Circulating levels of IGF-I and IGF-binding protein-1 throughout pregnancy: relation to birthweight and maternal weight

Regulation of placental amino acid transport in health and disease

Abnormal fetal growth, i.e., intrauterine growth restriction (IUGR) or fetal growth restriction (FGR) and fetal overgrowth, is associated with increased perinatal morbidity and mortality and is strongly linked to the development of metabolic and cardiovascular disease in childhood and later in life. Emerging evidence suggests that changes in placental amino acid transport may contribute to abnormal fetal growth. This review is focused on amino acid transport in the human placenta, however, relevant animal models will be discussed to add mechanistic insights. At least 25 distinct amino acid transporters with different characteristics and substrate preferences have been identified in the human placenta. Of these, System A, transporting neutral nonessential amino acids, and System L, mediating the transport of essential amino acids, have been studied in some detail. Importantly, decreased placental Systems A and L transporter activity is strongly associated with IUGR and increased placental activity of these two amino acid transporters has been linked to fetal overgrowth in human pregnancy. An array of factors in the maternal circulation, including insulin, IGF-1, and adiponectin, and placental signaling pathways such as mTOR, have been identified as key regulators of placental Systems A and L. Studies using trophoblast-specific gene targeting in mice have provided compelling evidence that changes in placental Systems A and L are mechanistically linked to altered fetal growth. It is possible that targeting specific placental amino acid transporters or their upstream regulators represents a novel intervention to alleviate the short- and long-term consequences of abnormal fetal growth in the future.

Fetal growth regulation via insulin-like growth factor axis in normal and diabetic pregnancy

OBJECTIVES

Diabetes mellitus (DM) in pregnancy and gestational diabetes remain a considerable cause of pregnancy complications, and fetal macrosomia is among them. Insulin, insulin-like growth factors (IGFs), and components of their signal-transduction axes belong to the predominant growth regulators and are implicated in glucose homeostasis. This study aimed to evaluate the available evidence on the association between the IGF axis and fetal anthropometric parameters in human diabetic pregnancy.

METHODS

PubMed, Medline, Web of Science, and CNKI databases (1981-2021) were searched.

RESULTS

Maternal and cord serum IGF-I levels are suggested to be positively associated with weight and length of neonates born to mothers with type 1 DM. The results concerning IGF-II and IGFBPs in type 1 DM or any of the IGF axis components in type 2 DM remain controversial. The alterations of maternal serum IGFs concentrations throughout diabetic and non-diabetic pregnancy do not appear to be the same. Maternal 1st trimester IGF-I level is positively associated with fetal birth weight in DM.

CONCLUSIONS

Research on the IGF axis should take gestational age of sampling, presence of DM, and insulin administration into account. Maternal 1st trimester IGF-I level might become a predictor for macrosomia development in diabetic pregnancy.

Circulating Insulin and IGF-1 and Frequency of Food Consumption during Pregnancy as Predictors of Birth Weight and Length

The aim of the study was to assess the relationships between maternal insulin and insulin-like growth factor-1 (IGF-1) concentration and food consumption frequency and the birth parameters of the newborn. A total of 157 mother-newborn pairs participated in the study. The study showed that more frequent consumption of sweet and salty snacks as well as fruit and fruit or vegetable juices may promote greater weight gain in pregnancy and higher newborn birth weight. A significantly higher insulin concentration was found among overweight women according to body mass index (BMI), and a significantly lower concentration of IGF-1 was demonstrated among women ≥35 years of age. There was no significant correlation between the concentration of insulin and IGF-1 in the mother’s blood plasma and the birth weight and length of the newborn. A significant relationship was only found between the concentration of IGF-1 in the mother’s blood and the Ponderal index of the newborn. A woman’s eating habits during pregnancy have a significant impact on the mother’s health and on the proper growth and development of the foetus.

Exploration of the potential roles of m6A regulators in the uterus in pregnancy and infertility

Infertility is a prevalent female reproductive disease worldwide. Currently, there are many unknown etiologies of infertility. N6-methyladenosine (m6A) is the most prevalent modification of eukaryotic mRNA. This study intended to investigate the implications of m6A regulators in the uterus for pregnancy and infertility. Pregnant ICR mice on days (D) 0, 4, 6, 10, and 15 were used to monitor m6A methylation in the uterus by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and then m6A methylation regulators were detected by real-time quantitative PCR (qPCR), western blot and immunohistochemistry (IHC). We found that m6A levels increased and that m6A regulators were expressed differently in the uterus during pregnancy. Then, we acquired expression data from endometrial tissue from women with infertility and recurrent pregnancy loss from the Gene Expression Omnibus (GEO) database. The expression of m6A regulators in infertility was significantly dysregulated according to the data mining technique. Specifically, the mRNA levels of METTL16 (p = 0.0147) and WTAP (p = 0.028) were lower and those of ALKBH5 (p = 0.0432) and IGF2BP2 (p = 0.0016) were higher in the endometrium of infertile patients. Meanwhile, many immunity-related pathways are abnormal in infertility, such as cytokine-cytokine receptor interactions, natural killer cell-mediated cytotoxicity and leukocyte transendothelial migration. In conclusion, we found that the m6A levels in the uterus increased as pregnancy progressed, and these regulators were dysregulated in the endometrium of infertility patients. These results suggest that m6A methylation may be very important in the establishment of implantation and maintenance of pregnancy and may become a new direction for research on infertility.

Dysregulation of the interleukin-17A pathway in endometrial tissue from women with unexplained infertility affects pregnancy outcome following assisted reproductive treatment

STUDY QUESTION

Which transcriptomic alterations in mid-luteal endometrial scratch biopsies, taken prior to the assisted reproductive treatment (ART) treatment cycle are associated with unsuccessful pregnancy?

SUMMARY ANSWER

Dysregulated interleukin-17 (IL-17) pathway components are demonstrated in women who fail to become pregnant after ART.

WHAT IS KNOWN ALREADY

Implantation failure is now recognised as a critical factor in unexplained infertility and may be an important component of failed ART.

STUDY DESIGN, SIZE, DURATION

Using a prospective longitudinal study design, 29 nulliparous women with unexplained infertility undergoing ART were recruited between October 2016 and February 2018. Mid-luteal stage endometrium and matched serum samples were collected, and patients underwent a single embryo transfer in the subsequent cycle. RNA-seq analysis of endometrial biopsies was performed on the discovery cohort (n = 20).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Gene set enrichment analysis of the differentially expressed genes (DEGs) was performed. Endometrium and serum were then prepared for IL-17A analysis by ELISA.

MAIN RESULTS AND THE ROLE OF CHANCE

There were 204 differentially expressed protein-coding genes identified in tissue from women who became pregnant (n = 9) compared with tissue from women who failed to become pregnant (n = 11) (false discovery rate; P < 0.05). Of the 204 DEGs, 166 were decreased while 38 were increased in the pregnant compared to the non-pregnant groups. Gene set enrichment analysis of the DEGs identified an over-representation of IL-17 and Pl3K-Akt signalling pathways. All the DEGs within the IL-17 signalling pathway (MMP3, MMP1, IL1β, LCN2, S100A9 and FOSL1) demonstrated decreased expression in the pregnant group. Serum IL-17 protein levels were increased in the non-pregnant discovery cohort (n = 11) and these findings were confirmed a validation cohort (n = 9).

LIMITATIONS, REASONS FOR CAUTION

Limitations of our study include the cohort size and the lack of aneuploidy data for the embryos; however, all embryos transferred were single good or top-quality blastocysts.

WIDER IMPLICATIONS OF THE FINDINGS

These findings demonstrate dysregulated IL-17 pathway components in women who fail to become pregnant after ART. Elevated serum levels of the pro-inflammatory cytokine IL-17 may predict failure of ART in women with unexplained infertility. Future trials of anti-IL-17 therapies in this cohort warrant further investigation.

STUDY FUNDING/COMPETING INTEREST(S)

Funding from the UCD Wellcome Institutional Strategic Support Fund, which was financed jointly by University College Dublin and the SFI-HRB-Wellcome Biomedical Research Partnership (ref 204844/Z/16/Z), is acknowledged. The authors have no competing interests.

TRIAL REGISTRATION NUMBER

NA.

Stunting at birth and associated factors among newborns delivered at the University of Gondar Comprehensive Specialized Referral Hospital

Background

Stunting at birth is a chronic form of undernutrition majorly attributable to poor prenatal nutrition, which could persist in children’s later life and impact their physical and cognitive health. Although multiple studies have been conducted in Ethiopia to show the magnitude of stunting and factors, all are concentrated on children aged between 6 to 59 months. Therefore, this study was done to determine the prevalence and associated factors of stunting at birth among newborns delivered at the University of Gondar Comprehensive Specialized Referral Hospital, Northwest, Ethiopia.

Methods

An institution-based cross-sectional study was conducted from February 26^th to April 25^th/2020. A systematic random sampling technique was used, to select a total of 422 newborn-mother pairs. The binary logistic regression was employed to identify factors associated with stunting and all independent variables were entered into the multivariable logistic regression model to adjust for confounders. Variables that had significant association were identified based on p-value < 0.05 and the adjusted odds ratio with its respective 95% confidence interval was applied to determine the strength as well as the direction of the association.

Results

About 30.5% (95% CI: 26.3%, 35.1%) of newborns were stunted at birth. Being male [Adjusted odds ratio (AOR) = 2.9(1.62, 5.21)], newborns conceived in Kiremt(rainy season) [AOR = 2.7(1.49, 4.97)], being low birth weight [AOR = 3.1(1.64, 6.06)] were factors associated with stunting at birth. Likewise, newborns born to short stature mothers [AOR = 2.8(1.21, 6.62)] and chronically malnourished mothers [AOR = 15.3(8.12, 29.1)] were at greater risk of being stunted.

Conclusion

Just under a third of newborns are stunted at birth, implying a pressing public health problem. Newborns born to chronically malnourished and short stature mothers were more stunted. Besides, stunting was prevalently observed among male neonates, newborns conceived in Kiremet, and being low birth weight. Thus, policymakers and nutrition programmers should work on preventing maternal undernutrition through nutrition education to reduce the burden of low birth weight and stunting. Further, paying due attention to newborns conceived in Kiremet season to improve nutritional status is recommended.

Early pregnancy serum IGFBP-1 relates to lipid profile in overweight and obese women

Lower level of insulin-like growth factor-binding protein (IGFBP-1) has been observed in insulin resistance, while higher level of matrix metalloproteinase-8 (MMP-8) has been linked to obesity. The aim here was to study in overweight and obese women, typically manifesting with insulin resistance, whether IGFBP-1 and MMP-8 are related to and reflect systemic low-grade inflammation, metabolism and diet. Fasting serum from overweight and obese pregnant women (n = 100) in early pregnancy were analysed for IGFBP-1, phosphorylated IGFBP-1 (phIGFBP-1) and MMP-8. High-sensitivity CRP and GlycA were used as markers for low grade inflammation. GlycA and lipids were quantified using NMR. IGFBP-1 associated negatively with GlycA, evidenced by higher concentrations in the lowest quartile (median 1.53 (IQR 1.45–1.72)) compared to the highest (1.46 (1.39–1.55)) (P = 0.03). Several lipid metabolites, particularly HDL-cholesterol, correlated inversely with phIGFBP-1 (FDR<0.1). Nutritional status and diet contributed to the levels of IGFBP-1, demonstrated as an inverse correlation with maternal weight (Spearman r = -0.205, P = 0.04) and dietary intake of vitamin A (r = -0.253, P = 0.014) and a direct correlation with dietary intake of polyunsaturated fatty acids (Spearman r = 0.222, P = 0.03). MMP-8 correlated inversely with pyridoxine (r = -0.321, P = 0.002) and potassium (r = -0.220, P = 0.033). Maternal serum IGFBP-1 may contribute to maternal lipid metabolism in overweight and obese women during early pregnancy. These findings may be of importance in identification of metabolic disturbances preceding the adverse metabolic outcomes in pregnancy.

Novel roles of mechanistic target of rapamycin signaling in regulating fetal growth†

Mechanistic target of rapamycin (mTOR) signaling functions as a central regulator of cellular metabolism, growth, and survival in response to hormones, growth factors, nutrients, energy, and stress signals. Mechanistic TOR is therefore critical for the growth of most fetal organs, and global mTOR deletion is embryonic lethal. This review discusses emerging evidence suggesting that mTOR signaling also has a role as a critical hub in the overall homeostatic control of fetal growth, adjusting the fetal growth trajectory according to the ability of the maternal supply line to support fetal growth. In the fetus, liver mTOR governs the secretion and phosphorylation of insulin-like growth factor binding protein 1 (IGFBP-1) thereby controlling the bioavailability of insulin-like growth factors (IGF-I and IGF-II), which function as important growth hormones during fetal life. In the placenta, mTOR responds to a large number of growth-related signals, including amino acids, glucose, oxygen, folate, and growth factors, to regulate trophoblast mitochondrial respiration, nutrient transport, and protein synthesis, thereby influencing fetal growth. In the maternal compartment, mTOR is an integral part of a decidual nutrient sensor which links oxygen and nutrient availability to the phosphorylation of IGFBP-1 with preferential effects on the bioavailability of IGF-I in the maternal-fetal interface and in the maternal circulation. These new roles of mTOR signaling in the regulation fetal growth will help us better understand the molecular underpinnings of abnormal fetal growth, such as intrauterine growth restriction and fetal overgrowth, and may represent novel avenues for diagnostics and intervention in important pregnancy complications.

The IGF system and longitudinal growth in preterm infants in relation to gestational age, birth weight and gender

OBJECTIVE

Growth factors in the blood of very preterm infants may reflect growth and contribute to the understanding of early development. We investigated postnatal levels of insulin-like growth factors (IGFs) in infants born very preterm and related them to early growth development.

DESIGN

Blood samples were analyzed weekly for IGF-I, IGF-II, IGF binding protein (BP)-1, IGFBP-3, and acid-label subunit (ALS).

METHODS

73 children born very preterm (gestational age (GA) <32 weeks) were divided according to their gender-specific birth weight standard deviation score (SDS) into either appropriate for GA (AGA) or small for GA (SGA). Fifty-two (71%) and forty-three (59%) infants completed follow-up with anthropometry at approximately 3 years and at 5 years of age respectively. Thirty-six subjects (49%) had blood sampling for IGF-I and IGFBP-3 measurements up to 3 years of age.

RESULTS

IGF-I, IGFBP-3, and ALS levels increased in all groups from week 31 to week 36, with generally lower levels in the SGAs, with a concomitant lower growth velocity. Postnatal ALS was strongly associated with IGF-I and IGFBP-3 in boys, girls and AGA infants. IGF-II was higher in earlier born preterms (GA < 27 weeks) at postmenstrual ages 27.5-29.9 weeks compared with SGAs and late GA (GA ≥ 27 weeks) preterms (p < .0001). IGF-II, in contrast to IGF-I, did not differ between SGAs and AGAs at weeks 31-36. Mean IGFBP-1 was highest in the SGAs compared to AGAs at mean week 28,5 and 31 (p = .001) and IGFBP-1 levels were elevated in relation to IGF-I in the SGAs at that period. At follow-up, the increase in IGF-I between week 31 and 33.5 was a significant positive determinant of height SDS at 3 and 5 years of age in forward multiple regression analysis, independent of target height.

CONCLUSION

This is the first study to investigate postnatal ALS levels in preterm infants. In very preterm infants, IGF-II is less affected by size at birth during early postnatal weeks compared with IGF-I. Early elevated IGFBP-1 might protect the SGA infants from an intense metabolic rate. Our results indicate that anabolic and metabolic processes during weeks 31-36 predicts later height.

IUGR Is Associated With Marked Hyperphosphorylation of Decidual and Maternal Plasma IGFBP-1

CONTEXT

The mechanisms underpinning intrauterine growth restriction (IUGR), as a result of placental insufficiency, remain poorly understood, no specific treatment is available, and clinically useful biomarkers for early detection are lacking.

OBJECTIVE

We hypothesized that human IUGR is associated with inhibition of mechanistic target of rapamycin (mTOR) and activation of amino acid response (AAR) signaling, increased protein kinase casein kinase-2 (CK2) activity, and increased insulin-like growth factor-binding protein 1 (IGFBP-1) expression and phosphorylation in decidua and that maternal plasma IGFBP-1 hyperphosphorylation in the first trimester predicts later development of IUGR.

DESIGN, SETTING, AND PARTICIPANTS

Decidua [n = 16 appropriate-for-gestational age (AGA); n = 16 IUGR] and maternal plasma (n = 13 AGA; n = 13 IUGR) were collected at delivery from two different cohorts. In addition, maternal plasma was obtained in the late first trimester from a third cohort of women (n = 7) who later delivered an AGA or IUGR infant.

MAIN OUTCOME MEASURES

Total IGFBP-1 expression and phosphorylation (Ser101/Ser119/Ser169), mTOR, AAR, and CK2 activity in decidua and IGFBP-1 concentration and phosphorylation in maternal plasma.

RESULTS

We show that decidual IGFBP-1 expression and phosphorylation are increased, mTOR is markedly inhibited, and AAR and CK2 are activated in IUGR. Moreover, IGFBP-1 hyperphosphorylation in first-trimester maternal plasma is associated with the development of IUGR.

CONCLUSIONS

These data are consistent with the possibility that the decidua functions as a nutrient sensor linking limited oxygen and nutrient availability to increased IGFBP-1 phosphorylation, possibly mediated by mTOR and AAR signaling. IGFBP-1 hyperphosphorylation in first-trimester maternal plasma may serve as a predictive IUGR biomarker, allowing early intervention.

Complex, coordinated and highly regulated changes in placental signaling and nutrient transport capacity in IUGR

The most common cause of intrauterine growth restriction (IUGR) in the developed world is placental insufficiency, a concept often used synonymously with reduced utero-placental and umbilical blood flows. However, placental insufficiency and IUGR are associated with complex, coordinated and highly regulated changes in placental signaling and nutrient transport including inhibition of insulin and mTOR signaling and down-regulation of specific amino acid transporters, Na⁺/K⁺-ATPase, the Na^+/H⁺-exchanger, folate and lactate transporters. In contrast, placental glucose transport capacity is unaltered and Ca²⁺-ATPase activity and the expression of proteins involved in placental lipid transport are increased in IUGR. These findings are not entirely consistent with the traditional view that the placenta is dysfunctional in IUGR, but rather suggest that the placenta adapts to reduce fetal growth in response to an inability of the mother to allocate resources to the fetus. This new model has implications for the understanding of the mechanisms underpinning IUGR and for the development of intervention strategies.

The correlation between birth weight and insulin-like growth factor-binding protein-1 (IGFBP-1), kisspeptin-1 (KISS-1), and three-dimensional fetal volume

PURPOSE

This study aimed to determine the relationship between birth weight, and maternal serum insulin-like growth factor-binding protein-1 (IGFBP-1) and kisspeptin-1 (KISS-1) levels, and first-trimester fetal volume (FV) based on three-dimensional ultrasonography.

MATERIALS AND METHODS

The study included 142 pregnant women at gestational week 11°-13⁶. All fetuses were imaged ultrasonographically by the same physician. Maternal blood samples were collected at the time of ultrasonographic evaluation and analyzed for IGFBP-1 and KISS-1 levels via enzyme-linked immunosorbent assay (ELISA). Maternal and neonatal weights were recorded at birth. Birth weight ≤10th and the >90th percentiles was defined as small and large for gestational age (SGA and LGA), respectively.

RESULTS

Median crown-rump length (CRL), FV, and maternal serum IGFBP-1 and KISS-1 levels were 58.2 mm (35.3-79.2 mm), 16.3 cm³ (3.8-34.4 cm³), 68.1 ng mL^-1 (3.8-377.9 mL^-1), and 99.7 ng L^-1 (42.1-965.3 ng L^-1), respectively. First-trimester IGFBP-1 levels were significantly lower in the mothers with LGA neonates (p < .05). There was a significant positive correlation between CRL and FV, and between the IGFBP-1 and KISS-1 levels. IGFBP-1 levels and maternal weight at delivery were negatively correlated with neonatal birth weight. There was no correlation between CRL or FV and maternal IGFBP-1 or KISS1 levels (p > .05). The maternal IGFBP-1 level during the first trimester was a significant independent factor for SGA and LGA neonates (Odds ratio (OR): 0.011, 95%CI: 1.005-1.018, p < .001; and OR: 1.297, 95%CI: 1.074-1.566, p = .007, respectively). There was no significant relationship between SGA or LGA, and CRL, FV, or the KISS-1 level.

CONCLUSIONS

As compared to the maternal KISS-1 level, the maternal IGFBP-1 level during the first trimester might be a better biomarker of fetal growth. Additional larger scale studies are needed to further delineate the utility of IGFBP-1 as a marker of abnormal birth weight.

Cytokines, growth factors and macromolecules as mediators of implantation in mammalian species

Implantation is one of the most critical steps in mammalian reproduction and implantation failure constitutes a major cause of infertility in both animals and humans. The mechanism of implantation is exclusively under the control of ovarian steroids progesterone and oestrogen whose actions are mediated in a complex phenomenon that involves a number of cytokines and growth factors. According to a plethora of literature on implantation in mammalian species, prominent of these cytokines and growth factor playing crucial roles in implantation include integrin, osteopontin, integrin, insulin-like growth factor and leukaemia inhibitory factor. Others are cluster domain 44, hyaluronan system and many non-adhesive molecules such as glycoprotein mucin 1. In this review, the specific roles played by these molecules are expatiated. Generally, they function as adhesive molecules that facilitate attachment of ligands/proteins on the trophectoderm to their respective receptors on endometrial luminal epithelia or vice versa. Sometimes, they also function as signalling molecules that enhance communication between implanting blastocyst and receptive endometrium. This is of particular importance in embryo culture and embryo transfer where in vitro derived blastocyst unlike the in vivo condition, is not exposed to these substances and hence, their absence may be partly responsible for the low implantation rate observed in the surrogate. Appreciation of the roles played by these cytokines, growth factors and molecules as revealed in this review will spur further research on these topics, facilitate their inclusion in embryo culture media (if positively required) and are considered as vital aspect while developing strategies to improve fertility.

The maternal plasma proteome changes as a function of gestational age in normal pregnancy: a longitudinal study

OBJECTIVE

Pregnancy is accompanied by dramatic physiological changes in maternal plasma proteins. Characterization of the maternal plasma proteome in normal pregnancy is an essential step for understanding changes to predict pregnancy outcome. The objective of this study was to describe maternal plasma proteins that change in abundance with advancing gestational age and determine biological processes that are perturbed in normal pregnancy.

STUDY DESIGN

A longitudinal study included 43 normal pregnancies that had a term delivery of an infant who was appropriate for gestational age without maternal or neonatal complications. For each pregnancy, 3 to 6 maternal plasma samples (median, 5) were profiled to measure the abundance of 1125 proteins using multiplex assays. Linear mixed-effects models with polynomial splines were used to model protein abundance as a function of gestational age, and the significance of the association was inferred via likelihood ratio tests. Proteins considered to be significantly changed were defined as having the following: (1) >1.5-fold change between 8 and 40 weeks of gestation; and (2) a false discovery rate-adjusted value of P < .1. Gene ontology enrichment analysis was used to identify biological processes overrepresented among the proteins that changed with advancing gestation.

RESULTS

The following results were found: (1) Ten percent (112 of 1125) of the profiled proteins changed in abundance as a function of gestational age; (2) of the 1125 proteins analyzed, glypican-3, sialic acid-binding immunoglobulin-type lectin-6, placental growth factor, C-C motif-28, carbonic anhydrase 6, prolactin, interleukin-1 receptor 4, dual-specificity mitogen-activated protein kinase 4, and pregnancy-associated plasma protein-A had more than a 5-fold change in abundance across gestation (these 9 proteins are known to be involved in a wide range of both physiological and pathological processes, such as growth regulation, embryogenesis, angiogenesis immunoregulation, inflammation etc); and (3) biological processes associated with protein changes in normal pregnancy included defense response, defense response to bacteria, proteolysis, and leukocyte migration (false discovery rate, 10%).

CONCLUSION

The plasma proteome of normal pregnancy demonstrates dramatic changes in both the magnitude of changes and the fraction of the proteins involved. Such information is important to understand the physiology of pregnancy and the development of biomarkers to differentiate normal vs abnormal pregnancy and determine the response to interventions.

Human placental growth hormone is increased in maternal serum at 20 weeks of gestation in pregnancies with large-for-gestational-age babies

To investigate the relationship between maternal serum concentrations of placental growth hormone (GH-V), insulin-like growth factor (IGF)-1 and 2, IGF binding proteins (IGFBP)-1 and 3 and birth weight in appropriate-for-gestational-age (AGA), large-for-gestational-age (LGA) and small-for-gestational-age (SGA) cases in a nested case-control study. Maternal serum samples were selected from the Screening for Pregnancy Endpoints (SCOPE) biobank in Auckland, New Zealand. Serum hormone concentrations were determined by ELISA. We found that maternal serum GH-V concentrations at 20 weeks of gestation in LGA pregnancies were significantly higher than in AGA and SGA pregnancies. Maternal GH-V concentrations were positively correlated to birth weights and customized birth weight centiles, while IGFBP-1 concentrations were inversely related to birth weights and customized birth weight centiles. Our findings suggest that maternal serum GH-V and IGFBP-1 concentrations at 20 weeks' gestation are associated with fetal growth.

Neuroendocrine Regulation of Growth Hormone Secretion

This article reviews the main findings that emerged in the intervening years since the previous volume on hormonal control of growth in the section on the endocrine system of the Handbook of Physiology concerning the intra- and extrahypothalamic neuronal networks connecting growth hormone releasing hormone (GHRH) and somatostatin hypophysiotropic neurons and the integration between regulators of food intake/metabolism and GH release. Among these findings, the discovery of ghrelin still raises many unanswered questions. One important event was the application of deconvolution analysis to the pulsatile patterns of GH secretion in different mammalian species, including Man, according to gender, hormonal environment and ageing. Concerning this last phenomenon, a great body of evidence now supports the role of an attenuation of the GHRH/GH/Insulin-like growth factor-1 (IGF-1) axis in the control of mammalian aging.

The role and regulation of IGFBP-1 phosphorylation in fetal growth restriction

Fetal growth restriction (FGR) increases the risk of perinatal complications and predisposes the infant to developing metabolic, cardiovascular, and neurological diseases in childhood and adulthood. The pathophysiology underlying FGR remains poorly understood and there is no specific treatment available. Biomarkers for early detection are also lacking. The insulin-like growth factor (IGF) system is an important regulator of fetal growth. IGF-I is the primary regulator of fetal growth, and fetal circulating levels of IGF-I are decreased in FGR. IGF-I activity is influenced by a family of IGF binding proteins (IGFBPs), which bind to IGF-I and decrease its bioavailability. During fetal development the predominant IGF-I binding protein in fetal circulation is IGFBP-1, which is primarily secreted by the fetal liver. IGFBP-1 binds IGF-I and thereby inhibits its bioactivity. Fetal circulating levels of IGF-I are decreased and concentrations of IGFBP-1 are increased in FGR. Phosphorylation of human IGFBP-1 at specific sites markedly increases its binding affinity for IGF-I, further limiting IGF-I bioactivity. Recent experimental evidence suggests that IGFBP-1 phosphorylation is markedly increased in the circulation of FGR fetuses suggesting an important role of IGFBP-1 phosphorylation in the regulation of fetal growth. Understanding of the significance of site-specific IGFBP-1 phosphorylation and how it is regulated to contribute to fetal growth will be an important step in designing strategies for preventing, managing, and/or treating FGR. Furthermore, IGFBP-1 hyperphosphorylation at unique sites may serve as a valuable biomarker for FGR.

Impact of maternal under nutrition on obstetric outcomes

Maternal malnutrition, ranging from under nutrition to over dietary intake before and in the pregnant state, is worldwide problem with significant consequences, not only for survival and increased risk for acute and chronic diseases both in mother and child, but also for economic productivity of individuals in the societies and additional costs on health system. Inter alia, pre-pregnancy underweight and insufficient gestational weight gain are considered as individual risk factors for the occurrence of spontaneous interruption, preterm birth, fetal growth restriction, and hypertensive disorders, strongly associated with poorer perinatal outcome. In a portion of this population, major eating disorders (anorexia and bulimia nervosa), once thought to be rare, but nowadays enlarged due to cultural pressure on the drive for thinness, have been identified as the etiology of an abnormal nutritional condition in developed countries, in contrast to long standing food deprivation in developing countries. Actually, even if without a complete weight management guidance for these selected pregnant women, an appropriate weight gain is recommended during pregnancy. Mainly, therapeutic approach is prevention using specific programs of improving weight before pregnant status. In this article, a review of the literature on selected obstetrical risks associated with maternal underweight has been performed and both the target prevention and management strategies have been described.

Insulin-like growth factor-binding protein 1 and 7 concentrations are lower in obese pregnant women, women with gestational diabetes and their fetuses

OBJECTIVE

To determine the effect of pre-existing maternal obesity and gestational diabetes mellitus (GDM) on the circulating levels of insulin growth factor-binding protein (IGFBPs) in cord and maternal plasma.

STUDY DESIGN

IGFBP-1-7 levels were measured on maternal and cord plasma from women with normal glucose tolerance (NGT) (30 non-obese and 36 obese) and GDM (44 non-obese and 26 obese) at the time of term elective cesarean section.

RESULT

Maternal plasma IGFBP-1, IGFBP-6 and IGFBP-rP1 concentrations were significantly lower in NGT obese compared with NGT non-obese women and in non-obese GDM women compared with non-obese NGT women. In cord plasma, IGFBP-1-3 and IGFBP-rP1 concentrations were significantly lower in NGT obese compared with NGT non-obese women and in non-obese GDM women compared with non-obese NGT women. Significant positive correlations were observed between maternal and cord plasma IGFBP-1 and IGFBP-rP1 levels and maternal insulin resistance. In cord plasma, significant positive correlations were observed between IGFBP-1-3 and IGFBP-rP1 levels and fetal insulin resistance. Fetal birthweight was inversely correlated with maternal plasma IGFBP-1 levels and cord plasma IGFBP-1 and IGFBP-2 levels. When corrected for maternal body mass index, the only significant relationship that still existed was between cord plasma IGFBP-1 concentrations and fetal birthweight.

CONCLUSION

At the time of term cesarean section, pre-existing maternal obesity and GDM are associated with lower IGFBP levels in maternal and cord plasma. Alterations in circulating IGF and IGFBPs may alter birthweight and/or neonatal adiposity. This may lead to alterations in optimal growth trajectory and lead to metabolic disorders later in life.

Circulating IGF1 and IGF2 and SNP genotypes in men and pregnant and non-pregnant women

Circulating IGFs are important regulators of prenatal and postnatal growth, and of metabolism and pregnancy, and change with sex, age and pregnancy. Single-nucleotide polymorphisms (SNPs) in genes coding for these hormones associate with circulating abundance of IGF1 and IGF2 in non-pregnant adults and children, but whether this occurs in pregnancy is unknown. We therefore investigated associations of plasma IGF1 and IGF2 with age and genotype at candidate SNPs previously associated with circulating IGF1, IGF2 or methylation of the INS-IGF2-H19 locus in men (n=134), non-pregnant women (n=74) and women at 15 weeks of gestation (n=98). Plasma IGF1 concentrations decreased with age (P<0.001) and plasma IGF1 and IGF2 concentrations were lower in pregnant women than in non-pregnant women or men (each P<0.001). SNP genotypes in the INS-IGF2-H19 locus were associated with plasma IGF1 (IGF2 rs680, IGF2 rs1004446 and IGF2 rs3741204) and IGF2 (IGF2 rs1004446, IGF2 rs3741204 and H19 rs217727). In single SNP models, effects of IGF2 rs680 were similar between groups, with higher plasma IGF1 concentrations in individuals with the GG genotype when compared with GA (P=0.016), or combined GA and AA genotypes (P=0.003). SNPs in the IGF2 gene associated with IGF1 or IGF2 were in linkage disequilibrium, hence these associations could reflect other genotype variations within this region or be due to changes in INS-IGF2-H19 methylation previously associated with some of these variants. As IGF1 in early pregnancy promotes placental differentiation and function, lower IGF1 concentrations in pregnant women carrying IGF2 rs680 A alleles may affect placental development and/or risk of pregnancy complications.

Maternal BMI, IGF-I Levels, and Birth Weight in African American and White Infants

At birth, elevated IGF-I levels have been linked to birth weight extremes; high birth weight and low birth weight are risk factors for adult-onset chronic diseases including obesity, cardiovascular disease, and type 2 diabetes. We examined associations between plasma IGF-I levels and birth weight among infants born to African American and White obese and nonobese women. Prepregnancy weight and height were assessed among 251 pregnant women and anthropometric measurements of full term infants (≥37 weeks of gestation) were taken at birth. Circulating IGF-I was measured by ELISA in umbilical cord blood plasma. Linear regression models were utilized to examine associations between birth weight and high IGF-I, using the bottom two tertiles as referents. Compared with infants with lower IGF-I levels (≤3rd tertile), those with higher IGF-I levels (>3rd tertile) were 130 g heavier at birth, (β-coefficient = 230, se = 58.0, P = 0.0001), after adjusting for gender, race/ethnicity, gestational age, delivery route, maternal BMI and smoking. Stratified analyses suggested that these associations are more pronounced in infants born to African American women and women with BMI ≥30 kg/m²; the cross product term for IGF-I and maternal BMI was statistically significant (P ≤ 0.0004). Our findings suggest that the association between IGF-I levels and birth weight depends more on maternal obesity than African American race/ethnicity.

Why the maternal brain?

In the rat, the change from a virgin/nulliparous female to the maternal animal takes place at many levels. A subtle developmental wave washes over the female nervous system and transforms her from largely self-centred to offspring-directed, from personal care and protection to care of genetically-related offspring, from indifference to ardour. Such change is preceded by substantial and apparently permanent neural alterations, the depth of which results in the maternal brain, and is the basis of the present review. The neuroplasticity of pregnancy, inherent to the female brain and, we believe, representative of the full expression of the female nervous system's capacity, is a result of significant hormonal and other neurochemical actions. It results in the striking brain changes that are associated with, and necessary for, successful reproduction. We discuss some of these changes and their ramifications. Collectively, they represent the culmination of mammalian evolution and have led to the development of the social brain characteristic of higher orders of mammal, including the human. We also examine different facets of the maternal brain, beginning with a review of the genes involved in maternal behaviour, and in the subsequent 'expression' of the maternal brain. We next discuss olfaction and the manner in which this major sense draws from the rich sensory milieu of the mother to regulate and support maternal behaviour. Last, we discuss the 'whys' of maternal behaviour, a theoretical foray into the reasons for such substantial maternal brain alterations. We focus on the male's potential role as the raison d'etre for the manifest alterations in his mate's brain. In the end, it is clear that the female brain undergoes a significant reorganisation en route to motherhood, the results of which are deep and enduring.

Maternal concentrations of insulin-like growth factor I and insulin-like growth factor binding protein 1 during pregnancy and birth weight of offspring

Maternal concentrations of insulin-like growth factor I (IGF-I) and insulin-like growth factor binding protein 1 (IGFBP-1) may influence fetal growth. Offspring birth weight related to maternal IGF-I and IGFBP-1 measured in pregnancy was studied in 368 randomly selected women without preeclampsia who delivered a singleton liveborn child in Norway between 1992 and 1994. Maternal IGF-I concentrations were not consistently associated with birth weight, but a 1-standard deviation stronger increase in IGF-I from the first to second trimester was associated with an 82-g (95% confidence interval (CI): 11, 153) higher birth weight. IGFBP-1 concentrations were inversely associated with birth weight: Birth weight was 71 g (95% CI: 14, 128) lower per 1-standard deviation higher IGFBP-1 in the second trimester, and an increase in IGFBP-1 from the first (below median) to second (above median) trimester was associated with a 342-g (95% CI: 124, 560) lower birth weight, compared with having low IGFBP-1 (below median) in both trimesters. Conversely, low IGFBP-1 in both trimesters was associated with a 200-350-g higher birth weight compared with other combinations of IGFBP-1. In conclusion, persistently low IGFBP-1 in pregnancy is associated with relatively higher birth weight. Maternal insulin resistance may provide a link between IGFBP-1 and offspring birth weight.

Effects of exercise training on maternal hormonal changes in pregnancy

CONTEXT & OBJECTIVE

A recent paper by our group reported that regular aerobic exercise during pregnancy led to lower foetal IGF-I and IGF-II concentrations and a modest reduction in offspring birth weight when compared with the offspring of nontraining control participants. Maternal hormonal alterations in response to exercise training may be associated with the regulation of nutrient availability for foetal growth through placental regulation of maternal metabolism.

OBJECTIVE

To determine whether the reduction in offspring size was associated with changes in the maternal IGF axis [including placental growth hormone (PGH)], leptin and/or free fatty acids (FFA) in response to aerobic exercise training in the second half of pregnancy.

DESIGN AND SETTING

A randomized, controlled trial of exercise in pregnancy.

PATIENTS

Eighty-four healthy nulliparous women (mean±SD age 30±4 year, BMI 25·5±4 kg/m(2) ).

MEASUREMENTS

Serum samples were drawn at 19 and 35 weeks gestation to determine serum IGF-I, IGF-II, IGF-binding protein-1, IGF-binding protein-3, PGH, leptin and FFA.

RESULTS

Exercise training in pregnancy had no impact on the pregnancy-related changes in the maternal IGF axis. Women in the exercise group experienced a 29% increase in leptin in late gestation (P=0·026 vs control) and a trend towards lower FFA (P=0·07 vs control). Late pregnancy changes in maternal leptin were inversely related to offspring birth weight (r= -0·24, P<0·05) and BMI (r= -0·25, P<0·05).

CONCLUSIONS

An increase in leptin in exercising pregnant women may reflect subtle changes within the placenta in response to regular exercise and may contribute to the reduction in offspring size previously reported in this cohort.

Obesity and the placenta: A consideration of nutrient exchange mechanisms in relation to aberrant fetal growth

The obesity epidemic, including childhood obesity, is rapidly gaining strength as one of the most significant challenges to the health of the global community in the 21st Century. The proportion of women who are obese at the beginning of pregnancy is also increasing. These women and their babies are at high risk of pregnancy complications, and of programming for metabolic disease in adult life. In particular, maternal obesity is associated with aberrant fetal growth, encompassing both growth restricted and large for gestational age, or macrosomic fetuses. This article considers the potential effect of obesity and adipose tissue on placental nutrient exchange mechanisms in relation to aberrant fetal growth. The review emphasizes the dearth of work on this topic to date despite its importance to current and future healthcare of the population.

Maternal serum concentrations of insulin-like growth factor (IGF)-I and IGF binding protein-1 before and during pregnancy in relation to maternal body weight and composition and infant birth weight

Maternal nutritional status, e.g. body weight and composition, is associated with fetal growth. It has been suggested that the insulin-like growth factor (IGF) system may be a mediator of this relationship. In twenty-three healthy Swedish women, we studied (1) the relationships before and during pregnancy between maternal serum concentrations of IGF-I and IGF binding protein-1 (IGFBP-1) and maternal body weight and composition; (2) interactions between serum concentrations of IGF-I (before and in early pregnancy) and maternal nutritional status in relation to infant birth weight. We found that serum IGF-I during pregnancy was positively correlated with maternal body weight (r 0.47-0.56) and fat-free body weight (r 0.61-0.65), whereas serum IGFBP-1 was negatively correlated with maternal body weight (r - 0.44 to - 0.69) and body fat (r - 0.64 to - 0.76) before and during pregnancy. Women with a lower body fat content (%) before pregnancy had greater increases in serum IGFBP-1 during pregnancy than women with a higher prepregnant body fat content (%). In addition, significant fractions of the variation in corrected infant birth weight were explained by variables related to the maternal nutritional status when these were combined with serum concentrations of IGF-I in gestational week 14 (adjusted r2 0.25-0.44, P = 0.001-0.021), but not when they were combined with such concentrations before pregnancy (adjusted r2 0.11-0.12, P = 0.105-0.121). These results suggest mechanisms by which the IGF system may be a mediator between maternal nutritional status and fetal growth.

The relationship between maternal insulin-like growth factors 1 and 2 (IGF-1, IGF-2) and IGFBP-3 to gestational age and preterm delivery

AIMS

To investigate the relationship between levels of insulin-like growth factors 1 and 2 (IGF-1, IGF-2), and insulin-like growth factor binding protein 3 (IGFBP-3) in antenatal maternal serum and gestational age at delivery.

METHODS

Prospective cohort study of 1650 low-risk Caucasian women in a London University teaching hospital. Maternal IGF-1, IGF-2 and IGFBP-3 were measured in maternal blood at booking and analyzed with respect to gestational age at delivery.

RESULTS

There was no significant association between maternal IGF-1 or IGF-2 and preterm birth (PTB). A significant reduction in mean IGFBP-3 levels was noted with delivery <32 completed weeks (P=0.02).

CONCLUSION

Maternal mean IGFBP-3 levels are significantly reduced in cases complicated by delivery <32 completed weeks.

Hormonal and metabolic factors associated with variations in insulin sensitivity in human pregnancy

OBJECTIVE

The objective of this study was to determine maternal hormonal and metabolic factors associated with insulin sensitivity in human pregnancy.

RESEARCH DESIGN AND METHODS

This was a prospective observational cross-sectional study of 180 normal pregnant women, using samples collected at the time of a blinded oral glucose tolerance test (OGTT) between 24 and 32 weeks' gestation as an ancillary to the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study. The study was conducted at two public university teaching hospitals, Cleveland, Ohio, and Brisbane, Australia. Fasting maternal serum cholesterol, triglycerides, free fatty acids, insulin, leptin, tumor necrosis factor-alpha, placental growth hormone (PGH), insulin-like growth factors (IGFs) 1 and 2, and insulin-like growth factor binding proteins (IGFBPs) 1 and 3 were assayed. Correlation and multiple regression analyses were used to determine factors associated with maternal insulin sensitivity (IS) estimated using both OGTT-derived (IS(OGTT)) and fasting (using the homeostasis model assessment [HOMA]; IS(HOMA)) insulin and glucose concentrations.

RESULTS

Insulin sensitivity correlated (r = x and y for IS(OGTT) and IS(HOMA,) respectively) with fasting maternal serum leptin (-0.44 and -0.52), IGFBP1 (0.42 and 0.39), and triglycerides (-0.31 and -0.27). These factors were significantly associated with insulin sensitivity in multiple regression analyses (adjusted R(2) 0.44 for IS(OGTT) and IS(HOMA)). These variables explained more than 40% of the variance in estimates of insulin sensitivity.

CONCLUSIONS

Maternal hormonal and metabolic factors related to the placenta, adipose tissue, and the growth hormone axis are associated with the variation in insulin sensitivity seen during normal human pregnancy.

Expression of the insulin-like growth factor receptor 1 during human embryogenesis

Insulin-like growth factor 1 and its receptor (IGF-1/IGF-2) may play important roles in the development of human fetal tissue, and its ligands IGF-1 and IGF-2 have been found in fetuses older than 3 months. Our objective was to study the immunohistochemical distribution of IGF 1-R in tissues obtained from human normal embryos following abortion or natural termination of pregnancy. Immunohistochemical staining was performed on autostainer, using an anti-IGF1-R rabbit polyclonal antibody (dilution 1:75), and the avidin-biotin peroxidase complex method. The embryos ranged between 28 days to 8 weeks gestation. Fully 3 cases were 28 days old, 1 case 32 days old, 2 cases 6 weeks old and 2 cases 8 weeks old. The IGF1-R stain decorated the surface ectoderm, the optic cup, and the lens placode, pharynx, respiratory diverticulum, foregut, liver cords, mesonephros, and metanephric blastema. Mesodermal structures, including limb mesoderm, and neural crest derivatives were IGF-1R negative. On study shows the preferential IGF-1R immunolocalizatrion in specific areas of the developing embryo, suggesting a role of IGF1-R for the optimal maturation of those areas, during developing human embryos.

Motherhood induces and maintains behavioral and neural plasticity across the lifespan in the rat

Maternal behavior is multidimensional, encompassing many facets beyond the direct care of the young. Formerly unfamiliar activities are required of the mother. These include behaviors such as retrieving, grouping, crouching-over, and licking young, and protecting them against predators, together with enhancements in other behaviors, such as nest building, foraging, and aggression (inter/intra-species, predatory, etc.). When caring for young, the mother must strike a seemingly lose-lose bargain: leave the relative safety of the nest and her helpless offspring to forage for food and resources where predators await both mother and her vulnerable young, or remain entrenched and safe, thereby ensuring a slow and inexorable fate. Two predictions thus arise from this maternal cost-benefit ratio: first, there may be enhancements in behaviors on which the female relies, for example, predation and spatial ability, used for acquiring food and resources and for navigating her environment. Second, there may be reductions in the fear and anxiety inherent to the decision to leave the nest and to forage in an unforgiving environment where encounters with predators or reluctant/resistant prey await. There is overwhelming support for both hypotheses, with improvements in learning and memory accompanied by a diminution in stress responses and anxiety. The current review will examine the background for the phenomenon that is the maternal brain, and recent relevant data. In sum, the data indicate a remarkable set of changes that take place in the maternal (and, to a lesser extent, the paternal), brain, arguably, for the natural, simple but singular experience of reproduction.

Exploring the underlying hormonal mechanisms of prenatal risk factors for breast cancer: a review and commentary

Prenatal factors have been hypothesized to influence subsequent breast cancer development. Directly evaluating the associations of in utero exposures with risk, however, presents several methodologic and theoretical challenges, including the long induction period between exposure and disease and the lack of certainty regarding the critical timing of exposure. Indirect evaluation of these associations has been achieved by use of proxies such as gestational and neonatal characteristics. Evidence suggests that preeclampsia is associated with a reduced breast cancer risk, whereas high birth weight and dizygotic twinning seem associated with an increased risk. Asians born in Asia have substantially lower breast cancer risks than women born in the West. Although data thus far are few, what exists is not consistent with a unifying hypothesis for a particular biological exposure (such as estrogens or androgens) during pregnancy as mediating the observed associations between pregnancy factors and breast cancer risk. This suggests that additional studies of prenatal factors should seek to broaden the range of hormones, growth, and other endocrine factors that are evaluated in utero. Once candidate biomarkers are identified, assessing them with respect to breast cancer and with intermediate end points in carcinogenesis should be a priority. In addition, investigations should explore the possibility that in utero exposures may not act directly on the breast, but may alter other physiologic pathways such as hormone metabolism that have their effect on risk later in life.

Longitudinal study of the maternal insulin-like growth factor system before, during and after pregnancy in relation to fetal and infant weight

BACKGROUND

The maternal insulin-like growth factor (IGF) system is considered to be involved in fetal growth regulation. However, available data linking this system to fetal growth are contradictory and incomplete.

AIMS

To measure components of the IGF system before, during and after pregnancy in healthy women and to relate these results, and their changes during pregnancy, to fetal weight (gestational week 31) and birth weight.

METHODS

Serum concentrations of IGF-I, IGF-II, IGF-binding protein (IGFBP)-1, IGFBP-3 and IGFBP-3 protease activity were assessed in 23 women before conception, at weeks 8, 14, 20, 32 and 35 of pregnancy and 2 weeks postpartum. The data were analyzed using simple and multiple linear regression.

RESULTS

One third of the variability in fetal weight was explained by IGF-I in combination with IGFBP-3 protease activity, both assessed at gestational week 32 (p = 0.013). Birth weight was negatively correlated (r = -0.43 to -0.59) with IGFBP-1 at gestational week 20 (p = 0.041), 32 (p = 0.012) and 35 (p = 0.003).

CONCLUSION

We propose there is a finely tuned balance among the components of the IGF system, providing a means for fetal growth regulation.

Insulin-like growth factor (IGF)-I and insulin in normal and growth-restricted mother/infant pairs

Insulin-like growth factor (IGF)-I and insulin are essential for fetal growth. We investigated perinatal changes of both factors in 40 mothers and their 20 appropriate-for-gestational-age (AGA) and 20 intrauterine-growth-restricted (IUGR) fetuses and neonates on day 1 (N1) and day 4 (N4) postpartum. Fetal and N1, but not N4, IGF-I levels were increased in AGA (P < .001 and P = .037, resp.). N1 insulin levels were lower in IUGR (P = .048). Maternal, fetal, and N1 IGF-I, and fetal insulin levels positively correlated with customized centiles (r = .374, P = .035, r = .608, P < .001, r = .485, P = .006, and r = .654, P = .021, resp.). Female infants presented elevated fetal and N4 IGF-I levels (P = .023 and P = .016, resp.). Positive correlations of maternal, fetal, and neonatal IGF-I levels, and fetal insulin levels with customized centiles underline implication of both hormones in fetal growth. IUGR infants present gradually increasing IGF-I levels. Higher IGF-I levels are documented in females.

Early treatment of the pregnant guinea pig with IGFs promotes placental transport and nutrient partitioning near term

Appropriate partitioning of nutrients between the mother and conceptus is a major determinant of pregnancy success, with placental transfer playing a key role. Insulin-like growth factors (IGFs) increase in the maternal circulation during early pregnancy and are predictive of fetal and placental growth. We have previously shown in the guinea pig that increasing maternal IGF abundance in early to midpregnancy enhances fetal growth and viability near term. We now show that this treatment promotes placental transport to the fetus, fetal substrate utilization, and nutrient partitioning near term. Pregnant guinea pigs were infused with IGF-I, IGF-II (both 1 mg.kg-1.day-1) or vehicle subcutaneously from days 20-38 of pregnancy (term=69 days). Tissue uptake and placental transfer of the nonmetabolizable radio analogs [3H]methyl-D-glucose (MG) and [14C]aminoisobutyric acid (AIB) in vivo was measured on day 62. Early pregnancy exposure to elevated maternal IGF-I increased placental MG uptake by>70% (P=0.004), whereas each IGF increased fetal plasma MG concentrations by 40-50% (P<0.012). Both IGFs increased fetal tissue MG uptake (P<0.048), whereas IGF-I also increased AIB uptake by visceral organs (P=0.046). In the mother, earlier exposure to either IGF increased AIB uptake by visceral organs (P<0.014), whereas IGF-I also enhanced uptake of AIB by muscle (P=0.044) and MG uptake by visceral organs (P=0.016) and muscle (P=0.046). In conclusion, exogenous maternal IGFs in early pregnancy sustainedly increase maternal substrate utilization, placental transport of MG to the fetus, and fetal utilization of substrates near term. This was consistent with the previously observed increase in fetal growth and survival following IGF treatment.

Birth weight and risk of cancer

BACKGROUND

It is well established that prenatal biologic processes are important for the development of some childhood cancers, whereas less is known regarding their influence on adult cancer risk. High birth weight has been associated with risk of breast cancer, whereas studies of other specific cancers and all cancers together have been less conclusive.

METHODS

The authors established a cohort of more than 200,000 men and women who were born between 1936 and 1975. Birth weights were obtained from school health records and information concerning cancer from the Danish Cancer Registry. Follow-up was performed between April 1, 1968 and December 31, 2003. During 6,975,553 person-years of follow-up, a total of 12,540 primary invasive cancers were diagnosed.

RESULTS

Analyses of site-specific cancers revealed that the majority of cancers had a positive linear association with birth weight. Departures from a positive linear association were found to be statistically significant for cancers of the pancreas and bladder, which demonstrated a V-shaped association, and testicular cancer, which demonstrated an inverse association with birth weight. Excluding these 3 exceptions, the trends for the individual cancer sites were not heterogeneous, and the overall trend was a relative risk of 1.07 (95% confidence interval, 1.03-1.11) per 1000-g increase in birth weight. This trend was the same in men and women and in all age groups.

CONCLUSIONS

A 7% increase in cancer risk was observed per 1000-g increase in birth weight. Few cancers demonstrated a nonlinear association with birth weight, and testicular cancer was found to be negatively associated with birth weight. The authors hypothesized that the biologic explanation behind the association between birth weight and cancer at different sites should be sought in a common pathway.

Role of birthweight in the etiology of breast cancer

Breast cancer may originate in utero. We reviewed the available evidence on the association between birthweight and the risk of breast cancer. To date, 26 research papers addressing this issue have been published. The majority of studies identified a positive link between birthweight and premenopausal, but not postmenopausal, breast cancer. The relative risk estimate for breast cancer comparing women with high birthweight to women with low birthweight combining all studies including both pre- and postmenopausal breast cancer was 1.23 (95% confidence interval 1.13-1.34). The mechanisms underlying this association likely include elevated levels of growth factors that may increase the number of susceptible stem cells in the mammary gland or initiate tumors through DNA mutations. Loss of imprinting (LOI) of growth hormone genes relevant for intrauterine growth, such as insulin-like growth factor 2 (IGF2), leads to abnormally high levels of these hormones evidenced by high birthweight. LOI of IGF2 has also been found in mammary tumor tissue. The role of environmental factors that stimulate such epigenetic regulation of gene expression remains to be elucidated.

Immunoassay of serine-phosphorylated isoform of insulin-like growth factor (IGF) binding protein (IGFBP)-1

OBJECTIVES

Development of an ELISA for phosphorylated isoform of IGFBP-1. Serine phosphorylation is an important regulator of IGFBP-1 bioactivity, but specific immunoassays for its measurement are currently lacking.

DESIGN AND METHODS

Assay design was based on a novel approach of first capturing the phosphorylated and non-phosphorylated IGFBP-1 by an anti-IGFBP-1 antibody and then selectively detecting the phosphorylated form by an anti-phosphoserine antibody. Method development involved pair-wise evaluation of the candidate antibodies and determinations of analytical performance and specificity. Specificity was monitored by reactivity with dephosphorylated IGFBP-1, with antibodies against other phosphorylated residues that are not expressed, and by comparative analysis of sample containing different IGFBP-1 phosphorylation profile.

RESULTS

Analytical evaluation demonstrated acceptable performance; detection limit 0.3 microg/L, dynamic range 1.56-100 microg/L; intra- and inter-assay CVs 2.1-8.6%; mean recovery (+/-SD) 97.8+/-9.2%, and mean recovery of sample dilution 93.4+/-6.0%. The phosphorylated and total IGFBP-1 medians in non-pregnant adult serum, which mostly contain the highly phosphorylated isoform, were 11.9 and 18.6 microg/L, respectively, and the sample values were tightly correlated (r=0.99). As expected, the corresponding medians in 1st trimester (17.4 and 63.0 microg/L) and 2nd trimester (30.9 and 75.8) samples with altered IGFBP-1 phosphorylation were significantly different (p<0.001). Similarly, a fraction (1.29%) of total IGFBP-1 (13.3 mg/L) in amniotic fluids was found to be phosphorylated (0.172 mg/L). There was no reactivity with dephosphorylated IGFBP-1.

CONCLUSIONS

The present ELISA is highly specific for the phosphorylated isoform of IGFBP-1 and its availability should help expedite further investigations of IGFBP-1 phosphorylation.

Changes in basal metabolic rate during pregnancy in relation to changes in body weight and composition, cardiac output, insulin-like growth factor I, and thyroid hormones and in relation to fetal growth

BACKGROUND

The total energy cost of pregnancy is largely due to an elevated basal metabolic rate (BMR). Large variations in the BMR response to pregnancy have been reported, but the factors associated with this variability are incompletely known.

OBJECTIVE

The objective was to identify factors associated with variability in the BMR response to pregnancy.

DESIGN

In 22 healthy women, BMR, body weight (BW), total body fat (TBF), fat-free mass (FFM), circulatory variables, serum concentrations of insulin-like growth factor I (IGF-I), and thyroid hormones were measured before pregnancy and in gestational weeks 14 and 32. BMR and BW were also measured in gestational weeks 8, 20, and 35. Fetal weight was estimated in gestational week 31.

RESULTS

In gestational week 14, the increase in BMR correlated significantly with the corresponding increase in BW and with the prepregnancy percentage of TBF. Together these variables explained approximately 40% of the variability in the BMR response. In gestational week 32, the increase in BMR correlated significantly with the corresponding changes in BW, TBF, FFM, IGF-I, cardiac output, and free triiodothyronine. The increase in BW in combination with fetal weight or with the elevated concentration of IGF-I in serum explained approximately 60% of the variability in the increase in BMR.

CONCLUSIONS

Weight gain and the prepregnancy percentage of TBF-ie, factors related to the maternal nutritional situation-are important factors with regard to the variability in the BMR response to pregnancy. Thus, it is important to consider the nutritional situation before and during gestation when assessing pregnancy energy requirements.

Maternal and fetal insulin-like growth factors 1 and 2 (IGF-1, IGF-2) and IGF BP-3, and their relationship to fetal acidosis at delivery

OBJECTIVE

To investigate the relationship between levels of insulin-like growth factors 1 and 2 (IGF-1, IGF-2), and insulin-like growth factor binding protein 3 (IGFBP-3) in antenatal maternal serum and in fetal cord blood at delivery.

METHODS

Prospective cohort study of 1650 low-risk Caucasian women in a University teaching hospital in London. Statistical analysis was performed using commercial software (SPSS for Windows, version 6.1, SPSS, Chicago, Illinois, USA), with p<0.05 as significant. Maternal IGF 1, IGF 2 and IGF BP-3 were assessed on maternal blood at booking and in fetal blood by cord blood analysis at delivery. Cord pH was also recorded.

RESULTS

There was no significant correlation between maternal IGF-1, IGF-2, or IGFBP-3 levels and fetal acidosis. However, a significant correlation does exist between cord IGF-1 levels and fetal acidosis.

CONCLUSION

Fetal cord IGF-1 has a significant correlation with fetal acidosis at delivery.

Insulin-Like Growth Factor-I as a Follicular Growth Promoter during Early Pregnancy in Thoroughbred Mares

To elucidate the physiological role of insulin-like growth factor-I (IGF-I) during early pregnancy in mares, number of ovarian follicles was monitored ultrasonically during different stages of the first trimester of pregnancy in 36 thoroughbred mares. From 9 of 36 mares, blood samples were collected weekly from the mating day till the end of the first trimester of pregnancy and plasma IGF-I profiles were examined with other hormones, like follicle stimulating hormone (FSH), luteinizing hormone (LH), ir-inhibin, progesterone and estradiol-17beta. Plasma IGF-I level fluctuated throughout the studied period with four peaks on the 7th, 28th, 49th and 84th days of pregnancy. Plasma IGF-I showed a positive correlation with plasma FSH (P<0.05), whereas no correlation was found with other hormones during the studied period. Plasma IGF-I had no correlation with the foetal size, but positive correlation with the number of large (> 30 mm) and medium (10-30 mm) follicles. These results suggested that IGF-I might produce from the medium and large follicles during early pregnancy and promote to develop their growth via pituitary FSH mediated effects in the mares.

Influence of smoking on serum and milk of mothers, and their infants' serum insulin-like growth factor-I and insulin-like growth factor binding protein-3 levels

OBJECTIVE

To investigate the serum and milk in active-smoking and nonsmoking mothers, and their infants' insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) levels.

DESIGN AND SETTING

A cohort study conducted at a tertiary medical center.

SUBJECTS

Forty-four mothers (age range: 21-34 years) and their newborns (7 days old) were enrolled in the study. Mothers were interviewed and classified according to their smoking status into one of two groups: the active-smoking mothers (n = 21) and the nonsmoking mothers (n = 23).

RESULTS

There was no difference noted in either IGF-I, IGFBP-3 or IGF-I/IGFBP-3 ratios in serum and milk of mothers, and their infants' serum samples according to maternal smoking.

CONCLUSION

This study demonstrated that maternal smoking (5-10 cigarettes/day) did not influence the maternal and infant serum levels of IGF-I and IGFBP-3 as well as the breast milk levels of these peptides.

Maternal insulin-like growth factor-I levels (IGF-I) reflect placental mass and neonatal fat mass

OBJECTIVE

This study was undertaken to test the null hypothesis that serial changes in maternal insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding-protein-1 (IGFBP-1) levels during pregnancy do not reflect differences in either corrected birth weight or placental mass at term. Study design Serial blood samples were obtained before pregnancy and at 8, 16, 24, 32, and 38 weeks from 56 healthy women enrolled in various exercise training regimens. Maternal, placental, and fetal morphometric parameters were monitored throughout. Enzyme-linking immunosorbent assays were used to determine IGF-I and IGFBP-1 levels.

RESULTS

IGF-I and IGFBP-1 levels varied widely among the subjects at all time points, but there was a consistent fall in IGF-I levels in early pregnancy, followed by a rapid increase between 16 and 36 weeks' gestation, whereas IGFBP-1 levels rose in the first 16 weeks and were unchanged thereafter. The strongest linear correlations with morphometric outcome were between the increase in maternal IGF-I levels from 16 to 32 weeks and corrected birth weight (r(2)=0.27), neonatal fat mass (r(2)=0.65), and placental mass at term (r(2)=0.50). These were improved when maternal glucose level was included in a stepwise regression analysis (r(2)=0.50-0.70).

CONCLUSION

There is a robust relationship among the rate of increase in individual maternal IGF-I levels after 16 weeks, placental mass, and neonatal fat mass. This does not imply causality but does indicate that midpregnancy changes in IGF-I levels may be a valuable marker for anomalous fetal growth.

Placental growth hormone during pregnancy in a growth hormone deficient woman with type 1 diabetes compared to a matching diabetic control group

In pregnancy, pituitary growth hormone (GH) is gradually replaced by placental growth hormone (hPGH). GH deficient pregnant women may take advantage of GH substitution during pregnancy, but this issue still remains unresolved. Also, in pregnancy diabetes may cause macrosomia. The combination of GH deficiency, GH substitution therapy and type 1 diabetes mellitus may influence pregnancy in unforeseen ways. We present a case of pregnancy in a GH deficient woman with type 1 diabetes who continued on GH replacement until week 21. In gestational week 37 a thin and mildly small-for gestational-age (length 55 cm, +3 SD, 99th centile and weight 2445 g., -1.4 SD, 10th centile) but otherwise healthy boy was born. The patient had levels of serum hPGH at the lower end of the range of values found in a matching group of diabetic women. Serum IGF-I levels were at the upper end of the range of values in the control group. A positive correlation between serum hPGH and IGF-I values was seen in the control group when using the area-under-the-curve (r=0.84; p<0.001). The patient's child had lower birth weight and ponderal index, but was otherwise healthy. Serum IGF-I, but not hPGH, correlated to the absolute birth weight (r=0.63; p=0.015) and the birth weight z-score (r=0.55; p=0.039) in the control group. Serum hPGH and IGF-I declined rapidly after delivery. In conclusion, hPGH correlated to IGF-I in type 1 diabetes mellitus (DM), and IGF-I values correlated to the birth weight. Both type 1 diabetes mellitus and GH deficiency (with GH substitution therapy) may influence fetal growth, and in combination, the net influence may be difficult to predict.