| [ Summary ] |
Endocrine fibroblast growth factors (FGFs) function as metabolic hormones and control specific states of homeostasis including bile acid biosynthesis, energy, phosphate, and vitamin D homeostasis. Endocrine FGFs regulate homeostasis through a common design of coreceptor system, consisting of the Klotho gene family of transmembrane proteins and cognate FGF receptors. Moreover, expression of endocrine FGFs is regulated by nuclear receptors whose lipophilic ligands are generated under the control these hormones in the target organs. Thus, novel endocrine axes have emerged that regulate diverse metabolic processes through feedback loops composed of the FGF, Klotho, FGF receptor, and nuclear receptor gene families. This review summarizes recent progress in understanding the roles of Klotho family proteins in the regulation of metabolic activity and expression of endocrine FGFs. |