Chronic apelin treatment improves hepatic lipid metabolism in obese and insulin-resistant mice by an indirect mechanism

Genomic predictors of fat mass response to the standardized exercise training

To explore the genetic architecture underlying exercise-induced fat mass change, we performed a genome-wide association study with a Chinese cohort consisting of 442 physically inactive healthy adults in response to a 12-week exercise training (High-intensity Interval Training or Resistance Training). The inter-individual response showed an exercise-induced fat mass change and ten novel lead SNPs were associated with the response on the level of P<1×10-5. Four of them (rs7187742, rs1467243, rs28629770 and rs10848501) showed a consistent effect direction in the European ancestry. The Polygenic Predictor Score (PPS) derived from ten lead SNPs, sex, baseline body mass and exercise protocols explained 40.3% of the variance in fat mass response, meanwhile importantly the PPS had the greatest contribution. Of note, the subjects whose PPS was lower than -9.301 had the highest response in exercise-induced fat loss. Finally, we highlight a series of pathways and biological processes regarding the fat mass response to exercise, e.g. apelin signaling pathway, insulin secretion pathway and fat cell differentiation biological process.

The Effect of a Multidisciplinary Lifestyle Intervention Program on Apelin-12, Vaspin and Resistin Concentrations in Children and Adolescents with Overweight and Obesity

Background: Obesity in childhood and adolescence has reached epidemic proportions in recent decades. Methods: In the present study, we determined the concentrations of apelin-12, vaspin and resistin in 106 children and adolescents with overweight or obesity before and after the implementation of a multidisciplinary, personalized lifestyle intervention program of diet, sleep and exercise for 1 year. All subjects attended our Center for the Prevention and Management of Overweight and Obesity in Childhood and Adolescence. Results: Following the lifestyle intervention, there were significant decreases in BMI (p < 0.01), apelin-12 (p < 0.05) and resistin (p < 0.01) concentrations, and an increase in vaspin (p < 0.01) concentration. Glucose was the best positive predictor of apelin-12 (b = 0.236, p < 0.05), and osteopontin was the best negative predictor of changes in apelin-12 (b = -0.299, p < 0.05). Vaspin correlated positively with adiponectin (b = 0.29, p < 0.05), while vitamin D (b = 0.621, p < 0.05) was the best positive predictor of vaspin. BMI z score (b = -0.794, p < 0.05), HDL (b = -0.284, p < 0.05) and HbA1C (b = -0.262, p < 0.05) were the best negative predictors of changes in vaspin. BMI z score was the best positive predictor of resistin (b = 0.437, p < 0.05). Conclusions: These findings suggest that apelin-12, vaspin and resistin correlate with indices of obesity, glucose, lipids and bone metabolism, while interaction with other proteins, such as osteopontin and adiponectin, was also noted. Therefore, apelin-12, vaspin and resistin may be used as biomarkers in children and adolescents with overweight and obesity.

Targeting the apelin system for the treatment of cardiovascular diseases

Cardiovascular disease is the leading cause of death worldwide. Its prevalence is rising due to ageing populations and the increasing incidence of diseases such as chronic kidney disease, obesity, and diabetes that are associated with elevated cardiovascular risk. Despite currently available treatments, there remains a huge burden of cardiovascular disease-associated morbidity for patients and healthcare systems, and newer treatments are needed. The apelin system, comprising the apelin receptor and its two endogenous ligands apelin and elabela, is a broad regulator of physiology that opposes the actions of the renin-angiotensin and vasopressin systems. Activation of the apelin receptor promotes endothelium-dependent vasodilatation and inotropy, lowers blood pressure, and promotes angiogenesis. The apelin system appears to protect against arrhythmias, inhibits thrombosis, and has broad anti-inflammatory and anti-fibrotic actions. It also promotes aqueous diuresis through direct and indirect (central) effects in the kidney. Thus, the apelin system offers therapeutic promise for a range of cardiovascular, kidney, and metabolic diseases. This review will discuss current cardiovascular disease targets of the apelin system and future clinical utility of apelin receptor agonism.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Plasma apelin and vascular endothelial growth factor levels in preterm infants: relationship to neonatal respiratory distress syndrome

AIM

The study aimed to determine the association between cord plasma levels of apelin and vascular endothelial growth factor (VEGF) with respiratory distress syndrome (RDS) in preterm infants.

METHODS

This case-control study included 120 preterm infants admitted to the neonatal intensive care unit of our hospital between January 2019 and January 2020. The infants were divided into RDS (n = 60) and non-RDS groups (n = 60). The cord plasma apelin and VEGF levels, perinatal characteristics, and neonatal complications were compared between the two groups.

RESULTS

The plasma apelin levels in the RDS group were significantly higher than in the non-RDS group (158.9 ± 24.8 vs. 125.2 ± 18.2 pg/mL, respectively), whereas VEGF levels in the non-RDS group were significantly higher than in the RDS group (187.4 ± 28.5 vs. 245.1 ± 44.8 pg/mL, respectively) (both p < .001). Infants with more severe RDS had higher plasma apelin levels and lower plasma VEGF levels. In the receiver operating characteristic curve analysis for the prediction of RDS, a cutoff of 148.4 pg/mL for apelin level yielded a sensitivity of 63.3% and a specificity of 95.0%, whereas a cutoff of 214.2 pg/mL for VEGF level showed a sensitivity of 86.7% and a specificity of 75.0%. Apelin levels were negatively correlated with VEGF levels in infants with RDS (r = 0.84, p < .001).

CONCLUSION

Differences in cord plasma apelin and VEGF levels may aid in the early diagnosis and treatment of RDS in preterm infants.

Potential Therapeutic Role for Apelin and Related Peptides in Diabetes: An Update

Type 2 diabetes mellitus (T2DM) is an epidemic with an ever-increasing global prevalence. Current treatment strategies, although plentiful and somewhat effective, often fail to achieve desired glycaemic goals in many people, leading ultimately to disease complications. The lack of sustained efficacy of clinically-approved drugs has led to a heightened interest in the development of novel alternative efficacious antidiabetic therapies. One potential option in this regard is the peptide apelin, an adipokine that acts as an endogenous ligand of the APJ receptor. Apelin exists in various molecular isoforms and was initially studied for its cardiovascular benefits, however recent research suggests that it also plays a key role in glycaemic control. As such, apelin peptides have been shown to improve insulin sensitivity, glucose tolerance and lower circulating blood glucose. Nevertheless, native apelin has a short biological half-life that limits its therapeutic potential. More recently, analogues of apelin, particularly apelin-13, have been developed that possess a significantly extended biological half-life. These analogues may represent a promising target for future development of therapies for metabolic disease including diabetes and obesity.

The Role of Apelin-APJ System in Diabetes and Obesity

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

The therapeutic potentials of apelin in obesity-associated diseases

Apelin, a peptide with several active isoforms ranging from 36 to 12 amino acids and its receptor APJ, a G-protein-coupled receptor, are widely distributed. However, apelin has emerged as an adipokine more than fifteen years ago, integrating the field of inter-organs interactions. The apelin/APJ system plays important roles in several physiological functions both in rodent and humans such as fluid homeostasis, cardiovascular physiology, angiogenesis, energy metabolism. Thus the apelin/APJ system has generated great interest as a potential therapeutic target in different pathologies. The present review will consider the effects of apelin in metabolic diseases such as obesity and diabetes with a focus on diabetic cardiomyopathy among the complications associated with diabetes and APJ agonists or antagonists of interest in these diseases.

Plasma levels of apelin are reduced in patients with liver fibrosis and cirrhosis but are not correlated with circulating levels of bone morphogenetic protein 9 and 10

BACKGROUND

The peptide apelin is expressed in human healthy livers and is implicated in the development of hepatic fibrosis and cirrhosis. Mutations in the bone morphogenetic protein receptor type II (BMPR-II) result in reduced plasma levels of apelin in patients with heritable pulmonary arterial hypertension. Ligands for BMPR-II include bone morphogenetic protein 9 (BMP9), highly expressed in liver, and BMP10, expressed in heart and to a lesser extent liver. However, it is not known whether reductions in BMP9 and/or BMP10, with associated reduction in BMPR-II signalling, correlate with altered levels of apelin in patients with liver fibrosis and cirrhosis.

METHODS

Plasma from patients with liver fibrosis (n = 14), cirrhosis (n = 56), and healthy controls (n = 25) was solid-phase extracted using a method optimised for recovery of apelin, which was measured by ELISA.

RESULTS

Plasma apelin was significantly reduced in liver fibrosis (8.3 ± 1.2 pg/ml) and cirrhosis (6.5 ± 0.6 pg/ml) patients compared with controls (15.4 ± 2.0 pg/ml). There was no obvious relationship between apelin and BMP 9 or BMP10 previously measured in these patients. Within the cirrhotic group, there was no significant correlation between apelin levels and disease severity scores, age, sex, or treatment with β-blockers.

CONCLUSIONS

Apelin was significantly reduced in plasma of patients with both early (fibrosis) and late-stage (cirrhosis) liver disease. Fibrosis is more easily reversible and may represent a potential target for new therapeutic interventions. However, it remains unclear whether apelin signalling is detrimental in liver disease or is beneficial and therefore, whether an apelin antagonist or agonist have clinical use.

The investigation effect of weight loss on serum vaspin, apelin-13, and obestatin levels in obese individual

Objectives

It was aimed to investigate if there were any significant corresponding changes on adipokine levels in obese subjects who achieved a 10% reduction in body weight.

Methods

Thirty obese and 25 healthy adults were enrolled in present study, and serum levels of vaspin, apelin-13, obestatin, and insulin were determined with the ELISA method.

Results

The serum obestatin and apelin-13 values of the obese group obtained as basal and after weight loss was significantly lower than in controls (p<0.05, p<0.01, p<0.01, p<0.05, respectively); however, weight loss did not cause significant changes on these parameters in obese groups (p>0.05). The vaspin level did not differ between the groups (p>0.05). The obese group had characterized increased serum insulin and insulin resistance assessment by the homeostatic assay (HOMA-IR) levels compared to controls (p<0.01, p<0.05, respectively); also, weight loss caused a significant decrease in these parameters compared to basal levels (p<0.01). No significant correlation was detected among the vaspin, apelin-13 and obestatin levels in the obese group (p>0.05).

Conclusions

Obese individuals exhibited decreased levels of apelin-13 and obestatin. Moreover, 10% weight loss caused a significant reduction of insulin resistance, but no significant change was detected on apelin-13, obestatin, and vaspin levels.

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

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

Adipokines: New Potential Therapeutic Target for Obesity and Metabolic, Rheumatic, and Cardiovascular Diseases

Besides its role as an energy storage organ, adipose tissue can be viewed as a dynamic and complex endocrine organ, which produces and secretes several adipokines, including hormones, cytokines, extracellular matrix (ECM) proteins, and growth and vasoactive factors. A wide body of evidence showed that adipokines play a critical role in various biological and physiological functions, among which feeding modulation, inflammatory and immune function, glucose and lipid metabolism, and blood pressure control. The aim of this review is to summarize the effects of several adipokines, including leptin, diponectin, resistin, chemerin, lipocalin-2 (LCN2), vaspin, omentin, follistatin-like 1 (FSTL1), secreted protein acidic and rich in cysteine (SPARC), secreted frizzled-related protein 5 (SFRP5), C1q/TNF-related proteins (CTRPs), family with sequence similarity to 19 member A5 (FAM19A5), wingless-type inducible signaling pathway protein-1 (WISP1), progranulin (PGRN), nesfatin-1 (nesfatin), visfatin/PBEF/NAMPT, apelin, retinol binding protein 4 (RPB4), and plasminogen activator inhibitor-1 (PAI-1) in the regulation of insulin resistance and vascular function, as well as many aspects of inflammation and immunity and their potential role in managing obesity-associated diseases, including metabolic, osteoarticular, and cardiovascular diseases.

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

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

Apelin-36-[L28A] and Apelin-36-[L28C(30kDa-PEG)] peptides that improve diet induced obesity are G protein biased ligands at the apelin receptor

BACKGROUND

Apelin signalling pathways have important cardiovascular and metabolic functions. Recently, apelin-36-[L28A] and apelin-36-[L28C(30kDa-PEG)], were reported to function independent of the apelin receptor in vivo to produce beneficial metabolic effects without modulating blood pressure. We aimed to show that these peptides bound to the apelin receptor and to further characterise their pharmacology in vitro at the human apelin receptor.

METHODS

[Pyr¹]apelin-13 saturation binding experiments and competition binding experiments were performed in rat and human heart homogenates using [¹²⁵I]apelin-13 (0.1 nM), and/or increasing concentrations of apelin-36, apelin-36-[L28A] and apelin-36-[L28C(30kDa-PEG)] (50pM-100μM). Apelin-36 and its analogues apelin-36-[F36A], apelin-36-[L28A], apelin-36-[L28C(30kDa-PEG)], apelin-36-[A28 A13] and [40kDa-PEG]-apelin-36 were tested in forskolin-induced cAMP inhibition and β-arrestin assays in CHO-K1 cells heterologously expressing the human apelin receptor. Bias signaling was quantified using the operational model for bias.

RESULTS

In both species, [Pyr¹]apelin-13 had comparable subnanomolar affinity and the apelin receptor density was similar. Apelin-36, apelin-36-[L28A] and apelin-36-[L28C(30kDa-PEG)] competed for binding of [¹²⁵I]apelin-13 with nanomolar affinities. Apelin-36-[L28A] and apelin-36-[L28C(30kDa-PEG)] inhibited forskolin-induced cAMP release, with nanomolar potencies but they were less potent compared to apelin-36 at recruiting β-arrestin. Bias analysis suggested that these peptides were G protein biased. Additionally, [40kDa-PEG]-apelin-36 and apelin-36-[F36A] retained nanomolar potencies in both cAMP and β-arrestin assays whilst apelin-36-[A13 A28] exhibited a similar profile to apelin-36-[L28C(30kDa-PEG)] in the β-arrestin assay but was more potent in the cAMP assay.

CONCLUSIONS

Apelin-36-[L28A] and apelin-36-[L28C(30kDa-PEG)] are G protein biased ligands of the apelin receptor, suggesting that the apelin receptor is an important therapeutic target in metabolic diseases.

Beyond adiponectin and leptin: adipose tissue-derived mediators of inter-organ communication

The breakthrough discoveries of leptin and adiponectin more than two decades ago led to a widespread recognition of adipose tissue as an endocrine organ. Many more adipose tissue-secreted signaling mediators (adipokines) have been identified since then, and much has been learned about how adipose tissue communicates with other organs of the body to maintain systemic homeostasis. Beyond proteins, additional factors, such as lipids, metabolites, noncoding RNAs, and extracellular vesicles (EVs), released by adipose tissue participate in this process. Here, we review the diverse signaling mediators and mechanisms adipose tissue utilizes to relay information to other organs. We discuss recently identified adipokines (proteins, lipids, and metabolites) and briefly outline the contributions of noncoding RNAs and EVs to the ever-increasing complexities of adipose tissue inter-organ communication. We conclude by reflecting on central aspects of adipokine biology, namely, the contribution of distinct adipose tissue depots and cell types to adipokine secretion, the phenomenon of adipokine resistance, and the capacity of adipose tissue to act both as a source and sink of signaling mediators.

The apelin/APJ system as a therapeutic target in metabolic diseases

INTRODUCTION

Apelin, a bioactive peptide, is the endogenous ligand of APJ, a G protein-coupled receptor which is widely expressed in peripheral tissues and in the central nervous system. The apelin/APJ system is involved in the regulation of various physiological functions and is a therapeutic target in different pathologies; the development of APJ agonists and antagonists has thus increased. Area covered: This review focuses on the in vitro and in vivo metabolic effects of apelin in physiological conditions and in the context of metabolic diseases. Expert opinion: In experimental models, novel APJ agonists are efficient in vivo, to treat metabolic diseases and associated complications. However, more clinical trials are necessary to determine whether molecules that target APJ could become an alternative therapeutic strategy in the treatment of metabolic diseases and associated complications.

High CONUT score predicts poor survival and postoperative HBV reactivation in HBV-related hepatocellular carcinoma patients with low HBV-DNA levels

BACKGROUND

Postoperative hepatitis B virus (HBV) reactivation (PHR) is associated with resection-induced immunosuppression in patients with HBV-related hepatocellular carcinoma (HCC). Controlling Nutritional Status (CONUT) score is an effective index for evaluating immune-nutrition function. However, the value of COUNT in predicting PHR in HBV-HCC patients remains unknown.

METHODS

Totally, 209 HCC patients were enrolled.

RESULTS

Preoperative immune function (CD3⁺CD4⁺, CD3⁺CD8⁺, IgG and IgM) in patients with high CONUT score was significantly worse than that in patients with low CONUT score (P<0.05). Blood test results on postoperative day 7 showed the same trend. In addition, patients with high CONUT score experienced a significantly larger decrease in the proportions of CD3⁺CD4⁺ and CD3⁺CD8⁺ than those with low CONUT score (P < 0.05). In patients with high CONUT score, the incidence of overall complications was also significantly higher (P = 0.029) and hospital-stay was significantly longer (P = 0.020). Besides, overall survival and recurrence free survival in patients with high CONUT score were significantly worse than those in patients with low CONUT score (48.32 vs. 38.12 months, P<0.001; 36.08 vs. 27.03 months, P = 0.001). The incidence of PHR was significantly higher in patients with high COUNT score (P<0.001), and CONUT score was strongly associated with PHR (P<0.001). Additionally, the fellow subgroup results also demonstrated that COUNT score was more effective in predicting PHR in patients with HBV-DNA level <500 copies/ml than patients with HBV-DNA 500-1000 copies/ml.

CONCLUSION

CONUT score is an effective indicator predicting survival and PHR in HBV-HCC patients, especially in those with HBV-DNA levels <500 copies/ml.