Characterization of fecal deglucuronidation activity in healthy subjects and in patients treated with fecal microbiota transplantation

Gut bacterial β-glucuronidase (GUS) enzymes contribute to the intestinal toxicity and/or enterohepatic recycling of glucuronidated compounds by cleaving glucuronide conjugates excreted into the intestinal lumen. The activities and substrate specificities of several GUS isoforms have been recently described. However, the extent of intraindividual and interindividual variability in gut microbial deglucuronidation activity has remained poorly characterized. In this study, we used pan-GUS reporter substrates as well as drug and steroid glucuronides to study the deglucuronidation activities of fecal lysates produced from individual fecal samples from healthy donors (n = 12), and sequential samples collected from fecal microbiota transplantation (FMT) donors (n = 3) and patients with recurrent Clostridioides difficile infection who underwent FMT (n = 7). To determine relationships between fecal deglucuronidation activity and gut microbiota composition, we used 16S rRNA gene sequencing to characterize the healthy donors' fecal microbiotas. Although we observed considerable interindividual variability specifically in the processing of steroid glucuronides, intraindividual variability in the fecal deglucuronidation activity of FMT donors was relatively modest. We observed the female sex and Alistipes, Faecalibacterium, and Gemmiger taxa to be associated with higher deglucuronidation activity, whereas the abundance of Roseburia correlated negatively with deglucuronidation activity. In addition, the baseline deglucuronidation activity of patients with recurrent C. difficile infection was low but increased by FMT treatment. The results of this study further highlight deglucuronidation as a function of a healthy gut microbiota. Moreover, these results improve our understanding of deglucuronidation activity as a source of individual variability in the pharmacokinetics and pharmacodynamics of glucuronidated drugs that undergo enterohepatic recycling. SIGNIFICANCE STATEMENT: Gut microbial deglucuronidation rates of specific compounds may vary considerably between individuals. Deglucuronidation activity is relatively stable within healthy individuals for ≥1 year, but fecal microbiota transplantation can significantly alter the deglucuronidation activity of an individual.