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American Journal of Clinical Nutrition, Vol. 88, No. 2, 333-339, August 2008
© 2008 American Society for Nutrition

ORIGINAL RESEARCH COMMUNICATION

Glutathione synthesis rates after amino acid administration directly after birth in preterm infants1,2,3

Frans WJ te Braake, Henk Schierbeek, Karien de Groof, Andras Vermes, Mariangela Longini, Giuseppe Buonocore and Johannes B van Goudoever

1 From the Department of Pediatrics, Division of Neonatology (FWJtB, HS, KdG, and JBvG), and Department of Clinical Pharmacy (AV) Erasmus MC–Sophia Children's Hospital, Rotterdam, Netherlands; the Department of Pediatrics, Obstetrics and Reproductive Medicine, University of Siena, Siena, Italy (ML and GB)

2 Supported by the Sophia Foundation for Scientific Research.

3 Reprints not available. Address correspondence to JB van Goudoever, Erasmus MC–Sophia Children's Hospital, Room Sp-3433, PO Box 2060, 3000 CB Rotterdam, Netherlands. E-mail: j.vangoudoever{at}erasmusmc.nl.


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 SUBJECTS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Background: The availability of glutathione, the main intracellular antioxidant, is compromised in preterm neonates. A possible explanation is the low availability of substrate for synthesis, because many neonatologists are reluctant to administer amino acids in the direct postnatal period for fear of intolerance.

Objective: The objective of the study was to determine the effects of amino acid administration directly after birth on glutathione synthesis rates and markers of oxidative stress.

Design: Premature infants (<1500 g) received from birth onward either dextrose (control group; n = 10) or dextrose plus 2.4 g amino acids · kg – 1 · d–1 (intervention group; n = 10). On postnatal day 2, [1-13C]glycine was administered to determine glutathione fractional synthesis rates (FSRGSH) and absolute synthesis rates (ASRGSH) in erythrocytes. In plasma, advanced oxidized protein products and dityrosine, both markers of oxidative stress, were measured. The results are expressed as means ± SDs.

Results: The FSRGSH was not different between groups: 44 ± 6 and 48 ± 9%/d in the control and intervention groups, respectively (P = 0.28). The concentration of erythrocyte glutathione was higher (P < 0.001) in the intervention group (2.28 ± 0.35 mmol/L) than in the control group (1.73 ± 0.37 mmol/L). ASRGSH values were 6.5 ± 1.5 and 11.3 ± 1.9 mg · kg–1 · d–1 in the control and intervention groups, respectively (P < 0.001). Advanced oxidized protein products and dityrosine concentrations were not significantly different between groups.

Conclusions: Amino acid administration directly after birth increases ASRGSH in preterm infants. Our data are consistent, however, with higher glutathione concentrations rather than a higher FSRGSH. Greater availability of glutathione, nevertheless, did not decrease markers of oxidative stress.


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
SUBJECTS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Birth coincides with a sharp increase in oxygen exposure. The formation of reactive species, such as superoxide, hydrogen peroxide, and hydroxyl radicals evokes up-regulation of antioxidant defense systems in full-term infants (1) and rabbits (2). This, however, does not seem to occur in preterm infants, as reflected by poor antioxidant availability and the presence of protein and lipid (per)oxidation products (3, 4). Yet, on their unanticipated transition to the extrauterine world, preterm neonates frequently receive, though not necessarily require, ventilation with high concentrations of oxygen. This may result in oxidative stress, which is strongly associated with neonatal diseases such as bronchopulmonary dysplasia, retinopathy of prematurity, and periventricular leukomalacia (5-8).

With concentrations in the millimolar range, glutathione (GSH) is the most important intracellular antioxidant. Most cells are equipped with the enzymatic machinery to synthesize this tripeptide of glutamate, cysteine, and glycine. Moreover, the enzymatic apparatus is present and active already in the second trimester of pregnancy and is thus not a limiting factor for GSH synthesis in preterm infants (9, 10). GSH concentrations in the erythrocytes and plasma of preterm infants are high immediately after birth, but then decrease to significantly lower concentrations than found in term neonates in the neonatal period (3, 11). This shortage may be due to the fact that preterm infants do not tolerate significant amounts of enteral nutrition in the first days of life, and are, therefore, given parenteral nutrition, typically starting off with dextrose only. Meanwhile, however, the safety of early amino acid (AA) administration in preterm infants is well established, because relevant studies have found no abnormal blood gas values or abnormal plasma AA profiles (12, 13). In addition, the catabolic state of the infant while receiving dextrose only was found to change to an anabolic state, which represents true growth during AA administration (14). Despite these findings, AA administration directly after birth is still not uniformly the standard of care.

We hypothesized that GSH production in preterm infants is compromised by a shortage of substrates, and that AA administration will stimulate GSH synthesis rates. To test this hypothesis, we conducted a stable-isotope study designed to determine synthesis rates of GSH in infants receiving either dextrose only or dextrose and AAs. The degree of oxidative stress was established by measuring concentrations of advanced oxidized protein products (AOPP) (15) and dityrosine (16, 17), both of which are markers of oxidative stress. We hypothesized that preterm infants receiving dextrose only would show the highest concentrations of AOPP and dityrosine.


   SUBJECTS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 SUBJECTS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Design
The study was a randomized clinical trial conducted in the neonatal intensive care unit of the Erasmus MC–Sophia Children's Hospital, Rotterdam, Netherlands. The study was investigator initiated and received no funding from industry. The protocol was approved by the Erasmus MC Medical Ethical Committee. and informed written parental consent was obtained prior to the study.

Subjects
The subjects were premature infants with a birth weight <1500 g, were born in the Erasmus MC–Sophia Children's Hospital, had an indwelling arterial catheter for clinical purposes, and were expected to be completely dependent on parenteral nutrition for the first 2 d of life. Directly after birth, they were randomly assigned to receive either only dextrose during the first 2 d (control group) or dextrose plus 2.4 g AAs · kg–1 · d–1 (Primene 10%; Baxter, Clintec Benelux NV, Brussels, Belgium) within 2 h after birth (intervention group). The composition of the AA solution is shown in Table 1Go. AA and dextrose solutions were infused constantly without interruptions during the study. Lipids were not administered until after the study period. Exclusion criteria included erythrocyte transfusions within 12 h before the study or during the study, known congenital abnormalities, chromosomal defects, and metabolic, endocrine, renal, or hepatic disorders. For all infants, we recorded birth weight, gestational age, birth weight z scores, and severity of illness at entry of the study by means of Apgar and CRIB scores (18). We recorded plasma AA concentrations, caloric intake, and AA intake. In addition, we recorded fractions of inspired oxygen, blood glucose concentrations, and incidence of sepsis as evidenced by bacteremia. According to our policy at the NICU, all infants being ventilated receive prophylactic antibiotics. Therefore, all infants included in the study received antibiotics. The administration of antibiotics was discontinued after 48–72 h whenever C-reactive protein concentrations were low and blood cultures were negative.


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  		TABLE 1 Composition of the amino acid solution Primene 10%1

 
Tracer infusion protocol and sample collection
[1-13C]Glycine (99% enriched, sterility and pyrogenicity tested) was purchased from Cambridge Isotope Laboratories (Andover, MA, USA) and was dissolved in a 0.9% saline solution, filtered (0.2 µm), and sterilized by the hospital's pharmacy. The final product was tested for identity, content, sterility, and pyrogenicity.

On postnatal day 2, neonates received a primed (40 µmol/kg) continuous (20 µmol · kg–1 · h–1) infusion of [1-13C]glycine for 6 h. Blood samples (400 µL each) were drawn from an indwelling arterial catheter after 4, 5, and 6 h and were collected in EDTA-containing microtainers to quantify erythrocyte free glycine enrichment, GSH-bound glycine enrichment, GSH concentrations, plasma oxidative stress markers, and plasma GSH precursor AA concentrations.

Samples were immediately put on melting ice after centrifugation at 3500 x g for 10 min at 4 °C. After the plasma fraction was removed, the lower layer containing primarily erythrocytes was reconstituted to its original volume with ice-cold distilled water to disrupt cell membranes. The plasma and cell fractions were subsequently stored at –80 °C until further analysis.

Glutathione enrichments and concentration
GSH concentrations and the enrichment of GSH and its precursor glycine were determined to measure the GSH fractional synthesis rate (FSRGSH) and the GSH absolute synthesis rate (ASRGSH). For this purpose, we used a new technique, described previously, using an LC-Isolink interface (Thermo Electron, Bremen, Germany) coupled to a Delta XP isotope-ratio mass spectrometer (Thermo Electron) (LC-IRMS) (19). This highly sensitive method requires only a very small sample volume and no derivatization. Briefly, erythrocytes were disrupted by freezing and thawing. Next, 40 µL of a mixture of 0.2 mg/mL norleucine and 1.0 mg/mL norvaline was added as internal standards, and the samples were deproteinized by adding 200 µL of 6% g/v perchloric acid, left on ice for 10 min, and finally centrifuged at 10 000 x g for 20 min. The supernatant was transferred to a clean tube, and the pH was adjusted to 8–9 with a potassium hydroxide (4 mol/L) solution. Excess perchloric acid was precipitated and removed by centrifugation at 10 000 x g for 10 min; 100 µL of NaHPO4 (0.5 mol/L) was added to maintain a pH of 9. The supernatant was filtered through a 0.2-µm Nylon membrane filter (Nylon; Alltech, Breda, Netherlands). A 150-µL aliquot was transferred to a sample vial, and 20 µL was injected for each analysis of both GSH concentration and 13C-isotopic enrichment by LC-IRMS. The remaining supernatant was used for analysis of 13C-isotopic enrichment of glycine by gas chromatography–combustion–isotope ratio mass spectrometry, similar to an earlier developed method for measurement of the isotopic enrichment of threonine (20). Plasma concentrations of the direct GSH precursors glutamate, glycine, and cysteine (measured as cystine) and the indirect precursors glutamine, methionine, and serine were determined with a Biochrom 30 amino acid analyzer by using ninhydrin detection (Biochrom Ltd, Cambridge, United Kingdom).

Calculations
The FSRGSH represents the fraction of the total intraerythrocytic GSH pool that is renewed per unit of time and is expressed as %/d. It was measured according to the product/precursor equation:

Formula 1(1)
where E is enrichment, expressed as mole percent excess (MPE). The nominator (product) of this equation represents the hourly increase of incorporated [1-13C]glycine into GSH as calculated from the increase in enrichment between 4 and 6 h of infusion. The denominator (precursor) represents the intraerythrocytic free [1-13C]glycine enrichment at isotopic steady state. A steady state plateau was defined as an insignificant change with time in intraerythrocytic enrichment. Subsequently, the intravascular ASRGSH was calculated by using the following equation:

Formula 2(2)
where conc is concentration in mmol/L of packed erythrocytes, 307 is the molecular weight of GSH, ht is hematocrit, and 0.075 is the estimated circulating blood volume in a preterm neonate (in L/kg).

Oxidative stress markers
We measured AOPP in plasma by the spectrophotometric assay described by Witko-Sarsat et al (15). Dityrosine concentrations were measured by using the method described by Abdelrahim et al (16), which is based on liquid-liquid extraction, reversed-phase chromatography, and fluorescence detection.

Glutathione kinetics in healthy adults
Because kinetic measurements require venous access and an indwelling arterial catheter, healthy term neonates cannot serve as controls. Thus far, GSH kinetics have only been studied in older infants and adults, because relatively high blood volumes are needed for a precise determination of enrichment and concentration. In 2 studies of GSH kinetics in healthy adults, mean FSRGSH was found to be 65%/d and 83%/d, respectively (21, 22). GSH concentrations, however, were found to vary substantially between studies (23). Even the minimal manipulation of samples can result in a loss of GSH, which thereby creates false assumptions with respect to the in vivo situation. To correct for different methods yielding different results, we determined GSH kinetics in healthy adults by exactly the same method we used for preterm infants. Studies were conducted after an overnight fast, and subjects remained in the fasting state throughout the study.

Statistics
Statistical analyses were performed by using SPSS version 15.0 (SPSS Inc, Chicago, IL) and GRAPHPAD PRISM version 4 (GraphPad Software, San Diego, CA). Data are expressed as means ± SDs or as medians (minimum –maximum). The primary outcome of the study was the FSRGSH. Based on an abstract by Shew et al (24), we calculated that with an {alpha} of 0.05, a power of 0.80, and a difference in ASRGSH of 0.22 mmol · L–1 · d–1) with an SD of 0.06, the group size needed to be ≥3 to detect a difference. We included 10 infants in each group to increase the power.

Differences between groups were determined by using independent t tests or Mann-Whitney U tests in the case of a normal or skewed distribution of the study groups, respectively. A P value < 0.05 was considered statistically significant.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 SUBJECTS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
The clinical characteristics of the subjects are listed in Table 2Go. All infants received additional oxygen as part of their treatment. We found no correlation between fractions of inspired oxygen and the GSH concentration or FSRGSH. Nutritional intakes before and during the study are shown in Table 3Go. Blood glucose concentrations were not different between groups, and none of the infants received insulin during or before the study (data not shown). Also, there were no differences in the incidence of hyperglycemia. In one blood culture, micrococcus was isolated; therefore, the sample was considered to be contaminated. None of the other infants had either a rise in C-reactive protein concentrations or positive blood cultures before or during the study.


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  		TABLE 2 Clinical characteristics

 

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  		TABLE 3 Nutritional intakes before and during the study1

 
Concentrations of plasma precursor AAs
Plasma concentrations of all AAs involved in GSH synthesis with reference values obtained from healthy term breastfed infants are shown in Table 4Go (25); AA concentrations were significantly higher in the intervention group. Concentrations of glutamate, cystine, and methionine in the control group were below reference ranges. Although the AA solution administered contained cysteine (1.89 g/L), cystine concentrations still were low in the intervention group as well.


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  		TABLE 4 Plasma concentrations of amino acids1

 
GSH concentrations and synthesis rates
Precursor and product enrichments are plotted against the duration of tracer infusion in Figure 1Go. Free intraerythrocytic [1-13C]glycine, considered to be the precursor for GSH synthesis, reached a plateau after 4 h of infusion—defined as no significant increase in enrichment. Precursor enrichments did not differ between the groups (3.6 ± 0.7 MPE in each). Levels of [1-13C]glycine bound to GSH linearly increased between 4 and 6 h of infusion, with a mean R2 of 0.996 and 0.994 between the values measured for the control and intervention groups, respectively. The LC-IRMS method used in this study quantified the [1-13C] enrichment of the total GSH pool, because IRMS is known to combust all carbon elements of GSH into carbon dioxide. We, therefore, were not able to discriminate between the [1-13C] enrichment of GSH originating from glycine or cysteine, which can be formed from glycine via serine. We studied, however, the cysteine peak in our chromatogram and did not find any enrichment, which thereby excluded the possible overestimation of the FSR.


Figure 1
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  		FIGURE 1. Mean (±SD) isotopic steady state of [1-13C]glycine (precursor) enrichment and [1-13C]glutathione (product; GSH) enrichment in the control ({circ}; n = 10) and intervention (•; n = 10) groups. There were no significant differences in the isotopic steady state of [1-13C]GSH enrichment or an increase in [1-13C]GSH enrichment (Student's t test).

 
GSH kinetic data are shown in Figure 2Go. FSRGSH did not differ between groups. The concentration of erythrocyte GSH in the intervention group was higher, however, than that in the control group. As a result, ASRGSH was also higher in the intervention group.


Figure 2
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  		FIGURE 2. Fractional synthesis rates of glutathione (GSH), GSH concentrations, and absolute synthesis rates of GSH in erythrocytes in the control ({circ}; n = 10) and intervention (•; n = 10) groups expressed as individual cases and as means and SDs (horizontal lines). There were no significant differences in fractional synthesis rates between groups (Student's t test). GSH concentrations and absolute synthesis rates were higher in the dextrose + amino acid (intervention) group than in the control group (P < 0.001 for both concentration and absolute synthesis rate; Student's t test).

 
Plasma concentrations of oxidative stress markers
Plasma concentrations of AOPP and dityrosine are shown in Figure 3Go. We found no differences in either marker between groups. These results agree with those of earlier studies on AOPP concentrations in preterm infants and indicate the presence of oxidative stress (4, 26). Increased GSH availability as a result of AA administration did not result in lower AOPP concentrations on postnatal day 2.


Figure 3
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  		FIGURE 3. Plasma concentrations of advanced oxidized protein products (AOPP) and dityrosine in the control ({circ}; n = 10) and intervention (•; n = 10) groups expressed as individual cases and as means and SDs (horizontal lines). There were no statistically significant differences in either AOPP or dityrosine concentrations between the dextrose + amino acid (intervention) and control groups (Student's t test).

 
GSH kinetics in healthy adults
We included 5 healthy nonsmoking adults in the study, who had a mean (±SD) age of 34 ± 8 y and a body mass index (kg/m2) of 22.5 ± 1.2. We found a mean concentration of 1.43 ± 0.13 mmol/L, which is comparable with the concentrations reported by Darmaun et al (22). The mean FSRGSH concentration in erythrocytes was 62 ± 2%/d, resulting in a mean ASRGSH of 7.7 ± 1.1 mg · kg – 1 · d–1). Thus, the ASRGSH of fasted adults is lower than that of fed preterm infants.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 SUBJECTS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
We showed AA administration to be a safe, simple, and efficacious means of increasing GSH synthesis rates. We showed a 32% increase in the erythrocyte GSH concentration and a 74% increase in ASRGSH after administration of 2.4 g AAs · kg–1 · d–1) compared with dextrose administration solely. These results clearly bring out the discrepancy between, on the one hand, demands of the body and, on the other hand, the scarce availability of substrates if only dextrose is administered. Antioxidant defense build-up was not associated, however, with lower concentrations of oxidative stress markers.

The observed increase in the ASRGSH was almost exclusively attributed to the increase in concentration. This is fascinating, because, in adults and children alike, increases in ASRGSH seem to arise primarily from increases in FSRGSH rather than from elevated concentrations (21, 27, 28). We have 2 explanations for this. First, the FSRGSH might have been elevated already on the first day of life and then have decreased as a result of negative feedback. A study performed on the first day of life under the same conditions could provide more insight. Second, the lack of increase in FSRGSH might be related to the function of GSH as an AA reservoir. The plasma glycine concentration rose 65% after AA administration (Table 3Go). It follows that plasma glycine enrichment must have been lower in the intervention group, because infusion rates of [1-13C]glycine were identical for both groups. Despite a theoretically lower plasma glycine enrichment in the intervention group than in the control group, intraerythrocytic enrichment did not differ between groups, as shown in Figure 2Go. Because GSH itself is the major intraerythrocytic pool of glycine, the most plausible explanation is the decreased breakdown of intracellular GSH in the intervention group as opposed to the control group, as proposed earlier (29). Note that GSH is an important AA reservoir, and its intracellular concentration is in the millimolar range, whereas the free fractions of its constituent AAs, especially cysteine, are in the micromolar range. Altogether, these data strongly suggest decreased consumption of GSH in the intervention group, possibly resulting—as we showed recently—from increased synthesis of other antioxidants, such as albumin (30).

An explanation for the overall lower FSRGSH in preterm neonates than in adults is an increased recycling of oxidized GSH (GSSG) to GSH in neonates. Normally, GSSG concentrations are kept very low to protect the cell from a shift in redox equilibrium. This is achieved by either reducing GSSG to GSH or exporting it to the extracellular space, which is dependent on the availability of the enzyme glutathione reductase and NADPH (31). Indeed, increased recycling of GSSG into GSH in the erythrocytes of preterm neonates as opposed to adults was observed earlier (32, 33). More efficient recycling could very well decrease the need for de novo synthesis and perfectly fits our finding, ie, a relatively low FSRGSH in preterm infants compared with that in adults.

Blood glucose concentrations and the incidence of sepsis were not different between groups. This is relevant, seeing that both hyperglycemia and sepsis are known to produce oxidative stress (34, 35).

The importance of GSH in maintaining health and preventing oxidative stress has been widely studied. Chessex et al (36) studied the individual effects of hyperoxia and nutrient restriction on liver and lung GSH availability in preterm guinea pigs. They concluded that total parenteral nutrition not only increased both liver and lung GSH concentrations but also protected against hyperoxic lung injury and associated mortality. In agreement, Welty and Smith (37) and Yeung (38) recommended the administration of antioxidants or their precursors as soon as possible after birth to prevent oxidative stress–related diseases, such as bronchopulmonary dysplasia.

GSH kinetics were measured by using a new technique, which transforms all GSH to its dimeric form (GSSG). We did not, therefore, discriminate between GSH and GSSG. However, because the FSR is a relative measure, it is not influenced by a difference in redox state. We measured GSH kinetics in erythrocytes, which are readily accessible as opposed to other tissues. Moreover, erythrocytes can protect other tissues, such as the lung, by providing intracellular antioxidants (39) or by directly taking up reactive oxygen species (40). In a very recent study, Giustarini et al (41) provided strong evidence of a role for erythrocytes as GSH donor for other tissues. They showed active GSH export toward the plasma, which indicated that, besides the liver, erythrocytes might significantly contribute to the extracellular GSH pool. These studies, however, failed to elucidate the mechanism by which GSH is exported, because it is assumed that GSH is unable to cross the cellular membrane intact.

We measured AOPP and dityrosine as markers of oxidative stress. Tyrosine is oxidized to dityrosine in response to oxidative stress and can be considered a good endogenous marker. Experiments that expose protein to oxygen-free radicals have demonstrated the formation of dityrosine. Dityrosine has been recognized as an oxidative stress product of the pathological response to disease or other environmental stress (17, 42). AOPP concentrations were higher than those found in older, more stable preterm infants and healthy adults (4, 15).

Cysteine is generally assumed to be the rate-limiting substrate for GSH synthesis. It is also considered to be an essential AA in preterm neonates on the grounds of high cystathionine concentrations (43) and because low cystathionase activity impedes the conversion of methionine into cysteine (44). Although evidence is mounting that preterm infants are able to synthesize cysteine (45, 46), demands may still exceed the capacity to synthesize. Indeed, we previously showed that plasma cyst(e)ine concentrations were below reference values, both in a group not receiving any AAs and in a group receiving AAs, including cysteine (14). The AA solution we used provides methionine and cysteine, delivered as cysteine-HCl. Premixed AA solutions can only contain modest amounts of cysteine-HCl because of the instability of cysteine at a higher pH.

We demonstrated that AA administration to preterm infants directly postnatally is a safe and efficient way to increase GSH synthesis rates. Our data suggest that this does not increase GSH consumption, because intracellular GSH breakdown seems to decline. Concentrations of oxidative stress markers nevertheless remained high. Plasma cystine concentrations rose on AA administration, but still remained low. Worthy of further research is the question of whether higher doses of AAs, or additional cysteine in particular, further increase the rate of GSH synthesis.


   ACKNOWLEDGMENTS
 
We thank Ko Hagoort for editorial critique, Chris van den Akker for assistance in performing the study, and Wistaria Rawlins for technical assistance in analyzing the AAs.

The authors' responsibilities were as follows—FWJtB, GB, and JBvG: participated in the design and implementation of the study; FWJtB: recruited the patients; FWJtB and KdG: prepared the blood samples; HS and ML: provided technical supervision of blood sample preparation; AV: prepared the stable-isotope solutions; and FWJtB: wrote the manuscript draft. All authors reviewed the manuscript and approved the final version. None of the authors had a personal or financial conflict of interest.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 SUBJECTS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Buhimschi IA, Buhimschi CS, Pupkin M, Weiner CP. Beneficial impact of term labor: nonenzymatic antioxidant reserve in the human fetus. Am J Obstet Gynecol 2003;189:181–8.[Medline]
  2. Frank L, Groseclose EE. Preparation for birth into an O2-rich environment: the antioxidant enzymes in the developing rabbit lung. Pediatr Res 1984;18:240–4.[Medline]
  3. Ahola T, Levonen AL, Fellman V, Lapatto R. Thiol metabolism in preterm infants during the first week of life. Scand J Clin Lab Invest 2004;64:649–58.[Medline]
  4. Buonocore G, Perrone S, Longini M, et al. Oxidative stress in preterm neonates at birth and on the seventh day of life. Pediatr Res 2002;52:46–9.[Medline]
  5. Saugstad OD. Oxygen and retinopathy of prematurity. J Perinatol 2006;26(suppl 1):S46–50; discussion S63–4.
  6. Ahola T, Fellman V, Kjellmer I, Raivio KO, Lapatto R. Plasma 8-isoprostane is increased in preterm infants who develop bronchopulmonary dysplasia or periventricular leukomalacia. Pediatr Res 2004;56:88–93.[Medline]
  7. Buonocore G, Perrone S, Bracci R. Free radicals and brain damage in the newborn. Biol Neonate 2001;79:180–6.[Medline]
  8. Ogihara T, Hirano K, Morinobu T, et al. Raised concentrations of aldehyde lipid peroxidation products in premature infants with chronic lung disease. Arch Dis Child Fetal Neonatal Ed 1999;80:F21–5.[Abstract/Free Full Text]
  9. Lestas AN, Rodeck CH. Normal glutathione content and some related enzyme activities in the fetal erythrocytes. Br J Haematol 1984;57:695–702.[Medline]
  10. Levonen AL, Lapatto R, Saksela M, Raivio KO. Expression of gamma-glutamylcysteine synthetase during development. Pediatr Res 2000;47:266–70.[Medline]
  11. Jain A, Mehta T, Auld PA, et al. Glutathione metabolism in newborns: evidence for glutathione deficiency in plasma, bronchoalveolar lavage fluid, and lymphocytes in prematures. Pediatr Pulmonol 1995;20:160–6.[Medline]
  12. Van Goudoever JB, Colen T, Wattimena JL, Huijmans JG, Carnielli VP, Sauer PJ. Immediate commencement of amino acid supplementation in preterm infants: effect on serum amino acid concentrations and protein kinetics on the first day of life. J Pediatr 1995;127:458–65.[Medline]
  13. Ibrahim HM, Jeroudi MA, Baier RJ, Dhanireddy R, Krouskop RW. Aggressive early total parental nutrition in low-birth-weight infants. J Perinatol 2004;24:482–6.[Medline]
  14. te Braake FW, van den Akker CH, Wattimena DJ, Huijmans JG, van Goudoever JB. Amino acid administration to premature infants directly after birth. J Pediatr 2005;147:457–61.[Medline]
  15. Witko-Sarsat V, Friedlander M, Capeillere-Blandin C, et al. Advanced oxidation protein products as a novel marker of oxidative stress in uremia. Kidney Int 1996;49:1304–13.[Medline]
  16. Abdelrahim M, Morris E, Carver J, Facchina S, White A, Verma A. Liquid chromatographic assay of dityrosine in human cerebrospinal fluid. J Chromatogr B Biomed Sci Appl 1997;696:175–82.[Medline]
  17. Giulivi C, Traaseth NJ, Davies KJ. Tyrosine oxidation products: analysis and biological relevance. Amino Acids 2003;25:227–32.[Medline]
  18. The CRIB (clinical risk index for babies) score: a tool for assessing initial neonatal risk and comparing performance of neonatal intensive care units. The International Neonatal Network. Lancet 1993;342:193–8.[Medline]
  19. Schierbeek H, Te Braake F, Godin JP, Fay LB, van Goudoever JB. Novel method for measurement of glutathione kinetics in neonates using liquid chromatography coupled to isotope ratio mass spectrometry. Rapid Commun Mass Spectrom 2007;21:2805–12.[Medline]
  20. Schaart MW, Schierbeek H, de Bruijn AC, Tibboel D, van Goudoever JB, Renes IB. A novel method to determine small intestinal barrier function in human neonates in vivo. Gut 2006;55:1366–7.[Free Full Text]
  21. Lyons J, Rauh-Pfeiffer A, Yu YM, et al. Blood glutathione synthesis rates in healthy adults receiving a sulfur amino acid-free diet. Proc Natl Acad Sci U S A 2000;97:5071–6.[Abstract/Free Full Text]
  22. Darmaun D, Smith SD, Sweeten S, Sager BK, Welch S, Mauras N. Evidence for accelerated rates of glutathione utilization and glutathione depletion in adolescents with poorly controlled type 1 diabetes. Diabetes 2005;54:190–6.[Medline]
  23. Rossi R, Milzani A, Dalle-Donne I, et al. Blood glutathione disulfide: in vivo factor or in vitro artifact? Clin Chem 2002;48:742–53.[Abstract/Free Full Text]
  24. Shew S, Jaksic T, Jahoor F, Heird W. Effects of cysteine on endogenous synthesis of taurine and glutathione by premature neonates receiving parenteral nutrition. Pediatr Res 2000;47:296A(abstr).
  25. Wu PY, Edwards N, Storm MC. Plasma amino acid pattern in normal term breast-fed infants. J Pediatr 1986;109:347–9.[Medline]
  26. Buonocore G, Perrone S, Longini M, Terzuoli L, Bracci R. Total hydroperoxide and advanced oxidation protein products in preterm hypoxic babies. Pediatr Res 2000;47:221–4.[Medline]
  27. Badaloo A, Reid M, Forrester T, Heird WC, Jahoor F. Cysteine supplementation improves the erythrocyte glutathione synthesis rate in children with severe edematous malnutrition. Am J Clin Nutr 2002;76:646–52.[Abstract/Free Full Text]
  28. Jackson AA, Gibson NR, Lu Y, Jahoor F. Synthesis of erythrocyte glutathione in healthy adults consuming the safe amount of dietary protein. Am J Clin Nutr 2004;80:101–7.[Abstract/Free Full Text]
  29. Darmaun D, Froguel P, Rongier M, Robert JJ. Amino acid exchange between plasma and erythrocytes in vivo in humans. J Appl Physiol 1989;67:2383–8.[Abstract/Free Full Text]
  30. van den Akker CH, te Braake FW, Schierbeek H, et al. Albumin synthesis in premature neonates is stimulated by parenterally administered amino acids during the first days of life. Am J Clin Nutr 2007;86:1003–8.[Abstract/Free Full Text]
  31. Ozaki M, Aoki S, Masuda Y. K(+)-linked release of oxidized glutathione induced by tert-butyl hydroperoxide in perfused rat liver is independent of lipid peroxidation and cell death. Jpn J Pharmacol 1994;65:183–91.[Medline]
  32. Clahsen PC, Moison RM, Holtzer CA, Berger HM. Recycling of glutathione during oxidative stress in erythrocytes of the newborn. Pediatr Res 1992;32:399–402.[Medline]
  33. Frosali S, Di Simplicio P, Perrone S, et al. Glutathione recycling and antioxidant enzyme activities in erythrocytes of term and preterm newborns at birth. Biol Neonate 2004;85:188–94.[Medline]
  34. Esposito K, Nappo F, Marfella R, et al. Inflammatory cytokine concentrations are acutely increased by hyperglycemia in humans: role of oxidative stress. Circulation 2002;106:2067–72.[Medline]
  35. Lyons J, Rauh-Pfeiffer A, Ming-Yu Y, et al. Cysteine metabolism and whole blood glutathione synthesis in septic pediatric patients. Crit Care Med 2001;29:870–7.[Medline]
  36. Chessex P, Lavoie JC, Laborie S, Vallee J. Survival of guinea pig pups in hyperoxia is improved by enhanced nutritional substrate availability for glutathione production. Pediatr Res 1999;46:305–10.[Medline]
  37. Welty SE, Smith CV. Rationale for antioxidant therapy in premature infants to prevent bronchopulmonary dysplasia. Nutr Rev 2001;59:10–7.[Medline]
  38. Yeung MY. Influence of early postnatal nutritional management on oxidative stress and antioxidant defence in extreme prematurity. Acta Paediatr 2006;95:153–63.[Medline]
  39. Moison RM, van Hoof EJ, Clahsen PC, van Zoeren-Grobben D, Berger HM. Influence of plasma preparations and donor red blood cells on the antioxidant capacity of blood from newborn babies: an in vitro study. Acta Paediatr 1996;85:220–4.[Medline]
  40. Richards RS, Roberts TK, Dunstan RH, McGregor NR, Butt HL. Erythrocyte antioxidant systems protect cultured endothelial cells against oxidant damage. Biochem Mol Biol Int 1998;46:857–65.[Medline]
  41. Giustarini D, Milzani A, Dalle-Donne I, Rossi R. Red blood cells as a physiological source of glutathione for extracellular fluids. Blood Cells Mol Dis 2008 Mar-Apr;40(2):174–9.[Medline]
  42. DiMarco T, Giulivi C. Current analytical methods for the detection of dityrosine, a biomarker of oxidative stress, in biological samples. Mass Spectrom Rev 2007;26:108–20.[Medline]
  43. Vina J, Vento M, Garcia-Sala F, et al. L-Cysteine and glutathione metabolism are impaired in premature infants due to cystathionase deficiency. Am J Clin Nutr 1995;61:1067–9.[Abstract/Free Full Text]
  44. Soghier L, Brion L. Cysteine, cystine or N-acetylcysteine supplementation in parenterally fed neonates. Cochrane Database Syst Rev 2006:CD004869.
  45. Riedijk MA, van Beek RH, Voortman G, de Bie HM, Dassel AC, van Goudoever JB. Cysteine: a conditionally essential amino acid in low-birth-weight preterm infants? Am J Clin Nutr 2007;86:1120–5.[Abstract/Free Full Text]
  46. Shew SB, Keshen TH, Jahoor F, Jaksic T. Assessment of cysteine synthesis in very low-birth weight neonates using a [13C6]glucose tracer. J Pediatr Surg 2005;40:52–6.[Medline]
Received for publication January 7, 2008. Accepted for publication April 15, 2008.





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