Role of the leptin signaling system in energy homeostasis

A regulated factor that contributes to maintenance of energy homeostasis is body weight and especially the size of its fat mass. Leptin as well as insulin are synthesized and secreted in proportion to body fat and each form a unique link between energy availability and CNS mechanisms that subserve the regulation of energy homeostasis. Both insulin and leptin affect signaling systems in the hypothalamus that involve a number of neuropeptides that serve a role in the regulation of food intake and energy expenditure. This chapter pays attention to to the interactions of leptin and insulin with hypopthalamic neuronal circuitry that contains neuropeptide Y (NPY), agouti-related peptide (AgRP) and proopiomelanocortin (POMC), and how these interactions affect appropriate changes in food intake and energy expenditure.