Role of tumor necrosis factor-alpha and interleukin-10 gene polymorphisms in irritable bowel syndrome

Irritable Bowel Syndrome Associated with Blastocystis hominis or Without Relationship to It? A Case-Control Study and Minireview

BACKGROUND

Blastocystis hominis (B. hominis) is a protozoan parasite that has a worldwide distribution. Some studies have suggested a link between B. hominis and the development of irritable bowel syndrome (IBS). The objective of this study was to determine the prevalence of B. hominis in patients with IBS compared to healthy individuals.

MATERIAL AND METHODS

A total of 65 stool samples from patients with IBS and 65 samples from healthy individuals in northern Iran were examined. The samples were tested using various methods including direct smear, formalin ether sedimentation and culture to detect the presence of B. hominis. Additionally, polymerase chain reaction (PCR) was performed on all culture-positive isolates to confirm the results and identify the genotype.

RESULTS

B. hominis was detected in 15.38% of IBS patients and 9.2% of the healthy group. The culture in RPMI1640 was found to be better than the formalin ether and direct smear methods. Positive samples were confirmed using the molecular method. No significant difference was observed in the order of B. hominis infection between the two groups.

CONCLUSIONS

The results of our study indicate that no significant difference was observed in the order of B. hominis infection between IBS patients and healthy groups. Therefore, further study is necessary to determine the potential pathogenic effects of this parasite and its role in causing IBS.

Impact of auricular percutaneous electrical nerve field stimulation on gut microbiome in adolescents with irritable bowel syndrome: A pilot study

OBJECTIVES

Percutaneous electrical nerve field stimulation (PENFS) has documented efficacy for irritable bowel syndrome (IBS) via plausible vagal neuromodulation effects. The vagus nerve may affect gut microbiome composition via brain-gut-microbiome signaling. We aimed to investigate gut microbiome alterations by PENFS therapy in adolescent IBS patients.

METHODS

A prospective study of females with IBS aged 11-18 years receiving PENFS therapy for 4 weeks with pre- and post-intervention stool sampling was conducted. Outcome surveys completed pre-therapy, weekly, and post-therapy included IBS-Severity Scoring System (IBS-SSS), Visceral Sensitivity Index (VSI), Functional Disability Inventory (FDI), and the global symptom response scale (SRS). Bacterial DNA was extracted from stool samples followed by 16S rRNA amplification and sequencing. QIIME 2 (version 2022.2) was used for analyses of α and β diversity and differential abundance by group.

RESULTS

Twenty females aged 15.6 ± 1.62 years were included. IBS-SSS, VSI, and FDI scores decreased significantly after PENFS therapy (P < 0.0001, P = 0.0003, P = 0.0004, respectively). No intra- or interindividual microbiome changes were noted pre- versus post-therapy or between responders and non-responders. When response was defined by 50-point IBS-SSS score reduction, α diversity was higher in responders compared with non-responders at week 4 (P = 0.033). There was higher abundance of Blautia in excellent responders versus non-responders.

CONCLUSIONS

There were no substantial microbial diversity alterations with PENFS. Subjects with excellent therapeutic response showed an enrichment of relative abundance of Blautia, which may indicate that patients with specific microbial signature have a more favorable response to PENFS.

Bidirectional association between alopecia areata and irritable bowel syndrome: A nationwide population-based cohort study

BACKGROUND

Alopecia areata (AA) and irritable bowel syndrome (IBS) are two distinct diseases that share a similar pathophysiology; however, the relationship between these two diseases is unknown. This study aimed to investigate the bidirectional relationship between AA and IBS.

METHODS

Participants were recruited from the National Health Insurance Research Database in Taiwan. We included 5446 patients with AA and 21 784 matched controls to assess the risk of IBS, and 56 429 patients with IBS and 225 716 matched controls to assess the risk of AA. The Cox proportional-hazards regression model was used to calculate the adjusted hazard ratio (aHR).

RESULTS

After adjustment for potential confounders, patients with AA had an aHR of 5.20 [95% confidence interval (CI) 3.97-6.82] for IBS in comparison with the controls. Furthermore, compared with the controls, IBS patients had an aHR of 5.38 (95% CI 3.95-7.34) for AA.

CONCLUSION

AA is bidirectionally associated with IBS. Further investigation is needed to elucidate the shared pathogenesis underlying these two diseases.

Targeted therapy of irritable bowel syndrome with anti-inflammatory cytokines

Irritable bowel syndrome (IBS) is a multifactorial disease of which infection, as well as inflammation, has recently been considered as an important cause. Inflammation works as a potential pathway for the pathogenesis of IBS. In this review, we have discussed the targeted therapy of IBS. We used the search term “inflammation in IBS” and “proinflammatory” and “antiinflammatory cytokines and IBS” using PubMed, MEDLINE, and Google Scholar. The literature search included only articles written in the English language. We have also reviewed currently available anti-inflammatory treatment and future perspectives. Cytokine imbalance in the systematic circulation and the intestinal mucosa may also characterize IBS presentation. Imbalances of pro-and anti-inflammatory cytokines and polymorphisms in cytokine genes have been reported in IBS. The story of targeted therapy of IBS with anti-inflammatory cytokines is far from complete and it seems that it has only just begun. This review describes the key issues related to pro-inflammatory cytokines associated with IBS, molecular regulation of immune response in IBS, inhibitors of pro-inflammatory cytokines in IBS, and clinical perspectives of pro- and anti-inflammatory cytokines in IBS.

Ethnic differences in genetic polymorphism associated with irritable bowel syndrome

Genetic polymorphism is associated with irritable bowel syndrome (IBS) in terms of susceptibility and clinical manifestations. Previous studies have shown that genetic polymorphism might play a key role in the onset and progression of IBS by modulating components of its pathogenesis such as the gut-brain axis, gastrointestinal motility, inflammatory activity, and immune status. Although underlying pathophysiological mechanisms have not been fully clarified, the potential ethnic differences that are present in worldwide genetic studies of IBS deserve attention. This review surveyed numerous studies focusing on IBS-associated single nucleotide polymorphisms, and investigated the ethnic disparities revealed by them. The results demonstrate the need for more attention on ethnic factors in IBS-related genetic studies. Taking ethnic backgrounds into accounts and placing emphasis on disparities potentially ascribed to ethnicity could help lay a solid and generalized foundation for transcultural, multi-ethnic, or secondary analyses in IBS, for example, a meta-analysis. Broader genetic studies considering ethnic factors are greatly needed to obtain a better understanding of the pathophysiological mechanisms of IBS and to improve the prevention, intervention, and treatment of this disease.

Intestinal inflammatory profile shows increase in a diversity of biomarkers in irritable bowel syndrome

Background: It has been proposed that irritable bowel syndrome (IBS) is a low-grade mucosal inflammatory disease.Objective: To characterize the intestinal inflammatory profile in IBS patients with or without fructose intolerance.Design: Patients referred to colonoscopy with IBS complaints were screened for participation. IBS patients diagnosed according to the Rome II criteria and with no organic gastrointestinal disease were included in the study. One subgroup was patients included in a fructose-reduced diet study for 2 months with effects based on VAS symptom scores. Healthy controls were subjects under investigation of colorectal cancer screening with no IBS or other gastrointestinal diseases. All patients included had normal histology from rectum. Mucosal cytokines, chemokines and growth factors were measured by multiplex technology.Results: Of 27 inflammatory markers tested in the mucosal tissue, 13 were significantly increased and none was significantly decreased in IBS as compared to controls. Significantly increased were the proinflammatory cytokines tumor necrosis factor, the typical TH1 markers IFNγ, IL-1β, IL-2 and RANTES, the typical TH2 markers IL-5 and IL-9, the TH17 marker IL-17, TNF, the pleiotropic IL-15, and the growth factors bFGF and GM-CSF. In IBS patients with fructose intolerance only IL-5 was significantly increased compared to patients without fructose intolerance.Conclusions: A dysregulated mucosal inflammatory profile with an increased level of TH1, TH2 and TH17 markers, and growth factors were observed in bowel mucosa in of IBS patients when compared to healthy controls.

Soy isoflavones and cholecalciferol reduce inflammation, and gut permeability, without any effect on antioxidant capacity in irritable bowel syndrome: A randomized clinical trial

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder that is more prevalent in women. Vitamin D deficiency and hormonal disorders are also prevalent in Iranian women, and may influence the severity of clinical outcomes mediated by microinflammation, oxidative stress and intestinal permeability pathways. Our objective was to investigate the effects of co-administration of soy and vitamin D on some inflammatory, antioxidant and gut permeability markers in women with IBS.

METHODS

In a randomized clinical trial, women (18-75 years of age) were randomly allocated into four groups to receive soy isoflavones (40 mg/day), cholecalciferol (50,000 IU/15 days), both soy isoflavones and cholecalciferol, or placebo for six weeks. The outcomes were plasma inflammatory markers, antioxidant status and fecal protease activity at week 0 and week 6.

RESULTS

After the intervention, plasma inflammatory markers and fecal protease activity were reduced significantly in all treatment groups compared to the placebo group; however, there was no significant effect on antioxidant status.

CONCLUSION

This study suggests combined supplementation of soy isoflavones and active vitamin D can improve some biochemical parameters regarding inflammation and intestinal permeability of IBS in women.

TRIAL REGISTRATION

Clinical.Trials.govNCT02026518.

Functional dyspepsia susceptibility is associated with TGFB1 gene polymorphisms (RS4803455, RS1800469) in H pylori-negative Chinese population

BACKGROUND

We previously published that altered expression of gastric TRPV1, BDNF, and peripheral cytokines was present in patients with functional dyspepsia. We herein examine whether genetic predisposition in altered biomarkers influences dyspeptic, sleep, and mood symptoms in patients with FD without previous infection.

METHODS

Consecutive adult FD patients (Rome III) with no recent history of gastroenteritis and asymptomatic age- and sex-matched healthy controls were recruited for upper endoscopy. Subjects with GERD and IBS as predominant symptoms, diabetes mellitus, current or previous H pylori infection, psychiatric illness, and recent use of NSAID or PPI were excluded. The genetic associations with dyspeptic symptoms, sleep quality, and mood symptoms were evaluated. Genetic polymorphisms in TRPV1, TGFB1, TNF, COMT, BDNF, IL6, IL8, IL10, and IL12 were analyzed.

KEY RESULTS

Twenty-nine male FD patients and 104 female FD patients were age matched (±3 years) with 81 healthy subjects. All had postprandial distress syndrome (PDS) as predominant subtype (PDS: 130, EPS: 3). SNPs in TGFB1 showed significant associations in dyspeptic patients after age and sex adjustment [for RS4803455: in the codominant model (C/A, OR = 0.34 (0.18-0.65), P = .004); in the dominant model (genotype C/C vs C/A-A/A, OR = 0.42 (0.23-0.77), P = .004); and in the overdominant model (genotype C/C-A/A vs C/A, OR = 0.38 (0.21-0.70), P < .001)] [for RS1800469: in dominant model (genotype A/A vs A/G-G/G, OR = 0.52 (0.27-0.99), P = .043)]. A allele in RS4803455 was associated with higher HADS depression score (P = .05) and epigastric burning sensation(P = .01).

CONCLUSIONS AND INFERENCES

Our data showed that dyspeptic patients predispose genetic difference in TGFB1 which may influence the severity of dyspepsia.

Post-infectious Irritable Bowel Syndrome: A Narrative Review

The Irritable bowel syndrome (IBS) is a functional disorder of alimentary system, which may be caused by infectious gastroenteritis determined as post infectious irritable bowel syndrome (PI-IBS). The prevalence of PI-IBS is reported to be 4-36% in patients with infectious gastroenteritis. The exact mechanism leading to PI-IBS is not fully understood and some factors pertaining to infectious agent and host response may have a role. Rome IV diagnostic criteria provided new definition for PI-IBS. Though it is now considered a well-defined functional disorder of gastrointestinal system, no specific treatment is yet available for PI-IBS. This article reviews the latest issues on these heading about PI-IBS.

Expression of Toll-like Receptors, Pro-, and Anti-inflammatory Cytokines in Relation to Gut Microbiota in Irritable Bowel Syndrome: The Evidence for Its Micro-organic Basis

Background/Aims

A Subset of patients with irritable bowel syndrome (IBS) may have mild inflammation due to immune activation. Toll-like receptors (TLRs) and cytokines may cause intestinal inflammation. We studied their expression in relation to gut microbiota.

Methods

Expression of TLRs and cytokines was assessed in 47 IBS patients (Rome III) and 25 controls using quantitative real-time polymerase chain reaction. Immunohistochemistry was further performed to confirm the expression of TLR-4 and TLR-5.

Results

Of 47 patients with IBS, 20 had constipation (IBS-C), 20 diarrhea (IBS-D), and 7 unclassified (IBS-U). The mRNA levels of TLR-4 and TLR-5 were up-regulated in IBS patients than controls (P = 0.013 and P < 0.001, respectively). Expression of TLR-4 and TLR-5 at protein level was 4.2-folds and 6.6-folds higher in IBS-D than controls. The mRNA levels of IL-6 (P = 0.003), C-X-C motif chemokine ligand 11 (CXCL-11) (P < 0.001) and C-X-C motif chemokine receptor 3 (CXCR-3) (P < 0.001) were higher among IBS patients than controls. Expression of IL-6 (P = 0.002), CXCL-11 (P < 0.001), and CXCR-3 (P < 0.001) were up-regulated and IL-10 (P = 0.012) was down-regulated in IBS-D patients than controls. Positive correlation was seen between TLR-4 and IL-6 (P = 0.043), CXCR-3, and CXCL-11 (P = 0.047), and IL-6 and CXCR-3 (P = 0.003). Stool frequency per week showed positive correlation with mRNA levels of TLR-4 (P = 0.016) and CXCR-3 (P = 0.005), but inversely correlated with IL-10 (P = 0.002). Copy number of Lactobacillus (P = 0.045) and Bifidobacterium (P = 0.011) showed correlation with IL-10 in IBS-C, while Gram-positive (P = 0.031) and Gram-negative bacteria (P = 0.010) showed correlation with CXCL-11 in IBS-D patients.

Conclusions

Altered immune activation in response to dysbiotic microbiota may promote intestinal inflammation in a subset of patients with IBS.

The Host Antimicrobial Protein Calgranulin C Participates in the Control of Campylobacter jejuni Growth via Zinc Sequestration

Campylobacter jejuni is a leading cause of bacterially derived gastroenteritis worldwide. Campylobacter is most commonly acquired through the consumption of undercooked poultry meat or through drinking contaminated water. Following ingestion, Campylobacter adheres to the intestinal epithelium and mucus layer, causing toxin-mediated inflammation and inhibition of fluid reabsorption. Currently, the human response to infection is relatively unknown, and animal hosts that model these responses are rare. As such, we examined patient fecal samples for the accumulation of the neutrophil protein calgranulin C during infection with Campylobacter jejuni In response to infection, calgranulin C was significantly increased in the feces of humans. To determine whether calgranulin C accumulation occurs in an animal model, we examined disease in ferrets. Ferrets were effectively infected by C. jejuni, with peak fecal loads observed at day 3 postinfection and full resolution by day 12. Serum levels of interleukin-10 (IL-10) and tumor necrosis factor alpha (TNF-α) significantly increased in response to infection, which resulted in leukocyte trafficking to the colon. As a result, calgranulin C increased in the feces of ferrets at the time when C. jejuni loads decreased. Further, the addition of purified calgranulin C to C. jejuni cultures was found to inhibit growth in a zinc-dependent manner. These results suggest that upon infection with C. jejuni, leukocytes trafficked to the intestine release calgranulin C as a mechanism for inhibiting C. jejuni growth.

Current insights into the innate immune system dysfunction in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a functional bowel disorder associated with abdominal pain and alterations in bowel habits. The presence of IBS greatly impairs patients' quality of life and imposes a high economic burden on the community; thus, there is intense pressure to reveal its elusive pathogenesis. Many etiological mechanisms have been implicated, but the pathophysiology of the syndrome remains unclear. As a result, novel drug development has been slow and no pharmacological intervention is universally accepted. A growing evidence implicates the role of low-grade inflammation and innate immune system dysfunction, although contradictory results have frequently been presented. Mast cells (MC), eosinophils and other key immune cells together with their mediators seem to play an important role, at least in subgroups of IBS patients. Cytokine imbalance in the systematic circulation and in the intestinal mucosa may also characterize IBS presentation. Toll-like receptors and their emerging role in pathogen recognition have also been highlighted recently, as dysregulation has been reported to occur in patients with IBS. This review summarizes the current knowledge regarding the involvement of any immunological alteration in the development of IBS. There is substantial evidence to support innate immune system dysfunction in several IBS phenotypes, but additional studies are required to better clarify the underlying pathogenetic pathways. IBS heterogeneity could potentially be attributed to multiple causes that lead to different disease phenotypes, thus explaining the variability found between study results.

A Novel Prebiotic Blend Product Prevents Irritable Bowel Syndrome in Mice by Improving Gut Microbiota and Modulating Immune Response

Irritable bowel syndrome (IBS) is the most common functional gastrointestinal disorder yet it still lacks effective prevention therapies. The aim of this study is to determine whether a novel prebiotic blend (PB) composed of fructo-oligosaccharide (FOS), galactooligosaccharide (GOS), inulin and anthocyanins could be effective in preventing the development of IBS. We explored the possible mechanisms both in animal and in cells. Post-infectious IBS models in C57BL/6 mice were established and were pretreated with the PB, PB and probiotic strains 8 weeks in advance of infection. Eight weeks after infection, intestinal tissues were collected for assessing histomorphology, visceral sensitivity, barrier function, pro-inflammatory cytokines expression and proteomics analysis. Fecal samples were also collected for microbiota analysis. The pro-inflammatory cytokines expression in Caco-2 cells were evaluated after co-incubation with PB and Salmonella typhimurium 14028. The results showed that PB significantly decreased the pro-inflammatory cytokines both in infected Caco-2 cells and PI-IBS models. The loss of body weight, decreased expression of tight junction protein Occludin (OCLN), and changes of the microbiota composition induced by infections could be greatly improved by PB intervention (p < 0.05). The proteomics analysis revealed that this function was associated with Peroxisome proliferator-activated receptor (PPAR)γ pathway.

Post-Infectious Irritable Bowel Syndrome

PURPOSE OF REVIEW

Post-infectious irritable bowel syndrome (PI-IBS) is characterized by persistent abdominal pain and diarrhea, typically following an episode of infectious gastroenteritis. The mechanisms that underlie IBS-D remain elusive, but PI-IBS provides a mechanistic model of this disorder. This review provides an up-to-date appraisal of the pathophysiology, clinical features, and management approaches for PI-IBS.

RECENT FINDINGS

Disordered immune reactions and release of cytokines with resultant gut inflammation and dysfunction appear to be key features of PI-IBS. Disordered brain-gut-microbiota interactions, type of infecting agent, and host-genetic susceptibility are risk factors but also are reasons for the varying spectrum of clinical severity. Although prognosis is generally good, symptoms and inflammation may persist for a long time. Symptomatic relief with antidiarrheals, antispasmodics, 5HT₃ antagonists, mesalamine, probiotics, and low-dose antidepressants remain the primary approaches, but in some difficult cases, a combination of drugs that target the pathophysiology may be helpful. PI-IBS has many overlapping features with IBS-D and shares similar pathophysiology and management approaches.

Influence of TNF-α-308 G/A gene polymorphism on temporomandibular disorder

INTRODUCTION

Tumor necrosis factor alpha (TNF-α) levels are significantly upregulated in the synovial fluid of patients with temporomandibular joint disorder (TMD). The TNF-α influences pain generation and maintenance. Therefore, the aim of this study was to investigate the influence of single nucleotide polymorphism TNFA-308 (rs1800629) on TMD risk and on the pressure pain threshold.

METHODS

The genotypic and allelic frequencies of candidate single nucleotide polymorphisms were compared among 152 TMD patients and 91 sex- and age-matched healthy subjects in the control group using the real-time polymerase chain reaction technique. The pressure pain threshold in the temporomandibular joint, anterior fascicle of the temporal muscle, masseter muscle, and Achilles tendon were recorded with an algometer. After the pressure test, all participants received a complete physical examination, including masticatory muscle evaluation, temporomandibular joint palpation, and assessment of mandibular range of motion.

RESULTS

The TNFA-308 polymorphism is positively associated with TMD. Subjects with TMD had a 2.87 (95% confidence interval, 1.256-6.569) times greater chance of having the GA genotype than did the control group. Rare A-allele homozygotes demonstrated decreased pain sensitivity for the temporomandibular joint and anterior fascicle of the temporal muscle in the pressure pain threshold test compared with ancestral allele homozygotes.

CONCLUSIONS

This study presents an unprecedented association between the TNFA-308 (rs1800629) polymorphism and TMD. Future studies are needed to enlighten the association between TNFA-308 G/A single nucleotide polymorphism and mechanical pain sensitivity.

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

PURPOSE

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

METHODS

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

FINDINGS

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

IMPLICATIONS

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

Blastocystis and irritable bowel syndrome: Frequency and subtypes from Iranian patients

There are inconsistent findings about the role of Blastocystis infection in irritable bowel syndrome (IBS). The present study was aimed to determine the frequency of Blastocystis and their subtypes (ST) in patients with IBS. A total of 122 patients with IBS and 122 healthy individuals referred to the medical laboratory centers in Ahvaz (southwest of Iran) participated in the study. The frequency of Blastocystis was determined. Blastocystis genomic DNA was extracted from positive feces, and PCR was performed using seven primer pairs targeting the SSU rDNA gene. Blastocystis was detected in 19.67% of patients with IBS and 17.2% of individuals without IBS. The difference between two groups was not statistically significant (P=0.3). Among the five subtypes of Blastocystis, ST3 was more common in patients with IBS and control group. However, there were no significant differences between two groups in terms of subtypes of Blastocystis (P=0.6). It seems, the role of Blastocystis in the etiology of IBS should be further investigated. Furthermore, a model of study should be designed to investigate the role of host factors in severity of parasitic disease.

[Current Status of Translational Research on Irritable Bowel Syndrome]

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder. The pathophysiology of IBS is not completely understood. Genetic, immune, environmental, inflammatory, neurological and psychological factors contribute to the risk of this condition. Traditional research explored gastrointestinal motor abnormalities, central neural dysregulation, abnormal psychological features, and visceral hypersensitivity. More recent investigations consider bacterial overgrowth, abnormal serotonin pathways, altered gut flora, immune activation and mucosal inflammation. The purpose of this article is to review recent translational research concerning the pathophysiology, biomarker and genetic factors of IBS and to encourage IBS research in Korea.

Immune response in irritable bowel syndrome: A systematic review of systemic and mucosal inflammatory mediators

OBJECTIVE

To systematically review the available data on cytokine and immune cells in the peripheral blood and mucosal biopsy samples from patients with irritable bowel syndrome (IBS).

METHODS

From a review of the literature, data on cytokines and immune cells that had been assayed in at least three independent studies were collated and trends examined.

RESULTS

Levels of interleukin (IL)-10 tended to be decreased and those of IL-6, IL-8, tumor necrosis factor-α and IL-1β increased in the systemic circulation in IBS, while in the mucosa, IL-10 was decreased and IL-8, mast cells, enterochromaffin cells and CD3⁺ T lymphocytes were increased. However, these findings were not consistent across all studies and, in some instances, were limited to certain IBS sub-populations.

CONCLUSIONS

The interpretation of this literature is limited by several factors, such as the intrinsic heterogeneity of IBS and a lack of standardization in study design. While a number of intriguing immunological observations have been made in IBS, more work is needed before a compelling case can be made for a role for immune-mediated events in the etiology of IBS.

High-sensitive C-Reactive Protein as a Marker for Inflammation in Irritable Bowel Syndrome

BACKGROUND

Recent studies demonstrated low-grade inflammation in patients with irritable bowel syndrome (IBS). However, these studies have been relatively small and do not enable examination of this factor in different subtypes of IBS and the possibility of confounding effects of comorbidities that may be associated with inflammatory responses.

GOALS

To investigate the association between high-sensitive C-reactive protein (hs-CRP) and the diagnosis of IBS, IBS subtypes, symptoms' severity, and IBS-associated comorbidities.

STUDY

This cross-sectional study uses data from a large matched case-control study of IBS subjects and healthy controls (HC). hs-CRP levels were measured in all subjects. IBS diagnosis was determined by Rome III criteria, negative screening blood tests, and normal colonoscopy. Subjects were evaluated for IBS severity and associated pain and psychological comorbidities.

RESULTS

A total of 242 IBS patients and 244 HC were studied. Median hs-CRP levels in the IBS group were significantly higher than in HC (1.80; interquartile range, 0.7 to 4.04 mg/L vs. 1.20, interquartile range, 0.5 to 2.97 mg/L respectively, P<0.006). Levels were highest in IBS-D patients with greater disease severity. Hs-CRP levels mildly correlated with symptoms severity (r=0.169, P=0.009); this correlation was stronger for the IBS-D patients (r=0.27, P=0.006). IBS was a significant independent predictor (P=0.025) for higher hs-CRP levels, whereas other pain and psychological comorbidities were not.

CONCLUSIONS

Given these observations of cross-sectional differences in hs-CRP between IBS subtypes and severity, independent of pain and comorbidities, more research is needed to explore a possible role of low-grade inflammation in the pathogenesis and/or clinical presentation of IBS.

Lessons learned--resolving the enigma of genetic factors in IBS

IBS is the most prevalent functional gastrointestinal disorder and phenotypically characterized by chronic abdominal discomfort, pain and altered defecation patterns. The pathophysiology of IBS is multifactorial, albeit with a substantial genetic component. To date, studies using various methodologies, ranging from family and twin studies to candidate gene approaches and genome-wide association studies, have identified several genetic variants in the context of IBS. Yet, despite enlarged sample sizes, increased statistical power and meta-analyses in the past 7 years, positive associations are still scarce and/or have not been reproduced. In addition, epigenetic and pharmacogenetic approaches remain in their infancy. A major hurdle is the lack of large homogenized case-control cohorts recruited according to standardized and harmonized criteria. The COST Action BM1106 GENIEUR (GENes in Irritable Bowel Syndrome Research Network EURope) has been established to address these obstacles. In this Review, the (epi)genetic working group of GENIEUR reports on the current state-of-the-art in the field, highlights fundamental flaws and pitfalls in current IBS (epi)genetic research and provides a vision on how to address and improve (epi)genetic approaches in this complex disorder in the future.

Immune dysregulation in the functional gastrointestinal disorders

Gastrointestinal conditions may be broadly classified into two: organic and functional disease, with functional disorders accounting for the majority of patients with chronic gastrointestinal symptoms. Functional gastrointestinal disorders (FGIDs) present with no obvious pathology or well-accepted biochemical mechanism and, as such, treatment strategies are limited and focus on symptoms rather than cure. Irritable bowel syndrome and functional dyspepsia are the most widely recognised FGIDs, and there is a growing body of evidence to suggest an underlying inflammatory phenotype in subsets with these conditions. Here, we discuss the current knowledge of immune involvement in FGIDs and the commonalities between the different manifestations of FGIDs and propose a new hypothesis, potentially defining an underlying immunopathological basis of these conditions.

Genetic epidemiology of irritable bowel syndrome

Irritable bowel syndrome (IBS) is the most common functional gastrointestinal disorder characterized by presence of abdominal pain or discomfort associated with altered bowel habits. It has three main subtypes - constipation predominant IBS (C-IBS), diarrhea predominant IBS (D-IBS) and IBS with mixed features of both diarrhea as well as constipation (M-IBS). Its pathophysiology and underlying mechanisms remain elusive. It is traditionally believed that IBS is a result of multiple factors including hypersensitivity of the bowel, altered bowel motility, inflammation and stress. Initial studies have shown familial aggregation of IBS suggesting shared genetic or environmental factors. Twin studies of IBS from different parts of world have shown higher concordance rates among monozygotic twins than dizygotic twins, and thus suggesting a genetic component to this disorder. Multiple studies have tried to link single-nucleotide polymorphisms (SNPs) to IBS but there is little evidence that these SNPs are functional. Various molecules have been studied and investigated by the researchers. Serotonin, a known neurotransmitter and a local hormone in the enteric nervous system, has been most extensively explored. At this time, the underlying gene pathways, genes and functional variants linked with IBS remain unknown and the promise of genetically-determined risk prediction and personalize medicine remain unfulfilled. However, molecular biological technologies continue to evolve rapidly and genetic investigations offer much promise in the intervention, treatment and prevention of IBS.

Epidemiology of Functional Gastrointestinal Disorders in Japan and in the World

Functional gastrointestinal disorders (FGIDs), represented by functional dyspepsia (FD) and irritable bowel syndrome (IBS), are a group of disorders that include variable combinations of chronic or recurrent gastrointestinal symptoms not explained by structural or biochemical abnormalities. FGIDs account for a significant percentage of patients seen in primary care settings with abdominal symptoms. Although the definition of FGIDs can easily affect the prevalence, the prevalences of dyspepsia/FD and IBS diagnosed by the Rome III criteria in the general population are 5.3–20.4% and 1.1–29.2%, respectively. Recent reports of FD and IBS defined by the Rome III criteria indicated a female predominance. Regarding the subtype prevalence of FD, postprandial distress syndrome was more prevalent than epigastric pain syndrome (5.6–13.9% vs 0.9–9.5%). The subtype prevalence of IBS is characterized by male predominance for IBS with diarrhea and female predominance for IBS with constipation. Factors affecting the development of FGIDs such as epidemiological factors including genetic and environmental factors, are important. Gene polymorphisms are involved in the development of FGIDs. The prevalence differs among races and geographic areas. Foods may affect the development of FGIDs, but the causal relationships between food and FGIDs are not conclusive. The symptoms often regress and appear in the course of these entities. Building a favorable patient-doctor relationship is effective for controlling symptoms of FGIDs. Physicians should explain that FGIDs are highly prevalent conditions, impair the patients’ quality of life even without evident underlying organic causes and are not life-threatening conditions to ensure patients’ understanding.

Food allergy in irritable bowel syndrome: The case of non-celiac wheat sensitivity

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders, having a prevalence of 12%-30% in the general population. Most patients with IBS attribute their symptoms to adverse food reactions. We review the role of diet in the pathogenesis of IBS and the importance of dietary factors in the management of these patients. The MEDLINE electronic database (1966 to Jan 2015) was searched using the following keywords: "food", "diet", "food allergy", "food hypersensitivity", "food intolerance", "IBS", "epidemiology", "pathogenesis", "pathophysiology", "diagnosis", "treatment". We found 153 eligible papers; 80 were excluded because: not written in English, exclusive biochemical and experimental research, case reports, reviews, and research otherwise not relevant to our specific interest. We selected 73 papers: 43 original papers, 26 reviews and 4 letters to the editor. These papers focused on IBS pathogenesis, the association between IBS and atopy, and between IBS and food allergy, the relationship between IBS and non-celiac wheat sensitivity, the role of diet in IBS. Pending further scientific evidence, a cautious approach is advisable but the concept of food allergy should be included as a possible cause of IBS, and a dietary approach may have a place in the routine clinical management of IBS.

A meta-analysis of immunogenetic Case-Control Association Studies in irritable bowel syndrome

BACKGROUND

To date, genetic-association studies of single nucleotide polymorphisms (SNP) in selected candidate genes with the symptom phenotype of irritable bowel syndrome (IBS) have typically involved hundreds to 2000 patients. SNPs in immune-related genes, such as cytokine and cytokine receptor encoding genes, have been reported to associate with IBS risk.

METHODS

We conducted two independent case-control studies on 16 SNPs in IL1R1, IL4, IL6, IL8, IL10, IL23R, TNFA, and TNFSF15, one from the UK (194 patients and 92 healthy volunteers) and one from the USA (137 patients and 96 healthy volunteers). The main aim was to examine the relationship between inherited immunological diversity and IBS risk in a meta-analysis which included 12 additional, earlier studies. The meta-analysis comprised a total of 2894 patients (839 IBS-C, 1073 IBS-D, 502 IBS-M), and 3138 healthy volunteers with self-reported Caucasian ancestry.

KEY RESULTS

The association of SNP rs4263839 (TNFSF15) was investigated in four studies and confirmed in the meta-analysis: IBS (OR 1.19, 95% CI 1.08-1.31), and IBS-C (OR 1.24, 95% CI 1.08-1.42). No additional SNPs residing in immunogenes associated with IBS symptom phenotypes.

CONCLUSIONS & INFERENCES

Our meta-analysis could not confirm a major role of most investigated SNPs, but a moderate association between rs4263839 TNFSF15 and IBS, in particular IBS-C. The analysis emphasizes the importance of definition and phenotype homogeneity, adequate study size and representativeness of the patient and control collective.

Pathways in gut-brain communication: evidence for distinct gut-to-brain and brain-to-gut syndromes

OBJECTIVE

The rich interconnectedness between gut and brain is increasingly being identified. This article reviews the evidence for brain-gut and gut-brain syndromes, particularly recent epidemiological evidence, and animal studies demonstrating bi-directionality at the formative stage of development.

METHOD

Narrative literature review with selection for relevance and quality.

RESULTS

Population surveys show a strong correlation between anxiety, depression, and functional gastrointestinal disorders, contradicting early suspicions that the high prevalence of anxiety and depression in the clinic was mainly due to neurotic health seeking behaviour. Five and 12 year follow-up shows that psychological distress can predict later onset of a functional gastrointestinal disorder and vice versa. Brain-gut pathways include the autonomic nervous system, hypothalamic-pituitary-adrenal axis including corticotrophin releasing factor directly acting on the gut. Gut-brain pathways include ascending pain pathways, cytokines including tumour necrosis factor alpha in response to bacterial translocation and inflammation, 5-hydroxytryptamine secretion by entero-endocrine cells and psychoactive chemicals of bacterial origin which may enter the blood stream, such as gamma-aminobutyric acid, fatty acids and 5-hydroxytryptamine precursors. The ability to control rodent temperament and HPA responsiveness with early modification of gastrointestinal flora, and the effects of early stress on the barrier function of the gastrointestinal tract and flora, suggests an ability of both systems to prime each other in early life for later problems. This hypothesis seems to be supported by a possible protective effect of a probiotic strain of bacteria in a model of early rat psychological trauma.

CONCLUSION

Psychological treatments are known to improve functional gastrointestinal disorders, the next wave of research may involve preventative microbiological gut based treatments for primary psychological presentations, both to treat the presenting complaint and inoculate against later functional gastrointestinal disorders.

Proinflammatory and anti-inflammatory cytokine profile in pediatric patients with irritable bowel syndrome

BACKGROUND AND OBJECTIVES

There is evidence that patients with irritable bowel syndrome (IBS) have a low degree of inflammation in the intestinal mucosa. The aim of the study was to evaluate the profile of pro- and anti-inflammatory cytokines in plasma in Mexican pediatric patients with IBS.

PATIENTS AND METHODS

Fifteen patients with IBS according to Rome III criteria for childhood and 15 healthy children, matched by age and sex, were included in the study. Plasma levels of tumoral necrosis factor alpha (TNF-α), interleukins 10 and 12 (IL-10, IL-12) and transforming growth factor beta (TGF-β) were quantified and compared between groups.

RESULTS

Plasma levels of IL-10 were lower in patients with IBS (86.07+21.3 pg/mL vs. 118.71+58.62 pg/mL: P=.045) and IL-12 levels were higher in patients with IBS compared to the control group of healthy children (1,204.2±585.9 pg/mL vs. 655.04±557.80 pg/mL; P=.011). The IL-10/IL-12 index was lower in patients with IBS (0.097±0.07 vs. 0.295±0.336; P=.025). Plasma concentration of TGF-β was higher in patients with IBS (545.67±337.69 pg/mL vs. 208.48±142.21 pg/mL; P=.001). There was no difference in plasma levels of TNF-α between groups.

CONCLUSIONS

This study suggests that children with IBS have a state of altered immune regulation. This is consistent with the theory of low-grade inflammatory state in these patients. Further studies are needed to elucidate the role played by these cytokines, specifically TGF-β in the pathogenesis of IBS.

Crosstalk at the mucosal border: importance of the gut microenvironment in IBS

The aetiology and pathology of IBS, a functional bowel disorder thought to lack an organic cause, is largely unknown. However, studies suggest that various features, such as altered composition of the gut microbiota, together with increased intestinal permeability, a changed balance in the enteroendocrine system and a dysregulated immune system in the gut, most likely have an important role in IBS. Exactly how these entities act together and give rise to symptoms is still unknown, but an altered gut microbiota composition could lead to dysregulation of the intestinal barrier as well as the enteroendocrine and the immune systems, which (through interactions with the nervous system) might generate symptoms. This Review highlights the crosstalk between the gut microbiota, the enteroendocrine system, the immune system and the role of intestinal permeability in patients with IBS.

IL-10 promoter polymorphisms influence susceptibility to aGvHD and are associated with proportions of CD4+FoxP3+ lymphocytes in blood after hematopoietic stem cell transplantation

Four hundred and ninety-five patients (390 and 105 grafted from unrelated and sibling (SIB) donors, respectively) and their donors were analyzed for the impact of interleukin-10 (IL-10) promoter genotype [rs18000896 (-1082 G/A), rs18000871 (-819 C/T) and rs18000872 (-592 C/A)] on the outcome of hematopoietic stem cell transplantation (HSCT). Patients having ACC haplotype were at a lower risk of acute graft versus host disease (aGvHD, grade > I) if transplanted from human leukocyte antigen (HLA) well-matched (10/10) unrelated donors (20/135 vs 39/117, P < 0.001, Pcorr = 0.002), which was not seen if patients were transplanted from either sibling (SIB) or poorly matched (<10/10) unrelated donors (MUD). In addition, GCC haplotype positive recipients of unrelated donor transplants tended to be more susceptible to aGvHD (68/199 vs 39/169, P = 0.019, Pcorr = 0.057). Multivariate logistic regression analysis in the MUD transplanted group showed that donor-recipient human leukocyte antigen (HLA) mismatch [odds ratio (OR) = 3.937, P = 0.001] and a lack of ACC haplotype in recipients (OR = 0.417, P = 0.013) played a significant role as independent risk factors of aGvHD grade > I. ACC carriers had higher proportions of FoxP3+ lymphocytes gated in CD4+ lymphocytes as compared with patients with other IL-10 haplotypes. It was seen at the time of hematological recovery (mean ± SEM: 3.80 ± 0.91% vs 2.06 ± 0.98%, P = 0.012) and 2 weeks later (5.32 ± 0.87% vs 2.50 ± 0.83%, P = 0.013); -592 C/A polymorphism was separately analyzed and it was found that AA homozygotes tended to have a higher incidence of aGvHD (8/15 vs 116/456, P = 0.034) and low proportions of FoxP3 CD4+ lymphocytes in blood (0.43 ± 0.22% vs 4.32 ± 0.71%, P = 0.051) measured 2 weeks after hematological recovery. Functional IL-10 polymorphism associated features influenced the risk of aGvHD with a positive effect of ACC on the pool of Treg in blood.

Associations between IL-1RA polymorphisms and small intestinal bacterial overgrowth among patients with irritable bowel syndrome from India

BACKGROUND

Low-grade inflammation (controlled by pro and anti-inflammatory molecules), induced by gut microbes in patients with small intestinal bacterial overgrowth (SIBO), may be associated with irritable bowel syndrome (IBS). Polymorphisms of IL-RA gene (anti-inflammatory) was evaluated in IBS and healthy subjects (HS); small intestinal mucosal IL-1α and β levels (pro-inflammatory) in relation to the presence of SIBO were evaluated in a subset of patients.

METHODS

Two hundred and twenty-one IBS patients and 273 age- and gender-matched HS were included. Exactly 209 of 221 patients (Rome III) and 273 HS were genotyped (PCR) for IL-1RA polymorphism. Mucosal IL-1α and β levels (pg/mg of biopsy) were estimated (ELISA) in 82/221 patients with and without SIBO (≥10(5)  CFU/mL upper gut aspirate bacteria).

KEY RESULTS

Genotype 1/1 (IL-1RA over-producer) was less frequent among patients than controls (p = 0.007); genotypes 1/3 (p = 0.012, OR = 3.301, 95% CI = 1.31-8.35) and 2/3 (both under-producers; p = 0.009, OR = 7.703, 95% CI = 1.66-35.82) were commoner among IBS. Fifteen of 82 (18.3%) patients had SIBO. Levels of IL-1α and β were higher among patients with SIBO than without (IL-1α: 35.4 [20.1-66.8] vs 25.5 [4.2-65.3], p < 0.001; IL-1β: 206.8 [133.5-365.9] vs 93.1 [25.5-197.7], p < 0.001) and those with bloating than without (p = 0.012; p = 0.015). IL-1β was higher among patients with Bristol stool type 6 than those with type 1-2 (p = 0.002) and type 3-5 (p = 0.007).

CONCLUSIONS & INFERENCES

Polymorphisms 1/1 (IL-1RA over-producer) was infrequent and 1/3 and 2/3 (under-producers) frequent among IBS. Increased IL-1α and β levels were associated with SIBO. Increased IL-1β level was predominantly associated with bloating and loose stools (Bristol type 6).

Aberrant mucosal lymphocyte number and subsets in the colon of post-infectious irritable bowel syndrome patients

BACKGROUND

Irritable bowel syndrome (IBS) is characterized by chronic abdominal symptoms such as pain, discomfort, and altered bowel habits. A subset of IBS patients, denoted as post-infectious IBS (PI-IBS) patients, develop symptoms after an enteric infection. Distinct abnormalities in the gut mucosa, including mucosal inflammation, have been proposed to contribute to or be the cause of PI-IBS. This study investigated lymphocyte subsets in PI-IBS patients compared to healthy controls.

MATERIALS AND METHODS

Ten PI-IBS patients and nine healthy controls participated. All PI-IBS patients met the Rome III diagnostic criteria for IBS and reported sustained symptoms at least 1 year after an episode of acute gastroenteritis. Intraepithelial lymphocytes and lamina propria lymphocytes (LPLs), isolated from mucosal tissue samples, were stained and analyzed for a comprehensive set of cell markers using flow cytometry.

RESULTS

The number of LPLs in PI-IBS was significantly increased compared to those in healthy controls (p < 0.05). PI-IBS patients showed significantly increased proportions of CD45RO(+) CD4(+) activated/memory T cells (p < 0.05) and double-positive CD4(+) CD8(+) cells (p < 0.05), respectively, in the lamina propria. The number of CD19(+) LPLs was decreased in PI-IBS patients compared to healthy controls (p < 0.001).

CONCLUSION

This study presents new evidence that PI-IBS is associated with a sustained aberrant mucosal immune response and support future studies of anti-inflammatory or immune-modulating treatments in these patients.

Relationship between IL-10 promoter gene polymorphisms and plasma level and susceptibility to overlap syndrome of diarrhea irritable bowel syndrome and functional dyspepsia

AIM: To investigate the relationship between interleukin-10 (IL-10) promoter gene polymorphisms and plasma levels and susceptibility to overlap syndrome of diarrhea irritable bowel syndrome (D-IBS) and functional dyspepsia (FD).

METHODS: Blood samples were collected from 164 patients and 200 healthy controls and genomic DNA was extracted. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to determine the genotypes in the -592A/C site, and amplification refractory mutation system polymerase chain reactions (ARMS-PCR) and DNA sequencing were performed to detect the polymorphism of the -1082G/A site. IL-10 plasma levels were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS: The -592A/C site in the IL-10 gene showed no significant differences in genotypes or allele frequency between the D-IBS-FD overlap syndrome group and control group, but the frequency of -592 CC genotype was significantly decreased in the D-IBS-FD overlap syndrome group. Compared with the CC genotype, the AA genotype and the AA+AC genotypes increased the risk of D-IBS-FD overlap syndrome 1.989 and 1.808 times, respectively. There were no significant differences in the distribution or the allele frequency of -1082 genotypes, the genotypes of the combination of -592 and -1082, and the distribution of the genotypes of different IL-10 levels between the D-IBS-FD overlap syndrome and healthy control groups. The average plasma IL-10 levels were significantly lower in patients with D-IBS-FD overlap syndrome than in healthy controls (14.60 pg/mL ± 7.14 pg/mL vs 22.86 pg/mL ± 10.62 pg/mL, P < 0.001). Among patients with D-IBS-FD overlap syndrome, the average plasma IL-10 levels in patients with -592 AA, -592 AC, -592 CC, and -592 AA+AC genotypes were 14.50 pg/mL ± 6.37 pg/mL, 14.85 pg/mL ± 7.75 pg/mL, 13.92 pg/mL ± 7.63 pg/mL, 14.68 pg/mL ± 7.10 pg/mL, respectively, which showed no significant differences. Plasma IL-10 levels showed no significant difference between the carriers of A allele and non-carriers.

CONCLUSION: The -592A site in IL-10 gene promoter and lower IL-10 plasma level may be associated with susceptibility to overlap syndrome of D-IBS and FD, but there is no association between them.

A role for the gut microbiota in IBS

The past decade has witnessed an explosion of knowledge regarding the vast microbial community that resides within our intestine-the gut microbiota. The topic has generated great expectations in terms of gaining a better understanding of disorders ranging from IBD to metabolic disorders and obesity. IBS is a condition for which investigators have long been in search of plausible underlying pathogeneses and it is inevitable that altered composition or function of the gut microbiota will be considered as a potential aetiological factor in at least a subset of patients with IBS. This Review describes the evidence implicating the gut microbiota in not only the expression of the intestinal manifestations of IBS, but also the psychiatric morbidity that coexists in up to 80% of patients with IBS. The evidence described herein ranges from proof-of-concept studies in animals to observational studies and clinical trials in humans. The gut microbiota is subject to influences from a diverse range of factors including diet, antibiotic usage, infection and stress. These factors have previously been implicated in the pathophysiology of IBS and further prompt consideration of a role for the gut microbiota in IBS.

Genetic variants in CDC42 and NXPH1 as susceptibility factors for constipation and diarrhoea predominant irritable bowel syndrome

OBJECTIVE

The complex genetic aetiology underlying irritable bowel syndrome (IBS) needs to be assessed in large-scale genetic studies. Two independent IBS cohorts were genotyped to assess whether genetic variability in immune, neuronal and barrier integrity genes is associated with IBS.

DESIGN

384 single nucleotide polymorphisms (SNPs) covering 270 genes were genotyped in an exploratory cohort (935 IBS patients, 639 controls). 33 SNPs with Puncorrected<0.05 were validated in an independent set of 497 patients and 887 controls. Genotype distributions of single SNPs were assessed using an additive genetic model in IBS and clinical subtypes, IBS-C and IBS-D, both in individual and combined cohorts. Trait anxiety (N=614 patients, 533 controls), lifetime depression (N=654 patients, 533 controls) and mRNA expression in rectal biopsies (N=22 patients, 29 controls) were correlated with SNP genotypes.

RESULTS

Two SNPs associated independently in the exploratory and validation cohort: rs17837965-CDC42 with IBS-C (ORexploratory=1.59 (1.05 to 1.76); ORvalidation=1.76 (1.03 to 3.01)) and rs2349775-NXPH1 with IBS-D (ORexploratory=1.28 (1.06 to 1.56); ORvalidation=1.42 (1.08 to 1.88)). When combining both cohorts, the association of rs2349775 withstood post hoc correction for multiple testing in the IBS-D subgroup. Additionally, three SNPs in immune-related genes (rs1464510-LPP, rs1881457-IL13, rs2104286-IL2RA), one SNP in a neuronal gene (rs2349775-NXPH1) and two SNPs in epithelial genes (rs245051-SLC26A2, rs17837965-CDC42) were weakly associated with total-IBS (Puncorrected<0.05). At the functional level, rs1881457 increased IL13 mRNA levels, whereas anxiety and depression scores did not correlate with rs2349775-NXPH1.

CONCLUSIONS

Rs2349775 (NXPH1) and rs17837965 (CDC42) were associated with IBS-D and IBS-C, respectively, in two independent cohorts. Further studies are warranted to validate our findings and to determine the mechanisms underlying IBS pathophysiology.

Irritable bowel syndrome: Emerging paradigm in pathophysiology

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders, characterized by abdominal pain, bloating, and changes in bowel habits. These symptoms cannot be explained by structural abnormalities and there is no specific laboratory test or biomarker for IBS. Therefore, IBS is classified as a functional disorder with diagnosis dependent on the history taking about manifested symptoms and careful physical examination. Although a great deal of research has been carried out in this area, the pathophysiology of IBS is complex and not completely understood. Multiple factors are thought to contribute to the symptoms in IBS patients; altered gastrointestinal motility, visceral hypersensitivity, and the brain-gut interaction are important classical concepts in IBS pathophysiology. New areas of research in this arena include inflammation, postinfectious low-grade inflammation, genetic and immunologic factors, an altered microbiota, dietary factors, and enteroendocrine cells. These emerging studies have not shown consistent results, provoking controversy in the IBS field. However, certain lines of evidence suggest that these mechanisms are important at least a subset of IBS patients, confirming that IBS symptoms cannot be explained by a single etiological mechanism. Therefore, it is important to keep in mind that IBS requires a more holistic approach to determining effective treatment and understanding the underlying mechanisms.

Cytokine changes in colonic mucosa associated with Blastocystis spp. subtypes 1 and 3 in diarrhoea-predominant irritable bowel syndrome

We determined cytokines (e.g. interleukin-8, 10, 12 and TNF-α) expression by peripheral blood mononuclear cells (PBMCs) and in rectal mucosa in diarrhoea-predominant irritable bowel syndrome (D-IBS) with Blastocystis spp. Eighty patients with D-IBS and Blastocystis spp. infection were classified as 'cases' and 80 with D-IBS without Blastocystis spp. infection were classified as 'control'. Cases were subdivided into D-IBS and Blastocystis sp. defined type 1 (subtype-specific primer SB83) and type 3 (SB227). Stool microscopy and culture were performed. Rectal biopsies were obtained for histology and cytokines by real-time PCR for mRNA expression of cytokines. PBMCs IL-8 was similar in different groups but in type 1, IL-8mRNA was increased compared with type 3 (P = 0·001) and control (P = 0·001). In type 1, IL-10 by PBMCs had a low mean value (14·5±1·6) compared with (16·7±1·5) type 3 and (16±2·3) in controls (P<0·001 and P<0·001, respectively). In Blastocystis sp. type 1, low IL-10 was associated with lymphocyte and plasma cell infiltration (P = 0·015 and P = 0·002, respectively). In Blastocystis sp. type 1 and type 3, IL-12 was associated with goblet cell depletion 23 (85%) (P<0·001) and 8 (29%) (P = 0·037), respectively. In Blastocystis sp. type 1, low IL-10 was associated with a proinflammatory response characterized by IL-8.

On the fiftieth anniversary. Postinfectious irritable bowel syndrome: mechanisms related to pathogens

BACKGROUND

Gastrointestinal (GI) infections resulting from bacterial, viral, and parasitic pathogens predispose to postinfectious irritable bowel syndrome (PI-IBS) and other functional GI disorders. Existing literature supports the role of enterochromaffin cell hyperplasia, serotonin synthesis and reuptake, impaired barrier function, altered immune activation, and potentially mast cell activation in the pathophysiology of PI-IBS.

PURPOSE

The objective of this review was to summarize from the literature the characteristics of the pathogens commonly implicated in PI-IBS, their acute enteritis phases, and the changes seen in the postinfectious phase that may contribute toward development of IBS. A limitation of our current understanding is that the postinfectious GI sequelae reported in prior studies followed epidemic diarrheal outbreaks often involving more than one pathogen, or the studies focused on highly selected, tertiary referral patients. Understanding the mechanisms, natural history, and optimized management of individuals suffering PI-IBS following the more typical sporadic infection requires larger studies of PI-IBS following GI infections encountered in community settings. These studies should include genetic, physiological, and molecular studies to provide more generalizable information that can ultimately be used to diagnose, manage, and potentially prevent the development of PI-IBS.

Irritable Bowel Syndrome: Peripheral Mechanisms and Therapeutic Implications

Irritable bowel syndrome (IBS) is the most common functional gastrointestinal disorder, affecting about 10 to 20% of the population in developed countries. The mechanisms underlying the symptoms of this condition are poorly understood. Considered initially as the consequence of abnormal gut motility, visceral hypersensitivity, psychosocial factors and brain-gut axis dysfunction, IBS is now acknowledged as a multifactorial disorder. Specific peripheral mechanisms are involved, including mucosal immune activation, increased intestinal permeability, entero-endocrine cell products, an excess of bile acids, gut dysbiosis. A better understanding of these mechanisms could help develop new and specific therapeutic pathways in patients suffering from IBS.

Association of interleukin-10 polymorphisms with risk of irritable bowel syndrome: A meta-analysis

AIM: To clarify the current understanding of the association between interleukin-10 (IL-10) polymorphisms and the risk of irritable bowel syndrome (IBS).

METHODS: We searched for studies in any language recorded in PubMed, Embase and Cochrane library before August 2013. The associations under allele contrast model, codominant model, dominant model, and recessive model were analyzed. The strengths of the association between IL-10 polymorphisms and IBS risk were estimated using odds ratios (OR) with 95% confidence interval (CI). Fixed effects model was used to pool the result if the test of heterogeneity was not significant, otherwise the random-effect model was selected.

RESULTS: Eight case-control studies analyzing three single-nucleotide polymorphisms rs1800870 (-1082 A/G), rs1800871 (-819C/T), and rs1800872 (-592A/C) of the IL-10 gene, which involved 928 cases and 1363 controls, were eligible for our analysis. The results showed that rs1800870 polymorphisms were associated with a decreased risk of IBS (GG+GA vs AA: OR = 0.80, 95%CI: 0.66-0.96), (AA+GA vs GG: OR = 0.68, 95%CI: 0.52-0.90). Subgroup analysis revealed such association only existed in Caucasian ethnicity (AA+GA vs GG, OR = 0.70, 95%CI: 0.55-0.89). The rs1800872 polymorphisms were associated with an increased risk of IBS in Asian ethnicity (CC vs GG: OR = 1.29, 95%CI: 1.01-1.16). There were no associations between rs1800871 polymorphisms and the IBS risk.

CONCLUSION: The results suggest that IL-10 rs1800870 confers susceptibility to the risk of IBS in Caucasian ethnicity, and the rs1800872 may associate with IBS risk in Asians. However, no significant associations are found between rs1800871 and IBS risk.

Susceptibility to stress-induced visceral sensitivity: a bad legacy for next generations

Despite high prevalence, the precise irritable bowel syndrome (IBS) pathophysiology remains poorly understood likely due to the heterogeneity of IBS populations and the multifactorial etiology of this disorder. Among risk factors, genetic predisposition and early life trauma have been reported. In this context, the debate on genetic or environmental influences in the IBS pathogenesis is still open. The study by van der Wijngaard et al., reporting for the first time that susceptibility to stress-induced visceral hypersensitivity in maternally separated rats can be transferred to the next generation without any further exposure of F2 individuals to maternal separation, supports the importance of environmental influence in the IBS phenotype. Epigenetic mechanisms such as hypermethylation in the promoter region of the glucocorticoid receptor gene mediating the long-term and transgenerational behavioral effects of maternal care on the development have been shown in some but not in all studies. Van der Wijngaard et al. incriminated maternal care in the transmitted susceptibility to stress-induced visceral hypersensitivity, but not changes in glucocorticoid receptor protein expression in the brain. This finding opens a broad field of future directions aimed at evaluating the mechanisms involved in the transmission across generations of the digestive features of IBS, including, for example, on the role of gut microbiota changes in vertical transmission or epigenetic modifications of intestinal mast cells and the junctional region of intestinal epithelial cells in vertical transfer.

Intestinal microbiota and immune function in the pathogenesis of irritable bowel syndrome

The pathophysiology of irritable bowel syndrome (IBS) is believed to involve alterations in the brain-gut axis; however, the etiological triggers and mechanisms by which these changes lead to symptoms of IBS remain poorly understood. Although IBS is often considered a condition without an identified "organic" etiology, emerging evidence suggests that alterations in the gastrointestinal microbiota and altered immune function may play a role in the pathogenesis of the disorder. These recent data suggest a plausible model in which changes in the intestinal microbiota and activation of the enteric immune system may impinge upon the brain-gut axis, causing the alterations in gastrointestinal function and the clinical symptoms observed in patients with IBS. This review summarizes the current evidence for altered intestinal microbiota and immune function in IBS. It discusses the potential etiological role of these factors, suggests an updated conceptual model for the pathogenesis of the disorder, and identifies areas for future research.

Sensory neuro-immune interactions differ between irritable bowel syndrome subtypes

OBJECTIVE

The gut is a major site of contact between immune and sensory systems and evidence suggests that patients with irritable bowel syndrome (IBS) have immune dysfunction. Here we show how this dysfunction differs between major IBS subgroups and how immunocytes communicate with sensory nerves.

DESIGN

Peripheral blood mononuclear cell supernatants from 20 diarrhoea predominant IBS (D-IBS) patients, 15 constipation predominant IBS (C-IBS) patients and 36 healthy subjects were applied to mouse colonic sensory nerves and effects on mechanosensitivity assessed. Cytokine/chemokine concentration in the supernatants was assessed by proteomic analysis and correlated with abdominal symptoms, and expression of cytokine receptors evaluated in colonic dorsal root ganglia neurons. We then determined the effects of specific cytokines on colonic afferents.

RESULTS

D-IBS supernatants caused mechanical hypersensitivity of mouse colonic afferent endings, which was reduced by infliximab. C-IBS supernatants did not, but occasionally elevated basal discharge. Supernatants of healthy subjects inhibited afferent mechanosensitivity via an opioidergic mechanism. Several cytokines were elevated in IBS supernatants, and levels correlated with pain frequency and intensity in patients. Visceral afferents expressed receptors for four cytokines: IL-1β, IL-6, IL-10 and TNF-α. TNF-α most effectively caused mechanical hypersensitivity which was blocked by a transient receptor potential channel TRPA1 antagonist. IL-1β elevated basal firing, and this was lost after tetrodotoxin blockade of sodium channels.

CONCLUSIONS

Distinct patterns of immune dysfunction and interaction with sensory pathways occur in different patient groups and through different intracellular pathways. Our results indicate IBS patient subgroups would benefit from selective targeting of the immune system.