beta-Carotene transport in human lipoproteins. Comparisons with a-tocopherol.
The purpose of this study was to investigate the temporal relationships of the transport of beta-carotene in human lipoproteins. We administered 60 mg beta-carotene with breakfast to nine fasting subjects, then blood samples were collected at intervals of up to 75 h, lipoproteins were isolated, and beta-carotene was quantitated. beta-Carotene concentrations in chylomicrons and very low density lipoproteins (VLDL) peaked at 6 and 9 h, respectively. Nonetheless, at all time points the majority of plasma beta-carotene was contained in low density lipoproteins (LDL), while high density lipoproteins (HDL) carried a smaller portion (at 24 h, 73 +/- 8% in LDL as compared with 23 +/- 5% in HDL). In three subjects, transport of beta-carotene was compared with the results of earlier studies on the transport of stereoisomers of alpha-tocopherol. Unlike plasma RRR-alpha-tocopherol concentrations, which are maintained by the preferential incorporation of RRR-alpha-tocopherol into VLDL by the liver, beta-carotene increased and decreased in VLDL similarly to SRR-alpha-tocopherol, a stereoisomer whose concentrations are not maintained in plasma. In conclusion, beta-carotene is primarily transported in the plasma in LDL, but its incorporation by the liver into lipoproteins does not appear to be enhanced.
Traber
M G
MG
Department of Medicine, New York University School of Medicine, New York 10016.
Diamond
S R
SR
Lane
J C
JC
Brody
R I
RI
Kayden
H J
HJ
D001692:Biological Transport; D002338:Carotenoids / Q000097:blood* / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D008074:Lipoproteins / Q000097:blood*; D008297:Male; D014810:Vitamin E / Q000097:blood* / Q000493:pharmacokinetics*; D019207:beta Carotene
D008074:Lipoproteins; D019207:beta Carotene; D014810:Vitamin E; D002338:Carotenoids