Global gray and white matter metabolic changes after simian immunodeficiency virus infection in CD8‐depleted rhesus macaques: proton MRS imaging at 3 T

To test the hypotheses that global decreased neuro‐axonal integrity reflected by decreased N ‐acetylaspartate (NAA) and increased glial activation reflected by an elevation in its marker, the myo ‐inositol ( m I), present in a CD8‐depleted rhesus macaque model of HIV‐associated neurocognitive disorders. To this end, we performed quantitative MRI and 16 × 16 × 4 multivoxel proton MRS imaging (TE/TR = 33/1400 ms) in five macaques pre‐ and 4–6 weeks post‐simian immunodeficiency virus infection. Absolute NAA, creatine, choline (Cho), and m I concentrations, gray and white matter (GM and WM) and cerebrospinal fluid fractions were obtained. Global GM and WM concentrations were estimated from 224 voxels (at 0.125 cm 3 spatial resolution over ~35% of the brain) using linear regression. Pre‐ to post‐infection global WM NAA declined 8%: 6.6 ± 0.4 to 6.0 ± 0.5 mM ( p  = 0.05); GM Cho declined 20%: 1.3 ± 0.2 to 1.0 ± 0.1 mM ( p  < 0.003); global m I increased 11%: 5.7 ± 0.4 to 6.5 ± 0.5 mM ( p  < 0.03). Global GM and WM brain volume fraction changes were statistically insignificant. These metabolic changes are consistent with global WM (axonal) injury and glial activation, and suggest a possible GM host immune response. Copyright © 2013 John Wiley & Sons, Ltd.