Endocrine and Exocrine Secretion of Leptin by the Gastric Mucosa

Abstract

S U M M A R YLeptin is a hormone that plays important roles in nutritional status and in obesity. By means of immunocytochemistry, two populations of leptin-secreting cells were found in the lower half of the gastric mucosa. One consists of numerous large cells located around the gastric pits, the Chief epithelial cells, whereas the second refers to much smaller cells, strongly stained, few in number, and scattered between the gastric pits, the endocrine cells. By double immunostaining, leptin and pepsinogen were colocalized in the Chief cells, whereas the endocrine cells were positive only for leptin. Immunoelectron microscopy showed that leptin is present along the rough endoplasmic reticulum-Golgi-granules secretory pathways of the Chief and endocrine cells. On the other hand, leptin-receptor (long and short forms) immunolabelings, although absent in the gastric epithelial cell plasma membranes, were present in enterocytes at the level of their apical and basolateral membranes. Duodenal, jejunal, and ileal enterocytes displayed similar labelings for the leptin receptor. Thus, exocrine and endocrine secretions of leptin together with the presence of leptin receptors on enterocyte plasma membranes constitute a gastroenteric axis that coordinates the role played by leptin in the digestive tract.

Hormonal Signaling in the Gut

“…Gastric leptin is predominantly secreted from the fundic region of the stomach (71,72) as well as in gastric epithelial cells (74). Although studies mostly focus on adipocyte-derived leptin and its central actions to control feeding, nutrient ingestion has been demonstrated to cause the release of gastric leptin (71,72) directly into the gastric lumen (74,75).…”

“…Although studies mostly focus on adipocyte-derived leptin and its central actions to control feeding, nutrient ingestion has been demonstrated to cause the release of gastric leptin (71,72) directly into the gastric lumen (74,75). Importantly, in order for gastric leptin to reach the intestine, it must withstand the harsh proteolytic environment of the stomach.…”

Immunolocalisation of leptin in the digestive system of juvenile European sea bass (Dicentrarchus labrax)

“…Besides adipose tissue, which is lacking in our 80-day-old specimens, the digestive system can be considered the most common location for leptin production in all vertebrates (Masuzaki et al 1997;Bado et al 1998;Wang et al 1998;Morash et al 1999;Cinti et al 2000;Harvey & Ashford 2003;Bosi et al 2004;Berthoud 2005;Cammisotto et al 2005), including fish (Johnson et al 2000). Among them, LIR has been localised in the gastric endocrine cells of the gastric tubular glands and the neuroendocrine cells in the stomach (Muruzàbal et al 2002).…”

“…Leptin, a 16-kDa protein circulating hormone produced by the ob gene (Zhang et al 1994), was recently discovered in mammals. This hormone is mainly produced in the adipose tissue and, in lower amounts, in other tissues and organs, such as the gastric epithelium (Bado et al 1998;Cinti et al 2000), gastric mucosa (Cammisotto et al 2005(Cammisotto et al , 2006(Cammisotto et al , 2007, stomach (Berthoud 2005), skeletal muscle (Wang et al 1998), placenta (Masuzaki et al 1997;Henson et al 1998;Mise et al 1998) and brain tissue (Morash et al 1999;Harvey & Ashford 2003). Leptin seems to be involved in regulating food intake and energy balance, as well as reproduction (Zhang et al 1994;Campfield et al 1995;Halaas et al 1995;Pelleymounter et al 1995;Auwerx & Staels 1998;Peyon et al 2001;Sahu 2004;Wetzler et al 2004).…”

Genes involved in obesity: Adipocytes, brain and microflora

“…Interestingly, one of the "adiposity signal", namely the adipocyte-derived hormone leptin, was recently reported to be secreted by cells of the gastric mucosa and therefore participate to the regulation of meals, leading to viewing gastric leptin as a neuroendocrine key for satiety (Cammisotto et al, 2005). Indeed, leptin is found in the stomach where it is mainly secreted by the lumen (Bado et al, 1998), and leptin receptors have been identified on the intestinal brush borders (Sobhani et al, 2000).…”