Effect of dietary supplementation of beta-carotene on human monocyte-macrophage-mediated oxidation of low density lipoprotein

Abstract

Oxidative modification of low density lipoprotein (LDL), a key step in early atherosclerosis, is protected by the lipoprotein-associated antioxidants. The present study analyzes the effect of beta-carotene in plasma, in LDL and in monocyte-macrophages, on macrophage-mediated oxidation of LDL. We investigated the effect of dietary supplementation of beta-carotene on plasma lipid peroxidation [induced by AAPH (2,2-Azobis-2-amidinopropane hydrochloride)] and on cell-free and cell-mediated oxidation of LDL by human monocyte-derived macrophages (HMDM) in the presence of CuSO4. Significant enrichment with beta-carotene was noted in plasma (twofold), in LDL (2.6-fold) and in HMDM (1.6-fold) 2 weeks after dietary supplementation with 180 mg/day of beta-carotene. Plasma lipid peroxidation analyzed by conjugated dienes generation decreased by 22% (P < 0.01) and LDL susceptibility to oxidation analyzed by malondialdehyde generation decreased by 40% (P < 0.01). After beta-carotene supplementation, beta-carotene-enrichment of HMDM capacity to oxidize native LDL, whereas beta-carotene enrichment of LDL significantly reduced LDL oxidation. In conclusion, then, our results suggest that beta-carotene content of LDL, but not that of the macrophages, is responsible for the inhibition of oxidation of LDL.