Mucins play an essential role in the protection and repair of gastrointestinal mucosa. We recently showed that luminal leptin strongly stimulated mucin secretion in vivo in rat colon. In the present study, we challenged the hypothesis that leptin may act directly on goblet cells to induce mucin expression in rat and human intestinal mucin-producing cells (DHE and HT29-MTX). The endoluminal effect of leptin was also studied in vivo in rat perfused colon model. The presence of leptin receptors was demonstrated in the two cell lines by western blot and RT-PCR. In rat DHE cells, leptin (0.01-10 nmol/L, 60-min) dose-dependently increased the secretion of mucins (210 +/-3 % of controls) and the expression of Muc2, Muc3 and Muc4 (2 fold basal level) but not of Muc1 and Muc5AC. Luminal perfusion of leptin (60-min, 0.1-100 nmol /L) in rat colon also increased the mRNA level of Muc2, Muc3 and Muc4 but not of Muc1. In human HT29-MTX cells, leptin (0.01-10 nmol/L, 60-min) dose-dependently enhanced MUC2, MUC5AC and MUC4 mRNA levels. These effects were prevented by pre-treatment of cells with the leptin mutein L39A/D40A/F41A which acts as a receptor antagonist. Finally, pathway inhibition experiments suggest that leptin increased mucin expression by activating PKC, PI3-kinase and MAPK-dependent pathways but not JAK/STAT pathway. In conclusion, leptin may contribute significantly to membrane-associated and secreted mucin production via a direct stimulation of colonic epithelial cells and the activation of leptin receptors. These data are consistent with a role for leptin in regulation of the intestinal barrier function.