The association of combined alpha and beta fibrinogen genotype on plasma fibrinogen levels in smokers and non-smokers

Protective Effects of Diets Rich in Polyphenols in Cigarette Smoke (CS)-Induced Oxidative Damages and Associated Health Implications

Cigarette smoking has been responsible for causing many life-threatening diseases such as pulmonary and cardiovascular diseases as well as lung cancer. One of the prominent health implications of cigarette smoking is the oxidative damage of cellular constituents, including proteins, lipids, and DNA. The oxidative damage is caused by reactive oxygen species (ROS, oxidants) present in the aqueous extract of cigarette smoke (CS). In recent years, there has been considerable interest in the potential health benefits of dietary polyphenols as natural antioxidant molecules. Epidemiological studies strongly suggest that long-term consumption of diets (fruits, vegetables, tea, and coffee) rich in polyphenols offer protective effects against the development of cancer, cardiovascular diseases, diabetes, osteoporosis, and neurodegenerative diseases. For instance, green tea has chemopreventive effects against CI-induced lung cancer. Tea might prevent CS-induced oxidative damages in diseases because tea polyphenols, such as catechin, EGCG, etc., have strong antioxidant properties. Moreover, apple polyphenols, including catechin and quercetin, provide protection against CS-induced acute lung injury such as chronic obstructive pulmonary disease (COPD). In CS-induced health problems, the antioxidant action is often accompanied by the anti-inflammatory effect of polyphenols. In this narrative review, the CS-induced oxidative damages and the associated health implications/pathological conditions (or diseases) and the role of diets rich in polyphenols and/or dietary polyphenolic compounds against various serious/chronic conditions of human health have been delineated.

Analysis of the effect of multiple genetic variants of cardiovascular disease risk on insulin concentration variability in healthy adults of the STANISLAS cohort

INTRODUCTION

Given the hypothesis of a common soil for atherosclerosis, type 2 diabetes and metabolic syndrome, we tested the contribution of gene polymorphisms involved in cardiovascular diseases on fasting insulin concentration (FIC).

METHODS

The polymorphisms were investigated by a multiplex assay in 308 apparently healthy French middle-aged men and women, taken from the STANISLAS cohort. FIC was measured by a microparticular enzymatic immunoassay.

RESULTS

After a series of regression analyses involving 34 polymorphisms, FGB -455G/A was the only polymorphism that remained significantly associated with FIC when adjusting the analyses for multiple testing. Stepwise models showed that FGB polymorphism accounted for 4.39% of FIC variability in men. Additionally, interactions between FGB and with environmental factors (alcohol and smoking in men, and BMI in women) were found.

DISCUSSION

To our knowledge, this is the first study reporting an influence of FGB polymorphism on FIC in a healthy population. Our results concord with the already shown link between fibrinogen concentration and FIC, and support the hypothesis of a relationship between fibrinogen and endothelium in FIC homeostasis whose alteration may induce several metabolic disorders. The contribution of this gene, although modest, is consistent with the polygenic nature of insulin levels.

Present status of outcome prediction of invasive coronary treatment by using genetic markers

A growing number of studies suggest that the outcome after invasive coronary treatment may be in part genetically determined. Here, we review the present status of outcome prediction of invasive coronary treatments by using genetic markers. Although some studies found an association between one or another genetic marker with one or another clinical endpoint, many other studies found no such relations; to date, none of the genetic markers that have been investigated in association studies are used in routine clinical practice to prospectively assess the prognosis following invasive coronary treatment or to decide upon therapeutic strategies. Many associations between genetic markers and certain clinical endpoints were initially reported in small studies but could not be confirmed in larger ones. Some of these discrepancies may be explained by publication bias. Some genetic variants may have true effects on clinical endpoints, which, albeit biologically interesting, do not bear much clinical relevance. On the other hand, many-if not most-studies that have been published to date are more or less grossly underpowered and very rarely report on the results of an a priori power analysis. Thus, there is still a need for further high-quality studies designed to investigate the specific contribution of genetic factors to the outcome after invasive coronary interventions.

Genetics of atherosclerosis

Atherosclerosis, the primary cause of coronary artery disease (CAD) and stroke, is a disorder with multiple genetic and environmental contributions. Genetic-epidemiologic studies have identified a surprisingly long list of genetic and nongenetic risk factors for CAD. However, such studies indicate that family history is the most significant independent risk factor (15, 52, 77). Many Mendelian disorders associated with atherosclerosis, such as familial hypercholesterolemia (FH), have been characterized, but they explain only a small percentage of disease susceptibility (although a substantial fraction of early CAD). Most cases of myocardial infarction (MI) and stroke result from the interactions of multiple genetic and environmental factors, none of which can cause disease by itself. Successful discovery of these genetic factors will require using complementary approaches with animal models, large-scale human genetic studies, and functional experiments. This review emphasizes the common, complex forms of CAD.

Relationship of the platelet glycoprotein PlA and fibrinogen T/G+1689 polymorphisms with peripheral arterial disease and ischaemic heart disease

INTRODUCTION

Genetic variation in plasma fibrinogen and the platelet receptor GP IIIa locus has been independently associated with increased risks of ischaemic heart disease, but there have been few reports on the relationship with peripheral arterial disease. This study determined the risk of peripheral arterial disease and ischaemic heart disease associated with polymorphisms of fibrinogen T/G(+1689) and platelet glycoprotein Pl(A) genes and the effects of cigarette smoking and fibrinogen.

MATERIALS AND METHODS

In the 5-year follow-up phase of the Edinburgh Artery Study, 939 subjects (60-79 years) had DNA extracted from a venous blood sample. One hundred sixteen subjects were identified as having angina, 87 a myocardial infarction, 104 had intermittent claudication and 663 subjects comprised a healthy group.

RESULTS

Distribution of the fibrinogen genotype was similar across the disease and healthy groups. Logistic regression analyses found no significant association between fibrinogen genotype and ischaemic heart disease and peripheral arterial disease. A lower percentage of claudicants had the Pl(A2) allele (8.3% vs. 15.2%, p=0.025). After adjustment for age and sex, the risk of IC associated with the Pl(A2) was half that of the homozygous Pl(A1) genotype (OR 0.49, 95% CI 0.25, 0.88; p<==0.05). Adjustment for lifetime smoking and fibrinogen levels increased the odds slightly to nonsignificance.

CONCLUSIONS

The Pl(A2) genotype was associated with a decreased risk of developing IC. There was no significant relationship between fibrinogen T/G(+1689) genotype and ischaemic and peripheral heart disease in this older population.

Genetic factors in cardiovascular disease. 10 questions

The common forms of cardiovascular disease (CVD) have a complex etiology, involving multiple genetic influences and important environmental interactions. Because of this complexity, it has proved difficult to apply the positional cloning approaches that have revolutionized understanding of Mendelian (single-gene) disorders; and the understanding of the genetics of CVD and its underlying cause, atherosclerosis, remains poor. This review, organized into 10 broad questions, summarizes the understanding of the genetics of common, complex forms of CVD. Implications for DNA-based diagnosis, pharmacogenetics, and risk assessment are also discussed.

Oxidative stress and smoking-induced vascular injury

The relative importance of mechanisms relevant to smoking-induced vascular injury is poorly understood. Cigarette smoke is a source of free radicals but also results in cellular activation and consequent generation of free radicals in vivo. Here we consider several approaches to estimating the consequences of free radical generation in vivo, using measurements of modified lipids, proteins, and DNA. Smoking appears to result in elevation of several biomarkers of oxidant stress, some in a dose-related fashion. There is also some evidence that disordered endothelial function in smokers may be partly attributable to oxidant stress. Other effects of smoking on hemostatic activation, sympathoadrenal function, and lipoprotein structure and function may also be modulated by smoking-induced oxidant stress. The emergence and application of rational quantitatively reliable indexes of oxidant stress in vivo is likely to elucidate the relative contribution of oxidant stress to smoking-induced vascular injury.

Combined segregation and linkage analysis of fibrinogen variability in Israeli families: evidence for two quantitative-trait loci, one of which is linked to a functional variant (-58G > A) in the promoter of the alpha-fibrinogen gene

The association of alpha- and beta-fibrinogen polymorphisms with plasma fibrinogen levels was examined in a sample of 452 family members from 80 Israeli kindreds. The measured genotype analysis indicated that the beta-fibrinogen -455G > A polymorphism was not associated with fibrinogen levels, while the alpha-fibrinogen -58G > A locus showed a significant association with fibrinogen levels (chi2= 17.7; df = 3; p < 0.001), with the -58A allele being associated with higher levels. Segregation analysis in this sample suggested a recessive quantitative-trait locus (QTL) with a major effect that controlled the sex- and age-adjusted fibrinogen levels. Results from a combined segregation/linkage analysis indicated that a single QTL influencing plasma fibrinogen is in gametic equilibrium with the beta-fibrinogen -455G > A and alpha-fibrinogen -58G > A polymorphisms. An extended analysis with a two-QTL model significantly improved the fit of the model (p < or = 0.001), and gave support for linkage between the fibrinogen QTL and the alpha-fibrinogen polymorphism. In vitro analysis with a DNA fragment containing this variant, linked to a reporter gene, showed 2-fold higher expression of the A allele compared to the G allele in the liver cell line HepG2, both under basal conditions and after stimulation with interleukin 6. These results demonstrate that two QTLs are jointly involved in determining plasma fibrinogen levels in this sample of families, one of which is located close to a functional variant in the alpha-fibrinogen locus.

Fibrinogen is a marker for nephropathy and peripheral vascular disease in type 1 diabetes: studies of plasma fibrinogen and fibrinogen gene polymorphism in the DCCT/EDIC cohort

We examined whether plasma fibrinogen levels and the beta-fibrinogen gene G(-455)-->A polymorphism were related to microvascular or macrovascular disease in patients (n = 909) with type 1 diabetes enrolled in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/ EDIC). Univariate regression showed that fibrinogen levels were correlated with BMI (r = 0.15; P < 0.0001), HbA(1c) (r = 0.11; P = 0.0014), total cholesterol (r = 0.17; P < 0.0001), and LDL cholesterol (r = 0.16; P < 0.0001) in all patients. In men, but not women, waist-to-hip ratio (r = 0.20; P < 0.0001) and triglycerides (r = 0.13; P = 0.0047) also became powerful predictors of fibrinogen level; in women, but not men, fibrinogen was correlated with both diastolic (r = 0.16; P = 0.0011) and systolic (r = 0.11; P = 0.0241) blood pressure. Fibrinogen was correlated with urinary albumin excretion rates in men (r = 0.13; P = 0.0033), but not in women. In both sexes, however, the development of proteinuria (albumin excretion >300 mg/24 h) was accompanied by 1.5-fold increment in plasma fibrinogen compared with patients with normal excretion or microalbuminuria. In addition, high fibrinogen levels were associated with a lower average ankle-brachial index in women (r = -0.13; P = 0.0075), but not men. Multiple regression analyses demonstrated that plasma fibrinogen was independently correlated with high albumin excretion rate in men, and with low average ankle-brachial index in women. Fibrinogen was not correlated with the severity of retinopathy. Carotid artery intima-medial thickness was not correlated with fibrinogen, and the G(-455)-->A polymorphism in the 5' promoter region of the beta-fibrinogen gene did not influence circulating fibrinogen levels. However, the presence of the more common G(-455) allele was associated with greater intima-medial thickness in the internal carotid artery (ANCOVA P = 0.045). Last, hyperfibrinogenemia in type 1 diabetes is associated with components of the insulin resistance syndrome trait cluster, and the association is influenced by sex.

Fibrinogen gene promoter -455 A allele as a risk factor for lacunar stroke

BACKGROUND AND PURPOSE

Elevated fibrinogen levels are suggested to increase the risk of myocardial infarction and stroke. Carriers of the A allele of the fibrinogen -455G/A polymorphism have increased plasma fibrinogen levels. We studied the association of this polymorphism with stroke subtype in the Stroke Aging Memory (SAM) cohort.

METHODS

The SAM cohort comprises 486 consecutive patients 55 to 85 years of age who, 3 months after ischemic stroke, completed a detailed stroke assessment. Stroke subtypes were examined with MRI. -455G/A genotype was determined by polymerase chain reaction. MRI and genotype data were available for the 299 patients who constitute the present study population.

RESULTS

Genotype distributions were 64.9% (GG), 31.8% (GA), and 3.3% (AA). In a logistic regression model with age, sex, hypertension, diabetes, hypercholesterolemia, hypertriglyceridemia, myocardial infarction, arrhythmia, atrial fibrillation, peripheral arterial disease, and smoking as possible confounders, there was a significant association between A+ genotype and >or=3 lacunar infarcts (odds ratio [OR], 2.57; 95% CI, 1.23 to 5.36; P=0.01). Hypertensive patients carrying the A allele had increased risk (OR, 4.24; 95% CI, 1.29 to 13.99; P=0.02) for >or=3 lacunar infarcts. A similar increase in risk was observed among smokers with the A+ genotype (OR, 2.67; 95% CI, 0.92 to 7.77; P=0.07).

CONCLUSIONS

Stroke patients carrying the A allele of the Bbeta-fibrinogen -455G/A polymorphism frequently presented with multiple lacunar infarcts. This association was stronger among hypertensives and smokers. These associations suggest that the A allele may predispose to atherothrombotic events in cerebrovascular circulation.

Genetic variations observed in arterial and venous thromboembolism--relevance for therapy, risk prevention and prognosis

We undertook genetic and biochemical assays in patients with arterial (n = 146) and venous (n = 199) thromboembolism and survivors of pulmonary embolism (n = 58) to study causation and gene-life style interactions. In the clinical material from North Western Russia, factor V Leiden was found to be a risk factor in venous thrombosis (OR = 3.6), while the methylenetetrahydrofolate reductase (MTHFR) C677T mutation was a significant variable in both venous (p = 0.03) and arterial thrombosis (p = 0.004). Homocysteine levels were determined (n = 84) and hyperhomocysteinemia correlated with the T allele of the MTHFR gene, and with smoking and coffee consumption. Vitamin supplementation reduced homocysteine levels dependent on MTHFR genotype (36% TT, 25% CT, 22% CC). In pulmonary embolism patients, frequency of the -455G/A beta-fibrinogen dimorphism was studied. Carriers of this allele were significantly underrepresented (p < 0.02) among pulmonary embolism survivors (34.5%) compared to controls (56.7%). Additionally, -455AA homozygotes were found in 11.7% controls but only 1.7% of pulmonary embolism patients (p = 0.006). In venous and arterial thrombosis cases, MTHFR and homocysteine data led to effective dietary supplementation with a reduced risk of disease progression. Results from the pulmonary embolism study may indicate that screening tests for the -455G/A beta-fibrinogen genetic variation could be of prognostic value, and may point the way for novel anticoagulation strategies.

Genetic influence on cigarette-induced cardiovascular disease

Cigarette smoking as an addictive habit has accompanied human beings for more than 4 centuries. It is also one of the most potent and prevalent environmental health risks human beings are exposed to, and it is responsible for more than 1000 deaths each day in the United States. With recent research progress, it becomes clear that cigarette smoking can cause almost all major diseases prevalent today, such as cancer or heart disease. These detrimental effects are not only present in active smokers who choose the risk, but also to innocent bystanders, as passive smokers, who are exposed to cigarettes not-by-choice. While the cigarette-induced harm to human health is indiscriminate and severe, the degree of damage also varies from individual to individual. This intersubject variability in cigarette-induced pathologies is partly mediated by genetic variants of genes that may participate in detoxification process, eg, cytochrome P450 (CYP), cellular susceptibility to toxins, such as p53, or disease development. Through population studies, we have learned that certain CYP1A1 variants, such as Mspl polymorphism, may render the carriers more susceptible to cigarette-induced lung cancer or severe coronary atherosclerosis. The endothelial nitric oxide synthase intron 4 rare allele homozygotes are more likely to have myocardial infarction if they also smoke. In vitro experimental approach has further demonstrated that cigarettes may specifically regulate these genes in genotype-dependent fashion. While we still know little about genetic basis and molecular pathways for cigarette-induced pathological changes, understanding these mechanisms will be of great value in designing strategies to further reduce smoking in targeted populations, and to implement more effective measures in prevention and treatment of cigarette-induced diseases.

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.

Genetic contributions to plasma total antioxidant activity

Oxidative stress plays important roles in a wide spectrum of pathological processes, such as atherosclerosis. Although several environmental factors are documented to influence redox metabolism, relatively little is known about genetic effects. In the present study, we evaluated genetic contributions to variation in plasma total antioxidant status (TAS), a measure of peroxyl-scavenging capacity, in 1337 members of 40 Mexican American families. TAS levels were significantly lower in women than in men (1.675+/-0.004 versus 1.805+/-0.005 mmol/L, respectively; P<0.001), and there was a significant decline of TAS levels with age in men but not in women (P<0.01 for the interaction). Quantitative genetic analysis indicated the heritability of TAS levels to be 0.509+/-0.052; ie, approximately 51% of the residual variance (after covariate adjustment) in TAS levels was due to the additive effects of genes (P<0.001). We have further observed a significant gene-by-smoking interaction (P<0.05). Additive genetic effects account for 83% of the residual phenotypic variance in TAS levels among smokers, but they account for only 49% in nonsmokers. However, genes contributing to TAS variation are the same in smokers and nonsmokers. Our study for the first time demonstrates that TAS, an indicator of redox homeostasis, is under strong genetic control, especially among smokers. With appropriate tools, such as genome screening, it should be possible to localize genes that regulate redox homeostasis and, ultimately, identify the DNA sequence variants predisposing subjects to oxidative damage.

Venous thrombosis in relation to fibrinogen and factor VII genes among African-Americans

We evaluated the relation between venous thrombosis and plasma fibrinogen levels, the HaeIII and BcI polymorphisms of the beta fibrinogen gene, and the MspI polymorphisms of the factor VII gene in a case-control study of African-Americans. The study included 91 venous thrombosis cases and 185 control subjects obtained from a hospital in Atlanta, Georgia. High plasma fibrinogen was associated with increased risk of venous thrombosis, but the finding was not statistically significant. There was little association between the HaeIII polymorphisms and the BclI polymorphisms and the risk of venous thrombosis. The prevalence of the M2/M2 genotype of the factor VII gene was higher among cases than controls, but the difference was not statistically significant. The prevalence of the HaeIII H2 allele and the BclI B2 allele of the beta fibrinogen gene, both of which have been associated with slightly higher levels of plasma fibrinogen in most studies, is considerably lower among African-Americans in this study than it is among Whites in the United States and among Northern Europeans. The study is limited by its small size. However, despite this limitation, it supports the belief that increased plasma fibrinogen levels are associated with increased venous thrombosis risk. The study also indicated that the HaeIII and the BclI polymorphisms of the beta fibrinogen gene and the MspI polymorphisms of the factor VII gene are not strong determinants of venous thrombosis.

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.

Uses of Evolutionary Theory in the Human Genome Project

▪ Abstract  The Human Genome Project (HGP) originally sought to sequence the human genome but excluded studies on genetic diversity. Now genetic diversity is a major focus, and evolutionary theory provides needed analytical tools. One type of diversity research focuses on complex traits. This is often done by screening genetic variation at candidate loci functionally related to a trait followed by gene/phenotype association tests. Linkage disequilibrium creates difficulties for association tests, but evolutionary analyses using haplotype trees can circumvent these problems and result in greater statistical power, better disease risk prediction, the elimination of some polymorphisms as causative, and physical localization of causative variation when combined with an analysis of recombination. The HGP also now proposes to map over 100,000 single nucleotide polymorphisms to test for gene/phenotype associations through linkage disequilibrium in isolated human populations affected by past founder or bottleneck events. This strategy requires prior knowledge of recent human evolutionary history and current population structure, but other evolutionary considerations dealing with disequilibrium and nonrandom mutation pose difficulties for this approach. Studies on population structure also focus upon traits of medical relevance, and an understanding of the evolutionary ultimate cause for the predisposition of some populations to certain diseases is a useful predictor for shaping public health policies. Studies on the genetic architecture of common traits reveal much epistasis and variation in norms of reaction, including drug response. Because of these interactions, context dependency and sampling bias exist in disease association studies that require population information for effective use. Overall, the population thinking of evolutionary biology is an important counterweight to naive genetic determinism in applying the results of the HGP to issues of human health and well-being.

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.

Detection of a Complex That Associates With the Bβ Fibrinogen G−455-A Polymorphism

The promoter region of the Bβ fibrinogen gene containing the polymorphic site (G−455-A) shows an increase in fibrinogen levels for individuals containing an adenine rather than a guanine. Two methods were used to explore the possible functional role of this region. Electrophoretic mobility shift assays (EMSAs) were performed using specific DNA probes containing base sequences pertinent to the allelic site. Specific DNA binding proteins were detected and their binding characteristics were determined. Secondly, we placed DNA fragments containing different −455 nucleotide substitutions of the Bβ promoter upstream of a luciferase reporter gene and transfected them into HepG2 cells to determine their effect on transactivation. An adenine at position −455 resulted in greater luciferase activity than when a guanine was present. UV cross-linking bound protein to the DNA demonstrated a 47-kD protein binding preferentially to the site when a guanine rather than an adenine was present at −455. We hypothesize that a transactivation protein complex associates with the site, but its association is stronger when guanine is present, thereby slowing downstream Bβ gene transcription. These data provide the first molecular evidence that accounts for the increase in fibrinogen in individuals carrying this allele.

© 1998 by The American Society of Hematology.

Detection of a Complex That Associates With the Bβ Fibrinogen G−455-A Polymorphism

The promoter region of the Bβ fibrinogen gene containing the polymorphic site (G−455-A) shows an increase in fibrinogen levels for individuals containing an adenine rather than a guanine. Two methods were used to explore the possible functional role of this region. Electrophoretic mobility shift assays (EMSAs) were performed using specific DNA probes containing base sequences pertinent to the allelic site. Specific DNA binding proteins were detected and their binding characteristics were determined. Secondly, we placed DNA fragments containing different −455 nucleotide substitutions of the Bβ promoter upstream of a luciferase reporter gene and transfected them into HepG2 cells to determine their effect on transactivation. An adenine at position −455 resulted in greater luciferase activity than when a guanine was present. UV cross-linking bound protein to the DNA demonstrated a 47-kD protein binding preferentially to the site when a guanine rather than an adenine was present at −455. We hypothesize that a transactivation protein complex associates with the site, but its association is stronger when guanine is present, thereby slowing downstream Bβ gene transcription. These data provide the first molecular evidence that accounts for the increase in fibrinogen in individuals carrying this allele.

© 1998 by The American Society of Hematology.

Segregation analysis of plasminogen activator inhibitor-1 and fibrinogen levels in the NHLBI family heart study

Elevated plasminogen activator inhibitor-1 (PAI-1) and fibrinogen concentrations are risk factors for coronary heart disease. We investigated environmental, familial, and genetic influences on PAI-1 antigen and fibrinogen concentrations in 2029 adults from 512 randomly ascertained families in 4 US communities. We used maximum-likelihood segregation analysis to fit several genetic and nongenetic modes of inheritance to the data to determine whether mendelian inheritance of a major gene could best explain the familial distributions of these 2 hemostatic factors. Age- and gender-adjusted familial correlations for PAI-1 antigen level averaged 0.16 in first-degree relatives (95% CI=0.11 to 0.21); the spouse correlation was positive but not statistically significant (r=0.10, 95% CI=-0.02 to 0.23). Complex segregation analysis indicated a major gene associated with higher PAI-1 concentrations in 65% of individuals from these families. Demographic, anthropometric, lifestyle, and metabolic characteristics together explained 37% to 47% of the variation in PAI-1 antigen levels, and the inferred major gene explained an additional 17% of the variance. Positive and statistically significant age- and gender-adjusted familial correlations in first-degree relatives indicated a possible heritable component influencing plasma fibrinogen concentration (r=0. 17, 95% CI=0.13 to 0.22); however, segregation analysis did not provide statistical evidence of a major gene controlling fibrinogen level. These family data suggest that there are modest familial and genetic effects on the concentration of PAI-1.

A common mutation (G-455--> A) in the beta-fibrinogen promoter is an independent predictor of plasma fibrinogen, but not of ischemic heart disease. A study of 9,127 individuals based on the Copenhagen City Heart Study

A common mutation (G-455--> A) in the promoter region of the beta-fibrinogen gene has been associated with elevated plasma fibrinogen levels. Whether fibrinogen genotype affects plasma fibrinogen levels and risk of ischemic heart disease in the general population has not been studied. We investigated the association between fibrinogen genotype, plasma fibrinogen levels, and ischemic heart disease in a general population sample (n = 9,127). The A-allele (relative frequency, 0.20) was associated with elevated plasma fibrinogen levels in both genders (P < 0.001). While the effect of the A-allele on fibrinogen level was additive in men, the effect was dominant in postmenopausal women. The A-allele raising effect appeared to be two- to threefold greater in individuals with ischemic heart disease than in those without. An increase of 1 SD in plasma fibrinogen increased the odds ratio for ischemic heart disease by approximately 20% (P < 0.01 for women and < 0.005 for men). However, the frequency of the A-allele was similar in those with and without ischemic heart disease, and genotype was not a predictor of disease. These results demonstrate that the (G-455--> A) mutation in the promoter region of the beta-fibrinogen gene is associated with an increase in plasma fibrinogen in both genders in the general population. This increase does not appear to cause ischemic heart disease.

Polymorphisms of factor V, factor VII, and fibrinogen genes. Relevance to severity of coronary artery disease

We explored the associations between G-->A mutations of factor V and factor VII genes and the Hae III polymorphism of the fibrinogen gene and the severity of coronary artery disease (CAD), as assessed angiographically in 545 white Australian patients (388 male and 157 female) aged < or = 65 years. We also assessed the relations with other potentially atherogenic variables. Elevated fibrinogen levels were associated with more severe CAD (P < .05), but none of the factor V, factor VII, and fibrinogen DNA variants were predictive of CAD severity, as assessed by the number of significantly diseased vessels (> 50% luminal obstruction). The rare allele frequencies of factor V (A allele), factor VII (M2 allele), and fibrinogen (H2 allele) were .025, .114, and .201 for men and .022, .077, and .169 for women, respectively, and were not different from those in healthy whites. In the patient population, there was a strong, positive association between lifetime smoking dose (in pack-years) and circulating fibrinogen levels (r = .184, P = .001). This association was stronger than that between current smoking habit and fibrinogen and is consistent with a dosage effect. However, there was no significant contribution of fibrinogen genotype to fibrinogen levels in this patient population. We conclude that elevated fibrinogen levels are associated not only with the occurrence of CAD but also with more severe CAD and that measurement of DNA variants of the factor V, factor VII, and fibrinogen genes that we assessed may not provide information in predicting CAD severity in addition to that obtained by measuring circulating levels of the relevant clotting factors. There is, moreover, a positive dosage effect (in pack-years) of smoking on circulating fibrinogen levels.