Mucin-derived O-glycans supplemented to diet mitigate diverse microbiota perturbations

Microbiota-accessible carbohydrates (MACs) are powerful modulators of microbiota composition and function. These substrates are often derived from diet, such as complex polysaccharides from plants or human milk oligosaccharides (HMOs) during breastfeeding. Host-derived mucus glycans on gut-secreted mucin proteins serve as a continuous endogenous source of MACs for resident microbes; here we investigate the potential role of purified, orally administered mucus glycans in maintaining a healthy microbial community. In this study, we liberated and purified O-linked glycans from porcine gastric mucin and assessed their efficacy in shaping the recovery of a perturbed microbiota in a mouse model. We found that porcine mucin glycans (PMGs) and HMOs enrich for taxonomically similar resident microbes. We demonstrate that PMGs aid recovery of the microbiota after antibiotic treatment, suppress Clostridium difficile abundance, delay the onset of diet-induced obesity, and increase the relative abundance of resident Akkermansia muciniphila. In silico analysis revealed that genes associated with mucus utilization are abundant and diverse in prevalent gut commensals and rare in enteric pathogens, consistent with these glycan-degrading capabilities being selected for during host development and throughout the evolution of the host-microbe relationship. Importantly, we identify mucus glycans as a novel class of prebiotic compounds that can be used to mitigate perturbations to the microbiota and provide benefits to host physiology.

Innovative gastric endoscopic muscle biopsy to identify all cell types, including myenteric neurons and interstitial cells of Cajal in patients with idiopathic gastroparesis: a feasibility study (with video)

BACKGROUND AND AIMS

The pathophysiology of some GI neuromuscular diseases remains largely unknown. This is in part due to the inability to obtain ample deep gastric wall biopsies that include the intermuscular layer of the muscularis propria (MP) to evaluate the enteric nervous system, interstitial cells of Cajal (ICCs), and related cells. We report on a novel technique for gastric endoscopic muscle biopsy (gEMB).

METHODS

Patients with idiopathic gastroparesis were prospectively enrolled in a feasibility study by using a novel "no hole" gEMB. Main outcome measures were technical success, adverse events, and histologic confirmation of the intermuscular layer, including myenteric neurons and ICC. The gEMB was a double resection clip-assist technique. A site was identified on the anterior wall of the gastric body as recommended by the International Working Group on histologic techniques. EMR was performed to unroof and expose the underlying MP. The exposed MP was then retracted into the cap of an over-the-scope clip. The clip was deployed, and the pseudopolyp of MP created was resected. This resulted in a no-hole gEMB.

RESULTS

Three patients with idiopathic gastroparesis underwent gEMB. Patients had severe delayed gastric emptying with a mean (± standard deviation [SD]) of 49 ± 16.8% of retained gastric contents at 4 hours. They had no history of gastric or small-bowel surgery and did not use steroids or other immunosuppressive drugs. The gEMB procedure was successfully performed, with no procedural adverse events. Postprocedural abdominal pain was controlled with nonsteroidal anti-inflammatory agents and opioid analgesics. Mean length of resected MP was 10.3 ± 1.5 mm. Mean procedure time was 25.7 ± 6 minutes. Hematoxylin and eosin (H&E) staining of tissue samples confirmed the presence of both inner circular and outer longitudinal muscle, as well as the intermuscular layer. H&E staining showed reduced myenteric ganglia in 1 patient. In 2 patients, specialized immunohistochemistry was performed, which showed a marked decrease in myenteric neurons as delineated by an antibody to protein gene product 9.5 and a severe decrease in ICC levels across the muscle layers. At 1 month follow-up, upper endoscopy showed a well-healed scar in 2 patients and minimal ulceration with a retained clip in 1 patient. CT of the abdomen confirmed the integrity of the gastric wall in all patients. Because of lack of an immune infiltrate in the resected samples, patients were not considered suitable for immunosuppressive or steroid therapy.

CONCLUSIONS

gEMB is feasible and easy to perform, with acquisition of tissue close to surgical samples to identify myenteric ganglia, ICCs, and multiple cell types. The ability to perform gEMB represents a paradigm shift in endoscopic tissue diagnosis of gastric neuromuscular pathologies.

Germ-free mice as a model to study effect of gut microbiota on host physiology

The alterations in resident gut microbiota seen in chronic gastrointestinal disorders have led to an increasing interest in the role of gut bacteria in maintaining intestinal barrier function. While acute alterations in colonic secretomotor function in response to pathogens have been well described, the effect of commensal bacteria on intestinal barrier function and colonic secretomotor function still remains poorly understood. Germ-free mice represent a model system to study effect of gut microbes on host gastrointestinal physiology. The study by Lomasney et al. represents an important step in this direction by demonstrating that the colonic secretomotor function is largely preserved in germ-free mice, hence making them a suitable model to study effect of gut microbiota on host function.

A metabolomic view of how the human gut microbiota impacts the host metabolome using humanized and gnotobiotic mice

Defining the functional status of host-associated microbial ecosystems has proven challenging owing to the vast number of predicted genes within the microbiome and relatively poor understanding of community dynamics and community-host interaction. Metabolomic approaches, in which a large number of small molecule metabolites can be defined in a biological sample, offer a promising avenue to 'fingerprint' microbiota functional status. Here, we examined the effects of the human gut microbiota on the fecal and urinary metabolome of a humanized (HUM) mouse using an optimized ultra performance liquid chromatography-mass spectrometry-based method. Differences between HUM and conventional mouse urine and fecal metabolomic profiles support host-specific aspects of the microbiota's metabolomic contribution, consistent with distinct microbial compositions. Comparison of microbiota composition and metabolome of mice humanized with different human donors revealed that the vast majority of metabolomic features observed in donor samples are produced in the corresponding HUM mice, and individual-specific features suggest 'personalized' aspects of functionality can be reconstituted in mice. Feeding the mice a defined, custom diet resulted in modification of the metabolite signatures, illustrating that host diet provides an avenue for altering gut microbiota functionality, which in turn can be monitored via metabolomics. Using a defined model microbiota consisting of one or two species, we show that simplified communities can drive major changes in the host metabolomic profile. Our results demonstrate that metabolomics constitutes a powerful avenue for functional characterization of the intestinal microbiota and its interaction with the host.

Body mass index and per capita income influence duodenal ulcer healing and H. pylori eradication whilst dietary factors play no part

BACKGROUND

The role of dietary and sociodemographic factors in the healing of duodenal ulcer following H. pylori eradication remains undefined.

AIM

To assess the role of diet, sociodemography and body mass index in the healing of duodenal ulcer and eradication of H. pylori.

METHODS

A cross-sectional study consisting of 67 consecutive duodenal ulcer patients was undertaken. Sociodemographic factors studied included age, sex, occupation, educational status, religion, type of family, number of family members, per capita income and residence (urban vs. rural). Personal habits studied included alcohol consumption and smoking. Regular dietary intake over a two-month period was assessed using the food frequency questionnaire. All patients had documented H. pylori infection at the time of inclusion and received standard triple eradication therapy. Follow-up endoscopy and testing for H. pylori were done 4 weeks after completion of eradication therapy.

RESULTS

The mean age of the 67 patients (60 male, 7 female) was 39.9+/-13.6 years. Healing of duodenal ulcer was documented in 51 patients. H. pylori infection was successfully eradicated in 31 patients but not in the other 36. There was no difference between the groups (Group A1: H. pylori eradicated, Group B1: H. pylori not eradicated) with regard to dietary and socio-demographic variables, except for BMI, which was significantly higher in patients in whom H. pylori had been eradicated. Per capita income was significantly higher in Group A2 (healed duodenal ulcer) as compared to Group B2 (duodenal ulcer not healed) while there was no difference in dietary and socio-demographic variables in these two groups.

CONCLUSION

We found that higher body mass index and higher per capita income were associated with successful H. pylori eradication and duodenal ulcer healing, respectively, and that diet had no role to play in either. Further epidemiological studies from different parts of India and studies that control for Helicobacter pylori are required to establish predictive factors.

Comparison of efficacy of pantoprazole alone versus pantoprazole plus mosapride in therapy of gastroesophageal reflux disease: a randomized trial

The present study aimed to compare the efficacy for the therapy of GERD of pantoprazole alone with a combination of pantoprazole and mosapride. The study was a prospective, randomized trial involving 68 patients suffering heartburn and/or regurgitation at least twice a week for 6 weeks. Sixty-one patients consented to be randomized to receive either pantoprazole 40 mg b.i.d. (n = 33, group A) or pantoprazole 40 mg b.i.d. plus mosapride 5 mg t.d.s. (n = 28, group B) for 8 weeks. Twenty-four-hour esophageal pH-metry and endoscopy were conducted at recruitment and endoscopy was repeated at 8 weeks in all the patients studied. There were no differences in symptomatic responses to therapy between the groups (69.7% vs 89.2%; P = 0.11). The mean symptom score after 8 weeks was significantly lower in group B (3.78 +/- 3.62 vs 1.67 +/- 2.09; P = 0.009). Nonerosive esophagitis was present in 29 patients. In patients with nonerosive GERD there was no significant difference in symptomatic response to either regimen (17/20 in group A and 7/9 in group B responded; P = 0.63). In erosive esophagitis, symptomatic responses occurred more frequently in group B, 18/19 (94.7%), than in group A, 6/13 (46.2%; P = 0.003). However endoscopic healing of esophagitis occurred equally with either regimen (6/11, 54.5% in group A; 12/17, 70.5% in group B; P = 0.44). In nonerosive GERD, the addition of mosapride offers no benefit over pantoprazole alone. A combination of pantoprazole and mosapride is more effective than pantoprazole alone in providing symptomatic relief to patients with erosive GERD.