Barbara T. Felt

Altered dopaminergic profile in the putamen and substantia nigra in restless leg syndrome.

Restless leg syndrome (RLS) is a sensorimotor disorder. Clinical studies have implicated the dopaminergic system in RLS, while others have suggested that it is associated with insufficient levels of brain iron. To date, alterations in brain iron status have been demonstrated but, despite suggestions from the clinical literature, there have been no consistent findings documenting a dopaminergic abnormality in RLS brain tissue. In this study, the substantia nigra and putamen were obtained at autopsy from individuals with primary RLS and a neurologically normal control group. A quantitative profile of the dopaminergic system was obtained. Additional assays were performed on a catecholaminergic cell line and animal models of iron deficiency. RLS tissue, compared with controls, showed a significant decrease in D2R in the putamen that correlated with severity of the RLS. RLS also showed significant increases in tyrosine hydroxylase (TH) in the substantia nigra, compared with the controls, but not in the putamen. Both TH and phosphorylated (active) TH were significantly increased in both the substantia nigra and putamen. There were no significant differences in either the putamen or nigra for dopamine receptor 1, dopamine transporters or for VMAT. Significant increases in TH and phosphorylated TH were also seen in both the animal and cell models of iron insufficiency similar to that from the RLS autopsy data. For the first time, a clear indication of dopamine pathology in RLS is revealed in this autopsy study. The results suggest cellular regulation of dopamine production that closely matches the data from cellular and animal iron insufficiency models. The results are consistent with the hypothesis that a primary iron insufficiency produces a dopaminergic abnormality characterized as an overly activated dopaminergic system as part of the RLS pathology.

Effect of manipulation of iron storage, transport, or availability on myelin composition and brain iron content in three different animal models

Several observations suggest that iron is an essential factor in myelination and oligodendrocyte biology. However, the specific role of iron in these processes remains to be elucidated. This role could be as an essential cofactor in metabolic processes or as a transcriptional or translational regulator. In this study, we used animals models each with a unique defect in iron availability, storage, or transfer to test the hypothesis that disruptions in these mechanisms affect myelinogenesis and myelin composition. Disruption of iron availability either by limiting dietary iron or by altering iron storage capacity resulted in a decrease in myelin proteins and lipids but not the iron content of myelin. Among the integral myelin proteins, proteolipid protein was most consistently affected, suggesting that limiting iron to oligodendrocytes results not only in hypomyelination but also in a decrease in myelin compaction. Mice deficient in transferrin must receive transferrin injections beginning at birth to remain viable, and these mice had increases in all of the myelin components and in the iron content of the myelin. This finding indicates that the loss of endogenous iron mobility in oligodendrocytes could be overcome by application of exogenous transferrin. Overall, the results of this study demonstrate how myelin composition can be affected by loss of iron homeostasis and reveal specific chronic changes in myelin composition that may affect behavior and attempts to rescue myelin deficits.

Persistent neurochemical and behavioral abnormalities in adulthood despite early iron supplementation for perinatal iron deficiency anemia in rats.

BACKGROUND Iron deficiency anemia (IDA) has been associated with altered cognitive, motor, and social-emotional outcomes in human infants. We recently reported that rats with chronic perinatal IDA, had altered regional brain iron, monoamines, and sensorimotor skill emergence during early development. OBJECTIVE To examine the long-term consequences of chronic perinatal IDA on behavior, brain iron and monoamine systems after dietary iron treatment in rats. METHODS Sixty dams were randomly assigned to iron-sufficient (CN) or low-iron (EID) diets during gestation and lactation. Thereafter, all offspring were fed the iron-sufficient diet, assessed for hematology and behavior after weaning and into adulthood and for brain measures as adults (regional brain iron, monoamines, dopamine and serotonin transporters, and dopamine receptor). Behavioral assessments included sensorimotor function, general activity, response to novelty, spatial alternation, and spatial water maze performance. RESULTS Hematology and growth were similar for EID and CN rats by postnatal day 35. In adulthood, EID thalamic iron content was lower. Monoamines, dopamine transporter, and dopamine receptor concentrations did not differ from CN. EID serotonin transporter concentration was reduced in striatum and related regions. EID rats had persisting sensorimotor deficits (delayed vibrissae-evoked forelimb placing, longer sticker removal time, and more imperfect grooming chains), were more hesitant in novel settings, and had poorer spatial water maze performance than CN. General activity and spatial alternation were similar for EID and CN. CONCLUSION Rats that had chronic perinatal IDA showed behavioral impairments that suggest persistent striatal dopamine and hippocampal dysfunction despite normalization of hematology, growth and most brain measures.

Moderate iron deficiency in infancy : Biology and behavior in young rats

Iron deficiency anemia in early childhood is associated with developmental delays and perhaps, irreversible alterations in neurological functioning. The goals were to determine if dietary induced gestational and lactational iron deficiency alters brain monoamine metabolism and behaviors dependent on that neurotransmitter system. Young pregnant rats were provided iron deficient or control diets from early in gestation through to weaning of pups and brain iron concentration, regional monoamine variables and achievement of specific developmental milestones were determined throughout lactation. Despite anemia during lactation, most brain iron concentrations did not fall significantly until P25, and well after significant changes in monoamine levels, transporter levels, and D2R density changed in terminal fields. The changes in D2R density were far smaller than previously observed models that utilized severe dietary restriction during lactation or after weaning. Iron deficient pups had normal birth weight, but were delayed in the attainment of a number of milestones (bar holding, vibrissae-evoked forelimb placing). This approach of iron deficiency in utero and during lactation sufficient to cause moderate anemia but not stunt growth demonstrates that monaminergic metabolism changes occur prior to profound declines in brain iron concentration and is associated with developmental delays. Similar developmental delays in iron deficient human infants suggest to us that alterations in iron status during this developmental period likely affects developing brain monaminergic systems in these infants.

Hypothalamic Pituitary Adrenal Axis Functioning in Reactive and Proactive Aggression in Children.

The purpose of this study was to examine the association between hypothalamic-pituitary-adrenal axis (HPA-axis) reactivity and proactive and reactive aggression in pre-pubertal children. After a 30-min controlled base line period, 73 7-year-old children (40 males and 33 females) were randomly assigned to one of two experimental tasks designed to elicit fear (N = 33) or frustration (N = 32), or a validity check condition (N = 8). This was followed by a 60-min controlled regulation phase. A total of 17 saliva samples for cortisol analysis were collected including 12 post-stress samples at 5-min intervals. Reactive and proactive aggression levels were assessed via the teacher-completed Aggression Behavior Teacher Checklist (Dodge and Coie, J Pers Soc Psychol, 53(6), 1146–1158, 1987). Reactive aggression significantly predicted total and peak post-stress cortisol regardless of stress modality. Proactive aggression was not a predictor of any cortisol index. Examination of pure reactive, proactive, combined, or non-aggressive children indicated that reactive aggressive children had higher cortisol reactivity than proactive and non-aggressive children. Our data suggest that while an overactive HPA-axis response to stress is associated with reactive aggression, stress induced HPA-axis variability does not seem to be related to proactive aggression.

Thy1 expression in the brain is affected by iron and is decreased in Restless Legs Syndrome.

Thy-1 is a cell adhesion molecule that plays a regulatory role in the vesicular release of neurotransmitters. The objective of this study is to examine the relationship between iron status and Thy1 expression in neuronal systems of varying complexity. Pheochromocytoma cell (PC12) cells were used to explore whether there was a direct relation between cellular iron status and Thy1 expression. Iron chelation significantly decreased expression of Thy1 in PC12 cells in a dose and time dependent manner. Transferrin receptor expression was increased with iron chelation demonstrating that a global decrease in protein synthesis could not account for the Thy1 changes. We also examined brain homogenates from adult rats that were nursed by dams on an iron deficient (ID) diet and found a significant decrease in Thy1 compared to control rats. Finally, the substantia nigra from individuals with Restless Legs Syndrome reportedly has lower than normal amounts of iron. Therefore, we examined this brain region from individuals with the clinical diagnosis of primary Restless Legs syndrome (RLS) and found the concentration of Thy1 was less than half that of controls. The results of these studies support the novel concept that there is a relationship between Thy1 and iron and point to a novel mechanism by which iron deficiency can affect brain function. They also indicate a possible mechanism by which iron deficiency compromises dopaminergic transmission in RLS, providing a potentially important link between decreased brain iron and the responsiveness to levodopa and iron supplementation treatment in RLS.

Maternal Serum Ferritin Concentration Is Positively Associated with Newborn Iron Stores in Women with Low Ferritin Status in Late Pregnancy

Iron deficiency (ID) is common in pregnant women and infants, particularly in developing countries. The relation between maternal and neonatal iron status remains unclear. This study considered the issue in a large sample of mother-newborn pairs in rural southeastern China. Hemoglobin (Hb) and serum ferritin (SF) were measured in 3702 pregnant women at ≥37 wk gestation and in cord blood of their infants born at term (37-42 wk gestation). Maternal anemia (Hb <110 g/L) was present in 27.5% and associated with maternal SF <20 μg/L in 86.9%. Only 5.6% of neonates were anemic (Hb <130 g/L) and 9.5% had cord-blood SF <75 μg/L. There were low-order correlations between maternal and newborn iron measures (r = 0.07-0.10 for both Hb and SF; P ≤ 0.0001 due to the large number). We excluded 430 neonates with suggestion of inflammation [cord SF >370 μg/L, n = 208 and/or C-reactive protein (CRP) >5 mg/L, n = 233]. Piecewise linear regression analyses identified a threshold for maternal SF at which cord-blood SF was affected. For maternal SF below the threshold of 13.6 μg/L (β = 2.4; P = 0.001), cord SF was 0.17 SD lower than in neonates whose mothers had SF above the threshold (167 ± 75 vs. 179 ± 80 μg/L). The study confirmed that ID anemia remains common during pregnancy in rural southeastern China. Despite widespread maternal ID, however, iron nutrition seemed to meet fetal needs except when mothers were very iron deficient. The impact of somewhat lower cord SF on iron status later in infancy warrants further study.

Aggressive Behavior, Bullying, Snoring, and Sleepiness in Schoolchildren

BACKGROUND To assess whether urban schoolchildren with aggressive behavior are more likely than peers to have symptoms suggestive of sleep-disordered breathing. METHODS Cross-sectional survey of sleep and behavior in schoolchildren. Validated screening assessments for conduct problems (Connors rating scale), bullying behavior, and sleep-disordered breathing (pediatric sleep questionnaire) were completed by parents. Teachers completed Connors teacher rating scale. RESULTS Among 341 subjects (51% female), 110 (32%) were rated by a parent or teacher as having a conduct problem (T-score ⩾65) and 78 (23%) had symptoms suggestive of sleep-disordered breathing. Children with conduct problems, bullying, or discipline referrals, in comparison to non-aggressive peers, more often had symptoms suggestive of sleep-disordered breathing (each p<0.05). Children with vs. without conduct problems were more likely to snore habitually (p<0.5). However, a sleepiness subscale alone, and not a snoring subscale, predicted conduct problems after accounting for age, gender, a measure of socioeconomic status, and stimulant use. CONCLUSIONS Urban schoolchildren with aggressive behaviors may have symptoms of sleep-disordered breathing with disproportionate frequency. Sleepiness may impair emotional regulation necessary to control aggression.

Behavior and Monoamine Deficits in Prenatal and Perinatal Iron Deficiency Are Not Corrected by Early Postnatal Moderate-Iron or High-Iron Diets in Rats

Developmental iron deficiency anemia (IDA) causes brain and behavioral deficits in rodent models, which cannot be reversed when treated at periods equivalent to later infancy in humans. This study sought to determine whether earlier iron treatment can normalize deficits of IDA in rats and what iron dose is optimal. The offspring of dams with IDA during gestation were cross-fostered at postnatal d (P) 8 to dams receiving diets with 1 of 3 iron concentrations until weaning (P21): 0.003-0.01 g/kg [totally iron deficient (TID)]; 0.04 g/kg [formerly iron deficient (FID-40)]; or 0.4 g/kg (FID-400). Always iron-sufficient control dams (CN-40) received a 0.04-g/kg iron diet. At P21, TID pups received a 0.01 g iron/kg diet; all others received a 0.04 g iron/kg diet. Hematocrit and brain iron and monoamine concentrations were assessed at P21 and P100. Pup growth, development, activity, object recognition, hesitancy, and watermaze performance were evaluated. Regional brain iron was restored by iron treatment. Regional monoamine and metabolite concentrations were elevated in FID-40 rats and reduced in FID-400 and TID rats compared with CN-40 rats. FID-40 offspring had motor delays similar to TID during lactation and FID-400 rats had elevated thigmotaxis similar to TID rats at P25 and P100 in the spatial watermaze. In conclusion, iron treatment at P8 in rats did not normalize all monoamine or behavioral measures after early IDA. Moderate iron treatment improved adult behavior, but higher iron treatment caused brain and behavioral patterns similar to TID in the short and long term.

Early Appearance of Functional Deficits after Neonatal Excitotoxic and Hypoxic-Ischemic Injury: Fragile Recovery after Development and Role of the NMDA Receptor

We sought to determine whether neonatal rats that sustain unilateral cerebral hypoxic-ischemic or excitotoxic insults (1) manifest contralateral sensorimotor deficits during development or in adulthood and (2) recover from those deficits. Seven-day-old (P7) rats received a right intrastriatal injection of the glutamate analog N-methyl-D-aspartate (NMDA). Unilateral hypoxia-ischemia (HI) was induced by right carotid ligation followed by 1.5 h in 8% O2. Both procedures produce neuronal loss in the striatum and sensorimotor cortex. Nonlesioned controls were included. We scored percent forepaw placement on the edge of a horizontal surface, with lateral vibrissa stimulation, from P9 to P19, and at P33 and P50. Then, on P50, rats were treated with the NMDA antagonist MK-801 to determine whether deficits could be reinstated. NMDA- and HI-lesioned rats exhibited a deficit in contralateral vibrissa-stimulated forepaw placing that emerged during the second week of life. Yet, by P33 and P50, the lesioned groups and controls were indistinguishable. MK-801 injection on P50 resulted in transient reinstatement of the placing deficit. After unilateral neonatal excitotoxic or HI brain injury, contralateral sensorimotor deficits are detected, but in many animals, these deficits have resolved by adulthood. Thus, timing of sensorimotor tests may influence their sensitivity for detection of focal neuropathology originating in the neonatal period.