Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto miocardico

Omega-3 fatty acids alter soluble markers of endothelial function in coronary heart disease patients

Several studies have indicated that omega-3 poly-unsaturated fatty acids in fish oil have protective effects on cardiovascular disease by reducing vascular endothelial inflammation in atherosclerosis. In a recent study, supplementation of patients with fish oil following coronary angioplasty elevated levels of lipid peroxides and two adhesion molecules in plasma suggesting a proinflammatory action of fish oil. However, decreases in several plasma markers of endothelial hemostatic activity indicated a healthier and better vasculature associated with fish oil supplementation.

Dietary supplementation with marine omega-3 fatty acids improve systemic large artery endothelial function in subjects with hypercholesterolemia

OBJECTIVE

This work was undertaken to determine whether dietary supplementation with marine omega-3 fatty acids improve systemic large artery endothelial function in subjects with hypercholesterolemia.

BACKGROUND

Marine omega-3 fatty acids improve vascular function, but the underlying mechanism(s) are unclear. We studied the effects of marine omega-3 fatty acids on large artery endothelial function in subjects with hypercholesterolemia.

METHODS

Hypercholesterolemic subjects with no other known cause for endothelial dysfunction were recruited to a prospective, placebo-controlled, randomized, double-blind, parallel-group study. Treatment with omega-3 fatty acids at a dose of 4 g/day (n = 15/group) was compared with placebo, at the beginning (day 0) and end (day 120) of a four-month treatment period. Endothelial function was assessed pre- and posttreatment by noninvasive ultrasonic vessel wall tracking of brachial artery flow-mediated dilation (FMD).

RESULTS

Treatment with marine omega-3 fatty acids resulted in a significant improvement in FMD (0.05 +/- 0.12 to 0.12 +/- 0.07 mm, p < 0.05) and a significant reduction in triglycerides (2.07 +/- 1.13 to 1.73 +/- 0.95 mmol/liter, p < 0.05), whereas treatment with placebo resulted in no change in FMD (0.03 +/- 0.10 to 0.04 +/- 0.10 mm) or triglycerides (2.29 +/- 2.09 to 2.05 +/- 1.36 mmol/liter) (both p < 0.05 treated compared with control). Responses to sublingual glyceryl trinitrate were unchanged.

CONCLUSIONS

Marine omega-3 fatty acids improve large artery endothelium-dependent dilation in subjects with hypercholesterolemia without affecting endothelium-independent dilation.

n-3 polyunsaturated fatty acids and the cardiovascular system

n-3 Polyunsaturated fatty acids, mainly those contained in fish oils, are candidates for inclusion in secondary prevention programmes for coronary heart disease, based on the results of recent randomized trials in humans. Marine n-3 polyunsaturated fatty acids retard coronary atherosclerosis and appear to prevent fatal arrhythmias; and they decrease mortality subsequent to myocardial infarction.

Endothelial dysfunctions: common denominators in vascular disease

The past 20 years have witnessed enormous progress in our understanding of the biology of vascular endothelium and its role in cardiovascular disease. Stemming from the seminal observations of Furchgott, the concept of a continuous regulation of vascular tone by normal endothelium and alterations of such control in disease states has become one of the most enlightening concepts of cardiovascular research. This review covers a few updates on the topic, illustrating selective areas of recent progress in our understanding of endothelial function in the control of leucocyte adhesion, atherogenesis and vascular tone, as well as the alterations that cause and accompany vascular disease.

Vitamin E supplementation and cardiovascular events in high-risk patients

BACKGROUND

Observational and experimental studies suggest that the amount of vitamin E ingested in food and in supplements is associated with a lower risk of coronary heart disease and atherosclerosis.

METHODS

We enrolled a total of 2545 women and 6996 men 55 years of age or older who were at high risk for cardiovascular events because they had cardiovascular disease or diabetes in addition to one other risk factor. These patients were randomly assigned according to a two-by-two factorial design to receive either 400 IU of vitamin E daily from natural sources or matching placebo and either an angiotensin-converting-enzyme inhibitor (ramipril) or matching placebo for a mean of 4.5 years (the results of the comparison of ramipril and placebo are reported in a companion article). The primary outcome was a composite of myocardial infarction, stroke, and death from cardiovascular causes. The secondary outcomes included unstable angina, congestive heart failure, revascularization or amputation, death from any cause, complications of diabetes, and cancer.

RESULTS

A total of 772 of the 4761 patients assigned to vitamin E (16.2 percent) and 739 of the 4780 assigned to placebo (15.5 percent) had a primary outcome event (relative risk, 1.05; 95 percent confidence interval, 0.95 to 1.16; P=0.33). There were no significant differences in the numbers of deaths from cardiovascular causes (342 of those assigned to vitamin E vs. 328 of those assigned to placebo; relative risk, 1.05; 95 percent confidence interval, 0.90 to 1.22), myocardial infarction (532 vs. 524; relative risk, 1.02; 95 percent confidence interval, 0.90 to 1.15), or stroke (209 vs. 180; relative risk, 1.17; 95 percent confidence interval, 0.95 to 1.42). There were also no significant differences in the incidence of secondary cardiovascular outcomes or in death from any cause. There were no significant adverse effects of vitamin E.

CONCLUSIONS

In patients at high risk for cardiovascular events, treatment with vitamin E for a mean of 4.5 years had no apparent effect on cardiovascular outcomes.

Re-emergence of fibrates in the management of dyslipidemia and cardiovascular risk

It is now widely accepted that low-density lipoprotein (LDL) is not the only atherogenic component of the lipid profile and that abnormalities in the metabolism and plasma levels of triglycerides and high-density lipoprotein (HDL) may lead to accelerated growth of atherosclerotic lesions. Fibrates are the drugs of first choice in the management of hypertriglyceridemia, and are also able to substantially raise HDL. The recently published Veterans Administration-High-density Lipoprotein Intervention Trial (VA-HIT) trial showed that fibrate treatment in patients with coronary heart disease (CHD), low HDL, modestly elevated triglycerides, and normal LDL reduces the risk of a recurrent coronary event by 25%. A reasonable approach to the dyslipidemic patient with high CHD risk is to tailor the intervention to the specific lipoprotein abnormality. Under these assumptions fibrate therapy should become widespread, considering that the most common lipid alteration in CHD and patients with diabetes is low HDL and high triglycerides.

Mechanisms of vitamin E regulation: research over the past decade and focus on the future

This paper discusses the developments in human vitamin E research since 1990. New methodologies such as the use of stable isotopes, advances in vitamin E measurements, and isolation and cloning of specific alpha-tocopherol binding proteins have facilitated investigation of alpha-tocopherol absorption, metabolism, and transport in humans in vivo. Changes in food production in the United States and dietary intake impacted vitamin E availability and intake. Epidemiologic and therapeutic studies have pointed to its role in disease prevention and in healing processes. Specific molecular functions of alpha-tocopherol have been the most recent and surprising new findings and are an important area for future experimentation. Given the aging of the American population and the potential role for alpha-tocopherol in preventive medicine, the study of the molecular functions of vitamin E promises to provide some of the most exciting discoveries of the next decade.

Vitamin E and heart disease: basic science to clinical intervention trials

A review is presented of studies on the effects of vitamin E on heart disease, studies encompassing basic science, animal studies, epidemiological and observational studies, and four intervention trials. The in vitro, cellular, and animal studies, which are impressive both in quantity and quality, leave no doubt that vitamin E, the most important fat-soluble antioxidant, protects animals against a variety of types of oxidative stress. The hypothesis that links vitamin E to the prevention of cardiovascular disease (CVD) postulates that the oxidation of unsaturated lipids in the low-density lipoprotein (LDL) particle initiates a complex sequence of events that leads to the development of atherosclerotic plaque. This hypothesis is supported by numerous studies in vitro, in animals, and in humans. There is some evidence that the ex vivo oxidizability of a subject's LDL is predictive of future heart events. This background in basic science and observational studies, coupled with the safety of vitamin E, led to the initiation of clinical intervention trials. The three trials that have been reported in detail are, on balance, supportive of the proposal that supplemental vitamin E can reduce the risk for heart disease, and the fourth trial, which has just been reported, showed small, but not statistically significant, benefits. Subgroup analyses of cohorts from the older three trials, as well as evidence from smaller trials, indicate that vitamin E provides protection against a number of medical conditions, including some that are indicative of atherosclerosis (such as intermittent claudication). Vitamin E supplementation also produces an improvement in the immune system and protection against diseases other than cardiovascular disease (such as prostate cancer). Vitamin E at the supplemental levels being used in the current trials, 100 to 800 IU/d, is safe, and there is little likelihood that increased risk will be found for those taking supplements. About one half of American cardiologists take supplemental vitamin E, about the same number as take aspirin. In fact, one study suggests that aspirin plus vitamin E is more effective than aspirin alone. There are a substantial number of trials involving vitamin E that are in progress. However, it is possible, or even likely, that each condition for which vitamin E provides benefit will have a unique dose-effect curve. Furthermore, different antioxidants appear to act synergistically, so supplementation with vitamin E might be more effective if combined with other micronutrients. It will be extremely difficult to do trials that adequately probe the dose-effect curve for vitamin E for each condition that it might affect, or to do studies of all the possible combinations of other micronutrients that might act with vitamin E to improve its effectiveness. Therefore, the scientific community must recognize that there never will be a time when the science is "complete." At some point, the weight of the scientific evidence must be judged adequate; although some may regard it as early to that judgement now, clearly we are very close. In view of the very low risk of reasonable supplementation with vitamin E, and the difficulty in obtaining more than about 30 IU/day from a balanced diet, some supplementation appears prudent now.

Dietary and pharmacological antioxidants in atherosclerosis

Antioxidants that inhibit LDL oxidation are thought to be potential anti-atherogenic compounds. The results of major human randomized trials with antioxidants have, however, been disappointing, except for probucol, which consistently inhibits restenosis. Similarly, animal intervention studies show that antioxidants do not generally inhibit atherosclerosis, although some compounds provide protection. Direct evidence for the oxidation of LDL causing atherosclerosis is needed. This article summarizes results from antioxidant intervention studies, and highlights some of the key issues that need to be addressed to link biochemical changes in the arterial wall more directly to the oxidation theory of atherosclerosis.

Vitamins for the management of cardiovascular disease: a simple solution to a complex problem?

Attention is focusing on the relationship between homocysteine and cardiovascular disease and the role of vitamins in the management of this prevalent ailment. Epidemiologic studies have shown that a relationship between elevated homocysteine concentrations and cardiovascular disease may exist; however, a cause-and-effect relationship has not been proven. The B vitamins are key components of homocysteine metabolism, and the trend is toward their being increasingly prescribed for cardiovascular disease. Prescribing of antioxidant vitamins, vitamin E in particular, has increased as well. Vitamin E may decrease the risk of nonfatal myocardial infarction in patients with coronary artery disease, but its benefit in preventing fatal myocardial infarction has not been shown. Vitamin supplements are not warranted in all patients with cardiovascular disease but may have a place in therapy for selected patients.

Cholesterol lowering and endothelial function

The pathophysiology of the association between cholesterol and atherosclerosis has been thought to involve the deposition, modification, and cellular uptake of cholesterol. We now believe that the process begins with vascular injury and involves inflammation and vessel remodeling. The vascular endothelium actively regulates vascular tone, lipid breakdown, thrombogenesis, inflammation, and vessel growth, all of which are important factors in the development of atherosclerosis. Endothelial dysfunction promotes atherosclerosis through vasoconstriction, monocyte and platelet adhesion, thrombogenesis, and cytokine and growth factor stimulation and release. An important component of endothelial dysfunction is reduced availability of nitric oxide, which is caused by low-density lipoproteins, especially if they are oxidized. This reduced availability appears to occur through a combination of decreased production, abnormal signaling, and increased destruction by oxygen-free radicals. Concurrently, endothelium-mediated vasoconstrictors, adhesion molecules, cytokines, growth factors, and thrombogenic factors, such as endothelin, are increased by oxidized low-density lipoprotein. Several studies have shown improvements in endothelial function with cholesterol lowering, which may explain the early and substantial reductions in major cardiovascular events associated with cholesterol lowering.