Association of the -262C/T polymorphism in the catalase gene promoter and the C242T polymorphism of the NADPH oxidase P22phox gene with essential arterial hypertension in patients with diabetes mellitus type 2

Non-Alcoholic Fatty Liver Disease Is Associated with a Decreased Catalase (CAT) Level, CT Genotypes and the T Allele of the -262 C/T CAT Polymorphism

BACKGROUND

It is well known that oxidative stress plays an important role in the development of non-alcoholic fatty liver disease (NAFLD). It has been suggested that an insufficient antioxidant defense system composed of antioxidant enzymes, including catalase (CAT) and nonenzymatic molecules, is a key factor triggering oxidative damage in the progression of liver disease. Therefore, the aim of our study was to assess whether the level of CAT and -262 C/T polymorphism in the promoter of CAT (rs1001179) are associated with NAFLD.

METHODS

In total, 281 adults (152/129 female/male, aged 65.61 ± 10.44 years) were included in the study. The patients were assigned to an NAFLD group (n = 139) or a group without NAFLD (n = 142) based on the results of an ultrasound, the Hepatic Steatosis Index, and the Fatty Liver Index (FLI). CAT levels were determined using an ELISA test, and genomic DNA was extracted via the standard phenol/chloroform-based method and genotyped via RFLP-PCR.

RESULTS

The CAT level was decreased in NAFLD patients (p < 0.001), and an ROC analysis revealed that a CAT level lower than 473.55 U/L significantly increases the risk of NAFLD. In turn, genotyping showed that the CT genotype and the T allele of -262 C/T CAT polymorphism elevate the risk of NAFLD. The diminished CAT level in the NAFLD group correlated with increased FLI, waist circumference and female gender.

CONCLUSION

The obtained results support observations that oxidative damage associated with NAFLD may be the result of a decreased CAT level as a part of the antioxidant defense system.

Myeloperoxidase and CYBA genetic variants in polycystic ovary syndrome

BACKGROUND

Oxidative stress plays a pivotal role in the pathogenesis of polycystic ovary syndrome (PCOS). Genetic variations in myeloperoxidase (MPO; G-463A) and NADPH oxidase p22phox subunit (CYBA; C242T) cause inter-individual variability in enzyme activities. Here, we investigated the associations between MPO activity and the MPO G-463A and CYBA C242T polymorphisms in Chinese women with PCOS.

METHODS

This case-control study included 1003 patients with PCOS and 810 controls. The G-463A and C242T polymorphisms were detected by polymerase chain reaction and restriction analysis, and clinical, hormonal, metabolic and oxidative stress parameters and MPO activity were analysed.

RESULTS

The frequencies of the GA + AA genotype and A allele frequency of the MPO G-463A polymorphism were significantly higher in the PCOS group than in the control group. Logistic regression analysis showed that the MPO-463A allele is a risk factor for PCOS (OR = 1.261, 95% CI: 1.042-1.526, P = .017). Patients with the AA genotype tended to have higher plasma MPO activity than those with the GG genotype. No statistical significance was found in the genotype and allele frequencies of the CYBA C242T polymorphism between the PCOS and control groups. However, we demonstrated that the coexistence of the MPO A allele (GA + AA genotypes) and the CYBA CC genotype was associated with an increased risk of PCOS when compared with the wild-type GG/CC genotypes (OR = 1.302, 95% CI: 1.030-1.646, P = .027).

CONCLUSION

The MPO G-463A variant, but not CYBA C242T variant, is associated with a risk of PCOS in Chinese women.

Association between p22PHOX gene C242T polymorphism and hypertension in end-stage kidney disease patients

Oxidative stress plays an important role in hypertension associated vascular damage. It is mediated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation. The C242T polymorphism in the p22PHOX gene encoding essential subunit of NADPH oxidase was associated with CVD, hypertension, and endothelial function. The aim of this study was to assess a potential association of C242T polymorphism with hypertension in end-stage kidney disease (ESKD) patients. DNA samples from 495 patients were genotyped by polymerase chain reaction (PCR) with subsequent cleavage with Rsa I restriction endonuclease. There were no significant differences in genotype and allele distribution between ESKD patients and healthy controls. When patients were stratified into male and female subgroups, there were no differences in the frequency of the T allele (0.35 and 0.34, respectively). Genotype and allele frequencies were also comparable between HY+ and HY- subgroups. We analyzed whether there were any differences between genders in the effect of C242T polymorphism on the presence of hypertension by comparing HY+ males with normotensive males and HY+ females with normotensive females. No difference in polymorphism distribution was found in female subgroup. The significant differences were observed in males. In HY+ subgroup, the frequencies of T allele and TT genotype were higher than in HY- males, with OR 1.91 (1.31-2.8), p = 0.0008 and OR 4.2 (1.67-10.6), p = 0.002, respectively. In conclusion, this is the first study to demonstrate significant association of the p22PHOX gene polymorphism with hypertension in male ESKD patients, with T allele as a risk factor for hypertension.

Genetic polymorphisms associated with reactive oxygen species and blood pressure regulation

Hypertension is the most prevalent cause of cardiovascular disease and kidney failure, but only about 50% of patients achieve adequate blood pressure control, in part, due to inter-individual genetic variations in the response to antihypertensive medication. Significant strides have been made toward the understanding of the role of reactive oxygen species (ROS) in the regulation of the cardiovascular system. However, the role of ROS in human hypertension is still unclear. Polymorphisms of some genes involved in the regulation of ROS production are associated with hypertension, suggesting their potential influence on blood pressure control and response to antihypertensive medication. This review provides an update on the genes associated with the regulation of ROS production in hypertension and discusses the controversies on the use of antioxidants in the treatment of hypertension, including the antioxidant effects of antihypertensive drugs.

Vulnerability of white matter tracts and cognition to the SOD2 polymorphism: A preliminary study of antioxidant defense genes in brain aging

Oxidative stress is a key mechanism of the aging process that can cause damage to brain white matter and cognitive functions. Polymorphisms in the superoxide dismutase 2 (SOD2) and catalase (CAT) genes have been associated with abnormalities in antioxidant enzyme activity in the aging brain, suggesting a risk for enhanced oxidative damage to white matter and cognition among older individuals with these genetic variants. The present study compared differences in white matter microstructure and cognition among 96 older adults with and without genetic risk factors of SOD2 (rs4880) and CAT (rs1001179). Results revealed higher radial diffusivity in the anterior thalamic radiation among SOD2 CC genotypes compared to CT/TT genotypes. Further, the CC genotype moderated the relationship between the hippocampal cingulum and processing speed, though this did not survive multiple test correction. The CAT polymorphism was not associated with brain outcomes in this cohort. These results suggest that the CC genotype of SOD2 is an important genetic marker of suboptimal brain aging in healthy individuals.

Heterozygote Advantage of the rs3794624 Polymorphism in CYBA for Resistance to Tuberculosis in Two Chinese Populations

Phagocyte Nicotinamide Adenine Dinucleotide Phosphate (NADPH) oxidase complex is a key enzyme that catalyzes the production of reactive oxygen species, which mediate oxygen-dependent killing of microorganisms, such as Mycobacterium tuberculosis. P22phox, encoded by CYBA, is the key regulatory subunit of NADPH oxidase. Our study aimed to investigate the association of CYBA polymorphisms with susceptibility to tuberculosis. Three SNPs (rs9932581, rs3794624 and rs4673) were genotyped in the discovery cohort composed of Chinese Han individuals. We found that the A allele of rs3794624 was a significant protective factor against tuberculosis (GA vs. GG: OR = 0.74, 95% CI 0.57-0.96; GA vs. GG+AA: OR = 0.73, 95% CI 0.56-0.95), which was then replicated in the Chinese Tibetan population (GA vs. GG: OR = 0.68, 95% CI 0.51-0.92; AA+GA vs. GG: OR = 0.70, 95% CI 0.52-0.93; GA vs. GG+AA: OR = 0.68, 95% CI 0.51-0.92). Meta-analysis including both cohorts identified overdominance as the best genetic model and provided robust evidence for the protective effect of the rs3794624 GA genotype against tuberculosis without any evidence of heterogeneity (GA vs. GG+AA: OR = 0.71, 95% CI 0.58-0.86). Our study found an association between the GA genotype of rs3794624 in CYBA with decreased tuberculosis susceptibility in two Chinese populations. Further analyses are needed to reveal the potential function of this SNP.

Angiotensin II and vascular injury

Vascular injury, characterized by endothelial dysfunction, structural remodelling, inflammation and fibrosis, plays an important role in cardiovascular diseases. Cellular processes underlying this include altered vascular smooth muscle cell (VSMC) growth/apoptosis, fibrosis, increased contractility and vascular calcification. Associated with these events is VSMC differentiation and phenotypic switching from a contractile to a proliferative/secretory phenotype. Inflammation, associated with macrophage infiltration and increased expression of redox-sensitive pro-inflammatory genes, also contributes to vascular remodelling. Among the many factors involved in vascular injury is Ang II. Ang II, previously thought to be the sole biologically active downstream peptide of the renin-angiotensin system (RAS), is converted to smaller peptides, [Ang III, Ang IV, Ang-(1-7)], that are functional and that modulate vascular tone and structure. The actions of Ang II are mediated via signalling pathways activated upon binding to AT1R and AT2R. AT1R activation induces effects through PLC-IP3-DAG, MAP kinases, tyrosine kinases, tyrosine phosphatases and RhoA/Rho kinase. Ang II elicits many of its (patho)physiological actions by stimulating reactive oxygen species (ROS) generation through activation of vascular NAD(P)H oxidase (Nox). ROS in turn influence redox-sensitive signalling molecules. Here we discuss the role of Ang II in vascular injury, focusing on molecular mechanisms and cellular processes. Implications in vascular remodelling, inflammation, calcification and atherosclerosis are highlighted.

Endothelial dysfunction in experimental models of arterial hypertension: cause or consequence?

Hypertension is a risk factor for other cardiovascular diseases and endothelial dysfunction was found in humans as well as in various commonly employed animal experimental models of arterial hypertension. Data from the literature indicate that, in general, endothelial dysfunction would not be the cause of experimental hypertension and may rather be secondary, that is, resulting from high blood pressure (BP). The initial mechanism of endothelial dysfunction itself may be associated with a lack of endothelium-derived relaxing factors (mainly nitric oxide) and/or accentuation of various endothelium-derived constricting factors. The involvement and role of endothelium-derived factors in the development of endothelial dysfunction in individual experimental models of hypertension may vary, depending on the triggering stimulus, strain, age, and vascular bed investigated. This brief review was focused on the participation of endothelial dysfunction, individual endothelium-derived factors, and their mechanisms of action in the development of high BP in the most frequently used rodent experimental models of arterial hypertension, including nitric oxide deficient models, spontaneous (pre)hypertension, stress-induced hypertension, and selected pharmacological and diet-induced models.

Endothelial dysfunction in experimental models of arterial hypertension: cause or consequence?

Hypertension is a risk factor for other cardiovascular diseases and endothelial dysfunction was found in humans as well as in various commonly employed animal experimental models of arterial hypertension. Data from the literature indicate that, in general, endothelial dysfunction would not be the cause of experimental hypertension and may rather be secondary, that is, resulting from high blood pressure (BP). The initial mechanism of endothelial dysfunction itself may be associated with a lack of endothelium-derived relaxing factors (mainly nitric oxide) and/or accentuation of various endothelium-derived constricting factors. The involvement and role of endothelium-derived factors in the development of endothelial dysfunction in individual experimental models of hypertension may vary, depending on the triggering stimulus, strain, age, and vascular bed investigated. This brief review was focused on the participation of endothelial dysfunction, individual endothelium-derived factors, and their mechanisms of action in the development of high BP in the most frequently used rodent experimental models of arterial hypertension, including nitric oxide deficient models, spontaneous (pre)hypertension, stress-induced hypertension, and selected pharmacological and diet-induced models.

The A930G polymorphism ofP22phox (CYBA) gene but not C242T variation is associated with hypertension: a meta-analysis

Background

Recently, it has been reported that the A930G and C242T polymorphisms within p22phox (CYBA) gene are involved in the pathogenesis of hypertension. However, the results remain controversial. Furthermore, no previous meta-analysis has been conducted to evaluate the relationship between the A930G and C242T polymorphisms and hypertension. Therefore, we performed this meta-analysis to clarify these controversies.

Objective and Methods

All of the included articles were retrieved from the PubMed and Embase databases, as well as the CNKI, CBM, Chongqing VIP and Wan Fang databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Odds ratios (OR) with corresponding 95% confidence intervals (CI) were used to assess the strength of the association. Accounting for heterogeneity, a fixed or random effects model was respectively adopted. Heterogeneity was checked using the Q test and the I² statistic. A cumulative meta-analysis was conducted to estimate the tendency of pooled OR. Funnel plots and Egger’s tests were performed to test for possible publication bias.

Results

Five articles on A930G with 2003 cases/2434 controls and eight articles on C242T with 2644 cases/1967 controls were identified. A significant association of A930G polymorphisms with the risk of hypertension was found in the dominant model (OR=0.59, 95% CI: 0.38–0.92, p=0.021) and allelic model (OR=0.66, 95% CI: 0.46–0.95, p=0.024). In the stratified analysis, a significant association could be found among the hospital-based and population-based studies. However, no evidence of a significant association of the C242T polymorphism with hypertension was found in the overall analysis and subgroup analysis.

Conclusions

This meta-analysis indicates that the A930G polymorphism, but not the C242T variation, might be a protective factor for hypertension.