Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jun 7, 2020; 26(21): 2768-2780
Published online Jun 7, 2020. doi: 10.3748/wjg.v26.i21.2768
Gut microbiome in primary sclerosing cholangitis: A review
Rebecca Little, Eytan Wine, Binita M Kamath, Anne M Griffiths, Amanda Ricciuto
Rebecca Little, Binita M Kamath, Anne M Griffiths, Amanda Ricciuto, Division of Gastroenterology, Hepatology and Nutrition, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
Eytan Wine, Division of Pediatric Gastroenterology and Nutrition, 7-142H Katz Group – Rexall Centre, University of Alberta, Edmonton, AB T6G 1C9, Canada
Author contributions: Ricciuto A contributed to paper conception, drafting the manuscript and revising the manuscript; Little R contributed to literature review and drafting the manuscript; Wine E, Griffiths AM and Kamath BM contributed to revising the manuscript; all authors approved the final manuscript as submitted.
Conflict-of-interest statement: Dr. Kamath BM reports - Consultant Shire, Albireo and Mirum since they make ASBT inhibitors. All other authors no disclosures to report.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Corresponding author: Amanda Ricciuto, MD, PhD, Assistant Professor, Division of Gastroenterology, Hepatology and Nutrition, The Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada.
Received: December 30, 2019
Peer-review started: December 30, 2019
First decision: January 13, 2020
Revised: March 27, 2020
Accepted: May 26, 2020
Article in press: May 26, 2020
Published online: June 7, 2020

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease characterized by biliary inflammation and stricturing. Exploration of the pathogenesis of PSC in light of its association with inflammatory bowel disease (IBD) and the “gut-liver” axis is an emerging area of interest. A growing number of studies have begun to elucidate the role of the gut microbiota, its metabolites and its influence on host immune responses in the development of PSC and PSC-IBD. Studies of the fecal microbiota have highlighted enriched levels of certain species, including Veillonella, Streptococcus and Enterococcus, among others. A heightened immune response to enteric dysbiosis and bacterial translocation have also been implicated. For example, Klebsiella pneumoniae strains derived from gnotobiotic mice transplanted with PSC-IBD microbiota were found to induce pore formation in human intestinal epithelial cells and enhanced Th17 responses. Gut microbes have additionally been hypothesized to be implicated in PSC pathogenesis through their role in the synthesis of various metabolites, including bile acids (BAs), which function as signaling molecules with important gut and hepatic effects. An expanded knowledge of the gut microbiome as it relates to PSC offers critical insight into the development of microbe-altering therapeutic interventions, such as antibiotics, nutritional interventions and fecal microbial transplantation. Some of these have already shown some preliminary evidence of benefit. Despite exciting progress in the field, much work remains to be done; areas that are particularly lacking include functional characterization of the microbiome and examination of pediatric populations. In this review, we summarize studies that have investigated the microbiome in PSC and PSC-IBD as well as putative mechanisms, including the potential role of metabolites, such as BAs. We then briefly review the evidence for interventions with microbe-altering properties for treating PSC.

Keywords: Bile acids, Colitis, Inflammatory bowel disease, Microbiome, Microbiota, Primary sclerosing cholangitis

Core tip: The frequent coexistence of primary sclerosing cholangitis (PSC) and inflammatory bowel disease (IBD) points to the gut-liver axis as central to pathogenesis. The gut microbiome is hypothesized to be involved. A growing body of literature supports that PSC and PSC-IBD are associated with a distinct gut microbiome and more recent animal studies suggest a potential causal relationship. Microbial metabolites, such as bile acids, may mediate the effects of the gut microbiota in PSC. A sound understanding of the PSC microbiome has the potential to inform the development of microbe-altering therapeutic interventions.