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

Serum copper concentrations in hospitalized newborns

BACKGROUND

Low serum Cu and ceruloplasmin (Cp) concentrations in newborns can be the first indication of a severe Cu deficient intake or, alternatively, of genetic diseases affecting Cu metabolism. However, Cu and Cp concentrations can also be influenced by other variables that render their quantitative results difficult to interpret. Therefore, it is necessary to identify these variables and stratify Cu and Cp concentrations according to these altering factors.

METHODS

Serum Cu and Cp concentrations for 564 hospitalized newborns (0-12days of life) are stratified according to their age, prematurity (birth weight or gestational age), type of feeding and inflammatory state (assessed by the serum high sensitivity C-reactive protein (hs-CRP) level) to identify potential correlations.

RESULTS

Serum Cu and Cp concentrations are influenced by all four variables analyzed, although inflammation is the most significant: the greater the hs-CRP concentration, the greater the serum Cu and Cp concentrations. Prematurity is also an important factor and preterm infants often show very low Cu and Cp concentrations. Age of life and type of feeding have in turn a more modest effect on these magnitudes, being slightly greater at 3-5days of age in breastfed newborns.

CONCLUSIONS

Inflammation and prematurity are the main variables affecting serum Cu and Cp concentrations in newborns. Therefore, hs-CRP should always be assayed in parallel to Cu status. When there is an inflammatory state proper interpretation of these concentrations can be challenging.

A novel approach to measure isotope ratios via multi-collector-inductively coupled plasma-mass spectrometry based on sample mixing with a non-enriched standard

In this work, a novel approach to measure isotope ratios via multi-collector-inductively coupled plasma-mass spectrometry (MC-ICP-MS) for low amounts of target element is proposed. The methodology is based on mixing of the sample (target element isolate) with a non-enriched in-house standard, previously characterized for its isotopic composition. This methodology has been applied to isotopic analysis of Cu and of Fe in whole blood samples. For this purpose, different mixtures of sample + in-house standard were prepared and adjusted to a final concentration of 500 μg/L of the target elements for isotopic analysis. δ(65)Cu, δ(56)Fe, and δ(57)Fe varied linearly as a function of the amount of in-house standard (or of sample) present in the mixture. The isotopic composition of the sample was calculated considering the isotope ratios measured for (i) the mixture and (ii) the in-house standard and (iii) the relative concentrations of target element contributed by the sample and the standard to the mixture, respectively. For validation purposes, the isotopic analysis of whole blood Cu was carried out using both the conventional (using 2 mL of whole blood) and the newly developed approach (using 500 μL of whole blood). The δ(65)Cu values obtained using mixtures containing 40 % (200 μg/L) of Cu from the blood samples and 60 % (300 μg/L) of Cu from the in-house standard were in good agreement with the δ(65)Cu value obtained using the conventional approach (bias ≤0.15 ‰).

Reference values for selected trace elements in serum of term newborns from the urban area of Rome

Reference values for Al, Cd, Co, Cu, Li, Mn, Mo, Ni, Rb, Se and Zn, and indicative intervals for Sb are proposed in serum from cord blood of 143 term newborns of the urban area of Rome. On the basis of the eligibility criteria adopted, only babies with gestational age > 37 weeks and body weight at the delivery > 2500 g, i.e., "normal" term infants, were included in this study. With the exception of Cd, Li, Ni and Sb, experimental data for each of the other analytes were found to approach a normal distribution. The estimated references values (in ng/ml) were the following: Al, 1. 12-6.79; Cd, 0.10-0.52; Co, 0.20-0.43; Cu, 140-691; Li, 0.31-2.23; Mn, 0.79-3.26; Mo, 0.36-1.56; Ni, 0.20-3.15; Rb, 196-1302; Sb, 0. 10-1.48 (indicative range); Se, 20.2-69.7; and Zn, 318-1405. For several elements, the information available in the relevant literature does not allow adequate comparisons to be performed. This was actually possible only for Cu, Se and Zn. The correlations between the weights at birth (BW), gestational ages (GA) and elemental concentrations were elucidated. As expected, significant positive correlations were found for Cu and Se with GA and BW, respectively. Strong mutual associations were observed for several other elements, but their interpretation is still debatable.

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.