title: Brain lactate responses during visual stimulation in fasting and hyperglycemic subjects: a proton magnetic resonance spectroscopy study at 1.5 Tesla.
abstract: Proton magnetic resonance spectroscopy ((1)H-MRS) studies showing increased lactate during neural activation support a broader role for lactate in brain energy metabolism than was traditionally recognized. Proton MRS measures of brain lactate responses have been used to study regional brain metabolism in clinical populations. This study examined whether variations in blood glucose influence the lactate response to visual stimulation in the visual cortex. Six subjects were scanned twice, receiving either saline or 21% glucose intravenously. Using (1)H-MRS at 1.5 Tesla with a long echo time (TE=288 ms), the lactate doublet was visible at 1.32 ppm in the visual cortex of all subjects. Lactate increased significantly from resting to visual stimulation. Hyperglycemia had no effect on this increase. The order of the slice-selective gradients for defining the spectroscopy voxel had a pronounced effect on the extent of contamination by signal originating outside the voxel. The results of this preliminary study demonstrate a method for observing a consistent activity-stimulated increase in brain lactate at 1.5 T and show that variations in blood glucose across the normal range have little effect on this response.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, University of California Davis, Sacramento, CA 95817, USA. rjmaddock@ucdavis.edu
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Maddock
authors.forename: Michael H
authors.initials: MH
authors.lastname: Buonocore
authors.forename: Shawn P
authors.initials: SP
authors.lastname: Lavoie
authors.forename: Linda E
authors.initials: LE
authors.lastname: Copeland
authors.forename: Shawn J
authors.initials: SJ
authors.lastname: Kile
authors.forename: Anne L
authors.initials: AL
authors.lastname: Richards
authors.forename: John M
authors.initials: JM
authors.lastname: Ryan
mesh_terms: D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism; D001921:Brain / Q000503:physiopathology*; D002794:Choline / Q000378:metabolism; D003401:Creatine / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology*; D005215:Fasting / Q000502:physiology*; D005260:Female; D006801:Humans; D006943:Hyperglycemia / Q000503:physiopathology*; D019344:Lactic Acid / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009474:Neurons / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation; D012016:Reference Values; D012815:Signal Processing, Computer-Assisted; D014793:Visual Cortex / Q000502:physiology
chemical_list: D001786:Blood Glucose; D001224:Aspartic Acid; D019344:Lactic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline