Cardiac arrhythmia in rats in response to dietary n-3 fatty acids from red meat, fish oil and canola oil

Dietary approaches for management of cardio-vascular health- a review

Dietary patterns of consumers have changed and the importance of diet as a therapeutic adjunct in the form of nutraceuticals has become the trend of the millennium. Major contributory factor behind this trend is the idea of improving health by modifying the diet that is more attractive to the health conscious consumer as compared to drugs. According to a recent report of WHO, prevalence of cardio vascular disease has increased progressively in the past few years. It has been estimated that one-fifth of deaths in India are due to coronary heart disease that is inflicting at a much younger age in Indians than in the West. Such an insight suggests that cardiac health needs protection. Food products containing functional ingredients that are useful in controlling various different diseases are expected to provide health benefits. Recent research indicates that foods rich in omega-3 fatty acids, antioxidant vitamins and fibres may be beneficial for cardio-vascular health.

Associations of plasma phospholipid and dietary alpha linolenic acid with incident atrial fibrillation in older adults: the Cardiovascular Health Study

BACKGROUND

Few studies have examined the relationship of α-linolenic acid (ALA 18:3n-3), an intermediate-chain essential n-3 polyunsaturated fatty acid derived from plants and vegetable oils, with incident atrial fibrillation (AF).

METHODS AND RESULTS

The study population included participants from the Cardiovascular Health Study, a community-based longitudinal cohort of adults aged 65 or older, free of prevalent coronary heart disease and atrial fibrillation. We assessed the associations of plasma phospholipid and dietary ALA with incident AF using Cox regression. The biomarker analysis comprised a total of 2899 participants, and the dietary analysis comprised 4337 participants. We found no association of plasma phospholipid ALA and incident AF. Comparing each of the second, third, and fourth quartiles to the lowest quartile, the hazard ratios for AF were 1.11 (95% CI, 0.90 to 1.37), 1.09 (95% CI, 0.88 to 1.35), and 0.92 (95% CI, 0.74 to 1.15), after adjustment for age, sex, race, clinic, education, smoking, alcohol, body mass index, waist circumference, diabetes, heart failure, stroke, treated hypertension, and physical activity (P trend=0.48). When dietary ALA was considered the exposure of interest, results were similar.

CONCLUSIONS

Results from this prospective cohort study of older adults indicate no association of plasma phospholipid or dietary ALA and incident AF.

Membrane basis for fish oil effects on the heart: linking natural hibernators to prevention of human sudden cardiac death

The concept that diet-induced changes in membrane lipids could modify heart function partly arose from observations that membrane composition and physical properties were closely associated with the capacity of the heart to respond appropriately to torpor and hibernation. Observations of natural hibernators further revealed that behavior of key membrane-bound enzymes could be influenced through the lipid composition of the cell membrane, either by changing the surrounding fatty acids through reconstitution into a foreign lipid milieu of different composition, or by alteration through diet. Myocardial responsiveness to beta-adrenoceptor stimulation, including initiation of spontaneous dysrhythmic contractions, was altered by both hibernation and dietary modulation of membrane fatty acids, suggesting modified vulnerability to cardiac arrhythmia. Subsequent studies using whole-animal models recognized that vulnerability to ventricular fibrillation decreased as the polyunsaturated: saturated fat (P:S) ratio of the diet increased. However, dietary fish oils, which typically contain at least 30% saturated fatty acids and only 30% long-chain n-3 (omega-3) polyunsaturated fatty acids (PUFA), exhibit antiarrhythmic effects that exceed the predicted influence of the P:S ratio, suggesting properties unique to the long-chain n-3 PUFA. Large-scale clinical trials and epidemiology have confirmed the arrhythmia prevention observed in vitro in myocytes, papillary muscles, and isolated hearts and in whole-animal models of sudden cardiac death. Some progress has been made towards a biologically plausible mechanism. These developments highlight nature's ability to provide guidance for the most unexpected applications.

Dietary fats and coronary heart disease pathogenesis

The intake of saturated fat seems to be the main environmental factor for coronary heart disease (CHD). However, decreasing the intake of saturated fat and replacing it in part with linoleic acid in primary or secondary intervention trials did not satisfactorily reduce CHD clinical manifestations. It is only when omega-3 fatty acids, alpha-linolenic acid (ALA), or eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were added to the diet that sudden cardiac death (ALA, EPA plus DHA) and nonfatal myocardial infarction (only ALA) were significantly lowered. The protective effect of omega-3 fatty acids occurs rapidly, within weeks. The mechanism for preventing ventricular fibrillation seems to be through a direct effect on myocytes. The additional effect of ALA on nonfatal myocardial infarction may be through thrombosis, at least partly caused by an effect on platelets.

Relation between dietary linolenic acid and coronary artery disease in the National Heart, Lung, and Blood Institute Family Heart Study

BACKGROUND

Epidemiologic studies suggest that a higher consumption of eicosapentaenoic acid and docosahexaenoic acid is associated with a reduced risk of cardiovascular disease. Studies in humans and animals also reported an inverse association between alpha-linolenic acid and cardiovascular disease morbidity and mortality.

OBJECTIVE

We examined the relation between dietary linolenic acid and prevalent coronary artery disease (CAD).

DESIGN

We studied 4584 participants with a mean (+/-SD) age of 52.1 +/- 13.7 y in the National Heart, Lung, and Blood Institute Family Heart Study in a cross-sectional design. Participants' diets were assessed with a semiquantitative food-frequency questionnaire. For each sex, we created age- and energy-adjusted quintiles of linolenic acid, and we used logistic regression to estimate prevalent odds ratios for CAD.

RESULTS

From the lowest to the highest quintile of linolenic acid, the prevalence odds ratios of CAD were 1.0, 0.77, 0.61, 0.58, and 0.60 for the men (P for trend = 0.012) and 1.0, 0.57, 0.52, 0.30, and 0.42 for the women (P for trend = 0.014) after adjustment for age, linoleic acid, and anthropometric, lifestyle, and metabolic factors. Linoleic acid was also inversely related to the prevalence odds ratios of CAD in the multivariate model (0.60 and 0.61 in the second and third tertiles, respectively) after adjustment for linolenic acid. The combined effect of linoleic and linolenic acids was stronger than the individual effects of either fatty acid.

CONCLUSIONS

A higher intake of either linolenic or linoleic acid was inversely related to the prevalence odds ratio of CAD. The 2 fatty acids had synergistic effects on the prevalence odds ratio of CAD.

Dietary polyunsaturated fatty acid and antioxidant modulation of vascular dysfunction in the spontaneously hypertensive rat

Two currently available edible oils-olive and canola-and two oil blends of plant origin having different n-3/n-6 polyunsaturated fatty acid (PUFA) ratios were evaluated for their ability to modify vascular dysfunction in the spontaneously hypertensive rat (SHR). Synthetic diets supplemented with test oils (5% w/w) were fed for 12 weeks, and segments of thoracic aorta used to assess vascular function. Vessels from the SHR displayed a spontaneous constrictor response after the inhibition of endothelial cell nitric oxide (NO) with N(omega)-nitro-L-arginine (NOLA). Dietary alpha -linoleate enrichment led to a reduction (P<0.05) in this abnormality with a dietary n-3/n-6 PUFA ratio of 1.0 (blend-1) yielding the best outcome. Relaxation to acetylcholine (ACh) was unaffected by dietary lipid supplementation. NOLA treated rings also displayed contractions to ACh that were abolished by indomethacin, thromboxane antagonists SQ29548, picotamide and flavonoids kaempferol and quercetin. In contrast, alpha-tocopherol, rutin and the lipoxygenase inhibitor esculetin resulted in only partial (30-55%) inhibition, and were ineffective against the NOLA-induced contraction suggesting the operation of different biochemical mechanisms in mediating the spontaneous and Ach-induced contractions. Results implicate plant-based oils and antioxidants as potential modulators of vascular function.

Coronary heart disease: dietary links and pathogenesis

For decades it has been postulated that the main environmental factor for coronary heart disease (CHD) was the intake of saturated fatty acids (SFA). Nevertheless, confirmation of the role of SFA in CHD through intervention trials has been disappointing. It was only when the diet was enriched in n-3 fatty acids that CHD was significantly prevented, especially cardiac death. In addition to n-3 fatty acids, many other foodstuffs or nutrients such as fibers, antioxidants, folic acid, calcium and even alcohol contribute to prevent CHD. Thus the relationship between diet and CHD morbidity and mortality appears to be much more complex than formerly suspected considering as key factors only SFA, linoleic acid, cholesterol and atherosclerosis. Some of the mechanisms are briefly described, but many additional nutrients (or non nutrients) may also play an important role in the pathogenesis of CHD. Finally, as a result of the most recent epidemiologic studies the ideal diet may comprise: 8% energy from SFA, 5% from polyunsaturated fatty acids with a ratio 5/1 of linoleic/alpha-linolenic acid+longer chains n-3, oleic acid as desired, large intake of cereals, vegetables, legumes and fruits, fish twice a week, cheese and yogurt as dairy products, rapeseed and olive oils as edible fat. Without side effects, such a diet can be highly palatable, easily enjoyed by many populations and may prevent effectively and rapidly (within a few weeks or months) CHD.

Types of dietary fat and risk of coronary heart disease: a critical review

During the past several decades, reduction in fat intake has been the main focus of national dietary recommendations to decrease risk of coronary heart disease (CHD). Several lines of evidence. however, have indicated that types of fat have a more important role in determining risk of CHD than total amount of fat in the diet. Metabolic studies have long established that the type of fat, but not total amount of fat, predicts serum cholesterol levels. In addition, results from epidemiologic studies and controlled clinical trials have indicated that replacing saturated fat with unsaturated fat is more effective in lowering risk of CHD than simply reducing total fat consumption. Moreover, prospective cohort studies and secondary prevention trials have provided strong evidence that an increasing intake of n-3 fatty acids from fish or plant sources substantially lowers risk of cardiovascular mortality. In this article, we review evidence from epidemiologic studies and dietary intervention trials addressing the relationship between dietary fat intake and risk of CHD, with a particular emphasis on different major types of fat, n-3 fatty acids and the optimal balance between n-3 and n-6 fatty acids. We also discuss the implications of the available evidence in the context of current dietary recommendations.

Influence of sources of dietary oils on the life span of stroke-prone spontaneously hypertensive rats

In recent studies, the life span of stroke-prone spontaneously hypertensive (SHRSP) rats was altered by a variety of dietary fats. It was relatively shorter in rats fed canola oil as the sole source of fat. The present study was performed to find out whether the fatty acid profile and the high content of sulfur compounds in canola oil could modulate the life span of SHRSP rats. SHRSP rats (47 d old, n = 23/group) were matched by body weight and systolic blood pressure and fed semipurified diets containing 10% canola oil, high-palmitic canola oil, low-sulfur canola oil, soybean oil, high-oleic safflower oil, a fat blend that mimicked the fatty acid composition of canola oil, or a fat blend high in saturated fatty acids. A 1% sodium chloride solution was used as drinking water to induce hypertension. After consuming the diets for 37 d, five rats from each dietary group were killed for collection of blood and tissue samples for biochemical analysis. The 18 remaining animals from each group were used for determining their life span. The mean survival time of SHRSP rats fed canola oil (87.4+/-4.0 d) was not significantly different (P > 0.05) from those fed low-sulfur canola oil (89.7+/-8.5 d), suggesting that content of sulfur in canola oil has no effect on the life span of SHRSP rats. The SHRSP rats fed the noncanola oil-based diets lived longer (mean survival time difference was 6-13 d, P < 0.05) than those fed canola and low-sulfur canola oils. No marked differences in the survival times were observed among the noncanola oil-based groups. The fatty acid composition of the dietary oils and of red blood cells and liver of SHRSP rats killed after 37 d of treatment showed no relationship with the survival times. These results suggest that the fatty acid profile of vegetable oils plays no important role on the life span of SHRSP rat. However, phytosterols in the dietary oils and in liver and brain were inversely correlated with the mean survival times,indicating that the differential effects of vegetable oils might be ascribed, at least partly, to their different phytosterol contents.

Dietary intake of alpha-linolenic acid and risk of fatal ischemic heart disease among women

BACKGROUND

Experimental studies in laboratory animals and humans suggest that alpha-linolenic acid (18:3n-3) may reduce the risk of arrhythmia.

OBJECTIVE

The objective was to examine the association between dietary intake of alpha-linolenic acid and risk of fatal ischemic heart disease (IHD).

DESIGN

This was a prospective cohort study. The intake of alpha-linolenic acid was derived from a 116-item food-frequency questionnaire completed in 1984 by 76283 women without previously diagnosed cancer or cardiovascular disease.

RESULTS

During 10 y of follow-up, we documented 232 cases of fatal IHD and 597 cases of nonfatal myocardial infarction. After adjustment for age, standard coronary risk factors, and dietary intake of linoleic acid and other nutrients, a higher intake of alpha-linolenic acid was associated with a lower relative risk (RR) of fatal IHD; the RRs from the lowest to highest quintiles were 1.0, 0.99, 0.90, 0.67, and 0.55 (95% CI: 0.32, 0.94; P for trend = 0.01). For nonfatal myocardial infarction there was only a modest, nonsignificant trend toward a reduced risk when extreme quintiles were compared (RR: 0.85; 95% CI: 0.61, 1.19; P for trend = 0.50). A higher intake of oil and vinegar salad dressing, an important source of alpha-linolenic acid, was associated with reduced risk of fatal IHD when women who consumed this food > or =5-6 times/wk were compared with those who rarely consumed this food (RR: 0.46; 95% CI: 0.27, 0.76; P for trend = 0.001).

CONCLUSIONS

This study supports the hypothesis that a higher intake of alpha-linolenic acid is protective against fatal IHD. Higher consumption of foods such as oil-based salad dressing that provide polyunsaturated fats, including alpha-linolenic acid, may reduce the risk of fatal IHD.

Dietary management of cardiovascular diseases

Since cholesterol was discovered in atherosclerotic plaques and was able, when given in diet, to induce the same type of lesions in animals, the aim of previous dietary changes was to reduce serum cholesterol as much as possible. For this purpose, the intake of saturated fats was decreased and replaced by linoleic acid, the main fatty acid lowering cholesterol. Nevertheless, this type of diet in primary or secondary prevention did not succeed in reducing satisfactorily cardiovascular and total mortality unless the intake of fish (DART and Hjermann trials) i.e. of n-3 fatty acids, was increased. On the other hand, the diet with the greatest life expectancy in the western world is that of Crete, largely vegetarian with a high intake of alpha-linolenic acid. Such a diet, compared to the usual prudent diet in 600 patients after a first myocardial infarction, reduced within a few months all cause mortality and cardiovascular events by more than 70%. Thus a highly palatable diet adapted from Crete seems to be much more efficient to prevent recurrences and death after a first myocardial infarction than the hypocholesterolemic diet presently advised.

Effect of a mediterranean type of diet on the rate of cardiovascular complications in patients with coronary artery disease. Insights into the cardioprotective effect of certain nutriments

OBJECTIVES

We sought to describe the various cardiovascular complications that occurred in the Lyon Diet Heart Study (a secondary prevention trial testing the protective effects of a Mediterranean type of diet), to analyze their relations with the associated drug treatments and to gain insights into the possible mechanisms underlying the beneficial effects of certain nutriments.

BACKGROUND

Dietary habits are implicated in coronary heart disease, and the traditional Mediterranean diet is thought to be cardioprotective. However, the exact mechanisms of this protection are unknown.

METHODS

A total of 605 patients (303 control subjects and 302 study patients) were studied over a mean period of 27 months. Major primary end points (cardiovascular death and nonfatal acute myocardial infarction), secondary end points (including unstable angina, stroke, heart failure and embolisms) and minor end points (stable angina, need for myocardial revascularization, postangioplasty restenosis and thrombophlebitis) were analyzed separately and in combination.

RESULTS

When major primary and secondary end points were combined, there were 59 events in control subjects and 14 events in the study patients, showing a risk reduction of 76% (p < 0.0001). When these end points were combined with the minor end points, there were 104 events in control subjects and 68 events in the study patients, giving a risk reduction of 37% (p < 0.005). By observational analysis, only aspirin among the medications appeared to be significantly protective (risk ratio after adjustment for prognosis factors 0.45; 95% confidence interval 0.25 to 0.80).

CONCLUSIONS

These data show a protective effect of the Mediterranean diet. However, the risk reduction varied depending on the type of end point considered. Our hypothesis is that different pathogenetic mechanisms were responsible for the development of the various complications. It is likely that certain nutriments characteristic of the Mediterranean diet (omega-3 fatty acids, oleic acid antioxidant vitamins) have specific cardioprotective effects.

Abnormal membrane concentrations of 20 and 22-carbon essential fatty acids: a common link between risk factors and coronary and peripheral vascular disease?

Although elevated levels of cholesterol are associated with increased risks of coronary and peripheral vascular disease, the association frequently fails to provide a causative explanation at the individual level. New hypotheses are required which, whether or not they are correct, will provide new lines of research. It is proposed here that the causes of vascular disease are abnormal membrane phospholipid concentrations of the 20-carbon and 22-carbon essential fatty acids (EFAs) of the n-6 and n-3 series. These levels become abnormal with ageing, with stress and in response to smoking, high cholesterol levels and high saturated fat intakes. They are also abnormal in patients with diabetes and hypertension. The effects of these EFAs and their metabolites include lowering of triglycerides, elevation of high-density lipoprotein (HDL)-cholesterol, reduction of blood pressure, vasodilatation, reduction of fibrinogen levels and inhibition of platelet aggregation and of cardiac arrhythmias. Prospective studies have shown that abnormal levels of these fatty acids are predictive of future coronary death. Controlled trials of treatment have demonstrated that provision of the fatty acids reduces both coronary and total mortality. Further experimental and clinical investigations of the roles of appropriate membrane concentrations of these fatty acids are justified.

Lipids and cardiac arrhythmia

In any discussion of lipids and heart disease it is beneficial from the outset to recognise that at least three different pathological processes may be involved. The first of these is atherosclerosis which involves the deposition of "fat" in the coronary vessels, another is thrombogenesis which describes the formation of blood clots in the coronary vessels, and the third is arrhythmia which refers to disorders in the beating of the heart which may become sufficiently serious to cause sudden cardiac death (SCD). Also it is this disturbance in the rhythmic beating of the heart which is responsible for much of the mortality from 'heart attacks' which occur 'outside-of-hospital' in societies like U.S.A., U.K. and Australia. It is this latter condition of cardiac arrhythmia which is the major concern of this review. Because it is often difficult to differentiate the role of lipids in 'heart disease' in man, it has frequently been assumed that all dietary fatty acids have similar effects on the different processes involved, and many unwarranted generalisations have been made which have led to conflicts of opinion amongst physicians and confusion in the lay public. From the animal studies discussed in this review, it is apparent that dietary fatty acids have an important role to play in determining the vulnerability of the myocardium to develop serious ventricular fibrillation (VF) and potentially lethal cardiac arrhythmia. In general, diets rich in saturated fatty acids promote a state of myocardial vulnerability, whilst diets rich in PUFA significantly diminish the probability of developing lethal disorders in cardiac rhythm when the heart is placed under pharmacological (or emotional) stress, or deprived of sufficient blood flow and supply of oxygen. Very recent experiments with the monounsaturated fatty acid (MUFA) oleic acid clearly demonstrate that, at least in rats subjected to ligation of their coronary artery, this acid is not 'neutral' as has been suggested by some for its role in atherosclerosis, but in fact is indistinguishable from saturated fatty acids in its effect in promoting arrhythmia during either regional ischaemia or reperfusion arrhythmia in this animal model of SCD.(ABSTRACT TRUNCATED AT 400 WORDS)