INS and pancreatic insulinoma: In insulinoma cells, the GLP-1R may represent a mediator of insulin secretion: in a model of GLP-1R transfected insulinoma cells, glucose-mediated insulin release was increased compared to control cells, in parallel with an increase of the intracellular second messenger of the GLP-1R (cAMP; Montrose-Rafizadeh et al., 1997).