Fetal and neonatal iron deficiency but not copper deficiency increases vascular complexity in the developing rat brain.

Objectives: Anemia caused by nutritional deficiencies, such as iron and copper deficiencies, is a global health problem. Iron and copper deficiencies have their most profound effect on the developing fetus/infant, leading to brain development deficits and poor cognitive outcomes. Tissue iron depletion or chronic anemia can induce cellular hypoxic signaling.

Impact of copper deficiency in humans.

Humans consume about 1 mg of copper daily, an amount thought adequate for most needs. Genetic, environmental, or physiological alterations can impose a higher copper set point, increasing risk for copper-limited pathophysiology. Humans express about a dozen proteins that require copper for function (cuproenzymes).

Fetal and neonatal iron deficiency exacerbates mild thyroid hormone insufficiency effects on male thyroid hormone levels and brain thyroid hormone-responsive gene expression.

Fetal/neonatal iron (Fe) and iodine/TH deficiencies lead to similar brain developmental abnormalities and often coexist in developing countries. We recently demonstrated that fetal/neonatal Fe deficiency results in a mild neonatal thyroidal impairment, suggesting that TH insufficiency contributes to the neurodevelopmental abnormalities associated with Fe deficiency. We hypothesized that combining Fe deficiency with an additional mild thyroidal perturbation (6-propyl-2-thiouracil [PTU]) during development would more severely impair neonatal thyroidal status and brain TH-responsive gene expression than either deficiency alone.

Maternofetal and neonatal copper requirements revealed by enterocyte-specific deletion of the Menkes disease protein.

The essential requirement for copper in early development is dramatically illustrated by Menkes disease, a fatal neurodegenerative disorder of early childhood caused by loss-of-function mutations in the gene encoding the copper transporting ATPase ATP7A. In this study, we generated mice with enterocyte-specific knockout of the murine ATP7A gene (Atp7a) to test its importance in dietary copper acquisition. Although mice lacking Atp7a protein within intestinal enterocytes appeared normal at birth, they exhibited profound growth impairment and neurological deterioration as a consequence of copper deficiency, resulting in excessive mortality prior to weaning.

Fetal and neonatal iron deficiency reduces thyroid hormone-responsive gene mRNA levels in the neonatal rat hippocampus and cerebral cortex.

Copper (Cu), iron (Fe), and thyroid hormone (TH) deficiencies produce similar defects in late brain development including hypomyelination of axons and impaired synapse formation and function, suggesting that these micronutrient deficiencies share a common mechanism contributing to these derangements. We previously demonstrated that fetal/neonatal Cu and Fe deficiencies lower circulating TH concentrations in neonatal rats. Fe deficiency also reduces whole-brain T(3) content, suggesting impaired TH action in the developing Fe-deficient brain.

Suppressed hepcidin expression correlates with hypotransferrinemia in copper-deficient rat pups but not dams.

Copper deficiency leads to anemia but the mechanism is unknown. Copper deficiency also leads to hypoferremia, which may limit erythropoiesis. The hypoferremia may be due to limited function of multicopper oxidases (MCO) hephaestin in enterocytes or GPI-ceruloplasmin in macrophages of liver and spleen whose function as a ferroxidase is thought essential for iron transfer out of cells.

Impact of copper limitation on expression and function of multicopper oxidases (ferroxidases).

Copper is an essential trace element whose recommended intake is met by most North American diets. However, incidence of new cases of secondary copper deficiency is rising due to complications of gastric bypass surgery and high zinc exposure. Patients frequently are ataxic and anemic.

Copper deficiency has minimal impact on ferroportin expression or function.

Interactions between copper and iron homeostasis have been known since the nineteenth century when anemia in humans was first described due to copper limitation. However, the mechanism remains unknown. Intestinal and liver iron concentrations are usually higher following copper deficiency (CuD).

Erythrocyte copper chaperone for superoxide dismutase is increased following marginal copper deficiency in adult and postweanling mice.

A sensitive and reliable biomarker has yet to be identified for marginal copper deficiency in humans. The need for such a biomarker is critical, because increased cases of human copper deficiency evolve following bariatric surgery and other secondary factors besides diet. Four experiments were devised to induce marginal copper deficiency through copper-deficient (CuD) diets (5 wk for mice and 4 wk for rats).

Rapid alteration in rat red blood cell copper chaperone for superoxide dismutase after marginal copper deficiency and repletion.

There is increased incidence of human copper deficiency (CuD). A sensitive and reliable blood biomarker may reveal additional cases of marginal deficiency. Two experiments were designed to test the hypothesis that the copper chaperone for superoxide dismutase (CCS) would be a robust marker after marginal CuD.

Glycosylphosphatidylinositol-linked ceruloplasmin is expressed in multiple rodent organs and is lower following dietary copper deficiency.

Ceruloplasmin (Cp), a multicopper ferroxidase, is expressed as both a secreted (sCp) plasma enzyme from the liver and a membrane-bound glycosylphosphatidylinositol-anchored (GPI-Cp) splice variant protein. Cp is thought to be essential for iron mobilization as selective iron overload occurs in aceruloplasminemia in humans and in Cp null mice. Dietary copper-deficient (CuD) rodents have near total loss of Cp activity, severe loss of Cp protein and develop anemia.

Maternal iron supplementation attenuates the impact of perinatal copper deficiency but does not eliminate hypotriiodothyroninemia nor impaired sensorimotor development.

Copper, iron and iodine/thyroid hormone (TH) deficiencies disrupt brain development. Neonatal Cu deficiency causes Fe deficiency and may impact thyroidal status. One purpose of these studies was to determine the impact of improved iron status following Cu deficiency by supplementing the diet with iron.

Ctr1 is an apical copper transporter in mammalian intestinal epithelial cells in vivo that is controlled at the level of protein stability.

Copper is an essential trace element that functions in a diverse array of biochemical processes that include mitochondrial respiration, neurotransmitter biogenesis, connective tissue maturation, and reactive oxygen chemistry. The Ctr1 protein is a high-affinity Cu(+) importer that is structurally and functionally conserved in yeast, plants, fruit flies, and humans and that, in all of these organisms, is localized to the plasma membrane and intracellular vesicles. Although intestinal epithelial cell-specific deletion of Ctr1 in mice demonstrated a critical role for Ctr1 in dietary copper absorption, some controversy exists over the localization of Ctr1 in intestinal epithelial cells in vivo.

Perinatal iron and copper deficiencies alter neonatal rat circulating and brain thyroid hormone concentrations.

Copper (Cu), iron (Fe), and iodine/thyroid hormone (TH) deficiencies lead to similar defects in late brain development, suggesting that these micronutrient deficiencies share a common mechanism contributing to the observed derangements. Previous studies in rodents (postweanling and adult) and humans (adolescent and adult) indicate that Cu and Fe deficiencies affect the hypothalamic-pituitary-thyroid axis, leading to altered TH status. Importantly, however, relationships between Fe and Cu deficiencies and thyroidal status have not been assessed in the most vulnerable population, the developing fetus/neonate.

Metabolic crossroads of iron and copper.

Interactions between the essential dietary metals, iron and copper, have been known for many years. This review highlights recent advances in iron-copper interactions with a focus on tissues and cell types important for regulating whole-body iron and copper homeostasis. Cells that mediate dietary assimilation (enterocytes) and storage and distribution (hepatocytes) of iron and copper are considered, along with the principal users (erythroid cells) and recyclers of red cell iron (reticuloendothelial macrophages).

Levels of plasma ceruloplasmin protein are markedly lower following dietary copper deficiency in rodents.

Ceruloplasmin (Cp) is a multicopper oxidase and the most abundant copper binding protein in vertebrate plasma. Loss of function mutations in humans or experimental deletion in mice result in iron overload consistent with a putative ferroxidase function. Prior work suggested plasma may contain multiple ferroxidases.

Anemic copper-deficient rats, but not mice, display low hepcidin expression and high ferroportin levels.

The transmembrane protein ferroportin (Fpn) is essential for iron efflux from the liver, spleen, and duodenum. Fpn is regulated predominantly by the circulating iron regulatory hormone hepcidin, which binds to cell surface Fpn, initiating its degradation. Accordingly, when hepcidin concentrations decrease, Fpn levels increase.

Perinatal copper deficiency alters rat cerebellar purkinje cell size and distribution.

Copper is required for activity of several key enzymes and for optimal mammalian development, especially within the central nervous system. Copper-deficient (CuD) animals are visibly ataxic, and previous studies in rats have demonstrated impaired motor function through behavioral experiments consistent with altered cerebellar development. Perinatal copper deficiency was produced in Holtzman rat dams by restricting dietary copper during the last two thirds of gestation and lactation.

Interactions of peptide amidation and copper: novel biomarkers and mechanisms of neural dysfunction.

Mammalian genomes encode only a small number of cuproenzymes. The many genes involved in coordinating copper uptake, distribution, storage and efflux make gene/nutrient interactions especially important for these cuproenzymes. Copper deficiency and copper excess both disrupt neural function.

Differential impact of copper deficiency in rats on blood cuproproteins.

Sensitive blood biochemical markers of dietary copper status are not yet known. Rat models were used to investigate the response of severe copper deficiency in dams and pups by comparing abundance of several cuproproteins in erythrocytes, white blood cells, and platelets. The hypothesis tested was that copper deficiency would result in changes in abundance of cuproproteins in blood cells.

Copper deficiency alters the neurochemical profile of developing rat brain.

Copper deficiency is associated with impaired brain development and mitochondrial dysfunction. Perinatal copper deficiency was produced in Holtzman rats. In vivo proton NMR spectroscopy was used to quantify 18 cerebellar and hippocampal metabolites on postnatal day 21 (P21).

Augmented cerebellar lactate in copper deficient rat pups originates from both blood and cerebellum.

Copper (Cu) is essential for proper brain development, particularly the cerebellum, and functions as a cofactor for enzymes including mitochondrial cytochrome c oxidase (CCO). Cu deficiency severely limits CCO activity. Augmented lactate in brain of Cu deficient (Cu-) humans and cerebella of Cu- rats is though to originate from impaired mitochondria.

Copper deficiency in rodents alters dopamine beta-mono-oxygenase activity, mRNA and protein level.

Cu is an essential cofactor for at least twelve mammalian enzymes including dopamine beta-mono-oxygenase (DBM), which converts dopamine (DA) to noradrenaline (NA). Previous studies reported that certain Cu-deficient (Cu-) rat tissues have lower NA and higher DA than Cu-adequate (Cu+) tissues, suggesting that DBM function was impaired. However, in vitro studies suggested that DBM activity is higher in Cu- tissue.

Variable response of selected cuproproteins in rat choroid plexus and cerebellum following perinatal copper deficiency.

Recent immunohistochemical characterization of the copper transport protein, Ctr1, reported enriched levels in mouse choroid plexus, and enhancement by copper deficiency. To extend and confirm this, experiments were conducted with Holtzman rats. Following perinatal copper deficiency there was an 80% reduction in brain copper of 24-27 day old copper-deficient (Cu-) rat pups compared to copper-adequate (Cu+) controls.