Survival of guinea pig pups in hyperoxia is improved by enhanced nutritional substrate availability for glutathione production

Parenteral nutrition and oxidant stress in the newborn: A narrative review

There is strong evidence that oxidant molecules from various sources contaminate solutions of parenteral nutrition following interactions between the mixture of nutrients and some of the environmental conditions encountered in clinical practice. The continuous infusion of these organic and nonorganic peroxides provided us with a unique opportunity to study in cells, in vascular and animal models, the mechanisms involved in the deleterious reactions of oxidation in premature infants. Potential clinical impacts of peroxides infused with TPN include: a redox imbalance, vasoactive responses, thrombosis of intravenous catheters, TPN-related hepatobiliary complications, bronchopulmonary dysplasia and mortality. This is a narrative review of published data.

Impact of glutathione supplementation of parenteral nutrition on hepatic methionine adenosyltransferase activity

Background

The oxidation of the methionine adenosyltransferase (MAT) by the combined impact of peroxides contaminating parenteral nutrition (PN) and oxidized redox potential of glutathione is suspected to explain its inhibition observed in animals. A modification of MAT activity is suspected to be at origin of the PN-associated liver disease as observed in newborns. We hypothesized that the correction of redox potential of glutathione by adding glutathione in PN protects the MAT activity.

Aim

To investigate whether the addition of glutathione to PN can reverse the inhibition of MAT observed in animal on PN.

Methods

Three days old guinea pigs received through a jugular vein catheter 2 series of solutions. First with methionine supplement, (1) Sham (no infusion); (2) PN: amino acids, dextrose, lipids and vitamins; (3) PN-GSSG: PN+10 μM GSSG. Second without methionine, (4) D: dextrose; (5) D+180 μM ascorbylperoxide; (6) D+350 μM H₂O₂. Four days later, liver was sampled for determination of redox potential of glutathione and MAT activity in the presence or absence of 1 mM DTT. Data were compared by ANOVA, p<0.05.

Results

MAT activity was 45±4% lower in animal infused with PN and 23±7% with peroxides generated in PN. The inhibition by peroxides was associated with oxidized redox potential and was reversible by DTT. Correction of redox potential (PN+GSSG) or DTT was without effect on the inhibition of MAT by PN. The slope of the linear relation between MAT activity and redox potential was two fold lower in animal infused with PN than in others groups.

Conclusion

The present study suggests that prevention of peroxide generation in PN and/or correction of the redox potential by adding glutathione in PN are not sufficient, at least in newborn guinea pigs, to restore normal MAT activity.

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Methionine adenosyltransferase (MAT) is essential for healthy liver.

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Parenteral nutrition (PN) inhibits hepatic MAT.

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The inhibition is caused by intrinsic peroxides and by unknown component of PN.

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Adding glutathione in PN is not sufficient to prevent PN-associated liver diseases.

Neonatal exposure to oxidants induces later in life a metabolic response associated to a phenotype of energy deficiency in an animal model of total parenteral nutrition

Failure to protect total parenteral nutrition (TPN) from ambient light exacerbates the generation of peroxides, which affects blood glucose and plasma triacylglyceride (TG) in neonates. Based on the concept that the origin of adult diseases can be traced back to perinatal life, it was hypothesized that neonatal exposure to peroxides may affect energy availability later in life. Three-day-old guinea pigs, fitted with a jugular catheter, were fed regular chow (sham) +/- i.v. 350 microM H2O2 (sham + H2O2) or nourished with light-protected TPN [TPN(-)L, 209 +/- 9 microM peroxides] or light-exposed TPN [TPN(+)L, 365 +/- 15 microM peroxides]. After 4 d, infusions were stopped and animals fed chow. Spontaneous ambulatory movements, fasting blood glucose, glucose tolerance, TG, hepatic activities of glucokinase, phosphofructokinase (key enzymes of glycolysis), and acetyl-CoA carboxylase (key enzymes of lipogenesis) were determined at 12-14 wk and compared by ANOVA (p < 0.05). Relative to sham, the animals from sham + H2O2, TPN(-)L and TPN(+)L groups had lower plasma TG explained for 36% by low phosphofructokinase activity; they had lower glucose tolerance, lower body weight, and lower physical activity. In conclusion, neonatal exposure to oxidant molecules such as peroxides has important consequences later in life on lipid and glucose metabolism leading to a phenotype of energy deficiency.

Long-term impact of an antioxidant-deficient neonatal diet on lipid and glucose metabolism

Newborn infants are at risk for oxidative stress leading to metabolic syndrome features. Oxidative stress can be induced by oxidant load such as oxygen supplementation, peroxides from intravenous nutrition, or low antioxidant defenses. We hypothesize that a modulation of antioxidant defenses during the neonatal period, without external oxidant challenge, will have a long-term influence on energy metabolism. Guinea pigs were fed between their third and their seventh day of life a regular chow leading to "mature" antioxidant defenses or a deficient chow leading to lower antioxidant defenses. Between weeks 1 and 14, the animals were fed regular chow. The hepatic oxidized redox status of glutathione associated with the deficient diet (-221 +/- 2 vs -228 +/- 1 mV, p < 0.01) was maintained until 14 weeks. At 13-14 weeks, animals fed the deficient diet presented lower plasma TG (479 +/- 57 vs 853 +/- 32 microM, p < 0.01), lower blood glucose (5.8 +/- 0.3 vs 6.9 +/- 0.3 mM, p < 0.05), and better tolerance to glucose (p < 0.05). Blood glucose correlated negatively with the redox status (r2 = 0.47, p < 0.01). Low antioxidant defenses during the neonatal period induce a better energy substrate profile associated with an oxidized redox status later in life. These findings suggest being aware of negative consequences when adopting "aggressive" antioxidant therapies in newborn infants.

Influence of lung oxidant and antioxidant status on alveolarization: role of light-exposed total parenteral nutrition

Parenteral multivitamins (MVP) are linked to the generation of peroxides, which cause oxidant injury in lungs associated with alveolar remodelling linked to lung disease of prematurity. This study was to investigate the relationship between alveolar development and lung oxidant-antioxidant status as modulated by the mode of administration of multivitamins with total parenteral nutrition (TPN). Four groups of guinea pig pups received parenteral nutrition differing by 1) mode of MVP admixture: with amino acid solution (AA-MVP) or lipid emulsion (LIP-MVP); 2) light exposure: TPN exposed (LE) or shielded from light (LP). After 2 or 4 days of TPN, vitamins C and E, 8-isoprostaneF2alpha and alveolarization index were determined in lungs and GSSG/GSH in lungs and blood. Exposure to light and the mode of MVP admixture did not influence vitamin E and isoprostane levels. Blood glutathione redox potential was more oxidized in LE and LIP-MVP groups after 4-day infusions, whereas lung redox potential was more reduced in LE groups. LP and LIP-MVP had a beneficial effect, with higher number of alveoli. Globally, results indicate that in this model, alveolarization and modifications in lung redox potential are two independent events induced by light exposed TPN.

Glutathione synthesis rates after amino acid administration directly after birth in preterm infants

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-(13)C]glycine was administered to determine glutathione fractional synthesis rates (FSR(GSH)) and absolute synthesis rates (ASR(GSH)) 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 FSR(GSH) 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). ASR(GSH) 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 ASR(GSH) in preterm infants. Our data are consistent, however, with higher glutathione concentrations rather than a higher FSR(GSH). Greater availability of glutathione, nevertheless, did not decrease markers of oxidative stress.

Is there a causal relationship between the receipt of blood transfusions and the development of chronic lung disease of prematurity?

The number and total volume of blood transfusions received by premature babies is, after gestational age and birth weight a good predictor of the likelihood of developing chronic lung disease of prematurity (CLD) and retinopathy of prematurity (ROP). Oxidative damage, inflammation and pulmonary infections are also strongly associated with the development of CLD. It is currently not clear whether there is a causal relationship between the receipt of blood transfusions and oxidative damage, infection, inflammation and CLD in these babies. Strong arguments may be made both for and against a causal relationship. The babies who receive blood transfusions are usually smaller than those who do not, and are ventilated, often with high oxygen levels, for a longer period of time. The longer the baby is on a ventilator the more likely it is to develop pulmonary infection and inflammation. All these factors will promote free radical production and oxidative damage irrespective of the receipt of blood transfusion. This would argue against a causal relationship. On the other hand, an argument may be presented which is based on iron promoted free radical generation, infection and fibrosis consequent to the breakdown of haeme released from transfused erythrocytes. Haeme is broken down by haeme oxygenase (HO) to iron, CO and bilirubin. Under normal circumstances the products of HO activity are beneficial to the organism, but when HO activity is excessive, the products are potentially damaging. Free iron, (in the Fe2+ form) if not sequestered with protein or urate, will generate highly toxic free radicals via the Fenton and Heber-Wiess reactions, predispose the tissue to infection and promote fibrosis. The iron chelating ability of the premature baby appears to be limited so that it would be difficult to deal with any increase in free iron production. Free iron will in turn induce HO activity leading to a potentially serious positive feedback process. The lung is particularly sensitive to iron induced HO activity. In addition, HO activity may be enhanced by other events occurring in the premature lung such as the production of proinflammatory cytokines and the reduced level of glutathione. Thus, the possibility of a causal relationship clearly exists and needs to be examined. This can be attempted by measuring the products of HO activity in relation to the receipt of blood transfusions.

Association between hydrogen peroxide-dependent byproducts of ascorbic acid and increased hepatic acetyl-CoA carboxylase activity

BACKGROUND

Parenteral multivitamin preparation (MVP) induces fatty liver in neonatal guinea pig pups; this is prevented by photoprotection. Photo-excited riboflavin present in MVP generates H(2)O(2) and molecules with masses of 136 and 208. We hypothesized that H(2)O(2) initiates the peroxidation of ascorbic acid (AA), producing biologically active byproducts affecting hepatic lipid metabolism.

METHODS

Mass spectrometry (MS) documented the participation of H(2)O(2) and photo-excited riboflavin (Ribo) in the formation of AA byproducts. Sixteen 3-day-old guinea pig pups received an intravenous solution (50 g/L dextrose + 4.5 g/L NaCl + 1 kIU/L heparin) at 240 mL x kg(-1) x day(-1), enriched with control or test mixtures, for 4 days. The control mixture was photo-protected AA + Ribo (without byproducts or H(2)O(2)), and the test mixture was AA + Ribo treated to generate AA byproducts without H(2)O(2). Hepatic acetyl-CoA carboxylase (ACC) activity was determined after 4 days. Fourth-day urine samples were analyzed by MS. Data were treated by ANOVA (alpha = 0.05).

RESULTS

H(2)O(2) did not influence the classic degradation of AA, as the generation of 2,3-diketogulonic acid was not affected. In contrast, the formation of molecules with masses of 136 and 208 was H(2)O(2) and time dependent. ACC activity was higher (P <0.01) in animals receiving high concentration of these molecules; its hepatic activation correlated (P <0.01) with the urinary concentration of molecule-208.

CONCLUSIONS

H(2)O(2) at concentrations found in the clinical setting of total parenteral nutrition induce the transformation of dehydroascorbic acid into compounds that have the potential to affect lipid metabolism. These molecules have peroxide and aldehyde functions.

Pulmonary antioxidant concentrations and oxidative damage in ventilated premature babies

OBJECTIVE

To determine the relation between lipid peroxidation and the antioxidants ascorbate, urate, and glutathione in epithelial lining fluid in ventilated premature babies, and to relate the biochemical findings to clinical outcome.

DESIGN

A cohort study conducted between January 1999 and June 2001.

SETTING

A NHS neonatal intensive care unit.

PATIENTS

An opportunity sample of 43 ventilated babies of less than 32 weeks gestation.

MAIN OUTCOME MEASURES

The duration of supplementary oxygen according to the definition of bronchopulmonary dysplasia (BPD; oxygen dependency at 36 weeks gestational age).

METHODS

Epithelial lining fluid was sampled by bronchoalveolar lavage. Ascorbate, urate, glutathione, and malondialdehyde (a marker of lipid peroxidation) were measured.

RESULTS

Babies who developed BPD had significantly lower initial glutathione concentrations (mean (SEM) 1.89 (0.62) v 10.76 (2.79) microM; p = 0.043) and higher malondialdehyde concentrations (mean (SEM) 1.3 (0.31) v 0.345 (0.09) microM; p < 0.05) in the epithelial lining fluid than those who were not oxygen dependent. These variables were poor predictors of the development of BPD. Gestational age, endotracheal infection, and septicaemia had good predictive power. The level of oxidative damage was associated with the presence of endotracheal infection/septicaemia rather than inspired oxygen concentration.

CONCLUSIONS

Endotracheal infection, septicaemia, and gestational age, rather than antioxidant concentrations, are the most powerful predictors of the development of BPD.

Photoprotection prevents TPN-induced lung procollagen mRNA in newborn guinea pigs

BACKGROUND

Photo-exposed intravenous multivitamin solutions (MVP) carry a peroxide load. Peroxidation induces gene expression of procollagen. We hypothesized that photo exposure of the MVP solution might promote pulmonary fibrosis. The aim of the study was to assess the potential for MVP to increase procollagen mRNA.

METHODS

Three day old guinea pigs were assigned to the following intravenous regimens, either: Control (C): 5% dextrose + 0.45% NaCl; C + 200 or 500 microM H(2)O(2); C + 500 microM H(2)O(2) + 10 microM GSSG; [C + 1% MVP +/- [amino acids + lipids]] +/- photoprotected. After 4 d, levels of pulmonary alpha1(I) procollagen mRNA and glutathione were determined. Results were compared by ANOVA.

RESULTS

Photoprotection of MVP or TPN prevents light induction of procollagen mRNA. The effect of MVP + light was associated with a peroxide load coupled with a low glutathione level. This was also observed with the 500 microM H(2)O(2) group. The addition of GSSG prevented the increase of procollagen mRNA caused by H(2)O(2).

CONCLUSION

An oxidant stress caused by the infusion of peroxides in an organism with a weak antiperoxide capacity induces the transcription of the gene encoding for procollagen alpha1(I). The results confirm the antiperoxide activity of lung glutathione. Parenteral nutrition could be a clinical condition favoring the initiation of lung fibrosis, especially in premature newborn infants who have low glutathione levels.

Extracellular glutathione inhibits oxygen-induced permeability changes in alveolar epithelial monolayers

Exposure to high fractional inspired oxygen for 24 h increases permeability of the alveolar epithelium, contributing to the clinical manifestations of oxygen toxicity. Utilizing a model of the alveolar epithelium in which isolated rat type II cells form polarized monolayers on polycarbonate filters [transepithelial resistance (R(t)) > 1 k Omega x cm(2) by day 4], we evaluated the ability of reduced glutathione (GSH) to ameliorate these changes. On day 4, apical fluid was replaced with culture medium containing 1) no additives, 2) GSH (500 microM), or 3) GSH (500 microM) + glutathione reductase (0.5 U/ml) + nicotinamide adenine dinucleotide phosphate (250 microM). Monolayers were exposed (for 24 h) to room air (control) or 95% O(2), each containing 5% CO(2). After 24 h of hyperoxia, R(t) for condition 1 decreased by 45% compared with control (P < 0.001). In conditions 2 and 3, R(t) did not decrease significantly (P = not significant). Hyperoxia-induced decreases in active ion transport were observed for conditions 1 and 2 (P < 0.05), but not for condition 3 (P = not significant). These findings indicate that extracellular GSH may protect the alveolar epithelium against hyperoxia-induced injury. Addition of glutathione reductase and nicotinamide adenine dinucleotide phosphate may further augment these protective effects of GSH.

Apoptosis in neonatal murine lung exposed to hyperoxia

Exposure to high concentrations of oxygen in the neonatal period may impair lung growth and is a major contributing factor to the development of bronchopulmonary dysplasia. Cell death from hyperoxic injury may occur through either an apoptotic or nonapoptotic pathway, and we were interested in determining the type of cell death that occurs in the lung of neonatal mice exposed to hyperoxia. We found increased levels of Bax messenger RNA, a gene associated with apoptosis, in the lungs of neonatal mice born and raised in 92% hyperoxia. We next determined the extent of apoptosis taking place in the lungs of neonatal mice exposed to hyperoxia using terminal deoxyribonucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end labeling in 3.5-, 4.5-, and 5.5-d-old neonatal lung. The number of apoptotic cells in peripheral lung was significantly higher in the 3.5-, 4.5-, and 5.5-d-old mice treated with oxygen compared with that in the room-air control mice. Further, the number of apoptotic cells in the lung increased with longer exposure duration. In murine lung bronchus cells exposed to hyperoxia, growth arrest occurred after 48 h of oxygen exposure. Using annexin V binding, necrotic cell death was found to be the major form of cell death in these cells after 72 h of hyperoxic exposure. We conclude that 92% hyperoxia causes significant lung injury in neonatal mice exposed to hyperoxia, and that the number of apoptotic cells in the lung increases the longer the duration of exposure. The increase in apoptosis from hyperoxic exposure during a critical period of lung development may be an important factor in the impaired lung growth and remodeling that occur in animals exposed to high oxygen concentrations. Finally, it appears that hyperoxic injured cells in neonatal lung undergo both apoptotic and nonapoptotic cell death.

Parenteral multivitamin supplementation induces both oxidant and antioxidant responses in the liver of newborn guinea pigs

BACKGROUND

The multivitamin solution is a major component of photo-induced generation of peroxides in parenteral nutrition. The aim of this study was to determine whether the parenteral multivitamin preparation induces in the liver a peroxide-induced oxidant challenge or an antioxidant protection associated with the antiradical components of the solution.

METHODS

Newborn guinea pigs were infused with dextrose supplemented with peroxides (250 micromol/L H2O2 or 350 micromol/L tert-butylhydroperoxide) or with a multivitamin preparation (MVP, 1% vol/vol). After 4 days, total glutathione and a free radical-sensitive eicosanoid marker (prostaglandin I2 [PGI2]/total prostaglandins) were measured in livers.

RESULTS

There was a significant decrease in the PGI2/total prostaglandin ratio (mean +/- SEM) [dextrose: 0.068 +/- 0.007 vs. (dextrose + H2O2: 0.048 +/- 0.001, dextrose + TBH: 0.043 +/- 0.001)] and glutathione concentrations decreased [dextrose: 55 +/- 7 vs. (dextrose + H2O2: 37 +/- 7, dextrose + TBH: 18 +/- 7 nmol/mg protein)] after infusion of peroxides. Despite the peroxide load in the multivitamin solution, it did not alter the measured variables as prostanoid ratio remained at control concentrations (dextrose: 0.066 +/- 0.008 vs. dextrose + MVP: 0.065 +/- 0.006), as did glutathione levels (dextrose: 52 +/- 6 vs. dextrose + MVP: 45 +/- 7 nmol/mg prot).

CONCLUSION

In the liver of guinea pig pups, infused peroxides cause oxidation of membrane-derived prostanoids. The decrease in glutathione in response to administration of peroxides suggests consumption rather than a response to a free radical attack. Despite the oxidant load associated with peroxides generated in MVP, the multivitamin preparation protected membranes as the prostanoid ratio, and glutathione levels remained at control levels.

Peroxide-like oxidant response in lungs of newborn guinea pigs following the parenteral infusion of a multivitamin preparation

The multivitamin solution is a major component responsible for the photo-induced generation of peroxides in parenteral nutrition. The lung is a target of oxidant injury; however, the specific role of infused peroxides is unknown. The aim of this study was to determine if parenteral multivitamins induce in the lung an oxidant challenge similar to that of peroxides. Newborn guinea pigs were infused with dextrose plus relevant concentrations of H(2)O(2) (0,250,500 microM) or multivitamins (0,1%), as well as parenteral nutrition supplemented with multivitamins (0,1%). After 4 days, total glutathione, glutathione-related enzymes, and oxidant-sensitive eicosanoids were measured in the lungs. Peroxides as well as multivitamins led to a significant decrease in glutathione and the activity of glutathione synthase, indicating that infused peroxides were not entirely transformed into free radicals, which would have stimulated glutathione synthesis. The multivitamin solution induced a response in oxidant-sensitive eicosanoids similar to the response to peroxides, suggesting an oxidant stress that was not alleviated by the antiradical properties of its components. The effects on prostaglandins occurred independently from the stimulation in glutathione levels induced by parenteral nutrition. The multivitamin solution carries an oxidant load and causes effects similar to those of peroxides in the lungs of newborn guinea pigs.

Continuous enteral nutrition attenuates pulmonary edema in rats exposed to 100% oxygen

Adult rats exposed to hyperoxia develop anorexia, weight loss, and a lung injury characterized by pulmonary edema and decreased lung liquid clearance. We hypothesized that maintenance of nutrition during hyperoxia could attenuate hyperoxia-induced pulmonary edema. To test this hypothesis, we enterally fed adult male Sprague-Dawley rats via gastrostomy tubes and exposed them to oxygen (inspired O(2) fraction >0.95) for 64 h. In contrast to controls, enterally fed hyperoxic animals did not lose weight and had smaller pleural effusions and wet-to-dry weight ratios (a measure of lung edema) that were not different from room air controls. Enterally fed rats exposed to hyperoxia had increased levels of mRNA for the Na(+)-K(+)-ATPase alpha(1)- and beta(1)-subunits and glutathione peroxidase. These findings suggest that maintenance of nutrition during an oxidative lung injury reduces lung edema, perhaps by allowing for continued expression and function of protective proteins such as the Na(+)-K(+)-ATPase.

Current total parenteral nutrition solutions for the neonate are inadequate

The amino acid requirements of the parenterally fed neonate are poorly defined. Newborn infants are at risk for amino acid deficiency and toxicity, due to lack of small intestinal metabolism and metabolic immaturity. We discuss recent evidence that identifies inadequacies of commercial amino acid solutions with respect to the balance and quantity of aromatic amino acids, and sulphur amino acids. We present data demonstrating that impaired small intestinal metabolism (or lack of first pass metabolism) alters the whole body requirement for methionine, threonine, and arginine, and discuss the potential adverse effects of excess or inadequate parenteral amino acid intake.