Extra Virgin Olive Oil Polyphenols Promote Cholesterol Efflux and Improve HDL Functionality

Abstract

Results of the present work give evidence from the beneficial role of extra virgin olive of oil (EVOO) consumption towards oxidative stress and cardiovascular diseases. Polyphenols contained in EVOO are responsible for inhibiting lipoproteins oxidative damages and promoting reverse cholesterol transport process via ABCA1 pathway.

Figure 1

EVOO-PC enrichment decreases the oxidizability of lipoproteins. Plasma was incubated with EVOO or EVOO-PC prior to isolating HDL and LDL. HDL and LDL pretreated with EVOO or EVOO-PC as well as untreated controls were oxidized by incubation with copper ions for 4 h. The resistance to lipid peroxidation and the oxidizability of HDL and LDL were monitored by determining the lag phase (a, b, d, e) and by measuring conjugated diene formation (OD_max), respectively (c, f). Results are expressed as the means ± SEM of three independent experiments. ^∗ p < 0.05, ^∗∗ p < 0.01, and ^∗∗∗ p < 0.001.

Figure 2

EVOO-PC protects macrophages against oxidation and promotes HDL-mediated cholesterol efflux. (a) THP-1-derived macrophages were loaded with [³H]-cholesterol (2 μCi/mL) for 24 h. The cells were then washed, equilibrated, and incubated for a further 24 h with 50 μg/mL of HDL-free medium, HDL, EVOO-enriched HDL (EVOO-HDL), or EVOO-PC-enriched HDL (EVOO-PC-HDL). (b) The macrophages were stressed with 0.2 mM Fe/Asc, and cholesterol efflux was assessed using 50 μg/mL of HDL. Results are expressed as the means ± SEM of at least three independent experiments. ^∗ p < 0.05, ^∗∗ p < 0.001, and ^∗∗∗ p < 0.001.

Figure 3

EVOO-PC increases ABCA1 protein expression and enhances apoA-I-mediated cholesterol efflux. (a) [³H]-Cholesterol-loaded J774 macrophages were incubated for 12 h with various concentrations of EVOO-PC (0 to 320 μg/mL) or with cAMP (positive control) to generate ABCA1-enriched cells, which were incubated with 25 μg/mL of apo-AI for 4 h. The small upper panel shows the positive correlation between EVOO-PC concentrations and ABCA1-dependent cholesterol efflux. (b) ABCA1 protein expression after incubating J774 macrophages with increasing concentrations of EVOO-PC as determined by densitometric analyses of protein bands on PVDF membranes. Results are expressed as the means ± SEM of at least three independent experiments. ^∗ p < 0.05, ^∗∗ p < 0.001, and ^∗∗∗ p < 0.001.

Figure 4

Tyrosol and hydroxytyrosol increase ABCA1 protein expression and enhance apoA-I-mediated cholesterol efflux. [³H]-Cholesterol-loaded J774 macrophages were incubated for 12 h with different concentrations (0 to 25 μM) of tyrosol (a) or hydroxytyrosol (b) to generate ABCA1-enriched cells, which were then incubated with 25 μg/mL of apo-AI for 4 h. Results are expressed as the means ± SEM of at least three independent experiments.