Zinc in human milk

Human Milk Micronutrients and Child Growth and Body Composition in the First 2 years: A Systematic Review

Human milk (HM) provides a plethora of nutritional and non-nutritional compounds that support infant development. For many compounds, concentrations vary substantially among mothers and across lactation, and their impact on infant growth is poorly understood. We systematically searched MEDLINE, Embase, the Cochrane Library, Scopus, and Web of Science to synthesize evidence published between 1980 and 2022 on HM components and anthropometry through 2 y of age among term-born infants. Outcomes included weight-for-length, length-for-age, weight-for-age, body mass index (in kg/m2)-for-age, and growth velocity. From 9992 abstracts screened, 144 articles were included and categorized based on their reporting of HM micronutrients, macronutrients, or bioactive components. Micronutrients (vitamins and minerals) are reported here, based on 28 articles involving 2526 mother-infant dyads. Studies varied markedly in their designs, sampling times, geographic and socioeconomic settings, reporting practices, and the HM analytes and infant anthropometrics measured. Meta-analysis was not possible because data were sparse for most micronutrients. The most-studied minerals were zinc (15 articles, 1423 dyads) and calcium (7 articles, 714 dyads). HM iodine, manganese, calcium, and zinc concentrations were positively associated with several outcomes (each in ≥2 studies), whereas magnesium (in a single study) was negatively associated with linear growth during early lactation. However, few studies measured HM intake, adjusted for confounders, provided adequate information about complementary and formula feeding, or adequately described HM collection protocols. Only 4 studies (17%) had high overall quality scores. The biological functions of individual HM micronutrients are likely influenced by other HM components; yet, only 1 study analyzed data from multiple micronutrients simultaneously, and few addressed other HM components. Thus, available evidence on this topic is largely inconclusive and fails to address the complex composition of HM. High-quality research employing chronobiology and systems biology approaches is required to understand how HM components work independently and together to influence infant growth and to identify new avenues for future maternal, newborn, or infant nutritional interventions.

Neurodevelopmental Consequences of Dietary Zinc Deficiency: A Status Report

Zinc is a tightly regulated trace mineral element playing critical roles in growth, immunity, neurodevelopment, and synaptic and hormonal signaling. Although severe dietary zinc deficiency is relatively uncommon in the United States, dietary zinc deficiency is a substantial public health concern in low- and middle-income countries. Zinc status may be a key determinant of neurodevelopmental processes. Indeed, limited cohort studies have shown that serum zinc is lower in people diagnosed with autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and depression. These observations have sparked multiple studies investigating the mechanisms underlying zinc status and neurodevelopmental outcomes. Animal models of perinatal and adult dietary zinc restriction yield distinct behavioral phenotypes reminiscent of features of ASD, ADHD, and depression, including increased anxiety and immobility, repetitive behaviors, and altered social behaviors. At the cellular and molecular level, zinc has demonstrated roles in neurogenesis, regulation of cellular redox status, transcription factor trafficking, synaptogenesis, and the regulation of synaptic architecture via the Shank family of scaffolding proteins. Although mechanistic questions remain, the current evidence suggests that zinc status is important for adequate neuronal development and may be a yet overlooked factor in the pathogenesis of several psychiatric conditions. This review aims to summarize current knowledge of the role of zinc in the neurophysiology of the perinatal period, the many cellular targets of zinc in the developing brain, and the potential consequences of alterations in zinc homeostasis in early life.

Micronutrient, Metabolic, and Inflammatory Biomarkers through 24 Months of Age in Infants Receiving Formula with Added Bovine Milk Fat Globule Membrane through the First Year of Life: A Randomized Controlled Trial

BACKGROUND

Bovine milk fat globule membrane (MFGM) added in infant formula supports typical growth and safety through 24 mo of age in term infants.

OBJECTIVES

To assess micronutrient (zinc, iron, ferritin, transferrin receptor), metabolic [glucose, insulin, Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), insulin-like growth factor-1 (IGF-1), triglycerides (TGs), total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C)], and inflammatory (leptin, adiponectin, high sensitivity C-reactive protein) secondary outcomes through 24 mo of age in infants who received standard cow's milk-based infant formula (SF), similar formula with added bovine MFGM (EF), or human milk (HM) through 1 y.

METHODS

Infants whose parents agreed to a blood draw at baseline (<120 d of age) (SF = 80; EF = 80; HM = 83) were included. Subsequent collections (2-4 h fasting) occurred at D180, D365, and D730. Biomarker concentrations were analyzed and group changes tested using generalized estimating equations models.

RESULTS

Only serum iron (+22.1 μg/dL) and HDL-C (+2.5 mg/dL) were significantly higher for EF compared with SF at D730. Prevalence of zinc deficiency for EF (-17.4%) and SF (-16.6%) at D180 and depleted iron stores for SF (+21.4%) at D180 and EF (-34.6%) and SF (-28.0%) at D365 were significantly different compared with HM. IGF-1 (ng/mL) for EF and SF was significantly higher at D180 (+8.9) and for EF (+8.8) at D365, and (+14.5) at D730 compared with HM. Insulin (μUI/mL) for EF (+2.5) and SF (+5.8) and HOMA-IR for EF (+0.5) and SF (+0.6) were significantly higher compared with HM at D180. TGs (mg/dL) for SF (+23.9) at D180, for EF (+19.0) and SF (+17.8) at D365, and EF (+17.3) and SF (+14.5) at D730 were significantly higher compared with HM. Zinc, ferritin, glucose, LDL-C and total cholesterol changes were higher in formula groups compared with HM between various time points.

CONCLUSIONS

Micronutrient, metabolic, and inflammatory biomarkers were generally similar through 2 y in infants who received infant formula with or without added bovine MFGM. Over the 2 y, differences were observed between infant formulas and HM reference group. This trial was registered at clinicaltrials.gov as NTC02626143.

The Effect of Zinc Administration in Short Adolescent Mothers who Breastfeed on Zinc Level, Insulin-1 Growth Factors, and Infant Growth

BACKGROUND: Zinc is an important nutrient for humans at all stages of life, whose needs increase during pregnancy and lactation. Zinc concentrations in breast milk are considered adequate for the first 6 months of life, despite an increase in the volume of milk consumed, zinc in breast milk is likely to be sufficient if there is no diet. weaning (9). Zinc levels in breast milk cannot compensate for the increased zinc requirements of the premature neonate due to higher than normal zinc requirements, small liver size with reduced zinc stores and a shortened digestive system. AIM:This study aims to measure serum zinc levels, IGF-1, and growth of infants aged 6 months in short adolescent mothers who are breastfeeding and have been intervened with zinc supplementation. MATERIAL AND METHOD: This study is a quantitative study using a quasi-experimental design, and a pretest-posttest approach with a control group. The sampling technique used purposive sampling with inclusion criteria, namely: infants from breastfeeding mothers aged <19 years, history of SEZ, maternal height <150 cm, so that the total sample size was 60 respondents (30 control samples and 30 intervention samples). Analysis of the data collected in the study was processed analytically with the Independent Sample T-Test and Paired T-Test tests. RESULT: From this study, it was found that the Paired Sample T Test results obtained p value < 0.001 indicating that there was a difference before and after the intervention, so it can be concluded that there was an effect of giving zinc supplementation on serum zinc and IGF-1 levels of infants in the intervention group. And through the Independent T test, the value of p = 0.001 < = 0.05. This shows that there is an effect of zinc supplementation on serum zinc and IGF-1 levels in infants. While the results of the Z-Score test for body weight and Z-Score values for body length obtained p <0.001. This illustrates that there is a difference between the intervention group and the control group, so it can be concluded that there is an effect of zinc supplementation on the growth of infants aged 6 months. CONCLUSSION: There was a significant difference between before and after the intervention in the two groups, so that zinc supplementation was effective in influencing serum zinc levels, IGF-1 and infant growth.

Determining the Actual Zinc and Iron Intakes in Breastfed Infants: Protocol for a Longitudinal Observational Study

BACKGROUND

Zinc and iron deficiencies among breastfed infants during the first 6 months of life have been reported in previous studies. The amounts of zinc and iron intakes from breast milk are factors that contribute to the zinc and iron status of breastfed infants.

OBJECTIVE

This study aims to quantitatively determine zinc and iron intakes by breastfed infants during the first 4 months of life and to investigate the factors that predict zinc and iron status in breastfed infants.

METHODS

Pregnant women at 28 to 34 weeks of gestation were enrolled. Zinc and iron status during pregnancy was assessed. At delivery, cord blood was analyzed for zinc and iron levels. Participants and their babies were followed at 2 and 4 months postpartum. Maternal dietary intakes and anthropometric measurements were performed. The amount of breast milk intake was assessed using the deuterium oxide dose-to-mother technique. Breast milk samples were collected for determination of zinc and iron levels. The amount of zinc and iron consumed by infants was calculated. Zinc and iron status was determined in mothers and infants at 4 months postpartum.

RESULTS

A total of 120 pregnant women were enrolled, and 80 mother-infant pairs completed the study (56 provided full breastfeeding, and 24 provided breast milk with infant formula). All data are being managed and cleaned. Statistical analysis will be done.

CONCLUSIONS

This study will provide information on zinc and iron intakes in exclusively breastfed infants during the first 4 months of life and explore predictive factors and the possible association of zinc and iron intakes with infant growth and nutrient status.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/19119.

Transient Symptomatic Zinc Deficiency in a Breastfed Infant Associated with Low Zinc Levels in Maternal Serum and Breast Milk Improving after Zinc Supplementation: An Uncommon Phenotype?

Acrodermatitis enteropathica (AE) is a rare, autosomal-recessive disorder of neonatal zinc deficiency due to SLC39A4 (intestinal zinc transporter, Zip4) gene mutation with onset after weaning while breastfeeding during this period will be protective. Transient symptomatic zinc deficiency is also acquired rarely in breastfed infants with increased zinc requirements and/or inadequate concentration of zinc in breast milk. The nursing mothers of transient symptomatic zinc deficiency infants show SLC30A2 (mammary epithelial zinc transporter, ZnT-2) gene mutation and abnormally low zinc levels in the breast milk despite normal serum zinc levels, which do not improve after zinc supplementation. A 2-month-old breastfed male infant had AE-like clinical features of zinc deficiency for two weeks. His symptoms and low serum zinc levels improved rapidly after zinc supplementation. The mother also had low serum and breast milk zinc concentration and both improved after oral zinc therapy indicating a non-heritable phenotype. The relevant literature is reviewed and significance of dietary zinc supplementation during pregnancy/lactation is emphasized.

The Comparison of Nutritional Value of Human Milk with Other Mammals' Milk

(1) Background: The variation in the concentration of different components found in milk depends on mammalian species, genetic, physiological, nutritional factors, and environmental conditions. Here, we analyse, for the first time, the content of different components (cholesterol concentration and fatty acids composition as well as the overall fat and mineral content determined using the same analytical methods) in milk of different mammal species. (2) Methods: The samples (n = 52) of human, cow, sheep, goat and mare milk were analyzed in triplicate for: cholesterol concentration, fatty acids profile and fat and mineral content (calcium, magnesium, sodium, potassium, iron, zinc). (3) Results: The highest fat content was reported in sheep milk (7.10 ± 3.21 g/dL). The highest cholesterol concentration was observed in bovine (20.58 ± 4.21 mg/dL) and sheep milk (17.07 ± 1.18 mg/dL). The saturated fatty acids were the lowest in human milk (46.60 ± 7.88% of total fatty acids). Goat milk had the highest zinc (0.69 ± 0.17 mg/dL), magnesium (17.30 ± 2.70 mg/dL) and potassium (183.60 ± 17.20 mg/dL) content. Sheep milk had the highest sodium (52.10 ± 3.20 mg/dL) and calcium (181.70 ± 17.20 mg/dL) concentration values. (4) Conclusions: The differences in nutritional value of milk could be perceived as a milk profile marker, helping to choose the best food for human nutrition.

High proportion of transient neonatal zinc deficiency causing alleles in the general population

Loss of function (LoF) mutations in the zinc transporter SLC30A2/ZnT2 result in impaired zinc secretion into breast milk consequently causing transient neonatal zinc deficiency (TNZD) in exclusively breastfed infants. However, the frequency of TNZD causing alleles in the general population is yet unknown. Herein, we investigated 115 missense SLC30A2/ZnT2 mutations from the ExAC database, equally distributed in the entire coding region, harboured in 668 alleles in 60 706 healthy individuals of diverse ethnicity. To estimate the frequency of LoF SLC30A2/ZnT2 mutations in the general population, we used bioinformatics tools to predict the potential impact of these mutations on ZnT2 functionality, and corroborated these predictions by a zinc transport assay in human MCF-7 cells. We found 14 missense mutations that were markedly deleterious to zinc transport. Together with two conspicuous LoF mutations in the ExAC database, 26 SLC30A2/ZnT2 alleles harboured deleterious mutations, suggesting that at least 1 in 2334 newborn infants are at risk to develop TNZD. This high frequency of TNZD mutations combined with the World Health Organization-promoted increase in the rate of exclusive breastfeeding highlights the importance of genetic screening for inactivating SLC30A2/ZnT2 mutations in the general population for the early diagnosis and prevention of TNZD.

Concentrations of trace elements in human milk: Comparisons among women in Argentina, Namibia, Poland, and the United States

Human milk contains essential micronutrients for growth and development during early life. Environmental pollutants, such as potentially toxic metals, can also be transferred to the infant through human milk. These elements have been well-studied, but changing diets and environments and advances in laboratory technology require re-examining these elements in a variety of settings. The aim of this study was to characterize the concentrations of essential and toxic metals in human milk from four diverse populations. Human milk samples (n = 70) were collected in Argentina (n = 21), Namibia (n = 6), Poland (n = 23), and the United States (n = 20) using a standardized mid-feed collection procedure. Milk concentrations of calcium, zinc, iron, copper, manganese, lead, arsenic, and cadmium were determined using inductively coupled plasma mass spectrometry (ICP-MS). We used standard multiple linear regression models to evaluate differences among populations, while including infant age, infant sex, and maternal parity status (multiparous or primiparous) as covariates. Concentrations of all elements, except zinc, varied across populations after controlling for infant age, infant sex, and maternal parity. Calcium and magnesium showed more differences across populations than iron or copper. There were no significant differences among population in zinc concentrations. Mean concentrations of lead, but not arsenic, were low compared to recently published values from other populations. The concentrations of trace elements in human milk are variable among populations. Limitations due to small sample sizes and environmental contamination of some samples prevent us from drawing robust conclusions about the causes of these differences.

Zinc concentrations in human milk and infant serum during the first six months of lactation

Normal supply of zinc to the newborn via milk is essential for normal development. Using ICP-OES, we analyzed changes in the level of Zn in milk and infant serum in the neonatal period (Day 1 and Day 28 post partum) and at 6 months after delivery, in the cohort of 60 mothers and exclusively breastfed babies. Zn level in the serum showed increase (significant at 6 months) during this period (mg/mL): Day 1: 0.52±0.12; Day 28: 0.59±0.19; 6 months: 0.68±0.28. The concentration of Zn in the milk showed an opposite (decreasing) trend during the follow up: Day 1: 4.70±1.74mg/L; Day 28: 2.65±1.06; 6 months: 0.46±0.36. A significant negative correlation was established between serum and milk [Zn] at day 28 (R=-0.338; p=0.008), whereas a positive correlation was found at 6 months between these parameters (R=0.306; p=0.018). There was no significant correlation between [Zn] in the milk and serum and infants' body mass, mothers' age and mass at delivery. The level of Zn in the milk at 6 months of lactation is not sufficient to meet the recommended values. This implies that in Serbian population, Zn supplementation might be needed in the later phase of lactation.

Zinc and infant nutrition

Zinc is essential for a wide variety of cellular processes in all cells. It is a critical dietary nutrient, particularly in the early stages of life. In the early neonatal period, adequate sources of zinc can be obtained from breast milk. In rare circumstances, the mammary gland produces zinc deficient milk that is potentially lethal for exclusively breast-fed infants. This can be overcome by zinc supplementation to the infant. Alterations to key zinc transporters provide insights into the mechanisms of cellular zinc homeostasis. The bioavailability of zinc in food depends on the presence of constituents that may complex zinc. In many countries, zinc deficiency is a major health issue due to poor nourishment. Young children are particularly affected. Zinc deficiency can impair immune function and contributes to the global burden of infectious diseases including diarrhoea, pneumonia and malaria. Furthermore, zinc deficiency may extend its influence across generations by inducing epigenetic effects that alter the expression of genes. This review discusses the significance of adequate zinc nutrition in infants, factors that influence zinc nutrition, the consequences of zinc deficiency, including its contribution to the global burden of disease, and addresses some of the knowledge gaps in zinc biology.

Genetic causes and gene–nutrient interactions in mammalian zinc deficiencies: acrodermatitis enteropathica and transient neonatal zinc deficiency as examples

Discovering genetic causes of zinc deficiency has been a remarkable scientific journey. It started with the description of a rare skin disease, its treatment with various agents, the successful therapy with zinc, and the identification of mutations in a zinc transporter causing the disease. The journey continues with defining the molecular and cellular pathways that lead to the symptoms caused by zinc deficiency. Remarkably, at least two zinc transporters from separate protein families are now known to be involved in the genetics of zinc deficiency. One is ZIP4, which is involved in intestinal zinc uptake. Its mutations can cause acrodermatitis enteropathica (AE) with autosomal recessive inheritance. The other one is ZnT2, the transporter responsible for supplying human milk with zinc. Mutations in this transporter cause transient neonatal zinc deficiency (TNZD) with symptoms similar to AE but with autosomal dominant inheritance. The two diseases can be distinguished in affected infants. AE is fatal if zinc is not supplied to the infant after weaning, whereas TNZD is a genetic defect of the mother limiting the supply of zinc in the milk, and therefore the infant usually will obtain enough zinc once weaned. Although these diseases are relatively rare, the full functional consequences of the numerous mutations in ZIP4 and ZnT2 and their interactions with dietary zinc are not known. In particular, it remains unexplored whether some mutations cause milder disease phenotypes or increase the risk for other diseases if dietary zinc requirements are not met or exceeded. Thus, it is not known whether widespread zinc deficiency in human populations is based primarily on a nutritional deficiency or determined by genetic factors as well. This consideration becomes even more significant with regard to mutations in the other 22 human zinc transporters, where associations with a range of diseases, including diabetes, heart disease, and mental illnesses have been observed. Therefore, clinical tests for genetic disorders of zinc metabolism need to be developed.

Metallothioneins pattern during ontogeny of coastal dolphin, Pontoporia blainvillei, from Argentina

Metallothioneins are signals of metal exposure and widely used in biomonitoring. Franciscana dolphin is an endemic cetacean from the Southwestern Atlantic Ocean, classified as Vulnerable A3d by the IUCN. Metallothionein, copper and zinc in Franciscana were assessed in two geographic groups; one inhabits La Plata River estuary, anthropogenically impacted, and the other inhabits marine coastal ecosystems, with negligible pollution. Despite the environment, hepatic and renal MT concentrations were similar, but there was a declining trend from early to later developmental stages. Metallothionein K/L, Cu and Zn levels corresponded to normal reported ranges. MT was not related with Cd. Fetal concentrations were higher than its mother. These results and the health status of dolphins are suggesting that MT correspond to physiological ranges for the species, and they are closely to homeostasis of Zn and Cu, according to its ontogenetic changes. The information constitutes the first MT information on Franciscana dolphin and can be considered as baseline for the species conservation.

The nutritive and immunoprotective quality of human milk beyond 1 year postpartum: are lactation-duration-based donor exclusions justified?

Donor human milk is critical for the fragile preterm infant who does not have access to his or her mother's milk, improving survival rates and quality of survival and decreasing hospital stay. Despite the opening of donor milk banks around the world, shortages continue as demand for donor milk exceeds supply. One potential means of increasing supply is by reducing exclusion criteria that prohibit mothers from donating milk based on duration of lactation. Minimal research has been done on the composition of human milk during the second year of lactation, with most research focusing on the nutritive compounds and not the immunoprotective compounds. Several immunoprotective compounds, including lysozyme, lactoferrin, secretory immunoglobulin A, and oligosaccharides, are abundant in human milk compared to bovine-based infant formula and are partially or fully retained during Holder pasteurization, making them an important differentiating feature of donor milk. A PubMed search was conducted to review studies in human milk composition during the second year of lactation. Limitations of existing research include sample collection protocols, small study sizes, and use of populations that may have been at risk for nutritional deficiencies. Stable concentrations of several components were reported including protein, lactose, iron, copper, lactoferrin, and secretory immunoglobulin A. Lysozyme concentration increased during extended lactation, while zinc and calcium concentrations declined into the second year. Conflicting findings were reported on fat content, and no information was available regarding oligosaccharide content. More research is needed to create evidence-based guidelines regarding the nutritive and immunoprotective value of donor milk throughout the course of lactation.

Zinc deficiency and its inherited disorders -a review

Zinc is an essential trace element required by all living organisms because of its critical roles both as a structural component of proteins and as a cofactor in enzyme catalysis. The importance of zinc in human metabolism is illustrated by the effects of zinc deficiency, which include a diminished immune response, reduced healing and neurological disorders. Furthermore, nutritional zinc deficiency can be fatal in newborn or growing animals. While zinc deficiency is commonly caused by dietary factors, several inherited defects of zinc deficiency have been identified. Acrodermatitis enteropathica is the most commonly described inherited condition found in humans. In several of the few cases that have been reported, this disorder is associated with mutations in the hZIP4 gene, a member of the SLC39 family, whose members encode membranebound putative zinc transporters. Mutations in other members of this family or in different genes may account for other cases of acrodermatitis in which defects in hZIP4 have not been detected. Another inherited form of zinc deficiency occurs in the lethal milk mouse, where a mutation in ZnT4 gene, a member of the SLC30 family of transmembrane proteins results in impaired secretion of zinc into milk from the mammary gland. A similar disorder to the lethal milk mouse occurs in humans. In the few cases studied, no changes in ZnT4 orthologue, hZnT4, were detected. This, and the presence of several minor phenotypic differences between the zinc deficiency in humans and mice, suggests that the human condition is caused by defects in genes that are yet to be identified. Taking into account the fact that there are no definitive tests for zinc deficiency and that this disorder can go undiagnosed, plus the recent identification of multiple members of the SCL30 and SLC39, it is likely that mutations in other genes may underlie additional inherited disorders of zinc deficiency.

Polymorphisms of SLC30A2 and selected perinatal factors associated with low milk zinc in Chinese breastfeeding women

The variability of breast-milk zinc concentration is high among breastfeeding women, and it is known to be independent of dietary zinc intake. As a result, transient neonatal zinc deficiency is not rare in the breastfed infants due to low milk zinc concentration in their breastfeeding mothers. Up to now, SLC30A2 has been documented the only candidate gene showing correlation with human milk zinc trait. In this study, 750 breastfeeding women were recruited and 10ml foremilk was collected on 42nd postpartum day. The milk zinc concentration was measured, and genomic DNA was isolated from breast-milk. Direct sequencing and Taqman assay were used to identify the SLC30A2 polymorphisms associated with low-milk-zinc. Subsequently, the factors associated with breast-milk zinc were investigated using regression model. The correlation study showed that SLC30A2/-697G>T and SLC30A2/1031A>G polymorphisms were associated with low-milk-zinc in our subjects. These two polymorphisms explained 3.23% of total variance in milk zinc level. For non-genetic variables, the obese breastfeeding women (BMI>25) secreted less zinc into their breast-milk. The variation of milk zinc was independent of pregnant age, birth weight, infant gender, cesarean delivery, preterm delivery and vitamin D supplementation. In conclusion, our results indicated that -697G>T and 1031A>G polymorphisms in the SLC30A2 gene may be associated with low-milk-zinc in Chinese breastfeeding women. Maternal BMI is significantly correlated with milk zinc level in negative manner. Our study demonstrated that both genetic and non-genetic factors could modulate milk zinc level.

A dominant negative heterozygous G87R mutation in the zinc transporter, ZnT-2 (SLC30A2), results in transient neonatal zinc deficiency

Zinc is an essential mineral, and infants are particularly vulnerable to zinc deficiency as they require large amounts of zinc for their normal growth and development. We have recently described the first loss-of-function mutation (H54R) in the zinc transporter ZnT-2 (SLC30A2) in mothers with infants harboring transient neonatal zinc deficiency (TNZD). Here we identified and characterized a novel heterozygous G87R ZnT-2 mutation in two unrelated Ashkenazi Jewish mothers with infants displaying TNZD. Transient transfection of G87R ZnT-2 resulted in endoplasmic reticulum-Golgi retention, whereas the WT transporter properly localized to intracellular secretory vesicles in HC11 and MCF-7 cells. Consequently, G87R ZnT-2 showed decreased stability compared with WT ZnT-2 as revealed by Western blot analysis. Three-dimensional homology modeling based on the crystal structure of YiiP, a close zinc transporter homologue from Escherichia coli, revealed that the basic arginine residue of the mutant G87R points toward the membrane lipid core, suggesting misfolding and possible loss-of-function. Indeed, functional assays including vesicular zinc accumulation, zinc secretion, and cytoplasmic zinc pool assessment revealed markedly impaired zinc transport in G87R ZnT-2 transfectants. Moreover, co-transfection experiments with both mutant and WT transporters revealed a dominant negative effect of G87R ZnT-2 over the WT ZnT-2; this was associated with mislocalization, decreased stability, and loss of zinc transport activity of the WT ZnT-2 due to homodimerization observed upon immunoprecipitation experiments. These findings establish that inactivating ZnT-2 mutations are an underlying basis of TNZD and provide the first evidence for the dominant inheritance of heterozygous ZnT-2 mutations via negative dominance due to homodimer formation.

Toxic metals (Pb and Cd) and their respective antagonists (Ca and Zn) in infant formulas and milk marketed in Brasilia, Brazil

In non-ideal scenarios involving partial or non-breastfeeding, cow's milk-based dairy products are mainstream in infant feeding. Therefore, it is important to study the concentrations of potentially neurotoxic contaminants (Pb and Cd) and their respective counteracting elements (Ca and Zn) in infant dairy products. Fifty-five brands of infant formulas and milk sold in Brasilia, Brazil were analyzed. The dairy products came from areas in the central-west (26%), southeast (29%) and south of Brazil (36%) extending as far as Argentina (7%) and the Netherlands (2%). For toxic Pb and Cd, median concentrations in powdered samples were 0.109 mg/kg and 0.033 mg/kg, respectively; in fluid samples median Pb concentration was 0.084 mg/kg, but median Cd concentration was below the limit of detection and overall values were below reference safety levels. However, 62% of these samples presented higher Pb concentration values than those established by FAO/WHO. Although the inverse correlation between Cd and Zn (Spearman r = -0.116; P = 0.590) was not statistically significant, the positive correlation between Ca and Pb was (Spearman r = 0.619; P < 0.0001). Additionally, there was a significant correlation between Pb and Cd. Furthermore, the study also revealed that provision of the essential trace element Zn in infant formulas can provide adequate amounts of the recommended daily requirements. Infant formulas and milk sold for consumption by infants and children can be an efficient tool to monitor neurotoxic metal risk exposure among young children.

Functional analysis of two single nucleotide polymorphisms in SLC30A2 (ZnT2): implications for mammary gland function and breast disease in women

Zinc transporter 2 (ZnT2) plays a major role in zinc (Zn) export from the mammary gland. Recently, we determined that ZnT2 is associated with secretory vesicles reflecting its role in Zn secretion during lactation. Herein, we identified two distinct single nucleotide polymorphisms (SNPs) in SLC30A2, which encodes ZnT2. SNP1 (rs35235055) results in a leucine-to-proline substitution (Leu(23)Pro), while SNP2 (rs35623192) results in an arginine-to-cysteine substitution (Arg(340)Cys). We examined the localization and function of each SNP in cells generated to express these polymorphic variants. SNP1 was mislocalized to lysosomes, while SNP2 was mislocalized to the Golgi apparatus. FluoZin-3 fluorescence illustrated increased lysosomal accumulation of Zn in cells expressing SNP1 concomitant with the abrogation of Zn secretion. In contrast, ectopic expression of SNP2 was associated with the expansion of cytoplasmic Zn pools, elevated reactive oxygen species, and increased Zn efflux. Taken together, our data indicate that polymorphic variants in ZnT2 distinctly alter mammary cell Zn metabolism. We speculate that these SNPs may compromise mammary cell function, which may have important implications in human health and breast disease.

Zinc and copper concentrations in human preterm milk

Zinc and copper are important trace elements in the nutrition of preterm infants. This study determined and compared the concentrations of zinc and copper in preterm milk of mothers receiving and not receiving zinc supplementation diets. The effects of maternal supplementation on the blood levels and anthropometric parameters were evaluated. Thirty-eight mothers and their preterm infants were enrolled in the study. Eighteen mothers were given a daily supplementation of 50 mg zinc, whereas the other 20 were not. Zinc and copper levels in milk were determined at 15-day intervals, as were blood zinc levels along with anthropometric parameters. Zinc and copper contents were determined by atomic absorption spectrophotometry. No significant differences were found between groups either for zinc values in maternal milk and infant blood or for anthropometric measurements. A pronounced decrease in copper levels was observed in mothers receiving supplemental zinc. Zinc supplementation given to mothers who were breastfeeding preterm infants had no significant effect on zinc secretion in milk.

Antioxidants in bovine colostrum

Quality, content and properties of colostrum are crucial for the neonate and its further development. Due to essential differences between intrauterine and extrauterine environment, the neonate is exposed to oxidative stress conditions. Colostrum apart from nutrient and immunological components should contain antioxidative systems necessary for the protection against reactive oxygen species. This review describes available data on enzymatic and non-enzymatic antioxidants in colostrum. Due to the fact that the literature concerning bovine colostrum is scanty, the information based on bovine mature milk determinations as well as other species is provided. Bovine colostrum is used not only by calves, but also for the production of hyperimmunized colostrum, medicines or feed supplements. Quality of colostrum influences quality of mature milk. This is another reason, except from health of neonate, why antioxidative properties of bovine colostrum are of special importance and require further detailed elucidation.

Daily fluctuations and distribution of xenobiotics, nutritional and biogenic elements in human milk in Southern Poland

Cadmium, lead, zinc, copper, calcium and magnesium levels were determined (with voltametric and AAS methods) in mature breast milk (obtained 12 weeks after birth) from women living in the Malopolska District, near Krakow, Poland. Milk was sampled from lactating women during a 14-day period three times a day: at 9:00 am, 3:00 pm, and 9:00 pm. A total of 210 milk samples was collected. In general we noticed the presence of differences both in the levels of Cd and Pb between milk samples taken from different women and statistically significant daily changes of Cd level in two cases and Pb level in three cases. We found daily fluctuations of trace elements levels in milk samples taken from two women in case of Zn, and from one woman in case of Cu. Among the nutritional elements magnesium and cadmium daily fluctuations were detected in isolated cases, respectively. The diferences in their levels among samples taken from different women were statistically significant. We found significant correlations between xenobiotics and two major nutritional elements and between xenobiotics and biogenic elements in breast milk samples. We found strong positive correlations between Cd and Ca (R = 0.220), Cd and Mg (R = 0.201), Cd and Zn (R = 0.279), Cu and Ca (R = 0.347), Cu and Mg (R = 0.084), Zn and Mg (R = -0.089) and negative correlation between Pb and Ca (R = -0.295). Our results suggest that xenobiotics such as Cd and Pb are transported to women's milk during lactation, and their presence has an important influence on trace and nutritional elements in breast milk. Breastfeeding mothers should avoid situations in which they run the risk of xenobiotics interactions.

Quality control of banked milk in Brasilia, Brazil

The authors studied quality control procedures at human milk banks and nutritional profiles of 909 milk samples (from 195 donors, aged 15 to 45 years) from banked human milk (BHM) in Brasília, Brazil. Number of donations per donor ranged from 1 to > 10 that consisted mostly of mature milk (90.9%) with a mean total energy of 529 +/- 85 kcal/L and a mean total lipid of 22.7 g/L +/- 13.2. Microbiological quality (titrable acidity-Dornic, degrees D) was suitable for infant feeding in 99.2% of samples (< 8 degrees D), ranging from 2 degrees D to 8 degrees D (mean 4.8 +/- 1.4 degrees D). Most BHM (98.1%) samples were dispensed to inpatient infants (1-7 days) diagnosed with respiratory distress (30.1%), prematurity (20.7%), metabolic distress (16.0%), jaundice (14.4%), bacterial infection (6.0%), pneumonia (3.3%), congenital cardiac distress (2.2%), or other conditions (6.2%). Well-motivated mothers and trained staff are serving and sustaining an important life-saving network with long-lasting impact on public health.

Selenium and breast-feeding

The objective of the present review is to discuss Se nutrition during breast-feeding, encompassing environmental and maternal constitutional factors affecting breast-milk-Se metabolism and secretion. A literature search of Medline and Webofscience was used to retrieve and select papers dealing with Se and breast milk. Although Se in natural foods occurs only in organic form, breast milk responds to organic and inorganic Se in supplements. Inorganic Se (selenite, selenate), which is largely used in maternal supplements, is not detectable in breast milk. The mammary-gland regulating mechanism controls the synthesis and secretion of seleno-compounds throughout lactation, with a high total Se level in colostrum that decreases as lactation progresses. Se appears in breast milk as a component of specific seleno-proteins and seleno-amino-acids in milk proteins that are well tolerated by breast-fed infants even in high amounts. Se in breast milk occurs as glutathione peroxidase (4-32 % total Se) > selenocystamine > selenocystine > selenomethionine. The wide range of breast-milk Se concentrations depends on Se consumed in natural foods, which reflects the Se content of the soils where they are grown. Se prophylaxis, either through soil Se fertilization or maternal supplements, is effective in raising breast-milk Se concentration. In spite of wide variation, the median Se concentration from studies worldwide are 26, 18, 15, and 17 microg/l in colostrum (0-5 d), transitional milk (6-21 d), mature milk (1-3 months) and late lactation (>5 months) respectively. Se recommendations for infants are presently not achieved in 30 % of the reported breast-milk Se concentrations; nevertheless Se status is greater in breast-fed than in formula-fed infants.

Zinc deficiency in nursing infants

Zinc deficiency during nursing can occur even in breast-fed infants. Zinc reserves accumulated during fetal development modulate the infant's susceptibility to zinc deficiency. Improvement of maternal zinc nutrition during pregnancy is the key for infant's zinc nutritional support and prevention of low-for-lactation-age zinc concentrations of breast-milk.