Measurement of gluconeogenesis and pyruvate recycling in the rat liver: a simple analysis of glucose and glutamate isotopomers during metabolism of [1,2,3-C-13(3)]propionate

Simple equations that relate glucose and glutamate C-13-NMR multiplet areas to gluconeogenesis and pyruvate recycling during metabolism of [1,2,3-C-13(3)]propionate are presented, In isolated rat livers, gluconeogenic flux was 1.2 times TCA cycle flux and about 40% of the oxaloacetate pool underwent recycling to pyruvate prior to formation of glucose, The C-13 spectra of glucose collected from rats after gastric versus intravenous administration of [1,2,3-C-13(3)]propionate indicated that pyruvate recycling was slightly higher in vivo (49%) while glucose production was unchanged, This indicates that a direct measure of gluconeogenesis and pyruvate recycling may be obtained from a single C-13-NMR spectrum of blood collected after oral administration of enriched propionate. (C) 1997 Federation of European Biochemical Societies.