Effects of oral N-acetylcysteine on walking capacity, leg reactive hyperemia, and inflammatory and angiogenic mediators in patients with intermittent claudication.

Increased oxidative stress and inflammation contribute to impaired walking capacity and endothelial dysfunction in patients with intermittent claudication (IC). The goal of the study was to determine the effects of oral treatment with the antioxidant N-acetylcysteine (NAC) on walking capacity, leg postocclusive reactive hyperemia, circulating levels of inflammatory mediators, and whole blood expression of angiogenic mediators in patients with IC. Following a double-blinded randomized crossover design, 10 patients with IC received NAC (1,800 mg/day for 4 days plus 2,700 mg before the experimental session) and placebo (PLA) before undergoing a graded treadmill exercise test. Leg postocclusive reactive hyperemia was assessed before and after the test. Blood samples were taken before and after NAC or PLA ingestions and 5 and 30 min after the exercise test for the analysis of circulating inflammatory and angiogenic markers. Although NAC increased the plasma ratio of reduced to oxidized glutathione, there were no differences between experimental sessions for walking tolerance and postocclusive reactive hyperemia. Plasma concentrations of soluble vascular cell adhesion protein-1, monocyte chemotactic protein-1, and endothelin-1 increased similarly following maximal exercise after PLA and NAC (P < 0.001). Whole blood expression of pro-angiogenic microRNA-126 increased after maximal exercise in the PLA session, but treatment with NAC prevented this response. Similarly, exercise-induced changes in whole blood expression of VEGF, endothelial nitric oxide synthase and phosphatidylinositol 3-kinase R2 were blunted after NAC. In conclusion, oral NAC does not increase walking tolerance or leg blood flow in patients with IC. In addition, oral NAC prevents maximal exercise-induced increase in the expression of circulating microRNA-126 and other angiogenic mediators in patients with IC.

Vascular reactivity and ACE activity response to exercise training are modulated by the +9/-9 bradykinin B2 receptor gene functional polymorphism.

The bradykinin receptor B2 (BDKRB2) gene +9/-9 polymorphism has been associated with higher gene transcriptional activity, and characteristics of cardiovascular phenotypes and physical performance. We hypothesized that vasodilation and ACE activity response to exercise training is modulated by BDKRB2 gene. We genotyped 71 healthy volunteers were genotyped for the BDKRB2 gene polymorphism. Heart rate (HR), mean blood pressure (MBP), and forearm blood flow (FBF) were evaluated. Angiotensin-I converting enzyme (ACE) activity was measured by fluorescence. Aerobic training was performed for 16 wk. All variables were reassessed after completion of the training period. In pretraining period, HR, MBP, FBF, and forearm vascular conductance (FVC) were similar among all genotypes. After physical training, the FBF and the FVC response during handgrip exercise such as area under the curve were higher in -9/-9 carriers than the other two groups. However, there were no changes in HR and MBP for all three groups. In addition, in posttraining period the decrease in ACE activity was higher in the -9/-9 group than the other two groups. These results suggest that reflex muscle vasodilation and ACE activity in response to exercise training are modulated by BDKRB2 gene +9/-9 polymorphism in healthy individuals.

Exercise training improves muscle vasodilatation in individuals with T786C polymorphism of endothelial nitric oxide synthase gene.

Allele T at promoter region of the eNOS gene has been associated with an increase in coronary disease mortality, suggesting that this allele increases susceptibility for endothelial dysfunction. In contrast, exercise training improves endothelial function. Thus, we hypothesized that: 1) Muscle vasodilatation during exercise is attenuated in individuals homozygous for allele T, and 2) Exercise training improves muscle vasodilatation in response to exercise for TT genotype individuals. From 133 preselected healthy individuals genotyped for the T786C polymorphism, 72 participated in the study: TT (n = 37; age 27 ± 1 yr) and CT+CC (n = 35; age 26 ± 1 yr). Forearm blood flow (venous occlusion plethysmography) and blood pressure (oscillometric automatic cuff) were evaluated at rest and during 30% handgrip exercise. Exercise training consisted of three sessions per week for 18 wk, with intensity between anaerobic threshold and respiratory compensation point. Resting forearm vascular conductance (FVC, P = 0.17) and mean blood pressure (P = 0.70) were similar between groups. However, FVC responses during handgrip exercise were significantly lower in TT individuals compared with CT+CC individuals (0.39 ± 0.12 vs. 1.08 ± 0.27 units, P = 0.01). Exercise training significantly increased peak VO(2) in both groups, but resting FVC remained unchanged. This intervention significantly increased FVC response to handgrip exercise in TT individuals (P = 0.03), but not in CT+CC individuals (P = 0.49), leading to an equivalent FVC response between TT and CT+CC individuals (1.05 ± 0.18 vs. 1.59 ± 0.27 units, P = 0.27). In conclusion, exercise training improves muscle vasodilatation in response to exercise in TT genotype individuals, demonstrating that genetic variants influence the effects of interventions such as exercise training.

Influence of angiotensinogen and angiotensin-converting enzyme polymorphisms on cardiac hypertrophy and improvement on maximal aerobic capacity caused by exercise training.

BACKGROUND: The allele threonine (T) of the angiotensinogen has been associated with ventricular hypertrophy in hypertensive patients and soccer players. However, the long-term effect of physical exercise in healthy athletes carrying the T allele remains unknown. We investigated the influence of methionine (M) or T allele of the angiotensinogen and D or I allele of the angiotensin-converting enzyme on left-ventricular mass index (LVMI) and maximal aerobic capacity in young healthy individuals after long-term physical exercise training. DESIGN: Prospective clinical trial. METHODS: Eighty-three policemen aged between 20 and 35 years (mean+/-SD 26+/-4.5 years) were genotyped for the M235T gene angiotensinogen polymorphism (TT, n = 25; MM/MT, n = 58) and angiotensin-converting enzyme gene insertion/deletion (I/D) polymorphism (II, n = 18; DD/DI, n = 65). Left-ventricular morphology was evaluated by echocardiography and maximal aerobic capacity (VO2peak) by cardiopulmonary exercise test before and after 17 weeks of exercise training (50-80% VO2peak). RESULTS: Baseline VO2peak and LVMI were similar between TT and MM/MT groups, and II and DD/DI groups. Exercise training increased significantly and similarly VO2peak in homozygous TT and MM/MT individuals, and homozygous II and DD/DI individuals. In addition, exercise training increased significantly LVMI in TT and MM/MT individuals (76.5+/-3 vs. 86.7+/-4, P = 0.00001 and 76.2+/-2 vs. 81.4+/-2, P = 0.00001, respectively), and II and DD/DI individuals (77.7+/-4 vs. 81.5+/-4, P = 0.0001 and 76+/-2 vs. 83.5+/-2, P = 0.0001, respectively). However, LVMI in TT individuals was significantly greater than in MM/MT individuals (P = 0.04). LVMI was not different between II and DD/DI individuals. CONCLUSION: Left-ventricular hypertrophy caused by exercise training is exacerbated in homozygous TT individuals with angiotensinogen polymorphism.

Lack of evidence of association between MTHFR C677T polymorphism and congenital heart disease in a TDT study design.

INTRODUCTION: Hyperhomocysteinemia is frequently associated with congenital defects of the heart and neural tube. A common missense mutation in the MTHFR gene (C to T substitution at position 677 changing valine to alanine) produces a variant with reduced enzymatic action, resulting in higher plasma levels of homocysteine. The aim of this study is to investigate whether MTHFR C677T functional genetic variant is associated with an increased risk of congenital heart disease (CHD) development using a family-based case-control design and the Transmission Disequilibrium Test (TDT) approach. METHODS: We selected 91 consecutive patients with congenital heart disease for the study. From these patients we were able to obtain samples on 147 parents. The C677T polymorphism at the MTHFR gene was determined from each participant. RESULTS: A statistically significant association was disclosed in univariate analysis using a family-based case-control design (p<0.0001 assuming an additive genetic model, p<0.0001 assuming a dominant genetic model, and p=0.01 assuming a recessive genetic model). This association was explained by an increased frequency of the T allele in patients as compared to their fathers. However, by using a TDT approach a highly non-significant result was obtained and no association could be defined between this locus and congenital heart disease. CONCLUSIONS: We did not find sufficient evidence for an association between MTHFR C677T genotype and congenital heart disease in our study group. Previous reports on such association may be due to population genetic structure.

The influence of tumor necrosis factor -308 and C-reactive protein G1059C gene variants on serum concentration of C-reactive protein: evidence for an age-dependent association.

BACKGROUND: C-reactive protein (CRP) synthesis and activity are modulated both by genetic and environmental factors. Data about the influence of genetic factors upon CRP concentration are sparse. We evaluated the hypothesis that allele variations in the genes encoding the CRP and TNF-alpha genes could modulate hs-CRP serum concentration in the general population. METHODS: Six hundred and eighty-four asymptomatic Brazilian individuals, selected between July 1998 and July 2001, 295 men (43.1%) and 389 women (56.9%) were studied. Laboratory assessment included: serum glucose, cholesterol, triglycerides, thyroid-stimulating hormone, uric acid and CRP measured by a high-sensitivity assay (hs-CRP). TNF -308 and CRP G1059C genotypes were obtained through PCR amplification and restriction enzyme digestion. RESULTS: Serum concentrations of hs-CRP were distributed into population quartiles. There was no significant difference of hs-CRP serum concentration regarding CRP gene G1059C polymorphism. However, there was a tendency for higher hs-CRP serum levels in individuals harboring the TNFA2 allele in quartile 4. In addition, ANOVA factorial modeling using log-transformed hs-CRP serum level as the dependent variable disclosed a significant association between hs-CRP and the TNFA2 allele following stratification for age quartiles (p=0.01). Finally, the presence of TNFA2 allele in this age group increased the odds of being in the fourth quartile of hs-CRP concentration (p<0.05, OR=5.1). CONCLUSION: These findings suggest an association between a functional genetic variant of the TNF-alpha gene and hs-CRP levels at particular age groups.

NPHS2 R229Q functional variant is associated with microalbuminuria in the general population.

BACKGROUND: Microalbuminuria is a risk factor for developing end-stage renal disease and cardiovascular events. Mutations in NPHS2 have been shown to cause autosomal-recessive nephrotic syndrome. Recently, a functional polymorphism of this gene (R229Q) was described and associated with a maturity-onset form of nephrotic syndrome. We have investigated whether the carrier status of this novel genetic variant is associated with microalbuminuria in individuals from the general population. METHODS: Demographic, cardiovascular risk factors, and renal phenotypes in 1577 individuals from a cross-sectional-based study were collected following the general guidelines of the WHO-MONICA project (monitoring trends and determinants in cardiovascular diseases). Blood and urine samples were obtained. Microalbuminuria was determined using a semiquantitative protocol, and DNA was extracted from peripheral lymphocytes. RESULTS: A strong association was found between the 229Q allele and microalbuminuria (P= 0.008). The presence of the 229Q allele was still associated with a 2.77-fold increased risk of presenting microalbuminuria even after adjustment for age, ethnicity, hypertension, obesity, and diabetes in a multiple logistic regression model. In addition, a statistically significant interaction was identified between the presence of the 229Q allele and body mass index (BMI) (P= 0.01), suggesting an additive effect between the 229Q allele and other risk factors for microalbuminuria. CONCLUSION: These data have important implications for the understanding of microalbuminuria in the general population and may contribute to better ways of disease prediction and prevention.

Beta2 adrenoceptor functional gene variants, obesity, and blood pressure level interactions in the general population.

We investigated the association of beta2 adrenoceptor functional gene variants (Arg16Gly, Gln27Glu, and Thr164Ile polymorphisms), obesity phenotypes, and blood pressure levels in a large, ethnically mixed urban population. The individuals (n=1576) were randomly selected for a cross-sectional study of cardiovascular risk factors in Vitória, Brazil. Statistically significant associations among systolic blood pressure and the Arg16Gly and Thr164Ile variants were identified in univariate analysis. The Gly16/Gly16 genotype was still associated with systolic blood pressure (SBP) in multivariate analysis adjusting for age, gender, ethnicity, total cholesterol, diabetes, and body mass index (BMI) (P=0.01). The Arg16 allele was the only genotypic variable associated with BMI, and, in a dominant model, it remained associated with an increased BMI even after adjustment for age, gender, ethnicity, triglycerides, HDL cholesterol, LDL cholesterol, diabetes, and hypertension status (P=0.02). Although the different polymorphisms did not interact in the determination of SBP, a significant interaction with BMI (P=0.02), not through linkage disequilibrium, was identified between the Gln27Glu and the Thr164Ile variants. Furthermore, a significant interaction among the Arg16Gly polymorphism and BMI (P=0.036) and waist-hip ratio (P=0.003) in determining SBP was disclosed by ANOVA factorial modeling, with SBP used as the dependent variable. An interaction between the Thr164Ile polymorphism and waist-hip ratio was also identified (P=0.018). Finally, multiple logistic regression models showed a 1.48-fold increase in the risk of hypertension in individuals harboring the Gly16/Gly16 genotype and a 1.31-fold (P=0.01) and a 1.49-fold (P=0.003) increased risk of obesity in individuals harboring the Gln27/Gln27 genotype or the presence of the Arg16 allele, respectively. Taken together, these data provide evidence for a strong but complex relation between beta-adrenoceptor gene variants, hypertension, and obesity.

Angiotensinogen 235T allele "dosage" is associated with blood pressure phenotypes.

The genetic mechanisms underlying interindividual blood pressure variation among humans may reflect, at least in part, clustering of functional gene variants belonging to complex blood pressure control systems. In this study, we investigated the association of specific functional gene variants of the renin-angiotensin system, ACE (I/D) and angiotensinogen (M/T) genes, with blood pressure phenotypes (systolic, mean, diastolic, and pulse pressure), in an ethnically mixed urban population in Brazil. Individuals (n=1421) were randomly selected from the general population of the Vitoria City Metropolitan area. Neither gender, age, smoking status, total cholesterol, triglycerides, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol, or diabetes was associated with ACE or AGT polymorphism in univariate analysis. No association was found between ACE variants and blood pressure phenotypes. However, a statistically significant association was revealed between the AGT 235T variant and all blood pressure phenotypes, consistent with an additive/codominant mode of action even after adjustment for age and gender (P<0.01). Genotypic analysis contemplating both ACE and AGT variants in the same model did not show any significant interaction between both genetic polymorphisms. In addition, the AGT 235T allele was significantly associated with hypertension in a recessive model, which remained as an independent risk factor for hypertension even after adjustment for age, gender, and ethnicity (OR, 1.33; 95% CI, 1.04 to 1.70). Taken together, these data indicate a linear relation between AGT 235T allele number ("dosage") and blood pressure in an ethnically mixed urban population and confirmed its role as an independent risk factor for hypertension for men and women when in homozygosity.