Casein and Soy Protein Isolate in Experimental Atherosclerosis: Influence on Hyperlipidemia and Lipoprotein Oxidation

Background/Aims: Nutrients able to modify the susceptibility of lipoproteins to oxidation and/or reduce the cholesterol levels of blood plasma are important for prevention and/or treatment of atherosclerosis. The influence of animal and vegetable proteins on hypercholesterolemia and atherogenesis has been studied, concerning the mechanisms able to modify the digestion, absorption and bioavailability of lipids. In this study, the influence of casein and soy protein isolate on lipoprotein oxidation and atherosclerosis progression was investigated in cholesterol-fed rabbits. Methods: During 2 months, 20 New Zealand rabbits were fed with diets containing 1% cholesterol and 27% casein or 27% soy protein isolate. Blood samples were collected at baseline, 15, 30, 45 and 60 days of feeding. Results: Casein feeding contributed to increasing cholesterol and triglyceride concentrations, lipoprotein oxidation and the area of aorta atherosclerotic lesions. In contrast, the soy protein isolate reduced, when compared to casein, the concentrations of cholesterol and lipid peroxides of β-VLDL and LDL fractions during the experimental time course, as well as the area of atherosclerotic lesions at the end of the study. Conclusion: Soy protein isolate, in comparison with casein, promoted a decrease of lipid peroxides, cholesterol and triglyceride content of atherogenic lipoproteins (β-VLDL and LDL), which had beneficial effects over atherosclerosis progression in cholesterol-fed rabbits.