Unraveling the ties between irritable bowel syndrome and intestinal microbiota

From-Toilet-to-Freezer: A Review on Requirements for an Automatic Protocol to Collect and Store Human Fecal Samples for Research Purposes

The composition, viability and metabolic functionality of intestinal microbiota play an important role in human health and disease. Studies on intestinal microbiota are often based on fecal samples, because these can be sampled in a non-invasive way, although procedures for sampling, processing and storage vary. This review presents factors to consider when developing an automated protocol for sampling, processing and storing fecal samples: donor inclusion criteria, urine-feces separation in smart toilets, homogenization, aliquoting, usage or type of buffer to dissolve and store fecal material, temperature and time for processing and storage and quality control. The lack of standardization and low-throughput of state-of-the-art fecal collection procedures promote a more automated protocol. Based on this review, an automated protocol is proposed. Fecal samples should be collected and immediately processed under anaerobic conditions at either room temperature (RT) for a maximum of 4 h or at 4 °C for no more than 24 h. Upon homogenization, preferably in the absence of added solvent to allow addition of a buffer of choice at a later stage, aliquots obtained should be stored at either -20 °C for up to a few months or -80 °C for a longer period-up to 2 years. Protocols for quality control should characterize microbial composition and viability as well as metabolic functionality.

Associations between irritable bowel syndrome and non-alcoholic fatty liver disease: A systematic review

BACKGROUND

Irritable bowel syndrome (IBS) is associated with obesity and metabolic syndrome. IBS and non-alcoholic fatty liver disease (NAFLD) are highly prevalent entities worldwide and may share similar mechanisms including gut dysbiosis, impaired intestinal mucosal barrier and immune system activation.

AIM

To systematically review their association according to the Preferred Reporting Items for Systemic Review and Meta-analyses guidelines.

METHODS

PubMed, EMBASE and Cochrane Database of Systematic Reviews were searched for relevant papers. Manual searches were also performed.

RESULTS

Six studies were included. Both IBS and NAFLD subjects had significantly more metabolic risk factors like hypertension, obesity, dyslipidaemia and diabetes. Our review showed that 23.2% to 29.4% of NAFLD patients had IBS. IBS was significantly higher in NAFLD patients compared with patients without NAFLD (23.2% vs 12.5%, P < 0.01). A higher proportion of IBS patients had NAFLD (65.8% to 74.0%). IBS patients were three times more likely to have NAFLD compared with non-IBS patients (P < 0.001). Two studies showed a significant correlation between the severity of IBS and NAFLD. The proportion of NAFLD subjects with IBS increased with NAFLD severity.

CONCLUSION

Further prospective studies are warranted to evaluate the relationship and shared pathways between IBS and NAFLD, potentially leading to the development of future therapeutics.

[Irritable bowel syndrome in the Russian Federation: results of the ROMERUS multicenter observational study]

BACKGROUND

Irritable bowel syndrome (IBS) is one of the most common functional disorders of the gastrointestinal tract. According to Russian guidelines, a standard examination using laboratory and instrumental evaluation methods, including colonoscopy, should be performed to establish the diagnosis of IBS.

AIM

To characterize the Russian population of IBS patients.

MATERIALS AND METHODS

A multicenter observational prospective study ROMERUS was conducted at 35 clinical centers in the Russian Federation. The study included male and female patients aged 18 to 50 with a diagnosis of IBS based on the Rome IV criteria, with no signs of structural gastrointestinal disease. The follow-up duration was 6 months and included three patients' visits to the study site. During the study, data were collected on patients' demographic and clinical characteristics, medical history, and drug therapy. The secondary parameters included the assessment of the proportion of patients with a diagnosis of IBS confirmed by a standard examination among all patients meeting the Rome IV criteria, the evaluation of the change over time of the IBS symptoms, quality of life (QoL), and adherence to therapy. Characterization of the population was performed using descriptive statistics methods. The standard examination results were presented as the percentage of patients with IBS confirmed by the standard examination among all patients meeting the Rome IV criteria, with a two-sided 95% confidence interval.

RESULTS

The study included 1004 patients with a diagnosis of IBS according to the Rome IV criteria, with 790 (78.7%) patients included in the final analysis. The mean age of patients was 34.0±7.5 years; they were predominantly female (70.4%), Caucasian (99.4%), married (55.1%), urban residents (97.5%) with higher education (64.5%) and a permanent position (74.9%). Patients enrolled in the study have low physical activity and lack a healthy diet. The smoking rate was 26.3%. IBS symptoms with predominant constipation (IBS-C) were observed in 28.1% of patients; 28.9% had IBS with predominant diarrhea (IBS-D), 11.9% had mixed-type IBS, and 31.1% had non-classified IBS. The main IBS symptoms were pain (99.7%), abdominal distension (71.1%), and fullness (36.8%). Biliary tract dysfunction (18.9%) and gastritis (17.2%) were the most frequently reported comorbidities. Prior to enrollment, 28% of patients received drug therapy. The most commonly prescribed drug during the study was mebeverine (54.1%). At 6 months of follow-up, there was a significant reduction of abdominal pain, bloating, and distention, and a twofold reduction in the incidence of constipation and diarrhea in the subgroups of patients with IBS-C and IBS-D, respectively. The overall QoL score measured by the IBS-QoL questionnaire increased from 83.0 to 95.2 points (p<0.05) during the study. In the overall assessment of their condition, 69.6% of patients noted no symptoms and 25.3% reported marked improvement, 35% were asymptomatic according to the physician's overall assessment of the patient's condition, and 51.8% showed significant improvement.

CONCLUSION

IBS patients in the Russian Federation were characterized. The diagnosis of IBS, established following the Rome IV criteria, is confirmed by the results of a standard examination in 96.3% of patients. The Rome IV criteria for the IBS diagnosis make it possible to establish a diagnosis with a probability of 94.7%. For 6 months of follow-up, there was a clinical improvement with a decrease in the severity of symptoms and a QoL improvement.

Diagnosis and management of irritable bowel syndrome-like symptoms in ulcerative colitis

Both ulcerative colitis (UC) and irritable bowel syndrome (IBS) are chronic gastrointestinal (GI) conditions that show some typical features. Persistent GI symptoms typical for IBS are observed in patients with diagnosed UC. Both IBS and UC are characterised by dysregulation of the enteric nervous system, alterations in the gut flora, low-grade mucosal inflammation, and activation of the brain-gut axis. Therefore, it appears that there may be some overlap between the two conditions. It is rather difficult to tell if the lower gastrointestinal symptoms are secondary to coexisting IBS or a hidden UC condition.

Fecal microbiota transplantation in the treatment of irritable bowel syndrome: a single-center prospective study in Japan

Background

Fecal microbiota transplantation (FMT) is a potential treatment for irritable bowel syndrome (IBS), but its efficacy in Japanese IBS patients is unknown. This study aimed to evaluate the efficacy, side effects, and microbiome changes following FMT in Japanese IBS patients.

Methods

Seventeen Japanese patients with refractory IBS received FMT (4 donors) under colonoscopy. Responders were defined by an improvement in the IBS severity index (IBS-SI) of 50 points or more after 12 weeks. We evaluated the IBS-SI and Bristol Stool Form Scale (BSFS) and compared the diversity and microbiome before and 12 weeks after FMT. For the microbiome, we analyzed the V3–V4 region of the 16S rRNA gene.

Results

IBS-SI decreased an average of 115.58 points after 12 weeks, and 10 patients (58.8%) were considered responders. Eight patients with diarrhea (66.7%) and three patients with constipation (60.0%) showed improvement in the BSFS. Two patients complained of mild abdominal pain, but there were no cases with severe side-effects. α-diversity was increased only in the responder group (p = 0.017). Patients who closely paralleled the donor microbiome had a higher rate of IBS-SI improvement. The relative abundance of Neisseria and Akkermansia increased and Desulfovibrio and Delftia were decreased in the responder group after FMT.

Conclusions

Following FMT, about 60% of Japanese patients with IBS showed improvement in both the IBS-SI and BSFS, without severe side effects. Increased α-diversity and similarity to the donor microbiome after FMT may be associated with better treatment effects.

Trial registration: This study was registered in the University Hospital Medical Information Network Clinical Trial Registration (UMIN000026363). Registered 31 May 2017, https://rctportal.niph.go.jp/s/detail/um?trial_id=UMIN000026363. The study was registered prospectively.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-022-02408-5.

Changes in colonic enteroendocrine cells of patients with irritable bowel syndrome following fecal microbiota transplantation

OBJECTIVES

The aim was to investigate the effect of fecal microbiota transplantation (FMT) on colonic enteroendocrine cells densities in patients with irritable bowel syndrome (IBS).

MATERIALS AND METHODS

This study is connected to the REFIT study, a double-blinded placebo-controlled trial to investigate using FMT for IBS treatment. Eighty-three subjects received either donor-FMT or placebo FMT (own feces) by colonoscope to cecum. Biopsies were obtained from sigmoid colon. Ten responders and ten non-responders consented to new biopsy one-year after FMT. Sixteen patients received donor-FMT and four received placebo FMT. Biopsies were immunostained for all of the colonic enteroendocrine cells and were quantified using computerized image analysis.Allocation sequence was revealed after obtaining re-biopsies and cells quantification.

RESULTS

Scores for IBS-SSS (mean ± SEM) of responders (eight of 10 patients who received donor FMT) and non-responders changed from baseline to one year after FMT (297 ± 11 and 81 ± 16, p < .0001, and 270 ± 17 and 291 ± 16, p = .15, respectively). Using paired t-test to compare enteroendocrine cells densities one-year after FMT to baseline showed significant increase only in somatostatin immunoreactive cells density in the total IBS responders group (p = .023) and who received donor-FMT (p = .038). The densities of peptide YY and enteroglucagon immunoreactive cells increased significantly (p = .04 and .035, respectively) in donor-FMT recipients. No significant changes were noted in placebo FMT or nonresponders subgroups.

CONCLUSION

This study shows that colonic enteroendocrine cells densities significantly change in responders group that received donor-FMT. The mechanisms for the cross talks between gut microbiota and colonic enteroendocrine cells remain to be investigated.

Gut Microbiota Manipulation in Irritable Bowel Syndrome

Increased knowledge suggests that disturbed gut microbiota, termed dysbiosis, might promote the development of irritable bowel syndrome (IBS) symptoms. Accordingly, gut microbiota manipulation has evolved in the last decade as a novel treatment strategy in order to improve IBS symptoms. In using different approaches, dietary management stands first in line, including dietary fiber supplements, prebiotics, and probiotics that are shown to change the composition of gut microbiota, fecal short-chain fatty acids and enteroendocrine cells densities and improve IBS symptoms. However, the exact mixture of beneficial bacteria for each individual remains to be identified. Prescribing nonabsorbable antibiotics still needs confirmation, although using rifaximin has been approved for diarrhea-predominant IBS. Fecal microbiota transplantation (FMT) has recently gained a lot of attention, and five out of seven placebo-controlled trials investigating FMT in IBS obtain promising results regarding symptom reduction and gut microbiota manipulation. However, more data, including larger cohorts and studying long-term effects, are needed before FMT can be regarded as a treatment for IBS in clinical practice.

Mind the Gap: Bridging the Divide from Sequencing Data to Empiric Phenotypes in the Human Gut Microbiota

The gut microbiome exerts a powerful influence on human health and disease. Elucidating the underlying mechanisms of the microbiota's influence is hindered by the immense complexity of the gut microbial community and the glycans they forage. Despite a wealth of genomic and metagenomic sequencing information, there remains a lack of informative phenotypic measurements. Pudlo NA, Urs K, Crawford R, Pirani A, et al. (mSystems 7: e00947-21, 2022, https://doi.org/10.1128/msystems.00947-21) decode this complexity by introducing a scalable assay to measure specific carbohydrate utilization in the dominant microbiota phylum Bacteroidetes. The results reveal a mosaic structure of glycan utilization, both genetic and functional, underpinning niche construction in the human gastrointestinal tract. This Commentary highlights the significance of their findings in connection to the field's growing appreciation for competition, cooperation, and horizontal gene transfer in shaping the highly complex microbial community.

Bifidobacteria Was Decreased in Adult Patients With Irritable Bowel Syndrome Based on PCR and Bacterial Culture: A Systematic Review and Meta-Analysis

The causes of irritable bowel syndrome remain unknown. Studies and meta-analyses revealed that intestinal microbiota disturbance was one of the causes of irritable bowel syndrome, but the results remained controversial. Therefore, we performed a systematic review and meta-analysis to identify the association between them. We performed a systematic meta-analysis of case-control studies from January 2000 to December 2020 to compare fecal microbes based on polymerase chain reaction and bacterial cul- ture between adult irritable bowel syndrome patients and healthy controls. The standardized mean difference value and a 95% CI were calculated. Two professional researchers used Newcastle-Ottawa Scale to reassess selected literature and extract high- quality studies. Six studies were included in our analysis. When all eligible studies were pooled into the meta-analysis, compared with healthy controls, the standardized mean differences of Bifidobacteria (standardized mean difference = -1.01, 95% CI =: -2.01 to -0.01) in irritable bowel syndrome patients decreased significantly, whereas the standardized mean differences of Enterococcus, Enterobacter, Lactobacillus, Bacteroides, and Escherichia coli did not change significantly in irritable bowel syndrome patients. However, heterogeneity was significant to perform sensitivity analysis and stratified analysis in all these special intestinal microbes. In summary, this study indicated that only Bifidobacteria was decreased in irritable bowel syndrome patients compared with healthy controls using Newcastle-Ottawa Scale standards to extract high-quality literature. Future studies are warranted to further dem- onstrate the relationship between them.

Gut Microbiome and the Role of Metabolites in the Study of Graves’ Disease

Graves’ disease (GD) is an autoimmune thyroid disease (AITD), which is one of the most common organ-specific autoimmune disorders with an increasing prevalence worldwide. But the etiology of GD is still unclear. A growing number of studies show correlations between gut microbiota and GD. The dysbiosis of gut microbiota may be the reason for the development of GD by modulating the immune system. Metabolites act as mediators or modulators between gut microbiota and thyroid. The purpose of this review is to summarize the correlations between gut microbiota, microbial metabolites and GD. Challenges in the future study are also discussed. The combination of microbiome and metabolome may provide new insight for the study and put forward the diagnosis, treatment, prevention of GD in the future.

The Role of the Gut Microbiota in the Development and Progression of Major Depressive and Bipolar Disorder

A growing number of studies in rodents indicate a connection between the intestinal microbiota and the brain, but comprehensive human data is scarce. Here, we systematically reviewed human studies examining the connection between the intestinal microbiota and major depressive and bipolar disorder. In this review we discuss various changes in bacterial abundance, particularly on low taxonomic levels, in terms of a connection with the pathophysiology of major depressive and bipolar disorder, their use as a diagnostic and treatment response parameter, their health-promoting potential, as well as novel adjunctive treatment options. The diversity of the intestinal microbiota is mostly decreased in depressed subjects. A consistent elevation of phylum Actinobacteria, family Bifidobacteriaceae, and genus Bacteroides, and a reduction of family Ruminococcaceae, genus Faecalibacterium, and genus Roseburia was reported. Probiotics containing Bifidobacterium and/or Lactobacillus spp. seemed to improve depressive symptoms, and novel approaches with different probiotics and synbiotics showed promising results. Comparing twin studies, we report here that already with an elevated risk of developing depression, microbial changes towards a “depression-like” microbiota were found. Overall, these findings highlight the importance of the microbiota and the necessity for a better understanding of its changes contributing to depressive symptoms, potentially leading to new approaches to alleviate depressive symptoms via alterations of the gut microbiota.

The Effects of Fecal Microbiota Transplantation on the Symptoms and the Duodenal Neurogenin 3, Musashi 1, and Enteroendocrine Cells in Patients With Diarrhea-Predominant Irritable Bowel Syndrome

Introduction

Interactions between the gut microbiota and enteroendocrine cells play important role in irritable bowel syndrome (IBS). Reduced stem cell densities and their differentiation into enteroendocrine cells may cause abnormal densities of the duodenal enteroendocrine cells in IBS patients.

Materials and Methods

We aimed to investigate the effects of fecal microbiota transplantation (FMT) on stem cell differentiation into enteroendocrine cells as detected by neurogenin 3, stem cells as detected by Musashi 1, and the enteroendocrine cells in the duodenum of IBS patients. The study included 16 IBS patients according to Rome III criteria. Four patients were excluded. The remaining patients (n = 12, four females and eight males) were divided according to the cause of IBS into post-infectious (n = 6) and idiopathic (n = 6) IBS. They completed the following questionnaires before and 3 weeks after FMT: IBS-Symptom Severity Scoring system (IBS-SSS) and IBS-Symptom Questionnaire (IBS-SQ). Feces donated by healthy relatives of the patients were transplanted via gastroscope. Biopsies were taken from the descending part of the duodenum at baseline and 3 weeks after FMT. They were immunostained for neurogenin 3, Musashi 1, and all types of duodenal enteroendocrine cells and quantified by computerized image analysis. Microbiota analyses of feces collected just before and 3 weeks after FMT were performed using GA-map™ Dysbiosis test (Genetic Analysis AS, Oslo, Norway).

Results

The total scores for IBS-SSS and IBS-SQ were significantly improved 3 weeks after receiving FMT, P = 0.0009 and <0.0001, respectively. The stem cell densities of neurogenin 3 increased significantly following FMT (P = 0.0006) but not for Musashi 1 (P = 0.42). The cell densities of chromogranin A, cholecystokinin, gastric inhibitory peptide, serotonin, and somatostatin, but not for secretin, have significantly changed in both IBS groups after 3 weeks from receiving FMT.

Conclusion

More than two-thirds of IBS patients experienced improvement in their symptoms parallel to changes in the enteroendocrine cells densities 3 weeks after FMT. The changes in the enteroendocrine cell densities do not appear to be caused by changes in the stem cells or their early progenitors rather by changes in the differentiation progeny as detected by neurogenin 3. The study was retrospectively registered at ClinicalTrials.gov (ID: NCT03333291).

Clinical Trial Registration

ClinicalTrials.gov, identifier NCT03333291.

Short chain fatty acids and monocarboxylate transporters in irritable bowel syndrome

BACKGROUND/AIMS

Gut microbiota ferments indigestible food that rests in the colon to produce short-chain fatty acids (SCFAs) acetate, propionate, and butyrate. Colonic SCFA stimulate the synthesis of serotonin which is central in irritable bowel syndrome (IBS) pathophysiology. Reduced SCFA have been linked to specific IBS symptoms like colonic hyperalgesia and hypersensitivity. SCFA enter the colonocyte mainly via 2 energy-dependent monocarboxylate transporters, MCT1 (SLC16A1) and SMCT1 (SLC5A8). We investigated specific gut microbiota, SCFA concentrations, and monocarboxylate transporter mRNA expression in patients with IBS.

MATERIAL AND METHODS

A total of 30 IBS patients-15 constipation-predominant (C-IBS) and 15 diarrhoea-predominant (D-IBS)-and 15 healthy controls were recruited. Bacteroidetes and Bifidobacterium species were analyzed using quantitative polymerase chain reaction (qPCR) on stool samples. SCFA concentrations were determined by gas chromatography/mass spectroscopy of stool samples. Monocarboxylate transporter mRNA was quantified by qPCR on colon biopsy specimens.

RESULTS

Bacteroides was significantly increased in the D-IBS group compared with the C-IBS group and healthy controls. Bifidobacterium was significantly reduced in both IBS groups. SCFA ratios were altered in both IBS groups with a reduction of all 3 measured SCFA in C-IBS and acetic acid in D-IBS. MCT1 and SMCT1 were significantly reduced in C-IBS and D-IBS.

CONCLUSION

In agreement with findings of previous studies, the microbiota assessed were significantly altered inferring dysbiosis in IBS. SCFA and their ratios were significantly altered in both IBS groups. SCFA transporters, MCT1 and SMCT1 were significantly reduced in both IBS groups, suggesting reduced colonocyte SCFA transfer. SCFA availability and transfer into the colonocytes may be important in IBS pathogenesis and should be prospectively studied.

The characteristics of intestinal flora of IBS-D with different syndromes

OBJECTIVE

To study the distribution of fecal microbiota in diarrhea-predominant irritable bowel syndrome (IBS-D) patients of spleen-kidney-yang deficiency and liver depression and spleen deficiency, to make an objective foundation for dialectics of different type of IBS-D. And to provide the clinical doctors an experimental basis for medication by regulating dysbacteriosis.

METHODS

We collected feces from the control group, spleen-kidney-yang deficiency IBS-D group, and liver-depression and spleen-deficiency IBS-D group. After the extraction of fecal DNA, global DNA was isolated from every sample, and 16S ribosomal RNA was sequenced, and then we analyzed the results for bacteria such as Alpha diversity, community composition, LEfSe, and partial least squares discriminant analysis.

RESULTS

We compared the changes among the fecal bacteria in the intestine of the IBS-D patients and healthy controls and found the specificity of spleen-kidney-yang deficiency syndrome and liver-depression and spleen-deficiency syndrome. The control group has the highest flora diversity (control group > liver-depression and spleen-deficiency > spleen-kidney-yang deficiency group). The control group, spleen-kidney-yang deficiency group, and liver-depression and spleen-deficiency group are different in phylum (Actinobacteria, Fusobacteria), class (Actinobacteria, Fusobacteria), order (Enterobacteriales, Bifidobacteriales, Fusobacteriales), and family (Bifidobacteriaceae, Ruminococcaceae, Enterobacteriaceae, Acidaminococcaceae, Veillonellaceae, Fusobacteriaceae). Bifidobacteriaceae and Ruminococcaceae in the control group, Enterobacteriales, Fusobacteriales, Acidaminococcaceae, and Phascolarctobacterium in the spleen-kidney-yang deficiency group, and streptococcus are the specific bacteria in the liver-depression and spleen-deficiency group. Intestinal flora disturbance is closely related to IBS-D.

CONCLUSIONS

There is a correlation between traditional Chinese medicine syndrome type and intestinal flora. The control group, the spleen-kidney-yang deficiency group, and the liver-depression and spleen-deficiency group have specific bacteria.

Epidemiology and associated microbiota changes in deployed military personnel at high risk of traveler's diarrhea

Travelers’ diarrhea (TD) is the most prevalent illness encountered by deployed military personnel and has a major impact on military operations, from reduced job performance to lost duty days. Frequently, the etiology of TD is unknown and, with underreporting of cases, it is difficult to accurately assess its impact. An increasing number of ailments include an altered or aberrant gut microbiome. To better understand the relationships between long-term deployments and TD, we studied military personnel during two nine-month deployment cycles in 2015–2016 to Honduras. To collect data on the prevalence of diarrhea and impact on duty, a total of 1173 personnel completed questionnaires at the end of their deployment. 56.7% reported reduced performance and 21.1% reported lost duty days. We conducted a passive surveillance study of all cases of diarrhea reporting to the medical unit with 152 total cases and a similar pattern of etiology. Enteroaggregative E. coli (EAEC, 52/152), enterotoxigenic E. coli (ETEC, 50/152), and enteropathogenic E. coli (EPEC, 35/152) were the most prevalent pathogens detected. An active longitudinal surveillance of 67 subjects also identified diarrheagenic E. coli as the primary etiology (7/16 EPEC, 7/16 EAEC, and 6/16 ETEC). Eleven subjects were recruited into a nested longitudinal substudy to examine gut microbiome changes associated with deployment. A 16S rRNA amplicon survey of fecal samples showed differentially abundant baseline taxa for subjects who contracted TD versus those who did not, as well as detection of taxa positively associated with self-reported gastrointestinal distress. Disrupted microbiota was also qualitatively observable for weeks preceding and following the incidents of TD. These findings illustrate the complex etiology of diarrhea amongst military personnel in deployed settings and its impacts on job performance. Potential factors of resistance or susceptibility can provide a foundation for future clinical trials to evaluate prevention and treatment strategies.

The relationship between dectin-1 and mast cells in patients with diarrhea-predominant irritable bowel syndrome

Background/Aims: Currently, the role of the microbiome GBA is being widely studied in the pathogenesis of visceral hypersensitivity in IBS. To investigate the role of fungus, the current study aimed to i) investigate the expression of Syk/CARD9-coupled Dectin-1 receptors in the ileocecal mucosa in D-IBS patients and (ii) explore the relationships between Dectin-1 and plasma MCT levels as well as anorectal sensory function in patients with D-IBS.Methods: Thirty-eight D-IBS patients who met the Rome III criteria and 2 groups of age- and sex-matched asymptomatic healthy controls were recruited from March 2015 to January 2017. Anorectal sensory function was quantified by HR-ARM. Plasma MCT titers were identified by ELISA, while the expression of Syk/CARD9 Dectin-1 receptors in ileocecal mucosa was identified by RT-qPCR.Results: (i) The expression of Syk/CARD9-coupled Dectin-1 receptors was significantly higher in D-IBS patients than in controls (p < .001). ii) The threshold values of first sensation and desire to defecate were significantly lower in D-IBS patientsthan in controls (the P value was0.007 and 0.001 respectively). (iii) There were negative correlations between plasma MCT levels and first sensation thresholds in D-IBS patients (r = -0.513, p = .012) and the desire to defecate thresholds (r = -0.423, p = .044). (iiii) There was a positive correlation between plasma MCT titers and the expression of Dectin-1 receptors in D-IBS patients (r = 0.565, p = .005).Conclusions: These results suggested that fungi may partially participate in the genesis of visceral hypersensitivity by activating mast cells, which is mediated by activation of the Dectin-1 receptor-mediated Syk/CARD9 signaling pathway.

Usefulness of the hydrogen breath test in patients with functional dyspepsia

Introduction

The pathogenesis of functional dyspepsia is complex and not well understood. Therefore, in this disease there should be considered involvement of different pathogenic factors, including intestinal bacteria.

Aim

To evaluate the results of the hydrogen breath test in relation to the clinical picture of functional dyspepsia.

Material and methods

The study included 40 healthy subjects (group I), 72 patients with postprandial distress syndrome (PDS, group II), and 84 patients with epigastric pain syndrome (EPS, group III). The diagnosis of functional dyspepsia was based on Rome Criteria IV. The urea breath test (13C-UBT) and lactulose hydrogen breath test (LHBT) were performed in all subjects. Patients with a positive urea breath test were excluded from the study. Patients with a positive LHBT test were assigned to antibiotic therapy (1200 mg daily for 14 days). Before treatment and 6 weeks after the end of antibiotic therapy the LHBT was performed, and severity of dyspeptic symptoms was assessed using a 10-points visual analogue scale.

Results

A positive LHBT test was found in 35 (48.6%) patients in the group with PDS, and in 40 (47.6%) patients with EPS (p > 0.05). A positive correlation between the results of the LHBT test and severity of dyspeptic symptoms was found in both group (p < 0.001). After treatment with rifaximin the mean LHBT result and the index of severity of dyspeptic complaints were significantly decreased (p < 0.001).

Conclusions

Quantitative and/or qualitative changes in the gut microbiota may be the cause of functional dyspepsia.

Relatively rare root endophytic bacteria drive plant resource allocation patterns and tissue nutrient concentration in unpredictable ways

PREMISE

Plant endophytic bacterial strains can influence plant traits such as leaf area and root length. Yet, the influence of more complex bacterial communities in regulating overall plant phenotype is less explored. Here, in two complementary experiments, we tested whether we can predict plant phenotype response to changes in microbial community composition.

METHODS

In the first study, we inoculated a single genotype of Populus deltoides with individual root endophytic bacteria and measured plant phenotype. Next, data from this single inoculation were used to predict phenotypic traits after mixed three-strain community inoculations, which we tested in the second experiment.

RESULTS

By itself, each bacterial endophyte significantly but weakly altered plant phenotype relative to noninoculated plants. In a mixture, bacterial strain Burkholderia BT03, constituted at least 98% of community relative abundance. Yet, plant resource allocation and tissue nutrient concentrations were disproportionately influenced by Pseudomonas sp. GM17, GM30, and GM41. We found a 10% increase in leaf mass fraction and an 11% decrease in root mass fraction when replacing Pseudomonas GM17 with GM41 in communities containing both Pseudomonas GM30 and Burkholderia BT03.

CONCLUSIONS

Our results indicate that interactions among endophytic bacteria may drive plant phenotype over the contribution of each strain individually. Additionally, we have shown that low-abundance strains contribute to plant phenotype challenging the assumption that the dominant strains will drive plant function.

Fecal microbiota transplantation in irritable bowel syndrome: A systematic review and meta-analysis

Background

Modulating gut microbiota is a potential treatment for irritable bowel syndrome (IBS). This meta-analysis explored whether fecal microbiota transplantation (FMT) is successful in treating IBS.

Methods

A systematic review was performed to find trials on FMT in IBS. Ratios and relative ratios (RR) of improvement for single-arm trials (SATs) and randomized controlled trials (RCTs) were calculated, respectively. Changes in IBS Severity Scoring System (IBS-SSS) and IBS Quality of Life (IBS-QOL) instrument compared to baseline in FMT versus placebo groups were pooled.

Results

In SATs, 59.5% (95% confidence interval (CI) 49.1-69.3) of IBS patients showed significant improvement. In RCTs, there were no differences between FMT and control in improvement (RR=0.93 (95% CI 0.50-1.75)) or changes in the IBS-SSS and IBS-QOL.

Conclusions

FMT was not effective in IBS. Variations in FMT methods and patient factors may contribute to the heterogeneous results of the trials.

The Potential Role of Gut Mycobiome in Irritable Bowel Syndrome

The human gut is inhabited by diverse microorganisms that play crucial roles in health and disease. Gut microbiota dysbiosis is increasingly considered as a vital factor in the etiopathogenesis of irritable bowel syndrome (IBS), which is a common functional gastrointestinal disorder with a high incidence all over the world. However, investigations to date are primarily directed to the bacterial community, and the gut mycobiome, another fundamental part of gut ecosystem, has been underestimated. Intestinal fungi have important effects on maintaining gut homeostasis just as bacterial species. In the present article, we reviewed the potential roles of gut mycobiome in the pathogenesis of IBS and the connections between the fungi and existing mechanisms such as chronic low-grade inflammation, visceral hypersensitivity, and brain-gut interactions. Moreover, possible strategies targeted at the gut mycobiome for managing IBS were also described. This review provides a basis for considering the role of the mycobiome in IBS and offers novel treatment strategies for IBS patients; moreover, it adds new dimensions to researches on microorganism.

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.

Lactose intolerance but not lactose maldigestion is more frequent in patients with irritable bowel syndrome than in healthy controls: A meta-analysis

BACKGROUND AND PURPOSE

Irritable bowel syndrome (IBS) affects 10%-20% of the adult population and is characterized by abdominal symptoms without relevant organic disease. There are numerous clinical trials available investigating the relationship between IBS, lactose maldigestion (LM), and lactose intolerance (LI), but there have been no meta-analyses on this topic yet. We aimed to assess the prevalence of LM, objective and subjective (self-reported) LI in IBS patients compared to healthy controls (HC) without IBS.

METHODS

A systematic literature search was conducted up to 24 April 2018 in PubMed, Embase, and Cochrane Library. Adult IBS patients had to be diagnosed according to the Rome criteria or other well-defined criteria system. We enrolled controlled studies including healthy adult participants without IBS, as control group. Odds ratios with 95% confidence intervals were calculated.

KEY RESULTS

Altogether 14 articles were suitable for statistical analyses. IBS patients reported themselves significantly more frequently lactose intolerant than HCs (odds ratio [OR] = 3.499; 95% confidence interval [CI] = 1.622-7.551). Generally, there was no significant difference in the prevalence of LM based on ingested lactose dose (OR = 1.122; 95% CI = 0.929-1.356) and test type (OR = 1.156; 95% CI = 0.985-1.356). However, significantly more IBS patients had objective LI (OR = 2.521; 95% CI = 1.280-4.965).

CONCLUSIONS AND INFERENCES

Lactose intolerance, but not LM is more frequent among patients with IBS compared to HCs. According to our results, IBS among other functional bowel disorders is a possible contributing factor of LI in people with LM.

The kinetics of gut microbial community composition in patients with irritable bowel syndrome following fecal microbiota transplantation

Background

Gut microbiota alterations are important in irritable bowel syndrome (IBS). The aim was to investigate the effect of fecal microbiota transplantation (FMT) on gut microbiota and the symptoms in patients with IBS.

Material and methods

The study included 13 IBS patients according to Rome III criteria and 13 healthy donors. Freshly donated feces were administered to the descending part of the duodenum via a gastroscope. Feces were collected from donors and patients before FMT, and from the patients at 1, 3 and 12 weeks and donors and patients at 20/28 weeks after FMT. Microbiota analysis was performed using GA-map Dysbiosis test (Genetic Analysis AS, Oslo, Norway). The patients completed the following questionnaires before and at the aforementioned weeks after FMT: IBS Symptom Questionnaire (IBS-SQ), IBS-Symptom Severity Scoring system (IBS-SSS), Short Form of Nepean Dyspepsia Index (SF-NDI), Bristol stool form scale, the Eysenck Personality Questionnaire-Neuroticism and Hospital Anxiety and Depression.

Results

Donors and IBS patients had significantly different bacterial strain signals before FMT (Ruminococcus gnavus, Actinobacteria and Bifidobacteria) that became non-significant after 3 weeks following FMT. The changes in gut microbiota were similar between donors and patients at 20/28 weeks after FMT. Thus, patients’ microbiota profiles became more-or-less similar to donors.

The scores of all the questionnaires were significantly improved at all time points following FMT. No reported adverse effects.

Conclusions

FMT was associated with a change in gut microbiota and improvement in IBS symptoms and quality of life lasting for up to 28 weeks.

Trial registration

ClinicalTrials.gov ID:NCT03333291

Fecal Clostridiales distribution and short-chain fatty acids reflect bowel habits in irritable bowel syndrome

Irritable bowel syndrome (IBS), a common functional gastrointestinal disorder, is classified according to bowel habits as IBS with constipation (IBS-C), with diarrhea (IBS-D), with alternating constipation and diarrhea (IBS-M), and unsubtyped (IBS-U). The mechanisms leading to the different IBS forms are mostly unknown. This study aims to evaluate whether specific fecal bacterial taxa and/or short-chain fatty acids (SCFAs) can be used to distinguish IBS subtypes and are relevant for explaining the clinical differences between IBS subcategories. We characterized five fecal samples collected at 4-weeks intervals from 40 IBS patients by 16S rRNA gene profiling and SCFA quantification. Finally, we investigated the potential correlations in IBS subtypes between the fecal microbial signatures and host physiological and clinical parameters. We found significant differences in the distribution of Clostridiales OTUs among IBS subtypes and reduced levels of SCFAs in IBS-C compared to IBS-U and IBS-D patients. Correlation analyses showed that the diverse representation of Clostridiales OTUs between IBS subtypes was associated with altered levels of SCFAs; furthermore, the same OTUs and SCFAs were associated with the fecal cytokine levels and stool consistency. Our results suggest that intestinal Clostridiales and SCFAs might serve as potential mechanistic biomarkers of IBS subtypes and represent therapeutic targets.

Astrovirus infections induce age-dependent dysbiosis in gut microbiomes of bats

Astroviruses (AstV) are a major cause of diarrhoea in children. Interestingly, some wildlife species, including bats, remain phenotypically asymptomatic after infection. Disease symptoms, however, may only be less visible in bats and enteric viruses may indeed perturb their gut microbial communities. Gut microbiomes represent an important driver of immune defence mechanisms but potential effects of enteric virus-host microbiome interactions are largely unexplored. Using bats as a natural model system, we show that AstV-infections affect the gut microbiome, with the strength of the effect depending on host age. The gut microbial α- and β-diversity and the predicted microbial functional orthologs decreased in young bats but surprisingly increased in adult AstV + bats. The abundance of bacterial taxa characteristic for healthy microbiomes was strongly reduced in young AstV+ bats, possibly attributable to their immature immune system. Regardless of age, pathogen-containing genera exhibited negative interactions with several commensal taxa and increased after AstV-infection, leading to pathobiont-like shifts in the gut microbiome of all infected bats. Thus, in apparently healthy bats, AstV-infections disturb gut bacterial homeostasis, possibly increasing previously suppressed health risks by promoting co-infections. If similar processes are present in humans, the effects of enteric virus infections might have longer-term impacts extending beyond the directly observed symptoms.

Fecal and Mucosa-Associated Intestinal Microbiota in Patients with Diarrhea-Predominant Irritable Bowel Syndrome

BACKGROUND

Irritable bowel syndrome (IBS) has been associated with changes in the intestinal microbiota. Only a few studies have explored differences in the mucosa-associated microbiota between IBS patients and healthy controls (HC).

AIMS

To characterize and compare the microbiota in mucosal and fecal samples from carefully selected patients with IBS-D and HC.

METHODS

The cohort was composed of 23 diarrhea-predominant IBS (IBS-D) patients and 24 HC. Fresh stool samples were collected from participants prior to the collection of colonic mucosal samples from an unprepped bowel. After DNA extraction, 16S rRNA genes were sequenced by 454 pyrosequencing and analyzed using the QIIME pipeline.

RESULTS

The fecal microbiota (luminal niche) of IBS-D patients was found to have reduced enteric richness compared to HC (P < 0.05), whereas no differences were observed between the two groups within the mucosal microbiota. Within the luminal niche, the relative proportions of Faecalibacterium genus were found to be lower in IBS-D than in HC and the Dorea genus was higher in IBS-D. None of the taxa proportions were significantly different in IBS-D patients versus HC using an FDR of ≤ 0.1 when analyzing samples that appeared in > 25% samples of either niche.

CONCLUSION

Fecal and mucosal microbiota of IBS-D patients and HC are very similar and are not sufficient to explain the reported altered physiology and symptomatology of IBS-D. Future studies should investigate intestinal microbiome-dependent functional activity in addition to the fecal and mucosal-associated microbial composition.

Effect of Probiotic Administration Immediately and 1 Month after Colonoscopy in Diarrhea-predominant Irritable Bowel Syndrome Patients

Background

Irritable bowel syndrome (IBS) is one of the most common disorders among young adults. Various studies have demonstrated that the use of probiotics can reduce the overall symptom of IBS, and thus, our aim was to evaluate the efficacy of probiotic products in the reduction of IBS syndrome after colonoscopy.

Materials and Methods

Our patients were divided among three groups, including immediate probiotic users, start use of probiotics 1 month after colonoscopy, and placebo group. All the patients were interviewed for having common IBS symptoms (stool consistency and frequency, gas, abdominal pain, and flatulence) at baseline, 3^rd month of follow-up, and 6^th month of follow-up.

Results

The mean reduction in abdominal pain was 3.05 ± 1.21, 3.86 ± 0.94, and 3.82 ± 0.63 in the control group, immediate probiotic users, and 1 month after colonoscopy, respectively (P < 0.001). The symptoms of the disease, such as stool consistency, the frequency of defecation, and flatulence (except gas) in the first quarter, in the two treatment groups were significantly improved more than in the control group (P < 0.05). In contrast, the frequency of defecation was not significantly different in the treatment group receiving the probiotics month after colonoscopy compared to the placebo users (P > 0.05).

Conclusion

According to our results, the use of probiotics had the beneficial effect on IBS symptoms. Furthermore, it can be said that reductions in symptoms and pain in the two treatment groups were not significantly different, but after 6 months of treatment, the effect of probiotics in patients who immediately use it after colonoscopy was more visible and more stable.

Impact of the Gut Microbiota on Intestinal Immunity Mediated by Tryptophan Metabolism

The gut microbiota influences the health of the host, especially with regard to gut immune homeostasis and the intestinal immune response. In addition to serving as a nutrient enhancer, L-tryptophan (Trp) plays crucial roles in the balance between intestinal immune tolerance and gut microbiota maintenance. Recent discoveries have underscored that changes in the microbiota modulate the host immune system by modulating Trp metabolism. Moreover, Trp, endogenous Trp metabolites (kynurenines, serotonin, and melatonin), and bacterial Trp metabolites (indole, indolic acid, skatole, and tryptamine) have profound effects on gut microbial composition, microbial metabolism, the host's immune system, the host-microbiome interface, and host immune system-intestinal microbiota interactions. The aryl hydrocarbon receptor (AhR) mediates the regulation of intestinal immunity by Trp metabolites (as ligands of AhR), which is beneficial for immune homeostasis. Among Trp metabolites, AhR ligands consist of endogenous metabolites, including kynurenine, kynurenic acid, xanthurenic acid, and cinnabarinic acid, and bacterial metabolites, including indole, indole propionic acid, indole acetic acid, skatole, and tryptamine. Additional factors, such as aging, stress, probiotics, and diseases (spondyloarthritis, irritable bowel syndrome, inflammatory bowel disease, colorectal cancer), which are associated with variability in Trp metabolism, can influence Trp-microbiome-immune system interactions in the gut and also play roles in regulating gut immunity. This review clarifies how the gut microbiota regulates Trp metabolism and identifies the underlying molecular mechanisms of these interactions. Increased mechanistic insight into how the microbiota modulates the intestinal immune system through Trp metabolism may allow for the identification of innovative microbiota-based diagnostics, as well as appropriate nutritional supplementation of Trp to prevent or alleviate intestinal inflammation. Moreover, this review provides new insight regarding the influence of the gut microbiota on Trp metabolism. Additional comprehensive analyses of targeted Trp metabolites (including endogenous and bacterial metabolites) are essential for experimental preciseness, as the influence of the gut microbiota cannot be neglected, and may explain contradictory results in the literature.

Gut dysbiosis and irritable bowel syndrome: The potential role of probiotics

OBJECTIVE

To discuss the role of gut dysbiosis in the development of irritable bowel syndrome (IBS) and the impact of probiotics as a potential therapeutic measure.

METHODS

PubMed was used to search for all of the studies published over the last 15 years using the key words: "irritable bowel syndrome" and "gut dysbiosis" or "probiotic". More than 800 articles were found, but only those published in English or providing evidence-based data were included in the evaluation.

RESULTS

IBS is a common disease for which no resolutive therapy is presently available. In recent years, strong evidence of a possible relationship between modifications of the gut microbiota composition and development of IBS has been collected. Moreover, the evidence showed that attempts to treat acute infectious and post-antibiotic gastroenteritis with some probiotics were significantly effective in a great number of patients, leading many experts to suggest the use of probiotics to address all of the clinical problems associated with IBS.

CONCLUSION

The available data are promising, but presently, a precise definition of which probiotic or which mixture of probiotics is effective cannot be made. Moreover, the dose and duration of treatment has not been established. Finally, we do not know whether probiotic treatment should be different according to the type of IBS. Further studies are needed before probiotics can be considered a reliable treatment for IBS.

Linking Gut Microbiota to Colorectal Cancer

Pre-clinical and clinical data produce mounting evidence that the microbiota is strongly associated with colorectal carcinogenesis. Dysbiosis may change the course of carcinogenesis as microbial actions seem to impact genetic and epigenetic alterations leading to dysplasia, clonal expansion and malignant transformation. Initiation and promotion of colorectal cancer may result from direct bacterial actions, bacterial metabolites and inflammatory pathways. Newer aspects of microbiota and colorectal cancer include quorum sensing, biofilm formation, sidedness and effects/countereffects of microbiota and probiotics on chemotherapy. In the future, targeting the microbiota will probably be a powerful weapon in the battle against CRC as gut microbiology, genomics and metabolomics promise to uncover important linkages between microbiota and intestinal health.

Effect of diet and individual dietary guidance on gastrointestinal endocrine cells in patients with irritable bowel syndrome (Review)

Irritable bowel syndrome (IBS) is a common chronic gastrointestinal (GI) disorder that is characterized by a combination of abdominal pain or discomfort, bloating and alterations in bowel movements. This review presents recent developments concerning the roles of diet and GI endocrine cells in the pathophysiology of IBS and of individual dietary guidance in the management of IBS. Patients with IBS typically report that food aggravates their IBS symptoms. The interactions between specific types of foodstuffs rich in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) and GI endocrine cells induce changes in cell densities. Providing individual dietary guidance about a low FODMAP intake, high soluble-fiber intake, and changing the proportions of protein, fat and carbohydrates helps to reduce the symptoms experienced by patients with IBS and to improve their quality of life. These improvements are due to restoring the densities of the GI endocrine cells back to normal. The reported observations emphasize the role of GI endocrine cells in the pathophysiology of IBS and support the provision of dietary guidance as a first-line treatment for managing IBS.

Lactobacillus reuteri DSM 17938 in the Treatment of Functional Abdominal Pain in Children: RCT Study

OBJECTIVES

Beneficial therapeutic effect of probiotics has been reported in children with the irritable bowel syndrome (IBS) but not consistently in other functional abdominal pain-related disorders. The aim of the present study was to investigate the effect of Lactobacillus reuteri DSM 17938 in the treatment of functional abdominal pain (FAP) and IBS in children.

METHODS

Children (age 4-18 years) referred to pediatric gastroenterologist at Children's Hospital Zagreb from May 2012 to December 2014, diagnosed as FAP or IBS, were randomized to receive L reuteri DSM 17938 10⁸ CFU daily or placebo. The study was a prospective, randomized, double-blind, placebo-controlled parallel study. Symptoms were evaluated using Wong-Baker FACES pain rating scale for pain and Bristol scale for stool shape and consistence.

RESULTS

Data were analyzed for 55 children (26 in the intervention group and 29 in the placebo group). Children in the intervention group had significantly more days without pain (median 89.5 vs 51 days, P = 0.029). Abdominal pain was less severe in children taking probiotics during the second month (P < 0.05) and fourth month (P < 0.01). The 2 groups did not differ in the duration of abdominal pain, stool type, or absence from school. Both groups experienced significant reduction in the severity of abdominal pain from first to fourth month, with the reduction more prominent in the intervention group (P < 0.001 vs P = 0.004).

CONCLUSIONS

Administration of L reuteri DSM 17938 was associated with a possible reduction of the intensity of pain and significantly more days without pain in children with FAP and IBS.

Review: chronic and persistent diarrhea with a focus in the returning traveler

Background

Travelers’ diarrhea is a common malady afflicting up to 50% of travelers after a 2-week travel period. An appreciable percentage of these cases will become persistent or chronic. We summarized the published literature reporting persistent/chronic diarrhea in travelers elucidating current understanding of disease incidence, etiology and regional variability.

Methods

We searched electronic databases (Medline, Embase, and Cochrane database of clinical trials) from 1990 to 2015 using the following terms: “chronic or persistent diarrh* and (returning) travel* or enteropathogen, GeoSentinel, and travel-associated infection. Included studies published in the English language on adult returning travelers (duration < 3-months) reporting denominator data. Point estimates and standard 95% confidence intervals were calculated for incidence using a random-effects model. Study incidence heterogeneity rates were assessed using x² heterogeneity statistics, graphically represented with Forest plots.

Results

We identified 19 studies meeting the inclusion criteria (all published after 1999). 18 studies reported upon the incidence of persistent/chronic diarrhea as a syndromic diagnosis in returning travelers; one study reported adequate denominator data from which to assess pathogen specific etiology. Giardiasis comprise an appreicaible percentage of infectious mediated persistent/chronic diarrhea in returning travelers. The overall estimate of persistent/chronic diarrhea incidence was 6% (0.05–0.07) in 321,454, travelers; with significant heterogeniety observed across regions. The total number of regional travelers, and point estimates for incidence (95% CI) for Latin American, African, and Asian travelers were [15816 (0.09 [0.07–0.11]), 42290 (0.06 [0.05–0.07]), and 27433 (0.07 [0.06–0.09])] respectively. We identified lower published rates of chronic diarrhea from Sub-Saharan Africa relative to [North Africa, South Central Asia, and Central America]. Persistent/chronic diarrhea ranked fourth as a syndromic diagnosis in all regions.

Conclusions

Persistent/Chronic diarrhea is a leading syndromic diagnosis in returning travelers across all regions. The 6% incidence [proportionate morbidity (PM) of 60] observed in over >300,000 global travelers is comparable to prior estimates. We identified lower published rates of chronic diarrhea from Sub-Saharan Africa relative to [North Africa, South Central Asia, and Central America]. Giardiasis comprises an appreciabile percentatge of travel-associated infectious mediated persistent/chronic diarrhea. There’s a dearth of published data characterizing the incidence of specific enteropathogenic etiologies for persistent/chronic diarrhea in returning travelers.

Ursodeoxycholic Acid and Its Taurine- or Glycine-Conjugated Species Reduce Colitogenic Dysbiosis and Equally Suppress Experimental Colitis in Mice

The promising results seen in studies of secondary bile acids in experimental colitis suggest that they may represent an attractive and safe class of drugs for the treatment of inflammatory bowel diseases (IBD). However, the exact mechanism by which bile acid therapy confers protection from colitogenesis is currently unknown. Since the gut microbiota plays a crucial role in the pathogenesis of IBD, and exogenous bile acid administration may affect the community structure of the microbiota, we examined the impact of the secondary bile acid ursodeoxycholic acid (UDCA) and its taurine or glycine conjugates on the fecal microbial community structure during experimental colitis. Daily oral administration of UDCA, tauroursodeoxycholic acid (TUDCA), or glycoursodeoxycholic acid (GUDCA) equally lowered the severity of dextran sodium sulfate-induced colitis in mice, as evidenced by reduced body weight loss, colonic shortening, and expression of inflammatory cytokines. Illumina sequencing demonstrated that bile acid therapy during colitis did not restore fecal bacterial richness and diversity. However, bile acid therapy normalized the colitis-associated increased ratio of Firmicutes to Bacteroidetes Interestingly, administration of bile acids prevented the loss of Clostridium cluster XIVa and increased the abundance of Akkermansia muciniphila, bacterial species known to be particularly decreased in IBD patients. We conclude that UDCA, which is an FDA-approved drug for cholestatic liver disorders, could be an attractive treatment option to reduce dysbiosis and ameliorate inflammation in human IBD.IMPORTANCE Secondary bile acids are emerging as attractive candidates for the treatment of inflammatory bowel disease. Although bile acids may affect the intestinal microbial community structure, which significantly contributes to the course of these inflammatory disorders, the impact of bile acid therapy on the fecal microbiota during colitis has not yet been considered. Here, we studied the alterations in the fecal microbial abundance in colitic mice following the administration of secondary bile acids. Our results show that secondary bile acids reduce the severity of colitis and ameliorate colitis-associated fecal dysbiosis at the phylum level. This study indicates that secondary bile acids might act as a safe and effective drug for inflammatory bowel disease.

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.

Alterations of gut microbiota in patients with irritable bowel syndrome: A systematic review and meta-analysis

BACKGROUND AND AIMS

Alterations of gut microbiota were assumed to be the etiology and pathogenesis of irritable bowel syndrome (IBS) in some studies. However, alterations of gut microbiota in IBS patients had not been systematically assessed with a meta-analysis. We performed a mate-analysis to explore and compare the alterations of gut microbiota in IBS patients from China and other regions around the world.

METHODS

Case-control studies detecting gut microbiota in IBS patients were identified through English and Chinese databases. The standardized mean difference (SMD) with 95% confidence interval (CI) of bacterial counts was calculated.

RESULTS

Ten studies from China and seven studies from other regions around the world were included in our study. As compared with healthy controls, the SMDs of Bifidobacteria, Lactobacillus, Escherichia Coli, and Enterobacter in Chinese IBS patients were -1.42 (CI: -2.10, -0.75), -0.91 (95% CI: -1.31, -0.52), 0.83 (95% CI: 0.26, 1.40), and 0.57 (95% CI: 0.33, 0.82), respectively. But the SMDs of Bacteroides and Enterococcus were found no significant differences in Chinese IBS patients. However, the SMDs of Bifidobacteria and Bacteroides in IBS patients from other regions were -0.76 (CI: -1.43, -0.09) and 1.17 (CI: 0.00, 2.35), while the SMDs of Lactobacillus, E. Coli, Enterobacter, and Enterococcus were found no significant differences.

CONCLUSIONS

There were alterations of gut microbiota in IBS patients, and it implied that alterations of gut microbiota might be involved in the pathogenesis of IBS. However, the species-specific alterations of gut microbiota were different between IBS patients from China and other regions.

Irritable bowel syndrome: a gut microbiota-related disorder?

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal (GI) disorders. Despite its prevalence, the pathophysiology of IBS is not well understood although multiple peripheral and central factors are implicated. Recent studies suggest a role for alterations in gut microbiota in IBS. Significant advances in next-generation sequencing technology and bioinformatics and the declining cost have now allowed us to better investigate the role of gut microbiota in IBS. In the following review, we propose gut microbiota as a unifying factor in the pathophysiology of IBS. We first describe how gut microbiota can be influenced by factors predisposing individuals to IBS such as host genetics, stress, diet, antibiotics, and early life experiences. We then highlight the known effects of gut microbiota on mechanisms implicated in the pathophysiology of IBS including disrupted gut brain axis (GBA), visceral hypersensitivity (VH), altered GI motility, epithelial barrier dysfunction, and immune activation. While there are several gaps in the field that preclude us from connecting the dots to establish causation, we hope this overview will allow us to identify and fill in the voids.

Autoimmune diseases, gastrointestinal disorders and the microbiome in schizophrenia: more than a gut feeling

Autoimmunity, gastrointestinal (GI) disorders and schizophrenia have been associated with one another for a long time. This paper reviews these connections and provides a context by which multiple risk factors for schizophrenia may be related. Epidemiological studies strongly link schizophrenia with autoimmune disorders including enteropathic celiac disease. Exposure to wheat gluten and bovine milk casein also contribute to non-celiac food sensitivities in susceptible individuals. Co-morbid GI inflammation accompanies humoral immunity to food antigens, occurs early during the course of schizophrenia and appears to be independent from antipsychotic-generated motility effects. This inflammation impacts endothelial barrier permeability and can precipitate translocation of gut bacteria into systemic circulation. Infection by the neurotropic gut pathogen, Toxoplasma gondii, will elicit an inflammatory GI environment. Such processes trigger innate immunity, including activation of complement C1q, which also functions at synapses in the brain. The emerging field of microbiome research lies at the center of these interactions with evidence that the abundance and diversity of resident gut microbiota contribute to digestion, inflammation, gut permeability and behavior. Dietary modifications of core bacterial compositions may explain inefficient gluten digestion and how immigrant status in certain situations is a risk factor for schizophrenia. Gut microbiome research in schizophrenia is in its infancy, but data in related fields suggest disease-associated altered phylogenetic compositions. In summary, this review surveys associative and experimental data linking autoimmunity, GI activity and schizophrenia, and proposes that understanding of disrupted biological pathways outside of the brain can lend valuable information regarding pathogeneses of complex, polygenic brain disorders.

Irritable bowel syndrome, the microbiota and the gut-brain axis

Irritable bowel syndrome is a common functional gastrointestinal disorder and it is now evident that irritable bowel syndrome is a multi-factorial complex of changes in microbiota and immunology. The bidirectional neurohumoral integrated communication between the microbiota and the autonomous nervous system is called the gut-brain-axis, which integrates brain and GI functions, such as gut motility, appetite and weight. The gut-brain-axis has a central function in the perpetuation of irritable bowel syndrome and the microbiota plays a critical role. The purpose of this article is to review recent research concerning the epidemiology of irritable bowel syndrome, influence of microbiota, probiota, gut-brain-axis, and possible treatment modalities on irritable bowel syndrome.

Local and Long-Distance Calling: Conversations between the Gut Microbiota and Intra- and Extra-Gastrointestinal Tract Infections

Preservation of health from infectious diseases depends upon both mucosal and systemic immunity via the collaborative effort of innate and adaptive immune responses. The proficiency of host immunity stems from robust defense mechanisms—physical barriers and specialized immune cells—and a failure of these mechanisms leads to pathology. Intriguingly, immunocompetence to pathogens can be shaped by the gut microbiome as recent publications highlight a dynamic interplay between the gut microbiome and host susceptibility to infection. Modulation of host immunity to enteric pathogens has long been studied where gut bacteria shape multiple facts of both innate and adaptive immunity. Conversely, the impact of gut commensals on host immunity to extra-gastrointestinal (GI) tract infections has only recently been recognized. In this context, the gut microbiome can augment host immunity to extra-GI tract bacterial, viral, and parasitic pathogens. This review explores the research that affords insight into the role of the gut microbiome in various infectious diseases, with a particular emphasis on extra-GI tract infections. A better understanding of the link between the gut microbiome and infectious disease will be critical for improving global health in the years ahead.

The relationship between faecal-associated and mucosal-associated microbiota in irritable bowel syndrome patients and healthy subjects

BACKGROUND

The faecal-associated microbiota is commonly seen as a surrogate of the mucosal-associated microbiota. However, previous studies indicate that they are different. Furthermore, analyses of the mucosal microbiota are commonly done after standard bowel cleansing, affecting the microbial composition.

AIM

To compare the mucosal-associated microbiota, obtained from unprepared colon, with faecal-associated microbiota in healthy subjects and irritable bowel syndrome (IBS) patients.

METHODS

Faecal and mucosal biopsies were obtained from 33 IBS patients and 16 healthy controls. Of IBS patients, 49% belonged to the diarrhoea-predominant subgroup and 80% suffered from IBS symptoms during at least 5 years. Biopsies were collected from unprepared sigmoid colon and faecal samples a day before colonoscopy. Microbiota analyses were performed with a phylogenetic microarray and redundancy discriminant analysis.

RESULTS

The composition of the mucosal- and the faecal-associated microbiota in unprepared sigmoid colon differs significantly (P = 0.002). Clinical characteristics of IBS did not correlate with this difference. Bacteroidetes dominate the mucosal-associated microbiota. Firmicutes, Actinobacteria and Proteobacteria dominate the faecal-associated microbiota. Healthy subjects had a significantly higher (P < 0.005) abundance (1.9%) of the bacterial group uncultured Clostridiales I in the mucosal-associated microbiota than IBS patients (0.3%). Bacterial diversity was higher in faecal- compared with mucosal-associated microbiota in IBS patients (P < 0.005). No differences were found in healthy subjects.

CONCLUSIONS

Differences in the mucosal-associated microbiota between healthy individuals and IBS patients are minimal (one bacterial group) compared to differences in the faecal microbiota of both groups (53 bacterial groups). Microbial aberrations characterising IBS are more pronounced in the faeces than in the mucosa.

Deviations in human gut microbiota: a novel diagnostic test for determining dysbiosis in patients with IBS or IBD

BACKGROUND

Dysbiosis is associated with many diseases, including irritable bowel syndrome (IBS), inflammatory bowel diseases (IBD), obesity and diabetes. Potential clinical impact of imbalance in the intestinal microbiota suggests need for new standardised diagnostic methods to facilitate microbiome profiling.

AIM

To develop and validate a novel diagnostic test using faecal samples to profile the intestinal microbiota and identify and characterise dysbiosis.

METHODS

Fifty-four DNA probes targeting ≥300 bacteria on different taxonomic levels were selected based on ability to distinguish between healthy controls and IBS patients in faecal samples. Overall, 165 healthy controls (normobiotic reference collection) were used to develop a dysbiosis model with a bacterial profile and Dysbiosis Index score output. The model algorithmically assesses faecal bacterial abundance and profile, and potential clinically relevant deviation in the microbiome from normobiosis. This model was tested in different samples from healthy volunteers and IBS and IBD patients (n = 330) to determine the ability to detect dysbiosis.

RESULTS

Validation confirms dysbiosis was detected in 73% of IBS patients, 70% of treatment-naïve IBD patients and 80% of IBD patients in remission, vs. 16% of healthy individuals. Comparison of deep sequencing and the GA-map Dysbiosis Test, (Genetic Analysis AS, Oslo, Norway) illustrated good agreement in bacterial capture; the latter showing higher resolution by targeting pre-determined highly relevant bacteria.

CONCLUSIONS

The GA-map Dysbiosis Test identifies and characterises dysbiosis in IBS and IBD patients, and provides insight into a patient's intestinal microbiota. Evaluating microbiota as a diagnostic strategy may allow monitoring of prescribed treatment regimens and improvement in new therapeutic approaches.

Increased gut microbiota diversity and abundance of Faecalibacterium prausnitzii and Akkermansia after fasting: a pilot study

Summary

Background

An impaired gut microbiota has been reported as an important factor in the pathogenesis of obesity. Weight reduction has already been mentioned to improve gut microbial subpopulations involved in inflammatory processes, though other subpopulations still need further investigation. Thus, weight reduction in the context of a fasting program together with a probiotic intervention may improve the abundance and diversity of gut microbiota.

Methods

In this pilot study, overweight people underwent a fasting program with laxative treatment for 1 week followed by a 6 week intervention with a probiotic formula. Gut microbiota were analyzed on the basis of 16s rDNA with a quantitative real time polymerase chain reaction. Additionally, a food frequency questionnaire with questions about nutritional behavior, lifestyle, and physical activity was administered before and after the intervention.

Results

We observed an increase in microbial diversity over the study period. No significant changes in abundance of total bacteria, or of Bacteroidetes, Prevotella, Clostridium cluster XIVa, or Clostridium cluster IV were found, although Faecalibacterium prausnitzii showed an increase over the study period. In addition, Akkermanisa and Bifidobacteria increased in abundance due to intervention. The inflammation-associated gut microbes Enterobacteria and Lactobacilli increased during the first week and then declined by the end of the intervention. Two-thirds of the study participants harbored Archaea. No significant improvements of eating habits were reported, although physical activity improved due to the intervention.

Conclusions

Our results show that caloric restriction affects gut microbiota by proliferating mucin-degrading microbial subpopulations. An additional intervention with a probiotic formula increased probiotic-administered gut microbial populations.

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

OBJECTIVE

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

METHOD

Narrative literature review with selection for relevance and quality.

RESULTS

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

CONCLUSION

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

IBS-like symptoms in patients with ulcerative colitis

Ulcerative colitis (UC) and irritable bowel syndrome (IBS) are chronic gastrointestinal disorders that, until recently, have been considered dichotomous conditions falling on either side of a functional-organic divide. However, persistent gastrointestinal symptoms, akin to those of IBS, are observed in up to one in three patients with quiescent UC. Whether these lower gastrointestinal symptoms are secondary to coexistent IBS or occult UC disease activity is uncertain, but when objective evidence of disease activity is lacking, escalation of conventional pharmacotherapy in such patients is often ineffective. The etiologies of both UC and IBS remain unclear, but dysregulation of the enteric nervous system, an altered microbiome, low-grade mucosal inflammation, and activation of the brain–gut axis is common to both; this suggests that some overlap between the two conditions is plausible. How best to investigate and manage IBS-type symptoms in UC patients remains unclear. Studies that have assessed patients with UC who meet criteria for IBS for subclinical inflammation have been conflicting in their results. Although evidence-based treatments for IBS exist, their efficacy in UC patients reporting these types of symptoms remains unclear. Given the disturbances in gut microbiota in UC, and the possible role of the brain–gut axis in the generation of such symptoms, treatments such as probiotics, fecal transfer, antidepressants, or psychological therapies would seem logical approaches to use in this group of patients. However, there are only limited data for all of these therapies; this suggests that randomized controlled trials to investigate their efficacy in this setting may be warranted.