Regional metabolite concentrations in human brain as determined by quantitative localized proton MRS

Abstract

The regional distribution of brain metabolites was studied in several cortical white and gray matter areas, cerebellum, and thalamus of young adults with use of quantitative single-voxel proton MRS at 2.0 T. Whereas the neuronal compound Nacetylaspartate is distributed homogeneously throughout the brain, N-acetylaspartylglutamate increases caudally and exhibits higher concentrations in white matter than in gray matter. Creatine, myo-inositol, glutamate, and glutamine are less concentrated in cortical white matter than in gray matter. The highest creatine levels are found in cerebellum, parallel to the distribution of creatine kinase and energy-requiring processes in the brain. Also myo-inositol has highest concentrations in the cerebellum. Choline-containing compounds exhibit a marked regional variability with again highest concentrations in cerebellum and lowest levels and a strong caudally decreasing gradient in gray matter. The present findings neither support a metabolic gender difference (except for a 1.3-fold higher myo-inositol level in parietal white matter of female subjects) nor a metabolic hemispheric asymmetry.

Increased Anterior Cingulate/Medial Prefrontal Cortical Glutamate and Creatine in Bipolar Depression

“…Generally, the Glx resonance is comprised of glutamate (60-70%) and glutamine (20-30%; Pouwels and Frahm, 1998). In this study, acceptably reliable peaks, as defined by LCModel quality control criteria, were recorded consistently for each of these.…”

N-Acetylaspartate in the CNS: From neurodiagnostics to neurobiology

“…While the peak at 2.02 ppm is prominently attributable to NAA, this signal includes smaller contributions from other acetylated compounds, such as from the neuron-specific dipeptide, N-acetylaspartylglutamate (NAAG) (Caramanos et al, 2005), Nacetylneuraminic acid (Varho et al, 1999), and underlying coupled resonances of glutamate and glutamine. NAAG, the most concentrated peptide in the brain, may contribute 15% to 25% (Pouwels and Frahm, 1997;Pouwels and Frahm, 1998) to the acetate signal that is usually ascribed to NAA (Barker et al, 2006), so the reductions in the NAA peak associated with various brain disorders either involve coincident reductions in NAAG, or they may underestimate the drop in NAA in situations where NAAG levels remain constant.…”

Automatic quantitation of localized in vivo1H spectra with LCModel

“…16 Precise concentration estimates of human brain metabolites have allowed single-voxel studies of regional variations (also of NAAG) 18 and of age dependence. 19 Smaller, precisely localized volumes permit studies of absolute concentrations and relaxation of metabolites in difficult regions such as the hippocampus.…”