Effects of linoleate-enriched and oleate-enriched diets in combination with alpha-tocopherol on the susceptibility of LDL and LDL subfractions to oxidative modification in humans.

Abstract

This report describes the effects of feeding linoleate-or oleate-enriched diets to subjects who were concurrently taking 1200 mg/d of a-tocopherol on the susceptibility of low-density lipoprotein (LDL) and buoyant and dense LDL subfractions to oxidation. LDL isolated from subjects who consumed linoleate-enriched diets was more susceptible to copper-mediated oxidation, as measured by formation of conjugated dienes and lipid peroxides and loss of unsaturated fatty acids, compared with LDL isolated from subjects who consumed their usual or oleate-enriched diets. In all subjects, buoyant LDL had a higher content of a-tocopherol per particle and a lower 18:2 to 18:1 ratio and was considerably more resistant to oxidation than dense LDL. Although dense LDL from all groups had comparable a-tocopherol levels, dense LDL from the linoleate group was most susceptible to oxidation, followed by that from the standard diet, whereas T here is evidence that oxidative modification of low-density lipoproteins (LDLs) occurs in vivo 14 and may increase LDL atherogenicity, as recently reviewed. Correspondence to Peter Reaven, MD, Department of Medicine 0682, University of California-San Diego, 9500 Gilman Dr, BSB 1080, La Jolla, CA 92093-0682. dense LDL isolated from the oleate diet group was most resistant. In summary, high dosages of a-tocopherol did not prevent enhanced susceptibility to oxidation of LDL isolated from subjects fed linoleate-enriched diets. Furthermore, dense LDL was more susceptible to oxidation than was buoyant LDL, and this effect was greatly exaggerated in the dense LDL isolated from subjects fed linoleate-enriched diets. Conversely, dense LDL isolated from subjects fed oleate-enriched diets was the most protected. If oxidation of LDL is important in the pathogenesis of atherosclerosis, then these data suggest that in people with increased amounts of small, dense LDL, dietary enrichment in oleic acid may decrease the susceptibility of their LDL to oxidation. (Arteriosder Thromb. 1994; 14:557-566.)

Effect of ingestion of virgin olive oil on human low-density lipoprotein composition

“…The effects observed on plasma LDL cholesterol and on susceptibility of LDL to oxidation are consistent with those reported in previous studies with MUFA-enriched diets (Mata et al, 1992;Reaven et al, 1994), but these studies were longer (3 -4 weeks). Other studies have also showed that extravirgin olive oil increases resistance to oxidation in animals (Wiseman et al, 1996), in healthy subjects (Carmena et al, 1996), and in subjects with cardiovascular disease (RamirezTortosa et al, 1999).…”

“…In a review, Parthasarathy et al, (1999) explain that the susceptibility of LDL to oxidation depends on the MUFA=PUFA ratio, their oleic acid and antioxidant contents and also on the size of LDL particle. It has been reported (Reaven et al, 1994) that small dense lipoprotein particles are more susceptible to oxidation and that oleic acid promotes the formation of larger particles.…”

“…Thus, apart from the fatty acid composition, exogenous antioxidants could be used to prevent this disease (Esterbauer et al, 1992). In quantitative terms, a-tocopherol is the major antioxidant among those present in LDL, thus it is considered the first line of defense against oxidation (Reaven et al, 1994). LDL resistance varies greatly among subjects and this variation is caused, in part, by differences in the atocopherol content of LDL, but it also depends on other variables that have not been identified as yet.…”

Increased lipid peroxidation during long-term intervention with high doses of n-3 fatty acids (PUFAs) following an acute myocardial infarction

“…In the present study, the change in n-6 PUFAs in serum phospholipids differed significantly between the groups, but the intragroup increase in linoleic acid during 1 y of corn oil treatment did not reach statistical significance. Several studies support the notion that a high intake of n-6 PUFAs may increase lipid peroxidation (Reaven et al, 1991(Reaven et al, , 1993(Reaven et al, , 1994, and may explain the increase over 1 y also in our control group. Therefore, the choice of control in our study may partly mask the effect of n-3 PUFAs intervention.…”

Health aspects of fish and n-3 polyunsaturated fatty acids from plant and marine origin

“…Linoleic acidenriched LDL particles are oxidised in vitro faster than LDL particles enriched with saturated or monounsaturated fatty acids (Reaven et al, 1994). Inconsistent in vitro results have been published with respect to both plant and marine n-3 PUFA (Suzukawa et al, 1995;Brude et al, 1997).…”