Common mechanisms of monoacylglycerol and fatty acid uptake by human intestinal Caco-2 cells.
Free fatty acids (FFA) and sn-2-monoacylglycerol (sn-2-MG), the two hydrolysis products of dietary triacylglycerol, are absorbed from the lumen into polarized enterocytes that line the small intestine. Intensive studies regarding FFA transport across the brush-border membrane of the enterocyte are available; however, little is known about sn-2-MG transport. We therefore studied the kinetics of sn-2-MG transport, compared with those of long-chain FFA (LCFA), by human intestinal Caco-2 cells. To mimic postprandial luminal and plasma environments, we examined the uptake of taurocholate-mixed lipids and albumin-bound lipids at the apical (AP) and basolateral (BL) surfaces of Caco-2 cells, respectively. The results demonstrate that the uptake of sn-2-monoolein at both the AP and BL membranes appears to be a saturable function of the monomer concentration of sn-2-monoolein. Furthermore, trypsin preincubation inhibits sn-2-monoolein uptake at both AP and BL poles of cells. These results suggest that sn-2-monoolein uptake may be a protein-mediated process. Competition studies also support a protein-mediated mechanism and indicate that LCFA and LCMG may compete through the same membrane protein(s) at the AP surface of Caco-2 cells. The plasma membrane fatty acid-binding protein (FABP(pm)) is known to be expressed in Caco-2, and here we demonstrate that fatty acid transport protein (FATP) is also expressed. These putative plasma membrane LCFA transporters may be involved in the uptake of sn-2-monoolein into Caco-2 cells.
Ho
S Y
SY
Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey 08901-8525, USA.
Storch
J
J
D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D018938:Caco-2 Cells; D005227:Fatty Acids / Q000493:pharmacokinetics*; D005989:Glycerides / Q000493:pharmacokinetics*; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects / Q000502:physiology*; D007413:Intestinal Mucosa / Q000378:metabolism*; D007700:Kinetics; D008823:Micelles; D019308:Palmitic Acid / Q000493:pharmacokinetics; D012710:Serum Albumin, Bovine / Q000493:pharmacokinetics; D013656:Taurocholic Acid / Q000493:pharmacokinetics; D014316:Tritium; D014357:Trypsin / Q000494:pharmacology
D005227:Fatty Acids; D005989:Glycerides; D008823:Micelles; D014316:Tritium; D012710:Serum Albumin, Bovine; D019308:Palmitic Acid; D013656:Taurocholic Acid; C005953:monoolein; D014357:Trypsin