Evidence of C-lactate oxidation in the human brain from hyperpolarized C-MRI.

PURPOSE

To test the hypothesis that lactate oxidation contributes to the C-bicarbonate signal observed in the awake human brain using hyperpolarized C MRI.

METHODS

Healthy human volunteers (N = 6) were scanned twice using hyperpolarized C-MRI, with increased radiofrequency saturation of C-lactate on one set of scans. C-lactate, C-bicarbonate, and C-pyruvate signals for 132 brain regions across each set of scans were compared using a clustered Wilcoxon signed-rank test.

RESULTS

Increased C-lactate radiofrequency saturation resulted in a significantly lower C-bicarbonate signal (p = 0.04). These changes were observed across the majority of brain regions.

CONCLUSION

Radiofrequency saturation of C-lactate leads to a decrease in C-bicarbonate signal, demonstrating that the C-lactate generated from the injected C-pyruvate is being converted back to C-pyruvate and oxidized throughout the human brain.