NUTRIENT INTAKE IS MODULATED BY PERIPHERAL PEPTIDE ADMINISTRATION

Many peptides have been shown to modulate nutrient intake. In most cas es,these peptides decrease food intake, but in a few cases they have b een demonstrated to stimulate feeding. Infusion of insulin peripherall y will decrease food intake unless hypoglycemia occurs where the reduc ed glucose is a stimulus to feeding. Other pancreatic hormones includi ng glucagon, amylin, pancreatic polypeptide, and enterostatin reduce f ood intake. Of the gastrointestinal hormones, cholecystokinin has been the most widely studied and reduces food intake in a number of specie s, including human beings. Gastrin-releasing peptide and its relative bombesin have been shown to decrease food intake in experimental anima ls and man. Somatostatin reduces food intake in experimental animals,b ut no clinical studies are available. Four pituitary peptides also mod ify food intake. Vasopressin decreases feeding. In contrast, injection s of desacetyl melanocyte stimulating hormone (dMSH), growth hormone, and prolactin are associated with increased food intake. Finally,there are a group of miscellaneous peptides which modulate feeding. beta-ca somorphin, a hepta peptide produced during the hydrolysis of casein, s timulates food intake in experimental animals. In contrast, the other peptides in this group including calcitonin, apolipoprotein A-TV, the cyclized form of histidyl-proline, several cytokines, and thyrotropin- releasing hormone decrease food intake. Many of these peptides act on gastrointestinal or hepatic receptors which relay messages to the brai n via the afferent vagus nerve. As a group they provide a number of le ads for potential drug development.