Glycogen storage disease type 0 liver provides a steady source of glucose from glycogen breakdown (or glycogenolysis). With prolonged fasting, glucose is generated in the liver from noncarbohydrate precursors through gluconeogenesis. Such precursors include alanine (derived from the breakdown of proteins in skeletal muscle) and glycerol (derived from the breakdown of triacylglycerols in fat cells). In patients with glycogen-storage disease type 0, fasting hypoglycemia occurs within a few hours after a meal because of the limited stores of hepatic glycogen and inadequate gluconeogenesis to maintain normoglycemia. Feeding characteristically results in postprandial hyperglycemia and glucosuria, in addition to increased blood lactate levels, because glycogen synthesis is
Glycogen-branching enzyme deficiency known as glycogen synthase. This bond may be broken by amylase when the body wishes to break down glycogen into glucose for energy. Glycogen branching enzyme is responsible for the required α-1,6-glycosidic bonds needed to start a branch off of these linear chains. These branches are important, as they provide additional "free ends" for linear chains of α-1,4-glycosidic bonds, which can then be broken down by amylase. This allows for glucose to be removed at a faster rate than if all glucose molecules were in a single chain with only two free ends on which amylase could attach. GBED is