Fetal iron deficiency alters the proteome of adult rat hippocampal synaptosomes

Iron Deficiency and Recovery in Yeast: A Quantitative Proteomics Approach

Iron is an essential element for life, as it is critical for oxygen transport, cellular respiration, DNA synthesis, and metabolism. Disruptions in iron metabolism have been associated with several complex diseases like diabetes, cancer, infection susceptibility, neurodegeneration, and others; however, the molecular mechanisms linking iron metabolism with these diseases are not fully understood. A commonly used model to study iron deficiency (ID) is yeast, Saccharomyces cerevisiae. Here, we used quantitative (phospho)proteomics to explore the early (4 and 6 h) and late (12 h) response to ID. We showed that metabolic pathways like the Krebs cycle, amino acid, and ergosterol biosynthesis were affected by ID. In addition, during the late response, several proteins related to the ubiquitin-proteasome system and autophagy were upregulated. We also explored the proteomic changes during a recovery period after 12 h of ID. Several proteins recovered their steady-state levels, but some others, such as cytochromes, did not recover during the time tested. Additionally, we showed that autophagy is active during ID, and some of the degraded proteins during ID can be rescued using KO strains for several key autophagy genes. Our results highlight the complex proteome changes occurring during ID and recovery. This study constitutes a valuable data set for researchers interested in iron biology, offering a temporal proteomic data set for ID, as well as a compendium the proteomic changes associated with episodes of iron recovery.

Prevalence and Utility of Low Mean Corpuscular Volume in Infants Admitted to the Neonatal Intensive Care Unit

OBJECTIVE

To determine the prevalence of low mean corpuscular volume (MCV) in newborn infants admitted to the neonatal intensive care unit and to assess low MCV as a diagnostic test for alpha thalassemia.

STUDY DESIGN

Retrospective analysis of all infants admitted to the neonatal intensive care unit between January 2010 and October 2018 for which a complete blood count was performed during the first 3 postnatal days. Infants with a low MCV were compared with those with a normal MCV. Infants with positive hemoglobin Bart (Hb Bart) were compared with those withnegative Hb Bart. Low MCV was also evaluated as a diagnostic test for alpha thalassemia.

RESULTS

A total of 3851 infants (1386 preterm, 2465 term) met the inclusion criteria and 853 (22.2%) had a low MCV. A low MCV was more common in term (25%) compared with preterm infants (17.1%, P < .001). Hb Bart positive newborn screening was identified in 133 infants (3.5%). Hb Bart was positive in 11.1% of infants with low MCV compared with 1.3% with normal MCV (P < .001). The sensitivity, specificity, positive predictive value, and negative predictive value of low MCV for the diagnosis of alpha thalassemia were 71.4%, 79.6%, 11.3%, and 98.7%, respectively.

CONCLUSIONS

As Hb Bart positive newborn screens were seen in only 11.1% of infants with microcytosis, further diagnostic investigation may be warranted in individual infants. Further research to correlate microcytosis with iron status in infants and mothers is needed as well as studies using DNA analysis for the evaluation of alpha thalassemia variants.

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.

Iron-deficient diet induces distinct protein profile related to energy metabolism in the striatum and hippocampus of adult rats

Iron deficiency is a public health problem that affects all age groups. Its main consequence is anemia, but it can also affect cognitive functions. Although the negative effects of iron deficiency on cognitive function have been extensively described, the underlying mechanism has not been fully investigated. Thus, to gain an unbiased insight into the effects of iron deficiency (ID) on discrete brain regions, we performed a proteomic analysis of the striatum and hippocampus of adult rats subjected to an iron restricted (IR) diets for 30 days. We found that an IR diet caused major alterations in proteins related to glycolysis and lipid catabolism in the striatum. In the hippocampus, a larger portion of proteins related to oxidative phosphorylation and neurodegenerative diseases were altered. These alterations in the striatum and hippocampus occurred without a reduction in local iron levels, although there was a drastic reduction in liver iron and ferritin. Moreover, the IR group showed higher fasting glycaemia than the control group. These results suggest that brain iron content is preserved during acute iron deficiency, but the alterations of other systemic metabolites such as glucose may trigger distinct metabolic adaptations in each brain region. Abnormal energy metabolism precedes and persists in many neurological disorders. Thus, altered energy metabolism can be one of the mechanisms by which iron deficiency affects cognitive functions.

Cord Blood-Derived Exosomal CNTN2 and BDNF: Potential Molecular Markers for Brain Health of Neonates at Risk for Iron Deficiency

Maternal iron deficiency anemia, obesity, and diabetes are prevalent during pregnancy. All are associated with neonatal brain iron deficiency (ID) and neurodevelopmental impairment. Exosomes are extracellular vesicles involved in cell–cell communication. Contactin-2 (CNTN2), a neural-specific glycoprotein, and brain-derived neurotrophic factor (BDNF) are important in neurodevelopment and found in exosomes. We hypothesized that exosomal CNTN2 and BDNF identify infants at risk for brain ID. Umbilical cord blood samples were measured for iron status. Maternal anemia, diabetes, and body mass index (BMI) were recorded. Cord blood exosomes were isolated and validated for the exosomal marker CD81 and the neural-specific exosomal marker CNTN2. Exosomal CNTN2 and BDNF levels were quantified by ELISA. Analysis of CNTN2 and BDNF levels as predictors of cord blood iron indices showed a direct correlation between CNTN2 and ferritin in all neonates (n = 79, β = 1.75, p = 0.02). In contrast, BDNF levels inversely correlated with ferritin (β = −1.20, p = 0.03), with stronger association in female neonates (n = 37, β = −1.35, p = 0.06), although there is no evidence of a sex-specific effect. Analysis of maternal risk factors for neonatal brain ID as predictors of exosomal CNTN2 and BDNF levels showed sex-specific relationships between infants of diabetic mothers (IDMs) and CNTN2 levels (Interaction p = 0.0005). While male IDMs exhibited a negative correlation (n = 42, β = −0.69, p = 0.02), female IDMs showed a positive correlation (n = 37, β = 0.92, p = 0.01) with CNTN2. A negative correlation between BNDF and maternal BMI was found with stronger association in female neonates (per 10 units BMI, β = −0.60, p = 0.04). These findings suggest CNTN2 and BNDF are respective molecular markers for male and female neonates at risk for brain ID. This study supports the potential of exosomal markers to assess neonatal brain status in at-risk infants.

Early-Life Iron Deficiency Alters Glucose Transporter-1 Expression in the Adult Rodent Hippocampus

BACKGROUND

Early-life iron deficiency (ID) impairs hippocampal energy production. Whether there are changes in glucose transporter (GLUT) expression is not known.

OBJECTIVE

The aim of this study was to investigate whether early-life ID and the treatment iron dose alter brain regional GLUT expression in adult rats and mice.

METHODS

In Study 1, ID was induced in male and female Sprague Dawley rat pups by feeding dams a 3-mg/kg iron diet during gestation and the first postnatal week, followed by treatment using low-iron [3-10 mg/kg; formerly iron-deficient (FID)-10 group], standard-iron (40-mg/kg; FID-40 group), or high-iron (400-mg/kg; FID-400 group) diets until weaning. The control group received the 40 mg/kg iron diet. GLUT1, GLUT3, hypoxia-inducible factor (HIF)-1α, and prolyl-hydroxylase-2 (PHD2) mRNA and protein expression in the cerebral cortex, hippocampus, striatum, cerebellum, and hypothalamus were determined at adulthood. In Study 2, the role of hippocampal ID in GLUT expression was examined by comparing the Glut1, Glut3, Hif1α, and Phd2 mRNA expression in adult male and female wild-type (WT) and nonanemic hippocampal iron-deficient and iron-replete dominant negative transferrin receptor 1 (DNTfR1-/-) transgenic mice.

RESULTS

In Study 1, Glut1, Glut3, and Hif1α mRNA, and GLUT1 55-kDa protein expression was upregulated 20-33% in the hippocampus of the FID-10 group but not the FID-40 group, relative to the control group. Hippocampal Glut1 mRNA (-39%) and GLUT1 protein (-30%) expression was suppressed in the FID-400 group, relative to the control group. Glut1 and Glut3 mRNA expression was not altered in the other brain regions in the 3 FID groups. In Study 2, hippocampal Glut1 (+14%) and Hif1α (+147%) expression was upregulated in the iron-deficient DNTfR1-/- mice, but not in the iron-replete DNTfR1-/- mice, relative to the WT mice (P < 0.05, all).

CONCLUSIONS

Early-life ID is associated with altered hippocampal GLUT1 expression in adult rodents. The mouse study suggests that tissue ID is potentially responsible.

Perinatal Ischemia Alters Global Expression of Synaptosomal Proteins Critical for Neural Plasticity in the Developing Mouse Brain

Ischemic perinatal stroke (IPS) affects 1 in 2,300-5,000 live births. Despite a survival rate >95%, approximately 60% of IPS infants develop motor and cognitive impairments. Given the importance of axonal growth and synaptic plasticity in neurocognitive development, our objective was to identify the molecular pathways underlying IPS-associated synaptic dysfunction using a mouse model. IPS was induced by unilateral ligation of the common carotid artery of postnatal day 10 (P10) mice. Five days after ischemia, sensorimotor and motor functions were assessed by vibrissae-evoked forepaw placement and the tail suspension test respectively, showing evidence of greater impairments in male pups than in female pups. Twenty-four hours after ischemia, both hemispheres were collected and synaptosomal proteins then prepared for quantification, using isobaric tags for relative and absolute quantitation. Seventy-two of 1,498 qualified proteins were altered in the ischemic hemisphere. Ingenuity Pathway Analysis was used to map these proteins onto molecular networks indicative of reduced neuronal proliferation, survival, and synaptic plasticity, accompanied by reduced PKCα signaling in male, but not female, pups. These effects also occurred in the non-ischemic hemisphere when compared with sham controls. The altered signaling effects may contribute to the sex-specific neurodevelopmental dysfunction following IPS, highlighting potential pathways for targeting during treatment.

Association between APOE4 and biomarkers in cerebral adrenoleukodystrophy

Cerebral adrenoleukodystrophy (cALD) is an inflammatory neurodegenerative disease associated with mutation of the ABCD1 gene. Proteomic analysis of cerebral spinal fluid (CSF) from young males with active cALD revealed markers of inflammation including APOE4. APOE4 genotype has been associated with an inferior prognosis following acute and chronic neurologic injury. We assessed APOE4 inheritance among 83 consecutive young males with cALD prior to hematopoietic cell transplant and its association with markers of cerebral disease. The allele frequency of APOE4 was not significantly different from that of the general population at 17%. Young males with cALD that were APOE4 carriers had similar CSF protein and chitotriosidase activity to that of non-carriers. In contrast, APOE4 carriers had an increased burden of cerebral disease involvement as determined by MRI severity score (10.5 vs 7.0 points, p = 0.01), higher gadolinium intensity score (2.0 vs 1.3 points, p = 0.007), inferior neurologic function (neurologic function score 2.4 vs 1.0, p = 0.001), and elevated CSF MMP2 levels compared to that of non-carriers (13168 vs 9472 pg/mL, p = 0.01). These are the first data showing that APOE4 is associated with increased severity of cerebral disease in cALD and suggest it may be a modifier of disease.

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.

The Effects of Prenatal Iron Deficiency and Risperidone Treatment on the Rat Frontal Cortex: A Proteomic Analysis

Prenatal iron deficiency (pID) has been described to increase the risk for neurodevelopmental disorders such as autism and schizophrenia; however, the precise molecular mechanisms are still unknown. Here, we utilized high-throughput MS to examine the proteomic effects of pID in adulthood on the rat frontal cortex area (FCA). In addition, the FCA proteome was examined in adulthood following risperidone treatment in adolescence to see if these effects could be prevented. We identified 1501 proteins of which 100 were significantly differentially expressed in the FCA at postnatal day 90. Pathway analysis of proteins affected by pID revealed changes in metabolic processes, including the tricyclic acid cycle, mitochondrial dysfunction, and P13K/Akt signaling. Interestingly, most of these protein changes were not present in the adult pID offspring who received risperidone in adolescence. Considering the link between pID and several neurodevelopmental disorders such as autism and schizophrenia these presented results bring new perspectives to understand the role of iron in metabolic pathways and provide novel biomarkers for future studies of pID.

Maternal hypomagnesemia alters hippocampal NMDAR subunit expression and programs anxiety-like behaviour in adult offspring

It is well established that maternal undernutrition and micronutrient deficiencies can lead to altered development and behaviour in offspring. However, few studies have explored the implications of maternal Mg deficiency and programmed behavioural and neurological outcomes in offspring. We used a model of Mg deficiency (prior to and during pregnancy and lactation) in CD1 mice to investigate if maternal Mg deficiency programmed changes in behaviour and NMDAR subunit expression in offspring. Hippocampal tissue was collected at postnatal day 2 (PN2), PN8, PN21 and 6 months, and protein expression of NMDAR subunits GluN1, GluN2A and GluN2B was determined. At 6 months of age, offspring were subject to behavioural tasks testing aspects of anxiety-like behaviour, memory, and neophobia. Maternal hypomagnesemia was associated with increased GluN1, GluN2A and GluN2B subunit expression in female offspring at 6 months, but decreased GluN1 and GluN2A expression in males. The GluN2B:GluN2A expression ratio was increased in both sexes. Male (but not female) offspring from Mg-deficient dams showed anxiety-like behaviour, with reduced head dips (Suok test), and reduced exploration of open arms (elevated plus maze). Both male and female offspring from Mg-deficient dams also showed impaired recognition memory (novel object test). These findings suggest that maternal Mg deficiency can result in behavioural deficits in adult life, and that these changes may be related to alterations in hippocampal NMDA receptor expression.

The iron status at birth of neonates with risk factors for developing iron deficiency: a pilot study

OBJECTIVE

Small-for-gestational-age (SGA) neonates, infants of diabetic mothers (IDM) and very-low-birth weight premature neonates (VLBW) are reported to have increased risk for developing iron deficiency and possibly associated neurocognitive delays.

STUDY DESIGN

We conducted a pilot study to assess iron status at birth in at-risk neonates by measuring iron parameters in umbilical cord blood from SGA, IDM, VLBW and comparison neonates.

RESULTS

Six of the 50 infants studied had biochemical evidence of iron deficiency at birth. Laboratory findings consistent with iron deficiency were found in one SGA, one IDM, three VLBW, and one comparison infant. None of the infants had evidence of iron deficiency anemia.

CONCLUSIONS

Evidence of biochemical iron deficiency at birth was found in 17% of screened neonates. Studies are needed to determine whether these infants are at risk for developing iron-limited erythropoiesis, iron deficiency anemia or iron-deficient neurocognitive delay.

Evidence Favoring a Positive Feedback Loop for Physiologic Auto Upregulation of hnRNP-E1 during Prolonged Folate Deficiency in Human Placental Cells

Background: Previously, we determined that heterogeneous nuclear ribonucleoprotein E1 (hnRNP-E1) functions as an intracellular physiologic sensor of folate deficiency. In this model, l-homocysteine, which accumulates intracellularly in proportion to the extent of folate deficiency, covalently binds to and thereby activates homocysteinylated hnRNP-E1 to interact with folate receptor-α mRNA; this high-affinity interaction triggers the translational upregulation of cell surface folate receptors, which enables cells to optimize folate uptake from the external milieu. However, integral to this model is the need for ongoing generation of hnRNP-E1 to replenish homocysteinylated hnRNP-E1 that is degraded.Objective: We searched for an interrelated physiologic mechanism that could also maintain the steady-state concentration of hnRNP-E1 during prolonged folate deficiency.Methods: A novel RNA-protein interaction was functionally characterized by using molecular and biochemical approaches in vitro and in vivo.Results: l-homocysteine triggered a dose-dependent high-affinity interaction between hnRNP-E1 and a 25-nucleotide cis element within the 5'-untranslated region of hnRNP-E1 mRNA; this led to a proportionate increase in these RNA-protein complexes, and translation of hnRNP-E1 both in vitro and within placental cells. Targeted perturbation of this RNA-protein interaction either by specific 25-nucleotide antisense oligonucleotides or mutation within this cis element or by small interfering RNA to hnRNP-E1 mRNA significantly reduced cellular biosynthesis of hnRNP-E1. Conversely, transfection of hnRNP-E1 mutant proteins that mimicked homocysteinylated hnRNP-E1 stimulated both cellular hnRNP-E1 and folate receptor biosynthesis. In addition, ferrous sulfate heptahydrate [iron(II)], which also binds hnRNP-E1, significantly perturbed this l-homocysteine-triggered RNA-protein interaction in a dose-dependent manner. Finally, folate deficiency induced dual upregulation of hnRNP-E1 and folate receptors in cultured human cells and tumor xenografts, and more selectively in various fetal tissues of folate-deficient dams.Conclusions: This novel positive feedback loop amplifies hnRNP-E1 during prolonged folate deficiency and thereby maximizes upregulation of folate receptors in order to restore folate homeostasis toward normalcy in placental cells. It will also functionally impact several other mRNAs of the nutrition-sensitive, folate-responsive posttranscriptional RNA operon that is orchestrated by homocysteinylated hnRNP-E1.

The impacts of maternal iron deficiency and being overweight during pregnancy on neurodevelopment of the offspring

Both maternal Fe deficiency (ID) and being overweight or obese (Ow/Ob, BMI≥25 kg/m2) may negatively affect offspring brain development. However, the two risk factors correlate and their independent effects on infant neurodevelopment are unclear. PREOBE is a prospective observational study that included 331 pregnant Spanish women, of whom 166 had pre-gestational Ow/Ob. Fe status was analysed at 34 weeks and at delivery, and babies were assessed using Bayley III scales of neurodevelopment at 18 months. In confounder-adjusted analyses, maternal ID at 34 weeks was associated with lower composite motor scores at 18 months (mean 113·3 (sd 9·9) v. 117·1 (sd 9·2), P=0·039). Further, the offspring of mothers with ID at delivery had lower cognitive scores (114·0 (sd 9·7) v. 121·5 (sd 10·9), P=0·039) and lower receptive, expressive and composite (99·5 (sd 8·6) v. 107·6 (sd 8·3), P=0·004) language scores. The negative associations between maternal ID at delivery and Bayley scores remained even when adjusting for maternal Ow/Ob and gestational diabetes. Similarly, maternal Ow/Ob correlated with lower gross motor scores in the offspring (12·3 (sd 2·0) v. 13·0 (sd 2·1), P=0·037), a correlation that remained when adjusting for maternal ID. In conclusion, maternal ID and pre-gestational Ow/Ob are both negatively associated with Bayley scores at 18 months, but independently and on different subscales. These results should be taken into account when considering Fe supplementation for pregnant women.

Glucose Starvation Alters Heat Shock Response, Leading to Death of Wild Type Cells and Survival of MAP Kinase Signaling Mutant

A moderate heat shock induces Neurospora crassa to synthesize large quantities of heat shock proteins that are protective against higher, otherwise lethal temperatures. However, wild type cells do not survive when carbohydrate deprivation is added to heat shock. In contrast, a mutant strain defective in a stress-activated protein kinase does survive the combined stresses. In order to understand the basis for this difference in survival, we have determined the relative levels of detected proteins in the mutant and wild type strain during dual stress, and we have identified gene transcripts in both strains whose quantities change in response to heat shock or dual stress. These data and supportive experimental evidence point to reasons for survival of the mutant strain. By using alternative respiratory mechanisms, these cells experience less of the oxidative stress that proves damaging to wild type cells. Of central importance, mutant cells recycle limited resources during dual stress by undergoing autophagy, a process that we find utilized by both wild type and mutant cells during heat shock. Evidence points to inappropriate activation of TORC1, the central metabolic regulator, in wild type cells during dual stress, based upon behavior of an additional signaling mutant and inhibitor studies.

The role of the dynein light intermediate chain in retrograde IFT and flagellar function in Chlamydomonas

The assembly of cilia and flagella depends on the activity of two microtubule motor complexes, kinesin-2 and dynein-2/1b, but the specific functions of the different subunits are poorly defined. Here we analyze Chlamydomonas strains expressing different amounts of the dynein 1b light intermediate chain (D1bLIC). Disruption of D1bLIC alters the stability of the dynein 1b complex and reduces both the frequency and velocity of retrograde intraflagellar transport (IFT), but it does not eliminate retrograde IFT. Flagellar assembly, motility, gliding, and mating are altered in a dose-dependent manner. iTRAQ-based proteomics identifies a small subset of proteins that are significantly reduced or elevated in d1blic flagella. Transformation with D1bLIC-GFP rescues the mutant phenotypes, and D1bLIC-GFP assembles into the dynein 1b complex at wild-type levels. D1bLIC-GFP is transported with anterograde IFT particles to the flagellar tip, dissociates into smaller particles, and begins processive retrograde IFT in <2 s. These studies demonstrate the role of D1bLIC in facilitating the recycling of IFT subunits and other proteins, identify new components potentially involved in the regulation of IFT, flagellar assembly, and flagellar signaling, and provide insight into the role of D1bLIC and retrograde IFT in other organisms.

Deletion of novel protein TMEM35 alters stress-related functions and impairs long-term memory in mice

The mounting of appropriate emotional and neuroendocrine responses to environmental stressors critically depends on the hypothalamic-pituitary-adrenal (HPA) axis and associated limbic circuitry. Although its function is currently unknown, the highly evolutionarily conserved transmembrane protein 35 (TMEM35) is prominently expressed in HPA circuitry and limbic areas, including the hippocampus and amygdala. To investigate the possible involvement of this protein in neuroendocrine function, we generated tmem35 knockout (KO) mice to characterize the endocrine, behavioral, electrophysiological, and proteomic alterations caused by deletion of the tmem35 gene. While capable of mounting a normal corticosterone response to restraint stress, KO mice showed elevated basal corticosterone accompanied by increased anxiety-like behavior. The KO mice also displayed impairment of hippocampus-dependent fear and spatial memories. Given the intact memory acquisition but a deficit in memory retention in the KO mice, TMEM35 is likely required for long-term memory consolidation. This conclusion is further supported by a loss of long-term potentiation in the Schaffer collateral-CA1 pathway in the KO mice. To identify putative molecular pathways underlying alterations in plasticity, proteomic analysis of synaptosomal proteins revealed lower levels of postsynaptic molecules important for synaptic plasticity in the KO hippocampus, including PSD95 and N-methyl-d-aspartate receptors. Pathway analysis (Ingenuity Pathway Analysis) of differentially expressed synaptic proteins in tmem35 KO hippocampus implicated molecular networks associated with specific cellular and behavioral functions, including decreased long-term potentiation, and increased startle reactivity and locomotion. Collectively, these data suggest that TMEM35 is a novel factor required for normal activity of the HPA axis and limbic circuitry.

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.

Helicobacter pylori Infection Induces Anemia, Depletes Serum Iron Storage, and Alters Local Iron-Related and Adult Brain Gene Expression in Male INS-GAS Mice

Iron deficiency anemia (IDA) affects > 500 million people worldwide, and is linked to impaired cognitive development and function in children. Helicobacter pylori, a class 1 carcinogen, infects about half of the world’s population, thus creating a high likelihood of overlapping risk. This study determined the effect of H. pylori infection on iron homeostasis in INS-GAS mice. Two replicates of INS-GAS/FVB male mice (n = 9-12/group) were dosed with H. pylori (Hp) strain SS1 or sham dosed at 6–9 weeks of age, and were necropsied at 27–29 weeks of age. Hematologic and serum iron parameters were evaluated, as was gene expression in gastric and brain tissues. Serum ferritin was lower in Hp SS1-infected mice than uninfected mice (p < 0.0001). Infected mice had a lower red blood cell count (p<0.0001), hematocrit (p < 0.001), and hemoglobin concentration (p <0.0001) than uninfected mice. Relative expression of gastric hepcidin antimicrobial peptide (Hamp) was downregulated in mice infected with Hp SS1 compared to sham-dosed controls (p<0.001). Expression of bone morphogenic protein 4 (Bmp4), a growth factor upstream of hepcidin, was downregulated in gastric tissue of Hp SS1-infected mice (p<0.001). Hp SS1-infected mice had downregulated brain expression of tyrosine hydroxylase (Th) (p = 0.02). Expression of iron-responsive genes involved in myelination (myelin basic protein (Mbp) and proteolipid protein 2 (Plp2)) was downregulated in infected mice (p = 0.001 and p = 0.02). Expression of synaptic plasticity markers (brain derived neurotrophic factor 3 (Bdnf3), Psd95 (a membrane associated guanylate kinase), and insulin-like growth factor 1 (Igf1)) was also downregulated in Hp SS1-infected mice (p = 0.09, p = 0.04, p = 0.02 respectively). Infection of male INS-GAS mice with Hp SS1, without concurrent dietary iron deficiency, depleted serum ferritin, deregulated gastric and hepatic expression of iron regulatory genes, and altered iron-dependent neural processes. The use of Hp SS1-infected INS-GAS mice will be an appropriate animal model for further study of the effects of concurrent H. pylori infection and anemia on iron homeostasis and adult iron-dependent brain gene expression.

Functional and Anatomic Consequences of Diabetic Pregnancy on Memory in Ten-Year-Old Children

OBJECTIVE

Pregnancies complicated by diabetes mellitus impair offspring memory functions during infancy and early childhood. The purpose of this study was to investigate the long-term consequences of such pregnancies on memory and memory-related brain regions in 10-year-old children.

METHODS

Nineteen children of diabetic mothers (CDMs) and 35 children of nondiabetic mothers participated in this 10-year follow-up study. Memory performance was assessed using a continuous recognition memory task during which children made old/new judgments in response to pictures of concrete and abstract objects presented after different lags or delays. In addition, the volume of the hippocampal formation (HF) was measured using high-resolution structural images.

RESULTS

At 10 years of age, recognition memory performance of CDMs did not differ from children of nondiabetic mothers. Similarly, the volume of the HF did not differ between groups. However, the size of the HF in CDMs predicted the time those children needed to provide accurate responses in the continuous recognition memory task.

CONCLUSIONS

CDMs do not show memory impairments by 10 years of age, despite evidence for such impairments early in life. However, subtle differences in underlying neural processes may still be present. These results have important implications for long-term cognitive development of CDMs.

Fetal iron deficiency induces chromatin remodeling at the Bdnf locus in adult rat hippocampus

Fetal and subsequent early postnatal iron deficiency causes persistent impairments in cognitive and affective behaviors despite prompt postnatal iron repletion. The long-term cognitive impacts are accompanied by persistent downregulation of brain-derived neurotrophic factor (BDNF), a factor critical for hippocampal plasticity across the life span. This study determined whether early-life iron deficiency epigenetically modifies the Bdnf locus and whether dietary choline supplementation during late gestation reverses these modifications. DNA methylation and histone modifications were assessed at the Bdnf-IV promoter in the hippocampus of rats [at postnatal day (PND) 65] that were iron-deficient (ID) during the fetal-neonatal period. Iron deficiency was induced in rat pups by providing pregnant and nursing dams an ID diet (4 mg/kg Fe) from gestational day (G) 2 through PND7, after which iron deficiency was treated with an iron-sufficient (IS) diet (200 mg/kg Fe). This paradigm resulted in about 60% hippocampal iron loss on PND15 with complete recovery by PND65. For choline supplementation, pregnant rat dams were given dietary choline (5 g/kg) from G11 through G18. DNA methylation was determined by quantitative sequencing of bisulfite-treated DNA, revealing a small alteration at the Bdnf-IV promoter. Chromatin immunoprecipitation analysis showed increased HDAC1 binding accompanied by reduced binding of RNA polymerase II and USF1 at the Bdnf-IV promoter in formerly ID rats. These changes were correlated with altered histone methylations. Prenatal choline supplementation reverses these epigenetic modifications. Collectively, the findings identify epigenetic modifications as a potential mechanism to explicate the long-term repression of Bdnf following fetal and early postnatal iron deficiency.

Proteomic profiling of a robust Wolbachia infection in an Aedes albopictus mosquito cell line

Wolbachia pipientis, a widespread vertically transmitted intracellular bacterium, provides a tool for insect control through manipulation of host-microbe interactions. We report proteomic characterization of wStr, a Wolbachia strain associated with a strong cytoplasmic incompatibility phenotype in its native host, Laodelphax striatellus. In the Aedes albopictus C/wStr1 mosquito cell line, wStr maintains a robust, persistent infection. MS/MS analyses of gel bands revealed a protein 'footprint' dominated by Wolbachia-encoded chaperones, stress response and cell membrane proteins, including the surface antigen WspA, a peptidoglycan-associated lipoprotein and a 73 kDa outer membrane protein. Functional classifications and estimated abundance levels of 790 identified proteins suggested that expression, stabilization and secretion of proteins predominate over bacterial genome replication and cell division. High relative abundances of cysteine desulphurase, serine/glycine hydroxymethyl transferase, and components of the α-ketoglutarate dehydrogenase complex in conjunction with above average abundances of glutamate dehydrogenase and proline utilization protein A support Wolbachia genome-based predictions for amino acid metabolism as a primary energy source. wStr expresses 15 Vir proteins of a Type IV secretion system and its transcriptional regulator. Proteomic characterization of a robust insect-associated Wolbachia strain provides baseline information that will inform further development of in vitro protocols for Wolbachia manipulation.

Striking while the iron is hot: Understanding the biological and neurodevelopmental effects of iron deficiency to optimize intervention in early childhood

Prenatal and early postnatal iron deficiency (ID) is associated with long-term neurobiological alterations and disruptions in cognitive, social, and behavioral development. Early life ID is particularly detrimental as this is a period of rapid neurodevelopment. Even after iron supplementation, cognitive and social disruptions often persist in formerly iron deficient individuals. Observational studies of the acute and long-term effects of early life ID yield different results based on the timing of ID. Further, intervention studies demonstrate some improvement for certain domains but still show residual effects years later, which are dependent on the timing of ID and treatment. This review will cover the effects of ID during infancy and early childhood on brain structure and function, cognition, and behavior in relation to preclinical models of ID and sensitive periods of human brain development.