Simultaneous assessment of cerebral glucose consumption
rate and associated major metabolic fluxes, such as TCA
cycle,
-ketoglutarate/glutamate
exchange and oxygen consumption, is crucial to
understanding neuroenergetics under various
physiological and pathological conditions. However, such
simultaneous measurement has not been possible. In this
study, a novel Deuterium MR (DMR) approach is proposed
and tested in rat brains at 16.4 T. Following a brief
injection of deuterated glucose, the dynamic glucose,
glutamate/glutamine (Glx) and water concentration
changes in the brain tissue were monitored by tracking
their separate resonance signals in the
2
H
spectra. To test the sensitivity of this method in
response to altering metabolic rates, dynamics of brain
deuterated glucose and Glx under 2% isoflurane
anesthesia and constant morphine infusion were compared.
As expected, increasing glucose consumption and labeled
Glx turnover rates were found in the morphine group. The
overall results indicate that the new
in
vivo
DMR
approach is robust and reliable for simultaneously
detecting the changes in glucose and Glx contents in the
rat brain with superior sensitivity. When combined with
metabolic modeling, simultaneous measurement of glucose
consumption rate, TCA cycle flux and
-ketoglutarate/glutamate
exchange rate can be achieved in animal and human
brains.