Fish intake and arterial wall characteristics in healthy people and diabetic patients

Modulation of endothelial cell responses and vascular function by dietary fatty acids

Healthy and functional endothelial cells play important roles in maintaining vascular homeostasis, whereas endothelial dysfunction initiates and exacerbates vascular disease progression. Interventional studies with dietary fatty acids have shown that these molecules have varying effects on vascular function. It is hypothesized that the actions of dietary fatty acids on vascular function may be mediated in part through endothelial cells. This review summarizes the results of studies that have examined the acute and chronic effects of dietary fatty acids on endothelial function and vascular properties in humans, as well as the potential mechanisms by which n-3 polyunsaturated fatty acids regulate endothelial function. Altogether, this article provides an extensive review of how fatty acids contribute to vascular function through their ability to modulate endothelial cells and discusses relationships between dietary fatty acids and endothelial cells in the context of vascular dysfunction.

The relation of red blood cell fatty acids with vascular stiffness, cardiac structure and left ventricular function: the Framingham Heart Study

Polyunsaturated fatty acids have been associated with beneficial influences on cardiovascular health. However, the underlying mechanisms are not clear, and data on the relations of polyunsaturated fatty acids to subclinical disease measures such as vascular stiffness and cardiac function are sparse and inconclusive. In a large community-based cohort, we examined the relations of omega-3 and other fatty acids to a comprehensive panel of vascular function measures (assessing microvascular function and large artery stiffness), cardiac structure and left ventricular function. Red blood cell (RBC) membrane fatty acid composition, a measure of long-term fatty acid intake, was assessed in participants of the Framingham Offspring Study and Omni cohorts and related to tonometry-derived measures of vascular stiffness and to a panel of echocardiographic traits using partial correlations. Up to n=3055 individuals (56% women, mean age 66 years) were available for analyses. In age- and sex-adjusted models, higher RBC omega-3 content was moderately associated (p≤0.002) with several measures of vascular stiffness and function in a protective direction. However, after multivariable adjustment, only an association of higher RBC omega-3 content with lower carotid-femoral pulse wave velocity (a measure of aortic stiffness) remained significant (r = -0.06, p=0.002). In secondary analyses, higher linoleic acid, the major nutritional omega-6 fatty acid, was associated with smaller left atrial size, even after multivariable adjustment (r = -0.064, p<0.001). In conclusion, in our cross-sectional community-based study, we found several associations consistent with the notion of protective effects of omega-3 and linoleic acid. The clinical significance of these modest associations remains to be elucidated.

Association of total marine fatty acids, eicosapentaenoic and docosahexaenoic acids, with aortic stiffness in Koreans, whites, and Japanese Americans

BACKGROUND

Few previous studies have reported the association of aortic stiffness with marine n-3 fatty acids (Fas) in the general population. The aim of this study was to determine the combined and independent associations of 2 major marine n-3 FAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), with aortic stiffness evaluated using carotid-femoral pulse wave velocity (cfPWV) in Korean, white, and Japanese American men.

METHODS

A population-based sample of 851 middle-aged men (299 Koreans, 266 whites, and 286 Japanese Americans) was examined for cfPWV during 2002-2006. Serum FAs, including EPA and DHA, were measured as a percentage of total FAs using gas chromatography. Multiple regression analysis was used to examine the association of EPA and DHA with cfPWV after adjusting for blood pressure and other confounders.

RESULTS

Mean EPA and DHA levels were 1.9 (SD = 1.0) and 4.8 (SD = 1.4) for Koreans, 0.8 (SD = 0.6) and 2.4 (SD = 1.2) for whites, and 1.0 (SD = 1.0) and 3.2 (SD = 1.4) for Japanese Americans. Both EPA and DHA were significantly higher in Koreans than in the other 2 groups (P < 0.01). Multiple regression analyses in Koreans showed that cfPWV had a significant inverse association with total marine n-3 FAs and with EPA alone after adjusting for blood pressure and other potential confounders. In contrast, there was no significant association of cfPWV with DHA. Whites and Japanese Americans did not show any significant associations of cfPWV with total marine n-3 FAs, EPA, or DHA.

CONCLUSIONS

High levels of EPA observed in Koreans have an inverse association with aortic stiffness.

Palmitic acid increases medial calcification by inducing oxidative stress

BACKGROUND

Aortic medial calcification is a cellular-regulated process leading to arterial stiffness. Although epidemiological studies have suggested an association between the saturation of fatty acids (FA) and arterial stiffness, there is no evidence that saturated FA can induce arterial calcification. This study investigated the capacity of palmitic acid (PA) to induce medial calcification and the signaling pathway(s) implicated in this process.

METHODS

Rat aortic segments and vascular smooth muscle cells (VSMC) were exposed to calcification medium supplemented with PA. In vivo, rats were treated with warfarin to induce calcification and fed a PA-enriched diet.

RESULTS

In vitro and ex vivo, palmitate increases calcification and ROS production. Palmitate increases extracellular-signal-regulated kinase (ERK1/2) phosphorylation and osteogenic gene expression. Inhibition of NADPH oxidase with apocynin or an siRNA prevents these effects. ERK1/2 inhibition attenuates the amplification of osteogenic gene expression and calcification induced by palmitate. In vivo, a PA-enriched diet amplified medial calcification and pulse wave velocity (PWV). These effects are mediated by ROS production as indicated by the inhibition of calcification and PWV normalization in rats concomitantly treated with apocynin.

CONCLUSION

ROS induction by palmitate leads to ERK1/2 phosphorylation and subsequently induces the osteogenic differentiation of VSMC. © 2013 S. Karger AG, Basel.

Omega-3 fatty acids and cognitive function in women

Omega-3 fatty acids (FAs) could play an important role in maintaining cognitive function in aging individuals. The omega-3 FA docosahexaenoic acid is a major constituent of neuronal membranes and, along with the other long-chain omega-3 FAs from fish such as eicosapentaentoic acid, has been shown to have a wide variety of beneficial effects on neuronal functioning, inflammation, oxidation and cell death, as well as on the development of the characteristic pathology of Alzheimer's disease. Omega-3 FAs may prevent vascular dementia via salutary effects on lipids, inflammation, thrombosis and vascular function. Epidemiologic studies have generally supported a protective association between fish and omega-3 FA levels and cognitive decline. Some of the small, short-term, randomized trials of docosahexaenoic acid and/or eicosapentaentoic acid supplementation have found positive effects on some aspects of cognition in older adults who were cognitively intact or had mild cognitive impairment, although little effect was found in participants with Alzheimer's disease. Large, long-term trials in this area are needed.

Noninvasive methods for assessing early markers of atherosclerosis: the role of body composition and nutrition

PURPOSE OF REVIEW

To present the methodology used to assess early atherosclerosis and its application in assessing the impact of body composition and nutrition on the cardiovascular system.

RECENT FINDINGS

Accumulating evidence supports the use of noninvasive markers of subclinical atherosclerosis, namely carotid intima-media thickness, flow-mediated dilatation of the brachial artery and augmentation index or pulse wave velocity, in the prediction of cardiovascular risk, especially in primary prevention settings. These markers reflect early initiation of the atherogenetic process, as well as the impact of the treatment currently used. Factors like smoking cessation, exercise and a balanced nutrition have a remarkable effect on these markers and consequently on vascular function. It is interesting to note that individual nutrients such as lipids, vitamins, antioxidants, ethanol, caffeine and isoflavones are capable of manipulating vascular function, which is depicted in these markers of atherosclerosis.

SUMMARY

A number of noninvasive markers of early atherosclerosis are currently used in order to detect possible initiation of atherosclerotic procedure. Vascular function is greatly affected by nutrition, which might prove to be an alternative to drug therapy for reversing dysfunction of the vessels.

Plasma Fatty Acid Composition as a Predictor of Arterial Stiffness and Mortality

Aortic stiffness predicts cardiovascular mortality and may be influenced by dietary fat composition. The hypothesis that plasma fat composition influences arterial stiffness and subsequent mortality was tested here in a prospective study. A total of 174 randomly sampled nondiabetic participants aged 45 to 74 years were recruited from local populations, stratified by ethnicity and gender, and followed up for mortality. Aortic pulse wave velocity (PWV), blood pressure, and fatty acid composition of plasma lipids were measured at baseline. PWV was associated with increased cardiovascular mortality and inversely related to the proportions of docosahexaenoic (ρ=−0.22; P =0.02) and arachidonic acids (ρ=−0.25; P <0.001) in plasma lipids. Principal component analyses identified a cluster characterized by higher proportions of palmitate, palmitoleic and oleic acid and lower proportions of linoleic, dihomo-γ linolenic, and arachidonic acids. This cluster was positively associated with PWV, central adiposity, smoking, and increased mortality (hazard ratio: 1.13; 95% CI: 1.01 to 1.27). A second cluster, with higher proportions of arachidonic, eicosapentaenoic, and docosahexaenoic and lower proportions of oleic, palmitic, and linoleic acid levels, was associated with lower PWV and systolic blood pressure but also decreased risk of mortality (hazard ratio: 0.57; 95% CI: 0.39 to 0.82), independent of PWV and blood pressure. These data suggest that plasma fatty acid profiles characterized by a higher proportion of long-chain polyunsaturated fatty acids are associated with decreased cardiovascular mortality, independent of the impact of aortic PWV. The results are consistent with an effect of dietary sources of n-3 long-chain polyunsaturates influencing arterial stiffness and mortality.

Vascular compliance in diabetes

The measurement of vascular compliance has assumed increasing importance as a powerful predictor of cardiovascular and all-cause mortality. Arterial stiffness increases with the duration of diabetes, older age, and concomitant hypertension. Hyperglycemia may increase arterial stiffness in diabetes by reducing the bioactivity of endothelium-derived nitric oxide (NO) either by decreasing NO production or inactivating NO by interaction with oxygen-derived free radicals. New approaches to therapy, such as the use of advanced glycation end product "breakers," may potentially benefit patients with diabetes.

Perceptions of recreational fishing boat captains: knowledge and effects of fish consumption advisories

The impacts of fish consumption advisories on recreational and subsistence fishing, particularly in fresh waters, have been examined extensively. By contrast, little attention has focused on organized recreational fishing, such as from party and charter boats, and particularly for salt water fish. We interviewed 93 New Jersey boat captains to determine their knowledge about fish consumption advisories, and whether, in their opinion, clients knew of fish consumption advisories, and whether they thought advisories had an effect on recreational fishing and their businesses. Advisories were ranked by captains as a moderate influence on the success of their business, less so than number of fish caught, strength of the economy, overfishing by commercial boats, and management regulations. Only one boat captain had not heard warnings about eating fish, but what captains said they had heard was mixed in its accuracy and completeness. Clients expect captains to know about fish, and about half of boat captains said clients had asked about the safety of eating fish. Captains who felt advisories were affecting their businesses tended to fish for species without high levels of mercury (except for bluefish) or PCBs, the primary contaminants of concern for state advisories and federal advice. However, these captains worked closer to areas (e.g., Raritan Bay complex and New York Harbor) subject to advisories than did other captains, and were more prone to say that management regulations (e.g., fish size, creel limits, seasons) and marketing and advertising by the industry or state were strong influences on the success of their seasons. Comparing captains who thought advisories had some or great effect (60%) versus those reporting "no effect" (40%), there was no difference in the mean percentage of trips targeting high mercury species such as swordfish and shark. Many captains said they would or might post advisories, but 42% of the boat captains said they would not post consumption warnings if the state provided them. The significant portion (at least 15%) of saltwater fishing supported by these businesses suggests that these captains are an important conduit for future risk communication.

Daily consumption of wild fish and game: exposures of high end recreationists

There has been widespread interest in the exposure of indigenous and subsistence populations to a variety of contaminants through the consumption of wild fish and game, yet there is little information on recreationists. Information on wild fish and game consumption in South Carolina are presented here, data on other sources of animal protein are presented elsewhere. Data are presented for use in probabilistic risk assessment. Fish and deer were the most commonly eaten wild-caught foods. High-end consumers were eating at nearly 10x the median consumption rate for most wild-caught foods. There were significant differences in consumption as a function of age and ethnicity that should be taken into account when conducting risk assessments for the consumption of wild-caught meat and fish. Men consumed more of these foods, while white sportsmen consumed more deer and black sportsmen consumed more fish. Similar data are not generally available, either for the U.S. as a whole, or for specific geographical locations, although there are data for self-caught fish because of the issuance of consumption advisories for U.S. waters.

Cardiovascular disease risk factors and n-3 fatty acid status in the adult population of James Bay Cree

BACKGROUND

Canadian native populations, which traditionally consume large amounts of fish, have lower rates of mortality from heart disease than do Canadian nonnative populations, which have low fish intakes. Fish oils rich in n-3 fatty acids may have a protective effect against cardiovascular disease (CVD) risk factors.

OBJECTIVES

The purposes were to examine the profile of plasma phospholipid concentrations of the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) among James Bay Cree and to verify the relation between these concentrations and CVD risk factors.

DESIGN

The study population consisted of 917 subjects aged 18-74 y who participated in the 1991 Santé Québec Health Survey. Data were obtained through home interviews and clinic visits. Plasma samples were analyzed for phospholipid fatty acid composition.

RESULTS

The mean fish consumption on the day before the survey was 60 g among the adult Cree population. Expressed as a percentage of total fatty acids, relative concentrations of EPA and DHA were 0.65% and 2.80%, respectively. n-3 Fatty acids were higher among coastal residents than among inland residents. A positive association was observed between plasma HDL and n-3 fatty acids. EPA and EPA+DHA were inversely associated with triacylglycerols. Among subjects aged 50-74 y, an inverse association between EPA and EPA:AA and total:HDL cholesterol was observed.

CONCLUSIONS

n-3 Fatty acids may favorably influence some CVD risk factors. The Cree population must be encouraged to maintain their traditional fish-based diet, which may be one of the factors protecting them against mortality from CVD.

Exposure of South Carolinians to commercial meats and fish within their meat and fish diet

There has been considerable interest in the public's exposure to a variety of contaminants through the consumption of wild fish and game, yet there is little information on consumption of commercial meats and fish, or the relationship between commercial and self-caught fish. We conducted a dietary survey in 1999 to estimate exposure levels of 464 individuals from people attending the Palmetto Sportsmen's Classic. Mean consumption was similar for beef, chicken/turkey, and wild-caught fish, and much lower for pork and store-bought fish, and still lower for restaurant fish. There were no ethnic differences in the consumption of most commercial fish and meats, although the differences for chicken approached significance. There were significant ethnic differences in consumption of wild-caught fish. Women ate significantly less of all meat types, except store-bought fish. People over 45 ate less beef than younger people, and people younger than 32 ate significantly more chicken than others. There were no significant differences in consumption patterns as a function of income, except for chicken and wild-caught fish; people with higher incomes ate more chicken than others, and people with lower incomes ate more wild-caught fish than others. When all wild-caught and commercial fish and meats are considered, there are significant differences only for ethnicity and gender. Blacks consume significantly more fish than Whites, and men consume significantly more than women.

Atherosclerosis and omega-3 fatty acids in the populations of a fishing village and a farming village in Japan

The effect of different dietary habits on atherosclerosis was investigated by examining the content of ordinary diets and relevant risk factors through a mass health survey on two village populations in Japan. In total, 261 inhabitants in the fishing village and 209 in the farming village were examined for body build, blood pressure, and blood chemistry. Information on smoking habits and food consumption was obtained using a semi-quantitative item-frequency questionnaire. Pulse wave velocity of the aorta, intima-media thickness of the carotid artery, and atherosclerotic plaques as obtained by ultrasonography were used as measures of atherosclerosis. All measures of atherosclerosis are lower in the fishing village than in the farming village in both men and women. There is a striking 5-8-fold difference in the number of atherosclerotic plaques (P < 0.0001) between the populations. The observed differences in atherosclerosis parallels differences in dietary habits and differences in the serum essential fatty acids. Evaluation of the omega-3 fatty acids over the combined populations reveals a negative association with the number of plaques in the common carotid while the omega-6 fatty acids shows a weak positive association with plaques.

Gender differences in meal patterns: role of self-caught fish and wild game in meat and fish diets

The hypothesis that there are gender differences in consumption patterns of self-caught fish and wild game in the meat and fish diet was examined for 415 people attending the Palmetto Sportsmen's Classic in Columbia, South Carolina. Women were less likely to eat most types of wild fish and game than were men, although there were no gender differences in the percentage eating beef, chicken, pork, and restaurant and store-bought fish. Similarly, women consumed significantly fewer meals of wild-caught fish and game than did men, although the number of meals of most store-bought foods did not differ. Both men and women who ate more meals of fish ate a higher percentage of wild-caught fish than either store-bought or restaurant fish. People with low number of fish and meat meals ate mainly fish; people eating over 30 meals of meat and fish a month ate mainly meat. Only about 9% of those interviewed said that they changed their fish consumption patterns when they, or their spouse, were pregnant. These gender-specific data on protein consumption can be used for exposure assessment and risk management decisions regarding consumption advisories for wild-caught fish and game.

Arterial compliance in obese subjects is improved with dietary plant n-3 fatty acid from flaxseed oil despite increased LDL oxidizability

The compliance or elasticity of the arterial system, an important index of circulatory function, diminishes with increasing cardiovascular risk. Conversely, systemic arterial compliance improves through eating of fish and fish oil. We therefore tested the value of high intake of alpha-linolenic acid, the plant precursor of fish fatty acids. Fifteen obese people with markers for insulin resistance ate in turn four diets of 4 weeks each; saturated/high fat (SHF), alpha-linolenic acid/low fat (ALF), oleic/low fat (OLF), and SHF. Daily intake of alpha-linolenic acid was 20 g from margarine products based on flax oil. Systemic arterial compliance was calculated from aortic flow velocity and aortic root driving pressure. Plasma lipids, glucose tolerance, and in vitro LDL oxidizability were also measured. Systemic arterial compliance during the first and last SHF periods was 0.42 +/- 0.12 (mean +/- SD) and 0.56 +/- 0.21 units based on milliliters per millimeter of mercury. It rose significantly to 0.78 +/- 0.28 (P < .0001) with ALF; systemic arterial compliance with OLF was 0.62 +/- 0.19, lower than with ALF (P < .05). Mean arterial pressures and results of oral glucose tolerance tests were similar during ALF, OLF, and second SHF; total cholesterol levels were also not significantly different. However, insulin sensitivity and HDL cholesterol diminished and LDL oxidizability increased with ALF. The marked rise in arterial compliance at least with alpha-linolenic acid reflected rapid functional improvement in the systemic arterial circulation despite a rise in LDL oxidizability. Dietary n-3 fatty acids in flax oil thus confer a novel approach to improving arterial function.

Fish consumption and the 30-year risk of fatal myocardial infarction

BACKGROUND

Epidemiologic data on the possible benefit of eating fish to reduce the risk of coronary heart disease have been inconsistent. We used data from the Chicago Western Electric Study to examine the relation between base-line fish consumption and the 30-year risk of death from coronary heart disease.

METHODS

The study participants were 1822 men who were 40 to 55 years old and free of cardiovascular disease at base line. Fish consumption, as determined from a detailed dietary history, was stratified (0, 1 to 17, 18 to 34, and > or = 35 g per day). Mortality from coronary heart disease, ascertained from death certificates, was classified as death from myocardial infarction (sudden or nonsudden) or death from other coronary causes.

RESULTS

During 47,153 person-years of follow-up, there were 430 deaths from coronary heart disease; 293 were due to myocardial infarctions (196 were sudden, 94 were nonsudden, and 3 were not classifiable). Cox proportional-hazards regression showed that for men who consumed 35 g or more of fish daily as compared with those who consumed none, the relative risks of death from coronary heart disease and from sudden or nonsudden myocardial infarction were 0.62 (95 percent confidence interval, 0.40 to 0.94) and 0.56 (95 percent confidence interval, 0.33 to 0.93), respectively, with a graded relation between the relative risks and the strata of fish consumption (P for trend = 0.04 and 0.02, respectively). These findings were accounted for by the relation of fish consumption to nonsudden death from myocardial infarction (relative risk, 0.33; 95 percent confidence interval, 0.12 to 0.91; P for trend= 0.007).

CONCLUSIONS

These data show an inverse association between fish consumption and death from coronary heart disease, especially nonsudden death from myocardial infarction.

Medial artery calcification. A neglected harbinger of cardiovascular complications in non-insulin-dependent diabetes mellitus

Medial artery calcification (MAC) is a nonobstructive condition leading to reduced arterial compliance that is commonly considered as a nonsignificant finding. The aim of our study was to investigate the predictive value of MAC in relation to 7-year cardiovascular mortality, coronary heart disease (CHD) events, stroke, and lower extremity amputation in 1059 patients (581 men and 478 women) with non-insulin-dependent diabetes mellitus (NIDDM). At baseline radiologically detectable MAC in femoral arteries was found in 439 patients (41.5%) and intimal-type calcification in 310 diabetic patients (29.3%). The mean fasting plasma glucose at baseline was somewhat higher in women and the duration of diabetes somewhat longer in patients with MAC than in those without, but otherwise the presence of MAC was unrelated to conventional cardiovascular risk factors. During the follow-up 305 diabetic patients died: 208 from cardiovascular disease, 158 from CHD, and 34 from stroke. Furthermore, 58 NIDDM patients underwent their first lower extremity amputation. MAC was a strong independent predictor of total (risk factor-adjusted odds ratio and 95% confidence interval: 1.6; 1.2, 2.2), cardiovascular (1.6; 1.1, 2.2), and CHD (1.5; 1.0, 2.2) mortality, and it was also a significant predictor of future CHD events (fatal or nonfatal myocardial infarction), stroke, and amputation. This relationship was observed regardless of glycemic control and known duration of NIDDM. MAC is a strong marker of future cardiovascular events in NIDDM unrelated to cardiovascular risk factors, supporting the hypothesis that reduced arterial elasticity could lead to clinical manifestations of diabetic macroangiopathy.

Elastic properties and Windkessel function of the human aorta

An understanding of the role of the aortic elastic properties indicates their relevance at several sites of cardiovascular function. Acting as an elastic buffering chamber behind the heart (the Windkessel function), the aorta and some of the proximal large vessels store about 50% of the left ventricular stroke volume during systole. In diastole, the elastic forces of the aortic wall forward this 50% of the volume to the peripheral circulation, thus creating a nearly continuous peripheral blood flow. This systolic-diastolic interplay represents the Windkessel function, which has an influence not only on the peripheral circulation but also on the heart, resulting in a reduction of left ventricular afterload and improvement in coronary blood flow and left ventricular relaxation. The elastic resistance (or stiffness), which the aorta sets against its systolic distention, increases with aging, with an increase in blood pressure, and with pathological changes such as atherosclerosis. This increased stiffness leads to an increase in systolic blood pressure and a decrease in diastolic blood pressure at any given mean pressure, an increase in systolic blood velocity, an increase in left ventricular afterload, and a decrease in subendocardial blood supply during diastole, and must be considered a major pathophysiological factor, for example, in systolic hypertension. The elastic properties of the aortic Windkessel can be assessed in vivo in humans in several ways, most easily by measuring the pulse wave velocity along the aorta. The higher this velocity, the higher the elastic resistance, that is, the stiffness. Other methods depend on assessment of the ratio between pulse pressure and aortic volume changes (delata P/delta V), which can be assessed noninvasively by ultrasonic or tomographic methods. All assessments of vessel stiffness have to take into account the direct effect of current blood pressure, and thus judgements about influences of interventions rely on an unchanged blood pressure. Alternatively, to derive the "intrinsic" stiffness of the aortic wall one has to correct for the effect of the blood pressure present. Recently reports about pharmacologic influences on the elastic properties of the aorta have emerged in the literature.(ABSTRACT TRUNCATED AT 400 WORDS)

Fish oil improves arterial compliance in non-insulin-dependent diabetes mellitus

In a double-blind, placebo-controlled study we investigated the effects of dietary fish oil supplementation on arterial wall characteristics in 20 patients with non-insulin-dependent diabetes mellitus. Estimates reflecting compliance values in the large arteries and more peripheral vasculature, as measured by pulse-contour analysis, improved significantly after 6 weeks of fish oil therapy compared with values recorded at baseline and after 6 weeks' administration of olive oil. The large-artery compliance estimate increased from 1.50 (confidence interval [CI], 1.31 to 1.69) mL/mm Hg at baseline to 1.68 (CI, 1.52 to 1.84) mL/mm Hg after fish oil administration (P < .01). The oscillatory compliance value increased from 0.015 (CI, 0.011 to 0.019) mL/mm Hg at baseline to 0.022 (CI, 0.016 to 0.028) mL/mm Hg after fish oil ingestion (P < .05). No changes occurred in arterial blood pressure, cardiac output, stroke volume, or systemic vascular resistance with either intervention. The improved compliance estimates with fish oil ingestion occurred without altering fasting blood glucose and cholesterol concentrations. These results support the hypothesis that fish oils alter vascular reactivity and favorably influence arterial wall characteristics in patients with non-insulin-dependent diabetes mellitus. These direct vascular effects, expressed at the level of the vessel wall, may contribute to the cardioprotective actions of fish oil in humans.

Aortic compliance measured by non-invasive Doppler ultrasound: application of a personal computer based MkII system and its repeatability

A non-invasive pulse-wave-velocity Doppler ultrasound technique for the assessment of aortic compliance is described. A computational approach for correcting for the effect of non-chronic changes in blood pressure is considered and applied to compliance measurements performed on an age-select cohort of 70 normotensive, normal healthy volunteers. In order to permit the wider availability of the pulse-wave-velocity Doppler ultrasound technique, the authors have developed a MkII system based on a standard 80486/33 MHz IBM compatible WINDOWS based personal computer; real-time spectral analysis being achieved using a relatively inexpensive but fast analogue to digital signal processing card. An overview of the new apparatus is provided and verification work to compare the repeatability of the MkI and MkII systems is described. Medical disorders such as atherosclerosis, diabetes mellitus, familial hypercholesterolaemia, growth hormone deficiency, and Ehlers-Danlos and Marfan's syndromes have all been shown to affect arterial wall compliance. We suggest that the in vivo clinical measurement of blood pressure corrected aortic distensibility using the MkII system may be a useful, reproducible, non-invasive tool for assessing such patients' susceptibility to atheromatous arterial disease as well as for monitoring their response to therapeutic interventions. Measurements in the aorta may be especially pertinent since the natural history of fatty streaks there tends to parallel that in the coronary vasculature thereby potentially affording a convenient surrogate estimate of coronary heart disease.

Epidemiologic studies on Eskimos and fish intake

Chronic diseases such as coronary heart disease and diabetes mellitus are uncommon in Eskimos. Total cholesterol levels are generally low, whereas HDL cholesterol levels are higher than those in an age- and sex-matched Danish population. It is frequently assumed that this is mainly due to their dietary pattern, especially with its high content of n-3 polyunsaturated fatty acids, derived from fish and other seafoods. Dietary surveys have shown that the intake of n-3 polyunsaturated fatty acids in Eskimos is about 14 g/day, whereas it is 3 g/day in Denmark and about 0.2 g/day in the United States. However, the Eskimo diet also differs from the Western diet in other aspects, especially in the intake of saturated fatty acids which is low (9 energy-%). The intake of dietary cholesterol is rather high because of the large consumption of seafood. Individually based studies are better suited to disentangle the health effects of different nutrients, inasmuch as confounding factors can be taken into account. Several cohort studies have now shown that the consumption of 1-2 fish meals per week is associated with a reduction in the risk of coronary heart disease. Recently, similar results concerning glucose intolerance and stroke were also reported. These combined data suggest that a diet low in saturated fatty acids, in combination with a low or moderate level of fish consumption, may be of importance in the prevention of diseases such as coronary heart disease, ischemic stroke, and diabetes mellitus.

The influence of a fish oil high in docosahexaenoic acid on plasma lipoprotein and vitamin E concentrations and haemostatic function in healthy male volunteers

Nine healthy male subjects consumed a daily fish oil supplement providing 2.1 g docosahexaenoic acid (22:6 n-3; DHA) and 0.8 g eicosapentaenoic acid (20:5 n-3; EPA) for 6 weeks. The proportion of EPA and DHA in plasma, erythrocytes, leucocytes and platelet phospholipids was increased by the supplement. Plasma concentration of triacylglycerol and very-low-density-lipoprotein-cholesterol were lowered and those of high-density-lipoprotein (HDL)- and HDL2-cholesterol and apoprotein B were increased. Platelet aggregation and thromboxane B2 production induced by collagen were partially inhibited. Both systolic and diastolic blood pressure fell during treatment and rose following withdrawal of the supplement. Statistically significant reductions in erythrocyte counts, packed cell volume and haemoglobin and increases in total leucocyte and monocyte counts occurred with the supplement. Plasma alpha-tocopherol concentrations fell below the normal range during the period of supplementation. It is suggested that future studies consider components other than EPA in fish oil. Further studies are needed to investigate the extent to which fish oil increases the requirement for antioxidant nutrients.

Fish food, fish oil and cardiovascular disease

During recent years there has been growing interest in the possibility that dietary fish confers some protection against ischaemic heart disease. In four prospective studies, people who ate moderate amounts of fish tend to have a lower mortality from heart disease than persons who ate little or no fish. A randomized controlled trial showed that mortality after myocardial infarction was less among men who were advised to increase their intake of fatty fish than in a control group. Studies of fish oil administered to volunteers suggest that it is the omega-3 fatty acids which are responsible. The effects of fish oil include a reduction in serum triglyceride concentration, a reduction in platelet activity, a reduction in blood pressure, and (in animals) prevention of arrhythmias. Some of these effects require doses much larger than those that would normally be supplied by dietary fish.

Polyunsaturated fatty acids and coronary heart disease

Polyunsaturated fatty acids can be used to replace saturated fatty acids in the diet in order to decrease plasma cholesterol concentrations. Intakes of up to 12% of the energy intake as linoleic do not decrease HDL cholesterol. Animal studies show a decreased incidence of atherosclerosis in animals fed polyunsaturated fats compared with saturated fats. Linoleic acid is required for the synthesis of eicosanoids, which are important in the regulation of platelet aggregation, blood pressure and coronary flow. Small amounts of linoleic acid are required for normal eicosanoid synthesis but larger intakes may lead to overproduction of eicosanoids. Dietary eicosapentaenoic and docosahexaenoic acids, which are provided by fish oils, have a protective effect on experimental myocardial infarction. Epidemiological evidence and secondary prevention trials suggest that these marine-derived polyunsaturates offer protection from CHD. Current advice on fat intake needs to be revised to take into account the neutrality of monounsaturated fatty acids and the need to balance the different types of polyunsaturated fatty acids.