Abstract 15024: High Concentration Mineral Oil, Corn Oil and Their Constitutive Fatty Acids Do Not Influence Low-Density Lipoprotein (LDL) Oxidation Rates in vitro

Abstract

Introduction: LDL transports dietary long chain fatty acids, constituents that may influence rates of lipid oxidation. Modified LDL promotes foam cell formation during atherosclerosis. The omega-3 fatty acid (n3-FA) eicosapentaenoic acid (EPA) administered as icosapent ethyl (IPE), reduced cardiovascular events in REDUCE-IT compared to mixed n3-FAs in similar high-risk patients (STRENGTH). Some have attributed these discordant outcomes, in part, to placebo choice (mineral versus corn oil) despite very limited oral absorption. We compared the effects of these oils and various FAs on rates of LDL oxidation at supra-pharmacologic doses. Methods: LDL was isolated from human plasma by isopycnic centrifugation, separated into test samples of 100 μg/mL before being incubated at 37°C for 30 min with pharmaceutical grade mineral or corn oil at high concentrations (100 μg/mL) that are comparable to treatment achieved n3-FAs (4 g/d) that have high oral absorption. We also tested FAs contained in these oils, including stearic acid (18:0), arachidic acid (20:0), and linoleic acid (18:2, n-6) as well as ascorbic acid (10 μM) and a water-soluble analog of vitamin E (Trolox, 10 μM) as controls. All samples then underwent copper-induced oxidation (20 μM) monitored by formation of malondialdehyde (MDA). Results: MDA formation increased from 0.28 ± 0.03 to 9.96 ± 0.58 μM ( p <0.001) with vehicle treatment from 0-2 h. Addition of either mineral or corn oil at 100 μg/mL did not significantly influence rates of MDA formation at 2 h (0.02% and 1.93% change vs vehicle, respectively). Nor did we observe any antioxidant activity with constituent FAs stearic acid, arachidic acid, or linoleic acid, FAs with no or two double bonds. As antioxidant controls, ascorbic acid and Trolox both reduced LDL oxidation by 93% and 94% (0.71 ± 0.11 and 0.62 ± 0.04 to 9.96 ± 0.58 μM, p <0.001) after 2 h. Conclusions: Neither mineral nor corn oils affected LDL oxidation even at supra-pharmacologic concentrations. Beyond poor oral absorption, mineral oil and its constituent fatty acids did not affect LDL oxidation, a property related to mechanisms of atherosclerosis.