Industrialized human gut microbiota increases CD8+ T cells and mucus thickness in humanized mouse gut

Immigration to a highly industrialized nation has been associated with metabolic disease and simultaneous shifts in microbiota composition, but the underlying mechanisms are challenging to test in human studies. Here, we conducted a pilot study to assess the differential effects of human gut microbiota collected from the United States (US) and rural Thailand on the murine gut mucosa and immune system. Colonization of germ-free mice with microbiota from US individuals resulted in an increased accumulation of innate-like CD8 T cells in the small intestine lamina propria and intra-epithelial compartments when compared to colonization with microbiota from Thai individuals. Both TCRγδ and CD8αα T cells showed a marked increase in mice receiving Western microbiota and, interestingly, this phenotype was also associated with an increase in intestinal mucus thickness. Serendipitously, an accidentally infected group of mice corroborated this association between elevated inflammatory response and increased mucus thickness. These results suggest that Western-associated human gut microbes contribute to a pro-inflammatory immune response.

Genesis of fecal floatation is causally linked to gut microbial colonization in mice

The origin of fecal floatation phenomenon remains poorly understood. Following our serendipitous discovery of differences in buoyancy of feces from germ-free and conventional mice, we characterized microbial and physical properties of feces from germ-free and gut-colonized (conventional and conventionalized) mice. The gut-colonization associated differences were assessed in feces using DNA, bacterial-PCR, scanning electron microscopy, FACS, thermogravimetry and pycnometry. Based on the differences in buoyancy of feces, we developed levô in fimo test (LIFT) to distinguish sinking feces (sinkers) of germ-free mice from floating feces (floaters) of gut-colonized mice. By simultaneous tracking of microbiota densities and gut colonization kinetics in fecal transplanted mice, we provide first direct evidence of causal relationship between gut microbial colonization and fecal floatation. Rare discordance in LIFT and microbiota density indicated that enrichment of gasogenic gut colonizers may be necessary for fecal floatation. Finally, fecal metagenomics analysis of 'floaters' from conventional and syngeneic fecal transplanted mice identified colonization of > 10 gasogenic bacterial species including highly prevalent B. ovatus, an anaerobic commensal bacteria linked with flatulence and intestinal bowel diseases. The findings reported here will improve our understanding of food microbial biotransformation and gut microbial regulators of fecal floatation in human health and disease.

Gut microbial β-glucuronidases regulate host luminal proteases and are depleted in irritable bowel syndrome

Intestinal proteases mediate digestion and immune signaling, while increased gut proteolytic activity disrupts the intestinal barrier and generates visceral hypersensitivity, which in common in irritable bowel syndrome (IBS). However, the mechanisms controlling protease function are unclear. Here we show that members of the gut microbiota suppress intestinal proteolytic activity through production of unconjugated bilirubin. This occurs via microbial β-glucuronidase-mediated conversion of bilirubin conjugates. Metagenomic analysis of fecal samples from patients with post-infection IBS (n=52) revealed an altered gut microbiota composition, in particular a reduction in Alistipes taxa, and high gut proteolytic activity driven by specific host serine proteases compared to controls. Germ-free mice showed 10-fold higher proteolytic activity compared with conventional mice. Colonization with microbiota from high proteolytic activity IBS patients failed to suppress proteolytic activity in germ-free mice, but suppression of proteolytic activity was achieved with colonization using microbiota from healthy donors. High proteolytic activity mice had higher intestinal permeability, a higher relative abundance of Bacteroides and a reduction in Alistipes taxa compared with low proteolytic activity mice. High proteolytic activity IBS patients had lower fecal β-glucuronidase activity and end-products of bilirubin deconjugation. Mice treated with unconjugated bilirubin and β-glucuronidase overexpressing E. coli, which significantly reduced proteolytic activity, while inhibitors of microbial β-glucuronidases increased proteolytic activity. Together, these data define a disease-relevant mechanism of host-microbial interaction that maintains protease homeostasis in the gut.

Oxidative ornithine metabolism supports non-inflammatory C. difficile colonization

The enteric pathogen Clostridioides difficile (Cd) is responsible for a toxin-mediated infection that causes more than 200,000 recorded hospitalizations and 13,000 deaths in the United States every year1. However, Cd can colonize the gut in the absence of disease symptoms. Prevalence of asymptomatic colonization by toxigenic Cd in healthy populations is high; asymptomatic carriers are at increased risk of infection compared to noncolonized individuals and may be a reservoir for transmission of Cd infection2,3. Elucidating the molecular mechanisms by which Cd persists in the absence of disease is necessary for understanding pathogenesis and developing refined therapeutic strategies. Here, we show with gut microbiome metatranscriptomic analysis that mice recalcitrant to Cd infection and inflammation exhibit increased community-wide expression of arginine and ornithine metabolic pathways. To query Cd metabolism specifically, we leverage RNA sequencing in gnotobiotic mice infected with two wild-type strains (630 and R20291) and isogenic toxin-deficient mutants of these strains to differentiate inflammation-dependent versus -independent transcriptional states. A single operon encoding oxidative ornithine degradation is consistently upregulated across non-toxigenic Cd strains. Combining untargeted and targeted metabolomics with bacterial and host genetics, we demonstrate that both diet- and host-derived sources of ornithine provide a competitive advantage to Cd, suggesting a mechanism for Cd persistence within a non-inflammatory, healthy gut.

Abstract LB226: Maternal microbiome protects host against clonal de novo transformation, early onset systemic metastasis, and sudden death

The role of maternal microbiome transmitted at birth in cancer control is poorly understood. We have developed the first germfree B6 mouse model of breast cancer to investigate the role of the maternal microbiome in controlling oncogenic/metastatic frequencies of pro-oncogenic mammary cells. In this model, a DNA barcoded, primitive normal mouse mammary epithelial cell encoding MMTV-PyMT oncogene, was transplanted in large numbers into conventional or germfree B6 mice. Next-gen sequencing analysis of the DNA barcodes in tissues enabled us to clonally track millions of cells and measure the frequency and growth dynamics of clones at the primary site and their systemic distribution in circulation and all vital organs, generating an unprecedented high-definition map of cancer progression. Our results show that in conventional B6 mice with maternal microbial transmission at-birth, a small fraction (~0.01%) of transplanted cells transform de novo and produce slow growing, late-onset benign tumors (mouse median survival of > 1 year). In contrast, in germfree B6 mice, a >10-fold higher frequency of cells transform de novo and generate early-onset, highly aggressive metastatic clones, and are frequently associated with features leading to early euthanasia or endpoint (i.e. sudden death, intracardiac metastasis, paralysis, swollen abdomen, early multiorgan aggressive metastasis) (median survival of ~4 months; p<0.005 vs conventional mice). However, postnatal intervention with healthy fecal implants reconstituted gut microbiota in germfree B6 mice and significantly restored protective effects against cancer progression and sudden death, as well as improved quality/duration of life (median survival of >1 year; p<0.005 vs germfree mice; p=ns vs conventional mice). We found maternal microbial transmission fully protected against systemic metastasis. GC-MS analysis identified significantly distinct primary tumor metabolome associated with conventional (non-metastatic) mice vs germfree (metastatic) mice. Metagenomic analysis of fecal samples from a subset of tumor bearing conventional (non-metastatic) mice vs fecal implanted (late-onset, less aggressive metastatic) germfree mice identified significant association between metastasis and altered microbial communities. These findings using novel germfree mouse model of metastasis and cellular DNA barcoding technology provide first direct evidence that diverse microbial communities transmitted at birth play a critical role in protecting the host from clonal de novo mammary cell transformation and progression to systemic disease and thereby improving quality and duration of life.

Citation Format: Nagarajan Kannan, Syed Mohammed Musheer Aalam, Xiaojia Tang, Krishna Kalari, Purna Kashyap, Jun Chen, Stephen Johnson, Anguraj Sadanandam, Mark Sherman. Maternal microbiome protects host against clonal de novo transformation, early onset systemic metastasis, and sudden death [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB226.

Berberine alters gut microbial function through modulation of bile acids

BACKGROUND

Berberine (BBR) is a plant-based nutraceutical that has been used for millennia to treat diarrheal infections and in contemporary medicine to improve patient lipid profiles. Reduction in lipids, particularly cholesterol, is achieved partly through up-regulation of bile acid synthesis and excretion into the gastrointestinal tract (GI). The efficacy of BBR is also thought to be dependent on structural and functional alterations of the gut microbiome. However, knowledge of the effects of BBR on gut microbiome communities is currently lacking. Distinguishing indirect effects of BBR on bacteria through altered bile acid profiles is particularly important in understanding how dietary nutraceuticals alter the microbiome.

RESULTS

Germfree mice were colonized with a defined minimal gut bacterial consortium capable of functional bile acid metabolism (Bacteroides vulgatus, Bacteroides uniformis, Parabacteroides distasonis, Bilophila wadsworthia, Clostridium hylemonae, Clostridium hiranonis, Blautia producta; B4PC2). Multi-omics (bile acid metabolomics, 16S rDNA sequencing, cecal metatranscriptomics) were performed in order to provide a simple in vivo model from which to identify network-based correlations between bile acids and bacterial transcripts in the presence and absence of dietary BBR. Significant alterations in network topology and connectivity in function were observed, despite similarity in gut microbial alpha diversity (P = 0.30) and beta-diversity (P = 0.123) between control and BBR treatment. BBR increased cecal bile acid concentrations, (P < 0.05), most notably deoxycholic acid (DCA) (P < 0.001). Overall, analysis of transcriptomes and correlation networks indicates both bacterial species-specific responses to BBR, as well as functional commonalities among species, such as up-regulation of Na+/H+ antiporter, cell wall synthesis/repair, carbohydrate metabolism and amino acid metabolism. Bile acid concentrations in the GI tract increased significantly during BBR treatment and developed extensive correlation networks with expressed genes in the B4PC2 community.

CONCLUSIONS

This work has important implications for interpreting the effects of BBR on structure and function of the complex gut microbiome, which may lead to targeted pharmaceutical interventions aimed to achieve the positive physiological effects previously observed with BBR supplementation.

The 'in vivo lifestyle' of bile acid 7α-dehydroxylating bacteria: comparative genomics, metatranscriptomic, and bile acid metabolomics analysis of a defined microbial community in gnotobiotic mice

The formation of secondary bile acids by gut microbes is a current topic of considerable biomedical interest. However, a detailed understanding of the biology of anaerobic bacteria in the genus Clostridium that are capable of generating secondary bile acids is lacking. We therefore sought to determine the transcriptional responses of two prominent secondary bile acid producing bacteria, Clostridium hylemonae and Clostridium hiranonis to bile salts (in vitro) and the cecal environment of gnotobiotic mice. The genomes of C. hylemonae DSM 15053 and C. hiranonis DSM 13275 were closed, and found to encode 3,647 genes (3,584 protein-coding) and 2,363 predicted genes (of which 2,239 are protein-coding), respectively, and 1,035 orthologs were shared between C. hylemonae and C. hiranonis. RNA-Seq analysis was performed in growth medium alone, and in the presence of cholic acid (CA) and deoxycholic acid (DCA). Growth with CA resulted in differential expression (>0.58 log₂FC; FDR < 0.05) of 197 genes in C. hiranonis and 118 genes in C. hylemonae. The bile acid-inducible operons (bai) from each organism were highly upregulated in the presence of CA but not DCA. We then colonized germ-free mice with human gut bacterial isolates capable of metabolizing taurine-conjugated bile acids. This consortium included bile salt hydrolase-expressing Bacteroides uniformis ATCC 8492, Bacteroides vulgatus ATCC 8482, Parabacteroides distasonis DSM 20701, as well as taurine-respiring Bilophila wadsworthia DSM 11045, and deoxycholic/lithocholic acid generating Clostridium hylemonae DSM 15053 and Clostridium hiranonis DSM 13275. Butyrate and iso-bile acid-forming Blautia producta ATCC 27340 was also included. The Bacteroidetes made up 84.71% of 16S rDNA cecal reads, B. wadsworthia, constituted 14.7%, and the clostridia made up <.75% of 16S rDNA cecal reads. Bile acid metabolomics of the cecum, serum, and liver indicate that the synthetic community were capable of functional bile salt deconjugation, oxidation/isomerization, and 7α-dehydroxylation of bile acids. Cecal metatranscriptome analysis revealed expression of genes involved in metabolism of taurine-conjugated bile acids. The in vivo transcriptomes of C. hylemonae and C. hiranonis suggest fermentation of simple sugars and utilization of amino acids glycine and proline as electron acceptors. Genes predicted to be involved in trimethylamine (TMA) formation were also expressed.

Serine proteases as luminal mediators of intestinal barrier dysfunction and symptom severity in IBS

OBJECTIVE

The intestinal lumen contains several proteases. Our aim was to determine the role of faecal proteases in mediating barrier dysfunction and symptoms in IBS.

DESIGN

39 patients with IBS and 25 healthy volunteers completed questionnaires, assessments of in vivo permeability, ex vivo colonic barrier function in Ussing chambers, tight junction (TJ) proteins, ultrastructural morphology and 16 s sequencing of faecal microbiota rRNA. A casein-based assay was used to measure proteolytic activity (PA) in faecal supernatants (FSNs). Colonic barrier function was determined in mice (ex-germ free) humanised with microbial communities associated with different human PA states.

RESULTS

Patients with IBS had higher faecal PA than healthy volunteers. 8/20 postinfection IBS (PI-IBS) and 3/19 constipation- predominant IBS had high PA (>95th percentile). High-PA patients had more and looser bowel movements, greater symptom severity and higher in vivo and ex vivo colonic permeability. High-PA FSNs increased paracellular permeability, decreased occludin and increased phosphorylated myosin light chain (pMLC) expression. Serine but not cysteine protease inhibitor significantly blocked high-PA FSN effects on barrier. The effects on barrier were diminished by pharmacological or siRNA inhibition of protease activated receptor-2 (PAR-2). Patients with high-PA IBS had lower occludin expression, wider TJs on biopsies and reduced microbial diversity than patients with low PA. Mice humanised with high-PA IBS microbiota had greater in vivo permeability than those with low-PA microbiota.

CONCLUSION

A subset of patients with IBS, especially in PI-IBS, has substantially high faecal PA, greater symptoms, impaired barrier and reduced microbial diversity. Commensal microbiota affects luminal PA that can influence host barrier function.

Model of personalized postprandial glycemic response to food developed for an Israeli cohort predicts responses in Midwestern American individuals

BACKGROUND

Controlled glycemic concentrations are associated with a lower risk of conditions such as cardiovascular disease and diabetes. Models commonly used to guide interventions to control the glycemic response to food have low efficacy, with recent clinical guidelines arguing for the use of personalized approaches.

OBJECTIVE

We tested the efficacy of a predictive model of personalized postprandial glycemic response to foods that was developed with an Israeli cohort and that takes into consideration food components and specific features, including the microbiome, when applied to individuals from the Midwestern US.

DESIGN

We recruited 327 individuals for this study. Participants provided information regarding lifestyle, dietary habits, and health, as well as a stool sample for characterization of their gut microbiome. Participants were connected to continuous glucose monitors for 6 d, and the glycemic response to meals logged during this time was computed. The ability of a model trained using meals logged by the Israeli cohort to correctly predict glycemic responses in the Midwestern cohort was assessed and compared with that of a model trained using meals logged by both cohorts.

RESULTS

When trained on the Israeli cohort meals only, model performance for predicting responses of individuals in the Midwestern cohort was better (R = 0.596) than that observed for models taking into consideration the carbohydrate (R = 0.395) or calorie content of the meals alone (R = 0.336). Performance increased (R = 0.618) when the model was trained on meals from both cohorts, likely because of the observed differences in age distribution, diet, and microbiome.

CONCLUSIONS

We show that the modeling framework described in Zeevi et al. for an Israeli cohort is applicable to a Midwestern population, and outperforms commonly used approaches for the control of blood glucose responses. The adaptation of the model to the Midwestern cohort further enhances performance and is a promising means for designing effective nutritional interventions to control glycemic responses to foods. This trial was registered at clinicaltrials.gov as NCT02945514.

Assessment of a Personalized Approach to Predicting Postprandial Glycemic Responses to Food Among Individuals Without Diabetes

IMPORTANCE

Emerging evidence suggests that postprandial glycemic responses (PPGRs) to food may be influenced by and predicted according to characteristics unique to each individual, including anthropometric and microbiome variables. Interindividual diversity in PPGRs to food requires a personalized approach for the maintenance of healthy glycemic levels.

OBJECTIVES

To describe and predict the glycemic responses of individuals to a diverse array of foods using a model that considers the physiology and microbiome of the individual in addition to the characteristics of the foods consumed.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study using a personalized predictive model enrolled 327 individuals without diabetes from October 11, 2016, to December 13, 2017, in Minnesota and Florida to be part of a study lasting 6 days. The study measured anthropometric variables, described the gut microbial composition, and assessed blood glucose levels every 5 minutes using a continuous glucose monitor. Participants logged their food and activity information for the duration of the study. A predictive model of individualized PPGRs to a diverse array of foods was trained and applied.

MAIN OUTCOMES AND MEASURES

Glycemic responses to food consumed over 6 days for each participant. The predictive model of personalized PPGRs considered individual features, including the microbiome, in addition to the features of the foods consumed.

RESULTS

Postprandial response to the same foods varied across 327 individuals (mean [SD] age, 45 [12] years; 78.0% female). A model predicting each individual's responses to food that considers several individual factors in addition to food features had better overall performance (R = 0.62) than current standard-of-care approaches using nutritional content alone (R = 0.34 for calories and R = 0.40 for carbohydrates) to control postprandial glycemic levels.

CONCLUSIONS AND RELEVANCE

Across the cohort of adults without diabetes who were examined, a personalized predictive model that considers unique features of the individual, such as clinical characteristics, physiological variables, and the microbiome, in addition to nutrient content was more predictive than current dietary approaches that focus only on the calorie or carbohydrate content of foods. Providing individuals with tools to manage their glycemic responses to food based on personalized predictions of their PPGRs may allow them to maintain their blood glucose levels within limits associated with good health.

Association of Toll-like receptor 4 with hepatitis A virus infection in Assam

Hepatitis A virus (HAV) which causes liver disease is recognized by Toll-like receptors (TLRs) through the viral nucleic acid, initiating the host defense response. The study aims to analyze the role of TLR4 rs11536889 polymorphism in the pathogenesis of hepatitis A cases from Assam. There was significant correlation between TLR4 SNP G/C (rs11536889) and between acute viral hepatitis (AVH) A cases and controls. The correlation of the 3 different genotypes GG, GC and CC of TLR4 rs11536889 with the TLR4 mRNA expression level in all the HAV cases groups have been found to be statistically significant (p <0.001). TLR4 expression was most significantly upregulated in the acute HAV cases, HAV with cholestasis cases and even the HAV caused fulminant hepatitis failure (FHF) cases with the CC genotype of TLR4 rs11536889. The upregulation is mostly seen in the cases with the CC genotype of TLR4 rs11536889 and thus indicates that the mutant variant of TLR4 rs11536899 (CC) may have an effect on the expression of TLR4 at the transcription level. Our study did not show any significant association between AVH and HAV caused FHF (p = 0.32, OR = 0; p = 0.59, OR = 2.06 at 95% CI) among the genotypes GG, GC and CC. Our data suggest that TLR4 gene polymorphism rs11536889 may play a prominent role in HAV disease susceptibility and TLR4 expression in population from Assam.

Exercise training-induced modification of the gut microbiota persists after microbiota colonization and attenuates the response to chemically-induced colitis in gnotobiotic mice

Exercise reduces the risk of inflammatory disease by modulating a variety of tissue and cell types, including those within the gastrointestinal tract. Recent data indicates that exercise can also alter the gut microbiota, but little is known as to whether these changes affect host function. Here, we use a germ-free (GF) animal model to test whether exercise-induced modifications in the gut microbiota can directly affect host responses to microbiota colonization and chemically-induced colitis. Donor mice (n = 19) received access to a running wheel (n = 10) or remained without access (n = 9) for a period of six weeks. After euthanasia, cecal contents were pooled by activity treatment and transplanted into two separate cohorts of GF mice. Two experiments were then conducted. First, mice were euthanized five weeks after the microbiota transplant and tissues were collected for analysis. A second cohort of GF mice were colonized by donor microbiotas for four weeks before dextran-sodium-sulfate was administered to induce acute colitis, after which mice were euthanized for tissue analysis. We observed that microbial transplants from donor (exercised or control) mice led to differences in microbiota β-diversity, metabolite profiles, colon inflammation, and body mass in recipient mice five weeks after colonization. We also demonstrate that colonization of mice with a gut microbiota from exercise-trained mice led to an attenuated response to chemical colitis, evidenced by reduced colon shortening, attenuated mucus depletion and augmented expression of cytokines involved in tissue regeneration. Exercise-induced modifications in the gut microbiota can mediate host-microbial interactions with potentially beneficial outcomes for the host.

Metabolites and microbial composition of stool of women with fecal incontinence: Study design and methods

AIMS

This paper aims to report the rationale, design, and the specific methodology of an ongoing nested observational study that will determine the association of the metabolite and microbial composition of stool with fecal incontinence (FI).

METHODS

Eligible cases are participants with FI enrolled in the Controlling Anal Incontinence in women by Performing Anal Exercises with Biofeedback or Loperamide (CAPABLe) trial, a Pelvic Floor Disorders Network trial across eight clinical centers in the United States. Women of similar age without FI in the last year served as controls. All subject collected stool samples at the baseline and 24-week visit at home using a standardized collection method. Samples were shipped to and stored at centralized laboratories.

RESULTS

Specimen collection commenced December 2014 and was completed in May 2016. Fecal water and DNA has been extracted and is currently being analyzed by targeted metabolic profiling for stool metabolites and 16S rRNA gene sequencing for stool microbiota.

CONCLUSIONS

This article describes the rationale and design of a study that could provide a paradigm shift for the treatment of FI in women.

Refractive index variation in a free-standing diamond thin film induced by irradiation with fully transmitted high-energy protons

Ion irradiation is a widely employed tool to fabricate diamond micro- and nano-structures for applications in integrated photonics and quantum optics. In this context, it is essential to accurately assess the effect of ion-induced damage on the variation of the refractive index of the material, both to control the side effects in the fabrication process and possibly finely tune such variations. Several partially contradictory accounts have been provided on the effect of the ion irradiation on the refractive index of single crystal diamond. These discrepancies may be attributable to the fact that in all cases the ions are implanted in the bulk of the material, thus inducing a series of concurrent effects (volume expansion, stress, doping, etc.). Here we report the systematic characterization of the refractive index variations occurring in a 38 µm thin artificial diamond sample upon irradiation with high-energy (3 MeV and 5 MeV) protons. In this configuration the ions are fully transmitted through the sample, while inducing an almost uniform damage profile with depth. Therefore, our findings conclusively identify and accurately quantify the change in the material polarizability as a function of ion beam damage as the primary cause for the modification of its refractive index.

Beware! Are bacteria raising your oxidative stress?

Peptostreptococcus anaerobius, enriched in patients with colon cancer, induces cellular proliferation and dysplasia by toll-like receptor (TLR) 2- and TLR4-dependent increase in oxidative stress and cholesterol biosynthesis.

Tune into the rhythm of your bugs

Diurnal changes in gut microbiota localization and function alter host physiology through circadian epigenetic and transcriptional changes.

Bugs clogging your arteries? Take an anti-B2 shot

Commensal microbiota promote atherosclerosis by activating immune cells.

Don’t mix zinc lozenges and antibiotics

Dietary zinc increases susceptibility to Clostridium difficile infection following antibiotic use in mice.

Gut microbiome predictors of treatment response and recurrence in primary Clostridium difficile infection

BACKGROUND

Clostridium difficile infection (CDI) may not respond to initial therapy and frequently recurs, but predictors of response and recurrence are inconsistent. The impact of specific alterations in the gut microbiota determining treatment response and recurrence in patients with CDI is unknown.

AIM

To assess microbial signatures as predictors of treatment response and recurrence in CDI.

METHODS

Pre-treatment stool samples and clinical metadata including outcomes were collected prospectively from patients with their first CDI episode. Next generation 16s rRNA sequencing using MiSeq Illumina platform was performed and changes in microbial community structure were correlated with CDI outcomes.

RESULTS

Eighty-eight patients (median age 52.7 years, 60.2% female) were included. Treatment failure occurred in 12.5% and recurrence after response in 28.5%. Patients who responded to treatment had an increase in Ruminococcaceae, Rikenellaceae, Clostridiaceae, Bacteroides, Faecalibacterium and Rothia compared to nonresponders. A risk-index built from this panel of microbes differentiated responders (mean 0.07 ± 0.24) from nonresponders (0.52 ± 0.42; P = 0.0002). Receiver operating characteristic (ROC) curve demonstrated that risk-index was a strong predictor of treatment response with an area under the curve (AUC) of 0.85. Among clinical parameters tested, only proton pump inhibitor use predicted recurrent CDI (OR 3.75, 95% CI 1.27-11.1, P = 0.01). Patients with recurrent CDI had statistically significant increases in Veillonella, Enterobacteriaceae, Streptococci, Parabacteroides and Lachnospiraceae compared to patients without recurrence and a risk index was able to predict recurrence (AUC = 0.78).

CONCLUSION

Gut microbiota signatures predict treatment response and recurrence potentially, allowing identification of patients with Clostridium difficile infection that may benefit from early institution of alternate therapies.

High risk of post-infectious irritable bowel syndrome in patients with Clostridium difficile infection

BACKGROUND

Infectious enteritis is a commonly identified risk factor for irritable bowel syndrome (IBS). The incidence of Clostridium difficile infection (CDI) is on the rise. However, there is limited information on post-infectious IBS (PI-IBS) development following CDI and the host- and infection-related risk factors are not known.

AIM

To determine the incidence and risk factors for PI-IBS following CDI.

METHODS

A total of 684 cases of CDI identified from September 2012 to November 2013 were surveyed. Participants completed the Rome III IBS questionnaire and details on the CDI episode. Predictive modelling was done using logistic regression to evaluate risk factors for PI-IBS development.

RESULTS

A total of 315 CDI cases responded (46% response rate) and 205 were at-risk (no pre-CDI IBS) for PI-IBS development. A total of 52/205 (25%) met the Rome III criteria for IBS ≥6 months following CDI. IBS-mixed was most common followed by IBS-diarrhoea. In comparison to those without subsequent PI-IBS, greater percentage of PI-IBS patients had CDI symptoms >7 days, nausea, vomiting, abdominal pain during CDI, anxiety and a higher BMI. Using logistic regression, CDI symptoms >7 days [Odds ratio (OR): 2.96, P = 0.01], current anxiety (OR: 1.33, P < 0.0001) and a higher BMI (OR: 1.08, P = 0.004) were independently associated with PI-IBS development; blood in the stool during CDI was protective (OR: 0.44, P = 0.06).

CONCLUSIONS

In this cohort study, new-onset IBS is common after CDI. Longer CDI duration, current anxiety and higher BMI are associated with the diagnosis of C. difficile PI-IBS. This chronic sequela should be considered during active management and follow-up of patients with CDI.

Blow the germs away

Lugdunin, a new antibiotic produced by commensal bacteria in the nose, prevents pathogen colonization in humans.

Mechanosensitive ion channel Piezo2 is important for enterochromaffin cell response to mechanical forces

KEY POINTS

The gastrointestinal epithelial enterochromaffin (EC) cell synthesizes the vast majority of the body's serotonin. As a specialized mechanosensor, the EC cell releases this serotonin in response to mechanical forces. However, the molecular mechanism of EC cell mechanotransduction is unknown. In the present study, we show, for the first time, that the mechanosensitive ion channel Piezo2 is specifically expressed by the human and mouse EC cells. Activation of Piezo2 by mechanical forces results in a characteristic ionic current, the release of serotonin and stimulation of gastrointestinal secretion. Piezo2 inhibition by drugs or molecular knockdown decreases mechanosensitive currents, serotonin release and downstream physiological effects. The results of the present study suggest that the mechanosensitive ion channel Piezo2 is specifically expressed by the EC cells of the human and mouse small bowel and that it is important for EC cell mechanotransduction.

ABSTRACT

The enterochromaffin (EC) cell in the gastrointestinal (GI) epithelium is the source of nearly all systemic serotonin (5-hydroxytryptamine; 5-HT), which is an important neurotransmitter and endocrine, autocrine and paracrine hormone. The EC cell is a specialized mechanosensor, and it is well known that it releases 5-HT in response to mechanical forces. However, the EC cell mechanotransduction mechanism is unknown. The present study aimed to determine whether Piezo2 is involved in EC cell mechanosensation. Piezo2 mRNA was expressed in human jejunum and mouse mucosa from all segments of the small bowel. Piezo2 immunoreactivity localized specifically within EC cells of human and mouse small bowel epithelium. The EC cell model released 5-HT in response to stretch, and had Piezo2 mRNA and protein, as well as a mechanically-sensitive inward non-selective cation current characteristic of Piezo2. Both inward currents and 5-HT release were inhibited by Piezo2 small interfering RNA and antagonists (Gd³⁺ and D-GsMTx4). Jejunum mucosal pressure increased 5-HT release and short-circuit current via submucosal 5-HT3 and 5-HT4 receptors. Pressure-induced secretion was inhibited by the mechanosensitive ion channel antagonists gadolinium, ruthenium red and D-GsMTx4. We conclude that the EC cells in the human and mouse small bowel GI epithelium selectively express the mechanosensitive ion channel Piezo2, and also that activation of Piezo2 by force leads to inward currents, 5-HT release and an increase in mucosal secretion. Therefore, Piezo2 is critical to EC cell mechanosensitivity and downstream physiological effects.

Keep it moving

Colonic transit time correlates with microbial composition and metabolism in the gut.

I’ll have a turkey and cheese sandwich

Aryl hydrocarbon receptor ligands from bacterial metabolism of tryptophan can mitigate inflammation in the gut and central nervous system.

Microbes make the cancer

Changes in gut microbiota can promote intestinal tumor development by activating the epithelial calcineurin-NFAT pathway.

Update on Fecal Microbiota Transplantation 2015: Indications, Methodologies, Mechanisms, and Outlook

The community of microorganisms within the human gut (or microbiota) is critical to health and functions with a level of complexity comparable to that of an organ system. Alterations of this ecology (or dysbiosis) have been implicated in a number of disease states, and the prototypical example is Clostridium difficile infection (CDI). Fecal microbiota transplantation (FMT) has been demonstrated to durably alter the gut microbiota of the recipient and has shown efficacy in the treatment of patients with recurrent CDI. There is hope that FMT may eventually prove beneficial for the treatment of other diseases associated with alterations in gut microbiota, such as inflammatory bowel disease, irritable bowel syndrome, and metabolic syndrome, to name a few. Although the basic principles that underlie the mechanisms by which FMT shows therapeutic efficacy in CDI are becoming apparent, further research is needed to understand the possible role of FMT in these other conditions. Although relatively simple to perform, questions regarding both short-term and long-term safety as well as the complex and rapidly evolving regulatory landscape has limited widespread use. Future work will focus on establishing best practices and more robust safety data than exist currently, as well as refining FMT beyond current "whole-stool" transplants to increase safety and tolerability. Encapsulated formulations, full-spectrum stool-based products, and defined microbial consortia are all in the immediate future.

Nephrogenic systemic fibrosis following acute kidney injury and exposure to gadolinium

Nephrogenic systemic fibrosis (NSF) is a scleroderma-like systemic fibrosing condition of unknown etiology described in patients with renal insufficiency. Gadolinium exposure has been strongly associated with the development of NSF though the mechanism of such injury is not known. There are only few reported cases of NSF in the setting of acute renal failure and fewer reported cases where skin lesions developed after kidney function had returned to normal. We report a case of NSF in a young Hispanic woman with lupus nephritis but normal creatinine, who received gadolinium during a brief episode of prerenal acute kidney injury not requiring dialysis, secondary to sepsis.

Production of an NKT cell stimulatory glycosphingolipid by a prominent member of the human gut microbiota (55.22)

While the human gut microbiota are suspected to produce diffusible small molecules that modulate host signaling pathways, few of these molecules have been identified. Species of Bacteroides and their relatives, which often comprise &gt;50% of the gut community, are unusual among bacteria in that their membrane is rich in sphingolipids, a class of signaling molecules that play a key role in modulating the host immune response. Although known for more than three decades, the full repertoire of Bacteroides sphingolipids has not been defined or linked to immune modulatory activity. We report that Bacteroides fragilis produces the glycosphingolipid α-galactosylceramide (α-GalCerBf), which is structurally related to a sponge-derived glycosphingolipid (α-GalCer, KRN7000) that is the prototypical agonist of CD1d-restricted natural killer T (NKT) cells. We demonstrate that α-GalCerBf binds to CD1d and stimulates the production of cytokines by both mouse and human NKT cells. In vivo, we show that α-GalCerBf stimulates NKT cells to induce the activation markers CD25 and CD69, secrete IFN-γ in a CD1d-dependent manner and can prevent cyclophosphamide-induced diabetes. These data suggest that NKT cells directly sense an endogenous antigen produced by a prominent human gut symbiont, uncovering a new mechanism by which the gut microbiota modulate a subset of immune cells relevant to pathogen response and autoimmune disease.

Immunoreactivity for Ano1 detects depletion of Kit-positive interstitial cells of Cajal in patients with slow transit constipation

BACKGROUND

Depletion of interstitial cells of Cajal (ICC) is associated with several gastrointestinal (GI) motility disorders. Changes in ICC networks are usually detected by immunolabeling for the receptor tyrosine kinase Kit. Ano1 (DOG1 or TMEM16A) was recently described as a marker of ICC in GI tract. Our aim was to determine whether Ano1 immunoreactivity can be used as a reliable marker for ICC in tissues from patients with motility disorders.

METHODS

Four tissues from patients with normal ICC numbers and four tissues from patients with slow transit constipation and loss of Kit-positive ICC were studied. Interstitial cells of Cajal were detected by double labeling using antisera to Kit and Ano1.

KEY RESULTS

Both the processes and cell bodies of ICC in tissue from controls and slow transit constipation were immunoreactive for Ano1. There was a near complete overlap between Kit and Ano1 immunoreactivity. Tissues from patients with slow transit constipation contained significantly fewer Ano1-positive ICC than control tissues. The numbers of ICC identified by Ano1 and Kit immunoreactivity were nearly identical across the range of ICC numbers from an average of 1.64 to 7.05 cells per field and correlated with an R(2) value of 0.99.

CONCLUSIONS & INFERENCES

Ano1 is a reliable and sensitive marker for detecting changes in ICC networks in humans. Labeling with antibodies selective for Ano1 reproducibly detects depletion of Kit-positive ICC in tissues from patients with slow transit constipation.

Oxidative stress: key player in gastrointestinal complications of diabetes

Gastrointestinal dysmotility presenting as nausea, vomiting, bloating, diarrhea, constipation or abdominal pain is seen in diabetic patients. Oxidative stress has recently been recognized as a significant player in the pathogenesis of gastrointestinal complications of diabetes. In this issue of Neurogastroenterology and Motility, a team of investigators from Emory University led by Dr. Srinivasan present new evidence on the effect of oxidative stress in the diabetic colon. They show in diabetic patients, increased oxidative stress is associated with loss of the inhibitory neuronal subpopulation of enteric neurons, and that the neuronal loss can be reversed in-vitro by anti-oxidant lipoic acid. This new information adds to the accumulating evidence on the deleterious effect of oxidative stress in the gastrointestinal tract and highlights the opportunity to develop newer therapies focused on augmenting anti-oxidant defenses in the gastrointestinal tract in diabetic patients.

Diabetic gastroparesis: what we have learned and had to unlearn in the past 5 years

Diabetic gastroparesis is a disorder that occurs in both type 1 and type 2 diabetes. It is associated with considerable morbidity among these patients and with the resultant economic burden on the health system. It is primarily a disease seen in middle-aged women, although the increased predisposition in women still remains unexplained. Patients often present with nausea, vomiting, bloating, early satiety and abdominal pain. The pathogenesis of this complex disorder is still not well understood but involves abnormalities in multiple interacting cell types including the extrinsic nervous system, enteric nervous system, interstitial cells of Cajal (ICCs), smooth muscles and immune cells. The primary diagnostic test remains gastric scintigraphy, although other modalities such as breath test, capsule, ultrasound, MRI and single photon emission CT imaging show promise as alternative diagnostic modalities. The mainstay of treatment for diabetic gastroparesis has been antiemetics, prokinetics, nutritional support and pain control. In recent years, gastric stimulation has been used in refractory cases with nausea and vomiting. As we better understand the pathophysiology, newer treatment modalities are emerging with the aim of correcting the underlying defect. In this review, what has been learned about diabetic gastroparesis in the past 5 years is highlighted. The epidemiology, pathogenesis, diagnosis and treatment of diabetic gastroparesis are reviewed, focusing on the areas that are still controversial and those that require more studies. There is also a focus on advances in our understanding of the cellular changes that underlie development of diabetic gastroparesis, highlighting new opportunities for targeted treatment.

The D2/D3 agonist PD128907 (R-(+)-trans-3,4a,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano[4,3-b]-1,4-oxazin-9-ol) inhibits stimulated pyloric relaxation and spontaneous gastric emptying

BACKGROUND

Enteric neuronal dopamine (DA) inhibits acetylcholine release and gastric motility; this has been thought to be mediated via neuronal dopamine-2 receptor (D2R). The aim of this study was to investigate the modulation of gastric motility by the dopamine-3 receptor (D3R).

METHODS

Adult Sprague-Dawley rats were used. Pyloric relaxation in response to electrical field stimulation (EFS) was assessed in an organ bath in the presence of varying concentrations of a selective D3R agonist, PD128907. Gastric emptying was assessed by the phenol red method after rats were treated with varying doses of PD128907 or DA with and without a selective D3R antagonist, L-nafadotride.

RESULTS

Immunoblotting and immunohistochemistry confirmed the presence of D3R in the myenteric neurons in the rat pylorus. D3R activation reduced EFS-induced relaxation of pyloric strips in a dose-dependent manner and significantly delayed gastric emptying compared with vehicle. The D3R antagonist partially reversed the effect of DA on gastric emptying.

CONCLUSIONS

Our data suggest a novel role for D3R in regulation of gastric motility. D3R activation delays gastric emptying, an effect that may be due to impairment of pyloric relaxation. D3R antagonists therefore hold promise as useful agents for treatment of gastric motility disorders.

Enteric autoantibodies and gut motility disorders

Increasing evidence suggests that a subset of gastrointestinal motility disorders is associated with the presence of circulating antibodies. These antibodies are directed against various molecular targets, the best known being anti-neuronal nuclear antibody (ANNA-1 or anti-Hu) associated with paraneoplastic motility disorders. There is also evidence that the presence of distinct autoantibody profiles is associated with non-paraneoplastic motility disorders. This review focuses on the types of antibodies associated with gastrointestinal motility disorders and the significance of these antibodies. Algorithms are suggested for the work-up and treatment of patients with circulating antibodies associated with gastrointestinal motility disorders.

Magnetic resonance imaging anatomy of the anal canal

The anatomy of the anal canal is complex but well demonstrated by MRI. Understanding the anatomy is a prerequisite for determining the true site and the extent of pathology, especially for surgical workup. In this article, the MRI anatomy of the anal canal has been displayed using highlighted MRI images and line diagrams.

Osteogenic pulmonary metastases originating from a phyllodes tumour of the breast with osteosarcomatous differentiation

Malignant phyllodes tumour is an uncommon breast neoplasm which undergoes osteosarcomatous differentiation in 1.3% of cases. We document the plain film, CT and scintigraphic features of a case of pulmonary metastases from this rare primary tumour.

Antroduodenal manometry in children and adults with severe non-ulcer dyspepsia

BACKGROUND

Nonulcer dyspepsia is common in adults but has been recognized only recently in children.

METHODS

We compared signs, symptoms, and antroduodenal motility findings in 34 children and 35 adults with severe nonulcer dyspepsia.

RESULTS

Symptoms and signs were similar in the two groups. Ten children (29%) and one adult (3%) required tube feedings (p = 0.01). Abdominal surgery had been performed on 6 of 34 (18%) children and 18 of 35 adults (51%) (p < 0.01), without relief of symptoms. Esophageal manometry was abnormal in 5 of 23 (22%) children and 6 of 31 (19%) adults. Antroduodenal manometry was suggestive of neuropathy in 25 children and 26 adults and of myopathy in 3 children and 2 adults. Absence of phase 3 of the migrating motor complex was found in 4 children and 17 adults (p = 0.01). Antroduodenal manometry was normal in six children and seven adults.

CONCLUSION

Signs, symptoms, and discrete manometric abnormalities of childhood nonulcer dyspepsia resembled those of adult nonulcer dyspepsia. Manometric findings in nonulcer dyspepsia resembled those reported in chronic intestinal pseudo-obstruction, suggesting that these conditions are on a continuum of enteric neuromuscular diseases.