title: Extracellular N-Acetylaspartate in Human Traumatic Brain Injury.
abstract: N-acetylaspartate (NAA) is an amino acid derivative primarily located in the neurons of the adult brain. The function of NAA is incompletely understood. Decrease in brain tissue NAA is presently considered symptomatic and a potential biomarker of acute and chronic neuropathological conditions. The aim of this study was to use microdialysis to investigate the behavior of extracellular NAA (eNAA) levels after traumatic brain injury (TBI). Sampling for this study was performed using cerebral microdialysis catheters (M Dialysis 71) perfused at 0.3 μL/min. Extracellular NAA was measured in microdialysates by high-performance liquid chromatography in 30 patients with severe TBI and for comparison, in radiographically "normal" areas of brain in six non-TBI neurosurgical patients. We established a detailed temporal eNAA profile in eight of the severe TBI patients. Microdialysate concentrations of glucose, lactate, pyruvate, glutamate, and glycerol were measured on an ISCUS clinical microdialysis analyzer. Here, we show that the temporal profile of microdialysate eNAA was characterized by highest levels in the earliest time-points post-injury, followed by a steady decline; beyond 70 h post-injury, average levels were 40% lower than those measured in non-TBI patients. There was a significant inverse correlation between concentrations of eNAA and pyruvate; eNAA showed significant positive correlations with glycerol and the lactate/pyruvate (L/P) ratio measured in microdialysates. The results of this on-going study suggest that changes in eNAA after TBI relate to the release of intracellular components, possibly due to neuronal death or injury, as well as to adverse brain energy metabolism.
authors.affiliation: 1 Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Shannon
authors.affiliation: 1 Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Susan
authors.initials: S
authors.lastname: van der Heide
authors.affiliation: 3 Division of Anaesthesia, Department of Medicine, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Eleanor L
authors.initials: EL
authors.lastname: Carter
authors.affiliation: 1 Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Jalloh
authors.affiliation: 2 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge , Cambridge, United Kingdom .|3 Division of Anaesthesia, Department of Medicine, University of Cambridge , Cambridge, United Kingdom .
authors.forename: David K
authors.initials: DK
authors.lastname: Menon
authors.affiliation: 1 Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge , Cambridge, United Kingdom .|2 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hutchinson
authors.affiliation: 1 Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge , Cambridge, United Kingdom .|2 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Keri L H
authors.initials: KL
authors.lastname: Carpenter
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D000070642:Brain Injuries, Traumatic / Q000175:diagnosis* / Q000378:metabolism*; D045604:Extracellular Fluid / Q000737:chemistry / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D017551:Microdialysis / Q000379:methods; D008875:Middle Aged; D013997:Time Factors; D055815:Young Adult
chemical_list: D015415:Biomarkers; D001224:Aspartic Acid; C000179:N-acetylaspartate
keywords: N-acetylaspartate; brain metabolism; microdialysis; traumatic brain injury (human)