Intestinal-fatty acid binding protein and lipid transport in human intestinal epithelial cells.
Intestinal-fatty acid binding protein (I-FABP) is a 14-15 kDa cytoplasmic molecule highly expressed in the enterocyte. Although different functions have been proposed for various FABP family members, the specific function of I-FABP in human intestine remains unclear. Here, we studied the role of I-FABP in molecularly modified normal human intestinal epithelial cells (HIEC-6). cDNA transfection resulted in 90-fold I-FABP overexpression compared to cells treated with empty pQCXIP vector. The high-resolution immunogold technique revealed labeling mainly in the cytosol and confirmed the marked phenotype abundance of I-FABP in cDNA transfected cells. I-FABP overexpression was not associated with alterations in cell proliferation and viability. Studies using these transfected cells cultured with [14C]oleic acid did not reveal higher efficiency in de novo synthesis or secretion of triglycerides, phospholipids, and cholesteryl esters compared to cells treated with empty pQCXIP vector only. Similarly, the incubation with [35S]methionine did not disclose a superiority in the biogenesis of apolipoproteins (apo) A-I, A-IV, B-48, and B-100. Finally, cells transfected with I-FABP did not exhibit an increased production of chylomicrons, VLDL, LDL, and HDL. Our observations establish that I-FABP overexpression in normal HIEC-6 is not related to cell proliferation, lipid esterification, apo synthesis, and lipoprotein assembly, and, therefore, exclude its role in intestinal fat transport.
Montoudis
Alain
A
Department of Nutrition, Université de Montréal and Research Center, CHU Sainte Justine, 3175 Côte Ste-Catherine, Montréal, Que., Canada H3T 1C5.
Delvin
Edgard
E
Menard
Daniel
D
Beaulieu
Jean-François
JF
Jean
Dominic
D
Tremblay
Eric
E
Bendayan
Moise
M
Levy
Emile
E
D001053:Apolipoproteins / Q000096:biosynthesis; D001692:Biological Transport; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D002788:Cholesterol Esters / Q000096:biosynthesis; D003600:Cytosol / Q000378:metabolism / Q000648:ultrastructure; D004847:Epithelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D050556:Fatty Acid-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D050356:Lipid Metabolism; D008074:Lipoproteins / Q000096:biosynthesis / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D010743:Phospholipids / Q000096:biosynthesis; D014280:Triglycerides / Q000096:biosynthesis
D001053:Apolipoproteins; D002788:Cholesterol Esters; D050556:Fatty Acid-Binding Proteins; D008074:Lipoproteins; D010743:Phospholipids; D014280:Triglycerides