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

Adipokines level in plasma, hypothalamus, ovaries and adipose tissue of rats with polycystic ovary syndrome

RESEARCH QUESTION

Do the levels of adipokines (adiponectin, apelin, chemerin and vaspin) in plasma, hypothalamus, ovaries and periovarian adipose tissue differ during polycystic ovarian syndrome (PCOS)?

DESIGN

The PCOS was induced in rats by oral administration of non-steroidal aromatase inhibitor letrozole. To determine the plasma levels of adiponectin, apelin, chemerin and vaspin enzyme-linked immunosorbent assays were carried out. To assess the expression (gene and protein) and immunolocalization of these adipokines and their receptors, namely Adipor1 and Adipor2 for adiponectin, Aplnr for apelin, Ccrl2, Cmklr1 and Gpr1 for chemerin and Grp78 for vaspin in the hypothalamus, real-time polymerase chain reaction, and Western blot and immunohistochemistry were used to analyse ovaries and periovarian adipose tissue respectively.

RESULTS

In PCOS, the plasma level of adiponectin decreased (P = 0.0003), whereas apelin, chemerin and vaspin increased (P ≤ 0.0479). Moreover, PCOS modulates the expression of adipokines and their receptors in the hypothalamus, ovaries and periovarian adipose tissue compared with healthy rats (P ≤ 0.487).

CONCLUSIONS

A strong relationship was found between PCOS and adipokines, which suggests that adipokines may be a biomarker of PCOS.

Circulating cytokines levels and the risk of polycystic ovary syndrome: A Mendelian randomization analysis

This study utilized Mendelian randomization (MR) analysis to explore the causal relationship between circulating cytokines and polycystic ovary syndrome (PCOS), and to identify potential biomarkers of PCOS mechanisms. Genetic instrumental variables for cytokines were derived from 2 large-scale genome-wide association studies (GWAS) involving 8293 and 14,824 European participants. Summary statistics from a GWAS meta-analysis (10,074 PCOS cases and 103,164 controls of European ancestry) were used in the discovery phase of MR analysis. Replication analysis utilized another GWAS meta-analysis dataset (3609 cases and 229,788 controls). The primary analysis employed the inverse-variance weighted (IVW) method, with secondary methods including constrained maximum likelihood model averaging, weighted median, and weighted mode. Meta-analysis was combined with MR results, while heterogeneity and horizontal pleiotropy were assessed using leave-one-out, MR-Egger intercept test, and Mendelian Randomization Pleiotropy Residual Sum and Outlier. Sensitivity analysis confirmed the robustness of the results. Reverse MR analysis was used to explore the association of PCOS with the identified cytokines. Meta-analysis revealed that increased CCL4 (C-C motif chemokine 4) levels were associated with a higher risk of PCOS (odds ratio [OR] = 1.123, 95% confidence interval [CI]: 1.056-1.195; P < .001). Decreased PCOS risk was linked to CXCL11 (C-X-C motif chemokine 11, OR = 0.930, 95% CI: 0.890-0.970; IVW-false discovery rate [FDR] P = 4.85 × 10-4) and CD6 (T-cell surface glycoprotein CD6 isoform, OR = 0.730, 95% CI: 0.890-0.970; IVW-FDR P = .008). Sensitivity analysis confirmed the robustness of the findings. MR analysis suggests a potential causal link between alterations in CCL4, CXCL11, CD6, and PCOS risk, highlighting the role of cytokines in PCOS development and progression, warranting further investigation.

Chemerin and Polycystic Ovary Syndrome: A Comprehensive Review of Its Role as a Biomarker and Therapeutic Target

Background: Chemerin, an adipokine implicated in inflammatory, metabolic, and adipogenic processes, has been detected in high serum concentration in women with polycystic ovary syndrome (PCOS) and seems to play a role in PCOS pathogenesis. Moreover, at present, no comprehensive and critical document is available in the literature on this topic. The aim of the current study was to comprehensively review the latest available data to confirm the evidence about the association between chemerin and PCOS, highlighting its potential role as an upcoming biomarker and therapeutic target. Methods: A search in the literature of studies published between 2019 and 2024 was conducted using PubMed, Cochrane Library, and Web of Science, focusing on research related to chemerin, PCOS, and PCOS-related features, comorbidities, and complications. A qualitative structured synthesis of key findings was performed according to the specific thematic areas selected, including and discussing clinical data on women with PCOS and experimental studies in humans and animal models of PCOS. Results: Available data confirm increased serum levels of chemerin in women with PCOS compared with controls, independent of obesity and body mass index. Chemerin is associated with insulin resistance, hyperandrogenism, and ovarian dysfunction in PCOS individuals, inhibiting folliculogenesis and steroidogenesis. Experimental animal models underscore chemerin's regulatory roles through its receptors within the hypothalamic-pituitary-ovarian axis and peripheral tissues. High systemic levels of chemerin in PCOS may also be related to the increased risk of pregnancy complications, especially gestational diabetes mellitus and preeclampsia. Conclusions: The current review study highlights the role of chemerin in PCOS pathophysiology, severity, and associated comorbidities and complications, assessing its value as a future biomarker and foreshadowing its potential as a therapeutic target.

Unraveling the complexity of follicular fluid: insights into its composition, function, and clinical implications

Follicular fluid (FF) plays a vital role in the bidirectional communication between oocytes and granulosa cells (GCs), regulating and promoting oocyte growth and development. This fluid constitutes a complex microenvironment, rich in various molecules including hormones, growth factors, cytokines, lipids, proteins, and extracellular vesicles. Understanding the composition and metabolic profile of follicular fluid is important for investigating ovarian pathologies such as polycystic ovary syndrome (PCOS) and endometriosis. Additionally, analyzing follicular fluid can offer valuable insights into oocyte quality, aiding in optimal oocyte selection for in vitro fertilization (IVF). This review provides an overview of follicular fluid composition, classification of its components and discusses the influential components of oocyte development. It also highlights the role of follicular fluid in the pathogenesis and diagnosis of ovarian diseases, along with potential follicular fluid biomarkers for assessing oocyte quality. By understanding the intricate relationship between follicular fluid and oocyte development, we can advance fertility research and improve clinical outcomes for infertility patients.

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.

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.