The biomarkers of fetal growth in intrauterine growth retardation and large for gestational age cases: from adipocytokines to a metabolomic all-in-one tool

The Gestational Effects of Maternal Appetite Axis Molecules on Fetal Growth, Metabolism and Long-Term Metabolic Health: A Systematic Review

Increased maternal food intake is considered a normal pregnancy adjustment. However, the overavailability of nutrients may lead to dysregulated fetal development and increased adiposity, with long-lasting effects on offspring in later life. Several gut-hormone molecules regulate maternal appetite, with both their orexigenic and anorectic effects being in a state of sensitive equilibrium. The aim of this manuscript is to systematically review literature on the effects of maternal gut-hormone molecules on fetal growth and metabolism, birth weight and the later metabolic health of offspring. Maternal serum ghrelin, leptin, IGF-1 and GLP-1 appear to influence fetal growth; however, a lack of consistent and strong correlations of maternal appetite axis hormones with birth weight and the concomitant correlation with fetal and birth waist circumference may suggest that these molecules primarily mediate fetal energy deposition mechanisms, preparing the fetus for survival after birth. Dysregulated intrauterine environments seem to have detrimental, sex-dependent effects on fetal energy stores, affecting not only fetal growth, fat mass deposition and birth weight, but also future metabolic and endocrine wellbeing of offspring.

The Role of the Adipokines in the Most Common Gestational Complications

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

Can adipokine visfatin be a novel marker of pregnancy-related disorders in women with obesity?

Overweight and obesity have become a dangerous disease requiring multiple interventions, treatment and preventions. In women of reproductive age, obesity is one of the most common medical conditions. Among others, obese state is characterized by low-grade systemic inflammation and enhanced oxidative stress. Increased maternal body mass index might amplify inflammation and reactive oxygen species production, which is associated with unfavourable clinical outcomes that affect both mother and child. Intrauterine growth retardation, preeclampsia, or gestational diabetes mellitus are examples of the hampered maternal and foetoplacental unit interactions. Visfatin is the obesity-related adipokine produced mainly by the visceral adipose tissue. Visfatin affects glucose homeostasis, as well as the regulation of genes related to oxidative stress and inflammatory response. Here, we review visfatin interactions in pregnancy-related disorders linked to obesity. We highlight the possible predictive and prognostic value of visfatin in diagnostic strategies on gravidas with obesity.

Differences in omentin-1 levels in term newborns according to birth weight

BACKGROUND

Adipokines are produced by adipose tissue and are involved in metabolic processes. Omentin-1 is an adipokine that has been shown in vitro to possibly be involved in insulin sensitivity modulation. The prenatal stage is a crucial period for development of metabolic diseases in the long term, therefore, small (SGA) and large (LGA) for gestational age newborns have an increased risk of type 2 diabetes and metabolic syndrome later in life.

AIMS

To evaluate the differences in omentin-1 concentrations in umbilical cord blood from healthy term newborns according to birth weight and explore the association between omentin-1 and anthropometry, glucose, insulin and insulin sensitivity.

STUDY DESIGN

This was a secondary analysis of stored umbilical cord blood of term newborns.

SUBJECTS

Newborns classified according to birth weight as SGA (n = 30), adequate for gestational age (AGA) (n = 12) and LGA (n = 34).

OUTCOME MEASURES

An analysis of omentin-1, glucose and insulin were performed.

RESULTS

Differences were found in serum omentin-1 levels (ng/mL) between SGA 328.17 ± 108.04, AGA 253.05 ± 98.25 and LGA 250.91 ± 100.48 (p = 0.009). In the linear regression analysis, the independent variables HOMA-IR, QUICK-I and FGIR were predictors of serum omentin-1 levels (r = 0.175, p = 0.003).

CONCLUSIONS

Omentin-1 cord blood levels have a differentiated behavior according to weight for gestational age with LGA newborns having lower levels and SGA newborns higher levels. HOMA-IR, QUICK-I and FGIR weakly predicted omentin-1 in cord blood, suggesting that omentin-1 possibly has an implication in insulin sensitivity since birth.

Intrauterine Growth Restriction: New Insight from the Metabolomic Approach

Recognizing intrauterine growth restriction (IUGR) is a matter of great concern because this condition can significantly affect the newborn's short- and long-term health. Ever since the first suggestion of the "thrifty phenotype hypothesis" in the last decade of the 20th century, a number of studies have confirmed the association between low birth weight and cardiometabolic syndrome later in life. During intrauterine life, the growth-restricted fetus makes a number of hemodynamic, metabolic, and hormonal adjustments to cope with the adverse uterine environment, and these changes may become permanent and irreversible. Despite advances in our knowledge of IUGR newborns, biomarkers capable of identifying this condition early on, and stratifying its severity both pre- and postnatally, are still lacking. We are also still unsure about these babies' trajectory of postnatal growth and their specific nutritional requirements with a view to preventing, or at least limiting, long-term complications. In this setting, untargeted metabolomics-a relatively new field of '-omics' research-can be a good way to investigate the metabolic perturbations typically associated with IUGR. The aim of this narrative review is to provide a general overview of the pathophysiological and clinical aspects of IUGR, focusing on evidence emerging from metabolomic studies. Though still only preliminary, the reports emerging so far suggest an "early" pattern of glucose intolerance, insulin resistance, catabolite accumulation, and altered amino acid metabolism in IUGR neonates. Further, larger studies are needed to confirm these results and judge their applicability to clinical practice.

Adiponectin concentration in mid-trimester amniotic fluid varies with the α-amylase level and maternal and neonatal outcomes

OBJECTIVE

Factors influencing intraamniotic adiponectin levels and their functional significance remain incompletely elucidated. We prospectively measured adiponectin in amniotic fluid and identified its associations with maternal parameters, mediators in amniotic fluid and pregnancy outcomes.

STUDY DESIGN

Mid-trimester amniotic fluid from 571 women was tested for adiponectin, interleukin (IL)-6, IL-8 and α-amylase by enzyme-linked immunosorbant assay (ELISA), after which clinical data were obtained. Correlations between adiponectin and clinical or laboratory variables were analyzed by the Kruskal-Wallis, Mann-Whitney and Spearman rank correlation tests.

RESULTS

As compared to median levels in 462 women with a term delivery (7.8 ng/mL), adiponectin was elevated in 14 women who subsequently developed preterm premature rupture of membranes (pPROM) (17.3 ng/mL) and 24 women with an iatrogenic preterm birth (IPTB) (13.9 ng/mL) (P=0.0003), but not in 30 women who subsequently had a spontaneous preterm birth with intact membranes (8.1 ng/mL) (P>0.05). Median adiponectin was also elevated in 13 women whose babies developed fetal growth restriction (FGR) (20.6 ng/mL) (P=0.0055) and in 22 women whose babies had respiratory distress syndrome (RDS) (23.0 ng/mL) (P<0.0001). The adiponectin concentration was positively correlated with amylase (P=0.0089) and inversely correlated with maternal body mass index (P=0.0045).

CONCLUSION

Adiponectin is a component of mid-trimester amniotic fluid and its concentration varies with maternal body mass index and subsequent development of pPROM, IPTB, FGR and RDS.

Leptin action in normal and pathological pregnancies

Leptin is now considered an important signalling molecule of the reproductive system, as it regulates the production of gonadotrophins, the blastocyst formation and implantation, the normal placentation, as well as the foeto-placental communication. Leptin is a peptide hormone secreted mainly by adipose tissue, and the placenta is the second leptin-producing tissue in humans. Placental leptin is an important cytokine which regulates placental functions in an autocrine or paracrine manner. Leptin seems to play a crucial role during the first stages of pregnancy as it modulates critical processes such as proliferation, protein synthesis, invasion and apoptosis in placental cells. Furthermore, deregulation of leptin levels has been correlated with the pathogenesis of various disorders associated with reproduction and gestation, including polycystic ovary syndrome, recurrent miscarriage, gestational diabetes mellitus, pre-eclampsia and intrauterine growth restriction. Due to the relevant incidence of the mentioned diseases and the importance of leptin, we decided to review the latest information available about leptin action in normal and pathological pregnancies to support the idea of leptin as an important factor and/or predictor of diverse disorders associated with reproduction and pregnancy.

Zinc protection in fetal rats for maternal mercury exposure-induced growth retardation is probably associated with S100B expression

AIM

The study was conducted to investigate the effects of maternal mercury exposure on fetal rat development and zinc protection in mercury-exposed rats.

METHODS

Pregnant rats were subjected to zinc sulfate pre-feeding, mercury exposure and zinc sulfate co-feeding. The control rats were administered distilled water. On day 19, the placental weight, overall weight, size and tail length of fetal rats, mercury content and S100B level in the placenta were determined using Western blot analysis.

RESULTS

Compared with the control, mercury exposure at 2.0 mg/kg.d significantly reduced placental weight and fetal development, resulting in reduced fetal weight, size and tail length, while zinc pre-feeding increased placental weight and other fetal developmental parameters. Compared with mercury exposure, co-feeding with zinc significantly reduced mercury-induced injury in the fetal rats. S100B and mercury content levels were significantly elevated in rats maternally exposed to methylmercury chloride, compared with the unexposed control, while co-feeding with methylmercury chloride and zinc sulfate significantly reduced S100B and mercury levels in the placenta.

CONCLUSION

Maternal exposure to mercury results in increased S100B in the placenta. Zinc sulfate feeding could reduce S100B and mercury levels, thereby protecting the rats from mercury damage. S100B level may be used to measure the antagonism between zinc and mercury during pregnancy.

Alterations in expression of imprinted genes from the H19/IGF2 loci in a multigenerational model of intrauterine growth restriction (IUGR)

BACKGROUND

The H19/IGF2 imprinted loci have attracted recent attention because of their role in cellular differentiation and proliferation, heritable gene regulation, and in utero or early postnatal growth and development. Expression from the imprinted H19/IGF2 locus involves a complex interplay of 3 means of epigenetic regulation: proper establishment of DNA methylation, promoter occupancy of CTCF, and expression of microRNA-675. We have demonstrated previously in a multigenerational rat model of intrauterine growth restriction the epigenetic heritability of adult metabolic syndrome in a F2 generation. We have further demonstrated abrogation of the F2 adult metabolic syndrome phenotype with essential nutrient supplementation of intermediates along the 1-carbon pathway and shown that alterations in the metabolome precede the adult onset of metabolic syndrome. The upstream molecular and epigenomic mediators underlying these observations, however, have yet to be elucidated fully.

OBJECTIVE

In the current study, we sought to characterize the impact of the intrauterine growth-restricted lineage and essential nutrient supplementation on both levels and molecular mediators of H19 and IGF2 gene expression in the F2 generation.

STUDY DESIGN

F2 intrauterine growth-restricted and sham lineages were obtained by exposing P1 (grandmaternal) pregnant dams to bilateral uterine artery ligation or sham surgery at gestational day 19.5. F1 pups were allocated to the essential nutrient supplemented or control diet at postnatal day 21, and bred at 6-7 weeks of age. Hepatic tissues from the resultant F2 offspring at birth and at weaning (day 21) were obtained. Bisulfite modification and sequencing was employed for methylation analysis. H19 and IGF2 expression was measured by quantitative polymerase chain reaction. Promoter occupancy was quantified by the use of chromatin immunoprecipitation, or ChIP, against CTCF insulator proteins.

RESULTS

Growth-restricted F2 on control diet demonstrated significant down-regulation in H19 expression compared with sham lineage (0.7831 vs 1.287; P < .05); however, essential nutrient supplementation diet abrogates this difference (4.995 vs 5.100; P > .05). Conversely, Igf2 was up-regulated by essential nutrient supplemented diet on the sham lineage (2.0 fold, P = .01), an effect that was not observed in the growth restricted offspring. A significant differential methylation was observed in the promoter region of region H19 among the intrauterine growth-restricted lineage (18% vs 25%; P < .05) on a control diet, whereas the essential nutrient supplemented diet was alternately associated with hypermethylation in both lineages (sham: 50%; intrauterine growth restriction: 84%, P < .05). Consistent with essential nutrient supplementation impacting the epigenome, a decrease of CTCF promoter occupancy was observed in CTCF4 of the growth restricted lineage (2.45% vs 0.56%; P < .05) on the control diet, an effect that was repressed with essential nutrient supplementation.

CONCLUSION

Heritable growth restriction is associated with changes in H19 gene expression; these changes are reversible with diet supplementation to favorably impact adult metabolic syndrome.

Visfatin: New marker of oxidative stress in preterm newborns

BACKGROUND

Oxidative stress is involved in several neonatal conditions characterized by an upregulation in the production of oxidative or nitrative free radicals and a concomitant decrease in the availability of antioxidant species. Oxygen, which is obviously vital to survival, can be highly damaging to neonatal tissue which is known to be poorly equipped to neutralize toxic derivatives. Thus, exposure of the newborn infant to high oxygen concentrations during resuscitation at birth increases oxidative damage. Visfatin is an adipocytokine involved in oxidative stress and an important mediator of inflammation that induces dose-dependent production of both pro-inflammatory and anti-inflammatory cytokines. To our knowledge, the diagnostic value of visfatin as a marker of oxidative stress in preterm newborns has not been investigated.

OBJECTIVE

The aim of this study was to evaluate visfatin levels in preterm neonates resuscitated with different concentrations of oxygen in the delivery room.

PATIENTS

Fifty-two preterm newborns with gestational age less than 32 weeks, resuscitated randomly with different oxygen concentrations (40%, 60%, or 100%) were enrolled at the University Hospital of Messina, over a 12-month period to evaluate serum visfatin levels at T0 (within 1 h after birth), T24 h, T72 h, and T168 h of life.

RESULTS

At T72 h and T168 h, higher serum visfatin values in the high-oxygen group compared to the low- and mild-oxygen subjects (P=0.002 and P<0.001, respectively) were noted.

CONCLUSION

The results of this study suggest that visfatin could be a new marker of oxidative stress in preterm newborns.

Exploring the Role of Different Neonatal Nutrition Regimens during the First Week of Life by Urinary GC-MS Metabolomics

In this study, a gas-chromatography mass spectrometry (GC-MS) metabolomics study was applied to examine urine metabolite profiles of different classes of neonates under different nutrition regimens. The study population included 35 neonates, exclusively either breastfed or formula milk fed, in a seven-day timeframe. Urine samples were collected from intrauterine growth restriction (IUGR), large for gestational age (LGA), and appropriate gestational age (AGA) neonates. At birth, IUGR and LGA neonates showed similarities in their urine metabolite profiles that differed from AGA. When neonates started milk feeding, their metabolite excretion profile was strongly characterized by the different diet regimens. After three days of formula milk nutrition, urine had higher levels of glucose, galactose, glycine and myo-inositol, while up-regulated aconitic acid, aminomalonic acid and adipic acid were found in breast milk fed neonates. At seven days, neonates fed with formula milk shared higher levels of pseudouridine with IUGR and LGA at birth. Breastfed neonates shared up-regulated pyroglutamic acid, citric acid, and homoserine, with AGA at birth. The role of most important metabolites is herein discussed.

Developmental origins of metabolic disorders: The need for biomarker candidates and therapeutic targets from adequate preclinical models

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The research on obesity and associated disorders should rely on contrasted biomarkers.

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The discovery of biomarkers is flawed by inherent variability of human data.

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Hence, preclinical studies in animal models are essential.

The investigation on obesity and associated disorders have changed from an scenario in which genome drove the phenotype to a dynamic setup in which prenatal and early-postnatal conditions are determinant. However, research in human beings is difficult due to confounding factors (lifestyle and socioeconomic heterogeneity) plus ethical issues. Hence, there is currently an intensive effort for developing adequate preclinical models, aiming for an adequate combination of basic studies in rodent models and specific preclinical studies in large animals. The results of these research strategies may increase the identification and development of contrasted biomarkers and therapeutic targets.

Investigating the metabolic fingerprint of term infants with normal and increased fetal growth

An NMR metabolomic approach was employed to highlight the metabolic changes underlying prenatal disorders and determine metabolites that could serve as potential markers in relation to large for gestational age (LGA) newborns.

Gender-specific effects of intrauterine growth restriction on the adipose tissue of adult rats: a proteomic approach

BACKGROUND

Intrauterine growth restriction (IUGR) may program metabolic alterations affecting physiological functions and lead to diseases in later life. The adipose tissue is an important organ influencing energy homeostasis. The present study was aimed at exploring the consequences of IUGR on the retroperitoneal adipose tissue of adult male and female rats, using a proteomic approach.

METHODS AND RESULTS

Pregnant Wistar rats were fed with balanced chow, either ad libitum (control group) or restricted to 50 % of control intake (restricted group) during the whole gestation. The offspring were weaned to ad libitum chow and studied at 4 months of age. Retroperitoneal fat was analyzed by two-dimensional gel electrophoresis followed by mass spectrometry. Both male and female restricted groups had low body weight at birth and at weaning but normal body weight at adulthood. The restricted males had normal fat pads weight and serum glucose levels, with a trend to hyperinsulinemia. The restricted females had increased fat pads weight with normal glucose and insulin levels. The restricted males showed up-regulated levels of proteasome subunit α type 3, branched-chain-amino-acid aminotransferase, elongation 1- alpha 1, fatty acid synthase levels, cytosolic malate dehydrogenase and ATP synthase subunit alpha. These alterations point to increased proteolysis and lipogenesis rates and favoring of ATP generation. The restricted females showed down-regulated levels of L-lactate dehydrogenase perilipin-1, mitochondrial branched-chain alpha-keto acid dehydrogenase E1, and transketolase. These findings suggest impairment of glycemic control, stimulation of lipolysis and inhibition of proteolysis, pentose phosphate pathway and lipogenesis rates. In both genders, several proteins involved in oxidative stress and inflammation were affected, in a pattern compatible with impairment of these responses.

CONCLUSIONS

The proteomic analysis of adipose tissue showed that, although IUGR affected pathways of substrate and energy metabolism in both males and females, important gender differences were evident. While IUGR males displayed alterations pointing to a predisposition to later development of obesity, the alterations observed in IUGR females pointed to a metabolic status of established obesity, in agreement with their increased fat pads mass.