Treatment of non-constipated irritable bowel syndrome with the histamine 1 receptor antagonist ebastine: a randomised, double-blind, placebo-controlled trial

Small intestine bacterial overgrowth (SIBO) breath test does not predict symptom severity in gut-brain interaction disorders: role of anxiety, depression, and inflammatory biomarkers

BACKGROUND

The high prevalence of disorders of the gut-brain interaction (DGBI), the availability of breath tests for the diagnosis of small intestine bacterial overgrowth (SIBO) together with some confusion about the concept of SIBO are leading to an increase in the number of SIBO diagnoses.

OBJECTIVE

We aimed to analyze the factors associated with the severity of gastrointestinal symptoms in patients undergoing a SIBO breath test.

METHODS

A cross-sectional observational study including 70 patients who underwent a SIBO test with lactitol and completed questionnaires including the ROME IV criteria for Irritable Bowel Syndrome (IBS), the Irritable Bowel Syndrome Severity Score (IBSSS), and the HAD anxiety and depression scales. Additionally, blood levels of histamine, citrulline, ghrelin, Intestinal-Fatty Acid Binding Protein (I-FABP) and Transient Receptor Potential Cation Channel Subfamily V, Member 1 (TRPV-1) were measured.

RESULTS

The mean age was 45±16 years and 70% were women. Abdominal pain and/or abdominal distension were present in 85% of patients. 44% met IBS Rome IV criteria. IBSSS total score had a correlation with age (-0.354, p<0.001), HAD-A (0.391, p<0.001) and HAD-D (0.409, p<0.001) scores, and histamine levels (0.279, p=0.019). Abdominal pain correlated with levels of histamine (0.320, p<0.05; 0.282, p<0.05) and ghrelin (0.252, p<0.05, 0.347, p<0.05), while abdominal distension correlated with I-FABP levels (0.314, p<0.05). The SIBO test was positive in 75% but did not correlate with symptom severity.

CONCLUSION

We hereby unveiled some factors associated with the severity of abdominal pain and distension such as age, auto-perceived anxiety and depression and some biomarkers but not SIBO test result.

Characterisation of MRGPRX2+ mast cells in irritable bowel syndrome

BACKGROUND

Mast cell activation is an important driver of abdominal pain in irritable bowel syndrome (IBS). While evidence supports the role of IgE-mediated mast cell activation in visceral pain development in IBS, the role of pseudoallergic MRGPRX2-mediated mast cell activation in this process remains unknown.

OBJECTIVE

We investigated whether MRGPRX2-mediated mast cell activation plays a role in abdominal pain development in patients with IBS.

DESIGN

MRGPRX2 expression in mast cells and other immune cells was characterised across colon layers using flow cytometry. We evaluated whether MRGPRX2 agonists trigger mast cell degranulation and transient receptor potential vanilloid 1 (TRPV1) sensitisation in healthy human colonic submucosal plexus samples using live imaging. Rectal biopsies were then collected from patients with IBS and healthy volunteers (HV) and MRGPRX2+ mast cell frequency, MRGPRX2 expression per cell, mast cell degranulation kinetics in response to MRGPRX2 agonists, MRGPRX2 agonistic activity and presence of MRGPRX2 agonists in biopsy supernatants were assessed.

RESULTS

MRGPRX2+ mast cells are enriched in the submucosa and muscularis of the healthy human colon. MRGPRX2 agonists induce mast cell degranulation and TRPV1 sensitisation in the healthy colon submucosa. While the frequency of rectal MRGPRX2+ mast cells was unaltered in IBS, submucosal mast cells showed increased degranulation in response to MRGPRX2 agonists in IBS compared with HV. MRGPRX2 agonistic activity was increased in IBS rectal biopsy supernatant compared with HV, which was associated with increased levels of substance P.

CONCLUSION

The MRGPRX2 pathway is functionally upregulated in the colon of patients with IBS, supporting its role in abdominal pain in IBS.

An evidence-based update on the diagnosis and management of irritable bowel syndrome

INTRODUCTION

Irritable bowel syndrome (IBS) is a disorder of gut-brain interaction affecting 5% of the population. The cardinal symptoms are abdominal pain and altered stool form or frequency.

AREAS COVERED

Diagnosis and management of IBS. We searched the literature for diagnostic accuracy studies, randomized controlled trials, and meta-analyses. A positive diagnosis of IBS, alongside testing to exclude celiac disease, is recommended. Exhaustive investigation has a low yield. Patients should be offered traditional dietary advice. If response is incomplete, specialist dietetic guidance should be considered. Probiotics may be beneficial, but quality of evidence is poor. First-line treatment of constipation is with laxatives, with secretagogues used where these are ineffective. Anti-diarrheal drugs should be used first-line for diarrhea, with second-line drugs including 5-hydroxytryptamine-3 antagonists, eluxadoline, or rifaximin, where available. First-line treatment of abdominal pain should be with antispasmodics, with gut-brain neuromodulators prescribed second-line. Low-dose tricyclic antidepressants, such as amitriptyline, are preferred. Brain-gut behavioral therapies are effective and have evidence for efficacy in patients refractory to standard therapies.

EXPERT OPINION

Despite substantial advances, there remains scope for improvement in terms of both the diagnosis and management of IBS. Reinforcement of positive diagnostic strategies for the condition and novel treatment paradigms are required.

Recent advances in clinical practice: mastering the challenge-managing IBS symptoms in IBD

Many patients with IBD report persisting symptoms, despite resolution of the inflammatory process. Although by definition, a diagnosis of IBS cannot be made, the prevalence of 'IBS in IBD' surpasses the rate of IBS in the global population by fivefold. Because IBS-like symptoms are associated with a decreased quality of life and increased healthcare utilisation in IBD, diagnosis and treatment are necessary. In this review, we summarise the current knowledge on IBS-like symptoms in IBD. A pathophysiological common ground is present, which includes genetic susceptibility, environmental triggers, gut microbial dysbiosis, increased intestinal permeability, visceral hypersensitivity and involvement of brain-gut interaction. When symptoms persist after resolution of inflammation, other GI diseases should be excluded based on the chief complaint, considering any possible psychological co-morbidity early in the diagnostic work-up. Subsequent treatment should be initiated that is evidence-based and often multimodal, including classical and non-classical pharmacological agents as well as lifestyle and microbiota-based approaches, spanning the breadth of the gut, brain and its interaction. Treatment goals in this substantial part of the IBD population should be adapted to not only focus on treating the inflammation but taking care of the patient.

Irritable bowel syndrome: When food is a pain in the gut

Irritable bowel syndrome (IBS) is a chronic gastrointestinal condition associated with altered bowel habits and recurrent abdominal pain, often triggered by food intake. Current treatments focus on improving stool pattern, but effective treatments for pain in IBS are still lacking due to our limited understanding of pathophysiological mechanisms. Visceral hypersensitivity (VHS), or abnormal visceral pain perception, underlies abdominal pain development in IBS, and mast cell activation has been shown to play an important role in the development of VHS. Our work recently revealed that abdominal pain in response to food intake is induced by the sensitization of colonic pain-sensing neurons by histamine produced by activated mast cells following a local IgE response to food. In this review, we summarize the current knowledge on abdominal pain and VHS pathophysiology in IBS, we outline the work leading to the discovery of the role of histamine in abdominal pain, and we introduce antihistamines as a novel treatment option to manage chronic abdominal pain in patients with IBS.

The gut microbiome in disorders of gut-brain interaction

Functional gastrointestinal disorders (FGIDs), chronic disorders characterized by either abdominal pain, altered intestinal motility, or their combination, have a worldwide prevalence of more than 40% and impose a high socioeconomic burden with a significant decline in quality of life. Recently, FGIDs have been reclassified as disorders of gut-brain interaction (DGBI), reflecting the key role of the gut-brain bidirectional communication in these disorders and their impact on psychological comorbidities. Although, during the past decades, the field of DGBIs has advanced significantly, the molecular mechanisms underlying DGBIs pathogenesis and pathophysiology, and the role of the gut microbiome in these processes are not fully understood. This review aims to discuss the latest body of literature on the complex microbiota-gut-brain interactions and their implications in the pathogenesis of DGBIs. A better understanding of the existing communication pathways between the gut microbiome and the brain holds promise in developing effective therapeutic interventions for DGBIs.