Longitudinal dynamics of fecal bile acids in pediatric patients with primary sclerosing cholangitis-ulcerative colitis (PSC-UC) undergoing oral vancomycin therapy (OVT)
Authors: Horvath Thomas , Engevik Melinda , Versalovic James , Haag Anthony , Devaraj Sridevi , Kellermayer Richard 
Published: May 2023

Background: Primary sclerosing cholangitis (PSC) is a rare cholestatic liver disease affecting ~1,500 pediatric patients in the US, with most also suffering from ulcerative colitis (PSC-UC), a subtype of chronic inflammatory bowel disease (IBD). Within ten years of diagnosis, many will develop clinical complications (50%) that may require liver transplantation (30%), and these patients have the highest lifetime risk of developing colorectal cancer amongst all IBD. There is currently no effective medical therapy to delay the progression of liver disease or the onset of clinical complications in PSC. Although the etiology of PSC is poorly understood, dysbiosis of the gut microbiome and bacterial-derived metabolites (i.e., bile acids (BAs) have been implicated in PSC. Given the potential for gut dysbiosis in PSC-UC pathogenesis, an empiric treatment with oral vancomycin therapy (OVT) has evolved and has shown some benefit in individual cases and small-uncontrolled case series. It remains unclear, however, how OVT affects the gut microbiome in this clinical setting. We have developed a targeted metabolomics method to study the dynamic response of fecal bile acid concentrations contained in stool specimens collected from pediatric patients with PSC-UC (pPSC-UC) in response to OVT. Longitudinal Study: An IRB-approved prospective longitudinal study (BCM-IRB# H-43759) was conducted at BCM/TCH to examine the fecal and salivary microbiome dynamics in pPSC-UC. The study included the following four groups: i) healthy controls (HC, n=18); ii) UC patients without PSC (UC, n=17); iii) pPSC-UC patients receiving OVT (VPUC, n=10); and, iv) pPSC-UC patients without OVT, i.e., “OVT-free controls” (PUC, n=5). Stool and salivary samples were collected from all subjects at study initiation, and for most (depending on retention in the study) at months 3, 6, 9, and 12; additional collections were made on days 2 and 7 for the VPUC study subjects after starting oral vancomycin therapy (250mg bid, or 125mg qid). M aterials & Results: 500 mg of stool was processed for microbiome analysis using the OMNIgene® GUT stool collection kit, and the bile acids were extracted from the resultant fecal slurry using an organic solvent system. The bile acid (e.g., CA, β-MCA, CDCA, DCA, UDCA, LCA, GCA, GCDCA, GDCA, GUDCA, GLCA, TLCA, TCA, TCDCA, TDCA, TUDCA) content of the extracted fecal sample extracts were quantified using a reverse-phase chromatography-tandem mass spectrometry (LC-MS/MS) method. In response to OVT therapy, we observed increasing fecal levels of several non-conjugated primary bile acids (CA, CDCA) and decreased levels in several secondary BAs (DCA & LCA) in the post-OVT fecal sample extracts. Conclusion: Our unprecedented cohort of longitudinal stool samples collected from pediatric patients with PSC-UC offers a unique opportunity to study the effects of OVT on the dynamics of a targeted set of BAs, which are bioactive metabolic products likely of functional relevance. Philanthropic support for the prospective, longitudinal pediatric PSC-UC study was provided by the Klaasmeyer family. Texas Children's Hospital Department of Pathology provides salary support to Texas Children's Microbiome Center-Metabolomics Lab staff, and purchased all of the reagents, the consumables and durable supplies, and the LC-MS/MS equipment described. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.