Hypocholesterolemic and antiatherosclerotic effect of flax lignan complex isolated from flaxseed

Abstract

Hypercholesterolemia, low HDL-C and oxygen radicals have been implicated in the development of atherosclerosis. Lignan complex isolated from flaxseed contains secoisolariciresinol diglucoside (SDG), 3-hydroxy-3methylglutaric acid (HMGA) and cinnamic acids. SDG and cinnamic acids are antioxidants, and HMGA is a hypocholesterolemic agent. Antioxidants are known to reduce hypercholesterolemic atherosclerosis. The objectives of this study were to determine if lignan complex reduces (i) serum cholesterol, (ii) oxidative stress, and (iii) atherosclerosis in hypercholesterolemic rabbits. Rabbits were assigned to four groups: Group I, control; Group II, lignan complex control (lignan complex, 40 mg/kg body weight daily orally); Group III, 0.5% cholesterol; Group IV, 0.5% cholesterol diet + lignan complex, (40 mg/kg body weight daily orally). Blood samples were collected before (time 0) and after 1 and 2 months of experimental diets for measurement of serum triglycerides (TG), total cholesterol (TC), LDL-C, HDL-C and serum malondialdehyde (MDA), a lipid peroxidation product. At the end of the protocol, the aorta was removed for measurement of atherosclerotic plaques, MDA and aortic tissue chemiluminescence (Aortic CL), a marker of antioxidant reserve. Rabbits in Group III developed atherosclerosis (50.84 ± 6.23% of the intimal surface of the aorta was covered with atherosclerotic changes) which was associated with an increase in the serum TG, TC, LDL-C, HDL-C, MDA and aortic MDA and antioxidant reserve. Lignan complex reduced the development of atherosclerosis by 34.37% and this was associated with a decrease in serum TC by 20%, LDL-C by 14%, TC/HDL-C by 34%, serum MDA by 35% and aortic MDA by 58%. Serum HDL-C was elevated by 30% in hypercholesterolemic rabbits and by 25% in normocholesterolemic rabbits with lignan complex. Lignan complex did not affect the TC and LDL-C and serum MDA in the normocholesterolemic rabbits. However, it increased the aortic MDA in the normocholesterolemic rabbits. These results suggest that lignan complex isolated from flaxseed reduced the extent of hypercholesterolemic atherosclerosis and this effect was associated with marked decreases in oxidative stress, serum total cholesterol, LDL-C and risk ratio, and elevation of serum HDL-C. Lignan complex may, therefore, be beneficial in preventing atherosclerosis, and reducing risk factors for coronary artery disease and stroke.