Journal of Human Hypertension (2000) 14, 369–372 2000 Macmillan Publishers Ltd All rights reserved 0950-9240/00 $15.00 www.nature.com/jhh
REVIEW ARTICLE
Genes, coagulation and cardiovascular risk MB Donati, F Zito, A Di Castelnuovo and L Iacoviello ‘Angela Valenti’ Laboratory of Genetic and Environmental Risk Factors for Thrombotic Disease, Department of Vascular Medicine and Pharmacology, Istituto di Ricerche Farmacologiche Mario Negri, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
Coronary artery disease (CAD) is a multifactorial disease influenced by both genetic and environmental determinants. Coagulation activation plays a key role in thrombus formation and variation in its factors has been associated with the risk of CAD. The levels of these factors are genetically determined and polymorphisms in their genes can also be responsible for disease development. Three polymorphic alleles of coagulation factor VII (FVII) gene have been associated with a protective effect on the risk of familial myocardial infarction. Their distribution in Europe covaries across populations with the rate of myocardial infarction mortality, being higher in countries (like Italy, Spain, Greece) at low risk. These
polymorphisms are major determinants of FVII variability in humans. They can also determine the response of FVII to environmental stimuli. Indeed, they modulate the association between triglycerides or smoking and FVII, while a gender-dependent regulation of FVII, probably related to sexual hormones, has also been described. Interestingly, lowering the plasma levels of FVII with low dose warfarin to the same low normal range as that associated with the ‘protective’ genotypes, results in protection against ischaemic heart disease, reducing mortality in high risk men. Journal of Human Hypertension (2000) 14, 369–372
Keywords: coronary artery disease, genetic polymorphisms; factor VII; thrombosis
Introduction Coronary artery disease is mainly responsible for mortality and morbidity in Europe. In Italy, approximately every 10 min a new case of myocardial infarction is recorded, and one out of three of these cases will die from myocardial infarction. Atherosclerosis is the major cause of coronary artery disease, however, it can be considered as a benign disease in the absence of thrombosis. A thrombus growing chronically or acutely on an atherosclerotic lesion is, indeed, the pathogenetic mechanism of coronary occlusion. Since the coagulation system plays a pivotal role in thrombus formation, changes in these factors are particularly relevant to the development of ischaemic cardiovascular diseases. The coagulation process is a ‘cascade’ of events that leads, through amplification of enzymatic reactions, to the formation of thrombin (Figure 1). The ‘cascade’ is started from the prompt binding of circulating factor VII to tissue factor locally produced by damaged endothelial cells and/or infiltrating macrophages, ie, at the level of an atheromatous plaque. The complex factor VII-tissue factor activates factor X in factor Xa, that continues the cascade in the presence of factor V, by activating
Correspondence: Dr Licia Iacoviello, ‘Angela Valenti’ Laboratory of Genetic and Environmental Risk Factors for Thrombotic Disease, Department of Vascular Medicine and Pharmacology, Consorzio Mario Negri Sud, 66030 Santa Maria Imbaro, Italy. E-mail:
[email protected]
Figure 1 Schematic representation for the activation of blood coagulation in vivo.
prothrombin into thrombin, the specific enzyme that converts fibrinogen into insoluble fibrin.
Genetic determinants of clotting factors In the last decade, several epidemiological studies have shown that changes in the blood levels of coagulation factors are associated with the risk of cardiovascular disease.1–3 The aggregation of acute myocardial infarction (AMI) in families and the observation that the blood levels of parameters considered as risk factors for AMI are genetically
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determined, generated the hypothesis that the susceptibility to atherothrombotic disease could also be determined by genetic factors.4,5 Recently, it has been shown that the levels of factors related to cardiovascular disease can be genetically determined.6 In particular, common variations (or polymorphisms) in the genes coding for coagulation/ fibrinolysis factors can contribute to their variability in blood within their normal range of distribution.7,8 Since the levels of some haemostatic factors have been associated to the risk of myocardial infarction, polymorphisms in genes related to them could also contribute to the risk of the disease. Moreover, it appears more and more evident that the genetic background for a specific locus, besides a direct association with the risk of the disease, should modulate, by amplification or reduction, the effect of environmental factors or dysmetabolic disorders on the risk of cardiovascular disease.
R353Q polymorphism, the −323 0/10 bp promoter has also been demonstrated to be functionally relevant; the rare insertion allele 10/bp, indeed, reduced the promoter activity, as compared to the common allele, in transfection experiments.17 Therefore, it is conceivable that the promoter polymorphism, due to its functionality and strong linkage disequilibrium with the R353Q polymorphism, could also contribute to the effect of FVII genotype on the risk of MI, or even be the main determinant of the effect. In fact, gene–gene interactions could be of fundamental importance in the regulation of FVII levels; recently, in a study on a normal Italian population we found that the effect of the rare 10/bp alleles in lowering FVII levels was significatively stronger in the presence of the H7 allele of the HVR4 polymorphism.14 Needless to say, it is nearly impossible to establish in epidemiological studies, the relative importance of different polymorphisms in regulating clinical phenotypes.
Modulation of coagulation factor VII: gene/gene and gene/environment interactions
Factor VII polymorphisms and the risk of myocardial infarction
Blood levels of coagulation factor VII (FVII) are genetically determined. Three common polymorphisms (R353Q in exon 8, HVR4 in intron 7 and −323 0/10 bp in position −323 of the promoter region) in factor VII gene have been described and reported to be associated with either coagulant factor VII, activated factor VII or mass factor VII levels.9,10 Factor VII polymorphisms may also influence the association of plasma F VII with trygliceride levels;11 a positive relationship between F VII and triglyceride levels is present in carriers of the R allele-variants but not of the Q allele-variants. These findings suggest that subjects carrying the Q allele-variant of F VII are protected from the activation of F VII in response to dietary fat intake. Indeed, the absolute and the percentual increase in F VII activation after a fat-rich meal is higher in subjects with the RR genotype than in carriers of the Q allele.12 A gender-dependent genetic regulation of F VII, probably related to sexual hormones, is also supported by the observation that the postmenopausal increase in F VII:c was present only in women homozygous for the R allele, and not in those carrying the Q allele.13 Furthermore, the effect of HVR4 and −323 0/10 bp polymorphic loci are genderdependent showing an effect in males but not in females.14 One of the mechanisms which could explain the effect of dietary fat on F VII involves the interaction with triglyceride-rich lipoproteins (VLDL). Indeed, it has been described that the binding of F VII to VLDL can prolong its half-life and enhances the process of F VII activation.15 The amino acid substitution Arg/Gln may alter this interaction and determines a decreased activation of F VII. However, a direct effect of this polymorphism on F VII antigen levels could also be proposed as a working hypothesis; recently, in transient transfection assays with F VII cDNA containing the base substitution, it has been shown that the Q allele determined a defective secretion of the molecule from the cells.16 Beside the
Studies conducted in Italy in the framework of the GISSI (Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto) collaboration18 have highlighted the relationship between genetic polymorphisms and the risk of MI. In a case-control study on patients with a family history of thrombosis, it has been shown that the alleles Q and H7 of R353Q and HVR4 polymorphisms of factor VII gene had a protective effect on the risk of MI and were associated with relatively low levels of factor VII.19 The presence of one of these alleles reduced by about 50% the risk of myocardial infarction; moreover, the risk was reduced four and 11 times, respectively, in subjects homozygous for the H7 and the Q allele, and more than 16 times in double homozygotes. The effect of the two alleles was independent and was possibly mediated by their effect on F VII activity levels (Table 1). The effect of the ‘protective’ allele Q was particularly evident in smokers.20 Indeed, the risk of MI induced by smoking, although still significant, was much less so in subjects carrying the Q353 allele (Figure 2). However, despite the presence of a ‘natural protection’, smoking still doubled the risk of MI even in Q353 carriers. Like air-bags in a car, ‘protective’ factors appear not to be necessary if driving style is safe and no accident occurs. Air-bags show their life-saving effect, however, in the case of hazardous driving leading to a crash, but carrying air-bags should not prevent people from driving carefully. The frequency of the ‘protective’ alleles of factor. VII gene in the general Italian population was 21.4% and 35.6%, respectively, for R353Q and HVR4 polymorphisms. In both cases, it was significantly higher than that found in northern Europe populations, such as in The Netherlands, Denmark and the United Kingdom, in agreement with the higher rate of MI mortality in such countries as compared to the south European populations.8,10 Taken together with other protective factors present in southern Europe, such as components of
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Table 1 Frequency of HVR4 and R353Q polymorphisms of coagulation factor VII in the Italian population and their association with the risk of myocardial infarction Polymorphism
Allele/genotype
Frequency
HVR4 R353Q HVR4 R353Q HVR4/R353Q
H7 Q H7H7 QQ H7H7/QQ
35.6 21.4 13.8 4.5 3.1
Odds ratio (95% CI) 0.52 0.58 0.22 0.08 0.06
(0.33–0.81) (0.33–1.0) (0.08–0.63) (0.01–0.91) (0.01–0.08)
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(Reduction) (50%) (50%) (4 times) (11 times) (16 times)
be found in about one out of three to five Italian subjects through genetically determined lower factor VII levels; in those subjects not carrying the protective genotypes, but having other known risk factors, lower factor VII levels might be achieved by lowdose warfarin. Would this old anticoagulant drug offer an effective prevention against MI and possibly other vascular ischaemic disease, in the absence of an increased haemorragic risk?22
Perspectives towards a pharmacogenetic approach
Figure 2 Odds ratios (and 95% Confidence Interval) for familial myocardial infarction according to smoking habits and R/Q353 coagulation factor VII polymorphism. Never smoked carrying the RR353 genotype is the reference group (modified from Thromb Haemost 1999; 81: 658).20
the mediterranean diet, these findings can help explaining the North–South gradient in MI mortality in Europe, and support the protective role of these polymorphisms in the development of the disease. The patients with MI included in the case-control study, have been selected from the GISSI-2 study population on the basis of their family history of thrombosis, ie, the presence of at least one firstdegree relative with MI and/or stroke before the age of 65 years.5,21 The patients were selected in 52 Coronary Care Units, distributed in 15 regions, all over Italy, in specialised centres as well as in general hospitals, in larger as well as in smaller cities, so that the population collected was really representative of our country and the results obtained reasonably applicable to all the Italians. The possibility to have access to a large database of patients with MI allowed the selection of a very homogeneous group of patients over 45 years and with a family history of thrombosis. The latter condition was selected because genetic variants related to the development of thrombosis should be found more frequently in these patients than in patients or controls without a family history. These findings add further evidence for the involvement of factor VII in the pathogenesis of MI and offer new tools for innovative or more selective strategies in the prevention and therapy of cardiovascular disease. Protection from the risk of MI may
An answer to this interesting question has been provided only few weeks after the publication of the factor VII polymorphism study. The Thrombosis Prevention Trial,23 conducted in the UK, by the Medical Research Council’s General Practice Research Framework, has reported that low-intensity oral anticoagulant therapy (average 4.1 mg warfarin daily) confers protection against ischaemic heart disease, reducing mortality in high-risk men. Low-dose aspirin was also effective, but only in nonfatal events, suggesting that the two treatments protected different high-risk subjects. The plasma levels of factor VII obtained with low dose warfarin were in the same low-normal range (60–80%) as those associated with the ‘protective’ genotypes. Therefore, the identification of subjects carrying the ‘protective’ factor VII genotypes could help identifying subgroups of subjects who might differentially benefit from different treatments. Therefore, it is conceivable that in the planning of future primary or secondary prevention trials, genotyping of the subjects may contribute to treat with higher efficacy a relatively smaller population of subjects. Genotyping a large number of people is still quite expensive, although it is technically easy and provides results which are not subjected, as in biochemical tests, to the day-to-day variability or to environmental modulation. The cost-effectiveness of genotyping could be weighed against the possibility of markedly reducing the size of future trials.
Acknowledgements This work was supported in part by the Italian National Research Council (CNR, Rome, Italy). Progetto Strategico ‘Myocardial Infarction’ ctr. n. 970054674. Francesco Zito is the recipient of a Mario Negri Institute ‘Alumni Association’ fellowship. Augusto Di Castelnuovo is the recipient of a fellowship from the Centro di Formazione e Studi Journal of Human Hypertension
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per il Mezzogiorno (FORMEZ, Progetto Speciale ‘Ricerca Scientifica Applicata nel Mezzogiorno’).
12
References 13 1 Meade TW et al. Haemostatic function and ischaemic heart disease: principal results of the Northwick Park Heart Study. Lancet 1986; 2: 533–537. 2 Meade TW et al. Fibrinolytic activity, clotting factors, and long-term incidence of ischaemic heart disease in the Northwick Park Heart Study. Lancet 1993; 342: 1076–1079. 3 Cortellaro M et al. The PLAT study: hemostatic function in relation to atherothrombotic ischemic events in vascular disease patients. Principal results. Arterioscler Thromb 1992; 12: 1063–1070. 4 Brenn T, Njolstad I. Coronary heart disease risk factors in subjects whose brothers, sisters or husbands developed premature myocardial infarction during 12 years of follow-up. The Finnmark Study (1977–1989). Cardiovasc Risk 1998; 5: 325–330. 5 Roncaglioni MC et al. Role of family history in patients with myocardial infarction: an Italian case-control study. Circulation 1992; 85: 2065–2072. 6 Sing CF, Moll PP. Genetics of variability of CHD risk. Int J Epidemiol 1989; 18 (Suppl 1): S183–S195. 7 Humphries SE. The genetic contribution to the risk of thrombosis and cardiovascular disease. Trends Cardiovasc Med 1994; 4: 8–17. 8 Iacoviello L et al. Contribution of factor VII, fibrinogen and fibrinolytic components to the risk of ischaemic cardiovascular disease: their genetic determinants. Fibrinolysis & Proteolysis 1998; 12: 259–276. 9 Green F et al. A common genetic polymorphism associated with lower coagulation factor VII levels in healthy individuals. Arterioscler Thromb 1991; 11: 540– 546. 10 Bernardi F et al. Contribution of factor VII genotype to activated FVII levels. Differences in genotype frequencies between Northern and Southern European populations. Arterioscler Thromb Vasc Biol 1997; 17: 2548–2553. 11 Humphries SE et al. Factor VII coagulant activity and antigen levels in healthy men are determined by interaction between factor VII genotype and plasma trigly-
Journal of Human Hypertension
14
15
16
17 18 19 20
21
22 23
ceride concentration. Arterioscler Thromb 1994; 14: 193–198. Silveira A et al. Elevated levels of factor VII activity in the postprandial state: effect of the factor VII ArgGln polymorphism. Thromb Haemost 1994; 72: 734 – 739. Meilahn E et al. Genetic determination of coagulation factor VIIc levels among healthy middle-aged women. Thromb Haemost 1995; 73: 623–625. Di Castelnuovo A et al. Genetic modulation of coagulation factor VII plasma levels: contribution of different polymorphisms and gender-related effects. Thromb Haemost 1998; 80: 592–597. Carvalho de Sousa J et al. Coagulation factor VII and plasma tryglicerides. Decreased catabolism as a possible mechanism of factor VII hyperactivity. Haemostasis 1989; 19: 125–130. Hunault M et al. The Arg353Gln polymorphism reduces the level of coagulation factor VII. In vivo and in vitro studies. Arterioscl Throm Vasc Biol 1997; 17: 2825–2829. Pollak ESI et al. Functional characterization of the human factor VII 5⬘-flanking region. J Biol Chem 1996; 271: 1738–1747. Rovelli F, Tognoni G. The health service as a laboratory. Lancet 1996; 348: 169–170. Iacoviello L et al. Polymorphisms in the coagulation factor VII gene and the risk of myocardial infarction. N Engl J Med 1998; 338: 79–85. Iacoviello L, Di Castlenuovo A, D’Orazio A, Donati MB. Cigarette smoking doubles the risk of myocardial infarction in carriers of a protective polymorphism in blood coagulation factor VII gene. Thromb Haemost 1999; 81: 658. Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto Miocardico. GISSI-2: A factorial randomised trial of alteplase versus streptokinase and heparin versus no heparin among 12,490 patients with acute myocardial infarction. Lancet 1990; 336: 65–71. Iacoviello L, Donati MB. Interpretation of Thrombosis Prevention Trial. Lancet 1998; 351: 1205. The Medical Research Council’s General Practice Research Framework. Thrombosis prevention trial: randomised trial of low-intensity oral anticoagulation with warfarin and low-dose aspirin in the primary prevention of ischaemic heart disease in men at increased risk. Lancet 1998; 351: 233–241.
