Dichloroacetate Effects on Glucose and Lactate Oxidation by Neurons and Astroglia in vitro and on Glucose Utilization by Brain in vivo

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 100; no. 8; pp. 4879 - 4884
• Main Authors: Itoh, Yoshiaki, Esaki, Takanori, Shimoji, Kazuaki, Cook, Michelle, Law, Mona J., Kaufman, Elaine, Sokoloff, Louis
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 15.04.2003; National Acad Sciences; The National Academy of Sciences
• Subjects: Animals; Astrocytes; Astrocytes - drug effects; Astrocytes - metabolism; Biological Sciences; Brain; Brain - drug effects; Brain - metabolism; Cells, Cultured; Citric Acid Cycle; Cultured cells; Dichloroacetic Acid - pharmacology; Energy metabolism; Flasks; Glucose; Glucose - metabolism; Glycolysis; In Vitro Techniques; Kinetics; Lactates; Lactic Acid - metabolism; Male; Metabolism; Neurology; Neurons; Neurons - drug effects; Neurons - metabolism; Oxidation; Oxidation-Reduction; Rats; Rats, Sprague-Dawley
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0831078100

Neuronal cultures in vitro readily oxidized both D-[14C] glucose and L-[14C] lactate to14CO2, whereas astroglial cultures oxidized both substrates sparingly and metabolized glucose predominantly to lactate and released it into the medium. [14C] Glucose oxidation to14CO2varied inversely with unlabeled lactate concentration in the medium, particularly in neurons, and increased progressively with decreasing lactate concentration. Adding unlabeled glucose to the medium inhibited [14C] lactate oxidation to14CO2only in astroglia but not in neurons, indicating a kinetic preference in neurons for oxidation of extracellular lactate over intracellular pyruvate/lactate produced by glycolysis. Protein kinase-catalyzed phosphorylation inactivates pyruvate dehydrogenase (PDH), which regulates pyruvate entry into the tricarboxylic acid cycle. Dichloroacetate inhibits this kinase, thus enhancing PDH activity. In vitro dichloroacetate stimulated glucose and lactate oxidation to CO2and reduced lactate release mainly in astroglia, indicating that limitations in glucose and lactate oxidation by astroglia may be due to a greater balance of PDH toward the inactive form. To assess the significance of astroglial export of lactate to neurons in vivo, we attempted to diminish this traffic in rats by administering dichloroacetate (50 mg/kg) intravenously to stimulate astroglial lactate oxidation and then examined the effects on baseline and functionally activated local cerebral glucose utilization (ICMRglc). Dichloroacetate raised baseline ICMRglcthroughout the brain and decreased the percent increases in ICMRglcevoked by functional activation. These studies provide evidence in support of the compartmentalization of glucose metabolism between astroglia and neurons but indicate that the compartmentalization may be neither complete nor entirely obligatory.