NMR measurement of brain oxidative metabolism in monkeys using 13C-labeled glucose without a 13C radiofrequency channel.
We detected glutamate C4 and C3 labeling in the monkey brain during an infusion of [U-13C6]glucose, using a simple 1H PRESS sequence without 13C editing or decoupling. Point-resolved spectroscopy (PRESS) spectra revealed decreases in 12C-bonded protons, and increases in 13C-bonded protons of glutamate. To take full advantage of the simultaneous detection of 12C- and 13C-bonded protons, we implemented a quantitation procedure to properly measure both glutamate C4 and C3 enrichments. This procedure relies on LCModel analysis with a basis set to account for simultaneous signal changes of protons bound to 12C and 13C. Signal changes were mainly attributed to 12C- and 13C-bonded protons of glutamate. As a result, we were able to measure the tricarboxylic acid (TCA) cycle flux in a 3.9 cm3 voxel centered in the monkey brain on a whole-body 3 Tesla system (VTCA = 0.55 +/- 0.04 micromol x g(-1) x min(-1), N = 4). This work demonstrates that oxidative metabolism can be quantified in deep structures of the brain on clinical MRI systems, without the need for a 13C radiofrequency (RF) channel.
Boumezbeur
Fawzi
F
CEA-SHFJ, Orsay, France.
Besret
Laurent
L
Valette
Julien
J
Vaufrey
Françoise
F
Henry
Pierre-Gilles
PG
Slavov
Velislav
V
Giacomini
Eric
E
Hantraye
Philippe
P
Bloch
Gilles
G
Lebon
Vincent
V
D000818:Animals; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry; D002247:Carbon Isotopes; D005947:Glucose / Q000378:metabolism*; D008252:Macaca fascicularis; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male
D002247:Carbon Isotopes; D005947:Glucose