31 List, J. F. He, H. Habener, J. F. 2006 Regul Pept 134 2-3 149-57 May 15 0167-0115 (Print) 16631262 Mice, Inbred C57BL Mice Intermediate Filament Proteins/biosynthesis Glucagon-Like Peptide 1/pharmacology Gene Expression Extracellular Signal-Regulated MAP Kinases/metabolism Cells, Cultured Cell Differentiation/drug effects C-Peptide/secretion Animals Skin/*metabolism Receptors, Glucagon/*biosynthesis Proglucagon/*biosynthesis Nerve Tissue Proteins/biosynthesis Inbred C57BL Cells Cultured Receptors Glucagon/*biosynthesis Glucagon-like peptide-1 (GLP-1) is an insulinotropic hormone expressed by alternative post-translational processing of proglucagon in the intestines, endocrine pancreas, and brain. The multiple antidiabetogenic actions of GLP-1 include stimulation of the proliferation and differentiation of the insulin-producing beta cells in the pancreas. The GLP-1 receptor is widely distributed and has been identified in the endocrine pancreas, intestinal tract, brain, lung, kidney, and heart. Here we report the expression of the GLP-1 receptor and proglucagon in the skin of newborn mice located predominantly in the hair follicles, as well as in cultures of skin-derived cells that also express nestin, a marker of cultured cells that have dedifferentiated by epithelial to mesenchymal transition. In cultured skin cells, GLP-1 activates the MAPK/ERK signal transduction pathway, associated with cellular proliferation, differentiation, and cytoprotection. No evidence was found for the activation of cAMP or Ca2+ signaling pathways. Further, redifferentiation of cultured skin-derived cells by incubation in differentiation medium containing GLP-1 induced expression of the proinsulin-derived peptide, C-peptide. These findings suggest a possible paracrine/autocrine role for GLP-1 and its receptor in skin development and possibly also in folliculogenesis. 5 T32 DK07028/DK/NIDDK NIH HHS/United StatesDK30834/DK/NIDDK NIH HHS/United StatesJournal ArticleResearch Support, N.I.H., ExtramuralNetherlands http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=16631262