Dietary regulation of mouse intestinal P450 expression and drug metabolism

Variation in Expression of Cytochrome P450 3A Isoforms and Toxicological Effects: Endo- and Exogenous Substances as Regulatory Factors and Substrates

The CYP3A subfamily, which includes isoforms CYP3A4, CYP3A5, and CYP3A7 in humans, plays important roles in the metabolism of various endogenous and exogenous substances. Gene and protein expression of CYP3A4, CYP3A5, and CYP3A7 show large inter-individual differences, which are caused by many endogenous and exogenous factors. Inter-individual differences can cause negative outcomes, such as adverse drug events and disease development. Therefore, it is important to understand the variations in CYP3A expression caused by endo- and exogenous factors, as well as the variation in the metabolism and kinetics of endo- and exogenous substrates. In this review, we summarize the factors regulating CYP3A expression, such as bile acids, hormones, microRNA, inflammatory cytokines, drugs, environmental chemicals, and dietary factors. In addition, variations in CYP3A expression under pathological conditions, such as coronavirus disease 2019 and liver diseases, are described as examples of the physiological effects of endogenous factors. We also summarize endogenous and exogenous substrates metabolized by CYP3A isoforms, such as cholesterol, bile acids, hormones, arachidonic acid, vitamin D, and drugs. The relationship between the changes in the kinetics of these substrates and the toxicological effects in our bodies are discussed. The usefulness of these substrates and metabolites as endogenous biomarkers for CYP3A activity is also discussed. Notably, we focused on discrimination between CYP3A4, CYP3A5, and CYP3A7 to understand inter-individual differences in CYP3A expression and function.

Comparison of CYP Induction by Coleus forskohlii Extract and Recovery in the Small Intestine and Liver of Mice

We examined CYP induction and recovery at various doses of Coleus forskohlii extract (CFE) to assess potential drug interactions by a mechanism involving intestinal CYP. Mice were administered diets with various doses of CFE up to 0.5% (equivalent to 700-800 mg/kg body weight) for 2 weeks, then CFE was withdrawn for 3 d. Changes in CYP activities and mRNA expression in the small intestine and liver were then evaluated. CFE induced CYP in the small intestine at a higher dose compared to the liver; CYP3A was induced at 0.5% and 0.005% CFE in the small intestine and liver, respectively. There was no sex difference in CFE dose for CYP induction. CYP induction quickly reverted after withdrawal of CFE, especially for CYP3A, in the small intestine; whereas, a gradual recovery was observed in the liver. In conclusion, CFE induced CYP in the small intestine and liver; however, a higher dose of CFE was needed for the small intestine. Moreover, the induction was soon recovered, suggesting actual interactions of CFE with prescription drugs are unlikely to occur through CYP in the small intestine.

Coordinated cytochrome P450 expression in mouse liver and intestine under different dietary conditions during liver regeneration after partial hepatectomy

Liver resection is performed to remove tumors in patients with liver cancer, but the procedure's suitability depends on the regenerative ability of the liver. It is important to consider the effects of exogenous factors, such as diets, on liver regeneration for the recovery of function. The evaluation of drug metabolism during liver regeneration is also necessary because liver dysfunction is generally observed after the operation. Here, we investigated the influence of a purified diet (AIN-93G) on liver regeneration and changes in the mRNA expression of several cytochrome P450 (CYP) isoforms in the liver and small intestine using a two-thirds partial hepatectomy (PH) mouse model fed with a standard diet (MF) and a purified diet. Liver regeneration was significantly delayed in the purified diet group relative to that in the standard diet group. The liver Cyp2c55 and Cyp3a11 expression was increased at 3 day after PH especially in the purified diet group. Bile acid may partly cause the differences in liver regeneration and CYP expression between two types of diets. On the other hand, Cyp3a13 expression in the small intestine was transiently increased at day 1 after PH in both diet groups. The findings suggest that compensatory induction of the CYP expression occurred in the small intestine after attenuation of drug metabolism potential in the liver. The present results highlight the importance of the relationship between liver regeneration, drug metabolism, and exogenous factors for the effective treatment, including surgery and medication, in patients after liver resection or transplantation.

Cryopreserved Human Intestinal Mucosal Epithelium: A Novel In Vitro Experimental System for the Evaluation of Enteric Drug Metabolism, Cytochrome P450 Induction, and Enterotoxicity

We report here a novel in vitro enteric experimental system, cryopreserved human intestinal mucosa (CHIM), for the evaluation of enteric drug metabolism, drug-drug interaction, drug toxicity, and pharmacology. CHIM was isolated from the small intestines of four human donors. The small intestines were first dissected into the duodenum, jejunum, and ileum, followed by collagenase digestion of the intestinal lumen. The isolated mucosa was gently homogenized to yield multiple cellular fragments, which were then cryopreserved in a programmable liquid cell freezer and stored in liquid nitrogen. After thawing and recovery, CHIM retained robust cytochrome P450 (P450) and non-P450 drug-metabolizing enzyme activities and demonstrated dose-dependent induction of transcription of CYP24A1 (approximately 300-fold) and CYP3A4 (approximately 3-fold) by vitamin D₃ as well as induction of CYP3A4 (approximately 3-fold) by rifampin after 24 hours of treatment. Dose-dependent decreases in cell viability quantified by cellular ATP content were observed for naproxen and acetaminophen, with higher enterotoxicity observed for naproxen, consistent with that observed in humans in vivo. These results suggest that CHIM may be a useful in vitro experimental model for the evaluation of enteric drug properties, including drug metabolism, drug-drug interactions, and drug toxicity.

An update on the role of intestinal cytochrome P450 enzymes in drug disposition

Oral administration is the most commonly used route for drug treatment. Intestinal cytochrome P450 (CYP)-mediated metabolism can eliminate a large proportion of some orally administered drugs before they reach systemic circulation, while leaving the passage of other drugs unimpeded. A better understanding of the ability of intestinal P450 enzymes to metabolize various clinical drugs in both humans and preclinical animal species, including the identification of the CYP enzymes expressed, their regulation, and the relative importance of intestinal metabolism compared to hepatic metabolism, is important for improving bioavailability of current drugs and new drugs in development. Here, we briefly review the expression of drug-metabolizing P450 enzymes in the small intestine of humans and several preclinical animal species, and provide an update of the various factors or events that regulate intestinal P450 expression, including a cross talk between the liver and the intestine. We further compare various clinical and preclinical approaches for assessing the impact of intestinal drug metabolism on bioavailability, and discuss the utility of the intestinal epithelium–specific NADPH-cytochrome P450 reductase-null (IECN) mouse as a useful model for studying in vivo roles of intestinal P450 in the disposition of orally administered drugs.

Regulation of intestinal cytochrome P450 expression by hepatic cytochrome P450: possible involvement of fibroblast growth factor 15 and impact on systemic drug exposure

Tissue-specific deletion of the gene for NADPH-cytochrome P450 (P450) reductase (CPR), the essential electron donor to all microsomal P450 enzymes, in either liver or intestine, leads to upregulation of many P450 genes in the tissue with the Cpr deletion. Here, by studying the liver-specific Cpr-null (LCN) mouse, we examined whether an interorgan regulatory pathway exists, such that a loss of hepatic CPR would cause compensatory changes in intestinal P450 expression and capacity for first-pass metabolism of oral drugs. We show for the first time that intestinal expression of CYP2B, 2C, and 3A proteins was increased in LCN mice by 2- to 3-fold compared with wild-type (WT) mice, accompanied by significant increases in small intestinal microsomal lovastatin-hydroxylase activity and systemic clearance of oral lovastatin (at 5 mg/kg). Additional studies showed that the hepatic Cpr deletion, which caused large decreases in bile acid (BA) levels in the liver, intestine, plasma, and intestinal content, led to drastic decreases in the mRNA levels of intestinal fibroblast growth factor 15 (FGF15), a target gene of the BA receptor farnesoid X receptor. Furthermore, treatment of mice with FGF19 (the human counterpart of mouse FGF15) abolished the difference between WT and LCN mice in small intestinal (SI) CYP3A levels at 6 hours after the treatment. Our findings reveal a previously unrecognized direct role of intestinal FGF15/19 in the regulation of SI P450 expression and may have profound implications for the prediction of drug exposure in patients with compromised hepatic P450 function.