Zinc Kinetics Research Articles

Zinc Kinetics Correlate With Length-for-Age z Scores in Bangladeshi Infants

Zinc Kinetics Correlate With Length-for-Age z Scores in Bangladeshi Infants

Zinc Kinetics Correlate With Length-for-Age z Scores in Bangladeshi Infants.

Stunting [length-for-age z score (LAZ) <-2] has multiple causes and is prevalent in areas with low dietary zinc (Zn) intake. Zinc kinetics from non-stunted infants were used in a published model for predicting linear growth; here, we directly measure zinc kinetics in stunted infants. Zinc kinetics were determined in 9-month-old Bangladeshi infants (n = 10), who were non-wasted [weight-for-length z score (WLZ) > -2], ranging in LAZ from -2.9 to -0.43. Stable isotopes were administered 2 hours after a meal as oral ( 70 Zn) and intravenous ( 67 Zn) tracers. After isotope administration, blood was sampled within 5 hours and all urine and feces were collected for 24 hours. Urine was sampled twice-daily out to 9 days. Data were analyzed by compartmental modeling. Daily zinc intake was estimated by the model as the sum of zinc used for growth plus that lost via urine and feces. Zinc absorbed (the amount required to maintain steady state) was the sum of zinc used for growth plus urine and endogenous fecal excretions. The LAZ score correlated with serum zinc concentration ( R = 0.77, P = 0.001), urinary zinc excretion ( R = 0.66, P = 0.010), and fractional zinc absorption from calculated daily intake ( R = 0.58, P = 0.030). In stunted infants (n = 8), the amount of zinc absorbed did not increase with calculated zinc intake unlike published values for non-stunted infants. Zinc kinetics in Bangladeshi infants correlate with LAZ and show that malabsorption of supplemental sources of zinc may occur in stunted infants.

Zinc Kinetics Correlate With Length-for-Age z Scores in Bangladeshi Infants

Zinc Kinetics Correlate With Length-for-Age z Scores in Bangladeshi Infants

Kinetics of Nano-zinc Oxide in Desert Calcareous Soils

A laboratory experiment was carried out to study the kinetics reaction of zinc added to calcareous soils from different fertilizer sources and extracted by DTPA solution. Where two types of fertilizers were added, the first, nano-zinc fertilizers in the form of nano-metallic zinc oxide (ZnnO), nano-chelated zinc (ZnnDTPA), and nano-zinc humate (ZnnHA), while the second type was the same fertilizer sources, but in their regular form (ZnO, ZnDTPA and ZnHA). All of them were added at a concentration of 100 mg kg-1 and the nano and regular zinc sources were incubated after they were added to the soil to know their physical and chemical behavior during different incubation periods of 0, 5, 10, 20, 40, 80, 120 and 160 days, with two replications for each incubation period. After the end of each period, zinc was extracted by DTPA, and the data of extracted zinc were subjected to five kinetic equations to reach the best equation describing the behavior of zinc release. The results showed a rapid decrease in the concentration of zinc extracted at the incubation period of 0 days for all fertilizer sources and the continuation of the decrease in concentration with the length of the incubation period gradually until the end of the period after 160 days. The percentage of decrease in nano-zinc fertilizer was less than that of regular fertilizers. The ZnnDTPA chelated zinc source was superior among the regular and nano fertilizer in giving the highest concentration of zinc throughout the incubation period. The second-order equation was the most efficient in describing the behavior and reaction of zinc kinetics in soil from its different sources. The behavior and kinetics reaction of zinc in soil from its different sources.

Removal of Zn and Cd from Overlying Water by Mangrove Sediments: Testing the Effects of Sediment Resuspension/Redeposition Events

Coastal sediment redeposition after resuspension events may change the sediment capacity to sequester pollutants after the formation of new sediment-water interfaces. To test this hypothesis, radiotracer experiments were performed to evaluate zinc (65Zn) and cadmium (109Cd) removal kinetics by redeposited mangrove sediments. After 24-h experiments, average inventories within redeposited sediments were close to those from control sediments (~ 20% lower in redeposited sediments), while average decreases of 41% (109Cd) and 27% (65Zn) in the half-removal times (t1/2) from overlying water were promoted by redeposited sediments in comparison with control sediments. High variability in metal removal rates, however, implied in no statistically significant differences between t1/2 values, suggesting a low influence of sediment redeposition on the metal removal capacity of mangrove sediments. More limited depth diffusion of metals was observed within redeposited sediments, always within the uppermost centimeter. Possible benefits to water quality by a slightly faster metal diffusion into redeposited sediments may be less effective due to this trend since the metal retention very close to the sediment top can facilitate new remobilization to the overlying water.

A dynamic model for predicting growth in zinc-deficient stunted infants given supplemental zinc

Zinc deficiency limits infant growth and increases susceptibility to infections, which further compromises growth. Zinc supplementation improves the growth of zinc-deficient stunted infants, but the amount, frequency, and duration of zinc supplementation required to restore growth in an individual child is unknown. A dynamic model of zinc metabolism that predicts changes in weight and length of zinc-deficient, stunted infants with dietary zinc would be useful to define effective zinc supplementation regimens. The aims of this study were to develop a dynamic model for zinc metabolism in stunted, zinc-deficient infants and to use that model to predict the growth response when those infants are given zinc supplements. A model of zinc metabolism was developed using data on zinc kinetics, tissue zinc, and growth requirements for healthy 9-mo-old infants. The kinetic model was converted to a dynamic model by replacing the rate constants for zinc absorption and excretion with functions for these processes that change with zinc intake. Predictions of the dynamic model, parameterized for zinc-deficient, stunted infants, were compared with the results of 5 published zinc intervention trials. The model was then used to predict the results for zinc supplementation regimes that varied in the amount, frequency, and duration of zinc dosing. Model predictions agreed with published changes in plasma zinc after zinc supplementation. Predictions of weight and length agreed with 2 studies, but overpredicted values from a third study in which other nutrient deficiencies may have been growth limiting; the model predicted that zinc absorption was impaired in that study. The model suggests that frequent, smaller doses (5-10 mg Zn/d) are more effective for increasing growth in stunted, zinc-deficient 9-mo-old infants than are larger, less-frequent doses. The dose amount affects the duration of dosing necessary to restore and maintain plasma zinc concentration and growth.

Plant-available zinc fixation kinetics in semi-arid alkaline soils of the Southern High Plains

ABSTRACTThis study examined zinc (Zn) fixation pattern and kinetics in three semiarid alkaline soils of the Southern High Plains, USA. Soil chemical data obtained from Zn-extraction experiments conducted at different depths were fitted to various kinetic models to examine Zn fixation patterns. Within the experimental period of 90 days, approximately 57% of the total plant-available Zn fixed occurred in the first 14 days when averaged across all soils and depths. Zinc fixation over the experimental period (90 days) was better described by the power function (pfxn) model (R2 = 0.87–0.92, standard error [SE] = 0.130–0.154), but poorly described by the zero-, first- and second-order models (R2 = 0.55–0.76, SE = 0.038–0.267). Average reaction rate constant (from the pfxn model) was higher in the subsurface soils (0.323), suggesting a more rapid Zn fixation, compared to the surface soils (0.293). Zinc fixation within the first 35 days was also more rapid and better described by both the second-order (R2 = 0.91, SE = 0.018) and pfxn (R2 = 0.92, SE = 0.119) models. Findings are applicable to field settings and kinetic parameters obtained will help to advance Zn studies and management in these semiarid soils.

First PET Imaging Studies With 63Zn-Zinc Citrate in Healthy Human Participants and Patients With Alzheimer Disease.

Abnormalities in zinc homeostasis are indicated in many human diseases, including Alzheimer disease (AD). 63Zn-zinc citrate was developed as a positron emission tomography (PET) imaging probe of zinc transport and used in a first-in-human study in 6 healthy elderly individuals and 6 patients with clinically confirmed AD. Dynamic PET imaging of the brain was performed for 30 minutes following intravenous administration of 63Zn-zinc citrate (∼330 MBq). Subsequently, body PET images were acquired. Urine and venous blood were analyzed to give information on urinary excretion and pharmacokinetics. Regional cerebral 63Zn clearances were compared with 11C-Pittsburgh Compound B (11C-PiB) and 18F-fluorodeoxyglucose (18F-FDG) imaging data. 63Zn-zinc citrate was well tolerated in human participants with no adverse events monitored. Tissues of highest uptake were liver, pancreas, and kidney, with moderate uptake being seen in intestines, prostate (in males), thyroid, spleen, stomach, pituitary, and salivary glands. Moderate brain uptake was observed, and regional dependencies were observed in 63Zn clearance kinetics in relationship with regions of high amyloid-β plaque burden (11C-PiB) and 18F-FDG hypometabolism. In conclusion, zinc transport was successfully imaged in human participants using the PET probe 63Zn-zinc citrate. Primary sites of uptake in the digestive system accent the role of zinc in gastrointestinal function. Preliminary information on zinc kinetics in patients with AD evidenced regional differences in clearance rates in correspondence with regional amyloid-β pathology, warranting further imaging studies of zinc homeostasis in patients with AD.

Influence of zinc administration on its tissue concetration and activity of serum antioxidant enzymes in rats at physical activity

Aim. To investigate the effect of zinc supplementation at physical exercise on the distribution of the metal in the tissues and the activity of serum antioxidant enzymes.
 Methods. Physical activity was simulated using the treadmill. Laboratory animals were distributed to 6 even (n=12) groups. The first and fourth groups of animals received no zinc-containing additives and were imposed to low and high physical activity, respectively. Animals of the 2 and 3 as well as 5 and 6 groups received 5 and 15 mg/kg/day of zinc asparaginate intragastrically and were imposed to low and high physical activity, respectively. The zinc concentrantion in the organs and tissues was determined by inductively coupled plasma mass spectrometry. The activity of antioxidant enzymes was determined by spectrophotometry.
 Results. Administration of zinc asparaginate to the laboratory animals with low physical activity resulted in a dose-dependent increase of the metal concentration in liver and kidney parenchyma and blood serum, as well as in increase of serum glutathione peroxidase activity. Intensive physical activity for 14 days was accompanied by a significant increase in serum and kidney tissue zinc level. At the 7-day exposure to zinc at physical activity, a dose-dependent increase in zinc concentration in the organs and increase of serum glutathione peroxidase activity was registered. Zinc administration together with physical activity for 14 days did not result in a significant change in the balance of metal in the body of animals. In contrast to the 7-day exposure, a combination of factors studied for 14 days was accompanied by increased activity of superoxide dismutase, but not glutathione peroxidase.
 Conclusion. Physical activity of different duration has a significant effect on the zinc kinetics at oral administration, and the activity of serum antioxidant enzymes in laboratory animals.

Zinc pharmacokinetic parameters in the determination of body zinc status in children

Serum or tissue zinc concentrations are often used to assess body zinc status. However, all of these methods are relatively inaccurate. Thus, we investigated three different kinetic methods for the determination of zinc clearance to establish which of these could detect small changes in the body zinc status of children. Forty apparently healthy children were studied. Renal handling of zinc was investigated during intravenous zinc administration (0.06537 mg Zn/kg of body weight), both before and after oral zinc supplementation (5 mg Zn/day for 3 months). Three kinetic methods were used to determine zinc clearance: CZn-Formula A and CZn-Formula B were both used to calculate systemic clearance; the first is a general formula and the second is used for the specific analysis of a single-compartment model; CZn-Formula C is widely used in medical practices to analyze kinetic routine. Basal serum zinc values, which were within the reference range for healthy children, increased significantly after oral zinc supplementation. The three formulas used gave different results for zinc clearance both before and after oral zinc supplementation. CZn-Formula B showed a positive correlation with basal serum zinc concentration after oral supplementation (R2=0.1172, P=0.0306). In addition, CZn-Formula B (P=0.0002) was more effective than CZn-Formula A (P=0.6028) and CZn-Formula C (P=0.0732) in detecting small variations in body zinc status. All three of the formulas used are suitable for studying zinc kinetics; however, CZn-Formula B is particularly effective at detecting small changes in body zinc status in healthy children.

Human zinc deficiency: discovery to initial translation.

Ananda S Prasad first suspected zinc deficiency in 1958 after he, at the request of James A Halsted, evaluated a patient with severe iron deficiency. In addition to iron deficiency, the patient appeared ∼10 y old and was severely stunted and prepubertal, though his chronological and bone age were much older. He also had hepatosplenomegaly and ate clay. The condition was not rare in that 11 cases were reported. In 1961 Prasad joined the Vanderbilt Nutrition Group led by William J. Darby at the US Naval Medical Research Unit-3, Cairo, Egypt. Prasad et al. studied 40 males similar to the index case. Contrasts with the index case included no clay eating and infection with schistosomiasis and hookworm. Zinc kinetics confirmed the zinc deficiency. Endocrine studies showed hypopituitarism. Treatment with zinc and an omnivorous diet was more efficacious for growth than no treatment, diet alone, or iron and diet. Later, Halsted et al. confirmed these findings in stunted Iranian farmers. The key role of diet in the illness became evident when Prasad found 16 severely stunted farmers from 2 oases who were not infected with schistosomiasis or hookworm. Later, Reinhold et al., in Halsted's group, reported that phytate and other indigestible zinc-binding ligands in unleavened bread prepared from high-extraction wheat flour suppress zinc absorption.

Maternal Zinc Intakes and Homeostatic Adjustments during Pregnancy and Lactation

Zinc plays critical roles during embryogenesis, fetal growth, and milk secretion, which increase the zinc need for pregnancy and lactation. Increased needs can be met by increasing the dietary zinc intake, along with making homeostatic adjustments in zinc utilization. Potential homeostatic adjustments include changes in circulating zinc, increased zinc absorption, decreased zinc losses, and changes in whole body zinc kinetics. Although severe zinc deficiency during pregnancy has devastating effects, systematic reviews and meta-analysis of the effect of maternal zinc supplementation on pregnancy outcomes have consistently shown a limited benefit. We hypothesize, therefore, that zinc homeostatic adjustments during pregnancy and lactation improve zinc utilization sufficiently to provide the increased zinc needs in these stages and, therefore, mitigate immediate detrimental effects due to a low zinc intake. The specific questions addressed are the following: How is zinc utilization altered during pregnancy and lactation? Are those homeostatic adjustments influenced by maternal zinc status, dietary zinc, or zinc supplementation? These questions are addressed by critically reviewing results from published human studies on zinc homeostasis during pregnancy and lactation carried out in different populations worldwide.

Zinc isotope ratio imaging of rat brain thin sections from stable isotope tracer studies by LA-MC-ICP-MS

Zinc stable isotope tracers (⁶⁷Zn and ⁷⁰Zn) were injected into rats at two different time points to investigate the feasibility of using tracers to study zinc kinetics at the microscale within distinct tissue features. Laser ablation coupled to multi-collector ICP-MS was used to analyse average isotope ratios in liver thin sections and to generate bio-images showing zinc isotope ratio distribution in brain thin sections. Average isotope ratios of all samples from treated animals were found to be statistically different (P < 0.05) from samples from untreated control animals. Furthermore, differing isotope ratios in physiological features of the brain, namely hippocampus, amygdala, cortex and hypothalamus, were identified. This indicates that these regions differ in their zinc metabolism kinetics. While cortex and hypothalamus contain more tracer two days after injection than 14 days after injection, the opposite is true for hippocampus and amygdala. This study showed that stable isotope tracer experiments can be combined with laser ablation MC-ICP-MS to measure trace element kinetics in tissues at a microscale level.

Plasma Zinc But Not the Exchangeable Zinc Pool Size Differs Between Young and Older Korean Women

This study was done to determine the effect of age on zinc metabolism and status among healthy Korean women. Measures of zinc metabolism and status were measured in eight young women (22–24 years) and seven elderly women (66–75 years) consuming a typical Korean diet. Oral and intravenous tracers highly enriched in 67Zn and 70Zn were administered simultaneously. Multiple plasma, 24-h urines, and fecal samples were collected after isotope administration. In the young women, additional plasma were collected to determine zinc kinetics using a seven-compartmental model. Exchangeable Zinc Pool (EZP) was estimated by Miller’s method. Plasma zinc concentrations were higher in older women than younger women (p < 0.05). EZP and urinary zinc tended to be higher in older women than younger women. Fractional and total zinc absorption and endogenous fecal zinc losses did not differ between young and older women. A comparison of the zinc kinetics of the Korean and American women showed no differences in plasma or EZP zinc parameters. However, absorbed zinc and zinc flux to slowly turning over tissues (Q7) were lower in Korean women than that of Americans (p < 0.01) suggesting the total body zinc content of Korean women is lower than that of American women.

Modeling zinc regulation in small mammals

Due to large zinc discharges into the global environment, both terrestrial and aquatic environments have been polluted with zinc. The embanked floodplains of the lower Rhine River in the Netherlands contain large amounts of heavy metals, including zinc. These large amounts of heavy metals may pose risks to flora and fauna by accumulation in food webs, and risk assessment may be required. However, toxicokinetic models for zinc metabolism in mammalian wildlife species are currently lacking. The present study describes the development of a zinc kinetics model that predicts internal zinc concentrations in small mammals by modeling zinc absorption and excretion dependent on the dietary zinc intake using adapted Michaelis-Menten equations. The equations were parameterized based on experimental data reported in the scientific literature. Within the dietary zinc range of 3 to 104 mg/kg dry weight, the model predicts internal zinc concentrations and shows that the internal zinc is regulated within this range. Outside this range, the model could not be calibrated due to a lack of data. Validation of the model with four small mammal species living in an embanked floodplain along a distributary of the Rhine River illustrated that the model predicts internal zinc concentrations differing up to a factor of 1.6 (Common shrew) to 1.7 (Common vole) from field measurements.

Sensitivity of Zinc Kinetics and Nutritional Assessment of Children Submitted to Venous Zinc Tolerance Test

Objective: The purposes of this study were to investigate the kinetics of zinc in schoolchildren between the ages of 6 and 9 years, of both sexes, and to verify its sensitivity in detecting alterations in body zinc status.Methods: Nutritional assessment was performed by body mass index. Food intake, venous zinc tolerance test, and zinc kinetics were carried out before and after 3-month oral zinc supplementation.Results: Of the 42 children studied, 76.2% had healthy weight. Only energy, calcium, and fiber intake were suboptimal before and after oral zinc supplementation. Serum zinc and total-body zinc clearance, although at normal levels, increased significantly after zinc supplementation.Conclusion: We concluded, therefore, that kinetics is a sensitive tool for detecting changes in body zinc status, even in children without a deficiency of this mineral. Furthermore, kinetics showed a positive response to supplementation and may be a sensitive parameter for evaluating the efficacy of this therapy.

A comparison of zinc metabolism and status among young and older Korean women

This study was done to determine the effect of age on zinc metabolism and status among healthy Korean women. Zinc measures were assessed in 8 young and 7 elderly women. Oral and intravenous tracers enriched in 67Zn and 70Zn, were administered. Multiple plasma and 24‐h urines were collected for 5 d with complete fecal samples for 9 d after isotope administration. In the young women, additional plasma samples were collected to determine zinc kinetics. The size of the Exchangeable Zinc Pool (EZP) was estimated by Miller's method. Plasma zinc was higher in older women than younger women (p&lt;0.05). EZP, EZP/kg, and urinary zinc tended to be higher in older women than younger women. Fractional and total zinc absorption and endogenous fecal zinc losses did not differ between young and older women. The zinc kinetics of the Korean and American women showed no differences in plasma or EZP parameters. However, total absorbed zinc and zinc flux to slowly turning over tissues (Q7) was significantly lower in Korean women than that of Americans (p &lt; 0.01). The zinc status of older Korean women, as measured by plasma zinc and EZP was higher than that of the younger women although there were no changes in zinc absorption or endogenous fecal excretion. The young Korean women absorbed less zinc and transferred less zinc to Q7 than American women suggesting the total body zinc content of the Korean women is lower than that of their American counterparts.

Human zinc kinetics using stable isotope tracers, with a special emphasis on the estimation of the critical value for plasma zinc in humans

Human zinc kinetics using stable isotope tracers, with a special emphasis on the estimation of the critical value for plasma zinc in humans

Development of a Compartmental Model of Zinc Kinetics in Mice

To investigate zinc (Zn) kinetics in mice, tracer (65Zn) was administered orally to 9-wk-old female mice in the fed state and tracer and Zn concentration were measured in 21 tissues over the following 8 d. Data were analyzed by compartmental modeling using WinSAAM. A published model for Zn kinetics in rats was modified to fit the data from mice and to calculate transfer rates and pool sizes of Zn. Parallel studies were performed in mice lacking genes for metallothionein (MT), MT-I and MT-II (MT−/−), to quantify differences in Zn kinetics in the absence of these proteins in vivo. We confirmed that tracer time course in most tissues was similar in wild-type mice and those lacking MT, except for the pancreas of MT−/−, which retained less tracer. By fitting tissue and intestinal data simultaneously, we found that intestinal tracer could be explained by unabsorbed isotope and loss of Zn from pancreas went through plasma. Differences in pancreatic data in MT−/− were explained by Zn turning over twice as fast in this tissue (4 h) compared with wild type (9 h). These kinetic studies provide parameter values for normal, fed mice that can be used to assess Zn kinetics in abnormal conditions, as demonstrated by the higher turnover of Zn in the pancreas of MT knockout mice.

Effect of maximal exercise on the short-term kinetics of zinc metabolism in sedentary men

Objective: To examine the effect of acute exhaustive exercise versus rest on short-term zinc kinetics in men. Design: Crossover design, wherein all subjects were their own control. Setting: University setting,...