Gene polymorphisms of the haemostatic system and the risk of arterial thrombotic disease

Plasminogen activator inhibitor-1 gene polymorphism as a risk factor for vascular complications in type 2 diabetes mellitus

Background

Diabetes mellitus (DM) can lead to microvascular and macrovascular damages through hyperglycemia that is the main cause of diabetic complications. Other factors such as hypertension, obesity, and hyperlipidemia may worsen or accelerate the others. Several studies have revealed definitive genetic predispositions to the development of type 2 diabetes mellitus (T2DM) and development of vascular complications. This study aimed to address the association between plasminogen activator inhibitor-1 (PAI-1) gene polymorphism and T2DM, and if this gene polymorphism may have a possible role in the development of vascular complications in T2DM. This study is a case control; it included 200 patients with T2DM, 117 patients had no vascular complications, and 83 had previous vascular complications (VCs). One hundred eighty volunteer blood donors were selected as a healthy control group. All patients and controls were subjected to clinical examination, and laboratory investigations included lipid profile, fasting and 2 h blood glucose, complete blood cell count, d-dimer, PAI-1, thrombin activatable fibrinolysis inhibitor (TAFI), and detection of PAI-1 gene polymorphism by real-time polymerase chain reaction (PCR).

Results

The most prevalent genotype of PAI-1 gene polymorphism in all studied groups, including controls, was 4G/5G with the highest allele frequency as 4G. The 4G/5G and 4G/4G genotypes were associated with increased risk of DM development as compared to 5G/5G genotype. The 4G/5G and 4G/4G genotypes also had a highly significant increased risk of VCs among diabetic patients, as compared to 5G/5G. The 4G allele also was highly associated with DM with VCs. The d-dimer TAFI, PAI-1 showed the highest levels in 4G/5G genotype followed by 4G/4G genotype. The lowest level was expressed in 5G/5G genotype in diabetic patients with and without VCs. The univariable analysis showed that genotypes 4G/5G and 4G/4G were potentially risk factors for development of VCs with T2DM patients.

Conclusion

This study concludes that the PAI-1 4G/5G polymorphism may be associated with T2DM and may be considered as a risk factor for development of thrombotic events. It may also help in selection and dosing of patients being treated with anticoagulant and fibrinolytic agents. Further large-scale studies are recommended to assess the possible role of environmental factors and gene interactions in the development of T2DM vascular risks.

Biomarkers for arterial and venous thrombotic disorders

The haemostatic system maintains the blood in a fluid state, but allows rapid clot formation at sites of vascular injury to prevent excessive bleeding. Unbalances within the haemostatic system can lead to thrombosis. Inspite of successful research our understanding of the disease pathogenesis is still incomplete. There is great hope that genetic, genomic, and epigenetic discoveries will enhance the diagnostic capability, and improve the treatment options. During the preceding 20 years, the identification of polymorphisms and the elucidation of their role in arterial and venous thromboses became an important area of research. Today, a large body of data is available regarding associations of single nucleotide polymorphisms (SNPs) in candidate genes with plasma concentrations and e. g. the risk of ischaemic stroke or myocardial infarction. However, the results for individual polymorphisms and genes are often controversial. It is now well established that besides acquired also hereditary risk factors influence the occurrence of thrombotic events, and environmental factors may add to this risk. Currently available statistical methods are only able to identify combined risk genotypes if very large patient collectives (>10,000 cases) are tested, and appropriate algorithms to evaluate the data have yet to be developed. Further research is needed to understand the functional effects of genetic variants in genes of blood coagulation proteins that are critical to the pathogenesis of arterial and venous thrombotic disorders. In this review genetic variants in selected genes of the haemostatic system and their relevance for arterial and venous thrombosis will be discussed.

Impact of the type of SERPINC1 mutation and subtype of antithrombin deficiency on the thrombotic phenotype in hereditary antithrombin deficiency

Mutations in the antithrombin (AT) gene can impair the capacity of AT to bind heparin (AT deficiency type IIHBS), its target proteases such as thrombin (type IIRS), or both (type IIPE). Type II AT deficiencies are almost exclusively caused by missense mutations, whereas type I AT deficiency can originate from missense or null mutations. In a retrospective cohort study, we investigated the impact of the type of mutation and type of AT deficiency on the manifestation of thromboembolic events in 377 patients with hereditary AT deficiencies (133 from our own cohort, 244 reported in the literature). Carriers of missense mutations showed a lower risk of venous thromboembolism (VTE) than those of null mutations (adjusted hazard ratio [HR] 0.39, 95% confidence interval [CI] 0.27-0.58, p<0.001), and the risk of VTE was significantly decreased among patients with type IIHBS AT deficiency compared to patients with other types of AT deficiency (HR 0.23, 95%CI 0.13-0.41, p<0.001). The risk of pulmonary embolism complicating deep-vein thrombosis was lower in all type II AT deficiencies compared to type I AT deficiency (relative risk 0.69, 95%CI 0.56-0.84). By contrast, the risk of arterial thromboembolism tended to be higher in carriers of missense mutations than in those with null mutations (HR 6.08-fold, 95%CI 0.74-49.81, p=0.093) and was 5.9-fold increased (95%CI 1.22-28.62, p=0.028) in type IIHBS versus other types of AT deficiency. Our data indicate that the type of inherited AT defect modulates not only the risk of thromboembolism but also the localisation and encourage further studies to unravel this phenomenon.

Plasminogen activator inhibitor-1 4G/5G gene polymorphism and coronary artery disease in the Chinese Han population: a meta-analysis

Background

The polymorphism of plasminogen activator inhibitor-1 (PAI-1) 4G/5G gene has been indicated to be correlated with coronary artery disease (CAD) susceptibility, but study results are still debatable.

Objective and Methods

The present meta-analysis was performed to investigate the association between PAI-1 4G/5G gene polymorphism and CAD in the Chinese Han population. A total of 879 CAD patients and 628 controls from eight separate studies were involved. The pooled odds ratio (OR) for the distribution of the 4G allele frequency of PAI-1 4G/5G gene and its corresponding 95% confidence interval (CI) was assessed by the random effect model.

Results

The distribution of the 4 G allele frequency was 0.61 for the CAD group and 0.51 for the control group. The association between PAI-1 4G/5G gene polymorphism and CAD in the Chinese Han population was significant under an allelic genetic model (OR = 1.70, 95% CI = 1.18 to 2.44, P = 0.004). The heterogeneity test was also significant (P<0.0001). Meta-regression was performed to explore the heterogeneity source. Among the confounding factors, the heterogeneity could be explained by the publication year (P = 0.017), study region (P = 0.014), control group sample size (P = 0.011), total sample size (P = 0.011), and ratio of the case to the control group sample size (RR) (P = 0.019). In a stratified analysis by the total sample size, significantly increased risk was only detected in subgroup 2 under an allelic genetic model (OR = 1.93, 95% CI = 1.09 to 3.35, P = 0.02).

Conclusions

In the Chinese Han population, PAI-1 4G/5G gene polymorphism was implied to be associated with increased CAD risk. Carriers of the 4G allele of the PAI-1 4G/5G gene might predispose to CAD.

Inherited thrombophilia in childhood arterial stroke: data from Lebanon

Pediatric ischemic stroke still represents a burden, and more than half of the survivors will experience cognitive or motor disabilities. The objective of this study was to investigate the role of thrombophilia in a cohort of children with arterial ischemic stroke. The records of infants and children with clinically and radiologically confirmed stroke were reviewed. Patients with venous or perinatal stroke were not included. Thirty-three patients were diagnosed with arterial ischemic stroke. The male/female ratio was 1.75:1. The median age was 4 years. The most frequent clinical manifestations were hemiparesis (54.5%) and seizures (33.3%). Genetic thrombophilia testing was available on 24 patients. Nine of the 24 patients (37.5%) were heterozygous for factor V Leiden. None of the patients carried the factor II G20210A variant. Ten patients (41.7%) were heterozygous and 3 (12.5%) were homozygous for methylenetetrahydrofolate reductase (MTHFR) C677T variant. Fifteen patients (62.5%) had one or more genetic polymorphism. Factor V Leiden was significantly associated with arterial ischemic stroke (P < 0.001). Stroke recurred in 2 children with multiple risk factors and MTHFR C677T mutation. Factor V Leiden is one of the major genetic risk factors for pediatric arterial ischemic stroke in Lebanon. MTHFR C677T was prevalent among patients with recurrent stroke.

Plasminogen Activator Inhibitor I 4G/5G Polymorphism in Neonatal Respiratory Distress Syndrome

Fibrin monomers inhibit surfactant function. 4G/5G insertion/deletion polymorphism plays an important role in the regulation of plasminogen activator inhibitor 1 (PAI-1) gene expression. To examine the genotype distribution of PAI-1 polymorphism in 60 infants with respiratory distress syndrome (RDS) and 53 controls, an allele-specific polymerase chain reaction (PCR) was used. The proportion of 4G/4G, 4G/5G, and 5G/5G genotypes did not differ statistically between the RDS and control groups (P > .05). Having PAI-1 4G/4G genotype polymorphism appears to increase the risk of RDS (odds ratio [OR] =1.5; 95% confidence interval [CI], 0.5-4.3), although it was not statistically significant. No relation was found between the PAI-1 4G/5G polymorphisms and RDS, but there was an increased risk associated with the 4G variant of the PAI-1 gene. We believe that our findings of increased 4G allele of the PAI-1 gene in infants with RDS would also help to clarify the pathogenesis of RDS.

Mutations and Polymorphisms in Genes Affecting Haemostasis Components in Children with Thromboembolic Events

The distribution of mutations/polymorphisms in genes affecting haemostasis [factor V Leiden (FVL), FV H1298R (FVR(2)), FII 20210A, b-Fib 455G-->A, FXIII V34L, PAI-1 4G, HPA-1b] among 141 children with thrombosis at various sites and 103 controls was compared. Additionally, the carriage of these mutations/polymorphisms was associated with the levels of their corresponding proteins in thrombosed children. Thrombosis was more frequent in boys (p = 0.021). No studied mutation/polymorphism was found to be a risk factor for thrombosis, except for FVL (odds ratio 3.8, 95% CI 1.4-10.6). The risk of thrombosis for FVL carriers was twice as high in children with an idiopathic thrombosis (odds ratio 5.4) than in thrombosed children with an underlying disease or a triggering event (odds ratio 2.7). FVL carriers had an odds ratio of 5.9 (95% CI 1.8-19.6) when FVR(2) was absent. In thrombosed children, the activated protein C resistance ratio was significantly lower in the presence of FVL (p < 0.001). Prothrombin and fibrinogen levels, although higher in FII 20210A and b-Fib 455G-->A carriers, did not reach statistical significance.

Renal vascular sclerosis is associated with inherited thrombophilias

Vascular sclerosis is often seen in renal biopsies. It is usually associated with diabetes mellitus, hypertension, smoking, etc. However, whether inherited thrombophilic states such as factor V gene mutation, prothrombin gene mutation, and methylenetetrahydrofolate reductase (MTHFR) gene mutation are associated with the vascular sclerosis is not known. Renal biopsies that showed vascular disease were grouped into five groups: (1) diabetic patients, (2) hypertensive patients, (3) diabetic and hypertensive patients, (4) smokers, and (5) vascular sclerosis of unknown etiology (idiopathic renal disease). Renal biopsies with no vascular sclerosis were used as controls. Frozen tissue was analyzed for factor V Leiden mutation, prothrombin G20210A mutation, and MTHFR C677T. Factor V Leiden mutation and prothrombin G20210A mutation was not seen in patients with diabetes, hypertension, or smoking, whereas MTHFR C677T polymorphism in these groups was not significant, compared to the controls. In the idiopathic renal disease group, three of the 17 patients (17.6%) had prothrombin G20210A mutation, two of the 17 patients (11.8%) had the factor V Leiden mutation, and five of the 17 (29.4%) were homozygous for the MTHFR C677T polymorphism. When the data were evaluated as a whole, 10 mutations were found in 17 patients (P<0.0005 compared to controls) or eight of the 17 patients (47%) were observed to have at least one of the three forms of inherited thrombophilia (P<0.001 compared to controls). These findings indicate that renal vascular lesions, in the absence of diabetes, hypertension, or smoking appears to be associated with inherited thrombophilias.

Mutations and polymorphisms in genes affecting hemostasis proteins and homocysteine metabolism in children with arterial ischemic stroke

BACKGROUND

The pathogenesis of thrombosis in childhood seems to be multifactorial implicating genetic and environmental factors.

AIM

To compare the distributions of mutations/polymorphisms in genes affecting hemostasis (factor V Leiden - FVL, FV H1298R-FVR2, FII 20210A, b-Fib 455G>A, FXIII V34L, PAI-1 4G, HPA-1b) or homocysteine metabolism (MTHFR C677T, MTHFR A1298C) among 90 children with arterial ischemic stroke (AIS) and 103 controls, and to associate the carriage of these mutations/polymorphisms with their corresponding proteins in children with AIS.

RESULTS

AIS was more frequent in boys (p < 0.01). No studied mutation/polymorphism was found to be a risk factor for AIS, except for FVL [odds ratio 4.2 (95% CI 1.5-12.1)], the presence of which was even higher in 31 children with congenital AIS [odds ratio 6.82 (95% CI 2.0-22.8)]. FVL carriers had an odds ratio of 5.76 (95% CI 1.6-6.4) when FVR2 was absent. In thrombosed children, activated protein C resistance, prothrombin and fibrinogen levels were higher in the presence of FVL, FII20210A or b-Fib 455G-->A, respectively. Double heterozygotes in both MTHFR C677T and A1298T or homozygotes in one had significantly elevated homocysteine levels.

CONCLUSION

Except for FVL, no definite conclusion could be reached regarding the involvement of the studied mutations/polymorphisms in childhood AIS.

Role of thrombogenic factors in the development of atherosclerosis

Hemostatic factors play a crucial role in generating thrombotic plugs at sites of vascular damage (atherothrombosis). However, whether hemostatic factors contribute directly or indirectly to the pathogenesis of atherosclerosis remains uncertain. Autopsy studies have revealed that intimal thickening represents the first stage of atherosclerosis and that lipid-rich plaque arises from such lesions. Several factors contribute to the start of intimal thickening. Platelets release several growth factors and bioactive agents that play a central role in development of not only thrombus but also of intimal thickening. We have been investigating which coagulation factors simultaneously, or subsequently with platelet aggregation, participate in thrombus formation. Tissue factor (TF) is an essential initiator of blood coagulation that is expressed in various stages of atherosclerotic lesions in humans and other animals. Factors including thrombin and fibrin, which are downstream of the coagulation cascade activated by TF, also contribute to atherosclerosis. TF is involved in cell migration, embryogenesis and angiogenesis. Thus TF, in addition to factors downstream of the coagulation cascade and the protease-activated receptor 2 activation system, would be a multifactorial regulator of atherogenesis.

Genes and atherosclerosis: at the origin of the predisposition

Atherosclerosis (ATS) is a multifactorial disease caused by the interaction of established or emerging risk factors with multiple predisposing genes that regulate ATS-related processes. This review will discuss the current knowledge concerning the potential role of the genetic variations that could promote and/or accelerate ATS, in both animal models and humans. Allelic polymorphisms or variations of distinct genes that enhance the risk of ATS frequently occur in the general population, but only adequate gene-environment interactions will lead to the disease. The main genes so far studied are involved in the regulation of processes such as endothelial function, antioxidant potential, coagulation, inflammatory response, and lipid, protein and carbohydrate metabolism. The detection of candidate genes associated with ATS could allow, in the near future, earlier interventions in genetically susceptible individuals. Further, large-scale population studies are needed to obtain more information on the specific gene-environment and drug-gene interactions capable of influencing ATS progression.

Genetics, genomics and proteomics in atherosclerosis research

Atherosclerosis and its clinical manifestations are the leading cause of death in Western countries. Atherosclerosis is a multifactorial disease characterized by endothelial dysfunction, smooth muscle cell (SMC) proliferation and migration, inflammation, lipid and matrix accumulation and thrombus formation. Multiple genetic and environmental features and interactions between these factors influence the disease process. To understand fundamental pathobiological mechanisms in atherogenesis and to develop and target new therapies, information on genetic factors (atherogenetics), gene expression patterns (atherogenomics) and protein expression patterns (atheroproteomics) are needed. This review will summarize current knowledge in these areas of atherosclerosis research with a special emphasis on microarray technology.

Trombosis arterial y polimorfismos genéticos: demasiados actores, escenario complejo

Arterial thrombosis results from complex gene-gene and gene-environment interactions. While Vichow's triad was traditionally referred to venous thrombosis, the same process has been applied to arterial thrombosis: abnormalities of hemorrheology, abnormal blood constituents and abnormal vessel wall/endothelial dysfunction. Research carried out in the past decade has identified several polymorphisms in genes related to coagulation and fibrinolytic factors, platelet receptors, endothelial dysfunction, homocysteine metabolism, endothelial nitric oxide synthase, abnormal blood flow and oxidative stress. Whereas the individual contribution of each polymorphism to the overall cardiovascular risk seems to be modest, multiple gene-gene and gene-environment interactions appear more relevant in the pathogenesis of arterial thrombosis.

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

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

Homozygosity of the T allele of the 46 C->T polymorphism in the F12 gene is a risk factor for ischemic stroke in the Spanish population

BACKGROUND AND PURPOSE

Ischemic stroke (IS) is a complex disease that involves genetic and environmental factors. In a family-based study (the Genetic Analysis of Idiopathic Thrombophilia [GAIT] Project) that included a genome-wide scan, we demonstrated that a common polymorphism (46 C-->T) in the exon 1 of the F12 gene jointly influences variability of plasma Factor XII levels and susceptibility to thrombotic disease. We have investigated the risk of IS related to this polymorphism in a case-control study.

METHODS

We studied 436 individuals: 205 diagnosed with IS and 231 age-gender-ethnic control subjects. We measured Factor VIIIc, fibrinogen, and Factor XIIc levels, and we genotyped the 46 C-->T polymorphism in the F12 gene.

RESULTS

There were 91 women and 114 men in the IS group and 109 women and 122 men in the control group. We confirmed our previous observation that individuals with different genotypes for the 46 C-->T polymorphism showed significant differences in Factor XIIc levels. Most importantly, the mutated T allele in the homozygous state (genotype T/T) was associated with an increased risk of IS with an adjusted odds ratio of 4.1 (95% CI, 1.1 to 15.9).

CONCLUSIONS

This study suggests that the 46 C-->T polymorphism is a genetic risk factor for IS in the Spanish population. In addition, our results confirm that the use of genetic linkage studies along with a case-control association study is an extremely valuable approach for identifying DNA variants that affect complex diseases.

Recurrent Pregnancy Loss and Its Relation to FV Leiden, FII G20210A and Polymorphisms of Plasminogen Activator and Plasminogen Activator Inhibitor

Thrombophilic disorders and hypofibrinolysis were demonstrated to be risk factors in a majority of women with recurrent pregnancy loss (RPL) and infertility. We investigated the association of FV G1691A mutation, F II G20210A gene polymorphism (PM), 4G/5G PAI-1 and Alu I/D tPA PM in 32 women with infertility and 49 women with at least 2 unexplained early abortions. FV Leiden mutation was significantly more common in women with RPL (10%, p = 0.02) and infertility (19%, p = 0.0005) compared with controls (2%). PAI-1 4G PM and t-PA Alu I PM, alone or in combination, were not associated with RPL or infertility. 9/49 women with RPL showed coagulation disorders with heterozygous FV Leiden mutation (5), FXII (1), protein C (1) or protein S (2) deficiency. However, due to the small number of patients studied, no definite conclusion can be drawn.

Predictive value of noninvasive measures of atherosclerosis for incident myocardial infarction: the Rotterdam Study

BACKGROUND

Several noninvasive methods are available to investigate the severity of extracoronary atherosclerotic disease. No population-based study has yet examined whether differences exist between these measures with regard to their predictive value for myocardial infarction (MI) or whether a given measure of atherosclerosis has predictive value independently of the other measures.

METHODS AND RESULTS

At the baseline (1990-1993) examination of the Rotterdam Study, a population-based cohort study among subjects age > or =55 years, carotid plaques and intima-media thickness (IMT) were measured by ultrasound, abdominal aortic atherosclerosis by x-ray, and lower-extremity atherosclerosis by computation of the ankle-arm index. In the present study, 6389 subjects were included; 258 cases of incident MI occurred before January 1, 2000. All 4 measures of atherosclerosis were good predictors of MI independently of traditional cardiovascular risk factors. Hazard ratios were equally high for carotid plaques (1.83 [1.27 to 2.62], severe versus no atherosclerosis), carotid IMT (1.95 [1.19 to 3.19]), and aortic atherosclerosis (1.94 [1.30 to 2.90]) and slightly lower for lower-extremity atherosclerosis (1.59 [1.05 to 2.39]), although differences were small. The hazard ratio for MI for subjects with severe atherosclerosis according to a composite atherosclerosis score was 2.77 (1.70 to 4.52) compared with subjects with no atherosclerosis. The predictive value of MI for a given measure of atherosclerosis was independent of the other atherosclerosis measures.

CONCLUSIONS

Noninvasive measures of extracoronary atherosclerosis are strong predictors of MI. The relatively crude measures directly assessing plaques in the carotid artery and abdominal aorta predict MI equally well as the more precisely measured carotid IMT.

Risk-factor profile in severe, generalized, obliterating vascular disease

A 74-year-old woman had a history over 25 years of endarterectomy of both renal arteries, iliac venous thrombosis, pulmonary embolism, left internal carotid artery endarterectomy, coronary angioplasty, aortocoronary bypass grafting, occlusion of the right axillary artery, lower-limb claudication due to common iliac artery aneurysm, external iliac artery stenosis, multiple femoral artery stenoses, bifurcational stent grafting, occlusion of the left brachial artery and the right external iliac artery, and stroke. Assessment of the risk-factor profile revealed an absence of classic risk factors but the presence of the factor V Leiden mutation, the methylenetetrahydrofolate reductase AI298C mutation, the HFE C282Y mutation, plasminogen activator inhibitor-1 gene mutation, the -455 G/A fibrinogen gene polymorphism, the epsilon3/epsilon4 apolipoprotein E -675 4G gene polymorphism, and hyperhomocysteinemia. This case shows that severe, generalized, occlusive vascular disease may be due to the combination of various genetic risk factors for atherosclerosis and venous thromboembolism.

Common gene polymorphisms and nutrition: emerging links with pathogenesis of multifactorial chronic diseases (review)

Rapid progress in human genome decoding has accelerated search for the role of gene polymorphisms in the pathogenesis of complex multifactorial diseases. This review summarizes the results of recent studies on the associations of common gene variants with multifactorial chronic conditions strongly affected by nutritional factors. Three main individual sections discuss genes related to energy homeostasis regulation and obesity, cardiovascular disease (CVD), and cancer. It is evident that several major chronic diseases are closely related (often through obesity) to deregulation of energy homeostasis. Multiple polymorphic genes encoding central and peripheral determinants of energy intake and expenditure have been revealed over the past decade. Food intake control may be affected by polymorphisms in the genes encoding taste receptors and a number of peripheral signaling peptides such as insulin, leptin, ghrelin, cholecystokinin, and corresponding receptors. Polymorphic central regulators of energy intake include hypothalamic neuropeptide Y, agouti-related protein, melanocortin pathway factors, CART (cocaine- and amphetamine-regulated transcript), some other neuropeptides, and receptors for these molecules. Potentially important polymorphisms in the genes encoding energy expenditure modulators (alpha- and beta- adrenoceptors, uncoupling proteins, and regulators of adipocyte growth and differentiation) are also discussed. CVD-related gene polymorphisms comprising those involved in the pathogenesis of atherosclerosis, blood pressure regulation, hemostasis control, and homocysteine metabolism are considered in a separate section with emphasis on multiple polymorphisms affecting lipid transport and metabolism and their interactions with diet. Cancer-associated polymorphisms are discussed for groups of genes encoding enzymes of xenobiotic metabolism, DNA repair enzymes, factors involved in the cell cycle control, hormonal regulation-associated proteins, enzymes related to DNA methylation through folate metabolism, and angiogenesis-related factors. There is an apparent progress in the field with hundreds of new gene polymorphisms discovered and characterized, however firm evidence consistently linking them with pathogenesis of complex chronic diseases is still limited. Ways of improving the efficiency of candidate gene approach-based studies are discussed in a short separate section. Successful unraveling of interaction between dietary factors, polymorphisms, and pathogenesis of several multifactorial diseases is exemplified by studies of folate metabolism in relation to CVD and cancer. It appears that several new directions emerge as targets of research on the role of genetic variation in relation to diet and complex chronic diseases. Regulation of energy homeostasis is a fundamental problem insufficiently investigated in this context so far. Impacts of genetic variation on systems controlling angiogenesis, inflammatory reactions, and cell growth and differentiation (comprising regulation of the cell cycle, DNA repair, and DNA methylation) are also largely unknown and need thorough analysis. These goals can be achieved by complex simultaneous analysis of multiple polymorphic genes controlling carefully defined and selected elements of relevant metabolic and regulatory pathways in meticulously designed large-scale studies.

The genetics of atherothrombotic disorders: a clinician's view

The development of coronary artery disease is dependent on the interaction of multiple biochemical pathways that lead to the development of plaque in the arterial wall and ultimately plaque instability, plaque rupture and thrombosis. The latter stages lead to vascular obstruction, tissue death and the final phenotype of myocardial infarction. Hemostasis gene association studies of atherothrombotic disorders have been unrewarding, with largely underpowered studies reporting inconsistent results. Clinical studies such as the Multiple Risk Factor Intervention Trial clearly indicate that clustering of classical risk increases the likelihood of myocardial infarction, and the addition of diabetes mellitus to the risk profile exponentially increases the risk of a vascular event. The development of insulin resistance is considered to be a pivotal event in vascular risk with associated clustering of dysglycemia, hyperinsulinemia, systolic hypertension, raised triglyceride and low high-density lipoprotein cholesterol. Additionally, elevated levels of plasminogen activator inhibitor-1, factor (F)VII, FXII, fibrinogen and tissue plasminogen activator occur with insulin resistance to create an atherothrombotic risk cluster. Heritability studies of insulin resistance and the vascular risk profile demonstrate genetic pleitropy between diabetes and vascular risk, which indicate that common genes have an important role. Increasingly, it is felt that inflammation underpins both diabetes and cardiovascular disease and that the expression of the final phenotype(s) may depend on complex gene-environment interactions with regulatory genes, including those for nuclear transcription factors and RNA-binding proteins. The complexity of coronary artery disease and the risk factor interactions make it unlikely that genetic epidemiology will identify genes involved in these processes without a better understanding of environmental influences.

Association studies between -1185A/G von Willebrand factor gene polymorphism and coronary artery disease

High levels of von Willebrand factor (vWF) have been associated with cardiovascular disease. The A allele of the -1185A/G polymorphism in the 5'-regulatory region of the vWF gene was associated with the highest plasma vWF levels in a normal population. To examine the association between -1185A/G polymorphism and coronary artery disease (CAD), 173 Brazilian Caucasian subjects submitted to coronary angiography were studied. Of these, 57 (33%) had normal coronary arteries (control group) and 116 (67%) had CAD (patient group). Plasma vWF levels were higher in patients (145 U/dl) than in controls (130 U/dl), but the differences were significant only for O blood group subjects. Polymerase chain reaction amplification of the 864-bp vWF promoter region followed by AccII restriction digestion was used to identify the -1185A/G genotypes. The -1185A allele frequency was 43.1% in patients and 44.7% in controls. Allele and genotype frequencies were not significantly different between patients and controls. No association was observed between the -1185A/G genotypes and plasma vWF levels in patients or controls. These results suggest that -1185A/G polymorphism is not an independent risk factor for CAD.

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.

Association of C807T, PlA, and −5 C/T Kozak genotypes with density of glycoprotein receptors on platelet surface

This study investigates whether three platelet glycoprotein (GP) polymorphisms, C807T in GP Ia, Pl(A1/A2) in GP IIIa, and -5 T/C Kozak in GP Ibalpha gene, influence the density of the three important adhesion and activation receptors on the platelet surface. Fifty-four healthy donors were genotyped according to the three polymorphisms, and densities of the corresponding GPs were measured by flow cytometry. Our study confirmed the association between C807T polymorphism and platelet surface expression of GP Ia-IIa and GP Ia and demonstrated that the density of GP Ibalpha or GP IX is not associated with the Kozak polymorphism. Although the Pl(A1/A2) polymorphism did not affect the expression of GP IIb-IIIa and GP IIIa on the platelet surface, flow-cytometric analysis employing murine monoclonal antibody SZ21 against GP IIIa can be applied to distinguish Pl(A1/A1) and Pl(A1/A2) polymorphism.