| Sources of hepatic glycogen synthesis during an oral glucose tolerance test: Effect of transaldolase exchange on flux estimates. | |
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MedLine Citation:
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PMID: 19780152 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Sources of hepatic glycogen synthesis during an oral glucose tolerance test were evaluated in six healthy subjects by enrichment of a 75-g glucose load with 6.67% [U-(13)C]glucose and 3.33% [U-(2)H(7)]glucose and analysis of plasma glucose and hepatic uridine diphosphate-glucose enrichments (sampled as urinary menthol glucuronide) by (2)H and (13)C nuclear magnetic resonance. The direct pathway contribution, as estimated from the dilution of [U-(13)C]glucose between plasma glucose and glucuronide, was unexpectedly low (36 +/- 5%). With [U-(2)H(7)]glucose, direct pathway estimates based on the dilution of position 3 (2)H-enrichment between plasma glucose and glucuronide were significantly higher (51 +/- 6%, P = 0.05). These differences reflect the exchange of the carbon 4, 5, and 6 moiety of fructose-6-phosphate and glyceraldehyde-3-phosphate catalyzed by transaldolase. As further evidence of this exchange, (2)H-enrichments in glucuronide positions 4 and 5 were inferior to those of position 3. From the difference in glucuronide positions 5 and 3 enrichments, the fraction of direct pathway carbons that experienced transaldolase exchange was estimated at 21 +/- 4%. In conclusion, the direct pathway contributes only half of hepatic glycogen synthesis during an oral glucose tolerance test. Glucose tracers labeled in positions 4, 5, or 6 will give significant underestimates of direct pathway activity because of transaldolase exchange. |
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Authors:
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Teresa C Delgado; Cla??dia Silva; Isabel Fernandes; Madalena Caldeira; Margarida Bastos; Carla Baptista; Manuela Carvalheiro; Carlos F G C Geraldes; John G Jones |
Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine Volume: 62 ISSN: 1522-2594 ISO Abbreviation: Magn Reson Med Publication Date: 2009 Nov |
Date Detail:
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Created Date: 2009-11-03 Completed Date: 2010-01-13 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8505245 Medline TA: Magn Reson Med Country: United States |
Other Details:
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Languages: eng Pagination: 1120-8 Citation Subset: IM |
Copyright Information:
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c) 2009 Wiley-Liss, Inc. |
Affiliation:
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NMR Laboratory, Center for Neurosciences and Cell Biology, Coimbra University, Coimbra, Portugal. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adult Blood Glucose / analysis* Female Glucose / administration & dosage, diagnostic use, pharmacokinetics* Glucose Tolerance Test / methods* Glycogen / biosynthesis* Humans Insulin / blood* Liver / metabolism* Magnetic Resonance Spectroscopy / methods* Male Metabolic Clearance Rate Middle Aged Transaldolase / blood* |
| Chemical | |
Reg. No./Substance:
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0/Blood Glucose; 11061-68-0/Insulin; 50-99-7/Glucose; 9005-79-2/Glycogen; EC 2.2.1.2/Transaldolase |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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