Metabolomic analysis of CSF indicates brain metabolic impairment precedes hematological indices of anemia in the iron-deficient infant monkey

Biomarkers of Brain Dysfunction in Perinatal Iron Deficiency

Iron deficiency in the fetal and neonatal period (perinatal iron deficiency) bodes poorly for neurodevelopment. Given its common occurrence and the negative impact on brain development, a screening and treatment strategy that is focused on optimizing brain development in perinatal iron deficiency is necessary. Pediatric societies currently recommend a universal iron supplementation strategy for full-term and preterm infants that does not consider individual variation in body iron status and thus could lead to undertreatment or overtreatment. Moreover, the focus is on hematological normalcy and not optimal brain development. Several serum iron indices and hematological parameters in the perinatal period are associated with a risk of abnormal neurodevelopment, suggesting their potential use as biomarkers for screening and monitoring treatment in infants at risk for perinatal iron deficiency. A biomarker-based screening and treatment strategy that is focused on optimizing brain development will likely improve outcomes in perinatal 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.

Bayesian predictive modeling of multi-source multi-way data

A Bayesian approach to predict a continuous or binary outcome from data that are collected from multiple sources with a multi-way (i.e., multidimensional tensor) structure is described. As a motivating example, molecular data from multiple 'omics sources, each measured over multiple developmental time points, as predictors of early-life iron deficiency (ID) in a rhesus monkey model are considered. The method uses a linear model with a low-rank structure on the coefficients to capture multi-way dependence and model the variance of the coefficients separately across each source to infer their relative contributions. Conjugate priors facilitate an efficient Gibbs sampling algorithm for posterior inference, assuming a continuous outcome with normal errors or a binary outcome with a probit link. Simulations demonstrate that the model performs as expected in terms of misclassification rates and correlation of estimated coefficients with true coefficients, with large gains in performance by incorporating multi-way structure and modest gains when accounting for differing signal sizes across the different sources. Moreover, it provides robust classification of ID monkeys for the motivating application.

Inhibition of VDAC1 Rescues Aβ 1-42-Induced Mitochondrial Dysfunction and Ferroptosis via Activation of AMPK and Wnt/β-Catenin Pathways

Beta-amyloid (Aβ) accumulation in the brains of Alzheimer's disease (AD) patients leads to mitochondrial dysfunction and ferroptosis in neurons. Voltage-dependent anion channel 1 (VDAC1) is a major protein in the mitochondrial outer membrane. It has been reported that VDAC1 associated with mitochondrial dysfunction and ferroptosis. However, the mechanism by which VDAC1 regulates mitochondrial dysfunction and ferroptosis of neurons in AD remains unclear. This study is aimed at investigating the mechanism of action of VDAC1 in mitochondrial dysfunction and ferroptosis in neurons of the AD model. In this study, we determined cell viability after treatment with Aβ _1-42 via the MTT assay. The SOD, MDA, ROS, and MMP production was measured via the SOD kit, MDA kit, DCFDA staining, and JC-1 staining. The memory abilities of mice were detected via the Morris water maze test. The expression of AMPK/mTOR, Wnt/β-catenin, and GPX4 regulated by VDAC1 was detected via western blotting. Our present study showed that PC12 cells had decreased cell viability, increased LDH release, and decreased GPX4 expression after Aβ _1-42 treatment. Meanwhile, Aβ _1-42 induced MMP and SOD downregulation and increased MDA and ROS generation in PC12 cells. In addition, the expression of VDAC1 is increased in the brain tissue of AD mice and Aβ _1-42-treated PC12 cells. Further investigation of the role of VDAC1 in regulating AD found that all effects induced by Aβ _1-42 were reversed by inhibition of VDAC1. Additionally, inhibition of VDAC1 activates the AMPK/mTOR and Wnt/β-catenin pathways. Taken together, these findings demonstrate that inhibition of VDAC1 alleviates mitochondrial dysfunction and ferroptosis in AD neurons by activating AMPK/mTOR and Wnt/β-catenin.

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.

Multiomic Profiling of Iron Deficient Infant Monkeys Reveals Alterations in Neurologically Important Biochemicals in Serum and CSF Prior to the Onset of Anemia

BACKGROUND

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.

OBJECTIVE

To determine whether serum and CSF biomarkers of ID-induced metabolic dysfunction are concordant in the pre/early anemic stage of ID prior to anemia in a nonhuman primate model of infantile IDA.

METHODS

Paired serum and CSF specimens were collected from iron-sufficient (IS; n = 12) and ID (n = 7) rhesus infants at 4-months (pre-anemic period) and 6-months of age (anemic). Hematological, metabolomic, and proteomic profiles were generated via HPLC/MS at both time points to discriminate serum bio markers of ID-induced brain metabolic dysfunction.

RESULTS

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.

CONCLUSIONS

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.

Iron deficiency during the first 1000 days of life: are we doing enough to protect the developing brain?

Iron is essential for the functioning of all cells and organs, most critically for the developing brain in the fundamental neuronal processes of myelination, energy and neurotransmitter metabolism. Iron deficiency, especially in the first 1000 days of life, can result in long-lasting, irreversible deficits in cognition, motor function and behaviour. Pregnant women, infants and young children are most vulnerable to iron deficiency, due to their high requirements to support growth and development, coupled with a frequently inadequate dietary supply. An unrecognised problem is that even if iron intake is adequate, common pregnancy-related and lifestyle factors can affect maternal-fetal iron supply in utero, resulting in an increased risk of deficiency for the mother and her fetus. Although preterm birth, gestational diabetes mellitus and intrauterine growth restriction are known risk factors, more recent evidence suggests that maternal obesity and delivery by caesarean section further increase the risk of iron deficiency in the newborn infant, which can persist into early childhood. Despite the considerable threat that early-life iron deficiency poses to long-term neurological development, life chances and a country's overall social and economic progress, strategies to tackle the issue are non-existent, too limited or totally inappropriate. Prevention strategies, focused on improving the health and nutritional status of women of reproductive age are required. Delayed cord clamping should be considered a priority. Better screening strategies to enable the early detection of iron deficiency during pregnancy and early-life should be prioritised, with intervention strategies to protect maternal health and the developing brain.

Hepcidin is a relevant iron status indicator in infancy: results from a randomized trial of early vs. delayed cord clamping

BACKGROUND

We aimed to evaluate whether serum hepcidin is a useful indicator of iron status in infants.

METHODS

Term infants (n = 400) were randomized to delayed (≥180 s) or early (≤10 s) cord clamping (CC). Iron status was assessed at 4 and 12 months. In all cases with iron depletion or iron deficiency (ID) (as defined in "Methods") (n = 30) and 97 randomly selected iron-replete infants, we analyzed hepcidin and explored its correlation to the intervention, iron status, and perinatal factors.

RESULTS

Serum hepcidin concentrations were significantly lower in the early CC group at both time points and in ID infants at 4 months. Median (2.5th-97.5th percentile) hepcidin in non-ID infants in the delayed CC group (suggested reference) was 64.5 (10.9-142.1), 39.5 (3.5-157.7), and 32.9 (11.2-124.2) ng/mL in the cord blood and at 4 and 12 months, respectively. The value of 16 ng/mL was a threshold detecting all cases of iron depletion/ID at 4 months. No similar threshold for ID was observed at 12 months. The strongest predictor of hepcidin at both ages was ferritin.

CONCLUSIONS

Hepcidin is relevant as iron status indicator in early infancy and may be useful to detect ID. Levels <16 ng/mL at 4 months of age indicates ID.

IMPACT

Serum hepcidin is a relevant indicator of iron status in early infancy. Normal reference in healthy infants is suggested in this study. Serum hepcidin may be useful in clinical practice to detect iron deficiency.

Correcting iron deficiency anemia with iron dextran alters the serum metabolomic profile of the infant Rhesus Monkey

BACKGROUND

The effects of infantile iron deficiency anemia (IDA) extend beyond hematological indices and include short- and long-term adverse effects on multiple cells and tissues. IDA is associated with an abnormal serum metabolomic profile, characterized by altered hepatic metabolism, lowered NAD flux, increased nucleoside levels, and a reduction in circulating dopamine levels.

OBJECTIVES

The objective of this study was to determine whether the serum metabolomic profile is normalized after rapid correction of IDA using iron dextran injections.

METHODS

Blood was collected from iron-sufficient (IS; n = 10) and IDA (n = 12) rhesus infants at 6 months of age. IDA infants were then administered iron dextran and vitamin B via intramuscular injections at weekly intervals for 2 to 8 weeks. Their hematological and metabolomic statuses were evaluated following treatment and compared with baseline and a separate group of age-matched IS infants (n = 5).

RESULTS

Serum metabolomic profiles assessed at baseline and after treatment via HPLC/MS using isobaric standards identified 654 quantifiable metabolites. At baseline, 53 metabolites differed between IS and IDA infants. Iron treatment restored traditional hematological indices, including hemoglobin and mean corpuscular volume, into the normal range, but the metabolite profile in the IDA group after iron treatment was markedly altered, with 323 metabolites differentially expressed when compared with an infant's own baseline profile.

CONCLUSIONS

Rapid correction of IDA with iron dextran resulted in extensive metabolic changes across biochemical pathways indexing the liver function, bile acid release, essential fatty acid production, nucleoside release, and several neurologically important metabolites. The results highlight the importance of a cautious approach when developing a route and regimen of iron repletion to treat infantile IDA.

Gut Microbial and Metabolic Profiling Reveal the Lingering Effects of Infantile Iron Deficiency Unless Treated with Iron

SCOPE

Iron deficiency (ID) compromises the health of infants worldwide. Although readily treated with iron, concerns remain about the persistence of some effects. Metabolic and gut microbial consequences of infantile ID were investigated in juvenile monkeys after natural recovery (pID) from iron deficiency or post-treatment with iron dextran and B vitamins (pID+Fe).

METHODS AND RESULTS

Metabolomic profiling of urine and plasma is conducted with ¹ H nuclear magnetic resonance (NMR) spectroscopy. Gut microbiota are characterized from rectal swabs by amplicon sequencing of the 16S rRNA gene. Urinary metabolic profiles of pID monkeys significantly differed from pID+Fe and continuously iron-sufficient controls (IS) with higher maltose and lower amounts of microbial-derived metabolites. Persistent differences in energy metabolism are apparent from the plasma metabolic phenotypes with greater reliance on anaerobic glycolysis in pID monkeys. Microbial profiling indicated higher abundances of Methanobrevibacter, Lachnobacterium, and Ruminococcus in pID monkeys and any history of ID resulted in a lower Prevotella abundance compared to the IS controls.

CONCLUSIONS

Lingering metabolic and microbial effects are found after natural recovery from ID. These long-term biochemical derangements are not present in the pID+Fe animals emphasizing the importance of the early detection and treatment of early-life ID to ameliorate its chronic metabolic effects.

Infantile Iron Deficiency Affects Brain Development in Monkeys Even After Treatment of Anemia

A high percent of oxidative energy metabolism is needed to support brain growth during infancy. Unhealthy diets and limited nutrition, as well as other environmental insults, can compromise these essential developmental processes. In particular, iron deficiency anemia (IDA) has been found to undermine both normal brain growth and neurobehavioral development. Even moderate ID may affect neural maturation because when iron is limited, it is prioritized first to red blood cells over the brain. A primate model was used to investigate the neural effects of a transient ID and if deficits would persist after iron treatment. The large size and postnatal growth of the monkey brain makes the findings relevant to the metabolic and iron needs of human infants, and initiating treatment upon diagnosis of anemia reflects clinical practice. Specifically, this analysis determined whether brain maturation would still be compromised at 1 year of age if an anemic infant was treated promptly once diagnosed. The hematology and iron status of 41 infant rhesus monkeys was screened at 2-month intervals. Fifteen became ID; 12 met clinical criteria for anemia and were administered iron dextran and B vitamins for 1-2 months. MRI scans were acquired at 1 year. The volumetric and diffusion tensor imaging (DTI) measures from the ID infants were compared with monkeys who remained continuously iron sufficient (IS). A prior history of ID was associated with smaller total brain volumes, driven primarily by significantly less total gray matter (GM) and smaller GM volumes in several cortical regions. At the macrostructual level, the effect on white matter volumes (WM) was not as overt. However, DTI analyses of WM microstructure indicated two later-maturating anterior tracts were negatively affected. The findings reaffirm the importance of iron for normal brain development. Given that brain differences were still evident even after iron treatment and following recovery of iron-dependent hematological indices, the results highlight the importance of early detection and preemptive supplementation to limit the neural consequences of ID.

Effect of High-Dose Erythropoietin on Blood Transfusions in Extremely Low Gestational Age Neonates: Post Hoc Analysis of a Randomized Clinical Trial

IMPORTANCE

Extremely preterm infants are among the populations receiving the highest levels of transfusions. Erythropoietin has not been recommended for premature infants because most studies have not demonstrated a decrease in donor exposure.

OBJECTIVES

To determine whether high-dose erythropoietin given within 24 hours of birth through postmenstrual age of 32 completed weeks will decrease the need for blood transfusions.

DESIGN, SETTING, AND PARTICIPANTS

The Preterm Erythropoietin Neuroprotection Trial (PENUT) is a randomized, double-masked clinical trial with participants enrolled at 19 sites consisting of 30 neonatal intensive care units across the United States. Participants were born at a gestational age of 24 weeks (0-6 days) to 27 weeks (6-7 days). Exclusion criteria included conditions known to affect neurodevelopmental outcomes. Of 3266 patients screened, 2325 were excluded, and 941 were enrolled and randomized to erythropoietin (n = 477) or placebo (n = 464). Data were collected from December 12, 2013, to February 25, 2019, and analyzed from March 1 to June 15, 2019.

INTERVENTIONS

In this post hoc analysis, erythropoietin, 1000 U/kg, or placebo was given every 48 hours for 6 doses, followed by 400 U/kg or sham injections 3 times a week through postmenstrual age of 32 weeks.

MAIN OUTCOMES AND MEASURES

Need for transfusion, transfusion numbers and volume, number of donor exposures, and lowest daily hematocrit level are presented herein.

RESULTS

A total of 936 patients (488 male [52.1%]) were included in the analysis, with a mean (SD) gestational age of 25.6 (1.2) weeks and mean (SD) birth weight of 799 (189) g. Erythropoietin treatment (vs placebo) decreased the number of transfusions (unadjusted mean [SD], 3.5 [4.0] vs 5.2 [4.4]), with a relative rate (RR) of 0.66 (95% CI, 0.59-0.75); the cumulative transfused volume (mean [SD], 47.6 [60.4] vs 76.3 [68.2] mL), with a mean difference of -25.7 (95% CI, 18.1-33.3) mL; and donor exposure (mean [SD], 1.6 [1.7] vs 2.4 [2.0]), with an RR of 0.67 (95% CI, 0.58-0.77). Despite fewer transfusions, erythropoietin-treated infants tended to have higher hematocrit levels than placebo-treated infants, most noticeable at gestational week 33 in infants with a gestational age of 27 weeks (mean [SD] hematocrit level in erythropoietin-treated vs placebo-treated cohorts, 36.9% [5.5%] vs 30.4% [4.6%] (P < .001). Of 936 infants, 160 (17.1%) remained transfusion free at the end of 12 postnatal weeks, including 43 in the placebo group and 117 in the erythropoietin group (P < .001).

CONCLUSIONS AND RELEVANCE

These findings suggest that high-dose erythropoietin as used in the PENUT protocol was effective in reducing transfusion needs in this population of extremely preterm infants.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01378273.

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.

Early-Life Iron Deficiency and Its Natural Resolution Are Associated with Altered Serum Metabolomic Profiles in Infant Rhesus Monkeys

BACKGROUND

Iron deficiency is the most common nutrient deficiency in human infants aged 6 to 24 mo, and negatively affects many cellular metabolic processes, including energy production, electron transport, and oxidative degradation of toxins. There can be persistent influences on long-term metabolic health beyond its acute effects.

OBJECTIVES

The objective was to determine how iron deficiency in infancy alters the serum metabolomic profile and to test whether these effects persist after the resolution of iron deficiency in a nonhuman primate model of spontaneous iron deficiency.

METHODS

Blood was collected from naturally iron-sufficient (IS; n = 10) and iron-deficient (ID; n = 10) male and female infant rhesus monkeys (Macaca mulatta) at 6 mo of age. Iron deficiency resolved without intervention upon feeding of solid foods, and iron status was re-evaluated at 12 mo of age from the IS and formerly ID monkeys using hematological and other indices; sera were metabolically profiled using HPLC/MS and GC/MS with isobaric standards for identification and quantification at both time points.

RESULTS

A total of 413 metabolites were measured, with differences in 40 metabolites identified between IS and ID monkeys at 6 mo (P$\le $ 0.05). At 12 mo, iron-related hematological parameters had returned to normal, but the formerly ID infants remained metabolically distinct from the age-matched IS infants, with 48 metabolites differentially expressed between the groups. Metabolomic profiling indicated altered liver metabolites, differential fatty acid production, increased serum uridine release, and atypical bile acid production in the ID monkeys.

CONCLUSIONS

Pathway analyses of serum metabolites provided evidence of a hypometabolic state, altered liver function, differential essential fatty acid production, irregular uracil metabolism, and atypical bile acid production in ID infants. Many metabolites remained altered after the resolution of ID, suggesting long-term effects on metabolic health.

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.

A metabolomic study on the gender-dependent effects of maternal exposure to fenvalerate on neurodevelopment in offspring mice

BACKGROUND

The general population is widely exposed to fenvalerate. However, the effects of maternal exposure to fenvalerate on neurodevelopment in offspring and the underlying metabolic mechanism are largely unknown.

METHODS

Pregnant mice were exposed to fenvalerate for 11 consecutive days. The forced swimming test (FST) was performed in 35 day-old offspring to investigate the effects of fenvalerate on neurobehavioral responses. Blood serum free T4 and free T3 concentrations were measured using commercial ELISA. Blood and thyroid samples were used for metabolomic analyses with UPLC Q-Exactive. The expression levels of neurotransmitter metaolite receptors were determined in the frontal cortex of offspring using real-time PCR.

RESULTS

The immobility time, free T4 and free T3, and expression levels of Htr1a and Htr2a were statistically changed in offspring male mice. Metabolomic analysis revealed that the pentose phosphate pathway, starch and sucrose metabolism, glutamic acid metabolism were the key changed pathways in the blood, and thiamine metabolism was the key changed pathway in the thyroid.

CONCLUSION

Prenatal exposure to fenvalerate affected neurodevelopment in male offspring mice both via the changed abundances of metabolites involved in glycolysis related metabolism and medium-chain fatty acid metabolism, and the changes in 5-HT receptor expression.

Maternal Prenatal Psychosocial Stress and Prepregnancy BMI Associations with Fetal Iron Status

BACKGROUND

Iron accrued in utero is critical for fetal and infant neurocognitive development. Psychosocial stress and obesity can each suppress fetal iron accrual. Their combined effects and differences by fetal sex are not known. In an observational pregnancy cohort study in Mexico City, we investigated associations of maternal prenatal life stressors, psychological dysfunction, and prepregnancy BMI with fetal iron status at delivery.

OBJECTIVES

We hypothesized that greater maternal prenatal psychosocial stress and prepregnancy overweight and obesity are associated with lower cord blood ferritin and hemoglobin (Hb), with stronger associations in boys than girls.

METHODS

Psychosocial stress in multiple domains of life stress (negative life events, perceived stress, exposure to violence) and psychological dysfunction symptoms (depression, generalized anxiety, and pregnancy-specific anxiety) were assessed with validated questionnaires during pregnancy. Prepregnancy BMI was predicted with a validated equation and categorized as normal/overweight/obese. Cord blood ferritin and Hb associations with prenatal psychosocial stress and BMI were modeled in multivariable linear regressions adjusted for maternal age, socioeconomic status, child sex, and prenatal iron supplementation. Interactions with child sex and 3-way stress-overweight/obesity-sex interactions were tested with product terms and likelihood ratio tests.

RESULTS

In 493 dyads, median (IQR) cord blood ferritin and Hb concentrations were 185 µg/L (126-263 g/dL) and 16 g/dL (14.7-17.1 g/dL), respectively. Ferritin was lower in infants of mothers with higher prenatal perceived stress (-23%; 95% CI: -35%, -9%), violence exposure (-28%; 95% CI: -42%, -12%), anxiety symptoms (-16%; 95% CI: -27%, -4%), and obesity (-17%; 95% CI: -31%, 0.2%). Interaction models suggested sex differences and synergism between maternal stress and overweight/obesity. No associations were observed between stress or BMI and Hb.

CONCLUSIONS

Multiple prenatal psychosocial stressors and excess prepregnancy BMI were each inversely associated with fetal iron status at birth. Pregnancies and infants at elevated risk of impaired fetal iron accrual may be identifiable according to observed synergism between maternal stress and obesity and differential associations with fetal iron status by infant sex.

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.

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.

The Benefits and Risks of Iron Supplementation in Pregnancy and Childhood

Iron deficiency is the most common micronutrient deficiency in the world and disproportionately affects pregnant women and young children. Iron deficiency has negative effects on pregnancy outcomes in women and on immune function and neurodevelopment in children. Iron supplementation programs have been successful in reducing this health burden. However, iron supplementation of iron-sufficient individuals is likely not necessary and may carry health risks for iron-sufficient and potentially some iron-deficient populations. This review considers the physiology of iron as a nutrient and how this physiology informs decision-making about weighing the benefits and risks of iron supplementation in iron-deficient, iron-sufficient, and iron-overloaded pregnant women and children.

Phosphocreatine Levels in the Left Thalamus Decline during Wakefulness and Increase after a Nap

Scientists have hypothesized that the availability of phosphocreatine (PCr) and its ratio to inorganic phosphate (Pi) in cerebral tissue form a substrate of wakefulness. It follows then, according to this hypothesis, that the exhaustion of PCr and the decline in the ratio of PCr to Pi form a substrate of fatigue. We used 31P-magnetic resonance spectroscopy (31P-MRS) to investigate quantitative levels of PCr, the γ-signal of ATP, and Pi in 30 healthy humans (18 female) in the morning, in the afternoon, and while napping (n = 15) versus awake controls (n = 10). Levels of PCr (2.40 mM at 9 A.M.) decreased by 7.0 ± 0.8% (p = 7.1 × 10-6, t = -5.5) in the left thalamus between 9 A.M. and 5 P.M. Inversely, Pi (0.74 mM at 9 A.M.) increased by 17.1 ± 5% (p = 0.005, t = 3.1) and pH levels dropped by 0.14 ± 0.07 (p = 0.002; t = 3.6). Following a 20 min nap after 5 P.M., local PCr, Pi, and pH were restored to morning levels. We did not find respective significant changes in the contralateral thalamus or in other investigated brain regions. Left hemispheric PCr was signficantly lower than right hemispheric PCr only at 5 P.M. in the thalamus and at all conditions in the temporal region. Thus, cerebral daytime-related and sleep-related molecular changes are accessible in vivo Prominent changes were identified in the thalamus. This region is heavily relied on for a series of energy-consuming tasks, such as the relay of sensory information to the cortex. Furthermore, our data confirm that lateralization of brain function is regionally dynamic and includes PCr.SIGNIFICANCE STATEMENT The metabolites phosphocreatine (PCr) and inorganic phosphate (Pi) are assumed to inversely reflect the cellular energy load. This study detected a diurnal decrease of intracellular PCr and a nap-associated reincrease in the left thalamus. Pi behaved inversely. This outcome corroborates the role of the thalamus as a region of high energy consumption in agreement with its function as a gateway that relays and modulates information flow. Conversely to the dynamic lateralization of thalamic PCr, a constantly significant lateralization was observed in other regions. Increasing fatigue over the course of the day may also be a matter of cerebral energy supply. Comparatively fast restoration of that supply may be part of the biological basis for the recreational value of "power napping."

Current practice of iron prophylaxis in preterm and low birth weight neonates: A survey among Italian Neonatal Units

BACKGROUND

Preterm babies are at high risk of iron deficiency.

METHODS

We investigated current practices regarding iron prophylaxis in preterm and low birth weight newborns among Local Neonatal Units (LNUs, n = 74) and Neonatal Intensive Care Units (NICUs, n = 20) of three Italian Regions (Piemonte, Marche and Lazio).

RESULTS

Birth weight is considered an indicative parameter in only 64% of LNUs and 71% of NICUs, with a significant difference between LNUs in the three regions (86%, 20% and 62%, respectively; p < 0.001). Iron is recommended to infants with a birth weight between 2000 and 2500 g in only 25% of LNUs and 21% of NICUs, and to late-preterm (gestational age between 34 and 37 weeks) in a minority of Units (26% of LNUs, 7% of NICUs).

CONCLUSIONS

Our pilot survey documents a great variability and the urgent need to standardize practices according to literature recommendations.

Reticulocyte hemoglobin content as an early predictive biomarker of brain iron deficiency

BACKGROUND

Fetal and neonatal brain iron content is compromised at the time of anemia, suggesting that screening for iron deficiency by measuring hemoglobin is inadequate to protect the brain. Reticulocyte hemoglobin (Ret-He) reflects iron-deficient (ID) erythropoiesis prior to anemia.

METHODS

At postnatal day (P), 10 and 20 iron-sufficient rat pups were fostered to ID dams to produce a postnatal ID (PNID) group, which was compared to 20 iron-sufficient (IS) pups fostered by IS dams. Pups were assessed from P13 to P15 for hemoglobin, hematocrit, reticulocyte count, and Ret-He. Hippocampal iron status was assessed by transferrin receptor-1 (Tfrc-1) and divalent metal transporter-1 (Slc11a2) mRNA expression.

RESULTS

At P13, brain iron status was similar between groups; only Ret-He was lower in the PNID group. At P14, the PNID group had lower Ret-He, hematocrit, mean corpuscular volume (MCV), and reticulocyte percentage (RET%). Tfrc-1 expression was increased, consistent with brain iron deficiency. Both Ret-He and MCV correlated with brain iron status at P14 and P15.

CONCLUSIONS

Ret-He was the only red cell marker affected prior to the onset of brain ID. The clinical practice of using anemia as the preferred biomarker for diagnosis of iron deficiency may need reconsidering.

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.

Metabolic phenotyping of malnutrition during the first 1000 days of life

Nutritional restrictions during the first 1000 days of life can impair or delay the physical and cognitive development of the individual and have long-term consequences for their health. Metabolic phenotyping (metabolomics/metabonomics) simultaneously measures a diverse range of low molecular weight metabolites in a sample providing a comprehensive assessment of the individual's biochemical status. There are a growing number of studies applying such approaches to characterize the metabolic derangements induced by various forms of early-life malnutrition. This includes acute and chronic undernutrition and specific micronutrient deficiencies. Collectively, these studies highlight the diverse and dynamic metabolic disruptions resulting from various forms of nutritional deficiencies. Perturbations were observed in many pathways including those involved in energy, amino acid, and bile acid metabolism, the metabolic interactions between the gut microbiota and the host, and changes in metabolites associated with gut health. The information gleaned from such studies provides novel insights into the mechanisms linking malnutrition with developmental impairments and assists in the elucidation of candidate biomarkers to identify individuals at risk of developmental shortfalls. As the metabolic profile represents a snapshot of the biochemical status of an individual at a given time, there is great potential to use this information to tailor interventional strategies specifically to the metabolic needs of the individual.

Approaches for Reducing the Risk of Early-Life Iron Deficiency-Induced Brain Dysfunction in Children

Iron deficiency is the most common micronutrient deficiency in the world. Women of reproductive age and young children are particularly vulnerable. Iron deficiency in late prenatal and early postnatal periods can lead to long-term neurobehavioral deficits, despite iron treatment. This may occur because screening and treatment of iron deficiency in children is currently focused on detection of anemia and not neurodevelopment. Anemia is the end-stage state of iron deficiency. The brain becomes iron deficient before the onset of anemia due to prioritization of the available iron to the red blood cells (RBCs) over other organs. Brain iron deficiency, independent of anemia, is responsible for the adverse neurological effects. Early diagnosis and treatment of impending brain dysfunction in the pre-anemic stage is necessary to prevent neurological deficits. The currently available hematological indices are not sensitive biomarkers of brain iron deficiency and dysfunction. Studies in non-human primate models suggest that serum proteomic and metabolomic analyses may be superior for this purpose. Maternal iron supplementation, delayed clamping or milking of the umbilical cord, and early iron supplementation improve the iron status of at-risk infants. Whether these strategies prevent iron deficiency-induced brain dysfunction has yet to be determined. The potential for oxidant stress, altered gastrointestinal microbiome and other adverse effects associated with iron supplementation cautions against indiscriminate iron supplementation of children in malaria-endemic regions and iron-sufficient populations.

Iron assessment to protect the developing brain

Iron deficiency (ID) before the age of 3 y can lead to long-term neurological deficits despite prompt diagnosis of ID anemia (IDA) by screening of hemoglobin concentrations followed by iron treatment. Furthermore, pre- or nonanemic ID alters neurobehavioral function and is 3 times more common than IDA in toddlers. Given the global prevalence of ID and the enormous societal cost of developmental disabilities across the life span, better methods are needed to detect the risk of inadequate concentrations of iron for brain development (i.e., brain tissue ID) before dysfunction occurs and to monitor its amelioration after diagnosis and treatment. The current screening and treatment strategy for IDA fails to achieve this goal for 3 reasons. First, anemia is the final state in iron depletion. Thus, the developing brain is already iron deficient when IDA is diagnosed owing to the prioritization of available iron to red blood cells over all other tissues during negative iron balance in development. Second, brain ID, independently of IDA, is responsible for long-term neurological deficits. Thus, starting iron treatment after the onset of IDA is less effective than prevention. Multiple studies in humans and animal models show that post hoc treatment strategies do not reliably prevent ID-induced neurological deficits. Third, most currently used indexes of ID are population statistical cutoffs for either hematologic or iron status but are not bioindicators of brain ID and brain dysfunction in children. Furthermore, their relation to brain iron status is not known. To protect the developing brain, there is a need to generate serum measures that index brain dysfunction in the preanemic stage of ID, assess the ability of standard iron indicators to detect ID-induced brain dysfunction, and evaluate the efficacy of early iron treatment in preventing ID-induced brain dysfunction.