• Title, Summary, Keyword: zinc homeostasis

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Estimation of the Endogenous Pancreatic/Biliary Zinc Pool and the Effect of Phytate and Calcium on Zinc Homeostasis

  • Kwun, In-Sook;Donald Oberleas
    • Preventive Nutrition and Food Science
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    • v.2 no.1
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    • pp.35-41
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    • 1997
  • The pancreas is an important organ in the maintenance of zinc homeostasis. Endogenous zinc is con-tinuously secreted via pancreatic exocrine fluid or to a lesser extent in bile. Much of the endogenous secretion must be reabsorbed to sustain zinc homeostasis. The objective of this study was to estimate the relative size of the pancreatic/biliary zinc pool in comparision to the dietary zinc intake, and to study the effect of the phytate and calcium on the zinc homeostasis using a rat model. At the termination of the experiment, pan-creatic/biliary fluid was collected from the rats. Both radioactivity and total zinc were measured and the relative size of the pancreatic/biliary zinc pool was estimated. To determine the effect of phytate and calcium on zinc homeostsis, dietary zinc intake, the amount of zinc in pancreatic.biliary fluid and fecal zinc excretion were measured. The flow rate of pancreatic/biliary fluid, as corrected for tubing constriction, gives the corrected zinc concentration in the pancreatic/biliary fluid was 2.2 times higher than dietary zinc intake. To maintain zinc homeostasis, zinc absorption/reabsorption was very efficient in the current model; 76%, 88% of absorption/reabsorption for low calcium group and high calcium group 81% for phytate group and non-phytate group, respectively.

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Effects of Phytate and Calcium on the Reabsorption of Endogenous Zinc in Zinc-Depleted Bats

  • Sook, Kwun-In;Oberleas Donald
    • Journal of Nutrition and Health
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    • v.30 no.4
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    • pp.394-405
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    • 1997
  • Endogenous zinc is important for maintaining zinc homeostasis because the size of endogenous zinc pool is almost 3-4 times bigger than that of dietary zinc. The purpose of this study was to examine the phytate effect on the reabsorption of endogenous zinc and the additional Ca effect on the phytate effect. Rats were fed a casein-based diet with added sodium phytate containing either high(1.6%) or low(0.8%) Ca concentrations for 4 weeks to reduce the body zinc pool. After the depletion period, $^{65}$ Zn was given by intraperitoneal injection to label the endogenous zinc pool. Rats were then assigned into phytate or non-phytate group within the same Ca group. feces were collected for 2 weeks of the initial collection period and 1 week after dietary crossover. The ratios of excreted fecal $^{65}$ Zn radioactivity of phytate group non-phytate group were determined as a measure of the phytate effect on the endogenous zinc. Mean fecal $^{65}$ Zn radioactivity was higher in the phytate group than in the non-phytate group during the entire 3 weeks of the collection period in the low Ca group, and during the initial collection period in the high Ca group(p <0.0001). This study showed an adverse phytate effect on endogenous zinc at both high and low dietary Ca levels. Elevated dietary Ca levels showed a synergistic effect on the phytate effect on endogenous zinc(p <0.05). These results imply greater phytate effect on zinc homeostasis rather than on zinc bioavailability through complexing with the endogenous zinc which is larger portion than the dietary zinc on zinc homeostasis.

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Cadmium Altered Gene Expression Related to Zinc Homeostasis in the Mouse Brain (카드뮴이 마우스 뇌에서 아연의 항상성에 관여하는 유전자발현에 미치는 영향)

  • Park Jong-An;Yoe Eun-Young;Nam Sang-Hun;Jang Bong-Ki;Lee Jong-Wha;Kim Wan-Jong
    • Environmental Analysis Health and Toxicology
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    • v.19 no.4
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    • pp.389-399
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    • 2004
  • Metallothionein (MT), a small protein molecule which can bind or release metal ions, is involved in the regulation of cellular metal homeostasis. This study was investigated the accumulation of cadmium in blood, tissue (liver, kidney and brain), and the effect of cadmium on several key genes (MT-I, MT-II, ZnT-1) in zinc metabolism in the mouse. Mouses weighing 20∼25 g were randomly assigned to control and cadmium treated group (Cd group). Cd group was intraperitoneally injected with cadmium 2, 4, 8 mg/kg and control group was administerd with saline. Mouses of each group were sacrificed by decapitation 4 hours after the administration of cadmium. Cadmium contents in blood, liver, kidney and brain were increased by a dose-dependent manner. Accumulation of cadmium was mainly occurred in liver and kidney. Induction of MT-I and MT-II protein was increased, but ZnT-1 expression was decreased in a dose-dependent manner by the treatment of 2∼8 mg/kg cadmium. These results suggested that cadmium can be transported to brain and alter the expression of several key genes in zinc homeostasis.

Zinc and Its Transporters in Epigenetics

  • Brito, Sofia;Lee, Mi-Gi;Bin, Bum-Ho;Lee, Jong-Soo
    • Molecules and Cells
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    • v.43 no.4
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    • pp.323-330
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    • 2020
  • Epigenetic events like DNA methylation and histone modification can alter heritable phenotypes. Zinc is required for the activity of various epigenetic enzymes, such as DNA methyltransferases (DNMTs), histone acetyltransferases (HATs), histone deacetylases (HDACs), and histone demethylases, which possess several zinc binding sites. Thus, the dysregulation of zinc homeostasis can lead to epigenetic alterations. Zinc homeostasis is regulated by Zinc Transporters (ZnTs), Zrt- and Irt-like proteins (ZIPs), and the zinc storage protein metallothionein (MT). Recent advances revealed that ZIPs modulate epigenetics. ZIP10 deficiency was found to result in reduced HATs, confirming its involvement in histone acetylation for rigid skin barrier formation. ZIP13 deficiency, which is associated with Spondylocheirodysplastic Ehlers-Danlos syndrome (SCD-EDS), increases DNMT activity, leading to dysgenesis of dermis via improper gene expressions. However, the precise molecular mechanisms remain to be elucidated. Future molecular studies investigating the involvement of zinc and its transporters in epigenetics are warranted.

Identifiaction and Molecular Size of Zine-Binding Ligands in Pancreatic/Biliary Fluid of Rats

  • Kwun, In-Sook;Donald Oberleas
    • Preventive Nutrition and Food Science
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    • v.2 no.1
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    • pp.42-48
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    • 1997
  • the exocrine pancreatic secretion is an important factor in the maintenance of zinc homeostasis. The daily pancreatic secretion of zinc into the gastrointestinal tract may be two or more times the daily dietary zinc intake. The objective of this study was to examine the distribution of proteins and zinc in pancreatic/biliary fluid following intraperitoneal {TEX}${65}^Zn${/TEX} injection into dietary prepared Sprague-Dawly rats. Distribution of zinc-binding protein in Sephadex G-75 subfractions showed a peak corresponding to the high molecular weight protein standard(<66kDa) in the pancreatic/biliary fluid. Zinc also was associated with the 29~35kDa mole-cular weight proteins. These are similar in size with zinc-containing enzymes, carboxypeptidase A and car-boxypeptidase B. A more remarkable small molecular weight fraction eluted beyond the 6.5kDa standard pro-tein peak. These results show the presence of small molecular weight compound in pancreatic/biliary fluid associated with zinc . These small molecular weight compounds may serve as zinc-binding ligands for the secretion of enogenous zinc into the duodenum. These findings suggest that these lignads may dissociate zinc in the duodenum thus making it vulnerable to complexation with phytate in the upper gastrointestinal tract rendering the zinc unavailable for reabsorption.

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Molecular Size and Distribution of Zinc-binding Ligands in Rat Pancreatic Tissue

  • Kwun, In-Sook;Donald Oberleas
    • Preventive Nutrition and Food Science
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    • v.2 no.3
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    • pp.219-224
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    • 1997
  • The pancreas is an important organ in the maintenance of zine homeostasis. The pancreatic tissue used in this study was obtained from rats fed varying levels of dietary Ca nd phytate followed by intraperitoneal {TEX}${65}^Zn${/TEX} injection. THe objective of this study was to determine the molecular size and distribution of compounds that may represent zinc-binding complexes in pancreatic tissue homogenates. The supernatant of the homogenized pancreatic tissue was separated using a Sephadex G-75 column with Tris buffer at pH 8.1. All subfractions were assayed for zinc, protein and {TEX}${65}^Zn${/TEX} activity. The elution of subfractions from pancreatic tissue homogenates showed a prominent peak corresponding to the high molecular weight protein standard (>66kd). A sall molecular weigth protein (<6.5kd), that was absorbed at 280nm, was also present: prominently in low Ca group, however not much as in high Ca group. These small compounds may combine weakly with zinc in pancreatic tissue an serve as zinc-binding ligands in pancreatic/biliary fluid. In the duodenum, these ligands dissociate zinc into an ionic form which becomes vulnerable to phytate complexation.

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Roles of Zinc-responsive Transcription Factor Csr1 in Filamentous Growth of the Pathogenic Yeast Candida albicans

  • Kim, Min-Jeong;Kil, Min-Kwang;Jung, Jong-Hwan;Kim, Jin-Mi
    • Journal of Microbiology and Biotechnology
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    • v.18 no.2
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    • pp.242-247
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    • 2008
  • In the fungal pathogen Candida albicans, the yeast-to-hyphal transition occurs in response to a broad range of environmental stimuli and is considered to be a major virulence factor. To address whether the zinc homeostasis affects the growth or pathogenicity of C. albicans, we functionally characterized the zinc-finger protein Csr1 during filamentation. The deduced amino acid sequence of Csr1 showed a 49% similarity to the zinc-specific transcription factor, Zap1 of Saccharomyces cerevisiae. Sequential disruptions of CSR1 were carried out in diploid C. albicans. The csr1/csr1 mutant strain showed severe growth defects under zinc-limited growth conditions and the filamentation defect under hypha-inducing media. The colony morphology and the germ-tube formation were significantly affected by the csr1 mutation. The expression of the hyphae-specific gene HWP1 was also impaired in csr1/csr1 cells. The C. albicans homologs of ZRTl and ZRT2, which are zinc-transporter genes in S. cerevisiae, were isolated. High-copy number plasmids of these genes suppressed the filamentation defect of the csr1/csr1 mutant strain. We propose that the filamentation phenotype of C. albicans is closely associated with the zinc homeostasis in the cells and that Csr1 plays a critical role in this regulation.

Assessment of Zinc Requirement for Human (인체의 아연필요량 측정방법)

  • 윤진숙
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.24 no.2
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    • pp.346-353
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    • 1995
  • The dietary requirement for zinc to maintain optimally the various metabolic and physiological funcitons is still under study. Human beings adapt to reductions in zinc intake by reducing the rate of growth or zinc excretion. Reductions in dietary zinc beyond the capacity to maintain homeostasis lead to utilization of zinc from an exchangeable pool. Loss of a small, critical amount of zinc from this pool leads to both biochemical and clinical signs of zinc deficiency. Zinc requirements have been assessed by balance studies and factorial method. As tissue zinc status influences endogenous losses and the dietary needs, individuls in good status may require higher amounts of zinc than those in poor status. While plasma zinc is insensitive to reducitons in dietary zinc, it is regarded as a valid, useful indicator of the exchangeable pool of zinc. Plasma metallothionein concentrations may prove useful for identifying poor zinc status. It has been suggested that functional end point measurement is the new direciton for zinc requirement. However, determination of the functional response to a marginal zinc intake is difficult because of the lack of a specific, sensitive indicator of zinc status. Presently, no good method for assessment of human zinc requirements exists.

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Cadmium altered zinc homeostasis in the Neuronal Cell

  • Ahn, Sung-Hee;Jang, Bong-Ki;Park, Jong-An;Lee, Jong-Wha
    • Proceedings of the PSK Conference
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    • pp.185.1-185
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    • 2003
  • In this study, we investigated the effect of cadmium on genes expression related to zinc homeostasis in HT22 hippocampal neuron cell line by RT -PCR and western blotting technics. In the time-course effect, cadmium up-regulated the relative levels of MT -I and MT -II to~b-actin at 4 hr after treatment. These effects were consistent with MT -I/II protein contents by western blot analysis. But MT -III, a specific MT isoform in brain, was not affected by cadmium. (omitted)

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