Thrombosis in the Young: Effect of Atherosclerotic Risk Factors on the Risk of Myocardial Infarction Associated with Prothrombotic Factors

Multi-Omics Approaches for Liver Reveal the Thromboprophylaxis Mechanism of Aspirin Eugenol Ester in Rat Thrombosis Model

Aspirin eugenol ester (AEE) is a novel medicinal compound synthesized by esterifying aspirin with eugenol using the pro-drug principle. Pharmacological and pharmacodynamic experiments showed that AEE had excellent thromboprophylaxis and inhibition of platelet aggregation. This study aimed to investigate the effect of AEE on the liver of thrombosed rats to reveal its mechanism of thromboprophylaxis. Therefore, a multi-omics approach was used to analyze the liver. Transcriptome results showed 132 differentially expressed genes (DEGs) in the AEE group compared to the model group. Proteome results showed that 159 differentially expressed proteins (DEPs) were identified in the AEE group compared to the model group. Six proteins including fibrinogen alpha chain (Fga), fibrinogen gamma chain (Fgg), fibrinogen beta chain (Fgb), orosomucoid 1 (Orm1), hemopexin (Hpx), and kininogen-2 (Kng2) were selected for parallel reaction monitoring (PRM) analysis. The results showed that the expression of all six proteins was upregulated in the model group compared with the control group. In turn, AEE reversed the upregulation trend of these proteins to some degree. Metabolome results showed that 17 metabolites were upregulated and 38 were downregulated in the model group compared to the control group. AEE could reverse the expression of these metabolites to some degree and make them back to normal levels. The metabolites were mainly involved in metabolic pathways, including linoleic acid metabolism, arachidonic acid metabolism, and the tricarboxylic acid (TCA) cycle. Comprehensive analyses showed that AEE could prevent thrombosis by inhibiting platelet activation, decreasing inflammation, and regulating amino acid and energy metabolism. In conclusion, AEE can have a positive effect on thrombosis-related diseases.

Admixture mapping scans identify a locus affecting retinal vascular caliber in hypertensive African Americans: the Atherosclerosis Risk in Communities (ARIC) study

Retinal vascular caliber provides information about the structure and health of the microvascular system and is associated with cardiovascular and cerebrovascular diseases. Compared to European Americans, African Americans tend to have wider retinal arteriolar and venular caliber, even after controlling for cardiovascular risk factors. This has suggested the hypothesis that differences in genetic background may contribute to racial/ethnic differences in retinal vascular caliber. Using 1,365 ancestry-informative SNPs, we estimated the percentage of African ancestry (PAA) and conducted genome-wide admixture mapping scans in 1,737 African Americans from the Atherosclerosis Risk in Communities (ARIC) study. Central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) representing summary measures of retinal arteriolar and venular caliber, respectively, were measured from retinal photographs. PAA was significantly correlated with CRVE (rho = 0.071, P = 0.003), but not CRAE (rho = 0.032, P = 0.182). Using admixture mapping, we did not detect significant admixture association with either CRAE (genome-wide score = -0.73) or CRVE (genome-wide score = -0.69). An a priori subgroup analysis among hypertensive individuals detected a genome-wide significant association of CRVE with greater African ancestry at chromosome 6p21.1 (genome-wide score = 2.31, locus-specific LOD = 5.47). Each additional copy of an African ancestral allele at the 6p21.1 peak was associated with an average increase in CRVE of 6.14 microm in the hypertensives, but had no significant effects in the non-hypertensives (P for heterogeneity <0.001). Further mapping in the 6p21.1 region may uncover novel genetic variants affecting retinal vascular caliber and further insights into the interaction between genetic effects of the microvascular system and hypertension.

Simultaneous subacute coronary drug-eluting stent thrombosis in two different vessels of a patient with factor V Leiden mutation

We review the case of a 46-year-old man who underwent elective percutaneous coronary intervention and stenting of the left anterior descending artery and right coronary artery with two sirolimus- and paclitaxel-eluting stents. Four days after angioplasty, he was readmitted with cardiogenic shock due to acute anterior and inferior myocardial infarction. Coronary angiography revealed subacute thrombosis of both stents, and balloon dilation was performed successfully thereafter. The follow-up investigations revealed that the patient was a carrier of factor V Leiden. We hereby discuss the importance of factor V Leiden as the most common cause of hypercoagulable state and its probable role in acute and subacute coronary stent thrombosis in drug-eluting stents.

Factor V Leiden and increased risk for arterial thrombotic disease in young Brazilian patients

The contribution of mutations in the prothrombin (FII G20210A), methylenetetrahydrofolate reductase (C677T) genes and factor V Leiden (FVL) to the pathogenesis of arterial thrombosis remains controversial. In this study, these polymorphisms were investigated by polymerase chain reaction-restriction fragment length polymorphism in a group of 53 patients that presented arterial thrombosis other than myocardial infarction as a first thrombotic event and 275 control subjects living in the state of Minas Gerais, Brazil. Odds ratio (OR) and chi tests were applied for statistical comparisons. Similar frequencies were detected among patients and control subjects for the C677T mutation. The 20210A mutation was present in 3.6% of the control subjects but was not detected among ischemic stroke patients. Significant differences were detected only for factor V Leiden (odds ratio 7.11; 95% confidence interval 1.55-32.73). Our data indicate that, among these genetic factors, factor V Leiden was identified as an important risk factor for arterial thrombosis in this group of patients. In addition, our results indicate regional differences in the incidence of these genetic factors in Brazil, as compared to the incidences reported in other studies.

Cumulative Effect of Predisposing Genotypes and Their Interaction With Modifiable Factors on the Risk of Ischemic Stroke in Young Adults

BACKGROUND AND PURPOSE

Combinations of multiple predisposing polymorphisms and their interactions with modifiable factors may result in synergistic effects on the risk of ischemic stroke. These mechanisms are more likely to play a relevant role in younger individuals.

METHODS

The cumulative effect of the 20210A variant of prothrombin gene, the 1691A variant of factor V gene, the TT677 genotype of the methylenetetrahydrofolate reductase (MTHFR) gene, and the epsilon4-carriership of the apolipoprotein (APOE) gene, as well as their interactions with modifiable predisposing factors, were determined in a series of 163 stroke patients aged younger than 45 years and 158 controls.

RESULTS

Odds ratios (ORs) for stroke were 1.73 (95% confidence interval [CI], 1.20 to 2.51) in subjects with 1 polymorphism and 3.00 (95% CI, 1.43 to 6.30) in those with > or =2. Compared with nonsmokers with none of the studied polymorphisms, ORs for stroke were 1.88 (95% CI, 1.18 to 3.00) and 3.55 (95% CI, 1.40 to 8.98) for nonsmokers with 1 and 2 polymorphisms, respectively, and 3.99 (95% CI, 2.00 to 7.96) and 15.99 (95% CI, 4.01 to 63.3) for smokers. Compared with nonhypertensive subjects bearing no polymorphisms, ORs were 1.91 (95% CI, 1.28 to 2.87) and 3.68 (95% CI, 1.64 to 8.26) for nonhypertensive subjects with 1 and 2 polymorphisms, 3.28 (95% CI, 1.01 to 10.7) and 10.79 (95% CI, 1.01 to 115.4) for hypertensive.

CONCLUSIONS

These data suggest a gene-dose effect of the examined prothrombotic and proatherogenic gene variants and a synergistic effect of these polymorphisms and modifiable risk factors in the pathogenesis of cerebral ischemia in young adults.

Relative impact of covariates in prescribing warfarin according to CYP2C9 genotype

Patients on warfarin anticoagulant therapy demonstrate wide variation in maintenance dose. Patients possessing variants (*2 and *3) of the cytochrome P450 2C9 gene require reduced maintenance doses compared to those having wild-type alleles (*1). Many other clinical factors have been shown to affect warfarin dose as well. To determine the relative impact of CYP2C9 genotype, age, gender, body surface area, concomitant medication, treatment indication and comorbidity, we conducted a retrospective cohort study in 453 patients managed by the anticoagulation service of a large, horizontally integrated, multispecialty group practice. In this largely Caucasian patient population, the CYP2C9 gene frequencies for *1/*1, *1/*2, *1/*3, *2/*2, *2/*3 and *3/*3 were 65.1%, 19.0%, 12.1%, 1.6%, 1.8% and 0.4%, respectively, approximating Hardy-Weinberg equilibrium. Mean maintenance doses for these genotypes were 36.5, 29.1, 23.5, 28.0, 18.1 and 5.5 mg/week, respectively. In univariate analyses, genotype alone accounted for 19.8% of the variability in maintenance dose. Age, body surface area and male gender accounted for 14.6%, 7.5% and 4.7%, respectively, while cardiac valve replacement as the indication for warfarin accounted for 5.4% of the variability. Collectively, these factors accounted for 33.7% of all dosing variability according to multiple regression. These results will help strengthen the mathematical models that are currently being developed for prospective gene-based warfarin dosing.

The 161TT genotype in the exon 6 of the peroxisome-proliferator-activated receptor γ gene is associated with premature acute myocardial infarction and increased lipid peroxidation in habitual heavy smokers

PPAR (peroxisome-proliferator-activated receptor) is a nuclear receptor. Activation of PPARγ by its ligands could modulate gene transcription, thereby leading to multiple anti-atherogenic and fibrinolytic effects. However, the association between the 161T allele in exon 6 of the PPARγ gene and premature AMI (acute myocardial infarction) is not clear. We recruited 146 patients with premature AMI (onset age ≤50 years) and 146 controls. The C161T polymorphism was examined using PCR and restriction-fragment-length polymorphism. Plasma levels of Ab-ox-LDL (antibody against oxidized low-density lipoprotein) were measured in 27 male smokers, whose genotypes have been identified. The frequency of the PPARγ TT genotype among patients with AMI was significantly higher than that in controls [13% compared with 5.5%; OR (95% CI) 2.7, (1.1–6.5), where OR and CI are odds ratio and confidence interval respectively]. This association was not observed in CC or CT genotypes. Using multivariate logistic regression analyses, we found that the homozygous TT genotype [OR (95% CI), 3.1 (1.2–7.9)], smoking [OR (95% CI), 3.5, (2.1–6.0)], hypertension [OR (95% CI), 3.6, (1.9–6.9)] and diabetes mellitus [OR (95% CI), 3.5 (1.5–8.4)] were independent risk factors for premature AMI. Plasma levels of Ab-ox-LDL were significantly higher in healthy volunteers with the TT genotype compared with those with the CC genotype (49.3±18.1 compared with 24.2±15.2 units/l respectively; P=0.02). Therefore in our study we observed an association between the PPARγ 161 TT genotype and premature AMI. Lipid peroxidation was significantly influenced by the 161T allele.

The platelet polymorphism PlA2 is a genetic risk factor for myocardial infarction

OBJECTIVES

Platelet glycoprotein (GP) receptor IIb/IIIa plays a key role in the development of myocardial infarction (MI), and Pl(A2) is a polymorphism in the gene encoding this receptor. The prevalence of Pl(A2) shows pronounced geographical variation and has to our knowledge not been presented for a Scandinavian population before. Platelets from Pl(A2)-positive individuals show increased aggregability compared with platelets from Pl(A2)-negative individuals, and Pl(A2) genotypes might be associated with MI. The purpose of this study was to investigate the relation between the Pl(A2) polymorphism and MI in a large Scandinavian population.

DESIGN

Case-control study. We included patients with angiographically verified CAD with and without previous MI and a group of healthy individuals matched for age, race, and sex.

RESULTS

We studied the frequency of Pl(A2) in 1191 healthy individuals and 1019 patients with coronary artery disease (CAD). Amongst these patients, 529 subjects had suffered an MI previously. Pl(A2) was present in 28% of healthy individuals, 28% of patients with CAD but no MI, and in 35% of patients with CAD and MI. The difference between healthy individuals and MI patients was significant (P = 0.002). Furthermore, a graded relationship between the number of Pl(A2) alleles and the risk of MI was seen (P = 0.011). Associations between Pl(A2) and traditional cardiovascular risk factors as well as mean platelet volume were investigated. We found a significant interaction between Pl(A2) and serum cholesterol.

CONCLUSION

In our Scandinavian study population the common platelet polymorphism Pl(A2) is significantly associated with an increased risk of MI, but not of CAD. Clinically, typing for Pl(A2) might have implications for antiplatelet therapy of patients with MI.

R353Q Polymorphism, Activated Factor VII, and Risk of Premature Myocardial Infarction in Japanese Men

BACKGROUND

The association between myocardial infarction (MI) and the R353Q polymorphism of the Factor VII (FVII) gene, which reportedly influences FVII concentrations, activated Factor VII (FVIIa), or FVII antigen (FVIIag), remains controversial.

METHODS AND RESULTS

The present case - control study in 127 Japanese men with their first MI at or before 45 years of age and 150 matched healthy controls was designed to clarify this association in premature MI. R353Q polymorphism was determined by polymerase chain reaction, and plasma concentrations of FVIIa and FVIIag were assayed. The distribution of the RR, RQ, and QQ genotypes with respect to R353Q polymorphism was 117, 10, and 0 in the patients, and 131, 17, and 2 in the controls. The Q allele was negatively associated with premature MI (odds ratio =0.41, p=0.038). The plasma concentration of FVIIa was slightly higher in patients (55.1+/-40.9 U/L) than in controls (44.8+/-20.2 U/L), but not significantly (p=0.078); the plasma concentration of FVIIag did not differ between patients (88.7+/-15.7%) and controls (87.0+/-9.0%) (p=0.557). Plasma FVIIa concentrations were influenced by R353Q polymorphism (p<0.001).

CONCLUSIONS

The Q allele may be protective against premature MI.

Prothrombotic coagulation defects and cardiovascular risk factors in young women with acute myocardial infarction

We investigated the effect of prothrombotic coagulation defects in combination with smoking and other conventional risk factors on the risk of myocardial infarction in young women. In 217 women with a first myocardial infarction before the age of 50 years and 763 healthy control women from a population-based case-control study, factor V Leiden and prothrombin 20210A status were determined. Data on major cardiovascular risk factors and oral contraceptive use were combined with the presence or absence of these prothrombotic mutations, and compared between patients and controls. The overall odds ratio for myocardial infarction in the presence of a coagulation defect was 1.1 [95% confidence interval (CI) 0.6-1.9]. The combination of a prothrombotic mutation and current smoking increased the risk of myocardial infarction 12-fold (95% CI 5.7-27) compared with non-smokers without a coagulation defect. Among women who smoked cigarettes, factor V Leiden presence versus absence increased the risk of myocardial infarction by 2.0 (95% CI 0.9-4.6), and prothrombin 20210A presence versus absence had an odds ratio of 1.0 (95% CI 0.3-3.5). We conclude that factor V Leiden and prothrombin 20210A do not add substantially to the overall risk of myocardial infarction in young women. However, in women who smoke, the presence of factor V Leiden increased the risk of myocardial infarction twofold.

Case report: Acute myocardial infarction in a 32-year-old white male found to have antiphospholipid antibody syndrome and MTHFR mutation homozygosity

We report the diagnosis and management of a 32-year-old Hungarian male, whose only known risk factor for coronary artery disease was smoking, who presented with an acute thrombotic anterolateral wall myocardial infarction requiring percutaneous transluminal coronary angioplasty (PTCA) stenting of his proximal left anterior descending coronary artery. He arrived to the emergency room with an abnormally prolonged partial thromboplastin time (PTT) that subsequently did not correct by mixing with normal plasma. This was suggestive of an underlying coagulopathy. An extensive coagulopathy work up found him to have the antiphospholipid antibody syndrome with antibodies positive for anticardiolipin, lupus anticoagulant and false-positive VDRL. Genetic typing found him to be homozygous for a mutation in the methylenetetrahydrofolate reductase (MTHFR A1298C) gene, which, in the presence of additional thrombophilic factors, may have increased his risk of myocardial infarction. He was discharged on high dose coumadin.

Classic risk factors, hypercoagulability and migraine in young women with cerebral lacunar infarctions

OBJECTIVE

Lacunar cerebral infarctions (LACI) in young women is a rare condition which pathogenesis is still not fully recognized. We explored the presence of classic risk factors, hypercoagulability and migraine in young women with LACI.

METHODS

Charts of 192 consecutive premenopausal women suffering cerebrovascular insult [125 (65%) haemorhagic, 58 (30%) ischaemic and 9 (5%) unclassified] during a period of 5 years were reviewed. Sixteen out of 58 (27%) patients with ischaemic stroke were identified to have LACI and included in a study.

RESULTS

Ten and seven out of 16 LACI women had at least one classical risk factor (hypertension, hyperlipidaemia, smoking or oral contraceptives) or migraine, respectively. LACI patients had slight hypercoagulable state indicated by shorter thrombin and thromboplastin times, higher fibrinogen and higher t-PA antigen than 47 age matched controls (all P < 0.05). In addition in LACI patients with migraine the trend toward more pronounced hypercoagulable state in comparison to LACI patients without migraine was found. The combination of migraine, at least one classic risk factor and hypercoagulability was present in 5/16 (31.25%) of patients.

CONCLUSIONS

The combination of slightly to moderately expressed classic risk factors, hypercoagulability and migraine might be a risk profile for LACI in young women. Further studies are needed to clarify risk profile, rather than isolated risk factors, for LACI in a specific group as young women are.

Fibrinolytic parameters and lipoprotein(a) in young women with myocardial infarction

Impaired fibrinolysis and elevated lipoprotein(a) (Lp[a]) are possible nonclassic risk factors for myocardial infarction (MI) at young age. The fibrinolytic system in young women with MI has not been evaluated yet and the role of Lp(a) is still controversial. The authors determined fibrinolytic parameters and Lp(a) in premenopausal women (mean age 42+/-3 years, n = 22) 0.5 to 6 (mean 3.5) years after MI, who were all without severe classic risk factors and had an otherwise low risk for MI. Elevated levels of tissue type plasminogen activator (t-PA) (p< 0.05) were measured in comparison to 52 age-matched controls; no difference was found in plasminogen activator inhibitor, plasminogen, fibrinogen, euglobulin clotting time and D-dimers. Significantly more MI patients had Lp(a) levels greater than 300 mg/L compared to controls (36% vs 13.5%, p< 0.05). The combination of elevated Lp(a), mild hyperlipidemia, and nonsevere smoking was found in 62.5% of MI patients who had elevated levels of Lp(a), in 23% of all women with MI, and in none of the controls. Elevated t-PA is probably only a marker of increased risk of MI, whereas elevated Lp(a) probably has a causative role. A combination of elevated Lp(a), hyperlipidemia, and nonsevere smoking seems to be a high-risk profile, relatively common in young women with MI.

Arterial strokes associated with factor V Leiden mutation

A 41-year-old Caucasian woman was admitted with right hemiparesis and blurred vision. There was no history of hypertension, diabetes, ischaemic heart disease, previous stroke, oral contraceptive use or miscarriages nor any family history of stroke. She was a non-smoker. Clinical examination confirmed the presence of right-sided weakness. There were no carotid bruits and her fundi were normal. Computed tomography scan of the brain confirmed the presence of a large infarct in the right middle cerebral artery territory (Figure 1). Full blood count, urea, creatinine, glucose and cholesterol levels were normal. Autoimmune profile, including antinuclear antibody, antineutrophil cytoplasmic antibody and anticardiolipin antibody, were negative. Other thrombophilia tests, including lupus anticoagulant, antithrombin III, plasminogen and protein S levels, were normal. Her electrocardiogram, chest X-ray, echocardiogram and a carotid Doppler study were unremarkable. A thrombophilia screen revealed markedly decreased activated protein C activity at 1.32 (normal ratio 2.25—2.63) when tested with factor V deficient plasma suggestive of factor V Leiden mutation.

Platelet glycoprotein gene polymorphisms and risk of thrombosis: facts and fancies

Over the past several years, platelet glycoprotein gene polymorphisms have received increasing attention as possible inherited determinants of prothrombotic tendency. However, their role in genetic susceptibility to thrombotic disease remains controversial. The glycoprotein IIIa Leu33Pro amino acid substitution appears to be associated with a subtle effect on platelet thrombogenicity in vitro, but is not a major risk factor for arterial thrombotic disease among the general population. Evidence suggests that the glycoprotein IIIa Pro33 allele may be associated with increased risk of thrombotic events following coronary re-vascularization and possibly among younger subjects with atherosclerosis. The nucleotide 807T variant of glycoprotein Ia is associated with increased platelet glycoprotein Ia/IIa receptor density, collagen-induced platelet adhesion and an increased risk of early onset myocardial infarction and stroke. Evaluation of the roles of the glycoprotein Ibalpha Thr145Met and variable number of tandem repeat polymorphisms has been complicated by their lack of well-defined effects on platelet adhesive function and the strong linkage disequilibrium between the two sites. Future epidemiologic studies of platelet glycoprotein gene polymorphisms will require larger sample sizes and family based approaches to further elucidate clinically important associations with thrombotic disease, including gene-environment and gene-gene interactions. Other polymorphisms of potential functional significance within genes encoding platelet membrane proteins will undoubtedly be discovered. The challenge will be to integrate advances in platelet biology with molecular and genetic epidemiology to enhance our understanding of the genetic determinants of common, but etiologically complex thrombotic diseases.

Correlation between cholesterol, soluble P-selectin, and D-dimer in obese children and adolescents

Thirty-eight obese children and adolescents were investigated for a possible relation between cholesterol and markers of platelet activation, endothelial cell dysfunction, and activation of the coagulation system. Soluble P-selectin, von Willebrand factor antigen (vWf-Ag), D-dimer, and prothrombin fragment 1 + 2 (F1 + 2) were determined by enzyme-linked immunosorbent assays, and factor VIII coagulant activity (VIIIc) was measured by means of one-stage clotting assay. Cholesterol correlated significantly with log P-selectin (r = 0.43, P = 0.003) and log D-dimer (r = 0.33, P = 0.02). Cholesterol did not correlate with vWf-Ag, factor VIIIc, and F1 + 2. Log P-selectin correlated significantly with log D-dimer (r = 0.42, P = 0.003), which remained significant after adjustment for cholesterol (P = 0.02). Log D-dimer correlated significantly with F1 + 2 (r = 0.38, P = 0.01). Our study demonstrates that, in obese children and adolescents, cholesterol is significantly associated with P-selectin and D-dimer, and suggests an unfavorable intercorrelation between metabolic and hemostatic risk factors for coronary heart disease in childhood obesity.

Clustering of procoagulation, inflammation, and fibrinolysis variables with metabolic factors in insulin resistance syndrome

The known metabolic cardiovascular disease risk factors associated with insulin resistance syndrome (IRS) do not adequately explain the excess cardiovascular disease risk attributed to this syndrome, and abnormalities in hemostatic variables may contribute to this excess risk. Using data from 322 nondiabetic elderly men and women (aged 65-100 years) participating in the Cardiovascular Health Study during 1989-1990, the authors performed factor analysis on 10 metabolic risk factors associated with IRS and 11 procoagulation, inflammation, and fibrinolysis variables to examine the clustering of the metabolic and hemostatic risk markers. Factor analysis of the metabolic variables confirmed four uncorrelated factors: body mass, insulin/glucose, lipids, and blood pressure. Adding the hemostatic variables yielded three new factors interpreted as inflammation, vitamin K-dependent proteins, and procoagulant activity. Plasminogen activator inhibitor-1 clustered with the body mass factor, supporting the hypothesis that obesity is related to impaired fibrinolysis. Fibrinogen clustered with the inflammation summary factor rather than procoagulant activity, supporting the position that fibrinogen principally reflects underlying inflammation rather than procoagulant potential. The authors conclude that should hemostatic variables be shown to contribute to IRS-related cardiovascular disease, apart from plasminogen activator inhibitor-1, they may do so independently of the established metabolic abnormalities.

The 20210 G-->A mutation in the 3'-untranslated region of the prothrombin gene and the risk for arterial thrombotic disease

A sequence variation in the 3'-untranslated region of the prothrombin (PT) gene (20210 G-->A) was recently claimed to be associated with elevated plasma prothrombin levels and an increased risk for venous and arterial thrombosis. We examined the prevalence of the 20210 A allele in the prothrombin gene in 400 healthy controls and in 263 patients with proven premature atherosclerotic disease. In addition, we measured prothrombin, prothrombin fragment 1 + 2, thrombin-antithrombin (TAT) complex and D-dimer levels in plasma from carrier and non-carrier patients. The frequency of the variant allele was 1% in the control subjects and 2.7% in the patient group, yielding a relative risk (RR) for the 20210 A allele of 2.7 (95% CI 0.8-9.4). All heterozygotes in the patient group were found to have had a myocardial infarction (MI), yielding a RR for MI of 4.2 (95% CI 1.2-14.6). Plasma prothrombin levels in carriers (126+/-10) were higher than in non-carriers (103+/-1, P=0.02). The levels of TAT complexes (16+/-9 v 6+/-1 microg/ml, P=0.02) as well as of prothrombin fragment 1 + 2 (1.5+/-0.3 v 1.0+/-0.1 nmol/l, P=0.02) were also elevated in carriers of the mutation. Our findings suggest that the 20210 G-->A mutation in the prothrombin gene is a genetic risk factor for MI. In addition, our data provide evidence for an association of the mutation with excessive thrombin generation, which may contribute to the understanding of its role in venous and arterial disease.

Effect of high- and low-molecular-weight heparins on thrombin-thrombomodulin interaction and protein C activation

BACKGROUND

Thrombin-thrombomodulin (TM) interaction, which is critical for accelerating the protein C anticoagulant pathway, involves the heparin-like domain of TM. This study was aimed at investigating the possible effect of heparin on thrombin-TM binding and protein C activation.

METHODS AND RESULTS

The affinity of thrombin-TM interaction was studied by a functional method, based on the ability of thrombin-TM adduct to activate protein C, and by evaluation of the binding of thrombin to immobilized TM. Both experimental approaches showed that the affinity of thrombin-TM interaction was decreased by micromolar heparin concentrations. Heparin had no significant effect when a recombinant TM form, lacking the chondroitin sulfate moiety, was used. Furthermore, it was also shown that the inhibitory effect of heparin was directly proportional to the heparin molecular mass (molecular weight range, 3 to 16 kDa), which suggests that the effect was mediated by formation of electrostatic bonds between heparin and thrombin.

CONCLUSIONS

These results indicate that heparin at therapeutic concentrations reduces the affinity of thrombin for TM and the rate of protein C activation. The magnitude of this effect is proportionally linked to the molecular mass of heparin.

A Common Prothrombin Variant (20210 G to A) Increases the Risk of Myocardial Infarction in Young Women

Using specimens from a population-based case control study among women ages 18 to 44 years in western Washington, we assessed the relationship between carriership of a genetic clotting factor II variant (20210 G→A) and myocardial infarction (MI). The factor II variant was previously shown to be present in 1% to 2% of the population, to increase the levels of factor II, and to be associated with venous thrombotic disease. Personal interviews and blood samples were obtained from 79 women with a first myocardial infarction and 381 control women identified through random-digit telephone dialing. Polymerase chain reaction (PCR) method was used to determine the factor II genotypes. The factor II 20210 G to A transition was present more often in women with MI (5.1%) than among control women (1.6%). The age-adjusted odds ratio for MI was 4.0 (95% confidence interval 1.1 to 15.1). The relative risk was high when another major cardiovascular risk factor was also present, such as smoking (odds ratio 43.3, 95% confidence interval 6.7 to 281), and the risk seemed limited to those with other risk factors. These results, in which the effect of major coronary risk factors is enhanced fourfold to sixfold by the prothrombin variant, are similar to those previously reported for another genetic clotting abnormality, factor V Leiden. We conclude that factor II 20210 G to A increases the risk of myocardial infarction in young women, especially in the women with other major risk factors for coronary heart disease.