Titrating dietary linoleate to in vivo platelet function in man

The effect of conjugated linoleic acid on platelet function, platelet fatty acid composition, and blood coagulation in humans

Despite extensive research on conjugated linoleic acid (CLA) showing multiple beneficial effects in animal models, little is known about the role of dietary CLA in human health. To investigate if the beneficial effects of CLA seen in animal models are relevant to humans, we conducted a study with 17 healthy female volunteers who lived in the Metabolic Research Unit of the Western Human Nutrition Research Center for 93 d. This paper reports only the results from this study that are related to the effects of CLA supplementation on blood coagulation, platelet function, and platelet fatty acid composition. Throughout the study, the subjects were fed a low-fat diet (30 en% fat, 19 en% protein, and 51 en% carbohydrate) consisting of natural foods with the recommended dietary allowances for all known nutrients. After a 30-d stabilization period, subjects were randomly assigned to either an intervention group (n = 10) whose diet was supplemented with 3.9 g/d of CLA or a control group (n = 7) who received an equivalent amount of sunflower oil consisting of 72.6% linoleic acid with no detectable CLA. Platelet aggregation was measured in platelet-rich plasma using adenosine diphosphate, collagen, and arachidonic acid agonists. No statistical difference was detected between the amount of agonist required to produce 50% aggregation of platelet-rich plasma before and after the subjects consumed the CLA, with the exception of a decrease in response to collagen. This decrease was found in both control and intervention groups with no significant difference between the groups, suggesting that both linoleic acid (sunflower oil) and CLA might have similar effects on platelet function. The prothrombin time, activated partial thromboplastin time, and the antithrombin III levels in the subjects were determined. Again, there was no statistically significant difference in these three parameters when pre- and post-CLA consumption values were compared. The in vivo bleeding times were also unaffected by CLA supplementation (10.4 + 2.8 min pre- and 10.2 + 1.6 min postconsumption). Platelet fatty acid composition was not markedly influenced by the consumption of dietary CLA, although there was a small increase in the amount of the 9 cis,11 trans-18:2 isomer normally present in platelets after feeding CLA for 63 days. In addition, small amounts of the 8 trans,10 cis-18:2 and the 10 trans,12 cis-18:2 isomers were detected in the platelets along with traces of some of the other isomers. Thus, when compared to sunflower oil, the blood-clotting parameters and in vitro platelet aggregation showed that adding 3.9 g/d of dietary CLA to a typical Western diet for 63 d produces no observable physiological change in blood coagulation and platelet function in healthy adult females. Short-term consumption of CLA does not seem to exhibit antithrombotic properties in humans.

Fatty acid and prostaglandin metabolism in children with diabetes mellitus. II. The effect of evening primrose oil supplementation on serum fatty acid and plasma prostaglandin levels

Our previous study demonstrated that levels of dihomo-gamma-linolenic acid (DGLA) and arachidonic acid in serum total lipids decreased in association with increased plasma levels of prostaglandins E2 (PGE2) and F2 alpha (PGF2 alpha) in patients with insulin-dependent diabetes mellitus. In this study, 11 children with insulin-dependent diabetes mellitus completed a double-blind, placebo-controlled study to assess the effect of dietary supplementation with gamma-linolenic acid (GLA) on serum essential fatty acid and plasma PGE2 and PGF2 alpha levels. GLA was given as the seed oil from the evening primrose (EPO) and all patients received either EPO capsules (containing 45 mg of GLA and 360 mg of linoleic acid) or indistinguishable placebo capsules for 8 months. Initially patients took 2 capsules daily for 4 months then 4 capsules daily for a further 4 months. All patients were assessed at the start of the study, after 4 months and at the end of the study, by measuring serum essential fatty acid and plasma PGE2 and PGF2 alpha levels. After administration of 4 capsules daily the DGLA levels increased and PGE2 levels decreased significantly (p less than 0.01) in the EPO compared with the placebo group. Neither fatty acid nor PGE2 and PGF2 alpha levels were altered by administration of 2 EPO capsules daily. This suggests that the altered essential fatty acid and PG metabolism in diabetes may be reversed by direct GLA supplementation.

Pathogenesis of diabetic neuropathy: the role of the n-6 essential fatty acids and their eicosanoid derivatives

A substantial disturbance of the metabolism of the n-6 essential fatty acids exists in both human and experimental diabetes mellitus. Disturbances of the essential fatty acids and of the 1- and 2-series prostaglandins derived from them create a variety of microvascular, haemorheological, and other abnormalities leading to reduced blood flow and neural hypoxia which will in turn produce a cycle of hypoxia. Disturbance of the n-6 pathway may also result in functional and structural abnormalities of the axon, the myelin, and membrane-bound proteins such as enzymes and receptors. Metabolic disturbances identified previously may have a synergistic effect in enhancing these pathogenetic changes.

The effect of gamma-linolenic acid on human diabetic peripheral neuropathy: a double-blind placebo-controlled trial

Twenty-two patients with distal diabetic polyneuropathy confirmed both clinically and by objective nerve function studies, completed a double-blind, placebo-controlled study to assess the effect of dietary supplementation with gamma-linolenic acid on their neuropathy. Patients received either 360 mg gamma-linolenic acid (12 patients) or indistinguishable placebo capsules (10 patients) for 6 months. All patients were assessed at the beginning and end of the study period by neuropathy symptom and sign scoring, motor and sensory nerve conduction studies, and thermal threshold measurements. When compared with the placebo group, patients on gamma-linolenic acid showed statistically significant improvement in neuropathy symptom scores (p less than 0.001), median nerve motor conduction velocity (p less than 0.01) and compound muscle action potential amplitude (p less than 0.01), peroneal nerve motor conduction velocity (p less than 0.05) and compound muscle action potential amplitude (p less than 0.05), median (p less than 0.01) and sural (p less than 0.001) sensory nerve action potential amplitude and ankle heat threshold (p less than 0.001) and cold threshold (p less than 0.01) values. gamma-Linolenic acid therapy might have a useful role in the prevention and treatment of distal diabetic polyneuropathy.

Dietary fats and platelet function among Finnish men

The aim of this study was to elucidate the role of platelet aggregation as a risk factor for ischemic heart disease (IHD) and the relationship between fatty acids and platelet function. Platelet aggregation upon adenosine diphosphate (ADP), adrenaline and thrombin were measured in middle aged men in east and west, two regions of Finland with a nearly twofold difference in IHD mortality. Platelet aggregation results were correlated with the fatty acid compositions of plasma lipid fractions, adipose tissue triglycerides and platelet phospholipids. There was no significant east-west difference in platelet reactivity to ADP, adrenaline and thrombin. ADP-induced platelet aggregation showed significant negative correlations with all the platelet C20-C22 n-3 polyunsaturated fatty acids (PUFA), but significant positive correlations with the percentage of 18:2n-6 in adipose tissue and plasma cholesterol esters (CE) and triglycerides (TG). Adrenaline-induced aggregation correlated negatively with the percentage of 20:5n-3 in plasma CE and TG, and positively with the total percentage of saturated fatty acids in platelets. Aggregation upon thrombin had a negative correlation with the 20:3n-6/20: 4n-6 ratio in plasma CE and a positive correlation with 18:2n-6 in adipose tissue. The percentages of the major PUFA in platelets correlated significantly with the same fatty acids in plasma CE and phospholipids PL. Platelet 20: 5n-3 had a highly significant negative correlation with the percentage of 18: 2n-6 in plasma and adipose tissue lipids. Platelet 20: 4n-6 was unrelated to its precursors in plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effects of dietary linoleic and alpha-linolenic acid on lipid metabolism in rat tissues

Comparative effects of feeding dietary linoleic (safflower oil) and alpha-linolenic (linseed oil) acids on the cholesterol content and fatty acid composition of plasma, liver, heart and epididymal fat pads of rats were examined. Animals fed hydrogenated beef tallow were used as isocaloric controls. Plasma cholesterol concentration was lower and the cholesterol level in liver increased in animals fed the safflower oil diet. Feeding the linseed oil diet was more effective in lowering plasma cholesterol content and did not result in cholesterol accumulation in the liver. The cholesterol concentration in heart and the epididymal fat pad was not affected by the type of dietary fatty acid fed. Arachidonic acid content of plasma lipids was significantly elevated in animals fed the safflower oil diet and remained unchanged by feeding the linseed oil diet, when compared with the isocaloric control animals fed hydrogenated beef tallow. Arachidonic acid content of liver and heart lipids was lower in animals fed diets containing safflower oil or linseed oil. Replacement of 50% of the safflower oil in the diet with linseed oil increased alpha-linolenic, docosapentaenoic and docosahexaenoic acids in plasma, liver, heart and epididymal fat pad lipids. These results suggest that dietary 18:2 omega 6 shifts cholesterol from plasma to liver pools followed by redistribution of 20:4 omega 6 from tissue to plasma pools. This redistribution pattern was not apparent when 18:3 omega 3 was included in the diet.

Fatty acid pattern of red blood cell membranes and risk of ischemic brain infarction: a case-control study

The fatty acid composition of red blood cell membranes (which reflects dietary fat intake) was studied in 28 male patients with recent (less than 3 days) ischemic stroke and 56 matched controls. Fifteen fatty acids were measured by means of chromatographic analysis. Percentages of linoleic, 22:5, and 22:6 acids were significantly lower in red blood cell membranes of stroke patients than in those of matched controls. The results suggest that a low unsaturated fatty acid diet could be an independent risk factor for ischemic brain infarction.

High content of dietary linoleic acid does not reduce platelet reactivity in patients with hyperlipoproteinaemia

Seventeen patients with hypertriglyceridaemia were given a lipid-lowering diet with a high P/S-ratio 2.1 during a 3-week period. The very low density lipoprotein triglycerides decreased by 43%, low density lipoprotein cholesterol by 19% and high density lipoprotein cholesterol by 12%. There was a marked increase of linoleic acid (18:2 n-6) in all plasma lipid esters with a concomitant decrease of the saturated and monounsaturated fatty acids. There was a slight increase of the linoleic acid metabolites 18:3 n-6, 20:3 n-6 and 20:4 n-6 in serum triglycerides whereas the fatty acids of the n-3 series decreased in all plasma lipid esters. In the platelets a similar pattern was found with an increase of linoleic acid and its metabolite 22:4 n-6 and a decrease of 18:1 n-9 as well as of the n-3 fatty acids. No significant differences in platelet reactivity was found. However, in a few patients there was an increased platelet aggregation after the diet period. Our results suggest that this diet based on a very high content of linoleic acid may not affect platelet reactivity in a beneficial way. The reason may be an increased turnover of arachidonic acid in the platelets or an imbalance between the n-6 and n-3 series of fatty acids.

Fatty acid composition of platelet phospholipids in non-insulin-dependent diabetics randomized for dietary advice

Two groups of patients with non-insulin-dependent diabetes mellitus (NIDDM), with dietary advice randomized between a low-carbohydrate (LC) diet and a modified-fat (MF) diet, were followed to determine the effect of diet on phospholipid fatty acid composition of platelets and on development of retinopathy in the 7 years following diagnosis. There was a tendency for retinopathy to occur more frequently in those randomized to the LC diet. This difference was not statistically significant, and fatty acid composition of platelets did not differ significantly in those with and without retinopathy. Linoleic acid values from platelet phospholipid fatty acids were significantly higher in NIDDM on an MF diet compared with an LC diet. There was no difference between the two dietary subgroups with respect to platelet arachidonic acid, but this was lower in the whole diabetic population when compared with non-diabetics. The arachidonic acid values correlated with neither glycosylated haemoglobin nor mean glycaemia. Significant correlation between the fatty acid values for platelets and plasma cholesterol esters was found only for 16:0.

Essential fatty acids in the serum and cerebrospinal fluid of multiple sclerosis patients

Statistical evaluation of essential fatty acids (determined by gas chromatography) in the serum and cerebrospinal fluid of patients with definite MS and acute CCT showed marked differences as compared to healthy subjects. It was also evident that the decrease of essential fatty acids in MS patients differed from that of CCT patients. Whereas the fatty acid levels in the serum of MS patients revealed only minor differences as compared to the controls and CCT patients, MS patients did show a clear decrease, especially of linoleic and arachidonic acids, in the CSF. This difference was most pronounced in cholesterol esters in the CSF. One absorption study with safflower oil demonstrated normal enteral absorption of essential fatty acids and the ability to cross the blood-CSF barrier.

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.

In vivo platelet aggregation and plasma catecholamines in acute myocardial infarction

In vivo platelet aggregation assessed with the Filtragometer and potential correlates were compared among (1) patients with acute myocardial infarction (AMI), (2) normal controls, (3) patients with acute chest pain in whom AMI was eventually ruled out (ROMI), and (4) chronic outpatients (Cardiac Clinic group) with a history of myocardial infarction and/or angina pectoris. The measure was independent of sex, age, platelet count, immediate food intake, serum cholesterol, and triglyceride levels. The AMI group showed higher in vivo platelet aggregation than any of the other three groups (p less than 0.01). Least in vivo aggregation was seen in the normal group. Despite lack of correlation with the platelet aggregation measure, plasma epinephrine and norepinephrine showed statistically significant differences between the AMI and each of the other three groups. Our data support an association between platelet function and AMI, although not necessarily a cause and effect relationship.

Low dietary intake of linoleic acid predisposes to myocardial infarction

Thirty-two men who had recently had a myocardial infarction were matched individually for age with controls who had no evidence of heart disease. The patients had a significantly lower proportion of linoleic acid and a higher proportion of palmitic acid in their plasma triglyceride fatty acids. Analysis of the composition of red-cell membrane phosphatidyl choline, which reflects long-term dietary fat intake, showed a significantly lower proportion of linoleic acid in the patients.These differences suggest that the type of dietary fat consumed might be an important factor in the genesis of ischaemic heart disease.

Increased platelet aggregation and decreased high-density lipoprotein cholesterol in women on oral contraceptives

In vivo platelet function, serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL), and serum triglycerides (TG) were determined in 26 women starting oral contraceptives (OCA). Studies were run prior to, and after one and two months of therapy. Platelet aggregation time decreased by 50 percent or more in eight of the 26 women from a pre-experimental mean value of 387 +/- 136 seconds. TC did not vary but after the women were on medication for two months, HDL decreased from 56 +/- 14.4 mg/dl to 52 +/- 12.3 mg/dl (p less than 0.05). There was a progressive increase in TG under treatment, 74 +/- 23.3 mg/dl on the pre-experimental measurement to 93 +/- 31.0 mg/dl after two months of therapy (p less than 0.005). Women planning to use OCA might best be advised to have aggregation and serum lipid studies done before and early in usage.

The relationship of dietary fats to prostaglandin biosynthesis

The direct and indirect evidence that the fatty acid composition of dietary fat is involved in the regulation of prostaglandin biosynthesis was reviewed. Direct evidence included effects of essential fatty acid deficiencies and excesses on endogenous tissue levels and production rates of prostaglandins by several tissues. Indirect evidence included lipolytic, platelet aggregatory, hypertensive, inflammatory and immune responses. In general, composition of dietary fat did not affect prostaglandin biosynthesis unless a biochemical essential fatty acid deficiency was induced or the linoleate to saturated fatty acids ratio of the dietary fat was greater than 5. Most results were interpreted in light of changing fatty acid composition; however, very few direct measurements have been made.

The hypercoagulability states

Although interest in coagulation has usually centered about the various hemorraghic disorders, it is hyperactivity of the hemostatic system with its thrombotic complications which has a far greater clinical impact. The hypercoagulability states are a vague group of disorders not well defined by the laboratory. They fall into two distinct groups: (1) conditions promoting venous thrombosis by activating the coagulation mechanism and (2) conditions promoting arterial thrombosis by platelet plug formation. Dealing with both of these groups separately the various disorders associated with a hypercoagulable state are discussed as well as their pathophysiologic basis; Special emphasis is placed on the laboratory evaluation of these disorders.

Modification of human platelet function by a diet enriched in saturated or polyunsaturated fat

Twelve healthy male subjects were maintained on a saturated fat (SF) dietary regimen followed by a polyunsaturated fat (PUF) regimen. At selected intervals a number of tests were carried out to assess the effect of SF or PUF on platelet composition and activation. Concomitant with the fall in serum cholesterol, associated with the PUF diet, there was a decrease in plasma heparin neutralizing activity (as measured by the heparin--thrombin clotting time), and a fall in the number of circulating platelet aggregates was also observed. These two parameters suggest diminished platelet activation. Malondialdehyde production (an index of prostaglandin synthesis) was unchanged throughout the two dietary periods. Changes in the quality of the dietary fat were manifested in the phospholipid fraction of platelet lipids, particularly phosphatidyl choline and sphingomyelin. Platelet counts of whole blood were significantly decreased when subjects were consuming PUF, but not all of these alterations were reflected in platelet-rich plasma. These results indicate that platelets may be activated in apparently normal people consuming a SF diet (the standard diet of developed countries) and that this activation may be decreased by replacement of dietary SF with PUF.

The effect of cholestyramine on serum lipids and platelet aggregation of hypercholesterolemic children (type II A) while on high linoleic acid diet

25 children with familial hypercholesterolemia (type II A) were treated with cholestyramine or placebo in a cross over study during 2 periods of each 10 weeks. The medication was added to a high linoleic acid diet, which had been started at least 1 year earlier. Serum lipids and platelet aggregation were investigated at the end of the 2 periods. On cholestyramine, serum cholesterol levels decreased significantly, whereas the linoleate and oleate content of cholesterylesters and serum triglycerides did not change systematically. Platelet aggregation time, measured with a filtragometer, did not systematically change either.

Effect of stress due to anticipated minor surgery upon in vivo platelet aggregation in humans

When measured just prior to hospital admission, platelet aggregation was faster and systolic and diastolic blood pressure were higher compared to measurements just prior to surgery and upon discharge fromthe hospital.