Assessment of hepatic pyruvate carboxylase activity using hyperpolarized [1-13 C]-l-lactate.

This study demonstrates that a unique biomarker of pyruvate carboxylase flux, the appearance of [1-13 C]aspartate from [1-13 C]-l-lactate, is sensitive to nutritional state and may be monitored in vivo at 3 Tesla. Because [13 C] HCO 3 - is largely produced by pyruvate dehydrogenase flux, these results suggest that the ratio of [1-13 C]aspartate and [13 C] HCO 3 - (aspartate/ HCO 3 - ) reflects the saturable pyruvate carboxylase/pyruvate dehydrogenase enzyme activities.