Influence of high-density lipoprotein cholesterol and rheological factors on the sex difference in cardiovascular disease

BACKGROUND

It is well established that the incidence of cardiovascular disease among men is higher than that among women.

OBJECTIVE

To determine whether differences between men and women in terms of a range of conventional and rheological risk factors could explain this sex difference.

DESIGN

This was a population-based cohort study (the Edinburgh Artery Study).

METHODS

Men and women aged 55-74 years (n = 1592) were selected at random from the general population of Edinburgh and followed up for 5 years. Baseline cardiovascular risk factors were measured and related to incidence of disease among men and women.

RESULTS

Men had higher levels of cigarette smoking, haematocrit and blood viscosity and lower levels of low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol and plasma fibrinogen than did women. The incidences of cardiovascular events among men and women were 48.3 and 26.1 per 1000 person-years, respectively. Adjustment for level of HDL cholesterol reduced the male:female ratio for sex-specific incidence rates of cardiovascular events from 1.80 [95% confidence interval (CI) 1.43-2.27] to 1.34 (95% CI 1.04-1.73). This reduction was partially reversed after further adjustment for the other cardiovascular risk factors. The impact of blood viscosity, plasma viscosity and plasma level of fibrinogen on the risk of cardiovascular disease was higher for men than it was for women (multivariate relative risk for blood viscosity were 1.24, 95% CI 1.08-1.43, for men and 0.81, 95% CI 0.61-1.06, for women).

CONCLUSIONS

Levels of HDL cholesterol levels in women being higher than those in men may explain some, but not all, of the sex difference in incidence of cardiovascular disease. Greater susceptibility of men to rheological factors might also be important.

The effect of dietary trans alpha-linolenic acid on plasma lipids and platelet fatty acid composition: the TransLinE study

OBJECTIVE

To collect (i) baseline data and (ii) execute a large multicentre study examining the effect of trans alpha-linolenic acid on its incorporation into plasma lipids and on risk factors for coronary heart disease.

DESIGN

Male volunteers were recruited and the habitual diet assessed by a 4-d weighed record. Fatty acid composition of plasma and platelet lipids were determined by gas chromatography at baseline. After a 6 week run-in period on a trans 'free' diet, male volunteers were randomised to consume 0.6 % of energy trans alpha-linolenic acid or to continue with a diet 'low' in trans alpha-linolenic acid for 6 weeks.

SETTING

Three European university research departments supported by the research and development departments of the food industry.

SUBJECTS

Male volunteers (88) recruited by local advertisement.

METHODS

Replacement of 30 % of the fat of the habitual diet by margarine, oil and foods. Rapeseed oil was deodorised especially to produce the trans 'free' and 'high' trans foods for this study. The incorporation and conversion of trans alpha-linolenic acid into plasma lipids and platelets was assessed by gas chromatography and dietary compliance was verified by 4-d weighed record.

RESULTS

Less trans alpha-linolenic acid isomers are incorporated into human plasma lipids in French volunteers than in Dutch or Scottish volunteers consuming their habitual diets. Trans 'free' alpha-linolenic acid-rich oil can be produced by careful deodorization during refining. The 'high' trans diet provided 1410+/-42 mg/d trans isomers of alpha-linolenic acid, whilst the 'low' trans group consumed 60+/-75 mg/d. The change in plasma lipid and platelet fatty acid composition documented that trans linolenic isomers are incorporated and converted to a trans isomer of eicosapentaenoic acid. Only the 15-trans alpha-linolenic acid is incorporated into plasma cholesteryl esters. The group consuming low trans diet had a slightly higher intake of fat, especially saturated and monounsaturated fat.

CONCLUSIONS

Trans 'free' rapeseed oil, rich in alpha-linolenic acid, can be produced by careful deodorization. Dietary records show good compliance. Dietary trans isomers of alpha-linolenic acid are incorporated in plasma lipids and converted to long-chain polyunsaturated fatty acids. Their effects on risk factors for coronary heart disease and their metabolism will be reported elsewhere.

SPONSORSHIP

European Commission (FAIR 95-0594 grant). European Journal of Clinical Nutrition (2000) 54, 104-113

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.

Functional food science and the cardiovascular system

Cardiovascular disease has a multifactorial aetiology, as is illustrated by the existence of numerous risk indicators, many of which can be influenced by dietary means. It should be recalled, however, that only after a cause-and-effect relationship has been established between the disease and a given risk indicator (called a risk factor in that case), can modifying this factor be expected to affect disease morbidity and mortality. In this paper, effects of diet on cardiovascular risk are reviewed, with special emphasis on modification of the plasma lipoprotein profile and of hypertension. In addition, dietary influences on arterial thrombotic processes, immunological interactions, insulin resistance and hyperhomocysteinaemia are discussed. Dietary lipids are able to affect lipoprotein metabolism in a significant way, thereby modifying the risk of cardiovascular disease. However, more research is required concerning the possible interactions between the various dietary fatty acids, and between fatty acids and dietary cholesterol. In addition, more studies are needed with respect to the possible importance of the postprandial state. Although in the aetiology of hypertension the genetic component is definitely stronger than environmental factors, some benefit in terms of the development and coronary complications of atherosclerosis in hypertensive patients can be expected from fatty acids such as alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid. This particularly holds for those subjects where the hypertensive mechanism involves the formation of thromboxane A2 and/or alpha 1-adrenergic activities. However, large-scale trials are required to test this contention. Certain aspects of blood platelet function, blood coagulability, and fibrinolytic activity are associated with cardiovascular risk, but causality has been insufficiently proven. Nonetheless, well-designed intervention studies should be initiated to further evaluate such promising dietary components as the various n-3 and n-6 fatty acids and their combination, antioxidants, fibre, etc. for their effect on processes participating in arterial thrombus formation. Long-chain polyenes of the n-3 family and antioxidants can modify the activity of immunocompetent cells, but we are at an early stage of examining the role of immune function on the development of atherosclerotic plaques. Actually, there is little, if any, evidence that dietary modulation of immune system responses of cells participating in atherogenesis exerts beneficial effects. Although it seems feasible to modulate insulin sensitivity and subsequent cardiovascular risk factors by decreasing the total amount of dietary fat and increasing the proportion of polyunsaturated fatty acids, additional studies on the efficacy of specific fatty acids, dietary fibre, and low-energy diets, as well as on the mechanisms involved are required to understand the real function of these dietary components. Finally, dietary supplements containing folate and vitamins B6 and/or B12 should be tested for their potential to reduce cardiovascular risk by lowering the plasma level of homocysteine.

Effects of the long acting beta agonist formoterol on asthma control in asthmatic patients using inhaled corticosteroids. The Netherlands and Canadian Formoterol Study Investigators

BACKGROUND

The long acting beta 2 agonist formoterol has proved to be an effective bronchodilator with a prolonged action of 12-14 hours. However, the precise role of formoterol in the maintenance treatment of asthma is still under debate. A study was performed to investigate the efficacy and safety of treatment with formoterol for six months in subjects with asthma.

METHODS

In a multicentre double blind, placebo controlled, parallel group study 239 subjects with mild to moderate asthma were randomly assigned to treatment with either inhaled formoterol 24 micrograms twice daily (n = 125) or placebo (n = 114) during eight months. The study consisted of a four week run in period, a 24 week treatment period, and a four week washout period. All subjects were using regular inhaled corticosteroids (100-3200 micrograms daily) but were still needing at least five inhalations of short acting beta 2 agonist per week for symptom relief. The study was performed in 10 outpatient clinics in Canada, and five outpatient clinics and one coordinating centre for 44 Dutch general practitioners in The Netherlands. Twice daily self-reported peak expiratory flow (PEF) measurements, symptom scores, and rescue beta 2 agonist use during the last 28 treatment days compared with baseline values were used as main outcome measures. Spirometric values were measured at entry, at the start of treatment, after four, 12 and 24 weeks of treatment, and after four weeks washout.

RESULTS

One hundred and twenty five subjects received formoterol 24 micrograms twice daily via Turbohaler and 114 received placebo. Baseline FEV1 was 67.1% predicted and mean bronchodilator reversibility was 26%. The mean total asthma symptom score was 3.6 (maximum possible 21). A significant decrease in symptoms in favour of formoterol (difference from placebo -0.64, 95% CI -0.04 to -1.23, p = 0.04) was observed. Compared with placebo, morning PEF increased (difference from placebo 28 l/min, 95% CI 18.3 to 37.7, p = 0.0001) and the use of short acting beta 1 agonists decreased (daytime difference from placebo -1.1 inhalation, 95% CI -1.4 to -0.7, p = 0.0001) in the formoterol group. PEF returned to baseline following discontinuation of formoterol, as did asthma symptom scores. Thirty three patients treated with formoterol and 32 treated with placebo required treatment with prednisolone during the study (58 and 55 courses, respectively).

CONCLUSIONS

Adding formoterol 24 micrograms twice daily by Turbohaler to inhaled corticosteroids was effective in improving symptom scores and morning PEF, and decreasing the use of rescue beta 2 agonists. There was no apparent loss of asthma control during 24 weeks of treatment with formoterol.

Quantitative gas chromatography-mass spectrometry isomer-specific measurement of hydroxy fatty acids in biological samples and food as a marker of lipid peroxidation

We have developed a capillary gas chromatography-mass spectrometry method for the quantitative analysis of individual positional isomers of monohydroxy fatty acids derived from linoleic, arachidonic, eicosapentaenoic, or docosahexaenoic acid. Peroxidation of a particular polyunsaturated fatty acid results already in a complex mixture of positional isomers of hydroperoxy and hydroxy fatty acids. Catalytic hydrogenation of lipid extracts produces stable saturated hydroxy lipids from the complex mixtures typical of oxidized biological samples, simultaneously simplifying the analytical problem and eliminating oxidation artifacts. After saponification and methylation, monohydroxy fatty acid methyl esters are purified by solid-phase extraction and partially resolved using a CP Sil 19 column following on-column derivatization of the hydroxy groups with tetramethylammonium hydroxide. The resulting methoxy fatty acid methyl esters are subjected to electron impact mass spectroscopy. Two characteristic ions are produced for each positional isomer. Quantitative measurements were achieved by using odd chain C17 and C19 monohydroxy fatty acids as internal standards. The limit of detection of individual hydroxy fatty acid isomers is dependent on the total number of ions monitored. Monitoring 11 pairs of ions simultaneously gives limits of detection of 10 ng. Sensitivity is much higher by monitoring fewer ions and as little as 0.2 ng of a single isomer can be detected. The method has been applied for the quantitative analysis of hydroxy (plus hydroperoxy) fatty acids in plasma, adipose tissue, oils, and foods. To date over 1000 samples have been analyzed using the method described in this paper.

Association between toenail selenium and risk of acute myocardial infarction in European men. The EURAMIC Study. European Antioxidant Myocardial Infarction and Breast Cancer

The association between selenium status and risk of acute myocardial infarction was examined in a multicenter case-control study in 10 centers from Europe and Israel in 1991-1992. Selenium in toenails was assessed for 683 nonfatal male cases with first acute myocardial infarction and 729 controls less than 70 years of age. Median toenail selenium content was 0.553 microgram/g for cases and 0.590 microgram/g for controls. After adjustment for age, center, and smoking, the odds ratio for myocardial infarction in the highest quintile of selenium as compared with the lowest was 0.63 (95 percent confidence interval 0.37-1.07, p for trend = 0.08). The observed inverse trend was somewhat stronger when the authors adjusted for vitamin E status (p = 0.05). Analysis stratified for smoking habits showed an inverse association in former smokers (odds ratio for the 75th-25th percentile contrast = 0.63 (95 percent confidence interval 0.43-0.94)), but not in current smokers (odds ratio = 0.97 (0.71-1.32)) or in those who had never smoked (odds ratio = 1.55 (0.87-2.76)). Analysis stratified by center showed a significant inverse association between selenium levels and risk of myocardial infarction for Germany (Berlin) only (75th to 25th percentile odds ratio = 0.62 (95 percent confidence interval 0.42-0.91)), which was the center with the lowest selenium levels. It appears that the increased risk of acute myocardial infarction at low levels of selenium intake is largely explained by cigarette smoking; selenium status does not appear to be an important determinant of risk of myocardial infarction at the levels observed in a large part of Europe.

Effect of mivazerol on myocardial lactate production, blood flow and electrocardiographic signs of ischaemia induced by coronary artery ligation in the anaesthetised dog

Ischaemic injury in a number of animal models is reduced by mivazerol (2-hydroxy-3-[(1-H-imidazol-4-yl) methyl]-benzamide, CAS 125472-02-8). This effect was accompanied by a reduction in heart rate. The effect of mivazerol on myocardial blood flow and lactate production in the ischaemic myocardium was examined at constant heart rate by right atrial pacing in an anaesthetised open-chest dog model. Three periods of ischaemic were induced by coronary occlusion for 5 min. The first (sham) and the second in the absence of the drug and the third 15 min after 10 nmol/kg i.v. Arteriovenous differences in plasma lactate using a local vein and coronary sinus draining the ischaemic and non-ischaemic myocardium, respectively, were measured before and after 4 min after coronary occlusion. Blood flow (microspheres) was determined at 3 min of ischaemia. Mivazerol reduced lactate production by the ischaemic area from 2.6 +/- 1.2 to 1.5 +/- 0.9 mmol/l (paired t-test, p < 0.01), but blood flow to the ischaemic sub-endocardium was not changed: 0.19 +/- 0.1 vs 0.21 +/- 0.12 ml.g-1.min-2. Mean ST segment elevation tended to be reduced 1.6 +/- 1.0 vs 3.8 +/- 3.0 mV (one-sided paired t-test, p = 0.05). Mivazerol exerts its anti-ischaemic effect at least in part by a reduction in ischaemic lactate production but not by increasing ischaemic blood flow.

Inter-relationships of plasma fibrinogen, low-density lipoprotein cholesterol, cigarette smoking and the prevalence of cardiovascular disease

BACKGROUND

The magnitude of the cardiovascular risk associated with plasma fibrinogen concentration is influenced separately by cigarette smoking and by low-density lipoprotein (LDL) cholesterol levels. The effects of combinations of these factors on risk and the extent to which inclusion of the plasma fibrinogen level further refines the risks associated with smoking and high LDL cholesterol levels are not known.

OBJECTIVE

To determine the inter-relationships among all of the three factors smoking, LDL cholesterol level and fibrinogen level with respect to the occurrence of cardiovascular disease.

METHODS

The study was part of the Edinburgh Artery Study, which was a cross-sectional random sample survey of 1592 men and women aged 55-74 years. The assessment of cardiovascular disease included recall of diagnosis by a doctor of angina or myocardial infarction, intermittent claudication determined by a questionnaire and measurement of ankle systolic blood pressure.

RESULTS

The odds ratio for disease in smokers in the top tertiles of plasma fibrinogen and LDL cholesterol levels was 7.7 (95% confidence interval 3.0-19.8; P < or = 0.001). Neither a multiplicative nor a synergistic effect of the three factors on the odds of disease was observed but the level of each contributed to the risk. For example, in current smokers in the bottom tertile of LDL cholesterol level, the odds of disease were 6.1 (95% confidence interval 2.2-17.0; P < or = 0.001) in the top tertile, 2.9 (95% confidence interval 1.0-8.6; P < or = 0.05) in the middle tertile and 1.6 (95% confidence interval 0.5-4.8; P > 0.05) in the bottom tertile of plasma fibrinogen level. Subjects in the bottom tertile of plasma fibrinogen level did not have significantly elevated (P < 0.05) risks irrespective of LDL cholesterol levels and smoking status.

CONCLUSION

The incorporation of plasma fibrinogen level permitted more precise delineation of the odds of disease within categories of smoking and LDL cholesterol concentration. These relationships need to be investigated further in prospective studies.

Cardiovascular protection by oestrogen is partly mediated through modulation of autonomic nervous function

Experimental studies have provided evidence that the autonomic nervous activity is modulated by oestrogen. Such modulation at central and peripheral levels tends to suppress sympathetic but elevate parasympathetic tone to the cardiovascular system. Thus, available data support the view that cardiovascular protection by oestrogen may, at least in part, be mediated by its influence on autonomic nervous function.

Association between beta-carotene and acute myocardial infarction depends on polyunsaturated fatty acid status. The EURAMIC Study. European Study on Antioxidants, Myocardial Infarction, and Cancer of the Breast

Because antioxidants may play a role in the prevention of coronary heart disease by inhibiting the peroxidation of polyunsaturated fatty acids (PUFAs), the combined association of diet-derived antioxidants and PUFAs with acute myocardial infarction (MI) was investigated. This multicenter case-control study included 674 patients and 725 control subjects in eight European countries and Israel. Fatty acid composition and alpha-tocopherol and beta-carotene levels were determined in adipose tissue; selenium level was determined in toenails. For alpha-tocopherol no association with MI was observed at any PUFA level. The overall multivariate odds ratio (OR) for low (10th percentile) versus high (90th percentile) beta-carotene was 1.98 (95% confidence interval [CI], 1.39 to 2.82). The strength of this inverse association with MI was dependent on PUFA levels (in tertiles): for low PUFA, the OR for low versus high beta-carotene was 1.79 (95% CI, 0.98 to 3.25), for medium PUFA the OR was 1.76 (95% CI, 1.00 to 3.11), and for high PUFA 3.47 (95% CI, 1.93 to 6.24). For selenium increased risk was observed only at the lowest PUFA tertile (OR, 2.49; 95% CI, 1.22 to 5.09). This interaction between selenium and PUFAs was not significant and may at least partly be explained by a higher proportion of smokers at the low PUFA level. These findings support the hypothesis that beta-carotene plays a role in the protection of PUFAs against oxidation and subsequently in the protection against MI. No evidence was found that alpha-tocopherol or selenium may protect against MI at any level of PUFA intake.

Lack of effect of recombinant platelet-derived growth factor on human neutrophil function

Platelet-derived growth factor (PDGF) has been reported to induce chemotaxis, degranulation, and superoxide anion generation, and to increase the expression of CD11b/CD18 in human neutrophils; hence, it has been proposed as an important regulator of neutrophil function. Most of the studies on PDGF, however, have been complicated by the use of nonrecombinant PDGF or the use of mixed leukocyte cell preparations. Assessment of the effects of recombinant human PDGF-AB or -BB which display agonist activity against both PDGF receptor subtypes failed to demonstrate any effect of this peptide on neutrophil shape change, respiratory burst activity, CD11/CD18, or CD62-L expression, inositol 1,4,5-trisphosphate accumulation, or phosphorylation of mitogen-activated protein kinase. This apparent lack of effect of PDGF was consistent with our findings that neutrophils display no specific 125I-PDGF-AB or -BB binding and lack detectable mRNA for PDGF alpha-receptor and beta-receptors. These data indicate that human neutrophils do not possess functional PDGF receptors and question previous reports of a functional effect of this peptide in these cells.

Lack of effect of recombinant platelet-derived growth factor on human neutrophil function

Platelet-derived growth factor (PDGF) has been reported to induce chemotaxis, degranulation, and superoxide anion generation, and to increase the expression of CD11b/CD18 in human neutrophils; hence, it has been proposed as an important regulator of neutrophil function. Most of the studies on PDGF, however, have been complicated by the use of nonrecombinant PDGF or the use of mixed leukocyte cell preparations. Assessment of the effects of recombinant human PDGF-AB or -BB which display agonist activity against both PDGF receptor subtypes failed to demonstrate any effect of this peptide on neutrophil shape change, respiratory burst activity, CD11/CD18, or CD62-L expression, inositol 1,4,5-trisphosphate accumulation, or phosphorylation of mitogen-activated protein kinase. This apparent lack of effect of PDGF was consistent with our findings that neutrophils display no specific 125I-PDGF-AB or -BB binding and lack detectable mRNA for PDGF alpha-receptor and beta-receptors. These data indicate that human neutrophils do not possess functional PDGF receptors and question previous reports of a functional effect of this peptide in these cells.

Adipose tissue isomeric trans fatty acids and risk of myocardial infarction in nine countries: the EURAMIC study

Dietary isomeric trans fatty acids-mainly produced by hydrogenation of oils-are suspected of increasing the risk of coronary heart disease. Dietary trans fatty acid intake is reflected in the fatty acid composition of adipose tissue. In an international multicentre study in eight European countries and Israel (EURAMIC), adipose tissue aspiration samples were obtained from 671 men with acute myocardial infarction (AMI), aged 70 years or less, and 717 men without a history of AMI (controls). The proportion of fatty acids, including isomeric trans monoenoic fatty acids with 18 carbon atoms (C18:1), was determined by gas chromatography. Although there were considerable differences between countries in mean (SD) proportion of adipose tissue C18:1 trans fatty acids, there was no overall difference between cases (1.61 [0.92]%) and the controls (1.57 [0.86]%). The risk of AMI did not differ significantly from 1.0 over quartiles of adipose C18:1 trans fatty acids: the multivariate odds ratio was 0.97 (95% CI 0.56-1.67) for the highest versus lowest quartile. After exclusion of subjects from Spanish centres because they had far lower proportions of adipose trans fatty acids than subjects from other countries, there was a tendency to increased risk of AMI in the upper quartiles of C18:1 trans; however, the trend was not statistically significant. Our results reflect considerable differences between countries in dietary intake of trans fatty acids but do not suggest a major overall effect of C18:1 trans fatty acids on risk of AMI. We cannot exclude the possibility that trans fatty acids have a significant impact on risk of AMI in populations with high intake.

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.

Color Doppler myocardial imaging: a new technique for the assessment of myocardial function

Color Doppler myocardial imaging is a new technique that has been developed specifically to allow color Doppler imaging of myocardial wall motion rather than blood pool imaging. Such a technique has the potential to interrogate velocities, accelerations, and Doppler signal strength within the myocardial wall. Moreover, the concomitant enhancement of the myocardial Doppler signal after an intravenous injection of a transpulmonary echocardiographic contrast agent could permit the noninvasive assessment of regional myocardial perfusion. Thus this new imaging modality could be a valuable adjunct to the ultrasound assessment of myocardial ischemia.

Sex differences in susceptibility to etiologic factors for peripheral atherosclerosis. Importance of plasma fibrinogen and blood viscosity

Cardiovascular risk factors in men, such as cigarette smoking, hypercholesterolemia, and hypertension, also increase risk in women, but the relative susceptibility to risk factors between the sexes is not established. Our aim was to investigate a wide range of possible etiologic factors in a single population study and identify those that were more strongly related to peripheral atherosclerosis in men or women. We studied personal factors (age and social class), lifestyle factors (smoking, exercise, alcohol intake, and dietary nutrients), and intermediary factors (obesity, diabetes, serum lipids, coagulation, and rheological factors). In the Edinburgh Artery Study in 1988 we measured cardiovascular risk factors in a random population sample of 1592 men and women aged 55 to 74 years. The ankle-brachial pressure index (ABPI), which is inversely related to the degree of peripheral atherosclerosis, was assessed in each subject. Lifetime cigarette smoking was correlated with a lower ABPI equally in men and women (r = -.27, P < .001). Dietary nutrients and alcohol intake were not related differently between the sexes with ABPI. However, recall of strenuous and moderate leisure time exercise during the age range of 35 to 45 years was related more strongly to a higher ABPI in men than in women (P < .05). Plasma fibrinogen, plasma viscosity, and blood viscosity were the only intermediary factors that had stronger univariate correlations with lower ABPI in men than in women. On multivariate analysis, the sex differences persisted for plasma fibrinogen (P < .05) and blood viscosity (P < .001); high-density lipoprotein cholesterol was related to ABPI in men only (sex difference, P < .1).(ABSTRACT TRUNCATED AT 250 WORDS)

Sex differences in the parasympathetic nerve control of rat heart

1. As it has been shown that oestrogen enhances the cholinergic muscarinic activity in the central nervous system, we studied sex differences in the response to parasympathetic nervous stimulation in the rat heart using in vivo and in vitro preparations. 2. In in situ perfused, innervated hearts, stimulation of bilateral vagus nerves (15 Hz with 1 mumol/L physostigmine) inhibited sympathetic nerve stimulation (5 Hz) induced noradrenaline release to a greater extent in female than in male rats (54 +/- 5 vs 72 +/- 5% of control). Similarly, vagus nerve stimulation at 1-20 Hz reduced heart rate (HR) more in females than males, and this sex difference became more marked in the presence of physostigmine. The chronotropic effect of vagal stimulation was attenuated after ovariectomy but potentiated after castration when compared with sham-operated controls. In contrast, the muscarinic agonist methacholine reduced neural NA release and HR equally well in both sexes. 3. In anaesthetized rats, reduction in HR and mean arterial pressure by vagus nerve stimulation (1-20 Hz) was more pronounced in females than in males after inhibition of acetylcholinesterase with physostigmine. 4. The results indicate that activation of parasympathetic nerve leads to greater presynaptic and postsynaptic effects in female than in male rat hearts, presumably due to a higher level of acetylcholine release following nerve activation.

The prevalence of smoking amongst patients attending an out-patient lipid clinic

The smoking habits of 184 attendees (mean age 47 years, 101 men) at a hospital-based lipid clinic were reviewed in conjunction with a measurement of serum thiocyanate level which is a marker for smoking over the previous two weeks. Advice against smoking is routinely given at the clinic. We found 84 (46%) patients to remain active smokers of whom 78 admitted to smoking and 6 were identified on the basis of a serum thiocyanate level greater than 100 micromol/l. Smoking was more prevalent amongst women than men (52% v 33%). We have identified a high proportion of patients attending an outpatient lipid clinic as remaining active smokers despite receiving advice against cigarette smoking. This emphasises the need for more effective counselling against smoking in a multiple risk factor intervention approach to ischaemic heart disease.

The long-term effects of metoprolol and epanolol on tissue-type plasminogen activator and plasminogen activator inhibitor 1 in patients with ischaemic heart disease

This double-blind, randomized parallel group study investigated the effect of 6 months beta-adrenoceptor antagonist therapy with either metoprolol (beta 1-selective without intrinsic sympathomimetic activity [ISA]) or epanolol (beta 1-selective with ISA) on markers of endogenous fibrinolysis in 20 patients with chronic stable angina receiving concurrent treatment with nifedipine. Neither drug had an effect on tissue-type plasminogen activator or plasminogen activator inhibitor type 1 (PAI-1). A significant correlation between fasting insulin and PAI-1 has previously been described and was confirmed in this study. The group treated with metoprolol showed a significant rise in fasting insulin after 6 months with no change in PAI-1. This suggests that the previously described link between these two may not be causal.

Hypoxia-stimulated glycerol production from the isolated, perfused rat heart is mediated by non-adrenergic mechanisms

Factors controlling hypoxia-induced myocardial glycerol release were studied in isolated, perfused rat hearts. A constant coronary flow rate 10 ml g-1 min-1 was maintained. The perfusion buffer was gassed with O2-N2 mixtures containing 5% CO2. The O2:N2 ratios were normoxia 95:0, hypoxia 30:65, and severe hypoxia 10:85 (v/v). Glycerol and lactate release were stimulated during a 30-min period of either hypoxia or severe hypoxia but remained constant during normoxia. Tissue glycerol-3-phosphate levels were increased after 30 min hypoxia compared with after a similar period of normoxic perfusion (p < 0.01) and further increased after severe hypoxia (p < 0.01 vs hypoxia). beta-Adrenoceptors remained sensitive to isoprenaline during hypoxia, demonstrated by an increase in glycerol release over a 30-min period of isoprenaline infusion from 897 +/- 317 to 1771 +/- 307 nmol g-1 wet weight (p < 0.05). The isoprenaline-induced increase in glycerol release during hypoxia was inhibited by both atenolol and timolol (1 x 10(-5) M). In contrast, beta-adrenoceptor blockade using these drugs failed to reduce glycerol release induced by either hypoxia or severe hypoxia. Both drugs attenuated the rise in glycerol-3-phosphate during hypoxia. Chronic denervation by pretreatment with 6-hydroxydopamine reduced hypoxia-stimulated glycerol release by only 30%. Thus, a major part of hypoxia-induced glycerol release is mediated by non-adrenergic mechanisms. The results of this study bring into question the validity of the use of glycerol production during hypoxia as a reliable measure of myocardial lipolysis.