Simultaneously Measuring Glucose Transport Constants and Cerebral Metabolic Rate of Glucose by In Vivo H MRS in the Rat Brain

Introduction: The basal brain activity and function rely on a constant supply of glucose in the brain tissue, which is regulated by glucose transportation through the blood-brain barrier (BBB) and the glucose consumption . Therefore, it is interesting to exploit in vivo approaches able to reliably measure the cerebral metabolic rate of glucose (CMRglc) and glucose transport constants (KT and Tmax) simultaneously. In a previous study , we observed a 37% decrease in CMRglc under the iso-electric (i.e., silent EEG activity) condition using high-dose pentobarbital as compared to mild isoflurane anesthesia condition. Meanwhile, we found that the brain glucose concentration also significantly reduced under the iso-electric condition which, though, only requires a minimal glucose metabolic activity for maintaining “housekeeping” power. This observation seemingly contradicted with other studies showing a decreased brain glucose concentration accompanied by the increased CMRglc elevated by brain stimulation. This apparent discrepancy can be explained by the change of plasma glucose concentration, which was found to be substantially decreased under the iso-electric condition. This change had a direct effect on the brain glucose concentration regulated by glucose transportation. Another possible reason is that glucose transport constants might vary under anesthesia conditions . The aim of the present study is to exploit an in vivo H MRS method for measuring CMRglc and glucose transport constants simultaneously.