Effects of α-tocopherol and astaxanthin on LDL oxidation and atherosclerosis in WHHL rabbits

Abstract

The aim of this study was to evaluate the influence of α-tocopherol and astaxanthin on low-density lipoprotein (LDL) oxidation lag time and atherosclerotic lesion formation in Watanabe heritable hyperlipidemic (WHHL) rabbits. Thirty-one, 3-month-old WHHL rabbits were divided into three experimental groups. One group ( n=10) was fed standard rabbit feed alone and served as a control, a second group ( n=11) was supplied with the same feed containing 500 mg α-tocopherol/kg and a third group ( n=10) was given a feed containing 100 mg astaxanthin/kg. Plasma lipids, lipoproteins and LDL oxidation lag time were followed for 24 weeks. At the end of the treatment period, the animals were killed and the thoracic aorta was used for evaluation of the degree of atherosclerosis. Colour photographs of the intimal surface of the vessel were taken for determination of the atherosclerotic area. Cross-sections of the thoracic aorta were used for histological examination and for determination of intimal thickening. Specimens of the vessel were used for determination of the tissue cholesterol content. Plasma cholesterol remained at a high level during the time of the experiment and there were no differences between the experimental groups. After 24 weeks, the LDL oxidation lag time was 53.7±1.7 min, 109±4 min ( P<0.001) and 56.4±3.4 min ( P=0.47) in the control, α-tocopherol and astaxanthin groups, respectively. In the thoracic aorta, the atherosclerotic area was 80.7±5.1%, 67.1±6.7% ( P=0.13) and 75.2±5.7% ( P=0.49) in the control, α-tocopherol and astaxanthin groups, respectively. The intimal thickening was 45.6±3.2%, 44.0±4.1% ( P=0.89) and 40.0±4.5% ( P=0.33) in the control, α-tocopherol and astaxanthin groups, respectively. Finally, the cholesterol content was 107±9 μmol/g, 95.7±11.5 μmol/g ( P=0.31) and 101±5 μmol/g ( P=0.33) in the control, α-tocopherol and astaxanthin groups, respectively. It can be concluded that α-tocopherol but not astaxanthin prolonged the LDL oxidation lag time. The two antioxidative substances did not prevent atherogenesis in WHHL rabbits in this setting.