Inherited disorders of carbohydrate metabolism in children studied by13C-labelled precursors, NMR and GC-MS
- A. Lapidot
- Journal of Inherited Metabolic Disease
Glucose recycling and production were determined in plasma of three children with glycogen storage disease type I (GSD-I) in comparison to normal children. A primed-constant infusion of (U-13C)glucose was introduced nasogastrically at different rates. Endogenous glucose production rates were found to be correlated with rates of glucose infusion. A range of glucose production of 3.5-1.8 mg kg-1 min-1 was found when glucose infusion rates increased from 0.13 to 6 mg kg-1 min-1. The isotopomer distribution of the infused (U-13C)glucose and the plasma glucose in GSD-I children, measured by chemical ionization gas chromatography/mass spectrometry, were identical, indicating absence of glucose recycling. However, a significant change in the isotopomer distribution of plasma glucose was observed in normal subjects. It is suggested that the origin of endogenous glucose production in GSD-I children, during (U-13C)glucose infusion, is from non-labelled sources. The absence of glucose recycling is indicative of a deficiency of glucose 6-phosphatase activity in the liver of GSD-I patients.