Uptake of micellar long-chain fatty acid and sn-2-monoacylglycerol into human intestinal Caco-2 cells exhibits characteristics of protein-mediated transport.
Long-chain fatty acid and sn-2-monoacylglycerol (2-MG) are the digestive products of dietary triacylglycerol (TG) hydrolysis. Although fatty acid uptake into the enterocyte has been examined widely, less is known about 2-MG uptake, and few studies have mimicked the physiologic conditions present in the postprandial situation. In this study, the cellular uptake of oleic acid and 2-monoolein, presented in taurocholate micellar solution, was examined in human intestinal Caco-2 cells to model the postprandial intestinal milieu. Initial uptake of oleic acid and 2-MG displayed a saturable function of their monomer concentrations, suggesting that fatty acid and 2-MG uptake may be protein-mediated processes at low unbound concentrations of lipid. The initial rate of oleate uptake was faster and the apparent Km was lower than values for 2-MG. Unlabeled oleic acid and, to a lesser extent, unlabeled 2-MG, inhibited the uptakes of both [3H]oleic acid and [3H]2-monoolein, suggesting competitive uptake. The nonphysiologic isomer sn-1-MG had effects similar to 2-MG, whereas the intermediate digestive product, diacylglycerol (DG), did not inhibit either oleate or 2-monoolein uptake. These results suggest that in the postprandial state, fatty acid and 2-MG derived from dietary TG are transported into the enterocyte, at least in part, via a protein-mediated pathway that is shared by both lipids, but not by the intermediate digestive product, DG.
Department of Nutritional Sciences, Cook College, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA.
Kaeko
K
Murota
Judith
J
Storch
D001692:Biological Transport; D045744:Cell Line, Tumor; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005989:Glycerides / Q000378:metabolism*; D006801:Humans; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D007700:Kinetics; D008823:Micelles; D019301:Oleic Acid
D005230:Fatty Acids, Nonesterified; D005989:Glycerides; D008823:Micelles; D019301:Oleic Acid