Vanessa Ronconi

Primary aldosteronism: cardiovascular, renal and metabolic implications.

For many years primary aldosteronism was considered a relatively benign form of hypertension. This assumption reflects the primacy accorded to elevated levels of angiotensin in terms of deleterious cardiovascular effects, and the fact that in primary aldosteronism renin and angiotensin levels are low. We now know that primary aldosteronism causes a constellation of cardiovascular, renal and metabolic sequelae which make it far from benign and that these are not merely effects of blood pressure elevation. In primary aldosteronism, tissue damage, on several indices, is higher than in age-, sex- and blood pressure-matched controls, reflecting the ability of inappropriately elevated aldosterone for salt status to produce structural and functional changes over and above those produced by high blood pressure.

Aldosterone as a key mediator of the cardiometabolic syndrome in primary aldosteronism : an observational study

Objective Primary aldosteronism (PA) is characterized by the onset of both cardiac and gluco-metabolic alterations. The aim of this study was to evaluate the impact of aldosterone excess on the development of such complications, and the effects of surgical and pharmacological treatment on their long-term outcome. Methods We prospectively re-examined 61 patients: 25 with aldosterone-producing adenoma (APA), after surgery, and 36 patients with idiopathic hyperaldosteronism (IHA) on pharmacological treatment. The lipid, fasting and dynamic glucose profiles and the echocardiographic parameters were evaluated at diagnosis and at follow-up. Results After adrenalectomy all patients had normalization of aldosterone levels and were cured of hypokalaemia, and a resolution of hypertension was achieved in 12 of 25 patients. APA patients showed a significant reduction of both plasma glucose (P = 0.017) and insulin levels (P = 0.001) after 75 g oral glucose tolerance test. Stabilization of glucose metabolism complications was observed in IHA patients. Multiple regression analysis at diagnosis showed a positive correlation between homeostasis model assessment (HOMA) insulin resistance index and HOMA β cell and serum aldosterone levels in both APA and IHA. Echocardiographic parameters were improved in both APA and IHA at follow-up and the difference was statistically significant for left ventricular mass index (P = 0.017) and interventricular septum thickness (P = 0.007) in APA patients. Conclusions The removal of aldosterone excess in APA patients induces the regression of both cardiac and gluco-metabolic complications, indicating aldosterone as a main determinant of such alterations. In IHA patients the medical treatment seems to avoid the possible progression of the these alterations that appear to be stable.

Aldosterone as a cardiovascular risk factor

Aldosterone exerts cardiovascular effects by influencing epithelial fluid and electrolyte excretion, and thus blood volume and pressure. Mineralocorticoid receptors (MR) are found in epithelial and non-epithelial tissues (vessel walls, heart, brain), with high affinity for aldosterone and physiological glucocorticoids cortisol and corticosterone. MR blockade by spironolactone or eplerenone favorably affects cardiovascular outcomes. In some situations (primary aldosteronism, experimental mineralocorticoid administration) activation of cardiovascular MR reflects aldosterone levels inappropriate for salt status. In others (heart failure, essential hypertension) aldosterone and Na(+) status are often normal pretreatment; cardiovascular MR may thus be activated by normal glucocorticoid levels after tissue damage and reactive oxygen species generation. Therefore, although unilateral adrenalectomy is preferred therapy for unilateral aldosterone-producing adenoma or hyperplasia, MR blockade may be useful in cardiovascular diseases where aldosterone levels are normal.

Somatic ATP1A1, ATP2B3, and KCNJ5 Mutations in Aldosterone-Producing Adenomas

Aldosterone-producing adenomas (APAs) cause a sporadic form of primary aldosteronism and somatic mutations in the KCNJ5 gene, which encodes the G-protein–activated inward rectifier K+ channel 4, GIRK4, account for ≈40% of APAs. Additional somatic APA mutations were identified recently in 2 other genes, ATP1A1 and ATP2B3, encoding Na+/K+-ATPase 1 and Ca2+-ATPase 3, respectively, at a combined prevalence of 6.8%. We have screened 112 APAs for mutations in known hotspots for genetic alterations associated with primary aldosteronism. Somatic mutations in ATP1A1, ATP2B3, and KCNJ5 were present in 6.3%, 0.9%, and 39.3% of APAs, respectively, and included 2 novel mutations (Na+/K+-ATPase p.Gly99Arg and GIRK4 p.Trp126Arg). CYP11B2 gene expression was higher in APAs harboring ATP1A1 and ATP2B3 mutations compared with those without these or KCNJ5 mutations. Overexpression of Na+/K+-ATPase p.Gly99Arg and GIRK4 p.Trp126Arg in HAC15 adrenal cells resulted in upregulation of CYP11B2 gene expression and its transcriptional regulator NR4A2. Structural modeling of the Na+/K+-ATPase showed that the Gly99Arg substitution most likely interferes with the gateway to the ion binding pocket. In vitro functional assays demonstrated that Gly99Arg displays severely impaired ATPase activity, a reduced apparent affinity for Na+ activation of phosphorylation and K+ inhibition of phosphorylation that indicate decreased Na+ and K+ binding, respectively. Moreover, whole cell patch-clamp studies established that overexpression of Na+/K+-ATPase Gly99Arg causes membrane voltage depolarization. In conclusion, somatic mutations are common in APAs that result in an increase in CYP11B2 gene expression and may account for the dysregulated aldosterone production in a subset of patients with sporadic primary aldosteronism.

Late-Onset Apparent Mineralocorticoid Excess Caused by Novel Compound Heterozygous Mutations in the HSD11B2 Gene

Abstract—Mutations in the gene encoding 11&bgr;-hydroxysteroid dehydrogenase type 2, 11&bgr;-HSD2 (HSD11B2), explain the molecular basis for the syndrome of apparent mineralocorticoid excess (AME), characterized by severe hypertension and hypokalemic alkalosis. Cortisol is the offending mineralocorticoid in AME, as the result of a lack of 11&bgr;-HSD2–mediated cortisol to cortisone inactivation. In this study, we describe mutations in the HSD11B2 gene in 3 additional AME kindreds in which probands presented in adult life, with milder phenotypes including the original seminal case reported by Stewart and Edwards. Genetic analysis of the HSD11B2 gene revealed that all probands were compound heterozygotes, for a total of 7 novel coding and noncoding mutations. Of the 7 mutations detected, 6 were investigated for their effects on gene expression and enzyme activity by the use of mutant cDNA and minigene constructs transfected into HEK 293 cells. Four missense mutations resulted in enzymes with varying degrees of activity, all <10% of wild type. A further 2 mutations generated incorrectly spliced mRNA and predicted severely truncated, inactive enzyme. The mothers of 2 probands heterozygous for missense mutations have presented with a phenotype indistinguishable from “essential” hypertension. These genetic and biochemical data emphasize the heterogeneous nature of AME and the effects that heterozygosity at the HSD11B2 locus can have on blood pressure in later life.

Aldosterone Suppression on Contralateral Adrenal During Adrenal Vein Sampling Does Not Predict Blood Pressure Response After Adrenalectomy

CONTEXT Adrenal vein sampling (AVS) is the only reliable means to distinguish between aldosterone-producing adenoma and bilateral adrenal hyperplasia, the two most common subtypes of primary aldosteronism (PA). AVS protocols are not standardized and vary widely between centers. OBJECTIVE The objective of the study was to retrospectively investigate whether the presence of contralateral adrenal (CL) suppression of aldosterone secretion was associated with improved postoperative outcomes in patients who underwent unilateral adrenalectomy for PA. SETTING The study was carried out in eight different referral centers in Italy, Germany, and Japan. PATIENTS From 585 consecutive AVS in patients with confirmed PA, 234 procedures met the inclusion criteria and were used for the subsequent analyses. RESULTS Overall, 82% of patients displayed contralateral suppression. This percentage was significantly higher in ACTH stimulated compared with basal procedures (90% vs 77%). The CL ratio was inversely correlated with the aldosterone level at diagnosis and, among AVS parameters, with the lateralization index (P = .02 and P = .01, respectively). The absence of contralateral suppression was not associated with a lower rate of response to adrenalectomy in terms of both clinical and biochemical parameters, and patients with CL suppression underwent a significantly larger reduction in the aldosterone levels after adrenalectomy. CONCLUSIONS For patients with lateralizing indices of greater than 4 (which comprised the great majority of subjects in this study), CL suppression should not be required to refer patients to adrenalectomy because it is not associated with a larger blood pressure reduction after surgery and might exclude patients from curative surgery.

The Functional c.-2G>C Variant of the Mineralocorticoid Receptor Modulates Blood Pressure, Renin, and Aldosterone Levels

The mineralocorticoid receptor (MR) is essential in the regulation of volemia and blood pressure. Rare mutations in the MR gene cause type 1 pseudohypoaldosteronism and hypertension. In this study we characterized the common MR polymorphism c.-2G>C (rs2070951) in vitro and tested its influence on parameters related to blood pressure regulation and the renin-angiotensin system. In vitro studies showed that the G allele was associated with decreased MR protein levels and reduced transcriptional activation compared with the C allele. Association studies were performed with several outcome variables in 3 independent cohorts: a mild hypertensive group subjected to a salt-sensitivity test, a healthy normotensive group included in a crossover study to receive both a high and low Na/K diet, and a large cohort (The Netherlands Study of Depression and Anxiety), in which blood pressure was measured. Subjects with the GG genotype had significantly higher plasma renin levels both in the mild hypertensive group and in normal volunteers compared with homozygous C carriers. The GG genotype was also correlated with higher plasma aldosterone levels in healthy subjects. In both the mild hypertensive group and The Netherlands Study of Depression and Anxiety cohort the genotype GG was associated with higher systolic blood pressure in males. In conclusion, the G allele of the common functional genetic polymorphism c.-2G>C in the MR gene associates with increased activation of the renin-angiotensin-aldosterone axis and with increased blood pressure, probably related to decreased MR expression.

Visceral adipose tissue: emerging role of gluco- and mineralocorticoid hormones in the setting of cardiometabolic alterations

Several clinical and experimental lines of evidence have highlighted the detrimental effects of visceral adipose tissue excess on cardiometabolic parameters. Besides, recent findings have shown the effects of gluco‐and mineralocorticoid hormones on adipose tissue and have also underscored the interplay existing between such adrenal steroids and their respective receptors in the modulation of adipose tissue biology. While the fundamental role played by glucocorticoids on adipocyte differentiation and storage was already well known, the relevance of the mineralocorticoids in the physiology of the adipose organ is of recent acquisition. The local and systemic renin–angiotensin–aldosterone system (RAAS) acting on adipose tissue seems to contribute to the development of the cardiometabolic phenotype so that its modulation can have deep impact on human health. A better understanding of the pathophysiology of the adipose organ is of crucial importance in order to identify possible therapeutic approaches that can avoid the development of such cardiovascular and metabolic sequelae.

Adipose cell-adrenal interactions: current knowledge and future perspectives

The central role of adipose tissue in the development of cardiovascular and metabolic pathology has been highlighted by the discovery of mediators (adipokines) secreted by adipose tissue and their involvement in the regulation of various biological processes. In light of recent experimental data, cross-talk between adipose tissue and the adrenal gland, particularly via the mineralocorticoid aldosterone, has been proposed. Aldosterone can induce adipogenesis, and human white adipose tissue is reported to release as-yet-uncharacterized factors that stimulate adrenocortical steroidogenesis and aldosterone production. These data could provide new insights into the pathophysiology of obesity-related disorders, including hypertension and aldosterone excess, with further studies necessary for confirming and better defining such adipose-adrenal interactions.

Reduced nitric oxide levels in acromegaly: cardiovascular implications

Acromegaly is characterized by major cardiovascular alterations. Although the underlying mechanisms of these vascular modifications have not been elucidated, recent studies have focused on endothelial dysfunction. Nitric oxide (NO) may contribute to increased vascular resistance, reduced platelet aggregation, inhibition of smooth muscle cell proliferation, and reduction of lipoxygenase activity. At present, no data on NO production in acromegalics are available. The aim of this study was to evaluate the effect of high levels of growth hormone (GH) and insulin‐like growth factor‐1 (IGF‐1) present in acromegaly on NO pathway to investigate the role played by this molecule in the cardiovascular changes experienced by these patients. We studied 13 acromegalics and 12 sex‐ and age‐matched normotensive controls. Platelet NO levels were measured in the supernatant of lysed platelets. Endothelial NO synthase (eNOS) was determined by Western blot analysis of platelets. NO concentrations were significantly reduced in patients (p<0.0001). There were no differences between male and female patients, nor were platelet NO levels and the presence/absence of hypertension related in acromegalics; by contrast, NO concentrations inversely correlated with GH (p = 0.03) and IGF‐1 (p = 0.04) levels, and with disease duration (p = 0.04). eNOS protein concentrations were significantly reduced in the platelets of patients compared with controls (p<0.0001). This study demonstrates for the first time a strong reduction in platelet NO concentrations in acromegalic patients due to reduced eNOS expression. Moreover the inverse correlation of NO levels with GH, IGF‐1 and disease duration suggests that reduced levels of platelet NO linked to GH excess may contribute to the vascular alterations affecting patients with acromegaly.