Quantification of brain glycogen concentration and turnover through localized C-13 NMR of both the C1 and C6 resonances

We have recently shown that at isotopic steady state C-13 NMR can provide a direct measurement of glycogen concentration changes, but that the turnover of glycogen was not accessible with this protocol. The aim of the present study was to design, implement and apply a novel dual-tracer infusion protocol to simultaneously measure glycogen concentration and turnover. After reaching isotopic steady state for glycogen Cl using [1-C-13] glucose administration, [1,6-C-13(2)] glucose was infused such that isotopic steady state was maintained at the Cl position, but the C6 position reflected C-13 label incorporation. To overcome the large chemical shift displacement error between the C1 and C6 resonances of glycogen, we implemented 2D gradient based localization using the Fourier series window approach, in conjunction with time-domain analysis of the resulting FIDs using jMRUI. The glycogen concentration of 5.1 +/- 1.6 mM measured from the Cl position was in excellent agreement with concomitant biochemical determinations. Glycogen turnover measured from the rate of label incorporation into the C6 position of glycogen in the a-chloralose anesthetized rat was 0.7 mu mol/g/h. Copyright (C) 2009 John Wiley & Sons, Ltd.