Glycogen storage disease type 0 fructose results in a marked rise in blood lactate levels. Liver biopsy for microscopic analysis and enzyme assay is required for definitive diagnosis. Diagnosis may include linkage analysis in families with affected members and sequencing of the entire coding region of the GSY2 gene for mutations. Histologic analysis of liver tissue demonstrates moderately decreased amounts of periodic acid-Schiff (PAS)–positive, diastase-sensitive glycogen stores. Evidence of increased fat accumulation in the liver may be observed, as in other glycogen-storage diseases. Electron microscopic analysis of liver sections shows normal glycogen structure. Muscle glycogen stores are normal. There are two types of this\\e condition
Glycogen synthase protein phosphatase 1 (PP1), which activates glycogen synthase via dephosphorylation. PP1 is targeted to the glycogen pellet by four targeting subunits, G, G, PTG and R6. These regulatory enzymes are regulated by insulin and glucagon signaling pathways. Mutations in the "GYS1" gene are associated with glycogen storage disease type 0. In humans, defects in the tight control of glucose uptake and utilization are also associated with diabetes and hyperglycemia. Patients with type 2 diabetes normally exhibit low glycogen storage levels because of impairments in insulin-stimulated glycogen synthesis and suppression of glycogenolysis. Insulin stimulates glycogen synthase by inhibiting glycogen synthase kinases