Review article: Associations between immune activation, intestinal permeability and the irritable bowel syndrome

Network pharmacology and experimental validation to explore the mechanism of Changji'an formula against irritable bowel syndrome with predominant diarrhea

Changji'an Formula (CJAF) is a Chinese herbal compound, which is effective against irritable bowel syndrome with predominant diarrhea (IBS-D) in clinic. However, the molecular mechanism has not been well defined. In the current study, the potential targets and signaling pathways of CJAF against IBS-D were predicted using network pharmacology analysis. The pharmacological mechanisms of CJAF against IBS-D and the potential mechanism were validated by using an IBS-D mouse model induced by enema with trinitrobenzene-sulfonic acid (TNBS) plus with restraint stress and further intervened with CJAF. A total of 232 active compounds of CJAF were obtained, a total of 397 potential targets for the active ingredients were retrieved and a total of 219 common targets were obtained as the potential targets of CJAF against IBS-D. GO and KEGG enrichment analyses showed that multiple targets were enriched and could be experimentally validated in a mouse model of IBS-D. The mechanisms were mainly converged on the immune and inflammatory pathways, especially the NF-κB, TNF and IL-17 signaling pathway, which were closely involved in the treatment of CJAF against IBS-D. Animal experiment showed that CJAF alleviated visceral hypersensitivity and diarrhea symptom of IBS-D. CJAF also restored the histological and ultrastructure damage of IBS-D. The result of Western blot showed that CJAF upregulated colonic tight junction proteins of ZO-1, Occludin and Claudin-1. Further results demonstrated that CJAF inhibited the protein expression of NF-κB/NLRP3 inflammasome pathway targets and downregulated proinflammatory mediators of IL-1β, IL-18, TNF-α. In conclusion, CJAF could effectively reduce inflammatory response and alleviate visceral hypersensitivity as well as diarrhea symptom of IBS-D by inhibiting the NF-κB/NLRP3 signaling pathway. This study not only reveals the mechanism of CJAF against IBS-D, but also provides a novel therapeutic strategy for IBS-D.

A systematic review of the association between environmental risk factors and the development of irritable bowel syndrome

BACKGROUND AND AIM

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder with roots in genetic, immune, psychological, and dietary factors. Recently, the potential correlation between environmental exposures, such as air pollution, and IBS has gained attention. This review aimed to systematically examine existing studies on environmental factors associated with IBS, elucidating this interplay and guiding future research.

METHODS

A literature search was conducted in Medline, EMBASE, Scopus, and Cochrane databases from database inception to October 10, 2023, using the keywords "Irritable Bowel" or IBS or "Irritable Colon" or "Mucous Colitis" or "Spastic Colitis" or "Spastic Colon" AND "environment* exposure*". Studies were included if they were original, published in English, described defined environmental exposure(s), and had documented diagnosis of IBS. For the purposes of this review, articles reporting physical (e.g. radiation and climate change), biological (e.g. bacteria and viruses), and chemical (e.g. harmful gases) exposures were included while psychological and dietary factors, which have been reviewed in detail elsewhere, are outside of the scope.

RESULTS

A total of seven studies focusing on air quality, microbial exposure, and other environmental factors were reviewed. Studies highlighted a potential association between air pollutants and increased IBS incidence. Microbial exposure, post-natural disaster or due to poor sanitation, was linked to IBS development and gut dysbiosis. Other exposures, such as early pet ownership, were also associated with IBS risk.

CONCLUSION

Existing research demonstrates an epidemiologic relationship between environmental exposures and the development of IBS. Further research is needed to understand these associations.

Irritable bowel syndrome (IBS): could we decide what is behind?

Functional visceral problems are frequently present nowadays in the medical practice probably due to the significant mental and emotional load on people. Although physicians and psychophysiologists are active on the field, still we are far from a complete knowledge, despite the fact that scientists like the Hungarian Professor György Ádám already had initiated a new approach called visceral psychophysiology already a long time ago. In this article, we commemorate Professor Ádám by analyzing one of the most frequent functional disorders, irritable bowel syndrome (IBS), calling psychophysiology for help. First, we try to give a definition, then show the general descriptions and characteristics of IBS. Factors like stress, gender, and gastrointestinal pain are followed by the potential role of the immune system and the neuronal factors as well as the supposed brain mechanisms. We hope that this overview of the IBS-history would show how significant scientists can be decisive in certain fields of the science and practice.

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

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

The Role of Intestinal Barrier Function in Overweight Patients with IBS with Diarrhea Undergoing a Long-Term Low Fermentable Oligo-, Di-, and Monosaccharide and Polyol Diet

Overweight and obesity have been suggested as significant factors in irritable bowel syndrome (IBS) development. However, the relationship between overweight/obesity and IBS is unclear. It is known that a modified intestinal barrier, especially the permeability of the small intestine (s-IP), can play a significant role in the pathogenesis of both obesity and IBS. Moreover, dietary interventions are essential for treating both pathologies. We evaluated the gastrointestinal (GI) symptoms and the urinary and circulating markers of GI barrier function and integrity, the markers of intestinal dysbiosis and bacterial translocation, in 40 IBS patients with predominant diarrhea (IBS-D) (32 females and 8 males; mean age = 43.5 ± 1.4 years), categorized using their Body Mass Index levels as normal (NW) and overweight (OW). Evaluations were performed before and after 12 weeks of a Low FODMAP Diet (LFD). At the baseline, OW patients showed a significantly higher s-IP than NW. After an LFD, a significant improvement of s-IP in OW patients occurred, along with a significant decrease in markers of epithelial integrity and bacterial translocation. Our findings highlight the close relationship between overweight and the intestinal barrier and support their involvement in IBS-D pathophysiology. Furthermore, the positive role of an LFD in managing overweight IBS-D was highlighted.

The Role of Bovine Kappa-Casein Glycomacropeptide in Modulating the Microbiome and Inflammatory Responses of Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder marked by chronic abdominal pain, bloating, and irregular bowel habits. Effective treatments are still actively sought. Kappa-casein glycomacropeptide (GMP), a milk-derived peptide, holds promise because it can modulate the gut microbiome, immune responses, gut motility, and barrier functions, as well as binding toxins. These properties align with the recognized pathophysiological aspects of IBS, including gut microbiota imbalances, immune system dysregulation, and altered gut barrier functions. This review delves into GMP's role in regulating the gut microbiome, accentuating its influence on bacterial populations and its potential to promote beneficial bacteria while inhibiting pathogenic varieties. It further investigates the gut microbial shifts observed in IBS patients and contemplates GMP's potential for restoring microbial equilibrium and overall gut health. The anti-inflammatory attributes of GMP, especially its impact on vital inflammatory markers and capacity to temper the low-grade inflammation present in IBS are also discussed. In addition, this review delves into current research on GMP's effects on gut motility and barrier integrity and examines the changes in gut motility and barrier function observed in IBS sufferers. The overarching goal is to assess the potential clinical utility of GMP in IBS management.

Diet in treatment of autism spectrum disorders

Altering the diet to treat disease dates to c. 400 BC when starvation was used to reduce seizures in persons with epilepsy. The current diversity of symptomology and mechanisms underlying autism spectrum disorders (ASDs) and a corresponding lack of disorder-specific effective treatments prompts an evaluation of diet as a therapeutic approach to improve symptoms of ASDs. In this review article, we summarize the main findings of nutritional studies in ASDs, with an emphasis on the most common monogenic cause of autism, Fragile X Syndrome (FXS), and the most studied dietary intervention, the ketogenic diet as well as other dietary interventions. We also discuss the gut microbiota in relation to pre- and probiotic therapies and provide insight into future directions that could aid in understanding the mechanism(s) underlying dietary efficacy.

New insights into irritable bowel syndrome pathophysiological mechanisms: contribution of epigenetics

Irritable bowel syndrome (IBS) is a complex multifactorial condition including alterations of the gut-brain axis, intestinal permeability, mucosal neuro-immune interactions, and microbiota imbalance. Recent advances proposed epigenetic factors as possible regulators of several mechanisms involved in IBS pathophysiology. These epigenetic factors include biomolecular mechanisms inducing chromosome-related and heritable changes in gene expression regardless of DNA coding sequence. Accordingly, altered gut microbiota may increase the production of metabolites such as sodium butyrate, a prominent inhibitor of histone deacetylases. Patients with IBS showed an increased amount of butyrate-producing microbial phila as well as an altered profile of methylated genes and micro-RNAs (miRNAs). Importantly, gene acetylation as well as specific miRNA profiles are involved in different IBS mechanisms and may be applied for future diagnostic purposes, especially to detect increased gut permeability and visceromotor dysfunctions. In this review, we summarize current knowledge of the role of epigenetics in IBS pathophysiology.

Network pharmacology and molecular docking reveal the immunomodulatory mechanism of rhubarb peony decoction for the treatment of ulcerative colitis and irritable bowel syndrome

Background: Ulcerative colitis (UC) and irritable bowel syndrome (IBS) share various similarities in clinical symptoms, pathogenesis, and treatment. UC concurrent IBS tends toward more severe symptoms and worse prognosis, and promising feasible therapies for the overlapping symptoms remains a challenge. Rhubarb peony decoction (RPD) is a well-known traditional Chinese medicine that has been widely applied in treating UC. RPD may exert extensive therapeutic effects on both IBS and UC. However, the common mechanism of its treatment remains unclear. We aimed to assess the potential pharmacological mechanism of RPD in the treatment of overlapping IBS and UC. Methods: The active components and targets of RPD were retrieved from ETCM, TCMSP, BATMAN-TCM, and TCM databases. The disease targets were screened by searching the DrugBank, OMIM, TTD, and PharmGKB databases. PPI network analysis was performed and visualized via the STRING platform and Cytoscape software. GO and KEGG enrichment analyses of the hub genes of RPD were predicted to elucidate the potential molecular mechanism. Subsequently, molecular docking was carried out to verify the combination of active compounds with core targets. Results: By integrating all targets of RPD and disease, a total of 31 bioactive ingredients were identified including quercetin, kaempferol, aloe-emodin, beta-sitosterol, and (+)-catechin, etc. JUN, TP53, MAPK1, RELA, MYC, and ESR1 were explored as potential therapeutic targets among 126 common drug-disease-related targets. They were enriched in the AGE-RAGE signaling pathway in diabetic complications, as well as the NF-kappa B signaling pathway and MAPK signaling pathway. Additionally, some active ingredients were identified as candidates for binding to the hub targets via molecular docking, further suggesting their anti-inflammatory and antioxidative properties. Conclusion: RPD may exert the overall treatment effect for UC and IBS overlap syndrome via the biological mechanism of "multi-ingredients, multi-targets, and multi-pathways" on inflammation, oxidative stress, immune, oncogenicity, and gut microbiota dysbiosis.

Role of inflammation in pediatric irritable bowel syndrome

BACKGROUND

IBS affects a large number of children throughout the world and is thought to be the result of disturbed neuroimmune function along with the brain-gut axis. Although the underlying pathophysiologic mechanisms are not clear, the role of low-grade inflammation and mucosal immune activation in IBS symptom generation has become evident also in subsets of pediatric patients. Animal models provided meaningful insight in the causal relationship between abnormal mucosal immune activation and changes in gastrointestinal (GI) sensory-motor function. Likewise, the development of long-standing GI symptoms fulfilling the current criteria for functional GI disorders after infection gastroenteritis and in patients with IBD or celiac disease in remission further supports this hypothesis. Immune activation, its impact on gut sensory-motor function, and potential implications for symptom generation emerged in both children and adults with IBS.

PURPOSE

The aim of this review is to summarize the main evidence on the presence of low-grade inflammation and immune activation in children with IBS, its possible role in symptom generation, and its potential implication for new therapeutic strategies.

Diarrhea-predominant Irritable Bowel Syndrome-like Symptoms in Patients With Quiescent Crohn's Disease: Comprehensive Analysis of Clinical Features and Intestinal Environment Including the Gut Microbiome, Organic Acids, and Intestinal Permeability

Background/Aims

Diarrhea-predominant irritable bowel syndrome (IBS-D)-like symptoms frequently occur in patients with quiescent Crohn's disease (CD). To investigate the factors underlying IBS-D-like symptoms in patients with quiescent CD, we performed a comprehensive analysis of the clinical features and intestinal environment in those patients.

Methods

We performed a prospective observational study of 27 patients with quiescent CD (CD activity index [CDAI] ≤ 150; C-reactive protein ≤ 0.3 mg/dL). The presence and severity of IBS-D-like symptoms, health-related quality of life, disease-specific quality of life, and status of depression and anxiety were evaluated. The level of intestinal permeability, fecal calprotectin and organic acids and the profiles of gut microbiome were analyzed.

Results

Twelve of the 27 patients with quiescent CD (44.4%) had IBS-like symptoms, and these patients showed a significantly higher CDAI, IBS severity index and anxiety score than those without. The inflammatory bowel disease questionnaire score was significantly lower in the patients with IBS-D-like symptoms. There were no significant differences in small intestinal/colonic permeability or the levels of organic acids between the patients with and without IBS-D-like symptoms. Fusicatenibacter was significantly less abundant in the patients with IBS-D-like symptoms whereas their fecal calprotectin level was significantly higher (384.8 ± 310.6 mg/kg) than in patients without (161.0 ± 251.0 mg/kg). The receiver operating characteristic curve constructed to predict IBS-D-like symptoms in patients with quiescent CD using the fecal calprotectin level (cutoff, 125 mg/kg) showed a sensitivity and specificity of 73.3% and 91.7%, respectively.

Conclusion

Minimal inflammation is closely associated with the development of IBS-D-like symptoms in patients with quiescent CD.

Effects of dietary chlorogenic acid on ileal intestinal morphology, barrier function, immune factors and gut microbiota of broilers under high stocking density stress

Aims: The purpose of this research was to assess the effect of chlorogenic acid (CGA) in the diet on ileac structure, barrier function, immunological state, and microbial profile of broiler chickens in a high stocking density (HD) environment. Methods: Four hundred and seventy-six male AA broiler chickens were randomly split into four groups, two with a normal stocking density (ND) of fourteen birds per m² and two with a high stocking density of twenty-two birds per m². Each of the treatments consisted of five replicates. One of the two ND and HD groups received the usual feed, while the other two were given at 1.5 g/kg CGA as part of their dietary regimen. Results: The ND CGA group showed a greater increase in villus height and villus height/crypt depth compared to the ND group at 35 and 42 days. The HD group experienced a greater elevation in villus height due to CGA supplementation than the HD group across days 28, 35, and 42. At day 42, the HD group saw a decline in OCLN and ZO-1 mRNA expression in the ileum, but CGA was able to restore them. The HD group experienced a greater rise in OCLN mRNA than the control HD group when supplemented with CGA. The expression of TNF-α, IL-1β, and IL-6 in the ileum was higher in the HD group, and CGA supplementation enhanced this effect. The HD group experienced a greater rise in IL-10 mRNA expression than the control group following the administration of CGA. The HD group showed reduced alpha diversity and an increase in detrimental microbes such as Turicibacter and Shigella in the gut compared to the ND group, while the HD CGA group saw a reduction in Turicibacter, Shigella, and other harmful microbes. These findings reveal that HD stress suppressed the growth of ileac villi, decreased the expression of tight-junction genes, amplified the expression of inflammatory genes, and disturbed the gut microbiota, ultimately leading to increased intestinal permeability. Conclusion: We conclude that when chickens are given dietary CGA, the disruption of the ileac barrier and increased oxidative damage and inflammation due to HD stress are reduced, which increases ileac integrity and the presence of beneficial intestinal bacteria.

Paeoniflorin alleviates inflammatory response in IBS-D mouse model via downregulation of the NLRP3 inflammasome pathway with involvement of miR-29a

Paeoniflorin has been traditionally used to treat pain and immunologic derangement in China. However, its detailed mechanism remains to be illuminated. We investigated the mechanism by which paeoniflorin alleviates the inflammatory response in a mouse model of irritable bowel syndrome with predominant diarrhea (IBS-D). C57BL/6 wild type (WT) and miR-29a knockout (KO) mice were randomly divided into control, model, rifaximin, and paeoniflorin groups (n = 7). IBS-D model was induced by single intracolonic instillation of 0.1 mL trinitro-benzene-sulfonic acid (TNBS, 50 mg/mL) combined with restraint stress for seven consecutive days. The treatment groups received rifaximin (100 mg/kg) and paeoniflorin (50 mg/kg) via intragastric administration for seven days, respectively. The results showed that the fecal water content, fecal pellet output, visceral sensitivity, and histopathological score after paeoniflorin treatment were lower than those of the model group in both WT and miR-29a KO mice (P < 0.05). In both lineage mice, damage was observed in the colon tissues of model group, while paeoniflorin treatment partially ameliorated the tissue damage. Serum levels of DAO, DLA, IL-1β, IL-18, TNF-α, and MPO were decreased after paeoniflorin treatment (P < 0.05), with miR-29a KO mice in a lower level compared with that of WT mice. RT-PCR showed that the relative expression of miR-29a, NF-κB (p65), NLRP3, ASC, caspase-1, IL-1β, and TNF-α was downregulated while NKRF was upregulated after paeoniflorin treatment (P < 0.05). Immunohistochemistry showed that intestinal epithelial protein levels of NLRP3, ASC, and caspase-1 decreased while those of Claudin-1 and ZO-1 increased in the paeoniflorin treatment group (P < 0.05). In general, compared with WT mice, NLRP3 inflammasome pathway targets was in much lower expression level than miR-29a KO mice. In conclusion, paeoniflorin could inhibit abnormal activation of the NLRP3 inflammasome pathway by inhibiting miR-29a in IBS-D, thereby relieving the inflammatory response of the intestinal mucosa and reconstructing the intestinal epithelial barrier.

Myrrh and Chamomile Flower Extract Inhibit Mediator Release from IgE-stimulated Mast-Cell-Like RBL-2H3 Cells

Recent clinical evidence supports the efficacy of a traditional medicinal product (TMP) containing a combination of myrrh (Commiphora myrrha (Nees) Engl.), coffee charcoal (Coffea arabica L.), and chamomile flower dry extract (Matricaria chamomilla L.) in the therapy of diarrhea and inflammatory bowel disease. Mast cells seem to play a key role in the symptom generation of irritable bowel syndrome (IBS). To evaluate the use of the TMP in IBS treatment, the effects of the herbal extracts on the release of mast-cell mediators from stimulated RBL-2H3 cells were investigated. Therefore, degranulation was induced by phorbol-12-myristate-13-acetate (PMA) and calcium ionophore A13187 (CI) or IgE stimulation, and the amounts of released β-hexosaminidase and histamine were quantified. The extracts showed no effect on the mediator release of PMA- and CI-stimulated RBL-2H3 cells. Myrrh and chamomile were able to reduce the β-hexosaminidase release of IgE-stimulated cells, while myrrh showed stronger inhibition of the mediator release than chamomile, which reduced only IgE-stimulated histamine release. Thus, these results indicate a mechanistic basis for the use of the herbal combination of myrrh, coffee charcoal, and chamomile flower extract in the symptom-oriented treatment of IBS patients with diarrheal symptoms.

A postbiotic fermented oat gruel may have a beneficial effect on the colonic mucosal barrier in patients with irritable bowel syndrome

Background

Impaired intestinal permeability and microbial dysbiosis are important pathophysiological mechanisms underlying irritable bowel syndrome (IBS). ReFerm^®, also called Profermin^®, is a postbiotic product of oat gruel fermented with Lactobacillus plantarum 299v. In this study, we investigated whether ReFerm^® has a beneficial effect on the intestinal epithelial barrier function in patients with IBS.

Materials and methods

Thirty patients with moderate to severe IBS-diarrhoea (IBS-D) or IBS-mixed (IBS-M) were treated with enema containing ReFerm^® or placebo. The patients underwent sigmoidoscopy with biopsies obtained from the distal colon at baseline and after 14 days of treatment with ReFerm^® or placebo twice daily. The biopsies were mounted in Ussing chambers, and paracellular and transcellular permeabilities were measured for 120 min. In addition, the effects of ReFerm^® or placebo on the epithelial barrier were investigated in vitro using Caco-2 cells.

Results

ReFerm^® reduced paracellular permeability (p < 0.05) and increased transepithelial resistance (TER) over time (p < 0.01), whereas the placebo had no significant effect in patients. In ReFerm^®-treated Caco-2 cells, paracellular and transcellular permeabilities were decreased compared to the control (p < 0.05) and placebo (p < 0.01). TER was increased in Caco-2 ReFerm^®-treated cells, and normalised TER was increased in ReFerm^®-treated Caco-2 cells compared to control (p < 0.05) and placebo-treated (p < 0.05) cells.

Conclusion

ReFerm^® significantly reduced paracellular permeability and improved TER in colonic biopsies collected from patients with IBS and in a Caco-2 cell model. Our results offer new insights into the potential benefits of ReFerm^® in IBS management. Further studies are needed to identify the molecular mechanisms underlying the barrier-protective properties of ReFerm^®.

Clinical trial registration

[https://clinicaltrials.gov/], identifier [NCT05475314].

Immune-mediated food reactions in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder characterized by recurrent abdominal pain and an altered defecation pattern. Depending on the criteria used, it affects between 5 and 10% of the general population and has a serious impact on quality of life. Most patients with IBS show an induction or exacerbation of their symptoms, particularly abdominal pain, after eating certain foods. This raises the question of the role played by food in IBS pathophysiology. In this review, we describe the multiple risk factors of IBS, and we give an overview of the role of food as a trigger of IBS, distinguishing between immune and non-immune reactions to food. We finally highlight recent findings identifying an immune-mediated mechanism underlying food-induced abdominal pain in IBS.

Role of the Gut-Brain Axis, Gut Microbial Composition, Diet, and Probiotic Intervention in Parkinson's Disease

Parkinson's disease (PD) is the second-most prevalent neurodegenerative or neuropsychiatric disease, affecting 1% of seniors worldwide. The gut microbiota (GM) is one of the key access controls for most diseases and disorders. Disturbance in the GM creates an imbalance in the function and circulation of metabolites, resulting in unhealthy conditions. Any dysbiosis could affect the function of the gut, consequently disturbing the equilibrium in the intestine, and provoking pro-inflammatory conditions in the gut lumen, which send signals to the central nervous system (CNS) through the vagus enteric nervous system, possibly disturbing the blood-brain barrier. The neuroinflammatory conditions in the brain cause accumulation of α-syn, and progressively develop PD. An important aspect of understanding and treating the disease is access to broad knowledge about the influence of dietary supplements on GM. Probiotics are live microorganisms which, when administered in adequate amounts, confer a health benefit on the host. Probiotic supplementation improves the function of the CNS, and improves the motor and non-motor symptoms of PD. Probiotic supplementation could be an adjuvant therapeutic method to manage PD. This review summarizes the role of GM in health, the GM-brain axis, the pathogenesis of PD, the role of GM and diet in PD, and the influence of probiotic supplementation on PD. The study encourages further detailed clinical trials in PD patients with probiotics, which aids in determining the involvement of GM, intestinal mediators, and neurological mediators in the treatment or management of PD.

Enterochromaffin Cells-Gut Microbiota Crosstalk: Underpinning the Symptoms, Pathogenesis, and Pharmacotherapy in Disorders of Gut-Brain Interaction

Disorders of gut-brain interaction (DGBIs) are common conditions in community and clinical practice. As specialized enteroendocrine cells, enterochromaffin (EC) cells produce up to 95% of total body serotonin and coordinate luminal and basolateral communication in the gastrointestinal (GI) tract. EC cells affect a broad range of gut physiological processes, such as motility, absorption, secretion, chemo/mechanosensation, and pathologies, including visceral hypersensitivity, immune dysfunction, and impaired gastrointestinal barrier function. We aim to review EC cell and serotonin-mediated physiology and pathophysiology with particular emphasis on DGBIs. We explored the knowledge gap and attempted to suggest new perspectives of physiological and pathophysiological insights of DGBIs, such as (1) functional heterogeneity of regionally distributed EC cells throughout the entire GI tract; (2) potential pathophysiological mechanisms mediated by EC cell defect in DGBIs; (3) cellular and molecular mechanisms characterizing EC cells and gut microbiota bidirectional communication; (4) differential modulation of EC cells through GI segment-specific gut microbiota; (5) uncover whether crosstalk between EC cells and (i) luminal contents; (ii) enteric nervous system; and (iii) central nervous system are core mechanisms modulating gut-brain homeostasis; and (6) explore the therapeutic modalities for physiological and pathophysiological mechanisms mediated through EC cells. Insights discussed in this review will fuel the conception and realization of pathophysiological mechanisms and therapeutic clues to improve the management and clinical care of DGBIs.

Effects of Commercial Probiotics on Colonic Sensitivity after Acute Mucosal Irritation

Gastrointestinal pathologies associated with abdominal pain, such as irritable bowel syndrome or inflammatory bowel disease, lack sufficiently effective treatments. In our study we have used a rat model of visceral pain (72 animals; n = 8–13 per experimental group) to analyze the consequences of intracolonic administration of the irritant acetic acid on visceral sensitivity, histology of the colonic wall, and inflammatory response. Moreover, we have studied the possible beneficial effects of a pretreatment with a commercial probiotic (Actimel^®). Contrary to expectations, acetic acid application (7 cm proximal to the anus) decreased the nociceptive response to intracolonic mechanical stimulation, with a slight increase in the histological damage of colonic mucosa. The intensity of these changes depended on the concentration (4% or 0.6%) and the time of application (30 or 60 min). Pretreatment with probiotics (by daily gavage, for 1 week) normalized the values obtained in the visceral sensitivity test but revealed an increase in the number of macrophages. These results suggest a possible activation of inhibitory mechanisms early after colonic irritation, not previously described (which need further experimental confirmation), and the ability of probiotics to normalize the effects of acetic acid. In addition, pretreatment with probiotics has a direct effect on immune functions, stimulating macrophagic activity.

Roles of Microbiota in Cancer: From Tumor Development to Treatment

Cancer as a second leading cause of death arises from multifactorial pathology. The association of microbiota and their products with various pathologic conditions including cancer is receiving significant attention over the past few years. Mounting evidence showed that human microbiota is an emerging target in tumor onset, progression, prevention, and even diagnosis. Accordingly, modulating this composition might influence the response to tumor therapy and therapeutic resistance as well. Through this review, one could conceive of complex interaction between the microbiome and cancer in either positive or negative manner by which may hold potential for finding novel preventive and therapeutic strategies against cancer.

Immune activation in irritable bowel syndrome: what is the evidence?

Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder that is characterized by abdominal pain and an altered defecation pattern. It affects between 5 and 20% of the general population and can seriously impact quality of life. The pathophysiology of IBS is rather complex and multifactorial including, for example, altered signalling by the gut-brain axis, dysbiosis, abnormal visceral pain signalling and intestinal immune activation. The latter has gained particular interest in recent years, with growing insight into the bidirectional communication between the nervous system and the immune system. In this Review, we detail the current evidence suggesting that immune activation contributes to the pathology seen in patients with IBS and discuss the potential mechanisms involved. Moreover, we describe how immune mediators, particularly those released by mast cells, can directly activate or sensitize pain-transmitting nerves, leading to increased pain signalling and abdominal pain. Finally, we discuss the potential of interventions targeting immune activation as a new therapeutic strategy for patients suffering from IBS.

[Functional Gastrointestinal Disorders in Patients with Inflammatory Bowel Disease]

With emerging more effective drugs, the therapeutic goal of inflammatory bowel disease (IBD) has progressed from clinical remission to mucosal healing. Although the inflammation could be controlled more effectively than before, symptoms such as abdominal pain and bowel habit change is still bothersome to some IBD patients. Recently, these "refractory functional gastrointestinal symptoms" in quiescent IBD patients has been paid more attention. The pathophysiology could be multifactorial with genetics, change in gut motility associated with post inflammatory condition, increased permeability, impaired colorectal function, visceral hypersensitivity and gut microbiota. Because both IBD and functional gastrointestinal disease (FGID) could share similar symptoms and some pathophysiology, it is sometimes challenging to distinguish them exactly. However, to reduce the risk of overtreatment or insufficient control of inflammation, exact diagnosis of functional disease or symptoms in quiescent IBD patients is important. Because there is limited randomized controlled trials or prospective study currently, most of the therapeutic approach in IBD patients are empirical or referred to those of functional gastrointestinal disorders. However, approaches based on pathophysiological mechanisms could give appropriate therapies for both IBD and FGIDs.

Current Treatment Options and Therapeutic Insights for Gastrointestinal Dysmotility and Functional Gastrointestinal Disorders

Functional gastrointestinal disorders (FGIDs) have been re-named as disorders of gut-brain interactions. These conditions are not only common in clinical practice, but also in the community. In reference to the Rome IV criteria, the most common FGIDs, include functional dyspepsia (FD) and irritable bowel syndrome (IBS). Additionally, there is substantial overlap of these disorders and other specific gastrointestinal motility disorders, such as gastroparesis. These disorders are heterogeneous and are intertwined with several proposed pathophysiological mechanisms, such as altered gut motility, intestinal barrier dysfunction, gut immune dysfunction, visceral hypersensitivity, altered GI secretion, presence and degree of bile acid malabsorption, microbial dysbiosis, and alterations to the gut-brain axis. The treatment options currently available include lifestyle modifications, dietary and gut microbiota manipulation interventions including fecal microbiota transplantation, prokinetics, antispasmodics, laxatives, and centrally and peripherally acting neuromodulators. However, treatment that targets the pathophysiological mechanisms underlying the symptoms are scanty. Pharmacological agents that are developed based on the cellular and molecular mechanisms underlying pathologies of these disorders might provide the best avenue for future pharmaceutical development. The currently available therapies lack long-term effectiveness and safety for their use to treat motility disorders and FGIDs. Furthermore, the fundamental challenges in treating these disorders should be defined; for instance, 1. Cause and effect cannot be disentangled between symptoms and pathophysiological mechanisms due to current therapies that entail the off-label use of medications to treat symptoms. 2. Despite the knowledge that the microbiota in our gut plays an essential part in maintaining gut health, their exact functions in gut homeostasis are still unclear. What constitutes a healthy microbiome and further, the precise definition of gut microbial dysbiosis is lacking. More comprehensive, large-scale, and longitudinal studies utilizing multi-omics data are needed to dissect the exact contribution of gut microbial alterations in disease pathogenesis. Accordingly, we review the current treatment options, clinical insight on pathophysiology, therapeutic modalities, current challenges, and therapeutic clues for the clinical care and management of functional dyspepsia, gastroparesis, irritable bowel syndrome, functional constipation, and functional diarrhea.

The prevalence and risk factors of irritable bowel syndrome in Saudi Arabia in 2019

Background:

Irritable bowel syndrome (IBS) is a common chronic functional gastrointestinal (GI) disorder. The aim of this study is to assess the prevalence of IBS and its risk factors among the general population of Saudi Arabia, as there is no previous study has done so.

Methods:

A cross-sectional study was carried out to evaluate the prevalence of IBS, IBS subtypes and IBS risk factors among the general population of Saudi Arabia from June 22 to November 30, 2019. A designed questionnaire that is based on ROME IV criteria and licensed from Rome Foundation was used. A total of 1,680 eligible individuals from different parts of Saudi Arabia took part in this national survey and were included in the statistical analysis. The statistical analysis was carried out using Statistical Package for the Social Sciences (SPSS) program (version 22).

Results:

The prevalence of IBS in the study was 18.2%. IBS-M was the most common subtype among IBS patients (42.3%). Risk factors that are significantly associated with IBS were shown to be smoking habits, gastroesophageal reflux disease (GERD), food allergy, anxiety, psychological stress, family history of IBS, regular use of non-steroidal anti-inflammatory drugs (NSAIDs), history of infection before occurrence of symptoms and residence in the south of Saudi Arabia (P < 0.05*).

Conclusions:

IBS is prevalent in Saudi Arabia. The most common risk factor among IBS patients is a positive family history of IBS (80%). Raising public awareness and further prospective studies are both advocated and needed.

Association of Fecal Microbiota with Irritable Bowel Syndrome-Diarrhea and Effect of Traditional Chinese Medicine for Its Management

Changes in intestinal microbiota have been linked to the development of diarrhea predominant irritable bowel syndrome (IBS-D). In order to better elucidate the relationship between intestinal microbiota changes and IBS-D, we compared fecal microbiota of IBS-D rats and healthy control using pyrosequencing of bacterial 16S rRNA gene targeted. Furthermore, we explored the effects of different traditional Chinese medicine (TCM) on intestinal microbiota of IBS-D in dose-dependent manner. Our results showed that there was no significant difference in fecal microbial community diversity among the healthy control group, IBS-D rats and IBS-D rats treated with traditional Chinese medicine, but the fecal microbial composition at different taxonomic levels have changed among these groups. Interestingly, the weight of IBS-D rats treated with moderate doses (13.4 g/kg) of TCM increased significantly, and the diarrhea-related symptoms improved significantly, which may be related to the enrichment in Deferribacteres, Proteobacteria, Tenericutes, Lachnospiraceae, and Ruminococcaceae and the reduction in Lactobacillus in fecal samples.

Gut microbiota dysbiosis in functional gastrointestinal disorders: Underpinning the symptoms and pathophysiology

Functional gastrointestinal disorders (FGIDs), currently known as disorders of gut-brain interaction, are emerging microbiota-gut-brain abnormalities that are prevalent worldwide. The pathogenesis of FGIDs is heterogeneous and is intertwined with gut microbiota and its derived molecule-modulated mechanisms, including gut dysmotility, visceral hypersensitivity, gut immune abnormalities, abnormal secretion, and impaired barrier function. There has been phenomenal progress in understanding the role of gut microbiota in FGIDs by underpinning the species alternations between healthy and pathological conditions such as FGIDs. However, the precise gut microbiota-directed cellular and molecular pathogeneses of FGIDs are yet enigmatic. Determining the mechanistic link between the gut microbiota and gastrointestinal (GI) diseases has been difficult due to (i) the lack of robust animal models imitating the various aspects of human FGID pathophysiology; (ii) the absence of longitudinal human and/or animal studies to unveil the interaction of the gut microbiota with FGID-relevant pathogenesis; (iii) uncertainty about connections between human and animal studies; and (iv) insufficient data supporting a holistic view of disease-specific pathophysiological changes in FGID patients. These unidentified gaps open possibilities to explore pathological mechanisms directed through gut microbiota dysbiosis in FGIDs. The current treatment options for dysbiotic gut microbiota are limited; dietary interventions, antibiotics, probiotics, and fecal microbiota transplantation are the front-line clinical options. Here, we review the contribution of gut microbiota and its derived molecules in gut homeostasis and explore the possible pathophysiological mechanisms involved in FGIDs leading to potential therapeutics options.

Effects of ingested nanocellulose and nanochitosan materials on carbohydrate digestion and absorption in an in vitro small intestinal epithelium model

Nanoscale materials derived from natural biopolymers like cellulose and chitosan have many potentially useful agri-food and oral drug delivery applications. Because of their large and potentially bioactive surface areas and other unique physico-chemical properties, it is essential when evaluating their toxicological impact to assess potential effects on the digestion and absorption of co-ingested nutrients. Here, the effects of cellulose nanofibers (CNF), cellulose nanocrystals (CNC), and chitosan nanoparticles (Chnp) on the digestion and absorption of carbohydrates were studied. Starch digestion was assessed by measuring maltose released during simulated digestion of starch solutions. Glucose absorption was assessed by measuring translocation from the resulting digestas across an in vitro transwell tri-culture model of the small intestinal epithelium and calculating the area under the curve increase in absorbed glucose, analogous to the glycemic index. At 1% w/w, CNF and Chnp had small but significant effects (11% decrease and 14% increase, respectively) and CNC had no effect on starch hydrolysis during simulated digestion of a 1% w/w rice starch solution. In addition, at 2% w/w CNC had no effect on amylolysis in 1% solutions of either rice, corn, or wheat starch. Similarly, absorption of glucose from digestas of starch solutions (i.e., from maltose), was unaffected by 1% w/w CNF or CNC, but was slightly increased (10%, p<0.05) by 1% Chnp, possibly due to the slightly higher maltose concentration in the Chnp-containing digestas. In contrast, all of the test materials caused sharp increases (~1.2, 1.5, and 1.6 fold for CNC, CNF, and Chnp, respectively) in absorption of glucose from starch-free digestas spiked with free glucose at a concentration corresponding to complete hydrolysis of 1% w/w starch. The potential for ingested cellulose and chitosan nanomaterials to increase glucose absorption could have important health implications. Further studies are needed to elucidate the mechanisms underlying the observed increases and to evaluate the potential glycemic effects in an intact in vivo system.

Minimally Invasive Image-Guided Gut Transport Function Measurement Probe

INTRODUCTION

Diseases such as celiac disease, environmental enteric dysfunction, infectious gastroenteritis, type II diabetes and inflammatory bowel disease are associated with increased gut permeability. Dual sugar absorption tests, such as the lactulose to rhamnose ratio (L:R) test, are the current standard for measuring gut permeability. Although easy to administer in adults, the L:R test has a number of drawbacks. These include an inability to assess for spatial heterogeneity in gut permeability that may distinguish different disease severity or pathology, additional sample collection for immunoassays, and challenges in carrying out the test in certain populations such as infants and small children. Here, we demonstrate a minimally invasive probe for real-time localized gut permeability evaluation through gut potential difference (GPD) measurement.

MATERIALS AND METHODS

The probe has an outer diameter of 1.2 mm diameter and can be deployed in the gut of unsedated subjects via a transnasal introduction tube (TNIT) that is akin to an intestinal feeding tube. The GPD probe consists of an Ag/AgCl electrode, an optical probe and a perfusion channel all housed within a transparent sheath. Lactated Ringer's (LR) solution is pumped through the perfusion channel to provide ionic contact between the electrodes and the gut lining. The optical probe captures non-scanning (M-mode) OCT images to confirm electrode contact with the gut lining. A separate skin patch probe is placed over an abraded skin area to provide reference for the GPD measurements. Swine studies were conducted to validate the GPD probe. GPD in the duodenum was modulated by perfusing 45 ml of 45 mM glucose.

RESULTS

GPD values of -13.1 ± 2.8 mV were measured in the duodenum across four swine studies. The change in GPD in the duodenum with the addition of glucose was -10.5 ± 2.4 mV (p < 0.001). M-mode OCT images provided electrode-tissue contact information, which was vital in ascertaining the probe's proximity to the gut mucosa.

CONCLUSION

We developed and demonstrated a minimally invasive method for investigating gastrointestinal permeability consisting of an image guided GPD probe that can be used in unsedated subjects.

Pharmacological treatments of Chinese herbal medicine for irritable bowel syndrome in adults: A network meta-analysis of randomized controlled trials

Introduction

Plenty of clinical studies have suggested the value of Chinese herbal medicine (CHM) for patients with irritable bowel syndrome (IBS), but their efficacy and safety have not been systematically concluded yet. This article aimed to compare and rank the therapeutic effect and safety of CHM with routine pharmacotherapies and placebo in the treatment of IBS.

Methods

Randomized controlled trials regarding CHM to treat IBS were searched in six databases from inception to Jan 31, 2020. A network meta-analysis was conducted to analyze the data of included publications. The quality assessment was assessed by Cochrane Handbook and GRADEpro software. The risk ratio was calculated for dichotomous outcomes while the standardized mean difference was used for continuous variables with 95% credible intervals. A Funnel plot was performed to evaluate publication bias. The surface under the cumulative ranking curve was conducted to rank the included interventions. Data were analyzed with STATA 15.0 and Review Manager 5.3.

Result

3194 records were searched, and 28 eligible trials involving 3323 patients ere identified. Compared with conventional therapies and placebo, Jianpi-Chushi therapy showed significant improvement in adequate relief and IBS symptom severity scale; Shugan-Jianpi therapy showed the best efficacy in relieving the abdominal pain and abdominal distension; Wenshen-Jianpi therapy had a better effect on avoiding adverse effects and improving stool character.

Conclusion

This study confirmed that CHM could be beneficial for patients with IBS in relieving their clinical symptoms and should be recommended as alternative therapies. The quality of evidence in this study based on the GRADE system was “low”.

Histamine Intolerance-The More We Know the Less We Know. A Review

The intake of food may be an initiator of adverse reactions. Food intolerance is an abnormal non-immunological response of the organism to the ingestion of food or its components in a dosage normally tolerated. Despite the fact that food intolerance is spread throughout the world, its diagnosing is still difficult. Histamine intolerance (HIT) is the term for that type of food intolerance which includes a set of undesirable reactions as a result of accumulated or ingested histamine. Manifestations may be caused by various pathophysiological mechanisms or a combination of them. The problem with a "diagnosis" of HIT is precisely the inconstancy and variety of the manifestations in the same individual following similar stimuli. The diagnosing of HIT therefore requires a complex time-demanding multidisciplinary approach, including the systematic elimination of disorders with a similar manifestation of symptoms. Among therapeutic approaches, the gold standard is a low-histamine diet. A good response to such a diet is considered to be confirmation of HIT. Alongside the dietary measures, DAO supplementation supporting the degradation of ingested histamine may be considered as subsidiary treatment for individuals with intestinal DAO deficiency. If antihistamines are indicated, the treatment should be conscious and time-limited, while 2nd or 3rd generation of H1 antihistamines should take precedence.

Impact of food-derived bioactive peptides on gut function and health

The gastrointestinal tract (GIT) is the largest interface between our body and the environment. It is an organ system extending from the mouth to the anus and functions for food intake, digestion, transport and absorption of nutrients, meanwhile providing protection from environmental factors, like toxins, antigens, and pathogens. Diet is one of the leading factors modulating the function of the GIT. Bioactive peptides presenting naturally in food or derived from food proteins during digestion or processing have been revealed multifunctional in diverse biological processes, including maintaining gut health and function. This review summarizes the available evidence regarding the effects of food-derived bioactive peptides on gut function and health. Findings and insights from studies based on in vitro and animal models are discussed. The gastrointestinal mucosa maintains a delicate balance between immune tolerance to nutrients and harmful components, which is crucial for the digestive system's normal functions. Dietary bioactive peptides positively impact gastrointestinal homeostasis by modulating the barrier function, immune responses, and gut microbiota. However, there is limited clinical evidence on the safety and efficacy of bioactive peptides, much less on the applications of dietary peptides for the treatment or prevention of diseases related to the GIT. Further study is warranted to establish the applications of bioactive peptides in regulating gut health and function.

The Interrelationships between Intestinal Permeability and Phlegm Syndrome and Therapeutic Potential of Some Medicinal Herbs

The gastrointestinal (GI) tract has an intriguing and critical role beyond digestion in both modern and complementary and alternative medicine (CAM), as demonstrated by its link with the immune system. In this review, we attempted to explore the interrelationships between increased GI permeability and phlegm, an important pathological factor in CAM, syndrome, and therapeutic herbs for two disorders. The leaky gut and phlegm syndromes look considerably similar with respect to related symptoms, diseases, and suitable herbal treatment agents, including phytochemicals even though limitations to compare exist. Phlegm may be spread throughout the body along with other pathogens via the disruption of the GI barrier to cause several diseases sharing some parts of symptoms, diseases, and mechanisms with leaky gut syndrome. Both syndromes are related to inflammation and gut microbiota compositions. Well-designed future research should be conducted to verify the interrelationships for evidence based integrative medicine to contribute to the promotion of public health. In addition, systems biology approaches should be adopted to explore the complex synergistic effects of herbal medicine and phytochemicals on conditions associated with phlegm and leaky gut syndromes.

A Review of the Complex Relationship between Irritable Bowel Syndrome and Infertility

Irritable bowel syndrome (IBS) is a gastrointestinal disease that negatively affects up to 20% of the population. Infertility is defined as a disorder of the reproductive system described by lack of success in achieving pregnancy after more than a year of regular unprotected sexual intercourse. The main purpose of our review was to analyze the available literature regarding the IBS-infertility connection. Another secondary purpose of the present paper was to find out if oxidative stress may be the missing puzzle that may explain this possible correlation. After analyzing the available literature we concluded that oxidative stress is a plausible mediator of the connection between both female and male fertility and IBS. However, the data lacks in direct evidence to confirm this hypothesis. Nevertheless, it is recommended that certain levels of oxidative stress should not be exceeded in order to decrease IBS symptoms and increase the odds of conception given that generation of reactive oxygen species (ROS) is an aftermath of metabolically active cells. Therefore, reducing the oxidative stress by living a healthier lifestyle with a balanced diet, rich in micronutrients, limited in caffeine and alcohol, avoiding smoking and maintaining a normal body mass index with regular physical exercise may promote fertility and help diminishing IBS symptomatology. Studies with measurements of biological samples are needed in order to assess the complex relationship between oxidative stress, IBS and infertility.

Inhibition of miRNA-29a regulates intestinal barrier function in diarrhea-predominant irritable bowel syndrome by upregulating ZO-1 and CLDN1

Diarrhea-predominant irritable bowel syndrome (IBS-D) is a common chronic functional gastrointestinal disorder. MicroRNAs (miRNAs) have been identified to be involved in different physiological and pathological processes. In this study, the role of miRNA-29a in the potential mechanism underlying the function of the intestinal mucosal barrier in IBS-D was analyzed. Human intestinal mucosal epithelia from patients with IBS-D (diagnosed as meeting the Rome IV criteria) and healthy volunteers were collected. An IBS-D mouse model was established via induction with trinitro-benzene-sulfonic acid (TNBS), and the mice were injected with miRNA-29a inhibitor. Using transmission electron microscopy (TEM), the epithelial ultrastructure of the human intestinal mucosa was examined. Using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis, the expression level of miRNA-29a was assessed. ELISA was used to analyze the activity of D-lactate (D-LA) and diamine oxidase (DAO). Through immunohistochemistry, RT-qPCR and western blotting, the expression of tight junction protein ZO-1 (ZO-1) and claudin-1 (CLDN1) was examined. In the human intestinal mucosal epithelia from patients with IBS-D, miRNA-29a was upregulated, ZO-1 and CLDN1 were downregulated, and the junctional complex (JC) was faint and discontinuous. In the IBS-D mouse model, treatment with miRNA-29a inhibitor downregulated D-LA and DAO activity, and increased the expression of ZO-1 and CLDN1 in the intestinal mucosal epithelium. In conclusion, the present study revealed that miRNA-29a is involved in the pathogenesis of IBS-D, probably by downregulating ZO-1 and CLDN1 expression, suggesting that miRNA-29a is likely to be an important regulator of intestinal barrier function and could be a possible therapeutic target for IBS-D.

Marshall and Warren Lecture 2019: A paradigm shift in pathophysiological basis of irritable bowel syndrome and its implication on treatment

Irritable bowel syndrome (IBS), a common functional gastrointestinal disorder (FGID), has often been considered rather inappropriately as psychogenic in the past. Though psychological issues are important comorbidities in a proportion of IBS patients, the evidences are far from enough to label this condition as psychogenic only. In the recent past, evidences are emerging that underscores the concept supporting pure psychogenic theory of IBS and suggest this disorder to be rather microorganic. Accordingly, a move of Rome IV Committee attempting to delete the term "functional" and designating these to be disorders of "gut-brain interaction" rather than that of "brain-gut interaction," it emphasizes the importance of the gut over the brain in the pathogenesis. The introduction of the concept of multidimensional clinical profile in Rome IV requires attention to diagnostic category of FGID, overlap, severity, psychological issues, and physiological dysfunction or biomarkers; this attempts to recognize clinical variability and multidimensionality of pathophysiology and management of these disorders. The recognition of the biological factors in the pathogenesis of IBS is a significant paradigm shift in the recent time. This is somewhat similar to the progress in the pathogenesis of peptic ulcer disease from psychological factor to acid to Helicobacter pylori infection. It is expected that in the near future, therapeutic modalities targeting the different pathogenic mechanisms of different subtypes of IBS may bring revolution in management of the disorder.

Gut permeability is affected by sex and increased in children with irritable bowel syndrome but not in functional abdominal pain

BACKGROUND

Gut permeability is increased in some children and adults with irritable bowel syndrome (IBS). We investigated whether this also is true for children with functional abdominal pain (FAP). We also determined whether sex affected permeability results.

METHODS

Sucrose, lactulose, mannitol, and sucralose were ingested after an overnight fast in well-phenotyped children with IBS (n = 95), FAP (n = 25), and healthy controls (HC) (n = 60). Urine was collected for 24 hours. Percent sucrose recovery was calculated based on the 0- to 3-hour collection; lactulose/mannitol ratio both on the 0- to 3-hour and 0- to 24-hour collections; and percent sucralose recovery on the 0- to 24-hours collection.

KEY RESULTS

Age was similar among the groups (P = .26). The lactulose/mannitol ratio was increased in IBS compared with HC at 0-3 and 0-24 hours (P = .023, P = .05, respectively). Percent sucralose recovery was greater in FAP than in HC (P = .045). No differences were noted among the groups in percent sucrose recovery. Taking sex into account, percent sucrose recovery was greater in girls with IBS vs HC girls (P = .008). The lactulose/mannitol ratio was greater in boys with IBS compared with HC boys at both time points (both P = .02). Percent sucralose recovery was greater in boys with IBS than in FAP or HC (both P < .001).

CONCLUSIONS AND INFERENCES

Sex is a critically important factor when measuring gut permeability. Boys with IBS have increased lactulose/mannitol ratios and percent sucralose recovery. Girls with IBS have increased percent recovery of sucrose. Children with FAP do not demonstrate abnormal gut 0permeability even taking sex into account.

Increased Gut Permeability in First-degree Relatives of Children with Irritable Bowel Syndrome or Functional Abdominal Pain

BACKGROUND & AIMS

Increased gut permeability might contribute to the pathogenesis of irritable bowel syndrome or functional abdominal pain (IBS or FAP). We investigated whether siblings and parents of children with IBS or FAP have increased gut permeability.

METHODS

We performed permeability tests (using sucrose, lactulose, mannitol, and sucralose) on 29 siblings and 43 parents of children with IBS or FAP, and 43 children (controls) and 42 parents of controls, from primary and secondary care. Permeability studies were repeated in 7 siblings and 37 parents of children with IBS or FAP and 23 controls and 36 parents of controls following ingestion of 400 mg of ibuprofen. Percent recovery of sucrose was calculated based on analyses of urine collected overnight; the lactulose/mannitol ratio and percent recovery of sucralose were based on analyses of urine samples collected over a 24-hour period.

RESULTS

When we controlled for age, sex, and family membership, siblings of children with IBS or FAP had increased small bowel permeability (urinary lactulose/mannitol ratio) vs controls (P = .004). There was no difference in gastroduodenal (percent sucrose recovery) or colonic (percent sucralose recovery) permeability between groups. Similarly, parents of children with IBS or FAP also had increased small bowel permeability, compared with parents of controls (P = .015), with no differences in gastric or colonic permeability. After administration of ibuprofen, gastroduodenal and small bowel permeability tended to be greater in IBS or FAP siblings (P = .08) and gastroduodenal permeability tended to be greater in IBS or FAP parents (P = .086).

CONCLUSIONS

Siblings and parents of children with IBS or FAP have increased baseline small intestinal permeability compared with control children and their parents. These results indicate that there are familial influences on gastrointestinal permeability in patients with IBS or FAP.

Expression of Neurotrophic Factors, Tight Junction Proteins, and Cytokines According to the Irritable Bowel Syndrome Subtype and Sex

Background/Aims

Emerging evidence shows that the mechanism of irritable bowel syndrome (IBS) is associated with neurotrophic factors and tight junction proteins (TJPs). It is known that there are sex differences in the pathophysiology of IBS. The aim of the present study is to determine expression levels of neurotrophic factors, TJPs, and cytokines according to IBS subtype and sex.

Methods

From 59 IBS (33 IBS-constipation, 21 IBS-diarrhea, and 5 IBS-mixed) and 36 control patients, colonic mucosa mRNA expression levels of transient receptor potential vanilloid-1 (TRPV1), nerve growth factor (NGF), glial cell-derived neurotrophic factor (GDNF), and various TJPs were assessed by real-time polymerase chain reaction. Western blot was performed to determine levels of zonular occludens-1 (ZO-1). Serum levels of cytokines were measured by enzyme-linked immunosorbent assay.

Results

TRPV1, GDNF, and NGF mRNA levels were significantly increased in those with IBS-constipation compared to those in controls (all P < 0.05). However, they showed no significant difference between those with IBS-diarrhea and controls. Expression level of TRPV1 correlated with that of GDNF (r = 0.741, P < 0.001) and NGF (r = 0.935, P < 0.001). ZO-1 RNA expression levels were lower (P = 0.021) in female IBS-diarrhea than those in controls, although they showed no significant differences between male IBS-diarrhea and controls. Serum IL-1β levels in female IBS were significantly higher than those of male IBS, especially in IBS-constipation (P < 0.001).

Conclusions

Our results suggest that neurotrophic factors and IL-1β are closely related to IBS-constipation and that decrease of ZO-1 is an important factor in female with IBS-diarrhea.

Animal Models for Functional Gastrointestinal Disorders

Functional gastrointestinal disorders (FGID), such as functional dyspepsia (FD) and irritable bowel syndrome (IBS) are characterized by chronic abdominal symptoms in the absence of an organic, metabolic or systemic cause that readily explains these complaints. Their pathophysiology is still not fully elucidated and animal models have been of great value to improve the understanding of the complex biological mechanisms. Over the last decades, many animal models have been developed to further unravel FGID pathophysiology and test drug efficacy. In the first part of this review, we focus on stress-related models, starting with the different perinatal stress models, including the stress of the dam, followed by a discussion on neonatal stress such as the maternal separation model. We also describe the most commonly used stress models in adult animals which brought valuable insights on the brain-gut axis in stress-related disorders. In the second part, we focus more on models studying peripheral, i.e., gastrointestinal, mechanisms, either induced by an infection or another inflammatory trigger. In this section, we also introduce more recent models developed around food-related metabolic disorders or food hypersensitivity and allergy. Finally, we introduce models mimicking FGID as a secondary effect of medical interventions and spontaneous models sharing characteristics of GI and anxiety-related disorders. The latter are powerful models for brain-gut axis dysfunction and bring new insights about FGID and their comorbidities such as anxiety and depression.

Adherence to the pro-inflammatory diet in relation to prevalence of irritable bowel syndrome

Objective

There is no prior study that examined the association between nutrient-based dietary inflammatory index (DII) and odds of Irritable Bowel Syndrome (IBS). We examined the association between DII score and odds of IBS and its severity among Iranian adults.

Methods

In this cross-sectional study, dietary intakes of 3363 Iranian adults were examined using a validated Dish-based 106-item Semi-quantitative Food Frequency Questionnaire (DS-FFQ). DII was calculated based on dietary intakes derived from DS-FFQ. IBS was assessed using a modified Persian version of Rome III questionnaire.

Results

After adjustment for potential confounders, we found that participants in the highest quintile of DII score had greater chance for IBS compared with those in the lowest quintile (OR: 1.36; 95% CI: 1.03–1.80). By gender, we found a significant association between DII score and IBS among women (OR: 1.41; 95% CI: 1.00–2.00). By BMI status, overweight or obese (BMI ≥ 25 kg/m²) individuals in top quintile of DII score had greater odds for IBS than those in the bottom quintile (OR: 1.64; 95% CI: 1.07–2.53). No significant association was observed between a pro-inflammatory diet and severity of IBS symptoms.

Conclusions

Consumption of a pro-inflammatory diet was associated with increased odds of IBS, in particular among women and those with BMI ≥ 25 kg/m².

New insights into irritable bowel syndrome: from pathophysiology to treatment

Irritable bowel syndrome (IBS) is the most common reason to visit a gastroenterologist. IBS was believed to be a functional disease, but many possible pathophysiologic mechanisms can now explain the symptoms. IBS patients are classified into subtypes according to their predominant bowel habit, based on the Rome IV criteria. These include diarrhea-predominant and constipation-predominant IBS, as well as the mixed type, a combination of the two. Usually, IBS treatment is based on the predominant symptoms, with many options for each subtype. A new promising treatment option, fecal microbiota transplantation, seems to have beneficial effects on IBS. However, treating the pathophysiological causative agent responsible for the symptoms is an emerging approach. Therefore, before the appropriate therapeutic option is chosen for treating IBS, a clinical evaluation of its pathophysiology should be performed.

Modulating and opposite actions of two aqueous extracts prepared from Cinnamomum cassia L. bark and Quercus ilex L. on the gastrointestinal tract in rats

Cinnamon bark and evergreen oak acorns, natural sources of functional ingredients, are effective for those suffering from diarrhea, constipation and irritable bowel syndrome. This study aimed to evaluate the dissimilar phytochemical composition and the opposite potential actions of Cinnamomum cassia bark (ACCE) and Quercus ilex aqueous extracts (GIAE) on gastrointestinal (GI)-physiological activities and disruptions. An HPLC-PDA/ESI-MS assay was used to identify the distinctive qualitative and quantitative profiles of phenolic compounds. The GI-physiological action of both extracts on gastric emptying (GE) and gastrointestinal transit time (GIT) were evaluated using the phenol-red colorimetric method and a test meal containing charcoal/gum arabic in water. Loperamide (LOP)-induced colonic constipation and delayed emptying of the stomach were used to explore the reverse effects of ACCE/GIAE on GI disorders. HPLC-PDA/ESI-MS showed that the main phenolic compounds detected in ACCE are trans-cinnamic acid, quinic acid, protocatechuic acid and rosmarinic acid, while gallic acid, quinic acid and protocatechuic acid are the major chemical constituents found in GIAE. GIAE at two doses (150 and 300 mg kg-1) exerted a reduction of GE (66.40% and 60.87%, respectively) compared to a control group (70.25%). However, ACCE at the same concentrations induced contradictory actions on GE/GIT in comparison to GIAE and antagonistic synthetic pharmacological drugs in rats. The protective effect of CCAE against constipation induced by LOP in rats was accompanied by a strong antioxidant property related to moderation of intracellular-mediator disorders. An absence of toxic actions was revealed in the case of the hematological profile and biochemical parameters. Hence, in-depth investigations of these nutrients of both extracts may help future researchers to derive the underlying mechanisms and potential molecular targets for the development of physiologically functional foods and future therapies.

Colonic hypersensitivity and low-grade inflammation in a spontaneous animal model for functional gastrointestinal disorders

BACKGROUND

A complex interplay between a failing intestinal barrier and low-grade inflammation leading to sensorimotor disturbances is an often-cited mechanism in the pathogenesis of functional gastrointestinal disorders (FGID). However, the cause-consequence relationship between these features has not been clearly established. We previously described jejunal alterations in the normoglycemic BB-rat (BBDP-N) model proposing this model as a suitable animal model to study FGID pathophysiology. The current study explores colonic permeability, inflammation, and sensitivity of the BB-rat.

METHODS

Colonic tissue of BBDP-N and control (BBDR) rats at 50, 90, 110, 160, and 220 days (n ≥ 7 per group) was used to assess intestinal permeability in Ussing chambers and inflammation, including infiltration by eosinophils, mast cells, and eosinophil peroxidase (EPO) activity. Anxiety-like symptoms were evaluated at 50, 90, and 220 days and colonic sensitivity at 160 and 220 days by measuring the visceromotor response (VMR) to isobaric colorectal distensions.

KEYS RESULTS

Lamina propria eosinophil and mast cell infiltration and increased EPO activity were demonstrated from 90 days onward. Increased permeability and myenteric ganglionitis were observed in the oldest BBDP-N rats. At 220 days, the VMR was significantly increased suggesting colonic hypersensitivity. At the same age, increased anxiety-like behavior was observed.

CONCLUSION AND INFERENCES

We demonstrated a lamina propria eosinophil and mast cell infiltration preceding visceral hypersensitivity in the colon of the BBDP-N rat, reminiscent of patients with FGID. These findings help elucidating pathogenetic pathways in FGID and further validate the BBDP-N rat as an attractive model to study pathophysiology and therapy of FGID.

An Overview and Proposed Research Framework for Studying Co-Occurring Mental- and Physical-Health Dysfunction

Mental- and physical-health conditions co-occur at a rate much higher than chance. Of patients who have a mental-health condition, more than half also have a physical disease, and these cases are associated with increased human suffering and societal cost. Comorbidity research to date has focused on co-occurring mental- and physical-health disorders separately, and relatively little research has examined the co-occurrence of mental- and physical-health dysfunction. In addition, even less is known about why mental- and physical-health dysfunction co-occurs or how to treat these cases. Thus, the aims of this article are to highlight the need for research at the intersection of physical- and mental-health dysfunction and to provide guidance on how to research cases of comorbidity. Toward these ends, we begin by presenting a selective overview of the possible role of biological processes in the co-occurrence of physical- and mental-health dysfunction using specific illustrative examples. Specifically, we outline how biological processes within the immune system and gastrointestinal system could underlie depression, irritable bowel syndrome, and their co-occurrence. We then advance and discuss a proposed research framework, including methodological and analytic guidance, that researchers could use when studying the phenomenon of co-occurring physical- and mental-health dysfunction.

The Microbiome and Irritable Bowel Syndrome - A Review on the Pathophysiology, Current Research and Future Therapy

Irritable bowel syndrome (IBS) is a functional disorder which affects a large proportion of the population globally. The precise etiology of IBS is still unknown, although consensus understanding proposes IBS to be of multifactorial origin with yet undefined subtypes. Genetic and epigenetic factors, stress-related nervous and endocrine systems, immune dysregulation and the brain-gut axis seem to be contributing factors that predispose individuals to IBS. In addition to food hypersensitivity, toxins and adverse life events, chronic infections and dysbiotic gut microbiota have been suggested to trigger IBS symptoms in tandem with the predisposing factors. This review will summarize the pathophysiology of IBS and the role of gut microbiota in relation to IBS. Current methodologies for microbiome studies in IBS such as genome sequencing, metagenomics, culturomics and animal models will be discussed. The myriad of therapy options such as immunoglobulins (immune-based therapy), probiotics and prebiotics, dietary modifications including FODMAP restriction diet and gluten-free diet, as well as fecal transplantation will be reviewed. Finally this review will highlight future directions in IBS therapy research, including identification of new molecular targets, application of 3-D gut model, gut-on-a-chip and personalized therapy.

Mucosal RNA and protein expression as the next frontier in IBS: abnormal function despite morphologically intact small intestinal mucosa

Irritable bowel syndrome (IBS) is one of the commonest gastrointestinal disorders. Although long-time considered a pure functional disorder, intense research in past years has rendered a very complex and varied array of observations indicating the presence of structural and molecular abnormalities underlying characteristic motor and sensitive changes and clinical manifestations. Analysis of gene and protein expression in the intestinal mucosa has shed light on the molecular mechanisms implicated in IBS physiopathology. This analysis uncovers constitutive and inductive genetic and epigenetic marks in the small and large intestine that highlight the role of epithelial barrier, immune activation, and mucosal processing of foods and toxins and several new molecular pathways in the origin of IBS. The incorporation of innovative high-throughput techniques into IBS research is beginning to provide new insights into highly structured and interconnected molecular mechanisms modulating gene and protein expression at tissue level. Integration and correlation of these molecular mechanisms with clinical and environmental data applying systems biology/medicine and data mining tools emerge as crucial steps that will allow us to get meaningful and more definitive comprehension of IBS-detailed development and show the real mechanisms and causality of the disease and the way to identify more specific diagnostic biomarkers and effective treatments.

Evidence for Local and Systemic Immune Activation in Functional Dyspepsia and the Irritable Bowel Syndrome: A Systematic Review

BACKGROUND

Subtle histopathologic features such as eosinophilia and increased mast cells have been observed in functional gastrointestinal disorders (FGIDs), including functional dyspepsia (FD) and the irritable bowel syndrome (IBS). The mechanisms that drive recruitment of these cells to the gastrointestinal tract remain unexplained, largely due to the heterogeneity in phenotypes among patients diagnosed with such conditions. We aimed to systematically review the literature and collate the evidence for immune activation in FD and IBS, and where possible, detail the nature of activation.

METHODS

Seven literature databases were searched using the keywords: 'functional gastrointestinal disorder', FGID, 'functional dyspepsia', 'non-ulcer dyspepsia', 'idiopathic dyspepsia', 'irritable bowel syndrome', IBS and 'immun*'.

RESULTS

Fifty-one papers reporting discordant immune features met the selection criteria for this review. Changes in lymphocyte populations, including B and T lymphocyte numbers and activation status were reported in IBS and FD, in conjunction with duodenal eosinophilia in FD and increased colonic mast cells in IBS. Increases in circulating α4+β7+ gut-homing T cells appear to be linked to the pathophysiology of both FD and IBS. Studies in the area are complicated by poor phenotyping of patients into subgroups and the subtle nature of the immune activity involved in FD and IBS.

CONCLUSIONS

Alterations in proportions of gut-homing T lymphocytes in both FD and IBS indicate that a loss of mucosal homeostasis may drive the symptoms of FD and IBS. There is indirect evidence that Th17 responses may play a role in FGIDs, however the evidence for a Th2 immune phenotype in FD and IBS is limited. Although immune involvement is evident, large, well-characterised patient cohorts are required to elucidate the immune mechanisms driving the development of FGIDs.

Effects of Vitamin D Supplementation in Patients with Irritable Bowel Syndrome: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

Objective:

There are some evidence that Vitamin D supplementation may be beneficial for patients with irritable bowel syndrome (IBS). The aim of this study was to evaluate the effects of Vitamin D supplementation on symptoms and quality of life (QOL) in patients with IBS.

Methods:

In a randomized, double-blind, placebo-controlled clinical trial, 116 patients with IBS were supplemented weekly with either a pearl of 50,000 IU Vitamin D or an identical pearl of placebo containing medium chain triglyceride for 6 weeks.

Results:

Mean age of patients was 42.24 ± 12.26, and 40.06 ± 13.37 in Vitamin D and placebo groups, respectively. Dietary intakes were similar between and within groups. Serum concentration of 25-hydroxy Vitamin D increased significantly from 21.10 ± 5.23 to 36.43 ± 12.34 in the Vitamin D group (P < 0.001), while it was not significantly different before and after the trial in placebo group. The IBS symptoms severity scores (SSSs), disease-specific QOL, and total score were evaluated at weeks 0 and 6. IBS-SSS, IBS-QOL, and the total score were improved significantly more in Vitamin D group in comparison to the placebo group (P < 0.05).

Conclusions:

This study indicates that Vitamin D therapy can improve the severity of symptoms and QOL in patients with IBS; however, the long-term effects remained to be elucidated. Trial registration at IRCT: IRCT201402234010N11 IRB Number: 116/3976

Overlapping irritable bowel syndrome and inflammatory bowel disease

The pathogenesis of irritable bowel-type symptoms occurring in patients with inflammatory bowel disease who are in apparent remission continues to generate scientific controversy and the interpretation and management of these symptoms, so distressing to the sufferer, represent major challenges for the clinician. On the one hand, these symptoms often satisfy Rome IV criteria for IBS and their occurrence correlates highly with anxiety, a known trigger for IBS. On the other hand, recent studies have shown that many of these patients exhibit subtle inflammatory changes. These observations beg the question: are these symptoms "true" IBS superimposed on IBD, or an active but subclinical form of IBD? While it is certain that earlier studies failed to detect subclinical inflammation, it is also evident that even with the use of sensitive biomarkers for inflammation, such as calprotectin and lactoferrin backed up by pan-endoscopy and biopsy to exclude ongoing inflammatory activity in its most subtle form, the prevalence of IBS-type symptoms remains higher than expected in the IBD patient. Pending further definition of its etiology and pathology, we coined the term irritable inflammatory bowel syndrome (IIBS) to refer to this phenomenon. Here we explore the risk factors for this entity, sift through clues to its pathogenesis and attempt to provide, albeit bereft of a robust evidence base, an approach to its management.