title: Contribution of extracellular glutamine as an anaplerotic substrate to neuronal metabolism: a re-evaluation by multinuclear NMR spectroscopy in primary cultured neurons.
abstract: Multinuclear NMR spectroscopy is used to investigate the effect of glutamine on neuronal glucose metabolism. Primary neurons were incubated with [1-(13C)]glucose in the absence or presence of glutamine (2 mM) and/or NH4Cl (5 mM). After ammonia-treatment, the concentrations of high-energy phosphates decreased up to 84% of control, which was aggravated in glutamine-containing medium (up to 42% of control). These effects could not be attributed to changes in mitochondrial glucose oxidation. Withdrawal of glutamine decreased amino acid concentrations, e.g. of glutamate to 53%, but also considerably lessened the 13C enrichment in [4-(13C)]glutamate to 8.3% of control, and decreased the 13C-enrichment in acetyl-CoA entering the Krebs cycle (P < 0.001). Thus, although glutamine is potent in replenishing neuronal glutamate stores, glutamate formation is mainly attributed to its de novo synthesis from glucose. Furthermore, mitochondrial glucose metabolism strongly depends on the supply of carbons from glutamine, indicating that exogenous glutamine is a well-suited substrate to replenish neuronal Krebs cycle intermediates.
authors.affiliation: Department of Organic Chemistry, University of Bremen, Bremen, Germany.
authors.forename: Touraj
authors.initials: T
authors.lastname: Shokati
authors.forename: Claudia
authors.initials: C
authors.lastname: Zwingmann
authors.forename: Dieter
authors.initials: D
authors.lastname: Leibfritz
mesh_terms: D000643:Ammonium Chloride / Q000378:metabolism; D000818:Animals; D002250:Carbon Radioisotopes / Q000737:chemistry / Q000378:metabolism; D002478:Cells, Cultured; D002952:Citric Acid Cycle / Q000502:physiology; D003470:Culture Media / Q000737:chemistry; D004734:Energy Metabolism; D005947:Glucose / Q000737:chemistry / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D051381:Rats
chemical_list: D002250:Carbon Radioisotopes; D003470:Culture Media; D000643:Ammonium Chloride; D005973:Glutamine; D005947:Glucose