GLUCOSE-PRODUCTION IN GLYCOGEN-STORAGE-DISEASE-I IS NOT ASSOCIATED WITH INCREASED CYCLING THROUGH HEPATIC GLYCOGEN

Children with glycogen storage disease type I (GSD I) lack the ability to convert glucose 6-phosphate to glucose and yet are able to produce glucose endogenously. To test the hypothesis that the source of this glucose is increased cycling of glucose moieties through hepatic glyco gen, six children with GSD I were studied on two occasions during whic h they received enteral glucose for 6 h at 35 or 50 mu mol . kg(-1). m in(-1) along with [6,6-H-2(2)]glucose to measure plasma glucose flux a nd [1-C-13]galactose to label intrahepatic uridyl diphosphate (UDP)glu cose. After 3 h, acetaminophen was given to estimate UDP-glucose flux (reflecting the rate of glycogen synthesis). Mean steady-state plasma glucose concentrations (4.8 +/- 0.2 vs. 5.8 +/- 0.1 mM) and total flux (34.8 +/- 1.7 vs. 47.5 +/- 2.0 mu mol . kg(-1). min(-1)) were increas ed (P < 0.05 or better) on the high-infusion day. Endogenous glucose p roduction was detectable only on the low-infusion day (2.0 +/- 0.5 mu mol . kg(-1). min(-1)). UDP-glucose flux was increased (P < 0.05) on t he high-infusion day (25.8 +/- 1.6 vs. 34.7 +/- 4.1), ruling out cycli ng of glucose moieties through glycogen with release of glucose by deb rancher enzyme as the source of glucose production.