Fetal iron deficiency disrupts the maturation of synaptic function and efficacy in area CA1 of the developing rat hippocampus

Effects of perinatal iron deficiency on spinal dorsal horn circuits

Clinical association studies have identified early life iron deficiency (ID) as a risk factor for the development of chronic pain. ID during the perinatal period has long-term consequences for the developing nervous system. Mounting evidence from both clinical and preclinical studies suggests that ID alters pain perception. However, nothing is yet known about how perinatal ID impacts nociceptive circuitry. The present study sought to characterize the effects of ID on the spinal superficial dorsal horn (SDH). Using ex vivo patch clamp electrophysiology in a mouse model of perinatal ID, the excitability of inhibitory and putative excitatory interneurons in the SDH was measured. It was found that early life ID did not significantly change the intrinsic excitability of either interneuron cell type in adolescence or adulthood. The investigation of synaptic inputs onto these two populations revealed that ID modulates spontaneous glutamatergic transmission within the SDH, but did not affect the excitatory drive or balance of synaptic excitation and inhibition. Interestingly, while ID altered the pattern of primary afferent inputs onto presumed glutamatergic interneurons in the mature SDH, the overall efficacy of these synapses was not affected by ID. Collectively, these results suggest that spinal nociceptive circuits are resilient to change following perinatal ID. PERSPECTIVE: This study demonstrates that perinatal iron deficiency (ID) elicits few changes to the intrinsic membrane excitability of superficial dorsal horn neurons or the efficacy of their synaptic inputs. These findings represent a critical first step towards elucidating the effects of ID on nociceptive processing in the central nervous system.

Ferroportin 1 depletion in neural stem cells promotes hippocampal neurogenesis and cognitive function in mice

In the adult brain, newborn granule cells continuously integrate into the hippocampal circuits, and fine-tuning the regulation of this process is crucial for improving hippocampal function. Iron is an essential element for the development and functionality of the brain. Ferroportin 1 (Fpn1) is an iron efflux transporter that plays a crucial role in regulating cellular iron release. In this study, Nestin-CreERT2-mediated Fpn1 conditional knockout (cKO) mice were established to investigate the impact of Fpn1 depletion in neural stem cells (NSCs) on adult hippocampal neurogenesis. Interestingly, we found that the cKO mice presented better learning and memory abilities and fewer anxiety-like behaviors. The numbers of self-renewing NSCs and NSCs undergoing proliferation and differentiation were significantly increased in the hippocampus of Fpn1 cKO mice, resulting in greater numbers of newborn neurons than in control mice. Further investigation revealed that the elevated iron levels in NSCs and iron-mediated increase in ROS generation in Fpn1 cKO mice contributed to the enhanced hippocampal neurogenesis through PI3K/Akt and MAPK signaling activation. Notably, iron supplementation promoted the proliferation of primary NSCs dose-dependently, whereas the presence of ROS inhibitor abolished this effect. This study reveals that Fpn1 of NSCs and its regulated iron levels are key modulators of hippocampal neurogenesis through promoting the proliferation of NSCs and ultimately controlling hippocampal function. These findings may provide valuable insights into stem cell-targeting treatments for neurological diseases.

Fetal Fornix-Hippocampus Complex and Hippocampus Height Measurements Between 18 and 24 Weeks of Gestation and the Effect of Maternal Iron Deficiency Anemia

PURPOSE

To construct nomograms for both sides of the fetal fornix-hippocampus complex (FHC) length and hippocampus height between 18 + 0 and 23 + 6 weeks of gestation using two-dimensional sonography. Additionally, we evaluated the effects of laterality, fetal sex, and maternal iron deficiency anemia on these measurements.

METHODS

This was a prospective cross-sectional study of 223 singleton pregnancies between 18 + 0 and 23 + 6 weeks of gestation. The FHC length and hippocampus height were measured on both sides in the parasagittal cranial plane of the fetus by 2D ultrasonography. Measurements from 30 women with iron deficiency anemia, out of 223 patients, were compared to those of normal controls.

RESULTS

Nomograms for FHC length and hippocampus height were constructed, showing a strong correlation with gestational age. No significant differences were found between the right and left side FHC lengths or hippocampus heights (p > 0.05), nor between male and female fetuses (p > 0.05). The FHC lengths (p > 0.05) and hippocampus heights (p > 0.05) of fetuses in anemic and non-anemic pregnancies also showed no significant differences.

CONCLUSION

2D ultrasound morphology of the fetal hippocampus and fornix during the second trimester is not significantly different between pregnancies with iron deficiency anemia and nonanemic women.

Correlative analysis of metallomic gene expression and metal ion content within the mouse hippocampus

Brain metal homeostasis is essential for healthy neurological function, and disturbed brain metal homeostasis has deleterious consequences for neurodevelopment or cognitive outcome following injury or during disease. Specific regions of the brain (e.g. the hippocampus and subregions within) are known to be enriched with transition metals (i.e. ions of iron, copper, and zinc). Neither the physiological need for localized enrichment, nor the mechanisms driving the enrichment, however, are well understood. In this study we have applied a multimodal template, incorporating elemental mapping using X-ray fluorescence microscopy with spatial transcriptomics, to help reveal a molecular basis for metallomic heterogeneity across key subregions of the hippocampus. Our results reveal that significant differences in iron, zinc, and copper enrichment are associated with regional enrichment of specific transcripts related to metal transport, metal storage, and metal regulatory proteins. In addition to providing novel biological insight into the neurometallomic profile of the hippocampus, this study also provides an important template for others to integrate transcriptomics into multimodal workflows investigating the neurometallome.

Iron metabolism dysfunction in neuropsychiatric disorders: Implications for therapeutic intervention

Iron is a trace metal that takes part in the maintenance of body homeostasis by, for instance, aiding in energy production and immunity. A body of evidence now demonstrates that dysfunction in iron metabolism can have detrimental effects and is intricately associated with the development of neuropsychiatric disorders, including Major Depressive Disorder (MDD), anxiety, and schizophrenia. For instance, changes in serum and central nervous system (CNS) levels of iron and in proteins mediating iron metabolism have been documented in patients grappling with the aforementioned diseases. By contrast, targeting iron metabolism by using iron chelators, for instance, has proven to be effective in alleviating disease burden. Therefore, here we review the state-of-the-art regarding the role of iron metabolism and its dysfunction in the context of neuropsychiatric disorders. Furthermore, we discuss how targeting iron metabolism can be an effective therapeutic option to tackle this class of diseases. Finally, we discuss the mechanisms linking this dysfunction to behavioral changes in these disorders. Harnessing the knowledge of iron metabolism is not only key to the characterization of novel molecular targets and disease biomarkers but also crucial to drug repurposing and drug design.

Neurovascular unit impairment in iron deficiency anemia

Iron is one of the crucial elements for CNS development and function and its deficiency (ID) is the most common worldwide nutrient deficit in the world. Iron deficiency anemia (IDA) in pregnant women and infants is a worldwide health problem due to its high prevalence and its irreversible long-lasting effects on brain development. Even with iron supplementation, IDA during pregnancy and/or breastfeeding can result in irreversible cognitive, motor, and behavioral impairments. The neurovascular unit (NVU) plays an important role in iron transport within the CNS as well as in the blood brain-barrier (BBB) formation and maturation, vasculogenesis/angiogenesis, neurovascular coupling and metabolic waste clearance. In animal models of IDA, significant changes have been observed at the capillary level, including alterations in iron transport, vasculogenesis, astrocyte endfeet, and pericytes. Despite these findings, the role of the NVU in IDA remains poorly understood. This review summarizes the potential effects of ID/IDA on brain development, myelination and neuronal function and discusses the role of NVU cells in iron metabolism, BBB, vasculogenesis/angiogenesis, neurovascular coupling and metabolic waste clearance. Furthermore, it emphasizes the need to view the NVU as a whole and as a potential target for ID/IDA. However, it remains unclear to what extent NVU alterations contribute to neuronal dysfunction, myelination abnormalities, and synaptic disturbances described in IDA.

Identification of Genes Responding to Iron or Choline Treatment for Early-Life Iron Deficiency in the Male Rat Hippocampal Transcriptomes

BACKGROUND

Developmental iron deficiency (ID) is associated with long-term cognitive and affective behavioral impairments in humans. Preclinical studies have shown that developmental ID has short- and long-term effects on gene regulation. Prenatal choline supplementation partially rescues early-life ID-induced cognitive deficits in adult male rats.

OBJECTIVES

To identify acute and long-term changes in biological processes regulated by developmental ID and modifiable by choline.

METHODS

This study compares the hippocampal transcriptomes of postnatal day (P) 15 iron-deficient (acute) and P65 formerly ID (persistent) rats with or without prenatal choline treatment. Pregnant rats were fed an ID (4 mg/kg Fe) or iron-sufficient (IS) (200 mg/kg Fe) diet from gestational day (G) 2 to P7 with or without choline supplementation (5 g/kg choline) from G11 to G18. Hippocampi were collected from P15 or P65 offspring and analyzed for gene expression by RNA sequencing.

RESULTS

Developmental ID-induced changes suggested modified activity of oxidative phosphorylation and fatty acid metabolism. Prenatal choline supplementation induced robust changes in gene expression, particularly in iron-deficient animals, where it partially mitigated the early-life ID-dysregulated genes. Choline supplementation also altered the hippocampal transcriptome in the IS rats, with indications for both beneficial and adverse effects.

CONCLUSIONS

This study provided global assessments of gene expression regulated by iron and choline. Our new findings highlight genes responding to iron or choline treatments, including a potentially novel choline-regulated transporter (IPO7), with shared effects on neuroinflammation in the male rat hippocampus.

Intranasal insulin treatment partially corrects the altered gene expression profile in the hippocampus of developing rats with perinatal iron deficiency

Perinatal iron deficiency (FeD) targets the hippocampus and leads to long-term cognitive deficits. Intranasal insulin administration improves cognitive deficits in adult humans with Alzheimer's disease and type 2 diabetes and could provide benefits in FeD-induced hippocampal dysfunction. To objective was to assess the effects of intranasal insulin administration intranasal insulin administration on the hippocampal transcriptome in a developing rat model of perinatal FeD. Perinatal FeD was induced using low-iron diet from gestational day 3 until postnatal day (P) 7, followed by an iron sufficient (FeS) diet through P21. Intranasal insulin was administered at a dose of 0.3 IU twice daily from P8 to P21. Hippocampi were removed on P21 from FeS control, FeD control, FeS insulin, and FeD insulin groups. Total RNA was isolated and profiled using next-generation sequencing. Gene expression profiles were characterized using custom workflows and expression patterns examined using ingenuity pathways analysis (n = 7-9 per group). Select RNAseq results were confirmed via qPCR. Transcriptomic profiling revealed that mitochondrial biogenesis and flux, oxidative phosphorylation, quantity of neurons, CREB signaling in neurons, and RICTOR-based mTOR signaling were disrupted with FeD and positively affected by intranasal insulin treatment with the most benefit observed in the FeD insulin group. Both perinatal FeD and intranasal insulin administration altered gene expression profile in the developing hippocampus. Intranasal insulin treatment reversed the adverse effects of FeD on many molecular pathways and could be explored as an adjunct therapy in perinatal FeD.

The Interaction between Psychological Stress and Iron Status on Early-Life Neurodevelopmental Outcomes

This review presents evidence from animal and human studies demonstrating the possible connection and significant impact of poor iron status and psychological distress on neurocognitive development during pregnancy and the neonatal period, with implications for long-term cognition. Stress and iron deficiency are independently prevalent and thus are frequently comorbid. While iron deficiency and early-life stress independently contribute to long-term neurodevelopmental alterations, their combined effects remain underexplored. Psychological stress responses may engage similar pathways as infectious stress, which alters fundamental iron metabolism processes and cause functional tissue-level iron deficiency. Psychological stress, analogous to but to a lesser degree than infectious stress, activates the hypothalamic-pituitary-adrenocortical (HPA) axis and increases proinflammatory cytokines. Chronic or severe stress is associated with dysregulated HPA axis functioning and a proinflammatory state. This dysregulation may disrupt iron absorption and utilization, likely mediated by the IL-6 activation of hepcidin, a molecule that impedes iron absorption and redistributes total body iron. This narrative review highlights suggestive studies investigating the relationship between psychological stress and iron status and outlines hypothesized mechanistic pathways connecting psychological stress exposure and iron metabolism. We examine findings regarding the overlapping impacts of early stress exposure to iron deficiency and children's neurocognitive development. We propose that studying the influence of psychological stress on iron metabolism is crucial for comprehending neurocognitive development in children exposed to prenatal and early postnatal stressors and for children at risk of early iron insufficiency. We recommend future directions for dual-exposure studies exploring iron as a potential mediating pathway between early stress and offspring neurodevelopment, offering opportunities for targeted interventions.

Iron status, development, and behavior in young children in the Pennsylvania foster care system

BACKGROUND

Children in foster care are classified as a highly vulnerable population and struggle with both physical and mental health problems. Medical conditions, like poor nutritional status, remain understudied in children in foster care. To our knowledge, few studies in children in U.S. foster care have quantified the prevalence of anemia, and no studies have examined the association between anemia status and relevant developmental and behavioral outcomes.

OBJECTIVE/AIMS

(1) To determine the prevalence of anemia among children in or adopted from Pennsylvania foster care, between the ages of six months to ten years and (2) To examine if a child's anemia status is associated with greater odds of relevant developmental and behavioral diagnoses.

METHODS

We conducted a secondary data analysis utilizing the Medicaid Analytic eXtract database between 2010-2015. Children six months-ten years were included in the analysis if they were in or had been adopted from Pennsylvania foster care. Logistic regression was used to calculate adjusted odds ratios (AOR) with 95% confidence intervals for the association between iron status and health outcomes.

RESULTS

A total of 50,311 children were included in our sample, of which 1,365 children (2.7%) were diagnosed with anemia. Children diagnosed with anemia had greater odds of delayed milestones (AOR: 2.38 [1.64-3.45]), specific delays in development (AOR: 1.59 [1.23-2.07]), adjustment disorder (AOR: 1.59 [1.06-2.39]), and irritability (AOR: 10.57 [3.36-33.25]), than children not diagnosed with anemia.

CONCLUSION

The prevalence of anemia among children between six months-ten years in or adopted from the Pennsylvania foster care system is within the national rate of U.S. childhood anemia. Odds of several relevant developmental and behavioral diagnoses were greater among children diagnosed with anemia than children who were not.

Early-Life Iron Deficiency Persistently Alters Nociception in Developing Mice

Clinical association studies have identified early-life iron deficiency (ID) as a risk factor for the development of chronic pain. While preclinical studies have shown that early-life ID persistently alters neuronal function in the central nervous system, a causal relationship between early-life ID and chronic pain has yet to be established. We sought to address this gap in knowledge by characterizing pain sensitivity in developing male and female C57Bl/6 mice that were exposed to dietary ID during early life. Dietary iron was reduced by ∼90% in dams between gestational day 14 and postnatal day (P)10, with dams fed an ingredient-matched, iron-sufficient diet serving as controls. While cutaneous mechanical and thermal withdrawal thresholds were not altered during the acute ID state at P10 and P21, ID mice were more sensitive to mechanical pressure at P21 independent of sex. During adulthood, when signs of ID had resolved, mechanical and thermal thresholds were similar between early-life ID and control groups, although male and female ID mice displayed increased thermal tolerance at an aversive (45 °C) temperature. Interestingly, while adult ID mice showed decreased formalin-induced nocifensive behaviors, they showed exacerbated mechanical hypersensitivity and increased paw guarding in response to hindpaw incision in both sexes. Collectively, these results suggest that early-life ID elicits persistent changes in nociceptive processing and appears capable of priming developing pain pathways. PERSPECTIVE: This study provides novel evidence that early-life ID evokes sex-independent effects on nociception in developing mice, including an exacerbation of postsurgical pain during adulthood. These findings represent a critical first step towards the long-term goal of improving health outcomes for pain patients with a prior history of ID.

Brain Iron Metabolism, Redox Balance and Neurological Diseases

The incidence of neurological diseases, such as Parkinson's disease, Alzheimer's disease and stroke, is increasing. An increasing number of studies have correlated these diseases with brain iron overload and the resulting oxidative damage. Brain iron deficiency has also been closely linked to neurodevelopment. These neurological disorders seriously affect the physical and mental health of patients and bring heavy economic burdens to families and society. Therefore, it is important to maintain brain iron homeostasis and to understand the mechanism of brain iron disorders affecting reactive oxygen species (ROS) balance, resulting in neural damage, cell death and, ultimately, leading to the development of disease. Evidence has shown that many therapies targeting brain iron and ROS imbalances have good preventive and therapeutic effects on neurological diseases. This review highlights the molecular mechanisms, pathogenesis and treatment strategies of brain iron metabolism disorders in neurological diseases.

Early life nutrition and brain development: breakthroughs, challenges and new horizons

The role of early life nutrition's impact on relevant health outcomes across the lifespan laid the foundation for the field titled the developmental origins of health and disease. Studies in this area initially concentrated on nutrition and the risk of adverse cardio-metabolic and cancer outcomes. More recently the role of nutrition in early brain development and the subsequent influence of later mental health has become more evident. Scientific breakthroughs have elucidated two mechanisms behind long-term nutrient effects on the brain, including the existence of critical periods for certain nutrients during brain development and nutrient-driven epigenetic modifications of chromatin. While multiple nutrients and nutritional conditions have the potential to modify brain development, iron can serve as a paradigm to understand both mechanisms. New horizons in nutritional medicine include leveraging the mechanistic knowledge of nutrient-brain interactions to propose novel nutritional approaches that protect the developing brain through better timing of nutrient delivery and potential reversal of negative epigenetic marks. The main challenge in the field is detecting whether a change in nutritional status truly affects the brain's development and performance in human subjects. To that end, a strong case can be made to develop and utilise bioindicators of a nutrient's effect on the developing brain instead of relying exclusively on biomarkers of the nutrient's status.

Synaptic plasticity in schizophrenia pathophysiology

Schizophrenia is a severe neuropsychiatric syndrome with psychotic behavioral abnormalities and marked cognitive deficits. It is widely accepted that genetic and environmental factors contribute to the onset of schizophrenia. However, the etiology and pathology of the disease remain largely unexplored. Recently, the synaptopathology and the dysregulated synaptic plasticity and function have emerging as intriguing and prominent biological mechanisms of schizophrenia pathogenesis. Synaptic plasticity is the ability of neurons to change the strength of their connections in response to internal or external stimuli, which is essential for brain development and function, learning and memory, and vast majority of behavior responses relevant to psychiatric diseases including schizophrenia. Here, we reviewed molecular and cellular mechanisms of the multiple forms synaptic plasticity, and the functional regulations of schizophrenia-risk factors including disease susceptible genes and environmental alterations on synaptic plasticity and animal behavior. Recent genome-wide association studies have provided fruitful findings of hundreds of risk gene variances associated with schizophrenia, thus further clarifying the role of these disease-risk genes in synaptic transmission and plasticity will be beneficial to advance our understanding of schizophrenia pathology, as well as the molecular mechanism of synaptic plasticity.

Nutrition and Brain Development

All nutrients are essential for brain development, but pre-clinical and clinical studies have revealed sensitive periods of brain development during which key nutrients are critical. An understanding of these nutrient-specific sensitive periods and the accompanying brain regions or processes that are developing can guide effective nutrition interventions as well as the choice of meaningful circuit-specific neurobehavioral tests to best determine outcome. For several nutrients including protein, iron, iodine, and choline, pre-clinical and clinical studies align to identify the same sensitive periods, while for other nutrients, such as long-chain polyunsaturated fatty acids, zinc, and vitamin D, pre-clinical models demonstrate benefit which is not consistently shown in clinical studies. This discordance of pre-clinical and clinical results is potentially due to key differences in the timing, dose, and/or duration of the nutritional intervention as well as the pre-existing nutritional status of the target population. In general, however, the optimal window of success for nutritional intervention to best support brain development is in late fetal and early postnatal life. Lack of essential nutrients during these times can lead to long-lasting dysfunction and significant loss of developmental potential.

Choline Supplementation Partially Restores Dendrite Structural Complexity in Developing Iron-Deficient Mouse Hippocampal Neurons

BACKGROUND

Fetal-neonatal iron deficiency causes learning/memory deficits that persist after iron repletion. Simplified hippocampal neuron dendrite structure is a key mechanism underlying these long-term impairments. Early life choline supplementation, with postnatal iron repletion, improves learning/memory performance in formerly iron-deficient (ID) rats.

OBJECTIVES

To understand how choline improves iron deficiency-induced hippocampal dysfunction, we hypothesized that direct choline supplementation of ID hippocampal neurons may restore cellular energy production and dendrite structure.

METHODS

Embryonic mouse hippocampal neuron cultures were made ID with 9 μM deferoxamine beginning at 3 d in vitro (DIV). At 11 DIV, iron repletion (i.e., deferoxamine removal) was performed on a subset of ID cultures. These neuron cultures and iron-sufficient (IS) control cultures were treated with 30 μM choline (or vehicle) between 11 and 18 DIV. At 18 DIV, the independent and combined effects of iron and choline treatments (2-factor ANOVA) on neuronal dendrite numbers, lengths, and overall complexity and mitochondrial respiration and glycolysis were analyzed.

RESULTS

Choline treatment of ID neurons (ID + Cho) significantly increased overall dendrite complexity (150, 160, 180, and 210 μm from the soma) compared with untreated ID neurons to a level of complexity that was no longer significantly different from IS neurons. The average and total length of primary dendrites in ID + Cho neurons were significantly increased by ∼15% compared with ID neurons, indicating choline stimulation of dendrite growth. Measures of mitochondrial respiration, glycolysis, and ATP production rates were not significantly altered in ID + Cho neurons compared with ID neurons, remaining significantly reduced compared with IS neurons. Iron repletion significantly improved mitochondrial respiration, ATP production rates, overall dendrite complexity (100-180 μm from the soma), and dendrite and branch lengths compared with untreated ID neurons.

CONCLUSIONS

Because choline partially restores dendrite structure in ID neurons without iron repletion, it may have therapeutic potential when iron treatment is not possible or advisable. Choline's mechanism in ID neurons requires further investigation.

Blocking effect of ferritin on the ryanodine receptor-isoform 2

Iron, an essential element for most living organism, participates in a wide variety of physiological processes. Disturbance in iron homeostasis has been associated with numerous pathologies, particularly in the heart and brain, which are the most susceptible organs. Under iron-overload conditions, the generation of reactive oxygen species leads to impairment in Ca2+ signaling, fundamentally implicated in cardiac and neuronal physiology. Since iron excess is accompanied by increased expression of iron-storage protein, ferritin, we examined whether ferritin has an effect on the ryanodine receptor - isoform 2 (RYR2), which is one of the major components of Ca2+ signaling. Using the method of planar lipid membranes, we show that ferritin induced an abrupt, permanent blockage of the RYR2 channel. The ferritin effect was strongly voltage dependent and competitively antagonized by cytosolic TEA+, an impermeant RYR2 blocker. Our results collectively indicate that monomeric ferritin highly likely blocks the RYR2 channel by a direct electrostatic interaction within the wider region of the channel permeation pathway.

Early-Life Iron Deficiency Anemia Programs the Hippocampal Epigenomic Landscape

Iron deficiency (ID) anemia is the foremost micronutrient deficiency worldwide, affecting around 40% of pregnant women and young children. ID during the prenatal and early postnatal periods has a pronounced effect on neurodevelopment, resulting in long-term effects such as cognitive impairment and increased risk for neuropsychiatric disorders. Treatment of ID has been complicated as it does not always resolve the long-lasting neurodevelopmental deficits. In animal models, developmental ID results in abnormal hippocampal structure and function associated with dysregulation of genes involved in neurotransmission and synaptic plasticity. Dysregulation of these genes is a likely proximate cause of the life-long deficits that follow developmental ID. However, a direct functional link between iron and gene dysregulation has yet to be elucidated. Iron-dependent epigenetic modifications are one mechanism by which ID could alter gene expression across the lifespan. The jumonji and AT-rich interaction domain-containing (JARID) protein and the Ten-Eleven Translocation (TET) proteins are two families of iron-dependent epigenetic modifiers that play critical roles during neural development by establishing proper gene regulation during critical periods of brain development. Therefore, JARIDs and TETs can contribute to the iron-mediated epigenetic mechanisms by which early-life ID directly causes stable changes in gene regulation across the life span.

Child Linear Growth During and After the First 1000 Days Is Positively Associated with Intellectual Functioning and Mental Health in School-Age Children in Vietnam

BACKGROUND

Millions of children fail to meet their developmental potential and experience mental health concerns globally. Evidence is mixed on whether growth beyond the first 1000 d of life influences intellectual functioning and mental health in school-age children.

OBJECTIVES

We examined associations of childhood growth before and after the first 1000 d of life with child intellectual functioning and mental health at age 6-7 y.

METHODS

We used data from a follow-up of a randomized controlled trial of preconception supplementation (PRECONCEPT study) in Vietnam. A total of 5011 women participated in the study and 1579 children were born during 2012-2014. At age 6-7 y, child intellectual functioning was assessed using the Wechsler Intelligence Scale for Children, and mental health concerns were measured using the Strengths and Difficulties Questionnaire. Multivariable linear models were used to examine the independent association of child size at age 2 y [height-for-age z-score (HAZ) and body-mass-index z-score (BMIZ)] and conditional measures of linear and ponderal growth between the ages of 2 and 7 y.

RESULTS

HAZ at 2 y was positively associated with the Full-Scale Intelligence Quotient (β = 1.4; 95% CI: 0.5, 2.2 points) and its subdomains, namely Perceptual Reasoning Index, Working Memory Index, and Processing Speed Index (β = 1.0-1.4 points). Higher HAZ at 2 y was associated with lower overall mental health concerns (β = -0.24; 95% CI: -0.47, -0.01) and peer problems (β = -0.08; 95% CI: -0.17, -0.01). Faster height gain between 2 and 7 y was associated with higher total intellectual functioning (β = 0.9; 95% CI: 0.02, 1.8) and fewer emotional issues (β = -0.09; 95% CI: -0.18, -0.01). BMIZ at 2 y was not associated with intellectual functioning but was marginally associated with higher conduct and peer problems. Conditional weight gain between 2 and 7 y was not associated with child intellectual functioning or mental health in young school-age children.

CONCLUSIONS

Child linear growth both during and beyond the first 1000 d is positively associated with intellectual functioning and mental health during the early school-age years.

Preconception micronutrient supplementation positively affects child intellectual functioning at 6 y of age: A randomized controlled trial in Vietnam

BACKGROUND

Although there is growing evidence on the role of preconception nutrition for birth outcomes, very few studies have evaluated the long-term effects of nutrition interventions during the preconception period on offspring cognitive outcomes.

OBJECTIVE

We evaluate the impact of preconception weekly multiple micronutrients (MMs) or iron and folic acid (IFA) supplementation compared with folic acid (FA) alone on offspring intellectual functioning at age 6-7 y.

METHODS

We followed 1599 offspring born to women who participated in a double-blinded randomized controlled trial of preconception supplementation in Vietnam. Women received weekly supplements containing either 2800 μg FA only, 60 mg iron and 2800 μg FA, or MMs (15 micronutrients including IFA) from baseline until conception, followed by daily prenatal IFA supplements until delivery. We used the Wechsler Intelligence Scale for Children to measure full-scale IQ (FSIQ) and 4 related domains of intellectual functioning [Verbal Comprehension Index (VCI), Perceptual Reasoning Index (PRI), Working Memory Index (WMI), and Processing Speed Index (PSI) scores] at 6-7 y. Group comparisons were done using ANOVA tests for all children and the subgroup born to women who consumed the supplements ≥26 wk before conception (per-protocol analyses).

RESULTS

The final sample with data at 6-7 y (n = 1321) was similar for baseline maternal and offspring birth characteristics and age at follow-up by treatment group. Compared with the offspring in the FA group, those in the MM group had higher FSIQ (β = 1.7; 95% CI: 0.1, 3.3), WMI (β = 1.7; 95% CI: 0.2, 3.2), and PSI (β = 2.5; 95% CI: 0.9, 4.1). Similar findings were observed in the per-protocol analyses. There were no significant differences by treatment group for VCI and PRI.

CONCLUSIONS

Preconception supplementation with MMs improved certain domains of intellectual functioning at age 6-7 y compared with FA. These findings suggest the potential for preconception micronutrient interventions to have long-term benefits for offspring cognition.

Iron Deficiency Reprograms Phosphorylation Signaling and Reduces O-GlcNAc Pathways in Neuronal Cells

Micronutrient sensing is critical for cellular growth and differentiation. Deficiencies in essential nutrients such as iron strongly affect neuronal cell development and may lead to defects in neuronal function that cannot be remedied by subsequent iron supplementation. To understand the adaptive intracellular responses to iron deficiency in neuronal cells, we developed and utilized a Stable Isotopic Labeling of Amino acids in Cell culture (SILAC)-based quantitative phosphoproteomics workflow. Our integrated approach was designed to comprehensively elucidate the changes in phosphorylation signaling under both acute and chronic iron-deficient cell models. In addition, we analyzed the differential cellular responses between iron deficiency and hypoxia (oxygen-deprived) in neuronal cells. Our analysis identified nearly 16,000 phosphorylation sites in HT-22 cells, a hippocampal-derived neuronal cell line, more than ten percent of which showed at least 2-fold changes in response to either hypoxia or acute/chronic iron deficiency. Bioinformatic analysis revealed that iron deficiency altered key metabolic and epigenetic pathways including the phosphorylation of proteins involved in iron sequestration, glutamate metabolism, and histone methylation. In particular, iron deficiency increased glutamine-fructose-6-phosphate transaminase (GFPT1) phosphorylation, which is a key enzyme in the glucosamine biosynthesis pathway and a target of 5' AMP-activated protein kinase (AMPK), leading to reduced GFPT1 enzymatic activity and consequently lower global O-GlcNAc modification in neuronal cells. Taken together, our analysis of the phosphoproteome dynamics in response to iron and oxygen deprivation demonstrated an adaptive cellular response by mounting post-translational modifications that are critical for intracellular signaling and epigenetic programming in neuronal cells.

Iron Deficiency and Iron Excess Differently Affect Dendritic Architecture of Pyramidal Neurons in the Hippocampus of Piglets

BACKGROUND

Both iron deficiency and overload may adversely affect neurodevelopment.

OBJECTIVES

The study assessed how changes in early-life iron status affect iron homeostasis and cytoarchitecture of hippocampal neurons in a piglet model.

METHODS

On postnatal day (PD) 1, 30 Hampshire × Yorkshire crossbreed piglets (n = 15/sex) were stratified by sex and litter and randomly assigned to experimental groups receiving low (L-Fe), adequate (A-Fe), or high (H-Fe) levels of iron supplement during the pre- (PD1-21) and postweaning periods (PD22-35). Pigs in the L-Fe, A-Fe, and H-Fe groups orally received 0, 1, and 30 mg Fe · kg weight-1 · d-1 preweaning and were fed a diet containing 30, 125, and 1000 mg Fe/kg postweaning, respectively. Heme indexes were analyzed weekly, and gene and protein expressions of iron regulatory proteins in duodenal mucosa, liver, and hippocampus were analyzed through qRT-PCR and western blot, respectively, on PD35. Hippocampal neurons stained using the Golgi-Cox method were traced and their dendritic arbors reconstructed in 3-D using Neurolucida. Dendritic complexity was quantified using Sholl and branch order analyses.

RESULTS

Pigs in the L-Fe group developed iron deficiency anemia (hemoglobin = 8.2 g/dL, hematocrit = 20.1%) on PD35 and became stunted during week 5 with lower final body weight than H-Fe group pigs (6.6 compared with 9.6 kg, P < 0.05). In comparison with A-Fe, H-Fe increased hippocampal ferritin expression by 38% and L-Fe decreased its expression by 52% (P < 0.05), suggesting altered hippocampal iron stores. Pigs in the H-Fe group had greater dendritic complexity in CA1/3 pyramidal neurons than L-Fe group pigs as shown by more dendritic intersections with Sholl rings (P ≤ 0.04) and a greater number of dendrites (P ≤ 0.016).

CONCLUSIONS

In piglets, the developing hippocampus is susceptible to perturbations by dietary iron, with deficiency and overload differentially affecting dendritic arborization.

Iron deficiency in pregnancy

Iron is essential for the function of all cells through its roles in oxygen delivery, electron transport, and enzymatic activity. Cells with high metabolic rates require more iron and are at greater risk for dysfunction during iron deficiency. Iron requirements during pregnancy increase dramatically, as the mother's blood volume expands and the fetus grows and develops. Thus, pregnancy is a condition of impending or existing iron deficiency, which may be difficult to diagnose because of limitations to commonly used biomarkers such as hemoglobin and ferritin concentrations. Iron deficiency is associated with adverse pregnancy outcomes, including increased maternal illness, low birthweight, prematurity, and intrauterine growth restriction. The rapidly developing fetal brain is at particular risk of iron deficiency, which can occur because of maternal iron deficiency, hypertension, smoking, or glucose intolerance. Low maternal gestational iron intake is associated with autism, schizophrenia, and abnormal brain structure in the offspring. Newborns with iron deficiency have compromised recognition memory, slower speed of processing, and poorer bonding that persist despite postnatal iron repletion. Preclinical models of fetal iron deficiency confirm that expected iron-dependent processes such as monoamine neurotransmission, neuronal growth and differentiation, myelination, and gene expression are all compromised acutely and long term into adulthood. This review outlines strategies to diagnose and prevent iron deficiency in pregnancy. It describes the neurocognitive and mental health consequences of fetal iron deficiency. It emphasizes that fetal iron is a key nutrient that influences brain development and function across the lifespan.

The Effects of Early-Life Iron Deficiency on Brain Energy Metabolism

Iron deficiency (ID) is one of the most prevalent nutritional deficiencies in the world. Iron deficiency in the late fetal and newborn period causes abnormal cognitive performance and emotional regulation, which can persist into adulthood despite iron repletion. Potential mechanisms contributing to these impairments include deficits in brain energy metabolism, neurotransmission, and myelination. Here, we comprehensively review the existing data that demonstrate diminished brain energetic capacity as a mechanistic driver of impaired neurobehavioral development due to early-life (fetal-neonatal) ID. We further discuss a novel hypothesis that permanent metabolic reprogramming, which occurs during the period of ID, leads to chronically impaired neuronal energetics and mitochondrial capacity in adulthood, thus limiting adult neuroplasticity and neurobehavioral function. We conclude that early-life ID impairs energy metabolism in a brain region- and age-dependent manner, with particularly strong evidence for hippocampal neurons. Additional studies, focusing on other brain regions and cell types, are needed.

Significant Effects of Maternal Diet During Pregnancy on the Murine Fetal Brain Transcriptome and Offspring Behavior

BACKGROUND

Maternal over- and undernutrition in pregnancy plays a critical role in fetal brain development and function. The effects of different maternal diet compositions on intrauterine programing of the fetal brain is a lesser-explored area. The goal of this study was to investigate the impact of two chowmaternal diets on fetal brain gene expression signatures, fetal/neonatal growth, and neonatal and adult behavior in a mouse model.

METHODS

Throughout pregnancy and lactation, female C57Bl/6J mice were fed one of two standard, commercially available chow diets (pellet versus powder). The powdered chow diet was relatively deficient in micronutrients and enriched for carbohydrates and n-3 long-chain polyunsaturated fatty acids compared to the pelleted chow. RNA was extracted from embryonic day 15.5 forebrains and hybridized to whole genome expression microarrays (N = 5/maternal diet group). Functional analyses of significantly differentially expressed fetal brain genes were performed using Ingenuity Pathways Analysis and Gene Set Enrichment Analysis. Neonatal behavior was assessed using a validated scale (N = 62 pellet-exposed and 31 powder-exposed). Hippocampal learning, locomotor behavior, and motor coordination were assessed in a subset of adults using fear conditioning, open field testing, and Rotarod tests (N = 16 pellet-exposed, 14 powder-exposed).

RESULTS

Comparing powdered to pelleted chow diets, neither maternal weight trajectory in pregnancy nor embryo size differed. Maternal powdered chow diet was associated with 1647 differentially expressed fetal brain genes. Functional analyses identified significant upregulation of canonical pathways and upstream regulators involved in cell cycle regulation, synaptic plasticity, and sensory nervous system development in the fetal brain, and significant downregulation of pathways related to cell and embryo death. Pathways related to DNA damage response, brain immune response, amino acid and fatty acid transport, and dopaminergic signaling were significantly dysregulated. Powdered chow-exposed neonates were significantly longer but not heavier than pelleted chow-exposed counterparts. On neonatal behavioral testing, powdered chow-exposed neonates achieved coordination- and strength-related milestones significantly earlier, but sensory maturation reflexes significantly later. On adult behavioral testing, powdered chow-exposed offspring exhibited hyperactivity and hippocampal learning deficits.

CONCLUSION

In wild-type offspring, two diets that differed primarily with respect to micronutrient composition had significant effects on the fetal brain transcriptome, neonatal and adult behavior. These effects did not appear to be mediated by alterations in gross maternal nutritional status nor fetal/neonatal weight. Maternal dietary content is an important variable to consider for investigators evaluating fetal brain development and offspring behavior.

Prenatal Ethanol Exposure Misregulates Genes Involved in Iron Homeostasis Promoting a Maladaptation of Iron Dependent Hippocampal Synaptic Transmission and Plasticity

Prenatal ethanol exposure (PAE) induces behavioral maladptations in offspring, including a deficit in memory formation which is part of the umbrella sign of fetal alcohol spectrum disorder. Clinical and preclinical studies have shown that iron depletion exacerbates cognitive problems in offspring exposed to ethanol in utero and that PAE promotes dysregulation in brain iron homeostasis. However, the mechanisms underlying brain iron dysregulation and neuronal activity defects in adolescent offspring of PAE are unclear and poorly understand. Here, we used a PAE rat model to analyze messenger RNA (mRNA) and protein expression of iron homeostasis genes such as transferrin receptor (TfR), divalent metal transporter (DMT1), ferroportin (FPN1), and ferritin (FT) in brain areas associated with memory formation such as the prefrontal cortex (PFC), ventral tegmental area, and hippocampus. Interestingly, we found that 21 day old PAE rats have higher mRNA expression of DMT1 in the PFC, and TfR in the hippocampus, compared to control animals. In contrast FPN has lower mRNA expression in the PFC, and FT and FPN1 have lower expression in the hippocampus. In agreement with these results, we found a 1.5–2 fold increase of TfR and DMT1 protein levels both in the hippocampus and the PFC. Additionally, using an electrophysiological approach, we found that in hippocampal slices from PAE rats, iron treatment decreased long-term potentiation (LTP), but not AMPAR basal transmission (AMPAR fEPSP). In contrast, in control slices Fe-NTA did not affect LTP but decreased significantly the AMPAR fEPSP. Meanwhile, iron chelation with deferiprone decreased AMPAR transmission in PAE and control slices and decreased LTP only in controls slices. These results suggest that PAE affects iron homeostasis of specific brain areas—PFC and hippocampus—which could be involved in maladaptive cognition observed in this animal model.

Impairment of the Developing Human Brain in Iron Deficiency: Correlations to Findings in Experimental Animals and Prospects for Early Intervention Therapy

Due to the necessity of iron for a variety of cellular functions, the developing mammalian organism is vulnerable to iron deficiency, hence causing structural abnormalities and physiological malfunctioning in organs, which are particularly dependent on adequate iron stores, such as the brain. In early embryonic life, iron is already needed for proper development of the brain with the proliferation, migration, and differentiation of neuro-progenitor cells. This is underpinned by the widespread expression of transferrin receptors in the developing brain, which, in later life, is restricted to cells of the blood–brain and blood–cerebrospinal fluid barriers and neuronal cells, hence ensuring a sustained iron supply to the brain, even in the fully developed brain. In embryonic human life, iron deficiency is thought to result in a lower brain weight, with the impaired formation of myelin. Studies of fully developed infants that have experienced iron deficiency during development reveal the chronic and irreversible impairment of cognitive, memory, and motor skills, indicating widespread effects on the human brain. This review highlights the major findings of recent decades on the effects of gestational and lactational iron deficiency on the developing human brain. The findings are correlated to findings of experimental animals ranging from rodents to domestic pigs and non-human primates. The results point towards significant effects of iron deficiency on the developing brain. Evidence would be stronger with more studies addressing the human brain in real-time and the development of blood biomarkers of cerebral disturbance in iron deficiency. Cerebral iron deficiency is expected to be curable with iron substitution therapy, as the brain, privileged by the cerebral vascular transferrin receptor expression, is expected to facilitate iron extraction from the circulation and enable transport further into the brain.

Potential Mechanisms Driving Mitochondrial Motility Impairments in Developing Iron-Deficient Neurons

Brain development is highly demanding energetically, requiring neurons to have tightly regulated and highly dynamic metabolic machinery to achieve their ultimately complex cellular architecture. Mitochondria are the main source of neuronal adenosine 5′-triphosphate (ATP) and regulate critical neurodevelopmental processes including calcium signaling, iron homeostasis, oxidative stress, and apoptosis. Metabolic perturbations during critical neurodevelopmental windows impair neurological function not only acutely during the period of rapid growth/development, but also in adulthood long after the early-life insult has been rectified. Our laboratory uses iron deficiency (ID), the most common nutrient deficiency, as a model of early-life metabolic disruptions of neuronal metabolism because iron has a central role in mitochondrial function. Recently, we published that ID reduces hippocampal neuronal dendritic mitochondrial motility and size. In this commentary, we delve deeper into speculation about potential cellular mechanisms that drive the effects of neuronal ID on mitochondrial dynamics and quality control pathways. We propose that understanding the basic cellular biology of how mitochondria respond and adapt to ID and other metabolic perturbations during brain development may be a key factor in designing strategies to reduce the risk of later-life psychiatric, cognitive, and neurodegenerative disorders associated with early-life ID.

Dysregulation of Neuronal Genes by Fetal-Neonatal Iron Deficiency Anemia Is Associated with Altered DNA Methylation in the Rat Hippocampus

Early-life iron deficiency results in long-term abnormalities in cognitive function and affective behavior in adulthood. In preclinical models, these effects have been associated with long-term dysregulation of key neuronal genes. While limited evidence suggests histone methylation as an epigenetic mechanism underlying gene dysregulation, the role of DNA methylation remains unknown. To determine whether DNA methylation is a potential mechanism by which early-life iron deficiency induces gene dysregulation, we performed whole genome bisulfite sequencing to identify loci with altered DNA methylation in the postnatal day (P) 15 iron-deficient (ID) rat hippocampus, a time point at which the highest level of hippocampal iron deficiency is concurrent with peak iron demand for axonal and dendritic growth. We identified 229 differentially methylated loci and they were mapped within 108 genes. Among them, 63 and 45 genes showed significantly increased and decreased DNA methylation in the P15 ID hippocampus, respectively. To establish a correlation between differentially methylated loci and gene dysregulation, the methylome data were compared to our published P15 hippocampal transcriptome. Both datasets showed alteration of similar functional networks regulating nervous system development and cell-to-cell signaling that are critical for learning and behavior. Collectively, the present findings support a role for DNA methylation in neural gene dysregulation following early-life iron deficiency.

Iron Deficiency Reduces Synapse Formation in the Drosophila Clock Circuit

Iron serves as a critical cofactor for proteins involved in a host of biological processes. In most animals, dietary iron is absorbed in enterocytes and then disseminated for use in other tissues in the body. The brain is particularly dependent on iron. Altered iron status correlates with disorders ranging from cognitive dysfunction to disruptions in circadian activity. The exact role iron plays in producing these neurological defects, however, remains unclear. Invertebrates provide an attractive model to study the effects of iron on neuronal development since many of the genes involved in iron metabolism are conserved, and the organisms are amenable to genetic and cytological techniques. We have examined synapse growth specifically under conditions of iron deficiency in the Drosophila circadian clock circuit. We show that projections of the small ventrolateral clock neurons to the protocerebrum of the adult Drosophila brain are significantly reduced upon chelation of iron from the diet. This growth defect persists even when iron is restored to the diet. Genetic neuronal knockdown of ferritin 1 or ferritin 2, critical components of iron storage and transport, does not affect synapse growth in these cells. Together, these data indicate that dietary iron is necessary for central brain synapse formation in the fly and further validate the use of this model to study the function of iron homeostasis on brain development.

Chronic Energy Depletion due to Iron Deficiency Impairs Dendritic Mitochondrial Motility during Hippocampal Neuron Development

During development, neurons require highly integrated metabolic machinery to meet the large energy demands of growth, differentiation, and synaptic activity within their complex cellular architecture. Dendrites/axons require anterograde trafficking of mitochondria for local ATP synthesis to support these processes. Acute energy depletion impairs mitochondrial dynamics, but how chronic energy insufficiency affects mitochondrial trafficking and quality control during neuronal development is unknown. Because iron deficiency impairs mitochondrial respiration/ATP production, we treated mixed-sex embryonic mouse hippocampal neuron cultures with the iron chelator deferoxamine (DFO) to model chronic energetic insufficiency and its effects on mitochondrial dynamics during neuronal development. At 11 days in vitro (DIV), DFO reduced average mitochondrial speed by increasing the pause frequency of individual dendritic mitochondria. Time spent in anterograde motion was reduced; retrograde motion was spared. The average size of moving mitochondria was reduced, and the expression of fusion and fission genes was altered, indicating impaired mitochondrial quality control. Mitochondrial density was not altered, suggesting that respiratory capacity and not location is the key factor for mitochondrial regulation of early dendritic growth/branching. At 18 DIV, the overall density of mitochondria within terminal dendritic branches was reduced in DFO-treated neurons, which may contribute to the long-term deficits in connectivity and synaptic function following early-life iron deficiency. The study provides new insights into the cross-regulation between energy production and dendritic mitochondrial dynamics during neuronal development and may be particularly relevant to neuropsychiatric and neurodegenerative diseases, many of which are characterized by impaired brain iron homeostasis, energy metabolism and mitochondrial trafficking.SIGNIFICANCE STATEMENT This study uses a primary neuronal culture model of iron deficiency to address a gap in understanding of how dendritic mitochondrial dynamics are regulated when energy depletion occurs during a critical period of neuronal maturation. At the beginning of peak dendritic growth/branching, iron deficiency reduces mitochondrial speed through increased pause frequency, decreases mitochondrial size, and alters fusion/fission gene expression. At this stage, mitochondrial density in terminal dendrites is not altered, suggesting that total mitochondrial oxidative capacity and not trafficking is the main mechanism underlying dendritic complexity deficits in iron-deficient neurons. Our findings provide foundational support for future studies exploring the mechanistic role of developmental mitochondrial dysfunction in neurodevelopmental, psychiatric, and neurodegenerative disorders characterized by mitochondrial energy production and trafficking deficits.

Early-Life Neuronal-Specific Iron Deficiency Alters the Adult Mouse Hippocampal Transcriptome

Background

Iron deficiency (ID) compromises the developing nervous system, including the hippocampus, resulting in later-life deficits despite iron repletion. The iron-dependent molecular changes driving these lasting deficits, and the effect of early iron repletion, are incompletely understood. Previous studies have utilized dietary models of maternal-fetal ID anemia (IDA) to address these questions; however, concurrent anemia prevents delineation of the specific role of iron.

Objective

The aim of the study was to isolate the effects of developmental ID on adult hippocampal gene expression and to determine if iron repletion reverses these effects in a mouse model of nonanemic hippocampal neuronal ID.

Methods

Nonanemic, hippocampus-specific neuronal ID was generated by using a Tet-OFF dominant negative transferrin receptor (DN-TFR1) mouse model that impairs cellular iron uptake. Hippocampal ID was reversed with doxycycline at postnatal day 21 (P21) in a subset of mice to create 2 experimental groups, chronically iron-deficient and formerly iron-deficient mice, which were compared with their respective doxycycline-treated and untreated iron-sufficient controls. RNA from adult male hippocampi was sequenced. Paired-end reads were analyzed for differential expression. Differentially expressed genes were analyzed in Ingenuity Pathway Analysis.

Results

A total of 346 genes were differentially expressed in adult, chronically iron-deficient hippocampi compared with controls. ID dysregulated genes in critical neurodevelopmental pathways, including axonal guidance, CDK5, Ephrin receptor, Rac, and Neurotrophin/Trk signaling. Iron repletion at P21 normalized adult hippocampal expression of 198 genes; however, genes involved in cAMP response element-binding protein (CREB) signaling, neurocognition, and neurologic disease remained dysregulated in adulthood.

Conclusions

Chronic ID during development, independent of anemia, alters the adult mouse hippocampal transcriptome. Restoring iron status during a known critical period of hippocampal neurodevelopment incompletely normalized these changes, suggesting a need for additional studies to identify the most effective timeline for iron therapy, and adjunctive treatments that can fully restore ID-induced molecular changes, particularly in human populations in whom chronic ID is endemic.

Atypical fetal development: Fetal alcohol syndrome, nutritional deprivation, teratogens, and risk for neurodevelopmental disorders and psychopathology

Accumulating evidence indicates that the fetal environment plays an important role in brain development and sets the brain on a trajectory across the life span. An abnormal fetal environment results when factors that should be present during a critical period of development are absent or when factors that should not be in the developing brain are present. While these factors may acutely disrupt brain function, the real cost to society resides in the long-term effects, which include important mental health issues. We review the effects of three factors, fetal alcohol exposure, teratogen exposure, and nutrient deficiencies, on the developing brain and the consequent risk for developmental psychopathology. Each is reviewed with respect to the evidence found in epidemiological and clinical studies in humans as well as preclinical molecular and cellular studies that explicate mechanisms of action.

Biomarkers of Nutrition for Development (BOND)-Iron Review

This is the fifth in the series of reviews developed as part of the Biomarkers of Nutrition for Development (BOND) program. The BOND Iron Expert Panel (I-EP) reviewed the extant knowledge regarding iron biology, public health implications, and the relative usefulness of currently available biomarkers of iron status from deficiency to overload. Approaches to assessing intake, including bioavailability, are also covered. The report also covers technical and laboratory considerations for the use of available biomarkers of iron status, and concludes with a description of research priorities along with a brief discussion of new biomarkers with potential for use across the spectrum of activities related to the study of iron in human health.The I-EP concluded that current iron biomarkers are reliable for accurately assessing many aspects of iron nutrition. However, a clear distinction is made between the relative strengths of biomarkers to assess hematological consequences of iron deficiency versus other putative functional outcomes, particularly the relationship between maternal and fetal iron status during pregnancy, birth outcomes, and infant cognitive, motor and emotional development. The I-EP also highlighted the importance of considering the confounding effects of inflammation and infection on the interpretation of iron biomarker results, as well as the impact of life stage. Finally, alternative approaches to the evaluation of the risk for nutritional iron overload at the population level are presented, because the currently designated upper limits for the biomarker generally employed (serum ferritin) may not differentiate between true iron overload and the effects of subclinical inflammation.

Zinc Protoporphyrin-to-Heme Ratio and Ferritin as Measures of Iron Sufficiency in the Neonatal Intensive Care Unit

OBJECTIVES

To evaluate ferritin and zinc protoporphyrin-to-heme (ZnPP/H) ratios as biomarkers of iron status in neonates, determine how specific clinical events affected these measures, and assess how iron status changed during hospitalization.

STUDY DESIGN

We performed a retrospective study of all infants with paired ferritin and ZnPP/H measurements between October 2014 and May 2016. Concordance of these measurements, effects of sepsis, red blood cell transfusion, erythropoietin treatment, and iron supplementation were assessed. Iron status was measured over time.

RESULTS

A total of 228 patients (mean birth weight 1.3 kg, median gestational age 29 weeks) were evaluated. Mean log ZnPP/H values in infants with and without sepsis were not significantly different (4.98 µmol/mol vs 4.97 µmol/mol, adjusted P = .103), whereas log-transformed ferritin values increased significantly during infection (5.23 ng/mL vs 4.04 ng/mL, adjusted P < .001). Ferritin also increased more significantly than ZnPP/H following red blood cell transfusion (ferritin: mean 5.03 ng/mL vs 4.0 ng/mL, P < .001; ZnPP/H: mean 4.85 µmol/mol vs 4.98 µmol/mol, P < .001). The mean iron supplementations at 30, 60, and 90 days were 5.4, 6.9, and 7.4 mg/kg/day, respectively. Ferritin values decreased with advancing postnatal age (adjusted P < .001), with 66% of ferritin values less than 76 ng/mL. Treatment with erythropoietin increased ZnPP/H, but not ferritin levels.

CONCLUSIONS

Ferritin is more significantly affected by inflammatory events such as sepsis and transfusion than ZnPP/H, thus, ZnPP/H may be a more reliable marker of iron status in this population. Infants showed worsening iron sufficiency over time despite supplementation above American Academy of Pediatrics guidelines.

Defiant: (DMRs: easy, fast, identification and ANnoTation) identifies differentially Methylated regions from iron-deficient rat hippocampus

BACKGROUND

Identification of differentially methylated regions (DMRs) is the initial step towards the study of DNA methylation-mediated gene regulation. Previous approaches to call DMRs suffer from false prediction, use extreme resources, and/or require library installation and input conversion.

RESULTS

We developed a new approach called Defiant to identify DMRs. Employing Weighted Welch Expansion (WWE), Defiant showed superior performance to other predictors in the series of benchmarking tests on artificial and real data. Defiant was subsequently used to investigate DNA methylation changes in iron-deficient rat hippocampus. Defiant identified DMRs close to genes associated with neuronal development and plasticity, which were not identified by its competitor. Importantly, Defiant runs between 5 to 479 times faster than currently available software packages. Also, Defiant accepts 10 different input formats widely used for DNA methylation data.

CONCLUSIONS

Defiant effectively identifies DMRs for whole-genome bisulfite sequencing (WGBS), reduced-representation bisulfite sequencing (RRBS), Tet-assisted bisulfite sequencing (TAB-seq), and HpaII tiny fragment enrichment by ligation-mediated PCR-tag (HELP) assays.

Beneficial effects of postnatal choline supplementation on long-Term neurocognitive deficit resulting from fetal-Neonatal iron deficiency

Early-life iron deficiency is a common nutrient condition worldwide and can result in cognitive impairment in adulthood despite iron treatment. In rodents, prenatal choline supplementation can diminish long-term hippocampal gene dysregulation and neurocognitive deficits caused by iron deficiency. Since fetal iron status is generally unknown in humans, we determined whether postnatal choline supplementation exerts similar beneficial effects. Male rat pups were made iron deficient (ID) by providing pregnant and nursing dams an ID diet (3-6ppm Fe) from gestational day (G) 3 through postnatal day (P) 7, and an iron-sufficient (IS) diet (200ppm Fe) thereafter. Control pups were provided IS diet throughout. Choline (5ppm) was given to half the nursing dams and weanlings in each group from P11-P30. P65 rat cognitive performance was assessed by novel object recognition (NOR). Real-time PCR was performed to validate expression levels of synaptic plasticity genes known to be dysregulated by early-life iron deficiency. Postnatal choline supplementation prevented impairment of NOR memory in formerly iron-deficient (FID) adult rats but impaired NOR memory in IS controls. Gene expression analysis revealed a recovery of 4 out of 10 dysregulated genes compared to 8 of the same 10 genes that we previously demonstrated to recover following prenatal choline supplementation. Recognition memory deficits induced by early-life iron deficiency can be prevented by postnatal choline supplementation and disrupted expression of a subset of synaptic plasticity genes can be ameliorated. The positive response to postnatal choline represents a potential adjunctive therapeutic supplement to treat iron-deficient anemic children in order to spare long-term neurodevelopmental deficits.

Neonatal mouse hippocampus: phlebotomy-induced anemia diminishes and treatment with erythropoietin partially rescues mammalian target of rapamycin signaling

BackgroundPhlebotomy-induced anemia (PIA) is common in premature infants and affects neurodevelopment. PIA alters hippocampal metabolism in neonatal mice through tissue hypoxia and iron deficiency. The mammalian target of rapamycin (mTOR) pathway senses the status of critical metabolites (e.g., oxygen, iron), thereby regulating hippocampal growth and function. We determined the effect of PIA and recombinant human erythropoietin (rHuEpo) treatment on mTOR signaling and expression of genes related to mTOR pathway functions.MethodsMice receiving an iron-supplemented diet were phlebotomized from postnatal day (P)3 to a target hematocrit of <25% by P7. Half were maintained at <25% until P14; half received rHuEpo from P7 to increase the hematocrit to 25-28%. Hippocampal phosphorylated to total protein ratios of four key mTOR pathway proteins were measured by western blotting at P14 and compared with non-phlebotomized, non-anemic control mice. mRNA levels of genes regulated by mTOR were measured by quantitative PCR.ResultsPIA suppressed phosphorylation of all mTOR proteins. rHuEpo restored AMP-activated protein kinase (AMPK) and AKT status, and partially rescued the mTOR output protein S6K. PIA and rHuEpo treatment also altered the expression of genes regulated by S6K.ConclusionPIA compromises and rHuEpo treatment partially rescues a pathway regulating neuronal DNA transcription, protein translation, and structural complexity.

Preconception Micronutrient Supplementation with Iron and Folic Acid Compared with Folic Acid Alone Affects Linear Growth and Fine Motor Development at 2 Years of Age: A Randomized Controlled Trial in Vietnam

Background: Maternal health and nutrition play a crucial role in early child growth and development. However, little is known about the benefits of preconception micronutrient interventions beyond the role of folic acid (FA) and neural tube defects.Objective: We evaluated the impact of weekly preconception multiple micronutrient (MM) or iron and folic acid (IFA) supplementation on child growth and development through the age of 2 y compared with FA alone.Methods: We followed 1599 offspring born to women who participated in a randomized controlled trial of preconception supplementation in Vietnam. Women received weekly supplements that contained either 2800 μg FA, 60 mg Fe and 2800 μg FA, or 15 MMs including IFA, from baseline until conception followed by daily prenatal IFA supplements until delivery. Child anthropometry was measured at birth and at 3, 6, 12, 18, and 24 mo. Child development was measured with the use of the Bayley Scales for Infant Development III at 24 mo.Results: The groups were similar for baseline maternal and offspring birth characteristics. At 24 mo of age, the offspring in the IFA group had significantly higher length-for-age z scores (LAZs) (0.14; 95% CI: 0.03, 0.26), reduced risk of being stunted (0.87; 95% CI: 0.76, 0.99), and smaller yearly decline in LAZs (0.10; 95% CI: 0.04, 0.15) than the offspring in the FA group. Similar trends were found for the offspring in the MM group compared with the FA group for LAZs (0.10; 95% CI: -0.02, 0.22) and the risk of being stunted (0.88; 95% CI: 0.77, 1.01). Offspring in the IFA group had improved motor development (P = 0.03), especially fine motor development (0.41; 95% CI: 0.05, 0.77), at the age of 24 mo, but there were no differences for measures of cognition or language.Conclusions: Preconception supplementation with IFA improved linear growth and fine motor development at 2 y of age compared with FA. Future studies should examine whether these effects persist and improve child health and schooling. The trial was registered at clinicaltrials.gov as NCT01665378.

The Relationship Between Iron Deficiency Anemia and Sensorineural Hearing Loss in the Pediatric and Adolescent Population

PURPOSE

A correlation between iron deficiency anemia (IDA) and sudden sensorineural hearing loss (SNHL) was described in adults. In this study, we examined if there is a relationship between IDA and hearing loss in the pediatric population.

METHOD

This was a retrospective cohort study of data collected from the Informatics for Integrating Biology and the Bedside database from 2011 to 2016. Children and adolescents 4-21 years old seen at Penn State Milton S. Hershey Medical Center, Hershey, PA, were examined for hearing loss and IDA status. Hearing loss was determined by International Classification of Disease-9 and -10 codes, and IDA was determined by both low hemoglobin and serum ferritin levels for age and sex.

RESULTS

We identified 20,113 patients. Prevalence of hearing loss and IDA was 1.7% and 2.3%, respectively. The prevalence of all hearing loss was 3.0% in the IDA cohort and 1.7% in those without IDA. Children and adolescents with IDA are at increased odds of developing SNHL (adjusted odds ratio: 3.67, 95% CI [1.60-7.30]).

CONCLUSIONS

Children with IDA demonstrate increased likelihood of SNHL. Although correction of IDA in those with hearing loss has yet to be linked to improvements in hearing outcomes, screening for and correcting IDA among pediatric patients will positively affect overall health status.

Supplemental Material: https://doi.org/10.23641/asha.5087071.

Metal ions influx is a double edged sword for the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a common form of dementia in aged people, which is defined by two pathological characteristics: β-amyloid protein (Aβ) deposition and tau hyperphosphorylation. Although the mechanisms of AD development are still being debated, a series of evidence supports the idea that metals, such as copper, iron, zinc, magnesium and aluminium, are involved in the pathogenesis of the disease. In particular, the processes of Aβ deposition in senile plaques (SP) and the inclusion of phosphorylated tau in neurofibrillary tangles (NFTs) are markedly influenced by alterations in the homeostasis of the aforementioned metal ions. Moreover, the mechanisms of oxidative stress, synaptic plasticity, neurotoxicity, autophagy and apoptosis mediate the effects of metal ions-induced the aggregation state of Aβ and phosphorylated tau on AD development. More importantly, imbalance of these mechanisms finally caused cognitive decline in different experiment models. Collectively, reconstructing the signaling network that regulates AD progression by metal ions may provide novel insights for developing chelators specific for metal ions to combat AD.

Insula and somatosensory cortical myelination and iron markers underlie individual differences in empathy

Empathy is a key component of our ability to engage and interact with others. In recent years, the neural mechanisms underlying affective and cognitive empathy have garnered intense interest. This work demonstrates that empathy for others depends upon a distributed network of regions such as the insula, parietal cortex, and somatosensory areas, which are also activated when we ourselves experience an empathized-with emotion (e.g., pain). Individuals vary markedly in their ability to empathize with others, which predicts the tendency to help others and relates to individual differences in the neuroanatomy of these areas. Here, we use a newly developed, high-resolution (800 μm isotropic), quantitative MRI technique to better elucidate the neuroanatomical underpinnings of individual differences in empathy. Our findings extend previous studies of the neuroanatomical correlates of cognitive and affective empathy. In particular, individual differences in cognitive empathy were associated with markers of myeloarchitectural integrity of the insular cortex, while affective empathy was predicted by a marker of iron content in second somatosensory cortex. These results indicate potential novel biomarkers of trait empathy, suggesting that microstructural features of an empathy and body-related network are crucial for understanding the mental and emotional states of others.

Eltrombopag, a thrombopoietin mimetic, crosses the blood-brain barrier and impairs iron-dependent hippocampal neuron dendrite development

Essentials Potential neurodevelopmental side effects of thrombopoietin mimetics need to be considered. The effects of eltrombopag (ELT) on neuronal iron status and dendrite development were assessed. ELT crosses the blood-brain barrier and causes iron deficiency in developing neurons. ELT blunts dendrite maturation, indicating a need for more safety studies before neonatal use.

SUMMARY

Background Thrombocytopenia is common in sick neonates. Thrombopoietin mimetics (e.g. eltrombopag [ELT]) might provide an alternative therapy for selected neonates with severe and prolonged thrombocytopenia, and for infants and young children with different varieties of thrombocytopenia. However, ELT chelates intracellular iron, which may adversely affect developing organs with high metabolic requirements. Iron deficiency (ID) is particularly deleterious during brain development, impairing neuronal myelination, dopamine signaling and dendritic maturation and ultimately impairing long-term neurological function (e.g. hippocampal-dependent learning and memory). Objective To determine whether ELT crosses the blood-brain barrier (BBB), causes neuronal ID and impairs hippocampal neuron dendrite maturation. Methods ELT transport across the BBB was assessed using primary bovine brain microvascular endothelial cells. Embryonic mouse primary hippocampal neuron cultures were treated with ELT or deferoxamine (DFO, an iron chelator) from 7 days in vitro (DIV) through 14 DIV and assessed for gene expression and neuronal dendrite complexity. Results ELT crossed the BBB in a time-dependent manner. 2 and 6 μm ELT increased Tfr1 and Slc11a2 (iron-responsive genes involved in neuronal iron uptake) mRNA levels, indicating neuronal ID. 6 μm ELT, but not 2 μm ELT, decreased BdnfVI, Camk2a and Vamp1 mRNA levels, suggesting impaired neuronal development and synaptic function. Dendrite branch number and length were reduced in 6 μm ELT-treated neurons, resulting in blunted dendritic arbor complexity that was similar to DFO-treated neurons. Conclusions Eltrombopag treatment during development may impair neuronal structure as a result of neuronal ID. Preclinical in vivo studies are warranted to assess ELT safety during periods of rapid brain development.

Iron Deficiency Impairs Developing Hippocampal Neuron Gene Expression, Energy Metabolism, and Dendrite Complexity

Iron deficiency (ID), with and without anemia, affects an estimated 2 billion people worldwide. ID is particularly deleterious during early-life brain development, leading to long-term neurological impairments including deficits in hippocampus-mediated learning and memory. Neonatal rats with fetal/neonatal ID anemia (IDA) have shorter hippocampal CA1 apical dendrites with disorganized branching. ID-induced dendritic structural abnormalities persist into adulthood despite normalization of the iron status. However, the specific developmental effects of neuronal iron loss on hippocampal neuron dendrite growth and branching are unknown. Embryonic hippocampal neuron cultures were chronically treated with deferoxamine (DFO, an iron chelator) beginning at 3 days in vitro (DIV). Levels of mRNA for Tfr1 and Slc11a2, iron-responsive genes involved in iron uptake, were significantly elevated in DFO-treated cultures at 11DIV and 18DIV, indicating a degree of neuronal ID similar to that seen in rodent ID models. DFO treatment decreased mRNA levels for genes indexing dendritic and synaptic development (i.e. BdnfVI,Camk2a,Vamp1,Psd95,Cfl1, Pfn1,Pfn2, and Gda) and mitochondrial function (i.e. Ucp2,Pink1, and Cox6a1). At 18DIV, DFO reduced key aspects of energy metabolism including basal respiration, maximal respiration, spare respiratory capacity, ATP production, and glycolytic rate, capacity, and reserve. Sholl analysis revealed a significant decrease in distal dendritic complexity in DFO-treated neurons at both 11DIV and 18DIV. At 11DIV, the length of primary dendrites and the number and length of branches in DFO-treated neurons were reduced. By 18DIV, partial recovery of the dendritic branch number in DFO-treated neurons was counteracted by a significant reduction in the number and length of primary dendrites and the length of branches. Our findings suggest that early neuronal iron loss, at least partially driven through altered mitochondrial function and neuronal energy metabolism, is responsible for the effects of fetal/neonatal ID and IDA on hippocampal neuron dendritic and synaptic maturation. Impairments in these neurodevelopmental processes likely underlie the negative impact of early life ID and IDA on hippocampus-mediated learning and memory.

Dietary LC-PUFA in iron-deficient anaemic pregnant and lactating guinea pigs induce minor defects in the offsprings' auditory brainstem responses

OBJECTIVES

We previously demonstrated that a mild pre-natal/early post-natal iron-deficient anaemic (IDA) diet devoid of long-chain polyunsaturated fatty acids (LC-PUFA) affected development, neurophysiology, and cerebral lipid biochemistry of the guinea pigs' progeny. Impacts of dietary LC-PUFA on altered cerebral development resulting from pre-natal IDA are unknown. To address this health issue, impacts of mild gestational IDA in the presence of dietary LC-PUFA on the offsprings' neural maturation were studied in guinea pigs using auditory brainstem responses (ABRs) and assessments of brain fatty acids (FAs).

METHODS

Female guinea pigs (n = 10/group) were fed an iron sufficient (IS) or IDA diet (146 and 12.7 mg iron/kg, respectively) with physiological amounts of LC-PUFA, during the gestation and lactation periods. From post-natal day (PNd) 9 onwards, the IS + PUFA diet was given to both groups of weaned offspring. Cerebral tissue and offsprings' ABR were collected on PNd24.

RESULTS

There was no difference in peripheral and brainstem transmission times (BTTs) between IS + PUFA and IDA + PUFA siblings (n = 10/group); the neural synchrony was also similar in both groups. Despite the absence of differences in auditory thresholds, IDA + PUFA siblings demonstrated a sensorineural hearing loss in the extreme range of frequencies (32, 4, and 2 kHz), as well as modified brain FA profiles compared to the IS + PUFA siblings.

DISCUSSION

The present study reveals that siblings born from dams exposed to a moderate IDA diet including balanced physiological LC-PUFA levels during pregnancy and lactation demonstrate minor impairments of ABR compared to the control siblings, particularly on the auditory acuity, but not on neural synchrony, auditory nerve velocity and BTT.

Prenatal Choline Supplementation Diminishes Early-Life Iron Deficiency-Induced Reprogramming of Molecular Networks Associated with Behavioral Abnormalities in the Adult Rat Hippocampus

BACKGROUND

Early-life iron deficiency is a common nutrient deficiency worldwide. Maternal iron deficiency increases the risk of schizophrenia and autism in the offspring. Postnatal iron deficiency in young children results in cognitive and socioemotional abnormalities in adulthood despite iron treatment. The rat model of diet-induced fetal-neonatal iron deficiency recapitulates the observed neurobehavioral deficits.

OBJECTIVES

We sought to establish molecular underpinnings for the persistent psychopathologic effects of early-life iron deficiency by determining whether it permanently reprograms the hippocampal transcriptome. We also assessed the effects of maternal dietary choline supplementation on the offspring's hippocampal transcriptome to identify pathways through which choline mitigates the emergence of long-term cognitive deficits.

METHODS

Male rat pups were made iron deficient (ID) by providing pregnant and nursing dams an ID diet (4 g Fe/kg) from gestational day (G) 2 through postnatal day (PND) 7 and an iron-sufficient (IS) diet (200 g Fe/kg) thereafter. Control pups were provided IS diet throughout. Choline (5 g/kg) was given to half the pregnant dams in each group from G11 to G18. PND65 hippocampal transcriptomes were assayed by next generation sequencing (NGS) and analyzed with the use of knowledge-based Ingenuity Pathway Analysis. Real-time polymerase chain reaction was performed to validate a subset of altered genes.

RESULTS

Formerly ID rats had altered hippocampal expression of 619 from >10,000 gene loci sequenced by NGS, many of which map onto molecular networks implicated in psychological disorders, including anxiety, autism, and schizophrenia. There were significant interactions between iron status and prenatal choline treatment in influencing gene expression. Choline supplementation reduced the effects of iron deficiency, including those on gene networks associated with autism and schizophrenia.

CONCLUSIONS

Fetal-neonatal iron deficiency reprograms molecular networks associated with the pathogenesis of neurologic and psychological disorders in adult rats. The positive response to prenatal choline represents a potential adjunctive therapeutic supplement to the high-risk group.

Incorporating Informatics for Integrating Biology and the Bedside (i2b2) into Predoctoral Trainee Curriculum to Evaluate Student-Generated Hypotheses

As part of the Clinical and Translational Science Institute predoctoral TL1 training program at the Pennsylvania State University, a multidisciplinary team of predoctoral trainees representing the Chemistry, Neurosurgery, Nutritional Sciences, and Public Health Sciences departments were introduced to the NIH-sponsored Informatics for Integrating Biology and the Bedside (i2b2) database to test the following student-generated hypothesis: children with iron deficiency anemia (IDA) are at increased risk of attention deficit-hyperactivity disorder (ADHD). Children aged 4-12 and 4-17 years were categorized into IDA and control groups. De-identified medical records from the Penn State Milton S. Hershey Medical Center (HMC) and the Virginia Commonwealth University Medical Center (VCUMC) were used for the analysis. Overall, ADHD prevalence at each institution was lower than 2011 state estimates. There was a significant association between IDA and ADHD in the 4-17-year-old age group for all children (OR: 1.902 [95% CI: 1.363-2.656]), Caucasian children (OR: 1.802 [95% CI: 1.133-2.864]), and African American children (OR: 1.865 [95% CI: 1.152-3.021]). Clinical and Translational Science Award (CTSA) infrastructure is particularly useful for trainees to answer de novo scientific questions with minimal additional training and technical expertise. Moreover, projects can be expanded by collaborating within the CTSA network.