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Tryptophan Metabolism in Post-Withdrawal Alcohol-Dependent Patients

Gabriele v. Gleissenthall, Simon Geisler, Peter Malik, Georg Kemmler, Hannah Benicke, Dietmar Fuchs, Sergei Mechtcheriakov
DOI: http://dx.doi.org/10.1093/alcalc/agu011 251-255 First published online: 18 March 2014

Abstract

Aims: The aim of the study was to investigate the parameters of tryptophan and phenylalanine metabolism and their associations to immune system activation and to behavioural symptoms during medium-term withdrawal (4–12 weeks of abstinence) in alcohol-dependent patients. Methods: Biochemical assays and clinical assessments at the beginning of treatment (fourth week of alcohol abstinence in average) and prior to the discharge after 8 weeks of treatment. Results: Kynurenine to tryptophan ratio (Kyn/Trp) slightly correlated with neopterin levels in early post-withdrawal period (Week 4 of abstinence) but this association disappeared after 12 weeks of abstinence. Phenylalanine and tyrosine concentrations as well as phenylalanine to tyrosine ratio (Phe/Tyr) decreased between Weeks 4 and 12 of abstinence. Kynurenine and Kyn/Trp increased significantly at 12th week of abstinence when compared with the beginning of the study (Week 4 of abstinence). At Week 12, Kyn/Trp significantly correlated with such behavioural symptoms as fatigue, irritability and sleep disturbances. Conclusions: Tryptophan breakdown in early stages may be influenced by the increased activity of indoleamine 2,3-dioxygenase but the increase of Kyn/Trp between Weeks 4 and 12 of abstinence seems to be independent of immune changes and correlates with behavioural symptoms in later stages of the post-withdrawal course. A possible role of kynurenine metabolites in mediation of the increased stress sensibility in post-withdrawal alcohol-dependent patients is discussed.

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