title: Tryptophan hydroxylase gene (TPH1) and peripheral tryptophan levels in depression.
abstract: BACKGROUND
  Genetic variants have been discovered in two genes encoding for tryptophan hydroxylase (TPH)-TPH1 and TPH2. Low tryptophan (TRP) levels are associated with depression and may arise because of stress. Evidence suggests that hypothalamic and peripheral 5HT systems have a significant role in appetite regulation, possibly a homeostatic mechanism in regulating peripheral TRP levels.
  
  
  METHODS
  We examined the association between a polymorphism in intron 7 of TPH1, 218A>C and plasma total TRP levels in 118 patients with major depression.
  
  
  RESULTS
  There was an interaction between 218A>C and gender in determining plasma TRP whereby presence of the 218C allele, in women, was associated with markedly reduced plasma TRP.
  
  
  CONCLUSIONS
  The study investigated only the TRP1 gene and did not use a haplotype analysis. The results only apply to a population of subjects suffering from major depression.
  
  
  CONCLUSIONS
  TPH1 may be associated with the regulation of peripheral tryptophan levels and therefore availability of tryptophan to the brain. This may have relevance to a range of neuropsychiatric conditions.
authors.affiliation: Department of Psychological Medicine, University of Otago, Christchurch, Christchurch, New Zealand. richard.porter@otago.ac.nz
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Porter
authors.forename: Roger T
authors.initials: RT
authors.lastname: Mulder
authors.forename: Peter R
authors.initials: PR
authors.lastname: Joyce
authors.forename: Allison L
authors.initials: AL
authors.lastname: Miller
authors.forename: Martin
authors.initials: M
authors.lastname: Kennedy
mesh_terms: D000328:Adult; D017931:DNA Primers / Q000235:genetics; D003865:Major Depressive Disorder / Q000097:blood* / Q000175:diagnosis / Q000235:genetics*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D005838:Genotype; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007438:Introns / Q000235:genetics; D008297:Male; D011110:Polymorphism, Genetic / Q000235:genetics; D011795:Surveys and Questionnaires; D014365:Tryptophan Hydroxylase / Q000097:blood* / Q000235:genetics*
chemical_list: D017931:DNA Primers; C497467:TPH1 protein, human; D014365:Tryptophan Hydroxylase