LEPTIN, LEPTIN RECEPTORS, AND THE CONTROL OF BODY-WEIGHT

The assimilation, storage, and disposition of nutrient energy constitu te a complex homeostatic system central to the survival of both prokar yotic and eukaryotic organisms. In vertebrates, and especially among l and dwelling mammalian species, the ability to store large quantifies of energy-dense fuel in the form of adipose tissue triglyceride permit s survival during prolonged periods of food deprivation. In order to m aintain such fuel stores during times of dietary scarcity or surfeit, some balance between energy intake and expenditure must be achieved. L esions of the hypothalamus alter body weight suggesting that this brai n region regulates nutritional state.(1) These and other studies led t o the hypothesis that body weight was regulated by a feedback loop in which peripheral signals reported nutritional information to an integr atory center in the brain. However, the identity of these nutrition si gnals proved elusive.