Zinc-induced upregulation of metallothionein (MT)-2A is predicted by gene expression of zinc transporters in healthy adults

Dietary Zinc Supplementation in Steers Modulates Labile Zinc Concentration and Zinc Transporter Gene Expression in Circulating Immune Cells

Zinc (Zn) is critical for immune function, and marginal Zn deficiency in calves can lead to suboptimal growth and increased disease susceptibility. However, in contrast to other trace minerals such as copper, tissue concentrations of Zn do not change readily in conditions of supplementation or marginal deficiency. Therefore, the evaluation of Zn status remains challenging. Zinc transporters are essential for maintaining intracellular Zn homeostasis, and their expression may indicate changes in Zn status in the animal. Here, we investigated the effects of dietary Zn supplementation on labile Zn concentration and Zn transporter gene expression in circulating immune cells isolated from feedlot steers. Eighteen Angus crossbred steers (261 ± 14 kg) were blocked by body weight and randomly assigned to two dietary treatments: a control diet (58 mg Zn/kg DM, no supplemental Zn) or control plus 150 mg Zn/kg DM (HiZn; 207 mg Zn/kg DM total). After 33 days, Zn supplementation increased labile Zn concentrations (as FluoZin-3 fluorescence) in monocytes, granulocytes, and CD4 T cells (P < 0.05) but had the opposite effect on CD8 and γδ T cells (P < 0.05). Zn transporter gene expression was analyzed on purified immune cell populations collected on days 27 or 28. ZIP11 and ZnT1 gene expression was lower (P < 0.05) in CD4 T cells from HiZn compared to controls. Expression of ZIP6 in CD8 T cells (P = 0.02) and ZnT7 in B cells (P = 0.01) was upregulated in HiZn, while ZnT9 tended (P = 0.06) to increase in B cells from HiZn. These results suggest dietary Zn concentration affects both circulating immune cell Zn concentrations and Zn transporter gene expression in healthy steers.

Biochemical Markers of Zinc Nutrition

Zinc is an important trace element involved in the biochemical and physiological functions of the organism and is essential in the human body. It has been reported that 17.3% of people around the world are at risk of many diseases due to zinc deficiency, which has already affected people's healthy lives. Currently, mild zinc deficiency is difficult to diagnose early due to the lack of typical clinical manifestations, so finding zinc biomarkers is crucial for people's health. The present article reviews the main representative zinc biomarkers, such as body fluid zinc levels, zinc-dependent proteins, tissue zinc, and zinc-containing enzymes, to provide a reference for actively promoting the study of zinc nutritional status and early clinical diagnosis.

Production and Evaluation of Encapsulated Zinc Oxide on Performance, Ileal Digestibility and Zinc Transporter Gene Expression in Broiler Chicken

The present study was undertaken for the production of encapsulated zinc and its evaluation in broiler chicken diet. The process of microencapsulation involved the use of polymers, gum arabic and maltodextrin with a maximum encapsulation of efficiency of 66%. Encapsulated material contained about 20% zinc oxide (ZnO) as core material following the freeze-drying process. One hundred and ninety-two-day-old broiler chicks were distributed in four groups in six replications having eight birds in each. The four groups comprised control (inorganic source of zinc), En-Zn-100 (encapsulated zinc at 100% of control), En-Zn-50 (encapsulated zinc at 50% of control), and Org-Zn-50 (Zn-methionine at 50% of control). The experiment was carried out for 35 days following standard management practices. The live weight gain, feed intake and FCR were comparable among groups. Plasma and muscle zinc (ppm) content was unaffected by the level or source of zinc supplementation. The zinc apparent ileal digestibility coefficient was significantly (P < 0.05) higher in En-Zn-50 fed groups, while crude protein digestibility was not affected by the level or form of Zn supplementation. Bone weight, length, and zinc content were comparable, and bone ash content was significantly different among the groups. Relative expression of ZnT2 was significantly upregulated in encapsulated zinc-fed groups. From the study, it could be concluded that supplementation of zinc either as encapsulated or organic form at 50% of inorganic source (ZnO) could be sufficient to maintain the growth performance, serum, tissue and bone mineral content in broiler chicken.

Comparative study on the effects of micro- and nano-sized zinc oxide supplementation on zinc-deficient mice

BACKGROUND

Zinc (Zn) is an essential cofactor for physiological homeostasis in the body. Zn oxide (ZnO), an inorganic compound that supplies Zn, exists in various sizes, and its bioavailability may vary depending on the size in vivo. However, comparative studies on the nutritional effects of micro-sized ZnO (M-ZnO) and nano-sized ZnO (N-ZnO) supplementation on Zn deficiency (ZnD) animal models have not been reported.

OBJECTIVES

This study investigated the nutritional bioavailability of N-ZnO and M-ZnO particles in dietary-induced ZnD mice.

METHODS

Animals were divided into six experimental groups: normal group, ZnD control group, and four ZnO treatment groups (Nano-Low, Nano-High, Micro-Low, and Micro-High). After ZnD induction, N-ZnO or M-ZnO was administered orally every day for 4 weeks.

RESULTS

ZnD-associated clinical signs almost disappeared 7 days after N-ZnO or M-ZnO administration. Serum Zn concentrations were higher in the Nano-High group than in the ZnD and M-ZnO groups on day 7 of ZnO treatment. In the liver and testis, Nano-Low and Nano-High groups showed significantly higher Zn concentrations than the other groups after 14-day treatment. ZnO supplementation increased Mt-1 mRNA expression in the liver and testis and Mt-2 mRNA expression in the liver. Based on hematoxylin-and-eosin staining results, N-ZnO supplementation alleviated histological damage induced by ZnD in the testis and liver.

CONCLUSIONS

This study suggested that N-ZnO can be utilized faster than M-ZnO for nutritional restoration at the early stage of ZnD condition and presented Mt-1 as an indicator of Zn status in the serum, liver, and testis.

Trace elements, peripheral blood film, and gene expression status in adolescents living near an industrial area in the Colombian Caribbean Coastline

BACKGROUND

Trace elements comprise both nutritionally essential and non-essential, and their presence in organisms plays important role in human health.

OBJECTIVE

The aim of this study was to evaluate the levels of trace elements, together with cellular and molecular biomarkers, in adolescents from Tierrabomba Island, a Caribbean community located near an industrial area, comparing them with a group living in San Onofre, a reference community.

METHODS

Hair and blood samples were obtained from 238 individuals aged 11-18 years old, 131 from Tierrabomba Island and 107 from San Onofre. Trace elements were quantified in hair using ICP-MS. The hematological evaluation was done by peripheral blood smears, and gene expression analysis was carried out through RT-PCR.

RESULTS

Thirteen elements were analyzed; eight showed significant differences between sites. In Tierrabomba, arsenic (As) and tungsten (W) registered mean values greater than in San Onofre. In contrast, in the reference site, average values for boron (B), cobalt (Co), zinc (Zn), yttrium (Y), tin (Sn), and barium (Ba) were greater. The peripheral blood film showed differences between populations. Mean lymphocyte percentage was higher in the Island, while eosinophil and monocyte percentages displayed greater means in San Onofre. Some correlations between trace elements and hematological parameters were found, mainly with platelets in Tierrabomba. This trend remained even when partial correlation coefficients were adjusted for age. Levels of gene expression of metallothionein 1X (MT1X) and superoxide dismutase (SOD) registered significant differences between sites, being greater in Tierrabomba. Negative correlations between SOD and As were observed in both sampling sites. Discriminant analysis suggested sampling locations could be differentiated by Zn, Mo, Ba, and MT1X levels.

SIGNIFICANCE

Trace elements and the relative gene expression associated with metal exposure are critical exposure biomarkers for coastal communities.

Sensitivity and reliability of zinc transporter and metallothionein gene expression in peripheral blood mononuclear cells as indicators of zinc status: responses to ex vivo zinc exposure and habitual zinc intake in humans

Zn is an essential nutrient for humans; however, a sensitive biomarker to assess Zn status has not been identified. The objective of this study was to determine the reliability and sensitivity of Zn transporter and metallothionein (MT) genes in peripheral blood mononuclear cells (PBMCs) to Zn exposure ex vivo and to habitual Zn intake in human subjects. In study 1, human PBMCs were cultured for 24 h with 0-50 µm ZnSO4 with or without 5 µm N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), and mRNA expression of SLC30A1-10, SLC39A1-14, MT1 subtypes (A, B, E, F, G, H, L, M and X), MT2A, MT3 and MT4 mRNA was determined. In study 2, fifty-four healthy male and female volunteers (31·9 (sd 13·8) years, BMI 25·7 (sd 2·9) kg/m2) completed a FFQ, blood was collected, PBMCs were isolated and mRNA expression of selected Zn transporters and MT isoforms was determined. Study 1: MT1E, MT1F, MT1G, MT1H, MT1L, MT1M, MT1X, MT2A and SLC30A1 increased with increasing concentrations of Zn and declined with the addition of TPEN. Study 2: Average daily Zn intake was 16·0 (sd 5·3) mg/d (range: 9-31 mg/d), and plasma Zn concentrations were 15·5 (SD 2·8) μmol/l (range 11-23 μmol/l). PBMC MT2A was positively correlated with dietary Zn intake (r 0·306, P = 0·03) and total Zn intake (r 0·382, P < 0·01), whereas plasma Zn was not (P > 0·05 for both). Findings suggest that MT2A mRNA in PBMCs reflects dietary Zn intake in healthy adults and may be a component in determining Zn status.

Specificity of the Metallothionein-1 Response by Cadmium-Exposed Normal Human Urothelial Cells

Occupational and environmental exposure to cadmium is associated with the development of urothelial cancer. The metallothionein (MT) family of genes encodes proteins that sequester metal ions and modulate physiological processes, including zinc homeostasis. Little is known about the selectivity of expression of the different MT isoforms. Here, we examined the effect of cadmium exposure on MT gene and isoform expression by normal human urothelial (NHU) cell cultures. Baseline and cadmium-induced MT gene expression was characterized by next-generation sequencing and RT-PCR; protein expression was assessed by Western blotting using isoform-specific antibodies. Expression of the zinc transporter-1 (SLC30A1) gene was also assessed. NHU cells displayed transcription of MT-2A, but neither MT-3 nor MT-4 genes. Most striking was a highly inducer-specific expression of MT-1 genes, with cadmium inducing transcription of MT-1A, MT-1G, MT-1H, and MT-1M. Whereas MT-1G was also induced by zinc and nickel ions and MT-1H by iron, both MT-1A and MT-1M were highly cadmium-specific, which was confirmed for protein using isoform-specific antibodies. Protein but not transcript endured post-exposure, probably reflecting sequestration. SLC30A1 transcription was also affected by cadmium ion exposure, potentially reflecting perturbation of intracellular zinc homeostasis. We conclude that human urothelium displays a highly inductive profile of MT-1 gene expression, with two isoforms identified as highly specific to cadmium, providing candidate transcript and long-lived protein biomarkers of cadmium exposure.

No Relation Between Zinc Status and Inflammatory Biomarkers in Adolescent Judokas

This study aimed to assess the relation between zinc status and inflammation biomarkers in adolescent judokas. This cross-sectional study included 52 male adolescents, aged between 14 and 19 years, who were subdivided into two groups: judoka group (n = 25) and control group (n = 27). Zinc intake was monitored using 3-day food records and the NutWin software version 1.5. The plasma and erythrocyte zinc concentrations were determined by flame atomic absorption spectrophotometry. Analysis of cytokines (IL-1β, IL-6, and TNF-α) was performed. The mean values of zinc concentration in the diet were found to be higher than those recommended (11.0±3.9 mg/day and 20.3±11.9 mg/day for control group and judokas, respectively) although there was no significant difference between the groups. The mean plasma concentrations of zinc were below the reference range (71.4±16.0 μg/dL and 71.9±13.8 μg/dL for control group and judokas, respectively), without a significant difference between the groups. The mean concentrations of zinc erythrocyte were within the reference range (41.2±8.6 μg/gHb and 42.6±11.3 μg/gHb for control group and judokas, respectively), without a significant difference between the groups. There was no significant difference in the inflammatory biomarkers between the judokas and controls. There was not a significant correlation between biochemical parameters of zinc and inflammation biomarkers in adolescent judokas. Regarding the data found in the study, it can be concluded that the athletes evaluated have low plasma zinc concentrations, normal erythrocyte values, and high dietary intake of zinc. Moreover, the study don't show a relationship between zinc parameters and inflammatory markers evaluated.

Drp1-Zip1 Interaction Regulates Mitochondrial Quality Surveillance System

Mitophagy, a mitochondrial quality control process for eliminating dysfunctional mitochondria, can be induced by a response of dynamin-related protein 1 (Drp1) to a reduction in mitochondrial membrane potential (MMP) and mitochondrial division. However, the coordination between MMP and mitochondrial division for selecting the damaged portion of the mitochondrial network is less understood. Here, we found that MMP is reduced focally at a fission site by the Drp1 recruitment, which is initiated by the interaction of Drp1 with mitochondrial zinc transporter Zip1 and Zn²⁺ entry through the Zip1-MCU complex. After division, healthy mitochondria restore MMP levels and participate in the fusion-fission cycle again, but mitochondria that fail to restore MMP undergo mitophagy. Thus, interfering with the interaction between Drp1 and Zip1 blocks the reduction of MMP and the subsequent mitophagic selection of damaged mitochondria. These results suggest that Drp1-dependent fission provides selective pressure for eliminating "bad sectors" in the mitochondrial network, serving as a mitochondrial quality surveillance system.

Zinc status at baseline is not related to acute changes in serum zinc concentration following bouts of running or cycling

Zinc status is implicated in physiological functions related to exercise performance and physical activity. We have previously demonstrated significant changes in serum zinc concentrations following a bout of aerobic exercise, suggestive of a relationship between zinc metabolism and exercise-related functions. In the present study, we aim to determine the association between pre-exercise serum zinc concentration and immediate changes in serum zinc concentration following an aerobic exercise bout. We have previously conducted a systematic literature search of PubMed, Web of Science, Scopus and SPORTDiscus, for studies that investigated the acute effects of aerobic exercise on zinc biomarkers. In the current study, we undertook a secondary analysis using mixed effects meta-regression modelling to determine the relationship between baseline serum zinc concentration and the change in serum zinc concentration immediately after exercise. Meta-regression models revealed no significant relationship between baseline serum zinc concentration and the change in serum zinc concentration following a bout of exercise when all comparisons were included (slope -0.11 ± 0.07 [standard error]; P > 0.05). When comparisons were stratified by exercise modality, no significant relationships were observed for exercise bouts involving cycling or running. The current analyses were limited by the available literature and low statistical power of the meta-regression models. Based on the current available data, the present analysis revealed limited evidence for a relationship between pre-exercise serum zinc concentration and immediate changes in serum zinc levels following a bout of aerobic exercise. Subgroup meta-regression analyses stratified by the mode of exercise bouts did not differ from the overall results. This suggests that zinc status at baseline is not related to acute changes in serum zinc concentration following bouts of aerobic exercise.

Expression of Metallothionein after Administration of Aspirin, Vitamin C or Zinc Supplement in the DMH Induced Colon Carcinoma in Rat

Background:

Chemoprevention refers to the use of specificnatural or synthetic chemical agents to suppress the development and progression to carcinoma. The purpose of this study was to assess the effect of aspirin, vitamin C or zinc on the metallothionein (MT) mRNA gene expression as well as MT protein content byimmunohistochemistry andradioimmunoassay (RIA) in 1, 2-dimethyl hydrazine (DMH) induced cancerous colonic tissuein rats.

Methods:

Rats were randomly divided into three groups, group 1 (aspirin), group 2 (vitamin C) group 3 (zinc), each of which was further sub divided into two groups and given subcutaneous injections of DMH (30 mg/kg body weight) twice a week for 3 months and sacrificed at either 4 months (A-precancer model) or at 6 months (B-cancer model). The control groups were administered 0.5 ml saline subcutaneously. All the 3 groups were simultaneouslyadministered aspirin, vitamin Cor zinc supplement respectively from the beginning till the end of the study.

Results:

It was observed that rats co-treated with aspirin, vitamin C or zinc resulted in a significant increase in the colonic MT mRNA expression in the precancer and cancer model as compared to the saline only controls. MT protein expression showed a 60%, 64% and 78% immunopositivity in the co-treated groups respectively. The mean MT content in the precancer and the cancer model was restored to near normal levels in all the three co-treated groups.

Conclusion:

These results suggest that co-administration of aspirin, vitamin C or zinc resulted in a significant increase in MT mRNA gene expression, MT protein expression and MT protein content which could possibly be one of the reasons for a chemo protective effect against progression to colonic cancer in a chemically induced DMH model in rat. Zinc supplement had a greater effect on metallothionein expression than aspirin or vitamin C.

Interrelationships among mediators of cellular zinc homeostasis in healthy and type 2 diabetes mellitus populations

SCOPE

The involvement of zinc in multiple physiological systems requires tight control of cellular zinc concentration. This study aims to explore the relationships among selected mediators of cellular zinc homeostasis in an apparently healthy (AH) population and a cohort with type 2 diabetes mellitus (T2DM).

METHODS AND RESULTS

Baseline data of three trials forming two cohorts, AH (n = 70) and T2DM (n = 42), were used for multivariate analyses to identify groupings within ten zinc transporter and metallothionein (MT) gene expressions, stratified by health status. Multiple regression models were used to explore relationships among zinc transporter/MT groupings and plasma zinc. Gene expression of zinc transporters and MTs, with the exception of ZnT6, were significantly lower in the T2DM cohort (p < 0.01). Cluster analysis showed that the groupings of zinc transporters and MTs were largely similar between the two cohorts, with the exception for ZnT1 and ZIP7. Zinc transporters and MTs were significant determinants of plasma zinc (r² = 0.48, p = 0.001) in the AH cohort, but not in the T2DM cohort.

CONCLUSION

The current study suggests altered cellular zinc homeostasis in T2DM and supports the use of multiple zinc transporters and MTs groupings to further understand zinc homeostasis in health and T2DM.

Immediate Effects of Aerobic Exercise on Plasma/Serum Zinc Levels: A Meta-analysis

BACKGROUND

Zinc is involved in numerous metabolic roles, including energy metabolism, immunity, and antioxidative effects. Zinc losses during exercise, in particular through sweat, are well documented. However, conflicting results have been reported for changes in circulating and tissue zinc concentration as a result of exercise. The purpose of this article is to quantify the immediate effect of aerobic exercise on plasma or serum zinc levels, in healthy participants.

METHODS

We conducted a systematic review of peer-reviewed articles published up to December 20, 2014, to identify studies that investigated the acute effects of exercise on selected indices of zinc status. Meta-analyses were conducted to determine the change in serum zinc concentration immediately after a bout of aerobic exercise.

RESULTS

Forty-five studies were included in the systematic literature review. Of the included studies, sufficient data were available from 34 studies (providing 46 comparisons) to quantify the change in serum zinc concentration after exercise. Serum zinc concentration was significantly higher immediately after exercise (0.45 ± 0.12 μmol·L(-1), P < 0.001; mean ± SE). Secondary analyses showed greater increase in serum zinc for untrained individuals and exercise sessions that involved running or maximal intensity. Insufficient data were available to determine the effects of exercise on urinary, sweat, and erythrocyte zinc.

CONCLUSIONS

The present systematic review and meta-analysis indicated significant increase in serum zinc concentration immediately after an aerobic exercise session, suggesting acute perturbations in zinc homeostasis. Further research is required to ascertain the long-term effects of exercise on zinc metabolism and potential consequences for dietary zinc requirement for physically active populations.

Assessing zinc in humans

PURPOSE OF REVIEW

To examine the most recent literature that provides new data regarding the potential and emerging biomarkers for zinc status in individuals.

RECENT FINDINGS

Suboptimal dietary zinc intake is estimated to affect 17% of the world's population; however, the assessment of zinc status is notoriously difficult. A systematic review and meta-analysis of studies investigating biochemical biomarkers of zinc status was conducted by the European Micronutrient Recommendations Aligned network. This review summarized the data published from inception to 2007. More recently (2016), an international expert panel, convened by the biomarker of nutrition for development initiative, published an extensive review of the literature addressing biomarkers of zinc status in populations and individuals and categorized the biomarkers as useful [dietary intake, serum Zn concentration and stunting], potentially useful [hair Zn concentration, urine Zn concentration and neurobehavioural function] and emerging [nail Zn concentration, oxidative stress and DNA integrity, zinc kinetics, zinc-dependent proteins and taste acuity].

SUMMARY

The most recent data on the potentially useful biomarkers support the further investigation of hair Zn concentration and indices of neurological function, particularly those assessing memory and attention. Of the emerging biomarkers, the measurement of DNA integrity and the expression of zinc transport proteins look promising.

Metallothionein and Zinc Transporter Expression in Circulating Human Blood Cells as Biomarkers of Zinc Status: a Systematic Review

Zinc is an essential nutrient for humans; however, a sensitive biomarker to assess zinc status has not been identified. The objective of this systematic review was to compile and assess studies that determined zinc transporter and/or metallothionein expression in various blood cell types and to determine their reliability and sensitivity to changes in dietary zinc. Sixteen studies were identified that determined the expression of zrt-, irt-like protein (ZIP) 1 [solute carrier family (SLC) 39A1], ZIP3 (SLC39A3), ZIP5 (SLC39A5), ZIP6 (SLC39A6), ZIP7 (SLC39A7), ZIP8 (SLC39A8), ZIP10 (SLC39A10), ZIP14 (SLC39A14), zinc transporter (ZnT)1 (SLC30A1), ZnT2 (SLC30A2), ZnT4 (SLC30A4), ZnT5 (SLC30A5), ZnT6 (SLC30A6), ZnT7 (SLC30A7), ZnT9 (SLC30A9), and/or metallothionein in various blood cells isolated from healthy adult men and women in response to zinc supplementation or depletion. Cell types included leukocytes, peripheral blood mononuclear cells, T lymphocytes, monocytes, and erythrocytes. ZIP1, ZnT1, and metallothionein were the most commonly measured proteins. Changes in ZIP1 and ZnT1 in response to zinc supplementation or depletion were not consistent across studies. Leukocyte metallothionein decreased with zinc depletion (-39% change from baseline, <5 mg Zn/d, n = 2 studies) and increased with zinc supplementation in a dose-dependent manner (35%, 15-22 mg Zn/d, n = 7 studies; 267%, 50 mg Zn/d, n = 2 studies) and at the earliest time points measured; however, no change or delayed response was observed in metallothionein in erythrocytes. A greater percentage of studies demonstrated that metallothionein in leukocyte subtypes was a more reliable (100%, n = 12; 69%, n = 16) and responsive (92%, n = 12; 82%, n = 11) indicator of zinc exposure than was plasma zinc, respectively. In conclusion, current evidence indicates that metallothionein in leukocyte subtypes may be a component in determining zinc status.