The intestine is an organ responsible for the absorption and metabolism of orally administered drugs. To predict pharmacokinetics behavior in the small intestine, it is necessary to examine the human intestinal expression profiles of the genes related to drug absorption, distribution, metabolism, and excretion (ADME). In this study, to obtain more accurate expression profiles in various regions of the human intestine, biopsy samples were collected from endoscopically noninflamed mucosa of the duodenum, jejunum, ileum, colon, and rectum from Japanese including Crohn's disease or ulcerative colitis patients, and both RNA-seq and quantitative proteomics analyses were performed. We also analyzed the expression of drug-metabolizing enzymes (cytochromes P450 (CYPs) and non-CYP enzymes), drug transporters, and nuclear receptors. Overall, the mRNA expression levels of these ADME-related genes correlated highly with the protein expression levels. The characteristics of the expression of ADME-related genes differed significantly between the small and large intestines, including the expression levels of CYP enzymes, which were higher and lower in the small and large intestines, respectively. Most CYPs were expressed dominantly in the small intestine, especially the jejunum, but were rarely expressed in the large intestine. On the other hand, non-CYP enzymes were expressed in the large intestine but at lower expression levels than in the small intestine. Moreover, the expression levels of drug metabolizing enzyme genes differed even between the proximal and distal small intestine. Transporters were expressed most highly in the ileum. The data in the present study will enhance understanding of the intestinal ADME of drug candidates and would be useful for drug discovery research.
Keywords: ADME-related genes; RNA-seq; proteomics; regional differences.