Aldosterone Response Research Articles

Knockout of Adam10 and Tfcp2l1 in mCCDcl1 Collecting Duct Cells Demonstrates Notch‐Dependent Cell Plasticity and Phenotype

The kidney cortical collecting duct (CCD) is responsible for the fine tuning of sodium, volume, and acid‐base homeostasis, and comprises of principal and intercalated cells (PCs and ICs) as well as a newly discovered ‘intermediate’ cell type (1). Plasticity between PCs and ICs has been reported previously in mice in which genes for factors implicated in the Notch pathway, such as Adam10 and Tfcp2l1, have been knocked out (KO) (2, 3). In vivo, disruption of the Notch pathway leads to a decreasing PC:IC ratio. The self‐immortalized mouse CCD cell line, mCCDcl1, shows functional characteristics of PCs and a response to physiological concentrations of hormones such as aldosterone; it also has been shown to express both PC and IC markers, a phenotype transmitted through single cell cloning (4). These characteristics make mCCDcl1 cells a useful platform for the study of plasticity in the CCD. Tfcp2l1 and Adam10 were knocked out in mCCDcl1 cells using CRISPR‐Cas9 technology and independent clones were isolated and expanded for study. Despite mCCDcl1 cells being polyploid, our strategy enabled all alleles for each gene to be successfully targeted and the knockout clones were verified using T7 endonuclease analysis, DNA sequencing and immunocytochemistry. Clones were cultured on Transwell filters over 10 days and their electrophysiological properties measured (trans‐epithelial resistance Rte, voltage Vte, calculated short‐circuit current Isc). Both Adam10 KO clones showed a slightly reduced baseline Rte compared to control (0.90±0.19 kΩ.cm2 vs 1.12±0.18 kΩ.cm2) but a complete reduction in baseline Isc (0.3±0.1 mA/cm2 vs −8.1±0.4 mA/cm2 for control) as well as aldosterone response, decreased by 95% ( fold change 0.19±0.03 down 3.70±0.11 for control). Both Tfcp2l1 KO clones failed to form a resistive cell monolayer, with a dramatic decrease in Rte compared to control (down to 0.10±0.02 kΩ.cm2) as well as a complete disappearance of baseline and epithelial sodium channel (ENaC) mediated amiloride‐sensitive current. These data suggest that genomic modification of mCCDcl1 cells provides an effective means to investigate the mechanisms through which CCD cells mediate their plasticity and, in combination with single cell RNA‐Seq data, will identify new pathways involved in regulating cell phenotype.Support or Funding InformationBritish Heart Foundation Centre for Research Excellence (BHF, RE/13/3/30183) Kidney Research UK (KRUK, RP/026/20180305)

GRK2-Mediated Crosstalk Between β-Adrenergic and Angiotensin II Receptors Enhances Adrenocortical Aldosterone Production In Vitro and In Vivo.

Aldosterone is produced by adrenocortical zona glomerulosa (AZG) cells in response to angiotensin II (AngII) acting through its type I receptors (AT1Rs). AT1R is a G protein-coupled receptor (GPCR) that induces aldosterone via both G proteins and the adapter protein βarrestin1, which binds the receptor following its phosphorylation by GPCR-kinases (GRKs) to initiate G protein-independent signaling. β-adrenergic receptors (ARs) also induce aldosterone production in AZG cells. Herein, we investigated whether GRK2 or GRK5, the two major adrenal GRKs, is involved in the catecholaminergic regulation of AngII-dependent aldosterone production. In human AZG (H295R) cells in vitro, the βAR agonist isoproterenol significantly augmented both AngII-dependent aldosterone secretion and synthesis, as measured by the steroidogenic acute regulatory (StAR) protein and CYP11B2 (aldosterone synthase) mRNA inductions. Importantly, GRK2, but not GRK5, was indispensable for the βAR-mediated enhancement of aldosterone in response to AngII. Specifically, GRK2 inhibition with Cmpd101 abolished isoproterenol’s effects on AngII-induced aldosterone synthesis/secretion, whereas the GRK5 knockout via CRISPR/Cas9 had no effect. It is worth noting that these findings were confirmed in vivo, since rats overexpressing GRK2, but not GRK5, in their adrenals had elevated circulating aldosterone levels compared to the control animals. However, treatment with the β-blocker propranolol prevented hyperaldosteronism in the adrenal GRK2-overexpressing rats. In conclusion, GRK2 mediates a βAR-AT1R signaling crosstalk in the adrenal cortex leading to elevated aldosterone production. This suggests that adrenal GRK2 may be a molecular link connecting the sympathetic nervous and renin-angiotensin systems at the level of the adrenal cortex and that its inhibition might be therapeutically advantageous in hyperaldosteronism-related conditions.

Kinetics and Interrelations of the Renin Aldosterone Response to Acute Psychosocial Stress: A Neglected Stress System.

ContextThe renin-angiotensin-aldosterone system (RAAS) plays an important role in cardiovascular homeostasis and its dysfunction relates to negative health consequences. Acute psychosocial stress seems to activate the RAAS in humans, but stress kinetics and interrelations of RAAS parameters compared with a nonstress control group remain inconclusive.ObjectiveWe systematically investigated in a randomized placebo-controlled design stress kinetics and interrelations of the reactivity of RAAS parameters measured in plasma and saliva to standardized acute psychosocial stress induction.Methods58 healthy young men were assigned to either a stress or a placebo control group. The stress group underwent the Trier Social Stress Test (TSST), while the control group underwent the placebo TSST. We repeatedly assessed plasma renin, and plasma and salivary aldosterone before and up to 3 hours after stress/placebo. We simultaneously assessed salivary cortisol to validate successful stress induction and to test for interrelations.ResultsAcute psychosocial stress induced significant increases in all endocrine measures compared with placebo-stress (all P ≤ .041). Highest renin levels were observed 1 minute after stress, and highest aldosterone and cortisol levels 10 and 20 minutes after stress, with salivary aldosterone starting earlier at 1 minute after stress. Renin completed recovery at 10 minutes, cortisol at 60 minutes, salivary aldosterone at 90 minutes, and plasma aldosterone at 180 minutes after stress. Stress increase scores of all endocrine measures related to each other, as did renin and cortisol areas under the curve with respect to increase (AUCi) and salivary and plasma aldosterone AUCi (all P ≤ .047).ConclusionsOur findings suggest that in humans acute psychosocial stress induces a differential and interrelated RAAS parameter activation pattern. Potential implications for stress-related cardiovascular risk remain to be elucidated.

Effect of Genetic and Nongenetic Factors on the Clinical Response to Mineralocorticoid Receptor Antagonist Therapy in Egyptians with Heart Failure.

This prospective cohort study evaluated the association between the renin angiotensin aldosterone system genotypes and response to spironolactone in 155 Egyptian patients with heart failure with reduced ejection fraction (HFrEF). Genotype frequencies for AGT rs699 were: CC = 16%, CT = 48%, and TT = 36%. Frequencies for CYP11B2 rs1799998 were: TT = 33%, TC = 50%, and CC = 17%. After 6 months of spironolactone treatment, change in the left ventricular ejection fraction (LVEF) differed by AGT rs699 (CC, 14.6%; TC, 7.9%; TT, 2.7%; P = 2.1E‐26), and CYP11B2 rs1799998 (TT, 9.1%; TC, 8.7%; CC, 1.4%; P = 0.0006) genotypes. Multivariate linear regression showed that the AGT rs699 and CYP11B2 rs1799998 polymorphisms plus baseline serum potassium explained 71% of variability in LVEF improvement (P = 0.001), 63% of variability in serum potassium increase (P = 2.25E‐08), and 39% of the variability in improvement in quality of life (P = 2.3E‐04) with spironolactone therapy. These data suggest that AGT and CYP11B2 genotypes as well as baseline serum K are predictors of spironolactone response in HFrEF.

Cortisol and Aldosterone Responses to Hypoglycemia and Na Depletion in Women With Non-Classic 21-Hydroxylase Deficiency.

Non-classic 21-hydroxylase deficiency is usually diagnosed in post-pubertal women because of androgen excess. Indication of systematic steroid replacement therapy is controversial because the risk of acute adrenal insufficiency is unknown. In order to specify this risk we evaluated the cortisol and aldosterone secretions in response to appropriate pharmacologic challenges. In this prospective case-control non-inferiority study we investigated 20 women with non-classic 21-hydroxylase deficiency carrying biallelic CYP21A2 mutations and with serum 17-hydroxyprogesterone (17OHP) >10 ng/mL after stimulation with Synacthen® (tetracosactrin) and 20 age- and body mass index-matched healthy women with 17OHP after Synacthen® <2 ng/mL. Each participant underwent sequentially an insulin tolerance test to evaluate cortisol secretion and a sodium depletion test, obtained by oral administration of 40 mg of furosemide under low sodium diet (<20 mmol during 24 hours), to evaluate renin and aldosterone secretion. The peak serum cortisol concentration after insulin hypoglycemia was lower in patients than in controls (mean difference -47 ng/mL, 90% CI, -66, P = 0.0026). A peak serum cortisol above a cutoff value of 170 ng/mL was obtained in all controls but only in 55% of patients (P = 0.0039). Twenty-four hours after sodium depletion, blood pressure, plasma sodium, potassium, and serum aldosterone concentrations were comparable between the two groups, but patients had higher stimulated renin concentrations than controls (P = 0.0044). Patients with non-classic 21-hydroxylase deficiency frequently display partial cortisol insufficiency and compensated defect in aldosterone secretion. Their clinical management should systematically include assessment of adrenal functions.

Role of estrogen receptors in modulating aldosterone biosynthesis and blood pressure

Blood pressure is lower in premenopausal women than in age-matched men; after menopause blood pressure values and the prevalence of hypertension show opposite trends indicating that estrogens contribute to maintaining normal blood pressure values in women. In experimental studies menopause increases aldosterone levels, an effect alleviated by estrogen treatment. We have recently discovered a role of estrogen receptors (ER) in controlling aldosterone biosynthesis in the human adrenocortical zona glomerulosa, which expresses both the classical ERα and β receptors and G protein-coupled estrogen receptor (GPER). We have also identified that GPER mediates an aldosterone-induced aldosterone response. We found that 17 β-estradiol exerts a dual effect: it blunts aldosterone production via ERβ, but displays a potent aldosterone secretagogue effect via GPER activation after ERβ blockade. Thus, in premenopausal women high estrogen levels might tonically blunt aldosterone synthesis via ERβ, thereby maintaining normal blood pressure; after menopause loss of this estrogen-mediated inhibition can contribute to increasing blood pressure via GPER-mediated aldosterone release. The additional findings that GPER mediates an aldosterone-induced stimulation of aldosterone biosynthesis and that GPER predominates in aldosterone-producing adenomas strongly involves this receptor in the pathophysiology of primary aldosteronism. Our purpose here was to provide an update on estrogen receptor function in the normal adrenal cortex and its relevance for the sex differences in blood pressure in light of the newly discovered role of GPER in regulating aldosterone synthesis. The implications of the novel knowledge for the treatment of estrogen-dependent malignancies with ER modulators are also discussed.

Interactions of the DASH Diet with the Renin-Angiotensin-Aldosterone System

ABSTRACTBackgroundThe Dietary Approaches to Stop Hypertension (DASH) diet is widely recommended to lower blood pressure, but its mechanisms of action are unclear. Lines of evidence suggest an interaction with the renin-angiotensin-aldosterone system (RAAS).ObjectiveWe conducted a randomized, controlled, cross-over feeding trial to test RAAS-related mechanisms underlying the DASH diet in patients with isolated systolic hypertension.MethodsParticipants entered a 1-wk run-in period on a control (CON) diet and then consumed the DASH or CON diets for 4 wk each in randomized sequence. Calorie content was controlled to maintain weight, and sodium intake was set at 3 g daily. After each diet, participants had hormonal and hemodynamic assessments obtained at baseline, in response to RAAS inhibition with captopril (CAP) 25 mg, and to graded angiotensin II (AngII) infusions (1 ng/kg and 3 ng/kg × 45 min). Primary outcomes were mean arterial pressure (MAP) and renal blood flow (RBF), and secondary outcomes were diastolic function, pulse wave velocity (PWV), plasma renin activity (PRA), and aldosterone (ALDO) responses by diet.ResultsIn total, 44 (19 female) participants completed the study. DASH + CAP significantly lowered MAP compared with CON + CAP (83 ± 11 mmHg compared with 88 ± 14 mmHg, P <0.01). RBF was increased with DASH + CAP compared with CON + CAP (486 ± 149 cc/min compared with 451 ± 171 cc/min, P <0.001). Study diet did not change PWV but CAP reduced diastolic function on the DASH diet (P <0.05). DASH + CAP significantly increased PRA compared with CON + CAP (1.52 ± 1.78 ng/mL/min compared with 0.89 ± 1.17 ng/mL/min; P <0.001). ALDO sensitivity to AngII infusion was greater with DASH when compared to CON (17.4 ± 7.7 ng/mL compared with 13.8 ± 6.2 ng/dL, P <0.05) as was DASH + CAP compared with CON + CAP (15.1 ± 5.3 ng/dL compared with 13.1 ± 5.9 ng/mL, P <0.05).ConclusionsThe DASH diet interacts with the RAAS resulting in vascular and hormonal responses similar to a natriuretic effect, which appears to augment the hypotensive effect of angiotensin-converting enzyme (ACE) inhibition in individuals with isolated systolic hypertension. This trial was registered at clinicaltrials.gov as NCT00123006.

The serine-threonine kinase PIM3 is an aldosterone-regulated protein in the distal nephron.

The mineralocorticoid hormone aldosterone plays a crucial role in the control of Na+ and K+ balance, blood volume, and arterial blood pressure, by acting in the aldosterone‐sensitive distal nephron (ASDN) and stimulating a complex transcriptional, translational, and cellular program. Because the complexity of the aldosterone response is still not fully appreciated, we aimed at identifying new elements in this pathway. Here, we demonstrate that the expression of the proto‐oncogene PIM3 (Proviral Integration Site of Moloney Murine Leukemia Virus 3), a serine/threonine kinase belonging to the calcium/calmodulin‐regulated group of kinases, is stimulated by aldosterone in vitro (mCCDcl1 cells), ex vivo (mouse kidney slices), and in vivo in mice. Characterizing a germline Pim3 − / − mouse model, we found that these mice have an upregulated Renin‐Angiotensin‐Aldosterone System (RAAS), with high circulating aldosterone and plasma renin activity levels on both standard or Na+‐deficient diet. Surprisingly, we did not observe any obvious salt‐losing phenotype in Pim3 KO mice as shown by normal blood pressure, plasma and urinary electrolytes, as well as unchanged expression levels of the major Na+ transport proteins. These observations suggest that the potential effects of the loss of the Pim3 gene are physiologically compensated. Indeed, the 2 other family members of the PIM kinase family, PIM1 and PIM2 are upregulated in the kidney of Pim3 − / − mice, and may therefore be involved in such compensation. In conclusion, our data demonstrate that the PIM3 kinase is a novel aldosterone‐induced protein, but its precise role in aldosterone‐dependent renal homeostasis remains to be determined.

OR04-3 Lysine-Specific Demethylase-1 (LSD1) Deficiency Increases Aldosterone Signaling via Mineralocorticoid Receptor Activation

Lysine-specific demethylase-1 (LSD1) is a histone demethylase that mediates epigenetic regulation of gene transcription. We have shown that human risk allele carriers of a LSD1 variant as well as a LSD1 heterozygous knockout mice (LSD1+/-) have salt sensitive hypertension (HTN), but low aldosterone (ALDO) and plasma renin activity (PRA) levels. However, in young mice ALDO levels are inappropriately increased for the level of salt intake. Thus, we hypothesize that despite the low ALDO levels, the salt sensitive HTN is mineralocorticoid mediated secondary to an overactive mineralocorticoid receptor(MR). To test our hypothesis, wild-type (LSD1+/+) and LSD1+/- mice were fed a liberal sodium (1.6% Na+) diet for 7 days and were then randomized to placebo or eplerenone (Epl) treatment for 2 weeks. Systolic blood pressures (SBP) were measured before and after the intervention; albumin/creatinine ratios (A/C), plasma ALDO, as well as urine ALDO, sodium and potassium were measured at the end of the study. Results: Compared with LSD1+/+, LSD1+/- mice displayed higher SBP at the beginning of the study (132 ± 2.6 mmHg vs 113.8 ± 2.0 mmHg; P<0.001). As compared to placebo, treatment with eplerenone significantly reduced SBP in LSD1+/- but not LSD1+/+ mice (LSD1+/-+ epl: 120.8 ± 1.6 mmHg vs LSD1+/- + placebo 134.1± 4.3 , P = 0.02). LSD1+/- mice also displayed significantly higher A/C ratios than the LSD1+/+ (68.0 ± 23.6 µg/mg vs 22.1 ± 1.6 µg/mg, P = 0.04), and treatment with eplerenone reduced A/C in LSD1+/- mice to levels indistinguishable from those in the LSD1+/+ (LSD1+/- + epl. 27.3 ± 2.9 µg/mg vs LSD1+/+ + epl 26.0 ± 1.7 µg/mg). Urine ALDO/creatinine ratios were significantly lower in LSD1+/- vs. LSD1+/+ (26.1 ± 4.0 pg/mg vs 39.4 ± 4.1 pg/mg ,P = 0.03). Plasma ALDO showed a similar trend for lower levels in LSD1+/- vs. LSD1+/+ (21.8 ± 5.1 ng/dl vs 33.5 ± 6.1 ng/dl). In contrast, LSD1+/- had significantly higher 24-hr urine potassium than the LSD1+/+ mice (0.29 ± 0.1 mmol vs 0.15 ± 0.02 mmol, P= 0.05), yet similar ALDO responses to eplerenone, suggesting increased MR activity. Conclusion: Our data support our hypothesis that inappropriately activated MR signaling mediates the cardio-renal defects in the LSD1 deficient mouse. These findings support the concept that treatment with an MR antagonist may result in improved cardio- and reno-vascular outcomes in human LSD1+/- risk allele carriers.

Influence of Sodium Citrate Supplementation after Dehydrating Exercise on Responses of Stress Hormones to Subsequent Endurance Cycling Time-Trial in the Heat.

Background and objectives: In temperate environments, acute orally induced metabolic alkalosis alleviates exercise stress, as reflected in attenuated stress hormone responses to relatively short-duration exercise bouts. However, it is unknown whether the same phenomenon occurs during prolonged exercise in the heat. This study was undertaken with aim to test the hypothesis that ingestion of an alkalizing substance (sodium citrate; CIT) after dehydrating exercise would decrease blood levels of stress hormones during subsequent 40 km cycling time-trial (TT) in the heat. Materials and Methods: Male non-heat-acclimated athletes (n = 20) lost 4% of body mass by exercising in the heat. Then, during a 16 h recovery period prior to TT in a warm environment (32 °C), participants ate the prescribed food and ingested CIT (600 mg·kg−1) or placebo (PLC) in a double-blind, randomized, crossover manner with 7 days between the two trials. Blood aldosterone, cortisol, prolactin and growth hormone concentrations were measured before and after TT. Results: Total work performed during TT was similar in the two trials (p = 0.716). In CIT compared to PLC trial, lower levels of aldosterone occurred before (72%) and after (39%) TT (p ˂ 0.001), and acute response of aldosterone to TT was blunted (29%, p ˂ 0.001). Lower cortisol levels in CIT than in PLC trial occurred before (13%, p = 0.039) and after TT (14%, p = 0.001), but there were no between-trial differences in the acute responses of cortisol, prolactin or growth hormone to TT, or in concentrations of prolactin and growth hormone before or after TT (in all cases p > 0.05). Conclusions: Reduced aldosterone and cortisol levels after TT and blunted acute response of aldosterone to TT indicate that CIT ingestion during recovery after dehydrating exercise may alleviate stress during the next hard endurance cycling bout in the heat.

Cortisol and Aldosterone Responses to Insulin-Induced Hypoglycemia and Sodium Depletion in Women with Non-Classic 21-Hydroxylase Deficiency

Background: Non-classic 21-hydroxylase deficiency is usually diagnosed in post-pubertal women because of androgen excess. Indication of systematic steroid replacement therapy is controversial because the risk of acute adrenal insufficiency is unknown. In order to specify this risk we evaluated the cortisol and aldosterone secretions in response to appropriate pharmacological challenges. Methods: In this prospective case-control non-inferiority study we investigated 20 women with non-classic 21-hydroxylase deficiency carrying biallelic CYP21A2 mutations and with serum 17-hydroxyprogesterone (17OHP) >10ng/mL after stimulation with Synacthen® (tetracosactrin) and 20 ageand BMI-matched healthy women with 17OHP after Synacthen® <2ng/mL. Each participant underwent sequentially an insulin tolerance test to evaluate cortisol secretion and a sodium depletion test, obtained by oral administration of 40 mg furosemide under low sodium diet (< 20 mmol during 24 hours), to evaluate renin and aldosterone secretion. Findings: The peak serum cortisol concentration after insulin hypoglycemia was lower in patients than in controls (mean difference -47 ng/mL, 90%CI: -66, p=0.0026). A peak serum cortisol above a cutoff value of 170 ng/mL was obtained in all controls but only in 55% of patients (p=0.0039). 24- hours after sodium depletion, blood pressure, plasma sodium, potassium and serum aldosterone concentrations were comparable between the two groups, but patients had higher stimulated renin concentrations than controls (p=0.0044). Interpretation: Patients with non-classic 21-hydroxylase deficiency frequently display partial cortisol insufficiency and compensated defect in aldosterone secretion. Their clinical management should systematically include assessment of adrenal functions. Trial Registration Number: The trial was registered in ClinicalTrials.gov number NCT01862380. Funding Statement: Institutional grant from APHP AOR11111. Declaration of Interests: The authors state that they have nothing to disclose. Ethics Approval Statement: The study was approved by the local Ethics Committee (Comite de Protection des Personnes Ile de France VII) and the competent authority (ANSM). All subjects gave written informed consent to participate to the study.

Histone demethylase LSD1 deficiency and biological sex: impact on blood pressure and aldosterone production.

Human risk allele carriers of lysine-specific demethylase 1 (LSD1) and LSD1-deficient mice have salt-sensitive hypertension for unclear reasons. We hypothesized that LSD1 deficiency causes dysregulation of aldosterone's response to salt intake resulting in increased cardiovascular risk factors (blood pressure and microalbumin). Furthermore, we determined the effect of biological sex on these potential abnormalities. To test our hypotheses, LSD1 male and female heterozygote-knockout (LSD1+/-) and WT mice were assigned to two age groups: 18 weeks and 36 weeks. Plasma aldosterone levels and aldosterone production from zona glomerulosa cells studied ex vivo were greater in both male and female LSD1+/- mice consuming a liberal salt diet as compared to WT mice consuming the same diet. However, salt-sensitive blood pressure elevation and increased microalbuminuria were only observed in male LSD1+/- mice. These data suggest that LSD1 interacts with aldosterone's secretory response to salt intake. Lack of LSD1 causes inappropriate aldosterone production on a liberal salt diet; males appear to be more sensitive to this aldosterone increase as males, but not females, develop salt sensitivity of blood pressure and increased microalbuminuria. The mechanism responsible for the cardiovascular protective effect in females is uncertain but may be related to estrogen modulating the effect of mineralocorticoid receptor activation.

Sex Differences in Coronary Microvascular Function in Individuals With Type 2 Diabetes.

Cardiovascular (CV) disease fatality rates are higher for women compared with men with diabetes despite lower rates of obstructive coronary artery disease (CAD). Impaired coronary flow reserve (CFR), the ratio of adenosine-stimulated to rest myocardial blood flow (MBF), is an indicator of coronary microvascular dysfunction and predicts major adverse CV events. We performed a post hoc analysis to determine whether there was a sex disparity in coronary microvascular dysfunction among 46 men and 27 women with well-controlled type 2 diabetes and without clinical evidence of obstructive CAD. We found that women had a higher rest MBF, lower CFR, and worse diastolic function compared with men. In addition, rest MBF was positively correlated with worse diastolic function in women. We previously showed that mineralocorticoid blockade improved CFR in men and women with type 2 diabetes, implicating aldosterone in the pathophysiology of coronary microvascular dysfunction. We therefore examined aldosterone levels and found that women had larger increases in aldosterone in response to an angiotensin-II infusion than did men. In conclusion, among individuals with type 2 diabetes and good cardiometabolic control, women had worse myocardial perfusion and diastolic function compared with men. The greater aldosterone responsivity in women may be a mechanism for this sex effect.

Role of the Renin Angiotensin System in Blood Pressure Allostasis-induced by Severe Food Restriction in Female Fischer rats

Severe food restriction (FR) is associated with blood pressure (BP) and cardiovascular dysfunction. The renin-angiotensin system (RAS) regulates BP and its dysregulation contributes to impaired cardiovascular function. Female Fischer rats were maintained on a control (CT) or severe FR (40% of CT) diet for 14 days. In response to severe FR, BP allostasis was achieved by up-regulating circulating Ang-[1–8] by 1.3-fold through increased angiotensin converting enzyme (ACE) activity and by increasing the expression of AT1Rs 1.7-fold in mesenteric vessels. Activation of the RAS countered the depressor effect of the severe plasma volume reduction (≥30%). The RAS, however, still underperformed as evidenced by reduced pressor responses to Ang-[1–8] even though AT1Rs were still responsive to the depressor effects of an AT1R antagonist. The aldosterone (ALDO) response was also inadequate as no changes in plasma ALDO were observed after the large fall in plasma volume. These findings have implications for individuals who have experienced a period(s) of severe FR (e.g., anorexia nervosa, dieters, natural disasters) and suggests increased activity of the RAS in order to achieve allostasis contributes to the cardiovascular dysfunction associated with inadequate food intake.

Clinical Implications

HomeHypertensionVol. 71, No. 6Clinical Implications Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBClinical Implications Originally published9 May 2018https://doi.org/10.1161/HYPERTENSIONAHA.118.11323Hypertension. 2018;71:955Biological Sex Modulates Aldosterone Levels (p 1083)Download figureDownload PowerPointSex differences in cardiovascular disease exist, with women being at greater risk than men for some hypertension-related cardiovascular diseases such as increased left ventricular hypertrophy. Salt sensitivity of blood pressure, the change in systolic blood pressure between high- and low-salt diet, is a risk factor for cardiovascular morbidity and mortality. In this study of 1592 normotensive and hypertensive individuals who participated in the Hypertensive Pathotype Consortium, women had increased salt sensitivity of blood pressure and increased blood pressure and aldosterone responses to angiotensin II as compared with men. In an animal model of aldosterone-dependent cardiovascular injury, female compared with male rodents had increased cardiovascular injury with increased aldosterone levels; mineralocorticoid receptor blockade was equally effective in both sexes in preventing the damage. These sex differences likely contribute to the increased salt sensitivity of blood pressure and to increased aldosterone-mediated cardiovascular disease in women compared with men. Thus, as compared with men, women are likely to receive a greater cardiovascular risk reduction from mineralocorticoid receptor blockade.MitoQ Treatment and Vascular Function With Aging (p 1056)Download figureDownload PowerPointAdvancing age is the primary risk factor for cardiovascular disease. The development of vascular dysfunction, including vascular endothelial dysfunction and stiffening of the large elastic arteries (aorta and carotid arteries), is a major mechanism of increased cardiovascular disease risk with aging. Excessive production of reactive oxygen species by mitochondria has emerged as a key driver of vascular dysfunction with aging. Results of preclinical studies from our laboratory demonstrate that 4 weeks of oral supplementation with the mitochondria-targeted antioxidant MitoQ ameliorates age-related endothelial dysfunction and aortic stiffening in mice. In this issue of Hypertension we report the successful translation of these preclinical findings to humans. We show that 6 weeks of supplementation with MitoQ is safe and well tolerated and improves vascular endothelial function in healthy late middle-aged and older adults. We present data from a unique functional bioassay suggesting that the mechanism of action for the improvement in endothelial function with MitoQ supplementation involves a reduction in mitochondrial reactive oxygen species-associated suppression of endothelium-dependent dilation. We also show that MitoQ treatment reduces aortic stiffness in individuals exhibiting age-related aortic stiffening and that MitoQ supplementation decreases plasma concentrations of oxidized low-density lipoprotein, a circulating marker of oxidative stress. Collectively, these findings indicate that mitochondria-targeted therapies such as MitoQ may hold promise for reducing mitochondrial-derived oxidative stress, improving vascular function and decreasing cardiovascular disease risk with aging.Media/Lumen Reference Values in Small Arteries (p 1193)Download figureDownload PowerPointSmall artery remodeling is an early feature of target organ damage in hypertension and retains a negative prognostic value. The gold standard for its assessment, media/lumen ratio (M/L), can be obtained by tissue biopsies. In this article, a cohort of 291 individuals with or without cardiovascular risk factors was pooled from 4 Italian centers to establish age- and sex-specific reference values and to explore M/L relationship with risk factors. M/L reference values obtained in a sufficiently large healthy population are useful in pathophysiological studies to establish the impact of classical and emerging risk factors on the microvasculature as well as the effect of treatment. Indeed, not only blood pressure, but also body mass index, cholesterol, smoking, and blood glucose were associated with increased M/L, highlighting especially the role of metabolic factors in inducing microvascular damage. From a clinical perspective, microvascular alterations are increasingly recognized as crucial mechanisms of cardiovascular and cerebrovascular disease, and they can be reversed by appropriate treatment. A better comprehension of microvascular damage accrual with age and risk factors may thus help identify novel treatment targets. Furthermore, the identification of a different impact of risk factors on M/L in the 2 sexes suggests a possible explanation for the well-known sex differences in the pathophysiology of cardiovascular disease, thus opening a novel pathway to personalized medicine. Previous Back to top Next FiguresReferencesRelatedDetails June 2018Vol 71, Issue 6 Advertisement Article InformationMetrics © 2018 American Heart Association, Inc.https://doi.org/10.1161/HYPERTENSIONAHA.118.11323 Originally publishedMay 9, 2018 PDF download Advertisement

Genetic Characterization of GnRH/LH-Responsive Primary Aldosteronism.

Recently, somatic β-catenin mutations (CTNNB1) identified in aldosterone-producing adenomas (APAs) from three women were suggested to be responsible for the aberrant overexpression of luteinizing hormone/choriogonadotropin receptor and gonadotropin-releasing hormone receptor in the APA. To genetically characterize patients with primary aldosteronism (PA) evaluated in vivo for gonadotropin-releasing hormone (GnRH)/luteinizing hormone (LH)-responsive aldosterone secretion. Patients with PA were evaluated in vivo to determine the possible regulation of aldosterone secretion by GnRH or LH. Genetic analysis of the CTNNB1, KCNJ5, ATP1A1, ATP2B3, CACNA1D, and GNAS genes were performed in this cohort and a control cohort of PA not tested in vivo for GnRH response. We studied 50 patients with confirmed PA, including 36 APAs, 12 bilateral macronodular adrenal hyperplasias, 1 oncocytoma, and 1 bilateral hyperplasia with cosecretion of cortisol. Among 23 patients tested in vivo for GnRH response of aldosterone, 7 (30.4%) had a positive response, 4 (17.4%) a partial response, and 12 (52.2%) no response. No somatic CTNNB1 mutations were identified, but the disease-causing c.451G>C KCNJ5 mutation was found in two individuals with partial and no GnRH responses and an individual showing a positive response to LH. Two additional somatic pathogenic mutations, CACNA1D c.776T>A and ATP1A1 c.311T>G, were identified in two patients with no GnRH responses. In the 26 patients not tested for GnRH response, we identified 2 CTNNB1 (7.7%), 13 KCNJ5 (50%), and 1 CACNA1D (3.8%) mutations. Aberrant regulation of aldosterone by GnRH is frequent in PA, but is not often associated with somatic CTNNB1, although it may be found with somatic KCNJ5 mutations.

Biological Sex Modulates the Adrenal and Blood Pressure Responses to Angiotensin II.

The relationship between biological sex and aldosterone on blood pressure (BP) is unclear. We hypothesized that sex would modify the interaction between aldosterone and vascular responses to salt intake and angiotensin II (AngII). To test this hypothesis, in 1592 subjects from the well-controlled Hypertensive Pathotype cohort, we compared responses of women and men to chronic (BP and aldosterone levels in response to dietary salt) and acute (BP, renal plasma flow, and aldosterone responses to AngII infusion) manipulations. Women had a 30% higher salt sensitivity of BP than men (P<0.0005) regardless of age or hypertension status, a greater BP response to AngII, and a 15% greater aldosterone response to AngII on both restricted and liberal salt diets (P<0.005). Furthermore, there was an interaction (P=0.003) between sex and aldosterone on BP response to AngII. Women also had a greater (P<0.01) increment in renal plasma flow in response to AngII than men. To assess potential mechanisms for this sex effect, we compared aldosterone responses to AngII or potassium from rat zona glomerulosa cells and observed greater aldosterone production in female than male zona glomerulosa cells basally and in response to both agonists (P<0.0001). In a rodent model of aldosterone-mediated cardiovascular disease induced by increased AngII and low NO, circulating aldosterone levels (P<0.01), myocardial damage (P<0.001), and proteinuria (P<0.05) were greater in female than male rats despite having similar BP responses. Thus, increased aldosterone production likely contributes to sex differences in cardiovascular disease, suggesting that women may be more responsive to mineralocorticoid receptor blockade than men.

Co‐regulation of Renal Function Genes by the Circadian Clock Protein PER1 and Aldosterone

Hypertension is the leading cause of cardiovascular disease. A subset of hypertensive patients experience salt‐sensitive hypertension, which causes elevations in blood pressure (BP) after high salt intake. With large increases in dietary salt worldwide, the prevalence of hypertension has reached 30%. BP follows a circadian rhythm. The circadian clock is a highly conserved mechanism that allows organisms to adapt to the light/dark cycles of our environment. The molecular clock is comprised of core transcription proteins, such as the clock protein PER1. Further, the renin angiotensin aldosterone system (RAAS) is an important homeostatic mechanism to manage sodium and BP homeostasis. Previous results from our lab show that the circadian clock and RAAS both contribute to sodium and BP homeostasis. Based on these studies, we hypothesized that aldosterone and Per1 coordinately regulate genes that contribute to kidney function. We tested this hypothesis first by using a cell culture model from the renal cortical collecting duct. Cells were treated with aldosterone and/or siRNA to knockdown down PER1 expression. Using an unbiased microarray approach, we determined PER1 and aldosterone‐dependent changes in gene expression. Several hundred genes exhibited significant changes in expression in response to hormone treatment and PER1 knockdown. For the first time, we identified secreted frizzled related protein 1 (sFRP1), Claudin‐1, and Rhesus glycoprotein C (Rhcg) as target genes of aldosterone and PER1. The expression of sFRP1 demonstrated a 1.5‐fold increase in response to aldosterone (p&lt;0.05, n=4), which was not affected in the absence of PER1, indicating that aldosterone and PER1 independently regulate sFRP1. In contrast, the 2.9‐fold (p&lt;0.05, n=4) and 1.9‐fold (p&lt;0.05, n=3) induction of Rhcg and Claudin‐1, respectively, by aldosterone was decreased significantly in the absence of PER1, suggesting that PER1 contributes to aldosterone‐mediated regulation of these genes. The ET‐1 gene is of particular interest due to its known role in the regulation of renal salt handling and BP. In the microarray study, knockdown of PER1 augmented the aldosterone response of ET‐1 mRNA by 3‐fold (p&lt;0.05, n=4). Importantly, a similar effect was observed in the kidneys of Per1 knockout mice treated with a high salt diet plus an aldosterone analogue: loss of Per1 augmented the response of ET‐1 by 50% (p&lt;0.01, n=6) compared to no change in WT mice. Interrogation of the database CircaDB revealed that Claudin‐1 and ET‐1 are both expressed with a significant circadian rhythm in the kidney (p&lt;0.001). Together these data demonstrate that multiple genes critical to renal function are co‐regulated by the circadian clock PER1 and RAAS. These data may have important implications for understanding the underlying mechanisms of, and designing novel treatments for, salt‐sensitive hypertension in humans.Support or Funding InformationR01DK109570; R21AG052861; American Heart Association Grant‐in‐aid; Gatorade Trust Fund, Division of Nephrology, Department of Medicine, University of Florida; NF/SG VAMCThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Renal intercalated cells and blood pressure regulation.

Type B and non-A, non-B intercalated cells are found within the connecting tubule and the cortical collecting duct. Of these cell types, type B intercalated cells are known to mediate Cl− absorption and HCO3− secretion largely through pendrin-dependent Cl−/HCO3− exchange. This exchange is stimulated by angiotensin II administration and is also stimulated in models of metabolic alkalosis, for instance after aldosterone or NaHCO3 administration. In some rodent models, pendrin-mediated HCO3− secretion modulates acid-base balance. However, the role of pendrin in blood pressure regulation is likely of more physiological or clinical significance. Pendrin regulates blood pressure not only by mediating aldosterone-sensitive Cl− absorption, but also by modulating the aldosterone response for epithelial Na+ channel (ENaC)-mediated Na+ absorption. Pendrin regulates ENaC through changes in open channel of probability, channel surface density, and channels subunit total protein abundance. Thus, aldosterone stimulates ENaC activity through both direct and indirect effects, the latter occurring through its stimulation of pendrin expression and function. Therefore, pendrin contributes to the aldosterone pressor response. Pendrin may also modulate blood pressure in part through its action in the adrenal medulla, where it modulates the release of catecholamines, or through an indirect effect on vascular contractile force. This review describes how aldosterone and angiotensin II-induced signaling regulate pendrin and the contributory role of pendrin in distal nephron function and blood pressure.

Dysregulation of Aldosterone Secretion in Mast Cell-Deficient Mice.

Resident adrenal mast cells have been shown to activate aldosterone secretion in rat and man. Especially, mast cell proliferation has been observed in adrenal tissues from patients with aldosterone-producing adrenocortical adenoma. In the present study, we show that the activity of adrenal mast cells is stimulated by low-sodium diet and correlates with aldosterone synthesis in C57BL/6 and BALB/c mice. We have also investigated the regulation of aldosterone secretion in mast cell-deficient C57BL/6 KitW-sh/W-sh mice in comparison with wild-type C57BL/6 mice. KitW-sh/W-sh mice submitted to normal sodium diet had basal plasma aldosterone levels similar to those observed in wild-type animals. Conversely, low-sodium diet unexpectedly induced an exaggerated aldosterone response, which seemed to result from an increase in adrenal renin and angiotensin type 1 receptor expression. Severe hyperaldosteronism was associated with an increase in systolic blood pressure and marked hypokalemia, which favored polyuria. Adrenal renin and angiotensin type 1 receptor overexpression may represent a compensatory mechanism aimed at activating aldosterone production in the absence of mast cells. Finally, C57BL/6 KitW-sh/W-sh mice represent an unexpected animal model of primary aldosteronism, which has the particularity to be triggered by sodium restriction.