Transport, deglycosylation, and metabolism of trans-piceid by small intestinal epithelial cells

Background: Numerous epidemiological and animal studies have shown that consumption of red wine is related to reduced incidence of cardiovascular diseases and cancer. Trans-resveratrol (3, 5, 4'-trihydroxystilbene), a phenolic compound present in wine, has been reported to have a potential cancer chemopreventive activity. Moreover, it may exert a protective effect against atherogenesis through its antioxidant properties. Trans-piceid (3-beta glucoside of trans-resveratrol) is present to a greater extent than its aglycone in red wine, but hydrolysis of this glycosylated derivative can occur in small intestine and liver, which would enhance the amount of the biological active trans-resveratrol. Aims: The present study aimed to investigate the rate of transepithelial transport of trans-piceid using human intestinal Caco-2 cell monolayers and metabolism of this compound during its absorption across the small intestine. Methods: The transport of trans-piceid was evaluated in the human epithelial cell line Caco-2, which possesses enterocyte-like properties in vitro. For transepithelial experiments, confluent monolayers of Caco-2 cells were grown on Transwell (R) inserts. For metabolic studies, we used both Caco-2 cells seeded on 6-well plates and rat small intestine cell-free extracts. Results: The time course of apical (AP) to basolateral (BL) transport of trans-piceid showed that the favorable apparent permeability coefficient (Papp) declined rapidly during the 6 h of the experiment. This observation could be correlated with the appearance of metabolites. After incubation of Caco-2 cells with trans-piceid, trans-resveratrol was detected on both AP and BL sides. By using protein extracts obtained from rat, we conclude that the Lactase Phlorizin Hydrolase (LPH) and Cytosolic-beta-Glucosidase (CBG) are involved in the hydrolysis of trans-piceid. Furthermore, we show that after deglycosylation, the resulting aglycone is metabolized in trans-resveratrol-3-O-beta-glucuronide and to a lesser extent in trans-resveratrol-4'-O-beta-glucuronide, and that UGT1A1 is mainly involved in this metabolism. Conclusions: This study demonstrates that the transepithelial transport of trans-piceid occurs at a high rate and that the compound is deglycosylated in trans-resveratrol. There are two possible pathways by which trans-piceid is hydrolyzed in the intestine. The first is a cleavage by the CBG, after passing the brush-border membrane by SGLT1. The second is deglycosylation on the luminal side of the epithelium by the membrane-bound enzyme LPH, followed by passive diffusion of the released aglycone, which is further metabolized inside the cells into two glucuronoconjugates.