A two-compartment mathematical model of neuroglial metabolism using [1-C-11] acetate

The purpose of this study was to develop a two-compartment metabolic model of brain metabolism to assess oxidative metabolism from [1-C-11] acetate radiotracer experiments, using an approach previously applied in C-13 magnetic resonance spectroscopy (MRS), and compared with an one-tissue compartment model previously used in brain [1-C-11] acetate studies. Compared with C-13 MRS studies, C-11 radiotracer measurements provide a single uptake curve representing the sum of all labeled metabolites, without chemical differentiation, but with higher temporal resolution. The reliability of the adjusted metabolic fluxes was analyzed with Monte-Carlo simulations using synthetic C-11 uptake curves, based on a typical arterial input function and previously published values of the neuroglial fluxes V-tca(g), V-x, V-nt, and V-tca(n) measured in dynamic C-13 MRS experiments. Assuming V-x(g)=10xV(tca)(g) and V-x(n)=V-tca(n), it was possible to assess the composite glial tricarboxylic acid (TCA) cycle flux V-gt(g) (Vgtg = V(x)(g)xV(tca)(g)/(V-x(g) + V-tca(g))) and the neurotransmission flux V-nt from C-11 tissue-activity curves obtained within 30 minutes in the rat cortex with a beta-probe after a bolus infusion of [1-C-11] acetate (n = 9), resulting in V-gt(g) = 0.136 +/- 0.042 and V-nt = 0.170 +/- 0.103 mu mol/g per minute (mean +/- s.d. of the group), in good agreement with 13C MRS measurements. Journal of Cerebral Blood Flow & Metabolism (2012) 32, 548-559; doi: 10.1038/jcbfm.2011.162; published online 30 November 2011