Blood aldosterone-to-renin ratio, ambulatory blood pressure, and left ventricular mass in children

Relationship Between the Aldosterone-to-Renin Ratio and Blood Pressure in Young Adults: A Longitudinal Study

[Figure: see text].

Resistant Hypertension: A Clinical Perspective

Resistant hypertension is a common clinical entity, defined as suboptimal blood pressure response to multiple therapies after excluding medication nonadherence and secondary forms of hypertension. Patients with resistant hypertension generally share several comorbidities. Resistant hypertension is more common in individuals of African descent. Blood pressure should be optimized using multiple strategies, including lifestyle changes and single-pill combination therapies, with the aim of reducing cardiovascular events while reducing side effects from using antihypertensive therapy. A renin/aldosterone-based diagnostic and treatment approach will help tailor therapy. The use of mineralocorticoid receptor antagonists or amiloride as appropriate is favored.

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.

Recent advances in understanding hypertension development in sub-Saharan Africa

Consistent reports indicate that hypertension is a particularly common finding in black populations. Hypertension occurs at younger ages and is often more severe in terms of blood pressure levels and organ damage than in whites, resulting in a higher incidence of cardiovascular disease and mortality. This review provides an outline of recent advances in the pathophysiological understanding of blood pressure elevation and the consequences thereof in black populations in Africa. This is set against the backdrop of populations undergoing demanding and rapid demographic transition, where infection with the human immunodeficiency virus predominates, and where under and over-nutrition coexist. Collectively, recent findings from Africa illustrate an increased lifetime risk to hypertension from foetal life onwards. From young ages black populations display early endothelial dysfunction, increased vascular tone and reactivity, microvascular structural adaptions as well as increased aortic stiffness resulting in elevated central and brachial blood pressures during the day and night, when compared to whites. Together with knowledge on the contributions of sympathetic activation and abnormal renal sodium handling, these pathophysiological adaptations result in subclinical and clinical organ damage at younger ages. This overall enhanced understanding on the determinants of blood pressure elevation in blacks encourages (a) novel approaches to assess and manage hypertension in Africa better, (b) further scientific discovery to develop more effective prevention and treatment strategies and

Aldosterone and Left Ventricular Remodeling

Experimental and clinical evidence obtained in the last 2 decades clearly indicates that protracted exposure to inappropriately elevated aldosterone levels causes significant changes in left ventricular structure and function. Animal studies have demonstrated that aldosterone induces myocardial inflammatory changes and fibrosis in the presence of a high salt diet. Moreover, the effects of aldosterone on the heart have been investigated in different clinical conditions. These conditions include systolic and diastolic heart failure, essential hypertension, and primary aldosteronism that offers a unique clinical model to study the cardiac effects of excess aldosterone because these effects are isolated from those of the renin-angiotensin axis. A relatively clear picture is emerging from these studies with regard to aldosterone-related changes in left ventricular mass and geometry. Conversely, no direct effect of aldosterone on left ventricular diastolic function can be demonstrated and improvement of diastolic function obtained in some studies that have employed mineralocorticoid receptor blockers could result from left ventricular mass reduction. Animal experiments demonstrate that effects of aldosterone on the left ventricle require high salt intake to occur, but the evidence of this contribution of salt to aldosterone-induced cardiac changes in humans remains weaker and needs further research. The article reviews the results of clinical studies addressing the role of aldosterone in regulation of LV remodeling and diastolic function, and focuses on the possible relevance of salt intake.

Aldosterone contributes to elevated left ventricular mass in black boys

BACKGROUND

Left ventricular hypertrophy (LVH) poses a great risk of cardiovascular morbidity and mortality in adults and may pose a serious risk in children. Adult studies have shown that renin-angiotensin-aldosterone system (RAAS) levels directly correlate with left ventricular mass index (LVMI). The purpose of this study is to explore race- and sex-related effects of the RAAS on LVMI in adolescents.

METHODS

Data were collected from a sample of 89 blacks (44 girls, 45 boys) and 102 whites (40 girls, 62 boys) aged 15-19. Data collected included sex, age, body mass index (BMI), LVMI, baseline blood pressure, and levels of aldosterone and angiotensin II.

RESULTS

In black males, increased aldosterone levels correlated with decreased sodium excretion (r= -0.336, p=0.024), increased blood pressure (r=0.358, p=0.016), and increased LVMI (r=0.342, p=0.022). In black females, increased aldosterone levels correlated with increased baseline blood pressure (r=0.356, p=0.018). In white males, increased aldosterone correlated with decreased sodium excretion (r= -0.391, p=0.002). In white females, aldosterone levels correlated with increased baseline blood pressure (r=0.323, p=0.042) and decreased sodium excretion (r= -0.342, p=0.031).

CONCLUSIONS

The results suggest the following model in black males: increased aldosterone leads to increased sodium retention, causing a volume-mediated increase in blood pressure; increased blood pressure results in increased left ventricular mass, and eventually LVH.

Positive association between aldosterone-renin ratio and carotid intima-media thickness in hypertensive children

INTRODUCTION

From an early age, hypertension can damage blood vessels through multiple mechanisms. The aim of this study was to evaluate the presence of vascular damage and whether it is associated with the mineralo- and glucocorticoid profiles of hypertensive children.

SUBJECTS AND METHODS

We studied 64 hypertensive children. Anthropometric parameters and serum aldosterone (SA), plasma renin activity (PRA), aldosterone/renin ratio (ARR), cortisol (F) and cortisone (E) were measured. The serum F/E ratio was calculated to estimate the activity of the enzyme 11β-HSD2. Vascular damage was determined by carotid intima-media thickness (cIMT) and flow-mediated dilation of the brachial artery (FMD) on ultrasound.

RESULTS

(median; Q1-Q3) Of the patients observed, 39% were females, and the median value for age (years) was 11.2 (9.1-13.3), for BMI (SDS) was 1.36 (0.84-1.80), for body fat mass (%) was 28.3 (17.8-36.0), for SBP index was 1.17 (1.12-1.25) and for the DBP index was 1.27 (1.16-1.36). Measurements revealed an SA level higher than 491 pmol/l in 4/64 patients, a PRA value lower than 0.5 ng/ml/h in 2/64, an ARR higher than 10 in 3/64 and serum F/E ratio higher than 4.3 in 10/64. The median brachial FMD (%) was 8.41 (5.61-10.91), and the median cIMT (mm) was 0.40 (0.37-0.43). The ARR was the only variable that explained changes in cIMT (β = 0.571, R(2 ) = 0.315, P < 0.0001).

CONCLUSION

Our results showed a positive association between cIMT and the ARR, suggesting an important role of the renin-aldosterone axis in the regulation of early vascular damage in hypertensive children.

Relationships between renin, aldosterone, and 24-hour ambulatory blood pressure in obese adolescents

Renin-angiotensin system (RAS) activation and abnormalities of ambulatory blood pressure (ABP) are present in obesity, but relationships between components of the RAS and ABP have not been defined in the young. Anthropometric measurements and 24-h ABP were obtained on 30 obese adolescents with and without type 2 diabetes mellitus. Plasma renin activity (PRA), aldosterone, and other cardiovascular risk factors were measured. Median PRA levels were 2.5 [interquartile range (IQR), 1.7-4.1] ng/mL/h and were higher in the diabetic subjects compared with the nondiabetics. Females had significantly higher PRA than males 3.2 (IQR, 2-4.8) versus 1.8 (IQR, 1.1-2.9) ng/mL/h (p = 0.04) and were more obese. BMI Z score and PRA were significantly correlated (rho = 0.46, p < 0.001). PRA inversely correlated with 24-h systolic ABP (rho = -0.46, p = 0.02) and strongly with 24-h pulse pressure (rho = -0.61, p = 0.001). Aldosterone levels were also correlated with 24-h pulse pressure (rho = -0.46, p = 0.02). In multivariate models, lower PRA was independently associated with 24-h systolic blood pressure. In this study, PRA was positively correlated with BMI, but the relationships between components of the RAS and ABP were inverse. Further studies are needed to define the pathophysiologic relationship between RAS components and blood pressure regulation in obese youth.

Aldosterone, Plasma Renin Activity, and Aldosterone/Renin Ratio in a Normotensive Healthy Pediatric Population

Primary aldosteronism is an important cause of secondary hypertension and is suspected in adults with an aldosterone/renin ratio ≥25. The normal aldosterone/renin ratio is unknown in children. The aim was to establish serum aldosterone, plasma renin activity, and aldosterone/renin ratio values in a healthy pediatric population. A cross-sectional study was performed in 211 healthy normotensive children (4 to 16 years old). Two subgroups of normotensive children were obtained: with hypertensive parents (NH) (n=113) and normotensive parents (n=98). Blood samples for measuring serum aldosterone, plasma renin activity, aldosterone/renin ratio, and DNA were collected. In subjects with aldosterone/renin ratio ≥25, the chimeric CYP11B1/CYP11B2 gene was investigated by long-extension PCR. Results are expressed as median [Q 1 –Q 3 ]. NH and normotensive parents groups were similar in serum aldosterone (6.5 [3.6 to 9.0] ng/dL versus 6.5 [2.9 to 9.7] ng/dL; P =0.968) and plasma renin activity (2.3 [1.6 to 3.1] versus 2.4 [1.7 to 3.7] ng/mL per hour; P =0.129). The aldosterone/renin ratio was higher in the NH group, but this difference did not reach statistical significance (2.8 [1.9 to 4.1] versus 2.5 [1.4 to 4.0], P =0.104). In one subject of the NH group, the chimeric CYP11B1/CYP11B2 gene was detected. We demonstrated that normal aldosterone/renin ratio values in a healthy pediatric population without NH were lower than those reported for an adult normotensive population.

Aldosterone: role in the cardiometabolic syndrome and resistant hypertension

The prevalence of diabetes, hypertension, and cardiovascular disease (CVD) and chronic kidney disease (CKD) is increasing in concert with obesity. Insulin resistance, metabolic dyslipidemia, central obesity, albuminuria. and hypertension commonly cluster to comprise the cardiometabolic syndrome (CMS). Emerging evidence supports a shift in our understanding of the crucial role of elevated serum aldosterone in promoting insulin resistance and resistant hypertension. Aldosterone enhances tissue generation of oxygen free radicals and systemic inflammation. This increase in oxidative stress and inflammation, in turn, contributes to impaired insulin metabolic signaling, reduced endothelial-mediated vasorelaxation, and associated cardiovascular and renal structural and functional abnormalities. In this context, recent investigation indicates that hyperaldosteronism, which is often associated with obesity, contributes to impaired pancreatic beta-cell function as well as diminished skeletal muscle insulin metabolic signaling. Accumulating evidence indicates that the cardiovascular and renal abnormalities associated with insulin resistance are mediated, in part, by aldosterone's nongenomic as well as genomic signaling through the mineralocorticoid receptor (MR). In the CMS, there are increased circulating levels of glucocorticoids, which can also activate MR signaling in cardiovascular, adipose, skeletal muscle, neuronal, and liver tissue. Furthermore, there is increasing evidence that fat tissue produces a lipid soluble factor that stimulates aldosterone production from the adrenal zona glomerulosa. Recently, we have learned that MR blockade improves pancreatic insulin release, insulin-mediated glucose utilization, and endothelium-dependent vasorelaxation as well as reduces the progression of CVD and CKD. In summary, aldosterone excess exerts detrimental metabolic effects that contribute to the development of the CMS and resistant hypertension as well as CVD and CKD.

Left ventricular geometry in children and adolescents with primary hypertension

BACKGROUND

Children with hypertension (HTN) are at increased risk for left ventricular hypertrophy (LVH). Increased left ventricular (LV) mass (LVM) by the process of remodeling in response to volume or pressure loading may be eccentric (increased LV diameter) or concentric (increased wall thickness). Our objective was to classify LV geometry among children with primary HTN and examine differences in ambulatory blood pressure (ABP).

METHODS

Subjects aged 7-18 years with suspected HTN were enrolled in this cross-sectional study. ABP and LVM index (LVMI) were measured within the same 24-h period. LV geometry was classified as normal, concentric remodeling, concentric LVH, or eccentric LVH.

RESULTS

Children with LVH had significantly higher ambulatory systolic BP (SBP) and diastolic blood pressure (BP) (DBP) levels and body mass index (BMI) Z-score. Sixty-eight children had HTN based upon ABP monitoring (ABPM). Thirty-eight percent of the hypertensive subjects had LVH, with equal distribution in the concentric and eccentric groups. There were significant differences in the 24-h DBP parameters when the eccentric LVH group was compared to the normal geometry and concentric LVH groups. Relative wall thickness (RWT) was inversely associated with night time DBP parameters. These relationships persisted after controlling for BMI Z-score.

CONCLUSIONS

Although the risk for LVH is associated with increased SBP and BMI Z-score, those with eccentric LVH had significantly higher DBP.

Left ventricular geometry in children and adolescents with primary hypertension

BACKGROUND

Children with hypertension (HTN) are at increased risk for left ventricular hypertrophy (LVH). Increased left ventricular (LV) mass (LVM) by the process of remodeling in response to volume or pressure loading may be eccentric (increased LV diameter) or concentric (increased wall thickness). Our objective was to classify LV geometry among children with primary HTN and examine differences in ambulatory blood pressure (ABP).

METHODS

Subjects aged 7-18 years with suspected HTN were enrolled in this cross-sectional study. ABP and LVM index (LVMI) were measured within the same 24-h period. LV geometry was classified as normal, concentric remodeling, concentric LVH, or eccentric LVH.

RESULTS

Children with LVH had significantly higher ambulatory systolic BP (SBP) and diastolic blood pressure (BP) (DBP) levels and body mass index (BMI) Z-score. Sixty-eight children had HTN based upon ABP monitoring (ABPM). Thirty-eight percent of the hypertensive subjects had LVH, with equal distribution in the concentric and eccentric groups. There were significant differences in the 24-h DBP parameters when the eccentric LVH group was compared to the normal geometry and concentric LVH groups. Relative wall thickness (RWT) was inversely associated with night time DBP parameters. These relationships persisted after controlling for BMI Z-score.

CONCLUSIONS

Although the risk for LVH is associated with increased SBP and BMI Z-score, those with eccentric LVH had significantly higher DBP.