期刊
JOURNAL OF NEUROCHEMISTRY
卷 107, 期 5, 页码 1414-1423出版社
WILEY-BLACKWELL PUBLISHING, INC
DOI: 10.1111/j.1471-4159.2008.05717.x
关键词
(13)C; insulin; nuclear magnetic resonance; turnover
资金
- 'Centre d'Imagerie Biomedicale' (CIBM)
- University of Lausanne (UNIL)
- Federal Institute of Technology in Lausanne (EPFL)
- University of Geneva (UniGe)
- Centre Hospitalier Universitaire Vaudois' (CHUV)
- 'Hopitaux Universitaires Genevois' (HUG)
- Leenards and the Jeantet Foundations
- NIH [R01NS042005]
The only currently available method to measure brain glycogen in vivo is (13)C NMR spectroscopy. Incorporation of (13)C-labeled glucose (Glc) is necessary to allow glycogen measurement, but might be affected by turnover changes. Our aim was to measure glycogen absolute concentration in the rat brain by eliminating label turnover as variable. The approach is based on establishing an increased, constant (13)C isotopic enrichment (IE). (13)C-Glc infusion is then performed at the IE of brain glycogen. As glycogen IE cannot be assessed in vivo, we validated that it can be inferred from that of N-acetyl-aspartate IE in vivo: After [1-(13)C]-Glc ingestion, glycogen IE was 2.2 +/- 0.1 fold that of N-acetyl-aspartate (n = 11, R(2) = 0.77). After subsequent Glc infusion, glycogen IE equaled brain Glc IE ( n = 6, paired t-test, p = 0.37), implying isotopic steady-state achievement and complete turnover of the glycogen molecule. Glycogen concentration measured in vivo by (13)C NMR (mean +/- SD: 5.8 +/- 0.7 mu mol/g) was in excellent agreement with that in vitro (6.4 +/- 0.6 mu mol/g, n = 5). When insulin was administered, the stability of glycogen concentration was analogous to previous biochemical measurements implying that glycogen turnover is activated by insulin. We conclude that the entire glycogen molecule is turned over and that insulin activates glycogen turnover.
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