Zinc and copper balances in preterm infants

Preterm infants are at risk for copper and zinc depletion if sufficient quantities of these nutrients are not provided in a bioavailable form in postnatal life. The purpose of this study was to determine whether the use of a whey-predominant, 50% medium chain triglyceride formula with relatively high concentrations of zinc and copper would promote the achievement of the in utero accretion rate for zinc and copper in the preterm infant. Two groups of five preterm infants were fed a diet containing 12.5 mg/L of zinc and either 0.9 mg/L or 2.1 mg/L of copper. Seventy-two-hour metabolic balance studies were performed at an average postconceptual age of 34 weeks and an average weight of 1,549 g. All infants were in positive zinc balance and nine of ten achieved the in utero accretion rate for zinc for a 34-week gestation fetus (greater than or equal to 0.432 mg/d). Three infants receiving the high copper formula and two receiving the lower copper formula were in positive copper balance. Two infants from each group achieved the in utero accretion rate for copper for a 34-week gestation fetus (0.088 mg/d). A formula that provides 12.5 mg/L of zinc permits positive zinc balance and zinc retention similar to in utero rates. A formula that provides as much as 2.1 mg/L of copper, however, may not always permit positive copper balance.     

早产儿和足月儿脐血及母亲静脉血硒含量的比较

目的：硒是一种人体必需的微量元素,在细胞抗氧化防御系统中发挥着主要的作用。在早期早产儿中,低水平的硒会增加诸如慢性新生儿肺疾病、早产儿视网膜病等并发症的发生。该研究旨在检测并比较早产儿和足月儿脐血及母亲静脉血硒含量。方法：选取2008年3~7月间30个足月儿（胎龄>37 周）和30个早产儿（胎龄< 34 周）及他们的母亲作为研究对象。用原子吸收光谱法测定脐血和母亲静脉血的硒含量。结果：足月儿的脐血硒平均含量高于早产儿,差异有非常显著性(124.80± 13.72 μg/L vs 100.30 ± 11.72 μg/L, P=0.0001) 。 足月儿母亲与早产儿母亲的的平均硒含量差异无显著性 (117.03±17.15 μg/L vs 110.56±17.49 μg/L, P=0.15)。将所有婴儿的资料一起分析时,发现脐血硒含量与胎龄和出生体重显著正相关(r=0.66, P<0.0001;r=0.59, P<0.0001)。60例婴儿母亲中,无一例的血硒含量低于正常参考值的下限（70.0 μg/L）。将所有婴儿及其母亲的资料一起分析时,发现母亲血硒含量与其婴儿脐血硒含量呈显著正相关 (r=0.40, P<0.001)。结论：在伊斯法罕地区,孕母的血硒水平处于一个良好的状态,血硒水平不是早产的预测指标。足月儿的脐血硒含量高于早产儿,但足月儿和早产儿的脐血硒含量均在正常参考范围。［中国当代儿科杂志,2009,11（7）：513-516］     

Zinc, copper, manganese, and selenium metabolism in patients with human growth hormone deficiency or acromegaly

This study was designed to evaluate trace metal metabolism in patients with known abnormalities of human growth hormone (hGH). The mean concentration of zinc in plasma and urine decreased in patients with hGH deficiency after hGH injection, whereas, after adenomectomy, in patients with acromegaly, zinc increased in plasma, remained the same in erythrocytes, and decreased in urine. There was a negative correlation between plasma zinc and serum hGH levels and a positive correlation between urinary zinc excretion and serum hGH levels in acromegaly. In hGH deficiency, the copper content remained unchanged in plasma and erythrocytes and rose in urine after treatment; however, in acromegaly, the copper content increased in plasma and remained unchanged in erythrocytes and urine after surgery. The mean concentration of erythrocyte manganese did not change significantly after treatment in patients with hGH deficiency or acromegaly, but the pre-hGH treatment level of erythrocyte manganese in hGH deficiency was lower than in the controls. Plasma selenium concentrations were decreased in hGH deficiency and increased in acromegaly patients after therapy. These results suggest that hGH affects the metabolism of zinc, copper, manganese, and selenium.     

Effect of blood transfusion on plasma selenium, glutathione peroxidase and manganese levels in very low birth weight infants.

Very low birth weight infants often receive multiple blood transfusions. We measured the plasma levels of the trace elements selenium, manganese, and glutathione peroxidase in 20 very low birth weight infants prior to blood transfusion and then at 24, 48 and 72 h after transfusion. There was no detectable change in mean selenium or glutathione peroxidase concentrations after transfusion, but the mean (SD) plasma manganese increased from 3.8 (1.5) to 6.0 (2.3) micrograms/l at 72 h.     

Zinc,copper and iron content of milk from mothers of preterm and full-term infants

Complete 24-hour expressions of milk were collected over the first month of lactation from mothers giving birth at term (FT) and prematurely (PT). Samples were analyzed for Cu, Fe and Zn concentration. Composition of PT and FT milks was similar during the first 4 weeks of lactation, but the concentrations of each mineral were higher during the first week than during the fourth week. From these data, the intakes of premature infants fed their own mother's milk were estimated and the proportion which must be absorbed and retained in order to accumulate the amounts laid down in utero were predicted. On the basis of these estimates, preterm infants who retain 25% of the Zn and 35% of the Cu in PT milk would approximate in utero accumulations. However, the Fe content of PT milk is unlikely to provide for in utero accretion rates, even if 100% absorption was achieved.     

Catecholamine and blood pressure levels in paralysed preterm ventilated infants

The effect of pancuronium administration on catecholamine levels and blood pressure was investigated. Noradrenaline levels prior to paralysis amongst infants fighting the ventilator were high, but were significantly reduced following treatment with pancuronium. There was no significant change in either blood pressure or adrenaline levels. Increasing peak inspiratory pressure (approx. 4 cmH2O) immediately prior to paralysis effectively prevented the hypoventilation previously associated with the administration of the first dose of pancuronium.     

Analyses of serum vitamin D-binding protein, ceruloplasmin and copper levels in preterm infants.

The cord blood specimens of 12 preterm and 20 term babies were investigated. We determined serum calcium (Ca), phosphorus (P), magnesium (Mg), vitamin-D binding protein (DBP), ceruloplasmin (Cp) and copper (Cu) levels in two groups. We found that Ca, P, and MG levels of cord sera did not differ between the groups (p > 0.05), but DBP, Cp and Cu values showed a significant decrease in the preterm group (p < 0.05). The Cu and Cp values of the preterm infants correlated with those of the term infants.     

Zinc deficiency in rapidly growing preterm infants

Symptomatic zinc deficiency was observed in a 24-week gestation, 640g birthweight infant fed exclusively with maternal breast milk. Our hypothesis was that subclinical Zn deficiency is not uncommon in very low birthweight infants because fortified human milk and preterm formula may contain little Zn. Zinc serum concentrations determined in 26 consecutive very low birthweight infants (gestational age 23-32, median 27 weeks), prior to discharge, at a chronological age of 37-121 (median 72) d, were found between 1.0 and 14.0 (median 6.4) μmol/l, in 14 infants they were below the normal range of 7.6-15.0μmol/l. Serum alkaline phosphatase and iron intake did not correlate with Zn concentrations. Nutritional supply of Zn and other trace elements by breast milk fortifiers and infant formulas currently used in Germany does not appear to meet the demands of rapidly growing extremely low birthweight infants during the first months of life.     

Glutathione peroxidase and selenium levels in the preterm infant

Glutathione peroxidase (GPX) and selenium are important in the prevention of cellular oxidant damage. Whole-blood GPX and plasma selenium were measured at birth and sequentially afterwards in 75 preterm babies. GPX activity at birth was 2.74 +/- 0.08 (mean +/- SEM) U/ml. Mean GPX activity remained relatively unchanged for up to 70 days postnatal age. Plasma selenium at birth was 0.43 +/- 0.02 (mean +/- SEM) mumol/l), decreasing to low levels by 10 weeks postnatal age. Neither GPX activity nor plasma selenium was related to birth weight, gestational age or infant sex.     

光疗对早产儿血内皮素及一氧化氮水平的影响及临床意义

目的观察光疗对早产儿血内皮素(ET)和一氧化氮(NO)水平的影响。方法以64例符合光疗条件的高未结合胆红素血症早产儿为研究对象,其中胎龄>32周组31例,胎龄≤32周组33例,并以26例符合光疗条件的高未结合胆红素血症足月儿为对照组,给予24 h连续光疗。用放射免疫法测定ET,用硝酸还原酶法测定NO。在光疗期间定期监测心率、呼吸(包括呼吸暂停)、平均动脉压。结果胎龄≤32周组:光疗24 h与光疗前比较血浆ET值明显升高(P<0.05);光疗12和24 h较光疗前血清NO值升高具有统计学意义(P<0.05);光疗24 h与光疗前血NO/ET比值的升高也具有统计学意义(P<0.05)。胎龄>32周组:仅光疗24 h较光疗前血清NO值升高有统计学意义(P<0.05)。胎龄≤32周组光疗24 h较光疗前心率增快、平均动脉压下降均有统计学意义(P<0.05),光疗24 h血NO/ET比值与平均动脉压呈负相关性。胎龄≤32周组较胎龄>32周组和足月组光疗中呼吸暂停发生例次数明显增多。结论光疗对早产儿尤其小胎龄早产儿血ET、NO影响明显,可能会导致血流动力学改变,应予关注。     

Zinc absorption, distribution, excretion, and retention by healthy preterm infants

Zinc (Zn) is an essential nutrient for growth, but little is known about Zn absorption, distribution, excretion, and retention in preterm infants. Nine infants with gestational age 32+/-1 wk (mean+/-SE), birth weight 1.44+/-0.08 kg, postnatal age 14+/-3 d, on Zn intake of 23+/-3 micromol/kg per d via enteral feeding of preterm formula were studied. A stable Zn isotope (70Zn) was administered orally or i.v., and plasma, red blood cells, urine, and feces were sampled for up to 30 d. Samples were analyzed for Zn by inductively coupled plasma atomic emission spectrometry and for isotope enrichment by inductively coupled plasma mass spectrometry. Data were analyzed by compartmental analysis using the Simulation Analysis and Modeling program, and absorption, distribution, excretion, and retention were calculated. Absorption was 36+/-5% or 7+/-1 micromol/kg per d; distribution in plasma was 15+/-1 micromol Zn/L and in RBC was 41+/-4 micromol Zn/L; excretion in urine was 0.55+/-0.03 micromol Zn/kg per d and in feces was 17+/-3 micromol Zn/kg per d and retention was 5+/-1 microl/kg per d. Results show that healthy preterm infants with Zn intake of 23 micromol/kg per d and expected growth rates (> 15 g/kg per d) absorb and retain Zn at rates comparable to in utero accretion. The values for absorption, distribution, and excretion by this population of healthy preterm infants provide a normal range for future studies, although further studies are required to determine endogenous excretion rates in healthy preterm infants. We speculate that these values can be used to determine whether Zn kinetics are abnormal in sick infants or in infants with slow growth.     

Selenium and human lactation in Australia: milk and blood selenium levels in lactating women, and selenium intakes of their breast-fed infants

A series of 20 mother-infant pairs were studied in Brisbane, Australia, at 6-12 weeks postpartum. The mean selenium concentration in maternal blood was 101 (SD +/- 19) ng/g and in maternal serum 81(+/- 15) ng/g; serum values appeared low in comparison with those reported for lactating women from Japan and the USA, but similar to those from Finland and from a previous Australian study. Breast milk selenium concentrations (11.9 +/- 3.5 ng/g) were also low by international standards, but not as low as in New Zealand or Scandinavia. There was no correlation between selenium concentrations in milk and blood (or serum). The infants' 24-h breast-milk intakes were 856 +/- 172 g, and their 24-h selenium intakes 10.7 +/- 4.1 micrograms (compared to the Australian RDI of 10 micrograms).     

Circulating levels of adiponectin in preterm infants

OBJECTIVE: To determine circulating levels of adiponectin in preterm infants and examine possible associations with anthropometric measurements, weight gain, and leptin and insulin levels. DESIGN: Prospective study. SETTING: A university hospital neonatal care unit. Study population: 62 preterm (mean (SD) gestational age 32.0 (2.1) weeks) and 15 full-term infants (reference group). INTERVENTIONS: Blood samples taken at discharge (40.9 (14.8) days of life) from the preterm infants and at a comparable postnatal age in full-term infants. All infants were fed the same commercial formula, but in nine preterms the formula contained long-chain polyunsaturated fatty acids (LCPUFAs). MAIN OUTCOME MEASURES: Serum levels of adiponectin, leptin and insulin. Associations of adiponectin levels were tested only in the preterm group. RESULTS: Serum levels of adiponectin were lower in preterm (40.9 (14.8) microg/ml) than full-term infants (53.1 (16.0) microg/ml, p<0.01). However, after adjustment for body weight, the influence of prematurity on adiponectin levels was no longer significant. In preterm infants, adiponectin levels independently correlated with being born small for gestational age (SGA) (beta=-0.35, p=0.01), weight gain (beta=0.28, p=0.03) and LCPUFA-supplemented formula (beta=0.34, p=0.009). Serum adiponectin levels did not correlate with insulin or leptin levels. However, insulin levels were higher in preterm than in full-term infants after adjustment for body weight. CONCLUSIONS: Adiponectin levels are lower in preterm infants at discharge than full-term infants probably due to decreased adiposity. The levels are influenced by being born SGA, weight gain and, possibly, by dietary LCPUFAs. The importance of these findings in the development of insulin or leptin resistance in children born prematurely needs to be further studied.     

Aldosterone cord levels in preterm newborn infants

We measured umbilical cord aldosterone concentrations in 64 premature newborn infants. The median serum aldosterone level was 74.5 ngdl^-1 (range 22-280 ng dl^-1). Of the studied perinatal factors, only gestational age and birthweight presented a significant influence on the umbilical cord aldosterone levels. Newborn infants with a gestational age of over 34 weeks and a birthweight of over 2000 g had a significantly higher aldosterone cord level than those aged 34 weeks or younger and 2000 g or less in weight.     

Zinc and copper in preterm neonates: Relationship with breast milk

The study was conducted to assess copper and zinc levels in neonate’s serum, mother’s serum, neonate’s hair and urine and to ascertain association between them. It is of concern whether zinc and copper deficiency is present at birth and maternal blood and breast milk zinc and copper levels have any effect on this. The study sample included 155 neonates with gestational age 26–41 wks and birth weight 0.550-3.800 kg. Mother’s serum, breast milk, neonate’s serum, hair, urine samples were analysed for zinc and copper by atomic absorption spectrophotometry. Gestational age was estimated either singly or by combination of date of last normal menses, fetal ultrasonography, and postnatal measures of physical and neurological development by clinical examination and weight by Secca electronic balance. The neonates were classified into term and preterm, small (SGA) and appropriate for gestational age (AGA). Neonates over 37 wks and 2.5 kg served as controls. To assess the dependency, relationship and effectiveness of quantitative predictive variables on the predictions of values, multiple regression analysis was used. Neonates between 26–30 wks gestational age and <2.5 kg birth weight had significantly low serum zinc and copper. Breast milk zinc was low in mothers delivering preterm and <2.5 kg neonates. Urinary copper and zinc levels were high in preterm appropriate for gestational age (Pre AGA) than term neonates. Multiple regression analysis revealed that neonate’s serum Cu, serum Zn, hair Cu, hair Zn, urine Cu and urine Zn had contribution variability of 49.8%, 51.8%, 49.2%, 16.6%, 52.2% and 68.9%, respectively. The effect of mother’s serum, breast milk, and neonate’s serum copper and zinc collectively was significant for serum copper (F = 29.59) and hair zinc (F = 32.03). Preterm and low birth weight infants during subsequent growth and development should be supplemented with zinc and copper when on breast feeding     

Factors associated with variation in plasma copper levels in preterm infants of very low birth weight

At 2-weekly intervals from age 4–14 weeks, the possible effects on plasma copper concentration of gestation, multiple birth, fractional weight change from birth (W/BW) and, up to 10 weeks, average daily total copper intake from birth were explored in 43 preterm infants of very low birth weight. There was no significant association between the logarithm of the plasma copper concentration (ln Cu) and multiple birth at any time and no significant association between lnCu and gestation was found from 4–12 weeks. From age 4–10 weeks, there was a significant negative correlation between lnCu and W/BW and at 4, 6 and 10 weeks there was also a significant negative correlation between lnCu and copper intake. W/BW and copper intake were correlated throughout. At 14 weeks, lnCu correlated positively with gestation and negatively with W/BW but, at this age, gestation and W/BW were correlated. The maximum total variation (R²) in lnCu explained by its regression on gestation, multiple birth, W/BW and/or copper intake combined was only about 31% (at 10 weeks). The potential for copper depletion may be greater in rapidly growing infants.