Zn-adequate Diet Research Articles

CHRONIC ZINC DEFICIENCY INDUCES AN ANTIOXIDANT ADAPTIVE RESPONSE IN RAT LUNG

Few studies are available about the role of dietary zinc (Zn) in respiratory diseases. Adult male rats were divided into 2 groups and fed respectively a moderate Zn-deficient diet and a Zn-adequate control diet. In lung tissue at 2 months, thiobarbituric acid-reactive species (TBARS), total glutathione, glutathione disulfide, protein carbonyls, metallothionein, and the activities of glutathione peroxidase (GPx), catalase, CuZn-superoxide dismutase (CuZnSOD) and glucose-6-phosphate dehydrogenase (G-6-PDH) were increased, but protein thiols decreased. In lung tissue at 4 months, TBARS, metallothionein, and the activities of CuZnSOD, Mn-superoxide dismutase (MnSOD) increased. The activities GPx, catalase, G-6-PDH were lower than control group. The changes were accompanied by histological alterations in Zn-deficient lung. The results provide evidence of the pro-oxidative effects of Zn-deficiency in lung, and suggest that the time of treatment play a key role in determining lung susceptibility to oxidative stress.

Development of iron deficiency decreases zinc requirement of rats.

Effects of the development of Fe deficiency on changes in Fe and Zn metabolism and its possible interactions with dietary Zn were determined. Adequate (25 microg/g) and marginally deficient (5 microg/g) Zn diets containing a sufficient (40 microg/g) dietary Fe levels were fed for 2 wk. Thereafter, both dietary Zn groups were fed an Fe-deficient (2.2 microg/g) diet for 4 wk. It was found that the effects of an Fe-deficient diet began to occur 7 and 14 d after feeding the Fe-deficient diet. At this time, tissue Fe concentrations were depleted and rats were unable to maintain hemoglobin levels. The Fe-deficient diet also induced an immediate fall in plasma Fe concentration, transferrin saturation, and apparent Fe absorption, while the concentrations of liver cytochrome c increased as Fe deficiency developed. Decreases in liver and spleen Fe levels, as well as the activities of blood and bone marrow aminolevulinic acid dehydratase (ALA-D, EC 4.2.1.24) were observed 3, 7, and 14 d after feeding the Fe-deficient diet, and thereafter they were increased. On the other hand, the activity of plasma alkaline phosphatase (ALK-P, EC 3.1.3.1) decreased continuously as Fe deficiency progressed. With severe development of Fe deficiency, rats fed the Zn-adequate diet had increased levels of Zn concentration in the plasma, liver, spleen, kidney, and femur, whereas apparent Zn absorption was decreased. The decrease in apparent Zn absorption and the increase in tissue Zn concentration of rats might be related to the lowered Zn requirement, which is associated with the depressed Zn metabolism caused by feeding Fe-deficient diets.

Zinc-Deficient Rat Embryos Have Increased Caspase 3-like Activity and Apoptosis

Caspase activity is a hallmark of apoptosis. Given that maternal zinc (Zn) deficiency results in apoptosis in the rat embryo, we assessed caspase activity in Zn-deficient embryos. Mid-gestation rat embryos were collected from dams fed either a Zn-deficient (0.5 μg Zn/g) diet ad libitum, or a Zn-adequate (25 μg Zn/g) diet ad libitum or pair fed to dams fed the Zn-deficient diet. Embryos from dams fed the Zn-adequate diet had a normal level of cell death, while embryos from the dams fed the Zn-deficient diet had either increased or normal levels of cell death. Zn-deficient embryos displaying increased cell death had increased caspase activity. Embryos with normal levels of cell death, regardless of maternal diet, had similar caspase activities. Thus, Zn-deficiency-induced apoptosis in vivo is associated with increased caspase activity.

Effects of zinc-methionine on performance of Angora goats

Effects of supplementation with zinc-methionine (Zn-Met), a source of potentially rumen protected methionine and zinc (Zinpro 40, Edina, MN), on mohair growth, BW gain and blood metabolites were investigated in Angora goats. Forty yearling Angora goats (20 wethers and 20 doelings) were offered a basal diet (11.2% CP, 22 ppm Zn, 2.3 Mcal/kg DM) at 4% BW of DM for 120 days. The treatments (1–5) were: 1, 3 and 5 g/day of Zn-Met, 150 mg/day of zinc oxide and control (no supplementation). Supplementation of the diet with Zn-Met (1, 3 and 5 g/day of Zn-Met) increased ( P < 0.07) ADG (65.5 versus 55.9 g/day for control). ADG for goats receiving ZnO was lower ( P < 0.04) than for goats receiving a similar amount of Zn from 3 g/d Zn-Met (50.5 versus 62.9 g/day), although Zn-Met inclusion in the diet numerically ( P = 0.13) increased clean mohair production, which also changed quadratically ( P < 0.09) as Zn-Met level increased (1.59, 1.51, 1.62, 1.60 and 1.59 kg in 120 days) for treatments 1, 2, 3, 4 and 5, respectively. Supplementation of the diet with Zn-Met increased ( P < 0.03) plasma Zn concentration (0.92 versus 0.72 mg/l for control); there were no differences in plasma Zn concentration between goats receiving the ZnO supplement and goats receiving a similar amount of Zn from Zn-Met (0.87 versus 0.92 mg/l; P > 0.56). Plasma methionine concentration was not affected by Zn-Met supplementation ( P > 0.53). In summary, supplementation of a Zn-adequate diet with Zn-Met increased ADG by yearling Angora goats regardless of level of Zn-Met added. Supplementation of 1 g Zn-Met may have positive effect on ADG and mohair growth when diet contains about 20 ppm Zn.

Dietary zinc-methionine enhances mononuclear-phagocytic function in young turkeys. Zinc-methionine, immunity, and Salmonella.

The ability of dietary zinc-methionine (Zn-Met) to enhance mononuclear-phagocytic function against Salmonella arizona and enteritidis was investigated in young turkeys. Feed/gain and body wt gain at 21 d of age were not affected by Zn-Met. The addition of 30 or 45 ppm Zn from Zn-Met to a Zn adequate diet significantly increased cutaneous basophil hypersensitivity to phytohemagglutinin-P. The clearance of intravenously administered S. enteritidis from blood was not affected by 30 ppm of supplemental Zn from Zn-Met. However, 30 ppm Zn from Zn-Met increased the reduction of intravenously administered S. arizona from spleen. Percentages of myeloid and mononuclear-phagocytic cells before and after S. enteritidis infection were not affected by supplemental Zn-Met. Turkeys supplemented with Zn-Met showed enhanced in vitro phagocytosis of S. enteritidis by Sephadex-elicited abdominal exudate cells. The phagocytosis of S. arizona was unaffected by Zn-Met.

Zinc deficiency affects the activity and protein concentration of angiotensin-converting enzyme in rat testes.

Zinc (Zn) deficiency causes hypogonadism in a number of different species. Previous work has shown that Zn deficiency reduces the activity of angiotensin-converting enzyme (ACE), a Zn-dependent enzyme, in the testes of prepubertal rats. These studies were designed to determine whether this effect was caused by a change in the concentration of ACE protein. Thirty-five male rats at 26 days of age were divided into three groups. One group was fed ad libitum a Zn-adequate diet (40 mg/kg); another group was fed a similar diet, but deficient in Zn (< 1.0 mg/kg); a third group was pair-fed to the deficient group. After 4 weeks on these regimens, all rats in the ad libitum-fed group and half of the rats in each of the deficient and pair-fed groups were sacrificed, and tissues were collected for analysis. The remaining animals in the Zn-deficient and pair-fed groups were fed a Zn-adequate diet ad libitum for another 2 weeks, then sacrificed. With the use of an enzyme-linked immunosorbent assay for testicular ACE protein, the effect of these treatments on the concentration of ACE protein in testes was determined. After 4 weeks, ACE activity in testes of the Zn-deficient rats was reduced by 74% compared to that in the ad libitum-fed controls. This was accompanied by a 64% reduction in the amount of ACE protein in the testes. There was not a significant effect of pair-feeding. Refeeding Zn-deficient rats a Zn-adequate diet for 2 weeks restored ACE protein concentrations and ACE activity to values not significantly different from those in pair-fed controls. Soluble ACE, but not particulate ACE, of the epididymis was significantly reduced by Zn deficiency. Because the ACE activity of testes has been found primarily in the germinal cells, and soluble ACE in the epididymis is derived from the testes, these findings suggest that the effects of Zn deficiency on testicular and epididymal ACE is caused by an impairment of spermatid development.

Functional capacity of the residual lymphocytes from zinc-deficient adult mice.

Zn deficiency has been shown to reduce host defence drastically. It was of interest to determine the capacity of the residual lymphocytes from Zn-deficient mice to proliferate and produce lymphokines in response to stimulation since there are many Zn-dependent metalloenzymes that might be altered by the deficiency. To address this question, young adult A/J mice were provided Zn-deficient or Zn-adequate diets or restricted amounts of a Zn-adequate diet for 30 d. Splenocytes from moderately or severely Zn-deficient adult A/J mice gave normal proliferative responses and generated adequate interleukin II (IL-2) activity when stimulated with the mitogen Concanavalin A. However, splenocytes from deficient mice exhibited a higher degree of proliferation (about 150%) and production of IL-2 in response to foreign target cells compared with T-cells prepared from mice provided a Zn-adequate diet. B-cells from deficient mice stimulated in vivo with sheep erythrocytes produced fewer total numbers of plaque-forming cells (PFC) per spleen. Nevertheless, the proportion or number of PFC/10(6) viable splenocytes and the amounts of IgM and IgG antibody produced per PFC were equivalent to those of adequately-fed and restricted-fed controls. The previously described responses were not significantly affected by whether the level of Zn in the culture medium was adequate or limiting. Based on these tests it appeared that the residual splenic lymphocytes of Zn-deficient mice were able to carry out many fundamental immune processes.

Effects of maternal marginal zinc deficiency on myelin protein profiles in the suckling rat and infant rhesus monkey.

In the current study, the effects of marginal Zn deficiency on myelin protein profiles in neonatal rats and rhesus monkeys were investigated. Following mating, rats were fed a Zn-adequate diet, ad libitum (50 micrograms Zn/g; 50 Zn AL), or a marginal Zn diet (10 micrograms Zn/g) from day 0 (10 Zn d0) or day 14 (10 Zn d14) of gestation to day 20 postnatal. An additional group of dams was restricted-fed the control diet to the food intake of the 10 Zn d0 group (50 Zn RF). Day 20 pup plasma and liver Zn concentrations in the 10 Zn groups were lower than in the 50 Zn groups. In a parallel experiment, rhesus monkeys were fed a Zn-adequate ad libitum diet (100 micrograms Zn/g) or a marginal Zn diet (4 micrograms Zn/g diet; MZD) throughout gestation and lactation. Day 30 monkey infant plasma and liver Zn levels were similar in the MZD and control groups. Rat brain and monkey brain cortex weights were similar among the dietary groups. The amount of myelin recovered (mg protein/g brain) from day 20 rat pups from the 10 Zn groups was lower than that recovered from the 50 Zn rat pups. Myelin recovery from the MZD and control monkey infants was similar. When myelin protein profiles were characterized, it was found that the percentages of high-molecular-weight (HMW) proteins and Wolfgram protein were higher, whereas the percentages of small and large basic proteins were lower in myelin from the 10 Zn d0 and 50 Zn RF pups compared to the distribution in the 50 Zn AL rat pups. Results for the 10 Zn d0 and 10 Zn d14 pups were similar for all of the parameters studied. The percentage of HMW proteins was higher and that of basic protein lower in myelin from MZD monkey infants compared to the percentage of these proteins in myelin from controls. Although the interpretation of the rat data is complicated because of the anorexia associated with Zn deficiency, the observed changes in monkey myelin protein profiles provide strong evidence that maternal Zn deficiency affects myelination in the offspring.

Effects of increased microsomal oxygen radicals on the function and stability of cytochrome P450 in dietary zinc deficient rats

It has been proposed that a biochemical function of Zn is maintenance of the membrane structure and function. Previous research has shown that dietary Zn deficiency causes a leakage of H 2O 2 from the NADPH-dependent P450 enzyme system. Microsomal membranes isolated from Zn-deficient rats are more susceptible to lipid peroxidation. The objectives of this study were to investigate the effects of dietary Zn deficiency on the function and stability of liver microsomal P450 in rats and to study the possible mechanisms involved. In rats fed the Zn-deficient diet, the concentration of total liver microsomal protein was unchanged, but P450 concentration and aminopyrine demethylase activity were significantly decreased compared with rats fed the Zn-adequate diet pair-fed or ad libitum. The decrease in P450 concentration was not accompanied by the appearance of P420. The decrease in enzyme activity was also reflected by impaired drug metabolism in vivo as indicated by increased pentobarbital-induced sleeping time, but a statistically significant difference was found only between the ZnDF and the ZnAL groups. However, membrane lipid peroxidation, as indicated by MDA concentration, was not affected by the dietary treatments. To understand the mechanism by which Zn deficiency causes reduced function and stability of P450, the results obtained from the microsomal membranes isolated from Zn-deficient rats were compared with the results obtained from the microsomal membranes treated with protein denaturants or free radical generating systems in vitro, or microsomal membranes isolated from rats challenged with CC1 4, or FeNTA in vivo. It is concluded that severe dietary Zn deficiency in rats caused a functional and structural impairment of liver microsomal P450 via a free radical medicated-like mechanism.

The effect of dietary zinc depletion and repletion on rats: Zn concentration in various tissues and activity of pancreatic γ-glutamyl hydrolase (EC3.4.22.12) as indices of Zn status

Unlike severe zinc deficiency, marginal Zn deficiency is difficult to identify in rats because no reliable indicator of suboptimal Zn status is currently available. We have previously observed reduced pancreatic gamma-glutamyl hydrolase (EC 3.4.22.12) activity and impaired pteroylpolyglutamate absorption in Zn-deficient rats. In the present study the effect of Zn depletion and repletion on the Zn concentration of various tissues and on the activity of this enzyme was investigated. The objective was to determine the sensitivity of these variables to Zn depletion and to evaluate their usefulness as indices of Zn status. Male Wistar rats (about 180 g), maintained from weanling on a purified Zn-adequate diet, were randomly allocated into twelve groups. A pretreatment control group was killed immediately. The remaining eleven groups were fed on a Zn-deficient diet and a group killed daily for 7 d (Zn-depleted groups). The remaining four groups were re-fed the Zn-adequate diet and a group killed daily (Zn-repleted groups). On analysis, pancreas and spleen Zn levels responded most rapidly to reduced Zn intake, followed by tibia, liver, kidney and plasma. Zn concentration was maintained in testes. Reduced plasma folate levels were also observed. A significant reduction in pancreatic gamma-glutamyl hydrolase activity before the depletion of many tissue Zn stores confirms the Zn sensitivity of the enzyme. It was concluded that future investigation into the inter-relationship between Zn and folate metabolism may be useful in identifying a sensitive, biochemical index of Zn status.

The effect of dietary zinc deficiency on pancreatic gamma-glutamyl hydrolase (EC 3.4.22.12) activity and on the absorption of pteroylpolyglutamate in rats.

The effect of dietary zinc deficiency on gamma-glutamyl hydrolase (EC 3.4.22.12) activity and on pteroylpolyglutamate absorption was investigated in rats. Enzyme activity was determined in pancreas and gut lumen washings. Pteroylpolyglutamate absorption was studied by determining the rise in plasma folate levels following pteroylpolyglutamate ingestion. Two experiments were performed; in each purified diets were given to three groups of immature male Wistar rats for approximately 2 weeks. One group was given a Zn-deficient diet ad lib. (ZD), the second was pair-fed daily with this group on a Zn-adequate diet (PF) and the third was given the Zn-adequate diet ad lib. (AL). In Expt 1, significantly reduced pancreatic gamma-glutamyl hydrolase activity was observed in ZD rats. In Expt 2, pteroylpolyglutamate was administered on day 14 and in the 3 h period following pteroylpolyglutamate ingestion, lumen gamma-glutamyl hydrolase activity and plasma folate levels were significantly lower in ZD rats. Pancreas is reported as the source of lumen gamma-glutamyl hydrolase in rats. The results presented indicate that the pancreatic enzyme is Zn-sensitive. It was concluded that, as a result, gamma-glutamyl hydrolase activity was reduced in the lumen of ZD rats. Consequently the hydrolysis and subsequent absorption of pteroylpolyglutamate was impaired in ZD rats, as indicated by the smaller rise in plasma folate levels that occurred following pteroylpolyglutamate ingestion. Results of this study concur with previous observations in human beings and rats that Zn deficiency has an adverse effect on folate metabolism.

Effect of zinc deficiency on the accumulation of metallothionein and cadmium in the rat liver and kidney.

The effects of zinc (Zn) deficiency and repeated exposure to cadmium (Cd) on the accumulation and distribution of metallothionein (MT), Cd and Zn in the liver and kidney were studied. Male Sprague-Dawley rats were fed either a Zn-deficient (1 ppm) or a Zn-adequate (40 ppm) diet during the experiment, and the rats were injected subcutaneously with a cadmium chloride solution (1.0 mg Cd/kg of body weight, 5 days a week) for 4 weeks. Cadmium, Zn, and Cd-induced MT concentrations in the liver and kidney were lower in the Zn-deficient rats (-Zn + Cd) than in the Zn-adequate rats (+Zn + Cd), while the content of Cd bound to high molecular weight proteins (HMWP) was greater in the Zn-deficient rats (-Zn + Cd). The Zn bound to Cd-induced MT was reduced to 30% in the liver and to 60% in the kidney of the Zn-deficient rats (-Zn + Cd) as compared with that of the Zn-adequate rats (+Zn + Cd). In the kidney of Zn-deficient rats, exposure to Cd caused a decrease in essential Zn associated with HMWP as compared with that of Zn-adequate rats (+Zn + Cd). Thus, Zn-deficiency affected the distribution of Cd in tissues, MT and HMWP and accelerated substantially Cd-induced Zn-deficiency in the kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental zinc deficiency in guinea-pigs: clinical signs and some haematological studies

Thirty-three male, weanling guinea-pigs were divided into two groups. One group was fed on a zinc-deficient (ZnD) diet (1.25 mg Zn/kg diet) for 45 d and then divided into two subgroups: subgroup 1 continued on diet ZnD while subgroup 2 was fed on a Zn-repleted diet (100 mg Zn/kg diet) for 15 d. The second group was fed on a Zn-adequate diet (50 mg Zn/kg diet) for 60 d. Zn deficiency could be produced within 21 d as evidenced by clinical signs and reduction in serum Zn concentration. Clinical signs exhibited were listlessness, scabby lesions on skin near the foot pads, mild alopecia and a reduction in body-weight gain. No effect was observed on food intake. Significant decreases in packed cell volume and total leucocyte count from 48 d onwards accompanied by absolute lymphocytopenia and relative neutrophilia were observed. Supplementation of Zn in the Zn-repleted group resulted in marked, through incomplete, improvement with regard to serum Zn concentration, clinical signs and haematological changes.

The Effects of Zinc Deficiency on Turnover of Cadmium-Metallothionein in Rat Liver

The object of this experiment was to determine the effects of Zn deficiency on the turnover of Cd-induced metallothionein (MT) in rat liver. Male rats were fed a purified Zn-deficient or Zn-adequate diet. After 13 days, the rats were given three daily injections of Cd2+ totaling 1.5 or 3.0 (Zn-deficient) and 3.0 or 6.0 (Zn-adequate) mg Cd/kg body weight. The MT was labeled by injecting the rats with [35S]cystine 2 hours after the final Cd injection. One, 3 or 5 days after labeling, the rats were killed, and their livers were assayed for MT 35S and metal content. The metal composition of MT (mole %) was 41–42% Cd, 51–54% Zn and 4–7% Cu in the Zn-adequate groups and 64% Cd, 27–31% Zn and 6–9% Cu in the Zn-deficient groups. The half-lives of Cd-induced MT in the Zn-deficient rats were 2.6 days (1.5 mg Cd/kg) and 2.8 days (3.0 mg Cd/kg). In the Zn-adequate rats, the half-lives were 3.6 days (3.0 mg Cd/kg) and 3.1 days (6.0 mg Cd/kg). The half-lives of general, soluble hepatic proteins were 4.1 to 4.3 days in all groups. Despite the stabilizing effect of the higher Cd content, the half-life of hepatic MT in the Zn-deficient rats was significantly shorter than in the Zn-adequate rats. These results indicate that hepatic MT degradation is faster in Zn-deficient animals.