The effect of leptin on glucose transport was studied in rat jejunal mucosa in Ussing chambers. Leptin was added in the luminal or the serosal compartment before the tissues were challenged with 1, 10, or 50 mmol/l glucose. In response to 10 mmol/l glucose, the increase in short-circuit current (DeltaIsc) reached 26.8 +/- 2.1 microA/cm(2). Luminal addition of leptin dramatically decreased glucose-induced Isc (90.5% for 10 nmol/l leptin). Inhibition was maximal after 5 min and dose dependent (IC(50) = 0.13 nM). Western blot analysis showed that rapid inhibition of glucose-induced Isc by leptin was associated with a parallel decrease in the abundance of sodium-glucose transporter-1 in brush border membranes. Inhibition by luminal leptin of DeltaIsc was prevented by inhibitor of conventional protein kinase C isoforms. Serosal addition of leptin did not decrease glucose-induced Isc within 5 min and reached maximum after 10 min. The effect of leptin from serosal side was blocked by cholecystokinin (CCK) receptor-2 receptor antagonist YM022. Altogether, these data demonstrate that luminal leptin induces rapid inhibition of glucose entry into enterocyte. The slower action of leptin on the serosal side of mucosa seems indirect and is likely mediated by endogenous CCK. They demonstrate that gut leptin is a major regulator of rapid intestinal glucose transport.