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Increased serum free tryptophan in patients with diarrhea-predominant irritable bowel syndrome.
MedLine Citation:
PMID:  21056283     Owner:  NLM     Status:  In-Process    
Abstract/OtherAbstract:
Irregularities of serotonin function in irritable bowel syndrome (IBS) may be due to changes in the metabolism of the serotonin precursor l-tryptophan. Dietary alteration of tryptophan intake may impact upon the mood and bowel symptoms of IBS. We hypothesized that diarrhea-predominant irritable bowel syndrome (d-IBS) patients would exhibit an increase in plasma tryptophan due to alterations in tryptophan metabolism. We also hypothesized that a diet low in tryptophan would reverse this change and reduce symptoms. Thirteen patients with d-IBS had fasting serum free and total tryptophan, large neutral amino acids, and 6 kynurenine metabolites measured before and after 2 weeks of a strict dairy-free diet. Baseline tryptophan parameters were compared with an age- and sex-matched control group. Changes in the specific tryptophan parameters before and after dairy-free diet were correlated with symptoms of IBS and mood. Compared with the control group, d-IBS patients at baseline exhibited significantly higher free serum tryptophan (10.5 ± 4.35 vs 4.75 ± 2.43 μmol/L [means ± standard deviation], P = .006) and significantly lower tryptophan dioxygenase and total tryptophan oxidation as measured by the kynurenine to free tryptophan and total kynurenines to free tryptophan ratios (23.37 ± 10.12 vs 55.33 ± 16.02, P < .001 and 49.34 ± 17.84 vs 258.46 ± 98.67, P < .001, respectively). Dairy-free diet did not modulate metabolites of the kynurenine pathway or symptoms. Tryptophan metabolism along the kynurenine pathway is inhibited in d-IBS, and a dairy-free diet does not alter this. Our findings are consistent with possible enhanced serotonin activity in d-IBS.
Authors:
David M Christmas; Abdulla A-B Badawy; Dana Hince; Simon J C Davies; Christopher Probert; Tom Creed; John Smithson; Muhammad Afzal; David J Nutt; John P Potokar
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Nutrition research (New York, N.Y.)     Volume:  30     ISSN:  1879-0739     ISO Abbreviation:  Nutr Res     Publication Date:  2010 Oct 
Date Detail:
Created Date:  2010-11-08     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8303331     Medline TA:  Nutr Res     Country:  United States    
Other Details:
Languages:  eng     Pagination:  678-88     Citation Subset:  IM    
Copyright Information:
Copyright © 2010 Elsevier Inc. All rights reserved.
Affiliation:
Academic Unit of Psychiatry, University of Bristol, Cotham House, Cotham Hill, BS6 6JL Bristol, UK. david.christmas@bristol.ac.uk
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Descriptor/Qualifier:
Grant Support
ID/Acronym/Agency:
069301//Wellcome Trust

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