Serum zonulin and its diagnostic performance in non-coeliac gluten sensitivity.

OBJECTIVE: Non-coeliac gluten sensitivity (NCGS) is characterised by intestinal and extraintestinal symptoms related to the ingestion of gluten-containing foods, in the absence of coeliac disease (CD) and wheat allergy. No biomarkers are available to diagnose NCGS and the gold standard double-blind placebo-controlled gluten challenge is clinically impractical. The aim of our work was to investigate the role of serum zonulin as a diagnostic biomarker of NCGS and to develop a diagnostic algorithm. DESIGN: In a multicentre study, we enrolled 86 patients with either self-reported or double-blind confirmed NCGS, 59 patients with diarrhoea-predominant IBS (IBS-D), 15 patients with CD and 25 asymptomatic controls (AC). Zonulin serum levels were assessed and the associated diagnostic power calculated. Clinical and symptomatic data were recorded. The effect of diet on zonulin levels was evaluated in a subgroup of patients with NCGS. RESULTS: Compared with ACs, the NCGS, irrespective of modality of diagnosis, and patients with CD had significantly increased levels of zonulin, as did both NCGS and patients with CD compared with participants with IBS-D. Self-reported NCGS showed increased zonulin levels compared with double-blind confirmed and not-confirmed NCGS. Six-month wheat avoidance significantly reduced zonulin levels only in HLA-DQ2/8-positive participants with NCGS. The diagnostic accuracy of zonulin levels in distinguishing NCGS from IBS-D was 81%. After exclusion of CD, a diagnostic algorithm combining zonulin levels, symptoms and gender improved the accuracy to 89%. CONCLUSION: Zonulin can be considered a diagnostic biomarker in NCGS and combined with demographic and clinical data differentiates NCGS from IBS-D with high accuracy. Wheat withdrawal was associated with a reduction in zonulin levels only in NCGS carrying HLA genotype.

Fecal Clostridiales distribution and short-chain fatty acids reflect bowel habits in irritable bowel syndrome.

Irritable bowel syndrome (IBS), a common functional gastrointestinal disorder, is classified according to bowel habits as IBS with constipation (IBS-C), with diarrhea (IBS-D), with alternating constipation and diarrhea (IBS-M), and unsubtyped (IBS-U). The mechanisms leading to the different IBS forms are mostly unknown. This study aims to evaluate whether specific fecal bacterial taxa and/or short-chain fatty acids (SCFAs) can be used to distinguish IBS subtypes and are relevant for explaining the clinical differences between IBS subcategories. We characterized five fecal samples collected at 4-weeks intervals from 40 IBS patients by 16S rRNA gene profiling and SCFA quantification. Finally, we investigated the potential correlations in IBS subtypes between the fecal microbial signatures and host physiological and clinical parameters. We found significant differences in the distribution of Clostridiales OTUs among IBS subtypes and reduced levels of SCFAs in IBS-C compared to IBS-U and IBS-D patients. Correlation analyses showed that the diverse representation of Clostridiales OTUs between IBS subtypes was associated with altered levels of SCFAs; furthermore, the same OTUs and SCFAs were associated with the fecal cytokine levels and stool consistency. Our results suggest that intestinal Clostridiales and SCFAs might serve as potential mechanistic biomarkers of IBS subtypes and represent therapeutic targets.

Interferon-γ is increased in the gut of patients with irritable bowel syndrome and modulates serotonin metabolism.

Mucosal immune activation and altered serotonin metabolism participate in the pathophysiology of irritable bowel syndrome (IBS). However, the reciprocal interplay between these two systems remains unknown. We evaluated the expression and release of interferon (IFN)-γ from the colonic mucosa of patients with IBS and its impact on serotonin reuptake transporter (SERT) gene expression in Caco-2 cells. qPCR was used to evaluate IFN-γ gene expression in colonic mucosal biopsies, whereas IFN-γ protein amount was assessed by ELISA. Colonic T box expressed in T cells (T-bet) and phosphorylated signal transducer and activator of transcription 4 protein amount were evaluated by Western blot. The impact of colonic mucosal mediators on SERT gene expression was evaluated in Caco-2 cells using qPCR. IFN-γ receptor was silenced in Caco-2 cells to determine the effect of IFN-γ released by mucosal biopsies. Compared with asymptomatic controls (ACs), the expression of IFN-γ gene and its transcription factor T-bet were markedly increased in the colonic mucosa of patients with IBS. Compared with ACs, IFN-γ protein tissue levels and its release by mucosal biopsies were significantly increased in IBS. The exposure of Caco-2 cells to IBS supernatants induced a significant decrease in SERT gene expression, independently of IBS subtypes, compared with AC mucosal supernatants. In Caco-2 cells, IFN-γ receptor silencing reversed the reduction of SERT expression evoked by IBS supernatants vs. nonsilenced cell lines. IFN-γ gene, its transcription factor T-bet, IFN-γ protein expression, and its release are increased in the colonic mucosa of patients with IBS and downregulate SERT gene expression in vitro. These results suggest that IFN-γ downregulates SERT expression, hence likely playing a role in altered serotonin metabolism of patients with IBS.

Nerve fiber outgrowth is increased in the intestinal mucosa of patients with irritable bowel syndrome.

BACKGROUND & AIMS: Mediators released by the intestinal mucosa of patients with irritable bowel syndrome (IBS) affect the function of enteric and extrinsic sensory nerves, which can contribute to the development of symptoms. Little is known about the effects of mucosal mediators on intestinal neuroplasticity. We investigated how these mediators affect the phenotypes of colonic mucosa nerve fibers, neuron differentiation, and fiber outgrowth. METHODS: We analyzed mucosal biopsy samples collected from 101 patients with IBS and 23 asymptomatic healthy individuals (controls). We measured levels of neuronal-specific enolase, growth-associated protein 43, nerve growth factor (NGF), and tyrosine kinase receptor A (NTRK1) by immunohistochemistry and enzyme-linked immunosorbent assay. Primary rat enteric neurons and human SH-SY5Y cells were incubated with supernatants from the mucosal biopsies and analyzed by morphometric and polymerase chain reaction analyses. RESULTS: Compared with mucosal tissues of controls, mucosa from patients with IBS had a significant increase in the area of lamina propria occupied by neuronal-specific enolase-positive (57.7% increase) and growth-associated protein 43-positive fibers (56.1% increase) and staining density of NGF (89.3% increase) (P < .05 for all). Levels of NGF protein were also increased in tissues from patients with IBS vs controls (18% increase; P = .16) along with levels of NTRK1 (64% increase; P < .05). Mucosal supernatants from tissues of patients with IBS induced higher levels of neuritogenesis in primary culture of enteric neurons, compared with controls, and more NGF-dependent neuronal sprouting in SH-SY5Y cells. CONCLUSIONS: Nerve fiber density and sprouting, as well as expression of NGF and NTRK1, are significantly increased in mucosal tissues of patients with IBS. Mucosal mediators participate to these neuroplastic changes.

Treatment of Diverticular Disease With Aminosalicylates: The Evidence.

Colonic diverticulosis is an increasingly common condition in Western industrialized countries. About 20% of patients develop symptoms, including abdominal pain, bloating, changes in bowel habits, and, eventually, diverticulitis or other complications. The management of symptomatic uncomplicated diverticular disease (SUDD) and the prevention of acute diverticulitis remains a challenge for the clinician. The rationale for the use of aminosalicylates, such as mesalazine, is based on the assumption of low-grade inflammation in SUDD and symptoms generation, whereas an overt inflammation may induce diverticulitis in patients with diverticular disease. Clinical scenarios in which the efficacy and safety of mesalazine have been studied include SUDD, prevention of diverticulitis, and of recurrent diverticulitis. Data from uncontrolled studies suggest a benefit of mesalazine on patients with SUDD, whereas data from randomized controlled trials showed some evidence of improvement of symptoms, although contrasting results are reported. The largest study so far published on the efficacy of mesalamine in the prevention of recurrence of diverticulitis showed that mesalamine was not superior to placebo. At this time, the role of mesalazine in the prevention of acute diverticulitis remains to be defined with many issues open and unresolved.

Salmonella gastroenteritis during childhood is a risk factor for irritable bowel syndrome in adulthood.

BACKGROUND & AIMS: Acute infectious gastroenteritis increases the risk for irritable bowel syndrome (IBS) and functional dyspepsia (FD). Children are particularly vulnerable to gastroenteritis because of the immaturity of their intestinal barrier, enteric nervous system, and immune response to pathogens. We investigated whether acute gastroenteritis in early life increases the risk of IBS and FD throughout adulthood. METHODS: In 1994, we identified and monitored a single culture-proven foodborne Salmonella enteritidis outbreak that involved 1811 patients (mostly pediatric) in Bologna, Italy. Clinical data were collected and a prospective, controlled, cohort study was designed. Long-term effects were assessed by mailing a questionnaire to 757 subjects 16 years after the outbreak (when all of the children were adults). We randomly selected a cohort of 250 adults exposed to Salmonella as children, all 127 individuals exposed as adults, and a cohort of nonexposed participants matched for number, age, sex, and area of residence (controls). RESULTS: Among 198 exposed participants, 64 reported FD (32.3%), compared with 51 of 188 controls (27.1%; P = .268). Among 204 exposed participants, 75 reported having IBS (36.8%) compared with 44 of 189 controls (23.3%; P = .004). The odds ratio for IBS among people exposed to the Salmonella was 1.92 (95% confidence interval: 1.23-2.98). The prevalence of IBS was higher in individuals exposed Salmonella as children than in controls (35.3% vs 20.5%; P = .008), but not in individuals exposed as adults, compared with controls. After multivariate logistic regression, post-infectious IBS was independently associated with anxiety and FD. CONCLUSIONS: Based on data collected from a single culture-proven foodborne Salmonella enteritidis outbreak in 1994, Salmonella-induced gastroenteritis during childhood (but not adulthood) is a risk factor for IBS.

Mucosal permeability and immune activation as potential therapeutic targets of probiotics in irritable bowel syndrome.

There is increasingly convincing evidence supporting the participation of the gut microenvironment in the pathophysiology of irritable bowel syndrome (IBS). Studies particularly suggest an interplay between luminal factors (eg, foods and bacteria residing in the intestine), the epithelial barrier, and the mucosal immune system. Decreased expression and structural rearrangement of tight junction proteins in the small bowel and colon leading to increased intestinal permeability have been observed, particularly in postinfectious IBS and in IBS with diarrhea. These abnormalities are thought to contribute to the outflow of antigens through the leaky epithelium, causing overstimulation of the mucosal immune system. Accordingly, subsets of patients with IBS show higher numbers and an increased activation of mucosal immunocytes, particularly mast cells. Immune factors, released by these cells, including proteases, histamine, and prostanoids, participate in the perpetuation of the permeability dysfunction and contribute to the activation of abnormal neural responses involved in abdominal pain perception and changes in bowel habits. All these mechanisms represent new targets for therapeutic approaches in IBS. Probiotics are an attractive therapeutic option in IBS given their recognized safety and by virtue of positive biological effects they can exert on the host. Of importance for the IBS pathophysiology is that preclinical studies have shown that selective probiotic strains exhibit potentially useful properties including anti-inflammatory effects, improvement of mucosal barrier homeostasis, beneficial effects on intestinal microbiota, and a reduction of visceral hypersensitivity. The effect of probiotics on IBS is positive in most randomized, controlled studies, although the gain over the placebo is small. Identifying tailored probiotic approaches for subgroups of IBS patients represents a challenge for the future.

Mechanisms underlying visceral hypersensitivity in irritable bowel syndrome.

Visceral hypersensitivity is currently considered a key pathophysiological mechanism involved in pain perception in large subgroups of patients with functional gastrointestinal disorders, including irritable bowel syndrome (IBS). In IBS, visceral hypersensitivity has been described in 20%-90% of patients. The contribution of the central nervous system and psychological factors to visceral hypersensitivity in patients with IBS may be significant, although still debated. Peripheral factors have gained increasing attention following the recognition that infectious enteritis may trigger the development of persistent IBS symptoms, and the identification of mucosal immune, neural, endocrine, microbiological, and intestinal permeability abnormalities. Growing evidence suggests that these factors play an important role in pain transmission from the periphery to the brain via sensory nerve pathways in large subsets of patients with IBS. In this review, we will report on recent data on mechanisms involved in visceral hypersensitivity in IBS, with particular attention paid to peripheral mechanisms.

An unusual cause of diarrhoea: case report and literature review of olmesartan-associated enteropathy.

Olmesartan is an angiotensin II receptor blocker, approved in 2002 by the Food and Drug Administration for the treatment of hypertension. During chronic therapy with olmesartan, sprue-like enteropathy can occur, being mainly characterised by non-bloody diarrhoea, weight loss and variable degrees of duodenal mucosal damage, which resolved after withdrawal of olmesartan. We hereby report the case of a 77-year-old, poli-treated male patient with a 3-month history of diarrhoea, vomiting and weight loss, associated with severe intestinal villous atrophy and lymphocytic infiltration of gastric and colonic mucosa. After extensive investigations aimed at excluding other possible causes of chronic diarrhoea, a diagnosis of olmesartan-associated enteropathy was made, which was later confirmed by clinical improvement after the discontinuation of the drug. Repeated endoscopy 8 months later showed complete healing of duodenal mucosa with normal villous architecture. Villous atrophy and lymphocytic infiltration of duodenal mucosa are the most described pathologic finding, but several cases of gastric and colonic involvement have also been reported. We, therefore, reviewed the available literature, focussing on the extent of mucosal damage throughout the whole intestine and on its possible causative factors.

Is gastroparesis a gastric disease?

BACKGROUND: Gastroparesis is a digestive syndrome characterized by delayed gastric emptying (GE) and by symptoms that are suggestive of gastroduodenal motor disorders. There are three grades of gastroparesis of increasing severity: (a) mild gastroparesis; (b) compensated gastroparesis; and (c) gastric failure. GE abnormalities are partially related to symptom type and severity, and other mechanisms may be involved. AIM: To investigate enteric dysmotility (ED) in patients with suspected gastroparesis. METHODS: Patients with symptoms suggestive of gastroparesis were consecutively included in the study and underwent a 13 C-octanoic acid GE breath test and small bowel manometry (SBM). Clinical features were recorded using predefined, validated questionnaires at entry. KEY RESULTS: The study enrolled 88 patients (71 women; mean age: 37.8 ± 14.3 years). Gastric emptying was delayed in 25 patients (28.4%), and 70 patients (79.5%) presented small bowel motor abnormalities including bursts, abnormal activity fronts, inability to respond to meal ingestion, and hypocontractility. Gastric emptying was delayed in 24 of the 70 patients with ED (34.3% vs 5.5% of patients with normal SBM). Enteric dysmotility was detected in 24 of 25 patients (96%) with delayed GE. Patients with and without delayed GE showed similar moderate/severe gastroparesis manifestations, but patients with ED significantly more often had moderate/severe gastroparesis manifestations than patients with normal SBM (grade 1:14% vs 39%, grade 2:62% vs 56%, grade 3:24% vs 5%, respectively). CONCLUSIONS AND INFERENCES: Enteric dysmotility was more frequent than delayed GE in patients with symptoms suggestive of gastroparesis. Gastroparesis severity was associated with small bowel motor abnormalities but not with delayed GE.

Effect of Lactobacillus paracasei CNCM I-1572 on symptoms, gut microbiota, short chain fatty acids, and immune activation in patients with irritable bowel syndrome: A pilot randomized clinical trial.

BACKGROUND: Evidence suggests a role of intestinal microbiota-host interactions in the pathophysiology and symptoms of irritable bowel syndrome (IBS). OBJECTIVE: The objective of this article is to assess the effects of Lactobacillus paracasei CNCM I-1572 on clinical and gut microbiota-related factors in IBS. METHODS: We conducted a multicenter, randomized, double-blind, cross-over, 18-week, placebo-controlled, pilot trial assessing the effect of Lactobacillus paracasei CNCM I-1572 on symptoms, gut microbiota composition, fecal short chain fatty acid (SCFA), immunoglobulin A, and cytokines in IBS. The intestinal microbial ecosystem was characterized by 16S rRNA gene profiling. RESULTS: Forty IBS patients were enrolled from five Italian centers. Lactobacillus paracasei CNCM I-1572 did not significantly improve IBS symptoms, including primary efficacy variables worst abdominal pain/discomfort and IBS degree of relief. Interestingly, Lactobacillus paracasei CNCM I-1572 induced a significant reduction in genus Ruminococcus, dominated by taxa related to Ruminococcus bromii and Ruminococcus callidus, a significant increase in the SCFAs acetate and butyrate, and a significant reduction in the pro-inflammatory cytokine interleukin-15. CONCLUSIONS: This pilot study shows that Lactobacillus paracasei CNCM I-1572 is able to modulate gut microbiota structure/function and reduce immune activation in IBS. As no statistically significant effect on IBS-symptoms was found, further studies are necessary to determine the role of this probiotic in IBS. The study was registered at ClinicalTrials.gov registry under identifier NCT02371499.

Diagnostic challenges of symptomatic uncomplicated diverticular disease.

Colonic diverticulosis is a common condition in Western industrialized countries occurring in up to 65% of people over the age of 60 years. Only a minority of these subjects (about 10-25%) experience symptoms, fulfilling Rome III Diagnostic Criteria for irritable bowel syndrome (IBS) diagnosis (IBS-like symptoms) in 10% to 66% of cases. Symptomatic uncomplicated diverticular disease (SUDD) is a syndrome characterized by recurrent abdominal symptoms attributed to diverticula in the absence of macroscopically evident alterations other than the presence of diverticula. Due to the different peak of incidence, the overlap between SUDD and IBS is predominantly present in middle-aged or older patients. In these cases, it is very complex to establish if the symptoms are related to the presence of diverticula or due to an overlapping IBS. In fact, the link between gastrointestinal symptoms and diverticula is unclear, and the mechanism by which diverticula may induce the development of IBS-like symptoms remains to be elucidated. Currently, the etiology and pathophysiology of SUDD, particularly when IBS-like symptoms are present, are not completely understood, and thus these two entities remain a diagnostic challenge not only for the general practitioner but also for the gastroenterologist. Although many issues remain open and unresolved, some minimize the importance of a distinction of these two entities as dietary and pharmacological management may be largely overlapping.

The immune system in irritable bowel syndrome.

The potential relevance of systemic and gastrointestinal immune activation in the pathophysiology and symptom generation in the irritable bowel syndrome (IBS) is supported by a number of observations. Infectious gastroenteritis is the strongest risk factor for the development of IBS and increased rates of IBS-like symptoms have been detected in patients with inflammatory bowel disease in remission or in celiac disease patients on a gluten free diet. The number of T cells and mast cells in the small and large intestine of patients with IBS is increased in a large proportion of patients with IBS over healthy controls. Mediators released by immune cells and likely from other non-immune competent cells impact on the function of enteric and sensory afferent nerves as well as on epithelial tight junctions controlling mucosal barrier of recipient animals, isolated human gut tissues or cell culture systems. Antibodies against microbiota antigens (bacterial flagellin), and increased levels of cytokines have been detected systemically in the peripheral blood advocating the existence of abnormal host-microbial interactions and systemic immune responses. Nonetheless, there is wide overlap of data obtained in healthy controls; in addition, the subsets of patients showing immune activation have yet to be clearly identified. Gender, age, geographic differences, genetic predisposition, diet and differences in the intestinal microbiota likely play a role and further research has to be done to clarify their relevance as potential mechanisms in the described immune system dysregulation. Immune activation has stimulated interest for the potential identification of biomarkers useful for clinical and research purposes and the development of novel therapeutic approaches.