Astrocyte-neuron metabolic coupling, lactate shuttle, and glutamate-glutamine cycle in brain energy metabolism

Abstract

Brain energy metabolism depends on intricate metabolic cooperation between astrocytes and neurons. This research investigated the astrocyte-neuron lactate shuttle and glutamate-glutamine cycle using primary cell cultures and brain slice preparations. Experiments conducted at Helsinki Institute of Applied Sciences from June 2023 to October 2024 employed isotope tracing and metabolite measurements to quantify intercellular metabolic fluxes. Results demonstrated that astrocytes exported lactate at rates of 4.8 nmol/min/mg protein during neuronal activation, representing a 3.2-fold increase over basal conditions. Glutamate uptake by astrocytes reached 2.1 nmol/min/mg with subsequent glutamine release at 1.7 nmol/min/mg, indicating 81% cycling efficiency. Inhibition of monocarboxylate transporters reduced neuronal ATP levels by 34% during stimulation. These findings confirm the importance of astrocyte-derived lactate for sustaining neuronal activity and validate the metabolic coupling model.