Functional variants of the angiotensinogen gene determine antihypertensive responses to angiotensin-converting enzyme inhibitors in subjects of African origin

Genetic Appraisal of RAAS-Associated SNPs: REN (rs16853055), AGT (rs3789678) and ACE (rs4305) in Preeclamptic Women Living with HIV Infection

PURPOSE OF REVIEW

The primary goal of this review article was to determine whether the three RAAS-associated SNPs, Renin-rs16853055, AGT-rs3789678 and ACE-rs4305 are genetically linked to the development of hypertension in preeclampsia. The secondary goal was to establish if there was a link between these SNPs and HIV infection.

RECENT FINDINGS

There is a paucity of findings related to the aforementioned SNPs and preeclampsia. There are no recent findings on the rs16853055 renin polymorphism. The rs3789678 angiotensinogen polymorphism correlated significantly with gestational hypertension. The rs4305 ACE polymorphism showed no significant association with the development of pregnancy-induced hypertension. There are conflicting findings when determining the relationship between ethnicity and the predisposition of preeclampsia and hypertension in relation to the discussed RAAS-associated SNPs. To date, the association between RAAS-associated SNPs and preeclamptic women co-morbid with HIV in South Africa has revealed that certain alleles of the AGT gene are more prominent in HIV-infected PE compared to normotensive pregnant HIV-infected women.

Analysis in silico of the single nucleotide polymorphism G–152A in the promoter of the angiotensinogen gene of Indonesian patients with essential hypertension

Background

Single nucleotide polymorphism (SNP) G–152A (rs11568020) in the promoter of the angiotensinogen gene (AGT) may modulate its transcription. Translation of mRNA to angiotensinogen induces hypertension during hypoxia. The G allele at position –152 is located within the hypoxia-response element (HRE) transcription factor-binding site for the hypoxia-inducible factor 1 (HIF-1) heterodimer. However, the function of the –152 site in HIF-1 binding is not fully elucidated.

Objectives

To determine the frequency of SNP G–152A in Indonesian patients with hypertension and the function of this SNP.

Methods

We determined the frequency of the SNP in 100 patients by direct sequencing, and the influence of SNP G–152A on predicted binding of HIF-1 to the HRE using a docking approach in silico.

Results

The AGT promoter in our patients had genetic variants –152G and –152A (19:1). Predicted binding indicated that HIF-1 directly contacts the major groove of the G allele, but not the A allele. Scoring according to weighted sum High Ambiguity Driven biomolecular DOCKing showed that the score for the A allele–HIF-1 complex (–47.1 ± 6.9 kcal/mol) was higher than that for the G allele–HIF-1 complex (–94.6 ± 14.1 kcal/mol), indicating more favorable binding of HIF-1 to the G allele.

Conclusions

SNP G–152A reduces the favorability of binding of HIF-1 to the HRE. The occurrence of this SNP in the AGT promoter of Indonesian patients with essential hypertension suggests that the G allele is a genetic susceptibility factor in hypertension regulated by HIF-1.

Genetic factors contributing to hypertension in African-based populations: A systematic review and meta-analysis

In a systematic review, the authors explored genetic association studies of essential hypertension in African populations. Studies reporting on the association of polymorphism(s) with hypertension in African populations were included. Appropriate studies were pooled using random effects model meta-analysis, under six potential inheritance models. In all, 46 polymorphisms in 33 genes were investigated for their association with hypertension or blood pressure levels. Meta-analysis was possible for three single nucleotide polymorphisms: rs4340, rs699, and rs5186. An association was found between rs5186, rs699, and hypertension under allele contrast and homozygous codominant models (odds ratio, 1.63 [95% confidence interval, 1.04-2.54] and 4.01 [95% confidence interval, 1.17-13.80] for rs5186, respectively; and 1.80 [95% confidence interval, 1.13-2.87] for rs699). Findings were mostly robust in sensitivity analyses. According to the systematic review, there is currently insufficient evidence on the specific polymorphisms that pose the risk of hypertension in African populations. Large-scale genetic studies are warranted to better understand susceptibility polymorphisms that may be specific to African populations.

African Americans, hypertension and the renin angiotensin system

African Americans have exceptionally high rates of hypertension and hypertension related complications. It is commonly reported that the blood pressure lowering efficacy of renin angiotensin system (RAS) inhibitors is attenuated in African Americans due to a greater likelihood of having a low renin profile. Therefore these agents are often not recommended as initial therapy in African Americans with hypertension. However, the high prevalence of comorbid conditions, such as diabetes, cardiovascular and chronic kidney disease makes treatment with RAS inhibitors more compelling. Despite lower circulating renin levels and a less significant fall in blood pressure in response to RAS inhibitors in African Americans, numerous clinical trials support the efficacy of RAS inhibitors to improve clinical outcomes in this population, especially in those with hypertension and risk factors for cardiovascular and related diseases. Here, we discuss the rationale of RAS blockade as part of a comprehensive approach to attenuate the high rates of premature morbidity and mortality associated with hypertension among African Americans.

Why do hypertensive patients of African ancestry respond better to calcium blockers and diuretics than to ACE inhibitors and β-adrenergic blockers? A systematic review

BACKGROUND

Clinicians are encouraged to take an individualized approach when treating hypertension in patients of African ancestry, but little is known about why the individual patient may respond well to calcium blockers and diuretics, but generally has an attenuated response to drugs inhibiting the renin-angiotensin system and to β-adrenergic blockers. Therefore, we systematically reviewed the factors associated with the differential drug response of patients of African ancestry to antihypertensive drug therapy.

METHODS

Using the methodology of the systematic reviews narrative synthesis approach, we sought for published or unpublished studies that could explain the differential clinical efficacy of antihypertensive drugs in patients of African ancestry. PUBMED, EMBASE, LILACS, African Index Medicus and the Food and Drug Administration and European Medicines Agency databases were searched without language restriction from their inception through June 2012.

RESULTS

We retrieved 3,763 papers, and included 72 reports that mainly considered the 4 major classes of antihypertensive drugs, calcium blockers, diuretics, drugs that interfere with the renin-angiotensin system and β-adrenergic blockers. Pharmacokinetics, plasma renin and genetic polymorphisms did not well predict the response of patients of African ancestry to antihypertensive drugs. An emerging view that low nitric oxide and high creatine kinase may explain individual responses to antihypertensive drugs unites previous observations, but currently clinical data are very limited.

CONCLUSION

Available data are inconclusive regarding why patients of African ancestry display the typical response to antihypertensive drugs. In lieu of biochemical or pharmacogenomic parameters, self-defined African ancestry seems the best available predictor of individual responses to antihypertensive drugs.

Tagging SNPs in REN, AGTR1 and AGTR2 genes and response of renin activity, angiotensin II and aldosterone concentrations to antihypertensive treatment in Kazakans

HYPOTHESIS

Polymorphisms of REN, AGTR1 and AGTR2 may be associated with responses of renin-angiotensin-aldosterone system (RAAS) activity phenotypes to angiotensin-converting enzyme inhibitor (ACEI) antihypertensive treatment.

MATERIALS AND METHODS

A total of 400 first diagnosed Kazak hypertensives were randomly allocated to two groups and received a 3-week course of either captopril and atenolol as monotherapy under double blinding. Genotype-phenotype association analyses were performed by covariance analyses between baseline level and responses of blood pressure, renin, angiotensin II and aldosterone concentrations with tagging single nucleotide polymorphisms (SNPs) in REN, AGTR1 and AGTR2 genes. A false discovery rate method was used to adjust multiple testing.

RESULTS

After adjustment for multiple testing, we found that the G allele of rs6676670 (T/G) in intron 1 of REN was significantly associated with higher baseline aldosterone concentrations (p < 0.0001, explained variance (EV) = 2.3%). Significant associations after adjustments were also found between the A allele of rs2887284, with higher baseline renin activity (p = 0.022, EV = 1.0%), higher responses of renin (p = 0.018 EV = 5.4%), and higher responses of angiotensin II (p = 0.0255, EV = 3.13%) to the treatment of ACEI. The carriers of the A allele of rs2887284 appeared to be more sensitive to the ACEI treatment.

CONCLUSION

rs2887284 in intron 9 of REN is associated with the response of renin and angiotensin II levels to ACEI treatment.

Interactions of renin–angiotensin system gene polymorphisms and antihypertensive effect of benazepril in Chinese population

Aim: Angiotensin-converting enzyme inhibitors are widely used antihypertensive drugs with individual response variation. We studied whether interactions of AGT, AGTR1 and ACE2 gene polymorphisms affect this response. Materials & methods: Our study is based on a 3-year field trial with 1831 hypertensive patients prescribed benazepril. Generalized multifactor dimensionality reduction was used to explore interaction models and logistic regressions were used to confirm them. Results: A two-locus model involving the AGT and ACE2 genes was found in males, the sensitive genotypes showed an odds ratio (OR) of 1.9 (95% CI: 1.3–2.8) when compared with nonsensitive genotypes. Two AGT–AGTR1 models were found in females, with an OR of 3.5 (95% CI: 2.0–5.9) and 3.1 (95% CI: 1.8–5.3). Conclusion: Gender-specific gene–gene interactions of the AGT, AGTR1 and ACE2 genes were associated with individual variation of response to benazepril. Further studies are needed to confirm this finding.

Original submitted 1 November 2010; Revision submitted 10 January 2011

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.

Implications of ethnicity for the treatment of hypertensive kidney disease, with an emphasis on African Americans

The recognition of chronic kidney disease (CKD) as an important public health issue has fostered an increasing number of strategies to increase CKD awareness and to reduce both the prevalence and the complications of CKD. Despite these advances, end-stage renal disease (ESRD) and cardiovascular events remain the major complications of CKD. Although the ESRD epidemic is attributed in greater part to the increasing rate of diabetes, hypertension remains the second most common reported cause of ESRD and is present in approximately 90% of cases of diabetes-related ESRD. The disproportionately high prevalence of hypertension in ethnic minorities, as well as the difficulty of achieving adequate blood-pressure control in these populations, contributes substantially to the high rate of CKD progression and complications in these groups. Although the role of hypertension as a primary cause of CKD is debated, hypertension is commonly recognized as the most important CKD progression factor. Important differences have been reported in the degree and likelihood of blood-pressure response to antihypertensive medications between ethnic groups, but ethnicity seems to be less important as a determinant of clinical outcomes. In this Review we examine key ethnic variations in hypertensive CKD in terms of pathophysiology, response to antihypertensive therapy, clinical outcomes, and evidence-based recommendations for blood-pressure control, with an emphasis on African Americans.

Racial differences in blood pressure response to angiotensin-converting enzyme inhibitors in children: a meta-analysis

Angiotensin-converting enzyme (ACE) inhibitors are frequently used to treat hypertension in children.(1) ACE inhibitors alter the balance between the vasoconstrictive, salt-retentive, and cardiac hypertrophic properties of angiotensin II and the vasodilatory and natriuretic properties of bradykinin; they also alter the metabolism of other vasoactive substances.(2) Through these mechanisms, ACE inhibitors decrease systemic vascular resistance and promote natriuresis without increasing heart rate. This study evaluated the results of six trials of ACE inhibitors in children, using meta-analytic techniques to estimate the effect of race on blood pressure response.

Genetic studies of African populations: an overview on disease susceptibility and response to vaccines and therapeutics

Africa is the ultimate source of modern humans and as such harbors more genetic variation than any other continent. For this reason, studies of the patterns of genetic variation in African populations are crucial to understanding how genes affect phenotypic variation, including disease predisposition. In addition, the patterns of extant genetic variation in Africa are important for understanding how genetic variation affects infectious diseases that are a major problem in Africa, such as malaria, tuberculosis, schistosomiasis, and HIV/AIDS. Therefore, elucidating the role that genetic susceptibility to infectious diseases plays is critical to improving the health of people in Africa. It is also of note that recent and ongoing social and cultural changes in sub-Saharan Africa have increased the prevalence of non-communicable diseases that will also require genetic analyses to improve disease prevention and treatment. In this review we give special attention to many of the past and ongoing studies, emphasizing those in Sub-Saharan Africans that address the role of genetic variation in human disease.