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    AZMAN ABDULLAH

    NAD(P)H:quinone oxidoreductase 1 (NQO1) is considered as one of the most significant enzyme in cellular defense due to its ability to detoxify reactive quinones and quinone imines to their less toxic hydroquinones forms. NQO1 is a... more
    NAD(P)H:quinone oxidoreductase 1 (NQO1) is considered as one of the most significant enzyme in cellular defense due to its ability to detoxify reactive quinones and quinone imines to their less toxic hydroquinones forms. NQO1 is a xenobiotic metabolizing cytosolic enzyme that catalyzes the reduction of two- or four-electron of numerous exogenous and endogenous quinones by utilizing flavin adenine dinucleotide (FAD) as a cofactor. NQO1 enzyme exists as a homodimer enzyme and is biochemically identified by its noticeable ability to utilize either NADH or NADPH as reducing cofactors and by its inhibition by anticoagulant agents such as dicumarol. NQO1 is a distinctly inducible enzyme and known to be controlled by the Nrf2-Keap1 pathway. The importance of the antioxidant activities exhibited by NQO1 enzyme in suppressing the oxidative stress status is provided by demonstration that induction or reduction of NQO1 levels are linked with increased and reduced susceptibilities to oxidative ...
    Tocotrienol (T3) is a subfamily of vitamin E known for its wide array of medicinal properties. This review aimed to summarize the health benefits of T3, particularly in prevention or treatment of non-communicable diseases (NCDs),... more
    Tocotrienol (T3) is a subfamily of vitamin E known for its wide array of medicinal properties. This review aimed to summarize the health benefits of T3, particularly in prevention or treatment of non-communicable diseases (NCDs), including cardiovascular, musculoskeletal, metabolic, gastric, and skin disorders, as well as cancers. Studies showed that T3 could prevent various NCDs, by suppressing 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) in the mevalonate pathway, inflammatory response, oxidative stress, and alternating hormones. The efficacy of T3 in preventing/treating these NCDs is similar or greater compared to tocopherol (TF). TF may lower the efficacy of T3 because the efficacy of the combination of TF and T3 was lower than T3 alone in some studies. Data investigating the effects of T3 on osteoporosis, arthritis, and peptic ulcers in human are limited. The positive outcomes of T3 treatment obtained from the preclinical studies warrant further validation from clini...
    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... more
    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 ...
    Introduction: This study was conducted to determine the effects of kesum leaves (Persicaria minor) methanol extract on antioxidant status and lipid peroxidation in mice. Methods: 30% ethanol solution was used as a vehicle for kesum leaves... more
    Introduction: This study was conducted to determine the effects of kesum leaves (Persicaria minor) methanol extract on antioxidant status and lipid peroxidation in mice. Methods: 30% ethanol solution was used as a vehicle for kesum leaves methanol extract. 36 male ICR mice weighing between 20 - 25 g were randomly assigned into six groups. Two control groups (mice given normal diet and mice given normal diet plus vehicle) and three oral treatment groups (dosed at 100, 500 and 1000 mg/kg body weight of the extract) were utilized in this study. A diet containing 0.5% butylated hydroxyanisole (BHA) and oral vehicle treatment were given to the positive control group. After 28 days of treatment, mice were sacrificed and their livers were harvested to determine the antioxidant status; superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and reduced glutathione (GSH) concentration. The level of lipid peroxidation was determined through malondi...
    Reusing cooking oil is a common practice in Malaysia. Oxidation and hydrolysis occur when oil is heated repeatedly due to thermal decomposition. It had been suggested that consumption of repeatedly heated oil could be a health hazard. It... more
    Reusing cooking oil is a common practice in Malaysia. Oxidation and hydrolysis occur when oil is heated repeatedly due to thermal decomposition. It had been suggested that consumption of repeatedly heated oil could be a health hazard. It is therefore interesting to measure the awareness level amongst Kuala Lumpur residents regarding the usage of repeatedly heated cooking oil. A cross-sectional study was conducted to assess the level of awareness based on knowledge, attitude and practice regarding the usage of repeatedly heated cooking oil. The study involved convenience sampling of 500 respondents at various locations in Kuala Lumpur within a one-month period (April 2009). A questionnaire was designed as a tool to collect data from the respondents by face-to-face interview. It was found that the mean awareness score of Kuala Lumpur residents was moderate (7.8 out of 12 points) with the majority of respondents (42%) scoring moderately in their level of awareness regarding the usage o...
    Tocotrienols are the lesser-known components of the vitamin E family. Vitamin E family represent eight different isomers that belong to two classes: α, β, γ, δ tocopherols and α, β, γ, δ tocotrienols. Numerous studies have been done to... more
    Tocotrienols are the lesser-known components of the vitamin E family. Vitamin E family represent eight different isomers that belong to two classes: α, β, γ, δ tocopherols and α, β, γ, δ tocotrienols. Numerous studies have been done to compare the properties of tocotrienols with those of tocopherols and it was found that some biological activities were demonstrated to be unique for tocotrienols. Tocotrienols are the active components of many plants including annatto, rice bran, and palm. Research has been mostly focused on examining the antioxidant properties and cell signaling activities of tocopherols and tocotrienols. Although the antioxidative capability of tocotrienols is higher than that of tocopherols, tocotrienols show a lower bioavailability after oral administration. In this review, recent developments in the understanding of the molecular targets of the tocotrienols beyond their antioxidant activity are elaborated
    Research Interests:
    The transcription factor Nrf2 regulates expression of multiple cellular defence proteins through the antioxidant response element (ARE). Nrf2-deficient mice (Nrf2(-/-)) are highly susceptible to xenobiotic-mediated toxicity, but it is not... more
    The transcription factor Nrf2 regulates expression of multiple cellular defence proteins through the antioxidant response element (ARE). Nrf2-deficient mice (Nrf2(-/-)) are highly susceptible to xenobiotic-mediated toxicity, but it is not known whether this reflects low basal expression or reduced inducibility of Nrf2-regulated genes in response to chemical insults. Wild type and Nrf2(-/-) mice were fed diet supplemented with the established Nrf2 inducer butylated hydroxyanisole (BHA) [0.5% (w/w)] for 14 days. To define the range of Nrf2-regulated proteins, both basally and following exposure to BHA, a comparison of the liver proteomes of Nrf2(-/-) and wild type mice was conducted. The two-dimensional gel electrophoresis (2-DE) technique and MALDI mass spectrometry were utilized in the attempt to define Nrf2-regulated proteins. Overall, 24 proteins were identified, which were regulated either basally (3 proteins), inducibly (16 proteins), or both (5 proteins). These included several well-established Nrf2-driven gene products e.g., aldo-keto reductase and glutathione transferases. Multiple consensus ARE/ARE-like sequences were found in the Nrf2-regulated genes. This study confirms the central role of Nrf2 in the induction of multiple defense proteins as well as its control in the constitutive expression of certain proteins.
    Precise control of the level of protein expression in cells can yield quantitative and temporal information on the role of a given gene in normal cellular physiology and on exposure to chemicals and drugs. This is particularly relevant to... more
    Precise control of the level of protein expression in cells can yield quantitative and temporal information on the role of a given gene in normal cellular physiology and on exposure to chemicals and drugs. This is particularly relevant to liver cells, in which the expression of many proteins, such as phase I and phase II drug-metabolizing enzymes, vary widely between species, among individual humans, and on exposure to xenobiotics. The most widely used gene regulatory system has been the tet-on/off approach. Although a second-generation tet-on transactivator was recently described, it has not been widely investigated for its potential as a tool for regulating genes in cells and particularly in cells previously recalcitrant to the first-generation tet-on approach, such as hepatocyte-derived cells. Here we demonstrate the development of two human (HepG2 and HuH7) and one mouse (Hepa1c1c7) hepatoma-derived cell lines incorporating a second-generation doxycycline-inducible gene expressi...