Intestinal barrier dysfunction in irritable bowel syndrome: a systematic review

Gender-specific insights into the irritable bowel syndrome pathophysiology. Focus on gut dysbiosis and permeability

Irritable bowel syndrome (IBS) is the most common functional gastrointestinal disorder involving the brain-gut interaction. IBS is characterized by persistent abdominal pain and changes in bowel habits. IBS exerts significant impacts on quality of life and imposes huge economic costs. Global epidemiological data reveal variations in IBS prevalence, both globally and between genders, necessitating comprehensive studies to uncover potential societal and cultural influences. While the exact pathophysiology of IBS remains incompletely understood, the mechanism involves a dysregulation of the brain-gut axis, leading to disturbed intestinal motility, local inflammation, altered intestinal permeability, visceral sensitivity, and gut microbiota composition. We reviewed several gender-related pathophysiological aspects of IBS pathophysiology, by focusing on gut dysbiosis and intestinal permeability. This perspective paves the way to personalized and multidimensional clinical management of individuals with IBS.

Sishen Wan enhances intestinal barrier function via regulating endoplasmic reticulum stress to improve mice with diarrheal irritable bowel syndrome

BACKGROUND

Diarrheal irritable bowel syndrome (IBS-D), characterized primarily by the presence of diarrhea and abdominal pain, is a clinical manifestation resulting from a multitude of causative factors. Furthermore, Sishen Wan (SSW) has demonstrated efficacy in treating IBS-D. Nevertheless, its mechanism of action remains unclear.

METHODS

A model of IBS-D was induced by a diet containing 45 % lactose and chronic unpredictable mild stress. Additionally, the impact of SSW was assessed by measuring body weight, visceral sensitivity, defecation parameters, intestinal transport velocity, intestinal neurotransmitter levels, immunohistochemistry, and transmission electron microscopy analysis. Immunofluorescent staining was used to detect the expression of Mucin 2 (MUC2) and Occludin in the colon. Western blotting was used to detect changes in proteins related to tight junction (TJ), autophagy, and endoplasmic reticulum (ER) stress in the colon. Finally, 16S rRNA amplicon sequencing was used to monitor the alteration of gut microbiota after SSW treatment.

RESULTS

Our study revealed that SSW administration resulted in reduced visceral sensitivity, improved defecation parameters, decreased intestinal transport velocity, and reduced intestinal permeability in IBS-D mice. Furthermore, SSW promotes the secretion of colonic mucus by enhancing autophagy and inhibiting ER stress. SSW treatment caused remodeling of the gut microbiome by increasing the abundance of Blautia, Muribaculum and Ruminococcus torques group.

CONCLUSION

SSW can improve intestinal barrier function by promoting autophagy and inhibiting ER stress, thus exerting a therapeutic effect on IBS-D.

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.

Intestinal Permeability, Irritable Bowel Syndrome with Constipation, and the Role of Sodium-Hydrogen Exchanger Isoform 3 (NHE3)

Increased intestinal permeability has been identified as one of the many pathophysiological factors associated with the development of irritable bowel syndrome (IBS), a common disorder of gut-brain interaction. The layer of epithelial cells that lines the intestine is permeable to a limited degree, and the amount of paracellular permeability is tightly controlled to enable the absorption of ions, nutrients, and water from the lumen. Increased intestinal permeability to macromolecules can be triggered by a variety of insults, including infections, toxins from food poisoning, or allergens, which in turn cause an inflammatory response and are associated with abdominal pain in patients with IBS. This review article discusses increased intestinal permeability in IBS, focusing on IBS with constipation (IBS-C) through the lens of a patient case with a reported prior diagnosis of "leaky gut syndrome" upon initial contact with a gastrointestinal specialist. We review advantages and disadvantages of several methods of measuring intestinal permeability in patients and discuss when measuring intestinal permeability is appropriate in the therapeutic journey of patients with IBS-C. Furthermore, we discuss a possible mechanism of restoring the intestinal barrier to its healthy state through altering intracellular pH by inhibiting sodium-hydrogen exchanger isoform 3 (NHE3). Tenapanor is a minimally absorbed, small-molecule inhibitor of NHE3 that has been approved by the US Food and Drug Administration for the treatment of IBS-C in adults. Preclinical studies showed that tenapanor may restore the intestinal barrier in IBS-C by affecting the conformation of tight junction proteins via NHE3 inhibition to block the paracellular transport of macromolecules from the intestinal lumen. Testing for increased permeability in patients with IBS-C who experience abdominal pain may help inform the choice of therapeutics and alter patients' misconceptions about "leaky gut syndrome".

Chronic Visceral Pain: New Peripheral Mechanistic Insights and Resulting Treatments

Chronic visceral pain is one of the most common reasons for patients with gastrointestinal disorders, such as inflammatory bowel disease or disorders of brain-gut interaction, to seek medical attention. It represents a substantial burden to patients and is associated with anxiety, depression, reductions in quality of life, and impaired social functioning, as well as increased direct and indirect health care costs to society. Unfortunately, the diagnosis and treatment of chronic visceral pain is difficult, in part because our understanding of the underlying pathophysiologic basis is incomplete. In this review, we highlight recent advances in peripheral pain signaling and specific physiologic and pathophysiologic preclinical mechanisms that result in the sensitization of peripheral pain pathways. We focus on preclinical mechanisms that have been translated into treatment approaches and summarize the current evidence base for directing treatment toward these mechanisms of chronic visceral pain derived from clinical trials. The effective management of chronic visceral pain remains of critical importance for the quality of life of suffers. A deeper understanding of peripheral pain mechanisms is necessary and may provide the basis for novel therapeutic interventions.

Gut microbiota and intestinal immunity-A crosstalk in irritable bowel syndrome

Irritable bowel syndrome (IBS), one of the most prevalent functional gastrointestinal disorders, is characterized by recurrent abdominal pain and abnormal defecation habits, resulting in a severe healthcare burden worldwide. The pathophysiological mechanisms of IBS are multi-factorially involved, including food antigens, visceral hypersensitivity reactions, and the brain-gut axis. Numerous studies have found that gut microbiota and intestinal mucosal immunity play an important role in the development of IBS in crosstalk with multiple mechanisms. Therefore, based on existing evidence, this paper elaborates that the damage and activation of intestinal mucosal immunity and the disturbance of gut microbiota are closely related to the progression of IBS. Combined with the application prospect, it also provides references for further in-depth exploration and clinical practice.

NHE3 inhibitor tenapanor maintains intestinal barrier function, decreases visceral hypersensitivity, and attenuates TRPV1 signaling in colonic sensory neurons

The pathogenesis of irritable bowel syndrome (IBS) is multifactorial, characterized in part by increased intestinal permeability, and visceral hypersensitivity. Increased permeability is associated with IBS severity and abdominal pain. Tenapanor is FDA-approved for the treatment of IBS with constipation (IBS-C) and has demonstrated improvements in bowel motility and a reduction in IBS-related pain; however, the mechanism by which tenapanor mediates these functions remains unclear. Here, the effects of tenapanor on colonic pain signaling and intestinal permeability were assessed through behavioral, electrophysiological, and cell culture experiments. Intestinal motility studies in rats and humans demonstrated that tenapanor increased luminal sodium and water retention and gastrointestinal transit versus placebo. A significantly reduced visceral motor reflex (VMR) to colonic distension was observed with tenapanor treatment versus vehicle in two rat models of visceral hypersensitivity (neonatal acetic acid sensitization and partial restraint stress; both P < 0.05), returning VMR responses to that of nonsensitized controls. Whole cell voltage patch-clamp recordings of retrogradely labeled colonic dorsal root ganglia (DRG) neurons from sensitized rats found that tenapanor significantly reduced DRG neuron hyperexcitability to capsaicin versus vehicle (P < 0.05), an effect not mediated by epithelial cell secretions. Tenapanor also attenuated increases in intestinal permeability in human colon monolayer cultures caused by incubation with proinflammatory cytokines (P < 0.001) or fecal supernatants from patients with IBS-C (P < 0.005). These results support a model in which tenapanor reduces IBS-related pain by strengthening the intestinal barrier, thereby decreasing permeability to macromolecules and antigens and reducing DRG-mediated pain signaling.NEW & NOTEWORTHY A series of nonclinical experiments support the theory that tenapanor inhibits IBS-C-related pain by strengthening the intestinal barrier. Tenapanor treatment reduced visceral motor responses to nonsensitized levels in two rat models of hypersensitivity and reduced responses to capsaicin in sensitized colonic nociceptive dorsal root ganglia neurons. Intestinal permeability experiments in human colon monolayer cultures found that tenapanor attenuates increases in permeability induced by either inflammatory cytokines or fecal supernatants from patients with IBS-C.

Rome III Criteria Capture Higher Irritable Bowel Syndrome SNP-Heritability and Highlight a Novel Genetic Link With Cardiovascular Traits

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) shows genetic predisposition, and large-scale genome-wide association studies (GWAS) are emerging, based on heterogeneous disease definitions. We investigated the genetic architecture of IBS defined according to gold standard Rome Criteria.

METHODS

We conducted GWAS meta-analyses of Rome III IBS and its subtypes in 24,735 IBS cases and 77,149 asymptomatic control subjects from 2 independent European cohorts (UK Biobank and Lifelines). Single-nucleotide polymorphism (SNP)-based heritability (h2SNP) and genetic correlations (rg) with other traits were calculated. IBS risk loci were functionally annotated to identify candidate genes. Sensitivity and conditional analyses were conducted to assess impact of confounders. Polygenic risk scores were computed and tested in independent datasets.

RESULTS

Rome III IBS showed significant SNP-heritability (up to 13%) and similar genetic architecture across subtypes, including those with manifestations at the opposite ends of the symptom spectrum (rg = 0.48 between IBS-D and IBS-C). Genetic correlations with other traits highlighted commonalities with family history of heart disease and hypertension, coronary artery disease, and angina pectoris (rg = 0.20-0.45), among others. Four independent GWAS signals (P < 5×10-8) were detected, including 2 novel loci for IBS (rs2035380) and IBS-mixed (rs2048419) that had been previously associated with hypertension and coronary artery disease. Functional annotation of GWAS risk loci revealed genes implicated in circadian rhythm (BMAL1), intestinal barrier (CLDN23), immunomodulation (MFHAS1), and the cyclic adenosine monophosphate pathway (ADCY2). Polygenic risk scores allowed the identification of individuals at increased risk of IBS (odds ratio, 1.34; P = 1.1×10-3).

CONCLUSIONS

Rome III Criteria capture higher SNP-heritability than previously estimated for IBS. The identified link between IBS and cardiovascular traits may contribute to the delineation of alternative therapeutic strategies, warranting further investigation.

Effect of a 12-Week Walking Program Monitored by Global Physical Capacity Score (GPCS) on Circulating Cell-Free mtDNA and DNase Activity in Patients with Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) involves low-grade mucosal inflammation. Among the various approaches capable of managing the symptoms, physical activity is still under investigation. Despite its benefits, it promotes oxidative stress and inflammation. Mitochondria impacts gut disorders by releasing damage-associated molecular patterns, such as cell-free mtDNA (cf-mtDNA), which support inflammation. This study evaluated the effects of a 12-week walking program on the cf-mtDNA and DNase in 26 IBS and 17 non-IBS subjects. Pro- and anti-inflammatory cytokines were evaluated by ELISA. Digital droplet PCR was used to quantify cf-mtDNA; DNase activity was assessed using a single radial enzyme diffusion assay. PCR-RFLP was used to genotype DNASE1 rs1053874 SNP. Significantly lower IL-10 levels were found in IBS than in non-IBS individuals. Exercise reduced cf-mtDNA in non-IBS subjects but not in IBS patients. DNase activity did not correlate with the cf-mtDNA levels in IBS patients post-exercise, indicating imbalanced cf-mtDNA clearance. Different rs1053874 SNP frequencies were not found between groups. The study confirms the positive effects of regular moderate-intensity physical activity in healthy subjects and its role in cf-mtDNA release and clearance. Walking alone might not sufficiently reduce subclinical inflammation in IBS, based on imbalanced pro- and anti-inflammatory molecules. Prolonged programs are necessary to investigate their effects on inflammatory markers in IBS.

Effectiveness of stabilization methods for the immediate and short-term preservation of bovine fecal and upper respiratory tract genomic DNA

Previous research on stabilization methods for microbiome investigations has largely focused on human fecal samples. There are a few studies using feces from other species, but no published studies investigating preservation of samples collected from cattle. Given that microbial taxa are differentially impacted during storage it is warranted to study impacts of preservation methods on microbial communities found in samples outside of human fecal samples. Here we tested methods of preserving bovine fecal respiratory specimens for up to 2 weeks at four temperatures (room temperature, 4°C, -20°C, and -80°C) by comparing microbial diversity and community composition to samples extracted immediately after collection. Importantly, fecal specimens preserved and analyzed were technical replicates, providing a look at the effects of preservation method in the absence of biological variation. We found that preservation with the OMNIgene®•GUT kit resulted in community structure most like that of fresh samples extracted immediately, even when stored at room temperature (~20°C). Samples that were flash-frozen without added preservation solution were the next most representative of original communities, while samples preserved with ethanol were the least representative. These results contradict previous reports that ethanol is effective in preserving fecal communities and suggest for studies investigating cattle either flash-freezing of samples without preservative or preservation with OMNIgene®•GUT will yield more representative microbial communities.

Menthacarin treatment attenuates nociception in models of visceral hypersensitivity

BACKGROUND

Chronic visceral hypersensitivity is closely associated with irritable bowel syndrome (IBS), a very common disorder which significantly impairs quality of life, characterized by abdominal pain, and distension. Imaging studies have found that IBS patients show higher metabolic activities and functional differences from normal controls in the anterior cingulate cortex (ACC), in response to visceral pain stimulation. Non-clinical data and clinical data suggest that medicinal products containing essential oils such as peppermint or caraway oil exert beneficial effects on IBS symptoms.

METHODS

We assessed acute and long-term treatment effects of a mixture of peppermint and caraway essential oils (Menthacarin) on brain electrophysiological markers of gut pain sensitivity in two rat models of visceral hypersensitivity.

KEY RESULTS

Chronic administration of corticosteroids and acute repeated mechanical hyperstimulation under anesthesia induced hyperalgesia and hypersensitivity, characterized by an increase in electrophysiological excitatory responses of ACC neurons to colorectal distension (CRD) and an increase in the proportion of neurons responding to otherwise subthreshold stimulation, respectively. Long-term, but not acute, oral administration of Menthacarin (60 mg kg-1 day-1) significantly reduced the net excitatory response to CRD in normally responsive control animals and counteracted the development of visceral hyperalgesia and hypersensitivity induced by repeated corticosterone administration and acute mechanical stimulation.

CONCLUSIONS & INFERENCES

The present study shows that, using the CRD method, chronic Menthacarin administration at a clinically relevant dose attenuates the neuronal discharge associated with visceral pain stimuli in the rat ACC, particularly in models of hypersensitivity, suggesting a potential for treating exaggerated visceral pain sensitivity.

Gastrointestinal and brain barriers: unlocking gates of communication across the microbiota-gut-brain axis

Crosstalk between gut and brain has long been appreciated in health and disease, and the gut microbiota is a key player in communication between these two distant organs. Yet, the mechanisms through which the microbiota influences development and function of the gut-brain axis remain largely unknown. Barriers present in the gut and brain are specialized cellular interfaces that maintain strict homeostasis of different compartments across this axis. These barriers include the gut epithelial barrier, the blood-brain barrier and the blood-cerebrospinal fluid barrier. Barriers are ideally positioned to receive and communicate gut microbial signals constituting a gateway for gut-microbiota-brain communication. In this Review, we focus on how modulation of these barriers by the gut microbiota can constitute an important channel of communication across the gut-brain axis. Moreover, barrier malfunction upon alterations in gut microbial composition could form the basis of various conditions, including often comorbid neurological and gastrointestinal disorders. Thus, we should focus on unravelling the molecular and cellular basis of this communication and move from simplistic framing as 'leaky gut'. A mechanistic understanding of gut microbiota modulation of barriers, especially during critical windows of development, could be key to understanding the aetiology of gastrointestinal and neurological disorders.

Role of gut-derived bacterial lipopolysaccharide and peripheral TLR4 in immobilization stress-induced itch aggravation in a mouse model of atopic dermatitis

Psychological stress and intestinal leakage are key factors in atopic dermatitis (AD) recurrence and exacerbation. Here, we demonstrate the mechanism underlying bacterial translocation across intestinal epithelial barrier damaged due to stress and further aggravation of trimellitic anhydride (TMA)-induced itch, which remain unclear, in AD mice. Immobilization (IMO) stress exacerbated scratching bouts and colon histological damage, and increased serum corticosterone and lipopolysaccharide (LPS). Orally administered fluorescein isothiocyanate (FITC)-dextran and surgically injected (into the colon) Cy5.5-conjugated LPS were detected in the serum and skin after IMO stress, respectively. The relative abundance of aerobic or facultative anaerobic bacteria was increased in the colon mucus layer, and Lactobacillus murinus, E. coli, Staphylococcus nepalensis, and several strains of Bacillus sp. were isolated from the spleens and mesenteric lymph nodes. Oral antibiotics or intestinal permeability blockers, such as lubiprostone (Lu), 2,4,6-triaminopyrimidine (TAP) and ML-7, inhibited IMO stress-associated itch; however, it was reinduced through intradermal or i.p. injection of LPS without IMO stress. I.p. injection of TAK-242 (resatorvid), a TLR4 inhibitor, abrogated IMO stress-associated itch, which was also confirmed in TLR4-KO mice. IMO stress alone did not cause itch in naïve mice. IMO stress-induced itch aggravation in TMA-treated AD mice might be attributed to the translocation of gut-derived bacterial cells and LPS, which activates peripheral TLR4 signaling.

Lipopolysaccharide, VE-cadherin, HMGB1, and HIF-1α levels are elevated in the systemic circulation in chronic migraine patients with medication overuse headache: evidence of leaky gut and inflammation

OBJECTIVE

Medication overuse headache (MOH) was recently shown to be associated with leaky gut in rodents. We aimed to investigate whether chronic migraine (CM) patients with MOH have elevated lipopolysaccharide levels and inflammatory molecules in blood circulation.

MATERIALS AND METHODS

The study included women participants (40 CM patients with NSAID overuse headache, 35 episodic migraine (EM) patients, and 20 healthy non-headache sufferers). Migraine duration, monthly migraine headache days, MigSCog, HADS-D, HADS-A, and HIT-6 scores were recorded. Serum samples were collected to measure circulating LPS, LPS binding protein (LBP), tight junction protein occludin, adherens junction protein vascular endothelial cadherin (VE-cadherin), CGRP, HMGB1, HIF-1α, IL-6, and IL-17 levels.

RESULTS

Serum LPS, VE-Cadherin, CGRP, HIF-1α, and IL-6 levels were significantly higher in the CM + MOH group compared to the EM group and healthy controls while serum LBP and HMGB1 were higher in the CM + MOH group compared to healthy controls. IL-17 and occludin levels were comparable between the three groups. Serum HMGB1 levels in EM patients were higher compared to the control group. Mig-SCog and HIT-6 scores were higher in the CM + MOH group compared to EM patients. HADS-A and HADS-D scores were significantly higher in the CM + MOH group compared to EM patients and healthy controls, and they were also higher in EM patients compared to healthy subjects. LPS levels were correlated with VE-cadherin and occludin levels. The number of monthly migraine headache days was positively correlated with serum LPS, HIF-1α, VE-cadherin, and IL-6 levels, HADS-A, HADS-D, HIT-6, and MigSCog scores.

CONCLUSION

We have evidence for the first time that CM + MOH is associated with elevated serum LPS and LBP levels suggestive of LPS leak into the systemic circulation. Higher levels of nociceptive and/or pro-inflammatory molecules such as HMGB1, HIF-1α, IL-6, and CGRP may play a role in trigeminal sensitization and neurobiology of MOH. Intestinal hyperpermeability and consequent inflammatory response should be considered as a potential contributory factor in patients with MOH.

The gut microbiome in disorders of gut-brain interaction

Functional gastrointestinal disorders (FGIDs), chronic disorders characterized by either abdominal pain, altered intestinal motility, or their combination, have a worldwide prevalence of more than 40% and impose a high socioeconomic burden with a significant decline in quality of life. Recently, FGIDs have been reclassified as disorders of gut-brain interaction (DGBI), reflecting the key role of the gut-brain bidirectional communication in these disorders and their impact on psychological comorbidities. Although, during the past decades, the field of DGBIs has advanced significantly, the molecular mechanisms underlying DGBIs pathogenesis and pathophysiology, and the role of the gut microbiome in these processes are not fully understood. This review aims to discuss the latest body of literature on the complex microbiota-gut-brain interactions and their implications in the pathogenesis of DGBIs. A better understanding of the existing communication pathways between the gut microbiome and the brain holds promise in developing effective therapeutic interventions for DGBIs.

Pasteurized akkermansia muciniphila improves irritable bowel syndrome-like symptoms and related behavioral disorders in mice

Gut - brain communications disorders in irritable bowel syndrome (IBS) are associated with intestinal microbiota composition, increased gut permeability, and psychosocial disturbances. Symptoms of IBS are difficult to medicate, and hence much research is being made into alternative approaches. This study assesses the potential of a treatment with pasteurized Akkermansia muciniphila for alleviating IBS-like symptoms in two mouse models of IBS with different etiologies. Two clinically relevant animal models were used to mimic IBS-like symptoms in C57BL6/J mice: the neonatal maternal separation (NMS) paradigm and the Citrobacter rodentium infection model. In both models, gut permeability, colonic sensitivity, fecal microbiota composition and colonic IL-22 expression were evaluated. The cognitive performance and emotional state of the animals were also assessed by several tests in the C. rodentium infection model. The neuromodulation ability of pasteurized A. muciniphila was assessed on primary neuronal cells from mice dorsal root ganglia using a ratiometric calcium imaging approach. The administration of pasteurized A. muciniphila significantly reduced colonic hypersensitivity in both IBS mouse models, accompanied by a reinforcement of the intestinal barrier function. Beneficial effects of pasteurized A. muciniphila treatment have also been observed on anxiety-like behavior and memory defects in the C. rodentium infection model. Finally, a neuroinhibitory effect exerted by pasteurized A. muciniphila was observed on neuronal cells stimulated with two algogenic substances such as capsaicin and inflammatory soup. Our findings demonstrate novel anti-hyperalgesic and neuroinhibitory properties of pasteurized A. muciniphila, which therefore may have beneficial effects in relieving pain and anxiety in subjects with IBS.

Cytolethal distending toxin B inoculation leads to distinct gut microtypes and IBS-D-like microRNA-mediated gene expression changes in a rodent model

Diarrhea-predominant irritable bowel syndrome (IBS-D), associated with increased intestinal permeability, inflammation, and small intestinal bacterial overgrowth, can be triggered by acute gastroenteritis. Cytolethal distending toxin B (CdtB) is produced by gastroenteritis-causing pathogens and may underlie IBS-D development, through molecular mimicry with vinculin. Here, we examine the effects of exposure to CdtB alone on gut microbiome composition, host intestinal gene expression, and IBS-D-like phenotypes in a rat model. CdtB-inoculated rats exhibited increased anti-CdtB levels, which correlated with increased stool wet weights, pro-inflammatory cytokines (TNFα, IL2) and predicted microbial metabolic pathways including inflammatory responses, TNF responses, and diarrhea. Three distinct ileal microbiome profiles (microtypes) were identified in CdtB-inoculated rats. The first microtype (most like controls) had altered relative abundance (RA) of genera Bifidobacterium, Lactococcus, and Rothia. The second had lower microbial diversity, higher Escherichia-Shigella RA, higher absolute E. coli abundance, and altered host ileal tissue expression of immune-response and TNF-response genes compared to controls. The third microtype had higher microbial diversity, higher RA of hydrogen sulfide (H2S)-producer Desulfovibrio, and increased expression of H2S-associated pain/serotonin response genes. All CdtB-inoculated rats exhibited decreased ileal expression of cell junction component mRNAs, including vinculin-associated proteins. Significantly, cluster-specific microRNA-mRNA interactions controlling intestinal permeability, visceral hypersensitivity/pain, and gastrointestinal motility genes, including several previously associated with IBS were seen. These findings demonstrate that exposure to CdtB toxin alone results in IBS-like phenotypes including inflammation and diarrhea-like stool, decreased expression of intestinal barrier components, and altered ileal microtypes that influenced changes in microRNA-modulated gene expression and predicted metabolic pathways consistent with specific IBS-D symptoms.

Epithelial Barrier Dysfunction in Diarrhea-Predominant Irritable Bowel Syndrome (IBS-D) via Downregulation of Claudin-1

BACKGROUND

In patients with diarrhea-predominant irritable bowel syndrome (IBS-D), the diarrheal mechanisms are largely unknown, and they were examined in this study on colon biopsies.

METHODS

Electrophysiological measurements were used for monitoring functional changes in the diarrheic colon specimens. In parallel, tight junction protein expression was analyzed by Western blot and confocal laser-scanning microscopy, and signaling pathway analysis was performed using RNA sequencing and bioinformatics.

RESULTS

Epithelial resistance was decreased, indicating an epithelial leak flux diarrheal mechanism with a molecular correlate of decreased claudin-1 expression, while induction of active anion secretion and impairment of active sodium absorption via the epithelial sodium channel, ENaC, were not detected. The pathway analysis revealed activation of barrier-affecting cytokines TNF-α, IFN-γ, IL-1β and IL-4.

CONCLUSIONS

Barrier dysfunction as a result of epithelial tight junction changes plays a role in IBS-D as a pathomechanism inducing a leak flux type of diarrhea.

Proenkephalin deletion in hematopoietic cells induces intestinal barrier failure resulting in clinical feature similarities with irritable bowel syndrome in mice

Opioid-dependent immune-mediated analgesic effects have been broadly reported upon inflammation. In preclinical mouse models of intestinal inflammatory diseases, the local release of enkephalins (endogenous opioids) by colitogenic T lymphocytes alleviate inflammation-induced pain by down-modulating gut-innervating nociceptor activation in periphery. In this study, we wondered whether this immune cell-derived enkephalin-mediated regulation of the nociceptor activity also operates under steady state conditions. Here, we show that chimeric mice engrafted with enkephalin-deficient bone marrow cells exhibit not only visceral hypersensitivity but also an increase in both epithelial paracellular and transcellular permeability, an alteration of the microbial topography resulting in increased bacteria-epithelium interactions and a higher frequency of IgA-producing plasma cells in Peyer's patches. All these alterations of the intestinal homeostasis are associated with an anxiety-like behavior despite the absence of an overt inflammation as observed in patients with irritable bowel syndrome. Thus, our results show that immune cell-derived enkephalins play a pivotal role in maintaining gut homeostasis and normal behavior in mice. Because a defect in the mucosal opioid system remarkably mimics some major clinical symptoms of the irritable bowel syndrome, its identification might help to stratify subgroups of patients.

Contribution of sex and gender roles to the incidence of post-infectious irritable bowel syndrome in a prospective study

Post-infectious irritable bowel syndrome (PI-IBS) occurs in about 10% of cases following gastroenteritis. The incidence of IBS is higher in females. However, it is not clear whether this is due to biological or psychosocial factors. We aimed to investigate the influence of gender roles on the incidence of PI-IBS, alongside traditional risk factors. Our study included 231 patients diagnosed with gastroenteritis who were hospitalized and treated with antibiotics between 2018 and 2021. The Korean Sex Role Inventory-Short Form (KSRI-SF), based on the Bem Sex Role Inventory (BSRI) was used to categorize patients (androgynous, masculine, feminine, and undifferentiated types). Six months after treatment, we conducted a telephone survey to confirm the presence of PI-IBS using the ROME IV criteria. Among the patients, 43.3% were female, and the mean age was 43.67 ± 16.09 years. After 6 months, 34 patients developed PI-IBS. Univariate analysis revealed that younger age, female sex, KSRI-SF undifferentiated type, and longer duration of antibiotic use independently influenced the occurrence of PI-IBS. Multivariate analysis showed that PI-IBS was associated with the KSRI-SF undifferentiated type and higher C-reactive protein (CRP) levels. Our study showed that the KSRI-SF undifferentiated type and high CRP levels at initial infection were associated with PI-IBS.

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.

Psychosocial stress-induced intestinal permeability in healthy humans: What is the evidence?

An impaired intestinal barrier function can be detrimental to the host as it may allow the translocation of luminal antigens and toxins into the subepithelial tissue and bloodstream. In turn, this may cause local and systemic immune responses and lead to the development of pathologies. In vitro and animal studies strongly suggest that psychosocial stress is one of the factors that can increase intestinal permeability via mast-cell dependent mechanisms. Remarkably, studies have not been able to yield unequivocal evidence that such relation between stress and intestinal permeability also exists in (healthy) humans. In the current Review, we discuss the mechanisms that are involved in stress-induced intestinal permeability changes and postulate factors that influence these alterations and that may explain the translational difficulties from in vitro and animal to human studies. As human research differs highly from animal research in the extent to which stress can be applied and intestinal permeability can be measured, it remains difficult to draw conclusions about the presence of a relation between stress and intestinal permeability in (healthy) humans. Future studies should bear in mind these difficulties, and more research into in vivo methods to assess intestinal permeability are warranted.

Stress-activated brain-gut circuits disrupt intestinal barrier integrity and social behaviour

Chronic stress underlies the etiology of both major depressive disorder (MDD) and irritable bowel syndrome (IBS), two highly prevalent and debilitating conditions with high rates of co-morbidity. However, it is not fully understood how the brain and gut bi-directionally communicate during stress to impact intestinal homeostasis and stress-relevant behaviours. Using the chronic social defeat stress (CSDS) model, we find that stressed mice display greater intestinal permeability and circulating levels of the endotoxin lipopolysaccharide (LPS) compared to unstressed control (CON) mice. Interestingly, the microbiota in the colon also exhibit elevated LPS biosynthesis gene expression following CSDS. Additionally, CSDS triggers an increase in pro-inflammatory colonic IFNγ+ Th1 cells and a decrease in IL4+ Th2 cells compared to CON mice, and this gut inflammation contributes to stress-induced intestinal barrier permeability and social avoidance behaviour. We next investigated the role of enteric neurons and identified that noradrenergic dopamine beta-hydroxylase (DBH)+ neurons in the colon are activated by CSDS, and that their ablation protects against gut pathophysiology and disturbances in social behaviour. Retrograde tracing from the colon identified a population of corticotropin-releasing hormone-expressing (CRH+) neurons in the paraventricular nucleus of the hypothalamus (PVH) that innervate the colon and are activated by stress. Chemogenetically activating these PVH CRH+ neurons is sufficient to induce gut inflammation, barrier permeability, and social avoidance behaviour, while inhibiting these cells prevents these effects following exposure to CSDS. Thus, we define a stress-activated brain-to-gut circuit that confers colonic inflammation, leading to impaired intestinal barrier function, and consequent behavioural deficits.

Serine proteases and metalloproteases are highly increased in irritable bowel syndrome Tunisian patients

Serine proteases are involved in many biological processes and are associated with irritable bowel syndrome (IBS) pathology. An increase in serine protease activity has been widely reported in IBS patients. While most of the studies focused on host proteases, the contribution of microbial proteases are poorly studied. In the present study, we report the analysis of proteolytic activities in fecal samples from the first Tunisian cohort of IBS-M patients and healthy individuals. We demonstrated, for the first time, that metalloproteases activities were fourfold higher in fecal samples of IBS patients compared to controls. Of interest, the functional characterization of serine protease activities revealed a 50-fold increase in trypsin-like activities and a threefold in both elastase- and cathepsin G-like activities. Remarkably, we also showed a fourfold increase in proteinase 3-like activity in the case of IBS. This study also provides insight into the alteration of gut microbiota and its potential role in proteolytic modulation in IBS. Our results stressed the impact of the disequilibrium of serine proteases, metalloproteases and gut microbiota in IBS and the need of the further characterization of these targets to set out new therapeutic approaches.

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.

The Crucial Role of the Interstitial Cells of Cajal in Neurointestinal Diseases

Neurointestinal diseases result from dysregulated interactions between the nervous system and the gastrointestinal (GI) tract, leading to conditions such as Hirschsprung's disease and irritable bowel syndrome. These disorders affect many people, significantly diminishing their quality of life and overall health. Central to GI motility are the interstitial cells of Cajal (ICC), which play a key role in muscle contractions and neuromuscular transmission. This review highlights the role of ICC in neurointestinal diseases, revealing their association with various GI ailments. Understanding the functions of the ICC could lead to innovative perspectives on the modulation of GI motility and introduce new therapeutic paradigms. These insights have the potential to enhance efforts to combat neurointestinal diseases and may lead to interventions that could alleviate or even reverse these conditions.

IBS randomized study: FODMAPs alter bile acids, phenolic- and tryptophan metabolites, while gluten modifies lipids

Diet is considered a culprit for symptoms in irritable bowel syndrome (IBS), although the mechanistic understanding of underlying causes is lacking. Metabolomics, i.e., the analysis of metabolites in biological samples may offer a diet-responsive fingerprint for IBS. Our aim was to explore alterations in the plasma metabolome after interventions with fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) or gluten versus control in IBS, and to relate such alterations to symptoms. People with IBS (n = 110) were included in a double-blind, randomized, crossover study with 1-wk provocations of FODMAPs, gluten, or placebo. Symptoms were evaluated with the IBS severity scoring system (IBS-SSS). Untargeted metabolomics was performed on plasma samples using LC-qTOF-MS. Discovery of metabolite alterations by treatment was performed using random forest followed by linear mixed modeling. Associations were studied using Spearman correlation. The metabolome was affected by FODMAP [classification rate (CR) 0.88, P < 0.0001], but less by gluten intake CR 0.72, P = 0.01). FODMAP lowered bile acids, whereas phenolic-derived metabolites and 3-indolepropionic acid (IPA) were higher compared with placebo. IPA and some unidentified metabolites correlated weakly to abdominal pain and quality of life. Gluten affected lipid metabolism weakly, but with no interpretable relationship to IBS. FODMAP affected gut microbial-derived metabolites relating to positive health outcomes. IPA and unknown metabolites correlated weakly to IBS severity. Minor symptom worsening by FODMAP intake must be weighed against general positive health aspects of FODMAP. The gluten intervention affected lipid metabolism weakly with no interpretable association to IBS severity. Registration: www.clinicaltrials.gov as NCT03653689.NEW & NOTEWORTHY In irritable bowel syndrome (IBS), fermentable oligo-, di-, monosaccharides, and polyols (FODMAPs) affected microbial-derived metabolites relating to positive health outcomes such as reduced risk of colon cancer, inflammation, and type 2 diabetes, as shown in previous studies. The minor IBS symptom induction by FODMAP intake must be weighed against the positive health aspects of FODMAP consumption. Gluten affected lipids weakly with no association to IBS severity.

Downregulated APOD and FCGR2A correlates with immune infiltration and lipid-induced symptoms of irritable bowel syndrome

Fat intake is among the most significant triggers for symptom development in patients with irritable bowel syndrome (IBS). Nevertheless, long-term restriction in fatty foods ingestion may lead to nutritional inadequacies. This study aimed to identify the crucial genes involved in lipid-induced gastrointestinal symptoms, contributing to helping IBS patients regulate fat. The clinical characteristics of the subjects were collected by questionnaire investigation and analyzed using multivariate logistic regression. Differentially expressed genes (DEG) and signaling pathways were analyzed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. ImmuInfiltration and CIBERSORT packages evaluated small intestine immune cell infiltration. Random forest and SVM-RFE algorithms were used to select hub genes. A receiver operating characteristic curve was used to access the diagnostic significance of each hub gene. Gene Set Enrichment Analysis (GSEA) was performed to identify hub genes' molecular processes in IBS development after lipid infusion. IBS patients' risk, severity, and quality of life increased with fat intake. In total, 116 robust DEGs were identified in IBS patients after lipid infusion using the GSE166869 dataset and were mainly clustered in the immune and inflammatory pathways. IBS patients had greater Neutrophils, CD4+ T cells, and M1 Macrophages than healthy controls. Furthermore, infiltration levels of Neutrophils and resting memory CD4+ T cells were inversely related to the expression of hub genes (IGKV1D-43, IGKV1-12, APOD, FCGR2A and IGKV2-29). After lipid infusion, GSEA results of each hub gene indicated the relevance of proinflammatory pathways in IBS pathogenesis. After verification, only APOD and FCGR2A were stably downregulated in small intestinal mucosa and plasma of IBS patients. The area under the curve of APOD combined with FCGR2A expression was 0.9. APOD and FCGR2A may be promising biomarkers for IBS diagnosis and lipid-sensitive IBS patients. Their potential roles in the immune microenvironment of the small intestinal mucosa may provide a vital clue to IBS precision therapy.

Associations between irritable bowel syndrome and non-alcoholic fatty liver disease: A systematic review

BACKGROUND

Irritable bowel syndrome (IBS) is associated with obesity and metabolic syndrome. IBS and non-alcoholic fatty liver disease (NAFLD) are highly prevalent entities worldwide and may share similar mechanisms including gut dysbiosis, impaired intestinal mucosal barrier and immune system activation.

AIM

To systematically review their association according to the Preferred Reporting Items for Systemic Review and Meta-analyses guidelines.

METHODS

PubMed, EMBASE and Cochrane Database of Systematic Reviews were searched for relevant papers. Manual searches were also performed.

RESULTS

Six studies were included. Both IBS and NAFLD subjects had significantly more metabolic risk factors like hypertension, obesity, dyslipidaemia and diabetes. Our review showed that 23.2% to 29.4% of NAFLD patients had IBS. IBS was significantly higher in NAFLD patients compared with patients without NAFLD (23.2% vs 12.5%, P < 0.01). A higher proportion of IBS patients had NAFLD (65.8% to 74.0%). IBS patients were three times more likely to have NAFLD compared with non-IBS patients (P < 0.001). Two studies showed a significant correlation between the severity of IBS and NAFLD. The proportion of NAFLD subjects with IBS increased with NAFLD severity.

CONCLUSION

Further prospective studies are warranted to evaluate the relationship and shared pathways between IBS and NAFLD, potentially leading to the development of future therapeutics.

The causal associations between growth factors and constipation: a two-sample Mendelian randomization study

Introduction: Certain growth factors (GFs) are associated with constipation, but few studies has analyzed the causal associations between the two. Therefore, this study used two-sample Mendelian randomization (MR) to systematically analyze the causal associations between GF levels and constipation based on data from genome-wide association studies (GWAS). Methods: Both GF and constipation data were obtained from European populations. GFs, as an exposure variable, were obtained from a genetic map of the human plasma proteome containing 3,301 samples, another GWAS dataset on 90 circulating proteins containing 30,931 samples, and a GWAS dataset containing 3,788 samples. Constipation, as an outcome variable, was obtained from the FinnGen project containing 26,919 cases and 282,235 controls and another UK Biobank dataset containing 3,328 cases and 459,682 controls. Single-nucleotide polymorphisms strongly associated with GFs were regarded as instrumental variables. Inverse-variance weighting, MR-Egger regression, weight median, simple mode, and weight mode methods were used to determine genetic associations. Cochran's Q test, Egger intercept, and Mendelian Randomization Pleiotropy RESidual Sum and Outlier tests were used to analyze sensitivity. Results: The IVW analysis based on FinnGen showed that NGFI-A-binding protein 2 and vascular endothelial growth factor receptor 2 were inversely associated with constipation, and that fibroblast growth factor 7 and transforming growth factor beta receptor II levels were positively associated with constipation. The IVW analysis based on UK Biobank showed that proheparin-binding epidermal growth factor, platelet-derived growth factor AA, and vascular endothelial growth factor₁₂₁ were inversely associated with constipation. Conclusion: This study showed that some GFs are genetically associated with the risk of constipation.

MicroRNA-29b-3p promotes intestinal permeability in IBS-D via targeting TRAF3 to regulate the NF-κB-MLCK signaling pathway

Irritable bowel syndrome with predominant diarrhea (IBS-D) is characterized by increased intestinal permeability. Previous studies have shown that the microRNA-29 gene is involved in the regulation of intestinal permeability in patients with IBS-D. NF-κB was proved to play a key role in inflammatory response of intestine and resultant disruption of tight junction integrity, whose activity could be inhibited by TNF Receptor-Associated Factor 3 (TRAF3). However, the exact mechanism that induces increased intestinal permeability in IBS-D patients has not been clarified. In this study, we found that microRNA-29b‑3p (miR-29b-3p) was significantly upregulated, while TRAF3 was decreased and the NF-κB-MLCK pathway was activated within the colonic tissue of IBS-D patients. Subsequently, we confirmed the targeting relationship between miR-29b-3p and TRAF3 through a double-luciferase reporter assay. Lentivirus transfection of NCM460 cells with miR-29b-3p-overexpressing and -silencing vectors demonstrated that the expression of TRAF3 was negatively correlated with the level of miR-29b-3p. The NF-κB/MLCK pathway was activated in the miR-29b-3p-overexpressing group and inhibited to some extent in the miR-29b-3p-silencing group. Results in WT and miR-29 knockout mice showed that miR-29b-3p levels were increased, TRAF3 levels were decreased, and the NF-κB/MLCK signaling was activated in the WT IBS-D group as compared with the WT control group. The protein levels of TRAF3 and TJs in the miR-29b-/- IBS-D group were partially recovered and NF-κB/MLCK pathway indicators were, to a certain extent, decreased as compared with the WT IBS-D group. These results suggested that miR-29b-3p deletion enhances the TRAF3 level in IBS-D mice and alleviates the high intestinal permeability. In brief, through the analysis of intestinal tissue samples from IBS-D patients and miR-29b-/- IBS-D mice, we showed that miR-29b-3p is involved in the pathogenesis of intestinal hyperpermeability in IBS-D via targeting TRAF3 to regulate the NF-κB-MLCK signaling pathway.

Overactive bladder syndrome symptoms in youth with abdominal pain-associated disorders of gut-brain interaction

The purpose of the current study was to assess the frequency of overactive bladder syndrome (OBS) symptoms and their relationship to gastrointestinal symptoms in youth with abdominal pain-associated disorders of gut-brain interaction (AP-DGBI). This is a retrospective study of 226 youth diagnosed with an AP-DGBI. As part of standard care, all patients completed a symptom questionnaire regarding gastrointestinal and non-gastrointestinal symptoms including increased urinary frequency, nighttime urination, and urinary urgency. Overall, 54% of patients reported at least one OBS symptom. Increased frequency of urination was reported by 19%, urinary urgency by 34%, and nighttime urination by 36%. Increased frequency of urination and urinary urgency were associated with a change in stool form, a change in stool frequency, and in those fulfilling criteria for IBS. Increased frequency of urination was reported more frequently in those reporting predominantly loose stools (33% vs. 12%). Urinary symptoms are common in youth with AP-DGBI. Increased urinary frequency and urinary urgency are specifically associated with IBS, with increased urinary frequency being primarily associated with diarrhea predominant IBS. Further studies are needed to determine the impact of OBS on AP-DGBI severity and quality of life, and whether they impact DGBI treatment.

Development of an Optimal In vitro Release and Permeation Testing Method for Rectal Suppositories

Currently there are no compendial assays for testing drug release from rectal suppositories. It is therefore essential to study different in vitro release testing (IVRT) and in vitro permeation testing (IVPT) methods for identifying a suitable technique to compare in vitro drug release and to predict in vivo performance of rectal suppositories. In the present study, three different rectal suppository formulations of mesalamine (CANASA, Generic, and In-house) were studied for in vitro bioequivalence. All the different suppository products were characterized by performing weight variation, content uniformity, hardness, melting time, and pH tests. Viscoelastic behavior of the suppositories was also tested both in presence and absence of mucin. Four different IVRT techniques such as Dialysis, Horizontal Ussing Chamber, Vertical Franz cell, and USP apparatus 4. IVPT studies were performed using Horizontal Ussing chamber and Vertical Franz cell methods. Q1/Q2 equivalent products (CANASA, Generic) and a half-strength product were studied to understand the reproducibility, bio relevance, and discriminatory ability of the IVRT and IVPT methods. This study is the first of its kind where molecular docking studies were performed to determine the potential interactions of drug (mesalamine) with mucin, IVRT studies were conducted with and without the presence of mucin, and porcine rectal mucosa was used to perform IVPT tests. The USP 4 method and Horizontal Ussing chamber methods were found to be suitable IVRT and IVPT techniques, respectfully, for rectal suppositories. RLD (Reference Listed Drug) and Generic rectal suppositories were found to exhibit similar release rate and permeation profiles obtained from USP 4, and the IVPT studies, respectfully. Wilcoxon Rank Sum/Mann-Whitney rank test, conducted for the IVRT profiles obtained using USP 4 method, proved the sameness of RLD and Generic suppository products.

Gut microbiota and irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder that poses a significant health concern. Although its etiology remains unknown, there is growing evidence that gut dysbiosis is involved in the development and exacerbation of IBS. Previous studies have reported altered microbial diversity, abundance, and composition in IBS patients when compared to controls. However, whether dysbiosis or aberrant changes in the intestinal microbiota can be used as a hallmark of IBS remains inconclusive. We reviewed the literatures on changes in and roles of intestinal microbiota in relation to IBS and discussed various gut microbiota manipulation strategies. Gut microbiota may affect IBS development by regulating the mucosal immune system, brain-gut-microbiome interaction, and intestinal barrier function. The advent of high-throughput multi-omics provides important insights into the pathogenesis of IBS and promotes the development of individualized treatment for IBS. Despite advances in currently available microbiota-directed therapies, large-scale, well-organized, and long-term randomized controlled trials are highly warranted to assess their clinical effects. Overall, gut microbiota alterations play a critical role in the pathophysiology of IBS, and modulation of microbiota has a significant therapeutic potential that requires to be further verified.

Understanding neuroimmune interactions in disorders of gut-brain interaction: from functional to immune-mediated disorders

Functional gastrointestinal disorders-recently renamed into disorders of gut-brain interaction-such as irritable bowel syndrome and functional dyspepsia are highly prevalent conditions with bothersome abdominal symptoms in the absence of structural abnormalities. While traditionally considered as motility disorders or even psychosomatic conditions, our understanding of the pathophysiology has evolved significantly over the last two decades. Initial observations of subtle mucosal infiltration with immune cells, especially mast cells and eosinophils, are since recently being backed up by mechanistic evidence demonstrating increased release of nociceptive mediators by immune cells and the intestinal epithelium. These mediators can activate sensitised neurons leading to visceral hypersensitivity with bothersome symptoms. The interaction between immune activation and an impaired barrier function of the gut is most likely a bidirectional one with alterations in the microbiota, psychological stress and food components as upstream players in the pathophysiology. Only few immune-targeting treatments are currently available, but an improved understanding through a multidisciplinary scientific approach will hopefully identify novel, more precise treatment targets with ultimately better outcomes.

HLA-A and HLA-B genes are involved in the pathogenesis of IBS

Irritable bowel syndrome (IBS) is the most common functional gastrointestinal disorder. The pathogenesis of IBS has not yet been fully elucidated, and the relationship between human leukocyte antigen (HLA) class I molecules and IBS is not clear. The present case-control study investigated the correlation between HLA-A and HLA-B genes and IBS. Peripheral blood samples were collected from 102 IBS patients and 108 healthy volunteers at Nanning First People's Hospital. DNA was extracted using a routine procedure, and HLA-A and HLA-B gene polymorphisms were identified by polymerase chain reaction with sequence-specific primers to determine the genotype and distribution frequency of HLA-A and HLA-B in IBS patients and healthy controls. Susceptibility and protective genes for IBS were identified using univariate and multivariate analyses. The frequency of HLA-A11 gene expression in the IBS group was significantly higher than that in the healthy control group, while the frequencies of HLA-A24, 26, and 33 gene expression were significantly higher in the healthy control group than in the IBS group (all P < .05). The frequencies of HLA-B56 and 75 (15) gene expression in the IBS group were significantly higher than those in the healthy control group, while the frequencies of HLA-B46 and 48 gene expression were significantly higher in the healthy control group than in the IBS group (all P < .05). Genes that may be related to the prevalence of IBS were included in the multivariate logistic regression, and the results suggested that the HLA-B75 (15) gene is a susceptibility gene for IBS (P = .031, odds ratio [OR] = 2.625, 95% confidence interval [CI]: 1.093-6.302), while the HLA-A24 (P = .003, OR = 0.308, 95% CI: 0.142-0.666), A26 (P = .009, OR = 0.162, 95% CI: 0.042-0.629), A33 (P = .012, OR = 0.173, 95% CI: 0.044-0.679), and B48 (P = .008, OR = 0.051, 95% CI: 0.006-0.459) genes are protective genes for IBS.

Irritable bowel syndrome: treatment based on pathophysiology and biomarkers

OBJECTIVE

To appraise the evidence that pathophysiological mechanisms and individualised treatment directed at those mechanisms provide an alternative approach to the treatment of patients with irritable bowel syndrome (IBS).

DESIGN

A PubMED-based literature review of mechanisms and treatment of IBS was conducted independently by the two authors, and any differences of perspective or interpretation of the literature were resolved following discussion.

RESULTS

The availability of several noninvasive clinical tests can appraise the mechanisms responsible for symptom generation in IBS, including rectal evacuation disorders, abnormal transit, visceral hypersensitivity or hypervigilance, bile acid diarrhoea, sugar intolerances, barrier dysfunction, the microbiome, immune activation and chemicals released by the latter mechanism. The basic molecular mechanisms contributing to these pathophysiologies are increasingly recognised, offering opportunities to intervene with medications directed specifically to food components, receptors and potentially the microbiome. Although the evidence supporting interventions for each mechanism is not at the same level of proof, the current state-of-the-art provides the opportunity to advance the practice from treatment based on symptoms to individualisation of treatment guided by pathophysiology and clinically identified biomarkers.

CONCLUSION

These advances augur well for the implementation of evidence-based individualised treatment for patients with IBS based on actionable biomarkers or psychological disturbances.

Study on the pathogenesis of MiR-6324 regulating diarrheal irritable bowel syndrome and bioinformatics analysis

Objective: To investigate the pathogenesis of IBS-D by bioinformatics analysis of the differential microRNAs in rat colon tissue and to analyze and predict the function of their target genes. Methods: Twenty male Wistar rats of SPF class were randomly divided into two groups, the model group was manipulated using the colorectal dilatation method + chronic restraint stress method to establish the IBS-D model; while the blank group stroked the perineum at the same frequency. Screening of differential miRNAs after High-throughput sequencing of rat colon tissue. GO and KEGG analysis of target genes using the DAVID website, further mapping using RStudio software; the STRING database and the Cytoscape software were used to obtain the protein interaction network (PPI) of the target genes as well as the core genes. Finally, qPCR was used to detect the expression of target genes in the colon tissue of two groups of rats. Results: After the screening, miR-6324 was obtained as the key of this study. The GO analysis of target genes of miR-6324 is mainly involved in protein phosphorylation, positive regulation of cell proliferation, and intracellular signal transduction; it affects a variety of cellular components such as cytoplasm, nucleus, and organelles on the intracellular surface; it is also involved in molecular functions such as protein binding, ATP binding, and DNA binding. KEGG analysis showed that the intersecting target genes were mainly enriched in cancer pathways, proteoglycans in cancer, neurotrophic signaling pathway, etc. The protein-protein interaction network screened out the core genes mainly Ube2k, Rnf41, Cblb, Nek2, Nde1, Cep131, Tgfb2, Qsox1, and Tmsb4x. The qPCR results showed that the expression of miR-6324 decreased in the model group, but the decrease was not significant. Conclusion: miR-6324 may be involved in the pathogenesis of IBS-D as a potential biological target and provide further ideas for research on the pathogenesis of the disease or treatment options.

TRIM27 maintains gut homeostasis by promoting intestinal stem cell self-renewal

Dysregulation of gut homeostasis is associated with irritable bowel syndrome (IBS), a chronic functional gastrointestinal disorder affecting approximately 11.2% of the global population. The poorly understood pathogenesis of IBS has impeded its treatment. Here, we report that the E3 ubiquitin ligase tripartite motif-containing 27 (TRIM27) is weakly expressed in IBS but highly expressed in inflammatory bowel disease (IBD), a frequent chronic organic gastrointestinal disorder. Accordingly, knockout of Trim27 in mice causes spontaneously occurring IBS-like symptoms, including increased visceral hyperalgesia and abnormal stool features, as observed in IBS patients. Mechanistically, TRIM27 stabilizes β-catenin and thus activates Wnt/β-catenin signaling to promote intestinal stem cell (ISC) self-renewal. Consistent with these findings, Trim27 deficiency disrupts organoid formation, which is rescued by reintroducing TRIM27 or β-catenin. Furthermore, Wnt/β-catenin signaling activator treatment ameliorates IBS symptoms by promoting ISC self-renewal. Taken together, these data indicate that TRIM27 is critical for maintaining gut homeostasis, suggesting that targeting the TRIM27/Wnt/β-catenin axis could be a potential treatment strategy for IBS. Our study also indicates that TRIM27 might serve as a potential biomarker for differentiating IBS from IBD.

Could the Microbiota Be a Predictive Factor for the Clinical Response to Probiotic Supplementation in IBS-D? A Cohort Study

BACKGROUND

Increasing evidence suggests the beneficial effects of probiotics in irritable bowel syndrome (IBS), but little is known about how they can impact the gut microbiota. Our objective was to evaluate the effects of a multistrain probiotic on IBS symptoms, gut permeability and gut microbiota in patients with diarrhoea-predominant IBS (IBS-D).

METHODS

Adults with IBS-D were enrolled in an open-label trial to receive a multistrain probiotic for 4 weeks. Abdominal pain, stool frequency, quality of life, gut permeability, and the luminal and adherent microbiota from colonic biopsies were evaluated before and after supplementation.

RESULTS

Probiotics significantly improved symptoms and quality of life, despite having no impact on permeability in the global population. In the population stratified by the response, the diarrhoea responders displayed reduced colonic permeability after supplementation. The luminal and adherent microbiota were specifically altered depending on the patients' clinical responses regarding pain and diarrhoea. Interestingly, we identified a microbial signature in IBS-D patients that could predict a response or lack of response to supplementation.

CONCLUSIONS

The multistrain probiotic improved the symptoms of IBS-D patients and induced distinct effects on the gut microbiota according to the patient's clinical response and initial microbiota composition. Our study further supports the need to develop individualised probiotic-based approaches regarding IBS.

Inflammatory Bowel Disease: A focus on the Role of Probiotics in Ulcerative Colitis

Inflammatory bowel disease (IBD) is a cluster of disorders of the gastrointestinal tract characterized by chronic inflammation and imbalance of the gut microbiota in a genetically vulnerable host. Crohn’s disease and ulcerative colitis (UC) are well-known types of IBD, and due to its high prevalence, IBD has attracted the attention of researchers globally. The exact etiology of IBD is still unknown; however, various theories have been proposed to provide some explanatory clues that include gene-environment interactions and dysregulated immune response to the intestinal microbiota. These diseases are manifested by several clinical symptoms that depend on the affected segment of the intestine such as diarrhea, abdominal pain, and rectal bleeding. In this era of personalized medicine, various options are developing starting from improved intestinal microecology, small molecules, exosome therapy, to lastly stem cell transplantation. From another aspect, and in parallel to pharmacological intervention, nutrition, and dietary support have shown effectiveness in IBD management. There is an increasing evidence supporting the benefit of probiotics in the prophylaxis and treatment of IBD. There are several studies that have demonstrated that different probiotics alleviate UC. The present review summarizes the progress in the IBD studies focusing and exploring more on the role of probiotics as a potential adjunct approach in UC management.

Fungal feelings in the irritable bowel syndrome: the intestinal mycobiome and abdominal pain

Although the gut microbiota consists of bacteria, viruses, and fungi, most publications addressing the microbiota-gut-brain axis in irritable bowel syndrome (IBS) have a sole focus on bacteria. This may relate to the relatively low presence of fungi and viruses as compared to bacteria. Yet, in the field of inflammatory bowel disease research, the publication of several papers addressing the role of the intestinal mycobiome now suggested that these low numbers do not necessarily translate to irrelevance. In this review, we discuss the available clinical and preclinical IBS mycobiome data, and speculate how these recent findings may relate to earlier observations in IBS. By surveying literature from the broader mycobiome research field, we identified questions open to future IBS-oriented investigations.

Multi-omics for biomarker approaches in the diagnostic evaluation and management of abdominal pain and irritable bowel syndrome: what lies ahead

Reliable biomarkers for common disorders of gut-brain interaction characterized by abdominal pain, including irritable bowel syndrome (IBS), are critically needed to enhance care and develop individualized therapies. The dynamic and heterogeneous nature of the pathophysiological mechanisms that underlie visceral hypersensitivity have challenged successful biomarker development. Consequently, effective therapies for pain in IBS are lacking. However, recent advances in modern omics technologies offer new opportunities to acquire deep biological insights into mechanisms of pain and nociception. Newer methods for large-scale data integration of complementary omics approaches have further expanded our ability to build a holistic understanding of complex biological networks and their co-contributions to abdominal pain. Here, we review the mechanisms of visceral hypersensitivity, focusing on IBS. We discuss candidate biomarkers for pain in IBS identified through single omics studies and summarize emerging multi-omics approaches for developing novel biomarkers that may transform clinical care for patients with IBS and abdominal pain.

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].

Fecal Luminal Factors from Patients with Gastrointestinal Diseases Alter Gene Expression Profiles in Caco-2 Cells and Colonoids

Previous in vitro studies have shown that the intestinal luminal content, including metabolites, possibly regulates epithelial layer responses to harmful stimuli and promotes disease. Therefore, we aimed to test the hypothesis that fecal supernatants from patients with colon cancer (CC), ulcerative colitis (UC) and irritable bowel syndrome (IBS) contain distinct metabolite profiles and establish their effects on Caco-2 cells and human-derived colon organoids (colonoids). The metabolite profiles of fecal supernatants were analyzed by liquid chromatography-mass spectrometry and distinguished patients with CC (n = 6), UC (n = 6), IBS (n = 6) and healthy subjects (n = 6). Caco-2 monolayers and human apical-out colonoids underwent stimulation with fecal supernatants from different patient groups and healthy subjects. Their addition did not impair monolayer integrity, as measured by transepithelial electrical resistance; however, fecal supernatants from different patient groups and healthy subjects altered the gene expression of Caco-2 monolayers, as well as colonoid cultures. In conclusion, the stimulation of Caco-2 cells and colonoids with fecal supernatants derived from CC, UC and IBS patients altered gene expression profiles, potentially reflecting the luminal microenvironment of the fecal sample donor. This experimental approach allows for investigating the crosstalk at the gut barrier and the effects of the gut microenvironment in the pathogenesis of intestinal diseases.

The relationship between hot flashes and fatty acid binding protein 2 in postmenopausal women

INTRODUCTION

Hot flashes, the most bothering symptom of menopause, are linked to a metabolic inflammation. Due to estrogen deficiency in menopause, dysbiosis is observed. The intestinal barrier affects the interaction of microbiota in healthy or unhealthy individuals. This study investigates the relationship between hot flashes and gut permeability in postmenopausal women.

PARTICIPANTS AND DESIGN

In this cross-sectional study, we divided 289 women, aged 40-65 years, into four groups based on their hot-flash severity: HF0: never experienced hot flashes; HFm: mild hot flashes; HFM: moderate hot flashes; HFS: severe hot flashes. The measured variables included the clinical parameters; hot flashes experience; fasting plasma levels of zonulin, fatty acid binding protein 2 (FABP2), endotoxin, and cytokines/chemokines. We used multiple linear regression analysis to evaluate the relationship between hot flashes and the previously mentioned gut barrier proteins.

SETTINGS

The study was performed in a hospital medical center.

RESULTS

The hot flashes had a positive tendency toward increased levels of circulating FABP2 (P-trend = 0.001), endotoxin (P-trend = 0.031), high-sensitivity C-reactive protein (hs-CRP) (P-trend = 0.033), tumor necrosis factor alpha (TNF-α) (P-trend = 0.017), and interferon-inducible protein-10 (IP10) (P-trend = 0.021). Spearman's correlation analysis revealed significant correlations of FABP2 with endotoxin, TNF-α, monocyte chemoattractant protein-1, IP10, and hs-CRP in the 289 postmenopausal women included in this study. Linear regression analysis revealed that hot-flash severity had significant assoiciations with FABP2 (P-trend = 0.002), but not with zonulin. After adjusting for body mass index, age, and menopause duration, multivariate linear regression analysis revealed the differences between HFs (% difference (95% confidence interval), 22.36 (8.04, 38.59), P = 0.01) and HF0 groups in terms of FABP2 levels.

CONCLUSIONS

This study shows that hot flashes are significantly associated with FABP2 levels in postmenopausal women. It suggests that severe hot flashes are linked to an increase in intestinal barrier permeability and low-grade systemic inflammation.

The Interplay between Gut Microbiota and Parkinson's Disease: Implications on Diagnosis and Treatment

The bidirectional interaction between the gut microbiota (GM) and the Central Nervous System, the so-called gut microbiota brain axis (GMBA), deeply affects brain function and has an important impact on the development of neurodegenerative diseases. In Parkinson’s disease (PD), gastrointestinal symptoms often precede the onset of motor and non-motor manifestations, and alterations in the GM composition accompany disease pathogenesis. Several studies have been conducted to unravel the role of dysbiosis and intestinal permeability in PD onset and progression, but the therapeutic and diagnostic applications of GM modifying approaches remain to be fully elucidated. After a brief introduction on the involvement of GMBA in the disease, we present evidence for GM alterations and leaky gut in PD patients. According to these data, we then review the potential of GM-based signatures to serve as disease biomarkers and we highlight the emerging role of probiotics, prebiotics, antibiotics, dietary interventions, and fecal microbiota transplantation as supportive therapeutic approaches in PD. Finally, we analyze the mutual influence between commonly prescribed PD medications and gut-microbiota, and we offer insights on the involvement also of nasal and oral microbiota in PD pathology, thus providing a comprehensive and up-to-date overview on the role of microbial features in disease diagnosis and treatment.

The chemistry and efficacy benefits of polysaccharides from Atractylodes macrocephala Koidz

Atractylodes macrocephala Koidz (AM), traditional Chinese medicine (TCM) with many medicinal values, has a long usage history in China and other oriental countries. The phytochemical investigation revealed the presence of volatile oils, polysaccharides, lactones, flavonoids, and others. The polysaccharides from AM are important medicinal components, mainly composed of glucose (Glc), galactose (Gal), rhamnose (Rha), arabinose (Ara), mannose (Man), galacturonic acid (GalA) and xylose (Xyl). It also showed valuable bioactivities, such as immunomodulatory, antitumour, gastroprotective and intestinal health-promoting, hepatoprotective, hypoglycaemic as well as other activities. At the same time, based on its special structure and pharmacological activity, it can also be used as immune adjuvant, natural plant supplement and vaccine adjuvant. The aim of this review is to summarize and critically analyze up-to-data on the chemical compositions, biological activities and applications of polysaccharide from AM based on scientific literatures in recent years.

Effect of a Multistrain Probiotic on Leaky Gut in Patients with Diarrhea-Predominant Irritable Bowel Syndrome: A Pilot Study

BACKGROUND

A probiotic mixture prevented epithelial barrier impairment in various experimental models. The objective was to evaluate its effects in patients suffering from IBS with diarrhea (IBS-D) with confirmed leaky gut.

METHODS

IBS-D patients with increased intestinal permeability measured by radionuclide tracers were enrolled in this pilot, open-label, prospective, interventional, single-center, Phase IV study. Patients received two capsules of a multistrain probiotic a day for 30 days and were evaluated by repeated intestinal permeability tests, the Bristol Stool Scale, and patient-perceived quality of life and satisfaction.

RESULTS

Of the 30 enrolled patients (mean age: 42.1 [SD: 13.1] years; female: 60%), 27 completed the study (full analysis set [FAS]), and 18 had no major protocol violation (per protocol set [PPS]). On D30, an improvement of intestinal permeability was observed in 81.5% of patients in FAS, normalization being observed in 37% of the participants (44% in PPS). The mean intestinal permeability was significantly decreased: baseline minus D30, 3.4 (95% CI: 1.7, 5.2); the IBS-QOL total score was significantly increased: D30 minus baseline, 8.0 (95% CI: 3.0, 12.9); and stool consistency was significantly improved. On D15 and D30, 96.3% of patients claimed that their IBS symptoms had been satisfactory alleviated, and a significant improvement was reported for the following VAS-IBS items: abdominal pain, diarrhea, and impact of gastrointestinal problems in daily life. Compliance and tolerance were satisfactory.

CONCLUSION

The multistrain probiotic tested may reduce intestinal permeability in a considerable proportion of patients and may improve abdominal pain, stool consistency, and quality of life. These results pave the way for larger, placebo-controlled clinical studies.

Maintenance of Intestinal Homeostasis in Diarrhea-Predominant Irritable Bowel Syndrome by Electroacupuncture Through Submucosal Enteric Glial Cell-Derived S-Nitrosoglutathione

Objective: To determine whether electroacupuncture (EA) maintains intestinal homeostasis in diarrhea-predominant irritable bowel syndrome (IBS-D) rats by repairing intestinal barrier function through enteric glial cell (EGC)-derived S-nitrosoglutathione (GSNO).

Methods: Sprague–Dawley rats were randomly divided into a control group (n = 10) and an IBS-D group (n = 20). These rats received senna solution by gavage and chronic unpredictable mild stress for 14 days and were further divided into a model group (n = 10) and an EA group (n = 10). Rats in the EA group were electroacupunctured at ST25 (Tianshu), ST36 (Zusanli), and LR3 (Taichong) for 20 min every day for 14 days. The abdominal withdrawal reflex (AWR), the percentage of time spent in open arms (OT%) in the elevated plus maze test, and the diarrhea index (DI) were measured. Histopathological examination was performed to evaluate the pathological features of the colon after sacrificing the rats. Transmission electron microscopy was used to observe the EGC in the muscle and submucosal layers. Enzyme-linked immunosorbent assay was performed to detect GSNO expression in the colon. Double immunofluorescence labeling was used to detect the colocalized GFAP and GSNO expressions in the muscle and submucosal layers. Plasma FITC-dextran was used to measure intestinal permeability, whereas western blot was used to detect ZO-1 and occludin expressions in the colon.

Results: OT% and ZO-1 and occludin expressions were significantly lower than those of the control group, whereas AWR scores, DI, GSNO expression in the colon, colocalized GFAP and GSNO expressions in the submucosal layer, and intestinal permeability were significantly higher than those of the control group. Structural EGC abnormalities were observed in the model group. After EA treatment, OT% and ZO-1 and occludin expressions increased significantly, whereas AWR scores, DI, GSNO expression, colocalized GFAP and GSNO expressions in the submucosal layer, and intestinal permeability decreased significantly. The EGC structure was then restored to its normal state.

Conclusion: EA treatment downregulates the submucosal EGC–derived GSNO expressions, repairs the intestinal barrier by upregulating the ZO-1 and occludin expression, and improves IBS-D symptoms, including visceral hypersensitivity, anxiety, and diarrhea, suggesting a potential role for EGC-derived GSNO in the regulation of intestinal homeostasis in IBS-D rats.