Research of anin vitro model to study the expression of fatty acid-binding proteins in the small intestine

Abstract

In order to find anin vitro model for studying the regulation of the biosynthesis of the cytoplasmic Fatty Acid-Binding Proteins (FABPc) expressed in the small intestine, Intestinal- and Liver-(I- and L-) FABPc expressions were tested by Northern blotting in 8 normal or cancerous intestinal cell lines from man, mouse and rat and in organ culture of mouse jejunal explants. Neither I- nor L-FABPc mRNA was detected in any cell strains tested except in the highly differentiated human enterocyte-like intestinal cell line Caco-2. In this line, Northern blot analysis revealed a single messenger of about 0.7 kb corresponding to the L-FABPc. A two-fold increase in mRNA L-FABPc occurred in differentiated Caco-2 cells treated for 7 days with 0.05 mM bezafibrate, a peroxisome-proliferating hypolipidemic drug. The lack of I-FABPc messengers in this strain led us to seek anotherin vitro model. I- and L-FABPc messengers were found using an organ culture of mouse jejunal explants. A clear rise in I- and, especially, L-FABPc mRNA levels occurred 6 and 24 hr after the addition of 0.05 mM bezafibrate in the culture medium. Our results demonstrate, to our knowledge for the first time, that: 1) organ culture of intestinal explants provides a useful model for studyingin vitro the simultaneous regulation of I- and L-FABPc expressions, 2) biosynthesis of L-FABPc may be exploredin vitro using the Caco-2 cell line, 3) fibrate peroxisome-proliferators exert a direct effect on I- and L-FABPc expression in the small intestine, 4) L-FABPc expression seems to be more sensitive to fibrate action than is I-FABPc expression.