Estimating gluconeogenesis by NMR isotopomer distribution analysis of [13C]bicarbonate and [1-13C]lactate.
The gluconeogenic contribution to glucose production in livers isolated from rats fasted for 24 h was determined by 13C-NMR isotopomer distribution analysis of secreted glucose enriched from 99% [13C]bicarbonate (n = 4) and 99% [1-13C]lactate (n = 4). Experiments with 3% 2H2O were also performed, allowing the gluconeogenic contribution to be measured by the relative 2H enrichments at positions 5 and 2 of glucose. From 13C-NMR analyses, the contribution of gluconeogenesis to glucose output was estimated to be 93 +/- 3% for [13C]bicarbonate perfusion and 91 +/- 3% for [1-13C]lactate perfusion, in good agreement with the 2H-NMR analysis of the gluconeogenic contribution to glucose production (100 +/- 1% and 99 +/- 1%, respectively) and consistent with the expected negligible contribution from glycogenolysis. These results indicate that 13C-NMR analysis of glucose 13C-isotopomer distribution from either [13C]bicarbonate or [1-13C]lactate precursor provides realistic estimates of the gluconeogenic contribution to hepatic glucose output.
Department of Biochemistry, Faculty of Sciences and Technology, University of Coimbra, Coimbra, Portugal.
Tiago Cardoso
TC
Alves
Patrícia Maria
PM
Nunes
Carlos Marques
CM
Palmeira
John Griffith
JG
Jones
Rui Albuquerque
RA
Carvalho
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002247:Carbon Isotopes; D003903:Deuterium; D005943:Gluconeogenesis; D005947:Glucose / Q000031:analogs & derivatives / Q000378:metabolism; D050261:Glycogenolysis; D007536:Isomerism; D019344:Lactic Acid / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D014867:Water / Q000378:metabolism
D001639:Bicarbonates; D002247:Carbon Isotopes; D014867:Water; C028223:1,2-O-isopropylidene-D-glucofuranose; D019344:Lactic Acid; D003903:Deuterium; D005947:Glucose