title: Brain slices from glutaminase-deficient mice metabolize less glutamine: a cellular metabolomic study with carbon 13 NMR.
abstract: In the brain, glutaminase is considered to have a key role in the provision of glutamate, a major excitatory neurotransmitter. Brain slices obtained from wild-type (control) and glutaminase-deficient (GLS1+/-) mice were incubated without glucose and with 5 or 1 mmol/L [3-(13)C]glutamine as substrate. At the end of the incubation, substrate removal and product formation were measured by both enzymatic and carbon 13 nuclear magnetic resonance ((13)C-NMR) techniques. Slices from GLS1+/- mice consumed less [3-(13)C]glutamine and accumulated less [3-(13)C]glutamate. They also produced less (13)CO(2) but accumulated amounts of (13)C-aspartate and (13)C-gamma-aminobutyric acid (GABA) that were similar to those found with brain slices from control mice. The newly formed glutamine observed in slices from control mice remained unchanged in slices from GLS1+/- mice. As expected, flux through glutaminase in slices from GLS1+/- mice was found diminished. Fluxes through all enzymes of the tricarboxylic acid cycle were also reduced in brain slices from GLS1+/- mice except through malate dehydrogenase with 5 mmol/L [3-(13)C]glutamine. The latter diminutions are consistent with the decreases in the production of (13)CO(2) also observed in the slices from these mice. It is concluded that the genetic approach used in this study confirms the key role of glutaminase for the provision of glutamate.
authors.affiliation: Metabolys, Faculté de Médecine R.T.H. Laennec, 7–11 rue G. Paradin, Lyon Cedex 08, France. maha-elhage@hotmail.com
authors.forename: Maha
authors.initials: M
authors.lastname: El Hage
authors.forename: Justine
authors.initials: J
authors.lastname: Masson
authors.forename: Agnès
authors.initials: A
authors.lastname: Conjard-Duplany
authors.forename: Bernard
authors.initials: B
authors.lastname: Ferrier
authors.forename: Gabriel
authors.initials: G
authors.lastname: Baverel
authors.forename: Guy
authors.initials: G
authors.lastname: Martin
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes; D005947:Glucose / Q000494:pharmacology*; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism*; D005972:Glutaminase / Q000235:genetics / Q000378:metabolism*; D005973:Glutamine / Q000235:genetics / Q000378:metabolism*; D008291:Malate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D055432:Metabolomics / Q000379:methods; D051379:Mice; D008817:Mice, Mutant Strains; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D013549:Sweetening Agents / Q000494:pharmacology*
chemical_list: D002247:Carbon Isotopes; D009419:Nerve Tissue Proteins; D013549:Sweetening Agents; D005973:Glutamine; D002245:Carbon Dioxide; D018698:Glutamic Acid; D008291:Malate Dehydrogenase; D005972:Glutaminase; D005947:Glucose