Immunological Biomarkers in Postinfectious Irritable Bowel Syndrome

Effects of FODMAPs and Gluten on Gut Microbiota and Their Association with the Metabolome in Irritable Bowel Syndrome: A Double-Blind, Randomized, Cross-Over Intervention Study

BACKGROUND

A mechanistic understanding of the effects of dietary treatment in irritable bowel syndrome (IBS) is lacking. Our aim was therefore to investigate how fermentable oligo- di-, monosaccharides, and polyols (FODMAPs) and gluten affected gut microbiota and circulating metabolite profiles, as well as to investigate potential links between gut microbiota, metabolites, and IBS symptoms.

METHODS

We used data from a double-blind, randomized, crossover study with week-long provocations of FODMAPs, gluten, and placebo in participants with IBS. To study the effects of the provocations on fecal microbiota, fecal and plasma short-chain fatty acids, the untargeted plasma metabolome, and IBS symptoms, we used Random Forest, linear mixed model and Spearman correlation analysis.

RESULTS

FODMAPs increased fecal saccharolytic bacteria, plasma phenolic-derived metabolites, 3-indolepropionate, and decreased isobutyrate and bile acids. Gluten decreased fecal isovalerate and altered carnitine derivatives, CoA, and fatty acids in plasma. For FODMAPs, modest correlations were observed between microbiota and phenolic-derived metabolites and 3-indolepropionate, previously associated with improved metabolic health, and reduced inflammation. Correlations between molecular data and IBS symptoms were weak.

CONCLUSIONS

FODMAPs, but not gluten, altered microbiota composition and correlated with phenolic-derived metabolites and 3-indolepropionate, with only weak associations with IBS symptoms. Thus, the minor effect of FODMAPs on IBS symptoms must be weighed against the effect on microbiota and metabolites related to positive health factors.

Assessing the relationship between gut microbiota and irritable bowel syndrome: a two-sample Mendelian randomization analysis

BACKGROUND

Growing evidence has suggested that gut microbiota is closely related to the risk of irritable bowel syndrome (IBS), but whether there is a causal effect remains unknown. We adopted a Mendelian randomization (MR) approach to evaluate the potential causal relationships between gut microbiota and the risk of IBS.

METHODS

Genetic instrumental variables for gut microbiota were identified from a genome-wide association study (GWAS) of 18,340 participants. Summary statistics of IBS were drawn from a GWAS including 53,400 cases and 433,201 controls. We used the inverse-variance weighted (IVW) method as the primary analysis. To test the robustness of our results, we further performed the weighted-median method, MR-Egger regression, and MR pleiotropy residual sum and outlier test. Finally, reverse MR analysis was performed to evaluate the possibility of reverse causation.

RESULTS

We identified suggestive associations between three bacterial traits and the risk of IBS (odds ratio (OR): 1.08; 95% confidence interval (CI): 1.02, 1.15; p = 0.011 for phylum Actinobacteria; OR: 0.95; 95% CI: 0.91, 1.00; p = 0.030 for genus Eisenbergiella and OR: 1.10; 95% CI: 1.03, 1.18; p = 0.005 for genus Flavonifractor). The results of sensitivity analyses for these bacterial traits were consistent. We did not find statistically significant associations between IBS and these three bacterial traits in the reverse MR analysis.

CONCLUSIONS

Our systematic analyses provide evidence to support a potential causal relationship between several gut microbiota taxa and the risk of IBS. More studies are required to show how the gut microbiota affects the development of IBS.

Multiple rather than specific autoantibodies were identified in irritable bowel syndrome with HuProt™ proteome microarray

Immune activation and several autoantibodies might be involved in the pathophysiology of irritable bowel syndrome (IBS). We aimed to identify serum biomarkers for IBS by HuProt™ microarray. IBS patients met Rome III criteria were enrolled. Control groups included healthy controls (HCs) and disease controls (DCs). In stage I, we profiled sera from IBS and control groups with HuProt™ microarrays. Based on significant different proteins in stage I, IBS focused microarrays were constructed and validated in a larger cohort in stage II, then decision tree models were generated to establish a combination of biomarkers. In stage III, 4 purified proteins were verified by ELISA. Finally, we analyzed the correlation of autoantibodies with symptoms. In stage I, we identified 47 significant different proteins including 8 autoantibodies of IgG, 2 of IgA between IBS and HCs; 13 autoantibodies of IgG, 13 of IgA between IBS and DCs. In stage II, we found the positive rates of 14 IgG and IgA autoantibodies in IBS were significantly higher than HCs. Five autoantibodies of IgG and 7 IgA were comprehensively involved in differentiating IBS and HCs with the sensitivity and specificity to diagnose IBS as 40%–46.7% and 79.4%–86.3%. The median optical density value of ELAVL4 (IgG) and PIGP (IgA) were significantly higher in IBS than HCs. Parts of autoantibodies above were related to IBS symptoms. We found a combination of autoantibodies to differentiate IBS with HCs, but no specific autoantibodies could serve as serum biomarkers for IBS.

Efficacy of probiotics for managing infantile colic due to their anti-inflammatory properties: a meta-analysis and systematic review

BACKGROUND

Infantile colic (IC) is excessive crying in otherwise healthy children. Despite vast research efforts, its etiology remains unknown.

PURPOSE

Most treatments for IC carry various side effects. The collection of evidence may inform researchers of new strategies for the management and treatment of IC as well as new clues for understanding its pathogenesis. This review and meta-analysis aimed to evaluate the efficacy and possible mechanisms of probiotics for mananaging IC.

METHODS

Ten papers met the study inclusion and exclusion criteria, and the meta-analysis was conducted using Review Manager (RevMan) software and a random-effects model.

RESULTS

This meta-analysis revealed that probiotics are effective for treating infantile colic, while the review showed that this efficacy may be due to their anti-inflammatory effects.

CONCLUSION

Probiotics may be an important treatment option for managing infantile colic due to their anti-inflammatory properties.

Gut microbiota profiles and the role of anti-CdtB and anti-vinculin antibodies in patients with functional gastrointestinal disorders (FGID)

BACKGROUND

Distinct faecal microbiota profiles are reported to be associated with various subtypes of IBS. Circulating antibodies to cytolethal distending toxin B (CdtB) and vinculin are proposed as biomarkers to identify post-infectious IBS. The aim of our study was to analyse serum levels of anti-CdtB and anti-vinculin antibodies in patients with different functional gastrointestinal disorders (FGID) and their correlation with the composition of faecal microbiome.

METHODS

The study cohort comprised 65 prospectively recruited individuals: 15 with diarrhoea-type-IBS (IBS-D), 13 with constipation-type-IBS (IBS-C), 15 with functional dyspepsia (FD) and 22 healthy controls. FGID subgroups were defined according to Rome III criteria. Serum levels of anti-CdtB and anti-vinculin antibodies were measured by ELISA. Faecal microbiome composition analysis and assessment of dysbiosis were performed by GA-map® Dysbiosis Test.

RESULTS

Positivity rate either for anti-CdtB or anti-vinculin antibodies was higher in the IBS-C group (76.9%) compared to IBS-D (40.0%), FD (60%) and healthy (63.6%) groups. Dysbiosis was more frequent in subjects positive for anti-CdtB antibodies and in IBS-C patients, who showed an increased amount of opportunistic/pro-inflammatory bacteria and reduced gut protective bacteria. IBS-C patients showed a high inter-individual variation of bacterial communities compared to other FGID subgroups and healthy individuals, whereas microbial profiles of patients with IBS-D and FD were overlapping with those of healthy controls. No bacteria markers showed significant differences between FGID subgroups and healthy controls.

CONCLUSION

Neither anti-CdtB/anti-vinculin antibodies nor faecal microbial profiles allowed to discriminate between specific FGID subgroups. Dysbiosis was more frequent in patients presenting with anti-CdtB antibodies and in IBS-C patients.

Systemic inflammation in the pathogenesis of irritable bowel syndrome associated with obesity

Investigation of the mechanisms promoting the development of irritable bowel syndrome (IBS) in obese patients is one of the most important issues of modern medicine. We examined 97 patients suffering from IBS. The group of comparison included 10 individuals with obesity. The control group included 21 practically healthy individuals. The levels of C-reactive protein (CRP) in the blood serum, tumor necrosis factor-α (TFNα), transforming growth factor-β1 (TGFβ1), interleukin-10 (IL-10), 8-isoprostane (IP), ceruloplasmin (CP) were examined. Endotoxicosis intensity was identified by the content of average molecular peptides in the blood and the Limulus Amebocyte Lysate (LAL) test. In the case of IBS with prevailing diarrhea, especially its comorbid course with obesity, cytokine imbalance was observed, which was manifested by a decreased amount of IL-10 in the blood serum and increased levels of TNFα and TGFβ1. Patients suffering from irritable bowel syndrome with prevailing diarrhea associated with obesity were characterized by high levels of C-reactive protein, fibrinogen and average molecules, increased content of pro-inflammatory cytokines (TFNα and TGFβ1) with a decreased content of IL-10, as well as imbalance of the pro-oxidant and anti-oxidant blood systems (increased content of 8-isoprostane and ceruloplasmin).

Ecological and network analyses identify four microbial species with potential significance for the diagnosis/treatment of ulcerative colitis (UC)

BACKGROUND

Ulcerative colitis (UC) is one of the primary types of inflammatory bowel disease (IBD), the occurrence of which has been increasing worldwide. Although IBD is an intensively studied human microbiome-associated disease, research on Chinese populations remains relatively limited, particularly on the mucosal microbiome. The present study aimed to analyze the changes in the mucosal microbiome associated with UC from the perspectives of medical ecology and complex network analysis.

RESULTS

In total, 56 mucosal microbiome samples were collected from 28 Chinese UC patients and their healthy family partners, followed by amplicon sequencing. Based on sequencing data, we analyzed species diversity, shared species, and inter-species interactions at the whole community, main phyla, and core/periphery species levels. We identified four opportunistic "pathogens" (i.e., Clostridium tertium, Odoribacter splanchnicus, Ruminococcus gnavus, and Flavonifractor plautii) with potential significance for the diagnosis and treatment of UC, which were inhibited in healthy individuals, but unrestricted in the UC patients. In addition, we also discovered in this study: (i) The positive-to-negative links (P/N) ratio, which measures the balance of species interactions or inhibition effects in microbiome networks, was significantly higher in UC patients, indicating loss of inhibition against potentially opportunistic "pathogens" associated with dysbiosis. (ii) Previous studies have reported conflicting evidence regarding species diversity and composition between UC patients and healthy controls. Here, significant differences were found at the major phylum and core/periphery scales, but not at the whole community level. Thus, we argue that the paradoxical results found in existing studies are due to the scale effect.

CONCLUSIONS

Our results reveal changes in the ecology and network structure of the gut mucosal microbiome that might be associated with UC, and these changes might provide potential therapeutic mechanisms of UC. The four opportunistic pathogens that were identified in the present study deserve further investigation in future studies.

Immunization with cytolethal distending toxin B produces autoantibodies to vinculin and small bowel bacterial changes in a rat model of postinfectious irritable bowel syndrome

BACKGROUND

Recent data substantiate the importance of acute gastroenteritis in the development of irritable bowel syndrome (IBS). An animal model of postinfectious IBS determined the importance of cytolethal distending toxin B (CdtB) during live Campylobacter jejuni infection and its development of autoimmunity to vinculin. In this study, we examine whether subcutaneous exposure to CdtB alone is sufficient to produce the postinfectious IBS effect and autoimmunity.

METHODS

Sixty adult Sprague Dawley rats were randomized into 2 groups to receive subcutaneous injection of either CdtB or vehicle and administered a booster injection of the same product 3 weeks later. Serum was collected for anti-CdtB and anti-vinculin titers. Duodenal and ileal luminal contents for total eubacterial qPCR, and ileal bowel segments were harvested for vinculin and ileal expression. In a second experiment, 4 adult, Sprague Dawley rats were injected with either Cy7-labeled anti-CdtB and anti-vinculin antibodies were injected into the tail vein and imaged to determine organ localization of the antibodies.

KEY RESULTS

Rats that received CdtB increased in serum anti-CdtB after injection. CdtB exposure also precipitated significant elevation in anti-vinculin antibodies (P < .001). This was associated with a reduction in intestinal vinculin expression (P < .001) that negatively correlated with serum anti-CdtB levels. CdtB exposure was also associated with greater levels of duodenal (P < .001) and ileal (P < .01) bacteria by qPCR that positively correlated with anti-CdtB levels.

CONCLUSIONS AND INFERENCES

Rats injected with CdtB developed a postinfectious IBS-like phenotype and autoimmunity to vinculin with corresponding reduction in intestinal vinculin expression.

Microbiome and Its Role in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is an extremely common and often very debilitating chronic functional gastrointestinal disorder. Despite its prevalence, significant associated healthcare costs, and quality-of-life issues for affected individuals, our understanding of its etiology remained limited. However, it is now evident that microbial factors play key roles in IBS pathophysiology. Acute gastroenteritis following exposure to pathogens can precipitate the development of IBS, and studies have demonstrated changes in the gut microbiome in IBS patients. These changes may explain some of the symptoms of IBS, including visceral hypersensitivity, as gut microbes exert effects on the host immune system and gut barrier function, as well as the brain-gut axis. Microbial differences also appear to underlie the two main functional categories of IBS: diarrhea-predominant IBS (IBS-D) is associated with small intestinal bacterial overgrowth, which can be diagnosed by a positive hydrogen breath test, and constipation-predominant IBS (IBS-C) is associated with increased levels of methanogenic archaea, which can be diagnosed by a positive methane breath test. Mechanistically, the pathogens that cause gastroenteritis and trigger subsequent IBS development produce a common toxin, cytolethal distending toxin B (CdtB), and antibodies raised against CdtB cross-react with the cytoskeletal protein vinculin and impair gut motility, facilitating bacterial overgrowth. In contrast, methane gas slows intestinal contractility, which may facilitate the development of constipation. While antibiotics and dietary manipulations have been used to relieve IBS symptoms, with varying success, elucidating the specific mechanisms by which gut microbes exert their effects on the host may allow the development of targeted treatments that may successfully treat the underlying causes of IBS.

Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome - An Update

Small intestinal bacterial overgrowth (SIBO) is one manifestation of gut microbiome dysbiosis and is highly prevalent in IBS (Irritable Bowel Syndrome). SIBO can be diagnosed either by a small bowel aspirate culture showing ≥10³ colony-forming units (CFU) per mL of aspirate, or a positive hydrogen lactulose or glucose breath test. Numerous pathogenic organisms have been shown to be increased in subjects with SIBO and IBS, including but not limited to Enterococcus, Escherichia coli, and Klebsiella. In addition, Methanobrevibacter smithii, the causal organism in a positive methane breath test, has been linked to constipation predominant irritable bowel syndrome (IBS-C). As M. smithii is an archaeon and can overgrow in areas outside of the small intestine, it was recently proposed that the term intestinal methanogen overgrowth (IMO) is more appropriate for the overgrowth of these organisms. Due to gut microbiome dysbiosis, patients with IBS may have increased intestinal permeability, dysmotility, chronic inflammation, autoimmunity, decreased absorption of bile salts, and even altered enteral and central neuronal activity. As a consequence, SIBO and IBS share a myriad of symptoms including abdominal pain, distention, diarrhea, and bloating. Furthermore, gut microbiome dysbiosis may be associated with select neuropsychological symptoms, although more research is needed to confirm this connection. This review will focus on the role of the gut microbiome and SIBO in IBS, as well as novel innovations that may help better characterize intestinal overgrowth and microbial dysbiosis.

Second-Generation Biomarker Testing for Irritable Bowel Syndrome Using Plasma Anti-CdtB and Anti-Vinculin Levels

BACKGROUND

ELISA testing for anti-CdtB and anti-vinculin can discriminate patients with irritable bowel syndrome with diarrhea (IBS-D) from those with inflammatory bowel disease (IBD). However, recent findings suggest the antigens can suffer from epitope instability.

AIM

This study aimed to assess effects of incorporating epitope stabilization on test characteristics for distinguishing IBS-D from IBD subjects.

METHODS

Plasma samples from IBS-D subjects from a large-scale clinical trial and subjects with endoscopically active IBD without concurrent immunomodulator therapy were used. After epitope stabilization, CdtB and vinculin were used in ELISA testing. Optical density readings were compared between IBS-D and IBD subjects.

RESULTS

Samples from 100 IBS-D and 31 IBD (22 UC and 9 CD) subjects were tested. IBS-D subjects had higher anti-CdtB titers (P = 0.0001) and higher anti-vinculin titers (P = 0.004) than IBD subjects. The specificities of anti-CdtB and anti-vinculin to differentiate IBS-D from IBD were 93.5% and 90.9%, respectively, with sensitivities of 43.0% and 52.2%, respectively. The positive likelihood ratios of identifying IBS-D with anti-CdtB and anti-vinculin were 6.7 and 5.7, respectively. Assuming a pretest probability of 57% for diagnosis of IBS-D in patients with abdominal pain and change in bowel habits, testing positive for both antibodies resulted in a posttest probability of > 98%.

CONCLUSIONS

Performing epitope stabilization for CdtB and vinculin enhances the test characteristics of ELISAs for anti-CdtB and anti-vinculin in discriminating IBS-D from IBD. Measurement of anti-CdtB and anti-vinculin with this second-generation methodology may further advance our understanding of the role of immunity in functional bowel diseases.

The Rome IV: Irritable bowel syndrome - A functional disorder

Functional gastrointestinal disorders are the most common disorders encountered in the clinical gastroenterology setting. Over the years the Rome process has generated consensus definitions of functional gastrointestinal disorders, and given diagnostic criteria, based on various symptom patterns, that have evolved over the years. The latest Rome IV consensus was presented in May 2016. This summary points out some of the important changes made from the Rome III 2006 consensus including evaluation of symptoms from the stand-point of basal normative values and disorders of gut-brain interaction, as well as additions of the importance of the microflora. However, we are all aware of the fact that there are limitations, and the Rome consensus does not pick up all patients with functional gastrointestinal disorders. Out of those that seek medical help for their functional gastrointestinal symptoms additional outlines of disease have to be considered and judgements made on the patients' actual symptoms, or rather presentation of their symptoms. The Rome IV consensus is a robust standard for a clinical and research approach to functional gastrointestinal disorders, but might be improved by use of exclusion criteria and additional biochemical biomarkers in order to accurately diagnose those patients who may achieve relief by an extended treatment approach in the clinical setting of gastroenterology. A biopsychosocial approach to the patient is recommended to improve compliance and optimize treatment and outcomes.

Leveraging Human Microbiome Features to Diagnose and Stratify Children with Irritable Bowel Syndrome

Accurate diagnosis and stratification of children with irritable bowel syndrome (IBS) remain challenging. Given the central role of recurrent abdominal pain in IBS, we evaluated the relationships of pediatric IBS and abdominal pain with intestinal microbes and fecal metabolites using a comprehensive clinical characterization and multiomics strategy. Using rigorous clinical phenotyping, we identified preadolescent children (aged 7 to 12 years) with Rome III IBS (n = 23) and healthy controls (n = 22) and characterized their fecal microbial communities using whole-genome shotgun metagenomics and global unbiased fecal metabolomic profiling. Correlation-based approaches and machine learning algorithms identified associations between microbes, metabolites, and abdominal pain. IBS cases differed from controls with respect to key bacterial taxa (eg, Flavonifractor plautii and Lachnospiraceae bacterium 7_1_58FAA), metagenomic functions (eg, carbohydrate metabolism and amino acid metabolism), and higher-order metabolites (eg, secondary bile acids, sterols, and steroid-like compounds). Significant associations between abdominal pain frequency and severity and intestinal microbial features were identified. A random forest classifier built on metagenomic and metabolic markers successfully distinguished IBS cases from controls (area under the curve, 0.93). Leveraging multiple lines of evidence, intestinal microbes, genes/pathways, and metabolites were associated with IBS, and these features were capable of distinguishing children with IBS from healthy children. These multi-omics features, and their links to childhood IBS coupled with nutritional interventions, may lead to new microbiome-guided diagnostic and therapeutic strategies.

Elevated serum neopterin levels in children with functional constipation: association with systemic proinflammatory cytokines

BACKGROUND

Functional constipation is a clinical problem with an incompletely understood etiology. Functional bowel diseases have been shown to be related to inflammation in many studies in adults. In this study, we aimed to evaluate leukocytes, C-reactive protein, proinflammatory and anti-inflammatory cytokines, and neopterin levels in children with functional constipation.

METHODS

Seventy-six children with constipation and 71 healthy controls (mean age 7.12 ± 3.46 years and 7.32 ± 4.33 years, respectively, P = 0.991) were included in the study. Leukocytes, C-reactive protein, interleukin (IL)-1β, IL-6, IL-10, IL-12, tumor necrosis factor-alpha (TNF-α) and neopterin levels were assessed in patients and healthy controls. Parameters were measured in the serum using enzyme-linked immunosorbent assay methods.

RESULTS

Mean IL-6 (20.31 ± 12.05 vs. 16.2 ± 10.25 pg/mL, respectively, P = 0.003), IL-12 (181.42 ± 133.45 vs. 135.6 ± 83.67 pg/mL, respectively, P = 0.018) and neopterin levels (2.08 ± 1.12 vs. 1.52 ± 1.02 pg/mL, respectively, P = 0.001) were significantly higher in constipated children than healthy controls. Leukocyte and thrombocyte counts, C-reactive protein, and IL-1β, IL-10 and TNF-α levels did not show any difference between the two groups.

CONCLUSIONS

In this study, IL-6, IL-12 and neopterin levels of constipated patients were found to be higher than those of controls. These results indicate the presence of subclinical inflammation in children with functional constipation.

The current state and future direction of DoD gut microbiome research: a summary of the first DoD gut microbiome informational meeting

The gut microbiome is increasingly recognized as integral to human health, and is emerging as a mediator of human physical and cognitive performance. This has led to the recognition that US Department of Defense (DoD) research supporting a healthy and resilient gut microbiome will be critical to optimizing the health and performance of future Warfighters. To facilitate knowledge dissemination and collaboration, identify resource capabilities and gaps, and maximize the positive impact of gut microbiome research on the Warfighter, DoD partners in microbiome research participated in a 2-day informational meeting co-hosted by the Natick Soldier Research, Engineering and Development Center (NSRDEC) and the US Army Research Institute of Environmental Medicine (USARIEM) on 16–17 November 2015. Attendee presentations and discussions demonstrated that multiple DoD organizations are actively advancing gut microbiome research. Common areas of research included the influence of military-relevant stressors on interactions between the microbiome and Warfighter biology, manipulation of the microbiome to influence Warfighter health, and use of the microbiome as a biomarker of Warfighter health status. Although resources and capabilities are available, they vary across laboratories and it was determined that centralizing certain DoD capabilities could accelerate progress. More significantly, the meeting created a foundation for a coordinated gut microbiome and nutrition research program aligning key DoD partners in the area of microbiome research. This report details the presentations and discussions presented during the 1st DoD Gut Microbiome Informational Meeting.

Infantile Colic Is Associated With Low-grade Systemic Inflammation

OBJECTIVES

Dysbiosis, an imbalance in the taxonomic composition of the gut bacteria occurring during the critical stages of development, induces lasting shifts in the immunological and metabolic phenotype if accompanied by an inflammatory response. Because altered gut microbiota and successful treatment with probiotics have both been demonstrated in cases of colic, we hypothesized here that infants with colic might have low-grade inflammation.

METHODS

In 28 infants with colic and in 12 healthy controls at the age of 1 month, we measured the following serum immunological biomarkers: cytokines interleukin 1β (IL-1β); IL-6; IL-10; tumor necrosis factor α; interferon γ (IFN-γ); chemokines IL-8; monocyte chemotactic protein-1 (MCP-1); macrophage inflammatory protein 1β (MIP-1β) and chemokine (C-X-C motif) ligand 16; and intestinal fatty acid-binding protein, a biomarker of enterocyte damage and zonulin, a biomarker of intestinal permeability. In addition, intestinal microbiota composition was correlated with immunological biomarkers.

RESULTS

Infants with colic had increased concentrations of IL-8, MCP-1, and MIP-1β in serum as compared with healthy children. All the other immunological biomarkers were comparable between the groups. Fecal levels of Clostridium leptum correlated negatively with the proinflammatory markers MCP-1 (r = -0.44, P = 0.02), MIP-1β (r = -0.43, P = 0.02), and tumor necrosis factor α (r = -0.38, P = 0.04). In addition, C coccoides group levels correlated negatively with MCP-1 (r = -0.43, P = 0.02) and Bifidobacterium breve levels positively with chemokine (C-X-C motif) ligand 16 (r = 0.38, P = 0.04).

CONCLUSIONS

In addition to gut microbiota alterations, colic in infants is associated with low-grade systemic inflammation. Specific bacterial species beyond conventional probiotics may have anti-inflammatory properties that may help to modulate microbiota and alleviate colic-related inflammation.

Proteomics and irritable bowel syndrome

INTRODUCTION

Irritable bowel syndrome (IBS) is a gastrointestinal disease that according to Rome IV criteria is subdivided into four subtypes. The pathophysiology of this disease is not well understood due to numerous factors playing multiple roles in disease development, such as diet, stress and hormones. IBS has a variety of symptoms and overlaps with many other gastrointestinal and non-gastrointestinal diseases. Area covered: This review aims to present an overview of implementation of proteomics in experimental studies in the field of IBS. Expert commentary: Proteomics is commonly used for biomarker discovery in and has also been extensively used in IBS research. The necessity of a sensitive and specific biomarker for IBS is apparent, but despite the intensive research performed in this field, an appropriate biomarker is not yet available.

Crosstalk between Inflammation and ROCK/MLCK Signaling Pathways in Gastrointestinal Disorders with Intestinal Hyperpermeability

The barrier function of the intestine is essential for maintaining the normal homeostasis of the gut and mucosal immune system. Abnormalities in intestinal barrier function expressed by increased intestinal permeability have long been observed in various gastrointestinal disorders such as Crohn's disease (CD), ulcerative colitis (UC), celiac disease, and irritable bowel syndrome (IBS). Imbalance of metabolizing junction proteins and mucosal inflammation contributes to intestinal hyperpermeability. Emerging studies exploring in vitro and in vivo model system demonstrate that Rho-associated coiled-coil containing protein kinase- (ROCK-) and myosin light chain kinase- (MLCK-) mediated pathways are involved in the regulation of intestinal permeability. With this perspective, we aim to summarize the current state of knowledge regarding the role of inflammation and ROCK-/MLCK-mediated pathways leading to intestinal hyperpermeability in gastrointestinal disorders. In the near future, it may be possible to specifically target these specific pathways to develop novel therapies for gastrointestinal disorders associated with increased gut permeability.

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.

The long-term functional consequences of acute infectious diarrhea

PURPOSE OF REVIEW

The study reviews recent publications that build on previous studies showing that acute enteric infection can produce persistent dysfunction in the lower gut (postinfectious irritable bowel syndrome) and proximal gut (postinfectious functional dyspepsia). The review addresses risk factors, the pathophysiological basis of persistent gut dysfunction, and the factors that initiate and maintain it.

RECENT FINDINGS

Recent work has identified several loci of host genetic predisposition to these syndromes that focus attention on host immune responses that may lead to gut dysfunction, including changes in intestinal barrier function and cytokine responses to the initial infection. Human and animal studies identify changes in the serotonergic and cannabinoid pathways regulating visceral pain responses and gut motility. Recent work has also focused attention on the putative role of the intestinal microbiota or dysbiosis in maintaining gut dysfunction and this is reviewed in depth.

SUMMARY

The development of long-term consequences following an acute episode of gastroenteritis reflects a convergence of host factors that include genetic predisposition and psychological factors, as well as the development of intestinal dysbiosis. It is anticipated that future research will generate biomarkers of susceptibility as well as novel microbiota-directed preventive and therapeutic strategies.