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Biochemical Titration of Glycogen In vitro
Published on: November 24, 2013
Non-invasive quantification of brain glycogen absolute concentration
Florence D Morgenthaler1, Ruud B van Heeswijk, Lijing Xin
1Centre d'Imagerie Biomédicale (CIBM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland. Florence.Morgenthaler@epfl.ch
Journal of Neurochemistry
|November 18, 2008
Summary
This study developed a new method to accurately measure brain glycogen concentration in rats using 13C NMR spectroscopy. The technique accounts for glucose turnover, revealing that insulin activates brain glycogen turnover.
Area of Science:
- Biochemistry
- Neuroscience
- Medical Imaging
Background:
- 13C NMR spectroscopy is the sole in vivo method for brain glycogen measurement.
- Incorporating 13C-labeled glucose (Glc) is essential but can be influenced by turnover rates.
- Accurate measurement requires eliminating label turnover as a variable.
Purpose of the Study:
- To determine absolute brain glycogen concentration in rats.
- To eliminate label turnover as a confounding factor in measurements.
- To investigate the effect of insulin on brain glycogen turnover.
Main Methods:
- Establishing a constant, elevated 13C isotopic enrichment (IE) of glucose.
- Infusing 13C-Glc at the established brain glycogen IE.
- Validating glycogen IE inference from N-acetyl-aspartate IE in vivo.
- Comparing in vivo 13C NMR measurements with in vitro analysis.
Main Results:
- Glycogen IE was found to be 2.2-fold that of N-acetyl-aspartate.
- Achieved isotopic steady-state confirmed complete turnover of brain glycogen.
- In vivo measured glycogen concentration (5.8 ± 0.7 µmol/g) closely matched in vitro values (6.4 ± 0.6 µmol/g).
- Insulin administration showed stability consistent with previous findings, indicating activated turnover.
Conclusions:
- The entire brain glycogen molecule undergoes turnover.
- Insulin plays a role in activating brain glycogen turnover.
- The developed method provides accurate in vivo measurement of brain glycogen concentration.
