title: Effects of saturated, mono-, and polyunsaturated fatty acids on the secretion of apo B containing lipoproteins by Caco-2 cells.
abstract: We studied the effects of addition of physiological concentrations (0.5 mM) of fatty acids i.e., palmitic (16:0), stearic (18:0), oleic (18:1) and linoleic acid (18:2) on lipoprotein secretion by polarized Caco-2 cells. With saturated fatty acids, secreted lipoproteins were at IDL/LDL density, 1.009 < d < 1.068 g/ml. The numbers of secreted lipoproteins, expressed as secreted apolipoprotein (apo) B, were comparable to control without fatty acid (palmitic acid, 551 +/- 185; stearic acid, 629 +/- 304 and control, 504 +/- 176 ng apo B/4.7 cm2 filter). With unsaturated fatty acids, apo B containing lipoproteins were secreted at chylomicron/VLDL density (d < 1.006 g/ml). Oleic acid caused a two-fold higher secretion of apo B than control (1058 +/- 87 vs. 504 +/- 176 ng/4.7 cm2 filter, P < 0.001). The increase in apo B secretion was attributed to a specific increase in apo B-48. Unsaturated fatty acid caused a two-fold higher secretion of triglyceride than saturated fatty acids but incorporation of newly synthesized lipid into the secreted lipoproteins, measured by incorporation of a fatty acid marker, was 10- to 20-fold higher, indicating preferential translocation of unsaturated triglycerides into lipoproteins. Mixtures rich in either polyunsaturated, monounsaturated, or saturated fatty acids, resembling nutritional fat and oils, were capable of a two-fold stimulation of secretion of apo B containing triglyceride-rich lipoproteins. The triglyceride/apo B ratio in the basolateral medium was higher with the monounsaturated 'olive oil' mixture (12 250 +/- 2000 mol/mol) than with the polyunsaturated 'corn oil' mixture (7830 +/- 2480 mol/mol) and incorporation of newly synthesized lipid into the secreted lipoproteins was 1.5-fold higher as well. In conclusion, unsaturated fatty acids were most potent in stimulating the secretion of apo B by specifically increasing apo B-48 secretion. Unsaturated triglycerides, that contain mainly oleic acid, were more efficiently incorporated into lipoproteins than saturated triglycerides, suggesting preferential translocation by microsomal triglyceride transfer protein.
authors.affiliation: Department of Medicine, Academic Hospital, Utrecht University, The Netherlands.
authors.forename: M M
authors.initials: MM
authors.lastname: van Greevenbroek
authors.forename: G
authors.initials: G
authors.lastname: van Meer
authors.forename: D W
authors.initials: DW
authors.lastname: Erkelens
authors.forename: T W
authors.initials: TW
authors.lastname: de Bruin
mesh_terms: D053299:Apolipoprotein B-100; D053283:Apolipoprotein B-48; D001055:Apolipoproteins B / Q000378:metabolism*; D002079:Butter / Q000032:analysis; D018938:Caco-2 Cells / Q000187:drug effects / Q000378:metabolism; D003314:Corn Oil / Q000737:chemistry; D017077:Culture Media, Conditioned / Q000737:chemistry; D005227:Fatty Acids / Q000737:chemistry / Q000145:classification / Q000494:pharmacology*; D006801:Humans; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000494:pharmacology; D008074:Lipoproteins / Q000378:metabolism*; D019301:Oleic Acid; D009829:Oleic Acids / Q000494:pharmacology; D000069463:Olive Oil; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000494:pharmacology; D010938:Plant Oils / Q000737:chemistry; D013229:Stearic Acids / Q000494:pharmacology; D014280:Triglycerides / Q000378:metabolism
chemical_list: D053299:Apolipoprotein B-100; D053283:Apolipoprotein B-48; D001055:Apolipoproteins B; D017077:Culture Media, Conditioned; D005227:Fatty Acids; D008041:Linoleic Acids; D008074:Lipoproteins; D009829:Oleic Acids; D000069463:Olive Oil; D010169:Palmitic Acids; D010938:Plant Oils; D013229:Stearic Acids; D014280:Triglycerides; D019301:Oleic Acid; D019308:Palmitic Acid; C031183:stearic acid; D003314:Corn Oil; D002079:Butter; D019787:Linoleic Acid