Isolation and characterization of a novel endogenous peptide ligand for the human APJ receptor

Immunological roles for resistin and related adipokines in obesity-associated tumors

Rationale Obesity is an independent risk factor for the occurrence and development of tumors. Obesity is influenced by signaling of adipokines, which are secreted factors from adipocytes and resident immune cells within adipose tissues that mediate lipid metabolism. More recently, adipokines have been implicated in chronic inflammation as well as in tumor formation and growth. Among them, resistin has received increasing attention in research related to the growth and expansion of solid tumors and hematological cancers through various signaling pathways. Objective and findings We reviewed the physiological, biochemical, and immune functions of adipose tissue, with a focus on the structure and expression of resistin and adipokines within multiple adipose cell types, their signaling pathways and putative effects on tumor cells, as well as their in vivo regulation. Current evidence indicates that adipokines such as resistin act as pro-inflammatory factors to stimulate immune cells which, in turn, promotes tumor angiogenesis, connective tissue proliferation, and matrix fibrosis. Concurrently, in states of metabolic dysfunction and lipotoxicity in obese individuals, the numbers and functions of immune cells are compromised, leading to an immunosuppressive environment that fosters tumor cell survival and weak cancer immune monitoring. Conclusion Adipokines such as resistin are important to the development of obesity-related tumors. Clarifying the roles for obesity-related factors in immune regulation and tumor progression may lead to the discovery of novel anti-tumor strategies for targeting obesity factors such as resistin to limit tumor growth and manage obesity, or both.

Investigation of serum apelin-13 and apelin-36 concentrations in pregnancies complicated by preeclampsia; a prospective case-control study

OBJECTIVE

We aimed to investigate the relationship between preeclampsia and maternal serum apelin-13 and apelin-36 concentrations.

METHODS

This cross-sectional study was carried out in the Gynecology and Obstetrics Clinic of Umraniye Training and Research Hospital. The preeclampsia group consisted of 40 pregnant women diagnosed with preeclampsia, and the control group consisted of 40 healthy pregnant women matched with the preeclampsia group in terms of age and body mass index. The two groups were compared in terms of maternal serum apelin-13 and apelin-36 concentrations.

RESULTS

Both groups were similar in terms of demographic characteristics and the gestational week at blood sampling. Maternal serum apelin-13 and apelin-36 concentrations were significantly lower in the preeclampsia group than in the control group (p = 0.005, p = 0.001, respectively). The optimal cutoff value for the prediction of preeclampsia in receiver operator curve analysis for apelin-13 was determined as 1781.67 pg/ml with 60% sensitivity and 60% specificity, and 885.5 pg/ml for apelin-36 with 67% sensitivity and 65% specificity. We divided the preeclampsia group into two groups mild and severe and compared the three groups in terms of maternal serum apelin-13 and apelin-36 concentrations. The lowest apelin-13 concentration was detected in the severe preeclampsia group, while the lowest apelin-36 concentration was detected in the mild preeclampsia group (p = 0.020, p = 0.003, respectively). Considering the onset of the disease, we divided the preeclampsia group into two groups early and late-onset, then compared the three groups in terms of maternal serum apelin-13 and apelin-36 concentrations. The lowest maternal serum apelin-13 and apelin-36 concentrations were detected in the early-onset preeclampsia group (p = 0.016, p = 0.001, respectively).

CONCLUSION

It was determined that serum apelin-13 and apelin-36 concentrations were significantly lower in preeclamptic pregnant women, this decrease was more significant in early-onset preeclampsia, and low maternal serum apelin-13 concentration was more associated with the severity of preeclampsia.

Expression of the apelin system in the porcine pituitary during the oestrous cycle and early pregnancy and the effect of apelin on LH and FSH secretion

Reproductive success requires considerable energy investment. Research has shown that some adipokines, i.e. the hormones produced in adipose tissue, affect reproductive functions by influencing all structures of the hypothalamic-pituitary-ovarian axis. Apelin is a recently identified member of the adipokine family. To the best of the authors' knowledge, this is the first study to investigate the gene and protein expression of the apelin system (the apelin hormone and the apelin receptor, APJ) in the anterior (AP) and posterior (PP) pituitary lobes of the domestic pig during different phases of the oestrous cycle (days 2 to 3, 10 to 12, 14 to 16, and 17 to 19) and in early pregnancy (days 10 to 11, 12 to 13, 15 to 16, and 27 to 28). It was also assumed that apelin participates in the regulation of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion and influences Akt, MAPK/Erk1/2, and AMPK signalling pathways in the AP during the oestrous cycle. Apelin, APJ mRNAs and proteins were detected in both pituitary lobes. Apelin was identified in gonadotropes, somatotropes, lactotropes, and thyrotropes. The study also revealed that apelin and APJ mRNA/protein levels fluctuate during the oestrous cycle and early gestation. Apelin affects basal, GnRH- and/or insulin-stimulated gonadotropin secretion in some phases of the cycle, as well as the phosphorylation of Akt, MAPK/Erk1/2, and AMPK proteins in AP cells. These findings suggest that apelin may be produced locally in the pituitary and that this gland is receptive to apelin's action. The study also suggest that apelin may influence female reproductive functions by controlling the release of LH and FSH from AP cells, and that it affects Akt, MAPK/Erk1/2, and AMPK signalling pathways.

Mechanisms by which obesity regulates inflammation and anti-tumor immunity in cancer

Obesity is associated with an increased risk for 13 different cancers. The increased risk for cancer in obesity is mediated by obesity-associated changes in the immune system. Obesity has distinct effects on different types of inflammation that are tied to tumorigenesis. For example, obesity promotes chronic inflammation in adipose tissue that is tumor-promoting in peripheral tissues. Conversely, obesity inhibits acute inflammation that rejects tumors. Obesity therefore promotes cancer by differentially regulating chronic versus acute inflammation. Given that obesity is chronic, the initial inflammation in adipose tissue will lead to systemic inflammation that could induce compensatory anti-inflammatory reactions in peripheral tissues to suppress chronic inflammation. The overall effect of obesity in peripheral tissues is therefore dependent on the duration and severity of obesity. Adipose tissue is a complex tissue that is composed of many cell types in addition to adipocytes. Further, adipose tissue cellularity is different at different anatomical sites throughout the body. Consequently, the sensitivity of adipose tissue to obesity is dependent on the anatomical location of the adipose depot. For example, obesity induces more inflammation in visceral than subcutaneous adipose tissue. Based on these studies, the mechanisms by which obesity promotes tumorigenesis are multifactorial and immune cell type-specific. The objective of our paper is to discuss the cellular mechanisms by which obesity promotes tumorigenesis by regulating distinct types of inflammation in adipose tissue and the tumor microenvironment.

Targeting Adipokines: A Promising Therapeutic Strategy for Epilepsy

Epilepsy affects 65 million people globally and causes neurobehavioral, cognitive, and psychological defects. Although research on the disease is progressing and a wide range of treatments are available, approximately 30% of people have refractory epilepsy that cannot be managed with conventional medications. This underlines the importance of further understanding the condition and exploring cutting-edge targets for treatment. Adipokines are peptides secreted by adipocyte's white adipose tissue, involved in controlling food intake and metabolism. Their regulatory functions in the central nervous system (CNS) are multifaceted and identified in several physiology and pathologies. Adipokines play a role in oxidative stress and neuroinflammation which are associated with brain degeneration and connected neurological diseases. This review aims to highlight the potential impacts of leptin, adiponectin, apelin, vaspin, visfatin, and chimerin in the pathogenesis of epilepsy.

Cholecystokinin regulates atrial natriuretic peptide secretion through activation of NOX4-Sirt1-LEF1 signaling in beating rat hypoxic atria

The mammalian cardiac myocytes not only synthesize and secrete atrial natriuretic peptide (ANP), but also express cholecystokinin (CCK) and its receptors (CCK1R and CCK2R). However, atrial CCK expression patterns and its effects on ANP secretion during hypoxia are unclear. Therefore, this study is aimed to investigate the effect of hypoxia on the expression levels of CCK and its receptors, as well as the underlying mechanisms involved in regulating hypoxia-induced ANP secretion in isolated beating atria. The results of this study showed that acute hypoxia significantly upregulated expression of CCK and CCK1R as well as CCK2R through activation of hypoxia-inducible factor 1α-apelin signaling. Endogenous CCK induced by hypoxia markedly upregulated the expression of silent information regulator factor 2-related enzyme 1 (Sirt1) and its downstream nuclear factor erythroid‑2‑related factor 2 (Nrf2) via the activation of nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4), leading to increase of activating T cell factor (TCF) 3 and TCF4/ lymphoid enhancer factor (LEF) 1, ultimately promoting hypoxia-induced ANP secretion. In addition, siRNA-mediated knockdown of LEF1 dramatically attenuated hypoxia-induced increase of ANP expression in HL-1 atrial myocytes. These results indicated endogenous CCK induced by hypoxia promoted hypoxia-induced ANP secretion by activation of NOX4-Sirt1-TCF3/4-LEF1 signaling pathway.

Apelin/APJ signaling in IGF-1-induced acute mitochondrial and antioxidant effects in spontaneously hypertensive rat myocardium

IGF-1 and apelin are released in response to exercise training with beneficial effects. Previously we demonstrated that a swimming routine is effective to convert pathological into physiological cardiac hypertrophy, and that IGF-1 improves contractility and the redox state, in spontaneously hypertensive rats (SHR). Now, we hypothesize that the apelinergic pathway is involved in the cardioprotective effects of IGF-1 in the SHR. We assessed the redox state and mitochondrial effects of IGF-1 or apelin in the presence/absence of AG1024 or ML221 [pharmacological antagonists of IGF1 (IGF1R) and apelin (APJ) receptors, respectively] in SHR isolated cardiomyocytes or perfused hearts. Acute IGF-1 (10 nmol/L) significantly: -reduced H2O2 production (IGF-1:62 ± 6; control:100 ± 8.1, %), -increased the activity of superoxide dismutase (IGF-1:193 ± 17, control: 100 ± 13,%), -prevented H2O2-induced ΔΨm loss (TMREF10min/F0 min: IGF-1:0.93 ± 0.017, control: 0.72 ± 0.029), -reduced mitochondrial permeability transition pore (mPTP) opening estimated by the calcium retention capacity (nmol/mg protein, IGF-1:251 ± 34, control:112 ± 5), and -increased P-AMPK (IGF-1:129 ± 0.9, control: 100 ± 2%) and P-AKT (IGF-1:143 ± 17 control:100 ± 6, %). These effects were suppressed not only by the antagonism of IGF1R but also of APJ. Moreover, IGF-1 significantly increased APJ (IGF-1:198 ± 29 control:100 ± 15,%) and apelin mRNAs (IGF-1:251 ± 48, control:100 ± 6,%). On the other hand, an equipotent dose of exogenous apelin (50 nmol/L) emulated IGF-1 effects being cancelled by the antagonism of APJ however not by AG1024. IGF-1/IGF1R stimulates the apelinergic pathway, improving the redox balance and mitochondria status in the pathologically hypertrophied myocardium of the SHR.

Effect of acute anaerobic performance on zinc alpha 2 glycoprotein, apelin and lipasin levels

The aim of this study was to investigate the effects of acute anaerobic exercise on serum levels of adipokines Zinc-α2-glycoprotein (ZAG), apelin, and lipasin. Eighteen male athletes who actively played soccer and trained at least four days a week, with a mean age of 19.11 ± 2.59 years, body weight of 70.61 ± 8.17 kg, height of 176.0 ± 7.71 cm, sport age of 7.22 ± 2.60 years and BMI of 22.76 ± 1.68 kg/m2 participated in the study. Athletes were subjected to the Running-Based Anaerobic Sprint Test (RAST) for anaerobic performance. Blood samples were collected from the athletes 4 times (at rest, 10 minutes, 60 minutes, and 24 hours after exercise). The results of the study showed that acute anaerobic exercise significantly increased ZAG levels (p < 0.05). However, no statistically significant difference was detected in apelin and lipasin levels (p > 0.05). In conclusion, the findings of this study indicate that acute anaerobic exercise is associated with an increase in ZAG levels, but not apelin or lipasin levels. The observations suggest that ZAG may have a specific response to anaerobic exercise, which provides valuable insight into its potential impact on energy metabolism.

Decoding Apelin: Its Role in Metabolic Programming, Fetal Growth, and Gestational Complications

Placental insufficiency and gestational diabetes, which are both serious pregnancy complications, are linked to altered fetal growth, whether restricted or excessive, and result in metabolic dysfunction, hypoxic/oxidative injury, and adverse perinatal outcomes. Although much research has been carried out in this field, the underlying pathogenetic mechanisms have not as yet been fully elucidated. Particularly because of the role it plays in cardiovascular performance, glucose metabolism, inflammation, and oxidative stress, the adipokine apelin was recently shown to be a potential regulator of fetal growth and metabolic programming. This review investigated the numerous biological actions of apelin in utero and aimed to shed more light on its role in fetal growth and metabolic programming. The expression of the apelinergic system in a number of tissues indicates its involvement in many physiological mechanisms, including angiogenesis, cell proliferation, energy metabolism, inflammation, and oxidative stress. Moreover, it appears that apelin has a major function in disorders such as diabetes mellitus, fetal growth abnormalities, fetal hypoxia, and preeclampsia. We herein describe in detail the regulatory effects exerted by the adipokine apelin on fetal growth and metabolic programming while stressing the necessity for additional research into the therapeutic potential of apelin and its mechanisms of action in pregnancy-related disorders.

The adipokine profile in the plasma and anterior pituitary of pigs during the estrous cycle

Adipokines play crucial roles in both reproductive and energy metabolic processes. This study aimed to compare the hormonal plasma profile of adiponectin, apelin, vaspin, chemerin, resistin, visfatin, and adipolin, and the expression of their receptors in the anterior pituitary (AP) between normal-weight Large White (LW) and fat Meishan (MS) pigs during different phases of the estrous cycle. We measured adipokine levels in the plasma and assessed their gene expression in the AP. We used Pearson's correlation analysis to examine potential links between adipokines levels, their receptors, and metabolic parameters (body weight; backfat thickness) and reproductive parameters (pituitary weight; age at puberty; levels of gonadotropins, steroid hormones; and gene expression of gonadotropin-releasing hormone receptor and gonadotropins in AP). The plasma levels of the evaluated adipokines fluctuated with phase and breed, except for visfatin and adipolin. Moreover, adipokine expression in AP varied significantly between breeds and estrous cycle phases, except for resistin receptor CAP1. Notably, we observed a positive correlation between plasma levels of adiponectin and its transcript in the AP only in MS pigs. Apelin gene expression correlated negatively with its receptor in MS, while we observed a breed-dependent correlation between chemerin gene expression and its receptor CMKLR1. We identified significant positive or negative correlations between adipokines or their receptor levels in plasma and AP as well as metabolic or reproductive parameters, depending on the breed. In conclusion, we have demonstrated breed-specific and estrous cycle-dependent regulation of adipokines in AP, underscoring their potential impact on metabolic and reproductive processes in swine.

Targeting PI3K/Akt in Cerebral Ischemia Reperfusion Injury Alleviation: From Signaling Networks to Targeted Therapy

Ischemia/reperfusion (I/R) injury is a pathological event that results in reperfusion due to low blood flow to an organ. Cerebral ischemia is a common cerebrovascular disease with high mortality, and reperfusion is the current standard intervention. However, reperfusion may further induce cellular damage and dysfunction known as cerebral ischemia/reperfusion injury (CIRI). Currently, strategies for the clinical management of CIRI are limited, necessitating the exploration of novel and efficacious treatment modalities for the benefit of patients. PI3K/Akt signaling pathway is an important cellular process associated with the disease. Stimulation of the PI3K/Akt pathway enhances I/R injury in multiple organs such as heart, brain, lung, and liver. It stands as a pivotal signaling pathway crucial for diminishing cerebral infarction size and safeguarding the functionality of brain tissue after CIRI. During CIRI, activation of the PI3K/Akt pathway exhibits a protective effect on CIRI. Furthermore, activation of the PI3K/Akt pathway has the potential to augment the activity of antioxidant enzymes, resulting in a decrease in reactive oxygen species (ROS) and the associated oxidative stress. Meanwhile, PI3K/Akt plays a neuroprotective role by inhibiting inflammatory responses and apoptosis. For example, PI3K/Akt interacts with NF-κB, Nrf2, and MAPK signaling pathways to mitigate CIRI. This article is aimed to explore the pivotal role and underlying mechanism of PI3K/Akt in ameliorating CIRI and investigate the influence of ischemic preconditioning and post-processing, as well as the impact of pertinent drugs or activators targeting the PI3K/Akt pathway on CIRI. The primary objective is to furnish compelling evidence supporting the activation of PI3K/Akt in the context of CIRI, elucidating its mechanistic intricacies. By doing so, the paper aims to underscore the critical contribution of PI3K/Akt in mitigating CIRI, providing a theoretical foundation for considering the PI3K/Akt pathway as a viable target for CIRI treatment.

The effects of apelin-13 in a mouse model of post-traumatic stress disorder

The objective is to investigate the effects of apelin-13 in models of post-traumatic stress disorder (PTSD). Mature male CD1 mice were subjected to the single prolonged stress method to induce PTSD-related behaviors. These behaviors were then evaluated using the elevated plus maze test, Morris water maze test, and open field test. Hippocampal neural cell death was assessed using propidium iodide labeling. The expression of hippocampal autophagy pathway-associated proteins was determined through immunoblotting analysis, and LC3 levels were also measured via quantitative real-time reverse transcription-PCR. The results demonstrate that administration of apelin-13 suppressed PTSD-induced hippocampal neural cell death and alleviated PTSD-related behaviors in mice. Additionally, PTSD led to an up-regulation of LC3 and FoxO3a, and down-regulation of P62, p-PI3K, p-Akt, and p-FoxO3a in the hippocampus. However, these changes were reversed by apelin-13 treatment. These findings support the hypothesis that apelin-13 prevents the development of PTSD-like behavior and inhibits autophagy of neuronal cells in a mouse model of PTSD. Apelin-13 may hold potential as a therapeutic agent for PTSD in clinical applications.

Research advances in understanding crosstalk between organs and pancreatic β-cell dysfunction

Obesity has increased dramatically worldwide. Being overweight or obese can lead to various conditions, including dyslipidaemia, hypertension, glucose intolerance and metabolic syndrome (MetS), which may further lead to type 2 diabetes mellitus (T2DM). Previous studies have identified a link between β-cell dysfunction and the severity of MetS, with multiple organs and tissues affected. Identifying the associations between pancreatic β-cell dysfunction and organs is critical. Research has focused on the interaction between the liver, gut and pancreatic β-cells. However, the mechanisms and related core targets are still not perfectly elucidated. The aims of this review were to summarize the mechanisms of β-cell dysfunction and to explore the potential pathogenic pathways and targets that connect the liver, gut, adipose tissue, muscle, and brain to pancreatic β-cell dysfunction.

Microparticle Mediated Delivery of Apelin Improves Heart Function in Post Myocardial Infarction Mice

BACKGROUND

Apelin is an endogenous prepropeptide that regulates cardiac homeostasis and various physiological processes. Intravenous injection has been shown to improve cardiac contractility in patients with heart failure. However, its short half-life prevents studying its impact on left ventricular remodeling in the long term. Here, we aim to study whether microparticle-mediated slow release of apelin improves heart function and left ventricular remodeling in mice with myocardial infarction (MI).

METHODS

A cardiac patch was fabricated by embedding apelin-containing microparticles in a fibrin gel scaffold. MI was induced via permanent ligation of the left anterior descending coronary artery in adult C57BL/6J mice followed by epicardial patch placement immediately after (acute MI) or 28 days (chronic MI) post-MI. Four groups were included in this study, namely sham, MI, MI plus empty microparticle-embedded patch treatment, and MI plus apelin-containing microparticle-embedded patch treatment. Cardiac function was assessed by transthoracic echocardiography. Cardiomyocyte morphology, apoptosis, and cardiac fibrosis were evaluated by histology. Cardioprotective pathways were determined by RNA sequencing, quantitative polymerase chain reaction, and Western blot.

RESULTS

The level of endogenous apelin was largely reduced in the first 7 days after MI induction and it was normalized by day 28. Apelin-13 encapsulated in poly(lactic-co-glycolic acid) microparticles displayed a sustained release pattern for up to 28 days. Treatment with apelin-containing microparticle-embedded patch inhibited cardiac hypertrophy and reduced scar size in both acute and chronic MI models, which is associated with improved cardiac function. Data from cellular and molecular analyses showed that apelin inhibits the activation and proliferation of cardiac fibroblasts by preventing transforming growth factor-β-mediated activation of Smad2/3 (supporessor of mothers against decapentaplegic 2/3) and downstream profibrotic gene expression.

CONCLUSIONS

Poly(lactic-co-glycolic acid) microparticles prolonged the apelin release time in the mouse hearts. Epicardial delivery of the apelin-containing microparticle-embedded patch protects mice from both acute and chronic MI-induced cardiac dysfunction, inhibits cardiac fibrosis, and improves left ventricular remodeling.

The protective effects of apelin-13 in HIV-1 tat- induced macrophage infiltration and BBB impairment

Impairment of the blood - brain barrier (BBB) and subsequent inflammatory responses contribute to the development of human immunodeficiency virus (HIV)-1-associated neurocognitive disorders (HAND). Apelin-13, the most abundant member of the apelin family, acts as the ligand of the angiotensin receptor-like 1 (APJ). However, its pharmacological function in HAND and its underlying mechanism are unknown. In the current study, we report that the presence of HIV-1 Tat reduced the levels of Apelin-13 and APJ in the cortex tissue of mice. Importantly, Apelin-13 preserved BBB integrity against HIV-1 Tat in mice by increasing the expression of the tight junction protein zonula occludens-1 (ZO-1) and occludin. Interestingly, increased macrophage infiltration, indicated by elevated CD68-positive staining was observed in the cortex after stimulation with HIV-1, which was mitigated by the administration of Apelin-13. Correspondingly, Apelin-13 reduced the expression of monocyte chemoattractant protein-1; (MCP-1). An in vitro two-chamber and two-cell trans-well assay demonstrated that HIV-1 Tat challenge significantly promoted macrophage migration, which was notably attenuated by the introduction of Apelin-13. Accordingly, treatment with Apelin-13 restored the HIV-1 Tat-induced reduction of occludin and ZO-1, while preventing the upregulation of MCP-1 in human brain microvascular endothelial cells (HBMVECs). Our results suggest that Apelin-13 may reduce macrophage infiltration into brain tissues and mitigate BBB dysfunction in patients with HAND.

Immunodetection of selected pancreatic hormones under intragastric administration of apelin-13, a novel endogenous ligand for an angiotensin-like orphan G-protein coupled receptor, in unweaned rats

Introduction

This study investigated the effects of intragastric administration of apelin-13 on the secretion of critical pancreatic hormones in a cohort of three-week-old Wistar rats. The research aimed to uncover apelin's modulatory roles in endocrine interactions dictating metabolic homeostasis during early life.

Material and Methods

Rats were randomly assigned to control or experimental groups, receiving apelin-13 or saline for 14 days. The study population consisted of three-week-old Wistar rats of both sexes, weighing between 20 and 25 grams. Histological examination, analysis of variance and t-tests were employed to assess significant differences.

Results

Distinctive alterations in large islet morphology were observed, indicating a notable reduction in size. Additionally, an increase in alpha- and beta-cell density within specific islet sizes was noted, suggesting significant changes in cell populations. The study found a substantial increase in mitotic activity and a decrease in apoptosis in small and medium-sized islets post apelin-13 administration, indicating its potential role in regulating cell survival and proliferation.

Conclusion

The notable reduction in large islet size coupled with increased alpha and beta cell density implies a targeted impact of apelin-13 on pancreatic cell dynamics. Also, the observed increase in mitotic activity and decrease in apoptosis in small and medium-sized islets suggest its potential regulatory role in cell survival and proliferation within the pancreatic microenvironment.

The significance of the apelinergic system in doxorubicin-induced cardiotoxicity

Cancer is the leading cause of death worldwide, and the number of cancer-related deaths is expected to increase. Common types of cancer include skin, breast, lung, prostate, and colorectal cancers. While clinical research has improved cancer therapies, these treatments often come with significant side effects such as chronic fatigue, hair loss, and nausea. In addition, cancer treatments can cause long-term cardiovascular complications. Doxorubicin (DOX) therapy is one example, which can lead to decreased left ventricle (LV) echocardiography (ECHO) parameters, increased oxidative stress in cellular level, and even cardiac fibrosis. The apelinergic system, specifically apelin and its receptor, together, has shown properties that could potentially protect the heart and mitigate the damages caused by DOX anti-cancer treatment. Studies have suggested that stimulating the apelinergic system may have therapeutic benefits for heart damage induced by DOX. Further research in chronic preclinical models is needed to confirm this hypothesis and understand the mechanism of action for the apelinergic system. This review aims to collect and present data on the effects of the apelinergic system on doxorubicin-induced cardiotoxicity.

Hormonal dependent expression of apelin and apelin receptor in the ovary and uterus of mice

Apelin and APJ have been shown to regulate female reproductive functions. However, its uterine expression during the oestrous cycle and its regulation by ovarian steroids, along with gonadotropin regulation in the ovary, has not been investigated. This study aimed to analyze the steroid-dependent uterine expression of apelin/APJ in the uterus along with the oestrous cycle. Furthermore, it also aimed to investigate gonadotropin-dependent ovarian expression of apelin and APJ. To investigate the uterine expression of apelin and APJ during estrous cycle in mice, uterus at different estrous stage were collected. To explore the ovarian steroids dependent expression of apelin system in the uterus, ovariectomized mice were treated with only estrogen at dose of 30 ng/g, only progesterone at dose of 150 μg/g and combined doses. To study the effect of gonadotropin on ovarian expression of apelin system, immature mice were injected with 2.5 IU of pregnant mare serum gonadotropin (PMSG) alone and both PMSG plus 2.5 IU of chorionic gonadotropin (hCG). Apelin and APJ protein expression are modulated by estrous phases in the uterus. The uterine apelin and APJ expression are up-regulated by estrogen and down-regulated by progesterone. The expression and localization of APJ showed increased abundance in the follicles of PMSG treated mice, however, the PMSG plus HCG treatment showed formation of corpus luteum with increased abundance of APJ and progesterone secretion. The expression of apelin and APJ are regulated by pituitary gonadotropin in the ovary and uterine apelin system by ovarian steroid hormone.

Reciprocal Interactions Between Apelin and Noncoding RNAs in Cancer Progression

Apelin, a bioactive peptide that serves as an endogenous ligand for the apelin receptor (APJ), is overexpressed in various types of cancers and contributes to cancer cell proliferation, viability, migration, angiogenesis, and metastasis, as well as immune deviation. Noncoding RNAs (ncRNAs) regulate gene expression, and there is growing evidence suggesting a bidirectional crosstalk between ncRNAs (including long noncoding RNAs [lncRNAs], circular RNAs [circRNAs], and microRNAs [miRNAs]) and apelin in cancers. Certain miRNAs can directly target the apelin and inhibit its expression, thereby suppressing tumor growth. It has been indicated that miR-224, miR-195/miR-195-5p, miR-204-5p, miR-631, miR-4286, miR-637, miR-4493, and miR-214-3p target apelin mRNA and influence its expression in prostate cancer, lung cancer, esophageal cancer, chondrosarcoma, melanoma, gastric cancer, glioma, and hepatocellular carcinoma (HCC), respectively. Moreover, circ-NOTCH1, circ-ZNF264, and lncRNA BACE1-AS upregulate apelin expression in gastric cancer, glioma, and HCC, respectively. On the other hand, apelin has been shown to regulate the expression of certain ncRNAs to affect tumorigenesis. It was revealed that apelin affects the expression of circ_0000004/miR-1303, miR-15a-5p, and miR-106a-5p in osteosarcoma, lung cancer, and prostate cancer, respectively. This review explains a bidirectional interplay between ncRNAs and apelin in cancers to provide insights concerning the molecular mechanisms underlying this crosstalk and potential implications for cancer therapy.

Gz Enhanced Signal Transduction assaY (GZESTY) for GPCR deorphanization

G protein-coupled receptors (GPCRs) are key pharmacological targets, yet many remain underutilized due to unknown activation mechanisms and ligands. Orphan GPCRs, lacking identified natural ligands, are a high priority for research, as identifying their ligands will aid in understanding their functions and potential as drug targets. Most GPCRs, including orphans, couple to Gi/o/z family members, however current assays to detect their activation are limited, hindering ligand identification efforts. We introduce GZESTY, a highly sensitive, cell-based assay developed in an easily deliverable format designed to study the pharmacology of Gi/o/z-coupled GPCRs and assist in deorphanization. We optimized assay conditions and developed an all-in-one vector employing novel cloning methods to ensure the correct expression ratio of GZESTY components. GZESTY successfully assessed activation of a library of ligand-activated GPCRs, detecting both full and partial agonism, as well as responses from endogenous GPCRs. Notably, with GZESTY we established the presence of endogenous ligands for GPR176 and GPR37 in brain extracts, validating its use in deorphanization efforts. This assay enhances the ability to find ligands for orphan GPCRs, expanding the toolkit for GPCR pharmacologists.

The emerging role of nuclear receptor coactivator 4 in health and disease: a novel bridge between iron metabolism and immunity

Nuclear receptor coactivator 4 (NCOA4) has recently been recognized as a selective cargo receptor of ferritinophagy participating in ferroptosis. However, NCOA4 is also a coactivator that modulates the transcriptional activity of many vital nuclear receptors. Recent novel studies have documented the role of NCOA4 in healthy and pathogenic conditions via its modulation of iron- and non-iron-dependent metabolic pathways. NCOA4 exhibits non-ferritinophagic and iron-independent features such as promoting tumorigenesis and erythropoiesis, immunomodulation, regulating autophagy, and participating in DNA replication and mitosis. Full-length human-NCOA4 is composed of 614 amino acids, of which the N-terminal (1-237) contains nuclear-receptor-binding domains, while the C-terminal (238-614) principally contains a ferritin-binding domain. The exploration of the protein structure of NCOA4 suggests that NCOA4 possesses additional significant and complex functions based on its structural domains. Intriguingly, another three isoforms of NCOA4 that are produced by alternative splicing have been identified, which may also display disparate activities in physiological and pathological processes. Thus, NCOA4 has become an important bridge that encompasses interactions between immunity and metabolism. In this review, we outline the latest advances in the important regulating mechanisms underlying NCOA4 actions in health and disease conditions, providing insights into potential therapeutic interventions.

Potential Involvement of Apelin/APJ System in Addiction and Neuroprotection Against Drugs of Abuse

Addiction, characterized by compulsive drug-seeking behavior and impaired self-control, remains a significant public health concern. Understanding the neurobiology of addiction is crucial for identifying novel therapeutic targets and further developing effective treatments. Recently, the apelin/APJ system, an emerging signaling pathway, has attracted attention for its involvement in various neuropsychiatric disorders. The cross-talk between the apelin/APJ system and hypothalamic mu opioid signaling, as well as its heterodimerization with kappa opioid receptors (KORs), supports the potential relevance of this system to addiction. Moreover, several protective effects of apelin against various addictive substances, including methamphetamine, morphine, and alcohol, underscore the need for further investigation into its role in substance use disorder. Understanding the contribution of the apelin/APJ system in addiction may offer valuable insights into the underlying neurobiology and pave the way for novel therapeutic interventions in substance use disorders. This review provides a concise overview of the apelin/APJ system, emphasizing its physiological roles and highlighting its relevance to addiction research.

Apelin receptor modulation mitigates letrozole-induced polycystic ovarian pathogenesis in mice

AIMS

Polycystic ovarian syndrome (PCOS) is one of the most common (about 5-20%) reproductive disorders in women of reproductive age; it is characterized by polycystic ovaries, hyperandrogenism, and oligo/ anovulation. The levels and expression of ovarian adipokines are deregulated in the PCOS. Apelin is an adipokine that acts through its receptor (APJ) and is known to express in the various tissues including the ovary. It has also been suggested that apelin and APJ could be targeted as therapeutic adjuncts for the management of PCOS. However, no study has been conducted on the management of PCOS by targeting the apelin system. Thus, we aimed to evaluate its impact on combating PCOS-associated ovarian pathogenesis.

METHODS

The current work employed a letrozole-induced-hyperandrogenism PCOS-like mice model to investigate the effects of apelin13 and APJ, antagonist ML221. The PCOS model was induced by oral administration of letrozole (1 mg/kg) for 21 days. A total of four experimental groups were made, control, PCOS control, PCOS + aplein13, and PCOS + ML221. The treatment of apelin13 and ML221 was given from day 22 for two weeks.

KEY FINDINGS

The letrozole-induced PCOS-like features such as hyperandrogenism, cystic follicle, decreased corpus luteum, elevated levels of LH/FSH ratio, and up-regulation of ovarian AR expression were ameliorated by apelin13 and ML221 treatment. However, the PCOS-augmented oxidative stress and apoptosis were suppressed by apelin 13 treatments only. ML221 treatment still showed elevated oxidative stress and stimulated apoptosis as reflected by decreased antioxidant enzymes and increased active caspase3 and Bax expression. The expression of ERs was elevated in all groups except control. Furthermore, the PCOS model showed elevated expression of APJ and apelin13 treatment down-regulated its own receptor. Overall, observing the ovarian histology, corpus luteum formation, and decreased androgen levels by both apelin13 and ML221 showed ameliorative effects on the cystic ovary.

SIGNIFICANCE

Despite the similar morphological observation of ovarian histology, apelin13 and ML221 exhibited opposite effects on oxidative stress and apoptosis. Therefore, apelin13 (which down-regulates APJ) and ML221 (an APJ antagonist) may have suppressed APJ signalling, which would account for our findings on the mitigation of polycystic ovarian syndrome. In conclusion, both apelin13 and ML221 mediated mitigation have different mechanisms, which need further investigation.

Serum apelin as a potential biomarker for infantile hemangiomas

BACKGROUND

Infantile hemangiomas (IHs) are common benign vascular tumors in infants. Apelin, an endogenous cytokine, is implicated in the angiogenesis of neoplastic diseases. We aimed to explore the association between apelin and IHs, providing a foundation for clinical applications.

METHODS

We identified differential expression of apelin in proliferative IHs compared to healthy controls (HCs) through bioinformatics analysis of publicly available databases and verified by Immunofluorescence. Enzyme-linked immunosorbent assay was used to quantify the serum levels of apelin and vascular endothelial growth factor (VEGF) in a cohort of 116 cases of proliferative IHs, 65 cases of capillary malformations (CMs), and 70 HCs.

RESULTS

Apelin and APJ (APLNR, apelin receptor) were identified as the significantly upregulated differentially expressed genes (DEGs) in proliferative IHs. Immunofluorescence staining indicated high expression of apelin in proliferative IHs, while minimal expression in non-IH lesions. Apelin in IHs was reduced following 6 months of propranolol treatment. Serum apelin levels were significantly higher in the IH group compared to both the CM and HC groups. Moreover, apelin exhibited excellent discriminatory ability in distinguishing IHs from HCs, with an area under the curve (AUC) exceeding 0.90. A positive correlation was observed between the levels of apelin and the size of superficial IHs. The expression profiles of VEGF and apelin in IHs were found to be consistent.

CONCLUSIONS

Apelin shows promise as a potential biomarker for IHs. The association between apelin and IH size, as well as its responsiveness to propranolol treatment, indicates its possible utility as a valuable indicator for the therapeutic evaluation of IHs.

The role of asprosin in regulating ovarian granulosa- and theca-cell steroidogenesis: a review with comparisons to other adipokines

Adipose tissues produce a variety of biologically active compounds, including cytokines, growth factors and adipokines. Adipokines are important as they function as endocrine hormones that are related to various metabolic and reproductive diseases. The goal of this review was to summarise the role of asprosin, a recently discovered adipokine, and compare its role in ovarian steroidogenesis with that of other adipokines including adiponectin, leptin, resistin, apelin, visfatin, chemerin, irisin, and gremlin 1. The summary of concentrations of these adipokines in humans, rats and other animals will help researchers identify appropriate doses to test in future studies. Review of the literature indicated that asprosin increases androstenedione production in theca cells (Tc), and when cotreated with FSH increases oestradiol production in granulosa cells (Gc). In comparison, other adipokines (1) stimulate Gc oestradiol production but inhibit Tc androgen production (adiponectin), (2) inhibit Gc oestradiol production and Tc androstenedione production (leptin and chemerin), (3) inhibit Gc steroidogenesis with no effect on Tc (resistin), (4) inhibit Gc oestradiol production but stimulate Tc androgen production (gremlin 1), and (5) increase steroid secretion by Gc, with unknown effects on Tc steroidogenesis (apelin and visfatin). Irisin has direct effects on Gc but its precise role (inhibitory or stimulatory) may be species dependent and its effects on Tc will require additional research. Thus, most adipokines have direct effects (either positive or negative) on steroid production in ovarian cells, but how they all work together to create a cumulative effect or disease will require further research.

Alared: Solvatochromic and Fluorogenic Red Amino Acid for Ratiometric Live-Cell Imaging of Bioactive Peptides

To fill the need for environmentally sensitive fluorescent unnatural amino acids able to operate in the red region of the spectrum, we have designed and synthesized Alared, a red solvatochromic and fluorogenic amino acid derived from the Nile Red chromophore. The new unnatural amino acid can be easily integrated into bioactive peptides using classical solid-phase peptide synthesis. The fluorescence quantum yield and the emission maximum of Alared-labeled peptides vary in a broad range depending on the peptide's environment, making Alared a powerful reporter of biomolecular interactions. Due to its red-shifted absorption and emission spectra, Alared-labeled peptides could be followed in living cells with minimal interference from cellular autofluorescence. Using ratiometric fluorescence microscopy, we were able to track the fate of the Alared-labeled peptide agonists of the apelin G protein-coupled receptor upon receptor activation and internalization. Due to its color-shifting environmentally sensitive emission, Alared allowed for distinguishing the fractions of peptides that are specifically bound to the receptor or unspecifically bound to different cellular membranes.

The biological efficacy of Apelin against focal transient cerebral ischemia-reperfusion injury. A systematic review and meta-analysis of animal studies

BACKGROUND

Apelin has been extensively studied, and emerging experimental evidence suggests that Apelin may have effects on stroke by reducing infarct volume and neurological deficits, inhibiting the apoptosis process and reducing brain water content. However, the credibility of the evidence is uncertain. Thus, we aimed to perform a systematic review and meta-analysis to evaluate preclinical studies that used Apelin for the treatment of transient focal cerebral ischemia.

METHODS

Electronic bibliographic databases including PubMed, EMBASE, Scopus, and Google Scholar were searched for finding relevant studies from January 2000 to July 2023. The methodological quality and risk of bias scores for animal studies were calculated based on the CAMARADES and the SYRCLE's RoB tools, respectively. The effect sizes were assessed using Comprehensive Meta-Analysis (CMA) software.

RESULTS

A total of twelve eligible studies were used for the systematic review and meta-analysis. The median scores of study quality and risk of bias were 7.5 out of 10, and 5 out of 10, respectively. Apelin treatment effectively decreased infarct volume (primary outcome) [Hedges' g = 2.72, 95 % CI (1.93, 3.51), p < 0.001], neurological deficit [Hedges' g = 1.76, 95 % CI (0.96, 2.55), p < 0.001], cleaved caspase 3 [Hedges' g = 2.16, 95 % CI (0.87, 3.44), p = 0.001], and apoptotic cell number [Hedges' g = 4.07, 95 % CI (1.25,6.89), p = 0.005] compared with the control group. According to subgroup analysis, more notable neuroprotective effects were observed with intravenous administration than with intracerebroventricular (ICV) administration. Moreover, we determined that effect size of infarct volume was markedly related to the species. The combined measurement of two studies demonstrated that Apelin could reduce BCL2 and TNF-α levels as well as brain water content compared with the control group. However, pooled measurement of two studies showed that no relevancy was discovered between CHOP and altering infarct volume.

CONCLUSION

The present meta-analysis was conducted to assess preclinical studies related to Apelin treatment in rodent ischemic stroke. Apelin can exert promising neuroprotective effects by reducing infarct volume, neurological deficit, caspase 3, apoptotic cell number, TNF- α and brain water content and increasing BCL2. The current evidence supports the anti-apoptotic and anti-inflammatory properties of Apelin, but its effectiveness in decreasing CHOP level in animal models of ischemic stroke needs further elucidation. This study was registered within the International Prospective Register of Systematic Reviews (PROSPERO) as number CRD42023460926.

Relationship between serum apelin, visfatin levels, and body composition in Polycystic Ovary Syndrome patients

OBJECTIVE

To investigate the relationship between body composition and serum visfatin and apelin levels in patients with polycystic ovary syndrome (PCOS).

METHODS

In this prospective observational study, the differences in body composition, levels of gonadal hormone concentrations, glucose metabolism, apelin, and visfatin were compared between PCOS patients and the control group. PCOS patients were further divided into different subgroups according to different obesity criteria and the differences between serum visfatin and apelin levels in different subgroups were compared. Finally, the correlation of serum visfatin levels and apelin levels with body composition, and metabolism-related indicators in PCOS patients was explored.

RESULTS

A total collected 178 cases of PCOS patients and 172 cases of healthy women (control group) between 2020 July and 2021 November. In PCOS patients, their weight, Body Mass Index (BMI), Waist Hip Rate (WHR), Fat-Free Mass Index (FFMI), Percent Body Fat (PBF), Fat mass index (FMI), PBF of Arm, PBF of Leg, PBF of the Trunk, Visceral Fat Level (VFL), fasting insulin (FINS), Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and Luteinizing hormone (LH) were significantly higher than in the control group (all P < 0.001), Percent Skeletal Muscle (PSM), PSM of Leg, and PSM of the Trunk were significantly decreased than in the control group (all P < 0.001). The PCOS patients had significantly higher serum visfatin levels and apelin levels compared with the control group (all P < 0.001). In PBF > 35 % PCOS patients, the apelin and visfatin levels were significantly higher than the PBF ≤ 35 % PCOS patients. In WHR ≥ 0.85 and BMI ≥ 24 kg/m2 PCOS patients, the visfatin levels were significantly higher than the WHR < 0.85 and BMI < 24 kg/m2 PCOS patients. Serum apelin and visfatin positively correlated with BMI level, WHR, FFMI, PBF, FMI, PBF of arms, PBF of legs, PBF of the trunk, VFL, FBG, HOMA-IR index and negatively correlated with PSM, PSM of legs, and PSM of the trunk (all P < 0.001).

CONCLUSIONS

Compared with healthy women, Patients with PCOS have an increased fat content in various parts of the body, reduced skeletal muscle content, and are often complicated by metabolic abnormalities. Serum visfatin and apelin correlated not only with obesity, fat mass, and fat distribution but also with muscle mass and distribution. It may be possible to reduce the long-term risk of metabolic disease in PCOS through the monitoring and management of the body composition in PCOS patients or to reflect the therapeutic effect of PCOS.

Neuroprotective effect of apelin-13 and other apelin forms-a review

Neurodegenerative diseases, which occur when neurons begin to deteriorate, affect millions of people worldwide. These age-related disorders are becoming more common partly because the elderly population has increased in recent years. While no treatments are accessible, every year an increasing number of therapeutic and supportive options become available. Various substances that may have neuroprotective effects are currently being researched. One of them is apelin. This review aims to illustrate the results of research on the neuroprotective effect of apelin amino acid oligopeptide which binds to the apelin receptor and exhibits neuroprotective effects in the central nervous system. The collected data indicate that apelin can protect the central nervous system against injury by several mechanisms. More studies are needed to thoroughly investigate the potential neuroprotective effects of this peptide in neurodegenerative diseases and various other types of brain damage.

Endocrine Aspects of Pain Pathophysiology: Focus on Adipose Tissue

BACKGROUND

Multiple factors, including neurobiological, hormonal, psychological, and social/cultural norms, influence the manner in which individuals experience pain. Adipose tissue, once considered solely an energy storage site, has been recognized as a significant endocrine organ that produces and releases a range of hormones and cytokines. In recent years, research has highlighted the role of adipose tissue and its endocrine factors in the pathophysiology of pain.

SUMMARY

This narrative review aimed to provide a comprehensive overview of the current knowledge on the endocrine aspects of pain pathophysiology, with a specific focus on adipose tissue. We examine the role of adipokines released by adipose tissue, such as leptin, adiponectin, resistin, visfatin, asprosin in pain perception and response. We also explore the clinical implications of these findings, including the potential for personalized pain management based on endocrine factors and adipose tissue.

KEY MESSAGES

Overall, given this background, this review intended to highlight the importance of understanding the endocrine aspects of pain pathophysiology, particularly focusing on the role of adipose tissue, in the development of chronic pain and adipokines. Better understanding the role of adipokines in pain modulation might have therapeutic implications by providing novel targets for addressing underlying mechanism rather than directly focusing on symptoms for chronic pain, particularly in obese individuals.

Effects of eicosapentaneoic acid on innate immune responses in an Atlantic salmon kidney cell line in vitro

Studies of the interplay between metabolism and immunity, known as immunometabolism, is steadily transforming immunological research into new understandings of how environmental cues like diet are affecting innate and adaptive immune responses. The aim of this study was to explore antiviral transcriptomic responses under various levels of polyunsaturated fatty acid. Atlantic salmon kidney cells (ASK cell line) were incubated for one week in different levels of the unsaturated n-3 eicosapentaneoic acid (EPA) resulting in cellular levels ranging from 2-20% of total fatty acid. These cells were then stimulated with the viral mimic and interferon inducer poly I:C (30 ug/ml) for 24 hours before total RNA was isolated and sequenced for transcriptomic analyses. Up to 200 uM EPA had no detrimental effects on cell viability and induced very few transcriptional changes in these cells. However, in combination with poly I:C, our results shows that the level of EPA in the cellular membranes exert profound dose dependent effects of the transcriptional profiles induced by this treatment. Metabolic pathways like autophagy, apelin and VEGF signaling were attenuated by EPA whereas transcripts related to fatty acid metabolism, ferroptosis and the PPAR signaling pathways were upregulated. These results suggests that innate antiviral responses are heavily influenced by the fatty acid profile of salmonid cells and constitute another example of the strong linkage between general metabolic pathways and inflammatory responses.

Apelin-13 modulates the endometrial transcriptome of the domestic pig during implantation

BACKGROUND

The peri-implantation period is a critical time during pregnancy that mostly defines the overall litter size. Most authors agree that the highest percentage of embryo mortality occurs during this time. Despite the brevity of the peri-implantation period, it is the most dynamic part of pregnancy in which the sequential and uninterrupted course of several processes is essential to the animal's reproductive success. Also then, the maternal uterine tissues undergo an intensive remodelling process, and their energy demand dramatically increases. It is believed that apelin, a member of the adipokine family, is involved in the control of female reproductive functions in response to the current metabolic state. The verified herein hypothesis assumed the modulatory effect of apelin on the endometrial tissue transcriptome on days 15 to 16 of gestation (beginning of implantation).

RESULTS

The analysis of data obtained during RNA-seq (Illumina HiSeq2500) of endometrial slices treated and untreated with apelin (n = 4 per group) revealed changes in the expression of 68 genes (39 up-regulated and 29 down-regulated in the presence of apelin), assigned to 240 gene ontology terms. We also revealed changes in the frequency of alternative splicing events (397 cases), as well as single nucleotide variants (1,818 cases) in the presence of the adipokine. The identified genes were associated, among others, with the composition of the extracellular matrix, apoptosis, and angiogenesis.

CONCLUSIONS

The obtained results indicate a potential role of apelin in the regulation of uterine tissue remodelling during the peri-implantation period.

Decreased plasma ELABELA level as a novel screening indicator for heart failure: a cohort and observational study

The predictive power of B-type natriuretic peptide (BNP) and left ventricular ejection fraction (LVEF) is limited by its low specificity in patients with heart failure (HF). Discovery of more novel biomarkers for HF better diagnosis is necessary and urgent. ELABELA, an early endogenous ligand for the G protein-coupled receptor APJ (Apelin peptide jejunum, Apelin receptor), exhibits cardioprotective actions. However, the relationship between plasma ELABELA and cardiac function in HF patients is unclear. To evaluate plasma ELABELA level and its diagnostic value in HF patients, a total of 335 patients with or without HF were recruited for our monocentric observational study. Plasma ELABELA and Apelin levels were detected by immunoassay in all patients. Spearman correlation analysis was used to analyze the correlation between plasma ELABELA or Apelin levels and study variables. The receiver operating characteristic curves were used to access the predictive power of plasma ELABELA or Apelin levels. Plasma ELABELA levels were lower, while plasma Apelin levels were higher in HF patients than in non-HF patients. Plasma ELABELA levels were gradually decreased with increasing New York Heart Association grade or decreasing LVEF. Plasma ELABELA levels were negatively correlated with BNP, left atrial diameter, left ventricular end-diastolic diameter, left ventricular end-systolic diameter, and left ventricular posterior wall thickness and positively correlated with LVEF in HF patients. In contrast, the correlation between plasma Apelin levels and these parameters is utterly opposite to ELABELA. The diagnostic value of ELABELA, Apelin, and LVEF for all HF patients was 0.835, 0.673, and 0.612; the sensitivity was 62.52, 66.20, and 32.97%; and the specificity was 95.92, 67.23, and 87.49%, respectively. All these parameters in HF patients with preserved ejection fraction were comparable to those in total HF patients. Overall, plasma ELABELA levels were significantly reduced and negatively correlated with cardiac function in HF patients. Decreased plasma ELABELA levels may function as a novel screening biomarker for HF. A combined assessment of BNP and ELABELA may be a good choice to increase the accuracy of the diagnosis of HF.

Adipokines in pregnancy

Reproductive success consists of a sequential events chronology, starting with the ovum fertilization, implantation of the embryo, placentation, and cellular processes like proliferation, apoptosis, angiogenesis, endocrinology, or metabolic changes, which taken together finally conduct the birth of healthy offspring. Currently, many factors are known that affect the regulation and proper maintenance of pregnancy in humans, domestic animals, or rodents. Among the determinants of reproductive success should be distinguished: the maternal microenvironment, genes, and proteins as well as numerous pregnancy hormones that regulate the most important processes and ensure organism homeostasis. It is well known that white adipose tissue, as the largest endocrine gland in our body, participates in the synthesis and secretion of numerous hormones belonging to the adipokine family, which also may regulate the course of pregnancy. Unfortunately, overweight and obesity lead to the expansion of adipose tissue in the body, and its excess in both women and animals contributes to changes in the synthesis and release of adipokines, which in turn translates into dramatic changes during pregnancy, including those taking place in the organ that is crucial for the proper progress of pregnancy, i.e. the placenta. In this chapter, we are summarizing the current knowledge about levels of adipokines and their role in the placenta, taking into account the physiological and pathological conditions of pregnancy, e.g. gestational diabetes mellitus, preeclampsia, or intrauterine growth restriction in humans, domestic animals, and rodents.

Expression of the apelin receptor, a novel potential therapeutic target, and its endogenous ligands in diverse stem cell populations in human glioblastoma

Glioblastoma multiforme (GBM) is one of the most common and lethal forms of brain cancer, carrying a very poor prognosis (median survival of ~15 months post-diagnosis). Treatment typically involves invasive surgical resection of the tumour mass, followed by radiotherapy and adjuvant chemotherapy using the alkylating agent temozolomide, but over half of patients do not respond to this drug and considerable resistance is observed. Tumour heterogeneity is the main cause of therapeutic failure, where diverse progenitor glioblastoma stem cell (GSC) lineages in the microenvironment drive tumour recurrence and therapeutic resistance. The apelin receptor is a class A GPCR that binds two endogenous peptide ligands, apelin and ELA, and plays a role in the proliferation and survival of cancer cells. Here, we used quantitative whole slide immunofluorescent imaging of human GBM samples to characterise expression of the apelin receptor and both its ligands in the distinct GSC lineages, namely neural-progenitor-like cells (NPCs), oligodendrocyte-progenitor-like cells (OPCs), and mesenchymal-like cells (MES), as well as reactive astrocytic cells. The data confirm the presence of the apelin receptor as a tractable drug target that is common across the key cell populations driving tumour growth and maintenance, offering a potential novel therapeutic approach for patients with GBM.

Intranasal Administration of Apelin-13 Ameliorates Cognitive Deficit in Streptozotocin-Induced Alzheimer's Disease Model via Enhancement of Nrf2-HO1 Pathways

BACKGROUND

The discovery of novel diagnostic methods and therapies for Alzheimer's disease (AD) faces significant challenges. Previous research has shed light on the neuroprotective properties of Apelin-13 in neurodegenerative disorders. However, elucidating the mechanism underlying its efficacy in combating AD-related nerve injury is imperative. In this study, we aimed to investigate Apelin-13's mechanism of action in an in vivo model of AD induced by streptozocin (STZ).

METHODS

We utilized an STZ-induced nerve injury model of AD in mice to investigate the effects of Apelin-13 administration. Apelin-13 was administered intranasally, and cognitive impairment was assessed using standardized behavioral tests, primarily, behavioral assessment, histological analysis, and biochemical assays, in order to evaluate synaptic plasticity and oxidative stress signaling pathways.

RESULTS

Our findings indicate that intranasal administration of Apelin-13 ameliorated cognitive impairment in the STZ-induced AD model. Furthermore, we observed that this effect was potentially mediated by the enhancement of synaptic plasticity and the attenuation of oxidative stress signaling pathways.

CONCLUSIONS

The results of this study suggest that intranasal administration of Apelin-13 holds promise as a therapeutic strategy for preventing neurodegenerative diseases such as AD. By improving synaptic plasticity and mitigating oxidative stress, Apelin-13 may offer a novel approach to neuroprotection in AD and related conditions.

Single-Cell RNA-Sequencing Analyses Identify APLNR, INS-IGF2, RGCC Genes May Be Involved in the Pathogenesis of Systemic Sclerosis Skin

Background

Systemic sclerosis represents a persistent autoimmune disorder marked with fibrosis affecting both skin and other organs, which leads to a diminished quality of life and increased mortality. The affected skin provides a valuable opportunity to explore the pathogenesis of systemic sclerosis. Nevertheless, the roles of various cell populations within scleroderma remain intricate.

Methods

We conducted a comprehensive reanalysis of recently published single-cell RNA-sequencing data from skin tissue cells in scleroderma. Through the utilization of Seurat, irGSEA, AUCell packages, and WGCNA analysis, we aimed to unveil crucial genes associated with the disease's etiological factors. Our investigation involved the characterization of heterogeneous pathway activities in both healthy and SSc-affected skin. Furthermore, we employed immunofluorescence techniques to validate the expression patterns of hub genes and differentially expressed genes.

Results

The Endothelial-to-Mesenchymal Transition (EndMT) pathway was upregulated in SSc skin. Notably, the M4 module within Endothelial cell subpopulation 1 exhibited a strong association with EndMT. Furthermore, we identified three overexpressed genes (APLNR, INS-IGF2, RGCC) that demonstrated a significant correlation with EndMT. Importantly, their expression levels were markedly higher in skin of individuals with SSc when compared to healthy controls.

Conclusion

APLNR, INS-IGF2 and RGCC serve as potential key players in the pathogenesis of SSc skin through EndMT-dependent mechanisms.

Persistent gene expression and DNA methylation alterations linked to carcinogenic effects of dichloroacetic acid

Background

Mechanistic understanding of transient exposures that lead to adverse health outcomes will enhance our ability to recognize biological signatures of disease. Here, we measured the transcriptomic and epigenomic alterations due to exposure to the metabolic reprogramming agent, dichloroacetic acid (DCA). Previously, we showed that exposure to DCA increased liver tumor incidence in B6C3F1 mice after continuous or early life exposures significantly over background level.

Methods

Using archived formalin-fixed liver samples, we utilized modern methodologies to measure gene expression and DNA methylation levels to link to previously generated phenotypic measures. Gene expression was measured by targeted RNA sequencing (TempO-seq 1500+ toxicity panel: 2754 total genes) in liver samples collected from 10-, 32-, 57-, and 78-week old mice exposed to deionized water (controls), 3.5 g/L DCA continuously in drinking water ("Direct" group), or DCA for 10-, 32-, or 57-weeks followed by deionized water until sample collection ("Stop" groups). Genome-scaled alterations in DNA methylation were measured by Reduced Representation Bisulfite Sequencing (RRBS) in 78-week liver samples for control, Direct, 10-week Stop DCA exposed mice.

Results

Transcriptomic changes were most robust with concurrent or adjacent timepoints after exposure was withdrawn. We observed a similar pattern with DNA methylation alterations where we noted attenuated differentially methylated regions (DMRs) in the 10-week Stop DCA exposure groups compared to the Direct group at 78-weeks. Gene pathway analysis indicated cellular effects linked to increased oxidative metabolism, a primary mechanism of action for DCA, closer to exposure windows especially early in life. Conversely, many gene signatures and pathways reversed patterns later in life and reflected more pro-tumorigenic patterns for both current and prior DCA exposures. DNA methylation patterns correlated to early gene pathway perturbations, such as cellular signaling, regulation and metabolism, suggesting persistence in the epigenome and possible regulatory effects.

Conclusion

Liver metabolic reprogramming effects of DCA interacted with normal age mechanisms, increasing tumor burden with both continuous and prior DCA exposure in the male B6C3F1 rodent model.

Apelin regulates skeletal muscle adaptation to exercise in a high-intensity interval training model

Plasma apelin levels are reduced in aging and muscle wasting conditions. We aimed to investigate the significance of apelin signaling in cardiac and skeletal muscle responses to physiological stress. Apelin knockout (KO) and wild-type (WT) mice were subjected to high-intensity interval training (HIIT) by treadmill running. The effects of apelin on energy metabolism were studied in primary mouse skeletal muscle myotubes and cardiomyocytes. Apelin increased mitochondrial ATP production and mitochondrial coupling efficiency in myotubes and promoted the expression of mitochondrial genes both in primary myotubes and cardiomyocytes. HIIT induced mild concentric cardiac hypertrophy in WT mice, whereas eccentric growth was observed in the left ventricles of apelin KO mice. HIIT did not affect myofiber size in skeletal muscles of WT mice but decreased the myofiber size in apelin KO mice. The decrease in myofiber size resulted from a fiber type switch toward smaller slow-twitch type I fibers. The increased proportion of slow-twitch type I fibers in apelin KO mice was associated with upregulation of myosin heavy chain slow isoform expression, accompanied with upregulated expression of genes related to fatty acid transport and downregulated expression of genes related to glucose metabolism. Mechanistically, skeletal muscles of apelin KO mice showed defective induction of insulin-like growth factor-1 signaling in response to HIIT. In conclusion, apelin is required for proper skeletal and cardiac muscle adaptation to high-intensity exercise. Promoting apelinergic signaling may have benefits in aging- or disease-related muscle wasting conditions.NEW & NOTEWORTHY Apelin levels decline with age. This study demonstrates that in trained mice, apelin deficiency results in a switch from fast type II myofibers to slow oxidative type I myofibers. This is associated with a concomitant change in gene expression profile toward fatty acid utilization, indicating an aged-muscle phenotype in exercised apelin-deficient mice. These data are of importance in the design of exercise programs for aging individuals and could offer therapeutic target to maintain muscle mass.

The effect of single nucleotide polymorphisms on depression in combination with coronary diseases: a systematic review and meta-analysis

Background

Depression and coronary heart disease (CHD) have common risk mechanisms. Common single nucleotide polymorphisms (SNPs) may be associated with the risk of depression combined with coronary heart disease.

Methods

This study was designed according to the PRISMA-P guidelines. We will include case-control studies and cohort studies investigating the relationship between gene SNPs and depression and coronary heart disease comorbidities. The Newcastle-Ottawa Scale (NOS) will be used to assess the risk of bias. When measuring dichotomous outcomes, we will use the odds ratio (OR) and 95% confidence interval (95%CIs) in a case-control study. Five genetic models (allele model, homozygous model, co-dominant model, dominant model, and recessive model) will be evaluated for each included study. Subgroup analysis by ethnicity will be performed. If necessary, post hoc analysis will be made according to different types.

Results

A total of 13 studies were included in this study, and the types of genes included are FKBP5 and SGK1 genes that act on glucocorticoid; miR-146a, IL-4-589, IL-6-174, TNF-α-308, CRP-717 genes that act on inflammatory mechanisms; eNOS genes from endothelial cells; HSP70 genes that act on the autoimmune response; ACE2 and MAS1 genes that act to mediate Ang(1-7) in the RAS system; 5-HTTLPR gene responsible for the transport of serotonin 5-HT and neurotrophic factor BDNF gene. There were three studies on 5-HTTLPR and BDNF genes, respectively, while there was only one study targeting FKBP5, SGK1, miR-146a, IL-4-589, IL-6-174, TNF-alpha-308, CRP-717, eNOS, HSP70, ACE2, and MAS1 genes. We did not perform a meta-analysis for genes reported in a single study, and meta-analysis was performed separately for studies exploring the 5-HTTLPR and BDNF genes. The results showed that for the 5-HTTLPR gene, there was a statistically significant association between 5-HTTLPR gene polymorphisms and depression in combination with coronary diseases (CHD-D) under the co-dominant model (LS vs LL: OR 1.76, 95%CI 1.20-2.59; SS vs LL: OR 2.80, 95%CI 1.45 to 5.41), the dominant model (LS+SS vs LL: OR 2.06, 95%CI 1.44 to 2.96), and the homozygous model (SS vs LL: OR 2.80 95%CI 1.45 to 5.5.41) were statistically significant for CHD-D, demonstrating that polymorphisms in the 5-HTTLPR gene are associated with the development of CHD-D and that the S allele in the 5-HTTLPR gene is likely to be a risk factor for CHD-D. For the BDNF gene, there were no significant differences between one of the co-dominant gene models (AA vs GG: OR 6.63, 95%CI 1.44 to 30.64), the homozygous gene model (AA vs GG: OR 6.63,95% CI 1.44 to 30.64), the dominant gene model (GA+AA vs GG: OR4.29, 95%CI 1.05 to 17.45), recessive gene model (AA vs GG+GA: OR 2.71, 95%CI 1.16 to 6.31), and allele model (A vs G: OR 2.59, 95%CI 1.18 to 5.67) were statistically significant for CHD-D, demonstrating that BDNFrs6265 gene polymorphisms are associated with the CHD-D development and that the A allele in the BDNFrs6265 gene is likely to be a risk factor for CHD-D. We analyzed the allele frequencies of SNPs reported in a single study and found that the SNPs in the microRNA146a gene rs2910164, the SNPs in the ACE2 gene rs2285666 and the SNPs in the SGK1 gene rs1743963 and rs1763509 were risk factors for the development of CHD-D. We performed a subgroup analysis of three studies involving the BDNFrs6265 gene. The results showed that European populations were more at risk of developing CHD-D than Asian populations in both dominant model (GA+AA vs GG: OR 10.47, 95%CI 3.53 to 31.08) and co-dominant model (GA vs GG: OR 6.40, 95%CI 1.98 to 20.73), with statistically significant differences. In contrast, the studies involving the 5-HTTLPR gene were all Asian populations, so subgroup analyses were not performed. We performed sensitivity analyses of studies exploring the 5-HTTLPR and BDNF rs6265 genes. The results showed that the results of the allele model, the dominant model, the recessive model, the homozygous model and the co-dominant model for both 5-HTTLPR and BDNF rs6265 genes were stable. Due to the limited number of studies of the 5-HTTLPR and BDNF genes, it was not possible to determine the symmetry of the funnel plot using Begg's funnel plot and Egger's test. Therefore, we did not assess publication bias.

Discussion

SNPs of the microRNA146a gene at rs2910164, the ACE2 gene at the rs2285666 and the SGK1 gene at rs1743963 and rs1763509, and the SNPs at the 5-HTTLPR and BDNF gene loci are associated with the onset of comorbid depression in coronary heart disease. We recommend that future research focus on studying SNPs' impact on comorbid depression in coronary heart disease, specifically targeting the 5-HTTLPR and BDNF gene at rs6265.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42021229371.

Integration of the Butina algorithm and ensemble learning strategies for the advancement of a pharmacophore ligand-based model: an in silico investigation of apelin agonists

Introduction: 3D pharmacophore models describe the ligand's chemical interactions in their bioactive conformation. They offer a simple but sophisticated approach to decipher the chemically encoded ligand information, making them a valuable tool in drug design. Methods: Our research summarized the key studies for applying 3D pharmacophore models in virtual screening for 6,944 compounds of APJ receptor agonists. Recent advances in clustering algorithms and ensemble methods have enabled classical pharmacophore modeling to evolve into more flexible and knowledge-driven techniques. Butina clustering categorizes molecules based on their structural similarity (indicated by the Tanimoto coefficient) to create a structurally diverse training dataset. The learning method combines various individual pharmacophore models into a set of pharmacophore models for pharmacophore space optimization in virtual screening. Results: This approach was evaluated on Apelin datasets and afforded good screening performance, as proven by Receiver Operating Characteristic (AUC score of 0.994 ± 0.007), enrichment factor of (EF1% of 50.07 ± 0.211), Güner-Henry score of 0.956 ± 0.015, and F-measure of 0.911 ± 0.031. Discussion: Although one of the high-scoring models achieved statistically superior results in each dataset (AUC of 0.82; an EF1% of 19.466; GH of 0.131 and F1-score of 0.071), the ensemble learning method including voting and stacking method balanced the shortcomings of each model and passed with close performance measures.

Diagnostic and prognostic significance of apelin-13, APJ for sepsis in the emergency department: A prospective study

Objectives

This study aimed to assess the diagnostic, risk stratification, and prognostic capabilities of apelin-13 and APJ in comparison to procalcitonin (PCT) for septic patients presenting to the emergency department (ED).

Methods

Two hundred and thirty-eight patients meeting the Third International Consensus Definition (Sepsis-3) criteria were enrolled from Beijing Chaoyang Hospital's ED, along with a control group of forty healthy individuals. Patients were categorized into two groups based on disease severity: those with sepsis or septic shock. Plasma levels of apelin-13, CD4+ Th cells, and PCT were measured. The expression levels of plasma APJ mRNA were quantified using real-time fluorescence quantitative PCR (RT-qPCR) methodology. The Sequential Organ Failure Assessment (SOFA) score was determined at the time of enrollment. The prognostic values of apelin-13 and APJ was evaluated in comparison to that of PCT and the SOFA score. All patients were followed up for a duration of 28 days.

Results

The plasma concentrations of apelin-13 and APJ exhibited a positive correlation with the severity of sepsis, while the number of CD4+ T cells decreased in septic patients. The areas under the receiver operating characteristic (AUC) curves for apelin-13 and APJ in the diagnosis and prediction of 28-day mortality were greater than that of PCT. In non-survivors at the 28-day follow-up, the plasma levels of apelin-13 and APJ were significantly higher compared to survivors. Furthermore, apelin-13 levels were notably higher in cases of sepsis-induced cardiomyopathy (SICM) than in those without SICM. Apelin-13 and APJ emerged as independent predictors of 28-day mortality among septic patients.

Conclusions

Apelin-13 and APJ demonstrate value in the assessment of risk stratification, early diagnosis, and prognosis of sepsis in the ED. Apelin-13 also proves to be an effective biomarker for assessing the prognosis of SICM in the ED. Sepsis may lead to immune function suppression.

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.

The biased apelin receptor agonist, MM07, reverses Sugen/hypoxia-induced pulmonary arterial hypertension as effectively as the endothelin antagonist macitentan

Introduction: Pulmonary arterial hypertension (PAH) is characterised by endothelial dysfunction and pathological vascular remodelling, resulting in the occlusion of pulmonary arteries and arterioles, right ventricular hypertrophy, and eventually fatal heart failure. Targeting the apelin receptor with the novel, G protein-biased peptide agonist, MM07, is hypothesised to reverse the developed symptoms of elevated right ventricular systolic pressure and right ventricular hypertrophy. Here, the effects of MM07 were compared with the clinical standard-of-care endothelin receptor antagonist macitentan. Methods: Male Sprague-Dawley rats were randomised and treated with either normoxia/saline, or Sugen/hypoxia (SuHx) to induce an established model of PAH, before subsequent treatment with either saline, macitentan (30 mg/kg), or MM07 (10 mg/kg). Rats were then anaesthetised and catheterised for haemodynamic measurements, and tissues collected for histopathological assessment. Results: The SuHx/saline group presented with significant increases in right ventricular hypertrophy, right ventricular systolic pressure, and muscularization of pulmonary arteries compared to normoxic/saline controls. Critically, MM07 was as at least as effective as macitentan in significantly reversing detrimental structural and haemodynamic changes after 4 weeks of treatment. Discussion: These results support the development of G protein-biased apelin receptor agonists with improved pharmacokinetic profiles for use in human disease.

Evaluation of elevated serum apelin-13 and D-dimer concentrations in individuals diagnosed with pulmonary embolism

BACKGROUND

Given the limited specificity of D-dimer, there is a perceived need to discover a more precise marker for diagnosing individuals who are suspected of having pulmonary embolism (PE). In this study, by evaluating the increase in the serum level of Apelin-13 and D-dimer, we found valuable findings about Apelin-13, which can be suggested as an auxiliary and non-invasive diagnostic biomarker in individuals with suspected PE, based on the obtained results.

METHODS

In this case-control study, 52 Iranian individuals were included, all of whom were suspected to have PE. These individuals were then divided into two groups based on the results of CT angiography, which is considered the gold standard imaging method for diagnosing PE. The two groups were patients with PE and patients without PE. Finally, the levels of certain markers in the serum were compared between the two groups.

RESULTS

The mean serum D-dimer levels in patients with PE were significantly elevated (p < 0.001) in comparison to those without PE (1102.47 to 456.2 ng/ml). Furthermore, the mean level of Apelin-13 was significantly higher in patients with PE (49.8 to 73.11 ng/L) (p < 0.001). The cutoff point of Apelin-13 has been calculated at 58.50 ng/ml, with 90.9% sensitivity and 90% specificity. The D-dimer cutoff point was 500 ng/ml, with 95.5% sensitivity and 43.3% specificity.

CONCLUSIONS

Based on the results of this study, the serum level of Apelin-13 can be used as a novel diagnostic and screening biomarker in patients with pulmonary thromboembolism.

Possible role of apelin on the ovarian steroidogenesis and uterine apoptosis of infantile mice: An in vitro study

The expression of adipokines is well-known in the ovary and uterus. Recently we have shown that apelin and its receptor, APJ are developmentally regulated in the ovary and uterus of mice with elevation at postnatal day 14 (PND14). However, its role in the ovary and uterus of PND14 has not been investigated. Thus, we aimed to unravel the role of the apelin system (by APJ antagonist, ML221) on ovarian steroid secretion, proliferation, and apoptosis along with its role in uterine apoptosis in PND14 mice by in vitro approaches. The treatment of ML221 decreased estrogen, testosterone, and androstenedione secretion while increasing the progesterone secretion from the infantile ovary. These results suggest that apelin signaling would be important for ovarian estrogen synthesis in infantile mice (PND14). The abundance of 3β-HSD, 17β-HSD, aromatase, and active caspase3 increased in the infantile ovary after ML221 treatment. The expression of ERs and BCL2 were also down-regulated by ML221 treatment. The decreased BCL2 and increased active caspase3 by ML221 suggest the suppressive role of apelin on ovarian apoptosis. The APJ antagonist treatment also down-regulated the ER expression in the uterus along with increased active caspase3 and decreased BCL2 expression. In conclusion, apelin signaling inhibits the ovarian and uterine apoptosis via estrogen signaling in the ovary and uterus.

The regulatory role of the apelin/APJ axis in scarring: Identification of upstream and downstream mechanisms

Scarring, a prevalent issue in clinical settings, is characterized by the excessive generation of extracellular matrix within the skin tissue. Among the numerous regulatory factors implicated in fibrosis across various organs, the apelin/APJ axis has emerged as a potential regulator of fibrosis. Given the shared attribute of heightened extracellular matrix production between organ fibrosis and scarring, we hypothesize that the apelin/APJ axis also plays a regulatory role in scar development. In this study, we examined the expression of apelin and APJ in scar tissue, normal skin, and fibroblasts derived from these tissues. We investigated the impact of the hypoxic microenvironment in scars on apelin/APJ expression to identify the transcription factors influencing apelin/APJ expression. Through overexpressing or knocking down apelin/APJ expression, we observed their effects on fibroblast secretion of extracellular matrix proteins. We further validated these effects in animal experiments while exploring the underlying mechanisms. Our findings demonstrated that the apelin/APJ axis is expressed in fibroblasts from keloid, hypertrophic scar, and normal skin. The regulation of apelin/APJ expression by the hypoxic environment in scars plays a significant role in hypertrophic scar and keloid development. This regulation promotes extracellular matrix secretion through upregulation of TGF-β1 expression via the PI3K/Akt/CREB1 pathway.

Exercise and insulin glargine administration in mothers with diabetes during pregnancy ameliorate function of testis in offspring: Consequences on apelin-13 and its receptor

AIMS

Despite the evidence exhibited that diabetes during gestation (DDG) is linked with reproductive dysfunction in offspring, the underlying cellular mechanisms involved are not precisely defined. This study was designed to assess the impact of voluntary exercise and insulin glargine on DDG-induced metabolic and reproductive disorders in male offspring.

MAIN METHODS

Fifty female Wistar rats (three weeks old) received a control diet (n = 10) or high-fat-high-sucrose diet (to induce DDG; n = 40) for six weeks before breeding. From the 7th day of pregnancy onwards, blood glucose over 140 mg/dL was characterized as DDG. Then, the DDG animals were randomly divided into four subgroups with/without voluntary exercise and/or insulin glargine. To evaluate insulin resistance, a glucose tolerance test was performed on the 15th day of pregnancy. After three weeks, male offspring were weaned, and fed a control diet until 12 weeks old. At the end of the experiment, the lipid profile, sex hormones, and apelin-13 in the serum, mRNA expression of apelin receptors (APJ) in the testis and sperm analysis were assessed.

KEY FINDINGS

Our results indicated that voluntary exercise and/or insulin glargine administration in mothers with DDG ameliorated lipid profile, and sex hormones alterations, reduced the serum level of apelin-13, as well as increased APJ expression in testis, and quality of sperm in offspring.

SIGNIFICANCE

Combined administration of voluntary exercise and insulin glargine during pregnancy by regulating of apelinergic system and inhibiting the metabolic and reproductive complications induced by DDG, can be considered as a suitable therapeutic strategy for improving sub-or in-fertility in the male offspring.

Isoxanthohumol reduces neointimal hyperplasia through the apelin/AKT pathway

The abnormal proliferation, migration, and inflammation of vascular smooth muscle cells (VSMCs) play crucial roles in the development of neointimal hyperplasia and restenosis. Exposure to inflammatory cytokines such as platelet-derived growth factor (PDGF)-BB and tumour necrosis factor-alpha (TNF-α) induces the transformation of contractile VSMCs into abnormal synthetic VSMCs. Isoxanthohumol (IXN) has significant anti-inflammatory, antiproliferative, and antimigratory effects. This study aimed to explore the therapeutic impact and regulatory mechanism of IXN in treating neointimal hyperplasia. The present findings indicate that IXN effectively hinders the abnormal proliferation, migration, and inflammation of VSMCs triggered by PDGF or TNF-α. This inhibition is primarily achieved through the modulation of the apelin/AKT or AKT pathway, respectively. In an in vivo model, IXN effectively reduced neointimal hyperplasia in denuded femoral arteries. These results suggest that IXN holds promise as a potential and innovative therapeutic candidate for the treatment of restenosis.

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.