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HORMONES AND SIGNALING
1INSERM, U773, Centre de Recherche Bichat Beaujon CRB3, BP 416, F-75018, Paris, France; 2Université paris 7 Denis Diderot, site Bichat, BP 416, F-75018, Paris, France; 3INSERM, U45 and 4Faculté de Médecine, Université Claude Bernard, Lyon, France; and 5INRA, Laboratoire d’Ecologie et de Physiologie du Système Digestif, Jouy-en-Josas, France
Submitted 14 September 2005 ; accepted in final form 10 November 2005
Leptin has been suggested to be involved in tissue injury and/or mucosal defence mechanisms. Here, we studied the effects of leptin on colonic mucus secretion and rat mucin 2 (rMuc2) expression. Wistar rats and ob/ob mice were used. Secretion of mucus was followed in vivo in the rat perfused colon model. Mucus secretion was quantified by ELISA, and rMuc2 mRNA levels were quantified by real-time RT PCR. The effects of leptin alone or in association with protein kinase C (PKC) and phosphatidylinositol 3-kinase (PI3K) inhibitors on mucin secreted by human mucus-secreting HT29-MTX cells were determined. Leptin was detected in the rat colonic lumen at substantial levels. Luminal perfusion of leptin stimulates mucus-secreting goblet cells in a dose-dependent manner in vivo in the rat. Leptin (10 nmol/l) increased mucus secretion by a factor of 3.5 and doubled rMuc2 mRNA levels in the colonic mucosa. There was no damage to mucosa 24 h after leptin, but the number of stained mucus cells significantly increased. Leptin-deficient ob/ob mice have abnormally dense mucus-filled goblet cells. In human colonic goblet-like HT29-MTX cells expressing leptin receptors, leptin increased mucin secretion by activating PKC- and PI3K-dependent pathways. This is the first demonstration that leptin, acting from the luminal side, controls the function of mucus-secreting goblet cells. Because the gel layer formed by mucus at the surface of the intestinal epithelium has a barrier function, our data may be relevant physiologically in defence mechanisms of the gastrointestinal tract.
rat mucin 2; mucus; ob/ob; protein kinase C; phosphatidylinositol 3-kinase; leptin receptor; intestinal defence
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