Introduction: We investigated tissue specific differences in markers of energy metabolism, including high energy phosphate compounds (beta and total NTP, PCr) and pH, in older adults with depression compared with healthy controls, before and after a 12-week treatment trial of sertraline.
Methods: Thirteen older adults, age > or =55, with Major Depressive Disorder (HAMD(17) score of > or =18) were recruited along with ten age-matched controls. The depression subjects had a pre- and post-treatment 4T (31)P-MRS scan using a three-dimensional chemical shift imaging sequence. The extracted brain images were segmented into white matter (WM), gray matter (GM) and CSF. A linear mixed effects model analyzed the effects of pre-treatment and post-treatment depression on phosphorus metabolite concentration estimates (including calculated pH and Mg(++)).
Results: Total tissue beta-NTP (-8%, t(18.66) = 3.50; p = 0.0024) and total tissue total NTP (-6%, t(17.41) = 2.68; p = 0.0156) were lower in subjects with geriatric depression compared with healthy controls. Total tissue levels of total-NTP changed significantly with treatment (-2%, t(14.84) = -2.47; p = 0.0259). Total NTP was reduced in the WM, but not the GM, in the pre-treatment depression group (t(51.65) = 4.02; p = 0.0002). Intracellular pH was higher in the GM of subjects with pre-treatment depression (t(1133.84) = -2.10; p = 0.0353) and decreased to approximate control levels after treatment (t(648.86) = -2.53; p = 0.0115).
Discussion: These findings demonstrate bioenergetic changes including tissue specific differences in (31)P-MRS metabolites in geriatric depression. Decreased white matter total NTP may reflect alterations in white matter function.