Leptin in the CNS: much more than a satiety signal

The discovery of the obese gene product, leptin has generated enormous interest in how the periphery signals the status of nutritional stores to specific hypothalamic nuclei involved in regulating feeding and energy balance. However it is emerging that leptin, in addition to its role as a circulating satiety factor, is a multi-faceted hormone that plays a key role in a variety of CNS functions. In this review, we summarise recent progress in leptin biology, with particular focus on its diversity of actions within the CNS, ranging from satiety signal, to regulator of bone formation and inhibitor of neuronal excitability.