Effect of zinc supplementation on metallothionein, copper, and zinc concentration in various tissues of copper-loaded rats

Serum Zinc and Copper Concentrations and Dyslipidemia as Risk Factors of Cardiovascular Disease in Adults: Data Mining Techniques

This study aimed to examine the relationship between serum cholesterol levels and the ratio of zinc (Zn) and copper (Cu) in the blood serum and the incidence of cardiovascular disease (CVD). In Phase I of the study, 9704 individuals between the age of 35 and 65 years were recruited. Phase II of the cohort study comprised 7561 participants who completed the 10-year follow-up. The variables which were measured at the baseline of the study included gender, age, systolic blood pressure (SBP), diastolic blood pressure (DBP); biochemical parameters including serum Cu, Zn, copper-zinc ratio (Cu/Zn), zinc-copper ratio (Zn/Cu); fasted lipid profile consisting of triglycerides (TG), total cholesterol (TC), high-density lipoprotein (HDL), low-density lipoprotein (LDL) as well as fasting serum glucose, and triglycerides-glucose (TyG) index. Decision tree (DT) and logical regression (LR) models were applied to examine the relationship between the aforementioned factors and CVD. CVD was diagnosed in 837 individuals (378 males and 459 females) out of 7561 participants. According to the LR models, SBP, TC, HDL, age, Zn/Cu, and TyG index for males and SBP, age, TyG index, HDL, TC, Cu/Zn, and Cu for females had the highest correlation with CVD (p-value ≤ 0.033). Based on the DT algorithm, 88% of males with SPB < 129.66 mmHg, younger age (age < 53 years), TyG index < 9.53, 173 ≤ TC < 187 mg/dL, and HDL ≥ 32 mg/dL had the lowest risk of CVD. Also, 98% of females with SBP < 128 mmHg, TyG index < 9.68, age < 44, TC < 222 mg/dL, and HDL ≥ 63.7 mg/dL had the lowest risk of CVD. It can be concluded that the Zn/Cu for men and Cu/Zn for women, along with dyslipidemia and SBP, could significantly predict the risk of CVD in this cohort from northeastern Iran.

Effect of oral zinc regimens on human hepatic copper content: a randomized intervention study

Zinc inhibits intestinal copper uptake, an effect utilized for treating Wilson’s disease (WD). We used copper-64 (⁶⁴Cu) PET/CT to examine how much four weeks of treatment with different zinc regimens reduced the hepatic ⁶⁴Cu content after oral ⁶⁴Cu administration and test if alternative regimens were noninferior to the standard regimen of zinc acetate 50 mg × 3 daily. Forty healthy persons were randomized to four different zinc protocols. The WD standard treatment zinc acetate 50 mg × 3 reduced the hepatic ⁶⁴Cu content from 26.9 ± 7.5% to 13.3 ± 5.6% of the administered ⁶⁴Cu. Zinc gluconate 50 mg × 3 was noninferior (P = 0.02) (35.8 ± 9.0% to 17.4 ± 7.5%). Zinc acetate 150 mg × 1 (33.1 ± 9.9% to 17.4 ± 7.5%) and zinc gluconate 150 mg × 1 (28.1 ± 6.7% to 22.0 ± 6.7%) were less effective. These effects were intra- and inter-individually highly variable, and 14% had no effect of any zinc regimen, which may explain disparities in zinc treatment efficacy in WD patients.

Copper biodistribution after acute systemic administration of copper gluconate to rats

Neurodegenerative disorders have been linked to the decrease of copper concentrations in different regions of the brain. Therefore, intake of micronutrient supplements could be a therapeutic alternative. Since the copper distribution profile has not been elucidated yet, the aim of this study was to characterize and to analyze the concentration profile of a single administration of copper gluconate to rats by two routes of administration. Male Wistar rats were divided into three groups. The control group received vehicle (n = 5), and the experimental groups received 79.5 mg/kg of copper orally (n = 4-6) or 0.64 mg/kg of copper intravenously. (n = 3-4). Blood, striatum, midbrain and liver samples were collected at different times. Copper concentrations were assessed using atomic absorption spectrophotometry. Copper concentration in samples from the control group were considered as baseline. The highest copper concentration in plasma was observed at 1.5 h after oral administration, while copper was quickly compartmentalized within the first hour after intravenous administration. The striatum evidenced a maximum metal concentration at 0.25 h for both routes of administration, however, the midbrain did not show any change. The highest concentration of the metal was held by the liver. The use of copper salts as replacement therapy should consider its rapid and discrete accumulation into the brain and the rapid and massive distribution of the metal into the liver for both oral and intravenous routes. Development of controlled-release pharmaceutical formulations may overcome the problems that the liver accumulation may imply, particularly, for hepatic copper toxicity.

Zn Induces Lipophagy via the Deacetylation of Beclin1 and Alleviates Cu-Induced Lipotoxicity at Their Environmentally Relevant Concentrations

In this study, the mechanisms of environmentally relevant doses of Cu and Zn mixtures influencing lipid deposition and metabolism were investigated in freshwater teleost yellow catfish Pelteobagrus fulvidraco (2 months old, 4.95 (t0.01 g, mean ± SEM). Our study indicated that waterborne Cu exposure increased lipid content, while Zn activated lipophagic flux and alleviated Cu-induced lipid accumulation. Yellow catfish hepatocytes treated with Zn or Zn + Cu activated autophagy-specific lipophagy, decreased lipid storage, and increased nonesterified fatty acid (NEFA) release, suggesting a causal relationship between lipophagy and lipid droplet (LD) breakdown under Zn and Zn + Cu conditions. Our further investigation found that Beclin1 deacetylation by sirtuin 1 (SIRT1) was required for Zn- and Zn + Cu-induced lipophagy and lipolysis, and lysine residues 427 and 434 were key sites for Beclin1 deacetylation. Taken together, these findings show that the Zn-induced deacetylation of Beclin1 promotes lipophagy as an important pathway to alleviate Cu-induced lipid accumulation in fish, which reveals a previously unidentified mechanism for understanding the antagonistic effects of Cu and Zn on metabolism at their environmentally relevant concentrations. Our results highlight the importance of combined exposure when the biological effects of heavy metals are evaluated during environmental risk assessments.

Environmental levels of Zn do not protect embryos from Cu toxicity in three species of amphibians

Contaminants often occur as mixtures in the environment, but investigations into toxicity usually employ a single chemical. Metal contaminant mixtures from anthropogenic activities such as mining and coal combustion energy are widespread, yet relatively little research has been performed on effects of these mixtures on amphibians. Considering that amphibians tend to be highly sensitive to copper (Cu) and that metal contaminants often occur as mixtures in the environment, it is important to understand the interactive effects that may result from multiple metals. Interactive effects of Cu and zinc (Zn) on amphibians have been reported as antagonistic and, conversely, synergistic. The goal of our study was to investigate the role of Zn in Cu toxicity to amphibians throughout the embryonic developmental period. We also considered maternal effects and population differences by collecting multiple egg masses from contaminated and reference areas for use in four experiments across three species. We performed acute toxicity experiments with Cu concentrations that cause toxicity (10-200 μg/L) in the absence of other contaminants combined with sublethal concentrations of Zn (100 and 1000 μg/L). Our results suggest very few effects of Zn on Cu toxicity at these concentrations of Zn. As has been previously reported, we found that maternal effects and population history had significant influence on Cu toxicity. The explanation for a lack of interaction between Cu and Zn in this experiment is unknown but may be due to the use of sublethal Zn concentrations when previous experiments have used Zn concentrations associated with acute toxicity. Understanding the inconsistency of amphibian Cu/Zn mixture toxicity studies is an important research direction in order to create generalities that can be used to understand risk of contaminant mixtures in the environment.

Metal and metallothionein distribution in different tissues of the Mediterranean clam Venerupis philippinarum during copper treatment and detoxification

Filter feeding animals can accumulate large amount of contaminants in their body through particles filtered from seawater. In particular, copper is interesting since it plays important roles as co-factor of numerous proteins but its toxicity is well established, also because it can readily generate free radicals or oxidize cellular components through their redox activity. Its availability is tightly regulated within cells: it is immediately transferred to metallothionein (MT) that in turn provides efficient and specific mechanisms for its intracellular storage and transport. The aim of this study was to evaluate the acute effect of sublethal copper concentrations in Venerupis philippinarum, by studying the kinetics of copper, zinc (for its interactions at the sites of intake or elimination with the accumulation of other essential and not essential trace metals) and metallothionein accumulation under laboratory conditions. The time-course of metal accumulation/elimination is similar in digestive gland and gills and importantly it is dose-dependent. Both copper and zinc increase slowly within cells, reaching a maximum concentration at the end of the exposure period. During the detoxification period, the metal levels in digestive gland and gills rapidly decrease, with different kinetics in the two tissues. Positive correlations between metallothionein accumulation and copper or zinc concentrations have been verified in both treated groups. The obtained data demonstrated the involvement of MTs in detoxification strategies after a recovery period in clean seawater.

Influence of dietary zinc and copper on apparent mineral retention and serum biochemical indicators in young male mink (Mustela vison)

An experiment was conducted in a 3 × 3 (Cu × Zn) factorial experiment based on a completely randomized design to evaluate the effects of dietary copper and zinc on apparent mineral retention and serum biochemical indicators in young male mink on a corn-fish meal based diet. Animals were fed basal diets supplemented with Cu from copper sulfate (CuSO4) and Zn from zinc sulfate (ZnSO4). Supplemental Cu levels were 0, 15, and 30 mg/kg copper, respectively, while supplemental Zn levels were 0, 150, and 300 mg/kg, respectively. A metabolism trial of 4 days was conducted during the last week of experimental feeding. Blood samples were collected via the toe clip to determine blood hematology and blood metabolites. Copper excretion, retention, and digestibility were influenced by dietary copper (P < 0.05), however, there was also a zinc-copper interaction. Copper digestibility and retention were substantially reduced when zinc was added to the low copper diet but showed little change with zinc supplementation of the high copper diet. Both plasma Cu and plasma Zn were influenced by dietary level of the respective mineral (P < 0.05). There was no influence of dietary copper on plasma zinc; however, high Zn in the diet reduced plasma Cu concentrations. There was a zinc-copper interaction for plasma Cu (P = 0.053). Cu-Zn superoxide dismutase (Cu-Zn SOD) activity tended to be influenced by dietary zinc (P = 0.065) and dietary copper (P = 0.035). Dietary copper had a significant effect on ceruloplasmin (CER) and triglyceride (TG) concentrations (P < 0.05). Our results show that moderately high Zn in the diet (Zn:Cu ratio of 40:1) significantly reduce the apparent Cu digestibility. Our results also show that moderately high Cu in the diet increases Cu retention, but not reduces Zn absorption, and moderately high Zn in the diet reduced plasma Cu concentrations and CER activity.

Effects of different sources and levels of copper on growth performance, nutrient digestibility, and elemental balance in young female mink (Mustela vison)

An experiment was conducted in a 3 × 3 + 1 factorial experiment based on a completely randomized design to evaluate the effects of different sources of copper on growth performance, nutrient digestibility and elemental balance in young female mink on a corn-fishmeal-based diet. Animals in the control group were fed a basal diet (containing 8.05 mg Cu/kg DM; control), which mainly consisted of corn, fish meal, meat bone meal, and soybean oil, with no copper supplementation. Minks in other nine treatments were fed basal diets supplemented with Cu from reagent-grade copper sulfate, tribasic copper chloride (TBCC) and copper methionate. Cu concentrations of experiment diets were 10, 25, and 40 mg/kg copper. A metabolism trial of 4 days was conducted during the last week of experimental feeding. Final body weight and average daily gain increased (linear and quadratic, P < 0.05) as Cu increased in the diet; maximal growth was seen in the Cu25 group. Cu supplementation slightly improved the feed conversion rate (P = 0.095). Apparent fat digestibility was increased by copper level (P = 0.020). Retention nitrogen was increased by copper level (linear, P = 0.003). Copper source had a significant effect on copper retention with Cu-Met and copper sulfate treatments retention more than TBCC treatments (P < 0.05). Our results indicate that mink can efficiently utilize added dietary fat and that Cu plays an important role in the digestion of dietary fat in mink, and mink can efficiently utilize Cu-Met and CuSO4.

Brain-Delivery of Zinc-Ions as Potential Treatment for Neurological Diseases: Mini Review

Homeostasis of metal ions such as Zn(2+) is essential for proper brain function. Moreover, the list of psychiatric and neurodegenerative disorders involving a dysregulation of brain Zn(2+)-levels is long and steadily growing, including Parkinson's and Alzheimer's disease as well as schizophrenia, attention deficit and hyperactivity disorder, depression, amyotrophic lateral sclerosis, Down's syndrome, multiple sclerosis, Wilson's disease and Pick's disease. Furthermore, alterations in Zn(2+)-levels are seen in transient forebrain ischemia, seizures, traumatic brain injury and alcoholism. Thus, the possibility of altering Zn(2+)-levels within the brain is emerging as a new target for the prevention and treatment of psychiatric and neurological diseases. Although the role of Zn(2+) in the brain has been extensively studied over the past decades, methods for controlled regulation and manipulation of Zn(2+) concentrations within the brain are still in their infancy. Since the use of dietary Zn(2+) supplementation and restriction has major limitations, new methods and alternative approaches are currently under investigation, such as the use of intracranial infusion of Zn(2+) chelators or nanoparticle technologies to elevate or decrease intracellular Zn(2+) levels. Therefore, this review briefly summarizes the role of Zn(2+) in psychiatric and neurodegenerative diseases and highlights key findings and impediments of brain Zn(2+)-level manipulation. Furthermore, some methods and compounds, such as metal ion chelation, redistribution and supplementation that are used to control brain Zn(2+)-levels in order to treat brain disorders are evaluated.

Interaction between copper and zinc in metal accumulation in rats with particular reference to the synthesis of induced-metallothionein

The effectiveness of Zn at moderating the pro-oxidant effects of Cu was evaluated in two rat models that differed in the route and mode of administration. The endpoints investigated included measurement of the concentrations of Cu, Zn, metallothionein and glutathione concentrations, as well as SOD and catalase activity, in liver, kidneys and intestine. In a sub-chronic animal model, the hepatic accumulation of Cu was achieved by administration of dietary Cu (1.8 g/kg solid diet) for 30 days after which oral Zn (6g/kg solid diet) was given. Cu treatment induced an increase in the hepatic and intestinal concentration of Cu of 66 and 455%, respectively, that was not associated with synthesis of metallothionein synthesis, but rather appeared to be related to the higher activity of SOD. Subsequent administration with Zn after dietary Cu induced an increase in the hepatic and intestinal metallothionein content of more twice and reduced the Cu content to control values. Thus, Zn could act as both a competitor for absorption on the luminal side of the intestinal epithelium inducing the synthesis of metallothionein. In the second animal model, we studied the effects of interaction between Cu and Zn administered by i.p. injection at the dose of 3 and 10mg/kg, respectively; Zn was administered subsequent to Cu overload. In this case, when Zn was administered, Cu was already deposited in tissues and thus there is no competition between two metals at the level of membrane transport. In this experimental model treatment with Cu alone induced liver metallothionein synthesis, and the subsequent treatment with Zn did not decrease the hepatic content of Cu. One explanation for these observations is that Zn induces the synthesis of metallothionein, which binds Cu for which it has a higher affinity. Moreover, after treatment with Zn, SOD activity in the liver decreases of almost 30% with respect to treatment with alone Cu, suggesting that Zn has a protective effect.

Zinc therapy increases duodenal concentrations of metallothionein and iron in Wilson's disease patients

OBJECTIVE

Wilson's disease is effectively treated by zinc administration which, in vitro, increases metallothionein concentrations. To ascertain whether the latter also occurs in humans we measured metallothionein and trace element concentrations in the duodenal mucosa of 15 Wilson's disease patients: 12 treated with zinc sulphate, two treated with penicillamine, and one not yet on treatment. The control group consisted of 17 patients with dyspepsia, who underwent the same study protocol.

METHODS

Metallothionein and trace element concentrations were measured in duodenal mucosa biopsies according to the silver-saturation hemolysate method and atomic absorption spectrophotometry.

RESULTS

Metallothionein concentrations increased by 1500% after zinc and 150% after penicillamine in Wilson's disease patients, with respect to controls who had negative endoscopy and Wilson's disease patients who were not treated. A significant correlation was found between metallothionein and duodenal zinc concentrations. Mucosal iron concentration increased in Wilson's disease patients whether they were treated with zinc or penicillamine. Duodenum with duodenitis also had significantly increased iron levels compared with normal duodenum.

CONCLUSIONS

Zinc administration increases intestinal metallothionein in Wilson's disease patients. The blockade of copper absorption and its elimination in the stools on desquamation of the intestinal cells probably explains one of the mechanisms underlying the effect of zinc treatment. Despite normal endoscopy, Wilson's disease patients present increased mucosal iron concentrations similar to those in controls with duodenitis. Metallothionein may therefore prevent oxidative damage caused by metal toxicity.

Copper toxicity and copper-zinc interactions in amphibian embryos

The copper hazard was evaluated by means of a 7-day toxicity test with Bufo arenarum embryos. The LC50 and LC10 values from 24 to 168 h of exposure were approx. 0.085 and 0.05 mg Cu2+/1, respectively, while the LC90 resulted in 0.155 mg Cu2+/1 but in this case from 96 h onwards the LC90 diminished up to approx. 0.105 mg Cu2+/1. These data plotted as Toxicity Profiles (TOP) provide a better understanding of concentration and time-dependent thresholds. For instance, exposure threshold occurs within the first 24 h of treatment while for concentration thresholds LC10 and LC90 seem to be more meaningful than LC50 because the S.D. of this last value is overlapping those of LC10 and LC90 for most of the exposure period evaluated. Toxicity data corresponds to a pH of 6.8 which is normal for the maintaining media. Combined treatments of copper and zinc point out a beneficial effect of zinc proportional to the zinc concentration in the maintaining media, e.g. 100% of protection was achieved with 30 mg Zn2+/1 for a copper concentration exerting 90% of mortality. The presence of Cu2+ did not enhance Zn2+ toxicity. The results are discussed in terms of water quality criteria for wildlife and human health protection purposes.