Uptake and metabolism of (-)-epicatechin in endothelial cells

Accumulating evidence suggest that diets rich in cocoa flavanols may have beneficial effects on cardiovascular health. The major cocoa flavanol monomer, (-)-epicatechin (EC), is readily absorbed and circulates primarily as glucuronidated, sulfated, and O-methylated metabolites in human plasma. However, cellular metabolism, for example in endothelial cells, is less well defined. In the present study we detail the uptake and cellular metabolism of EC and its major in vivo metabolites, (-)-epicatechin-3'-β-D-glucuronide (E3G), (-)-epicatechin-3'-sulfate (E3S), 3'-O-methyl-(-)-epicatechin-5-sulfate (3ME5S), and 3'-O-methyl-(-)-epicatechin-7-sulfate (3ME7S) in human endothelial (HUVEC), liver (HepG2) and intestinal epithelial cells (Caco-2 monolayer). Our results indicate that EC associates with HUVECs, leading to its intracellular metabolism to 3ME7G and 3ME7S. In contrast, none of the metabolites were taken up by the cells. The metabolic rate and pattern of metabolism in HUVECs was similar to that observed in HepG2 cells, whilst in Caco-2 cells EC was metabolized to E3G, 3ME5G, 3ME7G, 4ME5G, 4ME7G and 3ME7S. Our data support the notion that endothelial cells may contribute significantly to EC metabolism. However, major human circulating metabolites are not accounted for in these model systems underscoring that caution should be taken when drawing conclusions on in vivo flavanol metabolism from in vitro experiments.