Linoleic acid and risk of sudden cardiac death

Circulating Omega-3 Polyunsaturated Fatty Acids Levels in Coronary Heart Disease: Pooled Analysis of 36 Observational Studies

Long-chain n-3 polyunsaturated fatty acid (PUFA) supplementation has shown potential benefits in the prevention of coronary heart disease (CHD); however, the impact of omega-3 fatty acid levels on CHD risk remains a subject of debate. Here, we aimed to investigate the association between n-3 PUFA levels and the risk of CHD, with particular reference to the subtypes of n-3 PUFA.

METHODS

Prospective studies and retrospective case-control studies analyzing n-3 PUFA levels in CHD, published up to 30 July 2022, were selected. A random effects meta-analysis was used for pooled assessment, with relative risks (RRs) expressed as 95% confidence intervals (CIs) and standardized mean differences expressed as weight mean differences (WMDs). Subgroup and meta-regression analyses were conducted to assess the impact of n-3 PUFA exposure interval on the CHD subtype variables of the study.

RESULTS

We included 20 prospective studies (cohort and nested case-control) and 16 retrospective case-control studies, in which n-3 PUFAs were measured. Higher levels of n-3 PUFAs (ALA, EPA, DPA, DHA, EPA + DHA, total n-3 PUFAs) were associated with a reduced risk of CHD, with RRs (95% CI) of 0.89 (0.81, 0.98), 0.83 (0.72, 0.96); 0.80 (0.67,0.95), 0.75 (0.64, 0.87), 0.83 (0.73, 0.95), and 0.80 (0.70, 0.93), respectively, p < 0.05. CHD patients had significantly lower n-3 PUFA levels compared to healthy controls (p < 0.05). In the subgroup analysis, a significant inverse trend was found for both fatal CHD and non-fatal CHD with n-3 PUFA (EPA + DHA) levels. Also, the link between n-3 PUFA levels in erythrocytes with total CHD was generally stronger than other lipid pools.

CONCLUSIONS

n-3 PUFAs are significantly related to CHD risk, and these findings support the beneficial effects of n-3 PUFAs on CHD.

Statement on additional scientific evidence in relation to the essential composition of total diet replacement for weight control

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to revise the Opinion on the essential composition of total diet replacements for weight control (TDRs) regarding the minimum content of linoleic acid (LA) and alpha-linolenic acid (ALA) and the maximum content of magnesium (Mg). Through a comprehensive literature search, human studies were retrieved reporting on LA and ALA concentrations in adipose tissue (AT), on weight loss and gallstone formation following TDR consumption and on diarrhoea after supplemental Mg intake. The distribution of the amount of LA and ALA release from AT during weight loss when consuming TDRs was estimated using statistical simulations. Using the fifth percentile, the coverage of the adequate intake (AI) for both FA was estimated. For the risk of developing diarrhoea when consuming TDRs with an Mg content of 350 mg/day, four cross-over studies using 360-368 mg Mg/day were reviewed. The Panel concludes that (1) there is no need to add LA to TDRs, as the amount released from AT during weight loss when consuming TDRs is sufficient to cover the AI for LA; (2) a minimum of 0.8 g/day ALA is needed in TDRs in order to meet the AI for ALA; (3) the minimum fat content of TDRs of 20 g/day as derived in the Panel's previous opinion is proposed to be maintained until the availability of further evidence, given the considerable uncertainty as to the amount of fat required for reducing the risk of gallstone formation; and (4) the likelihood that Mg-induced diarrhoea occurs at a severity that may be considered of concern for overweight and obese individuals consuming TDRs is low when the total maximum Mg content in TDRs is 350 mg/day.

Dietary fat quality and risk of sudden cardiac death in women

BACKGROUND

Dietary n-3 PUFAs are inversely associated with risk of sudden cardiac death (SCD); however, little is known about other fats and SCD. Furthermore, concerns have been raised that high n-6 PUFA intake may attenuate the benefits of n-3 PUFAs.

OBJECTIVE

We examined associations and selected interactions between dietary fatty acids, expressed as a proportion of total fat and SCD.

DESIGN

We conducted a prospective cohort study among 91,981 women aged 34-59 y from the Nurses' Health Study in 1980. Over 30 y, we documented 385 SCDs.

RESULTS

In multivariable models, women in the highest compared with the lowest quintile of SFA intake had an RR of SCD of 1.44 (95% CI: 1.04, 1.98). Conversely, women in the highest compared with the lowest quintile of PUFA intake had an RR of SCD of 0.57 (95% CI: 0.41, 0.78). Intakes of n-6 and n-3 PUFAs were both significantly associated with a lower risk of SCD, and n-6 PUFAs did not modify the association between n-3 PUFAs and SCD. MUFAs and trans fats were not associated with SCD risk. After further adjustment for coronary heart disease (CHD) and CHD risk factors potentially in the causal pathway, the association between PUFAs and SCD remained significant, whereas the association for SFAs was no longer significant.

CONCLUSIONS

Intake of PUFAs as a proportion of fat was inversely associated with SCD risk, independent of traditional CHD risk factors. These results support dietary guidelines to improve dietary fat quality by replacing intake of SFAs with n-6 and n-3 PUFAs.

The prognostic value of adipose tissue fatty acids for incident cardiovascular disease: results from 3944 subjects in the Scottish Heart Health Extended Cohort Study

AIMS

Dietary fats are routinely considered key determinants of cardiovascular risk, yet the scientific basis of this association has never been demonstrated using objective measures of fat intakes in a large prospective study in a general population.

METHODS AND RESULTS

Adipose tissue was taken from 3944 participants, predominantly aged 40-59 years, in Scotland, 1984-87. Percentages of individual fatty acids were measured using gas chromatography. Over a median of 19.5 years, 870 incident cardiovascular disease (CVD) events occurred. Hazard ratios (HRs) were obtained from Cox models and the additional prognostic value, accounting for variables in the Framingham and ASSIGN CVD risk scores, were assessed using discrimination indices. Adjusting for age, sex, total and HDL-cholesterol, systolic blood pressure, smoking, hypertensive medication use, diabetes, socio-economic status and family history, the percentage of monounsaturated adipose tissue fatty acids had a positive log-linear relationship with incident CVD: the HR comparing risk between the fourth and first quartiles was 1.29 (95% confidence interval: 1.05, 1.59). n-3 polyunsaturated fat showed the reverse trend, the corresponding result being 0.77 (0.63, 0.94). These two composite variables improved the classification of incident CVD events by 1.0 and 6.4%, respectively, with only the latter being significant at the 5% level.

CONCLUSIONS

A diet which is proportionately rich in polyunsaturated fat, as opposed to other fats, is expected to decrease the risk of CVD independently of the effects of common CVD risk factors, including social deprivation. Taking account of such diets improves the classification of future CVD events.

Essential fatty acids and their metabolites could function as endogenous HMG-CoA reductase and ACE enzyme inhibitors, anti-arrhythmic, anti-hypertensive, anti-atherosclerotic, anti-inflammatory, cytoprotective, and cardioprotective molecules

Lowering plasma low density lipoprotein-cholesterol (LDL-C), blood pressure, homocysteine, and preventing platelet aggregation using a combination of a statin, three blood pressure lowering drugs such as a thiazide, a beta blocker, and an angiotensin converting enzyme (ACE) inhibitor each at half standard dose; folic acid; and aspirin-called as polypill- was estimated to reduce cardiovascular events by approximately 80%. Essential fatty acids (EFAs) and their long-chain metabolites: gamma-linolenic acid (GLA), dihomo-GLA (DGLA), arachidonic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) and other products such as prostaglandins E1 (PGE1), prostacyclin (PGI2), PGI3, lipoxins (LXs), resolvins, protectins including neuroprotectin D1 (NPD1) prevent platelet aggregation, lower blood pressure, have anti-arrhythmic action, reduce LDL-C, ameliorate the adverse actions of homocysteine, show anti-inflammatory actions, activate telomerase, and have cytoprotective properties. Thus, EFAs and their metabolites show all the classic actions expected of the "polypill". Unlike the proposed "polypill", EFAs are endogenous molecules present in almost all tissues, have no significant or few side effects, can be taken orally for long periods of time even by pregnant women, lactating mothers, and infants, children, and adults; and have been known to reduce the incidence cardiovascular diseases including stroke. In addition, various EFAs and their long-chain metabolites not only enhance nitric oxide generation but also react with nitric oxide to yield their respective nitroalkene derivatives that produce vascular relaxation, inhibit neutrophil degranulation and superoxide formation, inhibit platelet activation, and possess PPAR-gamma ligand activity and release NO, thus prevent platelet aggregation, thrombus formation, atherosclerosis, and cardiovascular diseases. Based on these evidences, I propose that a rational combination of omega-3 and omega-6 fatty acids and the co-factors that are necessary for their appropriate action/metabolism is as beneficial as that of the combined use of a statin, thiazide, a beta blocker, and an angiotensin converting enzyme (ACE) inhibitor, folic acid, and aspirin. Furthermore, appropriate combination of omega-3 and omega-6 fatty acids may even show additional benefits in the form of protection from depression, schizophrenia, Alzheimer's disease, and enhances cognitive function; and serve as endogenous anti-inflammatory molecules; and could be administered from childhood for life long.

Fatty acid composition of adipose tissue and blood in humans and its use as a biomarker of dietary intake

Accurate assessment of fat intake is essential to examine the relationships between diet and disease risk but the process of estimating individual intakes of fat quality by dietary assessment is difficult. Tissue and blood fatty acids, because they are mainly derived from the diet, have been used as biomarkers of dietary intake for a number of years. We review evidence from a wide variety of cross-sectional and intervention studies and summarise typical values for fatty acid composition in adipose tissue and blood lipids and changes that can be expected in response to varying dietary intake. Studies in which dietary intake was strictly controlled confirm that fatty acid biomarkers can complement dietary assessment methodologies and have the potential to be used more quantitatively. Factors affecting adipose tissue and blood lipid composition are discussed, such as the physical properties of triacylglycerol, total dietary fat intake and endogenous fatty acid synthesis. The relationship between plasma lipoprotein concentrations and total plasma fatty acid composition, and the use of fatty acid ratios as indices of enzyme activity are also addressed.

Tissue n-3 and n-6 fatty acids and risk for coronary heart disease events

BACKGROUND

Tissue proportions of long chain n-6 [especially arachidonic acid (AA)] and n-3 fatty acids [FA; eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) acids], or some ratio of these may be markers of risk for coronary heart disease (CHD). The purpose of this paper is to evaluate the published associations between risk for CHD events and tissue n-3 and n-6 FA composition.

METHODS

Case-control or prospective cohort data sets examining the risk for CHD endpoints as a function of tissue FA composition were identified. Effect sizes were computed for case versus control comparisons using standard meta-analytic methods.

RESULTS

Twenty-five studies were included, 18 examining the FA composition of phospholipid-rich and 7 of triglyceride-rich samples. DHA, with or without EPA, was significantly lower in cases than controls in all studies combined, in those with fatal endpoints, in those with prospective designs, and in both tissue types. The only setting where increased AA was associated with case status was in adipose tissue. The AA/EPA ratio in phospholipid-rich samples did not distinguish cases from controls. Lower linoleic acid content was associated with increased risk for non-fatal events.

CONCLUSIONS

The long-chain n-3 FA, especially DHA, were consistently and significantly reduced in patients experiencing CHD events. These findings add further support to the view that long-chain n-3 FA are cardioprotective.

Effect of varying the ratio of n-6 to n-3 fatty acids by increasing the dietary intake of alpha-linolenic acid, eicosapentaenoic and docosahexaenoic acid, or both on fibrinogen and clotting factors VII and XII in persons aged 45-70 y: the OPTILIP study

BACKGROUND

Elevated fibrinogen, activated factor XII (FXIIa), and factor VII coagulant activity (FVIIc) are associated with higher risk of fatal ischemic heart disease. This study tested the hypothesis that lowering the dietary ratio of n-6 to n-3 polyunsaturated fatty acids (n-6:n-3) would modify these risk factors in older men and women.

OBJECTIVE

The objective of the study was to measure fasting hemostatic risk factors and postprandial changes in activated FVII (FVIIa) concentrations after a 6-mo alteration in dietary n-6:n-3.

DESIGN

In a randomized, parallel design in 258 subjects aged 45-70 y, we compared 4 diets providing 6% of energy as polyunsaturated fatty acids at an n-6:n-3 between 5:1 and 3:1 with a control diet that had an n-6:n-3 of 10:1. The diets were enriched in alpha-linolenic acid, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid, or both.

RESULTS

Fasting and 3-h plasma triacylglycerol concentrations were 11.1% and 7.2% lower with the diet that had an n-6:n-3 of approximately 3:1 and that was enriched with EPA and DHA than with the other diets. Fasting fibrinogen, FXIIa, FVIIc, FVIIa, and FVII antigen and postprandial FVIIa were not influenced by the diets. Avoiding foods high in fat the day before measurement decreased FVIIc and FVIIa by 8% and 19.2%, respectively. A test meal containing 50 g fat resulted in a mean 47% (95% CI: 42%, 52%) increase in FVIIa 6 h later, but the response did not differ by n-6:n-3.

CONCLUSION

Decreasing the n-6:n-3 to approximately 3:1 by increasing the intake of EPA and DHA lowers fasting and postprandial plasma triacylglycerol concentrations in older persons but does not influence hemostatic risk factors.

Myocardial infarction occurrence in Jerusalem: a Mediterranean anomaly

BACKGROUND

The Jewish population of Israel consumes a diet rich in polyunsaturated fatty acids with a relatively low proportion of saturated fat, has a small alcohol intake and a lipid profile characterized by low HDL-cholesterol and high lipoprotein(a) (Lp(a)). It is therefore of interest to compare occurrence rates of coronary heart disease (CHD) with those elsewhere.

METHODS

The community-based event rate of CHD [comprising acute myocardial infarction (AMI) and CHD death] and case-fatality was determined in 1995-1997 by active surveillance among Jewish residents of the Jerusalem District aged 25-64 according to standardized WHO-MONICA criteria. We compared our findings with rates among MONICA populations in 21 countries. Twelve hundred and six events occurred in Jerusalem during approximately 399,000 [correction] person-years (930 non-fatal AMI and 276 CHD deaths).

RESULTS

The age-adjusted incidence of CHD ranked high compared with the 21 countries (men third highest, women eighth highest), far exceeding the Mediterranean countries. In contrast, the pre-hospital mortality rate was low, similar to countries in the Mediterranean basin, and the 28-day case fatality was remarkably low, far lower than for any MONICA population in men, and second lowest in women. Correspondingly, the incidence of non-fatal AMI ranked extraordinarily high (men first, women third). The low case-fatality ranking persisted upon adjustment for treatment differences between populations.

CONCLUSIONS

We report an unusual combination of a high incidence of CHD among Jewish residents of Jerusalem accompanied by extraordinarily low case fatality, the latter suggesting reduced susceptibility to lethal arrhythmias. Determinants of this anomaly require clarification.

Severity of Atherosclerosis in Parrots in Relation to the Intake of α-Linolenic Acid

Atherosclerosis is a common disease among parrots, but little is known about possible risk factors. Important risk factors in humans are an elevated plasma cholesterol concentration and increased platelet aggregation; high intakes of polyunsaturated fatty acids have beneficial effects. In this study, we tried to establish a relationship, if any, between dietary fatty acids and the severity of atherosclerosis in parrots. We collected dead parrots and scored the degree of atherosclerosis in the beginning of the aorta and the brachiocephalic arteries. It was not possible to assess the intake of fatty acids with food questionnaires so fatty acid composition of adipose tissue and breast muscle had to be used as an index of the dietary fatty acid composition. In all, 202 birds were collected. Gender was not related with atherosclerosis, but the degree of atherosclerosis increased with age and among the various species; African grey parrots appeared to be the most susceptible. The contents of linoleic acid in breast muscle or adipose tissue were not associated with the severity of atherosclerosis. For the relative percentage of alpha-linolenic acid in either breast muscle (P = 0.09; n = 175) or adipose tissue (P = 0.056; n = 21), a borderline significant relation with the degree of atherosclerosis was found. Parrots without atherosclerosis had significantly higher levels of alpha-linolenic acid than did the other animals. On the basis of these data, we suggest tentatively that a high dietary intake of alpha-linolenic acid protects against the development of atherosclerosis in parrots.

Sudden death and myocardial infarction in first degree relatives as predictors of primary cardiac arrest

The hypothesis that family history (FH) of myocardial infarction (MI) and FH of sudden death (SD) are both independent risk factors for primary cardiac arrest (PCA) was examined in a case-control study. PCA cases were attended by paramedics (1988-1994) and community-based age and sex matched controls were identified. Subjects (25-74 years) were free of prior clinically-recognized heart disease and major co-morbidity. Interviewers obtained a detailed history of MI and SD in first-degree relatives from spouses of 235 cases and 374 control subjects. A parental history of early-onset SD (age <65) was associated with an increased risk of PCA (odds ratio (OR)=2.69, 95% CI=1.35-5.36), after adjustment for parental history of MI and other risk factors. A parental history of late-onset SD was not associated with PCA risk (OR=0.94, 95% CI=0.55-1.62). Additionally, parental history of SD was related to early-onset PCA (OR=1.89, 95% CI=1.08-3.30) but not to late-onset PCA (OR=0.89, 95% CI=0.49-1.61). In contrast, parental MI (early/late) was related to PCA (early/late), after adjustment for other risk factors and parental history of SD. Similar results were observed in first-degree relatives. Findings suggest a potential role of familial factors related to both MI and SD in PCA. Stronger findings for a familial patterning of PCA were noted for early onset disease in cases and their relatives.

alpha-Linolenic acid intake is not beneficially associated with 10-y risk of coronary artery disease incidence: the Zutphen Elderly Study

BACKGROUND

Data on the relation between alpha-linolenic acid intake and coronary artery disease (CAD) are limited. Other dietary components appear to modify the reported relation between alpha-linolenic acid intake and CAD.

OBJECTIVE

We examined whether dietary alpha-linolenic acid intake was inversely associated with risk of CAD.

DESIGN

We prospectively studied 667 men aged 64-84 y from the Zutphen Elderly Study who were free of CAD at baseline. Dietary intake was assessed by using a cross-check dietary history method.

RESULTS

During the 10-y follow-up, we documented 98 cases of CAD. After adjustment for age, standard coronary risk factors, and intake of trans fatty acids and other nutrients, alpha-linolenic acid intake was not significantly associated with CAD risk. The relative risk of CAD for the highest compared with the lowest tertile of alpha-linolenic acid intake was 1.68 (95% CI: 0.86, 3.29). alpha-Linolenic acid intake from sources containing trans fatty acids was also nonsignificantly, yet positively, associated with CAD risk. alpha-Linolenic acid intake from foods that did not contain trans fatty acids was not associated with CAD risk, the relative risk of CAD for the highest compared with the lowest tertile was 1.15 (95% CI: 0.63, 2.11).

CONCLUSION

We did not observe a beneficial effect of dietary alpha-linolenic acid intake on the risk of 10-y CAD incidence. Investigating this hypothesis was complicated by the association between intakes of alpha-linolenic acid and trans fatty acids. Given the results of current prospective studies, a protective cardiac effect of alpha-linolenic acid is questionable.

Coronary risk factors, diet and vitamins as possible explanatory factors of the Swedish north-south gradient in coronary disease: a comparison between two MONICA centres

OBJECTIVE

To investigate whether differences in serum lipids, diet, plasma vitamins or other risk factors explain the higher incidence of cardiovascular disease in the northern parts of Sweden, compared to Göteborg on the west coast.

DESIGN

A comparison between the two Swedish MONICA populations in northern Sweden (NSW) and in Göteborg (GOT) in 1990.

SETTING

Norrbotten and Västerbotten counties in the north of Sweden and the city of Göteborg on the west coast.

SUBJECTS

In the north 1583 men and women aged 25-64 years were investigated, and in Göteborg 1574 men and women. Plasma vitamins were examined in a subsample of men aged 40-49 (n = 259).

MAIN OUTCOME MEASURES

Serum lipids, blood pressure, anthropometric measurements, smoking habits, physical activity, diet, education, and plasma vitamins.

RESULTS

NSW men and women had mean serum total cholesterol of 6.30 (standard deviation 1.23) mmol L-1 and 6.12 (1. 33) mmol L-1, compared to 5.75 (1.14) mmol L-1 and 5.67 (1.24) mmol L-1 in GOT men and women (P = 0.0001). NSW men and women were shorter and had higher body mass index than in Göteborg. Cigarette smoking was slightly more prevalent amongst GOT men and women. Göteborg men and women more often had more than compulsory school education, compared to NSW men and women, whereas there were no differences in physical activity during leisure time. There were no differences in vegetable consumption, whereas fruit was consumed more frequently by NSW women compared to GOT women, with a higher intake of fibre and ascorbate. Consumption of wine and total alcohol consumption were higher in Göteborg, whereas NSW men and women drank significantly more coffee. In the subsample of men (aged 40-49) who had plasma vitamins measured, men in Göteborg had slightly higher mean retinol concentrations (P = 0.005) and lutein and zeaxanthine levels (P = 0.006 and 0.009, respectively) compared to northern men, but there were no differences with respect to alpha- or beta-carotene, ascorbic acid or lipid-adjusted vitamin E. NSW men had slightly higher plasma iron and magnesium concentrations (P = 0.005 and 0.001, respectively).

CONCLUSION

The largest and most consistent differences between Göteborg and northern Sweden were found for serum cholesterol, probably reflecting differences in intake of saturated fat. The differences in serum cholesterol may explain a substantial part of the differences in coronary heart disease morbidity and mortality. We found no consistent differences concerning vegetable and fruit consumption. More alcohol was consumed in Göteborg. Differences in education and childhood conditions, as reflected in differences in height, may contribute to the north-south gradient with respect to CHD incidence and mortality.

Omega-3 fatty acids in adipose tissue and risk of myocardial infarction: the EURAMIC study

Omega-3 fatty acids have potential antiatherogenic, antithrombotic, and antiarrhythmic properties, but their role in coronary heart disease remains controversial. To evaluate the association of omega-3 fatty acids in adipose tissue with the risk of myocardial infarction in men, a case-control study was conducted in eight European countries and Israel. Cases (n=639) included patients with a first myocardial infarction admitted to coronary care units within 24 hours from the onset of symptoms. Controls (n=700) were selected to represent the populations originating the cases. Adipose tissue levels of fatty acids were determined by capillary gas chromatography. The mean (+/-SD) proportion of alpha-linolenic acid was 0.77% (+/-0.19) of fatty acids in cases and 0.80% (+/-0.19) of fatty acids in controls (P=0.01). The relative risk for the highest quintile of alpha-linolenic acid compared with the lowest was 0.42 (95% confidence interval [CI] 0.22 to 0.81, P-trend=0.02). After adjusting for classical risk factors, the relative risk for the highest quintile was 0.68 (95% CI 0.31 to 1.49, P-trend=0.38). The mean proportion of docosahexaenoic acid was 0.24% (+/-0.13) of fatty acids in cases and 0.25% (+/-0.13) of fatty acids in controls (P=0. 14), with no evidence of association with risk of myocardial infarction. In this large case-control study we could not detect a protective effect of docosahexaenoic acid on the risk of myocardial infarction. The protective effect of alpha-linolenic acid was attenuated after adjusting for classical risk factors (mainly smoking), but it deserves further research.

Alcohol, cardiac arrhythmias and sudden death

Studies in experimental animals have shown varying and apparently opposite effects of alcohol on cardiac rhythm and conduction. Given acutely to non-alcoholic animals, ethanol may even have anti-arrhythmic properties whereas chronic administration clearly increases the animals' susceptibility to cardiac arrhythmias. Chronic heavy alcohol use has been incriminated in the genesis of cardiac arrhythmias in humans. The evidence has come from clinical observations, retrospective case-control studies, controlled studies of consecutive admissions for arrhythmias, and prospective epidemiological investigations. Furthermore, electrophysiological studies have shown that acute alcohol administration facilitates the induction of tachyarrhythmias in selected heavy drinkers. The role of alcohol appears particularly conspicuous in idiopathic atrial fibrillation. Occasionally, ventricular tachyarrhythmias have also been provoked by alcohol intake. Several lines of evidence suggest that heavy drinking increases the risk of sudden cardiac death with fatal arrhythmia as the most likely mechanism. According to epidemiological studies this effect appears most prominent in middle-aged men and is only partly explained by confounding traits such as smoking and social class. The basic arrhythmogenic effects of alcohol are still insufficiently delineated. Subclinical heart muscle injury from chronic heavy use may be instrumental in producing patchy delays in conduction. The hyperadrenergic state of drinking and withdrawal may also contribute, as may electrolyte abnormalities, impaired vagal heart rate control, repolarization abnormalities with prolonged QT intervals and worsening of myocardial ischaemia or sleep apnoea. Most of what we know about alcohol and arrhythmias relates to heavy drinking. The effect of social drinking on clinical arrhythmias in non-alcoholic cardiac patients needs to be addressed further.

Dietary monounsaturated fatty acids promote aortic atherosclerosis in LDL receptor-null, human ApoB100-overexpressing transgenic mice

In mice with genetically engineered high levels of plasma low density lipoprotein (LDL), we tested the hypothesis that an increase in the dietary content of monounsaturated fatty acids but not of polyunsaturated fatty acids would promote atherosclerosis. The mouse model used was an LDL receptor-null, human apoB100-overexpressing strain. Six experimental groups of 19 to 38 mice of both sexes were established when the animals had reached 8 weeks of age. For the next 16 weeks, individual groups were fed either a commercial diet or prepared diets including fat as 10% of energy, with 5 different fatty acid enrichment patterns including the following: saturated (sat), cis and trans monounsaturated (mono), and n-3 and n-6 polyunsaturated (poly). Highly significant differences (ANOVA, P<0. 0001) in LDL cholesterol (in mg/dL) were found, with the rank order at 16 weeks being trans mono (mean, 1390)>sat (922)=cis mono (869)=n-6 poly (868)>n-3 poly (652)>commercial diet (526). Significant elevations in very low density lipoprotein cholesterol were also found in the trans and cis mono and sat groups, and triacylglycerol concentrations were also elevated in all groups. High density lipoprotein cholesterol concentrations were consistently low (20 to 50 mg/dL) in all groups. Highly significant differences (ANOVA, P<0.0001) in atherosclerosis, quantified by measurement of aortic cholesteryl ester concentration (mg/g protein) among dietary fatty acid groups were found, with the order being trans mono (mean, 50.4)>sat (35.6)=cis mono (34.6)>n-6 poly (18. 3)=n-3 poly (9.7)=commercial diet (7.8). Therefore, in this mouse model of hypercholesterolemia, dietary cis or trans monounsaturated fat did not protect against atherosclerosis development, whereas aortic atherosclerosis in either of the polyunsaturated fat groups was significantly less than in the saturated fat group.

Hypothesis: are fatty acid patterns characteristic of essential fatty acid deficiency indicative of oxidative stress?

Several unrelated diseases show plasma and tissue fatty acid patterns characteristic of those seen in Essential Fatty Acid Deficiency Disease (EFADD). A common feature occurring in all these diseases is oxidative stress. We hypothesize that reactive oxygen species or products of oxidative damage, particularly those derived from lipids, act as signal molecules to alter desaturase enzymes and induce the fatty acid patterns characteristic of EFADD.

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.

Endothelium-dependent vasorelaxant effect of trilinolein: mediated by nitric oxide and cyclic GMP

At concentrations ranged from 0.1 nM to 1 microM, trilinolein concentration-dependently relaxed the phenylephrine-induced constriction of isolated rat aorta. Concentration-response curves for the interaction between trilinolein and phenylephrine showed that trilinolein was unlikely a competitive antagonist of phenylephrine. The vasorelaxant effect of trilinolein was dependent on the presence of intact endothelium. Both NG-nitro-L-arginine methyl ester and methylene blue antagonized this vasorelaxant effect. L-arginine partially reversed the effect of L-NAME on trilinolein. Linoleic acid had no vasorelaxant effect. We concluded that trilinolein is an endothelium dependent vasorelaxant and the underlying mechanism could be a stimulation of the nitric oxide and cyclic GMP pathway.

trans isomers of oleic and linoleic acids in adipose tissue and sudden cardiac death

trans isomers of unsaturated fatty acids are formed by biological or industrial hydrogenation. A population case-control study of sudden cardiac death in mean was done to test the hypothesis that trans isomers of oleic acid and linoleic acid increase the risk of sudden cardiac death due to coronary artery disease. In adipose tissue obtained at necropsy from 66 cases of sudden cardiac death and taken from 286 healthy age and sex matched controls, the proportions of trans isomers of oleic and linoleic acid were measured by gas-liquid chromatography. In cases, the mean (SE) percentage of total trans fatty acids (C18:1 plus C18:2), expressed as a proportion of all fatty acids, was significantly lower (2.68 [0.08]%) than in healthy controls (2.86 [0.04]%; p < 0.05). trans C18:1 was 2.1 (0.7)% in cases compared with 2.27 (0.04)% (p < 0.05) in controls. The proportion of all trans isomers of linoleic acid was 0.58 (0.02)% in cases compared with 0.59 (0.01)% in controls (p = 0.98). The estimated relative risk for sudden cardiac death of trans C18:1 and C18:2 fatty acids combined did not differ significantly from 1.0 in relation to the distribution of these trans isomers by quintile in the control population. The relative risk (95% CI) of sudden cardiac death in the top quintile was 0.40 (0.15-1.02) for C18:1 and 1.08 (0.48-2.74) for C18:2 compared with the bottom quintiles of their respective control distributions. When these univariate relations for trans fatty acids were adjusted for coronary risk factors, smoking was the only factor that remained independently associated with risk of sudden cardiac death (2.27 [1.23-4.17]). Overall, there was no evidence of a relation between trans isomers of oleic and linoleic acids combined and sudden cardiac death. However, trans oleic acid was negatively associated with risk of sudden cardiac death, whereas no association with trans forms of linoleic acid was seen. This study does not support the hypothesis that trans isomers increase the risk of sudden cardiac death.

Fatty acid composition of adipose tissue in humans. Implications for the dietary fat-serum cholesterol-CHD issue

Interest in studies of the fatty acid composition of adipose tissue has arised from the dietary fat-serum cholesterol-CHD issue. The fatty acid composition of depot fat reflects that of the diet. Gas chromatography analysis of subcutaneous adipose tissue yield objective and reliable information of the fatty acid composition of the habitual diet of individuals. A relative linoleic acid deficiency, as depicted by low adipose tissue linoleate levels, has not convincingly been demonstrated to be of importance in the aetiology of atherosclerosis or related disorders. Inverse correlation between n-3 fatty acids and coronary artery disease has been reported. Dietary supplementation of n-3 fatty acids may be of relevance, however the risk of hazardous side-effects do exist. In conclusion, a simple reduction of the total fat content of the diet still seems to be the most important strategy for prevention of atherosclerosis.

Effects of glucose and fatty acids on myocardial ischaemia and arrhythmias

Evidence for the utilisation of substrates by the ischaemic myocardium and its dependence for viability on a critical supply of glucose was established many years ago. It was recognised that an excess of free fatty acids (FFA) could increase the severity of ischaemic damage and possibly be arrhythmogenic. But metabolic intervention to improve survival during acute myocardial infarction was not regarded as a priority, perhaps because of uncertainty about its value and the advent of trials of beta-blocker and antiarrhythmic drugs. There has never been an adequate trial of the benefit to the ischaemic or infarcting myocardium of increasing local glucose concentrations or reducing the availability of FFA. We have taken into account new knowledge of the effects of fatty acids on cation channels and brought up to date the arguments for metabolic intervention with glucose-insulin solutions or antilipolytic drugs sustained ischaemia.