Postprandial metabolic fate of tocotrienol-rich vitamin E differs significantly from that of alpha-tocopherol.
BACKGROUND
The detection of tocotrienols in human plasma has proven elusive, and it is hypothesized that they are rapidly assimilated and redistributed in various mammalian tissues.


OBJECTIVE
The primary study objective was to evaluate the postprandial fate of tocotrienols and alpha-tocopherol in human plasma and lipoproteins.


METHODS
Seven healthy volunteers (4 males, 3 females) were administered a single dose of vitamin E [1011 mg palm tocotrienol-rich fraction (TRF) or 1074 mg alpha-tocopherol] after a 7-d conditioning period with a tocotrienol-free diet. Blood was sampled at baseline (fasted) and 2, 4, 5, 6, 8, and 24 h after supplementation. Concentrations of tocopherol and tocotrienol isomers in plasma, triacylglycerol-rich particles (TRPs), LDLs, and HDLs were measured at each interval.


RESULTS
After intervention with TRF, plasma tocotrienols peaked at 4 h (4.79 +/- 1.2 microg/mL), whereas alpha-tocopherol peaked at 6 h (13.46 +/- 1.68 microg/mL). Although tocotrienols were similarly detected in TRPs, LDLs, and HDLs, tocotrienol concentrations were significantly lower than alpha-tocopherol concentrations. In comparison, plasma alpha-tocopherol peaked at 8 h (24.3 +/- 5.22 microg/mL) during the alpha-tocopherol treatment and emerged as the major vitamin E isomer detected in plasma and lipoproteins during both the TRF and the alpha-tocopherol treatments.


CONCLUSIONS
Tocotrienols are detected in postprandial plasma, albeit in significantly lower concentrations than is alpha-tocopherol. This finding confirms previous observations that, in the fasted state, tocotrienols are not detected in plasma. Tocotrienol transport in lipoproteins appears to follow complex biochemically mediated pathways within the lipoprotein cascade.
Fairus
Syed
S
Food Technology and Nutrition Unit, Malaysian Palm Oil Board, Selangor, Malaysia.
Nor
Rosnah M
RM
Cheng
Hwee M
HM
Sundram
Kalyana
K
D000328:Adult; D000975:Antioxidants / Q000378:metabolism; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D005260:Female; D006801:Humans; D008074:Lipoproteins / Q000097:blood*; D008297:Male; D019518:Postprandial Period; D012016:Reference Values; D013997:Time Factors; D024508:Tocotrienols / Q000097:blood*; D014280:Triglycerides / Q000097:blood; D014810:Vitamin E / Q000378:metabolism*; D024502:alpha-Tocopherol / Q000097:blood*
D000975:Antioxidants; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D008074:Lipoproteins; D024508:Tocotrienols; D014280:Triglycerides; D014810:Vitamin E; D024502:alpha-Tocopherol