Turnover of factor X and of prothrombin in rabbits fed on a standard or cholesterol-supplemented diet

Gut Microbiome, Functional Food, Atherosclerosis, and Vascular Calcifications-Is There a Missing Link?

The gut microbiome is represented by the genome of all microorganisms (symbiotic, potential pathogens, or pathogens) residing in the intestine. These ecological communities are involved in almost all metabolic diseases and cardiovascular diseases are not excluded. Atherosclerosis, with a continuously increasing incidence in recent years, is the leading cause of coronary heart disease and stroke by plaque rupture and intraplaque hemorrhage. Vascular calcification, a process very much alike with osteogenesis, is considered to be a marker of advanced atherosclerosis. New evidence, suggesting the role of dietary intake influence on the diversity of the gut microbiome in the development of vascular calcifications, is highly debated. Gut microbiota can metabolize choline, phosphatidylcholine, and L-carnitine and produce vasculotoxic metabolites, such as trimethylamine-N-oxide (TMAO), a proatherogenic metabolite. This review article aims to discuss the latest research about how probiotics and the correction of diet is impacting the gut microbiota and its metabolites in the atherosclerotic process and vascular calcification. Further studies could create the premises for interventions in the microbiome as future primary tools in the prevention of atherosclerotic plaque and vascular calcifications.

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.

Temporal variations in plasma vitamin K and lipid concentrations and clotting factor activity in humans

There is no information available on temporal variability in plasma vitamin K concentrations and its relationship to coagulation processes. We investigated the possible existence of temporal changes in plasma vitamin K and lipid concentrations and activity of clotting factors II, VII, IX, and X and relationships between these variables. Plasma vitamin K and lipid concentrations and clotting factor activity were measured at four-hour intervals for 28 hours in a group of healthy volunteers. Temporal variations existed in plasma vitamin K concentrations, with a mean maximum at 22:00 hr and a mean minimum (32% of the maximum) at 10:00 hr. Plasma triglycerol concentrations mirrored the changes in vitamin K concentrations. Mean factor VII activity was positively correlated with mean total plasma cholesterol concentrations (r = 0.714; P < 0.0001) and with mean plasma low density lipoprotein (LDL) cholesterol concentrations (r = 0.461; P < 0.0001). No distinct correlations were found between plasma vitamin K concentrations and either high density lipoprotein (HDL) or LDL cholesterol concentrations, or between triglycerol, HDL, or LDL cholesterol concentrations and functional activity of factors II, IX, and X. Plasma vitamin K concentrations did not correlate with the functional activity of any of the clotting factors. The presence of a correlation between plasma cholesterol concentrations and factor VII activity for blood samples collected at four-hour intervals suggests that plasma cholesterol concentrations may have a more acute effect on factor VII activity. Temporal variations in plasma vitamin K concentrations indicate that a single time point measurement may be an inappropriate method of establishing vitamin K status in an individual.

Genetic determinants of arterial thrombosis

This chapter describes examples of genetic variation involved in the function or regulation of a number of haemostatic proteins involved in the thrombotic process. In each case, the data suggest associations between genotype and disease and, particularly in the case of fibrinogen, PAI-1, Factor VII and Factor XIII, there is interaction between genotype and environment in determination of the relevant plasma level, providing a possible explanation for the differential response of individuals to their environment.

Enhanced monocyte tissue factor response after experimental balloon angioplasty in hypercholesterolemic rabbit: inhibition with dietary L-arginine

BACKGROUND

There is evidence that tissue factor (TF) is a major contributor to the thrombogenicity of a ruptured atherosclerotic plaque. Nitric oxide (NO) has antiatherogenic and antithrombotic properties. We investigated whether L-arginine (L-arg), the endogenous precursor of NO, might affect the ability of monocytes to produce TF.

METHODS AND RESULTS

We studied TF expression in 18 rabbits with atherosclerosis induced by bilateral iliac damage and 10 weeks of a 2% cholesterol diet. Six weeks after the initiation of the diet, an angioplasty was performed. After angioplasty, the surviving rabbits (n=15) were randomized to receive L-arg (2.25%) supplementation in drinking water (L-arg group, n=8) or no treatment (untreated group, n=7). TF expression was evaluated in mononuclear cells from arterial blood in the presence and absence of endotoxin stimulation. Monocyte TF expression, as assessed with an amidolytic assay, did not differ significantly before or after the induction of atherosclerotic lesions (87+/-15 versus 70+/-12 mU of TF/1000 monocytes, P=NS). Endotoxin-stimulated TF activity increased significantly 4 weeks after angioplasty (138+/-22 versus 70+/-12 mU of TF/1000 monocytes, P=0.02). This increase was blunted by L-arg (43+/-16 mU of TF/1000 monocytes, P=0.01).

CONCLUSIONS

This study demonstrates that angioplasty-induced plaque rupture is associated with a marked increase in monocyte TF response that is blunted by the oral administration of L-arg. This suggests that the documented antithrombotic properties of NO may be related in part to an inhibitory effect on monocyte TF response.

Haemostatic parameters and vascular risk

Associations between increased plasma concentrations of the three haemostatic factors--fibrinogen, Factor VII and plasminogen activator inhibitor 1 (PAI-1)--and cardiovascular disease (CVD) have recently been demonstrated in epidemiological studies. The relative risk of CVD is increased by 2-3 times in subjects whose levels of fibrinogen fall within the upper third of the general distribution in comparison to those subjects who fall into the lower third; a positive correlation exists between increased Factor VII activity and cardiovascular mortality. Many studies have demonstrated that elevated levels of PAI-1 and tPA antigen are associated with CVD. Several studies have also shown that there are important associations between conventional risk factors for atherothrombosis and haemostatic factors. Fibrinogen levels are strongly linked with smoking, and Factor VII levels are linked with cholesterol, triglycerides and fat intake. PAI-1 and tPA antigen levels, on the other hand, are closely associated with insulin resistance. This paper discusses the principal genetic and environmental determinants of the plasma levels of each of these three haemostatic factors and relates them to the risk of developing CVD.

Coagulation factor VII mass and activity in young men with myocardial infarction at a young age. Role of plasma lipoproteins and factor VII genotype

Factor VII (FVII) coagulant activity has been proven to be associated with the risk of future fatal coronary heart disease (CHD) in middle-aged men. Recent studies have emphasized the role of triglyceride-rich lipoproteins and FVII genotype in determining plasma levels of FVII protein and activity. The present study was undertaken to examine whether FVII activity state and protein concentration in fasting plasma are altered in young men with proven myocardial infarction (MI) and examined the relations of FVII to subfractions of apo B-containing lipoproteins and the Arg-->Gln polymorphism in the FVII gene. Activated FVII (FVIIa) was determined by a clotting assay using soluble, recombinant, truncated tissue factor. A total of 94 men with a first MI before the age of 45 (mean age +/- SD, 39.6 +/- 4.5 years) were included in the study along with 99 population-based, age-matched control subjects. In addition to FVIIa and FVII antigen (FVII:Ag), a panel of FVII activity assays were included for comparison with previous work in this field. The plasma level of FVII:Ag was higher in patients than in control subjects when the entire groups were compared (537 +/- 128 versus 479 +/- 93 ng/mL, P < .001), the differences being accounted for by patients with hypertriglyceridemic lipoprotein phenotypes. In contrast, FVIIa was similar in patients and control subjects (4.6 +/- 1.4 versus 4.3 +/- 1.3 ng/mL, NS), which means that the proportion of FVIIa molecules was unaltered or even lower in the patients. As expected, the Arg-->Gln polymorphism significantly influenced both FVII mass and activity levels. In addition, presence of the Gln allele appeared to be associated with a lower proportion of fully active FVII molecules. The polymorphism also affected the relation between the plasma concentration of VLDL and FVII:Ag. The triglyceride content and particle number of all VLDL subfractions, irrespective of particle size, correlated fairly strongly with FVII mass determinations but not at all with FVIIa. HDL cholesterol concentration, on the other hand, presumably reflecting the efficiency of lipoprotein lipase-mediated lipolysis of VLDL, related significantly to the FVIIa level. The Arg-->Gln polymorphism, independent of lipoprotein effects, explained 5% to 10% of the variation in FVII mass and activity. In conclusion, the present findings speak against a role of FVII as a risk factor for CHD, because a significantly increased potential for activation of coagulation (ie, raised basal concentration of FVIIa) was not observed among young postinfarction patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Genetic determinants of arterial thrombosis

This chapter describes examples of genetic variation determining plasma levels of three independent risk factors for arterial thrombotic disease, namely fibrinogen, coagulation factor VII and plasminogen activator inhibitor type 1, together with a discussion of the underlying molecular mechanisms. In each case, the data suggest that there is interaction between genotype and environment in determination of the relevant plasma level, providing a possible explanation for the differential response of different individuals to their environment.

Activation of coagulation factor VII during alimentary lipemia

Dietary studies have established a connection between plasma lipoproteins and coagulation factor VII. The present study was undertaken to specifically examine whether factor VII is activated during alimentary lipemia and to investigate the relations of factor VII mass and activity state with fasting and postprandial lipoproteins and free fatty acids (FFAs). Factor VII levels were therefore determined in plasma samples taken before and after intake of a standardized, oral fat load of a mixed-meal type in 33 men (mean age +/- SD, 48.8 +/- 3.2 years) with a previous myocardial infarction at a young age and 10 healthy, age-matched control subjects. A panel of methods for factor VII determination was used to ensure that changes in all potentially existing forms of the factor during alimentary lipemia would be included. Substantial activation of factor VII was found to occur during alimentary lipemia, whereas the number of factor VII molecules remained constant or even appeared to decrease after the test meal. Activation of factor VII was more pronounced in control subjects than patients, and the proportion of activated factor VII molecules was higher in control subjects. Interestingly, factor VII activation, which correlated quantitatively with the degree of postprandial triglyceridemia, seemed to be related to FFA production during lipolysis of triglyceride-rich lipoproteins that were generated in response to fat intake. Postheparin plasma lipoprotein lipase activity was lower in patients, which could offer one explanation why factor VII activity was lower during alimentary lipemia in these subjects despite their exaggerated postprandial triglyceridemia. Thus, activation of coagulation factor VII during alimentary lipemia may result in a procoagulant state that is likely to promote the formation of a coronary thrombus in individuals with established coronary artery disease.

Lipolysis of triglyceride-rich lipoproteins activates coagulant factor XII: a study in familial lipoprotein-lipase deficiency

A high factor VII coagulant activity (VIIc), a marker of increased risk of coronary heart disease, is frequently found in types IIb and IV hyperlipidaemia, but its cause is not fully understood. Factor VII can be activated by factor XIIa, generated from factor XII upon activation of the contact system of coagulation. Ten patients with familial lipoprotein-lipase (LPL) deficiency and 10 healthy control subjects were therefore compared to explore the hypothesis that high concentrations of unesterified fatty acids (UFA), released from triglyceride-rich lipoproteins by LPL, are a source of factor XII activation and hence the increased VIIc that is observed post-prandially and in non-LPL-deficient hypertriglyceridaemic states. Mean plasma cholesterol and triglyceride concentrations were, respectively, 1.5- and 19-fold higher in the patients than controls, due to increases in very-low-density lipoproteins and chylomicrons. The concentration and composition of plasma UFA were similar in both groups. In conformity with the hypothesis, VIIc was not increased in the LPL-deficient group, despite their massive hypertriglyceridaemia. Furthermore, when the patients' plasma was treated with LPL, factor XII was activated promptly and substantially, whereas no similar effect was observed in the controls. These results suggest that high concentrations of circulating triglyceride-rich lipoproteins will increase VIIc in the presence of LPL.

Genetic factors determining thrombosis and fibrinolysis

Raised plasma levels of fibrinogen, factor VIIc, and plasminogen activator inhibitor-1 (PAI-1) are associated with an increased risk of ischemic heart disease. Levels of these proteins are determined in part by environmental influences such as smoking and dietary fat intake. However, genetic variation explains much of the interindividual variation in plasma levels of these proteins not accounted for by environmental factors. We previously investigated the DNA variation at the fibrinogen gene locus and showed that BclI restriction fragment length polymorphism (RFLP) of the beta-fibrinogen gene is associated with between-person differences in plasma fibrinogen levels. This RFLP is unlikely to be the functional base change itself, since it lies downstream of the gene. The rate-limiting step in the production of the mature fibrinogen molecule in the human hepatoma cell-line HepG2 is the synthesis of the beta-polypeptide chain, which in turn is influenced by the amount of messenger (mRNA) available. One possibility is that BclI RFLP is in linkage disequilibrium with a base change in the region of the beta-gene controlling synthesis of its mRNA and ultimately of fibrinogen protein. We identified a base change in the 5'-flanking region of the beta-fibrinogen gene that is in linkage disequilibrium with the BclI RFLP, that is associated with plasma fibrinogen levels, and that may be involved in control of fibrinogen gene expression. For the factor VII gene, we identified a polymorphism, detected after Msp I digestion of polymerase chain reaction (PCR)-amplified genomic DNA, that is strongly associated with factor VII coagulant activity (factor VIIc). The base change that creates the Msp I polymorphism is a G to A substitution, leading to the replacement of arginine (Arg) with glutamine (Gln) in the protein product of the M2 allele. In a sample of 284 men from the United Kingdom the frequency of the Gln allele (M2 loss of cutting site) is 0.1, and individuals of genotype Arg/Gln have factor VIIc levels 22% below the sample mean. In this sample, the Msp I genotype was found to be the strongest predictor of factor VIIc, accounting for 20.2% of the variance, with cholesterol accounting for an additional 3.5%. Three individuals homozygous for the Gln allele had both low factor VIIc and low factor VII protein concentrations. The conformation of the factor VII Gln may be different from that of the Arg protein, affecting its intracellular processing, secretion, turnover in plasma, or activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Prothrombin plasma clearance is not mediated by hepatic asialoglycoprotein receptors

The hepatic asialoglycoprotein receptor (AGPR) system can efficiently internalize and degrade circulating glycoproteins which lack terminal sialic acids on their carbohydrate chains. Since pro-thrombin is a glycosylated plasma protein, possible involvement of AGPR system in its clearance from circulation was evaluated. The half lives of bovine 125I-prothrombin and 125I-asialoprothrombin, injected intravenously into rats, were 192 and 1.8 minutes, respectively. Asialoprothrombin appeared to be cleared by the hepatic AGPRs since 33% of it accumulated in the liver at 30 minutes and its clearance was competitively blocked by simultaneous administration of increasing amounts of asialofetuin. Only 5% of prothrombin accumulated in the liver at 3 hours and injections asialofetuin in amounts capable of saturating the AGPR for the duration of four asialoprothrombin half lives had no effect on the disappearance of prothrombin. Our observations indicate that, although asialoprothrombin is readily cleared from plasma by the AGPR system, prothrombin is not. Thus these receptors do not appear to be involved in physiological processes that control prothrombin half life.

A common genetic polymorphism associated with lower coagulation factor VII levels in healthy individuals

We have identified a genetic polymorphism of factor VII that is strongly associated with plasma factor VII coagulant activity (factor VIIc) in healthy individuals from the United Kingdom. This polymorphism was detected after Msp I digestion of polymerase chain reaction-amplified genomic DNA. In a sample of 284 men, the frequency of the M2 allele (loss of cutting site) is 0.1, and individuals with the M1M2 genotype have factor VIIc levels 22% below the sample mean (p less than 0.0001). Msp I genotype was found to be the strongest predictor of factor VIIc, accounting for 20.2% of the variance, with cholesterol accounting for an additional 3.5%. The base change that gives rise to the Msp I polymorphism is a G-to-A substitution in the codon for amino acid 353, leading to replacement of arginine (Arg) with glutamine (Gln) in the protein product of the M2 allele (designated Gln 353). Three individuals homozygous for the M2 allele have both low factor VIIc and low factor VII protein concentrations. The conformation of the Gln 353 molecule may be different from that of the Arg 353 protein, affecting its intracellular processing, secretion, turnover in plasma, or activity. In view of its association with lower factor VIIc levels, possession of the M2 allele may confer protection against thrombosis and myocardial infarction.

The prothrombin activation peptide regulates synthesis of the vitamin K-dependent proteins in the rabbit

The turnover of 125I-bovine prothrombin fragment 1 was studied in the rabbit. The t1/2 of the peptide in the intravascular compartment was 11.5 hours and this compartment accounted for between 7.9 and 14.4% of the injected radioactivity. The rest of the radioactivity was distributed between two compartments in the extravascular space. The injection of the peptide (10 mg/rabbit) was associated with a transient increase in the plasma concentration of prothrombin and of factor X, with maximum concentration of prothrombin between 40 and 66 hours from the injection and between 26 and 40 hours for factor X. It is concluded that the injection of fragment 1 in the rabbit induced a transient increase in the synthesis of the vitamin K-dependent proteins that is compensated for by an increased absolute catabolic rate. It is suggested that the prothrombin activation peptide serves as regulatory message which induces the subsequent restoration of the appropriate concentration of the vitamin K-dependent proteins.

Fat consumption and factor VII coagulant activity in middle-aged men. An association between a dietary and thrombogenic coronary risk factor

Diet was measured by 5-day weighed inventory to search for an association between fat intake in the general population and factor VII coagulant activity (VIIc), a strong predictor of coronary heart disease. Of 275 men aged 40-59 years registered with a medical practice, 203 (74%) participated and 170 (62%) provided a satisfactory record. After allowance for the increase in fat intake with body size, a statistically significant and positive association was found between dietary fat and VIIc (r = 0.18; P less than 0.05). The correlation coefficient was increased to 0.24 when adjusted for the effect of day-to-day variability in individual fat intake, thereby providing an improved estimate of the true strength of association. The mean difference in VIIc of 12% of standard between men in the highest and lowest quarters of the distribution of fat intake was similar to that reported between men experiencing coronary heart disease and those remaining free. The results support previous experimental fat-feeding studies and suggest that a high fat diet has adverse consequences for blood coagulability and coronary thrombosis.

Factor VII coagulant activity is strongly associated with the plasma concentration of large lipoprotein particles in middle-aged men

A community survey of factor VII coagulant activity (VIIc) and the lipoprotein profile in non-fasting plasma of middle-aged men in NW London was undertaken to search for the determinants of VIIc in the general community. The data demonstrates that associations between VIIc and the plasma concentrations of cholesterol and of triglycerides previously shown in the general population can be explained by the strong and positive associations between VIIc and the large lipoprotein particles, chylomicrons, VLDL and IDL. Consistent with the possibility that the concentration of large lipoproteins determines the in vivo reactivity of factor VII, the association between VIIc and the ratio of lipid in the d greater than 1.019 fraction to the total plasma lipid was also highly significant but negative. The observed correlations between VIIc and lipoproteins smaller than VLDL may be the product of the interrelations that exist between the lipoprotein fractions in plasma. However, the associations between VIIc and the chylomicron lipid concentrations are especially strong when allowance is made for the considerable bias towards zero in the observed correlation, due to large within-person variance in chylomicron concentration.