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Distributions of Carotenoids and α-Tocopherol among Lipoproteins Do Not Change when Human Plasma is Incubated In Vitro

J. E. Romanchik,Diane W. Morel,Earl H. Harrison

Published 1995 in Journal of NutriLife

ABSTRACT

Carotenoids and α-tocopherol are dietary, lipophilic antioxidants which may protect plasma lipoproteins from oxidation, a process believed to contribute to atherogenesis. In this study, the quantities and distributions of carotenoids, α-tocopherol and major lipids in the plasma and lipoproteins of seven normolipidemic humans were determined. Experiments were also conducted to determine if these antioxidants redistribute among lipoproteins when plasma is incubated in vitro. Virtually all of the total carotenoid in plasma associated with lipoproteins, primarily LDL [73 ± 10% (mean ± SD)] as did the more non-polar individual carotenoids, β-cryptoxanthin (68 ± 9%), lycopene (79 ± 9%), and β-carotene (72 ± 12%), in patterns which closely resembled the distribution of total cholesterol. Xanthophyll, the most polar carotenoid examined, distributed equally between LDL (44 ± 11%) and HDL (38 ± 14%), whereas α-tocopherol associated with LDL (43 ± 12%), HDL (26 ± 10%), and VLDL (27 ± 13%). These patterns closely resembled that of phospholipid. Approximately four carotenoid molecules associated with each VLDL and one with each LDL particle, whereas only 25 of every 1000 HDL particles contained carotenoid. Approximately 145 molecules of α-tocopherol associated with VLDL, 12 with LDL, and one with each HDL particle. Unlike triglyceride and cholesteryl ester, known to transfer among lipoproteins through the action of cholesteryl ester transfer protein, net transfer of carotenoids and α-tocopherol among lipoproteins did not occur. While these results suggest that the relative polarities of these antioxidants influence their distributions among lipoproteins, the extent to which carotenoids and α-tocopherol associate with specific lipoproteins does not appear to be governed by some of the mechanisms which lead to the establishment of major lipid distributions.

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