Comparison of Serum Levels and the Placental Expression of Resistin Between Patients with Preeclampsia and Normal Pregnant Women

Adipokines in pregnancy

Reproductive success consists of a sequential events chronology, starting with the ovum fertilization, implantation of the embryo, placentation, and cellular processes like proliferation, apoptosis, angiogenesis, endocrinology, or metabolic changes, which taken together finally conduct the birth of healthy offspring. Currently, many factors are known that affect the regulation and proper maintenance of pregnancy in humans, domestic animals, or rodents. Among the determinants of reproductive success should be distinguished: the maternal microenvironment, genes, and proteins as well as numerous pregnancy hormones that regulate the most important processes and ensure organism homeostasis. It is well known that white adipose tissue, as the largest endocrine gland in our body, participates in the synthesis and secretion of numerous hormones belonging to the adipokine family, which also may regulate the course of pregnancy. Unfortunately, overweight and obesity lead to the expansion of adipose tissue in the body, and its excess in both women and animals contributes to changes in the synthesis and release of adipokines, which in turn translates into dramatic changes during pregnancy, including those taking place in the organ that is crucial for the proper progress of pregnancy, i.e. the placenta. In this chapter, we are summarizing the current knowledge about levels of adipokines and their role in the placenta, taking into account the physiological and pathological conditions of pregnancy, e.g. gestational diabetes mellitus, preeclampsia, or intrauterine growth restriction in humans, domestic animals, and rodents.

Association Between Circulating Resistin Level and Preeclampsia: A Meta-Analysis

Resistin, a diminutive secretory adipokine, has been linked to obesity and its related ailments. A growing body of evidence suggests that resistin may also be related to the pathogenesis preeclampsia. However, results of previous studies were not consistent. We performed a systematic review and meta-analysis to evaluate the level of circulating resistin in women with PE. A systematic search of Medline, Web of Science, and Embase databases from inception to April 28, 2023, was conducted to identify studies that compared blood resistin levels in pregnant women with and without PE. A random-effects model was utilized to pool the results, accounting for heterogeneity. The present study analyzed eighteen datasets from sixteen observational studies. The results of the meta-analysis demonstrated a statistically significant increase in blood resistin levels among women with PE compared to the control group. (standardized mean difference=0.35, 95% confidence interval: 0.16 to 0.54, p<0.001; I2=74%). The findings of the subgroup analysis indicate that various study characteristics, including study design, timing, and methods for measuring resistin, matching of body mass index between cases and controls, and study quality scores did not exert a significant impact on the outcomes. Nonetheless, it is noteworthy that the diagnostic criteria for PE employed in the studies included in the analysis may have influenced the results (p for subgroup difference=0.001). Women with preeclampsia exhibit a greater concentration of resistin in circulation when compared to healthy pregnant controls.

Adipokines in Pregnancy: A Systematic Review of Clinical Data

Adipokines are signaling proteins involved in metabolic, endocrinological, vascular and immunogenic processes. Associations of various adipokines with not only insulin resistance but also with increased insulin sensitivity, increased systolic blood pressure, and atherosclerosis highlight the significance of adipokines in several components of metabolic syndrome and metabolic diseases in general. As pregnancy presents a unique metabolic state, the role of adipokines in pregnancy, and even in various pregnancy complications, appears to be key to elucidating these metabolic processes. Many studies in recent years have attempted to clarify the role of adipokines in pregnancy and gestational pathologies. In this review, we aim to investigate the changes in maternal adipokine levels in physiological gestation, as well as the association of adipokines with pregnancy pathologies, such as gestational diabetes mellitus (GDM) and preeclampsia (PE). Furthermore, we will analyze the association of adipokines in both maternal serum and cord blood with parameters of intrauterine growth and various pregnancy outcomes.

Circulating adipokine levels and preeclampsia: A bidirectional Mendelian randomization study

Background: Several observational studies have demonstrated that significantly rising circulating adipokine levels are pervasive in preeclampsia or eclampsia disorder (or preeclampsia toxemia (PET)). However, it remains unclear whether this relationship is causal. In this study, we sought to elucidate the causal effects of circulating adipokine levels on PET.

Methods: Summary-level data and independent genetic variants strongly associated with common adipokine molecule (adiponectin, leptin, resistin, sOB-R, and PAI-1) levels were drawn from public genome-wide association study (GWASs). Additionally, the corresponding effects between instrumental variables and PET outcomes were acquired from the FinnGen consortium, including 4,743 cases and 136,325 controls of European ancestry. Subsequently, an inverse-variance weighted (IVW) approach was applied for the principal two-sample Mendelian randomization (MR) and multivariable MR (MVMR) analyses. Various complementary sensitivity analyses were then carried out to determine the robustness of our models.

Results: The results of the IVW method did not reveal any causal relationship shared across genetically predisposed adipokine levels and PET risk (for adiponectin, OR = 0.86, 95% CI: 0.65–1.13, p = 0.274). Additionally, no significant associations were identified after taking into account five circulating adipokines in MVMR research. Complementary sensitivity analysis also supported no significant associations between them. In the reverse MR analysis, genetically predicted PET risk showed a suggestive association with elevating PAI-1 levels by the IVW method (Beta = 0.120, 95% CI: 0.014, 0.227, p = 0.026). Furthermore, there were no strong correlations between genetic liability to PET and other adipokine levels (p > 0.05).

Conclusion: Our MR study did not provide robust evidence supporting the causal role of common circulating adipokine levels in PET, whereas genetically predicted PET may instrumentally affect PAI-1 levels. These findings suggest that PAI-1 may be a useful biomarker for monitoring the diagnosis or therapy of PET rather than a therapeutic target for PET.

The role of resistin in early preeclampsia prediction

Resistin might be involved with general inflammation and endothelial dysfunction observed in preeclampsia. We aimed to investigate longitudinal changes in resistin concentrations during high-risk pregnancies and evaluate their significance in preeclampsia development. Ninety-one patients were recruited at 11-14 weeks of gestation. They were followed towards the end of each trimester and before their deliveries. Of the 91 pregnant women, 21 developed preeclampsia, while 70 women did not develop preeclampsia despite being at risk. Compared to the 1^st trimester, resistin concentration significantly increased during the 2^nd trimester (p<.001). When women were divided into groups of those who developed preeclampsia and those who did not develop preeclampsia, we noticed a significant difference only in women who did not develop preeclampsia (p<.001). Moreover, resistin concentration in the 1^st trimester was statistically higher in women who developed preeclampsia when compared to those who did not develop preeclampsia (p<.001). The analysis of the Receiver Operating Characteristics (ROC) curves indicated that inclusion of triglycerides (TG), high-sensitivity C-reactive protein (CRP), and resistin (AUC = 0.870) improved diagnostic accuracy of the basic model including demographic and clinical parameters (AUC = 0.777) for preeclampsia prediction (p<.05). If the concentration of resistin is high in the 1^st trimester, such pregnancy at risk is likely to develop preeclampsia as a complication, indicating that resistin concentration in the 1^st trimester might contribute to existing predictive and prognostic models for preeclampsia. A multi-marker model, possibly including also resistin and other clinical, metabolic, and inflammatory parameters, seems to be the best approach in late-onset preeclampsia prediction.

Antepartum and postpartum changes in adipokines, endothelial dysfunction, inflammatory markers and other biochemical parameters in preeclamptic women: A prospective observational cohort study

This study aimed at evaluating the role played by insulin resistance, lipid metabolism disorder, oxidative stress, resistin, vaspin, Interleukin-18 and asymmetric dimethyl arginine as a marker for endothelial dysfunction in the pathogenesis of preeclampsia. This prospective observational cohort study involved 60 women who were classified into: 20 non-pregnant women (group 1 or control group), 20 normally pregnant women (group 2) and 20 preeclamptic women (group 3) at their third trimester. The pregnant women were assessed at their third trimester and further re-evaluated four weeks after delivery. The assessment included demography, assessment of proteinuria and urinary protein to creatinine ratio, blood pressure measurement and assessment of fasting blood glucose, fasting insulin level, lipid panel and the circulating levels of malondialdehyde, resistin, vaspin, interleukin-18 and asymmetric dimethyl arginine. Preeclamptic women showed more atherogenic lipid profile, significantly higher Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and significantly elevated levels of malondialdehyde, resistin, vaspin and interleukin-18 than the other study groups. Serum asymmetric dimethyl arginine concentration showed non-significant difference among the three study groups. The levels of resistin and vaspin showed significant decrease four weeks postpartum in preeclamptic group. We concluded that, preeclampsia was associated with insulin resistance, dyslipidemia, oxidative stress, inflammation and significant changes in adipokines; resistin and vaspin. Furthermore, the significant increase in the serum levels of resistin and vaspin at the third trimester and their significant decline four weeks postpartum in preeclamptic group focus the attention on the role played by these adipokines in the pathogenesis of preeclampsia.

The Role of the Adipokines in the Most Common Gestational Complications

Adipocytokines are hormonally active molecules that are believed to play a key role in the regulation of crucial biological processes in the human body. Numerous experimental studies established significant alterations in the adipokine secretion patterns throughout pregnancy. The exact etiology of various gestational complications, such as gestational diabetes, preeclampsia, and fetal growth abnormalities, needs to be fully elucidated. The discovery of adipokines raised questions about their potential contribution to the molecular pathophysiology of those diseases. Multiple studies analyzed their local mRNA expression and circulating protein levels. However, most studies report conflicting results. Several adipokines such as leptin, resistin, irisin, apelin, chemerin, and omentin were proposed as potential novel early markers of heterogeneous gestational complications. The inclusion of the adipokines in the standard predictive multifactorial models could improve their prognostic values. Nonetheless, their independent diagnostic value is mostly insufficient to be implemented into standard clinical practice. Routine assessments of adipokine levels during pregnancy are not recommended in the management of both normal and complicated pregnancies. Based on the animal models (e.g., apelin and its receptors in the rodent preeclampsia models), future implementation of adipokines and their receptors as new therapeutic targets appears promising but requires further validation in humans.

The role of serum adipokine levels in preeclampsia: A systematic review

BACKGROUND

Preeclampsia represents a major pregnancy complication, associated with high rates of perinatal morbidity. The aim of this systematic review is to accumulate current literature evidence in order to examine the pattern of serum adipokine levels among preeclamptic women and asses their potential efficacy in the prediction of the disease.

METHODS

Medline, Scopus, CENTRAL, Clinicaltrials.gov and Google Scholar databases were systematically searched from inception. All observational studies reporting serum adipokine values among preeclamptic and healthy pregnant women were held eligible.

RESULTS

A total of 163 studies were included, comprising 23,482 women. Leptin was evaluated in 91 studies and its values were found to be significantly elevated in preeclamptic women during all pregnancy trimester, independently of disease onset and severity. Preeclampsia was also associated with increased serum fatty acid binding protein-4 and chemerin levels, when measured both during the 1st and 3rd trimester. Data concerning the rest adipokines were either conflicting or limited to reach firm conclusions. Quality of evidence was evaluated to be high for leptin, moderate for serum fatty acid binding protein-4 and chemerin and low for the other adipokines.

CONCLUSIONS

The existing evidence suggests that preeclampsia is linked to increased levels of leptin, chemerin and fatty acid binding protein-4 in all pregnancy trimesters and forms of the disease. Inconsistent data currently exists concerning the role of the other adipokines. Large-scale prospective studies should longitudinally evaluate the serum concentration of novel adipokines and define the optimal threshold and timing of measurement to be widely applied in clinical practice.

Adipokine profiles in preeclampsia

Objectives: Hypertensive disorders of pregnancy (HDP), including preeclampsia (PE), are associated with short- and long-term maternal health complications, and obesity is a leading attributable risk factor for HDP. Yet, most women identified as obese [by body mass index (BMI) ≥ 30 kg/m²] do not develop HDP, indicating limited predictability of BMI alone. In nonpregnant populations, increased visceral fat mass (VFM) is an obesity-associated phenotype increasing the risk of developing hypertension. We sought to assess whether, in pregnancy, obese women with PE would have higher circulating levels of adipokines preferential to VFM compared to obese women without PE.Study Design: We performed a case-control study of women with and without PE, including obese (n = 65; BMI ≥ 30 kg/m²) and normal weight (n = 52; BMI 18.4-24.9 kg/m²) women. Plasma concentrations of adipokines preferential to VFM (visfatin, resistin), adipokines reflecting overall adiposity (leptin, adiponectin), and inflammatory cytokines were compared.Results: We found that among obese women, cases had significantly higher levels of VFM-associated adipokines and cytokines compared to controls [visfatin (p < .01, t = -3.8), resistin (p = .002, t = 1.12), IFN gamma (p = .04, t = -2.0), IL-6 (p < .01, t = -2.65), IL1-beta (p < .01, t = -4.1), IL-2 (p < .01, t = -3.9)]. Interestingly, however, obese and normal weight cases had similar VFM-adipokine and cytokine levels [visfatin (p = .34, t = -0.35), resistin (p = .55, t = -0.25)], and inflammatory marker concentrations [IFN gamma (p = .86, t = -0.76), IL-6 (p = .91, t = -0.53), IL-1beta (p = .67, t = 1.18), and IL-2 (p = .45, t = -1.16)]. These data possibly suggest an association between VFM and PE that is present independent of BMI.Conclusion: In summary, we demonstrated that, in normal-weight and obese women, PE was associated with higher concentrations of VFM-preferential adipokines compared to normal-weight and obese controls without PE.

Serum levels of leptin, adiponectin and resistin in relation to clinical characteristics in normal pregnancy and preeclampsia

BACKGROUND

Alterations in serum adipokines in preeclampsia remain vague. We investigated the roles of leptin, adiponectin and resistin and their relationships with clinical characteristics in normotensive and preeclamptic patients.

METHODS

A case-control study was carried out in a cohort of 74 preeclampsia(PE) and 79 healthy pregnant women. Serum levels of leptin, adiponectin and resistin were measured by enzyme-linked immunosorbent assay.

RESULTS

The mean body mass index(BMI), the serum leptin and resistin levels were significantly higher in the PE group than in the control group (p<0.001). The resistin/creatinine ratio was also higher in the PE group than in the control group (p=0.018). No significant difference was observed in the serum adiponectin level between both groups. Serum leptin levels were positively correlated with BMI (r=0.301, p<0.001) and negatively correlated with newborn birth weight (r=-0.435, p<0.001). Serum resistin levels were also negatively correlated with birth weight (r=-0.229, p=0.005) but were unrelated to BMI. Logistic regression showed that BMI≥28 and serum leptin levels were independent factors of PE. Leptin was a potential mediator between BMI and PE (p<0.001), and the mediating effect accounted for 22.54% of the total effect.

CONCLUSIONS

Leptin, resistin, and obesity play important roles in the onset of PE. Leptin and resistin may have some impacts on the fetal growth and development.

The endocrine function of human placenta: an overview

During pregnancy, several tightly coordinated and regulated processes take place to enable proper fetal development and gestational success. The formation and development of the placenta is one of these critical pregnancy events. This organ plays essential roles during gestation, including fetal nourishment, support and protection, gas exchange and production of several hormones and other mediators. Placental hormones are mainly secreted by the syncytiotrophoblast, in a highly and tightly regulated way. These hormones are important for pregnancy establishment and maintenance, exerting autocrine and paracrine effects that regulate decidualization, placental development, angiogenesis, endometrial receptivity, embryo implantation, immunotolerance and fetal development. In addition, because they are released into maternal circulation, the profile of their blood levels throughout pregnancy has been the target of intense research towards finding potential robust and reliable biomarkers to predict and diagnose pregnancy-associated complications. In fact, altered levels of these hormones have been associated with some pathologies, such as chromosomal anomalies or pre-eclampsia. This review proposes to revise and update the main pregnancy-related hormones, addressing their major characteristics, molecular targets, function throughout pregnancy, regulators of their expression and their potential clinical interest.

Adipokines and the female reproductive tract

It is well known that adipose tissue can influence puberty, sexual maturation, and fertility in different species. Adipose tissue secretes molecules called adipokines which most likely have an endocrine effect on reproductive function. It has been revealed over the last few years that adipokines are functionally implicated at all levels of the reproductive axis including the gonad and hypothalamic-pituitary axis. Many studies have shown the presence and the role of the adipokines and their receptors in the female reproductive tract of different species. These adipokines regulate ovarian steroidogenesis, oocyte maturation, and embryo development. They are also present in the uterus and placenta where they could create a favorable environment for embryonic implantation and play a key role in maternal-fetal metabolism communication and gestation. Reproductive functions are strongly dependent on energy balance, and thereby metabolic abnormalities can lead to the development of some pathophysiologies such as polycystic ovary syndrome (PCOS). Adipokines could be a link between reproduction and energy metabolism and could partly explain some infertility related to obesity or PCOS.

Maternal serum resistin at 11 to 13 weeks' gestation in normal and pathological pregnancies

The objective was to examine maternal serum levels of resistin at 11 to 13 weeks' gestation in normal and pathological pregnancies. Serum resistin, pregnancy-associated plasma protein A (PAPP-A), and uterine artery pulsatility index (PI) at 11 to 13 weeks were measured in 480 singleton pregnancies, including 240 with normal outcome, 60 that subsequently developed preeclampsia (PE), 60 that developed gestational diabetes mellitus (GDM), 60 that delivered large for gestational age (LGA) neonates, and 60 that delivered small for gestational age (SGA) neonates. Each value in both the normal and pathological outcome groups was expressed as a multiple of the expected normal median (MoM), and the median MoM values in the outcome groups were compared. In the PE group, compared with the controls, there were an increase in median resistin (1.22 MoM, P = .003) and uterine artery PI (1.25 MoM, P < .0001) and a decrease in serum PAPP-A (0.72, P < .0001). There was no significant association between serum resistin with either uterine artery PI (P = .415) or serum PAPP-A (P = .290). In the SGA, LGA, and GDM groups, serum resistin MoM was not significantly different from that of the controls (P = .415, P = .702, and P = .549, respectively). In pregnancies that develop PE, maternal serum resistin concentration at 11 to 13 weeks is increased in a manner not related to altered placental perfusion or function. In pregnancies complicated by the development of GDM or delivery of SGA or LGA neonates, serum resistin is not significantly altered.

Retinol-binding protein-4 is decreased in patients with preeclampsia in comparison with normal pregnant women

AIMS

The aim of this study was to investigate retinol-binding protein-4 (RBP4) levels in maternal and umbilical cord serum in patients in the third trimester of pregnancy with preeclampsia in comparison to levels in normal pregnant women.

METHODS

The RBP4 levels in maternal and umbilical cord serum were measured and compared by enzyme-linked immunosorbent assay in 16 normal pregnant and 16 patients with preeclampsia.

RESULTS

Both maternal and umbilical cord serum RBP4 levels were significantly decreased in patients with preeclampsia, as compared to normal pregnant women (maternal serum, median 168.0 μg/mL vs. 202.0 μg/mL, P<0.001; umbilical cord serum, median 147.9 μg/mL vs. 193.0 μg/mL, P<0.001). Preeclampsia was independently related to RBP4 levels of maternal and umbilical cord serum.

CONCLUSION

Both maternal and umbilical cord serum RBP4 levels were lower in patients with preeclampsia than in normal pregnant women in the third trimester of pregnancy.