Platelet functions in relation to diet and serum lipids in British farmers

Mineral Intake and Cardiovascular Disease, Cancer, and All-Cause Mortality: Findings from the Golestan Cohort Study

Associations between mineral intake and mortality in non-Western countries have not been studied adequately. This study evaluated these associations in the Golestan Cohort Study, featuring a Middle Eastern population. The mineral intake was estimated from the baseline food frequency questionnaire, adjusted by using the nutrient density method, and divided into quintiles. We used Cox proportional hazards models to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the mortality. We analyzed 41,863 subjects with a mean age of 51.46 ± 8.73 years at the baseline. During 578,694 person-years of follow-up (median: 14.1 Years), 7217 deaths were recorded. Dietary calcium intake was inversely associated with the all-cause mortality (HRQ5 vs. Q1 = 0.91, 95%CI = 0.85-0.99). We observed significant associations between calcium (HRQ5 vs. Q1 = 0.82, 95% CI = 0.73-0.93), copper (HRQ5 vs. Q1 = 1.11, 95% CI = 0.99-1.26), and selenium intake (HRQ5 vs. Q1 = 1.14, 95% CI = 1.01-1.29) and CVD mortality. Dietary phosphorus (HRQ5 vs. Q1 = 0.81, 95%CI = 0.69-0.96) and copper intake (HRQ5 vs. Q1 = 0.84, 95%CI = 0.71-0.99) were inversely associated with cancer mortality. In this study within a Middle Eastern population, a higher dietary intake of calcium exhibited an inverse association with all-cause mortality. Furthermore, nuanced associations were observed in the cause-specific mortality, suggesting potential avenues for dietary interventions and emphasizing the importance of considering dietary factors in public health strategies.

Camel platelet aggregation responses and the antiplatelet effect of camel urine: comparison between black and white camels

Human black and white-skinned races exhibited differences in platelet aggregation. However, no similar differences were described on white and black camels. This study aims to find out whether black and white camel skin color is associated with differences in camel platelet aggregation responses or the platelet inhibitory activity of their urine. Platelet aggregometry was undertaken in black and white camels, in response to adenosine diphosphate (ADP), Arachidonic acid (AA), Epinephrine (EPN), collagen, and Ristocetin. Platelet aggregometry was also done in human PRP after the addition of raw and serially diluted (1:2, 1:4 and 1:8) white and black camel urines. In black camels, platelet aggregation in response to ADP, AA, EPN and Collagen were slightly higher than in white camels. The addition of raw camel urine collected from mixed population of black and white camels to human platelets resulted in inhibition of platelet aggregation. Serial dilutions of camel urine (1:2, 1:4, 1:8) resulted initially in loss of the inhibitory action followed by enhancement of human platelet aggregation responses to ADP and AA. The neat and serially diluted white camel urines caused more inhibition of the human platelet aggregation responses than the black camel urines. This study uncovered a new biological feature in the camels. The camel skin color seems to be associated with different platelet aggregation responses as well as different antiplatelet activity of the camel urine; white camel urine was found to cause more platelet inhibition than black camel urine.

Platelet lipidomics: modern day perspective on lipid discovery and characterization in platelets

Lipids are diverse families of biomolecules that perform essential structural and signaling roles in platelets. Their formation and metabolism are tightly controlled by enzymes and signal transduction pathways, and their dysregulation leads to significant defects in platelet function and disease. Platelet activation is associated with significant changes to membrane lipids, and formation of diverse bioactive lipids plays essential roles in hemostasis. In recent years, new generation mass spectrometry analysis of lipids (termed lipidomics) has begun to alter our understanding of how these molecules participate in key cellular processes. Although the application of lipidomics to platelet biology is still in its infancy, seminal earlier studies have shaped our knowledge of how lipids regulate key aspects of platelet biology, including aggregation, shape change, coagulation, and degranulation, as well as how lipids generated by platelets influence other cells, such as leukocytes and the vascular wall, and thus how they regulate hemostasis, vascular integrity, and inflammation, as well as contribute to pathologies, including arterial/deep vein thrombosis and atherosclerosis. This review will provide a brief historical perspective on the characterization of lipids in platelets, then an overview of the new generation lipidomic approaches, their recent application to platelet biology, and future perspectives for research in this area. The major platelet-regulatory lipid families, their formation, metabolism, and their role in health and disease, will be summarized.

Ethnic variations in platelet aggregation-comparison between saudi arabs, westerners (europeans and americans), asians and africans

SUMMARY. Platelet aggregation responses to adenosine diphosphate, adrenaline, collagen, arachidonic acid and ristocetin were measured in healthy subjects, predominantly blood donors residing in Riyadh, the capital city of Saudi Arabia. They were divided according to ethnic origin into Saudi Arabs n = 517, Westerners (Europeans and Americans) n = 93, South East Asians (Koreans and Filipinos) n = 154, and West Africans n = 77. Significant differences in the aggregation responses were found between the four ethnic groups. Saudi Arabs and Westerners showed better aggregation responses to ADP than Asians and Africans. Aggregability in response to collagen was greater in Saudis and Africans than in Westerners and Asians. There was remarkable inhibition of adrenaline induced-aggregation in Asians while other populations produced comparable results. Inhibited responses to arachidonic acid were most prevalent among Westerners and to a lesser extent in Asians than in Saudis and Africans. Ristocetin-induced aggregation was significantly inhibited in Africans and less so in Asians and Arabs and most pronounced in Westerners. These variations in platelet aggregability, which could not be related to blood group distribution, smoking habits, income, physical parameters of height and weight may be due to genetic and dietary factors. These ethnic differences should be taken into account when assessing aggregation responses in patients.

Wine in moderation: how could and should recentin vitroandin vivodata be interpreted?

In Australia, death from cardiovascular diseases accounts for approximately 25% of all deaths. Epidemiological data suggest that the moderate consumption of alcoholic beverages may significantly reduce the risk of death from cardiovascular disease and indeed from all causes. Data also suggest that the ethanol component common to all alcoholic beverages confers primarily this protection and other data suggests that the wine-specific polyphenolic compounds confer additional protective effects. Is the amount and pattern of consumption really relevant? In vitro and in vivo studies have been undertaken recently, the results of which have both weakened and strengthened the traditional arguments cited on the type, amount and pattern of the consumption of alcoholic beverages. For example, the components of wine may act in concert rather than individually for cancer and cardioprotection, and more rather than less may be required for activity. This paper reviews relevant studies and evaluates critically their results, putting them in context with actual dietary practices rather than guidelines and policies.

Dietary intake of calcium in relation to mortality from cardiovascular disease: the JACC Study

BACKGROUND AND PURPOSE

No prospective studies have examined the association between calcium intake and the risk of cardiovascular disease in Japanese populations with a low mean calcium intake.

METHODS

Between 1988 and 1990, 110,792 Japanese subjects (46,465 men and 64,327 women) 40 to 79 years of age without a history of stroke, coronary heart disease, or cancer, completed a lifestyle questionnaire including food intake frequency under the Japan Collaborative Cohort (JACC) Study for Evaluation of Cancer Risk Sponsored by Monbusho. By the end of 1999, after 515,029 person years of follow-up, 566 deaths from stroke (101 subarachnoid hemorrhages, 140 intraparenchymal hemorrhages, and 273 ischemic strokes) and 234 deaths from coronary heart disease had been documented.

RESULTS

The intake of total calcium tended to be inversely associated with mortality from total stroke but not from coronary heart disease or total cardiovascular disease for men and women. The inverse association with dairy calcium intake was apparent for total stroke, both hemorrhagic and ischemic. The multivariate relative risk for men with highest versus lowest quintiles of dairy calcium intake was 0.53 (95% CI, 0.34 to 0.81) for total stroke, 0.46 (0.23 to 0.91) for hemorrhagic stroke, and 0.53 (0.29 to 0.99) for ischemic stroke; corresponding relative risks for women were 0.57 (0.38 to 0.86), 0.51 (0.28 to 0.94), and 0.50 (0.27 to 0.95).

CONCLUSIONS

Dietary calcium intake from dairy products was associated with reduced mortality from stroke for Japanese men and women.

Moderate alcohol consumption and changes in postprandial lipoproteins of premenopausal and postmenopausal women: a diet-controlled, randomized intervention study

Moderate alcohol consumption is associated with a reduced risk of coronary heart disease. Earlier studies in men have shown that moderate alcohol consumption affects lipoprotein metabolism and hemostasis. In this diet-controlled, randomized, crossover trial, we investigated the effect on lipoprotein metabolism of moderate consumption of red wine or red grape juice with evening dinner for 3 weeks in premenopausal women using oral contraceptives and in postmenopausal women. After 3 weeks, blood samples were collected 1 hour before dinner up to 19 hours after starting dinner at 2-hour or 4-hour intervals. Plasma triglyceride concentrations and very low density lipoprotein (VLDL) triglyceride levels peaked 3 hours after dinner with wine in both premenopausal and postmenopausal women. After wine consumption, the overall high-density lipoprotein (HDL) cholesterol level was increased in postmenopausal women (mean increase 0.17 mmol/L, or 12%, p = 0.03), and the plasma low-density lipoprotein (LDL) cholesterol level was reduced in premenopausal women (mean reduction 0.35 mmol/L, or 12%, p = 0.01) as compared with grape juice consumption. The findings suggest that postprandial lipoprotein metabolism after moderate alcohol consumption differs between oral contraceptive-using premenopausal women and postmenopausal women. The response of postmenopausal women to alcohol resembled the response found in earlier studies in men.

Cis-unsaturated fatty acids and platelet function

The main method to study platelet function in dietary studies has been the platelet aggregation test in vitro. Even though it is well established that dietary cis-unsaturated fatty acids (FAs) modify platelet aggregation some uncertainty still exists how to interpret the in vitro results in the context of a situation in vivo. The other ways to look at platelet activation are measurements of thromboxane metabolites in urine or the concentration of beta-thromboglobulin (betaTG) released from alpha-granules. Dietary fish oil or long-chain n-3 FAs lower the high basal excretion rate of thromboxane, while only a modest effect is noticed at a low basal excretion rate. Results on the effects of other cis-unsaturated FAs on urinary TXB2 metabolites are almost totally lacking. Furthermore, platelet betaTG release in vivo does not seem to be affected by changes in dietary FAs. The regulatory function of dietary FAs in platelets is extremely complex, and clearly more should be understood about the association between dietary FAs and platelet membrane FAs in connection with platelet responses to physiological stimuli and subsequent signal transduction inside the platelets.

Dietary management of cardiovascular diseases

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

Effects of alcohol on platelet functions

Recent epidemiologic studies have consistently shown that moderate intake of alcoholic beverages protect against morbidity and mortality from coronary heart disease and ischemic stroke. By contrast, alcohol drinking may also predispose to cerebral hemorrhage. These observations suggest an effect of alcohol similar to that of aspirin. Several studies in humans and animals have shown that the immediate effect of alcohol, either added in vitro to platelets or 10 to 20 min after ingestion, is to decrease platelet aggregation in response to most agonists (thrombin, ADP, epinephrine, collagen). Several hours later, as, in free-living populations deprived of drinking since the previous day it is mostly secondary aggregation to ADP and epinephrine and aggregation to collagen that are still inhibited in alcohol drinkers. By contrast, in binge drinkers or in alcoholics after alcohol withdrawal, response to aggregation, especially that induced by thrombin, is markedly increased. This rebound phenomenon, easily reproduced in rats, may explain ischemic strokes or sudden death known to occur after episodes of drunkenness. The platelet rebound effect of alcohol drinking was not observed with moderate red wine consumption in man. The protection afforded by wine has been recently duplicated in rats by grape tannins added to alcohol. This protection was associated with a decrease in the level of conjugated dienes, the first step in lipid peroxidation. In other words, wine drinking does not seem to be associated with the increased peroxidation usually observed with spirit drinking. Although further studies are required, the platelet rebound effect of alcohol drinking could be associated with an excess of lipid peroxides known to increase platelet reactivity, especially to thrombin.

Habitual diet, platelet function, fibrinogen and factor VII coagulant activity in young Finns

OBJECTIVES

The objective of the study was to determine whether an association between diet and platelet function, plasma fibrinogen level and factor VII coagulant activity (VII:C) could be established in young subjects.

DESIGN

Data on the habitual diet of the subjects were collected either by a questionnaire on food habits (n = 204) or by a 48-h dietary recall interview (n = 53).

SUBJECTS

The subjects were participants in the project 'Cardiovascular Risk in Young Finns' (age range 15-30 years). A total of 204 subjects having a questionnaire on food habits participated in the platelet function tests and 53 also participated in a 48-h dietary recall interview. Plasma fibrinogen concentration and factor VII: C were measured from 79 subjects.

MAIN OUTCOME MEASURES

Platelet function was tested by turbidometric measurement of platelet aggregation using ADP and collagen as aggregation agents.

RESULTS

Platelet aggregation with ADP (at up to 4.0 mumol L-1) and collagen (at up to 5.0 micrograms mL-1 platelet-rich plasma PRP) showed that the diet characterized as 'saturated', i.e. containing high-fat milk and saturated fat, was associated with platelets less sensitive to aggregating agents in vitro when compared to the unsaturated type of diet. Collagen- but not ADP-induced aggregation decreased with age of the subjects (P = 0.026-0.057, regression coefficient). An inverse regression coefficient between plasma factor VII:C (101%; range 64-145%) and serum triglycerides (P = 0.006) and the intake of rye (g 1000 kcal-1; P = 0.03) were found.

CONCLUSIONS

In this study we showed that platelet reactivity and factor VII:C already differ considerably between subjects at a young age, and diet may explain some of this variation.

Young infarct patients with single-vessel occlusion do not have an underlying prothrombotic state to explain their coronary occlusion

To determine the importance of a prothrombotic state in the pathogenesis of coronary occlusion in young infarct patients, assessment of risk factor profile and thrombotic tendency was undertaken in 25 young male patients (age less than 45 yr) who were shown at angiography, following myocardial infarction, to have occlusion of a single coronary. Comparison was made with a control group of symptomatic males aged greater than 55 yr, who at angiography had significant disease in two or more coronary arteries (multi-vessel disease control group). At the time of the study more patients in the single-vessel disease study group smoked cigarettes (n = 12) compared to the control group (n = 5) (p less than 0.01). Serum cholesterol and triglycerides were higher, and high density lipoprotein-cholesterol lower, in the single-vessel disease group but the difference reached significance only with the high density lipoprotein-cholesterol. Quantitative platelet aggregability was similar in the two groups. Although the level of beta-thromboglobulin, was higher in the single-vessel disease study group the difference was not significant. There were also no significant differences between these groups in levels of fibrinogen, Factor XII and alpha-2 antiplasmin. Patients in the multi-vessel disease group, however, had increased Factor VII levels (p less than 0.01). There were no significant differences between the two groups in fibrinolytic potential or in levels of antithrombin III. Coronary occlusion in the young appears likely to be due primarily to an arterial (plaque) related event as opposed to an abnormal coagulation response to minor arterial plaque damage.

Platelet fatty acids and function in two distinct regions of Belgium: relationship to age and dietary habits

We compared the dietary habits, fatty acid composition of plasma and platelet phospholipids, and platelet function in two groups of healthy Belgian male subjects, known to differ in their mortality rate from coronary heart disease (CHD). In the Walloon subjects, there was a larger intake of saturated and a lower intake of (n-6) polyunsaturated fats, confirmed by the fatty acid composition of plasma and platelet phospholipids. While plasma HDL and total cholesterol were similar in the present samples of the two communities, platelet aggregation to epinephrine was significantly higher in the Walloon subjects. When the two populations were divided into younger (28-54 years) and older (55-73 years) age groups, the older Walloon subjects exhibited platelet hyper-aggregability to most of the agonists, compared to the other three groups. In addition to dietary fats, alcohol and smoking habits, age was an important determinant of platelet phospholipid fatty acids and platelet reactivity. The present results reinforce those of previous studies, indicating that platelet behaviour is significantly affected by the main risk factors for CHD.

Effects of dietary fats on prostanoid production and aortic and plasma fatty acid composition in rats

Male Sprague-Dawley rats were fed diets with 10%, 30%, or 50% of energy derived from fat for two weeks. The fats used were beef tallow, olive oil, peanut oil and butter. Aortic prostacyclin (PGI2) production, platelet aggregation and thromboxane A2 (TXA2) production and plasma and aortic phospholipid (PL) content were measured. Butter- and beef tallow-feeding reduced aortic PGI2 production and collagen-induced TXA2 production in a dose-dependent manner as the level of fat in the diet increased. Neither olive oil nor peanut oil had any effect on aortic PGI2 production or collagen-induced TXA2 production. Butter-feeding also resulted in a decrease in collagen-induced platelet aggregation; however, none of the other fats had any effect on collagen-induced platelet aggregation. The observed decreases in aortic PGI2 and collagen-induced TXA2 production were paralleled by similar decreases in aortic and plasma PL arachidonic acid content and an increase in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Only the most saturated fats, butter and beef tallow, had significant inhibitory effects on prostanoid production and platelet aggregation.

Platelet aggregability in rats with early atherosclerotic changes induced by parenterally-administered lipid emulsions

The present study is the first work to evaluate thrombin-, ADP-, and collagen-induced platelet aggregation in laboratory rats receiving alimentation with the parenterally-administered lipid emulsion, Lipofundin-S, in doses sufficient to induce early atherosclerotic changes in the aorta. The aggregometry parameters of percent maximum aggregation, slope, and b2 or b20 almost uniformly indicate that such lipid treatments result in a statistically significant increased sensitivity of the platelets to ADP and collagen, while no change is noted with thrombin as the aggregating agent. By varying the amounts of ADP and collagen during aggregometry, we also demonstrate that the concentrations of these reagents necessary for equivalent platelet aggregation is substantially lower in lipid-infused rats than in controls. We conclude from this study that such lipid infusions can cause increased platelet aggregation, and that these lipids probably act in a synergistic fashion by affecting a variety of components which comprise the atherogenic process and its clinical endpoint. In addition, we believe that this experimental approach is of interest in that infusions of clinically-useful lipid emulsions are easily controlled, while alterations in platelet physiology and aortic structure occur concurrently and rapidly.

Nutrients, platelet function and composition in nine groups of French and British farmers

In 260 male farmers (40-45 years) divided into 9 groups from different areas in France and Britain, coagulation, platelet aggregation, lipemia, fatty acids from plasma lipids and platelet phospholipids were determined in relation to the food intake evaluated by recall, weighing and chemical analysis of the diet. The clotting activity of platelets and their response to thrombin aggregation was significantly correlated on an individual basis with the intake of saturated fatty acids both in subsamples as well as in the whole study. Serum cholesterol was also significantly correlated with saturated fats but only on a group basis or on the totality of the study. Calcium, linolenic acid and alcohol in the diet were inversely related to certain platelet functions. Linoleic acid was inversely related to serum cholesterol and triglycerides. Dietary saturated fats were associated, with an increase in the platelet phospholipids not in saturated fatty acids but in 20:3 (n-9), known to promote platelet aggregation to thrombin, with a decrease in platelet cholesterol, also apparently regulating platelet functions. The present studies indicate that dietary saturated fats, calcium (hard water) and alcohol, influence platelet behaviour in a way strictly parallel to their known effect on coronary heart disease.

Effect of dietary (n--3) fatty acids on platelet function and lipid metabolism in rats

Six groups of rats were fed diets containing 40% (by weight) lipids, mostly as saturated fatty acids (from 78 to 90%), with a basic amount of linoleic acid (18:2) (1.9%). In four groups, 5% of the saturated fats were substituted with an oil (vegetable: corn, rapeseed; or fish: cod liver, maxepa) and in one group 0.6% of the saturated fats was replaced by eicosapentaenoic acid ethyl ester. The diets supplied different amounts of 18:2 (1.9 to 10%), 18:3 (0.2 to 1.2%), 20:5 (n--3) (eicosapentaenoic acid) (0 to 1.3%) and 22:6(n--3) (0 to 1.6%). After 3-8 months on diets, platelet aggregation, plasma and platelet cholesterol, fatty acids and incorporation of [14C]acetate and [14C]arachidonate into platelet lipids were investigated. The three diets supplying eicosapentaenoic acid (1.3%) induced an approximately 80-fold increase in this fatty acid in plasma and platelet phospholipids, mainly at the expense of arachidonic acid. This was associated with an increase of the incorporation of arachidonic acid into platelet PE and PS. The incorporation of acetate in the (n--3) fatty-acid-fed animals was markedly increased into 22:5 and 22:6(n--3) at the expense of 22:4(n--6). Platelet aggregation induced by ADP was similar in the six groups. The response to thrombin was lower in animals fed corn and maxepa oils. Collagen aggregation tended to be lower in the fish-oil groups. Platelet aggregation to collagen was significantly negatively correlated to the level of eicosapentaenoic acid in platelet phospholipids, while the aggregation to thrombin was related to the level of 20:3(n--9). In the present study in rat, the (n--3) fatty acids added in small amounts to a saturated fat diet over a period of several months induced drastic changes in platelet lipid metabolism and composition without comparable effects on platelet behaviour.

Prostaglandin E2-like activity of 20:3n-9 platelet lipoxygenase end-product

5,8,11-Icosatrienoic acid (20:3n-9), a fatty acid associated with platelet hyperactivity, was oxygenated by platelet lipoxygenase. The end-product of this pathway was purified by high-performance liquid chromatography (HPLC) and characterized as 12-hydroxy-5,8,10-icosatrienoic acid [12-OH-20:3(5,8,10)] by capillary gas-liquid mass spectrometry. When tested upon platelet aggregation, 12-OH-20:3(5,8,10) exhibited a biphasic effect. At low concentrations (below 5 X 10(-7) M) it potentiated aggregation but inhibited it at higher levels, a pattern similar to that obtained with prostaglandin E2. However, since the amounts of 12-OH-20:3(5,8,10) generated under thrombin stimulation are in the range of concentrations with potentiating effects, it seems that the 12-OH derivative is responsible for the hyperaggrebility of 20:3n-9-rich platelets.

Serum linoleic acid and cardiovascular death in postinfarction middle-aged men

Linoleic acid in serum total lipids was the first variable in the stepwise regression analysis of metabolic, nutritional and cardiovascular factors in a secondary preventive study of postinfarction middle-aged men. It was followed in the regression analysis where the dependent variable was cardiovascular death by previous myocardial infarction, heart volume index and hyperlipoproteinaemia. Linoleic acid was the only fatty acid entering the regression. Unlike other fatty acids, it exhibited by its low percentage an accumulation of deaths. The decreased percentage of linoleic acid was also evident in the comparison of fatty acid patterns of cardiovascular deaths to age- and triglyceride-matched men free from ischaemic heart disease. This study confirms prospective associations found in previously healthy men. Conclusions are drawn about the relevance of low serum linoleic acid to long term prognosis after MI.

Polyunsaturated fatty acids and diabetic retinopathy

One hundred and forty nine diabetic patients were ophthalmologically assessed seven years after randomisation to a low carbohydrate or modified fat diet (rich in linoleic acid). Glycaemic control, regardless of the type of diet, was a major determinant of the development of retinopathy. Poorly controlled patients (haemoglobin A1c greater than 8%) with low levels of linoleic acid in cholesterol ester had a significantly greater frequency of retinopathy than well controlled patients or patients with similarly unsatisfactory control but higher levels of linoleic acid. The findings support an earlier suggestion that linoleic acid might protect against diabetic retinopathy.

Effects of dietary lipids on behaviour, lipid biosynthesis and lipid composition, in rat platelets

Rats of either sex were fed for 18 and 34 weeks respectively diets containing 40% (by weight) lipids with polyunsaturated fatty acids representing 1.34% or 13.2% of total calories. Platelet reactivity to thrombin, platelet fatty acid composition and incorporation of [14C]acetate into platelet lipids were investigated. Diets rich in saturated fatty acids markedly increased platelet sensitivity to thrombin. The concentration of 20:3 and 22:3 of the (n - 9) series and of 20:3 and 22:5 of the (n - 6) series were increased at the expense of 18:2 and 22:4 of the (n - 6) family in platelet lipids. 20:4 (n - 6) was unchanged. The fatty acid changes were more pronounced in male rats and after 34 weeks. [14C]Acetate incorporation into total platelet lipids and particularly into choline phosphoglycerides and ceramides was lower in animals fed saturated fats. This diet reduced the synthesis of 16:0 and of 22:4(n - 6) in platelet total fatty acids, while that of 22:3(n - 9) was markedly enhanced. This study showed that long-term feeding of high-saturated-low-polyunsaturated fat diets in rats induced marked changes in platelet lipid synthesis and composition, in both sexes. The lipid synthesis modification appears to be more pronounced in males than in females. The changes in the fatty acids 20:3(n - 9), 22:3(n - 9) and 22:4(n - 6) appeared to be closely related to platelet behaviour. The balance between the content and synthesis of these last fatty acids might be of significance for the effect of diet on thrombogenesis.

Protective effects of dietary calcium and magnesium on platelet function and atherosclerosis in rabbits fed saturated fat

Male rabbits were fed for 6 months a purified diet rich in fat (45% of calories), mostly saturated (butter) containing per 100 g either 354 mg of calcium and 46 mg of magnesium (group I), 948 mg of calcium and 46 mg of magnesium (group II), or 354 mg of calcium and 356 mg of magnesium (group III). In group II, fed the additional calcium, significant (P less than 0.001) changes were observed; i.e. prolongation of clotting time (platelet clotting activity), decrease in platelet aggregation to thrombin, and in the concentration of the plasma total cholesterol, with a less significant (P less than 0.05) decrease in plasma triglycerides. A significant (P less than 0.01) decrease in the ratio monoemes/18:2 in the plasma cholesterol esters but not in the plasma or platelet phospholipids was also found in these rabbits. In relation to their lower activity, platelets from group II exhibited a significant increase in 22:4n-6 (phospholipids) and in the ratio cholesterol/phospholipids, both significantly correlated with the platelet function tests. In this same group, the excretion of fecal lipids and saturated fatty acid 18:0 was increased by 4.3-fold and 7.6-fold, respectively. The severity of atherosclerosis and the accumulation of cholesterol in the aorta were significantly lower in group II, while the plasma level of calcium was similar to that of group I. In group III, fed additional magnesium, results were similar to those of group II, but less significant.

Influence of sex and dietary fats on platelet lipid biosynthesis in rat

The platelet biosynthesis of total lipids, lipid fractions and fatty acids was determined by incorporation of [14C]acetate in normal and castrated rats of both sexes. Comparison was made between animals fed laboratory chow alone, and animals receiving, in addition, for 4 days by stomach tube a saturated (cream) or polyunsaturated (sunflower seed oil) fat. In male rats, the polyunsaturated fat increased slightly the total platelet lipid biosynthesis. The saturated fat drastically reduced it by 43% in comparison to the polyunsaturated fat-fed animals. Normal female rats did not exhibit a similar difference in the platelet lipid synthesis. However, the inhibitory effect of saturated fat on lipid synthesis could be observed in castrated females, although it was less pronounced (27% reduction) than in castrated or normal males (43%). Administration to castrated males of estradiol for 1 month almost completely inhibited the difference induced by the feeding of the different fats in the lipid platelet synthesis of male rats. This difference in the platelet lipid biosynthesis between male and female rats, normal and castrated, was observed mostly in the phospholipid (especially phosphatidylcholine), monoacylglycerol and triacylglycerol fractions and affected primarily the synthesis of the three main saturated fatty acids, 14:0, 16:0 and 18:0. Thus, it seems that, in rat, the short-term administration of a saturated fat induces drastic changes in the platelet lipid biosynthesis, but only in males. The protection observed in females appears to be essentially dependent upon estrogens.

Low phospholipid arachidonic acid values in diabetic platelets

Platelet aggregation is enhanced in diabetes mellitus, and platelets may be implicated in the pathogenesis of diabetic angiopathy. Increased platelet aggregation is probably mediated by the production of the proaggregatory prostaglandin thromboxane, which is synthesised from arachidonic acid (C20:4) by the action of the platelet enzymes cyclo-oxygenase and thromboxane synthetase. The fatty acid composition of platelet phospholipid was measured in 20 normal controls, 10 insulin-treated diabetics with no or minimal retinopathy, and 10 insulin-treated diabetics with proliferative retinopathy. The percentage of arachidonic acid was significantly higher in controls (mean 22.6%) than in the diabetics with no or minimal retinopathy (mean 18.5%; p less than 0.025) and the diabetics with proliferative retinopathy (mean 14.6%; p less than 0.001). The percentage of linoleic acid was lower in controls (mean 8.9%) than in the diabetics with no or minimal retinopathy (mean 12.6%; p less than 0.01) and diabetics with proliferative retinopathy (mean 13.1%; p less than 0.001). The mean percentage of linolenic acid was significantly lower in the diabetics with proliferative retinopathy (2.7%) than in the normal control group (4.4%; p less than 0.01). A significant negative correlation was found between the percentages of arachidonic acid and glycosylated haemoglobin (Rs = -0.58; p less than 0.001). A significant positive correlation was found between linoleic acid and the percentage of glycosylated haemoglobin (Rs = 0.51; p less than 0.01). The reciprocal correlation between percentages of arachidonic acid and glycosylated haemoglobin suggests that diabetic control may influence thromboxane release and platelet activity directly and that low percentages of arachidonic acid reflect the increased degree of in-vivo activation.