Evidence of Lactate Shuttling in the Human Brain using Hyperpolarized 13C-MRI
PurposeTo test the hypothesis that lactate shuttling contributes to the 13C-lactate and 13C-bicarbonate signal observed in the awake human brain using hyperpolarized 13C MRI. MethodsHealthy human volunteers (n = 6) were scanned twice using hyperpolarized 13C-MRI, with reduced radiofrequency saturation of 13C-lactate on one set of scans. 13C-lactate, 13C-bicarbonate, and 13C-pyruvate signals for 132 brain regions across each set of scans were compared using a clustered Wilcoxon sum rank test. ResultsReduced 13C-lactate radiofrequency saturation resulted in a significantly greater 13C-bicarbonate signal (p = 0.04). These changes were observed across the majority of brain regions. ConclusionRadiofrequency saturation of 13C-lactate leads to a decrease in 13C-bicarbonate signal, demonstrating that the 13C-lactate generated from the injected 13C-pyruvate is being converted back to 13C-pyruvate and oxidized throughout the human brain.