Zinc and small babies

Effect of reduced placental expression of zinc transporters on selective intrauterine growth restriction in monochorionic diamniotic twin pregnancies

Zinc is an essential trace element. The regulatory mechanism of zinc and its transporters in fetal growth in monochorionic diamniotic (MCDA) twins with selective intrauterine growth restriction (MCDA-sIUGR) is unclear. A total of 45 MCDA twins were divided into two groups, MCDA (n=37) and MCDA-sIUGR (n=8), to investigate their possible effects on fetal growth. Maternal and fetal serum zinc levels were measured using a microassay. Immunohistochemistry and western blotting were performed to quantify the expression and localization of zinc transporters. Correlation scatter plots and matrices were used to test the correlation between maternal and cord serum zinc levels, placental zinc transporters, and fetal growth. There was a significant difference in fetal birth weight and placental weight among MCDA TH (higher birth weight of twin), MCDA TL (lower birth weight of twin), MCDA-sIUGR TH, and MCDA-sIUGR TL groups (P < .05), among which the MCDA-sIUGR TL group was found to be significantly lower than the other three groups (P < .05). Placental zinc transporters, including Zip 2, metal regulatory transcription factor 1 (MTF 1), and ZnT1, were significantly decreased in the MCDA-sIUGR TL group compared to those in the other three groups (P < .05). Furthermore, we observed varying degrees of correlation between fetal weight and maternal/fetal serum zinc levels and placental zinc transporters. Our study indicates that placental zinc transporters are impaired in MCDA-sIUGR, particularly in lightweight twins. Therefore, we hypothesized that the reduced placental expression of zinc transporters may affect fetal growth in MCDA twins.

Dietary phytate, zinc and hidden zinc deficiency

Epidemiological data suggest at least one in five humans are at risk of zinc deficiency. This is in large part because the phytate in cereals and legumes has not been removed during food preparation. Phytate, a potent indigestible ligand for zinc prevents it's absorption. Without knowledge of the frequency of consumption of foods rich in phytate, and foods rich in bioavailable zinc, the recognition of zinc deficiency early in the illness may be difficult. Plasma zinc is insensitive to early zinc deficiency. Serum ferritin concentration≤20μg/L is a potential indirect biomarker. Early effects of zinc deficiency are chemical, functional and may be "hidden". The clinical problem is illustrated by 2 studies that involved US Mexican-American children, and US premenopausal women. The children were consuming home diets that included traditional foods high in phytate. The premenopausal women were not eating red meat on a regular basis, and their consumption of phytate was mainly from bran breakfast cereals. In both studies the presence of zinc deficiency was proven by functional responses to controlled zinc treatment. In the children lean-mass, reasoning, and immunity were significantly affected. In the women memory, reasoning, and eye-hand coordination were significantly affected. A screening self-administered food frequency questionnaire for office might help caregiver's identify patients at risk of zinc deficiency.

Zinc: The Metal of Life

The importance of zinc was 1st reported for Aspergillus niger. It took over 75 y to realize that zinc is also an essential trace element for rats, and an additional 30 y went by before it was recognized that this was also true for humans. The adult body contains about 2 to 3 g of zinc. Zinc is found in organs, tissues, bones, fluids, and cells. It is essential for many physiological functions and plays a significant role in a number of enzyme actions in the living systems. Bioinformatics estimates report that 10% of the human proteome contains zinc-binding sites. Based on its role in such a plethora of cellular components, zinc has diverse biological functions from enzymatic catalysis to playing a crucial role in cellular neuronal systems. Thus, based on the various published studies and reports, it is pertinent to state that zinc is one of the most important essential trace metals in human nutrition and lifestyle. Its deficiency may severely affect the homeostasis of a biological system. This review compiles the role of zinc in prophylaxis/therapeutics and provides current information about its effect on living beings.

Do multiple concurrent infections in African children cause irreversible immunological damage?

Much of the developing world, particularly sub-Saharan Africa, has high levels of morbidity and mortality associated with infectious diseases. The greatest risk of invasive disease is in the young, the malnourished and HIV-infected individuals. In many regions in Africa these vulnerable groups and the wider general population are under constant immune pressure from a range of environmental factors, under-nutrition and multiple concurrent infections from birth through to adulthood. Intermittent microbial exposure during childhood is required for the generation of naturally acquired immunity capable of protection against a range of infectious diseases in adult life. However, in the context of a resource-poor setting, the heavy burden of malarial, diarrhoeal and respiratory infections in childhood may subvert or suppress immune responses rather than protect, resulting in sub-optimal immunity. This review will explore how poor maternal health, HIV exposure, socio-economic and seasonal factors conspire to weaken childhood immune defences to disease and discuss the hypothesis that recurrent infections may drive immune dysregulation, leading to relative immune senescence and premature immunological aging.

Does lack of multinutrient supplementation during early pregnancy increase vulnerability to alcohol-related preterm or small-for-gestational-age births?

The objective of this study was to assess whether women who do not take multinutrient supplements during early pregnancy are more susceptible to the effects of low-to-moderate alcohol consumption on preterm birth and small-for-gestational-age birth (SGA) compared to women who do take multinutrients. This analysis included 800 singleton live births to mothers from a cohort of pregnant women recruited for a population-based cohort study conducted in the Kaiser Permanente Medical Care Program in Northern California. Participants were recruited in their first trimester of pregnancy and information about their alcohol use and supplement intake during pregnancy was collected. Preterm birth (n = 53, 7%) was defined as a delivery prior to 37 completed weeks of gestation and SGA birth (n = 124, 16%) was defined as birth weight less than the 10th percentile for the infant’s gestational age and sex compared to US singleton live births. A twofold increase in the odds of SGA birth attributed to low-to-moderate alcohol intake was found among multinutrient supplement non-users (95% CI: 1.1, 5.3). Yet, among multinutrient supplement users, there was no increased risk of an SGA birth for women who drank low-to-moderately compared to women who abstained (aOR: 0.97, 95% CI: 0.6, 1.6). Similar results emerged for preterm birth. Our findings provide marginal evidence that multinutrient supplementation during early pregnancy may modify the risk of SGA births and preterm birth associated with alcohol consumption during pregnancy and may have important implications for pregnant women and women of child-bearing age. However, future research needs to be conducted.

Prenatal zinc supplementation of zinc-adequate rats adversely affects immunity in offspring

We previously showed that zinc (Zn) supplementation of Zn-adequate dams induced immunosuppressive effects that persist in the offspring after weaning. We investigated whether the immunosuppressive effects were due to in utero exposure and/or mediated via milk using a cross-fostering design. Pregnant rats with adequate Zn nutriture were supplemented with either Zn (1.5 mg Zn in 10% sucrose) or placebo (10% sucrose) during pregnancy (3 times/wk). At postnatal d 3, 4 pups of Zn-supplemented dams (Zn-P) were exchanged with 4 of placebo-supplemented dams (P-Zn). The remaining pups continued with their biological mothers (Zn-Zn and P-P). Pups were orally immunized with dinitrophenol ovalbumin-BSA and/or cholera toxin B subunit (CTB), and serum Zn concentrations and cellular and humoral responses were assessed. Pups of Zn-supplemented dams had higher serum Zn when fostered either by placebo- or Zn-supplemented dams compared to pups of placebo-supplemented dams (P < 0.01). Postnatal Zn exposure reduced the number of Peyer's patches in both the Zn-Zn and P-Zn groups (P < 0.01). Prenatal Zn exposure suppressed CTB- (P = 0.05) and BSA-specific proliferation response of Peyer's Patch lymphocytes (P = 0.07). Prenatal Zn exposure effects on the splenocyte cytokine response were differently influenced by fostering mothers' Zn status. Antigen presenting cell (APC) activity of splenocytes was lower in the Zn-Zn group than in the P-P group (P < 0.08). In conclusion, prenatal Zn exposure increases serum Zn levels in pups and suppresses antigen-specific proliferation and antibody responses and APC function, whereas postnatal exposure may suppress the mucosal immune reservoir.

The plausibility of maternal nutritional status being a contributing factor to the risk for fetal alcohol spectrum disorders: the potential influence of zinc status as an example

There is increasing evidence that human pregnancy outcome can be significantly compromised by suboptimal maternal nutritional status. Poor diet results in a maternal-fetal environment in which the teratogenicity of other insults such as alcohol might be amplified. As an example, there is evidence that zinc (Zn) can interact with maternal alcohol exposure to influence the risk for fetal alcohol spectrum disorders (FASD). Studies with experimental animals have shown that the teratogenicity of alcohol is increased under conditions of Zn deficiency, whereas its teratogenicity is lessened when animals are given Zn-supplemented diets or Zn injections before the alcohol exposure. Alcohol can precipitate an acute-phase response, resulting in a subsequent increase in maternal liver metallothionein, which can sequester Zn and lead to decreased Zn transfer to the fetus. Importantly, the teratogenicity of acute alcohol exposure is reduced in metallothionein knockout mice, which can have improved Zn transfer to the conceptus relative to wild-type mice. Consistent with the above, Zn status has been reported to be low in alcoholic women at delivery. Preliminary data from two basic science and clinical nutritional studies that are ongoing as part of the international Collaborative Initiative on Fetal Alcohol Spectrum Disorders support the potential role of Zn, among other nutritional factors, relative to risk for FASD. Importantly, the nutrient levels being examined in these studies are relevant to general clinical populations and represent suboptimal levels rather than severe deficiencies. These data suggest that moderate deficiencies in single nutrients can act as permissive factors for FASD, and that adequate nutritional status or intervention through supplementation may provide protection from some of the adverse effects of prenatal alcohol exposure.

Do multivitamin supplements modify the relationship between prenatal alcohol intake and miscarriage?

OBJECTIVE

To determine whether multivitamin supplements modify the relationship between alcohol consumption during pregnancy and the risk of miscarriage.

STUDY DESIGN

We used data from a population-based cohort study of pregnant women (n=1061; response rate=39%). Participants were asked about their alcohol consumption and vitamin intake during pregnancy.

RESULTS

Among multivitamin nonusers, women who drank alcohol during their pregnancy were more likely to have a miscarriage compared with women who abstained (adjusted hazard ratio, 1.67; 95% confidence interval, 1.04-2.69). However, among multivitamin users, there was no difference in the risk of miscarriage between alcohol consumers and abstainers. Results suggest the volume of alcohol as well as the timing of multivitamin supplementation may also be important.

CONCLUSION

Our findings suggest that a woman of childbearing years might decrease her risk of miscarriage associated with alcohol intake by taking multivitamin supplements. However, our findings should be interpreted with caution and future research replicating these findings is necessary.

Zinc requirements and the risks and benefits of zinc supplementation

The adult human contains 2-3g of zinc, about 0.1% of which are replenished daily. On this basis and based on estimates of bioavailability of zinc, dietary recommendations are made for apparently healthy individuals. Absent chemical, functional, and/or physical signs of zinc deficiency are assumed indicative of adequacy. More specific data are seldom available. Changing food preferences and availability, and new food preparation, preservation, and processing technologies may require re-evaluation of past data. Conservative estimates suggest that 25% of the world's population is at risk of zinc deficiency. Most of the affected are poor, and rarely consume foods rich in highly bioavailable zinc, while subsisting on foods that are rich in inhibitors of zinc absorption and/or contain relatively small amounts of bioavailable zinc. In contrast, among the relatively affluent, food choice is a major factor affecting risk of zinc deficiency. An additional problem, especially among the relatively affluent, is risk of chronic zinc toxicity caused by excessive consumption of zinc supplements. High intakes of zinc relative to copper can cause copper deficiency. A major challenge that has not been resolved for maximum health benefit is the proximity of the recommended dietary allowance (RDA) and the reference dose (RfD) for safe intake of zinc. Present recommendations do not consider the numerous dietary factors that influence the bioavailability of zinc and copper, and the likelihood of toxicity from zinc supplements. Thus the current assumed range between safe and unsafe intakes of zinc is relatively narrow. At present, assessment of zinc nutriture is complex, involving a number of chemical and functional measurements that have limitations in sensitivity and specificity. This approach needs to be enhanced so that zinc deficiency or excess can be detected early. An increasing number of associations between diseases and zinc status and apparently normal states of health, where additional zinc might be efficacious to prevent certain conditions, point at the pharmacology of zinc compounds as a promising area. For example, relationships between zinc and diabetes mellitus are an area where research might prove fruitful. In our opinion, a multidisciplinary approach will most likely result in success in this fertile area for translational research.

The plausibility of micronutrient deficiencies being a significant contributing factor to the occurrence of pregnancy complications

Numerous studies support the concept that a major cause of pregnancy complications can be suboptimal embryonic and fetal nutrition. Although the negative effects of diets low in energy on pregnancy outcome are well documented, less clear are the effects of diets that are low in one or more essential micronutrients. However, several observational and intervention studies suggest that diets low in essential vitamins and minerals can pose a significant reproductive risk in diverse human populations. Although maternal nutritional deficiencies typically occur as a result of low dietary intakes of essential nutrients, nutritional deficiencies at the level of the conceptus can arise through multiple mechanisms. Evidence from experimental animals supports the concept that in addition to primary deficiencies, secondary embryonic and fetal nutritional deficiencies can be caused by diverse factors including genetics, maternal disease, toxicant insults and physiological stressors that can trigger a maternal acute phase response. These secondary responses may be significant contributors to the occurrence of birth defects. An implication of the above is that the frequency and severity of pregnancy complications may be reduced through an improvement in the micronutrient status of the mother.

Micronutrient status during pregnancy and outcomes for newborn infants in developing countries

More than 9 million neonatal deaths occur each year, 98% of them in developing countries. Neonatal deaths account for two-thirds of deaths in infancy and 40% of deaths before age 5 y. The major direct causes of neonatal death are infections, preterm delivery and asphyxia. Important indirect causes include low birth weight and hypothermia. The present body of work on multiple micronutrient interventions is not sufficient for us to draw conclusions on their effects on neonatal well-being. Because studies have generally concentrated on single micronutrients and a range of outcomes, this paper reviews the findings for individual nutrients and then summarizes the situation. The evidence for the contribution of micronutrient deficiencies to perinatal mortality and duration of gestation is limited, and the evidence base for individual micronutrient effects on neonatal mortality and morbidity is patchy. To translate knowledge into policy, community evaluations of effect and an expanded evidence base that includes affordability, acceptability and scalability are also required. A balance between supply-side and demand-side interventions must be struck, with an emphasis on effect and sustainability. Among the key requirements are randomized, controlled community effectiveness trials of the effect of micronutrient supplementation in pregnancy on perinatal mortality and neurodevelopment, studies on improving adherence and studies on the relation between micronutrient deficiencies and sepsis and neonatal encephalopathy. It would also be helpful to look at mechanisms for bringing the periconceptional period within the ambit of trials.

A randomized trial investigating an iron-rich natural mineral water as a prophylaxis against iron deficiency in pregnancy

Spatone Iron-Plus is a naturally occurring mineral water from Trefriw Wells Spa in Conwy County, North Wales, UK. It contains approximately 0.20 mg of iron per millilitre as ferrous sulphate and has been shown to provide iron in a highly bio-available form. A 24 ml sachet contains approximately 5 mg of iron. Iron deficiency is common in the obstetric population. However, compliance with traditional iron supplements is poor because of gastrointestinal side-effects. We designed a randomized, double-blind, placebo-controlled trial. A total of 102 low-risk antenatal patients, who were noncompliant with routinely prescribed ferrous sulphate tablets, were randomized to receive 48 ml of Spatone water or placebo. The study was conducted between 22 and 28 weeks gestation. Primary outcome measures were compliance, gastrointestinal side-effects and changes in ferritin levels during the trial period. Compliance in the intervention group was 57% compared with 67% in the control group, P = 0.22. Dyspepsia scores, as determined by a recognized and well-validated questionnaire, did not differ between the two groups. During the trial period, mean ferritin levels fell by 24% in the Spatone Iron-Plus group compared with a mean fall of 51% in ferritin levels among the control group, P = 0.016.

Association between lower hair zinc levels and neural tube defects

Though folic acid supplementation has reduced the incidence of Neural Tube Defects (NTD), NTD still constitutes one of the important congenital malformations having wide medical, social and ethical implications. Zinc deficiency has been reported to produce NTD in animals. This study was designed to evaluate zinc status of the newborn babies with NTD and their mothers. Eighty newborn babies with NTD and their mothers served as cases. Eighty apparently normal newborn babies and their mothers served as controls. Serum and scalp hair zinc levels were analyzed by atomic absorption spectrophotometry. The mean (+/- SD) serum and hair levels in normal mothers were 74.1 +/- 4.1 micrograms/dl and 142.3 +/- 8.0 micrograms/g respectively. The mean (+/- SD) serum and hair levels of the mothers who delivered NTD babies were 75.7 +/- 5.6 micrograms/dl and 129.9 +/- 5.3 micrograms/g respectively. The mean (+/- SD) serum and hair levels in normal newborn babies were 77.8 +/- 5.3 micrograms/dl and 188.8 +/- 6.2 micrograms/g respectively. The mean (+/- SD) serum and hair levels in NTD babies were 80.1 +/- 12.9 micrograms/dl and 174.2 +/- 10.7 micrograms/g respectively. The hair zinc levels of the affected babies and their mothers were significantly lower (P < 0.001) than the controls. This study has found association between NTD and decreased hair zinc levels and large population based studies are recommended to confirm the association between zinc and NTD and to investigate whether zinc supplementation would reduce the overall incidence of NTD.

Serum zinc and copper levels in the maternal blood and cord blood of neonates

Estimation of serum zinc and copper in the maternal blood and cord blood of neonates was carried out to correlate the trace metals in the neonates and their mothers in relation to gestational age and birth weight. Sixty-five healthy neonates, both term and preterm and their mothers were selected. This cross sectional study was done at Azimpur Maternity Centre, Dhaka Medical College Hospital and Chemistry Division, Atomic Energy Centre, Dhaka, Bangladesh from July 1997 to June 1998. The estimation of trace metals was carried out by Atomic Absorption Spectrophotometry (AAS). The mean serum zinc levels in the maternal blood and cord blood were 0.47 +/- 0.24 microgram/ml and 0.85 +/- 0.33 microgram/ml respectively and the mean copper levels in the maternal blood and cord blood were 1.37 +/- 0.62 micrograms/ml and 0.31 +/- 0.32 microgram/ml respectively. Cord blood zinc level was significantly higher and cord blood copper level was significantly lower than the corresponding maternal blood levels. There was no significant correlation between gestational age and serum zinc levels in the cord or maternal blood. But significant inverse correlation was found between gestational age and serum levels of copper in the maternal and cord blood.

Determinants of maternal zinc status during pregnancy

Zinc deficiency in pregnant experimental animals limits fetal growth and, if severe, causes teratogenic anomalies. Although the data from human studies are not consistent, similar outcomes have been observed and were associated with poor maternal zinc status. This paper reviews humans studies of zinc status and pregnancy outcome, describes the physiologic adjustments in zinc utilization during pregnancy to meet fetal needs while maintaining maternal status, and identifies dietary and environmental conditions that may override those physiologic adjustments and put the health of the mother and fetus at risk. Adjustments in intestinal zinc absorption appear to be the primary means by which zinc retention is increased to meet fetal demands. However, transfer of sufficient zinc to the fetus is dependent on maintenance of normal maternal serum zinc concentrations. Conditions that could interfere with zinc absorption include intake of cereal-based diets that are high in phytate, high intakes of supplemental iron, or any gastrointestinal disease. Conditions that may alter maternal plasma zinc concentrations and the transport of zinc to the fetus include smoking, alcohol abuse, and an acute stress response to infection or trauma. Supplemental zinc may be prudent for women with poor gastrointestinal function or with any of these conditions during pregnancy.

Changes in dietary zinc and copper affect zinc-status indicators of postmenopausal women, notably, extracellular superoxide dismutase and amyloid precursor proteins

BACKGROUND

Zinc is an essential trace element for human health and well-being; however, methods currently available for the assessment of zinc status in humans are unsatisfactory.

OBJECTIVE

The objective was to critically evaluate the use of various indicators of zinc status in humans in a controlled metabolic ward study.

DESIGN

Indicators of zinc status were measured in 25 healthy postmenopausal women aged 64.9 +/- 6.7 y. After a 10-d equilibration period, volunteers consumed a diet with either a low (1 mg/d; n = 12) or a high (3 mg/d; n = 13) copper content based on a total energy content of 8.4 MJ. They received the same amount of copper throughout the study. Both groups were fed the basal diet (3 mg Zn/d) with no zinc supplement for one 90-d period, and the diet supplemented with 50 mg Zn/d for another 90-d period.

RESULTS

Zinc supplementation significantly increased (P < 0.0001) extracellular but not erythrocyte superoxide dismutase activity. This increase was more apparent when subjects were fed the low-copper diet. Zinc supplementation in combination with the low-copper diet significantly decreased (P < 0.01) amyloid precursor protein expression in platelets. Other indicators of zinc status that were significantly elevated after zinc supplementation were as follows: plasma zinc and free thyroxine concentrations and mononuclear 5'-nucleotidase activity.

CONCLUSION

The measurement of serum extracellular superoxide dismutase activity may be useful as a marker for the functional assessment of zinc status in humans.

History of zinc as related to brain function

Zinc (Zn) is essential for synthesis of coenzymes that mediate biogenic-amine synthesis and metabolism. Zn from vesicles in presynaptic terminals of certain glutaminergic neurons modulates postsynaptic N-methyl-D-aspartate (NMDA) receptors for glutamate. Large amounts of Zn released from vesicles by seizures or ischemia can kill postsynaptic neurons. Acute Zn deficiency impairs brain function of experimental animals and humans. Zn deficiency in experimental animals during early brain development causes malformations, whereas deficiency later in brain development causes microscopic abnormalities and impairs subsequent function. A limited number of studies suggest that similar phenomena can occur in humans.

Maternal plasma zinc concentrations and pregnancy outcome

BACKGROUND

There is no consensus in the literature as to whether maternal zinc nutriture is associated with pregnancy outcome or fetal growth.

OBJECTIVE

We evaluated the associations between plasma zinc concentrations during pregnancy and various measures of pregnancy outcome and neonatal conditions at birth.

DESIGN

We measured zinc concentrations in plasma samples obtained at a mean of 16 wk of gestation (range: 6-34 wk) from 3448 women who were screened for a trial designed to evaluate the effect of zinc supplementation on fetal growth. Subjects were from low socioeconomic backgrounds and attended a public health clinic for their prenatal care. Plasma zinc concentrations were compared with pregnancy outcome, including complications during pregnancy and delivery, and anthropometric measures and Apgar scores of neonates.

RESULTS

Plasma zinc concentrations declined as gestation progressed. After plasma zinc concentrations were adjusted for gestational age, they were not significantly associated with any measure of pregnancy outcome or neonatal condition.

CONCLUSION

We conclude that plasma zinc concentrations during the late first trimester to the early third trimester do not predict pregnancy outcomes in women of a low socioeconomic background.

Zinc levels in women and newborns

Zinc is an important trace element having a definitive role in the metabolism, growth and development and reproduction. During pregnancy the requirements for zinc increase. This study was designed to evaluate the zinc status of normal women, normal pregnant women and their newborn babies. Forty normal adult females, 40 normal pregnant women and their newborn babies were randomly selected and their serum and hair zinc levels were analysed using atomic absorption spectrophotometer. The mean serum and hair zinc levels in normal women were 69.47 +/- 1.4 micrograms/dl and 147.45 +/- 6.12 micrograms/g respectively. The mean serum and hair zinc levels in normal pregnant women were 69.0 +/- 3.22 micrograms/dl and 142.83 +/- 4.39 micrograms/g respectively while the mean serum (cord blood) and hair levels in normal new born babies were 72.77 +/- 5.14 micrograms/dl and 188.36 +/- 4.12 micrograms/g respectively. There was a significant (p < 0.001) decrease in hair zinc levels during pregnancy. There was a significant (p < 0.05) decrease in zinc levels in new born babies when the time interval between the previous delivery and the present delivery was less than 3.4 years. The results of the present study reinforce the need for zinc supplementation during pregnancy especially if the interval between pregnancies is short.

Toxicant exposure and trace element metabolism in pregnancy

A review of the literature provides support for the concept that maternal nutritional status has a significant influence on embryonic and fetal development. The consumption of `poor' diets has been shown to be a risk factor for poor pregnancy outcome, while the provision of selected nutritional supplements prior to and during pregnancy has been associated with improved pregnancy outcome. Despite the above, it has been difficult to identify specific nutrient deficiencies as causative factors of abnormal development. One explanation for this failure is that embryo/fetal nutritional deficiencies can arise through a number of mechanisms in addition to a low maternal intake of a nutrient(s). Evidence is presented for the hypothesis that the developmental toxicity of a number of teratogens can be ascribed, in part, to their ability to induce alterations in the partitioning of essential trace elements between the maternal and fetal unit. An implication of the above hypothesis is that maternal diet can be an important modulator of the developmental toxicity of several agents.

Human fetal endothelial cells acquire zinc(II) from both the protein bound and nonprotein bound pools in serum

To help determine physiologically important routes by which zinc (Zn) is acquired by human fetal vascular endothelium, the authors incubated cultured umbilical vein endothelial cells with 65Zn(II)-tracer labeled human fetal whole serum, ultrafiltrate (containing low molecular mass serum zinc complexes), and dialyzed serum (containing protein-bound zinc). Zinc from whole serum and from both serum fractions entered a rapidly labeled cellular compartment, removable by edetic acid (EDTA), representing Zn bound to the outside cell surface, and accumulatively, an EDTA-resistant compartment-probably largely internalized Zn. Entry of Zn into the EDTA-resistant pool from both serum fractions was strongly temperature-dependent, and was not via the EDTA-sensitive pool. Entry from the ultrafiltrate was resolvable into high affinity saturable, and non- (or hardly-) saturable components. Transfer from the dialyzed serum fraction was not significantly saturable, but only partially accounted for by nonspecific pinocytosis. Thus, Zn is obtained by fetal vascular endothelium partly from low molecular mass serum species, probably through at least one carrier-mediated membrane transport system; but also from Zn complexed with serum protein, via at least one metabolism-related route.

Two major pathways of zinc(II) acquisition by human placental syncytiotrophoblast

Uptake of zinc into placental villous syncytiotrophoblast is the first step in its transfer from mother to fetus. To help characterise physiologically significant pathways of zinc accumulation by these cells, we incubated cultured layers of syncytiotrophoblast cells derived from human near-term placental tissue with serum ultrafiltrate (containing the zinc complexed with low molecular mass serum constituents), dialysed serum (containing the zinc bound to the serum proteins) and whole serum, each of whose endogenous zinc was tracer-labelled with 65Zn(II). Zinc label from both fractions of serum readily entered a rapidly labelled EDTA-sensitive cellular compartment, probably representing zinc bound to the outside cell surface and in accumulative fashion, an EDTA-resistant compartment, probably consisting largely of internalised cellular zinc. Movement of zinc into the EDTA-resistant pool was strongly temperature-dependent and did not occur via the EDTA-sensitive pool from either serum source. Transfer of zinc from the low molecular mass serum fraction into the EDTA-resistant pool was saturable, the concentration giving half-maximal rate being 1.2 mumol/l nonprotein-bound zinc. No nonsaturable component was detected. Zinc from the serum protein-bound fraction entered by a saturable component, already saturated at physiological total protein-bound zinc concentration, and by an apparently nonsaturable component, not appreciably accounted for by nonspecific fluid-phase endocytosis. The results show that zinc is acquired by placental syncytiotrophoblast from the low molecular mass serum zinc pool probably by a carrier-mediated process, and at least as importantly, from the zinc bound to serum protein, possibly by an endocytic mechanism.

Zinc supplementation and growth of infants born small for gestational age

To analyze the effect of zinc supplementation on postnatal growth of infants born small for gestational age, we selected 68 infants at birth and followed them monthly for 6 months. They were randomly assigned to a supplemented group (group S, n = 35) receiving 3 mg of Zn (acetate) per day, or to a placebo (group P, n = 33), in a double-blind study. Weight increments in group S were significantly higher than those in group P at 2 months (p < 0.003); z scores showed catch-up growth only in group S. Length increments were also greater in group S than in group P, ending at 6 months were 64.9 +/- 1.8 versus 63.4 +/- 3.5 cm (mean +/- SD; p < 0.01); changes in z scores for 6 months were -1.28 to -0.66 in group S and -1.43 to -1.47 in group P (p < 0.001). Weight-for-length improved similarly in both groups (z score, -2.2 to +0.2). The increase in weight-for-age was higher in group S girls (p < 0.034), ending at 6 months with -0.13 +/- 0.59, versus -0.52 +/- 0.62 in group S boys, -1.15 +/- 0.49 in group P girls, and -1.05 +/- 0.80 in group P boys (+/- SD). More infants in group P received cow milk-based formula before 4 months because of inadequate weight increments. An additive effect on weight increase was observed between Zn supplementation (p < 0.02), exclusive breast-feeding after 4 months of age (p < 0.001), and gender (p < 0.02). Plasma and hair Zn values showed a downward trend, less marked in group S than in group P. We conclude that Chilean infants born small for gestational age have better weight and linear growth during the first 6 months of life if they receive Zn supplementation.

The influence of dietary iron on zinc in rat

The purpose of this study was to clarify the influence of iron on zinc status. The animals were divided into four groups, consisting of five rats in each group. The control group was fed on basal diet with adequate levels of zinc and iron, whereas the experimental group was fed diets containing different levels of iron ad libitum for 15 d. Low levels of iron (LFe) significantly increased the zinc absorption percentage but there was a decrease in high (HFe) and very high iron (VHFe) level groups (p < 0.001). The retention percentage changes were found to be parallel to the changes in the absorption percentage curve. It was found that zinc (per total dry tissue) and Zn-65 (per total tissue) increased in the rats fed the LFe, whereas in general they decreased in the rats fed the HFe and VHFe diets. Significant changes were found in the duodenum and liver. Zn-65 (per g wet tissue) significantly increased in the brain and liver in the LFe group, but there was a decrease in the duodenum, ileum, kidney, liver, and brain in the HFe and VHFe groups. Changes in the level of zinc (per g dried tissue) were found to be parallel to the changes in Zn-65 in all the groups. The dietary proportions of iron appear to influence zinc metabolism at the intestinal and cellular transport levels over a given period of time.

Zinc, copper and selenium in reproduction

Of the nine biological trace elements, zinc, copper and selenium are important in reproduction in males and females. Zinc content is high in the adult testis, and the prostate has a higher concentration of zinc than any other organ of the body. Zinc deficiency first impairs angiotensin converting enzyme (ACE) activity, and this in turn leads to depletion of testosterone and inhibition of spermatogenesis. Defects in spermatozoa are frequently observed in the zinc-deficient rat. Zinc is thought to help to extend the functional life span of the ejaculated spermatozoa. Zinc deficiency in the female can lead to such problems as impaired synthesis/secretion of (FSH) and (LH), abnormal ovarian development, disruption of the estrous cycle, frequent abortion, a prolonged gestation period, teratogenicity, stillbirths, difficulty in parturition, pre-eclampsia, toxemia and low birth weights of infants. The level of testosterone in the male has been suggested to play a role in the severity of copper deficiency. Copper-deficient female rats are protected against mortality due to copper deficiency, and the protection has been suggested to be provided by estrogens, since estrogens alter the subcellular distribution of copper in the liver and increase plasma copper levels by inducing ceruloplasmin synthesis. The selenium content of male gonads increases during pubertal maturation. Selenium is localized in the mitochondrial capsule protein (MCP) of the midpiece. Maximal incorporation in MCP occurs at steps 7 and 12 of spermatogenesis and uptake decreases by step 15. Selenium deficiency in females results in infertility, abortions and retention of the placenta. The newborns from a selenium-deficient mother suffer from muscular weakness, but the concentration of selenium during pregnancy does not have any effect on the weight of the baby or length of pregnancy. The selenium requirements of a pregnant and lactating mother are increased as a result of selenium transport to the fetus via the placenta and to the infant via breast milk.

Zinc supplementation alters thyroid hormone metabolism in disabled patients with zinc deficiency

OBJECTIVE

We examined zinc (Zn) status in relation to thyroid function in disabled persons, because the association between Zn deficiency and thyroid function remains controversial.

METHODS

After measuring serum free 3,5,3'-triiodothyronine (T3) and free thyroxine (T4) in 134 persons, TSH-releasing hormone (TRH) injection test and estimation of Zn status were conducted in persons with low free T3.

RESULTS

Thirteen had low levels of serum free T3 and normal T4. Patients with elevated levels of serum 3,3',5'-triiodothyronine (rT3) showed an enhanced reaction of serum thyrotropin (TSH) after TRH injection. Nine of 13 patients had mild to moderate Zn deficiency evaluated by body Zn clearance and increased urinary Zn excretion. After oral supplementation of Zn sulphate (4-10 mg/kg body weight) for 12 months, levels of serum free T3 and T3 normalized, serum rT3 decreased, and the TRH-induced TSH reaction normalized. Serum selenium concentration (Type 1 T4 deionidase contains selenium in the rat) was unchanged by Zn supplementation.

CONCLUSION

Zn may play a role in thyroid hormone metabolism in low T3 patients and may in part contribute to conversion of T4 to T3 in humans.

Zinc kinetics in patients with bone demineralization due to physical immobilization

To examine the relationship between zinc (Zn) status and bone demineralization, a body Zn kinetics study was performed with 74 (37 male, 37 female) disabled persons ranging in age from 16 to 45 years. Three groups were classified according to degree of limited mobility: group 1 (n = 23), capable of walking; group 2 (n = 20), capable of crawling; group 3 (n = 31), bed-ridden, Serum Zn levels were similar in the three groups, whereas body Zn clearance and the distribution of Zn showed a pattern [group 1 < group 2 < group 3 (p < 0.01, p < 0.05)], with the reverse in cases of bone mineral density (BMD) [group 1 > group 2 > group 3 (p < 0.01)]. Renal handling of Zn did not different among the three groups. There was a negative correlation between Zn distribution volume and values of BMD (p < 0.005, gamma = 0.387). Thus, various organs, as well as the skeleton, are Zn deficient in immobilized patients.

Erythrocytes, erythrocyte membranes, neutrophils and platelets as biopsy materials for the assessment of zinc status in humans

During a controlled zinc depletion-repletion study, fifteen men aged 25.3 (SD 3.3) years were fed on a low-Zn diet with high phytate:Zn and phytate x calcium:Zn molar ratios for 7 weeks, followed by a 2 week repletion period when 30 mg supplemental Zn/d was given. Changes in plasma, urine, and hair Zn concentrations, taste acuity, and cellular immune response confirmed the development of mild Zn deficiency. Zn concentrations in neutrophils, platelets, erythrocytes and erythrocyte membranes, mean platelet volume, and activities of alkaline phosphatase (EC 3.1.3.1) and alpha-D-mannosidase (EC 3.2.1.24) in neutrophils did not respond to changes in Zn status. In contrast, alkaline phosphatase activity in erythrocyte membranes showed a significant decline which was consistent in all subjects (nmol product formed/min per mg protein; baseline v. 7-week Zn depletion, 0.656 (SD 0.279) v. 0.506 (SD 0.230), at 7 weeks; P < 0.05); neutral phosphatase activity remained unchanged. Alkaline phosphatase activity in erythrocyte membranes may be a potential index of Zn status in humans.

Maternal alpha-2-macroglobulin levels and fetal growth in Guatemala

Maternal serum alpha-2-macroglobulin (alpha 2M) levels were measured at the time of delivery in 244 women in the central highlands of Guatemala. Significantly higher alpha 2M levels were found in thin women and in poor women. In multiple regression analysis controlling for gestational age, race, sex, maternal triceps skinfold thickness and socioeconomic status, high alpha 2M levels were significantly associated with decreased birthweight. These findings agree with those in a predominantly black population in the United States and extend the relationship between alpha 2M and decreased birthweight to a developing country.

The role of zinc in reproduction. Hormonal mechanisms

Zinc is a very important element in the reproductive cycle of species. In humans, it is necessary for the formation and maturation of spermatozoa, for ovulation, and for fertilization. During pregnancy, zinc deficiency causes a number of anomalies: spontaneous abortion, pregnancy-related toxemia, extended pregnancy or prematurity, malformations, and retarded growth. Delivery is adversely affected by deficiency. These different effects of zinc can be explained by its multiple action on the metabolism of androgen hormones, estrogen and progesterone, together with the prostaglandins. Nuclear receptors for steroids are all zinc finger proteins. Zinc supplementation has already proven beneficial in male sterility and in reducing complications during pregnancy. However, it would be worth conducting larger-scale trials to confirm these beneficial effects.

Effects of a multivitamin mineral supplement on zinc and copper status during pregnancy

The effect of a multivitamin-mineral supplement was investigated during pregnancy according to a double-blind protocol by determining zinc and copper in maternal plasma, mononuclear and polynuclear zinc and copper at the third, sixth, eighth, and ninth months of gestation. The subjects were supplemented from the first trimester until delivery. A significant decrease was observed in plasma zinc that varied from 11.5 mumol/L to 10.8 mumol/L in the supplemented group (n = 29) and from 11 mumol/L to 10 mumol/L in the placebo group (n = 33) at 3 and 9 mo of gestation, respectively. In contrast, plasma copper levels increased in a way depending upon the stage of gestation in both groups: from 24.7 to 28.2 mumol/L in the treated group and from 24.9 to 30.9 mumol/L in the placebo group at 3 and 9 mo of gestation, respectively, but the difference was only significant in the placebo group. No difference between groups was observed in mononuclear and polynuclear zinc or copper levels. These trace elements were also determined in cord blood at delivery. There were no statistically significant differences in zinc and copper concentration found in placebo group and supplemented group. Finally, the beneficial effect of supplementation on muscular cramps and appearance of vergetures was noted.

A study of serum zinc levels in cord blood of neonates and their mothers

Serum zinc was estimated in the cord blood of 60 neonates of different gestational age and birth weight, and their mothers. Mean serum zinc levels in neonates FTGA, PTAGA and term SGA were 128.88 +/- 14.37, 94.32 +/- 17.79 and 111.8 +/- 9.2 ug/dl respectively. The maternal serum zinc levels in corresponding groups was 96.28 +/- 19.48, 115.44 +/- 15.41 and 93.8 +/- 7.62 ug/dl. Thus mean serum zinc level in cord blood of FT AGA newborns was significantly higher than that in PT AGA and FT SGA. Mean serum zinc level in mothers of FT AGA was significantly lower than that in mothers of PT AGA. However, there was no significant difference between the maternal serum zinc levels of FT AGA and FT SGAs. There was positive correlation between gestational age and serum zinc level in cord blood of AGAs while correlation was negative in case of their mothers. There was positive correlation between weight (keeping gestational age constant) and serum zinc level in case of neonates while corresponding maternal zinc levels did not vary. (FT AGA and FT SGA).

The relationship between maternal serum zinc levels during pregnancy and birthweight

A retrospective follow-up study to ascertain the relationship between the level of serum zinc and its rate of change during gestation and birthweight was conducted in 476 women of lower socioeconomic status. Serum zinc concentrations measured at approximately 16 (early) and 32 weeks (later) in gestation were both found to be significant predictors of birthweight. Even after controlling for gestational age at birth and other determinants of birthweight, for each microgram/dl increase in serum zinc early and later in pregnancy, birthweight increased by 5.8 and 8.6 g, respectively. Furthermore, after adjustment for initial zinc levels both the total change (beta = -7.0, P = 0.0007) and the rate of change (beta = -60.8, P = 0.007) in serum zinc during pregnancy were inversely associated with birthweight, i.e., the larger the fall in serum zinc during pregnancy, the smaller the infant. Low serum zinc level (less than 60 micrograms/dl) late in pregnancy was associated with greater than a five-fold increase in the odds (OR = 5.8, 95% CI = 1.8, 16.4) of giving birth to a low birthweight infant. The results of this study suggest a threshold for maternal serum zinc below which the prevalence of low birthweight increases rapidly.

The effect of nutritional intake on outcome of pregnancy in smokers and non-smokers

The relationship between nutrient intake and pregnancy outcome (adjusted birth weight and gestational age) was investigated in randomly selected non-smokers (n97) and in heavy smokers (15 + cigarettes/d) (n72) booking for ante-natal care at a hospital in South London. Weighted dietary intakes (7d) were obtained at 28 and 36 weeks gestation. Birth weight was adjusted for gestational age, maternal height, parity and sex of infant. Compared with non-smokers, intakes of micronutrients and fibre were lower in smokers at both 28 and 36 weeks, and smokers reduced their intakes more in late pregnancy. The babies of smokers had a lower adjusted birth weight but there was no difference in length of gestation between smokers and non-smokers. After controlling for smoking, social class and alcohol consumption, nutrient intakes at 28 weeks were found to have no effect on adjusted birth weight. However, intakes of protein, zinc, riboflavin and thiamin at 36 weeks, and the change in intakes of these nutrients (plus iron) between 28 and 36 weeks, had independent positive effects on birth weight. Some of the effect of smoking on birth weight appeared to be mediated through differences in nutrient intakes. Smoking explained 14.3% of the variance in birth weight in this population and a further 2.4-7.2% was explained by change in nutrient intakes between 28 and 36 weeks. It is recommended that women in pregnancy do not reduce their dietary intakes in late pregnancy.

Can methionine and zinc prevent the embryopathic effects of alcohol?

Alcoholism is a major and world-wide health problem. A characteristic pattern of congenital defects, known as the fetal alcohol syndrome, has been detected in the offspring of mothers who are chronic alcoholics. The mechanism underlying the teratogenic effects of ethanol is not known. An important hypothesis is that ethanol becomes teratogenic by inducing maternal/fetal nutritional deficiencies. Nutrients affected by ethanol consumption include methionine and zinc. Epidemiological and experimental studies have shown that zinc deficiency is associated with both fetal growth retardation and developmental defects. Furthermore, the ethanol metabolizing enzyme, alcohol dehydrogenase, is a zinc metalloenzyme. Zinc deficiency decreases alcohol dehydrogenase activity and thus slows down elimination of ethanol. Methionine, an essential amino acid, is a lipotrope, as well as a universal methyl donor. It is involved in hepatic detoxification. Studies on the effects of methionine and zinc might lead to appropriate therapeutic intervention in pregnancies of alcoholic mothers who are at a risk of giving birth to an impaired offspring. Furthermore, the results of such investigations will provide a better understanding of the mechanism of action of ethanol on the embryo.

The effects of dietary ligands on zinc uptake at the porcine intestinal brush-border membrane

Intestinal brush-border-membrane vesicles were prepared from the porcine small bowel by magnesium precipitation and differential centrifugation, and were functionally intact. The influence of dietary ligands on 65Zn uptake was determined using a 65Zn concentration of 5 microM, an incubation time of 1 min and a reaction temperature of 27 degrees, with a rapid filtration technique. At this low Zn concentration the addition of an excess of folate, histidine or glucose had no effect on Zn uptake. Addition of picolinate, citrate and phytate to the incubation medium significantly reduced Zn uptake at all concentrations of ligand examined. Any inhibitory effects of folic acid in vivo may thus be due to a mucosal rather than lumen interaction. Those ligands inhibiting absorption may have done so through the formation of Zn-ligand complexes, which are either insoluble, or which reduce the binding of Zn to its mucosal receptor. This in vitro model of Zn absorption is useful for comparing the effects of potential Zn-binding ligands in the diet.

Social determinants of nutrient intake in smokers and non-smokers during pregnancy

STUDY OBJECTIVE

The aim was to investigate the effects of social factors (education, income, marital status, partners' employment status, housing tenure, social class), smoking, and maternal height on the dietary intake of pregnant women.

DESIGN

The study was a prospective investigation on a two phase sample.

SETTING

The study involved women attending the antenatal clinic at a district general hospital.

PATIENTS

A group of pregnant Caucasian women, selected because they were heavy smokers (15+ cigarettes/day) (n = 94) and a randomly selected sample of never smokers (n = 112) were studied.

MEASUREMENTS AND MAIN RESULTS

Data on social factors were collected by interviewer administered questionnaire. A 7 day weighed intake method was used to determine dietary intake at 28 weeks gestation. In univariate analyses, income, housing tenure and social class had significant effects on intakes of both macro- and micronutrients, and maternal education and smoking had significant effects on intakes of micronutrients. Using a stepwise multivariate analysis with income, smoking and maternal education, income was a significant factor in the intake of most nutrients but this effect disappeared when social class and housing tenure factors were entered into the model. Only social class and housing tenure had any significant effect on intakes of macronutrients--energy, protein and fat. Smoking and maternal education were the most important determinants of quality of diet (nutrient density); other factors had only negligible effects. Income was the only significant factor in alcohol intake. It is suggested that the effects of social class and income are overlapping.

CONCLUSIONS

Smoking, being renters of accommodation, and being of minimum education and low social class are risk factors for poor dietary intake. It is recommended that such higher risk groups be specifically targeted for nutritional advice in pregnancy.