Preferential incorporation of alpha-tocopherol vs gamma-tocopherol in human lipoproteins.
Approximately 12 h after the ingestion of a single dose containing 1000 mg each of all-rac-alpha-tocopherol and RRR-gamma-tocopherol, the plasma and lipoproteins of normal subjects contained equal increases of both tocopherols; by 24 h the concentration of gamma-tocopherol, but not the alpha-tocopherol, decreased sharply. Similar studies in hyperlipidemic subjects demonstrated that the plasma and the chylomicron fraction from lipoprotein lipase-deficient patients (with elevated chylomicrons) contained both tocopherols up to 24 h, whereas plasma from a patient with dysbetalipoproteinemia (with elevated beta very-low-density lipoproteins) displayed the decrease in gamma-tocopherol at 24 h. These studies demonstrate that both alpha- and gamma-tocopherols are absorbed and secreted by the intestine in chylomicrons, and suggest that alpha-tocopherol is preferentially secreted by the liver in nascent lipoproteins. Furthermore, studies in post-gall bladder surgery patients suggest a preferential secretion of gamma-tocopherol in bile. Thus, the liver rather than the intestine appears to discriminate between alpha- and gamma-tocopherols.
Traber
M G
MG
Department of Medicine, New York University School of Medicine, NY 10016.
Kayden
H J
HJ
D000328:Adult; D001646:Bile / Q000378:metabolism; D005260:Female; D006801:Humans; D006952:Hyperlipoproteinemia Type III / Q000378:metabolism; D008071:Lipoprotein Lipase / Q000172:deficiency; D008074:Lipoproteins / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D014810:Vitamin E / Q000097:blood / Q000493:pharmacokinetics*
D008074:Lipoproteins; D014810:Vitamin E; D008071:Lipoprotein Lipase