Ondansetron for Low Anterior Resection Syndrome (LARS): A Double-Blind, Placebo-Controlled, Cross-Over, Randomized Study

OBJECTIVE

The aim of the study was to examine the efficacity and safety of ondansetron, a serotonin receptor antagonist, to treat patients with low anterior resection syndrome (LARS).

BACKGROUND

LARS after rectal resection is common and debilitating. Current management strategies include behavioral and dietary modifications, physiotherapy, antidiarrheal drugs, enemas, and neuromodulation, but the results are not always satisfactory.

METHODS

This is a randomized, multicentric, double-blinded, placebo-controlled, and cross-over study. Patients with LARS (LARS score >20) no longer than 2 years after rectal resection were randomized to receive either 4 weeks of ondansetron followed by 4 weeks of placebo (O-P group) or 4 weeks of placebo followed by 4 weeks of ondansetron (P-O group). The primary endpoint was LARS severity measured using the LARS score; secondary endpoints were incontinence (Vaizey score) and irritable bowel syndrome quality of life (IBS-QoL questionnaire). Patients' scores and questionnaires were completed at baseline and after each 4-week treatment period.

RESULTS

Of 46 randomized patients, 38 were included in the analysis. From baseline to the end of the first period, in the O-P group, the mean (SD) LARS score decreased by 25% [from 36.6 (5.6) to 27.3 (11.5)] and the proportion of patients with major LARS (score >30) went from 15/17 (88%) to 7/17 (41%), ( P =0.001). In the P-O group, the mean (SD) LARS score decreased by 12% [from 37 (4.8) to 32.6 (9.1)], and the proportion of major LARS went from 19/21 (90%) to 16/21 (76%). After crossover, LARS scores deteriorated again in the O-P group receiving placebo, but further improved in the P-O group receiving ondansetron. Mean Vaizey scores and IBS QoL scores followed a similar pattern.

CONCLUSIONS

Ondansetron is a safe and simple treatment that appears to improve both symptoms and QoL in LARS patients.

Association between selective serotonin reuptake inhibitor use and developing irritable bowel syndrome through retrospective analysis

BACKGROUND AND AIM

Serotonin affects the balance and integrity of the gut microbiome; however, studies have confirmed the influence of selective serotonin reuptake inhibitors (SSRIs) on irritable bowel syndrome (IBS). We evaluated the association between SSRI use and subsequent IBS occurrence in a real-world setting.

METHODS

A multivariate Cox proportional hazard model was adopted, and the National Health Insurance Service cohort claims database between 2010 and 2019 was used. Non-SSRI users were selected using the propensity score matching method. Subgroup analyses were performed using the point of use, cumulative dose, and duration of SSRI use. Additional analysis was performed using a control group without psychiatric medications.

RESULTS

We included 2901 SSRI users and 2727 non-SSRI users. After adjusting covariates, the risk of developing IBS in SSRI users was 1.54 times that in non-SSRI users (95% confidence interval [CI]: 1.01-2.33). The hazard ratio (HR) of the recent, heavy, and short-term user groups were 3.19 (95% CI: 2.03-4.99), 2.22 (95% CI: 1.50-3.29), and 4.83 (95% CI: 3.02-7.73), respectively, compared with that of non-users. In patients without a history of psychiatric medications, the risk of IBS incidence after SSRI use increased significantly (HR: 1.61, 95% CI: 1.06-2.42), whereas HR was insignificant in patients with a history of psychiatric medications (HR: 1.25, 95% CI: 0.98-1.60).

CONCLUSIONS

The risk of subsequent IBS occurrence following SSRI use was high in patients who initially took a heavy SSRI dose and those who did not have a history of psychiatric drug use.

Long-term safety of tenapanor in patients with irritable bowel syndrome with constipation in the T3MPO-3 study

BACKGROUND

Tenapanor, a first-in-class, minimally systemic inhibitor of intestinal sodium/hydrogen exchanger isoform 3 (NHE3), is approved for the treatment of irritable bowel syndrome with constipation (IBS-C) in adults based on two randomized, placebo-controlled, phase III studies (T3MPO-1 [NCT02621892], T3MPO-2 [NCT02686138]). The open-label T3MPO-3 extension study (NCT02727751) enrolled patients who completed these studies to investigate long-term safety and tolerability of tenapanor.

METHODS

Patients who completed T3MPO-1 (16 weeks) or T3MPO-2 (26 weeks) were eligible for enrollment in T3MPO-3. Patients in T3MPO-3 received open-label tenapanor 50 mg twice a day for up to an additional 39 (T3MPO-1) or 26 (T3MPO-2) weeks. Treatment-emergent adverse events (TEAEs) were evaluated in the entire T3MPO-3 safety population and in patients who received a total of ≥52 weeks of tenapanor.

KEY RESULTS

A total of 312 patients were enrolled in T3MPO-3; 90 received ≥52 weeks of tenapanor. TEAEs were reported in 117 (37.5%) patients in the safety population and in 52 (57.8%) patients who received ≥52 weeks of tenapanor. Diarrhea was the most common TEAE, occurring in 10.6% of the safety population and in 11.1% of patients who received ≥52 weeks of tenapanor. Most cases were mild or moderate in severity, with only two severe cases reported in the safety population. No deaths occurred during the T3MPO-3 study.

CONCLUSIONS

Tenapanor was tolerable over ≥52 weeks of treatment and showed similar safety to that seen in shorter studies. Combined results of the T3MPO studies indicate that tenapanor is a valuable new treatment option for patients with IBS-C.

Doctors Speak: A Qualitative Study of Physicians' Prescribing of Antidepressants in Functional Bowel Disorders

Tricyclic antidepressants (TCAs) are frequently prescribed for chronic functional pain disorders. Although the mechanism of action targets pain perception, treating patients with TCAs for disorders conceptualized as "functional" can promote stigmatization in these patients because it hints at psychological dimensions of the disorder. The goal of this study was to understand how physicians prescribe TCAs in the face of this challenge. We interviewed eleven gastroenterologists in tertiary care clinics specializing in functional gastrointestinal disorders, such as irritable bowel syndrome. We found that the physicians interviewed (1) were aware of the stigma attached to taking antidepressants for a medical condition, (2) emphasized biological, as opposed to psychological, mechanisms of action, (3) while focusing on biological mechanisms, they nevertheless prescribed TCAs in a way that is highly attentive to the psychology of expectations, making specific efforts to adjust patients' expectations to be realistic and to reframe information that would be discouraging and (4) asked patients to persist in taking TCAs despite common and, at times, uncomfortable side effects. In this context of shared decision making, physicians described nuanced understanding and behaviours necessary for treating the complexity of functional disorders and emphasized the importance of a strong patient-provider relationship.

Dietary monosodium glutamate increases visceral hypersensitivity in a mouse model of visceral pain

BACKGROUND

Monosodium glutamate (MSG) has been identified as a trigger of abdominal pain in irritable bowel syndrome (IBS), but the mechanism is unknown. This study examined whether MSG causes visceral hypersensitivity using a water-avoidance stress (WAS) mouse model of visceral pain.

METHODS

Mice were divided into four groups receiving treatment for 6 days: WAS + MSG gavage, WAS + saline gavage, sham-WAS + MSG gavage, and sham-WAS + saline gavage. The acute effects of intraluminal administration of 10 μM MSG on jejunal extrinsic afferent nerve sensitivity to distension (0-60 mmHg) were examined using ex vivo extracellular recordings. MSG was also applied directly to jejunal afferents from untreated mice. Glutamate concentration was measured in serum, and in the serosal compartment of Ussing chambers following apical administration.

KEY RESULTS

Acute intraluminal MSG application increased distension responses of jejunal afferent nerves from mice exposed to WAS + MSG. This effect was mediated by wide dynamic range and high-threshold units at both physiologic and noxious pressures (10-60 mmHg, p < 0.05). No effect of MSG was observed in the other groups, or when applied directly to the jejunal afferent nerves. Serum glutamate was increased in mice exposed to WAS + MSG compared to sham-WAS + saline, and serosal glutamate increased using WAS tissue (p = 0.0433).

CONCLUSIONS AND INFERENCES

These findings demonstrate that repeated exposure to MSG in mice leads to sensitization of jejunal afferent nerves to acute ex vivo exposure to MSG. This may contribute to visceral hypersensitivity reported in response to MSG in patients with IBS.

Isotretinoin and the risk of inflammatory bowel disease and irritable bowel syndrome: A large-scale global study

INTRODUCTION

Risk of inflammatory bowel disease under isotretinoin is a scope of a long-standing controversy. The burden of isotretinoin-related irritable bowel syndrome has not been investigated.

OBJECTIVE

To evaluate the risk of Crohn's disease, ulcerative colitis (UC), and irritable bowel syndrome in patients with acne starting isotretinoin vs oral antibiotics treatment.

METHODS

A global population-based retrospective cohort study assigned 2 groups of patients with acne initiating isotretinoin (n = 77,005) and oral antibiotics (n = 77,005). Comprehensive propensity-score matching was conducted.

RESULTS

The lifetime risk of Crohn's disease (hazard ratio [HR], 1.05; 95% CI, 0.89-1.24; P = .583) and UC (HR, 1.13; 95% CI, 0.95-1.34; P = .162) was comparable between study groups, whereas the lifetime risk of irritable bowel syndrome was lower in isotretinoin-prescribed patients (HR, 0.82; 95% CI, 0.76-0.89; P < .001). In time-stratified analysis, isotretinoin-related risk of UC was significantly increased during the first 6 months following drug initiation (HR, 1.93; 95% CI, 1.29-2.88; P = .001), but decreased afterward to level the risk of the comparator group. The absolute risk difference within the first 6 months was clinically marginal (5.0 additional UC cases/10,000 patients starting isotretinoin; 95% CI, 2.5-7.7).

LIMITATIONS

Retrospective data collection.

CONCLUSION

Isotretinoin does not confer an elevated risk of Crohn's disease, whilst it might be associated with a slight and transient increase in UC risk.

Colonic Mucosal Immune Activation in Mice with Ovalbumin-Induced Allergic Airway Disease: Association between Allergic Airway Disease and Irritable Bowel Syndrome

Recent studies on the pathophysiology of irritable bowel syndrome (IBS) have focused on the role of mast cells (MCs) in intestinal mucosal immunity. A link between allergic airway diseases (AADs) and IBS has been suggested because both diseases have similar pathophysiology. We aimed to investigate whether the induction of AAD in mice could lead to inflammation of the colonic mucosa, similar to IBS. We also evaluated whether this inflammatory response could be suppressed by administering a therapeutic agent. Mice were divided into three groups: control, AAD-induced, and salbutamol-treated. An AAD mouse model was established by intraperitoneal injection and nasal challenge with ovalbumin. Mice with AAD were intranasally administered salbutamol. Analyses of cytokine levels, MC count, and tryptase levels in the intestinal mucosa were performed to compare the changes in inflammatory responses among the three groups. Inflammation was observed in the intestinal mucosa of mice in the AAD group. This inflammation in AAD mice was suppressed after salbutamol treatment. Our study demonstrates that AAD induces an inflammatory response similar to that in IBS, suggesting a possible association between IBS and AADs. In patients with IBS with such allergic components, salbutamol may have the potential to alleviate the inflammatory response.

Fermentable Oligo-, Di-, and Mono-Saccharides and Polyols (FODMAPs) Consumption and Irritable Bowel Syndrome in the French NutriNet-Santé Cohort

(1) Background: Specific foods, and more particularly, fermentable oligo-, di-, and mono-saccharides and polyols (FODMAPs) are often considered as triggers of digestive symptoms in Irritable Bowel Syndrome (IBS). Our aim was to study FODMAP consumption in controls and IBS participants in a large French population-based cohort; (2) Methods: Participants from the NutriNet-Santé cohort study completed the Rome IV and IBS-SSS questionnaire in a cross sectional study. Among them, 27,949 eligible participants had previously completed three 24-h recalls as well as anthropometrics, socio-demographical and lifestyle data. Total FODMAP intake (in g/day) was computed using a specific composition table. The association between FODMAPs and IBS was estimated through multivariable logistic regression models; (3) Results: Included participants were mainly women (75.4%) and the mean age was 43.4 ± 14.1 years. FODMAPs accounted for a mean daily intake of 19.4 ± 9.5 g/day. Overall 1295 participants (4.6%) were identified with an IBS. After adjusting for confounding factors, IBS participants had lower intakes in FODMAPs than non-IBS ones (aOR: 0.88, 95% CI: 0.82–0.95, p-value: 0.001). IBS severity was associated with more frequent low FODMAP intakes (<9 g/day); (4) Conclusions: Participants tended to consume 19 g of FODMAPs per day, but slightly less for IBS participants than for controls. In IBS participants, higher severity was associated with lower intakes.

The mechanisms of action of WeiChang'An Pill (WCAP) treat diarrhoea-predominant irritable bowel syndrome (IBS-D) using network pharmacology approach and in vivo studies

ETHNOPHARMACOLOGICAL RELEVANCE

WeiChang'An Pill (WCAP) is used in Traditional Chinese Medicine (TCM) to clinically treat diarrhoea-predominant irritable bowel syndrome (IBS-D); however, the underlying pharmacological mechanisms are unclear to date.

AIM OF THE STUDY

To explore the mechanism underlying the therapeutic action of WCAP in IBS-D using a network pharmacology approach and in vivo experiments.

MATERIALS AND METHODS

The active compounds of WCAP were selected from the TCM Systems Pharmacology Database and TCM Integrated Database, and the potential targets were identified using the Swiss Target Prediction and Similarity Ensemble Approach (SEA) databases. The targets related to IBS-D were mined from the Therapeutic Target Database (TTD), National Center for Biotechnology Information Search database (NCBI), DrugBank database, and DisGeNET database. The intersecting protein-protein interactions (PPIs) of the drug-disease crossover genes were analysed, and the central PPI network was constructed using the String database, version 11.0, and Cytoscape version 3.7.2. Following Gene Ontology and Kyoto Encyclopaedia of Genes and Genomes pathway analyses, the gene-pathway network was constructed for identifying the key target genes and pathways. Based on the results and existing evidence, it was selected the cyclic adenosine monophosphate (cAMP) signalling pathway for further validation using in vivo experiments.

RESULTS

A total of 872 targets were identified from the 77 active compounds in WCAP, which shared 78 targets that were predicted to be related to IBS-D. Twenty-one core targets were identified from the PPI network, which was constructed from the common targets. The results of enrichment analysis revealed that HRT2B, ADRA1A, ADRA1D, and CHRM2 could be the key targets of WCAP in IBS-D, and 11 signalling pathways, including the neuroactive ligand-receptor interaction, calcium signalling, and cAMP signalling pathways, were identified as crucial for the therapeutic activity of WCAP in IBS-D. We also identified the possibility of several interactions and crosstalk between the different pathways. Subsequent molecular biology experiments revealed that the expression levels of cAMP, phospho-(Ser/Thr) protein kinase A substrates (p-PKA), 5-hydroxytryptamine, and proteins in the cAMP signalling pathway, including G protein-coupled receptor (GPCR), adenylyl cyclase 5 (AC5), and cAMP-response element binding protein (CREB), were significantly upregulated in rat models of IBS-D following treatment with WCAP (P < 0.05). However, a reverse trend was observed in the expression of nuclear factor kappa-B (NF-κB) (P < 0.05), which could be attributed to the low-grade inflammation that occurs in IBS-D.

CONCLUSION

We demonstrated that WCAP may alleviate the symptoms of diarrhoea and visceral sensitivity in IBS-D by regulating the cAMP signalling pathway.

Microbiome and Its Role in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is an extremely common and often very debilitating chronic functional gastrointestinal disorder. Despite its prevalence, significant associated healthcare costs, and quality-of-life issues for affected individuals, our understanding of its etiology remained limited. However, it is now evident that microbial factors play key roles in IBS pathophysiology. Acute gastroenteritis following exposure to pathogens can precipitate the development of IBS, and studies have demonstrated changes in the gut microbiome in IBS patients. These changes may explain some of the symptoms of IBS, including visceral hypersensitivity, as gut microbes exert effects on the host immune system and gut barrier function, as well as the brain-gut axis. Microbial differences also appear to underlie the two main functional categories of IBS: diarrhea-predominant IBS (IBS-D) is associated with small intestinal bacterial overgrowth, which can be diagnosed by a positive hydrogen breath test, and constipation-predominant IBS (IBS-C) is associated with increased levels of methanogenic archaea, which can be diagnosed by a positive methane breath test. Mechanistically, the pathogens that cause gastroenteritis and trigger subsequent IBS development produce a common toxin, cytolethal distending toxin B (CdtB), and antibodies raised against CdtB cross-react with the cytoskeletal protein vinculin and impair gut motility, facilitating bacterial overgrowth. In contrast, methane gas slows intestinal contractility, which may facilitate the development of constipation. While antibiotics and dietary manipulations have been used to relieve IBS symptoms, with varying success, elucidating the specific mechanisms by which gut microbes exert their effects on the host may allow the development of targeted treatments that may successfully treat the underlying causes of IBS.

Irritable Bowel Syndrome-Like Disorders in Endometriosis: Prevalence of Nickel Sensitivity and Effects of a Low-Nickel Diet. An Open-Label Pilot Study

Alimentary nickel (Ni) may result in allergic contact mucositis (ACM), whose prevalence is >30% and may present with IBS-like and extra-intestinal symptoms. These symptoms are also frequent in endometriosis, and Ni allergic contact dermatitis has already been observed in endometriosis. Therefore, intestinal and extra-intestinal symptoms in endometriosis may depend on a Ni ACM, and a low-Ni diet could improve symptoms. We studied the prevalence of Ni ACM in endometriosis and focused on the effects of a low-Ni diet on gastrointestinal, extra-intestinal, and gynecological symptoms. We recruited 84 women with endometriosis, symptomatic for gastrointestinal disorders. Thirty-one out of 84 patients completed the study. They underwent Ni oral mucosa patch test (omPT), questionnaire for intestinal/extra-intestinal/gynecological symptoms, and a low-Ni diet. Clinical evaluation was performed at baseline (T0) and after three months (T1). Twenty-eight out 31 (90.3%) patients showed Ni omPT positive results, with Ni ACM diagnosis, whereas three out of 31 (9.7%) patients showed negative Ni omPT. After three months of low-Ni diet, all gastrointestinal, extra-intestinal and gynecological symptoms showed a statistically significant reduction. Ni ACM has a high prevalence in endometriosis and a low-Ni diet may be recommended in this condition to reduce gastrointestinal, extra-intestinal and gynecological symptoms.

Activation of pruritogenic TGR5, MrgprA3, and MrgprC11 on colon-innervating afferents induces visceral hypersensitivity

Itch induces scratching that removes irritants from the skin, whereas pain initiates withdrawal or avoidance of tissue damage. While pain arises from both the skin and viscera, we investigated whether pruritogenic irritant mechanisms also function within visceral pathways. We show that subsets of colon-innervating sensory neurons in mice express, either individually or in combination, the pruritogenic receptors Tgr5 and the Mas-gene-related GPCRs Mrgpra3 and Mrgprc11. Agonists of these receptors activated subsets of colonic sensory neurons and evoked colonic afferent mechanical hypersensitivity via a TRPA1-dependent mechanism. In vivo intracolonic administration of individual TGR5, MrgprA3, or MrgprC11 agonists induced pronounced visceral hypersensitivity to colorectal distension. Coadministration of these agonists as an "itch cocktail" augmented hypersensitivity to colorectal distension and changed mouse behavior. These irritant mechanisms were maintained and enhanced in a model of chronic visceral hypersensitivity relevant to irritable bowel syndrome. Neurons from human dorsal root ganglia also expressed TGR5, as well as the human ortholog MrgprX1, and showed increased responsiveness to pruritogenic agonists in pathological states. These data support the existence of an irritant-sensing system in the colon that is a visceral representation of the itch pathways found in skin, thereby contributing to sensory disturbances accompanying common intestinal disorders.

Clostridium butyricum alleviates intestinal low-grade inflammation in TNBS-induced irritable bowel syndrome in mice by regulating functional status of lamina propria dendritic cells

BACKGROUND

Irritable bowel syndrome (IBS) is one of the most common functional gas-troenterological diseases characterized by abnormal visceral sensitivity and low-grade inflammation. The role of Clostridium butyricum (C. butyricum) in reducing intestinal low-grade inflammation via immune pathways has been well defined. However, the detailed mechanisms of the effects of C. butyricum on intestinal mucosal immunity, especially on immune cells of the lamina propria, remain unclear. Dendritic cells (DCs), which are important immune cells, secrete proinflammatory cytokines (IL-1β, IL-6, and others) and express T cell immuno-globulin and mucin domain-3 (TIM3), promoting proliferation and activation of DCs, and mediating Th1 and Th17 inflammatory responses.

AIM

To investigate the role of DCs in the development of IBS in a rat model and to understand the regulation of DCs after C. butyricum intervention.

METHODS

An IBS animal model was established using C57BL/6 mice, and C. butyricum was continuously administered via the intragastric route to simulate different intestinal immune states. Intestinal visceral hypersensitivity and histopathology were assessed using the abdominal withdrawal reflex (AWR) test and hematoxylin & eosin (H&E) staining, respectively. The expression of proinflammatory cytokines (IL-1β and IL-6) and TIM3 was analyzed by Western blot analysis and real-time PCR. Flow cytometry was applied to analyze the quantity, function, and membrane molecule TIM3 of the lamina propria dendritic cells (LPDCs). The regulatory effect of C. butyricum was verified in bone marrow-derived dendritic cells by in vitro experiments.

RESULTS

The secretion of proinflammatory cytokines (IL-1β and IL-6) in mice with IBS was significantly increased compared with that of the control group, which suggested that the intestinal mucosa in mice with IBS was in a low-grade inflammatory state. The expression of CD11C+CD80+ and CD11c+TIM3+ in intestinal LPDCs in mice with IBS increased significantly. Meanwhile, the cytokines (IL-1β and IL-6) were significantly reduced after the intervention with probiotic C. butyricum. The amount and function of LPDCs and the TIM3 on the surface of the LPDCs were decreased with the alleviation of the intestinal inflammatory response.

CONCLUSION

The results suggest that C. butyricum regulates the amount and functional status of LPDCs in the intestinal mucosa of mice with IBS, and therefore modulates the local immune response in the intestine.

Antibiotic treatment-induced dysbiosis differently affects BDNF and TrkB expression in the brain and in the gut of juvenile mice

Antibiotic use during adolescence may result in dysbiosis-induced neuronal vulnerability both in the enteric nervous system (ENS) and central nervous system (CNS) contributing to the onset of chronic gastrointestinal disorders, such as irritable bowel syndrome (IBS), showing significant psychiatric comorbidity. Intestinal microbiota alterations during adolescence influence the expression of molecular factors involved in neuronal development in both the ENS and CNS. In this study, we have evaluated the expression of brain-derived neurotrophic factor (BDNF) and its high-affinity receptor tropomyosin-related kinase B (TrkB) in juvenile mice ENS and CNS, after a 2-week antibiotic (ABX) treatment. In both mucosa and mucosa-deprived whole-wall small intestine segments of ABX-treated animals, BDNF and TrKB mRNA and protein levels significantly increased. In longitudinal muscle-myenteric plexus preparations of ABX-treated mice the percentage of myenteric neurons staining for BDNF and TrkB was significantly higher than in controls. After ABX treatment, a consistent population of BDNF- and TrkB-immunoreactive neurons costained with SP and CGRP, suggesting up-regulation of BDNF signaling in both motor and sensory myenteric neurons. BDNF and TrkB protein levels were downregulated in the hippocampus and remained unchanged in the prefrontal cortex of ABX-treated animals. Immunostaining for BDNF and TrkB decreased in the hippocampus CA3 and dentate gyrus subregions, respectively, and remained unchanged in the prefrontal cortex. These data suggest that dysbiosis differentially influences the expression of BDNF-TrkB in the juvenile mice ENS and CNS. Such changes may potentially contribute later to the development of functional gut disorders, such as IBS, showing psychiatric comorbidity.

Alleviation of Irritable Bowel Syndrome-Like Symptoms and Control of Gut and Brain Responses with Oral Administration of Dolichos lablab L. in a Mouse Model

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder manifesting as unexplained abdominal pain and bowel habit changes. The pathogenesis of post-infectious IBS is associated with gut–brain axis dysfunction, including low-grade colonic inflammation and anxiety-related long-term brain changes. This study analyzed the efficacy of a standardized extract of Dolichos lablab L. extract (DL), a bean species, in an IBS mouse model resembling post-infectious, diarrhea-dominant IBS. Using a zymosan-induced animal IBS model, we found that oral administration of DL significantly attenuated zymosan-induced increases in colonic macroscopic scores and minimized weight loss without affecting food intake. In the DL-treated mice, the mast cell count and tumor necrosis factor-α level in the colon markedly decreased, similar to results in sulfasalazine-treated mice and in mice with lipopolysaccharide-stimulated bone marrow-derived mast cells. The number of visceral pain-related behaviors was much lower in the DL-treated mice. Anxiety-like behaviors significantly improved, comparable to that after treatment with amitriptyline. The c-Fos expression level in the prefrontal cortex was significantly reduced. Our data suggest that DL could be beneficial for treating IBS by acting on the gut and brain.

FODMAP diet modulates visceral nociception by lipopolysaccharide-mediated intestinal inflammation and barrier dysfunction

Foods high in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) exacerbate symptoms of irritable bowel syndrome (IBS); however, their mechanism of action is unknown. We hypothesized that a high-FODMAP (HFM) diet increases visceral nociception by inducing dysbiosis and that the FODMAP-altered gut microbial community leads to intestinal pathology. We fed rats an HFM and showed that HFM increases rat fecal Gram-negative bacteria, elevates lipopolysaccharides (LPS), and induces intestinal pathology, as indicated by inflammation, barrier dysfunction, and visceral hypersensitivity (VH). These manifestations were prevented by antibiotics and reversed by low-FODMAP (LFM) diet. Additionally, intracolonic administration of LPS or fecal supernatant (FS) from HFM-fed rats caused intestinal barrier dysfunction and VH, which were blocked by the LPS antagonist LPS-RS or by TLR4 knockdown. Fecal LPS was higher in IBS patients than in healthy subjects (HS), and IBS patients on a 4-week LFM diet had improved IBS symptoms and reduced fecal LPS levels. Intracolonic administration of FS from IBS patients, but not FS from HS or LFM-treated IBS patients, induced VH in rats, which was ameliorated by LPS-RS. Our findings indicate that HFM-associated gut dysbiosis and elevated fecal LPS levels induce intestinal pathology, thereby modulating visceral nociception and IBS symptomatology, and might provide an explanation for the success of LFM diet in IBS patients.

P2Y1R is involved in visceral hypersensitivity in rats with experimental irritable bowel syndrome

AIM

To evaluate the role of P2Y1R in visceral hypersensitivity in rats with experimental irritable bowel syndrome.

METHODS

A rat model of irritable bowel syndrome was generated by intra-colonic administration of acetic acid (AA) and assessed by histology and myeloperoxidase (MPO) activity assay. Then P2Y1R expression in the colonic tissue was detected by Western blot. In order to explore the regulatory role of P2Y1R in visceral hypersensitivity, an agonist (MRS2365) and an antagonist (MRS2179) of P2Y1R were intra-colonically administered and effects were tested through a colorectal distension test. The abdominal withdrawal reflex and abdominal electromyography were tested during the course.

RESULTS

Model assessment tests showed an obvious inflammatory reaction that appeared on the 2^nd d after the AA injection, and the inflammatory reaction gradually recovered and almost disappeared on the 7^th d. The model finished on day 8 and showed a clear feature of IBS that had no organic lesion. The average expression of P2Y1R was significantly higher in the AA group than in the naïve group (0.319 ± 0.02 vs 0.094 ± 0.016, P < 0.001). MRS2365 could effectively raise the colonic hypersensitivity status at intervention doses of 10 (AUC value from 0.30 ± 0.089 to 1.973 ± 0.127 mv·s, P < 0.01) and 100 μmol/L (AUC value from 0.290 ± 0.079 to 1.983 ± 0.195 mv·s, P < 0.01); MRS2179 could effectively reduce the hypersensitivity status at intervention dose of 100 μmol/L (from a mean baseline AUC value of 1.587 ± 0.099 mv·s to 0.140 ± 0.089 mv·s, P < 0.0001). Differences between the MRS2179 group (1.88 ± 1.45) and either the MRS2365 group (3.96 ± 0.19) or the combined treatment (MRS2179 and MRS2365) group (3.28 ± 0.11) were significant (P < 0.01).

CONCLUSION

P2Y1R plays a regulatory role in visceral hypersensitivity in rats with experimental IBS. Specific antagonists of P2Y1R may have potential therapeutic value in treating abdominal pain in IBS.

Risk for Irritable Bowel Syndrome in Fibromyalgia Patients: A National Database Study

Various studies have shown that irritable bowel syndrome (IBS) is highly associated with other pathologies, including fibromyalgia (FM). The objective of this study was to analyze the differences among risk factors associated with IBS following FM in a nationwide prospective cohort study.We propose that a relationship exists between FM and IBS. This article presents evidence obtained from a cohort study in which we used data from the Taiwan National Health Insurance Research Database to clarify the relationship between FM and IBS. The follow-up period ran from the start of FM diagnosis to the date of the IBS event, censoring, or December 31, 2011. We analyzed the risk of IBS using Cox proportional hazard regression models, including sex, age, and comorbidities.During the follow-up period, from 2000 to 2011, the overall incidence of IBS was higher in FM patients than in non-FM patients (7.47 vs 4.42 per 1000 person-years), with a crude hazard ratio = 1.69 (95% confidence interval [CI] 1.59-1.79). After adjustment for age, sex, and comorbidities, FM was associated with a 1.54-fold increased risk for IBS.Mutually risk factors may influence the relationship between FM and IBS. We recommend that physiologists conduct annual examinations of FM patients to reduce the incidence of IBS progression.

The Protective Effects of Exclusive Enteral Nutrition Formulas on Growth Factor Expression and the Proximal Tibial Epiphyseal Growth Plate in a TNBS-Induced IBD Rat Model

OBJECTIVE

This study aimed to evaluate the effectiveness of different types of nutritional formulas in a rat model of TNBS-induced IBD.

METHODS

IBD was induced with TNBS in 4-week-old rats that were then fed different exclusive enteral nutrition diets for 7 days. The length of the tibia and the number of chondrocytes in the proximal tibias were analyzed at 7 days after supplementation. Immunohistochemical analysis, ELISA and real-time PCR were performed to evaluate the levels of growth hormone receptor (GHR) and insulin-like growth factor-I receptor (IGF-IR), the growth factors IGF-I and insulin-like growth factor-binding protein-3 (IGFBP3) , bone morphogenetic protein (BMP)-2 and BMP-6 respectively.

RESULTS

The results demonstrated that the tibia length of the peptide formula group was longer than that of the IBD-Modulen(®) formula and normal diet groups (P < 0.05). Furthermore, the number of chondrocytes of the proximal tibial was more pronounced in the peptide formula group compared to the other groups (P < 0.05). The peptide formula was also more effective in increasing the expression of GHR compared to the other groups (P < 0.05), while the expression of IGF-IR was not significantly different (P > 0.05). In addition, the IGF-I and IGFBP3 levels were more pronounced in the peptide formula supplement group (P < 0.05), and the expression of BMP-2 and BMP-6 mRNA in the proximal tibia growth plate from the peptide formula group was higher than that in the ordinary formula and normal diet groups (P < 0.05).

CONCLUSIONS

EEN, and particularly a peptide formula, exerted protective effects on the proximal tibial epiphyseal growth plate in a TNBS-induced IBD model.

[Effect of inherent depression on chronic visceral hypersensitivity induced by colon acetate stimulation in neonatal rats]

OBJECTIVE

To explore the effect of inherent depression on chronic visceral hypersensitivity. The differences of visceral sensitivity, colitis, and brain activation between Fawn-Hooded (FH/Wjd) and Sprague-Dawley(SD) rats were identified after neonatal colon acetate stimulation.

METHODS

The specific pathogen free Fawn-Hooded (FH/Wjd) and Sprague-Dawley(SD) rats were used to establish irritable bowel syndrome (IBS) model. The visceral sensitivity was measured by colorectal distension (CRD). The expression of 5-hydroxytryptamine (5-HT), mast cell (MC), indoleamine 2,3-dioxygenase (IDO) in colon and IDO in specific cerebral regions were detected through immunohistochemistry.

RESULTS

Abdominal withdrawal reflex (AWR) scores showed that visceral sensitivity of acetate-enema groups was significantly higher than that of saline-enema groups (FH/Wjd:2.44 ± 0.04 vs.1.96 ± 0.07, P < 0.05; SD: 1.75 ± 0.13 vs.1.32 ± 0.05, P < 0.05). Furthermore, FH/Wjd rats of IBS group scored significantly higher than SD rats of IBS group (2.44 ± 0.04 vs.1.75 ± 0.13, P < 0.05). The MC amounts of both SD and FH/Wjd IBS group rats were significantly more than those of their control groups (FH/Wjd:43.24 ± 1.72 vs. 24.92 ± 1.38, P < 0.01. SD: 23.80 ± 1.28 vs. 14.24 ± 0.92, P < 0.01). Besides, the MC amounts of control and IBS group of FH/Wjd rats were significantly more than that of SD IBS group rats (P < 0.01). The IDO and 5-HT positive cells in colonic mucosa of IBS group of both SD and FH/Wjd rats were significantly more than those of their control groups, respectively(P < 0.01). The IDO, 5-HT positive cells in colonic mucosa of both control and IBS group of FH/Wjd rats were significantly more than those of both control and IBS group of SD rats (control:IDO,24.64 ± 2.22 vs. 15.52 ± 1.39;5-HT,21.32 ± 1.26 vs. 12.72 ± 1.12. IBS: IDO,44.92 ± 2.31 vs. 20.85 ± 1.72; 5-HT, 31.84 ± 1.57 vs. 19.65 ± 1.09.P <0.01). The expression of IDO in prelimbic cortex (PrL) areas of FH/Wjd IBS rats was significantly higher than that of IBS group of SD rats (49.60 ± 4.31 vs. 35.60 ± 2.42, P <0.01), and the expression of IDO in rostral anterior cingulate cortex (rACC) areas of FH/Wjd IBS rats was significantly more than that of FH/Wjd control rats (45.44 ± 1.16 vs. 34.08 ± 2.76, P <0.01).

CONCLUSION

Inherent depressive FH/Wjd rats were more sensitive to neonatal colon acetate stimulation, presenting as visceral hypersensitivity which maybe associated with increased MC amounts and over-expression of 5-HT and IDO in colon, suggesting that depression disorder may aggravate functional disturbance of gastrointestinal tract by regulating the response to inflammatory stimulation.

Selective agonists of somatostatin receptor subtype 1 or 2 injected peripherally induce antihyperalgesic effect in two models of visceral hypersensitivity in mice

Somatostatin interacts with five G-protein-coupled receptor (sst1-5). Octreotide, a stable sst2≫3≥5 agonist, exerts a visceral anti-hyperalgesic effect in experimental and clinical studies. Little is known on the receptor subtypes involved. We investigated the influence of the stable sst1-5 agonist, ODT8-SST and selective receptor subtype peptide agonists (3 or 10μg/mouse) injected intraperitoneally (ip) on visceral hypersensitivity in mice induced by repeated noxious colorectal distensions (four sets of three CRD, each at 55mmHg) or corticotropin-releasing factor receptor 1 agonist, cortagine given between two sets of graded CRD (15, 30, 45, and 60mmHg, three times each pressure). The mean visceromotor response (VMR) was assessed using a non-invasive manometry method and values were expressed as percentage of the VMR to the 1st set of CRD baseline or to the 60mmHg CRD, respectively. ODT8-SST (10μg) and the sst2 agonist, S-346-011 (3 and 10μg) prevented mechanically induced visceral hypersensitivity in the three sets of CRD, the sst1 agonist (10μg) blocked only the 2nd set and showed a trend at 3μg while the sst4 agonist had no effect. The selective sst2 antagonist, S-406-028 blocked the sst2 agonist but not the sst1 agonist effect. The sst1 agonist (3 and 10μg) prevented cortagine-induced hypersensitivity to CRD at each pressure while the sst2 agonist at 10μg reduced it. These data indicate that in addition to sst2, the sst1 agonist may provide a novel promising target to alleviate visceral hypersensitivity induced by mechanoreceptor sensitization and more prominently, stress-related visceral nociceptive sensitization.

Epidermal growth factor upregulates serotonin transporter and its association with visceral hypersensitivity in irritable bowel syndrome

AIM: To investigate the role of epidermal growth factor (EGF) in visceral hypersensitivity and its effect on the serotonin transporter (SERT).

METHODS: A rat model for visceral hypersensitivity was established by intra-colonic infusion of 0.5% acetic acid in 10-d-old Sprague-Dawley rats. The visceral sensitivity was assessed by observing the abdominal withdrawal reflex and recording electromyographic activity of the external oblique muscle in response to colorectal distension. An enzyme-linked immunosorbent assay was used to measure the EGF levels in plasma and colonic tissues. SERT mRNA expression was detected by real-time PCR while protein level was determined by Western blot. The correlation between EGF and SERT levels in colon tissues was analyzed by Pearson’s correlation analysis. SERT function was examined by tritiated serotonin (5-HT) uptake experiments. Rat intestinal epithelial cells (IEC-6) were used to examine the EGF regulatory effect on SERT expression and function via the EGF receptor (EGFR).

RESULTS: EGF levels were significantly lower in the rats with visceral hypersensitivity as measured in plasma (2.639 ± 0.107 ng/mL vs 4.066 ± 0.573 ng/mL, P < 0.01) and in colonic tissue (3.244 ± 0.135 ng/100 mg vs 3.582 ± 0.197 ng/100 mg colon tissue, P < 0.01) compared with controls. Moreover, the EGF levels were positively correlated with SERT levels (r = 0.820, P < 0.01). EGF displayed dose- and time-dependent increased SERT gene expressions in IEC-6 cells. An EGFR kinase inhibitor inhibited the effect of EGF on SERT gene upregulation. SERT activity was enhanced following treatment with EGF (592.908 ± 31.515 fmol/min per milligram vs 316.789 ± 85.652 fmol/min per milligram protein, P < 0.05) and blocked by the EGFR kinase inhibitor in IEC-6 cells (590.274 ± 25.954 fmol/min per milligram vs 367.834 ± 120.307 fmol/min per milligram protein, P < 0.05).

CONCLUSION: A decrease in EGF levels may contribute to the formation of visceral hypersensitivity through downregulation of SERT-mediated 5-HT uptake into enterocytes.

Methylglyoxal induces systemic symptoms of irritable bowel syndrome

Patients with irritable bowel syndrome (IBS) show a wide range of symptoms including diarrhea, abdominal pain, changes in bowel habits, nausea, vomiting, headache, anxiety, depression and cognitive impairment. Methylglyoxal has been proved to be a potential toxic metabolite produced by intestinal bacteria. The present study was aimed at investigating the correlation between methylglyoxal and irritable bowel syndrome. Rats were treated with an enema infusion of methylglyoxal. Fecal water content, visceral sensitivity, behavioral tests and serum 5-hydroxytryptamine (5-HT) were assessed after methylglyoxal exposure. Our data showed that fecal water content was significantly higher than controls after methylglyoxal exposure except that of 30 mM group. Threshold volumes on balloon distension decreased in the treatment groups. All exposed rats showed obvious head scratching and grooming behavior and a decrease in sucrose preference. The serum 5-HT values were increased in 30, 60, 90 mM groups and decreased in 150 mM group. Our findings suggested that methylglyoxal could induce diarrhea, visceral hypersensitivity, headache as well as depression-like behaviors in rats, and might be the key role in triggering systemic symptoms of IBS.

Butyrate-induced colonic hypersensitivity is mediated by mitogen-activated protein kinase activation in rat dorsal root ganglia

OBJECTIVE

Increased faecal butyrate levels have been reported in irritable bowel syndrome. Rectal instillation of sodium butyrate (NaB) increases visceral sensitivity in rats by an unknown mechanism. We seek to examine the signal transduction pathways responsible for the enhanced neuronal excitability in the dorsal root ganglion (DRG) following NaB enemas and demonstrate that this is responsible for the colonic hypersensitivity reported in this animal model.

DESIGN

Colorectal distention (CRD) studies were performed in rats treated with NaB rectal instillation with/without intrathecal or intravenous administration of mitogen-activated protein (MAP) kinase kinase inhibitor U0126. Western blot analysis and immunocytochemistry studies elucidated intracellular signalling pathways that modulate IA. Patch-clamp recordings were performed on isolated DRG neurons treated with NaB, with/without U0126.

RESULTS

Visceromotor responses (VMR) were markedly enhanced in NaB-treated rats. Western blot analysis of DRG neurons from NaB-treated rats showed a 2.2-fold increase in phosphorylated ERK1/2 (pEKR1/2) and 1.9-fold increase in phosphorylated voltage-gated potassium channel subunit 4.2 (pKv4.2). Intrathecal or intravenous administration of U0126 reduced VMR to CRD in NaB-treated rats and prevented increases in pERK1/2 and pKv4.2. Patch-clamp recordings of isolated DRG neurons showed that NaB caused a reduction in IA to 48.9%±1.4% of control and an increase in neuronal excitability, accompanied by a twofold increase in pERK1/2 and pKv4.2. Concurrent U0126 administration prevented these changes.

CONCLUSIONS

Visceral hypersensitivity induced by colonic NaB treatment is mediated by activation of the MAP kinase-ERK1/2 pathway, which phosphorylates Kv4.2. This results in a reduction in IA and an enhancement of DRG neuronal excitability.

Role of nesfatin-1 in a rat model of visceral hypersensitivity

AIM: To explore the role of nesfatin-1 on irritable bowel syndrome (IBS)-like visceral hypersensitivity.

METHODS: The animal model of IBS-like visceral hypersensitivity was induced by intracolonic infusion of 0.5% acetic acid (AA) in saline once daily from postnatal days 8-21. Experiments were performed when rats became adults. The visceral sensitivity of rats was evaluated by abdominal withdrawal reflex (AWR) and electromyographic (EMG) activity of the external oblique muscle to graded colorectal distension. The content of nesfatin-1 in serum was determined using enzyme-linked immunosorbent assay. After implantation of an intracerebroventricular (ICV) cannula and two electrodes into the external oblique muscle, model rats were randomly divided into four groups. Animals then received ICV injection of 8 μg of anti-nesfatin-1/nucleobindin-2 (NUCB2), 50 μg of α-helical corticotropin releasing factor (CRF) 9-41 (non-selective CRF receptor antagonist), 50 μg of NBI-27914 (selective CRF1 receptor antagonist) or 5 μL of vehicle. After 1 h of ICV administration, visceral sensitivity of each group was measured again, and comparisons between groups were made.

RESULTS: Rats treated with AA showed higher mean AWR scores and EMG activity at all distension pressures compared with controls (P < 0.05). On histopathologic examination, no evidence of inflammation or abnormalities in structure were noted in the colon of either control or AA-treated groups. Myeloperoxidase values were not significantly different between the two groups. The level of nesfatin-1 in serum was significantly higher in the AA-treated group than in the control group (5.34 ± 0.37 ng/mL vs 4.81 ± 0.42 ng/mL, P < 0.01). Compared with rats injected with vehicle, rats which received ICV anti-nesfatin-1/NUCB2, α-helical CRF9-41 or NBI-27914 showed decreased mean AWR scores and EMG activity at all distension pressures (P < 0.05).

CONCLUSION: Nesfatin-1 may be associated with IBS-like visceral hypersensitivity, which may be implicated in brain CRF/CRF1 signaling pathways.

Use of broad-spectrum antibiotics and the development of irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a functional bowel disorder with an estimated prevalence of 9% to 22% in the United States. It is responsible for 28% of gastroenterology visits, with associated health care costs of $8 billion annually. Yet, IBS etiology is the subject of much debate.

OBJECTIVES

Our study examines a possible relationship between IBS and exposure to broad-spectrum antibiotics. It is known that antibiotics alter the colonic flora; we hypothesize that this can create the manifestations seen in IBS patients.

METHODS

Following approval by the Gundersen Clinic, Ltd Human Subjects Committee/IRB, the medical records of adults who were started on a broad-spectrum antibiotic at Gundersen Lutheran Health System between January 1, 2008, and December 31, 2008, were reviewed retrospectively. From this population, we identified those who developed IBS within 12 months and compared their demographic and clinical characteristics with the characteristics of those who did not.

RESULTS

Of the 26,107 adult patients exposed to broad-spectrum antibiotics during the study period, 115 received an IBS diagnosis within 12 months. Most were women (84%; n = 97), and they had a higher prevalence of associated comorbidities than those who did not develop IBS. Patients indicated for macrolide or tetracycline use had a higher proportion of IBS development within 12 months; indication for tetracycline use maintained significance even after controlling for sex and comorbid conditions (odds ratio; 1.48; P = .046).

CONCLUSION

Use of broad-spectrum antibiotics--particularly macrolides or tetracyclines--may be associated with IBS development. To date, we know of no other study that has associated these antibiotics with IBS development. Further studies are necessary.

Ameliorating effects of mirtazapine on visceral hypersensitivity in rats with neonatal colon sensitivity

BACKGROUND

The aim was to investigate the effects of mirtazapine on visceral hypersensitivity and gastric emptying in an established rodent model of colonic sensitization.

METHODS

Twenty colonic sensitized rats and 20 matched controls were used. Visceral sensitivity during colorectal distension (CRD) was assessed by the measurement of abdominal electromyogram (EMG) with the pressures of 20, 40, and 60 mmHg. Mirtazapine with doses of 1, 5, and 10 mg kg(-1) were administered orally. Gastric emptying and small intestinal transit were performed in a separated experiment after gavage of 1.5 mL of phenol red solution.

KEY RESULTS

(i) Visceral hypersensitivity after neonatal colonic sensitization was confirmed. (ii) Mirtazapine dose-dependently reduced visceral hypersensitivity in the colonic sensitized rats. The increases in EMG during CRD at 40, 60 mmHg were, 17.59 +/- 6.49 and 26.04 +/- 8.30, respectively, with saline session, and substantially reduced to 10.0 +/- 5.95 (P = 0.02 vs corresponding saline) and 12.58 +/- 7.43 (P < 0.001 vs saline) with mirtazapine at 10 mg kg(-1). Similar findings were noted at doses of 5 and 1 mg kg(-1) at a lesser degree. In the control rats, mirtazapine-reduced visceral sensitivity only during CRD at 60 mmHg. (iii) Mirtazapine 10 mg kg(-1) significantly accelerated gastric emptying (P = 0.045) but slightly and marginally delayed intestinal transit (P = 0.058) the colonic sensitized rats.

CONCLUSIONS & INFERENCES

Mirtazapine dose-dependently ameliorates visceral hypersensitivity in colonic sensitized rats. Mirtazapine at a high dose improves delayed gastric emptying in colonic sensitized rats but slightly and marginally delays small intestinal transit. Its roles in altering gastrointestinal motility need further investigation.

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

BACKGROUND & AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLA and n-3 PUFA differentially modulate clinical activity and colonic PPAR-responsive gene expression in a pig model of experimental IBD

BACKGROUND AND AIMS

Conjugated linoleic acid (CLA) and n-3 polyunsaturated fatty acids (PUFA) have been proposed as important pharmaco-nutrients for modulating mucosal immunity and therapeutic responses in patients with inflammatory bowel disease (IBD). We evaluated the ability of CLA and n-3 PUFA alone or in combination to modulate IBD in a pig model of dextran sodium sulfate (DSS)-induced colitis.

METHODS

Sixty-four, 15-day-old pigs were used to evaluate the effect of CLA, n-3 PUFA and a 50:50 mixture of CLA and n-3 PUFA on growth, clinical activity and colonic PPAR-responsive gene expression. Diets were formulated to contain: 1.33% soybean oil (control); 1.33% CLA; 1.33% fish oil; or 1.33% of a 50:50 mixture of CLA and fish oil. Intestinal inflammation was induced by an intragastric challenge with DSS on day 42 of dietary supplementation. The colonic expression of peroxisome proliferator-activated receptor-gamma (PPAR-gamma), PPAR gamma- and delta-responsive genes, keratinocyte growth factor (KGF) and tumor necrosis factor (TNF-alpha) were assayed by quantitative RT-PCR.

RESULTS

The onset of IBD was delayed, colitis less severe and growth suppression attenuated in pigs fed CLA, which correlated with induction of colonic PPAR gamma and its responsive gene PPAR gamma-coactivator-1alpha (PGC1-alpha) and downregulation of TNF-alpha. However, dietary supplementation with n-3 PUFA alone or in combination with CLA resulted in an early onset of disease (i.e., day 2) and faster recovery on days 6 and 7, which correlated with a marked induction of the PPAR delta-responsive gene uncoupling protein 3 (UCP3). CLA and n-3 PUFA acted synergistically to upregulate colonic KGF expression in DSS-challenged pigs but n-3 PUFA blocked CLA-induced PPAR gamma activation.

CONCLUSION

Dietary CLA-supplementation upregulated colonic PPAR gamma expression and contributed to delaying the onset of experimental IBD, whereas n-3 PUFA failed to protect from IBD, although it accelerated colonic regeneration and clinical remission by activating PPAR delta.

Specific probiotic therapy attenuates antibiotic induced visceral hypersensitivity in mice

BACKGROUND AND AIMS

Abdominal pain and discomfort are common symptoms in functional disorders and are attributed to visceral hypersensitivity. These symptoms fluctuate over time but the basis for this is unknown. Here we examine the impact of changes in gut flora and gut inflammatory cell activity on visceral sensitivity.

METHODS

Visceral sensitivity to colorectal distension (CRD) was assessed at intervals in healthy mice for up to 12 weeks, and in mice before and after administration of dexamethasone or non-absorbable antibiotics with or without supplementation with Lactobacillus paracasei (NCC2461). Tissue was obtained for measurement of myeloperoxidase activity (MPO), histology, microbiota analysis, and substance P (SP) immunolabelling.

RESULTS

Visceral hypersensitivity developed over time in healthy mice maintained without sterile precautions. This was accompanied by a small increase in MPO activity. Dexamethasone treatment normalised MPO and CRD responses. Antibiotic treatment perturbed gut flora, increased MPO and SP immunoreactivity in the colon, and produced visceral hypersensitivity. Administration of Lactobacillus paracasei in spent culture medium normalised visceral sensitivity and SP immunolabelling, but not intestinal microbiota counts.

CONCLUSION

Perturbations in gut flora and in inflammatory cell activity alter sensory neurotransmitter content in the colon, and result in altered visceral perception. Changes in gut flora may be a basis for the variability of abdominal symptoms observed in functional gastrointestinal disorders and may be prevented by specific probiotic administration.

Visceral hypersensitivity and altered colonic motility after subsidence of inflammation in a rat model of colitis

AIM: Irritable bowel syndrome (IBS) is a functional bowel disorder characterized by visceral hypersensitivity and altered bowel motility. There is increasing evidence suggesting the role of inflammation in the pathogenesis of IBS, which addresses the possibility that formerly established rat model of colitis could be used as an IBS model after the inflammation subsided.

METHODS: Colitis was induced by intracolonic instillation of 4% acetic acid in male Sprague-Dawley rats. The extent of inflammation was assessed by histological examination and myeloperoxidase (MPO) activity assay. After subsidence of colitis, the rats were subjected to rectal distension and restraint stress, then the abdominal withdrawal reflex and the number of stress-induced fecal output were measured, respectively.

RESULTS: At 2 days post-induction of colitis, the colon showed characteristic inflammatory changes in histology and 8-fold increase in MPO activity. At 7 days post-induction of colitis, the histological features and MPO activity returned to normal. The rats at 7 days post-induction of colitis showed hypersensitive response to rectal distension without an accompaning change in rectal compliance, and defecated more stools than control animals when under stress.

CONCLUSION: These results concur largely with the characteristic features of IBS, visceral hypersensitivity and altered defecation pattern in the absence of detectable disease, suggesting that this animal model is a methodologically convenient and useful model for studying a subset of IBS.