Dependence of plasma alpha-tocopherol flux on very low-density triglyceride clearance in humans.
To evaluate the effect of dietary fat-induced alterations in triglyceride (TG) metabolism on plasma and very low-density lipoprotein (VLDL)-alpha-tocopherol, nine healthy males (mean +/- SEM, age: 36 +/- 3 years, BMI: 24.7 +/- 1.1) consumed a 35%-fat diet (control) for one week followed by a 15% low-fat, high-carbohydrate diet for 5 weeks. After each dietary phase, the subjects ingested an evening meal along with a 50 mg capsule of (2)H(6)-RRR-alpha-tocopheryl acetate; blood samples were drawn over a 24 h period while the subjects remained fasted. Low-fat feeding increased fasting plasma TG concentrations by 53% (116 +/- 27 to 178 +/- 32, mg/dl, p < 0.0001) primarily by reducing VLDL-TG clearance. Total plasma alpha-tocopherol concentrations (labeled + unlabeled) were unchanged (25.8 +/- 2.3 vs. 26.4 +/- 3.0 nmol/ml plasma) and no differences between the diets were observed for plasma (2)H(6)-alpha-tocopherol concentration (4.8 +/- 0.6 nmol/ml, for both diets) or enrichments (18.1 +/- 1.8% average for both diets). However, low-fat feeding significantly increased the amount of alpha-tocopherol in the VLDL fraction (43%, p = 0.04) in concert with elevations in VLDL-apoB and TG. The alpha-tocopherol and TG content of VLDL varied in parallel in individual subjects and fractional replacement rates and clearance of alpha-tocopherol and TG in VLDL were closely correlated. Kinetic parameters were decreased by 32-39% from high-fat to low-fat. These data suggest that vitamin E bioavailability is similar between a 15 and 35% fat diet, with a redistribution of alpha-tocopherol in lipoproteins occurring during low-fat feeding (increased in the VLDL fraction, reduced in the other lipoproteins), and transfer of alpha-tocopherol from VLDL depends upon TG removal from the particle, consistent with previous observations in vitro and in animal studies.
Parks
E J
EJ
Department of Food Science and Nutrition, University of Minnesota, Twin Cities, St. Paul, MN 55108-6099, USA. eparks@tc.umn.edu
Dare
D
D
Frazier
K B
KB
Hellerstein
M K
MK
Neese
R A
RA
Hughes
E
E
Traber
M G
MG
D000328:Adult; D001055:Apolipoproteins B / Q000097:blood; D002784:Cholesterol / Q000097:blood; D003903:Deuterium; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage; D006801:Humans; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000097:blood; D008077:Lipoproteins, LDL / Q000097:blood; D008079:Lipoproteins, VLDL / Q000097:blood*; D008297:Male; D008657:Metabolic Clearance Rate; D024505:Tocopherols; D014280:Triglycerides / Q000097:blood*; D014810:Vitamin E / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000097:blood*; D024502:alpha-Tocopherol / Q000031:analogs & derivatives*
D001055:Apolipoproteins B; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D014280:Triglycerides; D014810:Vitamin E; D002784:Cholesterol; D003903:Deuterium; D024502:alpha-Tocopherol; D024505:Tocopherols