New Diversity Arrays Technology (DArT) markers for tetraploid oat (Avena magna Murphy et Terrell) provide the first complete oat linkage map and markers linked to domestication genes from hexaploid A. sativa L

Nutritional benefits of cultivated oat (Avena sativa L., 2n = 6x = 42, AACCDD) are well recognized; however, seed protein levels are modest and resources for genetic improvement are scarce. The wild tetraploid, A. magna Murphy et Terrell (syn A. maroccana Gdgr., 2n = 4x = 28, CCDD), which contains approximately 31% seed protein, was hybridized with cultivated oat to produce a domesticated A. magna. Wild and cultivated accessions were crossed to generate a recombinant inbred line (RIL) population. Although these materials could be used to develop domesticated, high-protein oat, mapping and quantitative trait loci introgression is hindered by a near absence of genetic markers. Objectives of this study were to develop high-throughput, A. magna-specific markers; generate a genetic linkage map based on the A. magna RIL population; and map genes controlling oat domestication. A Diversity Arrays Technology (DArT) array derived from 10 A. magna genotypes was used to generate 2,688 genome-specific probes. These, with 12,672 additional oat clones, produced 2,349 polymorphic markers, including 498 (21.2%) from A. magna arrays and 1,851 (78.8%) from other Avena libraries. Linkage analysis included 974 DArT markers, 26 microsatellites, 13 SNPs, and 4 phenotypic markers, and resulted in a 14-linkage-group map. Marker-to-marker correlation coefficient analysis allowed classification of shared markers as unique or redundant, and putative linkage-group-to-genome anchoring. Results of this study provide for the first time a collection of high-throughput tetraploid oat markers and a comprehensive map of the genome, providing insights to the genome ancestry of oat and affording a resource for study of oat domestication, gene transfer, and comparative genomics.

Acute and chronic effects of developmental iron deficiency on mRNA expression patterns in the brain

Because of the multiple biochemical pathways that require iron, iron deficiency can impact brain metabolism in many ways. The goal of this study was to identify a molecular footprint associated with ongoing versus long term consequences of iron deficiency using microarray analysis. Rats were born to iron-deficient mothers, and were analyzed at two different ages: 21 days, while weaning and iron-deficient; and six months, after a five month iron-sufficient recovery period. Overall, the data indicate that ongoing iron deficiency impacts multiple pathways, whereas the long term consequences of iron deficiency on gene expression are more limited. These data suggest that the gene array profiles obtained at postnatal day 21 reflect a brain under development in a metabolically compromised setting that given appropriate intervention is mostly correctable. There are, however, long term consequences to the developmental iron deficiency that could underlie the neurological deficits reported for iron deficiency.

Distribution of divalent metal transporter 1 and metal transport protein 1 in the normal and Belgrade rat

Iron accumulation in the brain occurs in a number of neurodegenerative diseases. Two new iron transport proteins have been identified that may help elucidate the mechanism of abnormal iron accumulation. The Divalent Metal Transporter 1 (DMT1), is responsible for iron uptake from the gut and transport from endosomes. The Metal Transport Protein 1 (MTP1) promotes iron export. In this study we determined the cellular and regional expression of these two transporters in the brains of normal adult and Belgrade rats. Belgrade rats have a defect in DMT1 that is associated with lower levels of iron in the brain. In the normal rat, DMT1 expression is highest in neurons in the striatum, cerebellum, thalamus, ependymal cells lining the third ventricle, and vascular cells throughout the brain. The staining in the ependymal cells and endothelial cells suggests that DMT1 has an important role in iron transport into the brain. In Belgrade rats, there is generalized decrease in immunodetectable DMT1 compared to normal rats except in the ependymal cells. This decrease in immunoreactivity, however, was absent on immunoblots. The immunoblot analysis indicates that this protein did not upregulate to compensate for the chronic defect in iron transport. MTP1 staining is found in most brain regions. MTP1 expression in the brain is robust in pyramidal neurons of the cerebral cortex but is not detected in the vascular endothelial cells and ependymal cells. MTP1 staining in Belgrade rats was decreased compared to normal, but similar to DMT1 this decrease was not corroborated by immunoblotting. These results indicate that DMT1 and MTP1 are involved in brain iron transport and this involvement is regionally and cellularly specific.

The intracellular location of iron regulatory proteins is altered as a function of iron status in cell cultures and rat brain

Iron regulatory proteins (IRPs) are proteins involved in the regulation of intracellular iron homeostasis that bind to specific mRNA structures termed iron responsive elements (IREs). Because the target mRNAs for the IRPs are both cytosolic and membrane associated, we hypothesize that movement of IRPs between the cytosolic and the membrane associated subcellular fractions occurs in response to intracellular iron changes. We tested this hypothesis in a cell culture model, using mouse fibroblast cells (NIH 3T3) and macrophage cells (J774), and in a rat model of early iron deficiency and excess. This presented the first opportunity to examine IRP binding activity in rat brain during states of dietary iron deficiency and excess. Binding activity for IRPs was demonstrated in both membrane and cytosolic fractions in the cell lines and the rat brain homogenates. Although IRP binding activity is predominantly located in the cytosol (90%), there was increased IRP/IRE binding activity in both cytosolic and membrane fractions when the cells were treated with deferoxamine, and decreased binding activity after treatment with iron. In the rat study, brain cortex, hippocampus and striatum homogenates had more IRP binding activity in iron-deficient rats and less in iron-supplemented rats in a region- and time-specific manner. The intracellular distribution of IRPs also changed between the cytosolic and membrane fractions of the brain homogenates in conjunction with changes in iron. These in vivo studies are consistent with the cell culture analyses showing intracellular redistribution of IRPs as a function of iron status. The results of these experiments extend our understanding of cytoplasmic mRNA binding protein activity and raise questions regarding the mechanism by which mRNA binding proteins can locate their target mRNAs within cells. The elucidation of this mechanism will have a significant impact on our understanding of eukaryotic gene regulation.

Resistance training affects iron status in older men and women

OBJECTIVE

To examine the effects of resistance training on hematological and selected indices of iron status in 17 women aged 54-71 years and 18 men aged 56-69 years.

DESIGN

Tests and evaluations were done before and after all subjects participated in a resistance-training program twice weekly for 12 weeks.

RESULTS

The resistance training was effective as evidenced by increases in skeletal muscle strength of 20 +/- 9% and 23 +/- 13% for the men and women, respectively. Hematological parameters and serum iron concentrations were within normal clinical ranges and were unchanged by resistance training for both the men and the women. Total iron binding capacity (TIBC) and transferrin saturation were also unaffected by resistance training in the women but were significantly affected in the men. The men showed a decreased TIBC (p < .0001) and an increased transferrin saturation (p = .050). Serum ferritin concentrations decreased significantly in the women (p = .041) but were unchanged in the men. Transferrin receptor concentrations were unaffected by resistance training in the women but increased significantly in the men (p = .030).

CONCLUSIONS

With resistance training, iron status of older men and women changes in a sex specific way.

Iron deficiency decreases dopamine D1 and D2 receptors in rat brain

Iron deficiency (ID) in early life is known to alter neurological development and functioning, but data regarding specific effects on dopamine biology are lacking. The objective of this study was to determine the extent of functional alterations in dopamine receptors in two dopaminergic tracts in young, growing, iron-deficient rats. Forty male and 40 female weanling Sprague-Dawley rats were fed either an iron-deficient (ID) diet or control (CN) diet for 6 weeks. ID decreased densities of D(1) and D(2) receptors in the caudate-putamen and decreased D(2) receptor densities in the nucleus accumbens. There were no apparent effects of ID on the affinities for the ligands in either receptor in several brain regions. In situ hybridization studies for both dopamine receptors revealed no significant effect of ID on mRNA expression for either receptor. Iron-deficient rats had a significantly higher ED(50) for raclopride-induced hypolocomotion in male and female rats compared to control rats of each sex. The loss of iron in the striatum due to dietary ID was significantly correlated with the decrease in D(2) receptor density; however, this relationship was not apparent in other brain regions. These experiments thus demonstrate abnormal dopamine receptor density and functioning in several brain regions that are related to brain regional iron loss. Importantly, the impact of ID on dopamine was more pronounced in males than females, demonstrating sex-related different sensitivities to nutrient deprivation.

Iron biology in immune function, muscle metabolism and neuronal functioning

The estimated prevalence of iron deficiency in the world suggests that there should be widespread negative consequences of this nutrient deficiency in both developed and developing countries. In considering the reality of these estimates, the Belmont Conference seeks to reconsider the accepted relationships of iron status to physiological, biochemical and neurological outcomes. This review focuses on the biological processes that we believe are the basis for alterations in the immune system, neural systems, and energy metabolism and exercise. The strength of evidence is considered in each of the domains and the large gaps in knowledge of basic biology or iron-dependent processes are identified. Iron is both an essential nutrient and a potential toxicant to cells; it requires a highly sophisticated and complex set of regulatory approaches to meet the demands of cells as well as prevent excess accumulation. It is hoped that this review of the more basic aspects of the biology of iron will set the stage for subsequent in-depth reviews of the relationship of iron to morbidity, mortality and functioning of iron-deficient individuals and populations.

Insight into the pathophysiology of restless legs syndrome

Restless Legs Syndrome (RLS) is a disorder of sensation with a prevalence of around 2-5% of the population. Relevant to understanding the possible pathophysiological mechanism is the fact that RLS is extremely responsive to dopaminergic agents. A second issue is that iron deficiency states may precipitate RLS in as much as 25-30% of people with iron deficiency. Studies looking at basal ganglia dopaminergic function using PET and SPECT techniques have shown a decrease in binding potential for the dopamine receptor and transporter. Similar phenomena occurs in iron-deficient animals. Using MRI techniques and CSF analysis of iron-related protein, studies have suggested a reduction in brain iron concentration occurs in RLS patients. The relevance of CNS iron metabolism to the pathophysiology of RLS is discussed.

Iron deficiency alters dopamine transporter functioning in rat striatum

Iron deficiency anemia in early life produces profound changes in both in vivo and in vitro evaluations of dopamine (DA) functioning. This study employed both behavioral and biochemical approaches to examine the biological bases of alterations in striatal DA metabolism seen in iron-deficient rats. The purpose was to determine whether the DA transporter (DAT) was functionally altered in postweaning iron deficiency. Male and female 21-d-old Sprague-Dawley rats (n = 40) were fed either an iron-deficient (ID) diet (3 mg Fe/kg diet) or a control (CN) diet (35 mg Fe/kg diet) for 4 wk before behavioral testing. Motor activity responses to graded doses (3.75-30 mg/kg body) of the DA uptake inhibitor, cocaine, were significantly blunted in iron-deficient rats with a 50% higher half-maximal effective dose (ED(50)) in both males and females (CN-female, 7.1 +/- 0.9 mg/kg; ID-female, 11.2 +/-1.3 mg/kg; CN-male, 12.0 +/- 0.7 mg/kg; and ID-male, 17.0 +/- 1.8 mg/kg). Radioligand binding assays with (3)H-1-(2-(diphenylmethoxy)-ethyl)-4-(3-phenylpropyl) piperazine ((3)H-GBR12935) demonstrated that iron deficiency did not alter the affinity of the ligand for the DAT but did significantly decrease the density of the transporter by 30% in caudate putamen and 20% in nucleus accumbens. Iron deficiency also significantly decreased (3)H-DA uptake into striatal synaptosomes, but did not affect release of DA with potassium chloride stimulation. These experiments provide supporting evidence that elevated levels of extracellular DA in the striatum of iron-deficient rats is likely to be the result of decreased DAT functioning and not increased rates of release.

Evidence of a role for neuropeptide Y and monoamines in mediating the appetite-suppressive effect of GH

Among the many responses to GH administration is suppression of voluntary feed intake (FI) in some species, attributed to improvement in the efficiency of nutrient utilization and, therefore, reduced need for ingested substrates. Commercial broiler chickens have been genetically selected for generations for rapid growth, realized largely via the major correlated response of increased voluntary feed consumption. Neuropeptide Y (NPY) and monoamines play very important roles in the central regulation of feeding. Preliminary studies from our laboratory suggest that the appetite-suppressive effect of GH may be independent of its actions as a repartitioning agent, and may involve alterations in NPY expression at the pre-translational level. The purpose of this investigation was to explore the dose-response nature of the appetite-suppressive effect of GH in juvenile broilers, and the possible involvement of NPY and monoamines in this process. A GH dose-response study was conducted using 8-week-old female broilers infused i.v. with GH in a pulsatile pattern for 7 days at 0, 10, 50, 100 or 200 microgram/kg body weight per day. Hypothalamic NPY and epinephrine (EP) concentrations decreased in a dose-related manner with GH. At the highest dosage, voluntary FI decreased 19% (P<0.05) and hypothalamic NPY mRNA decreased approximately 50% in the infundibular nuclei and midline region (P<0.0001). In contrast, birds pairfed to the high-GH dosage group did not differ from controls, verifying that changes in NPY and monoamines were not secondary to reduced FI. We conclude that hypothalamic NPY and EP are likely candidates to explore further as mediators of the appetite-suppressive effect of GH.

Iron status and stores decline with age in Lewis rats

In the context of a larger study examining the interaction of vitamin A (VA) status and age on immune function, we examined age-related changes in hematologic and iron status variables in male Lewis rats. Animals were fed a nutritionally adequate purified diet containing either 0.35 (marginal), 4.0 (control) or 50 (supplemented) mg retinol equivalents (as retinyl palmitate) per kg of diet from the time of weaning until killing at 8-10 (middle-aged) or 20-22 (old) mo of age. Neither VA nor VA and age interaction effects were significant for most iron variables examined. After controlling for body weight, old rats had significantly lower hemoglobin, hematocrit and plasma iron than middle-aged rats. This decrease in hematologic and transport iron variables was not accompanied by a shift of iron into other storage compartments. Old rats also had significantly lower total iron content and iron concentration in liver, spleen and bone marrow. Hemosiderin iron in marrow smears correlated significantly (r = 0.43-0.76, P: < 0.05) with chemical estimates of iron in storage, transport and functional pools. Old rats also tended to have less stained iron in femur marrow smears. Thus, body iron in functional, transport and storage compartments, namely the liver, spleen and bone marrow, were significantly lower in old than in middle-aged rats. Although iron stores and status are usually considered to increase with advancing age, our data show a consistent pattern of lower hematologic and storage iron variables in old than in middle-aged Lewis rats. Future research is indicated to understand the biology and functional consequences of the observed age-associated decline in body iron.

Iron deficiency alters H- and L-ferritin expression in rat brain

Ferritin (Ft) H and L subunits are independently regulated proteins with both transcriptional and translational regulation in response to cellular iron levels. While the heterogeneous distribution of ferritin and iron in the brain is now well established, the relative response of each subunit to iron deficiency and iron supplementation, is not well defined. Weanling male Sprague-Dawley rats (n=12 per group) were randomly assigned to an iron deficient (3.5 mg Fe/kg diet), control (35 mg Fe/kg diet) or supplemented (350 mg Fe/kg diet) diet for six weeks. The H-/L-ferritin subunit ratio and mRNA levels were determined. Overall, the protein ratio in control rats of H to L was approximately 45:1 compared to a ratio >60:1 in iron deficiency but the absolute amounts of each subunit varied greatly from one brain region to another. The ratio of H-:L-ferritin mRNA was 6:1 and was not affected by dietary iron deficiency in contrast to a potent effect on mRNA levels in liver. Severe iron deficiency reduced brain ferritin H protein levels significantly in all regions, whereas only ferritin L levels in striatum, substantia nigra and pons were affected by iron deficiency. Supplemental dietary iron increased both ferritin subunits, with the largest increase (50%) in the hippocampus. These data indicate that ferritin H and L subunits within the brain respond differently to iron status and suggest post transcription regulation as a key event.

Effectiveness and strategies of iron supplementation during pregnancy

Iron deficiency continues to be one of the most prevalent single-nutrient deficiencies in the world. Interventions are often designed to prevent the decrease in hemoglobin concentration and the decline in iron stores associated with pregnancy. Although this is believed to be desirable for both the health of the mother and the well-being of the growing fetus, some scientists disagree. Enrichment and fortification of food items, and dietary changes resulting from education interventions, have met with some success in developed countries, but not often in the developing world. A therapeutic approach to iron supplementation, rather than a public health-based approach, is used throughout much of the world but suffers from real, or perceived, problems of compliance. Large doses of iron are most often prescribed and are associated with side effects and with increased oxidative damage. Alternatively, delayed-release preparations and intermittent oral iron supplementation lead to better overall compliance and alleviate side effects. Daily iron intervention provides more protection against a decline in the storage iron pool in pregnant women than does an intermittent schedule, but the latter is generally associated with fewer side effects, better compliance, and possibly a reduction in risk of oxidative damage. An improved cost-benefit ratio associated with a lower-dose oral iron supplement may prove to be quite positive in the future. Currently, no single approach may be universally acceptable, although a moderate iron dosage protocol will likely provide the most benefit to those who require supplemental iron.

Kinetic analysis shows that iron deficiency decreases liver vitamin A mobilization in rats

In view of evidence that nutritional status of iron and vitamin A may affect the other nutrient's metabolism, we used model-based compartmental analysis to examine effects of iron deficiency on whole-body vitamin A dynamics in rats. Weanling male Sprague-Dawley rats were fed the AIN93G diet with 2.5 nmol retinyl palmitate/g and either 45 [control (CN)] or 4 microg/g Fe [iron-deficient (ID)] for 8 wk. ID rats consumed food ad libitum; CN rats were food-restricted so that their body weights were the same as ID rats. Two rats/group were killed; liver vitamin A was determined and used for vitamin A balance calculations. [(3)H]Retinol-labeled plasma was administered intravenously to remaining rats, and 27 serial blood samples were collected for 7 wk. At killing, plasma vitamin A was 0.52+/-0.12 (ID, n = 5) vs. 1.34+/-0.12 micromol/L (CN, n = 6; P<0.001), and liver vitamin A was 809+/-94 (ID) vs. 112+/-24 nmol (CN, P<0.001). Plasma tracer data were fit to a three- or four-compartment model using the Simulation, Analysis and Modeling computer program and kinetic parameters were calculated. Vitamin A transfer rate between the retinyl ester storage pool [14+/-3 (ID) vs. 24+/-4 nmol/d (CN), P<0.05] and plasma was lower in ID rats. Vitamin A remained longer in the body [44+/-11 (ID) vs. 22+/-3 d (CN), P<0.05]. Adjusted mean disposal rate was lower in ID (10.0) than CN rats (19.9 nmol/d), as was estimated vitamin A absorption efficiency [58% (ID) vs. 76% (CN)]. Our results suggest that iron deficiency inhibits mobilization of vitamin A stores and may decrease the absorption and irreversible utilization of vitamin A.

Abnormalities in CSF concentrations of ferritin and transferrin in restless legs syndrome

CSF and serum were obtained from 16 patients with idiopathic restless legs syndrome (RLS) and 8 age-matched healthy control subjects. Patients with RLS had lower CSF ferritin levels (1. 11 +/- 0.25 ng/mL versus 3.50 +/- 0.55 ng/mL; p = 0.0002) and higher CSF transferrin levels (26.4 +/- 5.1 mg/L versus 6.71 +/- 1.6 mg/L; p = 0.018) compared with control subjects. There was no difference in serum ferritin and transferrin levels between groups. The presence of reduced ferritin and elevated transferrin levels in CSF is indicative of low brain iron in patients with idiopathic RLS.

Iron requirements in adolescent females

Adolescence is characterized by a large growth spurt and the acquisition of adult phenotypes and biologic rhythms. During this period, iron requirements increase dramatically in both boys and girls as a result of the expansion of the total blood volume, the increase in lean body mass and the onset of menses in young females. The overall iron requirements increase from a preadolescent level of approximately 0.7-0.9 mg Fe/d to as much as 2.2 mg Fe/d or perhaps more in heavily menstruating young women. These increased requirements are associated with the timing and size of the growth spurt as well as sexual maturation and the onset of menses. The available data on iron intakes in adolescents suggest that adolescent girls are unlikely to acquire substantial iron stores during this time period because intakes may average as little as 10-11 mg Fe/d. The bioavailability from diets in developing and industrialized countries indicates a negative iron balance is likely in many female populations. The low iron stores in these young women of reproductive age will make them susceptible to iron deficiency anemia during pregnancy because dietary intakes alone are insufficient, in most cases, to meet the requirements of pregnancy.

Bone structural and mechanical properties are affected by hypotransferrinemia but not by iron deficiency in mice

Hypotransferrinemia is a genetic defect in mice resulting in <1% of normal plasma transferrin (Tf) concentrations; heterozygotes for this mutation (+/hpx) have low circulating Tf concentrations. We used this mutant mouse in conjunction with dietary iron deficiency to study the influence of Tf and iron on bone structural and mechanical properties. Twenty-one weanling wild-type BALB/cj +/+ mice and 21 weanling +/hpx mice were fed iron-deficient or iron-adequate diets for 8 weeks. Twelve hpx/hpx mice were fed the iron-adequate diet. Hypotransferrinemia resulted in increased tibia iron and calcium concentrations, lower femur failure load, and extrinsic stiffness. Because the femurs of the hpx/hpx mice were disproportionately small, these bones actually had increased tissue material properties (ultimate stress [US] and modulus of elasticity) than those of wild-type mice. This is the first report on the effect of dietary iron deficiency on bone structural and mechanical properties. Dietary iron deficiency in +/+ and +/hpx mice decreased tibia iron concentrations but had no effect on tibia calcium and phosphorus concentrations or femur structural or mechanical properties. Because the bones of the hpx/hpx mice were small, but had superior tissue mechanical properties, we conclude that Tf is important for normal bone mineralization.

Variations in dietary iron alter brain iron metabolism in developing rats

The rat has been widely used as a model for the study of iron deficiency (ID), but the differences in the timing of development of humans and rats must be taken into account to derive appropriate conclusions from the animal model. This study was designed to evaluate the effects of dietary ID and iron excess on rat brain iron and the iron metabolism proteins, transferrin (Tf), transferrin receptor (TfR) and ferritin. The experimental design is developmentally sensitive and permits control of the timing as well as the duration of the nutritional insult. Iron-deficient and iron-supplemented (SU) rats between postnatal day (PND) 10 and 21, PND 21 and 35 and PND 10 and 35 were used to study the effects of early, late, and long-term iron deficiency and supplementation. Some ID rats were iron repleted between PND 21 and 35. These experiments demonstrated several new findings: 1) Early ID/SU (PND 10-21) altered brain iron, TfR, Tf and ferritin concentration in many regions different from those observed in the later period (PND 21-35). 2) Two weeks of iron repletion were adequate for correcting the overall Fe concentration of the brain and of individual brain regions, although larger amounts of iron were necessary to fully normalize iron and its regulatory proteins. 3) Long-term ID/SU resulted accordingly in the continued decrease or increase in brain iron concentration in some brain regions and not others. In conclusion, brain regions regulate their iron concentration in response to local needs when faced with alterations in systemic iron delivery.

Effects of an omnivorous diet compared with a lactoovovegetarian diet on resistance-training-induced changes in body composition and skeletal muscle in older men

BACKGROUND

Very limited data suggest that meat consumption by older people may promote skeletal muscle hypertrophy in response to resistance training (RT).

OBJECTIVE

The objective of this study was to assess whether the consumption of an omnivorous (meat-containing) diet would influence RT-induced changes in whole-body composition and skeletal muscle size in older men compared with a lactoovovegetarian (LOV) (meat-free) diet.

DESIGN

Nineteen men aged 51-69 y participated in the study. During a 12-wk period of RT, 9 men consumed their habitual omnivorous diets, which provided approximately 50% of total dietary protein from meat sources (beef, poultry, pork, and fish) (mixed-diet group). Another 10 men were counseled to self-select an LOV diet (LOV-diet group).

RESULTS

Maximal strength of the upper- and lower-body muscle groups that were exercised during RT increased by 10-38% (P < 0.001), independent of diet. The RT-induced changes in whole-body composition and skeletal muscle size differed significantly between the mixed- and LOV-diet groups (time-by-group interactions, P < 0. 05). With RT, whole-body density, fat-free mass, and whole-body muscle mass increased in the mixed diet group but decreased in the LOV- diet group. Type II muscle fiber area of the vastus lateralis muscle increased with RT for all men combined (P < 0.01), and the increase tended to be greater in the mixed-diet group (16.2 +/- 4.4 %) than in the LOV diet group (7.3 +/- 5.1%). Type I fiber area was unchanged with RT in both diet groups.

CONCLUSION

Consumption of a meat-containing diet contributed to greater gains in fat-free mass and skeletal muscle mass with RT in older men than did an LOV diet.

Transferrin is required for normal distribution of 59Fe and 54Mn in mouse brain

Hypotransferrinemia (hpx/hpx) is a genetic defect in mice resulting in <1% of normal plasma transferrin (Tf) concentrations; heterozygotes for this mutation (+/hpx) have low circulating Tf concentrations. These mice provide a unique opportunity to examine the role of Tf in Fe and Mn transport in the brain. Twenty weanling wild-type BALB/cJ mice, 15 +/hpx mice, and 12 hpx/hpx mice of both sexes were injected i.v. with either 54MnCl(2) or 59FeCl(3) either 1 h or 1 week before killing at 12 weeks of age. Total brain counts of 54Mn and 59Fe were measured, and regional brain distributions were assessed by autoradiography. Hypotransferrinemia did not affect total brain Mn uptake. However, 1 week after i.v. injection, hpx/hpx mice had less 54Mn in forebrain structures including cerebral cortex, corpus callosum, striatum, and substantia nigra. The +/hpx mice had the highest total brain 59Fe accumulation 1 h after i.v. injection. A striking effect of regional distribution of 59Fe was noted 1 week after injection; in hpx/hpx mice, 59Fe was located primarily in choroid plexus, whereas in +/+ and +/hpx mice 59Fe was widely distributed, with relatively high amounts in cerebral cortex and cerebellum. We interpret these data to mean that Tf is necessary for the transport of Fe but not Mn across the blood-brain barrier, and that there is a Tf-independent uptake mechanism for iron in the choroid plexus. Additionally, these data suggest that endogenous synthesis of Tf is necessary for Fe transport from the choroid plexus.

New insights into the mechanism and actions of growth hormone (GH) in poultry

Despite well documented anabolic effects of GH in mammals, a clear demonstration of such responses in domestic poultry is lacking. Recently, comprehensive dose-response studies of GH have been conducted in broilers during late post-hatch development (8 to 9 weeks of age). GH reduced feed intake (FI) and body weight gain in a dose-dependent manner, whereas birds pair-fed to the level of voluntary FI of GH-infused birds did not differ from controls. The reduction in voluntary FI may involve centrally mediated mechanisms, as hypothalamic neuropeptide Y protein and mRNA were reduced with GH, coincident with the maximal depression in FI. Growth of breast muscle was also reduced in a dose-dependent manner. Circulating IGF-I was not enhanced by GH, despite evidence that early events in the GH signaling pathway were intact. A GH dose-dependent increase in circulating 3,3',5-triiodothyronine(T3) paralleled decreases in hepatic 5D-III monodeiodinase activity, whereas 5'D-I activity was not altered. This confirms that a marked hyperthyroid response to GH occurs in late posthatch chickens, resulting from a decrease in the degradative pathway of T3 metabolism. This secondary hyperthyroidism would account for the decreased skeletal muscle mass (52) and lack of enhanced IGF-I (53) in GH-treated birds. Based upon these studies, it is now evident that GH does in fact have significant effects in poultry, but metabolic responses may confound the anabolic potential of the hormone.

Iron deficiency and neural development: an update

In Latin America, 10-30% of reproductive age females and upwards of 40-70% of pregnant women may be iron deficient. The true prevalence in young children and infants is often hard to determine because of problems in survey design, data collection, or sampling. There is little doubt, however, that iron deficiency anemia is a significant nutritional problem in many infants within the first 5 years of life. Numerous intervention studies have been performed across the world with varying success and it is clear that in nearly all situations it is a preventable disease with preventable consequences. One such consequence is the alteration in cognition that occurs in iron deficient individuals during the early parts of their life cycle and perhaps at later times as well. While iron deficiency was once presumed to exert most of its deleterious effects only if anemia was present, it is now clear that many organs show morphologic, physiologic, and biochemical changes before there is any drop in hemoglobin concentration. Iron deficiency is associated with alterations in many metabolic processes that may impact brain functioning; among them are mitochondria electron transport, neurotransmitter synthesis and degradation, protein synthesis, organogenesis, and others. It is necessary to separate the developmental aspects of iron deficiency and neural functioning from the aspects of iron deficiency that could occur at any time in life. A number of reviews have discussed the links between brain iron and neuropathology, brain iron, nutrition, and development, and iron status and cognition. New knowledge concerning the acquisition of iron by the brain in early life is being generated by numerous research groups. In the next decade a much clearer understanding of the role of brain iron on neural functioning will probably emerge.

Iron deficiency in young rats alters the distribution of vitamin A between plasma and liver and between hepatic retinol and retinyl esters

We assessed whether iron deficiency alters the concentration of vitamin A (VA) in plasma or liver and the chemical distribution between hepatic unesterified and esterified retinol. Weanling male Sprague-Dawley rats (n = 10/group) were allocated to one of four diet groups: low iron (ID3, 3 mg of elemental iron/kg diet), marginal iron (ID15, 15 mg/kg), control diet food-restricted to the ID3 group (FR, 35 mg/kg), and control diet ad libitum consumption (AD, 35 mg/kg). Both ID3 and FR rats grew less than AD and ID15 rats. At the end of 5.5 wk, plasma retinol concentrations of the ID3 and FR rats were reduced >40% compared to ID15 and AD rats [Kruskal-Wallis test (K-W), P < 0.0042)]. Paradoxically, the hepatic VA concentration was greater in FR rats, with accumulation of more retinyl esters and retinol compared to the other dietary groups. Concentrations of hepatic retinyl esters and retinol did not differ among the other groups, but the molar ratio of hepatic retinyl esters to retinol was greater in ID3 rats (20.1 +/- 1.4) compared to ID15 rats (13.8 +/- 1.6, P = 0.02), AD (11.3 +/- 2.1, P < 0.0042) and FR (9.5 +/- 1.1, P < 0.0042). Iron deficiency may cause changes in liver and plasma VA that are refractory to VA intake, and thus a benefit may be derived from combining iron and VA supplements during nutrition interventions.

Existing and emerging mechanisms for transport of iron and manganese to the brain

The metals iron (Fe) and manganese (Mn) are essential for normal functioning of the brain. This review focuses on recent developments in the literature pertaining to Fe and Mn transport. These metals are treated together because they appear to share several transport mechanisms. In addition, several neurological diseases such as Alzheimer's Disease, Parkinson's Disease, and Huntington's Disease are all associated with Fe mismanagement in the brain, particularly in the striatum and basal ganglia. Similarly, Mn accumulation in brain also appears to target the same brain regions. Therefore, stringent regulation of the concentration of these metals in the brain is essential. The homeostatic mechanisms for these metals must be understood in order to design neurotoxicity prevention strategies.

A genetic developmental model of iron deficiency: biological aspects

Numerous studies have demonstrated the negative impact of iron deficiency on growth and development. The present study expands on the published literature by exploring the role of genetics and developmental timing on the impact of iron deficiency on development in two strains of mice. Growth rates, organ weights, and hematological responses to an iron-deficient diet differed by strain and sex. The results from this study provided novel insight into iron metabolism and the impact of iron deficiency in C57 and DBA strains of mice. Future studies should continue to examine the contributions of both genetics and sex to the development of iron deficiency.

Transferrin response in normal and iron-deficient mice heterozygotic for hypotransferrinemia; effects on iron and manganese accumulation

Hypotransferrinemia is a genetic defect in mice resulting < 1% of normal plasma transferrin (Tf) concentrations; heterozygotes for this mutation (+/hpx) have low circulating Tf concentrations. These mice provide a unique opportunity to examine the developmental pattern and response of Tf to iron-deficient diets, and furthermore, to address the controversial role of Tf in Mn transport. Twenty-three weanling +/hpx mice and forty-five wild-type BALB/cJ mice were either killed at weaning or fed diets containing either 13 or 72 mg kg-1 Fe, and killed after four or eight weeks. Plasma Tf concentrations were lower in +/hpx mice, plasma Tf nearly doubled and liver Tf was only 50% of normal in response to iron deficiency. Brain iron concentration did not correlate significantly with either plasma Tf or TIBC. However, iron accumulation into brain continued with iron deficiency whereas most other organs had less iron. These results imply that either there is a selected targeting of iron to the brain by plasma Tf or there is an alternative iron delivery system to the brain. Furthermore, we observed no differences in tissue distribution of 54Mn despite the differences in circulating Tf concentrations and body iron stores; this suggests that there are non-Tf dependent mechanisms for Mn transport.

Dietary iron deficiency results in cardiac eccentric hypertrophy in rats

This study reports the presence of eccentric cardiac hypertrophy in rats made anemic by feeding an iron-deficient diet. Male weanling Sprague-Dawley rats were provided free access to diets either adequate (n=9) or inadequate in iron (n=8) for a period of 7 weeks from weanling or until 10 weeks of age. At that time, blood was obtained for hematocrit and hemoglobin determination, and liver and hearts were collected for further analysis. Liver non-heme iron levels confirmed that the rats were iron-deficient, and the very low hematocrit and hemoglobin values revealed the presence of physiological anemia. Despite the lighter body weights in the iron-deficient rats, this group had greater absolute heart weights and heart:body weight, clearly demonstrating the presence of cardiac hypertrophy. Iron-deficient rats had elevated heart rates but lower norepinephrine levels than control rats. Sagittal sectioning of all hearts allowed for the measurements of the wall thicknesses, lumen volume, and width dimensions. Results revealed significantly greater left ventricular lesser diameter, apical thickness, and left ventricular volume in hearts from iron-deficient rats compared to iron-adequate rats. The hypertrophy pattern present in iron-deficiency anemia is in contrast to other nutritional models of hypertrophy, such as copper-deficiency, where a concentric hypertrophy occurs both in the presence and absence of anemia.

Plasma thyroid hormone kinetics are altered in iron-deficient rats

Iron deficiency anemia is associated with lower plasma thyroid hormone concentrations in rodents and, in some studies, in humans. The objective of this project was to determine if plasma triiodothyronine (T3) and thyroxine (T4) kinetics were affected by iron deficiency. Studies were done at a near-thermoneutral temperature (30 degrees C), and a cool environmental temperature (15 degrees C), to determine plasma T3 and T4 kinetics as a function of dietary iron intake and environmental need for the hormones. Weanling male Sprague-Dawley rats were fed either a low Fe diet [iron-deficient group (ID), <5 microg/g Fe] or a control diet [control group (CN), 35 microg/g Fe] at each temperature for 7 wk before the tracer kinetic studies. An additional ID group receiving exogenous thyroid hormone replacement was also used at the cooler temperature. For T4, the disposal rate was >60% lower (89 +/- 6 vs. 256 +/- 53 pmol/h, P < 0.001) in ID rats than in controls at 30 degrees C, and approximately 40% lower (192 +/- 27 vs. 372 +/- 26 pmol/h, P < 0.01) in ID rats at 15 degrees C. Exogenous T4 replacement in a cohort of ID rats at 15 degrees C normalized the T4 concentration and the disposal rate. For T3, the disposal rate was significantly lower in ID rats in a cool environment (92 +/- 11 vs. 129 +/- 11 pmol/h, P < 0.01); thyroxine replacement again normalized the T3 disposal rate (126 +/- 12 pmol/h). Neither liver nor brown fat thyroxine 5'-deiodinase activities were sufficiently different to explain the lower T3 disposal rates in iron deficiency. Thus, plasma thyroid hormone kinetics in iron deficiency anemia are corrected by simply providing more thyroxine. This suggests a central regulatory defect as the primary lesion and not peripheral alterations.

Selective ablation of human T-cell lymphotropic virus type 1 p12I reduces viral infectivity in vivo

Human T-cell lymphotropic virus type 1 (HTLV-1) is the etiologic agent of adult T-cell leukemia and HTLV-1-associated myelopathy. Novel, yet conserved RNA transcripts encoded from open reading frames (ORFs) I and II of the viral pX region are expressed both in vitro and in infected individuals. The ORF I mRNA encodes the protein p12(I), which has been shown to localize to cellular endomembranes, cooperate with bovine papillomavirus E5 in transformation, as well as bind to the IL-2 receptor beta and gamma chains and the H+ vacuolar ATPase. It is unknown what role p12(I) plays in the viral life cycle. Using an infectious molecular clone of HTLV-1 (ACH) and a derivative clone, ACH.p12(I), which fails to produce the p12(I) message, we investigated the importance of p12(I) in infected primary cells and in a rabbit model of the infection. ACH.p12(I) was infectious in vitro as shown by viral passage in culture and no qualitative or quantitative differences were noted between ACH and ACH.p12(I) in posttransfection viral antigen production. However, in contrast to ACH, ACH.p12(I) failed to establish persistent infection in vivo as indicated by reduced anti-HTLV-1 antibody responses, failure to demonstrate viral p19 antigen production in peripheral blood mononuclear cell (PBMC) cultures, and only transient detection of provirus by polymerase chain reaction in PBMC from ACH.p12(I)-inoculated rabbits. These results are the first to show the essential role of HTLV-1 p12(I) in the establishment of persistent viral infection in vivo and suggest potential new targets in antiviral strategies to prevent HTLV-1 infection.

In vivo dopamine metabolism is altered in iron-deficient anemic rats

Previous studies of dopamine metabolism in iron-deficient rats demonstrated an elevation in extraneuronal levels of dopamine and a depression in the number of dopamine D2 receptors; however, the importance of anemia per se and the reversibility of these observations are not completely resolved. The purpose of this study was to determine if in vivo reuptake of caudate dopamine is altered by iron deficiency anemia, if it is reversible with iron therapy, and if anemia per se produced the same effects on dopamine metabolism. Male Sprague-Dawley rats (21-d old) were fed an iron-deficient diet (4 mg Fe/kg diet) and then iron repleted (5 mg iron dextran), or were fed an iron adequate diet (35 mg Fe/kg diet) and then given phenylhydrazine to induce hemolytic anemia. In vivo microdialysis was performed in steady-state conditions both before and after iron or no therapy and was followed by an intraperitoneal injection of a dopamine reuptake blocker (cocaine-HCl 30 mg/kg). Thirty percent higher extracellular dopamine levels in the caudate-putamen were observed in iron-deficient rats compared with control rats, but no differences were observed in tissue levels. Hemolytic anemic and iron-repleted rats had normal extracellular dopamine levels. The response to dopamine reuptake blockade was significantly attenuated in iron-deficient rats compared with control, iron-repleted, or hemolytic anemic rats. These experiments provide evidence that iron deficiency blunts the dopamine reuptake mechanism, that this is a reversible process in postweaning rats, and that anemia per se does not cause the increased extracellular dopamine levels.

A sustainable solution for dietary iron deficiency through plant biotechnology and breeding to increase seed ferritin control

OBJECTIVES

To stimulate novel sustainable solutions to the problem of the nutritional iron deficiency, we asked: How does Nature insure proper iron nutrition of embryos and neonatal animals? Estimates of iron deficiency world-wide are 30% of the population, with women and children at the greatest risk. Recent studies linking iron deficiency with impeded cognitive development emphasizes the enormity of the impact of iron deficiency. Sustainable solutions to the problem of dietary iron deficiency have been elusive.

RESULTS

Data for storage iron was examined in seeds, developing plants, embryos and developing animals. In all cases, the common source of stored iron for development was ferritin. The protein component of ferritin concentrates iron billions of times above the solubility of the free metal ion. High conservation of ferritin sequences in bacteria, plants and animals and the specificity of ferritin bioavailability either added extrinsically or intrinsically enriched in a selected soybean cultivar, showed high efficacy in curing dietary iron deficiency in the rat model. Older data on ferritin were reevaluated in light of contemporary knowledge.

CONCLUSIONS

Enhancement of natural seed ferritin content by biotechnology and breeding has the potential for a sustainable solution to the problem of global dietary iron deficiency.

Regional brain iron, ferritin and transferrin concentrations during iron deficiency and iron repletion in developing rats

Iron deficiency in young rats leads to a decrease in brain iron and ferritin concentrations, an increase in transferrin (Tf) concentration, and an increased rate of uptake of iron from the plasma pool. We conducted two experiments to determine whether brain iron, Tf and ferritin respond quickly to iron repletion and to determine whether brain regions respond heterogeneously. Weanling male Sprague-Dawley rats were fed an iron-deficient diet (<5 mg/kg Fe) for 2 wk followed by an iron-adequate diet (REPL group, 35 mg/kg Fe in Experiment 1 and 15 mg/kg Fe in Experiment 2) for 2 or 4 wks, respectively. Age-matched iron-deficient (ID) and control rats composed the other two groups. Fourteen days of repletion with 35 mg/kg Fe dietary treatment were adequate to normalize hematology, brain microsomal and cytosolic Fe and brain ferritin (Experiment 1). Brain transferrin concentrations in REPL rats, however, were significantly above the levels of controls. Regional brain iron decreased heterogeneously due to dietary iron deficiency (Experiment 2), with some regions having a propensity to keep iron (e.g., substantia nigra, pons, and thalamus) and others losing significant amounts of iron (cortex and hippocampus). Ferritin and Tf concentrations also varied significantly across brain regions in ID and control rats. The hippocampus had the most dramatic Tf response to iron deficiency with elevations of approximately 100%, whereas other regions, except striatum, were unaffected. The brain of developing rats thus distributes iron and iron regulatory proteins differently from the brain of adult rats and is quite avid in its reacquisition of iron during iron therapy.

Chromium picolinate supplementation and resistive training by older men: effects on iron-status and hematologic indexes

Chromium competes with iron for binding to transferrin, and high-dose chromium supplementation has been hypothesized to adversely affect iron status. This study examined the effects of chromium picolinate supplementation on hematologic indexes and selected indexes of iron status in 18 men aged 56-69 y who participated in an introductory resistive training program. The men were randomly assigned (double-blind design) to groups (n = 9) that consumed either 17.8 mumol Cr/d (924 micrograms Cr/d) as chromium picolinate or a low-chromium placebo for 12 wk while engaging in resistive training twice weekly (3 sets of 8-12 repetitions at 80% of one repetition maximum for 5 exercises). Hematocrit, hemoglobin, red blood cell (erythrocyte) count, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, red blood cell distribution width, platelet count, and mean platelet volume were within normal clinical ranges and were unchanged by either chromium picolinate supplementation or resistive training. Resistive training decreased total-iron-binding capacity from 38.4 +/- 9.3 to 27.3 +/- 5.6 mumol/L (P < 0.0001) and increased transferrin saturation from 35.7 +/- 16.3% to 45.4 +/- 16.9% (P = 0.050). Chromium picolinate supplementation did not influence these responses. Serum iron concentrations and serum ferritin concentrations were unchanged by either resistive training or chromium picolinate supplementation. These data suggest that high-dose chromium picolinate supplementation for 12 wk did not influence hematologic indexes or indexes of iron metabolism or status in older men. The decrease in total-iron-binding capacity and increase in transferrin saturation (%) with resistive training are largely opposite to changes associated with iron depletion and suggest a novel effect of resistive training on iron transport.

Regional distribution of iron, transferrin, ferritin, and oxidatively-modified proteins in young and aged Fischer 344 rat brains

Iron dysregulation in the brain is thought to contribute to the oxidative damage seen in neurodegenerative diseases including Alzheimer's disease and Parkinson's disease. A role for iron in the oxidative stress thought to contribute to normal ageing is less certain. To better characterize the role of iron in normal ageing, the concentrations of iron, transferrin, ferritin, and protein carbonyl groups are measured in nine separate regions of Fischer 344 rats. The largest (approximately 30%) age-related increases in brain iron concentration are seen in the temporal cortex, medial septum, and cerebellum. Ferritin concentration in these same brain regions increases 50 to 250% with age, while protein carbonyl concentration is only -27 to +4%, of young rats. These results indicate that an increase in the major iron-binding protein ferritin compensates for any age-related increase in iron concentration, and suggest that the increased ferritin is cytoprotective, serving to prevent the accumulation of protein carbonyl groups (a principal product of metal-catalysed oxidation of proteins).

Age, fitness, and regional blood flow during exercise in the heat

During dynamic exercise in warm environments, the requisite increase in skin blood flow (SkBF) is supported by an increase in cardiac output (Qc) and decreases in splanchnic (SBF) and renal blood flows (RBF). To examine interactions between age and fitness in determining this integrated response, 24 men, i.e., 6 younger fit (YF), 6 younger sedentary (YS), 6 older fit (OF), and 6 older sedentary (OS) rested for 50 min, then exercised at 35 and 60% maximal O2 consumption (VO2max) at 36 degrees C ambient temperature. YF had a significantly higher Qc and SkBF than any other group during exercise, but fitness level had no significant effect on any measured variable in the older men. At 60% VO2max, younger subjects had significantly greater decreases in SBF and RBF than the older men, regardless of fitness level. Total flow redirected from these two vascular beds (deltaSBF + deltaRBF) followed YF >> YS > OF > OS. A rigorous 4-wk endurance training program increased exercise SkBF in OS, but deltaSBF and deltaRBF were unchanged. Under these conditions, older men distribute Qc differently to regional circulations, i.e., smaller increases in SkBF and smaller decreases in SBF and RBF. In younger subjects, the higher SkBF associated with a higher fitness level is a function of both a higher Qc and a greater redistribution of flow from splanchnic and renal circulations, but the attenuated splanchnic and renal vasoconstriction in older men does not appear to change with enhanced aerobic fitness.

Iron metabolism: a comprehensive review

Despite its abundance in the earth's crust, iron deficiency is a serious health issue in many parts of the world. Although fundamental observations about iron metabolism and the significance of iron nutriture were first noted some time ago, the molecular mechanisms involved in iron metabolism are just now being defined.

Iron nutrition in rural home bound elderly persons

The objective of this study was to describe the iron status of a sample of rural elderly home-delivered meals recipients as determined by a relatively non-invasive capillary blood sampling system. Fifty-six persons were assessed in their homes. The incidence of iron deficiency was considerable and was similar to incidences reported in other elderly populations. Females were at higher risk for iron deficiency than males despite a similar low dietary iron intake of 10-11 mg/day in both genders. Data were collected on drug use, general health conditions and other variables that may alter iron status in the elderly but they had no significant statistical effects in this study. We interpret this data on a high prevalence of iron deficiency in females as suggestive that they are at considerable risk of iron deficiency due to a lifelong poorer iron status than men.

The role of nutrition in the development of normal cognition

The goal of this section of the meeting was to review the relation between nutrition and cognition. The topics selected for discussion included generalized malnutrition, iodine deficiency, iron metabolism, and the relation of fatty acids to the development of the nervous system. Each subject is immense and demands a detailed exposition, but can be treated here only in brief form. However, these short essays should give some insight into the status of our current knowledge.

Purified ferritin and soybean meal can be sources of iron for treating iron deficiency in rats

Ferritin and soybean meal were reevaluated as dietary treatments of iron deficiency in rats. Isotopes that had been used in the past were avoided because of contemporary knowledge of the physiological and structural complexity of ferritin protein and the solid iron mineral. Rats made anemic by iron-deficient diets were given equivalent amounts of iron as FeSO4, horse spleen ferritin, baked soybean meal, or soybean meal plus ferritin. Full recovery (89-109%) from anemia and increased tissue iron occurred after 28 d of treatment with any of the iron sources, which contrasts to past bioavailability studies using 59Fe-labeled ferritin and generally shorter periods of observation. Cultivar-specific variability was observed in soybean seed soluble iron and ferritin content (1.9-2.0 times the control cultivar, Arksoy), which was apparently heritable. The combined data suggest that manipulating ferritin expression and other soluble components of seed iron in soybeans and possibly other seeds, using Mendelian and biotechnological approaches, could contribute to a sustainable solution to global problems of iron deficiency.

Sensory acceptability of meat and dairy products and dietary fat in male collegiate swimmers

This study was undertaken to determine whether high-level training alters food choice behavior with regard to meat and dairy products because of their high fat content. Twenty male collegiate swimmers were compared to 20 male sedentary students for dietary fat intake, nutrition knowledge, and liking of meat and dairy products. There was no significant difference between the two groups for restraint, energy intake, dietary fat intake, and energy derived from fat. Nutrition knowledge, energy derived from saturated fat, and cholesterol intake, however, were significantly higher in the athletes. The two groups did not differ in their hedonic ratings of flavor or in their overall degree of liking of the meat and dairy products, and the athletes actually liked the appearance and texture of the products significantly more than did the sedentary students. This study shows that the sensory appeal of fat-containing animal products is not affected in male swimmers by a high level of exercise.

Effect of thyroid hormone replacement in iron-deficient rats

To determine if the previously observed alterations in norepinephrine (NE) metabolism and resting metabolic rate in iron-deficient (ID) rats result from hypothyroidism, exogenous thyroxine (T4) and 3,5,3'-triiodothyronine (T3) were administered to ID rats in doses sufficient to normalize the plasma concentrations of these hormones, whereas other ID and control (CN) rats received placebo treatment. Resting oxygen consumption was approximately 25% higher in ID than CN rats; T4 but not T3 treatment alleviated this elevated oxygen uptake. The NE content of interscapular brown adipose tissue (IBAT), liver, and heart was 70-80% lower in ID than CN rats, and NE turnover in the same tissues was likewise 40-60% lower in ID than CN rats, with no systematic effect of either T3 or T4 treatment. Liver T(4)5'-deiodinase activity was 70% lower in ID than CN rats and increased with T4 but not T3 treatment. These experiments show that iron deficiency alters NE and energy metabolism in a way that is mostly independent of its effects on thyroid hormone metabolism.

Effects of long-term moderate exercise on iron status in young women

The impact of long-term (6-month) moderate exercise on the iron status of previously sedentary women was determined by randomly assigning 62 college-age women into one of the following four groups: 1) 50 mg.d-1 iron supplement, low iron diet (N = 16); 2) Placebo, free choice diet (N = 13); 3) Meat supplement to achieve 15 mg.d-1 iron intake (N = 13); and 4) Control, free choice diet (N = 20). All groups except the Control group exercised 3 d.wk-1 at 60%-75% of their heart rate reserve. VO2max was measured at baseline and week 24. Blood was sampled at baseline and every 4 wk thereafter for 24 wk to measure iron status and to elucidate the causes for alterations in iron status. Subjects had depleted iron stores throughout the study as indicated by their serum ferritin levels (< 15 ng.ml-1). Serum iron, total iron binding capacity and transferrin saturation were not compromised with exercise. Mean hemoglobin level in the Placebo/Ex group was significantly (P < 0.05) lower than the 50 Fe/Ex and the Meat/Ex groups by week 24. However, changes in serum albumin, haptoglobin, and erythropoietin data from the study cannot explain these changes.

Brain iron, transferrin and ferritin concentrations are altered in developing iron-deficient rats

To study the iron, transferrin, and ferritin distribution at subcellular levels in response to acute dietary iron deficiency, we tested the hypothesis that early post-weaning iron deficiency can change iron and iron regulatory protein concentrations in rat brain. Male Sprague-Dawley rats were fed diets containing either 2 or 35 micrograms iron/g for 2, 3 or 4 wk starting at 21 d of age. Brain iron, transferrin and ferritin concentrations in cytosolic and microsomal fractions of either whole brain or pons and cerebellum were then determined. After 14 d of dietary iron restriction, brain iron concentrations were 50% lower in the microsomal fraction and 30% lower in cytosol compared with controls. Brain cytosolic transferrin concentration almost doubled in the same animals. Brain ferritin concentration in fractions from rats fed the iron-deficient diet for 14 d was lower than in controls, but then remained fairly constant. Absolute brain weight and total brain protein contents were unaffected by iron restriction. This study extends previous research by demonstrating that the brain responds to changes in body iron status with a change in transferrin concentration. If the dietary restriction is quite severe, this adaptation is insufficient. This study also notes that brain ferritin decreases with decreasing body iron status, though it was less responsive than nonheme iron in liver. The concept that iron enters the brain through a highly regulated endocytotic process at the blood brain barrier, that undoubtedly involves the regulation of transferrin receptors in capillary endothelial cell, is supported by our observation of elevated transferrin concentrations in brain of iron-deficient rats.

Growth in iron-deficient rats

Poor growth in iron deficiency is commonly observed in animal studies. Previous studies from our laboratory showed that iron-deficient rats are metabolically inefficient and have less body fat than controls and proposed that iron deficiency was related to increased metabolic rates and heat loss. To examine these points more completely, we examined growth and metabolic rate of iron-deficient rats at two environmental temperatures, 25 degrees C and 32 degrees C, and feed efficiency in separate groups of rats during a period of rapid growth. Iron deficiency (hemoglobin [Hb] approximately 60 g/liter) was associated with a systematic elevation of metabolic rate over the 24-hr day with animals at 25 degrees C. This did not occur in animals living in thermoneutrality. Iron deficiency affected growth of animals at 25 degrees C but not at 32 degrees C. Feed efficiency (kcal retained/kcal absorbed) was 25 +/- 4.2 and 31 +/- 4.9 kcal (P < 0.0001), respectively, in iron deficient rats and animals were not anorexic. Use of food-restricted animals allowed the direct calculation that iron deficiency was associated with a 10%-15% increase requirement for growth. We conclude that iron deficiency anemia is associated with a poor feed efficiency and that it is attenuated when nonshivering thermogenesis is minimized by a thermoneutral environment.

Iron deficiency and anemia of chronic disease in elderly women: a discriminant-analysis approach for differentiation

To differentiate iron-deficiency anemia and anemia associated with chronic inflammatory diseases in elderly women, subsets of laboratory, dietary, and functional assessment variables were obtained by using discriminant analysis. Fifty-one subjects (70-79 y of age) were classified into one of four groups on the basis of the presence of iron deficiency and chronic inflammatory disease. Iron deficiency was defined on the basis of a significant response in hemoglobin concentration after iron supplementation. The discriminating subset of laboratory tests consisted of measures for serum ferritin, plasma transferrin receptors, and erythrocyte sedimentation rate. The discriminant function classified subjects into iron-deficient, anemia of chronic disease, or a category in which the two coexist, with an error rate of 18.6%. The addition of other variables (dietary iron and functional assessment information) did not appreciably improve the classification. The results of these three key laboratory tests may help to identify functional iron deficiency in the presence of chronic inflammation.

Classical selenium-dependent glutathione peroxidase expression is decreased secondary to iron deficiency in rats

While there are reports that classical selenium-dependent glutathione peroxidase (Se-GPX1) activity is decreased during iron deficiency, the relationship between tissue iron status and Se-GPX1 activity remains speculative. This study was undertaken to investigate the mechanism for the decrease in Se-GPX1 activity during iron deficiency. Male weanling Sprague-Dawley rats were given free access to either an iron-deficient or an iron-adequate diet for eight weeks, after which blood, livers, kidneys, hearts, brains and testes were surgically excised. During iron deficiency, Se-GPX1 mRNA levels in liver tissue were decreased by approximately 55%. Similarly, the concentration of immunoreactive Se-GPX1 protein and total selenium-dependent glutathione peroxidase (Se-GPX) activity were decreased by 55% and 60%, respectively. In kidney, heart and brain total Se-GPX activities were depressed as much as 33%. Selenium concentration in liver was reduced by 42%, whereas the decrease in Se concentrations in kidney, heart, and brain ranged from 17 to 25%. Concentrations of plasma Se also were reduced by 18%, but testes showed little change in either Se-GPX activity or Se concentration during iron deficiency. Results suggest that the synthesis of Se-GPX1 protein is decreased during iron deficiency possibly due to pretranslational regulation.

Altered monamine metabolism in caudate-putamen of iron-deficient rats

The effect of iron deficiency on brain monoamine metabolism using in vivo microdialysis techniques has not been previously reported. We, therefore, examined the monoamines, dopamine and norepinephrine, and their metabolites at steady state by in vivo microdialysis in rat brain caudate-putamen in 11-week-old iron-deficient anemic (hemoglobin < 7 g/dl) and control rats (Hb > 14 g/dl). Caudate-putamen dopamine (DA), dihydroxyphenyl acetic acid (DOPAC), and homovanillic acid (HVA) concentrations were increased by 53%, 57%, and 30% (p < 0.001), respectively, in iron-deficient rats in samples collected over a 4-h period. While diminished numbers of D2 receptors have been previously reported, the present findings suggest an additional defect in monoamine uptake and catabolism.

Iron deficiency: assessment during pregnancy and its importance in pregnant adolescents

The assessment of iron deficiency in pregnancy requires the accurate determination of indicators that have significant within-subject variability. For instance, serum ferritin concentrations may vary by as much as 25% from one day to the next. Added to this uncertainty about biological variability is the influence of plasma volume expansion on concentration-dependent indexes such as ferritin, plasma iron, and hemoglobin. Multiple measurements of iron status are suggested, and, if this is not possible, within-subject variability needs to be included in the confidence of assigning individuals to iron-status groups. An example of this former approach is shown for a group of pregnant adolescents with a very high prevalence of iron deficiency. Although the assessment of iron status in human populations is advanced compared with that of other nutrients, there is still a large uncertainty about absolute diagnosis during pregnancy.