Copper deficiency increases metallothionein-I mRNA content selectively in rat liver

Effects of Fructose and Stress on Rat Renal Copper Metabolism and Antioxidant Enzymes Function

The effects of a fructose-rich diet and chronic stress on copper metabolism in the kidneys are still understudied. We investigated whether fructose and/or chronic unpredictable stress modulate copper metabolism in a way that affects redox homeostasis, thus contributing to progression of metabolic disturbances in the kidney. We determined protein level of copper transporters, chaperones, and cuproenzymes including cytochrome c oxidase, as well as antioxidant enzymes function in the kidneys of male Wistar rats subjected to 20% liquid fructose supplementation and/or chronic stress. Liquid fructose supplementation increased level of copper chaperone of superoxide dismutase and decreased metallothionein level, while rendering the level of copper importer and copper chaperones involved in copper delivery to mitochondria and trans Golgi network unaffected. Stress had no effect on renal copper metabolism. The activity and expression of renal antioxidant enzymes remained unaltered in all experimental groups. In conclusion, fructose, independently of stress, decreased renal copper level, and modulated renal copper metabolism as to preserve vital cellular function including mitochondrial energy production and antioxidative defense, at the expense of intracellular copper storage.

Copper-induced alterations in rat brain depends on route of overload and basal copper levels

OBJECTIVES

Copper (Cu) is widely used in industry for the manufacture of a vast range of goods including Cu-intrauterine devices (IUDs), electronic products, agrochemicals, and many others. It is also one of the trace elements essential to human health in the right measure and is used as a parenteral supplement in patients unable to ingest food. Elevated Cu levels have been found in the plasma of women using Cu-IUDs and in farmers working with Cu-based pesticides. However, possible alterations due to Cu overload in the brain have been poorly studied. Therefore, the aim of this study was to investigate the effects of Cu administration on rat brain in Cu-sufficient and Cu-deficient animals fed on semi-synthetic diets with different doses of Cu (7 or 35 ppm).

METHODS

We aimed to investigate the effects of Cu administration using two routes of administration: oral and intraperitoneal (IP). Male Wistar rats were feeding (one month) a complete (7 ppm) or a deficient (traces) Cu diets subdivided into three categories oral-, intraperitoneal- (or both) supplemented with copper carbonate (7 to 35 ppm). Cu content in plasma, brain zones (cortex and hippocampus), antioxidant enzyme activities, and protease systems involved in programmed cell death were determined.

RESULTS

The results show that Cu levels and the concentration of Cu in plasma and brain were dose-dependent and administration route-dependent and demonstrated a prooxidative effect in plasma and brain homogenates. Oxidative stress biomarkers and antioxidative enzyme activity both increased under Cu overload, these effects being more noticeable when Cu was administered IP. Concomitantly, brain lipids from cortex and hippocampus were strongly modified, reflecting Cu-induced prooxidative damage. A significant increase in the activities of calpain (milli- and micro-) and caspase-3 activity also was observed as a function of dose and administration route.

CONCLUSION

The findings of this study could be important in evaluating the role of Cu in brain metabolism and neuronal survival.

Congestive heart failure in copper-deficient mice

Copper Deficiency (CuD) leads to hypertrophic cardiomyopathy in various experimental models. The morphological, electrophysiological, and molecular aspects of this hypertrophy have been under investigation for a long time. However the transition from compensated hypertrophy to decompensated heart failure has not been investigated in the study of CuD. We set out to investigate the contractile and hemodynamic parameters of the CuD mouse heart and to determine whether heart failure follows hypertrophy in the CuD heart. Dams of FVB mice were fed CuD or copper-adequate (CuA) diet starting from the third day post delivery and the weanling pups were fed the same diet for a total period of 5 weeks (pre- and postweanling). At week 4, the functional parameters of the heart were analyzed using a surgical technique for catheterizing the left ventricle. A significant decrease in left ventricle systolic pressure was observed with no significant change in heart rate, and more importantly contractility as measured by the maximal rate of left ventricular pressure rise (+dP/dt) and decline (-dP/dt) were significantly depressed in the CuD mice. However, left ventricle end diastolic pressure was elevated, and relaxation was impaired in the CuD animals; the duration of relaxation was prolonged. In addition to significant changes in the basal level of cardiac function, CuD hearts had a blunted response to the stimulation of the beta-adrenergic agonist isoproterenol. Furthermore, morphological analysis revealed increased collagen accumulation in the CuD hearts along with lipid deposition. This study shows that CuD leads to systolic and diastolic dysfunction in association with histopathological changes, which are indices commonly used to diagnose congestive heart failure.

Determination of metallothionein levels in tissues of young rats fed zinc-enriched diets

The objective of this work was to quantify metallothioneins (MT's) in tissues of rats fed different concentrations of zinc, in order to observe the animal response to the metal in relation to different types of diets, and to assess the nutritional status relating to zinc in the diets. Thirty-two Wistar newly-weaned male rats were distributed into four experimental groups and housed in individual cages. They had free access to water and diet containing different zinc concentrations, named RC (AIN 93-like diet), RH (customary diet of the university restaurant), both non-supplemented, and RCS and RHS, supplemented. After four weeks, the animals were killed and liver, kidneys, femurs and testes were isolated to determine metallothionein levels by a Cd/Hb affinity assay. Zinc content was determined by Flame Atomic Absorption Spectroscopy (FAAS). The results showed that zinc supplementation produced no change in the tissue metallothionein profile in the doses under analysis. The highest metallothionein mean concentration was found in the liver - 36.21 ± 0.88 µg/g (mean for RC-RCS groups), and 28.92 ± 5.32 µg/g (mean for RH-RHS groups). Metallothionein concentrations in testes were quite high, considering the small volume of the organ - 19.29 ± 0.54 µg/g (mean for RC-RCS groups), and 17.22 ± 1.07 µg/g (mean for RH-RHS groups). Significant increases in zinc concentration were observed in the liver of young supplemented rats - 38.94 ± 3.43 µg/g of tissue for RCS, and 42.83 ± 2.78 µg/g of tissue for RHS, and in the femurs - 140.04 ± 6.03 µg/g of tissue for RCS, and 86.57 ± 6.95 µg/g of tissue for RHS. The different carrying zinc food matrices caused no change in the adaptive response to metallothionein metabolism, and the lack of responsiveness towards metallothionein synthesis did not invalidate the results of tissue zinc concentration parameters, which suggest different degrees for zinc bioavailability.

Dietary copper deficiency alters protein levels of rat dopamine beta-monooxygenase and tyrosine monooxygenase

Perinatal copper (Cu) deficiency was studied by offering pregnant Sprague Dawley rats a basal diet low in copper, 0.44 mg/kg, and drinking water containing 0 (-Cu) or 20 (+Cu) mg Cu/L as CuSO4 starting at day 7 of gestation and continuing throughout lactation. To investigate dopamine-beta-monooxygenase (DBM) and tyrosine monooxygenase (TM) in adrenal gland and brain, offspring were weaned at Day 21 to treatments of their respective dams for 9 days. Offspring, 30 days old, of Cu-deficient (-Cu) dams were smaller, anemic, and had biochemical features characteristic of severe Cu deficiency. Adrenal DBM enzyme activity of 30-day-old -Cu rats was 40% higher than Cu-adequate (+Cu) rats and DBM protein levels, estimated by Western immunoblot, were 45% higher. Adrenal DBM mRNA levels of -Cu rats were 108% higher than +Cu rats. Adrenal TM protein levels of -Cu rats were 39% higher than +Cu rats. Hypothalamus DBM activity was significantly higher in -Cu than +Cu rats but no reproducible changes in DBM or TM protein levels could be detected by Western immunoblots. Diet history did not impact adrenal gland or hypothalamus levels of actin as detected on reblotted membranes. However, activity of the cuproenzyme Cu,Zn-superoxide dismutase was 50% lower and 30% lower, respectively, in extracts from rat adrenal gland and hypothalamus of -Cu than +Cu rats, indicating altered Cu status in the tissues studied. These data suggest that Cu deficiency is associated with increased formation of DBM and TM protein levels in adrenal gland. Further research will be required to determine the chemical signal responsible for this induction and if DBM or TM protein levels change in other tissues.

Alterações metabólicas e funcionais do cobre em diabetes mellitus

O objetivo desta revisão foi discutir aspectos que envolvem as alterações metabólicas e funcionais do cobre em Diabetes Mellitus. Na presença desta doença, alguns distúrbios funcionais de cobre têm sido caracterizados e explicados em parte por alterações nos processos de absorção, circulação e utilização do elemento. O estado hormonal pode modificar a secreção biliar de cobre e assim repercutir na regulação homeostática da absorção. A redução na atividade da lisil-oxidase, uma cuproenzima, altera a síntese de colágeno e de elastina, comprometendo assim a integridade dos vasos sangüíneos. Tal fato pode agravar o desenvolvimento de complicações vasculares nos diabéticos. Os estudos com diabetes experimental apontam um acúmulo tecidual de cobre nos rins, o que conduz à especulações quanto à gênese da nefropatia diabética. Os experimentos com pacientes diabéticos demonstram irregularidades no cobre circulante, aumento de peroxidação lipídica e estado nutricional inadequado deste micronutriente.