Apelin regulates FoxO3 translocation to mediate cardioprotective responses to myocardial injury and obesity

Localized apelin-17 analogue-bicelle interactions as a facilitator of membrane-catalyzed receptor recognition and binding

The apelinergic system encompasses two peptide ligand families, apelin and apela, along with the apelin receptor (AR or APJ), a class A G-protein-coupled receptor. This system has diverse physiological effects, including modulating heart contraction, vasodilation/constriction, glucose regulation, and vascular development, with involvement in a variety of pathological conditions. Apelin peptides have been previously shown to interact with and become structured upon binding to anionic micelles, consistent with a membrane-catalyzed mechanism of ligand-receptor binding. To overcome the challenges of observing nuclear magnetic resonance (NMR) spectroscopy signals of a dilute peptide in biological environments, 19F NMR spectroscopy, including diffusion ordered spectroscopy (DOSY) and saturation transfer difference (STD) experiments, was used herein to explore the membrane-interactive behaviour of apelin. NMR-optimized apelin-17 analogues with 4-trifluoromethyl-phenylalanine at various positions were designed and tested for bioactivity through ERK activation in stably-AR transfected HEK 293 T cells. Far-UV circular dichroism (CD) spectropolarimetry and 19F NMR spectroscopy were used to compare the membrane interactions of these analogues with unlabelled apelin-17 in both zwitterionic/neutral and net-negative bicelle conditions. Each analogue binds to bicelles with relatively weak affinity (i.e., in fast exchange on the NMR timescale), with preferential interactions observed at the cationic residue-rich N-terminal and mid-length regions of the peptide leaving the C-terminal end unencumbered for receptor recognition, enabling a membrane-anchored fly-casting mechanism of peptide search for the receptor. In all, this study provides further insight into the membrane-interactive behaviour of an important bioactive peptide, demonstrating interactions and biophysical behaviour that cannot be neglected in therapeutic design.

The Apelin/APJ System: A Potential Therapeutic Target for Sepsis

Apelin is the native ligand for the G protein-coupled receptor APJ. Numerous studies have demonstrated that the Apelin/APJ system has positive inotropic, anti-inflammatory, and anti-apoptotic effects and regulates fluid homeostasis. The Apelin/APJ system has been demonstrated to play a protective role in sepsis and may serve as a promising therapeutic target for the treatment of sepsis. Better understanding of the mechanisms of the effects of the Apelin/APJ system will aid in the development of novel drugs for the treatment of sepsis. In this review, we provide a brief overview of the physiological role of the Apelin/APJ system and its role in sepsis.

Protective Role of Short-term Aerobic Exercise Against Zinc Oxide Nanoparticles-Induced Cardiac Oxidative Stress Via Possible Changes of Apelin, Angiotensin II/Angiotensin II Type I Signalling Pathway

This study examined the protective role of short-term aerobic exercise on ZnO NPs-induced cardiac oxidative stress and possible changes of apelin, angiotensin II (AngII) and angiotensin II type I receptor (AT1R) signalling pathway. Thirty-five male Wistar rats were randomized into five groups of seven rats, including control, saline, ZnO NPs, exercise and exercise + ZnO NPs groups. The animal in ZnO NPs and exercise + ZnO NPs groups received 1 mg/kg of ZnO NPs. Rats underwent the treadmill exercise program. Treatments lasted four weeks, 5 days/week. After 4 weeks of treatment, superoxide dismutase (SOD) activity, malondialdehyde (MDA), apelin, Ang II and AT1R concentration were measured in heart tissue.Cardiac MDA, Ang II and AT1R levels significantly increased while SOD activity and apelin levels significantly decreased following ZnO NPs administration. The aerobic exercise induced a significant increase in the SOD activity and apelin levels and a significant decrease in the enhanced MDA, Ang II and AT1R levels in the heart of ZnO NPs-exposed rats. These results suggest that the exercise-induced attenuation of the Ang II-AT1R signalling pathway is mediated by reduced lipid peroxidation, augmented antioxidant defence and enhanced apelin synthesis that may be a protective mechanism to prevent and/or treatment ZnO NPs-induced cardiac oxidative stress.

Apelin/ELABELA-APJ system in cardiac hypertrophy: Regulatory mechanisms and therapeutic potential

Heart failure is one of the most significant public health problems faced by millions of medical researchers worldwide. And pathological cardiac hypertrophy is considered one of the possible factors of increasing the risk of heart failure. Here, we introduce apelin/ELABELA-APJ system as a novel therapeutic target for cardiac hypertrophy, bringing about new directions in clinical treatment. Apelin has been proven to regulate cardiac hypertrophy through various pathways. And an increasing number of studies on ELABELA, the newly discovered endogenous ligand, suggest it can alleviate cardiac hypertrophy through mechanisms similar or different to apelin. In this review, we elaborate on the role that apelin/ELABELA-APJ system plays in cardiac hypertrophy and the intricate mechanisms that apelin/ELABELA-APJ affect cardiac hypertrophy. We also illuminate and make comparisons of the newly designed peptides and small molecules as agonists and antagonists for APJ, updating the breakthroughs in this field.

Apelin Is a Prototype of Novel Drugs for the Treatment of Acute Myocardial Infarction and Adverse Myocardial Remodeling

In-hospital mortality in patients with ST-segment elevation myocardial infarction (STEMI) is 5-6%. Consequently, it is necessary to develop fundamentally novel drugs capable of reducing mortality in patients with acute myocardial infarction. Apelins could be the prototype for such drugs. Chronic administration of apelins mitigates adverse myocardial remodeling in animals with myocardial infarction or pressure overload. The cardioprotective effect of apelins is accompanied by blockage of the MPT pore, GSK-3β, and the activation of PI3-kinase, Akt, ERK1/2, NO-synthase, superoxide dismutase, glutathione peroxidase, matrix metalloproteinase, the epidermal growth factor receptor, Src kinase, the mitoK_ATP channel, guanylyl cyclase, phospholipase C, protein kinase C, the Na⁺/H⁺ exchanger, and the Na⁺/Ca²⁺ exchanger. The cardioprotective effect of apelins is associated with the inhibition of apoptosis and ferroptosis. Apelins stimulate the autophagy of cardiomyocytes. Synthetic apelin analogues are prospective compounds for the development of novel cardioprotective drugs.

FoxO3 and oxidative stress: a multifaceted role in cellular adaptation

Oxidative stress is a major cause of morbidity and mortality in human health and disease. In this review, we focus on the Forkhead Box (Fox) subclass O3 (FoxO3), an extensively studied transcription factor that plays a pleiotropic role in a wide range of physiological and pathological processes by regulating multiple gene regulatory networks involved in the modulation of numerous aspects of cellular metabolism, including fuel metabolism, cell death, and stress resistance. This review will also focus on regulatory mechanisms of FoxO3 expression and activity, such as crucial post-translational modifications and non-coding RNAs. Moreover, this work discusses and evidences some pathways to how this transcription factor and reactive oxygen species regulate each other, which may lead to the pathogenesis of various types of diseases. Therefore, in addition to being a promising therapeutic target, the FoxO3-regulated signaling pathways can also be used as reliable diagnostic and prognostic biomarkers and indicators for drug responsiveness.

FOXO transcription factors as therapeutic targets in human diseases

Forkhead box (FOX)O proteins are transcription factors (TFs) with four members in mammals designated FOXO1, FOXO3, FOXO4, and FOXO6. FOXO TFs play a pivotal role in the cellular adaptation to diverse stress conditions. FOXO proteins act as context-dependent tumor suppressors and their dysregulation has been implicated in several age-related diseases. FOXO3 has been established as a major gene for human longevity. Accordingly, FOXO proteins have emerged as potential targets for the therapeutic development of drugs and geroprotectors. In this review, we provide an overview of the most recent advances in our understanding of FOXO regulation and function in various pathological conditions. We discuss strategies targeting FOXOs directly or by the modulation of upstream regulators, shedding light on the most promising intervention points. We also reveal the most relevant clinical indications and discuss the potential, trends, and challenges of modulating FOXO activity for therapeutic purposes.

Homocysteine promotes cardiac fibrosis by regulating the Akt/FoxO3 pathway

Background

Evaluated plasma homocysteine (Hcy) is an independent risk factor for cardiac fibrosis which is a common feature of cardiovascular disease, although the mechanisms are still unclear. This study aims to explore the mechanism of Hcy-induced cardiac fibrosis.

Methods

The mRNA and protein levels of Forkhead box O3 (FoxO3) and differentiation markers were detected in primary cardiac fibroblasts (CFs) after 300 µM Hcy treatment. Scratch and transwell migration assay were used to determine the effect of Hcy on proliferation and migration in CFs. The protein levels involved in the fibrotic processes in mice fed with high methionine diet (HMD) for 4 or 8 weeks were investigated by western blot. CFs were infected with FoxO3 recombinant adenovirus to explore the potential role of FoxO3 in Hcy-induced cardiac dysfunction.

Results

Hcy treatment significantly promoted the differentiation, proliferation and migration of CFs, while FoxO3 activity were decreased in CFs. In HMD hearts, the protein levels of TIMP1, Fibronectin and α-SMA were increased after 4 or 8 weeks, but the FoxO3 activity was decreased. Moreover, the HMD hearts had a higher level of Bcl2 but lower of Bax and LC3II protein. In addition, FoxO3 overexpression attenuates Hcy-induced dysfunction in CFs.

Conclusions

Hcy promotes myofibroblast activation and resistance to autophagy and apoptosis in CFs, and eventually results in cardiac fibrosis by regulating the Akt/FoxO3 pathway. Thus, FoxO3 is a promising therapeutic target to prevent cardiac remodeling.

Pericardial Adipose Tissue-Derived Leptin Promotes Myocardial Apoptosis in High-Fat Diet-Induced Obese Rats Through Janus Kinase 2/Reactive Oxygen Species/Na+/K+-ATPase Signaling Pathway

Background

Pathophysiologic mechanisms underlying cardiac structural and functional changes in obesity are complex and linked to adipocytokines released from pericardial adipose tissue (PAT) and cardiomyocyte apoptosis. Although leptin is involved in various pathological conditions, its role in paracrine action of pericardial adipose tissue on myocardial apoptosis remains unknown. This study was designed to investigate the role of PAT‐derived leptin on myocardial apoptosis in high‐fat diet–induced obese rats.

Methods and Results

Hearts were isolated from lean or high‐fat diet–induced obese Wistar rats for myocardial remodeling studies. Obese rats had abnormal myocardial structure, diastolic dysfunction, greatly elevated cardiac apoptosis, enhanced cardiac fibrosis, and increased oxidative stress level. ELISA detected significantly higher than circulating leptin level in PAT of obese, but not lean, rats. Western blot and immunohistochemical analyses demonstrated increased leptin receptor density in obese hearts. H9c2 cardiomyoblasts, after being exposed to PAT‐conditioned medium of obese rats, exhibited pronounced reactive oxygen species–mediated apoptosis, which was partially reversed by leptin antagonist. Moreover, leptin derived from PAT of obese rats inhibited Na⁺/K⁺‐ATPase activity of H9c2 cells through stimulating reactive oxygen species, thereby activating calcium‐dependent apoptosis. Pretreatment with specific inhibitors revealed that Janus kinase 2/signal transducer and activator of transcription 3 and phosphoinositide 3‐kinase/protein kinase B signaling pathways were involved in leptin‐induced myocardial apoptosis.

Conclusions

PAT‐derived leptin induces myocardial apoptosis in high‐fat diet–induced obese rats via activating Janus kinase 2/signal transducer and activator of transcription 3/reactive oxygen species signaling pathway and inhibiting its downstream Na⁺/K⁺‐ATPase activity.

miR-19a/b-3p promotes inflammation during cerebral ischemia/reperfusion injury via SIRT1/FoxO3/SPHK1 pathway

Background

Stroke affects 3–4% of adults and kills numerous people each year. Recovering blood flow with minimal reperfusion-induced injury is crucial. However, the mechanisms underlying reperfusion-induced injury, particularly inflammation, are not well understood. Here, we investigated the function of miR-19a/b-3p/SIRT1/FoxO3/SPHK1 axis in ischemia/reperfusion (I/R).

Methods

MCAO (middle cerebral artery occlusion) reperfusion rat model was used as the in vivo model of I/R. Cultured neuronal cells subjected to OGD/R (oxygen glucose deprivation/reperfusion) were used as the in vitro model of I/R. MTT assay was used to assess cell viability and TUNEL staining was used to measure cell apoptosis. H&E staining was employed to examine cell morphology. qRT-PCR and western blot were performed to determine levels of miR-19a/b-3p, SIRT1, FoxO3, SPHK1, NF-κB p65, and cytokines like TNF-α, IL-6, and IL-1β. EMSA and ChIP were performed to validate the interaction of FoxO3 with SPHK1 promoter. Dual luciferase assay and RIP were used to verify the binding of miR-19a/b-3p with SIRT1 mRNA.

Results

miR-19a/b-3p, FoxO3, SPHK1, NF-κB p65, and cytokines were elevated while SIRT1 was reduced in brain tissues following MCAO/reperfusion or in cells upon OGD/R. Knockdown of SPHK1 or FoxO3 suppressed I/R-induced inflammation and cell death. Furthermore, knockdown of FoxO3 reversed the effects of SIRT1 knockdown. Inhibition of the miR-19a/b-3p suppressed inflammation and this suppression was blocked by SIRT1 knockdown. FoxO3 bound SPHK1 promoter and activated its transcription. miR-19a/b-3p directly targeted SIRT1 mRNA.

Conclusion

miR-19a/b-3p promotes inflammatory responses during I/R via targeting SIRT1/FoxO3/SPHK1 axis.

Apelin/APJ-Manipulated CaMKK/AMPK/GSK3β Signaling Works as an Endogenous Counterinjury Mechanism in Promoting the Vitality of Random-Pattern Skin Flaps

A random-pattern skin flap plays an important role in the field of wound repair; the mechanisms that influence the survival of random-pattern skin flaps have been extensively studied but little attention has been paid to endogenous counterinjury substances and mechanism. Previous reports reveal that the apelin-APJ axis is an endogenous counterinjury mechanism that has considerable function in protecting against infection, inflammation, oxidative stress, necrosis, and apoptosis in various organs. As an in vivo study, our study proved that the apelin/APJ axis protected the skin flap by alleviating vascular oxidative stress and the apelin/APJ axis works as an antioxidant stress factor dependent on CaMKK/AMPK/GSK3β signaling. In addition, the apelin/APJ-manipulated CaMKK/AMPK/GSK3β-dependent mechanism improves HUVECs' resistance to oxygen and glucose deprivation/reperfusion (OGD/R), reduces ROS production and accumulation, maintained the normal mitochondrial membrane potential, and suppresses oxidative stress in vitro. Besides, activation of the apelin/APJ axis promotes vascular migration and angiogenesis under relative hypoxia condition through CaMKK/AMPK/GSK3β signaling. In a word, we provide new evidence that the apelin/APJ axis is an effective antioxidant and can significantly improve the vitality of random flaps, so it has potential be a promising clinical treatment.

Identification of Key Pathways and Genes in Obesity Using Bioinformatics Analysis and Molecular Docking Studies

Obesity is an excess accumulation of body fat. Its progression rate has remained high in recent years. Therefore, the aim of this study was to diagnose important differentially expressed genes (DEGs) associated in its development, which may be used as novel biomarkers or potential therapeutic targets for obesity. The gene expression profile of E-MTAB-6728 was downloaded from the database. After screening DEGs in each ArrayExpress dataset, we further used the robust rank aggregation method to diagnose 876 significant DEGs including 438 up regulated and 438 down regulated genes. Functional enrichment analysis was performed. These DEGs were shown to be significantly enriched in different obesity related pathways and GO functions. Then protein-protein interaction network, target genes - miRNA regulatory network and target genes - TF regulatory network were constructed and analyzed. The module analysis was performed based on the whole PPI network. We finally filtered out STAT3, CORO1C, SERPINH1, MVP, ITGB5, PCM1, SIRT1, EEF1G, PTEN and RPS2 hub genes. Hub genes were validated by ICH analysis, receiver operating curve (ROC) analysis and RT-PCR. Finally a molecular docking study was performed to find small drug molecules. The robust DEGs linked with the development of obesity were screened through the expression profile, and integrated bioinformatics analysis was conducted. Our study provides reliable molecular biomarkers for screening and diagnosis, prognosis as well as novel therapeutic targets for obesity.

MiR-302a-3p aggravates myocardial ischemia-reperfusion injury by suppressing mitophagy via targeting FOXO3

OBJECTIVE

This study aimed to investigate whether the protection of miR-302a-3p in myocardial ischemia-reperfusion injury (MIRI) is mediated through the suppression of mitophagy.

METHODS

We constructed a mouse I/R model in vivo by the ligation of left anterior descending coronary artery for 45 min followed by 2 h reperfusion, and an in vitro model by treating mouse cardiomyocytes with hypoxia-reoxygenation (H/R). Knockdown experiments were then performed in vivo and in vitro to determine the effects of miR-302a-3p knockdown on the mitophagy, mitochondrial dysfunction and oxidative stress and apoptosis. The potential targets of miR-302a-3p were further studied by bioinformatics analysis, luciferase assays, quantitative real-time PCR and western blotting.

RESULTS

MiR-302a-3p expression was significantly upregulated in mice subjected to MIRI and in H/R-treated mouse cardiomyocytes. Functional analyses demonstrated that inhibition of miR-302a-3p protected cardiac tissues against I/R-induced apoptosis and mitophagy, mitochondrial damage and mitochondrial oxidative stress. Furthermore, FOXO3 was identified as the direct target of miR-302a-3p. Mechanistically, knockdown of FOXO3 partially reversed the cardioprotective effects of miR-302a-3p inhibitor.

CONCLUSION

Our study suggested that inhibition of miR-302a-3p promoted mitochondrial autophagy and inhibited oxidative stress by targeting FOXO3 to suppress myocardial apoptosis, representing a potential target for MIRI treatment.

Chronic treatment with apelin, losartan and their combination reduces myocardial infarct size and improves cardiac mechanical function

The renin-angiotensin system (RAS) has a deleterious and apelin/APJ system has protective effect on the ischaemic heart. The collaboration between these systems in the pathophysiology of myocardial infarction is not clear. We determined the effect of chronic pretreatment with apelin, losartan and their combination on ischaemia-reperfusion (IR) injury in the isolated perfused rat heart and on the expression of apelin-13 receptor (APJ) and angiotensin type 1 receptor (AT1R) in the myocardium. During 5 days before the induction of IR, saline (vehicle), apelin-13 (Apl), F13A (apelin antagonist), losartan (Los, AT1R antagonist) and the combination of Apl and Los were administered intraperitoneally in rats. Ischaemia was induced by left anterior descending (LAD) artery occlusion for 30 minutes followed by reperfusion for 55 minutes in the Langendorff isolated heart perfusion system. Pretreatment with Apl, Los and the combination of Apl + Los significantly reduced infarct size by about 30, 33 and 48 percent respectively; and significantly improved the left ventricular function indices such as left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure (LVEDP) and rate pressure product (RPP). IR increased AT1R protein level but it did not change APJ significantly. AT1R expression was reduced in groups treated with Apl, Los and Apl + Los. Findings showed that chronic pretreatment with apelin along with AT1R antagonist had more protective effects against IR injury. Combination therapy may diminish the risk of IR-induced heart damage, by reducing AT1R expression, in the heart of patients with coronary artery disease that are at the risk of MI and reperfusion injury.

In vitro and in vivo cardioprotective and metabolic efficacy of vitamin E TPGS/Apelin

AIMS

Apelin and vitamin E have been proposed as signaling molecules, but their synergistic role is unknown. The aim of this work was to develop vitamin E TPGS/Apelin system to test their cardioprotective and metabolic efficacy in vitro and in vivo.

METHODS

FDA-approved surfactant D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS-1000) and Apelin complex were characterized by physico-chemical methods (CMC determination, dynamic light scattering and circular dichroism). In vitro studies were carried out on H9C2 cardiomyoblasts and isolated murine cardiomyocytes. In vivo studies were performed in isoproterenol- and high-fat diet-induced cardiac remodeling models in mice.

RESULTS

We found that vitamin E TPGS/Apelin provide cardioprotective and metabolic efficacy in vitro and in vivo. In vitro studies revealed that vitamin E TPGS/Apelin reduces hypoxia-induced mitochondrial ROS production in cultured cardiomyocytes and H9C2 cardiomyoblasts. In addition, vitamin E TPGS/Apelin confers apoptotic response to hypoxic stress in cells. In a mouse model of isoproterenol-induced cardiac injury, TPGS is not able to affect cardiac remodeling, however combination of vitamin E TPGS and Apelin counteracts myocardial apoptosis, oxidative stress, hypertrophy and fibrosis. Furthermore, combination treatment attenuated obesity-induced cardiometabolic and fibrotic remodeling in mice.

CONCLUSION

Together, our data demonstrated the therapeutic benefits of vitamin E TPGS/Apelin complex to combat cardiovascular and metabolic disorders.

The apelinergic system: a perspective on challenges and opportunities in cardiovascular and metabolic disorders

The apelinergic pathway has been generating increasing interest in the past few years for its potential as a therapeutic target in several conditions associated with the cardiovascular and metabolic systems. Indeed, preclinical and, more recently, clinical evidence both point to this G protein-coupled receptor as a target of interest in the treatment of not only cardiovascular disorders such as heart failure, pulmonary arterial hypertension, atherosclerosis, or septic shock, but also of additional conditions such as water retention/hyponatremic disorders, type 2 diabetes, and preeclampsia. While it is a peculiar system with its two classes of endogenous ligand, the apelins and Elabela, its intricacies are a matter of continuing investigation to finely pinpoint its potential and how it enables crosstalk between the vasculature and organ systems of interest. In this perspective article, we first review the current knowledge on the role of the apelinergic pathway in the above systems, as well as the associated therapeutic indications and existing pharmacological tools. We also offer a perspective on the challenges and potential ahead to advance the apelinergic system as a target for therapeutic intervention in several key areas.

International Union of Basic and Clinical Pharmacology. CVII. Structure and Pharmacology of the Apelin Receptor with a Recommendation that Elabela/Toddler Is a Second Endogenous Peptide Ligand

The predicted protein encoded by the APJ gene discovered in 1993 was originally classified as a class A G protein-coupled orphan receptor but was subsequently paired with a novel peptide ligand, apelin-36 in 1998. Substantial research identified a family of shorter peptides activating the apelin receptor, including apelin-17, apelin-13, and [Pyr1]apelin-13, with the latter peptide predominating in human plasma and cardiovascular system. A range of pharmacological tools have been developed, including radiolabeled ligands, analogs with improved plasma stability, peptides, and small molecules including biased agonists and antagonists, leading to the recommendation that the APJ gene be renamed APLNR and encode the apelin receptor protein. Recently, a second endogenous ligand has been identified and called Elabela/Toddler, a 54-amino acid peptide originally identified in the genomes of fish and humans but misclassified as noncoding. This precursor is also able to be cleaved to shorter sequences (32, 21, and 11 amino acids), and all are able to activate the apelin receptor and are blocked by apelin receptor antagonists. This review summarizes the pharmacology of these ligands and the apelin receptor, highlights the emerging physiologic and pathophysiological roles in a number of diseases, and recommends that Elabela/Toddler is a second endogenous peptide ligand of the apelin receptor protein.

Forkhead box O3 protects the heart against paraquat-induced aging-associated phenotypes by upregulating the expression of antioxidant enzymes

Paraquat (PQ) promotes cell senescence in brain tissue, which contributes to Parkinson's disease. Furthermore, PQ induces heart failure and oxidative damage, but it remains unknown whether and how PQ induces cardiac aging. Here, we demonstrate that PQ induces phenotypes associated with senescence of cardiomyocyte cell lines and results in cardiac aging‐associated phenotypes including cardiac remodeling and dysfunction in vivo. Moreover, PQ inhibits the activation of Forkhead box O3 (FoxO3), an important longevity factor, both in vitro and in vivo. We found that PQ‐induced senescence phenotypes, including proliferation inhibition, apoptosis, senescence‐associated β‐galactosidase activity, and p16^INK4a expression, were significantly enhanced by FoxO3 deficiency in cardiomyocytes. Notably, PQ‐induced cardiac remolding, apoptosis, oxidative damage, and p16^INK4a expression in hearts were exacerbated by FoxO3 deficiency. In addition, both in vitro deficiency and in vivo deficiency of FoxO3 greatly suppressed the activation of antioxidant enzymes including catalase (CAT) and superoxide dismutase 2 (SOD2) in the presence of PQ, which was accompanied by attenuation in cardiac function. The direct in vivo binding of FoxO3 to the promoters of the Cat and Sod2 genes in the heart was verified by chromatin immunoprecipitation (ChIP). Functionally, overexpression of Cat or Sod2 alleviated the PQ‐induced senescence phenotypes in FoxO3‐deficient cardiomyocyte cell lines. Overexpression of FoxO3 and CAT in hearts greatly suppressed the PQ‐induced heart injury and phenotypes associated with aging. Collectively, these results suggest that FoxO3 protects the heart against an aging‐associated decline in cardiac function in mice exposed to PQ, at least in part by upregulating the expression of antioxidant enzymes and suppressing oxidative stress.

The Significance of the Effect of Visceral Adiposity on Left Ventricular Diastolic Function in the General Population

We evaluated the association between visceral adiposity and left ventricular (LV) diastolic function in association with plasma adiponectin levels in 213 subjects without overt cardiac diseases. Abdominal visceral fat area was quantified by computed tomography. Excessive visceral fat was significantly associated with impaired diastolic parameters including E/A, E′ and E/E′. Although serum adiponectin levels decreased with increased visceral adiposity, there was no independent association between serum adiponectin levels and diastolic parameters, which suggest that the role of adiponectin in this association might be indirect.

Hepatic and cardiac beneficial effects of a long-acting Fc-apelin fusion protein in diet-induced obese mice

BACKGROUND

Apelin is a peptide ligand of the G-protein-coupled receptor APJ and exhibits anti-diabetes and anti-heart failure activities. However, short serum half-life of the apelin peptide limits its potential clinical applications. This study aimed to develop a long-acting apelin analog.

METHODS

To extend apelin's in vivo half-life, we made a recombinant protein by fusing the IgG Fc fragment to apelin-13 (Fc-apelin-13), conducted pharmacokinetics studies in mice, and determined in vitro biological activities in suppressing cyclic adenosine monophosphate and activating extracellular signal-regulated kinase signalling by reporter assays. We investigated the effects of Fc-apelin-13 on food intake, body weight, fasting blood glucose and insulin levels, glucose tolerance test, hepatic steatosis, and cardiac function and fibrosis by subcutaneous administration of Fc-apelin-13 in diet-induced obese mice for 4 weeks.

RESULTS

The estimated half-life of Fc-apelin-13 in blood was approximately 33 hours. Reporter assays showed that Fc-apelin-13 was active in suppressing cyclic adenosine monophosphate response element and activating serum response element activities. Four weeks of Fc-apelin-13 treatment in obese mice did not affect food intake and body weight, but resulted in a significant improvement of glucose tolerance, and a decrease in hepatic steatosis and fibrosis, as well as in serum alanine transaminase levels. Moreover, cardiac stroke volume and output were increased and cardiac fibrosis was decreased in the treated mice.

CONCLUSIONS

Fc-apelin-13 fusion protein has an extended in vivo half-life and exerts multiple benefits on obese mice with respect to the improvement of glucose disposal, amelioration of liver steatosis and heart fibrosis, and increase of cardiac output. Hence, Fc-apelin-13 is potentially a therapeutic for obesity-associated disease conditions.

Differential protein profiling as a potential multi-marker approach for obese patients with heart failure: A retrospective study

Identification of novel circulating biomarkers predicting death and major cardio-metabolic events in obese patients with heart failure (HF) remains a research priority. In this study, we compared multi-marker profile of non-obese (NOB) and obese (OB) HF patients in relation to mortality outcome. The new multiplex proximity extension assay technology was used to analyze the levels of 92 proteins in plasma samples from HF patients according to body mass index (BMI) categories. At 2-year follow-up, all-cause mortality rates were significantly greater in NOB patients (BMI < 30 kg/m²) compared to the OB patients (BMI > 30 kg/m²) with HF (odds ratio 26; 95% CI: 1.14–624, p < 0,04). Quantitative proteomic analysis revealed thirteen distinct proteins expression profiles of OB and NOB HF patients. Among these proteins, RAGE, CXCL6, CXCL1, CD40, NEMO, VEGF-A, KLK6, PECAM1, PAR1, MMP1, BNP and NTproBNP were down-regulated, whereas leptin was up-regulated in OB HF patients. In addition, an inverse correlation between plasma BNP levels and leptin in OB HF patients was observed (r = −0.58 p = 0.02). This study identifies specific plasma protein signature in OB and NOB patients with HF in relation to mortality outcome.

Over-expression of growth differentiation factor 15 (GDF15) preventing cold ischemia reperfusion (I/R) injury in heart transplantation through Foxo3a signaling

Ischemia reperfusion (I/R) injury which inevitably occurs during heart transplantation is the major factor leading to organ failure and graft rejection. In order to develop new therapies to prevent I/R injury, we used both a murine heart transplantation model with 24 hour cold I/R and an in vitro cell culture system to determine whether growth differentiation factor 15 (GDF15) is a protective factor in preventing I/R injury in heart transplantation and to further investigate underlying mechanisms of I/R injury. We found that cold I/R caused severe damage to the endocardium, epicardium and myocardium of heart grafts from wild type C57BL/6 mice, whereas grafts from GDF15 transgenic (TG) mice showed less damage as demonstrated by decreased cell apoptosis/death, decreased neutrophils infiltration and the preservation of the normal structure of the heart. Over-expression of GDF15 reduced expression of phosphorylated RelA p65, pre-inflammatory and pro-apoptotic genes while it enhanced Foxo3a phosphorylation in vitro and in vivo. Over-expression of GDF15 inhibited cell apoptosis/death and reduced neutrophil infiltration. In conclusion, this study, for the first time, demonstrates that GDF15 is a promising target for preventing cold I/R injury in heart transplantation. This study also shows that the resultant protective effects are mediated by the Foxo3 and NFκB signaling pathways.

Inhibition of PIKfyve prevents myocardial apoptosis and hypertrophy through activation of SIRT3 in obese mice

PIKfyve is an evolutionarily conserved lipid kinase that regulates pleiotropic cellular functions. Here, we identify PIKfyve as a key regulator of cardiometabolic status and mitochondrial integrity in chronic diet‐induced obesity. In vitro, we show that PIKfyve is critical for the control of mitochondrial fragmentation and hypertrophic and apoptotic responses to stress. We also provide evidence that inactivation of PIKfyve by the selective inhibitor STA suppresses excessive mitochondrial ROS production and apoptosis through a SIRT3‐dependent pathway in cardiomyoblasts. In addition, we report that chronic STA treatment improves cardiometabolic profile in a mouse model of cardiomyopathy linked to obesity. We provide evidence that PIKfyve inhibition reverses obesity‐induced cardiac mitochondrial damage and apoptosis by activating SIRT3. Furthermore, treatment of obese mice with STA improves left ventricular function and attenuates cardiac hypertrophy. In contrast, STA is not able to reduce isoproterenol‐induced cardiac hypertrophy in SIRT3.KO mice. Altogether, these results unravel a novel role for PIKfyve in obesity‐associated cardiomyopathy and provide a promising therapeutic strategy to combat cardiometabolic complications in obesity.

Apelinergic System Structure and Function

Apelin and apela (ELABELA/ELA/Toddler) are two peptide ligands for a class A G-protein-coupled receptor named the apelin receptor (AR/APJ/APLNR). Ligand-AR interactions have been implicated in regulation of the adipoinsular axis, cardiovascular system, and central nervous system alongside pathological processes. Each ligand may be processed into a variety of bioactive isoforms endogenously, with apelin ranging from 13 to 55 amino acids and apela from 11 to 32, typically being cleaved C-terminal to dibasic proprotein convertase cleavage sites. The C-terminal region of the respective precursor protein is retained and is responsible for receptor binding and subsequent activation. Interestingly, both apelin and apela exhibit isoform-dependent variability in potency and efficacy under various physiological and pathological conditions, but most studies focus on a single isoform. Biophysical behavior and structural properties of apelin and apela isoforms show strong correlations with functional studies, with key motifs now well determined for apelin. Unlike its ligands, the AR has been relatively difficult to characterize by biophysical techniques, with most characterization to date being focused on effects of mutagenesis. This situation may improve following a recently reported AR crystal structure, but there are still barriers to overcome in terms of comprehensive biophysical study. In this review, we summarize the three components of the apelinergic system in terms of structure-function correlation, with a particular focus on isoform-dependent properties, underlining the potential for regulation of the system through multiple endogenous ligands and isoforms, isoform-dependent pharmacological properties, and biological membrane-mediated receptor interaction. © 2018 American Physiological Society. Compr Physiol 8:407-450, 2018.

Therapeutic Benefit and Gene Network Regulation by Combined Gene Transfer of Apelin, FGF2, and SERCA2a into Ischemic Heart

Despite considerable advances in cardiovascular disease treatment, heart failure remains a public health challenge. In this context, gene therapy appears as an attractive approach, but clinical trials using single therapeutic molecules result in moderate benefit. With the objective of improving ischemic heart failure therapy, we designed a combined treatment, aimed to simultaneously stimulate angiogenesis, prevent cardiac remodeling, and restore contractile function. We have previously validated IRES-based vectors as powerful tools to co-express genes of interest. Mono- and multicistronic lentivectors expressing fibroblast growth factor 2 (angiogenesis), apelin (cardioprotection), and/or SERCA2a (contractile function) were produced and administrated by intramyocardial injection into a mouse model of myocardial infarction. Data reveal that combined treatment simultaneously improves vessel number, heart function parameters, and fibrosis prevention, due to FGF2, SERCA2a, and apelin, respectively. Furthermore, addition of SERCA2a in the combination decreases cardiomyocyte hypertrophy. Large-scale transcriptome analysis reveals that the triple treatment is the most efficient in restoring angiogenic balance as well as expression of genes involved in cardiac function and remodeling. Our study validates the concept of combined treatment of ischemic heart disease with apelin, FGF2, and SERCA2a and shows that such therapeutic benefit is mediated by a more effective recovery of gene network regulation.

Predictive value of apelin-12 in patients with ST-elevation myocardial infarction with different renal function: a prospective observational study

OBJECTIVES

To investigate factors predicting the onset of major adverse cardiovascular events (MACEs) after primary percutaneous coronary intervention (pPCI) for patients with ST-segment elevation myocardial infarction (STEMI) .

BACKGROUND

Apelin-12 plays an essential role in cardiovascular homoeostasis. However, current knowledge of its predictive prognostic value is limited.

METHODS

464 patients with STEMI (63.0±11.9 years, 355 men) who underwent successful pPCI were enrolled and followed for 2.5 years. Multivariate cox regression analysis and receiver operating characteristic (ROC) curve analysis were performed to determine the factors predicting MACEs.

RESULTS

118 patients (25.4%) experienced MACEs in the follow-up period. Multivariate cox regression analysis found low apelin-12 (HR=0.132, 95% CI 0.060 to 0.292, P<0.001), low left ventricular ejection fraction (HR=0.965, 95% CI 0.941 to 0.991, P=0.007), low estimated glomerular filtration rate (eGFR) (HR=0.985, 95% CI 0.977 to 0.993, P<0.001), Killip's classification>I (HR=0.610, 95% CI 0.408 to 0.912, P=0.016) and pathological Q-wave (HR=1.536, 95% CI 1.058 to 2.230, P=0.024) were independent predictors of MACEs in the 2.5 year follow-up period. Low apelin-12 also predicted poorer in-hospital prognosis and MACEs in the 2.5 years follow-up period compared with Δapelin-12 (P=0.0115) and eGFR (P=0.0071) among patients with eGFR>90 mL/min×1.73 m². Further analysis showed Δapelin-12 <20% was associated with MACEs in patients whose apelin-12 was below 0.76 ng/mL (P=0.0075) on admission.

CONCLUSIONS

Patients with STEMI receiving pPCI with lower apelin-12 are more likely to suffer MACEs in hospital and 2.5 years postprocedure, particularly in those with normal eGFR levels.

Effects of apelin on retinal microglial cells in a rat model of oxygen-induced retinopathy of prematurity

This study explores the effects of apelin on retinal microglial cells in rat models of oxygen-induced retinopathy of prematurity (ROP). Totally, 274 rats were selected for establishing oxygen-induced retinopathy (OIR) models, and 92 healthy rats for control group. OIR rats were assigned into OIR, 10^-5  g/L apelin, 10^-4  g/L apelin, and 10^-3  g/L apelin groups. Immunohistochemistry was employed to determine morphology of microglial cells and cell number. CDllb, ionized calcium-binding adapter molecule 1 (IBA-1), TNF-α, and iNOS mRNA and protein expressions were identified using RT-qPCR and Western blotting, respectively. ELISA was employed to determine the levels of VEGF and glial fibrillary acidic protein (GFAP). The amoeboid microglial cells were found in the OIR and 10^-3  g/L apelin groups, while bipolar microglial cells were found in the normal control, 10^-5  g/L apelin and 10^-4  g/L apelin groups. In the 1, 2, 3, and 4th week after apelin treatment, there were significantly decreased bipolar microglial cells, lower mRNA and protein expressions of CDllb, IBA-1, TNF-α and iNOS, and the levels of VEGF and GFAP in the 10^-4  g/L apelin group than in the OIR, 10^-3  g/L apelin and 10^-5  g/L apelin groups. The differences between the normal control and 10^-4  g/L apelin groups are not significant. Compared with the OIR group, the 10^-5  g/L apelin and 10^-3  g/L apelin groups presented decreased microglial cells and mRNA and protein expressions of CDllb, IBA-1, TNF-α, and iNOS. Appropriate concentration of apelin may reduce retinal microglial cells in a rat model of oxygen-induced ROP.

The effect of Bacopa monnieri on gene expression levels in SH-SY5Y human neuroblastoma cells

Bacopa monnieri is a plant used as a nootropic in Ayurveda, a 5000-year-old system of traditional Indian medicine. Although both animal and clinical studies supported its role as a memory enhancer, the molecular and cellular mechanism underlying Bacopa's nootropic action are not understood. In this study, we used deep sequencing (RNA-Seq) to identify the transcriptome changes upon Bacopa treatment on SH-SY5Y human neuroblastoma cells. We identified several genes whose expression levels were regulated by Bacopa. Biostatistical analysis of the RNA-Seq data identified biological pathways and molecular functions that were regulated by Bacopa, including regulation of mRNA translation and transmembrane transport, responses to oxidative stress and protein misfolding. Pathway analysis using the Ingenuity platform suggested that Bacopa may protect against brain damage and improve brain development. These newly identified molecular and cellular determinants may contribute to the nootropic action of Bacopa and open up a new direction of investigation into its mechanism of action.

Association of apelin and apelin receptor with the risk of coronary artery disease: a meta-analysis of observational studies

It is well established that apelin-APLNR (apelin receptor) pathway plays a central role in cardiovascular system. In this meta-analysis, we summarized published results on circulating apelin concentration in association with coronary artery disease (CAD), apelin and APLNR genetic polymorphism(s) in predisposition to CAD risk and circulating apelin changes after surgical treatment for CAD. The results from 15 articles were pooled. Two authors independently took charge of literature search, article selection and information collection. Overall, circulating apelin concentration was significantly lower in CAD patients (N=1021) than in controls (N=654) (weighted mean difference [WMD]: -1.285 ng/mL, 95% confidence interval [CI]: -1.790 to -0.780, P<0001), with significant heterogeneity (I²=99.3%) but without publication bias. For the association of APLNR gene rs9943582 polymorphism with CAD (patients/controls: 5975/4717), the mutant T allele was associated with a 5.2% increased risk relative to the wild C allele (odds ratio: 1.052, 95% CI: 0.990 to 1.117, P=0.100), without heterogeneity (I²=0.0%) or publication bias. Circulating apelin was increased significantly after surgical treatment for CAD (N=202) (WMD: 2.011 ng/mL, 95% CI: 0.541 to 3.481, P=0.007), with significant heterogeneity (I²=98.0%). Stratified analyses showed that circulating apelin was significantly reduced in studies with age- and sex-matched patients and controls (WMD: -1.881 ng/mL, 95% CI: -2.457 to -1.304, P<0.001) and with total sample size ≥125 (WMD: -1.657 ng/mL, 95% CI: -2.378 to -0.936, P<0.001), relative to studies without matching reports and with total sample size <125. In brief, our results suggested that circulating apelin was a prominent athero-protective marker against the development of CAD.

Plasma apelin-12 levels may predict in-hospital major adverse cardiac events in ST-elevation myocardial infarction and the relationship between apelin-12 and the neutrophil/lymphocyte ratio in patients undergoing primary coronary intervention

OBJECTIVE

We aimed to investigate the compliance of plasma apelin-12 levels to show angiographic properties and hospital MACE in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).

MATERIAL AND METHODS

The association of apelin-12 levels with the N/L ratio on admission was assessed in 170 consecutive patients with primary STEMI undergoing primary PCI. All patient SYNTAX scores and thrombolysis in myocardial infarction (TIMI) flow grades were also assessed. Patients were divided into two groups according to their TIMI flow grade. Patients with a TIMI 0-2 flow and TIMI 3 flow with grade 0/1 myocardial blush grade (MBG) score were defined as the no-reflow group and patients with TIMI grade 3 flow with ⩾2 MBG were considered as the normal flow group.

RESULTS

Baseline apelin-12 levels were significantly lower in the no-reflow group than in the normal flow group (3.3±1.81 vs 6.2±1.74, p<0.001). In-hospital events, including death, myocardial infarction (MI) and re-infarction were significantly higher in patients in the no-reflow group than normal flow group (23% vs 7%, p<0.001). Apelin-12 level was negative correlated with the N/L ratio (r= -0.352, p<0.001), Hs-Crp (r=-0.272, p=0.01) and SYNTAX score (r= -0.246, p=0.029). In the multivariate regression analysis, apelin-12, presence of no-reflow and the SYNTAX score were independent predictors of in-hospital MACE (odds ratio [OR] 1.41, 95% confidence interval (CI) [1.27 to 1.67], p=0.001 for apelin-12, OR 1.085, [0.981 to 1.203], p<0.001 for no-reflow and OR 0.201, 95% CI [0.05 to 0.47], p= 0.004 for SYNTAX score).

CONCLUSION

We have shown that lower apelin-12 level on admission is associated with higher SYNTAX scores and no-reflow phenomenon and may be used as a prognostic marker for hospital MACE in patients with STEMI.