Selective absorption of dietary sphingoid bases from the intestine via efflux by p-glycoprotein in rats

Various physiological functions of dietary sphingolipids, such as preventing inflammation and improving the skin barrier function, have been recently demonstrated. The sphingolipid most commonly used as a foodstuff is glucosylceramide from plant sources, which is composed of sphingoid bases that are distinctive from those found in mammals. Although the structure of sphingoid bases in higher plants is more complicated than the structure of those in mammals, the fate of dietary sphingolipids of plant origin is still not understood. In the present study, we investigated the absorption of 4,8-sphingadienine that originated from maize glucosylceramide in the rat intestine by using a lipid absorption assay of lymph collected from the thoracic duct. The cumulative recovery of 4,8-sphingadienine in the lymph was lower than that of sphingosine. Verapamil, a P-glycoprotein inhibitor, significantly increased the absorption of 4,8-sphingadienine but did not affect the absorption of sphingosine. Plant-derived sphingoid bases were detected in the ceramide fraction of lymph fluid by using liquid chromatography-mass spectrometry analysis. These results indicate that 4,8-sphingadienine that originates from the glucosylceramide of higher plants is poorly absorbed in the intestine because of efflux by P-glycoprotein and can be incorporated into a ceramide moiety, at least in part, in intestinal endothelial cells.