Effects of fat saturation and vitamin E on fatty acid and vitamin E status in platelets and prostaglandins and cholesterol concentrations in serum
Two experiments were conducted to determine whether increasing dietary linoleate and vitamin E supplementation might interact to improve prostaglandin and lipid status, two indicators of risk for atherosclerosis. The influence of increasing dietary linoleate and d,1-[alpha]-tocopheryl acetate (vitamin E) on platelet fatty acid composition, platelet phospholipase A[subscript]2 activity, lipid peroxidation, vitamin E, aortic 6-keto-prostaglandin F[subscript]1[alpha] (6-keto-PGF[subscript]1[alpha]), serum thromboxane B[subscript]2 (TXB[subscript]2), 6-keto-PGF[subscript]1[alpha], total cholesterol, HDL-cholesterol, LDL-cholesterol, triglyceride and vitamin E concentrations was studied in 72 weanling male Sprague-Dawley rats. Rats were fed semipurified diets containing 11 or 18% of energy from linoleate (en% linoleate) and graded levels (0, 100 or 5000 ppm) of vitamin E for 10 weeks. Vitamin E status was confirmed by platelet and serum vitamin E levels. Rats fed no vitamin E had the lowest platelet and serum vitamin E concentrations while rats fed 5000 ppm vitamin E had the greatest platelet and serum vitamin E (p < 0.05). Lipid status was verified by platelet fatty acid composition. Platelet C18:1n-9 (oleic acid) was significantly greater in the 11 en% linoleate group than in the 18 en% linoleate group, and platelet C18:2n-6 (linoleic acid) was significantly greater in the 18 en% linoleate group than in the 11 en% linoleate group (p < 0.05). The treatments had no effect on food intake, body weight gain, platelet phospholipase A[subscript]2 activity, aortic 6-keto-PGFi[subscript]1[alpha], serum 6-keto-PGF[subscript]1[alpha], total cholesterol and LDL-cholesterol concentrations. Serum TXB[subscript]2 and platelet lipid peroxidation (TBARS) were significantly greater in the vitamin E-deficient rats than in vitamin E-adequate and vitamin E-supplemented rats (p < 0.05). Serum HDL-cholesterol level was significantly greater in the 100 and 5000 ppm vitamin E-treated rats compared with rats fed no vitamin E (p < 0.05). Serum triglyceride concentration was significantly greater in rats fed 11 en% linoleate compared with rats fed 18 en% linoleate. Increased dietary linoleate may be preventive against heart disease because of its triglyceride-lowering effects. Adequate vitamin E status prevented an increase in serum thromboxane and maintained HDL-cholesterol, two indicators of risk for atherosclerosis. Vitamin E supplementation did not confer a physiological benefit, in terms of the indicators of atherosclerotic risk studied.