title: The relation between plasma tyrosine concentration and fatigue in primary biliary cirrhosis and primary sclerosing cholangitis.
abstract: BACKGROUND
  In primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) fatigue is a major clinical problem. Abnormal amino acid (AA) patterns have been implicated in the development of fatigue in several non-hepatological conditions but for PBC and PSC no data are available. This study aimed to identify abnormalities in AA patterns and to define their relation with fatigue.
  
  
  METHODS
  Plasma concentrations of tyrosine, tryptophan, phenylalanine, valine, leucine and isoleucine were determined in plasma of patients with PBC (n = 45), PSC (n = 27), chronic hepatitis C (n = 22) and healthy controls (n = 73). Fatigue and quality of life were quantified using the Fisk fatigue severity scale, a visual analogue scale and the SF-36.
  
  
  RESULTS
  Valine, isoleucine, leucine were significantly decreased in PBC and PSC. Tyrosine and phenylalanine were increased (p < 0.0002) and tryptophan decreased (p < 0.0001) in PBC. In PBC, but not in PSC, a significant inverse relation between tyrosine concentrations and fatigue and quality of life was found. Patients without fatigue and with good quality of life had increased tyrosine concentrations compared to fatigued patients. Multivariate analysis indicated that this relation was independent from disease activity or severity or presence of cirrhosis.
  
  
  CONCLUSIONS
  In patients with PBC and PSC, marked abnormalities in plasma AA patterns occur. Normal tyrosine concentrations, compared to increased concentrations, may be associated with fatigue and diminished quality of life.
authors.affiliation: Department of Gastroenterology and Hepatology, Erasmus MC, Rotterdam, The Netherlands. pterborg@zonnet.nl
authors.forename: Pieter C J
authors.initials: PC
authors.lastname: ter Borg
authors.forename: Durk
authors.initials: D
authors.lastname: Fekkes
authors.forename: Jan Maarten
authors.initials: JM
authors.lastname: Vrolijk
authors.forename: Henk R
authors.initials: HR
authors.lastname: van Buuren
mesh_terms: D000328:Adult; D000368:Aged; D000596:Amino Acids / Q000097:blood; D015415:Biomarkers / Q000097:blood; D015209:Cholangitis, Sclerosing / Q000097:blood* / Q000150:complications* / Q000503:physiopathology; D005221:Fatigue / Q000209:etiology*; D005260:Female; D006801:Humans; D008105:Liver Cirrhosis, Biliary / Q000097:blood* / Q000150:complications* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D011788:Quality of Life; D012720:Severity of Illness Index; D014443:Tyrosine / Q000097:blood*
chemical_list: D000596:Amino Acids; D015415:Biomarkers; D014443:Tyrosine