Circulating omentin-1 levels in women with polycystic ovary syndrome: a meta-analysis

Biomarkers to inform the management of polycystic ovary syndrome: A review of systematic reviews

INTRODUCTION

Polycystic ovarian syndrome (PCOS) is the commonest endocrine condition affecting reproductive age women. Many biomarkers may aid assessment and management, however evidence is limited on their utility in clinical practice. We conducted a review of systematic reviews to identify the most useful biomarkers in the clinical management of PCOS.

METHODS

We searched MEDLINE, EMBASE, CENTRAL and HTA until August 2023 for reviews evaluating biomarkers in PCOS women compared to healthy controls. Methodological quality was assessed using the AMSTAR2 tool. We reported pooled evidence for each biomarker with 95% confidence intervals from the most recent, up-to-date, and best quality review.

RESULTS

From 3360 citations, we included 75 systematic reviews (88 biomarkers, 191,792 women). Most reviews (50/75, 67%) were moderate quality, but reported high heterogeneity (66/75, 88%). We identified 63 abnormal biomarkers in women with PCOS versus healthy controls. Of these, 22 core biomarkers could help evaluate the multisystemic impact of PCOS and inform patient management and surveillance: dehydroepiandrosterone, prolactin, sex hormone-binding globulin, total and free testosterone, anti-Mullerian hormone, systolic and diastolic blood pressure, c-reactive protein, fibrinogen, oral glucose tolerance test, homoeostatic model assessment-insulin resistance index, fasting insulin, total cholesterol, triglycerides, lipoprotein(a), HDL, LDL, non-HDL-cholesterol, ferritin, iron, and 25-hydroxy-vitamin D.

CONCLUSION

We identified 22 core biomarkers assessing the multisystemic impact of PCOS and inform its clinical management. Future research is required to establish validated healthcare pathways.

Immunological and Metabolic Causes of Infertility in Polycystic Ovary Syndrome

Infertility has been recognized as a civilizational disease. One of the most common causes of infertility is polycystic ovary syndrome (PCOS). Closely interrelated immunometabolic mechanisms underlie the development of this complex syndrome and lead to infertility. The direct cause of infertility in PCOS is ovulation and implantation disorders caused by low-grade inflammation of ovarian tissue and endometrium which, in turn, result from immune and metabolic system disorders. The systemic immune response, in particular the inflammatory response, in conjunction with metabolic disorders, insulin resistance (IR), hyperadrenalism, insufficient secretion of progesterone, and oxidative stress lead not only to cardiovascular diseases, cancer, autoimmunity, and lipid metabolism disorders but also to infertility. Depending on the genetic and environmental conditions as well as certain cultural factors, some diseases may occur immediately, while others may become apparent years after an infertility diagnosis. Each of them alone can be a significant factor contributing to the development of PCOS and infertility. Further research will allow clinical management protocols to be established for PCOS patients experiencing infertility so that a targeted therapy approach can be applied to the factor underlying and driving the "vicious circle" alongside symptomatic treatment and ovulation stimulation. Hence, therapy of fertility for PCOS should be conducted by interdisciplinary teams of specialists as an in-depth understanding of the molecular relationships and clinical implications between the immunological and metabolic factors that trigger reproductive system disorders is necessary to restore the physiology and homeostasis of the body and, thus, fertility, among PCOS patients.

Correlation Between Circulating Adropin Levels and Patients with PCOS: An Updated Systematic Review and Meta-analysis

An increasing number of young women suffer from polycystic ovary syndrome (PCOS). Reasonable diagnosis and monitoring are important steps in the treatment of PCOS. Therefore, we performed an updated meta-analysis between adropin levels and PCOS to identify their relationship. We searched 8 databases (Pubmed, EMBASE, Cochrane Library, CNKI, Wanfang, CBM, clinicaltrials.gov, OpenGrey) for relevant studies using the following search items: 'PCOS or polycystic ovary syndrome or Stein-Leventhal syndrome' AND 'adropin'. Standardized mean difference (SMD) and 95% confidence intervals(CIs) were used as the outcomes. Data were analyzed using Revman 5.3, Stata 16, and MetaXL. Nineteen articles were include in this meta-analysis. The PCOS group had significantly lower adropin levels than the healthy groups (SMD = -2.79 ng/ml, 95%CI (-3.42, -2.16), p < 0.00001). Significant publication bias (p < 0.05) was observed; additionally, the results were robust based on metatrim and fail-safe number (Nfs). Meta-regression analysis showed that age, glucose ratio and luteinizing hormone (LH) may be sources of heterogeneity (univariate meta-regression analysis: P = 0.058 vs P = 0.026 vs P = 0.091). Furthermore, BMI, insulin, glucose, HOMA-IR, total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) may be closely related to adropin levels (p < 0.05) owing to meta-analysis of correlation coefficient. We found there was a correlation between adropin levels and PCOS: circulating adropin levels were significantly lower in patients with PCOS than healthy controls, which may be helpful for clinical diagnosis and detection of PCOS.

The Complex Roles of Adipokines in Polycystic Ovary Syndrome and Endometriosis

Polycystic ovary syndrome (PCOS) and endometriosis are frequent diseases of the female reproductive tract causing high morbidity as they can significantly affect fertility and quality of life. Adipokines are pleiotropic signaling molecules secreted by white or brown adipose tissues with a central role in energy metabolism. More recently, their involvement in PCOS and endometriosis has been demonstrated. In this review article, we provide an update on the role of adipokines in both diseases and summarize previous findings. We also address the results of multi-omics approaches in adipokine research to examine the role of single nucleotide polymorphisms (SNPs) in genes coding for adipokines and their receptors, the secretome of adipocytes and to identify epigenetic alterations of adipokine genes that might be conferred from mother to child. Finally, we address novel data on the role of brown adipose tissue (BAT), which seems to have notable effects on PCOS. For this review, original research articles on adipokine actions in PCOS and endometriosis are considered, which are listed in the PubMed database.

Progress of Adipokines in the Female Reproductive System: A Focus on Polycystic Ovary Syndrome

Adipose tissue, one type of loose connective tissue in the human body, maintains the primary task of energy storage. Adipose tissue is not only an energy reservoir but also plays a vital role as the largest endocrine organ of the whole body via releasing a variety of adipokines, which participate in many pathophysiological processes, such as energy metabolism regulation, glucose and lipid metabolism, and inflammation. Polycystic ovary syndrome (PCOS) is a disorder that mainly involves the female reproductive system, affecting women of childbearing age particularly. Insulin resistance (IR) and hyperandrogenemia (HA) have been implicated as a critical link involving the etiology and outcome of PCOS. A great deal of studies has bridged the gap between adipokines (such as Adiponectin, Chemerin, Metrnl, Apelin, Resistin, Visfatin, Leptin, Vaspin, Lipocalin 2, and Omentin) and reproductive fitness. In this review, we will focus on the adipokines' functions on PCOS and come up with some points of view on the basis of current research.

Review of Novel Potential Insulin Resistance Biomarkers in PCOS Patients—The Debate Is Still Open

Research on proteins and peptides that play roles in metabolic regulation, which may be considered potential insulin resistance markers in some medical conditions, such as diabetes mellitus, obesity and polycystic ovarian syndrome (PCOS), has recently gained in interest. PCOS is a common endocrine disorder associated with hyperandrogenemia and failure of ovulation, which is often accompanied by metabolic abnormalities, including obesity, dyslipidemia, hyperinsulinemia, and insulin resistance. In this review, we focus on less commonly known peptides/proteins and investigate their role as potential biomarkers for insulin resistance in females affected by PCOS. We summarize studies comparing the serum fasting concentration of particular agents in PCOS individuals and healthy controls. Based on our analysis, we propose that, in the majority of studies, the levels of nesfastin-1, myonectin, omentin, neudesin were decreased in PCOS patients, while the levels of the other considered agents (e.g., preptin, gremlin-1, neuregulin-4, xenopsin-related peptide, xenin-25, and galectin-3) were increased. However, there also exist studies presenting contrary results; in particular, most data existing for lipocalin-2 are inconsistent. Therefore, further research is required to confirm those hypotheses, as well as to elucidate the involvement of these factors in PCOS-related metabolic complications.

Circulating chemerin levels in women with polycystic ovary syndrome: a meta-analysis

OBJECTIVE

The present meta-analysis was conducted to investigate the association between circulating chemerin levels and polycystic ovary syndrome (PCOS) in women.

METHODS

Relevant studies published up to May 2020 were searched from PubMed, Ovid, the Cochrane Library, and Clinical Trial Database. A random effects model was used to measure the strength of association between PCOS and chemerin by using the standardized mean difference (SMD) and 95% confidence interval (CI). All data were analyzed using Stata 12.0 (version 12; Stata-Corp, College Station, TX).

RESULTS

The final meta-analysis included eight studies with 15 results including a total of 897 participants (524 patients with PCOS and 373 controls). The circulating chemerin levels were higher in patients with PCOS (random effects SMD = 1.07; 95% CI: 0.55-1.59; p < .001) than in controls. However, considerable heterogeneity across studies was not eliminated in subgroup analyses. The meta-regression analysis further suggested that region is the main source of heterogeneity (p = .001).

CONCLUSIONS

Our meta-analysis indicated that women with PCOS have significantly higher circulating chemerin levels than in healthy women, indicating that chemerin may be involved in the pathogenesis of PCOS.

Association of increased levels of omentin-1 and carotid intima-media thickness with early signs of cardiovascular risk in patients with polycystic ovary syndrome: A prospective case control study

AIM

Omentin-1, an adipokine primarily secreted from visceral adipose tissue, regulates metabolic homeostasis, whereas carotid intima-media thickness (CIMT) is a valid marker for early diagnosis of atherosclerosis. We aimed to investigate whether polycystic ovary syndrome (PCOS) is related to levels of omentin-1 and CIMT and demonstrate the association with cardiovascular risk.

METHODS

A prospective case-control study was performed on 47 PCOS patients and 35 healthy subjects. Hormonal and metabolic parameters, levels of serum omentin-1, and CIMT were evaluated in the two groups.

RESULTS

The right, left, total CIMT, and levels of serum omentin-1 were significantly higher in the PCOS group than in the healthy controls (p = 0.015, p = 0.009, p = 0.021, and p = 0.002, respectively). Using multiple linear and backward elimination regression analyses, serum omentin-1 was found to be independently associated with age and Ln-transformed homeostasis model assessment of insulin resistance, and cardiovascular parameters were independently associated with body mass index (BMI). In the PCOS group, the means of right, left, and total CIMT were significantly higher in the subgroup with BMI levels ≥25 kg/m² compared to the subgroup with BMI levels <25 kg/m² (p < 0.001 for all comparisons).

CONCLUSION

A significant increase in CIMT is associated with cardiovascular risk in patients with PCOS. Levels of serum omentin-1 were found to be significantly higher in early PCOS cases at a younger age, acting as a protective acute-phase reactant.

Blood Circulating Levels of Adipokines in Polycystic Ovary Syndrome Patients: A Systematic Review and Meta-analysis

A body of studies has examined the circulating concentration of adipokines including apelin, vapin, resistin, and chemerin in polycystic ovary syndrome (PCOS) patients. However, their findings have been inconclusive. Therefore, we systematically reviewed available studies to illuminate the overall circulating concentration of adipokines in PCOS subjects. Cochrane's Library, PubMed, Scopus, and ISI Web of Science databases were searched from the earliest available date up to April 2021 for relevant articles. The quality of each study was assessed by the Newcastle-Ottawa Quality Assessment Scale. The pooled effect size was estimated based on the random effects model, and the standard mean differences (SMD) with a 95% confidence interval (CI) were reported. A total of 88 studies met the inclusion criteria and were included in the current systematic review and meta-analysis. The results of the analysis showed that serum levels of vaspin (SMD 0.69; 95% CI, 0.22 to 1.17; P = 0.004; I² = 90.6%), chemerin (SMD 1.87; 95% CI, 1.35 to 2.40; P < 0.001; I² = 94.4%), and resistin (SMD 0.66; 95% CI, 0.41 to 0.91; P < 0.001; I² = 92.6%) were significantly higher in the PCOS group compared to controls. However, there was no significant difference between the PCOS and control groups in relation to apelin levels (SMD - 0.17; 95% CI, - 1.06 to 0.73; P = 0.714; I² = 97.8%). We found that serum levels of vaspin, chemerin, and resistin were significantly higher in PCOS subjects compared with controls. It seems that these adipokines can be measured as a useful marker to predict the development of PCOS.

Role of adipokines in the ovarian function: Oogenesis and steroidogenesis

Adipokines are mainly produced by adipose tissue; however, their expression has been reported in other organs including female reproductive tissues. Therefore, adipokines have opened new avenues of research in female fertility. In this regard, studies reported different roles for certain adipokines in ovarian function, although the role of other recently identified adipokines is still controversial. It seems that adipokines are essential for normal ovarian function and their abnormal levels could be associated with ovarian-related disorders. The objective of this study is to review the available information regarding the role of adipokines in ovarian functions including follicular development, oogenesis and steroidogenesis and also their involvement in ovary-related disorders.

Circulating resistin and follistatin levels in obese and non-obese women with polycystic ovary syndrome: A systematic review and meta-analysis

This meta-analysis was performed to resolve the inconsistencies regarding resistin and follistatin levels in women with polycystic ovary syndrome (PCOS) by pooling the available evidence. A systematic literature search using PubMed and Scopus was carried out through November 2020 to obtain all pertinent studies. Weighted mean differences (WMDs) with corresponding 95% confidence intervals (CIs) were calculated to evaluate the strength of the association between the levels of resistin and follistatin with PCOS in the overall and stratified analysis by obesity status. A total of 47 publications, 38 for resistin (2424 cases; 1906 controls) and 9 studies for follistatin (815 cases; 328 controls), were included in the meta-analysis. Resistin levels were significantly higher in PCOS women compared with non-PCOS controls (WMD = 1.96 ng/ml; 95%CI = 1.25–2.67, P≤0.001) as well as in obese PCOS women vs. obese controls, and in non-obese PCOS women compared with non-obese controls, but not in obese PCOS vs. non-obese PCOS patients,. A significantly increased circulating follistatin was found in PCOS patients compared with the controls (WMD = 0.44 ng/ml; 95%CI = 0.30–0.58, P≤0.001) and in non-obese PCOS women compared with non-obese controls and in obese PCOS women vs. obese controls, but, no significant difference in follistatin level was observed in obese PCOS compared with non-obese PCOS women. Significant heterogeneity and publication bias was evident for some analyses. Circulating levels of resistin and follistatin, independent of obesity status, are higher in women with PCOS compared with controls, showing that these adipokines may contribute to the pathology of PCOS.

Metabolic Cytokines at Fasting and During Macronutrient Challenges: Influence of Obesity, Female Androgen Excess and Sex

Scope: Cytokines have pleiotropic functions within the organism and their levels may be influenced by obesity, visceral adiposity and sex hormones. Diet composition may also affect their systemic concentrations during fasting and in the postprandial period. Hence, we studied the influence of sex steroids and obesity on the circulating levels of a panel of metabolic cytokines in the fasting state and after single macronutrient challenges. Methods: On alternate days we submitted 17 women with polycystic ovary syndrome (PCOS) (9 non-obese, 8 obese), 17 non-hyperandrogenic control women (9 non-obese, 8 obese) and 19 control men (10 non-obese, 9 obese) to isocaloric oral glucose, lipid and protein loads. Serum levels of omentin-1, vaspin, lipocalin-2, adipsin, PAI-1, chemerin, FGF-21 and FGF-23 were determined by Luminex multiplex technology. Results: During fasting, obese patients presented higher levels of PAI-1, chemerin and adipsin but decreased FGF-23 and omentin-1 compared with non-obese subjects. Vaspin showed sexual dimorphism with lower levels in men than women with PCOS and female controls. Following macronutrient ingestion, most metabolic cytokines presented a similar physiological response consisting of a decrease in circulating concentrations, which was inversely associated with the fasting levels of these molecules. Protein intake caused the major postprandial decrease whereas glucose did not significantly reduce PAI-1, FGF-23 and vaspin, and even increased FGF-21. Regardless of the macronutrient administered, vaspin levels showed a larger reduction in non-obese individuals while the decrease in PAI-1 was particularly noticeable in the obese subgroup. The postprandial reductions of omentin-1 and FGF-23 after glucose and protein loads were influenced by obesity. No major differences were found between patients with PCOS and male and female controls. Conclusions: Obesity, but not PCOS or sex, markedly influences metabolic cytokine levels at fasting and after macronutrient ingestion. The observed postprandial decrease in their circulating concentrations might represent a physiological compensatory mechanism against food-induced inflammation and oxidative stress. This mechanism is altered by obesity and is differently modulated by macronutrients, suggesting a larger contribution of glucose to stressful postprandial responses.

Polycystic ovarian syndrome (PCOS): Long-term metabolic consequences

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women during their reproductive ages, associated with a plethora of cardiometabolic consequences, with obesity, insulin resistance and hyperandrogenemia playing a major role in the degree of such manifestations. These consequences include increased risk of glucose intolerance and diabetes mellitus (both type 2 and gestational), atherogenic dyslipidemia, systemic inflammation, non-alcoholic fatty liver disease, hypertension and coagulation disorders. Whether this cluster of metabolic abnormalities is also translated in increased cardiovascular disease (CVD) morbidity and mortality in later life, remains to be established. Data so far based on markers of subclinical atherosclerosis as well as retrospective and prospective cohort studies indicate a possible increased CVD risk, mainly for coronary heart disease. Future studies are needed to further elucidate this issue.

Population-based serum omentin-1 levels: paradoxical association with cardiometabolic disorders primarily in men

AIM

The conflicting relationships of serum omentin with inflammation markers and cardiometabolic disorders were investigated. Results & methods: Unselected 864 population-based middle-aged adults were cross-sectionally studied by sex-specific omentin tertiles. Men in the lowest omentin tertile (T1) had lower systolic blood pressure, HbA1c and glucose values and tended in T3 to higher lipoprotein(a) levels. Logistic regression analysis, adjusted for four covariates, revealed significant independent associations with the presence of hypertension and diabetes only in men. Sex- and age-adjusted odds ratio in gender combined for T2 & T3 versus T1 was 1.34 (95% CI: 1.00-1.79) for metabolic syndrome.

DISCUSSION & CONCLUSION

The elicited adverse relationships of omentin-1 support the notion of oxidative stress-induced proinflammatory conversion of omentin, rendering loss of anti-inflammatory properties.

Omentin-A Novel Adipokine in Respiratory Diseases

Adipokines, secreted by the adipose tissue, are extensively involved in the regulation and maintenance of various physiological and pathological processes, including insulin sensitivity, energy expenditure, glucose and lipid metabolism, inflammatory activity, neuroendocrine activity, immunity, cancer, homeostasis, angiogenesis, cardiovascular function, breeding and bone metabolism, and all functions of the endocrine-reproductive system axis. Omentin is a recently identified adipokine, which has become a research hotspot due to its pleiotropic effects on various diseases. However, the specific receptor for omentin has not been identified so far. In this study, we report that omentin levels fluctuate in various diseases. In addition, we have focused on the pleiotropic roles of omentin in pulmonary diseases, as it may act as a biomarker for malignant pleural mesothelioma (MPM) and is related to disease severity. Omentin may play significant roles in other pulmonary diseases, such as asthma, obstructive sleep apnea syndrome (OSAS), pulmonary arterial hypertension (PAH), acute respiratory distress syndrome (ARDS), and chronic obstructive pulmonary disease (COPD). This review summarizes the advances in current knowledge and future trends, which may provide a concise and general view on omentin and its effects on pulmonary biology.