Peripheral Effects of Melanocortins

Peptides derived from the proopiomelanocortin (POMC) prohormore precursor have been implicated in a wide variety of biologic functions since its discovery in 1977 (1,2), and the cloning of the POMC gene in 1979 (3). Some of the peptides derived from POMC are classified as melanocortins because of their ability to stimulate eumelanogenesis in the melanocyte or to stimulate steroid production in the adrenocortical cell. Although the two most thoroughly studied of the melanocortin biologic functions are adrenocorticotropic hormone (ACTH) stimulation of adrenal steroidogenesis and melanocyte stimulating hormone (MSH) stimulation of eumelanin production, numerous other effects of these peptides have been reported. Melanocortins have been implicated in the regulation of feeding and grooming behavior, learning and memory, thermogenesis, neural regeneration, metabolism, inflammmation, exocrine gland function, and natriuresis (54,79,115,127,134). Many of these alterations in biologic function are clearly mediated via melanocortin receptors in the central nervous system, while others are mediated at least partially by melanocortin receptors in the periphery. In this chapter, we discuss aspects of melanocortin function other than melanogenesis and steroidogenesis that appear to be at least partially a result of interaction with peripheral melanocortin receptors.