Apelin Counteracts the Effects of Fusobacterium nucleatum on the Migration of Periodontal Ligament Cells In Vitro.

To better understand the link between periodontitis and metabolic diseases, our in vitro study aimed to assess the influence of the adipokine apelin and/or the periodontal pathogen Fusobacterium nucleatum on periodontal cells. Periodontal ligament (PDL) cells were exposed to F. nucleatum in the presence and absence of apelin. Scratch assays were used to analyze the in vitro wound healing and velocity of cell migration. To investigate if F. nucleatum and/or apelin have a regulatory effect on cell proliferation and apoptosis, proliferation and viability assays were performed as well as an analysis of caspase 9 expression. Both the in vitro wound closure and the cell migration rate were significantly reduced by F. nucleatum. Simultaneous incubation with apelin counteracted the adverse effects of F. nucleatum. The proliferation assay demonstrated that neither apelin nor F. nucleatum significantly affected PDL cell proliferation. Furthermore, neither apelin nor F. nucleatum was cytotoxic or affected apoptosis after 48 h. Apelin could play a modulatory role in the pathogenesis of periodontitis, as it was able to compensate for the inhibitory effects of the periodontal pathogen F. nucleatum on PDL cell migration in vitro.

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.

Single-cell and spatial transcriptomics reveal apelin/APJ pathway's role in microvessel formation and tumour progression in hepatocellular carcinoma.

The apelin receptor (APJ) is a key player in tumour angiogenesis, but its role in hepatocellular carcinoma (HCC) remains unclear. This study aims to elucidate the function of the apelin/APJ pathway in HCC using a multi-omics approach and identify potential therapeutic biomarkers. Differentially expressed genes related to the apelin/APJ axis were identified from bulk transcriptomics to reveal HCC-associated disparities. Single-cell and spatial transcriptomics were used to localize and analyse the function of these genes. Machine learning models were constructed to predict outcomes based on apelin/APJ expression, and experimental validation was conducted to explore the pathway's impact on HCC angiogenesis. Single cell analysis revealed an overexpression of APJ/Aplin in the endothelium. The stemness of endothelial cell (EC) with high apelin/APJ was enhanced, as well as the expression of TGFb, oxidative stresses and PI3K/AKT pathway genes. Spatial transcriptomics confirmed that EC populations with high APJ scores were enriched within the tumour. Machine learning models showed high prognostic accuracy. High APJ expression was linked to worse outcomes (p = 0.001), and AUC values were high (1 year, 3 year, 5 year) (0.95, 0.97, 0.98). Immune suppression and non-responsiveness of immune therapy were also seen in high-risk groups. The experimental validation showed that silencing apelin reduced angiogenesis (p < 0.05), endothelial proliferation, decreased expression of ANG2, KLF2, VEGFA and lower ERK1/2 phosphorylation. Apelin may serve as a potential therapeutic target in HCC, given its role in promoting tumour angiogenesis and poor patient outcomes.

Apelin (APLN) is a biomarker contributing to the diagnosis and prognosis of hepatocellular carcinoma.

Liver cancer, classified as a malignant hepatic tumor, can be divided into two categories: primary, originating within the liver, and secondary, resulting from metastasis to the liver from other organs. Hepatocellular carcinoma (HCC) is the main form of primary liver cancer and the third leading cause of cancer-related deaths. The diagnosis and prognosis of HCC using current methods still face numerous challenges. This study aims to develop novel diagnostic and prognostic models while identifying new biomarkers for improved HCC treatment. Diagnostic and prognostic models for HCC were constructed using traditional binary classification methods and machine learning algorithms based on the TCGA database (Downloaded in August 2023). The mechanisms by which APLN (Apelin) affects HCC were investigated using single-cell sequencing data sourced from the GEO database (GSE149614). The diagnostic models yielded by various algorithms could effectively distinguished HCC samples from normal ones. The prognostic model, composed of four genes, was constructed using LASSO and Cox regression algorithms, demonstrating good performance in predicting the three-year survival rate of HCC patients. The HCC biomarker Apelin (APLN) was identified in this study. APLN in liver cancer tissues mainly comes from endothelial cells and is associated with the carcinogenesis of these cells. APLN expression is significantly upregulated in liver cancer tissues, marking it as a viable indicator of endothelial cell malignancy in HCC. Furthermore, APLN expression was determined to be an independent predictor of tumor endothelial cell carcinogenesis, unaffected by its modifications such as single nucleotide variation, copy number variation, and methylation. Additionally, liver cancers characterized by high APLN expression are likely to progress rapidly after T2 stage. Our study presents diagnostic and prognostic models for HCC with appreciably improved accuracy and reliability compared to previous reports. APLN is a reliable HCC biomarker and contributes to the establishment of our models.

Investigation of emotion regulation skills, salivary apelin, and serotonin levels in children in Türkiye: a cross-sectional study.

PURPOSE: Little is known about the relationship between apelin and serotonin in emotion regulation. This study aimed to examine children's emotional regulation skills and salivary apelin and serotonin levels. METHODS: This is a cross-sectional study performed in Türkiye. The research was completed with the participation of 146 children, 8-10 years old, from the general population. Emotion Regulation Skills Scale for Children (CERS) was used to assess children's levels of emotion regulation skills. Apelin and serotonin levels were examined by ELISA technique in saliva samples obtained from children. RESULTS: A statistically significant correlation was found between the mean total score of the CERS and the mean apelin and serotonin levels (p ˂ .01). We found that females had higher emotion regulation skills compared to males, older higher than younger ones (p ˂ .01). The regression analysis results show that age and gender together explain 50.5% of the variance in CERS scores, while apelin and serotonin together explain 35.8% of the variance. When all four variables (age, gender, apelin, and serotonin) are included in the model, they explain 51.3% of the variance in CERS scores. CONCLUSION: Older age and female gender explained most of emotion regulations skills.Key pointsIt was determined that the average salivary apelin and serotonin levels increased with increased age, and with increased age ERS also increased.More research is needed as this is the first time that the relationship between emotion regulation skills and serotonin and apelin levels has been examined.

Apelinergic system in acute kidney injury: Mechanistic insights and therapeutic potential.

Acute kidney injury (AKI) has emerged as a global health crisis, surpassing mortality rates associated with several cancers and heart failure. The lack of effective therapies, coupled with challenges in diagnosis and the high cost of kidney transplantation, underscores the urgent need to explore novel therapeutic targets and strategies for AKI. Understanding the intricate pathophysiology of AKI is paramount in this endeavor. The components of the apelinergic system-namely, apelin and elabela/toddler, along with their receptor-are prominently expressed in various kidney cells and have garnered significant attention in renal research. Recent studies have highlighted the renoprotective role of the apelinergic system in AKI. This system exerts its protective effects by modulating several pathophysiological processes, including reducing endoplasmic reticulum (ER) stress, improving mitochondrial dynamics, inhibiting inflammation and apoptosis, promoting diuresis through vasodilation of renal vasculature, and counteracting the effects of reactive oxygen species (ROS). Despite these advancements, the precise involvement of the apelinergic system in the progression of AKI remains unclear. Furthermore, the therapeutic potential of apelin-13 in AKI is not fully understood. This review aims to elucidate the role of the apelinergic system in AKI and its interactions with key pathomechanisms involved in the progression of AKI. Additionally, we discuss the current clinical status of exogenous apelin-13 therapy, providing insights that will guide future research on apelin against AKI.

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.

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-ß-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.

Apelin - A New Kid on the Block in Periodontology.

Periodontitis is associated with numerous systemic diseases, and it has been shown that these associations are partly causal in nature. It is assumed that such interactions between periodontal and systemic diseases are also medi- ated via adipokines. Apelin, an adipokine about which there is little research in the dental field, is also produced together with its receptor in periodontal cells. The aim of this review was to summarize the currently available literature on the apelin-APJ system to better understand the pathomechanistic relationship between periodontitis and obesity and to de- termine the potential clinical relevance of apelin for diagnostics and therapy. In vitro studies suggest that apelin can en- hance bacterial-induced synthesis of proinflammatory and proteolytic molecules, indicating a significant etiopathogenic role of this adipokine. Since serum levels of apelin are elevated in diabetes and/or obesity, it is possible that such sys- temic diseases promote the development and progression of periodontitis via apelin. On the other hand, it is also conceivable that apelin from the periodontium influences such systemic diseases. Further research is needed to better understand the role of apelin in the periodontium and the entire oral cavity, but also in the interactions between periodontal and sys- temic diseases. In particular, clinical intervention studies are needed to further decipher the etiopathogenic role of apelin in periodontitis.

Effects of apelin on neonatal brain neurogenesis in L-NAME-induced maternal preeclampsia.

The aim of this study was to investigate the possible protective effects of apelin, which is known to have antioxidant and anti-inflammatory effects, on changes in neurogenesis in newborns of pregnant rats with L-NAME-induced preeclampsia. Wistar albino female rats were divided into four experimental groups: Control, Apelin, Preeclampsia and Preeclampsia + Apelin. Blood pressure was measured on the 5th, 11th and 17th days of gestation, urine protein was analyzed from urine samples collected for 24 h on the 6th, 12th and 18th days and serum creatinine was analyzed from serum samples. Maternal kidney and placenta tissues were obtained to establish the preeclampsia model, and neonatal brain tissues including the cortex, hippocampus and cerebellum regions were obtained to investigate neurogenesis and examined by histological and immunohistochemical methods. The number of newborns, body weight and brain weight of the newborns were measured. eNOS, IL-10, nNOS and NO levels in the brain analyzed via ELISA. Mean arterial pressure, urine protein and serum creatinine increased in the preeclampsia. Newborn weight decreased in the Preeclampsia group, the values in the Preeclampsia + Apelin group were closer to the Control and Apelin groups. In the Preeclampsia group, edema and dilatation in the proximal and distal tubules of kidneys, perivillous fibrin deposition and increase in syncytial nodules of placenta were observed. VEGF immunoreactivity decreased and iNOS immunoreactivity increased in both kidney and placenta. In neonatal brain tissue examinations, cytotoxic edema accompanied by thinning of cortex, delayed migration and lower cell counts in the hippocampus, and increase in intercellular spaces and EGL thickening in the cerebellum were observed in the preeclampsia. Expression of NeuN, GFAP, MBP, IL-10, eNOS, nNOS and NO levels decreased, whereas expression of Iba-1 increased in the preeclampsia. In the Preeclampsia + Apelin group, these findings were similar to the Control and Apelin groups. Apelin administration was found to be beneficial for preventing the adverse consequences of preeclampsia, but further experimental and clinical studies are needed to better understand these effects.

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.

Hyperandrogenemia elevates expression of apelin and apelin receptor protein in the mice pituitary.

Hyperandrogenemia is associated with polycystic ovarian syndrome (PCOS) and imbalances in the pituitary hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels. Apelin and its receptor, APJ (class A, rhodopsin-like G- protein-coupled receptor), belongs to adipokines, and its expression has been shown in the pituitary. It is also well known that, hyperandrogenism and PCOS have deregulation of different adipokines. Whether hyperandrogenism also deregulates the apelin system in the pituitary has yet to be investigated. Thus, we have investigated the expression and localization of apelin and its receptor, APJ, in the letrozole-induced hyperandrogenised pituitary of female mice. Our results showed that the apelin, APJ and androgen receptor (AR) expression were upregulated in the anterior pituitary. Furthermore, the immunostaining of LH exhibited increased abundance than FSH. The circulating LH was also found to be elevated compared to FSH levels. The increased LH synthesis and secretion coincides with elevated apelin system in the pituitary of hyperandrogenised mice. Recently, a direct role of apelin has also been reported in the female pituitary, where apelin inhibits LH secretion. Thus, apelin could be one of the factors for deregulated gonadotropin secretion in hyperandrogenised conditions. However, more research is needed to fully understand the complex interactions between apelin and androgen regarding gonadotropin secretion in hyperandrogenised conditions.

Neural progenitor-derived Apelin controls tip cell behavior and vascular patterning.

During angiogenesis, vascular tip cells guide nascent vascular sprouts to form a vascular network. Apelin, an agonist of the G protein-coupled receptor Aplnr, is enriched in vascular tip cells, and it is hypothesized that vascular-derived Apelin regulates sprouting angiogenesis. We identify an apelin-expressing neural progenitor cell population in the dorsal neural tube. Vascular tip cells exhibit directed elongation and migration toward and along the apelin-expressing neural progenitor cells. Notably, restoration of neural but not vascular apelin expression in apelin mutants remedies the angiogenic defects of mutants. By functional analyses, we show the requirement of Apelin signaling for tip cell behaviors, like filopodia formation and cell elongation. Through genetic interaction studies and analysis of transgenic activity reporters, we identify Apelin signaling as a modulator of phosphoinositide 3-kinase and extracellular signal-regulated kinase signaling in tip cells in vivo. Our results suggest a previously unidentified neurovascular cross-talk mediated by Apelin signaling that is important for tip cell function during sprouting angiogenesis.

Apelin modulates inflammation and leukocyte recruitment in experimental autoimmune encephalomyelitis.

Demyelination due to autoreactive T cells and inflammation in the central nervous system are principal features of multiple sclerosis (MS), a chronic and highly disabling human disease affecting brain and spinal cord. Here, we show that treatment with apelin, a secreted peptide ligand for the G protein-coupled receptor APJ/Aplnr, is protective in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Apelin reduces immune cell entry into the brain, delays the onset and reduces the severity of EAE. Apelin affects the trafficking of leukocytes through the lung by modulating the expression of cell adhesion molecules that mediate leukocyte recruitment. In addition, apelin induces the internalization and desensitization of its receptor in endothelial cells (ECs). Accordingly, protection against EAE major outcomes of apelin treatment are phenocopied by loss of APJ/Aplnr function, achieved by EC-specific gene inactivation in mice or knockdown experiments in cultured primary endothelial cells. Our findings highlight the importance of the lung-brain axis in neuroinflammation and indicate that apelin targets the transendothelial migration of immune cells into the lung during acute inflammation.

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.

Fluorinated apelin-13 mediates neuroprotective effects in multiple sclerosis models.

Multiple sclerosis (MS) is an autoimmune and neurodegenerative disease leading to demyelination and axonal loss. Current treatments are immunomodulatory or immunosuppressive drugs acting on the inflammatory component. However, these treatments do not adequately address the crucial aspect of neuroprotection. Recently, an association between an altered balance of adipokines and MS has been proposed as both a risk factor for developing MS and a chronic disease aggravating factor. Specifically, a decrease of apelin plasma levels in MS patients compared to controls correlates with the number of relapses and disease severity. Here we report a dramatic downregulation of apelin levels in the CNS of EAE mice which is also detected in MS patients brain samples compared to controls. Exploiting innovative design and synthesis techniques, we engineered a novel fluorinated apelin-13 peptide characterized by enhanced plasmatic stability compared to its native counterpart. With this peptide, we assessed the potential therapeutic benefits of apelin preventive supplementation in the EAE mouse model. We show that the fluorinated Apelin-13 peptide ameliorates EAE clinical score and preserves myelin content in the EAE MOG model recapitulating the progressive form of disease. These results combined with ex-vivo experiments in brain organotypic slices and in vitro studies in neurons and primary microglia and macrophages suggest that apelin has neuroprotective effects and influences the microglia/macrophages function.

Adaptive enzyme-responsive self-assembling multivalent apelin ligands for targeted myocardial infarction therapy.

Microvascular dysfunction following myocardial infarction exacerbates coronary flow obstruction and impairs the preservation of ventricular function. The apelinergic system, known for its pleiotropic effects on improving vascular function and repairing ischemic myocardium, has emerged as a promising therapeutic target for myocardial infarction. Despite its potential, the natural apelin peptide has an extremely short circulating half-life. Current apelin analogs have limited receptor binding efficacy and poor targeting, which restricts their clinical applications. In this study, we utilized an enzyme-responsive peptide self-assembly technique to develop an enzyme-responsive small molecule peptide that adapts to the expression levels of matrix metalloproteinases in myocardial infarction lesions. This peptide is engineered to respond to the high concentration of matrix metalloproteinases in the lesion area, allowing for precise and abundant presentation of the apelin motif. The changes in hydrophobicity allow the apelin motif to self-assemble into a supramolecular multivalent peptide ligand-SAMP. This self-assembly behavior not only prolongs the residence time of apelin in the myocardial infarction lesion but also enhances the receptor-ligand interaction through increased receptor binding affinity due to multivalency. Studies have demonstrated that SAMP significantly promotes angiogenesis after ischemia, reduces cardiomyocyte apoptosis, and improves cardiac function. This novel therapeutic strategy offers a new approach to restoring coronary microvascular function and improving damaged myocardium after myocardial infarction.

Quercetin prevents kidney against diabetes mellitus (type 1) in rats by inhibiting TGF-ß/apelin gene expression.

BACKGROUND: One of the main causes of diabetic nephropathy is oxidative stress induced by hyperglycemia. Apelin inhibits insulin secretion. Besides, renal expression of TGF-ß is increased in diabetes mellitus (DM). The preventive effect of quercetin (Q) against renal functional disorders and tissue damage developed by DM in rats was assessed. METHODS: Forty male Wistar rats were grouped into normal control (NC), normal + quercetin (NQ: quercetin, 50 mg/kg/day by gavage), diabetic control (DC: streptozotocin, 65 mg/kg, i.p.), diabetic + quercetin pretreatment (D + Qpre), and diabetic + quercetin post-treatment (D + Qpost). All samples (24-hour urine, plasma, pancreatic, and renal tissues) were obtained at the terminal of the experiment. RESULTS: Compared to NC and NQ groups, DM ended in elevated plasma and glucose levels, decreased plasma insulin level, kidney dysfunction, augmented levels of malondialdehyde, decreased level of reduced glutathione, reduced enzymatic activities of superoxide dismutase and catalase, elevated gene expression levels of apelin and TGF-ß, also renal and pancreatic histological damages. Quercetin administration diminished entire the changes. However, the measure of improvement in the D + Qpre group was higher than that of the D + Qpost group. CONCLUSION: Quercetin prevents renal dysfunction induced by DM, which might be related to the diminution of lipid peroxidation, strengthening of antioxidant systems, and prevention of the apelin/ TGF-ß signaling pathway.