PEPT1-mediated uptake of dipeptides enhances the intestinal absorption of amino acids via transport system b(0,+).
Free amino acids and short chain peptides are the main digestion products of dietary proteins in the small intestine. Whether there is a direct interference in transport of both groups of degradation products is not known. We used human intestinal Caco-2 cells to investigate whether the absorption of dipeptides by the peptide transporter PEPT1 alters the apical uptake of free cationic and neutral amino acids. Influx of L-[3H]Arg into Caco-2 cells was Na+-independent and mediated mainly by the b(0,+) system recognizing both cationic and neutral amino acids. Preincubation of cells with 10 mM of selected neutral, mono- or dicationic dipeptides increased the influx of L-Arg up to fourfold. Preloading with equivalent concentrations of the corresponding free amino acids also increased L-Arg influx but dipeptides always proved to be more efficient. The observed trans-stimulation was found to be specific for cationic amino acids since transport of L-[3H]Ala remained unaffected. We here demonstrate for the first time a direct interplay in amino acid and peptide transport in intestinal cells that may selectively alter the kinetics of amino acid absorption.
Wenzel
U
U
Institute of Nutritional Sciences, Molecular Nutrition Unit, Technical University of Munich, Hochfeldweg 2, Freising-Weihenstephan, Germany.
Meissner
B
B
Döring
F
F
Daniel
H
H
D000409:Alanine / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism*; D001120:Arginine / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D003110:Colonic Neoplasms; D004151:Dipeptides / Q000378:metabolism*; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects / Q000502:physiology*; D007413:Intestinal Mucosa / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D007421:Intestine, Small / Q000502:physiology; D007700:Kinetics; D000074011:Peptide Transporter 1; D012964:Sodium / Q000494:pharmacology; D027981:Symporters; D014407:Tumor Cells, Cultured
D000596:Amino Acids; D002352:Carrier Proteins; D004151:Dipeptides; D000074011:Peptide Transporter 1; C082186:SLC15A1 protein, human; D027981:Symporters; D001120:Arginine; D012964:Sodium; D000409:Alanine