Protective Effects of Vitamin E Analogs against Carbon Tetrachloride-Induced Fatty Liver in Rats

Abstract

Recently, it has been reported that α-tocopherol (α-Toc) is effective for amelioration of liver damage. However, it is unknown whether other vitamin E analogs are effective. In this study, we investigated the effects of γ-tocopherol (γ-Toc) and tocotrienols (T3) in rats with fatty liver. Rats fed a vitamin E-deficient diet for four weeks were divided into eight groups: Control, carbon tetrachloride (CCl(4)), α-Toc, α-Toc + CCl(4), γ-Toc, γ-Toc + CCl(4), T3 mix, T3 mix + CCl(4). After a 24 h fast, the rats were administered 20 mg of each of the vitamin E analogs, respectively. Moreover, the CCl(4) group were given 0.5 ml/kg body weight corn oil preparation containing CCl(4) 6 h after vitamin E administration. We measured the activities of aspartate aminotransferase and alanine aminotransferase (ALT) in plasma, and the contents of triglyceride (TG), total cholesterol (T-Chol) and vitamin E analogs in the liver. Also, we determined the hepatic expression of mRNA for inflammatory cytokines. The liver TG content in the γ-Toc + CCl(4) and T3 mix + CCl(4) groups was decreased in comparison with the CCl(4) group. Moreover, ALT activity in the T3 mix + CCl(4) group was significantly lower than CCl(4) group. These findings suggest that γ-Toc and T3 are effective for amelioration of fatty liver.

Keywords: carbon tetrachloride; fatty liver; tocotrienol; γ-tocopherol.

Fig. 1

Effects of vitamin E analogs on lipid contents of rat liver after administration of CCl₄; (A) Liver TG content. (B) Liver T-Chol content. Rats were fed a vitamin E-deficient diet for four weeks. After a 24 h fast, 20 mg of each vitamin E analog was administered. Six hours later, a mixture of CCl₄ and stripped corn oil (1:1, 1 ml/kg body weight; 0.5 ml/kg body weight as CCl₄) was orally administered to the rats. The control rats were given stripped corn oil alone as a placebo. Six hours after CCl₄ administration, the liver was removed and its TG and T-Chol contents were measured. C; Control group, CCl₄; CCl₄ dosage group, αT; α-Toc dosage group, αT + CCl₄; α-Toc + CCl₄ dosage group, γT; γ-Toc dosage group, γT + CCl₄; γ-Toc + CCl₄ dosage group, T3; T3 mix dosage group, T3 + CCl₄; T3 mix + CCl₄ dosage group. The values are mean ± SD for 5 rats, *p<0.05, ***p<0.001 (one-way ANOVA followed by Bonferroni post hoc test).

Fig. 2

Histopathology of rat liver after administration of CCl₄. C; Control group, CCl₄; CCl₄ dosage group, γT + CCl₄; γ-Toc + CCl₄ dosage group, T3 + CCl₄; T3 mix + CCl₄ dosage group (stained with hematoxylin-eosin; original magnification ×400).

Fig. 3

Effects of vitamin E analogs on liver damage marker activity in plasma of rats administered CCl₄; (A) Plasma AST activity. (B) Plasma ALT activity. Rats were fed a vitamin E-deficient diet for four weeks. After a 24 h fast, 20 mg of each vitamin E analog was administered to the rats. Six hours later, a mixture of CCl₄ and stripped corn oil (1:1, 1 ml/kg body weight; 0.5 ml/kg body weight as CCl₄) was administered orally to the rats. The control rats were given stripped corn oil alone as a placebo. Six hours after CCl₄ administration, plasma samples were taken and the AST and ALT activities were measured. C; Control group, CCl₄; CCl₄ dosage group, αT; α-Toc dosage group, αT + CCl₄; α-Toc + CCl₄ dosage group, γT; γ-Toc dosage group, γT + CCl₄; γ-Toc + CCl₄ dosage group, T3; T3 mix dosage group, T3 + CCl₄; T3 mix + CCl₄ dosage group. The values are mean ± SD for 5 rats, *p<0.05, ***p<0.001 (one-way ANOVA followed by Bonferroni post hoc test).

Fig. 4

Effects of vitamin E analogs on expression of inflammatory cytokine mRNAs in liver of rats administered CCl₄; (A) Liver TNF-α mRNA expression. (B) Liver IL1-β mRNA expression. Rats were fed a vitamin E-deficient diet for four weeks. After a 24 h fast, 20 mg of each vitamin E analog was administered to the rats. Six hours later, a mixture of CCl₄ and stripped corn oil (1:1, 1 ml/kg body weight; 0.5 ml/kg body weight as CCl₄) was administered orally to the rats. The control rats were given stripped corn oil alone as a placebo. Six hours after CCl₄ administration, the liver was removed and its expression of TNF-α and IL1-β mRNAs was measured by real-time PCR. C; Control group, CCl₄; CCl₄ dosage group, αT; α-Toc dosage group, αT + CCl₄; α-Toc + CCl₄ dosage group, γT; γ-Toc dosage group, γT + CCl₄; γ-Toc + CCl₄ dosage group, T3; T3 mix dosage group, T3 + CCl₄; T3 mix + CCl₄ dosage group. The values are mean ± SD for 5 rats, *p<0.05, **p<0.01, ***p<0.001 (one-way ANOVA followed by Bonferroni post hoc test).

Fig. 5

Contents of individual vitamin E analogs in liver and plasma of rats administered CCl₄; (A) Liver α-Toc content. (B) Plasma α-Toc content. (C) Liver γ-Toc content. (D) Plasma α-T3 content. Rats were fed a vitamin E-deficient diet for four weeks. After a 24 h fast, 20 mg of each vitamin E analog was administered to the rats. Six hours later, a mixture of CCl₄ and stripped corn oil (1:1, 1 ml/kg body weight; 0.5 ml/kg body weight as CCl₄) was administered orally to the rats. The control rats were given stripped corn oil alone as a placebo. Six hours after CCl₄ administration, the liver and plasma were taken, and the quantity of each vitamin E analog was measured by HPLC. C; Control group, CCl₄; CCl₄ dosage group, αT; α-Toc dosage group, αT + CCl₄; α-Toc + CCl₄ dosage group, γT; γ-Toc dosage group, γT + CCl₄; γ-Toc + CCl₄ dosage group, T3; T3 mix dosage group, T3 + CCl₄; T3 mix + CCl₄ dosage group. The values are mean ± SD for 5 rats, *p<0.05 (one-way ANOVA followed by Bonferroni post hoc test).