Glucagon-like peptide 1 and the brain: central actions-central sources?

Glucagon-like peptide 1(GLP-1) is both an incretin released postprandially from the gut and a neuropeptide produced by select brainstem neurons. Its principal role is in the control of metabolic and cardiovascular functions, acting both in the periphery and within the central nervous system (CNS). Specifically, GLP-1 functions that involve the CNS include the suppression of food intake, the regulation of glucose homeostasis and the modulation of heart rate and blood pressure. Thus far, relatively little is known about the exact interplay between gut-derived and neuronally-produced GLP-1. This is partially due to the difficulty of identifying and targeting GLP-1 producing cells in vitro. This obstacle has recently been overcome by the generation of transgenic mice with fluorescently-tagged GLP-1 cells (mGLU-YFP mice). This review revisits what has been discovered about the central actions of GLP-1 during the past decade and puts it into context of the emerging findings from the mGLU-YFP mice.