Plasma lipoproteins enhance tissue factor-independent factor VII activation

Effects of astaxanthin on blood coagulation, fibrinolysis and platelet aggregation in hyperlipidemic rats

CONTEXT

Astaxanthin (ASTX) is a xanthophyll carotenoid that reduces hemostasis in hyperlipidemic organisms. Its antihemostatic mechanisms remain unclear.

OBJECTIVE

The effects of ASTX on coagulation, the fibrinolytic system and platelet aggregation were investigated in hyperlipidemic rats.

MATERIALS AND METHODS

Different doses of ASTX (5, 10 and 30 mg/kg/day, p.o.) were administered for four weeks to high-fat diet-induced hyperlipidemic rats. Serum lipid and lipoprotein levels were measured with an automatic biochemical analyzer. The prothrombin time (PT), activated partial thromboplastin time (APTT) and maximum platelet aggregation rate (MAR) were determined by a coagulation analyzer. The activities of the tissue-type plasminogen activator (t-PA), type-1 plasminogen activator inhibitor (PAI-1) and endothelial nitric oxide synthase (eNOS), as well as the levels of thromboxane B(2) [TXB(2)], 6-keto prostaglandin F(1α) [6-keto-PGF(1α)] and platelet granule membrane protein (GMP-140), were measured with enzyme-linked immunosorbent assay kits. Gene and protein expression levels were analyzed by reverse transcriptase polymerase chain reaction and Western blot, respectively.

RESULTS

ASTX (30 mg/kg) treatment in hyperlipidemic rats reduced serum TG (0.58 ± 0.14 versus 1.12 ± 0.24 mmol/L), serum TC (1.77 ± 0.22 versus 2.24 ± 0.21 mmol/L), serum LDL-C (1.13 ± 0.32 versus 2.04 ± 0.48 mmol/L), serum MDA (69%), plasma MAR (55%), serum TXB2/6-keto-PGF1α (34%) and serum GMP-140 levels (25%), plasma PAI-1 activity (48%) and downregulated the mRNA (33%) and protein (23%) expression of aorta eNOS, the mRNA (79%) and protein (72%) expression levels of aorta PAI-1. However, ASTX (30 mg/kg/d) treatment increased serum SOD activity (2.1 fold), serum GPx activity (1.8 fold), plasma PT (1.3 fold), plasma APTT (1.7 fold), serum NO (1.4-fold), serum 6-keto-PGF1α (1.3 fold).

CONCLUSIONS

ASTX reduced blood coagulation and platelet aggregation and promoted fibrinolytic activity in hyperlipidemic rats. These activities were closely correlated with ASTX, maintaining the balance of t-PA/PAI-1, NO/ROS and TXA2/PGI2 in vivo.

Does Lipid Profile Affect Thrombin Generation During Ramadan Fasting in Patients With Cardiovascular Risks?

There is evidence that diet and variation in lipid metabolism can influence blood coagulation, but little is known about the effect of Ramadan fasting on plasmatic coagulation pattern. We investigated the effect of Ramadan fasting on thrombin generation (TG) in patients with cardiovascular disease (CVD) risks, and we aimed to assess the effect of lipid profile on TG parameters. The study was conducted in 36 adults having at least 2 CVD risks and in 30 healthy controls. Coagulation pattern was assessed by both classical clotting times and TG test. A complete lipid profile was performed simultaneously. Patients were invited 2 times: 1 week before Ramadan and during the last week of the Ramadan. The TG parameters were not different in patients with CVD risks compared to healthy controls. Fasting had no effect on plasmatic coagulation parameters and on TG profile. Individual analysis of the mean rate index (MRI) of TG revealed 3 groups: group 1 with no modification of MRI, group 2 with a significant increase in MRI (81.64 nM/min vs 136.07 nM/min; P < .001), and group 3 with a significant decrease in MRI (125.27 nM/min vs 73.18 nM/min; P = .001). Only in group 2, a significant increase was observed in total cholesterol and low-density lipoprotein cholesterol. Changes in lipid profile during Ramadan fasting did not influence the global coagulation pattern in patients with CVD risks. Whereas, a significant increase in the propagation phase of TG was associated with a significant increase in cholesterol levels, which was not found with the other TG parameters.

Diurnal variation of haemostatic response to exercise in young sedentary males

The aim of this study was to evaluate diurnal variations in the haemostatic response to submaximal exercise performed by young, sedentary men. Fifteen healthy young sedentary males aged 25.6 ± 1.34 (mean ± SD) years performed two exercise sessions, morning and evening, at 70% of maximal oxygen consumption (V.O₂max) on a cycle ergometer for 30 min. Platelet count (PC), activated partial thromboplastin time (aPTT), prothrombin time (PT), fibrinogen, tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) activity were measured as dependent variables. Exercise produced significant increases in PC and fibrinogen for both sessions (P ≤ 0.05), which returned to the resting values after recovery only in the evening session. APTT and PT shortened immediately after exercise, which remained after recovery for both sessions (P ≤ 0.01). Exercise presented significant increases in tPA activity (P ≤ 0.001), which returned to the baseline after recovery in both exercises. PAI-1 activity was significantly higher during the morning than evening (P ≤ 0.05), but no longer demonstrated exercise-related changes. It was found that exercise caused activation of both coagulation and fibrinolysis processes, partly related to the time of the day when the exercise was performed.

Factor II activity is similarly increased in patients with elevated apolipoprotein CIII and in carriers of the factor II 20210A allele

Background

Few studies have so far investigated the relationship between apolipoprotein CIII (Apo CIII) and coagulation pathway in subjects with or without coronary artery disease (CAD).

Methods and Results

Serum Apo CIII concentrations and plasma coagulant activities of factor II (FII:c), factor V (FV:c), and factor VIII (FVIII:c), and activated factor VII (FVIIa) were analyzed in a total of 933 subjects, with (n=687) or without (n=246) angiographically demonstrated CAD and not taking anticoagulant drugs. Activated factor X (FXa) generation assay was performed on plasma from subgroups of subjects with low and high levels of Apo CIII. A statistical incremental concentration of FII:c, FV:c, and FVIIa levels was observed through the quartiles of Apo CIII distribution in the population considered as a whole. Significant results were confirmed for FII:c in CAD and CAD‐free subgroup when separately considered. Subjects within the highest Apo CIII quartile (>12.6 mg/dL) had high FII:c levels not statistically different from those of carriers of 20210A allele (n=40; 4.28%). In a multiple linear model, Apo CIII was the best predictor of FII:c variability, after adjustment for age, gender, plasma lipids, CRP, creatinine, diagnosis, and carriership of 20210A allele. FXa generation was increased and its lag time shortened in plasmas with high Apo CIII levels. However, after thrombin inhibition by hirudin, differences between low and high Apo C‐III samples disappeared.

Conclusions

Elevated concentrations of Apo CIII are associated with an increase of thrombin activity to an extent comparable with the carriership of G20210A gene variant and mainly modulating the thrombin generation.

A new ratio for better predicting future death/myocardial infarction than standard lipid measurements in women >50 years undergoing coronary angiography: the apolipoprotein A1 remnant ratio (Apo A1/ [VLDL₃+IDL])

BACKGROUND

Women often lag behind men in their risk of cardiovascular events. However, with age and the onset of menopause, women's cardiovascular risk eventually becomes similar to that of men. This change in risk may, in part, be attributable to a shift to a more atherogenic lipid profile. Our objective was to evaluate standard- and sub-lipid parameters and the apo A1 remnant ratio: (apo A1/[VLDL₃-C+IDL-C]) for their associations with death/myocardial infarction among peri- and post-menopausal women.

METHODS

Women (N=711) >50 years of age undergoing coronary angiography were evaluated. Baseline clinical and angiographic characteristics, lipids, and sub-lipid levels (Vertical Auto Profile method) were collected. Cox regression analysis, adjusted by standard cardiovascular risk factors, was utilized to determine associations of lipid and sub-lipid tertiles(T) with death/myocardial infarction at 1 and 3 years.

RESULTS

Patients averaged 67.7±9.4 years and 53.6% had underlying severe (≥70% stenosis) coronary artery disease. The apo A1 remnant ratio was found to have stronger associations for 1 year (T1 vs. T3: HR=2.13, p=0.03, T2 vs. T3: HR=1.57, p=0.21) and 3 year (T1 vs. T3: HR=2.32, p=0.002, T2 vs. T3: HR=1.97, p=0.01) death/myocardial infarction than any individual lipid (LDL-C, HDL-C, triglycerides, non-HDL-C) or sub-lipid (apo A1, apo B, VLDL₃-C+IDL-C) measure, or any other well-known ratio (triglyercies/HDL-C, apo B/A1, TChol/HDL-C, HDL-C/[VLDL₃-C+IDL-C]).

CONCLUSIONS

The apo A1 remnant ratio was a significant predictor of short and intermediate-term death/myocardial infarction risk among women >50 years of age. Furthermore, this ratio was found to have greater predictive ability than traditional lipid and sub-lipid parameters and represents a potential new risk marker.

Reevaluation of the role of HDL in the anticoagulant activated protein C system in humans

HDL has anti-atherogenic properties, and plasma levels of HDL cholesterol correlate inversely with risk of coronary artery disease. HDL reportedly functions as a cofactor to the anticoagulant activated protein C (APC) in the degradation of factor Va (FVa). The aim of the present study was to elucidate the mechanism by which HDL functions as cofactor to APC. Consistent with a previous report, HDL isolated from human plasma by ultracentrifugation was found to stimulate APC-mediated degradation of FVa. However, further purification of HDL by gel filtration revealed that the stimulating activity was not a property of HDL. Instead, the stimulating activity eluted completely separately from HDL in the high-molecular-weight void volume fractions. The active portion of these fractions stimulated FVa degradation by APC and supported the assembly of factor Xa and FVa into a functional prothrombinase complex. Both the procoagulant and anticoagulant activities were blocked by addition of annexin V, suggesting that the active portion was negatively charged phospholipid membranes. These results demonstrate that HDL does not stimulate the APC/protein S effect and that the activity previously reported to be a property of HDL is instead caused by contaminating negatively charged phospholipid membranes.

The role of phospholipid transfer protein in lipoprotein-mediated neutralization of the procoagulant effect of anionic liposomes

BACKGROUND

Serum has the ability to neutralize the procoagulant properties of anionic liposomes, with transfer of phospholipids (PLs) to both high-density lipoprotein (HDL) and low-density lipoprotein (LDL) particles. Phospholipid transfer protein (PLTP) mediates transfer of PLs between HDL and other lipoproteins and conversion of HDL into larger and smaller particles.

OBJECTIVES

To examine the role of PLTP in the neutralization of procoagulant liposomes.

METHODS

Procoagulant liposomes were incubated with different lipoproteins in the presence or absence of PLTP, and then tested for their ability to stimulate thrombin formation.

RESULTS AND CONCLUSIONS

In the absence of added PLTP, the lipoprotein-enriched fraction, total HDL, HDL(3) and very high-density lipoprotein (VHDL) were all able to neutralize the procoagulant properties of the liposomes. In these samples, endogenous PLTP was present, as judged by Western blotting. In contrast, no PLTP was present in LDL, HDL(2) and lipoprotein-deficient serum, all of which displayed no ability to neutralize the procoagulant liposomes. The phospholipid (PL) transfer activity was dependent on both enzyme (PLTP) and PL acceptor (lipoproteins). After treatment of the VHDL fraction with antiserum against PLTP, the neutralization of procoagulant activity was reduced, but could be regained by the addition of active PLTP. The neutralizing activity was dependent on a catalytically active form of PLTP, and addition of a low activity form of PLTP had no effect. In conclusion, PLTP was found to mediate transfer of anionic PLs to HDL and LDL, thereby neutralizing the effect of procoagulant liposomes, resulting in a reduction of procoagulant activity.

Triacylglycerol structure and interesterification of palmitic and stearic acid-rich fats: an overview and implications for cardiovascular disease

The position of fatty acids in the TAG molecule (sn-1, sn-2 and sn-3) determines the physical properties of the fat, which affects its absorption, metabolism and distribution into tissues, which may have implications for the risk of CHD. The TAG structure of fats can be manipulated by the process of interesterification, which is of increasing commercial importance, as it can be used to change the physical characteristics of a fat without the generation of trans-fatty acids. Interesterified fats rich in long-chain SFA are commercially important, but few studies have investigated their health effects. Evidence from animal and human infant studies suggests that TAG structure and interesterification affect digestibility, atherogenicity and fasting lipid levels, with fats containing palmitic and stearic acid in the sn-2 position being better digested and considered to be more atherogenic. However, chronic studies in human adults suggest that TAG structure has no effect on digestibility or fasting lipids. The postprandial effects of fats with differing TAG structure are better characterised but the evidence is inconclusive; it is probable that differences in the physical characteristics of fats resulting from interesterification and changes in TAG structure are key determinants of the level of postprandial lipaemia, rather than the position of fatty acids in the TAG. The present review gives an overview of TAG structure and interesterified palmitic and stearic acid-rich fats, their physical properties and their acute and chronic effects in human adults in relation to CHD.

Anionic phospholipids lose their procoagulant properties when incorporated into high density lipoproteins

Blood coagulation involves a series of enzymatic protein complexes that assemble on the surface of anionic phospholipid. To investigate whether apolipoproteins affect coagulation reactions, they were included during the preparation of anionic phospholipid vesicles using a detergent solubilization-dialysis method. Apolipoprotein components of high density lipoproteins, especially apolipoprotein A-I, had a pronounced anticoagulant effect. The anionic phospholipids lost their procoagulant effect when the vesicle preparation method was performed in the presence of apolipoprotein A-I. The anionic phospholipid-apolipoprotein A-I particles were 8-10 nm in diameter and contained around 60-80 phospholipid molecules, depending on the phospholipid composition. The phospholipids of these particles were unable to support the activation of prothrombin by factor Xa in the presence of factor Va and unable to support binding of factor Va, whereas binding of prothrombin and factor Xa were efficient. Phospholipid transfer protein was shown to mediate transfer of phospholipids from liposomes to apolipoprotein A-I-containing reconstituted high density lipoprotein. In addition, serum was also shown to neutralize the procoagulant effect of anionic liposomes and to efficiently mediate transfer of phospholipids from liposomes to either apolipoprotein A-I- or apolipoprotein B-containing particles. In conclusion, apolipoprotein A-I was found to neutralize the procoagulant properties of anionic phospholipids by arranging the phospholipids in surface areas that are too small to accommodate the prothrombinase complex. This anionic phospholipid scavenger function may be an important mechanism to control the exposure of such phospholipids to circulating blood and thereby prevent inappropriate stimulation of blood coagulation.

Intake of phenol-rich virgin olive oil improves the postprandial prothrombotic profile in hypercholesterolemic patients

BACKGROUND

Oxidative stress associated with postprandial lipemia contributes to endothelial dysfunction, which shifts hemostasis to a more thrombogenic state.

OBJECTIVE

We investigated whether a high concentration of phenols in olive oil can partly reverse this phenomenon.

DESIGN

Twenty-one hypercholesterolemic volunteers received 2 breakfasts rich in olive oils with different phenolic contents (80 or 400 ppm) according to a randomized, sequential crossover design. Plasma concentrations of lipid fractions, factor VII antigen (FVIIag), activated factor VII (FVIIa), and plasminogen activator inhibitor-1 (PAI-1) activity were measured at baseline and postprandially.

RESULTS

Concentrations of FVIIa increased less (P = 0.018) and plasma PAI-1 activity decreased more (P = 0.021) 2 h after the high-phenol meal than after the low-phenol meal. FVIIa concentrations 120 min after intake of the olive oil with a high phenol content correlated positively with fasting plasma triacylglycerols (P = 0.001), area under the curve (AUC) of triacylglycerols (P = 0.001), and AUC of nonesterified fatty acids (P = 0.024) and negatively with hydroxytyrosol plasma concentrations at 60 min (P = 0.039) and fasting HDL-cholesterol concentrations (P = 0.005). PAI-1 positively correlated with homeostasis model assessment of insulin resistance (P = 0.005) and fasting triacylglycerols (P = 0.025) and inversely with adiponectin (P = 0.026). In a multivariate analysis, the AUCs of nonesterified fatty acids (R(2) = 0.467; beta: 0.787; SE: 0.02; P < 0.001) and adiponectin (R(2) = 0.232; beta: -1.594; SE: 0.629; P < 0.05) were the strongest predictors of plasma FVIIa and PAI-1, respectively.

CONCLUSIONS

A virgin olive oil with a high content of phenolic compounds changes the postprandial hemostatic profile to a less thrombogenic state.

Relationship between metabolic syndrome and platelet responsiveness to leptin in overweight and obese patients

OBJECTIVE

To verify whether platelet responsiveness to leptin is associated with metabolic syndrome risk factors.

DESIGN

Cross-sectional study.

SUBJECTS

We studied 169 consecutive patients, mean age=43.6+/-9.9 years, with overweight (N=57) or obesity (N=112).

MEASUREMENTS

Cluster analysis was used to generate three clusters based on platelet responsiveness to increasing doses of leptin. Profiles of metabolic syndrome risk factors of the three clusters were compared by discriminant analysis.

RESULTS

Platelet responsiveness to leptin was absent in cluster 1, whereas cluster 3 had the greatest platelet aggregation response to leptin pre-incubation. Plasma leptin levels significantly decreased from cluster 1 to cluster 3 in both gender. Patients in cluster 2 had an intermediate profile of leptin responsiveness. Highest body mass index (BMI) values were more frequent in non-responders, whereas the prevalence of high waist circumference, as well as hypertriglyceridemia and hypertension, increased with increasing responsiveness to leptin from cluster 1 to cluster 3. Pattern of metabolic syndrome risk factors qualified as group specific in 69.0% of the cluster 1, 54.9% of the cluster 2 and 55.8% of the cluster 3. Circulating leptin, waist circumference, plasma triglycerides and BMI defined distinctive patterns of metabolic syndrome risk factors in the clusters.

CONCLUSIONS

In overweight and obese outpatients, metabolic syndrome risk factors parallel to some extent platelet responsiveness to leptin. Such a correlation involves plasma leptin levels, waist circumference, plasma triglycerides and BMI, and may contribute to the excess risk of cardiovascular events in overweight and obese patients.

Measures of Thrombosis and Fibrinolysis

Our recent understanding of acute coronary syndrome as an atherothrombotic process has led to research efforts in the development of markers of thrombosis and fibrinolysis for risk prediction in cardiovascular heart disease. Although American Heart Association/American College of Cardiology guidelines recommend fibrinogen as a category I risk factor and also suggest factor VII, plasminogen activator inhibitor-1, tissue-type plasminogen activator, and von Willebrand factor as other potentially clinically useful markers, these tests have not come into routine clinical use. Their development as predictors of risk may be hampered by inconsistent laboratory methodology, which causes difficulty in comparing result interpretation with published trial studies. This article presents the history of development for these tests, proper laboratory handling, the best trial data that present evidence of their accuracy, and current guidelines for clinical use.

Effect of varying the ratio of n-6 to n-3 fatty acids by increasing the dietary intake of alpha-linolenic acid, eicosapentaenoic and docosahexaenoic acid, or both on fibrinogen and clotting factors VII and XII in persons aged 45-70 y: the OPTILIP study

BACKGROUND

Elevated fibrinogen, activated factor XII (FXIIa), and factor VII coagulant activity (FVIIc) are associated with higher risk of fatal ischemic heart disease. This study tested the hypothesis that lowering the dietary ratio of n-6 to n-3 polyunsaturated fatty acids (n-6:n-3) would modify these risk factors in older men and women.

OBJECTIVE

The objective of the study was to measure fasting hemostatic risk factors and postprandial changes in activated FVII (FVIIa) concentrations after a 6-mo alteration in dietary n-6:n-3.

DESIGN

In a randomized, parallel design in 258 subjects aged 45-70 y, we compared 4 diets providing 6% of energy as polyunsaturated fatty acids at an n-6:n-3 between 5:1 and 3:1 with a control diet that had an n-6:n-3 of 10:1. The diets were enriched in alpha-linolenic acid, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid, or both.

RESULTS

Fasting and 3-h plasma triacylglycerol concentrations were 11.1% and 7.2% lower with the diet that had an n-6:n-3 of approximately 3:1 and that was enriched with EPA and DHA than with the other diets. Fasting fibrinogen, FXIIa, FVIIc, FVIIa, and FVII antigen and postprandial FVIIa were not influenced by the diets. Avoiding foods high in fat the day before measurement decreased FVIIc and FVIIa by 8% and 19.2%, respectively. A test meal containing 50 g fat resulted in a mean 47% (95% CI: 42%, 52%) increase in FVIIa 6 h later, but the response did not differ by n-6:n-3.

CONCLUSION

Decreasing the n-6:n-3 to approximately 3:1 by increasing the intake of EPA and DHA lowers fasting and postprandial plasma triacylglycerol concentrations in older persons but does not influence hemostatic risk factors.

Proteomic analysis of high-density lipoprotein

Plasma lipoproteins, such as high-density lipoprotein (HDL), can serve as carriers for a wide range of proteins that are involved in processes such as lipid metabolism, thrombosis, inflammation and atherosclerosis. The identification of HDL-associated proteins is essential with regards to understanding these processes at the molecular level. In this study, a combination of proteomic approaches including 1-DE and 2-DE MALDI-TOF, isotope-coded affinity tag and Western blot analysis were employed to identify proteins associated with human HDL. To minimize potential losses of HDL-associated proteins during isolation, a one-step ultracentrifugation technique was applied and the quality of purified HDL was confirmed by nephelometry, high-performance gel chromatography, and Western blot analysis. MS analysis revealed the presence of 56 HDL-associated proteins including all known apolipoproteins and lipid transport proteins. Furthermore, proteins involved in hemostasis and thrombosis, the immune and complement system were found. In addition, growth factors, receptors, hormone-associated proteins and many other proteins were found to be associated with HDL. Our approach thus resulted in the identification of a large number of proteins associated with HDL. The combination of proteomic technologies proved to be a powerful and comprehensive tool for the identification of proteins on HDL.

Circadian rhythms in mouse blood coagulation

The circadian clock, influencing many biological processes, has been demonstrated to modulate levels of specific coagulation factors, but its impact on the coagulation efficiency is unknown. In a mouse model, the authors evaluated the temporal variations in the initial rate of activated factor X (FXa) and thrombin generation. Upon coagulation activation through the FVIIa-TF pathway (extrinsic activation), both parameters showed rhythmic variations with a significant peak at ZT 12, the light-to-dark transition. In mice subjected to a 6-h delayed light-dark cycle, the peak was shifted as expected. These cyclic oscillations were also observed in constant darkness, thus demonstrating, for the first time, the existence of strong circadian rhythms of the initial rate of either FXa or thrombin generation activity levels. These circadian variations overlapped with those that have been recently described in factor VII (FVII) activity. The peak of FXa generation activity was simulated by the addition of purified human FVII, thus indicating that circadian variations in FVII activity are important determinants of the circadian rhythm of the procoagulant cascade efficiency. These findings help to elucidate the complex control on the coagulation process and might contribute in explaining the temporal variations in the frequency of cardiovascular events observed in humans.

Identification of a novel gene, HCR2, in aorta of hypercoagulable rats using suppression subtractive hybridization

Screening and identification of novel genes involved in hypercoagulable state (HCS) is important in understanding the underlying mechanisms of development of atheroslerosis, which implicated in critical vascular diseases such as coronary heart disease and stroke. HCS was induced in rats with high carbohydrate diet. Subtractive hybridization experiments between aorta tissues from hypercoagulable rats and controls showed that a novel cDNA (GenBank Accession No. AY234417), designated as hypercoagulability related gene-2 (HCR2), was highly expressed in aorta tissue. The predicted protein encoded by HCR2 contains 78 amino acids, which has a theoretical isoelectric point (pI) of 8.59 and molecular weight (MW) of 8841.7 based on sequence analysis. Our data suggest that HCR2 may be involved in HCS and identification of the gene may contribute to our understanding of the mechanisms for the production of a hypercoagulable state of several critical clinical disorders.

Dietary fatty acids and the haemostatic system

Studies of the effects of dietary fatty acids on the haemostatic system, and their potential relevance for the thrombotic component of coronary heart disease (CHD), have a pedigree as long as those linking dietary fat, plasma lipoprotein metabolism and atheroma. Achievements have not been as impressive, however, partly owing to the relatively slow evolution of our understanding of the complicated physiology, biochemistry and pathology of haemostasis and fibrinolysis, which remains incomplete. Progress was also retarded up to 1980 by a general reluctance to acknowledge the pathogenic importance of thrombosis for myocardial infarction. Interest in dietary fat and the haemostatic mechanism re-emerged with reports of associations of haemostatic variables with plasma triacylglycerol levels and risk of CHD. This review summarises the history, focuses on evidence for dietary C18-unsaturated fatty acids as important determinants of factor VII (FVII) activation and plasminogen activator inhibitor type 1 (PAI-1) levels, and discusses possible underlying mechanisms involving ATP binding cassette (ABC) transporters and peroxisome proliferator-activated receptors. The potential relevance of these effects for CHD is discussed. In the presence of unstable atheromatous plaques, increased levels of activated FVII and PAI-1 induced by diets rich in mixtures of saturated and unsaturated fats may raise the risk of occlusive thrombosis in the event of plaque rupture.

Cholesterol enhances phospholipid-dependent activated protein C anticoagulant activity

The influence of cholesterol on activated protein C (APC) anticoagulant activity in plasma and on factor Va inactivation was investigated. Anticoagulant and procoagulant activities of phosphatidylcholine/phosphatidylserine (PC/PS) vesicles containing cholesterol were assessed in the presence and absence of APC using factor Xa-1-stage clotting and factor Va inactivation assays. Cholesterol at approximate physiological membrane levels (30%) in PC/PS (60%/10% w/w) vesicles prolonged the factor Xa-1-stage clotting time dose-dependently in the presence of APC but not in the absence of APC. APC-mediated cleavage of purified recombinant factor Va variants that were modified at specific APC cleavage sites (Q306/Q679-factor Va; Q506/Q679-factor Va) was studied to define the effects of cholesterol on APC cleavage at R506 and R306. When compared to control PC/PS vesicles, cholesterol in PC/PS vesicles enhanced factor Va inactivation and the rate of APC cleavage at both R506 and R306. Cholesterol also enhanced APC cleavage rates at R306 in the presence of the APC cofactor, protein S. In summary, APC anticoagulant activity in plasma and factor Va inactivation as a result of cleavages at R506 and R306 by APC is markedly enhanced by cholesterol in phospholipid vesicles. These results suggest that cholesterol in a membrane surface may selectively enhance APC activities.

Thrombophilic factors are not the leading cause of thrombosis in Behçet's disease

BACKGROUND

Venous and arterial thromboses occur in patients with Behçet's disease and are associated with significant morbidity and mortality. Studies on a possible association between the occurrence of thrombosis and thrombophilia in patients with this disease have been controversial.

OBJECTIVE

To determine the prevalence of the most common thrombophilias and dyslipidaemia in patients with Behçet's disease with and without thrombosis.

METHODS

Blood samples from 107 patients with Behçet's disease who had or did not have thrombosis were analysed for factor V Leiden, prothrombin G20210A polymorphism, methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism, factor VIII level, homocysteine and C reactive protein concentrations, dyslipidaemia, and plasma glucosylceramide.

RESULTS

There was no difference between patients with and without thrombosis in the prevalence of prothrombin G20210A polymorphism, factor V Leiden, homozygous MTHFR C677T, or plasma concentrations of homocysteine, C reactive protein, or glucosylceramide. In contrast, patients with thrombosis were found to have significantly higher mean levels of factor VIII, total cholesterol, triglycerides, VLDL cholesterol, and apolipoproteins B-100, C-II, and C-III than those without thrombosis. Multistepwise logistic regression analysis showed that triglyceride concentration was the best marker associated with thrombosis (p = 0.008), with an estimated odds ratio of 1.58 (95% confidence interval, 1.09 to 2.30) for a difference of 40 mg/dl.

CONCLUSIONS

Thrombophilia does not seem to play a major role in the tendency to thrombosis in Behçet's disease. However, dyslipidaemia, predominantly hypertriglyceridaemia, might be a risk factor.

Clearance of coagulation factor VIII in very low-density lipoprotein receptor knockout mice

Low-density lipoprotein receptor-related protein (LRP) contributes to factor VIII (FVIII) catabolism in vivo. Besides LRP, FVIII also interacts with very low-density lipoprotein receptor (VLDLR) in vitro. We investigated the physiological role of VLDLR in FVIII catabolism, using knockout mouse models for VLDLR and LRP, alone and in combination. VLDLR(-/-) mice displayed normal plasma FVIII, whereas VLDLR(-/-) LRP(-) double-knockout mice had slightly increased FVIII compared with LRP-deficient mice. Remarkably, VLDLR deficiency slightly accelerated FVIII clearance. Adenovirus-mediated overexpression of VLDLR did not lower plasma FVIII in LRP-deficient mice. We conclude that VLDLR does not act in concert with LRP in FVIII clearance in vivo.

Effects of lipids and lipid-lowering therapy on hemostatic factors in patients with myocardial infarction

BACKGROUND

The risk of cardiovascular disease (CVD) is associated with specific hemostatic markers and lipid profiles, and evidence indicates that there are associations between lipid profiles and the levels of certain hemostatic factors. The disturbances in hemostasis and the risk of CVD can be ameliorated by lipid-lowering therapy.

OBJECTIVE

We investigated the associations of lipid profiles with factor (F)VIIa, von Willebrand factor (VWF), D-dimer and plasminogen activator inhibitor-1 (PAI-1), and examined whether lipid-lowering statin therapy would affect the levels of these hemostatic markers.

PATIENTS AND METHODS

This cross-sectional study analyzed 1045 postmyocardial infarction patients.

RESULTS

In multivariate regression analyses (without adjusting for clinical covariates) HDL-cholesterol (HDL-C) and HDL size were independent and significant predictors of FVIIa; HDL size was a predictor of VWF; HDL size, HDL-C and LDL size were predictors of D-dimer; and triglyceride and HDL size were predictors of PAI-1. After adjusting for clinical covariates, HDL-C, lipoprotein (Lp)(a), apolipoprotein B (apoB) and warfarin were independent and significant predictors of FVIIa; HDL size, age, diabetes mellitus, insulin, race and warfarin were predictors of VWF; HDL-C, HDL size, LDL size, age, warfarin, hypertension and gender were predictors of D-dimer; and triglyceride, HDL size, body mass index, insulin and hypertension were predictors of PAI-1. Patients on statin therapy had significantly lower levels of D-dimer than those who were not on this therapy.

CONCLUSION

There are significant associations of lipid profiles with hemostatic factors, the directions of which suggest novel pathways by which dyslipidemia may contribute to coronary heart disease.

Effect of the factor VII R353Q missense mutation on plasma apolipoprotein B levels: impact of visceral obesity

An atherogenic dyslipidemia, characterized by increased plasma triglyceride and apolipoprotein (apo) B levels, low HDL-cholesterol concentrations and the development of small, dense LDL particles has been associated with the presence of abdominal-visceral obesity. Visceral obesity is also associated with a hypercoagulate state and elevated concentrations of procoagulant factors such as factor VII. Moreover, it is known that some genetic variants in the gene encoding factor VII alter its activity and concentration, and consequently these variants may have an impact on atherosclerosis development. The objective of this study was to verify whether the factor VII R353Q polymorphism contributes to predict the risk of an atherogenic dyslipidemia in absence and in the presence of visceral obesity. A sample of 299 French-Canadian men, selected in order to cover a wide range of body fatness values, participated in this study. We observed that the R353 allele was more commonly observed among men characterized by apo B levels below 1.09 g/l than among men with apo B levels greater or above this threshold value (allele frequency of 92.1 vs 85.4%, chi(2)=6.18, P=0.01). Multivariate analyses further showed that the genotype R353/R353 was associated with a lower risk to exhibit atherogenic concentrations of total-apo B (>/=1.09 g/l) and LDL apo B (>/=0.95 g/l) before (odds ratio:0.47, 95%CI=0.27-0.90, P=0.02; odds ratio:0.46, 95%CI=0.25-0.85, P=0.01, respectively) and after adjustments for age and visceral AT (odds ratio:0.49, 95%CI=0.24-0.91, P=0.02; odds ratio:0.44, 95%CI=0.23-0.85, P=0.01, respectively). When the two genotype groups were further divided on the basis of visceral adipose tissue (AT) accumulation using a cutoff point of 130 cm(2), we observed that R353/R353 homozygotes with low visceral AT were characterized by a more favorable lipoprotein-lipid profile, mainly lower total-cholesterol, total-apo B, and LDL-apo B levels compared with R353/R353 homozygotes with high levels of visceral AT. In contrast, irrespective of obesity, plasma lipid levels among carriers of the Q353 allele were similar to those of viscerally obese men homozygous for the R353 allele. In conclusion, results of the present study suggest that the factor VII R353 allele is associated with lower concentrations of plasma apo B levels. However, the presence of visceral obesity abolishes this effect. Further studies will be necessary to confirm this association and the mechanism involved.

Effect of individual dietary fatty acids on postprandial activation of blood coagulation factor VII and fibrinolysis in healthy young men

BACKGROUND

Hypertriglyceridemia may represent a procoagulant state involving disturbances to the hemostatic system. Plasminogen activator inhibitor type 1 (PAI-1) is increased in the presence of hypertriglyceridemia. Free fatty acids (FFAs) in plasma may promote factor VII (FVII) activation.

OBJECTIVE

We tested the hypothesis that FVII activation would be less after consumption of saturated fatty acids than after other fatty acids.

DESIGN

The effects of 6 matching dietary test fats, rich in stearic (S), palmitic (P), palmitic + myristic (M), oleic (O), trans 18:1 (T), and linoleic (L) acid, respectively, on the postprandial lipid and hemostatic profile (after 2, 4, 6, and 8 h) were investigated in 16 young men. High-fat meals (1 g fat/kg body wt; 43% from the test fatty acid) were served in the morning on 6 separate days.

RESULTS

All fats increased FVII activation. The S fat resulted in a lower increase in activated FVII (FVIIa) than did the T fat and in a lower FVII coagulant activity (FVII:c) than did the O fat (P < 0.02, diet x time interaction). When the data were pooled, the saturated (S, P, and M) test fats resulted in a smaller postprandial increase in FVIIa (P = 0.036, diet effect), a smaller increase in FVII:c (P < 0.001, diet x time interaction), a greater rise in tissue plasminogen activator concentrations (P = 0.028, diet effect), and a tendency to a greater postprandial decline in PAI-1 (P = 0.06, diet effect) compared with the unsaturated test fats (O, T, and L). The increase in FVIIa was not significantly associated with the level of lipemia, plasma FFAs, or plasma lipoprotein lipase activity.

CONCLUSION

Our results indicate a lesser increase in FVIIa after the consumption of saturated fats, especially the S fat, than after unsaturated test fats.

Influence of triacylglycerol structure on the postprandial response of factor VII to stearic acid-rich fats

BACKGROUND

The consumption of a synthetic, randomized, stearic acid-rich triacylglycerol results in decreased postprandial lipemia and activated factor VII (FVII:a) compared with cocoa butter (a nonrandomized, symmetrical, stearic acid-rich triacylglycerol). It was hypothesized that this difference is a consequence of the differences in structure between the 2 triacylglycerols.

OBJECTIVE

The objective was to test whether the consumption of randomized cocoa butter decreases postprandial lipemia and FVII:a.

DESIGN

A randomized crossover trial with 17 male subjects compared the effects of meals containing 50 g fat provided as a symmetrical (cocoa butter) or an asymmetrical (randomized cocoa butter) triacylglycerol on postprandial changes in lipids, chylomicron composition, and FVII:a.

RESULTS

After randomization, the postprandial area under the curve for plasma triacylglycerol decreased by 41% (P < 0.01). At 3 h the plasma concentrations of triacylglycerol, palmitic acid, stearic acid, and oleic acid were 26%, 18%, 34%, and 19% lower, respectively. The proportion of oleic acid in the sn-2 position of the chylomicron triacylglycerol was reduced from 67.4 mol% to 35.9 mol% and resulted in an increase in the proportion of stearic acid in the sn-2 position from 9.2 mol% to 25.4 mol%. FVII:a did not increase 6 h after consumption of the randomized cocoa butter (: 1.2; 95% CI: -2.7, 4.6 U/L) but increased significantly (: 7.7; 95% CI: 2.5,12.9 U/L) 6 h after consumption of the unrandomized cocoa butter.

CONCLUSIONS

Symmetrical stearic acid-rich triacylglycerol with oleic acid in the sn-2 position appears to be absorbed more rapidly than is asymmetrical triacylglycerols with long-chain saturated fatty acids in the sn-2 position, which leads to activation of FVII.

Atorvastatin and omega-3 fatty acids protect against activation of the coagulation system in patients with combined hyperlipemia

Activation of factor (F)VII by tissue factor may represent a critical event during plaque rupture in acute coronary syndromes. Patients with combined hyperlipemia are at high risk for developing coronary heart disease and their tendency to thrombosis may be accelerated during postprandial hyperlipemia. In the present double-blind, placebo-controlled parallel study, 42 patients with combined hyperlipemia and serum triglycerides between 2.0 and 15.0 mmol L(-1 )and serum cholesterol >5.3 mmol L-1 at the end of a 3-month dietary run-in period were treated with atorvastatin at 10 mg day-1 for at least 10 weeks. During the last 5 weeks the patients were randomized into two groups receiving 1.68 g day(-1) omega-3 fatty acids (omega-3 FA) or placebo (corn oil). The fasting levels of FVII antigen (FVII-Ag) and FVII coagulant activity (FVII:C) were high compared with healthy males. The fasting levels of activated FVII (FVIIa) and FVII-Ag correlated both to serum triglycerides and apolipoprotein A1 (apoA1). FVIIa and FVII:C increased during postprandial hyperlipemia. This increase of FVIIa correlated to the fasting triglyceride and apoA1 levels, but not to the degree of postprandial hypertriglyceridemia. The concentrations of fasting FVIIa in these patients were reduced in parallel with a reduction of fasting triglycerides by treatment with atorvastatin + placebo. This treatment also reduced the postprandial level of FVIIa. omega-3 FA in addition to atorvastatin further reduced FVIIa concentrations, fasting and postprandially, and also significantly reduced FVII:C and FVII-Ag during postprandial hyperlipemia. Prothrombin fragment 1 + 2 (F1 + 2) increased during postprandial hyperlipemia. This increase was significantly reduced after treatment with atorvastatin plus omega-3 FA. The increase of F1 + 2 measured as incremental area under the curve (iAUC) during postprandial hyperlipemia correlated to the fasting levels of FVIIa, FVII:C and FVII-Ag and also to the levels of these factors during postprandial lipemia. In conclusion, patients with combined hyperlipemia are at risk for activation of the coagulation system, particularly during postprandial lipemia. This activation may be significantly reduced by statins and omega-3 FA.

A high fat meal activates blood coagulation factor VII in rats

In humans, high fat meals cause postprandial activation of blood coagulation factor VII (FVII), but human studies have not provided definite evidence for a prothrombotic effect of dietary FVII activation. An animal model would be an attractive way to pursue this question and therefore we tested the LEW/Mol rat. We gavaged 3 mL of a fat emulsion (n = 42) or 3 mL isotonic glucose (n = 42). Blood was sampled by heart puncture 2, 4 and 6 h (n = 14/group at each time) after the fat/glucose load. Furthermore, blood was sampled from 16 untreated rats to determine the baseline levels. Triglyceride concentrations, activated FVII (FVIIa), FVII coagulant activity (FVIIc), FVII amidolytic activity (FVIIam) and thrombin-antithrombin complexes (TAT) were determined. After fat administration, triglycerides were significantly elevated at 2 h (1.29 mmol/L) and 4 h (1.37 mmol/L) compared with baseline (0.78 mmol/L), and FVIIa was significantly raised at 4 h (54 U/L) and 6 h (58 U/L) compared with baseline (29 U/L). No postprandial changes in FVIIc, FVIIam and TAT were observed. Glucose administration did not affect any variable. We conclude that the LEW/Mol rat is a promising model for use in future studies of thrombotic effects of dietary FVII activation.

Different effects of oral contraceptives containing levonorgestrel or desogestrel on plasma lipoproteins and coagulation factor VII

OBJECTIVE

The objective of the study was to compare the effects of two different combined oral contraceptives on levels of plasma lipoproteins and coagulation factor VII.

STUDY DESIGN

A prospective randomized crossover study was undertaken. Thirty-five women were treated with combined oral contraceptives containing the same amount of ethinyl estradiol and either levonorgestrel or desogestrel. Levels of plasma lipoproteins and factor VII were determined before and after 2 months of treatment with each preparation.

RESULTS

Levels of high-density lipoprotein cholesterol were increased significantly with treatment with ethinyl estradiol/desogestrel when compared with baseline and treatment with ethinyl estradiol/levonorgestrel. A significant rise in plasma triglyceride levels was obtained with both preparations, although the increase was more pronounced with ethinyl estradiol/desogestrel. Plasma concentrations of factor VII mass concentration and activated factor VII were increased significantly only with ethinyl estradiol/desogestrel.

CONCLUSION

The rise in concentrations of high-density lipoprotein cholesterol may be advantageous, whereas the combined elevations of plasma triglyceride and factor VII levels obtained with ethinyl estradiol/desogestrel may reflect a hypercoagulable state.

A high-fat meal does not activate blood coagulation factor VII in minipigs

It is a matter of debate whether postprandial activation of blood coagulation factor VII (FVII) is associated with an increased risk of thrombosis. To clarify this question, an animal model in which consequences of dietary FVII activation can be studied in a more detailed way would be an important tool. We studied postprandial FVII activation in seven non-fasting Göttingen minipigs. Intralipid (4 g/kg) was administered through a gastric tube in two fractions at 9.00 a.m. (one-third of total dose) and 10.30 a.m. (two-thirds of total dose). Blood samples were drawn 0.5 h before (baseline) and 2, 3, 3.5, 4, 5, and 6 h after the first fat load. Triglycerides, activated FVII (FVIIa), FVII coagulant activity (FVIIc), FVII amidolytic activity (FVIIam) and prothrombin fragment I + 2 (F1 + 2) were analysed in plasma samples. Median plasma triglycerides were significantly raised from 0.67 mmol/l (baseline) to 2.56 mmol/l 5 h postprandially (P < 0.001). There were no significant changes in FVIIa (9.6 U/l at baseline), FVIIam (142% at baseline) and F1 + 2 (0.13 nmol/l at baseline). FVIIc decreased from 141% at baseline to 114% 6 h postprandially (P < 0.001). As a high-fat meal does not seem to activate blood coagulation FVII in minipigs, the pig is apparently not a relevant model for the study of dietary FVII activation and thrombin generation.

Thrombin-activatable fibrinolysis inhibitor (TAFI, plasma procarboxypeptidase B, procarboxypeptidase R, procarboxypeptidase U)

Recently, a new inhibitor of fibrinolysis was described. This inhibitor downregulated fibrinolysis after it was activated by thrombin, and was therefore named TAFI (thrombin-activatable fibrinolysis inhibitor; EC 3.4.17.20). TAFI turned out to be identical to previously described proteins, procarboxypeptidase U, procarboxypeptidase R, and plasma procarboxypeptidase B. In this overview, the protein will be referred to as TAFI. TAFI is a procarboxypeptidase and a member of the family of metallocarboxypeptidases. These enzymes are circulating in plasma and are present in several tissues such as pancreas. In this review, we will describe the properties of basic carboxypeptidases with the emphasis on the role of TAFI in coagulation and fibrinolysis. It cannot be ruled out, however, that TAFI has other, yet undefined, functions in biology.

Remnant lipoproteins as therapeutic targets

Increasing evidence suggests that subsets of triglyceride-rich lipoproteins are particularly atherogenic. These include particles with some, but not necessarily all the properties classically attributed to remnants. Cholesteryl ester-enrichment seems to be a common feature of these particles, some of which can be taken up by macrophages by a novel receptor that recognizes species of apolipoprotein B but not apolipoprotein E. These characteristics seem to be common to postprandial and hypertriglyceridemic very low density lipoproteins as well as chylomicron remnants. Remnant-like triglyceride-rich lipoproteins that exhibit several potentially atherogenic properties can be quantified by a simple test that shows promise for identifying individuals at high risk for lesion formation and clinical events. Available hygienic and pharmaceutical measures that effectively lower the concentration of atherogenic triglyceride-rich lipoproteins deserve wider use.