Leptinistheproteinproductencodedbytheobese(ob)gene.Itisacirculatinghormoneproducedprimarilybytheadiposetissue.ob/obmicewithmutationsofthegeneencodingleptinbecomemorbidlyobese,infertile,hyperphagic,hypothermic,anddiabetic.Sincethecloningofleptinin1994,ourknowledgeinbodyweightregulationandtheroleplayedbyleptinhasincreasedsubstantially.Wenowknowthatleptinsignalsthroughitsreceptor,OB-R,whichisamemberofthecytokinereceptorsuperfamily.Leptinservesasanadipositysignaltoinformthebraintheadiposetissuemassinanegativefeedbackloopregulatingfoodintakeandenergyexpenditure.Leptinalsoplaysimportantrolesinangiogenesis,immunefunction,fertility,andboneformation.Humanswithmutationsinthegeneencodingleptinarealsomorbidlyobeseandrespondtoleptintreatment,demonstratingthatenhancingorinhibitingleptin'sactivitiesinvivomayhavepotentialtherapeuticbenefits.
