The relation between peripheral and central glutamate and glutamine in healthy male volunteers

High-field strength proton magnetic resonance spectroscopy ((1)H-MRS) and peripheral blood analyses reported in the literature reveal glutamate (Glu) and glutamine (Gln) abnormalities in schizophrenia. Given the relative ease and feasibility of using peripheral measures, the present study investigates the relation between peripheral and brain Glu and Gln levels.

We recruited healthy volunteers (n = 17, mean age 21.9 [standard deviation 2.9, range 18-29] yr) between May and December 2005. All participants underwent 3 Tesla (1)H-MRS analysis with segmentation (grey matter, white matter, cerebrospinal fluid) at the Nuclear Magnetic Resonance Centre at the University of Alberta Hospital to quantify medial prefrontal cortical (mPFC) Glu and Glx (i.e., combination of Glu and Gln). Within 1 week of (1)H-MRS analysis, we collected plasma from the same participants for Glu and Gln quantification, using high-performance liquid chromatography at the Neurochemical Research Unit at the University of Alberta.

There was no correlation between plasma Glu and either medial prefrontal cortical Glu or Glx (R(1,15) = 0.019, p = 0.944 and R(1,15) = 0.081, p = 0.757, respectively). Similarly, there was no correlation between plasma Gln and either mPFC Glu or Glx (R(1,15) = 0.029, p = 0.911 and R(1,15) = 0.025, p = 0.925, respectively).

Our findings support the use of (1)H-MRS, instead of peripheral blood analysis, for investigating glutamatergic dysfunction in the brain.