title: Decreased γ-aminobutyric acid levels in the parietal region of patients with Alzheimer's disease.
abstract: OBJECTIVE
  To determine whether there are in vivo differences of γ-aminobutyric acid (GABA) levels in frontal and parietal regions of Alzheimer's disease (AD) patients, compared with healthy controls using magnetic resonance spectroscopy ((1) H-MRS).
  
  
  METHODS
  Fifteen AD patients and fifteen age- and gender-matched healthy controls underwent (1) H-MRS of the frontal and parietal lobes using the "MEGA-Point Resolved Spectroscopy Sequence" (MEGA-PRESS) technique, and cognitive levels of subjects were evaluated using Mini-Mental State Examination (MMSE) tests. MRS data were processed using the Gannet program. Because the signal detected by MEGA-PRESS includes contributions from GABA, macromolecules and homocarnosine, it is labeled as "GABA+" rather than GABA. Differences of GABA+/Cr ratios between AD patients and controls were tested using covariance analysis, adjusting for gray matter fraction. The relationship between GABA+/Cr and MMSE scores was also analyzed.
  
  
  RESULTS
  Significant lower GABA+/Cr ratios were found in the parietal region of AD patients compared with controls (P = 0.041). In AD patients, no significant correlations between GABA+/Cr and MMSE scores were found in either the frontal (r = -0.164; P = 0.558) or parietal regions (r = 0.025; P = 0.929).
  
  
  CONCLUSIONS
  Decreased GABA+/Cr levels were present in the parietal region of patients with AD in vivo, suggesting that abnormalities of the GABAergic system may be present in the pathogenesis of AD.
authors.affiliation: Shandong Medical Imaging Research Institute, Shandong University, Jinan, Shandong, China.
authors.forename: Xue
authors.initials: X
authors.lastname: Bai
authors.forename: Richard A E
authors.initials: RA
authors.lastname: Edden
authors.forename: Fei
authors.initials: F
authors.lastname: Gao
authors.forename: Guangbin
authors.initials: G
authors.lastname: Wang
authors.forename: Lebin
authors.initials: L
authors.lastname: Wu
authors.forename: Bin
authors.initials: B
authors.lastname: Zhao
authors.forename: Minzhong
authors.initials: M
authors.lastname: Wang
authors.forename: Queenie
authors.initials: Q
authors.lastname: Chan
authors.forename: Weibo
authors.initials: W
authors.lastname: Chen
authors.forename: Peter B
authors.initials: PB
authors.lastname: Barker
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D015536:Down-Regulation; D005260:Female; D005625:Frontal Lobe / Q000378:metabolism*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D057054:Molecular Imaging / Q000379:methods*; D010296:Parietal Lobe / Q000378:metabolism*; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D014018:Tissue Distribution; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D005680:gamma-Aminobutyric Acid
keywords: 1H-MRS; Alzheimer's disease; GABA; MEGA-PRESS; MMSE