High Frequency of Variants of Candidate Genes in Black Africans with Low Renin-Resistant Hypertension

Multifocal, Asymmetric Bilateral Primary Aldosteronism Cannot be Excluded by Strong Adrenal Vein Sampling Lateralization: An International Retrospective Cohort Study

BACKGROUND

Primary aldosteronism (PA) has been broadly dichotomized into unilateral and bilateral forms. Adrenal vein sampling (AVS) lateralization indices (LI) ≥2 to 4 are the standard-of-care to recommend unilateral adrenalectomy for presumed unilateral PA. We aimed to assess the rates and characteristics of residual PA after AVS-guided adrenalectomy.

METHODS

We conducted an international, retrospective, cohort study of patients with PA from 7 referral centers who underwent unilateral adrenalectomy based on LI≥4 on baseline and/or cosyntropin-stimulated AVS. Aldosterone synthase (CYP11B2) immunohistochemistry and next generation sequencing were performed on available formalin-fixed paraffin-embedded adrenal tissue.

RESULTS

The cohort included 283 patients who underwent AVS-guided adrenalectomy, followed for a median of 326 days postoperatively. Lack of PA cure was observed in 16% of consecutive patients, and in 22 patients with lateralized PA on both baseline and cosyntropin-stimulated AVS. Among patients with residual PA postoperatively, 73% had multiple CYP11B2 positive areas within the resected adrenal tissue (versus 23% in those cured), wherein CACNA1D mutations were most prevalent (63% versus 33% in those cured). In adjusted regression models, independent predictors of postoperative residual PA included Black versus White race (odds ratio, 5.10 [95% CI, 1.45-17.86]), AVS lateralization only at baseline (odds ratio, 8.93 [95% CI 3.00-26.32] versus both at baseline and after cosyntropin stimulation), and CT-AVS disagreement (odds ratio, 2.75 [95% CI, 1.20-6.31]).

CONCLUSIONS

Multifocal, asymmetrical bilateral PA is relatively common, and it cannot be excluded by robust AVS lateralization. Long-term postoperative monitoring should be routinely pursued, to identify residual PA and afford timely initiation of targeted medical therapy.

Pharmacogenomics of Hypertension in Africa: Paving the Way for a Pharmacogenetic-Based Approach for the Treatment of Hypertension in Africans

In Africa, the burden of hypertension has been rising at an alarming rate for the last two decades and is a major cause for cardiovascular disease (CVD) mortality and morbidity. Hypertension is characterised by elevated blood pressure (BP) ≥ 140/90 mmHg. Current hypertension guidelines recommend the use of antihypertensives belonging to the following classes: calcium channel blockers (CCB), angiotensin converting inhibitors (ACEI), angiotensin receptor blockers (ARB), diuretics, β-blockers, and mineralocorticoid receptor antagonists (MRAs), to manage hypertension. Still, a considerable number of hypertensives in Africa have their BP uncontrolled due to poor drug response and remain at the risk of CVD events. Genetic factors are a major contributing factor, accounting for 20% to 80% of individual variability in therapy and poor response. Poor response to antihypertensive drug therapy is characterised by elevated BPs and occurrence of adverse drug reactions (ADRs). As a result, there have been numerous studies which have examined the role of genetic variation and its influence on antihypertensive drug response. These studies are predominantly carried out in non-African populations, including Europeans and Asians, with few or no Africans participating. It is important to note that the greatest genetic diversity is observed in African populations as well as the highest prevalence of hypertension. As a result, this warrants a need to focus on how genetic variation affects response to therapeutic interventions used to manage hypertension in African populations. In this paper, we discuss the implications of genetic diversity in CYP11B2, GRK4, NEDD4L, NPPA, SCNN1B, UMOD, CYP411, WNK, CYP3A4/5, ACE, ADBR1/2, GNB3, NOS3, B2, BEST3, SLC25A31, LRRC15 genes, and chromosome 12q loci on hypertension susceptibility and response to antihypertensive therapy. We show that African populations are poorly explored genetically, and for the few characterised genes, they exhibit qualitative and quantitative differences in the profile of pharmacogene variants when compared to other ethnic groups. We conclude by proposing prioritization of pharmacogenetics research in Africa and possible adoption of pharmacogenetic-guided therapies for hypertension in African patients. Finally, we outline the implications, challenges, and opportunities these studies present for populations of non-European descent.

Identification of intrinsic genes across general hypertension, hypertension with left ventricular remodeling, and uncontrolled hypertension

The purpose of the present article is to identify intrinsic genes across general hypertension (HT), hypertension with left ventricular remodeling (HT-LVR), and uncontrolled hypertension (UN-HT). In total, four microarray datasets (GSE24752, GSE75360, GSE74144, and GSE71994) were downloaded from the GEO database and were used to identify differentially expressed genes (DEGs), respectively. Furthermore, gene set enrichment analysis (GSEA) was utilized to screen for significantly enriched biological pathways across the four datasets above, respectively. Furthermore, weighted gene co-expression network analysis (WGCNA) and functional enrichment analysis were applied to screen out gene modules of interest and potential biological functions, respectively. Finally, a Metascape-based multiple gene list meta-analysis was used to investigate intrinsic genes at different stages of the progression of hypertension. A total of 75 DEGs (63 upregulated genes and 12 downregulated genes, GSE24752) and 23 DEGs (2 upregulated genes and 21 downregulated genes, GSE74144) were identified. However, there were few DEGs identified in GSE75360, GSE71994, and part of the GSE74144 datasets. GSEA and functional enrichment of gene module of interest have indicated that "Heme metabolism," "TNF alpha/NFkB," and "interferon alpha response signaling," and MYC target v1/v2 were enriched significantly in different stages of hypertension progression. Significantly, findings from the multiple gene list meta-analysis suggested that FBXW4 and other 13 genes were unique to the hypertension group, and TRIM11 and other 40 genes were mainly involved in hypertension with the left ventricular remodeling group, while the other 18 genes including F13A1 significantly enriched in uncontrolled hypertension. Collectively, the precise switch of the "immune-metabolic-inflammatory" loop pathway was the most significant hallmark across different stages of hypertension, thereby providing a potential therapeutic target for uncontrolled hypertension treatment.

Salt sensitivity of blood pressure in childhood and adolescence

Although moderation of sodium intake is recommended population-wide, it remains uncertain who benefits from salt restriction. Salt sensitivity refers to changes in blood pressure in response to sodium intake and may occur with or without hypertension. Unfortunately, there is no practical way to assess salt sensitivity in daily practice. Assessment of salt sensitivity even in research studies is challenging with varying protocols utilized which may contribute to differing results. Building on studies in animals and adults, risk factors and conditions associated with salt sensitivity have been identified in the pediatric and young adult populations. This review presents the limited evidence linking obesity, low birth weight, diabetes, chronic kidney disease, and race/ethnicity with salt sensitivity in children, adolescents, and young adults. The impact of stress on sodium handling is also reviewed. The influence of age on the timing of introduction of dietary salt restriction and the long-term influence of salt sensitivity on risk for hypertension are considered. Lastly, interventions other than salt restriction that may improve salt sensitivity and may inform recommendations to families are reviewed.

Association of Manganese Biomarker Concentrations with Blood Pressure and Kidney Parameters among Healthy Adolescents: NHANES 2013-2018

Deficiency or excess exposure to manganese (Mn), an essential mineral, may have potentially adverse health effects. The kidneys are a major organ of Mn site-specific toxicity because of their unique role in filtration, metabolism, and excretion of xenobiotics. We hypothesized that Mn concentrations were associated with poorer blood pressure (BP) and kidney parameters such as estimated glomerular filtration rate (eGFR), blood urea nitrogen (BUN), and albumin creatinine ratio (ACR). We conducted a cross-sectional analysis of 1931 healthy U.S. adolescents aged 12-19 years participating in National Health and Nutrition Examination Survey cycles 2013-2014, 2015-2016, and 2017-2018. Blood and urine Mn concentrations were measured using inductively coupled plasma mass spectrometry. Systolic and diastolic BP were calculated as the average of available readings. eGFR was calculated from serum creatinine using the Bedside Schwartz equation. We performed multiple linear regression, adjusting for age, sex, body mass index, race/ethnicity, and poverty income ratio. We observed null relationships between blood Mn concentrations with eGFR, ACR, BUN, and BP. In a subset of 691 participants, we observed that a 10-fold increase in urine Mn was associated with a 16.4 mL/min higher eGFR (95% Confidence Interval: 11.1, 21.7). These exploratory findings should be interpreted cautiously and warrant investigation in longitudinal studies.

Stroke Prevention: Little-Known and Neglected Aspects

Combining available therapies has the potential to reduce the risk of stroke by 80% or more. A comprehensive review of all aspects of stroke prevention would be very lengthy; in this narrative review, we focus on some aspects of stroke prevention that are little-known and/or neglected. These include the following: (1) implementation of a Mediterranean diet; (2) B vitamins to lower homocysteine; (3) coordinated approaches to smoking cessation; (4) intensive lipid-lowering therapy; (5) lipid lowering in the elderly; (6) physiologically individualized therapy for hypertension based on renin/aldosterone phenotyping; (7) avoiding excessive blood pressure reduction in patients with stiff arteries; (8) treatment of insulin resistance with pioglitazone in stroke patients with prediabetes and diabetes; (9) impaired activation of clopidogrel in patients with variants of CYP2C19; (10) aspirin pseudoresistance due to enteric coating; (11) rationale for anticoagulation in patients with embolic stroke of unknown source; (12) pharmacologic properties of direct-acting oral anticoagulants that should be considered when choosing among them; (13) the identification of which patients with asymptomatic carotid stenosis are at a high enough risk to benefit from carotid endarterectomy or stenting; and (14) the importance of age in choosing between endarterectomy and stenting. Stroke prevention could be improved by better recognition of these issues and by implementation of the principles derived from them.

The importance of the epithelial sodium channel in determining salt sensitivity in people of African origin

Hypertension is highly prevalent in Black Africans and has been found to be associated with worse blood pressure (BP) control and more cardiovascular disease. Black Africans are more salt sensitive with low renin and aldosterone levels. This can be explained in part by variants in the epithelial sodium channel (ENaC) causing an increase in channel activity resulting in sodium and water retention. These variants in the ENaC are increased in the Black African populations presumably due to selective pressure for sodium retention in traditionally low-salt diets. Furthermore, increased endothelial sodium channel activity contributes to the risk of vascular stiffness, which may also result in more difficult to control hypertension. Patients with increased activity of the ENaC are more likely to respond to amiloride (a selective sodium channel antagonist), which has implications for the management of severe and resistant hypertension in Black Africans. A large-scale controlled trial on the use of amiloride compared to usual care is warranted in Blacks with severe or resistant hypertension.

Aldosterone sensitivity: an opportunity to explore the pathogenesis of hypertension

Aldosterone sensitivity is defined as an outcome variable for a given circulating level of aldosterone. In basic and translational studies, aldosterone sensitivity has been measured in differential tissue responses, e.g., lower urine sodium and higher urine potassium, as an index of the renal response; in clinical studies, aldosterone sensitivity has been measured in differential blood pressure responses. The concept of aldosterone sensitivity disrupts the conventional wisdom of the renin-angiotensin-aldosterone system and has the potential to uncover novel mechanisms of hypertension. Here, we review basic and translational science studies that uncovered differential renal responses to aldosterone and connect this earlier work to more recent observational studies and randomized trials that have demonstrated differential blood pressure responses for a given level of aldosterone in healthy and hypertensive persons. Black race and older age are associated with higher aldosterone sensitivity and blood pressure. We also discuss gaps in the field and how future basic and clinical studies might inform mechanisms of differential sensitivity.

Is hypertension in African-descent populations contributed to by an imbalance in the activities of the ACE2/Ang-(1-7)/Mas and the ACE/Ang II/AT1 axes?

Introduction:

Low plasma renin activity hypertension is prevalent in Afro-Caribbean persons. Reduced angiotensin converting enzyme 2 activity from the counter angiotensin converting enzyme 2 /angiotensin-(1-7)/Mas receptor axis of the renin angiotensin aldosterone system has been reported in people with pre-hypertension, type 2 diabetes mellitus and chronic renal disease. This study investigates whether an imbalance in the regulatory mechanisms between the pressor arm of the renin angiotensin aldosterone system (angiotensin converting enzyme/angiotensin II/AT1 receptor) and the depressor axis (angiotensin converting enzyme 2/angiotensin-(1-7)/Mas receptor) predisposes persons of African descent to hypertension.

Methods:

In total, 30 normotensives and 30 recently diagnosed hypertensives aged 18–55 of Afro-Caribbean origin who are naïve to antihypertensive treatment will be recruited from public sector polyclinics in Barbados. Demographic and anthropometric data, clinical blood pressure readings, 24-hour urine collections and venous blood samples will be collected. Biological samples will be analysed for renin angiotensin aldosterone system peptide markers using radioimmunoassay.

Conclusion:

We describe the design, methods and rationale for the characterization of renin angiotensin aldosterone system mechanisms that may contribute to hypertension predisposition in persons of African descent. Our findings will characterize any imbalance in the counter axes of the renin angiotensin aldosterone system in hypertensive Afro-Caribbeans with a potential view of identifying novel approaches with the use of renin angiotensin aldosterone system and mineralocorticoid blockers to manage the condition.

Trick or Treat? Licorice-Induced Hypokalemia: A Case Report

The by-products of black licorice metabolism are toxic in high concentrations. Patients who consume large quantities of black licorice are at risk of developing an acquired syndrome of apparent mineralocorticoid excess. This presents clinically as hypertension, hypernatremia, and hypokalemia. Here, we present the unique case of a 74-year-old woman with a past medical history of neurogenic orthostatic hypotension, on fludrocortisone, who presented to the emergency department with asymptomatic hypokalemia (2.4 mmol/L) as detected in outpatient laboratory studies. During her hospital stay, it was discovered that the patient was consuming excessive amounts of black licorice. With this information, the synergistic interaction of fludrocortisone and black licorice was recognized as the cause of the patient's severe hypokalemia. The patient's fludrocortisone was stopped and she was treated with multiple courses of potassium repletion. Upon discharge, her fludrocortisone was discontinued, and she was prescribed midodrine to treat her neurogenic orthostatic hypertension. While small amounts of black licorice are safe, excessive licorice consumption can cause severe disease. Our case presents an opportunity to appreciate the plethora of etiologies for severe hypokalemia and the importance of taking a thorough patient history to avoid potentially fatal clinical outcomes.

Frequency and factors linked to refractory hypertension among stroke survivors in Ghana

BACKGROUND

Refractory hypertension (RfH) is a rare, severe phenotype of resistant hypertension, linked to higher risk of adverse cardiovascular outcomes. Little is known about the association of RfH with stroke type and subtype.

OBJECTIVE

To determine the prevalence and predictors of RfH among stroke survivors in Ghana.

METHODS

We interrogated the dataset of a prospectively collected registry of hypertensive patients seen between July 2015 and June 2019, at five hospitals in Ghana. We compared stroke survivors to stroke-free controls. Clinic-based blood pressure was measured using a standardized protocol and antihypertensive medications were assessed via review of medical records and inspection of pills. Refractory hypertension was defined as office BP ≥140/90 mmHg on ≥5 classes of antihypertensive medications. Multivariate logistic regression models were constructed to assess factors associated with RfH.

RESULTS

Of 3927 hypertensive patients (1169 stroke survivors, 2758 controls), 86 had RfH for an overall prevalence of 2.2% (95% CI: 1.8-2.7%). Among patients with RfH, 5.8% (4.5-7.3%) were stroke survivors vs. 0.7% (0.4-1.0%) were stroke-free (p < .0001). Adjusted odds ratio (95% CI) for factors associated with RfH were being male (1.81, 1.15-2.85), age < 60 years (2.64, 1.59-4.40), chronic kidney disease (2.09, 1.21-3.60), and known stroke (7.53, 4.35-13.04). RfH was associated with intracerebral hemorrhage, (11.43, 5.65-23.14), ischemic stroke (9.76, 5.47-17.42), lacunar stroke (13.58, 6.45-28.61), and non-lacunar ischemic stroke (3.67, 1.04-13.02).

CONCLUSION

Presence of RfH is significantly accentuated among stroke survivors. Intensified efforts are warranted to identify and aggressively address barriers to control in these patients to avert subsequent vascular events.

Association of the genetic ancestry with resistant hypertension in the ReHOT (Resistant Hypertension Optimal Treatment) randomized study

Resistant hypertension (RH) is defined as uncontrolled blood pressure despite treatment with three or more antihypertensive medications, including, if tolerated, a diuretic in adequate doses. It has been widely known that race is associated with blood pressure control. However, intense debate persists as to whether this is solely explained by unadjusted socioeconomical variables or genetic variation. In this scenario, the main aim was to evaluate the association between genetic ancestry and resistant hypertension in a large sample from a multicenter trial of stage II hypertension, the ReHOT study. Samples from 1,358 patients were analyzed, of which 167 were defined as resistant hypertensive. Genetic ancestry was defined using a panel of 192 polymorphic markers. The genetic ancestry was similar in resistant (52.0% European, 36.7% African and 11.3% Amerindian) and nonresistant hypertensive patients (54.0% European, 34.4% African and 11.6% Amerindian) (p > 0.05). However, we observed a statistically suggestive association of African ancestry with resistant hypertension in brown patient group. In conclusion, increased African genetic ancestry was not associated with RH in Brazilian patients from a prospective randomized hypertension clinical trial.

ARMC 5 Variants and Risk of Hypertension in Blacks: MH- GRID Study

Background

We recently found that ARMC5 variants may be associated with primary aldosteronism in blacks. We investigated a cohort from the MH‐GRID (Minority Health Genomics and Translational Research Bio‐Repository Database) and tested the association between ARMC5 variants and blood pressure in blacks.

Methods and Results

Whole exome sequencing data of 1377 blacks were analyzed. Target single‐variant and gene‐based association analyses of hypertension were performed for ARMC5, and replicated in a subset of 3015 individuals of African descent from the UK Biobank cohort. Sixteen rare variants were significantly associated with hypertension (P=0.0402) in the gene‐based (optimized sequenced kernel association test) analysis; the 16 and one other, rs116201073, together, showed a strong association (P=0.0003) with blood pressure in this data set. The presence of the rs116201073 variant was associated with lower blood pressure. We then used human embryonic kidney 293 and adrenocortical H295R cells transfected with an ARMC5 construct containing rs116201073 (c.*920T>C). The latter was common in both the discovery (MH‐GRID) and replication (UK Biobank) data and reached statistical significance (P=0.044 [odds ratio, 0.7] and P=0.007 [odds ratio, 0.76], respectively). The allele carrying rs116201073 increased levels of ARMC5 mRNA, consistent with its protective effect in the epidemiological data.

Conclusions

ARMC5 shows an association with hypertension in blacks when rare variants within the gene are considered. We also identified a protective variant of the ARMC5 gene with an effect on ARMC5 expression confirmed in vitro. These results extend our previous report of ARMC5’s possible involvement in the determination of blood pressure in blacks.

Genetics of Hypertension in African Americans and Others of African Descent

Hypertension is the leading cause of cardiovascular disease in the United States, affecting up to one-third of adults. When compared to other ethnic or racial groups in the United States, African Americans and other people of African descent show a higher incidence of hypertension and its related comorbidities; however, the genetics of hypertension in these populations has not been studied adequately. Several genes have been identified to play a role in the genetics of hypertension. They include genes regulating the renin-aldosterone-angiotensin system (RAAS), such as Sodium Channel Epithelial 1 Beta Subunit (SCNN1B), Armadillo Repeat Containing 5 (ARMC5), G Protein-Coupled Receptor Kinase 4 (GRK4), and Calcium Voltage-Gated Channel Subunit Alpha1 D (CACNA1D). In this review, we focus on recent genetic findings available in the public domain for potential differences between African Americans and other populations. We also cover some recent and relevant discoveries in the field of low-renin hypertension from our laboratory at the National Institutes of Health. Understanding the different genetics of hypertension among various groups is essential for effective precision-guided medical therapy of high blood pressure.

Controlling resistant hypertension

Resistant hypertension (failure to achieve target blood pressures with three or more antihypertensive drugs including a diuretic) is an important and preventable cause of stroke. Hypertension is highly prevalent in China (>60% of persons above age 65), and only ~6% of hypertensives in China are controlled to target levels. Most strokes occur among persons with resistant hypertension; approximately half of strokes could be prevented by blood pressure control. Reasons for uncontrolled hypertension include (1) non-compliance; (2) consumption of substances that aggravated hypertension, such as excess salt, alcohol, licorice, decongestants and oral contraceptives; (3) therapeutic inertia (failure to intensify therapy when target blood pressures are not achieved); and (4) diagnostic inertia (failure to investigate the cause of resistant hypertension). In China, an additional factor is lack of availability of appropriate antihypertensive therapy in many healthcare settings. Sodium restriction in combination with a diet similar to the Cretan Mediterranean or the DASH (Dietary Approaches to Stop Hypertension) diet can lower blood pressure in proportion to the severity of hypertension. Physiologically individualised therapy for hypertension based on phenotyping by plasma renin activity and aldosterone can markedly improve blood pressure control. Renal hypertension (high renin/high aldosterone) is best treated with angiotensin receptor antagonists; primary aldosteronism (low renin/high aldosterone) is best treated with aldosterone antagonists (spironolactone or eplerenone); and hypertension due to overactivity of the renal epithelial sodium channel (low renin/low aldosterone; Liddle phenotype) is best treated with amiloride. The latter is far more common than most physicians suppose.

The Low-Renin Hypertension Phenotype: Genetics and the Role of the Mineralocorticoid Receptor

A substantial proportion of patients with hypertension have a low or suppressed renin. This phenotype of low-renin hypertension (LRH) may be the manifestation of inherited genetic syndromes, acquired somatic mutations, or environmental exposures. Activation of the mineralocorticoid receptor is a common final mechanism for the development of LRH. Classically, the individual causes of LRH have been considered to be rare diseases; however, recent advances suggest that there are milder and "non-classical" variants of many LRH-inducing conditions. In this regard, our understanding of the underlying genetics and mechanisms accounting for LRH, and therefore, potentially the pathogenesis of a large subset of essential hypertension, is evolving. This review will discuss the potential causes of LRH, with a focus on implicated genetic mechanisms, the expanding recognition of non-classical variants of conditions that induce LRH, and the role of the mineralocorticoid receptor in determining this phenotype.

Gut-Brain Axis in Regulation of Blood Pressure

Hypertension (HTN) is an escalating health issue worldwide. It is estimated that 1.56 billion people will suffer from high blood pressure (BP) by 2025. Recent studies reported an association between gut dysbiosis and HTN, thus proposing interesting avenues for novel treatments of this condition. The sympathetic nervous system (SNS) and the immune system (IS) play a recognized role in the onset and progression of HTN, while reciprocal communication between gut microbiota and the brain can regulate BP by modulating the interplay between the IS and SNS. This review presents the current state of the science implicating brain-gut connection in HTN, highlighting potential pathways of their interaction in control of BP.

Recent advances in preventing stroke recurrence

Recent advances in secondary stroke prevention include new evidence in hypertension, nutrition, anticoagulation, antiplatelet therapy, intracranial stenosis, percutaneous closure of patent foramen ovale, and lipid-lowering therapy. Individualized therapy for hypertension based on phenotyping with plasma renin and aldosterone markedly improves blood pressure control in patients with resistant hypertension. A Mediterranean diet can reduce the risk of stroke by nearly half. The diagnosis and treatment of metabolic vitamin B12 deficiency, and B vitamins to lower homocysteine, can reduce the risk of stroke by approximately 30%. There are problems with clopidogrel that can be overcome by using ticagrelor, and new anticoagulant drugs markedly improve anticoagulation for stroke prevention, particularly in atrial fibrillation. There are pharmacokinetic problems with dabigatran that deserve attention. Intensive medical therapy is better than stenting for intracranial stenosis, and new therapies directed at proprotein convertase subtilisin–kexin type 9 (PCSK9) will revolutionize lipid-lowering therapy. In the past, it was estimated that rational therapy could reduce recurrent stroke by about 80%. With recent advances, we should be able to do even better.