Endothelial progenitor cells in primary aldosteronism: a biomarker of severity for aldosterone vasculopathy and prognosis

Aldosterone promotes cardiac endothelial cell proliferation in vivo

BACKGROUND

Experimentally, aldosterone in association with NaCl induces cardiac fibrosis, oxidative stress, and inflammation through mineralocorticoid receptor activation; however, the biological processes regulated by aldosterone alone in the heart remain to be identified.

METHODS AND RESULTS

Mice were treated for 7 days with aldosterone, and then cardiac transcriptome was analyzed. Aldosterone regulated 60 transcripts (51 upregulated and 9 downregulated) in the heart (fold change ≥1.5, false discovery rate <0.01). To identify the biological processes modulated by aldosterone, a gene ontology analysis was performed. The majority of aldosterone-regulated genes were involved in cell division. The cardiac Ki-67 index (an index of proliferation) of aldosterone-treated mice was higher than that of nontreated mice, confirming microarray predictions. Costaining of Ki-67 with vinculin, CD68, α-smooth muscle actin, CD31, or caveolin 1 revealed that the cycling cells were essentially endothelial cells. Aldosterone-induced mineralocorticoid receptor-dependent proliferation was confirmed ex vivo in human endothelial cells. Moreover, pharmacological-specific blockade of mineralocorticoid receptor by eplerenone inhibited endothelial cell proliferation in a preclinical model of heart failure (transverse aortic constriction).

CONCLUSIONS

Aldosterone modulates cardiac gene expression and induces the proliferation of cardiac endothelial cells in vivo.

Risk of ischemic stroke in primary aldosteronism patients

BACKGROUND

High aldosterone concentrations are associated with the risk of stroke that is independent of blood pressure levels. We investigated the risk of ischemic stroke in primary aldosteronism (PA) patients.

METHODS

This retrospective case-control study was based on the Taiwan Primary Aldosteronism Investigation (TAIPAI) database from 2004 to 2010. The study group comprised the patients who developed ischemic stroke after the diagnosis of PA. The PA patients who did not develop stroke were matched according to age and sex as the control group. A multivariate logistic regression model was performed to determine the risk factors of ischemic stroke.

RESULTS

Of 339 patients diagnosed with PA, 22 patients (6.5%) developed de novo ischemic stroke. The PA patients with stroke suffered from a longer hypertensive period (11.0±6.5 vs 7.8±8.3, P=.007) and a higher prevalence of proteinuria than those who did not develop stroke (40.9% vs 12.9%, P=.002). A multivariate logistic regression model showed that PA patients with proteinuria (HR 3.58, P=.02), preexisting coronary artery disease (HR 11.12, P<.001) or left ventricular hypertrophy (HR 3.09, P=.047) were associated with an increased risk of ischemic stroke.

CONCLUSIONS

Proteinuria, a medical history of coronary artery disease or left ventricular hypertrophy, was associated with an increased risk of ischemic stroke in PA patients. Our results suggest that a public health initiative is necessary to enhance the follow-up of proteinuria and to manage subsequent stroke among patients with aldosteronism.

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.

Endothelial dysfunction in metabolic and vascular disorders

Vascular endothelium has important regulatory functions in the cardiovascular system and a pivotal role in the maintenance of vascular health and metabolic homeostasis. It has long been recognized that endothelial dysfunction participates in the pathogenesis of atherosclerosis from early, preclinical lesions to advanced, thrombotic complications. In addition, endothelial dysfunction has been recently implicated in the development of insulin resistance and type 2 diabetes mellitus (T2DM). Considering that states of insulin resistance (eg, metabolic syndrome, impaired fasting glucose, impaired glucose tolerance, and T2DM) represent the most prevalent metabolic disorders and risk factors for atherosclerosis, it is of considerable scientific and clinical interest that both metabolic and vascular disorders have endothelial dysfunction as a common background. Importantly, endothelial dysfunction has been associated with adverse outcomes in patients with established cardiovascular disease, and a growing body of evidence indicates that endothelial dysfunction also imparts adverse prognosis in states of insulin resistance. In this review, we discuss the association of insulin resistance and T2DM with endothelial dysfunction and vascular disease, with a focus on the underlying mechanisms and prognostic implications of the endothelial dysfunction in metabolic and vascular disorders. We also address current therapeutic strategies for the improvement of endothelial dysfunction.

Hemojuvelin modulates iron stress during acute kidney injury: improved by furin inhibitor

AIMS

Free iron plays an important role in the pathogenesis of acute kidney injury (AKI) via the formation of hydroxyl radicals. Systemic iron homeostasis is controlled by the hemojuvelin-hepcidin-ferroportin axis in the liver, but less is known about this role in AKI.

RESULTS

By proteomics, we identified a 42 kDa soluble hemojuvelin (sHJV), processed by furin protease from membrane-bound hemojuvelin (mHJV), in the urine during AKI after cardiac surgery. Biopsies from human and mouse specimens with AKI confirm that HJV is extensively increased in renal tubules. Iron overload enhanced the expression of hemojuvelin-hepcidin signaling pathway. The furin inhibitor (FI) decreases furin-mediated proteolytic cleavage of mHJV into sHJV and augments the mHJV/sHJV ratio after iron overload with hypoxia condition. The FI could reduce renal tubule apoptosis, stabilize hypoxic induced factor-1, prevent the accumulation of iron in the kidney, and further ameliorate ischemic-reperfusion injury. mHJV is associated with decreasing total kidney iron, secreting hepcidin, and promoting the degradation of ferroportin at AKI, whereas sHJV does the opposite.

INNOVATION

This study suggests the ratio of mHJV/sHJV affects the iron deposition during acute kidney injury and sHJV could be an early biomarker of AKI.

CONCLUSION

Our findings link endogenous HJV inextricably with renal iron homeostasis for the first time, add new significance to early predict AKI, and identify novel therapeutic targets to reduce the severity of AKI using the FI.

Primary aldosteronism: emerging trends

Primary aldosteronism (PA) is the most common etiology of endocrine hypertension (HTN), and recent prevalence studies suggest that it may be under-diagnosed. Indications for screening have been expanded with recognition that many patients with PA do not have hypokalemia and that the disease may be familial. The aldosterone:renin ratio (ARR) is the preferred screening test for PA. The ARR can be interpreted in patients on most anti-hypertensive agents, and can be used to guide medical therapy of HTN even in patients without PA. Once PA is confirmed, adrenal venous sampling (AVS) should be performed to determine if PA is due to bilateral disease or a unilateral adenoma, if surgery is being considered. Targeted medical or surgical therapy improves patient outcomes.

Diagnosis and management of primary aldosteronism: an updated review

Primary aldosteronism (PA) is the most common secondary form of arterial hypertension, with a particularly high prevalence among patients with resistant hypertension. Aldosterone has been found to be associated with cardiovascular toxicity. Prolonged aldosteronism leads to higher incidence of cardiac events, glomerular hyperfiltration, and potentially bone/metabolic sequels. The wider application of aldosterone/renin ratio as screening test has substantially contributed to increasing diagnosis of PA. Diagnosis of PA consists of two phases: screening and confirmatory testing. Adrenal imaging is often inaccurate for differentiation between an adenoma and hyperplasia, and adrenal venous sampling is essential for selecting the appropriate treatment modality. The etiologies of PA have two main subtypes: unilateral (aldosterone-producing adenoma) and bilateral (micro- or macronodular hyperplasia). Aldosterone-producing adenoma is typically managed with unilateral adrenalectomy, while bilateral adrenal hyperplasia is amenable to pharmacological approaches using mineralocorticoid antagonists. Short-term treatment outcome following surgery is determined by factors such as preoperative blood pressure level and hypertension duration, but evidence regarding long-term treatment outcome is still lacking. However, directed treatments comprising of unilateral adrenalectomy or mineralocorticoid antagonists still potentially reduce the toxicities of aldosterone. Utilizing a physician-centered approach, we intend to provide up-dated information on the etiology, diagnosis, and the management of PA.

Vascular actions of aldosterone

Aldosterone exerts direct effects on the vascular system by inducing oxidative stress, inflammation, hypertrophic remodeling, fibrosis, and endothelial dysfunction. Aldosterone exerts its effects through genomic and nongenomic pathways in a mineralocorticoid receptor (MR)-dependent or independent manner. Other aldosterone receptors such as GPR30 have been identified. A tight relation exists between the aldosterone and angiotensin II pathways, as well as with the endothelin-1 system. There is a correlation between plasma levels of aldosterone and cardiovascular risk. Recently, an increasing body of evidence has underlined the importance of aldosterone in cardiovascular complications associated with the metabolic syndrome, such as arterial remodeling and endothelial dysfunction. Blockade of MR is an increasingly used evidence-based therapy for many forms of cardiovascular disease, including hypertension, heart failure, chronic kidney disease, and diabetes mellitus.

Delayed diagnosis of primary aldosteronism in patients with autosomal dominant polycystic kidney diseases

Hypertension is a frequent early manifestation of autosomal dominant polycystic kidney disease (ADPKD). Several mechanisms can cause hypertension in ADPKD patients, although, primary aldosteronism (PA) as a possible manifestation of hypertension in ADPKD is extremely rare. We retrospectively reviewed the Taiwan Primary Aldosteronism Investigation (TAIPAI) database, which listed a total of 346 patients diagnosed with PA. Of these 346 patients, only three cases of concurrent PA and ADPKD were identified. These patients presented with hypertensive crisis and hypokalemia, and subsequent testing revealed aldosterone-producing adenomas (APAs) that were removed by laparoscopic adrenalectomy. Postoperatively, aldosterone-renin ratios (ARRs) and potassium levels normalized, and blood pressure improved. The diagnosis of PA in ADPKD is extremely challenging because multiple renal cysts can obscure the identification of adrenal adenomas, and ADPKD is associated with hypertension in almost all cases.(1) Because of frequent delays in the diagnosis of PA in ADPKD patients, future prospective studies to screen PA in hypertensive ADPKD patients may be necessary to evaluate the exact prevalence of coexistence of PA and ADPKD.

Primary aldosteronism in 2011: Towards a better understanding of causation and consequences

With primary aldosteronism now widely acknowledged as common and associated with both hypertension-related and non-hypertension-related pathology, research interest into its causes and consequences continues to grow. In 2011, major breakthroughs occurred in understanding the role and nature of underlying genetic disturbances and elucidating the pathophysiology of its cardiovascular sequelae.