Simultaneous Evaluation of Membrane Permeability and UDP-Glucuronosyltransferase-Mediated Metabolism of Food-Derived Compounds Using Human Induced Pluripotent Stem Cell-Derived Small Intestinal Epithelial Cells

Development of a human FaFg prediction system for polyphenols using human induced pluripotent stem cell-derived small intestinal epithelial cells

Precise prediction of the fraction of compounds reaching the portal vein (FaFg) in humans, which could indicate the rate-limiting step of polyphenol metabolism, is particularly important for accurately evaluating the efficacy and safety of polyphenols. In this study, we aimed to develop a novel in vitro method to predict human FaFg of polyphenols using commercially available human induced pluripotent stem cell-derived small intestinal epithelial cells (hiPSC-SIECs). First, the chemicals were used at fixed test concentrations, considering their physicochemical properties and cytotoxicity. The apparent permeability coefficient (Papp) values of the six tested polyphenols in hiPSC-SIECs were considerably higher than those of the seven tested pharmaceuticals, resulting in a poor correlation between Papp in hiPSC-SIECs and human FaFg. A detailed assessment of the relationship between in vitro test concentration and metabolic activity suggested that the higher Papp value of polyphenols would be due to inadequate reflection of phase II metabolism in the human intestine. By optimizing test concentrations to reflect enzymatic metabolism in the human intestine, a good correlation was observed between the Papp values in hiPSC-SIECs and human FaFg for tested polyphenols and pharmaceuticals (R2 = 0.81). The developed method could be useful for precisely predicting human FaFg of polyphenols.

Determination of human FaFg of polyphenols using allometric scaling

Certain polyphenols exhibit low permeability; precise prediction of their intestinal absorption is important for understanding internal exposure in humans. Intestinal availability, which represents the fraction of administered compounds that reach the portal blood (F_aF_g), is calculated by dividing bioavailability (F) by hepatic availability (F_h), and F is obtained from pharmacokinetic data from both intravenous (i.v.) and oral (p.o.) administration. However, human F_aF_g of polyphenols is hardly reported, as human i.v. data are extremely scarce. In this study, we developed an estimation method for F_aF_g of polyphenols in humans based on the extrapolation of rat clearance using allometric scaling (allometric scaling-based F_aF_g calculation method, AS- F_aF_gCM). First, for quercetin, for which human i.v. data have been reported, we compared the F_aF_g obtained by AS-F_aF_gCM with the traditional approach using human i.v. and p.o. data. Less than two-fold difference in FaFg values was observed between the two approaches. Next, we obtained F_aF_g of structurally diverse polyphenols (genistein, baicalein, resveratrol, and epicatechin) using AS-F_aF_gCM, demonstrating that all of them were poorly absorbable. Furthermore, to utilize the pharmacokinetic data of the total concentration, including aglycones and metabolites, we modified the AS-F_aF_gCM to focus on their excretion. The F_aF_g value of naringenin was obtained using modified AS-F_aF_gCM and was nearly equal to that of baicalein, a structural isomer of naringenin. This study provides quantitative information on the intestinal absorption of polyphenols using comprehensive estimation methods.