Temporal stability of fecal metabolomic profiles in irritable bowel syndrome

BACKGROUND

The potential of the fecal metabolome to serve as a biomarker for irritable bowel syndrome (IBS) depends on its stability over time. Therefore, this study aimed to determine the temporal dynamics of the fecal metabolome, and the potential relationship with stool consistency, in patients with IBS and healthy subjects.

METHODS

Fecal samples were collected in two cohorts comprising patients with IBS and healthy subjects. For Cohort A, fecal samples collected during 5 consecutive days were analyzed by gas chromatography-tandem mass spectrometry (GC-MS/MS). For Cohort B, liquid chromatography-MS (LC-MS) was used to analyze fecal samples collected at week 0 (healthy and IBS) and at week 4 (patients only). Stool consistency was determined by the Bristol Stool Form scale.

KEY RESULTS

Fecal samples were collected from Cohort A (seven healthy subjects and eight IBS patients), and Cohort B (seven healthy subjects and 11 IBS patients). The fecal metabolome of IBS patients was stable short-term (Cohort A, 5 days and within the same day) and long-term (Cohort B, 4 weeks). A similar trend was observed over 5 days in the healthy subjects of Cohort A. The metabolome dissimilarity was larger between than within participants over time in both healthy subjects and IBS patients. Further analyses showed that patients had greater range of stool forms (types) than healthy subjects, with no apparent influence on metabolomic dynamics.

CONCLUSION & INFERENCES

The fecal metabolome is stable over time within IBS patients as well as healthy subjects. This supports the concept of a stable fecal metabolome in IBS despite fluctuations in stool consistency, and the use of single timepoint sampling to further explore how the fecal metabolome is related to IBS pathogenesis.

Fecal Supernatants from Patients with Crohn's Disease Induce Inflammatory Alterations in M2 Macrophages and Fibroblasts

Intestinal macrophages and fibroblasts act as microenvironmental sentinels mediating inflammation and disease progression in Crohn's disease (CD). We aimed to establish the effects of fecal supernatants (FSs) from patients with CD on macrophage and fibroblast phenotype and function. FS were obtained by ultracentrifugation, and the metabolites were analyzed. Monocyte-derived M2 macrophages and fibroblasts were conditioned with FS, and secreted proteins, surface proteins and gene expression were analyzed. M2 macrophage efferocytosis was evaluated. Patients with CD (n = 15) had a skewed fecal metabolite profile compared to healthy subjects (HS, n = 10). FS from CD patients (CD-FS) induced an anti-inflammatory response in M2 macrophages with higher expression of IL-10, IL1RA and CD206 as compared to healthy FS (HS-FS) while the efferocytotic capacity was unaltered. CD-FS did not affect extracellular matrix production from fibroblasts, but increased expression of the pro-inflammatory proteins IL-6 and MCP-1. Conditioned media from M2 macrophages treated with CD-FS modulated gene expression in fibroblasts for TGFβ superfamily members and reduced IL-4 expression compared to HS-FS. We show that M2 macrophages and fibroblasts react abnormally to the fecal microenvironment of CD patients, resulting in altered protein expression related to inflammation but not fibrosis. This implies that the gut microbiota and its metabolites have an important role in the generation and/or perpetuation of inflammation in CD.

Fecal Biomarkers of Neutrophil and Eosinophil Origin Reflect the Response to Biological Therapy and Corticosteroids in Patients With Inflammatory Bowel Disease

INTRODUCTION

Fecal calprotectin (FC) is a noninvasive tool for examining response to biologics in inflammatory bowel disease (IBD), but its performance in relation to other novel fecal markers of various cellular origins is unknown.

METHODS

We performed a prospective multicenter cohort study and included patients with active IBD who provided a fecal sample at initiation of biological therapy. Levels of FC, myeloperoxidase (MPO), human neutrophil lipocalin (HNL), and eosinophil-derived neurotoxin (EDN) were analyzed and related to clinical remission status at 3 months. Changes in levels of markers at 3 months were calculated, and the impact of concomitant use of corticosteroids at baseline was estimated.

RESULTS

In patients achieving clinical remission (n = 27), a decrease in levels of FC ( P = 0.005), MPO ( P < 0.001), HNL ( P < 0.001), and EDN ( P < 0.001) was observed, whereas no significant decrease was seen in patients not achieving remission (n = 39). There was a significant difference in the change in the level of MPO ( P = 0.01) and HNL ( P = 0.02) between patients achieving clinical remission and those who did not, but changes in FC and EDN could not differentiate between these groups. Patients with concomitant systemic corticosteroids at inclusion had lower levels of HNL ( P = 0.01) and EDN ( P < 0.001) at baseline, compared with patients without corticosteroids.

DISCUSSION

Fecal MPO, HNL, and EDN are all promising biomarkers for assessing the treatment outcome of biologics in patients with IBD. Fecal levels of EDN and HNL are significantly affected by corticosteroids indicating a greater sensitivity to the effects of corticosteroids compared with levels of FC and MPO.

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

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

Randomised controlled trial: effects of gluten-free diet on symptoms and the gut microenvironment in irritable bowel syndrome

BACKGROUND

A gluten-free diet reduces symptoms in some patients with irritable bowel syndrome (IBS) through unclear mechanisms.

AIMS

To assess the effects of gluten-free versus gluten-containing diet on symptoms and the gut microenvironment, and to identify predictors of response to the gluten-free diet in IBS METHODS: Twenty patients with IBS and 18 healthy controls (HC) followed a gluten-free diet during two 14-day intervention periods where they sprinkled either gluten (14 g/day) or rice flour powder over their meals. Primary outcomes included effects of the interventions on IBS symptoms (IBS-SSS) and bowel habits. Secondary outcomes included effects of gluten-free diet on faecal microbiota and metabolite profile.

RESULTS

IBS symptoms improved during the gluten-free (p = 0.02), but not the gluten-containing period, with no difference between the interventions. IBS patients reported fewer loose stools during the gluten-free intervention (p = 0.01). Patients with IBS and HC presented distinct metabolite profiles based on the effects of the gluten-free diet (p < 0.001). True responders (reduced IBS-SSS by ≥50 solely after gluten-free period) and non-responders were discriminated based on the effects of the gluten-free diet on the microbiota (p < 0.01) and metabolite profiles (p < 0.001). The response to the gluten-free diet could be predicted by the metabolite profile before the intervention (p < 0.001).

CONCLUSIONS

A gluten-free diet may influence symptoms in a subset of patients with IBS, with a particular effect on bowel habits. A gluten-free diet seems to impact the gut microenvironment. Responsiveness to the gluten-free diet may be predicted by the metabolite profile.

CLINICALTRIALS

gov: NCT03869359.

Differences in Metabolite Composition of Aloe barbadensis Mill. Extracts Lead to Differential Effects on Human Blood T Cell Activity In Vitro

Aloe barbadensis Mill. (Aloe) is used for diverse therapeutic properties including immunomodulation. However, owing to the compositionally complex nature of Aloe, bioactive component(s) responsible for its beneficial properties, though thought to be attributed to polysaccharides (acemannan), remain unknown. We therefore aimed to determine the metabolite composition of various commercial Aloe extracts and assess their effects on human blood T cell activity in vitro. Peripheral blood mononuclear cells (PBMC) from healthy donors were stimulated polyclonally in presence or absence of various Aloe extracts. T cell phenotype and proliferation were investigated by flow cytometry. Aloe extracts were analyzed using targeted ¹H-NMR spectroscopy for standard phytochemical quality characterization and untargeted gas chromatography mass spectrometry (GC-MS) for metabolite profiling. Aloe extracts differing in their standard phytochemical composition had varying effects on T cell activation, proliferation, apoptosis, and cell-death in vitro, although this was not related to the acemannan content. Furthermore, each Aloe extract had its own distinct metabolite profile, where extracts rich in diverse sugar and sugar-derivatives were associated with reduced T cell activity. Our results demonstrate that all commercial Aloe extracts are unique with distinct metabolite profiles, which lead to differential effects on T cell activity in vitro, independent of the acemannan content.

Fecal luminal factors from patients with irritable bowel syndrome induce distinct gene expression of colonoids

BACKGROUND

Alteration of the host-microbiota cross talk at the intestinal barrier may participate in the pathophysiology of irritable bowel syndrome (IBS). Therefore, we aimed to determine effects of fecal luminal factors from IBS patients on the colonic epithelium using colonoids.

METHODS

Colon-derived organoid monolayers, colonoids, generated from a healthy subject, underwent stimulation with fecal supernatants from healthy subjects and IBS patients with predominant diarrhea, phosphate-buffered saline (PBS), or lipopolysaccharide (LPS). Cytokines in cell cultures and fecal LPS were measured by ELISA and mRNA gene expression of monolayers was analyzed using Qiagen RT² Profiler PCR Arrays. The fecal microbiota profile was determined by the GA-map^™ dysbiosis test and the fecal metabolite profile was analyzed by untargeted liquid chromatography/mass spectrometry.

KEY RESULTS

Colonoid monolayers stimulated with fecal supernatants from healthy subjects (n = 7), PBS (n = 4) or LPS (n = 3) presented distinct gene expression profiles, with some overlap (R² Y = 0.70, Q²  = 0.43). Addition of fecal supernatants from healthy subjects and IBS patients (n = 9) gave rise to different gene expression profiles of the colonoid monolayers (R² Y = 0.79, Q²  = 0.64). Genes (n = 22) related to immune response (CD1D, TLR5) and barrier integrity (CLDN15, DSC2) contributed to the separation. Levels of proinflammatory cytokines in colonoid monolayer cultures were comparable when stimulated with fecal supernatants from either donor types. Fecal microbiota and metabolite profiles, but not LPS content, differed between the study groups.

CONCLUSIONS

Fecal luminal factors from IBS patients induce a distinct colonic epithelial gene expression, potentially reflecting the disease pathophysiology. The culture of colonoids from healthy subjects with fecal supernatants from IBS patients may facilitate the exploration of IBS related intestinal micro-environmental and barrier interactions.

Randomised clinical trial and meta-analysis: mesalazine treatment in irritable bowel syndrome-effects on gastrointestinal symptoms and rectal biomarkers of immune activity

BACKGROUND

Low-grade immune activation in the gut is a potential treatment target in irritable bowel syndrome (IBS).

AIMS

To determine improvement in IBS symptoms after mesalazine treatment, and the utility of measures of immune activity in the rectal mucosa METHODS: This was a randomised, double-blind, placebo-controlled, parallel-arm, multicentre trial in subjects with IBS (Rome III criteria), with an eight-week treatment period of mesalazine 2400 mg or plcebo once-daily. The primary endpoint was the global assessment of satisfactory relief of IBS symptoms in ≥50% of weeks during intervention. IBS symptoms were also measured with the IBS severity scoring system; immune activity was measured by mucosal patch technology. A post hoc meta-analysis of randomised placebo-controlled trials of mesalazine in IBS was added.

RESULTS

Of 181 included patients, 91 received mesalazine and 90 received placebo. The primary endpoint was met by 32 (36%) patients after mesalazine and 27 (30%) after placebo (p = 0.40). There were no differences in response rates related to IBS subtype or post-infection symptom onset. More reduction of abdominal bloating was noted in the mesalazine group (p = 0.02). The meta-analysis showed no effect of mesalazine on IBS symptoms. No mucosal patch technology measure could predict response to mesalazine, and found no differences in the effects of intervention on levels of immune markers.

CONCLUSIONS

Mesalazine is ineffective in reducing IBS symptoms. Rectal measures of immune activity by the mucosal patch technology cannot predict a higher chance of response to mesalazine.

Downregulated Mucosal Autophagy, Alpha Kinase-1 and IL-17 Signaling Pathways in Active and Quiescent Ulcerative Colitis

Background

Improved mucosal immune profiling in active and quiescent colonic inflammatory bowel disease (IBD) is needed to develop therapeutic options for treating and preventing flares. This study therefore aimed to provide a comprehensive mucosal characterization with emphasis on immunological host response of patients with active ulcerative colitis (UC active), UC during remission (UC remission) and active colonic Crohn’s disease (CD active).

Methods

Colonic biopsies from 47 study subjects were collected for gene expression and pathway analyses using the NanoString host-response panel, including 776 genes and 56 immune-related pathways.

Results

The majority of mucosal gene expression and signaling pathway scores were increased in active IBD (n=27) compared to healthy subjects (n=10). However, both active IBD and UC remission (n=10) demonstrated decreased gene expression and signaling pathway scores related to autophagy, alpha kinase-1 and IL-17 signaling pathways compared to healthy subjects. Further, UC remission was characterized by decreased scores of several signaling pathways linked to homeostasis along with increased mononuclear cell migration pathway score as compared to healthy subjects. No major differences in the colonic mucosal gene expression between CD active (n=7) and UC (n=20) active were observed.

Conclusion

This study indicates that autophagy, alpha kinase-1 and IL-17 signaling pathways are persistently downregulated in UC irrespective of disease activity. Further, UC patients in remission present a unique mucosal environment, potentially preventing patients from reaching and sustaining true homeostasis. These findings may enable better comprehension of the remitting and relapsing pattern of colonic IBD and guide future treatment and prevention of flares.

Health-related quality of life in patients with long-standing ulcerative colitis in remission

INTRODUCTION

Ulcerative colitis (UC) contributes to impaired health-related quality of life (HRQoL). Although disease activity is the most important factor, reduced HRQoL has been reported even in quiescent UC. We aimed to determine HRQoL, and identify predictors thereof, in patients with long-standing UC in remission.

METHODS

In total, 66 patients with inactive UC were included 10 years after the disease onset. Clinical assessment including rigid sigmoidoscopy was performed to ensure remission. Data on demographic, clinical, treatment-related, and psychological determinants of HRQoL were obtained with a structured interview and self-assessment questionnaires measuring gastrointestinal (GI) and psychological symptoms and fatigue. HRQoL was measured with the Short Form Health Survey (SF-36).

RESULTS

The SF-36 domains were comparable to the general Swedish population, except for Vitality, where UC patients scored lower. Gender, smoking, comorbidity, or disease phenotype had no impact on HRQoL. In contrast, corticosteroid use and sick leave during the previous year were independently associated with Physical Functioning and Bodily Pain domains of SF-36; persisting GI symptoms during remission with Bodily Pain; and fatigue with Role Physical, General Health and Vitality. For all other SF-36 domains reflecting mental HRQoL (Social Function, Role Emotional, Mental Health), only psychological distress contributed uniquely.

CONCLUSIONS

Although overall HRQoL in long-standing UC in remission is comparable to the general population, previous disease activity as well as persisting GI symptoms, fatigue, and psychological distress are associated with a lower HRQoL among these patients. Improved HRQoL may allow for better UC patient health and reduced costs for health care.

The Effects of Human Milk Oligosaccharides on Gut Microbiota, Metabolite Profiles and Host Mucosal Response in Patients with Irritable Bowel Syndrome

Background: Human milk oligosaccharide supplementation safely modulates fecal bifidobacteria abundance and holds the potential to manage symptoms in irritable bowel syndrome (IBS). Here, we aimed to determine the role of a 4:1 mix of 2′-O-fucosyllactose and lacto-N-neotetraose (2′FL/LNnT) on the modulation of the gut microbiota composition and host mucosal response, as well as the link between the bifidobacteria abundance and metabolite modulation, in IBS patients. Methods: Biological samples were collected from IBS patients (n = 58) at baseline and week 4 post-supplementation with placebo, 5 g or 10 g doses of 2′FL/LNnT. The gut microbiota composition, metabolite profiles and expression of genes related to host mucosal response were determined. Results: Moderate changes in fecal, but not mucosal, microbial composition (β-diversity) was observed during the intervention with higher dissimilarity observed within individuals receiving 10g 2′FL/LNnT compared to placebo. Both fecal and mucosal Bifidobacterium spp. increased after 2′FL/LNnT intake, with increased proportions of Bifidobacterium adolescentis and Bifidobacterium longum. Moreover, the intervention modulated the fecal and plasma metabolite profiles, but not the urine metabolite profile or the host mucosal response. Changes in the metabolite profiles were associated to changes in bifidobacteria abundance. Conclusion: Supplementation with 2′FL/LNnT modulated the gut microbiota, fecal and plasma metabolite profiles, but not the host mucosal response in IBS. Furthermore, the bifidogenic effect was associated with metabolite modulation. Overall, these findings support the assertion that 2′FL/LNnT supplementation modulate the intestinal microenvironment of patients with IBS, potentially related to health.

Aloe barbadensis Mill. extract improves symptoms in IBS patients with diarrhoea: post hoc analysis of two randomized double-blind controlled studies

BACKGROUND

Aloe barbadensis Mill. (Aloe) extract was found to be well-tolerated, safe and showed beneficial effects in subsets of irritable bowel syndrome (IBS) patients in two randomized, double-blind, controlled studies. However, the individual studies were underpowered to perform subgroup analyses. We therefore determined the effect of Aloe extract in IBS subgroups in a post hoc analysis combining the results from the two studies.

METHODS

Data from the two controlled studies comparing Aloe and control treatment taken orally for 4 weeks, were pooled. Both studies included IBS patients fulfilling the ROME III criteria and IBS Symptom Severity Score (IBS-SSS) was assessed. We analysed the effect of Aloe extract on IBS symptom severity and the proportion of responders (IBS-SSS reduction ⩾ 50) in IBS subgroups.

RESULTS

In total, 213 IBS patients were included in the post hoc subgroup analyses. A reduction in overall symptom severity, primarily driven by effect on pain severity and frequency, comparing baseline versus end of treatment, was recorded in IBS patients with diarrhoea (IBS-D) receiving Aloe (n = 38, p < 0.001) but not control treatment (n = 33, p = 0.33), with difference between the treatment groups (p = 0.01). Moreover, the frequency of responders was higher in IBS-D patients receiving Aloe (n = 22, 58%) compared to control treatment (n = 10, 30%) (p = 0.02). The effect of Aloe extract treatment on IBS symptom severity was not superior to control treatment in the other IBS subtypes.

CONCLUSION

Aloe extract improves symptom severity in IBS-D patients and can be regarded as a safe and effective treatment option for this patient group.

Impaired Luminal Control of Intestinal Macrophage Maturation in Patients With Ulcerative Colitis During Remission

BACKGROUND & AIMS

Intestinal macrophages adopt a hyporesponsive phenotype through education by local signals. Lack of proper macrophage maturation in patients with ulcerative colitis (UC) in remission may initiate gut inflammation. The aim, therefore, was to determine the effects of fecal luminal factors derived from healthy donors and UC patients in remission on macrophage phenotype and function.

METHODS

Fecal supernatants (FS) were extracted from fecal samples of healthy subjects and UC patients in remission. Monocytes were matured into macrophages in the presence of granulocyte-macrophage colony-stimulating factor without/with FS, stimulated with lipopolysaccharide, and macrophage phenotype and function were assessed. Fecal metabolomic profiles were analyzed by gas-chromatography/mass-spectrometry.

RESULTS

Fecal luminal factors derived from healthy donors were effective in down-regulating Toll-like receptor signaling, cytokine signaling, and antigen presentation in macrophages. Fecal luminal factors derived from UC patients in remission were less potent in inducing lipopolysaccharide hyporesponsiveness and modulating expression of genes involved in macrophage cytokine and Toll-like receptor signaling pathways. Although phagocytic and bactericidal abilities of macrophages were not affected by FS treatment, healthy FS-treated macrophages showed a greater ability to suppress cluster of differentiation 4⁺ T-cell activation and interferon γ secretion compared with UC remission FS-treated counterparts. Furthermore, metabolomic analysis showed differential fecal metabolite composition for healthy donors and UC patients in remission.

CONCLUSIONS

Our data indicate that UC patients in remission lack luminal signals able to condition macrophages toward a hyporesponsive and tolerogenic phenotype, which may contribute to their persistent vulnerability to relapse.

A Distinct Faecal Microbiota and Metabolite Profile Linked to Bowel Habits in Patients with Irritable Bowel Syndrome

Patients with irritable bowel syndrome (IBS) are suggested to have an altered intestinal microenvironment. We therefore aimed to determine the intestinal microenvironment profile, based on faecal microbiota and metabolites, and the potential link to symptoms in IBS patients. The faecal microbiota was evaluated by the GA-map^TM dysbiosis test, and tandem mass spectrometry (GC-MS/MS) was used for faecal metabolomic profiling in patients with IBS and healthy subjects. Symptom severity was assessed using the IBS Severity Scoring System and anxiety and depression were assessed using the Hospital Anxiety and Depression Scale. A principal component analysis based on faecal microbiota (n = 54) and metabolites (n = 155) showed a clear separation between IBS patients (n = 40) and healthy subjects (n = 18). Metabolites were the main driver of this separation. Additionally, the intestinal microenvironment profile differed between IBS patients with constipation (n = 15) and diarrhoea (n = 11), while no clustering was detected in subgroups of patients according to symptom severity or anxiety. Furthermore, ingenuity pathway analysis predicted amino acid metabolism and several cellular and molecular functions to be altered in IBS patients. Patients with IBS have a distinct faecal microbiota and metabolite profile linked to bowel habits. Intestinal microenvironment profiling, based on faecal microbiota and metabolites, may be considered as a future non-invasive diagnostic tool, alongside providing valuable insights into the pathophysiology of IBS.

Fecal microbiota dynamics during disease activity and remission in newly diagnosed and established ulcerative colitis

Patients with ulcerative colitis (UC) have an altered gut microbiota composition, but the microbial relationship to disease activity needs to be further elucidated. Therefore, temporal dynamics of the fecal microbial community during remission and flare was determined. Fecal samples were collected at 2–6 time-points from UC patients during established disease (cohort EST) and at diagnosis (cohort NEW). Sampling range for cohort EST was 3–10 months and for cohort NEW 36 months. Relapses were monitored for an additional three years for cohort EST. Microbial composition was assessed by Genetic Analysis GA-map Dysbiosis Test, targeting ≥ 300 bacteria. Eighteen patients in cohort EST (8 with maintained remission and 10 experiencing a flare), provided 71 fecal samples. In cohort NEW, 13 patients provided 49 fecal samples. The microbial composition showed no clustering related to disease activity in any cohort. Microbial dissimilarity was higher between than within patients for both cohorts, irrespective of presence of a flare. Microbial stability within patients was constant over time with no major shift in overall composition nor modification in the abundance of any specific species. Microbial composition was not affected by intensified medical treatment or linked to future disease course. Thus in UC, the gut microbiota is highly stable irrespective of disease stage, disease activity or treatment escalation. This suggests that prolonged dietary interventions or repeated fecal transplantations are needed to be able to induce permanent alterations of the gut microbiota.

Diet and gut microbiome interactions of relevance for symptoms in irritable bowel syndrome

BACKGROUND

While several studies have documented associations between dietary habits and microbiota composition and function in healthy individuals, no study explored these associations in patients with irritable bowel syndrome (IBS), and especially with symptoms.

METHODS

Here, we used a novel approach that combined data from a 4-day food diary, integrated into a food tree, together with gut microbiota (shotgun metagenomic) for individuals with IBS (N = 149) and healthy controls (N = 52). Paired microbiota and food-based trees allowed us to detect new associations between subspecies and diet. Combining co-inertia analysis and linear regression models, exhaled gas levels and symptom severity could be predicted from metagenomic and dietary data.

RESULTS

We showed that individuals with severe IBS are characterized by a higher intake of poorer-quality food items during their main meals. Our analysis suggested that covariations between gut microbiota at subspecies level and diet could be explained with IBS symptom severity, exhaled gas, glycan metabolism, and meat/plant ratio. We provided evidence that IBS severity is associated with altered gut microbiota hydrogen function in correlation with microbiota enzymes involved in animal carbohydrate metabolism.

CONCLUSIONS

Our study provides an unprecedented resolution of diet-microbiota-symptom interactions and ultimately guides new interventional studies that aim to identify gut microbiome-based nutritional recommendations for the management of gastrointestinal symptoms.

TRIAL REGISTRATION

This trial was registered on the ClinicalTrials.gov, with the registration number NCT01252550 , on 3rd December 2010. Video abstract.

A novel stepwise integrative analysis pipeline reveals distinct microbiota-host interactions and link to symptoms in irritable bowel syndrome

Although incompletely understood, microbiota-host interactions are assumed to be altered in irritable bowel syndrome (IBS). We, therefore, aimed to develop a novel analysis pipeline tailored for the integrative analysis of microbiota-host interactions and association to symptoms and prove its utility in a pilot cohort. A multilayer stepwise integrative analysis pipeline was developed to visualize complex variable associations. Application of the pipeline was demonstrated on a dataset of IBS patients and healthy controls (HC), using the R software package to analyze colonic host mRNA and mucosal microbiota (16S rRNA gene sequencing), as well as gastrointestinal (GI) and psychological symptoms. In total, 42 IBS patients (57% female, mean age 33.6 (range 18–58)) and 20 HC (60% female, mean age 26.8 (range 23–41)) were included. Only in IBS patients, mRNA expression of Toll-like receptor 4 and genes associated with barrier function (PAR2, OCLN, TJP1) intercorrelated closely, suggesting potential functional relationships. This host genes-based “permeability cluster” was associated to mucosa-adjacent Chlamydiae and Lentisphaerae, and furthermore associated to satiety as well as to anxiety, depression and fatigue. In both IBS patients and HC, chromogranins, secretogranins and TLRs clustered together. In IBS patients, this host genes-based “immune-enteroendocrine cluster” was associated to specific members of Firmicutes, and to depression and fatigue, whereas in HC no significant association to microbiota was identified. We have developed a stepwise integrative analysis pipeline that allowed identification of unique host-microbiota intercorrelation patterns and association to symptoms in IBS patients. This analysis pipeline may aid in advancing the understanding of complex variable associations in health and disease.

Human milk oligosaccharide supplementation in irritable bowel syndrome patients: A parallel, randomized, double-blind, placebo-controlled study

OBJECTIVES

Human milk oligosaccharides safely and beneficially impact bifidobacteria abundance in healthy adults, while their effects in patients with irritable bowel syndrome (IBS) are unknown. Hence, we aimed to determine the dose of 4:1 mix of 2'-O-fucosyllactose and Lacto-N-neotetraose (2'FL/LNnT) that increases fecal bifidobacteria abundance without aggravating overall gastrointestinal symptoms in IBS patients in a randomized, double-blind, controlled study. Additionally, the impact of 2'FL/LNnT on the fecal bacterial profile was assessed.

METHODS

Irritable bowel syndrome patients diagnosed according to the Rome IV criteria received placebo (glucose), or 5 g or 10 g 2'FL/LNnT for 4 weeks followed by a four-week follow-up period. Gastrointestinal Symptom Rating Scale-IBS was used to assess gastrointestinal symptom severity; fecal microbiota composition was evaluated by GA-map™ Dysbiosis Test.

RESULTS

Of the included 60 patients, two (one placebo and one 10 g) discontinued prematurely. Fecal bifidobacteria abundance was increased at week 4, but not at week 8, in the 10 g group compared to the other groups. Severity of overall or individual gastrointestinal symptoms did not differ between the groups at week 4 or 8, and no symptom deterioration was seen in any of the groups. The 10 g dose influenced overall fecal microbiota composition, and responders-defined as bifidobacteria increase ≥50%-could be discriminated from non-responders based on fecal microbiota modulation.

CONCLUSIONS

The 10 g dose of 2'FL/LNnT induced an increase in the beneficial Bifidobacterium spp. without aggravating gastrointestinal symptoms in patients with IBS. This approach may be worthwhile to modulate gut microbiota of IBS patients toward a healthier profile.

Randomized clinical trial: Effects of Aloe barbadensis Mill. extract on symptoms, fecal microbiota and fecal metabolite profiles in patients with irritable bowel syndrome

BACKGROUND

Aloe barbadensis Mill. (Aloe) with potential prebiotic effects has been suggested to reduce symptoms in patients with irritable bowel syndrome (IBS). We therefore aimed to determine the effects of an Aloe extract on symptoms of IBS, and evaluate whether effects may be mediated by fecal microbiota and metabolites in a randomized, double-blind, controlled trial.

METHODS

Patient with IBS diagnosed according to the ROME III criteria (all subtypes), received Aloe or control treatment (inulin) for 4 weeks. IBS Symptom Severity Score (IBS-SSS) was assessed, and fecal samples collected before and at end of treatment. Fecal microbiota composition and metabolomic profile were determined.

KEY RESULTS

In total, 160 IBS patients completed the study. The overall severity of IBS symptoms was reduced in both Aloe and control treatment groups (P < .001, both groups, comparing baseline vs end of treatment), without difference between groups (P = .62). The frequency of responders (IBS-SSS reduction ≥ 50) did not differ between Aloe treatment (n = 33, 39%) and control (n = 34, 45%) (P = .49). However, fecal microbiota and metabolite profiles differed between Aloe, but not control treatment responders and non-responders both before and after treatment.

CONCLUSION

In a mixed group of IBS patients, Aloe was not superior to control treatment, although it showed potential to reduce IBS symptom severity in subsets of IBS patients which could be predicted by fecal microbiota and metabolite profiles. ClinicalTrials.gov no: NCT01400048.

Systemic Inflammatory Protein Profiles Distinguish Irritable Bowel Syndrome (IBS) and Ulcerative Colitis, Irrespective of Inflammation or IBS-Like Symptoms

BACKGROUND

Inflammatory mechanisms of ulcerative colitis (UC) and irritable bowel syndrome (IBS) may overlap or are part of different spectrums. However, potential links between inflammation and IBS-like symptoms in these patient groups are still unclear. The aim of this study was to determine if the systemic inflammatory protein (SIP) profiles differ between UC patients, with presence of inflammation or in remission with or without IBS-like symptoms, and IBS patients.

METHODS

Serum from patients with active UC (UCA), UC patients in remission with or without IBS-like symptoms (UCR + IBS, UCR-IBS), IBS patients (IBS), and healthy subjects (HS) was analyzed using the ProSeek Multiplex Inflammation kit, which detects 92 proteins.

RESULTS

The exploratory cohort consisted of 166 subjects (UCA, n = 40; UCR-IBS, n = 45; UCR + IBS, n = 20; IBS, n = 40; HS, n = 21). Systemic inflammatory protein profiles separated UC from non-UC (HS and IBS) patients in multivariate analysis, revealing caspase 8, axin 1, sulfotransferase 1A1, and tumor necrosis factor superfamily member 14 as the variables most important to clustering. Although minor differences were detected between UCR + IBS and UCR-IBS, SIP profiles discriminated UCA from UCR, and interleukin (IL) 17C, IL17A, chemokine ligand 9, and transforming growth factor-α characterized active inflammation. SIP profiles weakly discriminated HS from IBS, although fibroblast growth factor 21 and IL6 serum levels were higher in IBS. Results were confirmed in a validation cohort (UCA, n = 15; UCR + IBS, n = 9; IBS, n = 14).

CONCLUSIONS

SIP profiles distinguish UC patients from IBS patients, irrespective of inflammation or IBS-like symptoms, suggesting that inflammatory mechanisms of the diseases are part of different spectrums.

Fecal microbiota composition is linked to the postoperative disease course in patients with Crohn's disease

Background

The role of the fecal microbiota composition for the postoperative disease course of patients with Crohn’s disease (CD) who have undergone ileocecal resection remains to be established. In this study, we investigated if the fecal microbiota composition, determined by a high throughput test quantifying a pre-selected set of bacteria, is associated with the postoperative disease course of CD patients.

Methods

Fecal samples were obtained from healthy subjects as well as from CD patients, 3–10 weeks and 1 year after ileocaecal resection. The fecal microbial composition was analyzed by Genetic Analysis GA-map Dysbiosis test, targeting ≥300 bacteria on different taxonomic levels. Postoperative disease status was assessed endoscopically according to Rutgeerts scoring system 1 year after surgery. Differences in fecal microbiota composition between groups were analyzed by multivariate factor analyses and cluster analysis. Microbial stability over time was determined using Bray-Curtis dissimilarity.

Results

One year after surgery, the fecal microbiota composition differed between CD patients (n = 21) and healthy subjects (n = 7). At this time point, the microbiota composition of CD patients was associated with disease course, clearly separating patients with disease relapse (n = 8) and patients in remission (n = 13). Further, the microbial within-patient stability was high during the first year after surgery, irrespective of disease course.

Conclusion

The fecal microbiota composition of CD patients, analyzed by GA-map Dysbiosis test, is subject to little variation over time, and may potentially be used as a non-invasive diagnostic tool for the postoperative disease course.

Evidence of altered mucosa-associated and fecal microbiota composition in patients with Irritable Bowel Syndrome

Altered bacterial composition and small intestinal bacterial overgrowth (SIBO) may be associated with irritable bowel syndrome (IBS). This study aimed to determine the fecal and mucosa-associated bacterial composition along the gastrointestinal (GI) tract and to assess SIBO in IBS. Bacterial composition of feces, and mucosa of the duodenum and sigmoid colon was determined by 16S rRNA-amplicon-sequencing. SIBO was evaluated by bacterial culture of duodenal aspirate, glucose and lactulose breath tests. Mucosal antibacterial gene expression was assessed by PCR Array. The bacterial profiles of feces and the mucosa of sigmoid colon, but not duodenum, differed between IBS patients (n = 17) and HS (n = 20). The IBS specific bacterial profiles were linked to the colonic antibacterial gene expression. Fecal bacterial profile differed between IBS subtypes, while the mucosa-associated bacterial profile was associated with IBS symptom severity and breath tests results at baseline (H₂ and/or CH₄ ≥ 15 ppm). The prevalence of SIBO was similar between IBS patients and HS. This study demonstrates that alterations in the bacterial composition of the sigmoid colon of IBS patients were linked to symptoms and immune activation. While breath tests reflected the mucosa-associated bacterial composition, there was no evidence for high prevalence of SIBO or small intestinal bacterial alterations in IBS.

A distinct gut microbiota composition in patients with ankylosing spondylitis is associated with increased levels of fecal calprotectin

Background

Ankylosing spondylitis (AS) shares many characteristics with inflammatory bowel disease (IBD). Intestinal microbiota most likely plays an important role in the development of IBDs and may also be involved in the pathogenesis of AS. We aimed to define and compare the fecal microbiota composition in patients with AS, ulcerative colitis (UC), and healthy controls (HC) and to determine relationships between fecal microbiota, fecal calprotectin, and disease-related variables in AS.

Methods

Fecal microbiota composition was assessed with GA-map™ Dysbiosis Test (Genetic Analysis, Oslo, Norway), which also reports the degree of deviation of the microbiota composition compared with a healthy control population, a Dysbiosis Index (DI) score 1–5. The AS patients were assessed with questionnaires, back mobility tests, fecal calprotectin, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).

Results

Totally, 150 patients with AS (55% men, median age 55.5 years, median BASDAI 3.2), 18 patients with UC (56% men, median age 30.5 years), and 17 HC (65% men, median age 22 years) were included. Principal component analysis showed highly separate clustering of fecal microbiota from the patients with AS, UC, and HC. Compared with HC, fecal microbiota in AS was characterized by a higher abundance of Proteobacteria, Enterobacteriaceae, Bacilli, Streptococcus species, and Actinobacteria, but lower abundance of Bacteroides and Lachnospiraceae.

Further, fecal microbiota composition differed between patients with normal (≤ 50 mg/kg, n = 57) and increased (≥ 200 mg/kg, n = 36) fecal calprotectin. Patients with increased fecal calprotectin had lower abundance of bacteria with anti-inflammatory properties such as Faecalibacterium prausnitzii and Clostridium and higher abundance of the genus Streptococcus. No association was found between the fecal microbiota composition and HLAB27 status, disease activity, function, or medication. Dysbiosis (defined as DI ≥ 3) was found in 87% of AS patients.

Conclusions

Patients with AS have a distinct fecal microbiota signature, which is linked to fecal calprotectin levels, a marker of intestinal inflammation, but not to other clinical parameters. These findings suggest a local interplay between intestinal microbiota and gut inflammation in AS.

Trial registration

ClinicalTrials.gov, NCT00858819. Registered March 9, 2009.

Colonic mast cell numbers, symptom profile, and mucosal expression of elements of the epithelial barrier in irritable bowel syndrome

BACKGROUND

This study aimed to determine whether patients with IBS displayed altered mucosal mast cell (MC) numbers and proportions of MCs co-localizing with nerves compared with healthy subjects (HS) and whether these MC characteristics correlated with IBS symptoms, elements of the epithelial barrier, or visceral sensitivity.

METHODS

Mucosal MC characteristics were determined using immunoassay. IBS symptoms, gene expression of elements of the epithelial barrier, fecal serine protease activity, and visceral sensitivity were assessed.

KEY RESULTS

The MC numbers per mm² were 2.0 (0.0-6.0) in patients with IBS (n = 43) and 3.5 (1.1-9.1) in HS (n = 20, P = .26). Of these, MCs were 0.0 (0.0-20) % vs 3.1 (0.0-18) % (P = .76) in IBS and HS, respectively, in co-localization with nerve fibers. MC characteristics were equivalent in the different IBS subtypes. Hierarchical cluster analysis identified two distinct groups among patients with IBS: MC high (higher MC numbers and proportions of MCs co-localizing with nerves) and MC low (lower MC numbers and proportions of MCs co-localizing with nerves). The MC high and MC low groups could not be discriminated with regard to IBS symptoms, parameters of visceral sensitivity, gene expression of elements of the epithelial barrier, and fecal protease activity.

CONCLUSION AND INFERENCES

There was no evidence of increased infiltration or altered localization of MCs in the colonic mucosa of patients with IBS. These MC characteristics were not linked to global IBS symptoms or mucosal expression of elements of the epithelial barrier. These findings indicate that quantity and location of mucosal MCs are factors not involved in the pathophysiology of IBS.

Mucosal and Systemic Immune Profiles Differ During Early and Late Phases of the Disease in Patients With Active Ulcerative Colitis

BACKGROUND AND AIMS

Alterations in the immunopathogenesis in ulcerative colitis [UC] during the disease course have been proposed. We therefore aimed to determine mucosal and systemic immune profiles in individual patients at the time of diagnosis [early disease] and after 10 years [late disease].

METHODS

Patients with UC provided serum and mucosal biopsies during a flare in early and in late disease. Serum samples were analysed using the Olink Proseek Inflammation panel. mRNA gene expression of biopsies was analysed using the Qiagen RT2 Profiler PCR Arrays Antibacterial response and T Helper Cell Differentiation.

RESULTS

Orthogonal projections to latent structures discriminant analyses [OPLS-DA] demonstrated that the profile of 15 serum proteins discriminated in early and late disease [R2 = 0.84, Q2 = 0.65] in 15 UC patients. Eight of these proteins were differently expressed between the groups [Q <0.05]. Further, OPLS-DA of the mRNA profiles in biopsies strongly discriminated early and late disease with high predictability [R2 = 0.96, Q2 = 0.89]; 42 genes were differently expressed at the two time points [Q <0.05]. Finally, principal component analysis showed that T helper [Th] 1- and Th2-related genes were associated with early disease and late disease, respectively, and hierarchical cluster analysis was able to cluster patients with early from late disease with only minor overlap.

CONCLUSIONS

Mucosal and systemic immune profiles differ between early and late disease in patients with active UC, with a transition from a Th1- to a Th2-driven disease in the intestine. Improved understanding of the variation in immunopathogenesis during the disease course in UC is important to guide individualised treatment decision making.

Evidence for an association of gut microbial Clostridia with brain functional connectivity and gastrointestinal sensorimotor function in patients with irritable bowel syndrome, based on tripartite network analysis

BACKGROUND AND AIMS

Evidence from preclinical and clinical studies suggests that interactions among the brain, gut, and microbiota may affect the pathophysiology of irritable bowel syndrome (IBS). As disruptions in central and peripheral serotonergic signaling pathways have been found in patients with IBS, we explored the hypothesis that the abundance of serotonin-modulating microbes of the order Clostridiales is associated with functional connectivity of somatosensory brain regions and gastrointestinal (GI) sensorimotor function.

METHODS

We performed a prospective study of 65 patients with IBS and 21 healthy individuals (controls) recruited from 2011 through 2013 at a secondary/tertiary care outpatient clinic in Sweden. Study participants underwent functional brain imaging, rectal balloon distension, a nutrient and lactulose challenge test, and assessment of oroanal transit time within a month. They also submitted stool samples, which were analyzed by 16S ribosomal RNA gene sequencing. A tripartite network analysis based on graph theory was used to investigate the interactions among bacteria in the order Clostridiales, connectivity of brain regions in the somatosensory network, and GI sensorimotor function.

RESULTS

We found associations between GI sensorimotor function and gut microbes in stool samples from controls, but not in samples from IBS patients. The largest differences between controls and patients with IBS were observed in the Lachnospiraceae incertae sedis, Clostridium XIVa, and Coprococcus subnetworks. We found connectivity of subcortical (thalamus, caudate, and putamen) and cortical (primary and secondary somatosensory cortices) regions to be involved in mediating interactions among these networks.

CONCLUSIONS

In a comparison of patients with IBS and controls, we observed disruptions in the interactions between the brain, gut, and gut microbial metabolites in patients with IBS-these involve mainly subcortical but also cortical regions of brain. These disruptions may contribute to altered perception of pain in patients with IBS and may be mediated by microbial modulation of the gut serotonergic system.

Symptoms compatible with functional bowel disorders are common in patients with quiescent ulcerative colitis and influence the quality of life but not the course of the disease

BACKGROUND

Whether patients with inactive ulcerative colitis (UC) have symptoms compatible with functional bowel disorders (FBDs) other than irritable bowel syndrome (IBS) is unclear. Our aim was to investigate the prevalence and burden of these symptoms and determine impact on the UC course.

METHODS

We used Mayo score, sigmoidoscopy and calprotectin (f-cal) to define remission in 293 UC patients. Presence of symptoms compatible with FBD, severity of gastrointestinal, extraintestinal and psychological symptoms, stress levels and quality of life (QoL) were measured with validated questionnaires. At 1 year later, remission was determined by modified Mayo score and f-cal in 171 of these patients. They completed the same questionnaires again.

RESULTS

A total of 18% of remission patients had symptoms compatible with FBD other than IBS, and 45% subthreshold symptoms compatible with FBD. The total burden of gastrointestinal symptoms in patients with symptoms compatible with FBD was higher than in patients without FBD (p < 0.001), which had negative impact on QoL (p = 0.02). These symptoms were not correlated with psychological distress, systemic immune activity or subclinical colonic inflammation and were not a risk factor for UC relapse during follow up.

CONCLUSION

Symptoms compatible with FBD other than IBS are common during UC remission influencing patients' QoL but not the UC course.

Effects of the long-term storage of human fecal microbiota samples collected in RNAlater

The adequate storage of fecal samples from clinical trials is crucial if analyses are to be performed later and in long-term studies. However, it is unknown whether the composition of the microbiota is preserved during long-term stool storage (>1 year). We therefore evaluated the influence of long-term storage on the microbiota composition of human stool samples collected in RNAlater and stored for approximately five years at −80 °C. We compared storage effects on stool samples from 24 subjects with the effects of technical variation due to different sequencing runs and biological variation (intra- and inter-subject), in another 101 subjects, based on alpha-diversity, beta-diversity and taxonomic composition. We also evaluated the impact of initial alpha-diversity and fecal microbiota composition on beta-diversity instability upon storage. Overall, long-term stool storage at −80 °C had only limited effects on the microbiota composition of human feces. The magnitude of changes in alpha- and beta- diversity and taxonomic composition after long-term storage was similar to inter-sequencing variation and smaller than biological variation (both intra- and inter-subject). The likelihood of fecal samples being affected by long-term storage correlated with the initial relative abundance of some genera and tend to be affected by initial taxonomic richness.

Subgroups of IBS patients are characterized by specific, reproducible profiles of GI and non-GI symptoms and report differences in healthcare utilization: A population-based study

BACKGROUND

In a previous clinical sample of IBS patients, subgroups characterized by profiles of GI and non-GI symptoms were identified. We aimed to replicate these subgroups and symptom associations in participants fulfilling IBS diagnostic criteria from a population-based study and relate them to healthcare utilization.

METHODS

An Internet-based health survey was completed by general population adults from United States, Canada, and UK. Respondents fulfilling IBS diagnosis (Rome III and IV) were analyzed for latent subgroups using Gaussian mixture model analysis. Symptom measures were derived from validated questionnaires: IBS-related GI symptoms (Rome IV), extraintestinal somatic symptoms (PHQ-12), and psychological symptoms (SF-8).

KEY RESULTS

A total of 637 respondents fulfilled Rome III criteria (average age 46 years, range 18-87, 66% females) and 341 Rome IV criteria (average age 44, range 18-77, 64% female) for IBS. Seven subgroups were identified in the Rome III cohort, characterized by profiles of GI symptoms (constipation-related, diarrhea-related, and mixed, respectively), and further distinguished by the presence or absence of non-GI comorbidities. The Rome IV cohort showed five similar but less distinct subgroups with a preponderance of mixed symptom profiles. Higher severity of non-GI comorbidities was associated with more frequent healthcare visits and medication usage.

CONCLUSIONS AND INFERENCES

In line with previous findings in a clinical IBS cohort, we were able to identify population-based subgroups characterized by a combination of GI symptoms with the additional distinction made by varying severity of non-GI symptoms and with differences in healthcare utilization.

Evidence of increased fecal granins in children with irritable bowel syndrome and correlates with symptoms

BACKGROUND

Granins have been implicated in the pathophysiology of irritable bowel syndrome (IBS) in adults. We sought to determine whether fecal granins are altered in children with IBS and associated with symptoms.

METHODS

Children (7-12 years of age) with IBS and healthy controls (HC) kept daily pain and stool diaries for 2 weeks. Stool samples were analyzed for chromogranins A and B (CgA, CgB) and secretogranins II and III (SgII, SgIII). Children also completed psychological measures to assess anxiety, depression, somatization, and internalizing symptoms.

KEY RESULTS

Fecal CgB and SgIII concentrations were higher in all the boys (IBS plus HC, n = 48) than in all the girls (IBS plus HC, n = 75) (P = 0.02 and P = 0.046, respectively). CgA and SgIII were greater in children with IBS (n = 52) vs HC (n = 69) (P = 0.01, P = 0.017, respectively). CgB and SgII did not differ between groups. In children with IBS, the number of pain episodes per week and mean daily pain rating correlated positively with all four granins. The number of stools per day correlated positively with CgB and SgII, and the percent of diarrheal stools (6 or 7 on the Bristol Scale) correlated inversely with all four granins in boys but not in girls. Fecal granins did not correlate with psychological measures.

CONCLUSIONS AND INFERENCES

As measured by fecal granins, there is evidence of neuroimmune activation in children with IBS. Granins are related to abdominal pain symptoms, stooling frequency, and stool form in children with IBS. Sex influences the fecal concentration of CgB and SgIII.

Altered intestinal antibacterial gene expression response profile in irritable bowel syndrome is linked to bacterial composition and immune activation

BACKGROUND

Immune activity and gut microbiota may impact the pathophysiology of irritable bowel syndrome (IBS). We aimed to determine whether antibacterial gene expression of immune activity-defined IBS patients differed compared to healthy subjects (HS) and ulcerative colitis (UC) patients and whether antibacterial profiles reflected gut microbiota composition and IBS symptoms.

METHODS

Expression of 84 antibacterial genes in biopsies from HS, IBS patients (clustered according to immune activity (systemic and intestinal cytokines): immunonormal or immunoactive), and UC patients was assessed by Human Antibacterial Response RT² Profiler PCR Array. In IBS patients, 16S rRNA gene sequencing of fecal and mucosal bacteria was performed and symptom pattern and severity were assessed.

KEY RESULTS

Intestinal antibacterial gene expression profiles differed between IBS patients (n = 31) and HS (n = 16), but did not differ between IBS subgroups based on bowel habit predominance or symptom severity. Based on previously identified IBS clusters, IBS patients with normal (n = 15) and enhanced immune activity (n = 16) had clearly separate antibacterial gene expression profiles from active UC patients (n = 12) and differed compared to each other and to HS. The differences in antibacterial gene expression profiles between immunonormal and immunoactive IBS patients were also reflected in distinct fecal and mucosal microbiota composition profiles, but not in symptom pattern or severity.

CONCLUSIONS & INFERENCES

This study demonstrates an altered antibacterial gene expression profile in IBS patients compared to HS and UC patients. While not linked to symptoms, immune activity-defined IBS clusters showed different intestinal antibacterial gene expression and distinct fecal and mucosal bacterial profiles.

Systemic cytokines are elevated in a subset of patients with irritable bowel syndrome but largely unrelated to symptom characteristics

BACKGROUND

Serum levels of pro-inflammatory cytokines tend to be increased in irritable bowel syndrome (IBS) patients, or subgroups thereof. Still, the link between cytokine levels and IBS symptoms is unclear. We aim to determine systemic cytokine levels in IBS patients and healthy subjects (HS), confirm the presence of a subset of patients with an increased immune activity and to establish if cytokines are linked to IBS symptoms and pathophysiological factors.

METHODS

Serum levels of interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor (TNF), and IL-10 were measured. All subjects reported IBS symptoms using validated questionnaires and underwent colonic sensorimotor testing. Multivariate supervised orthogonal partial least squares-discriminant analysis (OPLS-DA) and unsupervised principal component analysis (PCA) and hierarchical cluster analysis (HCA) were implemented.

KEY RESULTS

Irritable bowel syndrome patients (n = 246) had higher serum levels of IL-1β, IL-6, IL-8, TNF, and IL-10 compared to HS (n = 21); however, serum cytokine profiles could not discriminate patients from HS. Moreover, cytokine levels were not correlated with symptoms among patients. Supervised OPLS-DA identified 104 patients (40% of patients) and unsupervised HCA analysis identified 49 patients (20%) with an increased immune activity indicated by elevated levels of serum cytokines compared to HS and the other patients. However, irrespective of how patients with increased immune activity were identified they were symptomatically similar to patients with no indication of increased immune activity.

CONCLUSIONS & INFERENCES

Serum cytokines are elevated in IBS patients compared to HS. Immune activation characterizes a subset of patients, but modest associations between cytokine profile and symptoms suggest immune activity does not directly influence symptoms in IBS.

Neither self-reported atopy nor IgE-mediated allergy are linked to gastrointestinal symptoms in patients with irritable bowel syndrome

BACKGROUND

Among patients with irritable bowel syndrome (IBS), atopic disease has been proposed as a common comorbidity increasing the IBS symptom burden. We therefore assessed the prevalence of self-reported atopy among patients with IBS as compared to non-IBS controls, and whether atopy and higher serum IgE levels were associated with increased IBS symptom severity.

METHODS

Levels of total and specific IgE in serum were measured and questionnaires assessing the presence of atopic disease (ie, eczema, asthma, rhinoconjunctivitis, and pollen allergy), gastrointestinal symptom burden, food intolerance, somatic, and psychological symptoms were completed.

KEY RESULTS

In total, 223 patients with IBS and 47 controls participated. Presence of atopic disease was reported in 55% of patients with IBS compared to 40% of controls (P = .07). IBS patients with atopic manifestations (N = 123) had higher total serum IgE levels (median 31 vs 16 kU_A /L, P < .001) and higher prevalence of self-reported food intolerance (28% vs 9%, P = .002) than non-atopic IBS patients (N = 100), respectively, but no major difference in gastrointestinal or psychological symptom burden was noted. However, severe somatic symptoms were more common among atopic than non-atopic patients with IBS (38% vs 27%, P = .028). We found no associations between self-reported atopy and IBS symptom severity using linear regression models.

CONCLUSIONS & INFERENCES

Atopic disease is common in patients with IBS, but that is also true for subjects without IBS. The presence of atopic disease in IBS is associated with self-reported food intolerance and somatic symptom severity, but unrelated to IBS symptom severity.

Heart rate variability characteristics of patients with irritable bowel syndrome and associations with symptoms

BACKGROUND

Disturbed brain-gut interactions are assumed to be of importance for symptom generation in patients with irritable bowel syndrome (IBS). The autonomic nervous system (ANS) is part of the bidirectional brain-gut communication, but previous studies in IBS show diverging results. We aimed to identify subgroups of IBS patients with distinct ANS characteristics differentiating them from healthy controls (HC), and to study associations between ANS status and symptoms.

METHODS

Heart rate variability (HRV) was measured in IBS patients and HC (Holter monitoring: supine and standing positions with controlled respiration and ambulatory 24-hour period). Frequency (5 minutes, supine, standing) and time domains (24 hours, day, night) were analyzed. Validated questionnaires were used to measure gastrointestinal and psychological symptoms in patients. Patients and HC were compared on a univariate and multivariate level (principal component analysis [PCA] and orthogonal partial least squares discriminatory analysis (OPLS-DA)).

KEY RESULTS

We analyzed 158 IBS patients (Rome III) and 39 HC. Patients differed significantly from HC in HRV parameters during daytime and in standing position. In the PCA, a majority of patients overlapped with HC, but the weighted means differed (P < .01). A subset of patients (n = 30; 19%) with an aberrant global HRV profile was identified through PCA and OPLS-DA; these patients reported more severe symptoms of frequent (P < .05) and loose stools (P = .03), as well as urgency (P = .01).

CONCLUSIONS AND INFERENCES

Altered ANS function was demonstrated in patients with IBS, and this might be of particular relevance for symptoms in a subset of the patients.

Multivariate modelling of faecal bacterial profiles of patients with IBS predicts responsiveness to a diet low in FODMAPs

OBJECTIVE

The effects of dietary interventions on gut bacteria are ambiguous. Following a previous intervention study, we aimed to determine how differing diets impact gut bacteria and if bacterial profiles predict intervention response.

DESIGN

Sixty-seven patients with IBS were randomised to traditional IBS (n=34) or low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) (n=33) diets for 4 weeks. Food intake was recorded for 4 days during screening and intervention. Faecal samples and IBS Symptom Severity Score (IBS-SSS) reports were collected before (baseline) and after intervention. A faecal microbiota dysbiosis test (GA-map Dysbiosis Test) evaluated bacterial composition. Per protocol analysis was performed on 61 patients from whom microbiome data were available.

RESULTS

Responders (reduced IBS-SSS by ≥50) to low FODMAP, but not traditional, dietary intervention were discriminated from non-responders before and after intervention based on faecal bacterial profiles. Bacterial abundance tended to be higher in non-responders to a low FODMAP diet compared with responders before and after intervention. A low FODMAP intervention was associated with an increase in Dysbiosis Index (DI) scores in 42% of patients; while decreased DI scores were recorded in 33% of patients following a traditional IBS diet. Non-responders to a low FODMAP diet, but not a traditional IBS diet had higher DI scores than responders at baseline. Finally, while a traditional IBS diet was not associated with significant reduction of investigated bacteria, a low FODMAP diet was associated with reduced Bifidobacterium and Actinobacteria in patients, correlating with lactose consumption.

CONCLUSIONS

A low FODMAP, but not a traditional IBS diet may have significant impact on faecal bacteria. Responsiveness to a low FODMAP diet intervention may be predicted by faecal bacterial profiles.

TRIAL REGISTRATION NUMBER

NCT02107625.

Effects of Anti-TNFα Treatment on Mucosal Expression of IL-17A, IL-21, and IL-22 and Cytokine-Producing T Cell Subsets in Crohn's Disease

T helper 17 (Th17) cells produce interleukin (IL) 17-A. In addition, Th17 cells produce IL-21 and IL-22. Th17 cells have a disease-promoting role in Crohn's disease (CD). We investigated the effects of anti-TNFα treatment on mucosal gene expression (qPCR) of IL-17A, IL-21, and IL-22 as well as on the frequency of lamina propria (LP) T cell subsets producing these cytokines (flow cytometry) in 12 active CD patients before and after 4 weeks of anti-TNFα treatment with adalimumab. At baseline, in inflamed mucosa we found increased gene expression of IL-17A and IL-22 but not IL-21 when compared to noninflamed mucosa. There were increased frequencies of IL-21-producing LP T cells but no differences in the frequencies of IL-17A- or IL-22-producing LP T cells when comparing inflamed versus noninflamed mucosa at baseline. There were no changes in the mucosal gene expression of IL-17A, IL-21, and IL-22 or the frequencies of IL-17A-, IL-21- and IL-22-producing LP T cell subsets between baseline and following 4 weeks of adalimumab initiation. Our results do not support the hypothesis that anti-TNFα treatment has an early effect on the mucosal levels of IL-17A, IL-21, and IL-22 or LP T cell production of these cytokines in CD.

Immunopathogenesis of inflammatory bowel disease and mechanisms of biological therapies

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract with a multifactorial pathophysiology. Full comprehension of IBD pathology is still out of reach and, therefore, treatment is far from ideal. Nevertheless, components involved in IBD pathogenesis including environmental, genetic, microbial, and immunological factors are continuously being investigated and the improved knowledge contributes to the development of new therapies. In this article we review the aspects of the immunopathogenesis of IBD, with focus on mucosal immunity, and discuss mechanisms of action for current and emerging biological therapies.

Mucosal immune system of the gastrointestinal tract: maintaining balance between the good and the bad

The gastrointestinal tract (GI tract) is a unique organ inhabited by a range of commensal microbes, while also being exposed to an overwhelming load of antigens in the form of dietary antigens on a daily basis. The GI tract has dual roles in the body, in that it performs digestion and uptake of nutrients while also carrying out the complex and important task of maintaining immune homeostasis, i.e., keeping the balance between the good and the bad. It is equally important that we protect ourselves from reacting against the good, meaning that we stay tolerant to harmless food, commensal bacteria and self-antigens, as well as react with force against the bad, meaning induction of immune responses against harmful microorganisms. This complex task is achieved through the presence of a highly efficient mucosal barrier and a specialized multifaceted immune system, made up of a large population of scattered immune cells and organized lymphoid tissues termed the gut-associated lymphoid tissue (GALT). This review provides an overview of the primary components of the human mucosal immune system and how the immune responses in the GI tract are coordinated and induced.

Mixture model analysis identifies irritable bowel syndrome subgroups characterised by specific profiles of gastrointestinal, extraintestinal somatic and psychological symptoms

BACKGROUND

Current subgrouping of Irritable Bowel Syndrome (IBS) is exclusively based on stool consistency without considering other relevant gastrointestinal (GI), extraintestinal somatic or psychological features.

AIM

To identify subgroups based on a comprehensive set of IBS-related parameters.

METHODS

Mixture model analysis was used, with the following input variables: 13 single-item scores from the IBS-specific Gastrointestinal Symptom Rating Scale, average stool consistency and frequency from a 7-day Bristol Stool Form diary, 12 single-item extraintestinal symptom scores from the Patient Health Questionnaire-12, and anxiety and depression subscale scores from the Hospital Anxiety and Depression scale. The resulting latent subgroups were compared regarding symptom profiles using analysis of variance followed by pair-wise comparisons.

RESULTS

One hundred and seventy-two IBS patients (Rome III; 69% female; mean age 33.7 [range 18-60] years) were included. The optimal subgrouping showed six latent groups, characterised by: (I) constipation with low comorbidities, (II) constipation with high comorbidities, (III) diarrhoea with low comorbidities, (IV) diarrhoea and pain with high comorbidities, (V) mixed GI symptoms with high comorbidities, (VI) a mix of symptoms with overall mild severity. The subgroups showed differences in the distribution of Rome III-subtypes, IBS severity, presence of anxiety and depression, and gender, but not regarding age, IBS duration or reported post-infectious onset of IBS.

CONCLUSIONS

This model-based subgrouping of IBS partly supports the distinction of subgroups based on bowel habits, but additionally distinguishes subgroups with or without co-morbid extraintestinal somatic and psychological symptoms. The resulting groups show specific profiles of symptom combinations.

Psychological distress, iron deficiency, active disease and female gender are independent risk factors for fatigue in patients with ulcerative colitis

Background

Patients with ulcerative colitis often report fatigue.

Objectives

To investigate prevalence of and risk factors for fatigue in patients with ulcerative colitis with active disease and during deep remission.

Methods

In this cross-sectional study, disease activity was evaluated with endoscopy and calprotectin, and patients were classified as having active disease (n = 133) or being in deep remission (n = 155). Blood samples were analysed to assess anaemia, iron deficiency and systemic immune activity. Patients completed questionnaires to assess fatigue, psychological distress, gastrointestinal symptoms and quality of life.

Results

The prevalence of high fatigue (general fatigue ≥ 13, Multidimensional Fatigue Inventory) was 40% in the full study population. Among patients with high fatigue, female gender and iron deficiency were more prevalent, and these patients had more severe disease activity and reported higher levels of anxiety, depression and decreased quality of life compared with patients with no/mild fatigue. A logistic regression analysis identified probable psychiatric disorder (odds ratio (OR) (confidence interval) 6.1 (3.1-12.2)), iron deficiency (OR 2.5 (1.2-5.1)), active disease (OR 2.2 (1.2-3.9)) and female gender (OR 2.1 (1.1-3.7)) as independent risk factors for high fatigue. Similar results were found concerning psychological distress, gender and quality of life, but immune markers did not differ in patients in deep remission with high vs. no/mild fatigue.

Conclusions

Probable psychiatric disorder, iron deficiency, active disease and female gender are independent risk factors for high fatigue in patients with ulcerative colitis. Low-grade immune activity does not seem to be the cause of fatigue among patients in deep remission.

A longitudinal study of fecal calprotectin and the development of inflammatory bowel disease in ankylosing spondylitis

Background

Patients with ankylosing spondylitis (AS) are at increased risk of developing inflammatory bowel disease (IBD). We aimed to determine the variation in fecal calprotectin in AS over 5 years in relation to disease activity and medication and also to study the incidence of and predictors for development of IBD.

Methods

Fecal calprotectin was assessed at baseline (n = 204) and at 5-year follow-up (n = 164). The patients answered questionnaires and underwent clinical evaluations. At baseline and at 5-year follow-up, ileocolonoscopy was performed in patients with fecal calprotectin ≥500 mg/kg and ≥200 mg/kg, respectively. The medical records were checked for diagnoses of IBD during the follow-up period.

Results

Fecal calprotectin >50 mg/kg was found in two-thirds of the patients at both study visits. In 80% of the patients, fecal calprotectin changed by <200 mg/kg between the two measuring points. Baseline fecal calprotectin was positively correlated with Ankylosing Spondylitis Disease Activity Score based on C-reactive protein, Bath Ankylosing Spondylitis Disease Activity Index, Bath Ankylosing Spondylitis Functional Index, C-reactive protein, erythrocyte sedimentation rate, and fecal calprotectin at 5-year follow-up. The use of nonsteroidal anti-inflammatory drugs (NSAIDs) was associated with higher fecal calprotectin, and 3-week cessation of NSAIDs resulted in a drop of a median 116 mg/kg in fecal calprotectin. The use of tumor necrosis factor (TNF) blockers was associated with lower fecal calprotectin at both visits, but the users of TNF receptor fusion proteins had significantly higher fecal calprotectin than users of anti-TNF antibodies at 5-year follow-up. The 5-year incidence of Crohn’s disease (CD) was 1.5% and was predicted by high fecal calprotectin.

Conclusions

Fecal calprotectin was elevated in a majority of the patients and was associated with disease activity and medication at both visits. CD developed in 1.5% of the patients with AS, and a high fecal calprotectin was the main predictor thereof. The results support a link between inflammation in the gut and the musculoskeletal system in AS. We propose that fecal calprotectin may be a potential biomarker to identify patients with AS at risk of developing IBD.

Trial registration

ClinicalTrials.gov identifier: NCT00858819. Registered 9 March 2009. Last updated 28 May 2015.

Identification of an Intestinal Microbiota Signature Associated With Severity of Irritable Bowel Syndrome

BACKGROUND & AIMS

We have limited knowledge about the association between the composition of the intestinal microbiota and clinical features of irritable bowel syndrome (IBS). We collected information on the fecal and mucosa-associated microbiota of patients with IBS and evaluated whether these were associated with symptoms.

METHODS

We collected fecal and mucosal samples from adult patients who met the Rome III criteria for IBS at a secondary/tertiary care outpatient clinics in Sweden, as well as from healthy subjects. The exploratory set comprised 149 subjects (110 with IBS and 39 healthy subjects); 232 fecal samples and 59 mucosal biopsy samples were collected and analyzed by 16S ribosomal RNA targeted pyrosequencing. The validation set comprised 46 subjects (29 with IBS and 17 healthy subjects); 46 fecal samples, but no mucosal samples, were collected and analyzed. For each subject, we measured exhaled H₂ and CH₄, oro-anal transit time, and the severity of psychological and gastrointestinal symptoms. Fecal methanogens were measured by quantitative polymerase chain reaction. Numerical ecology analyses and a machine learning procedure were used to analyze the data.

RESULTS

Fecal microbiota showed covariation with mucosal adherent microbiota. By using classic approaches, we found no differences in fecal microbiota abundance or composition between patients with IBS vs healthy patients. A machine learning procedure, a computational statistical technique, allowed us to reduce the 16S ribosomal RNA data complexity into a microbial signature for severe IBS, consisting of 90 bacterial operational taxonomic units. We confirmed the robustness of the intestinal microbial signature for severe IBS in the validation set. The signature was able to discriminate between patients with severe symptoms, patients with mild/moderate symptoms, and healthy subjects. By using this intestinal microbiota signature, we found IBS symptom severity to be associated negatively with microbial richness, exhaled CH₄, presence of methanogens, and enterotypes enriched with Clostridiales or Prevotella species. This microbiota signature could not be explained by differences in diet or use of medications.

CONCLUSIONS

In analyzing fecal and mucosal microbiota from patients with IBS and healthy individuals, we identified an intestinal microbiota profile that is associated with the severity of IBS symptoms.

TRIAL REGISTRATION NUMBER

NCT01252550.

Reduced numbers of mucosal DR(int) macrophages and increased numbers of CD103(+) dendritic cells during anti-TNF-α treatment in patients with Crohn's disease

OBJECTIVE

Anti-TNF-α treatment constitutes a mainstay in the treatment of Crohn's disease (CD), but its mechanisms of action are not fully understood. We aimed to investigate the effects of adalimumab, a human monoclonal TNF-α antibody, on macrophage (MQ) and dendritic cell (DC) subsets in mucosal biopsies and peripheral blood.

MATERIAL AND METHODS

Intestinal biopsies and blood samples were obtained from 12 different CD patients both before and 4 weeks after the initiation of the induction of adalimumab treatment. Endoscopic disease activity was estimated by the Simple Endoscopic Score for Crohn's Disease. Biopsies were obtained from inflamed and non-inflamed areas. The numbers of lamina propria CD14 (+) DR(int) and CD14 (+) DR(hi) MQs, CD141(+), CD141(-) and CD103(+) DCs subsets, and circulating monocytes and DCs were analyzed using flow cytometry.

RESULTS

At baseline, we observed higher numbers of DR(int) MQs and lower numbers of CD103(+) DCs in inflamed versus non-inflamed mucosa [843 vs. 391/10(5) lamina propria mononuclear cells (LPMCs) (p < 0.05) and 9 vs. 19 × 10(5) LPMCs (p = 0.01), respectively]. After four weeks of adalimumab treatment, the numbers of DR(int) MQs decreased [843 to 379/10(5) LPMCs (p = 0.03)], whereas the numbers of CD103(+) DCs increased [9-20 × 10(5) LPMCs (p = 0.003)] compared with baseline. In peripheral blood, no alterations were observed in monocyte or DC numbers between baseline and week 4.

CONCLUSIONS

In CD, mucosal inflammation is associated with high numbers of DR(int) MQs and low numbers of CD103(+) DCs. This composition of intestinal myeloid subsets is reversed by anti-TNF-α treatment. These results suggest that DR(int) MQs play a pivotal role in CD inflammation.

Autonomic nervous system function predicts the inflammatory response over three years in newly diagnosed ulcerative colitis patients

BACKGROUND

The autonomic nervous system (ANS) modulates intestinal inflammation in animal models. Human evidence confirming such modulating influence is limited. We aimed to investigate whether ANS function is associated with inflammatory parameters at disease onset, and whether it predicts the evolution of inflammation in patients with ulcerative colitis (UC).

METHODS

We prospectively monitored 51 patients from onset of UC for 3 years. Upon remission of the onset flare, ANS activity was assessed by heart rate variability analysis and compared with healthy controls. Inflammatory parameters in blood, stool, and colonic biopsies obtained at onset and during follow-up visits were analyzed. Generalized linear models were used to test cross-sectional associations between ANS activity and inflammatory parameters at onset; linear mixed models were used to test whether ANS function at onset predicted the evolution of inflammation over the following 3 years.

KEY RESULTS

Sympathovagal balance was different in UC patients compared to healthy controls, and cross-sectional associated with higher levels of systemic (erythrocyte sedimentation rate [ESR], CRP, TNF-α, IFN-γ) and mucosal inflammation (interleukin-8, IFN-γ) at onset. Conversely, a negative cross-sectional association with parasympathetic activity was found for ESR & TNF-α. Longitudinally, parasympathetic activity at onset predicted systemic (ESR, WBC), but not mucosal inflammation during follow-up.

CONCLUSIONS & INFERENCES

This study further strengthens the association between the ANS system and intestinal inflammation previously found in animal models and recently in patients with inflammatory bowel disease. These results may have important implications for the pathogenesis and treatment of UC.

Anti-TNF Therapy Response in Patients with Ulcerative Colitis Is Associated with Colonic Antimicrobial Peptide Expression and Microbiota Composition

BACKGROUND AND AIMS

Anti-tumour necrosis factor [TNF] therapy is used in patients with ulcerative colitis [UC], but not all patients respond to treatment. Antimicrobial peptides [AMPs] and the gut microbiota are essential for gut homeostasis and may be important for treatment outcome. The aim of this study was to determine AMP and microbiota profiles in patients with UC before anti-TNF therapy start and correlate these data to treatment outcome.

METHODS

Serum and biopsies were obtained from UC patients naïve to biological therapy [n = 56] before anti-TNF therapy start [baseline]. Fecal samples were taken at baseline and Weeks 2 and 6. Quantitative proteomic analysis was performed in mucosal biopsies. Expression of AMPs and cytokines was determined in biopsies and serum. Microbiota analysis of fecal samples was performed using GA-map™ Dysbiosis Test and real-time quantitative polymerase chain reaction [rtPCR]. Treatment response was evaluated 12-14 weeks after baseline.

RESULTS

At baseline, proteomic analysis of biopsies showed that treatment responders and non-responders had differential expression of AMPs. Eleven AMP and AMP-related genes were analysed by rtPCR in mucosal biopsies and could together discriminate responders from non-responders at baseline. The most important nominators for response were increased expression of defensin 5 and eosinophilic cationic protein. Microbiota analysis revealed lower dysbiosis indexes and higher abundance of Faecalibacterium prausnitzii in responders compared with non-responders at baseline. Also, abundance of F. prausnitzii increased during induction therapy in responders.

CONCLUSIONS

Anti-TNF therapy responders and non-responders display distinctly separate patterns of mucosal AMP expression and gut microbiota before treatment start. This indicates that intestinal antimicrobial/microbial composition can influence treatment outcome.

Global Cytokine Profiles and Association With Clinical Characteristics in Patients With Irritable Bowel Syndrome

OBJECTIVES

Evidence suggests that patients with irritable bowel syndrome (IBS) have an altered cytokine profile, although it is unclear whether cytokines are linked with symptom severity. We aimed to determine whether global serum and mucosal cytokine profiles differ between IBS patients and healthy subjects and whether cytokines are associated with IBS symptoms.

METHODS

Serum from 144 IBS patients and 42 healthy subjects was analyzed for cytokine levels of interleukin (IL)-5, IL-6, IL-8, IL-10, IL-12p70, IL-13, IL-17A, interferon (IFN)-γ, and tumor necrosis factor (TNF) by MSD MULTI-ARRAY. In total, 109 IBS and 36 healthy sigmoid colon biopsies were analyzed for mRNA expression of IL-8, IL-10, TNF, and FOXP3 by quantitative reverse transcription PCR. Multivariate discrimination analysis evaluated global cytokine profiles. Rectal sensitivity, oroanal transit time, and psychological and gastrointestinal symptom severity were also assessed.

RESULTS

Global cytokine profiles of IBS patients and healthy subjects overlapped, but cytokine levels varied more in IBS patients. Serum levels of IL-6 and IL-8 tended to be increased and levels of IFN-γ tended to be decreased in IBS patients. Mucosal mRNA expression of IL-10 and FOXP3 tended to be decreased in IBS patients. Within both the full study cohort and IBS patients alone, serum level of TNF was associated with looser stool pattern, while subjects with more widespread somatic symptoms had increased serum levels of IL-6. Although neither IBS bowel habit subgroups nor patients with possible post-infectious IBS were associated with distinct cytokine profiles, a small cluster of IBS patients with comparatively elevated immune markers was identified.

CONCLUSIONS

Global cytokine profiles did not discriminate IBS patients from healthy subjects, but cytokine profiles were more varied among IBS patients than among healthy subjects, and a small subgroup of patients with enhanced immune activity was identified. Also, association of inflammatory cytokines with some clinical symptoms suggests that immune activation may be of importance in a subset of IBS patients.