Submitted to: Free Radicals in Biology and Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/1998
Publication Date: N/A
Interpretive Summary: This report shows that feeding B-carotene (the colored pigment that makes carrots orange) but not the related compound lycopene (the colored pigment that makes tomatoes red) to human subjects protects the cholesterol-carrying complex in their blood (so called LDL or low-density lipoprotein) from oxidation, a process that might make the LDL more liable to cause heart disease. The results will benefit scientists studying the metabolism and function of carotenoids and those interested in cardiovascular disease and atherosclerosis.
Technical Abstract: Carotenoids may protect LDL from oxidation, a process implicated in atherogenesis. Our previous studies showed that in vitro enrichment of LDL with B-carotene protected it from cell-mediated oxidation whereas in vitro enrichment with either lutein or lycopene enhanced oxidation of the LDL. Here we have examined the impact of LDL carotenoid content on its oxidation by human aortic endothelial cells (EaHy-1) in culture, comparing the effects of in vitro supplementation with in vitro enrichments. The B-carotene content in human LDL was increased 3-6 fold by supplementation with 15 mg B-carotene per day for 4 weeks, and the lycopene content of LDL in other individuals was increased 2-3 fold by ingestion of one glass of tomato juice daily for 3 weeks. These LDL were incubated with cells in Ham's F-10 medium for up to 48 hours. Following dietary B-carotene supplementation, LDL oxidation (as assessed by formation of lipid hydroperoxides) was markedly inhibited, to an even greater extent than was observed for LDL enriched in vitro with B-carotene (which resulted in a 12-fold increase in LDL B-carotene). No effect on oxidation was seen for LDL enriched in vivo with lycopene. Thus, B-carotene appears to function as an antioxidant in protecting LDL from cell-mediated oxidation while lycopene does not. Moreover, enrichment of LDL with carotenoid by dietary supplementation provides more antioxidant protection than that afforded by in vitro enrichment.