Jon D. Blumenfeld

Diagnosis and Treatment of Primary Hyperaldosteronism

Primary aldosteronism is characterized by hypertension, hypokalemia, and low plasma renin activity and is most commonly caused by an adrenal adenoma that produces aldosterone. The plasma aldosterone level of affected patients usually fails to increase when renin activity increases during either upright posture or infusion of angiotensin II; thus, aldosterone will be secreted independently from the renin-angiotensin system [1]. A less common cause of this syndrome is idiopathic hyperaldosteronism, characterized by nonadenomatous hyperplasia and low plasma renin activity, in which the adrenal gland usually responds to angiotensin II. However, this syndrome has considerable phenotypic heterogeneity, with diagnostic variants differing from the more typical forms by their responsiveness to angiotensin. For example, a subset of adrenal hyperplasia mimics an aldosteronoma because it is associated with angiotensin-independent aldosterone overproduction and can be cured by unilateral adrenalectomy [2]. Conversely, some adenomas respond to angiotensin; Tunny and colleagues [3] have correlated the magnitude of this aldosterone response with the proportion of glomerulosa cells present in the tumor. This biochemical diversity is also manifested by characteristic patterns of steroid metabolism. In adenomas, levels of C-18 methyl oxidation metabolites of cortisol (18-oxocortisol and 18-hydroxycortisol) exceed those in idiopathic hyperaldosteronism and were elevated in patients with hyperplasia who were cured by adrenalectomy [4, 5]. The presence of an adrenal adenoma that produces aldosterone is considered the major clinical characteristic distinguishing primary aldosteronism that is curable by surgery. Refinements of imaging techniques have facilitated the detection of subtle adrenal abnormalities early in the clinical course. Coordinated use of these diagnostic approaches should improve the ability to determine which patients are likely to be cured by adrenalectomy. However, several studies have shown that the chances for curing hypertension are less predictable than those for the related biochemical abnormalities. Accordingly, these studies showed that only 50% of patients with adenomas were normotensive 5 years after adrenalectomy and that older patients were more likely to require postoperative antihypertensive medications [6, 7]. The clinical and biochemical diversity of this syndrome has important implications regarding its pathophysiology and responsiveness to therapy. We sought to characterize patients with primary aldosteronism who are followed at The Cardiovascular Center at The New York Hospital-Cornell Medical Center to identify features that would predict favorable responses to treatment and to attempt to understand why adrenalectomy often fails to produce a sustained reduction in blood pressure. Methods Patients A retrospective analysis of the medical records at The Cardiovascular Center of The New York Hospital-Cornell Medical Center indicated that 82 patients with primary aldosteronism were evaluated from 1976 to 1991. This diagnosis was established by the following criteria: 1) hypertension; 2) elevated rates of urinary aldosterone excretion as determined by an established nomogram that relates 24-hour urinary sodium excretion with urinary aldosterone and plasma renin activity [8]; 3) low renin activity [in most patients]; and 4) hypokalemia that was either spontaneous or diuretic-induced and associated with inappropriate renal potassium loss (>40 mmol/d). Diagnoses Adenomas (n = 52) were diagnosed when an adrenal tumor was observed by contrast-enhanced computed tomographic (CT) scan. When possible, this was corroborated by lateralization of adrenal aldosterone secretion by adrenal vein sampling or evidence of functional autonomy, defined by a failure of the plasma aldosterone level to increase when the patient was in upright posture. An adenoma was confirmed surgically in 47 patients. Five patients had radiographic and biochemical features that indicated adenoma, but they refused surgery and were treated medically. Idiopathic hyperaldosteronism was diagnosed in 22 patients whose CT scans showed unilateral or bilateral adrenal hyperplasia without an adenoma. These patients were treated with antihypertensive medication. Eight additional patients with nonadenomatous hyperplasia had adrenalectomy because their preoperative evaluation suggested an adrenal adenoma; 3 of these 8 patients had adrenal sampling and lateralized aldosterone secretion. Biochemical Studies In 56 patients (34 with adenomas and 22 with hyperplasia), medications were withdrawn approximately 2 weeks (for spironolactone, at least 1 month) before hemodynamic, biochemical, and hormonal evaluation. Dietary intake of sodium and potassium was not controlled in most patients during their evaluation. Hormonal profiling was usually done when patients were hypokalemic, although some received potassium supplements. Demographic, blood pressure, and biochemical data from 26 patients (18 with adenomas and 8 with idiopathic aldosteronism) who did not discontinue drug therapy before treatment were excluded from the statistical analysis of pretreatment diagnostic features. Assays for plasma renin activity [9], urinary and plasma aldosterone [10, 11], cortisol (Coat-A-Count Cortisol, Diagnostic Products Corporation, Los Angeles, California; 12), and atrial natriuretic peptide levels [13] have been described previously. In our laboratory, a plasma renin activity of 0.15 ng/mL per hour is at the lower limit of detection. We recently reported urinary excretion rates of 18-hydroxycortisol and 18-oxocortisol from 42 patients with primary aldosteronism [5]. We evaluated the clinical characteristics of a subset of these patients (15 with adenomas and 9 with hyperplasia) and include here the levels of these cortisol metabolites. A positive postural stimulation test result was defined by an ambulatory plasma aldosterone level that was either lower than the supine baseline level or that was increased less than 30% above that value [14]. For this test, plasma samples for aldosterone, renin, and cortisol were obtained from supine patients at 0800 h before they arose from their overnight recumbency, and again after 2 hours of ambulation. We excluded data from analysis if plasma cortisol and aldosterone levels simultaneously increased (for cortisol levels, an increase >30% greater than supine levels) because an increase in cortisol levels after 0800 h indicates a stress adrenocorticotropin hormone response that can also increase aldosterone secretion. We obtained adrenal vein aldosterone samples using percutaneous catheterization. Adrenal vein catheterization was considered successful when the plasma cortisol level from the adrenal vein was two times higher than the level from the inferior vena cava [15]. The mean plasma cortisol level for the adrenal vein was more than 10 times higher than that from the inferior vena cava (256 g/dL compared with 16 g/dL [difference, 240g/dL; CI of the difference, 320g/dL to 160g/dL; P < 0.001]). We defined lateralization of adrenal aldosterone secretion as a ratio of adrenal vein (aldosterone/cortisol levels)/inferior vena cava (aldosterone/cortisol levels) greater than 1.0 from the ipsilateral adrenal vein and 1.0 or less from the contralateral adrenal vein [16, 17]. Clinical Outcomes We considered hypertension to be cured when blood pressure decreased to 140/90 mm Hg or less after adrenalectomy and if postoperative antihypertensive medication was not required, to be improved when systolic pressure decreased by at least 10 mm Hg and diastolic pressure decreased by more than 5 mm Hg after adrenalectomy or medication, or to be not improved when the preceding criteria were not met after treatment. Statistical Analysis We used unpaired t-tests to compare baseline blood pressure and hormonal values between groups and used paired t-tests to compare treatment-related changes in these variables within groups. We calculated 95% confidence intervals for the differences in sample means. Chi-square analysis was used to evaluate differences in the numbers of patients in the diagnostic groups for demographic, blood pressure, and laboratory characteristics. Results Patient Characteristics Demographics Of the 82 patients with primary aldosteronism, 52 had adenomas and 30 had hyperplasia. Patients with adenomas were younger (46 years compared with 54 years [difference, 8 years; CI, 6 years to 10 years]). The sex and race distributions were similar in both groups. The 56 patients (34 with adenomas and 22 with nonadenomatous hyperplasia) who were studied after therapy with antihypertensive medication was discontinued were representative of all 82 patients with primary aldosteronism. Blood Pressure Patients with adenomas had higher mean systolic and diastolic blood pressures Table 1, although moderate to severe hypertension was common in both groups. After medical therapy was discontinued, systolic blood pressure was 175 mm Hg or greater in 66% of patients with adenomas but only in 15% of patients with hyperplasia (P < 0.001). Diastolic pressure was 114 mm Hg or greater in 50% of patients with adenomas and in 19% of those with hyperplasia (P = 0.09). Table 1. Blood Pressure and Laboratory Values before Treatment Renal Disease Baseline creatinine clearance was similar in both groups (1.88 mL/s for the adenoma group and 1.65 mL/s for the hyperplasia group; P = 0.18). Only one patient had an elevated serum creatinine level (>141.4 mol/L [1.6 mg/dL]). However, pathologic levels of proteinuria or microalbuminuria, defined as a daily protein excretion of greater than 0.2 g or an albumin excretion of greater than 0.03 g, were observed in more than 40% of patients in both groups. The most abundant proteinuria (1.5 g every 24 hours) occurred in the patient with adenoma who had the highest plasma renin activity (2.1 ng/mL per hour), although mean plasma renin activ

On the renal basis for essential hypertension: nephron heterogeneity with discordant renin secretion and sodium excretion causing a hypertensive vasoconstriction-volume relationship.

We propose herein that there are two functionally abnormal nephron populations in essential hypertension: (1) a group of ischemic nephrons with impaired sodium excretion which chronically hypersecrete renin. Numerically, these ischemic nephrons comprise a minor subgroup since most patients with essential hypertension exhibit no overt evidence of renal insufficiency. (2) In reaction to this, a more numerous group of normal nephrons appears in adaptive hypernatriuresis. They have an increased distal sodium supply and consequently, a chronically suppressed renin secretion. One difference between patients with renovascular hypertension and those with essential hypertension is the intermingling of these two populations of nephrons. In our hypothesis, the adapting hyperfiltering normal nephrons accomplish the hypernatriuresis in response to saline infusion, that is characteristic of all essential hypertension. However, the unsuppressed secretion of renin, that arises from the ischemic nephron population attenuates this compensatory natriuresis in the following ways: (1) by inappropriately acting on the hyperfiltering nephrons to enhance proximal tubular sodium reabsorption; (2) by activating TGF-mediated afferent constriction in these nephrons, and (3) simultaneously, the reactive secretion of renin from ischemic nephrons is diluted by non-participation of the adapting hypernatriuretic nephrons so that plasma renin settles at a level which is insufficient to fully compensate GFR in the ischemic nephrons. These adaptive responses provide a basis for the observation that the inhibition of renin activity with converting enzyme inhibitors in essential hypertension increases renal blood flow and sodium excretion. They also explain why converting enzyme inhibitors can effectively reduce blood pressure, even when renin levels are not absolutely elevated, since any circulating renin imposed upon the adapting hypernatriuretic nephrons inappropriately impairs their sodium excretion. In addition, the theory explains why basal renin secretion is either not suppressed or inadequately suppressed in patients with essential hypertension. As a result, whole kidney homeostatic function is compromised because individual nephrons are responding to their individual stimuli to fulfil their individual need, rather than acting in concert with other nephrons. The net effect of this uncoordinated response is to shift total renal function so that systemic arterial hypertension is sustained by abnormal sodium retention for the inappropriately high plasma renin level, or vice versa.(ABSTRACT TRUNCATED AT 400 WORDS)

β-adrenergic receptor blockade as a therapeutic approach for suppressing the renin-angiotensin-aldosterone system in normotensive and hypertensive subjects

Although beta-adrenergic-blocking drugs suppress the renin system (RAAS), plasma angiotensin II (Ang II) responses during beta-blockade have not been defined. This study quantifies the effects of beta-blockade on the RAAS and examines its impact on prorenin processing by measuring changes in the ratio of plasma renin activity (PRA) to total renin. In normotensive (N = 14) and hypertensive (N = 16) subjects, blood pressure (BP), heart rate, PRA, plasma prorenin, plasma total renin (prorenin + PRA), ratio of PRA to total renin (%PRA), plasma Ang II, and urinary aldosterone were measured before and after 1 week of beta-blockade. Plasma renin activity, Ang II, and urinary aldosterone levels were similar for normotensive and hypertensive subjects. Plasma renin activity correlated with Ang II. Total renin, which is proportional to (pro)renin gene expression, was lower in hypertensive subjects and was inversely related to BP. Beta-blockade decreased BP and heart rate in both groups, with medium- and high-renin hypertensive subjects responding more frequently than those with low renin. Beta-blockade consistently suppressed PRA, Ang II, and aldosterone. Total renin was unchanged, thus, %PRA fell. These results indicate that beta-blockers suppress plasma angiotensin II levels, in parallel with the marked reductions in PRA and urinary aldosterone levels in normotensive and hypertensive subjects. The suppression of Ang II levels was comparable to that produced during angiotensin converting enzyme (ACE) inhibition. However, by reducing prorenin processing to renin, beta-blockers do not stimulate renin secretion, unlike ACE inhibitors and Ang II receptor antagonists. This unique action of beta-blockers has important implications for the treatment of cardiovascular disease.

Management of hypertensive crises: the scientific basis for treatment decisions

The spectrum of disorders associated with an elevated blood pressure (BP) encompasses chronic uncomplicated hypertension and the hypertensive crises, including hypertensive urgencies and emergencies. Although these syndromes vary widely in their presentations, clinical courses, and outcomes they share pathophysiologic mechanisms and, consequently, therapeutic responses to specifically targeted antihypertensive drug types. Nevertheless, hypertensive crises are often treated with drugs which, in that setting are either unsafe or are of unsubstantiated efficacy. The purpose of this review is to examine the pathophysiology of commonly encountered hypertensive crises, including stroke, hypertensive encephalopathy, aortic dissection, acute pulmonary edema, and preeclampsia-eclampsia and to provide a rational approach to their treatment based upon relevant pathophysiologic and pharmacologic principles. Measurement of plasma renin activity (PRA) level often provides insight regarding pathophysiology and predicts efficacy of antihypertensive treatments in the individual patient. However, in hypertensive crises, drug therapy is initiated before the PRA level is known. Nevertheless, the renin-angiotensin dependence (R-type) or volume dependence (V-type) of hypertension can often be deduced by the BP response to drugs that interrupt the renin system (R-drugs) or that decrease body volume (V-drugs). Based upon these considerations, a treatment algorithm is provided to guide drug selection in patients presenting with a hypertensive crisis.

Novel method for genomic analysis of PKD1 and PKD2 mutations in autosomal dominant polycystic kidney disease.

Genetic testing of PKD1 and PKD2 is useful for diagnosis and prognosis of autosomal dominant polycystic kidney disease (ADPKD), particularly in asymptomatic individuals or those without a family history. PKD1 testing is complicated by the large transcript size, complexity of the gene region, and the extent of gene variations. A molecular assay was developed using Transgenomics SURVEYOR Nuclease and WAVE Nucleic Acid High Sensitivity Fragment Analysis System to screen for PKD1 and PKD2 variants, followed by sequencing of variant gene segments, thereby reducing the sequencing reactions by 80%. This method was compared to complete DNA sequencing performed by a reference laboratory for 25 ADPKD patients from 22 families. The pathogenic potential of gene variations of unknown significance was examined by evolutionary comparison, effects of amino acid substitutions on protein structure, and effects of splice‐site alterations. A total of 90 variations were identified, including all 82 reported by the reference laboratory (100% sensitivity). A total of 76 variations (84.4%) were in PKD1 and 14 (15.6%) in PKD2. Definite pathogenic mutations (seven nonsense, four truncation, and three splicing defects) were detected in 64% (14/22) of families. The remaining 76 variants included 26 missense, 33 silent, and 17 intronic changes. Two heterozygous nonsense mutations were incorrectly determined by the reference laboratory as homozygous. “Probably pathogenic” mutations were identified in an additional five families (overall detection rate 86%). In conclusion, the SURVEYOR nuclease method was comparable to direct sequencing for detecting ADPKD mutations, achieving high sensitivity with lower cost, providing an important tool for genetic analysis of complex genes. Hum Mutat 0, 1–10, 2008.

Urine MicroRNA as Potential Biomarkers of Autosomal Dominant Polycystic Kidney Disease Progression: Description of miRNA Profiles at Baseline

Background Autosomal dominant polycystic kidney disease (ADPKD) is clinically heterogenic. Biomarkers are needed to predict prognosis and guide management. We aimed to profile microRNA (miRNA) in ADPKD to gain molecular insight and evaluate biomarker potential. Methods Small-RNA libraries were generated from urine specimens of ADPKD patients (N = 20) and patients with chronic kidney disease of other etiologies (CKD, N = 20). In this report, we describe the miRNA profiles and baseline characteristics. For reference, we also examined the miRNA transcriptome in primary cultures of ADPKD cyst epithelia (N = 10), normal adult tubule (N = 8) and fetal tubule (N = 7) epithelia. Results In primary cultures of ADPKD kidney cells, miRNA cistrons mir-143(2) (9.2-fold), let-7i(1) (2.3-fold) and mir-3619(1) (12.1-fold) were significantly elevated compared to normal tubule epithelia, whereas mir-1(4) members (19.7-fold), mir-133b(2) (21.1-fold) and mir-205(1) (3.0-fold) were downregulated (P<0.01). Expression of the dysregulated miRNA in fetal tubule epithelia resembled ADPKD better than normal adult cells, except let-7i, which was lower in fetal cells. In patient biofluid specimens, mir-143(2) members were 2.9-fold higher in urine cells from ADPKD compared to other CKD patients, while expression levels of mir-133b(2) (4.9-fold) and mir-1(4) (4.4-fold) were lower in ADPKD. We also noted increased abundance mir-223(1) (5.6-fold), mir-199a(3) (1.4-fold) and mir-199b(1) (1.8-fold) (P<0.01) in ADPKD urine cells. In ADPKD urine microvesicles, miR-1(2) (7.2-fold) and miR-133a(2) (11.8-fold) were less abundant compared to other CKD patients (P<0.01). Conclusions We found that in ADPKD urine specimens, miRNA previously implicated as kidney tumor suppressors (miR-1 and miR-133), as well as miRNA of presumed inflammatory and fibroblast cell origin (miR-223/miR-199), are dysregulated when compared to other CKD patients. Concordant with findings in the primary tubule epithelial cell model, this suggests roles for dysregulated miRNA in ADPKD pathogenesis and potential use as biomarkers. We intend to assess prognostic potential of miRNA in a followup analysis.

Autosomal dominant polycystic kidney disease: genetics, mutations and microRNAs.

Autosomal dominant polycystic kidney disease (ADPKD) is a common, monogenic multi-systemic disorder characterized by the development of renal cysts and various extrarenal manifestations. Worldwide, it is a common cause of end-stage renal disease. ADPKD is caused by mutation in either one of two principal genes, PKD1 and PKD2, but has large phenotypic variability among affected individuals, attributable to PKD genic and allelic variability and, possibly, modifier gene effects. Recent studies have generated considerable information regarding the genetic basis and molecular diagnosis of this disease, its pathogenesis, and potential strategies for targeted treatment. The purpose of this article is to provide a comprehensive review of the genetics of ADPKD, including mechanisms responsible for disease development, the role of gene variations and mutations in disease presentation, and the putative role of microRNAs in ADPKD etiology. The emerging and important role of genetic testing and the advent of novel molecular diagnostic applications also are reviewed. This article is part of a Special Issue entitled: Polycystic Kidney Disease.

A new circulating hypertensive factor in the plasma of essential hypertensive subjects.

The pressor responses to dialyzed plasma extracts from normotensive (n = 15) and essential hypertensive (n = 14) human subjects were evaluated in anesthetized Sprague-Dawley rats. Hypertensive but not normotensive plasma raised mean arterial pressure (23.6 +/- 3.6 versus -0.5 +/- 2.5 mmHg, P less than 0.0001), and this effect was correlated significantly with its ability to stimulate 45Ca uptake in rat tail artery vascular smooth muscle (r = 0.883, P less than 0.002). These data suggest a humoral contribution to the pathophysiology of essential hypertension in at least some individuals. The time-course and molecular weight distribution of the dialyzed plasma suggest that this effect is not due to known vasopressor substances, but to a factor we tentatively term plasma hypertensive factor.

Molecular Diagnosis of Autosomal Dominant Polycystic Kidney Disease Using Next-Generation Sequencing

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in PKD1 and PKD2. However, genetic analysis is complicated by six PKD1 pseudogenes, large gene sizes, and allelic heterogeneity. We developed a new clinical assay for PKD gene analysis using paired-end next-generation sequencing (NGS) by multiplexing individually bar-coded long-range PCR libraries and analyzing them in one Illumina MiSeq flow cell. The data analysis pipeline has been optimized and automated with Unix shell scripts to accommodate variant calls. This approach was validated using a cohort of 25 patients with ADPKD previously analyzed by Sanger sequencing. A total of 250 genetic variants were identified by NGS, spanning the entire exonic and adjacent intronic regions of PKD1 and PKD2, including all 16 pathogenic mutations. In addition, we identified three novel mutations in a mutation-negative cohort of 24 patients with ADPKD previously analyzed by Sanger sequencing. This NGS method achieved sensitivity of 99.2% (95% CI, 96.8%-99.9%) and specificity of 99.9% (95% CI, 99.7%-100.0%), with cost and turnaround time reduced by as much as 70%. Prospective NGS analysis of 25 patients with ADPKD demonstrated a detection rate comparable with Sanger standards. In conclusion, the NGS method was superior to Sanger sequencing for detecting PKD gene mutations, achieving high sensitivity and improved gene coverage. These characteristics suggest that NGS would be an appropriate new standard for clinical genetic testing of ADPKD.

Plasma renin activity in the emergency department and its independent association with acute myocardial infarction.

Elevated plasma renin activity (PRA) is associated with increased risk of future myocardial infarction (MI) in ambulatory hypertensive patients. The present study evaluated the relationship of PRA to the diagnosis of acute MI in patients presenting to an emergency department with suspected acute MI. PRA was measured upon entry to the emergency department, before any acute treatment, as part of the standard evaluation of 349 consecutive patients who were hospitalized for suspected MI. Diagnosis of acute MI was confirmed in 73 patients, and ruled out in 276. They did not differ in age (65.9 +/- 2 v 66.1 +/- 1 years), systolic (143 +/- 4 v 140 +/- 2 mm Hg), or diastolic (81 +/- 2 v 81 +/- 1 mm Hg) pressures. Median PRA was 2.7-fold higher in acute MI (0.89 v 0.33 ng/L/s; P < .001). In a multivariate analysis controlling for other cardiac risk factors and prior drug therapy, PRA as a continuous variable was the predominant independent factor associated with acute MI (P < .0001), followed by white race (P = .002) and history of hypertension (P = .047). The height of the PRA level upon entry to the emergency department was directly and independently associated with the diagnosis of acute MI. These new findings extend earlier reports because they encompass acute MI patients, include both hypertensive and normotensive patients, and control for potentially confounding variables. Based on these observations, a randomized clinical trial is warranted to determine whether measurement of PRA in acute MI could refine the process by which treatments are applied.