Direct renin inhibition prevents cardiac dysfunction in a diabetic mouse model: comparison with an angiotensin receptor antagonist and angiotensin-converting enzyme inhibitor. Clin Sci (Lond). 2013;124:529-541. [PMID: 23116220 DOI: 10.1042/cs20120448]

Aliskiren-Loaded Nanoparticles Downregulate (Pro)renin Receptor and ACE Gene Expression in the Heart of Spontaneously Hypertensive Rats: Effect on NADPH Oxidase

We aimed to determine effects of aliskiren, a direct renin inhibitor, loaded onto polymeric nanoparticles on the (pro)renin receptor (Atp6ap2), angiotensin II type 1 receptor (Agtr1), and angiotensin-converting enzyme (ACE) gene expression in the heart of spontaneously hypertensive rats (SHR). Twelve-week-old male SHRs were divided into an untreated group and groups treated with powdered aliskiren or aliskiren-loaded nanoparticles (25 mg/kg/day). After three weeks, the accumulation of aliskiren, distribution of polymeric nanoparticles, gene expression of Atp6ap2 and Agtr1 receptors and ACE, and protein expression of NADPH oxidase along with the conjugated diene (CD) concentration were analyzed. The accumulation of aliskiren in the heart was higher in the aliskiren-loaded nanoparticle group than in the powdered group. The fluorescent signals of nanoparticles were visible in cardiomyocytes, vessel walls, and erythrocytes. Aliskiren-loaded nanoparticles decreased the gene expression of Atp6ap2 and ACE, while not affecting Agtr1. Both forms of aliskiren decreased the protein expression of NADPH oxidase, with a more pronounced effect observed in the aliskiren-loaded nanoparticle group. CD concentration was decreased only in the aliskiren-loaded nanoparticle group. We hypothesize that aliskiren-loaded nanoparticle-mediated downregulation of Atp6ap2 and ACE may contribute to a decrease in ROS generation with beneficial effects in the heart. Moreover, polymeric nanoparticles may represent a promising tool for targeted delivery of aliskiren.

Current challenges in the treatment of cardiac fibrosis: Recent insights into the sex-specific differences of glucose-lowering therapies on the diabetic heart: IUPHAR Review 33

A significant cardiac complication of diabetes is cardiomyopathy, a form of ventricular dysfunction that develops independently of coronary artery disease, hypertension and valvular diseases, which may subsequently lead to heart failure. Several structural features underlie the development of diabetic cardiomyopathy and eventual diabetes-induced heart failure. Pathological cardiac fibrosis (interstitial and perivascular), in addition to capillary rarefaction and myocardial apoptosis, are particularly noteworthy. Sex differences in the incidence, development and presentation of diabetes, heart failure and interstitial myocardial fibrosis have been identified. Nevertheless, therapeutics specifically targeting diabetes-associated cardiac fibrosis remain lacking and treatment approaches remain the same regardless of patient sex or the co-morbidities that patients may present. This review addresses the observed anti-fibrotic effects of newer glucose-lowering therapies and traditional cardiovascular disease treatments, in the diabetic myocardium (from both preclinical and clinical contexts). Furthermore, any known sex differences in these treatment effects are also explored. LINKED ARTICLES: This article is part of a themed issue on Translational Advances in Fibrosis as a Therapeutic Target. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.22/issuetoc.

Ferulic acid mitigates diabetic cardiomyopathy via modulation of metabolic abnormalities in cardiac tissues of diabetic rats

Cardiovascular abnormalities have been reported as a major contributor of diabetic mortality. The protective effect of ferulic acid on diabetic cardiomyopathy in fructose-streptozotocin induced type 2 diabetes (T2D) rat model was elucidated in this study. Type 2 diabetic rats were treated by oral administration of low (150 mg/kg b.w) and high (300 mg/kg b.w) doses of ferulic acid. Metformin was used as the antidiabetic drug. Rats were humanely euthanized after 5 weeks of treatment, and their blood and hearts were collected. Induction of T2D depleted the levels of reduced glutathione, glycogen, and HDL-cholesterol and the activities of superoxide dismutase, catalase, ENTPDase, and 5'nucleotidase. It simultaneously triggered increase in the levels of malondialdehyde, total cholesterol, triglyceride, LDL-cholesterol, creatinine kinase-MB as well as activities of acetylcholinesterase, angiotensin converting enzyme (ACE), ATPase, glucose-6-phopsphatase, fructose-1,6-bisphophatase, glycogen phosphorylase, and lipase. T2D induction further revealed an obvious degeneration of cardiac muscle morphology. However, treatment with ferulic acid markedly reversed the levels and activities of these biomarkers with concomitant improvement in myocardium structural morphology, which had favorable comparison with the standard drug, metformin. Additionally, T2D induction led to the depletion of 40%, 75%, and 33% of fatty acids, fatty esters, and steroids, respectively, with concomitant generation of eicosenoic acid, gamolenic acid, and vitamin E. Ferulic acid treatment restored eicosanoic acid, 2-hydroxyethyl ester, with concomitant generation of 6-octadecenoic acid, (Z)-, cis-11-eicosenoic acid, tridecanedioic acid, octadecanoic acid, 2-hydroxyethyl ester, ethyl 3-hydroxytridecanoate, dipalmitin, cholesterol isocaproate, cholest-5-ene, 3-(1-oxobuthoxy)-, cholesta-3,5-diene. These results suggest the cardioprotective potential of ferulic acid against diabetic cardiomyopathy.

Spirulina platensis Suppressed iNOS and Proinflammatory Cytokines in Lipopolysaccharide-Induced BV2 Microglia

The disease burden of neurodegenerative diseases is on the rise due to the aging population, and neuroinflammation is one of the underlying causes. Spirulina platensis is a well-known superfood with numerous reported bioactivities. However, the effect of S. platensis Universiti Malaya Algae Culture Collection 159 (UMACC 159) (a strain isolated from Israel) on proinflammatory mediators and cytokines remains unknown. In this study, we aimed to determine the anti-neuroinflammatory activity of S. platensis extracts and identify the potential bioactive compounds. S. platensis extracts (hexane, ethyl acetate, ethanol, and aqueous) were screened for phytochemical content and antioxidant activity. Ethanol extract was studied for its effect on proinflammatory mediators and cytokines in lipopolysaccharide (LPS)-induced BV2 microglia. The potential bioactive compounds were identified using liquid chromatography-mass spectrometric (LC-MS) analysis. Ethanol extract had the highest flavonoid content and antioxidant and nitric oxide (NO) inhibitory activity. Ethanol extract completely inhibited the production of NO via the downregulation of inducible NO synthase (iNOS) and significantly reduced the production of tumor necrosis factor (TNF)-α and interleukin (IL)-6. Emmotin A, palmitic amide, and 1-monopalmitin, which might play an important role in cell signaling, have been identified. In conclusion, S. platensis ethanol extract inhibited neuroinflammation through the downregulation of NO, TNF-α and IL-6. This preliminary study provided insight into compound(s) isolation, which could contribute to the development of precision nutrition for disease management.

Understanding diabetes-induced cardiomyopathy from the perspective of renin angiotensin aldosterone system

Experimental and clinical evidence suggests that diabetic subjects are predisposed to a distinct cardiovascular dysfunction, known as diabetic cardiomyopathy (DCM), which could be an autonomous disease independent of concomitant micro and macrovascular disorders. DCM is one of the prominent causes of global morbidity and mortality and is on a rising trend with the increase in the prevalence of diabetes mellitus (DM). DCM is characterized by an early left ventricle diastolic dysfunction associated with the slow progression of cardiomyocyte hypertrophy leading to heart failure, which still has no effective therapy. Although the well-known "Renin Angiotensin Aldosterone System (RAAS)" inhibition is considered a gold-standard treatment in heart failure, its role in DCM is still unclear. At the cellular level of DCM, RAAS induces various secondary mechanisms, adding complications to poor prognosis and treatment of DCM. This review highlights the importance of RAAS signaling and its major secondary mechanisms involving inflammation, oxidative stress, mitochondrial dysfunction, and autophagy, their role in establishing DCM. In addition, studies lacking in the specific area of DCM are also highlighted. Therefore, understanding the complex role of RAAS in DCM may lead to the identification of better prognosis and therapeutic strategies in treating DCM.

Long non-coding RNA KCNQ1OT1 increases the expression of PDCD4 by targeting miR-181a-5p, contributing to cardiomyocyte apoptosis in diabetic cardiomyopathy

AIMS

Diabetic cardiomyopathy (DCM) is a specific myocardial alteration in patients with diabetics. LncRNA KCNQ1OT1 has been previously demonstrated to be involved in various diabetic complications. Our aims are to further investigate the underlying regulatory mechanisms/pathways of KCNQ1OT1 in DCM.

METHODS

In vitro and in vivo models of DCM were established in high glucose (HG)-treated human cardiomyocytes and in streptozotocin (STZ)-induced diabetic mice, respectively. Gene and protein expressions were examined by qPCR, western blotting and ELISA. Cell proliferation and apoptosis were determined by CCK8 assay, flow cytometry and TUNEL staining. The association between KCNQ1OT1 and miR-181a-5p, miR-181a-5p and PDCD4 was predicted using bioinformatics methods and subsequently confirmed by dual luciferase reporter and RNA immunoprecipitation assays. Mouse cardiac tissues were collected and analysed using HE staining, Masson's staining and immunohistochemical analysis.

RESULTS

KCNQ1OT1 and PDCD4 were upregulated in HG-treated human cardiomyocytes, while miR-181a-5p was downregulated. In addition, KCNQ1OT1 could negatively regulate miR-181a-5p expression; meanwhile, miR-181a-5p also negatively regulated PDCD4 expression. KCNQ1OT1 silencing suppressed the expression of inflammatory cytokines and cell apoptosis in vitro, whereas inhibition of miR-181a-5p abrogated those effects of KCNQ1OT1 knockdown. Moreover, overexpressed PDCD4 abolished the inhibition on inflammation and apoptosis caused by miR-181a-5p overexpression. Finally, KCNQ1OT1 knockdown reduced the expression of PDCD4 via regulating miR-181a-5p and inhibited myocardial inflammation and cardiomyocyte apoptosis in the in vivo DCM model.

CONCLUSIONS

Our findings suggest that KCNQ1OT1 and its target gene miR-181a-5p regulate myocardial inflammation and cardiomyocyte apoptosis by modulating PDCD4 in DCM.

Therapeutic potential of targeting oxidative stress in diabetic cardiomyopathy

Even in the absence of coronary artery disease and hypertension, diabetes mellitus (DM) may increase the risk for heart failure development. This risk evolves from functional and structural alterations induced by diabetes in the heart, a cardiac entity termed diabetic cardiomyopathy (DbCM). Oxidative stress, defined as the imbalance of reactive oxygen species (ROS) has been increasingly proposed to contribute to the development of DbCM. There are several sources of ROS production including the mitochondria, NAD(P)H oxidase, xanthine oxidase, and uncoupled nitric oxide synthase. Overproduction of ROS in DbCM is thought to be counterbalanced by elevated antioxidant defense enzymes such as catalase and superoxide dismutase. Excess ROS in the cardiomyocyte results in further ROS production, mitochondrial DNA damage, lipid peroxidation, post-translational modifications of proteins and ultimately cell death and cardiac dysfunction. Furthermore, ROS modulates transcription factors responsible for expression of antioxidant enzymes. Lastly, evidence exists that several pharmacological agents may convey cardiovascular benefit by antioxidant mechanisms. As such, increasing our understanding of the pathways that lead to increased ROS production and impaired antioxidant defense may enable the development of therapeutic strategies against the progression of DbCM. Herein, we review the current knowledge about causes and consequences of ROS in DbCM, as well as the therapeutic potential and strategies of targeting oxidative stress in the diabetic heart.

Effects of (Pro)renin Receptor on Diabetic Cardiomyopathy Pathological Processes in Rats via the PRR-AMPK-YAP Pathway

Diabetic cardiomyopathy (DCM) is a common complication associated with diabetes. The (pro)renin receptor (PRR) is an important member of the local tissue renin-angiotensin system and plays a vital role in many cardiovascular diseases. Yes-associated protein (YAP) also plays a crucial role in many cardiovascular diseases. However, the mechanism responsible for the effects of PRR and YAP on DCM remains unclear. The purpose of this study was to determine the role of PRR in the pathological progression of DCM and whether PRR influences the pathological processes of diabetic cardiomyopathy through YAP. We first established diabetic cardiomyopathy rats model, downregulated the expression of PRR, and upregulated and downregulated the expression of YAP. The levels of myocardial inflammation and fibrosis were then measured and cardiac function was evaluated. In vitro, primary rat cardiac fibroblasts (CFs) were cultured with high glucose, with or without transfection with recombinant adenovirus expressing PRR, and GSK621 was used to observe the effect of AMPK. The levels of inflammation and fibrosis were measured in vitro. The results showed that PRR and YAP silencing alleviated myocardial inflammation and fibrosis. GSK621 blocked the effect of PRR on AMPK and YAP and improved CF inflammation and fibrosis. The inhibition of PRR expression offers a new therapeutic strategy for the treatment of DCM. The effects of PRR on the pathological process of DCM in rats may be mediated via the PRR-AMPK-YAP pathway.

Application of Animal Models in Diabetic Cardiomyopathy

Diabetic heart disease is a growing and important public health risk. Apart from the risk of coronary artery disease or hypertension, diabetes mellitus (DM) is a well-known risk factor for heart failure in the form of diabetic cardiomyopathy (DiaCM). Currently, DiaCM is defined as myocardial dysfunction in patients with DM in the absence of coronary artery disease and hypertension. The underlying pathomechanism of DiaCM is partially understood, but accumulating evidence suggests that metabolic derangements, oxidative stress, increased myocardial fibrosis and hypertrophy, inflammation, enhanced apoptosis, impaired intracellular calcium handling, activation of the renin-angiotensin-aldosterone system, mitochondrial dysfunction, and dysregulation of microRNAs, among other factors, are involved. Numerous animal models have been used to investigate the pathomechanisms of DiaCM. Despite some limitations, animal models for DiaCM have greatly advanced our understanding of pathomechanisms and have helped in the development of successful disease management strategies. In this review, we summarize the current pathomechanisms of DiaCM and provide animal models for DiaCM according to its pathomechanisms, which may contribute to broadening our understanding of the underlying mechanisms and facilitating the identification of possible new therapeutic targets.

Microvascular Disease and Small-Vessel Disease: The Nexus of Multiple Diseases of Women

Microvascular disease, or small-vessel disease, is a multisystem disorder with a common pathophysiological basis that differentially affects various organs in some patients. The prevalence of small-vessel disease in the heart has been found to be higher in women compared with men. Additionally, other diseases prominently affecting women, including heart failure with preserved ejection fraction, Takotsubo cardiomyopathy, cerebral small-vessel disease, preeclampsia, pulmonary arterial hypertension (PAH), endothelial dysfunction in diabetes, diabetic cardiomyopathy, rheumatoid arthritis, systemic lupus erythematosus, and systemic sclerosis, may have a common etiologic linkage related to microvascular disease. To the best of our knowledge this is the first article to investigate this potential linkage. We sought to identify various diseases with a shared pathophysiology involving microvascular/endothelial dysfunction that primarily affect women, and their potential implications for disease management. Advanced imaging technologies, such as magnetic resonance imaging and positron-emission tomography, enable the detection and increased understanding of microvascular dysfunction in various diseases. Therapies that improve endothelial function, such as those used in PAH, may also be associated with benefits across the full spectrum of microvascular dysfunction. A shared pathology across multiple organ systems highlights the need for a collaborative, multidisciplinary approach among medical subspecialty practitioners who care for women with small-vessel disease. Such an approach may lead to accelerated research in diseases that affect women and their quality of life.

Normalizing Plasma Renin Activity in Experimental Dilated Cardiomyopathy: Effects on Edema, Cachexia, and Survival

Heart failure (HF) patients frequently have elevated plasma renin activity. We examined the significance of elevated plasma renin activity in a translationally-relevant model of dilated cardiomyopathy (DCM), which replicates the progressive stages (A–D) of human HF. Female mice with DCM and elevated plasma renin activity concentrations were treated with a direct renin inhibitor (aliskiren) in a randomized, blinded fashion beginning at Stage B HF. By comparison to controls, aliskiren treatment normalized pathologically elevated plasma renin activity (p < 0.001) and neprilysin levels (p < 0.001), but did not significantly alter pathological changes in plasma aldosterone, angiotensin II, atrial natriuretic peptide, or corin levels. Aliskiren improved cardiac systolic function (ejection fraction, p < 0.05; cardiac output, p < 0.01) and significantly reduced the longitudinal development of edema (extracellular water, p < 0.0001), retarding the transition from Stage B to Stage C HF. The normalization of elevated plasma renin activity reduced the loss of body fat and lean mass (cachexia/sarcopenia), p < 0.001) and prolonged survival (p < 0.05). In summary, the normalization of plasma renin activity retards the progression of experimental HF by improving cardiac systolic function, reducing the development of systemic edema, cachexia/sarcopenia, and mortality. These data suggest that targeting pathologically elevated plasma renin activity may be beneficial in appropriately selected HF patients.

Current advances in the study of diabetic cardiomyopathy: From clinicopathological features to molecular therapeutics (Review)

The incidence of diabetes mellitus has become a major public health concern due to lifestyle alterations. Moreover, the complications associated with diabetes mellitus deeply influence the quality of life of patients. Diabetic cardiomyopathy (DC) is a type of diabetes mellitus complication characterized by functional and structural damage in the myocardium but not accompanied by coronary arterial disease. Currently, diagnosing and preventing DC is still a challenge for physicians due to its atypical symptoms. For this reason, it is necessary to summarize the current knowledge on DC, especially in regards to the underlying molecular mechanisms toward the goal of developing useful diagnostic approaches and effective drugs based on these mechanisms. There exist several review articles which have focused on these points, but there still remains a lot to learn from published studies. In this review, the features, diagnosis and molecular mechanisms of DC are reviewed. Furthermore, potential therapeutic and prophylactic drugs are discussed.

Renin Activity in Heart Failure with Reduced Systolic Function-New Insights

Regardless of the cause, symptomatic heart failure (HF) with reduced ejection fraction (rEF) is characterized by pathological activation of the renin–angiotensin–aldosterone system (RAAS) with sodium retention and extracellular fluid expansion (edema). Here, we review the role of active renin, a crucial, upstream enzymatic regulator of the RAAS, as a prognostic and diagnostic plasma biomarker of heart failure with reduced ejection fraction (HFrEF) progression; we also discuss its potential as a pharmacological bio-target in HF therapy. Clinical and experimental studies indicate that plasma renin activity is elevated with symptomatic HFrEF with edema in patients, as well as in companion animals and experimental models of HF. Plasma renin activity levels are also reported to be elevated in patients and animals with rEF before the development of symptomatic HF. Modulation of renin activity in experimental HF significantly reduces edema formation and the progression of systolic dysfunction and improves survival. Thus, specific assessment and targeting of elevated renin activity may enhance diagnostic and therapeutic precision to improve outcomes in appropriate patients with HFrEF.

Eicosanoids and HB-EGF/EGFR in cancer

Eicosanoids are bioactive lipids that play crucial roles in various pathophysiological conditions, including inflammation and cancer. They include both the COX-derived prostaglandins and the LOX-derived leukotrienes. Furthermore, the epidermal growth factor receptor (EGFR) pathways family of receptor tyrosine kinases also are known to play a central role in the tumorigenesis. Various antitumor modalities have been approved cancer treatments that target therapeutically the COX-2 and EGFR pathways; these include selective COX-2 inhibitors and EGFR monoclonal antibodies. Research has shown that the COX-2 and epidermal growth factor receptor pathways actively interact with each other in order to orchestrate carcinogenesis. This has been used to justify a targeted combinatorial approach aimed at these two pathways. Although combined therapies have been found to have a greater antitumor effect than the administration of single agent, this does not exempt them from the possible fatal cardiac effects that are associated with COX-2 inhibition. In this review, we delineate the contribution of HB-EGF, an important EGFR ligand, to the cardiac dysfunction related to decreased shedding of HB-EGF after COX-2/PGE2 inhibition. A better understanding of the molecular mechanisms underlying these cardiac side effects will make possible more effective regimens that use the dual-targeting approach.

Reversal of angiotensin ll-induced β-cell dedifferentiation via inhibition of NF-κb signaling

Background

Type 2 diabetes mellitus (T2DM) is characterized by pancreatic β-cell failure, which arises from metabolic stress and results in β cell dedifferentiation, leading to β-cell death. Pathological activation of the renin–angiotensin system (RAS) contributes to increase cell stress, while RAS intervention reduces the onset of T2DM in high-risk populations and promotes insulin secretion in rodents. In this study, we investigated whether and how RAS induces β-cell dedifferentiation and the mechanism underlying this process.

Methods

In vitro, with the methods of quantitative real-time reverse transcriptase-PCR (qRT-PCR) and western blotting, we examined the change of cell identity-related gene expression, progenitor like gene expression, cellular function, and nuclear factor kappa b (NF-κb) signaling activity in β cell lines after exposure to angiotensin II (AngII) and disruption of RAS. In vivo, parallel studies were performed using db/db mice. Related protein expression was detected by Immunofluorescence analysis.

Result

Activation of RAS induced dedifferentiation and impaired insulin secretion, eventually leading to β-cell failure. Mechanistically, Angll induced β-cell dedifferentiation via NF-κb signaling, while treatment with lrbesartan and sc-514 reversed the progenitor state of β cells.

Conclusion

The present study found that RAS might induce β-cell dedifferentiation via angiotensin II receptor type 1 activation, which was promoted by NF-κb signaling. Therefore, blocking RAS or NF-kb signaling efficiently reversed the dedifferentiated status of β cells, suggesting a potential therapy for patients with type 2 diabetes.

Electronic supplementary material

The online version of this article (10.1186/s10020-018-0044-3) contains supplementary material, which is available to authorized users.

Diabetic cardiomyopathy: where we are and where we are going

The global burden of diabetes mellitus and its related complications are currently increasing. Diabetes mellitus affects the heart through various mechanisms including microvascular impairment, metabolic disturbance, subcellular component abnormalities, cardiac autonomic dysfunction, and a maladaptive immune response. Eventually, diabetes mellitus can cause functional and structural changes in the myocardium without coronary artery disease, a disorder known as diabetic cardiomyopathy (DCM). There are many diagnostic tools and management options for DCM, although it is difficult to detect its development and effectively prevent its progression. In this review, we summarize the current research regarding the pathophysiology and pathogenesis of DCM. Moreover, we discuss emerging diagnostic evaluation methods and treatment strategies for DCM, which may help our understanding of its underlying mechanisms and facilitate the identification of possible new therapeutic targets.

Lipid metabolism and its implications for type 1 diabetes-associated cardiomyopathy

Diabetic cardiomyopathy was first defined over four decades ago. It was observed in small post-mortem studies of diabetic patients who suffered from concomitant heart failure despite the absence of hypertension, coronary disease or other likely causal factors, as well as in large population studies such as the Framingham Heart Study. Subsequent studies continue to demonstrate an increased incidence of heart failure in the setting of diabetes independent of established risk factors, suggesting direct effects of diabetes on the myocardium. Impairments in glucose metabolism and handling receive the majority of the blame. The role of concomitant impairments in lipid handling, particularly at the level of the myocardium, has however received much less attention. Cardiac lipid accumulation commonly occurs in the setting of type 2 diabetes and has been suggested to play a direct causal role in the development of cardiomyopathy and heart failure in a process termed as cardiac lipotoxicity. Excess lipids promote numerous pathological processes linked to the development of cardiomyopathy, including mitochondrial dysfunction and inflammation. Although somewhat underappreciated, cardiac lipotoxicity also occurs in the setting of type 1 diabetes. This phenomenon is, however, largely understudied in comparison to hyperglycaemia, which has been widely studied in this context. The current review addresses the changes in lipid metabolism occurring in the type 1 diabetic heart and how they are implicated in disease progression. Furthermore, the pathological pathways linked to cardiac lipotoxicity are discussed. Finally, we consider novel approaches for modulating lipid metabolism as a cardioprotective mechanism against cardiomyopathy and heart failure.

Resveratrol Ameliorates Diabetes-Induced Cardiac Dysfunction Through AT1R-ERK/p38 MAPK Signaling Pathway

The present study was to determine the preventive effect of resveratrol (Res) on diabetes-induced cardiac dysfunction and the possible signaling pathway involved. Diabetes was induced in rats by injection of streptozotocin (STZ) at 45 mg/kg. The animals were randomly divided into three groups (10 rats/group): normal group, diabetes groups with or without Res (80 mg/kg) treatment. Biochemistry, cardiac function and fibrosis were detected. Moreover, pro-inflammatory cytokines were evaluated, and heart tissues were homogenized for western blot analysis to analyze the possible mechanisms. The results indicated that Res might regulate glucose and lipid metabolism, ameliorate cardiac function and fibrosis response in STZ-induced diabetic rats. The protective effects were consistent with the inhibition of inflammatory factors such as TNF-α, IL-6 and IL-1β. In addition, Res favorably shifted STZ-induced AT1R, ERK1/2 and p38 MAPK activation in rat heart. In conclusion, the results suggested that Res attenuated diabetes-induced cardiac dysfunction, and the effects were associated with attenuation inflammatory response and down-regulation of AT1R-ERK/p38 MAPK signaling pathway.

Role of Hypoxia Inducible Factor 1 in Hyperglycemia-Exacerbated Blood-Brain Barrier Disruption in Ischemic Stroke

Diabetes is a major stroke risk factor and is associated with poor functional recovery after stroke. Accumulating evidence indicates that the worsened outcomes may be due to hyperglycemia-induced cerebral vascular complications, especially disruption of the blood-brain barrier (BBB). The present study tested a hypothesis that the activation of hypoxia inducible factor-1 (HIF-1) was involved in hyperglycemia-aggravated BBB disruption in an ischemic stroke model. Non-diabetic control and Streptozotocin-induced type I diabetic mice were subjected to 90min transient middle cerebral artery occlusion (MCAO) followed by reperfusion. Our results demonstrated that hyperglycemia induced higher expression of HIF-1α and vascular endothelial growth factor (VEGF) in brain microvessels after MCAO/reperfusion. Diabetic mice showed exacerbated BBB damage and tight junction disruption, increased infarct volume as well as worsened neurological deficits. Furthermore, suppressing HIF-1 activity by specific knock-out endothelial HIF-1α ameliorated BBB leakage and brain infarction in diabetic animals. Moreover, glycemic control by insulin abolished HIF-1α up-regulation in diabetic animals and reduced BBB permeability and brain infarction. These findings strongly indicate that HIF-1 plays an important role in hyperglycemia-induced exacerbation of BBB disruption in ischemic stroke. Endothelial HIF-1 inhibition warrants further investigation as a therapeutic target for the treatment of stroke patients with diabetes.

Aliskiren targets multiple systems to alleviate cancer cachexia

To examine the effects of aliskiren, a small-molecule renin inhibitor, on cancer cachexia and to explore the underlying mechanisms. A cancer cachexia model was established by subcutaneously injecting C26 mouse colon carcinoma cells into isogenic BALB/c mice. Aliskiren was administered intragastrically [10 mg/kg body weight (BW)] on day 5 (as a preventive strategy, AP group) or on day 12 (as a therapeutic strategy, AT group) after C26 injection. Mice that received no C26 injection (healthy controls, HC group) or only C26 injection but not aliskiren (cancer, CA group) were used as controls. BW, tumor growth, whole body functions, and survival were monitored daily in half of the mice in each group, whereas serum, tumors, and gastrocnemius muscles were harvested from the other mice after sacrifice on day 20 for further analysis. Aliskiren significantly alleviated multiple cachexia‑associated symptoms, including BW loss, tumor burden, muscle wasting, muscular dysfunction, and shortened survival. On the molecular level, aliskiren antagonized cachexia‑induced activation of the renin‑angiotensin system (RAS), systematic and muscular inflammation, oxidative stress, and autophagy‑lysosome as well as ubiquitin‑proteasome stimulation. In addition, early administration of aliskiren before cachexia development (AP group) resulted in more robust effects in alleviating cachexia or targeting underlying mechanisms than administration after cachexia development (AT group). Aliskiren exhibited potent anti‑cachexia activities. These activities were achieved through the targeting of at least four mechanisms underlying cachexia development: RAS activation, increase in systematic inflammation, upregulation of oxidative stress, and stimulation of autophagy-lysosome pathway (ALP) and ubiquitin-proteasome pathway (UPP).

Loss of myocardial retinoic acid receptor α induces diastolic dysfunction by promoting intracellular oxidative stress and calcium mishandling in adult mice

Retinoic acid receptor (RAR) has been implicated in pathological stimuli-induced cardiac remodeling. To determine whether the impairment of RARα signaling directly contributes to the development of heart dysfunction and the involved mechanisms, tamoxifen-induced myocardial specific RARα deletion (RARαKO) mice were utilized. Echocardiographic and cardiac catheterization studies showed significant diastolic dysfunction after 16wks of gene deletion. However, no significant differences were observed in left ventricular ejection fraction (LVEF), between RARαKO and wild type (WT) control mice. DHE staining showed increased intracellular reactive oxygen species (ROS) generation in the hearts of RARαKO mice. Significantly increased NOX2 (NADPH oxidase 2) and NOX4 levels and decreased SOD1 and SOD2 levels were observed in RARαKO mouse hearts, which were rescued by overexpression of RARα in cardiomyocytes. Decreased SERCA2a expression and phosphorylation of phospholamban (PLB), along with decreased phosphorylation of Akt and Ca²⁺/calmodulin-dependent protein kinase II δ (CaMKII δ) was observed in RARαKO mouse hearts. Ca²⁺ reuptake and cardiomyocyte relaxation were delayed by RARα deletion. Overexpression of RARα or inhibition of ROS generation or NOX activation prevented RARα deletion-induced decrease in SERCA2a expression/activation and delayed Ca²⁺ reuptake. Moreover, the gene and protein expression of RARα was significantly decreased in aged or metabolic stressed mouse hearts. RARα deletion accelerated the development of diastolic dysfunction in streptozotocin (STZ)-induced type 1 diabetic mice or in high fat diet fed mice. In conclusion, myocardial RARα deletion promoted diastolic dysfunction, with a relative preserved LVEF. Increased oxidative stress have an important role in the decreased expression/activation of SERCA2a and Ca²⁺ mishandling in RARαKO mice, which are major contributing factors in the development of diastolic dysfunction. These data suggest that impairment of cardiac RARα signaling may be a novel mechanism that is directly linked to pathological stimuli-induced diastolic dysfunction.

Role of Hypoxia Inducible Factor 1 in Hyperglycemia-Exacerbated Blood-Brain Barrier Disruption in Ischemic Stroke

Diabetes is a major stroke risk factor and is associated with poor functional recovery after stroke. Accumulating evidence indicates that the worsened outcomes may be due to hyperglycemia-induced cerebral vascular complications, especially disruption of the blood-brain barrier (BBB). The present study tested a hypothesis that the activation of hypoxia inducible factor-1 (HIF-1) was involved in hyperglycemia-aggravated BBB disruption in an ischemic stroke model. Non-diabetic control and Streptozotocin-induced type I diabetic mice were subjected to 90min transient middle cerebral artery occlusion (MCAO) followed by reperfusion. Our results demonstrated that hyperglycemia induced higher expression of HIF-1α and vascular endothelial growth factor (VEGF) in brain microvessels after MCAO/reperfusion. Diabetic mice showed exacerbated BBB damage and tight junction disruption, increased infarct volume as well as worsened neurological deficits. Furthermore, suppressing HIF-1 activity by specific knock-out endothelial HIF-1α ameliorated BBB leakage and brain infarction in diabetic animals. Moreover, glycemic control by insulin abolished HIF-1α up-regulation in diabetic animals and reduced BBB permeability and brain infarction. These findings strongly indicate that HIF-1 plays an important role in hyperglycemia-induced exacerbation of BBB disruption in ischemic stroke. Endothelial HIF-1 inhibition warrants further investigation as a therapeutic target for the treatment of stroke patients with diabetes.

Structure and functions of angiotensinogen

Angiotensinogen (AGT) is the sole precursor of all angiotensin peptides. Although AGT is generally considered as a passive substrate of the renin-angiotensin system, there is accumulating evidence that the regulation and functions of AGT are intricate. Understanding the diversity of AGT properties has been enhanced by protein structural analysis and animal studies. In addition to whole-body genetic deletion, AGT can be regulated in vivo by cell-specific procedures, adeno-associated viral approaches and antisense oligonucleotides. Indeed, the availability of these multiple manipulations of AGT in vivo has provided new insights into the multifaceted roles of AGT. In this review, the combination of structural and functional studies is highlighted to focus on the increasing recognition that AGT exerts effects beyond being a sole provider of angiotensin peptides.

Activation of Foxo1 by insulin resistance promotes cardiac dysfunction and β-myosin heavy chain gene expression

BACKGROUND

Heart failure is a leading cause of morbidity and mortality in the USA and is closely associated with diabetes mellitus. The molecular link between diabetes mellitus and heart failure is incompletely understood. We recently demonstrated that insulin receptor substrates 1, 2 (IRS1, 2) are key components of insulin signaling and loss of IRS1 and IRS2 mediates insulin resistance, resulting in metabolic dysregulation and heart failure, which is associated with downstream Akt inactivation and in turn activation of the forkhead transcription factor Foxo1.

METHODS AND RESULTS

To determine the role of Foxo1 in control of heart failure in insulin resistance and diabetes mellitus, we generated mice lacking Foxo1 gene specifically in the heart. Mice lacking both IRS1 and IRS2 in adult hearts exhibited severe heart failure and a remarkable increase in the β-isoform of myosin heavy chain (β-MHC) gene expression, whereas deletion of cardiac Foxo1 gene largely prevented the heart failure and resulted in a decrease in β-MHC expression. The effect of Foxo1 deficiency on rescuing cardiac dysfunction was also observed in db/db mice and high-fat diet mice. Using cultures of primary ventricular cardiomyocytes, we found that Foxo1 interacts with the promoter region of β-MHC and stimulates gene expression, mediating an effect of insulin that suppresses β-MHC expression.

CONCLUSIONS

Our study suggests that Foxo1 has important roles in promoting diabetic cardiomyopathy and controls β-MHC expression in the development of cardiac dysfunction. Targeting Foxo1 and its regulation will provide novel strategies in preventing metabolic and myocardial dysfunction and influencing MHC plasticity in diabetes mellitus.

A possible mechanism for the progression of chronic renal disease and congestive heart failure

Chronic neurologic diseases such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, as well as various forms of chronic renal disease and systolic congestive heart failure, are among the most common progressive degenerative disorders encountered in medicine. Each disease follows a nearly relentless course, albeit at varying rates, driven by progressive cell dysfunction and drop-out. The neurologic diseases are characterized by the progressive spread of disease-causing proteins (prion-like proteins) from cell to cell. Recent evidence indicates that cell autonomous renin angiotensin systems operate in heart and kidney, and it is known that functional intracrine proteins can also spread between cells. This then suggests that certain progressive degenerative cardiovascular disorders such as forms of chronic renal insufficiency and systolic congestive heart failure result from dysfunctional renin angiotensin system intracrine action spreading in kidney or myocardium.

Cardiac-specific suppression of NF-κB signaling prevents diabetic cardiomyopathy via inhibition of the renin-angiotensin system

Activation of NF-κB signaling in the heart may be protective or deleterious depending on the pathological context. In diabetes, the role of NF-κB in cardiac dysfunction has been investigated using pharmacological approaches that have a limitation of being nonspecific. Furthermore, the specific cellular pathways by which NF-κB modulates heart function in diabetes have not been identified. To address these questions, we used a transgenic mouse line expressing mutated IκB-α in the heart (3M mice), which prevented activation of canonical NF-κB signaling. Diabetes was developed by streptozotocin injections in wild-type (WT) and 3M mice. Diabetic WT mice developed systolic and diastolic cardiac dysfunction by the 12th week, as measured by echocardiography. In contrast, cardiac function was preserved in 3M mice up to 24 wk of diabetes. Diabetes induced an elevation in cardiac oxidative stress in diabetic WT mice but not 3M mice compared with nondiabetic control mice. In diabetic WT mice, an increase in the phospholamban/sarco(endo)plasmic reticulum Ca(2+)-ATPase 2 ratio and decrease in ryanodine receptor expression were observed, whereas diabetic 3M mice showed an opposite effect on these parameters of Ca(2+) handling. Significantly, renin-angiotensin system activity was suppressed in diabetic 3M mice compared with an increase in WT animals. In conclusion, these results demonstrate that inhibition of NF-κB signaling in the heart prevents diabetes-induced cardiac dysfunction through preserved Ca(2+) handling and inhibition of the cardiac renin-angiotensin system.

Aliskiren inhibits prorenin-induced human aortic smooth muscle cell migration

BACKGROUND

In the present study, we investigated the potential effect of aliskiren on smooth muscle cell (SMC) migration in response to prorenin.

METHODS

Cultured human SMCs were incubated with angiotensinogen (ANG) (1.5 × 10(-7)M) and increasing concentrations of aliskiren (10(-6)-10(-5)M). After 24 h, SMC migration was assessed by Boyden's chamber chemotactic assay using prorenin as chemotactic factor (10(-8)M). The effect of aliskiren on RhoA and Rac activity was also determined by G-LISA assay and the lamellipodia formation by rhodamine-phalloidin staining. Changes in cell morphology were recorded in real-time using the iCelligence system.

RESULTS

Aliskiren determined, at 10(-5)M, a significant inhibition of SMC migration induced by prorenin (-66.4 ± 18.1%; p < 0.05), while no significant effect was observed when PDGF-BB was utilized as chemotactic agent. Aliskiren also reduced Rac-GTP levels in response to prorenin (-54.2 ± 5.4%) without affecting the RhoA-GTP levels. Finally, aliskiren inhibited both the lamellipodia formation and morphological changes induced by prorenin with no significant effect on PDGF-BB activity.

CONCLUSIONS

Taken together, we provide the first evidence of the inhibitory action of aliskiren on SMC migration induced by prorenin.

Angiotensin type 1a receptor-deficient mice develop diabetes-induced cardiac dysfunction, which is prevented by renin-angiotensin system inhibitors

Background

Diabetes-induced organ damage is significantly associated with the activation of the renin-angiotensin system (RAS). Recently, several studies have demonstrated a change in the RAS from an extracellular to an intracellular system, in several cell types, in response to high ambient glucose levels. In cardiac myocytes, intracellular angiotensin (ANG) II synthesis and actions are ACE and AT₁ independent, respectively. However, a role of this system in diabetes-induced organ damage is not clear.

Methods

To determine a role of the intracellular ANG II in diabetic cardiomyopathy, we induced diabetes using streptozotocin in AT_1a receptor deficient (AT_1a-KO) mice to exclude any effects of extracellular ANG II. Further, diabetic animals were treated with a renin inhibitor aliskiren, an ACE inhibitor benazeprilat, and an AT₁ receptor blocker valsartan.

Results

AT_1a-KO mice developed significant diastolic and systolic dysfunction following 10 wks of diabetes, as determined by echocardiography. All three drugs prevented the development of cardiac dysfunction in these animals, without affecting blood pressure or glucose levels. A significant down regulation of components of the kallikrein-kinin system (KKS) was observed in diabetic animals, which was largely prevented by benazeprilat and valsartan, while aliskiren normalized kininogen expression.

Conclusions

These data indicated that the AT_1a receptor, thus extracellular ANG II, are not required for the development of diabetic cardiomyopathy. The KKS might contribute to the beneficial effects of benazeprilat and valsartan in diabetic cardiomyopathy. A role of intracellular ANG II is suggested by the inhibitory effects of aliskiren, which needs confirmation in future studies.

Diabetic cardiomyopathy: Pathophysiology, diagnostic evaluation and management

Diabetes affects every organ in the body and cardiovascular disease accounts for two-thirds of the mortality in the diabetic population. Diabetes-related heart disease occurs in the form of coronary artery disease (CAD), cardiac autonomic neuropathy or diabetic cardiomyopathy (DbCM). The prevalence of cardiac failure is high in the diabetic population and DbCM is a common but underestimated cause of heart failure in diabetes. The pathogenesis of diabetic cardiomyopathy is yet to be clearly defined. Hyperglycemia, dyslipidemia and inflammation are thought to play key roles in the generation of reactive oxygen or nitrogen species which are in turn implicated. The myocardial interstitium undergoes alterations resulting in abnormal contractile function noted in DbCM. In the early stages of the disease diastolic dysfunction is the only abnormality, but systolic dysfunction supervenes in the later stages with impaired left ventricular ejection fraction. Transmitral Doppler echocardiography is usually used to assess diastolic dysfunction, but tissue Doppler Imaging and Cardiac Magnetic Resonance Imaging are being increasingly used recently for early detection of DbCM. The management of DbCM involves improvement in lifestyle, control of glucose and lipid abnormalities, and treatment of hypertension and CAD, if present. The role of vasoactive drugs and antioxidants is being explored. This review discusses the pathophysiology, diagnostic evaluation and management options of DbCM.