Dilinoleoylphosphatidylcholine protects human low density lipoproteins against oxidation

LDL oxidation may promote atherosclerosis. We found that polyenyphosphatidylcholine (PPC), a mixture of polyunsaturated phospholipids extracted from soybeans, has antioxidant effects in in vivo models of oxidative stress. To assess whether components of PPC affect the in vitro oxidizability of LDL, plasma from 15 healthy volunteers was incubated with 10 μM of either dilinoleoyl-, palmitoyl-linoleoyl-, linoleoyl-palmitoyl- or distearoyl-phosphatidylcholine as well as 10 μM and 1 mM α-tocopherol. LDL oxidation was initiated with 5 μM Cu2+ sulfate and monitored by conjugated diene production, or with 2,2′-azobis (2-amidinopropane) dihydrochloride, a free radical generator, and monitored by O2 consumption. After addition of Cu2+, the lag phase (indicative of resistance of LDL to oxidation) was longer (140% of controls; P<0.001) for LDL incubated with dilinoleoyl-, but not with the other phosphatidylcholine species. This effect was similar to that of 1 mM α-tocopherol (135%). After addition of 2,2′-azobis (2-amidinopropane) dihydrochloride, the inhibition time (also reflecting the antioxidant content of LDL) was prolonged (P<0.001) for α-tocopherol (206%) and dilinoleoyl-(188%), but not for distearoyl-phosphatidyl-choline. Thus, dilinoleoyl-phosphatidylcholine (the main component of PPC) protects against LDL oxidation, a possible mechanism for its reported anti-atherosclerosis effects.