Tocotrienols inhibit liver HMG CoA reductase activity in the guinea pig

Khor, H. T.; Chieng, David; Ong, K.K.

doi:10.1016/0271-5317(95)00021-6

Cited by 57 publications

(36 citation statements)

References 20 publications

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“…Furthermore, Á-tocopherol was found to accumulate in the plasma in relatively very high concentrations in cases of ·-tocopherol deficiency [86]. Feeding of Á-tocotrienol was found to increase the levels of ·-tocotrienol as well as ·-and Á-tocopherol in pigs [87] and humans [88]. Combined, these results suggest that Á-tocopherol is transformed by the intestinal microflora into ·-tocopherol, implying participation of a bacterial methyltransferase in this transformation.…”

Section: Transformation Of á-Tocopherol Into ·-Tocopherol In Vivo?mentioning

confidence: 56%

Gamma-Tocopherol – An Underestimated Vitamin?

2004

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The main research activities of the last decades on tocopherols were mainly focused on α-tocopherol, in particular when considering the biological activities. However, recent studies have increased the knowledge on γ-tocopherol, which is the major form of vitamin E in the diet in the USA, but not in Europe. γ-Tocopherol provides different antioxidant activities in food and in-vitro studies and showed higher activity in trapping lipophilic electrophiles and reactive nitrogen and oxygen species. The lower plasma levels of γ- compared to α-tocopherol might be discussed in the light of different bioavailability, but also in a potential transformation from γ- into α-tocopherol. From the metabolism end product, only that of γ-tocopherol (2,7,8-trimethyl-2-(β-carboxyethyl)-6-hydroxychroman), but not that of α-tocopherol, was identified to provide natriuretic activity. Studies also indicate that only the γ-tocopherol plasma level served as biomarker for cancer and cardiovascular risk. Therefore, this paper provides a comprehensive review on γ-tocopherol with emphasis on its chemistry, biosynthesis, occurrence in food, different intake linking to different plasma levels in USA and Europe, absorption and metabolism, biological activities, and possible role in human health.

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Section: Transformation Of á-Tocopherol Into ·-Tocopherol In Vivo?mentioning

confidence: 56%

Gamma-Tocopherol – An Underestimated Vitamin?

2004

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“…Vitamin E also increased the controlled degradation of the reductase protein and decreased the efficiency of the translation of HMG-CoA-R messenger RNA [152,153]. By inhibiting the activity of HMG-CoA-R, the serum total and LDL cholesterol could be reduced; hence, the levels of cholesterol will be lowered [154].…”

Section: Vitamin Ementioning

confidence: 99%

By-products of Rice Processing: An Overview of Health Benefits and Applications

Esa¹,

Ling²

2016

J Rice Res

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Our study was centred on the increasing literature associated with rice by-products and main components, especially those intended to combat cancer, improve plasma lipid levels or control the blood glucose levels. Rice byproducts, such as rice straw, rice husks, rice bran, rice germ and broken rice, are extensively abundant agricultural wastes from the rice industry, and the percentage of their production depends on the milling rate and type of rice. Among all rice by-products, rice bran has been extensively studied.It contains phytochemicals such as γ-oryzanol, vitamin E, mainly tocotrienols and dietary fibre. This paper reviews the existing literature on the potential role of rice by-products, focusing not only on the role of rice bran but also on the roles of other rice by-products, such as rice germ and rice husk, in the management of the diseases, investigating their various potential uses in the food industry and all possible properties that may contribute to these effects.

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“…Evidence suggests that the protective effects of GT3 are mediated, in part, through down-regulating protein levels and the activity of HMG-CoA reductase (Pearce et al, 1992;Qureshi and Qureshi, 1993;Khor et al, 1995;Song and DeBose-Boyd, 2006;Berbée et al, 2011). The inhibitory effect of GT3 on HMG-CoA reductase activity is more pronounced at lower concentrations of GT3 and ␦-tocotrienol (Khor et al, 1995).…”

Section: Gt3 Protects Against Mitochondrial Dysfunction 335mentioning

confidence: 99%

“…The inhibitory effect of GT3 on HMG-CoA reductase activity is more pronounced at lower concentrations of GT3 and ␦-tocotrienol (Khor et al, 1995). Other tocols have no measurable effect on HMG-CoA reductase degradation (Song and DeBose-Boyd, 2006) and can attenuate down-regulation of this enzyme by GT3 (Qureshi et al, 1995).…”

Section: Gt3 Protects Against Mitochondrial Dysfunction 335mentioning

confidence: 99%

“…These tocotrienols mimic sterols and produce a dose-dependent decrease in HMG-CoA reductase activity by accelerating degradation of HMG-CoA reductase protein (Song and DeBose-Boyd, 2006). In contrast, ␣-and ␥-tocopherols do not show antiproliferative activity even at higher concentrations (McIntyre et al, 2000) and have no measurable effect on HMG-CoA reductase degradation, cholesterol levels, (Pearce et al, 1992), and tumor growth (Goh et al, 1994;Khor et al, 1995). Therefore, it has been postulated that the suppression of HMG-CoA reductase activity is a mechanism mediating the hypocholesterolemic, cardioprotective, and tumor-suppressive actions of ␥-and ␦-tocotrienols (Elson, 1995;Aggarwal et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

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γ-Tocotrienol Protects against Mitochondrial Dysfunction and Renal Cell Death

Nowak¹,

Bakajsova²,

Hayes³

et al. 2011

J Pharmacol Exp Ther

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Oxidative stress is a major mechanism of a variety of renal diseases. Tocopherols and tocotrienols are well known antioxidants. This study aimed to determine whether ␥-tocotrienol (GT3) protects against mitochondrial dysfunction and renal proximal tubular cell (RPTC) injury caused by oxidants. Primary cultures of RPTCs were injured by using tert-butyl hydroperoxide (TBHP) in the absence and presence of GT3 or ␣-tocopherol (AT). Reactive oxygen species (ROS) production increased 300% in TBHP-injured RPTCs. State 3 respiration, oligomycinsensitive respiration, and respiratory control ratio (RCR) decreased 50, 63, and 47%, respectively. The number of RPTCs with polarized mitochondria decreased 54%. F 0 F 1 -ATPase activity and ATP content decreased 31 and 65%, respectively. Cell lysis increased from 3% in controls to 26 and 52% at 4 and 24 h, respectively, after TBHP exposure. GT3 blocked ROS production, ameliorated decreases in state 3 and oligomycinsensitive respirations and F 0 F 1 -ATPase activity, and maintained RCR and mitochondrial membrane potential (⌬⌿ m ) in injured RPTCs. GT3 maintained ATP content, blocked RPTC lysis at 4 h, and reduced it to 13% at 24 h after injury. Treatment with equivalent concentrations of AT did not block ROS production and cell lysis and moderately improved mitochondrial respiration and coupling. This is the first report demonstrating the protective effects of GT3 against RPTC injury by: 1) decreasing production of ROS, 2) improving mitochondrial respiration, coupling, ⌬⌿ m , and F 0 F 1 -ATPase function, 3) maintaining ATP levels, and 4) preventing RPTC lysis. Our data suggest that GT3 is superior to AT in protecting RPTCs against oxidant injury and may prove therapeutically valuable for preventing renal injury associated with oxidative stress.

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Tocotrienols inhibit liver HMG CoA reductase activity in the guinea pig

Cited by 57 publications

References 20 publications

Gamma-Tocopherol – An Underestimated Vitamin?

Gamma-Tocopherol – An Underestimated Vitamin?

By-products of Rice Processing: An Overview of Health Benefits and Applications

γ-Tocotrienol Protects against Mitochondrial Dysfunction and Renal Cell Death

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