Alpha-adducin Gly460Trp polymorphism and essential hypertension in Korea

ADD1 Single Nucleotide Polymorphisms Are Associated With Essential Hypertension Among Han and Mongolian Population in Inner Mongolia Area

Aldosterone synthase (CYP11B2) and α-adducing (ADD1) are candidate genes that play key roles during essential hypertension (EH) incidence. However, the association between their genetic mutations and the risk of EH is unclear. The present study investigated specific single nucleotide polymorphisms (SNPs) from CYP11B2 and ADD1, and their potential role as risk factors for EH based on 423 Mongolian and 410 Han people in Inner Mongolia province. In the allelic model, people with ADD1 rs2239728-A presented a 0.74-fold risk than rs2239728-C, whereas the ADD1 rs4961-T was associated with a 1.37-fold higher risk than allele G in the Han population. The genetic model reported that the rs2239728-A carrier (AA + AC) was 0.59-fold lower than the CC carrier, whereas the rs4961-G carrier (GG + GT) was 0.59-fold lower than the TT carrier in the dominant model. After gender adjustment, people with rs2239728-A was a 0.63-fold risk than –C in EH, but the rs4961-T carrier was associated with a 1.63-times higher risk than –G in females. Haplotype analysis showed that GCCT was associated with essential hypertension in the Han population, and it was a risk factor for EH. Our identification reported novel SNPs of ADD1 with protective significance for EH among females in the Chinese Han population, together with its haplotype GCCT as a risk factor for EH.

The Association between Gly460Trp-Polymorphism of Alpha-Adducin 1 Gene (ADD1) and Arterial Hypertension Development in Ukrainian Population

Arterial hypertension (AH) belongs to the diseases with genetic predisposition that determines the necessity of research on the genetic component's influence on this disease development. It is suggested that one of the salt-sensitive arterial hypertension potential markers may be the alpha-adducin gene because its protein product is involved in the ion transport regulation in the renal epithelium. Thus, the aim of the study was to investigate the association between ADD1 Gly460Trp-polymorphism and the AH development risk among patients with different risk factors in the Ukrainian population. The study included 232 Ukrainians: 120 patients with diagnosed arterial hypertension and 112 practically healthy individuals. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis was used for ADD1 Gly460Trp-polymorphism genotyping. The ADD1 Gly460Trp-polymorphic locus is an important predictor of arterial hypertension development in the Ukrainian population, but other nongenetic factors should be considered in further studies.

A Review of the Epidemiological Evidence for Adducin Family Gene Polymorphisms and Hypertension

Hypertension is one of the most common cardiovascular diseases that seriously endangers human health and has become a significant public health problem worldwide. In the vast majority of patients, the cause of hypertension is unknown, called essential hypertension (EH), accounting for more than 95% of total hypertension. Epidemiological and genetic studies of humans and animals provide strong evidence of a causal relationship between high salt intake and hypertension. Adducin is one of the important candidate genes for essential hypertension. Adducin is a heterodimeric or heterotetrameric protein that consists of α, β, and γ subunits; the three subunits are encoded by genes (ADD1, ADD2, and ADD3) that map to three different chromosomes. Animal model experiments and clinical studies suggest that changes in single-nucleotide polymorphisms (SNPs) at part of the adducin family gene increase the Na⁺-K⁺-ATPase activity of the renal tubular basement membrane and increase the reabsorption of Na⁺ by renal tubular epithelial cells, which may cause hypertension. This review makes a summary on the structure, function, and mechanism of adducin and the role of adducin on the onset of EH, providing a basis for the early screening, prevention, and treatment of EH.

Alpha Adducin (ADD1) Gene Polymorphism and New Onset of Diabetes Under the Influence of Selective Antihypertensive Therapy in Essential Hypertension

BACKGROUND

Different antihypertensive therapies (especially diuretics) are reported to induce the new onset of diabetes in some hypertensive patients. α-adducin-1 (ADD1) gene is salt sensitive gene which has its role in etiology of hypertension via salt sensitivity. Therefore, the G460T polymorphism of ADD1 gene may be associated with new onset of diabetes under the influence of diuretic and other antihypertensive therapies.

AIM

To assess the correlation between genetic polymorphism (ADD1 G460T polymorphism) and glycaemic disturbance under influence of diuretic and other antihypertensive drug therapies.

MATERIALS AND METHODS

We recruited study subjects, 270 normotensive as control (150 male and 120 females), 270 hypertensive patients (95 male and 175 females) and 240 hypertensive with new onset of diabetes patients (80 male and 160 females). All study samples were genotyped for ADD1 polymorphic alleles and analyzed the relationship between different genotypes with respect to anthropometric and clinical parameters along with drug therapies.

RESULTS

Clinical and anthropometric parameters (such as age, SBP, DBP, FBG, height, weight, WC, HP, W/H ratio, and BMI) of study population were found highly statistically significant (p<0.05) at base value. Further, genotype wise comparison of all the above parameters revealed most of them as non-significant (p>0.05). Whereas, comparison between genotype and different antihypertensive drug therapy of hypertensive patients, specifically, diuretic therapy as mono in male (p=0.0227) and female (p=0.0292) and in combination with BBs in both male (p=0.0023) and female (p=0.0079) revealed a higher FBG level in variant T allele. In case of hypertensive with new onset of diabetes patients, only female population showed a slightly statistically significant (p=0.0413) difference in FBG level with diuretic mono therapy. Other antihypertensive drug therapies were safe and effective either as mono or in combination therapy.

DISCUSSION

Anthropometric parameters may be the indicative factors for hypertension and diabetes. Variant T allele of ADD1 gene may be considered as the risk factor for the development of diabetes in hypertensive patients. Diuretics as mono therapy and in combination with BBs may be considered as the risk factor for new onset of diabetes in EH patients carrying variant T allele (either as TG or TT).

Correlation of renin angiotensin system (RAS) candidate gene polymorphisms with response to Ramipril in patients with essential hypertension

Background:

The renin-angiotensin system (RAS) is an important facet of blood pressure regulation physiology. Treatment of essential hypertension targets the RAS using Angiotensin Converting Enzyme Inhibitors (ACEIs). However, ACEIs are not uniformly effective and show inter-individual pharmacodynamic variations.

Aim:

To assess the correlation between genetic polymorphisms in the genes coding for RAS components (angiotensin converting enzyme (ACE I/D), α-adducin (ADD1) and β₁-adrenoreceptor (β1-ADR)) and response to Ramipril.

Materials and Methods:

We recruited 120 patients with essential hypertension who were administered Ramipril monotherapy initially, followed by combination therapy, if needed, based on their responses. Relationship between genotypes of the three candidate genes and decrease in the blood pressure (BP) was analyzed.

Results:

One hundred and six patients were evaluable at the end of the study period and 21 different genotypes were observed among them. Seven of them were classified as responders after 8 weeks and at the end of 12 weeks, an additional 77 (72.64%) were deemed responders. 19/22 non-responders were treated with combination therapy and 7/19 (36.84%) showed a response to the same. There was a significant difference between the proportions of responders and non-responders among the genotypes of the ADD1 and β1-ADR genes (P = 0.005 and 0.003, respectively). The best predictors of response to Ramipril 5 mg daily were the II/GG/SS, II/TG/SS, II/GG/SG, ID/GG/SS, ID/GG/SG and ID/TT/SS and DD/GG/SS; II/GG/GG, II/TT/SG, ID/TG/SG, ID/TT/SG, DD/GG/SG and DD/GG/GG were moderately predictive and II/TT/SS, II/TG/GG, ID/TG/GG, DD/TG/SG and DD/TG/GG were poorly predictive of response.

Discussion:

Variable responses to Ramipril may be the result of genetic factors.

Conclusion:

Pre-prescription genotyping may help individualize treatment.

Association of alpha-ADD1 Gene and Hypertension Risk: A Meta-Analysis

Background

Results regarding the association between α-adducin (ADD1) gene and essential hypertension (EH) risk remain inconsistent. Therefore, we performed this meta-analysis to investigate this association.

Material/Methods

We comprehensively searched published literature from PubMed and Embase. All studies analyzing the association between ADD1 Gly460Trp polymorphism and EH risk were included. Fixed- or random-effects model was used to calculate pooled odds ratio (OR) with 95% confidence interval (CI).

Results

Data synthesis showed an increased risk of EH in T allele variant carriers with Asian descent, for GG vs. TT (OR=0.750, 95%CI: 0.585–0.960; P=0.022), recessive model (OR=1.196, 95%CI: 1.009–1.418; P=0.039), dominant model (OR=0.826, 95%CI: 0.693–0.985; P=0.033), and allelic model (OR=0.859, 95%CI: 0.756–0.964; P=0.01), respectively. However, no statistical differences were observed in Blacks and Caucasians.

Conclusions

The findings showed the association of the T allele in ADD1 gene with EH susceptibility in Asians. However, well-designed studies involving gene-gene and gene-environment interactions should be considered in future.

α-Adducin gene G614T polymorphisms in essential hypertension patients with high low density lipoprotein (LDL) levels

BACKGROUND & OBJECTIVES

The association between α-adducin gene G614T polymorphism and essential hypertension (EH) is not clear. The present study was carried out to examine a possible association between α-adducin gene G614T mutation and essential hypertension in Chinese population.

METHODS

A total of 170 patients with essential hypertension (EH group) and 154 normotensive subjects (Control group) were genotyped for the cytoskeletal protein single nucleotide polymorphism G614T of the α-adducin gene by PCR-RFLP technique. Systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), low density lipoprotein (LDL), high-density lipoprotein (HDL), high-sensitivity C-reactive protein (hs-CRP), left atrial diameter (LA DIA), left ventricular diameter (LV DIA) and other parameters were recorded in EH group.

RESULTS

There was significant association between EH and α-adducin genotypes (P<0.05). GT and TT genotypes in EH group had higher LDL levels as compared to GG carriers (P<0.05). The LDL concentration was significantly elevated in patients with GT and TT genotypes. The LDL levels also differed significantly in male patients with all the three genotypes.

INTERPRETATION & CONCLUSIONS

A significant association was found between ADD1 gene G614T polymorphism and EH in Chinese patients. Further studies need to be done to confirm these findings in a large sample.

Between candidate genes and whole genomes: time for alternative approaches in blood pressure genetics

Blood pressure has a significant genetic component, but less than 3% of the observed variance has been attributed to genetic variants identified to date. Candidate gene studies of rare, monogenic hypertensive syndromes have conclusively implicated several genes altering renal sodium balance, and studies of essential hypertension have inconsistently implicated over 50 genes in pathways affecting renal sodium balance and other functions. Genome-wide linkage scans have replicated numerous quantitative trait loci throughout the genome, and over 50 single nucleotide polymorphisms (SNPs) have been replicated in multiple genome-wide association studies. These studies provide considerable evidence that epistasis and other interactions play a role in the genetic architecture of blood pressure regulation, but candidate gene studies have limited scope to test for epistasis, and genome-wide studies have low power for both main effects and interactions. This review summarizes the genetic findings to date for blood pressure, and it proposes focused, pathway-based approaches involving epistasis, gene-environment interactions, and next-generation sequencing to further the genetic dissection of blood pressure and hypertension.

Gly460Trp polymorphism of the ADD1 gene and essential hypertension in an Indian population: A meta-analysis on hypertension risk

BACKGROUND:

Essential hypertension is a complex genetic trait. Genetic variant of alpha adducin (ADD1) gene have been implicated as a risk factor for hypertension. Given its clinical significance, we investigated the association between ADD1 Gly460Trp gene polymorphism and essential hypertension in an Indian population. Further, a meta-analysis was carried out to estimate the risk of hypertension.

METHODS:

In the current study, 432 hypertensive cases and 461 healthy controls were genotyped for the Gly460Trp ADD1 gene polymorphism. Genotyping was determined by real time PCR using Taqman assay. Multiple logistic regression analysis was used to detect the association between Gly460Trp polymorphism and hypertension.

RESULTS:

No significant association was found in the genotype and allele distribution of Gly460Trp polymorphism with hypertension in our study. A total of 15 case-control studies were included in the meta-analysis. There was no evidence of the association of Gly460Trp polymorphism with hypertension in general or in any of the sub group.

CONCLUSIONS:

We found that the Gly460Trp polymorphism is not a risk factor for essential hypertension in a south Indian Tamilian population. However, the role of ADD1 polymorphism may not be excluded by a negative association study. Further, large and rigorous case-control studies that investigate gene–gene–environment interactions may generate more conclusive claims about the molecular genetics of hypertension.

Alpha-adducin Gly460Trp polymorphism and hypertension risk: a meta-analysis of 22 studies including 14303 cases and 15961 controls

Background

No clear consensus has been reached on the alpha-adducin polymorphism (Gly460Trp) and essential hypertension risk. We performed a meta-analysis in an effort to systematically summarize the possible association.

Methodology/Principal Findings

Studies were identified by searching MEDLINE and EMBASE databases complemented with perusal of bibliographies of retrieved articles and correspondence with original authors. The fixed-effects model and the random-effects model were applied for dichotomous outcomes to combine the results of the individual studies. We selected 22 studies that met the inclusion criteria including a total of 14303 hypertensive patients and 15961 normotensive controls. Overall, the 460Trp allele showed no statistically significant association with hypertension risk compared to Gly460 allele (P = 0.69, OR = 1.02, 95% CI 0.94–1.10, P_{heterogeneity}<0.0001) in all subjects. Meta-analysis under other genetic contrasts still did not reveal any significant association in all subjects, Caucasians, East Asians and others. The results were similar but heterogeneity did not persist when sensitivity analyses were limited to these studies.

Conclusions/Significance

Our meta-analysis failed to provide evidence for the genetic association of α-adducin gene Gly460Trp polymorphism with hypertension. Further studies investigating the effect of genetic networks, environmental factors, individual biological characteristics and their mutual interactions are needed to elucidate the possible mechanism for hypertension in humans.

Genetic polymorphisms related to the renin-angiotensin-aldosterone system and response to antihypertensive drugs

IMPORTANCE OF THE FIELD

Only 23 - 41% of hypertensive patients receiving antihypertensive drugs achieve adequate blood pressure control. Multiple physiological systems regulate blood pressure and variation in genes involved in these systems may account for enhanced or diminished blood pressure lowering response to antihypertensive therapy.

AREAS COVERED IN THIS REVIEW

We explored explanations for variation in blood pressure response to antihypertensive drugs by linking genetic polymorphisms in renin-angiotensin-aldosterone system (RAAS) genes to antihypertensive drug response on intermediate parameters (e.g., potassium excretion, aldosterone levels). A MEDLINE search (1966 - 2008) was performed to identify publications reporting effects of genetic polymorphisms in the RAAS on antihypertensive drug response with regard to intermediate parameters.

WHAT THE READER WILL GAIN

With regard to the ACE insertion/deletion and the angiotensinogen -217G/A polymorphism variation in blood pressure response could be explained by effects on intermediate parameters. However, most studies that were identified with our search varied in study design, population and outcome, which complicate adequate comparisons.

TAKE HOME MESSAGE

Little evidence is available that explains these pharmacogenetic interactions. In the future, a better understanding of these mechanisms should provide a more solid evidence base for the individualized hypertension treatment based on genetic variation.

Association between alpha-adducin gene polymorphism (Gly460Trp) and genetic predisposition to salt sensitivity: a meta-analysis

Linkage and association studies suggested the relationship between alpha-adducin polymorphism (Gly460Trp; rs4961) and genetic susceptibility to salt-sensitivity. However, the currently available results were inconsistent. This study aimed to define quantitatively the association between salt-sensitivity and alpha-adducin Gly460Trp polymorphism in all published case-control studies. Publications from PubMed and other databases were retrieved. The major inclusion criteria were: (1) case-control design; (2) salt-sensitivity confirmed by sodium loading tests, and (3) the distribution of genotypes given in detail. Seven case-control studies fulfilled the inclusion criteria. In total they involved 820 subjects (454 salt-sensitive and 366 non-salt-sensitive). The meta-analysis shows that Gly460Trp polymorphism in general is not significantly associated with salt-sensitivity [OR (95%CI): 1.40 (0.96, 2.04), P = 0.08]. Subgroup analysis showed that the association is statistically significant in Asian people [OR (95%CI):1.33 (1.06, 1.69), P = 0.02] but not in Caucasian people [OR (95%CI):1.98 (0.57, 6.92), P = 0.28]. This indicates that blood pressure response to sodium varies between ethnical groups. More studies based on a larger population are required to evaluate further the role of alpha-adducin Gly460Trp polymorphism in salt-sensitive hypertension.

Definition of phenotype

Definition of the phenotype is crucial in designing any genetic study, especially an association study, intended to detect the disease predisposing genes. In this chapter, we review the different types of phenotypes such as discrete or continuous and discuss the issues impacting on the phenotype definition related to study design, specifically, the impact of diagnostic error (misclassification) in case-control studies and measurement error in continuous traits. We show that the power of a study depends heavily on the phenotype measured and that misclassification or measurement error can dramatically reduce the power. We also suggest some possible responses to these challenges.

Screening for the alpha-adducin Gly460Trp variant in hypertensive patients: a cost-effectiveness analysis

BACKGROUND

Studies have shown that approximately 80% of hypertensive patients do not take diuretics despite their recommendation as a first-line therapy. A recent study reported that hypertensive patients with the Gly460Trp variant in the alpha-adducin gene are more likely to benefit from diuretic therapy. The objective of this study was to evaluate the potential cost effectiveness of screening for the alpha-adducin Gly460Trp variant among hypertensive patients.

METHODS

A decision analytic Markov model was developed to estimate the clinical and economic outcomes comparing screening for the Gly460Trp variant to identify patients for addition of a diuretic compared to no screening and no addition of diuretic (usual care) in a hypothetical cohort of treated hypertensive patients not receiving diuretic therapy. We used a lifetime horizon and payer perspective. Cost, utility and epidemiological data were obtained from the literature. One-way, probabilistic, and scenario sensitivity analyses were conducted to evaluate the uncertainty in the results.

RESULTS

The screening strategy increased quality adjusted life years (QALYs) by 0.14 (95% confidence range [CR]: 0.05, 0.36) and saved dollar 1834 (dollar 505, dollar 5174) compared to usual care. The most influential input was the strength of the interaction between the alpha-adducin gene variant and diuretic effect.

CONCLUSIONS

Our results suggest that screening for the alpha-adducin gene variant may be a useful mechanism to identify patients most likely to benefit from diuretic therapy and improve compliance with current treatment guidelines.

RFX-1, a putative alpha Adducin interacting protein in a human kidney library

Adducin regulates tubular absorption of sodium by modulating the expression levels of the sodium-potassium-ATPase in renal tubular cells. Adducin is a candidate gene in the pathogenesis of hypertension. Yeast two hybrid screen showed a specific interaction between human alpha Adducin and the regulatory factor for X box (RFX-1), a nuclear protein that down regulates the expression of several proteins in non neuronal cells. The interaction was confirmed in cells through co-immunoprecipitation and colocalization experiments. The binding of alpha Adducin to RFX-I and their nuclear co-localization suggests that Adducin can have a role in modulating the transcriptional regulating activity of RFX-I.