Effects of intestinal fatty acid-binding protein overexpression on fatty acid metabolism in Caco-2 cells.

Intestinal fatty acid-binding protein (I-FABP) is a cytosolic protein expressed at high levels (up to 2% of cyto- solic proteins) in the small intestine epithelium. Despite cell transfection studies, its function is still unclear. Indeed, dif- ferent effects on fatty acid metabolism depending on the cell type and the amount of I-FABP expressed have been re- ported. Furthermore, a decrease in fatty acid incorporation has been unexpectedly obtained when I-FABP reached 0.72% of cytosolic proteins in fibroblasts ( Prows et al. 1997. Arch. Biochem. Biophys. 340: 135). In the present study, the effect of a high level of I-FABP similar to amounts present in the small intestine was investigated in the human colon adenocarcinoma cell line, Caco-2. After transfection with human I-FABP cDNA, a clone expressing 1.5% I-FABP and unchanged level of liver FABP was selected. These cells, which had a lower rate of proliferation as compared with mock-transfected cells, developed the typical morphologi- cal characteristics of differentiated enterocytes. Incubation of differentiated cells with ( 14 C)palmitate showed a 34% re- duction ( P , 0.01) of fatty acid incorporation, whereas the relative distribution of radiolabel into triglycerides was not affected. A nonsignificant 21% reduction of fatty acid incor- poration was observed with another clone expressing 10- fold less I-FABP. In conclusion, a high level of I-FABP ex- pressed in a differentiated enterocyte model inhibited fatty acid incorporation, by a mechanism which remains to be de- fined. —Darimont, C., N. Gradoux, E. Persohn, F. Cumin, and A. De Pover. Effects of intestinal fatty acid-binding pro- tein overexpression on fatty acid metabolism in Caco-2 cells. J. Lipid Res. 2000. 41: 84-92.