title: Plasma amino acid levels discriminate between control subjects and mildly depressed elderly women.
abstract: OBJECTIVE
  Depression is the most common of all psychiatric disorders and the role of amino acid transmitters in this pathology has been recently studied. We undertook this study to investigate if the plasma levels of L-arginine, L-citrulline, L-glutamic acid, L-glutamine, L-asparagine and other amino acids, the L-citrulline/L-arginine and the L-tyrosine/L-phenylalanine ratios, and the nitrite levels are modified in mildly depressed women and if such changes are related to olfactory dysfunction.
  
  
  METHODS
  Plasma samples were obtained from elderly female subjects (n = 21) with mild depression and (n = 48) controls. Amino acids were analyzed with high-performance liquid chromatography, plasma nitrite levels were measured using the Griess method, and olfactory performance was assessed by the combined testing of odor identification, odor discrimination, odor recognition, and the olfactory threshold.
  
  
  RESULTS
  Compared to controls, depressed patients had a significantly higher concentration of L-arginine and a significantly lower L-citrulline/L-arginine ratio when the effect of other variables is not taken into account. A logistic regression model allowed us to identify two risk factors for mild depression, L-arginine and L-glutamic acid, and two protective factors, L-asparagine and the L-tyrosine/L-phenylalanine ratio. Additionally, a significant increase in nitrite levels in depressed women was found. No significant differences were found between the percentage of depressed and control women that identified the odors.
  
  
  CONCLUSIONS
  We identified that the amino acids L-arginine and L-glutamic acid are risk factors for mild depression, whereas L-asparagine and the L-tyrosine/L-phenylalanine ratio are protective factors.
authors.affiliation: Departamento de Fisiología, Universidad Nacional Autónoma de México, DF, Mexico.
authors.forename: Adriana
authors.initials: A
authors.lastname: Mayoral-Mariles
authors.forename: Carmen
authors.initials: C
authors.lastname: Cruz-Revilla
authors.forename: Xochitl
authors.initials: X
authors.lastname: Vega-Manriquez
authors.forename: Rebeca
authors.initials: R
authors.lastname: Aguirre-Hernández
authors.forename: Patricia
authors.initials: P
authors.lastname: Severiano-Pérez
authors.forename: Eric
authors.initials: E
authors.lastname: Aburto-Arciniega
authors.forename: Araceli
authors.initials: A
authors.lastname: Jiménez-Mendoza
authors.forename: Rosalinda
authors.initials: R
authors.lastname: Guevara-Guzmán
mesh_terms: D000368:Aged; D000596:Amino Acids / Q000097:blood*; D016022:Case-Control Studies; D003863:Depression / Q000097:blood* / Q000175:diagnosis; D005260:Female; D006801:Humans; D016015:Logistic Models; D009573:Nitrites / Q000097:blood; D055696:Olfactory Perception; D012372:ROC Curve; D012307:Risk Factors; D012903:Smell
chemical_list: D000596:Amino Acids; D009573:Nitrites