Elevated homocarnosine and GABA in subject on isoniazid as assessed through 1H MRS at 7T

Typical magnetic resonance spectroscopy J-editing methods designed to quantify GABA suffer from contamination of both overlapping macromolecules and homocarnosine signal, introducing potential confounds. The aim of this study was to develop a novel method to assess accurately both the relative concentrations of homocarnosine as well as GABA free from overlapping creatine, homocarnosine and macromolecule signal. A novel method which utilized the combination of echo time STEAM and MEGA-sLASER magnetic resonance spectroscopy experiments at 7T were used to quantify the concentration of GABA and homocarnsoine independently, which are typically quantified in tandem. The metabolites GABA and homocarnosine were measured in brain of 6 healthy control subjects, and in a single subject medicated with isoniazid. It was found that (16.6±10.2)% of the supposed GABA signal in the brain originated from homocarnosine, and that isoniazid caused significantly elevated concentration of GABA and homocarnosine in a single subject compared to controls.