Anorexigenic and Orexigenic Gut Peptides

The presence of nutrients and nutrient digestive products in the gastrointestinal tract results in alterations in the secretions of peptides that can affect further food intake. These peptides and the signals they induce are important in maintaining body energy homeostasis in the short term by regulating food intake and in the long term by controlling body adiposity. The majority of gut peptides that affect food intake are anorexic. Cholecystokinin and glucagon are secreted immediately after meal onset and these peptides mediate meal termination. The levels of gut peptides, such as gastric inhibitory polypeptide, glucagon-like peptide, and peptide YY, remain elevated for a longer period after the meal is terminated and these can play roles both in meal termination and in subsequent energy intake. Ghrelin is the only known peptide secreted in the periphery that stimulates food intake. Ghrelin plasma levels peak just before a meal and the basal level correlates to body fat. Gut peptides generally exert their effect by acting on vagal afferents, in the hindbrain, or directly at hypothalamic sites involved in energy regulation. With the alarming rise in obesity rates throughout the developed world, there is a pressing need for new and effective treatments. The actions of gut peptides in controlling food intake have made them attractive targets for potential anti-obesity drug development.