Key result
Hemodialysis patients had increased neopterin, kynurenine, and kynurenine to tryptophan ratio, and decreased tryptophan concentrations compared to healthy controls (all p < 0.01).
Observational (n=115)
p-value: p=<0.01
Tryptophan degradation is increased in hemodialysis patients, potentially linked to chronic inflammation and immune activation, with a weak correlation to psychological presentation.
Supports hypothesis of inflammation-linked tryptophan degradation in hemodialysis; cross-sectional design leaves causality and clinical relevance open.
BACKGROUND: Hemodialysis patients often present with increased concentrations of tryptophan catabolites perhaps related to an enhanced activity of tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO) that is inducible by pro-inflammatory stimuli. The often chronic inflammation and immune activation status in dialysis patients may accelerate tryptophan degradation, which could influence patients' psychological performance. PATIENTS AND METHODS: In this study, plasma concentrations of kynurenine and tryptophan were determined by HPLC in 75 dialysis patients, aged 65.3 ± 15.0 years. Forty patients were female, 35 male; 21 (28%) had diabetes mellitus Type 1 or 2 and 32 (43%) suffered from sleep disturbances and/or depression. Their dialysis vintage was 4.26 ± 4.72 years. HPLC results were compared to concentrations obtained from 40 healthy blood donors, to immune activation marker neopterin, and to psychological test results based on INTERMED scores. RESULTS: Compared to those in healthy controls, tryptophan concentrations were decreased in patients. Neopterin, kynurenine and the kynurenine to tryptophan ratio (kyn/trp, an index of tryptophan degradation) were increased in patients (all p < 0.01). Kyn/trp correlated with neopterin concentrations (rs = 0.393, p < 0.01). INTERMED scores were 21.0 + 8.4 and slightly higher in females (U = -1.831, p < 0.07); they correlated with tryptophan concentrations (rs = -0.227, p < 0.05) but with no other parameter studied. Data point to a possible relationship between tryptophan metabolic disturbances and psychologic presentation of patients, although only a rather weak relationship was found. CONCLUSION: We conclude that tryptophan degradation is increased in dialysis patients. The association with increased neopterin concentrations indicates activated IDO.
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Koenig et al. (2010) conducted an observational in Hemodialysis (n=115). Hemodialysis vs. Healthy blood donors was evaluated on Plasma concentrations of tryptophan, neopterin, kynurenine, and kynurenine to tryptophan ratio (p=<0.01). Hemodialysis patients had increased neopterin, kynurenine, and kynurenine to tryptophan ratio, and decreased tryptophan concentrations compared to healthy controls (all p < 0.01).
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