title: Differential distribution of NAA and NAAG in human brain as determined by quantitative localized proton MRS.
abstract: Quantitative proton magnetic resonance spectroscopy was performed in frontal, parietal and occipital white and gray matter of young adults with use of a fully relaxed, short-echo time stimulated echo acquisition mode localization sequence at 2.0 T. Separate concentrations of the neuronal compounds N-acetylaspartate (NAA) and N-acetylaspartylglutamate (NAAG) were obtained by user-independent spectral analysis (LCModel). Except for occipital gray matter in which an NAA concentration of 10.1 +/- 1.0 mM correlated with enhanced neuronal density in visual cortex, NAA was found to be homogeneously distributed throughout cortical white and gray matter at a concentration of 8.0-8.9 mM. NAAG concentrations of 1.5-2.7 mM were higher in white matter than levels of 0.6-1.5 mM found in gray matter, contributing up to 25% of total N-acetyl-containing compounds. The frontal to parieto-occipital increase of both gray and white matter NAAG levels is also reflected in the distribution of total NAA.
authors.affiliation: Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany.
authors.forename: P J
authors.initials: PJ
authors.lastname: Pouwels
authors.forename: J
authors.initials: J
authors.lastname: Frahm
mesh_terms: D000293:Adolescent; D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D004151:Dipeptides / Q000378:metabolism*; D005240:Feasibility Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011522:Protons; D014018:Tissue Distribution
chemical_list: D004151:Dipeptides; D011522:Protons; C027172:isospaglumic acid; D001224:Aspartic Acid; C000179:N-acetylaspartate