Nutrient intake is modulated by peripheral peptide administration.

Many peptides have been shown to modulate nutrient intake. In most cases, these peptides decrease food intake, but in a few cases they have been demonstrated to stimulate feeding. Infusion of insulin peripherally will decrease food intake unless hypoglycemia occurs where the reduced glucose is a stimulus to feeding. Other pancreatic hormones including glucagon, amylin, pancreatic polypeptide, and enterostatin reduce food intake. Of the gastrointestinal hormones, cholecystokinin has been the most widely studied and reduces food intake in a number of species, including human beings. Gastrin-releasing peptide and its relative bombesin have been shown to decrease food intake in experimental animals and man. Somatostatin reduces food intake in experimental animals, but no clinical studies are available. Four pituitary peptides also modify food intake. Vasopressin decreases feeding. In contrast, injections 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-casomorphin, a hepta peptide produced during the hydrolysis of casein, stimulates food intake in experimental animals. In contrast, the other peptides in this group including calcitonin, apolipoprotein A-IV, 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 brain via the afferent vagus nerve. As a group they provide a number of leads for potential drug development.