Abstract 15019: Differential Effects of Omega-3 Fatty Acid Combinations on the Inhibition of Oxidation Of Human Low-density Lipoproteins in vitro

Abstract

Background: Omega-3 fatty acids (O3FAs) reduce levels of triglyceride but may also have additional atheroprotective benefits. Randomized trials have suggested potential clinical outcome differences among O3FAs formulations. Oxidative modification of low-density lipoproteins (LDL) contributes to endothelial dysfunction, inflammation, and other aspects of atherogenesis. Individual O3FAs have been shown to inhibit LDL oxidation to varying degrees, but the antioxidant effects of combining O3FAs is unknown. Objective: To compare the dose- and time-dependent antioxidant effects of eicosapentaenoic acid (EPA, 20:5) alone and in combination with either docosapentaenoic acid (DPA, 22:5) or docosahexaenoic acid (DHA, 22:6) in human LDL in vitro . Methods: Human LDL was isolated from healthy subjects and adjusted to a final ApoB concentration of 100 μg/mL in physiologic buffer (PBS) before being incubated with O3FAs at 37°C. The EPA levels in the combinations were fixed at either 2.0, 3.0, or 4.5 μM, while the DPA or DHA levels were set at 0, 0.5, 1.0, and 2.0 μM. Oxidation was initiated by copper sulfate (10 μM) and measured over time by formation of malondialdehyde (MDA), a lipid oxidation product. Results: When combined with EPA, both DPA and DHA increased inhibition of oxidation in a dose- and time-dependent manner, with DPA showing a greater effect and more prolonged inhibition. At high levels of EPA (4.5 μM), DPA showed significantly greater antioxidant activity than equimolar DHA; these differences were more apparent with time. After 8 hours, adding 1.0 μM DPA reduced MDA formation by 61% versus vehicle (3.10 ± 0.42 vs. 7.98 ± 0.56, p <0.001), while adding 1.0 μM DHA only reduced MDA formation by 20% (6.40 ± 1.23, p <0.05). When 2 μM DPA or DHA were added, after 10 hours only DPA still had a significant degree of inhibition versus vehicle (37%; 6.65 ± 0.95 vs. 8.21 ± 0.53, p <0.05). Similar trends were observed in combinations containing 2.0 and 3.0 μM EPA. Conclusion: Adding DPA or DHA to EPA provide dose-dependent incremental antioxidant effects, with DPA providing a larger degree and a longer duration of inhibition. These observations highlight potential differences among O3FAs (and their combinations) in novel mechanisms of atheroprotection.