Evidence of 13C-lactate oxidation in the human brain from hyperpolarized 13C-MRI
Biranavan Uthayakumar, Hany Soliman, Albert P. Chen, Nadia Bragagnolo, Nicole I.C. Cappelletto, Ruby Endre, William J. Perks, Nathan Ma, Chris Heyn, Kayvan R. Keshari, Charles H. Cunningham
Abstract
Purpose
To test the hypothesis that lactate oxidation contributes to the 13C-bicarbonate signal observed in the awake human brain using hyperpolarized 13C MRI.
Methods
Healthy human volunteers (N = 6) were scanned twice using hyperpolarized 13C-MRI, with increased 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 signed-rank test.
Results
Increased 13C-lactate radiofrequency saturation resulted in a significantly lower 13C-bicarbonate signal (p = 0.04). These changes were observed across the majority of brain regions.
Conclusion
Radiofrequency 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.