Short term vitamin E supplementation has no effect on platelet function, plasma phospholipase A2 and lyso-PAF in male volunteers

Protective Effect of Olive Oil Microconstituents in Atherosclerosis: Emphasis on PAF Implicated Atherosclerosis Theory

Atherosclerosis is a progressive vascular multifactorial process. The mechanisms underlining the initiating event of atheromatous plaque formation are inflammation and oxidation. Among the modifiable risk factors for cardiovascular diseases, diet and especially the Mediterranean diet (MedDiet), has been widely recognized as one of the healthiest dietary patterns. Olive oil (OO), the main source of the fatty components of the MedDiet is superior to the other "Mono-unsaturated fatty acids containing oils" due to the existence of specific microconstituents. In this review, the effects of OO microconstituents in atherosclerosis, based on data from in vitro and in vivo studies with special attention on their inhibitory activity against PAF (Platelet-Activating Factor) actions, are presented and critically discussed. In conclusion, we propose that the anti-atherogenic effect of OO is attributed to the synergistic action of its microconstituents, mainly polar lipids that act as PAF inhibitors, specific polyphenols and α-tocopherol that also exert anti-PAF activity. This beneficial effect, also mediated through anti-PAF action, can occur from microconstituents extracted from olive pomace, a toxic by-product of the OO production process that constitutes a significant ecological problem. Daily intake of moderate amounts of OO consumed in the context of a balanced diet is significant for healthy adults.

Micronutrients, Phytochemicals and Mediterranean Diet: A Potential Protective Role against COVID-19 through Modulation of PAF Actions and Metabolism

The new coronavirus disease 2019 (COVID-19) pandemic is an emerging situation with high rates of morbidity and mortality, in the pathophysiology of which inflammation and thrombosis are implicated. The disease is directly connected to the nutritional status of patients and a well-balanced diet is recommended by official sources. Recently, the role of platelet activating factor (PAF) was suggested in the pathogenesis of COVID-19. In the present review several micronutrients (vitamin A, vitamin C, vitamin E, vitamin D, selenium, omega-3 fatty acids, and minerals), phytochemicals and Mediterranean diet compounds with potential anti-COVID activity are presented. We further underline that the well-known anti-inflammatory and anti-thrombotic actions of the investigated nutrients and/or holistic dietary schemes, such as the Mediterranean diet, are also mediated through PAF. In conclusion, there is no single food to prevent coronavirus Although the relationship between PAF and COVID-19 is not robust, a healthy diet containing PAF inhibitors may target both inflammation and thrombosis and prevent the deleterious effects of COVID-19. The next step is the experimental confirmation or not of the PAF-COVID-19 hypothesis.

Platelet Oxidative Stress and its Relationship with Cardiovascular Diseases in Type 2 Diabetes Mellitus Patients

Enhanced platelet activation and thrombosis are linked to various cardiovascular diseases (CVD). Among other mechanisms, oxidative stress seems to play a pivotal role in platelet hyperactivity. Indeed, upon stimulation by physiological agonists, human platelets generate and release several types of reactive oxygen species (ROS) such as O2 -, H2O2 or OH-, further amplifying the platelet activation response via various signalling pathways, including, formation of isoprostanes, Ca2+ mobilization and NO inactivation. Furthermore, excessive platelet ROS generation, incorporation of free radicals from environment and/or depletion of antioxidants induce pro-oxidant, pro-inflammatory and platelet hyperaggregability effects, leading to the incidence of cardiovascular events. Here, we review the current knowledge regarding the effect of oxidative stress on platelet signaling pathways and its implication in CVD such as type 2 diabetes mellitus. We also summarize the role of natural antioxidants included in vegetables, fruits and medicinal herbs in reducing platelet function via an oxidative stress-mediated mechanism.

A metabolomic investigation of the effects of vitamin E supplementation in humans

Background

Vitamin E is a nutrient with both antioxidant and non-antioxidant activities and has been shown to modulate the function of a number of cell types in vitro and in human studies. However studies have also shown vitamin E to have detrimental interactions and therefore it is important to establish the extent to which this nutrient influences metabolism. Metabolomics can potentially identify nutrient-metabolism interactions and therefore the aim of this study was to use a non-targeted metabolomic approach to identify changes to the plasma metabolome following vitamin E supplementation in humans.

Methods

A relatively homogenous healthy adult male population (n = 10) provided a fasting blood sample immediately before and after a 4-week vitamin E supplementation regime (400 mg/d of RRR-α-tocopheryl acetate)) on top of their habitual diet. Plasma samples were analysed for vitamin E and clinical markers. Plasma underwent non-targeted metabolite profiling using liquid chromatography/mass spectroscopy and data was processed using multivariate statistical analysis.

Results

Plasma vitamin E concentrations were significantly increased following supplementation (p < 0.001). A partial least squares-discriminant analysis (PLS-DA) model was able to discriminate between samples taken pre and post vitamin E supplementation (goodness of fit R²Y = 0.82, predictive ability Q² = 0.50). Variable influence on projection and PLS-DA loadings highlighted a number of discriminating ions that were confirmed as discriminatory through pairwise analysis. From database searches and comparison with standards these metabolites included a number of lysophosphatidylcholine species (16:0, 18:0, 18:1, 18:2, 20:3 and 22:6) that were increased in intensity post supplementation by varying degrees from 4% to 29% with the greatest changes found for lysoPC 22:6 and 20:3.

Conclusions

Although a small scale study, these results potentially indicate that vitamin E supplementation influences phospholipid metabolism and induces lysoPC generation; a general pro-inflammatory response. Moreover the study identifies novel areas of vitamin E interactions and highlights the potential of metabolomics for elucidating interactions between nutrients and metabolic pathways in nutritional research.

Short-term, moderate dosage Vitamin E supplementation may have no effect on platelet aggregation, coagulation profile, and bleeding time in healthy individuals

OBJECTIVE

To investigate the in vivo effect of short-term, moderate dosage synthetic dl-alpha-tocopherol acetate supplementation on platelet aggregation, coagulation profile, and simulated bleeding time in healthy individuals. alpha-tocopherol is the most biologically active isomer of Vitamin E, traditionally promoted as an antioxidant and therapeutic agent in cardiovascular disease. In vitro studies have suggested that alpha-tocopherol plays a role in the inhibition of platelet aggregation. However, further investigations into the effect of alpha-tocopherol on bleeding in vivo have not duplicated these findings.

MATERIALS AND METHODS

A total of 42 healthy volunteers complied with a 2-week abstinence period from the use of anti-platelet agents followed by determination of baseline platelet aggregation properties and coagulation studies using citrated whole blood. Moderate dosage Vitamin E (800 IU of dl-alpha-tocopherol acetate) was then self-administered for 14 days with reevaluation of platelet aggregation and coagulation profile, and simulated bleeding time after 14 days of Vitamin E supplementation.

RESULTS

Forty subjects completed the 4-week study period. All 40 subjects demonstrated normal baseline coagulation studies and all had collagen-stimulated platelet aggregation assessment performed in triplicate. After Vitamin E supplementation, no significant difference was demonstrated in any study parameter.

CONCLUSIONS

Dietary supplementation with moderate dosage synthetic dl-alpha-tocopherol acetate did not significantly prolong bleeding or platelet aggregation in vivo. The affect of Vitamin E on platelet aggregation in vitro does not appear to be reproducible in vivo. Therefore, peri-operative discontinuation of Vitamin E may not be necessary.

Moderate supplementation with natural alpha-tocopherol decreases platelet aggregation and low-density lipoprotein oxidation

Previous studies have shown that oral administration of 300 mg alpha-tocopherol/day to healthy volunteers decreases platelet function and enhances their sensitivity to the platelet inhibitor, prostaglandin E(1), when full dose-response curves to a range of agonist concentrations are made. In this study, the effects of oral doses of natural alpha-tocopherol (75, 200 and 400 IU/day) were studied in order to determine whether the same effects might be achieved with lower intakes of vitamin E and whether inhibition is related to the platelet levels of the antioxidant in platelet membranes. Twenty two subjects undertook the supplementation regime, divided into three units of 2 weeks, each cycling through each of the dosages. The results show that uptake of vitamin E by the platelets was optimal at 75 IU/day, correlating with the maximal influence on platelet aggregation and platelet responsiveness to inhibition by PGE1, increased supplemental levels exerting no greater effects.

Uses of vitamins A, C, and E and related compounds in dermatology: a review

Vitamins have been increasingly used as prophylactic and therapeutic agents in the management of skin disorders. The current literature is replete with studies that promote the potential benefits of these compounds and attempt to elucidate their mechanisms of action. We review the literature and discuss the roles, safety, and efficacy of vitamins A, C, and E and related compounds in cutaneous health and disease.

Gemfibrozil-induced decrease in serum ubiquinone and alpha- and gamma-tocopherol levels in men with combined hyperlipidaemia

BACKGROUND

Low blood levels of antioxidants are associated with an increased risk of developing coronary artery disease. Lipophilic antioxidants are transported in lipoproteins, and hypolipidaemic therapy may therefore alter their blood concentrations.

METHODS

The present randomized, placebo-controlled cross-over study of 21 men with combined hyperlipidaemia examines whether 10-12 weeks of gemfibrozil treatment affects the serum concentrations of the antioxidants ubiquinone-10 or alpha- or gamma-tocopherol.

RESULTS

Gemfibrozil treatment lowered plasma triglycerides and both total and very low-density lipoprotein (VLDL)-cholesterol (P < 0.001 for all by ANOVA), whereas high-density lipoprotein (HDL)-cholesterol increased (P < 0.001). The median serum levels of ubiquinone-10 decreased from 1.30 mumol L-1 (interquartile range 0.87-1.71 mumol L-1) with placebo to 0.76 mumol L-1 (0.66-0.95) with gemfibrozil treatment (P < 0.001). Corresponding levels for alpha- and gamma-tocopherol were: 68.5 mumol L-1 (51.1-84.7) vs. 40.8 mumol L-1 (30.3-55.0) and 8.6 mumol L-1 (5.2-16.7) vs. 4.3 mumol L-1 (3.5-7.0) respectively (P < 0.001 for both). The decrease in serum antioxidants was also evident when standardized for total cholesterol (P < 0.05) or LDL-cholesterol (P < 0.001). Normolipaemic control subjects had significantly lower antioxidant levels than placebo-treated patients: ubiquinone 0.63 mumol L-1 (0.41-1.05), alpha-tocopherol 34.3 mumol L-1 (27.3-45.6) and gamma-tocopherol 3.2 mumol L-1 (2.5-4.2) (P < 0.001 for all). The association of antioxidants with lipoprotein lipids was further established by positive correlations between the levels of antioxidants and those of total cholesterol (r = 0.64, P < 0.001) or total triglycerides (r = 0.71, P < 0.001).

CONCLUSION

Gemfibrozil treatment of men with combined hyperlipidaemia reduces serum antioxidant levels to the levels seen in healthy normolipidaemic men. The mechanisms and the relevance of this finding remain unclear and need to be addressed in further studies.

Nutritional supplements and surgical patients

Surgical team members should be aware of which nutritional supplements may be harmful or helpful to surgical patients. Informed education of patients may prevent bleeding problems, wound-healing problems, prolonged hematomas, and dangerous immune system depletion.

Oxygen free radicals and platelet activation

This article reviews our current understanding of the role of oxygen free radicals in platelet activation. Several studies have indicated that platelets, in analogy to other circulating blood cells, are able to produce oxygen free radicals, which are likely to play an important role in the mechanism of platelet activation and aggregation. Platelet activation has been obtained with very low, physiologically relevant concentrations of radicals generated chemically, by leukocytes, and by hemoglobin derived from membrane leakage of erythrocytes. Knowledge of the role of reactive species in platelet physiology is relevant because platelets are brought into close contact with other cells capable of producing free radicals, such as neutrophils, macrophages, and endothelial cells, during the formation of thrombus. The physiopatological importance of these findings is high because it is now emerging that free radicals may have a role in the mechanism of atherosclerosis and its thrombotic complications, where the causative role of platelets is well documented. This background suggests therapeutic interventions with antioxidants as antiplatelet agents to improve the pharmacological effect of classical antiplatelet drug such as aspirin.

Surgically significant nutritional supplements

This is not an exhaustive study of all nutritional supplements that patients may be taking. The most frequently used and those potentially most detrimental or most beneficial for surgical patients have been chosen for review of pertinent effects. It is essential to ask patients specifically about supplements or unusual dietary habits that may affect their surgical outcome prior to their invasive procedure and to keep in mind the supplements that may improve their outcome.

Oxidized lipoproteins

The understanding of the role of lipoprotein oxidation is still incomplete. Much is still to be learned about the mechanism of action of oxidized lipoproteins on different types of cell, as well as the origin of the oxidation process, and how it links to the situation in vivo. The benefits or otherwise of anti-oxidant therapy or dietary advice will be solved only by long-term studies, some of which have been begun or are planned. It is useful to recall that information about the effects of cholesterol-lowering therapy with statins are only now becoming available after several years of use. Convincing data about the efficacy of anti-oxidants are some way off, even though, on balance, the results so far appear encouraging.

Vitamin E deficiency increases serum thromboxane A2, platelet arachidonate and lipid peroxidation in male Sprague-Dawley rats

This study was designed to determine whether dietary linoleate and all-rac-alpha-tocopheryl acetate (vitamin E) interact to affect serum thromboxane A2 (TXA2) and prostacyclin (PGI2) status and therefore, thrombogenic potential. 6 groups of 12 weanling male Sprague-Dawley rats were fed semipurified diets containing 11 or 18% of energy from linoleate and 0, 100 or 5000 mg vitamin E/kg diet for 10 weeks. Platelet and serum alpha-tocopherol concentrations increased logarithmically with increasing dietary vitamin E. Serum TXA2, measured as TXB2, platelet arachidonate and thiobarbituric acid reactive substances were significantly greater in the vitamin E deficient groups than in groups receiving vitamin E (p < 0.05). Serum PGI2 levels, determined as 6-keto-PGF1 alpha, were not affected by diets. No interaction was found between dietary linoleate and vitamin E. However, vitamin E supplementation produced significantly less serum TXB2 than did vitamin E deficient diets (p < 0.05). Vitamin E deficiency may be prothrombogenic by increasing platelet arachidonate, lipid peroxidation and serum TXA2 levels while vitamin E supplementation at levels used in this study may decrease such effects.

Prevention of platelet dysfunction by vitamin E in diabetic atherosclerosis

Premature atherosclerosis and other vascular disorders are serious complications of diabetes mellitus. Contributing factors include (i) increased peroxidation of LDL leading to foam cell formation, fatty streaks and plaque formation in the arterial wall, and (ii) hyperreactivity of blood platelets leading to increased platelet adhesion and aggregation. Vitamin E may play a protective role as an antioxidant and/or membrane stabilizing agent in either mechanism. In platelets it appears to regulate arachidonic acid metabolism. Decreased vitamin E levels in platelets are associated with increased aggregation. This is reversible by correction of the vitamin E status. In diabetics, platelet vitamin E levels tend to be reduced with concomitant increase in platelet aggregation. Several studies in patients with insulin-dependent diabetes mellitus and, to some extent, in those with non-insulin-dependent diabetes mellitus have shown that supplementation with several hundred IU vitamin E significantly reduced platelet aggregation and lipid peroxidation. In healthy volunteers high-dose supplementation had no notable effect on platelet aggregation. However, doses as low as 200 IU vitamin E significantly reduced platelet adhesion and inhibited the formation of protruding pseudopods typically occurring in activated platelets. In diabetic patients a decrease in the nonenzymatic glycation of proteins by vitamin E supplementation has been observed. Controlled studies are needed to confirm the effect of vitamin E on platelet function in well-defined groups of diabetics, followed by large-scale trials investigating the prevention of diabetic vascular complications as clinical end point.