Lactate is a preferential oxidative energy substrate over glucose for neurons in culture

The authors investigated concomitant lactate and glucose metabolism in primary neuronal cultures using C-13 and H-1-NMR spectroscopy. Neurons were incubated in a medium containing either [1-C-13] glucose and different unlabeled lactate concentrations, or unlabeled glucose and different [3-C-13] lactate concentrations. Overall, C-13-NMR spectra of cellular extracts showed that more C-13 was incorporated into glutamate when lactate was the enriched substrate. Glutamate C-13-enrichment was also found to be much higher in lactate-labeled than in glucose-labeled conditions. When glucose and lactate concentrations were identical (5.5 mmol/L), relative contributions of glucose and lactate to neuronal oxidative metabolism amounted to 21% and 79%, respectively. Results clearly indicate that when neurons are in the presence of both glucose and lactate, they preferentially use lactate as their main oxidative substrate.