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Transglutaminase 2 (TG2) plays a pivotal role in the pathogenesis of celiac disease (CeD) by deamidating dietary gluten peptides, which facilitates antigenic presentation and a strong anti-gluten T cell response. Here, we elucidate the molecular mechanisms underlying the efficacy of the TG2 inhibitor ZED1227 by performing transcriptional analysis of duodenal biopsies from individuals with CeD on a long-term gluten-free diet before and after a 6-week gluten challenge combined with 100 mg per day ZED1227 or placebo. At the transcriptome level, orally administered ZED1227 effectively prevented gluten-induced intestinal damage and inflammation, providing molecular-level evidence that TG2 inhibition is an effective strategy for treating CeD. ZED1227 treatment preserved transcriptome signatures associated with mucosal morphology, inflammation, cell differentiation and nutrient absorption to the level of the gluten-free diet group. Nearly half of the gluten-induced gene expression changes in CeD were associated with the epithelial interferon-γ response. Moreover, data suggest that deamidated gluten-induced adaptive immunity is a sufficient step to set the stage for CeD pathogenesis. Our results, with the limited sample size, also suggest that individuals with CeD might benefit from an HLA-DQ2 / HLA-DQ8 stratification based on gene doses to maximally eliminate the interferon-γ-induced mucosal damage triggered by gluten. Viiri and colleagues show that an orally administered transglutaminase 2 inhibitor prevented gluten-induced intestinal damage and inflammation at the transcriptional level.

Despite increased prescription of a gluten-free diet for gastrointestinal symptoms in individuals who do not have celiac disease, there is minimal evidence that suggests that gluten is a trigger. The aims of this study were to determine whether gluten ingestion can induce symptoms in non-celiac individuals and to examine the mechanism. A double-blind, randomized, placebo-controlled rechallenge trial was undertaken in patients with irritable bowel syndrome in whom celiac disease was excluded and who were symptomatically controlled on a gluten-free diet. Participants received either gluten or placebo in the form of two bread slices plus one muffin per day with a gluten-free diet for up to 6 weeks. Symptoms were evaluated using a visual analog scale and markers of intestinal inflammation, injury, and immune activation were monitored. A total of 34 patients (aged 29-59 years, 4 men) completed the study as per protocol. Overall, 56% had human leukocyte antigen (HLA)-DQ2 and/or HLA-DQ8. Adherence to diet and supplements was very high. Of 19 patients (68%) in the gluten group, 13 reported that symptoms were not adequately controlled compared with 6 of 15 (40%) on placebo (P=0.0001; generalized estimating equation). On a visual analog scale, patients were significantly worse with gluten within 1 week for overall symptoms (P=0.047), pain (P=0.016), bloating (P=0.031), satisfaction with stool consistency (P=0.024), and tiredness (P=0.001). Anti-gliadin antibodies were not induced. There were no significant changes in fecal lactoferrin, levels of celiac antibodies, highly sensitive C-reactive protein, or intestinal permeability. There were no differences in any end point in individuals with or without DQ2/DQ8. \"Non-celiac gluten intolerance\" may exist, but no clues to the mechanism were elucidated.

Background/Aims Non‐coeliac gluten sensitivity (NCGS) is a controversial entity, characterised by symptom improvement with gluten exclusion in the absence of coeliac disease. We primarily investigated the effects of acute and sub‐acute gluten on psychological and mood profiles, with secondary outcomes examining gastrointestinal symptoms and biological markers in healthy controls (HC) and individuals with NCGS. Methods A randomised, single‐blind, crossover study used acute (16 g gluten or whey in yoghurt) and sub‐acute (gluten‐containing (16 g) or gluten‐free muffins per day for 5 days) challenges. (Extra)intestinal symptoms, intestinal permeability, high‐sensitive C‐reactive protein and cortisol awakening response were assessed. Responses over time were analysed using generalised linear mixed models. Results Twenty HCs (15% men, mean age 30 years) and 16 individuals with NCGS (31% men, mean age 33 years) participated. No significant group‐by‐nutrient interactions were observed. Negative affect scores were higher and positive affect scores were lower in NCGS compared to HC (p = 0.01 and p = 0.04, respectively). Participants experienced higher tension scores after gluten compared with placebo (p = 0.01 acute; p = 0.05 sub‐acute) regardless of the group. After acute administration, fatigue scores increased in NCGS (p = 0.03) compared with HC regardless of nutrient intake. After sub‐acute administration, abdominal pain scores (p < 0.001) and bloating (p = 0.001) increased in NCGS compared with HC regardless of nutrient intake. No differences were found for biological markers. Conclusions These findings reveal that NCGS is characterised by baseline differences in affect, and higher acute fatigue and subacute gastrointestinal symptoms that are not gluten‐specific. This may be explained by nocebo effects, warranting research into novel mechanisms and re‐evaluating the NCGS definition. Trial Registration ClinicalTrials.gov no: NCT03798262; NCT03798249

The adherence to a gluten-free diet (GFD) is a trending topic in the management of celiac disease. The aim of our study was to evaluate the diagnostic performance of urinary gluten immunogenic peptides (GIP) determination to detect gluten contamination of the GFD. In study A, 25 healthy adults on a standard GFD performed 6 gluten challenges (0, 10, 50, 100, 500, and 1,000 mg) with quantification of urinary GIP before (T0) and during the following 24 hours. In study B, 12 participants on a gluten contamination elimination diet underwent urinary GIP determination at T0 and after challenge with 5 or 10 mg gluten. Urine GIP concentration was determined by an immunochromatographic assay. In study A, 51 of 150 baseline urine samples were GIP+ on GFD and 7 of 17 were GIP+ after the zero-gluten challenge, whereas only 55 of 81 were GIP+ after the 10-1,000 mg gluten challenges. There was no significant change in the 24-hour urinary GIP when increasing gluten from 10 to 1,000 mg. In study B, 24 of 24 baseline urine samples were GIP-, whereas 8 of 24 were GIP+ after 5 or 10 mg of gluten. Traces of gluten in the standard GFD may cause positivity of urinary GIP determination, whereas a false negativity is common after a gluten intake of 10-1,000 mg. Owing to the impossibility of standardizing the test in normal conditions, it seems unlikely that urinary GIP determination may represent a reliable tool to assess the compliance to the GFD of patients with celiac disease or other gluten-related disorders.

Background. To date, there is no reliable marker for the diagnosis of non-celiac gluten sensitivity (NCGS), which benefits from a gluten-free diet (GFD). This condition is characterized by functional gastrointestinal symptoms similar to those occurring in the course of irritable bowel syndrome (IBS). However, IBS has a higher prevalence, and often benefits from the administration of a low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet. The overlap of symptoms between these two pathologies has led to an overestimation of self-made diagnosis NCGS. Aims. To better identify NCGS in subjects with a previous diagnosis of IBS. Methods. All subjects received a low FODMAP diet that was also gluten-free (low FODMAP-GFD), and those presenting an improvement of symptoms were exposed to gluten or placebo (double-blind challenge with wash-out and crossover). The response to dietary treatments was evaluated by visual analogue scale (VAS). Results. Of 30 patients (23 women, seven men, aged 42.2 ± 12.5 years, body mass index (BMI) 24.7 ± 4.1 kg/m2), 26 benefited from the administration of low FODMAP-GFD and were exposed to the gluten/placebo challenge. After the challenge, using an increase of visual analogue scale VAS (Δ-VAS) ≥30%, 46.1% of the patients were NCGS+. However, this percentage became only 19.2% using a different method (mean ∆-VAS score plus two standard deviations). Conclusions. FODMAP intolerance could hide the response to a challenge test with gluten for the identification of NCGS in IBS patients. A low FODMAP-GFD followed by gluten/placebo challenge is able to identify patients with NCGS better. ClinicalTrials.gov registration number NCT04017585.

Celiac disease is a chronic, immune‐mediated enteropathy with symptoms triggered by exposure to dietary gluten in genetically predisposed individuals. The only available management option is lifelong adherence to a gluten‐free diet. This randomized, double‐blind, placebo‐controlled, parallel‐group, single‐center study tested the effects of the cathepsin S inhibitor RO5459072 on the immune response to a 13‐day gluten challenge in 19 participants with celiac disease (ClinicalTrials.gov: NCT02679014). Nine participants in the RO5459072 arm received 100 mg study drug b.i.d. (200 mg daily); 10 received a placebo. The primary end point was the number of responders to the gluten challenge (defined as individuals with an increase in the number of gliadin‐specific, IFNγ‐secreting T cells detected using an ELISPOT assay). However, there was a weak response to the gluten challenge across both arms. Few participants had an increase in gliadin‐specific, IFNγ‐secreting T cells, and the antigen‐specific responses (anti‐tTG and anti‐DGP antibodies) were weaker than expected in both arms. Therefore, the primary end point was not met, although the study was underpowered to detect a treatment effect under these circumstances. Pharmacodynamic findings suggested that RO5459072 had some beneficial effects. Fewer participants in the RO5459072 arm exhibited gliadin‐specific IFNγ‐secreting T cells after 6 days' gluten intake. Participants in the RO5459072 arm also showed decreased intestinal permeability, and a decrease in the number of circulating B cells, CD4+ and CD8+ T cells compared to baseline. Nevertheless, the absence of clear effects on the response to a gluten challenge indicates that inhibition of cathepsin S may not be an effective treatment strategy for celiac disease.

The role of gluten as a trigger of symptoms in non-coeliac gluten sensitivity has been questioned. To demonstrate that gluten is the trigger of symptoms in a subgroup of patients fulfilling the diagnostic criteria for non-coeliac gluten sensitivity (NCGS), which presented with lymphocytic enteritis, positive celiac genetics and negative celiac serology. Double-blind randomized clinical trial of gluten vs placebo rechallenge. >18 years of age, HLA-DQ2/8+, negative coeliac serology and gluten-dependent lymphocytic enteritis, and GI symptoms, with clinical and histological remission at inclusion. Eighteen patients were randomised: 11 gluten (20 g/day) and 7 placebo. Clinical symptoms, quality of life (GIQLI), and presence of gamma/delta+ cells and transglutaminase deposits were evaluated. 91% of patients had clinical relapse during gluten challenge versus 28.5% after placebo (p = 0.01). Clinical scores and GIQLI worsened after gluten but not after placebo (p<0.01). The presence of coeliac tissue markers at baseline biopsy on a gluten-free diet allowed classifying 9 out of the 18 (50%) patients as having probable 'coeliac lite' disease. This proof-of-concept study indicates that gluten is the trigger of symptoms in a subgroup of patients fulfilling the diagnostic criteria for NCGS. They were characterized by positive celiac genetics, lymphocytic enteritis, and clinical and histological remission after a gluten-free diet. ClinicalTrials.gov NCT02472704.

Up to 20% of people worldwide develop gastrointestinal symptoms following a meal 1 , leading to decreased quality of life, substantial morbidity and high medical costs. Although the interest of both the scientific and lay communities in this issue has increased markedly in recent years, with the worldwide introduction of gluten-free and other diets, the underlying mechanisms of food-induced abdominal complaints remain largely unknown. Here we show that a bacterial infection and bacterial toxins can trigger an immune response that leads to the production of dietary-antigen-specific IgE antibodies in mice, which are limited to the intestine. Following subsequent oral ingestion of the respective dietary antigen, an IgE- and mast-cell-dependent mechanism induced increased visceral pain. This aberrant pain signalling resulted from histamine receptor H 1 -mediated sensitization of visceral afferents. Moreover, injection of food antigens (gluten, wheat, soy and milk) into the rectosigmoid mucosa of patients with irritable bowel syndrome induced local oedema and mast cell activation. Our results identify and characterize a peripheral mechanism that underlies food-induced abdominal pain, thereby creating new possibilities for the treatment of irritable bowel syndrome and related abdominal pain disorders. In mice, oral tolerance to food antigens can break down after enteric infection, and this leads to food-induced pain resembling irritable bowel syndrome in humans.

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.

ObjectiveGluten-free diet (GFD) is the only management for coeliac disease (CD). Available methods to assess GFD compliance are insufficiently sensitive to detect occasional dietary transgressions that may cause gut mucosal damage. We aimed to develop a method to determine gluten intake and monitor GFD compliance in patients with CD and to evaluate its correlation with mucosal damage.DesignUrine samples of 76 healthy subjects and 58 patients with CD subjected to different gluten dietary conditions were collected. A lateral flow test (LFT) with the highly sensitive and specific G12 monoclonal antibody for the most dominant gluten immunogenic peptides (GIP) and a LFT reader were used to quantify GIP in solid-phase extracted urines.ResultsGIP were detectable in concentrated urines from healthy individuals previously subjected to GFD as early as 4–6 h after single gluten intake, and remained detectable for 1–2 days. The urine assay revealed infringement of the GFD in about 50% of the patients. Analysis of duodenal biopsies revealed that most of patients with CD (89%) with no villous atrophy had no detectable GIP in urine, while all patients with quantifiable GIP in urine showed incomplete intestinal mucosa recovery.ConclusionGIP are detected in urine after gluten consumption, enabling a new and non-invasive method to monitor GFD compliance and transgressions. The method was sensitive, specific and simple enough to be convenient for clinical monitoring of patients with CD as well as for basic and clinical research applications including drug development.Trial registration numberNCT02344758.