Vladimir Mlynarik1, Cristina Cudalbu1,
Hanne Frenkel1, Nicolas Costers1,2, Rolf Gruetter1,3
1Laboratory of Functional and Metabolic
Imaging, Ecole Polytechnique Fdrale de Lausanne, Lausanne, Switzerland; 2Katholieke
Universiteit Leuven, Leuven, Belgium; 3Departments of Radiology,
Universities of Lausanne and Geneva, Switzerland
Absolute
metabolic maps of 12 metabolites were obtained in rat brain at different
plasma glucose (Glc) concentrations (6.4 19 mmol/L) using short-echo-time
proton spectroscopic imaging. A satisfactory linear fit of brain Glc
concentration versus plasma Glc concentration in cortex, hippocampus and
thalamus was found. The slope of this fit was the same within experimental
error in all measured brain structures. The linear fit of increased lactate
concentrations at increased plasma Glc levels was poor, indicating that other
factors such as stress or impaired metabolism during long-term anesthesia can
affect the lactate concentration in brain. Concentrations of myo-inositol,
taurine, ascorbate, phosphoethanolamine, glutamine, GABA, N-acetylaspartate,
total creatine, total choline and macromolecules were not substantially
affected by acute hyperglycemia.