title: AMPK Activation Affects Glutamate Metabolism in Astrocytes.
abstract: Mammalian AMP-activated protein kinase (AMPK) functions as a metabolic switch. It is composed of 3 different subunits and its activation depends on phosphorylation of a threonine residue (Thr172) in the α-subunit. This phosphorylation can be brought about by 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR) which in the cells is converted to a monophosphorylated nucleotide mimicking the effect of AMP. We show that the preparation of cultured astrocytes used for metabolic studies expresses AMPK, which could be phosphorylated by exposure of the cells to AICAR. The effect of AMPK activation on glutamate metabolism in astrocytes was studied using primary cultures of these cells from mouse cerebral cortex during incubation in media containing 2.5 mM glucose and 100 µM [U-(13)C]glutamate. The metabolism of glutamate including a detailed analysis of its metabolic pathways involving the tricarboxylic acid (TCA) cycle was studied using high-performance liquid chromatography analysis supplemented with gas chromatography-mass spectrometry technology. It was found that AMPK activation had profound effects on the pathways involved in glutamate metabolism since the entrance of the glutamate carbon skeleton into the TCA cycle was reduced. On the other hand, glutamate uptake into the astrocytes as well as its conversion to glutamine catalyzed by glutamine synthetase was not affected by AMPK activation. Interestingly, synthesis and release of citrate, which are hallmarks of astrocytic function, were affected by a reduction of the flux of glutamate derived carbon through the malic enzyme and pyruvate carboxylase catalyzed reactions. Finally, it was found that in the presence of glutamate as an additional substrate, glucose metabolism monitored by the use of tritiated deoxyglucose was unaffected by AMPK activation. Accordingly, the effects of AMPK activation appeared to be specific for certain key processes involved in glutamate metabolism.
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark.
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Voss
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark.|Department of Clinical Medicine, The Department of Endocrinology and Diabetes, University of Aarhus, 8000, Århus, Denmark.
authors.forename: Kamilla
authors.initials: K
authors.lastname: Pajęcka
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark.
authors.forename: Malin H
authors.initials: MH
authors.lastname: Stridh
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark.
authors.forename: Jakob D
authors.initials: JD
authors.lastname: Nissen
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark.
authors.forename: Arne
authors.initials: A
authors.lastname: Schousboe
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark. Helle.Waagepetersen@sund.ku.dk.
authors.forename: Helle S
authors.initials: HS
authors.lastname: Waagepetersen
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000096:biosynthesis / Q000378:metabolism*; D000249:Adenosine Monophosphate / Q000378:metabolism; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000201:enzymology / Q000378:metabolism*; D002478:Cells, Cultured; D002952:Citric Acid Cycle / Q000187:drug effects; D003847:Deoxyglucose / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005971:Glutamates / Q000378:metabolism*; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects; D061251:Primary Cell Culture; D012265:Ribonucleotides / Q000494:pharmacology
chemical_list: D005971:Glutamates; D012265:Ribonucleotides; D000620:Aminoimidazole Carboxamide; D000249:Adenosine Monophosphate; D003847:Deoxyglucose; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide
keywords: AMPK; Astrocytes; Glutamate; Metabolism
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