Structural differences in gut microbiota lead to altered hepatic expression of Drug Disposition Genes (DDG) in mice

Abstract

Hepatic drug metabolism is a major route of drug elimination, and it is mediated by multiple DDG. Varied expression and activity of DDG leads to inter‐individual variability in drug response. Results from previous studies comparing conventional and germ‐free mice showed that the presence of gut microbiota is associated with the differential hepatic DDG expression. The purpose of this study was to examine whether structural differences in gut microbiota lead to altered DDG expression in the liver. Male C57BL/6 mice from two different vendors [Jackson Laboratory (JAX) and Taconic Laboratory (TAC)] were cohoused with mice from the same or the other vendor for 4 weeks, creating the following 4 groups (n=6–7/group): JAX, TAC, coJAX (JAX mice cohoused with TAC), and coTAC (TAC mice cohoused with JAX). Mice were sacrificed and RNAs were extracted from the liver tissues. RNA sequencing was performed (n=3 mice/group), followed by bioinformatics analysis of 225 DDG. Principle component analysis of RNA‐sequencing data revealed that overall expression profiles of DDG were distinct in JAX mice while those for the other groups were similar to each other. A similar pattern was observed in results from previous gut microbiome analysis (i.e., 16S rRNA sequencing of fecal samples collected from the same group of mice), suggesting that the differential expression of DDG may be due to structural differences in gut microbiota. To identify DDG whose expression is influenced by gut microbiota, the RNA‐sequencing results of 225 DDG were further examined in livers from the 4 groups of mice. Preliminary statistical analysis revealed that 30 genes (14 phase I; 12 phase II; and 4 transporters) showed significantly different expression between JAX and TAC. The majority (i.e., 27) of these 30 genes showed no difference between coJAX and coTAC, suggesting that expression of these genes may be determined by differential gut microbiota. To further verify the RNA‐sequencing results, quantitative real‐time PCR was performed (n=6–7/group) for 9 genes that were selected based on biological significance and previously reported effects of gut microbiota on their expression. Among them, Cyp4a10 and Cyp4a14 showed 6.0‐ and 33.8‐fold higher expression in JAX, respectively, and Fmo5 showed 1.4‐fold lower expression in JAX. Our study suggests that structural differences in gut microbiota may underlie differential expression of DDG in the liver, potentially contributing to the inter‐individual variability in drug response.Support or Funding InformationThis study was supported by Chicago Biomedical Consortium.