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.
Murota
Kaeko
K
Department of Nutritional Sciences, Cook College, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA.
Storch
Judith
J
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