Bile acid homeostasis is vital for numerous metabolic and immune functions in humans. The enterohepatic circulation of bile acids is extremely efficient, with ~95% of intestinal bile acids being reabsorbed. Disturbing intestinal bile acid uptake is expected to substantially affect intestinal and systemic bile acid levels. Here, we aimed to predict the effects of apical sodium-dependent bile acid transporter (ASBT)-inhibition on systemic plasma levels. For this, we combined in vitro Caco-2 cell transport assays with physiologically based (PBK) modeling. We used the selective ASBT-inhibitor odevixibat (ODE) as a model compound. Caco-2 cells grown on culture inserts were used to obtain transport kinetic parameters of glycocholic acid (GCA). The apparent Michaelis-Menten constant (Km,app), apparent maximal intestinal transport rate (Vmax,app), and ODE’s inhibitory constant (Ki) were determined for GCA. These kinetic parameters were incorporated into a PBK model and used to predict the ASBT inhibition effects on plasma bile acid levels. GCA is transported over Caco-2 cells in an active and sodium-dependent manner, indicating the presence of functional ASBT. ODE inhibited GCA transport dose-dependently. The PBK model predicted that oral doses of ODE reduced conjugated bile acid levels in plasma. Our simulations match in vivo data and provide a first proof-of-principle for the incorporation of active intestinal bile acid uptake in a bile acid PBK model. This approach could in future be of use to predict the effects of other ASBT-inhibitors on plasma and intestinal bile acid levels.
Keywords: Caco-2; apical sodium dependent bile acid transporter (ASBT); bile acids and salts; odevixibat; quantitative-in-vitro-to-in-vivo extrapolation (QIVIVE).
Bile acids regulate digestion and immune functions. Too little bile acid reuptake in the gut is related to several diseases, including inflammatory bowel disease. This study investigates how reducing bile acid absorption affects bile acid levels in humans using the drug odevixibat (ODE) as an example. ODE reduces bile acid absorption by blocking the intestinal bile acid transporter protein in gut cells. The transport of a bile acid through a gut cell line commonly used to model the intestinal barrier was measured with and without ODE, and mathematical modeling was used to translate the laboratory results to whole-body effects. This combined approach accurately predicted the known effects of ODE on intestinal and bloodstream bile acid levels in humans. This novel approach could be used to predict the effects of other chemicals on intestinal bile acid absorption and intestinal and bloodstream bile acid levels instead of animal testing.