Visceral hypersensitivity in irritable bowel syndrome

A low FODMAP diet plus traditional dietary advice versus a low-carbohydrate diet versus pharmacological treatment in irritable bowel syndrome (CARIBS): a single-centre, single-blind, randomised controlled trial

BACKGROUND

Dietary advice and medical treatments are recommended to patients with irritable bowel syndrome (IBS). Studies have not yet compared the efficacy of dietary treatment with pharmacological treatment targeting the predominant IBS symptom. We therefore aimed to compare the effects of two restrictive dietary treatment options versus optimised medical treatment in people with IBS.

METHODS

This single-centre, single-blind, randomised controlled trial was conducted in a specialised outpatient clinic at the Sahlgrenska University Hospital, Gothenburg, Sweden. Participants (aged ≥18 years) with moderate-to-severe IBS (Rome IV; IBS Severity Scoring System [IBS-SSS] ≥175) and no other serious diseases or food allergies were randomly assigned (1:1:1) by web-based randomisation to receive a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) plus traditional IBS dietary advice recommended by the UK National Institute for Health and Care Excellence (hereafter the LFTD diet), a fibre-optimised diet low in total carbohydrates and high in protein and fat (hereafter the low-carbohydrate diet), or optimised medical treatment based on predominant IBS symptom. Participants were masked to the names of the diets, but the pharmacological treatment was open-label. The intervention lasted 4 weeks, after which time participants in the dietary interventions were unmasked to their diets and encouraged to continue during 6 months' follow-up, participants in the LFTD group were instructed on how to reintroduce FODMAPs, and participants receiving pharmacological treatment were offered diet counselling and to continue with their medication. The primary endpoint was the proportion of participants who responded to the 4-week intervention, defined as a reduction of 50 or more in IBS-SSS relative to baseline, and was analysed per modified intention-to-treat (ie, all participants who started the intervention). Safety was analysed in the modified intention-to-treat population. This trial is registered with ClinicalTrials.gov, NCT02970591, and is complete.

FINDINGS

Between Jan 24, 2017, and Sept 2, 2021, 1104 participants were assessed for eligibility and 304 were randomly assigned. Ten participants did not receive their intervention after randomisation and thus 294 participants were included in the modified intention-to-treat population (96 assigned to the LFTD diet, 97 to the low-carbohydrate diet, and 101 to optimised medical treatment). 241 (82%) of 294 participants were women and 53 (18%) were men and the mean age was 38 (SD 13). After 4 weeks, 73 (76%) of 96 participants in the LFTD diet group, 69 (71%) of 97 participants in the low-carbohydrate diet group, and 59 (58%) of 101 participants in the optimised medical treatment group had a reduction of 50 or more in IBS-SSS compared with baseline, with a significant difference between the groups (p=0·023). 91 (95%) of 96 participants completed 4 weeks in the LFTD group, 92 (95%) of 97 completed 4 weeks in the low-carbohydrate group, and 91 (90%) of 101 completed 4 weeks in the optimised medical treatment group. Two individuals in each of the intervention groups stated that adverse events were the reason for discontinuing the 4-week intervention. Five (5%) of 91 participants in the optimised medical treatment group stopped treatment prematurely due to side-effects. No serious adverse events or treatment-related deaths occurred.

INTERPRETATION

Two 4-week dietary interventions and optimised medical treatment reduced the severity of IBS symptoms, with a larger effect size in the diet groups. Dietary interventions might be considered as an initial treatment for patients with IBS. Research is needed to enable personalised treatment strategies.

FUNDING

The Healthcare Board Region Västra Götaland, the Swedish Research Council, the Swedish Research Council for Health, Working Life and Welfare, AFA Insurance, grants from the Swedish state, the Wilhelm and Martina Lundgren Science Foundation, Skandia, the Dietary Science Foundation, and the Nanna Swartz Foundation.

Effects of oral administration of ondansetron, a 5-HT3 receptor antagonist, on anxiety-related behaviors and colonic hypercontractility in repeated stress-induced mice

PURPOSE

Chronic psychological stress develops and exacerbates irritable bowel syndrome (IBS). 5-hydroxytryptamine (5-HT) via activation of intestinal 5-HT3 receptors involves impairment of intestinal functions. This study aimed to investigate the effects of ondansetron, a 5-HT3 receptor antagonist, on locomotor activity, anxiety-related behaviors, and colonic functions in repeated water avoidance stress.

MATERIALS AND METHODS

Food intake and fecal pellet output (FPO) of sham stress (SS), water avoidance stress (WS), and water avoidance stress with oral administration of ondansetron (1 mg/kg BW) (WA) groups were monitored along the water avoidance stress protocol for 10 consecutive days. On day 11, locomotor activity and anxiety-related behaviors were determined using an open field test. Contractile properties of colonic tissues in response to KCl and a cumulative dose of carbachol (CCh) were determined using in vitro organ bath technique.

RESULTS

FPO was significantly increased in the WS group after 7 days of water avoidance stress, which was reversed in WA group. WS group decreased unsupported rearing behavior compared to WS group, which was not altered in the WA group. The colon of the WS group had a higher tonic contraction in response to CCh than the SS and WA groups, which was reversed with ondansetron pre-incubation.

CONCLUSIONS

Oral administration of ondansetron prevented increased FPO but did not affect anxiety-related behavior in repeated stress model. Colonic hypercontractility in the stressed mice was related to increased responses to cholinergic-induced contractions, which involved 5-HT3 receptors. Our findings suggest the modulatory roles of 5-HT3 receptors to mediate stress-induced colonic dysfunction.

Antihyperalgesic properties of gut microbiota: Parabacteroides distasonis as a new probiotic strategy to alleviate chronic abdominal pain

ABSTRACT

The potential role of gut microbiota in pain modulation is arousing an emerging interest since recent years. This study investigated neuromodulatory properties of gut microbiota to identify next-generation probiotics to propose alternative therapies for visceral pain management. Neuromodulation ability of 10 bacterial strains isolated from a healthy donor was assessed both on ND7/23 immortalized cell line and primary neuronal cells from rat dorsal root ganglia. This screening highlighted the neuroinhibitory property of Parabacteroides distasonis (F1-2) strain, supported both by its intracellular content and membrane fraction, which was further investigated in visceral pain mouse models. Oral administration of F1-2 resulted in a significant decrease of colonic hypersensitivity (CHS) in dextran sulfate sodium (0.5%) model associated with low-grade inflammation and a significant decrease of CHS in Citrobacter rodentium postinfectious models. No effect of F1-2 oral administration on CHS was observed in a neonatal maternal separation stress model. Antihyperalgesic effect unlikely involved modulation of inflammatory processes or restoration of intestinal barrier. Exploration of direct dialogue mechanisms between this strain and nervous system, assessed by calcium imaging experiments, revealed that F1-2 interacts directly with nociceptors by reducing activation level on capsaicin, inflammatory soup, and bradykinin stimulations. Our study provides new insights about bacteria-host interaction and places P distasonis as a potential therapeutic strategy in the treatment of visceral pain observed in leaky gut-associated pathologies.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Preventing and Treating Colic: An Update

Infantile colic (IC) is c is a self-limiting functional gastrointestinal disorder (FGID) with a favorable natural history. Worldwide, IC has a significant impact on many newborns and their families. Although not an indication of an illness, its symptoms are wide and generic and may indicate a potentially serious underlying issue in a tiny percentage of newborns who may require a medical evaluation. The pathogenesis appears to be multifactorial implying a complex relationship between the infant and the environment. One of the most studied theories attributes a key role to the gut microbiota in the pathogenesis of IC. A variety of approaches have been suggested for the clinical management of IC, and several randomized controlled trials have been reported in the literature. Probiotics can change the host's microbiota and positively impact health. They may be able to restore balance and create a better intestinal microbiota landscape since there is mounting evidence that the gut microbial environment of colicky newborns differs from that of healthy infants. In this review, we revise the most commonly studied probiotics and mixtures to treat and prevent IC and the most recent recommendations.

Low-level inflammation, immunity, and brain-gut axis in IBS: unraveling the complex relationships

Irritable bowel syndrome is a common functional gastrointestinal disorder, and it has been shown that the etiology of irritable bowel syndrome is a multifactorial complex of neurological, inflammatory, and immunological changes. There is growing evidence of low-grade chronic inflammation in irritable bowel patients. The peripheral action response of their intestinal immune factors is integrated into the central nervous system, while the microbiota interacts with the brain-gut axis contributing to the development of low-grade chronic inflammation. The objective of this review is to present a discussion about the impact of immune-brain-gut axis-inflammation interactions on irritable bowel syndrome, its clinical relevance in the course of irritable bowel syndrome disease, and possible therapeutic modalities.

The Importance of Visceral Hypersensitivity in Irritable Bowel Syndrome-Plant Metabolites in IBS Treatment

The visceral stimuli from the digestive tract are transmitted via afferent nerves through the spinal cord to the brain, where they are felt as pain. The overreaction observed in the brain of irritable bowel syndrome (IBS) patients may be due to increased peripheral sensitivity to stimuli from the gastrointestinal tract. Although the exact pathway is uncertain, attenuation of visceral hypersensitivity is still of interest in treating IBS. It has been shown that stress stimulates the sympathetic nervous system while inhibiting the vagus nerve (VN). In addition, stress factors lead to dysbiosis and chronic low-grade inflammation of the intestinal mucosa, which can lead to lower gastrointestinal visceral hypersensitivity. Therefore, an important goal in the treatment of IBS is the normalization of the intestinal microflora. An interesting option seems to be nutraceuticals, including Terminalia chebula, which has antibacterial and antimicrobial activity against various pathogenic Gram-positive and Gram-negative bacteria. Additionally, short-term transcutaneous vagus nerve stimulation can reduce the stress-induced increase in intestinal permeability, thereby reducing inflammation. The conducted studies also indicate a relationship between the stimulation of the vagus nerve (VN) and the activation of neuromodulatory networks in the central nervous system. Therefore, it seems reasonable to conclude that a two-way action through stimulating the VN and using nutraceuticals may become an effective therapy in treating IBS.

Multimodal hypersensitivity derived from quantitative sensory testing predicts pelvic pain outcome: an observational cohort study

ABSTRACT

Multimodal hypersensitivity (MMH)-greater sensitivity across multiple sensory modalities (eg, light, sound, temperature, pressure)-is associated with the development of chronic pain. However, previous MMH studies are restricted given their reliance on self-reported questionnaires, narrow use of multimodal sensory testing, or limited follow-up. We conducted multimodal sensory testing on an observational cohort of 200 reproductive-aged women, including those at elevated risk for chronic pelvic pain conditions and pain-free controls. Multimodal sensory testing included visual, auditory, and bodily pressure, pelvic pressure, thermal, and bladder pain testing. Self-reported pelvic pain was examined over 4 years. A principal component analysis of sensory testing measures resulted in 3 orthogonal factors that explained 43% of the variance: MMH, pressure pain stimulus response, and bladder hypersensitivity. The MMH and bladder hypersensitivity factors correlated with baseline self-reported menstrual pain, genitourinary symptoms, depression, anxiety, and health. Over time, MMH increasingly predicted pelvic pain and was the only component to predict outcome 4 years later, even when adjusted for baseline pelvic pain. Multimodal hypersensitivity was a better predictor of pelvic pain outcome than a questionnaire-based assessment of generalized sensory sensitivity. These results suggest that MMHs overarching neural mechanisms convey more substantial long-term risk for pelvic pain than variation in individual sensory modalities. Further research on the modifiability of MMH could inform future treatment developments in chronic pain.

The Effects of Serotonin Receptor Type 7 Modulation on Bowel Sensitivity and Smooth Muscle Tone in Patients With Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a gut-brain disorder involving alterations in intestinal sensitivity and motility. Currently, IBS has no cure, and treatment focuses on the management of symptoms. The diverse, and sometimes contradictory, collections of symptoms reported across the different subtypes of IBS make treatment, as well as diagnosis, difficult for physicians. All subtypes of IBS have one symptom in common: abdominal pain caused by differences in the level of visceral sensitivity. Though current research on this topic is in its infancy, some researchers have proven, through experimental studies, that 5-hydroxytryptamine (serotonin) receptor type 7 (5-HT7) affects both visceral sensitivity and smooth muscle tone in the bowel. Therefore, this review will be discussing the future possibility of alleviating abdominal pain in patients with IBS and related disorders by modulating the 5-HT7 receptor.

Probiotics and gastrointestinal diseases

During the past decades, scientists have discovered the intimate role of the gut microbiome in human health, and since then, several papers have been published to investigate if the use of biotics (probiotics, prebiotics, synbiotics, and postbiotics) may have a beneficial impact on human health both in treatment and prevention. We now ask ourselves whether we have reached the finish line or just a new starting point, as the evidence supporting the use of biotics in several conditions still needs a lot of work. Many questions remain unanswered today because the evidence differs depending on the indication, used strain, and amount and duration of administration. Herein we will summarize the evidence on probiotics in some gastrointestinal diseases such as infantile colic, functional abdominal pain disorders, celiac disease, acute gastroenteritis, inflammatory bowel disease, and Helicobacter pylori infection.

Infantile Colic and the Subsequent Development of the Irritable Bowel Syndrome

Background/Aims

Little is known about the association between infantile colic and the later onset of irritable bowel syndrome (IBS).

Methods

This study examined all 917 707 children who were born in Korea between 2007 and 2008. Infantile colic was defined with 1 or more diagnoses of ICD-10 code R10.4 or R68.1 at the age of 5 weeks to 4 months, and infants with a diagnosis of infantile colic and without were allocated into the infantile colic group and the control group. IBS was defined as 2 or more diagnoses of ICD-10 code K58.X after 4 years of age. Each child was traced until 2017. The risk of IBS with infantile colic was evaluated using a Cox proportional hazards model with propensity score inverse probability of treatment weighting (IPTW).

Results

After IPTW, 363 528 and 359 842 children were allocated to the control group and the infantile colic group, respectively. The infantile colic group had a higher risk of developing IBS in childhood (hazard ratio [95% CI], 1.12 [1.10 to 1.13]) than the control group. Moreover, the subgroup analyses according to the feeding status, birth weight, sex, or economic status, showed that the risk of IBS with former infantile colic remained statistically significant.

Conclusions

Children with a diagnosis of infantile colic during the infant period had a significant risk of developing IBS after 4 years of age. Understanding the pathogenesis of infantile colic in the neonatal period may reduce the prevalence and severity of functional gastrointestinal disorders from childhood to adolescence to adulthood.

Psychosocial and Sensory Factors Contribute to Self-Reported Pain and Quality of Life in Young Adults with Irritable Bowel Syndrome

AIMS

Psychosocial and sensory factors, including anxiety, depression, and pressure pain threshold have been used to cluster chronic symptoms in irritable bowel syndrome (IBS). This study examined the contribution of psychosocial sensory factors on pain interference and quality of life (QOL) in this population.

DESIGN

We performed a cross-sectional analysis of baseline data from a randomized controlled trial.

SETTINGS

Two gastrointestinal clinics, general communities, and two large campuses of a public university in the Northeastern United States.

PARTICIPANTS/SUBJECTS

Eighty young adults with IBS aged 21 ± 2.57 years (76.25% female).

METHODS

Demographic and psychosocial factors including anxiety, depression, fatigue, cognition or general concerns, sleep disturbance, self-efficacy, coping, and food intake were measured as independent variables. Quantitative sensory testing was conducted to measure mechanical, thermal, and pressure pain thresholds. Self-reported pain measured by the brief pain inventory (BPI) and IBS-QOL were assessed as the outcome variables. Regression analysis and mediation analysis were conducted to determine the associated factors of IBS pain and QOL.

RESULTS

Age, sex, and psychosocial factors including coping, self-efficacy, alcohol intake, mechanical pain sensitivity, and cold pain threshold were significantly associated with pain interference (all p < 0.05). Coping, and self-efficacy were significantly associated with IBS-QOL (all p < 0.05). In the mediation analysis, coping catastrophizing and self-efficacy were indirectly associated with IBS-QOL mediated by fatigue.

CONCLUSIONS

Psychosocial factors including coping and self-efficacy, and quantitative sensory testing factors significantly correlate with self-reported pain and QOL among young adults with IBS. This preliminary research calls for further interventional studies that target personalized psychosocial and quantitative sensory factors to improve pain management and quality of life in IBS patients.

A Hypothetical Case Example Illustrating the Importance of a Multidisciplinary Approach to Treating Chronic/Functional Abdominal Pain in Pediatric Patients

Irritable bowel syndrome (IBS) can have a substantial impact on the physical, academic, and psychosocial functioning of pediatric patients. As a functional gastrointestinal disorder, pediatric patients with IBS are thought to benefit from a multidisciplinary approach to target the biopsychosocial factors of this condition. In this co-authored article by a Pediatric Gastroenterologist, Pediatric Pain and Palliative Care specialist and Pediatric GI Psychologist, we present a hypothetical case of a pediatric patient who will undergo evaluation and treatment by each of these specialists demonstrating how a collaborative effort amongst multidisciplinary specialists is the ideal approach to care.

Peripheral apelin mediates visceral hypersensitivity and impaired gut barrier in a rat irritable bowel syndrome model

Growing evidence indicates that visceral hypersensitivity and impaired gut barrier play an important role in the pathophysiology of irritable bowel syndrome (IBS). In animal models, these changes are known to be mediated via corticotropin-releasing factor (CRF)-Toll like receptor 4 (TLR4)-proinflammatory cytokine signaling. Apelin, an endogenous ligand of APJ, was reported to modulate CRF-induced enhanced colonic motility. In this context, we hypothesized that apelin also modulates visceral sensation and gut barrier, and tested this hypothesis. We measured visceral pain threshold in response to colonic balloon distention by abdominal muscle contractions assessed by electromyogram in rats. Colonic permeability was estimated by quantifying the absorbed Evans blue in colonic tissue. Intraperitoneal (ip) administration of [Ala13]-apelin-13, an APJ antagonist, blocked lipopolysaccharide (LPS)- or CRF-induced visceral hypersensitivity and colonic hyperpermeability (IBS model) in a dose-response manner. These inhibitory effects were blocked by compound C, an AMPK inhibitor, N^G-nitro-L-arginine methyl ester, a nitric oxide (NO) synthesis inhibitor or naloxone in the LPS model. On the other hand, ip [Pyr1]-apelin-13, an APJ agonist, caused visceral hypersensitivity and colonic hyperpermeability, and these effects were reversed by astressin, a CRF receptor antagonist, TAK-242, a TLR4 antagonist or anakinra, an interleukin-1 receptor antagonist. APJ system modulated CRF-TLR4-proinflammatory cytokine signaling to cause visceral hypersensitivity and colonic hyperpermeability. APJ antagonist blocked these GI changes in IBS models, which were mediated via AMPK, NO and opioid signaling. Apelin may contribute to the IBS pathophysiology, and the inhibition of apelinergic signaling may be a promising therapeutic option for IBS.

Spinal Reflex Control of Arterial Blood Pressure: The Role of TRP Channels and Their Endogenous Eicosanoid Modulators

The spinal cord is an important integrative center for blood pressure control. Spinal sensory fibers send projections to sympathetic preganglionic neurons of the thoracic spinal cord and drive sympathetically-mediated increases in blood pressure. While these reflexes responses occur in able-bodied individuals, they are exaggerated following interruption of descending control - such as occurs following spinal cord injury. Similar reflex control of blood pressure may exist in disease states, other than spinal cord injury, where there is altered input to sympathetic preganglionic neurons. This review primarily focuses on mechanisms wherein visceral afferent information traveling via spinal nerves influences sympathetic nerve activity and blood pressure. There is an abundance of evidence for the widespread presence of this spinal reflex arch originating from virtually every visceral organ and thus having a substantial role in blood pressure control. Additionally, this review highlights specific endogenous eicosanoid species, which modulate the activity of afferent fibers involved in this reflex, through their interactions with transient receptor potential (TRP) cation channels.

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

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

Probiotics and Functional Gastrointestinal Disorders in Pediatric Age: A Narrative Review

Assessment and management of pain are essential components of pediatric care. Pain in pediatric age is characterized by relevant health and socio-economic consequences due to parental concern, medicalization, and long-term physical and psychological impact in children. Pathophysiological mechanisms of nociception include several pathways in which also individual perception and gut-brain axis seem to be involved. In this narrative review, we analyze the rational and the current clinical findings of probiotic use in the management of functional gastrointestinal disorders (FGID) in pediatric age, with special focus on infantile colic, irritable bowel syndrome, constipation, and gastroesophageal reflux. Some specific probiotics showed a significant reduction in crying and fussing compared to placebo in breastfed infants with colic, although their exact mechanism of action in this disorder remains poorly understood. In irritable bowel syndrome, a limited number of studies showed that specific strains of probiotics can improve abdominal pain/discomfort and bloating/gassiness, although data are still scarce. As for constipation, whilst some strains appear to reduce the number of hard stools in constipated children, the evidence is not adequate to support the use of probiotics in the management of functional constipation. Similarly, although some probiotic strains could promote gastric emptying with a potential improvement of functional symptoms related to gastroesophageal reflux, current evidence is insufficient to provide any specific recommendation for the prevention or treatment of gastroesophageal reflux. In conclusion, probiotics have been proposed as part of management of pain in functional gastrointestinal disorders in pediatric age, but mechanisms are still poorly understood and evidence to guide clinical practice is currently inadequate.

The Role of Carbohydrates in Irritable Bowel Syndrome: Protocol for a Randomized Controlled Trial Comparing Three Different Treatment Options

BACKGROUND

Although it is widely acknowledged that food intake can worsen symptoms in patients with irritable bowel syndrome (IBS), there is a lack of efficient treatments that can apply to all patients and subtypes of IBS. As IBS can manifest in different ways, it is likely that the most successful treatment option will differ among patients; therefore, this large, randomized controlled trial comparing 3 different treatment options for patients with IBS is highly warranted.

OBJECTIVE

This study aims to conduct a randomized controlled trial to evaluate the effectiveness of 3 different treatment options for patients with IBS.

METHODS

A total of 300 patients with IBS will be randomized (1:1:1) to receive one of the following three treatment options: a diet with low total carbohydrate content; a diet combining low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols and traditional dietary advice in IBS; and optimized medical treatment. The study will comprise a 10-day screening period, 28 days of intervention, and a 6-month follow-up for patients receiving dietary treatment. Questionnaires assessing both gastrointestinal and extraintestinal symptoms will be used as end points, as well as metabolomics, microbiota profiling, and immunological markers. Furthermore, qualitative methods will be used to evaluate the patients' experiences regarding diet treatments.

RESULTS

Recruitment for this study began in January 2017. By May 2021, of the proposed 300 participants, 270 (90%) had been randomized, and 244 (81.3%) participants had finished the 4-week intervention. The study is still in progress, and the results are expected to be published in 2022.

CONCLUSIONS

By collecting a wide range of data before, during, and after treatment in a large group of patients with IBS and diverse bowel habits, we will gain new insights into the predictors of response to treatment. That information can, in the future, be used to personalize treatment for the patient, based on the individual's phenotype and IBS symptoms. In addition, the long-term effects of 2 different dietary treatments will be evaluated regarding their impact on gut microbiota and clinical laboratory tests and to ensure that they are safe, effective, and applicable for patients with IBS.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02970591; https://clinicaltrials.gov/ct2/show/NCT02970591.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/31413.

Phlorizin attenuates visceral hypersensitivity and colonic hyperpermeability in a rat model of irritable bowel syndrome

Visceral hypersensitivity and impaired gut barrier are crucial contributors to the pathophysiology of irritable bowel syndrome (IBS), and those are mediated via corticotropin-releasing factor (CRF)-Toll like receptor 4-pro-inflammatory cytokine signaling. Phlorizin is an inhibitor of sodium-linked glucose transporters (SGLTs), and known to have anti-cytokine properties. Thus, we hypothesized that phlorizin may improve these gastrointestinal changes in IBS, and tested this hypothesis in rat IBS models, i.e., lipopolysaccharide (LPS) or CRF-induced visceral hypersensitivity and colonic hyperpermeability. The visceral pain threshold in response to colonic balloon distention was estimated by abdominal muscle contractions by electromyogram, and colonic permeability was measured by quantifying the absorbed Evans blue in colonic tissue. Subcutaneous (s.c.) injection of phlorizin inhibited visceral hypersensitivity and colonic hyperpermeability induced by LPS in a dose-dependent manner. Phlorizin also blocked CRF-induced these gastrointestinal changes. Phlorizin is known to inhibit both SGLT1 and SGLT2, but intragastric administration of phlorizin may only inhibit SGLT1 because gut mainly expresses SGLT1. We found that intragastric phlorizin did not display any effects, but ipragliflozin, an orally active and selective SGLT2 inhibitor improved the gastrointestinal changes in the LPS model. Compound C, an adenosine monophosphate-activated protein kinase (AMPK) inhibitor, N^G-nitro-L-arginine methyl ester, a nitric oxide (NO) synthesis inhibitor and naloxone, an opioid receptor antagonist reversed the effects of phlorizin. In conclusions, phlorizin improved visceral hypersensitivity and colonic hyperpermeability in IBS models. These effects may result from inhibition of SGLT2, and were mediated via AMPK, NO and opioid pathways. Phlorizin may be effective for the treatment of IBS.

Blockade of Erythropoietin-Producing Human Hepatocellular Carcinoma Receptor B1 in Spinal Dorsal Horn Alleviates Visceral Pain in Rats

Objective

This experiment was designed to determine whether erythropoietin-producing human hepatocellular carcinoma (Eph) receptors were involved in the development of visceral pain.

Methods

Adult male Sprague-Dawley rats were randomly divided into three groups receiving different treatments (n = 16 per group): intracolonic vehicle (control group), intracolonic 2, 4, 6-trinitrobenzene sulfonic acid (TNBS) (TNBS group), and intracolonic TNBS and intrathecal EphB1 receptor blocking reagent (TNBS + EphB2-Fc group). Visceral hyperalgesia was evaluated with quantification of visceral pain threshold induced by colorectal distention. The spinal expressions of EphB1 and ephrinB2 and levels of their phosphorylated forms (p-EphB1 and p-ephrinB2) were assessed by Western blotting and immunohistochemistry.

Results

The TNBS-treated rats developed significant visceral hyperalgesia. The spinal expressions of EphB1, p-EphB1, ephrinB2, and p-ephrinB2 were significantly increased in the TNBS group compared with the control group, but visceral hyperalgesia and elevation of spinal EphB1 and p-EphB1 expressions were evidently alleviated by intrathecal administration of EphB2-Fc in the TNBS + EphB2-Fc group. The number of EphB1- and p-EphB1-immunopositive cells, the average optical (AO) value of EphB1, and its phosphorylated form in the spinal dorsal horn were significantly increased in the TNBS group than in the control group, but they were obviously reduced by intrathecal administration of EphB2-Fc. There were no significant differences in the number of ephrinB2- and p-ephrinB2-immunopositive cells and the AO value of ephrinB2 and its phosphorylated form between the TNBS and TNBS + EphB2-Fc groups.

Conclusion

EphB1 receptors in the spinal dorsal horn play a pivotal role in the development of visceral pain and may be considered as a potential target for the treatment of visceral pain.

Comorbid irritable bowel syndrome symptoms and headache have greater association with anxiety than depression: Annual health check-up survey results

High rates of co-existing irritable bowel syndrome (IBS) and headache have been reported in western countries. We investigated that comorbidity in individuals in Japan, along with anxiety and depression in subjects with and without IBS symptoms and/or headache.This cross-sectional study was performed from April 2012 to January 2013 at the Matsue Seikyo General Hospital Health Check Center. Questionnaires concerning symptoms related to IBS (Rome III) and headache, as well as anxiety/depression score were sent to individuals scheduled to undergo an annual health check-up, then returned during the visit and analyzed in a blinded manner.A total of 2885 individuals returned completed questionnaires and were enrolled, of whom 218 (7.6%) met the IBS criteria. The rates of co-existing headache in subjects with and without IBS symptoms were 44.0% (96/218) and 22.9% (611/2667), respectively, indicating a significantly higher rate of co-existing headache in subjects with as compared to without IBS (odds ratio [OR] 2.65, P < .001). Furthermore, the percentage of subjects with anxiety along with comorbid IBS symptoms and headache was significantly greater as compared to those with IBS (OR 3.01, P = .001) or headache (OR 2.41, P < .001) alone. Unlike anxiety, the percentage of subjects with depression was not significantly different among the IBS/non-headache, non-IBS/headache, and IBS/headache groups.Subjects with IBS symptoms had a higher rate of co-existing headache as compared to those without IBS. Furthermore, those with comorbid IBS symptoms and headache had a greater association with anxiety than with depression, as compared to those with only IBS or headache.

PPARγ: A turning point for irritable bowel syndrome treatment

Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal (GI) disorder with negative impacts on quality of life of patients. Although the etiology of the disease is still unclear, there are a set of mechanisms and factors involved in IBS pathogenesis. Visceral hypersensitivity, impaired gut barrier, along with minor inflammation and oxidative stress are the most important triggers for IBS induction. Activation of peroxisome proliferator activated receptor-γ (PPAR-γ) has been shown to improve gut barrier, downregulate pro-inflammatory cytokines, reduce free radical production through antioxidative mechanisms, and exert anti-nociceptive effects against somatic pain. An electronic search in PubMed, Google Scholar, Scopus, and Cochrane library was performed and relevant clinical, in vivo and in vitro articles published between 2004 and June 2020 were collected. Search terms included "Irritable Bowel Syndrome" OR "IBS" OR "visceral hypersensitivity" OR "motility dysfunction" AND "peroxisome proliferator activated receptors" OR "PPAR". Herein, the efficacy of PPARγ signaling as a potential target for IBS treatment is reviewed.

Effects of vitamin D3 supplementation on clinical symptoms, quality of life, serum serotonin (5-hydroxytryptamine), 5-hydroxy-indole acetic acid, and ratio of 5-HIAA/5-HT in patients with diarrhea-predominant irritable bowel syndrome: A randomized clinical trial

Vitamin D deficiency, common in the population with irritable bowel syndrome (IBS), can induce the main factors that lead to IBS clinical symptoms, such as depression, anxiety, and inflammation. Serotonin (5-HT) plays an important role in the pathophysiology of IBS, and its production and secretion are increased from the lumen due to stress and inflammation. The aim of this study was to evaluate the effect of vitamin D3 supplementation on the pathogenesis of diarrhea-predominant IBS (IBS-D). Seventy-four IBS-D patients (age: 18-65 y) participated in a randomized, double-blind, placebo-controlled trial study from February 2017 to May 2018, at Rasoul-e-Akram Hospital, Tehran, Iran. Subjects were allocated into two groups receiving 50,000 IU/week of vitamin D3 or placebo for 9 weeks. IBS severity score system (IBS-SSS), IBS-quality of life questionnaire (QoL), hospital anxiety and depression Scale (HADs), visceral sensitivity index (VSI) and serum 25(OH) vitamin D3, serotonin, 5-hydroxy-indole acetic acid and ratio of 5-HIAA/5-HT were evaluated before and after the interventions. Symptoms severity, QoL, HADs-depression, and VSI score improved significantly in the vitamin D group as compared to the placebo group (P-values: <0.001, 0.049, 0.023, and 0.008; respectively). There were no significant differences in abdominal bloating, HADs-anxiety, serum 5-HT, 5-HIAA, and 5-HIAA/5-HT between the two groups at the end of the study. Based on our results, we recommend serum vitamin D be evaluated in the process of treatment of these patients to ameliorate symptoms and quality life of IBS-D patients with vitamin D deficiency and/or insufficiency.

Glucagon‑like peptide‑1 analogue exendin‑4 modulates serotonin transporter expression in intestinal epithelial cells

Serotonin-selective reuptake transporter (SERT) regulates extracellular availability of serotonin (5-hydroxytryptamine; 5-HT) and participates in the pathogenesis of functional disorders. Colonic SERT expression is decreased in colonic sensitized rats, and the glucagon-like peptide-1 analogue, exendin-4, reduces visceral hypersensitivity by decreasing 5-HT levels and increasing SERT expression. The present in vitro study aimed to further investigate the effects of exendin-4 on SERT expression, and to examine the role of GLP-1 and its receptor in the regulation of 5-HT. SERT mRNA and protein expression levels were detected by reverse transcription-quantitative PCR and western blotting. A ^[3H]−5-HT reuptake experiment was performed in IEC-6 rat intestinal epithelial cells treated with exendin-4. Effects on the adenosine cyclophosphate (AC)/PKA pathway were examined by variously treating cells with the AC activator forskolin, the protein kinase A (PKA) inhibitor H89 and the AC inhibitor SQ22536. Exendin-4 treatment upregulated SERT expression and enhanced 5-HT reuptake in IEC-6 cells. Also, PKA activity in IEC-6 cells was increased by both exendin-4 and forskolin, whereas these effects were abolished by the pre-treatment of exendin-9, which is a GLP-1R inhibitor, SQ22536 and H89. In conclusion, exendin-4 may be associated with the upregulation of SERT expression via the AC/PKA signaling pathway.

GPER-mediated, oestrogen-dependent visceral hypersensitivity in stressed rats is associated with mast cell tryptase and histamine expression

Visceral hypersensitivity (VH) is common in irritable bowel syndrome (IBS), and female patients are more likely to seek healthcare services for IBS-related abdominal pain. Oestrogen has been reported to mediate pain modulation via its receptor, and mast cells are known to participate in the development of visceral hypersensitivity. Our previous studies showed that the G-protein-coupled oestrogen receptor (GPER, also known as GPR30) was expressed by mast cells in human colonic tissues and was associated with IBS type and severity of visceral pain. However, whether GPER is involved in oestrogen-dependent visceral hypersensitivity via mast cell degranulation is still unknown. Rats were subjected to wrap partial restraint stress to induce visceral hypersensitivity and were ovariectomized (OVX) to eliminate the effects of oestrogen on visceral hypersensitivity. OVX rats were treated with oestrogen, an oestrogen receptor α and β antagonist (ICI 182.780), a GPER antagonist (G15) or a GPER agonist (G1), to evaluate the effects of oestrogen via its receptor. The colorectal distention test was performed to assess visceral sensitivity. Immunofluorescence studies were performed to evaluate GPER and mast cell tryptase co-expression. Mast cell number with degranulation was detected by specific staining. Mast cell tryptase expression in rat colon was also investigated by Western blot and immunohistochemistry. Substance P and histamine expression were examined by ELISA. GPER was expressed by the majority of tryptase-positive mast cells in the colonic mucosa. Stressed rats showed increased visceral sensitivity, increased mast cell degranulation, mast cell tryptase expression, and increased colon histamine levels. Ovariectomy reduced stress-induced VH in female rats and decreased mast cell degranulation, mast cell tryptase expression, and histamine levels, whereas oestrogen replacement reversed these effects. In OVX rats, the GPER antagonist G15 counteracted the enhancing effects of oestrogen on stress-induced VH, mast cell degranulation, mast cell tryptase, and histamine expression, whereas VH was preserved after treatment with ICI 182.780. On the other hand, pretreatment with the selective GPER agonist G1 at doses between 1 and 20 μg/kg significantly increased VH, mast cell tryptase, and histamine expression in OVX-stressed rats, mimicking the effects of oestrogen. GPER plays a pivotal role in the regulation of mast cell degranulation, mast cell tryptase expression, and histamine levels and contributes to the development of colonic hypersensitivity in a female rat model of IBS.

Blockade of BDNF signalling attenuates chronic visceral hypersensitivity in an IBS-like rat model

Background

Irritable bowel syndrome (IBS) is a common functional disease characterized by chronic abdominal pain and changes in bowel movements. Effective therapy for visceral hypersensitivity in IBS patients remains challenging. This study investigated the roles of brain‐derived neurotrophic factor (BDNF) and tyrosine kinase receptor B (TrkB) and the effect of ANA‐12 (a selective antagonist of TrkB) on chronic visceral hypersensitivity in an IBS‐like rat model.

Methods

An IBS‐like rat model was established through neonatal maternal separation (NMS), and visceral hypersensitivity was assessed by electromyographic (EMG) responses of the abdominal external oblique muscles to colorectal distention (CRD). Different doses of ANA‐12 were injected intrathecally to investigate the effect of that drug on visceral hypersensitivity, and the open field test was performed to determine whether ANA‐12 had side effects on movement. Thoracolumbar spinal BDNF, TrkB receptor and Protein kinase Mζ (PKMζ) expression were measured to investigate their roles in chronic visceral hypersensitivity. Whole‐cell recordings were made from thoracolumbar superficial dorsal horn (SDH) neurons of lamina II.

Results

The expression of BDNF and TrkB was enhanced in the thoracolumbar spinal cord of the NMS animals. ANA‐12 attenuated visceral hypersensitivity without side effects on motricity in NMS rats. PKMζ expression significantly decreased after the administration of ANA‐12. The frequency of spontaneous excitatory postsynaptic currents (sEPSCs) increased in the thoracolumbar SDH neurons of lamina II in NMS rats. The amplitude and frequency of sEPSCs were reduced after perfusion with ANA‐12 in NMS rats.

Conclusions

Neonatal maternal separation caused visceral hypersensitivity and increased synaptic activity by activating BDNF‐TrkB‐PKMζ signalling in the thoracolumbar spinal cord of adult rats. PKMζ was able to potentiate AMPA receptor (AMPAR)‐mediated sEPSCs in NMS rats. ANA‐12 attenuated visceral hypersensitivity and synaptic activity by blocking BDNF/TrkB signalling in NMS rats.

Significance

ANA‐12 attenuates visceral hypersensitivity via BDNF‐TrkB‐PKMζ signalling and reduces synaptic activity through AMPARs in NMS rats. This knowledge suggests that ANA‐12 could represent an interesting novel therapeutic medicine for chronic visceral hypersensitivity.

Grape Seed Extract Eliminates Visceral Allodynia and Colonic Hyperpermeability Induced by Repeated Water Avoidance Stress in Rats

Grape seed extract (GSE) is rich in polyphenols composed mainly of proanthocyanidins, which are known to attenuate proinflammatory cytokine production. Repeated water avoidance stress (WAS) induces visceral allodynia and colonic hyperpermeability via toll-like receptor 4 (TLR4) and proinflammatory cytokine pathways, which is a rat irritable bowel syndrome (IBS) model. Thus, we explored the effects of GSE on repeated WAS (1 h for 3 days)-induced visceral allodynia and colonic hyperpermeability in Sprague-Dawley rats. Paracellular permeability, as evaluated by transepithelial electrical resistance and flux of carboxyfluorescein, was analyzed in Caco-2 cell monolayers treated with interleukin-6 (IL-6) and IL-1β. WAS caused visceral allodynia and colonic hyperpermeability, and intragastric administration of GSE (100 mg/kg, once daily for 11 days) inhibited these changes. Furthermore, GSE also suppressed the elevated colonic levels of IL-6, TLR4, and claudin-2 caused by WAS. Paracellular permeability was increased in Caco-2 cell monolayers in the presence of IL-6 and IL-1β, which was inhibited by GSE. Additionally, GSE suppressed the claudin-2 expression elevated by cytokine stimulation. The effects of GSE on visceral changes appear to be evoked by suppressing colonic TLR4-cytokine signaling and maintaining tight junction integrity. GSE may be useful for treating IBS.

There might be a distinctive clinical phenotype of constipation with non-cardiac chest pain which responds to combination laxatives: A retrospective, longitudinal symptom analysis

Proton pump inhibitor (PPI)-refractory non-cardiac chest pain (NCCP) is often resolved when constipation was relieved. This study aimed to investigate the clinical features of patients with both NCCP and constipated functional bowel disorders (FBD).Among 692 consecutive patients diagnosed with functional constipation or irritable bowel syndrome with constipation and underwent anorectal manometry (ARM) in our hospital, PPI-refractory NCCP was present in 37. The clinical course of various torso symptoms including NCCP and ARM findings were retrospectively evaluated.The mean age was lower in the NCCP than in the non-NCCP group (57.4 vs 61.3 years, respectively, P = .042). Back pain (16.2% vs 2.0%, P < .001) and sharp abdominal pain (13.5% vs 0.9%, P < .001) were more common in the NCCP group. Increased resting pressure (16.2% vs 6.9%, P = .036) and squeezing pressure (62.2% vs 50.7%, P = .049) of the anal sphincter, increased urgency volume (40.5% vs 23.2%, P = .004), and maximal volume (25.7% vs 15.0%, P = .032) for rectal sensation were more frequently observed in the NCCP group. After taking laxatives for 1 to 3 months, 81.1% of patients with NCCP reported improvement.Subjects with NCCP showed decreased rectal sensation more frequently at anorectal manometry. Majority of patients with NCCP reported improvement of symptom upon relief of constipation. Constipation might be a therapeutic target in patients with NCCP related to constipated functional bowel disorders.

Central and Peripheral Mechanism of Acupuncture Analgesia on Visceral Pain: A Systematic Review

Background/Aims

Despite the wide use of acupuncture for the management of visceral pain and the growing interest in the pathophysiology of visceral pain, there is no conclusive elucidation of the mechanisms behind the effects of acupuncture on visceral pain. This systematic review aims to provide an integrative understanding of the treatment mechanism of acupuncture for visceral pain.

Methods

Electronic and hand searches were conducted to identify studies that involved visceral pain and acupuncture.

Results

We retrieved 192 articles, out of which 46 studies were included in our review. The results of our review demonstrated that visceral pain behaviors were significantly alleviated in response to acupuncture treatment in groups treated with this intervention compared to in sham acupuncture or no-treatment groups. Changes in the concentrations of β-endorphin, epinephrine, cortisol, and prostaglandin E2 in plasma, the levels of c-Fos, substance P, corticotropin-releasing hormone, P2X3, acetylcholinesterase (AchE), N-methyl-D-aspartate (NMDA) receptors, and serotonin in the gut/spinal cord, and the neuronal activity of the thalamus were associated with acupuncture treatment in visceral pain.

Conclusions

Acupuncture reduced visceral pain behavior and induced significant changes in neuronal activity as well as in the levels of pain/inflammation-related cytokines and neurotransmitters in the brain-gut axis. Further researches on the thalamus and on a standard animal model are warranted to improve our knowledge on the mechanism of acupuncture that facilitates visceral pain modulation.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Effects of Self-Management Interventions in Patients With Irritable Bowel Syndrome: Systematic Review

Irritable bowel syndrome (IBS) is a prevalent and costly condition, with expenditures exceeding US$21 billion annually. As there is no known cure for IBS, treatment is focused on symptom self-management strategies. The purpose of this systematic review was to investigate the efficacy and overall effect of self-management interventions for patients with IBS. Of the 64 publications that were identified, 20 were included in the systematic review. Self-management interventions were found in diverse formats, including web-based, self-training booklets, individual and/or group interventions with health care providers, and cognitive-behavioral therapy or exercise-based interventions. Different symptom measures were used across the studies, whereas measurement of quality of life was more standardized. Overall, there is robust evidence supporting self-management interventions for improving short-term symptom management and improving quality of life, whereas longer term outcomes are variable. Further studies are needed to use standardized symptom measures and tailor interventions for pediatric populations, and tracking longer term outcomes.

Altered colonic sensory and barrier functions by CRF: roles of TLR4 and IL-1

Visceral allodynia and increased colonic permeability are considered to be crucial pathophysiology of irritable bowel syndrome (IBS). Corticotropin-releasing factor (CRF) and immune-mediated mechanisms have been proposed to contribute to these changes in IBS, but the precise roles have not been determined. We explored these issues in rats in vivo. The threshold of visceromotor response, i.e., abdominal muscle contractions induced by colonic balloon distention was electrophysiologically measured. Colonic permeability was estimated by quantifying the absorbed Evans blue in colonic tissue. Intraperitoneal injection of CRF increased the permeability, which was blocked by astressin, a non-selective CRF receptor antagonist, but astressin2-B, a selective CRF receptor subtype 2 (CRF2) antagonist did not modify it. Urocortin 2, a selective CRF2 agonist inhibited the increased permeability by CRF. Eritoran, a toll-like receptor 4 (TLR4) antagonist or anakinra, an interleukin-1 receptor antagonist blocked the visceral allodynia and the increased gut permeability induced by CRF. Subcutaneous injection of lipopolysaccharide (immune stress) or repeated water avoidance stress (WAS, psychological stress), 1 h daily for 3 days induced visceral allodynia and increased gut permeability (animal IBS models), which were also blocked by astressin, eritoran or anakinra. In conclusion, stress-induced visceral allodynia and increased colonic permeability were mediated via peripheral CRF receptors. CRF induced these visceral changes via TLR4 and cytokine system, which were CRF1 dependent, and activation of CRF2 inhibited these CRF1-triggered responses. CRF may modulate immune system to alter visceral changes, which are considered to be pivotal pathophysiology of IBS.

Sustained pain hypersensitivity in the stressed colon: Role of mast cell-derived nerve growth factor-mediated enteric synaptic plasticity

BACKGROUND

Sustained pain hypersensitivity is the hallmark of stressed colon which could be partially explained by central sensitization with synaptic plasticity, the key mechanism of memory. We previously identified that synaptic plasticity of enteric nerve system (ENS) contributed to peripheral pain maintaining in the gut. However, the mechanisms of enteric "memory" formation remain elusive.

METHODS

In this study, rats were exposed to water avoidance stress (WAS) or sham stress (SS), with cromolyn sodium or physiological saline injected intraperitoneally 30 minutes before stress every day. The abdominal withdrawal reflex scores, mesenteric afferent nerve activity, enteric neural c-fos expression, and enteric synaptic plasticity were assessed, and mast cell infiltration and degranulation. Furthermore, colonic mucosal mediators-induced enteric synaptic plasticity and the role of mast cell-derived nerve growth factor (NGF), tryptase, and histamine were investigated via ex vivo longitudinal muscle-myenteric plexus (LMMP) organotypic culture.

KEY RESULTS

It is shown that mast cell stabilizing inhibited WAS-induced visceral hypersensitivity through enhancing visceral pain threshold, decreasing spontaneous and distention-induced mesenteric afferent firing, and downregulating enteric neural activation (c-fos). Importantly, WAS led to evident enteric synaptic plasticity, but decreased by cromolyn. Water avoidance stress-derived mucosal supernatants markedly enhanced the c-fos expression and enteric synaptic plasticity in LMMP tissues, which could be eliminated by mast cell inhibition or NGF neutralization, but not tryptase or histamine blocking.

CONCLUSIONS & INFERENCES

In conclusion, mast cells/NGF pathway may be the key regulator of synaptic plasticity of ENS and participate in the formation of chronic stress-induced sustained visceral hypersensitivity.

Risk Factors for Fecal Urgency Among Individuals With and Without Diarrhea, Based on Data From the National Health and Nutrition Examination Survey

BACKGROUND & AIMS

Fecal urgency is a common symptom among patients with gastrointestinal disorders, but can also occur in healthy individuals with normal bowel habits. There have been few studies of fecal urgency in the general population. We performed a cross-sectional analysis of data from the National Health and Nutrition Examination Survey (NHANES) to analyze the prevalence of and risk factors for this symptom.

METHODS

We analyzed data from 4676 persons who completed the Bowel Health Questionnaire from the NHANES, from 2009 through 2010. The NHANES sampled a nationally representative group of adults in the United States and provides information on demographics, medical comorbidities, and dietary habits of survey participants. The Bowel Health Questionnaire provided additional information about bowel symptoms such as urgency, incontinence, constipation, and diarrhea. We identified individuals with fecal urgency and calculated differences in fecal urgency among subgroups using chi-squared analysis. We used logistic regression to identify factors associated with urgency.

RESULTS

In our study population, the prevalence of fecal urgency was 3.3%; 29.5% of individuals with fecal urgency had diarrhea. The prevalence of fecal urgency was significantly higher in individuals who had diarrhea (14.8%) than in individuals without diarrhea (3.1%). Older age, female sex, poverty, urinary urge incontinence, diarrhea, and increased stool frequency were all associated with fecal urgency on multivariable analysis. Decreased fiber intake and increased carbohydrate intake were associated with urgency among individuals with diarrhea.

CONCLUSIONS

In an analysis of data from 4676 individuals who completed a Bowel Health Questionnaire from the NHANES, we found a significantly higher proportion of individuals with diarrhea to have fecal urgency. However, most individuals with fecal urgency do not have diarrhea. Factors associated with fecal urgency vary among individuals with and without diarrhea.

Role of stress in pathophysiology of irritable bowel syndrome

Irritable bowel syndrome (IBS), one of the most common functional gastrointestinal disorders in the world, is characterized by chronic intermittent abdominal discomfort and colon dysmotility with altered bowel habits, significantly impacting patients' quality of life. The pathophysiology of IBS remains incompletely understood although some contributing factors have been identified. Increased visceral sensitivity and intestinal permeability may play an important role in the pathophysiology of IBS. Psychological factors, especially stress, play an important role in the occurrence, development, and regulation of IBS. To facilitate further research of IBS, this review focuses on the relationship between stress and IBS in animal models, as well as the role of stress in increased visceral sensitivity and intestinal permeability in IBS.

Ambulatory colonoscopy under sedoanalgesia in adult patients with and without irritable bowel syndrome: A prospective, cross-sectional, and double-blind comparison

BACKGROUND/AIMS

It is unclear whether patients with irritable bowel syndrome (IBS) require a high dose of sedatives during colonoscopy. In this study, we investigated the pre-procedural anxiety levels, sedative consumption, procedure times, complications, and patient's satisfaction between patients with IBS and controls for ambulatory colonoscopy under sedation.

MATERIALS AND METHODS

Rome III criteria were used in the diagnosis of IBS. Anxiety levels were measured using Spielberger's State-Trait Anxiety Inventory (STAI) and Beck Anxiety Inventory (BAI). Patients received a fixed dose of midazolam (0.02 mg/kg), fentanyl (1 μg/kg), ketamine (0.3 mg/kg), and incremental doses of propofol under sedation protocol. Demographic data, heart rate, blood pressure, and oxygen saturation were measured. Procedure times, recovery and discharge times, drug doses used, complications associated with the sedation, and patient's satisfaction scores were also recorded.

RESULTS

The mean Trait (p=0.015), State (p=0.029), Beck anxiety scores (p=0.018), the incidence of disruptive movements (p=0.044), and the amount of propofol (p=0. 024) used were significantly higher in patients with IBS. There was a decline in mean systolic blood pressure at the 6th minute in patients with IBS (p=0.026). No association was found between the sedative requirement and the anxiety scores.

CONCLUSION

Patients with IBS who underwent elective colonoscopy procedures expressed higher pre-procedural anxiety scores, required more propofol consumption, and experienced more disruptive movements compared with controls. On the contrary, the increased propofol consumption was not associated with the increased pre-procedural anxiety scores.

Blockage of High-Affinity Choline Transporter Increases Visceral Hypersensitivity in Rats with Chronic Stress

Background

Visceral hypersensitivity is a common feature of irritable bowel syndrome. Cholinergic system involves in the development of visceral hypersensitivity, and high-affinity choline transporter (CHT1) is of crucial importance in choline uptake system. However, involvement of CHT1 in visceral hypersensitivity remains unknown. The research aimed to study the CHT1 expression in dorsal root ganglions (DRGs) and the role of CHT1 in visceral hypersensitivity.

Methods

Repetitive water avoidance stress (WAS) was used to induce visceral hypersensitivity in rats. Colorectal distension (CRD) was determined, and the abdominal withdrawal reflex (AWR) and threshold intensity data were recorded to measure the visceral sensitivity. After intraperitoneal injection of hemicholinium-3 (HC-3), the specific inhibitor of CHT1, CRD data were also recorded. The CHT1 expression of DRGs was investigated by Western blotting, immunohistochemistry, and quantitative RT-PCR. Acetylcholine levels in the DRGs were detected by the assay kit.

Results

Repetitive WAS increased the AWR score of CRD at high distension pressure and decreased the mean threshold of rats. The CHT1 expression and acetylcholine concentration of DRG were significantly increased in WAS rats. After the administration of HC-3, the AWR score in WAS group was significantly increased at higher distension pressure while the threshold intensity was significantly reduced compared to the normal saline group. Acetylcholine concentration was significantly lower than the normal saline rats.

Conclusion

Our research firstly reports that CHT1 is overexpressed in noninflammatory visceral hypersensitivity, and blockage of CHT1 can enhance the visceral hypersensitivity. CHT1 may play an inhibitory role in visceral hypersensitivity.

Pain self-management plus nurse-led support in young adults with irritable bowel syndrome: Study protocol for a pilot randomized control trial

Irritable bowel syndrome (IBS) is a functional gut disorder that typically manifests in early adult years. IBS patients report that pain is the most distressing symptom with the greatest impact on quality of life. Pain-sensitivity genes and the gut microbiome may influence severity of symptoms as well as response to self-management (SM) interventions. Based on current understanding of the science of SM, pain neurophysiology, and the gut-brain axis, our team developed a pain SM intervention to be added to evidence-based self-management instruction to increase the individual's SM knowledge and skills (self-efficacy, self-regulation, and goal-setting). The purpose of this randomized controlled longitudinal pilot study is to examine the feasibility, acceptability, and preliminary effectiveness of the IBS-pain SM intervention on IBS-pain SM behaviors and related health outcomes. A sample of 80 young adults (age 18-29 years old) will be recruited and randomly assigned to the experimental or control group. Both groups will receive 10 electronic video modules focused on IBS-pain SM knowledge and skills. The experimental group also will receive nurse-led one-on-one phone consultations to facilitate monitoring and problem-solving. All participants will be followed over 12 weeks. Primary outcomes will be measured at baseline, 6 weeks, and 12 weeks, including IBS-pain SM behaviors, quality of life, and well-being. The influence of pain-sensitivity genes and the gut microbiome on IBS-pain SM behaviors and health outcomes also will be assessed.

Intravenous Corticotropin-releasing Hormone Administration Increases Esophageal Electrical Sensitivity in Healthy Individuals

Background/Aims

When a person is experiencing stress, corticotropin-releasing hormone (CRH) can modulate gut physiologies, such as visceral sensation or gastrointestinal motility, and its intravenous administration mimics stress-induced physiological changes. However, the influence of CRH on the esophagus is yet unknown. Accordingly, we investigated whether intravenous CRH administration increases esophageal sensitivity to electrical stimulation in healthy Japanese subjects.

Methods

Twenty healthy subjects were recruited. We quantified the initial perception threshold (IPT) every 15 minutes after CRH injection. Venous blood was collected with a cannula, and both plasma adrenocorticotropic hormone (ACTH) and cortisol were measured at pre-stimulation, 0, 30, 60, 90, and 120 minutes. The results from each time point were compared against a baseline IPT obtained before electrical stimulation was initiated.

Results

When compared to the baseline IPT value (16.9 ± 4.5), CRH significantly decreased electrical threshold of the esophagus at 30, 45, 60, 75 minutes (14.1 ± 4.2, 13.1 ± 5.0, 12.1 ± 5.7, 14.0 ± 5.8 minutes, P 〈 0.01, respectively) after CRH injection, suggesting that CRH increased esophageal sensitivity to the electrical stimulus. CRH also significantly increased plasma ACTH levels at 30 minutes (50.3 ± 17.7, P 〈 0.01), and cortisol levels at 30 minutes (22.0 ± 6.7 minutes, P 〈 0.01) and 60 minutes (20.3 ± 6.7 minutes, P 〈 0.01) after CRH injection, when compared to the pre-stimulation ACTH and cortisol values.

Conclusion

Intravenous CRH administration increased esophageal electrical sensitivity in normal subjects, emphasizing the important role of stress in esophageal sensitivity.

Piezo2: A Candidate Biomarker for Visceral Hypersensitivity in Irritable Bowel Syndrome?

Background/Aims

Currently, there exists no biomarker for visceral hypersensitivity in irritable bowel syndrome (IBS). Piezo proteins have been proven to play an important role in the mechanical stimulation to induce visceral pain in other tissues and may also be a biomarker candidate. The aim of this study was to test the expressions of Piezo1 and Piezo2 proteins in the intestinal epithelial cells from different intestinal segments and to explore the correlation between Piezo proteins expression and visceral pain threshold.

Methods

Post-infectious IBS was induced in mice via a Trichinella spiralis infection. Visceral sensitivity was measured with abdominal withdrawal reflex to colorectal distention. Inflammation in the small intestine and colon was scored with H&E staining. Expression location of Piezo proteins was confirmed by immunohistochemistry. Abundance of Piezo proteins were measured with real-time reverse transcriptase polymerase chain reaction.

Results

Piezo1 and Piezo2 proteins were expressed in the intestinal epithelial cells. The expression levels of Piezo1 and Piezo2 were abundant in the colon than the small intestine (P < 0.001 for Piezo1, P = 0.003 for Piezo2). Expression of Piezo2 in the colon significantly correlated to the visceral sensitivity (r = −0.718, P = 0.001) rather than the mucosal inflammation.

Conclusion

Piezo2 is a candidate biomarker for visceral hypersensitivity in IBS.

The effect of intravenous corticotropin-releasing hormone administration on esophageal sensitivity and motility in health

Esophageal hypersensitivity is important in gastroesophageal reflux disease (GERD) patients who are refractory to acid-suppressive therapy. Stress affects visceral sensitivity and exacerbates heartburn in GERD. Peripheral CRH is a key mediator of the gut stress response. We hypothesize that CRH increases esophageal sensitivity and alters esophageal motility in health. Esophageal sensitivity to thermal, mechanical, electrical, and chemical stimuli was assessed in 14 healthy subjects after administration of placebo or CRH (100 μg iv). Perception scores were assessed for first perception, pain perception threshold (PPT), and pain tolerance threshold (PTT). Esophageal motility was investigated by high-resolution impedance manometry, before and after CRH and evaluated by distal contractile integral (DCI) and intrabolus pressure (IBP). Pressure flow analysis assessed bolus clearance (impedance ratio), degree of pressurization needed to propel bolus onward (IBP slope), and pressure flow (pressure flow index, PFI). Stress and mood were assessed during the study. Sensitivity to mechanical distention was increased after CRH compared with placebo (PPT: P = 0.0023; PTT: P = 0.0253). CRH had no influence on the other stimulations. DCI was increased for all boluses (liquid, P = 0.0012; semisolid, P = 0.0017; solid, P = 0.0107). Impedance ratio for liquid (P < 0.0001) and semisolid swallows (P = 0.0327) decreased after CRH. IBP slope increased after CRH for semisolid (P = 0.0041) and solid (P = 0.0003) swallows. PFI increased for semisolid (P = 0.0017) and solid swallows (P = 0.0031). CRH increased esophageal sensitivity to mechanical distention, not to the other stimulation modalities. CRH increased esophageal contractility and tone, decreased LES relaxation, increased esophageal bolus pressurization, improved esophageal bolus clearance, and increased pressure flow.NEW & NOTEWORTHY This is the first study to address the effect of corticotropin-releasing hormone (CRH) on esophageal sensitivity and alterations in motility in health. CRH administration increased esophageal sensitivity to mechanical distention. This effect is accompanied by an increase in esophageal contractility and tone and a decrease in lower esophageal sphincter relaxation. CRH increased esophageal bolus pressurization, improved esophageal bolus clearance, and increased pressure flow. The changes in esophageal contractile properties may underlie the increased sensitivity to mechanical distention after CRH.

Maternal Separation Induced Visceral Hypersensitivity from Childhood to Adulthood

Background/Aims

Early adverse life events (EALs) are relevant to irritable bowel syndrome in adulthood. Maternal separation (MS), as one of the EALs, has proved to induce visceral hypersensitivity in adult rats. However, the effect of MS on visceral hypersensitvity from the post-weaning period to adulthood remains unknown.

Methods

One hundred and ten neonatal Sprague-Dawley rats were randomly divided into 2 groups: rats in the MS group were exposed to 3 hours daily MS on postnatal day (PND) 2–14; the normal control (NC) group remained undisturbed. Visceral sensitivity was determined by measuring the visceromotor response to colorectal distention on PND21, 35, and 56. Anxiety-like behaviors were measured by the open field test.

Results

Compared with NC rats, MS rats showed significant visceral hypersensitivity from the post-weaning period to adult. The proportion of visceral hypersensitive rats decreased with age from 87.5% to 70.0% in the female MS group and from 90.0% to 66.7% in the male MS group. The relative VMR ratio of MS and NC on PND21 was higher than PND35 and PND56. MS rats showed decreased ability of movement and exploration to the novel environment in the post-weaning period, obesity in the prepubertal period, and more anxiety-like behaviors in adulthood.

Conclusions

MS can significantly affect visceral sensitivity and behaviors of rats in different age stages, especially in the post-weaning period. Visceral hypersensitivity of MS rats is more pronounced in the post-weaning period and slightly restored in adults. Thus, visceral hypersensitivity in the post-weaning period might play a more meaningful pathophysiologic role in the formation of adult irritable bowel syndrome.

Prokinetic effects of LD02GIFRO on functional gastrointestinal disorder in rats

LD02GIFRO is a novel prokinetic agent formulated with Poncirus fructus and Zanthoxylum sp. fruits. The aim of the present study was to evaluate the effect of LD02GIFRO on delayed gastrointestinal transit (GIT) and colorectal hypersensitivity. To investigate the effect of LD02GIFRO, a rat model of delayed GIT was induced via three mechanisms; postoperative ileus (POI), morphine, and POI plus morphine. Visceromotor responses (VMR) to colorectal distension (CRD) were also evaluated. POI was induced by laparotomy surgery and manipulation of the small intestine under anesthesia, and GIT was calculated by measuring the length that Evans Blue travelled through the gastrointestinal tract in a given time. Oral administration of 260 mg/kg LD02GIFRO caused Evans Blue to migrate significantly further in the delayed GIT models induced by POI, morphine and POI plus morphine compared with the control (P<0.05). This effect was inhibited by atropine, a muscarinic receptor antagonist, and completely abolished by GR125487, a 5-HT₄-receptor antagonist. Furthermore, intraperitoneal administration of 600 and 900 mg/kg LD02GIFRO significantly reduced VMR to CRD in acute and chronic colorectal hypersensitive rat models, induced by acetic acid and trinitrobenzenesulfonic acid, to almost normal levels (P<0.01). In the present study, LD02GIFRO successfully ameliorated delayed GIT models and colorectal hypersensitivity models, suggesting that LD02GIFRO may be an effective therapeutic treatment for patients with functional gastrointestinal disorders and abnormalities in GIT.

TRPA1 in the spinal dorsal horn is involved in post-inflammatory visceral hypersensitivity: in vivo study using TNBS-treated rat model

Introduction

The transient receptor potential ankyrin-1 (TRPA1) channel, a pain transducer and amplifier, is drawing increasing attention in the field of visceral hypersensitivity, commonly seen in irritable bowel syndrome and inflammatory bowel disease. However, the role of TRPA1 in visceral nociception during post-inflammatory states is not well defined. Here, we explore the correlation between TRPA1 expression in the spinal dorsal horn (SDH) and persistent post-inflammatory visceral hypersensitivity.

Methods

We injected rats intracolonically with 2,4,6-trinitrobenzene sulfonic acid (TNBS) or vehicle (n=12 per group). Post-inflammatory visceral hypersensitivity was assessed by recording the electromyographic activity of the external oblique muscle in response to colorectal distension. TRPA1 expression and distribution in the spinal cord and colon were examined by Western blotting and immunohistochemistry.

Results

Animals exposed to TNBS had more abdominal contractions than vehicle-injected controls (P<0.05), which corresponded to a lower nociceptive threshold. Expression of TRPA1 in the SDH (especially in the substantia gelatinosa) and the colon was significantly greater in the TNBS-treated group than in controls (P<0.05). In the SDH, the number of TRPA1-immunopositive neurons was 25.75±5.12 in the control group and 34.25±7.89 in the TNBS-treated group (P=0.023), and integrated optical density values of TRPA1 in the control and TNBS-treated groups were 14,544.63±6,525.54 and 22,532.75±7,608.11, respectively (P=0.041).

Conclusion

Our results indicate that upregulation of TRPA1 expression in the SDH is associated with persistent post-inflammatory visceral hypersensitivity in the rat and provides insight into potential therapeutic targets for the control of persistent visceral hypersensitivity.

Irritable bowel syndrome evaluation using computed tomography colonography

AIM

To evaluate the morphology of the colon in patients with irritable bowel syndrome (IBS) by using computed tomography colonography (CTC).

METHODS

Twelve patients with diarrhea type IBS (IBS-D), 13 patients with constipation type IBS (IBS-C), 12 patients with functional constipation (FC) and 14 control patients underwent colonoscopy following CTC. The lengths of the rectosigmoid colon, transverse colon and the total colon were measured. The diameters of the rectum, sigmoid colon, descending colon, transverse colon, and ascending colon were measured.

RESULTS

The mean length of the total colon was 156.5 cm in group C, 158.9 cm in group IBS-D, 172.0 cm in group IBS-C, and 188.8 cm in group FC. The total colon in group FC was significantly longer than that in group C (P < 0.05). The mean length of the rectosigmoid colon was 56.2 cm, 55.9 cm, 63.6cm, and 77.4 cm (NS). The mean length of the transverse colon was 49.9 cm, 43.1 cm, 57.0 cm, and 55.0 cm. The transverse colon in group IBS-D was significantly shorter than that in group IBS-C (P < 0.01) and that in group FC (P = 0.02). The mean diameter of the sigmoid colon was 4.0 cm, 3.3 cm, 4.2 cm, and 4.3 cm (NS). The mean diameter of the descending colon was 3.6 cm, 3.1 cm, 3.8 cm, and 4.3 cm. The descending colon diameter in group IBS-D was significantly less than that in group IBS-C (P = 0.03) and that in group FC (P < 0.001). The descending colon diameter in group FC was significantly greater than that in group C (P = 0.04). The mean diameter of the transverse colon was 4.4 cm, 3.3 cm, 4.2 cm, and 5.0 cm (NS).

CONCLUSION

CT colonography might contribute the clarification of subtypes of IBS.