Hormonal effects of zinc on growth in children

Instrumental neutron activation analysis (INAA) of zinc concentrations in scalp hair and fingernails samples of Algerian females with breast cancer

In the present work, zinc levels were measured in scalp hair and fingernails in order to identify potential risk factors for breast cancer. The samples were collected from 40 Algerian breast cancer female patients and from 20 normal subjects matching the same age range. The concentration of zinc was analyzed using Instrumental neutron activation analysis technique (INAA). In scalp hair samples it was found in the range 119–792 μg/g for the normal subjects and in the range 82–806 μg/g for the patients, with an increase rate of 10.9%. The range of concentration of zinc in fingernails was found between 89 and 247 μg/g for normal subjects and between 75 and 276 μg/g for the patients with an increase rate of 2.5%. The influence of age on zinc concentration was also investigated. The obtained results show some consistency with those obtained by other groups.

The association of serum levels of zinc and vitamin D with wasting among Iranian pre-school children

PURPOSE

Wasting is a main indicator of Child's undernutrition that is associated with several non-communicable diseases and child mortality. This is the first population-based study which evaluated the association of serum zinc and vitamin D levels with wasting in a Middle East region. We also reported the prevalence of vitamin D and zinc deficiencies among Iranian pre-school children aged 6 years.

METHODS

This was a multicenter cross-sectional study that included 425 children aged between 5 and 7 years (on average 6 years) with BMI-for-age Z-scores of < - 1 SD resident in urban and rural areas of Iran in the spring of 2012 as part of the National Integrated Micronutrient Survey 2 (NIMS-2). Anthropometric measurements and blood sampling were obtained. The prevalence of vitamin D and zinc deficiencies together with the correlations of these variables with the increase of BMI-for-age Z-scores were evaluated.

RESULTS

The prevalence of vitamin D and zinc deficiencies was 18.8% and 12.7%, respectively. In addition, 31.1% of children were wasted. Children in the second tertile of 25(OH)D levels were less likely to have wasting compared with those in the first tertile in both crude and adjusted models (OR 0.47, 95% CI 0.27-0.83). A significant inverse association was found between serum levels of zinc and wasting (OR 0.57, 95% CI 0.34-0.96); such that after adjusting for confounders, children in the highest tertile of serum zinc had 47% less odds of wasting compared with those in the first tertile (OR 0.53, 95% CI 0.31-0.91).

CONCLUSION

The prevalence of vitamin D and zinc deficiencies among Iranian pre-school children aged 6 years was 18.8 and 12.7%, respectively. Serum levels of vitamin D and zinc were inversely associated with wasting either before or after controlling for confounders.

LEVEL OF EVIDENCE

Level III, case-control analytic studies.

Toxic exposures and the senses of taste and smell

This review addresses the adverse influences of neurotoxic exposures on the ability to smell and taste. These chemical senses largely determine the flavor of foods and beverages, impact food intake, and ultimately nutrition, and provide a warning for spoiled or poisonous food, leaking natural gas, smoke, airborne pollutants, and other hazards. Hence, toxicants that damage these senses have a significant impact on everyday function. As noted in detail, a large number of toxicants encountered in urban and industrial air pollution, including smoke, solvents, metals, and particulate matter can alter the ability to smell. Their influence on taste, i.e., sweet, sour, bitter, salty, and savory (umami) sensations, is not well documented. Given the rather direct exposure of olfactory receptors to the outside environment, olfaction is particularly vulnerable to damage from toxicants. Some toxicants, such as nanoparticles, have the potential to damage not only the olfactory receptor cells, but also the central nervous system structures by their entrance into the brain through the olfactory mucosa.

Zinc gluconate toxicity in wild-type vs. MT1/2-deficient mice

Previous studies have suggested that oral zinc supplementation can help reduce the duration of the common cold; however, the use of intranasal (IN) zinc is strongly associated with anosmia, or the loss of the sense of smell, in humans. Prior studies from this lab showed that upregulation of metallothioneins (MT) is a rapid and robust response to zinc gluconate (ZG). Therefore, we assessed the role of MT in the recovery of nasal epithelial damage resulting from IN zinc administration. The main studies in this investigation used a high dose of ZG (170mM) to ensure ablation of the olfactory mucosa, so that the progression of histological and functional recovery could be assessed. In vivo studies using wild-type, MT1/2 knockout mice (MT KO), and heterozygotes administered ZG by IN instillation showed profound loss of the olfactory mucosa in the nasal cavity. Recovery was monitored, and a lower percentage of the MT KO mice were able to smell 28 d after treatment; however, no significant difference was observed in the rate of cell proliferation in the basal layer of the olfactory epithelium between MT KO and wild-type mice. A lower concentration of ZG (33mM), equivalent to that found in homeopathic IN ZG preparations, also caused olfactory epithelial toxicity in mice. These studies suggest that the use of zinc in drug formulations intended for IN administration in humans must be carefully evaluated for their potential to cause olfactory functional deficits.

Effect of micronutrient supplementation on height velocity of underprivileged girls in comparison with un-supplemented healthy controls

The aim of this study was to investigate the effect of 1-year micronutrient supplementation on the height velocity of underprivileged premenarchal girls in comparison with the natural growth of apparently healthy girls from an affluent class. A 1-year cluster-randomisation intervention trial was conducted in 119 premenarchal girls (8-12 years) from two schools catering to the lower socioeconomic strata (LSES) in Pune, India. Three classes of age-matched girls were randomly allocated to any one of the three intervention groups: (i) Ca+MZn+D group (C1: zinc, 15 mg/day+multivitamins; calcium, 500 mg/day; vitamin D, 30,000 IU/3 months); (ii) Ca+D group (C2: calcium, 500 mg/day; vitamin D, 30,000 IU/3 months); and (iii) M+D group (C3: multivitamins; vitamin D, 30,000 IU/3 months). Height, weight, and Tanner stage were assessed at baseline and endline. A total of 119 age-matched, apparently healthy school girls from a higher socioeconomic group (HSES) were assessed for their growth after 1 year without any supplementation. At baseline, mean height-for-age Z-scores and weight-for-age Z-scores by Indian references were >-2 in 99% of HSES girls and 28% of LSES girls had height-for-age Z-scores <-2. Post-intervention, increase in height-for-age Z-scores adjusted for Tanner stage was significantly higher in the Ca+MZn+D group (0.32±0.06) than in the respective age-matched controls (C1 group) (-0.02±0.05) (p<0.05) as well as in both the Ca+D group (0.18±0.06) and the M+D group (0.14±0.04) (p<0.05). After adjusting for Tanner stage, height velocity was significantly higher for the Ca+MZn+D group (6.7±0.4 cm/year) than for the M+D group (6.1±0.2), Ca+D group (5.6±0.5) as well as age-matched controls (C1 group) (5.0±0.3) (p<0.05). Supplementation with calcium+vitamin D, zinc and multivitamins may be effective in improving stature in underprivileged Indian premenarchal girls.

Enhanced effect of zinc and calcium supplementation on bone status in growth hormone-deficient children treated with growth hormone: a pilot randomized controlled trial

Reduced bone mineral content in growth hormone-deficient children (GHD) has been reported. Calcium, zinc, and vitamin D play an important role in bone formation. Hence, the aim of this pilot randomized controlled study was to evaluate the effect of calcium, vitamin D, and zinc supplementation in prepubertal GHD children treated with GH on bone health parameters. After 1 year of treatment with GH (20 mg/m(2)/week), 31 GHD (mean age 8.7 ± 2.8 years, 18 boys) prepubertal children were randomised to receive calcium (500 mg/day) and vitamin D (60,000 IU/3 months) [Group A] or a similar supplement of calcium, vitamin D, and zinc (as per Indian Recommended Allowance) [Group B] along with GH therapy for the next 12 months. The two groups were similar in anthropometric and body composition parameters at baseline (p > 0.1). After 1 year of GH therapy, height-adjusted % gain was similar in both groups, 48 % in bone mineral content (BMC) and 45 % in bone area (BA). Height-adjusted % increase in BMC was significantly (p < 0.05) higher in the second year than in the first in both the groups. This % increase in BMC and BA was greater in Group B (51 and 36 % respectively) than in Group A (49 and 34 %), although marginally (p < 0.05). Supplementation of calcium and vitamin D along with GH therapy in GHD Indian children has the potential for enhancing bone mass accrual; this effect was further enhanced through the addition of zinc supplement.

The toxicity redox mechanisms of cadmium alone or together with copper and zinc homeostasis alteration: its redox biomarkers

Cadmium (Cd) is a toxic metal and can induce and/or promote diseases in humans (cancer, aging diseases, kidney and bone diseases, etc.). Its toxicity involves many mechanisms including the alteration of copper (Cu) and zinc (Zn) homeostasis leading to reactive oxygen species (ROS) production, either directly or through the inhibition of antioxidant activities. Importantly, ROS can induce oxidative damages in cells. Cadmium, Cu and Zn are also able to induce glutathione (GSH) and metallothioneins (MT) synthesis in a cell-type-dependent manner. As a consequence, the effects induced by these three metals result simultaneously from the inhibition of antioxidant activities and the induction of other factors such as GSH and MT synthesis. MT levels are regulated not only by the p53 protein in a cell-type-dependent manner, or by transcription factors such as metal-responsive transcription factor 1 (MTF-1) and cellular Zn levels but also by cellular GSH level. As described in the literature, DNA damage, GSH and MT levels are sensitive biomarkers used to identify Cd-induced toxicity alone or together with Cu and Zn homeostasis alteration.

The ubiquitous role of zinc in health and disease

OBJECTIVE

To review zinc physiology and pathophysiology and the importance of zinc toxicity and deficiency in veterinary patients.

DATA SOURCES

A review of human and veterinary medical literature.

HUMAN DATA SYNTHESIS

There is a significant amount of original research in humans and animals on the role of zinc in multiple organ systems. There is also significant data available on human patients with zinc abnormalities.

VETERINARY DATA SYNTHESIS

Zinc deficiency has been studied in dogs with genetic disease and dietary deficiency leading to dermatological disease and immune deficiency. Zinc toxicity has been described after ingestion of metallic foreign bodies containing zinc.

CONCLUSIONS

Historically, the role of zinc in health and disease has been studied through patients with toxicity or severe deficiency with obvious clinical signs. As the ubiquitous contribution of zinc to structure and function in biological systems was discovered, clinically significant but subtle deficiency states have been revealed. In human medicine, mild zinc deficiencies are currently thought to cause chronic metabolic derangement leading to or exacerbating immune deficiency, gastrointestinal problems, endocrine disorders, neurologic dysfunction, cancer, accelerated aging, degenerative disease, and more. Determining the causal relationships between mild zinc deficiency and concurrent disease is complicated by the lack of sensitive or specific tests for zinc deficiency. The prevalence of zinc deficiency and its contribution to disease in veterinary patients is not well known. Continued research is warranted to develop more sensitive and specific tests to assess zinc status, to determine which patients are at risk for deficiency, and to optimize supplementation in health and disease.

How does zinc supplementation benefit anorexia nervosa?

BACKGROUND

A randomized controlled trial of zinc supplementation in anorexia nervosa (AN) reported a two-fold increase of the rate of increase of body mass index (BMI) in the zinc group. Zinc is inexpensive, readily available and free of significant side effects. However, oral zinc supplementation is infrequently prescribed as an adjunctive treatment for AN. Understanding the mechanism of action of zinc may increase its use.

HYPOTHESIS

Low zinc intake, which is very common in AN, adversely affects neurotransmitters in various parts of the brain, including gamma-amino butyric acid (GABA) and the amygdala, which are abnormal in AN. Zinc supplementation corrects these abnormalities, resulting in clinical benefit in AN.

CONCLUSIONS

Oral administration of 14 mg of elemental zinc daily for 2 months in all patients with AN should be routine.

Brain, aging and neurodegeneration: role of zinc ion availability

Actual fields of research in neurobiology are not only aimed at understanding the different aspects of brain aging but also at developing strategies useful to preserve brain compensatory capacity and to prevent the onset of neurodegenerative diseases. Consistent with this trend much attention has been addressed to zinc metabolism. In fact, zinc acts as a neuromodulator at excitatory synapses and has a considerable role in the stress response and in the functionality of zinc-dependent enzymes contributing to maintaining brain compensatory capacity. In particular, the mechanisms that modulate the free zinc pool are pivotal for safeguarding brain health and performance. Alterations in zinc homeostasis have been reported in Parkinson's and Alzheimer's disease as well as in transient forebrain ischemia, seizures and traumatic brain injury, but little is known regarding aged brain. There is much evidence that that age-related changes, frequently associated to a decline in brain functions and impaired cognitive performances, could be related to dysfunctions affecting the intracellular zinc ion availability. A general agreement emerges from studies of humans' and rodents' old brains about an increased expression of metallothionein (MT) isoforms I and II, but dyshomogenous results are reported for MT-III, and it is still uncertain whether these proteins maintain in aging the protective role, as it occurs in adult/young age. At the same time, there is considerable evidence that amyloid-beta deposition in Alzheimer's disease is induced by zinc, but the pathological significance and the causes of this phenomenon are still an open question. The scientific debate on the role of zinc and of some zinc-binding proteins in aging and neurodegenerative disorders, as well as on the beneficial effect of zinc supplementation in aged brain and neurodegeneration, is extensively discussed in this review.

The role of zinc in the growth and development of children

This review concerns the importance of zinc in growth, development, and cognitive function in children and the deleterious consequences of its deficiency on children's health. Possible strategies to overcome zinc deficiency and the results of some supplementation trials are discussed.

Effects of zinc on cell proliferation and proteoglycan characteristics of epiphyseal chondrocytes

Zinc has been postulated as an important nutritional factor involved in growth promotion; however, the cellular mechanisms involved in the effects of zinc on linear growth remain to be elucidated. This study was conducted to evaluate the effects of zinc on the proliferation rate of epiphyseal growth plate chondrocytes and on the structural characteristics of the proteoglycans synthesized by these cells. For these purposes, hypertrophic and proliferating chondrocytes were isolated from the tibiae of 1- and 5-week-old chickens, respectively. Chondrocytes were cultured under serum-free conditions and primary cultures were used. The results showed that zinc stimulated proliferation by 40-50% above the baseline in the case of proliferating chondrocytes, but it had no effect on hypertrophic chondrocytes. Zinc had neither any effects on mean charge density of proteoglycans synthesized by hypertrophic chondrocytes nor in their hydrodynamic size. In contrast, zinc induced an increase in mean charge density and a decrease of hydrodynamic size of proteoglycans synthesized by proliferating chondrocytes. In both cell types zinc had no effect on the composition and hydrodynamic size of the glycosaminoglycan chains. The increased ability of proliferating chondrocytes cultured in the presence of zinc to synthesize 3'-phosphoadenosine 5'-phosphosulfate (PAPS) could be explained by the induction of enzymes participating in the sulfation pathway of proteoglycans. Therefore, the increase in mean charge density of proteoglycans observed in this study may be explained by an increase of the degree of sulfation of proteoglycan molecules. We speculate that the effect of zinc on linear growth may be explained at a cellular level by: a) an increase in proliferation rates of proliferating chondrocytes, and b) increased synthesis of highly charged proteoglycan molecules which decreases mineralization.

Zinc sulfate supplementation improves thyroid function in hypozincemic Down children

In subjects affected by trisomy 21 (Down syndrome), hypothyroidism is the most common endocrinological deficit. Plasma zinc levels, which are commonly detected below the normal range in Down patients, are related to some endocrinological and immunological functions; in fact, zinc deficiency has been shown to impair immune response and growth rate. Aims of this study were to evaluate (1) the role of zinc deficiency in subclinical hypothyroidism and (2) thyroid function changes in Down children cyclically supplemented with zinc sulfate. Inverse correlations have been observed between age and triiodotironine (T3) and between zinc and thyroid-stimulating hormone (TSH); higher TSH levels have been found in hypozincemic patients at the beginning of the study. After 6 mo of supplementation, an improvement of thyroid function (TSH levels: 3.96 +/- 1.84 vs 2.64 +/- 1.33 mUI/mL basally and after 6 mo, respectively) was observed in hypozincemic patients. In the second cycle of supplementation, a similar trend of TSH was observed. At the end of the study, TSH significantly decreased in treated hypozincemic subjects (4.48 +/- 1.93 vs 2.96 +/- 1.20 mUI/mL) and it was no longer different in comparison to normozincemic patients. We suggest zinc supplementation to the diet in hypozincemic Down children as a simple and useful therapeutic tool.

Detecting subclinical deficiency of essential trace elements in children with special reference to zinc and selenium

OBJECTIVE

This article reviews situations in which we should be alert to the risk of trace element deficiencies, and the difficulties of assessing trace element status, as illustrated by states of potential subclinical deficiency of zinc and selenium in infants.

CONCLUSION

Deficiency states of many trace elements have been documented in infants, and there is probably an underdiagnosed group of infants with subclinical deficiency, from which however the great majority are protected by effective regulatory systems. Specific, sensitive, and reliable methods are needed for the detection of trace element imbalances.

Zinc deficiency in women, infants and children

Zinc deficiency in humans is widespread and is more prevalent in areas where the population subsists on cereal proteins. Conditioned deficiency of zinc is seen in many diseased states. A mild deficiency of zinc in pregnancy is associated with increased maternal morbidity, abnormal taste sensation, prolonged gestation, inefficient labor, atonic bleeding, and increased risks to the fetus. Among the urban poor in the US, a marginal zinc intake during pregnancy was associated with increased risk of preterm and very preterm delivery. Factors responsible for zinc deficiency in premature infants include high fecal losses of zinc, low body stores of zinc at birth, and increased zinc requirement during rapid growth. Zinc supplemented infants demonstrated improved linear growth velocity and maximum motor development scores. Marginal and moderate growth impairment in children as a consequence of inadequate zinc intake has been reported from many developed and developing countries. In one study from Japan, 21 prepubertal children were diagnosed to have zinc deficiency. The caloric intake, growth velocity, serum zinc, and plasma insulin-like growth factor-1 increased significantly in the zinc supplemented group. The clinical manifestations of zinc deficiency include growth retardation, hypogonadism in males, neurosensory disorders, cell-mediated immunological dysfunctions, and skin changes. Approximately 300 enzymes are known to require zinc for their activities. Zinc is required for DNA synthesis, cell division and protein synthesis. Several hundreds of zinc containing nucleoproteins are probably involved in gene expression of various proteins. A deficiency of zinc also affects proliferation and maturity of lymphocytes adversely.

Plasma zinc and copper in Paris area preschool children with growth impairment

Plasma zinc, copper, and parameters of growth were measured in a group of 116 French preschool children, 2-5 yr-old from low-income households. Participants were selected on the basis of Z-scores of weight for height (WHZ) and height for age (HAZ). Zinc and copper concentrations of children with growth impairment (GI), defined by a WHZ and/or HAZ < -1 Z-score, were compared to those of age, sex, and ethnic origin matched controls (WHZ and HAZ > -1 Z-score). Mean (+/- SD) plasma zinc concentration was 12.58 +/- 1.84 mumol/L in the GI group, and 13.27 +/- 1.98 mumol/L in the controls. The difference of the means of paired samples was 0.69 +/- 2.34, and by paired t-test the significance reached p = 0.028. This effect was primarily a result of the weight retarded group (WHZ < -1 Z-score, p < 0.009) and to the girls (p < 0.05). There were no significant differences in plasma copper concentrations between groups. These results suggest the presence of marginal zinc deficiency in French preschool children with low weight for height Z-scores.

Zinc supplements in breastfed infants

Among breastfed infants, growth faltering in comparison with reference growth curves is common in both developing and developed countries. We performed a zinc supplementation trial in Paris, France, to find out whether such growth faltering is due to nutritional zinc deficiency. 57 breastfed infants aged 4-9 (mean 5.7) months were randomly assigned to receive either 5 mg zinc daily or a placebo for 3 months. Most of the infants were from low-income immigrant families and the majority were of African origin. Before supplementation there were no significant differences between the zinc and placebo groups in weight, length, or corresponding Z-scores for age. After 3 months' supplementation, the length-for-age Z-score had increased in the zinc group and fallen in the placebo group (+0.21 vs -0.13, p = 0.029). This difference was due mainly to greater linear growth of boys in the zinc than in the placebo group (6.0 vs 4.6 cm, p = 0.02). Weight gain was also significantly greater with zinc supplementation (1.64 vs 1.28 kg, p = 0.047). Among infants breastfed for longer than 4 months, decreases in growth velocity result partly from inadequate zinc intake.