Statin treatment as a confounding factor in human trials with vitamin E

Cardiovascular and Metabolic Protection by Vitamin E: A Matter of Treatment Strategy?

Cardiovascular diseases (CVD) cause about 1/3 of global deaths. Therefore, new strategies for the prevention and treatment of cardiovascular events are highly sought-after. Vitamin E is known for significant antioxidative and anti-inflammatory properties, and has been studied in the prevention of CVD, supported by findings that vitamin E deficiency is associated with increased risk of cardiovascular events. However, randomized controlled trials in humans reveal conflicting and ultimately disappointing results regarding the reduction of cardiovascular events with vitamin E supplementation. As we discuss in detail, this outcome is strongly affected by study design, cohort selection, co-morbidities, genetic variations, age, and gender. For effective chronic primary and secondary prevention by vitamin E, oxidative and inflammatory status might not have been sufficiently antagonized. In contrast, acute administration of vitamin E may be more translatable into positive clinical outcomes. In patients with myocardial infarction (MI), which is associated with severe oxidative and inflammatory reactions, decreased plasma levels of vitamin E have been found. The offsetting of this acute vitamin E deficiency via short-term treatment in MI has shown promising results, and, thus, acute medication, rather than chronic supplementation, with vitamin E might revitalize vitamin E therapy and even provide positive clinical outcomes.

Changes in serum afamin and vitamin E levels after selective LDL apheresis

BACKGROUND

Afamin is a plasma vitamin E-binding glycoprotein partially associated with ApoA1-containing high-density lipoprotein (HDL) subfractions. In a previous study, the serum vitamin E decreased after low-density lipoprotein (LDL) apheresis, while vitamin E/cholesterol ratio increased. We aimed to study the effect of LDL apheresis on serum afamin level.

METHODS

The serum level of afamin and oxidized LDL were measured by enzyme-linked immunosorbent assay in six severe heterozygous FH patients before and after their first LDL apheresis treatments and in seven healthy controls. We also investigated the changes in total cholesterol, LDL-C, HDL-C, ApoB, ApoA1, HDL subfractions, and α- and γ-tocopherol levels during the treatment. HDL subfractions were detected by an electrophoretic method on polyacrylamide gel (Lipoprint). Serum α- and γ-tocopherol levels were detected by gas chromatography-mass spectrometry.

RESULTS

The first treatment sessions decreased serum afamin levels by an average of 9.4%. Total cholesterol, LDL-C, HDL-C and ApoA1 levels decreased by 52.6; 61.8; 10.5; and 14.1%, respectively. We found that α- and γ-tocopherol levels markedly decreased (by 34.1 and 32.9%, respectively), while α- tocopherol/cholesterol and γ-tocopherol/cholesterol ratios significantly increased (by 41.4 and 40.3%, respectively). Oxidized LDL levels significantly decreased. There was a shift toward the larger HDL subfractions.

CONCLUSION

LDL apheresis moderately decreases the circulating levels of afamin parallel to lowering HDL-C and ApoA1 levels. Tocopherol levels decreases markedly compared to afamin levels, however, beneficial changes in vitamin E/cholesterol ratios, oxidized LDL levels and HDL subfraction distribution were detected. These additional effects of LDL apheresis may result in further cardiovascular risk reduction in FH patients.

Similar Reduction of Cholesterol-Adjusted Vitamin E Serum Levels in Simple Steatosis and Non-Alcoholic Steatohepatitis

Objectives:

Reduced vitamin E levels have been reported in patients with non-alcoholic steatohepatitis (NASH), but no conclusive data on patients with simple steatosis (SS) are available. Aim of this study was to investigate the association between serum vitamin E levels and SS.

Methods:

A cohort of 312 patients with cardio-metabolic risk factors was screened for liver steatosis by ultrasonography (US). We reasonably classified as SS patients with US-fatty liver, normal liver function tests (LFTs) and with Cytokeratin 18 <246 mIU/ml. Liver biopsy was performed in 41 patients with US-fatty liver and persistent elevation of LFTs (>6 months). Serum cholesterol-adjusted vitamin E (Vit E/chol) levels were measured.

Results:

Mean age was 53.9±12.5 years and 38.4% were women. Non-alcoholic fatty liver disease (NAFLD) was detected at US in 244 patients; of those 39 had biopsy-proven NASH and 2 borderline NASH. Vit E/chol was reduced in both SS (3.4±2.0, P<0.001), and NASH (3.5±2.1, P=0.006) compared with non-NAFLD patients (4.8±2.0 μmol/mmol chol). No difference was found between SS and NASH (P=0.785). After excluding patients with NASH, a multivariable logistic regression analysis found that Vit E/chol (odds ratio (OR): 0.716, 95% confidence interval (CI) 0.602–0.851, P<0.001), alanine aminotransferase (ALT, OR: 1.093, 95% CI 1.029–1.161, P=0.004), body mass index (OR: 1.162, 95% CI 1.055–1.279, P=0.002) and metabolic syndrome (OR: 5.725, 95% CI 2.247–14.591, P<0.001) were factors independently associated with the presence of SS.

Conclusions:

Reduced vitamin E serum levels are associated with SS, with a similar reduction between patients with SS and NASH, compared with non-NAFLD patients. Our findings suggest that the potential benefit of vitamin E supplementation should be investigated also in patients with SS.

Cholesterol-adjusted vitamin E serum levels are associated with cardiovascular events in patients with non-valvular atrial fibrillation

BACKGROUND

Non-valvular atrial fibrillation is associated with an increase in thromboembolism, i.e. stroke, and atherosclerotic events, i.e. myocardial infarction. Vitamin E possesses anti-coagulant as well as anti-atherosclerotic properties. Our aim was to assess whether vitamin E is associated with cardiovascular events in patients with non-valvular atrial fibrillation.

METHODS

Serum levels of cholesterol-adjusted vitamin E were measured in 1012 patients with non-valvular atrial fibrillation. Patients were followed for a mean time of 27.0 months, and cardiovascular events, such as cardiovascular death and fatal and nonfatal stroke or myocardial infarction, were recorded.

RESULTS

During the follow-up period, cardiovascular events occurred in 109 (11%) patients (18 fatal and 14 nonfatal myocardial infarction; 13 fatal and 19 nonfatal ischemic strokes; 45 cardiovascular deaths). Lower vitamin E serum levels were found in patients who experienced cardiovascular events compared to those who did not (3.8±1.2 vs. 4.4±1.8 μmol/mmol cholesterol; p<0.001). Using a Cox proportional hazard model, age, diabetes, history of stroke and myocardial infarction and vitamin E serum levels (HR 0.77; 95% CI: 0.67-0.89; p=0.001) independently predicted cardiovascular events. Patients with vitamin E<4.2 μmol/mmol cholesterol (median values) had an increased risk of cardiovascular events (HR 1.87; 95% CI: 1.25-2.80: p=0.002).

CONCLUSIONS

Low vitamin E serum levels are associated with an increased risk of cardiovascular events in patients with non-valvular atrial fibrillation.

Why do homocysteine-lowering B vitamin and antioxidant E vitamin supplementations appear to be ineffective in the prevention of cardiovascular diseases?

Homocysteine has been established as a serious, independent risk factor for atherosclerosis. An elevated plasma homocysteine concentration is accompanied by increased cardiovascular risk; therefore, it can be assumed that lowering the plasma homocysteine level results in a decreased risk. Vitamin B complex (folic acid, and vitamins B6 and B12) substitution therapy decreases the plasma homocysteine level, inhibits oxidative stress, and ameliorates some biochemical and clinical parameters that indicate the progression of atherosclerosis. Vitamin E administration may also reduce atherogenesis through its antioxidant effect. The effectiveness of B and E vitamin substitution in decreasing cardiovascular risk has been suggested by cohort as well as prospective and retrospective studies undertaken during the last two decades. On the other hand, recent large, randomized clinical trials did not substantiate a beneficial effect of homocysteine-lowering B vitamin supplementation or vitamin E antioxidant therapies in reducing cardiovascular risk in humans. We analyzed eight B vitamin and four E vitamin trials from a critical point of view, and in this article we reviewed and commented on their results and focused on the contradictions found in them. We showed that the possible factors implicated in the failure of vitamin therapies included inappropriate designs. The protocols neglected an essential fact: that the impact of some confounding factors, such as concomitant use of statins, acetylsalicylic acid, folic acid, and other drugs, might have led to bias and an inappropriate interpretation of the data. The cardiovascular protective and preventive effects of statins and aspirin might have reduced or abolished the possibility of observing a difference in the number of events between the vitamin and placebo groups for the clinical endpoints. We concluded that the vitamin preventive effect on cardiovascular disease may not be rejected in reference to the negative trial evidence.

Antioxidant Supplements Improve Profiles of Hepatic Oxysterols and Plasma Lipids in Butter-fed Hamsters

Hypercholesterolemic diets are associated with oxidative stress that may contribute to hypercholesterolemia by adversely affecting enzymatically-generated oxysterols involved in cholesterol homeostasis. An experiment was conducted to examine whether the cholesterol-lowering effects of the antioxidants selenium and α-tocopherol were related to hepatic oxysterol concentrations. Four groups of male Syrian hamsters (n = 7-8) were fed high cholesterol and saturated fat (0.46% cholesterol, 14.3% fat) hypercholesterolemic semi-purified diets: 1) Control; 2) Control + α-tocopherol (67 IU all-racemic-α-tocopheryl-acetate/kg diet); 3) Control + selenium (3.4 mg selenate/kg diet); and 4) Control + α-tocopherol + selenium. Antioxidant supplementation was associated with lowered plasma cholesterol concentrations, decreased tissue lipid peroxidation and higher hepatic oxysterol concentrations. A second experiment examined the effect of graded selenium doses (0.15, 0.85, 1.7 and 3.4 mg selenate/kg diet) on mRNA expression of the oxysterol-generating enzyme, hepatic 27-hydroxylase (CYP27A1, EC 1.14.13.15), in hamsters (n = 8-9) fed the hypercholesterolemic diets. Supplementation of selenium at 3.4 mg selenate/kg diet was not associated with increased hepatic 27-hydroxylase mRNA. In conclusion, the cholesterol lowering effects of selenium and α-tocopherol were associated with increased hepatic enzymatically generated oxysterol concentrations, which appears to be mediated via improved antioxidant status rather than increased enzymatic production.