Atheroprotective effects of pure tocotrienol supplementation in the treatment of rabbits with experimentally induced early and established atherosclerosis

Abstract

Background: Atherosclerosis is the main cause of coronary artery disease -related deaths worldwide. The atheroprotective properties of pure tocotrienols (T3) in the absence of alpha-tocopherol (α-TCP) in vitamin E has not been extensively examined.

Aim: To determine the atheroprotective properties of T3 in early and established atherosclerosis rabbits.

Methods: Thirty New Zealand white rabbits were divided into two groups, B1 and B2 which represent early [fed 1% high cholesterol diet (HCD) for 2 weeks] and established (fed 1% HCD for 8 weeks) atherosclerosis. Each group was subdivided into three intervention arms: 1) T3-4 mg/kg, 2) T3-15 mg/kg and 3) vehicle without T3 (T3 negative) for 8 weeks. Serial fasting blood samples were obtained for lipid profile, and whole lengths of aorta were used to determine tissue markers of endothelial activation, inflammation and plaque stability.

Results: In B1, atherosclerotic lesion in T3-4 mg/kg group was significantly reduced (p=0.008), while aortic tissue expression of vascular cellular adhesion molecule 1 (VCAM-1), interleukin-6 (IL-6) and matrix metalloproteinase (MMP-12) was reduced in T3-4 mg/kg compared to T3-negative rabbits group (0.2±0.1 vs. 28.5±3.1%; 3.0±1.6 vs. 14.0±1.7%; and 5.2±2.2 vs. 27.7±0.8%, respectively, p<0.05). T3-15 mg/kg group showed reduction in VCAM-1, E-selectin, IL-6 and MMP-12 (3.9±1.9 vs. 28.5±3.1%; 10.3±0.5 vs. 59.8±8.5%; 2.6±1.7 vs. 14.0±1.7%; and 16.2±3.2 vs. 27.7 0.8%, respectively, p<0.05). In B2, T3-4 mg/kg group reduced aortic tissue expression of intercellular adhesion molecule 1 (ICAM-1), E-selectin, IL-6, MMP-12 and MMP-9 compared to T3-negative rabbits group (29.9±2.4 vs. 55.3±1.3%; 26.7±1.5 vs. 60.5±7.6%; 15.7±0.7 vs. 27.7±4.8%; 34.8±2.7 vs. 46.5±3.4%; and 25.89±3.9 vs. 45.9±1.7%, respectively, p<0.05). T3-15 mg/kg group showed reduced VCAM-1, ICAM-1, E-selectin, IL-6, MMP-12 and MMP-9 (20.5±3.3 vs. 35.6±2.5%; 24.9±1.3 vs. 55.3±1.3%; 29.9±6.7 vs. 60.5±7.6; 11.3±2.2 vs. 27.7±4.8%; 23.0±1.7 vs. 46.5±3.4%; and 17.6±1.9 vs. 45.9±1.7%, respectively, p<0.05.

Conclusion: These findings suggest the possible atheroprotective role T3 plays as an adjunct supplementation to standard treatment in the prevention of CAD.

Keywords: atherosclerosis; delta tocotrienol; gamma tocotrienol; hypercholesteroleamic rabbits; tissue biomarker.

Fig. 1

Quantitative analysis of atherosclerotic lesion in early and established atherosclerotic rabbit groups. The lesion area (Sudanophilic area) in each aortic segment was determined using soft imaging solution software (analySIS^® FIVE, Olympus, USA). Data are expressed as mean±SEM. **p<0.01 compared to T3-negative rabbits group.

Fig. 2

IHC expression of biomarkers in pure T3–4 mg/kg and T3–15 mg/kg treatment groups versus T3-negative rabbits group in early atherosclerosis. Data expressed as mean±SEM. (*) and (**) indicate significant differences (p<0.05 and p<0.01, respectively) between T3 and T3-negative rabbits group. (#) and (##) indicate significant differences (p<0.05 and p<0.01, respectively) between T3–4 mg/kg and T3–15 mg/kg.

Fig. 3

IHC expression of biomarkers in pure T3–4 mg/kg and T3–15 mg/kg treatment groups versus T3-negative rabbits group in established atherosclerosis. Data are expressed as mean±SEM. (*) and (**) indicate significant differences (p<0.05 and p<0.01, respectively) between T3 and T3-negative rabbits group. (^#) and (^##) indicate significant differences (p<0.05 and p<0.01, respectively) between T3–4 mg/kg and T3–15 mg/kg.