Discrete interplay of gut microbiota L-tryptophan metabolites in host biology and disease

The gut microbiota and the host maintain a conjoint relationship and together achieve optimal physiology via a multitude of interactive signalling cues. Dietary-derived L-tryptophan (L-trp) is enzymatically metabolized by the resident symbiotic gut microbiota to indole and various indole derivatives. Indole and indole metabolites secreted by the gut bacteria act locally in the intestinal cells as well as distally and modulate tissue-specific functions which are beneficial to the host. Functions attributed to these microbial indole metabolites in the host include regulation of intestinal permeability, immunity and mucosal roles, inflammation, and insulin sensitivity. On the other hand, dysregulation of gut microbiota L-trp metabolism compromises the optimal availability of indole and indole metabolites and can induce the onset of metabolic disorders, inflammation, liver steatosis, and decrease gut barrier integrity. Gut dysbiosis is regarded as one of the prime reasons for this deregulated microbial-derived indole metabolites. A number of indole metabolites from the gut bacteria have been identified recently displaying variable affinity towards xenobiotic nuclear receptors. Microbial metabolite mimicry concept can be used to design and develop novel indole-moiety-containing compounds with higher affinity towards the receptors and efficacy in preclinical studies. Such compounds may serve as therapeutic drugs in clinical trials in the future. In this article, I review L-trp metabolism in the host and gut microbiota and the various physiological functions, patho-physiologies associated with the microbial-released indole metabolites in the host, including the metabolite mimicry-based concept to develop tailored indole-containing novel experimental drugs.

Differential analysis of serum immunology and gut microbiota in patients with gastrointestinal diseases

Objective

Gastric and intestinal diseases possess distinct characteristics although they are interconnected. The primary objective of this study was to investigate the pathogenesis of gastrointestinal diseases through different analyses of clinical characteristics, serum immunology, and gut microbiota in patients with gastrointestinal diseases.

Methods

We collected serum samples from 89 patients with gastrointestinal diseases and 9 healthy controls for immunological assessment, stool samples for DNA extraction, library construction, sequencing, as well as clinical data for subsequent analysis.

Results

Regarding clinical characteristics, there were significant differences between the disease group and the healthy control (HC) group, particularly in terms of age, cancer antigen 125 (CA125), cancer antigen 199 (CA199), alpha-fetoprotein (AFP), total bilirubin (TBIL) and indirect bilirubin (IBIL). The intestinal disease (ID) group exhibited the highest IL-6 level, which significantly differed from the stomach disease (SD) group (p < 0.05). In comparing the HC with the ID groups, significant differences in abundance were detected across 46 species. The HC group displayed a greater abundance of Clostridiales, Clostridia, Firmicutes, Bifidobacterium, Bifidobacteriaceae, Bifidobacteriales, Actinobacteria, Veillonellaceae, Longum, Copri, Megamonas and Callidus than other species. Similarly, when comparing the HC with the SD groups, significant differences in abundance were identified among 49 species, with only one species that the Lachnospiraceae in the HC group exhibited a higher abundance than others. Furthermore, certain clinical characteristics, such as CA125, CA199, glucose (Glu), creatine kinase-MB (CKMB) and interleukin-22 (IL-22), displayed positive correlations with enriched gut species in the ID and SD groups, while exhibiting a negative correlation with the HC group.

Conclusion

The disturbance in human gut microbiota is intimately associated with the development and progression of gastrointestinal diseases. Moreover, the gut microbiota in the HC group was found more diverse than that in the ID and SD groups, and there were significant differences in microbial species among the three groups at different classification levels. Notably, a correlation was identified between specific clinical characteristics (e.g., CA125, CA199, Glu, CKMB and IL-22) and gut microbiota among patients with gastrointestinal diseases.

The critical role of gut-brain axis microbiome in mental disorders

The Gut-brain axis is a bidirectional neural and humoral signaling that plays an important role in mental disorders and intestinal health and connects them as well. Over the past decades, the gut microbiota has been explored as an important part of the gastrointestinal tract that plays a crucial role in the regulation of most functions of various human organs. The evidence shows several mediators such as short-chain fatty acids, peptides, and neurotransmitters that are produced by the gut may affect the brain's function directly or indirectly. Thus, dysregulation in this microbiome community can give rise to several diseases such as Parkinson's disease, depression, irritable bowel syndrome, and Alzheimer's disease. So, the interactions between the gut and the brain are significantly considered, and also it provides a prominent subject to investigate the causes of some diseases. In this article, we reviewed and focused on the role of the largest and most repetitive bacterial community and their relevance with some diseases that they have mentioned previously.

Randomised clinical trial: efficacy and safety of the live biotherapeutic product MRx1234 in patients with irritable bowel syndrome

BACKGROUND

MRx1234 is a live biotherapeutic product that contains a strain of Blautia hydrogenotrophica. It is in development for the treatment of irritable bowel syndrome (IBS).

AIMS

To assess the efficacy and safety of MRx1234 in patients with IBS with predominant constipation (IBS-C) or diarrhoea (IBS-D) METHODS: We conducted a multicentre, randomised, double-blind, placebo-controlled, phase 2 trial. Patients aged 18-70 years in two parallel cohorts (IBS-C; IBS-D) were randomised (1:1) to MRx1234 or placebo for 8 weeks. The primary efficacy endpoint was overall responder rate-a composite of improved bowel habit (IBS-C: stool frequency; IBS-D: stool consistency) and abdominal pain intensity-for ≥50% of the treatment period in each cohort. Statistical testing was at a one-sided 0.10 significance level.

RESULTS

Of 366 randomised patients (164 IBS-C; 202 IBS-D), 365 received any study medication (177 MRx1234, 188 placebo). Numerically, although not statistically significantly different, more patients who received MRx1234 than placebo were overall responders in the IBS-C (25.0% vs. 17.1%) and IBS-D (23.4% vs. 17.8%) cohorts. Similar results were observed in the additional combined cohort analysis (24.1% vs. 17.5%; p = 0.063). For the components of the primary endpoint, significantly more patients on MRx1234 than placebo reported improvement in bowel habit in the IBS-C, IBS-D and combined cohorts, while improvements in abdominal pain were observed in each cohort. The safety profile of MRx1234 was similar to placebo.

CONCLUSIONS

MRx1234 has the potential to become a novel, safe treatment option for patients with IBS-C or IBS-D, and for those who have mixed symptoms or transition between subtypes.

CLINICALTRIALS

gov #NCT03721107.

Global research trends in the microbiome related to irritable bowel syndrome: A bibliometric and visualized study

BACKGROUND

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder. Dysregulation of the gut–brain axis plays a central role in the pathophysiology of IBS. It is increasingly clear that the microbiome plays a key role in the development and normal functioning of the gut–brain axis.

AIM

To facilitate the identification of specific areas of focus that may be of relevance to future research. This study represents a bibliometric analysis of the literature pertaining to the microbiome in IBS to understand the development of this field.

METHODS

The data used in our bibliometric analysis were retrieved from the Scopus database. The terms related to IBS and microbiome were searched in titles or abstracts within the period of 2000–2019. VOSviewer software was used for data visualization.

RESULTS

A total of 13055 documents related to IBS were retrieved at the global level. There were 1872 scientific publications focused on the microbiome in IBS. There was a strong positive correlation between publication productivity related to IBS in all fields and productivity related to the microbiome in IBS (r = 0.951, P < 0.001). The United States was the most prolific country with 449 (24%) publications, followed by the United Kingdom (n = 176, 9.4%), China (n = 154, 8.2%), and Italy (n = 151, 8.1%). The h-index for all retrieved publications related to the microbiome in IBS was 138. The hot topics were stratified into four clusters: (1) The gut–brain axis related to IBS; (2) Clinical trials related to IBS and the microbiome; (3) Drug-mediated manipulation of the gut microbiome; and (4) The role of the altered composition of intestinal microbiota in IBS prevention.

CONCLUSION

This is the first study to evaluate and quantify global research productivity pertaining to the microbiome in IBS. The number of publications regarding the gut microbiota in IBS has continuously grown since 2013. This finding suggests that the future outlook for interventions targeting the gut microbiota in IBS remains promising.

An Intervention With Dance and Yoga for Girls With Functional Abdominal Pain Disorders (Just in TIME): Protocol for a Randomized Controlled Trial

BACKGROUND

Functional abdominal pain disorders (FAPDs) affect many children worldwide, predominantly girls, and cause considerable long-term negative consequences for individuals and society. Evidence-based and cost-effective treatments are therefore strongly needed. Physical activity has shown promising effects in the practical management of FAPDs. Dance and yoga are both popular activities that have been shown to provide significant psychological and pain-related benefits with minimal risk. The activities complement each other, in that dance involves dynamic, rhythmic physical activity, while yoga enhances relaxation and focus.

OBJECTIVE

This study aims to evaluate the effects of a dance and yoga intervention among girls aged 9 to 13 years with FAPDs.

METHODS

The study is a prospective randomized controlled trial among girls aged 9 to 13 years with functional abdominal pain, irritable bowel syndrome, or both. The target sample size was 150 girls randomized into 2 arms: an intervention arm that receives dance and yoga sessions twice weekly for 8 months and a control arm that receives standard care. Outcomes will be measured at baseline and after 4, 8, 12, and 24 months, and long-term follow-up will be conducted 5 years from baseline. Questionnaires, interviews, and biomarker measures, such as cortisol in saliva and fecal microbiota, will be used. The primary outcome is the proportion of girls in each group with reduced pain, as measured by the faces pain scale-revised in a pain diary, immediately after the intervention. Secondary outcomes are gastrointestinal symptoms, general health, mental health, stress, and physical activity. The study also includes qualitative evaluations and health economic analyses. This study was approved by the Regional Ethical Review Board in Uppsala (No. 2016/082 1-2).

RESULTS

Data collection began in October 2016. The intervention has been performed in 3 periods from 2016 through 2019. The final 5-year follow-up is anticipated to be completed by fall 2023.

CONCLUSIONS

Cost-effective and easily accessible interventions are warranted to reduce the negative consequences arising from FAPDs in young girls. Physical activity is an effective strategy, but intervention studies are needed to better understand what types of activities facilitate regular participation in this target group. The Just in TIME (Try, Identify, Move, and Enjoy) study will provide insights regarding the effectiveness of dance and yoga and is anticipated to contribute to the challenging work of reducing the burden of FAPDs for young girls.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT02920268); https://clinicaltrials.gov/ct2/show/NCT02920268.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/19748.

Upper Gastrointestinal Perforations: A Possible Danger of Antibiotic Overuse

BACKGROUND

The role of changes in gut microflora on upper gastrointestinal (UGI) perforations is not known. We conducted a retrospective case-control study to examine the relationship between antibiotic exposure-a proxy for microbiome modulation-and UGI perforations in a national sample.

METHODS

We queried a 5% random sample of Medicare (2009-2013) to identify patients ≥ 65 years old hospitalized with UGI (stomach or small intestine) perforations using International Classification of Diseases diagnosis codes. Cases with UGI perforations were matched with 4 controls, each based on age and sex. Exposure to outpatient antibiotics (0-30, 31-60, 61-90 days) prior to case patients' index hospitalization admission data was determined with Part D claims. Univariate and multivariable regression analyses were performed to evaluate the effect of antibiotic exposure on UGI perforation.

RESULTS

Overall, 504 cases and 2016 matched controls were identified. Compared to controls, more cases had antibiotic exposure 0-30 days (19% vs. 3%, p < 0.001) and 31-60 days (5% vs. 2%, p < 0.001) prior to admission. In adjusted analyses, antibiotic exposure 0-30 days prior to admission was associated with 6.8 increased odds of an UGI perforation (95% CI 4.8, 9.8); 31-60 days was associated with 1.9 increased odds (95% CI 1.1, 3.3); and 61-90 days was associated with 3.7 increased odds (95% CI 2.0, 6.9).

CONCLUSIONS

Recent outpatient antibiotic use, in particular in the preceding 30 days, is associated with UGI perforation among Medicare beneficiaries. Exposure to antibiotics, one of the most modifiable determinants of the microbiome, should be minimized in the outpatient setting.

Lactobacilli Supplemented with Larch Arabinogalactan and Colostrum Stimulates an Immune Response towards Peripheral NK Activation and Gut Tolerance

Probiotics possibly affect local and systemic immune reactions and maintain the intestinal immune homeostasis in healthy individuals and patients with diseases such as irritable bowel syndrome (IBS). In this single-center, blinded trial, we enrolled 40 individuals (20 patients with IBS and 20 healthy individuals) whose blood and fecal samples were collected before and after a 21-day administration of a product comprising Lactobacillus spp., larch arabinogalactan, and colostrum. The percentage of HLA-DR+ natural killer (NK) cells was higher in healthy individuals (p = 0.03) than in patients with IBS after product supplementation. In the fecal samples of patients with IBS, we observed a decline in IL-6, IFN-γ, TNF-α, and secretory IgA levels and, simultaneously, an increase in IL-10 and IL-17A levels after supplementation, although non-significant, whereas, in healthy individuals, we observed a significant decline in IL-6 and IFN-γ levels after supplementation (p < 0.001). Nevertheless, we observed a clinical improvement of symptoms in 65–75% of patients with IBS and the complete resolution of the initial symptoms in five of the 20 patients. We also observed a possible prophylactic effect by the inducing system antiviral impact accompanied by a trend for local immune tolerance in the gut in healthy individuals, where it is the desirable state.

The role of the microbiome for human health: from basic science to clinical applications

The 2017 annual symposium organized by the University Medical Center Groningen in The Netherlands focused on the role of the gut microbiome in human health and disease. Experts from academia and industry examined interactions of prebiotics, probiotics, or vitamins with the gut microbiome in health and disease, the development of the microbiome in early-life and the role of the microbiome on the gut–brain axis. The gut microbiota changes dramatically during pregnancy and intrinsic factors (such as stress), in addition to extrinsic factors (such as diet, and drugs) influence the composition and activity of the gut microbiome throughout life. Microbial metabolites, e.g. short-chain fatty acids affect gut–brain signaling and the immune response. The gut microbiota has a regulatory role on anxiety, mood, cognition and pain which is exerted via the gut–brain axis. Ingestion of prebiotics or probiotics has been used to treat a range of conditions including constipation, allergic reactions and infections in infancy, and IBS. Fecal microbiota transplantation (FMT) highly effective for treating recurrent Clostridium difficile infections. The gut microbiome affects virtually all aspects of human health, but the degree of scientific evidence, the models and technologies and the understanding of mechanisms of action vary considerably from one benefit area to the other. For a clinical practice to be broadly accepted, the mode of action, the therapeutic window, and potential side effects need to thoroughly be investigated. This calls for further coordinated state-of-the art research to better understand and document the human gut microbiome’s effects on human health.

Qualitative modelling of the interplay of inflammatory status and butyrate in the human gut: a hypotheses about robust bi-stability

Background

Gut microbiota interacts with the human gut in multiple ways. Microbiota composition is altered in inflamed gut conditions. Likewise, certain microbial fermentation products as well as the lipopolysaccharides of the outer membrane are examples of microbial products with opposing influences on gut epithelium inflammation status. This system of intricate interactions is known to play a core role in human gut inflammatory diseases. Here, we present and analyse a simplified model of bidirectional interaction between the microbiota and the host: in focus is butyrate as an example for a bacterial fermentation product with anti-inflammatory properties.

Results

We build a dynamical model based on an existing model of inflammatory regulation in gut epithelial cells. Our model introduces both butyrate as a bacterial product which counteracts inflammation, as well as bacterial LPS as a pro-inflammatory bacterial product. Moreover, we propose an extension of this model that also includes a feedback interaction towards bacterial composition. The analysis of these dynamical models shows robust bi-stability driven by butyrate concentrations in the gut. The extended model hints towards a further possible enforcement of the observed bi-stability via alteration of gut bacterial composition. A theoretical perspective on the stability of the described switch-like character is discussed.

Conclusions

Interpreting the results of this qualitative model allows formulating hypotheses about the switch-like character of inflammatory regulation in the gut epithelium, involving bacterial products as constitutive parts of the system. We also speculate about possible explanations for observed bimodal distributions in bacterial compositions in the human gut. The switch-like behaviour of the system proved to be mostly independent of parameter choices. Further implications of the qualitative character of our modeling approach for the robustness of the proposed hypotheses are discussed, as well as the pronounced role of butyrate compared to other inflammatory regulators, especially LPS, NF- κB and cytokines.

Electronic supplementary material

The online version of this article (10.1186/s12918-018-0667-6) contains supplementary material, which is available to authorized users.

Bile acids and FXR in functional gastrointestinal disorders

Functional gastrointestinal disorders (FGIDs), such as irritable bowel syndrome (IBS) and chronic constipation (CC), are commonly diagnosed conditions in clinical practice which create a substantial global burden. Since the farnesoid X receptor (FXR) and bile acids (BAs) are responsible for maintaining homeostasis in the GI tract, any disturbances in the expression of FXR or the composition of BAs may contribute to the development of the GI symptoms. Alterations in the mechanism of action of FXR directly affect the BAs pool and account for increased intestinal permeability and changes in abundance and diversity of gut microbiota leading to intestinal dysmotility. Current review focuses on the correlation between the FXR, BAs and the composition of gut microbiota and its influence on the occurrence of GI symptoms in FGIDs.

Consensus report: faecal microbiota transfer - clinical applications and procedures

BACKGROUND

Faecal microbiota transplantation or transfer (FMT) aims at replacing or reinforcing the gut microbiota of a patient with the microbiota from a healthy donor. Not many controlled or randomised studies have been published evaluating the use of FMT for other diseases than Clostridium difficile infection, making it difficult for clinicians to decide on a suitable indication.

AIM

To provide an expert consensus on current clinical indications, applications and methodological aspects of FMT.

METHODS

Well-acknowledged experts from various countries in Europe have contributed to this article. After literature review, consensus has been achieved by repetitive circulation of the statements and the full manuscript among all authors with intermittent adaptation to comments (using a modified Delphi process). Levels of evidence and agreement were rated according to the GRADE system. Consensus was defined a priori as agreement by at least 75% of the authors.

RESULTS

Key recommendations include the use of FMT in recurrent C. difficile infection characterised by at least two previous standard treatments without persistent cure, as well as its consideration in severe and severe-complicated C. difficile infection as an alternative to total colectomy in case of early failure of antimicrobial therapy. FMT in inflammatory bowel diseases (IBD), irritable bowel syndrome (IBS) and metabolic syndrome should only be performed in research settings.

CONCLUSIONS

Faecal microbiota transplantation or transfer is a promising treatment for a variety of diseases in which the intestinal microbiota is disturbed. For indications other than C. difficile infection, more evidence is needed before more concrete recommendations can be made.

Can probiotics modulate human disease by impacting intestinal barrier function?

Intestinal barrier integrity is a prerequisite for homeostasis of mucosal function, which is balanced to maximise absorptive capacity, while maintaining efficient defensive reactions against chemical and microbial challenges. Evidence is mounting that disruption of epithelial barrier integrity is one of the major aetiological factors associated with several gastrointestinal diseases, including infection by pathogens, obesity and diabetes, necrotising enterocolitis, irritable bowel syndrome and inflammatory bowel disease. The notion that specific probiotic bacterial strains can affect barrier integrity fuelled research in which in vitro cell lines, animal models and clinical trials are used to assess whether probiotics can revert the diseased state back to homeostasis and health. This review catalogues and categorises the lines of evidence available in literature for the role of probiotics in epithelial integrity and, consequently, their beneficial effect for the reduction of gastrointestinal disease symptoms.

Human Intestinal Barrier Function in Health and Disease

The gastrointestinal tract consists of an enormous surface area that is optimized to efficiently absorb nutrients, water, and electrolytes from food. At the same time, it needs to provide a tight barrier against the ingress of harmful substances, and protect against a reaction to omnipresent harmless compounds. A dysfunctional intestinal barrier is associated with various diseases and disorders. In this review, the role of intestinal permeability in common disorders such as infections with intestinal pathogens, inflammatory bowel disease, irritable bowel syndrome, obesity, celiac disease, non-celiac gluten sensitivity, and food allergies will be discussed. In addition, the effect of the frequently prescribed drugs proton pump inhibitors and non-steroidal anti-inflammatory drugs on intestinal permeability, as well as commonly used methods to assess barrier function will be reviewed.

Mechanistic and Technical Challenges in Studying the Human Microbiome and Cancer Epidemiology

This article reviews the significance of the microbiome in cancer epidemiology, mechanistic and technical challenges in the field, and characterization of the microbiome in different tumor types to identify biomarkers of risk, progression, and prognosis. Publications on the microbiome and cancer epidemiology were reviewed to analyze sample collection and processing, microbiome taxa characterization by 16S ribosomal RNA sequencing, and microbiome metabolite characterization (metabotyping) by nuclear magnetic resonance and mass spectrometry. The analysis identified methodology types, research design, sample types, and issues in integrating data from different platforms. Aerodigestive cancer epidemiology studies conducted by different groups demonstrated the significance of microbiome information in developing approaches to improve health. Challenges exist in sample preparation and processing (eg, standardization of methods for collection and analysis). These challenges relate to technology, data integration from "omics" studies, inherent bias in primer selection during 16S ribosomal RNA sequencing, the need for large consortia with well-characterized biospecimens, cause and effect issues, resilience of microbiota to exposure events (requires longitudinal studies), and expanding studies for fungal and viral diversity (most studies used bacterial 16S ribosomal RNA sequencing for microbiota characterization). Despite these challenges, microbiome and cancer epidemiology studies are significant and may facilitate cancer risk assessment, diagnosis, and prognosis. In the future, clinical trials likely will use microbiota modifications to improve the efficacy of existing treatments.

Effects of synbiotic fermented milk containing Lactobacillus acidophilus La-5 and Bifidobacterium animalis ssp. lactis BB-12 on the fecal microbiota of adults with irritable bowel syndrome: A randomized double-blind, placebo-controlled trial

We conducted a randomized double-blind, placebo-controlled multicentric study to investigate the influence of a synbiotic fermented milk on the fecal microbiota composition of 30 adults with irritable bowel syndrome (IBS). The synbiotic product contained Lactobacillus acidophilus La-5, Bifidobacterium animalis ssp. lactis BB-12, Streptococcus thermophilus, and dietary fiber (90% inulin, 10% oligofructose), and a heat-treated fermented milk without probiotic bacteria or dietary fiber served as placebo. Stool samples were collected after a run-in period, a 4-wk consumption period, and a 1-wk follow-up period, and were subjected to real-time PCR and 16S rDNA profiling by next-generation sequencing. After 4wk of synbiotic (11 subjects) or placebo (19 subjects) consumption, a greater increase in DNA specific for L. acidophilus La-5 and Bifidobacterium animalis ssp. lactis was detected in the feces of the synbiotic group compared with the placebo group by quantitative real-time PCR. After 1wk of follow-up, the content of L. acidophilus La-5 and B. animalis ssp. lactis decreased to levels close to initial levels. No significant changes with time or differences between the groups were observed for Lactobacillus, Enterobacteriaceae, Bifidobacterium, or all bacteria. The presence of viable BB-12- and La-5-like bacteria in the feces resulting from the intake of synbiotic product was confirmed by random amplification of polymorphic DNA (RAPD)-PCR. At the end of consumption period, the feces of all subjects assigned to the synbiotic group contained viable bacteria with a BB-12-like RAPD profile, and after 1wk of follow-up, BB-12-like bacteria remained in the feces of 87.5% of these subjects. The presence of La-5-like colonies was observed less frequently (37.5 and 25% of subjects, respectively). Next-generation sequencing of 16S rDNA amplicons revealed that only the percentage of sequences assigned to Strep. thermophilus was temporarily increased in both groups, whereas the global profile of the fecal microbiota of patients was not altered by consumption of the synbiotic or placebo. In conclusion, daily consumption of a synbiotic fermented milk had a short-term effect on the amount and proportion of La-5-like strains and B. animalis ssp. lactis in the fecal microbiome of IBS patients. Furthermore, both synbiotic and placebo products caused a temporary increase in fecal Strep. thermophilus.

Isolation and whole genome sequencing of a Ruminococcus-like bacterium, associated with irritable bowel syndrome

In our previous studies on the intestinal microbiota in irritable bowel syndrome (IBS), we identified a bacterial phylotype with higher abundance in patients suffering from diarrhea than in healthy controls. In the present work, we have isolated in pure culture strain RT94, belonging to this phylotype, determined its whole genome sequence and performed an extensive genomic analysis and phenotypical testing. This revealed strain RT94 to be a strict anaerobe apparently belonging to a novel species with only 94% similarity in the 16S rRNA gene sequence to the closest relatives Ruminococcus torques and Ruminococcus lactaris. The G + C content of strain RT94 is 45.2 mol% and the major long-chain cellular fatty acids are C16:0, C18:0 and C14:0. The isolate is metabolically versatile but not a mucus or cellulose utilizer. It produces acetate, ethanol, succinate, lactate and formate, but very little butyrate, as end products of glucose metabolism. The mechanisms underlying the association of strain RT94 with diarrhea-type IBS are discussed.

Gut microbiota role in irritable bowel syndrome: New therapeutic strategies

In the last decade the impressive expansion of our knowledge of the vast microbial community that resides in the human intestine, the gut microbiota, has provided support to the concept that a disturbed intestinal ecology might promote development and maintenance of symptoms in irritable bowel syndrome (IBS). As a correlate, manipulation of gut microbiota represents a new strategy for the treatment of this multifactorial disease. A number of attempts have been made to modulate the gut bacterial composition, following the idea that expansion of bacterial species considered as beneficial (Lactobacilli and Bifidobacteria) associated with the reduction of those considered harmful (Clostridium, Escherichia coli, Salmonella, Shigella and Pseudomonas) should attenuate IBS symptoms. In this conceptual framework, probiotics appear an attractive option in terms of both efficacy and safety, while prebiotics, synbiotics and antibiotics still need confirmation. Fecal transplant is an old treatment translated from the cure of intestinal infective pathologies that has recently gained a new life as therapeutic option for those patients with a disturbed gut ecosystem, but data on IBS are scanty and randomized, placebo-controlled studies are required.

Gut microbiota in health and disease: an overview focused on metabolic inflammation

In concern to the continuously rising global prevalence of obesity, diabetes and associated diseases, novel preventive and therapeutic approaches are urgently required. However, to explore and develop such innovative strategies, a meticulous comprehension of the biological basis of these diseases is extremely important. Past decade has witnessed an enormous amount of research investigation and advancement in the field of obesity, diabetes and metabolic syndrome, with the gut microbiota receiving a special focus in the triangle of nutrition, health and diseases. In particular, the role of gut microbiota in health and diseases has been one of the most vigorous and intriguing field of recent research; however, much still remains to be elucidated about its precise role in host metabolism and immune functions and its implication in the onset, progression as well as in the amelioration of metabolic ailments. Recent investigations have suggested a significant contribution of the gut microbiota in the regulation and impairment of energy homeostasis, thereby causing metabolic disorders, such as metabolic endotoxemia, insulin resistance and type 2 diabetes. Numerous inflammatory biomarkers have been found to be associated with obesity, diabetes and risk of other associated adverse outcomes, thereby suggesting that a persistent low-grade inflammatory response is a potential risk factor. In this milieu, this review intends to discuss potential evidences supporting the disturbance of the gut microbiota balance and the intestinal barrier permeability as a potential triggering factor for systemic inflammation in the onset and progression of obesity, type 2 diabetes and metabolic syndrome.

Hydrogen Sulfide in Physiology and Diseases of the Digestive Tract

Hydrogen sulfide (H₂S) is a Janus-faced molecule. On one hand, several toxic functions have been attributed to H₂S and exposure to high levels of this gas is extremely hazardous to health. On the other hand, H₂S delivery based clinical therapies are being developed to combat inflammation, visceral pain, oxidative stress related tissue injury, thrombosis and cancer. Since its discovery, H₂S has been found to have pleiotropic effects on physiology and health. H₂S is a gasotransmitter that exerts its effect on different systems, such as gastrointestinal, neuronal, cardiovascular, respiratory, renal, and hepatic systems. In the gastrointestinal tract, in addition to H₂S production by mammalian cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE), H₂S is also generated by the metabolic activity of resident gut microbes, mainly by colonic Sulfate-Reducing Bacteria (SRB) via a dissimilatory sulfate reduction (DSR) pathway. In the gut, H₂S regulates functions such as inflammation, ischemia/ reperfusion injury and motility. H₂S derived from gut microbes has been found to be associated with gastrointestinal disorders such as ulcerative colitis, Crohn’s disease and irritable bowel syndrome. This underscores the importance of gut microbes and their production of H₂S on host physiology and pathophysiology.

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.

Antibiotic-Induced Depletion of Murine Microbiota Induces Mild Inflammation and Changes in Toll-Like Receptor Patterns and Intestinal Motility

We examine the impact of changes in microbiota induced by antibiotics on intestinal motility, gut inflammatory response, and the function and expression of toll-like receptors (TLRs). Alterations in mice intestinal microbiota were induced by antibiotics and evaluated by q-PCR and DGGE analysis. Macroscopic and microscopic assessments of the intestine were performed in control and antibiotic-treated mice. TLR expression was determined in the intestine by q-RT-PCR. Fecal parameter measurements, intestinal transit, and muscle contractility studies were performed to evaluate alterations in intestinal motility. Antibiotics reduced the total bacterial quantity 1000-fold, and diversity was highly affected by treatment. Mice with microbiota depletion had less Peyer's patches, enlarged ceca, and mild gut inflammation. Treatment with antibiotics increased the expression of TLR4, TLR5, and TLR9 in the ileum and TLR3, TLR4, TLR6, TLR7, and TLR8 in the colon, and it reduced the expression of TLR2, TLR3, and TLR6 in the ileum and TLR2 and TLR9 in the colon. Antibiotics decreased fecal output, delayed the whole gut and colonic transit, and reduced the spontaneous contractions and the response to acetylcholine (ACh) in the ileum and colon. Activation of TLR4 by lipopolysaccharide (LPS) reverted the reduction of the spontaneous contractions induced by antibiotics in the ileum. Activation of TLR4 by LPS and TLR5 by flagellin reduced the response to ACh in the ileum in control mice. Our results confirm the role of the microbiota in the regulation of TLRs expression and shed light on the microbiota connection to motor intestinal alterations.

Effect of the probiotic strain Bifidobacterium animalis subsp. lactis, BB-12®, on defecation frequency in healthy subjects with low defecation frequency and abdominal discomfort: a randomised, double-blind, placebo-controlled, parallel-group trial

The aim of the present study was to investigate the effect of Bifidobacterium animalis subsp. lactis, BB-12^®, on two primary end points – defecation frequency and gastrointestinal (GI) well-being – in healthy adults with low defecation frequency and abdominal discomfort. A total of 1248 subjects were included in a randomised, double-blind, placebo-controlled trial. After a 2-week run-in period, subjects were randomised to 1 or 10 billion colony-forming units/d of the probiotic strain BB-12^® or a matching placebo capsule once daily for 4 weeks. Subjects completed a diary on bowel habits, relief of abdominal discomfort and symptoms. GI well-being, defined as global relief of abdominal discomfort, did not show significant differences. The OR for having a defecation frequency above baseline for ≥50 % of the time was 1·31 (95 % CI 0·98, 1·75), P=0·071, for probiotic treatment overall. Tightening the criteria for being a responder to an increase of ≥1 d/week for ≥50 % of the time resulted in an OR of 1·55 (95 % CI 1·22, 1·96), P=0·0003, for treatment overall. A treatment effect on average defecation frequency was found (P=0·0065), with the frequency being significantly higher compared with placebo at all weeks for probiotic treatment overall (all P<0·05). Effects on defecation frequency were similar for the two doses tested, suggesting that a ceiling effect was reached with the one billion dose. Overall, 4 weeks’ supplementation with the probiotic strain BB-12^® resulted in a clinically relevant benefit on defecation frequency. The results suggest that consumption of BB-12^® improves the GI health of individuals whose symptoms are not sufficiently severe to consult a doctor (ISRCTN18128385).

Symbiotics in irritable bowel syndrome--better than probiotics alone?

PURPOSE OF REVIEW

Irritable bowel syndrome (IBS) is a chronic gastrointestinal disorder associated with significant physical and psychological comorbidity. The etiology of the condition is uncertain but recent research suggests that the gut bacterial composition may play a role in its development. Therefore, manipulation of the intestinal microbiome by using probiotics and symbiotics has the potential to improve patient outcomes in IBS.

RECENT FINDINGS

Numerous randomized controlled trials suggest a benefit of probiotics in the management of IBS, with a significant reduction in the likelihood of symptoms persisting after therapy, and improvements in abdominal pain, bloating and flatulence when probiotics are compared with placebo. Evidence for the effect of probiotics on quality of life is conflicting. Relatively few randomized controlled trials have examined the effect of symbiotics on outcomes in IBS, but results thus far are promising.

SUMMARY

Probiotics appear to be beneficial in IBS. Data supporting the use of symbiotics is sparse. Whether symbiotics are superior to probiotics is unclear.

Fecal microbiota transplantation and bacterial consortium transplantation have comparable effects on the re-establishment of mucosal barrier function in mice with intestinal dysbiosis

Fecal microbiota transplantation (FMT) is a promising therapy, despite some reports of adverse side effects. Bacterial consortia transplantation (BCT) for targeted restoration of the intestinal ecosystem is considered a relatively safe and simple procedure. However, no systematic research has assessed the effects of FMT and BCT on immune responses of intestinal mucosal barrier in patients. We conducted complementary studies in animal models on the effects of FMT and BCT, and provide recommendations for improving the clinical outcomes of these treatments. To establish the dysbiosis model, male BALB/c mice were treated with ceftriaxone intra-gastrically for 7 days. After that, FMT and BCT were performed on ceftriaxone-treated mice for 3 consecutive days to rebuild the intestinal ecosystem. Post-FMT and post-BCT changes of the intestinal microbial community and mucosal barrier functions were investigated and compared. Disruption of intestinal microbial homeostasis impacted the integrity of mucosal epithelial layer, resulting in increased intestinal permeability. These outcomes were accompanied by overexpression of Muc2, significant decrease of SIgA secretion, and overproduction of defensins and inflammatory cytokines. After FMT and BCT, the intestinal microbiota recovered quickly, this was associated with better reconstruction of mucosal barriers and re-establishment of immune networks compared with spontaneous recovery (SR). Although based on a short-term study, our results suggest that FMT and BCT promote the re-establishment of intestinal microbial communities in mice with antibiotic-induced dysbiosis, and contribute to the temporal and spatial interactions between microbiota and mucosal barriers. The effects of BCT are comparable to that of FMT, especially in normalizing the intestinal levels of Muc2, SIgA, and defensins.

[Correlation of the microbiota and intestinal mucosa in the pathophysiology and treatment of irritable bowel, irritable eye, and irritable mind syndrome]

Accumulating clinical evidence supports co-morbidity of irritable bowel, irritable eye and irritable mind symptoms. Furthermore, perturbation of the microbiota-host symbiosis (dysbiosis) is considered a common pathogenic mechanism connecting gastrointestinal, ocular and neuropsychiatric symptoms. Consequently, maintaining or restoring microbiota-host symbiosis represents a new approach to treat these symptoms or to prevent their relapses. Current treatment approach assigned a primary role to live probiotics alone or in combination with prebiotics to enhance colonization of beneficial bacteria and to strengthen the symbiosis. However, several papers showed major benefits of heat-killed probiotics as compared to their live counterparts on both intestinal and systemic symptoms. Recently, in addition to killing probiotics, in a proof of concept study lysates (fragments) of probiotics in combination with vitamins A, B, D and omega 3 fatty acids were successfully tested. These findings suggested a conceptual change in the approach addressed to both the microbiota and host as targets for intervention.

Irritable bowel syndrome: contemporary nutrition management strategies

Irritable bowel syndrome is a complex disorder whose pathophysiology involves alterations in the enteric microbiota, visceral hypersensitivity, gut immune/barrier function, hypothalamic-pituitary-adrenal axis regulation, neurotransmitters, stress response, psychological factors, and more. The importance of diet in the management of irritable bowel syndrome has taken center stage in recent times as the literature validates the relationship of certain foods with the provocation of symptoms. Likewise, a number of elimination dietary programs have been successful in alleviating irritable bowel syndrome symptoms. Knowledge of the dietary management strategies for irritable bowel syndrome will help guide nutritionists and healthcare practitioners to deliver optimal outcomes. This tutorial reviews the nutrition management strategies for irritable bowel syndrome.