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Abstract #0528

Sources of Hepatic Glycogen Synthesis During an Oral Glucose Tolerance Test: Effect of Transaldolase Exchange on Flux Estimates

Teresa Cardoso Delgado1, Cladia Silva1, Isabel Fernandes2, Madalena Caldeira2, Margarida Bastos3, Carla Baptista3, Manuela Carvalheiro3, Carlos F.G.C. Geraldes1, John Griffith Jones1

1NMR Laboratory, Center for Neurosciences and Cell Biology of Coimbra, Coimbra, Portugal; 22Chemistry Department, Faculty of Sciences and Technology, Coimbra University, Coimbra, Portugal; 3Department of Endocrinology, Diabetes and Metabolism, University Hospital of Coimbra, Coimbra, Portugal

Sources of hepatic glycogen synthesis during a glucose tolerance test were evaluated in healthy subjects by enrichment of a glucose load with 6.67% [U-13C]glucose and 3.33% [U-2H7]glucose and 2H/13C NMR analysis of plasma glucose and hepatic UDP-glucose enrichments (sampled as urinary menthol glucuronide).The direct pathway contribution, as estimated from the dilution of [U-13C]glucose between plasma glucose and hepatic UDP-glucose, was unexpectedly low (365%).With [U-2H7]glucose, direct pathway estimates based on the dilution of position 3 2H-enrichment between plasma glucose and glucuronide were significantly higher (506%).These differences reflect the exchange of the carbon 456 moiety of fructose-6-phosphate and glyceraldehyde-3-phosphate catalyzed by transaldolase.