Exaggerated motility of the descending colon with repetitive distention of the sigmoid colon in patients with irritable bowel syndrome

The Imperative for Innovative Enteric Nervous System-Intestinal Organoid Co-Culture Models: Transforming GI Disease Modeling and Treatment

This review addresses the need for innovative co-culture systems integrating the enteric nervous system (ENS) with intestinal organoids. The breakthroughs achieved through these techniques will pave the way for a transformative era in gastrointestinal (GI) disease modeling and treatment strategies. This review serves as an introduction to the companion protocol paper featured in this journal. The protocol outlines the isolation and co-culture of myenteric and submucosal neurons with small intestinal organoids. This review provides an overview of the intestinal organoid culture field to establish a solid foundation for effective protocol application. Remarkably, the ENS surpasses the number of neurons in the spinal cord. Referred to as the "second brain", the ENS orchestrates pivotal roles in GI functions, including motility, blood flow, and secretion. The ENS is organized into myenteric and submucosal plexuses. These plexuses house diverse subtypes of neurons. Due to its proximity to the gut musculature and its cell type complexity, there are methodological intricacies in studying the ENS. Diverse approaches such as primary cell cultures, three-dimensional (3D) neurospheres, and induced ENS cells offer diverse insights into the multifaceted functionality of the ENS. The ENS exhibits dynamic interactions with the intestinal epithelium, the muscle layer, and the immune system, influencing epithelial physiology, motility, immune responses, and the microbiome. Neurotransmitters, including acetylcholine (ACh), serotonin (5-HT), and vasoactive intestinal peptide (VIP), play pivotal roles in these intricate interactions. Understanding these dynamics is imperative, as the ENS is implicated in various diseases, ranging from neuropathies to GI disorders and neurodegenerative diseases. The emergence of organoid technology presents an unprecedented opportunity to study ENS interactions within the complex milieu of the small and large intestines. This manuscript underscores the urgent need for standardized protocols and advanced techniques to unravel the complexities of the ENS and its dynamic relationship with the gut ecosystem. The insights gleaned from such endeavors hold the potential to revolutionize GI disease modeling and treatment paradigms.

Mechanosensing in the Physiology and Pathology of the Gastrointestinal Tract

Normal gastrointestinal function relies on sensing and transducing mechanical signals into changes in intracellular signaling pathways. Both specialized mechanosensing cells, such as certain enterochromaffin cells and enteric neurons, and non-specialized cells, such as smooth muscle cells, interstitial cells of Cajal, and resident macrophages, participate in physiological and pathological responses to mechanical signals in the gastrointestinal tract. We review the role of mechanosensors in the different cell types of the gastrointestinal tract. Then, we provide several examples of the role of mechanotransduction in normal physiology. These examples highlight the fact that, although these responses to mechanical signals have been known for decades, the mechanosensors involved in these responses to mechanical signals are largely unknown. Finally, we discuss several diseases involving the overstimulation or dysregulation of mechanotransductive pathways. Understanding these pathways and identifying the mechanosensors involved in these diseases may facilitate the identification of new drug targets to effectively treat these diseases.

The role of mechanosensitive ion channels in the gastrointestinal tract

Mechanosensation is essential for normal gastrointestinal (GI) function, and abnormalities in mechanosensation are associated with GI disorders. There are several mechanosensitive ion channels in the GI tract, namely transient receptor potential (TRP) channels, Piezo channels, two-pore domain potassium (K2p) channels, voltage-gated ion channels, large-conductance Ca²⁺-activated K⁺ (BKCa) channels, and the cystic fibrosis transmembrane conductance regulator (CFTR). These channels are located in many mechanosensitive intestinal cell types, namely enterochromaffin (EC) cells, interstitial cells of Cajal (ICCs), smooth muscle cells (SMCs), and intrinsic and extrinsic enteric neurons. In these cells, mechanosensitive ion channels can alter transmembrane ion currents in response to mechanical forces, through a process known as mechanoelectrical coupling. Furthermore, mechanosensitive ion channels are often associated with a variety of GI tract disorders, including irritable bowel syndrome (IBS) and GI tumors. Mechanosensitive ion channels could therefore provide a new perspective for the treatment of GI diseases. This review aims to highlight recent research advances regarding the function of mechanosensitive ion channels in the GI tract. Moreover, it outlines the potential role of mechanosensitive ion channels in related diseases, while describing the current understanding of interactions between the GI tract and mechanosensitive ion channels.

Disorders of the enteric nervous system - a holistic view

The enteric nervous system (ENS) is the largest division of the peripheral nervous system and closely resembles components and functions of the central nervous system. Although the central role of the ENS in congenital enteric neuropathic disorders, including Hirschsprung disease and inflammatory and functional bowel diseases, is well acknowledged, its role in systemic diseases is less understood. Evidence of a disordered ENS has accumulated in neurodegenerative diseases ranging from amyotrophic lateral sclerosis, Alzheimer disease and multiple sclerosis to Parkinson disease as well as neurodevelopmental disorders such as autism. The ENS is a key modulator of gut barrier function and a regulator of enteric homeostasis. A 'leaky gut' represents the gateway for bacterial and toxin translocation that might initiate downstream processes. Data indicate that changes in the gut microbiome acting in concert with the individual genetic background can modify the ENS, central nervous system and the immune system, impair barrier function, and contribute to various disorders such as irritable bowel syndrome, inflammatory bowel disease or neurodegeneration. Here, we summarize the current knowledge on the role of the ENS in gastrointestinal and systemic diseases, highlighting its interaction with various key players involved in shaping the phenotypes. Finally, current flaws and pitfalls related to ENS research in addition to future perspectives are also addressed.

The effect of colonic tissue electrical stimulation and celiac branch of the abdominal vagus nerve neuromodulation on colonic motility in anesthetized pigs

BACKGROUND

Knowledge on optimal electrical stimulation (ES) modalities and region-specific functional effects of colonic neuromodulation is lacking. We aimed to map the regional colonic motility in response to ES of (a) the colonic tissue and (b) celiac branch of the abdominal vagus nerve (CBVN) in an anesthetized porcine model.

METHODS

In male Yucatan pigs, direct ES (10 Hz, 2 ms, 15 mA) of proximal (pC), transverse (tC), or distal (dC) colon was done using planar flexible multi-electrode array panels and CBVN ES (2 Hz, 0.3-4 ms, 5 mA) using pulse train (PT), continuous (10 min), or square-wave (SW) modalities, with or without afferent nerve block (200 Hz, 0.1 ms, 2 mA). The regional luminal manometric changes were quantified as area under the curve of contractions (AUC) and luminal pressure maps generated. Contractions frequency power spectral analysis was performed. Contraction propagation was assessed using video animation of motility changes.

KEY RESULTS

Direct colon ES caused visible local circular (pC, tC) or longitudinal (dC) muscle contractions and increased luminal pressure AUC in pC, tC, and dC (143.0 ± 40.7%, 135.8 ± 59.7%, and 142.0 ± 62%, respectively). The colon displayed prominent phasic pressure frequencies ranging from 1 to 12 cpm. Direct pC and tC ES increased the dominant contraction frequency band (1-6 cpm) power locally. Pulse train CBVN ES (2 Hz, 4 ms, 5 mA) triggered pancolonic contractions, reduced by concurrent afferent block. Colon contractions propagated both orally and aborally in short distances.

CONCLUSION AND INFERENCES

In anesthetized pigs, the dominant contraction frequency band is 1-6 cpm. Direct colonic ES causes primarily local contractions. The CBVN ES-induced pancolonic contractions involve central neural network.

EphrinB2/ephB2-mediated myenteric synaptic plasticity: mechanisms underlying the persistent muscle hypercontractility and pain in postinfectious IBS

Patients with irritable bowel syndrome (IBS) show pain hypersensitivity and smooth muscle hypercontractility in response to colorectal distension (CRD). Synaptic plasticity, a key process of memory formation, in the enteric nervous system may be a novel explanation. This study aimed to explore the regulatory role of ephrinB2/ephB2 in enteric synaptic plasticity and colonic hyperreactive motility in IBS. Postinfectious (PI)-IBS was induced by Trichinella spiralis infection in rats. Isometric contractions of colonic circular muscle strips, particularly neural-mediated contractions, were recorded ex vivo. Meanwhile, ephrinB2/ephB2-mediated enteric structural and functional synaptic plasticity were assessed in the colonic muscularis, indicating that ephrinB2 and ephB2 were located on enteric nerves and up-regulated in the colonic muscularis of PI-IBS rats. Colonic hypersensitivity to CRD and neural-mediated colonic hypercontractility were present in PI-IBS rats, which were correlated with increased levels of cellular homologous fos protein (c-fos) and activity-regulated cystoskeleton-associated protein (arc), the synaptic plasticity-related immediate early genes, and were ameliorated by ephB2Fc (an ephB2 receptor blocker) or MK801 (an NMDA receptor inhibitor) exposure. EphrinB2/ephB2 facilitated synaptic sprouting and NMDA receptor-mediated synaptic potentiation in the colonic muscularis of PI-IBS rats and in the longitudinal muscle-myenteric plexus cultures, involving the Erk-MAPK and PI3K-protein kinase B pathways. In conclusion, ephrinB2/ephB2 promoted the synaptic sprouting and potentiation of myenteric nerves involved in persistent muscle hypercontractility and pain in PI-IBS. Hence, ephrinB2/ephB2 may be an emerging target for the treatment of IBS.-Zhang, L., Wang, R., Bai, T., Xiang, X., Qian, W., Song, J., Hou, X. EphrinB2/ephB2-mediated myenteric synaptic plasticity: mechanisms underlying the persistent muscle hypercontractility and pain in postinfectious IBS.

Irritable bowel syndrome – psychiatric issues

Introduction: Irritable bowel syndrome is a chronic gastrointestinal disease classified as a functional gastrointestinal disorder. It has been diagnosed on the basis of the so-called Rome IV criteria since 2016. The prevalence of IBS in the general population is about 10–20%, with most patients being women. The etiology of the syndrome is multifactorial and is associated with visceral sensory dysfunction, abnormalities of motor and secretory bowel function, a history of infectious diarrhea and abnormalities in gut microbiota, dysregulation of the brain–gut axis (the influence of the hypothalamic-pituitary-adrenal axis and sex hormones), genetic, psychosocial, and environmental factors, and the patient's personality traits. IBS patients may show differences in the structure and function of the brain when compared to healthy control individuals. Treatment of IBS involves the use of non-pharmacological interventions (psychotherapy, education, hypnotherapy, dietary modifications, regular physical activity) and pharmacotherapy (cholinolytic drugs, opioid receptor antagonists, tricyclic antidepressants, serotonin 5-HT3 receptor antagonists and 5-HT4 agonists).

Aim: The aim of the authors of this work is to draw attention to certain psychiatric aspects of the irritable bowel syndrome. It meets the criteria for a somatization disorder. Somatization is an important psychological factor directly related to the severity of IBS. It is estimated that the prevalence of psychiatric disorders among IBS patients ranges from 40% to 90% and is higher than in the general population. Affective disorders and anxiety disorders are the most commonly diagnosed.

Method: The article reviews the research and works available in the Google Scholar and PubMed databases combining the issue of IBS with psychiatric aspects, i.e. common for IBS and psychiatric disorders, etiopathogenesis, the concept of somatization in the context of IBS, and the coexistence of diseases and mental disorders with the irritable bowel syndrome.

Conclusion: Further research is needed to determine the causes of comorbidity of IBS and mental disorders.

Association between gastrointestinal symptoms and affectivity in patients with bipolar disorder

AIM

To study if anxiety, depression and experience of stress are associated with gastrointestinal (GI) symptoms in patients with bipolar disorder.

METHODS

A total of 136 patients with bipolar disorder (mean age 49.9 years; 61% women) and 136 controls from the general population (mean age 51.0 years; 60% women) were included in the study. GI symptoms were assessed with The Gastrointestinal Symptom Rating Scale-irritable bowel syndrome (GSRS-IBS), level of anxiety and depression with The Hospital Anxiety and Depression Scale (HADS) and stress-proneness with Perceived Stress Questionnaire. Over a ten year period, all visits in primary care were retrospectively recorded in order to identify functional GI disorders.

RESULTS

In subjects with low total HADS-score, there were no significant differences in GI-symptoms between patients and controls (GSRS-IBS 7.0 vs 6.5, P = 0.513). In the patients with bipolar disorder there were significant correlations between all GSRS and HADS subscores for all symptom clusters except for “constipation” and “reflux”. Factors associated to GI symptoms in the patient group were female sex (adjusted OR = 2.37, 95%CI: 1.07-5.24) and high HADS-Depression score (adjusted OR = 3.64, 95%CI: 1.07-12.4). These patients had also significantly more visits for IBS than patients with low HADS-Depression scores (29% vs 8%, P = 0.008). However, there was no significant differences in consulting behaviour for functional GI disorders between patients and controls (25% vs 17%, P = 0.108).

CONCLUSION

Female patients and patients with high HADS depression score reported significantly more GI symptoms, whereas patients with low HADS scores did not differ from control subjects.

Corticotropin-releasing factor receptor type 1 and type 2 interaction in irritable bowel syndrome

Irritable bowel syndrome (IBS) displays chronic abdominal pain or discomfort with altered defecation, and stress-induced altered gut motility and visceral sensation play an important role in the pathophysiology. Corticotropin-releasing factor (CRF) is a main mediator of stress responses and mediates these gastrointestinal functional changes. CRF in brain and periphery acts through two subtype receptors such as CRF receptor type 1 (CRF1) and type 2 (CRF2), and activating CRF1 exclusively stimulates colonic motor function and induces visceral hypersensitivity. Meanwhile, several recent studies have demonstrated that CRF2 has a counter regulatory action against CRF1, which may imply that CRF2 inhibits stress response induced by CRF1 in order to prevent it from going into an overdrive state. Colonic contractility and sensation may be explained by the state of the intensity of CRF1 signaling. CRF2 signaling may play a role in CRF1-triggered enhanced colonic functions through modulation of CRF1 activity. Blocking CRF2 further enhances CRF-induced stimulation of colonic contractility and activating CRF2 inhibits stress-induced visceral sensitization. Therefore, we proposed the hypothesis, i.e., balance theory of CRF1 and CRF2 signaling as follows. Both CRF receptors may be activated simultaneously and the signaling balance of CRF1 and CRF2 may determine the functional changes of gastrointestinal tract induced by stress. CRF signaling balance might be abnormally shifted toward CRF1, leading to enhanced colonic motility and visceral sensitization in IBS. This theory may lead to understanding the pathophysiology and provide the novel therapeutic options targeting altered signaling balance of CRF1 and CRF2 in IBS.

Brain and gut interactions in irritable bowel syndrome: new paradigms and new understandings

Irritable bowel syndrome (IBS) is characterized by abdominal pain and altered bowel habits. Visceral hypersensitivity is believed to be a key underlying mechanism that causes pain. There is evidence that interactions within the brain and gut axis (BGA), that involves both the afferent-ascending and the efferent-descending pathways, as well as the somatosensory cortex, insula, amygdala, anterior cingulate cortex, and hippocampus, are deranged in IBS showing both the activation and inactivation. Clinical manifestations of IBS such as pain, altered gut motility, and psychological dysfunction may each be explained, in part, through the changes in the BGA, but there is conflicting information, and its precise role is not fully understood. A better understanding of the BGA may shed more knowledge regarding the pathophysiology of IBS that in turn may lead to the discovery of novel therapies for this common disorder.

Effect of ramosetron on stool consistency in male patients with irritable bowel syndrome with diarrhea

BACKGROUND & AIMS

Ramosetron, a serotonin (5-hydroxytryptamine)-3 receptor antagonist with high selectivity, reduced stress-induced diarrhea and defecation caused by corticotropin-releasing hormone in rats. However, there have been no clinical trials of its effect in patients with diarrhea and irritable bowel syndrome (IBS-D). We performed a randomized, double-blind, placebo-controlled trial to determine whether ramosetron reduces diarrhea in these patients.

METHODS

Our study included 296 male outpatients with IBS-D treated at 52 centers in Japan. Patients were given 5 μg oral ramosetron (n = 147) or placebo (n = 149) once daily for 12 weeks after a 1-week baseline period. The primary end point was increased stool consistency in the first month. Secondary end points included relief of overall IBS symptoms and increased IBS-related quality of life.

RESULTS

More patients given ramosetron (74, 50.3%) than those given placebo (29, 19.6%) reported improved stool consistency in the first month (P < .001). The relative risk and number needed to treat were 2.57 (95% confidence interval, 1.79-3.70) and 3.25 (95% confidence interval, 2.44-4.89), respectively. The ramosetron group had significantly higher monthly rates of relief of overall IBS symptoms and IBS-related quality of life than the placebo group.

CONCLUSIONS

Ramosetron (5 μg oral, once daily for 12 weeks) improved stool consistency in male patients with IBS-D, compared with placebo. These study results, along with the pharmacologic profile of ramosetron, indicate that increased stool consistency is the best end point for studies of ramosetron in patients with IBS-D. Clinicaltrials.gov No, NCT01225237.

Gastrointestinal specific anxiety in irritable bowel syndrome: validation of the Japanese version of the visceral sensitivity index for university students

OBJECTIVE

The visceral sensitivity index (VSI) is a useful self-report measure of the gastrointestinal symptom-specific anxiety (GSA) of patients with irritable bowel syndrome (IBS). Previous research has shown that worsening GSA in IBS patients is related to the severity of GI symptoms, suggesting that GSA is an important endpoint for intervention. However, there is currently no Japanese version of the VSI. We therefore translated the VSI into Japanese (VSI-J) and verified its reliability and validity.

MATERIAL AND METHODS

Participants were 349 university students aged 18 and 19 years and recruited from an academic class. We analyzed data from the VSI-J, Anxiety Sensitivity Index (ASI), Hospital Anxiety and Depression scale (HAD), and Irritable Bowel Syndrome Severity Index (IBS-SI). The internal consistency, stability, and factor structure of the VSI-J and its associations with anxiety, depression and severity measures were investigated.

RESULTS

The factor structure of the VSI-J is unidimensional and similar to that of the original VSI (Cronbach's α = 0.93). Construct validity was demonstrated by significant correlations with ASI (r = 0.43, p < 0.0001), HAD-ANX (r = 0.19, p = 0.0003), and IBS-SI scores (r = 0.45, p < 0.0001). Furthermore, the VSI-J was a significant predictor of severity scores on the IBS-SI and demonstrated good discriminant (p < 0.0001) and incremental (p < 0.0001) validity.

CONCLUSION

These findings suggest that the VSI-J is a reliable and valid measure of visceral sensitivity.

Stress and visceral pain: focusing on irritable bowel syndrome

Recent advances in brain science have shown that the brain function encoding emotion depends on interoceptive signals such as visceral pain. Visceral pain arose early in our evolutionary history. Bottom-up processing from gut-to-brain and top-down autonomic/neuroendocrine mechanisms in brain-to-gut signaling constitute a circuit. Brain imaging techniques have enabled us to depict the visceral pain pathway as well as the related emotional circuit. Irritable bowel syndrome (IBS) is characterized by chronic recurrent abdominal pain or abdominal discomfort associated with bowel dysfunction. It is also thought to be a disorder of the brain-gut link associated with an exaggerated response to stress. Corticotropin-releasing hormone (CRH), a major mediator of the stress response in the brain-gut axis, is an obvious candidate in the pathophysiology of IBS. Indeed, administration of CRH has been shown to aggravate the visceral sensorimotor response in IBS patients, and the administration of peptidergic CRH antagonists seems to alleviate IBS pathophysiology. Serotonin (5-HT) is another likely candidate associated with brain-gut function in IBS, as 5-HT3 antagonists, 5-HT4 agonists, and antidepressants were demonstrated to regulate 5-HT neurotransmission in IBS patients. Autonomic nervous system function, the neuroimmune axis, and the brain-gut-microbiota axis show specific profiles in IBS patients. Further studies on stress and visceral pain neuropathways in IBS patients are warranted.

Effects of preceding stimulation on brain activation in response to colonic distention in humans

OBJECTIVE

It has been suggested that the pattern of distension (moderate following mild and vice versa) might influence brain activation and the experience of hypersensitivity, offset analgesia, and anticipation. Nevertheless, how the pattern of stimulation affects sensitization and/or desensitization to visceral stimulation remains unknown.

METHODS

In 45 nonclinical healthy participants (12 women, 33 men; 20-26 years old), brain processing of visceral sensation induced by colonic distension was examined using H2(15)O positron emission tomography. Subjective feelings regarding the stimuli were also measured. The descending colon was stimulated using six patterns of three bag pressures (0, 20, and 40 mm Hg). To evaluate the neural sensitization to visceral stimulation arising from the precedence effect, the effects of a 20- or 40-mm Hg distention after a sham or 20- or 40-mm Hg distension were analyzed using statistical parametric mapping. The level of significance was set at a voxelwise level of p < .0001, with cluster extent sizes of k > 50.

RESULTS

The midbrain, insula, and cerebellum, were more strongly activated by a 20-mm Hg distension with a preceding 40-mm Hg distention than by a 20-mm Hg distention without a preceding stimulation (p < .0001). Conversely, a sham stimulation after the experience of an intense stimulation activated the midcingulate cortex, compared with a sham stimulation without the experience of actual visceral stimulation (p < .0001).

CONCLUSIONS

By directly comparing different patterns of visceral stimuli, preceding visceral stimuli may affect neural sensitization and/or desensitization in humans, including elevated midbrain, insula, and midcingulate cortex.

Pooled analysis of brain activity in irritable bowel syndrome and controls during rectal balloon distension

BACKGROUND

Brain-imaging literature of irritable bowel syndrome (IBS) suggests an abnormal brain-gut communication. We analyzed the literature to evaluate and compare the aspects of brain activity in individuals with IBS and control subjects experiencing controlled rectal stimulation.

METHODS

PubMed was searched until September 2010. Data from 16 articles reporting brain activity during rectal balloon distensions in IBS compared to control groups was analyzed. Prevalence rates and pairwise activations were assessed using binomial distributions for 11 selected regions of interest. The data were aggregated to adjust for center effect.

KEY RESULTS

There was considerable variability in the literature regarding regions and their activity patterns in controls and individuals with IBS. There was no significant difference found in the thalamus, anterior cingulate cortex, posterior cingulate cortex, and prefrontal cortex, however, results show limited evidence of consensus for the anterior insula (AI) (P = 0.22). Pairwise activity results suggest that pairs involving the AI tend to have more consistent activity together than pairs which do not involve the AI (posterior insula and AI, P = 0.08; posterior cingulate cortex and AI, P = 0.16), however, no pairwise evaluation reached significance.

CONCLUSIONS & INFERENCES

Our pooled analysis demonstrates that the literature reports are quite heterogeneous but there is some evidence that there may be patterns of higher activity more common in individuals with IBS than in controls. A consensus, though, regarding study designs, analysis approach and reporting could create a clearer understanding of brain involvement in IBS pathophysiology.

Peripherally acting therapies for the treatment of irritable bowel syndrome

Gut-acting therapies are common therapies for irritable bowel syndrome (IBS). Most of these peripheral acting agents are primarily targeted at individual symptoms. The evidence supporting the use of these agents in IBS is largely anecdotal. Serotonergic agents and the chloride channel activator lubiprostone have shown efficacy in treating symptoms of IBS. The clinical evidence supporting the use of these agents is based on data from high-quality clinical trials. The use of serotonergic agents for IBS in the United States is limited to the 5-hydroxytryptamine-3 antagonist alosetron in the treatment of women with severe IBS with diarrhea refractory to traditional therapy.

Asian motility studies in irritable bowel syndrome

Altered motility remains one of the important pathophysiologic factors in patients with irritable bowel syndrome (IBS) who commonly complain of abdominal pain and stool changes such as diarrhea and constipation. The prevalence of IBS has increased among Asian populations these days. Gastrointestinal (GI) physiology may vary between Asian and Western populations because of differences in diets, socio-cultural backgrounds, and genetic factors. The characteristics and differences of GI dysmotility in Asian IBS patients were reviewed. MEDLINE search work was performed including following terms, 'IBS,' 'motility,' 'transit time,' 'esophageal motility,' 'gastric motility,' 'small intestinal motility,' 'colonic motility,' 'anorectal function,' and 'gallbladder motility' and over 100 articles were categorized under 'esophagus,' 'stomach,' 'small intestine,' 'colon,' 'anorectum,' 'gallbladder,' 'transit,' 'motor pattern,' and 'effect of stressors.' Delayed gastric emptying, slow tansit in constipation predominant IBS patients, rapid transit in diarrhea predominant IBS patients, accelerated motility responses to various stressors such as meals, mental stress, or corticotrophin releasing hormones, and altered rectal compliance and altered rectal accomodation were reported in many Asian studies regarding IBS. Many conflicting results were found among these studies and there are still controversies to conclude these as unique features of Asian IBS patients. Multinational and multicenter studies are needed to be performed vigorously in order to elaborate characteristics as well as differences of altered motililty in Asian patients with IBS.

Abnormal colonic motility: a possible association with urge fecal incontinence

PURPOSE

Fecal incontinence is a distressing condition affecting up to 7% of the population. Severe urgency is a symptom associated with hypersensitivity of the rectum, a common finding in both fecal incontinence and irritable bowel syndrome. The purpose of this study was to investigate whether patients with fecal incontinence, urgency, and rectal hypersensitivity have abnormal hindgut motility, suggestive of a more generalized motility problem.

METHODS

Eleven females with urgency-associated incontinence and without anal sphincter injury were compared with 5 controls. After full clinical, ultrasonographic, and physiological assessment, patients underwent prolonged colonic manometry studies. Motility patterns were recorded and, in particular, the response to a standard gastrocolic reflex was noted.

RESULTS

Rectal sensation values in patients were as follows: first sensation, 22 (range, 5-58) mls; desire to defecate, 31 (range, 13-166) mls; and maximum tolerated volume, 64 (range, 21-254) mls. Compared with controls, patients had significantly higher numbers of 1) low amplitude waves (>5 mmHg) in both the sigmoid colon (101 vs 46.5; P = .028) and the descending colon (101.5 vs 41; P = .036) in the hour before the meal stimulus, and 2) high amplitude waves (>50 mmHg) in the sigmoid colon (2 vs 0; P = .006) in the fasting state.

CONCLUSION

Patients with fecal incontinence associated with severe urgency may have rectal hypersensitivity and a more global colonic motility problem similar to irritable bowel syndrome.

Irritable bowel syndrome and inflammatory bowel disease: infectious gastroenteritis-related disorders?

Infectious gastroenteritis may be one of the important factors in the development of irritable bowel syndrome (IBS), with affected individuals often categorized as having post-infectious IBS (PI-IBS), and is linked to the onset of symptoms in approximately 10-20% of patients diagnosed with IBS. Intestinal mucosal infiltration of T cells and mast cells, and enterochromaffin cell hyperplasia are significant immunological and pathological findings that reveal the pathogenesis of PI-IBS, and results of laboratory studies using animal models of PI-IBS clearly support clinical evidence. Recently, infectious gastroenteritis has also been suggested to be associated with the development of inflammatory bowel disease (IBD), and various studies have suggested that individuals with IBS or IBS-like symptoms may be susceptible to initiation of IBD. However, it is still unclear whether infectious gastroenteritis is directly or indirectly (through PI-IBS) linked to the initiation of IBD. Additional studies are necessary to understand the clinical overlap among infectious gastroenteritis, IBS, and IBD.

Contributions of pain sensitivity and colonic motility to IBS symptom severity and predominant bowel habits

OBJECTIVES

Irritable bowel syndrome (IBS) patients show pain hypersensitivity and hypercontractility in response to colonic or rectal distention. Aims were to determine whether predominant bowel habits and IBS symptom severity are related to pain sensitivity, colon motility, or smooth muscle tone.

METHODS

One hundred twenty-nine patients classified as IBS with diarrhea (IBS-D, N = 44), IBS with constipation (IBS-C, N = 29), mixed IBS (IBS-M, N = 45), and unspecified IBS (IBS-U, N = 11) based on stool consistency, and 30 healthy controls (HC) were studied. A manometric catheter containing a 600-mL capacity plastic bag was positioned in the descending colon. Pain threshold was assessed using a barostat. Motility was assessed for 10 min with the bag minimally inflated (individual operating pressure [IOP]), 10 min at 20 mmHg above the IOP, and for 15-min recovery following bag inflation. Motility was also recorded for 30 min following an 810-kcal meal.

RESULTS

Compared with HC, IBS patients had lower pain thresholds (medians 30 vs 40 mmHg, P < 0.01), but IBS subtypes were not different. IBS symptom severity was correlated with pain thresholds (rho =-0.36, P < 0.001). During distention, the motility index (MI) was significantly higher in IBS compared with HC (909 +/- 73 vs 563 +/- 78, P < 0.01). Average barostat bag volume at baseline was higher (muscle tone lower) in HC compared with IBS-D and IBS-M but not compared with IBS-C. The baseline MI and bag volume differed between IBS-D and IBS-C and correlated with symptoms of abdominal distention and dissatisfaction with bowel movements. Pain thresholds and MI during distention were uncorrelated.

CONCLUSIONS

Pain sensitivity and colon motility are independent factors contributing to IBS symptoms. Treatment may need to address both, and to be specific to predominant bowel habit.

Corticotropin-releasing hormone receptor 1 antagonist blocks colonic hypersensitivity induced by a combination of inflammation and repetitive colorectal distension

Gastroenteritis is one of the risk factors for developing irritable bowel syndrome (IBS). However, the precise mechanism of postinfectious IBS is still unknown. We tested the hypothesis that a combination of previous inflammation and repetitive colorectal distention (CRD) makes the colon hypersensitive and that treatment with a corticotropin-releasing hormone receptor 1 (CRH-R1) antagonist blocks this colonic hypersensitivity. Rats were pretreated with vehicle or 2,4,6-trinitrobenzene sulphonic acid (TNBS) 6 weeks before CRD. For the CRD experiment, the colorectum was distended once a day for six consecutive days. The CRH-R1 antagonist (CP-154,526, 20 mg kg(-1)) or vehicle was injected subcutaneously 30 min before CRD. Visceral perception was quantified as visceromotor response (VMR) using an electromyograph. For histological examination, the rats were killed on the last day of CRD experiment, and haematoxylin and eosin-staining of colon segments was performed. Although from the first to the third day of CRD, VMRs increased in both the vehicle-treated rats and TNBS-treated rats, they were significantly higher in TNBS-treated rats than those in vehicle-treated controls. On the fifth day of CRD, however, VMRs in the vehicle-treated rats were significantly greater than those in TNBS-treated rats. Pretreatment of rats with CP-154,526 significantly attenuated the increase in VMR induced by repetitive CRD with previous inflammation. Finally, we found that repetitive CRD and repetitive CRD after colitis induced visceral inflammation. These results indicate that a combination of previous inflammation and repetitive CRD induces visceral hypersensitivity and that a CRH-R1 antagonist attenuates this response in rats.

Factors influencing functional abdominal pain in children

Functional gastrointestinal disorders (FGIDs) commonly affect children and are associated with short- and long-term morbidity. Although the pathogenesis of pain-related FGIDs remains incompletely understood, most investigators agree on a multifactorial etiology and the presence of an altered brain-gut interaction. A continuous interplay of genetic and environmental factors appears to shape the development of the central and enteric nervous systems. The biopsychosocial model is the current operational framework for children with FGIDs, as it recognizes the interaction between social and environmental influences and psychological and physiologic processes. The biopsychosocial model proposes that specific permutations of genetic susceptibility, early life experiences, sociocultural issues, and coping mechanisms could explain the variability in clinical presentation and outcome among individuals.

New insights into the pathogenesis and pathophysiology of irritable bowel syndrome

The pathogenesis and pathophysiology of irritable bowel syndrome is complex and still incompletely known. Potential pathogenetic factors include genes, infectious events, psychological symptoms and other loosely defined environmental factors. Both alterations at the central and peripheral level are thought to contribute to the symptoms of irritable bowel syndrome, including psychosocial factors, abnormal gastrointestinal motility and secretion, and visceral hypersensitivity. Today irritable bowel syndrome is viewed upon as a disorder of dysregulation of the so-called brain-gut axis, involving abnormal function in the enteric, autonomic and/or central nervous systems, with peripheral abnormalities probably dominating in some patients and disturbed central processing of signals from the periphery in others. Lines of evidence also suggest that inflammation within the gastrointestinal tract may be of great importance in at least subgroups of irritable bowel syndrome patients. To conclude, a complex picture of the pathogenesis and pathophysiology of irritable bowel syndrome is emerging, with interactions between several different alterations resulting in the divergent symptom pattern in these patients.

Mechanisms of hypersensitivity in IBS and functional disorders

General introduction The concept of visceral hypersensitivity is accepted as being germane to several functional gastrointestinal disorders (FGIDs). The causes or risk factors associated with this hypersensitivity are unclear. This article addresses the proposed mechanisms leading to hypersensitivity: from genetic to inflammatory disorders, from central to peripheral alterations of function. However, in order to place visceral hypersensitivity in a more global perspective as an aetiological factor for FGIDs, it also provides a review of recent evidence regarding the role of other peripheral mechanisms (the intraluminal milieu), as also genetic factors in the pathophysiology of these disorders. The article has been divided into five independent sections. The first three sections summarize the evidence of visceral hypersensitivity as a biological marker of functional gut disorders, the peripheral and central mechanisms involved, and the role of inflammation on hypersensitivity. In opposition to visceral hypersensitivity as an isolated phenomenon in functional gut disorders, the last two sections focus on the importance of peripheral mechanisms, like motor disturbances, specifically those resulting on altered transport of intestinal gas, and alterations of the intraluminal milieu and genetics.

Role of motility in chronic diarrhoea

Patients complaining of 'chronic diarrhoea' usually mean the passage of loose, urgent stools. Chronic diarrhoea is a feature of malabsorption; it may also be seen in the 'dumping syndrome' which follows gastric surgery, small intestinal bacterial overgrowth, bile salt malabsorption and in malabsorption of simple sugars including most commonly lactose, fructose and sorbitol. Excessively rapid entry of chyme into the small or large intestine generates propulsive motor patterns leading to accelerated transit. Inflammation is associated with decreased normal mixing motor patterns but increased propulsive motility including high amplitude propagated contractions (HAPCs). Evidence for abnormal small intestinal motility in the diarrhoea associated with irritable bowel syndrome (IBS) is conflicting and any difference appears small. Increased colonic HAPCs with increased propulsion is seen in IBS with diarrhoea (IBS-D). Stress-induced colonic motility is increased in IBS-D with hyper-responsiveness to corticotrophin releasing factor (CRF). Long-lasting increases in mucosal serotonin availability may contribute to the chronic diarrhoea seen in IBS-D and coeliac disease. Treatments for abnormal motility in chronic diarrhoea include those designed to correct specific underlying abnormalities including octreotide, antibiotics, colestyramine, specific food avoidance and anti-inflammatory agents. There are also treatments aimed primarily at altering motility directly including opiates, 5HT3 receptor antagonists and amitriptyline.

Acupuncture for functional gastrointestinal disorders

Functional gastrointestinal (GI) symptoms are common in the general population. Especially, motor dysfunction of the GI tract and visceral hypersensitivity are important. Acupuncture has been used to treat GI symptoms in China for thousands of years. It is conceivable that acupuncture may be effective in patients with functional GI disorders because it has been shown to alter acid secretion, GI motility, and visceral pain. Acupuncture at the lower limbs (ST-36) causes muscle contractions via the somatoparasympathetic pathway, while at the upper abdomen (CV-12) it causes muscle relaxation via the somatosympathetic pathway. In some patients with gastroesophageal reflux disease (GERD) and functional dyspepsia (FD), peristalsis and gastric motility are impaired. The stimulatory effects of acupuncture at ST-36 on GI motility may be beneficial to patients with GERD or FD, as well as to those with constipation-predominant irritable bowel syndrome (IBS), who show delayed colonic transit. In contrast, the inhibitory effects of acupuncture at CV-12 on GI motility may be beneficial to patients with diarrhea-predominant IBS, because enhanced colonic motility and accelerated colonic transit are reported in such patients. Acupuncture at CV-12 may inhibit gastric acid secretion via the somatosympathetic pathway. Thus, acupuncture may be beneficial to GERD patients. The antiemetic effects of acupuncture at PC-6 (wrist) may be beneficial to patients with FD, whereas the antinociceptive effects of acupuncture at PC-6 and ST-36 may be beneficial to patients with visceral hypersensitivity. In the future, it is expected that acupuncture will be used in the treatment of patients with functional GI disorders.

Repetitive rectal painful distention induces rectal hypersensitivity in patients with irritable bowel syndrome

BACKGROUND

A reduced rectal perceptual threshold has been reported in patients with irritable bowel syndrome (IBS), but this phenomenon may be induced by a comorbid psychological state. We evaluated the rectal pain threshold at baseline and after conditioning (repetitive rectal painful distention: RRD) in patients with IBS or functional abdominal pain syndrome (FAPS), which is an abdominal pain disorder, and in healthy controls, and determined whether rectal hypersensitivity is a reliable marker for IBS.

METHODS

The rectal sensory threshold was assessed by a barostat. First, a ramp distention of 40 ml/min was induced, and the threshold of pain and the maximum tolerable pressure (mmHg) were measured. Next, RRD (phasic distentions of 60-s duration separated by 30-s intervals) was given with a tracking method until the subjects had complained of pain six times. Finally, ramp distention was induced again, and the same parameters were measured. The normal value was defined by calculating the 95% confidence intervals of controls.

RESULTS

Five or six of the seven IBS patients showed a reduced rectal pain threshold or maximum tolerable pressure, respectively, at baseline. In all patients with IBS, both thresholds were reduced after RRD load, but they were reduced in none of the patients with FAPS. RRD significantly reduced both thresholds in the IBS group (P < 0.05), but it had no effect in the control or FAPS groups.

CONCLUSIONS

Rectal hypersensitivity induced by RRD may be a reliable marker for IBS. Conditioning-induced visceral hypersensitivity may play a pathophysiologic role in IBS.

Colonic regular contractile frequency patterns in irritable bowel syndrome: the 'spastic colon' revisited

BACKGROUND

Irritable bowel syndrome is a frequent gastrointestinal disorder of which the pathophysiological basis is still not completely understood. Among the various proposed mechanisms, colonic motility may play a role, at least in a subset of patients.

AIMS

To investigate the regular colonic contractile patterns in patients with irritable bowel syndrome. Our working hypothesis was that an increase of these patterns in such condition might represent a motility equivalent of the so-called 'spastic colon'.

PATIENTS AND METHODS

Twelve patients of both genders were investigated by means of 24 h colonic manometry, and the results were compared to those from 20 healthy controls. Regular contractile patterns (with frequencies ranging from 2 to 8 per min) were calculated for the entire recording period and in single colonic segments.

RESULTS

Overall, colonic frequency patterns were significantly more frequent in patients than controls (12.6% vs 6.4% of the total contractile activity, P < 0.001); in both groups, the 3 cycles/min frequency was predominant, especially in the sigmoid colon. More than 40% patients displayed a correlation between abdominal pain and occurrence of regular contractile frequencies.

CONCLUSIONS

Abnormal colonic motility may play some role in the pathogenesis of symptoms related to irritable bowel syndrome, with an excess of regular contractile activity related to the so-called 'spastic colon'.

Brain activity during distention of the descending colon in humans

Brain-gut interaction is considered to be a major factor in the pathophysiology of irritable bowel syndrome. However, only limited information has been provided on the influence of gastrointestinal tract stimulation on the brain. Our aim in this study was to determine the specific regions of the brain that are responsible for visceral perception and emotion provoked by distention of the descending colon in humans. Fifteen healthy males aged 22 +/- 1 participated in this study. Using a colonoscope, a balloon was inserted into the descending colon of each subject. After sham stimulation, the colon was randomly stimulated with bag pressures of 20 and 40 mmHg, and regional cerebral blood flow was measured by [(15)O] positron emission tomography. The subjects were asked to report visceral perception and emotion using an ordinate scale of 0-10. Colonic distention pressure dependently induced visceral perception and emotion, which significantly correlated with activation of specific regions of the brain including the prefrontal, anterior cingulate, parietal cortices, insula, pons, and the cerebellum. In conclusion, distention of the descending colon induces visceral perception and emotion. These changes significantly correlate with activation of specific regions in the brain including the limbic system and the association cortex, especially the prefrontal cortex.

Management of irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders. The prevalence rate is 10-20% and women have a higher prevalence. IBS adversely affects quality of life and is associated with health care use and costs. IBS comprises a group of functional bowel disorders in which abdominal discomfort or pain is associated with defecation or a change in bowel habit, and with features of disordered defecation. The consensus definition and criteria for IBS have been formalized in the "Rome II criteria". Food, psychiatric disorders, and gastroenteritis are risk factors for developing IBS. The mechanism in IBS involves biopsychosocial disorders; psychosocial factors, altered motility, and heightened sensory function. Brain-gut interaction is the most important in understanding the pathophysiology of IBS. Effective management requires an effective physician-patient relationship. Dietary treatment, lifestyle therapy, behavioral therapy, and pharmacologic therapy play a major role in treating IBS. Calcium polycarbophil can benefit IBS patients with constipation or alternating diarrhea and constipation.

Irritable bowel syndrome in women: a common health problem

Irritable bowel syndrome is a common but complex problem that disproportionately affects women. Nurses are ideally situated to provide accurate information regarding the disorder and to provide symptom management. Currently, the diagnosis is based on the presence of abdominal pain and alterations in bowel habits. A multicomponent approach beginning with education and reassurance is more likely to be effective than one focused on a predominant symptoms (eg., constipation) alone. Building a therapeutic relationship with the patient over time will likely enhance the effectiveness of the prescribed therapy. Treatment paradigms that include new drugs that affect more than one symptom of IBS, along with nondrug therapies (eg, relaxation and cognitive behavioral strategies), will likely hold the greatest promise for management.