α-Tocopherol supplementation does not affect monocyte endothelial adhesion or C-reactive protein levels but reduces soluble vascular adhesion molecule-1 in the plasma of healthy subjects

Consumption of plant extract supplement reduces platelet activating factor-induced platelet aggregation and increases platelet activating factor catabolism: a randomised, double-blind and placebo-controlled trial

Platelet-activating factor (PAF) is a potent mediator of inflammation that plays a crucial role in atherosclerosis. The purpose of this study was to evaluate the effect of a dietary supplement containing mainly plant extracts on PAF actions and metabolism in healthy volunteers. A double-blind, placebo-controlled, 8 weeks' duration study was performed. Healthy volunteers were randomly allocated into the supplement or the placebo group and fifty-eight of them completed the study. The supplement contained plant extracts (Aloe gel, grape juice, Polygonum cuspidatum) and vitamins. The activities of PAF metabolic enzymes: the two isoforms of acetyl-CoA:lyso-PAF acetyltransferase, cytidine 5'-diphospho-choline:1-alkyl-2-acetyl-sn-glycerol cholinephosphotransferase (PAF-cholinephosphotransferase) and platelet-activating factor-acetylhydrolase (PAF-AH) in leucocytes and lipoprotein associated phospholipase-A2 in plasma were measured along with several markers of endothelial function. Platelet aggregation against PAF, ADP and thrombin receptor activating peptide was measured in human platelet-rich plasma by light transmission aggregometry. No difference was observed on soluble vascular cell adhesion molecule-1, sP-selectin and IL-6 levels at the beginning or during the study period between the two groups. Concerning PAF metabolism enzymes' activity, no difference was observed at baseline between the groups. PAF-AH activity was only increased in the supplement group at 4 and 8 weeks compared with baseline levels. In addition, supplement consumption led to lower platelet sensitivity against PAF and ADP compared with baseline levels. However, a trial effect was only observed when platelets were stimulated by PAF. In conclusion, supplementation with plant extracts and vitamins ameliorates platelet aggregation primarily against PAF and secondarily against ADP and affects PAF catabolism by enhancing PAF-acetylhydrolase activity in healthy subjects.

MicroRNA-492 reverses high glucose-induced insulin resistance in HUVEC cells through targeting resistin

The development of atherosclerosis (AS) is a multifactorial process, in which elevated plasma resistin (a key factor leading to insulin resistance) levels play an important role. Emerging evidence indicate that microRNAs (miRNAs) are involved in AS; However, the regulation and function of miRNAs in response to AS remain poorly understood. Our study analyzed the effects of miR-492 on insulin resistance, endothelial activation, and resistin expression in apoE knock-out mice and human umbilical vein endothelial cells after high-glucose treatment and miR-492 mimics transfection. We also investigated the underlying molecular mechanisms. Our results showed that high glucose stress induced a significant decrease in miR-492 expression, with a remarkable upregulation of resistin expression. We then identified resistin as a novel direct target of miR-492 using 3′-UTR luciferase reporter assay. Histopathologic examination demonstrated that upregulation of miR-492 attenuated endothelial cells migration and lipid accumulation induced by high glucose stress. Further investigation demonstrated that the upregulation of p-STAT3, SOCS, and P-selectin activation induced by high glucose stress was attenuated by upregulation of miR-492. Together, our findings indicate that miR-492 contributes to insulin resistance and endothelial dysfunction induced by high glucose, via directly downregulating resistin expression, and involving STAT3 phosphorylation, SOCS, and P-selectin activation.

Effect of supplementation with B vitamins and antioxidants on levels of asymmetric dimethylarginine (ADMA) and C-reactive protein (CRP): a double-blind, randomised, factorial design, placebo-controlled trial

PURPOSE

Cardiovascular risk factors such as elevated levels of asymmetric dimethylarginine (ADMA)/C-reactive protein (CRP) and homocysteine are potentially related to essential micronutrients such as certain B vitamins and antioxidant vitamins. The aim of the present study was to investigate whether supplementation with moderate doses of B vitamins and/or antioxidants could alter either ADMA and/or CRP concentrations in middle-aged, apparently healthy men with mildly elevated homocysteine levels.

METHODS

A randomised, double-blind, factorial design, intervention study was carried out on 132 men with mildly elevated homocysteine levels, allocated to four groups (a) B vitamins alone--1 mg folic acid, 7.2 mg pyridoxine, 0.02 mg cyanocobalamin daily, (b) antioxidants alone--150 mg ascorbic acid, 67 mg vitamin E, 9 mg β-carotene daily, (c) B vitamins with antioxidant vitamins, or (d) placebo. A total of 101 men completed the study to 8 weeks.

RESULTS

When the percentage of baseline ADMA and CRP was examined at 8 weeks, no statistically significant differences were observed between the four groups (p = 0.21 and p = 0.90, respectively). Similar non-significant results were observed when analysis was stratified based on baseline CRP levels (<1.0 mg/L, p = 0.10; ≥1.0 mg/L, p = 0.64) and smoking status (all p ≥ 0.05).

CONCLUSIONS

Supplementation with moderate doses of B vitamins and/or antioxidants did not alter either ADMA or CRP concentrations in these middle-aged, apparently healthy men with mildly elevated homocysteine levels.

Alpha-tocopherol modulates human umbilical vein endothelial cell expression of Cu/Zn superoxide dismutase and catalase and lipid peroxidation

Recent studies suggest the potential of alpha-tocopherol as a gene regulator, possibly through peroxisome proliferator-activated receptor gamma (PPARgamma) activation due to the structural similarity of alpha-tocopherol to a PPARgamma ligand, troglitazone. Other investigators have suggested that a link exists between induction of the antioxidant enzymes Cu/Zn superoxide dismutase (SOD) and catalase and PPARgamma activation. This study was designed to examine whether alpha-tocopherol modulates expression of Cu/Zn SOD and catalase in human umbilical vein endothelial cells through redox-sensitive transcription factors, PPARgamma, and nuclear factor-kappaB (NF-kappaB). Alpha-tocopherol treatments showed significant increases in both PPARgamma (1.4- to 2.2-fold, P < .01) and NF-kappaB p50 (1.3- to 1.5-fold, P < .005) DNA binding activities compared with vehicle control. Significant increases in Cu/Zn SOD mRNA levels (6.0-fold, P < .005) and catalase mRNA (8.0-fold, P < .005) and its protein levels (2.3-fold, P < .005) and lipid peroxidation levels (5.3-fold, P < .005) were observed at the lowest concentration (10 mumol/L) of alpha-tocopherol treatments. Both mRNA and protein levels of these 2 antioxidant enzymes were positively associated with lipid peroxidation (P < .05). Alpha-tocopherol may play a role not only in preventing against oxidative damage as an exogenous antioxidant by scavenging free radicals and superoxide but also in modulating the expression of the endogenous antioxidant enzymes as a gene regulator through PPARgamma and NF-kappaB in the vascular cells. The alpha-tocopherol-mediated gene expression is either stimulatory or inhibitory, depending on its oxidative status or its concentrations.

Vitamin E does not modulate plasma lipid profile or C-reactive protein despite suppressing oxidative stress in orchiectomized rats

Vitamin E is known to improve antioxidant status and to prevent lipoprotein oxidation. However, the effect of vitamin E on other cardiovascular risk factors, including C-reactive protein (CRP) and lipid profile status, in orchiectomized rats is unknown. In the present study, 32 1-year-old male rats were randomized into two groups: a sham-control group (n = 8) and an orchiectomized group (n = 24). The orchiectomized group was divided into three groups of eight and assigned to one of the following treatments: orchiectomy (ORX), ORX + vitamin E mixture (65.6 mg/kg) diet, or ORX + vitamin E mixture (656 mg/kg) diet. For 120 days all four groups consumed a basal AIN-93M diet, while the vitamin E groups ate diets containing an additional vitamin E mixture. Four months after the study began, all the rats were killed, the blood was collected, and the plasma was assayed for antioxidant status, CRP, lipid profile, and indices of peroxidation. ORX decreased (P < .05) the plasma antioxidant status, superoxide dismutase (SOD) activity, and CRP level and increased (P < .05) the plasma malondialdeyde, nitrite, and lipid profile compared with that of the sham-control group. In contrast to the ORX group, supplementation with vitamin E mixture increased (P < .05) plasma antioxidant status and dose-dependently increased (P < .05) SOD activity, while the vitamin E decreased (P < .05) plasma malondialdeyde and nitrite. The vitamin E mixture had no effect on CRP or on lipid profiles when compared to the orchiectomized rats. In conclusion, vitamin E appears to reduce oxidative stress without modulating lipid profile or inflammatory response.

Cellular, molecular and clinical aspects of vitamin E on atherosclerosis prevention

Randomised clinical trials and epidemiologic studies addressing the preventive effects of vitamin E supplementation against cardiovascular disease reported both positive and negative effects, and recent meta-analyses of the clinical studies were rather disappointing. In contrast to that, many animal studies clearly show a preventive action of vitamin E in several experimental settings, which can be explained by the molecular and cellular effects of vitamin E observed in cell cultures. This review is focusing on the molecular effects of vitamin E on the cells playing a role during atherosclerosis, in particular on the endothelial cells, vascular smooth muscle cells, monocytes/macrophages, T cells, and mast cells. Vitamin E may act by normalizing aberrant signal transduction and gene expression in antioxidant and non-antioxidant manners; in particular, over-expression of scavenger receptors and consequent foam cell formation can be prevented by vitamin E. In addition to that, the cellular effects of alpha-tocopheryl phosphate and of EPC-K1, a composite molecule between alpha-tocopheryl phosphate and l-ascorbic acid, are summarized.