Age-dependent decreases of high energy phosphates in cerebral gray matter of patients with bipolar I disorder: a preliminary phosphorus-31 magnetic resonance spectroscopic imaging study.

Objectives: To identify abnormalities in high energy phosphate cerebral metabolism in euthymic bipolar disorder.

Methods: Phosphorus-31 magnetic resonance spectroscopic imaging ((31)P MRSI) data were acquired from the entire brain of 9 euthymic adults with bipolar disorder and 13 healthy adults. Estimates of phosphocreatine (PCr) and adenosine triphosphate (ATP) in homogeneous gray and white matter were obtained by tissue regression analysis.

Results: Analyses of covariance revealed the effect of age to be significantly different between bipolar and healthy groups for concentrations of PCr (p=0.0018) and ATP (p=0.013) in gray matter. These metabolites were negatively correlated with age in gray matter in bipolar subjects while PCr was positively correlated with age in gray matter of healthy subjects. Additionally, age-corrected concentrations of PCr in gray matter were significantly elevated in bipolar subjects (p=0.0048).

Limitations: Given that this cross-sectional study possessed a small sample and potentially confounding effects of medication status, we recommend a larger, longitudinal study to more robustly study relationships between bioenergetic impairment and duration of disease.

Conclusions: Our results suggest bioenergetic impairment related to mitochondrial function may be progressive in multi-episode bipolar subjects as they age.