Elevated blood apelin levels in type 2 diabetes mellitus: A systematic review and meta-analysis

Exploring exercise-driven exerkines: unraveling the regulation of metabolism and inflammation

Exercise has many beneficial effects that provide health and metabolic benefits. Signaling molecules are released from organs and tissues in response to exercise stimuli and are widely termed exerkines, which exert influence on a multitude of intricate multi-tissue processes, such as muscle, adipose tissue, pancreas, liver, cardiovascular tissue, kidney, and bone. For the metabolic effect, exerkines regulate the metabolic homeostasis of organisms by increasing glucose uptake and improving fat synthesis. For the anti-inflammatory effect, exerkines positively influence various chronic inflammation-related diseases, such as type 2 diabetes and atherosclerosis. This review highlights the prospective contribution of exerkines in regulating metabolism, augmenting the anti-inflammatory effects, and providing additional advantages associated with exercise. Moreover, a comprehensive overview and analysis of recent advancements are provided in this review, in addition to predicting future applications used as a potential biomarker or therapeutic target to benefit patients with chronic diseases.

Variations in protein levels of the apelinergic system in adipose tissue of hypertensive individuals with class 3 obesity

The aim of this study was to investigate the expression of apelin (APLN) and its receptor (APLNR) in visceral adipose tissue (VAT), and its effect on the downstream expression of endothelial nitric oxide synthase (eNOS) in individuals with class 3 obesity, with or without hypertension. Seventy-five unrelated individuals presenting obesity class 3 with or without hypertension were included. Gene expression of APLN, and APLNR were analyzed in VAT, by reverse transcription quantitative polymerase chain reaction. The APLN, APLNR and eNOS (total and phosphorylated) levels in VAT were evaluated by Western blot. Analysis of differences between groups of APLN, APLNR and eNOS were performed by a logistic regression adjusting by confounding factors. Forty-five individuals with hypertension formed the case group, and 30 individuals constituted the control group. The APLN mRNA and protein levels were higher in the group of individuals with hypertension versus individuals without hypertension (p = 0.027 and p = 0.036, respectively). Meanwhile, APLNR mRNA and protein levels in subjects with hypertension were lower versus the group of subjects without hypertension (p = 0.001 and p = 0.008, respectively). Further, the group with hypertension presented a lower level of phosphorylation of eNOS Ser1177, compared to the control group (p = 0.002). In conclusion, individuals with class 3 obesity and hypertension present a modified APLN/APLNR expression in visceral adipose tissue, which could be secondary to reduced eNOS phosphorylation.

Interplay between Myokine Profile and Glycemic Control in Type 2 Diabetes Mellitus Patients with Heart Failure

Type 2 diabetes mellitus (T2DM) remains a powerful predictor of progressive heart failure (HF), but it is not clear whether altered glycemic control interferes with HF progression via an impaired profile of circulating myokines. The aim was to investigate plausible effects of glucose control on a myokine signature in T2DM patients affected by chronic HF. We selected 372 T2DM patients from the local database and finally included 314 individuals suffering from chronic HF and subdivided them into two groups according to glycosylated hemoglobin (HbA1c) levels (<6.9% and ≥7.0%). Echocardiography and Doppler examinations along with biomarker measurements were performed at the baseline of the study. The results showed that irisin levels were significantly lower in patients with HbA1c ≥ 7.0% than in those with HbAc1 < 6.9%, whereas concentrations of apelin, myostatin and adropin did not significantly differ between these two groups. We also identified numerous predictors of poor glycemic control, but only N-terminal brain natriuretic propeptide (odds ratio [OR] = 1.07; 95% confidence interval [CI] = 1.02−1.10, p = 0.04) and irisin (OR = 1.09; 95% CI = 1.04−1.17, p = 0.001) remained independent predictors of the dependent variable. In conclusion, we found that decreased levels of irisin were associated with poor glycemic control in T2DM patients with HF regardless of clinical conditions and other biomarkers.

Identification and verification of immune-related biomarkers and immune infiltration in diabetic heart failure

PURPOSE

Diabetic heart failure (DHF) or cardiomyopathy is a common complication of diabetes; however, the underlying mechanism is not clear. In the present study, the authors searched for differentially expressed genes associated with DHF and the molecular types of immune cells based on bioinformatics.

METHODS

The RNA expression dataset of DHF was obtained from the NCBI Gene Expression Omnibus (GEO) database. After preprocessing the data, the differentially expressed genes (DEGs) between the DHF group and the non-diabetic heart failure (NHF) group were screened and intersected with immune-related genes (IRGs) in the ImmPort database. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed using the DAVID tool. The ssGSEA algorithm was used to evaluate immune infiltration of the heart tissue in each group. In addition, the protein-protein interaction (PPI) network and miRNA-mRNA network were constructed using the STRING online website and Cytoscape program. Finally, validation analysis was performed using animal models.

RESULTS

Eight immune-related core genes were identified. GO and KEGG showed that core genes were mainly enriched in angiogenesis and cytokine-cytokine receptor interaction. Immune infiltration results showed that activated dendritic cells, central memory CD4 T cells, central memory CD8 T cells, myeloid-derived suppressor cells (MDSCs), neutrophils, and regulatory T cells may be involved in DHF. Neutrophils may play a key role in the pathogenesis of HF in diabetes.

CONCLUSION

Immune-related core genes and immune infiltrating cells provide a new perspective on the pathogenesis of DHF.

Apelin levels in pregnant women with and without gestational diabetes mellitus: a collaborative systematic review and meta-analysis

Aims: This systematic review and meta-analysis investigated maternal apelin levels in pregnant women with and without GDM. Secondary outcomes were glucose- and lipid-related results.Methods: Databases including PubMed, Embase, Cochrane Library, LILACS, CNKI, and Wang Fang were searched. The methodological quality of included studies was evaluated with the Newcastle-Ottawa Scale. Mean differences (MDs) or standardized MDs (SMDs) with their 95% confidence intervals (CIs) were evaluated. Random effect model analyses were carried out and heterogeneity with the I² and Tau² statistics.Results: Fourteen observational studies (sample size: 1033 women with GDM and 1053 for control women) with a low or moderate risk of bias were included in the analysis. During the second half of pregnancy, maternal apelin estimate was significantly higher in women with GDM (SMD = 0.64; 95% CI: 0.03 to 1.25), as well as insulin (SMD = 1.41% CI: 0.84 to 1.99), glucose (SMD = 1.56; 95% CI 1.20 to 1.91), glycated hemoglobin (SMD = 1.11, 95% CI: 0.69 to 1.54), HOMA-IR (MD = 2.25; 95%CI: 1.51 to 2.98), BMI (MD = 0.80 kg/m², 95%CI: 0.52 to 1.08), total cholesterol (SMD = 0.42, 0.12 to 0.73), LDL-cholesterol (SMD = 0.63, 95%CI: 0.23 to 1.02), and triglycerides (SMD = 0.40, 95%CI: 0.19 to 0.61) as compared to control women. There was heterogeneity between studies as evidence by high I² values. Meta-regression analysis indicated statistically significant regression coefficients for age of women, glucose and total cholesterol.Conclusions: GDM was associated with increased circulating apelin, insulin, glucose, glycated hemoglobin, total cholesterol, LDL-cholesterol levels, and HOMA-IR index.

Circulating apelin and chemerin levels in patients with polycystic ovary syndrome: A meta-analysis

BACKGROUND

Polycystic ovary syndrome (PCOS) is one of the most common gynecological endocrine disorders. Apelin and chemerin are newly identified adipokines, which are higher in obesity and diabetes. Studies have found that the serum apelin and chemerin levels in patients with PCOS are significantly increased. However, other studies showed the opposite results. Therefore, the relationship between those two adipokines and PCOS is still controversial.

AIM

This meta-analysis was conducted to statistically evaluate the apelin and chemerin levels of patients with PCOS.

METHODS

We searched the Web of Science, Embase, PubMed, and Google Scholar databases for potential studies. "Polycystic ovary syndrome" or "PCOS" in combination with the terms "apelin" or "chemerin" were used as keywords search titles or abstracts. The publication period examined was between 1990 and 2021. Standardized mean differences (SMD) with corresponding 95% confidence intervals (CIs) were determined as the results of the meta-analysis.

RESULTS

A total of 148 articles were initially retrieved, and 18 qualified articles were finally obtained through preliminary screening and quality evaluation. The publications together contain 1,265 cases and 894 controls. The results of the meta-analysis showed that the circulating chemerin levels in patients with PCOS were significantly higher than those in the controls (SMD: 0.79, 95% CI [0.36, 1.23]), and there was no significant difference in circulating apelin between patients with PCOS and controls (SMD: 0.57, 95% CI [-0.21, 1.35]).

CONCLUSIONS

This meta-analysis is the first to evaluate circulating apelin and chemerin levels in patients with PCOS. Our findings suggest that circulating chemerin levels of patients with PCOS are significantly higher than those of healthy controls.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=218316, identifier CRD42020218316.

Serum miRNA Profile in Diabetic Patients With Ischemic Heart Disease as a Promising Non-Invasive Biomarker

The increasing morbidity and mortality of type 2 diabetic mellitus (T2DM) patients with ischemic heart disease (IHD) highlight an urgent need to identify early biomarkers, which would help to predict individual risk of development of IHD. Here, we postulate that circulating serum-derived micro RNAs (miRNAs) may serve as potential biomarkers for early IHD diagnosis and support the identification of diabetic individuals with a predisposition to undergo IHD. We obtained serum samples from T2DM patients either with IHD or IHD-free and analysed the expression levels of 798 miRNAs using the NanoString nCounter technology platform. The prediction of the putative miRNAs targets was performed using the Ingenuity Pathway Analysis (IPA) software. Gene Ontology (GO) analysis was used to identify the biological function and signalling pathways associated with miRNA target genes. Hub genes of protein-protein interaction (PPI) network were identified by STRING database and Cytotoscape tool. Receiver operating characteristic (ROC) analysis was used to assess the diagnostic value of identified miRNAs. Real-time quantitative polymerase chain reaction (qRT-PCR) was used for nCounter platform data validation. Our data showed that six miRNAs (miR-615-3p, miR-3147, miR-1224-5p, miR-5196-3p, miR-6732-3p, and miR-548b-3p) were significantly upregulated in T2DM IHD patients compared to T2DM patients without IHD. Further analysis indicated that 489 putative target genes mainly affected the endothelin-1 signalling pathway, glucocorticoid biosynthesis, and apelin cardiomyocyte signalling pathway. All tested miRNAs showed high diagnostic value (AUC = 0.779 - 0.877). Taken together, our research suggests that circulating miRNAs might have a crucial role in the development of IHD in diabetic patients and may be used as a potential biomarker for early diagnosis.

Ontology of the apelinergic system in mouse pancreas during pregnancy and relationship with β-cell mass

The apelin receptor (Aplnr) and its ligands, Apelin and Apela, contribute to metabolic control. The insulin resistance associated with pregnancy is accommodated by an expansion of pancreatic β-cell mass (BCM) and increased insulin secretion, involving the proliferation of insulin-expressing, glucose transporter 2-low (Ins+Glut2LO) progenitor cells. We examined changes in the apelinergic system during normal mouse pregnancy and in pregnancies complicated by glucose intolerance with reduced BCM. Expression of Aplnr, Apelin and Apela was quantified in Ins+Glut2LO cells isolated from mouse pancreata and found to be significantly higher than in mature β-cells by DNA microarray and qPCR. Apelin was localized to most β-cells by immunohistochemistry although Aplnr was predominantly associated with Ins+Glut2LO cells. Aplnr-staining cells increased three- to four-fold during pregnancy being maximal at gestational days (GD) 9-12 but were significantly reduced in glucose intolerant mice. Apelin-13 increased β-cell proliferation in isolated mouse islets and INS1E cells, but not glucose-stimulated insulin secretion. Glucose intolerant pregnant mice had significantly elevated serum Apelin levels at GD 9 associated with an increased presence of placental IL-6. Placental expression of the apelinergic axis remained unaltered, however. Results show that the apelinergic system is highly expressed in pancreatic β-cell progenitors and may contribute to β-cell proliferation in pregnancy.

Comparing High-Intensity Interval Training (HIIT) and Continuous Training on Apelin, APJ, NO, and Cardiotrophin-1 in Cardiac Tissue of Diabetic Rats

BACKGROUND AND AIMS

Exercise activity is an important method for managing type 2 diabetes. This investigation examined the HIIT and continuous training on apelin, APJ receptor, NO, and cardiotrophin-1 in the cardiac tissue of diabetic rats.

METHODS

The animals were categorized into 3 groups of HIIT, continuous (CO), and control (C) (all animals were sacrificed immediately and 2 days after exercise training period). Rats underwent the treadmill exercise program either HIIT (12 bouts at 90-95% of VO₂ max with 60 s rest at 50% of VO₂ max) or CO (60-65% VO₂ max for 40 min). Protocols performed 5 days per week for 8 weeks. Apelin, APJ receptor, NO, and cardiotrophin-1 protein expressions were measured using the Western blotting method in the left ventricle.

RESULTS

Immediately after HIIT and CO exercise protocols, apelin and CT-1 protein showed a significant difference in contrast by the C-0 group (p < 0.01). However, NO values were substantially higher in HIIT-0 compared to C-0 and CO-0 groups rats (p < 0.01). After two days of exercise protocols, apelin and NO protein showed a significant increase in HIIT and CO groups in contrast to the C animals (p < 0.01). Moreover, APJ and CT-1 protein significantly upregulated in CO-2 and HIIT-2 compared to the other groups (p < 0.01).

CONCLUSIONS

This study indicates that exercise training, despite the type, is an efficient method to modify apelin, APJ receptor, NO, and cardiotrophin-1 values in animals with type 2 diabetes.

Elabela and Apelin actions in healthy and pathological pregnancies

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