A 14-year-old adolescent girl with a 2-year history of type 1 diabetes is brought to the ER 1 hour after awakening from sleep at 2:30 am in a cold sweat, tremulous and confused. She normally selfadministers 4 injections of insulin daily, and the last injection was administered before she went to bed. Measurement of her blood glucose concentration indicates it is 40 mg/dL. Following an injection of glucagon, her serum glucose concentration increases to 175 mg/dL, and she shows clinical improvement. The beneficial effect of glucagon in this patient results from which of the following actions of this hormone in the liver?

Question

Quizplus · Accepted Answer

Glucagon increases blood glucose levels by stimulating adenylate cyclase in the liver, which increases cAMP levels, leading to glycogenolysis and gluconeogenesis. When glucagon binds to its receptor on hepatocytes it triggers the activation of a G-protein that in turn activates adenylate cyclase. The activation of adenylate cyclase results in increased production of cAMP which then activates PKA. Activated PKA results in phosphorylation of numerous substrates in the hepatocyte that dramatically increases glycogen breakdown and the activation of the gluconeogenic pathway. Both of these events lead to increased glucose release from the liver accounting for the observed increase in blood glucose.

A 14-Year-Old Adolescent Girl with a 2-Year History of Type