Aldosterone induces vascular insulin resistance by increasing insulin-like growth factor-1 receptor and hybrid receptor

Decoding the role of aldosterone in glycation-induced diabetic complications

Diabetes-mediated development of micro and macro-vascular complications is a global concern. One of the factors is hyperglycemia induced the non-enzymatic formation of advanced glycation end products (AGEs). Accumulated AGEs bind with receptor of AGEs (RAGE) causing inflammation, oxidative stress and extracellular matrix proteins (ECM) modifications responsible for fibrosis, cell damage and tissue remodeling. Moreover, during hyperglycemia, aldosterone (Aldo) secretion increases, and its interaction with mineralocorticoid receptor (MR) through genomic and non-genomic pathways leads to inflammation and fibrosis. Extensive research on individual involvement of AGEs-RAGE and Aldo-MR pathways in the development of diabetic nephropathy (DN), cardiovascular diseases (CVDs), and impaired immune system has led to the discovery of therapeutic drugs. Despite mutual repercussions, the cross-talk between AGEs-RAGE and Aldo-MR pathways remains unresolved. Hence, this review focuses on the possible interaction of Aldo and glycation in DN and CVDs, considering the clinical significance of mutual molecular targets.

Recent progress in unraveling cardiovascular complications associated with primary aldosteronism: a succinct review

This comprehensive review offers a thorough exploration of recent advancements in our understanding of the intricate cardiovascular complications associated with Primary Aldosteronism (PA). PA encompasses a spectrum of conditions characterized by hypertension and excessive production of aldosterone operating independently of the renin-angiotensin system. Given its association with an elevated risk of cardiovascular and cerebrovascular complications, as well as a higher incidence of metabolic syndrome in comparison to individuals with essential hypertension (EH), an accurate diagnosis of PA is of paramount importance. This review delves into the intricate interplay between PA and cardiovascular health and focuses on the key pathophysiological mechanisms contributing to adverse cardiac outcomes. The impact of different treatment modalities on cardiovascular health is also examined, offering insights into potential therapeutic approaches. By highlighting the significance of recognizing PA as a significant contributor to cardiovascular morbidity, this review emphasizes the need for improved screening, early diagnosis, and tailored management strategies to both enhance patient care and mitigate the burden of cardiovascular diseases. The findings presented herein underscore the growing importance of PA in the context of cardiovascular medicine and emphasize the potential for translating these insights into targeted interventions to improve patient outcomes.

The Effect of Aldosterone on Cardiorenal and Metabolic Systems

Aldosterone, a vital hormone of the human body, has various pathophysiological roles. The excess of aldosterone, also known as primary aldosteronism, is the most common secondary cause of hypertension. Primary aldosteronism is associated with an increased risk of cardiovascular disease and kidney dysfunction compared to essential hypertension. Excess aldosterone can lead to harmful metabolic and other pathophysiological alterations, as well as cause inflammatory, oxidative, and fibrotic effects in the heart, kidney, and blood vessels. These alterations can result in coronary artery disease, including ischemia and myocardial infarction, left ventricular hypertrophy, heart failure, arterial fibrillation, intracarotid intima thickening, cerebrovascular disease, and chronic kidney disease. Thus, aldosterone affects several tissues, especially in the cardiovascular system, and the metabolic and pathophysiological alterations are related to severe diseases. Therefore, understanding the effects of aldosterone on the body is important for health maintenance in hypertensive patients. In this review, we focus on currently available evidence regarding the role of aldosterone in alterations of the cardiovascular and renal systems. We also describe the risk of cardiovascular events and renal dysfunction in hyperaldosteronism.

New-onset diabetes mellitus risk associated with concurrent autonomous cortisol secretion in patients with primary aldosteronism

Concurrent autonomous cortisol secretion (ACS) in patients with primary aldosteronism (PA patients) is not uncommon. This work aimed to determine the effect of cortisol levels on incident new-onset type 2 diabetes mellitus (NODM) in PA patients. Using the prospectively designed observational TAIPAI cohort, the PA patients were grouped by cortisol level after an overnight low-dose dexamethasone suppression test (1-mg DST). Of the 476 PA patients, 387 (43.7% men; mean age 52.8 years) did not have baseline DM. After a mean follow-up of 4.3 ± 2.9 years, 32 patients (8.3%) developed NODM. The cutoff value obtained via a generalized additive model showed that a serum cortisol level ≥ 2.65 µg/dL after 1-mg DST was a risk factor for developing NODM (HR, 3.5, p = 0.031) by Cox proportional- hazards model.. In PA patients with a higher body mass index (>25 kg/m²; HR, 3.16), lower estimated glomerular filtration rate (<90 ml/min/1.73 m²; HR, 3.18), longer hypertension duration (>7 years; HR, 3.34), and higher waist-to-hip ratio (>0.9; HR, 3.07), a concomitant cortisol level ≥ 2.65 μg/dL after 1-mg DST were more likely to develop NODM. The high-cortisol group of patients with aldosterone-producing adenoma (APA) using mineralocorticoid receptor antagonist (MRA) was associated with an increased risk of NODM (HR, 5.72). Our results showed that PA patients with a concomitant cortisol level ≥ 2.65 µg/dL after 1-mg DST, independent of the aldosterone level, had a higher incidence of NODM. Such PA patients should be carefully evaluated and managed to achieve better glucose control and prevent metabolic syndrome.

Cardiovascular outcomes and all-cause mortality in primary aldosteronism after adrenalectomy or mineralocorticoid receptor antagonist treatment: a meta-analysis

BACKGROUND

In patients with primary aldosteronism (PA), long-term cardiovascular and mortality outcomes after adrenalectomy vs mineralocorticoid receptor antagonist (MRA) have not been compared yet. We aim to compare the clinical outcomes of these patients after treatment.

DESIGN AND METHODS

A systematic review and meta-analysis was conducted by searching PubMed, Cochrane library, and Embase from no start date restriction to 18 December 2021. Our composite primary outcomes were long-term all-cause mortality and/or major adverse cardiovascular events (MACE), including coronary artery disease (CAD), stroke, arrhythmia, and congestive heart failure. We adopted the random-effects model and performed subgroup analyses, meta-regression, and trial sequential analysis (TSA).

RESULTS

A total of 9 studies with 8473 adult patients with PA (≥18 years) were enrolled. A lower incidence of composite primary outcomes was observed in the adrenalectomy group (odds ratio (OR): 0.46 (95% CI: 0.38-0.56), P < 0.001). We found a lower incidence of all-cause mortality (OR: 0.33 (95% CI: 0.15-0.73), P = 0.006) and MACE (OR: 0.55, (95% CI: 0.40-0.74), P = 0.0001) in the adrenalectomy group. The incidence of CAD (OR: 0.33 (95% CI: 0.15-0.75), P = 0.008), arrhythmias (OR: 0.46 (95% CI: 0.27-0.81), P = 0.007), and congestive heart failure (OR: 0.52 (95% CI: 0.33-0.81), P = 0.004) was also lower in adrenalectomy group. The metaregression showed patient's age may attenuate the benefits of adrenalectomy on composite primary outcomes (coefficient: 1.084 (95% CI: 1.005-1.169), P = 0.036). TSA demonstrated that the accrued sample size and effect size were sufficiently large to draw a solid conclusion, and the advantage of adrenalectomy over MRA was constant with the chronological sequence.

CONCLUSIONS

In conclusion, adrenalectomy could be preferred over MRA for patients with PA in reducing the risk of all-cause mortality and/or MACE and should be considered as the treatment of choice. That patients with PA could get less benefit from adrenalectomy as they age warrants further investigation.

Skeletal Muscle Microvascular Dysfunction in Obesity-Related Insulin Resistance: Pathophysiological Mechanisms and Therapeutic Perspectives

Obesity is a worrisomely escalating public health problem globally and one of the leading causes of morbidity and mortality from noncommunicable disease. The epidemiological link between obesity and a broad spectrum of cardiometabolic disorders has been well documented; however, the underlying pathophysiological mechanisms are only partially understood, and effective treatment options remain scarce. Given its critical role in glucose metabolism, skeletal muscle has increasingly become a focus of attention in understanding the mechanisms of impaired insulin function in obesity and the associated metabolic sequelae. We examined the current evidence on the relationship between microvascular dysfunction and insulin resistance in obesity. A growing body of evidence suggest an intimate and reciprocal relationship between skeletal muscle microvascular and glucometabolic physiology. The obesity phenotype is characterized by structural and functional changes in the skeletal muscle microcirculation which contribute to insulin dysfunction and disturbed glucose homeostasis. Several interconnected etiologic molecular mechanisms have been suggested, including endothelial dysfunction by several factors, extracellular matrix remodelling, and induction of oxidative stress and the immunoinflammatory phenotype. We further correlated currently available pharmacological agents that have deductive therapeutic relevance to the explored pathophysiological mechanisms, highlighting a potential clinical perspective in obesity treatment.

Salt-Sensitivity of Blood Pressure and Insulin Resistance

Salt sensitivity of blood pressure (SSBP) is an independent risk factor for cardiovascular morbidity and mortality that is seen in both hypertensive and normotensive populations. Insulin resistance (IR) strongly correlates with SSBP and affects nearly 50% of salt sensitive people. While the precise mechanism by which IR and SSBP relate remains elusive, several common pathways are involved in the genesis of both processes, including vascular dysfunction and immune activation. Vascular dysfunction associated with insulin resistance is characterized by loss of nitric oxide (NO)-mediated vasodilation and heightened endothelin-1 induced vasoconstriction, as well as capillary rarefaction. It manifests with increased blood pressure (BP) in salt sensitive murine models. Another common denominator in the pathogenesis of insulin resistance, hypertension, and salt sensitivity (SS) is immune activation involving pro-inflammatory cytokines like tumor necrosis factor (TNF)-α, IL-1β, and IL-6. In the last decade, a new understanding of interstitial sodium storage in tissues such as skin and muscle has revolutionized traditional concepts of body sodium handling and pathogenesis of SS. We have shown that interstitial Na⁺ can trigger a T cell mediated inflammatory response through formation of isolevuglandin protein adducts in antigen presenting cells (APCs), and that this response is implicated in salt sensitive hypertension. The peroxisome proliferator-activated receptor γ (PPARγ) is a transcription factor that modulates both insulin sensitivity and BP. PPARγ agonists increase insulin sensitivity and ameliorate salt sensitivity, whereas deficiency of PPARγ results in severe insulin resistance and hypertension. These findings suggest that PPARγ plays a role in the common pathogenesis of insulin sensitivity and salt sensitivity, perhaps via effects on the immune system and vascular function. The goal of this review is to discuss those mechanisms that may play a role in both SSBP and in insulin resistance.

Elevated Secretion of Aldosterone Increases TG/HDL-C Ratio and Potentiates The Ox-LDL-Induced Dysfunction of HUVEC

Objective

Atherosclerosis (AS) is one of the most common causes of human death and disability. This study is designed to investigate the roles of aldosterone (Aldo) and oxidized low-density lipoprotein (Ox-LDL) in this disease by clinical data and cell model.

Materials and Methods

In this experimental study, clinical data were collected to investigate the Aldo role for the patients with primary aldosteronism or adrenal tumors. Cell viability assay, fluorescence-activated cell sorting (FACS) assay, apoptosis assay, cell aging analysis, and matrigel tube formation assay were performed to detect effects on human umbilical vein endothelial cells (HUVECs) treated with Aldo and/or Ox-LDL. Quantitative polymerase chain reaction (qPCR) and Western blot analysis were performed to figure out critical genes in the process of endothelial cells dysfunction induced by Aldo and/or Ox-LDL.

Results

We found that the Aldo level had a positive correlation with the TG/HDL-C ratio. Endothelial cell growth, angiogenesis, senescence, and apoptosis were significantly affected, and eNOS/Sirt1, the value of Bcl-2/Bax and Angiopoietin1/2 were significantly affected when cells were co-treated by Aldo and Ox-LDL.

Conclusion

Elevated Aldo with high Ox-LDL together may accelerate the dysfunction of HUVEC, and the Ox-LDL, especially for those patients with high Aldo should be well controlled. The assessment of the role of Aldo may provide a theoretical basis for the effective prevention and investigation of a new treatment of AS.

Association of visceral adiposity and clinical outcome among patients with aldosterone producing adenoma

INTRODUCTION

Primary aldosteronism (PA) is a common form of secondary hypertension that has significant cardiovascular events and increased prevalence of metabolic syndrome and diabetics. Although plasma aldosterone concentration is positively correlated with visceral fat area (VFA) in non-PA individuals, the role of visceral adiposity associated with clinical success after surgery is not known.

RESEARCH DESIGN AND METHODS

We analyzed patients who underwent adrenalectomy for aldosterone-producing adenoma (APA) at the Taiwan PA Investigator group. VFA was calculated from the abdominal CT scan at APA diagnosis, and all patients received adrenalectomy.

RESULTS

The study involved 100 consecutive patients with APA (42 males; mean age 49.3 years) matched with 41 essential hypertension (EH) patients. Patients with APA had smaller VFA (p=0.010) than their EH counterparts. Multiple linear regression analysis revealed that the duration of hypertension (p=0.007), but not plasma aldosterone, was negatively correlated with VFA in patients with APA. Logistic regression analysis showed that log VFA (OR=0.065, p<0.001) and duration of hypertension before PA diagnosis (OR=0.919, p=0.011) can predict complete clinical success after adrenalectomy. Multifactor-adjusted generalized additive model demonstrated that log VFA <9.2 was associated with complete cure of hypertension. Furthermore, VFA was increased at 6 months after adrenalectomy (p=0.045).

CONCLUSIONS

Patients with APA had smaller VFA than their EH counterparts, and VFA increased after adrenalectomy. Clinical complete cure of hypertension after surgery was associated with smaller VFA and shorter duration of hypertension at PA diagnosis, suggesting a potential interplay of visceral adiposity and aldosterone of the patients with APA.

Hyperglycemia-induced transcriptional regulation of ROCK1 and TGM2 expression is involved in small artery remodeling in obese diabetic Göttingen Minipigs

Obesity and diabetes in humans are associated with hypertrophic remodeling and increased media:lumen ratio of small resistance arteries, which is an independent predictor of cardiovascular events. In order to minimize increases in media:lumen ratio, hypertrophic remodeling should be accompanied by outward remodeling. We aimed to investigate the mechanisms of structural remodeling in small pial arteries (PAs) and terminal mesenteric arteries (TMAs) from obese Göttingen Minipigs with or without diabetes. Göttingen Minipigs received either control diet (lean control (LC)), high fat/high fructose/high cholesterol diet (FFC), or FFC diet with streptozotocin (STZ)-induced diabetes (FFC/STZ) for 13 months. At the end of the study (20 months), we assessed body weight, fasting plasma biochemistry, passive vessel dimensions, mRNA expression (matrix metallopeptidases 2/9 (MMP2, MMP9), tissue inhibitor of metallopeptidase 1 (TIMP1), transglutaminase 2 (TGM2), Rho-kinase 1 (ROCK1), TGFβ-receptor 2 (TGFBR2), and IGF1-receptor (IGFR1) genes), and immunofluorescence in PAs and TMAs. We performed multiple linear correlation analyses using plasma values, structural data, and gene expression data. We detected outward hypertrophic remodeling in TMAs and hypertrophic remodeling in PAs from FFC/STZ animals. ROCK1 and TGM2 genes were up-regulated in PAs and TMAs from the FFC/STZ group. Passive lumen diameter (PLD) of TMAs was correlated with plasma values of glucose (GLU), fructosamine (FRA), total cholesterol (TC), and triglycerides (TGs). ROCK1 and TGM2 expressions in TMAs were correlated with PLD, plasma GLU, fructosamine, and TC. ROCK1 and TGM2 proteins were immunolocalized in the media of PAs and TMAs, and their fluorescence levels were increased in the FFC/STZ group. Hyperglycemia/hyperlipidemia is involved in regulation of ROCK1 and TGM2 expression leading to outward remodeling of small resistance arteries in obese diabetic Göttingen Minipigs.

Glucocorticoid regulation of amino acid transport in primary human trophoblast cells

Excess maternal glucocorticoids reduce placental amino acid transport and fetal growth, but whether these effects are mediated directly on the syncytiotrophoblast remains unknown. We hypothesised that glucocorticoids inhibit mechanistic target of rapamycin (mTOR) signaling and insulin-stimulated System A amino acid transport activity in primary human trophoblast (PHT) cells. Syncytialised PHTs, isolated from term placentas (n = 15), were treated with either cortisol (1 μM) or dexamethasone (1 μM), ± insulin (1 nM) for 24 h. Compared to vehicle, dexamethasone increased mRNA expression, but not protein abundance of the mTOR suppressor, regulated in development and DNA damage response 1 (REDD1). Dexamethasone enhanced insulin receptor abundance, activated mTOR complex 1 and 2 signaling and stimulated System A activity, measured by Na+-dependent 14C-methylaminoisobutyric acid uptake. Cortisol also activated mTORC1 without significantly altering insulin receptor or mTORC2 read-outs or System A activity. Both glucocorticoids downregulated expression of the glucocorticoid receptor and the System A transporter genes SLC38A1, SLC38A2 and SLC38A4, without altering SNAT1 or SNAT4 protein abundance. Neither cortisol nor dexamethasone affected System L amino acid transport. Insulin further enhanced mTOR and System A activity, irrespective of glucocorticoid treatment and despite downregulating its own receptor. Contrary to our hypothesis, glucocorticoids do not inhibit mTOR signaling or cause insulin resistance in cultured PHT cells. We speculate that glucocorticoids stimulate System A activity in PHT cells by activating mTOR signaling, which regulates amino acid transporters post-translationally. We conclude that downregulation of placental nutrient transport in vivo following excess maternal glucocorticoids is not mediated by a direct effect on the placenta.

Impaired Glucose Metabolism in Primary Aldosteronism Is Associated With Cortisol Cosecretion

CONTEXT

Primary aldosteronism (PA) is associated with higher cardiovascular morbidity and metabolic risks. Recent studies report glucocorticoid cosecretion as a relevant phenotype of PA, which could contribute to associated risks, including type 2 diabetes mellitus (T2DM). The relationship between autonomous cortisol secretion (ACS) and glucose metabolism in PA has not been investigated.

OBJECTIVE

To evaluate the prevalence of impaired glucose homeostasis in patients with PA according to cortisol cosecretion.

DESIGN

We performed oral glucose tolerance tests (OGTTs) and complete testing for hypercortisolism [1-mg dexamethasone suppression test (DST), late-night salivary cortisol, 24-hour urinary free cortisol] in 161 newly diagnosed patients with PA of the German Conn Registry. Seventy-six of 161 patients were reevaluated at follow-up. We compared our results to a population-based sample from the Cooperative Health Research in the Region of Augsburg (KORA)-F4 study matched to the participants with PA (3:1) by sex, age, and body mass index.

RESULTS

At the time of diagnosis, 125 patients (77.6%) had a pathological response in at least one of the Cushing screening tests; T2DM was diagnosed in 6.4% of these 125 cases. Patients with a pathological DST exhibited significantly higher 2-hour plasma glucose in OGTTs and were significantly more often diagnosed with T2DM than were patients with a normal DST (20% vs 0.8%, P < 0.0001) and matched controls from the KORA study (20.6% vs 5.9%, P = 0.022). Patients with PA without ACS tended to have higher homeostatic model assessment of insulin resistance levels than did KORA control subjects (P = 0.05).

CONCLUSION

ACS appears frequently in patients with PA and is associated with impaired glucose metabolism, which could increase the risk of T2DM. PA itself seems to enhance insulin resistance.

Vascular Dysfunction and Insulin Resistance in Aging

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Insulin was discovered in 1922 by Banting and Best. Since that time, extensive research on the mechanisms of insulin activity and action has continued. Currently, it is known that the role of insulin is much greater than simply regulating carbohydrate metabolism. Insulin in physiological concentration is also necessary to maintain normal vascular function.

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Insulin resistance is defined as a pathological condition characterized by reduced sensitivity of skeletal muscles, liver, and adipose tissue, to insulin and its downstream metabolic effects under normal serum glucose concentrations. There are also selective forms of insulin resistance with unique features, including vascular insulin resistance. Insulin resistance, both classical and vascular, contributes to vascular impairment resulting in increased risk of cardiovascular disease. Furthermore, in the elderly population, additional factors including redistribution of fat concentrations, low-grade inflammation, and decreased self-repair capacity [or cell senescence] amplify the vascular abnormalities related to insulin resistance.

Links between aldosterone excess and metabolic complications: A comprehensive review

Shortly after the first description of primary aldosteronism (PA) appeared in the 1950s by Jerome Conn, an association of the condition with diabetes mellitus was documented. However, a clear pathophysiological interrelationship linking the two entities has yet to be established. Nevertheless, so far, many mechanisms contributing to insulin resistance and dysregulation of glucose uptake have been described. At the same time, many observational studies have reported an increased prevalence of the metabolic syndrome (MetS) among patients with PA. Regarding the relationship between aldosterone levels and obesity, a vicious cycle of adipokine-induced aldosterone production and aldosterone adipogenic action may be further contributing to MetS manifestations in PA patients. However, whether aldosterone excess affects lipid metabolism is still under investigation. Also, recent findings of the coexistence of glucocorticoid excess in many cases of PA highlight the need for further studies to examine the presumed link between high aldosterone levels and various metabolic parameters. In the present review, our focus is to comprehensively present the spectrum of available research findings concerning the possible associations between aldosterone excess and metabolic alterations, including impaired glucose metabolism, insulin resistance and, consequently, diabetes, altered lipid metabolism and the development of fatty liver. In addition, the complex relationship between obesity and aldosterone is discussed in detail.

Pathophysiological mechanisms of mineralocorticoid receptor-dependent cardiovascular and chronic kidney disease

Accumulating evidence has indicated the potential contributions of aldosterone and mineralocorticoid receptor (MR) to the pathophysiology of cardiovascular disease (CVD) and chronic kidney disease (CKD). Patients with primary aldosteronism have a higher risk of CVD and CKD than those with essential hypertension. MR is strongly expressed in endothelial cells, vascular smooth muscle cells, cardiomyocytes, fibroblasts, macrophages, glomerular mesangial cells, podocytes, and proximal tubular cells. In these cardiovascular and renal cells, aldosterone-induced cell injury is prevented by MR blockade. Interestingly, MR antagonists elicit beneficial effects on CVD and CKD in subjects with low or normal plasma aldosterone levels. Recent studies have shown that during development of CVD and CKD, cardiovascular and renal MR is activated by glucocorticoid and ligand-independent mechanisms, such as Rac1 signaling pathways. These data indicate that inappropriate activation of local MR contributes to cardiovascular and renal tissue injury through aldosterone-dependent and -independent mechanisms. In this review, recent findings on the specific role of cardiovascular and renal MR in the pathogenesis of CVD and CKD are summarized.

Inhibition of adenosine deaminase and xanthine oxidase by valproic acid abates hepatic triglyceride accumulation independent of corticosteroids in female rats treated with estrogen-progestin

Elevated circulating uric acid has been postulated to play an important pathophysiological role in estrogen-progestin combined oral contraceptive (COC)-induced hypertension and endothelial dysfunction. We hypothesized that disruption of glucoregulation and liver triglyceride (TG) accumulation induced by COC use would be abated by valproic acid (VPA) treatment through suppression of adenosine deaminase (ADA) and xanthine oxidase (XO) activities. Female Wistar rats aged 9-10 weeks were treated with a combination of estrogen-progestin COC steroids (1.0 μg ethinylestradiol and 5.0 μg levonorgestrel; p.o.) with or without VPA (100.0 mg/kg; p.o.) daily for 6 weeks. The result shows that the disrupted glucoregulation and associated elevated hepatic ADA activity, plasma and hepatic XO activity, uric acid (UA), TG/HDL-cholesterol, total cholesterol, and malondialdehyde induced by COC treatment were attenuated by VPA treatment. However, VPA did not have any effect on plasma aldosterone, corticosterone, ADA, circulating and hepatic free fatty acid. Our results demonstrate that suppression of plasma and hepatic XO activities, along with hepatic ADA activity and UA by VPA treatment, protects against disrupted glucoregulation and increased liver TG by COC independent of elevated corticosteroids. The findings imply that VPA would provide protection against the development of cardiometabolic disorder via inhibition of the ADA/XO/UA-mediated pathway.

No Significant Role for Smooth Muscle Cell Mineralocorticoid Receptors in Atherosclerosis in the Apolipoprotein-E Knockout Mouse Model

Objective: Elevated levels of the hormone aldosterone are associated with increased risk of myocardial infarction and stroke in humans and increased progression and inflammation of atherosclerotic plaques in animal models. Aldosterone acts through the mineralocorticoid receptor (MR) which is expressed in vascular smooth muscle cells (SMCs) where it promotes SMC calcification and chemokine secretion in vitro. The objective of this study is to explore the role of the MR specifically in SMCs in the progression of atherosclerosis and the associated vascular inflammation in vivo in the apolipoprotein E knockout (ApoE^−/−) mouse model.

Methods and Results: Male ApoE^−/− mice were bred with mice in which MR could be deleted specifically from SMCs by tamoxifen injection. The resulting atheroprone SMC-MR-KO mice were compared to their MR-Intact littermates after high fat diet (HFD) feeding for 8 or 16 weeks or normal diet for 12 months. Body weight, tail cuff blood pressure, heart and spleen weight, and serum levels of glucose, cholesterol, and aldosterone were measured for all mice at the end of the treatment period. Serial histologic sections of the aortic root were stained with Oil Red O to assess plaque size, lipid content, and necrotic core area; with PicroSirius Red for quantification of collagen content; by immunofluorescent staining with anti-Mac2/Galectin-3 and anti-smooth muscle α-actin antibodies to assess inflammation and SMC marker expression; and with Von Kossa stain to detect plaque calcification. In the 16-week HFD study, these analyses were also performed in sections from the brachiocephalic artery. Flow cytometry of cell suspensions derived from the aortic arch was also performed to quantify vascular inflammation after 8 and 16 weeks of HFD. Deletion of the MR specifically from SMCs did not significantly change plaque size, lipid content, necrotic core, collagen content, inflammatory staining, actin staining, or calcification, nor were there differences in the extent of vascular inflammation between MR-Intact and SMC-MR-KO mice in the three experiments.

Conclusion: SMC-MR does not directly contribute to the formation, progression, or inflammation of atherosclerotic plaques in the ApoE^−/− mouse model of atherosclerosis. This indicates that the MR in non-SMCs mediates the pro-atherogenic effects of MR activation.

Mineralocorticoid receptor antagonism reverses diabetes-related coronary vasodilator dysfunction: A unique vascular transcriptomic signature

Coronary microvascular dysfunction predicts and may be a proximate cause of cardiac dysfunction and mortality in diabetes; however, few effective treatments exist for these conditions. We recently demonstrated that mineralocorticoid receptor (MR) antagonism reversed cardiovascular dysfunction in early-stage obesity/insulin resistance. The mechanisms underlying this benefit of MR antagonism and its relevance in the setting of long-term obesity complications like diabetes; however, remain unclear. Thus, the present study evaluated the impact of MR antagonism on diabetes-related coronary dysfunction and defines the MR-dependent vascular transcriptome in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat recapitulating later stages of human diabetes. OLETF rats were treated with spironolactone (Sp) and compared to untreated OLETF and lean Long-Evans Tokushima Otsuka rats. Sp treatment attenuated diabetes-associated adipose and cardiac inflammation/fibrosis and improved coronary endothelium-dependent vasodilation but did not alter enhanced coronary vasoconstriction, blood pressure, or metabolic parameters in OLETF rats. Further mechanistic studies using RNA deep sequencing of OLETF rat aortas revealed 157 differentially expressed genes following Sp including upregulation of genes involved in the molecular regulation of nitric oxide bioavailability (Hsp90ab1, Ahsa1, Ahsa2) as well as novel changes in α_1D adrenergic receptors (Adra1d), cyclooxygenase-2 (Ptgs2), and modulatory factors of these pathways (Ackr3, Acsl4). Further, Ingenuity Pathway Analysis predicted inhibition of upstream inflammatory regulators by Sp and inhibition of 'migration of endothelial cells', 'differentiation of smooth muscle', and 'angiogenesis' biological functions by Sp in diabetes. Thus, this study is the first to define the MR-dependent vascular transcriptome underlying treatment of diabetes-related coronary microvascular dysfunction by Sp.

The Vasculature in Prediabetes

The frequency of prediabetes is increasing as the prevalence of obesity rises worldwide. In prediabetes, hyperglycemia, insulin resistance, and inflammation and metabolic derangements associated with concomitant obesity cause endothelial vasodilator and fibrinolytic dysfunction, leading to increased risk of cardiovascular and renal disease. Importantly, the microvasculature affects insulin sensitivity by affecting the delivery of insulin and glucose to skeletal muscle; thus, endothelial dysfunction and extracellular matrix remodeling promote the progression from prediabetes to diabetes mellitus. Weight loss is the mainstay of treatment in prediabetes, but therapies that improved endothelial function and vasodilation may not only prevent cardiovascular disease but also slow progression to diabetes mellitus.

Vascular dysfunction in obese diabetic db/db mice involves the interplay between aldosterone/mineralocorticoid receptor and Rho kinase signaling

Activation of aldosterone/mineralocorticoid receptors (MR) has been implicated in vascular dysfunction of diabetes. Underlying mechanisms are elusive. Therefore, we investigated the role of Rho kinase (ROCK) in aldosterone/MR signaling and vascular dysfunction in a model of diabetes. Diabetic obese mice (db/db) and control counterparts (db/+) were treated with MR antagonist (MRA, potassium canrenoate, 30 mg/kg/day, 4 weeks) or ROCK inhibitor, fasudil (30 mg/kg/day, 3 weeks). Plasma aldosterone was increased in db/db versus db/+. This was associated with enhanced vascular MR signaling. Norepinephrine (NE)-induced contraction was increased in arteries from db/db mice. These responses were attenuated in mice treated with canrenoate or fasudil. Db/db mice displayed hypertrophic remodeling and increased arterial stiffness, improved by MR blockade. Vascular calcium sensitivity was similar between depolarized arteries from db/+ and db/db. Vascular hypercontractility in db/db mice was associated with increased myosin light chain phosphorylation and reduced expression of PKG-1α. Vascular RhoA/ROCK signaling and expression of pro-inflammatory and pro-fibrotic markers were exaggerated in db/db mice, effects that were attenuated by MRA. Fasudil, but not MRA, improved vascular insulin sensitivity in db/db mice, evidenced by normalization of Irs1 phosphorylation. Our data identify novel pathways involving MR-RhoA/ROCK-PKG-1 that underlie vascular dysfunction and injury in diabetic mice.

30 YEARS OF THE MINERALOCORTICOID RECEPTOR: Nongenomic effects via the mineralocorticoid receptor

The mineralocorticoid receptor (MR) belongs to the steroid hormone receptor family and classically functions as a ligand-dependent transcription factor. It is involved in water-electrolyte homeostasis and blood pressure regulation but independent from these effects also furthers inflammation, fibrosis, hypertrophy and remodeling in cardiovascular tissues. Next to genomic effects, aldosterone elicits very rapid actions within minutes that do not require transcription or translation and that occur not only in classical MR epithelial target organs like kidney and colon but also in nonepithelial tissues like heart, vasculature and adipose tissue. Most of these effects can be mediated by classical MR and its crosstalk with different signaling cascades. Near the plasma membrane, the MR seems to be associated with caveolin and striatin as well as with receptor tyrosine kinases like EGFR, PDGFR and IGF1R and G protein-coupled receptors like AT1 and GPER1, which then mediate nongenomic aldosterone effects. GPER1 has also been named a putative novel MR. There is a close interaction and functional synergism between the genomic and the nongenomic signaling so that nongenomic signaling can lead to long-term effects and support genomic actions. Therefore, understanding nongenomic aldosterone/MR effects is of potential relevance for modulating genomic aldosterone effects and may provide additional targets for intervention.

Endoplasmic Reticulum Chaperon Tauroursodeoxycholic Acid Attenuates Aldosterone-Infused Renal Injury

Aldosterone (Aldo) is critically involved in the development of renal injury via the production of reactive oxygen species and inflammation. Endoplasmic reticulum (ER) stress is also evoked in Aldo-induced renal injury. In the present study, we investigated the role of ER stress in inflammation-mediated renal injury in Aldo-infused mice. C57BL/6J mice were randomized to receive treatment for 4 weeks as follows: vehicle infusion, Aldo infusion, vehicle infusion plus tauroursodeoxycholic acid (TUDCA), and Aldo infusion plus TUDCA. The effect of TUDCA on the Aldo-infused inflammatory response and renal injury was investigated using periodic acid-Schiff staining, real-time PCR, Western blot, and ELISA. We demonstrate that Aldo leads to impaired renal function and inhibition of ER stress via TUDCA attenuates renal fibrosis. This was indicated by decreased collagen I, collagen IV, fibronectin, and TGF-β expression, as well as the downregulation of the expression of Nlrp3 inflammasome markers, Nlrp3, ASC, IL-1β, and IL-18. This paper presents an important role for ER stress on the renal inflammatory response to Aldo. Additionally, the inhibition of ER stress by TUDCA negatively regulates the levels of these inflammatory molecules in the context of Aldo.

Up-regulation of the mammalian target of rapamycin complex 1 subunit Raptor by aldosterone induces abnormal pulmonary artery smooth muscle cell survival patterns to promote pulmonary arterial hypertension

Activation of the mammalian target of rapamycin complex 1 (mTORC1) subunit Raptor induces cell growth and is a downstream target of Akt. Elevated levels of aldosterone activate Akt, and, in pulmonary arterial hypertension (PAH), correlate with pulmonary arteriole thickening, which suggests that mTORC1 regulation by aldosterone may mediate adverse pulmonary vascular remodeling. We hypothesized that aldosterone-Raptor signaling induces abnormal pulmonary artery smooth muscle cell (PASMC) survival patterns to promote PAH. Remodeled pulmonary arterioles from SU-5416/hypoxia-PAH rats and monocrotaline-PAH rats with hyperaldosteronism expressed increased levels of the Raptor target, p70S6K, which provided a basis for investigating aldosterone-Raptor signaling in human PASMCs. Aldosterone (10(-9) to 10(-7) M) increased Akt/mTOR/Raptor to activate p70S6K and increase proliferation, viability, and apoptosis resistance in PASMCs. In PASMCs transfected with Raptor-small interfering RNA or treated with spironolactone/eplerenone, aldosterone or pulmonary arterial plasma from patients with PAH failed to increase p70S6K activation or to induce cell survival in vitro Optimal inhibition of pulmonary arteriole Raptor was achieved by treatment with Staramine-monomethoxy polyethylene glycol that was formulated with Raptor-small interfering RNA plus spironolactone in vivo, which decreased arteriole muscularization and pulmonary hypertension in 2 experimental animal models of PAH in vivo Up-regulation of mTORC1 by aldosterone is a critical pathobiologic mechanism that controls PASMC survival to promote hypertrophic vascular remodeling and PAH.-Aghamohammadzadeh, R., Zhang, Y.-Y., Stephens, T. E., Arons, E., Zaman, P., Polach, K. J., Matar, M., Yung, L.-M., Yu, P. B., Bowman, F. P., Opotowsky, A. R., Waxman, A. B., Loscalzo, J., Leopold, J. A., Maron, B. A. Up-regulation of the mammalian target of rapamycin complex 1 subunit Raptor by aldosterone induces abnormal pulmonary artery smooth muscle cell survival patterns to promote pulmonary arterial hypertension.

Aldosterone and type 2 diabetes mellitus

Primary hyperaldosteronism (PA) has recently been demonstrated to be strictly associated to metabolic syndrome as compared with essential hypertension (EH). Besides, the characteristics of metabolic syndrome are different in PA compared to EH, as high fasting glucose is more frequent in the former condition. The adverse effect of excess aldosterone on insulin metabolic signaling has generated increasing interest in the role of hyperaldosteronism in the pathogenesis of insulin resistance and resistant hypertension. Moreover, aldosterone receptor antagonist therapy in diabetic and cardiopathic patients improved coronary flow. The aim of this review is to present recent knowledge about the relationship between aldosterone, insulin resistance and diabetes.

Glucose Metabolism in Primary Aldosteronism

In recent years, an increasing number of studies have revealed deleterious effects of aldosterone via the mineralocorticoid receptor (MR). Especially in patients with primary aldosteronism (PA) a significant higher estimated risk of developing cardiovascular comorbidities and comortalities compared to essential hypertensives was reported. As diabetes mellitus and the metabolic syndrome are one of the major contributors to cardiovascular morbidity and mortality their connection to aldosterone excess became a focus of research in PA patients. Several studies assessed the effect of PA on glucose metabolism, the prevalence of diabetes mellitus, and the effect of PA treatment on both revealing different results. Therefore, we performed an extensive literature research. This review focuses on the current knowledge of the connection between aldosterone excess, glucose homeostasis, and diabetes mellitus in patients with PA. We have highlighted this topic from a pro and contra perspective followed by a summarizing concluding remark. Additionally, we have briefly reviewed the data on possible underlying mechanisms and indicated future considerations on the possible impact of cortisol co-secretion in PA.

Role of the renal sympathetic nerve in renal glucose metabolism during the development of type 2 diabetes in rats

AIMS/HYPOTHESIS

Recent clinical studies have shown that renal sympathetic denervation (RDX) improves glucose metabolism in patients with resistant hypertension. We aimed to elucidate the potential contribution of the renal sympathetic nervous system to glucose metabolism during the development of type 2 diabetes.

METHODS

Uninephrectomised diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats underwent RDX at 25 weeks of age and were followed up to 46 weeks of age.

RESULTS

RDX decreased plasma and renal tissue noradrenaline (norepinephrine) levels and BP. RDX also improved glucose metabolism and insulin sensitivity, which was associated with increased in vivo glucose uptake by peripheral tissues. Furthermore, RDX suppressed overexpression of sodium-glucose cotransporter 2 (Sglt2 [also known as Slc5a2]) in renal tissues, which was followed by an augmentation of glycosuria in type 2 diabetic OLETF rats. Similar improvements in glucose metabolism after RDX were observed in young OLETF rats at the prediabetic stage (21 weeks of age) without changing BP.

CONCLUSIONS/INTERPRETATION

Here, we propose the new concept of a connection between renal glucose metabolism and the renal sympathetic nervous system during the development of type 2 diabetes. Our data demonstrate that RDX exerts beneficial effects on glucose metabolism by an increase in tissue glucose uptake and glycosuria induced by Sglt2 suppression. These data have provided a new insight not only into the treatment of hypertensive type 2 diabetic patients, but also the pathophysiology of insulin resistance manifested by sympathetic hyperactivity.

Increased prevalence of diabetes mellitus and the metabolic syndrome in patients with primary aldosteronism of the German Conn's Registry

DESIGN

Abnormalities in glucose homeostasis have been described in patients with primary aldosteronism (PA) but most studies show inconsistent results. Therefore, we aimed to compare the prevalence of type 2 diabetes mellitus and metabolic syndrome (MetS) in newly diagnosed PA patients to a matched control cohort of the background population.

METHODS

In total, 305 PA patients of the prospective German Conn's Registry were compared to the population-based Study of Health In Pomerania (SHIP1; n=2454). A 1:1 match regarding sex, age, and BMI resulted in 269 matched pairs regarding type 2 diabetes and 183 matched pairs regarding MetS. Of the total, 153 PA patients underwent oral glucose tolerance testing (OGTT) at diagnosis and 38 PA patients were reevaluated at follow-up.

RESULTS

Type 2 diabetes and MetS were significantly more frequent in PA patients than in the control population (17.2% vs 10.4%, P=0.03; 56.8% vs 44.8%, P=0.02 respectively). Also, HbA1c levels were higher in PA patients than in controls (P<0.01). Of the total, 35.3% of non-diabetic PA patients showed an abnormal OGTT (¼ newly diagnosed type 2 diabetes and ¾ impaired glucose tolerance). PA patients with an abnormal OGTT at baseline presented with significantly improved 2 h OGTT glucose (P=0.01) at follow-up. We detected a negative correlation between 2 h OGTT glucose levels and serum potassium (P<0.01).

CONCLUSIONS

Type 2 diabetes and MetS are more prevalent in patients with PA than in controls matched for sex, age, BMI, and blood pressure. This may explain in part the increased cardiovascular disease morbidity and mortality in PA patients.

Spironolactone treatment attenuates vascular dysfunction in type 2 diabetic mice by decreasing oxidative stress and restoring NO/GC signaling

Type 2 diabetes (DM2) increases the risk of cardiovascular disease. Aldosterone, which has pro-oxidative and pro-inflammatory effects in the cardiovascular system, is positively regulated in DM2. We assessed whether blockade of mineralocorticoid receptors (MR) with spironolactone decreases reactive oxygen species (ROS)-associated vascular dysfunction and improves vascular nitric oxide (NO) signaling in diabetes. Leptin receptor knockout [LepR(db)/LepR(db) (db/db)] mice, a model of DM2, and their counterpart controls [LepR(db)/LepR(+), (db/+) mice] received spironolactone (50 mg/kg body weight/day) or vehicle (ethanol 1%) via oral per gavage for 6 weeks. Spironolactone treatment abolished endothelial dysfunction and increased endothelial nitric oxide synthase (eNOS) phosphorylation (Ser(1177)) in arteries from db/db mice, determined by acetylcholine-induced relaxation and Western Blot analysis, respectively. MR antagonist therapy also abrogated augmented ROS-generation in aorta from diabetic mice, determined by lucigenin luminescence assay. Spironolactone treatment increased superoxide dismutase-1 and catalase expression, improved sodium nitroprusside and BAY 41-2272-induced relaxation, and increased soluble guanylyl cyclase (sGC) β subunit expression in arteries from db/db mice. Our results demonstrate that spironolactone decreases diabetes-associated vascular oxidative stress and prevents vascular dysfunction through processes involving increased expression of antioxidant enzymes and sGC. These findings further elucidate redox-sensitive mechanisms whereby spironolactone protects against vascular injury in diabetes.

Mineralocorticoid receptor blockade prevents vascular remodelling in a rodent model of type 2 diabetes mellitus

Mineralocorticoid receptors (MRs), which are activated by mineralocorticoids and glucocorticoids, actively participate in mechanisms that affect the structure and function of blood vessels. Although experimental and clinical evidence shows that vascular damage in diabetes is associated with structural alterations in large and small arteries, the role of MR in this process needs further studies. Thus, we tested the hypothesis that MR, through redox-sensitive mechanisms, plays a role in diabetes-associated vascular remodelling. Male, 12-14-weeks-old db/db mice, a model of type 2 diabetes and their non-diabetic counterpart controls (db/+) were treated with spironolactone (MR antagonist, 50 mg/kg/day) or vehicle for 6 weeks. Spironolactone treatment did not affect blood pressure, fasting glucose levels or weight gain, but increased serum potassium and total cholesterol in both, diabetic and control mice. In addition, spironolactone significantly reduced serum insulin levels, but not aldosterone levels in diabetic mice. Insulin sensitivity, evaluated by the HOMA (homoeostatic model assessment)-index, was improved in spironolactone-treated diabetic mice. Mesenteric resistance arteries from vehicle-treated db/db mice exhibited inward hypertrophic remodelling, increased number of smooth muscle cells and increased vascular stiffness. These structural changes, determined by morphometric analysis and with a myography for pressurized arteries, were prevented by spironolactone treatment. Arteries from vehicle-treated db/db mice also exhibited augmented collagen content, determined by Picrosirius Red staining and Western blotting, increased reactive oxygen species (ROS) generation, determined by dihydroethidium (DHE) fluorescence, as well as increased expression of NAD(P)H oxidases 1 and 4 and increased activity of mitogen-activated protein kinases (MAPKs). Spironolactone treatment prevented all these changes, indicating that MR importantly contributes to diabetes-associated vascular dysfunction by inducing oxidative stress and by increasing the activity of redox-sensitive proteins.

Effects of aldosterone on insulin sensitivity and secretion

Dr. Conn originally reported an increased risk of diabetes in patients with hyperaldosteronism in the 1950s, although the mechanism remains unclear. Aldosterone-induced hypokalemia was initially described to impair glucose tolerance by impairing insulin secretion. Correction of hypokalemia by potassium supplementation only partially restored insulin secretion and glucose tolerance, however. Aldosterone also impairs glucose-stimulated insulin secretion in isolated pancreatic islets via reactive oxygen species in a mineralocorticoid receptor-independent manner. Aldosterone-induced mineralocorticoid receptor activation also impairs insulin sensitivity in adipocytes and skeletal muscle. Aldosterone may produce insulin resistance secondarily by altering potassium, increasing inflammatory cytokines, and reducing beneficial adipokines such as adiponectin. Renin-angiotensin system antagonists reduce circulating aldosterone concentrations and also the risk of type 2 diabetes in clinical trials. These data suggest that primary and secondary hyperaldosteronism may contribute to worsening glucose tolerance by impairing insulin sensitivity or insulin secretion in humans. Future studies should define the effects of MR antagonists and aldosterone on insulin secretion and sensitivity in humans.

Mineralocorticoid receptor signaling: crosstalk with membrane receptors and other modulators

The mineralocorticoid receptor (MR) belongs to the steroid receptor superfamily. Classically, it acts as a ligand-bound transcription factor in epithelial tissues, where it regulates water and electrolyte homeostasis and controls blood pressure. Additionally, the MR has been shown to elicit pathophysiological effects including inflammation, fibrosis and remodeling processes in the cardiovascular system and the kidneys and MR antagonists have proven beneficial for patients with certain cardiovascular and renal disease. The underlying molecular mechanisms that mediate MR effects have not been fully elucidated but very likely rely on interactions with other signaling pathways in addition to genomic actions at hormone response elements. In this review we will focus on interactions of MR signaling with different membrane receptors, namely receptor tyrosine kinases and the angiotensin II receptor because of their potential relevance for disease. In addition, GPR30 is discussed as a new aldosterone receptor. To gain insights into the problem why the MR only seems to mediate pathophysiological effects in the presence of additional permissive factors we will also briefly discuss factors that lead to modulation of MR activity as well. Overall, MR signaling is part of an intricate network that still needs to be investigated further.

Hyperglycemia causes cellular senescence via a SGLT2- and p21-dependent pathway in proximal tubules in the early stage of diabetic nephropathy

AIMS

Kidney cells in patients with diabetic nephropathy are reported to be senescent. However, the mechanisms that regulate cellular senescence in the diabetic kidney are still unknown. In the present study, we evaluated the contribution of high glucose to renal cell senescence in streptozotocin (STZ)-induced diabetic mice.

METHODS

Non-diabetic and streptozotocin (STZ, 10mgkg(-1)day(-1) for 7days, i.p.)-induced type 1 diabetic C57BL/6J mice and cultured human proximal tubular cells were used in this study.

RESULTS

Hyperglycemia dramatically increased the renal expression of p21 but not other CDK inhibitors such as p16 and p27 at 4weeks after STZ injection. These changes were accompanied by an increase in senescence-associated β-galactosidase staining in tubular epithelial cells. Administration of insulin at doses that maintained normoglycemia or mild hypoglycemia suppressed the changes induced by STZ. Insulin did not affect the senescent markers in non-diabetic mice. Exposure of cultured human proximal tubular cells to 25mmol/L, but not 8mmol/L, glucose medium increased the expression of senescence markers, which was suppressed by knock-down of p21 or sodium glucose cotransporter (SGLT) 2.

CONCLUSIONS

These results suggest that hyperglycemia causes tubular senescence via a SGLT2- and p21-dependent pathway in the type 1 diabetic kidney.

The involvement of aldosterone on vascular insulin resistance: implications in obesity and type 2 diabetes

Aldosterone, a mineralocorticoid hormone produced at the adrenal glands, controls corporal hydroelectrolytic balance and, consequently, has a key role in blood pressure adjustments. Aldosterone also has direct effects in many organs, including the vasculature, leading to many cellular events that influence proliferation, migration, inflammation, redox balance and apoptosis. Aldosterone effects depend on its binding to mineralocorticoid receptors (MR). Aldosterone binding to MR triggers two pathways, the genomic pathway and the non-genomic pathway. In the vasculature e.g., activation of the non-genomic pathway by aldosterone induces rapid effects that involve activation of kinases, phosphatases, transcriptional factors and NAD(P)H oxidases. Aldosterone also plays a crucial role on systemic and vascular insulin resistance, i.e. the inability of a tissue to respond to insulin. Insulin has a critical role on cell function and vascular insulin resistance is considered an early contributor to vascular damage. Accordingly, aldosterone impairs insulin receptor (IR) signaling by altering the phosphatidylinositol 3-kinase (PI3K)/nitric oxide (NO) pathway and by inducing oxidative stress and crosstalk between the IR and the insulin-like growth factor-1 receptor (IGF-1R). This mini-review focuses on the relationship between aldosterone and vascular insulin resistance. Evidence indicating MR antagonists as therapeutic tools to minimize vascular injury associated with obesity and diabetes type 2 is also discussed.

Preconditioning actions of aldosterone through p38 signaling modulation in isolated rat hearts

Although persistent excessive actions of aldosterone have unfavorable effects on the cardiovascular system, primarily via mineralocorticoid receptor (MR)-dependent pathways, the pathophysiological significance of aldosterone cascade activation in heart diseases has not yet been fully clarified. We herein examined the effects of short-term aldosterone stimulation at a physiological dose on cardiac function during ischemia-reperfusion injury (IRI). In order to study the effects of aldosterone preconditioning, male Wistar rat Langendorff hearts were perfused with 10(-9) mol/l of aldosterone for 10 min before ischemia, and the response to IRI was assessed. Although aldosterone did not affect the baseline hemodynamic parameters, preconditioning actions of aldosterone significantly improved the recovery in left ventricular contractility and left ventricular end-diastolic pressure associated with a reduced activity of creatine phosphokinase released into the perfusate after ischemia-reperfusion. Notably, the MR inhibitor eplerenone did not abrogate these beneficial effects. Biochemical analyses revealed that p38MAPK phosphorylation was significantly increased during aldosterone preconditioning before ischemia, whereas its phosphorylation was substantially attenuated during sustained ischemia-reperfusion, compared with the results for in the non-preconditioned control hearts. This dual regulation of p38MAPK was not affected by eplerenone. The phosphorylation levels of other MAPKs were not altered by aldosterone preconditioning. In conclusion, the temporal induction of the aldosterone cascade, at a physiological dose, has favorable effects on cardiac functional recovery and injury following ischemia-reperfusion in a MR-independent manner. Phasic dynamism of p38MAPK activation may play a key role in the physiological compensatory pathway of aldosterone under severe cardiac pathological conditions.

The Renin-Angiotensin-aldosterone system in vascular inflammation and remodeling

The RAAS through its physiological effectors plays a key role in promoting and maintaining inflammation. Inflammation is an important mechanism in the development and progression of CVD such as hypertension and atherosclerosis. In addition to its main role in regulating blood pressure and its role in hypertension, RAAS has proinflammatory and profibrotic effects at cellular and molecular levels. Blocking RAAS provides beneficial effects for the treatment of cardiovascular and renal diseases. Evidence shows that inhibition of RAAS positively influences vascular remodeling thus improving CVD outcomes. The beneficial vascular effects of RAAS inhibition are likely due to decreasing vascular inflammation, oxidative stress, endothelial dysfunction, and positive effects on regeneration of endothelial progenitor cells. Inflammatory factors such as ICAM-1, VCAM-1, TNFα, IL-6, and CRP have key roles in mediating vascular inflammation and blocking RAAS negatively modulates the levels of these inflammatory molecules. Some of these inflammatory markers are clinically associated with CVD events. More studies are required to establish long-term effects of RAAS inhibition on vascular inflammation, vascular cells regeneration, and CVD clinical outcomes. This review presents important information on RAAS's role on vascular inflammation, vascular cells responses to RAAS, and inhibition of RAAS signaling in the context of vascular inflammation, vascular remodeling, and vascular inflammation-associated CVD. Nevertheless, the review also equates the need to rethink and rediscover new RAAS inhibitors.

New insights into insulin action and resistance in the vasculature

Two-thirds of adults in the United States are overweight or obese, and another 26 million have type 2 diabetes. Decreased insulin sensitivity in cardiovascular tissue is an underlying abnormality in these individuals. Insulin metabolic signaling increases endothelial cell nitric oxide (NO) production. Impaired vascular insulin sensitivity is an early defect leading to impaired vascular relaxation. In overweight and obese persons, as well as in those with hypertension, systemic and vascular insulin resistance often occur in conjunction with activation of the cardiovascular tissue renin-angiotensin-aldosterone system (RAAS). Activated angiotensin II type 1 receptor and mineralocorticoid receptor signaling promote the development of vascular insulin resistance and impaired endothelial NO-mediated relaxation. Research in this area has implicated excessive serine phosphorylation and proteasomal degradation of the docking protein insulin receptor substrate and enhanced signaling through hybrid insulin/insulin-like growth factor receptor as important mechanisms underlying RAAS impediment of downstream vascular insulin metabolic signaling. This review will present recent evidence supporting the notion that RAAS signaling represents a potential pathway for the development of vascular insulin resistance and impaired endothelial-mediated vasodilation.

Insulin receptor (IR) and insulin-like growth factor receptor 1 (IGF-1R) signaling systems: novel treatment strategies for cancer

Insulin and insulin-like growth factor (IGF) signaling system, commonly known for fine-tuning numerous biological processes, has lately made its mark as a much sought-after therapeutic targets for diabetes and cancer. These receptors make an attractive anticancer target owing to their overexpression in variety of cancer especially in prostate and breast cancer. Inhibitors of IGF signaling were subjected to clinical cancer trials with the main objective to confirm the effectiveness of these receptors as a therapeutic target. However, the results that these trials produced proved to be disappointing as the role played by the cross talk between IGF and insulin receptor (IR) signaling pathways at the receptor level or at downstream signaling level became more lucid. Therapeutic strategy for IGF-1R and IR inhibition mainly encompasses three main approaches namely receptor blockade with monoclonal antibodies, tyrosine kinase inhibition (ATP antagonist and non-ATP antagonist), and ligand neutralization via monoclonal antibodies targeted to ligand or recombinant IGF-binding proteins. Other drug-discovery approaches are employed to target IGF-1R, and IR includes antisense oligonucleotides and recombinant IGF-binding proteins. However, therapies with monoclonal antibodies and tyrosine kinase inhibition targeting the IGF-1R are not evidenced to be satisfactory as expected. Factors that are duly held responsible for the unsuccessfulness of these therapies include (a) the existence of the IR isoform A overexpressed on a variety of cancers, enhancing the mitogenic signals to the nucleus leading to the endorsement of cell growth, (b) IGF-1R and IR that form hybrid receptors sensitive to the stimulation of all three IGF axis ligands, and (c) IGF-1R and IR that also have the potential to form hybrid receptors with other tyrosine kinase to potentiate the cellular transformation, tumorigenesis, and tumor vascularization. This mini review is a concerted effort to explore and fathom the well-recognized roles of the IRA signaling system in human cancer phenotype and the main strategies that have been so far evaluated to target the IR and IGF-1R.

Calcium channel blocker enhances beneficial effects of an angiotensin II AT1 receptor blocker against cerebrovascular-renal injury in type 2 diabetic mice

Recent clinical trials have demonstrated that combination therapy with renin-angiotensin system inhibitors plus calcium channel blockers (CCBs) elicits beneficial effects on cardiovascular and renal events in hypertensive patients with high cardiovascular risks. In the present study, we hypothesized that CCB enhances the protective effects of an angiotensin II type 1 receptor blocker (ARB) against diabetic cerebrovascular-renal injury. Saline-drinking type 2 diabetic KK-A^y mice developed hypertension and exhibited impaired cognitive function, blood-brain barrier (BBB) disruption, albuminuria, glomerular sclerosis and podocyte injury. These brain and renal injuries were associated with increased gene expression of NADPH oxidase components, NADPH oxidase activity and oxidative stress in brain and kidney tissues as well as systemic oxidative stress. Treatment with the ARB, olmesartan (10 mg/kg/day) reduced blood pressure in saline-drinking KK-A^y mice and attenuated cognitive decline, BBB disruption, glomerular injury and albuminuria, which were associated with a reduction of NADPH oxidase activity and oxidative stress in brain and kidney tissues as well as systemic oxidative stress. Furthermore, a suppressive dose of azelnidipine (3 mg/kg/day) exaggerated these beneficial effects of olmesartan. These data support the hypothesis that a CCB enhances ARB-associated cerebrovascular-renal protective effects through suppression of NADPH oxidase-dependent oxidative stress in type 2 diabetes.

Aldosterone aggravates glucose intolerance induced by high fructose

We previously reported that aldosterone impaired vascular insulin signaling in vivo and in vitro. Fructose-enriched diet induces metabolic syndrome including hypertension, insulin resistance, hyperlipidemia and diabetes in animal. In the current study, we hypothesized that aldosterone aggravated fructose feeding-induced glucose intolerance in vivo. Rats were divided into five groups for six-week treatment; uninephrectomy (Unx, n=8), Unx+aldosterone (aldo, 0.75 µg/h, s.c., n=8), Unx+fructose (fruc, 10% in drinking water, n=8), Unx+aldo+fruc, (aldo+fruc, n=8), and Unx+aldo+fruc+spironolactone, a mineralocorticoid receptor antagonist (aldo+fruc+spiro, 20mg/kg/day, p.o., n=8). Aldo+fruc rats manifested the hypertension, and induced glucose intolerance compared to fruc intake rats assessed by oral glucose tolerance test, homeostasis model assessment of insulin resistance and hyperinsulinemic-euglycemic clamp study. Spironolactone, significantly improved the aldosterone-accelerated glucose intolerance. Along with improvement in insulin resistance, spironolactone suppressed upregulated mineralocorticoid receptor (MR) target gene, serum and glucocorticoid-regulated kinases-1 mRNA expression in skeletal muscle in aldo+fruc rats. In conclusion, these data suggested that aldosterone aggravates fructose feeding-induced glucose intolerance through MR activation.

Antioxidant N-acetylcysteine protects pancreatic β-cells against aldosterone-induced oxidative stress and apoptosis in female db/db mice and insulin-producing MIN6 cells

Previous studies have shown that primary aldosteronism is associated with glucose-related metabolic disorders. However, the mechanisms by which aldosterone (ALDO) triggers β-cell dysfunction remains unclear. This study aimed to investigate whether oxidative stress is involved in and whether the antioxidant N-acetylcysteine (NAC) or the mineralocorticoid receptor antagonist spironolactone (SPL) could prevent or delay β-cell damage in vivo and in vitro. As expected, 8 weeks after ALDO treatment, 12-week-old female diabetic db/db mice exhibited impaired oral glucose tolerance, decreased β-cell mass, and heightened levels of oxidative stress marker (urinary 8-hydroxy-2'-deoxyguanosine). NAC reversed these symptoms completely, whereas SPL treatment did so only partially. After exposure to ALDO, the mouse pancreatic β-cell line MIN6 exhibited decreased viability and increased caspase-3 activity, as well as reduced expression of Bcl-2/Bax and p-AKT, even if mineralocorticoid receptor was completely suppressed with small interfering RNA. NAC, but not SPL, suppressed oxidative stress in MIN6 cells, as revealed by the decrease in inducible NOS levels and expression of the proteins p22-phox and p67-phox. These findings suggest that oxidative stress may be involved in ALDO-induced β-cell dysfunction and that NAC, but not SPL, may protect pancreatic β-cells of mice from ALDO-induced oxidative stress and apoptosis in a manner independent of its receptor.

Resistance to insulin and kidney disease in the cardiorenal metabolic syndrome; role for angiotensin II

The presence of insulin resistance is increasingly recognized as an important contributor to early stage kidney disease independent of the contribution of diabetes. Important in this relationship is the strong correlation between hyperinsulinemia and low levels of albuminuria (e.g. microalbuminuria). Recent work highlight mechanisms for glomerular/tubulointerstitial injury with excess insulin and emerging evidence identifies a unique role for insulin metabolic signaling and altered handling of salt reabsorption at the level of the proximal tubule. Evidence is also emerging for the role of insulin signaling in the glomerulus both epithelial and endothelial. Central to the mechanism of injury is inappropriate activation of the RAAS.

The role of the renin-angiotensin-aldosterone system in obesity-related renal diseases

Obesity is an independent risk factor for the development and progression of chronic kidney disease and one of the emerging reasons for end-stage renal disease owing to its dramatic increase worldwide. Among the potential underlying pathophysiologic mechanisms, activation of the renin-angiotensin-aldosterone-system (RAAS) plays a central role. Increased angiotensin II (AngII) levels also are central in hypertension, dyslipidemia, and insulin resistance, which, taken together with obesity, represent the metabolic syndrome. Increased AngII levels contribute to hyperfiltration, glomerulomegaly, and subsequent focal glomerulosclerosis by altering renal hemodynamics via afferent arteriolar dilation, together with efferent renal arteriolar vasoconstriction as well as by its endocrine and paracrine properties linking the intrarenal and the systemic RAAS, adipose tissue dysfunction, as well as insulin resistance and hypertension. The imbalance between increased AngII levels and the angiotensin converting enzyme 2/Ang (1-7)/Mas receptor axis additionally contributes to renal injury in obesity and its concomitant metabolic disturbances. As shown in several large trials and experimental studies, treatment of obesity by weight loss is associated with an improvement of kidney disease because it also is beneficial in dyslipidemia, hypertension, and diabetes. The most promising data have been seen by RAAS blockade, pointing to the central position of RAAS within obesity, kidney disease, and the metabolic syndrome.

Importance of insulin resistance to vascular repair and regeneration

Metabolic insulin resistance is apparent across a spectrum of clinical disorders, including obesity and diabetes, and is characterized by an adverse clustering of cardiovascular risk factors related to abnormal cellular responses to insulin. These disorders are becoming increasingly prevalent and represent a major global public health concern because of their association with significant increases in atherosclerosis-related mortality. Endogenous repair mechanisms are thought to retard the development of vascular disease, and a growing evidence base supports the adverse impact of the insulin-resistant phenotype upon indices of vascular repair. Beyond the impact of systemic metabolic changes, emerging data from murine studies also provide support for abnormal insulin signaling at the level of vascular cells in retarding vascular repair. Interrelated pathophysiological factors, including reduced nitric oxide bioavailability, oxidative stress, altered growth factor activity, and abnormal intracellular signaling, are likely to act in conjunction to impede vascular repair while also driving vascular damage. Understanding of these processes is shaping novel therapeutic paradigms that aim to promote vascular repair and regeneration, either by recruiting endogenous mechanisms or by the administration of cell-based therapies.

Mineralocorticoid receptor-mediated vascular insulin resistance: an early contributor to diabetes-related vascular disease?

Two-thirds of adults in the U.S. are overweight or obese, and another 26 million have type 2 diabetes (T2D). Patients with diabetes and/or the metabolic syndrome have a significantly increased risk of heart attack and stroke compared with people with normal insulin sensitivity. Decreased insulin sensitivity in cardiovascular tissues as well as in traditional targets of insulin metabolic signaling, such as skeletal muscle, is an underlying abnormality in obesity, hypertension, and T2D. In the vasculature, insulin signaling plays a critical role in normal vascular function via endothelial cell nitric oxide production and modulation of Ca(2+) handling and sensitivity in vascular smooth muscle cells. Available evidence suggests that impaired vascular insulin sensitivity may be an early, perhaps principal, defect of vascular function and contributor to the pathogenesis of vascular disease in persons with obesity, hypertension, and T2D. In the overweight and obese individual, as well as in persons with hypertension, systemic and vascular insulin resistance often occur in concert with elevations in plasma aldosterone. Indeed, basic and clinical studies have demonstrated that elevated plasma aldosterone levels predict the development of insulin resistance and that aldosterone directly interferes with insulin signaling in vascular tissues. Furthermore, elevated plasma aldosterone levels are associated with increased heart attack and stroke risk. Conversely, renin-angiotensin-aldosterone system and mineralocorticoid receptor (MR) antagonism reduces cardiovascular risk in these patient populations. Recent and accumulating evidence in this area has implicated excessive Ser phosphorylation and proteosomal degradation of the docking protein, insulin receptor substrate, and enhanced signaling through hybrid insulin/IGF-1 receptor as important mechanisms underlying aldosterone-mediated interruption of downstream vascular insulin signaling. Prevention or restoration of these changes via blockade of aldosterone action in the vascular wall with MR antagonists (i.e., spironolactone, eplerenone) may therefore account for the clinical benefit of these compounds in obese and diabetic patients with cardiovascular disease. This review will highlight recent evidence supporting the hypothesis that aldosterone and MR signaling represent an ideal candidate pathway linking early promoters of diabetes, especially overnutrition and obesity, to vascular insulin resistance, dysfunction, and disease.

The IGF-1 receptor and regulation of nitric oxide bioavailability and insulin signalling in the endothelium

The insulin-like growth factor-1 receptor (IGF-1R), like the insulin receptor (IR), plays a significant role in determining bioavailability of the critical signalling molecule nitric oxide (NO) and hence, modulates endothelial cell function, particularly in response to stimulation with insulin. In particular, the ability of the IGF-1R to form hybrid receptors with the IR appears to be highly significant in determining the sensitivity of the endothelial cell to insulin. This review will examine the structure of the IGF-1R and how this, with particular reference to the ability of the IGF-1R and the IR to form hybrid receptors, may have an effect both on endothelial cell function and the development of cardiovascular disease.

Vascular actions of aldosterone

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