Effect of Dietary Supplementation of Different β-Carotene Isomers on Lipoprotein Oxidative Modification

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Abstract
Atherogenesis involves oxidative modification of low-density lipoprotein (LDL), which is associated with the depletion of the LDL endogenous anti-oxidants. Thus, enrichment of LDL with the anti-oxidant β-carotene has the potential of reducing the susceptibility of LDL to lipid peroxidation. We compared a pure synthetic all-trans β-carotene isomer with a stereoisomeric mixture of 9-cis and all-trans β-carotene derived from the alga Dunaliella bardawil. Ingestion of β-carotene either in a single dose (300 mg) or for 14 days (180 mg/day) by healthy subjects resulted in a significant elevation in the plasma and the LDL content of the pro-vitamin. However, there was substantially less elevation in β-carotene in response to the Dunaliella β-carotene, with a 1.8-fold elevation in plasma in comparison to a 3.6-fold elevation upon synthetic β-carotene supplementation. Oxidative modification of LDL, measured both after 14 days and a single-dose intake, was similarly reduced, as measured by the thiobarbituric acid-reactive substances (TBARS) generation (which indicated LDL susceptibility to in vitro lipid perodixation, in the presence of copper ions), by 40% or 49%, after 14-day supplementation of the synthetic or the Dunaliella fi-carotene, respectively. The present study thus demonstrates an inhibitory effect by both isomers of β-carotene on the susceptibility of LDL to oxidative modification. Supplementation with fi-carotene may be an important approach to reducing atherosclerosis via its inhibitory effect on the formation of atherogenic oxidized LDL.