OLEIC-ACID DISTRIBUTION IN SMALL-INTESTINAL EPITHELIAL-CELLS EXPRESSING INTESTINAL-FATTY ACID-BINDING PROTEIN

Intestinal-fatty acid binding protein (I-FABP) has been proposed to ta rget long chain fatty acids (LCFA) to triglyceride synthesis pathways in the intestinal epithelium. In the present studies hBRIE 380i cells, which endogenously express I-FABP only when fully differentiated, wer e used to investigate the role of I-FABP in LCFA incorporation and tar geting by examining the relative distribution of [H-3]-oleic acid in c ellular lipids in these cells. [H-3]-oleic acid incorporation into tri glyceride was significantly higher in hBRIE 380i cells expressing I-FA BP than in cells not expressing I-FABP. After 15 min, 1 and 4 h of inc ubation, cells expressing I-FABP incorporated 24.0%, 34.0% and 43.9% o f [H-3]-oleic acid into triglyceride, while newly confluent cells (no I-FABP expression) incorporated 15.6%, 18.3% and 31.9%. An I-FABP nega tive cell line, hBRIE 380i-neg cells, was stably transfected to invest igate the effect of adding I-FABP to small intestinal epithelial cell lines. No measurable differences in [H-3]-oleic acid incorporation int o triglyceride was detected in these transfectants. Additionally I-FAB P expression had no effect on [H-3]-oleic acid incorporation or distri bution within phospholipid subclasses in hBRIE 380i or transfected hBR IE 380i-neg (fabpi) cells. Our data from hBRIE 380i cells suggest that I-FABP can target LCFA to triglyceride synthesis pathway. However, en dogenous I-FABP expression was also correlated to cellular differentia tion and therefore raises the possibility that other differentiation-d ependent factors may have a role in LCFA targeting. Because no effects of I-FABP were detected in the transfected hBRIE 380i-neg(fabpi) cell s, it is concluded that factors in addition to I-FABP play a major rol e in determining the metabolic fate of LCFA in small intestinal epithe lial cells. (C) 1998 Elsevier Science B.V.