Host responses to intestinal microbial antigens in gluten-sensitive mice

Limited support for a direct connection between prebiotics and intestinal permeability - a systematic review

The intestinal barrier is a selective interface between the body´s external and the internal environment. Its layer of epithelial cells is joined together by tight junction proteins. In intestinal permeability (IP), the barrier is compromised, leading to increased translocation of luminal contents such as large molecules, toxins and even microorganisms. Numerous diseases including Inflammatory Bowel Disease (IBD), Coeliac disease (CD), autoimmune disorders, and diabetes are believed to be associated with IP. Dietary interventions, such as prebiotics, may improve the intestinal barrier. Prebiotics are non-digestible food compounds, that promote the growth and activity of beneficial bacteria in the gut. This systematic review assesses the connection between prebiotic usage and IP. PubMed and Trip were used to identify relevant studies conducted between 2010-2023. Only six studies were found, which all varied in the characteristics of the population, study design, and types of prebiotics interventions. Only one study showed a statistically significant effect of prebiotics on IP. Alteration of intestinal barrier function was measured by lactulose/mannitol, chromium-labelled Ethylenediaminetetraacetic acid (51Cr-EDTA), lactulose/rhamnose, and sucralose/erythritol excretion as well as zonulin and glucagon-like peptide 2 levels. Three studies also conducted gut microbiota assessment, and one of them showed statistically significant improvement of the gut microbiome. This study also reported a decrease in zonulin level. The main conclusion from this review is that there is a lack of human studies in this important field. Futhermore, large population studies and using standardized protocols, would be required to properly assess the impact of prebiotic intervention and improvement on IP.

Bacteria: Potential Make-or-Break Determinants of Celiac Disease

Celiac disease is an autoimmune disease triggered by dietary gluten in genetically susceptible individuals that primarily affects the small intestinal mucosa. The sole treatment is a gluten-free diet that places a social and economic burden on patients and fails, in some, to lead to symptomatic or mucosal healing. Thus, an alternative treatment has long been sought after. Clinical studies on celiac disease have shown an association between the presence of certain microbes and disease outcomes. However, the mechanisms that underlie the effects of microbes in celiac disease remain unclear. Recent studies have employed disease models that have provided insights into disease mechanisms possibly mediated by bacteria in celiac disease. Here, we have reviewed the bacteria and related mechanisms identified so far that might protect from or incite the development of celiac disease. Evidence indicates bacteria play a role in celiac disease and it is worth continuing to explore this, particularly since few studies, to the best of our knowledge, have focused on establishing a mechanistic link between bacteria and celiac disease. Uncovering host-microbe interactions and their influence on host responses to gluten may enable the discovery of pathogenic targets and development of new therapeutic or preventive approaches.

In vivo sensitization to gliadin by oral administration

Celiac disease is a highly prevalent immune-mediated enteropathy that develops in genetically susceptible individuals expressing HLA-DQ2 or HLA-DQ8 after ingestion of gluten and results in decreased quality of life and increased morbidity. This pathology is triggered by immunogenic peptides generated from gliadins present in gluten, which act on the intestinal mucosa in a context of high intestinal permeability, activating the innate and adaptive response of the immune system. Several in vivo rodent models attempt to reproduce some phases of the intestinal inflammatory process that occurs in celiac disease. Allergic sensitization to gluten simulates, or enhances in some animal models, the loss of tolerance to gliadin peptides and the initial events that lead to celiac disease in a specific genetic or environmental context. Here we describe a simple method for performing gliadin sensitization in an in vivo animal model.

Gut barrier-microbiota imbalances in early life lead to higher sensitivity to inflammation in a murine model of C-section delivery

BACKGROUND

Most interactions between the host and its microbiota occur at the gut barrier, and primary colonizers are essential in the gut barrier maturation in the early life. The mother-offspring transmission of microorganisms is the most important factor influencing microbial colonization in mammals, and C-section delivery (CSD) is an important disruptive factor of this transfer. Recently, the deregulation of symbiotic host-microbe interactions in early life has been shown to alter the maturation of the immune system, predisposing the host to gut barrier dysfunction and inflammation. The main goal of this study is to decipher the role of the early-life gut microbiota-barrier alterations and its links with later-life risks of intestinal inflammation in a murine model of CSD.

RESULTS

The higher sensitivity to chemically induced inflammation in CSD mice is related to excessive exposure to a too diverse microbiota too early in life. This early microbial stimulus has short-term consequences on the host homeostasis. It switches the pup's immune response to an inflammatory context and alters the epithelium structure and the mucus-producing cells, disrupting gut homeostasis. This presence of a too diverse microbiota in the very early life involves a disproportionate short-chain fatty acids ratio and an excessive antigen exposure across the vulnerable gut barrier in the first days of life, before the gut closure. Besides, as shown by microbiota transfer experiments, the microbiota is causal in the high sensitivity of CSD mice to chemical-induced colitis and in most of the phenotypical parameters found altered in early life. Finally, supplementation with lactobacilli, the main bacterial group impacted by CSD in mice, reverts the higher sensitivity to inflammation in ex-germ-free mice colonized by CSD pups' microbiota.

CONCLUSIONS

Early-life gut microbiota-host crosstalk alterations related to CSD could be the linchpin behind the phenotypic effects that lead to increased susceptibility to an induced inflammation later in life in mice. Video Abstract.

Paracellular permeability and tight junction regulation in gut health and disease

Epithelial tight junctions define the paracellular permeability of the intestinal barrier. Molecules can cross the tight junctions via two distinct size-selective and charge-selective paracellular pathways: the pore pathway and the leak pathway. These can be distinguished by their selectivities and differential regulation by immune cells. However, permeability increases measured in most studies are secondary to epithelial damage, which allows non-selective flux via the unrestricted pathway. Restoration of increased unrestricted pathway permeability requires mucosal healing. By contrast, tight junction barrier loss can be reversed by targeted interventions. Specific approaches are needed to restore pore pathway or leak pathway permeability increases. Recent studies have used preclinical disease models to demonstrate the potential of pore pathway or leak pathway barrier restoration in disease. In this Review, we focus on the two paracellular flux pathways that are dependent on the tight junction. We discuss the latest evidence that highlights tight junction components, structures and regulatory mechanisms, their impact on gut health and disease, and opportunities for therapeutic intervention.

Maternal procymidone exposure has lasting effects on murine gut-liver axis and glucolipid metabolism in offspring

There is increasing evidence that maternal exposure to environmental pollutants can cause intestinal and metabolic diseases, and these disease risks still exist in offspring. Here, female C57BL/6 mice were orally treated with procymidone (PRO) (10 and 100 mg/kg body weight/day) by dietary supplementation during the gestation and lactation periods. Then, we discovered PRO changed the physiology, intestinal barrier and metabolism both in the generations of F₀ and different developmental stages of F₁ (7 weeks and 30 weeks old, respectively). Maternal PRO exposure affected the growth phenotypes and the glucolipid metabolism related indicators and genes of mice, especially the male mice of F₁ generations. The changes in bile acids (BAs) metabolism demonstrated that PRO disordered glucolipid metabolism through enterohepatic circulation. Furthermore, PRO reduced mucus secretion in the gut and altered the composition of gut microbiota, leading more bacteria to disseminate in the gut and inflammatory responses both in F₀ and F₁ regenerations. And PRO-induced gut microbiota dysbiosis was tightly related to BAs metabolites. Together, the results indicated that PRO destructed the functional integrity of intestinal barrier and the inflammatory reaction was triggered. And then, the disorder of glucolipid metabolism was induced through the BAs enterohepatic circulation. This study indicated that the cross-generation effects of PRO could not be ignored.

Elucidating the role of microbes in celiac disease through gnotobiotic modeling

Celiac disease (CeD) is a common immune-mediated disease triggered by the ingestion of gluten in genetically predisposed individuals. CeD is unique in that the trigger (gluten), necessary genes (HLA-DQ2 and DQ8), and the autoantigen (tissue transglutaminase) have been identified, allowing additional environmental co-factors, like the intestinal microbiota, to be studied through relevant in vivo models. Murine models for CeD have come a long way in the past decade and there are now in vitro and in vivo tools available that mimic certain aspects of clinical disease. These models, many of which express the CeD risk genes, have recently been used to study the mechanisms through which the microbiota play a role in CeD pathogenesis through a gnotobiotic approach. Historically, the generation of gnotobiology technology in mid-20th century allowed for the study of immunity and physiology under a complete absence of microbes (axenic) or known colonized status (gnotobiotic). This enabled understanding of mechanisms by which certain bacteria contribute to health and disease. With this perspective, here, we will discuss the various murine models currently being used to study CeD. We will then describe how utilizing axenic and gnotobiotic CeD models has increased our understanding of how microbes influence relevant steps of CeD pathogenesis, and explain key methodology involved in axenic and gnotobiotic modeling.

Disordered Expression of Tight Junction Proteins Is Involved in the Mo-induced Intestinal Microenvironment Dysbiosis in Sheep

To evaluate the molybdenum (Mo)-induced changes of intestinal morphology and the relationship of intestinal tight junction (TJ) proteins expression and intestinal barrier function, a total of 20 healthy sheep were randomly divided into five groups of four: 0, 5, 10, 20, and 50 mg/kg BW/day Na₂MoO₄·2H₂O were administrated in five groups named control group, Mo 5 group, Mo 10 group, Mo 20 group, and Mo 50 group, respectively. After 28 days of Mo treatment, the duodenum, the jejunum, and the ileum tissue were collected. The histopathology and the developmental parameters were evaluated by hematoxylin-eosin staining. The intestinal epithelial cell DNA damage was detected by TdT-mediated dUTP nick end labeling assay. The intestinal glycoprotein and the goblet cells were analyzed by Alcian Blue-Periodic Acid-Schiff (AB-PAS) staining and PAS staining, respectively. TJ proteins were determined by immunofluorescence technology. Results showed that excessive Mo significantly decreased the small intestinal villus height (VH), crypt depth (CD), VH/CD, and mucosal thickness (P < 0.05 or P < 0.01) while induced the damage of DNA in small intestinal epithelial cells. Moreover, excessive Mo injured intestinal barrier function by decreasing the percent of glycoprotein distribution area (P < 0.05) and the relative density of intestinal goblet cells (P < 0.05). Mo treatment induced decreased (P < 0.01) expression of Zonula Occludens-1, Occludin, and Claudin-1. In conclusion, excessive Mo interfered with the expression of TJ proteins, inhibited intestinal epithelial development, and further aggravated the intestinal barrier function damage, leading to disturbing the small intestinal microenvironment balance.

Co-factors, Microbes, and Immunogenetics in Celiac Disease to Guide Novel Approaches for Diagnosis and Treatment

Celiac disease (CeD) is a frequent immune-mediated disease that affects not only the small intestine but also many extraintestinal sites. The role of gluten proteins as dietary triggers, HLA-DQ2 or -DQ8 as major necessary genetic predisposition, and tissue transglutaminase (TG2) as mechanistically involved autoantigen, are unique features of CeD. Recent research implicates many cofactors working in synergism with these key triggers, including the intestinal microbiota and their metabolites, nongluten dietary triggers, intestinal barrier defects, novel immune cell phenotypes, and mediators and cytokines. In addition, apart from HLA-DQ2 and -DQ8, multiple and complex predisposing genetic factors and interactions have been defined, most of which overlap with predispositions in other, usually autoimmune, diseases that are linked to CeD. The resultant better understanding of CeD pathogenesis, and its manifold manifestations has already paved the way for novel therapeutic approaches beyond the lifelong strict gluten-free diet, which poses a burden to patients and often does not lead to complete mucosal healing. Thus, supported by improved mouse models for CeD and in vitro organoid cultures, several targeted therapies are in phase 2-3 clinical studies, such as highly effective gluten-degrading oral enzymes, inhibition of TG2, cytokine therapies, induction of tolerance to gluten ingestion, along with adjunctive and preventive approaches using beneficial probiotics and micronutrients. These developments are supported by novel noninvasive markers of CeD severity and activity that may be used as companion diagnostics, allow easy-to perform and reliable monitoring of patients, and finally support personalized therapy for CeD.

Maternal exposure to imazalil disrupts intestinal barrier and bile acids enterohepatic circulation tightly related IL-22 expression in F0, F1 and F2 generations of mice

There is a growing body of evidence linking maternal exposure of environmental pollutants to intestinal and metabolic diseases that can be conserved across multiple generations. Here, female C57BL/6 mice were treated imazalil (IMZ) at dietary levels of 0, 0.025‰ and 0.25‰ during the gestation and lactation periods. The results demonstrated that IMZ treatment not only induced significant changes in the mucus secretion and ionic transport, but also disrupted the expression of antimicrobial peptides in the intestine of F0, F1 and F2 generations. In addition, IMZ exposure altered BAs metabolism and the affected the expression levels of critical genes involved in BAs synthesis, signaling, transportation and apical uptake. The immune cell-produced cytokines were displaying extraordinary changes after IMZ exposure. In particular, whether it was in F0, F1-20d, F1-7 w or F2-20d, the expression of IL-22 had the trend of markedly increasing upon IMZ exposure. Correlation analyses revealed that the expression of IL-22 was positively correlated with the change of BAs metabolites. Together, all these results indicated that IMZ exposure was perceived as a major stress by the intestinal epithelium that strongly affected the intestinal barrier function (including mucus, CFTR, AMPs, inflammation), largely in response to an alteration of BAs metabolism.

The Infant-Derived Bifidobacterium bifidum Strain CNCM I-4319 Strengthens Gut Functionality

Bifidobacteria are among the first colonisers of the gastrointestinal tract of breast-fed newborns due to, among other things, their ability to metabolise oligosaccharides naturally occurring in human milk. The presence of bifidobacteria in the infant gut has been shown to promote intestinal health and homeostasis as well as to preserve a functional gut barrier, thus positively influencing host health and well-being. Among human-associated gut commensals, Bifidobacterium bifidum has been described as the only species capable of the extracellular degradation of both mucin-type glycans and HMOs, thereby giving this species a special role as a commensal gut forager of both host and diet-derived glycans. In the present study, we assess the possible beneficial properties and probiotic potential of B. bifidum strain CNCM I-4319. In silico genome analysis and growth experiments confirmed the expected ability of this strain to consume HMOs and mucin. By employing various animal models, we were also able to assess the ability of B. bifidum CNCM I-4319 to preserve gut integrity and functionality from stress-induced and inflammatory damage, thereby enforcing its potential as an effective probiotic strain.

Effects of Bacillus Subtilis-Zinc on Rats with Congenital Zinc Deficiency

This study investigated the effects of dietary supplementation of Bacillus subtilis-zinc on growth rates of the body and organs, nutrient utilization, microbial diversity in caecum, and contents of zinc (Zn) in organs of rats fed a Zn-deficient diet. In trial 1, 72 female pregnant SD rats were allocated to two groups and respectively fed the basal diet containing 13 mg Zn/kg, or the control diet containing 38 mg Zn/kg by supplementing ZnSO₄ from day 10 of pregnancy until the offspring rats 24 days old. In trial 2, 18 offspring rats from the control group were fed the control diet. Ninety offspring from the Zn deficiency group were allocated to 5 groups and were fed the basal diet drenched with ZnSO₄ solution (the total Zn 38 mg/kg), the basal diet only, or the basal diet drenched with Bacillus subtilis-Zn at doses of 2, 17, and 32 mg/kg Zn respectively. Each group had 3 replicates of 6 rats. The experiment lasted for 5 weeks. We found feeding young rats the Zn-deficient diet reduced feed intake, growth rate, unitization efficiencies of nitrogen (N), and Zn content in the organs. Administration of Bacillus subtilis-Zn to rats increased feed intake and the growth rates of the body and liver, kidney and heart, increased N utilization efficiency, and the contents of Zn in heart and brain but not in liver, regulated microbial diversity in the cecal content. The optimal amount of Bacillus subtilis-Zn ranged 15~20 mg Zn/kg, with the corresponding total Zn level at 28~33 mg/kg diet, the effects of which were superior to these by adding ZnSO₄ at 38 mg/kg.

Motility Disorders in Celiac Disease and Non-Celiac Gluten Sensitivity: The Impact of a Gluten-Free Diet

Background: There is evidence that digestive motor disorders are frequently present in untreated celiac disease (CD) patients. Similarly, non-celiac gluten sensitivity (NCGS) can be associated with gut motor disorders. In both cases, gut dysmotility can improve or be completely reversed with a gluten-free diet (GFD). Methods: A literature search for motility disorders in CD and NCGS patients was carried out using the online databases PubMed, Medline and Cochrane. Results: Esophageal, gastric, small bowel and gallbladder motor disorders are common in both children and adults with CD. Although the clinical consequences of these disorders are not clearly defined, gastric dysfunction could affect drug absorption and metabolism in the thyroid and neurological conditions associated with CD. The impact of a GFD on motility disorders is, however, controversial. No systematic studies are available on NCGS. NCGS frequently overlaps with irritable bowel syndrome (IBS) and similar pathophysiological mechanisms may be hypothesized. Conclusions: Mucosal damage may affect gut motility in untreated CD through perturbation of hormonal and neuro-immunomodulatory regulation. A persistent low-grade mucosal inflammation could explain the cases of persistent motor disorders despite a GFD. Further studies are needed to definitely assess the role of gut motor disorders in NCGS.

The Role of Bacteria, Probiotics and Diet in Irritable Bowel Syndrome

Irritable bowel syndrome is a highly prevalent gastrointestinal disorder that threatens the quality of life of millions and poses a substantial financial burden on healthcare systems around the world. Intense research into the human microbiome has led to fascinating discoveries which directly and indirectly implicate the diversity and function of this occult organ in irritable bowel syndrome (IBS) pathophysiology. The benefit of manipulating the gastrointestinal microbiota with diet and probiotics to improve symptoms has been demonstrated in a wealth of both animal and human studies. The positive and negative mechanistic roles bacteria play in IBS will be explored and practical probiotic and dietary choices offered.

Dietary therapies for functional bowel symptoms: Recent advances, challenges, and future directions

BACKGROUND

Functional gastrointestinal symptoms in irritable bowel syndrome (IBS) and quiescent inflammatory bowel disease (IBD) cause significant morbidity and a reduction in quality of life. Multiple dietary therapies are now available to treat these symptoms, but supporting evidence for many is limited. In addition to a further need for studies demonstrating efficacy and mechanism of action of dietary therapies, the risk of nutritional inadequacy, alterations to the microbiome and changes in quality of life are key concerns requiring elucidation. Identifying predictors of response to dietary therapy is an important goal as management could be tailored to the individual to target specific dietary components, and thereby reduce the level of dietary restriction necessary.

PURPOSE

This review discusses the available dietary therapies to treat symptoms in patients with IBS and patients with quiescent IBD suffering from IBS symptoms, with the aim to understand where current dietary evidence lies and how to move forward in dietary research in this field.

The Overlapping Area of Non-Celiac Gluten Sensitivity (NCGS) and Wheat-Sensitive Irritable Bowel Syndrome (IBS): An Update

Gluten-related disorders have recently been reclassified with an emerging scientific literature supporting the concept of non-celiac gluten sensitivity (NCGS). New research has specifically addressed prevalence, immune mechanisms, the recognition of non-immunoglobulin E (non-IgE) wheat allergy and overlap of NCGS with irritable bowel syndrome (IBS)-type symptoms. This review article will provide clinicians with an update that directly impacts on the management of a subgroup of their IBS patients whose symptoms are triggered by wheat ingestion.

The intestinal epithelial barrier: a therapeutic target?

A fundamental function of the intestinal epithelium is to act as a barrier that limits interactions between luminal contents such as the intestinal microbiota, the underlying immune system and the remainder of the body, while supporting vectorial transport of nutrients, water and waste products. Epithelial barrier function requires a contiguous layer of cells as well as the junctions that seal the paracellular space between epithelial cells. Compromised intestinal barrier function has been associated with a number of disease states, both intestinal and systemic. Unfortunately, most current clinical data are correlative, making it difficult to separate cause from effect in interpreting the importance of barrier loss. Some data from experimental animal models suggest that compromised epithelial integrity might have a pathogenic role in specific gastrointestinal diseases, but no FDA-approved agents that target the epithelial barrier are presently available. To develop such therapies, a deeper understanding of both disease pathogenesis and mechanisms of barrier regulation must be reached. Here, we review and discuss mechanisms of intestinal barrier loss and the role of intestinal epithelial barrier function in pathogenesis of both intestinal and systemic diseases. We conclude with a discussion of potential strategies to restore the epithelial barrier.

Non-coeliac gluten/wheat sensitivity: advances in knowledge and relevant questions

Non-coeliac gluten/wheat sensitivity (NCG/WS) is a syndrome characterized by intestinal and extra-intestinal symptoms occurring a few hours or days after the ingestion of gluten and wheat proteins in patients testing negative for coeliac disease and wheat allergy. Areas covered: The present review deals with recent scientific acquisitions of this gluten-related syndrome, including pathogenetic mechanisms, clinical picture, symptom score, biomarkers and double-blind placebo-controlled trial for diagnosis, and treatment. The methodology used was a literature search on NCG/WS using Medline and Premedline from 1970 to August 2016. Expert commentary: We discussed the pathogenesis of symptom generation and altered gut physiology in NCG/WS. Possible mechanisms include innate and adaptive immune activation, impaired intestinal epithelial barrier and changes in gut microbiome. These interlinked factors may be exploited for their clinical relevance as possible biomarkers. A systemic immune response to microbial and wheat antigens, together with intestinal cell damage, occurs in patients with NCG/WS. Due to the lack of established biomarkers, it is mandatory to validate the diagnosis of the syndrome by means of a well-defined work-up involving dietary challenge. Finally, dietary and other therapeutic indications have been thoroughly reviewed.

Duodenal Bacteria From Patients With Celiac Disease and Healthy Subjects Distinctly Affect Gluten Breakdown and Immunogenicity

BACKGROUND & AIMS

Partially degraded gluten peptides from cereals trigger celiac disease (CD), an autoimmune enteropathy occurring in genetically susceptible persons. Susceptibility genes are necessary but not sufficient to induce CD, and additional environmental factors related to unfavorable alterations in the microbiota have been proposed. We investigated gluten metabolism by opportunistic pathogens and commensal duodenal bacteria and characterized the capacity of the produced peptides to activate gluten-specific T-cells from CD patients.

METHODS

We colonized germ-free C57BL/6 mice with bacteria isolated from the small intestine of CD patients or healthy controls, selected for their in vitro gluten-degrading capacity. After gluten gavage, gliadin amount and proteolytic activities were measured in intestinal contents. Peptides produced by bacteria used in mouse colonizations from the immunogenic 33-mer gluten peptide were characterized by liquid chromatography tandem mass spectrometry and their immunogenic potential was evaluated using peripheral blood mononuclear cells from celiac patients after receiving a 3-day gluten challenge.

RESULTS

Bacterial colonizations produced distinct gluten-degradation patterns in the mouse small intestine. Pseudomonas aeruginosa, an opportunistic pathogen from CD patients, exhibited elastase activity and produced peptides that better translocated the mouse intestinal barrier. P aeruginosa-modified gluten peptides activated gluten-specific T-cells from CD patients. In contrast, Lactobacillus spp. from the duodenum of non-CD controls degraded gluten peptides produced by human and P aeruginosa proteases, reducing their immunogenicity.

CONCLUSIONS

Small intestinal bacteria exhibit distinct gluten metabolic patterns in vivo, increasing or reducing gluten peptide immunogenicity. This microbe-gluten-host interaction may modulate autoimmune risk in genetically susceptible persons and may underlie the reported association of dysbiosis and CD.

Generating Transgenic Mouse Models for Studying Celiac Disease

This chapter provides a brief overview of current animal models for studying celiac disease, with a focus on generating HLA transgenic mouse models. Human Leukocyte Antigen class II molecules have been a particular target for transgenic mice due to their tight association with celiac disease, and a number of murine models have been developed which had the endogenous MHC class II genes replaced with insertions of disease susceptible HLA class II alleles DQ2 or DQ8. Additionally, transgenic mice that overexpress interleukin-15 (IL-15), a key player in the inflammatory cascade that leads to celiac disease, have also been generated to model a state of chronic inflammation. To explore the contribution of specific bacteria in gluten-sensitive enteropathy, the nude mouse and rat models have been studied in germ-free facilities. These reductionist mouse models allow us to address single factors thought to have crucial roles in celiac disease. No single model has incorporated all of the multiple factors that make up celiac disease. Rather, these mouse models can allow the functional interrogation of specific components of the many stages of, and contributions to, the pathogenic mechanisms that will lead to gluten-dependent enteropathy. Overall, the tools for animal studies in celiac disease are many and varied, and provide ample space for further creativity as well as to characterize the complete and complex pathogenesis of celiac disease.

Long-lived plasma cells are generated in mucosal immune responses and contribute to the bone marrow plasma cell pool in mice

During systemic immune responses, plasma blasts are generated in secondary lymphoid organs and migrate to the bone marrow, where they can become long-lived, being responsible for the maintenance of long-term antibody titers. Plasma blasts generated in mucosal immune responses of the small intestine home to the lamina propria (LP), producing mainly immunoglobulin A. The migration of these antibody-secreting cells is well characterized during acute immune responses. Less is known about their lifetime and contribution to the long-lived bone marrow compartment. Here we investigate the lifetime of plasma cells (PCs) and the relationship between the PC compartments of the gut and bone marrow after oral immunization. Our findings indicate that PCs in the LP can survive for extended time periods. PCs specific for orally administered antigens can be detected in the bone marrow for at least 9 months after immunization, indicating that the mucosal PC compartment can contribute to the long-lived PC pool in this organ, independent of the participation of splenic B cells. Our findings suggest that the compartmentalization between mucosal and systemic PC pools is less strict than previously thought. This may have implications for the development of vaccines as well as for autoantibody-mediated diseases.

Sensitivity to wheat, gluten and FODMAPs in IBS: facts or fiction?

IBS is one of the most common types of functional bowel disorder. Increasing attention has been paid to the causative role of food in IBS. Food ingestion precipitates or exacerbates symptoms, such as abdominal pain and bloating in patients with IBS through different hypothesised mechanisms including immune and mast cell activation, mechanoreceptor stimulation and chemosensory activation. Wheat is regarded as one of the most relevant IBS triggers, although which component(s) of this cereal is/are involved remain(s) unknown. Gluten, other wheat proteins, for example, amylase-trypsin inhibitors, and fructans (the latter belonging to fermentable oligo-di-mono-saccharides and polyols (FODMAPs)), have been identified as possible factors for symptom generation/exacerbation. This uncertainty on the true culprit(s) opened a scenario of semantic definitions favoured by the discordant results of double-blind placebo-controlled trials, which have generated various terms ranging from non-coeliac gluten sensitivity to the broader one of non-coeliac wheat or wheat protein sensitivity or, even, FODMAP sensitivity. The role of FODMAPs in eliciting the clinical picture of IBS goes further since these short-chain carbohydrates are found in many other dietary components, including vegetables and fruits. In this review, we assessed current literature in order to unravel whether gluten/wheat/FODMAP sensitivity represent 'facts' and not 'fiction' in IBS symptoms. This knowledge is expected to promote standardisation in dietary strategies (gluten/wheat-free and low FODMAP) as effective measures for the management of IBS symptoms.

Role of the gastrointestinal ecosystem in the development of type 1 diabetes

A new emphasis has been put on the role of the gastrointestinal (GI) ecosystem in autoimmune diseases; however, there is limited knowledge about its role in type 1 diabetes (T1D). Distinct differences have been observed in intestinal permeability, epithelial barrier function, commensal microbiota, and mucosal innate and adaptive immunity of patients and animals with T1D, when compared with healthy controls. The non-obese diabetic (NOD) mouse and the BioBreeding diabetes prone (BBdp) rat are the most commonly used models to study T1D pathogenesis. With the increasing awareness of the importance of the GI ecosystem in systemic disease, it is critical to understand the basics, as well as the similarities and differences between rat and mouse models and human patients. This review examines the current knowledge of the role of the GI ecosystem in T1D and indicates the extensive opportunities for further investigation that could lead to biomarkers and therapeutic interventions for disease prevention and/or modulation.

Non-Celiac Gluten Sensitivity Has Narrowed the Spectrum of Irritable Bowel Syndrome: A Double-Blind Randomized Placebo-Controlled Trial

Several studies have shown that a large number of patients who are fulfilling the criteria for irritable bowel syndrome (IBS) are sensitive to gluten. The aim of this study was to evaluate the effect of a gluten-free diet on gastrointestinal symptoms in patients with IBS. In this double-blind randomized, placebo-controlled trial, 148 IBS patients fulfilling the Rome III criteria were enrolled between 2011 and 2013. However, only 72 out of the 148 commenced on a gluten-free diet for up to six weeks and completed the study; clinical symptoms were recorded biweekly using a standard visual analogue scale (VAS). In the second stage after six weeks, patients whose symptoms improved to an acceptable level were randomly divided into two groups; patients either received packages containing powdered gluten (35 cases) or patients received placebo (gluten free powder) (37 cases). Overall, the symptomatic improvement was statistically different in the gluten-containing group compared with placebo group in 9 (25.7%), and 31 (83.8%) patients respectively (p < 0.001). A large number of patients labelled as irritable bowel syndrome are sensitive to gluten. Using the term of IBS can therefore be misleading and may deviate and postpone the application of an effective and well-targeted treatment strategy in gluten sensitive patients.

Non-celiac gluten sensitivity: a work-in-progress entity in the spectrum of wheat-related disorders

Non-celiac gluten sensitivity is an undefined syndrome with gastrointestinal and extra-intestinal manifestations triggered by gluten in patients without celiac disease and wheat allergy. The pathogenesis involves immune-mediated mechanisms requiring further research. Symptoms disappear in a few hours or days after gluten withdrawal and recur rapidly after gluten ingestion. Besides gluten, other wheat proteins as well as fermentable oligo-, di-, mono-saccharides and polyols (FODMAPs) may contribute to this syndrome. This syndrome occurs mainly in young women, being rare in children. Its prevalence ranges from 0.6% to 6%, based on primary or tertiary care center estimates. No biomarker is available, but half of patients tests positive for IgG anti-gliadin antibodies, which disappear quickly after gluten-free diet together with symptoms. Also, genetic markers are still undefined. Although currently limited to a research setting, double-blind, placebo-controlled, cross-over trial strategy is recommended to confirm the diagnosis. Treatment is based on dietary restriction with special care to nutrient intake.

Faecalibacterium prausnitzii prevents physiological damages in a chronic low-grade inflammation murine model

BACKGROUND

The human gut houses one of the most complex and abundant ecosystems composed of up to 10(13)-10(14) microorganisms. The importance of this intestinal microbiota is highlighted when a disruption of the intestinal ecosystem equilibrium appears (a phenomenon called dysbiosis) leading to an illness status, such as inflammatory bowel diseases (IBD). Indeed, the reduction of the commensal bacterium Faecalibacterium prausnitzii (one of the most prevalent intestinal bacterial species in healthy adults) has been correlated with several diseases, including IBD, and most importantly, it has been shown that this bacterium has anti-inflammatory and protective effects in pre-clinical models of colitis. Some dysbiosis disorders are characterized by functional and physiological alterations. Here, we report the beneficial effects of F. prausnitzii in the physiological changes induced by a chronic low-grade inflammation in a murine model. Chronic low-grade inflammation and gut dysfunction were induced in mice by two episodes of dinitro-benzene sulfonic acid (DNBS) instillations. Markers of inflammation, gut permeability, colonic serotonin and cytokine levels were studied. The effects of F. prausnitzii strain A2-165 and its culture supernatant (SN) were then investigated.

RESULTS

No significant differences were observed in classical inflammation markers confirming that inflammation was subclinical. However, gut permeability, colonic serotonin levels and the colonic levels of the cytokines IL-6, INF-γ, IL-4 and IL-22 were higher in DNBS-treated than in untreated mice. Importantly, mice treated with either F. prausnitzii or its SN exhibited significant decreases in intestinal permeability, tissue cytokines and serotonin levels.

CONCLUSIONS

Our results show that F. prausnitzii and its SN had beneficial effects on intestinal epithelial barrier impairment in a chronic low-grade inflammation model. These observations confirm the potential of this bacterium as a novel probiotic treatment in the management of gut dysfunction and low-grade inflammation.

Lactobacillus rhamnosus CNCM I-3690 and the commensal bacterium Faecalibacterium prausnitzii A2-165 exhibit similar protective effects to induced barrier hyper-permeability in mice

Impaired gut barrier function has been reported in a wide range of diseases and syndromes and in some functional gastrointestinal disorders. In addition, there is increasing evidence that suggests the gut microbiota tightly regulates gut barrier function and recent studies demonstrate that probiotic bacteria can enhance barrier integrity. Here, we aimed to investigate the effects of Lactobacillus rhamnosus CNCM I-3690 on intestinal barrier function. In vitro results using a Caco-2 monolayer cells stimulated with TNF-α confirmed the anti-inflammatory nature of the strain CNCM I-3690 and pointed out a putative role for the protection of the epithelial function. Next, we tested the protective effects of L. rhamnosus CNCM I-3690 in a mouse model of increased colonic permeability. Most importantly, we compared its performance to that of the well-known beneficial human commensal bacterium Faecalibacterium prauznitzii A2-165. Increased colonic permeability was normalized by both strains to a similar degree. Modulation of apical tight junction proteins expression was then analyzed to decipher the mechanism underlying this effect. We showed that CNCM I-3690 partially restored the function of the intestinal barrier and increased the levels of tight junction proteins Occludin and E-cadherin. The results indicate L. rhamnosus CNCM I-3690 is as effective as the commensal anti-inflammatory bacterium F. prausnitzii to treat functional barrier abnormalities.

BL-7010 demonstrates specific binding to gliadin and reduces gluten-associated pathology in a chronic mouse model of gliadin sensitivity

Celiac disease (CD) is an autoimmune disorder in individuals that carry DQ2 or DQ8 MHC class II haplotypes, triggered by the ingestion of gluten. There is no current treatment other than a gluten-free diet (GFD). We have previously shown that the BL-7010 copolymer poly(hydroxyethyl methacrylate-co-styrene sulfonate) (P(HEMA-co-SS)) binds with higher efficiency to gliadin than to other proteins present in the small intestine, ameliorating gliadin-induced pathology in the HLA-HCD4/DQ8 model of gluten sensitivity. The aim of this study was to investigate the efficiency of two batches of BL-7010 to interact with gliadin, essential vitamins and digestive enzymes not previously tested, and to assess the ability of the copolymer to reduce gluten-associated pathology using the NOD-DQ8 mouse model, which exhibits more significant small intestinal damage when challenged with gluten than HCD4/DQ8 mice. In addition, the safety and systemic exposure of BL-7010 was evaluated in vivo (in rats) and in vitro (genetic toxicity studies). In vitro binding data showed that BL-7010 interacted with high affinity with gliadin and that BL-7010 had no interaction with the tested vitamins and digestive enzymes. BL-7010 was effective at preventing gluten-induced decreases in villus-to-crypt ratios, intraepithelial lymphocytosis and alterations in paracellular permeability and putative anion transporter-1 mRNA expression in the small intestine. In rats, BL-7010 was well-tolerated and safe following 14 days of daily repeated administration of 3000 mg/kg. BL-7010 did not exhibit any mutagenic effect in the genetic toxicity studies. Using complementary animal models and chronic gluten exposure the results demonstrate that administration of BL-7010 is effective and safe and that it is able to decrease pathology associated with gliadin sensitization warranting the progression to Phase I trials in humans.

The effect of Lactobacillus rhamnosus hsryfm 1301 on the intestinal microbiota of a hyperlipidemic rat model

BACKGROUND

Growing evidence indicates that intestinal microbiota regulate our metabolism. Probiotics confer health benefits that may depend on their ability to affect the gut microbiota. The objective of this study was to examine the effect of supplementation with the probiotic strain, Lactobacillus rhamnosus hsryfm 1301, on the gut microbiota in a hyperlipidemic rat model, and to explore the associations between the gut microbiota and the serum lipids.

METHODS

The hyperlipidemic rat model was established by feeding rats a high-fat diet for 28 d. The rats' gut microbiota were analyzed using high-throughput sequencing before and after L. rhamnosus hsryfm 1301 supplementation or its fermented milk for 28 d. The serum lipids level was also tested.

RESULTS

The rats' primary gut microbiota were composed of Bacteroidetes, Firmicutes, Proteobacteria, Spirochaetes and Verrucomicrobia. The abundance and diversity of the gut microbiota generally decreased after feeding with a high-fat diet, with a significant decrease in the relative abundance of Bacteroidetes, but with an increase in that of Firmicutes (P < 0.05). Administration of L. rhamnosus hsryfm 1301 or its fermented milk for 28 d, could recover the Bacteroidetes and Verrucomicrobia abundance and could decrease the Firmicutes abundance, which was associated with a significant reduction in the serum lipids' level in the hyperlipidemic rats with high-fat diet induced. The abundance of 22 genera of gut bacteria was changed significantly after probiotic intervention for 28 d (P < 0.05). A positive correlation was observed between Ruminococcus spp. and serum triglycerides, Dorea spp. and serum cholesterol (TC) and low-density lipoprotein (LDL-C), and Enterococcus spp. and high-density lipoprotein. The Butyrivibrio spp. negatively correlated with TC and LDL-C.

CONCLUSIONS

Our results suggest that the lipid metabolism of hyperlipidemic rats was improved by regulating the gut microbiota with supplementation of L.rhamnosus hsryfm 1301 or its fermented milk for 28 d.

Non-celiac gluten sensitivity: literature review

BACKGROUND

A significant percentage of the general population report problems caused by wheat and/or gluten ingestion, even though they do not have celiac disease (CD) or wheat allergy (WA), because they test negative both for CD-specific serology and histopathology and for immunoglobulin E (IgE)-mediated assays. Most patients report both gastrointestinal and nongastrointestinal symptoms, and all report improvement of symptoms on a gluten-free diet. This clinical condition has been named non-celiac gluten sensitivity (NCGS).

AIM

We attempt to define the current pathogenic, clinical, and diagnostic criteria of this "new" disease, to provide a practical view that might be useful to evaluate, diagnose, and manage NCGS patients.

METHODS

We reviewed the international literature through PubMed and Medline, using the search terms "wheat (hyper)sensitivity," "wheat allergy," "wheat intolerance," "gluten (hyper)sensitivity," and "gluten intolerance," and we discuss current knowledge about NCGS.

RESULTS

It has been demonstrated that patients suffering from NCGS are a heterogeneous group, composed of several subgroups, each characterized by different pathogenesis, clinical history, and, probably, clinical course. NCGS diagnosis can be reached only by excluding CD and WA. Recent evidence shows that a personal history of food allergy in infancy, coexistent atopy, positive for immunoglobulin G (IgG) antigliadin antibodies and flow cytometric basophil activation test, with wheat and duodenal and/or ileum-colon intraepithelial and lamina propria eosinophil counts, could be useful to identify NCGS patients.

CONCLUSIONS

Future research should aim to identify reliable biomarkers for NCGS diagnosis and to better define the different NCGS subgroups. Key teaching points: • Most patients report both gastrointestinal and nongastrointestinal symptoms, and all agree that there is an improvement of symptoms on a gluten-free diet. • NCGS diagnosis can be reached only by excluding celiac disease and wheat allergy. • Patients suffering from NCGS are a heterogeneous group, composed of several subgroups, each characterized by different pathogenesis, clinical history, and, probably, clinical course. • A personal history of food allergy in infancy, coexistent atopy, positive IgG antigliadin antibodies (AGA) and flow cytometric basophil activation test, with wheat and duodenal and/or ileum-colon intraepithelial and lamina propria eosinophil counts, could be useful to identify NCGS patients. • Future research should aim to identify reliable biomarkers for NCGS diagnosis and to better define the different NCGS subgroup.

Gliadin intake alters the small intestinal mucosa in indomethacin-treated HLA-DQ8 transgenic mice

Celiac disease (CD) is an enteropathy caused by the ingestion of wheat gluten in genetically susceptible individuals. A complete understanding of the pathogenic mechanisms in CD has been hindered because of the lack of adequate in vivo models. In the present study, we explored the events after the intragastric administration of gliadin and of the albumin/globulin fraction from wheat in human leukocyte antigen-DQ8 transgenic mice (DQ8 mice) treated with indomethacin, an inhibitor of cyclooxygenases (COXs). After 10 days of treatment, mice showed a significant reduction of villus height, increased crypt depth, increased number of lamina propria-activated macrophages, and high basal interferon-γ secretion in mesenteric lymph nodes, all of which were specifically related to gliadin intake, whereas the albumin/globulin fraction of wheat was unable to induce similar changes. Cotreatment with NS-398, a specific inhibitor of COX-2, also induced the intestinal lesion. Enteropathy onset was further characterized by high levels of oxidative stress markers, similar to CD. Biochemical assessment of the small intestine revealed the specific activation of matrix metalloproteinases 2 and 9, high caspase-3 activity, and a significant increase of tissue transglutaminase protein levels associated with the intestinal lesion. Notably, after 30 days of treatment, enteropathic mice developed serum antibodies toward gliadin (IgA) and tissue transglutaminase (IgG). We concluded that gliadin intake in combination with COX inhibition caused a basal inflammatory status and an oxidative stress condition in the small intestine of DQ8 mice, thus triggering the mucosal lesion and, subsequently, an antigen-specific immunity.

Intraluminal administration of poly I:C causes an enteropathy that is exacerbated by administration of oral dietary antigen

Systemic administration of polyinosinic:polycytidylic acid (poly I:C), mimics virally-induced activation of TLR3 signalling causing acute small intestine damage, but whether and how mucosal administration of poly I:C causes enteropathy is less clear. Our aim was to investigate the inflammatory pathways elicited after intraluminal administration of poly I:C and determine acute and delayed consequences of this locally induced immune activation. Intraluminal poly I:C induced rapid mucosal immune activation in C57BL/6 mice involving IFNβ and the CXCL10/CXCR3 axis, that may drive inflammation towards a Th1 profile. Intraluminal poly I:C also caused enteropathy and gut dysfunction in gliadin-sensitive NOD-DQ8 mice, and this was prolonged by concomitant oral administration of gliadin. Our results indicate that small intestine pathology can be induced in mice by intraluminal administration of poly I:C and that this is exacerbated by subsequent oral delivery of a relevant dietary antigen.

Novel role of the serine protease inhibitor elafin in gluten-related disorders

OBJECTIVES

Elafin, an endogenous serine protease inhibitor, modulates colonic inflammation. We investigated the role of elafin in celiac disease (CD) using human small intestinal tissues and in vitro assays of gliadin deamidation. We also investigated the potential beneficial effects of elafin in a mouse model of gluten sensitivity.

METHODS

Epithelial elafin expression in the small intestine of patients with active CD, treated CD, and controls without CD was determined by immunofluorescence. Interaction of elafin with human tissue transglutaminase-2 (TG-2) was investigated in vitro. The 33-mer peptide, a highly immunogenic gliadin peptide, was incubated with TG-2 and elafin at different concentrations. The degree of deamidation of the 33-mer peptide was analyzed by liquid chromatography-mass spectrometry. Elafin was delivered to the intestine of gluten-sensitive mice using a recombinant Lactococcus lactis vector. Small intestinal barrier function, inflammation, proteolytic activity, and zonula occludens-1 (ZO-1) expression were assessed.

RESULTS

Elafin expression in the small intestinal epithelium was lower in patients with active CD compared with control patients. In vitro, elafin significantly slowed the kinetics of the deamidation of the 33-mer peptide to its more immunogenic form. Treatment of gluten-sensitive mice with elafin delivered by the L. lactis vector normalized inflammation, improved permeability, and maintained ZO-1 expression.

CONCLUSIONS

The decreased elafin expression in the small intestine of patients with active CD, the reduction of 33-mer peptide deamidation by elafin, coupled to the barrier enhancing and anti-inflammatory effects observed in gluten-sensitive mice, suggest that this molecule may have pathophysiological and therapeutic importance in gluten-related disorders.

Pathogen-specific risk of celiac disease following bacterial causes of foodborne illness: a retrospective cohort study

BACKGROUND

The US CDC recently estimated over 2 million foodborne illnesses annually are caused by 4 major enteropathogens: non-typhoid Salmonella spp., Campylobacter spp., Shigella spp., and Yersinia enterocolitica. While recent data suggest functional gastrointestinal disorders are associated with these infections, studies linking foodborne illness to celiac disease (CD) are limited. We utilized a US Department of Defense medical encounter database to evaluate the risk of CD following select foodborne infections.

METHODS

We identified subjects with acute gastroenteritis between 1998 and 2009 attributed to Salmonella (nontyphoidal) spp., Shigella spp., Campylobacter spp., or Y. enterocolitica and matched each with up to 4 unexposed subjects. Exposed and unexposed subjects were followed for incident CD diagnosis for their entire military record duration (or a minimum of 1 year). Relative risks were calculated using modified Poisson regression to determine the relationship between pathogen-attributable gastroenteritis and CD while controlling for covariates.

RESULTS

A total of 1,753 pathogen-specific gastroenteritis cases (Campylobacter: 738; Salmonella: 624; Shigella: 376; Yersinia: 17) were identified and followed for a median of 3.8 years. The incidence (per 100,000 person-years) of CD was 0.05. We found a suggested risk of CD after Campylobacter, but not other foodborne infection etiologies.

CONCLUSIONS

These data support a previous study demonstrating increased risk of CD following Campylobacteriosis and highlight the need for additional research into how infections might trigger CD in susceptible individuals.

Intestinal permeability defects: is it time to treat?

An essential role of the intestinal epithelium is to separate luminal contents from the interstitium, a function primarily determined by the integrity of the epithelium and the tight junction that seals the paracellular space. Intestinal tight junctions are selectively permeable, and intestinal permeability can be increased physiologically in response to luminal nutrients or pathologically by mucosal immune cells and cytokines, the enteric nervous system, and pathogens. Compromised intestinal barrier function is associated with an array of clinical conditions, both intestinal and systemic. Although most available data are correlative, some studies support a model where cycles of increased intestinal permeability, intestinal immune activation, and subsequent immune-mediated barrier loss contribute to disease progression. This model is applicable to intestinal and systemic diseases. However, it has not been proven, and both mechanistic and therapeutic studies are ongoing. Nevertheless, the correlation between increased intestinal permeability and disease has caught the attention of the public, leading to a rise in popularity of the diagnosis of "leaky gut syndrome," which encompasses a range of systemic disorders. Proponents claim that barrier restoration will cure underlying disease, but this has not been demonstrated in clinical trials. Moreover, human and mouse studies show that intestinal barrier loss alone is insufficient to initiate disease. It is therefore uncertain whether increased permeability in these patients is a cause or effect of the underlying disorder. Although drug targets that may mediate barrier restoration have been proposed, none have been proven effective. As such, current treatments for barrier dysfunction should target the underlying disease.

Non-celiac gluten sensitivity: questions still to be answered despite increasing awareness

Recently, the increasing number of patients worldwide who are sensitive to dietary gluten without evidence of celiac disease or wheat allergy has contributed to the identification of a new gluten-related syndrome defined as non-celiac gluten sensitivity. Our knowledge regarding this syndrome is still lacking, and many aspects of this syndrome remain unknown. Its pathogenesis is heterogeneous, with a recognized pivotal role for innate immunity; many other factors also contribute, including low-grade intestinal inflammation, increased intestinal barrier function and changes in the intestinal microbiota. Gluten and other wheat proteins, such as amylase trypsin inhibitors, are the primary triggers of this syndrome, but it has also been hypothesized that a diet rich in fermentable monosaccharides and polyols may elicit its functional gastrointestinal symptoms. The epidemiology of this condition is far from established; its prevalence in the general population is highly variable, ranging from 0.63% to 6%. From a clinical point of view, non-celiac gluten sensitivity is characterized by a wide array of gastrointestinal and extraintestinal symptoms that occur shortly after the ingestion of gluten and improve or disappear when gluten is withdrawn from the diet. These symptoms recur when gluten is reintroduced. Because diagnostic biomarkers have not yet been identified, a double-blind placebo-controlled gluten challenge is currently the diagnostic method with the highest accuracy. Future research is needed to generate more knowledge regarding non-celiac gluten sensitivity, a condition that has global acceptance but has only a few certainties and many unresolved issues.

Semisynthetic diet ameliorates Crohn's disease-like ileitis in TNFΔARE/WT mice through antigen-independent mechanisms of gluten

BACKGROUND

Enteral nutrition is used to treat a subset of patients with inflammatory bowel diseases. Because dietary factors may contribute to an aggressive immune response toward the intestinal microbiota in the disease susceptible host, we used TNFΔARE/WT mice to study the therapeutic effect of a semisynthetic experimental diet in the pathogenesis of Crohn's disease (CD)-like inflammation in the ileum.

METHODS

TNFΔARE/WT mice were fed chow and experimental diets partially fortified with gluten in a dose and time-dependent manner. Histopathology, markers of inflammation, intraepithelial lymphocytes phenotypes, and antigen-specific reactivation of CD4⁺ T cells were determined.

RESULTS

TNFΔARE/WT mice being transferred to an experimental diet with 7 but not with 10 or 14 weeks of age were protected from development of Crohn's disease-like ileitis. Although disease-related CD8αβ⁺ intraepithelial lymphocytes were increased irrespective of dietary intervention, the protective effect of experimental diet was associated with decreased expression of inflammation markers in ileal tissues. In addition, CD4⁺ T-cell reactivation in bacterial antigen-primed dendritic cell cocultures was not altered between semisynthetic and chow diet-fed TNFΔARE/WT mice, suggesting bacteria-independent mechanisms. Most importantly, gluten-fortified experimental diet induced chronic ileitis in TNFΔARE/WT mice, despite the fact that gluten-derived peptides failed to induce CD4⁺ T-cell activation. Reduced occludin expression levels suggest a negative role of gluten-fortified experimental diet on intestinal barrier integrity.

CONCLUSIONS

Crohn's disease-like ileitis can be prevented at early stages of disease development using a semisynthetic experimental diet. Gluten was identified as antigen-independent dietary factor relevant for the induction of chronic inflammation in the small intestine of TNFΔARE/WT mice.

Latest in vitro and in vivo models of celiac disease

INTRODUCTION

Currently, the only treatment for celiac disease is a gluten-free diet, and there is an increased desire for alternative therapies. In vitro and in vivo models of celiac disease have been generated in order to better understand the pathogenesis of celiac disease, and this review will discuss these models as well as the testing of alternative therapies using these models.

AREAS COVERED

The research discussed describes the different in vitro and in vivo models of celiac disease that currently exist and how they have contributed to our understanding of how gluten can stimulate both innate and adaptive immune responses in celiac patients. We also provide a summary on the alternative therapies that have been tested with these models and discuss whether subsequent clinical trials were done based on these tests done with these models of celiac disease.

EXPERT OPINION

Only a few of the alternative therapies that have been tested with animal models have gone on to clinical trials; however, those that did go on to clinical trial have provided promising results from a safety standpoint. Further trials are required to determine if some of these therapies may serve as an effective adjunct to a gluten-free diet to alleviate the adverse affects associated with accidental gluten exposure. A "magic-bullet" approach may not be the answer to celiac disease, but possibly a future cocktail of these different therapeutics may allow celiac patients to consume an unrestricted diet.

Intestinal microbiota in functional bowel disorders: a Rome foundation report

It is increasingly perceived that gut host-microbial interactions are important elements in the pathogenesis of functional gastrointestinal disorders (FGID). The most convincing evidence to date is the finding that functional dyspepsia and irritable bowel syndrome (IBS) may develop in predisposed individuals following a bout of infectious gastroenteritis. There has been a great deal of interest in the potential clinical and therapeutic implications of small intestinal bacterial overgrowth in IBS. However, this theory has generated much debate because the evidence is largely based on breath tests which have not been validated. The introduction of culture-independent molecular techniques provides a major advancement in our understanding of the microbial community in FGID. Results from 16S rRNA-based microbiota profiling approaches demonstrate both quantitative and qualitative changes of mucosal and faecal gut microbiota, particularly in IBS. Investigators are also starting to measure host-microbial interactions in IBS. The current working hypothesis is that abnormal microbiota activate mucosal innate immune responses which increase epithelial permeability, activate nociceptive sensory pathways and dysregulate the enteric nervous system. While we await important insights in this field, the microbiota is already a therapeutic target. Existing controlled trials of dietary manipulation, prebiotics, probiotics, synbiotics and non-absorbable antibiotics are promising, although most are limited by suboptimal design and small sample size. In this article, the authors provide a critical review of current hypotheses regarding the pathogenetic involvement of microbiota in FGID and evaluate the results of microbiota-directed interventions. The authors also provide clinical guidance on modulation of gut microbiota in IBS.

Non-celiac wheat sensitivity diagnosed by double-blind placebo-controlled challenge: exploring a new clinical entity

OBJECTIVES

Non-celiac wheat sensitivity (WS) is considered a new clinical entity. An increasing percentage of the general population avoids gluten ingestion. However, the real existence of this condition is debated and specific markers are lacking. Our aim was thus to demonstrate the existence of WS and define its clinical, serologic, and histological markers.

METHODS

We reviewed the clinical charts of all subjects with an irritable bowel syndrome (IBS)-like presentation who had been diagnosed with WS using a double-blind placebo-controlled (DBPC) challenge in the years 2001-2011. One hundred celiac disease (CD) patients and fifty IBS patients served as controls.

RESULTS

Two hundred and seventy-six patients with WS, as diagnosed by DBPC challenge, were included. Two groups showing distinct clinical characteristics were identified: WS alone (group 1) and WS associated with multiple food hypersensitivity (group 2). As a whole group, the WS patients showed a higher frequency of anemia, weight loss, self-reported wheat intolerance, coexistent atopy, and food allergy in infancy than the IBS controls. There was also a higher frequency of positive serum assays for IgG/IgA anti-gliadin and cytometric basophil activation in "in vitro" assay. The main histology characteristic of WS patients was eosinophil infiltration of the duodenal and colon mucosa. Patients with WS alone were characterized by clinical features very similar to those found in CD patients. Patients with multiple food sensitivity were characterized by clinical features similar to those found in allergic patients.

CONCLUSIONS

Our data confirm the existence of non-celiac WS as a distinct clinical condition. We also suggest the existence of two distinct populations of subjects with WS: one with characteristics more similar to CD and the other with characteristics pointing to food allergy.

Modulation of intestinal barrier by intestinal microbiota: pathological and therapeutic implications

Mammals and their intestinal microbiota peacefully coexist in a mutualistic relationship. Commensal bacteria play an active role in shaping and modulating physiological processes in the host, which include, but are not restricted to, the immune system and the intestinal barrier. Both play a crucial role in containing intestinal bacteria and other potentially noxious luminal antigens within the lumen and mucosal compartment. Although mutualism defines the relationship between the host and the intestinal microbiota, disruptions in this equilibrium may promote disease. Thus, alterations in gut microbiota (dysbiosis) have been linked to the recent increased expression of obesity, allergy, autoimmunity, functional and inflammatory disorders such as irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). In this article, we review the evidence supporting a role of gut microbiota in regulating intestinal barrier function. We discuss the hypothesis that microbial factors can modulate the barrier in ways that can prevent or promote gastrointestinal disease. A better understanding of the role of the intestinal microbiota in maintaining a functional intestinal barrier may help develop targeted strategies to prevent and treat disease.

The incidence and risk of celiac disease in a healthy US adult population

OBJECTIVES

Celiac disease (CD) is an increasingly common disease that may affect as many as 1% of the North American population. Recent population-based data suggest a substantial increase in the prevalence of CD over the last several decades. Several factors are hypothesized as possible disease triggers including intercurrent illnesses, such as gastroenteritis, surgeries, and trauma. We used the active duty US military, a unique healthy worker population with essentially complete medical diagnostic coding, as an opportunity to describe trends in CD and deployment-related risk factors.

METHODS

Using electronic medical encounter data (1999-2008) on active duty US military (over 13.7 million person-years), a matched, nested case-control study describing the epidemiology and risk determinants of CD (based on ≥2 ICD-9 medical encounters) was conducted. Incidence and duration of CD-related medical care were estimated, and conditional logistic regression was utilized to evaluate CD risk following infectious gastroenteritis (IGE) occurring within 3 years before CD diagnosis while controlling for other risk factors.

RESULTS

A total of 455 incident cases of CD were identified and age, gender, and time matched to 1,820 controls. The incidence of CD increased five-fold from 1.3 per 100,000 in 1999 to 6.5 per 100,000 in 2008, with the highest rates of increase among those over 34 years of age (average annual increase of 0.8 cases per 100,000). A total of 172 IGE episodes, predominately of "viral etiology" (60.5%), were documented. In multivariate models, a significant association between IGE and CD was found (Odds ratio (OR): 2.06, 95% confidence interval (CI) 1.43, 2.97). Risk generally increased with temporal proximity to, and non-viral etiology of, exposure. Other notable risk factors for CD in multivariate models were Caucasian race (OR: 3.1, P<0.001), non-Army service (OR: 1.5, P=0.001), and greater than a high-school education (OR: 1.3, P=0.05).

CONCLUSIONS

Incidence of CD diagnosis in the US military is increasing, particularly among those in the fourth and fifth decades of life and appears higher than other population-based estimates. An association between antecedent IGE and risk of CD was noted, but the potential for exposure misclassification cannot be ruled out and further study is needed to link pathogen-specific exposure to incident CD anti-gluten antibody development or symptom onset.

Animal models to study gluten sensitivity

The initial development and maintenance of tolerance to dietary antigens is a complex process that, when prevented or interrupted, can lead to human disease. Understanding the mechanisms by which tolerance to specific dietary antigens is attained and maintained is crucial to our understanding of the pathogenesis of diseases related to intolerance of specific dietary antigens. Two diseases that are the result of intolerance to a dietary antigen are celiac disease (CD) and dermatitis herpetiformis (DH). Both of these diseases are dependent upon the ingestion of gluten (the protein fraction of wheat, rye, and barley) and manifest in the gastrointestinal tract and skin, respectively. These gluten-sensitive diseases are two examples of how devastating abnormal immune responses to a ubiquitous food can be. The well-recognized risk genotype for both is conferred by either of the HLA class II molecules DQ2 or DQ8. However, only a minority of individuals who carry these molecules will develop either disease. Also of interest is that the age at diagnosis can range from infancy to 70-80 years of age. This would indicate that intolerance to gluten may potentially be the result of two different phenomena. The first would be that, for various reasons, tolerance to gluten never developed in certain individuals, but that for other individuals, prior tolerance to gluten was lost at some point after childhood. Of recent interest is the concept of non-celiac gluten sensitivity, which manifests as chronic digestive or neurologic symptoms due to gluten, but through mechanisms that remain to be elucidated. This review will address how animal models of gluten-sensitive disorders have substantially contributed to a better understanding of how gluten intolerance can arise and cause disease.

Chronic gastrointestinal consequences of acute infectious diarrhea: evolving concepts in epidemiology and pathogenesis

Acute infectious diarrhea is a frequent occurrence both in the developing world, where it results in considerable mortality, and in developed countries, where it accounts for a significant number of health visits, hospitalizations, and medical and non-medical losses. Recent evidence in basic, clinical, and epidemiological science domains has emerged that suggest that the burden caused by these infections is not limited to the acute illness, but may result in triggering or contributing to the pathogenesis of a number of chronic health problems. This review considers the breadth of this information for the purpose of consolidating what is currently known, identifying gaps in knowledge, and describing future directions and policy implications related to the chronic consequences of acute infectious diarrhea. A unifying hypothesis of this review is that infections may trigger a number of long-lasting changes in gut physiology and immunity that can increase the risk to a variety of chronic gastrointestinal diseases, particularly in genetically susceptible individuals.

Larazotide acetate regulates epithelial tight junctions in vitro and in vivo

Tight junctions (TJs) control paracellular permeability and apical-basolateral polarity of epithelial cells, and can be regulated by exogenous and endogenous stimuli. Dysregulated permeability is associated with pathological conditions, such as celiac disease and inflammatory bowel disease. Herein we studied the mechanism by which larazotide acetate, an 8-mer peptide and TJ regulator, inhibits the cellular changes elicited by gliadin fragments, AT-1002, and cytokines. Previously, we demonstrated that AT-1002, a 6-mer peptide derived from the Vibrio cholerae zonula occludens toxin ZOT, caused several biochemical changes in IEC6 and Caco-2 cells resulting in decreased transepithelial electrical resistance (TEER) and increased TJ permeability. In this study, larazotide acetate inhibited the redistribution and rearrangement of zonula occludens-1 (ZO-1) and actin caused by AT-1002 and gliadin fragments in Caco-2 and IEC6 cells. Functionally, larazotide acetate inhibited the AT-1002-induced TEER reduction and TJ opening in Caco-2 cells. Additionally, larazotide acetate inhibited the translocation of a gliadin 13-mer peptide, which has been implicated in celiac disease, across Caco-2 cell monolayers. Further, apically applied larazotide acetate inhibited the increase in TJ permeability elicited by basolaterally applied cytokines. Finally, when tested in vivo in gliadin-sensitized HLA-HCD4/DQ8 double transgenic mice, larazotide acetate inhibited gliadin-induced macrophage accumulation in the intestine and preserved normal TJ structure. Taken together, our data suggest that larazotide acetate inhibits changes elicited by AT-1002, gliadin, and cytokines in epithelial cells and preserves TJ structure and function in vitro and in vivo.