Dietary habits affect the susceptibility of low‐density lipoprotein to oxidation

Abstract

Objective: To study, if there are differences in the fatty acid composition of low-density lipoprotein (LDL) in people eating three different long-standing habitual diets: vegetarian, high ®sh intake, or high saturated fat (milk fat) diet as a control group, and to study if these differences in¯uence the oxidation susceptibility of LDL. Design: Cross-sectional study using blood samples and a validated dietary frequency questionnaire with illustrations. Setting: Helsinki University Central Hospital, Finland. Subjects: The effect of three different types of long-standing diets of different fatty acid content (a strict vegetarian diet, n 11; a high ®sh intake diet, n 9; and a high saturated fat (milk fat) diet, controls, n 7) on the serum and LDL fatty acid content, and on the susceptibility of LDL to oxidation in vitro, was studied in healthy normocholesterolemic volunteers who had been on these diets for years. Oxidation of LDL was carried out by using CuSO 4 as a pro-oxidant. Results: There were no statistically signi®cant differences in the serum lipids or lipoproteins, though the vegetarian group exhibited lowest mean values of total, high-density lipoprotein (HDL) and LDL cholesterol levels. Both the serum and LDL eicosapentaenoic, docosapentaenoic and docosahexaenoic acid proportions were highest in the ®sh and lowest in the vegetarian groups. Linoleic acid was highest among the vegetarians. In the ®sh group, the vitamin A concentration in serum was higher than in vegetarians and controls and b-carotene lower than in controls, but in a-tocopherol, or lycopene concentrations there were no statistically signi®cant differences. The lag phase of LDL oxidation was shortest (116 min) in the ®sh group and longest (165 min) in the vegetarian group, and the control group was between them (129 min). The mean oxidation percentage after 2.5 h of copper-induced oxidation was highest (44%) in the ®sh group and lowest (22%) in the vegetarian group and intermediate (31%) in the control group. Conclusion: Long-term dietary habits predict the fatty acid composition of serum and LDL, and in¯uence the susceptibility of LDL to oxidation. In the ®sh group with the highest content of omega-3 fatty acids in LDL, the oxidation susceptibility of LDL was highest. In the vegetarian group with less omega-3 fatty acids in LDL, the LDL was more resistant to oxidation.

Effects of vitamin E on the toxicity of oxidized LDL on endothelial cells in vitro in smokers vs nonsmokers on diets rich in fish

“…Our previous study in subjects on a habitual fish diet (mean intake of fish 320 g/day), demonstrated a significantly higher oxidation susceptibility of LDL than in those on a diet containing about 30 g/day of fish (Korpela et al, 1999). A similar degree of oxidation susceptibility of LDL was observed in the nonsmoking fish group in our previous Table 3 LDL-related production of prostacyclin (measured as 6-keto-PGF 1a ) and cyclic AMP in endothelial cell culture during 24 h incubation (mean7s.e.m.…”

“…Some of native LDL samples were oxidized by CuSO 4 (10 mM) in order to get 45% and totally ox-LDL. The oxidation of LDL samples and the calculation of oxidation percentage were performed as described earlier (Korpela et al, 1999). The oxidation capacity curve was also measured in order to determine at which time point the oxidation should be stopped on the next oxidation process.…”

“…In addition, in persons who consumed preferentially fish, the oxidation was enhanced compared to LDL isolated from vegetarians (Korpela et al, 1999). There were also some differences between different diet groups in vitro in the vasoactive responses in rat vessel segments Seppo et al, 2000).…”

“…Size and fatty acid composition of low density lipoprotein (LDL) affect the oxidation capacity (Esterbauer et al, 1992). Most reports suggest that intake of n-3 fatty acids promote increased peroxidation of LDL in vitro and in vivo (Korpela et al, 1999;Pedersen et al, 2003;Roberts et al, 2003). However, it has also been reported on unaltered peroxidation with dietary intake of n-3 fatty acids (Piolot et al, 2003).…”

Possible effects of diets on serum lipids, fatty acids and blood pressure levels in male and female Japanese university students

“…In addition to regulation for serum lipids (1,2), high serum levels of n-3 polyunsaturated fatty acids (3,4) and balance of n-3 and n-6 fatty acids (5,6) have a beneficial effect by preventing coronary heart disease through inhibition of platelet aggregation and lowering of blood pressure levels. In a series of studies, we reported that fish consumption increased the proportion of serum n-3 polyunsaturated fatty acids (7)(8)(9)(10).…”