Quantitative assessment of brain glucose metabolic rates using in vivo deuterium magnetic resonance spectroscopy

Quantitative assessment of cerebral glucose consumption rate (CMRglc) and tricarboxylic acid cycle flux (V-TCA) is crucial for understanding neuroenergetics under physiopathological conditions. In this study, we report a novel in vivo Deuterium (H-2) MRS (DMRS) approach for simultaneously measuring and quantifying CMRglc and V-TCA in rat brains at 16.4 Tesla. Following a brief infusion of deuterated glucose, dynamic changes of isotope-labeled glucose, glutamate/glutamine (Glx) and water contents in the brain can be robustly monitored from their well-resolved H-2 resonances. Dynamic DMRS glucose and Glx data were employed to determine CMRglc and V-TCA concurrently. To test the sensitivity of this method in response to altered glucose metabolism, two brain conditions with different anesthetics were investigated. Increased CMRglc (0.46 vs. 0.28 mmol/g/min) and V-TCA (0.96 vs. 0.6 mmol/g/min) were found in rats under morphine as compared to deeper anesthesia using 2% isoflurane. This study demonstrates the feasibility and new utility of the in vivo DMRS approach to assess cerebral glucose metabolic rates at high/ultrahigh field. It provides an alternative MRS tool for in vivo study of metabolic coupling relationship between aerobic and anaerobic glucose metabolisms in brain under physiopathological states.