title: Variation in plasma cystathionine and its relation to changes in plasma concentrations of homocysteine and methionine in healthy subjects during a 24-h observation period.
abstract: BACKGROUND
  Plasma cystathionine measurement may be a useful complement to total homocysteine measurement in the assessment of B vitamin status. Information on the within-person variation in cystathionine is currently sparse.
  
  
  OBJECTIVE
  The goal was to study the daily variation in plasma cystathionine concentrations in healthy subjects.
  
  
  METHODS
  Twelve subjects (aged 22-29 y) were followed for 24 h. During the observation period, the subjects received a breakfast (containing 15-18 g protein) at 0900 and a beef dinner (containing approximately 50 g protein) at 1500. Multiple blood samples for metabolite analyses were collected during the day, and a final sample was obtained the next morning. The results are expressed as medians and interquartile ranges.
  
  
  RESULTS
  All subjects had normal fasting cystathionine concentrations [0.120 (0.100-0.160) micro mol/L]. Cystathionine concentrations increased significantly after breakfast, reached a maximum after 4 h of 142.4% (100.0-170.3%) of the fasting concentration, and then declined to fasting concentrations before dinner. After dinner, plasma cystathionine started to increase within 0.5 h and reached a maximum after 6 h [281.3% (194.1-351.4%) of the concentration measured before dinner]. The changes in plasma methionine and total homocysteine concentrations during the day were less pronounced.
  
  
  CONCLUSIONS
  Food intake, even of foods with low protein content, causes an increase in plasma cystathionine concentrations that is more pronounced than the concomitant changes in total homocysteine and methionine. In studies including plasma cystathionine measurement, blood sampling in the fasting state should be considered.
authors.affiliation: Department of Anaesthesia and Intensive Care and the Centre for Clinical Research, Haukeland University Hospital, Bergen, Norway. anne.guttormsen@helse-bergen.no
authors.forename: Anne B
authors.initials: AB
authors.lastname: Guttormsen
authors.forename: Einar
authors.initials: E
authors.lastname: Solheim
authors.forename: Helga
authors.initials: H
authors.lastname: Refsum
mesh_terms: D000328:Adult; D002940:Circadian Rhythm; D003540:Cystathionine / Q000097:blood*; D005215:Fasting / Q000097:blood*; D005260:Female; D005502:Food; D008401:Gas Chromatography-Mass Spectrometry; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D008297:Male; D008715:Methionine / Q000097:blood*
chemical_list: D006710:Homocysteine; D003540:Cystathionine; D008715:Methionine