OXIDATION RESISTANCE, OXIDATION RATE, AND EXTENT OF OXIDATION OF HUMAN LOW-DENSITY-LIPOPROTEIN DEPEND ON THE RATIO OF OLEIC-ACID CONTENT TOLINOLEIC-ACID CONTENT - STUDIES IN VITAMIN-E-DEFICIENT SUBJECTS

The purpose of this study was to understand better the factors providi ng oxidation resistance to human low-density lipoprotein (LDL). Theref ore. the susceptibility to copper-induced in vitro oxidation of LDL fr om vitamin E deficient patients and normal healthy subjects was studie d. Surprisingly, the LDL of vitamin E deficient patients appeared less susceptible to oxidation than control LDL. Both oxidation rate and ex tent of oxidation, measured as diene production, were reduced when com pared to control LDL. The lag time, a measure of resistance to oxidati on. was not different from the lag time of LDL from healthy subjects. No relation was found between vitamin E content and resistance against oxidation. LDL from vitamin E deficient patients contained lower amou nts of vitamin E. less cholesteryl esters, and increased amounts of tr iglycerides. Furthermore, its oleic acid content was increased and its linoleic acid content decreased. Linear regression analyses revealed that the ratio of oleic acid content to linoleic acid content was stro ngly correlated with the lag time, and inversely correlated with oxida tion rate and extent of oxidation. Thus, LDL rich in oleic acid and po or in linoleic acid was less easily oxidized. It is concluded that the susceptibility of LDL to oxidation is determined not only by its anti oxidant content, but also by other compositional factors, and more spe cifically by the ratio of oleic acid content to linoleic acid content.