Chromatin accessibility and H3K9me3 landscapes reveal long-term epigenetic effects of fetal-neonatal iron deficiency in rat hippocampus.

BACKGROUND: Iron deficiency (ID) during the fetal-neonatal period results in long-term neurodevelopmental impairments associated with pervasive hippocampal gene dysregulation. Prenatal choline supplementation partially normalizes these effects, suggesting an interaction between iron and choline in hippocampal transcriptome regulation. To understand the regulatory mechanisms, we investigated epigenetic marks of genes with altered chromatin accessibility (ATAC-seq) or poised to be repressed (H3K9me3 ChIP-seq) in iron-repleted adult rats having experienced fetal-neonatal ID exposure with or without prenatal choline supplementation. RESULTS: Fetal-neonatal ID was induced by limiting maternal iron intake from gestational day (G) 2 through postnatal day (P) 7. Half of the pregnant dams were given supplemental choline (5.0 g/kg) from G11-18. This resulted in 4 groups at P65 (Iron-sufficient [IS], Formerly Iron-deficient [FID], IS with choline [ISch], and FID with choline [FIDch]). Hippocampi were collected from P65 iron-repleted male offspring and analyzed for chromatin accessibility and H3K9me3 enrichment. 22% and 24% of differentially transcribed genes in FID- and FIDch-groups, respectively, exhibited significant differences in chromatin accessibility, whereas 1.7% and 13% exhibited significant differences in H3K9me3 enrichment. These changes mapped onto gene networks regulating synaptic plasticity, neuroinflammation, and reward circuits. Motif analysis of differentially modified genomic sites revealed significantly stronger choline effects than early-life ID and identified multiple epigenetically modified transcription factor binding sites. CONCLUSIONS: This study reveals genome-wide, stable epigenetic changes and epigenetically modifiable gene networks associated with specific chromatin marks in the hippocampus, and lays a foundation to further elucidate iron-dependent epigenetic mechanisms that underlie the long-term effects of fetal-neonatal ID, choline, and their interactions.

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.

Cellular Iron Deficiency Disrupts Thyroid Hormone Regulated Gene Expression in Developing Hippocampal Neurons.

BACKGROUND: Developing neurons have high thyroid hormone and iron requirements to support their metabolically demanding growth. Early-life iron and thyroid-hormone deficiencies are prevalent and often coexist, and each independently increases risk of permanently impaired neurobehavioral function in children. Early-life dietary iron deficiency reduces thyroid-hormone concentrations and impairs thyroid hormone-responsive gene expression in the neonatal rat brain, but it is unclear whether the effect is cell-intrinsic. OBJECTIVES: This study determined whether neuronal-specific iron deficiency alters thyroid hormone-regulated gene expression in developing neurons. METHODS: Iron deficiency was induced in primary mouse embryonic hippocampal neuron cultures with the iron chelator deferoxamine (DFO) beginning at 3 d in vitro (DIV). At 11DIV and 18DIV, thyroid hormone-regulated gene messenger ribonucleic acid (mRNA)concentrations indexing thyroid hormone homeostasis (Hairless, mu-crystallin, Type II deiodinase, solute carrier family member 1c1, and solute carrier family member 16a2) and neurodevelopment (neurogranin, Parvalbumin, and Krüppel-like factor 9) were quantified. To assess the effect of iron repletion, DFO was removed at 14DIV from a subset of DFO-treated cultures, and gene expression and adenosine 5'-triphosphate (ATP) concentrations were quantified at 21DIV. RESULTS: At 11DIV and 18DIV, neuronal iron deficiency decreased neurogranin, Parvalbumin, and mu-crystallin, and by 18DIV, solute carrier family member 16a2, solute carrier family member 1c1, Type II deiodinase, and Hairless were increased, suggesting cellular sensing of a functionally abnormal thyroid hormone state. Dimensionality reduction with Principal component analysis reveals that thyroid hormone homeostatic genes strongly correlate with and predict iron status. Iron repletion from 14-21DIV did not restore ATP concentration, and Principal component analysis suggests that, after iron repletion, cultures maintain a gene expression signature indicative of previous iron deficiency. CONCLUSIONS: These novel findings suggest there is an intracellular mechanism coordinating cellular iron/thyroid hormone activities. We speculate this is a part of the homeostatic response to acutely match neuronal energy production and growth signaling. However, the adaptation to iron deficiency may cause permanent deficits in thyroid hormone-dependent neurodevelopmental processes even after recovery from iron deficiency.

Prognostic Performance of Hematological and Serum Iron and Metabolite Indices for Detection of Early Iron Deficiency Induced Metabolic Brain Dysfunction in Infant Rhesus Monkeys.

BACKGROUND: The current pediatric practice of monitoring for infantile iron deficiency (ID) via hemoglobin (Hgb) screening at one y of age does not identify preanemic ID nor protect against later neurocognitive deficits. OBJECTIVES: To identify biomarkers of iron-related metabolic alterations in the serum and brain and determine the sensitivity of conventional iron and heme indices for predicting risk of brain metabolic dysfunction using a nonhuman primate model of infantile ID. METHODS: Simultaneous serum iron and RBC indices, and serum and cerebrospinal fluid (CSF) metabolomic profiles were determined in 20 rhesus infants, comparing iron sufficient (IS; N = 10) and ID (N = 10) infants at 2 and 4 mo of age. RESULTS: Reticulocyte hemoglobin (RET-He) was lower at 2 wk in the ID group. Significant IS compared with ID differences in serum iron indices were present at 2 mo, but Hgb and RBC indices differed only at 4 mo (P < 0.05). Serum and CSF metabolomic profiles of the ID and IS groups differed at 2 and 4 mo (P < 0.05). Key metabolites, including homostachydrine and stachydrine (4-5-fold lower at 4 mo in ID group, P < 0.05), were altered in both serum and CSF. Iron indices and RET-He at 2 mo, but not Hgb or other RBC indices, were correlated with altered CSF metabolic profile at 4 mo and had comparable predictive accuracy (area under the receiver operating characteristic curve scores, 0.75-0.80). CONCLUSIONS: Preanemic ID at 2 mo was associated with metabolic alterations in serum and CSF in infant monkeys. Among the RBC indices, only RET-He predicted the future risk of abnormal CSF metabolic profile with a predictive accuracy comparable to serum iron indices. The concordance of homostachydrine and stachydrine changes in serum and CSF indicates their potential use as early biomarkers of brain metabolic dysfunction in infantile ID.

Phlebotomy-induced anemia reduces oxygen-induced retinopathy severity and dampens retinal developmental transcriptomic pathways in rats.

BACKGROUND: Phlebotomy-induced-anemia (PIA), which induces tissue hypoxia and angiogenesis, occurs universally among infants at risk for severe retinopathy of prematurity (ROP). We hypothesized that PIA exacerbates pathologic retinal neovascularization in ROP. METHODS: We induced PIA to a hematocrit of 18% among rats undergoing the established 50/10 oxygen-induced retinopathy (OIR) model. Rats were euthanized at P15 and P20, during the avascular and neovascular phases of OIR, respectively. Retinal vascular morphometry, cytokine/chemokine concentrations, transcriptomes, and mRNA expression of angiogenic and iron-deficiency markers were compared to non-PIA controls. RESULTS: In OIR, PIA decreased percent avascular area at P15 by 35%, percent neovascular area at P20 by 42%, and select pro-inflammatory cytokine/chemokine concentrations at both time points. At P20, PIA increased mRNA expression of angiopoietin 2/ vascular endothelial growth factor-A 2-fold and transferrin and transferrin receptor 5-fold. RNA sequencing showed dampened pathways of angiogenesis, inflammation, and neural development in anemic OIR females. CONCLUSION: Contrary to our hypothesis, PIA decreased OIR severity and retinal cytokine and chemokine levels and dampened transcriptomic pathways central to retinal vascular and neural development in neonatal rats. These data suggest PIA provides a protective effect from OIR. Further investigation into the functional effect of these molecular changes is warranted. IMPACT: This is the first preclinical study to investigate the impact of neonatal anemia on oxygen-induced retinopathy (OIR) outcomes. This study adds to the literature that anemia decreases neovascularization, decreases cytokine and chemokine levels, and dampens angiogenic and neural transcriptomic pathways in the rat 50/10 OIR model. The study identifies a sex-specific transcriptomic response to anemia in the 50/10 OIR model, with females primarily impacted.

Effect of Malaria and Malaria Chemoprevention Regimens in Pregnancy and Childhood on Neurodevelopmental and Behavioral Outcomes in Children at 12, 24, and 36 Months: A Randomized Clinical Trial.

BACKGROUND: Malaria in pregnancy has been associated with worse cognitive outcomes in children, but its association with behavioral outcomes and the effectiveness of malaria chemoprevention on child neurodevelopment are not well characterized. METHODS: To determine if more effective malaria chemoprevention in mothers and their children results in better neurodevelopment, 305 pregnant women were randomly assigned to 3 doses of sulfadoxine-pyrimethamine, 3 doses of dihydroartemisinin-piperaquine (DP), or monthly DP during pregnancy, and their 293 children were assigned to DP every 3 months or monthly DP from 2 to 24 months of age. Cognition, language, and motor function were assessed at 12, 24. and 36 months of age, and attention, memory, behavior, and executive function were assessed at 24 and 36 months of age. RESULTS: Children of mothers with versus without malaria in pregnancy had worse scores on cognitive, behavioral, and executive function outcomes at 24 months. Clinical malaria in children within the first 12 months was similarly associated with poorer scores in behavior and executive function at 24 months, language at 24 and 36 months, and motor function scores at 36 months. However, more effective malaria chemoprevention in the mothers and children was not associated with better outcomes. CONCLUSIONS: Malaria in pregnancy was associated with worse cognitive, behavioral, and executive function scores in affected children, but more effective malaria chemoprevention measures did not result in better outcomes. Malaria chemoprevention prior to and early in gestation and with even higher efficacy in mothers and children may be required to prevent neurodevelopmental impairment in children. Clinical Trials Registration. NCT02557425.

Predictors of Human Milk Feeding and Direct Breastfeeding for Infants with Single Ventricle Congenital Heart Disease: Machine Learning Analysis of the National Pediatric Cardiology Quality Improvement Collaborative Registry.

OBJECTIVE: To identify factors that support or limit human milk (HM) feeding and direct breastfeeding (BF) for infants with single ventricle congenital heart disease at neonatal stage 1 palliation (S1P) discharge and at stage 2 palliation (S2P) (∼4-6 months old). STUDY DESIGN: Analysis of the National Pediatric Cardiology Quality Improvement Collaborative (NPC-QIC) registry (2016-2021; 67 sites). Primary outcomes were any HM, exclusive HM, and any direct BF at S1P discharge and at S2P. The main analysis involved multiple phases of elastic net logistic regression on imputed data to identify important predictors. RESULTS: For 1944 infants, the strongest predictor domain areas included preoperative feeding, demographics/social determinants of health, feeding route, clinical course, and site. Significant findings included: preoperative BF was associated with any HM at S1P discharge (OR = 2.02, 95% CI = 1.74-3.44) and any BF at S2P (OR = 2.29, 95% CI = 1.38-3.80); private/self-insurance was associated with any HM at S1P discharge (OR = 1.91, 95% CI = 1.58-2.47); and Black/African-American infants had lower odds of any HM at S1P discharge (OR = 0.54, 95% CI = 0.38-0.65) and at S2P (0.57, 0.30-0.86). Adjusted odds of HM/BF practices varied among NPC-QIC sites. CONCLUSIONS: Preoperative feeding practices predict later HM and BF for infants with single ventricle congenital heart disease; therefore, family-centered interventions focused on HM/BF during the S1P preoperative time are needed. These interventions should include evidence-based strategies to address implicit bias and seek to minimize disparities related to social determinants of health. Future research is needed to identify supportive practices common to high-performing NPC-QIC sites.

Reticulocyte Hemoglobin Equivalent has Comparable Predictive Accuracy as Conventional Serum Iron Indices for Predicting Iron Deficiency and Anemia in a Nonhuman Primate model of Infantile Iron Deficiency.

BACKGROUND: Infantile iron deficiency (ID) causes anemia and compromises neurodevelopment. Current screening relies on hemoglobin (Hgb) determination at 1 year of age, which lacks sensitivity and specificity for timely detection of infantile ID. Low reticulocyte Hgb equivalent (RET-He) indicates ID, but its predictive accuracy relative to conventional serum iron indices is unknown. OBJECTIVES: The objective was to compare diagnostic accuracies of iron indices, red blood cell (RBC) indices, and RET-He for predicting the risk of ID and IDA in a nonhuman primate model of infantile ID. METHODS: Serum iron, total iron binding capacity, unsaturated iron binding capacity, transferrin saturation (TSAT), Hgb, RET-He, and other RBC indices were determined at 2 wk and 2, 4, and 6 mo in breastfed male and female rhesus infants (N = 54). The diagnostic accuracies of RET-He, iron, and RBC indices for predicting the development of ID (TSAT < 20%) and IDA (Hgb < 10 g/dL + TSAT < 20%) were determined using t tests, area under the receiver operating characteristic curve (AUC) analysis, and multiple regression models. RESULTS: Twenty-three (42.6%) infants developed ID and 16 (29.6%) progressed to IDA. All 4 iron indices and RET-He, but not Hgb or RBC indices, predicted future risk of ID and IDA (P < 0.001). The predictive accuracy of RET-He (AUC = 0.78, SE = 0.07; P = 0.003) for IDA was comparable to that of the iron indices (AUC = 0.77-0.83, SE = 0.07; P ≤ 0.002). A RET-He threshold of 25.5 pg strongly correlated with TSAT < 20% and correctly predicted IDA in 10 of 16 infants (sensitivity: 62.5%) and falsely predicted possibility of IDA in only 4 of 38 unaffected infants (specificity: 89.5%). CONCLUSIONS: RET-He is a biomarker of impending ID/IDA in rhesus infants and can be used as a hematological parameter to screen for infantile ID.

Blood Levels of Environmental Heavy Metals are Associated with Poorer Iron Status in Ugandan Children: A Cross-Sectional Study.

BACKGROUND: Iron deficiency (ID) and environmental exposure to metals frequently co-occur among Ugandan children, but little is known about their associations, although iron and other divalent metals share the same intestinal absorption transporter, divalent metal transporter 1 (DMT1). OBJECTIVES: We examined associations between iron status and blood concentrations of lead, manganese (Mn), cobalt (Co), and cadmium, both singly and as a mixture. METHODS: We used data on sociodemographic status, iron biomarkers, and blood concentrations of heavy metals collected from a cross-sectional survey of 100 children aged 6-59 mo in Kampala, Uganda. We compared blood concentrations of metals in ID with iron-sufficient children. We examined associations between a metal mixture and iron biomarkers using multiple linear regression and weighted quintile sum regression. RESULTS: The median (interquartile range) blood Mn (µg/L) was higher in ID children defined by soluble transferrin receptor (sTfR) and ferritin (ID compared with iron-sufficient children): (sTfR [21.3 {15.1, 28.8}, 11.2 {8.6, 18.5}], ferritin [19.5 {15.0, 27.2}, 11.2 {8.8, 19.6}]; P < 0.001 for both). Similarly, the median (interquartile range) blood Co (µg/L) was higher in ID children by ferritin ([0.5 {0.4, 0.9}, 0.4 {0.3, 0.5}], P = 0.05). Based on the multiple linear regression results, higher blood Co and Mn were associated with poorer iron status (defined by all 4 iron indicators for Co and by sTfR for Mn). The weighted quintile sum regression result showed that higher blood concentrations of a metal mixture were associated with poorer iron status represented by sTfR, ferritin, and hepcidin, mainly driven by Co and Mn. CONCLUSIONS: Our study findings suggest that poorer iron status is associated with overall heavy metal burden, predominantly Co and Mn, among Ugandan children. Further prospective studies should confirm our primary findings and investigate the combined effects of coexposures to neurotoxicants on the neurodevelopment of young children.

Iron supplementation and the risk of bronchopulmonary dysplasia in extremely low gestational age newborns.

BACKGROUND: The aim of this study was to determine the relationship between iron exposure and the development of bronchopulmonary dysplasia (BPD). METHODS: A secondary analysis of the PENUT Trial dataset was conducted. The primary outcome was BPD at 36 weeks gestational age and primary exposures of interest were cumulative iron exposures in the first 28 days and through 36 weeks' gestation. Descriptive statistics were calculated for study cohort characteristics with analysis adjusted for the factors used to stratify randomization. RESULTS: Of the 941 patients, 821 (87.2%) survived to BPD evaluation at 36 weeks, with 332 (40.4%) diagnosed with BPD. The median cohort gestational age was 26 weeks and birth weight 810 g. In the first 28 days, 76% of infants received enteral iron and 55% parenteral iron. The median supplemental cumulative enteral and parenteral iron intakes at 28 days were 58.5 and 3.1 mg/kg, respectively, and through 36 weeks' 235.8 and 3.56 mg/kg, respectively. We found lower volume of red blood cell transfusions in the first 28 days after birth and higher enteral iron exposure in the first 28 days after birth to be associated with lower rates of BPD. CONCLUSIONS: We find no support for an increased risk of BPD with iron supplementation. TRIAL REGISTRATION NUMBER: NCT01378273. https://clinicaltrials.gov/ct2/show/NCT01378273 IMPACT: Prior studies and biologic plausibility raise the possibility that iron administration could contribute to the pathophysiology of oxidant-induced lung injury and thus bronchopulmonary dysplasia in preterm infants. For 24-27-week premature infants, this study finds no association between total cumulative enteral iron supplementation at either 28-day or 36-week postmenstrual age and the risk for developing bronchopulmonary dysplasia.

Maternal gestational iron status and infant haematological and neurodevelopmental outcomes.

Prevention of iron deficiency (ID), the most common micronutrient deficiency in infants and children, begins prenatally by ensuring adequate fetal loading. Adequate intrauterine iron status is crucial for normal fetal brain development, postnatal brain performance and prevention of early postnatal iron deficiency, particularly in infants fed exclusively human milk. Adequate fetal loading may be achieved in some cases through adequate maternal iron levels prior to pregnancy and oral iron supplementation during pregnancy. However, because so many women are iron-deficient leading up to pregnancy, coupled with the negative iron balance induced by pregnancy, a large number of women remain iron-deficient during pregnancy. More consistent iron-specific early screening and more effective iron delivery approaches are needed to solve this global problem.

Developmental Iron Deficiency Dysregulates TET Activity and DNA Hydroxymethylation in the Rat Hippocampus and Cerebellum.

Iron deficiency (ID) during neurodevelopment is associated with lasting cognitive and socioemotional deficits and increased risk for neuropsychiatric disease throughout the lifespan. These neurophenotypical changes are underlain by gene dysregulation in the brain that outlasts the period of ID; however, the mechanisms by which ID establishes and maintains gene expression changes are incompletely understood. The epigenetic modification of 5-hydroxymethylcytosine (5hmC), or DNA hydroxymethylation, is one candidate mechanism because of its dependence on iron-containing TET enzymes. The aim of the present study was to determine the effect of fetal-neonatal ID on regional brain TET activity, Tet expression, and 5hmC in the developing rat hippocampus and cerebellum and to determine whether changes are reversible with dietary iron treatment. Timed pregnant Sprague Dawley rats were fed iron-deficient diet (ID; 4 mg/kg Fe) from gestational day 2 to generate iron-deficient anemic (IDA) offspring. Control dams were fed iron-sufficient diet (IS; 200 mg/kg Fe). At postnatal day (P)7, a subset of ID-fed litters was randomized to IS diet, generating treated IDA (TIDA) offspring. At P15, the hippocampus and cerebellum were isolated for subsequent analysis. TET activity was quantified by ELISA from nuclear proteins. Expression of Tet1, Tet2, and Tet3 was quantified by qPCR from total RNA. Global %5hmC was quantified by ELISA from genomic DNA. ID increased DNA hydroxymethylation (p = 0.0105), with a corresponding increase in TET activity (p < 0.0001) and Tet3 expression (p < 0.0001) in the P15 hippocampus. In contrast, ID reduced TET activity (p = 0.0016) in the P15 cerebellum, with minimal effect on DNA hydroxymethylation. Neonatal dietary iron treatment resulted in partial normalization of these changes in both brain regions. These results demonstrate that the TET/DNA hydroxymethylation system is disrupted by developmental ID in a brain region-specific manner. Differential regional disruption of this epigenetic system may contribute to the lasting neural circuit dysfunction and neurobehavioral dysfunction associated with developmental ID.

Sex Differences in the Association of Pretransfusion Hemoglobin Levels with Brain Structure and Function in the Preterm Infant.

OBJECTIVE: To assess sex-specific differences in early brain structure and function of preterm infants after red blood cell (RBC) transfusions. STUDY DESIGN: A single-center subset of infants with a birth weight <1000 g and gestational age 22-29 weeks were enrolled from the National Institute of Child Health and Human Development's Neonatal Research Network Transfusion of Prematures Trial. Hemoglobin (Hb) concentration obtained directly before each transfusion (pretransfusion Hb [ptHb]) was obtained longitudinally throughout each infant's neonatal intensive care unit stay and used as a marker of degree of anemia (n = 97). Measures of regional brain volumes using magnetic resonance imaging were obtained at ∼40 weeks postmenstrual age or at hospital discharge, if earlier (n = 29). Measures of brain function were obtained at 12 months corrected age using the Bayley Scales of Infant & Toddler Development, 3rd Edition (n = 34). RESULTS: PtHb was positively correlated with neonatal cerebral white matter volume in males (B = +0.283; P = .006), but not females (B = -0.099; P = .713), resulting in a significant sex interaction (P = .010). Bayley-III gross motor scores and a pooled mean score were significantly lower in association with higher ptHb in females (gross motor score: B = -3.758; P = .013; pooled mean score: B = -1.225; P = .030), but not males (gross motor score: B = +1.758; P = .167; pooled mean score: B = +0.621; P = .359). Higher ptHb was associated with descriptively lower performance on multiple Bayley-III subscales in females, but not in males. CONCLUSIONS: This study demonstrates sex-specific associations between an early marker of anemia and RBC transfusion status (ie, ptHb) with both neonatal white matter volume and early cognitive function at age 12 months in preterm infants.

Multiomic profiling of iron-deficient infant monkeys reveals alterations in neurologically important biochemicals in serum and cerebrospinal fluid before the onset of anemia.

The effects of iron deficiency (ID) during infancy extend beyond the hematologic compartment and include short- and long-term adverse effects on many tissues including the brain. However, sensitive biomarkers of iron-dependent brain health are lacking in humans. To determine whether serum and cerebrospinal fluid (CSF) biomarkers of ID-induced metabolic dysfunction are concordant in the pre/early anemic stage of ID before anemia in a nonhuman primate model of infantile iron deficiency anemia (IDA). ID (n = 7), rhesus infants at 4 mo (pre-anemic period) and 6 mo of age (anemic) were examined. Hematological, metabolomic, and proteomic profiles were generated via HPLC/MS at both time points to discriminate serum biomarkers of ID-induced brain metabolic dysfunction. We identified 227 metabolites and 205 proteins in serum. Abnormalities indicating altered liver function, lipid dysregulation, and increased acute phase reactants were present in ID. In CSF, we measured 210 metabolites and 1,560 proteins with changes in ID infants indicative of metabolomic and proteomic differences indexing disrupted synaptogenesis. Systemic and CSF proteomic and metabolomic changes were present and concurrent in the pre-anemic and anemic periods. Multiomic serum and CSF profiling uncovered pathways disrupted by ID in both the pre-anemic and anemic stages of infantile IDA, including evidence for hepatic dysfunction and activation of acute phase response. Parallel changes observed in serum and CSF potentially provide measurable serum biomarkers of ID that reflect at-risk brain processes prior to progression to clinical anemia.

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.

Dose- and sex-dependent effects of phlebotomy-induced anemia on the neonatal mouse hippocampal transcriptome.

BACKGROUND: Phlebotomy-induced anemia (PIA) is universal and variable in degree among preterm infants and may contribute to neurodevelopmental risk. In mice, PIA causes brain tissue hypoxia, iron deficiency, and long-term sex-dependent neurobehavioral abnormalities. The neuroregulatory molecular pathways disrupted by PIA underlying these effects are unknown. METHODS: Male and female pups were phlebotomized daily from postnatal day (P)3-P14 via facial venipuncture to target hematocrits of 25% (moderate, mPIA) and 18% (severe, sPIA). P14 hippocampal RNA from non-bled control and PIA mice was sequenced by next-generation sequencing to identify differentially expressed genes (DEGs) that were analyzed using Ingenuity Pathway Analysis. RESULTS: mPIA females showed the least DEGs (0.5% of >22,000 genes) whereas sPIA females had the most (8.6%), indicating a dose-dependent effect. mPIA and sPIA males showed similar changes in gene expression (5.3% and 4.7%, respectively), indicating a threshold effect at mPIA. The pattern of altered genes induced by PIA indicates sex-specific and anemia-dose-dependent effects with increased pro-inflammation in females and decreased neurodevelopment in males. CONCLUSION: These gene-expression changes may underlie the reduced recognition memory function in male and abnormal social-cognitive behavior in female adult mice following neonatal PIA. These results parallel clinical studies demonstrating sex-specific behavioral outcomes as a function of neonatal anemia. IMPACT: Phlebotomy-induced anemia (PIA) in neonatal mice results in an altered hippocampal transcriptome and the severity of changes are dependent upon degree of anemia and sex of neonatal mice. The reported findings provide context to the sex-specific outcomes that have been reported in transfusion threshold clinical trials of preterm infants and therefore may inform treatment strategies that may be based on sex. These data advance the field by showing that consequences of PIA may be based in sex-specific transcriptomic alterations. Such changes may also result from other causes of neonatal anemia that also affect term infants.

Sex-specific cytokine responses and neurocognitive outcome after blood transfusions in preterm infants.

BACKGROUND: The objective of this study was to determine sex-specific differences in inflammatory cytokine responses to red blood cell (RBC) transfusion in preterm infants in the neonatal period and their relationship to later neurocognitive status. METHODS: Infants with a birth weight <1000 g and gestational age 22-29 weeks were enrolled in the Transfusion of Prematures (TOP) trial. The total number of transfusions was used as a marker of transfusion status. Nineteen cytokines and biomarkers were analyzed from 71 infants longitudinally during the neonatal period. Twenty-six infants completed the Bayley Scales of Infant & Toddler Development, 3rd Edition (Bayley-III) at 12 months' corrected age. RESULTS: Nine cytokine levels were significantly elevated in proportion to the number of transfusions received. Of those, one cytokine showed a sex-specific finding (p = 0.004): monocyte chemoattractant protein-1, MCP-1, rose substantially in females (8.9% change per additional transfusion), but not in males (-0.8% change). Higher concentrations of MCP-1 exclusively were associated with worse Bayley-III scores: decreased cognitive raw scores (p = 0.0005) and motor scaled scores (p < 0.0001). CONCLUSIONS: This study provides evidence of a sex-specific difference in the inflammatory response to RBC transfusions during neonatal life, with MCP-1 levels rising only in females and inversely correlating with neurocognitive status at 12 months old. IMPACT: It is important to understand the risk factors for abnormal neurodevelopment in preterm infants, including anemia and RBC transfusion, in order to improve outcomes and provide potential targets for therapy. Our study investigates and provides the first evidence of sex-specific differences in inflammatory cytokine responses to RBC transfusions in preterm infants in the neonatal period, and their relationship to later cognitive outcomes. This study critically suggests that different transfusion thresholds may have a sex-specific effect on neurodevelopment: females have worse cognitive outcomes with increased number of transfusions, while males have worse outcomes with lower number of transfusions.

Timing of iron deficiency and recognition memory in infancy.

Objective: To determine the relationship between iron deficiency (or iron-deficient, ID) and neural correlates of recognition memory depending on ID timing (gestation vs. infancy) and infant age at testing (9 vs. 18 months).Study design: Event-related potentials (ERP) were used in a visual recognition memory task (mother vs. stranger face) to compare healthy term infants according to iron status at birth and 9 months. Fetal-neonatal ID was defined as cord serum ferritin < 75 µg/l or zinc protoporphrin/heme ratio > 118 µmol/mol, postnatal ID as ≥ 2 abnormal iron measures at 9 months with normal cord-blood iron status, and iron-sufficient as not ID at birth or 9 months. Recognition of mother faces was measured by negative component (Nc) and late slow wave (LSW). These ERP components reflect attention and memory updating processes, respectively.Results: All groups showed differences in Nc amplitude elicited by mother and stranger faces at 9 months. At 18 months, only postnatal ID and iron-sufficient groups showed condition differences in Nc amplitude. However, the 2 groups were different in the involved brain regions. For LSW, only the 2 ID groups showed condition differences in amplitude at 9 months. At 18 months, condition differences were not observed in any group.Conclusions: This study indicates that the timing of ID in early life (fetal-neonatal vs. postnatal) modulates the impact of ID on recognition memory. Such impact also varies depending on the age of infants at testing (9 vs. 18 months).

Birthweight moderates the association between chronological age and infants' abilities to respond to cues for joint attention.

Infants born preterm are more likely than ever to survive, but relatively little is known about the factors that influence their subsequent sociocognitive development. Responding to joint attention (RJA) is a pivotal skill that is likely supported by biological preparedness at birth and ex-utero social experience. The goals of this study are to evaluate the relative roles of chronological age, gestation duration, and birthweight for early RJA and examine birthweight as a potential moderator of the associations between chronological age and RJA. This study leveraged a mixed longitudinal design of infants (N = 256, obs = 421) from 8 to 16 months of chronological age. Results show that chronological age and gestation duration both explain unique variation in RJA. Further, birthweight exhibits quadratic relations with RJA. Birthweight moderates the association between chronological age and RJA; infants born heavier demonstrate faster RJA growth compared to those born smaller. Findings suggest that birth weight, an index of nutrient sufficiency in utero and biological preparedness, may constrain or afford early RJA development, consistent with the Developmental Origins of Health and Disease (DoHAD) hypothesis. Findings inform our understanding of the roles of biological preparedness and experience in shaping RJA and help disaggregate potential mechanisms of prematurity-related challenges to social cognitive development.

Study Protocol: Multimodal Longitudinal Assessment of Infant Brain Organization and Recovery in Perinatal Brain Injury.

PURPOSE: Perinatal brain injury is a primary cause of cerebral palsy, a condition resulting in lifelong motor impairment. Infancy is an important period of motor system development, including development of the corticospinal tract (CST), the primary pathway for cortical movement control. The interaction between perinatal stroke recovery, CST organization, and resultant motor outcome in infants is not well understood. METHODS: Here, we present a protocol for multimodal longitudinal assessment of brain development and motor function following perinatal brain injury using transcranial magnetic stimulation and magnetic resonance imaging to noninvasively measure CST functional and structural integrity across multiple time points in infants 3 to 24 months of age. We will further assess the association between cortical excitability, integrity, and motor function. DISCUSSION: This protocol will identify bioindicators of motor outcome and neuroplasticity and subsequently inform early detection, diagnosis, and intervention strategies for infants with perinatal stroke, brain bleeds, and related diagnoses.