NMR visibility of deuterium‐labeled liver glycogen in vivo

Purpose Deuterium metabolic imaging (DMI) combined with [6,6’‐ 2 H 2 ]‐glucose has the potential to detect glycogen synthesis in the liver. However, the similar chemical shifts of [6,6’‐ 2 H 2 ]‐glucose and [6,6’‐ 2 H 2 ]‐glycogen in the 2 H NMR spectrum make unambiguous detection and separation difficult in vivo, in contrast to comparable approaches using 13 C MRS. Here the NMR visibility of 2 H‐labeled glycogen is investigated to better understand its potential contribution to the observed signal in liver following administration of [6,6’‐ 2 H 2 ]‐glucose. Methods Mice were provided drinking water containing 2 H‐labeled glucose. High‐resolution NMR analyses was performed of isolated liver glycogen in solution, before and after the addition of the glucose‐releasing enzyme amyloglucosidase. Results 2 H‐labeled glycogen was barely detectable in solution using 2 H NMR because of the very short T 2 (<2 ms) of 2 H‐labeled glycogen, giving a spectral line width that is more than five times as broad as that of 13 C‐labeled glycogen (T 2 = ~10 ms). Conclusion 2 H‐labeled glycogen is not detectable with 2 H MRS(I) under in vivo conditions, leaving 13 C MRS as the preferred technique for in vivo detection of glycogen.