Sophie Laborie

Paradoxical Role of Ascorbic Acid and Riboflavin in Solutions of Total Parenteral Nutrition: Implication in Photoinduced Peroxide Generation

In the presence of light, a multivitamin preparation is the main source of peroxides in solutions of total parenteral nutrition (TPN). This preparation contains two photosensitive products, 5′-phosphate flavin mononucleotide(FMN) and polysorbates (PS), as well as electron donors such as ascorbate(AH). We hypothesized that the admixture of FMN or PS with electron donors generates peroxides in TPN and alters the quality of nutrients. Using xylenol orange, peroxide concentrations were measured in solutions containing AH, FMN, and/or PS in water, a dextrose solution, an amino acid preparation, and a lipid emulsion. Thiol functions were evaluated by reduction of 5,5-dithiobis(2-nitrobenzoic acid) in the amino acid preparation. After 24-h light exposure, dextrose solutions with admixtures of AH + FMN or AH + FMN + PS generated peroxides at concentrations similar to those observed in a 1% multivitamin solution, and over three times higher than those observed with FMN, PS, or AH alone. However, in the presence of amino acids, FMN alone induced a generation of peroxides comparable to that observed with FMN + AH. In the lipid emulsion, peroxides increased over 3-fold in the presence of FMN or FMN + AH. The addition of catalase suggested that lipid peroxides and H2O2 were produced, and the loss of thiol function suggested that an oxidation of amino acids occurred. When exposed to light, FMN induces reactions with amino acids, polyunsaturated fatty acids, and even AH, altering the quality of nutrients. Paradoxically, AH without FMN has a protective effect on peroxide generation in TPN.

Protecting solutions of parenteral nutrition from peroxidation

BACKGROUND Light exposure induces the generation of peroxides in solutions of total parenteral nutrition (TPN). Peroxide toxicity has been documented in cell, in tissue, and in isolated organs. To decrease the infused peroxide load and to protect the quality of the parenteral nutrients, we tested the photoprotective properties of different infusion sets. METHODS Solutions of fat-free TPN and all-in-one total nutrient admixture (TNA) were run through sets of bags (clear and covered) and tubings (clear and colored: black, orange, and yellow) offering different levels of protection against light. Peroxide levels were determined by ferrous oxidation of xylenol orange, thiol functions by the 5,5,-dithiobis(2-nitrobenzoic acid) technique, and absorbance of tubings by spectroscopy. RESULTS Protection of only the bag had little effect on peroxide generation. In fat-free TPN solutions kept in covered bags, peroxide concentrations were 1.5 to 2 times higher when run through clear compared with colored tubings. When exposed to phototherapy or in the presence of lipids, peroxides were two to three times higher with the clear compared with the black tubing; meanwhile, orange and yellow tubings offered varying levels of protection related to their light-absorbing properties. Colored tubings offered a greater protection against the disappearance of thiol functions. CONCLUSIONS Covering bags and using orange and yellow tubings may be a practical solution to reduce infused peroxide loads from about 400 to 100 microM. This is especially relevant in patients with an immature or a compromised antioxidant capacity or when phototherapy or preparations of TNA are used.

Contribution of Multivitamins, Air, and Light in the Generation of Peroxides in Adult and Neonatal Parenteral Nutrition Solutions

OBJECTIVE: To compare the concentrations of peroxides between adult and neonatal total parenteral nutrition (TPN) solutions in response to protection against inducers of peroxidation such as multivitamins and exposure to light or air. METHODS: Peroxide concentrations were measured in freshly prepared adult and neonatal solutions of fat-free TPN in four settings: with or without an air inlet, and protected or unprotected from ambient light. An oxygen washout was performed by exposing a fat-free neonatal TPN solution to a continuous flow of nitrogen. RESULTS: Globally, light was the main inducer of peroxides in adult and neonatal solutions. However, in adult solutions the concentration of peroxides remained <15 μmol/L, while in neonatal solutions the peroxide concentration was as high as 300 μmol/L in ambient light. Although the oxygen washout did prevent the generation of peroxides, avoiding air inlet was not as effective as was photoprotection in decreasing the important peroxide load in the neonatal TPN solution. CONCLUSIONS: The higher concentration of peroxides found in neonatal solutions compared with adult solutions is explained by the differences in nutrient composition between the two solutions. Contamination of parenteral solutions by air during compounding accounts for the photoinduced generation of peroxides in TPN solutions. It is more convenient to protect TPN solutions from light exposure after the admixture of the multivitamin solution than to avoid contact with oxygen.

Survival of Guinea Pig Pups in Hyperoxia Is Improved by Enhanced Nutritional Substrate Availability for Glutathione Production

The imbalance between high oxidant loads and immature antioxidant defenses is associated with long-term complications of prematurity. Glutathione is a central element among the antioxidants. Depletion of pulmonary glutathione accelerates the development of oxygen-induced lung injury in neonatal animal models. After the observation that newborn infants exposed to oxygen have low glutathione levels, a study was designed to test the hypothesis that in neonates from a species susceptible to oxygen toxicity, the lethal effect of hyperoxia is related to a low availability of substances for glutathione production rather than an impairment in synthetic activity. One-day-old guinea pigs, randomly assigned to room air or oxygen (>95%), were fed by their mothers (n = 16) or i.v. by dextrose (n = 14) or by total parenteral nutrition (TPN, n = 20). After 3 d, glutathione and activities of enzymes involved in maintaining intracellular glutathione levels were determined in lungs and liver. The lethal effect of oxygen (p < 0.05) observed in animals without TPN was not related to glutathione depletion, as oxygen induced a 33% increase in lung glutathione, positively correlated (r2 = 0.35) with enhanced synthesis. With TPN, the animals were protected against the lethal effects of hyperoxia and lung glutathione increased by 67% in oxygen. The results suggest that the glutathione demand by the lungs in the presence of an oxidant stimulus was met by the increased (p < 0.001) hepatic production supported by TPN. Under hyperoxic conditions, early nutritional support is of vital importance.

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.

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 &mgr;mol/L H2O2 or 350 &mgr;mol/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.

Multivitamin solutions for enteral supplementation : a source of peroxides

OBJECTIVE We investigated whether solutions of enteral vitamin supplementation are involved in the generation of peroxides and whether that contamination is biologically significant. METHODS Peroxide contents of oral multivitamin preparations were measured over 3 wk after the initial opening of the containers. In selected premature infants (younger than 35 wk gestation), urinary peroxides were measured after initiating oral multivitamin supplementation. RESULTS Peroxides in multivitamin solutions for enteral use are predominantly organic peroxides because they resist catalase. After the initial opening of the containers, there was a two-fold increase in total peroxides levels (P < 0.05) even in the preparation without riboflavin, a catalyst for the generation of peroxides. Initiation of oral vitamin supplementation was associated with increased (P < 0.05) urine peroxide levels. The high organic peroxide load did not correlate with its urinary excretion, mostly in the form of H(2)O(2). The excretion of H(2)O(2) corresponded to its oral intake from the multivitamin solution. CONCLUSIONS Compared with parenteral multivitamin solutions, the enteral preparations contained higher organic peroxide levels starting with the initial opening of the bottles. The increased urinary excretion of H(2)O(2) after enteral multivitamin supplementation suggested a systemic diffusion of peroxides or of components of the multivitamin preparation responsible for the generation of peroxides. This oxidant load was not quenched by the immature antioxidant defenses of premature infants.

Shielding Parenteral Nutrition Solutions From Light: A Randomized Controlled Trial.

INTRODUCTION Oxidant stress is implicated in the pathogenesis of bronchopulmonary dysplasia (BPD). Light induces peroxide generation in parenteral nutrition (PN) solutions, creating an oxidant stress. Shielding PN from light decreases its peroxide content, which has nutrition and biochemical benefits in animals and humans. This study aims at determining whether full light protection of PN decreases the rate of bronchopulmonary dysplasia and/or death in very low-birth-weight infants. METHODS Multicenter randomized controlled trial of photoprotection, using amber bags and tubing initiated during compounding of PN and maintained throughout infusion in the light-protected (LP) group. The control group (light exposed [LE]) received PN exposed to ambient light. Depending on centers, lipids were infused either separately or as all-in-one PN. RESULTS In total, 590 infants born <30 weeks gestational age were included. At randomization, LE and LP groups did not differ clinically except for maximal FiO2 before 12 hours. The rate of BPD/death was not different between groups at 28 days (77% LP vs 72% LE, P = .16) or at 36 weeks corrected age (30% LP vs 27% LE, P = .55). Multivariate analysis showed no significant effect of photoprotection on BPD and/or death. The rate of BPD/death was significantly lower (odds ratio, 0.54; 95% confidence interval, 0.32-0.93; P = .02) in infants receiving all-in-one PN vs those who received lipids separately. CONCLUSION This study did not show significant beneficial effects of photoprotection. Since the decreased rate of BPD/death found with all-in-one PN relates to a center-dependent variable, this warrants further investigation.

Shielding Parenteral Nutrition From Light Improves Survival Rate in Premature Infants: A Meta-Analysis.

Background: Intravenous nutrition preparations that are not photoprotected generate oxidants, which are deleterious for cell survival. The question remains: are these observations of clinical relevance in individuals receiving parenteral nutrition (PN), especially in those who exhibit immature antioxidant defenses such as premature infants? Objective: To review clinical trials reporting the effect of light-exposed vs light-protected PN to determine whether photoprotection reduces neonatal mortality in preterm infants. Data source: Electronic databases, abstracts in relevant journals, and references in manuscripts between 1980 and 2014. Selection criteria: Newborn, premature infants, PN, photoprotection, shielding from light, randomization, mortality, death. Methods: Consensus for inclusion reached by 2 reviewers; meta-analysis of trials and observational studies reporting mortality at 36 weeks’ gestational age or hospital discharge. Results: Four trials meeting selection criteria, which involved a total of 800 newborn premature infants, were included. Across trials, gestational age (mean ± SD) ranged from 26 ± 1 to 31 ± 2 weeks, birth weight from 775 ± 161 to 1588 ± 366 g, and mortality from 5%–32%. Mortality in the light-protected group was half of that in the light-exposed group (95% confidence interval, 0.32–0.87) and twice as high in males compared with females (&khgr;2, P = .01). Conclusion: Shielding PN from light has vital repercussions that call for action to provide photoprotected delivery systems and infusion sets in premature infants. Further studies should be extended to the increasing number of children and adults receiving long-term home PN to evaluate the effects of light protection on severe complications that impede their quality of life.

Influence of Dietary Cholesterol on Vitamin D Metabolism in Formula-fed Preterm Neonates

Objectives Supplementation of preterm formulas with cholesterol could help to mimic the fat composition of human milk. However, this could possibly influence vitamin D 25-hydroxylation because this reaction is catalyzed in part by the mitochondrial cytochrome P-450, the enzyme responsible for the 27-hydroxylation of cholesterol. The purpose of this study was to verify whether the addition of cholesterol to preterm formulas could interfere with vitamin D metabolism in preterm neonates. Methods In a prospective study, 30 preterm neonates were randomly assigned to a low (< 0.03 g/L), medium (0.15 g/L), or high (0.30 g/L) cholesterol-content preterm formula until theoretical term (i.e., 40 weeks post-conceptional age). Anthropometric data and serum hydroxy-vitamin D and 1,25 dihydroxy-vitamin D concentrations were measured at study entry and theoretical term. In a subgroup of 14 subjects, serum cholesterol and lymphocyte 3-hydroxy-3-methylglutaryl coenzyme A reductase mRNA were also assessed. Results (median [25th, 75 th centiles]): At theoretical term, there were no significant differences in serum hydroxy-vitamin D concentrations among the three groups, even after adjustment for confounding variables (65 [50, 78] nmol/L, 79 [59, 86] nmol/L, and 67 [43, 103] nmol/L, respectively, P = 0.65) or 1,25 dihydroxy-vitamin D (P = 0.88). Furthermore, there were no significant differences in 3-hydroxy-3-methylglutaryl coenzyme A reductase mRNA copy numbers. Conclusions In preterm neonates fed formulas with a cholesterol content similar to or higher than that of human milk, we did not observe deleterious effects on vitamin D metabolism. However, long-term effects of cholesterol supplementation require further studies.