Increased Serum Retinol-Binding Protein 4 Concentrations in Women With Gestational Diabetes Mellitus

Retinol-binding protein 4 (RBP4) circulating levels and gestational diabetes mellitus: a systematic review and meta-analysis

Background

Gestational diabetes mellitus (GDM) is a prevalent condition where diabetes is diagnosed during pregnancy, affecting both maternal and fetal outcomes. Retinol-binding protein 4 (RBP4) is a circulating adipokine which belongs to the lipocalin family and acts as a specific carrier protein that delivers retinol (vitamin A) from the liver to the peripheral tissues. Growing data indicate that circulating RBP4 levels may positively correlate with GDM. Thus, this systematic review and meta-analysis aimed to investigate the potential relationship between circulating RBP4 levels and GDM when measured at various stages of pregnancy.

Methods

MEDLINE, CINAHL, EMCARE, EMBASE, Scopus, and Web of Science databases were searched to identify studies comparing pregnant women with and without GDM, whose circulating RBP4 levels were measured in at least one pregnancy trimester. Findings were reported using standardized mean difference (SMD) and random-effects models were used to account for variability among studies. Furthermore, the risk of bias was assessed using the RoBANS tool.

Results

Out of the 34 studies identified, 32 were included in the meta-analysis (seven with circulating RBP4 levels measured in the first trimester, 19 at 24-28 weeks, and 14 at >28 weeks of pregnancy). RBP4 levels were statistically higher in the GDM group than in controls when measured during all these pregnancy stages, with the noted RBP4 SMD being 0.322 in the first trimester (95% CI: 0.126-0.517; p < 0.001; 946 GDM cases vs. 1701 non-GDM controls); 0.628 at 24-28 weeks of gestation (95% CI: 0.290-0.966; p < 0.001; 1776 GDM cases vs. 1942 controls); and 0.875 at >28 weeks of gestation (95% CI: 0.252-1.498; p = 0.006; 870 GDM cases vs. 1942 non-GDM controls). Significant study heterogeneity was noted for all three pregnancy timepoints.

Conclusion

The present findings indicate consistently higher circulating RBP4 levels in GDM cases compared to non-GDM controls, suggesting the potential relevance of RBP4 as a biomarker for GDM. However, the documented substantial study heterogeneity, alongside imprecision in effect estimates, underscores the need for further research and standardization of measurement methods to elucidate whether RBP4 can be utilized in clinical practice as a potential GDM biomarker.

Systematic review registration

PROSPERO (CRD42022340097: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022340097).

Proteins and metabolites fingerprints of gestational diabetes mellitus forming protein-metabolite interactomes are its potential biomarkers

Gestational diabetes mellitus (GDM) is a consequence of glucose intolerance with an inadequate production of insulin that happens during pregnancy and leads to adverse health consequences for both mother and fetus. GDM patients are at higher risk for preeclampsia, and developing diabetes mellitus type 2 in later life, while the child born to GDM mothers are more prone to macrosomia, and hypoglycemia. The universally accepted diagnostic criteria for GDM are lacking, therefore there is a need for a diagnosis of GDM that can identify GDM at its early stage (first trimester). We have reviewed the literature on proteins and metabolites fingerprints of GDM. Further, we have performed protein-protein, metabolite-metabolite, and protein-metabolite interaction network studies on GDM proteins and metabolites fingerprints. Notably, some proteins and metabolites fingerprints are forming strong interaction networks at high confidence scores. Therefore, we have suggested that those proteins and metabolites that are forming protein-metabolite interactomes are the potential biomarkers of GDM. The protein-metabolite biomarkers interactome may help in a deep understanding of the prognosis, pathogenesis of GDM, and also detection of GDM. The protein-metabolites interactome may be further applied in planning future therapeutic strategies to promote long-term health benefits in GDM mothers and their children.

Association between Retinol-Binding Protein 4 Levels and Preeclampsia: A Systematic Review and Meta-Analysis

Retinol-binding protein 4 (RBP4) is claimed to be associated with the development of preeclampsia, yet the reports are inconclusive. This systematic review and meta-analysis aimed to assess the association between RBP4 levels and preeclampsia. The PubMed, Google Scholar and ScienceDirect databases were searched for studies that investigated RBP4 levels in preeclampsia patients and compared them with normal controls. The meta-analysis was conducted by calculating the standardized mean difference (SMD) of RBP4 between cases and controls. The meta package with the R software was used to perform all statistical analysis. A total of 13 studies, comprising 569 cases and 1411 controls, met the inclusion criteria and were thus included in the meta-analysis. According to the random effect model, the SMD of RBP4 was significantly higher in women with preeclampsia compared with normal controls [SMD of RBP4: 0.55 ng/mL; 95% CI (0.06; 1.05); p = 0.028; I² = 89%]. Likewise, the stratified meta-analysis showed the same pattern in the studies which measured RBP4 levels in the third trimester, as well as in the studies that investigated severe preeclampsia. Meta-regression did not identify any factor that significantly affected the overall estimate. There was no evidence of reporting bias (Egger's test; t = 0.43; p = 0.587). This meta-analysis with high heterogeneity showed that higher levels of RBP4 were associated with preeclampsia risk. More longitudinal studies spanning the three trimester periods are needed to clarify the association of RBP4 and its dynamics in preeclampsia cases throughout pregnancy.

Relationship of ANGPTL6 With Neonatal Glucose Homeostasis and Fat Mass Is Disrupted in Gestational Diabetic Pregnancies

CONTEXT

Angiopoietin-like protein 6 (ANGPTL6) is a hepatokine, which, in animal studies, improves insulin sensitivity and increases energy expenditure to counteract insulin resistance.

OBJECTIVE

Evaluate in a human population, the role of serum ANGPTL6 in gestational diabetes mellitus (GDM) or its presence in fetal circulation.

RESEARCH DESIGN AND METHODS

A total of 190 women (115 controls and 75 GDM) and their offspring were studied. Insulin, glucose, ANGPTL6, retinol binding protein 4 (RBP4), and retinol, as well as leptin and adiponectin, were determined in maternal serum obtained at term and from umbilical artery blood at delivery.

RESULTS

At term, pregnant women with GDM showed higher serum concentrations of ANGPTL6, insulin, homeostatic model assessment, and apo-RBP4 (free RBP4) than controls but not of glucose, which remained similar in both groups. Also, in arterial cord serum, ANGPTL6 concentration was increased in GDM neonates with respect to the control group (201 ± 12 ng/mL vs 119 ± 8 ng/mL, respectively). No effect of maternal insulin treatment of some GDM mothers in neonates of either sex on ANGPTL6 levels was observed. In GDM, circulating ANGPTL6 showed no correlation with glucose or insulin concentration or with neonatal adiposity. However, in control pregnancies, the variation in glucose concentration was positively correlated with ANGPTL6 concentration, both in maternal and in cord samples, and cord ANGPTL6 was negatively correlated with neonatal fat mass. Furthermore, in control pregnant women, serum concentrations of ANGPTL6 and apo-RBP4 were negatively correlated.

CONCLUSION

Serum ANGPTL6 levels are associated with maternal glucose homeostasis and fetal adiposity in normal pregnancy. ANGPTL6 levels in maternal and cord serum GDM pregnancy at term are increased, although its mechanism and physiological role are unknown yet.

Role of adipokines in embryo implantation

Embryo implantation is a complex process in which multiple molecules acting together under strict regulation. Studies showed the production of various adipokines and their receptors in the embryo and uterus, where they can influence the maternal-fetal transmission of metabolites and embryo implantation. Therefore, these cytokines have opened a novel area of study in the field of embryo-maternal crosstalk during early pregnancy. In this respect, the involvement of adipokines has been widely reported in the regulation of both physiological and pathological aspects of the implantation process. However, the information about the role of some recently identified adipokines is limited. This review aims to highlight the role of various adipokines in embryo-maternal interactions, endometrial receptivity, and embryo implantation, as well as the underlying molecular mechanisms.

Emerging Protein Biomarkers for the Diagnosis or Prediction of Gestational Diabetes-A Scoping Review

Introduction: Gestational diabetes (GDM), defined as hyperglycemia with onset or initial recognition during pregnancy, has a rising prevalence paralleling the rise in type 2 diabetes (T2DM) and obesity. GDM is associated with short-term and long-term consequences for both mother and child. Therefore, it is crucial we efficiently identify all cases and initiate early treatment, reducing fetal exposure to hyperglycemia and reducing GDM-related adverse pregnancy outcomes. For this reason, GDM screening is recommended as part of routine pregnancy care. The current screening method, the oral glucose tolerance test (OGTT), is a lengthy, cumbersome and inconvenient test with poor reproducibility. Newer biomarkers that do not necessitate a fasting sample are needed for the prompt diagnosis of GDM. The aim of this scoping review is to highlight and describe emerging protein biomarkers that fulfill these requirements for the diagnosis of GDM. Materials and Methods: This scoping review was conducted according to preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines for scoping reviews using Cochrane Central Register of Controlled Trials (CENTRAL), the Cumulative Index to Nursing & Allied Health Literature (CINAHL), PubMed, Embase and Web of Science with a double screening and extraction process. The search included all articles published in the literature to July 2020. Results: Of the 3519 original database citations identified, 385 were eligible for full-text review. Of these, 332 (86.2%) were included in the scoping review providing a total of 589 biomarkers studied in relation to GDM diagnosis. Given the high number of biomarkers identified, three post hoc criteria were introduced to reduce the items set for discussion: we chose only protein biomarkers with at least five citations in the articles identified by our search and published in the years 2017-2020. When applied, these criteria identified a total of 15 biomarkers, which went forward for review and discussion. Conclusions: This review details protein biomarkers that have been studied to find a suitable test for GDM diagnosis with the potential to replace the OGTT used in current GDM screening protocols. Ongoing research efforts will continue to identify more accurate and practical biomarkers to take GDM screening and diagnosis into the 21st century.

Association of apolipoprotein C3 with insulin resistance and coronary artery calcium in patients with type 1 diabetes

BACKGROUND

Apolipoprotein C3 (APOC3) is a risk factor for incident coronary artery disease in people with type 1 diabetes (T1D). The pathways that link elevated APOC3 levels to an increased risk of incident cardiovascular disease in people with T1D are not understood.

OBJECTIVE

To explore potential mechanisms, we investigated the association of APOC3 with insulin resistance and coronary artery calcium (CAC).

METHODS

In a random subcohort of participants with T1D from Coronary Artery Calcification in Type 1 Diabetes (n = 134), serum APOC3, high-density lipoprotein (HDL)-associated APOC3, and retinol binding protein 4 (RBP4; a potential marker of insulin resistance) were measured by targeted mass spectrometry. We used linear regression to evaluate associations of serum APOC3 and HDL-APOC3 with APOB, non-HDL cholesterol, serum- and HDL-associated RBP4, and estimated insulin sensitivity and logistic regression to evaluate association with presence of CAC, adjusted for age, sex, and diabetes duration.

RESULTS

Serum APOC3 correlated positively with APOB and non-HDL cholesterol and was associated with increased odds of CAC (odds ratio: 1.68, P = .024). Estimated insulin sensitivity was not associated with serum- or HDL-RBP4 but was negatively associated with serum APOC3 in men (ß estimate: -0.318, P = .0040) and decreased odds of CAC (odds ratio: 0.434, P = .0023).

CONCLUSIONS

Serum APOC3 associates with increased insulin resistance and CAC in T1D.

First trimester secreted Frizzled-Related Protein 4 and other adipokine serum concentrations in women developing gestational diabetes mellitus

Background

The aim of this study was to evaluate whether soluble frizzled-related protein 4 (sFRP4) concentration in the first trimester of pregnancy is individually, or in combination with Leptin, Chemerin and/or Adiponectin, associated with the development of gestational diabetes (GDM).

Methods

In a nested case-control study, 50 women with GDM who spontaneously conceived and delivered a live-born infant were matched with a total of 100 uncomplicated singleton control pregnancies based on body mass index (± 2 kg/m²), gestational age at sampling (exact day) and maternal age (± 2 years). In serum samples, obtained between 70–90 days gestational age, sFRP4, Chemerin, Leptin and Adiponectin concentrations were determined by ELISA. Statistical comparisons were performed using univariate and multi-variate logistic regression analysis after logarithmic transformation of the concentrations. Discrimination of the models was assessed by the area under the curve (AUC).

Results

First trimester sFRP4 concentrations were significantly increased in GDM cases (2.04 vs 1.93 ng/ml; p<0.05), just as Chemerin (3.19 vs 3.15 ng/ml; p<0.05) and Leptin (1.44 vs 1.32 ng/ml; p<0.01). Adiponectin concentrations were significantly decreased (2.83 vs 2.94 ng/ml; p<0.01) in GDM cases. Further analysis only showed a weak, though significant, correlation of sFRP4 with Chemerin (R² = 0.124; p<0.001) and Leptin (R² = 0.145; p<0.001), and Chemerin with Leptin (R² = 0.282; p<0.001) in the control group. In a multivariate logistic regression model of these four markers, only Adiponectin showed to be significantly associated with GDM (odds ratio 0.12, 95%CI 0.02–0.68). The AUC of this model was 0.699 (95%CI 0.605–0.793).

Conclusion

In the first trimester of pregnancy, a multi-marker model with sFRP4, Leptin, Chemerin and Adiponectin is associated with the development of GDM. Therefore, this panel seems to be an interesting candidate to further evaluate for prediction of GDM in a prospective study.

Sex dimorphism in the associations of gestational diabetes with cord blood adiponectin and retinol-binding protein 4

INTRODUCTION

Gestational diabetes (GD) is associated with impaired insulin sensitivity in newborns. Adiponectin and retinol-binding protein 4 (RBP-4) are involved in regulating insulin sensitivity. Females are more likely to develop diabetes at young ages than males. We tested the hypothesis that GD may affect RBP-4 and adiponectin levels in early life, and there may be sex-dimorphic associations.

RESEARCH DESIGN AND METHODS

In a nested case-control study of 153 matched pairs of neonates of mothers with GD and euglycemic pregnancies in the Shanghai Birth Cohort, we evaluated cord plasma leptin, high molecular weight (HMW) and total adiponectin and RBP-4 concentrations.

RESULTS

Comparing GD versus euglycemic pregnancies adjusted for maternal and neonatal characteristics in female newborns, cord plasma total adiponectin (mean±SD: 30.8±14.3 vs 37.1±16.1 µg/mL, p=0.048) and HMW adiponectin (14.6±7.7 vs 19.3±8.3 µg/mL, p=0.004) concentrations were lower, while RBP-4 concentrations were higher (21.7±5.4 vs 20.0±4.8 µg/mL, p=0.007). In contrast, there were no differences in male newborns (all p>0.2). RBP-4 concentrations were higher in female versus male newborns (21.7±5.4 vs 18.8±4.5 µg/mL, p<0.001) in GD pregnancies only. HMW adiponectin concentrations were significantly higher in female versus male newborns in euglycemic pregnancies only (19.3±8.3 vs 16.1±7.4 µg/mL, p=0.014).

CONCLUSIONS

GD was associated with lower cord plasma HMW adiponectin and higher RBP-4 concentrations in female newborns only. The study is the first to reveal a sex-dimorphic early life impact of GD on metabolic health biomarkers in the offspring. GD may alter the normal presence (HMW adiponectin) or absence (RBP-4) of sex dimorphism in some insulin sensitivity regulation-relevant adipokines in early life.

Retinol-binding protein 4, fetal overgrowth and fetal growth factors

BACKGROUND

Retinol-binding protein 4 (RBP-4) is an adipokine involved in regulating insulin sensitivity which would affect fetal growth. It is unclear whether RBP-4 is associated with fetal overgrowth, and unexplored which fetal growth factor(s) may mediate the association.

METHODS

In the Shanghai Birth Cohort, we studied 125 pairs of larger-for-gestational-age (LGA, birth weight >90th percentile, an indicator of fetal overgrowth) and optimal-for-gestational-age (OGA, 25-75th percentiles) control infants matched by sex and gestational age. We measured cord blood concentrations of RBP-4, insulin, proinsulin, insulin-like growth factor-I (IGF-I), and IGF-II.

RESULTS

Cord blood RBP-4 concentrations were elevated in LGA vs. OGA infants (21.9 ± 6.2 vs. 20.2 ± 5.1 µg/ml, P = 0.011), and positively correlated with birth weight z score (r = 0.19, P = 0.003), cord blood proinsulin (r = 0.21, P < 0.001), IGF-I (r = 0.24, P < 0.001), and IGF-II (r = 0.15, P = 0.016). Adjusting for maternal and neonatal characteristics, each SD increment in cord blood RBP-4 was associated with a 0.28 (0.12-0.45) increase in birth weight z score (P < 0.001). Mediation analyses showed that IGF-I could account for 31.7% of the variation in birth weight z score in association with RBP-4 (P = 0.01), while IGF-II was not an effect mediator.

CONCLUSIONS

RBP-4 was positively associated with fetal overgrowth. IGF-I (but not IGF-II) may mediate this association.

Association between retinol-binding protein 4 concentrations and gestational diabetes mellitus (A1GDM and A2GDM) in different pregnancy and postpartum periods

Background

Gestational diabetes mellitus (GDM) can cause severe adverse effects on fetal and neonatal outcomes. The following study investigates the relationship between retinol-binding protein 4 (RBP4) and GDM in pregnant women with different grades (A1 and A2) and different gestational weeks.

Methods

In this retrospective study, 194 GDM patients (GDM group) and 67 normal glucose tolerance pregnant women (control group) were enrolled from 2014 to 2017. Elbow venous blood samples were collected from all subjects. Enzyme electrode method and enzyme linked immunosorbent assay (ELISA) were used for fasting plasma glucose (FPG) and RBP4/insulin levels (FINS) analysis, respectively.

Results

At middle pregnancy and late stage, FINS, insulin resistance index (HOMA-IR) and RBP4 were all significantly higher in the GDM group compared to control group (P<0.05). Higher HOMA-IR and RBP4 levels, and lower levels of FPG were observed at late stage than those middle pregnancy in the GDM group (P<0.05). Moreover, FINS and RBP4 gradually decreased from middle pregnancy and late stage after delivery in the GDM group. Levels of FINS and RBP4 in postpartum GDM group were higher than those in normal control group (P<0.05). The optimal cut-off value of RBP4 at middle pregnancy diagnostic GDM was 34.84 µg/mL with sensitivity of 79.4% and specificity of 79.1%. The OGTT0h, 2h in A2GDM group was higher than that in A1GDM group, but there was no difference in OGTT1h, age and FINS, RBP4 in both A1GDM and A2GDM group.

Conclusions

RBP4 is closely related to GDM, and its levels increases with the increase of gestational weeks, which may reflect the development of insulin resistance in GDM. RBP4 suggests that the impaired insulin function of GDM in pregnant women is still difficult to recover in the short term after delivery. Compared with OGTT1h, the increase in OGTT0h and 2h levels during middle pregnancy is more helpful for predicting the risk of developing A2GDM at late stage.

Relationships of SLC2A4, RBP4, PCK1, and PI3K Gene Polymorphisms with Gestational Diabetes Mellitus in a Chinese Population

Background

Solute carrier family 2 member 4- (SLC2A4-) retinol binding protein-4- (RBP4-) phosphoenolpyruvate carboxykinase 1 (PCK1)/phosphoinositide 3-kinase (PI3K) is an adipocyte derived “signalling pathway” that may contribute to the pathogenesis of type 2 diabetes mellitus (T2DM). We explored whether single nucleotide polymorphisms (SNPs) of these “signalling pathway” genes are associated with gestational diabetes mellitus (GDM).

Methods

Case-control studies were conducted to compare GDM and control groups. A total of 334 cases and 367 controls were recruited. Seventeen candidate SNPs of the pathway were selected. Chi-square tests, logistic regression, and linear regression were used to estimate the relationships of SNPs with GDM risk and oral glucose tolerance test (OGTT), fasting insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) levels. Model-based multifactor dimensionality reduction was used to estimate the adjusted interactions between genes. Regression and interaction analyses were adjusted by maternal age, prepregnancy BMI, and weekly BMI growth. The Bonferroni correction was applied for multiple comparisons.

Results

RBP4 rs7091052 was significantly associated with GDM risk. SLC2A4 rs5435, RBP4 rs7091052, PCK1 rs1042531 and rs2236745, and PIK3R1 (coding gene of the PI3K P85 subunit) rs34309 were associated with OGTT, fasting insulin, and HOMA-IR levels in the linear regression analysis. The gene-gene interaction analysis showed that, compared with pregnant women with other genotype combinations, women with SLC2A4 rs5435 (CC/CT), RBP4 rs7091052 (CC), PCK1 rs1042531 (TT/TG) and rs2236745 (TT), and PIK3R1 rs34309 (AA) had lower GDM risk.

Conclusion

SLC2A4, RBP4, PCK1, and PIK3R1 genes may be involved in the pathogenesis of GDM.

The Role of Inflammation in the Development of GDM and the Use of Markers of Inflammation in GDM Screening

Gestational diabetes mellitus is a hyperglycaemic state first recognised in pregnancy. GDM affects both mother and child. Women with GDM and their new-borns are at risk of developing type 2 diabetes in the future. The screening and diagnostic criteria for GDM are inconsistent and thus novel biomarkers of GDM are required to strengthen the screening and diagnostic processes in GDM. Chronic low-grade inflammation is linked to the majority of the well-established risk factors of GDM such as old age, obesity and PCOS. This review provides an overview of the present knowledge on the pathology of GDM, the screening criteria applied, the role of inflammation in the development of GDM and the use of markers of inflammation namely cytokines, oxidative stress markers, lipids, amino acids and iron markers in screening and diagnosis of GDM.

Biomarkers for Macrosomia Prediction in Pregnancies Affected by Diabetes

Large birthweight, or macrosomia, is one of the commonest complications for pregnancies affected by diabetes. As macrosomia is associated with an increased risk of a number of adverse outcomes for both the mother and offspring, accurate antenatal prediction of fetal macrosomia could be beneficial in guiding appropriate models of care and interventions that may avoid or reduce these associated risks. However, current prediction strategies which include physical examination and ultrasound assessment, are imprecise. Biomarkers are proving useful in various specialties and may offer a new avenue for improved prediction of macrosomia. Prime biomarker candidates in pregnancies with diabetes include maternal glycaemic markers (glucose, 1,5-anhydroglucitol, glycosylated hemoglobin) and hormones proposed implicated in placental nutrient transfer (adiponectin and insulin-like growth factor-1). There is some support for an association of these biomarkers with birthweight and/or macrosomia, although current evidence in this emerging field is still limited. Thus, although biomarkers hold promise, further investigation is needed to elucidate the potential clinical utility of biomarkers for macrosomia prediction for pregnancies affected by diabetes.

Sitagliptin down-regulates retinol-binding protein 4 and reduces insulin resistance in gestational diabetes mellitus: a randomized and double-blind trial

Gestational diabetes mellitus (GDM) is a condition that affects increasing number of pregnant women worldwide. Sitagliptin was reported to alleviate symptoms of type 2 diabetes mellitus by reducing serum levels of retinol-binding protein 4 (RBP-4). We investigated the effectiveness of sitagliptin on insulin sensitivity parameters in GDM patients. Pregnant GDM women in the 2nd trimester were recruited for this study. Participants were then assigned randomly to sitagliptin treatment group or placebo treatment group, and administered sitagliptin or placebo daily for 16 weeks. Glucose and insulin profiles, as well as serum RBP-4 level, were measured at both baseline and end of the study. After 16 weeks of treatment, participants in the STL group exhibited significantly improved levels of fasting plasma glucose and serum insulin, homeostasis model of assessment of β cell function (HOMA-β) and insulin resistance (HOMA-IR), compared with those in the placebo group. Serum levels of RBP-4 were also markedly decreased in the sitagliptin treatment group, and more importantly it was positively correlated with improved insulin resistance parameters. Our study supports a potentially promising role of sitagliptin in improving insulin resistance by decreasing RBP-4 in GDM-affected women.

Characterization of visceral and subcutaneous adipose tissue transcriptome in pregnant women with and without spontaneous labor at term: implication of alternative splicing in the metabolic adaptations of adipose tissue to parturition

OBJECTIVE

The aim of this study was to determine gene expression and splicing changes associated with parturition and regions (visceral vs. subcutaneous) of the adipose tissue of pregnant women.

STUDY DESIGN

The transcriptome of visceral and abdominal subcutaneous adipose tissue from pregnant women at term with (n=15) and without (n=25) spontaneous labor was profiled with the Affymetrix GeneChip Human Exon 1.0 ST array. Overall gene expression changes and the differential exon usage rate were compared between patient groups (unpaired analyses) and adipose tissue regions (paired analyses). Selected genes were tested by quantitative reverse transcription-polymerase chain reaction.

RESULTS

Four hundred and eighty-two genes were differentially expressed between visceral and subcutaneous fat of pregnant women with spontaneous labor at term (q-value <0.1; fold change >1.5). Biological processes enriched in this comparison included tissue and vasculature development as well as inflammatory and metabolic pathways. Differential splicing was found for 42 genes [q-value <0.1; differences in Finding Isoforms using Robust Multichip Analysis scores >2] between adipose tissue regions of women not in labor. Differential exon usage associated with parturition was found for three genes (LIMS1, HSPA5, and GSTK1) in subcutaneous tissues.

CONCLUSION

We show for the first time evidence of implication of mRNA splicing and processing machinery in the subcutaneous adipose tissue of women in labor compared to those without labor.

Serum level and polymorphisms of retinol-binding protein-4 and risk for gestational diabetes mellitus: a meta-analysis

BACKGROUND

Retinol-binding protein-4 (RBP4) has been reported to be potentially involved in the pathogenesis of gestational diabetes mellitus (GDM); however, the findings are inconsistent. Our aims were to review the studies that investigated the association of serum levels and polymorphisms of RBP4 with GDM risk, and to provide recommendations for future research.

METHODS

The databases PubMed, EBSCO, ScienceDirect, and Web of Knowledge were searched up to October 2015 to find out studies evaluating the relationship between serum RBP4 level/ RBP4 polymorphisms and GDM risk. In the meta-analysis of serum RBP4 levels the key inclusion was that studies were designed as BMI-matched studies or had observed non-significant differences in BMI between cases and controls.

RESULTS

Fourteen case-control studies (647 cases and 620 controls) reporting the association between serum RBP4 level and GDM risk, and three studies (1012 cases and 1605 controls) investigating the association between RBP4 polymorphisms and GDM risk were involved. Our results showed that high serum RBP4 levels represent a risk factor for GDM (pooled standardized mean difference =0.758, 95% confidence interval [0.387, 1.128]). The results of subgroup analyses based on "gestational age at blood sampling" or "diagnostic criteria" are consistent with the overall results. However, the postpartum subgroup and "before 24 weeks" subgroup both only include one article and indicate no association between serum RBP4 level and GDM risk. The meta-analysis on the association between rs3758539 polymorphism and GDM risk shows that RBP4 rs3758539 polymorphism is not associated with the development of GDM.

CONCLUSIONS

The results of this meta-analysis support the hypothesis that RBP4 is a modest independent risk factor for GDM (i.e., nonobese patients with GDM might express RBP4 at abnormal levels). The serum RBP4 level is associated with the risk of GDM. However, the association in the first-trimester and postpartum period should be validated by further research. The association between RBP4 rs3758539 polymorphism and GDM risk was not confirmed.

Characterization of Visceral and Subcutaneous Adipose Tissue Transcriptome and Biological Pathways in Pregnant and Non-Pregnant Women: Evidence for Pregnancy-Related Regional-Specific Differences in Adipose Tissue

Objective

The purpose of this study was to compare the transcriptome of visceral and subcutaneous adipose tissues between pregnant and non-pregnant women.

Study Design

The transcriptome of paired visceral and abdominal subcutaneous adipose tissues from pregnant women at term and matched non-pregnant women (n = 11) was profiled with the Affymetrix Human Exon 1.0 ST array. Differential expression of selected genes was validated with the use of quantitative reverse transcription–polymerase chain reaction.

Results

Six hundred forty-four transcripts from 633 known genes were differentially expressed (false discovery rate (FDR) <0.1; fold-change >1.5), while 42 exons from 36 genes showed differential usage (difference in FIRMA scores >2 and FDR<0.1) between the visceral and subcutaneous fat of pregnant women. Fifty-six known genes were differentially expressed between pregnant and non-pregnant subcutaneous fat and three genes in the visceral fat. Enriched biological processes in the subcutaneous adipose tissue of pregnant women were mostly related to inflammation.

Conclusion

The transcriptome of visceral and subcutaneous fat depots reveals pregnancy-related gene expression and splicing differences in both visceral and subcutaneous adipose tissue. Furthermore, for the first time, alternative splicing in adipose tissue has been associated with regional differences and human parturition.

The Relationship between Retinol-Binding Protein 4 Concentrations and Gestational Diabetes Mellitus in Chinese Women

BACKGROUND

This study aimed to investigate the relationship between retinol-binding protein 4 (RBP4) and gestational diabetes mellitus (GDM).

METHODS

Seventy-six women with and without GDM were recruited. Their blood samples were collected to detect RBP4, fasting plasma glucose (FPG), fasting insulin (Fins), triglyceride (TG), total cholesterol (TC), low-density lipoprotein, high-density lipoprotein (HDL) and glycosylated hemoglobin (HbA1c) levels.

RESULTS

RBP4 (21.42 ± 3.846 vs. 39.08 ± 8.293 μg/ml), FPG, Fins, homeostasis model assessment of insulin resistance (HOMA-IR), HbA1c, and TG levels were higher, while HDL levels were lower in women with GDM (p < 0.01). In healthy controls, RBP4 concentrations were positively correlated with HOMA-IR and TG and inversely correlated with FPG and HDL (p < 0.05). Serum concentrations of RBP4 in women with GDM were inversely correlated with TC and positively correlated with maternal weight gain during pregnancy (p < 0.05). The ROC curve was drawn with a correct rate of 93.4%.

CONCLUSIONS

Concentrations of serum RBP4 were significantly higher in women with GDM, suggesting that elevated RPB4 level may play a role in the pathogenesis of GDM. Meanwhile, RBP4 might be a good predictor of GDM. RBP4 is correlated with TG and HDL, indicating that RBP4 plays a role in alterations of lipid metabolism in pregnant women. © 2015 S. Karger AG, Basel.

Circulating retinol-binding protein 4 levels in gestational diabetes mellitus: a meta-analysis of observational studies

Retinol-binding protein 4 (RBP4) is a novel adipocyte-derived cytokine playing an important role in the regulation of energy metabolism and insulin sensitivity. Although the association between RBP4 and metabolic dysfunction is well established, studies on the relationship between circulating RBP4 levels and the risk of gestational diabetes mellitus (GDM) have yielded inconclusive results. We performed a meta-analysis to investigate whether women with GDM had higher circulating RBP4 levels than the normglycemic pregnant women. PubMed, Web of Science and EMBASE were searched up to 1 August 2014. A total of 14 studies comprised of 884 women with GDM and 1251 normglycemic pregnant women were included. The overall results suggested that maternal circulating RBP4 levels were significantly higher in GDM than their normal controls (SMD: 0.49 μg/ml, 95% CI: 0.23-0.75 μg/ml, p < 0.001, random effect model). However, stratified results indicated that this significant difference only existed in the second/third trimester and was limited to Asian populations. Furthermore, subgroup analysis according to matched maternal age and BMI still demonstrated that GDM had higher circulating RBP4 levels than the normal controls. Our findings suggested that Asian women with GDM had increased circulating RBP4 levels in their second/third trimester.

Proteomic analysis of reproduction proteins involved in litter size from porcine placenta

A gel-free and label-free quantitative proteomic approach based on a spectral counting strategy was performed to discover prolificacy-related proteins. Soluble proteins of porcine placenta from small litter size group (SLSG) and large litter size group (LLSG) were extracted and subsequently applied to in-solution tryptic digestion followed by liquid chromatography-tandem mass spectrometry analysis. Six and thirteen proteins were highly expressed in SLSG and LLSG, respectively. Of the dominantly expressed proteins, we chose prolificacy-related proteins such as puromycin-sensitive aminopeptidase (PSA) and retinol-binding protein 4 (RBP4). Western blot analysis confirmed that the processed form (70 kDa) of PSA was more expressed and RBP4 (23 kDa) was dominantly expressed in LLSG. These results indicate that PSA and RBP4 are representative proteins involved in porcine fertility traits, and this finding may help to increase litter size of pigs.

Gestational diabetes: a risk of puerperal hypovitaminosis A?

The influence of gestational diabetes on vitamin A deficiency in lactating women and, consequently, in their newborn has been verified through a cross-sectional case-control study conducted with volunteer puerperal women. The control group consisted of healthy women and the test group was composed of women with gestational diabetes. One hundred and seven women were recruited, corresponding to 71 controls and 36 cases. Personal, gestational and newborn data were collected directly from medical records during hospitalization. The retinol was determined in maternal colostrum and serum by High Performance Liquid Chromatography. Postpartum women with gestational diabetes were older, had more children and a higher prevalence of cesarean delivery. No difference was found in retinol concentration in maternal milk and serum between the groups. However, it was observed that 16.7% had vitamin A deficiency in the group of patients with diabetes and only 4.1% had such deficiency in the control group. Although no difference was found in colostrum and serum retinol concentration between women with and without gestational diabetes, the individual analysis shows that those with diabetes are at higher risk of being vitamin A deficient.

RBP4 gene variants are associated with insulin resistance in women with previous gestational diabetes

Objective. This study aimed to examine possible genetic effects of some retinol binding protein-4 (RBP4) single nucleotide polymorphisms (SNPs) on the risk of gestational diabetes mellitus (GDM). In addition, the SNPs were examined for their possible association with insulin resistance at 6 weeks after delivery. Methods. This was a prospective study of 100 women with GDM and 100 participants with normal gestation who were evaluated at gestational week 30 and 6 weeks postpartum. Three SNPs of RBP4 (rs3758539, rs116736522, and rs34571439) were genotyped using TaqMan assay. The genotype distributions between GDM patients and normal controls were analyzed using logistic regression models. In addition, differences in clinical characteristics among subjects grouped by genotype were assessed using the analysis of covariance test. Results. The frequencies of the rare alleles were not significantly different between GDM patients and controls. However, we identified two variants rs3758539 and rs34571439 associated with insulin levels and insulin resistance in women with previous GDM. Conclusion. Noncoding SNPs of the RBP4 gene are not associated with GDM, but two SNPs showed associations with insulin resistance and insulin levels in women with prior GDM. Additional studies with increased sample size will be necessary in other GDM cohorts.

Significance of RBP4 in patients with gestational diabetes mellitus: a case-control study of Han Chinese women

The role of retinol binding protein 4 (RBP4) in insulin resistance was recently identified. Our study investigated the correlation between RBP4 levels with lipid and glucose metabolism in a case-control study of women with gestational diabetes mellitus (GDM). Between May 2008 and May 2010, 70 pregnant women (24-28 weeks gestation) were recruited, including 35 women with GDM and 35 healthy controls. Blood samples were collected prior to and after oral glucose tolerance tests (OGTT) to detect serum RBP4, insulin, glycated hemoglobin, triglyceride (TG) and total cholesterol (TC) levels; the insulin resistance index (HOMA-IR) was calculated. Serum RBP4 levels in the GDM group were significantly higher than the control group (22.9 ± 3.09 µg/ml versus 17.9 ± 3.91 µg/ml; p < 0.01). Insulin, TC and TG levels in the GDM group and the control group were all significantly higher than the control group (p < 0.05). Serum RBP4 levels in the GDM group were correlated with HOMA-IR, TG and blood glucose levels at 1 h and 2 h after glucose was administered (r = 0.49, 0.49, 0.52,0.52, respectively; p < 0.01). In conclusion, serum RBP4 levels are elevated in GDM cases than controls. In addition, RBP4 correlates with abnormalities of insulin resistance, glucose and lipid metabolism.

Maternal serum retinol-binding protein-4 at 11-13 weeks' gestation in normal and pathological pregnancies

OBJECTIVE

To examine maternal serum levels of retinol-binding protein-4 (RBP4) at 11-13 weeks' gestation in normal and pathological pregnancies.

METHODS

Serum RBP4 at 11-13 weeks was 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 (SGA) neonates. The values in each adverse pregnancy outcome group were compared to those of normal pregnancies.

RESULTS

Serum concentration of RBP4 was not significantly different in women who subsequently developed PE (p=0.925), or GDM (p=0.074), or had pregnancies that led to delivery to SGA (p=0.085), LGA (p=0.332) neonates.

CONCLUSION

Maternal serum RBP4 in the first trimester is not significantly altered in pathological pregnancies.

Proteomic profiling for peritoneal dialysate: differential protein expression in diabetes mellitus

Peritoneal dialysis (PD) is an increasingly accepted modality of renal replacement therapy. It provides the advantages of having a flexible lifestyle, stable hemodynamics, and better preservation of residual renal function. To enhance our understanding of the peritoneal dialysate of diabetes mellitus (DM), peritoneal dialysate proteins were identified by two-dimensional gel electrophoresis (2DE) combined with reverse-phase nano-ultra performance liquid chromatography electrospray ionization tandem mass spectrometry (RP-nano-UPLC-ESI-MS/MS) followed by peptide fragmentation patterning. To validate the differential proteins, ELISA and Western blotting analyses were applied to detect candidate proteins that may be related to DM. We performed 2DE on the peritoneal dialysate samples, with detection of more than 300 spots. From this, 13 spots were excised, in-gel digested, and identified by RP-nano-UPLC-ESI-MS/MS. Ten of these showed significant differential expression between the DM and chronic glomerulonephritis (CGN) peritoneal dialysate samples. In this study, we conducted a comparative proteomic study on these two groups of dialysate that may provide evidence for understanding the different peritoneal protein changes. These proteins may not be new biomarkers; however, they may indicate a situation for possible drug treatment and can be the predictors of peritonitis for a validation study in the future.

Retinol-binding protein 4 in patients with gestational diabetes mellitus

OBJECTIVE

It is still unknown if serum retinol-binding protein 4 (RBP4) relates to metabolic control and the occurrence of gestational diabetes mellitus (GDM). We studied RBP4 levels in patients with insulin-treated GDM and healthy pregnant women twice during pregnancy.

METHODS

Sixty-three women with GDM and 38 healthy pregnant women were included. Serum RBP4 levels were measured at 24-28 weeks of gestation and 8 weeks later. Patients with GDM were treated with insulin.

RESULTS

Serum RBP4 levels increased significantly between the two measurements in patients with GDM (p = 0.03). In patients with GDM, RBP4 concentrations at 33 weeks of gestation correlated positively with mean blood glucose, hemoglobin A1c values, and cord blood insulin values right after delivery. Regression analyses showed that the diagnosis of GDM (p = 0.04) and hemoglobin A1c levels (p < 0.001) were related to RBP4 levels at 33 weeks of gestation.

CONCLUSIONS

Serum RBP4 levels increase during pregnancy in patients with insulin-treated GDM.

Association of retinol binding protein 4 with risk of gestational diabetes

AIM

We investigated association of maternal retinol binding protein 4 (RBP4) with risk of gestational diabetes (GDM).

METHODS

GDM cases (N=173) and controls (N=187) were selected from among participants of a cohort study of risk factors of pregnancy complications. Early pregnancy (16 weeks on average) serum RBP4 concentration was measured using an ELISA-based immunoassay. Logistic regression was used to estimate unadjusted and adjusted odds ratios (ORs/aORs) and 95% confidence intervals (95%CI).

RESULTS

Mean serum RBP4 was significantly higher among GDM cases compared with controls (47.1 vs. 41.1 μg/ml, respectively; p-value <0.05). Participants in the highest quartile for serum RBP4 had a 1.89-fold higher risk of GDM compared with participants in the lowest quartile (95%CI: 1.05-3.43). However, this relationship did not reach statistical significance after adjustment for confounders (aOR: 1.54; 95%CI: 0.82-2.90). Women who were ≥35 years old and who had high RBP4 (≥38.3 μg/ml, the median) had a 2.31-fold higher risk of GDM compared with women who were <35 years old and had low RBP4 (<38.3 μg/ml) (aOR: 2.31; 95%CI: 1.26-4.23; p-value for interaction=0.021).

CONCLUSION

Overall, there is modest evidence of a positive association of early pregnancy elevated RBP4 concentration with increased GDM risk, particularly among women with advanced age.

Chemerin is present in human cord blood and is positively correlated with birthweight

OBJECTIVE

Chemerin, a novel adipokine, has been implicated in adipogenesis, inflammation, and metabolism. The aims of this study were to determine the presence of chemerin in cord blood and its association with birthweight.

STUDY DESIGN

This cross-sectional study included the following: (1) twins with (n = 24) or without (n = 28) birthweight discordancy; and (2) singletons subclassified into small-for-gestational-age (SGA; n = 18); appropriate for gestational age (AGA; n = 33); and large-for-gestational-age (LGA; n = 8). Cord blood chemerin was determined. Parametric and nonparametric statistics were used for analysis.

RESULTS

The results of the study included the following: (1) within the discordant twins group, the median chemerin concentration was significantly lower in the SGA group than in their cotwins; (2) within singletons, the median chemerin concentration was significantly higher in the LGA than the AGA newborns; and (3) the regression model revealed that chemerin was independently associated with birthweight.

CONCLUSION

Cord blood chemerin is present in cord blood and its concentrations are positively correlated with birthweight. These novel findings support a role of adipokines in fetal growth.

Retinol-binding protein 4 is not associated with insulin resistance in pregnancy

Retinol-binding protein 4 (RBP4) is an adipokine proposed to be specifically associated with insulin resistance (IR). We examined whether serum levels of RBP4 were associated with IR in pregnancy. One hundred seventy-two women with gestational diabetes mellitus (GDM) and 361 pregnant Thai women who did not have GDM but had a positive 50-g glucose challenge test result (plasma glucose level was ≥7.2 mmol/L after 1 hour) were enrolled. We measured fasting serum levels of RBP4 and assessed IR at a 100-g oral glucose tolerance test. We found a higher degree of IR in the GDM group compared with the non-GDM group, but serum RBP4 levels between the 2 groups were not different. Retinol-binding protein 4 levels were associated with serum triglyceride levels but were not associated with the degree of IR assessed by homeostasis model assessment or quantitative insulin sensitivity check index. Our results suggest that serum RBP4 levels in pregnancy are not associated with IR.

Role of adipokines and other inflammatory mediators in gestational diabetes mellitus and previous gestational diabetes mellitus

Previous Gestational Diabetes Mellitus (pGDM) is a common condition and has been associated with future development of Type 2 Diabetes Mellitus (T2DM) and Metabolic Syndrome (MS) in women affected. The pathogenesis and risk factors implicated in the development of these conditions later in the lives of women with pGDM are not as yet fully understood. Research has recently focused on a group of substances produced mainly by adipose tissue called adipokines, this group including, among others, adiponectin, leptin, Retinol-Binding Protein-4 (RBP-4), and resistin. These substances as well as other inflammatory mediators (CRP, IL-6, PAI-1, TNF-α) seem to play an important role in glucose tolerance and insulin sensitivity dysregulation in women with pGDM. We summarize the data available on the role of these molecules.

Leptin, adiponectin and other adipokines in gestational diabetes mellitus and pre-eclampsia

Proteins secreted from adipocytes - so-called adipokines - influence metabolic and vascular function. Recent data suggest that various adipokines are dysregulated in gestational diabetes mellitus (GDM) and pre-eclampsia (PE) and might be of pathophysiological and prognostic significance in these complications of pregnancy. This review gives an overview on the regulation and pathophysiology of leptin and adiponectin in GDM and PE. Furthermore, data on novel adipokines including resistin, visfatin, retinol-binding protein 4 and vaspin are summarized.

Relationship between circulating adipokines and insulin resistance during pregnancy and postpartum in women with gestational diabetes

BACKGROUND AND AIMS

We undertook this study to assess the relationship between circulating adipokines and insulin resistance during pregnancy and postpartum in women with gestational diabetes mellitus (GDM).

METHODS

This was a prospective study including 60 women with GDM and 60 subjects with normal gestation who were evaluated at gestational week 30, 6 weeks and 6 months postpartum. Circulating adipokines that were evaluated during the study were leptin, adiponectin, retinol-binding protein-4 (RBP4), and tumor necrosis factor-alpha (TNF-α).

RESULTS

Women with GDM showed higher insulin resistance measured by HOMA-IR than subjects with normal gestation (2.3 ± 2.3 vs. 1.3 ± 0.95). There was no difference between groups in adipokines; however, in women with a healthy pregnancy, RBP4 was associated with insulin resistance (r = 0.47, p <0.05). At 6 weeks and 6 months postpartum, women with previous GDM exhibited persistent elevated leptin and insulin resistance. RBP4 was associated with insulin resistance only in women with a previous healthy pregnancy (r = 0.51, p <0.05). In addition, progressively impaired glucose tolerance was observed after delivery in women with previous GDM.

CONCLUSIONS

It was demonstrated that GDM is associated with greater insulin resistance than observed in normal pregnancy; however, adipokines are similar in both groups. RBP4 levels are significantly associated with insulin resistance in healthy women during pregnancy and postpartum. After a pregnancy complicated by GDM, leptin and insulin resistance remain elevated and glucose tolerance worsens.

Retinol-binding protein 4 in adipose and placental tissue of women with gestational diabetes

In the present study, we evaluated serum levels of retinol-binding protein 4 (RBP4) and the expression of RBP4, glucose transporter-4 (GLUT4) and peroxisome proliferator activated receptor gamma (PPARγ) mRNA (using quantitative real time-PCR) in subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT) and placental tissue obtained from patients with gestational diabetes (GDM) and healthy pregnant women. Serum RBP4 concentrations and its expression in SAT were higher in the women with GDM than in the controls (p = 0.03). No association between serum or tissue RBP4 and the indices of insulin resistance was noted. In the GDM group serum RBP4 correlated with its mRNA expression in SAT (r = 0.67, p = 0.007). Stepwise regression analysis revealed that RBP4 mRNA expression in SAT was independently predicted by GLUT4 mRNA expression (β= 0.59, p = 0.003) and the presence of GDM (β=0.46, p = 0.01), whereas RBP4 mRNA expression in VAT was related to PPARγ mRNA expression (β= 0.64, p = 0.0003) and the patient's age (β= -0.38, p = 0.03). In conclusion, our results suggest that the elevated expression of RBP4 in SAT may contribute to the increase in circulating RBP4 in GDM subjects.

Gestational diabetes mellitus causes changes in the concentrations of adipocyte fatty acid-binding protein and other adipocytokines in cord blood

OBJECTIVE

To determine the concentrations of adipocyte fatty acid-binding protein (AFABP) and other adipocytokines in maternal and cord serum of pregnant women with gestational diabetes mellitus (GDM) and of control subjects and to relate them to indexes of insulin sensitivity.

RESEARCH DESIGN AND METHODS

In 86 control and 98 GDM pregnant women, venous blood was collected before vaginal delivery and arterial blood from cord immediately after delivery. Serum insulin and adipocytokines were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

GDM women had higher prepregnancy BMI, and data were adjusted for it. Maternal serum insulin, insulin-to-glucose ratio, homeostasis model assessment (HOMA), AFABP, and retinol-binding protein 4 (RBP4) were higher and adiponectin was lower in GDM than in control subjects, whereas serum glucose, insulin, insulin-to-glucose ratio, HOMA, nonesterified fatty acids, and RBP4 were higher and glycerol, AFABP, and adiponectin were lower in cord blood serum of GDM than of control subjects. AFABP and adiponectin in cord serum of control subjects were higher than in maternal serum; in GDM women no difference was found for AFABP in cord versus maternal serum, although adiponectin remained higher in cord. Values of leptin in both groups were lower in cord than in maternal serum, and those of RBP4 were lower in only GDM women.

CONCLUSIONS

It is suggested that fetal tissues are the main source of cord arterial serum AFABP, and in GDM fetuses AFABP values correlate with adiposity markers. A downregulation of adiponectin and upregulation of RBP4 in GDM mothers and their fetuses may be related to their insulin-resistant condition, whereas changes in AFABP do not seem to be related.

The effects of adipose tissue and adipocytokines in human pregnancy

During pregnancy, important changes take place in maternal metabolism because of the growing fetus and placental formation. The increase in insulin resistance during pregnancy is paralleled by the progressive increase of maternal adipose tissue deposition. This review examines the topography of fat mass deposition during pregnancy in relation to factors such as parity and maternal age that might affect this deposition. We also examine adipose tissue markers, such as pregravid weight and weight gain during pregnancy, and their effect on fetal growth and pregnancy outcomes. In addition, this review studies the possible effects of cytokines that are produced by adipose tissue and the placenta on maternal metabolism and its complications. Finally, we also consider the possible role of maternal adipocytokines and fetal adipocytokines on fetal growth.

Retinol-binding protein 4 in neonates born small for gestational age

BACKGROUND

Retinol-binding protein 4 (RBP4) is an adipocyte-derived 'signal' that may contribute to the pathogenesis of insulin resistance and Type 2 diabetes. The relationship of RBP4 with insulin resistance and metabolic risk in human beings has been the subject of several studies. Subjects born small for gestational age (SGA) are at risk of insulin resistance and Type 2 diabetes. Though RBP4 could represent an early marker of insulin resistance, to date, none have determined RBP4 in SGA children.

AIM

Our aim was to measure RBP4 concentrations in cord blood of SGA newborns compared with those in children born with a birth weight appropriate for gestational age (AGA) and to determine whether serum RBP4 levels at birth correlate with insulin sensitivity markers.

SUBJECTS AND METHODS

Sixty-four newborns, 17 born SGA (mean gestational age: 36.4+/-2.1 weeks), and 47 born AGA (mean gestational age: 37.0+/-3.6 weeks) were studied. The main outcome measures included anthropometry, lipid profile, insulin, homeostasis model assessment, quantitative insulin-sensitivity check index, adiponectin, and RBP4.

RESULTS

RBP4 concentrations were significantly reduced in SGA newborns (p<0.002). No relationship was found between RBP4 and insulin sensitivity parameters. Stepwise regression analysis revealed that birth weight was the major predictor of RBP4 serum concentrations (p<0.001).

CONCLUSION

RBP4 is reduced in SGA newborns, birth weight representing the major determinant of RBP4 concentrations, and is not related to insulin sensitivity. No significant difference in adiponectin levels and insulin sensitivity markers was found between SGA and AGA neonates.

Retinol binding protein 4--a novel association with early-onset preeclampsia

OBJECTIVE

Dysregulation of maternal circulating adipokines has been implicated in several "great obstetrical syndromes" including preeclampsia (PE), small-for-gestational age (SGA) neonate and fetal death (FD). It has been suggested that adipokines provide a molecular link between metabolic derangements and inflammatory response in complicated pregnancies. Retinol binding protein 4 (RBP4), a novel adipokine, plays a role in obesity-related disorders, as well as in the regulation of the immune response. The aim of this study was to determine whether there are changes in maternal plasma concentrations of RBP4 in patients with PE and in those with an SGA neonate or FD.

STUDY DESIGN

This cross-sectional study included patients in the following groups: 1) normal pregnancy (n=134); 2) PE (n=104); 3) SGA neonate (n=28); and 4) FD (n=37). Maternal plasma RBP4 concentrations were determined by ELISA. Non-parametric statistics were used for analysis.

RESULTS

1) The median maternal plasma RBP4 concentration was higher among patients with PE than in those with a normal pregnancy (P=0.03); 2) The median maternal plasma RBP4 concentrations of patients with preterm PE (<37 weeks) was higher than that of those with term PE (P=0.017) and than that of those with a normal pregnancy (P=0.002); 3) The median maternal plasma RBP4 concentration did not differ significantly between patients with a normal pregnancy and those with an SGA neonate or with an FD; 4) Among normal pregnant women, the maternal plasma RBP4 concentrations did not correlate with pre-pregnancy body mass index, gestational age at blood sampling and neonatal birthweight.

CONCLUSIONS

1) Preeclampsia, but not pregnancy with an SGA neonate or an FD, is associated with a higher median maternal plasma concentration of RBP4 than normal pregnancy; 2) Preterm PE, and specifically early-onset PE, is associated with higher median RBP4 concentrations in maternal plasma compared to term PE. These findings suggest a role for RBP4 in the pathogenesis of preterm PE, but not in SGA and FD.

Retinol-binding protein 4: a novel adipokine implicated in the genesis of LGA in the absence of gestational diabetes mellitus

OBJECTIVE

Adipokines (cytokines produced by adipose tissue) play a major role in the control of body weight and energy distribution. Retinol-binding protein 4 (RBP4), only recently recognized as an adipokine, has been proposed to modulate systemic insulin sensitivity. The goal of this study was to determine whether there is an association between maternal plasma RBP4 concentration and the birth of a large-for-gestational-age (LGA) newborn in women with and without gestational diabetes mellitus (GDM).

STUDY DESIGN

This cross-sectional study included pregnant women at term in the following groups: 1) normal pregnancy with an appropriate-for-gestational-age (AGA) neonate (n=64); 2) normal pregnancy with an LGA neonate (n=44); 3) GDM with an AGA neonate (n=55); and 4) GDM with an LGA neonate (n=42). Maternal plasma RBP4 concentration was determined by ELISA. Parametric and non-parametric statistics were used for analyses.

RESULTS

1) Patients with GDM, either with AGA or LGA neonates, had a higher median plasma concentration of RBP4 than normal pregnant women who delivered an AGA neonate (P=0.01 and P=0.008, respectively); 2) mothers without GDM but with LGA neonates had a higher median plasma concentration of RBP4 than those with normal pregnancy and AGA newborns (P=0.001); 3) these findings remained significant after adjusting for maternal age, body mass index and gestational age at blood sampling.

CONCLUSION

GDM is characterized by alterations in maternal circulating RBP4 concentrations akin to those of Type 2 diabetes mellitus. RBP4 concentrations in maternal plasma may play a role in accelerated fetal growth in the absence of overt carbohydrate intolerance.

Impact of type 1 diabetes and insulin treatment on plasma levels and fractional synthesis rate of retinol-binding protein 4

CONTEXT

Retinol binding protein 4 (RBP4) levels are elevated in insulin-resistant states and reduced in type 1 diabetes (T1D), but it is unknown whether changes in insulin levels and glycemic control alter RBP4 levels. In vivo synthesis rates of RBP4 and their relationship to RBP4 levels remain to be determined.

OBJECTIVE

The aim of the study was to determine whether the synthesis rate of RBP4 is altered in people with T1D during both insulin deficiency and insulin treatment.

DESIGN

Seven T1D participants were studied on two occasions, during 8 h of insulin deprivation and during insulin treatment, and compared with nondiabetic (ND) controls.

MAIN OUTCOME MEASURES

We measured in vivo fractional synthesis rate of RBP4 using [ring-(13)C(6)]phenylalanine as a tracer and RBP4 concentration in plasma by nephelometric assay and Western blot analyses.

RESULTS

Plasma RBP4 levels were lower (P < 0.01) in insulin-treated T1D than in ND but were not different between insulin-deprived T1D and ND participants. Synthesis rates of RBP4 in ND (2.46 +/- 0.29%/h) were higher than in insulin-treated T1D (1.45 +/- 0.21) (P = 0.02), but there was no difference between ND and insulin-deprived T1D (2.24 +/- 0.24). Glucose levels were not different between ND and insulin-treated T1D, but insulin levels were higher in insulin-treated T1D (82.8 +/- 2 pmol/liter) than in ND (28.7 +/- 6) and insulin-deprived T1D (4.6 +/- 1.6) (P < 0.01).

CONCLUSIONS

Insulin treatment that achieved normoglycemia but relative hyperinsulinemia was associated with lower RBP4 synthesis and levels in T1D. Short-term insulin deprivation and hyperglycemia had no effect on RBP4 levels and synthesis rates in T1D.

Serum retinol-binding protein 4 (RBP4) and retinol in a cohort of borderline obese women with and without gestational diabetes

OBJECTIVES

To evaluate whether serum RBP4 correlates with gestational diabetes mellitus (GDM) in a cohort of borderline obese (BMI>30) pregnant women.

DESIGN AND METHODS

Serum RBP4 and retinol were measured in pregnant women with (n=12) and without (n=10) GDM.

RESULTS

RBP4, retinol and RBP4:retinol molar ratio were not different between the groups and were not associated with markers of insulin resistance.

CONCLUSIONS

GDM is not associated with RBP4 or retinol among borderline obese pregnant women.

Preliminary report: Serum levels of retinol-binding protein 4 in preeclampsia

The objective of the study was to investigate serum levels of the adipokine retinol-binding protein 4 (RBP4) in patients with preeclampsia (PE) as compared with healthy controls of similar gestational age. Retinol-binding protein 4 serum levels were quantified by enzyme-linked immunosorbent assay in control (n = 20) and PE (n = 16) patients. Mean maternal RBP4 concentrations were not significantly different in PE (24.5 mg/L) as compared with controls (22.3 mg/L). Furthermore, RBP4 did not correlate to clinical and biochemical measures of pregnancy outcome, renal function, glucose, and lipid metabolism, as well as inflammation. Our results do not support a role of RBP4 in the pathogenesis of PE.

Serum retinol-binding protein 4 levels in nonobese women with polycystic ovary syndrome

OBJECTIVE

To test whether there was a difference in serum retinol-binding protein 4 (RBP4) levels between subjects with polycystic ovary syndrome (PCOS) and those with a healthy regular menstrual cycle and, in addition, to correlate serum RBP4 levels with a variety of parameters.

DESIGN

Clinical study.

SETTING

University hospital.

PATIENT(S)

A total of 74 nonobese women were evaluated. Thirty-seven had PCOS, whereas the remaining 37 served as control subjects.

INTERVENTION(S)

Serum RBP4 levels were analyzed using ELISA.

MAIN OUTCOME MEASURE(S)

Serum levels of FSH, LH, TSH, E(2), T, insulin, glucose, cholesterol, triglycerides, and RBP4.

RESULT(S)

The women with PCOS had higher levels of serum RBP4, waist-to-hip ratio, LH, T, insulin, homeostatic model assessment of insulin resistance, cholesterol, and triglycerides. Logistic regression analyses revealed a significant association between odds ratio (OR) values of PCOS and both T (OR = 1.125; 95% confidence interval [CI] 1.050-1.205), and cholesterol levels (OR = 1.029; 95% CI 1.004-1.056). Age and triglycerides were significantly correlated to serum RBP4 levels by multiple linear regression analysis.

CONCLUSION(S)

Our study has shown that [1] elevated RBP4 levels might arise from triglyceride metabolism, and that RBP4 levels might not be influenced by PCOS itself. [2] RBP4 might not be a useful marker of insulin resistance in subjects with PCOS.

High plasma retinol binding protein-4 and low plasma adiponectin concentrations are associated with severity of glucose intolerance in women with previous gestational diabetes mellitus

CONTEXT

Women with previous gestational diabetes mellitus (pGDM) are at high risk of developing type 2 diabetes mellitus in the future. The role of adipokines in women with pGDM has not been established.

OBJECTIVE

We investigated whether circulating adipokine concentration is associated with abnormal glucose homeostasis in women with pGDM. DESIGN, SETTING, PATIENTS, AND MAIN OUTCOME MEASURES: We measured the plasma concentrations of retinol-binding protein-4 (RBP4), transthyretin (TTR), and adiponectin and metabolic parameters in four groups of women who exhibited normal glucose tolerance (NGT) during a previous pregnancy (NP, n = 17), NGT after GDM (GDM-NGT, n = 72), impaired glucose tolerance after GDM (GDM-IGT, n = 60), and type 2 diabetes after GDM (GDM-DM, n = 8).

RESULTS

Plasma RBP4 concentration was significantly higher in women with GDM-DM, GDM-IGT, and GDM-NGT than in those with NP. RBP4 concentration correlated positively with TTR concentration; fasting plasma glucose, insulin, and triglyceride concentrations; blood pressure; abdominal fat area; and homeostasis model assessment of insulin resistance. Plasma TTR concentration was elevated in women with GDM-DM compared with other groups. In contrast, adiponectin concentration was lowest in the GDM-DM group and correlated inversely with parameters of insulin resistance. Resistin concentration was higher only in the GDM-NGT and GDM-IGT groups, whereas leptin did not differ between groups. Plasma RBP4 and adiponectin concentrations were inversely correlated.

CONCLUSIONS

The severity of glucose intolerance in women with pGDM is associated with high RBP4 and low adiponectin concentrations.

Retinol to retinol-binding protein (RBP) is low in obese adults due to elevated apo-RBP

Elevated serum retinol-binding protein (RBP) concentration has been associated with obesity and insulin resistance, but accompanying retinol values have not been reported. Assessment of retinol is required to discriminate between apo-RBP, which may act as an adipokine, and holo-RBP, which transports vitamin A. The relations between serum RBP, retinol, retinyl esters, BMI, and measures of insulin resistance were determined in obese adults. Fasting blood (> or =8 h) was collected from obese men and women (n = 76) and blood chemistries were obtained. Retinol and retinyl esters were quantified by HPLC and RBP by ELISA. RBP and retinol were determined in age and sex-matched, nonobese individuals (n = 41) for comparison. Serum apo-RBP was two-fold higher in obese (0.90 +/- 0.62 microM) than nonobese subjects (0.44 +/- 0.56 microM) (P < 0.001). The retinol to RBP ratio (retinol:RBP) was significantly lower in obese (0.73 +/- 0.13) than nonobese subjects (0.90 +/- 0.22) (P < 0.001) and RBP was strongly associated with retinol in both groups (r = 0.71 and 0.90, respectively, P < 0.0001). In obese subjects, RBP was associated with insulin (r = 0.26, P < 0.05), homeostatic model assessment of insulin resistance (r = 0.29, P < 0.05), and quantitative insulin sensitivity check index (r = -0.27, P < 0.05). RBP was associated with BMI only when obese and nonobese subjects were combined (r = 0.25, P < 0.01). Elevated serum RBP, derived in part from apo-RBP, was more strongly associated with retinol than with BMI or measures of insulin resistance in obese adults. Investigations into the role of RBP in obesity and insulin resistance should include retinol to facilitate the measurement of apo-RBP and retinol:RBP. When evaluating the therapeutic potential of lowering serum RBP, consideration of the consequences of vitamin A metabolism is paramount.

Serum concentrations of retinol-binding protein 4 in women with and without gestational diabetes

AIMS/HYPOTHESIS

Pregnancy is characterised by temporarily increased insulin resistance. Gestational diabetes occurs when pancreatic beta cell function is unable to compensate for this insulin resistance. Retinol-binding protein 4 (RBP4) could be related to insulin resistance. We hypothesised that RBP4 is elevated in gestational diabetes.

METHODS

Serum RBP4, transthyretin and retinol were cross-sectionally measured in 42 women with gestational diabetes and 45 pregnant controls. Of these, 20 women with and 22 without gestational diabetes were included in an additional longitudinal study. RBP4 was determined by enzyme immunometric assay (EIA) and western blot.

RESULTS

Women with gestational diabetes had lower RBP4 EIA and western blot levels than controls (median 6.8 [interquartile range, 3.9-14.3] vs 11.3 [7.8-19.9] microg/ml, p < 0.001 and 25.1 [21.7-29.6] vs 26.6 [23.5-32.2] microg/ml, p = 0.026). Transthyretin and the RBP4:transthyretin molar ratio were comparable between the groups. Serum retinol was lower (p < 0.001) and the RBP4 Western blot level: retinol molar ratio was higher in women with gestational diabetes (p = 0.044). RBP4 was not associated with the glucose or homeostasis model assessment of insulin resistance (HOMA-IR), but in gestational diabetes the RBP4:retinol molar ratio correlated with blood glucose and negatively with 2 h post-load insulin. The RBP4:transthyretin ratio correlated with HOMA-IR and fasting insulin in controls. In women with gestational diabetes RBP4 EIA and western blot levels increased after delivery. Retinol increased in both groups, while transthyretin and the RBP4:transthyretin ratio were not altered after parturition.

CONCLUSIONS/INTERPRETATION

RBP4 measured by two different techniques is not elevated, but the RBP4:retinol molar ratio is higher and correlates with fasting blood glucose in women with gestational diabetes. Thus, the RBP4:retinol ratio and the RBP4:transthyretin ratio are more informative than RBP4 levels alone when assessing insulin-glucose homeostasis during pregnancy.

Retinol-binding protein-4 is not strongly associated with insulin sensitivity in normal pregnancies

OBJECTIVE

Recently, experimental and clinical studies suggest that retinol-binding protein-4 (RBP4) may provide a link between obesity and insulin resistance. However, no previous studies have investigated the impact of circulating RBP4 on measures of insulin resistance in normal pregnant women, and the objective of this study is to measure serum RBP4 in early and late pregnancy and relate these to measures of insulin resistance and secretion controlling for changes in fat mass.

DESIGN AND METHODS

Samples were obtained during oral glucose tolerance test (OGTT) from 44 normal pregnancies at weeks 14-16 and 30-32. Measures of fat mass were body mass index (BMI) and leptin while insulin sensitivity and secretion were predicted from OGTT. Leptin and RPB4 were measured by immunoassay.

RESULTS

Insulin sensitivity decreased during the course of pregnancy. Insulin sensitivity and secretion were best explained by BMI and circulating leptin, but not RBP4, both in early and late pregnancy. However, a marked increase in fasting RBP4 from early to late pregnancy was observed, and this change was associated with a decline in insulin sensitivity. A marked increase in RBP4 was found during OGTT at weeks 14-16 with an opposite temporal course at weeks 30-32.

CONCLUSION

The increased fat mass and insulin resistance during normal pregnancy was best explained by measures of fat mass. However, the increase in RBP4 from early to late pregnancy, associated with a decline in insulin sensitivity, potentially indicates interactions with glucose metabolism.