Cardiomyocyte-derived adiponectin is biologically active in protecting against myocardial ischemia-reperfusion injury

AdipoRon ameliorates chronic ethanol induced cardiac necroptosis by reducing ceramide mediated mtROS

Chronic ethanol (EtOH) consumption has been widely recognized as a significant contributor to cardiotoxicity. However, no specific treatment is currently available to ameliorate chronic ethanol induced cardiotoxicity. Adiponectin receptor agonist AdipoRon exerts protective effects in multiple organs through alleviating lipotoxicity. Our previous study showed that chronic ethanol consumption increased de novo ceramide synthesis and necroptosis in myocardium. In this study, we investigated the role of AdipoRon on ceramide metabolism and necroptosis in chronic ethanol-treated myocardium. Eight-week-old C57/BL6J mice were fed with a Lieber-Decarli diet containing vehicle or AdipoRon for 12 weeks. Cardiac function, histology and oxidative stress were assessed. We found that chronic ethanol treatment decreased expression of AdipoR2 in myocardium and H9c2 cells, whereas AdipoRon improved cardiac function, reduced myocardium ceramide levels and suppressed necroptosis. By pharmacological interventions, RNA interference and point mutations in AdipoR2, we demonstrated that AdipoRon reduced ceramide levels through PPARα mediated lipid metabolism rather than AdipoR2's ceramidase activity. Using transmission electron microscope and reactive oxygen species (ROS) staining, we showed that chronic ethanol induced myocardium mitochondria damage and mitochondrial reactive oxygen species (mtROS) accumulation. Meanwhile, we found that AdipoRon ameliorated chronic ethanol induced cardiac necroptosis via the SIRT3-SOD2-mtROS pathway. Moreover, C6 ceramide treatment recapitulated chronic ethanol in inducing mtROS and necroptosis, whereas the ceramide synthesis inhibitors myriocin (MYR) and fumonisin B1 (FB1) attenuated chronic ethanol induced mtROS and necroptosis. Collectively, AdipoRon ameliorates chronic ethanol induced cardiac necroptosis by reducing ceramide de novo synthesis and mtROS, which highlights the therapeutic potential of targeting ceramide metabolism and oxidative stress pathways in treating ethanol induced cardiotoxicity.

Adiponectin and Adiponectin Receptors in Atherosclerosis

Adiponectin is an abundantly secreted hormone that communicates information between the adipose tissue, and the immune and cardiovascular systems. In metabolically healthy individuals, adiponectin is usually found at high levels and helps improve insulin responsiveness of peripheral tissues, glucose tolerance, and fatty acid oxidation. Beyond its metabolic functions in insulin-sensitive tissues, adiponectin plays a prominent role in attenuating the development of atherosclerotic plaques, partially through regulating macrophage-mediated responses. In this context, adiponectin binds to its receptors, adiponectin receptor 1 (AdipoR1) and AdipoR2 on the cell surface of macrophages to activate a downstream signaling cascade and induce specific atheroprotective functions. Notably, macrophages modulate the stability of the plaque through their ability to switch between proinflammatory responders, and anti-inflammatory proresolving mediators. Traditionally, the extremes of the macrophage polarization spectrum span from M1 proinflammatory and M2 anti-inflammatory phenotypes. Previous evidence has demonstrated that the adiponectin-AdipoR pathway influences M1-M2 macrophage polarization; adiponectin promotes a shift toward an M2-like state, whereas AdipoR1- and AdipoR2-specific contributions are more nuanced. To explore these concepts in depth, we discuss in this review the effect of adiponectin and AdipoR1/R2 on 1) metabolic and immune responses, and 2) M1-M2 macrophage polarization, including their ability to attenuate atherosclerotic plaque inflammation, and their potential as therapeutic targets for clinical applications.

Adipokines and their potential impacts on susceptibility to myocardial ischemia/reperfusion injury in diabetes

Coronary artery disease has a high mortality rate and is a striking public health concern, affecting a substantial portion of the global population. On the early onset of myocardial ischemia, thrombolytic therapy and coronary revascularization could promptly restore the bloodstream and nutrient supply to the ischemic tissue, efficiently preserving less severely injured myocardium. However, the abrupt re-establishment of blood flow triggers the significant discharge of previously accumulated oxidative substances and inflammatory cytokines, leading to further harm referred to as ischemia/reperfusion (I/R) injury. Diabetes significantly raises the vulnerability of the heart to I/R injury due to disrupted glucose and lipid processing, impaired insulin sensitivity and metabolic signaling, and increased inflammatory responses. Numerous studies have indicated that adipokines are crucial in the etiology and pathogenesis of obesity, diabetes, hyperlipidemia, hypertension, and coronary artery disease. Adipokines such as adiponectin, adipsin, visfatin, chemerin, omentin, and apelin, which possess protective properties against inflammatory activity and insulin resistance, have been shown to confer myocardial protection in conditions such as atherosclerosis, myocardial hypertrophy, myocardial I/R injury, and diabetic complications. On the other hand, adipokines such as leptin and resistin, known for their pro-inflammatory characteristics, have been linked to elevated cardiac lipid deposition, insulin resistance, and fibrosis. Meteorin-like (metrnl) exhibits opposite effects in various pathological conditions. However, the data on adipokines in myocardial I/R, especially in diabetes, is still incomplete and controversial. This review focuses on recent research regarding the categorization and function of adipokines in the heart muscle, and the identification of different signaling pathways involved in myocardial I/R injury under diabetic conditions, aiming to facilitate the exploration of therapeutic strategies against myocardial I/R injury in diabetes.

Depleting inositol pyrophosphate 5-InsP7 protected the heart against ischaemia-reperfusion injury by elevating plasma adiponectin

AIMS

Adiponectin is an adipocyte-derived circulating protein that exerts cardiovascular and metabolic protection. Due to the futile degradation of endogenous adiponectin and the challenges of exogenous administration, regulatory mechanisms of adiponectin biosynthesis are of significant pharmacological interest.

METHODS AND RESULTS

Here, we report that 5-diphosphoinositol 1,2,3,4,6-pentakisphosphate (5-InsP7) generated by inositol hexakisphosphate kinase 1 (IP6K1) governed circulating adiponectin levels via thiol-mediated protein quality control in the secretory pathway. IP6K1 bound to adiponectin and DsbA-L and generated 5-InsP7 to stabilize adiponectin/ERp44 and DsbA-L/Ero1-Lα interactions, driving adiponectin intracellular degradation. Depleting 5-InsP7 by either IP6K1 deletion or pharmacological inhibition blocked intracellular adiponectin degradation. Whole-body and adipocyte-specific deletion of IP6K1 boosted plasma adiponectin levels, especially its high molecular weight forms, and activated AMPK-mediated protection against myocardial ischaemia-reperfusion injury. Pharmacological inhibition of 5-InsP7 biosynthesis in wild-type but not adiponectin knockout mice attenuated myocardial ischaemia-reperfusion injury.

CONCLUSION

Our findings revealed that 5-InsP7 is a physiological regulator of adiponectin biosynthesis that is amenable to pharmacological intervention for cardioprotection.

Adiponectin protects against myocardial ischemia-reperfusion injury: a systematic review and meta-analysis of preclinical animal studies

BACKGROUND

Myocardial ischemia-reperfusion injury (MIRI) is widespread in the treatment of ischemic heart disease, and its treatment options are currently limited. Adiponectin (APN) is an adipocytokine with cardioprotective properties; however, the mechanisms of APN in MIRI are unclear. Therefore, based on preclinical (animal model) evidence, the cardioprotective effects of APN and the underlying mechanisms were explored.

METHODS

The literature was searched for the protective effect of APN on MIRI in six databases until 16 November 2023, and data were extracted according to selection criteria. The outcomes were the size of the myocardial necrosis area and hemodynamics. Markers of oxidation, apoptosis, and inflammation were secondary outcome indicators. The quality evaluation was performed using the animal study evaluation scale recommended by the Systematic Review Center for Laboratory animal Experimentation statement. Stata/MP 14.0 software was used for the summary analysis.

RESULTS

In total, 20 papers with 426 animals were included in this study. The pooled analysis revealed that APN significantly reduced myocardial infarct size [weighted mean difference (WMD) = 16.67 (95% confidence interval (CI) = 13.18 to 20.16, P < 0.001)] and improved hemodynamics compared to the MIRI group [Left ventricular end-diastolic pressure: WMD = 5.96 (95% CI = 4.23 to 7.70, P < 0.001); + dP/dtmax: WMD = 1393.59 (95% CI = 972.57 to 1814.60, P < 0.001); -dP/dtmax: WMD = 850.06 (95% CI = 541.22 to 1158.90, P < 0.001); Left ventricular ejection fraction: WMD = 9.96 (95% CI = 7.29 to 12.63, P < 0.001)]. Apoptosis indicators [caspase-3: standardized mean difference (SMD) = 3.86 (95% CI = 2.97 to 4.76, P < 0.001); TUNEL-positive cells: WMD = 13.10 (95% CI = 8.15 to 18.05, P < 0.001)], inflammatory factor levels [TNF-α: SMD = 4.23 (95% CI = 2.48 to 5.98, P < 0.001)], oxidative stress indicators [Superoxide production: SMD = 4.53 (95% CI = 2.39 to 6.67, P < 0.001)], and lactate dehydrogenase levels [SMD = 2.82 (95% CI = 1.60 to 4.04, P < 0.001)] were significantly reduced. However, the superoxide dismutase content was significantly increased [SMD = 1.91 (95% CI = 1.17 to 2.65, P < 0.001)].

CONCLUSION

APN protects against MIRI via anti-inflammatory, antiapoptotic, and antioxidant effects, and this effect is achieved by activating different signaling pathways.

Hypoadiponectinemia-induced upregulation of microRNA449b downregulating Nrf-1 aggravates cardiac ischemia-reperfusion injury in diabetic mice

Diabetes enhances myocardial ischemic/reperfusion (MI/R) injury via an incompletely understood mechanism. Adiponectin (APN) is a cardioprotective adipokine suppressed by diabetes. However, how hypoadiponectinemia exacerbates cardiac injury remains incompletely understood. Dysregulation of miRNAs plays a significant role in disease development. However, whether hypoadiponectinemia alters cardiac miRNA profile, contributing to diabetic heart injury, remains unclear. Methods and Results: Wild-type (WT) and APN knockout (APN-KO) mice were subjected to MI/R. A cardiac microRNA profile was determined. Among 23 miRNAs increased in APN-KO mice following MI/R, miR-449b was most significantly upregulated (3.98-fold over WT mice). Administrating miR-449b mimic increased apoptosis, enlarged infarct size, and impaired cardiac function in WT mice. In contrast, anti-miR-449b decreased apoptosis, reduced infarct size, and improved cardiac function in APN-KO mice. Bioinformatic analysis predicted 73 miR-449b targeting genes, and GO analysis revealed oxidative stress as the top pathway regulated by these genes. Venn analysis followed by luciferase assay identified Nrf-1 and Ucp3 as the two most important miR-449b targets. In vivo administration of anti-miR-449b in APN-KO mice attenuated MI/R-stimulated superoxide overproduction. In vitro experiments demonstrated that high glucose/high lipid and simulated ischemia/reperfusion upregulated miR-449b and inhibited Nrf-1 and Ucp3 expression. These pathological effects were attenuated by anti-miR-449b or Nrf-1 overexpression. In a final attempt to validate our finding in a clinically relevant model, high-fat diet (HFD)-induced diabetic mice were subjected to MI/R and treated with anti-miR-449b or APN. Diabetes significantly increased miR-449b expression and downregulated Nrf-1 and Ucp3 expression. Administration of anti-miR-449b or APN preserved cardiac Nrf-1 expression, reduced cardiac oxidative stress, decreased apoptosis and infarct size, and improved cardiac function. Conclusion: We demonstrated for the first time that hypoadiponectinemia upregulates miR-449b and suppresses Nrf-1/Ucp3 expression, promoting oxidative stress and exacerbating MI/R injury in this population. Dysregulated APN/miR-449b/oxidative stress pathway is a potential therapeutic target against diabetic MI/R injury.

Diminished AdipoR1/APPL1 Interaction Mediates Reduced Cardioprotective Actions of Adiponectin against Myocardial Ischemia/Reperfusion Injury in Type-2 Diabetic Mice

Background

Obesity-related diseases have important implications for the occurrence, severity, and outcome of ischemic heart disease. Patients with obesity, hyperlipidemia, and diabetes mellitus (metabolic syndrome) are at increased risk of heart attack with decreased plasma lipocalin levels, and lipocalin is negatively correlated with heart attack incidence. APPL1 is a signaling protein with multiple functional structural domains and plays an important role in the APN signaling pathway. There are two known subtypes of lipocalin membrane receptors, AdipoR1 and AdipoR2. AdioR1 is mainly distributed in skeletal muscle while AdipoR2 is mainly distributed in the liver.

Objective

To clarify whether the AdipoR1-APPL1 signaling pathway mediates the effect of lipocalin in reducing myocardial ischemia/reperfusion injury and its mechanism will provide us with a new approach to treat myocardial ischemia/reperfusion injury using lipocalin as an intervention and therapeutic target.

Methods

(1) Induction of hypoxia/reoxygenation in SD mammary rat cardiomyocytes to simulate myocardial ischemia/reperfusion; (2) downregulation of APPL1 expression in cardiomyocytes to observe the effect of lipocalin on myocardial ischemia/reperfusion and its mechanism of action.

Results

(1) Primary mammary rat cardiomyocytes were isolated and cultured and induced to simulate MI/R by hypoxia/reoxygenation; (2) lipocalin inhibited H/R-induced apoptosis in cardiomyocytes; and (3) APN attenuated MI/R injury through AdipoR1-APPL1 and the possible mechanism.

Conclusion

This study demonstrates for the first time that lipocalin can attenuate myocardial ischemia/reperfusion injury through the AdipoR1-APPL1 signaling pathway and that the reduction of AdipoR1/APPL1 interaction plays an important role in cardiac APN resistance to MI/R injury in diabetic mice.

Constant-moderate versus high-intensity interval training on heart adiponectin levels in high-fat fed mice: a preventive and treatment approach

CONTEXT

Research has described that adiponectin plays a key role in cardiomyocytes metabolism, however, the effects of exercise during obesity on cardiac adiponectin levels is unclear.

OBJECTIVE

To investigate the effects of constant-moderate endurance (END) and high-intensity interval training (HIIT), on heart adiponectin levels in mice.

MATERIAL AND METHODS

Two experiments were conducted: (1) preventive (EX1): 10 week-old male mice were fed standard (CHOW) or high-fat diet (HFD;45% fat) and simultaneously trained with END and HIIT for 10 weeks; (2) Treatment (EX2): after 10 weeks of dietary intervention, another cohort of 10 week-old mice were trained by both programmes for 10 weeks.

RESULTS

In EX1, END and HIIT decreased low-molecular weight adiponectin (∼0.5-fold; p < 0.05) and increased GLUT4 levels (∼2-fold; p < .05). In EX2, HFD significantly decreased high-molecular weight adiponectin (∼0.7-fold; p < .05), and END reversed this change.Discussion and conclusion: HFD and exercise influence heart adiponectin isoforms and therefore might impact cardiomyocyte metabolism.

The importance of caveolin as a target in the prevention and treatment of diabetic cardiomyopathy

The diabetic population has been increasing in the past decades and diabetic cardiomyopathy (DCM), a pathology that is defined by the presence of cardiac remodeling and dysfunction without conventional cardiac risk factors such as hypertension and coronary heart diseases, would eventually lead to fatal heart failure in the absence of effective treatment. Impaired insulin signaling, commonly known as insulin resistance, plays an important role in the development of DCM. A family of integral membrane proteins named caveolins (mainly caveolin-1 and caveolin-3 in the myocardium) and a protein hormone adiponectin (APN) have all been shown to be important for maintaining normal insulin signaling. Abnormalities in caveolins and APN have respectively been demonstrated to cause DCM. This review aims to summarize recent research findings of the roles and mechanisms of caveolins and APN in the development of DCM, and also explore the possible interplay between caveolins and APN.

Rosiglitazone Does Not Show Major Hidden Cardiotoxicity in Models of Ischemia/Reperfusion but Abolishes Ischemic Preconditioning-Induced Antiarrhythmic Effects in Rats In Vivo

Clinical observations are highly inconsistent with the use of the antidiabetic rosiglitazone regarding its associated increased risk of myocardial infarction. This may be due to its hidden cardiotoxic properties that have only become evident during post-marketing studies. Therefore, we aimed to investigate the hidden cardiotoxicity of rosiglitazone in ischemia/reperfusion (I/R) injury models. Rats were treated orally with either 0.8 mg/kg/day rosiglitazone or vehicle for 28 days and subjected to I/R with or without cardioprotective ischemic preconditioning (IPC). Rosiglitazone did not affect mortality, arrhythmia score, or infarct size during I/R. However, rosiglitazone abolished the antiarrhythmic effects of IPC. To investigate the direct effect of rosiglitazone on cardiomyocytes, we utilized adult rat cardiomyocytes (ARCMs), AC16, and differentiated AC16 (diffAC16) human cardiac cell lines. These were subjected to simulated I/R in the presence of rosiglitazone. Rosiglitazone improved cell survival of ARCMs at 0.3 μM. At 0.1 and 0.3 μM, rosiglitazone improved cell survival of AC16s but not that of diffAC16s. This is the first demonstration that chronic administration of rosiglitazone does not result in major hidden cardiotoxic effects in myocardial I/R injury models. However, the inhibition of the antiarrhythmic effects of IPC may have some clinical relevance that needs to be further explored.

Targeting Adiponectin Receptor 1 Phosphorylation Against Ischemic Heart Failure

BACKGROUND

Despite significantly reduced acute myocardial infarction (MI) mortality in recent years, ischemic heart failure continues to escalate. Therapeutic interventions effectively reversing pathological remodeling are an urgent unmet medical need. We recently demonstrated that AdipoR1 (APN [adiponectin] receptor 1) phosphorylation by GRK2 (G-protein-coupled receptor kinase 2) contributes to maladaptive remodeling in the ischemic heart. The current study clarified the underlying mechanisms leading to AdipoR1 phosphorylative desensitization and investigated whether blocking AdipoR1 phosphorylation may restore its protective signaling, reversing post-MI remodeling.

METHODS

Specific sites and underlying molecular mechanisms responsible for AdipoR1 phosphorylative desensitization were investigated in vitro (neonatal and adult cardiomyocytes). The effects of AdipoR1 phosphorylation inhibition upon APN post-MI remodeling and heart failure progression were investigated in vivo.

RESULTS

Among 4 previously identified sites sensitive to GRK2 phosphorylation, alanine substitution of Ser²⁰⁵ (AdipoR1^S205A), but not other 3 sites, rescued GRK2-suppressed AdipoR1 functions, restoring APN-induced cell salvage kinase activation and reducing oxidative cell death. The molecular investigation followed by functional determination demonstrated that AdipoR1 phosphorylation promoted clathrin-dependent (not caveolae) endocytosis and lysosomal-mediated (not proteasome) degradation, reducing AdipoR1 protein level and suppressing AdipoR1-mediated cytoprotective action. GRK2-induced AdipoR1 endocytosis and degradation were blocked by AdipoR1^S205A overexpression. Moreover, AdipoR1^S205E (pseudophosphorylation) phenocopied GRK2 effects, promoted AdipoR1 endocytosis and degradation, and inhibited AdipoR1 biological function. Most importantly, AdipoR1 function was preserved during heart failure development in AdipoR1-KO (AdipoR1 knockout) mice reexpressing hAdipoR1^S205A. APN administration in the failing heart reversed post-MI remodeling and improved cardiac function. However, reexpressing hAdipoR1^WT in AdipoR1-KO mice failed to restore APN cardioprotection.

CONCLUSIONS

Ser²⁰⁵ is responsible for AdipoR1 phosphorylative desensitization in the failing heart. Blockade of AdipoR1 phosphorylation followed by pharmacological APN administration is a novel therapy effective in reversing post-MI remodeling and mitigating heart failure progression.

Angiotensin(1-7) Improves Islet Function in Diabetes Through Reducing JNK/Caspase-3 Signaling

The aim of this study is to investigate whether Angiotensin (1-7), the physiological antagonist of Angiotensin II (AngII), has antidiabetic activity and the possible mechanism. Male Wistar rats were randomly divided into 3 groups: control group fed the normal diet, DM group fed high-fat diet and injected with STZ, and Angiotensin (1-7) group receiving injection of STZ followed by Angiotensin (1-7) treatment. Serum Ang II, fasting blood glucose, insulin, HOMA-IR, and HOMA-beta were determined in control, diabetes and Angiotensin (1-7) groups. The increased AngII and insulin resistance in diabetes group were accompanied by changes in islet histopathology. However, Angiotensin (1-7) improved the islet function and histopathology in diabetes without affecting the level of AngII. Western blot confirmed that Angiotensin (1-7) decreased the cleaved caspase 3 levels in pancreas of DM. The increased expression of JNK, Bax, and Bcl2 genes under diabetic conditions were partially reversed after Angiotensin (1-7) administration in pancreas. Immunofluorescence analysis showed that p-JNK was markedly increased in islet of DM rats, which was markedly alleviated after Angiotensin (1-7) treatment. Furthermore, Angiotensin (1-7) reversed high glucose(HG) induced mitochondrial apoptosis augments. Finally, Angiotensin (1-7) attenuated the apoptosis of INS-1 cells through reducing JNK activation in diabetes, which was blocked by anisomycin (a potent agonist of JNK). Our findings provide supporting evidence that Angiotensin (1-7) improved the islet beta-cells apoptosis by JNK-mediated mitochondrial dysfunction, which might be a novel target for the treatment and prevention of beta-cells dysfunction in DM.

Coronary Heart Disease in Type 2 Diabetes Mellitus: Genetic Factors and Their Mechanisms, Gene-Gene, and Gene-Environment Interactions in the Asian Populations

Asians are more susceptible to type 2 diabetes mellitus (T2D) and its coronary heart disease (CHD) complications than the Western populations, possibly due to genetic factors, higher degrees of obesity, insulin resistance, and endothelial dysfunction that could occur even in healthy individuals. The genetic factors and their mechanisms, along with gene-gene and gene-environment interactions associated with CHD in T2D Asians, are yet to be explored. Therefore, the objectives of this paper were to review the current evidence of genetic factors for CHD, summarize the proposed mechanisms of these genes and how they may associate with CHD risk, and review the gene-gene and gene-environment interactions in T2D Asians with CHD. The genetic factors can be grouped according to their involvement in the energy and lipoprotein metabolism, vascular and endothelial pathology, antioxidation, cell cycle regulation, DNA damage repair, hormonal regulation of glucose metabolism, as well as cytoskeletal function and intracellular transport. Meanwhile, interactions between single nucleotide polymorphisms (SNPs) from different genes, SNPs within a single gene, and genetic interaction with environmental factors including obesity, smoking habit, and hyperlipidemia could modify the gene's effect on the disease risk. Collectively, these factors illustrate the complexities of CHD in T2D, specifically among Asians.

Egyptian practical guidance in hypertriglyceridemia management 2021

Hypertriglyceridemia (HTG) is a very common, yet underappreciated problem in clinical practice. Elevated triglyceride (TG) levels are independently associated with atherosclerotic cardiovascular disease (ASCVD) risk. Furthermore, severe HTG may lead to acute pancreatitis. Although LDL-guided statin therapy has improved ASCVD outcomes, residual risk remains. Recent trials have demonstrated that management of high TG levels, in patients already on statin therapy, reduces the rate of major vascular events. Few guidelines were issued, providing important recommendations for HTG management strategies. The goal of treatment is to reduce the risk of ASCVD and acute pancreatitis. The management stands on lifestyle modification, detection of secondary causes of HTG and pharmacological therapy, when indicated. In this guidance we review the causes and classification of HTG and summarize the current methods for risk estimation, diagnosis and treatment. The present guidance provides a focused update on the management of HTG, outlined in a simple user-friendly format, with an emphasis on the latest available data.

Crossroads between Estrogen Loss, Obesity, and Heart Failure with Preserved Ejection Fraction

The prevalence of obesity and heart failure with preserved ejection fraction (HFpEF) increases significantly in postmenopausal women. Although obesity is a risk factor for left ventricular diastolic dysfunction (LVDD), the mechanisms that link the cessation of ovarian hormone production, and particularly estrogens, to the development of obesity, LVDD, and HFpEF in aging females are unclear. Clinical, and epidemiologic studies show that postmenopausal women with abdominal obesity (defined by waist circumference) are at greater risk for developing HFpEF than men or women without abdominal obesity. The study presents a review of clinical data that support a mechanistic link between estrogen loss plus obesity and left ventricular remodeling with LVDD. It also seeks to discuss potential cell and molecular mechanisms for estrogen-mediated protection against adverse adipocyte cell types, tissue depots, function, and metabolism that may contribute to LVDD and HFpEF.

HMOX1 upregulation promotes ferroptosis in diabetic atherosclerosis

OBJECTIVE

Atherosclerotic vascular disease remains the principal cause of death and disability among patients with type 2 diabetes. Unfortunately, the problem is not adequately resolved by therapeutic strategies with currently available drugs or approaches that solely focus on optimal glycemic control. To identify the key contributors and better understand the mechanism of diabetic atherosclerotic vascular disease, we aimed to elucidate the key genetic characteristics and pathological pathways in atherosclerotic vascular disease through nonbiased bioinformatics analysis and subsequent experimental demonstration and exploration in diabetic atherosclerotic vascular disease.

METHODS AND RESULTS

Sixty-eight upregulated and 23 downregulated genes were identified from the analysis of gene expression profiles (GSE30169 and GSE6584). A comprehensive bioinformatic assay further identified that ferroptosis, a new type of programmed cell death and HMOX1 (a gene that encodes heme oxygenase), were vital factors in atherosclerotic vascular disease. We further demonstrated that diabetes significantly increased ferroptosis and HMOX1 levels compared to normal controls. Importantly, the ferroptosis inhibitor ferrostatin-1 (Fer-1) effectively attenuated diabetic atherosclerosis, suggesting the causative role of ferroptosis in diabetic atherosclerosis development. At the cellular level, Fer-1 ameliorated high glucose high lipid-induced lipid peroxidation and downregulated ROS production. More importantly, HMOX1 knockdown attenuated Fe2+ overload, reduced iron content and ROS, and alleviated lipid peroxidation, which led to a reduction in ferroptosis in diabetic human endothelial cells.

CONCLUSIONS

We demonstrated that HMOX1 upregulation is responsible for the increased ferroptosis in diabetic atherosclerosis development, suggesting that HMOX1 may serve as a potential therapeutic or drug development target for diabetic atherosclerosis.

The adiponectin signalling pathway - A therapeutic target for the cardiac complications of type 2 diabetes?

Diabetes is associated with an increased risk of heart failure (HF). This is commonly termed diabetic cardiomyopathy and is often characterised by increased cardiac fibrosis, pathological hypertrophy, increased oxidative and endoplasmic reticulum stress as well as diastolic dysfunction. Adiponectin is a cardioprotective adipokine that is downregulated in settings of type 2 diabetes (T2D) and obesity. Furthermore, both adiponectin receptors (AdipoR1 and R2) are also downregulated in these settings which further results in impaired cardiac adiponectin signalling and reduced cardioprotection. In many cardiac pathologies, adiponectin signalling has been shown to protect against cardiac remodelling and lipotoxicity, however its cardioprotective actions in T2D-induced cardiomyopathy remain unresolved. Diabetic cardiomyopathy has historically lacked effective treatment options. In this review, we summarise the current evidence for links between the suppressed adiponectin signalling pathway and cardiac dysfunction, in diabetes. We describe adiponectin receptor-mediated signalling pathways that are normally associated with cardioprotection, as well as current and potential future therapeutic approaches that could target this pathway as possible interventions for diabetic cardiomyopathy.

Heme-oxygenase and lipid mediators in obesity and associated cardiometabolic diseases: Therapeutic implications

Obesity-mediated metabolic syndrome remains the leading cause of death worldwide. Among many potential targets for pharmacological intervention, a promising strategy involves the heme oxygenase (HO) system, specifically its inducible form, HO-1. This review collects and updates much of the current knowledge relevant to pharmacology and clinical medicine concerning HO-1 in metabolic diseases and its effect on lipid metabolism. HO-1 has pleotropic effects that collectively reduce inflammation, while increasing vasodilation and insulin and leptin sensitivity. Recent reports indicate that HO-1 with its antioxidants via the effect of bilirubin increases formation of biologically active lipid metabolites such as epoxyeicosatrienoic acid (EET), omega-3 and other polyunsaturated fatty acids (PUFAs). Similarly, HO-1and bilirubin are potential therapeutic targets in the treatment of fat-induced liver diseases. HO-1-mediated upregulation of EET is capable not only of reversing endothelial dysfunction and hypertension, but also of reversing cardiac remodeling, a hallmark of the metabolic syndrome. This process involves browning of white fat tissue (i.e. formation of healthy adipocytes) and reduced lipotoxicity, which otherwise will be toxic to the heart. More importantly, this review examines the activity of EET in biological systems and a series of pathways that explain its mechanism of action and discusses how these might be exploited for potential therapeutic use. We also discuss the link between cardiac ectopic fat deposition and cardiac function in humans, which is similar to that described in obese mice and is regulated by HO-1-EET-PGC1α signaling, a potent negative regulator of the inflammatory adipokine NOV.

Rethinking pioglitazone as a cardioprotective agent: a new perspective on an overlooked drug

Since 1985, the thiazolidinedione pioglitazone has been widely used as an insulin sensitizer drug for type 2 diabetes mellitus (T2DM). Although fluid retention was early recognized as a safety concern, data from clinical trials have not provided conclusive evidence for a benefit or a harm on cardiac function, leaving the question unanswered. We reviewed the available evidence encompassing both in vitro and in vivo studies in tissues, isolated organs, animals and humans, including the evidence generated by major clinical trials. Despite the increased risk of hospitalization for heart failure due to fluid retention, pioglitazone is consistently associated with reduced risk of myocardial infarction and ischemic stroke both in primary and secondary prevention, without any proven direct harm on the myocardium. Moreover, it reduces atherosclerosis progression, in-stent restenosis after coronary stent implantation, progression rate from persistent to permanent atrial fibrillation, and reablation rate in diabetic patients with paroxysmal atrial fibrillation after catheter ablation. In fact, human and animal studies consistently report direct beneficial effects on cardiomyocytes electrophysiology, energetic metabolism, ischemia–reperfusion injury, cardiac remodeling, neurohormonal activation, pulmonary circulation and biventricular systo-diastolic functions. The mechanisms involved may rely either on anti-remodeling properties (endothelium protective, inflammation-modulating, anti-proliferative and anti-fibrotic properties) and/or on metabolic (adipose tissue metabolism, increased HDL cholesterol) and neurohormonal (renin–angiotensin–aldosterone system, sympathetic nervous system, and adiponectin) modulation of the cardiovascular system. With appropriate prescription and titration, pioglitazone remains a useful tool in the arsenal of the clinical diabetologist.

The adipokine Retnla deficiency increases responsiveness to cardiac repair through adiponectin-rich bone marrow cells

Resistin-like alpha (Retnla) is a member of the resistin family and known to modulate fibrosis and inflammation. Here, we investigated the role of Retnla in the cardiac injury model. Myocardial infarction (MI) was induced in wild type (WT), Retnla knockout (KO), and Retnla transgenic (TG) mice. Cardiac function was assessed by echocardiography and was significantly preserved in the KO mice, while worsened in the TG group. Angiogenesis was substantially increased in the KO mice, and cardiomyocyte apoptosis was markedly suppressed in the KO mice. By Retnla treatment, the expression of p21 and the ratio of Bax to Bcl2 were increased in cardiomyocytes, while decreased in cardiac fibroblasts. Interestingly, the numbers of cardiac macrophages and unsorted bone marrow cells (UBCs) were higher in the KO mice than in the WT mice. Besides, phosphorylated histone H3(+) cells were more frequent in bone marrow of KO mice. Moreover, adiponectin in UBCs was notably higher in the KO mice compared with WT mice. In an adoptive transfer study, UBCs were isolated from KO mice to transplant to the WT infarcted heart. Cardiac function was better in the KO-UBCs transplanted group in the WT-UBCs transplanted group. Taken together, proliferative and adiponectin-rich bone marrow niche was associated with substantial cardiac recovery by suppression of cardiac apoptosis and proliferation of cardiac fibroblast.

Mechanisms Involved in Cardioprotection Induced by Physical Exercise

Significance: Regular exercise training can reduce myocardial damage caused by acute ischemia/reperfusion (I/R). Exercise can reproduce the phenomenon of ischemic preconditioning, due to the capacity of brief periods of ischemia to reduce myocardial damage caused by acute I/R. In addition, exercise may also activate the multiple kinase cascade responsible for cardioprotection even in the absence of ischemia. Recent Advances: Animal and human studies highlighted the fact that, besides to reduce risk factors related to cardiovascular disease, the beneficial effects of exercise are also due to its ability to induce conditioning of the heart. Exercise behaves as a physiological stress that triggers beneficial adaptive cellular responses, inducing a protective phenotype in the heart. The factors contributing to the exercise-induced heart preconditioning include stimulation of the anti-radical defense system and nitric oxide production, opioids, myokines, and adenosine-5'-triphosphate (ATP) dependent potassium channels. They appear to be also involved in the protective effect exerted by exercise against cardiotoxicity related to chemotherapy. Critical Issues and Future Directions: Although several experimental evidences on the protective effect of exercise have been obtained, the mechanisms underlying this phenomenon have not yet been fully clarified. Further studies are warranted to define precise exercise prescriptions in patients at risk of myocardial infarction or undergoing chemotherapy.

Ube2s-stabilized β-catenin protects against myocardial ischemia/reperfusion injury by activating HIF-1α signaling

The activation of hypoxia-inducible factor (HIF) is an important event for mediating the adaptive response to myocardial ischemia/reperfusion (MI/R) injury. The ubiquitin-conjugating enzyme E2S (Ube2s) catalyzes ubiquitin conjugation to target proteins. Here, we report the positive regulation of HIF-1α signaling by Ube2s via stabilizing β-catenin, by which Ube2s acts to protect against MI/R injury. We show that Ube2s expression is upregulated in the hearts of mice subjected to MI/R injury. Functionally, Ube2s depletion exacerbates and its overexpression ameliorates MI/R injury. In addition, Ube2s augments the activation of HIF-1α and reduces myocardial apoptosis. Moreover, Ube2s induces the accumulation of β-Catenin through increasing its stabilization. Importantly, β-Catenin knockdown abrogates Ube2s-augmented HIF-1α activation, and meanwhile, diminishes the protective effect of Ube2s on MI/R injury, thus establishing a causal link between Ube2s-stabilized β-catenin and HIF-1α-mediated myocardial protection. Altogether, this study identifies the Ube2s/β-catenin/HIF-1α axis as a novel protective regulator involved in MI/R injury, and also implies that it might represent a potential therapeutic target for ameliorating MI/R injury.

C1q/TNF-related protein 5 contributes to diabetic vascular endothelium dysfunction through promoting Nox-1 signaling

OBJECTIVE

Dysregulated adipokine profiles contribute to the pathogenesis of diabetic cardiovascular complications. Endothelial cell (EC) dysfunction, a common pathological alteration in cardiovascular disorders, is exaggerated in diabetes. However, it is unclear whether and how dysregulated adipokines may contribute to diabetic EC dysfunction.

METHODS AND RESULTS

Serum C1q/TNF-Related Protein 5 (CTRP5) were determined in control/diabetes patients, and control/diabetic mice (high-fat diet, HFD). We observed for the first time that serum total CTRP5 was increased, high molecular weight (HMW) form was decreased, but the globular form (gCTRP5) was significantly increased in diabetic patients. These pathological alterations were reproduced in diabetic mice. To determine the pathological significance of increased gCTRP5 in diabetes, in vivo, ex vivo and in vitro experiments were performed. Diabetic atherosclerosis and EC dysfunction were significantly attenuated by the in vivo administration of CTRP5 neutralization antibody (CTRP5Ab). EC apoptosis was significantly increased in diabetic EC (isolated from HFD animal aorta) or high glucose high lipid (HGHL) cultured HUVECs. These pathological alterations were further potentiated by gCTRP5 and attenuated by CTRP5Ab. Pathway specific discovery-driven approach revealed that Nox1 expression was one of the signaling molecules commonly activated by HFD, HGHL, and gCTRP5. Treatment with CTRP5Ab reversed HFD-induced Nox1 upregulation. Finally, Nox1siRNA was used to determine the causative role of Nox1 in gCTRP5 induced EC apoptosis in diabetes. Results showed that gCTRP5 activated the mitochondrial apoptotic signal of EC in diabetes, which was blocked by the silencing Nox1 gene.

CONCLUSION

We demonstrated for the first time that gCTRP5 is a novel molecule contributing to diabetic vascular EC dysfunction through Nox1-mediated mitochondrial apoptosis, suggesting that interventions blocking gCTRP5 may protect diabetic EC function, ultimately attenuate diabetic cardiovascular complications.

Peripheral adiponectin levels in anxiety, mood, trauma- and stressor-related disorders: A systematic review and meta-analysis

BACKGROUND

Anxiety, mood, trauma- and stressor-related disorders confer increased risk for metabolic disease. Adiponectin, a cytokine released by adipose tissue is associated with these disorders and obesity via inflammatory processes. Available data describing associations with mental disorders remain limited and conflicted.

METHODS

A systematic search was conducted for English, peer-reviewed articles from inception until February 2019 that assessed for serum or plasma adiponectin levels in adults with an anxiety, mood or trauma-related disorder. Diagnoses were determined by psychiatric interview, based on DSM-IV, DSM-5 or ICD-10 criteria. Analyses were performed using STATA 15 and Standardized mean difference (SMD) with 95% confidence interval was applied to pool the effect size of meta-analysis studies.

RESULTS

In total 65 eligible studies were included in the systematic review and 30 studies in this meta-analysis. 19,178 participants (11,262 females and 7916 males), comprising healthy adults and adults with anxiety, mood and trauma-related disorders, were included. Overall results indicated an inverse association between adiponectin levels and examined mental disorders. Specifically, patients with an anxiety disorder (SMD  = -1.18 µg/mL, 95% CI, -2.34; -0.01, p  = 0.047); trauma or stressor-related disorder (SMD  =  -0.34 µg/mL, 95% CI, -0.52; -0.17, p  = 0.0000) or bipolar disorder (SMD  =  -0.638 µg/mL, 95% CI, -1.16, -0.12, p  = 0.017) had significant lower adiponectin levels compared to healthy adults.

LIMITATIONS

Heterogeneity, potential publication bias, and lack of control for important potential confounders were significant limitations.

CONCLUSION

Peripheral adiponectin levels appear to be inversely associated with anxiety, mood, trauma- and stressor related disorders and may be a promising biomarker for diagnosis and disease monitoring.

Adiponectin determines farnesoid X receptor agonism-mediated cardioprotection against post-infarction remodelling and dysfunction

Aims

The farnesoid X receptor (FXR) is a member of the metabolic nuclear receptor superfamily that plays a critical regulatory role in cardiovascular physiology/pathology. However, the role of systemic FXR activation in the chronic phase in myocardial infarction (MI)-induced cardiac remodelling and dysfunction remains unclear. In this study, we aimed to elucidate the role of long-term FXR activation on post-MI cardiac remodelling and dysfunction.

Methods and results

Mice underwent either MI surgery or sham operation. At 1 week after MI, both sham and MI mice were gavaged with 25 mg/kg/d of a synthetic FXR agonist (GW4064) or a vehicle control for 7 weeks, and cardiac performance was assessed by consecutive echocardiography studies. Administration of GW4064 significantly increased left ventricular ejection fraction at 4 weeks and 8 weeks after MI (both P < 0.01). Moreover, GW4064 treatment increased angiogenesis and mitochondrial biogenesis, reduced cardiomyocyte loss and inflammation, and ameliorated cardiac remodelling as evidenced by heart weight, lung weight, atrial natriuretic peptide/brain natriuretic peptide levels, and myocardial fibrosis at 8 weeks post-MI. At the molecular level, GW4064 significantly increased FXR mRNA expression and transcriptional activity in heart tissue. Moreover, over-expression of myocardial FXR failed to exert significant cardioprotection in vivo, indicating that GW4064 improved post-MI heart remodelling and function independent of myocardial FXR expression/activity. Among the four down-stream soluble molecules of FXR, plasma adiponectin was most significantly increased by GW4064. In cultured adipocytes, GW4064 increased mRNA levels and protein expression of adiponectin. Conditioned medium of GW4064-treated adipocytes activated AMPK-PGC-1α signalling and reduced hypoxia-induced cardiomyocyte apoptosis, all of which were attenuated by an adiponectin neutralizing anti-body. More importantly, when knocking-out adiponectin in mice, the cardioprotective effects of GW4064 were attenuated.

Conclusions

We are the first to show that FXR agonism ameliorated post-MI cardiac dysfunction and remodelling by stimulating adiponectin secretion. Thus, we demonstrated that FXR agonism is a potential therapeutic strategy in post-MI heart failure.

Withaferin A Prevents Myocardial Ischemia/Reperfusion Injury by Upregulating AMP-Activated Protein Kinase-Dependent B-Cell Lymphoma2 Signaling

BACKGROUND

Withaferin A (WFA), an anticancer constituent of the plant Withania somnifera, inhibits tumor growth in association with apoptosis induction. However, the potential role of WFA in the cardiovascular system is little-studied and controversial.

METHODS AND RESULTS

Two different doses of WFA were tested to determine their cardioprotective effects in myocardial ischemia/reperfusion (MI/R) injury through evaluation of cardiofunction in wild-type and AMP-activated protein kinase domain negative (AMPK-DN) gentransgenic mice. Surprisingly, cardioprotective effects (improved cardiac function and reduced infarct size) were observed with low-dose WFA (1 mg/kg) delivery but not high-dose (5 mg/kg). Mechanistically, low-dose WFA attenuated myocardial apoptosis. It decreased MI/R-induced activation of caspase 9, the indicator of the intrinsic mitochondrial pathway, but not caspase 8. It also upregulated the level of AMP-activated protein kinase (AMPK) phosphorylation and increased the MI/R inhibited ratio of Bcl2/Bax. In AMPK-deficient mice, WFA did not ameliorate MI/R-induced cardiac dysfunction, attenuate infarct size, or restore the Bcl2/Bax (B-cell lymphoma2/Mcl-2-like protein 4) ratio.

CONCLUSIONS

These results demonstrated for the first time that low-dose WFA is cardioprotective via upregulation of the anti-apoptotic mitochondrial pathway in an AMPK-dependent manner.

Exenatide reduces cardiomyocyte apoptosis by stimulating adiponectin secretion and activating APPL1-AMPK-PPARα axis

Background

To explore the mechanism that exenatide reduces cardiomyocyte apoptosis via the adiponectin pathway in vitro.

Methods

Cardiomyocytes were randomly divided into the control group (group C), diabetic group (group D), diabetic + exenatide treatment group (group DE), diabetic + exenatide treatment + APPL1 overexpression group (group OE), and diabetic + exenatide treatment + APPL1 knock-down group (group KD). After 48 h culture, the apoptosis rate, the adiponectin level in the cell culture fluid, and the expression levels of APPL1, p-AMPK, PPARα and NF-κB were detected by TUNEL, ELISA, and Western blotting, respectively.

Results

Compared to group C, the apoptosis rate was markedly increased, the adiponectin level was decreased, the expression of APPL1, p-AMPK and PPARα was down-regulated and that of NF-κB was up-regulated in group D (P<0.05); in group DE, the apoptosis rate was significantly decreased, the expression of APPL1, p-AMPK and PPARα was up-regulated and that of NF-κB was down-regulated, as compared with group D (P<0.05). The apoptosis rate in group OE was lower than that in group DE, the expression of APPL1, p-AMPK and PPARα was up-regulated and that of NF-κB was down-regulated (P<0.05). In group KD, the adiponectin level was elevated and the cardiomyocyte apoptosis rate was increased, as compared to group D (P<0.05). Furthermore, the expression of APPL1, p-AMPK and PPARα was down-regulated and that of NF-κB was up-regulated compared with group DE (P<0.05).

Conclusions

Exenatide can activate the "APPL1-AMPK-PPARα" anti-apoptosis signaling axis by promoting adiponectin expression in cardiomyocytes and reducing the apoptosis of diabetic cardiomyocytes, thus protecting cardiomyocytes.

Metabolic Messengers: Adiponectin

Adiponectin is one of the most widely studied adipokines to date. First described in the mid-1990's, studying its regulation, biogenesis and physiological effects has proven to be extremely insightful and improved our understanding of the mechanisms that ensure systemic metabolic homeostasis. Here, we provide a brief overview of the current state of the field with respect to adiponectin, its history, sites and mechanisms of action, and the critical questions that will need to be addressed in the future.

Withaferin A inhibits apoptosis via activated Akt-mediated inhibition of oxidative stress

Withaferin A (WFA), a withanolide derived from medicinal plant Withania somnifera, possesses anti-tumorigenic and immunomodulatory activities against various cancer cells. However, the role of WFA in myocardial ischemia reperfusion (MI/R) injury remains unclear. In the present study, we determined whether WFA may regulate cardiac ischemia reperfusion injury and elucidate the underlying mechanisms. We demonstrated that WFA enhanced H9c2 cells survival ability against simulated ischemia/reperfusion (SI/R) or hydrogen peroxide (H₂O₂)-induced cell apoptosis. In addition, the enhanced oxidative stress induced by SI/R was inhibited by WFA. Among the multiple antioxidant molecules determined, antioxidants SOD2, SOD3, Prdx-1 was obviously upregulated by WFA. When Akt inhibitor IV was administrated, WFA's suppression effect on oxidative stress was obviously abolished. Additional experiments demonstrated that WFA successfully inhibited H₂O₂ induced upregulation of SOD2, SOD3, and Prdx-1, ameliorated cardiomyocyte caspase-3 activity via an Akt dependent manner. Collectively, these results support the therapeutic potential of WFA against cardiac ischemia reperfusion injury and highlight the application of WFA in cardiovascular diseases holding great promise for the future.

Tanshinone modulates the expression of Bcl-2 and Bax in cardiomyocytes and has a protective effect in a rat model of myocardial ischemia-reperfusion

OBJECTIVE

To investigate the protective activity of tanshinone in a rat model of myocardial ischemia-reperfusion and determine its effect on the expression of Bcl-2 and Bax in cardiomyocytes.

METHODS

We established a rat model of myocardial ischemia-reperfusion. Rats were randomly divided into blank (no surgery); saline; and low-dose (2 mg/ml), medium-dose (15 mg/ml), and high-dose (50 mg/ml) tanshinone groups. We measured heart rate and troponin (cTnI) levels, performed TUNEL to detect cardiomyocyte apoptosis, and detected LDH and CK-MB activities in serum by ELISA. We performed RT-qPCR and western blot to detect the expression of Bcl-2 and Bax mRNA and protein in cardiomyocytes.

RESULTS

Rats treated with tanshinone experienced more stable heart rate after ischemia-reperfusion compared with those in the saline control group. cTnI decreased after ischemia-reperfusion in mice injected with tanshinone, while cTnI in saline-treated mice increased significantly compared with that in the blank control group. TUNEL staining showed that there were greater apoptotic cardiomyocytes in the saline group, but the tanshinone groups showed fewer apoptotic cardiomyocytes. LDH and CK-MB activities were significantly increased after reperfusion in the saline group (p<0.01) and also in the low- and medium-dose tanshinone groups (p<0.05). However, no significant differences were found in the high-dose tanshinone group (p>0.05). The expression levels of Bcl-2 mRNA and protein in cardiomyocytes of rats were higher in the three tanshinone groups in a dose-sensitive manner than those in the blank and saline groups (p<0.05). By contrast, the expression levels of Bax mRNA and protein were reduced in the three tanshinone groups in a dose-sensitive manner compared to those in the blank and saline groups (p<0.05).

CONCLUSION

Tanshinone shows a protective effect in a dose-dependent manner in a rat model of myocardial ischemia-reperfusion, suggesting its potential therapeutic use.

Cardiac-derived CTRP9 protects against myocardial ischemia/reperfusion injury via calreticulin-dependent inhibition of apoptosis

Cardiokines play an essential role in maintaining normal cardiac functions and responding to acute myocardial injury. Studies have demonstrated the heart itself is a significant source of C1q/TNF-related protein 9 (CTRP9). However, the biological role of cardiac-derived CTRP9 remains unclear. We hypothesize cardiac-derived CTRP9 responds to acute myocardial ischemia/reperfusion (MI/R) injury as a cardiokine. We explored the role of cardiac-derived CTRP9 in MI/R injury via genetic manipulation and a CTRP9-knockout (CTRP9-KO) animal model. Inhibition of cardiac CTRP9 exacerbated, whereas its overexpression ameliorated, left ventricular dysfunction and myocardial apoptosis. Endothelial CTRP9 expression was unchanged while cardiomyocyte CTRP9 levels decreased after simulated ischemia/`reperfusion (SI/R) in vitro. Cardiomyocyte CTRP9 overexpression inhibited SI/R-induced apoptosis, an effect abrogated by CTRP9 antibody. Mechanistically, cardiac-derived CTRP9 activated anti-apoptotic signaling pathways and inhibited endoplasmic reticulum (ER) stress-related apoptosis in MI/R injury. Notably, CTRP9 interacted with the ER molecular chaperone calreticulin (CRT) located on the cell surface and in the cytoplasm of cardiomyocytes. The CTRP9-CRT interaction activated the protein kinase A-cAMP response element binding protein (PKA-CREB) signaling pathway, blocked by functional neutralization of the autocrine CTRP9. Inhibition of either CRT or PKA blunted cardiac-derived CTRP9's anti-apoptotic actions against MI/R injury. We further confirmed these findings in CTRP9-KO rats. Together, these results demonstrate that autocrine CTRP9 of cardiomyocyte origin protects against MI/R injury via CRT association, activation of the PKA-CREB pathway, ultimately inhibiting cardiomyocyte apoptosis.

Osmotin Protects H9c2 Cells from Simulated Ischemia-Reperfusion Injury through AdipoR1/PI3K/AKT Signaling Pathway

Objective: This study aimed to investigate the effect of osmotin on myocardial ischemia/reperfusion (I/R), as well as the underlying mechanisms.

Methods:In vitro I/R injury model was established on rat cardiac myoblast H9c2 cells by oxygen and glucose deprivation followed by reperfusion (OGD/R). Cells were administrated with osmotin, and transfected with small interfering RNAs (siRNAs) which specifically target adiponectin receptor 1 or 2 (AdipoR1/2). Besides, the cells were incubated with or without LY294002 as inhibitor of phosphatidylinositol 3-kinase (PI3K) under OGD/R condition. Cell viability, apoptosis, expressions of apoptosis-related proteins and inflammatory factors were analyzed.

Results: The results showed that osmotin significantly increased H9c2 cells viability compared with the cells treated with vehicle (P < 0.05), and decreased H9c2 cells apoptosis by regulating expressions of apoptosis-related proteins. Moreover, we observed that osmotin statistically reduced the release of proinflammatory factors and increased the release of anti-inflammatory factors in H9c2 cells (P < 0.05). However, these effects were markedly reversed by AdipoR1 silence but not AdipoR2. Furthermore, osmotin dramatically upregulated the phosphorylation levels of PI3K, AKT, ERK, and downregulated the phosphorylation level of NF-κB (P < 0.05). While administration of LY294002 reduced cell viability, increased cell apoptosis, and aggravated inflammatory response (P < 0.05).

Conclusion: Our results suggested that the protective effect of osmotin on the simulated OGD/R injured H9c2 cells might be associated with AdipoR1/PI3K/AKT signaling pathway.

Nitric oxide/cyclic GMP pathway mediates the endothelin-1-upregulation of adiponectin expression in rat cardiomyocytes

Endothelin-1 (ET-1) serves an important role in the development of cardiac dysfunction and heart failure. ET-1 and angiotensin II (AngII) comprise a mutually reciprocal signalling network in the myocardium and serve similar or additive roles in the development of heart failure. Our previous study previously demonstrated that AngII upregulated the expression of APN in cardiomyocytes through an AngII receptor type 2/nitric oxide (NO)/cyclic GMP(cGMP)-dependent pathway. The purpose of the present study was to determine the effects of ET-1 and the additive effects of ET-1 and AngII on the gene expression and secretion of APN, and the underlying mechanisms involved. ELISA was used to determine the secretion of adiponectin (APN) and reverse transcription-quantitative polymerase chain reaction was used to evaluate the gene expression of APN. ET-1 induced APN secretion in a time- and dose-dependent manner, and induced APN secretion with AngII simultaneously, as determined via APN mRNA analyses. ETA and ETB receptors were also involved. The use of a NO synthase inhibitor and an analogue of cGMP antagonist resulted in a diminished ET-1- and/or AngII-mediated APN induction in cardiomyocytes. These results suggested that ET-1, as well as AngII, upregulated the gene expression and secretion of APN via the common NO/cGMP-mediated mechanism.

Down-regulation of lncRNA KCNQ1OT1 protects against myocardial ischemia/reperfusion injury following acute myocardial infarction

This study aimed to investigate the protective effects of long non-coding RNA KCNQ1OT1 against myocardial ischemia/reperfusion (I/R) injury following acute myocardial infarction, as well as its regulatory mechanism. We used the cardiac muscle H9c2 cells under condition of oxygen glucose deprivation followed by reperfusion (OGD/R) to induce myocardial I/R injury. Then H9C2 cells were transfected with si-NC, si-KCNQ1OT1, pc-NC, pc-KCNQ1OT1, si-AdipoR1 and si-AdipoR2, respectively. The myocardial cell viability and apoptosis were respectively detected. In addition, the expression levels of inflammatory factors, apoptosis-related proteins and p38 MAPK/NF-κB pathway-related proteins were detected. Besides, an inhibitor of p38 MAPK/NF-κB pathway SB203580 was used to treat cells to verify the relationship between KCNQ1OT1 and p38 MAPK/NF-κB pathway. The expression of KCNQ1OT1 was significantly up-regulated in OGD/R-induced myocardial H9C2 cells. The OGD/R-induced decreased cell viability and AdipoR1 expression could be reversed after suppression of KCNQ1OT1. In addition, suppression of KCNQ1OT1 reduced OGD/R-induced increased expressions of TNF-α, IL-6 and IL-1β and OGD/R-induced increased cell apoptosis, which were reversed after knockdown of AdipoR1. Besides, suppression of KCNQ1OT1 significantly down-regulated the OGD/R-induced increased expression of p-p38 and p-NF-κB, which were also reversed after knockdown of AdipoR1. Moreover, SB203580, an inhibitor of p38 MAPK/NF-κB signal pathway, could further enhance the inhibitory effects of KCNQ1OT1 suppression on the expression of p-p38, TNF-α, IL-6, IL-1β and p-NF-κB in OGD/R-induced myocardial H9C2 cells. Suppression of KCNQ1OT1 may prevent myocardial I/R injury following acute myocardial infarction via regulating AdipoR1 and involving in p38 MAPK/NF-κB signal pathway.

Induced Pluripotent Stem Cells-Derived Mesenchymal Stem Cells Attenuate Cigarette Smoke-Induced Cardiac Remodeling and Dysfunction

The strong relationship between cigarette smoking and cardiovascular disease (CVD) has been well-documented, but the mechanisms by which smoking increases CVD risk appear to be multifactorial and incompletely understood. Mesenchymal stem cells (MSCs) are regarded as an important candidate for cell-based therapy in CVD. We hypothesized that MSCs derived from induced pluripotent stem cell (iPSC-MSCs) or bone marrow (BM-MSCs) might alleviate cigarette smoke (CS)-induced cardiac injury. This study aimed to investigate the effects of BM-MSCs or iPSC-MSCs on CS-induced changes in serum and cardiac lipid profiles, oxidative stress and inflammation as well as cardiac function in a rat model of passive smoking. Male Sprague-Dawley rats were randomly selected for exposure to either sham air (SA) as control or 4% CS for 1 h per day for 56 days. On day 29 and 43, human adult BM-MSCs, iPSC-MSCs or PBS were administered intravenously to CS-exposed rats. Results from echocardiography, serum and cardiac lipid profiles, cardiac antioxidant capacity, cardiac pro- and anti-inflammatory cytokines and cardiac morphological changes were evaluated at the end of treatment. iPSC-MSC-treated group showed a greater effect in the improvement of CS-induced cardiac dysfunction over BM-MSCs-treated group as shown by increased percentage left ventricular ejection fraction and percentage fractional shortening, in line with the greater reversal of cardiac lipid abnormality. In addition, iPSC-MSCs administration attenuated CS-induced elevation of cardiac pro-inflammatory cytokines as well as restoration of anti-inflammatory cytokines and anti-oxidative markers, leading to ameliorate cardiac morphological abnormalities. These data suggest that iPSC-MSCs on one hand may restore CS-induced cardiac lipid abnormality and on the other hand may attenuate cardiac oxidative stress and inflammation via inhibition of CS-induced NF-κB activation, leading to improvement of cardiac remodeling and dysfunction. Thus, iPSC-MSCs may be a promising candidate in cell-based therapy to prevent cardiac complications in smokers.

Cardiovascular Adiponectin Resistance: The Critical Role of Adiponectin Receptor Modification

For the past two decades, a great deal of research has been published concerning adiponectin (APN), an abundant protein responsible for regulating numerous biologic functions including antioxidative, antinitrative, anti-inflammatory, and cardioprotective effects. A review of APN and its two major receptors is timely because of new findings concerning the mechanisms by which APN signaling may be altered in pathologic processes such as diabetes and heart failure. In this review we elaborate on currently known information regarding the physiologic role of APN and the known mechanisms underlying pathologic APN resistance - namely, APN receptor downregulation and phosphorylation - and provide insight regarding the future directions of APN research including an assessment of the clinical applicability of preventing pathologic post-translational modification of the APN receptor.

Role of Adipokines in Cardiovascular Disease

Cardiovascular disease (CVD) is the greatest cause of death, accounting for nearly one-third of all deaths worldwide. The increase in obesity rates over 3 decades is widespread and threatens the public health in both developed and developing countries. Obesity, the excessive accumulation of visceral fat, causes the clustering of metabolic disorders, such as type 2 diabetes, dyslipidemia, and hypertension, culminating in the development of CVD. Adipose tissue is not only an energy storage organ, but an active endocrine tissue producing various biologically active proteins known as adipokines. Since leptin, a central regulator of food intake and energy expenditure, was demonstrated to be an adipose-specific adipokine, attention has focused on the identification and characterization of unknown adipokines to clarify the mechanisms underlying obesity-related disorders. Numerous adipokines have been identified in the past 2 decades; most adipokines are upregulated in the obese state. Adipokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1β, and resistin are pro-inflammatory, and exacerbate various metabolic and cardiovascular diseases. However, a small number of adipokines, including adiponectin, are decreased by obesity, and generally exhibit antiinflammatory properties and protective functions against obesity-related diseases. Collectively, an imbalance in the production of pro- and antiinflammatory adipokines in the obese condition results in multiple complications. In this review, we focus on the pathophysiologic roles of adipokines with cardiovascular protective properties.

Cardioprotection of ischemic preconditioning in rats involves upregulating adiponectin

It has been reported that ischemic preconditioning (IPC) and adiponectin (APN) are cardioprotective in many cardiovascular disorders. However, whether APN mediates the effect of IPC on myocardial injury has not been elucidated. This study was conducted to investigate whether IPC affects myocardial ischemic injury by increasing APN expression. Male adult rats with cardiac knockdowns of APN and its receptors via intramyocardial small-interfering RNA injection were subjected to IPC and then myocardial infarction (MI) at 24 h after IPC. Globular APN (gAd) was injected at 10 min before MI. APN mRNA and protein levels in myocardium as well as the plasma APN concentration were markedly high at 6 and 12 h after IPC. IPC ameliorated myocardial injury as evidenced by improved cardiac functions and a reduced infarct size. Compared with the control MI group, rats in the IPC + MI group had elevated levels of left ventricular ejection fraction and fractional shortening and a smaller MI size (P < 0.05). However, the aforementioned protective effects were ameliorated in the absence of APN and APN receptors, followed by the inhibition of AMP-activated protein kinase (AMPK) phosphorylation, but reversed by gAd treatment in wild-type rats, and AMPK phosphorylation increased (P < 0.05). Overall, our results suggest that the cardioprotective effects of IPC are partially due to upregulation of APN and provide a further insight into IPC-mediated signaling effects.

Adiponectin protects the rats liver against chronic intermittent hypoxia induced injury through AMP-activated protein kinase pathway

This study was performed to assess the effect of chronic intermittent hypoxia (CIH) on the liver, the associated mechanisms and the potential therapeutic roles of adiponectin (Ad). Sixty rats were randomly assigned to four groups: the normal control (NC), NC and Ad supplement (NC + Ad), CIH, and CIH and Ad supplement (CIH + Ad) groups. The rats in the CIH and CIH + Ad groups were exposed to a hypoxic environment for 4 months. Rats in the NC + Ad and CIH + Ad groups were also treated with an intravenous injection of Ad (10 ug), twice a week. The plasma levels of hepatic enzymes, serum triglyceride, liver triglyceride, fasting blood glucose and hepatic cell apoptosis in hepatic tissue, were higher in the CIH group than in the NC and NC + Ad groups. However, the Ad supplementation in the CIH + Ad group rescued the hepatic tissue insult by activating the AMP-activated protein kinase (AMPK) pathway. In conclusion, Ad could protect against CIH-induced hepatic injury partly through the AMPK pathway.

Hyperglycemia Abrogates Ischemic Postconditioning Cardioprotection by Impairing AdipoR1/Caveolin-3/STAT3 Signaling in Diabetic Rats

Signal transducer and activator of transcription 3 (STAT3) activation is key for ischemic postconditioning (IPo) to attenuate myocardial ischemia-reperfusion injury (MIRI), but IPo loses cardioprotection in diabetes in which cardiac STAT3 activation is impaired and adiponectin (APN) reduced. We found that IPo increased postischemic cardiomyocyte-derived APN, activated mitochondrial STAT3 (mitoSTAT3), improved mitochondrial function, and attenuated MIRI in wild-type but not in APN knockout (Adipo(-/-)) mice subjected to 30 min coronary occlusion, followed by 2 or 24 h of reperfusion. Hypoxic postconditioning-induced protection against hypoxia/reoxygenation injury was lost in Adipo(-/-) cardiomyocytes but restored by recombinant APN, but this APN beneficial effect was abolished by specific STAT3 or APN receptor 1 (AdipoR1) gene knockdown, or caveolin-3 (Cav3) disruption. APN activated cardiac STAT3 and restored IPo cardioprotection in 4-week diabetic rats where AdipoR1 and Cav3 were functionally interactive but not in 8-week diabetic rats whose cardiac Cav3 was severely reduced and AdipoR1/Cav3 signaling impaired. We concluded that IPo activates mitoSTAT3 through APN/AdipoR1/Cav3 pathway to confer cardioprotection, whereas in diabetes, IPo loses cardioprotection due to impaired APN/AdipoR1/Cav3 signaling. Therefore, effective means that may concomitantly activate APN and repair APN signaling (i.e., AdipoR1/Cav3) in diabetes may represent promising avenues in the treatment of MIRI in diabetes.

Long-term allergen exposure induces adipose tissue inflammation and circulatory system injury

The purpose of this study was to study whether allergen exposure can induce inflammation and lower the anti-inflammation levels in serum and in adipose tissues, and further develop cardiovascular injury. Our data showed that heart rate was significantly higher in the OVA-challenged mice compared to control mice. Moreover, there were higher expressions of pro-inflammation genes in the OVA-challenged mice in adipose tissues, and the expressions of anti-inflammation genes were lower. The levels of inflammation mediators were associated in serum and adipose tissues. The level of circulatory injury lactate dehydrogenase was significantly associated with the levels of E-selectin, resistin and adiponectin in the serum. The hematoxylin and eosin and immunohistochemistry stains indicated the OVA-challenged mice had higher levels of inflammation. In summary, the current study demonstrated allergen exposure can cause cardiovascular injury, and inflammatory mediators in adipose tissues play an important role in the pathogenesis of cardiovascular injury.

Nrf2 signaling and redox homeostasis in the aging heart: A potential target to prevent cardiovascular diseases?

Aging process is often accompanied with a high incidence of cardiovascular diseases (CVD) due to the synergistic effects of age-related changes in heart morphology/function and prolonged exposure to injurious effects of CVD risk factors. Oxidative stress, considered a hallmark of aging, is also an important feature in pathologies that predispose to CVD development, like hypertension, diabetes and obesity. Approaches directed to prevent the occurrence of CVD during aging have been explored both in experimental models and in controlled clinical trials, in order to improve health span, reduce hospitalizations and increase life quality during elderly. In this review we discuss oxidative stress role as a main risk factor that relates CVD with aging. As well as interventions that aim to reduce oxidative stress by supplementing with exogenous antioxidants. In particular, strategies of improving the endogenous antioxidant defenses through activating the nuclear factor related-2 factor (Nrf2) pathway; one of the best studied molecules in cellular redox homeostasis and a master regulator of the antioxidant and phase II detoxification response.

Adiponectin downregulation is associated with volume overload-induced myocyte dysfunction in rats

AIM

Adiponectin has been reported to exert protective effects during pathological ventricular remodeling, but the role of adiponectin in volume overload-induced heart failure remains unclear. In this study we investigated the effect of adiponectin on cardiac myocyte contractile dysfunction following volume overload in rats.

METHODS

Volume overload was surgically induced in rats by infrarenal aorta-vena cava fistula. The rats were intravenously administered adenoviral adiponectin at 2-, 6- and 9-weeks following fistula. The protein expression of adiponectin, adiponectin receptors (AdipoR1/R2 and T-cadherin) and AMPK activity were measured using Western blot analyses. Isolated ventricular myocytes were prepared at 12 weeks post-fistula to examine the contractile performance of myocytes and intracellular Ca(2+) transient.

RESULTS

A-V fistula resulted in significant reductions in serum and myocardial adiponectin levels, myocardial adiponectin receptor (AdipoR1/R2 and T-cadherin) levels, as well as myocardial AMPK activity. Consistent with these changes, the isolated myocytes exhibited significant depression in cell shortening and intracellular Ca(2+) transient. Administration of adenoviral adiponectin significantly increased serum adiponectin levels and prevented myocyte contractile dysfunction in fistula rats. Furthermore, pretreatment of isolated myocytes with recombinant adiponectin (2.5 μg/mL) significantly improved their contractile performance in fistula rats, but had no effects in control or adenoviral adiponectin-administered rats.

CONCLUSION

These results demonstrate a positive correlation between adiponectin downregulation and volume overload-induced ventricular remodeling. Adiponectin plays a protective role in volume overload-induced heart failure.

TNF-α antagonism ameliorates myocardial ischemia-reperfusion injury in mice by upregulating adiponectin

Tumor necrosis factor-α (TNF-α) antagonism alleviates myocardial ischemia-reperfusion (MI/R) injury. However, the mechanisms by which the downstream mediators of TNF-α change after acute antagonism during MI/R remain unclear. Adiponectin (APN) exerts anti-ischemic effects, but it is downregulated during MI/R. This study was conducted to investigate whether TNF-α is responsible for the decrease of APN, and whether antagonizing TNF-α affects MI/R injury by increasing APN. Male adult wild-type (WT), APN knockout (APN KO) mice, and those with cardiac knockdowns of APN receptors via siRNA injection were subjected to 30 min of MI followed by reperfusion. The TNF-α antagonist etanercept or globular domain of APN (gAD) was injected 10 min before reperfusion. Etanercept ameliorated MI/R injury in WT mice as evidenced by improved cardiac function, and reduced infarct size and cardiomyocyte apoptosis. APN concentrations were augmented in response to etanercept, followed by an increase in AMP-activated protein kinase phosphorylation. Etanercept still increased cardiac function and reduced infarct size and apoptosis in both APN KO and APN receptors knockdown mice. However, its potential was significantly weakened in these mice compared with the WT mice. TNF-α is responsible for the decrease in APN during MI/R. The cardioprotective effects of TNF-α neutralization are partially due to the upregulation of APN. The results provide more insight into the TNF-α-mediated signaling effects during MI/R and support the need for clinical trials to validate the efficacy of acute TNF-α antagonism in the treatment of MI/R injury.

C1q-TNF-related protein-9, a novel cardioprotetcive cardiokine, requires proteolytic cleavage to generate a biologically active globular domain isoform

Prevalence and severity of postmyocardial infarction heart failure continually escalate in type 2 diabetes via incompletely understood mechanisms. The discovery of the cardiac secretomes, collectively known as "cardiokines", has significantly enhanced appreciation of the local microenvironment's influence on disease development. Recent studies demonstrated that C1q-TNF-related protein-9 (CTRP9), a newly discovered adiponectin (APN) paralog, is highly expressed in the heart. However, its relationship with APN (concerning diabetic cardiovascular injury in particular) remains unknown. Plasma CTRP9 levels are elevated in APN knockout and reduced in diabetic mice. In contrast to APN, which circulates as full-length multimers, CTRP9 circulates in the plasma primarily in the globular domain isoform (gCTRP9). Recombinant full-length CTRP9 (fCTRP9) was cleaved when incubated with cardiac tissue extracts, generating gCTRP9, a process inhibited by protease inhibitor cocktail. gCTRP9 rapidly activates cardiac survival kinases, including AMPK, Akt, and endothelial NOS. However, fCTRP9-mediated kinase activation is much less potent and significantly delayed. Kinase activation by fCTRP9, but not gCTRP9, is inhibited by protease inhibitor cocktail. These results demonstrate for the first time that the novel cardiokine CTRP9 undergoes proteolytic cleavage to generate gCTRP9, the dominant circulatory and actively cardioprotective isoform. Enhancing cardiac CTRP9 production and/or its proteolytic posttranslational modification are of therapeutic potential, attenuating diabetic cardiac injury.