Altered Bile Acid and Pouch Microbiota Composition in Patients With Chronic Pouchitis

Abstract

Background: Patients with ulcerative colitis and total abdominal proctocolectomy with ileal pouch-anal anastomosis have a 50% risk of pouchitis and a 5% to 10% risk of chronic pouchitis.

Aims: The goal of the study was to compare pouch microbiota and stool bile acid composition in patients with chronic pouchitis, chronic pouchitis and primary sclerosing cholangitis, and normal pouch.

Methods: Patients with ulcerative colitis and ileal pouch-anal anastomosis were recruited from March 20, 2014, to August 6, 2019, and categorized into normal pouch, chronic pouchitis, and chronic pouchitis/primary sclerosing cholangitis groups. Stool samples were subjected to bile acid quantification and 16S rRNA gene sequencing. Statistical comparisons of absolute bile acid abundance and pouch microbiota α-diversity, β-diversity, and taxa abundance were performed among the patient groups.

Results: A total of 51 samples were analyzed. Both α-diversity (P = .01, species richness) and β-diversity (P = .001) significantly differed among groups. Lithocholic acid was significantly lower in patients with chronic pouchitis/primary sclerosing cholangitis than in those with chronic pouchitis (P = .01) or normal pouch (P = .03). Decreased α-diversity was associated with an increased primary to secondary bile acid ratio (P = .002), which was also associated with changes in β-diversity (P = .006).

Conclusions: Pouch microbiota α- and β-diversity differed among patients with normal pouch, chronic pouchitis, and chronic pouchitis/primary sclerosing cholangitis. Lithocholic acid level and primary to secondary bile acid ratio were highly associated with pouch microbiota richness, structure, and composition. These findings emphasize the associations between pouch microbiota and bile acid composition in dysbiosis and altered metabolism, suggesting that secondary bile acids are decreased in chronic pouchitis.

Keywords: inflammatory bowel disease; microbiome; pouchitis; primary sclerosing cholangitis; ulcerative colitis.

Figure 1.

Analysis of α-diversity of pouch microbiota. A and B, Species richness measured by the observed amplicon sequencing variant (ASV) number (P = .01, linear regression). C and D, Overall diversity measured by the Shannon index (P = .047, linear regression). Rarefaction curves (A, C) and rarefied data at 2476 reads (B, D) are shown. Study groups included patients with chronic pouchitis (CP), with CP and primary sclerosing cholangitis (CP/PSC), and with a normal pouch (normal).

Figure 2.

Analysis of β-diversity according to 4 distance measures. A, Unweighted UniFrac distance. B, Generalized UniFrac distance. C, Weighted UniFrac distance. D, Bray-Curtis distance. Omnibus P values determined with permutational multivariate analysis of variance. Study groups included patients with chronic pouchitis (CP), with CP and primary sclerosing cholangitis (CP/PSC), and with a normal pouch (normal). Abbreviations: PC1 indicates principal component 1; PC2, principal component 2.

Figure 3.

Absolute abundance of bile acids among study groups. Study groups included patients with chronic pouchitis (CP), with CP and primary sclerosing cholangitis (CP/PSC), and with a normal pouch (normal). Abbreviations: CA, cholic acid; CDCA, chenodeoxycholic acid; DCA, deoxycholic acid; LCA, lithocholic acid; PBA, total primary bile acids; PSR, primary to secondary bile acid ratio; SBA, total secondary bile acids; UDCA, ursodeoxycholic acid.

Figure 4.

Association of pouch microbiota composition with individual bile acids. A, Lithocholic acid (LCA) and species richness. B, LCA and overall diversity by Shannon index. C, LCA and β-diversity according to UniFrac distance. D, Chenodeoxycholic acid (CDCA) and species richness. E, Cholic acid (CA) and species richness. F, CA and β-diversity according to UniFrac distance. Associations were tested with multiple linear regression, and omnibus P values were determined with permutational multivariate analysis of variance. Abbreviations: ASV, amplicon sequencing variant; PC1, principal component 1; PC2, principal component 2.

Figure 5.

Association of pouch microbiota composition with primary to secondary ratio (PSR) of bile acids. A, Association of PSR with species richness measured by observed amplicon sequencing variant (ASV) number. B, Association of PSR with species richness according to Shannon index. C, Association of PSR with β-diversity measures. Associations were tested with multiple linear regression, and omnibus P values were determined with permutational multivariate analysis of variance. PC1 indicates principal component 1.