The present outline of astrocytic metabolic pathways involved in glucose and amino acid metabolism provides detailed information about the enzymatic pathways involved, as well as a description of the basic properties of the enzymes including regulatory mechanisms. Hence, the glycolytic pathway and glycogen metabolism are outlined, followed by a detailed account of pyruvate oxidation and its role as a substrate for the tricarboxylic acid (TCA) cycle. Moreover, a detailed description of the main enzymes involved in glutamate metabolism is provided and the role of the glutamate-glutamine cycle is explained. Since this text is primarily covering astrocytic metabolism, an emphasis has been placed on a discussion of the significance of the astrocyte specific enzymes pyruvate carboxylase and glutamine synthetase, which enable these cells to perform a net synthesis of glutamine, the precursor for synthesis of glutamate and γ-aminobutyrate (GABA), the main neurotransmitters of the brain. With this, we have underlined the fundamental importance of astrocytic metabolism for neuronal function with a particular emphasis on the fact that, without continuous support from the astrocytic partners in synaptic function, glutamatergic and GABAergic neurotransmission would not be possible. It is thought provoking that these neurotransmission processes, which account for the vast majority of synaptic activity in the brain, have been made totally dependent on astrocytic metabolic support, particularly with regard to replenishment of the respective neurotransmitters.
About the Author: Arne Schousboe obtained a Ph. D. in biochemistry from the University of Copenhagen in 1968 and, after a short period as Assistant Professor at the University of Copenhagen, he completed a post-doc period ( January 1972-September 1973) with Dr. Eugene Roberts at the Department of Neuroscience, City of Hope National Medical Center in Los Angeles. He subsequently joined the University of Copenhagen to resume a tenured position as Associate Professor in the Medical Faculty there and in 1978 he got his doctorate in science (D. Sc.) from the University of Copenhagen. In 1990 he moved to the Royal Danish School of Pharmacy as a Full Professor of biochemistry. This institution has subsequently become a part of the Faculty of Health and Medical Sciences at the University of Copenhagen. He served as Department Chair from 2005-2010 and is now a part-time Professor of Neuropharmacology at the Department of Drug Design and Pharmacology at this Faculty. He has been working on astrocyte function, focusing on amino acid neurotransmission, for more than 4o years and is currently engaged in studies of glutamate and GABA homeostasis and metabolism. He has published over 550 papers on these topics. He has served on the editorial boards of numerous neuroscience journals over the years and is currently the Editor-in-Chief of Neurochemical Research and editor of the book series Advances in Neurobiology.