Carotenoids and cardiovascular health

Effects of lycopene on the induction of foam cell formation by modified LDL

The effect of lycopene on macrophage foam cell formation induced by modified low-density lipoprotein (LDL) was studied. Human monocyte-derived macrophages (HMDM) were incubated with lycopene in the presence or absence of native LDL (nLDL) or LDL modified by oxidation (oxLDL), aggregation (aggLDL), or acetylation (acLDL). The cholesterol content, lipid synthesis, scavenger receptor activity, and the secretion of inflammatory [interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha] and anti-inflammatory (IL-10) cytokines was determined. Lycopene was found to decrease the synthesis of cholesterol ester in incubations without LDL or with oxLDL while triacylglycerol synthesis was reduced in the presence of oxLDL and aggLDL. Scavenger receptor activity as assessed by the uptake of acLDL was decreased by approximately 30% by lycopene. In addition, lycopene inhibited IL-10 secretion by up to 74% regardless of the presence of nLDL or aggLDL but did not affect IL-1beta or TNF-alpha release. Lycopene also reduced the relative abundance of mRNA transcripts for scavenger receptor A (SR-A) in THP-1 macrophages treated with aggLDL. These findings suggest that lycopene may reduce macrophage foam cell formation induced by modified LDL by decreasing lipid synthesis and downregulating the activity and expression of SR-A. However, these effects are accompanied by impaired secretion of the anti-inflammatory cytokine IL-10, suggesting that lycopene may also exert a concomitant proinflammatory effect.

Antioxidants and other novel cardiovascular risk factors in subjects with rheumatoid arthritis in a large population sample

OBJECTIVE

To compare antioxidants and other novel and traditional cardiovascular disease (CVD) risk factors in participants with rheumatoid arthritis (RA) and non-RA controls in a large population sample.

METHODS

The Third National Health and Nutrition Examination Survey (NHANES-III) was a cross-sectional population survey in which subjects ages >or=60 underwent a musculoskeletal examination. RA subjects were defined as those who met >or=3 of 6 available 1987 American College of Rheumatology (ACR) criteria. Non-RA subjects were defined as those who met no ACR criteria. We performed univariate and multivariate analyses of the association between RA and each novel and traditional CVD risk factor in RA versus non-RA subjects.

RESULTS

The sample included 5,302 subjects ages >or=60, with 131 (2.5%) RA and 4,444 (84%) non-RA participants. A total of 727 subjects were excluded. Plasma levels of antioxidants alpha-carotene, beta-cryptoxanthin, lutein/zeaxanthin, and lycopene were significantly lower in RA subjects compared with non-RA subjects in multivariate analysis adjusting for potential confounders. Compared with non-RA participants, RA subjects were more likely to have increased C-reactive protein (CRP) levels in multivariate analysis adjusting for potential confounders. RA and non-RA participants had similar prevalence of traditional CVD risk factors and previous CVD.

CONCLUSION

In this large population study, RA subjects had similar prevalence of previous CVD and traditional CVD risk factors as controls. Among novel CVD risk factors, plasma carotenoid levels were significantly lower and CRP level was significantly higher in RA compared with non-RA subjects after adjustment for potential confounders. Further research should evaluate whether these differences account for the observed increased incidence of CVD in individuals with RA.

Lack of effect of oral supplementation with antioxidants on cholesterol oxidation product concentration of human plasma, as revealed by an improved gas chromatography method

A gas chromatographic method was successfully applied to determine cholesterol oxidation products (COPs) in human plasma. The linearity, precision, recovery and sensitivity of the method were determined. Oral supplementation with a combination of vitamin E (800 IU), C (1 g) and beta-carotene (24 mg), given for 21 days to 21 patients, did not significantly decrease plasma COP content. No correlations (n = 26) were found between initial plasma COP content and the following parameters: age, body mass index, plasma content of alpha-tocopherol, cholesterol, high-density lipoprotein cholesterol and triglycerides, and fat, natural antioxidant and oxidized lipid intake. Differences in plasma COP content between type 2 diabetic (n = 6) and nondiabetic (n = 20) patients were not statistically significant. The results from this study lead us to hypothesize that the nonenzymatic oxidation of cholesterol in plasma is negligible compared to COPs originating from the diet. This article also includes a comprehensive review of the drawbacks of the analytical methods of COP determination in plasma and serum.

beta-Cryptoxanthin, a novel natural RAR ligand, induces ATP-binding cassette transporters in macrophages

Despite its serious adverse effects, recent accumulating evidence suggests that a physiological retinoic acid receptor (RAR) agonist, all-trans retinoic acid (atRA), exhibits preventive effects on atherogenesis. Therefore, the present study was designed to explore novel natural RAR ligands with anti-atherogenic effects in order to identify and develop a drug without severe side effects. Among xanthophylls and carotenoids studied, beta-cryptoxanthin and lutein exhibited RAR ligand activity in yeast two-hybrid system that was found to be completely abolished by the RAR pan-antagonist LE540. Furthermore, these molecules can bind the RAR ligand-binding domain in the CoA-BAP system but not RXR ligand-binding domain. These results indicate that both beta-cryptoxanthin and lutein serve as ligands for RAR, but not RXR, although their binding affinity was three orders of magnitude lower than that of atRA. Additionally, when applied to macrophages, beta-cryptoxanthin indeed was found to induce the ATP-binding cassette transporter A1 (ABCA1) and ABCG1 mRNAs, which exert anti-atherosclerotic effects by preventing cholesteryl ester accumulation in macrophages. The induction of ABCA1 proteins by beta-cryptoxanthin as well as atRA was abrogated by LE540. In summary, beta-cryptoxanthin appears to be more an efficient provitamin A source than other carotenoids and xanthophylls including beta-carotene, since beta-cryptoxanthin can act not only as a RAR agonist but also a source of vitamin A. Taking into account that the pharmacodynamics difference between beta-cryptoxanthin and atRA, beta-cryptoxanthin appears to exert beneficial effects on atherogenesis through RAR activation in the manner different from atRA.

Carotenoids and chronic diseases

Chronic diseases such as cancer and cardiovascular diseases are the major causes of deaths in North America. Dietary intake of fruits and vegetables has been suggested to have protective effects against such chronic diseases. Carotenoids are important plant pigments which are thought to contribute towards the beneficial effects of fruit and vegetable consumption. This review focuses on the role of carotenoids and particularly lycopene in chronic diseases.