Daily zinc supplementation effect on zinc deficiency in rats during prolonged restriction of motor activity

The objective of this investigation was to evaluate the effect of 47 mg zinc supplementation on deficiency of zinc in rats during 98 d of restriction of motor activity (hypokinesia), which appeared by higher plasma zinc concentration. One Hundred 13-week-old Sprague-Dawley male rats weighing 360–390 g were used to perform the studies: They were equally divided into four groups: 1. Unsupplemented control animals (UCA); 2. Unsupplemented hypokinetic animals (UHA); 3. Supplemented control animals (SCA); and 4. Supplemented hypokinetic animals (SHA). For the simulation of the effect of hypokinesia (HK), the UHA and SHA were kept in small individual cages made of wood, which restricted their movements in all directions without hindering food and water intake. The SCA and SHA received daily with their food an additional amount of zinc. Before and during the experimental period of 98 d, plasma, urinary and fecal zinc, balance of zinc, food intake, and body weight were determined at different intervals. In the SHA and UHA, the concentration of zinc in plasma, and the elimination of zinc in urine and feces increased significantly when compared with the SCA and UCA, whereas the balance of zinc was negative. The body weight and food intake decreased significantly in the SHA and UHA when compared with the SCA and UCA. The increased plasma concentration of zinc in both the SHA and UHA groups was in contrast to the observed hypozincnemia during prolonged immobilization as during prolonged hospitalization. This reaction suggests that there may be some other mechanisms that are affecting the process of control and regulation of zinc metabolism during prolonged HK. It was concluded that exposure to prolonged restriction of motor activity of rats induces significant increases in plasma concentration, fecal and urinary elimination of zinc in the presence of negative zinc balance and regardless the daily intake of large amounts of zinc with their food, leading to zinc deficiency.     

Effects of zinc and melatonin deficiency on testicular tissue of rats

The present study was designed to investigate the effects of zinc and/or melatonin deficiency on rat testes. A total of 24 adult male Sprague-Dawley rats were used in this study. The rats were divided into four groups of six rats each, as follows: (I) controls, (II) zinc deficient, (III) pinealectomized, zinc normal, and (IV) pinealectomized, zinc deficient. The plasma zinc levels in the control group were higher than in all the other groups (p<0.01), and those of the zinc-deficient groups II and IV were significantly lower than for group III (p<0.01). The melatonin levels in the controls were also significantly higher than for all other groups (p<0.01) There was no significant difference in sperm production between the controls and the group of animals that had no epiphysis. A significant suppression was observed in the spermatogenetic activity of the zinc-deficient groups (p<0.01). The suppression was higher in group II than in group IV. These results indicate that testicular damage caused by zinc deficiency may be reduced by melatonin deficiency.     

Copper deficiency halves serum dehydroepiandrosterone in rats

DHEA (dehydroepiandrosterone) is a hormone often taken as a dietary supplement to prevent the normal decline with age and in the hope of preventing heart attacks. Rats in two experiments were made deficient in copper by standard methods and criteria. Copper deficiency decreased DHEA in serum by approximately 50%. People who associate higher serum concentrations of DHEA with health probably should eat a diet adequate in copper.     

Zinc availability from zinc lipoate and zinc sulfate in growing rats

The purpose of this study was to investigate the effect of zinc lipoate and zinc sulfate on zinc availability in growing rats. 6 . 6 male albino rats were fed purified diets based on corn starch, egg albumen, sucrose, soy bean oil and cellulose over a 4-week period (diet Ia: 10 mg Zn/kg as zinc sulfate, diet Ib: 10 mg Zn/kg as zinc lipoate, diet IIa: 10 mg Zn/kg as zinc sulfate +0.4% phytic acid, diet IIb: 10 mg Zn/kg as zinc lipoate +0.4% phytic acid, diet IIIa: 20 mg Zn/kg as zinc sulfate + 0.4% phytic acid, diet IIIb: 20 mg Zn/kg as zinc lipoate + 0.4% phytic acid). Zinc lipoate and zinc sulfate both proved to be highly available zinc sources. When 0.4% phytic acid were present in the diets, apparent zinc absorption was generally depressed but was higher from zinc lipoate in tendency than from zinc sulfate. Comparable results were evident for femur zinc, plasma zinc and metallothionein concentrations in liver tissues. This indicates that zinc lipoate could be a valuable zinc source under conditions of low zinc availability. Nevertheless the absence or presence of phytic acid was a more important factor influencing zinc availability than the type of zinc source investigated.     

Zinc status does not affect aluminum deposition in tissues of rats

To examine whether zinc deficiency would increase the toxicity of dietary aluminum, weanling, male Sprague-Dawley rats were fed purified diets containing either 2 or 30 mg Zn/kg diet, with or without 500 mg Al/kg diet for 28 d. Individually pair-fed rats were fed the 30 mg Zn/kg diet with or without added aluminum to control for inanition secondary to zinc deficiency. Rats fed the 2 μg Zn/kg diet showed evidence of zinc deficiency, including anorexia, growth retardation, and depressed concentrations of zinc in tibias and livers. Zinc deficiency did not significantly increase the concentrations of aluminum in the tibias, livers, kidneys, or regions of the brain examined (cerebrum, cerebellum, midbrain, and hippocampus). Inclusion of aluminum in the diet did not alter aluminum concentrations in the various tissues. Under the conditions of this study, zinc deficiency did not result in greater sensitivity to dietary aluminum exposure.     

Testicular atrophy, zinc concentration, and angiotensin-converting enzyme activity in the testes of vitamin a-deficient rats

Angiotensin-converting enzyme (ACE) as a part of the renin angiotensin system (RES) regulates blood pressure and fluid and electrolyte homeostasis, and the enzyme is considered to have a function in reproduction. Reduced enzyme activities have been observed in atrophied testes as a results of zinc and pituitary deficiencies. Vitamin A deficiency causes atrophy of testes. The present study was conducted on three groups of male, 3-wk-old, Wistar rats. After 54 d of the experimental period, testicular weights of the vitamin A-deficient rats (Agroup, allowed free access to vitamin Adeficient diet) was significantly lower than its pair-fed, PF (given restricted amount control diet) and A+ (allowed free access to control diet) groups. Zinc concentrations and both soluble and particulate ACE activities in the testes of vitamin A-deficient rats (Agroup) were significantly lower than the other two groups. No significant differences were observed regarding zinc concentration, particulate ACE, and total ACE activities in the testes of PF and A+ groups. Vitamin A deficiency did not significantly affect the enzyme activity in the lung. From the observations of the present study, we speculate that testicular atrophy in vitamin A deficiency may have resulted from lower zinc concentration and decreased ACE activity in that organ.     

Dietary chromium deficiency effect on sperm count and fertility in rats

Male rats raised on a low chromium diet containing less than 100 ppb chromium had decreased sperm counts and decreased fertility at age 8 months compared to the Cr-supplemented controls. Decreased sperm cell production and fertility were not apparent at age 4 months. At age 7–8 months the frequency of conception was 25 percent or less and the sperm count of the low chromium males was approximately 50 percent of that of the Cr-supplemented rats.     

Zinc deficiency decreases plasma level and hepatic mRNA abundance of apolipoprotein A-I in rats and hamsters

The influence of Zn deficiency on the plasma level as well asthe hepatic and intestinal gene expression of apolipoprotein (apo) A-Iwas examined in rats and hamsters. Male Sprague-Dawley rats (8 wk old)and Golden Syrian hamsters (7 wk old) were assigned to three dietarytreatments: Zn adequate (ZA, 30 mg Zn/kg diet), Zn deficient (ZD,<0.5 mg Zn/kg diet), and Zn replete (ZDA, ZD animals fed the ZA dietfor the last 2 days). The dietary treatments lasted for 18 days forrats or 6 wk for hamsters. For the measurement of apoA-I mRNAabundance, hamster apoA-I cDNA was cloned from the small intestine. Thefull-length 905-base pair cDNA shared ~80% similarity with thehuman, rat, and mouse apoA-I cDNAs. Hepatic and plasma Zn levels werereduced in ZD animals but normalized in ZDA rats and increased in ZDAhamsters compared with ZA animals. Zn deficiency reduced plasma apoA-Iand hepatic apoA-I mRNA levels 13 and 38%, respectively, in ZD rats.The 2 days of Zn replenishment raised plasma apoA-I and hepatic apoA-ImRNA levels in ZDA rats by 34 and 28%, respectively, higher than ZArats. Similarly, these levels were decreased by 18 and 25%,respectively, in ZD hamsters but normalized in ZDA hamsters comparedwith ZA hamsters. In contrast to the alterations of hepatic apoA-I mRNAlevels, neither Zn deficiency nor subsequent Zn repletion producedalterations in the intestinal apoA-I mRNA abundance. Data from thisstudy demonstrated that Zn deficiency specifically decreases hepaticapoA-I gene expression, which may at least be partly responsible forthe reduction of plasma apoA-I levels.

     

Zinc deficiency in rats decreases thrombin-stimulated platelet aggregation by lowering protein kinase C activity secondary to impaired calcium uptake

Aggregation of rat platelets, when stimulated by adenosine diphosphate (ADP) or fluoride, is impaired by zinc deficiency, and the defect is associated with a decreased uptake of external Ca²⁺. Zinc deficiency also impairs the aggregatory response of platelets to phorbol myristate acetate (PMA), an activator of protein kinase C, but low zinc status decreases the PMA response only when calcium is added to the external medium. The purpose of this study was to determine the role of protein kinase C in rat platelet function and its relationship to the zinc deficiency pathology observed in platelets stimulated by thrombin (THR). The percent of maximal aggregation and the concentration of cytosolic-free Ca²⁺ were measured in washed platelets stimulated by THR and PMA. For the protein kinase C experiments platelets were obtained from rats fed a grain-based diet, and for the thrombin experiments they were from rats fed purified diets. In the latter experiments, immature male rats were fed for 2 weeks a low zinc diet (<1 mg/kg) ad libitum or a zinc adequate (100 mg/kg) diet either ad libitum or pair-fed. Zinc deficiency impaired the aggregation of platelets stimulated by 0.045 U/mL of THR by approximately 40%, and the external calcium uptake (0.03 U/mL of THR) was decreased by approximately 30%. Staurosporine, a protein kinase C inhibitor, decreased thrombin-induced aggregation in a concentration-dependent manner, but it had no effect on the external calcium uptake. While PMA had a synergistic effect with thrombin in the stimulation of platelet aggregation, it actually decreased the cytosolic-free calcium response to thrombin. It is concluded that zinc deficiency impairs thrombin-stimulated platelet aggregation and calcium uptake and that protein kinase C activity is essential for rat platelet aggregation. Protein kinase C does not stimulate calcium uptake and must act downstream of the calcium uptake defect. A model of rat platelet activation is presented depicting impaired Ca²⁺ uptake as the primary defect in zinc deficiency.     

Cardioprotective effects of recombinant human erythropoietin in rats with experimental autoimmune myocarditis

Erythropoietin (EPO) has been known to have cytoprotective effects on several types of tissues, presumably through modulation of apoptosis and inflammation. The effect of EPO on myocardial inflammation, however, has not yet been clarified. We investigated the cardioprotective effects of EPO in rats with experimental autoimmune myocarditis (EAM). Seven-week-old Lewis rats immunized with cardiac myosin were treated either with EPO or vehicle and were examined on day 22. EPO attenuated the functional and histological severity of EAM along with suppression of mRNAs of tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 in the hearts as well as a reduction of apoptotic cardiomyocytes. The EPO receptor (EPO-R) was upregulated in the myocardium of EAM compared with that of healthy rats. These results may suggest that EPO ameliorated the progression of EAM by modulating myocardial inflammation and apoptosis.     

Influence of prolonged physical exercise on the erythropoietin concentration in blood

Erythropoietin (EPO) and red blood cells were studied in 15 well-trained men before and several times after a marathon run. Changes in red blood cells reflected changes of plasma volume. Immediately after the run, red blood cells were increased due to haemoconcentration, whereas 31 h later the values were decreased due to haemodilution. The EPO concentration was increased 3 h, and more impressive 31 h, after the run. This long-lasting increase in EPO concentration after the marathon run would seem to be responsible for the increased red blood cell mass in long distance runners.     

Zinc deficiency and the formation of white structures in immature embryo cultures of wheat (Triticum aestivum L.)

The effect of microelements on the induction of embryogenic callus from epiblast and scutellum of wheat (Triticum aestivum L.) embryos was studied by the sequential omission of each of the microelements from Murashige & Skoog medium. Omission of iron caused a marked decrease in yield and poor shoot formation from embryogenic callus. The yield of embryogenic callus on medium without added manganese was also reduced. Omission of boron, copper-cobalt, iodine, and molybdenum had little effect on the induction of embryogenic epiblast callus. By contrast there was a marked increase in the formation of white structures on the medium without any microelements or, specifically without addition of zinc. Since the formation of typical embryoids of wheat is associated with the formation of white structures, our result highlights the importance of certain microelements on somatic embryogenesis of wheat.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - MS medium Murashige & Skoog medium     

Zinc homeostasis in the secretory pathway in yeast

It is estimated that up to 10% of proteins in eukaryotes require zinc for their function. Although the majority of these proteins are located in the nucleus and cytosol, a small subset is secreted from cells or is located within an intracellular compartment. As many of these compartmentalized metalloproteins fold to their native state and bind their zinc cofactor inside an organelle, cells require mechanisms to maintain supply of zinc to these compartments even under conditions of zinc deficiency. At the same time, intracellular compartments can also be the site for storing zinc ions, which then can be mobilized when needed. In this review, we highlight insight that has been obtained from yeast models about how zinc homeostasis is maintained in the secretory pathway and vacuole.     

Zinc uptake by blood cells of rats in zinc deficiency and inflammation

In zinc deficiency, the function of leukocytes is impaired. However, the results of studies on the zinc concentration of blood cells in zinc deficiency are conflicting, probably in part because of technical and analytical problems. The aim of this study was to investigate, under standard conditions, the uptake of⁶⁵Zn-labeled zinc by blood cells, taken from zinc-deficient rats and from rats in which an inflammation is induced. In both conditions, the serum zinc concentration is reduced. In clinical practice, this makes it difficult to determine whether the decrease in serum zinc is the result of a real or an apparent zinc deficiency. In stress, like an inflammatory disease, the decrease of zinc reflects an apparent zinc deficiency because of redistribution of serum zinc into the liver and because of decrease in serum albumin concentration. Over 70% of the serum zinc is bound to albumin. Blood cells from zinc-deficient and control rats were isolated using a discontinuous Percoll gradient and incubated under nearly physiological conditions in a⁶⁵Zn-containing medium. A significant increase in the in vitro uptake of⁶⁵Zn-labeled zinc by the blood cells of zinc-deficient rats was seen: erythrocytes 1.3, mononuclear cells 2.0, and polymorphonuclear cells 2.6 times the control values. During inflammation, no change in⁶⁵Zn-labeled zinc uptake by erythrocytes and mononuclear cells was demonstrated after 2 d, although the serum zinc and albumin concentrations were decreased, but a small but significant increase in zinc uptake by polymorphonuclear cells was observed. This study of⁶⁵Zn uptake in vitro under standard conditions may prove of value for distinguishing in patients real zinc deficiency from apparent zinc deficiency owing to, e.g., stress, although additional experiments should be performed. A part of this study has been presented at the Meeting of The American Gastroenterological Association on May 12–18, 1990, San Antonio, TX, and has been published in abstract inGastroenterology 98 suppl., A423.     

Zinc deficiency during growth: influence on renal function and morphology

This study was designed to investigate the effects of moderate zinc deficiency during growth on renal morphology and function in adult life. Weaned male Wistar rats were divided into two groups and fed either a moderately zinc-deficient diet (zinc: 8 mg/kg, n=12) or a control diet (zinc: 30 mg/kg, n=12) for 60 days. We evaluated: renal parameters, NADPH-diaphorase and nitric oxide synthase activity in kidney, renal morphology and apoptotic cells in renal cortex. Zinc-deficient rats showed a decrease in glomerular filtration rate and no changes in sodium and potassium urinary excretion. Zinc deficiency decreased NADPH diaphorase activity in glomeruli and tubular segment of nephrons, and reduced activity of nitric oxide synthase in the renal medulla and cortex, showing that zinc plays an important role in preservation of the renal nitric oxide system. A reduction in nephron number, glomerular capillary area and number of glomerular nuclei in cortical and juxtamedullary areas was observed in zinc deficient kidneys. Sirius red staining and immunostaining for alpha-smooth muscle-actin and collagen III showed no signs of fibrosis in the renal cortex and medulla. An increase in the number of apoptotic cells in distal tubules and cortical collecting ducts neighboring glomeruli and, to a lesser extent, in the glomeruli was observed in zinc deficient rats. The major finding of our study is the emergence of moderate zinc deficiency during growth as a potential nutritional factor related to abnormalities in renal morphology and function that facilitates the development of cardiovascular and renal diseases in adult life.     

Zinc deficiency as a critical problem in wheat production in Central Anatolia

In a soil and plant survey, and in field and greenhouse experiments the nutritional status of wheat plants was evaluated for Zn, Fe, Mn and Cu in Central Anatolia, a semi-arid region and the major wheat growing area of Turkey.All 76 soils sampled in Central Anatolia were highly alkaline with an average pH of 7. 9. More than 90% of soils contained less than 0.5 mg kg^-1 DTPA-extractable Zn, which is widely considered to be the critical deficiency concentration of Zn for plants grown on calcareous soils. About 25% of soils contained less than 2.5 mg kg^-1 DTPA-extractable Fe which is considered to be the critical deficiency concentration of Fe for plants. The concentrations of DTPA-extractable Mn and Cu were in the sufficiency range. Also the Zn concentrations in leaves were very low. More than 80% of the 136 leaf samples contained less than 10 mg Zn kg^–1. By contrast, concentrations of Fe, Mn and Cu in leaves were in the sufficient range.In the field experiments at six locations, application of 23 kg Zn ha^-1 increased grain yield in all locations. Relative increases in grain yield resulting from Zn application ranged between 5% to 554% with a mean of 43%. Significant increases in grain yield (more than 31%) as a result of Zn application were found for the locations where soils contained less than 0.15 mg kg^-1 DTPA-extractable Zn.In pot experirnents with two bread (Triticum aestivum, cvs. Gerek-79 and Kirac-66) and two durum wheats (Triticum durum, cvs. Kiziltan-91 and Kunduru-1149), an application of 10 mg Zn kg^-1 soil enhanced shoot dry matter production by about 3.5-fold in soils containing 0.11 mg kg^-1 and 0.15 mg kg^-1 DTPA-extractable Zn. Results from both field observations and greenhouse experiments showed that durum wheats were more susceptible to Zn deficiency than the bread wheats. On Zn deficient soils, durum wheats as compared to bread wheats developed deficiency symptoms in shoots earlier and to a greater extent, and had lower Zn concentration in shoot tissue and lower Zn content per shoot than the bread wheats.The results presented in this paper demonstrate that (i) Zn deficiency is a critical nutritional problem in Central Anatolia substantially limiting wheat production, (ii) durum wheats possess higher sensitivity to Zn deficient conditions than bread wheats, and (iii) wheat plants grown in calcareous soils containing less than 0.2 mg kg^-1 DTPA-extractable Zn significantly respond to soil Zn applications. The results also indicate that low levels of Zn in soils and plant materials (i.e. grains) could be a major contributing factor for widespread occurrence of Zn deficiency in children in Turkey, whose diets are dominated by cereal-based foods.     

Zinc deficiency does not enhance LDL uptake by P 388 D1 macrophages in vitro

The aim of the study was to investigate the effect of zinc depletion on the susceptibility of Wistar rat low-density lipoproteins (LDL) to peroxidation and their uptake by macrophages, before and after in vitro oxidation. The rats were fed for 7 wk a Zn-adequate diet (100 ppm) ad libitum (AL), a Zn-deficient diet (0.2 ppm) ad libitum (ZD), or a Zn-adequate diet according to the pair-feeding method (PF). Zinc status was determined and, for each group, blood was pooled, and LDL were isolated and labeled with¹²⁵Iodine. An aliquot of each LDL sample was oxidized using Fe^II 10 μM/ascorbate 250 μM. Oxidized and nonoxidized (native) LDL were incubated with P 388 D1 macrophages, and their rates of uptake and degradation by macrophages were measured. Before oxidation, LDL uptake and degradation were not modified by the diet, suggesting that Zn deficiency did not modify rat LDL in vivo. After oxidation, both LDL uptake and degradation were significantly enhanced in the three groups. Nevertheless, we did not observe a significant effect of Zn deficiency. This observation suggests that, in our experimental conditions, Zn deficiency did not modify LDL catabolism.     

Dietary iron deficiency decreases serum osteocalcin concentration and bone mineral density in rats

We investigated the effects of dietary iron deficiency on bone metabolism by measuring markers of bone turnover in rats. Twelve 3-week-old male Wistar-strain rats were fed a control diet or an iron-deficient diet for 4 weeks. Dietary iron deficiency decreased hemoglobin concentration and increased heart weight. Serum osteocalcin concentration, bone mineral content, bone mineral density, and mechanical strength of the femur were significantly lower in the iron-deficient group than in the control group. These results suggested that dietary iron deficiency affected bone, which might have been due to a decrease in bone formation in rats.     

A short-term zinc-deficient diet decreases bone formation through down-regulated BMP2 in rat bone

We investigated the effects of a short-term dietary zinc deficiency on bone metabolism. Zinc deficiency increased the mRNA expression of zinc uptake transporters such as Zip1, Zip13, and Zip14 in bone. However, zinc deficiency might not maintain zinc storage in bone, resulting in a decrease in bone formation through downregulation of the expression levels of osteoblastogenesis-related genes.