[Peptides are opening the door for novel treatments of obesity and loss of appetite].

A wide spectrum of diseases, as well as states of attenuated ability to heal and recover, can be traced to over- or underweight. Patients at the extremes of the energy balance spectrum are becoming more and more common. In order to provide adequate care for such patients an understanding of the mechanisms governing feeding behaviour is required. In the last decade, important advances have been made in this direction, as several factors mediating signals of hunger and satiety to and within the brain have been identified. These factors include hormonal signals (such as leptin and insulin) from the energy stores as well as neuronal influences (via the vagus nerve) from the digestive tract. The information encoded therein is routed to specific nuclei of the hypothalamus and brain stem, respectively, leading to activation of complex neuronal networks spanning the most rostral regions of the brain all the way to the effector neurones of the autonomic nervous system located in the spinal cord. Several recently characterized neuropeptides showing potent stimulation of appetite (neuropeptide Y, agouti gene-related peptide, orexin, melanin-concentrating hormone) and satiety (melanocortins, cholecystokinin, cocaine- and amphetamine-regulated transcript) have been localized to these pathways. These peptides, and the mechanisms through which they operate, offer promise for new therapeutic strategies in the treatment of obesity and anorexia.