Zinc supplementation inhibits hepatic apoptosis in mice subjected to a long-term ethanol exposure

Hepatocyte apoptosis has been documented in both clinical and experimental alcoholic liver disease. This study was undertaken to examine the effect of dietary zinc supplementation on hepatic apoptosis in mice subjected to a long-term ethanol exposure. Male adult 129S6 mice fed an ethanol-containing liquid diet for 6 months developed hepatitis, as indicated by neutrophil infiltration and elevation of hepatic keratinocyte chemoattractant (KC) and monocyte chemoattractant protein-1 (MCP-1) levels. Apoptotic cell death was detected in ethanol-exposed mice by a terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and was confirmed by the increased activities of caspase-3 and -8. Zinc supplementation attenuated alcoholic hepatitis and reduced the number of TUNEL-positive cells in association with inhibition of caspase activities. Ethanol exposure caused oxidative stress, as indicated by reactive oxygen species accumulation, mitochondrial glutathione depletion, and decreased metallothionein levels in the liver, which were suppressed by zinc supplementation. The mRNA levels of tumor necrosis factor (TNF)-alpha, TNF-R1, FasL, Fas, Fas-associated factor-1, and caspase-3 in the liver were upregulated by ethanol exposure, which were attenuated by zinc supplementation. Zinc supplementation also prevented ethanol-elevated serum and hepatic TNF-alpha levels and TNF-R1 and Fas proteins in the liver. In conclusion, zinc supplementation prevented hepatocyte apoptosis in mice subjected to long-term ethanol exposure, and the action of zinc is likely through suppression of oxidative stress and death receptor-mediated pathways.     

Zinc coadministration attenuates melatonin’s effect on nitric oxide production in mice

Both melatonin (MEL) and zinc (Zn) are considered beneficial for anti-immunosenescence. MEL’s effects on immune functions are partly attributed to an interaction with Zn. However, the augmentation of or interference with MEL’s effects by coadministration of Zn remains unclear. In this study, adult older mice received either MEL (10 μg/mL), Zn (22 μg/mL), MEL+Zn, or null supplementation from drinking water for 3 mo. The results showed that treated mice, irrespective of the type of added chemicals, had higher body-weight gain and body-fat content than control mice. MEL- and Zn-treated mice also had increased serum free fatty acid levels. In addition, the MEL group had decreased serum NO_X (nitrite+nitrate) values. Serum tumor necrosis factor-alpha levels were increased, although nonsignificantly, in mice that received either MEL or Zn supplementation. However, the differences described were not retained in the mice that received MEL+Zn treatment. We conclude that a high-dose Zn coadministration might exert negative influences on MEL’s regulatory effects, at least on nitric oxide production.     

Influence of short-term maternal zinc deficiency on the in vitro development of preimplantation mouse embryos

In this study, we evaluated the use of mouse preimplantation embryos as a model to study zinc deficiency-induced abnormal development. In Experiment 1, the effect of culture medium Zn concentrations on blastocyst development was studied. Preimplantation embryos (2 and 4 cells) obtained from superovulated females developed normally in media containing 0.7-30 microM Zn for up to 72 hr; higher levels of medium Zn resulted in abnormal development. In Experiment 2A, females were fed diets containing 50 (+Zn) or 0.4 (-Zn) micrograms Zn/g (760 vs 6 nmol/g, respectively) from 1 day before to 1 day after mating (3 days total). Preimplantation embryos were removed from the dams and cultured for 72 hr in 0.7 microM Zn medium. Embryos from the -Zn dams were morphologically normal at time zero; however, over the 72-hr period, these embryos tended to develop at a slower rate than controls, although compaction and cavitation frequency were similar. By the end of the 72-hr culture period, embryos from -Zn dams had significantly fewer cells than did embryos from control dams. In Experiment 2B, an extended period of maternal Zn deprivation (6 days) was used to investigate the potential for further impairment of in vitro preimplantation embryo development observed in Experiment 2A. Results from this experiment were consistent with those from Experiment 2A, in addition to providing evidence that the developmental progress of embryos obtained from mice fed Zn-deficient diets for 6 days was significantly impaired. In Experiment 3, the potential for supplemental Zn in culture medium to overcome the impairment in development due to maternal Zn deficiency was investigated. Embryos from female mice subjected to the same dietary regimen described in Experiment 2A were cultured to the blastocyst stage in medium containing Zn at a concentration of either 0.7 or 7.7 microM. Medium Zn supplementation did not improve development of embryos from dams fed Zn-deficient diets. In summary, embryos from mice fed -Zn diets for a 3- or 6-day period encompassing oocyte maturation and fertilization exhibited impaired development in vitro. This impairment was not overcome by medium Zn supplementation.     

Effects of dietary fat and zinc on adiposity,serum leptin and adipose fatty acid composition in C57BL/6J mice

Zinc (Zn) has been implicated in altered adipose metabolism, insulin resistance and obesity. The objective of this study was to investigate the effects dietary Zn deficiency and supplementation on adiposity, serum leptin and fatty acid composition of adipose triglycerides and phospholipid in C57BL/6J mice fed low-fat (LF) or high-fat (HF) diets for a 16 week period. Weanling C57BL/6J mice were fed LF (16% kcal from soybean oil) or HF (39% kcal from lard and 16% kcal from soybean oil) diets containing 3, 30 or 150 mg Zn/kg diet (ZD = Zn-deficient, ZC = Zn control and ZS = Zn-supplemented, respectively). HF-fed mice had higher fat pad weights and lower adipose Zn concentrations than the LF-fed mice. The ZD and ZS groups had a reduced content of fatty acids in adipose triglycerides compared to the ZC group, suggesting that zinc status may influence fatty acid accumulation in adipose tissue. Serum leptin concentration was positively correlated with body weight and body fat, and negatively correlated with adipose Zn concentration. Dietary fat, but not dietary Zn, altered the fatty acid composition of adipose tissue phospholipid and triglyceride despite differences in Zn status assessed by femur Zn concentrations. The fatty acid profile of adipose triglycerides generally reflected the diets. HF-fed mice had a higher percentage of C20:4 n-6, elevated ratio of n-6/n-3, lower ratio of PUFA/SAT and reduced percentage of total n-3 fatty acids in adipose phospholipid, a fatty acid profile associated with obesity-induced risks for insulin resistance and impaired glucose transport. In summary, the reduced adipose Zn concentrations in HF-fed mice and the negative correlation between serum leptin and adipose Zn concentrations support an interrelationship among obesity, leptin and Zn metabolism.     

Dietary zinc mediates inflammation and protects against wasting and metabolic derangement caused by sustained cigarette smoke exposure in mice

In mouse asthma models, inflammation can be modulated by zinc (Zn). Given that appetite loss, muscle wasting and poor nutrition are features of chronic obstructive pulmonary disease (COPD) and that poor dietary Zn intake is in itself accompanied by growth retardation and appetite loss, we hypothesised that dietary Zn limitation would not only worsen airway inflammation but also exaggerate metabolic effects of cigarette smoke (CS) exposure in mice. Conversely, Zn supplementation would lessen inflammation. Mice were exposed to CS [2× 2RF, 3×/day; 15 min/cigarette] and fed diets containing 2, 20 or 140 mg/kg Zn ad libitum. Airway cells were collected by bronchoalveolar lavage (BAL). Plasma Zn was measured by fluorometric assay. Inflammatory, metabolic and Zn transport markers were measured by real-time RT-PCR. Mice fed low Zn diets had less plasma labile zinc (0–0.18 μM) than mice fed moderate (0.61–0.98 μM) or high (0.77–1.1 μM) Zn diets (SDs 0.1–0.4, n = 8–10). Smoke exposure increased plasma and BAL labile Zn (1.5–2.5 fold, P < 0.001), bronchoalveolar macrophages (2.0 fold, P < 0.0001) and MT-1 (1.5 fold), MIP-2 (2.3 fold) and MMP-12 (3.5 fold) mRNA. Zn supplementation reduced alveolar macrophage numbers by 62 and 52% in sham and smoke-exposed mice, respectively (Zn effect: P = 0.011). Gastrocnemius, soleus and tibialis anterior muscle mass were affected by both smoke and dietary Zn in the order of 3–7%. The 50–60% reduction in alveolar macrophages in Zn-supplemented mice supports our evolving hypothesis that Zn is an important anti-inflammatory mediator of airway inflammation. Restoring airway Zn levels through dietary supplementation may lessen the severity of lung inflammation when Zn intake is low.     

Slc39a1 to 3 (subfamily II) Zip genes in mice have unique cell-specific functions during adaptation to zinc deficiency

Subfamily II of the solute carrier (Slc)39a family contains three highly conserved members (ZIPs 1-3) that share a 12-amino acid signature sequence present in the putative fourth transmembrane domain and function as zinc transporters in transfected cells. The physiological significance of this genetic redundancy is unknown. Here we report that the complete elimination of all three of these Zip genes, by targeted mutagenesis and crossbreeding mice, causes no overt phenotypic effect. When mice were fed a zinc-adequate diet, several indicators of zinc status were indistinguishable between wild-type and triple-knockout mice, including embryonic morphogenesis and growth, alkaline phosphatase activity in the embryo, ZIP4 protein in the visceral yolk sac, and initial rates (30 min) of accumulation/retention of (67)Zn in liver and pancreas. When mice were fed a zinc-deficient diet, embryonic membrane-bound alkaline phosphatase activity was reduced to a much greater extent, and 80% of the embryos of the triple-knockout mice developed abnormally compared with 12% of the embryos of wild-type mice. During zinc deficiency, the accumulation/retention (3 h) of (67)Zn in the liver and pancreas of weanlings was significantly impaired in the triple-knockout mice compared with wild-type mice. Thus none of these three mammalian Zip genes apparently plays a critical role in zinc homeostasis when zinc is replete, but they play important, noncompensatory roles when this metal is deficient.     

Displacement of zinc and copper from copper-induced metallothionein by cadmium and by mercury: in vivo and ex vivo studies

The in vitro affinity of metals for metallothionein (MT) is Zn less than Cd less than Cu less than Hg. In a previous study Cd(II) and Hg(II) displaced Zn(II) from rat hepatic Zn7-MT in vivo and ex vivo (Day et al., 1984, Chem. Biol. Interact. 50, 159-174). The ability of Cd(II) or Hg(II) to displace Zn(II) and/or Cu(II) from metallothionein in copper-preinduced rat liver (Zn, Cu-MT) was assessed. Cd(II) and Hg(II) can displace zinc from (Zn, Cu)-MT both in vivo and ex vivo. The in vitro displacement of copper from MT by Hg(II) was not confirmed in vivo and ex vivo. Cd(II) treatment did not alter copper levels in (Zn, Cu)-MT, as expected. Hg(II) treatment, however, did not decrease copper levels in MT, but rather increased them. The sum of the copper increase and mercury incorporation into MT matched the zinc decrease under in vivo conditions and actually exceeded the zinc decrease under ex vivo conditions. Short-term exposure of rat liver to exogenous metals can result in incorporation of these metals into MT by displacement of zinc from pre-existing MT. Displacement of copper from pre-existing MT by mercury, as predicted by in vitro experiments, was not confirmed under the conditions of our in vivo and ex vivo experiments. This result is explainable based on the differing affinities and/or preferences of the two metal clusters in MT.     

The plant CDF family member TgMTP1 from the Ni/Zn hyperaccumulator Thlaspi goesingense acts to enhance efflux of Zn at the plasma membrane when expressed in Saccharomyces cerevisiae

To avoid metal toxicity, organisms have evolved mechanisms including efflux of metal ions from cells and sequestration into internal cellular compartments. Members of the ubiquitous cation diffusion facilitator (CDF) family are known to play an important role in these processes. Overexpression of the plant CDF family member metal tolerance protein 1 (MTP1) from the Ni/Zn hyperaccumulator Thlaspi goesingense (TgMTP1), in the Saccharomyces cerevisiaeDelta zinc resistance conferring (zrc)1Delta cobalt transporter (cot)1 double mutant, suppressed the Zn sensitivity of this strain. T. goesingense was found to contain several allelic variants of TgMTP1, all of which confer similar resistance to Zn in Deltazrc1Deltacot1. Similarly, MTP1 from various hyperaccumulator and non-accumulator species also confer similar resistance to Zn. Deltazrc1Deltacot1 lacks the ability to accumulate Zn in the vacuole and has lower accumulation of Zn after either long- or short-term Zn exposure. Expression of TgMTP1 in Deltazrc1Deltacot1 leads to further lowering of Zn accumulation and an increase in Zn efflux from the cells. Expression of TgMTP1 in a V-type ATPase-deficient S. cerevisiae strain also confers increased Zn resistance. In vivo and in vitro immunological staining of hemagglutinin (HA)-tagged TgMTP1::HA reveals the protein to be localized in both the S. cerevisiae vacuolar and plasma membranes. Taken together, these data are consistent with MTP1 functioning to enhance plasma membrane Zn efflux, acting to confer Zn resistance independent of the vacuole in S. cerevisiae. Transient expression in Arabidopsis thaliana protoplasts also reveals that TgMTP1::green fluorescent protein (GFP) is localized at the plasma membrane, suggesting that TgMTP1 may also enhance Zn efflux in plants.     

Dietary zinc attenuates renal lead deposition but metallothionein is not directly involved

Chronic lead exposure irreversibly damages the kidneys and may be associated with hypertension and renal insufficiency at sub-clinically toxic levels. Zinc supplementation reduces lead absorption and tissue retention in rodent models but the mechanisms are unknown. Metallothionein (MT) may function in lead detoxification. Our objective was to investigate the effects of marginal zinc (MZ) and supplemental zinc (SZ) intakes on renal lead and zinc accumulation, renal MT immunolocalization and levels. Weanling Sprague Dawley rats were assigned to MZ (8 mg Zn/kg diet), zinc-adequate control (CT; 30 mg Zn/kg), zinc-adequate diet-restricted (DR; 30 mg Zn/kg) or SZ (300 mg Zn/kg) groups, with and without lead acetate-containing drinking water (200 mg Pb/L) for 3 weeks. Kidneys were analyzed for lead and zinc by inductively coupled plasma spectroscopy and MT by immunolocalization and Western blotting. MZ had higher renal lead and lower renal zinc concentrations than CT. SZ was more protective than CT against renal lead accumulation. Renal MT levels reflected dietary intake (SZ ≥ DR ≥ CT ≥ MZ) but lead had no effect on MT staining intensity, distribution, or relative protein amounts. In summary, while SZ lowered renal lead concentration, MT did not appear to function in renal lead accumulation. Future studies should explore alternate mechanisms of renal lead detoxification.     

Metallothionein response to cadmium and zinc exposures compared in two freshwater bivalves, Dreissena polymorpha and Corbicula fluminea

Metallothionein (MT) response to cadmium (Cd) and zinc (Zn) bioaccumulation after single or combined direct exposure was compared in two freshwater bivalves, Dreissena polymorpha (zebra mussel) and Corbicula fluminea (Asiatic clam). Bivalves were exposed to 0.133 μM Cd and/or 15.3 μM Zn, with metal and MT concentrations analysed in the whole soft body after 1, 3, 10 and 24 days of exposure and compared with controls. Results showed significant increase in MT concentrations in both species exposed to Cd and Cd+Zn with a higher accumulation of the protein compared to the control in D. polymorpha for nevertheless similar Cd levels accumulated with time. Exposure to Zn alone led to a significant increase in MT concentrations only in C. fluminea, whereas there was a lack of MT gene induction in the zebra mussels which was confirmed by MT mRNA quantification in gills (RT-PCR). Mussel mortality after 10 days of exposure to Zn and Cd + Zn is discussed with regard to detoxification mechanisms, which include metallothioneins.     

肉苁蓉多糖的促淋巴细胞增殖作用

目的研究肉苁蓉多糖（CDPS）对小鼠淋巴细胞增殖的影响。方法MTT法检测小鼠脾淋巴细胞的增殖。环磷酰胺（Cy）复制免疫功能低下的动物模型,分别测定正常及免疫低下动物脾脏、胸腺指数。胸腺细胞增殖法测定白细胞介素-2（IL-2）活性。结果CDPS对丝裂原（ConA及LPS）活化淋巴细胞及未活化正常细胞均有明显促增殖作用,并促进淋巴细胞IL-2的分泌。腹腔给药显示CDPS具明显提高正常及免疫低下小鼠的脾指数,对因Cy所致胸腺指数的降低也有显著的对抗作用。结论CDPS可显著促进小鼠脾淋巴细胞增殖,该作用可能与其促IL-2分泌有关。     

The effect of dietary zinc - and polyphenols intake on DMBA-induced mammary tumorigenesis in rats

Background

The aim of the study was to investigate the effect of dietary supplementation with zinc and polyphenol compounds, i.e. resveratrol and genistein, on the effectiveness of chemically induced mammary cancer and the changes in the content of selected elements (Zn, Cu, Mg, Fe, Ca) in tumors as compared with normal tissue of the mammary gland.

Methods

Female Sprague-Dawley rats were divided into study groups which, apart from the standard diet and DMBA (7,12-dimethyl-1,2- benz[a]anthracene), were treated with zinc ions (Zn) or zinc ions + resveratrol (Zn + resveratrol) or zinc ions + genistein (Zn + genistein) via gavage for a period from 40 days until 20 weeks of age. The ICP-OES (inductively coupled plasma optical emission spectrometry) technique was used to analyze the following elements: magnesium, iron, zinc and calcium. Copper content in samples was estimated in an atomic absorption spectrophotometer.

Results

Regardless of the diet (standard; Zn; Zn + resveratrol; Zn + genistein), DMBA-induced breast carcinogenesis was not inhibited. On the contrary, in the Zn + resveratrol supplemented group, tumorigenesis developed at a considerably faster rate. On the basis of quantitative analysis of selected elements we found - irrespectively of the diet applied - great accumulation of copper and iron, which are strongly prooxidative, with a simultaneous considerable decrease of the magnesium content in DMBA-induced mammary tumors. The combination of zinc supplementation with resveratrol resulted in particularly large differences in the amount of the investigated elements in tumors as compared with their content in normal tissue.

Conclusions

Diet supplementation with zinc and polyphenol compounds, i.e. resveratrol and genistein had no effect on the decreased copper level in tumor tissue and inhibited mammary carcinogenesis in the rat. Irrespectively of the applied diet, the development of the neoplastic process in rats resulted in changes of the iron and magnesium content in the cancerous tissue in comparison with the healthy mammary tissue. The application of combined diet supplementation with zinc ions and resveratrol considerably promoted the rate of carcinogenesis and increased the number of DMBA-induced mammary tumors.     

Zinc deprivation of methanol fed anaerobic granular sludge bioreactors

The effect of omitting zinc from the influent of mesophilic (30 degrees C) methanol fed upflow anaerobic sludge bed (UASB) reactors, and latter zinc supplementation to the influent to counteract the deprivation, was investigated by coupling the UASB reactor performance to the microbial ecology of the bioreactor sludge. Limitation of the specific methanogenic activity (SMA) on methanol due to the absence of zinc from the influent developed after 137 days of operation. At that day, the SMA in medium with a complete trace metal solution except Zn was 3.4 g CH4-COD g VSS(-1) day(-1), compared to 4.2 g CH4-COD g VSS(-1) day(-1) in a medium with a complete (including zinc) trace metal solution. The methanol removal capacity during these 137 days was 99% and no volatile fatty acids accumulated. Two UASB reactors, inoculated with the zinc-deprived sludge, were operated to study restoration of the zinc limitation by zinc supplementation to the bioreactor influent. In a first reactor, no changes to the operational conditions were made. This resulted in methanol accumulation in the reactor effluent after 12 days of operation, which subsequently induced acetogenic activity 5 days after the methanol accumulation started. Methanogenesis could not be recovered by the continuous addition of 0.5 microM ZnCl2 to the reactor for 13 days. In the second reactor, 0.5 microM ZnCl2 was added from its start-up. Although the reactor stayed 10 days longer methanogenically than the reactor operated without zinc, methanol accumulation was observed in this reactor (up to 1.1 g COD-MeOH L(-1)) as well. This study shows that zinc limitation can induce failure of methanol fed UASB reactors due to acidification, which cannot be restored by resuming the continuous supply of the deprived metal.     

Effect of pulsed electric fields upon accumulation of zinc in Saccharomyces cerevisiae

Cultures of Saccharomyces cerevisiae were treated with pulsed electric fields to improve accumulation of zinc in the biomass. Under optimized conditions, that is, on 15 min exposure of the 20 h grown culture to PEFs of 1500 V and 10 microns pulse width, accumulation of zinc in the yeast biomass reached a maximum of 15.57 mg/g d.m. Under optimum zinc concentration (100 microgram/ml nutrient medium), its accumulation in the cells was higher by 63% in comparison with the control (without PEFs). That accumulation significantly correlated against zinc concentration in the medium. Neither multiple exposure of the cultures to PEFs nor intermittent supplementation of the cultures with zinc increased the zinc accumulation. The intermittent supplementation of the cultures with zinc and multiple exposures on PEFs could even reduce the accumulation efficiency, respectively, by 57% and 47%.     

Effect of Selenomethionine Supplementation in Food on the Excretion and Toxicity of Arsenic Exposure in Female Mice

Selenium (Se) is an essential component of several major metabolic pathways and controls immune function. Arsenic (As) is a human carcinogen with immunotoxic and genotoxic activities, functioning mainly by producing oxidative stress. Due to the ability of Se to interact with As and to possibly block its toxic effects, we investigated the impact of dietary Se-methionine (Se-Met) supplementation on the toxicity of As exposure in vivo in a mouse model. Sufficient and excess levels of Se-Met (0.2 and 2 ppm, respectively) were fed to C57BL/6N female mice exposed to sodium arsenite (3, 6 and 10 mg/kg) in tap water for 9 days. We observed that As exposure increased Se-Met excretion in the urine. Se-Met supplementation increased the relative liver weight and decreased the concentration of total liver proteins in animals exposed to 10 mg/kg of As. Se-Met supplementation maintained a normal pool of glutathione in the liver and increased glutathione peroxidase concentration, although the lipoperoxidation level was increased by Se-Met even without As exposure. Se-Met supplementation helped to maintain the CD4/CD8 ratio of lymphocytes in the spleen, although it increased the proportion of B cells. Se-Met supplementation prior to As exposure increased the secretion of interleukin-4, IL-12 and interferon-γ and the stimulation index of the spleen cells in in vitro assays. Se-Met intake improved the basal immunological parameters but did not reduce the damage caused by oxidative stress after low-dose As exposure.     

Dietary zinc supplementation attenuates hyperglycemia in db/db mice

Although zinc (Zn) deficiency has been associated with insulin resistance, and altered Zn metabolism (e.g., hyperzincuria, low-normal plasma Zn concentrations) may be present in diabetes, the potential effects of Zn on modulation of insulin action in Type II diabetes have not been established. The objective of this study was to compare the effects of dietary Zn deficiency and Zn supplementation on glycemic control in db/db mice. Weanling db/db mice and lean littermate controls were fed Zn-deficient (3 ppm Zn; dbZD and InZD groups), Zn-adequate control (30 ppm Zn; dbC and InC groups) or Zn-supplemented (300 ppm Zn; dbZS and InZS groups) diets for 6 weeks. Mice were assessed for Zn status, serum and urinary indices of diabetes, and gastrocnemius insulin receptor concentration and tyrosine kinase activity. Fasting serum glucose concentrations were significantly lower in the dbZS group compared with the dbZD group (19.3 +/- 2.9 and 27.9 +/- 4.1 mM, respectively), whereas the dbC mice had an intermediate value. There was a negative correlation between femur Zn and serum glucose concentrations (r = -0.59 for lean mice, P = 0.007). The dbZS group had higher pancreatic Zn and lower circulating insulin concentrations than dbZC mice. Insulin-stimulated tyrosine kinase activity in gastrocnemius muscle was higher in the db/db genotype, and insulin receptor concentration was not altered. In summary, dietary Zn supplementation attenuated hyperglycemia and hyperinsulinemia in db/db mice, suggesting that the roles of Zn in pancreatic function and peripheral tissue glucose uptake need to be further investigated.     

Effects of zinc supplementation on the plasma glucose level and insulin activity in genetically obese (ob/ob) mice

The effects of zinc supplementation (20 mM ZnCl₂ from the drinking water for eight weeks) on plasma glucose and insulin levels, as well as its in vitro effect on lipogenesis and lipolysis in adipocytes were studied in genetically obese (ob/ob) mice and their lean controls (+/?). Zinc supplementation reduced the fasting plasma glucose levels in both obese and lean mice by 21 and 25%, respectively (p < 0.05). Fasting plasma insulin levels were significantly decreased by 42% in obese mice after zinc treatment. In obese mice, zinc supplementation also attenuated the glycemic response by 34% after the glucose load. The insulin-like effect of zinc on lipogenesis in adipocytes was significantly increased by 80% in lean mice. However, the increment of 74% on lipogenesis in obese mice was observed only when the zinc plus insulin treatment was given. This study reveals that zinc supplementation alleviated the hyperglycemia of ob/ob mice, which may be related to its effect on the enhancement of insulin activity.     

Cd/Zn exposure interactions on metallothionein response in Eisenia fetida (Annelida, Oligochaeta)

We studied metallothionein (MT) response in the manure worm Eisenia fetida after exposures to cadmium (Cd), zinc (Zn) or cadmium and zinc spiked media. MT was studied both at the protein level by Dot Immunobinding Assay, (DIA) and at the expression level by Northern blotting. Cd was highly accumulated by worms whereas Zn body concentration was regulated. In addition, Zn would limit Cd accumulation in worms exposed to low Cd concentrations (1 and 8 mg Cd kg(-1) of dry soil). Exposure to a mixture of Cd and Zn at high concentrations increased cytosolic MT levels. This increase would allow worms to regulate body Zn concentrations and also to limit Cd toxicity. Cd exposures increased gene expression of Cd-binding MT isoform (MT 2A) whereas Zn did not. However, when both metals were at high concentrations in the exposure medium, this expression was further increased. Several hypotheses are proposed to explain the results and the best approach to estimate metal exposure of this earthworm species is given. Further experiments have now to be performed to evaluate the usefulness of these MT responses for field contaminated soils toxicity assessment using this earthworm species.