Serum and colonic mucosal immune markers in irritable bowel syndrome

Functional Bowel Disorders Are Associated with a Central Immune Activation

Background

Subjects with depression and unexplained neurological symptoms have a high prevalence of gastrointestinal comorbidity probably related to the brain-gut communication. This study explored associations between functional gastrointestinal disorders (FGID) and inflammatory markers in subjects with these disorders.

Methods

The FGID, including irritable bowel syndrome (IBS), were classified according to the Rome III criteria, and degree of symptoms was assessed with IBS symptom severity score (IBS-SSS). A range of interleukins (IL), chemokines and growth factors, tryptophan, and kynurenine were analysed in serum and the cerebrospinal fluid (CSF), and short-chain fatty acids (SCFA) were analysed in the faeces. The results are reported as partial correlation (pc) and p values.

Results

Sixty-six subjects were included. IBS was associated with high levels of tryptophan (p = 0.048) and kynurenine (p = 0.019) and low level of IL-10 (p = 0.047) in the CSF. IBS-SSS was associated with high tumor necrosis factor and low IL-10 in the CSF; pc = 0.341 and p = 0.009 and pc = −0.299 and p = 0.023, respectively. Propionic minus butyric acid in faeces was negatively associated with IL-10 in the CSF (pc = −0.416, p = 0.005).

Conclusions

FGID were associated with a proinflammatory immune activation in the central nervous system and a disturbed tryptophan metabolism that could have been mediated by the faecal microbiota.

Sex-Related Differences in GI Disorders

Epidemiological studies indicate sex-related differences among functional gastrointestinal disorders (FGIDs) wherein females are more likely to receive a diagnosis than their male counterparts. However, the mechanism by which females exhibit an increased vulnerability for development of these pathophysiologies remains largely unknown, and therapeutic treatments are limited. The current chapter focuses on clinical research outlining our current knowledge of factors that contribute to the female predominance among FGID patients such as the menstrual cycle and sex hormones. In addition, we will discuss progress in preclinical research, including animal models, which serve as valuable tools for the investigation of the development and long term manifestation of symptoms observed within the patient population. Although much progress has been made, additional longitudinal studies in both clinical and preclinical research are necessary to identify more specific mechanisms underlying sex-related differences in FGIDs as well as targets for improved therapeutic approaches.

A Systematic Review of the Effects of Polyols on Gastrointestinal Health and Irritable Bowel Syndrome

Polyols are sugar alcohols found in certain fruits, vegetables, and sugar-free sweeteners. They make up a component of the diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols, which is gaining popularity in the treatment of patients with irritable bowel syndrome (IBS). We conducted a systematic review to evaluate the effects of polyols on the gastrointestinal tract in healthy men and women and in patients with IBS. Utilizing PubMed, Ovid, and Embase databases, we conducted a search on individual polyols and each of these terms: fermentation, absorption, motility, permeability, and gastrointestinal symptoms. Standard protocols for a systematic review were followed. We found a total of 1823 eligible articles, 79 of which were included in the review. Overall, available work has shown that polyol malabsorption generally occurs in a dose-dependent fashion in healthy individuals, and malabsorption increases when polyols are ingested in combination. However, studies in patients with IBS have shown conflicting results pertaining to polyol malabsorption. Polyol ingestion can lead to intestinal dysmotility in patients with IBS. Regarding the microbiome, moderate doses of polyols have been shown to shift the microbiome toward an increase in bifidobacteria in healthy individuals and may therefore be beneficial as prebiotics. However, data are limited regarding polyols and the microbiome in patients with IBS. Polyols can induce dose-dependent symptoms of flatulence, abdominal discomfort, and laxative effects when consumed by both healthy volunteers and patients with IBS. Further research is needed to better understand the effects of specific polyols on gastrointestinal function, sensation, and the microbiome in health and gastrointestinal disorders such as IBS.

Brief Report: Examining Executive and Social Functioning in Elementary-Aged Children with Autism

There is a paucity of literature examining the relationship between executive and social functioning in children with autism spectrum disorder (ASD). Twenty-three school-aged children with ASD participated. Executive functioning was measured using the Developmental Neuropsychological Assessment, Second Edition and Differential Ability Scales, Second Edition, and the teacher-rated Behavior Rating of Inventory of Executive Function. Independent assessors observed children's social functioning on the playground while children with ASD and their peers completed a survey to measure peer friendships and rejections. Overall, poorer executive functioning was associated with increased playground isolation and less engagement with peers. This suggests that metacognitive skills such as initiation, working memory, and planning and organization are associated with children's social functioning.

Neuroimmune factors in functional gastrointestinal disorders: A focus on irritable bowel syndrome

BACKGROUND

Abnormal abdominal pain perception is the most bothersome and difficult to treat symptom of functional gastrointestinal disorders (FGIDs). Visceral pain stimuli are perceived and transmitted by afferent neurons residing in the dorsal root ganglia that have sensory nerve endings in the gut wall and mesentery. Accumulating evidence indicates that peripheral activation and sensitization of these sensory nerve endings by bioactive mediators released by activated immune cells, in particular mast cells, can lead to aberrant neuroimmune interactions and the development and maintenance of visceral hypersensitivity. Besides direct neuronal activation, low concentrations of proteases, histamine, and serotonin can chronically sensitize nociceptors, such as TRP channels, leading to persistent aberrant pain perception.

PURPOSE

This review discusses the potential mechanisms underlying aberrant neuroimmune interactions in peripheral sensitization of sensory nerves. A better understanding of the cells, mediators, and molecular mechanisms triggering persistent aberrant neuroimmune interactions brings new insights into their contribution to the physiology and pathophysiology of visceral pain perception and provides novel opportunities for more efficient therapeutic treatments for these disorders.

Inflammatory cytokines and oxidative stress biomarkers in irritable bowel syndrome: Association with digestive symptoms and quality of life

A growing body of evidence suggests a possible role for low-grade inflammation in the pathogenesis of irritable bowel syndrome (IBS). The objectives of this study were to measure serum levels of tumor necrosis factor (TNF)-α, interleukin (IL)-17, interleukin (IL)-10, malondialdehyde (MDA) and total antioxidant capacity (TAC) in IBS patients and healthy controls (HCs), and to evaluate possible correlations of such markers with gastrointestinal (GI) symptoms and quality of life (QoL). Ninety Rome III positive IBS patients and 90 sex and age matched HCs were recruited. GI symptoms, IBS-QoL, IBS severity score system (IBSSS), and the serum levels of inflammatory cytokines and oxidative stress biomarkers were evaluated. In IBS patients, TNFα, IL-17 and MDA cytokines were significantly (P<0.05) higher, and IL-10 cytokine and TAC were significantly (P<0.05) lower vs. HCs. When comparing IBS subtypes, TNFα and IL-17 were significantly (P<0.05) higher, and IL-10 was significantly (P<0.05) lower in diarrhea predominant IBS (IBS-D) compared to HCs, whereas the inflammatory cytokine profile of other subtypes more closely resembled that of HCs. The serum levels of MDA and TAC were significantly different (P<0.05) in all the subtypes vs. HCs. All the inflammatory cytokines had significant (P<0.05) correlations with GI symptoms, IBSSS and IBS-QoL, whereas no significant association was found between oxidative stress biomarkers and these symptoms. IBS-D patients display increased pro-inflammatory cytokines and decreased anti-inflammatory cytokines. Present study demonstrated a correlation between inflammatory cytokines and both IBS symptoms and QoL.

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.

The human intestinal microbiota of constipated-predominant irritable bowel syndrome patients exhibits anti-inflammatory properties

The intestinal microbiota of patients with constipated-predominant irritable bowel syndrome (C-IBS) displays chronic dysbiosis. Our aim was to determine whether this microbial imbalance instigates perturbation of the host intestinal mucosal immune response, using a model of human microbiota-associated rats (HMAR) and dextran sulfate sodium (DSS)-induced experimental colitis. The analysis of the microbiota composition revealed a decrease of the relative abundance of Bacteroides, Roseburia-Eubacterium rectale and Bifidobacterium and an increase of Enterobacteriaceae, Desulfovibrio sp., and mainly Akkermansia muciniphila in C-IBS patients compared to healthy individuals. The bacterial diversity of the gut microbiota of healthy individuals or C-IBS patients was maintained in corresponding HMAR. Animals harboring a C-IBS microbiota had reduced DSS colitis with a decreased expression of pro-inflammatory cytokines from innate, Th1, and Th17 responses. The pre-treatment of conventional C57BL/6 mice or HMAR with A. muciniphila, but not with Escherichia coli, prior exposure to DSS also resulted in a reduction of colitis severity, highlighting that the anti-inflammatory effect of the gut microbiota of C-IBS patients is mediated, in part, by A. muciniphila. This work highlights a novel aspect of the crosstalk between the gut microbiota of C-IBS patients and host intestinal homeostasis.

Neuroimmune Cross Talk in the Gut. Neuroendocrine and neuroimmune pathways contribute to the pathophysiology of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common disorder characterized by recurrent abdominal pain, bloating, and disturbed bowel habit, symptoms that impact the quality of life of sufferers. The pathophysiological changes underlying this multifactorial condition are complex and include increased sensitivity to luminal and mucosal factors, resulting in altered colonic transit and visceral pain. Moreover, dysfunctional communication in the bidirectional signaling axis between the brain and the gut, which involves efferent and afferent branches of the peripheral nervous system, circulating endocrine hormones, and local paracrine and neurocrine factors, including immune and perhaps even microbial signaling molecules, has a role to play in this disorder. This minireview will examine recent advances in our understanding of the pathophysiology of IBS and assess how cross talk between hormones, immune, and microbe-derived factors and their neuromodulatory effects on peripheral nerves may underlie IBS symptomatology.

Serum immune biomarkers in irritable bowel syndrome

BACKGROUND AND OBJECTIVES

Irritable bowel syndrome (IBS) is the most prevalent functional gastrointestinal (GI) disorder, which presents with abdominal pain and changes in the bowel habits. Although the exact cause of IBS remains uncertain, some studies have shown that the inflammation and cytokine imbalance may act as potential etiological factors. The aim of our study is to compare the serum levels of interleukin 6 (IL-6), interleukin 8 (IL-8), and tumor necrosis factor-alpha (TNF-α) in patients with IBS with the healthy controls. The other aim of this study is to evaluate possible association between above-mentioned cytokines and IBS subtypes.

METHODS

Seventy-four IBS patients diagnosed based on Rome III criteria and 75 gender and age-matched healthy controls were included in this study. Cytokines were measured in the serum using enzyme-linked immunosorbent assays (ELISA).

RESULTS

Patients were classified into groups of IBS with diarrhea (IBS-D): 34, IBS with constipation (IBS-C): 29, and IBS with mixed symptoms (IBS-M): 11. The serum levels of IL-6, IL-8 and TNF-α were significantly higher in patients with IBS as compared to controls (P<0.001). There was no difference in serum levels of cytokines based on IBS subtypes.

CONCLUSIONS

Higher serum level of IL-6, IL-8 and TNF-α in IBS suggests an important role of cytokines as immune mediators in the pathogenesis of this functional GI disorder. To understand any association between cytokines and IBS subtypes, further investigations with larger sample sizes are desired.

Repeated Water Avoidance Stress Alters Mucosal Mast Cell Counts, Interleukin-1β Levels with Sex Differences in the Distal Colon of Wistar Rats

Background/Aims

This study was aimed at evaluating differences in the effects of repeated water avoidance stress (rWAS) on colonic movement, mucosal mast cell counts, cytokine levels, and visceromotor response (VMR) to colorectal distension (CRD) in rats of both sexes.

Methods

Wistar rats were divided into stress and no-stress groups. Rats in the stress group were exposed to rWAS (1 hr/day) for 10 days. Mucosal mast cells were immunohistochemically stained with anti-mast cell tryptase antibody and counted. The colonic mucosal cytokine levels were measured with enzyme-linked immunosorbent assay. The VMR to CRD (visceral analgesia) was assessed by using a barostat and noninvasive manometry.

Results

The mean number of fecal pellets in the rWAS group increased significantly as compared with that in the no-stress group in both sexes. After adjustment for body weight, the female rats had a significantly higher pellet output than the male rats. The mucosal mast cell count of the female rWAS group was higher than that of the male rWAS group (13.0 ± 0.9 vs 8.8 ± 0.6; P < 0.001). The colonic mucosal interleukin-1β level was also higher only in the female rats of the rWAS group than in those of the no-stress group. On days 10 and 11, a decrease in VMR to CRD was observed at 40 and 60 mmHg in both sexes of the rWAS group, without a sex-based difference.

Conclusions

The colonic response to stress appeared to be more sensitive in the female rats than in the male rats. However, stress-induced visceral analgesia had no sex-related difference and the underlying mechanism needs to be further evaluated.

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.

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.

Small Intestinal Bacterial Overgrowth in Patients with Irritable Bowel Syndrome: Clinical Characteristics, Psychological Factors, and Peripheral Cytokines

Small intestinal bacterial overgrowth (SIBO) has been implicated in the pathogenesis of irritable bowel syndrome (IBS). Psychosocial factors and low-grade colonic mucosal immune activation have been suggested to play important roles in the pathophysiology of IBS. In total, 94 patients with IBS and 13 healthy volunteers underwent a 10 g lactulose hydrogen breath test (HBT) with concurrent ^99mTc scintigraphy. All participants also completed a face-to-face questionnaire survey, including the Hospital Anxiety and Depression Scale, Life Event Stress (LES), and general information. Serum tumour necrosis factor-α, interleukin- (IL-) 6, IL-8, and IL-10 levels were measured. The 89 enrolled patients with IBS and 13 healthy controls had no differences in baseline characteristics. The prevalence of SIBO in patients with IBS was higher than that in healthy controls (39% versus 8%, resp.; p = 0.026). Patients with IBS had higher anxiety, depression, and LES scores, but anxiety, depression, and LES scores were similar between the SIBO-positive and SIBO-negative groups. Psychological disorders were not associated with SIBO in patients with IBS. The serum IL-10 level was significantly lower in SIBO-positive than SIBO-negative patients with IBS.

Recent advances in the diagnosis of irritable bowel syndrome

The symptom-based diagnosis of irritable bowel syndrome (IBS) has not been established in everyday clinical practice, and the diagnosis of this disorder remains one of exclusion. It has been demonstrated that the densities of duodenal chromogranin A, rectal peptide YY and somatostatin cells are good biomarkers for the diagnosis of sporadic IBS, and low-grade mucosal inflammation is a promising biomarker for the diagnosis of postinfectious IBS. Genetic markers are not useful as biomarkers for IBS since the potential risk genes have yet to be validated, and the intestinal microbiota cannot be used because of the lack of an association between a specific bacterial species and IBS. Furthermore, gastrointestinal dysmotility and visceral hypersensitivity tests produce results that are too nonconsistent and noncharacteristic to be used in the diagnosis of IBS. A combination of symptom-based assessment, exclusion of overlapping gastrointestinal diseases and positive biomarkers appears to be the best way to diagnose IBS.

Interferon-γ is increased in the gut of patients with irritable bowel syndrome and modulates serotonin metabolism

Mucosal immune activation and altered serotonin metabolism participate in the pathophysiology of irritable bowel syndrome (IBS). However, the reciprocal interplay between these two systems remains unknown. We evaluated the expression and release of interferon (IFN)-γ from the colonic mucosa of patients with IBS and its impact on serotonin reuptake transporter (SERT) gene expression in Caco-2 cells. qPCR was used to evaluate IFN-γ gene expression in colonic mucosal biopsies, whereas IFN-γ protein amount was assessed by ELISA. Colonic T box expressed in T cells (T-bet) and phosphorylated signal transducer and activator of transcription 4 protein amount were evaluated by Western blot. The impact of colonic mucosal mediators on SERT gene expression was evaluated in Caco-2 cells using qPCR. IFN-γ receptor was silenced in Caco-2 cells to determine the effect of IFN-γ released by mucosal biopsies. Compared with asymptomatic controls (ACs), the expression of IFN-γ gene and its transcription factor T-bet were markedly increased in the colonic mucosa of patients with IBS. Compared with ACs, IFN-γ protein tissue levels and its release by mucosal biopsies were significantly increased in IBS. The exposure of Caco-2 cells to IBS supernatants induced a significant decrease in SERT gene expression, independently of IBS subtypes, compared with AC mucosal supernatants. In Caco-2 cells, IFN-γ receptor silencing reversed the reduction of SERT expression evoked by IBS supernatants vs. nonsilenced cell lines. IFN-γ gene, its transcription factor T-bet, IFN-γ protein expression, and its release are increased in the colonic mucosa of patients with IBS and downregulate SERT gene expression in vitro. These results suggest that IFN-γ downregulates SERT expression, hence likely playing a role in altered serotonin metabolism of patients with IBS.

Gender-related differential effect of tachykinin NK2 receptor-mediated visceral hyperalgesia in guinea pig colon

BACKGROUND AND PURPOSE

The tachykinin NK2 receptor antagonist ibodutant is under Phase III clinical investigation to treat female patients with irritable bowel syndrome. The aim of this study was to investigate the NK2 receptor-related gender specificity in a model of colitis.

EXPERIMENTAL APPROACH

Colitis was induced by rectal instillation of 2,4,6-trinitrobenzenesulfonic acid (TNBS, 0.5 mL, 30 mg·mL(-1) in 30% ethanol) in female and male guinea pigs. Electromyographic recording of the responses to colorectal distension (CRD) was made 3 days later. Ibodutant (0.33 , 0.65, 1.9 and 6.5 mg·kg(-1) ) was given s.c., 30 min before CRD. Release of neurokinin A and substance P from isolated mucosal and smooth muscle tissues following treatment with KCl (80 mM) or capsaicin (10 μM) was measured by EIA. Plasma pharmacokinetics of ibodutant following a single s.c. administration (0.73 or 2.1 mg·kg(-1) ) were measured over 24 h.

KEY RESULTS

Ibodutant did not affect abdominal contractions in control animals. After TNBS-induced colitis, ibodutant prevented the increased visceral hypersensitivity to CRD in females, at lower doses than in males. Ibodutant pharmacokinetics did not differ between females and males. Tachykinins release was greater in smooth muscle than in mucosal samples. Capsaicin-stimulated release of tachykinins from inflamed mucosal samples from females was significantly lower than in males.

CONCLUSIONS AND IMPLICATIONS

Ibodutant prevented abdominal nociception in a model of visceral hypersensitivity in guinea pigs with a greater efficacy in females than in males. Our results highlight a gender-related difference in colonic visceral hypersensitivity and mucosal nerve activation.

Overlapping irritable bowel syndrome and inflammatory bowel disease: less to this than meets the eye?

Though distinct in terms of pathology, natural history and therapeutic approach, irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) have some features in common. These include shared symptomatology and largely similar demographics. However, in most instances, clinical presentation, together with laboratory, imaging and endoscopic findings will readily permit the differentiation of active IBD from IBS. More problematic is the situation where a subject with IBD, in apparent remission, continues to complain of symptoms which, in aggregate, satisfy commonly employed criteria for the diagnosis of IBS. Access to methodologies, such the assay for levels of calprotectin in feces, now allows identification of ongoing inflammation in some such individuals and prompts appropriate therapy. More challenging is the IBD patient with persisting symptoms and no detectable evidence of inflammation; is this coincident IBS, IBS triggered by IBD or an even more subtle level of IBD activity unrecognized by available laboratory or imaging methods? Arguments can be advanced for each of these proposals; lacking definitive data, this issue remains unresolved. The occurrence of IBS-type symptoms in the IBD patient, together with some data suggesting a very subtle level of 'inflammation' or 'immune activation' in IBS, raises other questions: is IBS a prodromal form of IBD; and are IBS and IBD part of the spectrum of the same disease? All of the available evidence indicates that the answer to both these questions should be a resounding 'no'. Indeed, the whole issue of overlap between IBS and IBD should be declared moot given their differing pathophysiologies, contrasting natural histories and divergent treatment paths. The limited symptom repertoire of the gastrointestinal tract may well be fundamental to the apparent confusion that has, of late, bedeviled this area.

Gut microbiota as potential orchestrators of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a multifactorial functional disorder with no clearly defined etiology or pathophysiology. Modern culture-independent techniques have improved the understanding of the gut microbiota’s composition and demonstrated that an altered gut microbiota profile might be found in at least some subgroups of IBS patients. Research on IBS from a microbial perspective is gaining momentum and advancing. This review will therefore highlight potential links between the gut microbiota and IBS by discussing the current knowledge of the gut microbiota; it will also illustrate bacterial-host interactions and how alterations to these interactions could exacerbate, induce or even help alleviate IBS.

Activation of colo-rectal high-threshold afferent nerves by Interleukin-2 is tetrodotoxin-sensitive and upregulated in a mouse model of chronic visceral hypersensitivity

BACKGROUND

Chronic visceral pain is a defining feature of irritable bowel syndrome (IBS). IBS patients often show alterations in innate and adaptive immune function which may contribute to symptoms. Immune mediators are known to modulate the activity of viscero-sensory afferent nerves, but the focus has been on the innate immune system. Interleukin-2 (IL-2) is primarily associated with adaptive immune responses but its effects on colo-rectal afferent function in health or disease are unknown.

METHODS

Myeloperoxidase (MPO) activity determined the extent of inflammation in health, acute trinitrobenzene-sulfonic acid (TNBS) colitis, and in our post-TNBS colitis model of chronic visceral hypersensitivity (CVH). The functional effects of IL-2 on high-threshold colo-rectal afferents and the expression of IL-2R and NaV 1.7 mRNA in colo-rectal dorsal root ganglia (DRG) neurons were compared between healthy and CVH mice.

KEY RESULTS

MPO activity was increased during acute colitis, but subsided to levels comparable to health in CVH mice. IL-2 caused direct excitation of colo-rectal afferents that was blocked by tetrodotoxin. IL-2 did not affect afferent mechanosensitivity in health or CVH. However, an increased proportion of afferents responded directly to IL-2 in CVH mice compared with controls (73% vs 33%; p < 0.05), and the abundance of IL-2R and NaV 1.7 mRNA was increased 3.5- and 2-fold (p < 0.001 for both) in colo-rectal DRG neurons.

CONCLUSIONS & INFERENCES

IL-2, an immune mediator from the adaptive arm of the immune response, affects colo-rectal afferent function, indicating these effects are not restricted to innate immune mediators. Colo-rectal afferent sensitivity to IL-2 is increased long after healing from inflammation.

Balance of Autonomic Nervous System Predicts Who Benefits from a Self-management Intervention Program for Irritable Bowel Syndrome

Background/Aims

To determine if potential biomarkers can be used to identify subgroups of people with irritable bowel syndrome (IBS) who will benefit the most or the least from a comprehensive self-management (CSM) intervention.

Methods

In a two-armed randomized controlled trial a CSM (n = 46) was compared to a usual care (n = 46) group with follow-up at 3 and 6 months post randomization. Biomarkers obtained at baseline included heart rate variability, salivary cortisol, interleukin-10 produced by unstimulated peripheral blood mononuclear cells, and lactulose/mannitol ratio. Linear mixed models were used to test whether these biomarkers predicted improvements in the primary outcomes including daily abdominal pain, Gastrointestinal Symptom score and IBS-specific quality of life.

Results

The nurse-delivered 8-session CSM intervention is more effective than usual care in reducing abdominal pain, reducing Gastrointestinal Symptom score, and enhancing quality of life. Participants with lower nighttime high frequency heart rate variability (vagal modulation) and increased low frequency/high frequency ratio (sympathovagal balance) had less benefit from CSM on abdominal pain. Salivary cortisol, IL-10, and lactulose/mannitol ratio were not statistically significant in predicting CSM benefit. Baseline symptom severity interacts with treatment, namely the benefit of CSM is greater in those with higher baseline symptoms.

Conclusions

Cognitively-focused therapies may be less effective in reducing abdominal pain in IBS patients with higher sympathetic tone. Whether this a centrally-mediated patient characteristic or related to heightened arousal remains to be determined.

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.

Recent developments in the pathophysiology of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder, the pathophysiology of which is not completely known, although it has been shown that genetic/social learning factors, diet, intestinal microbiota, intestinal low-grade inflammation, and abnormal gastrointestinal endocrine cells play a major role. Studies of familial aggregation and on twins have confirmed the heritability of IBS. However, the proposed IBS risk genes are thus far nonvalidated hits rather than true predisposing factors. There is no convincing evidence that IBS patients suffer from food allergy/intolerance, with the effect exerted by diet seemingly caused by intake of poorly absorbed carbohydrates and fiber. Obesity is a possible comorbidity of IBS. Differences in the microbiota between IBS patients and healthy controls have been reported, but the association between IBS symptoms and specific bacterial species is uncertain. Low-grade inflammation appears to play a role in the pathophysiology of a major subset of IBS, namely postinfectious IBS. The density of intestinal endocrine cells is reduced in patients with IBS, possibly as a result of genetic factors, diet, intestinal microbiota, and low-grade inflammation interfering with the regulatory signals controlling the intestinal stem-cell clonogenic and differentiation activities. Furthermore, there is speculation that this decreased number of endocrine cells is responsible for the visceral hypersensitivity, disturbed gastrointestinal motility, and abnormal gut secretion seen in IBS patients.

Serum biomarkers for irritable bowel syndrome

Background and aim

Irritable bowel syndrome (IBS) is one of the most frequent and common functional gastrointestinal diseases. For its diagnosis, clinical criteria are still used. Our objective was to asses if there are specific serum biomarkers for the diagnosis of IBS, and as secondary purpose we aimed to analyze the specificity and sensitivity – where determined – for the proposed biomarkers.

Methods

We performed a review in order to find potential serum biomarkers useful for the diagnosis of IBS. MEDLINE and Cochrane databases were searched in May 2015. Inclusion criteria were: original studies that assessed serological markers in IBS patients, markers potentially useful for diagnosing IBS or in differentiating subtypes of IBS. Exclusion criteria were biomarkers assessed in IBS patients not for the diagnosis of IBS, but used in order to exclude other conditions or diseases in these patients; or markers that were not addressed to IBS; or papers that assessed only fecal biomarkers, or histological or surrogate - indirect biomarkers.

Results

From the 268 papers retrieved by our initial search, using a modified strategy we identified 58 papers. Out of the 58 papers retrieved by the search, six papers were selected and other nine studies were eventually analyzed. Of the results of the computerized search, a number of papers were not included for various reasons: some were not related to the subject (26), others were not appropriate for the subject (19) because they addressed inflammatory bowel disorders, in others fecal markers were the subject of the study, six were reviews, others were impossible to gain access to (1). Twelve out of the 14 studies included are case-control studies, IBS diagnosis being established in all of the selected results based on the Rome criteria. A higher sensitivity of 81% was found using a combination of markers but with lower specificity, while one study that assessed also a combination of markers, found a higher specificity but sensitivity was only 50 %; none reached the characteristics for an ideal biomarker.

Conclusions

For the moment, just one serum biomarker with a high specificity and sensitivity useful in the diagnosis of IBS was identified. We consider that in the future a combination of several biomarkers could better identify IBS than a single biomarker. Therefore, clinical criteria are still to be used for the diagnosis of IBS in attendance for newer research or validation of results.

Immunological Biomarkers in Postinfectious Irritable Bowel Syndrome

BACKGROUND

There is a recognized need for biological markers to facilitate diagnoses of irritable bowel syndrome (IBS) and to distinguish it from other functional and organic disorders. As postinfectious IBS (PI-IBS) is believed to account for as many as one third of all IBS cases, here we sought to identify differences in specific cytokines and serologic responses across patients with idiopathic IBS and PI-IBS and healthy controls.

METHODS

At total of 120 US military personnel were identified from the Defense Medical Surveillance System-based International Classification of Diseases, 9th Revision, Clinical Modification (ICD9-CM) codes recorded during medical encounters and were grouped based on infectious gastroenteritis (IGE) episode (Shigella, Campylobacter, Salmonella, or an unspecified pathogen) followed by IBS, IBS without antecedent IGE, or IGE without subsequent IBS within 2 years of the IGE exposure. Sera from subjects were assayed for cytokine levels and antibodies against a panel of microbiome antigens.

RESULTS

In total, 10 of 118 markers considered were shown to differ between IBS patients and healthy controls, including cytokines interleukin-6 (IL-6), IL-8, IL-1β, and macrophage inflammatory protein-1β (MIP-1β), as well as antibody responses to microbial antigens. Antimicrobial antibody response profiles also differed between PI-IBS cases compared with IBS cases without an antecedent episode of acute IGE. Comparisons also suggest that immunoglobulin A (IgA) and IgG profiles may point to pathogen-specific origins among PI-IBS cases.

CONCLUSION

Taken together, these results provide further evidence as to the molecular distinctness of classes of IBS cases and that serum biomarkers may prove useful in elucidating their pathobiological pathways.

Immunomodulation of enteric neural function in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder which is characterised by symptoms such as bloating, altered bowel habit and visceral pain. It’s generally accepted that miscommunication between the brain and gut underlies the changes in motility, absorpto-secretory function and pain sensitivity associated with IBS. However, partly due to the lack of disease-defining biomarkers, understanding the aetiology of this complex and multifactorial disease remains elusive. Anecdotally, IBS patients have noted that periods of stress can result in symptom flares and many patients exhibit co-morbid stress-related mood disorders such as anxiety and depression. However, in addition to psychosocial stressors, infection-related stress has also been linked with the initiation, persistence and severity of symptom flares. Indeed, prior gastrointestinal infection is one of the strongest predictors of developing IBS. Despite a lack of overt morphological inflammation, the importance of immune factors in the pathophysiology of IBS is gaining acceptance. Subtle changes in the numbers of mucosal immune cell infiltrates and elevated levels of circulating pro-inflammatory cytokines have been reproducibly demonstrated in IBS populations. Moreover, these immune mediators directly affect neural signalling. An exciting new area of research is the role of luminal microbiota in the modulation of neuro-immune signalling, resulting in local changes in gastrointestinal function and alterations in central neural functioning. Progress in this area has begun to unravel some of the complexities of neuroimmune and neuroendocrine interactions and how these molecular exchanges contribute to GI dysfunction

Diagnosis of Irritable Bowel Syndrome: Role of Potential Biomarkers

Irritable bowel syndrome is a disorder diagnosed on symptom-based criteria without inclusion of any objective parameter measurable by known diagnostic methods. Heterogeneity of the disorder and overlapping with more serious organic diseases increase uncertainty for the physician's work and increase the cost of confirming the diagnosis. This paper is an attempt to summarize the efforts to find adequate biomarkers for irritable bowel syndrome, which should shorten the time to diagnosis and reduce the cost. Most of the reviewed papers were observational studies from secondary care institutions. Since publication of the Rome III criteria in 2006, most recent studies use these for the recruitment of IBS patients. This is a positive step forward as future studies should use the same criteria, facilitating comparison of their results. Among the studied biomarkers, most evidence is provided for fecal calprotectin. Cutoff values for fecal calprotectin have still to be investigated prior to inclusion in the irritable bowel syndrome diagnostic algorithm.

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.

Soluble mediators in plasma from irritable bowel syndrome patients excite rat submucosal neurons

BACKGROUND

Episodic bouts of abdominal pain and altered bowel habit are characteristic of irritable bowel syndrome (IBS). Although a comprehensive understanding of IBS pathophysiology remains elusive, support is growing for a primary role for immune activation in disease severity as evidenced by altered cytokine profiles in IBS plasma. Additionally, aberrant stimulation of the stress axis is likely to result in altered plasma constituents.

METHODS

Whole-mount preparations of submucosal plexus from adult male Sprague Dawley rats were exposed to plasma from IBS patients and healthy controls. Ratiometric calcium imaging recordings were used to measure changes in intracellular calcium ([Ca(2+)]i) as a marker of neuronal excitability.

KEY RESULTS

IBS plasma stimulated a robust increase in [Ca(2+)]i (0.09 ± 0.02) whereas plasma from healthy volunteers had little effect (-0.02 ± 0.02, n=24, p<0.001). The neuromodulatory actions of IBS plasma were reduced by pre-neutralisation with anti-interleukin (IL)-6 (p<0.01) but not IL-8, immunoglobulin G or C-reactive protein. Moreover, IBS plasma-evoked responses (0.22 ± 0.06) were inhibited by the corticotrophin releasing factor receptor (CRFR) 1 antagonist, antalarmin (1μM, 0.015 ± 0.02, n=14, p<0.05), but not the CRFR2 antagonist, astressin 2B. Neuronal activation was mediated by ERK/MAPK signalling.

CONCLUSIONS

These data provide evidence that factors present in IBS plasma modulate neuronal activity in the submucosal plexus and that this is likely to involve CRFR1 activation and IL-6 signalling. These neuromodulatory actions of stress and immune factors indicate a potential mechanism by which immune activation during periods of stress may lead to symptom flares in 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.

Validating biomarkers of treatable mechanisms in irritable bowel syndrome

BACKGROUND

A valid biomarker is 'an indicator of normal biologic or pathogenic processes, or pharmacological responses to a therapeutic intervention'. There is no validated biomarker for irritable bowel syndrome (IBS). The aim of the study was to assess ability of three quantitative traits to identify treatable processes to discriminate between IBS-diarrhea (IBS-D) patients, IBS-constipation (IBS-C) patients and healthy volunteers (HV).

METHODS

In 30 HV, 30 IBS-C patients and 64 IBS-D patients, we characterized bowel symptoms and quantitated pathophysiological mechanisms: bile acid (BA) synthesis (serum C4 and FGF19), fecal BA and fat, colonic transit (CT), and intestinal permeability (IP). We used multiple logistic regression and receiver-operating characteristic (ROCAUC ) to appraise three factors (fecal BA, CT, and IP) individually and in combination to identify discriminant targets for treatment in IBS.

KEY RESULTS

There were significant associations between the three subgroups and symptoms reflecting bowel function and the quantitative traits. There were significant associations between fecal BA and CT at 48 h (r = 0.43; p < 0.001) and between fecal BA and IP (r = 0.23; p = 0.015). Individually, fecal BA and CT48 (but not IP) were significant independent predictors for distinguishing HV from IBS. In combination, they discriminated HV from IBS-D patients (ROCAUC 0.70), HV from IBS-C patients (ROCAUC 0.73), and IBS-C patients from IBS-D patients (ROCAUC 0.86). Colonic transit and fecal BA excretion together discriminate between healthy volunteers and IBS-C patients or IBS-D patients, or between the IBS subgroups with 75-90% specificity at 60% sensitivity.

CONCLUSIONS & INFERENCES

Colonic transit and fecal BA individually and together constitute useful biomarkers to identify treatable mechanisms in IBS and to differentiate subgroups of IBS.

Associations among gut permeability, inflammatory markers, and symptoms in patients with irritable bowel syndrome

BACKGROUND

Alterations in gastrointestinal (GI) permeability and immune measures are present in some patients with irritable bowel syndrome (IBS) but the relationship to symptoms is poorly defined. In adults with IBS, we compared permeability, unstimulated peripheral blood monocyte (PBMC) interleukin-10 (IL-10) levels, IBS life interference, and GI and psychological distress symptoms.

METHODS

In 88 women and 18 men with IBS, GI permeability was quantitated as percent recovery of urinary sucrose and the lactulose/mannitol (L/M) ratio. IL-10 was measured in supernatants from 72-h incubated, unstimulated PBMCs. Participants completed a 4-week daily diary recording IBS life interference on daily activities and work, IBS symptoms, and psychological distress symptoms. They also completed the Brief Symptom Inventory.

RESULTS

The L/M ratio but not percent sucrose recovery was significantly correlated with IBS interference with activities and work and retrospectively measured anxiety and depression. Unstimulated PBMC production of IL-10 correlated significantly with IBS interference with daily work, IBS symptom score, and abdominal pain. We identified a subgroup of IBS subjects with higher IL-10 and/or higher L/M ratio who had substantially higher IBS interference and IBS symptom scores.

CONCLUSIONS

Our findings suggest a distinct subgroup of IBS patients with alterations in gut barrier function. This subgroup is characterized by increased GI permeability and/or increased PBMC production of IL-10. These physiologic alterations reflect more severe IBS as measured by interference of IBS with daily activities and daily IBS symptoms.

Convergence of neuro-endocrine-immune pathways in the pathophysiology of irritable bowel syndrome

Disordered signalling between the brain and the gut are generally accepted to underlie the functional bowel disorder, irritable bowel syndrome (IBS). However, partly due to the lack of disease-defining biomarkers, understanding the aetiology of this complex and multifactorial disease remains elusive. This common gastrointestinal disorder is characterised by alterations in bowel habit such as diarrhoea and/or constipation, bloating and abdominal pain, and symptom exacerbation has been linked with periods of stress, both psychosocial and infection-related. Indeed, a high level of comorbidity exists between IBS and stress-related mood disorders such as anxiety and depression. Moreover, studies have observed alterations in autonomic output and neuro-endocrine signalling in IBS patients. Accumulating evidence indicates that a maladaptive stress response, probably mediated by the stress hormone, corticotropin-releasing factor contributes to the initiation, persistence and severity of symptom flares. Other risk factors for developing IBS include a positive family history, childhood trauma, dietary factors and prior gastrointestinal infection. An emerging role has been attributed to the importance of immune factors in the pathophysiology of IBS with evidence of altered cytokine profiles and increased levels of mucosal immune cells. These factors have also been shown to have direct effects on neural signalling. This review discusses how pathological changes in neural, immune and endocrine pathways, and communication between these systems, contribute to symptom flares in IBS.

Irritable bowel syndrome: A disease still searching for pathogenesis, diagnosis and therapy

Irritable bowel syndrome (IBS) is the most frequently diagnosed functional gastrointestinal disorder in primary and secondary care. It is characterised by abdominal discomfort, pain and changes in bowel habits that can have a serious impact on the patient’s quality of life. The pathophysiology of IBS is not yet completely clear. Genetic, immune, environmental, inflammatory, neurological and psychological factors, in addition to visceral hypersensitivity, can all play an important role, one that most likely involves the complex interactions between the gut and the brain (gut-brain axis). The diagnosis of IBS can only be made on the basis of the symptoms of the Rome III criteria. Because the probability of organic disease in patients fulfilling the IBS criteria is very low, a careful medical history is critical and should pay particular attention to the possible comorbidities. Nevertheless, the severity of the patient’s symptoms or concerns sometimes compels the physician to perform useless and/or expensive diagnostic tests, transforming IBS into a diagnosis of exclusion. The presence of alarming symptoms (fever, weight loss, rectal bleeding, significant changes in blood chemistry), the presence of palpable abdominal masses, any recent onset of symptoms in patient aged over 50 years, the presence of symptoms at night, and a familial history of celiac disease, colorectal cancer and/or inflammatory bowel diseases all warrant investigation. Treatment strategies are based on the nature and severity of the symptoms, the degree of functional impairment of the bowel habits, and the presence of psychosocial disorders. This review examines and discusses the pathophysiological aspects and the diagnostic and therapeutic approaches available for patients with symptoms possibly related to IBS, pointing out controversial issues and the strengths and weaknesses of the current knowledge.

Cytokine imbalance in irritable bowel syndrome: a systematic review and meta-analysis

BACKGROUND

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder of unknown etiology; although infection and inflammation have recently been considered as important etiologic agents. A recent meta-analysis showed correlations between cytokine [interleukin-10 (IL-10) and tumor necrosis factor (TNF)] gene polymorphisms and IBS; however, it is still unknown whether patients with IBS have different cytokine profiles compared to healthy population.

METHODS

To determine the relationships between serum/plasma levels or mucosal expression of IL-10/TNF-α and IBS, we conducted a systematic review and meta-analysis based on case-control studies retrieved from PubMed and EMBASE search through August 2013. Standardized mean difference (SMD) was generated by using the inverse variance method. Heterogeneity was assessed based on I(2) values.

KEY RESULTS

Serum/plasma levels of TNF-α tended to be higher in IBS vs controls (p = 0.09); this reached significance in IBS subtypes vs controls and in female patients with IBS. However, serum/plasma levels of IL-10 were not significantly different in IBS patients vs controls. Further analysis of serum/plasma IL-10 levels in IBS subtypes did not show any difference; however, analysis based on gender showed a significantly lower serum/plasma IL-10 levels in male patients with IBS vs male controls (p = 0.02). Colonic IL-10 mRNA had a significantly lower expression in IBS vs control (p = 0.001).

CONCLUSIONS & INFERENCES

There is an imbalance of proinflammatory TNF-α, and anti-inflammatory IL-10, cytokines in IBS. Stratifying IBS patients based on cytokine profile may represent an opportunity for personalized treatment of this condition.

Update on irritable bowel syndrome program of research

PURPOSE

This article provides an update and overview of a nursing research program focused on understanding the pathophysiology and management of irritable bowel syndrome (IBS).

METHODS

This review includes English language papers from the United States, Europe, and Asia (e.g., South Korea) from 1999 to 2013. We addressed IBS as a health problem, emerging etiologies, diagnostic and treatment approaches and the importance of a biopsychosocial model.

RESULTS

IBS is a chronic, functional gastrointestinal disorder characterized by recurrent episodes of abdominal pain and alterations in bowel habit (diarrhea, constipation, mixed). It is a condition for which adults, particularly women ages 20-45, seek health care services in both the United States and South Korea. Clinically, nurses play key roles in symptom prevention and management including designing and implementing approaches to enhance the patients' self-management strategies. Multiple mechanisms are believed to participate in the development and maintenance of IBS symptoms including autonomic nervous system dysregulation, intestinal inflammation, intestinal dysbiosis, dietary intolerances, alterations in emotion regulation, heightened visceral pain sensitivity, hypothalamic-pituitary-adrenal dysregulation, and dysmotility. Because IBS tends to occur in families, genetic factors may also contribute to the pathophysiology. Patients with IBS often report a number of co-morbid disorders and/or symptoms including poor sleep.

CONCLUSION

The key to planning effective management strategies is to understand the heterogeneity of this disorder. Interventions for IBS include non-pharmacological strategies such as cognitive behavior therapy, relaxation strategies, and exclusion diets.

Microbiota, gastrointestinal infections, low-grade inflammation, and antibiotic therapy in irritable bowel syndrome: an evidence-based review

BACKGROUND

Post-infectious irritable bowel syndrome (PI-IBS) prevalence, small intestinal bacterial overgrowth (SIBO), altered microbiota, low-grade inflammation, and antibiotic therapy in IBS are all controversial issues.

AIMS

To conduct an evidence-based review of these factors.

METHODS

A review of the literature was carried out up to July 2012, with the inclusion of additional articles as far as August 2013, all of which were analyzed through the Oxford Centre for Evidence-Based Medicine (OCEBM) system.

RESULTS

1.There is greater SIBO probability in IBS when breath tests are performed, but prevalence varies widely (2-84%). 2.The gut microbiota in individuals with IBS is different from that in healthy subjects, but a common characteristic present in all the patients has not been established. 3.The incidence and prevalence of PI-IBS varies from 9-10% and 3-17%, respectively, and the latter decreases over time. Bacterial etiology is the most frequent but post-viral and parasitic cases have been reported. 4.A sub-group of patients has increased enterochromaffin cells, intraepithelial lymphocytes, and mast cells in the intestinal mucosa, but no differences between PI-IBS and non-PI-IBS have been determined. 5.Methanogenic microbiota has been associated with IBS with constipation. 6.Rifaximin at doses of 400mg TID/10days or 550mg TID/14days is effective treatment for the majority of overall symptoms and abdominal bloating in IBS. Retreatment effectiveness appears to be similar to that of the first cycle.

CONCLUSIONS

Further studies are required to determine the nature of the gut microbiota in IBS and the differences in low-grade inflammation between PI-IBS and non-PI-IBS. Rifaximin has shown itself to be effective treatment for IBS, regardless of prior factors.

Irritable bowel syndrome: recent developments in diagnosis, pathophysiology, and treatment

The diagnosis of irritable bowel syndrome (IBS) remains a diagnosis of exclusion, whereby an extensive investigation is performed to exclude other organic diseases that may explain the symptoms of patients. Attempts to have a positive diagnosis based on symptom assessments failed to achieve widely use in clinical practice. Abnormalities in the gastrointestinal endocrine cells in IBS patients have been reported recently, providing evidence that IBS is an organic disorder, and opening the door to the use of these abnormalities as markers for a positive diagnosis of IBS. New and promising drugs for the treatment of IBS with constipation as the predominant symptom are currently on the market, and the treatment results have been satisfactory thus far.

Chemotactic chemokines are important in the pathogenesis of irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most frequently diagnosed disorders, affecting about 20% of the general population in Western countries. This syndrome poses an enormous socio-economic burden, impairs the quality of life substantially, and increases healthcare costs. IBS can be classified as either idiopathic (ID-IBS) with unknown etiology or post-infectious (PI-IBS), which develops after a bout of acute diarrhea or gastroenteritis. Little is known about the immunopathogenesis of these two forms of IBS. We evaluated various biomarkers in clinical samples of ID-IBS and PI-IBS patients with the goal to test the hypothesis that the immunologic presentations of these forms of IBS are similar, despite their apparent different etiologic origins. Sera and stool samples from PI-IBS, ID-IBS, and healthy volunteers were analyzed for relative amounts of 36 different biomarkers using the Proteome Profiler Human Cytokine Array Panel A Kit and quantitative ELISA. Our results demonstrated significantly high levels of chemotactic chemokines monocytes chemotactic protein-1 (CCL2) [p-value  = 0.003], macrophage inflammatory protein-1β (CCL4) [p-value  = 0.010], and CXCL16 (p-value 0.001) in the sera and stools of both ID-IBS and PI-IBS patients. Furthermore, pro-inflammatory cytokines (IFN-γ, IL-1β, and TNF-α) were significantly higher in IBS patients. Anti-inflammatory cytokines (IL-10, IL-4, and IL-13) were variable except IL-10, which was significantly higher in the healthy volunteers than the IBS patients. Remarkably, the amounts and expression pattern of these biomarkers were not significantly different between ID-IBS and PI-IBS. Thus, ID-IBS and PI-IBS present similar immunologic and clinical phenotypes, in spite of their different etiologic origins.

Neuroimmune interactions at different intestinal sites are related to abdominal pain symptoms in children with IBS

BACKGROUND

Neuroimmune interactions and inflammation have been proposed as factors involved in sensory-motor dysfunction and symptom generation in adult irritable bowel syndrome (IBS) patients. In children with IBS and healthy controls, we measured ileocolonic mast cell infiltration and fecal calprotectin and evaluated the relationships between these parameters and abdominal pain symptoms and stooling pattern.

METHODS

Irritable bowel syndrome patients diagnosed according to Pediatric Rome III criteria and healthy controls kept a 2-week pain/stooling diary. Ileocolonic mucosal mast cells (MC) and MC in close proximity to nerve fibers (MC-NF) were identified immunohistochemically and quantified. Fecal calprotectin concentration was measured.

KEY RESULTS

21 IBS patients and 10 controls were enrolled. The MC-NF count was significantly higher in the ileum (p = 0.01), right colon (p = 0.04), and left colon (p < 0.001) of IBS patients compared with controls. No differences in fecal calprotectin concentration were noted. Abdominal pain intensity score correlated with ileal MC count (r(s) = 0.47, p = 0.030) and right colon MC-NF count (r(s) = 0.52, p = 0.015). In addition, children with IBS with >3 abdominal pain episodes/week had greater ileal (p = 0.002) and right colonic (p = 0.01) MC counts and greater ileal (p = 0.05) and right colonic (p = 0.016) MC-NF counts than children with less frequent pain. No relationship was found between MC and MC-NF and fecal calprotectin or stooling pattern.

CONCLUSIONS & INFERENCES

Mast cells-nerve fibers counts are increased in the ileocolonic mucosa of children with IBS. Mast cells and MC-NF counts are related to the intensity and frequency of abdominal pain.

Characteristics of functional bowel disorder patients: a cross-sectional survey using the Rome III criteria

BACKGROUND

There is some evidence that, despite attempts to classify them separately, functional bowel disorders are not distinct entities and that such divisions are artificial.

AIM

To examine this issue in a large cohort of secondary care patients.

METHODS

Consecutive, unselected adults with gastrointestinal (GI) symptoms attending out-patient clinics at two hospitals in Hamilton, Ontario were recruited. Demographic data, symptoms and presence of anxiety, depression or somatisation were collected prospectively. We used validated questionnaires, including the Rome III questionnaire, with patients categorised as having irritable bowel syndrome (IBS), functional diarrhoea or chronic idiopathic constipation (CIC). We compared data between these disorders, and measured degree of overlap between them by suspending their mutual exclusivity.

RESULTS

Of 3656 patients providing complete lower GI symptom data, 1551 (42.4%) met criteria for a functional bowel disorder. Diarrhoea-predominant IBS (IBS-D) patients were younger, and more were female, met criteria for anxiety, and reported somatisation-type behaviour, compared with functional diarrhoea. Only loose, mushy or watery stools were more common in functional diarrhoea. When mutual exclusivity was suspended, overlap occurred in 27.6%. Constipation-predominant IBS (IBS-C) patients were younger, and more were female, had never married, reported anxiety type symptoms and exhibited somatisation-type behaviour. One in five CIC patients reported abdominal pain or discomfort. All constipation symptoms were more common in IBS-C. When the mutual exclusivity was suspended, overlap occurred in 18.1%.

CONCLUSIONS

There were significant differences in demographics between individuals with functional bowel disorders. Despite this, the Rome III classification system falls short of describing unique entities.