Luminal leptin inhibits L-glutamine transport in rat small intestine: involvement of ASCT2 and B0AT1.
L-glutamine is the primary metabolic fuel for enterocytes. Glutamine from the diet is transported into the absorptive cells by two sodium-dependent neutral amino acid transporters present at the apical membrane: ASCT2/SLC1A5 and B(0)AT1/SLC6A19. We have demonstrated that leptin is secreted into the stomach lumen after a meal and modulates the transport of sugars after binding to its receptors located at the brush border of the enterocytes. The present study was designed to address the effect of luminal leptin on Na(+)-dependent glutamine (Gln) transport in rat intestine and identify the transporters involved. We found that 0.2 nM leptin inhibited uptake of Gln and phenylalanine (Phe) (substrate of B(0)AT1) using everted intestinal rings. In Ussing chambers, 10 mM Gln absorption followed as Na(+)-induced short-circuit current was inhibited by leptin in a dose-dependent manner (maximum inhibition at 10 nM; I(C50) = approximately 0.1 nM). Phe absorption was also decreased by leptin. Western blot analysis after 3-min incubation of the intestinal loops with 10 mM Gln, showed marked increase of ASCT2 and B(0)AT1 protein in the brush-border membrane that was reduced by rapid preincubation of the intestinal lumen with 1 nM leptin. Similarly, the increase in ASCT2 and B(0)AT1 gene expression induced by 60-min incubation of the intestine with 10 mM Gln was strongly reduced after a short preincubation period with leptin. Altogether these data demonstrate that, in rat, leptin controls the active Gln entry through reduction of both B(0)AT1 and ASCT2 proteins traffic to the apical plasma membrane and modulation of their gene expression.
Ducroc
Robert
R
Institut National de la Santé et de la Recherche Médicale (INSERM), U773, CRB3, Digestive Physiology and Neuroendocrinology, 16 Rue Henri Huchard, 75890 Paris, Cedex 18, France. robert.ducroc@inserm.fr
Sakar
Yassine
Y
Fanjul
Carmen
C
Barber
Ana
A
Bado
André
A
Lostao
Maria Pilar
MP
D026962:Amino Acid Transport System ASC / Q000235:genetics / Q000378:metabolism*; D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D005786:Gene Expression Regulation; D005973:Glutamine / Q000378:metabolism*; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism*; D020738:Leptin / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials; D015778:Minor Histocompatibility Antigens; D010455:Peptides / Q000494:pharmacology; D010649:Phenylalanine / Q000378:metabolism; D021381:Protein Transport; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D054411:Receptors, Leptin / Q000037:antagonists & inhibitors / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012704:Serous Membrane / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013997:Time Factors
D026962:Amino Acid Transport System ASC; D026921:Amino Acid Transport Systems, Neutral; D020738:Leptin; D015778:Minor Histocompatibility Antigens; D010455:Peptides; D012333:RNA, Messenger; D054411:Receptors, Leptin; D011994:Recombinant Proteins; C520324:SLC6A19 protein, rat; C498849:Slc1a5 protein, rat; D005973:Glutamine; D010649:Phenylalanine; D012964:Sodium
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