According to the World Health Organization, every year ~50 million people succumb due to ischemic heart diseases, particularly myocardial infarction (MI), which is a worldwide leading cause of fatality (1). In general, MI is a result of myocardium necrosis, which occurs when the latter does not receive enough oxygen, due to a sudden occlusive thrombosis of the coronary artery that irrigates this section of myocardium (2).

Several studies have identified that genetic in addition to known risk factors (including age, gender, arterial hypertension, smoking, diabetes and dyslipidemia) strongly increases the risk of MI occurrence (3). Among the numerous genes that were previously found to be in association with MI susceptibility, 5,10-methylenetetrahydrofolate reductase (MTHFR) and factor II prothrombin (FII) genes are the most widely reported.

The MTHFR gene is located on chromosome 1 at the ‘Ip36.3’ position; the corresponding cDNA sequence comprises 11 exons spanning 2.2 kb (4). The main product of the MTHFR gene is a protein of 77 kDa with catalytic activity, composed of 656 amino acids (5). It is involved in folate metabolism by catalyzing the irreversible conversion of 5,10-methylenetetrahydrofolate (5,10-CH₂-FH₄) into 5-methyltetrahydrofolate (5-CH₃-FH₄), which is the major circulating form of folic acid and the cosubstrate for remethylation of homocysteine to methionine (6,7).

In its 5-methyl form, folate participates in single carbon transfers that occur during nucleotide synthesis; S-adenosylmethionine formation; remethylation of homocysteine to methionine; and methylation of DNA, proteins, neurotransmitters and phospholipids (8).

The C677T allele of the MTHFR gene is the conversion of cytosine (C) to thymine (T) at position 677, which results in a conversion of alanine to valine at the binding site of the flavin adenine dinucleotide, the cofactor of MTHFR enzyme (9). This allele is commonly known as ‘labile’; it facilitates the separation of the enzyme from its cofactor, reducing the activity of the encoded enzyme at ≥37°C (10,11). Thus, if the folate intake is insufficient, the activity of the homozygote decreases by 50–60% at 37°C, and by 65% at 46°C; heterozygotes are in the intermediate range, and homozygotes tend to have slightly increased plasmatic homocysteine levels (10).

Prothrombin is a precursor of thrombin. It has an essential role in fibrin formation and coagulation procedure. Numerous studies have demonstrated that a single base-pair change in the prothrombin gene (G20210A) is associated with increased plasma prothrombin levels (12–15); this has generated significant interest and it has been suggested that this polymorphism may lead to increased risks of arterial and venous thrombosis (16).

Located on chromosome 11 (11p11), in a 3′-untranslated region of the prothrombin gene, the G20210A variant replaces a single base of guanine (G) with adenine (A) at position 20210, where the pre-mRNA receives the poly A-tail (17). Patients with one copy of this polymorphism have ~5-fold greater risk of blood clot formation compared to patients without. The risk becomes 50-fold higher among subjects with two copies of the 20210A allele. In such conditions, they become prone to earlier or severe arterial and venous thrombosis, particularly with the addition of a family history of such events (12,18,19).

Although mutation in the prothrombin gene has been frequently studied, data regarding this mutation to the risks of MI are limited and their interpretation has been controversial (13–15).

In the present study, the main aim was to investigate the association of the C677T and G20210A variants of MTHFR and FII prothrombin genes with MI among Moroccan patients.

With a complex pathology, numerous factors are involved in the occurrence of MI. In interaction with environmental factors, the genetic background has an essential role in MI susceptibility. A number of studies began, over the few past years, focusing on the implication of hemostatic markers in MI development, and have suggested that numerous genes affecting coagulation proteins are prothrombotic risk factors (23,24), among which are the FII (G20210A variant) and MTHFR (C677T variant) genes.

Several studies have investigated the association of prothrombotic genetic markers, including FII and MTHFR genes with MI risk, but have provided divergent and inconclusive results (5,25,26).

To the best of our knowledge, this is the first study to explore the potential association of the G20210A FII and C677T MTHFR polymorphisms with MI risk in the Moroccan population.

In the present study sample, the majority of patients were >50 years of age (66%) and were predominantly male (70 vs. 30% who were female). This was in agreement with the Croatian study by Jukic et al (27) regarding the implication of the ABO blood group genotypes and the prothrombotic mutations of factor V Leiden, prothrombin G20210A FII and MTHFR C677T on MI occurrence. The study noted that 75.3% of the patients recruited were >55 years of age, with a male predominance (63.2 male vs. 36.8% female). In addition, the same study reported that males had a 1.5-fold greater risk of developing MI compared to females (P<0.05), and that older age patients (>55 years) had >20-fold greater risk (OR=21.1; 95% CI, 12.64–35.23).

Hyperhomocysteinemia is known to be an important risk factor for cardiovascular diseases, such as MI. The C677T polymorphism of MTHFR gene has been associated with decreased MTHFR enzyme efficiency and its thermolability (28). Previous studies have reported that individuals carrying a double copy of the 677T allele had significantly increased plasma levels of homocysteine, and suggested that this variant may be a potential genetic risk factor for cardiovascular diseases (29–31).

According to the present data, the C677T MTHFR variant was significantly associated to obesity (P=0.02) (Table II). The CT genotype was the most frequent among patients (52%) compared to the other genetic profiles (38% CC and 10% TT). In healthy controls, the CC genotype was the most frequent (52.2%) vs. 41.8 and 6% for the CT and TT genetic profiles, respectively. Similar findings were reported by Spiroski et al (32), which found that the CT genotype was the most frequent genotype among patients (51.3%) vs. 35.5% CC and 13.2% TT. According to this study, the T allele frequency was higher in patients compared to controls, which consists with the present findings (T allele frequency in patients group was 36% compared to 26.9% among healthy controls).

Other studies reported that the higher frequency of homozygous mutated genotype TT (18–19%) was found in the Italian population (29,33,34). It was 16.7% in Greece, 6.2% in Germany and 6% in Croatia (35,36). Xuan et al (37) reported that the 677T allele frequency was 28.99% in Caucasian children vs. 42.28% in Asian pediatric patients, and 31.76% in the Caucasian maternal vs. 41.51% in the Asian maternal population.

Regarding the present results, no statistically significant association was observed between the C677T MTHFR polymorphism and MI risk in Morocco. Numerous studies have investigated this association among different populations and have noted similar findings (38–43). Other studies suggest a significant association of C677T MTHFR with MI risk (30,37,44,45).

The G20210A polymorphism of the FII prothrombin gene is correlated with higher plasma levels of prothrombin among subjects carrying this variant compared to normal subjects, making them prone to blood clots and thrombotic events (13,19,46,47). Regarding the biology, high plasma concentrations of prothrombin associated with the presence of the G20210A FII polymorphism may confer an elevated risk for cardiovascular disease (48).

The present results show that no genetic profile was the most frequent in the patient group compared to the controls, and no statistically significant association of the G20210A FII polymorphism with any one of the risk factors analyzed was observed. There was more heterozygote genotype (GA) among patients compared to the healthy controls (59 and 5.5%, respectively). Consistent results were reported by Ercan et al (48) among the Turkish population, and even the heterozygote exhibited a significant association of the G20210A FII polymorphism with coronary artery disease risk.

According to the present data, the homozygous mutated genotype (AA) frequency was 10% among patients and 0% among controls. The 20210A allele frequency was higher in the patient group (39.5%) compared to the control group (2.7%). The study performed by Ercan et al (48) reported similar results among healthy controls, signaling that the homozygous mutated profile of G20210A FII polymorphism was absent in the control group. The study also reported that this genotype was not detected among patients. Other similar findings were reported by Doggen et al (14), signaling that the 20210A allele was present in only 2% of healthy controls, and suggesting that the G20210A FII polymorphism is associated with the risk of venous thromboembolism (OR=2.8). In 2009, Gohil et al (49) reported that this variant was correlated the venous thromboembolism risk (OR=3.2), and that the risk associated with the homozygous genetic profile of the polymorphism was 6.7-fold higher.

The present results show that the G20210A polymorphism of the FII prothrombin gene was significantly associated with susceptibility to MI. The results of the previous studies regarding this association remain inconsistent (14,15,20,48,50–55).

The divergences in results regarding the association of C677T MTHFR and G20210A FII variants with MI risk may be explained by numerous factors, such as differences in genetic background among the studied populations; differences in the selection of patients and controls; studies sample sizes and ethnicity.

In conclusion, to the best of our knowledge this is the first study to evaluate the association of C677T MTHFR and G20210A FII prothrombin polymorphisms with MI in Morocco. According to the data, no significant association was observed between the C677T MTHFR variant and MI risk. The heterozygote genetic profile (CT) was more frequent among patients compared to the controls. By contrast, the G20210A FII variant was significantly correlated to MI risk, with a predominance of the heterozygote genotype (GA) and the high frequency of the 20210A allele among patients compared to the controls, thus suggesting that this polymorphism may be a potential genetic marker for MI in Morocco. As a multifactorial disease, the development of MI may be synergistically influenced by numerous factors at different intensities. Thus, further investigations are required to assess these associations in greater detail (gene-gene and gene-environment interactions).