Dietary sodium restriction restores nocturnal reduction of blood pressure in patients with primary aldosteronism

High plasma aldosterone concentration is associated with worse 24-h ambulatory blood pressure profile in patients with primary aldosteronism

Patients with primary aldosteronism (PA) have a higher risk of cardiovascular disease (CVD) than essential hypertension due to underlying hyperaldosteronism. However, the association between high plasma aldosterone concentrations (PACs) and diurnal blood pressure (BP) variation has not been fully elucidated. Because abnormal ambulatory blood pressure monitoring (ABPM) profiles are associated with increased CVD risk, we investigated the association between PACs and the ABPM profile in 36 patients with PA diagnosed by confirmatory tests who underwent adrenal venous sampling (AVS). The clinical parameters were measured during hospitalization for AVS. The dietary salt intake of hospitalized patients was controlled at 6 g/day. During AVS, blood samples were collected from the inferior vena cava before and 1 h after adrenocorticotropic hormone (ACTH) stimulation to measure the PACs. The post-stimulation PAC had a significant negative correlation with nocturnal BP dipping rates (R = -0.387, p = 0.020), whereas pre-stimulation PAC did not (R = -0.217, p = 0.204). The nocturnal BP dipping rates were significantly lower in the high PAC group (PAC higher than the median) than low PAC group (PAC lower than the median) (p = 0.009). Multiple regression analysis revealed that high PAC was an independent factor contributing to low nocturnal BP dipping rates (β = -0.316, p = 0.038). In conclusion, in patients with PA, hyperaldosteronism is associated with nocturnal hypertension, which is an important risk factor for CVD. Additionally, ACTH stimulation may improve the sensitivity of PACs as a clinical indicator of nocturnal hypertension.

Low sodium intake ameliorates hypertension and left ventricular hypertrophy in mice with primary aldosteronism

The goal of this paper is to elucidate the effects of sodium restriction on hypertension and left ventricular (LV) hypertrophy in a mouse model with primary aldosteronism (PA). Mice with genetic deletion of TWIK-related acid-sensitive K (TASK)-1 and TASK-3 channels (TASK^-/-) were used as the animal model of PA. Parameters of the LV were assessed using echocardiography and histomorphology analysis. Untargeted metabolomics analysis was conducted to reveal the mechanisms underlying the hypertrophic changes in the TASK^-/- mice. The TASK^-/- adult male mice exhibited the hallmarks of PA, including hypertension, hyperaldosteronism, hypernatremia, hypokalemia, and mild acid-base balance disorders. Two weeks of low sodium intake significantly reduced the 24-h average systolic and diastolic BP in TASK^-/- but not TASK^+/+ mice. In addition, TASK^-/- mice showed increasing LV hypertrophy with age, and 2 weeks of the low-sodium diet significantly reversed the increased BP and LV wall thickness in adult TASK^-/- mice. Furthermore, a low-sodium diet beginning at 4 weeks of age protected TASK^-/- mice from LV hypertrophy at 8-12 weeks of age. Untargeted metabolomics demonstrated that the disturbances in heart metabolism in the TASK^-/- mice (e.g., Glutathione metabolism; biosynthesis of unsaturated fatty acids; amino sugar and nucleotide sugar metabolism; pantothenate and CoA biosynthesis; D-glutamine and D-glutamate metabolism), some of which were reversed after sodium restriction, might be involved in the development of LV hypertrophy. In conclusion, adult male TASK^-/- mice exhibit spontaneous hypertension and LV hypertrophy, which are ameliorated by a low-sodium intake.

Therapeutic Outcomes with Surgical and Medical Management of Primary Aldosteronism

PURPOSE OF REVIEW

Primary aldosteronism (PA) is the most common cause of secondary hypertension and is significantly under-diagnosed. Delays in diagnosis and treatment can lead to cardiovascular morbidity and mortality. The goal of this study is to review the management of PA, with a focus on medical and surgical treatment outcomes.

RECENT FINDINGS

PA causes cardiovascular dysfunction in excess of degree of hypertension. Adrenalectomy demonstrates a therapeutic advantage over mineralocorticoid antagonist (MRA) therapy, after controlling for degree of hypertension and subtype of PA. Higher rates of atrial fibrillation, heart failure, stroke, and incidence of chronic kidney disease are observed in subjects treated with MRAs than in subjects treated with adrenalectomy. The therapeutic benefit of surgery may reflect definitive resolution of excess aldosterone. Complete mineralocorticoid blockade may achieve similar benefit to adrenalectomy. Adrenalectomy is the most effective treatment for unilateral PA. Biomarkers for MRA therapy might inform optimal medical therapy of bilateral adrenal hyperplasia.

Using Predicted Atherosclerotic Cardiovascular Disease Risk for Discrimination of Awake or Nocturnal Hypertension

BACKGROUND

Several atherosclerotic cardiovascular disease (ASCVD) risk factors are associated with awake and nocturnal hypertension.

METHODS

We assessed the association between a composite ASCVD risk score and awake or nocturnal hypertension using data from participants aged 40-79 years who completed ambulatory blood pressure monitoring at the Year 30 Coronary Artery Risk Development in Young Adults study exam in 2015-2016 (n = 716) and the baseline Jackson Heart Study exam in 2000-2004 (n = 770). Ten-year predicted ASCVD risk was calculated using the Pooled Cohort risk equations. Awake hypertension was defined as mean awake systolic blood pressure (SBP) ≥135 mm Hg or diastolic blood pressure (DBP) ≥85 mm Hg and nocturnal hypertension was defined as mean asleep SBP ≥120 mm Hg or DBP ≥70 mm Hg.

RESULTS

Among participants with a 10-year predicted ASCVD risk <5%, 5% to <7.5%, 7.5% to <10%, and ≥10%, the prevalence of awake or nocturnal hypertension as a composite outcome was 29.5%, 47.8%, 62.2%, and 69.7%, respectively. After multivariable adjustment, higher ASCVD risk was associated with higher prevalence ratios for awake or nocturnal hypertension among participants with clinic-measured SBP/DBP <130/85 mm Hg but not ≥130/85 mm Hg. The C-statistic for discriminating between participants with vs. without awake or nocturnal hypertension was 0.012 (95% confidence interval 0.003, 0.016) higher when comparing a model with ASCVD risk and clinic-measured blood pressure (BP) together vs. clinic-measured BP without ASCVD risk.

CONCLUSIONS

Using 10-year predicted ASCVD risk in conjunction with clinic BP improves discrimination between individuals with and without awake or nocturnal hypertension.

Translating research evidence into clinical practice: a reminder of important clinical lessons in management of resistant hypertension through a case study in general practice

A case of a 59-year-old man with resistant hypertension, despite 8 months of non-pharmacological and pharmacological management up to maximal doses of triple antihypertensive therapy. Review of the literature found a study that reported improved blood pressure control with bedtime dosing of antihypertensive treatment. Changing to bedtime dosage of antihypertensives resulted in significant improvement in blood pressure control to below target levels. This highlights the importance of the clinicians' awareness and implementation of research findings and hence delivery of best evidence-based care.

Blood Pressure Increases Before Pulse Rate During the Nocturnal Period in Hypertensive Patients

Ambulatory blood pressure monitoring (ABPM) is used for the evaluation of out-of-office blood pressure (BP), however, knowledge concerning the detailed behavior of nocturnal blood pressure (BP) and pulse rate (PR) is limited.A total of 190 participants (64 ± 15 years, 46.3% males) underwent ABPM for diagnosis of hypertension or evaluation of hypertensive therapy. BP and PR were measured automatically by the oscillometric method. From the hourly average ABPM values, the nocturnal time courses (0 AM to 6 AM) of SBP and PR were determined and compared to each other.In general, SBP fell to the lowest level at around midnight and started to increase progressively towards dawn while PR stayed unchanged until 7 AM. Age and gender affected the time course of SBP, most distinctly in the female patients aged ≥ 60 years. The time course of the increase of SBP was very similar in the patients, with BP dipping and non-dipping. The cardiothoracic ratio (CTR) slightly and renal dysfunction modestly facilitated the increase of nocturnal SBP. The nocturnal increase in SBP was not accompanied by an increase of PR in any group or subgroup. The pathophysiology and clinical significance of the early and exclusive increase in nocturnal BP need to be investigated.Average ABPM values in these hypertensive patients showed that BP starts to increase toward dawn without an increase in PR and that this discrepant behavior between BP and RP was most distinct in females 60 or older. The mechanism and clinical significance of such a discordant variation in BP and PR need to be elucidated.

Patients With Primary Aldosteronism Respond to Unilateral Adrenalectomy With Long-Term Reduction in Salt Intake

CONTEXT

High dietary salt intake is known to aggravate arterial hypertension. This effect could be of particular relevance in the setting of primary aldosteronism (PA), which is associated with cardiovascular damage independent of blood pressure levels. The aim of this study was to determine the impact of therapy on salt intake in PA patients.

PATIENTS AND METHODS

A total of 148 consecutive PA patients (66 with unilateral and 82 with bilateral PA) from the database of the German Conn's Registry were included. Salt intake was quantified by 24-hour urinary sodium excretion before and after initiation of PA treatment.

STUDY DESIGN

Observational longitudinal cohort study.

SETTING

Tertiary care hospital.

RESULTS

At baseline, unilateral PA patients had a significantly higher urinary sodium excretion than patients with bilateral disease (205 vs 178 mmol/d, P = 0.047). Higher urinary sodium excretion correlated with an increased cardiovascular risk profile including proteinuria, impaired lipid, and glucose metabolism and was associated with higher daily doses of antihypertensive drugs to achieve blood pressure control. In unilateral disease, urinary sodium excretion dropped spontaneously to 176 mmol/d (P = 0.012) 1 year after unilateral adrenalectomy and remained low at 3 years of follow-up (174 mmol/d). In contrast, treatment with mineralocorticoid receptor antagonists (MRA) in bilateral PA patients was not associated with a significant change in urinary sodium excretion at follow-up (179 mmol/d vs 183 mmol/d).

CONCLUSION

PA patients consuming a high-salt diet, estimated based on urinary sodium excretion, respond to adrenalectomy with a significant reduction of salt intake, in contrast to MRA treatment.

The Prevalence of Primary Aldosteronism and Evolving Approaches for Treatment

Over six decades since primary aldosteronism was first described, much has been learned about its prevalence and optimal treatment. Estimates of the prevalence of primary aldosteronism have increased considerably over the years, even exceeding 20% in some populations of resistant hypertension. Even in patients with normal blood pressures, the prevalence of overt primary aldosteronism and dysregulated aldosterone production may be more common than appreciated. Emerging data support the concept that primary aldosteronism may be better characterized as a continuum of renin-independent aldosterone production, whose severity influences the clinical presentation and risk for incident cardiovascular disease. Mineralocorticoid receptor antagonists and adrenalectomy are the mainstay treatments for primary aldosteronism and have long been considered equally efficacious. However, recent data suggest that while surgical adrenalectomy can effectively reduce cardiovascular risk, mineralocorticoid receptor antagonist therapy may require a physiologic approach to optimize efficacy.

The Expanding Spectrum of Primary Aldosteronism: Implications for Diagnosis, Pathogenesis, and Treatment

Primary aldosteronism is characterized by aldosterone secretion that is independent of renin and angiotensin II and sodium status. The deleterious effects of primary aldosteronism are mediated by excessive activation of the mineralocorticoid receptor that results in the well-known consequences of volume expansion, hypertension, hypokalemia, and metabolic alkalosis, but it also increases the risk for cardiovascular and kidney disease, as well as death. For decades, the approaches to defining, diagnosing, and treating primary aldosteronism have been relatively constant and generally focused on detecting and treating the more severe presentations of the disease. However, emerging evidence suggests that the prevalence of primary aldosteronism is much greater than previously recognized, and that milder and nonclassical forms of renin-independent aldosterone secretion that impart heightened cardiovascular risk may be common. Public health efforts to prevent aldosterone-mediated end-organ disease will require improved capabilities to diagnose all forms of primary aldosteronism while optimizing the treatment approaches such that the excess risk for cardiovascular and kidney disease is adequately mitigated. In this review, we present a physiologic approach to considering the diagnosis, pathogenesis, and treatment of primary aldosteronism. We review evidence suggesting that primary aldosteronism manifests across a wide spectrum of severity, ranging from mild to overt, that correlates with cardiovascular risk. Furthermore, we review emerging evidence from genetic studies that begin to provide a theoretical explanation for the pathogenesis of primary aldosteronism and a link to its phenotypic severity spectrum and prevalence. Finally, we review human studies that provide insights into the optimal approach toward the treatment of primary aldosteronism.

Circadian clock-mediated regulation of blood pressure

Most bodily functions vary over the course of a 24h day. Circadian rhythms in body temperature, sleep-wake cycles, metabolism, and blood pressure (BP) are just a few examples. These circadian rhythms are controlled by the central clock in the suprachiasmatic nucleus (SCN) of the hypothalamus and peripheral clocks located throughout the body. Light and food cues entrain these clocks to the time of day and this synchronicity contributes to the regulation of a variety of physiological processes with effects on overall health. The kidney, brain, nervous system, vasculature, and heart have been identified through the use of mouse models and clinical trials as peripheral clock regulators of BP. The dysregulation of this circadian pattern of BP, with or without hypertension, is associated with increased risk for cardiovascular disease. The mechanism of this dysregulation is unknown and is a growing area of research. In this review, we highlight research of human and mouse circadian models that has provided insight into the roles of these molecular clocks and their effects on physiological functions. Additional tissue-specific studies of the molecular clock mechanism are needed, as well as clinical studies including more diverse populations (different races, female patients, etc.), which will be critical to fully understand the mechanism of circadian regulation of BP. Understanding how these molecular clocks regulate the circadian rhythm of BP is critical in the treatment of circadian BP dysregulation and hypertension.

The association of nocturnal hypertension and nondipping blood pressure with treatment-resistant hypertension: The Jackson Heart Study

Apparent treatment-resistant hypertension (aTRH), nocturnal hypertension, and nondipping blood pressure (BP) have shared risk factors. The authors studied the association between aTRH and nocturnal hypertension and aTRH and nondipping BP among 524 black Jackson Heart Study participants treated for hypertension. Nocturnal hypertension was defined by mean nighttime systolic BP ≥120 mm Hg or diastolic BP ≥70 mm Hg. Nondipping BP was defined by mean nighttime to daytime systolic BP ratio >0.90. aTRH was defined by mean clinic systolic BP ≥140 mm Hg and/or diastolic BP ≥90 mm Hg with three medication classes or treatment with four or more classes. The risk for developing aTRH associated with nondipping BP and nocturnal hypertension was estimated. After multivariable adjustment, participants with aTRH were more likely to have nocturnal hypertension (prevalence ratio, 1.20; 95% confidence interval, 1.03-1.39) and nondipping (prevalence ratio, 1.25; 95% confidence interval, 1.09-1.43). Over a median 7.3 years of follow-up, nocturnal hypertension and nondipping BP at baseline were not associated with developing aTRH after adjustment.

Outcomes of drug-based and surgical treatments for primary aldosteronism

Treatments for primary aldosteronism (PA) aim to correct or prevent the deleterious consequences of hyperaldosteronism: hypertension, hypokalemia, and direct target organ damage. Patients with unilateral PA considered fit for surgery can undergo laparoscopic adrenalectomy, which significantly decreases blood pressure (BP) and medications in most cases and cures hypertension in about 40%. Mineralocorticoid receptor antagonists (MRA) are used to treat patients with bilateral PA and those with unilateral PA if surgery is not possible or not desired. Spironolactone is more potent than eplerenone, but high doses are poorly tolerated in men. MRA can be replaced or complemented with epithelial sodium channel blockers, such as amiloride. Thiazide diuretics and calcium channel blockers are used when the first-line drugs are insufficient to control BP. Dietary sodium restriction should be implemented in all cases because the deleterious consequences of hyperaldosteronism are dependent on salt loading. Several studies comparing the results of surgery and MRA have reported no differences in terms of BP, serum potassium concentration, or cardiovascular and kidney outcomes, although the benefits of treatment tend to be observed sooner with surgery. Patients with PA display relative glomerular hyperfiltration, which is reversed by specific treatment, revealing CKD in 30% of patients. However, further kidney damage is lessened by the treatment of PA.

The value of losartan suppression test in the confirmatory diagnosis of primary aldosteronism in patients over 50 years old

OBJECTIVE

The diagnosis of primary aldosteronism (PA) among the older-aged population has posed a crucial challenge. Among patients over 50 years old, this trial assessed comparability of the performance of two PA diagnostic tests: losartan and captopril suppression tests.

METHODS

A post-hoc subgroup analysis from a prospective cohort was conducted by the TAIPAI (Taiwan Primary Aldosteronism Investigation) group between July 2003 and July 2006. Of the 160 patients in the cohort, 60 patients over 50 years old received captopril and losartan tests to confirm PA.

RESULTS

Among the 60 patients over 50 years old, 31 patients had PA confirmed by standardized protocol. The area under the receiver-operating characteristic (ROC) curve for post-captopril aldosterone was significantly less than that for post-losartan plasma aldosterone concentration (PAC) (0.87 vs 0.94, p=0.02). Using the aldosterone-renin ratio (ARR)>35 with PAC>10 ng/dl, the specificity was 82.76% vs 93.1% and the sensitivity was 77.42% vs 87.10% for the captopril and losartan tests, respectively. The equivalence between the two tests were confirmed by the exact McNemar's test (p=1.0).

CONCLUSION

The losartan test showed comparable accuracy to confirm PA. Verification of this "elderly-friendly" confirmatory test will be the first step to prepare a specific diagnostic model of PA for the older-aged population.

The circadian clock in the kidney

Circadian variations in renal function were first described in the 19th century, and GFR, renal blood flow, urine production, and electrolyte excretion exhibit daily oscillations. These clinical observations are well established, but the underlying mechanisms that govern circadian fluctuations in kidney are not fully understood. Here we provide a brief overview of the machinery governing the circadian clock and examine the clinical and molecular evidence supporting a critical role for circadian rhythm in the kidney. There is a connection between BP oscillation and renal disease that supports the use of chronotherapy in the treatment of hypertension or correction of nondipping BP. Such studies support a developing model of clock controlled sodium and water transport in renal epithelial cells. Recent advances in identifying novel clock-controlled genes using rodent and cellular models also shed light on the molecular mechanisms by which the circadian clock controls renal function; however, the field is new and much more work remains.

Salt sensitivity and circadian rhythm of blood pressure: the keys to connect CKD with cardiovascular events

In healthy subjects, blood pressure (BP) drops by 10-20% during the night. Conversely, in patients with the salt-sensitive type of hypertension or chronic kidney disease, nighttime BP does not fall, resulting in an atypical pattern of circadian BP rhythm that does not dip. This pattern is referred to as the 'non-dipper' pattern. Loss of renal functional reserve, due to either reduced ultrafiltration capacity or enhanced tubular sodium reabsorption, induces the salt-sensitive type of hypertension. When salt intake is excessive in patients with salt-sensitive hypertension, the defect in sodium excretory capability becomes evident, resulting in elevated BP during the night. This nocturnal hypertension compensates for diminished natriuresis during the daytime and enhances pressure natriuresis during the night. Nocturnal hypertension and the non-dipper pattern of circadian BP rhythm cause cardiovascular events. When excess salt intake is loaded in patients who are in a salt-sensitive state, glomerular capillary pressure is also elevated, resulting in glomerular sclerosis and eventual renal failure. In this way, salt sensitivity and excess salt intake contribute to both cardiovascular and renal damage at the same time. We propose that salt sensitivity of BP and excess salt intake have important roles in the genesis of the cardiorenal connection. Salt sensitivity and circadian rhythm of BP are the keys to understanding the connections between cardiovascular and renal complications.

Primary aldosteronism can alter peripheral levels of transforming growth factor beta and tumor necrosis factor alpha

Primary aldosteronism (PA) is the most common secondary cause of hypertension that has recently been implicated in alterations of the immune system and progression of cardiovascular disease.

OBJECTIVE

To study the cytokines transforming growth factor beta1 (TGF-beta1), tumor necrosis factor alpha (TNF-alpha), and interleukin 10 (IL-10) in patients with PA and essential hypertensives (EH) and evaluate its association with the renin-angiotensin-aldosterone system.

PATIENTS AND METHODS

We studied 26 PA and 52 EH patients as controls, adjusted by their blood pressure, body mass index, age, and gender. In both groups, PA and EH, we measured serum aldosterone (SA), plasma renin activity (PRA), and cytokines TGF- beta1, TNF-alpha, and IL-10. In addition, 17 PA patients were treated for 6 months with spironolactone, a mineralocorticoid receptor (MR) antagonist.

RESULTS

PA patients had lower levels of TGF-beta1 (17.6+/-4.1 vs 34.5+/-20.5 pg/ml, p<0.001) and TNF-alpha (17.0+/-4.4 vs 35.6+/-21.7 pg/ml, p<0.001) and similar IL-10 levels (99.7+/-18.7 vs 89.4+/-49.5 pg/ml, p: ns), as compared with EH controls. TGF-beta1 and TNF-alpha levels showed a remarkable correlation with SA/PRA ratio in the total group (PA+EH). The treatment of PA patients with spironolactone increased the TGF-beta1 levels (18.3+/-5.9 to 28.4+/-6.3 pg/ml, p<0.001), while TNF-alpha, and IL-10 remained unchanged.

CONCLUSION

Our results showed that PA patients have lower TGF-beta1 and TNF-alpha cytokine serum levels than EH. TGF-beta1 levels were restored with spironolactone, showing a MR-dependent regulation. In this way, the chronic aldosterone excess modifies the TGF-beta1 levels, which could produce an imbalance in the immune system homeostasis that may promote an early proinflammatory cardiovascular phenotype.

The circadian clock protein Period 1 regulates expression of the renal epithelial sodium channel in mice

The mineralocorticoid aldosterone is a major regulator of sodium transport in target epithelia and contributes to the control of blood pressure and cardiac function. It specifically functions to increase renal absorption of sodium from tubular fluid via regulation of the alpha subunit of the epithelial sodium channel (alphaENaC). We previously used microarray technology to identify the immediate transcriptional targets of aldosterone in a mouse inner medullary collecting duct cell line and found that the transcript induced to the greatest extent was the circadian clock gene Period 1. Here, we investigated the role of Period 1 in mediating the downstream effects of aldosterone in renal cells. Aldosterone treatment stimulated expression of Period 1 (Per1) mRNA in renal collecting duct cell lines and in the rodent kidney. RNA silencing of Period 1 dramatically decreased expression of mRNA encoding alphaENaC in the presence or absence of aldosterone. Furthermore, expression of alphaENaC-encoding mRNA was attenuated in the renal medulla of mice with disruption of the Per1 gene, and these mice exhibited increased urinary sodium excretion. Renal alphaENaC-encoding mRNA was expressed in an apparent circadian pattern, and this pattern was dramatically altered in mice lacking functional Period genes. These results suggest a role for Period 1 in the regulation of the renal epithelial sodium channel and more broadly implicate the circadian clock in control of sodium balance.

Aldosterone excess and resistance to 24-h blood pressure control

BACKGROUND

Aldosterone excess has been reported to be a common cause of resistant hypertension. To what degree this represents true treatment resistance is unknown.

OBJECTIVE

The present study aimed to compare the 24-h ambulatory blood pressure monitoring (ABPM) levels in resistant hypertensive patients with or without hyperaldosteronism.

METHODS

Two hundred and fifty-one patients with resistant hypertension were prospectively evaluated with an early-morning plasma renin activity (PRA), 24-h urinary aldosterone and sodium, and 24-h ABPM. Daytime, night-time, and 24-h blood pressure (BP) and nocturnal BP decline were determined. Hyperaldosteronism (H-Aldo) was defined as suppressed PRA (<1.0 ng/ml per h or <1.0 mug/l per h) and elevated 24-h urinary aldosterone excretion (>/= 12 mug/24-h or >/= 33.2 nmol/day) during ingestion of the patient's routine diet.

RESULTS

In all patients, the mean office BP was 160.0 +/- 25.2/89.4 +/- 15.3 mmHg on an average of 4.2 medications. There was no difference in mean office BP between H-Aldo and normal aldosterone status (N-Aldo) patients. Daytime, night-time, and 24-h systolic and diastolic BP were significantly higher in H-Aldo compared to N-Aldo males. Daytime, night-time, and 24-h systolic BP were significantly higher in H-Aldo compared to N-Aldo females. Multivariate analysis indicated a significant interaction between age and aldosterone status such that the effects of aldosterone on ambulatory BP levels were more pronounced with increasing age.

CONCLUSIONS

In spite of similar office BP, ABPM levels were higher in resistant hypertensive patients with H-Aldo. These results suggest that high aldosterone levels impart increased cardiovascular risk not reflected by office BP measurements.

Diurnal blood pressure pattern in patients with primary aldosteronism

BACKGROUND

The aim of the study was to evaluate diurnal blood pressure (BP) profiles in patients with primary aldosteronism and to compare them to those in subjects with essential hypertension. The effects of specific therapy on the circadian BP profiles have been studied.

MATERIALS AND METHODS

Sixty-four patients with primary aldosteronism were included in the study. Thirty of them revealed an aldosterone-producing adenoma (APA) and 34 had idiopathic hyperaldosteronism (IHA) due to bilateral adrenal hyperplasia.

RESULTS

We did not find any significant differences in ambulatory BP monitoring (ABPM) between patients with APA and IHA. However, the circadian BP variation in the patients with primary hyperaldosteronism due to APA was preserved, while the patients with IHA showed lower nocturnal decline in comparison with patients with essential hypertension. There was a significant decline in office and ambulatory BP levels after treatment in the patients with both APA and IHA. The awake-sleep BP difference in patients with APA remained unchanged after surgical treatment, while in patients with IHA the night-time systolic and diastolic BP decline was significantly higher after spironolactone treatment.

CONCLUSIONS

Primary hyperaldosteronism due to APA was associated with normal circadian BP variability and the surgical treatment led to highly significant decline in all BP parameters but had no influence on the extent of nocturnal BP variation. Spironolactone therapy restored normal nocturnal BP decline in patients with IHA. Reduction of night-time BP decline in patients with IHA is more likely to be related to the duration of the disease rather than to the aldosterone levels.

Augmentation of Intrarenal Angiotensin II Levels in Uninephrectomized Aldosterone/Salt-Treated Hypertensive Rats; Renoprotective Effects of an Ultrahigh Dose of Olmesartan

Recent studies have suggested that aldosterone plays a role in the pathogenesis of renal injury. In this study, we investigated whether local angiotensin II (Ang II) activity contributes to the progression of renal injury in aldosterone/salt-induced hypertensive rats. Uninephrectomized rats were treated with 1% NaCl in a drinking solution and one of the following combinations for 6 weeks: vehicle (2% ethanol, s.c.; n=9), aldosterone (0.75 mug/h, s.c.; n=8), aldosterone+Ang II type 1 receptor blocker olmesartan (10 mg/kg/day, p.o.; n=8), or aldosterone+olmesartan (100 mg/kg/day, p.o.; n=9). Aldosterone/salt-treated hypertensive rats exhibited severe proteinuria and renal injury characterized by glomerular sclerosis and tubulointerstitial fibrosis. Aldosterone/salt-induced renal injury was associated with augmented expression of angiotensin converting enzyme and Ang II levels in the renal cortex and medullary tissues. Renal cortical and medullary mRNA expression of transforming growth factor-beta (TGF-beta) and connective tissue growth factor (CTGF) as well as the collagen contents were increased in aldosterone/salt-treated hypertensive rats. Treatment with olmesartan (10 or 100 mg/kg/day) had no effect on blood pressure but attenuated proteinuria in a dose-dependent manner. Olmesartan at 10 mg/kg/day tended to decrease renal cortical and medullary Ang II levels, TGF-beta and CTGF expression, and collagen contents; however, these changes were not significant. On the other hand, an ultrahigh dose of olmesartan (100 mg/kg/day) significantly decreased these values and ameliorated renal injury. These data suggest that augmented local Ang II activity contributes, at least partially, to the progression of aldosterone/salt-dependent renal injury.

Hypothesis on renal mechanism of non-dipper pattern of circadian blood pressure rhythm

In some patients with sodium sensitive type of hypertension or kidney disease, blood pressure (BP) fails to dip during night and they have been called "non-dipper", whereas those with a normal nocturnal dip are called "dipper". Many investigators reported that non-dippers were certainly exposed to greater risks of cardiovascular complications. We have recently proposed that kidneys play an important role in determining the circadian rhythm of BP, in addition to long-term BP regulation. When sodium intake is high, the defect in sodium excretory capability of kidneys becomes evident, making BP during night elevated, that is non-dipper, in order to compensate for diminished natriuresis during daytime and to enhance pressure-natriuresis during night. Therefore, as renal function deteriorates, longer duration may be required before BP begins to dip during night. Non-dipping may be one mechanism causing cardiovascular events in chronic kidney disease.

Circadian blood pressure rhythm is disturbed by nephrectomy

We recently illustrated a close relationship between glomerular filtration rate and circadian rhythm of blood pressure (BP) in patients with chronic kidney disease. However, it remains undetermined from such cross-sectional findings which occurs first, the loss of kidney function or the lack of nocturnal BP fall. In the present study, we examined whether circadian rhythm of BP is affected by unilateral nephrectomy for kidney donation to clarify this important issue. Fifteen healthy subjects (4 men, 11 women; aged 33 to 65 years; mean age 55 +/- 2 years) who underwent unilateral nephrectomy for kidney donation were studied. Ambulatory BP was monitored for 24 h, while serum and urinary samples were collected to estimate creatinine clearance before and on the 8th day after nephrectomy. Then, changes in the night/day ratios of mean arterial BP were analyzed in relation to the decrease in 24-h creatinine clearance as a marker of glomerular filtration rate by nephrectomy. Creatinine clearance was reduced by 29% in average from 84 +/- 6 to 60 +/- 4 ml/min by nephrectomy, while 24-h mean arterial BP values were 91 +/- 3 and 94 +/- 4 mmHg (p=0.08) before and after nephrectomy. Although mean BP (daytime, nighttime or night/day ratio) was not altered significantly by nephrectomy, the decrease in creatinine clearance was positively correlated with the increase in the night/ day ratio of mean BP (r=0.61, p=0.017). The decrease in creatinine clearance was not correlated with changes in either 24-h, daytime or nighttime mean BP. Our results suggest that unilateral nephrectomy disturbs the circadian rhythm of BP as a function of renal dysfunction without affecting absolute levels of BP. Non-dipping of BP seems the consequence of the loss of renal function, rather than the cause.

Event-Related Brain Potentials in Elderly Dippers and Nondippers with Recently Diagnosed Hypertension

Several studies have shown a relationship between blood pressure (BP) and cognitive function. Yet very few studies have addressed circadian BP patterns in this context, perhaps due to poor availability of suitable methods to detect slight changes in the cognitive state. Today, brain event-related potentials (ERPs) allow us to detect subclinical changes in cognitive function. We enrolled 30 elderly patients with recently diagnosed hypertension (<2 years) that had never been treated: 18 dippers and 12 nondippers. Patients underwent 24-h ambulatory blood pressure monitoring (ABPM). Careful assessment of their cognitive state was carried out using the mini mental state examination (MMSE), and the recording of P300 and N2 ERPs. No significant differences between the two groups were found. MMSE scores in dippers and nondippers were similar (29.5+/-0.71 vs. 29.3+/-1.07, respectively; p =0.611), as were P300 latency values (377.78+/-33.28 vs. 364.67+/-35.12 in the central (Cz) position, p =0.310; 379.22+/-32.94 vs. 365.25+/-35.07 in the occipital (Pz) position, p =0.277) and N2 wave latency values (253.83+/-24.9 vs. 249.17+/-24.47 in the Cz position, p =0.617; 251.56+/-25.86 vs. 246.58+/-25.46 in the Pz position, p =0.608). These data show no association between the nondipping pattern and lower cognitive function in elderly subjects with recent hypertension.

Aldosterone-Induced Organ Damage: Plasma Aldosterone Level and Inappropriate Salt Status

In recent years, it has been clarified that aldosterone can directly damage various organs, such as the heart, blood vessel, and kidneys, via non-epithelial mineralocorticoid receptors, independent of changes in blood pressure. Anti-aldosterone drugs have been clinically reported to be useful for their organ-protecting effects. The fact that these effects have been considered important for almost 10 years seems to indicate that aldosterone-induced organ damage can develop as a consequence of plasma aldosterone levels being in disproportion to salt status. In a previous study, cardiac fibrosis could not be induced in an experimental model of hyperaldosteronism with a low-salt diet. It is, therefore, extremely important to understand the relationship between plasma aldosterone level and inappropriate salt balance when considering diseases or states for which an anti-aldosterone drug is called for. In this paper we review the fundamental and clinical studies reported to date, mainly to investigate the pathology of organ damage induced by aldosterone and excess salt. Aldosterone-induced direct organ damage mediated through vasculitis essentially requires salt, which is inappropriate for plasma aldosterone level, and studies performed from this standpoint may provide a clue to the clarification of the involvement of salt in the actions of aldosterone via non-epithelial mineralocorticoid receptors. In humans, it is also strongly suggested that organ damage may occur, even at a plasma aldosterone level within a normal range, if salt intake is imbalanced to the aldosterone level. This means that the new aldosterone blocker eplerenone may also have significance as a drug inhibiting inflammation, possibly serving as a trigger of organ damage.

Salt sensitivity of Japanese from the viewpoint of gene polymorphism

Excess salt intake is an important environmental risk for the predisposition to essential hypertension. Previous physiological studies have shown that salt sensitivity is associated with insulin resistance, enhancement of sympathetic nerve activity and decrease of blood pressure decline at night. We have been examining the genetic importance of candidate gene polymorphisms of salt-sensitive hypertension using several populations. The angiotensinogen gene (AGT) is a thrifty gene which increases the risk for common disease with growth of civilization via sodium and body fluid retention. The CC genotype of the AGT/T+31C polymorphism, which is in complete linkage disequilibrium with the TT genotype of the M235T polymorphism, was associated with a decrease of blood pressure decline at night in the Ohasama Study. On the other hand, the Gly460Trp genotype of the alpha-adducin gene (ADD1) is associated with erythrocyte sodium transport and increases tubular sodium reabsorption and risk for hypertension. We also revealed in the Ohasama Study that the Trp460 allele of ADD1 is associated with hypertension in young subjects with low renin activity. In addition to these polymorphisms, the T(-344)C polymorphism in the promoter of the aldosterone synthase gene (CYP11B2) and the C825T polymorphism of the G-protein beta3 subunit gene (GNB3) are considered candidates for the genetic risk of salt-sensitive hypertension. We compared the allele frequency of five candidate genes between Japanese and Caucasians; the results showed that the frequencies of all alleles were significantly higher in Japanese than in Caucasians. This interesting finding might suggest a feasible explanation for the huge interracial differences in the frequency of salt-sensitive hypertension.