title: Tricarboxylic acid cycle inhibition by Li+ in the human neuroblastoma SH-SY5Y cell line: a 13C NMR isotopomer analysis.
abstract: Li+ effects on glucose metabolism and on the competitive metabolism of glucose and lactate were investigated in the human neuroblastoma SH-SY5Y cell line using 13C NMR spectroscopy. The metabolic model proposed for glucose and lactate metabolism in these cells, based on tcaCALC best fitting solutions, for both control and Li+ conditions, was consistent with: (i) a single pyruvate pool; (ii) anaplerotic flux from endogenous unlabelled substrates; (iii) no cycling between pyruvate and oxaloacetate. Li+ was shown to induce a 38 and 53% decrease, for 1 and 15 mM Li+, respectively, in the rate of glucose conversion into pyruvate, when [U-13C]glucose was present, while no effects on lactate production were observed. Pyruvate oxidation by the tricarboxylic acid cycle and citrate synthase flux were shown to be significantly reduced by 64 and 84% in the presence of 1 and 15 mM Li+, respectively, suggesting a direct inhibitory effect of Li+ on tricarboxylic acid cycle flux. This work also showed that when both glucose and lactate are present as energetic substrates, SH-SY5Y cells preferentially consumed exogenous lactate over glucose, as 62% of the acetyl-CoA was derived from [3-13C]lactate while only 26% was derived from [U-13C]glucose. Li+ did not significantly affect the relative utilisation of these two substrates by the cells or the residual contribution of unlabelled endogenous sources for the acetyl-CoA pool.
authors.affiliation: Department of Biochemistry, NMR Center and Center for Neuroscience and Cell Biology, University of Coimbra, P.O. Box 3126, 3001-401 Coimbra, Portugal.
authors.forename: Carla P
authors.initials: CP
authors.lastname: Fonseca
authors.forename: John G
authors.initials: JG
authors.lastname: Jones
authors.forename: Rui A
authors.initials: RA
authors.lastname: Carvalho
authors.forename: F Mark H
authors.initials: FM
authors.lastname: Jeffrey
authors.forename: Liliana P
authors.initials: LP
authors.lastname: Montezinho
authors.forename: Carlos F G C
authors.initials: CF
authors.lastname: Geraldes
authors.forename: M M C A
authors.initials: MM
authors.lastname: Castro
mesh_terms: D000105:Acetyl Coenzyme A / Q000096:biosynthesis; D018692:Antimanic Agents / Q000494:pharmacology; D001714:Bipolar Disorder / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D001923:Brain Chemistry / Q000187:drug effects* / Q000502:physiology; D002247:Carbon Isotopes; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002950:Citrate (si)-Synthase / Q000187:drug effects / Q000378:metabolism; D002952:Citric Acid Cycle / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004734:Energy Metabolism / Q000187:drug effects* / Q000502:physiology; D025461:Feedback, Physiological / Q000187:drug effects / Q000502:physiology; D005947:Glucose / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D008094:Lithium / Q000494:pharmacology*; D009682:Magnetic Resonance Spectroscopy; D009447:Neuroblastoma / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D019289:Pyruvic Acid / Q000378:metabolism
chemical_list: D018692:Antimanic Agents; D002247:Carbon Isotopes; D019344:Lactic Acid; D000105:Acetyl Coenzyme A; D019289:Pyruvic Acid; D008094:Lithium; D002950:Citrate (si)-Synthase; D005947:Glucose