Serum levels of the adipokine lipocalin-2 are increased in preeclampsia

Overview of the expression patterns and roles of Lipocalin 2 in the reproductive system

The 25 kDa-sized protein Lipocalin 2 (LCN2) was originally isolated from human neutrophil granulocytes more than 30 years ago. LCN2 is an emerging player in innate immune defense, as it reduces bacterial growth due to its ability to sequester iron-containing bacterial siderophores. On the other hand, LCN2 also serves as a transporter for various hydrophobic substances due to its β-barrel shaped structure. Over the years, LCN2 has been detected in many other cell types including epithelial cells, astrocytes, and hepatocytes. Studies have clearly shown that aberrant expression of LCN2 is associated with a variety of disorders and malignancies, including several diseases of the reproductive system. Furthermore, LCN2 was proposed as a non-invasive prognostic and/or diagnostic biomarker in this context. Although several studies have shed light on the role of LCN2 in various disorders of the female and male reproductive systems, including tumorigenesis, a comprehensive understanding of the physiological function of LCN2 in the reproductive tract is still lacking. However, there is evidence that LCN2 is directly related to fertility, as global depletion of Lcn2 in mice has a negative effect on their pregnancy rate. Since LCN2 expression can be regulated by steroid hormones, it is not surprising that its expression fluctuates greatly during remodeling processes in the female reproductive tract, especially in the uterus. Well-founded details about the expression and regulation of LCN2 in a healthy reproductive state and also about possible changes during reproductive aging could contribute to a better understanding of LCN2 as a target in various diseases. Therefore, the present review summarizes current knowledge about LCN2 in the reproductive system, including studies in rodents and humans, and discusses changes in LCN2 expression during pathological events. The limited data suggest that LCN2 is expressed and regulated differently in healthy male and female reproductive organs.

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.

Neutrophil Gelatinase-Associated Lipocalin and Hypertensive Disorders of Pregnancy: A Cohort Study in Twin Pregnancies

Hypertensive disorders complicate more than 10% of twin pregnancies. Several studies showed increased neutrophil gelatinase-associated lipocalin (NGAL) values in women with singleton pregnancies and preeclampsia. This study aimed to assess NGAL values in twin pregnancies complicated by hypertensive disorders. We conducted a study of 242 consecutive twin pregnancies at the Medical University of Vienna. Serum NGAL was evaluated twice during pregnancy and once in the postpartum period. Furthermore, serum NGAL values were compared between women who developed hypertensive disorders and those who had normal blood pressure. In all twin pregnancies, mean NGAL values increased significantly from the first to the second visit (p = 0.004) and, further, after delivery (p < 0.001). NGAL was significantly higher in pregnancies that developed pregnancy hypertension or preeclampsia when compared to the control group at the first visit (109.2 ± 48.9 ng/mL vs. 91.9 ± 29.4 ng/mL, p = 0.04, respectively). The predictive power of first visit NGAL values for development of pregnancy hypertension or preeclampsia was evaluated. When using a cut-off value of 115 ng/mL, we obtained a sensitivity of 45% with a specificity of 77%. We conclude that women with twin pregnancies who develop hypertensive disorders of pregnancy showed increased NGAL values at 11−16 weeks.

Postpartum human breast milk levels of neutrophil gelatinase-associated lipocalin (NGAL) and matrix metalloproteinase-9 (MMP-9)/NGAL complex in normal and pregnancies complicated with insulin-dependent gestational diabetes mellitus. A prospective pilot case-control study

Neutrophil gelatinase-associated lipocalin (NGAL) and its complex with matrix metalloproteinase-9 (MMP-9) are present in a variety of human tissues and extracellular fluids. The aim of this pilot prospective case-control study was to detect NGAL and MMP-9/NGAL complex in human breast milk postpartum in women with normal and pregnancies that developed insulin-depended gestational diabetes mellitus (iGDM). We detected both biomarkers in human breast milk and concentrations were determined at the first day of colostrum secretion and two days after, in 22 normal pregnancies and 13 pregnancies with iGDM. Mean NGAL concentration decreased significantly from the first to the second sample, in both groups. Mean MMP-9/NGAL complex concentration decreased also significantly from the first to the second sample in normal pregnancies. Mean complex concentration was significantly higher in diabetic pregnancies compared to normal ones in the second sample.IMPACT STATEMENTWhat is already known on this subject? There is limited information on the presence of Neutrophil gelatinase-associated lipocalin (NGAL) in human milk and its physiological role.What the results of this study add? It is the first time that MMP-9/NGAL complex is detected in human milk in both normal and pregnancies complicated with insulin-depended gestational diabetes mellitus (iGDM). We confirm the presence of NGAL in colostrum of normal pregnancies and for the first time we detected NGAL in milk of pregnancies with iGDM. Concentrations of NGAL and MMP-9/NGAL complex tend to lessen postpartum in both groups. Pregnancies with iGDM compared to normal ones showed significantly higher concentration of MMP-9/NGAL complex two days after the beginning of lactation.What the implications are of these findings for clinical practice and/or further research? Further studies are necessary to determine the levels of NGAL and MMP-9/NGAL complex in human milk postpartum in normal and pathological pregnancies. Taking into consideration the well-established NGAL's ability to act as a bacteriostatic agent and its mucosal healing activity in gastrointestinal track, early breastfeeding of neonates is a logical recommendation. Finally, new studies on the actual physiological role of milk NGAL in neonates are necessary.

Preeclampsia biomarkers: An assessment of maternal cardiometabolic health

Preeclampsia is a serious pregnancy condition defined as new-onset hypertension and proteinuria, commonly characterized as either early, 'placental', or late onset, 'maternal', using a cut-off of 34 weeks gestation. However, it may be more useful to differentiate between the vascular remodelling and placental invasion vs. inflammation and metabolic pathophysiology that underlie these forms of preeclampsia. Due to rising rates of obesity, the late-onset, maternal form is increasingly occurring earlier in pregnancy. Predictive tests for preeclampsia typically include biophysical markers such as maternal body mass index and mean arterial pressure, indicating the importance of cardiovascular and metabolic health in its pathophysiology. In contrast, the placental, inflammatory, endothelial and/or metabolic biomarkers used in these tests are generally thought to indicate an abnormal response to placentation and predict the disease. However, many of these non-placental biomarkers are known to predict impaired metabolic health in non-pregnant subjects with obesity (metabolically unhealthy obesity) and coronary artery disease or stroke in people at risk for cardiovascular events. Similarities between the performance of these markers in the prediction of cardiovascular and metabolic health outside of pregnancy suggests that they may be more indicative of maternal health than predictive for preeclampsia. This paper reviews the biophysical and biochemical markers in preeclampsia prediction and compares their performance to tests assessing metabolic health and risk of cardiovascular disease, particularly in the obese population.

Shared biomarkers between female diastolic heart failure and pre-eclampsia: a systematic review and meta-analysis

Evidence accumulates for associations between hypertensive pregnancy disorders and increased cardiovascular risk later. The main goal of this study was to explore shared biomarkers representing common pathogenic pathways between heart failure with preserved ejection fraction (HFpEF) and pre‐eclampsia where these biomarkers might be potentially eligible for cardiovascular risk stratification in women after hypertensive pregnancy disorders. We sought for blood markers in women with diastolic dysfunction in a first literature search, and through a second search, we investigated whether these same biochemical markers were present in pre‐eclampsia.This systematic review and meta‐analysis presents two subsequent systematic searches in PubMed and EMBASE. Search I yielded 3014 studies on biomarkers discriminating women with HFpEF from female controls, of which 13 studies on 11 biochemical markers were included. Cases had HFpEF, and controls had no heart failure. The second search was for studies discriminating women with pre‐eclampsia from women with non‐hypertensive pregnancies with at least one of the biomarkers found in Search I. Search II yielded 1869 studies, of which 51 studies on seven biomarkers were included in meta‐analyses and 79 studies on 12 biomarkers in systematic review.Eleven biological markers differentiated women with diastolic dysfunction from controls, of which the following 10 markers differentiated women with pre‐eclampsia from controls as well: C‐reactive protein, HDL, insulin, fatty acid‐binding protein 4, brain natriuretic peptide, N terminal pro brain natriuretic peptide, adrenomedullin, mid‐region pro adrenomedullin, cardiac troponin I, and cancer antigen 125.Our study supports the hypothesis that HFpEF in women shares a common pathogenic background with pre‐eclampsia. The biomarkers representing inflammatory state, disturbances in myocardial function/structure, and unfavourable lipid metabolism may possibly be eligible for future prognostic tools.

Diagnostic and predictive biomarkers for pre-eclampsia in patients with established hypertension and chronic kidney disease

Women with chronic kidney disease (CKD) and chronic hypertension (CHT) frequently develop superimposed pre-eclampsia, but distinction from pre-existing disease is challenging. Plasma placental growth factor (PlGF), B-type natriuretic peptide (BNP), neutrophil gelatinase-associated lipocalin (NGAL), and serum relaxin concentrations were quantified in a longitudinal prospective cohort of 121 women with CKD: 44 with chronic hypertension, and 79 healthy controls. Biomarker concentrations were compared with 32 women with pre-eclampsia without pre-existing disease. Test performance was evaluated for diagnosis of superimposed pre-eclampsia requiring delivery within 14 days of sampling. PlGF was evaluated as a promising marker in a validation cohort of women with suspected pre-eclampsia (29 with CKD; 94 with chronic hypertension; 29 with superimposed pre-eclampsia requiring delivery within 14 days) and compared with women without pre-existing disease (290 with no pre-eclampsia and 176 with pre-eclampsia requiring delivery within 14 days). From 20 and up to 42 weeks of gestation, lower maternal PlGF concentrations had high diagnostic accuracy for superimposed pre-eclampsia requiring delivery within 14 days (receiver operator characteristic 0.85) and confirmed in the validation cohort. The other plasma and serum biomarkers were not discriminatory. Thus, plasma PlGF concentrations could potentially help guide clinical decision making regarding admission and delivery for superimposed pre-eclampsia.

Adipokines in reproductive function: a link between obesity and polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy associated with infertility and metabolic disorder in women of reproductive age. Dysfunction of adipose tissue has been implicated in the pathophysiology of PCOS. Increasing evidence shows that the dysregulated expression of adipokines, the secreted products of adipose tissue, plays an important role in the pathology of PCOS. Here, we review the role of several identified adipokines that may act as a link between obesity and PCOS. PCOS also reciprocally influences the profile of adipokines. Insight into the underlying mechanisms will help better understand the pathology of PCOS and identify new therapeutic targets of this syndrome.

Serum levels of the adipokine fibroblast growth factor-21 are increased in preeclampsia

BACKGROUND

Preeclampsia (PE) is a serious cardiovascular complication in pregnancy, which is associated with an increased future metabolic and cardiovascular risk for mother and newborn. Fibroblast growth factor (FGF)-21 was recently introduced as a novel adipokine improving glucose metabolism in vitro and in vivo.

MATERIAL AND METHODS

We investigated serum FGF-21 levels in patients with PE (n=51) as compared to healthy, age-matched controls (n=51) during and 6 months after pregnancy. Furthermore, association of FGF-21 with markers of renal function, glucose and lipid metabolism, as well as inflammation, was elucidated in all individuals.

RESULTS

Median maternal FGF-21 serum concentrations adjusted for body mass index and gestational age at blood sampling were significantly, almost 3-fold increased in PE patients (309.6 ng/l) as compared to healthy, age-matched pregnant women (105.2 ng/l) (p<0.001). Furthermore, FGF-21 concentrations were independently and positively correlated with triglycerides whereas an independent and negative association was observed with glomerular filtration rate and low density lipoprotein (LDL) cholesterol in pregnant women. Moreover, FGF-21 serum levels significantly decreased in former PE patients 6 months after pregnancy approaching levels found in control patients.

CONCLUSIONS

Maternal FGF-21 serum concentrations are significantly increased in PE during pregnancy. Furthermore, triglycerides, glomerular filtration rate, and LDL cholesterol are independent predictors of circulating FGF-21 in pregnant women.

Serum levels of the adipokine zinc-α2-glycoprotein are increased in preeclampsia

BACKGROUND

Preeclampsia (PE) is associated with facets of the metabolic syndrome and an increased future metabolic and cardiovascular risk for mother and newborn. Recently, zinc-α2-glycoprotein (ZAG) has been proposed as a new adipokine involved in the pathogenesis of obesity.

AIM

In the current study, we investigated ZAG serum levels in PE patients as compared to healthy gestational age-matched controls.

SUBJECTS AND METHODS

We quantified serum concentrations of ZAG in patients with PE (no.=37) as compared to healthy gestational age-matched controls (no.=37) by enzyme-linked immunosorbent assay. Furthermore, association of this adipokine with renal function, glucose and lipid metabolism, as well as inflammation was studied.

RESULTS

Median serum ZAG levels were 1.4-fold higher in PE patients (58.8 mg/l) as compared to controls (41.9 mg/l) (p<0.01). Furthermore, circulating ZAG was positively correlated to systolic and diastolic blood pressure, creatinine, triglycerides, and leptin in univariate analyses. In multiple regression analysis, creatinine remained independently associated with ZAG.

CONCLUSIONS

We demonstrate that maternal ZAG serum concentrations are significantly increased in PE. Furthermore, renal function is an independent predictor of circulating ZAG.

Small lipid-binding proteins in regulating endothelial and vascular functions: focusing on adipocyte fatty acid binding protein and lipocalin-2

Dysregulated production of adipokines from adipose tissue plays a critical role in the development of obesity-associated cardiovascular abnormalities. A group of adipokines, including adipocyte fatty acid binding protein (A-FABP) and lipocalin-2, possess specific lipid-binding activity and are up-regulated in obese human subjects and animal models. They act as lipid chaperones to promote lipotoxicity in endothelial cells and cause endothelial dysfunction under obese conditions. However, different small lipid-binding proteins modulate the development of vascular complications in distinctive manners, which are partly attributed to their specialized structural features and functionalities. By focusing on A-FABP and lipocalin-2, this review summarizes recent advances demonstrating the causative roles of these newly identified adipose tissue-derived lipid chaperones in obesity-related endothelial dysfunction and cardiovascular complications. The specific lipid-signalling mechanisms mediated by these two proteins are highlighted to support their specialized functions. In summary, A-FABP and lipocalin-2 represent potential therapeutic targets to design drugs for preventing vascular diseases associated with obesity.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Serum levels of the adipokine chemerin are increased in preeclampsia during and 6 months after pregnancy

Preeclampsia is a serious cardiovascular complication in pregnancy which is associated with an increased future metabolic and cardiovascular risk for mother and newborn. Recently, chemerin was introduced as a novel adipokine inducing insulin resistance in vitro and in vivo. In the current study, we investigated serum concentrations of chemerin by ELISA in control and preeclampsia patients during pregnancy (

CONTROL

n=37, preeclampsia: n=37) and 6 months after delivery (

CONTROL

n=35, preeclampsia: n=36). Furthermore, the association between chemerin and markers of renal function, glucose and lipid metabolism, as well as inflammation was studied in pregnant patients. Median maternal chemerin concentrations were significantly elevated in preeclampsia patients (249.5 [range: 123.1-366.9] μg/l) as compared to controls (204.8 [138.5-280.8] μg/l) (p<0.001). Furthermore, chemerin serum levels positively correlated with blood pressure, creatinine, free fatty acids, cholesterol, triglycerides (TG), leptin, adiponectin, and C-reactive protein in univariate analyses. In multivariate analyses, TG and leptin remained independently associated with circulating chemerin. Interestingly, median chemerin concentrations 6 months after delivery remained significantly higher in former preeclampsia patients (196.0 [119.8-368.7] μg/l) as compared to controls (152.2 [102.8-216.4] μg/l). Taken together, maternal chemerin serum concentrations are significantly increased in preeclampsia during and after pregnancy. Furthermore, TG and leptin are independent predictors of circulating chemerin during pregnancy.