Quantitation of gluconeogenesis by H-2 nuclear magnetic resonance analysisof plasma glucose following ingestion of (H2O)-H-2

We present a simple H-2 MMR assay of the fractional contribution of glucone ogenesis to hepatic glucose output following ingestion of (H2O)-H-2. The as say is based on the measurement of relative deuterium enrichment in hydroge ns 2 and 3 of plasma glucose. Plasma glucose was enzymatically converted to gluconate, which displays fully resolved deuterium 2 and 3 resonances in i ts H-2 NMR spectrum at 14.1 T. The signal intensity of deuterium 3 relative to deuterium 2 in the gluconate derivative as quantitated by H-2 NMR was S hown to provide a precise and accurate measurement of glucose enrichment in hydrogen 3 relative to hydrogen 2. This measurement was used to estimate t he fractional contribution of gluconeogenesis to hepatic glucose output for two groups of rats; one group was fasted for 7 h and the other was fasted for 29 h, Rats were administered (H2O)-H-2 to enrich total body water to 5% over the last 4-5 h of each fasting period. For the 7-h fasted group, the hydrogen 3/hydrogen 2 enrichment ratio of plasma glucose was 0.32 +/- 0.09 (n = 7). This indicates that gluconeogenesis contributed 32 +/- 9% of total hepatic glucose output with glycogenolysis contributing the remainder, For the 29-h fasted group, the hydrogen 3/hydrogen 2 enrichment ratio of plasm a glucose was 0.81 +/- 0.10 (n = 6), indicating that gluconeogenesis suppli ed the bulk of hepatic glucose output (81 +/- 10%). (C) 2000 Academic Press .