Abstract Magnetic resonance imaging (MRI) of hyperpolarized (HP) 1-13Cpyruvate is a promising method for measuring cerebral energy metabolism in vivo. The substantial increase in signal provided by HP makes it possible to dynamically monitor the conversion of 1-13Cpyruvate to 1-13Clactate and 13Cbicarbonate. The HP 1-13Clactate signal is commonly associated with glycolic activity, whereas 13Cbicarbonate, a by-product of the reaction that forms acetyl-CoA, is linked to oxidative metabolism. However, there is compelling evidence that other factors, such as the concentration of monocarboxylate transporters, influence the production of HP 1-13Clactate. To clarify the processes responsible for producing the topography of HP 1-13Cpyruvate and its metabolites, we spatially correlated group-average HP 13C MRI images with 18FFDG, 15OH2O, 15OO2, and 15OCO positron emission topography (PET) images from a separate group of 35 age and sex matched adults. We found that 1-13Cpyruvate correlated best with cerebral blood volume (CBV), whereas 1-13Clactate and 13Cbicarbonate were most strongly associated with cerebral blood flow (CBF), glucose consumption (CMRglc), and oxygen metabolism (CMRO2). Neither 1-13Clactate nor 13Cbicarbonate were correlated with non-oxidative glucose consumption, also known as aerobic glycolysis. These results are consistent with the view that in the healthy brain, the production of 1-13Clactate reflects overall energy metabolism rather than being specific to glycolysis.
Blazey et al. (Wed,) studied this question.