Disturbances of motility and visceral hypersensitivity in irritable bowel syndrome: biological markers or epiphenomenon

Leveraging 16S rRNA Microbiome Sequencing Data to Identify Bacterial Signatures for Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a chronic gastrointestinal disorder characterized by abdominal pain or discomfort. Previous studies have illustrated that the gut microbiota might play a critical role in IBS, but the conclusions of these studies, based on various methods, were almost impossible to compare, and reproducible microorganism signatures were still in question. To cope with this problem, previously published 16S rRNA gene sequencing data from 439 fecal samples, including 253 IBS samples and 186 control samples, were collected and processed with a uniform bioinformatic pipeline. Although we found no significant differences in community structures between IBS and healthy controls at the amplicon sequence variants (ASV) level, machine learning (ML) approaches enabled us to discriminate IBS from healthy controls at genus level. Linear discriminant analysis effect size (LEfSe) analysis was subsequently used to seek out 97 biomarkers across all studies. Then, we quantified the standardized mean difference (SMDs) for all significant genera identified by LEfSe and ML approaches. Pooled results showed that the SMDs of nine genera had statistical significance, in which the abundance of Lachnoclostridium, Dorea, Erysipelatoclostridium, Prevotella 9, and Clostridium sensu stricto 1 in IBS were higher, while the dominant abundance genera of healthy controls were Ruminococcaceae UCG-005, Holdemanella, Coprococcus 2, and Eubacterium coprostanoligenes group. In summary, based on six published studies, this study identified nine new microbiome biomarkers of IBS, which might be a basis for understanding the key gut microbes associated with IBS, and could be used as potential targets for microbiome-based diagnostics and therapeutics.

Gut Microbial Dysbiosis in the Irritable Bowel Syndrome: A Systematic Review and Meta-Analysis of Case-Control Studies

BACKGROUND

Irritable bowel syndrome (IBS) is the most common functional digestive condition in the industrialized world. The gut microbiota plays a key role in disease pathogenesis.

OBJECTIVE

A systematic review and meta-analysis on case-control studies was conducted to determine whether there is gut microbial dysbiosis in participants with IBS in comparison with healthy controls and, if so, whether the dysbiosis pattern differs among IBS subtypes and geographic regions.

METHODS

This review was conducted and reported according to the MOOSE (Meta-Analysis of Observational Studies in Epidemiology) 2000 and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2009 guidelines. Research articles published up to May 9, 2018 were identified through MEDLINE (PubMed), Cochrane Central Register of Controlled Trials (Cochrane Library), ClinicalTrials.gov, EMBASE, and Web of Science. Study quality was assessed using the Newcastle-Ottawa Scale. Case-control studies of participants with IBS who had undergone quantitative gut microbial stool analysis were included. The primary exposure measure of interest is log₁₀ bacterial counts per gram of stool. Meta-analyses were performed to estimate the mean difference (MD) in gut microbiota between participants with IBS and healthy controls using the random-effects model with inverse variance in Revman 5.3 and R 3.5.1. Publication bias was assessed with funnel plots and Egger's test. Between-study heterogeneity was analyzed using Higgins I² statistic with 95% CIs.

RESULTS

There were 6,333 unique articles identified; 52 qualified for full-text screening. Of these, 23 studies were included for analysis (n=1,340 participants from North America, Europe, and Asia). Overall, the studies were moderate in quality. Comparing participants with IBS to healthy controls, lower fecal Lactobacillus (MD= -0.57 log₁₀ colony-forming unit [CFU]/g; P<0.01) and Bifidobacterium (MD= -1.04 log₁₀CFU/g; P<0.01), higher Escherichia coli (MD=0.60 log₁₀CFU/g; P<0.01), and marginally higher Enterobacter (MD=0.74 log₁₀CFU/g; P=0.05). No difference was found between participants with IBS and healthy controls in fecal Bacteroides and Enterococcus (P=0.18 and 0.68, respectively). Publication bias was not observed except in Bifidobacterium (P=0.015). Subgroup analyses on participants with diarrhea-predominant and constipation-predominant IBS showed consistent results with the primary results. A subgroup analysis of Chinese studies was consistent with the primary results, except for fecal Bacteroides, which was increased in participants with IBS vs healthy controls (MD=0.29; 95% CI 0.13 to 0.46; P<0.01). Although substantial heterogeneity was detected (I²>75%) in most comparisons, the direction of the effect estimates is relatively consistent across studies.

CONCLUSIONS

IBS is characterized by gut microbial dysbiosis. Prospective, large-scale studies are needed to delineate how gut microbial profiles can be used to guide targeted therapies in this challenging patient population.

Eosinophilic gastroenteritis: diagnosis and clinical perspectives

Eosinophilic gastroenteritis (EGE) is a digestive disorder in children and adults that is characterized by eosinophilic infiltration in the stomach and intestine. The underlying molecular mechanisms predisposing to this disease are unknown, but it seems that hypersensitivity response plays a major role in its pathogenesis, as many patients have a history of seasonal allergies, food sensitivities, asthma, and eczema. Symptoms and clinical presentations vary, depending on the site and layer of the gastrointestinal wall infiltrated by eosinophils. Laboratory results, radiological findings, and endoscopy can provide important diagnostic evidence for EGE; however, the cornerstone of the diagnosis remains the histological examination of gastric and duodenal specimens for evidence of eosinophilic infiltration (>20 eosinophils per high-power field), and finally clinicians make the diagnosis in correlation with and by exclusion of other disorders associated with eosinophilic infiltration. Although spontaneous remission is reported in around 30%–40% of EGE cases, most patients require ongoing treatment. The management options for this disorder include both dietary and pharmacological approaches, with corticosteroids being the mainstay of therapy and highly effective. The subsequent course is quite variable. Some patients have no recurrences, while a few experience recurrent symptoms during or immediately after corticosteroid interruption. An alternative therapeutic armamentarium includes mast-cell stabilizers, leukotriene antagonists, antihistamines, immunomodulators, and biological agents. In this review, we provide a summary of the different diagnostic tools utilized in practice, as well as the different therapeutic approaches available for EGE management.

Association Between Irritable Bowel Syndrome and Overactive Bladder: A Research Survey

OBJECTIVE

To investigate the relationship between irritable bowel syndrome (IBS) and overactive bladder (OAB) in men and women using questionnaires.

MATERIALS AND METHODS

This research survey was based on multicenter data (men and women older than 20 years). The Korean version of the Rome III criteria was used for the diagnosis of IBS, Overactive Bladder Symptom Score (OABSS) was used for screening OAB, Self-Rating Depression Scale was used for depressive symptoms, and International Prostate Symptom Score and Quality of Life were used to determine the degrees of lower urinary tract symptoms.

RESULTS

A total of 609 (men: 257, women: 352) people answered the questionnaire. The prevalence of IBS and OAB was 31.9% (men vs women: 27.3% vs 39.2%) and 19.2% (men vs women: 25.3% vs 18.5%), respectively. The OABSS values of patients with IBS and non-IBS patients were 1.70 ± 2.48 and 2.48 ± 2.79 (P <.001). On the Self-Rating Depression Scale, individuals with IBS had a higher score than non-IBS individuals (n = 201) (44.92 ± 13.71 vs 39.19 ± 10.39, P <.001). In men, non-IBS (n = 56) had higher OABSS and OABSS question number 3 responses than patients with IBS (OABSS: 2.56 ± 2.69 vs 1.57 ± 2.43, P = .01, OABSS Q3: 0.92 ± 1.26 vs 0.66 ± 1.13, P = .17). Also, in women, non-IBS (n = 214) had higher OABSS and OABSS question number 3 responses than patients with IBS (n = 138) (OABSS: 2.40 ± 2.87 vs 1.76 ± 2.52, P = .03, OABSS Q3: 0.83 ± 1.25 vs 0.70 ± 1.18, P = .32).

CONCLUSION

IBS in adults had no relationship with OAB in our study. These data suggest that more studies are needed to determine the relationship between IBS and OAB.

Smoking in Irritable Bowel Syndrome: A Systematic Review

OBJECTIVE

The aim of this review was to examine (1) the prevalence of smoking in subjects with irritable bowel syndrome (IBS), (2) whether smoking prevalence significantly differs between subjects with and without IBS, and (3) whether smoking significantly predicts the presence or the development of IBS.

METHODS

Articles were retrieved by systematically searching the Scopus, Web of Science, and PubMed electronic databases from inception to July 2016, using the keywords "smoking" and "tobacco" combined with "irritable bowel syndrome." Reference lists of included articles were also searched. Articles were included if they (1) reported data on smoking prevalence in subjects with IBS and/or on the association (assessed by means of multivariate analyses) between smoking and IBS, (2) identified IBS according to Manning criteria or Rome I-III criteria, (3) were English-language articles, and (4) involved only adult subjects.

RESULTS

The electronic searches yielded a total of 1,637 records, and 42 articles met inclusion criteria. Another 13 articles were retrieved through manual search, leading to a total of 55 included articles. Smoking prevalence in subjects with IBS was assessed by 48 articles and ranged from 0% in university students to 47.1% in patients with microscopic colitis. Thirty-three articles compared smoking prevalence between subjects with and without IBS. In 25 articles no significant difference was found. In seven articles smoking was significantly more frequent in subjects with IBS compared to those without IBS, while one study found a significantly higher smoking prevalence in controls. Eighteen multivariate analyses assessing the association between smoking and IBS were presented in 16 articles. Only one study employed a prospective design. In 11 analyses, smoking was not significantly associated with IBS after adjusting for covariates. In seven studies smoking independently predicted the presence of IBS.

CONCLUSIONS

According to the selected articles, a significant association between smoking and IBS cannot be confirmed. However, different shortcomings may hinder generalizability and comparability of many studies. A dimensional assessment of smoking, a prospective design, the differentiation between IBS subgroups, and the recruitment of patients in clinical settings, especially in primary care, are necessary to clarify the role of smoking in IBS.

Strain-dependent variations in visceral sensitivity: relationship to stress, anxiety and spinal glutamate transporter expression

Responses to painful stimuli differ between populations, ethnic groups, sexes and even among individuals of a family. However, data regarding visceral pain are still lacking. Thus, we investigated differences in visceral nociception across inbred and outbred mouse strains using colorectal distension. Anxiety and depression-like behaviour were assessed using the open field and forced swim test as well as the corticosterone stress response. Possible mechanistic targets [excitatory amino acid transporter (EAAT-1), brain-derived neurotrophic factor (BDNF) and 5HT1A receptor] were also assessed using quantitative real-time polymerase chain reaction. Adult, male, inbred and outbred mouse strains were used in all assays (inbred strains; CBA/J Hsd, C3H/HeNHsd, BALB/c OlaHsd, C57 BL/6JOlaHsd, DBA/2J RccHsd, CAST/EiJ, SM/J, A/J OlaHsd, 129P2/OlaHsd, FVB/NHan Hsd and outbred strains: Swiss Webster, CD-1). mRNA expression levels of EAAT-1, BDNF and 5HT1A receptor (HTR1A) were quantified in the lumbosacral spinal cord, amygdala and hippocampus. A significant effect of strain was found in visceral sensitivity, anxiety and depressive-like behaviours. Strain differences were also seen in both baseline and stress-induced corticosterone levels. CBA/J mice consistently exhibited heightened visceral sensitivity, anxiety behaviour and depression-like behaviour which were associated with decreased spinal EAAT-1 and hippocampal BDNF and HTR1A. Our results show the CBA/J mouse strain as a novel mouse model to unravel the complex mechanisms of brain-gut axis disorders such as irritable bowel syndrome, in particular the underlying mechanisms of visceral hypersensitivity, for which there is great need. Furthermore, this study highlights the importance of genotype and the consequences for future development of transgenic strains in pain research.

Irritable bowel syndrome: A microbiome-gut-brain axis disorder?

Irritable bowel syndrome (IBS) is an extremely prevalent but poorly understood gastrointestinal disorder. Consequently, there are no clear diagnostic markers to help diagnose the disorder and treatment options are limited to management of the symptoms. The concept of a dysregulated gut-brain axis has been adopted as a suitable model for the disorder. The gut microbiome may play an important role in the onset and exacerbation of symptoms in the disorder and has been extensively studied in this context. Although a causal role cannot yet be inferred from the clinical studies which have attempted to characterise the gut microbiota in IBS, they do confirm alterations in both community stability and diversity. Moreover, it has been reliably demonstrated that manipulation of the microbiota can influence the key symptoms, including abdominal pain and bowel habit, and other prominent features of IBS. A variety of strategies have been taken to study these interactions, including probiotics, antibiotics, faecal transplantations and the use of germ-free animals. There are clear mechanisms through which the microbiota can produce these effects, both humoral and neural. Taken together, these findings firmly establish the microbiota as a critical node in the gut-brain axis and one which is amenable to therapeutic interventions.

In Vivo and In Vitro Antinociceptive Effect of Fagopyrum cymosum (Trev.) Meisn Extracts: A Possible Action by Recovering Intestinal Barrier Dysfunction

Fagopyrum cymosum (Trev.) Meisn (Fag) is a herb rhizome which has been widely used to treat diseases. To investigate the effects and mechanisms of the Fag on irritable bowel syndrome (IBS), in vivo neonatal pups maternal separation (NMS) combined with intracolonic infusion of acetic acid (AA) was employed to establish IBS rat models. Fag reduced their visceral hyperalgesia and the whole gut permeability, ameliorated colonic mucosa inflammation and injury, and upregulated the expression of decreased tight junction proteins (TJs) of claudin-1, occludin, and ZO-1 (except ZO-2) in colonic epithelium. Caco-2 monolayer cells were incubated with TNF-α and IFN-γ   in vitro to establish an epithelial barrier dysfunction model whose transepithelial electrical resistance (TER) depended more on dose of Fag than that of the controls, and whose TJs levels were lower than those of the controls. Fag upregulated the NP-40 insoluble and soluble components of the four TJs markedly in a dose-dependent manner. These data suggest that Fag alleviated the hyperalgesia of IBS rats by reducing intestinal inflammation and enhancing mucosal epithelial function after regulating the structure and function of TJs.

Probiotics in the management of functional bowel disorders: promise fulfilled?

Irritable bowel syndrome (IBS) and chronic constipation (CC) are common problems worldwide and are associated with significant impact on activities of daily living and quality of life. Recent interest, in IBS in particular, has focused on the potential roles of the microbiota and its interaction with the host's immune system. Recently, high-quality clinical trials have been performed on prebiotics and probiotics in IBS or CC. Although strategies that seek to modify the microbiota, such as the use of probiotics, offer much promise in IBS and CC, more high-quality trials and, studies of longer duration are required.

Bugs on the brain; brain in the gut--seeking explanations for common gastrointestinal symptoms

INTRODUCTION

Gastrointestinal symptoms such as heartburn, indigestion (or dyspepsia), bloating, distension, constipation, abdominal pain, abdominal discomfort and diarrhoea are extremely common worldwide. For some, such symptoms can prove to be chronic and disabling.

METHODS

The recent literature on irritable bowel syndrome and, in particular, work emanating form this authors research group, was reviewed.

RESULTS

These functional symptoms commonly occur in aggregations, referred to as functional gastrointestinal disorders (FGIDs). Some of the FGIDs and, most notably irritable bowel syndrome (IBS), have achieved a degree of scientific and clinical credibility as coherent entities. Several lines of evidence ranging from gut motility to the microbiota are under investigation in attempts to explain IBS or its symptomatology.

CONCLUSION

Though biomarkers for IBS and other FGIDs have proven elusive, considerable progress has been made in understanding possible aetiological factors in IBS; progress which may well lead to better therapeutic strategies.

"Irritable bowel symptoms" in inflammatory bowel disease: diagnostic uncertainty meets pathological reality

Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) are common, chronic, relapsing, and potentially disabling disorders in the West which are increasing in prevalence in the rest of the world. They typically afflict young adults in the prime of their lives and, consequently, may inflict a considerable emotional, personal, and socioeconomic toll. Not surprisingly, therefore, their management requires considerable clinical acumen and a fundamental commitment to the many dimensions of the patient-doctor relationship. There the similarities end. Despite a considerable body of recent data reporting a number of abnormalities (both upregulation and downregulation) in various components of the mucosal and systemic immune response in IBS, none of these findings come even close to the inflammatory processes that typify IBD. Furthermore, there is little evidence that those with an established diagnosis of IBS (in contrast to those with IBS-type symptoms in which IBD may have been missed (1)) can evolve into IBD; IBS, regardless of immunological or microbiological findings, should not be considered as a part of the spectrum of IBD. If IBS and IBD are distinct entities, then can they co-exist and lead to diagnostic confusion for the clinician?

Chronic gastrointestinal consequences of acute infectious diarrhea: evolving concepts in epidemiology and pathogenesis

Acute infectious diarrhea is a frequent occurrence both in the developing world, where it results in considerable mortality, and in developed countries, where it accounts for a significant number of health visits, hospitalizations, and medical and non-medical losses. Recent evidence in basic, clinical, and epidemiological science domains has emerged that suggest that the burden caused by these infections is not limited to the acute illness, but may result in triggering or contributing to the pathogenesis of a number of chronic health problems. This review considers the breadth of this information for the purpose of consolidating what is currently known, identifying gaps in knowledge, and describing future directions and policy implications related to the chronic consequences of acute infectious diarrhea. A unifying hypothesis of this review is that infections may trigger a number of long-lasting changes in gut physiology and immunity that can increase the risk to a variety of chronic gastrointestinal diseases, particularly in genetically susceptible individuals.

Altered peripheral toll-like receptor responses in the irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a stress-related disorder with disturbed brain-gut communication, gastrointestinal homeostasis and, based on recent evidence, low grade inflammation and an altered microbiota. The immune system is a critical regulator of the brain-gut axis. Toll-like receptors (TLRs) are pattern recognition molecules regulating innate immunity.

AIM

To characterise toll-like receptor activity in IBS.

METHODS

Thirty IBS patients and 30 healthy controls (HC) were recruited. Venous blood was collected, and cultured with a panel of toll-like receptor agonists for 24 h. Cell supernatants were analysed using a multiplex ELISA approach to measure IL1β, IL6, IL8 and TNFα. Plasma was analysed for levels of inflammatory cytokines and cortisol.

RESULTS

Toll-like receptor agonist-induced cytokine (IL1β, IL6, IL8 and TNFα) release was markedly enhanced in stimulated whole blood from IBS (n = 30) patients compared with healthy controls (n = 30). An exaggerated response to the TLR8 agonist for all cytokines investigated was seen in IBS patients. In addition, enhanced TLR2-induced TNFα release, TLR3-induced IL-8 release, TLR4-induced IL1β and TNFα release, TLR5-induced IL1β and TNFα release and TLR7-induced IL-8 release were also observed in IBS patients. No differences in TLR1, TLR6 or TLR9 activity were detected. In addition, plasma levels of cortisol, IL-6 and IL-8 were significantly increased in IBS patients.

CONCLUSION

Taken together, these data demonstrate elevated cytokine levels and toll-like receptor activity in the periphery of patients with the irritable bowel syndrome, indicating some immune dysregulation in these patients.

Editorial: Can gluten contribute to irritable bowel syndrome?

Functional gastrointestinal disorders are the most common gastroenterological problem in our society. Changes in gut function, including pain perception, motility, and intestinal permeability, and low-grade inflammation have been described in patients with irritable bowel syndrome (IBS). The triggering factors for the described immunity and gut functional changes in patients with IBS are not completely understood. Similarly to post-infective IBS, some patients with IBS symptoms exhibit immunological evidence of gluten sensitivity but have no overt intestinal mucosal injury. They have symptoms that meet the diagnostic criteria for IBS and respond symptomatically to exclusion of gluten from the diet. Thus, gluten sensitivity may be involved in the pathogenesis of a subgroup of IBS patients. Unfortunately, there remain many unanswered questions regarding the mechanistic link between gluten sensitivity and functional gastrointestinal symptoms.

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.

Gastrointestinal eosinophils in health, disease and functional disorders

Eosinophils are potent innate immune cells that home to the gastrointestinal tract where they participate in host immunity to luminal pathogens, and help to maintain intestinal epithelial homeostasis. However, these cells are now recognized to have key functions in the pathogenesis of numerous other disorders of the gastrointestinal tract, including primary eosinophilic gastrointestinal disease, common functional conditions, such as dyspepsia, and also in gastrointestinal disorders in patients with allergic disease. We are just beginning to understand the potential pathological role of eosinophils in gastrointestinal disease, and it is increasingly likely that gastroenterologists and histopathologists will need to account for the presence of gastrointestinal eosinophils and relate their presence to gastrointestinal symptoms. This Review discusses the role of gastrointestinal eosinophils in health and disease, including their associations with functional and allergic disorders.

Irritable bowel syndrome: towards biomarker identification

Irritable bowel syndrome (IBS), the most common functional gastrointestinal disorder referred to gastroenterologists, affects 7-10% of the general population worldwide. The lack of suitable disease-defining biological markers coupled with a poorly understood underlying pathophysiology complicates patient diagnosis and seriously hampers drug discovery efforts. Over the past few years, a number of potential biomarkers have emerged, and in this review we critically evaluate such candidates. In particular, we highlight the increasing number of studies supporting a low-grade immune activation in IBS and consider how the latest preclinical developments can contribute to the development of more robust and reliable biological markers of this disorder. The successful identification of biomarkers is critical to progressing our understanding of IBS and addressing the unmet therapeutic needs of this debilitating condition.

Voltage-gated potassium channels in IB4-positive colonic sensory neurons mediate visceral hypersensitivity in the rat

OBJECTIVES

Irritable bowel syndrome (IBS) is associated with a state of chronic visceral hypersensitivity, but the underlying molecular mechanisms of visceral hyperalgesia remain elusive. This study was designed to examine changes in the excitability and alterations of voltage-gated K+ currents in subpopulations of colonic dorsal root ganglion (DRG) neurons in a rat model of IBS-like visceral hypersensitivity.

METHODS

The model of IBS-like visceral hypersensitivity was induced by intracolonic infusion of 0.5% acetic acid (AA) in saline from postnatal days 8 -21. Experiments were conducted when rats became adults. DRG neurons innervating the colon were identified by 1,1'-dioleoyl-3,3,3',3-tetramethylindocarbocyanine methanesulfonate (DiI) fluorescence labeling and were immunostained for isolectin B4 (IB4) binding to classify these colonic neurons. Patch-clamp recordings were made from acutely dissociated DiI-labeled DRG neurons, and the expression of K+ channel in L6-S2 DRG was examined by reverse transcription-polymerase chain reaction (RT-PCR) and western blot.

RESULTS

(1) Neonatal AA treatment induced long-lasting visceral hypersensitivity without significant inflammation but with mast cell hyperplasia. (2) Colonic DRG neurons contained IB4-positive and negative neurons with different electrophysiological properties. IB4-positive colonic neurons have longer action potentials (APs) and larger A-type K+ currents (I(A)) than the IB4-negative neurons, and IB4 phenotypic changes of colonic neurons were not involved in the chronic visceral hypersensitivity. (3) Neonatal AA treatment decreased I(A) density and changed the electrophysiological properties of I(A) and I(K) by shifting the steady-state inactivation toward a negative direction in IB4-positive colonic neurons. The excitability of these cells increased. (4) Kv4.3 was downregulated in neonatal AA-treated rats compared with control rats, which suggests a possible mechanism regarding the changes in electrical activity of DRG neurons in these rats.

CONCLUSIONS

A new model for chronic visceral hypersensitivity following a diluted AA stimulus in the neonatal period is described. The hypersensitivity may be associated with mast cell hyperplasia in the colon and increased excitability of IB4-positive colonic neurons as a result of suppression of I(A) density and a shift in the inactivation curves of I(A) and I(K) in a hyperpolarizing direction in these cells. This study identifies for the first time a specific molecular mechanism in subpopulations of colonic DRG neurons that underlies chronic visceral hypersensitivity.

The language of medicine: words as servants and scoundrels

Progress in complex disorders requires clear thinking facilitated by clear language. Clinicians and scientists occasionally become captive to inaccurate language or meaningless terminology and this generates lazy thinking and impedes progress. Has this happened in the case of the functional gastrointestinal disorders (FGIDs), in general, and irritable bowel syndrome (IBS), in particular? FGIDs and, especially IBS, are common illnesses and an important burden on healthcare resources but, in general, have suffered from a lack of progress in the development of safe and effective treatment. Among FGIDs, IBS may be the best defined but significant lapses of accuracy in terminology persist. Among other FGIDs, the situation is more serious; imprecision and lack of consistency in terminology continue to mar progress. This article reviews the chequered history of terminology in this area and concludes that removing the obfuscation generated by poor usage of language should be the first step towards understanding the pathogenesis and improving the management of these, and similar, disorders.

The efficacy of probiotics in IBS

The clear delineation of a postinfective variety of irritable bowel syndrome (IBS), and the description, in a number of studies, of evidence of low-grade inflammation and immune activation in IBS, suggest a role for a dysfunctional relationship between the indigenous flora and the host in IBS and, accordingly, provide a clear rationale for the use of probiotics in this disorder. Other modes of action, including bacterial displacement and alterations in luminal contents, are also plausible. Although clinical evidence of efficacy is now beginning to emerge, a review of available trials emphasizes the importance of clear definition of strain selection, dose, and viability. The possible roles of cotherapy or sequential therapy with antibiotics, probiotics, prokinetics, or other agents, also deserve further study. The role of the enteric flora is evidently an area of great potential in IBS; we are on the threshold of a new era of research and therapy for this common disorder.

Vagal dysfunction in irritable bowel syndrome assessed by rectal distension and baroreceptor sensitivity

Autonomic nervous system dysfunction has been implicated in the pathophysiology of irritable bowel syndrome (IBS). This study characterized the autonomic response to rectal distension in IBS using baroreceptor sensitivity (BRS), a measure of autonomic function. Rectal bag pressure, discomfort, pain, ECG, blood pressure and BRS were continuously measured before, during and after rectal distension in 98 healthy volunteers (34 +/- 12 years old, 52 females) and 39 IBS patients (39 +/- 11 years old, 35 females). In comparison with the healthy volunteers, IBS patients experienced significantly more discomfort (69 +/- 2.2% vs 56 +/- 3.6%; P < 0.05), but not pain (9 +/- 1.4% vs 6 +/- 2.4%; ns) with rectal distension despite similar distension pressures (51 +/- 1.4 vs 54 +/- 2.4 mmHg; ns) and volumes (394 +/- 10.9 vs 398 +/- 21.5 mL; ns). With rectal distension, heart rate increased in both healthy volunteers (66 +/- 1 to 71 +/- 1 bpm; P < 0.05) and IBS patients (66 +/- 2 to 74 +/- 3 bpm; P < 0.05). Systolic blood pressure also increased in both healthy volunteers (121 +/- 2 to 143 +/- 2 mmHg; P < 0.05) and patients (126 +/- 3 to 153 +/- 4 mmHg (P < 0.05) as did diastolic blood pressure, 66 +/- 2 to 80 +/- 2 mmHg (P < 0.05), compared with 68 +/- 3 to 84 +/- 3 mmHg (P < 0.05) in IBS patients. The systolic blood pressure increase observed in IBS patients was greater than that seen in healthy volunteers and remained elevated in the post distension period (139 +/- 3 mmHg vs 129 +/- 2 mmHg; P < 0.05). IBS patients had lower BRS (7.85 +/- 0.4 ms mmHg(-1)) compared with healthy volunteers (9.4 +/- 0.3; P < 0.05) at rest and throughout rectal distension. Greater systolic blood pressure response to rectal distension and associated diminished BRS suggests a compromise of the autonomic nervous system in IBS patients.

Probiotics in irritable bowel syndrome: an immunomodulatory strategy?

The clear delineation of a post-infective variety of IBS, as well as the description, in a number of studies, of evidence of low-grade inflammation and immune activation in IBS, suggest a role for a dysfunctional relationship between the indigenous flora and the host in IBS and, accordingly, provide a clear rationale for the use of probiotics in this disorder. Other modes of action, including bacterial displacement and alterations in luminal contents, are also plausible. While clinical evidence of efficacy is now beginning to emerge, a review of available trials emphasizes the importance of a clear definition of strain selection, dose and viability. The possible roles of co-therapy or sequential therapy with antibiotics, probiotics, prokinetics, or other agents also deserves further study. The role of the enteric flora is evidently an area of great potential in IBS; we are on the threshold of a new era of research and therapy for this common disorder.

Bacteria: a new player in gastrointestinal motility disorders--infections, bacterial overgrowth, and probiotics

Irritable bowel syndrome (IBS) may result from a dysfunctional interaction between the indigenous flora and the intestinal mucosa, which in turn leads to immune activation in the colonic mucosa. Some propose that bacterial overgrowth is a common causative factor in the pathogenesis of symptoms in IBS; others point to evidence suggesting that the cause stems from more subtle qualitative changes in the colonic flora. Bacterial overgrowth will probably prove not to be a major factor in what will eventually be defined as IBS. Nevertheless, short-term therapy with either antibiotics or probiotics seems to reduce symptoms among IBS patients. However, in the long term, safety issues will favor the probiotic approach; results of long-term studies with these agents are eagerly awaited.

Review article: the role of antibiotics vs. conventional pharmacotherapy in treating symptoms of irritable bowel syndrome

BACKGROUND

The concept of augmenting the management of irritable bowel syndrome with antibiotics is evolving, and many questions remain regarding this therapy relative to known and hypothesized irritable bowel syndrome pathophysiology. The clinical evidence of small intestinal bacterial overgrowth as an important aetiology of irritable bowel syndrome continues to accumulate. Clinical symptoms of bacterial overgrowth and irritable bowel syndrome are similar; however, a definitive cause-and-effect relationship remains unproven. It is unclear whether motility dysfunction causes bacterial overgrowth or gas products of enteric bacteria affect intestinal motility in irritable bowel syndrome.

AIM

To discusses the efficacy and tolerability of current symptom-directed pharmacotherapies and of antibiotics in the treatment of irritable bowel syndrome.

METHODS

A computerized search of PubMed was performed with search terms "IBS", "pharmacotherapy" and "antibiotics". Relevant articles were selected, and the reference list of selected articles was reviewed to identify additional references.

RESULTS

Antibiotic treatment benefits a subset of irritable bowel syndrome patients. The non-absorbed antibiotic rifaximin has a favourable safety and tolerability profile compared with systemic antibiotics and demonstrates a therapeutic efficacy comparable with symptom-based irritable bowel syndrome pharmacotherapies.

CONCLUSION

Rifaximin is the only antibiotic with demonstrated sustained benefit beyond therapy cessation in irritable bowel syndrome patients in a placebo-controlled trial. Whether antibiotics can improve quality of life in patients with irritable bowel syndrome warrants further research.

Functional chest pain: esophageal or overlapping functional disorder

BACKGROUND

Whether patients with functional chest pain have an esophageal or overlapping functional disorder of the gut is unclear. We investigated the prevalence of functional gastrointestinal disorders in patients with functional chest pain.

METHODS

One hundred patients with functional chest pain and normal cardiac, endoscopic, and manometric studies were evaluated for esophageal hypersensitivity with a balloon distension test. Subsequently, a modified Rome II functional bowel disorder questionnaire was mailed to these subjects. Prevalence of irritable bowel syndrome (IBS) and other functional disorder were determined using the Rome II criteria. In addition, we assessed the prevalence of chest pain in 81 patients with functional constipation.

RESULTS

There were 69 responders (54 women); 2 were excluded. Fifty-five patients (82%) fulfilled criteria for other functional disorders besides chest pain. Although there was an overlap, IBS (27%) and abdominal bloating (22%) were most common; dyspepsia (7%), dysphagia (7%), nonspecific bowel disorder (7%), constipation (4%), abdominal pain (3%), and diarrhea (1%) were less common. Among responders, 52 (78%) had esophageal hypersensitivity and 15 (22%) had normosensitivity, with similar prevalence of functional disorders. Thirty-two (39%) of the subjects with functional constipation reported chest pain occasionally, and 5 (6%) frequently.

CONCLUSIONS

Approximately 80% of patients with functional chest pain exhibit features of other functional disorders including IBS suggesting an overlap. This association is independent of esophageal hypersensitivity. Recognition of this overlap may facilitate better management of these patients.

Probiotics and irritable bowel syndrome: a rationale for their use and an assessment of the evidence to date

Probiotics, defined as live organisms that, when ingested in adequate amounts, exert a health benefit on the host, have been used for almost a century in the management of a variety of medical disorders, usually on the basis of little evidence. Advances in our understanding of the gut flora and of its relationship to the host, together with progress in microbiology, molecular biology and clinical research have identified important biological properties for probiotics and demonstrated efficacy in a number of gastrointestinal disorders. The clear delineation of a post-infective variety of irritable bowel syndrome (IBS), as well as the description, in a number of studies, of evidence of low-grade inflammation and immune activation in IBS, suggest a role for a dysfunctional relationship between the indigenous flora and the host in IBS and, accordingly, provide a clear rationale for the use of probiotics in this disorder. Other modes of action, including bacterial displacement and alterations in luminal contents, are also plausible. While clinical evidence of efficacy is now beginning to emerge, a review of available trials emphasises the importance of clear definition of strain selection, dose and viability. This is evidently an area of great potential in IBS and deserves further study at all levels.

The vanilloid receptor initiates and maintains colonic hypersensitivity induced by neonatal colon irritation in rats

BACKGROUND & AIMS

Robust chemical or mechanical irritation of the colon of neonatal rats leads to chronic visceral hypersensitivity. The clinical and physiologic relevance of such noxious stimulation in the context of human irritable bowel syndrome is questionable. The aims of this study were to determine whether mild chemical irritation of the colon of neonatal rats produced persistent changes in visceral sensitivity and to evaluate the role of transient receptor potential vanilloid 1 (TRPV1) in the initiation and maintenance of visceral hypersensitivity.

METHODS

Ten-day-old rat pups received an intracolonic infusion of 0.5% acetic acid in saline. TRPV1 inhibitors were administered 30 minutes before acetic acid sensitization. Sensitivity of the colon to balloon distention (CRD) in adults was measured by grading their abdominal withdrawal reflex and electromyographic responses. In adult rats, TRPV1 antagonist was injected intraperitoneally 30 minutes before CRD.

RESULTS

Neonatal acetic acid treatment resulted in higher sensitivity to CRD in adult rats compared with controls in the absence of histopathologic signs of inflammation. Treatment of colons of adult rats with acetic acid did not produce persistent sensitization. Antagonism of the TRPV1 before neonatal administration of acetic acid and after established visceral hypersensitivity attenuated sensitivity to CRD. TRPV1 expression was increased in dorsal root ganglia-containing colon afferent neurons.

CONCLUSIONS

We have described a new model for persistent colonic sensory dysfunction following a transient noxious stimulus in the neonatal period and a potentially important role for TRPV1 in initiation and maintenance of persistent visceral hypersensitivity.

Serotonergic and non-serotonergic targets in the pharmacotherapy of visceral hypersensitivity

Visceral hypersensitivity is considered a key mechanism in the pathogenesis of functional gastrointestinal (GI) disorders. Targeting visceral hypersensitivity seems an attractive approach to the development of drugs for functional GI disorders. This review summarizes current knowledge on targets for the treatment of visceral hypersensitivity, and the status of current and future drug and probiotic treatment development, and the role of pharmacogenomic factors.

Public speaking stress-induced neuroendocrine responses and circulating immune cell redistribution in irritable bowel syndrome

OBJECTIVES

Augmented neuroendocrine stress responses and altered immune functions may play a role in the manifestation of functional gastrointestinal (GI) disorders. We tested the hypothesis that IBS patients would demonstrate enhanced psychological and endocrine responses, as well as altered stress-induced redistribution of circulating leukocytes and lymphocytes, in response to an acute psychosocial stressor when compared with healthy controls.

METHODS

Responses to public speaking stress were analyzed in N = 17 IBS patients without concurrent psychiatric conditions and N = 12 healthy controls. At baseline, immediately following public speaking, and after a recovery period, state anxiety, acute GI symptoms, cardiovascular responses, serum cortisol and plasma adrenocorticotropic hormone (ACTH) were measured, and numbers of circulating leukocytes and lymphocyte subpopulations were analyzed by flow cytometry.

RESULTS

Public speaking led to significant cardiovascular activation, a significant increase in ACTH, and a redistribution of circulating leukocytes and lymphocyte subpopulations, including significant increases in natural killer cells and cytotoxic/suppressor T cells. IBS patients demonstrated significantly greater state anxiety both at baseline and following public speaking. However, cardiovascular and endocrine responses, as well as the redistribution of circulating leukocytes and lymphocyte subpopulations after public speaking stress, did not differ for IBS patients compared with controls.

CONCLUSIONS

In IBS patients without psychiatric comorbidity, the endocrine response as well as the circulation pattern of leukocyte subpopulations to acute psychosocial stress do not differ from healthy controls in spite of enhanced emotional responses. Future studies should discern the role of psychopathology in psychological and biological stress responses in IBS.

Cilansetron: A New Selective Serotonin Type 3 (5-HT3)-Receptor Antagonist for the Treatment of Irritable Bowel Syndrome in Males and Females

Irritable Bowel Syndrome (IBS) is a significant problem that affects a large proportion of the US population. The past several years have seen advances in our understanding of the pathophysiology associated with IBS and the development of new therapies. Older therapies have few well-designed clinical studies to support their use. The older studies tended to evaluate the impact of therapy on only one symptom and were ineffective at improving the overall symptomology in this functional disorder. In addition, the older drugs tended to produce side effects that often led to discontinuation of the therapy. Newer therapies, such as the FDA approved serotonergic agents (eg, alosetron and tegaserod), target abnormalities in gut physiology seen in IBS and not just the symptomatic presentation of the disease. In women, these medications have shown to be effective treatments for IBS with diarrhea (IBS-D) and IBS with constipation (IBS-C). Pending FDA approval, cilansetron represents the second 5-HT3 antagonist for the treatment of IBS-D. It has shown promising results in both men and women, which is an improvement over alosetron, since it is only approved for use in females. Similar to alosetron, the most common side effect seen with cilansetron therapy is constipation. Few cases of ischemic colitis, like those seen during alosetron therapy, have been reported in the cilansetron clinical trials and all have resolved without complication. A thorough review of the available data regarding cilansetron will be discussed in this article.

Intestinal epithelial cell signalling and host-derived negative regulators under chronic inflammation: to be or not to be activated determines the balance towards commensal bacteria

Advancing knowledge regarding the cellular mechanisms of intestinal inflammation has led to a better understanding of the disease pathology in patients with chronic disorders of the gut including inflammatory bowel disease, coeliac disease, lymphocytic colitis and irritable bowel syndrome. An emerging new paradigm suggests that changes in the homeostasis of bacteria- and host-derived signal transduction at the epithelial cell level may lead to functional and immune disturbances of the intestinal epithelium. It has become clear from numerous studies that enteric bacteria are a critical component in the development and prevention/treatment of chronic intestinal inflammation. Signal-specific activation of mitogen-activated protein kinases (MAPK), interferon-regulated factors (IRF) and the transcription factor NF-kappaB through pattern recognition receptor signalling effectively induce inflammatory defence mechanisms. Unbalanced activation of these innate signalling pathways because of host genetic predispositions and/or the lack of adequate anti-inflammatory feedback mechanisms may turn a physiological response into a pathological situation including failure of bacterial clearance and development of chronic inflammation. Host-derived regulators from the immune and enteric nerve system crosstalk to the innate signalling network of the intestinal epithelium in order to shape the extent and duration of inflammatory processes.

Changing face of irritable bowel syndrome

Recent years have witnessed tremendous progress in our understanding of irritable bowel syndrome (IBS). It is evident that this is a truly global disease associated with significant symptoms and impairments in personal and social functioning for afflicted individuals. Advances in our understanding of gut flora-mucosal interactions, the enteric nervous system and the brain-gut axis have led to substantial progress in the pathogenesis of symptoms in IBS and have provided some hints towards the basic etiology of this disorder, in some subpopulations, at the very least. We look forward to a time when therapy will be addressed to pathophysiology and perhaps, even to primary etiology. In the meantime, a model based on a primary role for intestinal inflammation serves to integrate the various strands, which contribute to the presentation of IBS

Effect of stress on expression of neuronal nitric oxide synthase in colonic nervous system in rats

AIM: To investigate the effect of stress on the expression of neuronal nitric oxide synthase (nNOS) in colonic nerv-ous system in rats.

METHODS: Thirty male SD rats were randomly divided into control group, stress group and NG-nitro-L-arginine methyl ester (L-NAME) group. The rat model of water immersion-restraint stress (WRS) was established. The expression of nNOS in colonic submucous plexus and myenteric plexus in the rats was examined by immuno-histochemical staining and analyzed by computer image analysis system.

RESULTS: nNOS immune-positive substance was mostly expressed in the neurons of submucous plexus and myenteric plexus. In comparison with that in contr-ol group, the gray value of nNOS positive neurons in submucous plexus and myenteric plexus was signifi-cantly decreased (P = 0.02 or P = 0.005), and the den-sity of nNOS positive neurons was increased markedly (P = 0.04 or P = 0.01) in stress group. Moreover, nNOS expression in mucosal epithelial cells and lamina pro-pria lymphocytes were also observed. In comparison with that in stress group, the gray value of nNOS posi-tive neurons in submucous plexus and myenteric plexus was increased (P = 0.04), and the density of nNOS positive neurons was decreased (P = 0.04 or P = 0.03) in L-NAME group. nNOS expression was not significantly different between the rats of L-NAME and control group (P >0.05).

CONCLUSION: WRS can increase the expression of nNOS in colonic nervous system in rats, which suggests nitric oxide (NO) may play an important role in WRS-induced function disorder of colon.

Proteomic analysis of colonic mucosa by two-dimensional gel electrophoresis in constipation-predominant irritable bowel syndrome

AIM: To analyze the differential expression of proteome in colonic mucosa between patients with constipation-predominant irritable bowel syndrome (C-IBS) and the healthy controls.

METHODS: Two dimensional polyacrylamide gel elect-rophoresis (2-DE) technique and computer-assisted image analysis were used to separate the protein spots and analyze the differential expression of proteome in the colonic mucosa of the healthy controls and patients with C-IBS.

RESULTS: A total of 308 protein spots were identified in the av-erage gel of the healthy controls, and 238 in patients with C-IBS. A total of 178 protein spots were matched, and the mean matching rate was 74.49%. There were 18 protein spots that were significantly differentially expressed. Of those 18 protein spots, the expression of 3 spots were increased markedly, while 15 were decreased significantly.

CONCLUSION: The proteomic expression in colonic mu-cosa of patients with C-IBS is significantly different from that of the healthy contr ols, which may be associated with the pathogenesis of C-IBS.