pathways. This review considers findings of recent research on the core roles of farnesoid X receptor (FXR), G protein-coupled bile acid receptor (TGR5), and vitamin D receptor (VDR) signaling pathways in microbial-host interactions in health and disease. Studying the relationship between these pathways can help us understand the pathogenesis of human diseases, and lead to new solutions for their treatments.

Vitamin D and microbiota: Two sides of the same coin in the immunomodulatory aspects

The gut microbiota is crucial for host immune response, vitamin synthesis, short chain fatty acids (SCFAs) production, intestinal permeability, nutrient digestion energy metabolism and protection from pathogens. Therefore, gut microbiota guarantees the host's predisposition to gastrointestinal diseases. Intestinal microbiota may be damaged by environmental components with negative health conditions. Dysbiosis consisting in alteration in the gut microbiota has been involved in several disorders including inflammation, allergic reactions, autoimmune diseases, heart diseases, obesity, and metabolic syndrome and even in the state of malignant carcinogenesis existing in humans. Several epidemiological studies have shown that inadequate solar exposure results in vitamin D insufficiency/deficiency which has a strong impact on different immune responses and the occurrence of a wide range of pathological conditions. Additionally, new evidence indicates that the vitamin D pathway plays a key role in gut homeostasis. Due to the strong connection between vitamin D and microbiota, herein we focus on the new findings about intestinal bacteria-immune crosstalk and the impact of vitamin D in gut microbiota regulation, in order to offer new clarifications on their interaction. Understanding the mechanism by which vitamin D can affect the gut microbiota composition and its dynamic activities, as well as the innate and adaptive state of the immune system, is not only a fundamental research but also an opportunity to improve health status.

Effect of Vitamin D Supplementation on Faecal Microbiota: A Randomised Clinical Trial

In animal studies, vitamin D supplementation has been shown to improve gut microbiota and intestinal inflammation. However, limited evidence exists on the effect of vitamin D supplementation on the human gut microbiota. We examined the effect of vitamin D supplementation on faecal microbiota in 26 vitamin D-deficient (25-hydroxyvitamin D (25(OH)D) ≤50 nmol/L), overweight or obese (BMI ≥25 kg/m²) otherwise healthy adults. Our study was ancillary to a community based double-blind randomised clinical trial, conducted between 2014 and 2016. The participants provided stool samples at baseline and after 100,000 international units (IU) loading dose of cholecalciferol followed by 4000 IU daily or matching placebo for 16 weeks. Faecal microbiota was analysed using 16S rRNA sequencing; V6-8 region. There was no significant difference in microbiome α-diversity between vitamin D and placebo groups at baseline and follow-up (all p > 0.05). In addition, no clustering was found based on vitamin D supplementation at follow-up (p = 0.3). However, there was a significant association between community composition and vitamin D supplementation at the genus level (p = 0.04). The vitamin D group had a higher abundance of genus Lachnospira, and lower abundance of genus Blautia (linear discriminate analysis >3.0). Moreover, individuals with 25(OH)D >75 nmol/L had a higher abundance of genus Coprococcus and lower abundance of genus Ruminococcus compared to those with 25(OH)D <50 nmol/L. Our findings suggest that vitamin D supplementation has some distinct effects on faecal microbiota. Future studies need to explore whether these effects would translate into improved clinical outcomes.

Intestinal epithelial HMGB1 inhibits bacterial infection via STAT3 regulation of autophagy

Extracellular HMGB1 (high mobility group box 1) is considered as a damage-associated molecular pattern protein. However, little is known about its intracellular role. We studied the mechanism whereby intestinal epithelial HMGB1 contributes to host defense, using cell culture, colonoids, conditional intestinal epithelial HMGB1-knockout mice with Salmonella-colitis, il10-/- mice, and human samples. We report that intestinal HMGB1 is an important contributor to host protection from inflammation and infection. We identified a physical interaction between HMGB1 and STAT3. Lacking intestinal epithelial HMGB1 led to redistribution of STAT3 and activation of STAT3 post bacterial infection. Indeed, Salmonella-infected HMGB1-deficient cells exhibited less macroautophagy/autophagy due to decreased expression of autophagy proteins and transcriptional repression by activated STAT3. Then, increased p-STAT3 and extranuclear STAT3 reduced autophagic responses and increased inflammation. STAT3 inhibition restored autophagic responses and reduced bacterial invasion in vitro and in vivo. Moreover, low level of HMGB1 was correlated with reduced nuclear STAT3 and enhanced p-STAT3 in inflamed intestine of il10-/- mice and inflammatory bowel disease (IBD) patients. We revealed that colonic epithelial HMGB1 was directly involved in the suppression of STAT3 activation and the protection of intestine from bacterial infection and injury. Abbreviations: ATG16L1: autophagy-related 16-like 1 (S. cerevisiae); DAMP: damage-associated molecular pattern; HBSS: Hanks balanced salt solution; HMGB1: high mobility group box 1; IBD: inflammatory bowel disease; IL1B/Il-1β: interleukin 1 beta; IL10: interleukin 10; IL17/IL-17: interleukin 17; MEFs: mouse embryonic fibroblasts; STAT3: signal transducer and activator of transcription 3; TLR: toll-like receptor; TNF/TNF-α: tumor necrosis factor.

Low serum vitamin D levels increase the mortality of cardiovascular disease in older adults: A dose-response meta-analysis of prospective studies

Lower circulating vitamin D is common in older adults and may be a potential reversible risk factor for cardiovascular disease (CVD) in older adults, however, presented controversial results.Database was searched update to February 2018. Key data were extracted from eligible studies. Dose-response meta-analysis were conducted for synthesizing data from eligible studies.A total of 13 eligible studies involving 21,079 participants were included in this meta-analysis. Person with lower 25-hydroxyvitamin D status (25 (OH)D level <50 nmol/L) appeared to have higher mortality of CVD in older adults (RR = 1.54, 95% CI 1.24-1.91). Furthermore, a significantly higher mortality of CVD in older adults was observed for the deficient (<25 nmol/L; RR = 1.47, 95% CI 1.15-1.81) and insufficient (25-50 nmol/L; RR = 1.16, 95% CI 1.04-1.27) categories of 25 (OH)D, compared to the reference category of >75 nmol/L. Additionally, decrease of 10 nmol/L 25-hydroxyvitamin D was associated with a 7% incremental in the risk of CVD mortality in older adults.Considering these promising results, circulating vitamin D is associated with CVD mortality increment in older adults.

Imbalance of autophagy and apoptosis in intestinal epithelium lacking the vitamin D receptor

Apoptosis and autophagy are dynamic processes that determine the fate of cells. Vitamin D receptor (VDR) deficiency in the intestine leads to abnormal Paneth cells and impaired autophagy function. Here, we will elucidate the mechanisms of the intestinal epithelial VDR regulation of autophagy and apoptosis. We used in vivo VDR^lox and VDR^∆IEC mice and ex vivo organoids generated from small intestine and colon tissues. We found that VDR deficiency induced more apoptotic cells and significantly increased cell death in the small intestine and colon of VDR^∆IEC mice. The proapoptotic protein B-cell lymphoma 2 (BCL-2) associated X protein (Bax) was enhanced, whereas autophagy related 16 like 1 (ATG16L1) and Beclin-1 were decreased in the intestines of VDR^ΔIEC mice. Apoptosis induced by Bax reduced autophagy by decreasing Beclin-1. Physical interactions between Beclin-1 and Bcl-2 were increased in the VDR-deficient epithelia from mice. The growth of VDR^∆IEC organoids was significantly slower with fewer Paneth cells than that of VDR^+/+ organoids. The expression levels of Beclin-1 and lysozyme were decreased in VDR^∆IEC organoids. Bacterial endotoxin levels were high in the serum from VDR^∆IEC mice and made mice susceptible to colitis. In the organoids and colitis IL-10^-/- mice, vitamin D₃ treatment increased VDR and ATG16L1 protein expression levels, which activated autophagic responses. In summary, intestinal epithelial VDR regulates autophagy and apoptosis through ATG16L1 and Beclin-1. Our studies provide fundamental insights into the tissue-specific function of VDR in modulating the balance between autophagy and apoptosis.-Lu, R., Zhang, Y.-G., Xia, Y., Sun, J. Imbalance of autophagy and apoptosis in intestinal epithelium lacking the vitamin D receptor.

Aligning the Paradoxical Role of Vitamin D in Gastrointestinal Immunity

Inflammatory bowel disease (IBD) is a chronic disorder characterized by inflammation of the gastrointestinal tract and an immune-mediated attack against the commensal microbiota. Vitamin D is an essential vitamin that not only promotes calcium and phosphate absorption but also regulates immune function. The active form of vitamin D [1,25(OH)₂D] has been shown to suppress symptoms of IBD by inhibiting T cell responses. Host protection from gastrointestinal infection depends on T cells. Paradoxically, vitamin D deficiency increases susceptibility to IBD and gastrointestinal infection. Here we review the roles of vitamin D in immune cells using a kinetic model of the vitamin D-mediated effects on infection to explain the sometimes paradoxical effects of vitamin D on gastrointestinal immunity.

Efeitos contrastantes da vitamina D sobre a resposta imune inata e adquirida e seu impacto na recuperação da tuberculose

A vitamina D é um hormônio essencial para o organismo, podendo ser obtida da dieta ou, principalmente, gerada pela pele após exposição à luz solar ultravioleta B. Na sua forma ativa (1,25(OH)2D) ela controla a absorção de cálcio e fósforo do intestino para a corrente sanguínea e participa de diversos processos celulares e fisiológicos. A ligação da 1,25(OH)2D ao receptor da vitamina D (VDR) presente em diversas células, como as células do sistema imunológico, induz a transcrição de genes que podem, por exemplo, modular a resposta imune inata e adquirida. A deficiência de vitamina D ou do VDR é associada a problemas de saúde como desordens esqueléticas, hipertensão, doenças cardiovasculares, diabetes mellitus, dislipidemias, doenças autoimunes e doenças infecciosas. Neste sentido, a suplementação com vitamina D tem sido proposta como uma possível medida preventiva, podendo ser aplicada em muitas patologias, em especial na tuberculose. Principal causa de morte por um único agente infeccioso, a tuberculose é responsável por cerca de 1,3 milhões de óbitos por ano no mundo. Publicações recentes apontam efeitos diversos da vitamina D na resposta imune inata e adquirida. A 1,25(OH)2D3 na presença do interferon (IFN)-γ é capaz de aumentar a atividade bactericida do macrófago contra o M. tuberculosis, aumentando a produção de peptídios antimicrobianos e estimulando a autofagia, favorecendo assim a lise de bacilos localizados em fagossomos. Por outro lado, a vitamina D em linfócitos T mostra efeito tolerogênico que favorece o controle de respostas inflamatórias excessivas. Neste trabalho de revisão são apresentados estudos recentes envolvendo efeitos da vitamina D na resposta imune inata e adquirida. Além disso, considerações sobre deficiência de vitamina D e maior risco de contrair tuberculose, e efeitos contrastantes da suplementação com vitamina D na prevenção e tratamento da TB, são discutidos.

Vitamin D receptor expression in peripheral blood mononuclear cells is inversely associated with disease activity and inflammation in lupus patients

OBJECTIVE

Systemic lupus erythematosus (SLE) is characterized by uncontrolled production of pro-inflammatory cytokines. Vitamin D receptor (VDR) has potent anti-inflammatory activities. The aim of this study was to examine the correlation between VDR expression and inflammation and disease activity in patients with SLE.

METHODS

Ninety-five SLE patients were recruited and divided into two groups, active and inactive, according to their SLE disease activity index (SLEDAI)-2 K, and 40 healthy individuals served as controls. The expression of VDR and NF-κB p65 in peripheral blood mononuclear cells (PBMCs) was determined by quantitative RT-PCR and Western blotting. VDR expression was correlated with inflammatory and diseases parameters in SLE patients. VDR regulation was also studied in THP-1 and Jurkat cell lines.

RESULTS

PBMC VDR expression was downregulated in SLE patients, especially in the active SLE group. VDR mRNA levels were negatively correlated with SLEDAI-2 K (r = - 0.348, P = 0.001), Systemic Lupus International Collaborating Clinics (SLICC) renal activity scores (r = - 0.346, P = 0.014), and proteinuria (r = - 0.309, P = 0.002) and positively associated with serum complement C3 levels (r = 0.316, P = 0.002). Multiple stepwise regression analysis indicated that PBMC VDR downregulation was an independent risk factor for SLEDAI-2 K. VDR levels were also negatively correlated with NF-κB p65 (r = - 0.339, P = 0.001), TNF-α (r = - 0.268, P = 0.009), and IL-6 (r = - 0.313, P = 0.002) levels. In monocyte and T lymphocyte cell lines, TNF-α suppressed VDR expression, whereas 1,25-dihydroxyvitamin D blocked TNF-α-induced VDR downregulation.

CONCLUSION

PBMC VDR expression is inversely associated with disease activity and inflammation in SLE patients, and VDR downregulation is likely driven by inflammation.

Factors affecting vitamin D deficiency in active inflammatory bowel diseases

BACKGROUND

Hypovitaminosis D is prevalent in inflammatory bowel disease (IBD) and may be associated with disease activity.

AIM

This study evaluated vitamin D (VitD) status in an Italian cohort of IBD patients, not taking VitD supplementation. We investigated risk factors for VitD deficiency and its correlation with disease activity.

METHODS

VitD levels were measured in 300 consecutive outpatients (42% with Crohn's Disease (CD) and 58% with ulcerative colitis (UC), 56% male) from a tertiary referral center. Data from the IBD cohort were compared with those of 234 healthy controls, matched by sex, age, and the month in which VitD levels were measured.

RESULTS

The mean VitD level in IBD patients was significantly lower than in controls (18.9 ng/ml vs. 25 ng/ml, p < 0.001) when accounting for gender, age, and season. VitD deficiency was present in 62% of IBD patients. Risk factors for deficiency were: age <40 and ≥60 years, winter, previous surgery, C-reactive protein (CRP) ≥0.5 mg/dl, and erythrocyte sedimentation rate ≥20 mm/h. In multivariate analysis, VitD levels were negatively influenced by disease location and CRP in UC.

CONCLUSIONS

Although VitD deficiency was more prevalent than expected in healthy controls living in a Mediterranean country not at high risk of hypovitaminosis D, it was more common and severe in IBD patients. This study also found an association between VitD status and disease activity.

Impact of Micronutrients on the Immune Response of Animals

Vitamins and minerals (micronutrients) play an important role in regulating and shaping an immune response. Deficiencies generally result in inadequate or dysregulated cellular activity and cytokine expression, thereby affecting the immune response. Decreased levels of natural killer, granulocyte, and phagocytic cell activity and T and B cell proliferation and trafficking are associated with inadequate levels of micronutrients, as well as increased susceptibility to various adverse health conditions, including inflammatory disorders, infection, and altered vaccine efficacy. In addition, most studies of micronutrient modulation of immune responses have been done in rodents and humans, thus limiting application to the health and well-being of livestock and companion animals. This exploratory review elucidates the role of vitamins and minerals on immune function and inflammatory responses in animals (pigs, dogs, cats, horses, goats, sheep, and cattle), with reference to rodents and humans.

The effects of two vitamin D regimens on ulcerative colitis activity index, quality of life and oxidant/anti-oxidant status

Background

The optimum dosage for vitamin D supplementation has not yet been elucidated in patients with Ulcerative colitis (UC). The aim of this study was to investigate the effects of two vitamin D regimens in UC patients with vitamin D deficiency.

Methods

In this double blind randomized clinical trial, 50 patients with mild to moderate UC, who met inclusion criteria, received either 1000 or 2000 IU/day of vitamin D (as low dose or high dose group, respectively) for 12 weeks. Serum 25-hydroxy vitamin D (25-OHD) level, total antioxidant capacity (TAC), and Total Oxidant Status (TOS), the inflammatory bowel disease questionnaire − 9 (IBDQ-9) score and the Simple Clinical Colitis Activity Index Questionnaire (SCCAI) score were assessed before and after intervention.

Results

At the end of study, serum 25-OHD levels significantly increased in the high dose group (P < 0.001) and the increase was significantly more than low dose group (6.7 ± 3.8 ng/mL in the high dose group versus 0.2 ± 0.5 ng/mL in the low dose group) (P < 0.001). Serum TOS concentration decreased significantly (− 0.37 ± 0.26) only in the high dose group (P value = 0.023). There was no statistically significant change in serum TAC between two groups during the study. IBDQ-9 mean score significantly increased in high dose group compared to the low dose group (P value = 0.001) and SCCAI score in both groups reduced (− 2.58 ± 2.16 and − 0.9 ± 0.3 in high dose and low dose respectively), while this reduction was significant only in the high dose group (P value ≥0.001).

Conclusion

Our results indicate that 2000 IU daily dose of vitamin D can increase serum 25-OHD concentration, and quality of life, while it reduces disease activity in UC patients with vitamin D deficiency. We recommend assessment of the vitamin D status in all patients with UC because they may benefit from vitamin D therapy.

Can YKL-40 be an Inflammatory Biomarker in Vitamin D Deficiency?

Vitamin D deficiency is associated with several non-homeostatic conditions and/or diseases like inflammation, atherosclerosis, cardiovascular disease and mortality. YKL-40 is a glycoprotein, secreted by macrophages, neutrophils and different cell types and it is also associated with inflammation and pathological tissue remodeling. In this study, we aimed to evaluate relationship between the proinflammatory biomarkers YKL-40 and hs-CRP levels and vitamin D deficiency. Our study group includes 45 subjects with vitamin D deficiency (Group 1) (20 M, 25 F; mean age 37.72 ± 7.70 years) and 40 age and sex-matched healthy subjects with normal serum levels of vitamin D (Group 2) (19 M, 21 F; mean age 39.26 ± 7.41 years). Plasma 25 (OH) vitamin D levels were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Plasma YKL-40 analysis was performed by ELISA. Serum hs-CRP levels were measured by nephelometric method. Plasma vitamin D levels below 20 ng/mL were accepted as vitamin D deficiency. Although we could not find any significant differences by means of serum hs-CRP levels between Group 1 and Group 2 (2.21 (0.27-11.70); 1.79 (0.16-9.85) mg/L, p = 0.247), plasma YKL-40 levels were significantly higher in group 1 than group2 (70.47 (17.84-198.50); 47.14 (4.80-135.48) ng/mL, p = 0.047). In literature, vitamin D deficiency is associated with inflammation. In our study, we found similar hs-CRP levels between groups and higher YKL-40 levels in group 1. Vitamin D deficiency may be related to high YKL-40 levels in terms of causing chronic inflammation.

Vitamin D Is Required for ILC3 Derived IL-22 and Protection From Citrobacter rodentium Infection

Citrobacter rodentium is a gastrointestinal infection that requires early IL-22 from group 3 innate lymphoid cells (ILC3) for resistance. The role of vitamin D in the clearance of C. rodentium infection was tested in vitamin D sufficient (D+) and vitamin D deficient (D-) wildtype (WT) and Cyp27B1 (Cyp) KO mice (unable to produce the high affinity vitamin D ligand 1,25(OH)2D, 1,25D). Feeding Cyp KO mice D- diets reduced vitamin D levels and prevented synthesis of 1,25D. D- (WT and Cyp KO) mice had fewer ILC3 cells and less IL-22 than D+ mice. D- Cyp KO mice developed a severe infection that resulted in the lethality of the mice by d14 post-infection. T and B cell deficient D- Rag KO mice also developed a severe and lethal infection with C. rodentium compared to D+ Rag KO mice. D- WT mice survived the infection but took significantly longer to clear the C. rodentium infection than D+ WT or D+ Cyp KO mice. Treating infected D- Cyp KO mice with IL-22 protected the mice from lethality. Treating the D- WT mice with 1,25D reconstituted the ILC3 cells in the colon and protected the mice from C. rodentium. IL-22 treatment of D- WT mice eliminated the need for vitamin D to clear the C. rodentium infection. Vitamin D is required for early IL-22 production from ILC3 cells and protection from enteric infection with C. rodentium.

Nuclear Receptors in the Pathogenesis and Management of Inflammatory Bowel Disease

Nuclear receptors (NRs) are ligand-dependent transcription factors that regulate the transcription of target genes. Previous epidemiological and genetic studies have documented the association of NRs with the risk of inflammatory bowel disease (IBD). Although the mechanisms of action of NRs in IBD have not been fully established, accumulating evidence has demonstrated that NRs play complicated roles in regulating intestinal immunity, mucosal barriers, and intestinal flora. As one of the first-line medications for the treatment of IBD, 5-aminosalicylic acid (5-ASA) activates peroxisome proliferator-activated receptor gamma (PPARγ) to attenuate colitis. The protective roles of rifaximin and rifampicin partly depend on promoting pregnane X receptor (PXR) expression. The aims of this review are to discuss the roles of several important NRs, such as PPARγ, PXR, vitamin D receptor (VDR), farnesoid X receptor (FXR), and RAR-related orphan receptor gammat (RORγt), in the pathogenesis of IBD and management strategies based on targeting these receptors.

The intestinal vitamin D receptor in inflammatory bowel disease: inverse correlation with inflammation but no relationship with circulating vitamin D status

BACKGROUND

The intestinal vitamin D receptor (VDR) remains poorly characterized in patients with inflammatory bowel disease (IBD).

METHODS

Colonoscopic biopsies and intestinal resection specimens from the terminal ileum, ascending and sigmoid colon, from patients with and without IBD, were analyzed for VDR mRNA quantification by polymerase chain reaction, and protein localization and semi-quantification by immunohistochemistry. The relationship between VDR and intestinal inflammation, serum 25(OH)D and oral vitamin D intake was elicited.

RESULTS

A total of 725 biopsies from 20 patients with Crohn's disease (CD), 15 with ulcerative colitis (UC) and 14 non-IBD controls who underwent colonoscopy were studied. VDR gene expression and protein staining intensity was similar across all three groups, and across the intestinal segments. Sigmoid colon VDR mRNA expression inversely correlated with faecal calprotectin (r = -0.64, p = 0.026) and histological score (r = -0.67, p = 0.006) in UC, and histological score (r = -0.58, p = 0.019) in patients with CD. VDR staining intensity was higher in quiescent than diseased segments. No relationship with serum 25(OH)D or oral vitamin D intake was noted. Immunohistochemical staining of 28 intestinal resection specimens from 15 patients (5 each with CD, UC and non-IBD controls) showed diffuse VDR staining in the mucosa, submucosa and circular muscle.

CONCLUSIONS

VDR transcript expression and protein staining intensity are inversely related to inflammation in IBD, but unrelated to serum 25(OH)D, and similar to non-IBD controls. Strategies to upregulate intestinal VDR, potentially translating to modulation of disease activity, require investigation.

Study Bacteria-Host Interactions Using Intestinal Organoids

The intestinal epithelial cells function to gain nutrients, retain water and electrolytes, and form an efficient barrier against foreign microbes and antigens. Researchers employed cell culture lines derived from human or animal cancer cells as experimental models in vitro for understanding of intestinal infections. However, most in vitro models used to investigate interactions between bacteria and intestinal epithelial cells fail to recreate the differentiated tissue components and structure observed in the normal intestine. The in vitro analysis of host-bacteria interactions in the intestine has been hampered by a lack of suitable intestinal epithelium culture systems. Here, we present a new experimental model using an organoid culture system to study bacterial infection.

Lack of Vitamin D Receptor Leads to Hyperfunction of Claudin-2 in Intestinal Inflammatory Responses

BACKGROUND

Vitamin D3 and vitamin D receptor (VDR) are involved in the pathogenesis of inflammatory bowel disease (IBD) and bacterial infection. Claudin-2 is a junction protein that mediates paracellular water transport in epithelia. Elevation of Claudin-2 is associated with active IBD. However, VDR involved in epithelial junctions under inflammation and infection remains largely unknown. We investigated the mechanisms on how VDR and Claudin-2 are related in inflamed states.

METHODS

Using cultured VDR-/- enteroids, human intestinal epithelial cells, VDR-/- mice with Salmonella- or DSS-colitis, and human IBD samples, we investigated the mechanisms how VDR and Claudin-2 are related in inflamed states.

RESULTS

After Salmonella infection had taken place, we observed significantly enhanced Claudin-2 and an increased bacterial invasion and translocation. A lack of VDR regulation led to a robust increase of Claudin-2 at the mRNA and protein levels post-infection. In DSS-treated VDR-/- mice, Claudin-2 was significantly increased. Location and quantification of Claudin-2 protein in the mouse colons treated with DSS also confirmed these results. Inflammatory cytokines were significantly higher in the serum and mRNA levels in intestine, which are known to increase Claudin-2. Furthermore, in inflamed intestine of ulcerative colitis patients, VDR expression was low and Claudin-2 was enhanced. Mechanistically, we identified the enhanced Claudin-2 promoter activity through the binding sites of NF-κB and STAT in inflamed VDR-/- cells.

CONCLUSIONS

Our studies have identified a new role for intestinal epithelial VDR in regulating barrier functions in the context of infection and inflammation.

Vitamin D: Nutrient, Hormone, and Immunomodulator

The classical functions of vitamin D are to regulate calcium-phosphorus homeostasis and control bone metabolism. However, vitamin D deficiency has been reported in several chronic conditions associated with increased inflammation and deregulation of the immune system, such as diabetes, asthma, and rheumatoid arthritis. These observations, together with experimental studies, suggest a critical role for vitamin D in the modulation of immune function. This leads to the hypothesis of a disease-specific alteration of vitamin D metabolism and reinforces the role of vitamin D in maintaining a healthy immune system. Two key observations validate this important non-classical action of vitamin D: first, vitamin D receptor (VDR) is expressed by the majority of immune cells, including B and T lymphocytes, monocytes, macrophages, and dendritic cells; second, there is an active vitamin D metabolism by immune cells that is able to locally convert 25(OH)D₃ into 1,25(OH)₂D₃, its active form. Vitamin D and VDR signaling together have a suppressive role on autoimmunity and an anti-inflammatory effect, promoting dendritic cell and regulatory T-cell differentiation and reducing T helper Th 17 cell response and inflammatory cytokines secretion. This review summarizes experimental data and clinical observations on the potential immunomodulating properties of vitamin D.

Altered duodenal bile salt concentration and receptor expression in functional dyspepsia

Background

Functional dyspepsia is a common functional gastrointestinal disorder in which a variety of pathophysiological mechanisms such as increased intestinal permeability and low-grade inflammation are involved. The factor causing these alterations, however, has not been identified.

Objective

We aimed to evaluate the luminal bile salt content and receptor expression in patients with functional dyspepsia and healthy volunteers.

Methods

Gastroduodenoscopy was performed to obtain duodenal biopsies from 25 healthy volunteers and 25 patients with functional dyspepsia (Rome III) to measure duodenal bile salt receptor expression with Western blot. Duodenal fluid aspirates were collected at fixed time points during fasted and fed state conditions and bile salt composition analysis was performed by liquid chromatography-mass spectrometry/mass spectrometry.

Results

Patients (N = 17) displayed decreased fasted bile salt concentrations compared to healthy volunteers (N = 20) over time (1.8 ± 0.3 mM vs 3.6 ± 0.5 mM; p = 0.03). In addition, an increased expression of duodenal bile salt sensor vitamin D receptor was found in patients (3.7 ± 1.0-fold; p < 0.0005; N = 24 for both groups).

Conclusion

Patients with functional dyspepsia are characterized by a decreased duodenal bile salt concentration in fasted state and an increased duodenal vitamin D receptor expression.

Diet-induced vitamin D deficiency triggers inflammation and DNA damage profile in murine myometrium

Background

Previously, we reported a significantly higher prevalence of uterine fibroids (UFs) in African American women. This minority group also commonly suffers from vitamin D deficiency. We have demonstrated that 1,25(OH)₂D₃ attains a fibroid growth inhibitory impact through its ability to block the G1/S (gap 1/synthesis) phase of the cell cycle. Vitamin D is involved in DNA damage as well as in immune response regulation, anti-inflammation, autoimmunity and cancer. Since most of the prior data on vitamin D and UF were generated in vitro via established cell lines, it was necessary to verify and validate this observation in vivo using a diet-induced vitamin D-deficient mouse model.

Materials and Methods

Our model of vitamin D lacking function was established using 8-week exposure of C57/BL6 mice to vitamin D-deficient diet provides evidence of different functions accomplished by vitamin D in the regulation of myometrium homeostasis disrupted in the context of uterine fibroid.

Results

We found that vitamin D deficiency was associated with increased expression of sex steroid receptors in murine myometrium, increased expression of proliferation related genes, the promotion of fibrosis and enhanced inflammation, and promoted immunosuppression through Tregs expansion in murine myometrium. We also showed that a vitamin D deficient diet enhanced DNA damage in murine myometrium.

Conclusion

Our model mimics the effects in humans that a lack of vitamin D has and propels the study of in vivo interaction between inflammation, genomic instability and cell proliferation in the myometrium.

No effects without causes: the Iron Dysregulation and Dormant Microbes hypothesis for chronic, inflammatory diseases

Since the successful conquest of many acute, communicable (infectious) diseases through the use of vaccines and antibiotics, the currently most prevalent diseases are chronic and progressive in nature, and are all accompanied by inflammation. These diseases include neurodegenerative (e.g. Alzheimer's, Parkinson's), vascular (e.g. atherosclerosis, pre-eclampsia, type 2 diabetes) and autoimmune (e.g. rheumatoid arthritis and multiple sclerosis) diseases that may appear to have little in common. In fact they all share significant features, in particular chronic inflammation and its attendant inflammatory cytokines. Such effects do not happen without underlying and initially 'external' causes, and it is of interest to seek these causes. Taking a systems approach, we argue that these causes include (i) stress-induced iron dysregulation, and (ii) its ability to awaken dormant, non-replicating microbes with which the host has become infected. Other external causes may be dietary. Such microbes are capable of shedding small, but functionally significant amounts of highly inflammagenic molecules such as lipopolysaccharide and lipoteichoic acid. Sequelae include significant coagulopathies, not least the recently discovered amyloidogenic clotting of blood, leading to cell death and the release of further inflammagens. The extensive evidence discussed here implies, as was found with ulcers, that almost all chronic, infectious diseases do in fact harbour a microbial component. What differs is simply the microbes and the anatomical location from and at which they exert damage. This analysis offers novel avenues for diagnosis and treatment.

The Effect of Vitamin D on Intestinal Inflammation and Faecal Microbiota in Patients with Ulcerative Colitis

BACKGROUND AND AIMS

Vitamin D may be immunomodulatory and alter faecal microbiota, but results from clinical studies in humans to date have been inconclusive. This study aimed to assess the effect of vitamin D replacement in vitamin D-deficient patients with and without ulcerative colitis [UC] on inflammation and faecal microbiota.

METHODS

Vitamin D was replaced over 8 weeks in patients with active UC [defined by faecal calprotectin ≥ 100 µg/g], inactive UC [faecal calprotectin < 100 µg/g] and non-inflammatory bowel disease [IBD] controls with baseline serum 25[OH] vitamin D <50 nmol/l, and markers of inflammation and faecal microbiota were analysed.

RESULTS

Eight patients with active UC, nine with inactive UC and eight non-IBD controls received 40000 units cholecalciferol weekly for 8 weeks. Mean baseline 25[OH] vitamin D increased from 34 [range 12-49] to 111 [71-158] nmol/l [p < 0.001], with no difference across the groups [p = 0.32]. In patients with active UC, faecal calprotectin levels decreased from a median 275 to 111 µg/g [p = 0.02], platelet count decreased [mean 375 to 313 × 109/l, p = 0.03] and albumin increased [mean 43 to 45 g/l, p = 0.04]. These parameters did not change in patients with inactive UC or non-IBD controls. No changes in overall faecal bacterial diversity were noted although a significant increase in Enterobacteriaceae abundance was observed in patients with UC [p = 0.03].

CONCLUSIONS

Vitamin D supplementation was associated with reduced intestinal inflammation in patients with active UC, with a concomitant increase in Enterobacteriaceae but no change in overall faecal microbial diversity.

A Single Nucleotide Polymorphism in the Vitamin D Receptor Gene Is Associated With Decreased Levels of the Protein and a Penetrating Pattern in Crohn's Disease

BACKGROUND

Vitamin D signaling modulates inflammation through the vitamin D receptor (VDR). The synonymous single nucleotide polymorphism (SNP) rs731236, located in the VDR gene, has been associated with a higher risk of Crohn's disease (CD). We analyzed differences in VDR expression levels among CD patients who were homozygous for allelic variants in this SNP and their relevance for disease course.

METHODS

DNA was extracted from blood samples of CD patients, and SNP genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism. Fresh blood from patients was used to isolate peripheral blood mononuclear cells (PBMCs) or to determine the expression of adhesion molecules by flow cytometry. We analyzed the gene expression of VDR and several cytokines in PBMCs using real-time polymerase chain reaction and the protein levels of VDR, NFκB, and IκBα by immunoblot. In addition, we collected complete clinical data for a group of 103 patients, including age at diagnosis, disease location, and disease behavior to compare patient characteristics with respect to genotype.

RESULTS

We found that CD patients who were homozygous for the risk allele presented lower levels of VDR protein in PBMCs, and that this was associated with an upregulation of IL1β mRNA and activation of lymphocytic adhesion molecules. These patients had a higher risk of developing a B3-penetrating phenotype and of needing to undergo surgery.

CONCLUSION

Our data highlight the relevance of vitamin D/VDR signaling in modulating the subjacent inflammation that leads to CD-related complications.

Ancient Nuclear Receptor VDR With New Functions: Microbiome and Inflammation

The biological functions of 1α,25-dihydroxyvitamin D3 are regulated by nuclear receptor vitamin D receptor (VDR). The expression level of VDR is high in intestine. VDR is an essential regulator of intestinal cell proliferation, barrier function, and immunity. Vitamin D/VDR plays a protective role in inflammatory bowel diseases (IBDs), both ulcerative colitis and Crohn's disease. Emerging evidence demonstrates low VDR expression and dysfunction of vitamin D/VDR signaling in patients with IBD. Here, we summarize the progress made in vitamin D/VDR signaling in genetic regulation, immunity, and the microbiome in IBD. We cover the mechanisms of intestinal VDR in regulating inflammation through inhibiting the NF-ĸB pathway and activating autophagy. Recent studies suggest that the association of VDR single nucleotide polymorphisms with immune and intestinal pathology may be sex dependent. We emphasize the tissue specificity of VDR and its sex- and time-dependent effects. Furthermore, we discuss potential clinical application and future direction of vitamin D/VDR in preventing and treating IBD.

Inflammatory bowel disease and immunonutrition: novel therapeutic approaches through modulation of diet and the gut microbiome

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the gastrointestinal tract, thought to at least in part reflect an aberrant immune response to gut bacteria. IBD is increasing in incidence, particularly in populations that have recently immigrated to western countries. This suggests that environmental factors are involved in its pathogenesis. We hypothesize that the increase in IBD rates might reflect the consumption of an unhealthy Western diet, containing excess calories and lacking in key nutritional factors, such as fibre and vitamin D. Several recent studies have determined that dietary factors can dramatically influence the activation of immune cells and the mediators they release through a process called immunonutrition. Moreover, dietary changes can profoundly affect the balance of beneficial versus pathogenic bacteria in the gut. This microbial imbalance can alter levels of microbiota-derived metabolites that in turn can influence innate and adaptive intestinal immune responses. If the diet-gut microbiome disease axis does indeed underpin much of the 'western' influence on the onset and progression of IBD, then tremendous opportunity exists for therapeutic changes in lifestyle, to modulate the gut microbiome and to correct immune imbalances in individuals with IBD. This review highlights four such therapeutic strategies - probiotics, prebiotics, vitamin D and caloric restriction - that have the potential to improve and add to current IBD treatment regimens.

Krill oil, vitamin D and Lactobacillus reuteri cooperate to reduce gut inflammation

Current research into original therapies to treat intestinal inflammation is focusing on no-drug therapies. KLD is a mixture of krill oil (KO), probiotic Lactobacillus reuteri (LR), and vitamin D (VitD3). The aim of this study was to assess in vitro and in vivo the potential cooperative effects of KLD in reducing gut inflammation. Colorectal adenocarcinoma cell lines, CACO2 and HT29, and C57BL/6 mice were used for in vitro and in vivo analyses, respectively. Cells were exposed to cytomix (interferon gamma + tumour necrosis factor alpha (TNF-α)) to induce inflammation or co-exposed to cytomix and KO, LR and VitD3 alone or to cytomix and KLD. Animals were treated for 7 days with dextran sodium sulphate (DSS) to induce colitis or with DSS and KLD. In vitro assays: F-actin expression was analysed by immunofluorescence; scratch test and trans-epithelial electric resistance test were performed to measure wound healing; adhesion/invasion assays of adhesive and invasive Escherichia coli (AIEC) bacteria were made; mRNA expression of TNF-α, interleukin (IL)-8 and vitamin D receptor (VDR) was detected by quantitative PCR. In vivo assays: body weight, clinical score, histological score and large intestine weight and length were estimated; mRNA expression of TNF-α, IL-1β, IL-6, IL-10 by quantitative PCR; VDR expression was detected by quantitative PCR and immunohistochemistry. In vitro: KLD restores epithelial cell-cell adhesion and mucosal healing during inflammation, while decreases the adhesiveness and invasiveness of AIEC bacteria and TNF-α and IL-8 mRNA expression and increases VDR expression. In vivo: KLD significantly improves body weight, clinical score, histological score and large intestine length of mice with DSS-induced colitis and reduces TNF-α, IL-1β and IL-6 mRNA levels, while increases IL-10 mRNA and VDR levels. KLD has significant effects on the intestinal mucosa, strongly decreasing inflammation, increasing epithelial restitution and reducing pathogenicity of harmful commensal bacteria.

Infection with enteric pathogens Salmonella typhimurium and Citrobacter rodentium modulate TGF-beta/Smad signaling pathways in the intestine

Salmonella and Citrobacter are gram negative, members of Enterobacteriaceae family that are important causative agents of diarrhea and intestinal inflammation. TGF-β1 is a pleiotropic multifunctional cytokine that has been implicated in modulating the severity of microbial infections. How these pathogens alter the TGF-β1 signaling pathways in the intestine is largely unknown. Streptomycin-pretreated C57BL/6J mouse model colonized with S. typhimurium for 8 hours (acute) and 4 days (chronic) infection and FVB/N mice infected with C. rodentium for 6 days were utilized. Results demonstrated an increase in TGF-β1 receptor I expression (p<0.05) in S. typhimurium infected mouse ileum at both acute and chronic post-infection vs control. This was associated with activation of Smad pathways as evidenced by increased phosphorylated (p)-Smad2 and p-Smad3 levels in the nucleus. The inhibitory Smad7 mRNA levels showed a significant up regulation during acute phase of Salmonella infection but no change at 4d post-infection. In contrast to Salmonella, infection with Citrobacter caused drastic downregulation of TGF receptor I and II concomitant with a decrease in levels of Smad 2, 3, 4 and 7 expression in the mouse colon. We speculate that increased TGF-β1 signaling in response to Salmonella may be a host compensatory response to promote mucosal healing; while C. rodentium decreases TGF-β1 signaling pathways to promote inflammation and contribute to disease pathogenesis. These findings increase our understanding of how enteric pathogens subvert specific aspects of the host-cellular pathways to cause disease.

Serum 25-hydroxyvitamin D concentrations are associated with nuclear factor kappa-B activity but not with inflammatory markers in healthy normoglycemic adults

Vitamin D has been reported to have anti-inflammatory properties in in vitro and animal studies, which are thought to occur via inhibition of the nuclear factor kappa-B (NFκB) pathway. However, the association between vitamin D and in vivo NFκB activity in humans has not previously been reported. The aim of the present study was to examine the associations between circulating 25-hydroxyvitamin D (25(OH)D) concentrations and NFκB activity in peripheral blood mononuclear cells (PBMCs) as well as plasma inflammatory markers in healthy individuals. We hypothesized that 25(OH)D concentrations would be negatively associated with NFκB activity and pro-inflammatory markers downstream of NFκB, and positively associated with anti-inflammatory markers. We measured circulating 25(OH)D (chemiluminescent immunoassay); anthropometry: body mass index (BMI), waist-to-hip ratio (WHR), and % body fat (dual X-ray absorptiometry); plasma pro- and anti-inflammatory markers: high sensitivity C-reactive protein (hsCRP), tumor necrosis factor (TNF), monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), and IL-10 (ELISA); and NFκB activity in PBMCs (DNA-binding assay). Forty-nine participants were included in the study (21M/28F; age=31.6±10.2years (mean±SD); BMI=28.4±4.6kg/m²; % body fat=30.2±9.3%). Mean 25(OH)D concentration was 48.2±24.5 nmol/l. There were no differences in 25(OH)D concentrations between genders and no association between 25(OH)D concentrations and age, BMI, or % body fat (all p>0.1). Serum 25(OH)D concentrations were positively associated with NFκB activity in PBMCs (r=0.48, p=0.0008) but not with any of the pro- or anti-inflammatory markers measured (all p>0.1). After adjusting for age, sex, and % body fat, 25(OH)D concentrations remained positively associated with NFκB activity in PBMCs (β=0.55, p<0.0001). Although in-vitro studies suggest that vitamin D inhibits NFκB activity, our novel cross-sectional data from a cohort of healthy individuals suggest that vitamin D may regulate rather than inhibit the NFκB pathway. Large-scale intervention and mechanistic studies are needed to further investigate the effects of vitamin D on NFκB activity in vivo in humans.

Impact of vitamin D supplementation on C-reactive protein; a systematic review and meta-analysis of randomized controlled trials

Background

To evaluate the effect of vitamin D supplementation on C-reactive protein (CRP) through a systematic review and meta-analysis of randomized control trials (RCTs).

Methods

PubMed-Medline, SCOPUS, Google Scholar and Web of Science databases were searched (up until April 2016) to identify RCTs evaluating the impact of vitamin D supplementation on CRP. We used random effects models (using DerSimonian-Laird method) as well as the generic inverse variance methods for quantitative data synthesis. For sensitivity analysis, we applied leave-one-out approach. To examine the heterogeneity we used I2 index. Registration code: CRD42016036932.

Results

Among 1274 search items, 24 studies met the inclusion criteria in the final evaluation. Pooling the data together indicated a non-significant decrease in CRP level following administration of vitamin D (weighted mean difference [WMD] -0.26(mg/l), (95% CI -0.75 to 0.22, N = 26 arms, heterogeneity p = 0.042; I² 54.2%). The WMDs for IL6 was 0.67 pg/ml, (95% CI 0.29 to 1.06, N = 16 arms, heterogeneity p = 0.234; I² 19.1%), 0.43 pg/ml, (95% CI 0.08 to 1.05, N = 26 arms, heterogeneity p = 0.120; I² 42.1%), for IL10, and −0.11 pg/ml, (95% CI -0.53 to 0.30, N = 12 arms, heterogeneity p = 0.423; I² 9.2%) for TNF-α, 4.03 pg/ml, (95% CI 3.50 to 4.57, N = 3 arms, heterogeneity p = 0.752; I² 8.1%) for adiponectin. Sensitivity analyses confirmed the robustness of the findings.

Conclusions

This study provided evidence that vitamin D supplementation had no impact on serum CRP, IL10, and TNF-α, while significantly increased serum IL6. We recommend RCTs with longer period of follow-up time (12 months) for future studies to provide explicit results.

Electronic supplementary material

The online version of this article (10.1186/s40795-017-0207-6) contains supplementary material, which is available to authorized users.