title: Inhibitors of the alpha-ketoglutarate dehydrogenase complex alter [1-13C]glucose and [U-13C]glutamate metabolism in cerebellar granule neurons.
abstract: Diminished activity of the alpha-ketoglutarate dehydrogenase complex (KGDHC), an important component of the tricarboxylic acid (TCA) cycle, occurs in several neurological diseases. The effect of specific KGDHC inhibitors [phosphonoethyl ester of succinyl phosphonate (PESP) and the carboxy ethyl ester of succinyl phosphonate (CESP)] on [1-13C]glucose and [U-13C]glutamate metabolism in intact cerebellar granule neurons was investigated. Both inhibitors decreased formation of [4-13C]glutamate from [1-13C]glucose, a reduction in label in glutamate derived from [1-13C]glucose/[U-13C]glutamate through a second turn of the TCA cycle and a decline in the amounts of gamma-aminobutyric acid (GABA), aspartate, and alanine. PESP decreased formation of [U-13C]aspartate and total glutathione, whereas CESP decreased concentrations of valine and leucine. The findings are consistent with decreased KGDHC activity; increased alpha-ketoglutarate formation; increased transamination of alpha-ketoglutarate with valine, leucine, and GABA; and new equilibrium position of the aspartate aminotransferase reaction. Overall, the findings also suggest that some carbon derived from alpha-ketoglutarate may bypass the block in the TCA cycle at KGDHC by means of the GABA shunt and/or conversion of valine to succinate. The results suggest the potential of succinyl phosphonate esters for modeling the biochemical and pathophysiological consequences of reduced KGDHC activity in brain diseases.
authors.affiliation: Instituto de Biologia Experimental e Tecnológica/Instituto de Tecnologia Química e Biológica (IBET/ITQB), Oeiras, Portugal.
authors.forename: Sónia Sá
authors.initials: SS
authors.lastname: Santos
authors.forename: Gary E
authors.initials: GE
authors.lastname: Gibson
authors.forename: Arthur J L
authors.initials: AJ
authors.lastname: Cooper
authors.forename: Travis T
authors.initials: TT
authors.lastname: Denton
authors.forename: Charles M
authors.initials: CM
authors.lastname: Thompson
authors.forename: Victoria I
authors.initials: VI
authors.lastname: Bunik
authors.forename: Paula M
authors.initials: PM
authors.lastname: Alves
authors.forename: Ursula
authors.initials: U
authors.lastname: Sonnewald
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002247:Carbon Isotopes / Q000378:metabolism; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005947:Glucose / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D051379:Mice; D015233:Models, Statistical; D009433:Neural Inhibition / Q000502:physiology*; D009474:Neurons / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D018698:Glutamic Acid; D007655:Ketoglutarate Dehydrogenase Complex; D005947:Glucose