Effect of dietary zinc deficiency on reproductive function in male rats: Biochemical and morphometric parameters

Effects of the toxic metal zinc on the growth, development, and reproduction of the wolf spider Pardosa laura through its food Drosophila melanogaster

In recent years, toxic metal pollution has become a serious problem, and its influence on human society and the ecological environment has become a hot topic for people. Toxic metal pollution is ubiquitous in the environment, and it can affect the growth, development, and reproduction of organisms through food chain transmission. In this study, we used ZnSO4 and set three different Zn concentrations [0 mg/mL (CK), 0.25 mg/mL, and 0.50 mg/mL] to study the enrichment of toxic zinc metal in the wolf spider Pardosa laura through the food chain (medium-Drosophila melanogaster-P. laura) and the effects on the growth, development, and reproduction of D. melanogaster and P. laura. The results of the study showed that the Zn content in D. melanogaster and P. laura significantly increased with the increase of Zn concentration in the culture medium, reflecting the obvious food chain enrichment phenomenon. The inhibitory effect of zinc treatment on the growth, development, and reproduction of D. melanogaster was significant and more pronounced with increasing Zn concentration. The transfer of zinc through the food chain also had a significant inhibitory effect on the growth, development, and reproduction of P. laura. The developmental duration and preoviposition period were significantly prolonged. Moreover, the survival rate, body size, and egg laying amount were significantly reduced. This study will enrich and improve the research on the effects of toxic Zn metal pollution on spiders and provide a theoretical basis for monitoring and evaluating the environmental quality using farmland spiders.

Effects of Zinc Methionine Hydroxy Analog Chelate on Laying Performance, Serum Hormone Levels, and Expression of Reproductive Axis Related Genes in Aged Broiler Breeders

Inorganic zinc (Zn) supplements are commonly used in poultry feeds, but their low utilization results in the increase of Zn excretion. Thus, to provide a new perspective for the substitution of inorganic Zn, a novel Zn methionine hydroxy analog chelate (Zn-MHA) was studied in the present study to evaluate its effects on laying performance, serum hormone indexes and reproductive axis-related genes in broilers breeders. A total of 480 Hubbard breeders (56-week-old) were fed a basal diet (containing 27.81 mg Zn/kg) without Zn addition for 2 weeks, and then allocated to 4 groups with 6 replicates (each replicate consisting of 10 cages and 2 breeders per cage) for 10 weeks. Four treatment diets given to broiler breeders included the basal diet added with 25, 50, and 75 mg/kg of Zn-MHA and 100 mg/kg of Zn sulfate (ZnSO₄). The laying rate, egg weight and feed conversation ratio increased in the 75 mg/kg Zn-MHA group compared to the ZnSO₄ group. The eggshell thickness was not decreased with the addition of 50 mg/kg and 75 mg/kg Zn-MHA in the diet compared to the 100 mg/kg ZnSO₄ group. There was a significant improvement in the reproductive performance of breeders in the 75 mg/kg Zn-MHA group, including the fertility and 1-day-old offspring weight. Besides, serum sex hormone levels including FSH and P₄ increased significantly in 75 mg/kg Zn-MHA group. No significant effect on the ovarian weight or the number of follicles in broiler breeders was observed by supplementing Zn-MHA. Compared to the 100 mg/kg ZnSO₄ group, dietary supplementation with 75 mg/kg of Zn-MHA showed an up-regulation of the FSHR mRNA in the granular layer of follicles. However, dietary supplementation of Zn-MHA had no effects on mRNA expressions of the ovarian LHR and PRLR genes. These findings reinforce the suggestion that Zn-MHA (75 mg/kg) could replace ZnSO₄ (100 mg/kg) as a Zn supplement in diet of broiler breeders, which resulted in better laying and reproduction performances by regulating the expression levels of reproductive axis related genes and serum hormone levels.

Ameliorative effect of edible Halopteris scoparia against cadmium-induced reproductive toxicity in male mice: A biochemical and histopathologic study

Cadmium (Cd) is a toxic metal affecting the reproductive system. Halopteris scoparia (brown algae) is generally consumed as a salad in the Far East countries. This study was conducted to compare and determine the possible protective effects of H. scoparia and vitamin E and C combination (VEC) against cadmium chloride (CdCl2 )-induced reproductive toxicity. A total of 36 male mice were equally divided into as control, CdCl2 (2 mg/kg), CdCl2  + H. scoparia (900 mg/kg), CdCl2  + VEC (200 mg/kg), H. scoparia alone and VEC alone groups. Blood and testis samples were taken for biochemical, histochemical and immunohistochemical analyses. H. scoparia was also examined for antioxidant activity (by DPPH assay) and mineral/trace element content (by ICP-MS method). CdCl2 exposure caused a significant deterioration in body weight, sperm parameters (count, motility, viability and morphology) (p < .001), histopathology, immunoreactivity and testosterone levels. However, H. scoparia improved CdCl2 -induced deterioration effects more successfully than VEC-treated group. The present study suggests that edible H. scoparia can be used as a natural protective agent against Cd-induced testicular damage by possibly enhancing essential element levels or increasing antioxidant defence system.

Zinc supplement ameliorates phthalates-induced reproductive toxicity in male rats

People are inevitably exposed to phthalates (PEs) ubiquitously existing in environment. Our previous studies, simulating the actual situations of people exposure to PEs, have shown that the sub-chronic exposure to low-doses PEs mixture (MIXPs) impaired reproductive function in male rats. Zinc is an important element in maintaining male reproductive functions. However, it is still unknown whether zinc supplement could mitigate PEs-induced male reproductive toxicity or not with sub-chronic low-dose mixture exposure. This study aimed to explore the effect of zinc supplement on the reproductive toxicity caused by sub-chronic MIXPs exposure (160 mg/(kg•body weight)/d, for 90 days) in male rats, and further to reveal the underlying mechanisms. Testosterone (T), FSH and LH in serum, early toxicity indicators in urine, PIWI proteins (PIWIL1 and PIWIL2) expression in testes and pathological examination were performed for toxicity evaluation. Steroidogenic proteins (17β-HSD, StAR, CYP17A1, P450scc and SRD5A) were measured for mechanisms of exploration. The results indicated that zinc supplement could inhibit the T, LH, FSH level decreases in serum, abolish the effect of 5 early toxicity indicators' levels in urine, restrain the alteration of PIWI proteins expression and improve the constructional injury of testes. These effects might be relevant with the suppressed alteration of the expression of steroidogenic proteins induced by MIXPs in rat testicular cells. This work may offer further insights into reducing health risks of MIXPs exposure.

Effects of Bacillus Subtilis-Zinc on Rats with Congenital Zinc Deficiency

This study investigated the effects of dietary supplementation of Bacillus subtilis-zinc on growth rates of the body and organs, nutrient utilization, microbial diversity in caecum, and contents of zinc (Zn) in organs of rats fed a Zn-deficient diet. In trial 1, 72 female pregnant SD rats were allocated to two groups and respectively fed the basal diet containing 13 mg Zn/kg, or the control diet containing 38 mg Zn/kg by supplementing ZnSO₄ from day 10 of pregnancy until the offspring rats 24 days old. In trial 2, 18 offspring rats from the control group were fed the control diet. Ninety offspring from the Zn deficiency group were allocated to 5 groups and were fed the basal diet drenched with ZnSO₄ solution (the total Zn 38 mg/kg), the basal diet only, or the basal diet drenched with Bacillus subtilis-Zn at doses of 2, 17, and 32 mg/kg Zn respectively. Each group had 3 replicates of 6 rats. The experiment lasted for 5 weeks. We found feeding young rats the Zn-deficient diet reduced feed intake, growth rate, unitization efficiencies of nitrogen (N), and Zn content in the organs. Administration of Bacillus subtilis-Zn to rats increased feed intake and the growth rates of the body and liver, kidney and heart, increased N utilization efficiency, and the contents of Zn in heart and brain but not in liver, regulated microbial diversity in the cecal content. The optimal amount of Bacillus subtilis-Zn ranged 15~20 mg Zn/kg, with the corresponding total Zn level at 28~33 mg/kg diet, the effects of which were superior to these by adding ZnSO₄ at 38 mg/kg.

Influence of Cyperus esculentus tubers (tiger nut) on male rat copulatory behavior

Background

Cyperus esculentus tubers (tiger nut) are one of the ancient food sources known to humanity. It is traditionally used in the Middle East to stimulate sexual arousal in men. However, there has been no scientific evidence about its assumed aphrodisiac properties. This study aimed to investigate the influence of tiger nut on the copulatory behavior of sexually active male rats.

Methods

Two sets of sexually active male rats -highly active and moderately active- were identified depending on baseline sexual activity. Rats in each set were randomly divided into a control and treated groups. Highly active rats were treated with doses of 1 and 2 g/kg/d of raw tiger nut powder, while moderately active rats were treated with a dose of 2 g/kg/d. After 30 days’ treatment, copulatory behavior and serum hormonal levels were measured and compared between the groups within each experimental set. Phytochemical analyses including liquid chromatography/mass spectrometry and atomic absorption were performed to elucidate the main constituents of tiger nut that may be responsible for altering serum hormones.

Results

Tiger nut stimulated sexual motivation in both highly and moderately active rats, indicated by reduced mount and intromission latencies in these rats compared to controls. Furthermore, tiger nut improved sexual performance, indicated by increased intromission frequency and ratio, in treated moderately active rats compared to controls. Serum testosterone levels increased significantly after tiger nut administration. Lastly, phytochemical analyses revealed the presence of quercetin, vitamin C, vitamin E, and mineral zinc in tiger nut.

Conclusions

Tiger nut has positive effects on the copulatory behavior of adult male rats.

Comparative analysis of antioxidants against cadmium induced reproductive toxicity in adult male rats

The present study was conducted to compare and evaluate the potential benefits of three different antioxidants in reversing cadmium (Cd)-induced reproductive toxicity in adult male rats. Rats (n = 5) weighing 180 +/- 20 gm were divided into five groups (control, Cd, Cd + sulforaphane, Cd + vitamin E, and Cd + plant extract). Treated groups received CdCl2 (0.2 mg/kg), sulforaphane (25 µg/rat), vitamin E (75 mg/kg), and plant extract (100 mg/kg) for 15 days. Blood samples and testicular tissues were obtained for estimation of testosterone, Zn, and Cd concentration and daily sperm production/efficiency of sperm production. Cadmium exposure caused a significant decrease in final body weight (p < 0.0001). The plasma concentrations of Cd were significantly increased and Zn concentration decreased (p < 0.0001) in the Cd group as compared to the control group. The testicular concentrations of Cd were significantly increased and Zn concentration decreased (p < 0.0001) in the Cd group as compared to the control group. Cadmium exposure caused a significant decrease (p < 0.0001) in plasma testosterone concentrations and daily sperm production as compared to the control group. More significant effects were observed with Cd+sulforaphane, Cd + vitamin E, and Cd + plant extract treated groups in slashing Cd-induced toxicity. Present findings suggest that Ficus religiosa and sulforaphane are more powerful antioxidants as compared to vitamin E in reversing the oxidative stress and can have a protective role against Cd induced reproductive toxicity in adult male rats. Part of the mechanism involved in this protective role seems to be associated with the antioxidant properties of these agents in reducing reproductive damage.

Effects of different sources and levels of zinc on H2O2-induced apoptosis in IEC-6 cells

Zinc has been shown to be an inhibitor of apoptosis for many years. The present study was designed to investigate effects of three zinc chemical forms on H2O2-induced cell apoptosis in IEC-6 cells via analysis of cell vitality, LDH activity, apoptosis percentage, caspase-3 activity, and Bcl-2, Bax, and caspase-3, -8, and -9 gene expression. Cells were divided into H2O2 and zinc sources+H2O2 groups, and there are three different zinc sources [zinc oxide nanoparticle (nano-ZnO), zinc oxide (ZnO), and zinc sulfate (ZnSO4)] and three concentrations (normal = 25 μM, medium = 50 μM, and high = 100 μM) used in this article. In the present study, we found the striking cytotoxicity of H2O2 higher than 200 μM on cell vitality, LDH activity, and apoptosis percentage in the cells using five different concentrations (50, 100, 200, 400, and 800 μM) of H2O2 for 4 h. Moreover, we observed that cell vitality was increased, LDH activity and apoptotic percentage were decreased, and gene expression level of Bax and caspase-3 and -9 was markedly reduced, while gene expression level of Bcl-2 and ratio of Bcl-2/Bax were increased in normal concentration groups of nano-ZnO and ZnSO4 compared with H2O2 group, but no significant difference was observed in caspase-8 gene expression. Furthermore, medium or, more intensely, high concentrations of nano-ZnO and ZnSO4 enhanced H2O2-induced cell apoptosis. Compared with nano-ZnO and ZnSO4, ZnO showed weakest protective effect on H2O2-induced apoptosis at normal concentration and was less toxic to cells at high level. Taken together, we proposed that preventive and protective effects of zinc on H2O2-induced cell apoptosis varied in IEC-6 cells with its chemical forms and concentrations, and maybe for the first time, we suggested that nano-ZnO have a protective effect on H2O2-induced cell apoptosis in IEC-6 cells.

Effect of zinc ions on differentiation of bone marrow-derived mesenchymal stem cells to male germ cells and some germ cell-specific gene expression in rams

This is the first report to describe the effects of zinc (Zn) ions on the expression of germ cell (GC) genes from bone marrow-derived mesenchymal stem cells (BM-MSCs). Zn plays an important role in germinal epithelium maintenance, testosterone secretion, differentiation of GCs, and spermatogenesis. In addition, several studies have suggested that MSCs have the potential for differentiation into numerous cells types, including male GCs. In this study, we have treated passage-3 ram BM-MSCs with 0.14 μg/ml Zn sulfate (ZnSO₄) for a period of 21 days with the intent to determine whether Zn treatment can stimulate MSCs to differentiate into male GCs in vitro. We also sought to determine the type of changes seen in MSCs by Zn treatment. Differentiation into male GCs was evaluated by the assessment of expressions of the following GC-specific markers: VASA, PIWIL2, OCT4, beta1 INTEGRIN (ITG b1), DAZL (by reverse transcription polymerase chain reaction (RT-PCR) and quantitative RT-PCR), and PGP 9.5 (by immunocytochemistry). Also studied were morphological characteristics and changes in alkaline phosphatase activity. Interestingly, Zn upregulated the expressions of VASA and ITG b1 but downregulated PIWIL2 and OCT4. DAZL and PGP 9.5 were not expressed in the treatment group. According to our results, Zn ions did not stimulate BM-MSCs to transdifferentiate into male GCs; however, it changed the expression of GC genes in BM-MSCs. It can be concluded that a possible mechanism by which Zn ions can increase male fertility is by regulation of the expression of testis GC-specific genes in the differentiation process and spermatogenesis.

Pancreatic metallothionein-I may play a role in zinc homeostasis during maternal dietary zinc deficiency in mice

Herein, the function of pancreatic metallothionein (MT)-I during zinc deficiency in pregnancy was examined using transgenic mice, which constitutively express the mouse MT-I gene driven by the rat elastase I promoter. Pancreatic MT protein levels and zinc levels were elevated significantly in the transgenic mice compared with those in control mice. Pregnant transgenic and control mice were fed zinc-deficient (1 micro g/g beginning at d 8) or zinc-adequate (50 micro g/g) diets during pregnancy, and the effects on the morphology of embryos were determined at d 14 of pregnancy (d 1 = vaginal plug). As other indicators of zinc deficiency, maternal pancreatic MT levels, as well as the expression of zinc-regulated genes in the embryonic visceral yolk sac were examined. Under these experimental conditions of moderate dietary zinc deficiency, 21.3% of the embryos in control mice exhibited morphological defects, whereas only 5.8% of the embryos in the elastase-MT-I transgenic females had developed abnormally by d 14. Surprisingly, dietary zinc deficiency caused a >95% decrease in pancreatic MT protein concentration in these transgenic mice. This suggests the post-transcriptional control of MT protein levels during zinc deficiency because the rat elastase I promoter is not metal-regulated. The decrease in pancreatic MT protein levels was paralleled by a dramatic decrease in the relative abundance of MT-I mRNA and a dramatic increase in the relative abundance of the zinc/iron regulated transporter-related zinc transporter-4 (ZIP4) mRNA in the embryonic visceral yolk sac. Thus, the constitutive overexpression of pancreatic MT-I in these mice attenuated, but did not prevent the effects of maternal or embryonic zinc deficiency under these conditions. Overall, these findings are consistent with the hypothesis that mouse pancreatic MT-I may participate in providing a labile pool of maternal zinc for the developing embryo during periods of zinc deficiency.

Determination of metallothionein levels in tissues of young rats fed zinc-enriched diets

The objective of this work was to quantify metallothioneins (MT's) in tissues of rats fed different concentrations of zinc, in order to observe the animal response to the metal in relation to different types of diets, and to assess the nutritional status relating to zinc in the diets. Thirty-two Wistar newly-weaned male rats were distributed into four experimental groups and housed in individual cages. They had free access to water and diet containing different zinc concentrations, named RC (AIN 93-like diet), RH (customary diet of the university restaurant), both non-supplemented, and RCS and RHS, supplemented. After four weeks, the animals were killed and liver, kidneys, femurs and testes were isolated to determine metallothionein levels by a Cd/Hb affinity assay. Zinc content was determined by Flame Atomic Absorption Spectroscopy (FAAS). The results showed that zinc supplementation produced no change in the tissue metallothionein profile in the doses under analysis. The highest metallothionein mean concentration was found in the liver - 36.21 ± 0.88 µg/g (mean for RC-RCS groups), and 28.92 ± 5.32 µg/g (mean for RH-RHS groups). Metallothionein concentrations in testes were quite high, considering the small volume of the organ - 19.29 ± 0.54 µg/g (mean for RC-RCS groups), and 17.22 ± 1.07 µg/g (mean for RH-RHS groups). Significant increases in zinc concentration were observed in the liver of young supplemented rats - 38.94 ± 3.43 µg/g of tissue for RCS, and 42.83 ± 2.78 µg/g of tissue for RHS, and in the femurs - 140.04 ± 6.03 µg/g of tissue for RCS, and 86.57 ± 6.95 µg/g of tissue for RHS. The different carrying zinc food matrices caused no change in the adaptive response to metallothionein metabolism, and the lack of responsiveness towards metallothionein synthesis did not invalidate the results of tissue zinc concentration parameters, which suggest different degrees for zinc bioavailability.

Expression of the gene encoding metallothionein-3 in organs of the reproductive system

Metallothionein-3 (MT-3) is a new MT gene-family member that inhibits survival of rat neurons cultured in presence of brain extracts. Contrary to other MT genes, which are expressed in most tissues and which are highly inducible by metals, MT-3 expression was reported to be mainly in the brain, and it failed to respond to metals in vivo. We show here that MT-3 mRNA is present in several organs other than the brain, as assayed by Northern analyses. In the rat, MT-3 mRNA was detected in the testis, prostate, epididymis, tongue, ovary, uterus, stomach, heart, and seminal vesicles. The MT-3 mRNA levels in the testis, epididymis, prostate, and tongue were 22% of those in brain, while in ovary, uterus, and stomach, they were 4% of the brain level, and they were lower still in the other organs. The MT-3 gene was not inducible by CdCl2 or lipopolysaccharide in rat testis and prostate. In the mouse and the human, relative MT-3 mRNA levels were lower than those found in the rat when compared with those present in brain. Testicular MT-3 transcript levels remained quite constant during rat postnatal development in animals aged from 6 to 43 days. In situ hybridization analyses on human testis sections showed that MT-3 mRNA was present at different levels in both the Leydig cells and the seminiferous tubules. In orchiectomized rats, prostatic MT-3 mRNA was decreased by 75%, and injections of dihydrotestosterone restored MT-3 mRNA levels to control values. Overall, these results show that MT-3 tissue-specific gene expression is broader than previously reported and provide new experimental systems to study the function and mechanism of action of the MT-3 protein.