Clinical Rheumatology

, Volume 25, Issue 3, pp 334–337 | Cite as

Tryptophan degradation increases with stage in patients with rheumatoid arthritis

  • Katharina Schroecksnadel
  • Christiana Winkler
  • Christian Duftner
  • Barbara Wirleitner
  • Michael Schirmer
  • Dietmar Fuchs
Original Article


Immune system activation is known to be involved in the progression of rheumatoid arthritis (RA). The proinflammatory cytokine interferon-γ in various cells, including monocytes, induces the enzyme indoleamine (2,3)-dioxygenase (IDO), which converts tryptophan to kynurenine. In sera of 22 patients (17 women and 5 men) with RA stages 1 to 4 according to Steinbrocker, the concentrations of tryptophan and kynurenine were measured by high-pressure liquid chromatography. To estimate IDO activity, the kynurenine to tryptophan ratio (kyn/trp) was calculated. In parallel, concentrations of the macrophage activation marker neopterin were determined by enzyme-linked immunosorbent assay. Tryptophan concentrations were lower in patients with RA, and the decrease in serum tryptophan correlated with increase in stage (p<0.05). Kyn/trp correlated well with neopterin concentrations, which were elevated in most patients. Whereas higher C-reactive protein concentrations and erythrocyte sedimentation rates were observed in patients with greater disease activity, tryptophan and neopterin concentrations did not differ between patients with different subjective disease activity graded by the physician. Deficiency of the essential amino acid tryptophan in patients with RA most likely results from immune activation involved in the pathogenesis of the disease. It could also be relevant for the mood of patients, as tryptophan is the precursor of serotonin.


Disease activity Indoleamine (2,3)-dioxygenase Neopterin Rheumatoid arthritis Stage Tryptophan degradation 



This work was supported by the Austrian Federal Ministry of Social Affairs and Generations.


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Copyright information

© Clinical Rheumatology 2005

Authors and Affiliations

  • Katharina Schroecksnadel
    • 1
    • 2
  • Christiana Winkler
    • 1
    • 2
  • Christian Duftner
    • 3
  • Barbara Wirleitner
    • 1
    • 2
  • Michael Schirmer
    • 3
  • Dietmar Fuchs
    • 1
    • 2
  1. 1.Division of Biological Chemistry, Biocentre FritzInnsbruck Medical UniversityInnsbruckAustria
  2. 2.Ludwig Boltzmann Institute of AIDS–ResearchInnsbruckAustria
  3. 3.Department of Internal MedicineInnsbruck Medical UniversityInnsbruckAustria

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