Background: The most common preparation of tocotrienols is the tocotrienol-rich fraction (TRF). This study aimed to investigate whether TRF induced liver Nrf2 nuclear translocation and influenced the expression of Nrf2-regulated genes. Methods: In the Nrf2 induction study, mice were divided into control, 2000 mg/kg TRF and diethyl maleate treated groups. After acute treatment, mice were sacrificed at specific time points. Liver nuclear extracts were prepared and Nrf2 nuclear translocation was detected through Western blotting. To determine the effect of increasing doses of TRF on the extent of liver nuclear Nrf2 translocation and its implication on the expression levels of several Nrf2-regulated genes, mice were divided into 5 groups (control, 200, 500 and 1000 mg/kg TRF, and butylated hydroxyanisole-treated groups). After 14 days, mice were sacrificed and liver RNA extracted for qPCR assay. Results: 2000 mg/kg TRF administration initiated Nrf2 nuclear translocation within 30 min, reached maximum level around 1 h and dropped to half-maximal levels by 24 h. Incremental doses of TRF resulted in dose-dependent increases in liver Nrf2 nuclear levels, along with concomitant dose-dependent increases in the expressions of Nrf2-regulated genes. Conclusion: TRF activated the liver Nrf2 pathway resulting in increased expression of Nrf2-regulated cytoprotective genes.

A diet rich in tocotrienols has been shown to be beneficial for health. However, its detailed mechanism of action is still not fully understood. NAD(P)H:quinone oxidoreductase 1 (NQO1) is important in cellular defence due to its ability to detoxify reactive quinones and quinoneimines to their less toxic hydroquinones forms. The objective of this study is to investigate the effects of different doses of palm oil-derived tocotrienol rich fraction (palm TRF) supplementation on NQO1 gene and protein expression in mice livers. Western blot and qPCR assays were used to detect NQO1 expression levels. It was found that palm TRF significantly induced NQO1 expression at all doses given. In conclusion, palm TRF treatment increased NQO1 gene and protein expression in mice liver dose dependently, with the highest expression seen in mice treated with 1000 mg/kg palm TRF, followed by 500 and 200 mg/kg respectively.

Objective: Heme oxygenase-1 (HO-1) is enzyme that possesses antioxidant, anti-inflammatory, and cytoprotective functions. Induction of HO-1 occurs as an adaptive and beneficial response to various injurious stimuli such as oxidative stress. This study is aimed at monitoring the effects of administration of equal doses (50 mg/kg) of sulforaphane (SFN), curcumin, quercetin, indole-3-carbinol, and butylated hydroxyanisole (BHA) for 14 days on the levels of liver HO-1 gene and protein expression in mice. Method: A total of 48 adult male ICR white mice (25–30 g) were divided into eight groups: Normal control group (n=6), SFN-treated group (n=6), quercetin-treated group (n=6), curcumin-treated group (n=6), BHA-treated group (n=6), indole-3-carbinol treated group (n=6), vehicle 1 control group (n=6), and vehicle 2 control group (n=6). All chemicals were administered intraperitoneally at a dose of 50 mg/kg for 14 days. Vehicle 1 (dimethyl sulfoxide, TweenTM 20, and normal saline at a ratio of 0.05:0.1:0.85) was used to dissolve SFN, quercetin, and curcumin. Vehicle 2 (corn oil) was used to dissolve indole-3-carbinol and BHA. At day 15, the animals were sacrificed and their livers were isolated. From the liver, total RNA was extracted, reverse transcribed and subjected to quantitative real‐time polymerase chain reaction to detect HO-1 gene expression. Agarose gel electrophoresis was also performed to verify the specificity of the amplification. HO-1 protein expression was determined by Western blotting. Results: HO-1 gene expression showed significant increase of 4.6±0.3, 3.6±0.2, 3.6±0.4, 3.3±0.3, and 3.0±0.4-fold and HO-1 protein expression showed significant increase of 2.3±0.2, 2.2±0.2, 2.2±0.1, 1.8±0.1, and 1.7±0.2-fold following treatment with 50 mg/kg of SFN, indole-3-carbinol, BHA, curcumin, and quercetin, respectively, compared to controls (p<0.05). Conclusion: At a dose of 50 mg/kg, SFN administration for 14 days resulted in the highest induction of HO-1 gene and protein expression level in mice liver, and quercetin the lowest.

Glutathione S-transferase isoenzymes (GSTs) catalyze the conjugation reaction between glutathione and electrophilic compounds. GSTs are involved in the detoxification of toxic and carcinogenic compounds, thus protecting the body from toxic injuries. Tocotrienols are part of the vitamin E family and is believed to possess potent antioxidant activity. The objective of this study was to determine the effect of increasing doses of tocotrienol rich fraction (TRF) supplementation on liver GSTs gene and protein expression. A total of 30 male ICR white mice were divided into five groups (n=6 for each group) and given treatment for 14 days through oral supplementation. Groups were divided as follows:-three groups administered with TRF at doses of 200, 500 and 1000 mg/kg, respectively, a positive control group administered with 100 mg/kg butylated hydroxyanisole (BHA) and a control group administered with only the vehicle (corn oil). At day 15, the mice were sacrificed and their livers isolated. Total RNA was extracted from the liver and quantitative real-time polymerase chain reaction (qPCR) assays were performed to analyze GSTs gene expression. Total liver protein was also extracted and the protein expression of GSTs was determined by Western blotting. The results showed that TRF oral supplementation caused a significant dose-dependent increase in liver GST isoenzymes gene and protein expression, compared to controls. In conclusion, TRF oral supplementation for 14 days resulted in increased gene and protein expression of GST isoenzymes in mice liver dose-dependently, with the highest expression seen in mice treated with 1000 mg/kg TRF.

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