Irritable bowel syndrome: methods, mechanisms, and pathophysiology. The confluence of increased permeability, inflammation, and pain in irritable bowel syndrome

A clinical model for identifying an inflammatory phenotype in mood disorders

Increasingly, clinical research has found inflammatory correlates of psychiatric disorders, particularly mood symptomatology. Biological measures may provide greater precision in many cases and may capture clinically-relevant inflammatory signposts, such as central obesity risk, inflammation-associated co-morbid medical conditions, or proinflammatory lifestyle choices. In order to expand understanding of the role of inflammation in mood disorders, we propose a more inclusive clinical model for capturing an inflammatory phenotype of depression by identifying clinically-relevant inflammatory phenotypes grounded in biology. Our model includes chronic conditions and lifestyle behaviors associated with clinically elevated inflammation in mood disorders. Elements of this "inflamed depression" model include: obesity, low HDL concentrations, elevated triglyceride concentrations, chronically elevated blood pressure, clinical diagnosis of hypothyroidism, migraines, rheumatoid arthritis, adult onset diabetes, inflammatory bowel diseases, inflammatory skin conditions, and lifestyle factors including smoking cigarettes and chronic stress.

Escherichia coli K12: An evolving opportunistic commensal gut microbe distorts barrier integrity in human intestinal cells

Commensal enteric microbes under specific conditions viz. immunocompromised system, altered microbiota or uncompetitive niche induce their otherwise dormant pathogenic phenotype to distort host cellular functioning. Here we investigate how under in vitro environment established by using Caco-2 cells, commensal gut microbe E. coli K12 (ATCC 14849) disrupt intestinal epithelial barrier function. Caco-2 cells exposed to E. coli showed the time dependent significant (P < 0.01) decrease in transepithelial electrical resistance (TEER) and concomitantly increased phenol red flux across cell monolayer in contrast to non infected control cells. E. coli infected intestinal cells were observed with suppressed (p < 0.05) mRNA levels of ZO-1, Claudin-1, Occludin and Cingulin-1 in contrast to significantly (p < 0.05) higher PIgR and hbd-2 mRNA fold changes. Immunofluorescent and electron micrographs revealed the disrupted distribution and localisation of specific tight junction proteins (Zo-1 and Claudin-1) and actin filament in E. coli infected Caco-2 cells that ultimately resulted in deformed cellular morphology. Taken together, E. coli K12 under compromised in vitro milieu disrupted the intestinal barrier functions by decreasing the expression of important tight junction genes along with the altered distribution of associated proteins that increased the intestinal permeability as reflected by phenol red flux and TEER values.

Metformin prevents colonic barrier dysfunction by inhibiting mast cell activation in maternal separation-induced IBS-like rats

BACKGROUND

Intestinal barrier dysfunction is a key etiologic factor of irritable bowel syndrome (IBS). Metformin improves intestinal barrier function, although the underlying mechanism has yet to be fully explained. This study evaluates the protective effect of metformin on colonic barrier integrity and explores the underlying cellular mechanisms.

METHODS

IBS-like rats were induced by maternal separation. Metformin was administered daily by gavage at 08:30, and rat pups were then separated from their mother. Visceral hyperalgesia and depression-like behaviors were evaluated by colorectal distension, sucrose preference tests, and forced swimming tests. Intestinal integrity was analyzed using sugar probes and transmission electron microscopy. Inflammatory factors and the levels of corticotropin-releasing factor were assessed by PCR and ELISA. The number of mast cells was evaluated by toluidine blue staining. Protein expression and localization were determined using Western blot and immunochemistry.

KEY RESULTS

Metformin pretreatment (a) reduced visceral hypersensitivity to colorectal distension, immobility time and enhanced sucrose consumption; (b) decreased urine lactulose/mannitol ratio and sucralose output; (c) inhibited the dilation of tight junction and prevented claudin-4 translocation; (d) inhibited mast cell activation and downregulated the expression of IL-6, IL-18, tryptase, PAR-2, and ERK activation; (e) inhibited claudin-4 phosphorylation at serine sites and interactions between clau-4 and ZO-1.

CONCLUSIONS & INFERENCES

Metformin may block mast cell activation to reduce PAR-2 expression and subsequently inhibit ERK activation and clau-4 phosphorylation at serine sites to normalize the interaction of clau-4 and ZO-1 and clau-4 distribution. Metformin may be clinically beneficial for patients with IBS or IBS-like symptoms.

Self-reported Food Intolerance in Korean Patients With Irritable Bowel Syndrome

Background/Aims

Various foods trigger and/or worsen the symptoms of irritable bowel syndrome (IBS). However, Korean food-related gastrointestinal (GI) symptoms in IBS patients have not yet been investigated. This study aims to evaluate the prevalence of self-reported food intolerance in Korean IBS patients and determine the Korean food items and food groups perceived by patients to worsen their GI symptoms.

Methods

We recruited 393 study subjects, comprising 101 IBS patients, 167 symptomatic non-IBS subjects, and 125 control subjects. All participants completed a questionnaire to identify the most problematic foods and assess the occurrence of GI symptoms caused by 119 Korean food items. They also completed the validated Rome III questionnaire for IBS.

Results

The prevalence of self-reported food intolerance in Korean IBS patients was 79.2%, which was significantly higher than that in control subjects (44.8%, P < 0.001). The most problematic foods reported by IBS patients who experienced food intolerance were high-fat foods (25.0%), gluten foods (23.8%), spicy foods (15.0%), and dairy products (15.0%). A total of 63.4% of IBS patients reported GI symptoms related to the consumption of foods high in fermentable oligo-, di-, mono-saccharides, and polyols (FODMAP), while 48.5% of IBS patients reported symptoms associated with high-fat foods. Gas problems and loose stools were the most frequently reported symptoms.

Conclusions

A large proportion of Korean IBS patients complained of intolerance to certain food items, with high-fat and high-FODMAP foods being the main triggers. This study provides a basis for planning food intervention studies for Korean IBS patients.

Rhein protects against barrier disruption and inhibits inflammation in intestinal epithelial cells

BACKGROUND AND AIMS

Intestinal epithelial barrier and intestinal inflammation play indispensable roles in the development of intestinal diseases. The major aims of the current study were to investigate the potential of rhein, a major flavonoid compound isolated from Rheum rhabarbarum, in the treatment of intestinal diseases and its underlying mechanisms in vitro.

METHODS

The protective role of rhein on intestinal epithelial barrier was evaluated in a monolayer of IEC-6 cells stimulated by TNF-α, while the anti-inflammatory effects were investigated in an IEC-6 cell model with LPS stimulation.

RESULTS

Rhein inhibited the increase of phenol red flux and the decrease of TEER, as well as recovered the expression and distribution of ZO-1 and weakened MLC phosphorylation, MLCK expression and NF-κB activation. Meanwhile, LPS-stimulated IL-1β and IL-6 were down-regulated, expression levels of TLR4, NLRP3 and cleaved caspase1 were weakened and NF-κB was inactivated.

CONCLUSIONS

These results suggested that rhein has potential therapeutic effects against intestinal diseases by maintaining intestinal epithelial barrier and suppressing intestinal inflammation.

Personalized medicine in functional gastrointestinal disorders: Understanding pathogenesis to increase diagnostic and treatment efficacy

There is overwhelming evidence that functional gastrointestinal disorders (FGIDs) are associated with specific mechanisms that constitute important targets for personalized treatment. There are specific mechanisms in patients presenting with functional upper gastrointestinal symptoms (UGI Sx). Among patients with UGI Sx, approximately equal proportions (25%) of patients have delayed gastric emptying (GE), reduced gastric accommodation (GA), both impaired GE and GA, or neither, presumably due to increased gastric or duodenal sensitivity. Treatments targeted to the underlying pathophysiology utilize prokinetics, gastric relaxants, or central neuromodulators. Similarly, specific mechanisms in patients presenting with functional lower gastrointestinal symptoms, especially with diarrhea or constipation, are recognized, including at least 30% of patients with functional constipation pelvic floor dyssynergia and 5% has colonic inertia (with neural or interstitial cells of Cajal loss in myenteric plexus); 25% of patients with diarrhea-predominant irritable bowel syndrome (IBSD) has evidence of bile acid diarrhea; and, depending on ethnicity, a varying proportion of patients has disaccharidase deficiency, and less often sucrose-isomaltase deficiency. Among patients with predominant pain or bloating, the role of fermentable oligosaccharides, disaccharides, monosaccharides and polyols should be considered. Personalization is applied through pharmacogenomics related to drug pharmacokinetics, specifically the role of CYP2D6, 2C19 and 3A4 in the use of drugs for treatment of patients with FGIDs. Single mutations or multiple genetic variants are relatively rare, with limited impact to date on the understanding or treatment of FGIDs. The role of mucosal gene expression in FGIDs, particularly in IBS-D, is the subject of ongoing research. In summary, the time for personalization of FGIDs, based on deep phenotyping, is here; pharmacogenomics is relevant in the use of central neuromodulators. There is still unclear impact of the role of genetics in the management of FGIDs.

IRRITABLE BOWEL SYNDROME, FOOD INTOLERANCE AND NON- CELIAC GLUTEN SENSITIVITY. A NEW CLINICAL CHALLENGE

Approximately 80% of irritable bowel syndrome (IBS) patients report that their symptoms are triggered after ingesting one or specific food groups. Gluten, wheat and related proteins (e.g., amylase-trypsin inhibitors, and fermentable oligo-di-mono-saccharides and polyols (FODMAPs) are the most relevant IBS symptom triggers, although the true 'culprit(s)' is/are still not well established. The concept of causal relationship between gluten intake and the occurrence of symptoms in the absence of celiac disease and wheat allergy was termed non-celiac gluten sensitivity (NCGS). The borderline between celiac disease, wheat allergy, IBS and NCGS is not always clearly distinguishable, and the frequency and clinical identity of NGCS are still unclear. An overlap between IBS and NCGS has been detected. The incomplete knowledge of the etiopathogenesis of these clinical conditions, lack of data on their real epidemiology, as well as the absence of a gold standard for their diagnosis, make the overall picture difficult to understand "It is crucial to well define the interaction between IBS, food intolerance and NGCS, since the role of diet in IBS and its dietary management is an essential tool in the treatment of a large number of these patients". The objective of the present review is to provide an overview highlighting the interaction between IBS, food intolerance and NCGS in order to unravel whether gluten/wheat/FODMAP sensitivity represents 'facts' and not 'fiction' in IBS symptoms.

Duodenal and Rectal Mucosa Inflammation in Patients With Non-celiac Wheat Sensitivity

BACKGROUND & AIMS

Studies of non-celiac gluten or wheat sensitivity (NCGWS) have increased but there are no biomarkers of this disorder. We aimed to evaluate histologic features of colon and rectal tissues from patients with NCGWS.

METHODS

We performed a prospective study of 78 patients (66 female; mean age, 36.4 years) diagnosed with NCGWS by double-blind wheat challenge at 2 tertiary care centers in Italy, from January 2015 through September 2016. Data were also collected from 55 patients wither either celiac disease or self-reported NCGWS but negative results from the wheat-challenge test (non-NCGWS controls). Duodenal and rectal biopsies were collected and analyzed by immunohistochemistry to quantify intra-epithelial CD3⁺ T cells, lamina propria CD45⁺ cells, CD4⁺ and CD8⁺ T cells, mast cells, and eosinophils and to determine the presence and size of lymphoid nodules in patients with NCGWS vs patients with celiac disease or non-NCGWS controls.

RESULTS

Duodenal tissues from patients with NCGWS had significantly higher numbers of intra-epithelial CD3⁺ T cells, lamina propria CD45⁺ cells, and eosinophils than duodenal tissues from non-NCGWS controls. Duodenal tissues from patients with NCGWS and dyspepsia had a higher number of lamina propria eosinophils than patients with NCGWS without upper digestive tract symptoms. Rectal mucosa from patients with NCGWS had a larger number of enlarged lymphoid follicles, intra-epithelial CD3⁺ T cells, lamina propria CD45⁺ cells, and eosinophils than rectal mucosa from non-NCGWS controls. Duodenal and rectal mucosal tissues from patients with celiac disease had more immunocytes (CD45⁺ cells, CD3⁺ cells, and eosinophils) than tissues from patients with NCGWS or non-NCGWS controls.

CONCLUSIONS

We identified markers of inflammation, including increased numbers of eosinophils, in duodenal and rectal mucosa from patients with NCGWS. NCGWS might therefore involve inflammation of the entire intestinal tract. Eosinophils could serve as a biomarker for NCGWS and be involved in its pathogenesis. Clinicaltrials.gov: NCT01762579.

Intestinal Mucosal Mast Cells: Key Modulators of Barrier Function and Homeostasis

The gastrointestinal tract harbours the largest population of mast cells in the body; this highly specialised leukocyte cell type is able to adapt its phenotype and function to the microenvironment in which it resides. Mast cells react to external and internal stimuli thanks to the variety of receptors they express, and carry out effector and regulatory tasks by means of the mediators of different natures they produce. Mast cells are fundamental elements of the intestinal barrier as they regulate epithelial function and integrity, modulate both innate and adaptive mucosal immunity, and maintain neuro-immune interactions, which are key to functioning of the gut. Disruption of the intestinal barrier is associated with increased passage of luminal antigens into the mucosa, which further facilitates mucosal mast cell activation, inflammatory responses, and altered mast cell⁻enteric nerve interaction. Despite intensive research showing gut dysfunction to be associated with increased intestinal permeability and mucosal mast cell activation, the specific mechanisms linking mast cell activity with altered intestinal barrier in human disease remain unclear. This review describes the role played by mast cells in control of the intestinal mucosal barrier and their contribution to digestive diseases.

Overlap of Irritable Bowel Syndrome and Functional Dyspepsia in the Clinical Setting: Prevalence and Risk Factors

BACKGROUND

According to Rome IV criteria, functional dyspepsia (FD) and irritable bowel syndrome (IBS) are distinct functional gastrointestinal disorders (FGID); however, overlap of these conditions is common in population-based studies, but clinical data are lacking.

AIMS

To determine the overlap of FD and IBS in the clinical setting and define risk factors for the overlap of FD/IBS.

METHODS

A total of 1127 consecutive gastroenterology outpatients of a tertiary center were recruited and symptoms assessed with a standardized validated questionnaire. Patients without evidence for structural or biochemical abnormalities as a cause of symptoms were then categorized based upon the symptom pattern as having FD, IBS or FD/IBS overlap. Additionally, this categorization was compared with the clinical diagnosis documented in the integrated electronic medical records system.

RESULTS

A total of 120 patients had a clinical diagnosis of a FGID. Based upon standardized assessment with a questionnaire, 64% of patients had FD/IBS overlap as compared to 23% based upon the routine clinical documentation. In patients with severe IBS or FD symptoms (defined as symptoms affecting quality of life), the likelihood of FD/IBS overlap was substantially increased (OR = 3.1; 95%CI 1.9-5.0) and (OR = 9.0; 95%CI 3.5-22.7), respectively. Thus, symptom severity for IBS- or FD symptoms were significantly higher for patients with FD/IBS overlap as compared to patients with FD or IBS alone (p all < 0.01). Age, gender and IBS-subtype were not associated with overlap.

CONCLUSION

In the clinical setting, overlap of FD and IBS is the norm rather than the exception. FD/IBS overlap is associated with a more severe manifestation of a FGID.

Randomised clinical trial: pregabalin vs placebo for irritable bowel syndrome

BACKGROUND

Pregabalin is a calcium channel α2δ ligand that modifies visceral hypersensitivity in IBS patients. Clinical data for pregabalin in IBS are lacking.

AIM

To test the efficacy of pregabalin on gastrointestinal symptoms in IBS patients.

METHODS

A double-blind, placebo-controlled trial was performed. Adults meeting IBS Rome III criteria with ≥3 pain attacks per month were randomised to pregabalin 225 mg vs placebo twice daily for 12 weeks. Questionnaires were completed weekly. The primary endpoint was average pain Bowel Symptom Scale (BSS) scores weeks 9-12. An intention-to-treat analysis of covariance evaluated treatment effects on quantitative endpoints, adjusting for age and gender. Adequate relief and change in pain score were assessed using a chi-squared test.

RESULTS

Eighty-five patients were recruited and randomised. Sample characteristics include: mean age 39.4 (SD = 14.6); 73 (86%) female; 37 (44%) IBS-D, 29 (35%) IBS-M, 18 (21%) IBS-C. The pregabalin arm had lower average pain-BSS scores weeks 9-12 (25 vs 42, P = 0.008). Compared with placebo, the overall IBS BSS severity score was lower in the pregabalin arm (26 vs 42, P = 0.009). Differences were observed for the diarrhoea-BSS and bloating-BSS scores (P = 0.049 and 0.016, respectively). No differences between groups were seen for constipation-BSS scores. Adequate relief was not different between the two arms (46% vs 36%, P = 0.35). 63% pregabalin vs 45% placebo had a change in pain score ≥30 at week 12 from baseline (P = 0.10). Post-treatment IBS-QoL scores did not differ between groups.

CONCLUSION

This trial suggests that pregabalin may be beneficial for IBS abdominal pain, bloating and diarrhoea.

Serum zonulin is elevated in IBS and correlates with stool frequency in IBS-D

Background

Studies have shown increased intestinal permeability in irritable bowel syndrome. Validating serum biomarkers for altered intestinal permeability in irritable bowel syndrome will facilitate research and pathophysiology-based therapy.

Objective

To measure serum zonulin and intestinal fatty acid binding protein levels in diarrhea-predominant irritable bowel syndrome and constipation-predominant irritable bowel syndrome and compare with healthy controls and celiac disease.

Methods

Serum zonulin and intestinal fatty acid binding protein levels were measured using enzyme-linked immunosorbent assays in constipation-predominant irritable bowel syndrome (n = 50), diarrhea-predominant irritable bowel syndrome (n = 50), celiac disease (n = 53) and healthy controls (n = 42). Irritable bowel syndrome symptom severity was measured using the irritable bowel syndrome-symptom severity scale.

Results

Patients with constipation-predominant irritable bowel syndrome and diarrhea-predominant irritable bowel syndrome had higher zonulin levels compared with healthy controls (p = 0.006 and 0.009 respectively), which was comparable to those with active celiac disease. Although zonulin levels did not correlate with the overall irritable bowel syndrome symptom severity scale, it positively correlated with stool frequency per week (p = 0.03) and dissatisfaction with bowel habits (p = 0.007) in diarrhea-predominant irritable bowel syndrome. Patients with diarrhea-predominant irritable bowel syndrome and constipation-predominant irritable bowel syndrome had lower intestinal fatty acid binding protein levels compared with celiac patients (p = 0.005 and p = 0.047 respectively).

Conclusion

Serum zonulin is upregulated in irritable bowel syndrome and the levels are comparable to those in celiac disease. Zonulin levels correlated with severity of bowel habits in diarrhea-predominant irritable bowel syndrome. Intestinal fatty acid binding protein levels in irritable bowel syndrome patients were not increased suggesting no significant increase in enterocyte death.

Investigating Gut Permeability in Animal Models of Disease

A growing number of investigations report the association between gut permeability and intestinal or extra-intestinal disorders under the basis that translocation of gut luminal contents could affect tissue function, either directly or indirectly. Still, in many cases it is unknown whether disruption of the gut barrier is a causative agent or a consequence of these conditions. Adequate experimental models are therefore required to further understand the pathophysiology of health disorders associated to gut barrier disruption and to develop and test pharmacological treatments. Here, we review the current animal models that display enhanced intestinal permeability, and discuss (1) their suitability to address mechanistic questions, such as the association between gut barrier alterations and disease and (2) their validity to test potential treatments for pathologies that are characterized by enhanced intestinal permeability.

New Protocol for Production of Reduced-Gluten Wheat Bread and Pasta and Clinical Effect in Patients with Irritable Bowel Syndrome: A randomised, Double-Blind, Cross-Over Study

It has been suggested that sourdough fermented products have beneficial health effects. Fungal proteases and selected sourdough lactic acid bacteria were used to produce wheat bread and pasta with a reduced-gluten content (<50% of traditional products). Fermentable oligo-, di- and mono- saccharides and polyols and amylase/trypsin inhibitors were also evaluated. The sensorial features of new products were similar to traditional ones. The efficacy of these new products in reducing the severity of symptoms in Irritable Bowel Syndrome (IBS) patients were compared to traditional bread and pasta using a randomized, crossover-controlled trial. While on a strict gluten-free diet, patients were randomized to consume a reduced- or normal-gluten diet for 2weeks; then, patients from both arms started the wash-out period of one week, and subsequently started the final 2-week period on a normal or reduced-gluten diet. Compared to normal-gluten content, the administration of a reduced-gluten content diet resulted in a decrease of the Visual Analogue Scale score (p = 0.042), while no differences were found in the IBS-Severity Score, Hospital Anxiety and Depression Scale, and IBS-Quality of Life. Data herein reported are novel encouraging findings that should spur a new avenue of research aiming to develop products specifically designed for IBS patients.

Serum-derived bovine immunoglobulin for children with diarrhea-predominant irritable bowel syndrome

Background

Oral serum-derived bovine immunoglobulin (SBI)/protein isolate is a medical food intended to manage chronic diarrhea. It has been shown to improve pain and diarrhea in adults with diarrhea-predominant irritable bowel syndrome (d-IBS).

Aim

To determine if SBI can improve symptoms in children with d-IBS.

Methods

We performed a randomized, double-blind, placebo-controlled, pilot study (NCT02609529) to evaluate the effectiveness of SBI in children 8–18 years with d-IBS. We recorded stool number, abdominal pain, and stool form in all patients for 1 week and then assigned the patients at a ratio of 2:1 to treatment with SBI 5 g BID or placebo for 3 weeks. The patients and their parents completed the Pediatric Quality of Life Inventory™ for Gastrointestinal Symptoms (PedsQOL) and the Pediatric Functional Disability Index (FDI). In addition, complete blood counts and serum chemistries were recorded at the start and end of treatment to evaluate safety.

Results

Fifteen patients (nine SBI, six placebo) completed the study. Both SBI and placebo groups reported nonstatistical reductions in stool frequency per week. The SBI group showed a significant reduction in stool frequency at weeks 1 and 2 but not at the end of treatment. The SBI group also demonstrated statistical improvements in abdominal pain and stool form by 3 weeks. The placebo group did not achieve similar improvements. The overall FDI and PedsQOL scores, as well as PedsQOL subscale scores for pain, discomfort when eating, diarrhea, worry about stomach aches, and communication, improved significantly in the SBI group, but not in the placebo group. No serious adverse events occurred. Serum chemistries and hemograms were normal at baseline and at the end of study in all patients.

Conclusion

In this single-center, exploratory pilot study, we demonstrated that 10 g SBI per day was safe in children with d-IBS and improved symptoms. Larger studies, with longer treatment duration, seem warranted based on these initial positive results.

Gluten-Free Diet and Its 'Cousins' in Irritable Bowel Syndrome

Functional disorders are common, with irritable bowel syndrome (IBS) being the commonest and most extensively evaluated functional bowel disorder. It is therefore paramount that effective therapies are available to treat this common condition. Diet appears to play a pivotal role in symptom generation in IBS, with a recent interest in the role of dietary therapies in IBS. Over the last decade, there has been a substantial increase in awareness of the gluten-free diet (GFD), with a recent focus of the role of a GFD in IBS. There appears to be emerging evidence for the use of a GFD in IBS, with studies demonstrating the induction of symptoms following gluten in patients with IBS. However, there are questions with regards to which components of wheat lead to symptom generation, as well as the effect of a GFD on nutritional status, gut microbiota and long-term outcomes. Further studies are required, although the design of dietary studies remain challenging. The implementation of a GFD should be performed by a dietitian with a specialist interest in IBS, which could be achieved via the delivery of group sessions.

Linaclotide improves gastrointestinal transit in cystic fibrosis mice by inhibiting sodium/hydrogen exchanger 3

Gastrointestinal dysfunction in cystic fibrosis (CF) is a prominent source of pain among patients with CF. Linaclotide, a guanylate cyclase C (GCC) receptor agonist, is a US Food and Drug Administration-approved drug prescribed for chronic constipation but has not been widely used in CF, as the cystic fibrosis transmembrane conductance regulator (CFTR) is the main mechanism of action. However, anecdotal clinical evidence suggests that linaclotide may be effective for treating some gastrointestinal symptoms in CF. The goal of this study was to determine the effectiveness and mechanism of linaclotide in treating CF gastrointestinal disorders using CF mouse models. Intestinal transit, chloride secretion, and intestinal lumen fluidity were assessed in wild-type and CF mouse models in response to linaclotide. CFTR and sodium/hydrogen exchanger 3 (NHE3) response to linaclotide was also evaluated. Linaclotide treatment improved intestinal transit in mice carrying either F508del or null Cftr mutations but did not induce detectable Cl^- secretion. Linaclotide increased fluid retention and fluidity of CF intestinal contents, suggesting inhibition of fluid absorption. Targeted inhibition of sodium absorption by the NHE3 inhibitor tenapanor produced improvements in gastrointestinal transit similar to those produced by linaclotide treatment, suggesting that inhibition of fluid absorption by linaclotide contributes to improved gastrointestinal transit in CF. Our results demonstrate that linaclotide improves gastrointestinal transit in CF mouse models by increasing luminal fluidity through inhibiting NHE3-mediated sodium absorption. Further studies are necessary to assess whether linaclotide could improve CF intestinal pathologies in patients. GCC signaling and NHE3 inhibition may be therapeutic targets for CF intestinal manifestations. NEW & NOTEWORTHY Linaclotide's primary mechanism of action in alleviating chronic constipation is through cystic fibrosis transmembrane conductance regulator (CFTR), negating its use in patients with cystic fibrosis (CF). For the first time, our findings suggest that in the absence of CFTR, linaclotide can improve fluidity of the intestinal lumen through the inhibition of sodium/hydrogen exchanger 3. These findings suggest that linaclotide could improve CF intestinal pathologies in patients.

Gluten and Functional Abdominal Pain Disorders in Children

In children, functional gastrointestinal disorders (FGIDs) are common at all ages. Consumption of certain foods, particularly gluten, is frequently associated with the development and persistence of FGIDs and functional abdominal pain disorders (FAPDs) in adults and children. However, this association is not well defined. Even without a diagnosis of celiac disease (CD), some people avoid gluten or wheat in their diet since it has been shown to trigger mostly gastrointestinal symptoms in certain individuals, especially in children. The incidence of conditions such as non-celiac gluten sensitivity (NCGS) is increasing, particularly in children. On the other hand, CD is a chronic, autoimmune small intestinal enteropathy with symptoms that can sometimes be mimicked by FAPD. It is still unclear if pediatric patients with irritable bowel syndrome (IBS) are more likely to have CD. Abdominal, pain-associated FGID in children with CD does not seem to improve on a gluten-free diet. The threshold for gluten tolerance in patients with NCGS is unknown and varies among subjects. Thus, it is challenging to clearly distinguish between gluten exclusion and improvement of symptoms related solely to functional disorders.

Immunopathological and molecular basis of functional dyspepsia and current therapeutic approaches

INTRODUCTION

Functional dyspepsia (FD) is widespread with 20% prevalence worldwide and a significant economic burden due to health care cost and constraints on daily activities of patients. Despite extensive investigation, the underlying causes of dyspepsia in a majority of patients remain unknown. Common complaints include abdominal discomfort, pain, burning, nausea, early satiety, and bloating. Motor dysfunction of the gut was long considered a major cause, but recent investigations suggest immune-based pathophysiological and molecular events in the duodenum are more probable contributing factors. Areas Covered: Inflammatory mediators and immune cells including duodenal eosinophils, intraepithelial lymphocytes, and T-cells have been implicated in the underlying cause of disease process, as have genetic factors. In this article, we critically reviewed findings, identified gaps in knowledge and suggested future directions for further investigation to identify targets and develop better therapeutic approaches. Expert commentary: Impaired gastric accommodation, slow gastric emptying, and increased visceral sensitivity have long been thought of as main causal factors of FD. However, more recent identification of eosinophilic degranulation and recruitment of T cells that induce mild duodenal inflammation are giving rise to new insights into immune-mediated pathophysiology. These insights offer promising avenues to explore for immune-mediated therapy in the future.

Guidelines on the management of irritable bowel syndrome: In memory of Professor Witold Bartnik

These guidelines constitute an update of the previous "Recommendations on the management of irritable bowel syndrome" issued in 2008. They have been developed by a Task Force organized by the Governing Board of the Polish Society of Gastroenterology. They discuss, with particular emphasis on new scientific data covering papers published since 2008, the aetiology, epidemiology, clinical presentation, diagnostic principles and criteria for the diagnosis, and recommendations for the treatment of irritable bowel syndrome (IBS). The English-language acronym for the syndrome (IBS) has become popular in medical and popular scientific language. It is also widely recognized by patients who identify with this diagnosis. Therefore, in the discussed guidelines, this is what we will use.

Recent advances in pharmacological research on the management of irritable bowel syndrome

Irritable bowel syndrome (IBS), a common gastrointestinal (GI) disorder, is associated with various factors, including lifestyle, infection, stress, intestinal flora, and related diseases. The pharmacotherapeutic stimulation of receptors and downstream signaling pathways is effective in reducing IBS symptoms; however, it is still associated with adverse effects. Various receptors related to GI motility and visceral hypersensitivity should be considered to enhance the benefit/risk ratio of IBS treatments. This review discusses recent pharmacological advances in IBS management. Several receptors related to GI motility and abdominal pain are investigated in various angles. 5-Hydroxytryptamine (5-HT) is an important neurotransmitter that activates the colonic mucosal 5-HT₄ receptor without causing severe cardiovascular adverse effects. The clinical potential of ramosetron for diarrhea-predominant IBS has been suggested because of a lower risk of ischemic colitis than conventional 5-HT₃ receptor antagonists. Toll-like receptors (TLRs), especially TLR2 and TLR4, show a significant effect on the post-infection symptoms and lipopolysaccharide-mediated regulation of GI motility. Histamine is a well-known nitrogenous compound that regulates inflammatory responses and visceral hypersensitivity. Histamine 1 receptor-mediated sensitization of the transient receptor potential vanilloid 1 is associated with IBS. Pharmacological approaches based on these signaling pathways could be useful in the development of novel IBS treatments.

Estrogen signaling deregulation related with local immune response modulation in irritable bowel syndrome

The etiology and pathogenesis underlying irritable bowel syndrome (IBS), a common gastrointestinal disorder are still unclear. Cumulating data suggest dysregulation of inflammatory and immune response pathways and changes of epithelial barrier function. The role of estrogens albeit varied, in responses of immune system is well documented. The aim of this study was to investigate estrogen receptors engagment in IBS subtypes, i.e. constipation predominant (IBS-C) and diarrhea predominant (IBS-D). Furthermore, we analyzed whether estrogen signaling is accompanied by alteration in expression of pro- and anti-inflammatory cytokines and microRNAs that can regulate among others genes involved in immune responses. It was found that estrogen receptor α (ERα) and G protein-coupled estrogen receptor (GPER) expression is up-regulated in IBS while estrogen receptor β (ERβ) appears to be down-regulated at mRNA but up-regulated at the protein level. When gender and female age were included statistically significant overexpression of ERα in IBS-D women under the age of 50, while of GPER in IBS-D men was stated. In all studied IBS samples disturbances in expression of cytokines IL-6, IL-10 and TNF-α as well as miR-145, miR-148-5p and miR-592 were observed. This research reveals the association of estrogen receptors with IBS. Simultaneous alterations of studied immunomodulatory cytokines and microRNAs suggest that in IBS dysregulation of local immune response may involve estrogen-dependent way.

All disease begins in the gut: Influence of gastrointestinal disorders and surgery on oral drug performance

The term "disease" conjures a plethora of graphic imagery for many, and the use of drugs to combat symptoms and treat underlying pathology is at the core of modern medicine. However, the effects of the various gastrointestinal diseases, infections, co-morbidities and the impact of gastrointestinal surgery on the pharmacokinetic and pharmacodynamic behaviour of drugs have been largely overlooked. The better elucidation of disease pathology and the role of underlying cellular and molecular mechanisms have increased our knowledge as far as diagnoses and prognoses are concerned. In addition, the recent advances in our understanding of the intestinal microbiome have linked the composition and function of gut microbiota to disease predisposition and development. This knowledge, however, applies less so in the context of drug absorption and distribution for orally administered dosage forms. Here, we revisit and re-evaluate the influence of a portfolio of gastrointestinal diseases and surgical effects on the functionality of the gastrointestinal tract, their implications for drug delivery and attempt to uncover significant links for clinical practice.

What Has Bariatric Surgery Taught Us About the Role of the Upper Gastrointestinal Tract in the Regulation of Postprandial Glucose Metabolism?

The interaction between the upper gastrointestinal tract and the endocrine system is important in the regulation of metabolism and of weight. The gastrointestinal tract has a heterogeneous cellular content and comprises a variety of cells that elaborate paracrine and endocrine mediators that collectively form the entero-endocrine system. The advent of therapy that utilizes these pathways as well as the association of bariatric surgery with diabetes remission has (re-)kindled interest in the role of the gastrointestinal tract in glucose homeostasis. In this review, we will use the changes wrought by bariatric surgery to provide insights into the various gut-pancreas interactions that maintain weight, regulate satiety, and limit glucose excursions after meal ingestion.

FABP4 blocker attenuates colonic hypomotility and modulates white adipose tissue-derived hormone levels in mouse models mimicking constipation-predominant IBS

BACKGROUND

The role of fatty acid binding protein 4 (FABP4) in lower gastrointestinal (GI) motility is unknown. We aimed to verify the effect of inhibition of FABP4 on GI transit in vivo, and to determine the expression of FABP4 in mouse and human tissues.

METHODS

Fatty acid binding protein 4 inhibitor, BMS309403, was administered acutely or chronically for 6 and 13 consecutive days and its effect on GI transit was assessed in physiological conditions and in loperamide-induced constipation. Intracellular recordings were made to examine the effects of BMS309403 on colonic excitatory and inhibitory junction potentials. Abdominal pain was evaluated using behavioral pain response. Localization and expression of selected adipokines were determined in the mouse colon and serum using immunohistochemistry and Enzyme-Linked ImmunoSorbent Assay respectively. mRNA expression of FABP4 and selected adipokines in colonic and serum samples from irritable bowel syndrome (IBS) patients and control group were assessed.

KEY RESULTS

Acute injection of BMS309403 significantly increased GI motility and reversed inhibitory effect of loperamide. BMS309403 did not change colonic membrane potentials. Chronic treatment with BMS309403 increased the number of pain-induced behaviors. In the mouse serum, level of resistin was significantly decreased after acute administration; no changes in adiponectin level were detected. In the human serum, level of adiponectin and resistin, but not of FABP4, were significantly elevated in patients with constipation-IBS (IBS-C). FABP4 mRNA expression was significantly downregulated in the human colon in IBS-C.

CONCLUSIONS AND INFERENCES

Fatty acid binding protein 4 may be involved in IBS pathogenesis and become a novel target in the treatment of constipation-related diseases.

Stool and urine trefoil factor 3 levels: associations with symptoms, intestinal permeability, and microbial diversity in irritable bowel syndrome

Previously we showed that urine trefoil factor 3 (TFF3) levels were higher in females with irritable bowel syndrome (IBS) compared to non-IBS females. To assess if TFF3 is associated with symptoms and/or reflect alterations in gastrointestinal permeability and gut microbiota in an IBS population, we correlated stool and urine TFF3 levels with IBS symptoms, intestinal permeability, stool microbial diversity and relative abundance of predominant bacterial families and genera. We also tested the relationship of stool TFF3 to urine TFF3, and compared results based on hormone contraception use. Samples were obtained from 93 females meeting Rome III IBS criteria and completing 4-week symptom diaries. TFF3 levels were measured by ELISA. Permeability was assessed with the urine lactulose/mannitol (L/M) ratio. Stool microbiota was assessed using 16S rRNA. Stool TFF3, but not urine TFF3, was associated positively with diarrhoea and loose stool consistency. Higher stool TFF3 was also associated with lower L/M ratio and microbial diversity. Of the 20 most abundant bacterial families Mogibacteriaceae and Christensenellaceae were inversely related to stool TFF3, with only Christensenellaceae remaining significant after multiple comparison adjustment. There were no significant relationships between stool or urine TFF3 levels and other symptoms, nor between stool and urine levels. In premenopausal females, urine TFF3 levels were higher in those reporting hormone contraception. Collectively these results suggest that higher stool TFF3 levels are associated with IBS symptoms (loose/diarrhoeal stools), lower gut permeability, and altered stool bacteria composition (decreased diversity and decreased Christensenellaceae), which further suggests that TFF3 may be an important marker of host-bacteria interaction.

Development, content validity, and cross-cultural adaptation of a patient-reported outcome measure for real-time symptom assessment in irritable bowel syndrome

BACKGROUND

End-of-day questionnaires, which are considered the gold standard for assessing abdominal pain and other gastrointestinal (GI) symptoms in irritable bowel syndrome (IBS), are influenced by recall and ecological bias. The experience sampling method (ESM) is characterized by random and repeated assessments in the natural state and environment of a subject, and herewith overcomes these limitations. This report describes the development of a patient-reported outcome measure (PROM) based on the ESM principle, taking into account content validity and cross-cultural adaptation.

METHODS

Focus group interviews with IBS patients and expert meetings with international experts in the fields of neurogastroenterology & motility and pain were performed in order to select the items for the PROM. Forward-and-back translation and cognitive interviews were performed to adapt the instrument for the use in different countries and to assure on patients' understanding with the final items.

KEY RESULTS

Focus group interviews revealed 42 items, categorized into five domains: physical status, defecation, mood and psychological factors, context and environment, and nutrition and drug use. Experts reduced the number of items to 32 and cognitive interviewing after translation resulted in a few slight adjustments regarding linguistic issues, but not regarding content of the items.

CONCLUSIONS AND INFERENCES

An ESM-based PROM, suitable for momentary assessment of IBS symptom patterns was developed, taking into account content validity and cross-cultural adaptation. This PROM will be implemented in a specifically designed smartphone application and further validation in a multicenter setting will follow.

Irritable bowel syndrome and endometriosis: New insights for old diseases

Irritable bowel syndrome and endometriosis are two diseases affecting a significant part of the female population, either together or individually, with remarkable consequences in the quality of life. Several studies suggest an epidemiological association between them. Their association may not be just an epidemiological phenomenon, but the manifestation of a pathophysiological correlation, which probably generates a mutual promotion phenomenon. In particular, both clinical entities share the presence of a chronic low-grade inflammatory state at the basis of the disease persistence. Recognizing this association is highly significant due to their prevalence and the common clinical manifestation occurring with a chronic abdominal pain. A further multi disciplinary approach is suggested in these patients' management in order to achieve an adequate diagnostic work up and a targeted therapy. This paper analyses some common pathophysiological mechanisms, such as activation of mast cell line, neuronal inflammation, dysbiosis and impaired intestinal permeability. The aim was to investigate their presence in both IBS and endometriosis, and to show the complexity of their relationship in the generation and maintenance of chronic inflammation.

The Role of Diet in the Treatment of Irritable Bowel Syndrome: A Systematic Review

Irritable bowel syndrome (IBS) is a multifaceted illness involving maladaptive shifts in the gut microbiota that affect the enteric nervous and immune systems, mucosal barrier function, the balance of neurotransmitters and hormones, and emotional well-being. There is abundant evidence indicating that certain foods elicit symptoms in IBS. Numerous elimination-type diets have been shown to alleviate symptoms. However, among these, the most controversial is a group of foods called fructo, oligo-, di-, and monosaccharides and polyols (FODMAPs). This paper reviews the role of diet and systematically analyze the literature for the role of FODMAPs in IBS.

Gut Microbiota-Based Therapies for Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a common, heterogeneous disorder characterized by abdominal pain associated with changes in bowel habits. The pathogenesis of IBS is multifactorial and may relate to alterations in the gut microbiota, changes in visceral sensation and motility, and genetic and environmental factors. Administration of systemic antibiotics may increase the risk of IBS by altering gastrointestinal homeostasis. Therapeutic interventions for IBS with diarrhea that are thought to target alterations in the gut microbiota include the nonsystemic antibiotic rifaximin, the medical food serum-derived bovine immunoglobulin, prebiotics, probiotics, and dietary modification. SYN-010 is a modified-release statin formulation that reduces methane production by Methanobrevibacter smithii and is currently in development for the treatment of patients with constipation-predominant IBS. Use of these interventions in the management of patients with IBS may function to restore a healthy gut microbiota and ameliorate symptoms of IBS.

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.

Modelling the structure of a ceRNA-theoretical, bipartite microRNA-mRNA interaction network regulating intestinal epithelial cellular pathways using R programming

OBJECTIVE

We report a method using functional-molecular databases and network modelling to identify hypothetical mRNA-miRNA interaction networks regulating intestinal epithelial barrier function. The model forms a data-analysis component of our cell culture experiments, which produce RNA expression data from Nanostring Technologies nCounter® system. The epithelial tight-junction (TJ) and actin cytoskeleton interact as molecular components of the intestinal epithelial barrier. Upstream regulation of TJ-cytoskeleton interaction is effected by the Rac/Rock/Rho signaling pathway and other associated pathways which may be activated or suppressed by extracellular signaling from growth factors, hormones, and immune receptors. Pathway activations affect epithelial homeostasis, contributing to degradation of the epithelial barrier associated with osmotic dysregulation, inflammation, and tumor development. The complexity underlying miRNA-mRNA interaction networks represents a roadblock for prediction and validation of competing-endogenous RNA network function.

RESULTS

We developed a network model to identify hypothetical co-regulatory motifs in a miRNA-mRNA interaction network related to epithelial function. A mRNA-miRNA interaction list was generated using KEGG and miRWalk2.0 databases. R-code was developed to quantify and visualize inherent network structures. We identified a sub-network with a high number of shared, targeting miRNAs, of genes associated with cellular proliferation and cancer, including c-MYC and Cyclin D.

Gut Microbiota and the Neuroendocrine System

The microbial ecosystem that inhabits the gastrointestinal tract of all mammals-the gut microbiota-has been in a symbiotic relationship with its hosts over many millennia. Thanks to modern technology, the myriad of functions that are controlled or modulated by the gut microbiota are beginning to unfold. One of the systems that is emerging to closely interact with the gut microbiota is the body's major neuroendocrine system that controls various body processes in response to stress, the hypothalamic-pituitary-adrenal (HPA) axis. This interaction is of pivotal importance; as various disorders of the microbiota-gut-brain axis are associated with dysregulation of the HPA axis. The present contribution describes the bidirectional communication between the gut microbiota and the HPA axis and delineates the potential underlying mechanisms. In this regard, it is important to note that the communication between the gut microbiota and the HPA axis is closely interrelated with other systems, such as the immune system, the intestinal barrier and blood-brain barrier, microbial metabolites, and gut hormones, as well as the sensory and autonomic nervous systems. These communication pathways will be exemplified through preclinical models of early life stress, beneficial roles of probiotics and prebiotics, evidence from germ-free mice, and antibiotic-induced modulation of the gut microbiota.

Systematic review and meta-analysis of traditional Chinese medicine in the treatment of constipation-predominant irritable bowel syndrome

AIM

This meta-analysis analyzed the efficacy and safety of traditional Chinese medicine (TCM) for the treatment of irritable bowel syndrome with constipation (IBS-C).

METHODS

We searched seven electronic databases for randomized controlled trials investigating the efficacy of TCM in the treatment of IBS-C. The search period was from inception to June 1, 2017. Eligible RCTs compared TCM with cisapride and mosapride. Article quality was evaluated with the Cochrane Risk Bias Tool in the Cochrane Handbook by two independent reviewers. Begg's test was performed to evaluate publication bias. Review Manager 5.3 and Stata 12.0 were used for analyses.

RESULTS

Eleven eligible studies comprising a total of 906 participants were identified. In the primary outcome, TCM showed significant improvement in overall clinical efficacy compared with cisapride and mosapride (odds ratio [OR] = 4.00; 95% confidence interval [CI]: 2.74,5.84; P < 0.00001). In terms of secondary outcomes, TCM significantly alleviated abdominal pain (OR = 5.69; 95% CI: 2.35, 13.78; P = 0.0001), defecation frequency (OR = 4.38; 95% CI: 1.93, 9.93. P = 0.0004), and stool form (OR = 4.96; 95% CI: 2.11, 11.65; P = 0.0002) in the treatment group as compared to the control group. A lower recurrence rate was associated with TCM as compared to cisapride and mosapride (OR = 0.15; 95% CI: 0.08, 0.27; P < 0.00001). No adverse effects were observed during TCM treatment.

CONCLUSIONS

TCM showed greater improvement in terms of clinical efficacy in the treatment of IBS-C than cisapride and mosapride, although it was not possible to draw a definitive conclusion due to the small sample size, high risk, and low quality of the studies. Large multi-center and long-term high-quality randomized control trials are needed.

Early weaning stress induces chronic functional diarrhea, intestinal barrier defects, and increased mast cell activity in a porcine model of early life adversity

BACKGROUND

Early life adversity (ELA) is a risk factor for development of gastrointestinal disorders later in life. The underlying mechanisms through which ELA and sex interact to influence disease susceptibility remains poorly understood.

METHODS

Utilizing a porcine early weaning stress (EWS) model to mimic ELA, we investigated the long-term effects of EWS on functional diarrhea, ileal permeability, mast cell activity and mast cell relationship with enteric ganglia.

KEY RESULTS

Juvenile and adult EWS pigs exhibited chronic, functional diarrhea (EWS 43.6% vs late wean control(LWC) 4.8%, P<.0001), increased intestinal permeability (2 fold increase EWS vs LWC, P<.0001), and mast cell numbers (at 7 weeks and 20 weeks ~1.6 fold increase EWS vs LWC, P<.05). Compared with EWS male castrates (Male-C), females EWS pigs exhibited more frequent diarrhea (58.8% vs 29.9%, P=.0016), and increased intestinal permeability (1-2 fold higher in EWS females, P<.001). Increased mast cell numbers and their enhanced co-localization with neuronal ganglia were observed in both Male-C and female EWS pigs; however, female pigs exhibited greater release of mast cell tryptase upon activation with c48/80 (~1.5 fold increase, P<.05), compared with Male-C pigs.

CONCLUSIONS AND INFERENCES

These data demonstrate that pigs exposed to ELA exhibit increased vulnerability to functional diarrhea, intestinal permeability and mast cell activity. Further, these studies also showed that EWS female and Male-C pigs exhibited dimorphic responses to EWS with female piglets exhibited greater susceptibility and severity of diarrhea, intestinal permeability and mast cell tryptase release. Together, these findings mimic some of the key pathophysiologic findings in human functional GI disorders functional gastrointestinal disorders (FGIDs) suggesting that the EWS porcine model could be a valuable preclinical translational model for FGID research associated with ELA.

AAPT Diagnostic Criteria for Chronic Abdominal, Pelvic, and Urogenital Pain: Irritable Bowel Syndrome

In conjunction with the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks public-private partnership with the U.S. Food and Drug Administration and the American Pain Society, the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks-American Pain Society Pain Taxonomy (AAPT) initiative strove to develop the characteristics of a diagnostic system useful for clinical and research purposes across disciplines and types of chronic pain conditions. After the establishment of these characteristics, a working group of clinicians and clinical and basic scientists with expertise in abdominal, pelvic, and urogenital pain began generating core diagnostic criteria and defining the related extraintestinal somatic pain and other symptoms experienced by patients. Systematic diagnostic criteria for several common abdominal, pelvic, and urogenital pain conditions are in development. In this report, we present the proposed AAPT criteria for irritable bowel syndrome (IBS), the most common chronic, noncancer abdominal pain condition. A systematic review and synthesis was conducted to complement the Rome IV Diagnostic Criteria for IBS. Future efforts will subject these proposed AAPT criteria to systematic empirical evaluation of their feasibility, reliability, and validity. The AAPT IBS criteria are part of an evidence-based classification system that provides a consistent vocabulary regarding diagnostic criteria, common features, comorbidities, consequences, and putative mechanisms of the disorder. A similar approach is being applied to other chronic and often debilitating abdominal, pelvic, and urogenital pain conditions.

PERSPECTIVE

The AAPT's goal is to develop an evidence-based taxonomy for chronic pain on the basis of a consistently applied multidimensional framework, and encourage experts to apply this taxonomy to specific chronic pain conditions. In this report, the taxonomy is applied to IBS, a chronic abdominal pain condition.

MicroRNA-29a increased the intestinal membrane permeability of colonic epithelial cells in irritable bowel syndrome rats

Background

The whole pathogenesis of diarrhea-predominant irritable bowel syndrome(IBS-D) is poorly understood. Our goal was to evaluate the expression change of microRNA-29a(miR-29a) in colonic epithelial cells in IBS rats and clarify the mechanism of miR-29a increasing the intestinal membrane permeability through aquaporins(AQPs).

Methods

The IBS-D rats models were induced by rectal distention pressure combining with extremities constraint. The colonic epithelial cells were divided into four groups. A: normal group. B: IBS-D control group. C: IBS-D +miR-29a NC. D: IBS-D + miR-29a antagomir. The expression of miR-29a, the concentration of the K⁺ and Lactate Dehydrogenase(LDH) and the expression of AQPs were detected.

Results

The miR-29a expression increased in IBS-D control group(2.090±0.022) compared with the control group(1.00±0.031) (P<0.001) while it decreased in IBS-D+miR-29a antagomir group(1.403±0.042) compared with IBS-D control group(P<0.001). The K⁺ decreased in IBS-D control group(1.305±0.289) compared with the control group(2.171±0.204)(P<0.05) while it increased in IBS-D+miR-29a antagomir group(1.813±0.102)(P<0.05) compared with IBS-D control group. The LDH increased in IBS-D control group(4153.440±177.365) compared with the control group(1434.573±96.111)(P<0.001) while it decreased in IBS-D+miR-29a antagomir group(2700.473±275.414) compared with IBS-D control group (P<0.01). The expression of AQP1, AQP3 and AQP8 decreased in IBS-D control group(0.132±0.010,0.110±0.005,0.108±0.007) compared with the control group (P<0.001) while it increased in IBS-D+miR-29a antagomir group(0.197±0.005,0.182±0.011,0.194±0.003) compared with IBS-D control group(P<0.001). The IBS-D+miR-29a negative control(NC) group, a comparison with IBS-D+miR-29a antagomir group, each date showed the similar trend to the IBS-D control group.

Conclusions

MiR-29a increased the intestinal membrane permeability of colonic epithelial cells by reducing the AQPs expression in IBS-D rats.

The global impact of IBS: time to think about IBS-specific models of care?

Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal (GI) disorder that can significantly erode the quality of life (QoL) of sufferers and places a major cost burden on healthcare services. This paper reviews the literature on the impact of IBS on healthcare services and society, including a recent report on the subject, in order to formulate a plan for the future. A completely different model of care for these patients is recommended based on this review and the experience of the two authors who have been treating patients with functional GI disorders for 20 and 35 years, respectively.

Gastrointestinal neuroendocrine peptides/amines in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic recurrent condition whose etiology is unknown, and it includes ulcerative colitis, Crohn’s disease, and microscopic colitis. These three diseases differ in clinical manifestations, courses, and prognoses. IBD reduces the patients’ quality of life and is an economic burden to both the patients and society. Interactions between the gastrointestinal (GI) neuroendocrine peptides/amines (NEPA) and the immune system are believed to play an important role in the pathophysiology of IBD. Moreover, the interaction between GI NEPA and intestinal microbiota appears to play also a pivotal role in the pathophysiology of IBD. This review summarizes the available data on GI NEPA in IBD, and speculates on their possible role in the pathophysiology and the potential use of this information when developing treatments. GI NEPA serotonin, the neuropeptide Y family, and substance P are proinflammatory, while the chromogranin/secretogranin family, vasoactive intestinal peptide, somatostatin, and ghrelin are anti-inflammatory. Several innate and adaptive immune cells express these NEPA and/or have receptors to them. The GI NEPA are affected in patients with IBD and in animal models of human IBD. The GI NEPA are potentially useful for the diagnosis and follow-up of the activity of IBD, and are candidate targets for treatments of this disease.

Frontline Science: Corticotropin-releasing factor receptor subtype 1 is a critical modulator of mast cell degranulation and stress-induced pathophysiology

Life stress is a major risk factor in the onset and exacerbation of mast cell-associated diseases, including allergy/anaphylaxis, asthma, and irritable bowel syndrome. Although it is known that mast cells are highly activated upon stressful events, the mechanisms by which stress modulates mast cell function and disease pathophysiology remains poorly understood. Here, we investigated the role of corticotropin-releasing factor receptor subtype 1 (CRF₁) in mast cell degranulation and associated disease pathophysiology. In a mast cell-dependent model of IgE-mediated passive systemic anaphylaxis (PSA), prophylactic administration of the CRF₁-antagonist antalarmin attenuated mast cell degranulation and hypothermia. Mast cell-deficient Kit^W-sh/W-sh mice engrafted with CRF₁^-/- bone marrow-derived mast cells (BMMCs) exhibited attenuated PSA-induced serum histamine, hypothermia, and clinical scores compared with wild-type BMMC-engrafted Kit^W-sh/W-sh mice. Kit^W-sh/W-sh mice engrafted with CRF₁^-/- BMMCs also exhibited suppressed in vivo mast cell degranulation and intestinal permeability in response to acute restraint stress. Genetic and pharmacologic experiments with murine BMMCs, rat RBL-2H3, and human LAD2 mast cells demonstrated that although CRF₁ activation did not directly induce MC degranulation, CRF₁ signaling potentiated the degranulation responses triggered by diverse mast cell stimuli and was associated with enhanced release of Ca²⁺ from intracellular stores. Taken together, our results revealed a prominent role for CRF₁ signaling in mast cells as a positive modulator of stimuli-induced degranulation and in vivo pathophysiologic responses to immunologic and psychologic stress.

Efficacy of Bifidobacterium infantis 35624 in patients with irritable bowel syndrome: a meta-analysis

BACKGROUND

The treatment of irritable bowel syndrome (IBS) is a challenge because its cause remains unknown. Previous clinical trials to examine the efficacy of probiotic Bifidobacterium infantis 35624 (B. infantis) in patients with IBS have shown inconsistent findings. This study aimed to assess the combined effect of B. infantis on reducing the symptom severity of IBS based on the published data.

METHODS

A meta-analysis was conducted using fixed-effect models to estimate the combined effect of B. infantis on primary outcomes, which included abdominal pain, bloating/distention, and bowel habit satisfaction. A systematic review was performed based on PubMed, Cochrane Library, and EMBASE databases to identify the randomized controlled trials comparing probiotic B. infantis with placebo in treating IBS symptoms, published up until 31 December 2016. The standardized mean difference (SMD) method was used to combine data since scales to measure the efficacy of probiotics were different among studies.

RESULTS

A total of five studies were identified as suitable for inclusion, including three studies with single probiotic B. infantis and two studies with composite probiotics containing B. infantis. Treatment with single probiotic B. infantis didn't impact on abdominal pain, bloating/distention, or bowel habit satisfaction among IBS patients. However, patients who received composite probiotics containing B. infantis had significantly reduced abdominal pain (SMD, 0.22; 95% CI, 0.03-0.41) and bloating/distention (SMD, 0.30; 95% CI, 0.04-0.56). After combining the data from six studies, the improvement of bloating/distention among IBS patients remained significant (SMD, 0.21; 95% CI, 0.07-0.35).

CONCLUSION

Composite probiotics containing B. infantis might be an effective therapeutic option for IBS patients, which could significantly alleviate the symptoms of IBS without significant adverse effects. However, the efficacy of single probiotic B. infantis on IBS has not been confirmed yet, which needs to be further validated by more large-sized randomized clinical trials.

Gene expression profiles in peripheral blood mononuclear cells correlate with salience network activity in chronic visceral pain: A pilot study

BACKGROUND

Distinct gene expression profiles in peripheral blood mononuclear cells (PBMCs) consistent with increased sympathetic nervous system activity have been described in different populations under chronic stress. Neuroinflammatory brain changes, possibly related to the migration of primed monocytes to the brain, have been implicated in the pathophysiology of chronic pain. Irritable bowel syndrome (IBS) is a stress-sensitive gastrointestinal disorder associated with altered brain-gut interactions and increased sympathetic/vagal tone and anxiety. Reports about immune alterations in IBS are conflicting. This pilot study aimed to test how PBMC gene expression inflammatory profiles are correlated with altered brain signatures in the salience system.

METHODS

Sixteen IBS and 16 healthy controls (HCs) completed resting state MRI scans. Gene expression profiles in PBMCs were assessed using human transcriptome array-2. Bioinformatic analyses determined differential expression of PBMCs between IBS and HCs. Partial least squares, a multivariate analysis technique, was used to identify disease correlations between PBMC gene expression profiles and functional activity in the brain's salience network.

KEY RESULTS

Regions of the salience network, including the mid cingulate cortex, and mid and superior temporal gyrus were positively correlated with several pro-inflammatory genes (interleukin 6, APOL2) in IBS, but negatively correlated with several anti-inflammatory genes (KRT8, APOA4) in HCs.

CONCLUSIONS & INFERENCES

Based on rodent studies, one may speculate that chronically activated stress signaling pathways in IBS maintain a pro-inflammatory state in the periphery. Alternatively, primed monocytes may migrate to the brain during stress, inducing regional neuroinflammatory changes in salience regions involved in the modulation of visceral sensitivity.

Constipation-Predominant Irritable Bowel Syndrome Females Have Normal Colonic Barrier and Secretory Function

OBJECTIVES

The objective of this study was to determine whether constipation-predominant irritable bowel syndrome (IBS-C) is associated with changes in intestinal barrier and secretory function.

METHODS

A total of 19 IBS-C patients and 18 healthy volunteers (all females) underwent saccharide excretion assay (0.1 g ¹³C mannitol and 1 g lactulose), measurements of duodenal and colonic mucosal barrier (transmucosal resistance (TMR), macromolecular and Escherichia coli Bio-Particle translocation), mucosal secretion (basal and acetylcholine (Ach)-evoked short-circuit current (Isc)), in vivo duodenal mucosal impedance, circulating endotoxins, and colonic tight junction gene expression.

RESULTS

There were no differences in the in vivo measurements of barrier function between IBS-C patients and healthy controls: cumulative excretion of ¹³C mannitol (0-2 h mean (s.e.m.); IBS-C: 12.1 (0.9) mg vs. healthy: 13.2 (0.8) mg) and lactulose (8-24 h; IBS-C: 0.9 (0.5) mg vs. healthy: 0.5 (0.2) mg); duodenal impedance IBS-C: 729 (65) Ω vs. healthy: 706 (43) Ω; plasma mean endotoxin activity level IBS-C: 0.36 (0.03) vs. healthy: 0.35 (0.02); and in colonic mRNA expression of occludin, zonula occludens (ZO) 1-3, and claudins 1-12 and 14-19. The ex vivo findings were consistent, with no group differences: duodenal TMR (IBS-C: 28.2 (1.9) Ω cm² vs. healthy: 29.8 (1.9) Ω cm²) and colonic TMR (IBS-C: 19.1 (1.1) Ω cm² vs. healthy: 17.6 (1.7) Ω cm²); fluorescein isothiocyanate (FITC)-dextran (4 kDa) and E. coli Bio-Particle flux. Colonic basal Isc was similar, but duodenal basal Isc was lower in IBS-C (43.5 (4.5) μA cm^-2) vs. healthy (56.9 (4.9) μA cm^-2), P=0.05. Ach-evoked ΔIsc was similar.

CONCLUSIONS

Females with IBS-C have normal colonic barrier and secretory function. Basal duodenal secretion is decreased in IBS-C.

New therapeutic options for IBS: the role of the first in class mixed µ- opioid receptor agonist and δ-opioid receptor antagonist (mudelta) eluxadoline

Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal disorder which represents a major cost to healthcare services. IBS-D patients represent about one-third of the IBS population and are currently treated with antispasmodics, loperamide, bile acid sequestrants and antidepressants. Alosetron and rifaximin are also available in USA, ramosetron in Japan, Korea and Thailand and ondansetron as an off-label treatment. Areas covered: This article focuses on eluxadoline, a novel pharmacological agent that has recently been approved by both the FDA and EMA for treatment of patients with IBS-D. Expert commentary: The efficacy and safety of eluxadoline in treating bowel habit alterations and pain, both in the short and long-term, make the drug a welcome addition to our therapeutic alternatives in IBS-D. Its positioning in any IBS algorithm will depend on the 'real world' prevalence of the small risk of sphincter of Oddi spasm and mild pancreatitis.

Biomarkers as a diagnostic tool for irritable bowel syndrome: where are we?

Irritable bowel syndrome (IBS) is a common condition in clinical practice. There are currently no objective tests to rule in the disease, but rather tests to rule out other diseases. Biomarkers in IBS may provide the tools needed for diagnosis, prognosis and therapy. These include identification of differences in microbial composition, immune activation, bile acid composition, colonic transit, and alteration in sensation in subgroups of IBS patients. Areas covered: Studies included in our review were chosen based on a PubMed search for 'biomarkers' and 'IBS'. We have reviewed the literature on biomarkers to appraise their accuracy, validity and whether they are actionable. We have not covered genetic associations as biomarkers in this review. Expert commentary: There is significant promise in the usefulness of biomarkers for IBS. The most promising actionable biomarkers are markers of changes in bile acid balance, such as elevated bile acid in the stool, and altered colonic transit. However, there is also potential for microbial studies and mucosal proteases as future actionable biomarkers.

Derivation and validation of a diagnostic test for irritable bowel syndrome using latent class analysis

BACKGROUND

The accuracy of symptom-based diagnostic criteria for irritable bowel syndrome (IBS) is modest.

AIMS

To derive and validate a new test that utilises latent class analysis.

METHODS

Symptom, colonoscopy, and histology data were collected from 1981 patients and 360 patients in two cohorts referred to secondary care for investigation of their gastrointestinal symptoms in Canada and the UK, respectively. Latent class analysis was used to identify naturally occurring clusters in patient-reported symptoms in the Canadian dataset, and the latent class model derived from this was then applied to the UK dataset in order to validate it. Sensitivity, specificity, and positive and negative likelihood ratios (LRs) were calculated for the latent class models.

RESULTS

In the Canadian cohort, the model had a sensitivity of 44.7% (95% CI 40.0-50.0) and a specificity of 85.3% (95% CI 83.4-87.0). Positive and negative LRs were 3.03 (95% CI 2.57-3.56) and 0.65 (95% CI 0.59-0.71) respectively. A maximum positive LR of 3.93 was achieved following construction of a receiver operating characteristic curve. The performance in the UK cohort was similar, with a sensitivity and specificity of 52.5% (95% CI 42.2-62.7) and 84.3% (95% CI 79.3-88.6), respectively. Positive and negative LRs were 3.35 (95% CI 2.38-4.70) and 0.56 (95% CI 0.45-0.68), respectively, with a maximum positive LR of 4.15.

CONCLUSIONS

A diagnostic test for IBS, utilising patient-reported symptoms incorporated into a latent class model, performs as accurately as symptom-based criteria. It has potential for improvement via addition of clinical markers, such as coeliac serology and faecal calprotectin.

Interleukin-10: A Compelling Therapeutic Target in Patients With Irritable Bowel Syndrome

PURPOSE

Pro- and antiinflammatory cytokines are important modulators of the immune response and play a major role in conditions of intestinal inflammation, such as irritable bowel syndrome (IBS). Cytokine production is regulated genetically, and imbalances in cytokine secretion may affect disease susceptibility and clinical outcomes of various conditions. There is a rapidly growing body of evidence to support an etiologic role for gastrointestinal infection and the associated immune activation in the development of postinfectious IBS. Other factors such as psychological stress, anxiety, and depression may likely be involved in the altered profiles of pro- and antiinflammatory cytokines that lead to chronic IBS.

METHODS

We searched the literature using PubMed, MEDLINE, and Google Scholar with related key terms and prepared this review article on that basis.

FINDINGS

Interleukin (IL)-10 is a regulatory cytokine that inhibits both antigen presentation and the release of proinflammatory cytokines. Therefore, it is proposed as a potent antiinflammatory biological therapy for IBS.

IMPLICATIONS

Recently, a strong interest in the therapeutic potential of IL-10 for IBS has developed. The diverse roles of IL-10 in IBS are reviewed here. We conducted an in-depth review on IL-10 and IBS to address this question. Future studies of IL-10 may provide new insights into IBS therapy.