Pathophysiology of irritable bowel syndrome

Enteric Microbiota-Mediated Serotonergic Signaling in Pathogenesis of Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a chronic functional disorder that affects the gastrointestinal tract. Details regarding the pathogenesis of IBS remain largely unknown, though the dysfunction of the brain-gut-microbiome (BGM) axis is a major etiological factor, in which neurotransmitters serve as a key communication tool between enteric microbiota and the brain. One of the most important neurotransmitters in the pathology of IBS is serotonin (5-HT), as it influences gastrointestinal motility, pain sensation, mucosal inflammation, immune responses, and brain activity, all of which shape IBS features. Genome-wide association studies discovered susceptible genes for IBS in serotonergic signaling pathways. In clinical practice, treatment strategies targeting 5-HT were effective for a certain portion of IBS cases. The synthesis of 5-HT in intestinal enterochromaffin cells and host serotonergic signaling is regulated by enteric resident microbiota. Dysbiosis can trigger IBS development, potentially through aberrant 5-HT signaling in the BGM axis; thus, the manipulation of the gut microbiota may be an alternative treatment strategy. However, precise information regarding the mechanisms underlying the microbiota-mediated intestinal serotonergic pathway related to the pathogenesis of IBS remains unclear. The present review summarizes current knowledge and recent progress in understanding microbiome–serotonin interaction in IBS cases.

Irritable Bowel Syndrome, Depression, and Neurodegeneration: A Bidirectional Communication from Gut to Brain

Patients with irritable bowel syndrome (IBS) are increasingly presenting with a wide range of neuropsychiatric symptoms, such as deterioration in gastroenteric physiology, including visceral hypersensitivity, altered intestinal membrane permeability, and gastrointestinal motor dysfunction. Functional imaging of IBS patients has revealed several abnormalities in various brain regions, such as significant activation of amygdala, thinning of insular and anterior cingulate cortex, and increase in hypothalamic gray matter, which results in poor psychiatric and cognitive outcomes. Interrelations between the enteric and central events in IBS-related gastrointestinal, neurological, and psychiatric pathologies have compelled researchers to study the gut-brain axis-a bidirectional communication that maintains the homeostasis of the gastrointestinal and central nervous system with gut microbiota as the protagonist. Thus, it can be disrupted by any alteration owing to the gut dysbiosis or loss of diversity in microbial composition. Available evidence indicates that the use of probiotics as a part of a balanced diet is effective in the management of IBS and IBS-associated neurodegenerative and psychiatric comorbidities. In this review, we delineate the pathogenesis and complications of IBS from gastrointestinal and neuropsychiatric standpoints while also discussing the neurodegenerative events in enteric and central nervous systems of IBS patients and the therapeutic potential of gut microbiota-based therapy established on clinical and preclinical data.

Bioactive Compounds in Food as a Current Therapeutic Approach to Maintain a Healthy Intestinal Epithelium

The intestinal epithelium serves as an effective barrier against the external environment, hampering the passage of potentially harmful substances (such as pathogenic microbes) that could trigger an exacerbated host immune response. The integrity of this barrier is thus essential for the maintenance of proper intestinal homeostasis and efficient protective reactions against chemical and microbial challenges. The principal consequence of intestinal barrier defects is an increase in intestinal permeability, which leads to an increased influx of luminal stressors, such as pathogens, toxins, and allergens, which in turn trigger inflammation and immune response. The fine and fragile balance of intestinal homeostasis can be altered by multiple factors that regulate barrier function, many of which are poorly understood. This review will address the role of gut microbiota as well as food supplements (such as probiotics, prebiotics, and synbiotics) in modulating gut health and regulating intestinal barrier function. In particular, we will focus on three human pathologies: inflammatory bowel disease, irritable bowel syndrome, and food allergy.

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

ETHNOPHARMACOLOGICAL RELEVANCE

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

AIM OF THE STUDY

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

The Effect of Bifidobacterium on Reducing Symptomatic Abdominal Pain in Patients with Irritable Bowel Syndrome: A Systematic Review

Probiotics, specifically Bifidobacteria, may improve abdominal pain in patients with irritable bowel syndrome (IBS); however, results from randomised controlled trials (RCTs) are conflicting. Here, we systematically reviewed the efficacy of Bifidobacteria on abdominal pain in IBS. We searched MEDLINE, EMBASE and the Cochrane Controlled Trials Register from inception to 20 May 2019, without language or date restrictions. The search strategy comprised of the combination of three concepts: supplementation, abdominal pain, and IBS. Inclusion criteria included double-blind placebo-controlled RCTs featuring Bifidobacteria supplementation in Rome-diagnosed IBS patients. A total of 8 RCTs involving a total of 1045 patients with Rome diagnosed IBS were included. The dose of total Bifidobacteria ranged from 10⁶ to > 10¹¹ cfu (colony-forming unit) and duration of supplementation ranged between 2 and 8 weeks. Bifidobacteria was delivered through either intake of fermented milk products, encapsulation or via a malted milk beverage, with all studies assessing abdominal pain via a visual analogue Likert scale. From the studies included, 50% (n = 4) of studies found a statistically significant improvement in abdominal pain following Bifidobacteria supplementation compared to placebo, 38% (n = 3) of studies found non-significant improvements and 12% (n = 1) showed a statistically significant dose-response effect of improvement. The evidence shows a heterogeneity of effect for Bifidobacteria dependent upon strain, dosage and delivery method. While not all studies demonstrate significant improvements in abdominal pain, none of the selected studies reported an increase in pain or other adverse effects.

Distinct Small Intestine Mast Cell Histologic Changes in Patients With Hereditary Alpha-tryptasemia and Mast Cell Activation Syndrome

Mast cells (MCs) are important in intestinal homeostasis and pathogen defense but are also implicated in many of the clinical manifestations in disorders such as irritable bowel syndrome. The utility of specific staining for MCs to quantify and phenotype them in intestinal biopsies in patients with gastrointestinal (GI) symptoms is controversial and is not a widely adopted practice. Whether or not intestinal MCs are increased or have a unique phenotype in individuals with hereditary alpha-tryptasemia (HαT), who have extra copies of the MC tryptase gene TPSAB1 and typically elevated baseline serum tryptase levels >8 ng/mL is not known. We examined the duodenal biopsies of 17 patients with HαT and compared them to 15 patients with mast cell activation syndrome who had baseline serum tryptases <8 ng/mL (MCAS-NT) and 12 GI-controls. We determined that the HαT subjects had increased MCs in the duodenum compared with MCAS-NT and GI-controls (median=30.0; interquartile range [IQR]: 20.0 to 40.0 vs. median=15.0; IQR: 5.00 to 20.0; P=0.013 and median=15.0; IQR: 13.8 to 20.0; P=0.004, respectively). These MCs were significantly found in clusters (<15 MCs) and were located throughout the mucosa and submucosa including the superficial villi compared with MCAS-NT and GI-control patients. Spindle-shaped MCs were observed in all groups including controls. These data demonstrate that HαT is associated with increased small intestinal MCs that may contribute to the prevalent GI manifestations observed among individuals with this genetic trait.

Impact of Psychological Comorbidity on the Prognosis of Irritable Bowel Syndrome

INTRODUCTION

Psychological comorbidities are associated with irritable bowel syndrome (IBS), but little is known about their cumulative effect on its prognosis. We examined this issue in a longitudinal 12-month follow-up study.

METHODS

We collected complete demographic, symptom, and psychological comorbidity data (anxiety, depression, somatic symptom disorder, perceived stress, and gastrointestinal symptom-specific anxiety) at baseline from 807 adults who met Rome IV criteria for IBS. At 12 months, we collected data regarding IBS symptom severity and impact, consultation behavior, and treatments commenced from 452 individuals successfully followed up. We examined the cumulative effects of psychological comorbidities at baseline on subsequent IBS disease behavior.

RESULTS

At baseline, among the 807 participants, 177 (21.9%) had 1, 139 (17.2%) 2, 103 (12.8%) 3, 89 (11.0%) 4, and 54 (6.7%) 5 psychological comorbidities. IBS symptom severity at baseline increased significantly with the number of psychological comorbidities (72.2% of those with 5 psychological comorbidities reported severe symptoms, vs 29.1% of those with none, P < 0.001). Among 452 (56.0%) participants followed up at 12 months, those with a higher number of psychological comorbidities at baseline were significantly more likely to have seen a gastroenterologist (33.3% of those with 5 psychological comorbidities, vs 21.4% of those with none, P = 0.001), cycle through more treatments (P < 0.0001), to report more severe IBS symptoms (66.7% with 5, vs 24.4% with none, P < 0.001) and continuous abdominal pain (22.1% with none, vs 61.9% with 5, P < 0.001), and to report that symptoms impacted on daily activities ≥50% of the time (90.5% with 5, vs 41.2% with none, P < 0.001).

DISCUSSION

The prognosis of individuals with Rome IV-defined IBS worsens according to incremental increases in psychological comorbidity. This has important clinical and research implications.

The effect of faecal microbiota transplantation on abdominal pain, stool frequency, and stool form in patients with moderate-to-severe irritable bowel syndrome: results from a randomised, double-blind, placebo-controlled study

BACKGROUND

Irritable bowel syndrome (IBS) is associated with intestinal dysbiosis. Therefore, faecal microbiota transplantation (FMT) has been hypothesised to have a positive effect in patients with IBS. In this study, we analysed previously unexamined data from our randomised, double-blind, placebo-controlled study (trial registration number NCT02788071). The objective was to evaluate the effect of FMT on abdominal pain, stool frequency, and stool form.

METHOD

The study included 52 adult patients with moderate-to-severe IBS assigned randomly to treatment with FMT capsules or placebo capsules (1:1) for 12 days. The patients were followed for a total of six months, during which they kept a daily symptom diary tracking their abdominal pain on a scale from 0-10 and their bowel movements using the Bristol Stool Form Scale (BSFS). Diary data were not collected before treatment start.

RESULTS

A statistically significant improvement in stool frequency was found in the FMT group from during treatment to post-treatment and 1 month. No statistically significant differences were found between groups at any time during the study for any of abdominal pain, stool frequency, and stool form (as measured by weighted stool score).

CONCLUSION

In this analysis of results from a randomised, double-blind, placebo-controlled study, we found no clinically beneficial effect of FMT on abdominal pain, stool frequency, or stool form. However, since the current literature on the potential role of FMT in treating IBS shows conflicting results, further studies are required. To assess treatment efficacy, we recommend future studies to include daily symptom diaries both before and after treatment intervention.

Corneal neuropathic pain in irritable bowel syndrome: clinical findings and in vivo corneal confocal microscopy

PURPOSE

Ocular discomfort is a common symptom in central sensitization syndromes. The aim of this study was to evaluate ocular surface discomfort and related corneal changes in patients with irritable bowel syndrome.

METHODS

Twenty-nine patients with IBS (20 female, 9 male, mean age: 45.3 ± 10.1 years) and 37 healthy control subjects (25 female, 12 male, mean age: 44.95 ± 9.76 years) were included. A detailed ophthalmological examination was performed to all participants including tear break-up time (TBUT) and Schirmer test I with anesthetic (SIT). Ocular discomfort was evaluated using the ocular surface disease index (OSDI) questionnaire and corneal sensation was evaluated with Cochet-Bonnet esthesiometer. Corneal subbasal nerve plexus was evaluated with in vivo corneal confocal microscopy (IVCM).

RESULTS

There was no significant difference between the groups for age, gender distribution, and visual acuity. OSDI scores were significantly higher (p = 0.008) and TBUT was significantly reduced in patients with IBS compared to controls (p = 0.001 for right eye, p = 0.014 for left eye). However, there was no significant difference in corneal touch sensation and SIT results between the groups. IVCM revealed that corneal nerve fiber density, corneal nerve branch density, and corneal nerve fiber length were significantly reduced in patients with IBS (p < 0.001, p < 0.001, and p = 0.023, respectively).

CONCLUSION

Patients with IBS have increased dry eye-associated ocular surface complaints and nerve fiber loss in corneal subbasal nerve plexus. IBS should be remembered in the differential diagnosis, when there is discordance between the level of ocular surface discomfort and dry eye disease associated corneal findings.

"Association between dietary inflammatory index (DII) and risk of irritable bowel syndrome: a case-control study"

Background

Pathophysiology of IBS is not well recognized; however, several studies have shown the possible relationship between diet and risk of IBS. We assessed the ability of the dietary inflammatory index (DII) to predict the risk of IBS.

Methods

The subjects were 155 IBS cases and 310 age- and sex-matched healthy controls (aged ≥18 years). The participants were recruited from June, 2019 to March, 2020. IBS was recognized using the Rome IV criteria. DII score was computed based on dietary intake using a 168-item FFQ. The DII score was calculated based on energy-adjusted amounts of nutrients using residual method. Logistic regression models were used to estimate multivariable odds ratios (ORs).

Results

The mean DII score was significantly higher among IBS patients in comparison to healthy controls (0.78 ± 2.22 vs. − 0.39 ± 2.27). In crude model, increase in DII as continuous variable was associated with a significant increase in the risk of IBS (OR (95% CI): 1.26 (1.1–15.38)). Furthermore, the association remained significant even after adjusting for age and sex (OR (95% CI): 1.28 (1.1–17.41)) and after multivariate adjustment (OR (95% CI): 1.38 (1.2–1.56)). In crude, age and sex adjusted and multivariate-adjusted models subjects in fourth quartile of DII had higher OR in comparison to subjects in first quartile.

Conclusions

This study showed a possible positive association between a pro-inflammatory diet and the risk of IBS. Thus, encouraging intake of more anti-inflammatory dietary factors and reducing intake of pro-inflammatory factors may be a strategy for reducing risk of IBS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12937-021-00721-5.

Disruption of the pro-inflammatory, anti-inflammatory cytokines and tight junction proteins expression, associated with changes of the composition of the gut microbiota in patients with irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a pathologic condition characterized by changes in gut microbiome composition, low-grade inflammation, and disruption of intestinal wall permeability. The interaction between the gut microbiome and the disease manifestation remains unclear. The changing of tight junction proteins and cytokines expression throughout the gastrointestinal tract in IBS patients has not been studied yet.

AIM OF THE STUDY

To assess the changes of gut microbiome composition, tight junction proteins, and cytokines expression of intestinal mucosa from the duodenum to the distal part of the colon in IBS patients and healthy volunteers.

METHODS

In 31 IBS patients (16 patients with IBS-D; 15 patients with IBS-C) and 10 healthy volunteers the expression of CLD-2, CLD-3, CLD-5, IL-2, IL-10, and TNF-α in mucosal biopsy specimens was determined by morphological and immune-histochemical methods. The qualitative and quantitative composition of the intestinal microbiota was assessed based on 16S rRNA gene sequencing in both groups of patients.

RESULTS

The expression of IL-2 and TNF-α was significantly increased in IBS patients compared with the controls (p<0.001), with a gradual increase from the duodenum to the sigmoid colon. The expression of IL-10, CLD-3, and CLD-5 in mucosal biopsy specimens of these patients was lower than in the control group (p<0.001). Increased ratios of Bacteroidetes and decreased ratios of Firmicutes were noted in IBS patients compared to healthy volunteers (p<0.05).

CONCLUSION

IBS patients have impaired gut permeability and persisting low-grade inflammation throughout the gastrointestinal tract. Changes in the gut microbiota may support or exacerbate these changes.

Updates on the epidemiology, pathogenesis, diagnosis, and management of postinfectious irritable bowel syndrome

PURPOSE OF REVIEW

With its impact on quality of life and increasing awareness, postinfectious irritable bowel syndrome (PI-IBS) is now gaining attention as one of the major health problems commonly encountered in gastrointestinal practice. Literature investigating the various pathogenic mechanisms involved is rapidly emerging. The objective of the current review is to provide an update on recent evidence published in the past 2 years describing advances in our understanding of the epidemiology, pathogenesis, diagnosis, and treatment of PI-IBS.

RECENT FINDINGS

Significant proportion of research in the recent past was preclinical in nature. Epidemiological studies continue to highlight the risk of IBS after infection, with recent studies documenting postprotozoal effects. Advances in pathogenic mechanisms included clinical studies, which documented micro-RNA down-regulation and Peroxiredoxin-1 up-regulation in colonic mucosa of PI-IBS patients. Protease-activated receptor-2 (PAR-2) activation in PI-IBS mice models resulted in increase in epithelial permeability, mucosal inflammation, visceral hypersensitivity. Moxibustion and rifamycin reduced intestinal inflammation by inhibiting cytokine and chemokine release via different mechanisms. Miltefosine reduced mast cell degranulation and TRPV1 activation, thereby reducing visceral hypersensitivity.

SUMMARY

At present, generalization of limited diagnostic and therapeutic strategies across a heterogeneous prevalent patient population impedes the ability to provide effective personalized care in PI-IBS. Further development in pathogenesis discovery, diagnostic tool development are needed in order to design well tolerated and effective therapies that guide treatments based on distinct pathways of disease.

Local Colonic Administration of a Serine Protease Inhibitor Improves Post-Inflammatory Visceral Hypersensitivity in Rats

Dysregulation of the protease–antiprotease balance in the gastrointestinal tract has been suggested as a mechanism underlying visceral hypersensitivity in conditions such as inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). We aimed to study the potential therapeutic role of an intracolonically administered serine protease inhibitor for the treatment of abdominal pain in a post-inflammatory rat model for IBS. An enema containing 2,4,6-trinitrobenzene sulfonic acid (TNBS) was used to induce colitis in male Sprague–Dawley rats, whereas controls received a saline solution. Colonoscopies were performed to confirm colitis and follow-up mucosal healing. In the post-inflammatory phase, the serine protease inhibitor UAMC-00050 (0.1–5 mg/kg) or its vehicle alone (5% DMSO in H₂O) was administered in the colon. Thirty minutes later, visceral mechanosensitivity to colorectal distensions was quantified by visceromotor responses (VMRs) and local effects on colonic compliance and inflammatory parameters were assessed. Specific proteolytic activities in fecal and colonic samples were measured using fluorogenic substrates. Pharmacokinetic parameters were evaluated using bioanalytical measurements with liquid chromatography–tandem mass spectrometry. Post-inflammatory rats had increased trypsin-like activity in colonic tissue and elevated elastase-like activity in fecal samples compared to controls. Treatment with UAMC-00050 decreased trypsin-like activity in colonic tissue of post-colitis animals. Pharmacokinetic experiments revealed that UAMC-00050 acted locally, being taken up in the bloodstream only minimally after administration. Local administration of UAMC-00050 normalized visceral hypersensitivity. These results support the role of serine proteases in the pathophysiology of visceral pain and the potential of locally administered serine protease inhibitors as clinically relevant therapeutics for the treatment of IBS patients with abdominal pain.

Nociplastic pain: towards an understanding of prevalent pain conditions

Nociplastic pain is the semantic term suggested by the international community of pain researchers to describe a third category of pain that is mechanistically distinct from nociceptive pain, which is caused by ongoing inflammation and damage of tissues, and neuropathic pain, which is caused by nerve damage. The mechanisms that underlie this type of pain are not entirely understood, but it is thought that augmented CNS pain and sensory processing and altered pain modulation play prominent roles. The symptoms observed in nociplastic pain include multifocal pain that is more widespread or intense, or both, than would be expected given the amount of identifiable tissue or nerve damage, as well as other CNS-derived symptoms, such as fatigue, sleep, memory, and mood problems. This type of pain can occur in isolation, as often occurs in conditions such as fibromyalgia or tension-type headache, or as part of a mixed-pain state in combination with ongoing nociceptive or neuropathic pain, as might occur in chronic low back pain. It is important to recognise this type of pain, since it will respond to different therapies than nociceptive pain, with a decreased responsiveness to peripherally directed therapies such as anti-inflammatory drugs and opioids, surgery, or injections.

Comparison of acupuncture and pinaverium bromide in the treatment of irritable bowel syndrome: A protocol for systematic review and meta-analysis

BACKGROUND

Irritable bowel syndrome (IBS) is one of the most common chronic gastrointestinal diseases, and the current diagnosis of IBS is still based on symptoms and examination. Pinaverium bromide is commonly used as an antispasmodic in the treatment of IBS. But adverse effects of pinaverium bromide are common. Meta-analyses show that acupuncture has a positive therapeutic effect on IBS.

METHODS

Randomized controlled trials of comparing the efficacy of acupuncture and pinaverium bromide in the treatment of IBS will be searched in the relevant database: PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang Database, Chinese Biomedical Literature Database (CBM), and Chinese Scientific Journal Database (VIP database). The studies selected will be exported to EndNote V.9.1 software. Data will be carried out independently from the selected articles by 2 reviewers. Any disagreement will be solved in consultation with a third reviewer.

RESULTS

Our study aims to compare the efficacy of acupuncture and pinaverium bromide in the treatment of IBS and to fill the lack of relevant evidence.

CONCLUSION

Through the inclusion of relevant literature, the overall efficacy of acupuncture and pinaverium bromide in the treatment of IBS will be evaluated, and the gap between various acupuncture treatment measures will be further analyzed.

INPLASY REGISTRATION NUMBER

INPLASY 202130068.

Global research trends in the microbiome related to irritable bowel syndrome: A bibliometric and visualized study

BACKGROUND

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder. Dysregulation of the gut–brain axis plays a central role in the pathophysiology of IBS. It is increasingly clear that the microbiome plays a key role in the development and normal functioning of the gut–brain axis.

AIM

To facilitate the identification of specific areas of focus that may be of relevance to future research. This study represents a bibliometric analysis of the literature pertaining to the microbiome in IBS to understand the development of this field.

METHODS

The data used in our bibliometric analysis were retrieved from the Scopus database. The terms related to IBS and microbiome were searched in titles or abstracts within the period of 2000–2019. VOSviewer software was used for data visualization.

RESULTS

A total of 13055 documents related to IBS were retrieved at the global level. There were 1872 scientific publications focused on the microbiome in IBS. There was a strong positive correlation between publication productivity related to IBS in all fields and productivity related to the microbiome in IBS (r = 0.951, P < 0.001). The United States was the most prolific country with 449 (24%) publications, followed by the United Kingdom (n = 176, 9.4%), China (n = 154, 8.2%), and Italy (n = 151, 8.1%). The h-index for all retrieved publications related to the microbiome in IBS was 138. The hot topics were stratified into four clusters: (1) The gut–brain axis related to IBS; (2) Clinical trials related to IBS and the microbiome; (3) Drug-mediated manipulation of the gut microbiome; and (4) The role of the altered composition of intestinal microbiota in IBS prevention.

CONCLUSION

This is the first study to evaluate and quantify global research productivity pertaining to the microbiome in IBS. The number of publications regarding the gut microbiota in IBS has continuously grown since 2013. This finding suggests that the future outlook for interventions targeting the gut microbiota in IBS remains promising.

Exploring Quality of Life, Stress, and Risk Factors Associated with Irritable Bowel Syndrome for Female University Students in Taiwan

Irritable bowel syndrome (IBS) is a common recurrent functional gastrointestinal disorder that impacts on patients physically and mentally. Studies on IBS have focused on adults, yet few studies have examined IBS among female university students. The aim of this study was to investigate the prevalence of IBS for female university students and its related factors. Using a cross-sectional study design, a total of 2520 female university students were recruited in southern Taiwan. The structured questionnaires, including the Rome III IBS diagnostic questionnaire, IBS symptom severity scale, Perceived Stress Scale, and World Health Organization Quality of Life BREF questionnaire (WHOQOL-BREF) were used for data collection. A total of 1894 female students complete the questionnaires. The response rate was 75.15%. The results indicated 193 female students with IBS and the prevalence of IBS was 10.1%. IBS female students had higher levels of stress and lower QOL than non-IBS female students. The risk factors for female university students developing IBS were dysmenorrhea, food avoidance, class absenteeism, and the lower physical domain of QOL. It is advised to consider these factors when providing students with counselling and relevant services in the expectation of alleviating their IBS symptoms, reducing the incidence rate of IBS, and further improving their QOL.

Fructose malabsorption: causes, diagnosis and treatment

This review intends to act as an overview of fructose malabsorption (FM) and its role in the aetiology of diseases including, but not limited to, irritable bowel syndrome (IBS) and infantile colic and the relationship between fructose absorption and the propagation of some cancers. IBS results in a variety of symptoms including stomach pains, cramps and bloating. Patients can be categorised into two groups, depending on whether the patients’ experiences either constipation (IBS-C) or diarrhoea (IBS-D). FM has been proposed as a potential cause of IBS-D and other diseases, such as infantile colic. However, our knowledge of FM is limited by our understanding of the biochemistry related to the absorption of fructose in the small intestine and FM’s relationship with small intestinal bacterial overgrowth. It is important to consider the dietary effects on FM and most importantly, the quantity of excess free fructose consumed. The diagnosis of FM is difficult and often requires indirect means that may result in false positives. Current treatments of FM include dietary intervention, such as low fermentable oligo-, di-, monosaccharides and polyols diets and enzymatic treatments, such as the use of xylose isomerase. More research is needed to accurately diagnose and effectively treat FM. This review is designed with the goal of providing a detailed outline of the issues regarding the causes, diagnosis and treatment of FM.

Management of irritable bowel syndrome with diarrhea: focus on eluxadoline

OBJECTIVE

We sought to summarize current recommendations for the diagnosis of diarrhea-predominant irritable bowel syndrome (IBS-D) and describe available management options, highlighting a newer US Food and Drug Administration (FDA)-approved agent, eluxadoline.

METHODS

Literature on IBS-D was assessed up to January 2020 using PubMed, with key search terms including "IBS-D diagnosis", "IBS-D management", and "eluxadoline".

RESULTS

IBS is a common gastrointestinal disorder affecting up to 14% of US adults and is particularly prevalent in women and those aged under 50. Symptoms include abdominal pain associated with altered bowel habits (i.e. diarrhea and/or constipation subtyped based on the predominant stool pattern). As IBS-D is challenging to manage with varying symptom severity, effective treatment requires a personalized management approach. Evidence-based therapeutic options endorsed by the American Gastroenterological Association and the American College of Gastroenterology can be used to effectively guide treatment. Dietary and lifestyle modifications, including adequate hydration, reducing caffeine and alcohol intake, and increasing soluble fiber intake may lead to symptom improvement. Over-the-counter medications such as loperamide are frequently recommended and may improve stool frequency and rectal urgency; however, for the outcome of abdominal pain, mixed results have been observed. Several off-label prescription medications are useful in IBS-D management, including tricyclic antidepressants, bile acid sequestrants, and antispasmodics. Three prescription medications have been approved by the FDA for IBS-D: alosetron, eluxadoline, and rifaximin.

CONCLUSIONS

IBS-D can be effectively managed in the primary care setting in the absence of alarm features. Benefits and risks of pharmacologic interventions should be weighed during treatment selection.

Supplementation of Bovine Colostrum in Inflammatory Bowel Disease: Benefits and Contraindications

Inflammatory bowel disease (IBD) is a group of chronic relapsing disorders whose etiology has not been fully explained. Therefore, available therapeutic approaches for IBD patients are still insufficient. Current treatment strategies are targeted to immune system dysfunctions, often associated with alternations in the microbiota, which contribute to the development of chronic intestinal inflammation. Therapeutics include anti-inflammatory drugs such as aminosalicylates and corticosteroids, immunosuppressive agents, antibiotics, and biological agents such as infliximab and vedolizumab. Auxiliary therapies involve a balanced and personalized diet, healthy lifestyle, avoiding stress, as well as dietary supplements. In this review, we discuss the use of bovine colostrum (BC) as a therapeutic agent, including its advantages and contraindications. We summarize our knowledge on well-researched BC constituents and their effects on the gastrointestinal tract as evidenced in in vitro and in vivo studies.

Mechanisms of Food-Induced Symptom Induction and Dietary Management in Functional Dyspepsia

Functional dyspepsia (FD) is a common disorder of gut-brain interaction, characterised by upper gastrointestinal symptom profiles that differentiate FD from the irritable bowel syndrome (IBS), although the two conditions often co-exist. Despite food and eating being implicated in FD symptom induction, evidence-based guidance for dietetic management of FD is limited. The aim of this narrative review is to collate the possible mechanisms for eating-induced and food-related symptoms of FD for stratification of dietetic management. Specific carbohydrates, proteins and fats, or foods high in these macronutrients have all been reported as influencing FD symptom induction, with removal of 'trigger' foods or nutrients shown to alleviate symptoms. Food additives and natural food chemicals have also been implicated, but there is a lack of convincing evidence. Emerging evidence suggests the gastrointestinal microbiota is the primary interface between food and symptom induction in FD, and is therefore a research direction that warrants substantial attention. Objective markers of FD, along with more sensitive and specific dietary assessment tools will contribute to progressing towards evidence-based dietetic management of FD.

Lactoferrin: an overview of its main functions, immunomodulatory and antimicrobial role, and clinical significance

Lactoferrin (LF), a glycoprotein found in mucosal secretions, is characterized by a wide range of functions, including immunomodulatory and anti-inflammatory activities. Moreover, several investigations confirmed that LF displays high effectiveness against multiple bacteria and viruses and may be regarded as a potential inhibitor of enveloped viruses, such as presently prevailing SARS-CoV-2. In our review, we discuss available studies about LF functions and bioavailability of different LF forms in in vitro and in vivo models. Moreover, we characterize the potential benefits and side effects of LF use; we also briefly summarize the latest clinical trials examining LF application. Finally, we point potential role of LF in inflammatory bowel disease and indicate its use as a marker for disease severity.

No distinction in the gut microbiota between diarrhea predominant-irritable bowel syndrome and healthy subjects: matched case-control study in Thailand

Background

Alteration in the gut microbiota has been proposed in irritable bowel syndrome (IBS) pathogenesis, especially in the diarrheal type (IBS-D). We conducted this study to evaluate the fecal microbiota in Thai IBS-D patients when compared with healthy subjects as well as to evaluate the effects of probiotics on changes in the gut microbiota correlated with symptoms.

Methods

A matched case–control study was conducted on diagnosed IBS-D patients, based on the Rome IV criteria and healthy controls. Stool samples were collected in preservation tubes. Bacterial deoxyribonucleic acid extraction was performed and amplified. Next, 16S ribosomal ribonucleic acid genes sequencing was performed to identify the microbiome in both the groups. IBS-D patients were provided with a probiotic mixture that was rich in Lactobacillus acidophillus and Bifidobacterium bifidum over 8 weeks. Changes in the symptoms, stool characteristics, and fecal microbiota were evaluated and compared with the corresponding baseline values.

Results

Twenty IBS-D patients with 20 age and gender-matched controls were included in this study. The baseline characteristics were not significantly different between the groups, including the mode of birth and the history of breastfeeding in infancy. No significant difference was noted in the fecal microbiota between the IBS-D patients and controls. The IBS symptom severity scales (IBS-SSS) were not statistically different after probiotic prescription; although, the bowel movements, the sense of urgency to go to the toilet and passing of mucous stool had obviously decreased. No change was noted in the fecal microbiota after receiving the experimental probiotic, except for an increase in the proportion of B. bifidum.

Conclusion

Alteration in the gut microbiota composition was probably not the main pathogenic mechanism in the Thai IBS-D patients assessed in this study. However, modifying microbiomes with potentially protective bacteria seems to be a beneficial therapy.

Thai Clinical trial registry: TCTR20191211006, Date of registration: 10 Dec 2019. Retrospectively registered, Clinical trial URL: www.clinicaltrials.in.th

Gastrointestinal Food Allergies and Intolerances

Adverse reactions to food include immune-mediated food allergies, celiac disease, and nonimmune-mediated food intolerances. Differentiating between these many disorders is important to guide us toward appropriate testing and management. Double-blind placebo-controlled food challenges are the gold standard for food allergy diagnosis but are difficult and time-consuming. In place of this, strong clinical history, other supportive tests, and oral food challenges are helpful. Some commonly available tests for food allergy and intolerances lack sufficient evidence for efficacy. Food intolerance diagnosis is largely based on history and supported by symptom improvement with appropriate dietary manipulation.

The role of intestinal mast cell infiltration in irritable bowel syndrome

As an essential part of the immune system, mast cells (MCs) play an important role in the pathogenesis of irritable bowel syndrome (IBS). Accumulating evidence has identified altered MC count and density in intestinal mucosa of patients with IBS; however, conflicting findings yield inconsistent conclusions. Currently, most studies have suggested intestinal MC infiltration in IBS patients. Considering the pivotal role of MCs in IBS, it is necessary to achieve a better understanding about the pathological changes in the intestine. The risk factors for IBS, including dietary habits, psychological factors, infection, and dysbiosis, are implicated to induce intestinal MC infiltration. Mechanistically, food may trigger immune-related allergic reactions and affect the intestinal microbiota activity. Some exogenous pathogens and altered profile of commensal bacteria promote intestinal MC recruitment through promoted release of chemokines from epithelial cells or direct activation of the immune system. In addition, psychological factors may affect the microenvironment where MCs live. MCs have been proven to interact with the enteric neurons and other immunocytes, evidenced by the close proximity of MCs to neurons and regional altered immune system components. A variety of mediators released by the enteric neurons, immunocytes, and MCs per se, such as neurotrophins, neuropeptides, cytokines, and chemokines, may have stimulant effects on MCs by modulating the survival, proliferation, and recruitment process of MCs in the intestine. In this review, the associations between IBS and intestinal MC density and the underlying mechanisms are discussed.

Intestinal barrier dysfunction in irritable bowel syndrome: a systematic review

BACKGROUND AND AIM

Irritable bowel syndrome (IBS) is a complex and heterogeneous disorder. Sensory, motor and barrier dysfunctions are the key physiological endophenotypes of IBS. Our aim is to review studies evaluating barrier dysfunction in adults and children with IBS, as well as to link those changes with IBS symptomatology and quality of life.

METHODS

A comprehensive and systematic review of multiple databases was performed up to March 2020 to identify studies comparing intestinal permeability in IBS patients with healthy controls. Both in vivo and in vitro studies were considered.

RESULTS

We identified 66 studies, of which 27 used intestinal probes to quantify barrier function. The prevalence of barrier dysfunction differed between PI-IBS (17-50%), IBS-D (37-62%) and IBS-C (4-25%). At a group level, permeability was increased compared with healthy controls in IBS-D (9/13 studies) and PI-IBS (4/4 studies), but only a minority of IBS-C (2/7 studies) and not in the only IBS-M study. All four studies in children with IBS demonstrated loss of barrier function. A heterogeneous set of tight junction genes were found to be altered in small and large intestines of adults with IBS, but these have not been evaluated in children. Positive associations were identified between barrier dysfunction and bowel disturbances (6/9 studies), abdominal pain (9/13 studies), overall symptom severity (1/6 studies), depression and anxiety (1/1 study) and quality of life (1/4 studies). Fecal slurry or supernatants of IBS patients were found to induce barrier disruption in animal models (5/6 studies).

CONCLUSIONS

Barrier dysfunction is present in a significant proportion of adult and all pediatric IBS studies, especially in the IBS-D and PI-IBS subtype. The majority of studies indicated a positive association between loss of barrier function and symptoms such as abdominal pain and changes in the bowel function.

Efficacy of a low-FODMAP diet in adult irritable bowel syndrome: a systematic review and meta-analysis

Purpose

This review provides an updated overview of observational and intervention studies investigating the effect of a low-FODMAP (fermentable oligo-, di- and monosaccharides, and polyols) diet (LFD) on gastrointestinal (GI) symptoms, quality of life (QoL), nutritional adequacy, and gut microbiome in irritable bowel syndrome (IBS) patients.

Methods

We systematically searched available literature until October 2020 for studies that investigated the effect of LFDs on GI symptoms, QoL, nutritional adequacy, and the gut microbiome in IBS patients. The data were represented as standardized mean differences (SMD) for IBS severity, and as mean differences (MD) for IBS-QoL. Meta-analyses were performed for the quantitative analyses using random effects models with inverse variance weighing.

Results

Twelve papers (nine parallel trials, three crossover studies) were included for the meta-analysis. The LFD reduced IBS severity by a moderate-to-large extent as compared to a control diet (SMD − 0.66, 95% CI − 0.88, − 0.44, I² = 54%). When analyzing only studies that used the validated IBS-SSS questionnaire, a mean reduction of 45 points (95% CI − 77, − 14; I² = 89%) was observed. Subgroup analyses on adherence, age, intervention duration, IBS subtype, outcome measure, and risk of bias revealed no significantly different results. The LFD also increased IBS-QoL scores, when compared with a control diet (MD 4.93; 95% CI 1.77, 8.08; I² = 42%).

Conclusions

The low-FODMAP diet reduces GI symptoms and improves quality of life in IBS subjects as compared to control diets. Future work is required to obtain definitive answers regarding potential long-term effects of such diets on nutritional adequacy and the gut microbiome.

PROSPERO registration number

CRD42020175157.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-020-02473-0.

6-(methylsulfinyl)hexyl isothiocyanate (6-MITC) from Wasabia japonica alleviates inflammatory bowel disease (IBD) by potential inhibition of glycogen synthase kinase 3 beta (GSK-3β)

Inflammatory bowel disease (IBD) describes a set of disorders involving alterations to gastrointestinal physiology and mucosal immunity. Unravelling its complex pathophysiology is important since many IBD patients are refractory to or suffer adverse side effects from current treatments. Isothiocyanates (ITCs), such as 6-(methylsulfinyl)hexyl ITC (6-MITC) in Wasabia japonica, have potential anti-inflammatory activity. We aimed to elucidate the pathways through which 6-MITC alleviates inflammation by examining its role in the nuclear factor-kappa B (NF-κB) pathway through inhibition of glycogen synthase kinase 3 beta (GSK-3β) using a chemically induced murine model of IBD, cell-based and in silico techniques. The effects of 6-MITC and two NF-κB inhibitors, sulfasalazine (SS), pyrrolidine dithiolcarbamate (PDTC) were investigated on a dextran sulfate sodium (DSS)-induced murine mouse model of acute and chronic colitis using macroscopic measurements and pro-inflammatory markers. The effect of 6-MITC on NF-κB induction was assessed using a murine macrophage cell line. Complexes of GSK-3β-6-MITC and GSK-3β-ATP were generated in silico to elucidate the mechanism of 6-MITC's direct inhibition of GSK-3β. Changes in pro-inflammatory markers, inducible nitric oxide synthase (iNOS) (increased) and interleukin-6 (IL-6) (decreased) demonstrated that iNOS regulation occurred at the translational level. Intraperitoneal (ip) injection of 6-MITC to the colitis-induced mice ameliorated weight loss whereas oral administration had negligible effect. Fecal blood and colon weight/length ratio parameters improved on treatment with 6-MITC and the other NF-κB inhibitors. Levels of NF-κB decreased upon addition of 6-MITC in vitro while structural studies showed 6-MITC acts competitively to inhibit GSK-3β at the ATP binding site. In this study we demonstrated that 6-MITC inhibits NF-κB signaling via GSK-3β inhibition ameliorating fecal blood, colonic alterations and DSS-induced weight loss indirectly indicating reduced intestinal stress. Taken together these results suggest a role for 6-MITC in the treatment of IBD acting to alleviate inflammation through the GSK-3β/NF-κB pathway. Furthermore, the GSK-3β-6-MITC model can be utilized as a basis for development of novel therapeutics targeting GSK-3β for use in other disorders including cancer.

Effect of Heat-killed Lactobacillus casei DKGF7 on a Rat Model of Irritable Bowel Syndrome

Non-viable bacteria, referred to as “paraprobiotics,” have attracted attention as potentially safer alternatives to probiotics. The aim of this study was to investigate the efficacy of heat-killed Lactobacillus casei DKGF7 on the symptomatic improvement of irritable bowel syndrome (IBS) in a rat disease model and to elucidate the underlying mechanisms that contribute to the beneficial effects of heat-killed probiotics. Seven male Wistar rats were induced with IBS by restraint stress and administered heat-killed L. casei DKGF7 for four weeks and then compared with seven rats in the control group. Stool consistency measured four weeks after initial treatment was the primary outcome measure. To investigate the mechanism of action of the heat-killed bacteria on IBS, we measured serum corticosterone levels, inflammatory cytokines in colon tissue, and expression of tight junction proteins (TJPs) in the epithelium. The treatment group showed significantly better stool consistency scores than the control group at week 4, as well as at every measured time point (all p values < 0.05). The treatment group showed lower serum corticosterone levels, lower colonic inflammatory cytokine levels, and higher expression of TJPs compared with the control group. Paraprobiotics such as heat-killed L. casei DKGF7 can improve stool consistency in a rat IBS model, which may indicate a potential therapeutic strategy for IBS treatment.

Identification of potential biomarkers for abdominal pain in IBS patients by bioinformatics approach

Background

Irritable bowel syndrome (IBS) is the most common functional gastrointestinal disease characterized by chronic abdominal discomfort and pain. The mechanisms of abdominal pain, as a relevant symptom, in IBS are still unclear. We aimed to explore the key genes and neurobiological changes specially involved in abdominal pain in IBS.

Methods

Gene expression data (GSE36701) was downloaded from Gene Expression Omnibus database. Fifty-three rectal mucosa samples from 27 irritable bowel syndrome with diarrhea (IBS-D) patients and 40 samples from 21 healthy volunteers as controls were included. Differentially expressed genes (DEGs) between two groups were identified using the GEO2R online tool. Functional enrichment analysis of DEGs was performed on the DAVID database. Then a protein–protein interaction network was constructed and visualized using STRING database and Cytoscape.

Results

The microarray analysis demonstrated a subset of genes (CCKBR, CCL13, ACPP, BDKRB2, GRPR, SLC1A2, NPFF, P2RX4, TRPA1, CCKBR, TLX2, MRGPRX3, PAX2, CXCR1) specially involved in pain transmission. Among these genes, we identified GRPR, NPFF and TRPA1 genes as potential biomarkers for irritating abdominal pain of IBS patients.

Conclusions

Overexpression of certain pain-related genes (GRPR, NPFF and TRPA1) may contribute to chronic visceral hypersensitivity, therefore be partly responsible for recurrent abdominal pain or discomfort in IBS patients. Several synapses modification and biological process of psychological distress may be risk factors of IBS.

Dysregulation of the gut-brain-skin axis and key overlapping inflammatory and immune mechanisms of psoriasis and depression

The occurrence, progression and recurrence of psoriasis are thought to be related to mood and psychological disorders such as depression. Psoriasis can lead to depression, and depression, in turn, exacerbates psoriasis. No specific mechanism can explain the association between psoriasis and depression. The gut-brain-skin axis has been used to explain correlations among the gut microbiota, emotional states and systemic and skin inflammation, and this axis may be associated with overlapping mechanisms between psoriasis and depression. Therefore, in the context of the gut-brain-skin axis, we systematically summarized and comparatively analysed the inflammatory and immune mechanisms of psoriasis and depression and illustrated the dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and the gut microbiota. This review provides a theoretical basis and new targets for the treatment of psoriasis and depression.

Lipi Guben decoction in treating diarrheal irritable bowel syndrome: A study protocol for a randomized controlled trial

BACKGROUND

Irritable bowel syndrome (IBS) is a common functional bowel disorder. The global incidence of IBS is as high as 9% to 23%, accounting for about 50% of outpatients in gastroenterology, and the new case detection rate is 0.2% every year. IBS has become a global gastrointestinal functional disease. Although IBS is not a life-threatening disease, it seriously affects the quality of life of patients, causing huge economic and mental burden to individuals, society and families. Lipi Guben decoction (LPGBD) is an important auxiliary treatment for IBS, but lack of robust Evidence-based medicine evidence proving its efficacy. Therefore, we designed a randomized controlled trial to evaluate the efficacy and safety of LPGBD in the treatment of IBS.

METHODS

In this randomized controlled trial, a total of 100 eligible patients will be allocated to the blank control group or LPGBD group in a ratio of 1:1. The treatment period was 12 weeks. The primary outcome measure will be the total clinical effective rate. The Secondary outcomes will include IBS clinical symptom scores, IBS-Severity Scoring System, IBS-Quality of life, Hamilton Rating Scale for Anxiety, Hamilton Rating Scale for Depression, and Bristol Stool Form Scale. The safety outcome will include Echocardiogram, blood examination (including blood routine test, liver function test, and renal function test), urine routine test and stool routine test. The evaluation indicators and all safety results will be performed at baseline, week 4, week 8 and week 12.

RESULTS

This study will be helpful to evaluate the efficacy and safety of LPGBD in the treatment of IBS.

CONCLUSION

LPGBD may improve the clinical efficacy of patients with IBS, which has important value in practical application.

TRIAL REGISTRATION

Chictr20000039617, registration time: November 3, 2020.

Comparison of the Gut Microbiota Disturbance in Rat Models of Irritable Bowel Syndrome Induced by Maternal Separation and Multiple Early-Life Adversity

Background

The study aimed to identify the effects of modeling procedures on bacterial communities and to investigate whether different modeling procedures lead to consistent patterns of gut microbiome compositions.

Methods

Two irritable bowel syndrome (IBS) rat models maternal separation (MS) alone and multiple-early-adversity modeling (MAM) were established and the gut microbiome were analyzed using 16S-rRNA-based high-throughput sequencing methods.

Results

Rats from both models exhibited visceral hypersensitivity and the two model groups exhibited differences in the extent of visceral sensitivity and fecal water content. The microbial community structure of the two models exhibited significant differences compared to the controls, while the two model groups also exhibited significant differences between them. Furthermore, microbial community functional predictions suggested that the two models exhibited different abundances of metabolisms and pathways. Several common and distinct characteristic differences were also observed between the two model groups. Alloprevotella were more abundant in both model groups, while Butyricicoccus, Turicibacter, Ruminococcus, and Clostridium_sensu_stricto along with the family it belongs to were less abundant relative to controls. In addition, the abundance of Clostridium_IV, Corynebacterium, Rothia, Elusimicrobium, Romboutsia, Allobaculum, Parasutterella, and their related taxa were specifically associated with MS group, whereas Butyricimonas and Vampirovibrio along with its related taxa were specifically associated with MAM group. Among those, Butyricimonas, Butyricicoccus and Corynebacterium were found to partially mediate early adversity exposure-induced visceral hypersensitivity.

Conclusions

Our results highlight the importance in evaluating gut microbiota characteristics in IBS research while also systematically considering potential modeling procedural differences. The microbial compositional/functional differences identified in this study were suggestive to further investigation of mechanisms of early adversity induced IBS.

Effects of Rifaximin on Luminal and Wall-Adhered Gut Commensal Microbiota in Mice

Rifaximin is a broad-spectrum antibiotic that ameliorates symptomatology in inflammatory/functional gastrointestinal disorders. We assessed changes in gut commensal microbiota (GCM) and Toll-like receptors (TLRs) associated to rifaximin treatment in mice. Adult C57BL/6NCrl mice were treated (7/14 days) with rifaximin (50/150 mg/mouse/day, PO). Luminal and wall-adhered ceco-colonic GCM were characterized by fluorescent in situ hybridization (FISH) and microbial profiles determined by terminal restriction fragment length polymorphism (T-RFLP). Colonic expression of TLR2/3/4/5/7 and immune-related markers was assessed (RT-qPCR). Regardless the period of treatment or the dose, rifaximin did not alter total bacterial counts or bacterial biodiversity. Only a modest increase in Bacteroides spp. (150 mg/1-week treatment) was detected. In control conditions, only Clostridium spp. and Bifidobacterium spp. were found attached to the colonic epithelium. Rifaximin showed a tendency to favour their adherence after a 1-week, but not 2-week, treatment period. Minor up-regulation in TLRs expression was observed. Only the 50 mg dose for 1-week led to a significant increase (by 3-fold) in TLR-4 expression. No changes in the expression of immune-related markers were observed. Rifaximin, although its antibacterial properties, induces minor changes in luminal and wall-adhered GCM in healthy mice. Moreover, no modulation of TLRs or local immune systems was observed. These findings, in normal conditions, do not rule out a modulatory role of rifaximin in inflammatory and or dysbiotic states of the gut.

Posttranslational modifications as therapeutic targets for intestinal disorders

A variety of biological processes are regulated by posttranslational modifications. Posttranslational modifications including phosphorylation, ubiquitination, glycosylation, and proteolytic cleavage, control diverse physiological functions in the gastrointestinal tract. Therefore, a better understanding of their implications in intestinal diseases, including inflammatory bowel disease, irritable bowel syndrome, celiac disease, and colorectal cancer would provide a basis for the identification of novel biomarkers as well as attractive therapeutic targets. Posttranslational modifications can be common denominators, as well as distinct biomarkers, characterizing pathological differences of various intestinal diseases. This review provides experimental evidence that identifies changes in posttranslational modifications from patient samples, primary cells, or cell lines in intestinal disorders, and a summary of carefully selected information on the use of pharmacological modulators of protein modifications as therapeutic options.

Irritable bowel syndrome and Parkinson's disease risk: register-based studies

To examine whether irritable bowel syndrome (IBS) was related to the future risk of Parkinson's disease (PD), we conducted a nested case-control study in the Swedish total population including 56,564 PD cases identified from the Swedish Patient Register and 30 controls per case individually matched by sex and year of birth. Odds ratios (ORs) with 95% confidence intervals (CIs) for having a prior diagnosis of IBS were estimated using conditional logistic regression. We furthermore conducted a cohort study using the Swedish Twin Registry following 3046 IBS patients identified by self-reported abdominal symptoms and 41,179 non-IBS individuals. Through Cox proportional hazard models, we estimated hazard ratios (HRs) and 95% CIs for PD risk. In the nested case-control study, 253 (0.4%) PD cases and 5204 (0.3%) controls had a previous IBS diagnosis. IBS diagnosis was associated with a 44% higher risk of PD (OR = 1.44, 95% CI 1.27-1.63). Temporal relationship analyses showed 53% and 38% increased risk of PD more than 5 and 10 years after IBS diagnosis, respectively. In the cohort analysis based on the Swedish Twin Registry, there was no statistically significantly increased risk of PD related to IBS (HR = 1.25, 95% CI = 0.87-1.81). Our results suggest a higher risk of PD diagnosis after IBS. These results provide additional evidence supporting the importance of the gut-brain axis in PD.

Increased colon transit time and faecal load in irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a bowel disorder involving abdominal pain or discomfort along with irregularity of stool form and passage frequency. The pathophysiology is poorly understood and seems to be multifactorial. Investigations of possible causes of IBS have included only a few colonic transit studies and no simultaneous determination of the colonic faecal content.

AIM

To compare colon transit time and faecal load between IBS-patients and healthy control subjects.

METHODS

The study included 140 patients with IBS, with a mean age of 50.0 years. The control group comprised 44 healthy persons with a mean age of 43.4 years, who were selected at random from the National Civil Register. Both the patient group and the control group underwent a marker study to measure colon transit time (CTT) and to calculate a faecal loading score. The patient group underwent treatment with a combined prokinetic regime, after which their CTT and faecal loading were reassessed. Analyses were performed to compare measurements between the control group and the patient group before and after treatment.

RESULTS

Compared to healthy controls, IBS-patients exhibited a significantly prolonged mean CTT (45.48 h vs 24.75 h, P = 0.0002) and significantly greater mean faecal loading scores in all colonic segments (P < 0.001). Among IBS patients, we found no significant differences between the 48 h and 96 h radiographs. Among patients exhibiting increased CTT and faecal loading, approximately half exhibited a palpable mass in the right iliac fossa. After intervention with a prokinetic treatment, the mean CTT among IBS patients was reduced from 45.48 h to 34.50 h (P = 0.091), with the post-treatment CTT not significantly differing from the CTT among control subjects (P = 0.095). The faecal loading score among IBS patients did not significantly differ before and after treatment (P = 0.442). The post-treatment faecal loading score in IBS patients remained significantly higher compared to that in controls (5.3 vs 4.3, P = 0.014). After treatment, half of the IBS-patients were relieved of bloating, while the majority no longer experienced abdominal pain and achieved a daily consistent stool.

CONCLUSION

IBS-patients exhibited prolonged CTT and heavier faecal loading. These assessments may aid in diagnosis. Faecal retention may contribute to IBS symptoms, which can be treated using a prokinetic regime.

Brain Functional Interaction of Acupuncture Effects in Diarrhea-Dominant Irritable Bowel Syndrome

Acupuncture is a traditional Chinese medicine treatment that has widely been used to modulate gastrointestinal dysfunction caused by irritable bowel syndrome (IBS) and to alleviate the resulting pain. Recent studies have shown that gastrointestinal dysfunction caused by IBS is associated with dysregulation of the brain's central and peripheral nervous system, while functional magnetic resonance imaging (fMRI) helps explore functional abnormality of the brain. However, previous studies rarely used fMRI to study the correlations between brain functional connection, interaction, or segregation (e.g., network degree and clustering coefficient) and acupuncture stimulation in IBS. To bridge this knowledge gap, we study the changed brain functional connection, interaction, and segregation before and after acupuncture stimulation for diarrhea-dominant IBS (IBS-D) with the help of complex network methods based on fMRI. Our results indicate that the abnormal functional connections (FCs) in the right hippocampus, right superior occipital gyrus, left lingual gyrus, left middle occipital gyrus, and the cerebellum, and abnormal network degree in right middle occipital gyrus, where normal controls are significantly different from IBS-D patients, are improved after acupuncture stimulation. These changed FCs and the network degree before and after acupuncture stimulation have significant correlations with the changed clinical information including IBS symptom severity score (r = −0.54, p = 0.0065) and IBS quality of life (r = 0.426, p = 0.038). We conclude that the changes of the brain functional connection, interaction, and segregation in the hippocampus, middle and superior occipital gyrus, cerebellum, and the lingual gyrus may be related to acupuncture stimulation. The abnormal functional connection, interaction, and segregation in IBS-D may be improved after acupuncture stimulation.

IBS-Symptoms in IBD Patients-Manifestation of Concomitant or Different Entities

Irritable bowel syndrome (IBS) is a functional heterogenous disease with a multifactorial pathogenesis. It is characterized by abdominal pain, discomfort, and alteration in gut motility. The occurrence of similar symptoms was observed in patients in clinical remission of inflammatory bowel diseases (IBD) that is Crohn's disease (CD) and ulcerative colitis (UC), which pathogenesis is also not fully understood. Hence, arose the question if these symptoms are "true IBS" imposed on IBD, or is it a subclinical form of IBD or even pre-IBD? In this article, based on a narrative overview of the literature, we try to find an answer to this query by discussing the pathogenesis and overlaps between these conditions.

Ileocolonic Histopathological and Microbial Alterations in the Irritable Bowel Syndrome: A Nested Community Case-Control Study

INTRODUCTION

Histopathological alterations in the ileum and colon in irritable bowel syndrome (IBS) are controversial, and normal values are poorly established. We hypothesized that changes in mucosal immune cells characterize IBS and key changes in immune composition are associated with the mucosa-associated microbiota (MaM).

METHODS

A nested case-control study (48 IBS and 106 controls included) from 745 colonoscopy participants in a random population sample. Intraepithelial lymphocytes (IELs)/100 enterocytes and eosinophils/5 nonoverlapping high-power fields counted; mast cells identified by immunocytochemistry (CD117)/5 high-power fields. Paneth cells quantified per 5 crypts. 16S rRNA gene amplicon sequencing performed on available sigmoid MaM, n = 55 and fecal microbiota, n = 20. Microbiota profiles compared between samples with high and low IEL counts.

RESULTS

IBS had increased IELs in the terminal ileum (relative risk ratio = 1.70, 95% confidence interval 1.08-2.76, P = 0.022 adjusted for age, sex, and smoking). Cecal IELs were increased in IBS-diarrhea (relative risk ratio = 2.03, 95% confidence interval 1.13-3.63, P = 0.017). No difference was observed in alpha diversity of MaM or fecal microbiota based on IEL count. There was no difference in beta diversity of the MaM according to IEL count in the terminal ileal (TI) (P = 0.079). High TI IEL counts associated with a significant expansion of the genus Blautia (P = 0.024) and unclassified Clostridiales (P = 0.036) in colon MaM.

DISCUSSION

A modest but significant increase in IELs was observed in IBS vs. controls in a population-based setting. Subtle TI and cecal inflammation may play a pathogenic role in IBS but needs confirmation. Modest but discernible differences in the colonic MaM were seen according to TI IEL count but not IBS status.

Alterations in Heart Rate Variability Associated With Irritable Bowel Syndrome or Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis

INTRODUCTION:

Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) are gastrointestinal pathologies affecting large numbers of the global population and incurring significant healthcare costs. Disruptions in the gut-brain axis occurring in these conditions can lead to increased inflammation, affecting gastrointestinal and autonomic nervous system function. Heart rate variability (HRV) is commonly used to assess the state of the sympathetic and parasympathetic function of the autonomic nervous system, but it remains unclear how HRV measures are associated with gastrointestinal pathologies. Here, we conduct a systematic review of the literature comparing HRV of subjects diagnosed with IBS or IBD to HRV in healthy controls (HC).

METHODS:

We searched PubMed, Cochrane Library, and CINAHL (EBSCO) for eligible studies up to 2018. We included any study comparing a recognized measure of HRV between a group of patients with either IBS or IBD to a group of matched HC before any intervention. Studies were screened, and data were extracted from included articles using predefined criteria. Random effects meta-analysis was performed for each outcome, with effect size reported as the standardized mean difference.

RESULTS:

There were significant differences between IBD and HC in time domain HRV and significant decreases in high-frequency power measures were also noted, in both IBS and IBD compared with HC.

DISCUSSION:

Parasympathetic nervous system activity, represented through high-frequency power, seems to be lower in people with IBS and IBD, but conclusions are limited by the small number of studies that provide usable data, methodological heterogeneity, and high risks of bias in primary study methods and measures.

Bidirectional association between irritable bowel syndrome and restless legs syndrome: a systematic review and meta-analysis

BACKGROUND

Several observational studies have shown that patients with irritable bowel syndrome (IBS) may have a high risk of restless legs syndrome (RLS). This systematic review and meta-analysis aimed to comprehensively investigate the bidirectional association between IBS and RLS.

METHODS

All conservational studies on IBS and RLS were searched in MEDLINE (assessed by PubMed), Embase, Web of Science, CINAHL, the Cochrane Library database and Google Scholar from inception to June 14, 2020. The Newcastle-Ottawa Scale and Agency for Healthcare Research and Quality were used to assess the methodological quality of the cohort and cross-sectional studies, respectively. The pooled odds ratio (OR) and 95% confidence interval (CI) were calculated using Reviewer Manager 5.3.

RESULT

A total of five cross-sectional studies of moderate methodological quality and one cohort study of high methodological quality were included in our review. Four cross-sectional studies and one cohort study involving 86 438 individuals met the criteria of IBS predicating the onset of RLS. Patients with IBS had a nearly three-fold increased odds of RLS compared with controls (OR = 2.60, 95%CI: 2.17-3.12, P < 0.00001; I² = 48%, P = 0.11). Three sensitivity analyses confirmed the robustness of the pooled result. Two cross-sectional studies involving 3581 individuals met the criteria of RLS predicating the onset of IBS. RLS patients had a nearly four-fold increased odds of IBS compared with controls without RLS (OR = 3.87, 95%CI: 1.73-8.66, P = 0.0010; I² = 77%, P = 0.04).

CONCLUSION

In this systematic review and meta-analysis, we found a substantial bidirectional association between IBS and RLS. More prospective, high-quality, population-based studies are warranted in the future.

Food Additives, Gut Microbiota, and Irritable Bowel Syndrome: A Hidden Track

The interactions between diet, gut microbiota, and irritable bowel syndrome (IBS) have many complex mechanisms that are not fully understood. Food additives are one component of the modern human diet that deserves attention from science and government policies. This review aims at identifying the current knowledge about the impact of food additives on gut microbiota and their potential role in the development of IBS. To date, few data on the effect of food additives on gut microbiota in IBS patients are available. However, exposure to food additives could induce the dysbiosis and dysregulation of gut homeostasis with an alteration of the gut barrier and activation of the immune response. These microbial changes could exacerbate the gut symptoms associated with IBS, such as visceral pain, low-grade inflammation, and changes in bowel habits. Some additives (polyols) are excluded in the low fermentable oligo-, di- and monosaccharide, and polyol (FODMAP), diets for IBS patients. Even if most studies have been performed in animals, and human studies are required, many artificial sweeteners, emulsifiers, and food colorants could represent a potential hidden driver of IBS, through gut microbiota alterations. Consequently, food additives should be preventively avoided in the diet as well as dietary supplements for patients with IBS.

Irritable bowel syndrome

Irritable bowel syndrome is a functional gastrointestinal disorder with symptoms including abdominal pain associated with a change in stool form or frequency. The condition affects between 5% and 10% of otherwise healthy individuals at any one point in time and, in most people, runs a relapsing and remitting course. The best described risk factor is acute enteric infection, but irritable bowel syndrome is also more common in people with psychological comorbidity and in young adult women than in the rest of the general population. The pathophysiology of irritable bowel syndrome is incompletely understood, but it is well established that there is disordered communication between the gut and the brain, leading to motility disturbances, visceral hypersensitivity, and altered CNS processing. Other less reproducible mechanisms might include genetic associations, alterations in gastrointestinal microbiota, and disturbances in mucosal and immune function. In most people, diagnosis can be made on the basis of clinical history with limited and judicious use of investigations, unless alarm symptoms such as weight loss or rectal bleeding are present, or there is a family history of inflammatory bowel disease or coeliac disease. Once the diagnosis is made, an empathetic approach is key and can improve quality of life and symptoms, and reduce health-care expenditure. The mainstays of treatment include patient education about the condition, dietary changes, soluble fibre, and antispasmodic drugs. Other treatments tend to be reserved for people with severe symptoms and include central neuromodulators, intestinal secretagogues, drugs acting on opioid or 5-HT receptors, or minimally absorbed antibiotics (all of which are selected according to predominant bowel habit), as well as psychological therapies. Increased understanding of the pathophysiology of irritable bowel syndrome in the past 10 years has led to a healthy pipeline of novel drugs in development.

Molecular Mechanisms of Microbiota-Mediated Pathology in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is one of the most prevalent functional gastrointestinal disorders, and accumulating evidence gained in both preclinical and clinical studies indicate the involvement of enteric microbiota in its pathogenesis. Gut resident microbiota appear to influence brain activity through the enteric nervous system, while their composition and function are affected by the central nervous system. Based on these results, the term “brain–gut–microbiome axis” has been proposed and enteric microbiota have become a potential therapeutic target in IBS cases. However, details regarding the microbe-related pathophysiology of IBS remain elusive. This review summarizes the existing knowledge of molecular mechanisms in the pathogenesis of IBS as well as recent progress related to microbiome-derived neurotransmitters, compounds, metabolites, neuroendocrine factors, and enzymes.

Efficacy of Tong-Xie-Yao-Fang granule and its impact on whole transcriptome profiling in diarrhea-predominant irritable bowel syndrome patients: study protocol for a randomized controlled trial

BACKGROUND

Irritable bowel syndrome (IBS) is one kind of common functional bowel disease with obscure pathogenesis, and exploration about whole transcriptome profiling in IBS-D is still negligible. Conventional medications have limited effects, which makes focus shifted to traditional Chinese medicine (TCM). Tong-Xie-Yao-Fang, as a classic herbal formula in TCM, is pretty effective and safe for the treatment of diarrhea-predominant irritable bowel syndrome (IBS-D), but the underlying therapeutic mechanism remains unknown. We aim to verify the efficacy and safety of TXYF granule (the formula particles mixed together) in IBS-D and elucidate the gene-level mechanism of IBS-D and therapeutic targets of TXYF granule based on whole transcriptome analysis.

METHODS/DESIGN

This is a randomized, double-blind, and placebo-controlled clinical trial consisting of 2 weeks of run-in period, 12 weeks of treatment period, and 8 weeks of follow-up period. We will enroll 120 participants with IBS-D, who will be randomly assigned to the TXYF granule group and the placebo group, and recruit additional 10 healthy individuals as controls for mechanistic outcome. The two groups respectively take TXYF granule or placebo orally for treatment. The primary outcome is the response rate of IBS-Symptom Severity Score (IBS-SSS). The secondary outcomes include adequate relief (AR), IBS-Quality of Life Questionnaire (IBS-QOL), and long-term efficacy. Mechanistic outcome is the whole transcriptome profiling of the intestinal mucosae from IBS participants before and after the treatment and healthy individuals.

DISCUSSION

This trial will prove the effectiveness and safety of TXYF granule with high-quality evidence and provide a penetrating and comprehensive perspective on the molecular mechanism of IBS-D by whole transcriptome analysis, which makes us pinpoint specific biomarkers of IBS-D and therapeutic targets of TXYF.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR-IOR-1900021785 . Registered on 9 March 2019.

Gut fungal dysbiosis and altered bacterial-fungal interaction in patients with diarrhea-predominant irritable bowel syndrome: An explorative study

BACKGROUND

Little is known about intestinal fungi in IBS patients whose gut bacteria have been investigated a lot. In order to explore causal relationship between IBS and gut mycobiome, and use gut fungi to diagnose or even treat IBS, further characterization of it in IBS is required.

METHODS

Fifty-five diarrhea-predominant IBS (D-IBS) patients fulfilling Rome III criteria, and 16 healthy controls (HC) were recruited. Fresh fecal samples were collected and used for 16s rRNA and ITS2 high-throughput sequencing. Diversity and composition of gut bacteria and fungi, as well as bacterial-fungal interactions in D-IBS patients, were characterized. Specific fungal taxa differentiating D-IBS from HC were recognized by LEfSe and RandomForest methods, and their association with clinical symptoms was assessed by Spearman's correlation.

RESULTS

Diarrhea-predominant irritable bowel syndrome patients showed abnormal (IBS-dysbiosis) or normal (HC-like IBS) fecal bacterial structure and diversity compared with healthy controls. However, fecal fungal signatures differed absolutely between D-IBS and HC, which indicated a more susceptible alteration of gut fungi than bacteria in D-IBS. Fecal fungi showed significant correlations with IBS symptoms, especially Mycosphaerella, Aspergillus, Sporidiobolus, and Pandora which were identified to potentially differentiate D-IBS from HC. Moreover, compared with HC there were markedly declined bacterial-fungal interactions in D-IBS, in which Candida changed from negative to positive correlations with bacteria, and Eurotium changed from positive correlations to irrelevance, while Debaryomyces gained negative correlations with bacteria.

CONCLUSIONS

Gut fungal dysbiosis and altered bacterial-fungal interactions were present in patients with D-IBS, and gut fungi could be used to diagnose D-IBS.