Protective effects of soy protein on the peroxidizability of lipoproteins in cerebrovascular diseases.

To study the mechanism of dyslipoproteinemia, lipoproteins [very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL)] were isolated from stroke patients and healthy persons by ultracentrifugation. Lipoproteins were dialyzed into copper dichloride solution to study the effects of soycreme administration on lipoprotein peroxidation. Blood was drawn from 15 patients with cerebral thrombosis who were not administered soycreme, 10 patients with cerebral thrombosis who were administered soycreme and 11 healthy persons. The lipoproteins were dialyzed into 5 mol/l copper dichloride solution for various lengths of time, and then lipid constituents in the lipoproteins were measured by thin-layer chromatography. After the dialysis, percentages of cholesteryl ester and triglyceride in various lipoproteins decreased significantly (P < 0.05 or 0.01) in both patient groups and in healthy persons. Spot X1 was found between triglyceride and free fatty acid on the thin-layer chromatography, and spot X2 was located between free fatty acid and free cholesterol after dialysis. Spots X1 and X2 reflect lipoprotein peroxidation. Percentages of these spots were higher in VLDL, LDL and HDL in the patient groups than in the healthy subjects. Soycreme administration suppressed the appearance of spots X1 and X2. Furthermore, blood cholesterol concentrations were reduced by the administration of soy protein. Thus, soy may be useful in the prevention and/or treatment of atherosclerosis.