Chapter 3: One Receptor for Multiple Pathways: Focus on Leptin Signaling

The adipokine leptin, due to its dual nature as hormone and cytokine, can be described as a cytokine-like hormone with pleiotropic actions. It exerts a multitude of regulatory functions including energy homeostasis, regulation of various endocrine axes, bone metabolism, thermoregulation and modulation of immune and inflammatory response. Leptin exerts its biological influence by binding to its receptors, which are encoded by the diabete gene (db). Leptin receptors belong to the class I cytokine receptor superfamily. Alternative splicings of the db gene give rise to multiple isoforms, but only the long form Ob-Rb appears to be capable of transducing the leptin signal. The JAK-STAT pathway seems to be the main route by which Ob-Rb transmits the extracellular signal it receives. Other alternative pathways, however, are also involved. Here, we discuss the most recent advances on leptin biology with particular attention to its receptor signaling.