Fibrinogen b-455 GA and prothrombin 20210 GA [601188]

Fibrinogen b-455 G/A and prothrombin 20210 G/A
polymorphisms and coronary heart disease:an Egyptian case–control study
Olfat Shakera, Salwa Fayeza, Waheba Zaroukband Mohamed Shehatac
Objective Coronary heart disease (CHD) is a complex
disease with both environmental and genetic determinants.The aim of this study was to assess the presence offibrinogen b-chain (FGB)-455 G/A and prothrombin (PT)
20210 G/A polymorphisms in CHD Egyptian patients andto correlate the co-existence of both polymorphisms withthe clinical and laboratory data of the patients.Methods Thirty adult patients with angiographically
documented CHD from the National Heart Institute,scheduled for elective coronary artery bypass graft surgery,were included in this study and compared with 30 age-matched and sex-matched healthy individuals. DNA wasextracted from the peripheral blood and identification ofFGB-455 and PT 20210 genotypes was carried out.Results The fibrinogen-455 locus showed three
polymorphisms (GG, GA, and AA), whereas the PT 20210locus showed two polymorphisms (GG and GA). Thegenotype distribution and frequency of the mutated allelesin both polymorphisms showed no significant differencebetween patient and control groups ( P> 0.05).Conclusion Accordingly, none of the polymorphisms
can be considered as a risk factor for CHD in thestudied Egyptian patients, and the co-existence ofFGB-455 G/A and PT 20210 G/A cannot be implicated inthe occurrence of CHD and, moreover, was not reportedin the studied Egyptian participants. Med Res J
10:102–109
/C13c2011 Medical Research Journal.
Medical Research Journal 2011, 10:102–109
Keywords: coronary heart disease, fibrinogen-455 G/A, genetic poly-morphism and myocardial infarction, prothrombin 20210 G/A, thrombosis
aDepartment of Biochemistry and Molecular Biology, Faculty of Medicine,
Cairo University,bDepartment of Molecular Genetics and Enzymology,
National Research Center of Egypt andcDepartment of Coronary Care Unit,
National Heart Institute, Cairo, EgyptCorrespondence to Mohamed Shehata, Department of Coronary Care Unit,National Heart Institute, 16624 Cairo, EgyptTel: + 20117255329; fax: + 202 3479893;e-mail: [anonimizat] 7 July 2011 accepted 23 September 2011
Coronary heart disease (CHD) is a complex disease withboth environmental and genetic determinants. Each year,CHD kills more Americans than cancer [1,2]. Many riskfactors are involved, such as hypertension, hypercholes-terolemia, diabetes mellitus, obesity, unhealthy diet,protein C deficiency, protein S deficiency, antithrombinIII deficiency, elevated clotting factors VIII, IX, XI, andelevated fibrinogen. In addition, a positive family historyis a strong independent risk factor for CHD [3].The development of CHD and myocardial infarction (MI)involves hyperplasia of arterial smooth muscles, thepresence of fatty streaks, atheroma formation, plaquerupture, thrombus formation, and vessel occlusion. Thepresence of a first-degree relative with MI was found tobe associated with a seven-fold increased risk for MI [4].A l s o ,i tw a sf o u n dt h a ta m o n gt h eu n d e r l y i n gc a u s e so fCHD, the blood coagulation system is thought todetermine the onset of MI through its role in blood clotformation [5]. The coagulation cascade is a series ofreactions, in which a zymogen (inactive enzyme precursor)and its glycoprotein cofactor are activated to become activecomponents that then catalyze the next reaction inthe cascade, ultimately resulting in the cross-linked fibrin.A very important step in thrombus formation is prothrom-bin’s (PT) conversion to thrombin, which converts fibrino-gen to fibrin [6].Fibrinogen is a protein that is composed of a,b, and g
polypeptide chains and plays a key role in bloodclotting [7]. Patients with CHD tended to have higherfibrinogen levels than those without the disease [8]. Thepercent mortality rate increased by over seven-fold inthose with the highest fibrinogen levels, compared withthose with the lowest levels [1]. The three polypeptidechains of fibrinogen ( a,b, and gchains) are encoded
by three different genes clustered on chromosome 4 inregion q28. In-vitro studies have suggested that b-chain
synthesis limits the rate of production of maturefibrinogen. Thus, most studies focus on the associationof polymorphisms in the fibrinogen b-chain (FGB) gene
with MI. The FGB-455 G/A promoter polymorphism wasfound to be associated with increased plasma fibrinogenlevels, but the role of the FGB polymorphisms as a riskfactor of MI has been debated [9].Another component of the coagulation cascade is PT(factor II), which is a blood-clotting protein neededto form fibrin. A common point mutation in the3
0-untranslated region of the PT gene (20210 G/A) has
been reported to be associated with elevated plasma PTlevels, making the blood more likely to clot and increasingthe risk for venous thrombosis by three to five folds.Thus, attention has been paid to investigate whetherthere is a relationship between this mutation and CHDand MI [10].The aim of this study was to assess the frequencies ofFGB-455 G/A and PT 20210 G/A polymorphisms in CHDEgyptian patients.102 Original article
2090-6242 /C13c2011 Medical Research Journal DOI: 10.1097/01.MJX.0000407612.30230.96
Copyright © Medical Research Journal. Unauthorized reproduction of this article is prohibited.

Methods
Thirty adult patients with age ranging between 41 and 70years and angiographically documented CHD, scheduledfor elective coronary artery bypass graft surgery, wereincluded in this study. Patients were included irrespec-tive of concomitant risk factors for atherosclerosis such ashypertension, diabetes mellitus, and cigarette smoking.These patients were compared with 30 age-matched andsex-matched, healthy individuals without any clinicaldisorders selected from the general population. Coronaryangiography was not performed for these individuals andtherefore, the presence of atherosclerotic coronariescannot be excluded. Informed consents were obtainedfrom all the patients and healthy participants according tothe guidelines of our ethics committee.
Analysis of polymorphisms
The assay for the identification of FGB-455 and PT20210 genotypes was based on PCR and reverse-hybridization using CVD StripAssay kit (ViennaLabLabordiagnostika GmbH, Vienna, Austria) [11–13]. Theprocedure included three steps as follows: (a) DNAisolation, (b) PCR amplification using biotinylatedprimers, and (c) hybridization of amplification productsto a test strip containing allele-specific oligonucleotideprobes immobilized as an array of parallel lines. Thebound biotinylated sequences were detected usingstreptavidin–alkaline phosphatase and color substrates.
Statistical analysis
The statistical analysis of the results was performed usingthe program of Statistical Package for Social Scienceversion 11 (Berkeley, California, USA); the analysis wasperformed using arithmetic mean, SD, Student t-test,
w
2-test, and odds ratio (OR). *P-values less than or equal
to 0.05 were considered significant, whereas P-values
more than 0.05 were considered nonsignificant [14].
Results
The patients included eight women (26.67%) and 22men (73.33%), with a mean age of 57.5 (± 6.80) years,and a range from 41 to 70 years. The 30 control personsincluded six women (20%) and 24 men (80%), with amean age of 54.93 (± 5.73) years and a range from 45years to 68 years. There was no significant differencebetween patients and control individuals with regard tothe age and sex distribution (Table 1).Family history of angina and/or MI was irrelevant in bothpatient and control groups, and hence, comment on it wasexcluded. All patients and control participants weresmokers, and hence, comment on smoking was excluded.The medical problems in the patient group, obtained byhistory, clinical examinations, ECG, and echocardiogram,are shown in Table 2.
The mean value of serum cholesterol
It was significantly higher ( P< 0.05) in the patient group
compared with the control group. The recorded meanvalue was 259.83 (± 27.74) mg/dl in the patient groupcompared with 152.93 (± 15.53) mg/dl in the controlgroup (Table 3) (Fig. 1).
The mean value of serum triglycerides
It was significantly higher ( P< 0.05) in the patient group
compared with the control group. The recorded meanvalue was 184.30 (± 17.29) mg/dl in the patient groupcompared with 97.60 (± 13.60) mg/dl in the controlgroup (Table 3) (Fig. 1).
The mean value of serum HDL-cholesterol
It was significantly lower ( P< 0.05) in the patient group
compared with the control group. The recorded meanvalue was 26.00 (± 3.02) mg/dl in the patient groupcompared with 50.73 (± 4.97) mg/dl in the control group(Table 3) (Fig. 1).
The mean value of serum LDL-cholesterol
It was significantly higher ( P< 0.05) in the patient group
compared with the control group. The recorded meanvalue was 123.50 (± 15.91) mg/dl in the patient groupcompared with 93.50 (± 9.48) mg/dl in the control group(Table 3) (Fig. 1).
Table 1 Age and sex difference between patient and
control groups
ParameterPatient group
(N=3 0 )Control group
(N=3 0 ) P-value
Age mean ± SD (years) 57 .5 ± 6.80 54.93 ± 5.73 0.120Female : male No. (%) 8 (26.67) : 22 (73.33) 6 (20) : 24 (80) 0.307Significant P-value ( < 0.05).Fig. 1
050100150200250300
4 3 2 1
Cholesterol TAG HDL-C LDL-CMean values
mg/dl
Lipid profile of patient (blue) and control (red) groups. TAG,triacylglycerol.Table 3 Lipid profile of patient and controls groups
ParameterPatients
(mean ± SD)Control
(mean ± SD) P-value
Cholesterol (mg/dl) 259.83 ± 27 .74 152.93 ± 15.53 0.000 *
Triglycerides (mg/dl) 184.30 ± 17 .29 97 .60 ± 13.60 0.000 *
HDL-cholesterol (mg/dl) 26.00 ± 3.02 50.73 ± 4.97 0.000 *
LDL-cholesterol (mg/dl) 123.50 ± 15.91 93.50 ± 9.48 0.000 *
*Significant P-value ( < 0.05).Table 2 Medical problems in the patient group
Medical problem Number of patients (%)DM 12 (40)Hypertension 8 (26.67)Ischemia or infarction 19 (63.33)Cardiac dilatation (mild or severe) 19 (63.33)DM, diabetes mellitus.Fibrinogen B-455 G/A and Prothrombin 20210 G/A in CHD Shaker et al. 103
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Table 4 shows the results of liver and kidney functiontests in addition to some hematological investigations. Allparameters showed a nonsignificant difference betweenthe studied groups except the mean total bilirubin, whichwas significantly higher in the patients as compared withthe controls.
Genotypes and alleles of the analyzed polymorphismsFibrinogen b-455 gene locus
The GG polymorphism was the genotype found in 20patients (66.67%), whereas the GA polymorphism wasfound in nine patients (30%) and the AA polymorphismwas found in only one patient (3.33%). Meanwhile, in thecontrol group, the numbers were 24 individuals (80%), sixindividuals (20%), and none (0%), respectively (Table 5)(Fig. 2).There was no significant difference between patient andcontrol groups regarding the frequency of FGB-455 G/Gpolymorphism ( P= 0.243) (Table 5). Also, there was no
significant difference between patient and control groupsregarding the frequency of FGB-455 G/A polymorphism(P= 0.371) or the frequency of FGB-455 A/A polymorph-
ism ( P= 1.000) (Table 5).
It was found that FGB-455 G/G is more likely to beassociated with CHD (OR < 1), whereas FGB-455 G/A isless likely to be associated with CHD (OR > 1) (Table 5).The frequency of the A allele was 11 (nine GA and oneAA) (18.33%) in the patient group compared with six (sixGA and zero AA) (10%) in the control group, whichshowed a nonsignificant difference ( P-value = 0.148)
(Table 6).
Prothrombin 20210 gene locus
The patient group contained 29 individuals (96.67%)with the GG polymorphism, compared with 30 individ-uals (100%) in the control group. There was only onepatient (3.33%) with the GA polymorphism, comparedwith none (0%) in the control group (Table 7) (Fig. 3).There was no significant difference between patient andcontrol groups regarding the frequency of the GGpolymorphism ( P= 1.000) or the frequency of GA
polymorphism ( P= 1.000) (Table 7).
Discussion
CHD shows high and increasing rates of morbidity andmortality [2], and its development involves hyperplasia ofarterial smooth muscles, the presence of fatty streaks,atheroma formation, plaque rupture, thrombus formation,and vessel occlusion [4]. The blood coagulation system isthought to determine the onset of MI through its role inblood clot formation. Searching for genetic variations thatmay affect this sequential mechanism may be veryTable 5 Fibrinogen b-chain-455 genotypes frequencies and
significance
GenotypePatients
No. (%)Controls
No. (%) P-valueOdds ratio
( – ve/ + ve)95% CI
for OR
GG 20 (66.67) 24 (80) 0.243 0.50 0.15–1.61GA 9 (30) 6 (20) 0.371 1.71 0.52–5.62AA 1 (3.33) 0 (0) 1.000 – –CI, confidence interval; OR, odds ratio.Significant P-value ( < 0.05).
Fig. 2
FGB 455 genotypes
0.00%50.00%100.00%
123
GG GA AA
Fibrinogen b-chain (FGB)-455 genotype frequencies of patient (blue)
and control (red) groups.Table 6 Frequency and significance of the A allele of fibrinogen
b-chain-455 gene locus in both studied groups
Frequency of A allele
n(%) Pvalue
Patient group 11 (18.33) 0.148Control group 6 (10)Significant P-value ( < 0.05).
Table 7 Genotype frequencies and significance of prothrombin
20210 gene locus of the studied groups
GenotypePatients
No. (%)Controls
No. (%) P-value
GG 29 (96.67) 30 (100) 1.000GA 1 (3.33) 0 (0) 1.000Significant P-value ( < 0.05).
Table 4 Biochemical characteristics of the studied groups
Parameter in bloodPatients
(mean ± SD)Control
(mean ± SD) P-value
ALT (U/l) 4.63 ± 1.47 4.66 ± 1.34 0.927AST (IU/l) 7 .33 ± 1.26 6.93 ± 1.33 0.239Total bilirubin (mg/dl) 0.65 ± 0.15 0.57 ± 0.13 0.044 *
Urea (mg/dl) 26.20 ± 5.05 26.83 ± 5.63 0.649Creatinine (mg/dl) 0.76 ± 0.12 0.77 ± 0.11 0.912INR 1.08 ± 0.07 1.09 ± 0.07 0.612Hemoglobin (g/l) 12.9 ± 0.82 13.1 ± 0.81 0.530Platelet count ( /C210
9/l) 203.3 ± 31.7 203.3 ± 31.7 1.000
ALT, alanine aminotransferase; AST, aspartate aminotransferase; INR, interna-tional normalized ratio.*Significant P-value ( < 0.05).Fig. 3
0.00%20.00%40.00%60.00%80.00%100.00%120.00%
2 1
GG GA
Prothrombin 20210 genotype frequencies of patient (blue) and control(red) groups.104 Medical Research Journal 2011, Vol 10 No 2
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important for the prediction of the disease occurrenceand/or prognosis [5].Many epidemiological studies have identified the plasmafibrinogen level as a powerful predictor of future CHD.However, fibrinogen is also an acute-phase reactant, andin recent years, the evidence for inflammation as a causeof vascular disease has steadily grown. Investigators havetherefore frequently turned to genetic studies thathave the potential to provide evidence supporting apathogenic role of fibrinogen in ischemic heart disease. Ifgenetic polymorphisms causing elevated levels of fibrino-gen were shown to be associated with an increased risk ofischemic heart disease, then this would be good evidencefor fibrinogen playing a causal role in the disease [15].However, despite the clear association between fibrino-gen levels and ischemic heart disease in both prospectiveand cross-sectional studies, and the consistent associationbetween genetic polymorphisms of the b-chain and
fibrinogen levels, none of the large population-basedstudies have shown an association between the poly-morphisms and ischemic heart disease [8].Carriers of the A allele of the FGB-455 G/A polymorph-ism have increased plasma fibrinogen levels, and studieson this polymorphism have been performed mainlyamong Caucasians. The association between FGB-455G/A polymorphism and thrombophilic diseases, such asvenous thromboembolism and CHD, in the Chinese Hanpopulation had been investigated and the presence of theA allele was found to be a greater risk factor in cases thanin controls [16].The present study aimed at elucidating the association ofFGB-455 G/A polymorphism with CHD in Egyptianpatients. The FGB-455 G/G wild-type polymorphism wasfound to be the most frequent among the studied CHDEgyptian patients (66.67%) and the control persons(80%). Although it was found to be more likely associatedwith CHD in Egypt (OR < 1); yet, there was nosignificant difference between the patient group andthe control group regarding its frequency ( P= 0.243).
FGB-455 G/A was found to be less frequent than FGB-455 G/G among the studied CHD Egyptian patients(30%) and control persons (20%). Also, it was found to beless likely associated with CHD in Egypt (OR > 1), andthere was no significant difference between the patientgroup and the control group regarding its frequency(P= 0.371). No significant difference was found between
the patient group and the control group regarding thefrequency of FGB-455 AA polymorphism ( P= 1.000), and
it was found to be a rare polymorphism in the studiedEgyptian participants (3.33% of the patient group and 0%of the control group). Thus, none of the polymorphismsof the FGB-455 locus differs significantly betweenpatient and control groups ( P-values > 0.05). Accord-
ingly, none of the three polymorphisms can be consideredas a risk factor for CHD in the studied Egyptianpopulation.The results of this study were in agreement with Cartyet al. [1], who investigated whether common ( Z5% minor
allele frequency) variation in the fibrinogen genes (FGA,FGB, FGG) is associated with fibrinogen concentrationvariations, carotid artery intimal-medial thickening, anda risk of incident MI, ischemic stroke, and cardio vasculardisease (CVD) mortality in European-American andAfrican-American descent adults ( Z65 years). They
found that among European American, minor alleles ofFGA3807, FGB1437 (which is FGB-455 G/A polymorph-ism), and FGG902 were associated with higher fibrinogenlevels ( P< 0.004 for each). The strongest associations
were seen for FGB1437; each additional copy of the minorallele was associated with a 13 mg/dl higher fibrinogenlevel [1]. However, whereas fibrinogen genetic variation wasstrongly associated with fibr inogen levels, there was less
evidence of an association with the more complex outcomesof intimal-medial thickening and CVD events [1].Also Lu et al. [17], studied the association between the
genetic polymorphisms of the FGB gene and MI in theChinese Han population. They found that the cases hadsignificantly lower frequencies of FGB-455 G/A poly-morphism than the controls; accordingly, they concludedthat the FGB-455 G/A polymorphism was not associatedwith MI in the Chinese Han population after adjustment
for the other traditional risk factors.The most obvious possible explanation for a failure tofind a relationship between genotype and disease is thatfibrinogen plays no pathogenic role in coronary arterydisease. In this scenario, fibrinogen acts as a marker ofsome other process, most probably inflammatory, whichcauses ischemic heart disease independently. This issupported by the finding that fibrinogen levels correlateclosely with other acute-phase reactants in patients withischemic heart disease, raising the possibility thatfibrinogen is simply an indicator of disease rather thanhaving a causal role [18]. A second possible explanation isthat fibrinogen does play a pathogenic role in ischemicheart disease, but the effect of genotype is smallcompared with other modifiers of fibrinogen level. Also,an effect of the genotype may be apparent only inconjunction with some other risk factor such as smokingor the acute-phase reaction and the presence of apolymorphic variation in genes for intermediaries suchas IL-6, which is an inflammatory cytokine known to bethe main regulator of fibrinogen synthesis [19].Rather than directly affecting the levels of proteins or therisk of disease, polymorphisms can amplify the effect ofenvironmental or intermediate conditions on the finalphenotype. The genetic control of fibrinogen has to beconsidered together with the environmental factors:fibrinogen genotypes may interact with cigarette smok-ing, physical activity, use of drugs, hormonal status,and infections in determining the increase in fibrinogenlevels and perhaps the risk of ischemic heart disease [20].Thus, in conclusion, it can be said that CVD events arethe result of complex interactions among elevatedfibrinogen level and cytokines, especially IL-6, whichnot only increase the fibrinogen level but also stimulateother events incorporated in the CHD pathogenesissuch as vascular smooth muscles proliferation and theinflammatory nature of atherosclerotic plaques forma-tion [21,22].
Fibrinogen B-455 G/A and Prothrombin 20210 G/A in CHD Shaker et al. 105
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However, the present study does have some limitations.First, the lack of an association between the FGB-455G/A polymorphism and MI may be due to the relativelysmall sample size. Second, the study participants werenot recruited prospectively. Thus, a selection bias couldnot be excluded. Another limitation is that the plasmalevels of fibrinogen were not determined. However, alarger cohort will ultimately be required to confirmwhether or not the results of the present study arereliable.The results of the present study were opposed by Reineret al. [7] and Chen et al. [8], in different studies on
different populations, who linked FGB-455 G/A poly-morphism with CHD through the effect of the genotypeon the circulating fibrinogen level. Reiner et al. [7]
analyzed the association between common polymorph-isms in the fibrinogen genes and the circulating levels ofboth functional fibrinogen and total fibrinogen in a large,multicenter, biracial cohort of young US adults inEuropean-American and African-American populations,and reported that a common haplotype tagged by the Aminor allele of the well-studied FGB-455 G/A promoterpolymorphism was confirmed to be strongly associatedwith increased plasma fibrinogen levels, which is a strongrisk factor for the development of CHD. However, Chenet al. [8] evaluated the correlation between FGB-455 G/A
polymorphism and susceptibility to coronary arterydisease in the Chinese population using a meta-analyticapproach and found that the combined OR for the ninestudies on the susceptibility to coronary artery disease inFGB-455 A allele carriers (G/A and A/A) compared withthe FGB-455 G/G wild-type homozygote was 1.75,suggesting the possibility that FGB-455 G/A polymorph-ism (in particular, allele A) increases the susceptibility toCHD in the Chinese population.Also, the results of the present study oppose the resultsof a similar study conducted by Dilley et al. [23], who
focused on the evaluation of the relationship betweenLegg–Perthes disease and the FGB-455 G/A polymorph-ism. Legg-Perthes disease is a pediatric hip disordercharacterized by avascular necrosis of the femoral head,and its etiology involves repeated interruptions of theblood supply to the proximal femur. Accordingly, the roleof thrombosis in the disease is of interest. They foundthat individuals who possessed either the G/A or the A/Agenotype were over three times more likely to have Legg-Perthes disease compared with those without thepolymorphism [23].Several studies have shown that the A allele of the FGB-455 G/A polymorphism is associated with an elevatedplasma fibrinogen concentration and that A instead ofG in the FGB-455 position produces a 1.2–1.5-foldincrease in the FGB transcription [24–28]. The b-chain
transcription is a rate-limiting step in the synthesis of thetotal functional fibrinogen molecule. Increased viscosityand a higher available substrate quantity resulting from anelevated plasma fibrinogen concentration may promotecoagulation and act as a risk for small-vessel thromboticocclusion, thus affecting the phenotype of the cerebralinfarction. The results of the study conducted byMartiskainen et al. [29], to assess the fibrinogen gene
promoter-455 A Allele as a risk factor for lacunar stroke,concluded that stroke patients carrying the A allele of theFGB-455 G/A polymorphism frequently presented withmultiple lacunar infarcts, and this association suggeststhat the A allele may predispose to atherothromboticevents in the cerebrovascular circulation. Their explana-tion was that the A genotype and the resulting increasedfibrinogen concentration in circulation may contribute tothe progression of arteriosclerosis, primarily in smallercerebral arteries with slower blood flow rather than inlarge vessels [30]. In this way, it may predispose one tothe development of occlusions in small cerebral arteriesand finally to multiple lacunar infarcts [29]. Accordingly,the previous studies that oppose the results of thepresent study can explain their findings.Inherited abnormalities of the hemostatic system thatmay predispose one to thrombosis are termed as inheritedthrombophilias. One of them is PT 20210 G/A mutation,the prevalence of which in the general population isestimated to be 2.3% for its heterozygous form. However,this mutation is very rare in China. It implies that thevariant of the PT gene is probably not the main cause ofthe thrombophilic diseases, such as venous thromboem-bolism and CHD, in the Chinese population [16].PT 20210 G/A polymorphism has also been investigated inthe present study, but current evidence does not supportthe hypothesis that this polymorphism might be a riskfactor for CHD. PT 20210 G/A polymorphism was found tobe rare among the studied CHD Egyptian patients (3.33%)
and absent in the control persons. There was no significantdifference between patient and control groups regarding itsfrequency ( P= 1.000). Although PT 20210 G/G wild-type
was predominant among CHD Egyptian patients (96.67%)and control persons (100%), there was no significantdifference between the patient and the control groupsregarding its frequency ( P= 1.000). Although it was found
that PT 20210 G/G is more likely to be associated withCHD (relative risk > 1) and PT 20210 G/A is less likely tobe associated with CHD (relative risk < 1), neither poly-morphism differs significantly between the patient and thecontrol groups ( P-value > 0.05). Accordingly, neither poly-
morphism can be considered as a risk factor for CHD in theEgyptian population studied.The results of the present study are in agreement withRahimi et al. [31], who assessed the contribution of factor
V Leiden 1691 G/A, PT gene 20210 G/A, and methy-lentetrahydrofolate reductase (MTHFR) 677 C/T muta-tions in the development of CHD and their associationwith diabetes. Their results indicated that there was nosignificant difference between the prevalence of throm-bophilic mutations of factor V Leiden, PT 20210 G/Avariant, and MTHFR 677 C/T in CHD patients with orwithout diabetes compared with controls. Also, O ¨zmen
et al. [32] failed to show any relation between PT gene
mutation and increased risk of arterial thrombosis in theirstudy that investigated the prevalence rates of factor V ,MTHFR, and PT gene mutations in patients with arterialthrombosis and in healthy controls. Their findingssuggested the MTHFR mutation as a synergistic risk
106 Medical Research Journal 2011, Vol 10 No 2
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factor for thrombosis in patients with factor V mutation,whereas PT gene mutation has no effect on arterialthrombosis as there was only one patient in their studywith PT mutation, who was negative for the other twomutations. Thus, it can be proposed that this type ofpolymorphism may be harmless when alone, but mayincrease the risk for CHD when associated with othergene(s) polymorphisms. Also, Geng et al. [33], in their
study to determine whether polymorphisms in the genesfor coagulation factors II, V , and VII could predispose anindividual to an increased risk of CHD and/or MI in theChinese, found that factor II (20210 G/A), V (1691 G/A)mutation is absent and may not be a major genetic factorfor CHD and/or MI.Almawi et al. [34] studied factor V 1691 G/A, PT 20210
G/A, and MTHFR 677 C/T gene polymorphism inangiographically documented CHD; the results from thisstudy clearly demonstrated a strong association ofhyperhomocysteinemia and homozygosity of the MTHFR677 C/T , but not factor V Leiden or PT 20210 G/A,mutations with confirmed CHD, which is consistent withour results. A mutation in the PT gene was identified tobe associated with increased PT levels, but CHDdevelopment requires more complex interactions amongseveral risk factors [35].The results of the present study were opposed byMugnolo et al. [36], who reported a case of MI at a young
age in a person with a medical history of repeatedthrombophlebitis, who was heterozygous for the PT20210 G/A mutation and homozygous for factor V Leidenmutation. A coronary angiography revealed the presenceof a moderate atherosclerotic plaque (60%) in the leftanterior descending coronary artery, which gave rise tosuspicion of a relationship between prothrombotic genemutations and atherosclerosis. Accordingly, they recom-mended that the genetic screening for inherited throm-bophilia, especially in the presence of a strong familiarityor previous venous thrombosis, and the evaluation ofatherosclerotic risk factors, may be critical information forprimary prevention of arterial thrombosis [36].Also, Ye et al. [37] performed a meta-analysis on seven
hemostatic gene polymorphisms in CHD patients; one ofthem was PT 20210 G/A. The study involved a total of66 155 CHD cases and 91 307 controls. Their results,which oppose the results of the present study, concludedthat the 20210 A variant of the PT gene increasescirculating thrombin generation and might be moderatelyassociated with the risk of CHD [37]. Thus, whether PT20210 G/A mutation could be considered as a risk factorfor CHD or not remains controversial although it wasestablished that this mutation increases the amount ofPT in the blood stream. It is not yet fully understood asto how increased levels of PTact as a risk factor for CHD,but some studies have indicated that extra PT mayinterfere with the body’s natural ability to dissolve clots.About 1–2% of people with European ancestry carry thePT 20210 G/A mutation [38].However, in the present study, the lipid profile of thepatients was significantly higher than that of the controls(P-values = 0.00), which ensures the concept thatatherosclerosis and CHD are more related to theelevation in serum cholesterol, triglycerides, and theLDL-cholesterol/HDL-cholesterol ratio in addition to anunhealthy lifestyle [39,40]. Alber et al. [41] investigated
the relationship between HDL cholesterol and theprevalence and severity of coronary artery disease(CHD) in 5641 consecutive patients undergoing coronaryangiography. They found that HDL-cholesterol wassignificantly higher in non-CHD persons than in CHDpatients ( P< 0.001). Accordingly, they concluded that
HDL-cholesterol is a stronger predictor of CHD thansome other major classical risk factors [41]. Furthermore,the results of the present study showed a nonsignificantdifference between patients and controls with regard tothe age ( P= 0.120) and sex distribution ( P= 0.307),
which again potentiates the value of the significant lipidprofile difference between patients and control personsover other traditional risk factors such as age and sex.Although the present study was conducted on CHDEgyptian patients, yet, its results may be applicable toother CVDs such as lacunar stroke and peripheral arterialischemia [29,30]. This is due to the similar pathogenesisof the diseases and similar involvement of the two genesof the study. This is similar with the results of Banerjeeet al. [30], who stated that the plasma fibrinogen level is a
valuable index for the peripheral arterial ischemiapatients with stable intermittent claudications and ahigh risk of early mortality. Their results also providefurther evidence for the involvement of fibrinogen in thepathogenesis of ischemic arterial diseases [30]. Also, ameta-analysis, where 41 publications that examined 44gene polymorphisms were included, was performed byElias Zintzaras and Nikos Zdoukopoulos [42], on thebasis of the similarity among ischemic arterial diseases inthe pathophysiological pathways. FGB-455 G/A and PT20210 G/A polymorphisms were included in that study,and the results concluded that their association withperipheral arterial ischemia remains controversial [42].
Conclusion
Although a specific genotype may be associated, inhealthy participants, with modest differences in thelevels of a risk factor for thrombosis, this effect may belarger or smaller in subgroups of participants. Document-ing such gene–environment interactions is important ifgenotype information is ever to be used in a clinical ordiagnostic setting. Understanding the molecular mechan-isms of such interactions is very important for thedevelopment of novel therapeutic approaches to reducethe risk of MI. Future studies should be designedspecifically to investigate interactions between potentialgenetic polymorphisms and acquired risk factors.
Acknowledgments
Conflicts of interest
There are no conflicts of interest.
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