Last update:
05-Jul-2004

The recent discovery of ghrelin led to new interesting developments in the study of the regulation of food intake. Ghrelin is a 28 amino acid peptide, which is mainly produced in the stomach. It is a powerful growth hormone secretagogue and an orexigenic signal from the gastrointestinal tract to the brain, acting through the NPY and AGRP neurons of the hypothalamic arcuate nucleus. Its production is stimulated by a low fat diet and inhibited by leptin, growth hormone, interleukin-1b and a high fat diet. Ghrelin levels are low in obese people and increase during weight loss. The discovery that ghrelin receptors are very widely distributed throughout the body led to the revelation of its benign effect on various cardiovascular diseases, as well as its association with conditions of cachexia and the mechanisms of stress. Ghrelin was found to have a complex interaction with a multitude of hormones, such as leptin, insulin and thyroid hormones. The association of ghrelin with the mechanisms of food intake has made the possible use of its antagonists as antiobesity drugs an intriguing but also difficult prospect, mostly because of the complexity of its actions, especially as a growth hormone secretagogue. The treatment of cachectic conditions by the exogenous administration of ghrelin is another interesting possibility. The late discovery that the gut peptide PYY3-36 exerts an anorectic effect through the same pathways but in opposition to ghrelin, has opened new and exciting prospects in the field of food intake mechanisms.

Key words: Neuropeptides, Obesity.