Integration of [U-13C]glucose and 2H2O for quantification of hepatic glucose production and gluconeogenesis.
Glucose metabolism in five healthy subjects fasted for 16 h was measured with a combination of [U-13C]glucose and 2H2O tracers. Phenylbutyric acid was also provided to sample hepatic glutamine for the presence of 13C-isotopomers derived from the incorporation of [U-13C]glucose products into the hepatic Krebs cycle. Glucose production (GP) was quantified by 13C NMR analysis of the monoacetone derivative of plasma glucose following a primed infusion of [U-13C]glucose and provided reasonable estimates (1.90 +/- 0.19 mg/kg/min with a range of 1.60-2.15 mg/kg/min). The same derivative yielded measurements of plasma glucose 2H-enrichment from 2H2O by 2H NMR from which the contribution of glycogenolytic and gluconeogenic fluxes to GP was obtained (0.87 +/- 0.14 and 1.03 +/- 0.10 mg/kg/min, respectively). Hepatic glutamine 13C-isotopomers representing multiply-enriched oxaloacetate and [U-13C]acetyl-CoA were identified as multiplets in the 13C NMR signals of the glutamine moiety of urinary phenylacetylglutamine, demonstrating entry of the [U-13C]glucose tracer into both oxidative and anaplerotic pathways of the hepatic Krebs cycle. These isotopomers contributed 0.1-0.2% excess enrichment to carbons 2 and 3 and approximately 0.05% to carbon 4 of glutamine.
Perdigoto
Rui
R
Medicine III, Transplantation Unit, University Hospital of Coimbra, 3049, Coimbra, Portugal.
Rodrigues
Tiago B
TB
Furtado
Alexandre L
AL
Porto
Armando
A
Geraldes
Carlos F G C
CF
Jones
John G
JG
D000105:Acetyl Coenzyme A / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism*; D003903:Deuterium / Q000378:metabolism*; D005260:Female; D005943:Gluconeogenesis; D005947:Glucose / Q000031:analogs & derivatives / Q000378:metabolism*; D005973:Glutamine / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008297:Male; D008968:Molecular Conformation; D019906:Nuclear Magnetic Resonance, Biomolecular; D010071:Oxaloacetates / Q000378:metabolism
D001786:Blood Glucose; D002247:Carbon Isotopes; D010071:Oxaloacetates; D005973:Glutamine; D000105:Acetyl Coenzyme A; D003903:Deuterium; D005947:Glucose