Obesogenic Diet in Mice Leads to Inflammation and Oxidative Stress in the Mother in Association with Sex-Specific Changes in Fetal Development, Inflammatory Markers and Placental Transcriptome

BACKGROUND

Obesity during pregnancy is related to adverse maternal and neonatal outcomes. Factors involved in these outcomes may include increased maternal insulin resistance, inflammation, oxidative stress, and nutrient mishandling. The placenta is the primary determinant of fetal outcomes, and its function can be impacted by maternal obesity. The aim of this study on mice was to determine the effect of obesity on maternal lipid handling, inflammatory and redox state, and placental oxidative stress, inflammatory signaling, and gene expression relative to female and male fetal growth.

METHODS

Female mice were fed control or obesogenic high-fat/high-sugar diet (HFHS) from 9 weeks prior to, and during, pregnancy. On day 18.5 of pregnancy, maternal plasma, and liver, placenta, and fetal serum were collected to examine the immune and redox states. The placental labyrinth zone (Lz) was dissected for RNA-sequencing analysis of gene expression changes.

RESULTS

the HFHS diet induced, in the dams, hepatic steatosis, oxidative stress (reduced catalase, elevated protein oxidation) and the activation of pro-inflammatory pathways (p38-MAPK), along with imbalanced circulating cytokine concentrations (increased IL-6 and decreased IL-5 and IL-17A). HFHS fetuses were asymmetrically growth-restricted, showing sex-specific changes in circulating cytokines (GM-CSF, TNF-α, IL-6 and IFN-γ). The morphology of the placenta Lz was modified by an HFHS diet, in association with sex-specific alterations in the expression of genes and proteins implicated in oxidative stress, inflammation, and stress signaling. Placental gene expression changes were comparable to that seen in models of intrauterine inflammation and were related to a transcriptional network involving transcription factors, LYL1 and PLAG1.

CONCLUSION

This study shows that fetal growth restriction with maternal obesity is related to elevated oxidative stress, inflammatory pathways, and sex-specific placental changes. Our data are important, given the marked consequences and the rising rates of obesity worldwide.

Blood oxidative stress biomarkers in women: influence of oral contraception, exercise, and N-acetylcysteine

Purpose

To compare physiological responses to submaximal cycling and sprint cycling performance in women using oral contraceptives (WomenOC) and naturally cycling women (WomenNC) and to determine whether N-acetylcysteine (NAC) supplementation mediates these responses.

Methods

Twenty recreationally trained women completed five exercise trials (i.e., an incremental cycling test, a familiarisation trial, a baseline performance trial and two double-blind crossover intervention trials). During the intervention trials participants supplemented with NAC or a placebo 1 h before exercise. Cardiopulmonary parameters and blood biochemistry were assessed during 40 min of fixed-intensity cycling at 105% of gas-exchange threshold and after 1-km cycling time-trial.

Results

WomenOC had higher ventilation (β [95% CI] = 0.07 L·min⁻¹ [0.01, 0.14]), malondialdehydes (β = 12.00 mmol·L⁻¹ [6.82, 17.17]) and C-reactive protein (1.53 mg·L⁻¹ [0.76, 2.30]), whereas glutathione peroxidase was lower (β =  22.62 mU·mL⁻¹ [− 41.32, − 3.91]) compared to WomenNC during fixed-intensity cycling. Plasma thiols were higher at all timepoints after NAC ingestion compared to placebo, irrespective of group (all p < 0.001; d = 1.45 to 2.34). For WomenNC but not WomenOC, the exercise-induced increase in malondialdehyde observed in the placebo trial was blunted after NAC ingestion, with lower values at 40 min (p = 0.018; d = 0.73). NAC did not affect cycling time-trial performance.

Conclusions

Blood biomarkers relating to oxidative stress and inflammation are elevated in WomenOC during exercise. There may be an increased strain on the endogenous antioxidant system during exercise, since NAC supplementation in WomenOC did not dampen the exercise-induced increase in malondialdehyde. Future investigations should explore the impact of elevated oxidative stress on exercise adaptations or recovery from exercise in WomenOC.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00421-022-04964-w.

Transcriptional profiles of genes related to mitochondrial aging in placental pathologies

As the placenta develops across gestation, the mitochondria and other organelles like the endoplasmic reticulum (ER) must continue to adapt to stressors such as oxidative stress. As pregnancy approaches term, these stressors may contribute to placental aging, including mitochondrial changes leading to cellular senescence. When these processes are exacerbated, pregnancy pathologies arise. This study aimed to identify correlations between genes related to mitochondria, ER and cellular senescence in placentae complicated by pregnancy complications. Placental samples from pregnancies classified as preterm, term, post-term, preterm with fetal growth restriction (FGR), preterm with preeclampsia (PE) and preterm with PE and FGR were used to measure gene expression of TOMM20, MFN1, TFAM, MFN2, PARK2, PINK1, EIF2AK3, TP53 and ERN1. MetaboAnalyst 5.0 was used to generate heatmaps, principal component analysis (PCA) plots, correlation graphs and receiver operating characteristic (ROC) analysis. This study found that genes related mitochondrial dynamics and aging undergo changes in placentae affected by pregnancy pathologies. The TOMM20/PARK2 ratio may be a promising marker to discriminate between healthy and unhealthy placental tissue. Future studies should explore circulating biomarkers of mitochondrial aging and dysfunction as indicators of placental health.

A Novel Ferritin-Core Analog Is a Safe and Effective Alternative to Oral Ferrous Iron for Treating Iron Deficiency during Pregnancy in Mice

BACKGROUND

Many women enter pregnancy with iron stores that are insufficient to maintain maternal iron balance and support fetal development and consequently, often require iron supplements. However, the side effects associated with many currently available iron supplements can limit compliance.

OBJECTIVE

This study aimed to test the safety and efficacy of a novel nanoparticulate iron supplement, a dietary ferritin analog termed iron hydroxide adipate tartrate (IHAT), in pregnant mice.

METHODS

Female C57BL/6 mice were maintained on either an iron-deficient or a control diet for 2 wk prior to timed mating to develop iron-deficient or iron-sufficient pregnancy models, respectively. Mice from each model were then gavaged daily with 10 mg iron/kg body weight as either IHAT or ferrous sulfate, or with water only, beginning on embryonic day (E) 4.5. Mice were killed on E18.5 and maternal iron and hematological parameters were measured. The expression of genes encoding iron transporters and oxidative stress markers in the duodenum and placenta were determined, along with hepatic expression of the gene encoding the iron regulatory hormone hepcidin and fetal iron.

RESULTS

Oral IHAT and ferrous sulfate were equally effective at increasing maternal hemoglobin (20.2% and 16.9%, respectively) and hepatic iron (30.2% and 29.3%, respectively), as well as total fetal iron (99.7% and 83.8%, respectively), in iron-deficient pregnant mice compared with those gavaged with water only, with no change in oxidative stress markers seen with either treatment. However, there was a significant increase in the placental expression of the oxidative stress marker heme oxygenase 1 in iron-replete pregnant mice treated with ferrous sulfate when compared with iron-replete pregnant mice gavaged with IHAT (96.9%, P <0.05).

CONCLUSIONS

IHAT has proved a safe and effective alternative to oral ferrous sulfate in mice, and it has potential for treating iron deficiency in human pregnancy.

Nutritional properties of selected superfood extracts and their potential health benefits

Background

The term 'superfoods' is used to market foods considered to have significant health benefits. 'Superfoods' are claimed to prevent diseases as well as improving overall health, though the lack of explicit criteria means that any food can be labelled 'super' without support from scientific research. Typically, these 'superfoods' are rich in a particular nutrient for example antioxidants or omega-3 fatty acids. The objective of this study was to investigate the nutritional properties of a selection of superfood seeds: flax, chia, hulled sunflower and two types of processed hemp seeds and determine whether they may have potential health benefits.

Methods

We developed a simple aqueous extraction method for ground seeds and analysed their composition by mineral, protein and monosaccharide analyses. Cell viability assays were performed on Caco-2 and IEC-6 intestinal epithelial cells using increasing doses of the prepared extracts.

Results

Increased cell viability was observed in both cell lines with increasing concentrations of the flax seed, chia seed or hulled sunflower extracts (P < 0.05). Compositional analyses revealed the presence of polysaccharides, proteins and essential minerals in the aqueous extracts and in vitro assays showed sunflower had the highest antioxidant activity. However, differences in extract composition and antioxidant properties could not be directly related to the observed increase in cell viability suggesting that other components in the extracts may be responsible. Future studies will further characterize these extracts and investigate whether they are beneficial for gastrointestinal health.

Circulating trace elements for the prediction of preeclampsia and small for gestational age babies

INTRODUCTION

Poor gestational outcomes due to placental insufficiency can have lifelong consequences for mother and child.

OBJECTIVE

There is a need for better methods of diagnosis, and elemental metabolomics may provide a means to determine the risk of gestational disorders.

METHODS

This study used blood plasma samples collected at 36 weeks' gestation from women who later developed preeclampsia (n = 38), or small-for-gestational age babies (n = 91), along with matched controls (n = 193). Multi-element analysis was conducted by inductively coupled plasma mass spectrometer (ICP-MS), allowing simultaneous measurement of 28 elements.

RESULTS

Women who later developed PE, exhibited significantly increased concentrations of K, Rb and Ba. For SGA pregnancies, there was a significant increase in Cu and a decrease in As concentrations. Despite significant differences in single elements, the elemental profile of groups indicated no clustering of control, PE, or SGA samples. Positive predicative values correctly identified approximately 60% of SGA and 70% of PE samples.

CONCLUSION

This is the first-time elemental metabolomics has been used to predict SGA and PE at 36 weeks. Though significant changes were identified, routine clinical use may be limited but may contribute to a multi marker test. Future analysis should include other biomarkers, metabolic data or clinical measurements made throughout gestation.

Sex-Specific Differences in Lysine, 3-Hydroxybutyric Acid and Acetic Acid in Offspring Exposed to Maternal and Postnatal High Linoleic Acid Diet, Independent of Diet

BACKGROUND

Linoleic acid (LA) is an essential polyunsaturated fatty acid (PUFA) that is required for foetal growth and development. Excess intake of LA can be detrimental for metabolic health due to its pro-inflammatory properties; however, the effect of a diet high in LA on offspring metabolites is unknown. In this study, we aimed to determine the role of maternal or postnatal high linoleic acid (HLA) diet on plasma metabolites in adult offspring.

METHODS

Female Wistar Kyoto (WKY) rats were fed with either low LA (LLA) or HLA diet for 10 weeks prior to conception and during gestation/lactation. Offspring were weaned at postnatal day 25 (PN25), treated with either LLA or HLA diets and sacrificed at PN180. Metabolite analysis was performed in plasma samples using Nuclear Magnetic Resonance.

RESULTS

Maternal and postnatal HLA diet did not alter plasma metabolites in male and female adult offspring. There was no specific clustering among different treatment groups as demonstrated by principal component analysis. Interestingly, there was clustering among male and female offspring independent of maternal and postnatal dietary intervention. Lysine was higher in female offspring, while 3-hydroxybutyric acid and acetic acid were significantly higher in male offspring.

CONCLUSION

In summary, maternal or postnatal HLA diet did not alter the plasma metabolites in the adult rat offspring; however, differences in metabolites between male and female offspring occurred independently of dietary intervention.

The Placental Ferroxidase Zyklopen Is Not Essential for Iron Transport to the Fetus in Mice

BACKGROUND

The ferroxidase zyklopen (Zp) has been implicated in the placental transfer of iron to the fetus. However, the evidence for this is largely circumstantial.

OBJECTIVES

This study aimed to determine whether Zp is essential for placental iron transfer.

METHODS

A model was established using 8- to 12-wk-old pregnant C57BL/6 mice on standard rodent chow in which Zp was knocked out in the fetus and fetal components of the placenta. Zp was also disrupted in the entire placenta using global Zp knockout mice. Inductively coupled plasma MS was used to measure total fetal iron, an indicator of the amount of iron transferred by the placenta to the fetus, at embryonic day 18.5 of gestation. Iron transporter expression in the placenta was measured by Western blotting, and the expression of Hamp1, the gene encoding the iron regulatory hormone hepcidin, was determined in fetal liver by real-time PCR.

RESULTS

There was no change in the amount of iron transferred to the fetus when Zp was disrupted in either the fetal component of the placenta or the entire placenta. No compensatory changes in the expression of the iron transport proteins transferrin receptor 1 or ferroportin were observed, nor was there any change in fetal liver Hamp1 mRNA. Hephl1, the gene encoding Zp, was expressed mainly in the maternal decidua of the placenta and not in the nutrient-transporting syncytiotrophoblast. Disruption of Zp in the whole placenta resulted in a 26% increase in placental size (P < 0.01).

CONCLUSIONS

Our data indicate that Zp is not essential for the efficient transfer of iron to the fetus in mice and is localized predominantly in the maternal decidua. The increase in placental size observed when Zp is knocked out in the entire placenta suggests that this protein may play a role in placental development.

Temporal changes in blood oxidative stress biomarkers across the menstrual cycle and with oral contraceptive use in active women

PURPOSE

To examine the temporal changes in blood oxidative stress biomarkers in recreationally-trained women that were naturally-cycling (WomenNC) or using oral contraceptives (WomenOC) across one month.

METHODS

Blood samples were acquired at three timepoints of the menstrual cycle (1: early-follicular, 2: late-follicular and 3: mid-luteal) and oral contraceptive packet (1: InactiveOC, 2: Mid-activeOC and 3: Late-activeOC) for determination of estradiol, progesterone, oxidative stress, C-reactive protein (CRP) and other cardiometabolic biomarkers in plasma and serum.

RESULTS

There was a Group by Time effect on estradiol (p < 0.001, partial η² = 0.64) and progesterone (p < 0.001, partial η² = 0.77). Malondialdehyde, lipid hydroperoxides and CRP concentrations were higher in WomenOC during Late-activeOC compared to InactiveOC (+ 96%, + 23% and + 104%, respectively, p < 0.05). However, there were no changes in these biomarkers across the menstrual cycle in WomenNC (p > 0.05). At all timepoints (i.e., 1, 2 and 3), WomenOC had elevated lipid hydroperoxides (+ 28, + 48% and + 50%) and CRP (+ 71%, + 117% and + 130%) compared to WomenNC (p < 0.05, partial η² > 0.25). There was no Group by Time effect on non-enzymatic antioxidants or glutathione peroxidase; however, glutathione peroxidase was lower in WomenOC, i.e., main effect of group (p < 0.05, partial η² > 0.20).

CONCLUSION

These findings demonstrate that WomenOC not only have higher oxidative stress and CRP than WomenNC, but also a transient increase across one month of habitual oral contraceptive use. Since changes in oxidative stress and CRP often relate to training stress and recovery, these outcomes may have implications to workload monitoring practices in female athletes.

Elemental Metabolomics for Prediction of Term Gestational Outcomes Utilising 18-Week Maternal Plasma and Urine Samples

A normal pregnancy is essential to establishing a healthy start to life. Complications during have been associated with adverse perinatal outcomes and lifelong health problems. The ability to identify risk factors associated with pregnancy complications early in gestation is vitally important for preventing negative foetal outcomes. Maternal nutrition has been long considered vital to a healthy pregnancy, with micronutrients and trace elements heavily implicated in maternofoetal metabolism. This study proposed the use of elemental metabolomics to study multiple elements at 18 weeks gestation from blood plasma and urine to construct models that could predict outcomes such as small for gestational age (SGA) (n = 10), low placental weight (n = 18), and preterm birth (n = 13) from control samples (n = 87). Samples collected from the Lyell McEwin Hospital in Adelaide, South Australia, were measured for 27 plasma elements and 37 urine elements by inductively coupled plasma mass spectrometry. Exploratory analysis indicated an average selenium concentration 20 μg/L lower than established reference ranges across all groups, low zinc in preterm (0.64 μg/L, reference range 0.66-1.10 μg/L), and higher iodine in preterm and SGA gestations (preterm 102 μg/L, SGA 111 μg/L, reference range 40-92 μg/L). Using random forest algorithms with receiver operating characteristic curves, low placental weight was predicted with 86.7% accuracy using plasma, 78.6% prediction for SGA with urine, and 73.5% determination of preterm pregnancies. This study indicates that elemental metabolomic modelling could provide a means of early detection of at-risk pregnancies allowing for more targeted monitoring of mothers, with potential for early intervention strategies to be developed.

Low serum selenium in pregnancy is associated with reduced T3 and increased risk of GDM

Thyroid disorders are the most common endocrine disorders affecting women commencing pregnancy. Thyroid hormone metabolism is strongly influenced by selenium status; however, the relationship between serum selenium concentrations and thyroid hormones in euthyroid pregnant women is unknown. This study investigated the relationship between maternal selenium and thyroid hormone status during pregnancy by utilizing data from a retrospective, cross-sectional study (Maternal Outcomes and Nutrition Tool or MONT study) with cohorts from two tertiary care hospitals in South East Queensland, Australia. Pregnant women (n = 206) were recruited at 26-30 weeks gestation and serum selenium concentrations were assessed using inductively coupled plasma mass spectrometry. Thyroid function parameters were measured in serum samples from women with the lowest serum selenium concentrations (51.2 ± 1.2 µg/L), women with mean concentrations representative of the entire cohort (78.8 ± 0.4 µg/L) and women with optimal serum selenium concentrations (106.9 ± 2.3 µg/L). Women with low serum selenium concentrations demonstrated reduced fT3 levels (P < 0.05) and increased TPOAb (P < 0.01). Serum selenium was positively correlated with fT3 (P < 0.05) and negatively correlated with TPOAb (P < 0.001). Serum fT4 and thyroid-stimulating hormone (TSH) were not different between all groups, though the fT4/TSH ratio was increased in the low selenium cohort (P < 0.05). Incidence of pregnancy disorders, most notably gestational diabetes mellitus, was increased within the low serum selenium cohort (P < 0.01). These results suggest selenium status in pregnant women of South East Queensland may not be adequate, with possible implications for atypical thyroid function and undesirable pregnancy outcomes.

Mitochondrial dysfunction in placental trophoblast cells experiencing gestational diabetes mellitus

KEY POINTS

Mitochondrial dysfunction is known to occur in diabetic phenotypes including type 1 and 2 diabetes mellitus. The incidence of gestational diabetes mellitus (GDM) is increasing and defined as the onset of a diabetic phenotype during pregnancy. The role of placental mitochondria in the aetiology of GDM remains unclear and is an emerging area of research. Differing mitochondrial morphologies within the placenta may influence the pathogenesis of the disorder. This study observed mitochondrial dysfunction in GDM placenta when assessing whole tissue. Upon further investigation into mitochondrial isolates from the cytotrophoblast and syncytiotrophoblast, mitochondrial dysfunction appears exaggerated in syncytiotrophoblast. Assessing mitochondrial populations individually enabled the determination of differences between cell lineages of the placenta and established varying levels of mitochondrial dysfunction in GDM, in some instances establishing significance in pathways previously inconclusive or confounded when assessing whole tissue. This research lays the foundation for future work into mitochondrial dysfunction in the placenta and the role it may play in the aetiology of GDM.

ABSTRACT

Mitochondrial dysfunction has been associated with diabetic phenotypes, yet the involvement of placental mitochondria in gestational diabetes mellitus (GDM) remains inconclusive. This is in part complicated by the different mitochondrial subpopulations present in the two major trophoblast cell lineages of the placenta. To better elucidate the role of mitochondria in this pathology, this study examined key aspects of mitochondrial function in placentas from healthy pregnancies and those complicated by GDM in both whole tissue and isolated mitochondria. Mitochondrial content, citrate synthase activity, reactive oxygen species production and gene expression regulating metabolic, hormonal and antioxidant control was examined in placental tissue, before examining functional differences between mitochondrial isolates from cytotrophoblast (Cyto-Mito) and syncytiotrophoblast (Syncytio-Mito). Our study observed evidence of mitochondrial dysfunction across multiple pathways when assessing whole placental tissue from GDM pregnancies compared with healthy controls. Furthermore, by examining isolated mitochondria from the cytotrophoblast and syncytiotrophoblast cell lineages of the placenta we established that although both mitochondrial populations were dysfunctional, they were differentially impacted. These data highlight the need to consider changes in mitochondrial subpopulations at the feto-maternal interface when studying pregnancy pathologies.

Elemental metabolomics in human cord blood: Method validation and trace element quantification

BACKGROUND

Trace elements are an essential requirement for human health and development and changes in trace element status have been associated with pregnancy complications such as gestational diabetes mellitus (GDM), pre-eclampsia (PE), fetal growth restriction (FGR), and preterm birth. Elemental metabolomics, which involves the simultaneous quantification and characterisation of multiple elements, could provide important insights into these gestational disorders.

METHODS

This study used an Agilent 7900 inductively coupled plasma mass spectrometer (ICP-MS) to simultaneously measure 68 elements, in 166 placental cord blood samples collected from women with various pregnancy complications (control, hypertensive, PE, GDM, FGR, pre-term, and post-term birth).

RESULTS

There were single element differences across gestational outcomes for elements Mg, P, Cr, Ni, Sr, Mo, I, Au, Pb, and U. Hypertensive and post-term pregnancies were significantly higher in Ni concentrations when compared to controls (control = 2.74 μg/L, hypertensive = 6.72 μg/L, post-term = 7.93 μg/L, p < 0.05), iodine concentration was significantly higher in post-term pregnancies (p < 0.05), and Pb concentrations were the lowest in pre-term pregnancies (pre-term = 2.79 μg/L, control = 4.68 μg/L, PE = 5.32 μg/L, GDM = 8.27 μg/L, p < 0.01). Further analysis was conducted using receiver operating characteristic (ROC) curves for differentiating pregnancy groups. The ratio of Sn/Pb showed the best diagnostic power in discriminating between control and pre-term birth with area under the curve (AUC) 0.86. When comparing control and post-term birth, Mg/Cr (AUC = 0.84), and Cr (AUC = 0.83) had the best diagnostic powers. In pre-term and post-term comparisons Ba was the best single element (81.5%), and P/Cu provided the best ratio (91.7%).

CONCLUSIONS

This study has shown that analysis of multiple elements can enable differentiation between fetal cord blood samples from control, hypertensive, PE, GDM, FGR, pre and post-term pregnancies. This data highlights the power of elemental metabolomics and provides a basis for future gestational studies.

Proteomic Analysis of Placental Mitochondria Following Trophoblast Differentiation

As gestation proceeds the human placenta is in a constant state of renewal and placental debris is released into the maternal circulation where it can trigger adverse physiological and immunological responses. Trophoblast cells of the placenta differentiate from mononuclear cytotrophoblast cells to fuse and form the syncytiotrophoblast, a multinuclear layer that covers the entire surface of the placenta. As part of this process there are significant changes to cellular cytoskeletal organization and organelle morphology. In this study we have examined the molecular changes that occur in mitochondria from these two cellular compartments and identified differential expression of key proteins that underpin changes in mitochondrial morphology, metabolism and function. Mitochondria were isolated for term placental tissue and separated according to size and density by sequential differential centrifugation. Isolated mitochondrial populations were then subjected to proteomics using HPLC separation of peptides and MS identification. Differential expression of proteins of interest was confirmed by western blots. Using a bioinformatics approach we also examined published protein databases to confirm our observations. In total 651 proteins were differentially regulated in mitochondria from cytotrophoblast versus syncytiotrophoblast. Of these 29 were statistically significant and chosen for subsequent analysis. These included subunits of ATP synthase that would affect ATP production and cristae structure, carbohydrate metabolizing enzymes phospoenolpyruvate carboxykinase-2, pyruvate carboxylase (PC) and pyruvate dehydrogenase (PDH), fatty acid metabolizing enzyme acyl-CoA dehydrogenase, stress responses such a glucose regulated protein-78 and protein disulfide isomerase, and mitochondrial dynamics proteins mitofusin 1 and 2. Placental cell biology and mitochondrial function is central to the pathogenesis of many gestational disorders such as preeclampsia, pre-term birth, fetal growth restriction and gestational diabetes. These studies show important shifts in mitochondrial metabolism and dynamics post trophoblast differentiation and provide key molecular targets for study in pathological pregnancies.

Maternal selenium deficiency during pregnancy in mice increases thyroid hormone concentrations, alters placental function and reduces fetal growth

KEY POINTS

Inappropriate intake of key micronutrients in pregnancy is known to alter maternal endocrine status, impair placental development and induce fetal growth restriction. Selenium is an essential micronutrient required for the function of approximately 25 important proteins. However, the specific effects of selenium deficiency during pregnancy on maternal, placental and fetal outcomes are poorly understood. The present study demonstrates that maternal selenium deficiency increases maternal triiodothyronine and tetraiodothyronine concentrations, reduces fetal blood glucose concentrations, and induces fetal growth restriction. Placental expression of key selenium-dependent thyroid hormone converting enzymes were reduced, whereas the expression of key placental nutrient transporters was dysregulated. Selenium deficiency had minimal impact on selenium-dependent anti-oxidants but increased placental copper concentrations and expression of superoxide dismutase 1. These results highlight the idea that selenium deficiency during pregnancy may contribute to thyroid dysfunction, causing reduced fetal growth, that may precede programmed disease outcomes in offspring.

ABSTRACT

Selenium is a trace element fundamental to diverse homeostatic processes, including anti-oxidant regulation and thyroid hormone metabolism. Selenium deficiency in pregnancy is common and increases the risk of pregnancy complications including fetal growth restriction. Although altered placental formation may contribute to these poor outcomes, the mechanism by which selenium deficiency contributes to complications in pregnancy is poorly understood. Female C57BL/6 mice were randomly allocated to control (>190 µg kg-1 , n = 8) or low selenium (<50 µg kg-1 , n = 8) diets 4 weeks prior to mating and throughout gestation. Pregnant mice were killed at embryonic day 18.5 followed by collection of maternal and fetal tissue. Maternal and fetal plasma thyroid hormone concentrations were analysed, as was placental expression of key selenoproteins involved in thyroid metabolism and anti-oxidant defences. Selenium deficiency increased plasma tetraiodothyronine and triiodothyronine concentrations. This was associated with a reduction in placental expression of key selenodependent deiodinases, DIO2 and DIO3. Placental expression of selenium-dependent anti-oxidants was unaffected by selenium deficiency. Selenium deficiency reduced fetal glucose concentrations, leading to reduced fetal weight. Placental glycogen content was increased within the placenta, as was Slc2a3 mRNA expression. This is the first study to demonstrate that selenium deficiency may reduce fetal weight through increased maternal thyroid hormone concentrations, impaired placental thyroid hormone metabolism and dysregulated placental nutrient transporter expression. The study suggests that the magnitude of selenium deficiency commonly reported in pregnant women may be sufficient to impair thyroid metabolism but not placental anti-oxidant concentrations.

Essential Mineral Intake During Pregnancy and Its Association With Maternal Health and Birth Outcomes in South East Queensland, Australia

Micronutrient supplements are often recommended during pregnancy, yet their role and necessity remain poorly understood in the Australian population. This study aimed to determine the essential mineral intake of a population of pregnant women in South East Queensland and investigate the effects of supplements on their micronutrient status and birth outcomes. Women completing the Oral Glucose Tolerance Test at two South East Queensland hospitals between 180 and 210 days gestation provided fasting blood samples and dietary data using the Maternal Outcomes and Nutrition Tool (n = 127). Birth outcomes were sourced from medical records. Serum elemental profiles were determined by inductively coupled plasma mass spectrometry (ICP-MS) analysis. Intake of 8 essential minerals was compared with Australian dietary recommendations; matched serum mineral levels were compared with the current Queensland pregnancy reference ranges. Data were examined using cross-sectional cohort design and independent sample t-tests. Supplement use had no significant influence on serum values of trace elements or the incidence of hypertensive disorders, gestational diabetes, preterm birth or infant birthweight. Dietary selenium, zinc and iodine were significantly higher in women birthing beyond 41 completed weeks; selenium (P = .026) and zinc (P = .034) both made unique contributions to the regression models when controlling for confounders. Women exhibited adequate to excessive serum micronutrient levels compared with pregnancy reference ranges, a finding consistent with dietary intake calculations. Data suggest that excessive essential mineral intake contributed to prolonged pregnancy in this cohort, supporting previous studies in this population. Further research is required to determine individual needs and eliminate the potential for harm before recommending pregnancy supplements.

Elemental Metabolomics and Pregnancy Outcomes

Trace elements are important for human health and development. The body requires specific micronutrients to function, with aberrant changes associated with a variety of negative health outcomes. Despite this evidence, the status and function of micronutrients during pregnancy are relatively unknown and more information is required to ensure that women receive optimal intakes for foetal development. Changes in trace element status have been associated with pregnancy complications such as gestational diabetes mellitus (GDM), pre-eclampsia (PE), intrauterine growth restriction (IUGR), and preterm birth. Measuring micronutrients with methodologies such as elemental metabolomics, which involves the simultaneous quantification and characterisation of multiple elements, could provide insight into gestational disorders. Identifying unique and subtle micronutrient changes may highlight associated proteins that are affected underpinning the pathophysiology of these complications, leading to new means of disease diagnosis. This review will provide a comprehensive summary of micronutrient status during pregnancy, and their associations with gestational disorders. Furthermore, it will also comment on the potential use of elemental metabolomics as a technique for disease characterisation and prediction.

Placental adaptations to micronutrient dysregulation in the programming of chronic disease

Poor nutrition during pregnancy is known to impair foetal development and increase the risk of chronic disease in offspring. Both macronutrients and micronutrients are required for a healthy pregnancy although significantly less is understood about the role of micronutrients in the programming of chronic disease. This is despite the fact that modern calorie rich diets are often also deficient in key micronutrients. The importance of micronutrients in gestational disorders is clearly understood but how they impact long term disease in humans requires further investigation. In contrast, animal studies have demonstrated how diets high or low in specific micronutrients influence offspring physiology. Many of these studies highlight the importance of the placenta in determining disease risk. This review will explore the effects of individual vitamins, minerals and trace elements on offspring disease outcomes and discuss several key placental adaptations that are affected by multiple micronutrients. These placental adaptations include micronutrient induced dysregulation of oxidative stress, altered methyl donor availability and its impact on epigenetic mechanisms as well as endocrine dysfunction. Critical gaps in our current knowledge and the relative importance of different micronutrients at different gestational ages will also be highlighted. Finally, this review will discuss the need for further studies to characterise the micronutrient status of Australian women of reproductive age and correlate micronutrient status to placental adaptations, pregnancy complications and offspring disease.