title: A Vitamin B-6 Antagonist from Flaxseed Perturbs Amino Acid Metabolism in Moderately Vitamin B-6-Deficient Male Rats.
abstract: BACKGROUND
  Pyridoxal 5'-phosphate (PLP) plays a crucial role as a cofactor in amino acid metabolism. There is a prevalence of moderate vitamin B-6 deficiency in the population that may be exacerbated through the ingestion of 1-amino d-proline (1ADP), a vitamin B-6 antagonist found in flaxseed.
  
  
  OBJECTIVE
  Given prior evidence of the impact of synthetic 1ADP on indexes of pyridoxine metabolism, the current study was designed to investigate the effects of 1ADP derived from flaxseed on amino acid metabolism in moderately vitamin B-6-deficient rats.
  
  
  METHODS
  Male weanling rats (n = 8/treatment) consumed a semipurified diet containing either 7 mg pyridoxine hydrochloride/kg diet [optimum vitamin B-6 (OB)] or 0.7 mg pyridoxine hydrochloride/kg diet [moderately vitamin B-6 deficient (MB)], each with 0 or 10 mg vitamin B-6 antagonist/kg diet, in either a synthetic form (1ADP) or as a flaxseed extract (FE), for 5 wk. At the end of the experiment, plasma vitamin B-6 and amino acid concentrations and the activities of hepatic PLP-dependent enzymes were analyzed.
  
  
  RESULTS
  Compared with the MB control group, plasma PLP concentrations were 26% and 69% lower, respectively, in the MB+FE and MB+1ADP rats (P ≤ 0.001). In the MB+FE group, the plasma cystathionine concentration was 100% greater and the plasma α-aminobutyric acid and glutamic acid concentrations were 59% and 30% lower, respectively, than in the MB control group. Both synthetic 1ADP and FE significantly (P < 0.001) inhibited the in vitro hepatic activities of 2 PLP-dependent enzymes, cystathionine β-synthase (up to 44%) and cystathionine γ-lyase (up to 60%), irrespective of vitamin B-6 concentrations. Because of vitamin B-6 antagonist exposure, observed perturbations in plasma biomarkers and hepatic enzyme activities were not evident or of lesser magnitude in rats consuming adequate vitamin B-6.
  
  
  CONCLUSIONS
  The current data from a rat model provide evidence that a vitamin B-6 antagonist now prevalent in the human food supply may pose challenges to individuals of moderate vitamin B-6 status.
authors.affiliation: Department of Human Nutritional Sciences and.
authors.forename: Shyamchand
authors.initials: S
authors.lastname: Mayengbam
authors.affiliation: Department of Human Nutritional Sciences and.
authors.forename: Sara
authors.initials: S
authors.lastname: Raposo
authors.affiliation: Department of Human Nutritional Sciences and St-Boniface Hospital Research Centre, Winnipeg, Canada.
authors.forename: Michel
authors.initials: M
authors.lastname: Aliani
authors.affiliation: Department of Human Nutritional Sciences and Department of Animal Science, University of Manitoba, Winnipeg, Canada; and St-Boniface Hospital Research Centre, Winnipeg, Canada james.house@umanitoba.ca.
authors.forename: James D
authors.identifier: http://orcid.org/0000-0003-1389-5491
authors.initials: JD
authors.lastname: House
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000613:Aminobutyrates / Q000097:blood; D000818:Animals; D003540:Cystathionine / Q000097:blood; D003541:Cystathionine beta-Synthase / Q000378:metabolism; D003542:Cystathionine gamma-Lyase / Q000378:metabolism; D004032:Diet; D004195:Disease Models, Animal; D019597:Flax / Q000737:chemistry*; D018698:Glutamic Acid / Q000097:blood; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D011392:Proline / Q000008:administration & dosage / Q000031:analogs & derivatives; D011736:Pyridoxine / Q000008:administration & dosage; D051381:Rats; D025101:Vitamin B 6 / Q000037:antagonists & inhibitors* / Q000097:blood*; D026681:Vitamin B 6 Deficiency / Q000097:blood*
chemical_list: D000596:Amino Acids; D000613:Aminobutyrates; D003540:Cystathionine; D018698:Glutamic Acid; C012179:1-aminoproline; D025101:Vitamin B 6; C012223:alpha-aminobutyric acid; D011392:Proline; D003541:Cystathionine beta-Synthase; D003542:Cystathionine gamma-Lyase; D011736:Pyridoxine
keywords: 1-amino d-proline; amino acid; flaxseed; vitamin B-6; vitamin B-6 antagonist