Palm tocotrienol-rich fraction improves vascular proatherosclerotic changes in hyperhomocysteinemic rats

Abstract

This study investigated the effects of palm tocotrienol-rich fraction (TRF) on aortic proatherosclerotic changes in rats fed with a high methionine diet. Forty-two male Wistar rats were divided into six groups. The first group was the control (fed with a basal diet). Another five groups were fed with 1% methionine diet for 10 weeks. From week 6 onward, folate (8 mg/kg diet) or palm TRF (30, 60, and 150 mg/kg diets) was added into the diet of the last four rat groups, respectively. The high methionine diet raised the plasma total homocysteine and aortic lipid peroxidation, which were reduced by the palm TRF and folate supplementations. Plasma nitric oxide was reduced in the high methionine group compared to the control (3.72 ± 0.57 versus 6.65 ± 0.53 μ mol/L, P < 0.05), which reduction was reversed by the palm TRF (60 and 150 mg/kg) and folate supplementations. The increased aortic vascular cell adhesion molecule-1 expression in the methionine group (2.58 ± 0.29) was significantly reduced by the folate (1.38 ± 0.18) and palm TRF at 150 mg/kg (1.19 ± 0.23). Palm TRF was comparable to folate in reducing high methionine diet-induced plasma hyperhomocysteinemia, aortic oxidative stress, and inflammatory changes in rats.

Figure 1

Total food intake in rats fed with a high methionine diet (M) (weeks 1–10) and supplemented with palm tocotrienol-rich fraction (TRF) at three different doses (30, 60, and 150 mg/kg diets) or folate (8 mg/kg diet) for 5 weeks (weeks 6–10). Bars represent means ± SEM (n = 7). No significant difference was seen between groups.

Figure 2

Total plasma homocysteine level at weeks 0, 5, and 10 in rats fed high methionine diet (M) (week 0–10) and supplemented with either folate (8 mg/kg diet) or palm tocotrienol-rich fraction (TRF) (30, 60, or 150 mg/kg diets) for 5 weeks (weeks 6–10). The result is expressed as means ± SEM (n = 7). *Significantly different from the control at the same duration of treatment (P < 0.05), ^#significantly different from the methionine group at week 10 (P < 0.05), ^§significantly different from week 0, and ^¥significantly different from week 5, respectively (P < 0.05).

Figure 3

The thiobarbituric acid reactive substance (TBARS) content (pmol MDA/mg protein) in aorta of rat fed either basal (control), high methionine (M, 1%) (week 0–10), methionine + folate (8 mg/kg diet) or palm tocotrienol rich fraction (TRF) (30, 60 or 150 mg/kg) diets (week 6–10). Bars represent means ± SEM (n = 7). *Significantly different from the control (P < 0.05), ^#Significantly different from the M group (P < 0.05).

Figure 4

Plasma nitric oxide in rats given high methionine (M) (1%) diet for 10 weeks and supplemented with palm tocotrienol rich fraction (TRF, 30, 60 and 150 mg/kg diet from weeks 6 to 10) or folate (8 mg/kg diet). Bars represent means ± SEM (n = 7). *Significantly different from the control (P < 0.05), ^#significantly different from the M group (P < 0.05), ^§significantly different from week 0 respectively and ^¥significantly different from the TRF30-treated group (P < 0.05).

Figure 5

Intimal layer of aorta positively expressing vascular cell adhesion molecule-1 (VCAM-1, brown streaks indicated by arrows) (×400 magnification) in rats fed basal (control, (a)), high methionine (1%, (b)) (weeks 0–10) diets and supplemented with folate (8 mg/kg, (c)) or palm tocotrienol-rich fraction (TRF) at 30 (d), 60 (e), or 150 (f) mg/kg for 5 weeks (weeks 6–10), in addition to high methionine diet. L: lumen, I: intima, and M: media.

Figure 6

The effects of folate (F; 8 mg/kg diet) and palm tocotrienol-rich fraction (TRF; 30, 60, and 150 mg/kg diets) for 5 weeks (From weeks 6 to 10) on aortic vascular cell adhesion molecule 1 (VCAM-1) expression in rats fed high methionine diet (M) (From weeks 0 to 10). Bars represent means ± SEM (n = 7). *Significantly different from the control (P < 0.05) and ^#significantly different from the methionine group (P < 0.05).

Figure 7

Verhoeff van Gieson staining of the aorta (×200 magnification) in rats fed basal (control, (a)), high methionine (weeks 0–10, (b)) diets and supplemented with folate (8 mg/kg diet, (c)) or palm tocotrienol-rich fraction (TRF) at 30 (d), 60 (e), or 150 (f) mg/kg diets) for 5 weeks (week 6–10) in addition to high methionine diet. L: lumen, I: intima, M: media, and A: adventitia.

Figure 8

Systolic blood pressure in rats given high methionine (M) (1%) diet (From weeks 1 to 10) and supplemented with palm tocotrienol-rich fraction (TRF; 30, 60, and 150 mg/kg diets from weeks 6 to 10) or folate (8 mg/kg diet). Bars represent means ± SEM (n = 7). No significant different was seen amongst groups.