Gene expression patterns of insulin-like growth factor 1, 2 (IGF-1, IGF-2) and insulin-like growth factor binding protein 3 (IGFBP-3) in human placenta from preterm deliveries: influence of additional factors

The effect of genistein on IGF-1, PlGF, sFLT-1 and fetoplacental development

The mechanisms by which genistein, a phytoestrogen, affects fetoplacental development adversely are still poorly understood. It is reported that genistein ingestion modulates thyroid functions, leptin hormone, C-reactive protein, and thyroxin kinase activities. In this study, we evaluated changes in serum and placental insulin-like growth factor-I (IGF-1), placental growth factor (PIGF), and soluble fms-like tyrosine kinase-1 (sFLT-1) in pregnant rats exposed to genistein using ELISA. According to the treatments, Rats were divided into control, 2 mg genistein, and 4 mg genistein groups. Genistein groups were administered with the doses orally from gestational day (GD) one onwards until sacrifice, while the control group received an equal volume of distilled water the vehicle. At GD-12, GD-16, and GD-20, serum samples and placenta homogenates were prepared from maternal blood samples and the placenta and were analysed to determine the concentration of IGF-1, sFLT-1, and PIGF. Serum IGF-1 and PIGF were both increased in all genistein groups at GD-12 and GD-16, and at GD-20 in the 4 mg group. However, serum IGF-1and PIGF levels were decreased in the placenta from all genistein groups at GD-20. Placenta sFLT-1 levels increased at both GD-16 and GD-20 in genistein-treated rat serum. An initial decrease in placental sFLT-1 at GD-12 was followed by an increase at GD-16 and finally a decrease at GD-20 in all genistein-treated rats. The sFL-1/PlGF ratio in placenta samples of genistein-exposed rats was decreased at GD-16 and increased at GD-20, while the reverse was recorded in the serum sample at the same gestational periods. The fetoplacental growth disruption mechanism of genistein can be partly explained by its interference with placental growth factor signalling.

Preterm birth and genitourinary tract infections: assessing gene-environment interaction

BACKGROUND

Preterm birth (PTB) is the leading cause of perinatal morbimortality worldwide. Genetic and environmental factors could raise PTB risk. The aim of this study was to analyze the contribution of the statistical interaction between genes and vaginal-urinary tract infections (VI-UTI) to the risk of PTB by clinical subtype.

METHODS

Twenty-four SNPs were genotyped in 18 candidate genes from 352 fetal triads and 106 maternal triads. Statistical interactions were evaluated with conditional logistic regression models based on genotypic transmission/disequilibrium test.

RESULTS

In PTB-idiopathic subtype mothers exposed to UTI, fetal SNPs rs11686474 (FSHR), rs4458044 (CRHR1, allele G), rs883319 (KCNN3), and maternal SNP rs1882435 (COL4A3) showed a nominal significant increment in prematurity risk. In preterm premature rupture of membranes (PPROM), fetal SNP rs2277698 (TIMP2) showed a nominal significant risk increment. In mothers exposed to VI, fetal SNP rs5742612 (IGF1) in PTB-PPROM and maternal SNP rs4458044 (CRHR1, allele C) in spontaneous PTB showed nominal significant increment in prematurity risk.

CONCLUSIONS

Certain maternal and fetal genes linked to infectious/inflammatory and hormonal regulation processes increase prematurity risk according to clinical subtype when mothers are exposed to UTI or VI. These findings may help in the understanding of PTB etiology and PTB prevention.

IMPACT

Preterm birth is a major cause of perinatal morbimortality worldwide and its etiology remains unknown. This work provides evidence on the statistical interaction of six genes with gestational vaginal or urinary infections leading to the occurrence of preterm births. Statistical interactions vary according to infection type, genotype (maternal and fetal), and clinical subtype of prematurity. Certain maternal and fetal genetic variants of genes linked to infectious/inflammatory and hormonal regulation processes would increase the risk of prematurity according to clinical subtype and infection type. Our findings may help in the study of etiology of preterm birth and its prevention.

An antibody-free LC-MS/MS method for the quantification of intact insulin-like growth factors 1 and 2 in human plasma

Insulin-like growth factors 1 and 2 (IGF-1 and IGF-2) are important biomarkers in research and diagnosis of growth disorders. Quantitative analysis is performed using various ligand-binding assays or enzymatic digestion LC-MS/MS methods, whose widespread adoption is hampered by time-consuming sample preparation procedures. We present a simple and fast antibody-free LC-MS/MS method for the quantification of intact IGF-1 and IGF-2 in human plasma. The method requires 50 μL of plasma and uses fully ¹⁵N-labelled IGF-1 as internal standard. It features trifluoroethanol (TFE)-based IGF/IGF-binding protein complex dissociation and a two-step selective protein precipitation workflow, using 5% acetic acid in 80/20 acetone/acetonitrile (precipitation 1) and ice-cold ethanol (precipitation 2). Detection of intact IGF-1 and IGF-2 is performed by means of a Waters XEVO TQ-S triple quadrupole mass spectrometer in positive electrospray ionisation (ESI+) mode. Lower limits of quantification were 5.9 ng/mL for IGF-1 and 8.4 ng/mL for IGF-2. Intra-assay imprecision was below 4.5% and inter-assay imprecision was below 5.8% for both analytes. An excellent correlation was found between nominal and measured concentrations of the WHO reference standard for IGF-1. Comparison with the IDS-iSYS IGF-1 immunoassay showed good correlation (R² > 0.97), although a significant bias was observed with the immunoassay giving substantially higher concentrations. The LC-MS/MS method described here allows for reliable and simultaneous quantification of IGF-1 and IGF-2 in plasma, without the need for enzymatic digestion. The method can be readily implemented in clinical mass spectrometry laboratories and has the potential to be adapted for the analysis of different similarly sized peptide hormones.

Placental phenotype and the insulin-like growth factors: resource allocation to fetal growth

The placenta is the main determinant of fetal growth and development in utero. It supplies all the nutrients and oxygen required for fetal growth and secretes hormones that facilitate maternal allocation of nutrients to the fetus. Furthermore, the placenta responds to nutritional and metabolic signals in the mother by altering its structural and functional phenotype, which can lead to changes in maternal resource allocation to the fetus. The molecular mechanisms by which the placenta senses and responds to environmental cues are poorly understood. This review discusses the role of the insulin-like growth factors (IGFs) in controlling placental resource allocation to fetal growth, particularly in response to adverse gestational environments. In particular, it assesses the impact of the IGFs and their signalling machinery on placental morphogenesis, substrate transport and hormone secretion, primarily in the laboratory species, although it draws on data from human and other species where relevant. It also considers the role of the IGFs as environmental signals in linking resource availability to fetal growth through changes in the morphological and functional phenotype of the placenta. As altered fetal growth is associated with increased perinatal morbidity and mortality and a greater risk of developing adult-onset diseases in later life, understanding the role of IGFs during pregnancy in regulating placental resource allocation to fetal growth is important for identifying the mechanisms underlying the developmental programming of offspring phenotype by suboptimal intrauterine growth.

Maternal IGF1 and IGF1R polymorphisms and the risk of spontaneous preterm birth

BACKGROUND

The insulin-like growth factor (IGF) pathway was involved in the occurrence of spontaneous preterm birth (SPTB), but little is known regarding the relationship between genetic variations in IGF pathway and the risk of SPTB. We aimed to investigate the associations of IGF1 rs972936 and IGF1 receptor (IGF1R) rs2229765 polymorphisms with SPTB risk in a Chinese population.

METHOD

A total of 114 cases of SPTB and 250 controls of term delivery were included from Guangzhou Women and Children's Medical Center, China. The odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were calculated using multivariate logistic regression.

RESULTS

We found that the GA and GA/AA genotypes of IGF1 rs972936 were associated with an increased risk of SPTB, and the adjusted ORs (95% CI) were 1.74 (1.01-3.02) and 1.75 (1.04-2.93) respectively. Women carrying GA and GA/AA genotypes of IGF1R rs2229765 had a reduced risk compared to those with the GG genotype (0.60 [0.37-0.98] and 0.64 [0.40-1.00] respectively). There were significant interactions between IGF1 rs972936 and GDM status (P for interaction=.02), as well as between IGF1R rs2229765 and pre-pregnancy BMI (P for interaction <.001) on the risk of SPTB.

CONCLUSION

Our findings suggest that polymorphisms of IGF1 rs972936 and IGF1R rs2229765 were associated with the risk of SPTB in Chinese pregnant women and these effects depend on the maternal metabolic status.

Targeted Sequencing and Meta-Analysis of Preterm Birth

Understanding the genetic contribution(s) to the risk of preterm birth may lead to the development of interventions for treatment, prediction and prevention. Twin studies suggest heritability of preterm birth is 36-40%. Large epidemiological analyses support a primary maternal origin for recurrence of preterm birth, with little effect of paternal or fetal genetic factors. We exploited an "extreme phenotype" of preterm birth to leverage the likelihood of genetic discovery. We compared variants identified by targeted sequencing of women with 2-3 generations of preterm birth with term controls without history of preterm birth. We used a meta-genomic, bi-clustering algorithm to identify gene sets coordinately associated with preterm birth. We identified 33 genes including 217 variants from 5 modules that were significantly different between cases and controls. The most frequently identified and connected genes in the exome library were IGF1, ATM and IQGAP2. Likewise, SOS1, RAF1 and AKT3 were most frequent in the haplotype library. Additionally, SERPINB8, AZU1 and WASF3 showed significant differences in abundance of variants in the univariate comparison of cases and controls. The biological processes impacted by these gene sets included: cell motility, migration and locomotion; response to glucocorticoid stimulus; signal transduction; metabolic regulation and control of apoptosis.

[Association between IGF system and PAPP-A in coronary atherosclerosis]

Atherosclerosis is a condition that involves multiple pathophysiological mechanisms and whose knowledge has not been fully elucidated. Often, scientific advances on the atherogenic pathophysiology generate that molecules not previously considered in the scene of this disease, were attributed actions on the onset or progression of it. A representative example is the study of a new mechanism involved in the atherogenic process, consisting of the association between the insulin-like growth factor (IGF) system and pregnancy-associated plasma protein-A (PAPP-A). Insulin-like growth factor system is a family of peptides that include 3 peptide hormones, 4 transmembrane receptors and 6 binding proteins. Insulin-like growth factor-1 (IGF-1) is the main ligand of the IGF system involved in coronary atherosclerosis. IGF-1 exerts its effects via activation of the IGF-1R receptor on vascular smooth muscle cells or macrophages. In vascular smooth muscle cells promotes migration and prevents apoptosis which increases plaque stability while in macrophages reduces reverse cholesterol transport leading to the formation of foam cells. Regulation of IGF-1 endothelial bioavailability is carried out by IGFBP proteases, mainly by PAPP-A. In this review, we address the mechanisms between IGF system and PAPP-A in atherosclerosis with emphasis on molecular effects on vascular smooth muscle cells and macrophages.

Insulin-like growth factor axis in pregnancies affected by fetal growth disorders

Background

Insulin-like growth factors 1 and 2 (IGF1 and IGF2) and their binding proteins (IGFBPs) are expressed in the placenta and known to regulate fetal growth. DNA methylation is an epigenetic mechanism which involves addition of methyl group to a cytosine base in the DNA forming a methylated cytosine-phosphate-guanine (CpG) dinucleotide which is known to silence gene expression. This silences gene expression, potentially altering the expression of IGFs and their binding proteins. This study investigates the relationship between DNA methylation of components of the IGF axis in the placenta and disorders in fetal growth. Placental samples were obtained from cord insertions immediately after delivery from appropriate, small (defined as birthweight <10th percentile for the gestation [SGA]) and macrosomic (defined as birthweight > the 90th percentile for the gestation [LGA]) neonates. Placental DNA methylation, mRNA expression and protein levels of components of the IGF axis were determined by pyrosequencing, rtPCR and Western blotting.

Results

In the placenta from small for gestational age (SGA) neonates (n = 16), mRNA and protein levels of IGF1 were lower and of IGFBPs (1, 2, 3, 4 and 7) were higher (p < 0.05) compared to appropriately grown neonates (n = 37). In contrast, in the placenta from large for gestational age (LGA) neonates (n = 20), mRNA and protein levels of IGF1 was not different and those of IGFBPs (1, 2, 3 and 4) were lower (p < 0.05) compared to appropriately grown neonates. Compared to appropriately grown neonates, CpG methylation of the promoter regions of IGF1 was higher in SGA neonates. The CpG methylation of the promoter regions of IGFBP1, IGFBP2, IGFBP3, IGFBP4 and IGFBP7 was lower in the placenta from SGA neonates as compared to appropriately grown neonates, but was unchanged in the placenta from LGA neonates.

Conclusions

Our results suggest that changes in CpG methylation contribute to the changes in gene expression of components of the IGF axis in fetal growth disorders. Differential methylation of the IGF1 gene and its binding proteins is likely to play a role in the pathogenesis of SGA neonates.

Placental gene expression of transforming growth factor beta 1 (TGF-β1) in small for gestational age newborns

OBJECTIVE

The gene expression of transforming growth factor beta-1 (TGF-β1) in human placental samples obtained from pregnancies with small for gestational age fetuses (SGA) was compared to those of normal pregnancies.

METHODS

In 2011 placental samples from 101 pregnancies with SGA and from 140 normal pregnancies were obtained for analysis of TGF-β1 gene expression. Several clinical parameters were also assessed for correlation between genetic and clinical parameters.

RESULTS

There were no significant differences in gene activity of the TGF-β1 gene between the SGA versus normal pregnancy groups (Ln2α: 0.16; p = 0.07). Within the SGA group, no fetal gender-dependent differences were seen in TGF-β1 gene expression (Ln2α: −0.11; p = 0.05). Similarly, no significant differences in gene activity were observed by the degree of severity of SGA as assessed by percentile fetal birth-weight (Ln2α: 0.32; p = 0.06).

CONCLUSION

We found no change in gene expression of TGF-β1 in placental samples obtained from SGA pregnancies versus normal pregnancy suggesting an absence of a direct role of the TGF-β1 gene in the development of SGA. However, the absence of increased gene expression of TGF-β1 in SGA can be conceptualized as a failure to mount a compensatory response in the SGA environment.

Maternal nutritional history modulates the hepatic IGF-IGFBP axis in adult male rat offspring

Alterations in early life nutrition lead to an increased risk of obesity and metabolic syndrome in offspring. We have shown that both relative maternal undernutrition (UN) and maternal obesity result in metabolic derangements in offspring, independent of the postnatal dietary environment. Since insulin-like growth factor binding protein 2 (IGFBP2) has been shown to be independently associated with obesity and diabetes risk, we examined the IGF-IGFBP axis in male rat offspring following either maternal UN or maternal obesity to explain possible common pathways in the development of metabolic disorders. Wistar rats were time-mated and fed either a control diet (CONT), 50 % of CONT (UN) or a high-fat (HF) diet throughout pregnancy. Male offspring were weaned onto a standard chow diet and blood and tissues were collected at postnatal day 160. Plasma and hepatic tissue samples were analysed for key players in the IGF-IGFBP system. Both maternal UN and HF resulted in increased fat mass, hyperinsulinemia, hyperleptinemia and altered blood lipid profiles in offspring compared to CONT. Circulating IGF-1 and IGFBP3 levels and hepatic mRNA expression of IGFBP1 and IGFBP2 were significantly decreased in UN and HF offspring compared to CONT. DNA methylation of the IGFBP2 promotor region was similar between maternal dietary groups. Although chaperone gene heat-shock protein 90 and hepatic IGFBP1 were significantly correlated in CONT offspring this effect was absent in both UN and HF offspring. In conclusion, this study is one of the first to directly compare two experimental models of developmental programming representing both ends of the maternal dietary spectrum. Our data suggest that two disparate nutritional models that elicit similar adverse metabolic phenotypes in offspring are characterised by common alterations in the IGF-IGFBP pathway.

Paternally expressed, imprinted insulin-like growth factor-2 in chorionic villi correlates significantly with birth weight

Context

Fetal growth involves highly complex molecular pathways. IGF2 is a key paternally expressed growth hormone that is critical for in utero growth in mice. Its role in human fetal growth has remained ambiguous, as it has only been studied in term tissues. Conversely the maternally expressed growth suppressor, PHLDA2, has a significant negative correlation between its term placental expression and birth weight.

Objective

The aim of this study is to address the role in early gestation of expression of IGF1, IGF2, their receptors IGF1R and IGF2R, and PHLDA2 on term birth weight.

Design

Real-time quantitative PCR was used to investigate mRNA expression of IGF1, IGF2, IGF1R, IGF2R and PHLDA2 in chorionic villus samples (CVS) (n = 260) collected at 11–13 weeks' gestation. Expression was correlated with term birth weight using statistical package R including correction for several confounding factors.

Results

Transcript levels of IGF2 and IGF2R revealed a significant positive correlation with birth weight (0.009 and 0.04, respectively). No effect was observed for IGF1, IGF1R or PHLDA2 and birth weight. Critically, small for gestational age (SGA) neonates had significantly lower IGF2 levels than appropriate for gestational age neonates (p = 3·6×10⁻⁷).

Interpretation

Our findings show that IGF2 mRNA levels at 12 weeks gestation could provide a useful predictor of future fetal growth to term, potentially predicting SGA babies. SGA babies are known to be at a higher risk for type 2 diabetes. This research reveals an imprinted, parentally driven rheostat for in utero growth.

Retinopathy of prematurity

The immature retinas of preterm neonates are susceptible to insults that disrupt neurovascular growth, leading to retinopathy of prematurity. Suppression of growth factors due to hyperoxia and loss of the maternal-fetal interaction result in an arrest of retinal vascularisation (phase 1). Subsequently, the increasingly metabolically active, yet poorly vascularised, retina becomes hypoxic, stimulating growth factor-induced vasoproliferation (phase 2), which can cause retinal detachment. In very premature infants, controlled oxygen administration reduces but does not eliminate retinopathy of prematurity. Identification and control of factors that contribute to development of retinopathy of prematurity is essential to prevent progression to severe sight-threatening disease and to limit comorbidities with which the disease shares modifiable risk factors. Strategies to prevent retinopathy of prematurity will depend on optimisation of oxygen saturation, nutrition, and normalisation of concentrations of essential factors such as insulin-like growth factor 1 and ω-3 polyunsaturated fatty acids, as well as curbing of the effects of infection and inflammation to promote normal growth and limit suppression of neurovascular development.

Chronic morbidities of premature newborns

The most important chronic morbidities of premature newborns, deeply influencing quality of life, are retinopathy of prematurity, bronchopulmonary dysplasia, intraventricular hemorrhage and periventricular leukomalacia. Since the rate of premature birth has not decreased in recent years in Hungary, and treatments of these end stage disorders are extremely difficult, prevention gains tremendous significance. Effective prevention is based on detailed knowledge of the pathophysiological mechanisms of these special diseases having multifactorial nature sharing several common risk factors, and one is the pathological angiogenesis. This sensitive system is affected by several stress situations which are the consequences of prematurity leading to abnormal vascular growth. After birth, relative hyperoxia, compared to intrauterine life, and decreasing concentrations of vascular growth factors result in vascular injury, moreover, may cause vessel apoptosis. The consequence of this phenomenon is the activation of hypoxia responsible genes resulting in robust pathological neovascularization and organ damage during the later phase. Saving normal angiogenesis and inhibiting reactive neovascularization may lead to better quality of life in these premature infants. Orv. Hetil., 2013, 154, 1498–1511.

Placental gene expression patterns of epidermal growth factor in intrauterine growth restriction

OBJECTIVE

In this study, we compared human placental gene expression patterns of epidermal growth factor (EGF) in pregnancies with intrauterine growth restriction (IUGR) vs. normal pregnancies as control.

STUDY DESIGN

Gene expression of EGF was determined from human placental samples collected from all pregnancies presenting with IUGR at our institution during the study period January 1, 2010-January 1, 2011. Multiple clinical variables were also assessed including maternal age, gestational weight gain, increase of BMI during pregnancy and fetal gender.

RESULTS

A total of 241 samples were obtained (101 in the IUGR pregnancy group, 140 in the normal pregnancy group). EGF was found to be underexpressed in the IUGR group compared to normal pregnancy (Ln2(α): -1.54; p<0.04). Within the IUGR group no fetal gender-dependent difference was seen in EGF gene expression (Ln2(α): 0.44; p<0.06). Similarly, no significant difference in EGF expression was noted in cases with more vs. less severe forms of IUGR (Ln2(α): -0.08; p=0.05). IUGR pregnancies were significantly more common in the maternal age group 35-44 years compared to other age groups. Gestational weight gain and gestational BMI increase were significantly lower in IUGR pregnancies compared to controls.

CONCLUSIONS

Placental expression of EGF was found to be reduced in IUGR pregnancies vs. normal pregnancies. This may partly explain the smaller placental size and placental dysfunction commonly seen with IUGR. An increased incidence of IUGR was observed with maternal age exceeding 35 years. The probability of IUGR correlated with lower gestational weight gain and lower BMI increase during pregnancy.

The obstetric syndromes: clinical relevance of placental hormones

Preterm delivery, preeclampsia and intrauterine growth restriction are the major diseases of pregnancy. A key role in their pathogenesis is played by the placenta, which is the source of hormones and other important regulatory molecules providing the metabolic and endocrine homeostasis of the fetal-placental unit. Since obstetric syndromes are characterized by important maternal and neonatal morbidity and mortality worldwide, numerous efforts have been made over the years to prevent and treat them. Due to their complex pathogenesis, however, the therapy is poor and not very effective. Therefore, great emphasis is currently given to the prevention of these diseases through the identification of biochemical and biophysical markers, among which placental factors play a crucial role. The increasing knowledge of the role of placental molecules can indeed lead to the development of new therapeutic and diagnostic tools.

Genetic and non-genetic influences during pregnancy on infant global and site specific DNA methylation: role for folate gene variants and vitamin B12

Inter-individual variation in patterns of DNA methylation at birth can be explained by the influence of environmental, genetic and stochastic factors. This study investigates the genetic and non-genetic determinants of variation in DNA methylation in human infants. Given its central role in provision of methyl groups for DNA methylation, this study focuses on aspects of folate metabolism. Global (LUMA) and gene specific (IGF2, ZNT5, IGFBP3) DNA methylation were quantified in 430 infants by Pyrosequencing®. Seven polymorphisms in 6 genes (MTHFR, MTRR, FOLH1, CβS, RFC1, SHMT) involved in folate absorption and metabolism were analysed in DNA from both infants and mothers. Red blood cell folate and serum vitamin B₁₂ concentrations were measured as indices of vitamin status. Relationships between DNA methylation patterns and several covariates viz. sex, gestation length, maternal and infant red cell folate, maternal and infant serum vitamin B₁₂, maternal age, smoking and genotype were tested. Length of gestation correlated positively with IGF2 methylation (rho = 0.11, p = 0.032) and inversely with ZNT5 methylation (rho = −0.13, p = 0.017). Methylation of the IGFBP3 locus correlated inversely with infant vitamin B₁₂ concentration (rho = −0.16, p = 0.007), whilst global DNA methylation correlated inversely with maternal vitamin B₁₂ concentrations (rho = 0.18, p = 0.044). Analysis of common genetic variants in folate pathway genes highlighted several associations including infant MTRR 66G>A genotype with DNA methylation (χ² = 8.82, p = 0.003) and maternal MTHFR 677C>T genotype with IGF2 methylation (χ² = 2.77, p = 0.006). These data support the hypothesis that both environmental and genetic factors involved in one-carbon metabolism influence DNA methylation in infants. Specifically, the findings highlight the importance of vitamin B₁₂ status, infant MTRR genotype and maternal MTHFR genotype, all of which may influence the supply of methyl groups for DNA methylation. In addition, gestational length appears to be an important determinant of infant DNA methylation patterns.