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Dissertation
Characterization of carotenoid transport and antioxidant function in humans
Doctor of Philosophy (Ph.D.), Medical College of Pennsylvania
23 Jul 1996
DOI:
https://doi.org/10.17918/00007303
Abstract
Carotenoids are dietary, lipophilic antioxidants transported in vivo with plasma lipoproteins. These antioxidants may help prevent atherosclerosis, a disease believed to involve the oxidation of LDL. One goal of this research was to characterize the transport of carotenoids with lipoproteins. The hypothesis that carotenoids inhibit LDL oxidation and that individual carotenoids vary in effectiveness as antioxidants, was also tested. Total carotenoid in fasted human plasma associated primarily with LDL (73%), as did the more non-polar [beta]-cryptoxanthin (68%), lycopene (79%), and [beta]-carotene (72%), in patterns similar to cholesteryl ester. The more polar lutein distributed equally between LDL (44%) and HDL (38%) in a pattern similar to phospholipid. Relative polarities of carotenoids appear to influence their distributions. However, bulk solubility does not, as only four carotenoid molecules associated with each VLDL, one with each LDL, while only 25 of every 1,000 HDL particles contained carotenoid. These amounts represent a small 0.02 to 0.04 mole % of major lipids. Lecithin cholesterol acyl transferase and cholesteryl ester transfer protein, factors responsible for major lipid distributions, do not appear to influence carotenoid distributions as net transfer of carotenoids among lipoproteins did not occur when plasma was incubated in vitro, unlike triglyceride and cholesteryl ester. When LDL were oxidized in vitro (0.25 mg protein/ml, 5[mu]M CuSO4, 37[degrees]C), lutein, [beta]-cryptoxanthin, lycopene, and [beta]-carotene were destroyed at different rates (7, 3, 17, 11 pmols/min) and before the formation of lipid peroxidation products. To test the hypothesis that carotenoids differ in their antioxidant abilities, amounts of carotenoids in LDL were increased by adding each carotenoid in solvent to either isolated LDL or serum. LDL were enriched 4-134, 2-15, and 4-28 fold with lutein, lycopene, or [beta]-carotene, respectively, increasing concentrations to 52, 9.3, and 7.5 nmols/mg protein. The onset of oxidation in LDL enriched with [beta]-carotene (65 min) was significantly delayed compared to controls (19 min) as was the destruction of lutein, lycopene, and [beta]-carotene (t1/2min = 85, 21, 19, respectively) compared to controls (20, 9, 10, respectively). However, increased concentrations of lutein and lycopene did not protect LDL from oxidation. Thus, [beta]-carotene is unique in its ability to alter LDL oxidation. In summary, these studies provide new information on the transport of carotenoids with lipoproteins and their potential for preventing the oxidation of LDL.
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Details
- Title
- Characterization of carotenoid transport and antioxidant function in humans
- Creators
- Joelle Elizabeth Romanchick
- Contributors
- Gerald Harrison (Advisor) - Drexel University, Medical College of Pennsylvania (1970-1993)Diane W. Morel (Advisor) - Drexel University, Medical College of Pennsylvania (1970-1993)
- Awarding Institution
- Medical College of Pennsylvania
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Medical College of Pennsylvania; Philadelphia, Pennsylvania
- Number of pages
- xii, 161 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Medical College of Pennsylvania (1970-1993)
- Other Identifier
- 991021888773404721