title: Increased serum levels of serine enantiomers in patients with depression.
abstract: OBJECTIVE
  Glutamatergic neurotransmission via the N-methyl-d-aspartate (NMDA) receptor is integral to the pathophysiology of depression. This study was performed to examine whether amino acids related to NMDA receptor neurotransmission are altered in the serum of patients with depression.
  
  
  METHODS
  We measured the serum levels of d-serine, l-serine, glycine, glutamate and glutamine in patients with depression (n=70), and age-matched healthy subjects (n=78).
  
  
  RESULTS
  Serum levels of d-serine and l-serine in patients with depression were significantly higher than those of healthy controls (p<0.001). In contrast, serum levels of glycine, glutamate and glutamine did not differ between the two groups. Interestingly, the ratio of l-serine to glycine in patients was significantly higher than that of healthy controls (p<0.001).
  
  
  CONCLUSIONS
  This study suggests that serine enantiomers may be peripheral biomarkers for depression, and that abnormality in the d-serine-l-serine-glycine cycle plays a role in the pathophysiology of depression.
authors.affiliation: 1Division of Clinical Neuroscience,Chiba University Center for Forensic Mental Health,Chiba,Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Hashimoto
authors.affiliation: 2Department of Psychiatry,Chiba University Graduate School of Medicine,Chiba,Japan.
authors.forename: Taisuke
authors.initials: T
authors.lastname: Yoshida
authors.affiliation: 2Department of Psychiatry,Chiba University Graduate School of Medicine,Chiba,Japan.
authors.forename: Masatomo
authors.initials: M
authors.lastname: Ishikawa
authors.affiliation: 1Division of Clinical Neuroscience,Chiba University Center for Forensic Mental Health,Chiba,Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Fujita
authors.affiliation: 2Department of Psychiatry,Chiba University Graduate School of Medicine,Chiba,Japan.
authors.forename: Tomihisa
authors.initials: T
authors.lastname: Niitsu
authors.affiliation: 2Department of Psychiatry,Chiba University Graduate School of Medicine,Chiba,Japan.
authors.forename: Michiko
authors.initials: M
authors.lastname: Nakazato
authors.affiliation: 2Department of Psychiatry,Chiba University Graduate School of Medicine,Chiba,Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Watanabe
authors.affiliation: 2Department of Psychiatry,Chiba University Graduate School of Medicine,Chiba,Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Sasaki
authors.affiliation: 2Department of Psychiatry,Chiba University Graduate School of Medicine,Chiba,Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Shiina
authors.affiliation: 2Department of Psychiatry,Chiba University Graduate School of Medicine,Chiba,Japan.
authors.forename: Tasuku
authors.initials: T
authors.lastname: Hashimoto
authors.affiliation: 2Department of Psychiatry,Chiba University Graduate School of Medicine,Chiba,Japan.
authors.forename: Nobuhisa
authors.initials: N
authors.lastname: Kanahara
authors.affiliation: 2Department of Psychiatry,Chiba University Graduate School of Medicine,Chiba,Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Hasegawa
authors.affiliation: 2Department of Psychiatry,Chiba University Graduate School of Medicine,Chiba,Japan.
authors.forename: Masayo
authors.initials: M
authors.lastname: Enohara
authors.affiliation: 2Department of Psychiatry,Chiba University Graduate School of Medicine,Chiba,Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kimura
authors.affiliation: 2Department of Psychiatry,Chiba University Graduate School of Medicine,Chiba,Japan.
authors.forename: Masaomi
authors.initials: M
authors.lastname: Iyo
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D003863:Depression / Q000097:blood*; D005260:Female; D018698:Glutamic Acid / Q000097:blood*; D005973:Glutamine / Q000097:blood*; D005998:Glycine / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012694:Serine / Q000097:blood*; D013237:Stereoisomerism; D055815:Young Adult
chemical_list: D015415:Biomarkers; D005973:Glutamine; D018698:Glutamic Acid; D012694:Serine; D005998:Glycine
keywords:     d-serine;     l-serine; NMDA receptor; biomarker; depression