We previously reported that the
ethanol extract from polished rice suppresses
inflammation and the formation of
aberrant crypt foci in the mouse colon and particularly focused on the plant
sphingolipid glucosylceramide (GlcCer). Here, we investigated the effects of rice
lipid fractions and GlcCer on differentiated Caco-2 cells treated with
lipopolysaccharide (LPS), in particular, we evaluated the mechanism of action of GlcCer using related substances and metabolic
enzyme inhibitors. Rice-derived polar
lipids suppressed the LPS-induced reduction in the number of cells. The polar
lipids with higher GlcCer content exerted a better effect than the other fractions. GlcCer-related substances reversed the LPS-induced reduction in the number of cells, and GlcCer-metabolic inhibitors, including a
sphingosine kinase inhibitor, suppressed the beneficial effects of GlcCer-related substances. These results suggest that GlcCer is a rice component with intestinal protection. Secondly, GlcCer is metabolized during
inflammation and protects intestinal cells by maintaining the
sphingolipid levels in cells and producing sphingoid base-1-phosphate.