Underestimation of the pentose-phosphate pathway in intact primary neurons as revealed by metabolic flux analysis

Abstract

The rates of glucose oxidized at glycolysis and pentose-phosphate pathway (PPP) in neurons are controversial. Using [3- 3 H]-, [1- 14 C]-, and [6- 14 C]glucose to estimate fluxes through these pathways in resting, intact rat cortical primary neurons, we found that the rate of glucose oxidized through PPP was, apparently, ∼14% of total glucose metabolized. However, inhibition of PPP rate-limiting step, glucose-6-phosphate (G6P) dehydrogenase, increased approximately twofold the glycolytic rate; and, knockdown of phosphoglucose isomerase increased ∼1.8-fold the PPP rate. Thus, in neurons, a considerable fraction of fructose-6-phosphate returning from the PPP contributes to the G6P pool that re-enters PPP, largely underestimating its flux. © 2013 ISCBFM.