Journal of Neural Transmission

, Volume 107, Issue 3, pp 343–353

Tryptophan degradation and immune activation in Alzheimer's disease

  • B. Widner
  • F. Leblhuber
  • J. Walli
  • G. P. Tilz
  • U. Demel
  • D. Fuchs

DOI: 10.1007/s007020050029

Cite this article as:
Widner, B., Leblhuber, F., Walli, J. et al. J Neural Transm (2000) 107: 343. doi:10.1007/s007020050029

Summary.

Alzheimer's disease (AD) is likely associated with systemic immune activation. During immune response, interferon-gamma stimu-lates indoleamine 2,3-dioxygenase (IDO) converting tryptophan to N-formylkynurenine followed by kynurenine in an ensuing step. Thus, IDO activity is estimated by the kynurenine per tryptophan quotient (Kyn/Trp). In 21 patients suffering from AD, in 20 controls of similar age, and in 49 blood donors we measured serum tryptophan and kynurenine concentrations by HPLC. Lower tryptophan concentrations were found in elderly control subjects compared to blood donors (62.1 vs. 73.0 μM, p < 0.005). Tryptophan concentrations tended to be still lower in AD patients (54.4 μM, p = 0.07) compared to elderly controls. Enhanced tryptophan degradation in patients was reflected by significantly increased Kyn/Trp (46.1 vs. 34.1 in elderly controls, p < 0.05). Correlations were found in patients between Kyn/Trp and concentrations of soluble immune markers in serum, i.e., neopterin, interleukin-2 receptor and tumor necrosis factor receptor (all p < 0.001). Increased Kyn/Trp was associated with reduced cognitive performance. Tryptophan degradation due to immune activation may exert impact on the pathogenesis of AD.

Keywords: Alzheimer's disease, tryptophan, kynurenine, kynurenine per tryptophan quotient, immune activation, soluble immune markers, neopterin. 

Copyright information

© Springer-Verlag Wien 2000

Authors and Affiliations

  • B. Widner
    • 1
  • F. Leblhuber
    • 2
  • J. Walli
    • 2
  • G. P. Tilz
    • 3
  • U. Demel
    • 3
  • D. Fuchs
    • 1
  1. 1. Institute of Medical Chemistry and Biochemistry, University of Innsbruck,AT
  2. 2. Department of Gerontology, Neurological Clinic Wagner-Jauregg, Linz, andAT
  3. 3. Department of Internal Medicine, University of Graz, AustriaAT

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