Gliadin, zonulin and gut permeability: Effects on celiac and non-celiac intestinal mucosa and intestinal cell lines

Role of the gut microbiota in the pathogenesis of coeliac disease and potential therapeutic implications

PURPOSE

Although genetic predisposition and exposure to dietary gluten are considered necessary triggers for the development of coeliac disease, alterations in the gut microbial composition may also contribute towards the pathogenesis of coeliac disease. This review aims to provide an overview of the available data on the potential mechanisms through which the gut microbiota plays a role in the causation of coeliac disease and to discuss the potential therapeutic strategies that could diminish the consequences of microbial dysbiosis.

METHOD

A search of the literature was performed using the PubMed, Embase, and JSTOR databases; relevant articles were included.

RESULTS

Recent studies in patients with coeliac disease have reported an increase in the relative amounts of gram negative bacterial genera such as Bacteroides, Prevotella, and Escherichia, and reduced amounts of protective anti-inflammatory bacteria such as Bifidobacteria and Lactobacilli. Dysbiotic microbiota may lead to a dysregulated immune response that may contribute to the pathogenesis of coeliac disease. In infancy, antibiotic use and certain infant feeding practices may lead to alterations in the developing gut microbiota to influence the immune maturation process and predispose to coeliac disease.

CONCLUSION

The induction of the intestinal immune system and gluten intolerance may be influenced by the relative abundance of certain microbiota. Factors such as infant feeding practices, diet, antibiotics, and infections, may be involved in the development of coeliac disease due to their influence on gut microbial composition. The efficacy of potential modulators of the gut microbiota such as probiotics, prebiotics, and fecal microbial transplant as adjunctive treatments to gluten-free diet in coeliac disease is unproven and requires further investigation.

Inconsistent effects of gluten on obesity: is there a role for the haptoglobin isoforms?

BACKGROUND AND AIMS

There is no clear evidence about the effects of gluten intake on obesity. It is known that gluten's effects on gut permeability are mediated by zonulin, a protein identified as pre-haptoglobin 2, a physiological regulator of the intestinal barrier. We investigated the obesogenic and inflammatory effects of gluten and its association with the haptoglobin genotype.

METHODS

This was a single blinded, crossover study, including 40 overweight or obesity women free of celiac disease. Participants adopted a gluten-free diet (GFD) for 8 weeks and consumed a gluten-free muffin (GF-M) or a gluten-containing muffin (GLU-M, 24 g gluten) for 4 weeks, switching muffin type during the subsequent 4 weeks. During a follow-up period of 4 weeks we evaluated the usual diet (UD). Food diaries were collected to estimate the macronutrient intake and dietary inflammatory index (DII®). Bodyweight and composition, resting energy expenditure (REE), and cytokines were assessed. Haptoglobin alleles (Hp1 and Hp2) were genotyped to characterize zonulin expression.

RESULTS

Energy and macronutrient intakes were similar during both periods, except for protein intake, which was higher during GLU-M. DII scores indicated a more inflammatory profile during the GF-M and GLU-M periods compared to UD. No differences were observed in body composition or REE between interventions when the Hp genotype was not considered. Nonetheless, those carrying the Hp2-2 genotype (overexpressing zonulin) presented lower REE and higher levels of IL6 and IL1beta only during gluten intake (GLU-M and UD) compared to age- and body mass index-matched Hp1-1 carrier. These results suggest an obesogenic and inflammatory action of gluten only in those overexpressing zonulin (Hp2-2).

CONCLUSION

These results highlight the importance of zonulin as the mediator of gluten obesogenic and inflammatory effects. Our data suggest that in the presence of gluten, zonulin release is associated with a reduction of REE and an increase of inflammatory markers that are not seen in zonulin low producers.

Dietary Carbohydrates and Lipids in the Pathogenesis of Leaky Gut Syndrome: An Overview

This review summarizes the recent knowledge on the effects of dietary carbohydrates and lipids on the pathophysiology of leaky gut syndrome (LGS). Alterations in intestinal barrier permeability may lead to serious gastrointestinal (GI) disorders. LGS is caused by intestinal hyperpermeability due to changes in the expression levels and functioning of tight junctions. The influence of dietary habits on intestinal physiology is clearly visible in incidence rates of intestinal diseases in industrial and developing countries. Diseases which are linked to intestinal hyperpermeability tend to localize to Westernized countries, where a diet rich in fats and refined carbohydrates predominates. Several studies suggest that fructose is one of the key carbohydrates involved in the regulation of the intestinal permeability and its overuse may cause harmful effects, such as tight junction protein dysfunction. On the other hand, short chain fatty acids (mainly butyrate) at appropriate concentrations may lead to the reduction of intestinal permeability, which is beneficial in LGS. However, long chain fatty acids, including n-3 and n-6 polyunsaturated fatty acids have unclear properties. Some of those behave as components untightening and tightening the intestinal membrane.

Novel Therapeutic Strategies for Celiac Disease

Celiac disease (CeD) is a widespread autoimmune enteropathy caused by dietary gluten peptides in genetically susceptible individuals, which includes a range of intestinal and extraintestinal manifestations. Currently, there is no effective treatment for CeD other than strict adherence to a gluten-free diet (GFD). However, persistent or frequent symptoms and also partial villus atrophy were observed in some patients with CeD due to intentional or inadvertent gluten exposure during the use of GFD. It means that GFD alone is not enough to control CeD symptoms and long-term complications. Accordingly, new therapeutic approaches for CeD treatment such as gluten proteolysis, removing gluten from the digestive tract, promoting tight junction assembly, inhibiting intestinal tissue transglutaminase 2, using probiotics, and developing immunotherapeutic methods have been proposed through different strategies. This review focused on discussing the novel therapeutic strategies for CeD management.

Current Evidence on the Efficacy of Gluten-Free Diets in Multiple Sclerosis, Psoriasis, Type 1 Diabetes and Autoimmune Thyroid Diseases

In this review, we summarize the clinical data addressing a potential role for gluten in multiple sclerosis (MS), psoriasis, type 1 diabetes (T1D) and autoimmune thyroid diseases (ATDs). Furthermore, data on the prevalence of celiac disease (CD) and gluten-related antibodies in the above patient groups are presented. Adequately powered and properly controlled intervention trials investigating the effects of a gluten-free diet (GFD) in non-celiac patients with MS, psoriasis, T1D or ATDs are lacking. Only one clinical trial has studied the effects of a GFD among patients with MS. The trial found significant results, but it is subject to major methodological limitations. A few publications have found beneficial effects of a GFD in a subgroup of patients with psoriasis that were seropositive for anti-gliadin or deamidated gliadin antibodies, but no effects were seen among seronegative patients. Studies on the role of gluten in T1D are contradictive, however, it seems likely that a GFD may contribute to normalizing metabolic control without affecting levels of islet autoantibodies. Lastly, the effects of a GFD in non-celiac patients with ATDs have not been studied yet, but some publications report that thyroid-related antibodies respond to a GFD in patients with concomitant CD and ATDs. Overall, there is currently not enough evidence to recommend a GFD to non-celiac patients with MS, psoriasis, ATDs or T1D.

Zonulin as a potential putative biomarker of risk for shared type 1 diabetes and celiac disease autoimmunity

The incidence of type 1 diabetes (T1D) is increasing annually, in addition to other childhood-onset autoimmune diseases. This review is inspired by recent strides in research defining the pathophysiology of autoimmunity in celiac disease, a disease that has significant genetic overlap with T1D. Population genetic studies have demonstrated an increased proportion of newly diagnosed young children with T1D also have a higher genetic risk of celiac disease, suggesting that shared environmental risk factors are driving the incidence of both diseases. The small intestine barrier forms a tightly regulated interface of the immune system with the outside world and largely controls the mucosal immune response to non-self-antigens, dictating the balance between tolerance and immune response. Zonulin is the only known physiological modulator of the intercellular tight junctions, important in antigen trafficking, and therefore, is a key player in regulation of the mucosal immune response. While usually tightly controlled, when the zonulin pathway is dysregulated by changes in microbiome composition and function, antigen trafficking control is lost, leading to loss of mucosal tolerance in genetically susceptible individuals. The tenant of this hypothesis is that loss of tolerance would not occur if the zonulin-dependent intestinal barrier function is restored, thereby preventing the influence of environmental triggers in individuals genetically susceptible to autoimmunity. This review outlines the current research and a structured hypothesis on how a dysregulated small intestinal epithelial barrier, a "leaky gut," may be important in the pathogenesis of autoimmunity in certain individuals at risk of both T1D and celiac disease.

Effect of Gluten-Free Diet on Gut Microbiota Composition in Patients with Celiac Disease and Non-Celiac Gluten/Wheat Sensitivity

Celiac disease (CD) and non-celiac gluten/wheat sensitivity (NCG/WS) are the two most frequent conditions belonging to gluten-related disorders (GRDs). Both these diseases are triggered and worsened by gluten proteins ingestion, although other components, such as amylase/trypsin inhibitors (ATI) and fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs), seem to be involved in the NCG/WS onset. Therefore, the only effective treatment to date is the long-life adherence to a strictly gluten-free diet. Recently, increasing attention has been paid to the intestinal barrier, a dynamic system comprising various components, which regulate the delicate crosstalk between metabolic, motor, neuroendocrine and immunological functions. Among the elements characterizing the intestinal barrier, the microbiota plays a key role, modulating the gut integrity maintenance, the immune response and the inflammation process, linked to the CD and NCG/WS outbreak. This narrative review addresses the most recent findings on the gut microbiota modulation induced by the gluten-free diet (GFD) in healthy, CD and NCG/WS patients.

Intestinal Permeability in Children with Celiac Disease after the Administration of Oligofructose-Enriched Inulin into a Gluten-Free Diet-Results of a Randomized, Placebo-Controlled, Pilot Trial

Abnormalities in the intestinal barrier are a possible cause of celiac disease (CD) development. In animal studies, the positive effect of prebiotics on the improvement of gut barrier parameters has been observed, but the results of human studies to date remain inconsistent. Therefore, this study aimed to evaluate the effect of twelve-week supplementation of a gluten-free diet (GFD) with prebiotic oligofructose-enriched inulin (10 g per day) on the intestinal permeability in children with CD treated with a GFD. A pilot, randomized, placebo-controlled nutritional intervention was conducted in 34 children with CD, being on a strict GFD. Sugar absorption test (SAT) and the concentrations of intestinal permeability markers, such as zonulin, intestinal fatty acid-binding protein, claudin-3, calprotectin, and glucagon-like peptide-2, were measured. We found that the supplementation with prebiotic did not have a substantial effect on barrier integrity. Prebiotic intake increased excretion of mannitol, which may suggest an increase in the epithelial surface. Most children in our study seem to have normal values for intestinal permeability tests before the intervention. For individuals with elevated values, improvement in calprotectin and SAT was observed after the prebiotic intake. This preliminary study suggests that prebiotics may have an impact on the intestinal barrier, but it requires confirmation in studies with more subjects with ongoing leaky gut.

Review of Structural Features and Binding Capacity of Polyphenols to Gluten Proteins and Peptides In Vitro: Relevance to Celiac Disease

Polyphenols have been extensively studied due to their beneficial effects on human health, particularly for the prevention and treatment of diseases related to oxidative stress. Nevertheless, they are also known to have an anti-nutritional effect in relation to protein metabolism. This effect is a consequence of its binding to digestive enzymes and/or protein substrates. Dietary gluten is the main trigger of celiac disease, a common immune-based disease of the small intestine and for which the only treatment available is the adherence to a gluten-free diet. Recent studies have addressed the use of dietary polyphenols to interact with gluten proteins and avoid its downstream deleterious effects, taking the advantage of the anti-nutritive nature of polyphenols by protein sequestering. Flavonoids, coumarins and tannins have shown the ability to form insoluble complexes with gluten proteins. One of the most promising molecules has been epigallocatechin-3-gallate, which through its binding to gliadins, was able to reduce gliadins digestibility and its ability to stimulate monolayer permeability and transepithelial transport of immunodominant peptides in cell models. This review focuses on the structural features and binding capacity of polyphenols to gluten proteins and peptides, and the prospects of developing an adjuvant therapy in celiac disease.

Nutrition, IBD and Gut Microbiota: A Review

Inflammatory bowel disease (IBD) is a chronic relapsing–remitting systemic disease of the gastrointestinal tract, characterized by an inflammatory process that requires lifelong treatment. The underlying causes of IBD are still unclear, as this heterogeneous disorder results from a complex interplay between genetic variability, the host immune system and environmental factors. The current knowledge recognizes diet as a risk factor for the development of IBD and attributes a substantial pathogenic role to the intestinal dysbiosis inducing an aberrant mucosal immune response in genetically predisposed individuals. This review focused on the clinical evidence available that considers the impact of some nutrients on IBD onset and the role of different diets in the management of IBD and their effects on the gut microbiota composition. The effects of the Specific Carbohydrate Diet, low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet, gluten free diet, anti-inflammatory diet and Mediterranean diet are investigated with regard to their impact on microbiota and on the evolution of the disease. At present, no clear indications toward a specific diet are available but the assessment of dysbiosis prior to the recommendation of a specific diet should become a standard clinical approach in order to achieve a personalized therapy.

Exit Gluten-Free and Enter Low FODMAPs: A Novel Dietary Strategy to Reduce Gastrointestinal Symptoms in Athletes

Exercise-associated physiological disturbances alter gastrointestinal function and integrity. These alterations may increase susceptibility to dietary triggers, namely gluten and a family of short-chain carbohydrates known as FODMAPs (fermentable oligo-, di-, monosaccharides and polyols). A recent surge in the popularity of gluten-free diets (GFDs) among athletes without celiac disease has been exacerbated by unsubstantiated commercial health claims and high-profile athletes citing this diet to be the secret to their success. Up to 41% of athletes at least partially adhere to a GFD diet, with the belief that gluten avoidance improves exercise performance and parameters influencing performance, particularly gastrointestinal symptoms (GIS). In contrast to these beliefs, seminal work investigating the effects of a GFD in athletes without celiac disease has demonstrated no beneficial effect of a GFD versus a gluten-containing diet on performance, gastrointestinal health, inflammation, or perceptual wellbeing. Interestingly, the subsequent reduction in FODMAPs concurrent with the elimination of gluten-containing grains may actually be the factors affecting GIS improvement, not gluten. Pre-existent in the gastrointestinal tract or ingested during exercise, the osmotic and gas-producing effects of variably absorbed FODMAPs may trigger or increase the magnitude of exercise-associated GIS. Research using FODMAP reduction to address gastrointestinal issues in clinically healthy athletes is emerging as a promising strategy to reduce exercise-associated GIS. Applied research and practitioners merging clinical and sports nutrition methods will be essential for the effective use of a low FODMAP approach to tackle the multifactorial nature of gastrointestinal disturbances in athletes.

Analysis of Faecal Zonulin and Calprotectin Concentrations in Healthy Children During the First Two Years of Life. An Observational Prospective Cohort Study

Factors affecting the intestinal-barrier permeability of newborns, such as body mass index (BMI), nutrition and antibiotics, are assumed to affect intestinal-barrier permeability in the first two years of life. This study assessed 100 healthy, full-term newborns to 24 months old. Faecal zonulin/calprotectin concentrations were measured at 1, 6, 12, 24 months as gut-permeability markers. Zonulin concentrations increased between 1 and 12 months (medians: 114.41, 223.7 ng/mL; respectively), whereas calprotectin concentrations decreased between one and six months (medians: 149. 29, 109.28 µg/mL); both then stabilized (24 months: 256.9 ng/mL zonulin; 59.5 µg/mL calprotectin). In individual children, high levels at one month gave high levels at older ages (correlations: calprotectin: between 1 and 6 or 12 months: correlation coefficient (R) = 0.33, statistical significance (p) = 0.0095; R = 0.28, p = 0.032; zonulin: between 1 and 24 months: R = 0.32; p = 0.022, respectively). Parameters which gave marker increases: antibiotics during pregnancy (calprotectin; six months: by 80%, p = 0.038; 12 months: by 48%, p = 0.028); vaginal birth (calprotectin: 6 months: by 140%, p = 0.005); and > 5.7 pregnancy-BMI increase (zonulin: 12 months: by 74%, p = 0.049). Conclusions: “Closure of the intestines” is spread over time and begins between the sixth and twelfth month of life. Antibiotic therapy, BMI increase > 5.7 during pregnancy and vaginal birth are associated with increased intestinal permeability during the first two years of life. Stool zonulin and calprotectin concentrations were much higher compared with previous measurements at older ages; clinical interpretation and validation are needed (no health associations found).

Lactobacillus Rhamnosus GG Affects the BDNF System in Brain Samples of Wistar Rats with Pepsin-Trypsin-Digested Gliadin (PTG)-Induced Enteropathy

Celiac disease (CD) presents as chronic low-grade inflammation of the small intestine often characterized by psychiatric comorbidities. The brain-derived neurotrophic factor (BDNF), which we have shown to be reduced in the serum of CD patients, acts as the bridge between immune activation and the nervous system adaptive response. Since Lactobacillus has been shown to upregulate BDNF, this study aimed to evaluate whether the administration of Lactobacillus rhamnosus GG (L.GG) could positively affect the brain BDNF system in rats mimicking the CD lesions. Data have shown that the administration of pepsin-trypsin digested gliadin (PTG) and L.GG alter the levels of mature BDNF (mBDNF), as evaluated by Western blotting. PTG provoked a reduction of mBDNF compared to controls, and a compensatory increase of its receptor TrkB. L.GG induced a slight positive effect on mBDNF levels under normal conditions, while it was able to rescue the PTG-induced reduced expression of mBDNF. The curative effect of L.GG was finely tuned, accompanied by the reduction of TrkB, probably to avoid the effect of excessive BDNF.

Pathogenesis of Celiac Disease and Other Gluten Related Disorders in Wheat and Strategies for Mitigating Them

Wheat is a major cereal crop providing energy and nutrients to the billions of people around the world. Gluten is a structural protein in wheat, that is necessary for its dough making properties, but it is responsible for imparting certain intolerances among some individuals, which are part of this review. Most important among these intolerances is celiac disease, that is gluten triggered T-cell mediated autoimmune enteropathy and results in villous atrophy, inflammation and damage to intestinal lining in genetically liable individuals containing human leukocyte antigen DQ2/DQ8 molecules on antigen presenting cells. Celiac disease occurs due to presence of celiac disease eliciting epitopes in gluten, particularly highly immunogenic alpha-gliadins. Another gluten related disorder is non-celiac gluten-sensitivity in which innate immune-response occurs in patients along with gastrointestinal and non-gastrointestinal symptoms, that disappear upon removal of gluten from the diet. In wheat allergy, either IgE or non-IgE mediated immune response occurs in individuals after inhalation or ingestion of wheat. Following a life-long gluten-free diet by celiac disease and non-celiac gluten-sensitivity patients is very challenging as none of wheat cultivar or related species stands safe for consumption. Hence, different molecular biology, genetic engineering, breeding, microbial, enzymatic, and chemical strategies have been worked upon to reduce the celiac disease epitopes and the gluten content in wheat. Currently, only 8.4% of total population is affected by wheat-related issues, while rest of population remains safe and should not remove wheat from the diet, based on false media coverage.

Therapeutic options for coeliac disease: What else beyond gluten-free diet?

Coeliac disease is a chronic and systemic autoimmune condition triggered by gluten ingestion in genetically predisposed subjects. Currently, the only effective treatment available is a strict, lifelong gluten-free diet. However, patients perceive gluten withdrawal as an unsustainable burden in their life and some of them can exhibit persistent symptoms despite a strict diet. Thus, gluten-free diet represents a challenge, leading scientists to look for alternative or complementary treatments. This review will focus on non-dietary therapies for coeliac disease highlighting six therapeutic strategies: (1) decreasing gluten immunogenic content before it reaches the intestine; (2) sequestering gluten in the gut lumen before absorption; (3) blocking the passage of gluten through a leaky intestinal barrier; (4) preventing the enhancement of immune response against gliadin; (5) dampening the downstream immune activation; (6) inducing immune tolerance to gluten. Most developing therapies are only in the pre-clinical phase with only a few being tested in phase 2b or 3 trials. Although new approaches raise the hope for coeliacs giving them a chance to come back to gluten, for the time being a cautionary appraisal of new therapies suggests that they may have a complementary role to gluten withdrawal, mainly to prevent inadvertent gluten contamination.

All disease begins in the (leaky) gut: role of zonulin-mediated gut permeability in the pathogenesis of some chronic inflammatory diseases

Improved hygiene leading to reduced exposure to microorganisms has been implicated as one possible cause for the recent "epidemic" of chronic inflammatory diseases (CIDs) in industrialized countries. That is the essence of the hygiene hypothesis that argues that rising incidence of CIDs may be, at least in part, the result of lifestyle and environmental changes that have made us too "clean" for our own good, so causing changes in our microbiota. Apart from genetic makeup and exposure to environmental triggers, inappropriate increase in intestinal permeability (which may be influenced by the composition of the gut microbiota), a "hyper-belligerent" immune system responsible for the tolerance-immune response balance, and the composition of gut microbiome and its epigenetic influence on the host genomic expression have been identified as three additional elements in causing CIDs. During the past decade, a growing number of publications have focused on human genetics, the gut microbiome, and proteomics, suggesting that loss of mucosal barrier function, particularly in the gastrointestinal tract, may substantially affect antigen trafficking, ultimately influencing the close bidirectional interaction between gut microbiome and our immune system. This cross-talk is highly influential in shaping the host gut immune system function and ultimately shifting genetic predisposition to clinical outcome. This observation led to a re-visitation of the possible causes of CIDs epidemics, suggesting a key pathogenic role of gut permeability. Pre-clinical and clinical studies have shown that the zonulin family, a group of proteins modulating gut permeability, is implicated in a variety of CIDs, including autoimmune, infective, metabolic, and tumoral diseases. These data offer novel therapeutic targets for a variety of CIDs in which the zonulin pathway is implicated in their pathogenesis.

Wheat gluten intake increases the severity of experimental colitis and bacterial translocation by weakening of the proteins of the junctional complex

Gluten is only partially digested by intestinal enzymes and can generate peptides that can alter intestinal permeability, facilitating bacterial translocation, thus affecting the immune system. Few studies addressed the role of diet with gluten in the development of colitis. Therefore, we investigate the effects of wheat gluten-containing diet on the evolution of sodium dextran sulphate (DSS)-induced colitis. Mice were fed a standard diet without (colitis group) or with 4·5 % wheat gluten (colitis + gluten) for 15 d and received DSS solution (1·5 %, w/v) instead of water during the last 7 d. Compared with the colitis group, colitis + gluten mice presented a worse clinical score, a larger extension of colonic injury area, and increased mucosal inflammation. Both intestinal permeability and bacterial translocation were increased, propitiating bacteria migration for peripheral organs. The mechanism by which diet with gluten exacerbates colitis appears to be related to changes in protein production and organisation in adhesion junctions and desmosomes. The protein α-E-catenin was especially reduced in mice fed gluten, which compromised the localisation of E-cadherin and β-catenin proteins, weakening the structure of desmosomes. The epithelial damage caused by gluten included shortening of microvilli, a high number of digestive vacuoles, and changes in the endosome/lysosome system. In conclusion, our results show that wheat gluten-containing diet exacerbates the mucosal damage caused by colitis, reducing intestinal barrier function and increasing bacterial translocation. These effects are related to the induction of weakness and disorganisation of adhesion junctions and desmosomes as well as shortening of microvilli and modification of the endocytic vesicle route.

Prevalance of Celiac Disease in Patients with Inflammatory Bowel Disease in Turkish Population

Background

Celiac disease (CD) and inflammatory bowel disease (IBD) involve inflammation of the gastrointestinal lumen, which environmental, genetic, and immunological factors have a role in their pathogenesis. The prevalence of celiac disease in IBD ranges from 0% to 14%. In this study, our aim was to determine the prevalence of CD in IBD patients followed by us who are attending the hospital or outpatient clinic over a period of time of seven years.

Methods

Seven hundred and fifty nine patients (425 M, 334 F, mean age: 46.75, 396 ulcerative colitis (UC), 363 Crohn's disease (CrD)) diagnosed and followed up for IBD between January 2009 and July 2016 were evaluated retrospectively, and clinical, demographic, laboratory, and endoscopic data were collected.

Results

CD was investigated in 79 (%10.4) inflammatory bowel disease patients according to symptoms, and in 5.06% (n = 4) of them, we diagnosed CD. The most common indication for investigating for CD was iron deficiency anemia unreponsive to iron supplementation.

Conclusions

We did not find an increased prevalance of celiac disease in Turkish IBD patients in this study. In the presence of refractory iron deficiency anemia without any other cause in IBD patients, investigations for celiac disease should be considered.

Popular Diet Trends for Inflammatory Bowel Diseases: Claims and Evidence

PURPOSE OF REVIEW

Patients with inflammatory bowel disease (IBD) frequently look to diet to improve symptoms. Although regularly asked for dietary guidance, gastroenterologists are often unprepared to provide evidence-based recommendations. This review will summarize popular diets claiming benefits in IBD, as well as current data evaluating their efficacies.

RECENT FINDINGS

The Specific Carbohydrate Diet has demonstrated symptom improvement and even mucosal healing; however, large trials and prospective data are lacking. The low FODMAP diet has shown benefit for functional symptoms in IBD, yet efficacy regarding inflammation is lacking. Large studies for the gluten-free diet yielded mixed results in IBD outcomes, while suggesting a negative impact on psychological well-being. Data on an "anti-inflammatory" diet were positive but remain severely limited. A currently planned large trial for the Mediterranean diet in IBD may provide much needed clinical data. We provide an overview of frequently utilized diets in IBD. The body of evidence does not currently support clear dietary recommendations in IBD, as larger, prospective studies are needed.

Intestinal Epithelium Modulates Macrophage Response to Gliadin in Celiac Disease

Celiac disease is an immune-mediated enteropathy triggered by ingestion of gluten. Although its pathogenesis has been extensively studied and the contribution from both innate and adaptive immune responses has been reported, little is still known about the contribution of macrophages to the onset or maintenance of the disease. Macrophages are extremely plastic immune cells that can be directed toward a pro- or anti-inflammatory phenotype by the surrounding microenvironment. Of note, gliadin, the most prominent causative agent of the disease, has been reported to trigger the production of pro-inflammatory cytokines in this cell population. In the present study, we aimed at investigating how the intestinal milieu and more specifically the epithelium can shape the macrophage response to gliadin. Using patient-derived organoids we showed that the intestinal epithelium derived from celiac disease donors releases anti-inflammatory factors that curb the macrophage response to gliadin. Furthermore, we uncovered that the celiac macrophages were better responders than macrophages derived from non-celiac controls. Finally, we demonstrated that IFNγ released by the epithelium is in part responsible of the observed anti-inflammatory effect. Our data shed light on the cross–talk between the immune system and the epithelium and its critical role in the intestinal homeostasis. Furthermore, we provide more evidence how alterations in the innate immune machinery in celiac patients may contribute to the onset of the disease.

Recurrent Fever and Failure to Thrive in an 11-Year-Old Boy

Recurrent fever is frequent among children and mostly associated with viral infections inoculated via social contacts with others of the same age. Rarely, severe conditions such as hematological malignancies, pediatric rheumatoid diseases, chronic infections, or inherited recurrent fever syndromes are causative. Herein, we present the case of an 11-year-old boy with frequently recurring high-fever episodes since early childhood, failure to thrive, and iron deficiency who was found to have classical celiac disease (CD) with highly elevated tissue transglutaminase and anti-gliadin antibodies and marked duodenal villous atrophy. Upon implementation of a gluten-free diet, the boy ceased to have fevers, antibodies decreased markedly, his iron status improved, and he significantly gained weight. Although infrequent, recurrent fever should be included into the polymorphic clinical picture of CD, and the threshold of testing for diagnostic antibodies should be low in such patients.

Lack of Efficacy of the Neutropenic Diet in Decreasing Infections among Cancer Patients: A Systematic Review

The objective of this systematic review is to evaluate the existing evidence supporting the effectiveness of the neutropenic diet in decreasing infection and mortality among cancer patients. We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials and Scopus for relevant articles published from database inception until March 2019. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were followed for this review. Individual studies were evaluated using the Oxford Center for Evidence-Based Medicine guidelines. A total of 473 articles were identified and 11 articles were selected after assessing eligibility. Our review showed that the neutropenic diet does not decrease infection rates or mortality among cancer patients. Currently, there is no uniform definition for the neutropenic diet across different institutions. For example, some institutions follow general food safety practices while others avoid foods that increase exposure to microbes and bacteria, and some follow both. Given these differences in practice regarding what constitutes a neutropenic diet, it is advisable that safe food handling and preparation practices recommended by the Food and Drug Administration be uniformly followed for neutropenic patients.

Intestinal Barrier Function in Gluten-Related Disorders

Gluten-related disorders include distinct disease entities, namely celiac disease, wheat-associated allergy and non-celiac gluten/wheat sensitivity. Despite having in common the contact of the gastrointestinal mucosa with components of wheat and other cereals as a causative factor, these clinical entities have distinct pathophysiological pathways. In celiac disease, a T-cell mediate immune reaction triggered by gluten ingestion is central in the pathogenesis of the enteropathy, while wheat allergy develops as a rapid immunoglobulin E- or non-immunoglobulin E-mediated immune response. In non-celiac wheat sensitivity, classical adaptive immune responses are not involved. Instead, recent research has revealed that an innate immune response to a yet-to-be-defined antigen, as well as the gut microbiota, are pivotal in the development in this disorder. Although impairment of the epithelial barrier has been described in all three clinical conditions, its role as a potential pathogenetic co-factor, specifically in celiac disease and non-celiac wheat sensitivity, is still a matter of investigation. This article gives a short overview of the mucosal barrier of the small intestine, summarizes the aspects of barrier dysfunction observed in all three gluten-related disorders and reviews literature data in favor of a primary involvement of the epithelial barrier in the development of celiac disease and non-celiac wheat sensitivity.

Celiac disease: a comprehensive current review

BACKGROUND

Celiac disease remains a challenging condition because of a steady increase in knowledge tackling its pathophysiology, diagnosis, management, and possible therapeutic options.

MAIN BODY

A major milestone in the history of celiac disease was the identification of tissue transglutaminase as the autoantigen, thereby confirming the autoimmune nature of this disorder. A genetic background (HLA-DQ2/DQ8 positivity and non-HLA genes) is a mandatory determinant of the development of the disease, which occurs with the contribution of environmental factors (e.g., viral infections and dysbiosis of gut microbiota). Its prevalence in the general population is of approximately 1%, with female predominance. The disease can occur at any age, with a variety of symptoms/manifestations. This multifaceted clinical presentation leads to several phenotypes, i.e., gastrointestinal, extraintestinal, subclinical, potential, seronegative, non-responsive, and refractory. Although small intestinal biopsy remains the diagnostic 'gold standard', highly sensitive and specific serological tests, such as tissue transglutaminase, endomysial and deamidated gliadin peptide antibodies, have become gradually more important in the diagnostic work-up of celiac disease. Currently, the only treatment for celiac disease is a life-long, strict gluten-free diet leading to improvement in quality of life, ameliorating symptoms, and preventing the occurrence of refractory celiac disease, ulcerative jejunoileitis, and small intestinal adenocarcinoma and lymphoma.

CONCLUSIONS

The present review is timely and provides a thorough appraisal of various aspects characterizing celiac disease. Remaining challenges include obtaining a better understanding of still-unclear phenotypes such as slow-responsive, potential (minimal lesions) and seronegative celiac disease. The identification of alternative or complementary treatments to the gluten-free diet brings hope for patients unavoidably burdened by diet restrictions.

Breaking Down Barriers: How Understanding Celiac Disease Pathogenesis Informed the Development of Novel Treatments

For decades, the pathogenesis of a variety of human diseases has been attributed to increased intestinal paracellular permeability even though scientific evidence supporting this hypothesis has been tenuous. Nevertheless, during the past decade, there have been a growing number of publications focused on human genetics, the gut microbiome, and proteomics, suggesting that loss of mucosal barrier function, particularly in the gastrointestinal tract, may substantially affect antigen trafficking, ultimately causing chronic inflammation, including autoimmunity, in genetically predisposed individuals. The gut mucosa works as a semipermeable barrier in that it permits nutrient absorption and also regulates immune surveillance while retaining potentially harmful microbes and environmental antigens within the intestinal lumen. Celiac disease (CD), a systemic, immune-mediated disorder triggered by gluten in genetically susceptible individuals, is associated with altered gut permeability. Pre-clinical and clinical studies have shown that gliadin, a prolamine component of gluten that is implicated in CD pathogenesis, is capable to disassembling intercellular junctional proteins by upregulating the zonulin pathway, which can be inhibited by the zonulin antagonist larazotide acetate. In this review, we will focus on CD as a paradigm of chronic inflammatory diseases in order to outline the contribution of gut paracellular permeability toward disease pathogenesis; moreover, we will summarize current evidence derived from available clinical trials of larazotide acetate in CD.

Human gut derived-organoids provide model to study gluten response and effects of microbiota-derived molecules in celiac disease

Celiac disease (CD) is an immune-mediated disorder triggered by gluten exposure. The contribution of the adaptive immune response to CD pathogenesis has been extensively studied, but the absence of valid experimental models has hampered our understanding of the early steps leading to loss of gluten tolerance. Using intestinal organoids developed from duodenal biopsies from both non-celiac (NC) and celiac (CD) patients, we explored the contribution of gut epithelium to CD pathogenesis and the role of microbiota-derived molecules in modulating the epithelium’s response to gluten. When compared to NC, RNA sequencing of CD organoids revealed significantly altered expression of genes associated with gut barrier, innate immune response, and stem cell functions. Monolayers derived from CD organoids exposed to gliadin showed increased intestinal permeability and enhanced secretion of pro-inflammatory cytokines compared to NC controls. Microbiota-derived bioproducts butyrate, lactate, and polysaccharide A improved barrier function and reduced gliadin-induced cytokine secretion. We concluded that: (1) patient-derived organoids faithfully express established and newly identified molecular signatures characteristic of CD. (2) microbiota-derived bioproducts can be used to modulate the epithelial response to gluten. Finally, we validated the use of patient-derived organoids monolayers as a novel tool for the study of CD.

Treatment Interventions for the Management of Intestinal Permeability: A Cross-Sectional Survey of Complementary and Integrative Medicine Practitioners

Objectives: This study aims to explore the treatment interventions complementary and integrative medicine (CIM) practitioners use in the management of an emerging health condition, increased intestinal permeability (IP), and the association these methods have on the observed time to resolve this condition. Design and setting: A cross-sectional survey of Australian naturopaths, nutritionists, and Western herbal medicine practitioners was undertaken (n = 227) through the Practitioner Research and Collaboration Initiative (PRACI) network. Outcome measures: Frequencies and percentages of the treatment methods, including chi-square analysis to examine the associations between treatment methods and observed time to resolve IP. Results: Thirty-six CIM practitioners responded to the survey (response rate 15.9%). CIM practitioners were found to use a multimodal approach in the management of IP with 92.6% of respondents using three or more categories of treatment interventions (nutritional, herbal, dietary, and lifestyle) with a mean total of 43.0 ± 24.89 single treatment interventions frequently prescribed. The main treatments prescribed in the management of IP were zinc (85.2%), probiotics: multistrain (77.8%), vitamin D (75.0%), glutamine (73.1%), Curcuma longa (73.1%), and Saccharomyces boulardii (70.4%). CIM practitioners also advocate patients with IP to reduce alcohol (96.3%), gluten (85.2%), and dairy (75.0%) consumption. Evaluation of antibiotics (75.0%) and nonsteroidal anti-inflammatory drugs (73.1%) prescriptions were frequently advised by CIM practitioners. A longer observed time to resolve IP was seen in CIM practitioners who did not reduce intense exercise in the management of IP (p = 0.02). Conclusions: This study represents the first survey of the treatments prescribed by CIM practitioners for IP and suggests that CIM practitioners use numerous integrative treatment methods for the management of IP. The treatment interventions frequently prescribed by CIM practitioners align with preclinical research, suggesting that CIM practitioners prescribe in accordance with the published literature. The findings of this study contribute to the implementation of clinical research in the management of IP, which considers multiple concurrent treatments.

An In Vitro Study on Mitochondrial Compensatory Response Induced by Gliadin Peptides in Caco-2 Cells

Dietary gliadin may show a broad spectrum of toxicity. The interplay between mitochondria and gliadin-induced oxidative stress has not been thoroughly examined in the intestinal epithelium. In this kinetic study, Caco-2 cells were exposed for 24 h to pepsin-trypsin-digested gliadin, alone or in combination with the antioxidant 2,6-di-tbutyl-p-cresol (BHT), and the effects on mitochondrial biogenesis and mtDNA were studied. Cells ability to recover from stress was determined after 24 h and 48 h of incubation in the culture medium. Gliadin-induced oxidative stress evoked a compensatory response. The stressor triggered a rapid and significant increase of Peroxisome proliferator-activated receptor γ coactivator-1alpha (PGC-1α) and Peroxiredoxin III (PrxIII) proteins, and mtDNA amount. As for the effects of gliadin on mtDNA integrity, strand breaks, abasic sites, and modified bases were analyzed in three mtDNA regions. D-loop appeared a more fragile target than Ori-L and ND1/ND2. The temporal trend of the damage at D-loop paralleled that of the amount of mtDNA. Overall, a trend toward control values was shown 48 h after gliadin exposure. Finally, BHT was able to counteract the effects of gliadin. Results from this study highlighted the effects of gliadin-induced oxidative stress on mitochondria, providing valuable evidence that might improve the knowledge of the pathophysiology of gluten-related disorders.

Trehalose Modulates Autophagy Process to Counteract Gliadin Cytotoxicity in an In Vitro Celiac Disease Model

Celiac disease (CD) is a chronic systemic autoimmune disorder that is triggered by the ingestion of gliadin peptides, the alcohol-soluble fraction of wheat gluten. These peptides, which play a key role in the immune response that underlies CD, spontaneously form aggregates and exert a direct toxic action on cells due to the increase in the reactive oxygen species (ROS) levels. Furthermore, peptic-tryptic digested gliadin peptides (PT-gliadin) lead to an impairment in the autophagy pathway in an in vitro model based on Caco-2 cells. Considering these premises, in this study we have analyzed different mTOR-independent inducers, reporting that the disaccharide trehalose, a mTOR-independent autophagy activator, rescued the autophagy flux in Caco-2 cells treated with digested gliadin, as well as improved cell viability. Moreover, trehalose administration to Caco-2 cells in presence of digested gliadin reduced the intracellular levels of these toxic peptides. Altogether, these results showed the beneficial effects of trehalose in a CD in vitro model as well as underlining autophagy as a molecular pathway whose modulation might be promising in counteracting PT-gliadin cytotoxicity.

The Influence of Maternal-Foetal Parameters on Concentrations of Zonulin and Calprotectin in the Blood and Stool of Healthy Newborns during the First Seven Days of Life. An Observational Prospective Cohort Study

Background: It can be hypothetically assumed that maternal and perinatal factors influence the intestinal barrier. Methods: The study was conducted with 100 healthy, full-term newborns breastfed in the first week of life, with similar analyses for their mothers. Zonulin and calprotectin levels were used as intestinal permeability markers. Results: The median (range) zonulin concentrations (ng/mL) were in mothers: serum, 21.39 (6.39–57.54); stool, 82.23 (42.52–225.74); and newborns: serum cord blood, 11.14 (5.82–52.34); meconium, 54.15 (1.36–700.65); and stool at age seven days, 114.41 (29.38–593.72). Calprotectin median (range) concentrations (µg/mL) in mothers were: stool, 74.79 (3.89–211.77); and newborns: meconium, 154.76 (6.93–8884.11); and stool at age seven days 139.12 (11.89–627.35). The use of antibiotics during pregnancy resulted in higher zonulin concentrations in umbilical-cord serum and calprotectin concentrations in newborn stool at seven days, while antibiotic therapy during labour resulted in higher zonulin concentrations in the stool of newborns at seven days. Zonulin concentrations in the stool of newborns (at seven days) who were born via caesarean section were higher compared to with vaginal birth. With further analyses, caesarean section was found to have a greater effect on zonulin concentrations than prophylactic administration of antibiotics in the perinatal period. Pregnancy mass gain >18 kg was associated with higher calprotectin concentrations in maternal stool. Body Mass Index (BMI) increase >5.7 during pregnancy was associated with decreased zonulin concentrations in maternal stool and increased calprotectin concentrations in stool of mothers and newborns at seven days. There was also a negative correlation between higher BMI increase in pregnancy and maternal zonulin stool concentrations and a positive correlation between BMI increase in pregnancy and maternal calprotectin stool concentrations. Conclusion: Maternal-foetal factors such as caesarean section, antibiotic therapy during pregnancy, as well as change in mother’s BMI during pregnancy may increase intestinal permeability in newborns. Changes in body mass during pregnancy can also affect intestinal permeability in mothers. However, health consequences associated with increased intestinal permeability during the first days of life are unknown. Additionally, before the zonulin and calprotectin tests can be adopted as universal diagnostic applications to assess increased intestinal permeability, validation of these tests is necessary.

Targeted genotyping for the prediction of celiac disease autoimmunity development in patients with type 1 diabetes and their family members

BACKGROUND

Patients with type 1 diabetes (T1D) and their first-degree relatives (FDRs) have an increased risk of developing celiac disease (CD) compared to the general population. This is largely explained by the shared association with major histocompatibility class II human leukocyte antigen (HLA) DQ2 and/or DQ8 between the two disease states.

AIM

To describe the frequency of CD autoimmunity (CDA) and the distribution of HLA and haptoglobin genotypes in patients with T1D and their FDRs. Additionally, we aimed at identifying predictors associated with an increased risk of developing CDA in patients with T1D and their family members.

METHODS

We obtained clinical information and blood samples from 1027 participants (302 with T1D and 725 FDRs) over a five-year period. Samples were tested for autoantibodies associated with CD, HLA-DQ alleles, and haptoglobin genotype. We fit univariate and multiple logistic regression models for CDA separately for subjects with T1D and for FDRs of subjects with T1D.

RESULTS

Implementation of a screening program increased the frequency of CDA by 2-fold in participants with T1D and 2.8-fold in their FDRs. Multivariate analysis found that, in participants with T1D, having both DR7-DQ2 and DR4-DQ8 was associated with an increased frequency of CDA. In FDRs of T1D patients, reported CD in the family was associated with an increased frequency of CDA during screening. Haptoglobin 2 genotype was not associated with developing CDA in the multivariate analysis.

CONCLUSION

Patients with T1D and their FDRs have a high frequency of CDA. Carrying both DR7-DQ2 and DR4-DQ8 was associated with development of CDA in patients with T1D.

Nondietary Therapies for Celiac Disease

Celiac disease (CD) is an autoimmune enteropathy triggered by gluten. Gluten-free diets can be challenging because of their restrictive nature, inadvertent cross-contaminations, and the high cost of gluten-free food. Novel nondietary therapies are at the preclinical stage, clinical trial phase, or have already been developed for other indications and are now being applied to CD. These therapies include enzymatic gluten degradation, binding and sequestration of gluten, restoration of epithelial tight junction barrier function, inhibition of tissue transglutaminase-mediated potentiation of gliadin oligopeptide immunogenicity or of human leukocyte antigen-mediated gliadin presentation, induction of tolerance to gluten, and antiinflammatory interventions.

Coeliac disease: beyond genetic susceptibility and gluten. A narrative review

Coeliac disease (CD) is an immune-mediated disorder triggered by the ingestion of gluten in genetically susceptible individuals. However, only a small proportion of subjects harbouring CD-related genetic risk develop the disease. Among the environmental factors that may influence CD risk, pre- and perinatal factors, delivery methods, parental lifestyle, infant feeding practices, seasonality, dietary factors, drug use, childhood infections and variability in gut microbiota are those most widely studied regarding the risk to develop CD. Although for many of these external factors the exact mechanism of action is unknown, most of them are thought to act by disrupting the intestinal barrier, facilitating contact between potential antigens and the immune system effector cells. Management of CD is relatively easy in patients with a definite diagnosis and requires a strict, lifelong, gluten-free diet. Better knowledge of environmental exposures apart from gluten can facilitate understanding of the pathogenesis of the disorder and the wide heterogeneity of its clinical spectrum. The purpose of this review is to discuss current knowledge on environmental CD risk factors, as well as possible interaction between them, on the grounds of the reliable scientific evidence available. Key messages The risk of developing CD is influenced not only by gluten ingestion but also by a number of environmental factors including childhood infections and variability in gut microbiota, pre- and perinatal factors, infant feeding practices, delivery methods, parental lifestyle, seasonality, dietary factors and drug use, acting mainly by disrupting intestinal permeability. Better knowledge of exposure to these factors can facilitate their identification, and subsequent elimination, in the individual patient.

Involvement of gliadin, a component of wheat gluten, in increased intestinal permeability leading to non-steroidal anti-inflammatory drug-induced small-intestinal damage

Gliadin, a component of wheat gluten known to be an important factor in the etiology of celiac disease, is related to several other diseases through its enhancing effect on intestinal paracellular permeability. We investigated the significance of gliadin in non-steroidal anti-inflammatory drug (NSAID)-induced small-intestinal damage in mice. 7-week-old C57BL/6 male mice were divided into the following groups: standard diet group, in which mice were fed with wheat-containing standard rodent diet (CE-2); gluten-free diet group, in which mice were fed with gluten-free diet (AIN-76A); and gliadin-administered group, in which mice fed with gluten-free diet were administered with gliadin (~250 mg/kg BW). Each group was subdivided into negative, healthy control group and NSAID-treated group. To some mice fed with gluten-free diet and administered with gliadin, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor was administered for clarification of the significance of EGFR in NSAID-induced small intestinal damage and intestinal permeability. In mice fed with a gluten-free diet, indomethacin or diclofenac induced very mild mucosal damage in the small intestine compared with that in mice fed with a wheat-containing standard diet. Gliadin exacerbated the NSAID-induced small-intestinal damage in mice fed with a gluten-free diet. With the administration of indomethacin, MPO activity, a marker of neutrophil infiltration into the mucosa and mRNA expression level of tumor necrosis factor α and interleukin-1β in the small intestine were higher in the gliadin-administered mice. Gliadin increased the intestinal paracellular permeability without indomethacin administration (4.3-fold) and further increased the permeability after indomethacin administration (2.1-fold). Gliadin induced phosphorylation of epidermal growth factor receptor (EGFR) in small-intestinal tissues, and erlotinib (an EGFR tyrosine kinase inhibitor) attenuated the indomethacin-induced intestinal damage and permeability exacerbated by gliadin, accompanied by inhibition of EGFR phosphorylation. These results suggest that gliadin plays an important role in the induction and exacerbation of NSAID-induced small-intestinal damage, and that increase in intestinal permeability via the EGFR signalling pathway is involved in its mechanism.

The Dietary Intervention of Transgenic Low-Gliadin Wheat Bread in Patients with Non-Celiac Gluten Sensitivity (NCGS) Showed No Differences with Gluten Free Diet (GFD) but Provides Better Gut Microbiota Profile

The study evaluated the symptoms, acceptance, and digestibility of bread made from transgenic low-gliadin wheat, in comparison with gluten free bread, in Non-coeliac gluten sensitivity (NCGS) patients, considering clinical/sensory parameters and gut microbiota composition. This study was performed in two phases of seven days each, comprising a basal phase with gluten free bread and an E82 phase with low-gliadin bread. Gastrointestinal clinical symptoms were evaluated using the Gastrointestinal Symptom Rating Scale (GSRS) questionnaire, and stool samples were collected for gluten immunogenic peptides (GIP) determination and the extraction of gut microbial DNA. For the basal and E82 phases, seven and five patients, respectively, showed undetectable GIPs content. The bacterial 16S rRNA gene V1-V2 hypervariable regions were sequenced using the Illumina MiSeq platform and downstream analysis was done using a Quantitative Insights into Microbial Ecology (QIIME) pipeline. No significant differences in the GSRS questionnaires were observed between the two phases. However, we observed a significantly lower abundance of some gut genera Oscillospira, Dorea, Blautia, Bacteroides, Coprococcus, and Collinsella, and a significantly higher abundance of Roseburia and Faecalibacterium genera during the E82 phase compared with the basal phase. The consumption of low-gliadin bread E82 by NCGS subjects induced potentially positive changes in the gut microbiota composition, increasing the butyrate-producing bacteria and favoring a microbial profile that is suggested to have a key role in the maintenance or improvement of gut permeability.

A pathogenic role for cystic fibrosis transmembrane conductance regulator in celiac disease

Intestinal handling of dietary proteins usually prevents local inflammatory and immune responses and promotes oral tolerance. However, in ~ 1% of the world population, gluten proteins from wheat and related cereals trigger an HLA DQ2/8‐restricted T_H1 immune and antibody response leading to celiac disease. Prior epithelial stress and innate immune activation are essential for breaking oral tolerance to the gluten component gliadin. How gliadin subverts host intestinal mucosal defenses remains elusive. Here, we show that the α‐gliadin‐derived LGQQQPFPPQQPY peptide (P31–43) inhibits the function of cystic fibrosis transmembrane conductance regulator (CFTR), an anion channel pivotal for epithelial adaptation to cell‐autonomous or environmental stress. P31–43 binds to, and reduces ATPase activity of, the nucleotide‐binding domain‐1 (NBD1) of CFTR, thus impairing CFTR function. This generates epithelial stress, tissue transglutaminase and inflammasome activation, NF‐κB nuclear translocation and IL‐15 production, that all can be prevented by potentiators of CFTR channel gating. The CFTR potentiator VX‐770 attenuates gliadin‐induced inflammation and promotes a tolerogenic response in gluten‐sensitive mice and cells from celiac patients. Our results unveil a primordial role for CFTR as a central hub orchestrating gliadin activities and identify a novel therapeutic option for celiac disease.

Lactobacillus rhamnosus GG Protects the Epithelial Barrier of Wistar Rats from the Pepsin-Trypsin-Digested Gliadin (PTG)-Induced Enteropathy

Celiac disease (CD) is a chronic immune-mediated disorder, characterized by enhanced paracellular permeability across the intestinal epithelium. The complex system of intercellular junctions, including tight junctions (TJs) and adherens junctions (AJs), seals together the epithelial cells to form a continuous layer. The improvements in barrier integrity have been related to modifications in intercellular junction protein expression. Polyamines (spermidine, spermine, and putrescine) actively participate in the modulation of the AJ expression. Both in vitro and in vivo studies have demonstrated that also probiotics can promote the integrity and the function of the intestinal barrier. On these bases, the present work investigated the protective effects exerted by Lactobacillus rhamnosus GG (L.GG) against the pepsin-trypsin-digested gliadin (PTG)-induced enteropathy in jejunal tissue samples of Wistar rats. In particular, the probiotic effects have been evaluated on the intestinal mucosal architecture, polyamine metabolism and intercellular junction protein expression (ZO-1, Occludin, Claudin-1, β-catenin and E-cadherin). The results from this study indicate that L.GG protects the intestinal mucosa of rats from PTG-induced damage, by preventing the reduction of the expression of the intercellular junction proteins. Consequently, a role for L.GG in the therapeutic management of the gluten-related disorders in humans could be hypothesized.

Cross-Talk Between Gluten, Intestinal Microbiota and Intestinal Mucosa in Celiac Disease: Recent Advances and Basis of Autoimmunity

Celiac disease (CD) is an autoimmune disorder of the small intestine, caused by gluten induced inflammation in some individuals susceptible to genetic and environmental influences. To date, pathophysiology of CD in relation to intestinal microbiota is not known well. This review relies on contribution of intestinal microbiome and oral microbiome in pathogenesis of CD based on their interactions with gluten, thereby highlighting the role of upper gastrointestinal microbiota. It has been hypothesized that CD might be triggered by additive effects of immunotoxic gluten peptides and intestinal dysbiosis (microbial imbalance) in the people with or without genetic susceptibilities, where antibiotics may be deriving dysbiotic agents. In contrast to the intestinal dysbiosis, genetic factors even seem secondary in disease outcome thus suggesting the importance of interaction between microbes and dietary factors in immune regulation at intestinal mucosa. Moreover, association of imbalanced counts of some commensal microbes in intestine of CD patients suggests the scope for probiotic therapies. Lactobacilli and specific intestinal and oral bacteria are potent source of gluten degrading enzymes (glutenases) that may contribute to commercialization of a novel glutenase therapy. In this review, we shall discuss advantages and disadvantages of food based therapies along with probiotic therapies where probiotic therapies are expected to emerge as the safest biotherapies among other in-process therapies. In addition, this review emphasizes on differential targets of probiotics that make them suitable to manage CD as along with glutenase activity, they also exhibit immunomodulatory and intestinal microbiome modulatory properties.

Gluten intake and risk of type 2 diabetes in three large prospective cohort studies of US men and women

AIMS/HYPOTHESIS

We investigated the association between gluten intake and long-term type 2 diabetes risk among Americans.

METHODS

We followed women from the Nurses' Health Study (NHS, n = 71,602, 1984-2012) and NHS II (n = 88,604, 1991-2013) and men from the Health Professionals Follow-Up Study (HPFS, n = 41,908, 1986-2012). Gluten intake was estimated using a validated food frequency questionnaire every 2-4 years. Incident type 2 diabetes was defined as self-reported physician-diagnosed diabetes confirmed using a supplementary questionnaire.

RESULT

Gluten intake was strongly correlated with intakes of carbohydrate components, especially refined grains, starch and cereal fibre (Spearman correlation coefficients >0.6). During 4.24 million years of follow-up, 15,947 people were confirmed to have type 2 diabetes. After multivariate adjustment, pooled HRs and 95% CIs for type 2 diabetes, from low to high gluten quintiles, were (p_trend < 0.001): 1 (reference); 0.89 (0.85, 0.93); 0.84 (0.80, 0.88); 0.78 (0.74, 0.82) and 0.80 (0.76, 0.84). The association was slightly weakened after further adjusting for cereal fibre, with pooled HRs (95% CIs) of (p_trend < 0.001): 1 (reference); 0.91 (0.87, 0.96); 0.88 (0.83, 0.93); 0.83 (0.78, 0.88) and 0.87 (0.81, 0.93). Dose-response analysis supported a largely linear inverse relationship between gluten intake up to 12 g/day and type 2 diabetes. The association between gluten intake and type 2 diabetes was stronger when intake of added bran was also higher (p_interaction = 0.02).

CONCLUSIONS/INTERPRETATION

Gluten intake is inversely associated with type 2 diabetes risk among largely healthy US men and women. Limiting gluten in the diet is associated with lower intake of cereal fibre and possibly other beneficial nutrients that contribute to good health.

Yogurt inhibits intestinal barrier dysfunction in Caco-2 cells by increasing tight junctions

Chronic inflammation disrupts intestinal barrier function and may contribute to the pathology of obesity and other diseases. The goal of this study was to determine the mechanism by which yogurt improves intestinal barrier function. Caco-2 cells were differentiated on Transwell inserts and used as a model of intestinal barrier permeability. Transepithelial electrical resistance (TEER) and flux of 4 kDa fluorescein isothiocyanate-dextran (FD) and lucifer yellow (LY) were used as indicators of monolayer integrity and paracellular permeability. Immunofluorescence microscopy and real time quantitative polymerase chain were used to assess the localization and expression of tight junction proteins known to regulate intestinal permeability. Differentiated cells were treated with a vehicle control (C), inflammatory stimulus (I) (interleukin-1β, tumor necrosis factor-α, interferon-γ, and lipopolysaccharide), or I and 0.03 g mL^-1 yogurt (IY). After 48 h, I reduced Caco-2 TEER by 46%, while IY reduced TEER by only 27% (P < 0.0001). FD and LY flux reflected TEER measurements, with IY having significantly lower permeability than I (P < 0.05). Yogurt also improved localization of occludin and zona occludens protein 1 (ZO-1) at tight junctions of differentiated Caco-2 cells. IY increased Caco-2 claudin-1, ZO-1, and occludin mRNA relative to I (P < 0.05). In a simulated digestion, the barrier-improving bioactivity of yogurt was maintained through the gastric phase, but was reduced to the level of I after intestinal digestion (P < 0.05). Therefore, yogurt improved inflammation-disrupted intestinal barrier function in a Caco-2 model by increasing tight junctions, but the beneficial effect on barrier function was reduced at latter stages of digestion.

The Use of Human Mesenchymal Stem Cells as Therapeutic Agents for the in vivo Treatment of Immune-Related Diseases: A Systematic Review

Background: One of the greatest challenges for medicine is to find a safe and effective treatment for immune-related diseases. However, due to the low efficacy of the treatment available and the occurrence of serious adverse effects, many groups are currently searching for alternatives to the traditional therapy. In this regard, the use of human mesenchymal stem cells (hMSCs) represents a great promise for the treatment of a variety of immune-related diseases due to their potent immunomodulatory properties. The main objective of this study is, therefore, to present and summarize, through a systematic review of the literature, in vivo studies in which the efficacy of the administration of hMSCs for the treatment of immune-related diseases was evaluated. Methods: The article search was conducted in PubMed/MEDLINE, Scopus and Web of Science databases. Original research articles assessing the therapeutic potential of hMSCs administration for the in vivo treatment immune-related diseases, published from 1984 to December 2017, were selected and evaluated. Results: A total of 132 manuscripts formed the basis of this systematic review. Most of the studies analyzed reported positive results after hMSCs administration. Clinical effects commonly observed include an increase in the survival rates and a reduction in the severity and incidence of the immune-related diseases studied. In addition, hMSCs administration resulted in an inhibition in the proliferation and activation of CD19⁺ B cells, CD4⁺ Th1 and Th17 cells, CD8⁺ T cells, NK cells, macrophages, monocytes, and neutrophils. The clonal expansion of both Bregs and Tregs cells, however, was stimulated. Administration of hMSCs also resulted in a reduction in the levels of pro-inflammatory cytokines such as IFN-γ, TNF-α, IL-1, IL-2, IL-12, and IL-17 and in an increase in the levels of immunoregulatory cytokines such as IL-4, IL-10, and IL-13. Conclusions: The results obtained in this study open new avenues for the treatment of immune-related diseases through the administration of hMSCs and emphasize the importance of the conduction of further studies in this area.

Serum zonulin in patients with inflammatory bowel disease: a pilot study

BACKGROUND

In recent years it has been supposed that impaired intestinal permeability represents an early event preceding the onset of inflammatory bowel disease (IBD). Since zonulin has been proposed as a biomarker of intestinal permeability, we investigated its role in patients with IBD and the correlation between serum and fecal zonulin.

METHODS

A total of 118 IBD patients (86 Crohn's disease [CD] and 32 ulcerative colitis [UC]) and 23 healthy controls (HC) were prospectively enrolled. A serum sample was collected for all the subjects included in the study. A stool specimen collected in the same day of blood drawing was available for a subgroup of 33 IBD patients. Serum and fecal zonulin were tested by ELISA. Non-parametric statistical tests were used for data analysis.

RESULTS

Serum zonulin concentration was higher in IBD patients compared to HC (34.5 [26.5-43.9] ng/mL vs. 8.6 [6.5-12.0] ng/mL, P<0.001) showing an area under the curve of 0.98 for their discrimination. No difference in serum zonulin concentration was observed between patients with CD and those with UC (P=0.074). An inverse correlation was observed between serum zonulin concentration and disease duration (rs=-0.30, P=0.001); no correlation was observed between serum and fecal zonulin (rs=0.15, P=0.394).

CONCLUSIONS

Serum zonulin is highly sensitive for the evaluation of intestinal permeability in IBD patients. There is no correlation between zonulin values in serum and feces.

The Human Gut Microbiome - A Potential Controller of Wellness and Disease

Interest toward the human microbiome, particularly gut microbiome has flourished in recent decades owing to the rapidly advancing sequence-based screening and humanized gnotobiotic model in interrogating the dynamic operations of commensal microbiota. Although this field is still at a very preliminary stage, whereby the functional properties of the complex gut microbiome remain less understood, several promising findings have been documented and exhibit great potential toward revolutionizing disease etiology and medical treatments. In this review, the interactions between gut microbiota and the host have been focused on, to provide an overview of the role of gut microbiota and their unique metabolites in conferring host protection against invading pathogen, regulation of diverse host physiological functions including metabolism, development and homeostasis of immunity and the nervous system. We elaborate on how gut microbial imbalance (dysbiosis) may lead to dysfunction of host machineries, thereby contributing to pathogenesis and/or progression toward a broad spectrum of diseases. Some of the most notable diseases namely Clostridium difficile infection (infectious disease), inflammatory bowel disease (intestinal immune-mediated disease), celiac disease (multisystemic autoimmune disorder), obesity (metabolic disease), colorectal cancer, and autism spectrum disorder (neuropsychiatric disorder) have been discussed and delineated along with recent findings. Novel therapies derived from microbiome studies such as fecal microbiota transplantation, probiotic and prebiotics to target associated diseases have been reviewed to introduce the idea of how certain disease symptoms can be ameliorated through dysbiosis correction, thus revealing a new scientific approach toward disease treatment. Toward the end of this review, several research gaps and limitations have been described along with suggested future studies to overcome the current research lacunae. Despite the ongoing debate on whether gut microbiome plays a role in the above-mentioned diseases, we have in this review, gathered evidence showing a potentially far more complex link beyond the unidirectional cause-and-effect relationship between them.