PCSK9 polymorphism in a Tunisian cohort: identification of a new allele, L8, and association of allele L10 with reduced coronary heart disease risk.

The c.61_63dupCTG (L10) allele of rs72555377 polymorphism in PCSK9 has been reported to be associated with low-density lipoprotein-cholesterol (LDL-C) levels and with a decreased risk of coronary artery disease (CAD). We investigated the effect of two known alleles for rs72555377, L10 and L11, on the risk of CAD in a Tunisian cohort (218 patients diagnosed by angiography and 125 control subjects). Two subgroups of patients were defined by their level of stenosis: ≥50% for CAD and <50% for no-CAD. The genotypes were obtained by the size measurement of fluorescent-labeled PCR products. We identified a novel allele for the rs72555377 polymorphism: an in-frame deletion, c.61_63delCTG (L8). The frequency of the L10 allele was significantly higher in the no-CAD subgroup than in the CAD subgroup (0.210 vs 0.114, p = 0.045), and than in the subgroup of CAD patients presenting a stenosis ≥50% in two or three major coronary arteries (0.210 vs 0.125, p = 0.028). Multiple regression analysis showed that the L10 allele was significantly associated with a reduced risk of CAD (p = 0.049, OR = 0.51[0.26-1.00]), and with its reduced severity (p = 0.045, OR = 0.44[0.20-0.98]). The L10 allele is associated with a reduced risk and severity of CAD, seemingly independently of its LDL-lowering effect, suggesting a direct effect of PCSK9 on atherogenesis.

Cardiac iron overload detection using longitudinal strain in asymptomatic children with beta thalassemia major.

Cardiomyopathy mediated by iron disposition in cardiomyocytes is a dreadful cause of morbidity and mortality in patients with beta thalassemia major (BTM). Conventional transthoracic echocardiography (TTE) parameters are preserved at late stages of cardiomyopathy induced by iron overload. Therefore, cardiac imaging modalities based on myocardial deformation such as strain imaging are used for early detection of cardiac iron overload. To demonstrate the contribution of longitudinal strain (LS) in early detection of cardiac iron overload in children with BTM. Sixty children (30 children with BTM and 30 healthy controls) were enrolled in this study. Conventional TTE study was performed in both patient and control groups. LV regional longitudinal strain (RLS) were determined and compared between the two study groups. Mean age was 10.4 ± 5 years in BTM group compared to 10.2 ± 5 years in control group (p = 0.876). Compared to control group, there was no significant difference in conventional TTE parameters except for indexed left atrium (LA) area and volume. LA was significantly larger in BTM children (27.59 ± 13.1 ml/m2 vs. 18.23 ± 4.33 ml/m2, p = 0.001). RLS was lower in anterior, septal and inferior walls in basal and middle segments of LV in BTM group while there was no significant difference in RLS in apical segment between the two groups (- 27.30 ± 5.1 vs.- 28.83 ± 4.33, p = 0.22). In asymptomatic BMT children with normal conventional TTE parameters, LS could be used for the detection of subclinical myocardial dysfunction.

Effect of E670G Polymorphism in PCSK9 Gene on the Risk and Severity of Coronary Heart Disease and Ischemic Stroke in a Tunisian Cohort.

The association of E670G (rs505151) polymorphism in PCSK9 gene with an increased risk of coronary artery disease (CAD) and ischemic stroke (IS) was reported in previous studies. We investigated the effect of the E670G (rs505151) on the risk of CAD and IS in a Tunisian cohort. Genotyping of the PCSK9 E670G was performed using polymerase chain reaction (PCR)-based restriction fragment length polymorphism (RFLP) and then confirmed by direct sequencing. The frequency of the 670G allele was significantly higher in the CAD than in the no-CAD subgroup (0.132 vs. 0.068, p = 0.030). As expected, the incidence of E670G was significantly important in IS subgroup than control group (0.122 vs. 0.073, p = 0.032). Furthermore in CAD patients, the 670G carriers showed significantly increased plasma total cholesterol and LDL-cholesterol levels compared to E670 carriers (6.78 [6.47-7.00] vs. 4.92 [4.02-5.46] mmol/l, p < 0.0001 and 4.60 [4.00-5.04] vs. 3.00 [2.22-3.70] mmol/l p = 0.001, respectively). The risk and severity of CAD were significantly increased in 670G carriers between no-CAD subgroup and CAD patients presenting a stenosis ≥50 % in two or three major coronary arteries (0.068 vs. 0.198, p = 0.001, OR = 3.39 [1.55-7.37]). The E670G polymorphism of the PCSK9 gene is mainly associated with a increased risk and severity of CAD and IS in Tunisian cohort.

Association between serum cystatin C levels and cardiovascular disease in type 2 diabetic patients.

Serum cystatin C concentration was recently reported as a marker of cardiovascular disease (CVD). In the present study, we evaluated the association between the increase of serum cystatin C levels and the risk of CVD in type 2 diabetes. 42 patients with type 2 diabetes were included in the present study; 27 of them have CVD. The control group consisted of 30 healthy adults. Cystatin C, creatinine, microalbuminuria and CRP were measured on Cobas 6000(TM). Cystatine C level was significantly higher in patients with CVD. A significant difference in serum cystatin C was found in patients with and without CVD among albuminuria. No difference in serum cystatin C levels was found according to number of affected vessels. A cystatin C level above 1.10 mg/L was associated with increase of risk of CVD with significant difference (OR = 42.52; IC 95% 1.455 to 1242.827 and p = 0.029). Our results suggested that the increase of serum cystatin C concentrations is a potential marker for CVD in diabetes.

Effect of mutations in LDLR and PCSK9 genes on phenotypic variability in Tunisian familial hypercholesterolemia patients.

BACKGROUND: Autosomal dominant hypercholesterolemia (ADH) is commonly caused by mutations in the low-density lipoprotein (LDL) receptor gene (LDLR), in the apolipoprotein B-100 gene (APOB), or in the proprotein convertase subtilisin kexine 9 gene (PCSK9). ADH subjects carrying a mutation in LDLR present highly variable plasma LDL-cholesterol (LDL-C). This variability might be due to environmental factors or the effect of some modifying genes such as PCSK9 and APOE. AIMS: We investigated the molecular basis of thirteen Tunisian ADH families and attempted to determine the impact of PCSK9 and APOE gene variations on LDL-cholesterol levels and on the variable phenotypic expression of the disease. METHODS AND RESULTS: Fifty six subjects were screened for mutations in the LDLR gene through direct sequencing. The causative mutation was found to segregate with the disease in each family and a new frameshift mutation, p.Met767CysfsX21, was identified in one family. The distribution of total- and LDL-cholesterol levels, adjusted for age and gender, among homozygous and heterozygous ADH patients varied widely. Within seven families, nine subjects presented low LDL-cholesterol levels despite carrying a mutation in the LDLR gene. To identify the molecular actors underlying this phenotypic variability, the PCSK9 gene was screened using direct sequencing and/or enzymatic restriction analysis, and the apo E genotypes were determined. A new missense variation (p.Pro174Ser) in the PCSK9 gene was identified and characterized as a new putative loss-of-function mutation. CONCLUSION: Genetic variations in PCSK9 and APOE genes could explain only part of the variability observed in the phenotypic expression in Tunisian ADH patients carrying mutations in the LDLR gene. Other genetic variants and environmental factors very probably act to fully explain this phenotypic variability.

Matrix metalloproteinase-1 and matrix metalloproteinase-12 gene polymorphisms and the outcome of coronary artery disease.

OBJECTIVES: In this study, we investigated the association between matrix metalloproteinase-1 (MMP-1) G-1607GG, MMP-12 A-82G and MMP-12 A1082G genotypes and haplotypes and the prognosis of coronary artery disease (CAD). METHODS: A total of 129 Tunisian patients with CAD were followed prospectively for a median of 2.5 years. Genotypes were determined by a PCR-based restriction fragment length polymorphism. Two endpoints were considered: restenosis and incidence of clinical vascular events (restenosis, myocardial infarction, stroke, cardiac death). RESULTS: Genotypes of MMP-1 G-1607GG, MMP-12 A-82G and MMP-12 A1082G were not associated with the incidence of restenosis or clinical events. Analysis of haplotypes consisting of alleles of MMP-1 G-1607GG and MMP-12 A1082G showed that the rate of clinical events was significantly higher in patients carrying the GG-A haplotype than those with other haplotypes (0.637 vs. 0.424, respectively, odds ratio=1.45; 95% confidence interval=1.04-2.04; P<0.05; P adjusted for multiple risk factors). However, after Bonferroni correction for multiple comparisons, this difference did not reach statistical significance (P=0.093), showing that there was a tendency for the association between the GG-A haplotype and future clinical events in patients with CAD. CONCLUSION: These findings showed a trend of the GG-A haplotype of MMP-1 G-1607GG/MMP-12 A1082G towards the prediction of future clinical events in patients with CAD and suggested a possible importance of these loci in the prediction of the prognosis of CAD. Studies with large sample size are warranted to better investigate this association, as MMP genotyping could aid in identifying patients who are likely to have unfavourable prognosis.

Increased phospholipid transfer protein activity associated with the impaired cellular cholesterol efflux in type 2 diabetic subjects with coronary artery disease.

Reverse cholesterol transport (RCT) is the pathway, by which the excess of cholesterol is removed from peripheral cells to the liver. An early step of RCT is the efflux of free cholesterol from cell membranes that is mediated by high-density lipoproteins (HDL). Phospholipid transfer protein (PLTP) transfers phospholipids between apolipoprotein-B-containing lipoproteins (i.e., chylomicrons and very low-density lipoproteins) and HDL. PLTP contributes to the HDL maturation and increases the ability of HDL to extract the cellular cholesterol. It is known that RCT is impaired in type 2 diabetic patients, especially when cardiovascular complication is associated with. In this study, we measured the serum capacity that promotes cellular cholesterol efflux and the plasma PLTP activity in type 2 diabetic patients with coronary artery disease (CAD) (n = 35), those without CAD (n = 24), and 35 healthy subjects as a sex- and age-matched control. In patients with CAD, plasma triglyceride level was higher compared to controls (p < 0.01) and HDL-cholesterol was lower (p < 0.01 vs control and the patients without CAD). In diabetic patients with or without CAD, PLTP activity was consistently increased, compared to controls, while cellular cholesterol efflux activity was decreased by 20% (p < 0.001) or 13.5% (p < 0.01), respectively. In conclusion, plasma PLTP activity was increased in type 2 diabetic patients with or without CAD, which could impair cellular cholesterol removal and might accelerate atherosclerosis in diabetic patients.

Association of left-heart dysfunction with severe exacerbation of chronic obstructive pulmonary disease: diagnostic performance of cardiac biomarkers.

RATIONALE: Cardiac biomarkers are used to distinguish acute dyspnea due to left-heart dysfunction from that of pulmonary origin. However, they have not been assessed in the specific setting of acute exacerbation of chronic obstructive pulmonary disease (AECOPD), where they might be released without left-heart impairment. OBJECTIVE: To assess the accuracy of troponin T and of amino-terminal pro-brain natriuretic peptide (NT-proBNP) in the diagnosis of AECOPD associated with left ventricular (LV) dysfunction. METHODS: Both biomarkers were measured in 148 consecutive patients on intensive care unit admission for AECOPD. A panel of physicians adjudicated blindly the cause of AECOPD to be unlikely, possibly associated, or definitely associated with LV dysfunction. MEASUREMENTS AND MAIN RESULTS: The final diagnosis was AECOPD definitely associated with acute left-heart dysfunction in 31.1%, possibly associated with LV dysfunction in 13.5%, and probably not associated with LV dysfunction in 55.4%. Both NT-proBNP and troponin T levels were significantly different among the three groups. The area under the receiver operating characteristic curve was greater for NT-proBNP (0.95 vs. 0.67). A cutoff of 1,000 pg/ml was accurate to rule out left-heart involvement in AECOPD (sensitivity, 94%; negative predictive value, 94%; negative likelihood ratio, 0.08). A cutoff of 2,500 pg/ml had the best operating characteristics to rule in the diagnosis (positive likelihood ratio, 5.16). Left-heart involvement in AECOPD was the only variable independently associated with increased secretion of NT-proBNP (odds ratio, 74; 95% confidence interval, 15-375; p = 0.0001). CONCLUSION: NT-proBNP and troponin T are useful in excluding AECOPD associated with left ventricular dysfunction. NT-proBNP was the more accurate of the two.