Vascular prostacyclin is increased in patients ingesting omega-3 polyunsaturated fatty acids before coronary artery bypass graft surgery

Pharmacologic effects of calcium channel blockers on restenosis

The understanding and control of the healing process after percutaneous transluminal coronary angioplasty (PTCA) and of the pathogenesis of restenosis are incomplete. To date, only stent implantation has been shown to successfully reduce the rate of restenosis. Calcium channel blockers have positive effects on a number of processes that may be associated with restenosis, including reduction of platelet aggregation, minimization of vasospasm, and inhibition of mitogens. Clinical trials have therefore been performed to assess the effect of calcium channel blockers on restenosis and ischemia. A meta-analysis of five restenosis trials investigating calcium channel blockers demonstrated a 30% reduction in the risk for restenosis. The Coronary Angioplasty Amlodipine Restenosis Study (CAPARES) is therefore assessing the effect of amlodipine, a long-acting, third-generation calcium channel blocker in angioplasty patients. Therapy (amlodipine 5 mg with a forced titration to 10 mg once daily, or placebo), is begun 2 weeks before angioplasty and is continued for 4 months after the procedure. The rationale of CAPARES is that amlodipine may offer anti-ischemic protection before, during, and after angioplasty, may have more beneficial effects on restenosis and various clinical end points than calcium channel blockers used in previous trials, and may improve the long-term outcome of PTCA therapy.

Mechanisms of neointima formation--lessons from experimental models

The lamina intima of an artery is the region between the endothelial cell surface and the internal elastic lamina, which forms the luminal margin of the media. In humans the intima of atherosclerosis-prone arteries becomes thicker due to accumulation of smooth muscle cells, which originate from the media. The introduction of percutaneous transluminal coronary angioplasty (PTCA) boosted scientific interest in intimal thickening, because restenosis remains an unresolved problem of this intervention. In order to unravel the mechanisms of intimal thickening there is a need for appropriate animal models. A brief overview of these models is given together with factors that control proliferation and/or migration. Despite intensive research on neointima formation, an effective therapy for restenosis has not emerged to date. This may be due to the fact that other processes, such as acute elastic recoil and chronic constrictive remodeling may contribute to lumen narrowing as well. Other limitations of neointima models are related to species and anatomical differences. Most studies are performed in arteries that are either lesion-free, or contain relatively mild plaques, in contrast to the complicated, stenotic lesions that are the substrate for human PTCA. Other differences are the severity of the injury and incorporation of a mural fibrin-rich thrombus. Nevertheless, studies based on superficial injury, like the frequently used balloon denudation model, are useful. There are similarities with angioplasty, such as endothelial cell damage and proliferation of medial and intimal smooth muscle cells. The use of techniques such as differential display, gene transfer and application of antisense oligonucleotides may provide new therapeutic approaches to reduce neointima formation.

Alteration of n-3 fatty acid composition in lung tissue after short-term infusion of fish oil emulsion attenuates inflammatory vascular reaction

OBJECTIVES

To investigate whether modulation of the fatty acid profile can be achieved by the short-term infusion of a fish oil emulsion which may attenuate the pulmonary response to inflammatory stimulation. Changes of fatty acid pattern in-lung tissue and perfusate were analyzed and correlated with physiologic data after a 3-hr infusion of fish oil in comparison with a soybean oil preparation.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Experimental laboratory in a university teaching hospital.

SUBJECTS

Forty standard breed rabbits of either gender.

INTERVENTIONS

Isolated lungs from anesthetized rabbits were ventilated and recirculation-perfused (200 mL/min) with 200 mL of cell-free buffer solution to which either 2 mL of saline (control, n = 6), 2 mL of a 10% soybean oil preparation (n = 6), or 2 mL of a 10% fish oil emulsion (n = 6) were added. Samples of perfusate and lung tissue were collected for analysis of fatty acid composition. Tissue and perfusate fatty acid composition were analyzed by capillary gas chromatography. To study metabolic alterations in states of inflammatory stimulation, lungs of each group were stimulated with small doses of the calcium ionophore, A23187 (10(-8) M), during the 180-min lipid perfusion period and again after washing out the lipids by exchanging the perfusion fluid. Pulmonary arterial pressure and lung weight gain were monitored, and eicosanoids were analyzed in the perfusate.

MEASUREMENTS AND MAIN RESULTS

Free eicosapentaenoic acids increased several-fold in lung tissue and perfusate during a 3-hr infusion with fish oil. The intravenously administered n-3 fatty acids were rapidly hydrolyzed, as indicated by the appearance of substantial quantities of eicosapentaenoic acid in the perfusate free fatty acid fraction. This increase of perfusion levels of eicosapentaenoic acid was paralleled by an attenuated pressure increase and edema formation due to calcium ionophore challenge and an altered eicosanoid spectrum determined in the perfusate compared with soybean oil-treated lungs.

CONCLUSION

Short-term n-3 lipid application (fish oil emulsion) exerts anti-inflammatory effects on lung vasculature, which may be due to the metabolism of eicosapentaenoic acid resulting in the generation of less potent inflammatory eicosanoids.

Experimental approaches to therapy and prophylaxis for heat stress and heatstroke

New developments in the fields of biochemistry, physiology, sepsis, cancer therapy, and molecular genetics have led to opportunities for the development of new therapies and prophylaxes for heat illnesses and for improving human performance during conditions of environmental stress. These include antilipopolysaccharide agents, anticytokines, potassium channel agents, a diet rich in omega-3 fatty acids, and psychological conditioning. This review summarizes the backgrounds and recent findings in the above fields and provides specific suggestions for potential therapy and prophylaxis for classic and exertional heatstroke and for improving athletic performance.

Immunostimulation following fish oil-based parenteral nutrition in tumor-bearing rats

Tumor-bearing (TB) and control rats were maintained for four to seven days on total parenteral nutrition (TPN) in which the lipid component (11.1% of total calories) was Intralipid or fish oil. Although no TB rats maintained on standard Intralipid-based TPN died prematurely in these experiments, one-third of the TB rats maintained on fish oil-based TPN died of bleeding complications by Day 4 of TPN infusion. The bleeding appeared to be due to the particle size in the fish oil emulsion, because a subsequent study employing a better emulsified TPN with smaller lipid particles exhibited fewer bleeding problems. Tumor growth, skeletal muscle atrophy, and gut hypoplasia were not reduced in the TB group maintained on fish oil-based TPN. However, immunosuppression observed in the Intralipid-based TPN group, as measured by mitogen response of cultured splenocytes, was significantly improved in the rats maintained on fish oil-based TPN. Levels of eicosapentaenoic acid were reduced in all rats receiving TPN. Although the hypothesized antitumor and anticachexia effects of fish oil administration were not realized, significant improvement in immunosuppression was noted. These results suggest that intravenously administered fish oil may have potential positive effects for the host.

Effect of dietary supplementation with n-3 fatty acids on coronary artery bypass graft patency

Epidemiologic and experimental data suggest that a high dietary intake of long-chain polyunsaturated n-3 fatty acids may reduce the risk of atherothrombotic disease. In a randomized, controlled study, 610 patients undergoing coronary artery bypass grafting were assigned either to a fish oil group, receiving 4 g/day of fish oil concentrate, or to a control group. All patients received antithrombotic treatment, either aspirin or warfarin. Their diet and serum phospholipid fatty acid profiles were monitored. The primary end point was 1-year graft patency, which was assessed by angiography in 95% of patients. Vein graft occlusion rates per distal anastomoses were 27% in the fish oil group and 33% in the control group (odds ratio 0.77, 95% confidence interval, 0.60 to 0.99, p = 0.034). In the fish oil group, 43% of the patients had > or = 1 occluded vein graft(s) compared with 51% in the control group (odds ratio 0.72, 95% confidence interval, 0.51 to 1.01, p = 0.05). Moreover, in the entire patient group, there was a significant trend to fewer patients with vein graft occlusions with increasing relative change in serum phospholipid n-3 fatty acids during the study period (p for linear trend = 0.0037). Thus, in patients undergoing coronary artery bypass grafting, dietary supplementation with n-3 fatty acids reduced the incidence of vein graft occlusion, and an inverse relation between relative change in serum phospholipid n-3 fatty acids and vein graft occlusions was observed.

Effects of chronic vitamin E deficiency and a high polyunsaturated fatty acid diet on rat mesenteric arterial function

1. Male rats were deprived as weanlings of dietary vitamin E and fed on a high polyunsaturated fatty acid (PUFA) diet for 6 months. Rats fed on a high PUFA or on an untreated diet served as controls. Mesenteric arterial beds were isolated and perfused at a constant flow rate (5 ml min-1) and the function of sympathetic nerves, smooth muscle and endothelium was assessed. 2. Electrical field stimulation (4-32 Hz, 90 V, 1 ms, for 30 s) elicited frequency-dependent vasoconstriction of the mesenteric arterial preparations. Response curves were similar between untreated control and PUFA-fed control groups. Maximum vasoconstrictor responses (at 24 and 32 Hz) were significantly attenuated in rats deprived of vitamin E and on a high PUFA diet compared to the PUFA-fed controls (P < 0.05). 3. Exogenous noradrenaline (NA; 0.15-500 nmol) elicited dose-dependent constriction of the mesenteric arterial beds. Preparations from rats fed on a high PUFA diet elicited significantly smaller responses compared to the control group. There was no significant difference in constrictor responses of PUFA rats deprived of vitamin E compared to the PUFA controls. Vasoconstrictor responses to doses of adenosine 5'-triphosphate (ATP) (5-5000 nmol) were significantly impaired in vitamin E-deficiency with a high PUFA diet compared to a high PUFA diet alone (P < < 0.001). Constrictor responses to potassium chloride (0.15 mmol) were significantly impaired in vitamin E-deficient PUFA rats compared to the PUFA-fed control group (P < 0.05). 4. Vasodilator responses were assessed in preparations in which tone was raised by continuous perfusion with methoxamine (4-25 microM). Mesenteric arterial beds from PUFA-fed rats deprived of vitamin E acquired significantly less tone, 59.8 +/- 4.6 mmHg (n = 7), than PUFA-fed controls 116.9 +/- 7.6 mmHg (n = 7) (P < 0.001) and were refractory to further increases in tone with further additions of methoxamine. Methoxamine-induced tone of PUFA-fed controls was greater than in P that in the untreated controls (83.9 +/- 7.4 mmHg; n = 5) (P < 0.05). Responses to the endothelium-dependent vasodilators acetylcholine (ACh) and ATP were significantly reduced in preparations from rats fed on the vitamin E-deficient high-PUFA diet compared to PUFA controls. Vasodilator responses to ACh were greater in PUFA controls than in untreated controls and this reached statistical significance at 5 nmol ACh. 5. Vasodilator responses to sodium nitroprusside, which acts directly on the vascular smooth muscle, were similar in untreated control and PUFA control groups. Responses were significantly attenuated in vitamin E-deficient PUFA rats compared to the PUFA control group (P < < 0.001). 6. These results indicate that a combination of a high PUFA diet and vitamin E deficiency impairs mesenteric arterial function at the level of the vascular smooth muscle. A high PUFA diet alone attenuates responses to NA and augments endothelium-dependent vasodilation. The detrimental effects of loss of antioxidant activity due to vitamin E-deficiency on vascular function may be exacerbated by a high PUFA diet.

Effect of n-3 fatty acid ethyl ester supplementation on fatty acid composition of the single platelet phospholipids and on platelet functions

Twenty healthy male volunteers were randomly assigned to receive either four 1-g capsules of n-3 polyunsaturated fatty acids (PUFA) ethyl esters or four 1-g capsules of olive oil (as placebo) for a period of 4 months, followed by a 3-month wash-out period. Fatty acids of platelet phospholipid fractions, platelet aggregation, and thromboxane B2 (TXB2) formation were analyzed at 0, 2, and 4 months of treatment and at 1, 2, and 3 months of wash-out. During n-3 PUFA supplementation, accumulations of eicosapentaenoic (EPA), docosapentaenoic (DPA), and docosahexaenoic (DHA) acids were markedly increased after 2 months, with slight differences in further accumulation up to 4 months among the various phospholipid fractions. Significant decreases in platelet sensitivity to collagen, serum TXB2 levels, and urinary TXB2 metabolites were also observed following n-3 PUFA treatment. During the first and second month of wash-out, slight differences were observed in changes of various fatty acids among different phospholipid fractions, but after 3 months of wash-out, alterations were no longer detectable with respect to pretreatment values. After 3 months of wash-out, platelet function parameters also were returned to baseline. Thus, both platelet lipids and function are influenced by n-3 PUFA ethyl ester supplementation, and significant alterations are still detectable after 2 months of wash-out.

How do fish oils affect vascular function?

1. This is a review on the mechanisms by which fish oils affect vascular function and how such changes contribute to their documented cardioprotective effects. 2. Evidence that fish oils depress vascular responses to contractile agents will be examined. It is concluded that this effect of fish oils is mediated predominantly by alterations in prostanoid profile. 3. Effects of fish oils on arterial relaxation are discussed with particular emphasis on endothelium dependent relaxation. It is suggested that the functional impairment of endothelium dependent relaxation documented in a number of cardiovascular disease states can be reversed by dietary fish oils. 4. In addition, possible effects of fish oils on growth factors, inositol trisphosphate and lipid metabolism, the sympathetic nervous system, rheological and membrane properties and inducible nitric oxide are reviewed.

Prostacyclin, nitric oxide, and atherosclerosis

Disorders in arterial production of PGI2 and NO occur in atherosclerosis. Exogenous PGI2 and NO are capable of interacting pharmacologically. We claim that no such direct interactions occur between endogenous endothelial PGI2 and NO. Studying mechanisms of cardiac reactive hyperemia in guinea pigs and of thrombolysis in cats, we surmise that in vivo vascular intima releases PGI2 intraluminally while NO is secreted abluminally and thus these two ephemeral mediators do not see each other. Hence, in any disease, the disturbances in endothelial generation of PGI2 or NO have to be scrutinized separately. It may well be that endogenous PGI2 maintains endothelial thromboresistance while NO controls arterial myocytes and tissues in which microcirculation is embedded. These responsibilities remain unshared. Interactions between PGI2 and NO are confined to pharmacological domains.

Cyclosporine-induced hypertension after transplantation

OBJECTIVE

To describe the features and mechanisms of posttransplantation hypertension and suggest appropriate management of the disorder.

DESIGN

We review our own experience and reports from the literature on hypertension in cyclosporine A (CSA)-treated transplant recipients.

RESULTS

Soon after immunosuppression with CSA and corticosteroids, hypertension develops in most patients who undergo transplantation. The blood pressure increases, which are usually moderate, occur universally because of increased peripheral vascular resistance. Disturbances in circadian patterns of blood pressure lead to loss of the normal nocturnal decline, a feature that magnifies hypertensive target effects. Changes in blood pressure sometimes are severe and associated with rapidly developing target injury, including intracranial hemorrhage, left ventricular hypertrophy, and microangiopathic hemolysis. The complex mechanisms that underlie this disorder include alterations in vascular reactivity that cause widespread vasoconstriction. Vascular effects in the kidney lead to reduced glomerular filtration and impaired sodium excretion. Many of these changes affect local regulation of vascular tone, including stimulation of endothelin and suppression of vasodilating prostaglandins. Effective therapy includes use of vasodilating agents, often calcium channel blocking drugs. Caution must be exercised to avoid interfering with the disposition of CSA or aggravating adverse effects relative to kidney and electrolyte homeostasis.

CONCLUSION

Recognition and treatment of CSA-induced hypertension and vascular injury are important elements in managing the transplant recipient.

Reduction in human neutrophil superoxide anion generation by n-3 polyunsaturated fatty acids: role of cyclooxygenase products and endothelium-derived relaxing factor

Dietary supplementation with n-3 polyunsaturated acids (PUFAs) results in augumented vasorelaxation and reduction in superoxide anion generation. Augmented vasorelaxation may be mediated by enhanced generation of vasodilator prostaglandins and/or endothelium-derived relaxing factor (EDRF), now thought to be nitric oxide (NO). To determine the importance of enhanced vasodilator prostaglandins or EDRF-NO in reduction in superoxide anion generation during n-3 PUFAs intake, human polymorphonuclear leukocytes (PMNs) were incubated with n-6 PUFA arachidonic acid (AA), or n-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (each 10(-7) M) for 1 hr at 37 degrees C. Parallel sets of PMNs were treated with the cyclooxygenase inhibitors indomethacin (10(-5) M), or aspirin (10(-5) M), or the EDRF-NO synthase inhibitor L-NMMA (10(-3) M) prior to incubation with PUFAs. Superoxide anion generation by PMNs was determined by measuring the superoxide dismutase (SOD) inhibitable reduction of ferricytochrome C. PMNs incubated with EPA or DHA, but not AA, demonstrated marked reduction in superoxide anion generation. This reduction in superoxide anion generation by n-3 PUFAs was abolished by treatment of PMNs with indomethacin or aspirin, but not by L-NMMA. These observations suggest that n-3 PUFAs decrease superoxide anion generation primarily by a prostaglandin-dependent pathway.

n-3 fatty acid ethyl ester administration to healthy subjects and to hypertriglyceridemic patients reduces tissue factor activity in adherent monocytes

n-3 Fatty acids are known to influence several functions of monocytes, including adhesion, cytokine synthesis, and superoxide generation. Monocytes express tissue factor, a membrane-bound glycoprotein, that acts as a catalyst in the coagulation cascade. In this study we evaluated the effects of administration of n-3 fatty acid ethyl esters to healthy volunteers and to hypertriglyceridemic patients on tissue factor activity (TF activity) in adherent monocytes. n-3 Fatty acids containing 75% eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (ratio of EPA to DHA, 1.34) were administered (3 g/d) to normal volunteers for 18 weeks. In addition, the effects of this treatment were evaluated in 30 hypertriglyceridemic patients for 24 weeks by using a double-blind, placebo-controlled study. TF activity in adherent monocytes was evaluated with a one-stage clotting assay. Plasma and monocyte fatty acid compositions were determined by gas-liquid chromatography. In healthy volunteers, n-3 fatty acids significantly reduced TF activity in adherent monocytes either in the unstimulated condition or after exposure to endotoxin. The inhibitory effect was observed after 12 weeks of treatment and was more pronounced after 18 weeks (> 70%, P < .001 versus baseline). Concomitantly, levels of EPA and DHA increased in plasma and monocyte lipids. Interestingly, after stopping treatment, monocyte TF activity remained inhibited for at least 14 weeks. Treatment with n-3 fatty acids for 24 weeks also resulted in a significant reduction of TF activity in adherent monocytes from hypertriglyceridemic patients (-31% and -40% in unstimulated and endotoxin-stimulated cells; P < .05 versus baseline).(ABSTRACT TRUNCATED AT 250 WORDS)

n-3 fatty acids and renal diseases

There are numerous biologic rationales for the use of n-3 fatty acids in renal diseases, including a possible increase in the renal vasodilatory capacity by a rearrangement of renal prostanoid production, a reduction in the production of proinflammatory leukotrienes, a reduction in the transcapillary escape rate of albumin, and actions limiting cyclosporine-related nephrotoxicity. Studies of animal models of renal disease, mostly of immune-renal disease, support the idea of the possible usefulness of these compounds. The most promising areas of clinical investigation include the reduction of proteinuria in some chronic glomerular diseases, the treatment of immunoglobulin A nephropathy, and the prevention of cyclosporine-induced nephrotoxicity. However, the results of larger clinical studies, some of which are ongoing, are necessary to support the use of n-3 fatty acids in human renal diseases.

Effects of dietary marine oil supplementation on reactivity of human buttock subcutaneous arteries and forearm veins in vitro

1. The vascular reactivity of resistance arteries isolated from gluteal skin biopsies and veins isolated from forearms of subjects fed marine oils were examined. 2. Twenty seven healthy adult males were randomly allocated to one of two different treatment groups. The first group received maxEPA (eicosapentaenoic acid 0.178 g g-1; docosahexaenoic acid 0.116 g g-1) capsules 10 g per day for 28 days while the second group received an equivalent amount of mixed oil placebo capsules. Biopsies were performed on day 29 (13 for gluteal sections; 14 for forearm vein biopsies). Subcutaneous arteries and veins were mounted in myographs and standard organ baths, respectively. 3. The internal diameter of the subcutaneous arteries at a calculated transmural pressure of 100 mmHg averaged 183.7 +/- 10.3 microns in the maxEPA group and 182.6 +/- 19.8 microns in the placebo controls. Arteries from subjects on maxEPA demonstrated increased sensitivity to angiotensin II (maxEPA vs placebo: -log EC50 (M) -8.36 +/- 0.18 vs -7.91 +/- 0.14) but not to noradrenaline or 5-hydroxytryptamine. Concentration-response curves to acetylcholine, substance P and sodium nitroprusside obtained for noradrenaline precontracted vessels were unaltered with marine oil treatment as was the concentration-response curve to calcium in K(+)-depolarized vessels. 4. Vein internal diameter at a calculated transmural pressure of 20 mmHg averaged 3.06 +/- 0.23 mm in the maxEPA group and 2.96 +/- 0.89 in the placebo group. Responses to noradrenaline, 5-hydroxytryptamine, angiotensin II and endothelin-1 were obtained in the absence and presence of indomethacin (1 microM) in veins from both maxEPA and placebo-treated subjects. Neither dietary supplementation with marine oils nor indomethacin had any effect on the responses obtained to these agonists.5. The major finding of the present study was that in general, maxEPA supplementation did not affect responses to various vasoactive substances on isolated subcutaneous arteries or forearm veins. An exception was the observation of an enhanced response to angiotensin II in subcutaneous resistance arteries studied in vitro. This effect was selective for angiotensin II and was not apparent in veins isolated from the forearm.

The effect of linoleic, arachidonic and eicosapentaenoic acid supplementation on prostacyclin production in rats

We examined the effect of dietary supplementation of linoleic acid (LA), arachidonic acid (AA) or eicosapentaenoic acid (EPA) to rats fed a diet low in linoleic acid on in vitro and in vivo production of prostacyclin. Male Sprague Dawley rats were fed a high-fat diet (50% energy as fat, 1.5% linoleic acid) for two weeks. Three of the groups were then supplemented orally with either 90 mg/d of LA, AA or EPA, all as the ethyl esters, for a further two weeks while remaining on the high-fat diet. Forty-eight hour urine samples were collected at the end of the second and fourth weeks. In vivo prostacyclin production was determined by a stable isotope dilution, gas chromatography/mass spectrometry assay for the major urinary metabolite of prostacyclins (2,3-dinor-6-keto-PGF1 alpha or PGI2-M and delta 17-2,3-dinor-6-keto-PGF1 alpha or PGI3-M). In vitro prostacyclin production was determined by radioimmunoassay of the stable metabolite (6-keto-PGF 1 alpha) following incubation of arterial tissue. Oral supplementation with AA resulted in a rise in plasma and aorta 20:4n-6, and increased in vitro prostacyclin and urinary PGI2-M production. EPA supplementation resulted in a rise in plasma and aorta 20:5n-3 and 22:5n-3, and a decline in plasma 20:4n-6, but not in the aorta. In the EPA-supplemented group, the in vitro prostacyclin and the urinary PGI3-M increased, but urinary PGI2-M decreased. The increase in in vitro prostacyclin production in the EPA-supplemented rats was unexpected and without obvious explanation.(ABSTRACT TRUNCATED AT 250 WORDS)

New antithrombotic strategies for resistant thrombotic processes

Life-threatening thrombo-occlusive events producing heart attacks and strokes develop in patients at sites of atherosclerotic arterial stenoses when plaques rupture, a process resistant to both aspirin and heparin. Resistant thrombotic complications are also troublesome during therapeutic thrombolytic or mechanical interventions for symptomatic atherosclerotic vascular disease, including angioplasty, various types of atherectomies, endarterectomy, endovascular stent deployment, or implanted small caliber vascular grafts. In this review therapeutic strategies for more effective management of these resistant, platelet-dependent, occlusive thrombi are discussed, including: a) inhibition of platelet recruitment by anti-GPIIb/IIIa monoclonal antibodies, naturally occurring peptides containing RGD sequences, or synthetic competitive analogs; b) direct inactivation of thrombin bound to thrombus by natural or synthetic antithrombin peptides; c) interruption of thrombin's production by natural or synthetic antagonists of Factor Xa or extrinsic and intrinsic coagulation pathways; and d) elimination of thrombogenicity at sites of vascular injury by immediately restoring confluent endothelium or prior therapy with dietary n-3 fatty acids. However, antagonists of both GPIIb/IIIa- and thrombin-dependent platelet recruitment produce equivalent inhibition of thrombus formation and platelet hemostatic function. Interestingly, hemostasis is spared by therapies that inhibit thrombin's production. Recommendations for development strategies are related to the relative hemostatic risks and antithrombotic benefits.

n-3 fatty acids reduce proteinuria in patients with chronic glomerular disease

Dietary supplementation with n-3 polyunsaturated fatty acids (n-3 PUFA) has been shown to reduce proteinuria in experimental models of renal diseases, but their potential role in the treatment of human renal disease is unknown. We administered n-3 PUFA in the form of triglycerides [with eicosapentaenoic (EPA)+docosahexaenoic (DHA) = 3 g/day into 4 patients] and of ethyl esters (EPA+DHA = 7.7 g/day) into 10 patients (one patient twice) with chronic glomerular disease (membranous glomerulonephritis and focal glomerular sclerosis), all diagnosed histologically. Serum albumin was > 2.4 g/dl and serum creatinine < 2.5 mg/dl in all patients. Treatment was given for periods of six weeks, followed by a prolonged follow-up for 27 weeks in 10 cases. Dietary supplementation with n-3 PUFA caused the expected reduction in platelet generation of thromboxane B2 (mean +/- SEM, from 490 +/- 70 ng/ml at baseline, to 342 +/- 147 ng/ml at 6 weeks, P < 0.05) of serum triglycerides (from 236 +/- 60 to 170 +/- 43, P < 0.01), and a prolongation of the bleeding time (from 5.8 +/- 0.4 min to 7.7 +/- 0.4 min, P < 0.01) in patients treated with ethyl esters. A modest but significant reduction in serum total cholesterol was noticed (from 275 +/- 27 to 252 +/- 24 mg/dl).(ABSTRACT TRUNCATED AT 250 WORDS)

Interruption of vascular thrombus formation and vascular lesion formation by dietary n-3 fatty acids in fish oil in nonhuman primates

BACKGROUND

Because of discrepant claims regarding the relative biological effects of n-3 fatty acids (n-3FAs), we have concurrently measured the effects of dietary n-3FAs on blood and vascular lipid composition, hemostatic function, blood thrombotic responses, vascular thrombus formation, and vascular lesion formation in baboons.

METHODS AND RESULTS

Dietary n-3FAs displaced n-6FAs in plasma, platelets, blood vessels, and corresponding urinary eicosanoid metabolites (p < 0.01 in all cases) within weeks after initiation of a semipurified diet containing 1 g/kg per day n-3FA-ethyl ester concentrate (composed of two thirds eicosapentanoic acid and one third docosahexanoic acid). Coincidentally, platelet hemostatic function became minimally impaired (template bleeding times prolonged from 4.3 +/- 0.5 minutes to 7.6 +/- 1.3 minutes, p = 0.039); concentrations of collagen producing half-maximal platelet aggregation increased (from 6.4 +/- 2.1 to 8.5 +/- 2.5 micrograms/mL, p = 0.045); and tissue factor expression by endotoxin-stimulated blood monocytes fell (from 6.5 +/- 1.2 to 1.7 +/- 0.14 mU/10(6) cells, p < 0.005). Dietary n-3FAs decreased deposition of platelets onto thrombogenic segments of Dacron vascular graft incorporated into chronic exteriorized femoral arteriovenous (AV) shunts, a thrombotic process resistant to the effects of both aspirin and heparin (111In-labeled platelet deposition decreased from 14.1 +/- 1.4 x 10(9) platelets/5-cm segment at 40-60 minutes with occlusion to 7.5 +/- 0.8 x 10(9) platelets/5-cm segment without occlusion; p < 0.001). Platelet deposition onto segments of endarterectomized homologous normal aorta in the AV shunts of n-3FA-treated animals was similarly reduced (from 4.4 +/- 0.9 to 1.8 +/- 0.4 x 10(9) platelets; p < 0.01). Dietary n-3FAs interrupted vascular thrombus formation at sites of surgical carotid endarterectomy (platelet deposition, 1.5 +/- 0.4 versus 4.4 +/- 1.0 x 10(9) platelets in untreated controls; p < 0.001). Moreover, endarterectomized aortic segments (EASs) from n-3FA-treated donors exhibited little capacity to induce thrombus formation when tested in the AV shunts of control recipient animals (0.24 +/- 0.10 versus 4.4 +/- 0.90 x 10(9) platelets). However, in the converse crossover experiments, EASs from control animals actively accumulated platelets when studied in the AV shunts of n-3FA-treated animals (1.8 +/- 0.4 x 10(9) platelets; p < 0.01 versus n-3FA-treated EASs in shunts of normal animals). Dietary n-3FAs also abolished vascular lesion formation at sites of carotid endarterectomy 6 weeks after surgery (cross-sectional area of neointima 0.048 +/- 0.031 mm2 compared with 0.428 +/- 0.104 mm2 in control arteries; p = 0.010).

CONCLUSIONS

In nonhuman primates, dietary n-3FAs in high doses eliminate both vascular thrombus formation and vascular lesion formation after mechanical vascular injury while largely sparing hemostatic function and modestly reducing blood thrombotic responses. These effects are attributed to selective n-3FA-dependent alterations in cellular membrane functions.

Dietary n-3 fatty acid effects on neutrophil lipid composition and mediator production. Influence of duration and dosage

Healthy volunteers supplemented their usual Western diets with Promega fish oil supplement (eicosapentaenoic acid [EPA], 0.28 g; docosahexaenoic acid [DCHA], 0.12 g; other n-3 fatty acids 0.10 g per capsule) using three protocols. Initial experiments (protocol 1 and 2) investigated the kinetics of incorporation of n-3 fatty acids into serum and neutrophil lipids after 10 capsules/d of Promega. EPA was rapidly detected in both serum and neutrophil lipids; the arachidonic acid (AA) to EPA ratio in neutrophil phospholipids showed a maximal reduction of 49:1 to 8:1 within 1 wk of beginning supplementation. EPA was preferentially incorporated into phosphatidyl-ethanolamine and phosphatidylcholine but not phosphatidylinositol. Long-term supplementation for up to 7 wk did not influence the AA/EPA ratio or the distribution of EPA among neutrophil phospholipids in a manner that was not observed after the first week. Neutrophils produced similar quantities of platelet-activating factor and slightly lower quantities of leukotriene B4 during long-term supplementation when compared with presupplementation values. Experiments examining the influence of Promega dosage indicated that the AA/EPA ratio in neutrophil lipids decreased in a dose-dependent manner. Only when the dose was increased to 15 capsules/d was there a reduction in the AA/DCHA ratio in neutrophil lipids. The quantity of AA in neutrophil lipids remained relatively constant at all supplement doses. Taken together, the current study demonstrates the capacity of n-3 fatty acids provided with a Western diet to be rapidly incorporated into neutrophil lipids. However, dietary n-3 fatty acids appear not to significantly reduce arachidonate content within neutrophil phospholipids. Constant arachidonate levels may account for the lack of large reductions in the biosynthesis of lipid mediators by neutrophils after fish-oil supplementation.

Dietary fish oil reduces leukocyte/endothelium interaction following systemic administration of oxidatively modified low density lipoprotein

BACKGROUND

In vitro and in vivo experiments have demonstrated the role of oxidatively modified low density lipoprotein (oxLDL) in eliciting leukocyte/endothelium interaction during early atherogenesis.

METHODS AND RESULTS

In the present study we investigated the effect of dietary fish oil on oxLDL-induced leukocyte/endothelium interaction using intravital fluorescence microscopy in the dorsal skinfold chamber model in awake Syrian golden hamsters. Hamsters were fed for 4 weeks prior to the experiments with either standard laboratory chow or a diet supplemented with 5% of a fish oil concentrate (18% eicosapentaenoate, 12% docosahexaenoate). The efficacy of the fish oil diet was demonstrated by the incorporation of fish oil-derived omega-3 fatty acids into plasma, leukocyte, and erythrocyte lipids. In control hamsters (n = 7) and fish oil-fed hamsters (n = 7), leukocyte/endothelium interaction was assessed in the time course after intravenous injection of human LDL (4 mg/kg), oxidized by 7.5 microM Cu2+ (6 hours, 37 degrees C). In control hamsters, injection of oxLDL elicited the rolling and sticking of leukocytes to the endothelium of arterioles and postcapillary venules with a maximum 15 minutes after injection (arterioles: from 3 +/- 1 to 91 +/- 25 cells/mm2 at 15 minutes; venules: from 13 +/- 6 to 150 +/- 46 cells/mm2 at 15 minutes; mean +/- SD). This phenomenon was significantly reduced in fish oil-fed hamsters, where 15 minutes after injection of oxLDL leukocyte sticking reached a maximum of only 15 +/- 7 and 20 +/- 5 cells/mm2 in arterioles and postcapillary venules, respectively (p less than 0.01 versus control animals).

CONCLUSIONS

The results of the present study suggest that inhibition of leukocyte/endothelium interaction may be one of the mechanisms by which dietary fish oil exerts its protective effects on experimental and clinical atherogenesis.

Effects of dietary omega 3 fatty acids on vascular contractility in preanoxic and postanoxic aortic rings

BACKGROUND

Vasomotor reactivity may contribute to the pathophysiology of ischemic injury. The atherosclerotic vessel may be particularly susceptible to vasoconstriction because of the damaged endothelial layer with resultant loss of vasodilatory factors. While dietary omega 3 fatty acids have been proposed to protect against vascular occlusion, it is not clear to what extent this results from alterations in the function of platelets or from changes intrinsic to the blood vessel itself.

METHODS AND RESULTS

The effects of dietary supplementation with fish oils on vascular contractility were examined in endothelialized and de-endothelialized aortic rings under pre- and postanoxic conditions. De-endothelialization was defined functionally by the loss of acetylcholine-induced vasodilation in norepinephrine-preconstricted aortic rings from rats fed normal rat chow. Three groups of rats were fed diets containing either 20% menhaden oil or 20% beef tallow, both supplemented with 3% corn oil or 23% corn oil for longer than 4 weeks. All animals received vitamin E. Under well-oxygenated conditions, de-endothelialized aortic rings from rats fed fish oil and corn oil contracted to similar extents with norepinephrine and vasopressin and less than rings from rats fed beef tallow. Endothelialized (intact) and de-endothelialized rings from rats fed fish oil relaxed more in response to acetylcholine than rings from rats fed beef tallow and corn oil. After anoxic exposure and reoxygenation, KCl-induced contraction of intact rings from rats fed fish oil and corn oil was similar and less than rings from rats fed beef tallow. Intact and de-endothelialized rings from rats fed fish oil relaxed more to acetylcholine than did rings from rats fed beef tallow and corn oil.

CONCLUSIONS

Under preanoxic or postanoxic conditions, rings from rats fed fish oil and corn oil contracted less than rings from rats fed beef tallow. The relaxation response to acetylcholine, however, was greater in rings from rats fed fish oil than from rats fed either corn oil or beef tallow. These vascular effects of fish oil feeding may result in increased blood flow to ischemic and reperfused tissues in vivo.

Dietary fish oil blocks the microcirculatory manifestations of ischemia-reperfusion injury in striated muscle in hamsters

Epidemiologic observations and experimental studies have demonstrated a protective effect of dietary fish oil on the clinical manifestations of ischemia-reperfusion injury. To investigate the underlying mechanisms, we used the dorsal skinfold chamber model for intravital fluorescence microscopy of the microcirculation in striated muscle of awake hamsters. In control hamsters (n = 7), reperfusion after a 4-hr pressure-induced ischemia to the muscle tissue elicited the adhesion of fluorescently stained leukocytes to the endothelium of postcapillary venules, capillary obstruction, and the break-down of endothelial integrity. These microvascular manifestations of ischemia-reperfusion injury were significantly attenuated in animals (n = 7) when fed with a fish oil-enriched diet for 4 weeks prior to the experiments. In leukocyte total lipids, the fish oil diet resulted in a substantial displacement of arachidonic acid, the precursor of the potent adhesion-promoting leukotriene (LT) B4, by fish oil-derived eicosapentaenoic acid, the precursor of biologically less potent LTB5, emphasizing the mediator role of LTB4 in ischemia-reperfusion injury. These results suggest that the preservation of microvascular perfusion by dietary fish oil contributes to its protective effects on the clinical manifestations of ischemia-reperfusion injury.