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  • Title: Tryptophan hydroxylase gene (TPH1) and peripheral tryptophan levels in depression.
    Author: Porter RJ, Mulder RT, Joyce PR, Miller AL, Kennedy M.
    Journal: J Affect Disord; 2008 Jul; 109(1-2):209-12. PubMed ID: 18177948.
    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. LIMITATIONS: 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.
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