Dapagliflozin suppresses glucagon signaling in rodent models of diabetes

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a class of anti- diabetic drug used for the treatment of diabetes. These drugs are thought to lower blood glucose by blocking reabsorption of glucose by SGLT2 in the proximal convoluted tubules of the kidney. To in- vestigate the effect of inhibiting SGLT2 on pancreatic hormones, we treated perfused pancreata from rats with chemically induced diabe- tes with dapagliflozin andmeasured the response of glucagon secre- tion by alpha cells in response to elevated glucose. In these type 1 diabetic rats, glucose stimulated glucagon secretion by alpha cells; this was prevented by dapagliflozin. Two models of type 2 diabetes, severely diabetic Zucker rats and db/db mice fed dapagliflozin, showed significant improvement of blood glucose levels and glucose disposal, with reduced evidence of glucagon signaling in the liver, as exemplified by reduced phosphorylation of hepatic cAMP-responsive element binding protein, reduced expression of phosphoenolpyruvate carboxykinase 2, increased hepatic glycogen, and reduced hepatic glucose production. Plasma glucagon levels did not change signifi- cantly. However, dapagliflozin treatment reduced the expression of the liver glucagon receptor. Dapagliflozin in rodents appears to lower blood glucose levels in part by suppressing hepatic glucagon signaling through down-regulation of the hepatic glucagon receptor.