Feeding the Gut–Liver Axis in PSC: What Makes It Different from IBD?

With great interest we read the article by Kummen et al1 on altered gut microbial metabolism of essential nutrients in primary sclerosing cholangitis (PSC). The authors are to be commended for this important and extensive exploratory work on the putative role of the gut–liver axis in PSC. Disentangling the interactions of the gut microbiota with its myriad of constituents and metabolic output and the liver is challenging and should start with proper delineation of both cases and controls. Given the strong association between PSC and inflammatory bowel disease (IBD), and more particularly, colitis with involvement of the cecum/ascending colon,2 identifying which microbiome compositional and/or metabolic pathway differences exist between PSC/IBD versus properly matched IBD-only controls on top of the immanent dysbiotic changes owing to IBD seems to be crucial.