α-cell Gq signaling is critical for maintaining euglycemia.

Glucagon, a hormone released from pancreatic α-cells, plays a key role in maintaining euglycemia. New insights into the signaling pathways that control glucagon secretion may stimulate the development of novel therapeutic agents. In this study, we investigated the potential regulation of α-cell function by G proteins of the Gq family. The use of a chemogenetic strategy allowed us to selectively activate Gq signaling in mouse α-cells in vitro and in vivo. Acute stimulation of α-cell Gq signaling led to elevated plasma glucagon levels, accompanied by increased insulin release and improved glucose tolerance. Moreover, chronic activation of this pathway greatly improved glucose tolerance in obese mice. We also identified an endogenous Gq-coupled receptor (vasopressin 1b receptor; V1bR) that is enriched in mouse and human α-cells. Agonist-induced activation of the V1bR strongly stimulated glucagon release in a Gq-dependent fashion. In vivo studies indicated that V1bR-mediated glucagon release plays a key role in the counter-regulatory hyperglucagonemia under hypoglycemic and glucopenic conditions. These data indicate that α-cell Gq signaling represents an important regulator of glucagon secretion, resulting in multiple beneficial metabolic effects. Thus, drugs that target α-cell enriched Gq-coupled receptors may prove useful to restore euglycemia in various pathophysiological conditions.