title: Alpha-tocotrienol is the most abundant tocotrienol isomer circulated in plasma and lipoproteins after postprandial tocotrienol-rich vitamin E supplementation.
abstract: BACKGROUND
  Tocotrienols (T3) and tocopherols (T), both members of the natural vitamin E family have unique biological functions in humans. T3 are detected in circulating human plasma and lipoproteins, although at concentrations significantly lower than α-tocopherol (α-T). T3, especially α-T3 is known to be neuropotective at nanomolar concentrations and this study evaluated the postprandial fate of T3 and α-T in plasma and lipoproteins.
  
  
  METHODS
  Ten healthy volunteers (5 males and 5 females) were administered a single dose of vitamin E [526 mg palm tocotrienol-rich fraction (TRF) or 537 mg α-T] after 7-d pre-conditioning on a T3-free diet. Blood was sampled at baseline (fasted) and 2, 4, 5, 6, 8, and 24 h after supplementation. Concentrations of T and T3 isomers in plasma, triacylglycerol-rich particles (TRP), LDL, and HDL were measured at each postprandial interval.
  
  
  RESULTS
  After TRF supplementation, plasma α-T3 and γ-T3 peaked at 5 h (α-T3: 4.74 ± 1.69 μM; γ-T3: 2.73 ± 1.27 μM). δ-T3 peaked earlier at 4 h (0.53 ± 0.25 μM). In contrast, α-T peaked at 6 h (30.13 ± 2.91 μM) and 8 h (37.80 ± 3.59 μM) following supplementation with TRF and α-T, respectively. α-T was the major vitamin E isomer detected in plasma, TRP, LDL, and HDL even after supplementation with TRF (composed of 70% T3). No T3 were detected during fasted states. T3 are detected postprandially only after TRF supplementation and concentrations were significantly lower than α-T.
  
  
  CONCLUSIONS
  Bio-discrimination between vitamin E isomers in humans reduces the rate of T3 absorption and affects their incorporation into lipoproteins. Although low absorption of T3 into circulation may impact some of their physiological functions in humans, T3 have biological functions well below concentration noted in this study.
authors.affiliation: Malaysian Palm Oil Board (MPOB), 6, Persiaran Institusi, Bandar Baru Bangi, 43000, Kajang, Selangor, Malaysia.
authors.forename: Syed
authors.initials: S
authors.lastname: Fairus
authors.forename: Rosnah M
authors.initials: RM
authors.lastname: Nor
authors.forename: Hwee M
authors.initials: HM
authors.lastname: Cheng
authors.forename: Kalyana
authors.initials: K
authors.lastname: Sundram
mesh_terms: D000328:Adult; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D008074:Lipoproteins / Q000097:blood*; D008075:Lipoproteins, HDL / Q000097:blood; D008297:Male; D000073878:Palm Oil; D010938:Plant Oils; D019518:Postprandial Period; D024505:Tocopherols / Q000097:blood; D024508:Tocotrienols / Q000097:blood; D014810:Vitamin E / Q000008:administration & dosage* / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D008074:Lipoproteins; D008075:Lipoproteins, HDL; D010938:Plant Oils; D024508:Tocotrienols; D014810:Vitamin E; D000073878:Palm Oil; C082032:tocotrienol, alpha; D024505:Tocopherols