Is aldosterone the missing link in refractory hypertension?: aldosterone-to-renin ratio as a marker of inappropriate aldosterone activity

Is the plasma aldosterone-to-renin ratio associated with blood pressure response to treatment in general practice?

BACKGROUND

Individualized antihypertensive treatment based on specific biomarkers such as renin may lead to more effective blood pressure control in patients with newly diagnosed essential hypertension. Recent studies suggested that the plasma aldosterone-to-renin ratio (ARR) may also be a candidate predictor for this purpose.

OBJECTIVE

To assess whether the ARR is associated with the blood pressure response to antihypertensive treatment in patients with newly diagnosed hypertension.

METHODS

In this prospective cohort study in primary care, we determined the ARR in patients with newly diagnosed hypertension prior to starting treatment. Treatment was categorized in five groups: no medication, use of angiotensin-converting-enzyme inhibitor or angiotensin receptor blocker, use of calcium channel blocker, use of diuretic, or use of beta blocker. We examined the relation between the ARR and blood pressure response within 1 year of treatment, taking into account the type of antihypertensive treatment and adjusting for gender, age, baseline blood pressure, and comorbidity.

RESULTS

Out of 304 patients, we used 947 measurements (727 no medication, 220 medication) for analysis. There was no association between the ARR and the response in blood pressure, and this applied to each treatment group. Target blood pressure, defined as systolic blood pressure <140 mmHg, was reached in 31% of patients. There was no association between the ARR and reaching target blood pressure (OR 1.002, 95% CI 0.983-1.022).

CONCLUSION

The ARR is not associated with the response in blood pressure within 1 year of antihypertensive treatment in primary care.

Effects of Reduced Kidney Function Because of Living Kidney Donation on Left Ventricular Mass

Living kidney donation is associated with a small but significant increase in cardiovascular mortality. In addition, mildly decreased kidney function is associated with an increase of left ventricular mass and with cardiovascular disease in patients with chronic kidney disease. To investigate this association, we evaluated the impact of mildly decreased kidney function after living kidney donation on subclinical cardiac structural and functional changes. In this prospective cohort study, cardiac and renal magnetic resonance imaging and laboratory analyses were performed in 23 living kidney donors (mean age 54±10 years, 52% male) before donation and at 4 and 12 months after nephrectomy. Mean estimated glomerular filtration rate was 102±15 mL min −1 1.73 m −2 before donation and 70±13 mL min −1 1.73 m −2 at 12 months ( P <0.001). Left ventricular mass increased from 112±22 to 115±23 g ( P <0.001). In addition, heart rate was significantly increased (65±7 to 74±14; P =0.04). Concurrently, kidney and adrenal gland volume increased from 163±33 to 195±34 mL ( P <0.001) and from 7.6±2.2 to 8.4±2.4 mL ( P =0.032), respectively, as did procollagen type III (Δ0.11 ng/mL, P <0.001) and not N-terminal probrain natriuretic peptide (Δ14 pg/mL, P =0.25). The mild decrease in kidney function after living kidney donation leads to a significant but clinically negligible increase in left ventricular mass 12 months after living kidney donation. This study of a longitudinal analysis of living kidney donors provides direct evidence of a kidney–heart link.

Review: Aldosterone — the future challenge in cardiovascular disease?

Mineralocorticoid receptor activation plays a key role in cardiovascular disease and hypertension, which are particularly prevalent in diabetes mellitus; secondary hyperaldosteronism contributes to cardiac failure. Major intervention trials in heart failure have demonstrated unequivocal benefit from aldosterone receptor antagonism. Focused experimental studies in humans and in animal models of hypertension have shown that aldosterone blockade improves a number of pathogenic abnormalities including vascular endothelial dysfunction and altered baroreflex function, and prevents the development of cardiac hypertrophy and renal histological damage. Based on recent outcomes studies, the challenge is now to transfer the experimental evidence into clinical M practice.

Association of aldosterone-to-renin ratio with hypertension differs by sodium intake: the Ohasama study

BACKGROUND

In cross-sectional studies, the aldosterone-to-renin ratio (ARR) has been reported to be associated with hypertension under conditions of higher sodium intake. The objective of this prospective study was to investigate the association between ARR and the development of hypertension in community residents stratified by dietary sodium intake.

METHODS

From the general population of Ohasama, we obtained plasma renin activity (PRA) and plasma aldosterone concentrations (PACs) for 608 participants (mean age = 57.6 years; 71.4% women) without hypertension at baseline. Using the Cox model, we computed the adjusted hazard ratio (HR) of natural log-transformed ARR (lnARR) for the development of hypertension, defined as blood pressure ≥140/90mm Hg or start of treatment with antihypertensive drugs during follow-up.

RESULTS

During a mean follow-up of 6.8 years, 298 participants developed hypertension. The median PRA, PAC, and ARR were 1.2ng/ml/hour, 6.6ng/dl, and 5.5ng/dl per ng/ml/hour, respectively. Each 1 SD increase in lnARR was associated with an increased risk for the development of hypertension in participants overall (HR = 1.18; P = 0.007). In participants with higher sodium intake (median ≥4,102mg/day), a significant association of lnARR with hypertension remained (HR = 1.25; P = 0.009), whereas no significant association was observed in participants with lower sodium intake (P = 0.18). Participants who developed hypertension had significantly lower PRA than those who did not (P = 0.003), despite no differences in PAC (P = 0.91).

CONCLUSIONS

These results raise the hypothesis that relative aldosterone excess may have a deleterious effect on the development of hypertension by contributing to salt/volume-related hypertension.

NP-59 SPECT/CT imaging in stage 1 hypertensive and atypical primary aldosteronism: a 5-year retrospective analysis of clinicolaboratory and imaging features

OBJECTIVE

We retrospectively analyzed all primary aldosteronism (PA) patients undergoing NP-59 SPECT/CT imaging with regard to their clinicolaboratory and imaging features, investigation, and outcomes.

MATERIAL AND METHODS

11 PA patients who presented to our hospital for NP-59 SPECT/CT imaging between April 2007 and March 2012 and managed here were analyzed.

RESULTS

Among 11 PA patients, eight (73%) had stage 1 hypertension, three (27%) stage 2 hypertension, four (36%) normal plasma aldosterone concentration, nine (82%) nonsuppressed plasma renin activity (PRA), six (55%) normal aldosterone-renin-ratio (ARR), eight (73%) serum potassium ≧3 mEq/L, seven (64%) subclinical presentation, seven (64%) negative confirmatory testing, and four (36%) inconclusive results on CT scan and seven (64%) on planar NP-59 scan. All 11 (100%) patients had positive results on NP-59 SPECT/CT scan. Two (18%) met typical triad and nine (82%) atypical triad. Among nine atypical PA patients, three (33%) had clinical presentation, six (67%) subclinical presentation, six (67%) negative confirmatory testing, and four (44%) inconclusive results on CT scan and six (67%) on planar NP-59 scan. All patients had improved outcomes. Significant differences between typical and atypical PA existed in PRA and ARR.

CONCLUSIONS

NP-59 SPECT/CT may provide diagnostic potential in stage 1 hypertensive and atypical PA.

Aldosterone and angiotensin: Role in diabetes and cardiovascular diseases

The present review shall familiarize the readers with the role of renin-angiotensin aldosterone system (RAAS), which regulates blood pressure, electrolyte and fluid homeostasis. The local RAAS operates in an autocrine, paracrine and/or intracrine manner and exhibits multiple physiological effects at the cellular level. In addition to local RAAS, there exists a complete pancreatic RAAS which has multi-facet role in diabetes and cardiovascular diseases. Aldosterone is known to mediate hyperinsulinemia, hypertension, cardiac failure and myocardial fibrosis while angiotensin II mediates diabetes, endothelial dysfunction, vascular inflammation, hypertrophy and remodeling. As the understanding of this biology of RAAS increases, it serves to exploit this for the pharmacotherapy of diabetes and cardiovascular diseases.

Aldosterone-to-renin ratio as a predictor of stroke under conditions of high sodium intake: the Ohasama study

BACKGROUND

Aldosterone is thought to have deleterious effects on the cardiovascular system. The aldosterone-to-renin ratio (ARR) is more reproducible than aldosterone levels alone and could be an index for inappropriate aldosterone secretion or activity. We previously reported the apparent relation between ARR and hypertension in subjects with high sodium intake. This prospective study investigated the risk of ARR for a first stroke in a general population stratified by sodium intake.

METHODS

We obtained plasma renin activity (PRA) and plasma aldosterone concentrations (PAC) for 883 participants aged ≥ 35 years not receiving antihypertensive treatment in the general population of Ohasama (mean age: 59.0 ± 11.3 years; 65.6% women).

RESULTS

Over a mean of 10.9 follow-up years, 45 strokes occurred. The median PRA, PAC, and ARR were 1.2 ng/ml/h, 6.4 ng/dl, and 5.3 ng/dl per ng/ml/h, respectively. Using Cox regression, we computed hazard ratios adjusted for sex, age, body mass index (BMI), and systolic blood pressure. No association between logARR and stroke was observed in subjects overall. However, in subjects with high sodium intake (≥ median of 4,058 mg/day (salt equivalent, 10.5 g/day)), each 1 s.d. increase in logARR was associated with an increased hazard ratio for stroke (hazard ratio: 1.49, P = 0.04). No significant association was observed in subjects with low sodium intake (P = 0.7). When we repeated all the analyses using logPRA or logPAC, no significant associations were found.

CONCLUSION

These results suggest that high ARR, that is, relative aldosterone excess, is a predictor for stroke under conditions of high sodium intake.

Kininogen gene (KNG) variation has a consistent effect on aldosterone response to antihypertensive drug therapy: the GERA study

Recent experimental and clinical studies suggested that apart from playing an essential role in blood pressure homeostasis, aldosterone is involved in the pathophysiology of cardiovascular and renal diseases by inducing structural changes in the heart, kidney, and vessel wall. The interindividual variation of aldosterone response to antihypertensive treatment is considerable, and is at least partially explained by genetic variation. In this study, we investigated aldosterone response to two antihypertensive drugs-a thiazide diuretic and an angiotensin receptor blocker (ARB). Genetic variations in 50 candidate genes were tested for association with aldosterone response in four independent samples: African American (AA) responders to a diuretic (n = 289), AA responders to an ARB (n = 252), European American (EA) responders to a diuretic (n = 295) and EA responders to an ARB (n = 300). Linear regression was used to test the association with inclusion of age, sex, and body mass index as covariates. The results indicated the existence of one or more variants in the kininogen gene (KNG) that influence interindividual variation in aldosterone response. The significant association was replicated in three of four studied groups. The single nucleotide polymorphism rs4686799 was associated in AA and EA responders to the diuretic (P = 0.04 and P = 0.07, respectively), and rs5030062 and rs698078 were significantly associated in EA responders to the diuretic (P = 0.05 and P = 0.01) and EA responders to the ARB (P = 0.04 and P = 0.02). Although the clinical implication of KNG gene variation to antihypertensive drug response is yet to be determined, this novel candidate locus provides important new insights into drug response physiology.

TASK channel deletion in mice causes primary hyperaldosteronism

When inappropriate for salt status, the mineralocorticoid aldosterone induces cardiac and renal injury. Autonomous overproduction of aldosterone from the adrenal zona glomerulosa (ZG) is also the most frequent cause of secondary hypertension. Yet, the etiology of nontumorigenic primary hyperaldosteronism caused by bilateral idiopathic hyperaldosteronism remains unknown. Here, we show that genetic deletion of TWIK-related acid-sensitive K (TASK)-1 and TASK-3 channels removes an important background K current that results in a marked depolarization of ZG cell membrane potential. Although TASK channel deletion mice (TASK-/-) adjust urinary Na excretion and aldosterone production to match Na intake, they produce more aldosterone than control mice across the range of Na intake. Overproduction of aldosterone is not the result of enhanced activity of the renin-angiotensin system because circulating renin concentrations remain either unchanged or lower than those of control mice at each level of Na intake. In addition, TASK-/- mice fail to suppress aldosterone production in response to dietary Na loading. Autonomous aldosterone production is also demonstrated by the failure of an angiotensin type 1 receptor blocker, candesartan, to normalize aldosterone production to control levels in TASK-/- mice. Thus, TASK-/- channel knockout mice exhibit the hallmarks of primary hyperaldosteronism. Our studies establish an animal model of nontumorigenic primary hyperaldosteronism and identify TASK channels as a possible therapeutic target for primary hyperaldosteronism.

Effect of salt on isoprostanes in salt-sensitive essential hypertension

The controversy over beneficial versus harmful effects of salt on cardiovascular outcomes may be caused by different effects of salt on intermediate phenotypes of hypertension not characterized in epidemiological studies. Hence, we investigated acute effects of salt on oxidative stress in hypertensive subjects classified as salt sensitive (SS, n=14) or salt resistant (SR, n=13) by an inpatient protocol of salt loading (460 mmol NaCl) and salt depletion (10 mmol NaCl and furosemide). Oxidative stress was assessed by measuring the plasma isoprostane 8-iso-PGF2alpha. SS had lower plasma renin activity, higher aldosterone/renin ratios, and exaggerated endothelin and catecholamine responses to salt depletion compared with SR. Baseline lipid-bound isoprostanes (749+/-70 pmol/L) were 83% of the total and were slightly but not significantly higher in SS than SR. Baseline free isoprostanes did not differ between groups. After salt loading, lipid-bound isoprostanes were higher in SS (945+/-106) than SR (579+/-57; P<0.01). Salt depletion significantly decreased them in SS (-174+/-84) and increased them in SR (+129+/-58), equalizing their levels (771+/-61 versus 708+/-91; P value not significant). Free isoprostanes were decreased by salt depletion only if data in all of the patients were analyzed together. Total isoprostanes followed the pattern of the lipid-bound fraction. Correlations between salt depletion-induced changes in lipid-bound isoprostanes, plasma renin activity (r=0.45; P<0.02), and aldosterone/renin ratios (r=-0.41; P<0.04) suggested that the more SS the patient, the greater the reduction of oxidative stress by salt depletion. Our research is the first to show that salt affects oxidative stress acutely in humans, particularly in SS hypertension, which may explain the controversial results of epidemiological studies on salt and morbidity and may have implications for therapy.

Pharmacogenomics and cardiovascular drugs: need for integrated biological system with phenotypes and proteomic markers

Personalized medicine is based on a better knowledge of biological variability, considering the important part due to genetics. When trying to identify involved genes and their products in differential cardiovascular drug responses, a five-step strategy is to be followed: 1) Pharmacokinetic-related genes and phenotypes (2) Pharmacodynamic targets, genes and products (3) Cardiovascular diseases and risks depending on specific or large metabolic cycles (4) Physiological variations of previously identified genes and proteins (5) Environment influences on them. After summarizing the most well-known genes involved in drug metabolism, we will take as example of drugs, the statins, considered as very important drugs from a Public-Health standpoint, but also for economical reasons. These drugs respond differently in human depending on multiple polymorphisms. We will give examples with common ApoE polymorphisms influencing the hypolipemic effects of statins. These drugs also have pleiotropic effects and decrease inflammatory markers. This illustrates the need to separate clinical diseases phenotypes in specific metabolic pathways, which could propose other classifications, of diseases and related genes. Hypertension is also a good example of clinical phenotype which should be followed after various therapeutic approaches by genes polymorphisms and proteins markers. Gene products are under clear environmental expression variations such as age, body mass index and obesity, alcohol, tobacco and dietary interventions which are the first therapeutical actions taken in cardiovascular diseases. But at each of the five steps, within a pharmacoproteomic strategy, we also need to use available information from peptides, proteins and metabolites, which usually are the gene products. A profiling approach, i.e., dealing with genomics, but now also with proteomics, is to be used. In conclusion, the profiling, as well as the large amount of data, will more than before render necessary an organized interpretation of DNA, RNA as well as proteins variations, both at individual and population level.

The aldosterone antagonist and facultative diuretic eplerenone: a critical review

Eplerenone is a new aldosterone-receptor blocker that differs from spironolactone by virtue of higher selectivity for the aldosterone receptor. Therefore, eplerenone treatment is associated with comparative and absolute low incidences of gynecomastia, mastodynia, and abnormal vaginal bleeding. Similarly, a lower incidence of sexual impotence than that associated with spironolactone administration may be anticipated. Eplerenone and spironolactone increase natriuresis and cause renal retention of potassium when plasma aldosterone is high, i.e., both agents are facultative diuretics. Eplerenone reduces high blood pressure effectively. The results of a recent large study and an ensuing meta-analysis on antihypertensive treatment suggest that a diuretic should be the first-choice agent in most circumstances. Low-dose eplerenone combinations with a low-dose thiazide-type diuretic appear to be options worth investigating, since the overall cardiovascular benefit brought about by reducing blood pressure with the thiazide would be increased, inter alia, by the antikaliuretic action and by the blockade of extrarenal aldosterone receptors provoked by eplerenone. Eplerenone should replace spironolactone as a natriuretic and antikaliuretic in heart failure and as add-on treatment in severe systolic cardiac insufficiency, and it is indicated after an acute myocardial infarction complicated by left ventricular dysfunction and heart failure. The finding that hypertension control with diuretic-based pharmacotherapy results in better prevention of heart failure than pressure reduction with other drugs makes it pertinent to investigate whether diuretics in general, and eplerenone in particular, should constitute part of the initial pharmacotherapy for heart failure when there is no overt fluid retention and independent of the etiology. Eplerenone may cause hyperkalemia, and it might favor the development of metabolic acidosis or hyponatraemia in some circumstances.

The syndromes of low-renin hypertension: "separating the wheat from the chaff"

Primary aldosteronism (PA) is characterized by hypertension and suppressed renin activity with or without hypokalemia and comprises the aldosterone-producing adenoma (APA) and bilateral adrenal hyperplasia or idiopatic hyperaldosteronism (IHA). In recent series employing the aldosterone (aldo, ng/dL):renin (ng/mL·h) ratio (ARR) for screening, prevalence of PA among hypertensives soars to 8-20%; current predominance of IHA (>80%) over APA suggests the inclusion of former low-renin essential hypertensives (LREH), in whom plasma aldo can be reduced by suppressive maneuvers. We evaluated the test characteristics of the ARR obtained retrospectively from 127 patients with PA (81 APA; 46 IHA) and 55 with EH (30 LREH; 25 NREH) studied from 1975 to 1990. Using the combined ROC-defined cutoffs of 27 for the ARR and 12ng/dL for aldo, we obtained 89.8% sensitivity (Ss) and 98.2% specificity (Sp) in discriminating PA from EH: all APA and 72% of the IHA patients had values above these limits, but only one (3%) with LREH. Among the 46 IHA patients, 10 (21.7%) had ARR <27, four of whom with aldo <12ng/dL, virtually indistinguishable from LREH. Use of higher cutoff values (ARR >100; aldo >20) may attain 84%Ss and 82.6%Sp in separating APA from IHA. Because IHA and LREH ("the chaff") may be spectrum stages from the same disease, definite discrimination between these entities seems immaterial. However, precise identification of the APA ("the wheat") is critical, since it is the only surgically curable form of PA. Thus, while patients who may harbor an APA must be thoroughly investigated and surgically treated, non-tumoral disease (IHA and LREH) may be best treated with an aldo-receptor antagonist that will also prevent the aldo-mediated inflammatory effects involved in myocardial fibrosis and abnormal cardiac remodeling.

Endothelin???aldosterone interaction and proteinuria in low-renin hypertension

OBJECTIVE

To investigate whether endothelin and aldosterone participate in the increased prevalence and severity of nephrosclerosis in human low-renin hypertension, analogous to observations in experimental hypertension.

DESIGN

Comparison of endothelin, aldosterone and their relationships with proteinuria, in hypertensive patients with high aldosterone : renin ratios (HARR group, n = 14) or normal aldosterone : renin ratios (NARR group, n = 15).

METHODS

Urine protein and radioimmunoassay measurements of plasma renin activity, endothelin and aldosterone were carried out in individuals taking their usual diet, and after salt loading and salt depletion.

RESULTS

Compared with the NARR group, patients in the HARR group had higher blood pressure, greater salt sensitivity of their blood pressure, significantly greater urine protein and lower serum potassium concentrations, lower renin activities [0.14 +/- 0.03 ng AngiotensinI (AI)/l per s compared with 0.76 +/- 0.16 ng AI/l per s; P < 0.005], blunted renin-aldosterone responses to salt loading and salt depletion, enhanced catecholamine responses to salt depletion, and increased plasma endothelin (5.1 +/- 0.5 fmol/ml compared with 3.7 +/- 0.3 fmol/ml; P < 0.03). In the HARR group, endothelin and aldosterone concentrations were highly correlated, and both correlated with blood pressure and urine protein. In contrast, in the NARR group, endothelin and aldosterone did not correlate between them or with blood pressure, and only endothelin, not aldosterone, correlated with urine protein. Multivariate regression confirmed that the interaction between aldosterone and endothelin was the major predictor of urine protein in the HARR group (r = 0.442), whereas endothelin, renin and their interaction were predictors in the NARR group (r = 0.467).

CONCLUSIONS

Our results concur with experimental evidence for participation of endothelin in renal damage of angiotensin-dependent hypertension and for that of an endothelin-aldosterone interaction in low-renin hypertension. We propose that combined pharmacological antagonism of endothelin and aldosterone may confer renal protection beyond blood pressure reduction in patients with low-renin hypertension, a population at high risk for hypertensive nephrosclerosis.

Primary aldosteronism and hypertensive disease

Recent studies in hypertensive populations that have used the serum aldosterone (SA) to plasma renin activity (PRA) ratio as a screening test have demonstrated a high prevalence of primary aldosteronism (PA). This frequency is higher than that previously described when hypokalemia was used as a screening tool. However, other factors, such as the characteristics of hypertensive disease, could also influence the prevalence of PA. We studied 609 essential hypertensive patients, classified according to the Joint National Committee VI (JNC VI), in 3 different stages depending on the severity of their hypertensive disease. We measured SA and PRA and calculated the SA-PRA ratio for all patients. An SA-PRA ratio >25 was detected in 63 of 609 patients, and the fludrocortisone test confirmed the PA diagnoses in 37 of 609 (6.1%) cases. PA prevalence according to hypertension stage was as follows: stage 1, 6 of 301 cases (1.99%); stage 2, 15 of 187 cases (8.02%); and stage 3, 16 of 121 cases (13.2%). PA patients were slightly younger than the other hypertensive patients (48.4+/-10.5 vs 53.6+/-10.2 years; P<0.05). Serum potassium levels were normal in 36 of 37 PA patients; only 1 patient had minor hypokalemia. Computed tomography scans showed bilateral adrenal enlargement in 7 and an adrenal nodule in 2 cases. In summary, we found a high frequency of PA in essential hypertensives classified in stages 2 and 3 according to the JNC VI. The low frequency of computed tomography scan abnormalities and hypokalemia suggests that the diagnosis for most PA patients corresponds to attenuated forms of the disease.

20-HETE and furosemide-induced natriuresis in salt-sensitive essential hypertension

Cyclooxygenase metabolites of arachidonic acid modulate the natriuretic effect of furosemide. It is not known whether 20-HETE, a monooxygenase metabolite of arachidonic acid that also inhibits sodium transport, participates in the action of furosemide. We measured urine sodium (UNaV) and 20-HETE during furosemide diuresis (40 mg three times over 12 hours) in 12 salt-sensitive (SS) and 11 salt-resistant (SR), salt-replete hypertensive subjects (126+/-24 mmol/24 hours positive sodium balance produced by 160-mmol-sodium diet and 2 L saline infusion). Individual systolic blood pressure decreases from the salt-replete to the salt-depleted state were the index of salt-sensitivity. SS had low plasma renin with blunted responses to changes in salt balance, inappropriate plasma aldosterone, and an increased aldosterone/renin ratio. UNaV by furosemide was less in SS (263+/-25 mmol/12 hours) than in SR (351+/-25 mmol/12 hours, P<0.02) patients. 20-HETE was not different between SS and SR patients before (1.92+/-0.38 versus 1.37+/-0.34 microg/h) or after furosemide (1.52+/-0.27 versus 2.01+/-0.40 microg/h), but furosemide changed 20-HETE excretion in opposite direction in SR (0.63+/-0.26) versus SS (-0.40+/-0.17, P<0.005) patients. In all patients together, %Delta20-HETE by furosemide correlated with %DeltaUNaV (r=0.56, P<0.01) and negatively with salt-sensitivity of blood pressure (r=-0.55, P<0.01). In SS, Delta20-HETE by furosemide correlated with Deltaaldosterone/renin ratio (r=0.60, P<0.05), whereas 20-HETE during furosemide had a negative correlation with body mass index (r=-0.73, P<0.01). Our data suggest that 20-HETE modulates the natriuretic response to furosemide, and impaired natriuresis of SS involves a mechanism that alters the 20-HETE response to furosemide and is linked to salt-sensitivity of blood pressure.