Apelin/APJ system: A novel promising target for anti-aging intervention

Methods to predict heart failure in diabetes patients

INTRODUCTION

Type 2 diabetes mellitus (T2DM) is one of the leading causes of cardiovascular disease and powerful predictor for new-onset heart failure (HF).

AREAS COVERED

We focus on the relevant literature covering evidence of risk stratification based on imaging predictors and circulating biomarkers to optimize approaches to preventing HF in DM patients.

EXPERT OPINION

Multiple diagnostic algorithms based on echocardiographic parameters of cardiac remodeling including global longitudinal strain/strain rate are likely to be promising approach to justify individuals at higher risk of incident HF. Signature of cardiometabolic status may justify HF risk among T2DM individuals with low levels of natriuretic peptides, which preserve their significance in HF with clinical presentation. However, diagnostic and predictive values of conventional guideline-directed biomarker HF strategy may be non-optimal in patients with obesity and T2DM. Alternative biomarkers affecting cardiac fibrosis, inflammation, myopathy, and adipose tissue dysfunction are plausible tools for improving accuracy natriuretic peptides among T2DM patients at higher HF risk. In summary, risk identification and management of the patients with T2DM with established HF require conventional biomarkers monitoring, while the role of alternative biomarker approach among patients with multiple CV and metabolic risk factors appears to be plausible tool for improving clinical outcomes.

Influence of Adipokines on Metabolic Dysfunction and Aging

Currently, 30% of the global population is overweight or obese, with projections from the World Obesity Federation suggesting that this figure will surpass 50% by 2035. Adipose tissue dysfunction, a primary characteristic of obesity, is closely associated with an increased risk of metabolic abnormalities, such as hypertension, hyperglycemia, and dyslipidemia, collectively termed metabolic syndrome. In particular, visceral fat accretion is considered as a hallmark of aging and is strongly linked to higher mortality rates in humans. Adipokines, bioactive peptides secreted by adipose tissue, play crucial roles in regulating appetite, satiety, adiposity, and metabolic balance, thereby rendering them key players in alleviating metabolic diseases and potentially extending health span. In this review, we elucidated the role of adipokines in the development of obesity and related metabolic disorders while also exploring the potential of certain adipokines as candidates for longevity interventions.

Identification of Potential Blood-Based Biomarkers for Frailty by Using an Integrative Approach

INTRODUCTION

Although frailty is a geriatric syndrome that is associated with disability, hospitalization, and mortality, it can be reversible and preventable with the appropriate interventions. Additionally, as the current diagnostic criteria for frailty include only physical, psychological, cognitive, and social measurements, there is a need for promising blood-based molecular biomarkers to aid in the diagnosis of frailty.

METHODS

To identify candidate blood-based biomarkers that can enhance current diagnosis of frailty, we conducted a comprehensive analysis of clinical data, messenger RNA-sequencing (RNA-seq), and aging-related factors using a total of 104 older adults aged 65-90 years (61 frail subjects and 43 robust subjects) in a cross-sectional case-control study.

RESULTS

We identified two candidate biomarkers of frailty from the clinical data analysis, nine from the RNA-seq analysis, and six from the aging-related factors analysis. By using combinations of the candidate biomarkers and clinical information, we constructed risk prediction models. The best models used combinations that included skeletal muscle mass index measured by dual-energy X-ray absorptiometry (adjusted p = 0.026), GDF15 (adjusted p = 1.46E-03), adiponectin (adjusted p = 0.012), CXCL9 (adjusted p = 0.011), or apelin (adjusted p = 0.020) as the biomarker. These models achieved a high area under the curve of 0.95 in an independent validation cohort (95% confidence interval: 0.79-0.97). Our risk prediction models showed significantly higher areas under the curve than did models constructed using only basic clinical information (Welch's t test p < 0.001).

CONCLUSION

All five biomarkers showed statistically significant correlations with components of the frailty diagnostic criteria. We discovered several potential biomarkers for the diagnosis of frailty. Further refinement may lead to their future clinical use.

Quercetin Attenuates Atherosclerosis via Modulating Apelin Signaling Pathway Based on Plasma Metabolomics

OBJECTIVE

To interpret the pharmacology of quercetin in treatment of atherosclerosis (AS).

METHODS

Fourteen apolipoprotein E-deficient (ApoE-/-) mice were divided into 2 groups by a random number table: an AS model (ApoE-/-) group and a quercetin treatment group (7 in each). Seven age-matched C57 mice were used as controls (n=7). Quercetin [20 mg/(kg·d)] was administered to the quercetin group intragastrically for 8 weeks for pharmacodynamic evaluation. Besides morphological observation, the distribution of CD11b, F4/80, sirtuin 1 (Sirt1) and P21 was assayed by immunohistochemistry and immunofluorescence to evaluate macrophage infiltration and tissue senescence. Ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MSC/MS) was performed to study the pharmacology of quercetin against AS. Then, simultaneous administration of an apelin receptor antagonist (ML221) with quercetin was conducted to verify the possible targets of quercetin. Key proteins in apelin signaling pathway, such as angiotensin domain type 1 receptor-associated proteins (APJ), AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), tissue plasminogen activator (TPA), uncoupling protein 1 (UCP1) and angiotensin II receptor 1 (AT1R), were assayed by Western blot.

RESULTS

Quercetin administration decreased lipid deposition in arterial lumen and improved the morphology of ApoE-/- aortas in vivo. Quercetin decreased the densities of CD11b, F4/80 and P21 in the aorta and increased the level of serum apelin and the densities of APJ and Sirt1 in the aorta in ApoE-/- mice (all P<0.05). Plasma metabolite profiling identified 118 differential metabolites and showed that quercetin affected mainly glycerophospholipids and fatty acyls. Bioinformatics analysis suggested that the apelin signaling pathway was one of the main pathways. Quercetin treatment increased the protein expressions of APJ, AMPK, PGC-1α, TPA and UCP1, while decreased the AT1R level (all P<0.05). After the apelin pathway was blocked by ML221, the effect of quercetin was abated significantly, confirming that quercetin attenuated AS by modulating the apelin signaling pathway (all P<0.05).

CONCLUSION

Quercetin alleviated AS lesions by up-regulation the apelin signaling pathway.

Hypophagia induced by intracerebroventricular injection of apelin-13 is mediated via CRF1/CRF2 and MC3/MC4 receptors in neonatal broiler chicken

Previous studies have shown the role of apelin and its receptors in the regulation of food intake. In the present study, we investigate the mediating role of melanocortin, corticotropin, and neuropeptide Y systems in apelin-13- induced food intake in broilers. Eight trials were run in the current investigation to ascertain the relationships between the aforementioned systems and apelin-13 on food intake and behavioral changes after apelin-13 administration. In experiment 1, hens were given an intracerebroventricular administration of a solution for control in addition to apelin-13 (0.25, 0.5, and 1 µg). Astressin-B (a CRF1/CRF2 receptor antagonist, 30 µg), apelin-13 (1 µg), and administration of astressin-B and apelin-13 concurrently, were all injected into the birds in experiment 2. Experiments 3 through 8 were quite similar to experiment 2, with the exception of astressin2-B (CRF2 receptor antagonist, 30 µg), SHU9119 (MC3/MC4 receptor antagonist, 0.5 nmol), MCL0020 (MC4 receptor antagonist, 0.5 nmol), BIBP-3226 (NPY1 receptor antagonist, 1.25 nmol), BIIE 0246 (NPY2 receptor antagonist, 1.25 nmol), and CGP71683A (NPY5 receptor antagonist, 1.25 nmol) were injected instead of astressin-B. After then, total food consumption was monitored for 6 h. Apelin-13 injections of 0.5 and 1 µg decreased feeding (P < 0.05). The hypophagic effects of apelin were attenuated following the simultaneous administration of Astressin-B and Astressin2-B with apelin-13 (P > 0.05). Co-infusion of SHU9119 and apelin-13 reduced the appetite-decreasing effects of apelin-13 (P > 0.05). When MCL0020 and apelin-13 were injected at the same time, the hypophagia that apelin-13 induced was eliminated (P > 0.05). BIBP-3226, BIIE 0246, and CGP71683A had no effect on the hypophagia brought on by apelin-13 (P > 0.05). Also, apelin-13 significantly increased number of steps, jumps, exploratory food, pecks and standing time while decreased siting time (P < 0.05). These findings suggest that apelin-13-induced hypophagia in hens may involve the CRF1/CRF2 and MC3/MC4 receptors.

Precious1GPT: multimodal transformer-based transfer learning for aging clock development and feature importance analysis for aging and age-related disease target discovery

Aging is a complex and multifactorial process that increases the risk of various age-related diseases and there are many aging clocks that can accurately predict chronological age, mortality, and health status. These clocks are disconnected and are rarely fit for therapeutic target discovery. In this study, we propose a novel approach to multimodal aging clock we call Precious1GPT utilizing methylation and transcriptomic data for interpretable age prediction and target discovery developed using a transformer-based model and transfer learning for case-control classification. While the accuracy of the multimodal transformer is lower within each individual data type compared to the state of art specialized aging clocks based on methylation or transcriptomic data separately it may have higher practical utility for target discovery. This method provides the ability to discover novel therapeutic targets that hypothetically may be able to reverse or accelerate biological age providing a pathway for therapeutic drug discovery and validation using the aging clock. In addition, we provide a list of promising targets annotated using the PandaOmics industrial target discovery platform.

Transcriptome-wide association study identifies new susceptibility genes for degenerative cervical spondylosis

AIMS

Degenerative cervical spondylosis (DCS) is a common musculoskeletal disease that encompasses a wide range of progressive degenerative changes and affects all components of the cervical spine. DCS imposes very large social and economic burdens. However, its genetic basis remains elusive.

METHODS

Predicted whole-blood and skeletal muscle gene expression and genome-wide association study (GWAS) data from a DCS database were integrated, and functional summary-based imputation (FUSION) software was used on the integrated data. A transcriptome-wide association study (TWAS) was conducted using FUSION software to assess the association between predicted gene expression and DCS risk. The TWAS-identified genes were verified via comparison with differentially expressed genes (DEGs) in DCS RNA expression profiles in the Gene Expression Omnibus (GEO) (Accession Number: GSE153761). The Functional Mapping and Annotation (FUMA) tool for genome-wide association studies and Meta tools were used for gene functional enrichment and annotation analysis.

RESULTS

The TWAS detected 420 DCS genes with p < 0.05 in skeletal muscle, such as ribosomal protein S15A (RPS15A) (PTWAS = 0.001), and 110 genes in whole blood, such as selectin L (SELL) (PTWAS = 0.001). Comparison with the DCS RNA expression profile identified 12 common genes, including Apelin Receptor (APLNR) (PTWAS = 0.001, PDEG = 0.025). In total, 148 DCS-enriched Gene Ontology (GO) terms were identified, such as mast cell degranulation (GO:0043303); 15 DCS-enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were identified, such as the sphingolipid signalling pathway (ko04071). Nine terms, such as degradation of the extracellular matrix (R-HSA-1474228), were common to the TWAS enrichment results and the RNA expression profile.

CONCLUSION

Our results identify putative susceptibility genes; these findings provide new ideas for exploration of the genetic mechanism of DCS development and new targets for preclinical intervention and clinical treatment.Cite this article: Bone Joint Res 2023;12(1):80-90.

Dicer1 deficient mice exhibit premature aging and metabolic perturbations in adipocytes

Age-related diseases are major concern in developed countries. To avoid disabilities that accompany increased lifespan, pharmaceutical approaches are considered. Therefore, appropriate animal models are required for a better understanding of aging processes and potential in vivo assays to evaluate the impact of molecules that may delay the occurrence of age-related diseases. Few mouse models exhibiting pathological aging exist, but currently, none of them reproducibly mimics human diseases like osteoporosis, cognitive dysfunctions or sarcopenia that can be seen in some, but not all, elders. Here, we describe the premature aging phenotypes of Dicer-deficient mature animals, which exhibit an overall deterioration of many organs and tissues (skin, heart, and adipose tissue) ultimately leading to a significant reduction of their lifespan. Molecular characterization of transcriptional responses focused on the adipose tissue suggested that both canonical and non-canonical functions of DICER are involved in this process and highlight potential actionable pathways to revert it.

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Dicer1-deficient mice have a reduced lifespan with early age-related symptoms

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Mutant mice are resistant to high fat diet-induced disorders

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Myokines FGF21 and GDF15 are likely key regulators of adipocytes metabolism

Neuropeptide apelin presented in the dopaminergic neurons modulates the neuronal excitability in the substantia nigra pars compacta

The dopaminergic neurons in the substantia nigra pars compacta are characterized by autonomous pacemaking activity. The spontaneous firing activity of nigral dopaminergic neurons plays an important role in physiological function and is essential for their survival. Importantly, the spontaneous firing activity may also be involved in the preferential vulnerability of the nigral dopaminergic neurons in Parkinson's disease (PD). The neuropeptide apelin was reported to exert neuroprotective effects in neurodegenerative diseases, including PD. And it was noticed that apelin modulates neuronal activity in some brain regions. The present study investigated the electrophysiological and behavioral effects of apelin in the substantia nigra. Double-labeling immunofluorescence showed that apelin was present in nigral dopaminergic neurons and that these neurons expressed apelin receptor APJ. Further single unit in vivo electrophysiological recordings revealed that endogenous apelin tonically increased the firing rate of nigral dopaminergic neurons in both normal and parkinsonian animals. Exogenous apelin-13 exerted excitatory effects on the majority of nigral dopaminergic neurons, yet reduced excitability in a subset of neurons. In addition, nigral application of apelin-13 increased motor activity in normal rats and blocking endogenous apelin reduced motor activity. Considering the involvement of the spontaneous firing activity of nigral dopaminergic neurons in the development of PD and the possibility that apelin acts in an autocrine manner on apelin receptors expressed by nigral dopaminergic neurons, the modulation of the spontaneous firing activity of nigral dopaminergic neurons by apelin may serve as a neuroprotective factor in PD.

Liuwei Dihuang Decoction Alleviates Cognitive Dysfunction in Mice With D-Galactose-Induced Aging by Regulating Lipid Metabolism and Oxidative Stress via the Microbiota-Gut-Brain Axis

Background

Aging is an important cause of cognitive dysfunction. Liuwei Dihuang decoction (LW), a commonly applied Chinese medicine formula, is widely used for the treatment of aging-related diseases in China. Previously, LW was confirmed to be effective in prolonging life span and reducing oxidative stress in aged mice. Unfortunately, the underlying mechanism of LW remains unclear. The aim of this study was to interpret the mechanism by which LW alleviates cognitive dysfunction related to aging from the perspective of the microbiota-gut-brain axis.

Method

All C57BL/6 mice (n = 60) were randomly divided into five groups: the control, model, vitamin E (positive control group), low-dose LW and high-dose LW groups (n = 12 in each group). Except for those in the control group, D-galactose was subcutaneously injected into mice in the other groups to induce the aging model. The antiaging effect of LW was evaluated by the water maze test, electron microscopy, 16S rRNA sequencing, combined LC–MS and GC–MS metabolomics, and ELISA.

Results

Liuwei Dihuang decoction ameliorated cognitive dysfunction and hippocampal synaptic ultrastructure damage in aging mice. Moreover, LW decreased Proteobacteria abundance and increased gut microbiota diversity in aging mice. Metabolomic analysis showed that LW treatment was associated with the significantly differential abundance of 14 metabolites, which were mainly enriched in apelin signaling, sphingolipid metabolism, glycerophospholipid and other metabolic pathways. Additionally, LW affected lipid metabolism and oxidative stress in aging mice. Finally, we also found that LW-regulated microbial species such as Proteobacteria and Fibrobacterota had potential relationships with lipid metabolism, oxidative stress and hippocampal metabolites.

Conclusion

In brief, LW improved cognitive function in aging mice by regulating lipid metabolism and oxidative stress through restoration of the homeostasis of the microbiota-gut-brain axis.

The microRNA-204-5p inhibits APJ signalling and confers resistance to cardiac hypertrophy and dysfunction

BACKGROUND

MicroRNAs regulate cardiac hypertrophy development, which precedes and predicts the risk of heart failure. microRNA-204-5p (miR-204) is well expressed in cardiomyocytes, but its role in developing cardiac hypertrophy and cardiac dysfunction (CH/CD) remains poorly understood.

METHODS

We performed RNA-sequencing, echocardiographic, and molecular/morphometric analysis of the heart of mice lacking or overexpressing miR-204 five weeks after trans-aortic constriction (TAC). The neonatal rat cardiomyocytes, H9C2, and HEK293 cells were used to determine the mechanistic role of miR-204.

RESULTS

The stretch induces miR-204 expression, and miR-204 inhibits the stretch-induced hypertrophic response of H9C2 cells. The mice lacking miR-204 displayed a higher susceptibility to CH/CD during pressure overload, which was reversed by the adeno-associated virus serotype-9-mediated cardioselective miR-204 overexpression. Bioinformatic analysis of the cardiac transcriptomics of miR-204 knockout mice following pressure overload suggested deregulation of apelin-receptor (APJ) signalling. We found that the stretch-induced extracellular signal-regulated kinase 1/2 (ERK1/2) activation and hypertrophy-related genes expression depend on the APJ, and both of these effects are subject to miR-204 levels. The dynamin inhibitor dynasore inhibited both stretch-induced APJ endocytosis and ERK1/2 activation. In contrast, the miR-204-induced APJ endocytosis was neither inhibited by dynamin inhibitors (dynasore and dyngo) nor associated with ERK1/2 activation. We find that the miR-204 increases the expression of ras-associated binding proteins (e.g., Rab5a, Rab7) that regulate cellular endocytosis.

CONCLUSIONS

Our results show that miR-204 regulates trafficking of APJ and confers resistance to pressure overload-induced CH/CD, and boosting miR-204 can inhibit the development of CH/CD.

The Role of Apelin-APJ System in Diabetes and Obesity

Nowadays, diabetes and obesity are two main health-threatening metabolic disorders in the world, which increase the risk for many chronic diseases. Apelin, a peptide hormone, exerts its effect by binding with angiotensin II protein J receptor (APJ) and is considered to be linked with diabetes and obesity. Apelin and its receptor are widely present in the body and are involved in many physiological processes, such as glucose and lipid metabolism, homeostasis, endocrine response to stress, and angiogenesis. In this review, we summarize the literatures on the role of the Apelin-APJ system in diabetes and obesity for a better understanding of the mechanism and function of apelin and its receptor in the pathophysiology of diseases that may contribute to the development of new therapies.

Research Progress on Mechanism of Neuroprotective Roles of Apelin-13 in Prevention and Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is the most common type of dementia. Currently, more than 50 million people live with dementia worldwide, and this number is expected to increase. Some of the typical pathological changes of AD include amyloid plaque, hyperphosphorylation of tau protein, secretion of inflammatory mediators, and neuronal apoptosis. Apelin is a neuroprotective peptide that is widely expressed in the body. Among members of apelin family, apelin-13 is the most abundant with a high neuroprotective function. Apelin-13/angiotensin domain type 1 receptor-associated proteins (APJ) system regulates several physiological and pathophysiological cell activities, such as apoptosis, autophagy, synaptic plasticity, and neuroinflammation. It has also been shown to prevent AD development. This article reviews the research progress on the relationship between apelin-13 and AD to provide new ideas for prevention and treatment of AD.

Declined ELABELA plasma levels in hypertension patients with atrial fibrillation: a case control study

Background

Atrial fibrillation (AF) is a common arrhythmia in patients with hypertension. ELABELA, which has cardioprotective effects, is decreased in the plasma of patients with hypertension and might be associated with AF in the hypertensive population. This study aims to measure the ELABELA plasma levels in hypertension patients with and without AF and to analyse the related factors.

Methods

A total of 162 hypertension patients with or without AF were recruited for our monocentric observational study. Subjects were excluded if they had a history of valvular heart disease, rheumatic heart disease, cardiomyopathy, thyroid diseases, or heart failure. The patients’ histories were recorded, and laboratory examinations were conducted. Plasma ELABELA was detected by immunoassay. Echocardiographs were performed, and parameters were collected by two experienced doctors. Binary logistic regression analysis was used to identify the association between ELABELA plasma level and AF in patients with hypertension.

Results

Plasma ELABELA levels were lower in hypertension patients with AF than in those without AF (2.0 [1.5, 2.8] vs. 4.0 [3.4, 5.0] ng/ml, P < 0.001). ELABELA levels were correlated with age, heart rate, BNP levels and left atrial dimension. In addition to the left atrial dimension, ELABELA plasma levels were associated with AF in patients with hypertension (OR 0.081, 95% CI 0.029–0.224, P < 0.001). ELABELA levels were further decreased in the persistent AF subgroup compared with the paroxysmal AF subgroup (1.8 [1.4, 2.5] vs. 2.2 [1.8, 3.0] ng/ml, P = 0.012) and correlated with HR, BNP and ESR levels.

Conclusions

ELALABELA levels were decreased in hypertension patients with AF and further lowered in the persistent AF subgroup. Decreased ELABELA plasma levels were associated with AF in hypertension patients and may be an underlying risk factor.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02197-x.

Apelin/APJ system: A novel therapeutic target for locomotor system diseases

Apelin is an endogenous ligand of G protein-coupled receptor APJ. Apelin/APJ system is widely expressed in abundant tissues, especially bone, joint and muscle tissue. This review focus on the effects of apelin/APJ system on locomotor system. An increasing number of evidence suggests that apelin/APJ system plays a crucial role in many physiological and pathological processes of locomotor system. Physiologically, apelin/APJ system promotes bone formation, muscle metabolism and skeletal muscle production. Pathologically, apelin/APJ system exacerbates osteoarthritis pathogenesis, whereas it alleviates osteoporosis. Besides, the level of apelin expression is regulated by different training modes, including continuous aerobic exercise, high-intensity interval training and resistance exercises. More importantly, exercise-induced apelin may be a potent pharmacological agent for the treatment of diseases and the regulation of physiological processes. Considering the pleiotropic effects of apelin on locomotor system, apelin/APJ system may be an important therapeutic target for locomotor system diseases.

The Apelin-Apelin Receptor Axis Triggers Cholangiocyte Proliferation and Liver Fibrosis During Mouse Models of Cholestasis

BACKGROUND AND AIMS

Apelin (APLN) is the endogenous ligand of its G protein-coupled receptor, apelin receptor (APJ). APLN serum levels are increased in human liver diseases. We evaluated whether the APLN-APJ axis regulates ductular reaction and liver fibrosis during cholestasis.

APPROACH AND RESULTS

We measured the expression of APLN and APJ and serum APLN levels in human primary sclerosing cholangitis (PSC) samples. Following bile duct ligation (BDL) or sham surgery, male wild-type (WT) mice were treated with ML221 (APJ antagonist) or saline for 1 week. WT and APLN^-/- mice underwent BDL or sham surgery for 1 week. Multidrug resistance gene 2 knockout (Mdr2^-/- ) mice were treated with ML221 for 1 week. APLN levels were measured in serum and cholangiocyte supernatants, and cholangiocyte proliferation/senescence and liver inflammation, fibrosis, and angiogenesis were measured in liver tissues. The regulatory mechanisms of APLN-APJ in (1) biliary damage and liver fibrosis were examined in human intrahepatic biliary epithelial cells (HIBEpiCs) treated with APLN and (2) hepatic stellate cell (HSC) activation in APLN-treated human HSC lines (HHSteCs). APLN serum levels and biliary expression of APLN and APJ increased in PSC samples. APLN levels were higher in serum and cholangiocyte supernatants from BDL and Mdr2^-/- mice. ML221 treatment or APLN^-/- reduced BDL-induced and Mdr2^-/- -induced cholangiocyte proliferation/senescence, liver inflammation, fibrosis, and angiogenesis. In vitro, APLN induced HIBEpiC proliferation, increased nicotinamide adenine dinucleotide phosphate oxidase 4 (Nox4) expression, reactive oxygen species (ROS) generation, and extracellular signal-regulated kinase (ERK) phosphorylation. Pretreatment of HIBEpiCs with ML221, diphenyleneiodonium chloride (Nox4 inhibitor), N-acetyl-cysteine (NAC, ROS inhibitor), or PD98059 (ERK inhibitor) reduced APLN-induced cholangiocyte proliferation. Activation of HHSteCs was induced by APLN but reduced by NAC.

CONCLUSIONS

The APLN-APJ axis induces cholangiocyte proliferation through Nox4/ROS/ERK-dependent signaling and HSC activation through intracellular ROS. Modulation of the APLN-APJ axis may be important for managing cholangiopathies.

Neuroprotective gain of Apelin/APJ system

Apelin is an endogenous ligand of G protein-coupled receptor APJ. In recent years, many studies have shown that the apelin/APJ system has neuroprotective properties, such as anti-inflammatory, anti-oxidative stress, anti-apoptosis, and regulating autophagy, blocking excitatory toxicity. Apelin/APJ system has been proven to play a role in various neurological diseases and may be a promising therapeutic target for nervous system diseases. In this paper, the neuroprotective properties of the apelin/APJ system and its role in neurologic disorders are reviewed. Further understanding of the pathophysiological effect and mechanism of the apelin/APJ system in the nervous system will help develop new therapeutic interventions for various neurological diseases.

ACE2 in the second act of COVID-19 syndrome: Peptide dysregulation and possible correction with oestrogen

Coronavirus disease 2019 (COVID-19) has become the most critical pandemic of the 21st Century and the most severe since the 1918 influenza pandemic. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects the host by binding to angiotensin-converting enzyme 2 (ACE2). The role of ACE2 in the pathophysiology of coronavirus disease 2019 (COVID-19) is a topic of debate, with clinical and experimental evidence indicating a multifaceted relationship between ACE2 activity and disease severity. Here, we review the mechanisms by which the peptidergic substrates and products of ACE and ACE2 contribute to physiological and pathophysiological processes and hypothesise how down-regulation of ACE2 by SARS-CoV-2 cellular entry disrupts homeostasis. A better understanding of the endocrinology of the disease, in particular the neuroendocrinology of ACE2 during COVID-19, may contribute to the timely design of new therapeutic strategies, including the regulation of ACE2 itself by steroid hormones, to ameliorate the severity of COVID-19.

miR-15b-5p promotes expression of proinflammatory cytokines in human placenta by inhibiting Apelin signaling pathway

INTRODUCTION

The timing of parturition at end of human gestation may be controlled by fetal signals. The signaling molecules contributing to activation of human labor may be mediated by fetal exosomes. In this study, we focused on investigation of the role of microRNAs (miRNAs) derived from fetal exosomes in the regulation of human placental gene expression.

METHODS

Using immunofluorescent labeling, array-based miRNA profiling assay, target prediction analysis, and conducting a variety of biochemical approaches including miRNA mimics, dual-luciferase, siRNA-mediated gene silencing, and immunohistochemical staining assay in primary trophoblast culture and formalin-fixed paraffin-embedded placental tissues, we examined whether fetal exosomal miRNAs can stimulate expression of proinflammatory mediators in human placenta.

RESULTS

We showed placental uptake of exosomes derived from the umbilical artery, and found that 9 fetal exosomal miRNAs: let-7i-5p, miR-185-5p, miR-15b-5p, miR-376c-3p, miR-548d-5p, miR-92b-3p, miR-16-5p, and miR-1301-3p were significantly increased in placentas of women delivering following term labor compared to those delivering by Cesarean section in the late preterm period. Target prediction analysis identified miR-15b-5p of particular interest, because one of its predicted targets is Apelin, a potent inhibitor of proinflammatory mediators. We further found that miR-15b-5p repressed Apelin protein levels and activated pro-labor hormones and cytokines including IL-1, IL-6, IL-8, and TNF-α.

DISCUSSION

These data suggest a potential fetal-to-placental signal that could play a role in the length of human gestation and onset of human labor.

Adipokines, Myokines, and Cardiokines: The Role of Nutritional Interventions

It is now established that adipose tissue, skeletal muscle, and heart are endocrine organs and secrete in normal and in pathological conditions several molecules, called, respectively, adipokines, myokines, and cardiokines. These secretory proteins constitute a closed network that plays a crucial role in obesity and above all in cardiac diseases associated with obesity. In particular, the interaction between adipokines, myokines, and cardiokines is mainly involved in inflammatory and oxidative damage characterized obesity condition. Identifying new therapeutic agents or treatment having a positive action on the expression of these molecules could have a key positive effect on the management of obesity and its cardiac complications. Results from recent studies indicate that several nutritional interventions, including nutraceutical supplements, could represent new therapeutic agents on the adipo-myo-cardiokines network. This review focuses the biological action on the main adipokines, myokines and cardiokines involved in obesity and cardiovascular diseases and describe the principal nutraceutical approaches able to regulate leptin, adiponectin, apelin, irisin, natriuretic peptides, and follistatin-like 1 expression.

Lack of association between circulating apelin level and frailty-related functional parameters in older adults: a cross-sectional study

BACKGROUND

Apelin, an active endogenous peptide, has been recently receiving great attention as a promising target for antiaging intervention, primarily based on results from genetically altered mice. To validate previous experimental data and investigate the possible role of apelin in humans, in this study, we examined serum apelin level in relation to frailty and its associated parameters in a cohort of ambulatory, community-dwelling older adults.

METHODS

Blood samples were collected from 80 participants who underwent a comprehensive geriatric assessment, and apelin level was measured using an enzyme immunoassay kit. Phenotypic frailty and deficit-accumulation frailty index (FI) were assessed using widely validated approaches, proposed by Fried and Rockwood groups, respectively.

RESULTS

After adjustment for sex, age, and body mass index, serum apelin level was found to be not significantly different according to phenotypic frailty status (P = 0.550) and not associated with FI, grip strength, gait speed, time to complete 5 chair stands, and muscle mass (P = 0.433 to 0.982). To determine whether the association between serum apelin level and frailty has a threshold effect, we divided the participants into quartiles according to serum apelin level. However, there were no differences in terms of frailty-related parameters and the risk for frailty among the quartile groups (P = 0.248 to 0.741).

CONCLUSIONS

The serum apelin level was not associated with both phenotypic frailty and functional parameters in older adults, despite its beneficial effects against age-related physiologic decline in animal models. Further large-scale longitudinal studies are necessary to understand the definite role of circulating apelin in frailty risk assessment.

Apelin/APJ system: an emerging therapeutic target for respiratory diseases

Apelin is an endogenous ligand of G protein-coupled receptor APJ. It is extensively expressed in many tissues such as heart, liver, and kidney, especially in lung tissue. A growing body of evidence suggests that apelin/APJ system is closely related to the development of respiratory diseases. Therefore, in this review, we focus on the role of apelin/APJ system in respiratory diseases, including pulmonary arterial hypertension (PAH), pulmonary embolism (PE), acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), obstructive sleep apnoea syndrome (OSAS), non-small cell lung cancer (NSCLC), pulmonary edema, asthma, and chronic obstructive pulmonary diseases. In detail, apelin/APJ system attenuates PAH by activating AMPK-KLF2-eNOS-NO signaling and miR424/503-FGF axis. Also, apelin protects against ALI/ARDS by reducing mitochondrial ROS-triggered oxidative damage, mitochondria apoptosis, and inflammatory responses induced by the activation of NF-κB and NLRP3 inflammasome. Apelin/APJ system also prevents the occurrence of pulmonary edema via activating AKT-NOS3-NO pathway. Moreover, apelin/APJ system accelerates NSCLC cells' proliferation and migration via triggering ERK1/2-cyclin D1 and PAK1-cofilin signaling, respectively. Additionally, apelin/APJ system may act as a predictor in the development of OSAS and PE. Considering the pleiotropic actions of apelin/APJ system, targeting apelin/APJ system may be a potent therapeutic avenue for respiratory diseases.

Cardiovascular response to small-molecule APJ activation

Heart failure (HF) remains a grievous illness with poor prognosis even with optimal care. The apelin receptor (APJ) counteracts the pressor effect of angiotensin II, attenuates ischemic injury, and has the potential to be a novel target to treat HF. Intravenous administration of apelin improves cardiac function acutely in patients with HF. However, its short half-life restricts its use to infusion therapy. To identify a longer acting APJ agonist, we conducted a medicinal chemistry campaign, leading to the discovery of potent small-molecule APJ agonists with comparable activity to apelin by mimicking the C-terminal portion of apelin-13. Acute infusion increased systolic function and reduced systemic vascular resistance in 2 rat models of impaired cardiac function. Similar results were obtained in an anesthetized but not a conscious canine HF model. Chronic oral dosing in a rat myocardial infarction model reduced myocardial collagen content and improved diastolic function to a similar extent as losartan, a RAS antagonist standard-of-care therapy, but lacked additivity with coadministration. Collectively, this work demonstrates the feasibility of developing clinical, viable, potent small-molecule agonists that mimic the endogenous APJ ligand with more favorable drug-like properties and highlights potential limitations for APJ agonism for this indication.

Role of Apelin/APJ axis in cancer development and progression

Apelin is an endogenous peptide, which is expressed in a vast board of organs such as the brain, placenta, heart, lungs, kidneys, pancreas, testis, prostate and adipose tissues. The apelin receptor, called angiotensin-like-receptor 1 (APJ), is also expressed in the brain, spleen, placenta, heart, liver, intestine, prostate, thymus, testis, ovary, lungs, kidneys, stomach, and adipose tissue. The apelin/APJ axis is involved in a number of physiological and pathological processes. The apelin expression is increased in various kinds of cancer and the apelin/APJ axis plays a key role in the development of tumors through enhancing angiogenesis, metastasis, cell proliferation and also through the development of cancer stem cells and drug resistance. The apelin also stops the apoptosis of cancer cells. The apelin/APJ axis was considered in this review as an attractive therapeutic target for cancer treatment.

Apelin Promotes ECM Synthesis by Enhancing Autophagy Flux via TFEB in Human Degenerative NP Cells under Oxidative Stress

Background

Apelin alleviates oxidative stress which contributes to the development of aging. IVDD is a disease closely correlated to aging and oxidative stress which is known to be harmful to NP cells' matrix synthesis. The purpose of the present study was to investigate the role and underlying mechanism of Apelin in NP cells' matrix degradation under oxidative stress.

Methods

First, the mRNA and protein expressions of Apelin were checked by RT-PCR and Western blot in NP from normal and degenerative IVD to explore the relationship between Apelin and IVDD preliminarily. Then, H₂O₂ was used to mimic oxidative stress of NP cells. After treated with Apelin 13 and CQ, the GAG content was assessed by DMMB and the mRNA/protein expressions of NP matrix macromolecules (Collagen II and Aggrecan) and autophagy-related markers (LC3 and p62) were assessed by RT-PCR/Western blot. Finally, TFEB was knocked down by esiRNA-TFEB transfection and the nucleoprotein expression of TFEB and autophagy-related markers (LC3 and p62) were assessed by Western blot to discuss whether TFEB is involved in Apelin regulating autophagy flux in NP cells under oxidative stress.

Results

Our data first confirmed that the mRNA and protein expressions of Apelin were decreased with IVDD. Furthermore, Apelin increased GAG content of NP cells and mRNA/protein expressions of NP matrix macromolecules (Collagen II and Aggrecan) and promoted autophagic flux (LC3II/I increased and p62 decreased) under oxidative stress. Finally, after transfected with esiRNA-TFEB, Apelin cannot promote autophagic flux any more in human degenerative NP cells.

Conclusion

Our data indicated that Apelin promotes ECM synthesis by enhancing autophagy flux via TFEB in human degenerative NP cells under oxidative stress. This viewpoint may provide a new therapeutic idea for IVDD.

A Nomogram Based on Apelin-12 for the Prediction of Major Adverse Cardiovascular Events after Percutaneous Coronary Intervention among Patients with ST-Segment Elevation Myocardial Infarction

Objective

This study aimed to establish a clinical prognostic nomogram for predicting major adverse cardiovascular events (MACEs) after primary percutaneous coronary intervention (PCI) among patients with ST-segment elevation myocardial infarction (STEMI).

Methods

Information on 464 patients with STEMI who performed PCI procedures was included. After removing patients with incomplete clinical information, a total of 460 patients followed for 2.5 years were randomly divided into evaluation (n = 324) and validation (n = 324) and validation (

Results

Apelin-12 change rate, apelin-12 level, age, pathological Q wave, myocardial infarction history, anterior wall myocardial infarction, Killip's classification > I, uric acid, total cholesterol, cTnI, and the left atrial diameter were independently associated with MACEs (all P < 0.05). After incorporating these 11 factors, the nomogram achieved good concordance indexes of 0.758 (95%CI = 0.707–0.809) and 0.763 (95%CI = 0.689–0.837) in predicting MACEs in the evaluation and validation cohorts, respectively, and had well-fitted calibration curves. The decision curve analysis (DCA) revealed that the nomogram was clinically useful.

Conclusions

We established and validated a novel nomogram that can provide individual prediction of MACEs for patients with STEMI after PCI procedures in a Chinese population. This practical prognostic nomogram may help clinicians in decision making and enable a more accurate risk assessment.

APLNR promotes the progression of osteosarcoma by stimulating cell proliferation and invasion

Osteosarcoma is the most common type of bone malignancies with a poor prognosis. In recent years, targeted therapy has shown great potential in the treatment of osteosarcoma, and more effective therapeutic targets for this disease need to be developed. APLNR is a seven transmembrane G-protein-coupled receptor expressed widely in multiple tissues. As has been reported, APLNR is involved in various physiological and pathological processes. Although APLNR plays a role in the development and progression of multiple tumors, the potential role of APLNR in osteosarcoma, a highly malignant tumor, remains unclear. Here, we reported that APLNR expression was correlated positively with clinical features including tumor size and stage of osteosarcoma. We found that APLNR knockdown inhibited the proliferation and invasion of osteosarcoma cells in vitro. In addition, APLNR could promote the progression and metastasis of osteosarcoma in mice. Collectively, this study showed the potential link between APLNR and osteosarcoma and suggested APLNR as a novel therapeutic target for osteosarcoma.

Elabela and Apelin actions in healthy and pathological pregnancies

Pregnancy is a dynamic and precisely organized process during which one or more baby develops. Embryonic development relies on the formation of the placenta, allowing nutrient and oxygen exchange between the mother and the fetus. Dysfunction of placental formation lead to pregnancy disorders such as preeclampsia (PE) with serious deleterious consequences for fetal and maternal health. Identifying factors involved in fetoplacental homeostasis could inform better diagnostic and therapeutic strategies for these pathological pregnancies. Here, we summarize actions of elabela, apelin and their common receptor APJ in the fetoplacental unit. Studies indicate that elabela is crucial for embryo cardiovascular system formation and early placental development, while apelin acts in mid/late gestation to modulate fetal angiogenesis and energy homeostasis. Most of these findings, drawn from animal models, indicate a key role of elabela/apelin-APJ system in the fetoplacental unit. This review also provides an overview of clinical studies investigating elabela/apelin-APJ system in pathological complicated pregnancies such as PE and gestational diabetes mellitus (GDM). While elabela-deficient mice display all the features of PE, current clinical studies show no difference in circulating elabela levels between PE and control patients which does not support a role in PE development. Conversely, apelin levels are increased during PE, but the use of apelin as an early PE marker remains to be fully investigated.