Palm tocotrienols protect ApoE +/- mice from diet-induced atheroma formation

Palm-based tocotrienol-rich fraction (TRF) supplementation modulates cardiac sod1 expression, fxr target gene expression, and tauro-conjugated bile acid levels in aleptinemic mice fed a high-fat diet

Tocotrienol-rich fraction (TRF) has been reported to protect the heart from oxidative stress-induced inflammation. It is, however, unclear whether the protective effects of TRF against oxidative stress involve the activation of farnesoid X receptor (fxr), a bile acid receptor, and the regulation of bile acid metabolites. In the current study, we investigated the effects of TRF supplementation on antioxidant activities, expression of fxr and its target genes in cardiac tissue, and serum untargeted metabolomics of high-fat diet-fed mice. Mice were divided into high-fat diet (HFD) with or without TRF supplementation (control) for 6 weeks. At the end of the intervention, body weight (BW), waist circumference (WC), and random blood glucose were measured. Heart tissues were collected, and the gene expression of sod1, sod2, gpx, and fxr and its target genes shp and stat3 was determined. Serum was subjected to untargeted metabolomic analysis using UHPLC-Orbitrap. In comparison to the control, the WC of the TRF-treated group was higher (p >0.05) than that of the HFD-only group, in addition there was no significant difference in weight or random blood glucose level. Downregulation of sod1, sod2, and gpx expression was observed in TRF-treated mice; however, only sod1 was significant when compared to the HFD only group. The expression of cardiac shp (fxr target gene) was significantly upregulated, but stat3 was significantly downregulated in the TRF-treated group compared to the HFD-only group. Biochemical pathways found to be influenced by TRF supplementation include bile acid secretion, primary bile acid biosynthesis, and biotin and cholesterol metabolism. In conclusion, TRF supplementation in HFD-fed mice affects antioxidant activities, and more interestingly, TRF also acts as a signaling molecule that is possibly involved in several bile acid-related biochemical pathways accompanied by an increase in cardiac fxr shp expression. This study provides new insight into TRF in deregulating bile acid receptors and metabolites in high-fat diet-fed mice.

Tocotrienols: Dietary Supplements for Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death worldwide. Emphysema and chronic bronchitis are the two major phenotypes of COPD, which have many symptoms, such as dyspnea, chronic cough, and mucus overproduction. Emphysema is characterized by the destruction of the alveolar wall, while chronic bronchitis is characterized by limitations in expiratory airflow. Cigarette smoking is the most significant risk factor for the pathogenesis of COPD in the developed world. Chronic inflammation contributes to the onset and progression of the disease and furthers the risk of comorbidities. Current treatment options and prevention strategies for COPD are very limited. Tocotrienols are a group of vitamin E molecules with antioxidant and anti-inflammatory properties. Individual tocotrienols (α, γ, and δ) have shown their ability to attenuate inflammation specifically via suppressing nuclear factor-κB-mediated cytokine production. The δ- and γ-forms of tocotrienols have been indicated as the most effective in the prevention of macrophage infiltration, production of reactive oxygen species, and cytokine secretion. This review briefly discusses the pathogenesis of COPD and the role of inflammation therein. Furthermore, we summarize the in vitro and in vivo evidence for the anti-inflammatory activity of tocotrienols and their potential application to COPD management. Coupled with the bioavailability and safety profile of tocotrienols, the ability of these compounds to modulate COPD progression by targeting the inflammation pathways renders them potential candidates for novel therapeutic approaches in the treatment of COPD patients.

Measurements of Singlet Oxygen-Quenching Activity of Vitamin E Homologs and Palm Oil and Soybean Extracts in a Micellar Solution

Recently, a new assay method that can quantify the singlet oxygen-absorption capacity (SOAC) of antioxidants (AO) and food extracts in homogeneous organic solvents has been proposed. In the present study, second-order rate constants (kQ ) for the reaction of singlet oxygen (1 O2 ) with vitamin E homologs (α-, β-, γ-, and δ-tocopherols [Toc] and α-, β-, γ-, and δ-tocotrienols [Toc-3]) were measured in an aqueous Triton X-100 (5.0 wt%) micellar solution (pH 7.4). Toc-3 showed kQ values larger than those of Toc in a micellar solution, although Toc and Toc-3 showed the same kQ values in a homogeneous solution. Similar measurements were performed for 5 palm oil extracts 1-5 and one soybean extract 6, which contained different concentrations of Toc, Toc-3, and carotenoids. It has been clarified that the 1 O2 -quenching rates (kQ ) (that is, the relative SOAC value) obtained for extracts 3-6 may be explained as the sum of the product Σ k Q AO - i AO - i / 100 of the rate constant ( k Q AO - i ) and the concentration ([AO-i]/100) of AO-i contained. The UV-vis absorption spectra of Toc and Toc-3 were measured in a micellar solution and chloroform. The results obtained demonstrated that the kQ values of AO in homogeneous and heterogeneous solutions vary notably depending on (1) polarity (dielectric constant [ε]) of the reaction field between 1 O2 and AO, (2) the local concentration of AO, and (3) the mobility of AO in solution. The results suggest that the SOAC method is applicable to the measurement of 1 O2 -quenching activity of general food extracts in a heterogeneous micellar solution.

High purity tocotrienols attenuate atherosclerotic lesion formation in apoE-KO mice

Previous studies have demonstrated that tocotrienol (T3) has antiatherogenic effects. However, the T3 preparations used in those studies contained considerable amounts of tocopherol (Toc), which might affect the biological activity of T3. There is little information on the effect of highly purified T3 on atherosclerosis formation. This study investigated the effect of high-purity T3 on atherosclerotic lesion formation and the underlying mechanisms. Male apolipoprotein E knockout (apoE-KO) mice were fed a cholesterol-containing diet either alone or supplemented with T3 concentrate (Toc-free T3) or with α-Toc for 12 weeks. ApoE-KO mice fed the 0.2% T3-supplemented diet showed reduced atherosclerotic lesion formation in the aortic root. The 0.2% T3 diet induced Slc27a1 and Ldlr gene expression levels in the liver, whereas the α-Toc-supplemented diet did not affect those expression levels. T3 was predominantly deposited in fat tissue in the T3 diet-fed mice, whereas α-Toc was preferentially accumulated in liver in the α-Toc diet-fed mice. Considered together, these data demonstrate that dietary T3 exerts anti-atherosclerotic effect in apoE-KO mice. The characteristic tissue distribution and biological effects of T3, that are substantially different from those of Toc, may contribute to the antiatherogenic properties of T3.

Regulation of Obesity and Metabolic Complications by Gamma and Delta Tocotrienols

Tocotrienols (T3s) are a subclass of unsaturated vitamin E that have been extensively studied for their anti-proliferative, anti-oxidative and anti-inflammatory properties in numerous cancer studies. Recently, T3s have received increasing attention due to their previously unrecognized property to attenuate obesity and its associated metabolic complications. In this review, we comprehensively evaluated the recent published scientific literature about the influence of T3s on obesity, with a particular emphasis on the signaling pathways involved. T3s have been demonstrated in animal models or human subjects to reduce fat mass, body weight, plasma concentrations of free fatty acid, triglycerides and cholesterol, as well as to improve glucose and insulin tolerance. Their mechanisms of action in adipose tissue mainly include (1) modulation of fat cell adipogenesis and differentiation; (2) modulation of energy sensing; (3) induction of apoptosis in preadipocytes and (4) modulation of inflammation. Studies have also been conducted to investigate the effects of T3s on other targets, e.g., the immune system, liver, muscle, pancreas and bone. Since δT3 and γT3 are regarded as the most active isomers among T3s, their clinical relevance to reduce obesity should be investigated in human trials.

Kinetic study of the quenching reaction of singlet oxygen by seven rice bran extracts in ethanol solution. Development of a singlet oxygen absorption capacity (SOAC) assay method

Measurements of singlet oxygen (1O2) quenching rates (kQ (S)) and the relative singlet oxygen absorption capacity (SOAC) values were performed for seven rice bran extracts 1–7, which contained different concentrations of antioxidants (AOs) (such as α-, β-, γ-, and δ-tocopherols and -tocotrienols, three carotenoids (lutein, β-carotene, and zeaxanthin), and γ-oryzanol), in ethanol at 35 °C using UV–vis spectrophotometry. The concentrations of four tocopherols and four tocotrienols, three carotenoids, and γ-oryzanol contained in the extracts were determined using HPLC-MS/MS, UV-HPLC, and UV–vis absorption spectroscopy, respectively. Furthermore, comparisons of kQ (S) (Obsd.) values observed for the above extracts 1–7 with the sum of the product { [AO-i]} of the values obtained for each AO-i and the concentration ([AO-i]) of AO-i contained in extracts 1–7 were performed. From the results, it has been ascertained that the SOAC method is applicable to general food extracts to evaluate their 1O2-quenching activity.

Kinetic study of the scavenging reaction of the aroxyl radical by seven kinds of rice bran extracts in ethanol solution. Development of an aroxyl radical absorption capacity (ARAC) assay method

Recently, a new assay method that can quantify the aroxyl radical (ArO•) absorption capacity (ARAC) of antioxidants (AOHs) was proposed. In the present work, the second-order rate constants (ks(Extract)) and ARAC values for the reaction of ArO• with seven kinds of rice bran extracts 1-7, which contain different concentrations of α-, β-, γ-, and δ-tocopherols and -tocotrienols (α-, β-, γ-, and δ-Tocs and -Toc-3s) and γ-oryzanol, were measured in ethanol at 25 °C using stopped-flow spectrophotometry. The ks(Extract) value (1.26 × 10(-2) M(-1) s(-1)) of Nipponbare (extract 1) with the highest activity was 1.5 times larger than that (8.29 × 10(-3)) of Milyang-23 (extract 7) with the lowest activity. The concentrations (in mg/100 g) of α-, β-, γ-, and δ-Tocs and -Toc-3s and γ-oryzanol found in the seven extracts 1-7 were determined using HPLC-MS/MS and UV-vis absorption spectroscopy, respectively. From the results, it has been clarified that the ArO•-scavenging rates (ks(Extract)) (that is, the relative ARAC value) obtained for the seven extracts 1-7 may be approximately explained as the sum of the product {Σ ks(AOH-i) [AOH-i]/10(5)} of the rate constant (ks(AOH-i)) and the concentration ([AOH-i]/10(5)) of AOH-i (Tocs, Toc-3s, and γ-oryzanol) included in rice bran extracts. The contribution of γ-oryzanol to the ks(Extract) value was estimated to be between 3.0-4.7% for each extract. Taken together, these results suggest that the ARAC assay method is applicable to general food extracts.

Study of the effects of a diet supplemented with active components on lipid and glycemic profiles

OBJECTIVES

Currently, there are numerous studies on risk factors for cardiovascular disease and the potential for functional foods to bring benefits or improve people's health. However, most of these studies are conducted with middle-aged individuals. The aim of this study was to evaluate the effects of supplementing a typical diet with some functional components, which are substances that when consumed in small quantities can improve people's welfare.

METHODS

The participants in this study were young; slightly overweight; had normal glucose tolerance; and had lipid values indicating dyslipidemia or close dyslipidemia. Following a 4-wk run-in phase, participants followed either a diet containing foods enriched with ω-3 fatty acids, β-glucans, phytosterols, and vitamin E or an isoenergetic diet without the active components. Sixteen individuals (age range 20 to 37 y) were randomly assigned to one of two groups. At the end of treatment, while fasting, plasma concentrations of triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and total cholesterol were measured. Furthermore, blood glucose was evaluated after fasting and after a meal enriched with β-glucans.

RESULTS

There was a statistically significant reduction (α < 0.05) across the lipid profile. A meal rich in β-glucans produced a glycemic response significantly lower than the nonenriched meal.

CONCLUSION

The dietary supplements used in this work, based on the integration of functional components into the usual diet of the population, have proved effective in reducing peak levels of postprandial glucose and the risk for dyslipidemia. Therefore, these functional components proved a valuable aid in the prevention of cardiovascular diseases and metabolic disorders.

Finding of synergistic and cancel effects on the aroxyl radical-scavenging rate and suppression of prooxidant effect for coexistence of α-tocopherol with β-, γ-, and δ-tocopherols (or -tocotrienols)

Measurements of aroxyl radical (ArO•)-scavenging rate constants (k(s)(AOH)) of antioxidants (AOHs) [α-, β-, γ-, and δ-tocopherols (TocHs) and -tocotrienols (Toc-3Hs)] were performed in ethanol solution via stopped-flow spectrophotometry. k(s)(AOH) values of α-, β-, γ-, and δ-Toc-3Hs showed good agreement with those of the corresponding α-, β-, γ-, and δ- TocHs. k(s)(AOH) values were measured not only for each antioxidant but also for mixtures of two antioxidants: (i) α-TocH with β-, γ-, or δ-TocH and (ii) α-TocH with α-, β-, γ-, or δ-Toc-3H. A synergistic effect in which the k(s)(AOH) value increases by 12% for γ-TocH (or by 12% for γ-Toc-3H) was observed for solutions including α-TocH and γ-TocH (or γ-Toc-3H). On the other hand, a cancel effect in which the k(s)(AOH) value decreases (a) by 7% for β-TocH (or 11% for β-Toc-3H) and (b) by 24% for δ-TocH (or 25% for δ-Toc-3H) was observed for solutions including two kinds of antioxidants. However, only a synergistic effect may function in edible oils, because contents of β- and δ-TocHs (and β- and δ-Toc-3Hs) are much less than those of α- and γ-TocHs (and α- and γ-Toc-3Hs) in many edible oils. UV-vis absorption of α-Toc•, which was produced by reaction of α-TocH with ArO•, decreased remarkably for coexistence of α-TocH with β-, γ-, or δ-TocH (or β-, γ-, or δ-Toc-3H), indicating that the prooxidant effect of α-Toc• is suppressed by the coexistence of other TocHs and Toc-3Hs.

Kinetic study of the quenching reaction of singlet oxygen by α-, β-, γ-, δ-tocotrienols, and palm oil and soybean extracts in solution

Measurements of the singlet oxygen ((1)O2) quenching rates (kQ (S)) and the relative singlet oxygen absorption capacity (SOAC) values were performed for 11 antioxidants (AOs) (eight vitamin E homologues (α-, β-, γ-, and δ-tocopherols and -tocotrienols (-Tocs and -Toc-3s)), two vitamin E metabolites (α- and γ-carboxyethyl-6-hydroxychroman), and trolox) in ethanol/chloroform/D2O (50:50:1, v/v/v) and ethanol solutions at 35 °C. Similar measurements were performed for five palm oil extracts 1-5 and one soybean extract 6, which included different concentrations of Tocs, Toc-3s, and carotenoids. Furthermore, the concentrations (wt%) of Tocs, Toc-3s, and carotenoids included in extracts 1-6 were determined. From the results, it has been clarified that the (1)O2-quenching rates (kQ (S)) (that is, the relative SOAC value) obtained for extracts 1-6 may be explained as the sum of the product {Σ kQ(AO-i) (S) [AO-i]/100} of the rate constant (kQ(AO-i) (S)) and the concentration ([AO-i]/100) of AO-i (Tocs, Toc-3s, and carotenoid) included.

Physiological effects and tissue distribution from large doses of tocotrienol in rats

Supplementation to an AIN93G-based diet of tocotrienol (T3) for 13 weeks administered to Fischer 344/slc rats showed a safety profile with no side effects. Dose-dependent T3 levels were detected in many tissues. Under the present experimental conditions, a continuous intake of the T3 concentrate would be safe in the rats as long as the T3 content was less than 0.20% of the dietary intake.

Actions of "antioxidants" in the protection against atherosclerosis

This review addresses the role of oxidative processes in atherosclerosis and its resulting cardiovascular disease by focusing on the outcome of antioxidant interventions. Although there is unambiguous evidence for the presence of heightened oxidative stress and resulting damage in atherosclerosis, it remains to be established whether this represents a cause or a consequence of the disease. This critical question is complicated further by the increasing realization that oxidative processes, including those related to signaling, are part of normal cell function. Overall, the results from animal interventions suggest that antioxidants provide benefit neither generally nor consistently. Where benefit is observed, it appears to be achieved at least in part via modulation of biological processes such as increase in nitric oxide bioavailability and induction of protective enzymes such as heme oxygenase-1, rather than via inhibition of oxidative processes and lipid oxidation in the arterial wall. Exceptions to this may be situations of multiple/excessive stress, the relevance of which for humans is not clear. This interpretation is consistent with the overall disappointing outcome of antioxidant interventions in humans and can be rationalized by the spatial compartmentalization of cellular oxidative signaling and/or damage, complex roles of oxidant-producing enzymes, and the multifactorial nature of atherosclerosis.

Tocotrienol attenuates triglyceride accumulation in HepG2 cells and F344 rats

Tocotrienol (T3) is an important phytonutrient found in rice bran and palm oil. T3 has gained much interest for lipid lowering effects, especially for cholesterol (Cho) by inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A reductase. Also, usefulness of T3 in improving triglyceride (TG) profiles has been suggested, but its efficacy and mechanism have been unclear. We investigated how T3 decreases TG concentration in cultured cells and animals. In a cell culture study, human hepatoma cells (HepG2) were incubated in a control or a fat (1 mM oleic acid)-loaded medium containing γ-T3 for 24 h. We found that 10-15 μM γ-T3 inhibited cellular TG accumulation significantly, especially in the fat-loaded medium. This manifestation was supported by mRNA and protein expressions of fatty acid synthase, carnitine palmitoyltransferase 1, and cytochrome P450 3A4. In concordance with these results, rice bran T3 supplementation to F344 rats (5 or 10 mg T3/day/rat) receiving a high fat diet for 3 weeks significantly reduced TG and the oxidative stress marker (phospholipid hydroperoxides, PLOOH) in the liver and blood plasma. T3 supplementation did not show changes in the Cho level. These results provided new information and the mechanism of the TG-lowering effect of T3. The lipid lowering effects of dietary T3 might be mediated by the reduction of TG synthesis.

Multifaceted role of tocotrienols in cardioprotection supports their structure: function relation

Tocotrienols are a class of vitamin E which modulates several mechanisms associated with cardioprotection, anti-cancer, anti-diabetic, and neuroprotection. Unlike other Vitamin E-like compounds, tocotrienols possess inimitable properties. Quite a lot of studies have determined the cardioprotective abilities of tocotrienols and have been shown to possess novel hypocholesterolemic effects together with an ability to reduce the atherogenic apolipoprotein and lipoprotein plasma levels. In addition, tocotrienol has been suggested to have an antioxidant, anti-thrombotic, and anti-tumor effect indicating that tocotrienol may serve as an effective agent in the prevention and/or treatment of cardiovascular disease and cancer. The bioactivity exhibited is due to the structural characteristics of tocotrienols. Rich sources of tocotrienols which include rice bran, palm oil, and other edible oils exhibit protective effect against cardiovascular disorders. The conclusions drawn from the early literature that vitamin E group of compounds provides an inevitable role in cardioprotection is sustained in many more recent studies.

Protective effects of vitamin E against hypercholesterolemia-induced age-related diseases

Hypercholesterolemia is a major risk factor for age-related diseases such as atherosclerosis and Alzheimer's disease (AD). Changes in human plasma cholesterol levels results from the interaction between multiple genetic and environmental factors. The accumulation of excess cholesterol in blood vessels leads to atherosclerosis. Many studies on this field show that differential expression of oxidative stress-related proteins, lipid metabolism-related enzymes, and receptors response to atherogenic diet. Additionally, excess brain cholesterol has been associated with increased formation and deposition of amyloid-β peptide from amyloid precursor protein which may contribute to the risk and pathogenesis of AD. To consider genetically, more than 50 genes have been reported to influence the risk of late-onset AD. Some of these genes might be also important in cholesterol metabolism and transport. Epidemiological studies have shown an association between high intake and high serum concentrations of antioxidant vitamins like vitamin E and lower rates of ischemic heart diseases. It has been known that vitamin E also inhibits smooth muscle cell proliferation by non-antioxidant mechanism. On the basis of the previous results, vitamin E has been accepted as an important protective factor against hypercholesterolemia-induced age-related diseases.

Dietary supplementation with tocotrienols enhances immune function in C57BL/6 mice

alpha-Tocopherol (alpha-Toc) enhances T cell function, whereas little is known in this regard for tocotrienols (T3), the less-known members of the vitamin E family. We pair-fed young (4 mo) and old (23 mo) C57BL/6 mice 0.1% Tocomin 50%, a mixture of T3 and alpha-Toc or a control diet containing an equal amount of alpha-Toc for 6 wk. As expected, lymphocyte proliferation was lower in the old mice compared with the young mice. Lymphocyte proliferation in the old T3 group was significantly higher than that in the old control group, whereas no significant difference was found in young mice. Splenocytes from old mice produced less interleukin (IL)-2, IL-4, IL-6, and IL-10 compared with young mice, whereas no significant age-related difference was found in IL-1beta, tumor necrosis factor-alpha, and interferon-gamma. T3 feeding was associated with a higher IL-1beta production in old mice but not in young mice. Peritoneal macrophages from old mice produced significantly more IL-1beta, IL-6, IL-10, and prostaglandin E(2) (PGE(2)) compared with those from young mice. Mice of both ages fed T3 had higher production of IL-1beta but not PGE(2) or other cytokines. In the in vitro study, splenocytes isolated from young and old mice were supplemented with the purified form of each individual T3 (0.01-10 mumol/L) and mitogen-stimulated cell proliferation was determined. All T3 enhanced lymphocyte proliferation in old but not young mice with a potency order of alpha- > gamma- > delta-T3. Together, these results suggest a beneficial effect of T3 in improving the age-related decline in T cell function.

Tocotrienol enriched palm oil prevents atherosclerosis through modulating the activities of peroxisome proliferators-activated receptors

Palm oil is enriched in vitamin E in the form of alpha-, gamma-, and delta-tocotrienols. Dietary tocotrienol supplements have been shown to prevent atherosclerosis development in patients and preclinical animal models. However, the mechanistic basis for this health beneficial effect is not well established. Peroxisome proliferator-activated receptors alpha, gamma, and delta (PPARalpha, PPARgamma, and PPARdelta) are ligand regulated transcription factors that play essential preventive roles in the development of atherosclerosis through regulating energy metabolism and inflammation. In this study, we presented data that the tocotrienol rich fraction (TRF) of palm oil activated PPARalpha, PPARgamma, and PPARdelta in reporter based assays. Importantly, TRF attenuated the development of atherosclerosis in ApoE-/- mice through inducing PPAR target gene liver X receptor alpha (LXRalpha) and its down-stream target genes apolipoproteins and cholesterol transporters, suggesting that modulating the activities of PPARs is a key aspect of the in vivo action of tocotrienols.

Chemical reactivities and physical effects in comparison between tocopherols and tocotrienols: physiological significance and prospects as antioxidants

Vitamin E is a generic term for all tocopherol and tocotrienol derivatives. The most abundant and active form of vitamin E isoforms in vivo is alpha-tocopherol, but recently the roles of other forms of vitamin E have received renewed attention. In this review, we summarize the differences among alpha-, beta-, gamma-, delta-tocopherols and tocotrienols specifically regarding the following points; (i) their radical-scavenging efficacies and chemical reactivity with metal ions in solution, (ii) their physical effects at the liposomal membrane interior, and (iii) their protective effects against cell toxicity. Moreover, the physiological significance and future prospects for using vitamin E, especially tocotrienols, for the prevention and treatment of disease are discussed.

Intestinal Epithelial Cells Absorb γ-Tocotrienol Faster than α-Tocopherol

To elucidate the transepithelial transport characteristics of lipophilic compounds, the cellular uptake of tocopherol and tocotrienol isomers were investigated in Caco2 cell monolayer models. These vitamin E isomers formed mixed micelles consisting of bile salts, lysophospholipids, free fatty acid, and 2-monoacylglycerols, then the micelles were supplied to Caco2 cells. The initial accumulation of tocotrienol isomers in Caco2 cells was larger than those of corresponding tocopherol isomers. There was little difference among the cellular accumulations of four tocopherol isomers. These findings suggested that the difference between the molecular structures of the C16 hydrocarbon chain tail in tocopherol and tocotrienol was strongly responsible for the rapid epithelial transport into the Caco2 cells membranes rather than the difference in the molecular structures of their chromanol head groups. Furthermore, the secretion of alpha-tocopherol and gamma-tocotrienol from Caco2 cells was investigated using Caco2 cells plated on a transwell. The time courses of their secretions from Caco2 cells showed that the initial secretion rate of gamma-tocotrienol was also larger than that of alpha-tocopherol. To investigate the intestinal uptake of alpha-tocopherol and gamma-tocotrienol in vivo, the mice were fed single doses of alpha-tocopherol or gamma-tocotrienol with triolein. The gamma-tocotrienol responded faster in plasma than alpha-tocopherol, although the maximal level of gamma-tocotrienol was lower than that of alpha-tocopherol. This suggested that the intestinal uptake properties of administered alpha-tocopherol and gamma-tocotrienol would characterize their plasma level transitions in mice.

Modulation of signal transduction by vitamin E

The ability of vitamin E to modulate signal transduction and gene expression has been observed in numerous studies; however, the detailed molecular mechanisms involved are often not clear. The eight natural vitamin E analogues and synthetic derivatives affect signal transduction with different potency, possibly reflecting their different ability to interact with specific proteins. Vitamin E modulates the activity of several enzymes involved in signal transduction, such as protein kinase C, protein kinase B, protein tyrosine kinases, 5-, 12-, and 15-lipoxygenases, cyclooxygenase-2, phospholipase A2, protein phosphatase 2A, protein tyrosine phosphatase, and diacylglycerol kinase. Activation of some these enzymes after stimulation of cell surface receptors with growth factors or cytokines can be normalized by vitamin E. At the molecular level, the translocation of several of these enzymes to the plasma membrane is affected by vitamin E, suggesting that the modulation of protein-membrane interactions may be a common theme for vitamin E action. In this review the main effects of vitamin E on enzymes involved in signal transduction are summarized and the possible mechanisms leading to enzyme modulation evaluated. The elucidation of the molecular and cellular events affected by vitamin E could reveal novel strategies and molecular targets for developing similarly acting compounds.

Vitamin E: inflammation and atherosclerosis

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the western world with its incidence increasing lately in developing countries. Several lines of evidence support a role for inflammation in atherogenesis. Hence, dietary micronutrients having antiinflammatory properties may have a potential beneficial effect with regard to CVD. Vitamin E is a potent antioxidant with antiinflammatory properties. It comprises eight different isoforms: four tocopherols (T) (alpha, beta, gamma, and delta) and four tocotrienols (T3) (alpha, beta, gamma, and delta). A wealth of data is available for the preventive efficacy of alpha-T. alpha-T supplementation in human subjects and animal models has been shown to be antioxidant and antiinflammatory in terms of decreasing C-reactive protein (CRP) and release of proinflammatory cytokines, the chemokine IL-8 and PAI-1 levels especially at high doses. gamma-T is effective in decreasing reactive nitrogen species and also appears to have antiinflammatory properties; however, there are scanty data examining pure gamma-T preparations. Furthermore, tocotrienols (alpha and gamma) also have implications for prevention of CVD; however, there are conflicting and insufficient data in the literature with regards to their potency. In this chapter, we have gathered recent emerging data on alpha-T specifically and also have given a composite view of gamma-T and tocotrienols especially with regards to their effect on inflammation as it relates to CVD.

Tocotrienols: the emerging face of natural vitamin E

Natural vitamin E includes eight chemically distinct molecules: alpha-, beta-, gamma-, and delta-tocopherols and alpha-, beta-, gamma-, and delta-tocotrienols. More than 95% of all studies on vitamin E are directed toward the specific study of alpha-tocopherol. The other forms of natural vitamin E remain poorly understood. The abundance of alpha-tocopherol in the human body and the comparable efficiency of all vitamin E molecules as antioxidants led biologists to neglect the non-tocopherol vitamin E molecules as topics for basic and clinical research. Recent developments warrant a serious reconsideration of this conventional wisdom. The tocotrienol subfamily of natural vitamin E possesses powerful neuroprotective, anticancer, and cholesterol-lowering properties that are often not exhibited by tocopherols. Current developments in vitamin E research clearly indicate that members of the vitamin E family are not redundant with respect to their biological functions. alpha-Tocotrienol, gamma-tocopherol, and delta-tocotrienol have emerged as vitamin E molecules with functions in health and disease that are clearly distinct from that of alpha-tocopherol. At nanomolar concentration, alpha-tocotrienol, not alpha-tocopherol, prevents neurodegeneration. On a concentration basis, this finding represents the most potent of all biological functions exhibited by any natural vitamin E molecule. Recently, it has been suggested that the safe dose of various tocotrienols for human consumption is 200-1000/day. A rapidly expanding body of evidence supports that members of the vitamin E family are functionally unique. In recognition of this fact, title claims in publications should be limited to the specific form of vitamin E studied. For example, evidence for toxicity of a specific form of tocopherol in excess may not be used to conclude that high-dosage "vitamin E" supplementation may increase all-cause mortality. Such conclusion incorrectly implies that tocotrienols are toxic as well under conditions where tocotrienols were not even considered. The current state of knowledge warrants strategic investment into the lesser known forms of vitamin E. This will enable prudent selection of the appropriate vitamin E molecule for studies addressing a specific health need.

γ-Tocotrienol Inhibits Nuclear Factor-κB Signaling Pathway through Inhibition of Receptor-interacting Protein and TAK1 Leading to Suppression of Antiapoptotic Gene Products and Potentiation of Apoptosis

Unlike the tocopherols, the tocotrienols, also members of the vitamin E family, have an unsaturated isoprenoid side chain. In contrast to extensive studies on tocopherol, very little is known about tocotrienol. Because the nuclear factor-kappaB (NF-kappaB) pathway has a central role in tumorigenesis, we investigated the effect of gamma-tocotrienol on the NF-kappaB pathway. Although gamma-tocotrienol completely abolished tumor necrosis factor alpha (TNF)-induced NF-kappaB activation, a similar dose of gamma-tocopherol had no effect. Besides TNF, gamma-tocotrienol also abolished NF-kappaB activation induced by phorbol myristate acetate, okadaic acid, lipopolysaccharide, cigarette smoke, interleukin-1beta, and epidermal growth factor. Constitutive NF-kappaB activation expressed by certain tumor cells was also abrogated by gamma-tocotrienol. Reducing agent had no effect on the gamma-tocotrienol-induced down-regulation of NF-kappaB. Mevalonate reversed the NF-kappaB inhibitory effect of gamma-tocotrienol, indicating the role of hydroxymethylglutaryl-CoA reductase. Gamma-tocotrienol blocked TNF-induced phosphorylation and degradation of IkappaBalpha through the inhibition of IkappaBalpha kinase activation, thus leading to the suppression of the phosphorylation and nuclear translocation of p65. gamma-Tocotrienol also suppressed NF-kappaB-dependent reporter gene transcription induced by TNF, TNFR1, TRADD, TRAF2, TAK1, receptor-interacting protein, NIK, and IkappaBalpha kinase but not that activated by p65. Additionally, the expressions of NF-kappaB-regulated gene products associated with antiapoptosis (IAP1, IAP2, Bcl-xL, Bcl-2, cFLIP, XIAP, Bfl-1/A1, TRAF1, and Survivin), proliferation (cyclin D1, COX2, and c-Myc), invasion (MMP-9 and ICAM-1), and angiogenesis (vascular endothelial growth factor) were down-regulated by gamma-tocotrienol. This correlated with potentiation of apoptosis induced by TNF, paclitaxel, and doxorubicin. Overall, our results demonstrate that gamma-tocotrienol inhibited the NF-kappaB activation pathway, leading to down-regulation of various gene products and potentiation of apoptosis.

Dietary comparison of conjugated linolenic acid (9 cis, 11 trans, 13 trans) and alpha-tocopherol effects on blood lipids and lipid peroxidation in alloxan-induced diabetes mellitus in rats

The present study investigated the dietary effect of conjugated linolenic acid (CLnA) on lipid profiles and lipid peroxidations in alloxan-induced diabetes mellitus in rats. Diabetic rats were fed with 20% sunflower oil (diabetic control), sunflower oil supplemented with 0.5% CLnA, sunflower oil supplemented with 0.15% alpha-tocopherol, and sunflower oil containing 0.25% CLnA + 0.15% alpha-tocopherol. The results demonstrated that 0.5% CLnA, 0.15% alpha-tocopherol, and 0.25% CLnA + 0.15% alpha-tocopherol each on supplementation significantly lowered total cholesterol and non-HDL-cholesterol in comparison with the diabetic control group. The TAG level was significantly lowered in both the 0.15% alpha-tocopherol and 0.25% CLnA + 0.15% alpha-tocopherol groups. LDL-lipid peroxidation and erythrocyte membrane lipid peroxidation were reduced significantly in each of the experimental groups vs. the control group. The CLnA + alpha-tocopherol diet induced a greater reduction in membrane lipid and liver lipid peroxidation than the alpha-tocopherol diet alone. In conclusion, dietary CLnA exerts antioxidant activity as evidenced by reduced lipid peroxidation in chemically induced diabetes mellitus.

Tocotrienols: Vitamin E beyond tocopherols

In nature, eight substances have been found to have vitamin E activity: alpha-, beta-, gamma- and delta-tocopherol; and alpha-, beta-, gamma- and delta-tocotrienol. Yet, of all papers on vitamin E listed in PubMed less than 1% relate to tocotrienols. The abundance of alpha-tocopherol in the human body and the comparable efficiency of all vitamin E molecules as antioxidants, led biologists to neglect the non-tocopherol vitamin E molecules as topics for basic and clinical research. Recent developments warrant a serious reconsideration of this conventional wisdom. Tocotrienols possess powerful neuroprotective, anti-cancer and cholesterol lowering properties that are often not exhibited by tocopherols. Current developments in vitamin E research clearly indicate that members of the vitamin E family are not redundant with respect to their biological functions. alpha-Tocotrienol, gamma-tocopherol, and delta-tocotrienol have emerged as vitamin E molecules with functions in health and disease that are clearly distinct from that of alpha-tocopherol. At nanomolar concentration, alpha-tocotrienol, not alpha-tocopherol, prevents neurodegeneration. On a concentration basis, this finding represents the most potent of all biological functions exhibited by any natural vitamin E molecule. An expanding body of evidence support that members of the vitamin E family are functionally unique. In recognition of this fact, title claims in manuscripts should be limited to the specific form of vitamin E studied. For example, evidence for toxicity of a specific form of tocopherol in excess may not be used to conclude that high-dosage "vitamin E" supplementation may increase all-cause mortality. Such conclusion incorrectly implies that tocotrienols are toxic as well under conditions where tocotrienols were not even considered. The current state of knowledge warrants strategic investment into the lesser known forms of vitamin E. This will enable prudent selection of the appropriate vitamin E molecule for studies addressing a specific need.

Analysis of the variable effect of dietary vitamin E supplements on experimental atherosclerosis

Vitamin E inhibits processes thought to be important in the development of atherosclerosis but clinical trials to determine its effect on cardiovascular disease have given variable results, the majority being negative. The reasons for this are unclear. Animal trials can be better controlled and use more rigorous measures of lesion progression than human trials. The present study reviewed trials using rabbits and mice to determine whether they also are variable and, if so, to uncover methodological differences that may account for the different outcomes. A large number of trials examining the effect of vitamin E supplements on experimental atherosclerosis were identified. Using rigorous selection criteria, a well-defined group was selected for further investigation. Almost all the mice trials showed a significant effect of vitamin E, but only around one-third of the rabbit trials did so. When the rabbit trials were divided into those that did and those that did not observe significant effects, no single factor was found that could account for the dichotomy. However, when the percentage reduction in disease was considered, rather than the within-trial significance level, there were clear dose-dependent effects of vitamin E on disease severity in heritable hyperlipidaemic rabbits, and in genetically normal rabbits made hyperlipidaemic with cholesterol alone; the dose dependence was different in the two groups, the heritable hyperlipidaemic rabbits showing a near ten-fold lower sensitivity. The high doses required to affect experimental atherosclerosis may, if applicable to other species, help explain the absence of effects in many human trials.

Tocotrienols: constitutional effects in aging and disease

Tocotrienols, a class of vitamin E analogs, modulate several mechanisms associated with the aging process and aging-related diseases. Most studies compare the activities of tocotrienols with those of tocopherols ("classical vitamin E"). However, some biological effects were found to be unique for tocotrienols. Although the absorption mechanisms are essentially the same for all vitamin E analogs, tocotrienols are degraded to a greater extent than tocopherols. The levels of tocotrienols in the plasma of animals and humans were estimated to reach low micromolar concentrations. One hallmark in the origin of disease and aging is the overproduction of reactive oxygen species (ROS). Tocotrienols possess excellent antioxidant activity in vitro and have been suggested to suppress ROS production more efficiently than tocopherols. In addition, tocotrienols show promising nonantioxidant activities in various in vitro and in vivo models. Most notable are the interactions of tocotrienols with the mevalonate pathway leading to the lowering of cholesterol levels, the prevention of cell adhesion to endothelial cells, and the suppression of tumor cell growth. Furthermore, glutamate-induced neurotoxicity is suppressed in the presence of tocotrienols. This review summarizes the main antioxidant and nonantioxidant effects of tocotrienols and assesses their potential as health-maintaining compounds.

Tocotrienols reduce 25-hydroxycholesterol-induced monocyte-endothelial cell interaction by inhibiting the surface expression of adhesion molecules

The migration of circulating monocytes into the subendothelial space occurs through the expressing of some adhesion molecules on endothelial cells. In the present study, using human aortic endothelial cells (HAECs), we investigated whether a model compound for oxysterols, 25-hydroxycholesterol, can enhance the monocyte adherence to HAECs exposed to 25-hydroxycholesterol via increasing expression of vascular cell adhesion molecule-1 (VCAM-1). We also aimed to determine the in vitro effects of tocotrienols on the enhanced interaction between monocytes and endothelial cells. We found that 25-hydroxycholesterol enhances surface expression determined by ELISA, induces VCAM-1 mRNA expression by real time-PCR, and stimulates adhesiveness of HAECs to U937 monocytic cells in a dose-dependent fashion. The combination treatment with anti-VCAM-1 and anti-CD11b monoclonal antibodies significantly reduced the monocyte adherence to 25-hydroxycholesterol-stimulated HAECs. Compared to alpha-tocopherol, tocotrienols displayed a more profound inhibitory effect on adhesion molecule expression and monocytic cell adherence. We observed that delta-tocotrienol exerted a most profound inhibitory action on monocytic cell adherence when compared to alpha-tocopherol and alpha-, beta-, and gamma-tocotrienols. Tocotrienols accumulated in HAECs to levels approximately 25-95-fold greater than that of alpha-tocopherol. In conclusion, these results indicate that a model compound 25-hydroxycholesterol can enhance the interaction between monocytes and HAECs, and that tocotrienols had a profound inhibitory effect on monocytic cell adherence to HAECs relative to alpha-tocopherol via inhibiting the VCAM-1 expression. These superior inhibitory effects of tocotrienols may be dependent on their intracellular accumulation.

Distribution of tocopherols and tocotrienols to rat ocular tissues after topical ophthalmic administration

With increasing evidence suggesting the involvement of oxidative stress in various disorders and diseases, the role of antioxidants in vivo has received much attention. Chemically, tocopherols and tocotrienols are closely related; however, it has been observed that they have widely varying degrees of biological effectiveness. The present study has been carried out in an attempt to deepen our understanding of whether there is a significant difference in distribution between tocopherol and tocotrienol homologs to rat eye tissues. Rats were administered 5 microL of pure tocopherol or tocotrienol to each eye once a day for 4 d. Various tissues of the eyes were separated and analyzed for tocopherol and tocotrienol concentrations. The concentration of alpha-to-cotrienol increased markedly in every tissue to which it was administered; however, no significant increase was observed in the case of alpha-tocopherol. The intraocular penetration of gamma-tocopherol and gamma-tocotrienol did not differ significantly. Additionally, a significant increase in total vitamin E concentration was observed in ocular tissues, including crystalline lens, neural retina, and eye cup, with topical administration using a relatively small amount (5 microL) of vitamin E, whereas no significant increase was observed when the same amount of vitamin E was administered orally. Topical administration of tocotrienols is thus an effective way to increase ocular tissue vitamin E concentration.

Comparative study on the action of tocopherols and tocotrienols as antioxidant: chemical and physical effects

alpha-Tocopherol is known as the most abundant and active form of vitamin E homologues in vivo, but recently the role of other forms of vitamin E has received renewed attention. The antioxidant properties were compared for alpha-, beta-, gamma- and delta-tocopherols and tocotrienols. The following results were obtained: (1). the corresponding tocopherols and tocotrienols exerted the same reactivities toward radicals and the same antioxidant activities against lipid peroxidation in solution and liposomal membranes; (2). tocopherols gave more significant physical effect than tocotrienols on the increase in rigidity at the membrane interior; (3). tocopherols and tocotrienols showed similar mobilities within the membranes, but tocotrienols were more readily transferred between the membranes and incorporated into the membranes than tocopherols; (4). alpha-tocopherol and alpha-tocotrienol, but not the other forms, reduced Cu(II) to give Cu(I) together with alpha-tocopheryl and alpha-tocotrienyl quinones, respectively and exerted prooxidant effect in the oxidation of methyl linoleate in SDS micelles.

Dietary alpha-tocopherol decreases alpha-tocotrienol but not gamma-tocotrienol concentration in rats

We previously showed that alpha- and gamma-tocotrienols accumulate in adipose tissue and skin but not in plasma or other tissues of rats fed a tocotrienol-rich fraction extracted from palm oil containing alpha-tocopherol and alpha- and gamma-tocotrienols. To clarify the nature of tocotrienol metabolism, we studied the distribution of alpha- or gamma-tocotrienol in rats fed alpha- or gamma-tocotrienol without alpha-tocopherol, and the effect of alpha-tocopherol on their distribution. Wistar rats (4-wk-old) were fed a diet with 50 mg alpha-tocotrienol/kg alone or with 50 mg alpha-tocopherol/kg in expt. 1, and a diet with 50 mg gamma-tocotrienol/kg alone or with 50 mg alpha-tocopherol/kg in expt. 2, for 8 wk. alpha-Tocotrienol was detected in various tissues and plasma of the rats fed alpha-tocotrienol alone, and the alpha-tocotrienol concentrations in those tissues and plasma decreased (P < 0.05) by the dietary alpha-tocopherol in the rats fed alpha-tocotrienol with alpha-tocopherol. However, gamma-tocotrienol preferentially accumulated in the adipose tissue and skin of the rats fed gamma-tocotrienol alone, and the dietary alpha-tocopherol failed either to decrease (P >/= 0.05) gamma-tocotrienol concentrations in the adipose tissue and skin or to increase (P >/= 0.05) in the urinary excretion of 2,7,8-trimethyl-2(2'-carboxymethyl)-6-hydroxycroman, a metabolite of gamma-tocotrienol, in the rats fed gamma-tocotrienol with alpha-tocopherol. These data suggest that alpha-tocopherol enhances the alpha-tocotrienol metabolism but not the gamma-tocotrienol metabolism in rats.

Alpha-tocopherol protects against diet induced atherosclerosis in New Zealand white rabbits

In this study, we asked the question "does alpha-tocopherol supplementation prevent an increase in total plasma cholesterol (TPC) concentration and reduce the deposition of cholesterol in arterial plaques of rabbits fed atherogenic diets?" Isocaloric diets containing 0.1% cholesterol to induce atherosclerosis were enriched in one of three fats: saturated fats (SAT), monounsaturated fats (MONO), or n-6 polyunsaturated fats (POLY). Half of each of the three diets were supplemented with 2,500 IU alpha-tocopherol/kg-diet. Unsupplemented diets contained 25 IU alpha-tocopherol/kg-diet. Rabbits supplemented with alpha-tocopherol had plasma alpha-tocopherol concentrations 10-fold higher and an average TPC concentration 31% lower, P = 0.017, than rabbits fed unsupplemented diets. Among the three fat-fed groups, the difference was greatest for the POLY fat fed group (54%, P = 0.041). POLY fat-fed rabbits without alpha-tocopherol supplementation had plasma HDL cholesterol concentrations that were less than half that of rabbits fed other fats, P < or = 0.0001. In general, differences in mean esterified artery cholesterol concentrations among the three fat-fed groups, with and without alpha-tocopherol supplementation, paralleled differences in TPC concentration among the groups. This study suggests that for rabbits fed high pharmacological doses of alpha-tocopherol, atherosclerosis can be diminished in situations where the plasma cholesterol concentrations are also significantly lower.

Policosanol safely down-regulates HMG-CoA reductase - potential as a component of the Esselstyn regimen

Many of the wide-ranging health benefits conferred by statin therapy are mediated, not by reductions in LDL cholesterol, but rather by inhibition of isoprenylation reactions essential to the activation of Rho family GTPases; this may be the mechanism primarily responsible for the favorable impact of statins on risk for ischemic stroke, senile dementia, and fractures, as well as the anti-hypertensive and platelet-stabilizing actions of these drugs. Indeed, the extent of these benefits is such as to suggest that most adults would be wise to take statins; however, owing to the significant expense of statin therapy, as well as to the potential for dangerous side effects that mandates regular physician follow-up, this strategy appears impractical. However, policosanol, a mixture of long-chain aliphatic alcohols extractable from sugar cane wax, has shown cholesterol-lowering potency comparable to that of statins, and yet appears to be devoid of toxic risk. Recent evidence indicates that policosanol down-regulates cellular expression of HMG-CoA reductase, and thus has the potential to suppress isoprenylation reactions much like statins do. Consistent with this possibility, the results of certain clinical and animal studies demonstrate that policosanol has many effects analogous to those of statins that are not likely explained by reductions of LDL cholesterol. However, unlike statins, policosanol does not directly inhibit HMG-CoA reductase, and even in high concentrations it fails to down-regulate this enzyme by more than 50% - thus likely accounting for the safety of this nutraceutical. In light of the fact that policosanol is quite inexpensive and is becoming available as a non-prescription dietary supplement, it may represent a practical resource that could enable the general public to enjoy health benefits comparable to those conferred by statins. In a long-term clinical study enrolling patients with significant symptomatic coronary disease, Esselstyn has demonstrated that a low-fat, whole-food vegan diet, coupled with sufficient statin therapy to maintain serum cholesterol below 150 mg/dL, can stop the progression of coronary disease and virtually eliminate further risk for heart attack. A comparable regimen, in which policosanol is used in place of statins, may represent a practical strategy whereby nearly everyone willing to commit to health-protective eating can either prevent coronary disease, or prevent pre-existing coronary disease from progressing to a life-threatening event.

Identification of potential physiological activators of protein phosphatase 5

The protein serine/threonine phosphatase designated PP5 has little basal activity, and physiological activators of the enzyme have never been identified. Purified PP5 can, however, be activated by partial proteolysis or by the binding of supraphysiological concentrations of polyunsaturated long-chain fatty acids to its tetratricopeptide repeat (TPR) domain. To test whether activation of PP5 by polyunsaturated but not saturated fatty acids was an artifact of the lower solubility of saturated fatty acids, the effects of fatty acyl-CoA esters were examined. Saturated and unsaturated long-chain fatty acids are both freely water-soluble when esterified to CoA. Long-chain fatty acyl-CoA esters activated PP5 at physiological concentrations, with the saturated compounds being more effective. We investigated the effects of chain length and of the CoA moiety on PP5 activation. Chains of 16 carbons or more were required for optimal activation, with no activation observed below 10 carbons. On the basis of competition studies using acetyl-CoA, the function of the CoA moiety appeared to be to increase solubility of the fatty acyl moiety rather than to interact with a specific binding site. These data suggested that long-chain fatty acid-CoA esters might be physiological activators of PP5 and point to a potential link between fatty acid metabolism and signal transduction via this enzyme. Because heat shock protein 90 is also known to bind to the TPR domain of PP5 via its C-terminal domain (C90), we investigated its effect on PP5 activity. C90 activated the enzyme approximately 10-fold. Thus, we have identified two potential physiological activators of PP5.

Dietary gamma-linolenic acid suppresses aortic smooth muscle cell proliferation and modifies atherosclerotic lesions in apolipoprotein E knockout mice

The present study was conducted to evaluate the antiatherogenic effects of dietary gamma-linolenic acid (GLA) (primrose oil) in apolipoprotein E (apoE) genetic knockout mice. Five-wk-old male mice were fed cholesterol-free diets containing 10 g/100 g lipid as corn oil (CO) [control diet, 0 mol/100 mol GLA and (n-3) polyunsaturated fatty acids (PUFA)], primrose oil (PO, 10 mol/100 mol GLA), fish oil-CO mix [FC; 9:1 wt/wt, 0 mol/100 mol GLA and 17 mol/100 mol (n-3) PUFA] or fish oil-PO mix [FP, 1:3 wt/wt, 8 mol/100 mol GLA and 5 mol/100 mol (n-3) PUFA] for 15 wk. Subsequently, diets were supplemented with cholesterol (1.25 g/100 g) and sodium cholate (0.5 g/100 g) and fed for an additional 10 and 16 wk. Plasma cholesterol and triglyceride levels generally did not differ among groups at 20, 30 and 36 wk of age. Mice fed GLA-containing diets (PO and FP) had significantly (P < 0.05) higher liver phospholipid levels of dihomo-gamma-linolenic acid, the elongated product of GLA, relative to CO and FC groups. Consumption of GLA (PO and FP diets) significantly reduced (P < 0.05) aortic vessel wall medial layer thickness at 20 and 30 wk. A parallel GLA-dependent suppression in the number of proliferating (proliferating cell nuclear antigen positive) aortic smooth muscle cells was also observed. Diets containing either GLA or (n-3) PUFA reduced (P < 0.05) atherosclerotic lesion size in 30-wk-old mice. These results indicate that dietary GLA can suppress smooth muscle cell proliferation in vivo and retard the development of diet-induced atherosclerosis in apoE knockout mice.