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Background: Most studies on gut microbiome of irritable bowel syndrome (IBS) have focused on fecal microbiota, instead of mucosa-associated microbiota (MAM). Aims: The aim of this study wasto investigate the MAM in IBS patients including the difference in subtypes of IBS, namely, diarrhea-predominant IBS (IBS-D) and constipation-predominant IBS (IBS-C). Methods: Endoscopic brush samples were taken from terminal ileum and sigmoid colon of patients with IBS (17 IBS-D patients and 7 IBS-C patients) and 10 healthy controls. The MAM of samples was profiled by 16S rRNA gene amplicon sequencing. Potential changes in the MAM at the functional level were evaluated using PICRUSt software and the KEGG database. Results: There were no differences in MAM composition between terminal ileum and sigmoid colon according to β-diversity based on the UniFrac distance. In view of α-diversity, Shannon (evenness) but not Chao1 (richness) or observed operational taxonomic units tended to be lower in sigmoid colon MAM of IBS-C and IBS-D than the control group. The abundance of 4 genera in the sigmoid colon and 7 genera in the terminal ileum was significantly different among the 3 groups. Linear discriminant analysis effect size (LEfSe) showed that the genera of Ruminococcus, Akkermansia, Butyrivibrio, Methylobacterium, and Microbacterium and the family Erysipelotrichaceae were significantly higher in the IBS-C group, and the abundance of the genera Streptococcus, Acidaminococcus, Butyricicoccus, and Parvimonas was significantly higher in the IBS-D group. In addition, the proportion of genes responsible for the secretion system and LPS biosynthesis was significantly higher and that for methane metabolism, lysine biosynthesis, and enzyme families was significantly lower in the IBS-D group than in the IBS-C group. Conclusion: Dysbiosis pattern and the function of the microbiome seem to be different among subtypes of IBS, and MAM may play a crucial role in IBS symptom generation.

Background/Aim: The use of proton pump inhibitors (PPIs) is known to lead to hypergastrinemia; however, the data in patients with atrophic gastritis is still lacking. The aim of this study was to investigate the effects of long-term PPIs use on the gastrin levels in patients with atrophic gastritis and to determine factors affecting hypergastrinemia in long-term users of PPIs. Methods: Serum Helicobacter pylori IgG, gastrin and pepsinogen levels were measured. Atrophic gastritis was assessed by upper gastrointestinal endoscopies based on the Kimura-Takemoto classification and pepsinogen levels. CYP2C19 polymorphisms were assessed using DNA extracted from peripheral blood. Results: A total number of 382 patients (275 men and 107 women) were enrolled. Median serum gastrin levels were higher in PPI users than in non- users (234 vs. 113 pg/mL, p < 0.001) and in women than in men (252 vs. 155 pg/mL, p = 0.006). Gastrin levels were significantly associated with corpus atrophy only in the subgroup of non-users of PPIs. Multivariate analysis revealed that hypergastrinemia (over 150 pg/mL) was significantly associated with PPI use (OR 5.30; 95% CI 3.32–8.47), women (OR 2.22; 95% CI 1.33–3.72) and corpus atrophy (OR 1.82; 95% CI 1.14–2.90). Conclusion: PPI use, women and corpus atrophy were risk factors for hypergastrinemia. Gender, but not corpus atrophy, affected the gastrin levels in long-term users of PPIs.