Organic Anion Transporting Polypeptide (OATP) transporter expression, localization and function in the human intestine

Intestinal transporter proteins, along with drug metabolizing enzymes, play a major role in the disposition of orally administered drugs, nutrients and xenobiotics. In this regard, efflux transporters such as ABCB1 and ABCG2 can limit oral bioavailability, while uptake carriers such as PEPT1 have the potential to facilitate intestinal absorption. In contrast to the extensive information on intestinal efflux pumps, detailed knowledge about the respective uptake carriers is rather limited. During the last decade, organic anion transporting polypeptide (OATP) transporters have been frequently discussed as clinically relevant uptake transporters for endogenous compounds as well as drugs. Many drug-drug interactions or food-drug interactions that have been observed have been attributed to inhibition of intestinal OATPs. Moreover, an OATP-mediated drug delivery approach assumes OATPs to be target for improving oral drug absorption. However, recent data from several research groups question the established paradigm of intestinal OATPs as uptake carriers. This review aims to provide a comprehensive up-to-date overview regarding the expression, localization and function of OATP transporters in the human intestine.