Role of visceral sensitivity in the pathophysiology of irritable bowel syndrome

Exploration of differential responses to FODMAPs and gluten in people with irritable bowel syndrome- a double-blind randomized cross-over challenge study

INTRODUCTION

There is large variation in response to diet in irritable bowel syndrome (IBS) and determinants for differential response are poorly understood.

OBJECTIVES

Our aim was to investigate differential clinical and molecular responses to provocation with fermentable oligo-, di-, monosaccharides, and polyols (FODMAPs) and gluten in individuals with IBS.

METHODS

Data were used from a crossover study with week-long interventions with either FODMAPs, gluten or placebo. The study also included a rapid provocation test. Molecular data consisted of fecal microbiota, short chain fatty acids, and untargeted plasma metabolomics. IBS symptoms were evaluated with the IBS severity scoring system. IBS symptoms were modelled against molecular and baseline questionnaire data, using Random Forest (RF; regression and clustering), Parallel Factor Analysis (PARAFAC), and univariate methods.

RESULTS

Regression and classification RF models were in general of low predictive power (Q2 ≤ 0.22, classification rate < 0.73). Out of 864 clustering models, only 2 had significant associations to clusters (0.69 < CR < 0.73, p < 0.05), but with no associations to baseline clinical measures. Similarly, PARAFAC revealed no clear association between metabolome data and IBS symptoms.

CONCLUSION

Differential IBS responses to FODMAPs or gluten exposures could not be explained from clinical and molecular data despite extensive exploration with different data analytical approaches. The trial is registered at www.

CLINICALTRIALS

gov as NCT03653689 31/08/2018.

Systematic Review on Herbal Preparations for Controlling Visceral Hypersensitivity in Functional Gastrointestinal Disorders

BACKGROUND

Visceral hypersensitivity (VH) is an overreaction of the gastrointestinal (GI) tract to various stimuli and is characterized by hyperalgesia and/or allodynia. VH contributes to the etiology of many GI dysfunctions, particularly irritable bowel syndrome (IBS). Although the exact mechanisms underlying VH are yet to be found, inflammation and oxidative stress, psychosocial factors, and sensorimotor alterations may play significant roles in it.

OBJECTIVE

In this review, we provide an overview of VH and its pathophysiological function in GI disorders. Adverse effects of synthetic drugs may make herbal agents a good candidate for pain management. Therefore, in this review, we will discuss the efficacy of herbal agents in the management of VH with a focus on their anti-inflammatory and antioxidant potentials.

METHODS

Data were extracted from clinical and animal studies published in English between 2004 and June, 2020, which were collected from PubMed, Google Scholar, Scopus, and Cochrane Library.

RESULTS

Overall, Radix, Melissia, Glycyrrhizae, Mentha, and Liquorice were the most efficient herbals for VH management in IBS and dyspepsia, predominantly through modulation of the mRNA expression of transient receptor potential vanilloid type-1 (TRPV1) and suppression of 5- hydroxytryptamine 3 (5-HT3) or the serotonin receptors.

CONCLUSION

Considering the positive effects of herbal formulations in VH management, further research on novel herbal and/or herbal/chemical preparations is warranted.

Effects of chronic unpredictable mild stress on gut sensation and function in male mice

Stress has been linked to the development of irritable bowel syndrome (IBS), and various methods have been explored to model IBS in combination with other stimuli. However, it remains unclear whether stress alone can induce IBS in animals. This study aimed to investigate the impact of chronic unpredictable mild stress (CUMS) on gastrointestinal sensation and function in mice and assess the potential of CUMS as a modeling approach for IBS. To evaluate the mice's behavior, we conducted open field test, sucrose preference test and weighed the mice, revealing that CUMS indeed induced anxiety and depression in the mice and caused weight loss. Further analyses, including fecal analysis, a total gastrointestinal transport test, and a colon propulsion test, demonstrated that CUMS led to abnormal defecation and disruptions in gastrointestinal motility in the mice. Additionally, the abdominal withdrawal reflex test indicated an increase in visceral sensitivity in CUMS-exposed mice. Histological examination using hematoxylin and eosin staining revealed no significant histological alterations in the colons of CUMS-exposed mice, but it did show a minor degree of inflammatory cell infiltration. In summary, the findings suggest that CUMS can replicate IBS-like symptoms in mice, offering a novel top-down approach to modeling IBS.

Opposing effects of 5-HT1A receptor agonist buspirone on supraspinal abdominal pain transmission in normal and visceral hypersensitive rats

The serotonergic 5-HT1A receptors are implicated in the central mechanisms of visceral pain, but their role in these processes is controversial. Considering existing evidences for organic inflammation-triggered neuroplastic changes in the brain serotonergic circuitry, the ambiguous contribution of 5-HT1A receptors to supraspinal control of visceral pain in normal and post-inflammatory conditions can be assumed. In this study performed on male Wistar rats, we used microelectrode recording of the caudal ventrolateral medulla (CVLM) neuron responses to colorectal distension (CRD) and electromyography recording of CRD-evoked visceromotor reactions (VMRs) to evaluate post-colitis changes in the effects of 5-HT1A agonist buspirone on supraspinal visceral nociceptive transmission. In rats recovered from trinitrobenzene sulfonic acid colitis, the CRD-induced CVLM neuronal excitation and VMRs were increased compared with those in healthy animals, revealing post-inflammatory intestinal hypersensitivity. Intravenous buspirone (2 and 4 mg/kg) under urethane anesthesia dose-dependently suppressed CVLM excitatory neuron responses to noxious CRD in healthy rats, but caused dose-independent increase in the already enhanced nociceptive activation of CVLM neurons in post-colitis animals, losing also its normally occurring faciliatory effect on CRD-evoked inhibitory medullary neurotransmission and suppressive action on hemodynamic reactions to CRD. In line with this, subcutaneous injection of buspirone (2 mg/kg) in conscious rats, which attenuated CRD-induced VMRs in controls, further increased VMRs in hypersensitive animals. The data obtained indicate a shift from anti- to pronociceptive contribution of 5-HT1A-dependent mechanisms to supraspinal transmission of visceral nociception in intestinal hypersensitivity conditions, arguing for the disutility of buspirone and possibly other 5-HT1A agonists for relieving post-inflammatory abdominal pain.

IBS randomized study: FODMAPs alter bile acids, phenolic- and tryptophan metabolites, while gluten modifies lipids

Diet is considered a culprit for symptoms in irritable bowel syndrome (IBS), although the mechanistic understanding of underlying causes is lacking. Metabolomics, i.e., the analysis of metabolites in biological samples may offer a diet-responsive fingerprint for IBS. Our aim was to explore alterations in the plasma metabolome after interventions with fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) or gluten versus control in IBS, and to relate such alterations to symptoms. People with IBS (n = 110) were included in a double-blind, randomized, crossover study with 1-wk provocations of FODMAPs, gluten, or placebo. Symptoms were evaluated with the IBS severity scoring system (IBS-SSS). Untargeted metabolomics was performed on plasma samples using LC-qTOF-MS. Discovery of metabolite alterations by treatment was performed using random forest followed by linear mixed modeling. Associations were studied using Spearman correlation. The metabolome was affected by FODMAP [classification rate (CR) 0.88, P < 0.0001], but less by gluten intake CR 0.72, P = 0.01). FODMAP lowered bile acids, whereas phenolic-derived metabolites and 3-indolepropionic acid (IPA) were higher compared with placebo. IPA and some unidentified metabolites correlated weakly to abdominal pain and quality of life. Gluten affected lipid metabolism weakly, but with no interpretable relationship to IBS. FODMAP affected gut microbial-derived metabolites relating to positive health outcomes. IPA and unknown metabolites correlated weakly to IBS severity. Minor symptom worsening by FODMAP intake must be weighed against general positive health aspects of FODMAP. The gluten intervention affected lipid metabolism weakly with no interpretable association to IBS severity. Registration: www.clinicaltrials.gov as NCT03653689.NEW & NOTEWORTHY In irritable bowel syndrome (IBS), fermentable oligo-, di-, monosaccharides, and polyols (FODMAPs) affected microbial-derived metabolites relating to positive health outcomes such as reduced risk of colon cancer, inflammation, and type 2 diabetes, as shown in previous studies. The minor IBS symptom induction by FODMAP intake must be weighed against the positive health aspects of FODMAP consumption. Gluten affected lipids weakly with no association to IBS severity.

Non-pharmacologic approaches to treatment of pediatric functional abdominal pain disorders

Functional abdominal pain disorders (FAPDs) affect up to 25% of children in the United States. These disorders are more recently known as disorders of "brain-gut" interaction. The diagnosis is based on the ROME IV criteria, and requires the absence of an organic condition to explain the symptoms. Although these disorders are not completely understood, several factors have been involved in the pathophysiology including disordered gut motility, visceral hypersensitivity, allergies, anxiety/stress, gastrointestinal infection/inflammation, as well dysbiosis of the gut microbiome. The pharmacologic and non-pharmacologic treatments for FAPDs are directed to modifying these pathophysiologic mechanisms. This review aims to summarize the non-pharmacologic interventions used in the treatment of FAPDs including dietary modifications, manipulation of the gut microbiome (neutraceuticals, prebiotics, probiotics, synbiotics and fecal microbiota transplant) and psychological interventions that addresses the "brain" component of the brain-gut axis (cognitive behavioral therapy, hypnotherapy, breathing and relaxation techniques). In a survey conducted at a large academic pediatric gastroenterology center, 96% of patients with functional pain disorders reported using at least 1 complementary and alternative medicine treatment to ameliorate symptoms. The paucity of data supporting most of the therapies discussed in this review underscores the need for large randomized controlled trials to assess their efficacy and superiority compared to other treatments.

Targeting the endocannabinoid system for the treatment of abdominal pain in irritable bowel syndrome

The management of visceral pain in patients with disorders of gut-brain interaction, notably irritable bowel syndrome, presents a considerable clinical challenge, with few available treatment options. Patients are increasingly using cannabis and cannabinoids to control abdominal pain. Cannabis acts on receptors of the endocannabinoid system, an endogenous system of lipid mediators that regulates gastrointestinal function and pain processing pathways in health and disease. The endocannabinoid system represents a logical molecular therapeutic target for the treatment of pain in irritable bowel syndrome. Here, we review the physiological and pathophysiological functions of the endocannabinoid system with a focus on the peripheral and central regulation of gastrointestinal function and visceral nociception. We address the use of cannabinoids in pain management, comparing them to other treatment modalities, including opioids and neuromodulators. Finally, we discuss emerging therapeutic candidates targeting the endocannabinoid system for the treatment of pain in irritable bowel syndrome.

Randomised clinical trial: effects of MD-7246 on irritable bowel syndrome with diarrhoea

BACKGROUND

MD-7246, a delayed-release formulation of linaclotide, is designed to target the ileocaecal junction and caecum with the aim of relieving abdominal pain independently of bowel function.

AIMS

To evaluate the efficacy, safety and dose-response of MD-7246 in patients with irritable bowel syndrome with diarrhoea (IBS-D).

METHODS

A randomised, double-blind, phase 2 clinical trial enrolled adult patients with IBS-D (Rome IV criteria). Patients were randomised to placebo or once-daily oral MD-7246 300, 600 or 1200 μg for 12 weeks. Abdominal and bowel symptoms were assessed daily. Key efficacy endpoints were change from baseline in abdominal pain and responder rates for a 30% reduction in abdominal pain in 6/12 weeks. Additional abdominal pain responder and exploratory bowel function endpoints were also assessed.

RESULTS

Among the 388 randomised patients, there was no significant difference in mean change from baseline in abdominal pain between the MD-7246 300 μg, 600 μg and 1200 μg groups and placebo (-1.93, -1.58, -1.95 and - 2.01, respectively; p > 0.05 for each group vs placebo). The abdominal pain responder rates in the MD-7246 groups were similar to or lower than those in the placebo group. All doses of MD-7246 had a minimal effect on bowel function and were generally well tolerated.

CONCLUSIONS

MD-7246 at the doses studied did not improve abdominal pain relative to placebo in an IBS-D patient population. Similarly, most additional efficacy endpoints showed no improvement with MD-7246 relative to placebo.

Similarities and differences in constipation phenotypes between Lep knockout mice and high fat diet-induced obesity mice

CRISPR-Cas9-mediated leptin (Lep) knockout (KO) mice exhibited prominent phenotypes for constipation, even though they were not compared with other model animals. This study compared the stool excretion, gastrointestinal motility, histological structure, mucin secretion, and enteric nerve function in Lep KO and high fat diet (HFD)-treated mice to determine if there were differences in their phenotypes for constipation. Most obesity phenotypes, including fat weight, adipocyte size, expression of lipolytic proteins (HSL, perilipin, and ATGL), and glucose concentrations, were detected similarly in the Lep KO and HFD-treated mice. They showed a similar decrease in the excretion parameters, including the stool number, weight, and water content, while the same pattern was detected in the gastrointestinal motility and intestinal length. A similar decrease in the mucosal layer thickness, muscle thickness, ability for mucin secretion, and expression of water channel (aquaporin 3 and 8) genes was detected in the mid-colon of the Lep KO and HFD-treated mice, but the alteration rate in some levels was greater in the HFD-treated group than the Lep KO mice. On the other hand, the levels of c-kit, nNOS, NSE, and PGP9.5 expression for the enteric neurons and intestitial cells of Cajal (ICC) were remarkably lower in the mid-colon of the HFD-treated mice than in the Lep KO mice, but the level of most proteins in both groups remained lower than those in the control group. A similar alteration pattern in the expression of muscarinic acetylcholine receptors (mAChRs) and serotonin receptors was detected in the Lep KO and HFD-treated mice. These results suggest that most phenotypes for obesity-induced constipation were similarly detected in the Lep KO and HFD-treated mice, but there was a difference in the regulatory function of the enteric nervous system (ENS).

The effect of self-management online modules plus nurse-led support on pain and quality of life among young adults with irritable bowel syndrome: A randomized controlled trial

BACKGROUND

Irritable bowel syndrome is a chronic pain condition that needs life-long self-management. However, the effect of self-management among young adults with irritable bowel syndrome is limited.

OBJECTIVES

This study aimed to examine the effect of a nurse-led self-management program on pain, symptoms, and quality of life among young adults with irritable bowel syndrome.

DESIGN

A randomized controlled trial.

SETTINGS AND PARTICIPANTS

Eighty young adults with irritable bowel syndrome recruited from two campuses of a public university and two gastrointestinal clinics were randomly assigned into a self-management online education and learning modules alone group (Online Modules, n = 41) or a nurse-led one-to-one consultation plus self-management online education and learning modules group (Nurse-Led Online Modules, n = 39). Twenty-one healthy controls were also recruited from these two campuses.

METHODS

Both the intervention groups received ten online modules after baseline data collection. Participants in the Nurse-Led Online Modules group received additional three nurse-led one-to-one consultations at baseline, 6- and 12-week follow-ups. Self-reported pain, symptoms, quality of life, self-efficacy for managing chronic disease, and coping were measured at baseline, and 6- and 12-week follow-ups among the participants with irritable bowel syndrome. The healthy controls completed data collection of pain and symptoms at baseline and the 12-week follow-up. The intervention effects across study time points and the comparisons between the two interventional groups were analyzed using linear mixed models. A longitudinal mediation analysis was also conducted to explore the mediation effects of self-management mechanisms of the interventions.

RESULTS

Both the intervention groups showed significant interventional effects on decreasing pain intensity and pain interference and increasing quality of life at the 12-week follow-up (all p < 0.05). At the 12-week follow-up, the Nurse-Led Online Modules significantly reduced anxiety (p = 0.016) and had a significant greater improvement in quality of life than the Online Modules (p = 0.040). Increased self-efficacy mediated the intervention effect of the Nurse-Led Online Modules group on reducing pain interference and improving quality of life, while the effect of the Online Modules was mediated through decreasing inefficient coping strategy-catastrophizing.

CONCLUSIONS

This study showed that both the pain self-management online education and nurse-led intervention were effective for alleviating pain and improving quality of life among young adults with irritable bowel syndrome by targeting the self-management process. The nurse-led intervention had a better outcome than the online education alone in improving quality of life.

REGISTRATION NUMBER

NCT03332537.

Irritable bowel syndrome is strongly associated with the primary and idiopathic mast cell disorders

BACKGROUND

Mounting evidence supports a mechanistic association between irritable bowel syndrome (IBS) symptoms and mast cell hyperactivity. Yet, association between IBS and mast cell disorders (MCDs) has not been studied. We examined this association using two large databases and verified with manual chart review.

METHODS

The IBM Watson Health Explorys database (Somers, NY), an aggregate of electronic health record (EHR) data from over two dozen US healthcare systems, and Epic's SlicerDicer tool, a self-service tool containing de-identified data from the Epic EHR, were used to identify patients with IBS and MCDs. Patients with organic gastrointestinal disease or diseases associated with secondary mast cell hyperproliferation were excluded. Results were verified with manual chart review from two academic centers.

KEY RESULTS

Up to 4% of IBS patients had a comorbid MCD. IBS was strongly associated with all MCDs. The strongest association was between IBS and mast cell activation syndrome (OR 16.3; 95% CI 13.1-20.3). Odds ratios for IBS+urticaria, IBS+idiopathic urticaria, IBS+non-malignant mastocytosis, and IBS+mast cell malignancy ranged from 4.5 to 9.9. Patients from each of these overlap cohorts were predominantly female, and the overlap occurred with all IBS subtypes. Thorough endoscopic evaluation and comorbid mood disorders and migraines are more common in the overlap cohorts than in IBS alone.

CONCLUSIONS/INFERENCES

In a large US database encompassing >53 million patients over >20 years, patients with IBS are at least 4 times more likely to have a MCD than the general population. Further study of mast cell involvement in the pathogenesis of IBS is warranted.

Pathophysiological Commonality Between Irritable Bowel Syndrome and Metabolic Syndrome: Role of Corticotropin-releasing Factor-Toll-like Receptor 4-Proinflammatory Cytokine Signaling

Irritable bowel syndrome (IBS) displays chronic abdominal pain with altered defecation. Most of the patients develop visceral hypersensitivity possibly resulting from impaired gut barrier and altered gut microbiota. We previously demonstrated that colonic hyperpermeability with visceral hypersensitivity in animal IBS models, which is mediated via corticotropin-releasing factor (CRF)-Toll-like receptor 4 (TLR4)-proinflammatory cytokine signaling. CRF impairs gut barrier via TLR4. Leaky gut induces bacterial translocation resulting in dysbiosis, and increases lipopolysaccharide (LPS). Activation of TLR4 by LPS increases the production of proinflammatory cytokines, which activate visceral sensory neurons to induce visceral hypersensitivity. LPS also activates CRF receptors to further increase gut permeability. Metabolic syndrome (MS) is a cluster of cardiovascular risk factors, including insulin resistance, obesity, dyslipidemia, and hypertension, and recently several researchers suggest the possibility that impaired gut barrier and dysbiosis with low-grade systemic inflammation are involved in MS. Moreover, TLR4-proinflammatory cytokine contributes to the development of insulin resistance and obesity. Thus, the existence of pathophysiological commonality between IBS and MS is expected. This review discusses the potential mechanisms of IBS and MS with reference to gut barrier and microbiota, and explores the possibility of existence of pathophysiological link between these diseases with a focus on CRF, TLR4, and proinflammatory cytokine signaling. We also review epidemiological data supporting this possibility, and discuss the potential of therapeutic application of the drugs used for MS to IBS treatment. This notion may pave the way for exploring novel therapeutic approaches for these disorders.

Dietary Fat Effect on the Gut Microbiome, and Its Role in the Modulation of Gastrointestinal Disorders in Children with Autism Spectrum Disorder

Children with autism spectrum disorder (ASD) report a higher frequency and severity of gastrointestinal disorders (GID) than typically developing (TD) children. GID-associated discomfort increases feelings of anxiety and frustration, contributing to the severity of ASD. Emerging evidence supports the biological intersection of neurodevelopment and microbiome, indicating the integral contribution of GM in the development and function of the nervous system, and mental health, and disease balance. Dysbiotic GM could be a contributing factor in the pathogenesis of GID in children with ASD. High-fat diets may modulate GM through accelerated growth of bile-tolerant bacteria, altered bacterial ratios, and reduced bacterial diversity, which may increase the risk of GID. Notably, saturated fatty acids are considered to have a pronounced effect on the increase of bile-tolerant bacteria and reduction in microbial diversity. Additionally, omega-3 exerts a favorable impact on GM and gut health due to its anti-inflammatory properties. Despite inconsistencies in the data elaborated in the review, the dietary fat composition, as part of an overall dietary intervention, plays a role in modulating GID, specifically in ASD, due to the altered microbiome profile. This review emphasizes the need to conduct future experimental studies investigating the effect of diets with varying fatty acid compositions on GID-specific microbiome profiles in children with ASD.

[Irritable bowel syndrome: Role of gut microbiota]

Irritable Bowel Syndrome (IBS) is a functional disorder of the gastrointestinal tract with high prevalence. IBS, in particular the diarrheic subtype, is associated with alterations in gut microbiota composition and functionality, called dysbiosis. However, the treatment of this disease mainly relies on the patient's symptoms without considering the gut microbiota perturbations. In this review, we present epidemiological data about IBS-D. Then, we describe the main pathophysiological mechanisms associated with this disease, by focusing on gut microbiota alterations. We end up discussing the current therapies now available.

Specific and common mediators of gastrointestinal symptom improvement in patients undergoing education/support vs. cognitive behavioral therapy for irritable bowel syndrome

Objective: This study sought to characterize change mechanisms that underlie gastrointestinal (GI) symptom improvement in IBS patients undergoing two dosages of CBT for IBS as compared to a nondirective education/support (EDU) condition. Method: Data were collected in the context of a large clinical trial that randomized 436 Rome III-diagnosed IBS patients (Mage = 41, 80 % female) to standard, clinic-based CBT (S-CBT), a largely home-based version with minimal therapist contact (MC-CBT) or Education/Support that controlled for nonspecific effects. Outcome was measured with the IBS-version of the Clinical Global Improvement scale that was administered at Week 5 and 2-week posttreatment (Week 12). Potential mediators (IBS Self-efficacy (IBS-SE), pain catastrophizing, fear of GI symptoms, and treatment alliance were assessed at Weeks 3, 5, and 8 during treatment with the exception of treatment expectancy that was measured at the end of Session 1. Results: IBS-SE, a positive treatment expectancy for symptom improvement, and patient-therapist agreement on tasks for achieving goals mediated effects of CBT early in treatment (rapid response, RR) and at posttreatment. Notwithstanding their different intensities, both CBT conditions had comparable RR rates (43%-45%) and significantly greater than the EDU RR rate of 22%. While pain catastrophizing, fear of GI symptoms, and patient-therapist emotional bonding related to posttreatment symptom improvement, none of these hypothesized mediators explained differences between CBT and EDU, thereby lacking the mechanistic specificity of IBS-SE, task agreement, and treatment expectancy. Conclusion: Findings suggest that CBT-induced GI symptom improvement may be mediated by a constellation of CBT-specific (IBS-SE) and nonspecific (task agreement, treatment expectancy) processes that reciprocally influence each other in complex ways to catalyze, improve, and sustain IBS symptom relief. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The Ventrolateral Periaqueductal Gray Contributes to Depressive-Like Behaviors in Recovery of Inflammatory Bowel Disease Rat Model

BACKGROUND

Patients with inflammatory bowel disease (IBD) experience depression, even in the remission phase of IBD symptoms. Although mapping depression-associated brain regions through the gut-brain axis can contribute to understanding the process, the mechanisms remain unclear. Our previous results support the idea that glutamatergic transmission in the ventrolateral periaqueductal gray (vlPAG) mediates stress-induced depression-like behaviors. Thus, we hypothesize that the vlPAG plays a role in regulating depression during remission of IBD.

METHODS

We used dextran sulfate sodium (DSS)-induced visceral pain model to evoke depression-like behaviors, assessed by tail suspension test (TST) and sucrose preference test (SPT), and electrophysiological recordings from vlPAG.

RESULTS

Symptoms of animals modeling IBD were relieved by replacing DSS solution with normal drinking water, but their depression-like behaviors sustained. Moreover, the impairment of glutamatergic neurotransmission in vlPAG was sustained as well. Pharmacologically, microinfusion of the glutamate receptor 1 (GluR1) antagonist NASPM into vlPAG mimicked the depression-like behaviors. Furthermore, intra-vlPAG application of AMPA and AMPA receptor-mediated antidepressant (2R,6R)-hydroxynorketamine [(2R,6R)-HNK] reversed the DSS-induced depression-like behaviors in the remission phase of visceral abnormalities.

CONCLUSION

Our results suggest that vlPAG glutamatergic transmission mediates depression-like behaviors during remission of DSS-induced visceral pain, suggesting that vlPAG mapping to the gut-brain axis contributes to depression during remission of IBD.

Increased expression of brain-derived neurotrophic factor is correlated with visceral hypersensitivity in patients with diarrhea-predominant irritable bowel syndrome

BACKGROUND

Visceral hypersensitivity is considered to play a vital role in the pathogenesis of irritable bowel syndrome (IBS). Neurotrophins have drawn much attention in IBS recently. Brain-derived neurotrophic factor (BDNF) was found to mediate visceral hypersensitivity via facilitating sensory nerve growth in pre-clinical studies. We hypothesized that BDNF might play a role in the pathogenesis of diarrhea-predominant IBS (IBS-D).

AIM

To investigate BDNF levels in IBS-D patients and its role in IBS-D pathophysiology.

METHODS

Thirty-one IBS-D patients meeting the Rome IV diagnostic criteria and 20 age- and sex-matched healthy controls were recruited. Clinical and psychological assessments were first conducted using standardized questionnaires. Visceral sensitivity to rectal distension was tested using a high-resolution manometry system. Colonoscopic examination was performed and four mucosal pinch biopsies were taken from the rectosigmoid junction. Mucosal BDNF expression and nerve fiber density were analyzed using immunohistochemistry. Mucosal BDNF mRNA levels were quantified by quantitative real-time polymerase chain reaction. Correlations between these parameters were examined.

RESULTS

The patients had a higher anxiety score [median (interquartile range), 6.0 (2.0-10.0) vs 3.0 (1.0-4.0), P = 0.003] and visceral sensitivity index score [54.0 (44.0-61.0) vs 21.0 (17.3-30.0), P < 0.001] than controls. The defecating sensation threshold [60.0 (44.0-80.0) vs 80.0 (61.0-100.0), P = 0.009], maximum tolerable threshold [103.0 (90.0-128.0) vs 182.0 (142.5-209.3), P < 0.001] and rectoanal inhibitory reflex threshold [30.0 (20.0-30.0) vs 30.0 (30.0-47.5), P = 0.032] were significantly lower in IBS-D patients. Intestinal mucosal BDNF protein [3.46E-2 (3.06E-2-4.44E-2) vs 3.07E-2 (2.91E-2-3.48E-2), P = 0.031] and mRNA [1.57 (1.31-2.61) vs 1.09 (0.74-1.42), P = 0.001] expression and nerve fiber density [4.12E-2 (3.07E-2-7.46E-2) vs 1.98E-2 (1.21E-2-4.25E-2), P = 0.002] were significantly elevated in the patients. Increased BDNF expression was positively correlated with abdominal pain and disease severity and negatively correlated with visceral sensitivity parameters.

CONCLUSION

Elevated mucosal BDNF may participate in the pathogenesis of IBS-D via facilitating mucosal nerve growth and increasing visceral sensitivity.

Comparison of Rectal and Esophageal Sensitivity in Women With Functional Heartburn

This study tested the primary hypothesis that there is a correlation of maximum pain threshold (MPT) in the esophagus and rectum in persons with functional heartburn. Secondary aims evaluated correlations with initial perception threshold (IPT) and pain threshold (PT). This study explored objective sensory endpoints of IPT, PT, and MPT in the esophagus and rectum of 14 females with functional heartburn to determine whether visceral hypersensitivity is generalized or organ-specific. Data on volume and pressure measurements at IPT, PT, and MPT with esophageal and rectal barostat distention were collected. The relationship of sensation and pain to volume, pressure, and compliance was analyzed. Esophageal and rectal IPT balloon volume scores were highly and significantly correlated (r = .61, p = .02). Esophageal and rectal PT balloon volume scores were highly and significantly correlated (r = .6, p = .02). Esophageal and rectal MPT balloon volume scores were not correlated (r = .35, p = .26). The correlation of visceral sensitivity in the esophagus and rectum in persons with functional heartburn supports the hypothesis that visceral sensory changes in functional gastrointestinal disorders are not organ specific.

BDNF contributes to IBS-like colonic hypersensitivity via activating the enteroglia-nerve unit

The over-expressed colonic brain-derived neurotrophic factor (BDNF) has been reported to be associated with abdominal pain in patients with irritable bowel syndrome (IBS). However, the neuropathological mechanism is unclear. We here investigated the involvement of enteroglial cells (EGCs) and enteric nerves in IBS-like visceral hypersensitivity. We showed that glial fibrillary acidic protein (GFAP), tyrosine receptor kinase B (TrkB) and substance P (SP) were significantly increased in the colonic mucosa of IBS patients. The upregulation of those proteins was also observed in the colon of mice with visceral hypersensitivity, but not in the colon of BDNF(+/-) mice. Functionally, TrkB or EGC inhibitors, or BDNF knockdown significantly suppressed visceral hypersensitivity in mice. Using the EGC cell line, we found that recombinant human BDNF (r-HuBDNF) could directly activate EGCs via the TrkB-phospholipase Cγ1 pathway, thereby inducing a significant upregulation of SP. Moreover, supernatants from r-HuBDNF-activated EGC culture medium, rather than r-HuBDNF alone, triggered markedly augmented discharges in isolated intestinal mesenteric afferent nerves. r-HuBDNF alone could cause mesenteric afferent mechanical hypersensitivity independently, and this effect was synergistically enhanced by activated EGCs. We conclude that EGC-enteric nerve unit may be involved in IBS-like visceral hypersensitivity, and this process is likely initiated by BDNF-TrkB pathway activation.

Targeting tachykinin receptors for the treatment of functional gastrointestinal disorders with a focus on irritable bowel syndrome

BACKGROUND

Tachykinins (TKs) are a family of endogenous peptides widely expressed in the central and in the peripheral nervous systems as well as in the gastrointestinal (GI) tract. They act as full agonists at three different membrane receptors neurokinin (NK) 1, NK2, and NK3, which are G protein-coupled receptors and in the GI tract are expressed both on neurons and effector cells.

PURPOSE

This article reviews the literature concerning the role of TKs in the GI tract function in physiological and pathological conditions and their potential relevance in the treatment of functional GI disorders with particular reference to irritable bowel syndrome (IBS). The efficacy of NK1 antagonists in chemotherapy-induced and postoperative nausea and vomiting is well established. While pharmacodynamic studies have reported conflicting and negative results concerning the effects of NK1 and of NK3 antagonists, respectively, on the GI tract function in humans, clinical studies applying the NK3 antagonist talnetant in IBS-D were negative. Pharmacodynamic studies applying NK2 antagonists have suggested a role for antagonism of NK2 receptors in modulation of GI chemical-induced altered motility and of stress-induced altered bowel habits. Clinical studies and in particular a recently completed Phase 2 study have reported that the NK2 antagonist ibodutant is effective and safe in treating symptoms of D-IBS, especially in females.

Visceral Hypersensitivity and Altered Colonic Motility in Type 2 Diabetic Rat

Background/Aims

Abnormal visceral sensitivity and disordered motility are common in patients with diabetes mellitus. The purpose of the present study was to investigate whether visceral sensation and bowel motility were altered in a rat model of type 2 diabetes mellitus accompanied by weight loss.

Methods

A type 2 diabetic rat model in adulthood was developed by administrating streptozotocin (STZ; 90 mg/kg, i.p.) to neonatal rats. Eight weeks after STZ administration, rats with blood glucose level of 200 mg/dL or higher were selected and used as diabetic group (n = 35) in this study. Abdominal withdrawal reflex and arterial pulse rate were measured to examine visceral nociception induced by colorectal distension (0.1–1.0 mL). The amplitude, frequency, and area under the curve (AUC) of spontaneous phasic contractions of colonic circular muscles were recorded in vitro to examine colonic motility.

Results

STZ-treated diabetic rats gained significantly less weight for 8 weeks than control (P < 0.01). Forty-eight percent of the diabetic rats showed enhanced visceral nociceptive response to colorectal distension. Diabetic rats did not differ from control rats in colorectal compliance. However, the frequency and AUC, not the amplitude, of colonic spontaneous contraction in vitro was significantly decreased in diabetic rats compared to control rats (P < 0.01 in frequency and P < 0.05 in AUC).

Conclusions

These results demonstrate visceral hypersensitivity and colonic dysmotility in a rat model of type 2 diabetes mellitus accompanied by weight loss.

Irritable bowel syndrome: Is it "irritable brain" or "irritable bowel"?

Irritable bowel syndrome (IBS) has been recognized as one of the most common and best studied disorders among the group of functional gastrointestinal disorders. It is a functional bowel disorder in which abdominal pain or discomfort is associated with defecation or a change in bowel habit. In the Western world, IBS appears to affect up to 20% of the population at any given time but in Asian countries, the median value of IBS prevalence defined by various criteria ranges between 6.5% and 10.1%, and community prevalence of 4% is found in North India. Those attending gastroenterology clinics represent only the tip of the iceberg. The disorder substantially impairs the quality of life, and the overall health-care costs are high. IBS has therefore gained increased attention from clinicians, researchers, and pharmaceutical industries. It is often frustrating to both patients and physicians as the disease is usually chronic in nature and difficult to treat. However, the understanding of IBS has been changing from time to time and still most of its concepts are unknown. In this review we have discussed, debated, and synthesized the evidence base, focusing on underlying mechanisms in the brain and bowel. We conclude that it is both brain and bowel mechanisms that are responsible. The clinical implication of such mechanisms is discussed.

New and Emerging Treatment Options for Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder associated with abdominal pain, diarrhea, constipation, or a mix of symptoms. The pathophysiology of IBS is not completely understood but appears to involve genetics, the gut microbiome, immune activation, altered intestinal permeability, and brain-gut interactions. There is no gold standard for diagnosis. Several sets of symptom-based guidelines exist. Treatment strategies for IBS may include both nonpharmacologic and pharmacologic approaches. Lifestyle modifications that aim to improve exercise, sleep, diet, and stress may be warranted. Recent data suggest that a gluten-free diet and a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) may benefit some patients. For patients with diarrhea-predominant IBS, treatment options include the synthetic peripheral μ-opioid receptor agonist loperamide, antispasmodic agents, antidepressants, serotonin 5-HT3 antagonists, and the gut-specific antibiotic rifaximin. Ongoing research is evaluating the use of probiotics. For patients with constipation-predominant IBS, therapeutic strategies may include dietary fiber, laxatives, and the prosecretory agents lubiprostone and linaclotide. Research is continuing to optimize the use of available agents and evaluating new approaches to further improve the care of patients with IBS.

Chronic severe constipation: current pathophysiological aspects, new diagnostic approaches, and therapeutic options

Chronic constipation is a considerable problem because it significantly affects the quality of a patient's life. Constipation can be diagnosed at every age and is more frequent in women and among the elderly. In epidemiological studies, its incidence is estimated at 2-27% in the general population. Chronic constipation may be primary or secondary. However, primary constipation (functional or idiopathic) can be classified into normal transit constipation, slow transit constipation, and pelvic outlet obstruction. In this review we make an attempt to present the current pathophysiological aspects and new therapeutic options for chronic idiopathic constipation, particularly highlighting the value of patient assessment for accurate diagnosis of the cause of the problem, thus helping in the choice of appropriate treatment.

Abdominal Pain-Predominant Functional Gastrointestinal Disorders in Jordanian School Children

Background

Recurrent abdominal pain (RAP) is a common complaint in children. Significant portion of them are of functional origin. This study aimed to assess the prevalence of abdominal pain-predominant functional gastrointestinal disorder (FGID) and its types in Jordanian school children.

Methods

This is a school-based survey at south Jordan. Information using the self-reporting form of the Questionnaire on Pediatric Gastrointestinal Symptoms-Rome III Version (QPGS-RIII) - the official Arabic translation - was collected. Classes from academic years (grades) 6 - 8 were selected. SPSS Statistical Package Version 17 (IBM, Armonk, NY, USA) was used. Categorical data were analyzed using Fisher’s exact test, and continuous data were analyzed using t-test. P < 0.05 was considered significant.

Results

Five hundred questionnaires were distributed, and 454 returned answered (91%). Two hundred twenty-nine (50.8%) were males. The average age of participants was 12.7 years (11 - 15 years). One hundred sixteen (25.7%) had abdominal pain-predominant FGID. Seventy-nine (68%) of them were females. Forty-seven (10.6%) had irritable bowel syndrome (IBS). Thirty-six (8%), 17 (3.8%), 11 (2.4%) and five (1.1%) had abdominal migraine, functional abdominal pain, functional abdominal pain syndrome and functional dyspepsia, respectively.

Conclusion

Abdominal pain-predominant FGID has become a major health issue in Jordanian children. One of four children between the ages of 11 and 15 years exhibits at least one abdominal pain-predominant FGID. The most common form of abdominal pain-predominant FGID in our children was IBS. Females are affected more often than males. Intestinal and extra-intestinal symptoms are seen regularly with abdominal pain-predominant FGIDs.

Effects of Chili Treatment on Gastrointestinal and Rectal Sensation in Diarrhea-predominant Irritable Bowel Syndrome: A Randomized, Double-blinded, Crossover Study

Background/Aims

Whether, chronic chili ingestion can desensitize transient receptor potential vanilloid type 1 receptors in gastrointestinal (GI) tract leading to decrease GI symptoms and sensation in diarrhea-predominant irritable bowel syndrome (IBS-D) patients has not been well explored. The aim of this study was to determine the effects of 6-week chili treatment on postprandial GI symptoms and rectal sensation in response to balloon distention in IBS-D patients.

Methods

Sixteen IBS-D patients received placebo or chili capsules before meals 3 times/day for 6 weeks in a randomized, double-blinded, crossover fashion with 4-week washout period. Postprandial GI symptoms were evaluated. All patients underwent a rectal barostat study to evaluate rectal sensory threshold at the end of each treatment.

Results

The maximum postprandial abdominal burning scores were similar between both treatments at baseline (1.4 [0.0–2.0] vs. 1.1 [0.0–2.8], P > 0.05) but were significantly decreased after chili (0.0 [0.0–0.5] vs. 0.3 [0.0–1.6], P < 0.05) at the end of treatment. The chili treatment significantly increased sensory threshold for the first rectal sensation (median [interquartile range]:16 [12–16] mmHg vs. 8 [8–16] mmHg, P < 0.05) however, there was no significant effect on rectal compliance (7.3 ± 1.0 vs. 7.1 ± 1.8 mL/mmHg). Other postprandial GI symptoms did not vary significantly between both treatments at baseline and the end of treatment.

Conclusions

In IBS-D patients, 6-week chili ingestion significantly decreased postprandial abdominal burning and increased the rectal sensory threshold. These findings suggest a desensitization effect of chili ingestion on transient receptor potential vanilloid type 1 receptors in the proximal gut and rectum.

Effect of DA-9701 on colorectal distension-induced visceral hypersensitivity in a rat model

BACKGROUND/AIMS

DA-9701 is a newly developed drug made from the vegetal extracts of Pharbitidis semen and Co-rydalis tuber. The aim of this study was to evaluate the effect of DA-9701 on colorectal distension (CRD)-induced visceral hypersensitivity in a rat model.

METHODS

Male Sprague-Dawley rats were subjected to neonatal colon irritation (CI) using CRD at 1 week after birth (CI group). At 6 weeks after birth, CRD was applied to these rats with a pressure of 20 to 90 mm Hg, and changes in the mean arterial pressure (MAP) were measured at baseline (i.e., without any drug administration) and after the administration of different doses of DA-9701.

RESULTS

In the absence of DA-9701, the MAP changes after CRD were significantly higher in the CI group than in the control group at all applied pressures. In the control group, MAP changes after CRD were not significantly affected by the administration of DA-9701. In the CI group, however, the administration of DA-9701 resulted in a significant decrease in MAP changes after CRD. The administration of DA-9701 at a dose of 1.0 mg/kg produced a more significant decrease in MAP changes than the 0.3 mg/kg dose.

CONCLUSIONS

The administration of DA-9701 resulted in a significant increase in pain threshold in rats with CRD-induced visceral hypersensitivity.

Psychological disorders in gastrointestinal disease: epiphenomenon, cause or consequence?

BACKGROUND

Psychological disorders have been associated with irritable bowel syndrome (IBS) for decades in the absence of other objective etiology. However, such associations are also evident in other chronic diseases with more clearly defined pathogenesis such as ulcerative colitis. In this study, we examined the prevalence and severity of psychological disorders among IBS and ulcerative colitis (UC) patients relative to healthy controls.

METHODS

A review was conducted of English-language literature to identify case-control studies reporting the prevalence of depression or anxiety in IBS and UC populations relative to healthy controls. Our primary endpoint was the pooled prevalence or average score of depression or anxiety in an IBS or UC population relative to healthy control.

RESULTS

Seven case-control studies evaluating IBS and three evaluating UC were included. All IBS and UC studies reported excess prevalence and severity of depression as well as anxiety, relative to healthy controls. The prevalence of depression in excess of healthy controls was 39% in UC case-control trials and 33% in IBS studies, and excess anxiety was present in UC (42%) and IBS (19%) case-control trials as well. Anxiety and depression scores were higher (representing more severe symptoms) in both UC and IBS patients compared to healthy controls.

CONCLUSIONS

Anxiety and depressive disorders are associated with both IBS and UC. The non-specific association between these psychological and gastrointestinal disorders could suggest that chronic gastrointestinal illness might affect psychosocial behavior.

Effect of early-life stress on chronic functional visceral pain and CRH R1 expression in the paraventricular nucleus in adult rats

AIM: To assess the effect of early-life stress on chronic functional visceral pain and expression of corticotropin releasing hormone receptor 1 (CRH R1) in the hypothalamic paraventricular nucleus (PVN) of rats with chronic functional visceral pain to provide a theoretical basis for the prevention and treatment of abdominal pain-related functional gastrointestinal disorders.

METHODS: Neonatal rats were randomly divided into six groups (n = 10), including a male control group, a female control group, a male separation group, a female separation group, a male distension group and a female distension group. HE staining was used to detect histologic changes in the colon tissue. Western blot and immunofluorescence were used to detect the changes in CRH R1 expression in the PVN. Brain tissue sections were immunostained for c-fos as a marker for activation of the PVN. Furthermore, normal male adult rats were randomly divided into three groups (normal control, saline and lidocaine, n = 6 for each group) to observe the role of PVN in the regulation of chronic functional visceral pain in normal rats by intra-PVN administration of lidocaine (1%, 0.3 µL).

RESULTS: Neonatal maternal separation (NMS) or colorectal distension (CRD) resulted in chronic visceral hypersensitivity without pathological changes in the colon tissue. There was no gender difference in the above change. Electrical discharge of the abdominal external oblique muscle in rats 10, 20, and 30 min after intra-PVN microinjection of 1% lidocaine was decreased significantly under the stimulation of CRD at 60 mmHg compared with normal controls and saline rats. The expression of CRH R1 and c-fos in the PVN of NMS and CRD rats increased compared with control rats.

CONCLUSION: Early-life stress can lead to chronic functional visceral pain in rats in adulthood. Allodynia caused by NMS is more obvious than that by CRD. The PVN and CRH R1 may be involved in the pathogenesis of chronic functional visceral pain caused by early-life stress.

Possible etiology of improvements in both quality of life and overlapping gastroesophageal reflux disease by proton pump inhibitor treatment in a prospective randomized controlled trial

Background

Symptoms suggestive of functional dyspepsia (FD) and irritable bowel syndrome (IBS) frequently overlap with those of gastroesophageal reflux disease. Despite the high prevalence of symptomatic overlap, the underlying etiology remains poorly defined. We assessed the correlation of symptomatic relief and health-related quality of life (HRQoL) with healing of reflux esophagitis to further derive insights into the underlying etiology.

Methods

626 patients with reflux esophagitis were enrolled into one of two treatment groups (classical healing concept or the complete remission concept) to investigate differences in treatment intensity. Patients were treated with pantoprazole until esophageal mucosal healing. Remission was followed for up to 6 months without treatment. Gastro-intestinal symptoms and HRQoL were analyzed using disease-specific, psychometrically validated patient-reported outcome instruments (ReQuest™, GERDyzer™).

Results

Symptomatic burden reflected by ReQuest™ substantially decreased from baseline to end of treatment by 83% and 88% in either treatment group, respectively. ReQuest™ scores significantly decreased in patients with or without heartburn and in those with symptoms suggestive of FD and IBS, indicating response of all symptom categories to treatment (p < 0.005). Therapy-associated relief of symptoms was paralleled by substantial gains in HRQoL, which continued to stabilize post-treatment.

Conclusions

Pantoprazole is effective in relieving upper and lower gastro-intestinal symptoms overlapping with erosive esophagitis, and provides sustained improvement in HRQoL post-treatment. Our results propose a link between both healing of erosive esophagitis and the slower remission of upper and lower gastro-intestinal symptoms. Since the improvement observed is likely to be multifactorial, the possibility for an immune-mediated etiology and identification of putative susceptibility factors by genome-wide association study may provide focus for future research.

Trial registration

ClinicalTrials.gov identifier: NCT00325676.

Antinociceptive effect of berberine on visceral hypersensitivity in rats

AIM: To assess the protective effect of berberine administration and the role of nitric oxide (NO) in visceral hypersensitivity.

METHODS: Fifty male Sprague-Dawley rats were randomly assigned to five groups. An inflammatory bowel disease model was induced in rats by intracolonic instillation of 1 mL 4% acetic acid at 8 cm proximal to the anus for 30 s and restraint stress. After subsidence of inflammation on day 7 of the experiment, the rats were subjected to rectal distension, performed by a balloon (6-Fr, 2 mm external diameter, disposable silicon balloon-urethral catheter for pediatric use) which was rapidly inflated with increasing volumes of prewarmed (37 °C) water (0.1, 0.2, 0.3, 0.4, 0.6, 0.8 and 1 mL) for 30 s at four-minute intervals, and then the abdominal withdrawal reflex (AWR) and the level of fecal output were measured, respectively. AWR scores either 0, 1, 2, 3 or 4 were obtained by blinded observers. Rats had been pretreated with berberine or aminoguanidine (NO synthetase inhibitor) or berberine + aminoguanidine before measurement.

RESULTS: The rats in the placebo group showed a hypersensitive response to rectal distension (2.69 ± 0.08 vs 1.52 ± 0.08, P = 0.000) and defecated more frequently than those in the control group (5.0 ± 0.16 vs 0.44 ± 0.16, P = 0.000). Comparing the berberine with placebo group, the AWR scores were reduced for all distension volumes and were significant at 0.2-1 mL (1.90 ± 0.08 vs 2.69 ± 0.08, P = 0.000), while the numbers of hard pellets, soft pellets, formless stools, and total fecal output in the placebo group were significantly larger than in the berberine group (5.0 ± 0.16 vs 2.56 ± 0.16, P = 0.000). Administration of aminoguanidine or berberine + aminoguanidine before VH score measurement reversed the antinociceptive effect of berberine (2.52 ± 0.08 vs 1.90 ± 0.08, P = 0.000; 2.50 ± 0.08 vs 1.90 ± 0.08, P = 0.000). The numbers of hard pellets, soft pellets, formless stool, and total of fecal output in aminoguanidine group were significantly larger than the corresponding values in control group, berberine group, and berberine + aminoguanidine group (4.81 ± 0.16 vs 0.44 ± 0.16, P = 0.000; 4.81 ± 0.16 vs 2.56 ± 0.16, P = 0.000; 4.81 ± 0.16 vs 3.75 ± 0.16, P = 0.000). The berberine and berberine + aminoguanidine groups showed reduced defecation, but aminoguanidine alone did not reduce defecation (2.56 ± 0.16 vs 4.81 ± 0.16, P = 0.000; 3.75 ± 0.16 vs 4.81 ± 0.16, P = 0.000).

CONCLUSION: Berberine had an antinociceptive effect on visceral hypersensitivity, and NO might play a role in this effect.

IBS and the role of otilonium bromide

INTRODUCTION

Awareness of the seriousness of irritable bowel disorder (IBS) remains low among clinicians. In this review, we summarize the current knowledge of IBS and highlight the major personal, economic, and social burden of the disease, and the importance of adequate treatment of what is still often viewed as a trivial disorder. In fact, IBS is a major reason for referral.

PATHOPHYSIOLOGY

It is crucial that the varied pathophysiologies of this complex heterogeneous disease are understood in order to be able to treat both the presenting symptoms (pain, bloating, flatulence, abnormal defecation, diarrhea, constipation) and the underlying disorder effectively. Low-grade inflammatory and immune activation has been observed, but the precise triggers and mechanisms, and the relevance to symptom generation, remain to be established.

TREATMENT

IBS patients require different treatment strategies according to the pattern, severity, frequency, and symptoms. While initial therapy traditionally targets the most bothersome symptom, long-term therapy aims at maintaining symptom control and preventing recurrence. In addition to dietary/lifestyle interventions and psychosocial strategies, a wide range of pharmacologic therapies are approved for use in IBS depending on the symptoms reported. Musculotropic spasmolytics, which act directly on intestinal smooth muscle contractility, such as otilonium bromide, are effective, particularly in the relief of abdominal pain and bloating, and are well tolerated in IBS. THE OBIS TRIAL: The recent large placebo-controlled Otilonium Bromide in Irritable Bowel Syndrome study demonstrated the superiority of otilonium bromide versus placebo not only in the reduction of pain and bloating, but also in protection from relapse due to the long-lasting effect.

Increased pain sensitivity among adults reporting irritable bowel syndrome symptoms in a large population-based study

The aim of this study was to examine whether irritable bowel syndrome (IBS) is associated with increased somatic pain sensitivity in a large population-based sample and to test whether this association was independent of sex, age, comorbid chronic pain, and psychological distress. Pain sensitivity tests included assessment of heat-pain threshold (N=4054) and pressure-pain threshold (N=4689) and of cold-pressor pain intensity and tolerance (N=10,487). Cox regression and analysis of variance (ANOVA) were used to assess the relationship between IBS and pain sensitivity in stepwise multivariate models. The prevalence of IBS symptoms meeting the ROME II criteria was 5.3%. Compared with control subjects, IBS cases had reduced cold-pressor tolerance (hazard ratio=1.4, P<.01), increased cold-pressor pain intensity ratings (z-score=+0.20, P<0.01), and lower heat-pain thresholds (z-score=-0.20, P<0.01), after adjusting for sex and age. These results were only slightly attenuated and remained significant when controlling for comorbid chronic pain and psychological distress. Results for pressure-pain threshold were not significant. Heat- and cold-pressor pain sensitivity was greatest for the IBS reporting severe chronic abdominal pain, indicating that hyperalgesia in IBS is related to degree of clinical pain rather than to the diagnosis per se. Because all pain tests were all carried out on the upper extremities, our findings indicate the presence of widespread hyperalgesia in IBS, which may be a contributing factor to the high rate of comorbid pain seen in this patient group.

Targeted therapies for diarrhea-predominant irritable bowel syndrome

Irritable bowel syndrome (IBS) causes gastrointestinal symptoms such as abdominal pain, bloating, and bowel pattern abnormalities, which compromise patients’ daily functioning. Common therapies address one or two IBS symptoms, while others offer wider symptom control, presumably by targeting pathophysiologic mechanisms of IBS. The aim of this targeted literature review was to capture clinical trial reports of agents receiving the highest recommendation (Grade 1) for treatment of IBS from the 2009 American College of Gastroenterology IBS Task Force, with an emphasis on diarrhea-predominant IBS. Literature searches in PubMed captured articles detailing randomized placebo-controlled trials in IBS/diarrhea-predominant IBS for agents receiving Grade I (strong) 2009 American College of Gastroenterology IBS Task Force recommendations: tricyclic antidepressants, nonabsorbable antibiotics, and the 5-HT₃ receptor antagonist alosetron. Studies specific for constipation-predominant IBS were excluded. Tricyclic antidepressants appear to improve global IBS symptoms but have variable effects on abdominal pain and uncertain tolerability; effects on stool consistency, frequency, and urgency were not adequately assessed. Nonabsorbable antibiotics show positive effects on global symptoms, abdominal pain, bloating, and stool consistency but may be most efficacious in patients with altered intestinal microbiota. Alosetron improves global symptoms and abdominal pain and normalizes bowel irregularities, including stool frequency, consistency, and fecal urgency. Both the nonabsorbable antibiotic rifaximin and the 5-HT₃ receptor antagonist alosetron improve quality of life. Targeted therapies provide more complete relief of IBS symptoms than conventional agents. Familiarization with the quantity and quality of evidence of effectiveness can facilitate more individualized treatment plans for patients with this heterogeneous disorder.

Evaluation of harm in the pharmacotherapy of irritable bowel syndrome

OBJECTIVE

Current treatment options for irritable bowel syndrome are limited and often poorly studied. A select few drugs have been studied in irritable bowel syndrome, and the number needed to treat is frequently used to assess the relative efficacy of these treatments. However, side effects are an important consideration in the clinical decision on which particular treatment to use. This study examines trials of subjects with irritable bowel syndrome with diarrhea and constipation who are receiving a drug intervention deemed of merit by the American College of Gastroenterology task force and compares these therapies to examine the number needed to harm using a systematic review and meta-analysis approach.

METHODS

Potential studies of irritable bowel syndrome treatments were identified through a search of MEDLINE (1950 to April 2011), EMBASE (1980 to April 2011), the Cochrane central register of controlled trials, and the bibliography of recent meta-analyses. Clinical trials of pharmacotherapy for irritable bowel syndrome were eligible for inclusion only if a description of adverse events and the number of patients who discontinued treatment because of adverse events were reported. The relative risk of experiencing an adverse event requiring discontinuation of treatment was used to determine the number needed to harm. In addition, the number and severity of adverse events were summarized.

RESULTS

Twenty-six clinical trials (4 with selective serotonin reuptake inhibitors, 3 with lubiprostone, 6 with tricyclic antidepressants, 8 with alosetron, and 5 with rifaximin) were included. Lubiprostone was safe with insignificant harm in one combined phase III trial. Selective serotonin reuptake inhibitors did not have enough data for a reliable meta-analysis of harm but seemed to be safe. More rigorous data were available for tricyclic antidepressants, alosetron, and rifaximin; the numbers needed to harm were 18.3, 19.4, and 8971, respectively, and the numbers needed to treat were 8, 7.5, and 10.6, respectively. For tricyclic antidepressant and alosetron, an adverse event resulting in discontinuation of the study medication occurred for every 2.3 and 2.6 patients who benefited from a drug, respectively. For rifaximin, this number was 846 patients. In addition, adverse events were more common with tricyclic antidepressants and alosetron.

CONCLUSION

In irritable bowel syndrome with diarrhea, tricyclic antidepressants and alosetron are associated with a significant number needed to harm compared with rifaximin. Apart from lubiprostone, treatment of irritable bowel syndrome with constipation is limited to small studies (with poor descriptions of side effects), although lubiprostone and selective serotonin reuptake inhibitors appear safe.

Targeted therapies for diarrhea-predominant irritable bowel syndrome

Irritable bowel syndrome (IBS) causes gastrointestinal symptoms such as abdominal pain, bloating, and bowel pattern abnormalities, which compromise patients' daily functioning. Common therapies address one or two IBS symptoms, while others offer wider symptom control, presumably by targeting pathophysiologic mechanisms of IBS. The aim of this targeted literature review was to capture clinical trial reports of agents receiving the highest recommendation (Grade 1) for treatment of IBS from the 2009 American College of Gastroenterology IBS Task Force, with an emphasis on diarrhea-predominant IBS. Literature searches in PubMed captured articles detailing randomized placebo-controlled trials in IBS/diarrhea-predominant IBS for agents receiving Grade I (strong) 2009 American College of Gastroenterology IBS Task Force recommendations: tricyclic antidepressants, nonabsorbable antibiotics, and the 5-HT(3) receptor antagonist alosetron. Studies specific for constipation-predominant IBS were excluded. Tricyclic antidepressants appear to improve global IBS symptoms but have variable effects on abdominal pain and uncertain tolerability; effects on stool consistency, frequency, and urgency were not adequately assessed. Nonabsorbable antibiotics show positive effects on global symptoms, abdominal pain, bloating, and stool consistency but may be most efficacious in patients with altered intestinal microbiota. Alosetron improves global symptoms and abdominal pain and normalizes bowel irregularities, including stool frequency, consistency, and fecal urgency. Both the nonabsorbable antibiotic rifaximin and the 5-HT(3) receptor antagonist alosetron improve quality of life. Targeted therapies provide more complete relief of IBS symptoms than conventional agents. Familiarization with the quantity and quality of evidence of effectiveness can facilitate more individualized treatment plans for patients with this heterogeneous disorder.

Abdominal pain-predominant functional gastrointestinal diseases in children and adolescents: prevalence, symptomatology, and association with emotional stress

BACKGROUND AND OBJECTIVE

Functional gastrointestinal disorders (FGD) are common among children, but little is known regarding their prevalence in developing countries. We assessed the prevalence of abdominal pain-predominant FGD, in addition to the predisposing factors and symptomatology, in Sri Lankan children.

PATIENTS AND METHODS

A cross-sectional survey was conducted among a randomly selected group of 10- to 16-year-olds in 8 randomly selected schools in 4 provinces in Sri Lanka. A validated, self-administered questionnaire was completed by children independently in an examination setting. FGD were diagnosed using Rome III criteria.

RESULTS

A total of 2180 questionnaires were distributed and 2163 (99.2%) were included in the analysis (1189 [55%] boys, mean age 13.4 years, standard deviation 1.8 years). Of them, 270 (12.5%) had at least 1 abdominal pain-predominant FGD. Irritable bowel syndrome (IBS) was seen in 107 (4.9%), functional dyspepsia in 54 (2.5%), functional abdominal pain in 96 (4.4%), and abdominal migraine (AM) in 21 (1.0%) (2 had AM and functional dyspepsia, 6 had AM and IBS). Extraintestinal symptoms were more common among affected children (P < 0.05). Abdominal pain-predominant FGD were higher in girls and those exposed to stressful events (P < 0.05). Prevalence negatively correlated with age (r = -0.05, P = 0.02).

CONCLUSIONS

Abdominal pain-predominant FGD affects 12.5% of children ages 10 to 16 years and constitutes a significant health problem in Sri Lanka. IBS is the most common FGD subtype present. Abdominal pain-predominant FGD are higher in girls and those exposed to emotional stress. Prevalence of FGD decreased with age. Extraintestinal symptoms are more frequent in affected children.

Effect of red pepper on symptoms of irritable bowel syndrome: preliminary study

BACKGROUND

Abdominal pain, that characterizes irritable bowel syndrome (IBS) together with bloating and disordered defecation, is mainly related to a visceral hypersensitivity due to an increase of TRPV(1) nociceptive nerve fiber activity.

AIM

As capsaicin contained in red pepper is able to desensitize the TRPV(1) fibres, we evaluated whether the red pepper oral administration can decrease the symptoms of visceral hypersensitivity in IBS patients.

METHODS

The study was performed on 50 patients with IBS diagnosed following Rome II criteria. After a 2-week washout period, 23 patients were planned to receive 4 pills/day, for 6 weeks randomly and in a double blind manner, each containing 150 mg of red pepper powder with a coat that dissolves in the colon, and 27 patients placebo. The patients scored each day in a diary the abdominal pain and bloating intensities following the 5-point Likert scale. The weekly symptom mean scores and the final patient subjective evaluation on treatment effectiveness were statistically compared among groups and intra-groups with appropriate tests.

RESULTS

Eight patients dropped from the study: 6 in the red pepper group for abdominal pain and 2 in the placebo group. In 8 patients, the pills were reduced to 2/day, because of the abdominal pain at the onset of treatment. The intra-group comparisons showed that in patients taking red pepper the abdominal pain and bloating mean score values of the last weeks of treatment were significantly improved with respect to pre-treatment values, unlike patients taking placebo. The final patient subjective evaluation on the treatment effectiveness showed that red pepper group scored significantly better than placebo.

CONCLUSIONS

The results of this preliminary study indicate that the chronic administration of red pepper powder in IBS patients with enteric-coated pills was significantly more effective than placebo in decreasing the intensity of abdominal pain and bloating and was considered by the patients more effective than placebo.

Treatment of postinfectious irritable bowel syndrome and noninfective irritable bowel syndrome with mesalazine

CONTEXT

Recent studies support the hypothesis that postinfectious irritable bowel syndrome and some irritable bowel syndrome patients display persistent signs of minor mucosal inflammation. Mesalazine has intestinal anti-inflammatory properties including cyclooxygenase and prostaglandin inhibition. The effects of mesalazine on postinfectious irritable bowel syndrome and noninfective irritable bowel syndrome patients are still unknown.

OBJECTIVE

To observe the effects of mesalazine on postinfectious irritable bowel syndrome and noninfective irritable bowel syndrome with diarrhea patients.

METHODS

Based on Rome III criteria, 61 irritable bowel syndrome with diarrhea patients (18 years old or more) were included in the evaluation. Patients were divided into two groups: postinfectious irritable bowel syndrome group, with 18 patients medicated with mesalazine 800 mg 3 times a day for 30 days; noninfective irritable bowel syndrome group, with 43 patients medicated with mesalazine 800 mg 3 times a day for 30 days. Symptom evaluations at baseline and after treatment were performed by means of a four-point Likert scale including stool frequency, stool form and consistency (Bristol Stool Scale), abdominal pain and distension (maximum score: 16; minimum score: 4).

RESULTS

Postinfectious irritable bowel syndrome group presented a statistically significant reduction of the total symptom score (P<0.0001). The stool frequency was significantly reduced (P<0.0001), and stool consistency, improved (P<0.0001). Abdominal pain (P<0.0001) and abdominal distension were significantly reduced (P<0.0001). Noninfective irritable bowel syndrome group presented a statistically significant reduction of total symptom score (P<0.0001). Also, the stool frequency was significantly reduced (P<0.0001) and stool consistency, improved (P<0.0001). Abdominal pain (P<0.0001) and abdominal distention were significantly reduced (P<0.0001). There was no statistical difference between postinfectious irritable bowel syndrome group and noninfective irritable bowel syndrome group on total symptom score results at 30th day of therapy with mesalazine 800 mg 3 times a day. (P = 0.13).

CONCLUSION

Mesalazine reduced key symptoms of postinfectious irritable bowel syndrome and noninfective irritable bowel syndrome with diarrhea patients.

Antinociceptive effect of VSL#3 on visceral hypersensitivity in a rat model of irritable bowel syndrome: a possible action through nitric oxide pathway and enhance barrier function

Irritable bowel syndrome (IBS) is a functional bowel disorder characterized by visceral hypersensitivity and altered bowel function. There are increasing evidences suggested that VSL#3 probiotics therapy has been recognized as an effective method to relieve IBS-induced symptoms. The aim of this study was to examine the effects of VSL#3 probiotics on visceral hypersensitivity (VH), nitric oxide (NO), fecal character, colonic epithelium permeability, and tight junction protein expression. IBS model was induced by intracolonic instillation of 4% acetic acid and restraint stress in rats. After subsidence of inflammation on the seventh experimental day, the rats were subjected to rectal distension, and then the abdominal withdrawal reflex and the number of fecal output were measured, respectively. Also, colonic permeability to Evans blue was measured in vivo, and tight junction protein expression was studied by immunohistochemistry and immunoblotting method. Rats had been pretreated with VSL#3 or aminoguanidine (NOS inhibitor) or VSL#3+ aminoguanidine before measurements. The rats at placebo group showed hypersensitive response to rectal distension (P < 0.05) and defecated more stools than control rats (P < 0.05), whereas VSL#3 treatment significantly attenuated VH and effectively reduced defecation. Aminoguanidine reduced the protective effects of VSL#3 on VH. A pronounced increase in epithelial permeability and decreased expression of tight junction proteins (occludin, ZO-1) in placebo group were prevented by VSL#3, but not aminoguanidine. VSL#3 treatment reduce the hypersensitivity, defecation, colonic permeability and increase the expression of tight junction proteins (occludin, ZO-1). As the part of this effect was lowered by NOS inhibitor, NO might play a role in the protective effect of VSL#3 to some extent.

Systematic review of modulators of benzodiazepine receptors in irritable bowel syndrome: Is there hope?

Several drugs are used in the treatment of irritable bowel syndrome (IBS) but all have side effects and variable efficacy. Considering the role of the gut-brain axis, immune, neural, and endocrine pathways in the pathogenesis of IBS and possible beneficial effects of benzodiazepines (BZD) in this axis, the present systematic review focuses on the efficacy of BZD receptor modulators in human IBS. For the years 1966 to February 2011, all literature was searched for any articles on the use of BZD receptor modulators and IBS. After thorough evaluation and omission of duplicate data, 10 out of 69 articles were included. BZD receptor modulators can be helpful, especially in the diarrhea-dominant form of IBS, by affecting the inflammatory, neural, and psychologic pathways, however, controversies still exist. Recently, a new BZD receptor modulator, dextofisopam was synthesized and studied in human subjects, but the studies are limited to phase IIb clinical trials. None of the existing trials considered the neuroimmunomodulatory effect of BZDs in IBS, but bearing in mind the concentration-dependent effect of BZDs on cytokines and cell proliferation, future studies using pharmacodynamic and pharmacokinetic approaches are highly recommended.

Pathogenic factors involved in the development of irritable bowel syndrome: focus on a microbial role

Irritable bowel syndrome (IBS) is a symptom complex characterized by recurrent abdominal pain or discomfort, and accompanied by abnormal bowel habits, in the absence of any discernible organic abnormality. Its origin remains unclear, partly because multiple pathophysiologic mechanisms are likely to be involved. A significant proportion of patients develop IBS symptoms after an episode of gastrointestinal infection. In addition to gastrointestinal pathogens, recent evidence suggests that patients with IBS have abnormal composition and higher temporal instability of their intestinal microbiota. Because the intestinal microbiota is an important determinant of normal gut function and immunity, this instability may constitute an additional mechanism that leads to symptom generation and IBS. More importantly, a role for altered microbiota composition in IBS raises the possibility of therapeutic interventions through selective antibiotic or probiotic administration. The new concept of functional bowel diseases incorporates the bidirectional communication between the gut and the central nervous system (gut-brain axis), which may explain the multiple facets of IBS by linking emotional and cognitive centers of the brain with peripheral functioning of the gastrointestinal tract and vice versa.

Enhanced excitability and down-regulated voltage-gated potassium channels in colonic drg neurons from neonatal maternal separation rats

Irritable bowel syndrome (IBS), characterized mainly by abdominal pain, is a functional bowel disorder. The present study aimed to examine changes in the excitability and the activity of the voltage-gated K(+) channel in dorsal root ganglia (DRG) neurons innervating the colon of rats subjected to neonatal maternal separation (NMS). Colonic DRG neurons from NMS rats as identified by FAST DiI™ labeling showed an increased cell size compared with those from nonhandled (NH) rats. Whole cell current-clamp recordings showed that colonic DRG neurons from NMS rats displayed: 1) depolarized resting membrane potential; 2) increased input resistance; 3) a dramatic reduction in rheobase; and 4) a significant increase in the number of action potentials evoked at twice rheobase. Whole cell voltage-clamp recordings revealed that neurons from both groups exhibited transient A-type (I(A)) and delayed rectifier (I(K)) K(+) currents. Compared with NH rat neurons, the averaged density of I(K) was significantly reduced in NMS rat neurons. Furthermore, the Kv1.2 expression was significantly decreased in NMS rat colonic DRG neurons. These results suggest that NMS increases the excitability of colonic DRG neurons mainly by suppressing the I(K) current, which is likely accounted for by the downregulation of the Kv1.2 expression and somal hypertrophy.

PERSPECTIVE

This study demonstrates the alteration of delayed rectifier K current and Kv1.2 expression in DRG neurons from IBS model rats, representing a molecular mechanism underlying visceral pain and sensitization in IBS, suggesting the potential of Kv1.2 as a therapeutic target for the treatment of IBS.

Effect of electroacupuncture on visceral hyperalgesia, serotonin and fos expression in an animal model of irritable bowel syndrome

Background/Aims

While it is well established that acupuncture relieves somatic pain, its therapeutic effect on visceral pain such as irritable bowel syndrome (IBS) is unclear. We evaluated the effect of acupuncture in treating visceral hyperalgesia in an animal model.

Methods

Sprague-Dawley rats (n = 8 per group) with prior neonatal maternal separation stress were randomly allocated to receive 3-day treatment of either electroacupuncture (EA) or sham acupuncture at acupoint ST-36. Another group of rats without prior maternal separation was included as non-handled controls. Colorectal distension was performed on the day after acupuncture treatment. The 3 groups were compared for pain threshold as determined by abdominal withdrawal reflex and visceromotor response as measured by electromyogram. Colon, spinal cord, and brainstem were sampled for topographic distribution and quantitative assessment of serotonin and Fos expression by immunohistochemistry.

Results

Rats in EA group had significantly higher pain threshold compared to those in sham acpuncture group (25.0 ± 5.7 mmHg vs 18.7 ± 5.2 mmHg, p = 0.01) and it was comparable with that of non-handled treatment naïve controls (29.4 ± 9.3 mmHg, p = 0.28). They also had lower visceromotor response as measured by electromyogram compared to those received sham acupuncture at all colorectal distension pressures. EA significantly suppressed Fos expression in doral raphe nuclei of brainstem, superficial dorsal horn of spinal cord and colonic epithelium but suppressed 5-HT expression only in brainstem and spinal cord.

Conclusions

Electro acupuncture attenuates visceral hyperlagesia through down-regulation of central serotonergic activities in the brain-gut axis.

Unexplained gastrointestinal symptoms and joint hypermobility: is connective tissue the missing link?

BACKGROUND Unexplained gastrointestinal (GI) symptoms and joint hypermobility (JHM) are common in the general population, the latter described as benign joint hypermobility syndrome (BJHS) when associated with musculo-skeletal symptoms. Despite overlapping clinical features, the prevalence of JHM or BJHS in patients with functional gastrointestinal disorders has not been examined. METHODS The incidence of JHM was evaluated in 129 new unselected tertiary referrals (97 female, age range 16-78 years) to a neurogastroenterology clinic using a validated 5-point questionnaire. A rheumatologist further evaluated 25 patients with JHM to determine the presence of BJHS. Groups with or without JHM were compared for presentation, symptoms and outcomes of relevant functional GI tests. KEY RESULTS Sixty-three (49%) patients had evidence of generalized JHM. An unknown aetiology for GI symptoms was significantly more frequent in patients with JHM than in those without (P < 0.0001). The rheumatologist confirmed the clinical impression of JHM in 23 of 25 patients, 17 (68%) of whom were diagnosed with BJHS. Patients with co-existent BJHS and GI symptoms experienced abdominal pain (81%), bloating (57%), nausea (57%), reflux symptoms (48%), vomiting (43%), constipation (38%) and diarrhoea (14%). Twelve of 17 patients presenting with upper GI symptoms had delayed gastric emptying. One case is described in detail. CONCLUSIONS & INFERENCES In a preliminary retrospective study, we have found a high incidence of JHM in patients referred to tertiary neurogastroenterology care with unexplained GI symptoms and in a proportion of these a diagnosis of BJHS is made. Symptoms and functional tests suggest GI dysmotility in a number of these patients. The possibility that a proportion of patients with unexplained GI symptoms and JHM may share a common pathophysiological disorder of connective tissue warrants further investigation.

The effects of mechanical forces on intestinal physiology and pathology

The epithelial and non-epithelial cells of the intestinal wall experience a myriad of physical forces including strain, shear, and villous motility during normal gut function. Pathologic conditions alter these forces, leading to changes in the biology of these cells. The responses of intestinal epithelial cells to forces vary with both the applied force and the extracellular matrix proteins with which the cells interact, with differing effects on proliferation, differentiation, and motility, and the regulation of these effects involves similar but distinctly different signal transduction mechanisms. Although normal epithelial cells respond to mechanical forces, malignant gastrointestinal epithelial cells also respond to forces, most notably by increased cell adhesion, a critical step in tumor metastasis. This review will focus on the phenomenon of mechanical forces influencing cell biology and the mechanisms by which the gut responds these forces in both the normal as well as pathophysiologic states when forces are altered. Although more is known about epithelial responses to force, information regarding mechanosensitivity of vascular, neural, and endocrine cells within the gut wall will also be discussed, as will, the mechanism by which forces can regulate epithelial tumor cell adhesion.