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

Anemia, Iron Supplementation, and the Brain

The developing brain is particularly vulnerable to extrinsic environmental events such as anemia and iron deficiency during periods of rapid development. Studies of infants with postnatal iron deficiency and iron deficiency anemia clearly demonstrated negative effects on short-term and long-term brain development and function. Randomized interventional trials studied erythropoiesis-stimulating agents and hemoglobin-based red blood cell transfusion thresholds to determine how they affect preterm infant neurodevelopment. Studies of red blood cell transfusion components are limited in preterm neonates. A biomarker strategy measuring brain iron status and health in the preanemic period is desirable to evaluate treatment options and brain response.

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.

Associations of Mitochondrial Function, Stress, and Neurodevelopmental Outcomes in Early Life: A Systematic Review

Early life stress is commonly experienced by infants, especially preterm infants, and may impact their neurodevelopmental outcomes in their early and later lives. Mitochondrial function/dysfunction may play an important role underlying the linkage of prenatal and postnatal stress and neurodevelopmental outcomes in infants. This review aimed to provide insights on the relationship between early life stress and neurodevelopment and the mechanisms of mitochondrial function/dysfunction that contribute to the neuropathology of stress. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement was used to develop this systematic review. PubMed, Scopus, PsycINFO, and Biosis databases were searched for primary research articles published between 2010 and 2021 that examined the relationships among mitochondrial function/dysfunction, infant stress, and neurodevelopment. Thirty studies were identified. There is evidence to support that mitochondrial function/dysfunction mediates the relationship between prenatal and postnatal stress and neurodevelopmental outcomes in infants. Maternal transgenerational transmission of mitochondrial bioenergetic patterns influenced prenatal stress induced neurodevelopmental outcomes and behavioral changes in infants. Multiple functionally relevant mitochondrial proteins, genes, and polymorphisms were associated with stress exposure. This is the first review of the role that mitochondrial function/dysfunction plays in the association between stress and neurodevelopmental outcomes in full-term and preterm infants. Although multiple limitations were found based on the lack of data on the influence of biological sex, and due to invasive sampling, and lack of longitudinal data, many genes and proteins associated with mitochondrial function/dysfunction were found to influence neurodevelopmental outcomes in the early life of infants.

Effect of acute iron infusion on insulin secretion: A randomized, double-blind, placebo-controlled trial

Background

Chronic exposure to high iron levels increases diabetes risk partly by inducing oxidative stress, but the consequences of acute iron administration on beta cells are unknown. We tested whether the acute administration of iron for the correction of iron deficiency influenced insulin secretion and the production of reactive oxygen species.

Methods

Single-center, double-blinded, randomized controlled trial conducted between June 2017 and March 2020. 32 women aged 18 to 47 years, displaying symptomatic iron deficiency without anaemia, were recruited from a community setting and randomly allocated (1:1) to a single infusion of 1000 mg intravenous ferric carboxymaltose (iron) or saline (placebo). The primary outcome was the between group mean difference from baseline to day 28 in first and second phase insulin secretion, assessed by a two-step hyperglycaemic clamp. All analyses were performed by intention to treat. This trial was registered in ClinicalTrials.gov NCT03191201.

Findings

Iron infusion did not affect first and second phase insulin release. For first phase, the between group mean difference from baseline to day 28 was 0 μU × 10 min/mL [95% CI, -22 to 22, P = 0.99]. For second phase, it was -5 μUx10min/mL [95% CI, -161 to 151; P = 0.95] at the first plateau of the clamp and -249 μUx10min/mL [95% CI, -635 to 137; P = 0.20] at the second plateau. Iron infusion increased serum ascorbyl/ascorbate ratio, a marker of plasma oxidative stress, at day 14, with restoration of normal ratio at day 28 relative to placebo. Finally, high-sensitive C-reactive protein levels remained similar among groups.

Interpretation

In iron deficient women without anaemia, intravenous administration of 1000 mg of iron in a single sitting did not impair glucose-induced insulin secretion despite a transient increase in the levels of circulating reactive oxygen species.

Funding

The Swiss National Science Foundation, University of Lausanne and Leenaards, Raymond-Berger and Placide Nicod Foundations.

Transfusion prevention using erythropoietin, parenteral sucrose iron, and fewer phlebotomies in infants born at ≤30 weeks gestation at a high altitude center: a 10-year experience

INTRODUCTION

Red blood cell transfusions in infants born at ≤30 weeks gestation are frequent. Erythropoietin therapy reduces transfusions. An increase in hematocrit is an adaptive response at high altitudes but a guaranteed source of iron is necessary for adequate erythropoiesis.

METHODS

A retrospective cohort study was done to compare red blood cell transfusion practices of the 2019 EpicLatino (EPIC) Latin America network database with a single unit at 2650 m above sea level (LOCAL). The data from LOCAL for three time periods were compared over 10 years based on changes in erythropoietin dose and fewer phlebotomies. The number of cases that received transfusions and the total number of transfusions required were compared. Adjustments were made for known risk factors using a multivariate regression analysis.

RESULTS

Two hundred and twenty-one cases in LOCAL and 382 cases from EPIC were included. Overall basic demographic characteristics were similar. In EPIC a significantly higher rate of infection (28% vs. 15%) and outborn (10% vs. 1%) was found, but less necrotizing enterocolitis (9% vs. 15%) and use of prenatal steroids (62% vs. 93%) than LOCAL (p < 0.05). EPIC patients received more transfusions (2.6 ± 3 vs. 0.6 ± 1 times) than LOCAL (p < 0.001) and received them significantly more frequently (61% vs. 25%). Within the LOCAL time periods, no statistically significant differences were found other than the need for transfusions (1st 32%, 2nd 28%, 3rd 9%, p = 0.005) and the average number of transfusions (1st 0.8 ± 1.6, 2nd 0.7 ± 1.3, 3rd 0.1 ± 0.3, p = 0.004). These differences remained significant after multivariate regression analysis and adjusting for risk variables.

CONCLUSION

The combination of erythropoietin, parenteral sucrose iron, fewer phlebotomies during the first 72 h, and delayed umbilical cord clamping seem to reduce red blood cell transfusion needs. This can be extremely important in high altitude units where higher hematocrit is desirable but may also be valuable at sea level.

Sex differences in adult social, cognitive, and affective behavioral deficits following neonatal phlebotomy-induced anemia in mice

INTRODUCTION

Anemia is common in prematurely born infants due to blood loss resulting from frequent phlebotomies and may contribute to their neurobehavioral deficits. Preclinical models of phlebotomy-induced anemia (PIA) have revealed metabolic and genomic changes in multiple brain structures of young mice, yet the impact of neonatal PIA on early-life and adult behavior has not been assessed.

METHODS

The present study employed a range of behavioral measures in phlebotomized anemic neonatal mice to investigate short- and long-term neurodevelopmental effects. PIA from postnatal (P) days 3 to 14 caused sex-specific changes in social behavior, novelty preference, and anxiety at P17 that persisted into adulthood.

RESULTS

Our preclinical model suggests that PIA may contribute to acute and long-term behavioral and affective deficits and warrants further substantiation of the observed behavioral phenomena in larger samples.

CONCLUSIONS

We conclude that this model is a useful tool for beginning to better understand the lasting effect that early-life PIA might have on the developing brain. The differential impact of PIA on male and female subjects warrants further exploration for the development of appropriately targeted interventions.

Iron Nutrition, Erythrocytes, and Erythropoietin in the NICU: Erythropoietic and Neuroprotective Effects

Prematurity, maternal diabetes, maternal smoking, being medically underserved, and small size for gestational age are common characteristics of neonates in the NICU and can predispose them to develop congenital iron deficiency. Iron is critical for organ development. In the fetus and newborn, iron is prioritized for red blood cell production, sometimes at the expense of other tissues, including the brain. It is critical to optimize iron levels in newborns to support erythropoiesis, growth, and brain development. Available studies support improved neurodevelopmental outcomes with either iron supplementation or delayed umbilical cord clamping at birth. Erythropoietic doses of erythropoietin/erythrocyte-stimulating agents may also improve neurocognitive outcomes. However, the literature on the effect of liberal red blood cell transfusions on long-term neurodevelopment is mixed. Understanding age-specific normal values and monitoring of iron indices can help individualize and optimize the iron status of patients in the NICU.

Transfusions and neurodevelopmental outcomes in extremely low gestation neonates enrolled in the PENUT Trial: a randomized clinical trial

BACKGROUND

Outcomes of extremely low gestational age neonates (ELGANs) may be adversely impacted by packed red blood cell (pRBC) transfusions. We investigated the impact of transfusions on neurodevelopmental outcome in the Preterm Erythropoietin (Epo) Neuroprotection (PENUT) Trial population.

METHODS

This is a post hoc analysis of 936 infants 24-0/6 to 27-6/7 weeks' gestation enrolled in the PENUT Trial. Epo 1000 U/kg or placebo was given every 48 h × 6 doses, followed by 400 U/kg or sham injections 3 times a week through 32 weeks postmenstrual age. Six hundred and twenty-eight (315 placebo, 313 Epo) survived and were assessed at 2 years of age. We evaluated associations between BSID-III scores and the number and volume of pRBC transfusions.

RESULTS

Each transfusion was associated with a decrease in mean cognitive score of 0.96 (95% CI of [-1.34, -0.57]), a decrease in mean motor score of 1.51 (-1.91, -1.12), and a decrease in mean language score of 1.10 (-1.54, -0.66). Significant negative associations between BSID-III score and transfusion volume and donor exposure were observed in the placebo group but not in the Epo group.

CONCLUSIONS

Transfusions in ELGANs were associated with worse outcomes. We speculate that strategies to minimize the need for transfusions may improve outcomes.

IMPACT

Transfusion number, volume, and donor exposure in the neonatal period are associated with worse neurodevelopmental (ND) outcome at 2 years of age, as assessed by the Bayley Infant Scales of Development, Third Edition (BSID-III). The impact of neonatal packed red blood cell transfusions on the neurodevelopmental outcome of preterm infants is unknown. We speculate that strategies to minimize the need for transfusions may improve neurodevelopmental outcomes.

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.

Erythropoietin induces synaptogenesis and neurite repair after hypoxia ischemia-mediated brain injury in neonatal rats

The memory dysfunction is one of the disastrous outcomes for perinatal hypoxia ischemia. Erythropoietin (EPO) has been demonstrated as a neuroprotective agent with multiple effects in a series of neurological diseases. We hypothesized that disruption of neural network including synapses and neurites would contribute to memory dysfunction induced by hypoxia ischemia. The aim of the present study was to elucidate the involvement of EPO on synaptogenesis and neurite repair following perinatal hypoxia ischemia. Using a neonatal hypoxia ischemia rat model, we found that EPO rescued hypoxia ischemia-induced decrease of synaptic proteins including Synapsin1 and PSD95 rather than GluR1 in the cortex and hippocampus. In addition, EPO reduced the expression of APP (an axonal injury marker), induced the expression of microtubule-associated protein MAP-2 (a dendritic marker), and restored axonal density after hypoxia ischemia. These changes contributed to improving electrophysiological properties of synapses and spatial memory performance. In summary, our data revealed an important role of EPO in synaptogenesis and neurite repair, providing a new insight into cellular mechanisms underlying cognitive and memory dysfunction associated with perinatal hypoxia ischemia.

Iron dysregulation in vascular dementia: Focused on the AMPK/autophagy pathway

Recent researches suggested that iron dysregulation play an important role in the pathogenesis of vascular dementia (VD). Iron deposition had been found in hippocampus in vascular dementia model in recent research. Nevertheless, the underlying mechanisms of iron deposition and its neurotoxicity in vascular dementia was still unclear. Thus, our research was aimed at whether the neurotoxicity of iron was associated with autophagy regulation. We established a chronic cerebral hypoperfusion model in the rat brain in order to mimic the vascular dementia using permanent bilateral common carotid artery occlusion (2VO). The preparation of iron overloaded rats model by intraperitoneal injection of iron dextran. Following, we tested the learning and memory function of each group using Morris Water Maze. Consequently, we analyzed the iron content and iron transport related molecules (TFR1, DMT1) in hippocampus. Furthermore, we examined the effect of iron deposition on autophagy-related molecules including AMPK, Beclin1 and LC3 and the number of autophagosomes in hippocampus. Last, we tested the apoptosis of neurons in hippocampus. We found that iron deposition in hippocampus in model groups which accompanied the decline of learning and memory function. And the expression of TFR1 and DMT1 were up-regulated in model groups. Moreover, iron deposition up-regulated the expression of AMPK, Beclin1 and LC3 and increase the number of autophagosomes in hippocampus. And the expression of Bax was up-regulated and Bcl-2 was down-regulated in iron deposition groups. To sum up, our data suggested that iron deposition increased AMPK/autophagy pathway associated molecules in the hippocampus and promoted neuronal apoptosis, which might be a new pathogenesis in vascular dementia.

Anemia induces gut inflammation and injury in an animal model of preterm infants

BACKGROUND

While very low birth weight (VLBW) infants often require multiple red blood cell transfusions, efforts to minimize transfusion-associated risks have resulted in more restrictive neonatal transfusion practices. However, whether restrictive transfusion strategies limit transfusions without increasing morbidity and mortality in this population remains unclear. Recent epidemiologic studies suggest that severe anemia may be an important risk factor for the development of necrotizing enterocolitis (NEC). However, the mechanism whereby anemia may lead to NEC remains unknown.

STUDY DESIGN AND METHODS

The potential impact of anemia on neonatal inflammation and intestinal barrier disruption, two well-characterized predisposing features of NEC, was defined by correlation of hemoglobin values to cytokine levels in premature infants and by direct evaluation of intestinal hypoxia, inflammation and gut barrier disruption using a pre-clinical neonatal murine model of phlebotomy-induced anemia (PIA).

RESULTS

Increasing severity of anemia in the preterm infant correlated with the level of IFN-gamma, a key pro-inflammatory cytokine that may predispose an infant to NEC. Gradual induction of PIA in a pre-clinical model resulted in significant hypoxia throughout the intestinal mucosa, including areas where intestinal macrophages reside. PIA-induced hypoxia significantly increased macrophage pro-inflammatory cytokine levels, while reducing tight junction protein ZO-1 expression and increasing intestinal barrier permeability. Macrophage depletion reversed the impact of anemia on intestinal ZO-1 expression and barrier function.

CONCLUSIONS

Taken together, these results suggest that anemia can increase intestinal inflammation and barrier disruption likely through altered macrophage function, leading to the type of predisposing intestinal injury that may increase the risk for NEC.