The role of NPY and ghrelin in anorexia nervosa.

Complex mechanisms have evolved that control feeding and energy homeostasis in mammals. Centrally, particularly in the hypothalamus, numerous neurotransmitters have been identified that regulate appetite and energy homeostasis. On the other hand, hormones released from the gut signal states of hunger and satiety to the brain. From the large number of players involved in this interplay, peptides from the neuropeptide Y (NPY) family are unique, with the predominantly neuronally expressed NPY being one of the most strongly stimulating agents for food intake while its two other closely related family members peptide YY (PYY) and pancreatic polypeptide (PP) released from the gut induce satiety. Another major player in this circuitry is ghrelin, which is released from the stomach and is the only known hormone that signals hunger to the brain. It is doing this by stimulating hypothalamic NPY production and release, subsequently leading to increased appetite and feeding behaviour. Deregulation of these processes can lead to either the development of obesity or the other extreme, anorexia. The aim of this review is to summarize the recent literature on NPY and ghrelin and its involvement in anorexia nervosa.