Impaired glucose tolerance and predisposition to the fasted state in liver glycogen synthase knock-out mice.

Irimia JM, Meyer CM, Peper CL, Zhai L, Bock CB, Previs SF, McGuinness OP, DePaoli-Roach A, Roach PJ
J Biol Chem. 2010 285 (17): 12851-61

PMID: 20178984 · PMCID: PMC2857087 · DOI:10.1074/jbc.M110.106534

Conversion to glycogen is a major fate of ingested glucose in the body. A rate-limiting enzyme in the synthesis of glycogen is glycogen synthase encoded by two genes, GYS1, expressed in muscle and other tissues, and GYS2, primarily expressed in liver (liver glycogen synthase). Defects in GYS2 cause the inherited monogenic disease glycogen storage disease 0. We have generated mice with a liver-specific disruption of the Gys2 gene (liver glycogen synthase knock-out (LGSKO) mice), using Lox-P/Cre technology. Conditional mice carrying floxed Gys2 were crossed with mice expressing Cre recombinase under the albumin promoter. The resulting LGSKO mice are viable, develop liver glycogen synthase deficiency, and have a 95% reduction in fed liver glycogen content. They have mild hypoglycemia but dispose glucose less well in a glucose tolerance test. Fed, LGSKO mice also have a reduced capacity for exhaustive exercise compared with mice carrying floxed alleles, but the difference disappears after an overnight fast. Upon fasting, LGSKO mice reach within 4 h decreased blood glucose levels attained by control floxed mice only after 24 h of food deprivation. The LGSKO mice maintain this low blood glucose for at least 24 h. Basal gluconeogenesis is increased in LGSKO mice, and insulin suppression of endogenous glucose production is impaired as assessed by euglycemic-hyperinsulinemic clamp. This observation correlates with an increase in the liver gluconeogenic enzyme phosphoenolpyruvate carboxykinase expression and activity. This mouse model mimics the pathophysiology of glycogen storage disease 0 patients and highlights the importance of liver glycogen stores in whole body glucose homeostasis.

MeSH Terms (16)

Animals Blood Glucose Crosses, Genetic Fasting Gluconeogenesis Glucose Clamp Technique Glucose Tolerance Test Glycogen Glycogen Storage Disease Glycogen Synthase Hypoglycemia Liver Mice Mice, Knockout Organ Specificity Time Factors

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