Primary Aldosteronism and Drug Resistant Hypertension: A "Chicken-Egg" Story.

Drug-resistant arterial hypertension (RH) is a major risk factor for cardiovascular disease, often due to overlooked underlying causes. Identification of such causes poses significant clinical challenges. In this setting, primary aldosteronism (PA) is a frequent cause of RH and its prevalence in RH patients is likely higher than 20%.The pathophysiological link between PA and the development and maintenance of RH involves target organ damage and the cellular and extracellular effects of aldosterone excess that promote pro-inflammatory and pro-fibrotic changes in the kidney and vasculature.The feasibility of adrenal vein sampling in PA patients with RH, and the clinical benefit achieved by adrenalectomy, further emphasize the need to implement systematic screening for this common form of secondary hypertension in the management of a high-risk population as RH patients.: We herein review the current knowledge of the factors that contribute to the RH phenotype with a focus on PA and discuss the issues regarding the screening for PA in this setting and the therapeutic approaches (surgical and medical) aimed at resolving RH caused by PA.

Serum levels of autoantibodies against the angiotensin II type I receptor are not associated with serum dicarbonyl or AGE levels in patients with an aldosterone-producing adenoma.

Patients with an aldosterone-producing adenoma (APA) carry a higher risk of cardiovascular disease and commonly have high levels of autoantibodies (AT1AA) that may activate the angiotensin II type 1 receptor (AT1R). AT1R activation is linked to an increase of the glucose metabolite methylglyoxal (MGO), a potential precursor of advanced glycation endproducts (AGEs) and driver of vascular inflammation. We investigated whether serum AT1AA levels are associated with serum MGO and AGE levels in APA patients. In a case series of 26 patients with APA we measured levels of dicarbonyls MGO, glyoxal (GO) and 3-deoxyglucosone (3-DG), and dicarbonyl-derived AGEs 5-hydro-5-methylimidazolone (MG-H1), Nε-(carboxyethyl)lysine (CEL) and Nε-(carboxymethyl)lysine (CML) with UPLC-MS/MS. We also measured AT1AA by ELISA. These measurements were repeated 1-month after adrenalectomy in a subset of 14 patients. Panels of inflammation and endothelial function were also measured by immunoassays. Although baseline higher AT1AA levels tended to be correlated with higher baseline serum MGO, GO and 3-DG levels (r = 0.18, p = 0.38; r = 0.20, p = 0.33; r = 0.23, p = 0.26; respectively), these correlations were not statistically significant. We observed no obvious correlations between higher AT1AA levels and protein-bound and free MG-H1, CEL and CML levels, and markers of inflammation and endothelial function. No decrease was observed in any of the dicarbonyls, protein-bound AGE levels and markers of inflammation and endothelial function after adrenalectomy. In patients with APA the serum levels of AT1AA were not significantly correlated with serum dicarbonyls, protein-bound and free AGE levels. Increased signalling of the AT1AA receptor may therefore be unlikely to overtly increase systemic dicarbonyl levels.

Prospective appraisal of the prevalence of primary aldosteronism in hypertensive patients presenting with atrial flutter or fibrillation (PAPPHY Study): rationale and study design.

Primary aldosteronism (PA) is the most common endocrine form of hypertension and may carry an increased risk of atrial flutter or fibrillation (AFF). The primary goal of this multicentre cohort study is thus to prospectively establish the prevalence of PA in consecutive hypertensive patients referred for lone (non-valvular), paroxysmal or permanent AFF. Secondary objectives are to determine: (1) the predictors of AFF in patients with PA; (2) the rate of AFF recurrence at follow-up after specific treatment in the patients with PA; (3) the effect of AFF that can increase atrial natriuretic peptide via the atrial stretch and thereby blunt aldosterone secretion, on the aldosterone-to-renin ratio (ARR), and thus the case detection of PA; (4) the diagnostic accuracy of ARR based on plasma renin activity or on the measurement of active renin (DRA) for diagnosing PA in AFF patients. Case detection and subtyping of PA will be performed according to established criteria, including the 'four corners criteria' for diagnosing aldosterone-producing adenoma. Pharmacologic or direct current cardioversion will be undertaken whenever indicated following current guidelines. The hormonal values and ARR will be compared within patient between AFF and sinus rhythm. Organ damage, cardiovascular events and recurrence of AFF will also be assessed during follow-up in patients with PA.

The Medical and Endovascular Treatment of Atherosclerotic Renal Artery Stenosis (METRAS) study: rationale and study design.

It is unclear whether revascularization of renal artery stenosis (RAS) by means of percutaneous renal angioplasty and stenting (PTRAS) is advantageous over optimal medical therapy. Hence, we designed a randomized clinical trial based on an optimized patient selection strategy and hard experimental endpoints. Primary objective of this study is to determine whether PTRAS is superior or equivalent to optimal medical treatment for preserving glomerular filtration rate (GFR) in the ischemic kidney as assessed by 99mTcDTPA sequential renal scintiscan. Secondary objectives of this study are to establish whether the two treatments are equivalent in lowering blood pressure, preserving overall renal function and regressing target organ damage, preventing cardiovascular events and improving quality of life. The study is designed as a prospective multicentre randomized, un-blinded two-arm study. Eligible patients will have clinical and angio-CT evidence of RAS. Inclusion criteria is RAS affecting the main renal artery or its major branches either >70% or, if <70, with post-stenotic dilatation. Renal function will be assessed with 99mTc-DTPA renal scintigraphy. Patients will be randomized to either arms considering both resistance index value in the ischemic kidney and the presence of unilateral/bilateral stenosis. Primary experimental endpoint will be the GFR of the ischemic kidney, assessed as quantitative variable by 99TcDTPA, and the loss of ischemic kidney defined as a categorical variable.

Primary aldosteronism - part I: prevalence, screening, and selection of cases for adrenal vein sampling.

Over the last few years compelling evidence has been gathered to support the view that primary aldosteronism (PA) is far more prevalent than usually held: its prevalence rate among consecutive newly diagnosed hypertensive patients referred to hypertension centers can be as high as 11.2%. Moreover, about 4.8% of cases are a surgically curable endocrine form of hypertension, and the majority of cases do not exhibit hypokalemia at the time of clinical presentation. The impact of these results on the strategy to be used in the clinical investigation of patients with hypertension is discussed in light of novel information on the optimal screening strategy to be used for pinpointing the PA patients from the vast array of hypertensive patients.

Primary aldosteronism: part II: subtype differentiation and treatment.

After discussing in Part I (Rossi et al, J Nephrol. 2008;21:447-454) the screening strategy to identify the hypertensive patients with primary aldosteronism (PA), we report here an update on the methodology for the further diagnostic work-up and treatment of PA patients. The most common forms of PA are aldosterone-producing adenoma (APA) and adrenocortical hyperplasia (BAH), which are unilateral or bilateral sources of aldosterone excess secretion, respectively. Since APA needs a surgical approach, in contrast to BAH which requires medical treatment, it is crucial to clearly delineate a diagnostic work-up aimed at discriminating the 2 forms. Clinical usefulness and accuracy of adrenal vein sampling, imaging tests (e.g., computed tomography and magnetic resonance) and mineralocorticoid adrenocortical scintigraphy are discussed in detail.

Reciprocal regulation of endothelin-1 and nitric oxide: relevance in the physiology and pathology of the cardiovascular system.

The endothelium plays a crucial role in the regulation of cardiovascular structure and function by releasing several mediators in response to biochemical and physical stimuli. These mediators are grouped into two classes: (1) endothelium-derived constricting factors (EDCFs) and (2) endothelium-derived relaxing factors (EDRFs), the roles of which are considered to be detrimental and beneficial, respectively. Endothelin-1 (ET-1) and nitric oxide (NO) are the prototypes of EDCFs and EDRFs, respectively, and their effects on the cardiovascular system have been studied in depth. Numerous conditions characterized by an impaired availability of NO have been found to be associated with enhanced synthesis of ET-1, and vice versa, thereby suggesting that these two factors have a reciprocal regulation. Experimental studies have provided evidence that ET-1 may exert a bidirectional effect by either enhancing NO production via ETB receptors located in endothelial cells or blunting it via ETA receptors prevalently located in the vascular smooth muscle cells. Conversely, NO was found to inhibit ET-1 synthesis in different cell types. In vitro and in vivo studies have started to unravel the molecular mechanisms involved in this complex interaction. It has been clarified that several factors affect in opposite directions the transcription of preproET-1 and NO-synthase genes, nuclear factor-KB and peroxisome proliferator-activated receptors playing a key role in these regulatory mechanisms. ET-1 and NO interplay seems to have a great relevance in the physiological regulation of vascular tone and blood pressure, as well as in vascular remodeling. Moreover, an imbalance between ET-1 and NO systems may underly the mechanisms involved in the pathogenesis of systemic and pulmonary hypertension and atherosclerosis.

Abnormal transport of inorganic phosphate in left ventricular mitochondria from spontaneously hypertensive rats.

INTRODUCTION: The aim of this study was to investigate the kinetic properties of inorganic phosphate (Pi) translocator in intact mitochondria isolated from the hypertrophied left ventricular tissue of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) at the ages of 5 and 24 weeks, before and after the development of hypertension. METHODS: The dependence of the Pi uptake rate on substrate concentration was measured in both absence and presence of mersalyl by spectroscopic techniques. RESULTS: Saturation characteristics were found (Km 250.0 +/- 25.0 and 15.0 +/- 1.5 microM for 5- and 24-week-old SHR, and 300.0 +/- 30.0 and 40.0 +/- 4.5 microM for WKY rat mitochondria, respectively, p < 0.05; Vmax 1.2 +/- 0.16 and 0.1 +/- 0.01 delta A/min x mg mitochondrial proteins for 5- and 24-week-old SHR, and 4.1 +/- 0.39 and 1.4 +/- 0.12 delta A/min x mg mitochondrial proteins for 5- and 24-week-old WKY rats, respectively, p < 0.05). When Pi carrier activity was measured using concentrations which are assumed to be in the cytosol under physiological conditions, Pi carrier velocity was 1.1 and 0.1 in SHR and 4.6 and 1.4 delta A/min x mg mitochondrial proteins in WKY, at 5 and 24 weeks, respectively. CONCLUSIONS: The significant decrease in the activity of the Pi carrier could imply that pressure overload is critical in SHR. Nevertheless, as decreased activity was found in SHR also at an early age when animals do not show stable increased blood pressure levels, we suggest that other factors might contribute to the abnormalities of Pi transport in mitochondria. An altered gene expression possibly related to a primary defect in this strain or, alternatively, to an abnormal regulation of protein synthesis might be proposed as additional factors affecting Pi carrier activity. The results of this study, together with previous data of the literature showing abnormalities in energy production mechanisms, allow us to hypothesize a profound rearrangement of energy metabolism at the mitochondrial level in this model of left ventricular hypertrophy and hypertension.

Extracellular matrix gene expression in the left ventricular tissue of spontaneously hypertensive rats.

The aim of this study was to investigate the extracellular matrix gene expression in the hypertrophied left ventricular tissue of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats, at early and mature ages. Interestingly, with age, a marked increase (+85% and +187% at 25 and 30 weeks of age, respectively, p < 0.01, vs 5 weeks) in matrix metalloproteinase-1 (MMP-1) mRNA levels in SHR and a progressive decrease (-50%, -70%, -78%, -70% at 10, 15, 25 and 30 weeks, respectively, p < 0.01, vs 5 weeks) in WKY were seen. Moreover, mRNA levels were significantly lower in SHR at 5 weeks. The analysis of mRNA expression for the tissue inhibitor of metalloproteinase-1 (TIMP-1) showed a significant increase in WKY (+44% and +44%, vs 15 and 25 weeks, respectively, p < 0.05), whereas there were no significant changes in SHR with development. At 30 weeks TIMP-1 mRNA levels were significantly reduced in SHR. Temporal trends of procollagen alpha1(I) and procollagen alpha1(III) mRNA levels were similar in both strains, but lower levels for procollagen alpha1(III) were found in SHR at 5 and 30 weeks. Although no significant differences were measured between the strains, mRNA levels for fibronectin were found decreased in WKY and increased in SHR with age. The results of the present study suggest an altered balance between collagen deposition and collagen degradation with development in this model of left ventricular hypertrophy and hypertension.

ATP synthesis and export in heart left ventricle mitochondria from spontaneously hypertensive rat.

Use was made of mitochondria isolated from heart left ventricles of either spontaneously hypertensive or age-matched Wistar-Kyoto rats used as a control to find out whether hypertrophy (5-week-old rats) or hypertrophy/hypertension (24-week-old rats) can cause change in the mechanisms by which ATP is synthesised via ATP synthase and subsequently exported via the ADP/ATP translocator outside mitochondria. To do this, photometric measurements were made of the rate of ATP appearance in the extramitochondrial phase, which occurs as a result of ADP addition to mitochondria. In mitochondria from spontaneously hypertensive rats deficit of ATP production was found dependent on changes in the KmADP and Vmax values of both the ADP/ATP translocator and the ATP synthase. The ADP/ATP translocator was found to determine the rate of ATP production outside mitochondria in all the tested samples. In an initial investigation carried out to ascertain how cell ATP deficit can be counterbalanced, an increase in both adenylate kinase and creatine kinase activities was found in both hypertrophy and hypertrophy/hypertension. A possible increase in anaerobic glycolysis was also suggested by the increased lactate dehydrogenase activity.

L-type calcium channels modulate the regression of left ventricular hypertrophy after ace-inhibition in genetic hypertension.

The aim of this study was to investigate the possible link between the regression of the left ventricular mass induced by ACE-inhibition and L-type calcium channels. For this purpose, an evaluation of both L-type calcium channels and AT1 receptor patterns in the left ventricular tissue of adult spontaneously hypertensive rats (SHR) was made before and after long-term treatment with ramipril. An abnormal density of both dihydropyridine and AT1 receptors was observed in SHR at 24 weeks, compared to age-matched control Wistar-Kyoto (WKY) rats (dihydropyridine receptor Bmax: 1. 30+/-0.09 vs 1.14+/-0.06 pmol mg-1 proteins, P<0.001; AT1 receptor Bmax: 1.35+/-0.07 vs 2.62+/-0.08, P<0.001 pmol mg-1 proteins). A treatment for 10 weeks with ramipril induced a significant decrease in the left ventricular mass index of SHR, as well as a significant decrease in dihydropyridine receptor density (Bmax: 0.96+/-0.01 vs 1. 39+/-0.08 pmol mg-1 proteins, P<0.001) and a significant increase in AT1 receptor density (Bmax: 3.08+/-0.26 vs 2.78+/-0.09 pmol mg-1 proteins, ramipril-treated SHR vs vehicle-treated SHR, P<0.001). These results suggest that the decrease in left ventricular mass after treatment with ramipril may be dependent on changes in L-type calcium channels other than the direct effect on circulating and tissue angiotensin II (ang II) levels: involvement of calcium channels and subsequent calcium influx into cardiac cells could be proposed as an additional mechanism for the regression of left ventricular mass after ACE-inhibition.

Mitochondrial energy metabolism in the left ventricular tissue of spontaneously hypertensive rats: abnormalities in both adeninenucleotide and phosphate translocators and enzyme adenylate-kinase and creatine-phosphokinase activities.

The aim of this study was to investigate the oxidative phosphorylation and additional adenosinetriphosphate (ATP) production mechanisms in mitochondria isolated from hypertrophied left ventricles of spontaneously hypertensive rats (SHR). Measurements of adenosinediphosphate (ADP)/ ATP and inorganic phosphate (Pi) carrier activities showed a significant reduction of Vmax values thus suggesting a general decrease of ATP supply in the hypertrophied ventricles. Investigation of mitochondrial enzyme activities showed 45% and 90% increases of adenylate-kinase and 80% and 110% increases of creatine-phosphokinase in 5- and 24-week-old SHR, before and after the development of the hypertensive state, respectively. The abnormalities found in SHR at the mitochondrial level suggest a profound rearrangement of energy production mechanisms in this model of left ventricular hypertrophy; whether the defects are determined genetically, and then worsen with the hypertensive state, remains to be determined.

Carrier-mediated transport controls hydroxyproline catabolism in heart mitochondria from spontaneously hypertensive rat.

In this study we have investigated hydroxyproline transport in rat heart mitochondria and, in particular, in heart left ventricle mitochondria isolated from both spontaneously hypertensive and Wistar-Kyoto rats. Hydroxyproline uptake by mitochondria, where its catabolism takes place, occurs via a carrier-mediated process as demonstrated by the occurrence of both saturation kinetics and the inhibition shown by phenylsuccinate and the thiol reagent mersalyl. In any case, hydroxyproline transport was found to limit the rate of mitochondrial hydroxyproline catabolism. A significant change in Vmax and Km values was found in mitochondria from hypertensive/hypertrophied rats in which the Km value decreases and the Vmax value increases with respect to normotensive rats, thus accounting for the increase of hydroxyproline metabolism due to its increased concentration in a hypertrophic/hypertensive state.

[Aging and isomyosin pattern of the left ventricle in spontaneously hypertensive and Wistar Kyoto rats]. / Invecchiamento e pattern isomiosinico del ventricolo sinistro di ratti spontaneamente ipertesi e Wistar Kyoto.

Changes of the contractile proteins in the left ventricle from spontaneously hypertensive rats (SHR) are extensively documented with the development of the hypertensive state and with ageing. This study was undertaken to determine whether also the left ventricle from normotensive rats exhibits age-related changes of the myosin pattern. The relative distribution of myosin isoforms was investigated in Wistar Kyoto (WKY, n = 50) and SHR (n = 50), both at the 5th, 9th, 24th, 48th and the 72nd week of life. A significant decrease in V1 as well as an increase in V3 percentage values, compared to the data obtained at the 5th week were observed in SHR from the 9th week, concomitantly to the rise in blood pressure values. These changes were more consistent with ageing (5 weeks: V1 99.0 +/- 0.9%, V2 0.6 +/- 0.1%, V3 0.4 +/- 0.3%; 72 weeks: V1 5.3 +/- 3.9%, V2 3.0 +/- 2.7%, V3 91.7 +/- 9.7%). In WKY rats, a significant decrease in V1 percentage values was detected at the 24th week and it was evident till the 72nd week. V3 significantly changed only at the 48th and the 72nd week (5 weeks: V1 100.0 +/- 0.0%; 72 weeks: V1: 41.4 +/- 6.5%, V2 13.3 +/- 2.8%, V3 45.5 +/- 6.9%). The results of this study confirm that alterations in the left ventricle isomyosin pattern occur early in SHR with the rise in blood pressure values and the increase in left ventricular mass. In contrast, modifications in the myosin isoform distribution were found only in WKY with ageing. These findings may be related to the biochemical changes occurring in the myocardial tissue either gradually, during the advanced ages of life, or early due to the hypertensive state.

Changes in enzyme levels in hypertensive heart tissue.

The levels of activity of some enzymes involved in oxidative metabolism have been determined in left ventricular tissue from spontaneously hypertensive rats compared with those in normotensive controls. Levels of pyruvate kinase were increased about 1.3 fold indicative of elevated glycolytic activity. Similarly, enhanced levels of lactate dehydrogenase were found, consistent with a requirement for increased oxidation of cytosolically-generated NADH. In addition a more active malate-aspartate shuttle, which in heart provides the major route for transfer of reducing equivalents to the mitochondria, was suggested by elevated levels of the cytosolic isoenzyme of aspartate aminotransferase; malate dehydrogenase did not increase but the activity of this enzyme is very high and unlikely to be rate-limiting in the shuttle. The levels of expression of mRNAs for three of these enzymes (pyruvate kinase, aspartate aminotransferase and malate dehydrogenase) were also determined and correlated well with the extent of change, if any, in the changes in enzymatic activity. Thus it seems that one response to development of hypertension in rats is an increase in expression of the genes for certain key enzymes involved in oxidative metabolism.

Left ventricular hypertrophy in spontaneously hypertensive rat: effects of ACE-inhibition on myocardiocyte ultrastructure.

The aim of this study is to investigate the effects of two ACE-inhibitors with different chemical formulae, cilazapril (CLZ) and captopril (CPT), on left ventricular myocardiocytes from spontaneously hypertensive rats (SHR), characterized by ultrastructural alterations associated with left ventricular hypertrophy, and from Wistar-Kyoto (WKY) rats, considered as controls. After CLZ-treatment, not remarkable changes are observed in WKY myocardiocytes, whereas SHR ones show a considerable reduction in their original alterations in ultrastructure. After CPT-treatment, both SHR and WKY myocardiocytes are altered in ultrastructure. The morphometric investigation confirms that CPT and CLZ produce different effects. Even if the drugs induce a similar decrease in blood pressure and left ventricular mass index, CLZ unlike CPT seems to improve the ultrastructural abnormalities associated with left ventricular hypertrophy. These changes could be related to the different chemical structure of CLZ and CPT, or to a different affinity of the two drugs for the local renin-angiotensin system.

Non-invasive haemodynamic study in hypertensive subjects after treatment with verapamil slow release.

Aim of this study is to investigate the haemodynamic effects, after the short and long-term antihypertensive treatment. After a wash-out period and a placebo treatment period, 30 hypertensive patients received verapamil SR (slow release, 240 mg o.d.) for 30 days. A significant decrease in systolic and diastolic blood pressure was obtained already 4 h after the first administration of verapamil; it was more evident and persistent throughout the study. No significant changes of heart rate or PR interval in ECG were observed. A significant decrease in total vascular resistances, both supine and upright, was evident already 4 h after the drug intake and observed throughout the study. The major effect was obtained after one month. No significant changes of cardiac output, cardiac index and stroke volume were recorded. Furthermore, plasma verapamil levels were measured to confirm that the haemodynamic effects are obtained by low drug concentrations. The present study provides evidence that the antihypertensive effect of verapamil, whose mechanism is the reduction of total vascular resistances, is progressive, long acting and achieved by low plasma levels, when slow release formulation is considered.

[Plasma levels and noninvasive hemodynamic profile of slow release verapamil (240 mg). A multicenter study]. / Livelli plasmatici e profilo emodinamico non invasivo del verapamil slow release (240 mg). Studio multicentrico.

Aim of this study was to evaluate the antihypertensive efficacy, tolerability, drug plasma levels and hemodynamic effects after long-term treatment with the slow release (SR) formulation of verapamil (240 mg od). After a wash-out period of two weeks, 96 subjects (39 M, 57 F; mean age: 55 +/- 8.4 years; recruited in 9 centers) with mild to moderate, uncomplicated hypertension received verapamil 240 mg SR od for 24 weeks. The following parameters were considered: systolic (SBP) and diastolic (DBP) blood pressure, heart rate (HR), ECG, echocardiogram, routine blood and urine chemistries, drug plasma levels. In addition, hemodynamic parameters were assessed in 30 subjects. A significant decrease in SBP and DBP (p < 0.01) was observed already after 1 week of treatment and was evident during all the study. HR was significantly reduced after 4 weeks (p < 0.01). No changes of ECG and echocardiographic parameters occurred. A significant increase in drug plasma levels was measured after 12 and 24 weeks of treatment (p < 0.05), when compared to the values recorded after 1 week. After 24 weeks drug levels were slightly decreases, even if not significantly, when compared to the values observed at the 12th week. No significant changes of cardiac output (CO), cardiac index (CI), stroke volume (SV) were evident. Total vascular resistances (TVR) decreases significantly (p < 0.001) 80 subjects completed the study. These results confirm the antihypertensive efficacy and tolerability of SR formulation of verapamil and suggest that the effective mechanism by which it reduces blood pressure is the progressive reduction of TVR without a sympathetic reflex stimulation. This hemodynamic effect is achieved by small drug concentrations. In conclusion, SR formulation of verapamil allows a good therapeutic control in hypertensive subjects when it is administered od and, therefore, it can be considered a drug of first choice in the treatment of arterial hypertension.