Glucagon, the Alpha Cell, and Potential Targets for Diabetes Treatment

Glucagon is a 29-amino acid hormone synthesized and secreted by the pancreatic alpha cell in the islets of Langerhans. It is the primary glucose counter-regulatory hormone, secreted by the alpha cell to maintain euglycemia by stimulating hepatic gluconeogenesis and glycogenolysis. In addition to glucose, the alpha cell senses and responds to a number of inputs, such as paracrine factors, neurotransmitters, and other nutrients, including amino acids, to regulate the secretion of glucagon. Disruption of this fine regulation results in excessive glucagon secretion (hyperglucagonemia) and contributes to the pathogenesis of diabetes. In this mini-review, we summarize the current understanding of glucagon biosynthesis and intracellular trafficking, and we discuss emerging concepts in amino acid sensing and signaling that underpin the biology of the alpha cell and that may provide clues to the control of the hyperglucagonemia of diabetes.