Endothelial nitric oxide synthase genetic variation and essential hypertension risk in Han Chinese: the Fangshan study

Genetic Polymorphisms of Endothelial Nitric Oxide Synthase Associated with Hypertension and Blood Homocysteine Levels

Purpose

Endothelial dysfunction is a key mechanism in the development of hypertension and is closely linked to impairment of endothelial nitric oxide synthase (eNOS) and hyperhomocysteinemia. Genetic polymorphisms of eNOS (rs1799983 and rs2070744) are strongly associated with the risk of hypertension in individuals of Asian ethnicities. This study aimed to investigate the relationship between these polymorphisms and the risk of hypertension associated with homocysteine levels.

Participants and Methods

For this cross-sectional study, we enrolled 370 Thai men aged 40-60 years from the Electricity Generating Authority of Thailand cohort study for both variants genotyping by TaqMan allelic discrimination analysis. Clinical, anthropometric, and biochemical parameters were also analyzed.

Results

In the high blood pressure group (n = 267), systolic and diastolic blood pressure and triglyceride levels were higher in those with homocysteine levels ≥ 15 µmol/L than in those with homocysteine levels < 15 µmol/L (p < 0.05). Significant risk of hypertension was found in GG and GT of rs1799983 (G894T), and in TT and TC of rs2070744 (T-786C), with higher ORs in heterozygous genotypes (all p values < 0.05). Further evaluation of the interactions between SNPs and HCY revealed that individuals with the GT or TC genotype, together with hyperhomocysteinemia, had an increased risk of hypertension (all p<0.05).

Conclusion

eNOS variants rs1799983 and rs2070744 may be risk factors for hypertension linked to hyperhomocysteinemia. These findings provide potentially useful healthcare strategies for the management of hypertension.

The Role of Genetic Polymorphism in the Formation of Arterial Hypertension, Type 2 Diabetes and their Comorbidity

BACKGROUND

Hereditary component plays a significant role in the formation of insulin resistance (IR) - one of the pathogenetic links of arterial hypertension (AH) and type 2 diabetes mellitus (DM2). However, the genetic predisposition to IR can not be realized and does not manifest itself clinically in the absence of appropriate factors of the environment (excessive nutrition, low physical activity, etc.).

OBJECTIVE

The review summarizes the results of studies which describe the contribution of genetic polymorphism to the formation and progression of AH, DM2 and their comorbidity in various populations.

RESULTS

In many studies, it has been established that genetic polymorphism of candidate genes is influenced by the formation, course and complication of AH and DM2. According to research data, the modulating effect of polymorphism of some genetic markers of AH and DM2 on metabolism and hemodynamics has been established. The results of numerous studies have shown a higher frequency of occurrence of AH and DM2, as well as their more severe course with adverse genetic polymorphisms. At the same time, the role of genetic polymorphism in the formation of AH and DM2 differs in different populations.

CONCLUSION

Contradictory data on the influence of gene polymorphisms on the formation of AH and DM2 in different populations, as well as a small number of studies on the combined effects of several polymorphisms on the formation of comorbidity, determine the continuation of research in this direction.

Effect of L-citrulline supplementation on blood pressure: a systematic review and meta-analysis of randomized controlled trials

The objective of this study was to systematically investigate the efficacy of oral L-citrulline supplementation on systolic and diastolic blood pressure. Studies were identified by a search of electronic databases from inception to April 2018, and combined and stratified analyses were used. Fifteen trials were identified, and data from 424 participants were included. Pooled analysis showed significant reductions in systolic blood pressure by -7.54 mmHg (95% confidence interval (CI): -9.44, -5.63; P < 0.001, I² = 14%) and diastolic blood pressure by -3.77 mmHg (95% CI: -5.67, -1.86, P < 0.001, I² = 42%) following oral supplementation of L-citrulline or a watermelon extract. No changes were detected in controls. Significant heterogeneity (I² = 42%, P = 0.04) was found for diastolic blood pressure, and subgroup analysis showed significant improvements in systolic and diastolic blood pressure, particularly for study durations: ≥6 weeks, lower doses: ≤4 g/day, and in participants with higher baseline values: ≥130/85 mmHg. In conclusion, L-citrulline improves systolic and diastolic blood pressure and may be more efficacious in pre-hypertensive and hypertensive populations.

The association between endothelial nitric oxide synthase gene G894T polymorphism and hypertension in Han Chinese: a case-control study and an updated meta-analysis

Abstract Background: The G894T (rs1799983) polymorphism in endothelial nitric oxide synthase (eNOS/NOS3) gene has been implicated in susceptibility to essential hypertension (EH) in some studies, but no clear consensus has been reached in the Chinese population.

AIMS

This study aimed to investigate the association of the G894T polymorphism and EH in Han Chinese.

SUBJECTS AND METHODS

First, a case-control study was performed involving 1525 subjects in northern Han Chinese to study the association between G894T variants and EH and then a meta-analysis was conducted of all available studies in Han Chinese. A total of 25 studies comprising 13,443 subjects were finally included in this meta-analysis.

RESULTS

The present case-control study failed to show significant association of G894T variant with EH in northern Han Chinese. The subsequent meta-analysis showed that this polymorphism might be associated with EH in Han Chinese (p < 0.001, OR = 1.32), especially in southern Han Chinese (p < 0.001, OR = 1.59), but not in northern Han Chinese (p = 0.12, OR = 1.16). The meta-regression analysis suggested that the geographic difference of subjects was related to heterogeneity (p = 0.029).

CONCLUSIONS

The relationship between the G894T polymorphism and hypertension in Han Chinese may be attributed to the difference in geographic background of subjects. It is necessary to carry out further research with a large sample size and focusing on gene-environment interactions.

An updated meta-analysis of endothelial nitric oxide synthase gene: three well-characterized polymorphisms with hypertension

Background

Numerous individually underpowered association studies have been conducted on endothelial nitric oxide synthase (eNOS) genetic variants across different ethnic populations, however, the results are often irreproducible. We therefore aimed to meta-analyze three eNOS widely-evaluated polymorphisms, G894T (rs1799983) in exon 7, 4b/a in intron 4, and T−786C (rs2070744) in promoter region, in association with hypertension from both English and Chinese publications, while addressing between-study heterogeneity and publication bias.

Methods

Data were analyzed using Stata software (version 11.0), and random-effects model was applied irrespective of between-study heterogeneity, which was evaluated by subgroup and meta-regression analyses. Publication bias was weighed using the Egger's test and funnel plot.

Results

There were total 19284/26003 cases/controls for G894T, and 6890/6858 for 4b/a, and 5346/6392 for T−786C polymorphism. Overall comparison of allele 894T with 894G in all study populations yielded a 16% increased risk for hypertension (odds ratio [OR] = 1.16; 95% confidence interval [95% CI]: 1.07–1.27; P = 0.001), and particularly a 32% increased risk (95% CI: 1.16–1.52; P<0.0005) in Asians and a 40% increased risk (95% CI: 1.19–1.65; P<0.0005) in Chinese. Further subgroup analyses suggested that published languages accounted for the heterogeneity for G894T polymorphism. The overall OR of allele 4a versus 4b was 1.29 (95% CI: 1.13–1.46; P<0.0005) in all study populations, and this estimate was potentiated in Asians (OR = 1.42; 95% CI: 1.16–1.72; P<0.0005). For T−786C, ethnicity-stratified analyses suggested a significantly increased risk for −786C allele (OR = 1.25; 95% CI: 1.06–1.47; P = 0.007) and −786CC genotype (OR = 1.69; 95% CI: 1.20–2.38; P = 0.003) in Whites. As an aside, the aforementioned risk estimates reached significance after Bonferroni correction. Finally, meta-regression analysis on other study-level covariates failed to provide any significance for all polymorphisms.

Conclusion

We, via a comprehensive meta-analysis, ascertained the role of eNOS G894T and 4b/a polymorphisms on hypertension in Asians, and T−786C polymorphism in Whites.

Variants in genes involved in functional pathways associated with hypertension in African Americans

Essential hypertension (HBP) is a complex trait with a substantial heritable component. The purpose of this study was to determine if variants in the G-protein coupled receptor Kinase-4 (GRK4), nitric oxide synthase-3 (NOS3), or angiotensin converting enzyme (ACE) genes are associated singly or through complex interactions, with HBP in African Americans aged 18-49 years. TaqMan Assays were used for genotyping the GRK4 and NOS3 variants. The ACE I/D variant was obtained by polymerase chain reaction and electrophoresis. Allelic association tests were performed for the five markers using PLINK. Logistic regression models were fitted to investigate associations between HBP status and the genetic markers. Multilocus analyses were also conducted. The study included 173 hypertensives and 239 normotensives, with stratification into obese and nonobese groups. The GRK4 A486V variant was negatively associated with HBP in the nonobese group (p = 0.048). The TT/CT genotype of GRK4 A486V was associated with decreased risk for HBP relative to the CC genotype after adjusting for age, sex, and body mass index (p = 0.028). Individuals having at least one NOS3 A allele and GRK4 R65L genotype GG had odds of HBP of 2.97 relative to GG homozygotes for NOS3 and GRK4 R65L. These results show very modest effects and do not fully replicate previous studies.

Association of renin BglI polymphism with essential hypertension: a meta-analysis involving 1811 cases and 1626 controls

In an effort to clarify association of an intronic polymorphism BglI in a renin gene with essential hypertension, we performed a meta-analysis of the case-control association studies. Publications in the English language and human subjects were searched in PubMed and EMBASE as of July 10, 2009. A fixed-effects model was applied to pool data in the absence of between-studies heterogeneity, and a random-effects model otherwise. Data and study quality were assessed in duplicate. Publication bias was evaluated using the fail-safe number. From three studies with four populations including 1811 patients with essential hypertension and 1626 controls, we found a significant association of renin BglI B with an increased risk for essential hypertension (OR = 1.25; 95% CI, 1.11 to 1.41; P = 0.0002). In addition, significance persisted after assuming the dominant (OR = 1.30; 95% CI, 1.13 to 1.51; P = 0.0004) mode of inheritance, while no significance was observed for the recessive mode (OR = 1.46; 95% CI, 0.82 to 2.60; P = 0.20). The fail-safe number at the level of 0.05 supported these significant associations. In sum, our meta-analysis expands previous findings by showing that the presence of renin BglI B allele is associated with an increased risk in developing essential hypertension, and this effect might act in a dominant mode of inheritance. Further studies are warranted to fully address questions about the etiologic mechanisms of this positive association.

Association of the angiotensin II type I receptor gene +1166 A>C polymorphism with hypertension risk: evidence from a meta-analysis of 16474 subjects

Mounting evidence suggests the potential susceptibility of individuals with a mutation in the angiotensin II type I receptor (AT1R) gene to hypertension. One polymorphism, +1166 A>C, has been extensively studied, but the results have often been irreproducible. We therefore aimed to meta-analyze all available case-control studies from the English language literature to explore the association of this polymorphism with hypertension. A total of 22 studies with 24 populations involving 8249 patients and 8225 controls were identified as of 25 February 2010. A random-effects model was performed regardless of the between-study heterogeneity. The study quality was assessed in duplicate. The data were analyzed using RevMan software (version 5.0.23). Overall, the presence of the +1166 C allele significantly conferred an increased risk of hypertension (odds ratio (OR)=1.14; 95% confidence interval, 1.00-1.30; P=0.05). Under the assumption of three genetic modes of inheritance, an elevated hypertension risk was observed for each comparison (codominant: AC vs. AA, OR=1.10 (P=0.20) and CC vs. AA, OR=1.21 (P=0.36); dominant: OR=1.13 (P=0.09); recessive: OR=1.21 (P=0.36)). Upon stratification by study design, more obvious associations were observed for the population-based design, whereas there were no changes in direction and only slight changes in magnitude upon stratification by sample size and geographical area. No publication biases were indicated by the fail-safe number. Our study pooled previous findings and showed that the AT1R +1166 C allele conferred an increased risk of hypertension. We suggest that confirmation in a large, well-designed study or from functional aspects of this polymorphism is critical.