Human adipocytes induce an ERK1/2 MAP kinases-mediated upregulation of steroidogenic acute regulatory protein (StAR) and an angiotensin II — sensitization in human adrenocortical cells

Nonsteroidal mineralcorticoid receptor antagonists: Novel therapeutic implication in the management of patients with type 2 diabetes

Growing evidencehas described a correlation between aldosterone, obesity, and insulin resistance, suggesting that adipocyte-related factors and mineralocorticoid receptor (MR) overactivation may alter aldosterone secretion, potentially leading to obesity and glucose intolerance. Preclinical studies showed that pharmacological antagonism of MR prevents white adipose tissue dysfunction(s) and expansion, activates brown adipose tissue, and improves glucose tolerance. The clinical use of nonsteroidal MR antagonists has been shown to reduce the risk of diabetic kidney disease progression and cardiovascular events in patients with diabetes. This review aims to summarize the effects of pharmacological MR blockade on obesity and its associated metabolic comorbidities, with a particular focus on the therapeutic implications of nonsteroidal MR antagonists in the management of patients with diabetes.

Paradoxical Increase of 24-Hour Urinary Aldosterone Levels in Obese Patients With Resistant Hypertension on a High Salt Diet

BACKGROUND

Having previously reported that aldosterone levels increase progressively with body mass index (BMI), the current analysis was done to determine to what extent this association is related to dietary high salt intake. We anticipated that aldosterone levels would decrease with higher sodium status consistent with classical suppression of aldosterone release secondary to progressive fluid retention induced by high dietary sodium intake.

METHODS

Cross-sectional analysis of a large diverse cohort of 2,705 patients with resistant hypertension (HTN) seen in a referral HTN Clinic. Dietary sodium intake was indexed by 24-hour (h) urinary sodium (UNa), aldosterone status was determined by plasma aldosterone concentration, plasma renin activity, and 24 h urinary aldosterone (UAldo). Patients with normal weight served as control.

RESULTS

In this study, 1,572 individuals with complete 24 h urine collections were analyzed. Mean BMI was 32.5 ± 7.1 kg/m2 and ranged from 24.6 ± 2.4 kg/m2 (first quartile) to 41.0 ± 4.2 kg/m2 (fourth quartile). BMI was positively associated with 24 h UNa and UAldo levels (P < 0.0001), 24 h UNa and UAldo. There was a positively stronger correlation in obese (r = 0.273, P < 0.0001) compared with normal weight individuals (r = 0.108, P = 0.0342) independent of number and classes of antihypertensive medications.

CONCLUSIONS

Our analysis shows that there is an altered regulation of aldosterone in obese patients in the setting of high dietary salt intake.

Higher prevalence of metabolic disorders in patients with bilateral primary aldosteronism than unilateral primary aldosteronism

OBJECTIVE

Metabolic syndrome (MetS) is a frequent clinical condition in hypertension patients and is more frequently reported in primary aldosteronism (PA). This study is aimed at investigating the prevalence of MetS and its components in the two major types of patients with adrenal venous sampling (AVS)-confirmed unilateral PA and bilateral PA.

DESIGN AND PATIENTS

This was a retrospective cross-section study. We analysed metabolic parameters from 169 PA patients subtyped by AVS, including 85 unilateral PA patients and 84 bilateral PA patients, and we also included 169 non-PA patients matched for age and sex.

RESULTS

Patients with unilateral PA had higher concentrations of aldosterone and lower serum potassium than patients with bilateral PA. However, patients with bilateral PA had higher prevalence of MetS (79.8% vs 64.7%, P = .029), obesity (40.5% vs 24.7%, P = .029), dyslipidemia (72.6% vs 55.3%, P = .019) and hyperglycaemia (29.8% vs 16.5%, P = .040) than those with unilateral PA. Meanwhile, bilateral PA had higher BMI (27.55 ± 4.58 vs 25.57 ± 3.28 kg/m² , P = .001), waist circumference (98.54 ± 11.44 vs 93.32 ± 10.64 cm, P = .003) and fasting plasma glucose (4.98 ± 1.16 vs 4.64 ± 0.93 mmol/L, P = .034). The logistic regression analysis also showed that bilateral PA was associated with the presence of MetS after adjustment for age, sex and duration of hypertension.

CONCLUSIONS

Patients with bilateral PA have a higher prevalence of MetS than those with unilateral PA, despite unilateral PA patients exhibiting higher concentrations of aldosterone and lower serum potassium, suggesting that unilateral PA and bilateral PA may have differing mechanisms of MetS.

Management of primary aldosteronism and mineralocorticoid receptor-associated hypertension

Resistant hypertension is associated with a poor prognosis due to organ damage caused by prolonged suboptimal blood pressure control. The concomitant use of mineralocorticoid receptor (MR) antagonists with other antihypertensives has been shown to improve blood pressure control in some patients with resistant hypertension, and such patients are considered to have MR-associated hypertension. MR-associated hypertension is classified into two subtypes: one with a high plasma aldosterone level, which includes primary aldosteronism (PA), and the other with a normal aldosterone level. In patients with unilateral PA, adrenalectomy may be the first-choice procedure, while in patients with bilateral PA, MR antagonists are selected. In addition, in patients with other types of MR-associated hypertension with high aldosterone levels, MR antagonists may be selected as a first-line therapy. In patients with normal aldosterone levels, ARBs or ACE inhibitors are used as a first-line therapy, and MR antagonists may be used as an add-on agent. Since MR antagonist therapy may have efficacy as a first-line or add-on agent in these patients, it is important to recognize this type of hypertension. Further studies are needed to elucidate the pathogenesis and management of MR-associated hypertension in more detail to improve the clinical outcomes of patients with MR-associated hypertension.

Hypertensive Heart Disease and Obesity: A Review

Metabolic syndrome is an increasingly prevalent constellation of disease processes among the global population. Hypertension and obesity are among the contributing etiologies, and obesity increases the likelihood of hypertensive heart disease by creating a proinflammatory state, as well as increasing sympathetic tone and formation of reactive oxygen species. Hypertensive heart disease is characterized by myocardial fibrosis, which portends higher risk of developing reduced ejection fraction, diastolic dysfunction, ischemia, and arrhythmias, making early diagnosis and treatment essential to the prevention of cardiac events.

Body mass index predicts aldosterone production in hypertensive postmenopausal women

Hypertension is a common clinical problem, and increased aldosterone is the most prevalent underlying characteristic. Related works have shown exciting results on the effects of various conditions on aldosterone content, but the correlation between aldosterone levels and body mass index (BMI) in premenopausal women has not yet been investigated. We herein report a cross-sectional analysis aimed to determine whether BMI is proportional to plasma aldosterone concentration in premenopausal and postmenopausal hypertensive women. The analysis of consecutive admitted female patients with hypertension revealed potential relationships among plasma aldosterone concentration, plasma renin activity, oestrogen, and BMI. It should be noted that plasma aldosterone concentration was significantly correlated with BMI (p < .05) in postmenopausal women, and both plasma aldosterone and oestrogen levels were decreased in premenopausal women. These findings suggest that BMI has a positive impact on aldosterone in postmenopausal hypertensive women but not in premenopausal women. Additionally, we predict that endogenous oestrogen may be an important indication of aldosterone changes in premenopausal hypertensive women of different body weights.

High Prevalence of Diabetes in Patients With Primary Aldosteronism (PA) Associated With Subclinical Hypercortisolism and Prediabetes More Prevalent in Bilateral Than Unilateral PA: A Large, Multicenter Cohort Study in Japan

OBJECTIVE

To investigate the prevalence and causes of diabetes in patients with primary aldosteronism (PA) in a multi-institutional cohort study in Japan.

RESEARCH DESIGN AND METHODS

The prevalence of diabetes was determined in 2,210 patients with PA (diagnosed or glycated hemoglobin [HbA_1c] ≥6.5% [≥48 mmol/mol]; NGSP) and compared with that of the Japanese general population according to age and sex. In 1,386 patients with PA and clear laterality (unilateral or bilateral), the effects of plasma aldosterone concentration (PAC), hypokalemia (<3.5 mEq/L), suspected subclinical hypercortisolism (SH; serum cortisol ≥1.8 µg/dL after 1-mg dexamethasone suppression test), and PA laterality on the prevalence of diabetes or prediabetes (5.7% ≤ HbA_1c <6.5% [39 mmol/mol ≤ HbA_1c <48 mmol/mol]) were examined.

RESULTS

Of the 2,210 patients with PA, 477 (21.6%) had diabetes. This prevalence is higher than that in the general population (12.1%) or in 10-year cohorts aged 30-69 years. Logistic regression or χ² test revealed a significant contribution of suspected SH to diabetes. Despite more active PA profiles (e.g., higher PAC and lower potassium concentrations) in unilateral than bilateral PA, BMI and HbA_1c values were significantly higher in bilateral PA. PA laterality had no effect on the prevalence of diabetes; however, the prevalence of prediabetes was significantly higher in bilateral than unilateral PA.

CONCLUSIONS

Individuals with PA have a high prevalence of diabetes, which is associated mainly with SH. The prevalence of prediabetes is greater for bilateral than unilateral PA, suggesting a unique metabolic cause of bilateral PA.

Paracrine Regulation of Aldosterone Secretion in Physiological and Pathophysiological Conditions

Aldosterone secretion by the zona glomerulosa of the adrenal cortex is controlled by circulating factors including the renin angiotensin system (RAS) and potassium. Mineralocorticoid production is also regulated through an autocrine/paracrine mechanism by a wide variety of bioactive signals released in the vicinity of adrenocortical cells by chromaffin cells, nerve endings, cells of the immune system, endothelial cells and adipocytes. These regulatory factors include conventional neurotransmitters and neuropeptides. Their physiological role in the control of aldosterone secretion is not fully understood, but it is likely that they participate in the RAS-independent regulation of zona glomerulosa cells. Interestingly, recent observations indicate that autocrine/paracrine processes are involved in the pathophysiology of primary aldosteronism. The intraadrenal regulatory systems observed in aldosterone-producing adenomas (APA), although globally similar to those occurring in the normal adrenal gland, harbor alterations at different levels, which tend to strengthen the potency of paracrine signals to activate aldosterone secretion. Enhancement of paracrine stimulatory tone may participate to APA expansion and aldosterone hypersecretion together with somatic mutations of driver genes which activate the calcium signaling pathway and subsequently aldosterone synthase expression. Intraadrenal regulatory mechanisms represent thus promising pharmacological targets for the treatment of primary aldosteronism.

Circulating steroid levels as correlates of adipose tissue phenotype in premenopausal women

Background Obesity-related alterations in the circulating steroid hormone profile remain equivocal in women. Our objective was to identify circulating steroid levels that relate to increased adiposity and altered adipose phenotype in premenopausal women. Materials and methods In a sample of 42 premenopausal women [age 46 ± 3 years; body mass index (BMI) 27.1 ± 4.2 kg/m2], 19 plasma steroids were quantified by electrospray ionization-liquid chromatography-tandem mass spectroscopy (ESI-LC-MS/MS). Body composition and fat distribution were assessed by dual-energy X-ray absorptiometry (DXA) and computed tomography (CT), respectively. Markers of adipose tissue function including adipocyte size distributions, radiological attenuation and macrophage infiltration were also analyzed in surgically obtained visceral and subcutaneous fat samples. Results Many negative correlations were observed between adiposity measurements such as BMI, body fat percentage or total abdominal adipose tissue area and plasma levels of androstenedione (Δ4) (r = -0.33 to -0.39, p ≤ 0.04), androsterone (ADT) (r = -0.30 to -0.38, p ≤ 0.05) and steroid precursor pregnenolone (PREG) (r = -0.36 to -0.46, p ≤ 0.02). Visceral adipocyte hypertrophy was observed in patients with low PREG concentrations (p < 0.05). Visceral adipose tissue radiologic attenuation, a potential marker of adipocyte size, was also positively correlated with PREG levels (r = 0.33, p < 0.05). Low levels of PREG were related to increased number of macrophages infiltrating visceral and subcutaneous adipose tissue (p < 0.05). Conclusion Plasma levels of androgens and their precursors are lower in women with increased adiposity and visceral adipocyte hypertrophy. Low circulating PREG concentration may represent a marker of adipose tissue dysfunction.

Obesity-stimulated aldosterone release is not related to an S1P-dependent mechanism

Aldosterone has been identified as an important factor in obesity-associated hypertension. Here, we investigated whether sphingosine-1-phosphate (S1P), which has previously been linked to obesity, increases aldosterone release. S1P-induced aldosterone release was determined in NCI H295R cells in the presence of S1P receptor (S1PR) antagonists. In vivo release of S1P (100-300 µg/kg_bw) was investigated in pithed, lean Sprague Dawley (SD) rats, diet-obese spontaneous hypertensive rats (SHRs), as well as in lean or obese Zucker rats. Aldosterone secretion was increased in NCI H295R cells by S1P, the selective S1PR1 agonist SEW2871 and the selective S1PR2 antagonist JTE013. Treatment with the S1PR1 antagonist W146 or fingolimod and the S1PR1/3 antagonist VPbib2319 decreased baseline and/or S1P-stimulated aldosterone release. Compared to saline-treated SD rats, plasma aldosterone increased by ~50 pg/mL after infusing S1P. Baseline levels of S1P and aldosterone were higher in obese than in lean SHRs. Adrenal S1PR expression did not differ between chow- or CD-fed rats that had the highest S1PR1 and lowest S1PR4 levels. S1P induced a short-lasting increase in plasma aldosterone in obese, but not in lean SHRs. However, 2-ANOVA did not demonstrate any difference between lean and obese rats. S1P-induced aldosterone release was also similar between obese and lean Zucker rats. We conclude that S1P is a local regulator of aldosterone production. S1PR1 agonism induces an increase in aldosterone secretion, while stimulating adrenal S1PR2 receptor suppresses aldosterone production. A significant role of S1P in influencing aldosterone secretion in states of obesity seems unlikely.

Hypertension in Obese Black Women is Not Caused by Increased Sympathetic Vascular Tone

Background

Black women have one of the highest prevalence rates of hypertension and obesity in the United States. We previously reported that sympathetic activation induced by obesity is a significant contributor to hypertension in white patients. It is unknown whether sympathetic activity similarly contributes to hypertension in obese black women.

Methods and Results

We studied 42 obese women (16 white, body mass index 36±4 kg/m², 44% with hypertension; 26 black, body mass index 35±4 kg/m², 46% with hypertension). Antihypertensive medications were discontinued for 2 weeks before the day of the study. All patients underwent complete autonomic blockade with trimethaphan at a dosage of 4 mg/min. Resting sympathetic activity determined from muscle sympathetic nerve recordings was similar between obese black women with hypertension and those with normotension. In whites, sympathetic activity was elevated in obese patients with hypertension compared with normotension; the decrease in mean arterial blood pressure produced by trimethaphan was greater in obese white patients with hypertension compared with those with normotension (−26.8±9.7 mm Hg versus −14.8±7.9 mm Hg, P=0.02). In contrast, there was no difference in the depressor responses induced by trimethaphan between obese black women with hypertension and those with normotension (−15.5±10.5 mm Hg versus −12.3±10.2 mm Hg, P=0.45). Mean arterial blood pressure remained elevated in obese blacks with hypertension compared with those with normotension during trimethaphan infusion (83.7±15.0 mm Hg versus 71.7±9.8 mm Hg, P=0.02). Heart rate increased similarly with trimethaphan between white (P=0.11) and black (P=0.76) women with hypertension and normotension.

Conclusions

These findings suggest that sympathetic activity does not contribute to hypertension in obese black women and provide further evidence for racial differences in hypertension mechanisms.

Very low-density lipoprotein (VLDL)-induced signals mediating aldosterone production

Aldosterone, secreted by the adrenal zona glomerulosa, enhances sodium retention, thus increasing blood volume and pressure. Excessive production of aldosterone results in high blood pressure and contributes to cardiovascular and renal disease, stroke and visual loss. Hypertension is also associated with obesity, which is correlated with other serious health risks as well. Although weight gain is associated with increased blood pressure, the mechanism by which excess fat deposits increase blood pressure remains unclear. Several studies have suggested that aldosterone levels are elevated with obesity and may represent a link between obesity and hypertension. In addition to hypertension, obese patients typically have dyslipidemia, including elevated serum levels of very low-density lipoprotein (VLDL). VLDL, which functions to transport triglycerides from the liver to peripheral tissues, has been demonstrated to stimulate aldosterone production. Recent studies suggest that the signaling pathways activated by VLDL are similar to those utilized by AngII. Thus, VLDL increases cytosolic calcium levels and stimulates phospholipase D (PLD) activity to result in the induction of steroidogenic acute regulatory (StAR) protein and aldosterone synthase (CYP11B2) expression. These effects seem to be mediated by the ability of VLDL to increase the phosphorylation (activation) of their regulatory transcription factors, such as the cAMP response element-binding (CREB) protein family of transcription factors. Thus, research into the pathways by which VLDL stimulates aldosterone production may identify novel targets for the development of therapies for the treatment of hypertension, particularly those associated with obesity, and other aldosterone-modulated pathologies.

VLDL-activated cell signaling pathways that stimulate adrenal cell aldosterone production

Aldosterone plays an important role in regulating ion and fluid homeostasis and thus blood pressure, and hyperaldosteronism results in hypertension. Hypertension is also observed with obesity, which is associated with additional health risks, including cardiovascular disease. Obese individuals have high serum levels of very low-density lipoprotein (VLDL), which has been shown to stimulate aldosterone production; however, the mechanisms underlying VLDL-induced aldosterone production are still unclear. Here we demonstrate in human adrenocortical carcinoma (HAC15) cells that submaximal concentrations of angiotensin II and VLDL stimulate aldosterone production in an additive fashion, suggesting the possibility of common mechanisms of action. We show using inhibitors that VLDL-induced aldosterone production is mediated by the PLC/IP3/PKC signaling pathway. Our results suggest that PKC is upstream of the extracellular signal-regulated kinase (ERK) activation previously observed with VLDL. An understanding of the mechanisms mediating VLDL-induced aldosterone production may provide insights into therapies to treat obesity-associated hypertension.

Body Mass Index Predicts 24-Hour Urinary Aldosterone Levels in Patients With Resistant Hypertension

Prospective studies indicate that hyperaldosteronism is found in 20% of patients with resistant hypertension. A small number of observational studies in normotensive and hypertensive patients suggest a correlation between aldosterone levels and obesity while others could not confirm these findings. The correlation between aldosterone levels and body mass index (BMI) in patients with resistant hypertension has not been previously investigated. Our objective was to determine whether BMI is positively correlated with plasma aldosterone concentration, plasma renin activity, aldosterone:renin ratio, and 24-hour urinary aldosterone in black and white patients. We performed a cross-sectional analysis of a large diverse cohort (n=2170) with resistant hypertension. The relationship between plasma aldosterone concentration, plasma renin activity, aldosterone:renin ratio, 24-hour urinary aldosterone, and BMI was investigated for the entire cohort, by sex and race (65.3% white, 40.3% men). We demonstrate that plasma aldosterone concentration and aldosterone:renin ratio were significantly correlated to BMI (P<0.0001) across the first 3 quartiles, but not from the 3rd to 4th quartile of BMI. Plasma renin activity was not correlated with BMI. Twenty-four-hour urinary aldosterone was positively correlated across all quartiles of BMI for the cohort (P<0.0001) and when analyzed by sex (men P<0.0001; women P=0.0013) and race (P<0.05), and stronger for men compared with women (r=0.19, P<0.001 versus r=0.05, P=0.431, P=0.028) regardless of race. In both black and white patients, aldosterone levels were positively correlated to increasing BMI, with the correlation being more pronounced in black and white men. These findings suggest that obesity, particularly the abdominal obesity typical of men, contributes to excess aldosterone in patients with resistant hypertension.

Adipocytes, aldosterone and obesity-related hypertension

Understanding the mechanisms linking obesity with hypertension is important in the current obesity epidemic as it may improve therapeutic interventions. Plasma aldosterone levels are positively correlated with body mass index and weight loss in obese patients is reported to be accompanied by decreased aldosterone levels. This suggests a relationship between adipose tissue and the production/secretion of aldosterone. Aldosterone is synthesized principally by the adrenal glands, but its production may be regulated by many factors, including factors secreted by adipocytes. In addition, studies have reported local synthesis of aldosterone in extra-adrenal tissues, including adipose tissue. Experimental studies have highlighted a role for adipocyte-secreted aldosterone in the pathogenesis of obesity-related cardiovascular complications via the mineralocorticoid receptor. This review focuses on how aldosterone secretion may be influenced by adipose tissue and the importance of these mechanisms in the context of obesity-related hypertension.

Role of ACTH in the Interactive/Paracrine Regulation of Adrenal Steroid Secretion in Physiological and Pathophysiological Conditions

In the normal human adrenal gland, steroid secretion is regulated by a complex network of autocrine/paracrine interactions involving bioactive signals released by endothelial cells, nerve terminals, chromaffin cells, immunocompetent cells, and adrenocortical cells themselves. ACTH can be locally produced by medullary chromaffin cells and is, therefore, a major mediator of the corticomedullary functional interplay. Plasma ACTH also triggers the release of angiogenic and vasoactive agents from adrenocortical cells and adrenal mast cells and, thus, indirectly regulates steroid production through modulation of the adrenal blood flow. Adrenocortical neoplasms associated with steroid hypersecretion exhibit molecular and cellular defects that tend to reinforce the influence of paracrine regulatory loops on corticosteroidogenesis. Especially, ACTH has been found to be abnormally synthesized in bilateral macronodular adrenal hyperplasia responsible for hypercortisolism. In these tissues, ACTH is detected in a subpopulation of adrenocortical cells that express gonadal markers. This observation suggests that ectopic production of ACTH may result from impaired embryogenesis leading to abnormal maturation of the adrenogonadal primordium. Globally, the current literature indicates that ACTH is a major player in the autocrine/paracrine processes occurring in the adrenal gland in both physiological and pathological conditions.

New insights into the controversy of adrenal function during critical illness

Critical illness represents a life-threatening disorder necessitating recruitment of defence mechanisms for survival. Herein, the hypothalamic-pituitary-adrenal axis is essential. However, the relevance of a relative insufficiency of the hypothalamic-pituitary-adrenal axis in critical illness, which is diagnosed by a suppressed cortisol response to exogenous adrenocorticotropic hormone (ACTH) irrespective of the plasma cortisol concentration, is controversial. Findings from several studies have provided insights that clarify at least part of this controversy. Rather than an activated hypothalamic-pituitary-adrenal axis, ACTH-independent regulators have been reported to contribute to increased cortisol availability during critical illness. One of these regulators is reduced cortisol breakdown, mediated by suppressed expression and activity of cortisol metabolising enzymes in the liver and kidneys. This downstream mechanism increases concentrations of plasma cortisol, but the ensuing feedback-inhibited ACTH release, when sustained for more than 1 week, has been shown to negatively affect adrenocortical integrity and function. Reduced adrenocortical ACTH signalling could explain reduced cortisol responses to exogenous ACTH. Whether such reduced cortisol responses in the presence of raised plasma (free) cortisol identifies adrenal failure needing treatment is unlikely. Additionally, reduced cortisol breakdown affects the optimum dose of hydrocortisone treatment during critical illness. Identification of patients with an insufficient hypothalamic-pituitary-adrenal axis response and the optimum treatment for this disorder clearly need more well designed preclinical and clinical studies.

Mineralocorticoid receptor in adipocytes and macrophages: a promising target to fight metabolic syndrome

Aldosterone is the primary ligand for the mineralocorticoid receptor (MR) and has been considered long time a "renal" hormone, acting at this site as a key regulator of plasma volume, electrolyte homeostasis and blood pressure. A new exciting era of MR biology began with the identification of MR in different non-epithelial tissues such as brain, heart, vessels, macrophages/monocytes, and adipose tissue. The distribution of MR in such a wide range of tissues has suggested novel and unexpected roles for MR, for example in energy metabolism and inflammation. An increasing body of evidence suggests a detrimental effect of aldosterone excess on the development of metabolic alterations. Disturbances in glucose metabolism due to inappropriate activation of MR are frequently observed in patients with primary aldosteronism as well as in obese subjects. MR antagonists have beneficial effects on glucose tolerance and metabolic parameters in experimental animals, whereas their role in humans remains unclear. The aim of this review is to discuss the pathophysiology of MR activation in experimental models, particularly at the level of adipocytes and macrophages, to discuss novel and sometimes contrasting insights from emerging studies, and to highlight deficiencies in the field.

Changes in morphology and function of adrenal cortex in mice fed a high-fat diet

BACKGROUND/OBJECTIVES

Obesity is a major risk factor for the development of type 2 diabetes and other debilitating diseases. Obesity and diabetes are intimately linked with altered levels of adrenal steroids. Elevated levels of these hormones induce insulin resistance and cause cardiovascular diseases. The mechanisms underlying obesity-related alterations in adrenal steroids are still not well understood. Here, we investigated how diet-induced obesity affects the morphology and function of the mouse adrenal cortex.

METHODS

We fed animals either a high-fat diet (HFD) or a normal diet (60% kcal from fat or 10% kcal from fat, respectively) for 18 weeks. We then assessed various aspects of adrenal gland morphology and function, as well as basal plasma concentrations of steroid hormones and ACTH.

RESULTS

We show that adrenal glands of mice fed a HFD release more corticosterone and aldosterone, resulting in higher plasma levels. This increase is driven by adrenal cortical hyperplasia, and by increased expression of multiple genes involved in steroidogenesis. We demonstrate that diet-induced obesity elevates Sonic hedgehog signaling in Gli1-positive progenitors, which populate the adrenal capsule and give rise to the steroidogenic cells of the adrenal cortex. Feeding animals with a HFD depletes Gli1-positive progenitors, as the adrenal cortex expands.

CONCLUSIONS

This work provides insight into how diet-induced obesity changes the biology of the adrenal gland. The association of these changes with increased Shh signaling suggests possible therapeutic strategies for obesity-related steroid hormone dysfunction.

Management of patients with resistant hypertension: current treatment options

Resistant hypertension (RHTN) is an increasingly common clinical problem that is often heterogeneous in etiology, risk factors, and comorbidities. It is defined as uncontrolled blood pressure on optimal doses of three antihypertensive agents, ideally one being a diuretic. The definition also includes controlled hypertension with use of four or more antihypertensive agents. Recent observational studies have advanced the characterization of patients with RHTN. Patients with RHTN have higher rates of cardiovascular events and mortality compared with patients with more easily controlled hypertension. Secondary causes of hypertension, including obstructive sleep apnea, primary aldosteronism, renovascular disease, are common in patients with RHTN and often coexist in the same patient. In addition, RHTN is often complicated by metabolic abnormalities. Patients with RHTN require a thorough evaluation to confirm the diagnosis and optimize treatment, which typically includes a combination of lifestyle adjustments, and pharmacologic and interventional treatment. Combination therapy including a diuretic, a long-acting calcium channel blocker, an angiotensin-converting enzyme inhibitor, a beta blocker, and a mineralocorticoid receptor antagonist where warranted is the classic regimen for patients with treatment-resistant hypertension. Mineralocorticoid receptor antagonists like spironolactone or eplerenone have been shown to be efficacious in patients with RHTN, heart failure, chronic kidney disease, and primary aldosteronism. Novel interventional therapies, including baroreflex activation and renal denervation, have shown that both of these methods may be used to lower blood pressure safely, thereby providing exciting and promising new options to treat RHTN.

Adipose tissue renin-angiotensin-aldosterone system (RAAS) and progression of insulin resistance

This review focuses on the expression of the key components of the renin-angiotensin-aldosterone axis in fat tissue. At the center of this report is the role of RAAS in normal and excessive fat mass enlargement, the leading etiology of insulin resistance. Understanding the expression and regulation of RAAS components in various fat depots allows insight not only into the processes by which these complex patterns are modified by the enlargement of adipose tissue, but also into their impact on local and systemic response to insulin.

Blood pressure response to angiotensin II is enhanced in obese Zucker rats and is attributed to an aldosterone-dependent mechanism

BACKGROUND AND PURPOSE

Plasma aldosterone levels correlate positively with obesity, suggesting a link between the hypertension associated with obesity and increased mineralocorticoid levels. We tested the hypothesis that aldosterone is involved in the BP response to angiotensin II (AngII) in obese rats.

EXPERIMENTAL APPROACH

Lean (LZR) and obese (OZR) Zucker rats were treated with AngII (9 µg·h(-1) ; 4 weeks), and BP and plasma AngII and aldosterone were determined.

KEY RESULTS

Chronic AngII increased the BP in OZR markedly more so than in LZR. Plasma AngII levels in LZR and OZR were similar after AngII treatment. The AngII stimulated a rise in plasma aldosterone that was sixfold more in OZR than in LZR. The thickness of the zona glomerulosa of the adrenal glands was selectively increased by AngII in OZR. Adrenal mRNA levels of CYP11B2 aldosterone synthase and the AT(1B) receptor were selectively increased in AngII-treated OZR. The BP response to chronic AngII stimulation was diminished in OZR after adrenalectomy when plasma aldosterone was absent. Acute bolus injections of AngII did not increase the BP response or aldosterone release in OZR.

CONCLUSIONS AND IMPLICATIONS

The AngII-induced BP response is enhanced in obesity and this is associated with a specific increase in circulating aldosterone. Due to the AngII-induced growth of the zona glomerulosa in OZR, the AT(1B) receptors and aldosterone synthase may be selectively enhanced in obesity under concomitant AngII stimulation, increasing the adrenal synthesis of aldosterone. Our results confirm functionally that aldosterone plays a major role in obesity-related hypertension.

Mineralocorticoid receptor-associated hypertension and its organ damage: clinical relevance for resistant hypertension

The role of aldosterone in the pathogenesis of hypertension and cardiovascular diseases has been clearly shown in congestive heart failure and endocrine hypertension due to primary aldosteronism. In resistant hypertension, defined as a failure of concomitant use of three or more different classes of antihypertensive agents to control blood pressure (BP), add-on therapy with mineralocorticoid receptor (MR) antagonists is frequently effective, which we designate as "MR-associated hypertension". The MR-associated hypertension is classified into two subtypes, that with elevated plasma aldosterone levels and that with normal plasma aldosterone levels. The former subtype includes primary aldosteronism (PA), aldosterone-associated hypertension which exhibited elevated aldosterone-to-renin ratio and plasma aldosterone levels, but no PA, aldosterone breakthrough phenomenon elicited when angiotensin-converting enzyme inhibitor (ACE-I) or angiotensin II receptor blocker (ARB) is continued to be given, and obstructive sleep apnea. In contrast, the latter subtype includes obesity, diabetes mellitus, chronic kidney disease (CKD), and polycystic ovary syndrome (PCOS). The pathogenesis of MR-associated hypertension with normal plasma aldosterone levels is considered to be mediated by MR activation by pathways other than high aldosterone levels, such as increased MR levels, increased MR sensitivity, and MR overstimulation by other factors such as Rac1. For resistant hypertension with high plasma aldosterone levels, MR antagonist should be given as a first-line therapy, whereas for resistant hypertension with normal aldosterone levels, ARB or ACE-I should be given as a first-line therapy and MR antagonist would be given as an add-on agent.

A case of myelolipoma with bilateral adrenal hyperaldosteronism cured after unilateral adrenalectomy

Myelolipomas are adrenal tumors composed of both adipose and hematopoietic tissues which are rarely associated with primary aldosteronism (PA). Here, we report a case of myelolipoma associated with PA. Aldosterone hypersecretion from bilateral adrenal glands had been confirmed by adrenal venous sampling and pathological analyses, but PA was clinically cured after surgical removal of the unilateral adrenal gland together with the myelolipoma that was not producing aldosterone. It is suggested that myelolipomas may release some factors which stimulate aldosterone production in adrenal glands, although further investigation is necessary. Obesity-related hyperaldosteronism might in part participate in generation of hypertension in the present case.

The role of specific mitogen-activated protein kinase signaling cascades in the regulation of steroidogenesis

Mitogen-activated protein kinases (MAPKs) comprise a family of serine/threonine kinases that are activated by a large variety of extracellular stimuli and play integral roles in controlling many cellular processes, from the cell surface to the nucleus. The MAPK family includes four distinct MAPK cascades, that is, extracellular signal-regulated kinase 1/2 (ERK1/2), p38 MAPK, c-Jun N-terminal kinase or stress-activated protein kinase, and ERK5. These MAPKs are essentially operated through three-tiered consecutive phosphorylation events catalyzed by a MAPK kinase kinase, a MAPK kinase, and a MAPK. MAPKs lie in protein kinase cascades. The MAPK signaling pathways have been demonstrated to be associated with events regulating the expression of the steroidogenic acute regulatory protein (StAR) and steroidogenesis in steroidogenic tissues. However, it has become clear that the regulation of MAPK-dependent StAR expression and steroid synthesis is a complex process and is context dependent. This paper summarizes the current level of understanding concerning the roles of the MAPK signaling cascades in the regulation of StAR expression and steroidogenesis in different steroidogenic cell models.

Management of high blood pressure in Blacks: an update of the International Society on Hypertension in Blacks consensus statement

Since the first International Society on Hypertension in Blacks consensus statement on the "Management of High Blood Pressure in African American" in 2003, data from additional clinical trials have become available. We reviewed hypertension and cardiovascular disease prevention and treatment guidelines, pharmacological hypertension clinical end point trials, and blood pressure-lowering trials in blacks. Selected trials without significant black representation were considered. In this update, blacks with hypertension are divided into 2 risk strata, primary prevention, where elevated blood pressure without target organ damage, preclinical cardiovascular disease, or overt cardiovascular disease for whom blood pressure consistently <135/85 mm Hg is recommended, and secondary prevention, where elevated blood pressure with target organ damage, preclinical cardiovascular disease, and/or a history of cardiovascular disease, for whom blood pressure consistently <130/80 mm Hg is recommended. If blood pressure is ≤10 mm Hg above target levels, monotherapy with a diuretic or calcium channel blocker is preferred. When blood pressure is >15/10 mm Hg above target, 2-drug therapy is recommended, with either a calcium channel blocker plus a renin-angiotensin system blocker or, alternatively, in edematous and/or volume-overload states, with a thiazide diuretic plus a renin-angiotensin system blocker. Effective multidrug therapeutic combinations through 4 drugs are described. Comprehensive lifestyle modifications should be initiated in blacks when blood pressure is ≥115/75 mm Hg. The updated International Society on Hypertension in Blacks consensus statement on hypertension management in blacks lowers the minimum target blood pressure level for the lowest-risk blacks, emphasizes effective multidrug regimens, and de-emphasizes monotherapy.

Adiponectin and adiponectin receptor system in the rat adrenal gland: ontogenetic and physiologic regulation, and its involvement in regulating adrenocortical growth and steroidogenesis

Adiponectin (ADN) is a regulatory peptide secreted mostly by adipose tissue and acting via two receptors: AdipoR1 and AdipoR2. Our aim was to investigate expression of adiponectin system genes in the rat adrenal gland as well as its ontogenetic and physiological control. Furthermore, we examined the effects of acute and prolonged activation of HPA axis on ADN system in adipose tissue. By means of QPCR, ADN and AdipoR1 expression was demonstrated in rat adrenal cortex both at mRNA and protein levels, while AdipoR2 could only be detected at mRNA levels. ADN expression level was significantly upregulated in a developing and regenerating adrenal cortex. Globular domain of adiponectin at 10(-9) M stimulated corticosterone output and BrdU incorporation by cultured rat adrenocortical cells. Moreover, both acute (ACTH and ether stress) and prolonged (ACTH) adrenal stimulation resulted in lowered ADN levels, while expression of AdipoR1 and AdipoR2 was upregulated by the acute treatment. Depending on its site of origin, visceral (VAT) or subcutaneous (SAT) adipose tissue responded differently to alterations in HPA axis. VAT expression of ADN and its receptors remained almost unchanged by experimental manipulations. In SAT, on the other hand, expression of ADN and AdipoR2 was markedly increased by ACTH treatment and stress, while dexamethasone suppressed ADN and AdipoR1 mRNA levels. The results of this study provide new evidence for direct and indirect interactions between adipokines and HPA axis.

The role of aldosteronism in causing obesity-related cardiovascular risk

A large body of evidence strongly links aldosterone to development and progression of cardiovascular disease, including vascular stiffness, left ventricular hypertrophy, congestive heart failure, chronic kidney disease, and, especially, hypertension. Emerging data suggest that adipocytes may serve as a source of aldosterone, either directly or indirectly, through the release of aldosterone-stimulating factors. If adipocytes are confirmed to have an important contribution to hyperaldosteronism, it would have significant clinical implications in linking aldosterone to obesity-related increases in cardiovascular risk. Such a cause-and-effect situation would then provide the opportunity to reverse that risk with preferential use of aldosterone antagonists in obese patients.

Elevated mineralocorticoid receptor activity in aged rat vascular smooth muscle cells promotes a proinflammatory phenotype via extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase and epidermal growth factor receptor-dependent pathways

Arterial aging is a predominant risk factor for the onset of cardiovascular diseases, such as hypertension, myocardial infarction, or stroke. Aging is associated with intravascular renin-angiotensin system activation, increased vascular stiffness, intima-media thickening, and a proinflammatory phenotype. Little is known about the influence of aldosterone on arterial aging. Hence, we hypothesized that aldosterone and mineralocorticoid receptor (MR) activation might contribute to and possibly accelerate the arterial aging process. We demonstrate increased MR expression in whole aortae and early passage aortic vascular smooth muscle cells from aged (30 months) compared with adult (8 months) F344XBN rats. Sensitivity to aldosterone-induced extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase activity is increased in aged cells. MR blockade and extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase inhibition prevent age-associated increases of transforming growth factor-beta, intercellular adhesion molecule 1, and procollagen 1. Aldosterone increases expression of proinflammatory marker proteins, shifting the phenotype of adult vascular smooth muscle cells toward the proinflammatory phenotype of aged rats. Epidermal growth factor receptor expression is increased with age and by aldosterone, and inhibition of epidermal growth factor receptor tyrosine kinase decreases age-associated proinflammatory marker expression. Our data support the hypothesis that increased constitutive MR signaling may promote and amplify age-associated inflammation that accompanies arterial aging through increased angiotensin II-stimulated expression of MR and enhanced sensitivity to aldosterone-mediated extracellular signal-regulated kinase 1/2 activation, likely related to increased epidermal growth factor receptor expression.

Angiotensin II-activated protein kinase D mediates acute aldosterone secretion

Dysregulation of the renin-angiotensin II (AngII)-aldosterone system can contribute to cardiovascular disease, such that an understanding of this system is critical. Diacylglycerol-sensitive serine/threonine protein kinase D (PKD) is activated by AngII in several systems, including the human adrenocortical carcinoma cell line NCI H295R, where this enzyme enhances chronic (24h) AngII-evoked aldosterone secretion. However, the role of PKD in acute AngII-elicited aldosterone secretion has not been previously examined. In primary cultures of bovine adrenal glomerulosa cells, which secrete detectable quantities of aldosterone in response to secretagogues within minutes, PKD was activated in response to AngII, but not an elevated potassium concentration or adrenocorticotrophic hormone. This activation was time- and dose-dependent and occurred through the AT1, but not the AT2, receptor. Adenovirus-mediated overexpression of constitutively active PKD resulted in enhanced AngII-induced aldosterone secretion; whereas overexpression of a dominant-negative PKD construct decreased AngII-stimulated aldosterone secretion. Thus, we demonstrate for the first time that PKD mediates acute AngII-induced aldosterone secretion.

Regulation of aldosterone synthase by activator transcription factor/cAMP response element-binding protein family members

Aldosterone synthesis is regulated by angiotensin II (Ang II) and K(+) acting in the adrenal zona glomerulosa, in part through the regulation of aldosterone synthase (CYP11B2). Here, we analyzed the role of cAMP response element (CRE)-binding proteins (CREBs) in the regulation of CYP11B2. Expression analysis of activator transcription factor (ATF)/CREB family members, namely the ATF1 and ATF2, the CREB, and the CRE modulator, in H295R cells and normal human adrenal tissue was performed using quantitative real-time PCR. Ang II-induced phosphorylation of ATF/CREB members was analyzed by Western blot analysis, and their subsequent binding to the CYP11B2 promoter using chromatin immunoprecipitation assay. Aldosterone production and CYP11B2 expression were measured in small interfering RNA-transfected cells to knockdown the expression of ATF/CREB members. CYP11B2 promoter activity was measured in H295R cells cotransfected with NURR1 (NR4A2) alone or with constitutively active vectors for ATF/CREB members. Ang II induced phosphorylation of ATF1, ATF2, and CRE modulator in a time-dependent manner. Based on chromatin immunoprecipitation analysis, there was an increased association of these proteins with the CYP11B2 promoter after Ang II and K(+) treatment. Phosphorylated ATF/CREB members also bound the CYP11B2 promoter. Knockdown of ATF/CREB members reduced Ang II and K(+) induction of adrenal cell CYP11B2 mRNA expression and aldosterone production. The constitutively active ATF/CREB vectors increased the promoter activity of CYP11B2 and had a synergistic effect with NURR1. In summary, these results suggest that ATF/CREB and NGFI-B family members play a crucial role in the transcriptional regulation of CYP11B2 and adrenal cell capacity to produce aldosterone.

Hypocretin/orexin increases the expression of steroidogenic enzymes in human adrenocortical NCI H295R cells

Hypocretins/orexins act through two receptor subtypes: OX(1) and OX(2). Outside the brain, orexin receptors are expressed in adrenal glands, where orexins stimulate the release of glucocorticoids. To further address the regulation of steroidogenesis, we analyzed the effect of orexins on the expression of steroidogenic enzymes in human adrenocortical National Cancer Institute (NCI) H295R cells by qPCR. In NCI H295R cells, OX(2) receptors were highly expressed, as they were in human adrenal glands. After treatment of NCI H295R cells with orexin A for 12-24 h, the cortisol synthesis rate was significantly increased, whereas 30 min of treatment showed no effect. While CYP11B1 and CYP11B2 mRNA levels were increased already at earlier time points, the expression of HSD3B2 and CYP21 mRNA was significantly up-regulated after treatment with orexin A for 12 h. Likewise, orexin B increased CYP21 and HSD3B2 mRNA levels showing, however, a lower potency compared with orexin A. The mRNA levels of CYP11A and CYP17 were unaffected by orexin A. OX(2) receptor mRNA levels were down-regulated after 12 and 24 h of orexin A treatment. Orexin A increased intracellular Ca(2+) but not cAMP concentrations in NCI H295R cells. Furthermore, inhibition of PKC and MAPK kinase/ERK kinase (MEK1/2) prevented the increase of HSD3B2 expression by orexin A. Accordingly, orexin A treatment of NCI H295R cells markedly enhanced ERK1/2 phosphorylation that was prevented by PKC and, in part, PKA inhibition. In conclusion, orexins may influence adrenal steroidogenesis by differential regulation of the expression of steroidogenic enzymes involving Ca(2+), as well as PKC-ERK1/2 signaling.

Orexins stimulate steroidogenic acute regulatory protein expression through multiple signaling pathways in human adrenal H295R cells

Orexins mediate a variety of physiological processes, including feeding behavior, the circadian pathway, and cortisol secretion. Steroidogenesis is regulated by a variety of neuropeptides, and one of the key rate-limiting steps is cholesterol transport across the mitochondrial membrane by the steroidogenic acute regulatory protein (StAR). StAR expression can be regulated through several different signaling pathways. Despite the clear link between orexins and steroid production, the actions of the orexin family of hormones on steroid biosynthesis are not fully understood. We present data showing that 100 nm of both orexins A and B for 4 or 24 h significantly up-regulates StAR, in H295R pluripotent adrenocortical cells. We present the dose-dependent and time-dependent characteristics of StAR up-regulation at the protein level, showing significant increases after 4 h at a relatively low agonist concentration (1 nm). We have provided a key analysis of the precise G protein-coupled signaling pathways required for the up-regulation of StAR in response to orexins A and B. This has involved dominant-negative G protein analysis, and the direct inhibition of the protein kinase A, protein kinase C, ERK1/2, and p38 pathways. This shows a fundamental role for multiple G protein-coupled and MAPK-mediated signaling pathways leading to StAR expression. Antagonist analysis also showed that orexin effects on StAR were primarily, but not exclusively, acting through the orexin receptor type 1. This is the first study linking orexin action on StAR expression and comprehensively describes the signaling pathways involved in regulating the complexity of hormone biosynthesis.

Renin-angiotensin system, natriuretic peptides, obesity, metabolic syndrome, and hypertension: an integrated view in humans

The obesity pandemic is closely related to hypertension and metabolic syndrome. Visceral adipose tissue plays a key role in the metabolic and cardiovascular complications of being overweight. The pathophysiological link between visceral adiposity and cardiometabolic complications focuses on insulin sensitivity, sympathetic nervous system, renin-angiotensin-aldosterone system (RAAS) and, only recently, on cardiac natriuretic peptide system (CNPS). RAAS and CNPS are endogenous antagonistic systems on sodium balance, cardiovascular system, and metabolism. The circulating RAAS is dysregulated in obese patients, and adipose tissue has a full local renin-angiotensin system that is active at local and systemic level. Adipocyte biology and metabolism are influenced by local renin-angiotensin system, with angiotensin II acting as a 'growth factor' for adipocytes. CNPS induces natriuresis and diuresis, reduces blood pressure, and, moreover, has powerful lipolytic and lipomobilizing activity in humans but not in rodents. In obesity, lower plasmatic natriuretic peptides levels with increasing BMI, waist circumference, and metabolic syndrome have been documented. Thus, reduced CNPS effects coupled with increased RAAS activity have a central role in obesity and its deadly complications. We propose herein an integrated view of the dysregulation of these two antagonistic systems in human obesity complicated with hypertension, metabolic syndrome, and increased cardiovascular risk.

[Adrenal protein expressions after Pinggan Qianyang Formula treatment in hypertensive rats with liver-yang hyperactivity: a comparative proteomic analysis]

OBJECTIVE

To explore the pathogenic mechanism of liver-yang hyperactivity type of hypertension and to observe the effects of Pinggan Qianyang Formula (PGQYF), a compound of traditional Chinese herbals for calming the liver and suppressing yang, so as to provide experimental evidence for new marker proteins of drug therapy.

METHODS

A rat model of liver-yang hyperactivity was prepared with spontaneous hypertensive rats (SHRs) by administration of Aconiti Praeparatae Decoction. Adrenal proteins were separated by 2D gel electrophoresis (2-DE). The differentially expressed proteins were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and database analysis.

RESULTS

The rat model of liver-yang hyperactivity was successfully reproduced, and the PGQYF could decrease the grades of irritability, conjunctival congestion and systolic blood pressure of the rats (P<0.05, P<0.01). After analysis, twelve obviously differentially expressed proteins were found, eight of which were identified. The expression levels of isocitrate dehydrogenase and steroidogenic acute regulatory protein in the untreated group were up-regulated as compared with those in the normal control group, and down-regulated in the treatment group. The expression levels of ferritin light chain, elongation factor Tu, Rho GDP disassociation inhibitor 1, flavin reductase and basic transcription factor 3 in the untreated group were down-regulated as compared with those in the normal control group, and up-regulated in the treatment group.

CONCLUSION

Differentially expressed adrenal proteins in SHRs with live-yang hyperactivity are successfully identified. This approach may lay a foundation for the further investigation of pathogenic mechanisms in hypertension with liver-yang hyperactivity and the mechanisms of PGQYF treatment.

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.