Trait-related alterations of N-acetylaspartate in euthymic bipolar patients: A longitudinal proton magnetic resonance spectroscopy study.

BACKGROUND: Neurochemical changes are responsible for bipolar disorder (BD) pathophysiology. Despite current progress in BD research, mood- and trait-related alterations in BD continue to elicit further investigation. METHODS: In this study, we report a longitudinal proton magnetic resonance spectroscopy study evaluating dorsomedial prefrontal cortex (DMPFC) metabolites N-acetylaspartate (NAA), creatine plus phosphocreatine (total creatine [tCr]), phosphorylcholine plus glycerophosphocholine, myo-inositol, and glutamate plus glutamine levels of manic and euthymic adult BD type I patients (n=48) treated with standard antimanic medicines, compared to matching healthy controls (n=44). RESULTS: DMPFC NAA values and NAA/tCr ratio were significantly lower in euthymic BD patients when compared with healthy controls with similar levels of other metabolites in all groups, indicating a trait-related NAA abnormality in euthymic BD patients. LIMITATIONS: of our study include a relatively low (1.5T) magnetic resonance field strength and variable drugs administered to achieve euthymia despite the best efforts to standardize the open fashion treatment. CONCLUSIONS: Our study contributes to the integrating models of trait-related metabolite alterations observed in euthymia since NAA is considered as a marker of neuronal viability and mitochondrial energy metabolism. In light of supporting and conflicting results reported previously, future studies with longitudinal designs and larger patient groups are warranted to better define both state- and trait-related cerebral metabolic alterations associated with BD pathophysiology.