Sounira Mehri

Relationship between genetic polymorphisms of angiotensin-converting enzyme and methylenetetrahydrofolate reductase as risk factors for type 2 diabetes in Tunisian patients.

BACKGROUND/AIMS The role of methylenetetrahydrofolate reductase (MTHFR) and angiotensin-converting enzyme (ACE) gene polymorphisms as being risk factors for diabetes is still controversial. The aim was to investigate the distribution of ACE and MTHFR genotypes as well as to evaluate the role of plasmatic total homocysteine levels (tHcy) and ACE activity in Tunisian patients with type 2 diabetes mellitus (T2DM). DESIGN AND METHODS 115 T2DM patients compared to 116 healthy volunteers. RESULTS The ACE I/D polymorphism was significantly associated with diabetes (p<0.0001). The DD genotype and D allele were more frequent in patients compared to control group [DD: OR=4.93; p<0.0001; 95 % CI: 2.71-8.97; D: OR=3.08, 95% CI: 2.09-4.51 p<0.0001]. MTHFR allele and genotype frequencies did not differ between patients and controls. The susceptibility to diabetes in individuals with genotypes DD+vTT was 13.39 and in the individuals with DD+CT was 6.57 times that of the controls. However, individuals with genotypes ID+CC or II+CT have a protective effect against diabetes. The DD and TT genotypes were associated with significantly higher ACE activity and tHcy levels in diabetics. CONCLUSION Our data suggest that ACE ID polymorphism may act synergistically with MTHFR C677T polymorphism to assess diabetes risk.

Association of homocysteine thiolactonase activity and PON1 polymorphisms with the severity of acute coronary syndrome.

INTRODUCTION Excess of total homocysteine (tHcy) and decrease of thiolactonase activities (HTase) have been proposed as risk factors for coronary artery diseases (CAD). OBJECTIVES We evaluated the relationship of tHcy and HTase with paraoxonase 1 (PON1) gene polymorphism according to CAD severity. DESIGN AND METHODS 118 healthy volunteers and 91 CAD patients were compared. RESULTS Serum levels of tHcy and oxidized LDL (ox-LDL) increased significantly by 26% and 48% in CAD patients and were associated with significantly lower levels of HDL cholesterol (p=0.02) and 42% of decrease in HTase activities (p<0.05). In these patients the HTase activity was negatively associated with tHcy and Hs CRP levels (r=-0.622, p=0.00 and r=-0.355, p=0.007 respectively) but positively associated with apoB and triglyceride levels (r=0.35, p=0.042 and r=0.308, p=0.003 respectively). HTase activity decreased inversely to the number of affected vessels and according to PON1 polymorphism. PON1 Q192R RR and PON1 L55M MM genotypes were associated with higher HTase activities. Only PON1 L55M (MM) genotype frequency was significantly higher in CAD patients than in controls (P<0.05), while its frequency was similar between the two subgroups according to CAD severity. In a multivariate analysis, tHcy levels were the only independent factor affecting the severity of cardiovascular disease (p=0.029). CONCLUSIONS High tHcy levels are associated with the severity of cardiovascular disease and may be partly explained by the diminished HTase activities in these patients.

Genotypic interactions of renin-angiotensin system genes with diabetes type 2 in a Tunisian population.

AIMS To explore the role of genetic variants of angiotensinogen (AGT M235T), angiotensin-converting enzyme (ACE I/D), and angiotensin type 1 receptor (AT1R A1166C) as predictors of diabetes risk and to examine their combined effects on type 2 diabetes mellitus (T2DM) patients. MAIN METHODS One hundred and fourteen T2DM patients were compared to 175 healthy controls with similar age and sex. KEY FINDINGS The genotypic frequencies for all three genes alone were significantly associated with increased risk of developing diabetes. Logistic regression analysis of classic coronary risk factors and the genetic polymorphisms demonstrated that hypertension and ACE DD genotype were the most significant contributors to T2DM. For the renin-angiotensin system (RAS) genes, the risk of T2DM in individuals with one risk genotype was 1.9 (95%CI: 1.1-3.0, p=0.017) higher than those with zero risk genotype. Individuals who carried two risk genotypes had a 4.0 (95%CI 1.7-9.4, p=0.001) times higher risk of T2DM than those who did not carry any risk genotypes of the RAS genes. Most interestingly, the risk of T2DM for individuals with three risk genotypes was 26.2 (95%CI: 5.8-117.9, p<0.001) higher than those with zero risk genotype. SIGNIFICANCE The results of the present study imply that genotyping of renin-angiotensin system genes could become an important part of the clinical process of risk identification for T2DM in Tunisian population.

Angiotensinogen gene polymorphism in acute myocardial infarction patients

Introduction. The objective of the study was to explore the role of a genetic variant of angiotensinogen (AGT), M235T, as an independent risk factor for acute myocardial infarction (AMI) and to investigate the possible association with the severity of coronary artery disease (CAD), estimated on the basis of the number of coronary stenoses and critical arterial occlusions. Patients and methods. 123 AMI patients were compared to 144 healthy controls. AGT genotypes were determined by PCR. Results. A significant association was found between AGT M235T polymorphism and AMI (p = .021). By logistic regression, the TT genotype appeared to confer 1.9-fold increased risk for AMI in both the univariate and the multivariate model. The frequencies of the TT genotype and T allele increased with the number of stenoses in coronary vessels. Moreover, the TT genotype and the T allele were more frequent in the subgroup of patients with stenoses in at least four coronary vessels than in other patients, including subjects with one- to three-vessel disease. Furthermore, the TT genotype and the T allele were significantly more frequent in patients with critical arterial occlusions (> 90%) than in subjects without critical stenoses. Conclusions. The AGT M235T polymorphism associates with AMI risk and influences CAD severity.

Angiotensin-converting enzyme insertion/deletion gene polymorphism in a Tunisian healthy and acute myocardial infarction population.

INTRODUCTION The role of the insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme gene (ACE) on acute myocardial infarction (AMI) is controversial. OBJECTIVES To assess the effect of the ACE I/D polymorphism on AMI compared with the healthy controls and its relationship with serum ACE activity in a Tunisian population. DESIGN AND METHODS A total of 119 patients with AMI were compared with 238 healthy controls from the same geographical area. ACE genotyping was determined by polymerase chain reaction, and serum ACE activity was measured with N-[3-(2-furylacryloyl]-L-phenylalanyl-L-glycyl-L-glycine as substrate. RESULTS The ACE I/D polymorphism was significantly different between patients and controls (p < 0.0001). The frequencies of the DD genotype and the D allele were statistically higher in patients with AMI as compared with the controls and were associated with increased risk of AMI (DD vs. ID and II: odds ratio = 4.27, p < 0.0001, 95% confidence interval = 2.65-6.86; D vs. I: odds ratio = 3.15, p < 0.0001, 95% confidence interval = 2.26-4.40). This association was independent of other cardiovascular risk factors but dyslipidemia (p = 0.002) that was not represented in AMI patients with II genotype and in a lower extent with hypertension (p < 0.05). Serum ACE activity was significantly higher in AMI patients with ACE DD genotype compared with the subjects with ID or II genotype (p = 0.034) and was not correlated with other cardiovascular risk factors. CONCLUSIONS ACE DD genotype associated with higher serum ACE activity is increased in the studied population and might be clinically useful as markers to assess risk for AMI.

Transition m.3308T>C in the ND1 gene is associated with left ventricular hypertrabeculation/noncompaction.

Though left ventricular hypertrabeculation/noncompaction (LVNC) is frequently associated with mitochondrial DNA (mtDNA) mutations, it has not been reported in association with the transition m.3308T>C of the NADH dehydrogenase subunit 1 (ND1) gene. The index patient is a 16-year-old Tunisian female who was investigated for a systolic murmur and cardiomegaly. Echocardiography revealed tricuspid insufficiency, moderate left ventricular dilatation, Ebstein’s anomaly, a superior caval vein draining into the coronary sinus and, surprisingly, LVNC of the apex and the lateral wall. LVNC was absent in all other cardiologically investigated siblings. RNA and mtDNA sequence analysis revealed the known homoplasmic mutation m.3308T>C resulting in the replacement of the first amino acid methionine by threonine in the ND1 subunit of respiratory chain complex I. The m.3308T>C mutation was also present in the patient’s mother and several other family members but absent in 350 controls. Additionally, the index patient carried the polymorphisms m.8248A>G in the COX2 gene and m.8468C>T in the ATP8 gene. It is concluded that LVNC may be associated with the known homoplasmic m.3308T>C mutation in the ND1 gene. However, the pathogenetic role of this mutation in the development of LVNC remains elusive.

Association of ACE I/D polymorphism in Tunisian patients with dilated cardiomyopathy

Primary cardiomyopathies are multifactorial diseases. Genetic factors other than the causal mutations in the modified genes affect the phenotypic expression of dilated cardiomyopathy. The aim of this study was to determine the association of angiotensin-converting enzyme I/D polymorphism with the risk of dilated cardiomyopathy in a Tunisian population. A total of 76 patients with dilated cardiomyopathy was compared to 151 ethnically, age- and gender-matched controls. The frequencies of the DD genotype and D allele were significantly higher in patients as compared with controls, and were associated with increased risk of dilated cardiomyopathy (ACE DD versus ID and II: OR = 3.05 (95% CI, 1.58—5.87; p = 0.001)); D versus I: OR = 2 (95% CI: 1.35—2.97; p = 0.001)). No association was found between the combined genotypes (DD+ID) or D allele and left ventricular end diastolic diameter in dilated cardiomyopathy patients with severe and moderate clinical phenotypes. DD genotype and D allele of angiotensin-converting enzyme I/D gene polymorphism are associated with increased risk of dilated cardiomyopathy in a Tunisian population but do not influence the cardiac phenotype severity.

HLA class II polymorphisms in Tunisian patients with dilated cardiomyopathy

Cardiomyopathies (CMs) are primary disorders of cardiac muscle. They are a major cause of morbidity and mortality for all ages and, like acquired forms of cardiovascular disease, often result in heart failure. Molecular genetic studies have made remarkable progress in defining the pathogenesis of CM. The present study was the first report to evaluate the relationship between class II major histocompatibility complex (MHC) genes (HLA-DRB1 and HLA-DQB1) and the genetic susceptibility to primary dilated cardiomyopathy (DCM) in Tunisian patients. The human leukocyte antigen (HLA)-DRB1 and -DQB1 alleles were analyzed in 76 patients with primary DCM and 111 ethnically matched healthy controls using polymerase chain reaction-sequence specific primers technique. An increased frequencies of HLA-DRB1*0401 (OR = 2.67, P < 0.001), HLA-DQB1*0302 (OR = 3.28, P = 0.001) and HLA-DQB1*0401 (OR = 6.26, P = 0.005) alleles were found in the patients with primary DCM compared with healthy controls. Individuals with HLA-DRB1*1301 (OR = 0.24, P < 0.001) and HLA-DQB1*0201 (OR = 0.49, P = 0.002) alleles have a protective effect against primary DCM. Two haplotypes were associated with increased risk of primary DCM: DRB1*0401/DQB1*0302 (OR = 4.53, P = 0.002) and DRB1*0401/DQB1*0401 (OR = 9.42, P = 0.004). In conclusion, our data suggest that the variation in class II HLA alleles could be a genetic factor involved in the susceptibility to primary DCM in the Tunisian population.

Association of the C677T MTHFR Polymorphism With Homocysteine, Ox-LDL Levels, and Thiolactonase Activities in the Severity of Coronary Syndrome

Coronary artery diseases (CAD) are influenced by multiple genes of modest effect as the methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism, related to MTHFR activity and total plasma homocysteine (tHcy) concentration. This study was designed to evaluate tHcy, oxidized low-density lipoprotein (LDL) (ox-LDL), high-sensibility C-reactive protein (Hs CRP) levels, and homocysteine thiolactonase (HTase) activities as new risk factors for CAD and to investigate an association between MTHFR polymorphism tHcy concentrations and coronary syndrome severity. Our results showed significantly higher levels of tHcy and ox-LDL in patients associated with lower HTase activities. These levels increased proportionally to disease severity. Total plasma Hcy levels were negatively correlated to HTase activities in patients where the TT genotype was significantly more frequent. In a multivariate analysis, tHcy level was the only independent factor affecting the coronary syndrome severity. High tHcy levels are associated with coronary syndrome severity and may be explained either by the elevated prevalence of TT genotype or by the diminished HTase activities.

The CC genotype of the angiotensin II type I receptor gene independently associates with acute myocardial infarction in a Tunisian population

Acute myocardial infarction (AMI) is a multifactorial disease influenced by environmental and genetic factors. The aim of this study was to assess the association of angiotensin II type 1 receptor (ATR1) gene polymorphisms with AMI as well as to evaluate the role of serum angiotensin-converting enzyme (ACE) activity and that of cardiac troponin I (cTnI) in Tunisian AMI patients. One hundred and eighteen AMI patients were compared to 150 healthy controls. ATR1 genotypes were determined by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). The ATR1 A1166C polymorphism was significantly associated with AMI (p = 0.024). CC genotype and C allele frequencies were associated with increased AMI risk [CC vs. AC and AA: OR = 2.06; p = 0.045; 95 % CI (1.02–4.18); C vs. A: OR = 1.68; p = 0.004; 95 % CI (1.17–2.41)]. By multivariate logistic regression analysis, CC genotype, hypertension, diabetes, serum ACE activity and peak-cTnI were significant independent predictors of AMI. Increased serum ACE activity and cTnI peak levels were associated with the CC genotype in AMI patients. In conclusion, the ATR1 A1166C polymorphism is associated with AMI and the CC genotype associated with increased ACE activity and cTnI levels appear to predispose for AMI risk.