Copper levels after oral zinc

Distinct function of Chlamydomonas CTRA-CTR transporters in Cu assimilation and intracellular mobilization

Successful acclimation to copper (Cu) deficiency involves a fine balance between Cu import and export. In the green alga Chlamydomonas reinhardtii, Cu import is dependent on a transcription factor, Copper Response Regulator 1 (CRR1), responsible for activating genes in Cu-deficient cells. Among CRR1 target genes are two Cu transporters belonging to the CTR/COPT gene family (CTR1 and CTR2) and a related soluble protein (CTR3). The ancestor of these green algal proteins was likely acquired from an ancient chytrid and contained conserved cysteine-rich domains (named the CTR-associated domains, CTRA) that are predicted to be involved in Cu acquisition. We show by reverse genetics that Chlamydomonas CTR1 and CTR2 are canonical Cu importers albeit with distinct affinities, while loss of CTR3 did not result in an observable phenotype under the conditions tested. Mutation of CTR1, but not CTR2, recapitulates the poor growth of crr1 in Cu-deficient medium, consistent with a dominant role for CTR1 in high-affinity Cu(I) uptake. On the other hand, the overaccumulation of Cu(I) (20 times the quota) in zinc (Zn) deficiency depends on CRR1 and both CTR1 and CTR2. CRR1-dependent activation of CTR gene expression needed for Cu over-accumulation can be bypassed by the provision of excess Cu in the growth medium. Over-accumulated Cu is sequestered into the acidocalcisome but can become remobilized by restoring Zn nutrition. This mobilization is also CRR1-dependent, and requires activation of CTR2 expression, again distinguishing CTR2 from CTR1 and consistent with the lower substrate affinity of CTR2.

ONE SENTENCE SUMMARY

Regulation of Cu uptake and sequestration by members of the CTR family of proteins in Chlamydomonas.

Dietary Zinc and Fibre Source can Influence the Mineral and Antioxidant Status of Piglets

The study investigated the effect of dietary zinc glycine chelate and potato fibre on the absorption and utilisation of Zn, Cu, Fe, and Mn; the activity of Zn-containing enzymes (superoxide dismutase, SOD; alkaline phosphatase, ALP); and zinc transporter concentrations (metalothionein1, MT1; zinc transporter1, ZnT1) in tissues, with a special emphasis on the small intestine. Twenty-four barrows (Danbred × Duroc) were randomly allotted to four diets (supplemented with 10 g/kg of crude fibre and 120 mg Zn/kg) that consisted of cellulose and either zinc sulphate (C) or zinc glycinate (ZnGly), or contained potato fibre supplemented with ZnSO4 (PF) or ZnGly (PF + ZnGly). Feeding PF can influence the Zn absorption in the small intestine due to reduced zinc transporters MT1 and ZnT1 in the jejunum. The activity of antioxidant enzyme SOD and liver ZnT1, and duodenal iron concentrations were increased in the PF treatments. Dietary ZnGly did not significantly influence the Zn distribution, but it may alter the absorption of Fe and Mn. Given the elevated content of thiol groups and the Zn/Cu ratio in plasma, as well as the altered SOD activity and MT content in the tissues, we can conclude that feeding PF and ZnGly can influence the mineral and antioxidant status of growing piglets. However, further research is needed in order to elucidate the effect of both dietary sources on the transport systems of other minerals in enterocytes.

Factors determining percutaneous metal absorption

Metals play a vital role in human, animal and plant physiology, and important research, past and ongoing, is directed towards exploring the interrelated mechanisms that govern their penetration through skin. Much insight has been gained through these efforts, but our understanding of the process is still incomplete, mainly due to the failure to allow for the effects of chemical speciation of metallic elements, especially the transition metals. Also, the skin as target organ presents imponderable and wide margins of variability. In vivo permeability is subject to homeostasis regulating the overall organism; in vitro, the sections of skin used for diffusion experiments are likely to present artifacts. Endeavors to define rules governing skin penetration to give predictive quantitative structure-diffusion relationships for metallic elements for risk assessment purposes have been unsuccessful, and penetration of the skin still needs to be determined separately for each metal species, either by in vitro or in vivo assays. Phenomena observed by us and other investigators, which appear to determine the process of skin permeation for a number of metals, are reviewed, separating the exogenous factors from the characteristics of the skin or other endogenous factors.

Blood levels of copper, iron, zinc, and lead in adults in India and Pakistan and the effect of oral zinc supplementation for six weeks

Deficiency in the intake of trace elements, such as copper (Cu), iron (Fe), selenium (Se), and zinc (Zn), is very common in the general population of most developing countries. A preliminary study in India and Pakistan showing the plasma levels of Zn and Fe indicates that approx 50% of the subjects who participated have low levels of both Fe and Zn, suggesting a marginal deficiency. The low plasma levels of these elements are more pronounced in females. The mean levels of Ze, Cu, and Fe in the plasma of 83 subjects were 0.71 +/- 0.11, 0.96 +/- 0.10, and 0.80 +/- 0.12 mg/L, respectively. The Cu:Zn ratio in the plasma was 1.43 +/- 0.16. Three groups of 15 subjects each were given three different levels of oral supplements of Zn (15, 30, and 45 mg of Zn as Zn gluconate) for 6 wk, and blood samples were analyzed during various intervals. Plasma concentration of Zn increased significantly (p < 0.001) in all the groups after 4 wk of supplementation and reached almost normal levels after 6 wk. Along with the increase in Zn, there was a significant decrease (p < 0.001) in plasma Cu levels. There were no changes in the concentration of Fe during the supplementation period. The supplementation was well tolerated by most subjects. The results of this pilot study indicate that Zn supplementation is a practical possibility comparable to that of Fe supplementation in order to prevent marginal Zn deficiency in vulnerable groups in the general population of developing countries.

Wilson's disease: resolution of MRI lesions following long-term oral zinc therapy

A 28-year-old man with Wilson's disease developed neurological deterioration after a low-dose of d-penicillamine treatment for 2 weeks. He showed an akinetic rigid syndrome with generalized dystonia. Brain magnetic resonance images (MRI) on T2 and proton weighted images showed an increased signal intensity over the thalamus, basal ganglia and brainstem, especially the midbrain and pons. After treatment had been changed to zinc sulphate, the akinetic-rigid syndrome and dystonia were improved slowly in the following 4 years. Serial MRI studies showed a gradual resolution of the lesions. His current neurological status was almost normal except for dysarthria and mild intention tremor.

Effect of dietary caffeine and zinc on the activity of antioxidant enzymes, zinc, and copper concentration of the heart and liver in fast-growing rats

The purpose of this study was to determine the relationship between concentrations of Zn and Cu and the activities of superoxide dismutase and glutathione peroxidase in the heart and liver of young rat pups whose dams were fed a diet supplemented with caffeine and/or Zn. Four groups of dams with their newborn pups were fed one of the following diets for 22 d: 20% protein basal diet; the basal diet supplemented with caffeine (2 mg/100 body wt); the basal diet supplemented with Zn (300 mg/kg diet); or the basal diet supplemented with caffeine plus Zn. The Cu levels in the livers of the pups were decreased by maternal intake of the caffeine and Zn diet. The maternal intake of the caffeine diet increased Mn-superoxide dismutase (MnSOD) activity and Cu, Zn-superoxide dismutase (Cu,ZnSOD) in the heart of the pups. On the other hand, the activity of Cu,ZnSOD was significantly reduced in the liver of pups whose dams consumed a caffeine, Zn, or caffeine plus Zn diet. Cu,ZnSOD activity in the liver of the pups seems to be correlated with Cu levels in the tissue. Selenium-dependent glutathione peroxidase (GSH-Px) activities in the heart and liver showed no difference among the groups. The effect of dietary caffeine and/or Zn on the activity of antioxidant enzymes in the heart and liver were different in young rats. The activities of these enzymes in the heart were lower than in the liver of 22-d-old rats. Our experiments indicate that the heart has limited defenses against the toxic effects of peroxides when compared to the liver.

Interactions related to trace elements in parenteral nutrition

Trace elements (TE) are now commonly added into the nutritive admixtures used in total parenteral nutrition (TPN) to prevent deficiencies which can be observed in patients undergoing long-term intravenous feeding. Although the needs in TE are not exactly known during a TPN, some of them must be considered as essential according to the results of studies dealing with general nutritional deficiencies. Among essential TE copper, iron and zinc are found at relatively high levels in organism. Chromium, manganese and selenium are also very important even though they are present at lower levels. In the case of a parenteral nutrition, the composition of the mixture is precisely defined and both digestion and absorption steps are shunted. Nevertheless, beneficial and/or negative physicochemical and metabolic interactions can occur between TE and the other nutrients. These interactions must be studied and taken into account because they can modify the bioavailability of the trace elements. In this article, our aim is to review the main recent bodies of knowledge which could be helpful to understand and prevent nutritional problems linked to these interactions during parenteral nutrition.

Zinc-induced copper deficiency

Copper deficiency was found in an adult patient who had received excessive daily oral zinc for 10 mo. The deficiency was characterized by hypochromic-microcytic anemia, leukopenia, and neutropenia. Although initially thought to be caused by iron deficiency, the anemia did not respond to oral or intravenous iron. Cessation of zinc tablets and ingestion of an oral copper preparation daily for 2 mo failed to correct the anemia or leukopenia. It was not until shortly after intravenous administration of a cupric chloride solution during a 5-day period, at a total dose of 10 mg, that serum copper and ceruloplasmin levels increased and the anemia, leukopenia, and neutropenia resolved. These data suggest that the elimination of excess zinc is slow and that, until such elimination occurs, the intestinal absorption of copper is blocked.

3 years of continuous oral zinc therapy in 4 patients with Wilson's disease

A competitive relationship exists between copper and zinc: among other effects, excessive dietary zinc is known to decrease the absorption of copper from the gastro-intestinal tract. The purpose of this study is to investigate the effectiveness of oral zinc therapy in 4 patients with Wilson's disease, who, during a 3-year period, took zinc as their only medication to influence their copper metabolism. Physical examinations, oral 64Cu loading tests, plasma concentrations of copper, zinc and ceruloplasmin, and the urinary copper excretion were used to monitor the effect of therapy. The dosages used ranged from 3 x 100 to 3 x 400 mg zinc sulphate per day. The clinical and biochemical results of the oral zinc therapy were good in all 4 patients and no toxic side-effects were seen. Our conclusion from this study is that oral zinc may well be a low toxic alternative to D-penicillamine in the treatment of Wilson's disease.

Zinc concentrations in hair, plasma, and saliva and changes in taste acuity of adults supplemented with zinc

The effect of zinc supplementation as zinc acetate (15 mg Zn/day for 5 weeks) was determined on stimulated parotid salivary zinc levels and taste acuity. In addition, zinc and copper levels of hair and plasma in 10 healthy subjects (five male and five female) between the ages of 17 and 37 years were studied. Presupplementation and 5 weeks postsupplementation levels were evaluated as well. Taste acuity for sweet improved with zinc supplementation and returned to presupplementation levels after supplementation ceased. No changes in plasma copper or salivary zinc levels were found with zinc supplementation although stimulated parotid saliva flow rate increased. Plasma zinc levels increased significantly while hair copper increased slightly with supplementation. All indices returned to presupplementation levels by 5 weeks after cessation of supplementation.