Positive Association of the β Fibrinogen H1/H2 Gene Variation to Basal Fibrinogen Levels and to the Increase in Fibrinogen Concentration during Acute Phase Reaction but not to Coronary Artery Disease and Myocardial Infarction

Quantile-specific heritability of plasma fibrinogen concentrations

Background

Fibrinogen is a moderately heritable blood protein showing different genetic effects by sex, race, smoking status, pollution exposure, and disease status. These interactions may be explained in part by “quantile-dependent expressivity”, where the effect size of a genetic variant depends upon whether the phenotype (e.g. plasma fibrinogen concentration) is high or low relative to its distribution.

Purpose

Determine whether fibrinogen heritability (h²) is quantile-specific, and whether quantile-specific h² could account for fibrinogen gene-environment interactions.

Methods

Plasma fibrinogen concentrations from 5689 offspring-parent pairs and 1932 sibships from the Framingham Heart Study were analyzed. Quantile-specific heritability from offspring-parent (β_OP, h² = 2β_OP/(1+r_spouse)) and full-sib regression slopes (β_FS, h² = {(1+8r_spouseβ_FS)^0.05–1}/(2r_spouse)) were robustly estimated by quantile regression with nonparametric significance assigned from 1000 bootstrap samples.

Results

Quantile-specific h² (±SE) increased with increasing percentiles of the offspring’s age- and sex-adjusted fibrinogen distribution when estimated from β_OP (P_trend = 5.5x10^-6): 0.30±0.05 at the 10^th, 0.37±0.04 at the 25^th, 0.48±0.05 at the 50^th, 0.61±0.06 at the 75^th, and 0.65±0.08 at the 90^th percentile, and when estimated from β_FS (P_trend = 0.008): 0.28±0.04 at the 10^th, 0.31±0.04 at the 25^th, 0.36±0.03 at the 50^th, 0.41±0.05 at the 75^th, and 0.50±0.06 at the 90^th percentile. The larger genetic effect at higher average fibrinogen concentrations may contribute to fibrinogen’s greater heritability in women than men and in Blacks than Whites, and greater increase from smoking and air pollution for the FGB -455G>A A-allele. It may also explain greater fibrinogen differences between: 1) FGB -455G>A genotypes during acute phase reactions than usual conditions, 2) GTSM1 and IL-6 -572C>G genotypes in smokers than nonsmokers, 3) FGB -148C>T genotypes in untreated than treated diabetics, and LPL PvuII genotypes in macroalbuminuric than normoalbuminuric patients.

Conclusion

Fibrinogen heritability is quantile specific, which may explain or contribute to its gene-environment interactions. The analyses do not disprove the traditional gene-environment interpretations of these examples, rather quantile-dependent expressivity provides an alternative explanation that warrants consideration.

Fibrinogen beta-chain -C148T polymorphism is associated with increased fibrinogen, C-reactive protein, and interleukin-6 in patients undergoing coronary artery bypass grafting

The fibrinogen beta-chain (FGB) -C148T polymorphism is linked with plasma fibrinogen concentration in the general population. We examined whether the -C148T polymorphism is associated with pre- and early postoperative levels of fibrinogen, C-reactive protein (CRP), and interleukin-6 (IL-6) in 243 consecutive patients undergoing coronary artery bypass grafting (CABG) surgery. Plasma inflammatory markers were measured prior to and 5-7 days after surgery. The -C148T polymorphism was analyzed with the restriction fragment-length polymorphism method. The genotype distribution was as follows: CC-142 (58%), CT-85 (35%), and TT-16 (7%). Carriers of the -148T allele had higher preoperative plasma fibrinogen (4.42 ± 0.14 vs. 4.07 ± 0.11 mg/L, p = 0.04) and CRP levels (7.49 ± 1.2 vs. 4.26 ± 1.0 mg/L, p = 0.04) compared with non-carriers; 5 to 7 days after CABG, patients carrying -148T allele had increased CRP (70.4 ± 5.0 vs. 51.6 ± 4.25 mg/L, p = 0.005) and IL-6 levels (22.34 ± 2.64 vs. 15.53 ± 2.28 pg/L, p = 0.05), but not fibrinogen, compared with the remaining subjects. In-hospital nonfatal stroke occurred more frequently in -148T allele carriers (4% vs. 0%, p = 0.02). No genotype-associated differences were found in the occurrence of postoperative myocardial infarction and death. Presence of the -148T allele has also been associated with longer intensive care stay and intubation time (p = 0.01). Multivariate analysis identified the CT+TT genotype as an independent predictor of pre- and postoperative CRP levels. The results indicate that the presence of the -148T FGB allele determines higher pre- and postoperative levels of inflammatory markers, which might be associated with in-hospital clinical outcomes.

Gelatinase B C(‐1562)T polymorphism in relation to ischaemic heart disease

OBJECTIVE

Matrix metalloproteinases, such as gelatinase B, are important in connective tissue remodelling processes associated with atherogenesis and plaque rupture. The T allele of the gelatinase B C((-1562)) T polymorphism has been reported to be associated with an almost 2-fold increase in promoter activity and with the extent of coronary artery disease (CAD). The aim of this study was to analyse the relation of this gene variation to the risk and severity of CAD and the risk of myocardial infarction (MI).

MATERIAL AND METHODS

This case-control study comprised 535 healthy controls and 2731 participants who had undergone coronary angiography.

RESULTS

In the total sample, the gelatinase B promoter polymorphism was not associated with the risk of CAD and MI or with the extent of CAD defined either by the number of diseased coronary arteries or--in patients with coronary angiography--by a score for coronary heart disease (CHD) according to the Gensini score. However, patients with TT genotype had higher CHD scores than the other genotypes in subgroups of individuals with high apolipoprotein B levels, high lipoprotein (a) plasma concentrations and high fibrinogen levels, or with combinations of increased levels of these coronary risk factors. These observations were made in the entire sample of individuals with coronary angiography and in the population of patients with documented CHD.

CONCLUSIONS

Obviously, the gelatinase B C((-1562))T gene polymorphism is not a risk indicator for CAD and MI. With respect to the extent of CHD, the impact of this gene variation may be restricted to individuals with high apolipoprotein B, lipoprotein (a) and/or fibrinogen levels.

Inherited Thrombophilia

Inherited thrombophilia can be defined as a genetically determined predisposition to the development of thromboembolic complications. Since the discovery of activated protein C resistance in 1993, several additional disorders have been described and, at present, it is possible to identify an inherited predisposition in about 60 to 70% of patients with such complications. These inherited prothrombotic risk factors include qualitative or quantitative defects of coagulation factor inhibitors, increased levels or function of coagulation factors, defects of the fibrinolytic system, altered platelet function, and hyperhomocysteinemia. In this review, the main inherited prothrombotic risk factors are analyzed from epidemiological, laboratory, clinical, and therapeutic points of view. Finally, we discuss the synergism between genetic and acquired prothrombotic risk factors in particular conditions such as childhood and pregnancy.

Fibrinogen Genes and Myocardial Infarction

Objective— Fibrinogen has a role in inflammatory processes and participates in atherosclerotic plaque formation. Despite intensive investigation, there is no clear evidence for a role of variations in the genes coding for the fibrinogen-α, fibrinogen-β, and fibrinogen-γ polypeptide chains in myocardial infarction. We examined the association of haplotypes in the 50-kb fibrinogen gene region with myocardial infarction in 2 large case-control samples.

Methods and Results— Study sample 1 consisted of 3657 patients with myocardial infarction and 1211 control individuals and sample 2 comprised 1392 patients and 1392 controls. Haplotypes were inferred from genotype analyses of tagging single nucleotide polymorphisms dispersed among the fibrinogen genes. The frequencies of these haplotypes were not significantly different between the case and control groups in either sample ( P ≥0.07). In addition, haplotypes specific for individual fibrinogen genes were analyzed. No substantial differences in the frequencies of these haplotypes were observed between the groups ( P ≥0.13). Finally, haplotypes composed of SNPs that exhibited relatively low pairwise allelic associations among each other were examined. The proportions of the haplotypes were not significantly different between cases and controls ( P ≥0.12).

Conclusion— A haplotype analysis did not reveal a link between genetic variations in the fibrinogen gene region and myocardial infarction.

TagSNP evaluation for the association of 42 inflammation loci and vascular disease: evidence of IL6, FGB, ALOX5, NFKBIA, and IL4R loci effects

Inflammatory markers have consistently been associated with vascular disease. Evidence of genetic polymorphisms in inflammatory loci that predict severe carotid artery disease (CAAD) would suggest that this relationship is not secondary to other correlated factors, but related to inflammation itself. We examined the full common genetic variation in 42 inflammatory loci for prediction of severe CAAD versus ultrasound proven controls using a tagSNP approach. For selected loci, monocyte RNA levels were contrasted in subjects with and without CAAD. We confirm the association of IL6(-174), FGB (-455), and ALOX5 with CAAD and show that multiple ALOX5 SNPs independently predict CAAD. We provide evidence for previously unreported associations of SNPs in IL4R, NFKBIA, and PLG with CAAD, and weaker evidence for associations with CSF3, IL10RA, and VCAM1. The NFKBIA and IL10RA expression levels significantly differed between subjects with CAAD and controls. These results support a role for genetic variation related to inflammation in CAAD and a causal role for specific gene products.

Fibrinogen and coronary heart disease: test of causality by 'Mendelian randomization'

BACKGROUND

Blood concentrations of fibrinogen have been associated with coronary heart disease risk in epidemiological studies, but it is uncertain whether this association is causal or reflects residual confounding by other risk factors. We investigated the relationship between the single nucleotide polymorphism at position -148 in the beta-fibrinogen gene promoter (beta - 148C/T), blood fibrinogen levels, and risk of myocardial infarction (MI) in sufficiently large numbers of coronary disease cases to reliably address this question.

METHODS

Genotyping and measurement of blood fibrinogen concentration were carried out in 4,685 cases of confirmed MI and 3,460 controls with no history of coronary disease. A meta-analysis of ISIS and 19 other studies of beta-fibrinogen genotypes involving a total of 12,220 coronary disease cases and 18,716 controls was conducted.

RESULTS

Among the ISIS controls, mean plasma fibrinogen concentrations with the C/C, C/T and T/T genotypes were 3.34 (SE 0.015), 3.48 (0.022), and 3.60 (0.064) g/l, respectively, corresponding to an increase of 0.14 (0.024) g/l per T allele (trend P < 0.0001). In the case-control comparison, 0.14 g/l higher usual plasma fibrinogen concentration was associated with an age-adjusted and sex-adjusted risk ratio for MI of 1.17 [95% confidence interval (95% CI) 1.14-1.19; P < 0.0001]. But, after further adjustment for smoking, body mass index, and plasma apolipoprotein B/A(1) ratio, this risk ratio fell to 1.03 (95% CI 1.00-1.05; P = 0.05). Moreover, fibrinogen genotype was not significantly associated with MI incidence: risk ratio of 1.06 (95% CI 0.96-1.16) per higher-fibrinogen allele in ISIS alone and of 1.00 (95% CI 0.95-1.04) per allele in the meta-analysis.

CONCLUSIONS

Genotypes that produce lifelong differences in fibrinogen concentrations do not materially influence coronary disease incidence. As these genotype-dependent differences in fibrinogen were allocated randomly at conception (Mendelian randomization), this association is not likely to be confounded by other factors. Consequently, these genetic results provide strong evidence that long-term differences in fibrinogen concentrations are not a major determinant of coronary disease risk.

Does Elevated Plasma Fibrinogen Increase the Risk of Coronary Heart Disease?

OBJECTIVE

The purpose of this study was to assess whether a genetic variant associated with higher fibrinogen levels is associated with increased coronary heart disease (CHD) risk, as a test of the causal influence of fibrinogen on CHD.

METHODS AND RESULTS

We performed a meta-analysis of case-control and prospective studies of the G-455-->A and C-148-->T beta-fibrinogen promoter region variants, in relation to CHD risk. The 19 studies found included 12,393 cases and 21,649 controls. Fibrinogen levels were robustly related to the genetic variants (mean increase per allele, 0.117 g/L; 95% CI, 0.091-0.142 g/L). However, the genetic variants were unrelated to CHD risk (odds ratio per allele, 0.976; 95% CI, 0.916-1.040). The predicted causal odds ratio for a 1 g/L higher plasma fibrinogen level, given the genetic variant-fibrinogen and genetic variant-CHD associations, was 0.81 (95% CI, 0.46-1.40).

CONCLUSIONS

Although imprecise, the predicted causal effect of fibrinogen on CHD is clearly different from the odds ratio of 1.8 (95% CI, 1.6-2.0) for an increase of 1 g/L derived from a meta-analysis of observational studies. This evidence suggests that lowering the fibrinogen level may not, in itself, reduce CHD risk.

No association between pulmonary embolism or deep vein thrombosis and the -455G/A beta-fibrinogen gene polymorphism

Hyperfibrinogenaemia has been reported to be associated with deep vein thrombosis (DVT). However, whether or not the "fibrinogen-raising"-455G/A polymorphism of the beta-fibrinogen gene is associated with DVT is uncertain and there are no data on whether this polymorphism is associated with pulmonary embolism (PE). We have studied relationships between the -455G/A beta-fibrinogen gene polymorphism and the occurrence of PE and/or DVT (n = 339) (PE only, n = 76; DVT only, n = 216; PE and DVT, n = 47). There was no difference between the -455A allelic frequencies for the control (n = 190) and patient groups - PE, 0.187 and 0.171, respectively [P = 0.6087, chi test; odds ratio (OR), 1.12; 95% confidence interval (CI), 0.72-1.74]; DVT, 0.187 and 0.171, respectively (P = 0.5408, chi test; OR, 1.11; 95% CI, 0.78-1.59). This also applied when only Caucasian individuals were considered - PE allelic frequencies, 0.192 and 0.193, respectively (P = 0.9764, chi test; OR, 0.99; 95% CI, 0.62-1.60); DVT allelic frequencies, 0.192 and 0.186, respectively (P = 0.8404, chi test; OR, 1.04; 95% CI, 0.71-1.51). While the results should be interpreted with caution as the frequency of the -455A allele is rare, the -455A allele of the beta-fibrinogen gene does not appear to be associated with an increased risk of PE or DVT.

Fibrinogen heterogeneity: inherited and noninherited

PURPOSE OF REVIEW

Many noninherited or inherited variations have been described in fibrinogen and they may affect the different functions of fibrinogen.

RECENT FINDINGS

A number of the acquired variations in fibrinogen affect the properties of the fibrinogen molecule, such as the conversion rate to fibrin and/or the characteristics of the fibrin clot. Also, genetic polymorphisms are known that can affect the function of the fibrinogen molecule. In addition, some other genetic variants are associated with plasma levels of fibrinogen and with the increase of fibrinogen levels during an acute-phase reaction.

SUMMARY

In this review the authors discuss the noninherited and inherited variations of fibrinogen and the clinical implications (e.g. when determining the risk of cardiovascular disease).

Candidate gene susceptibility variants predict intermediate end points but not angiographic coronary artery disease

BACKGROUND

Moderate-sized studies have suggested that variants of candidate genes can influence laboratory markers of coronary artery disease (CAD), but whether they predict parallel changes in clinical CAD risk is unknown.

METHODS

We studied a single nucleotide polymorphism (SNP) from each of the 5 candidate genes for intermediate (laboratory) and clinical (angiographic CAD) end points in a large cohort of patients. The 5 gene SNPs were cholesteryl ester transfer protein (CETP) TaqIB (N = 3219), ATP-binding cassette (ABCA1) G596A (N = 3302), lipoprotein lipase (LPL) HindIII (N = 909), plasminogen activator inhibitor, type 1 (PAI1), 4G/5G (N = 1142), and hepatic lipase (HL) C-541T (N = 4704). Intermediate outcomes were high-density lipoprotein cholesterol (HDL-C) and triglycerides (TGs). Cases had 1- to 3-vessel CAD (> or = 70% stenosis); controls had angiographically normal coronaries.

RESULTS

Cholesteryl ester transfer protein predicted HDL (mean, B1B1 35.0 mg/dL, B2B2 38.6 mg/dL; P < .001) but not CAD (B1B1 74%, B2B2 70%; adjusted P = .35, odds ratio [OR] = 0.89). ABCA1 predicted HDL (mean, GG = 36.4 mg/dL, AA = 39.2 mg/dL; P = .02) but not CAD (GG 74%, AA 75%; adjusted P = .96, OR = 0.99). HL predicted HDL (CC 37.1 mg/dL, TT 40.9 mg/dL; P = .002) but not CAD (CC 71%, TT 68%, adjusted P = .66, OR = 0.94). LPL predicted TG (median: [++] 134, [--] 98 mg/dL; P < .001) but not CAD ([++] 79%, [--] 79%; adjusted P = .99, OR = 1.00). PAI1 predicted TG (median, 4G4G 130 mg/dL, 5G5G 148 mg/dL; P = .16), but not CAD (4G4G 77%, 5G5G 76%; adjusted P = .62, OR = 1.11).

CONCLUSIONS

Five SNPs predicted differences in risk-related lipids but not angiographic CAD. These discrepancies suggest that genetic determinants of CAD are complex and intermediate phenotypes are poor surrogates. These findings have important implications for future directions in genetic research.

Beta-fibrinogen haplotypes and the risk for cardiovascular disease in a dialysis cohort

BACKGROUND

Elevated plasma fibrinogen levels are common in dialysis patients and may be related to an elevated risk for cardiovascular disease (CVD). We tested the hypothesis that genetic variation in the beta-fibrinogen ( FGB ) gene, shown to explain 1% to 5% of fibrinogen level variation in the general population, has an important role in elevated fibrinogen levels and excess CVD risk in dialysis patients.

METHODS

Plasma fibrinogen was measured in 735 dialysis patients a median of 3 months from the start of dialysis therapy by using an automated clot-rate assay. Seven polymorphisms of the FGB gene were determined. Haplotype analysis was conducted using the Phase program to estimate haplotypes, with stratification for race. CVD events were ascertained from medical records.

RESULTS

During a median follow-up of 2.1 years, 279 CVD events occurred. Genotype frequencies were in Hardy-Weinberg equilibrium. Four common haplotypes identified were not associated with fibrinogen levels or CVD risk in the entire cohort or after stratification by race. The -455A allele, known to increase gene expression in vitro, was marginally associated with fibrinogen levels only in patients without diabetes (regression coefficient [beta], 20 mg/dL [for +1 copy of the A allele; P = 0.06]), adjusted for age, sex, race, smoking, baseline dialysis modality, comorbidity, and history of diabetes and CVD. Post hoc analysis showed that -249C-->T (defining haplotype 3) was associated with greater fibrinogen levels and CVD risk among patients without diabetes and current smokers.

CONCLUSION

The FGB gene likely does not have an important role in determining the variation in elevated plasma fibrinogen levels or excess CVD risk in dialysis patients.

A genome search for genetic determinants that influence plasma fibrinogen levels

BACKGROUND

Fibrinogen levels are a widely accepted risk factor for cardiovascular disease, but the extent of the genetic component is unknown.

MATERIALS AND RESULTS

To search for these genes, we conducted a genome-wide scan using 21 Spanish families from the Genetic Analysis of Idiopathic Thrombophila (GAIT) Project. Two loci were detected: 1 on chromosome 12 and another on chromosome 14. There are no cardiovascular-related candidate genes on chromosome 14, which implies that this locus represents a novel cardiovascular risk factor. Importantly, the locus on chromosome 12 contains the hepatocyte nuclear factors (TCF1), a candidate gene involved in the hepatocyte-specific transcription of the fibrinogen alpha-chain and beta-chain genes. Three polymorphisms in TCF1 showed significant association with fibrinogen levels, supporting the implication of TCF1 in the determination of this phenotype.

CONCLUSIONS

Two loci, 1 on chromosome 12 (most likely the TCF1) and another on chromosome 14, are important determinants of fibrinogen levels in Spanish families. These data should help define the relationship between fibrinogen levels and the risk of cardiovascular disease.

Plasma fibrinogen levels are associated with a strong family history of myocardial infarction

Family history of myocardial infarction (MI) is a known risk factor for coronary artery disease (CAD). The aim of the present study was to investigate whether there is a specific risk factor profile for CAD in individuals with a strong family history of MI occurring at any age. The Study of Health in Pomerania is a cross-sectional, population-based study in the north-east of Germany. A random sample was drawn from the population aged 20-79 years. From 3793 subjects with siblings, 34 (0.9%) reported a history of MI in at least one parent and one sibling. We matched these cases with 136 controls (1 : 4 matching for age, sex and presence of sibling). We then compared cases and controls with respect to known risk factors for MI. Subjects with a dual parental and sibling history of MI had higher plasma fibrinogen levels (3.5 versus 3.0 g/l, respectively), and also more often angina pectoris than the matched controls (P < 0.05). Multivariable analysis revealed an independent association between dual parental and sibling history of MI and plasma fibrinogen levels. We conclude that plasma fibrinogen levels may indicate an inheritable risk for CAD in subjects with a strong family history of MI.

Fibrinogen--marker or mediator of vascular disease?

Fibrinogen plays a key role in platelet aggregation, the final step of the coagulation cascade, i.e. the formation of fibrin, and it is a major determinant of plasma viscosity and erythrocyte aggregation. It is both constitutively expressed and inducible during an acute phase reaction. Increased plasma fibrinogen levels are associated with an increased risk of coronary heart disease and myocardial infarction. The question as to whether fibrinogen is only a marker of the inflammatory process involved in atherosclerosis or a mediator, i.e. a pathogenic factor, has not yet been answered. Human in vivo studies do not permit a conclusive answer to this question. If it is a pathogenic factor, fibrinogen lowering would be a therapeutic option. Selective fibrinogen-lowering agents do not exist however. All agents that lower fibrinogen also have other cardiovascular effects such as a decrease in cholesterol or inflammation. Newer information stems from molecular biology. Polymorphisms in the human fibrinogen gene with higher fibrinogen levels do not increase the risk for myocardial infarction. Fibrinogen knockout mice crossed with an atherosclerosis-susceptible strain (apoprotein E null mice) did not show a decreased extent of atherosclerosis despite the absence of fibrinogen, and a mouse strain over-expressing fibrinogen did not show an increased degree of atherosclerosis. Thus, fibrinogen seems to be a marker rather than a mediator of vascular disease, which would make selective fibrinogen lowering a useless preventive or therapeutic strategy.

–455G/A β-fibrinogen gene polymorphism, factor V Leiden, prothrombin G20210A mutation and MTHFR C677T, and placental vascular complications

Hyperfibrinogenaemia is associated with systemic arterial and venous thromboembolism and therefore may contribute to placental vascular disease associated with obstetric complications. The fibrinogen-raising -455G/A beta-fibrinogen gene polymorphism may enhance the physiological increase in fibrinogen levels during pregnancy and thereby predispose to obstetric complications. This retrospective case-control study looked at the association between the beta-fibrinogen gene polymorphism -455G/A, the hereditary thrombophilic markers factor V Leiden, prothrombin G20210A mutation (PGM) and C677T methylene tetrahydrofolate reductase (MTHFR), and obstetric complications associated with placental vascular disease. The study group (n = 247) comprised 147 women (90 Caucasian) who met the clinical criteria and a control group of 100 parous women (90 Caucasian) with no history of obstetric or medical complications. No significant differences were observed in the -455A allelic frequencies of the patient and normal control groups, with (allelic frequencies, 0.156 and 0.178, respectively; P = 0.5716, chi2 test, odds ratio = 1.17, 95% confidence interval = 0.65-2.13) or without (allelic frequencies, 0.129 and 0.170, respectively; P = 0.2077, chi2 test, odds ratio = 1.38, 95% confidence interval = 0.81-2.35) the exclusion of non-Caucasian women. There was an increased prevalence of factor V Leiden among Caucasian patients compared with normal controls (allelic frequencies, 0.056 and 0.017, respectively; P = 0.048, chi2 test, odds ratio = 0.29, 95% confidence interval = 0.05-1.15) but there were no differences in the prevalences of PGM or MTHFR. These data suggest that factor V Leiden is associated with an increased risk of obstetric complications, but that the -455A allele of beta-fibrinogen, PGM and MTHFR do not appear to be implicated.

Polymorphisms in coagulation factor genes and their impact on arterial and venous thrombosis

Arterial and venous thromboses, with their clinical manifestations such as stroke, myocardial infarction (MI), or pulmonary embolism, are the major causes of death in developed countries. Several studies in twins and siblings have shown that genetic factors contribute significantly to the development of these diseases. Since the advent of molecular genetics in medicine, it has been a focus of interest to elucidate the role of mutations in various candidate genes and their impact on hemostatic disorders such as arterial and venous thromboses. In this article, we review the current knowledge of the contribution of polymorphisms in coagulation factors to the development of thrombotic diseases. We show that in arterial thrombosis, results are controversial. Only for factor XIII 34Leu a protective effect on the development of myocardial infarction has been demonstrated in several studies. No other single polymorphism in a coagulation factor could be confirmed as a relevant risk factor, although there is evidence for a role of factor V Arg506Gln, factor VII Arg353Gln, and vWF Thr789Ala polymorphisms in patient subgroups. Further studies will be necessary to confirm the value of testing for genetic polymorphisms in arterial thrombosis. A large body of data is available on the role of factor V Arg506Gln and the prothrombin G20210A mutation in venous thrombosis. Some papers already recommend diagnosis and treatment strategies. We will discuss these recent publications on venous thrombosis in our review.

The T allele of the missense Glu(298)Asp endothelial nitric oxide synthase gene polymorphism is associated with coronary heart disease in younger individuals with high atherosclerotic risk profile

AIMS

Nitric oxide (NO) plays a protective role during atherogenesis. In the endothelium, NO is synthesised by the constitutive NO synthase (ecNOS). We analysed the relation of the ecNOS Glu(298)Asp and 4a/b gene polymorphisms to coronary artery disease (CAD) and myocardial infarction (MI) in a population of 3250 German subjects (533 healthy controls and 2717 individuals who underwent coronary angiography).

RESULTS

Although in the total sample, the ecNOS T allele was not associated with the risk of CAD (P=0.054) and the extent of this disease (P=0.078), a restriction to younger individuals (age</=61, mean age) revealed an association of the ecNOS T allele with an increased risk of CAD (1.43, 1.05-1.96; P=0.025) and with the severity of this disease (P=0.037). Similar observations were made in various high-risk populations. These associations were even more pronounced when the high-risk subgroups were restricted to younger individuals. For example, an odds ratio of 7.66 for CAD (95% CI, 2.0-29; P=0.003) was detected in diabetic individuals who were younger than 61 years. Also with respect to MI, the most pronounced associations of the ecNOS T allele with the risk of this disease were detected in younger individuals with at least one other cardiovascular risk factor. For example, in diabetics younger than 61 years, the relative risk for ecNOS T allele carriers was 9.73 (95% CI, 1.8-53; P=0.008). In contrast, the allele frequencies of the ecNOS 4a/b gene variation were essentially the same in controls and in CAD and MI patients.

CONCLUSION

The present data extends earlier observations by the findings that predominantly younger T allele carriers of the ecNOS Glu(298)Asp gene polymorphism with various coronary high-risk profiles had an increased risk to suffer CAD and/or MI. In contrast, no evidence was found for an association of the ecNOS 4a/b gene polymorphism with coronary heart disease.

Genetic variation in coagulation and fibrinolytic proteins and their relation with acute myocardial infarction: a systematic review

BACKGROUND

It is pathophysiologically conceivable that genetic variations in coagulation and fibrinolytic proteins are associated with the risk of myocardial infarction. Methods and Results- We performed a literature search to identify published case-control studies correlating the factor V Leiden or prothrombin G20210A mutations or fibrinogen G-455A or plasminogen activator inhibitor-1 (PAI-1) 4G/5G polymorphisms with the risk of myocardial infarction. Studies were included only if they used solid diagnostic criteria and complied with published methodological criteria. A common OR with corresponding 95% CI was calculated for the risk of myocardial infarction in a fixed-effect model according to Mantel-Haenszel. The factor V Leiden and prothrombin G20201A mutations did not significantly correlate with myocardial infarction (OR 1.26, 95% CI 0.94 to 1.67, P=0.12 and OR 0.89, 95% CI 0.59 to 1.35, P=0.6, respectively). Inclusion of the studies that investigated young patients (<55 years) made the association significant for factor V Leiden (OR 1.29, 95% CI 1.03 to 1.61, P=0.02). Homozygosity for the fibrinogen -455A allele was significantly associated with a decreased risk of myocardial infarction (OR 0.66, 95% CI 0.44 to 0.99, P=0.04), whereas the PAI-1 4G4G genotype was significantly associated with increased risk (OR 1.20, 95% CI 1.04 to 1.39, P=0.04).

CONCLUSIONS

Associations between these genetic variations and myocardial infarction were weak or absent. In the absence of clinical implications, our results indicate that screening of patients with myocardial infarction for these genetic variations is not warranted.

Genes encoding fibrinogen and cardiovascular risk

The role of fibrinogen in cardiovascular disease has been extensively studied, and meta-analyses have definitively confirmed that high levels of fibrinogen are associated with an increased risk of the disease. In recent years, several polymorphisms have been identified in the fibrinogen chain genes that contribute to determine the levels of fibrinogen in the general population. The fibrinogen beta-chain gene has been more extensively studied because the beta-chain synthesis is the limiting step in the production of mature fibrinogen. Overall, the studies show an association between beta-fibrinogen chain polymorphisms and the levels of fibrinogen. In contrast, the majority of the studies did not find any relation with the risk of cardiovascular disease. The individual responses to gender or to environmental stimuli such as smoking, physical exercise, or infections may be genetically determined, and genetic variability underlies changes in biological reactions that contribute to differences in cardiovascular risk. In the future, gene-environment interactions should be considered in evaluating the relevance of genetic variations on the risk of cardiovascular disease.

Interleukin-6 gene -174g>c and -572g>c promoter polymorphisms are strong predictors of plasma interleukin-6 levels after coronary artery bypass surgery

Interleukin-6 (IL-6) synthesized in response to diverse stimuli may play an important role in bridging the inflammatory and atherosclerotic processes. The acute-phase response after coronary artery bypass graft surgery (CABG) is associated with the induction and release of cytokines, such as IL-6. We have examined the effect of common polymorphisms in the IL-6 gene promoter (-174G>C, -572G>C, and -597G>A) on IL-6 levels after elective CABG. DNA extracted from the peripheral blood of 127 patients was amplified by polymerase chain reaction. IL-6 genotypes were resolved by gel electrophoresis after restriction enzyme digestion. Serum IL-6 was measured before surgery and in serial samples at 6, 24, 48, and 72 hours after CABG. Genotype distribution was as expected for a population in Hardy-Weinberg equilibrium for all polymorphisms. Rare allele frequencies (+/-95% CIs) were similar to those reported previously: -597A 0.36 (0.30 to 0.42), -572C 0.07 (0.04 to 0.10), and -174C 0.37 (0.31 to 0.43). The -174G>C and -597G>A genotypes were in strong allelic association (Delta=0.97, P<0.001). Baseline IL-6 levels did not significantly differ between patients with different genotypes for any polymorphism. However, 6 hours after CABG, peak IL-6 levels were significantly higher (P=0.03) in carriers of the -572C allele than in those of the -572GG genotype (355+/-67 versus 216+/-13 pg/mL, respectively) and in those with genotype -174CC compared with -174G allele carriers (287+/-31 versus 227+/-15 pg/mL, respectively; P=0.04). These effects remained statistically significant after adjusting for possible confounders, including age, sex, smoking, duration of cardiopulmonary bypass, aortic cross-clamp time, and total duration of surgery. These data demonstrate that IL-6 promoter polymorphisms influence peak IL-6 production after CABG, suggesting that these polymorphisms, which are functional in vitro, are also functional in vivo, suggesting a genetic influence on IL-6 levels after acute severe injury.

Identification of four novel polymorphisms in the Aalpha and gamma fibrinogen genes and analysis of association with plasma levels of the protein

Four novel polymorphisms were identified in the fibrinogen gene cluster. Three of them were localized in the promoter regions of the Aalpha-chain (alpha -128 C/G, alpha -58 G/A) or the gamma-chain (gamma -239 A/G) gene, while the remaining one was identified in intron 9 of the gamma-chain gene (gamma 7792 C/T). Genotype distributions for these polymorphisms were analyzed in 200 healthy Italian individuals and were in Hardy-Weinberg equilibrium. Since high levels of plasma fibrinogen have been associated with an increased risk of cardiovascular disease and genetic variations have been evaluated as thrombotic risk predictors, we analyzed their role in determining the plasma levels of this protein. Owing to the low frequency of the rare allele of alpha -128 C/G and gamma -239 A/G polymorphisms, association with plasma fibrinogen levels was investigated for only alpha -58 G/A and gamma 7792 C/T. We also investigated in the same population two previously identified polymorphisms in the fibrinogen gene cluster (alpha TaqI and beta -455 G/A) chosen for their widely studied association with plasma fibrinogen levels. In the multivariate linear regression analysis, no statistically significant association with plasma fibrinogen levels was found.

Effects of diet, drugs, and genes on plasma fibrinogen levels

Plasma levels of fibrinogen have been identified as independent risk predictors of cardiovascular disease. This has greatly increased interest in the regulation of plasma fibrinogen levels. Many demographic and environmental factors are known to affect fibrinogen levels, such as diet, use of several drugs, age, smoking, body mass, gender, physical exercise, race, and season. Additionally, it is also known that genetic factors determine the fibrinogen levels, and also that they determine the response of fibrinogen levels to environmental factors. Estimates, based on twin studies, suggest that 30-50% of the plasma fibrinogen level is genetically determined. The effect of dietary components on plasma fibrinogen levels is modest. Several components have been identified as factors that influence fibrinogen levels. Among those are fish oil, other lipids, and fibers. Dietary components that were expected to have an effect on fibrinogen, but for which no association was observed are black and green tea. Several drugs are known to influence fibrinogen levels, the most studied of which are platelet aggregation inhibiting drugs, such as ticlopidine, and the lipid lowering fibric acid derivatives (fibrates). Both types of drugs decreased the plasma fibrinogen level by about 10%, and bezafibrate lowers fibrinogen even more in patients with diabetes. No clear effect was observed for the HMG-CoA reductase inhibitors (statins). In the Bezalip study, fibrinogen levels decreased in patients treated with bezafibrate, but this had no clear effect on the risk of cardiovascular disease. This suggests that several mechanisms influence the fibrinogen level and that these mechanisms may contribute differently to cardiovascular disease. Several variations in the fibrinogen genes have been described and especially variations in the promoter region of the fibrinogen beta-gene are interesting, because the synthesis of the fibrinogen B beta chain is considered to be the rate limiting step in the fibrinogen biosynthesis. In many studies the fibrinogen beta-gene polymorphisms (-455G/A, -148C/T, and BclI) are found to be associated with the plasma levels of fibrinogen. However, they are not associated with the risk of cardiovascular events, although in several studies an association with the severity and progression of atherosclerosis has been reported. It has also been observed frequently that the fibrinogen beta-gene promoter polymorphisms are associated with the response of fibrinogen levels to environmental factors, such as exercise and trauma. In conclusion, plasma fibrinogen levels are regulated by an interesting and complex interplay between environmental and genetic factors.

Identification and characterization of five new fibrinogen gene polymorphisms

It is clear that plasma fibrinogen levels are strongly influenced by genetic factors. To date 14 polymorphic sites have been identified within the fibrinogen gene cluster, mainly by restriction fragment length polymorphism (RFLP) and single-stranded conformation polymorphism (SSCP) analyses. Since elevated plasma fibrinogen is an independent risk factor for cardiovascular disease, these and other polymorphisms are of practical interest in defining haplotypes that correlate with fibrinogen levels. Here, DNA sequencing of fibrinogen genes from four patients led to the identification of 17 variations from the published sequence. Nine of these occurred in all chromosomes sequenced and were considered to be errors in the published data. Of the remaining eight, five represented novel variations, three having been previously described. The population frequency of the five novel variations, together with six known polymorphisms, was estimated by genotyping 50 normal individuals at each locus. The five new variations were all found at polymorphic frequencies in this group. Two of these new polymorphisms, B beta intron 2 and B beta codon 159, belong to the B beta linkage group defined by Behague et al., since their rare alleles occurred in complete concordance with the rare alleles of B beta Mnl I and B beta Bcl I. Calculation of pairwise linkage disequilibrium coefficients showed that the three remaining novel polymorphisms, A alpha Dde I, B beta Hinf I, and gamma intron 9 exhibited linkage equilibrium with respect to all other loci examined, including nearby polymorphisms that are themselves in strong linkage disequilibrium. This data indicates that these polymorphisms occur randomly with respect to background haplotype, and suggests that they are mutational hot spots.

Fibrinogen polymorphisms and atherothrombotic disease

Common polymorphisms of the fibrinogen gene cluster are associated with circulating fibrinogen level and with susceptibility to and/or severity of atherothrombotic disease. The frequencies of the polymorphisms vary among different ethnic groups but there is strong linkage disequilibrium at the beta-fibrinogen gene locus so that, in caucasian populations, there are only four common beta-fibrinogen haplotypes. One of these haplotypes, defined by the beta-fibrinogen -455A allele, is associated with elevated fibrinogen level and increased risk of atherothrombotic disease. The molecular mechanism of these associations is currently under investigation.

The genetics of venous and arterial thromboembolism

There is substantial evidence to indicate that the pathologic processes of venous and arterial thromboembolism involve both genetic and environmental influences. Scientific progress over the past decade has revealed a growing number of genetic factors, such as factor V Leiden and the prothrombin gene variant, that are present in more than 1% of the population and increase the relative risk of venous thrombosis between two- and sevenfold. Furthermore, several of these factors have been demonstrated to interact adversely with environmental influences, such as oral contraceptives and smoking. Although these traits are present at relatively high prevalence in the population, the magnitude of the increased thrombotic risk associated with these factors is substantially less than that related to inherited deficiency of the natural anticoagulant protein antithrombin, and somewhat less than the elevated risk with protein C and protein S deficiencies. In contrast to the progress that has been made in understanding the genetic contributions to venous thromboembolism, much still remains to be learned about the genetic basis of arterial thrombosis. Despite the documentation of associations between several genetic polymorphisms with plasma procoagulant levels, consistent associations with arterial thrombotic disease have not been found.

Beta-fibrinogen gene -455G/A polymorphism and coronary heart disease incidence: the Atherosclerosis Risk in Communities (ARIC) Study

PURPOSE

The -455G/A (HaeIII) polymorphism of the beta-fibrinogen gene influences levels of plasma fibrinogen. We determined whether it influences risk of coronary heart disease.

METHODS

We conducted a case-cohort study nested within a prospective investigation, the Atherosclerosis Risk in Communities Study. We accumulated 398 incident coronary heart disease cases over a median of 5.3 years of follow-up and compared their -455G/A status with a random sample of the cohort (n = 498).

RESULTS

Plasma fibrinogen was higher (p = 0.04) in AA homozygous participants (341 mg/dL) than in persons carrying the G allele: GA (290 mg/dL), GG (298 mg/dL). However, there was no significant association between -455G/A and incident CHD.

CONCLUSIONS

Although a small effect cannot be excluded, -455G/A does not appear to be an important genetic determinant of CHD.

Established and emerging cardiovascular risk factors

BACKGROUND

In the context of a comprehensive population strategy to reduce tobacco use, encourage healthy food choices, and increase physical activity for the whole population, the medical priority is to focus on those who have developed symptoms of coronary heart disease (CHD) or other major atherosclerotic disease, and those who are at high risk of developing such diseases in the future. To give cardiologists the best possible advice to facilitate their work in the prevention of CHD, the Joint European Societies (European Society of Cardiology, European Atherosclerosis Society and European Society of Hypertension) Task Force developed a set of recommendations on coronary disease prevention.

METHODS

Published studies were reviewed, and a consensus document on risk factors and their management in cardiovascular disease prevention was developed with input from members of the Task Force representing several European and international societies devoted to the study of heart disease, family medicine and behavioral medicine.

RESULTS

For patients with established CHD and individuals at high multifactorial risk of developing CHD, the same lifestyle and risk factor goals have been set (blood pressure <140/90 mm Hg, total cholesterol <190 mg/dL, LDL cholesterol <115 mg/dL), and the appropriate use of prophylactic drug therapies is recommended. The role of emerging risk factors-thrombogenic factors, homocysteine, markers of inflammation, infection and genetic factors-in risk prediction and management remains to be established. The scientific evidence for established risk factors is sufficiently strong to justify preventive action at a societal and medical level.

CONCLUSIONS

Physicians have considerable opportunities to take preventive action, based on the present scientific evidence, to prevent CHD or other atherosclerotic diseases. However, the control of risk factors remains inadequate in many patients. Physicians are in an excellent position to motivate patients to make lifestyle changes and comply with drug therapies, to advocate better risk management in the hospital and the community, and to call for increased resources for preventive cardiology.

Fibrinogen polymorphisms are not associated with the risk of myocardial infarction

In the Study of Myocardial Infarctions Leiden, we investigated the prevalence of three polymorphisms in the alpha- and beta-fibrinogen genes among 560 patients with a myocardial infarction and 646 control subjects. Secondly, we studied the relationships between these polymorphisms and fibrinogen activity and antigen levels. The TaqI, HaeIII and BclI polymorphisms in the fibrinogen gene were not associated with myocardial infarction. As we found an association of the rare B2 allele with fibrinogen levels and a similar, but weak, effect for the rare H2 allele, we conclude that a genetic propensity to high fibrinogen levels does not affect the risk of myocardial infarction. This is evidence against a causal role for fibrinogen levels in the aetiology of myocardial infarction.

Fibrinogen bellingham: a gamma-chain R275C substitution and a beta-promoter polymorphism in a thrombotic member of an asymptomatic family

Congenital dysfibrinogenemia is a rare cause of unexplained thrombosis. However, most individuals with dysfibrinogenemia are asymptomatic, suggesting that co-morbid factors contribute to thrombo-embolic events. The potential roles of additional genetic or acquired prothrombotic risk factors are poorly understood because detailed family studies are lacking. Herein, we describe a family whose propositus was a young Caucasian man with recurrent venous thrombo-emboli and dysfibrinogenemia due to heterozygosity for an Arg-->Cys substitution at residue 275 in the gamma-chain. The only additional thrombophilic abnormality found in the proband was heterozygosity for a G/A transition at position -455 in the fibrinogen beta-chain promoter; a genotype associated with high acute phase levels of fibrinogen. The proband's father, who died of a cerebral artery thrombosis, carried the gammaR275C substitution but not the beta-promoter -455 variant. Among 14 living relatives, eight were heterozygous for one or the other mutation and only one, a 21-year-old niece, was dually affected. None had suffered bleeding or thrombosis. In vitro studies of the proband's purified fibrinogen revealed markedly abnormal thrombin-catalyzed polymerization and delayed fibrin clot lysis by tPA-activated plasmin. We hypothesize that the gammaR275C substitution predisposes to thrombosis by generating clots that are relatively resistant to fibrinolysis. The clinical risk is low, however, in the absence of an additional thrombophilic mutation. The beta-promoter variant could, theoretically, contribute to this risk by augmenting expression of the dysfibrinogen under conditions of stress. Like the common hereditary thrombophilias, heterozygous familial dysfibrinogenemia induces thrombosis in the setting of multiple prothrombotic influences.

Genetic variation in coronary heart disease and myocardial infarction: methodological overview and clinical evidence

The precise molecular mechanisrms that lead to coronary artery disease (CAD) and myocardial infarction (MI) are not understood, despite a wealth of knowledge on predisposing risk factors and pathomechanisms. CAD and MI are complex genetic diseases; neither the environment alone nor a single gene cause disease, but a mix of environmental and genetic factors lead to atherosclerosis of the coronary arteries and subsequent manifestation of clinical disease. The biological complexity of atherosclerotic disease results from unknown or unpredictable interactions of many genetic and environmental factors which, by themselves, have only been partially identified. According to current knowledge, genetic variations in causative or susceptihility genes form the basis of molecular mechanisms that, together with environmental impact, lead to CAD/MI and determine its clinical course. Linkage analysis, which follows 'disease' alleles in families, or genetic association in a population of unrelated individuals are tools used in the search for chromosomal loci and candidate genes that are involved in these complex diseases. Progress in sequencing and mapping of the human genorne and efforts to identify all of the expected one million single nucleotide polymorphisms (SNPs) expected to be present in mankind will allow new approaches such as genome-wide association studies. The contribution of the current state of knowledge on genetic variation in man towards the dissection of CAD/MI as complex traits is sobering. Raised expectations with regard to the power of molecular genetic studies as compared to the traditional pathophysiological experimental approaches, lack of precise clinical phenotyping, lack of functional characterisation of gene variants, and the vast number of yet undetected genes may provide some explanation. Except for certain polymorphisms in lipid genes (i.e., apolipoprotein E [apo E]) or rare genetic variations (i.e., LDL receptor), which have a causal effect on both the intermediate (LDL-cholesterol level in plasma) and the clinical phenotypes (CAD/MI), the role of most gene polymorphisms is controversial or unknown. Despite the enormous progress in sequencing the human genome and in molecular genetic and bioinformatic techniques during the past decade, the progress in mapping and identifying genes responsible for complex traits such as CAD/MI has been modest and presents a formidable challenge to medical research in the 21st century.

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.

The p22 phox A640G gene polymorphism but not the C242T gene variation is associated with coronary heart disease in younger individuals

BACKGROUND

Most recently, evidence has been presented that the NADH/NADPH oxidase p22 phox C242T, but not the A640G gene polymorphism is associated with a reduced risk of coronary artery disease (CAD).

METHODS AND RESULTS

We analysed the relationships of both p22 phox gene polymorphisms to CAD in 2205 male Caucasians whose coronary anatomy was defined by means of coronary angiography. In the total population and in high and low risk groups the relative frequencies of the C242T alleles were essentially the same in patients without or with CAD and in individuals without or with myocardial infarction. In contrast, the G allele of the A640G polymorphism was significantly more frequent in subjects without CAD than in patients with CAD (Odds ratio (OR) 0.74 (0.57-0.98); P = 0.038 in multiple logistic regression (MLR)). Correspondingly, the AA genotype of A640G was preferentially found in patients with CAD. These associations did not disappear when the analyses were corrected for multiple comparisons for other gene polymorphisms (ACE I/D gene variation, angiotensinogen T174M and M235T gene polymorphisms, AT1 receptor gene variation, phox C242T gene polymorphism, paraoxonase PON54 and PON191 gene variations) (2p = 0.01 in MLR for the presence of CAD; 2p = 0.039 in multiple regression for the extent of CAD). The association of the A640G gene variation with the presence and extent of CAD was not only identified in the total sample, but was even stronger in various high risk subpopulations of younger individuals (e.g. with hypertension with or without increased apolipoprotein B plasma levels).

CONCLUSIONS

Our observations allow the assumption that the p22 phox A640G gene polymorphism is independently associated with the presence and extent of coronary artery disease.

Association of the Platelet Glycoprotein Ia C807T Gene Polymorphism With Nonfatal Myocardial Infarction in Younger Patients

Recently, we have shown that two alleles of the glycoprotein (GP) Ia gene, designated C807 and T807, are associated with low or high platelet GPIa-IIa density and consequently with slower or faster rate of platelet adhesion to type I collagen, respectively. This polymorphism could therefore present a genetic predisposition for the development of thrombotic disease and hemostasis. We investigated the relationship of the GPIa C807T dimorphism to the risk of coronary artery disease (CAD) and myocardial infarction (MI). An allele-specific polymerase chain reaction (PCR) was developed for genotyping of C807T polymorphism. DNA samples from 2237 male patients who underwent coronary angiography on account of coronary heart disease as verified illness or presumptive diagnosis were genotyped. The odds ratio was calculated as an estimate of the relative risk by multiple logistic regression. We found a strong association between the T allele and nonfatal MI among individuals younger than the mean age of 62 years (n = 1,057; odds ratio, 1.57; P = .004). The odds ratio of MI increased for T807 carriers with decreasing age. The highest odds ratio was detected within the youngest 10% of the study sample (&lt;49 years; n = 223; odds ratio, 2.61; P = .009). In contrast, no evidence of an association between C807T dimorphism with CAD was found. Our findings suggest that inherited platelet GP variations might have an important impact on acute thrombotic disease.

Association of the Platelet Glycoprotein Ia C807T Gene Polymorphism With Nonfatal Myocardial Infarction in Younger Patients

Recently, we have shown that two alleles of the glycoprotein (GP) Ia gene, designated C807 and T807, are associated with low or high platelet GPIa-IIa density and consequently with slower or faster rate of platelet adhesion to type I collagen, respectively. This polymorphism could therefore present a genetic predisposition for the development of thrombotic disease and hemostasis. We investigated the relationship of the GPIa C807T dimorphism to the risk of coronary artery disease (CAD) and myocardial infarction (MI). An allele-specific polymerase chain reaction (PCR) was developed for genotyping of C807T polymorphism. DNA samples from 2237 male patients who underwent coronary angiography on account of coronary heart disease as verified illness or presumptive diagnosis were genotyped. The odds ratio was calculated as an estimate of the relative risk by multiple logistic regression. We found a strong association between the T allele and nonfatal MI among individuals younger than the mean age of 62 years (n = 1,057; odds ratio, 1.57; P = .004). The odds ratio of MI increased for T807 carriers with decreasing age. The highest odds ratio was detected within the youngest 10% of the study sample (<49 years; n = 223; odds ratio, 2.61; P = .009). In contrast, no evidence of an association between C807T dimorphism with CAD was found. Our findings suggest that inherited platelet GP variations might have an important impact on acute thrombotic disease.

Association between polymorphisms in the fibrinogen alpha- and beta-genes on the post-trauma fibrinogen increase

Fibrinogen is an acute phase reactant, and therefore its plasma levels increase after severe injury. Polymorphisms in the fibrinogen alpha and beta genes have been found to be associated with plasma levels of fibrinogen, and it has also been suggested that they are associated with the fibrinogen increase in acute phase situations. In forty-five consecutive patients admitted to the Intensive Care Unit after acute cranial or thoracic trauma, we investigated the influence of four polymorphisms at the fibrinogen loci (-455G/A and BclI (beta gene), TaqI and T/A312 (alpha gene)) on the post-trauma increase of the fibrinogen levels. At admission, fibrinogen levels were comparable in the patients with the different genotypes for the four polymorphisms studied. However, patients carrying the -455A allele of the -455G/A polymorphism had a significantly wider variation and higher peak levels of fibrinogen, during their stay at the intensive care unit, than did the -455GA homozygotes (5.1 g/l (SD 1.3) and 5.9 g/l (SD 1.0), respectively, p<0.05). Such difference was not found for the other studied polymorphisms. The present study suggests that the increase of fibrinogen level in acute phase situations like severe trauma is associated with the beta-gene -455G/A polymorphism.

Elevated plasma fibrinogen: cause or consequence of cardiovascular disease?

An association between increased plasma fibrinogen and an increased risk for myocardial infarction (MI) is well established, but the nature of this association is subject to debate. Our aim was to shed light on the potentially causal nature of this association. We examined whether increased plasma fibrinogen, due to a condition that is independent of cardiovascular events, also increases the risk for MI. A case-control study was performed in 139 subjects with a history of MI and 287 control subjects selected from the Rotterdam Study, a population-based cohort of 7983 subjects aged 55 years and older. The genotype of the -455G/A polymorphism in the fibrinogen beta-gene was determined by polymerase chain reaction. Functional plasma fibrinogen levels were determined according to von Clauss. The plasma level of fibrinogen was significantly higher in subjects with one or two A alleles compared with subjects with the GG genotype: 3.8 (95% confidence interval [CI], 3.6 to 3.9) g/L and 3.6 (3.5 to 3.7) g/L, respectively. With increasing plasma fibrinogen level, the risk for MI increased gradually; a rise in fibrinogen of 1 g/L was associated with a 45% increased risk (odds ratio adjusted for age, sex, and smoking, 1.45; 95% CI, 1.12 to 1.88). There was no association between the genotype of the -455G/A polymorphism and the risk for MI. The -455G/A polymorphism is therefore associated with increased plasma fibrinogen levels but not with an increased risk for MI. These findings indicate that an increased plasma fibrinogen level due to this genetic factor does not increase the risk for MI.