Increased lipid peroxidation after lipid infusion as measured by breath pentane output

Effects of Different Combinations of Sodium Butyrate, Medium-Chain Fatty Acids and Omega-3 Polyunsaturated Fatty Acids on the Reproductive Performance of Sows and Biochemical Parameters, Oxidative Status and Intestinal Health of Their Offspring

The aim of the study was to investigate the comparative effects of different combinations of sodium butyrate (SB), medium-chain fatty acids (MCFAs), and omega-3 polyunsaturated fatty acids (n-3 PUFAs) on the reproductive performances of sows, as well as on the biochemical parameters, oxidative statuses, and intestinal health of the sucking piglets. A total of 30 sows were randomly allocated to five treatments: (1) control diet (CON); (2) CON with 1 g/kg of coated SB and 7.75 g/kg of coated MCFAs (SM); (3) CON with 1 g/kg of coated SB and 68.2 g/kg of coated n-3 PUFAs (SP); (4) CON with 7.75 g/kg of coated MCFAs and 68.2 g/kg of coated n-3 PUFAs (MP); (5) CON with 1 g/kg of coated SB, 7.75 g/kg of coated MCFAs and 68.2 g/kg of coated n-3 PUFA (SMP). The results showed that sows fed the SP, MP, and SMP diets had shorter weaning-to-estrus intervals than those fed the CON diet (p < 0.01). The piglets in the SM, SP, and MP groups showed higher increases in the plasma catalase and glutathione peroxidase activities than those of the CON group (p < 0.01). The diarrhea incidence of piglets in the SM, SP and SMP groups was lower than that of piglets in the CON group (p < 0.01). Additionally, the addition of SM, SP, MP, and SMP to the sow diets increased the contents of immunoglobulin A, immunoglobulin G, fat, and proteins in the colostrum (p < 0.01), as well as the plasma total superoxide dismutase activities (p < 0.01) in the suckling piglets, whereas it decreased the mRNA expressions of tumor necrosis factor-α, interleukin-1β, and toll-like receptor 4 in the jejunum mucosa of the piglets. The relative abundances of Prevotella, Coprococcus, and Blautia in the colonic digesta of the piglets were increased in the SM group (p < 0.05), and the relative abundances of Faecalibacterium increased in the SMP group (p < 0.05), compared with the CON group. The relative abundances of Collinsella, Blautia, and Bulleidia in the MP group were higher than those in the CON group (p < 0.05). Collectively, dietary combinations of fatty acids with different chain lengths have positive effects on the growth performances and intestinal health of suckling piglets.

Effect of medium-chain triglycerides on growth performance, nutrient digestibility, plasma metabolites and antioxidant capacity in weanling pigs

The aim of this study was to investigate the effect of medium-chain triglycerides (MCTs) on growth performance, nutrient digestibility, plasma metabolites and antioxidant capacity in weanling pigs. A total of 160 weanling (Duroc × Landrace × Yorkshire) pigs (age: 21 ± 1 d; body weight: 7.50 ± 0.28 kg) were randomly allotted to 4 treatments, receiving the following diets for 28 d: control diet [containing 3.5% soybean oil (SO)], MCT1 diet (containing 0.7% MCTs and 2.8% SO), MCT2 diet (containing 1.4% MCTs and 2.1% SO) and MCT3 diet (containing 2.1% MCTs and 1.4% SO). Dietary inclusion of MCTs improved the average daily gain and feed efficiency (FE) of pigs compared with the control during the first 2 weeks post-weaning (P < 0.05). A similar positive effect was also observed for the overall FE in MCT2 group (P < 0.05). Compared with the control, apparent total tract digestibility (ATTD) of ether extract was improved by MCT2 and MCT3 treatment from day 12–14 post-weaning (P < 0.05). In addition, MCT2 treatment also exerted a beneficial effect on the ATTD of dry matter (P < 0.05). The increased total protein concentration and decreased urea nitrogen and malondialdehyde levels of plasma were observed in both MCT2 and MCT3 groups on day 14 post-weaning (P < 0.05). In conclusion, MCTs could improve growth performance, nutrients utilization, and antioxidant ability of weanling piglets.

Fat emulsion given to very low-birthweight infants increases urinary L-FABP

BACKGROUND

In premature infants, many factors influence the function of renal tubules, such as asphyxia, respiratory disorders, use of high-concentration oxygen, hypotension, and drug treatment. When tubular ischemia and oxidative stress develop due to renal microcirculatory pathology, urinary L-type fatty acid-binding protein (L-FABP) level increases.

METHODS

Urinary L-FABP level was measured over time in very low-birthweight infants (VLBWI), and the effect of fat emulsion on L-FABP level was investigated. Thirty-one VLBWI were divided into two groups with regard to treatment with fat emulsion: the lipid group (n = 20) and the control group (n = 11). Urinary L-FABP was measured before (0-3 days of age), during (7-14 days of age), and after fat emulsion treatment (21-28 days of age) in the two groups.

RESULTS

Median urinary L-FABP level before treatment was 459 ng/mgCr (range, 22.7-5100 ng/mgCr; mean, 1067 ± 1570 ng/mgCr) and 797 ng/mgCr (range, 69-3900 ng/mgCr; mean, 1066 ± 1188 ng/mgCr) in the lipid and control groups, respectively, showing no significant difference. Median urinary L-FABP level was 624 ng/mgCr (range, 50-2050 ng/mgCr; mean ± SD, 799 ± 655 ng/mgCr) and 273 ng/mgCr (range, 31-987 ng/mgCr; mean ± SD, 359 ± 323 ng/mgCr) at 7-14 days of age, respectively, showing that the level was significantly higher in the lipid group. At 21-28 days of age, the median level was 462 ng/mgCr (range, 49-1867 ng/mgCr; mean ± SD, 557 ± 534 ng/mgCr) and 130 ng/mgCr (range, 20-993 ng/mgCr; mean ± SD, 290 ± 329 ng/mgCr), respectively, showing that L-FABP level tended to be higher in the lipid group.

CONCLUSIONS

Fat emulsion treatment induced a significant increase in urinary L-FABP level, suggesting that fat emulsion affected the proximal tubule in VLBWI.

Fish oil emulsions in the management of intestinal failure-associated liver disease

The role of parenteral lipid emulsions in the treatment of intestinal failure-associated liver disease (IFALD) is both topical and controversial. There is strong evidence supporting plant-based (soy, olive) lipid emulsions as a key cause for IFALD, especially in neonates. As a result, alternate lipid formulations, most notably fish oil emulsions (FOE) have come into widespread use despite somewhat limited clinical data on their overall benefit and potential long-term consequences. This review examines putative mechanisms of action of FOE in reversing cholestasis associated with IFALD, and critically reviews published clinical studies of the use of FOE in pediatric patients with IFALD. From these works, it appears the mechanism of action of FOE is most likely related to the reduction of serum phytosterols associated with plant-based lipid emulsions rather than a specific positive benefit of the fish oils themselves. Although the use of FOE seems to correlate with a reduction in cholestasis, their actual individual benefit is not established, and data on long-term outcomes and safety are not yet available.

Short-term use of parenteral nutrition with a lipid emulsion containing a mixture of soybean oil, olive oil, medium-chain triglycerides, and fish oil: a randomized double-blind study in preterm infants

BACKGROUND

For premature neonates needing parenteral nutrition (PN), a balanced lipid supply is crucial. The authors hypothesized that a lipid emulsion containing medium-chain triglycerides (MCTs) and soybean, olive, and fish oils would be as safe and well tolerated as a soybean emulsion while beneficially influencing the fatty acid profile.

METHODS

Double-blind, controlled study in 53 neonates (<34 weeks' gestation) randomized to receive at least 7 days of PN containing either an emulsion of MCTs and soybean, olive, and fish oils or a soybean oil emulsion. Target lipid dosage was 1.0 g fat/kg body weight [BW]/d on days 1-3, 2 g/kg BW/d on day 4, 3 g/kg BW/d on day 5, and 3.5 g/kg BW/d on days 6-14.

RESULTS

Test emulsion vs control, mean ± SD: baseline triglyceride concentrations were 0.52 ± 0.16 vs 0.54 ± 0.19 mmol/L and increased similarly in both groups to 0.69 ± 0.38 vs 0.67 ± 0.36 on day 8 of treatment (P = .781 for change). A significantly higher decrease in total and direct bilirubin vs baseline was seen in the test group compared with the control group P < .05 between groups). In plasma and red blood cell phospholipids, eicosapentaenoic acid and docosahexaenoic acid were higher, and the n-6/n-3 fatty acid ratio was lower in the test group (P < .05 vs control).

CONCLUSIONS

The lipid emulsion, based on a mixture of MCTs and soybean, olive, and fish oils, was safe and well tolerated by preterm infants while beneficially modulating the fatty acid profile.

F2-isoprostanes and total radical-trapping antioxidant potential in preterm infants receiving parenteral lipid emulsions

OBJECTIVE

We assessed the effects of three different parenteral lipid emulsions (long-chain triacylglycerols, medium-chain/long-chain triacylglycerols, olive oil) on lipid peroxidation in preterm infants. The hypothesis to be tested was that preterm infants receiving the olive oil-based lipid emulsion would undergo less peroxidation than preterm infants receiving lipid emulsions based on long- or medium-chain triacylglycerols. The secondary aim was to evaluate whether the lipid peroxidation persists beyond the cessation of parenteral nutrition (PN).

METHODS

A randomized controlled trial was designed. Thirty-six consecutive preterm infants (gestational age 28-33 wk) were enrolled in the study. Preterm infants were randomized to receive one of the three emulsions within the first 24h of life. Plasma F2-isoprostanes (F2-Ip) and total radical-trapping antioxidant potential (TRAP) were determined at baseline, on day 7 of PN, and on day 7 after stopping PN.

RESULTS

The F2-Ip and TRAP concentrations were not statistically different within and among the three groups at any time of the study. No significant interaction effect between the type of lipid emulsion administered and the repeated values of F2-Ip and TRAP was found. F2-Ip values showed a trend to decrease throughout the study in all the three groups.

CONCLUSION

No significant difference in oxidative stress of preterm infants was detected according to the type of lipid emulsion received.

4-Hydroxynonenal is Markedly Higher in Patients on a Standard Long-term Home Parenteral Nutrition

Parenteral nutrition, a commonly used procedure in patients with gastrointestinal disorders, may lead with time to liver steatosis and fibrosis, whose pathogenesis has yet to be elucidated. Oxidative stress and particularly lipid peroxidation likely contribute to the expression of such hepatobiliary complications, by means of their recognized proinflammatory and profibrogenic effects. To evaluate the adequacy against oxidative insult of a standard micronutrient supplementation in patients under long term parenteral nutrition, a comprehensive patterns of redox indices has been determined on peripheral blood samples from forty one adults in comparison to fifty eight blood donors taken as controls. A sustained oxidative stress in peripheral blood of home parenteral patients was observed. Of the two lipid peroxidation markers found to be markedly increased, namely fluorescent plasma protein adducts with malondialdehyde and 4-hydroxynonenal, respectively, only the second was statistically correlated with all the antioxidant-related changes consistently detected in the patients, namely decreased plasma alpha-tocopherol and selenium intake and higher erythrocyte oxidized glutathione. Plasma level of 4-hydroxynonenal-protein adducts appears to be a reliable and easily measurable marker of oxidative status, particularly indicated to monitor the adequacy of dietary regimen during parenteral nutrition.

Increased Oxidants and Reduced Antioxidants in Irradiated Parenteral Nutrition Solutions May Contribute to the Inflammatory Response

Background/Objectives: To measure reactive oxidant production and the decline in antioxidant potential in commercially available, irradiated parenteral nutrition (PN) solutions and the effect that these have on oxidant production in patients in the intensive care unit. Subjects and Methods: Vitamin E and malondialdehyde in irradiated and nonirradiated commercially available, PN solutions were measured. The PBN (α-phenyl-n-test-butylnitrone (PBN) spin trap was used to measure free radicals and TEMPOL (2,2,6,6-tetramethyl-4-hydroxy-piperidine-oxyl) was used to assess antioxidant capacity. The irradiated PN was administered (as per unit protocol) to 10 patients with gut failure and plasma and urinary isoprostanes and interleukin-6 (IL-6) were measured 1 hour preadministration, at the time of, and 1 and 2 hours postadministration of PN. Results: Irradiation reduced vitamin E significantly (P < .0025). Malondialdehyde products were present in both samples, but more so in irradiated samples (P < .0001), as were free radicals measured by PBN spin trapping. Irradiated samples had a higher scavenging capacity of TEMPOL free radical due to depletion of antioxidants in irradiated samples. Urinary isoprostanes increased at time 2 by 6.3 units relative to time 0 and by 5.23 units relative to time 1(Friedman ANOVA: P < .01413). Conclusions: Lipid hydroperoxides are formed in PN solutions and increase further following irradiation. This is associated with a significant reduction in vitamin E and antioxidant potential. The increase in urinary isoprostanes indicates a potentially proinflammatory effect of irradiated PN.

Propofol and in vivo oxidative stress: effects of preservative

Reactive oxygen species are associated with tissue inflammation and injury. Our laboratory has demonstrated that ethane, a stable product of lipid peroxidation, in exhaled breath can be used to measure total body oxidative stress. An ischemia-reperfusion model of lung injury in sheep has been studied in which pulmonary and bronchial lung perfusion could be interrupted and restored. The goal of this study was to investigate whether two commercial formulations of propofol and the individual components of the commercial formulations attenuated the oxidative stress produced in this model. Breath ethane and breath carbon monoxide were measured as biomarkers of oxidative stress that occur at reperfusion of ischemic tissue. Data were analyzed by a standard least-squares-fit model. One of the formulations for propofol, which contained the preservative ethylenediaminetetraacetic acid (EDTA), was found to decrease the overall level of oxidative stress in sheep. Furthermore, while several models of severe lung injury demonstrate additional production of reactive oxygen species, our model of ischemia/reperfusion of lung tissue did not.

No evidence for oxidative stress in patients on home parenteral nutrition

BACKGROUND & AIMS

Patients on total parenteral nutrition depend on the composition of the nutritional formulation for maintenance of their oxidant-antioxidant balance. The present observational study was conducted to evaluate a substantial part of our patient population for evidence of oxidative stress.

METHODS

Venous blood samples were obtained from 41 patients on home parenteral nutrition (HPN) and 41 healthy controls. Glutathione in plasma and whole blood, glutathione peroxidase and superoxide dismutase in erythrocytes and total plasma antioxidant capacity were measured to assess the antioxidant status. Oxidant status was evaluated by measuring the production of reactive oxygen species by leukocytes. Oxidative damage was assessed by measuring lipid peroxidation and protein oxidation products.

RESULTS

Patients on HPN showed some signs of increased oxidative stress, however, there were no signs for oxidative damage, compared with healthy controls. In addition, activity of any underlying disease was not associated with increased oxidative stress.

CONCLUSIONS

The current treatment regime for patients on HPN at our center apparently prevents the development of significant oxidative damage, despite signs of some oxidative stress. Based on these data, adaptations in the composition of parenteral nutritional formulations do not seem mandatory.

Regional accumulation of aluminium in the rat brain is affected by dietary vitamin E

The regional accumulation of aluminium in the brain of male albino Wistar rats was investigated following 4 weeks of administration by intraperitoneal injection of aluminium lactate (10mg aluminium/kg body weight). The consequences of concomitant dietary vitamin E (5, 15, or 20 mg vitamin E/g of food) were also studied. Rat brains were dissected into functional regions, for the measurement of aluminium and markers of oxidative stress. Plasma aluminium levels were increased in all groups of animals receiving aluminium lactate (p < 0.01), and these levels were significantly reduced in rats receiving concomitant vitamin E (p < 0.05). In the group of rats receiving aluminium alone, levels of brain tissue aluminium were increased in all regions of brain examined (p< 0.01). Brain tissue aluminium levels were reduced by concomitant dietary vitamin E. Catalase and reduced glutathione levels were both reduced in several regions of brain in animals treated with aluminium (p < 0.05). Aluminium treatment was not associated with a significant increase in reactive oxygen species (ROS) generation (p > 0.05), although ROS production was attenuated by dietary vitamin E (p < 0.05) in some regions.

Peroxidation potential of lipid emulsions after compounding in all-in-one solutions

OBJECTIVES

We investigated the peroxidation potential of fat emulsions in all-in-one solutions (AIOs).

METHODS

Three 20% emulsions were compared: soybean oil (SO; 60% polyunsaturated fatty acids [PUFAs], alpha-tocopherol:PUFAs = 0.44), soybean plus medium-chain triacylglycerol (SO-MCT; 31% PUFAs, alpha-tocopherol:PUFAs = 0.35), and olive oil (OO; 21% PUFAs, alpha-tocopherol:PUFAs = 1.42). For each emulsion, six AIO solutions were prepared by adding 250 mL of emulsion to a lipid-free solution. Lipid peroxide (LPX) and malondialdehyde (MDA) concentrations were evaluated in fat emulsions, lipid-free solutions, and AIOs immediately (T0) and 24 h (T24) after lipid addition. Statistical analysis was done with analysis of variance.

RESULTS

Fat emulsion LPX in SO-MCT was lower than that in SO (P = 0.015) and OO (P = 0.024); LPX in SO was greater than that in OO (P = 0.013); MDA in SO was greater than that in SO-MCT (P = 0.001) and OO (P = 0.013); and MDA in SO-MCT was greater than that in OO (P = 0.001). In comparison with MDA at AIO-T0, MDA at AIO-T24 increased in SO (P = 0.005) and SO-MCT (P < 0.001) and decreased in OO (P = 0.003); at AIO-T24, LPX was greater in SO, but not significantly.

CONCLUSIONS

In AIO bags, LPX occurred within 24 h after the addition of the lipid emulsion and seemed to be directly related to the PUFA content and inversely related to the alpha-tocopherol:PUFA ratio of the emulsion.

Tocopherol isoforms in parenteral lipid emulsions and neutrophil activation

BACKGROUND AND AIMS

Tocopherol is a lipid-soluble anti-oxidant that exists in several isoforms. Patients on total parenteral nutrition depend on lipid emulsions for their tocopherol intake. In the present study, we analysed the content of tocopherol isoforms in various lipid emulsions. We also tested the hypothesis that immune-modulating effects of lipid emulsions could be attributed to different concentrations of alpha-tocopherol (alpha-toc) or peroxidation products.

METHOD

alpha-, beta-, gamma- and delta-toc were measured in emulsions containing long-chain triglycerides (LCT), mixed long- and medium-chain triglycerides (LCT/MCT), structured lipids (SL), olive oil (OO) or fish oil (FO). As a measure for cellular activation, neutrophil membrane adhesion markers were assessed after exposure to two LCT/MCT emulsions that differ only in alpha-toc content.

RESULTS

Various emulsions differed widely in tocopherol contents, especially with respect to the alpha- isoform. The latter isomer also was subject to considerable degradation despite adequate storage conditions. The previously observed activation of neutrophils by LCT/MCT was not influenced by the increased concentration of alpha-toc or the decreased concentration of lipid peroxidation products in a new LCT/MCT emulsion.

CONCLUSIONS

Tocopherol supplementation by parenteral lipid emulsions strongly depends on the lipid source and the storage lifetime of the emulsion. The effects of LCT/MCT on the immune system are not modulated by alpha-toc or by lipid peroxidation products.

Metabolism and nutritional support in the surgical neonate

Various factors can influence the metabolism of surgical neonates. These include prematurity, operative stress, critical illness, and sepsis. The nutritional management of surgical infants with congenital or acquired intestinal abnormalities has improved after the introduction of parenteral nutrition. This article is focused on the energy and protein metabolism of surgical neonates with particular reference to the metabolic response to operative trauma and sepsis. The metabolic utilization of intravenous nutrients also is discussed. The metabolic response to operative trauma is different between neonates and adults. Infants have high rates of protein turnover and are avid retainers of nitrogen. Energy expenditure increases only transiently (4 to 6 hours) after major surgery in neonates. Protein turnover and catabolism seems not to be affected by major operative procedures in neonates. In neonates on parenteral nutrition, carbohydrate and fat have an equivalent effect on protein metabolism. The main determinants of fat utilization are carbohydrate intake and resting energy expenditure. Parenteral nutrition in surgical neonates is associated with increased production of oxygen-free radicals. This seems to be related to intravenous fat administration. Promoting fat utilization by reducing the carbohydrate to fat ratio in the intravenous diet reduces free radical activity to a similar extent as fat exclusion. Glutamine appears to be safe for use in neonates and infants and is "conditionally essential" in very-low birth weight infants and in septic neonates. Enteral glutamine supplementation in very-low birth weight infants reduces the risk of sepsis. The metabolism of surgical neonates is affected by operative trauma, critical illness, and sepsis. Nutritional support in surgical neonates has a profound impact on outcome. Exogenous glutamine can modulate immune, metabolic, and inflammatory responses. Further investigations are needed to clarify the clinical benefit of parenteral or enteral glutamine administration in surgical neonates.

Breath isoprene in patients with heart failure

BACKGROUND

Chronic heart failure (CHF) is characterised by increased vascular resistance. This increased after load on the left ventricle contributes to the vicious cycle that leads to progression of myocardial failure, multiple organ failure and death. There is evidence for increased oxidative stress in heart failure, which will influence the myocardium but also peripheral vasculature endothelium.

AIMS

The aim of the present study was to examine the production of isoprene, reputed to reflect oxidative stress, in patients with CHF compared to control subjects.

METHODS

Twelve patients with CHF and thirty-one healthy control subjects free from heart disease were studied. Breath was collected via a two-way non-re-breathing valve into a 60-l gas collection bag. A sample of ambient air was collected at the same time. A measured aliquot of patient breath and ambient air (approx. 1.5 l) was adsorbed onto a gas adsorption tube packed with poropak-Q. Isoprene was measured using GC/MS and the production rate calculated. All samples of breath were collected at 10.00 h after subjects had been sitting at rest for 15 min.

RESULTS

Breath isoprene production in subjects with CHF was significantly reduced compared to controls 83(23) vs. 168(20) pmol min(-1) kg(-1).

CONCLUSION

Breath isoprene does not directly reflect oxidative stress in CHF.

Pro-oxidant effect of vitamin E in cigarette smokers consuming a high polyunsaturated fat diet

Dietary polyunsaturated fats and vitamin E are associated with reduced risk for atherosclerosis, but in smokers, they could promote lipid oxidation. Therefore, we examined the effects of a high polyunsaturated fat diet and vitamin E supplementation on measures of lipid oxidation in cigarette smokers. Ten subjects who smoked >1 pack of cigarettes per day were sequentially fed the following: a baseline diet in which the major fat source was olive oil, a diet in which the major fat source was high-linoleic safflower oil, and finally, the safflower oil diet plus 800 IU vitamin E per day. LDL oxidation lag time and rate and plasma total F(2)-isoprostanes and prostaglandin F(2alpha) (PGF(2alpha)) were determined after 3 weeks on each diet. The safflower oil diet increased total F(2)-isoprostanes from 53.0+/-7.2 to 116.2+/-11.2 nmol/L and PGF(2alpha) from 3.5+/-0.2 to 5.5+/-0.5 nmol/L, without changing LDL oxidation parameters. Addition of vitamin E prolonged mean LDL oxidation lag time but, paradoxically, further increased F(2)-isoprostanes to 188.2+/-10.9 nmol/L and PGF(2alpha) to 7.8+/-0.4 nmol/L. These data suggest that vitamin E may function as a pro-oxidant in cigarette smokers consuming a high polyunsaturated fat diet.

Plasma antioxidant status after high-dose chemotherapy: a randomized trial of parenteral nutrition in bone marrow transplantation patients

BACKGROUND

Chemotherapy and radiation therapy result in increased free radical formation and depletion of tissue antioxidants. It is not known whether parenteral nutrition (PN) administered during bone marrow transplantation (BMT) supports systemic antioxidant status.

OBJECTIVE

The aims of the study were to determine 1) whether high-dose chemotherapy decreases concentrations of major circulating antioxidants in patients undergoing BMT and 2) whether administration of standard PN maintains systemic antioxidant concentrations compared with PN containing micronutrients and minimal lipids alone.

DESIGN

Twenty-four BMT patients were randomly assigned to receive either standard PN containing conventional amounts of dextrose, amino acids, micronutrients, and lipid (120 kJ/d) or a solution containing only micronutrients (identical to those in standard PN) and a small amount of lipid (12 kJ/d). Plasma antioxidant status was measured before conditioning therapy and serially at days 1, 3, 7, 10, and 14 after BMT.

RESULTS

Plasma glutathione (GSH) and alpha- and gamma-tocopherol concentrations decreased and the GSH redox state became more oxidized after conditioning chemotherapy. Plasma cysteine concentrations were unchanged, whereas cystine concentrations increased. Plasma vitamin C and zinc concentrations and GSH peroxidase activity increased over time. Plasma alpha-tocopherol concentrations were lower in patients given standard PN. There were no differences in other plasma antioxidants between groups.

CONCLUSIONS

A significant decline in GSH-glutathione disulfide, cysteine-cystine, and vitamin E status occurs after chemotherapy and BMT. Standard PN does not improve antioxidant status compared with administration of micronutrients alone. Further evaluation of PN formulations to support patients undergoing high-dose chemotherapy and BMT are needed.

Antioxidant status of surgical patients receiving TPN with an omega-3-fatty acid-containing lipid emulsion supplemented with alpha-tocopherol

BACKGROUND

LCT lipid emulsions and even more fish oil-containing lipid emulsions are under debate regarding their tocopherol and PUFA content as well as their effect on the antioxidative status especially in patients with oxidative stress.

METHODS

Thirty-three patients undergoing major abdominal surgery were randomly assigned to receive either an alpha-tocopherol-supplemented (562 micromol/l) MCT/LCT/omega-3-acid triglycerides (MLF, 5/4/1 w/w/w, 20%) emulsion or a soybean oil-based LCT emulsion (20%). The TPN regimen continuously provided 1.4 g fat kg bw(-1)d(-1)over 5 days.

RESULTS

Plasma antioxidant concentrations were strongly reduced by surgical treatment. Following 5 days of TPN with the MLF emulsion, mean plasma alpha-tocopherol increased by 20.0 micromol/l (1.98 micromol/mmol lipid), while nearly no change was observed in the LCT emulsion group. In both groups, plasma concentrations of all non-supplemented antioxidants (vitamin C, carotenoids, selenium) as well as serum total antioxidant capacity further decreased during TPN. The concentrations of plasma cholesterol oxidation products as a measure of in vivo lipid peroxidation revealed no changes over the TPN period in either group.

CONCLUSION

In contrast to the LCT emulsion, administration of the a-tocopherol supplemented MLF lipid emulsion normalized a-tocopherol plasma concentrations. Despite its high long-chain PUFA content, no hint for increased lipid peroxidation was found.

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 micromol/L, while in neonatal solutions the peroxide concentration was as high as 300 micromol/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.

Breath alkanes as a marker of oxidative stress in different clinical conditions

We assessed oxidative stress in three different clinical conditions: smoking, human immunodeficiency virus (HIV) infection, and inflammatory bowel disease, using breath alkane output and other lipid peroxidation parameters such as plasma lipid peroxides (LPO) and malondialdehyde (MDA). Antioxidant micronutrients such as selenium, vitamin E, C, beta-carotene and carotenoids were also measured. Lipid peroxidation was significantly higher and antioxidant vitamins significantly lower in smokers compared to nonsmokers. Beta-carotene or vitamin E supplementation significantly reduced lipid peroxidation in that population. However, vitamin C supplementation had no effect. In HIV-infected subjects, lipid peroxidation parameters were also elevated and antioxidant vitamins reduced compared to seronegative controls. Vitamin E and C supplementation resulted in a significant decrease in lipid peroxidation with a trend toward a reduction in viral load. In patients with inflammatory bowel disease, breath alkane output was also significantly elevated when compared to healthy controls. A trial with vitamin E and C is underway. In conclusion, breath alkane output, plasma LPO and MDA are elevated in certain clinical conditions such as smoking, HIV infection, and inflammatory bowel disease. This is associated with lower levels of antioxidant micronutrients. Supplementation with antioxidant vitamins significantly reduced these lipid peroxidation parameters. The results suggest that these measures are good markers for lipid peroxidation.

Oxidative stress in humans during work at moderate altitude

Increased oxidative stress has been associated with work at high altitude; however, it is not known whether oxidative stress is a significant problem at moderate altitudes. The oxidative stress indicators, breath pentane (BP), 8-hydroxydeoxyguanosine (8-OHdG), oxygen radical absorption capacity (ORAC), 4-hydroxynonenal (4-HNE), malondialdehyde (MDA), and lipid peroxides (LPO) were measured in breath, blood and urine samples of U.S. Marines engaged in moderate altitude ( approximately 3000 m) cold weather field training. The test subjects were divided into a placebo and four antioxidant supplement groups (n = 15/group) and received the following supplements for 28 d: 1) vitamin E, 440 alpha-tocopherol equivalents (alpha-TE); 2) vitamin A, 2000 retinol equivalents (RE) of beta-carotene; 3) vitamin C, 500 mg ascorbic acid; 4) a mixture of 440 alpha-TE, 2000 RE of beta-carotene, 500 mg ascorbic acid, 100 microg selenium and 30 mg zinc daily. Strenuous work ( approximately 23 MJ/d) in cold weather at moderate altitude was accompanied by increases in several indicators of oxidative stress that were not effectively controlled by conventional antioxidant supplements. The group receiving the antioxidant mixture exhibited lower BP (P < 0. 05) compared with those receiving single antioxidant supplements; however, not all markers of oxidative stress responded like BP. Because these markers did not respond in the same manner, it is important to include markers from more than one source to assess the effect of supplemental dietary antioxidants.

Phagocyte-induced lipid peroxidation of different intravenous fat emulsions and counteractive effect of vitamin E

Unsaturated fatty acids, a major component of fat emulsions used in parenteral nutrition, are prone to peroxidation which is an important feature of oxygen-associated tissue damage. We used the nitroblue tetrazolium (NBT) reduction test to measure the production of superoxide radicals by stimulated polymorphonuclear neutrophils (PMN) in the presence of different fat emulsions: Intralipid (containing 100% long-chain triacylglycerols, LCT), Vasolipid (a physical mixture of 50% LCT and 50% medium-chain triacylglycerols, MCT) and Structolipid (structured triacylglycerols containing 63% LCT and 37% MCT). We measured the amount of malonaldehyde (MDA) and 4-hydroxyalkenal to determine the lipid peroxidation of the three fat emulsions in the presence of stimulated neutrophils. Further, we investigated the role of vitamin E (alpha-tocopherol) in preventing lipid peroxidation in vitro. The results showed that the values of NBT reduction of PMN were significantly decreased in each of the three fat emulsions and that increasing concentrations of fat emulsions were associated with decreased values of NBT reductions, in a dose-dependent way (P<0.001). There were, however, no statistically significant differences between the values of the three different types of fat emulsions (P>0.05). Lipid peroxidation increased significantly in the presence of all three types of fat emulsions, and was more pronounced for Intralipid than for Vasolipid and Structolipid after 1 and 2 h of incubation with resting as well as with stimulated phagocytes. The increased lipid peroxidation of the fat emulsions was markedly reduced by vitamin E, and the inhibition was concentration dependent. In conclusion, lipid peroxidation in vitro is more pronounced when PMNs are incubated with fat emulsions. This increase in lipid peroxidation can be reduced by adding vitamin E to the fat emulsions.

Clinical use of lipid emulsions

Substantial progress has been made in the understanding of the metabolism of intravenous lipid emulsions and the delivery of their various components to specific tissues or cells. Lipid emulsions should be considered not only as a means of providing energy substrates but also specific compounds that participate in the regulation of key metabolic functions. Such improved knowledge should find applications in the metabolic care of different types of patients.

Lipid peroxidation can be reduced in infants on total parenteral nutrition by promoting fat utilisation

BACKGROUND/PURPOSE

Increased oxygen-derived free radical activity has been reported during total parenteral nutrition (TPN) in infants and has been specifically linked to the fat infusion. The aim of this study was to test the hypothesis that during TPN, oxygen-derived free radical production can be reduced by increasing the utilisation of fat.

METHODS

In experiment A (17 patients) the fat infusion was kept constant (3 g/kg/d) and the carbohydrate infusion was changed from 18 g/kg/d on day 1 to 10 g/kg/d on day 2. In experiment B (six patients) the carbohydrate infusion remained constant and the fat infusion was changed from 3 g/kg/d on day 1 to 0 g/kg/d on day 2. Fat utilisation was measured by indirect calorimetry. Plasma malondialdehyde, an index of lipid peroxidation resulting from increased oxygen-derived free radical activity, was measured by a colorimetric assay.

RESULTS

In both experiments there was no significant change between the two study phases in oxygen consumption, carbon dioxide production, and resting energy expenditure demonstrating that the patients were metabolically stable. In experiment A there was a significant (P = .0005) increase in fat utilisation and a significant (P = .009) decrease in malondialdehyde (MDA) concentration between the two phases. In experiment B there was also a significant (P = .007) decrease in MDA concentration. The decrease in MDA concentration was similar between the two experiments.

CONCLUSIONS

It is not necessary to stop the infusion of fat to reduce free radical production. Promoting fat utilisation by reducing the carbohydrate-fat ratio of the TPN reduces free radical activity to a similar extent as fat exclusion. These findings have important implications for the composition of TPN.

Increased oxidative stress in patients with congestive heart failure

OBJECTIVES

We sought to study the markers of lipid peroxidation and defenses against oxidative stress in patients with varying degrees of heart failure.

BACKGROUND

Despite advances in other areas of cardiovascular disease, the morbidity and mortality from congestive heart failure (CHF) are increasing. Data mainly from animal models suggest that free radical injury may promote myocardial decompensation. However, there are no studies in humans correlating the severity of heart failure with increased free radical injury and antioxidants.

METHODS

Fifty-eight patients with CHF and 19 control subjects were studied. In addition to complete clinical and echocardiographic evaluations, the prognosis of these patients was established by measuring the levels of soluble tumor necrosis factor-alpha receptors 1 and 2 (sTNF-R1 and sTNF-R2). Oxidative stress was evaluated by measuring plasma lipid peroxides (LPO), malondialdehyde (MDA), glutathione peroxidase (GSHPx) and vitamin E and C levels.

RESULTS

The patients' age range, cause of heart failure and drug intake were comparable across the different classes of heart failure. Heart failure resulted in a significant increase in LPO (p < 0.005), MDA (p < 0.005), sTNF-R1 (p < 0.005) and sTNF-R2 (p < 0.005). There was a significant positive correlation between the clinical class of heart failure and LPO, MDA, sTNF-R1 and sTNF-R2 levels. There was an inverse correlation between GSHPx and LPO. With increased lipid peroxidation in patients with CHF, the levels of vitamin C decreased, but vitamin E levels were maintained.

CONCLUSIONS

These data demonstrate a progressive increase in free radical injury and encroachment on antioxidant reserves with the evolution of heart failure; they also suggest that oxidative stress may be an important determinant of prognosis. The therapeutic benefit of administering antioxidant supplements to patients with CHF should be evaluated.

Solid-phase microextraction for the analysis of human breath

Solid-phase microextraction (SPME) has been applied to the quantitative determination of ethanol, acetone, and isoprene in human breath. The method involves extraction and preconcentration with a fused silica fiber coated with a polymeric stationary phase, desorption at 200 degrees C, and assay by gas chromatography/mass spectrometry. Three different fiber coatings have been evaluated with regard to sensitivity, linear range, precision, and detection limits. Typical RSD values in the range 2%-6% could be obtained, depending on the fiber coating and the compound investigated. The calibration curves for the compounds are reproducible and linear over the concentration ranges found in human breath samples. The method is capable of detecting concentrations of acetone and isoprene reported for healthy subjects. The influence of temperature and humidity on the extraction process has been studied in detail. A linear relationship between log K versus 1/T allows the calibration of the method for any given temperature. The device is portable, economical, and easy to use in patient sampling.

Influence of long chain unsaturated fatty acids in formula feeds on lipid peroxidation and antioxidants in preterm infants

The influence of long chain polyunsaturated fatty acids (LCP) in formula feeds on lipid peroxidation and antioxidants was studied in 35 healthy preterm infants (gestational age 30-35 wk) during the first 6 postnatal weeks. Infants received a preterm formula supplemented with n-3 LCP (LCP group, n = 13), or standard preterm formula (NO-LCP group, n = 15); 7 infants fed human milk served as a reference group. With LCP supplementation, erythrocyte C22:6n-3 levels were stable; without supplementation, the levels declined (difference p < 0.001). LCP supplementation did not decrease vitamin E or C levels, or increase lipid peroxidation products (thiobarbituric acid-reactive substances) in plasma. In erythrocytes, LCP supplementation did not markedly influence the reduced/oxidized glutathione ratio; however, the susceptibility to H2O2-induced oxidative stress was reduced. Our results suggest that healthy preterm infants are able to cope with any extra peroxidative stress produced by n-3 LCP supplementation. However, these findings might not be generally applicable to other formulas containing LCP supplements.

Effects of administration of different intravenous lipid emulsions on plasma LP-X concentrations in the rat

BACKGROUND

Prolonged parenteral nutrition with lipid emulsions is essential to provide sufficient energy supply and to avoid essential fatty acid deficiency in preterm infants. However, chronic administration of lipid emulsions may lead to the development of pathological plasma lipid and LP-X concentrations. The aim of this study was to evaluate the relative importance of the phospholipid-triglyceride (PL-TG) ratio and the source of phospholipid in lipid emulsions, with respect to plasma lipid and LP-X levels.

METHODS

Rats were infused for 9 days with IV lipid emulsion containing 10% (IL-10) or 20% (IL-20) egg lecithin or Lipofundin containing 20% soya lecithin (LF), with PL-TG ratios of .12, .06, and 0.75, respectively.

RESULTS

LF significantly increased plasma triglyceride concentration (p < .01), whereas the rise in cholesterol levels observed with all emulsions was primarily caused by the increase in low-density lipoprotein cholesterol concentrations. The plasma phospholipid concentration was increased most by IL-10 (p < .005). There was a strong correlation between the PL-TG ratio of emulsions and the developing plasma phospholipid and LP-X concentrations (r2 = .91 and .96, respectively), despite the different origin of phospholipids in the emulsions, suggesting that it is the PL-TG ratio, rather than the source of phospholipids in lipid emulsions that primarily influences developing plasma lipid and LP-X concentrations.

CONCLUSION

These results indicate that the administration of lipid emulsions with lower PL-TG ratios should be considered, to avoid the development of pathological plasma lipoprotein concentrations.

Decreased antioxidant status and increased lipid peroxidation in patients with septic shock and secondary organ dysfunction

OBJECTIVE

To determine antioxidant vitamin concentrations, lipid peroxidation, and an index of nitric oxide production in patients in the intensive care unit (ICU) with septic shock and relate the findings to the presence of secondary organ failure.

DESIGN

A prospective, observational study.

SETTING

A nine-bed ICU in a University teaching hospital.

PATIENTS

Sixteen consecutive patients with septic shock, defined as: a) clinical evidence of acute infection; b) hypo- or hyperthermia (< 35.6 degrees C or > 38.3 degrees C); c) tachypnea (> 20 breaths/min or being mechanically ventilated); d) tachycardia (> 90 beats/min); e) shock (systolic pressure < 90 mm Hg) or receiving inotropes. Fourteen patients also had secondary organ dysfunction.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Antioxidant vitamin concentrations were significantly lower in the patients than the reference range obtained from a comparable group of healthy controls. The mean plasma retinol (vitamin A) concentration was 26.5 +/- 19.3 micrograms/dL compared with 73.5 +/- 18.3 micrograms/dL in healthy subjects (p < .01). Additionally, 13 (81%) patients had retinol values below the lower limit of our reference range (< 37.0 micrograms/dL). Tocopherol (vitamin E) plasma concentrations were below the reference range in all patients (< 9.0 mg/L), with a mean value of 3.6 +/- 2.0 mg/L compared with 11.5 +/- 1.3 mg/L in healthy subjects (p < .001). Plasma beta carotene and lycopene concentrations were undetectable (< 15 micrograms/L) in eight (50%) patients, and below our reference range (< 101 micrograms/L and < 154 micrograms/L, respectively) in the remaining patients. In the five patients with three or more dysfunctional secondary organs, plasma thiobarbituric acid-reactive substances were significantly increased (p < .05), suggesting increased lipid peroxidation. Concentrations of thiobarbituric acid-reactive substances correlated negatively with both plasma retinol and plasma tocopherol (r2 = .42, p < .01 and r2 = .48, p < .005, respectively). In the five patients from whom we were able to collect urine, nitrite excretion was increased approximately 400-fold (p < .001).

CONCLUSIONS

These data indicate decreased antioxidant status in the face of enhanced free radical activity, and suggest potential therapeutic strategies involving antioxidant repletion.

[Role of trace elements and vitamins in peri-operative nutrition]

The micronutriment requirements, whether trace elements (inorganic) or vitamins (organic), are tightly linked to the carbohydrate, lipid and protein metabolism, since they are involved in all metabolic pathways as cofactors. The micronutriments also have major immunological, endocrinological and antioxydant functions. Especially in the surgical patient, individual requirements may vary considerably and will be particularly increased in case of prior deficiency, anabolic states, or increased losses (burns, diarrhoea, gastric aspiration, intestinal fistulae, alcoholism, use of renal replacement techniques). In some of these settings, the micronutriment requirements will be independent from the macronutriments: this has been demonstrated for burns and intestinal fistulae. In the case of depletion prior to surgery, an isolated supplementation may be required without starting a proper nutrition. In general, micronutriment supplements will have to be started upon initiation of any artificial nutrition. After elective surgery and in absence of specific losses, the micronutriment requirements will be linked to the metabolic state of the patient and to the energy-protein intakes. This is most striking for the vitamin B group, where the requirements are indicated in mg per 1000 kcal. Vitamins A and E are also at risk in the surgical patient. Recommended micronutriment supplements have been revised in 1994. Some trace element deficiencies (Se, Cr, Mo) can initiate very serious complications and will require special caution in the perioperative period. Other deficiencies (Cu, Zn) result in more slowly evolving clinical pictures, with lesser life-threatening potential, resulting in infections and prolonged wound healing. In such cases, multi-elementary supplements are inadequate, and single element solutions supplements are required. All the micronutriments are characterized by a dose-response curve. The quantity avoiding biochemical dysfunctioning in human pathological situations has not yet been established, and it is unsatisfactory to merely compensate for the losses. This notion of biochemical dysfunctioning phase preceeding the clinical deficiency syndrome is in investigation for many nutriments, especially as the importance of some micronutriments, such as Se and vitamin E, in maintaining antioxidant defences is clearly established. The potential for preventing free radical induced overproduction of cytokines by means of nutritional strategy and enhanced antioxidant defences clearly exists, and is only at an early phase of investigation in patients. The future will be marked by the development of nutritional pharmacology based on pathology-specific micronutriment supplements.

The potential of the hydrocarbon breath test as a measure of lipid peroxidation

The straight chain aliphatic hydrocarbons ethane and pentane have been advocated as noninvasive markers of free-radical induced lipid peroxidation in humans. In in vitro studies, the evolution of ethane and pentane as end products of n-3 and n-6 polyunsaturated fatty acids, respectively, correlates very well with other markers of lipid peroxidation and even seems to be the most sensitive test available. In laboratory animals the use of both hydrocarbons as in vivo markers of lipid peroxidation has been validated extensively. Although there are other possible sources of hydrocarbons in the body, such as protein oxidation and colonic bacterial metabolism, these apparently are of limited importance and do not interfere with the interpretation of the hydrocarbon breath test. The production of hydrocarbons relative to that of other end products of lipid peroxidation depends on variables that are difficult to control, such as the local availability of iron(II) ions and dioxygen. In addition, hydrocarbons are metabolized in the body, which especially influences the excretion of pentane. Because of the extremely low concentrations of ethane and pentane in human breath, which often are not significantly higher than those in ambient air, the hydrocarbon breath test requires a flawless technique regarding such factors as: (1) the preparation of the subject with hydrocarbon-free air to wash out ambient air hydrocarbons from the lungs, (2) the avoidance of ambient air contamination of the breath sample by using appropriate materials for sampling and storing, and (3) the procedures used to concentrate and filter the samples prior to gas chromatographic determination. For the gas chromatographic separation of hydrocarbons, open tubular capillary columns are preferred because of their high resolution capacity. Only in those settings where expired hydrocarbon levels are substantially higher than ambient air levels might washout prove to be unnecessary, at least in adults. Although many investigators have concentrated on one marker, it seems preferable to measure both ethane and pentane concurrently. The results of the hydrocarbon breath test are not influenced by prior food consumption, but both vitamin E and beta-carotene supplementation decrease hydrocarbon excretion. Nevertheless, the long-term use of a diet high in polyunsaturated fatty acids, such as in parenteral nutrition regimens, may result in increased hydrocarbon exhalation. Hydrocarbon excretion slightly increases with increasing age. Short-term increases follow physical and intellectual stress and exposure to hyperbaric dioxygen.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of dietary supplementation with very-long-chain n-3 fatty acids in patients with psoriasis

BACKGROUND

In several studies dietary fish oil has been found to have beneficial effect on psoriasis, but the results are contradictory and based mainly on open studies or studies of small numbers of patients.

METHODS

In a four-month double-blind, multicenter trial, we randomly assigned 145 patients with moderate-to-severe psoriasis to receive in their diet either highly purified ethyl esters of n-3 fatty acids ("fish oil"; 6 g of oil per day, containing 5 g of eicosapentaenoic and docosahexaenoic acid) or an isoenergetic amount of corn oil containing mainly n-6 fatty acids. All the patients were advised to reduce their intake of saturated fatty acids. A 48-hour dietary recall was performed, and the fatty-acid pattern in the serum phospholipids was monitored in a subgroup of patients.

RESULTS

In the fish-oil group, n-3 fatty acids were increased in serum phospholipids (P < 0.001), the ratio of arachidonic acid to eicosapentaenoic acid decreased (P < 0.001), and the level of n-6 fatty acids decreased (P < 0.001). In the corn-oil group, only docosahexaenoic acid increased significantly (P < 0.05). The ratio of polyunsaturated to saturated fatty acids increased in both groups. Plasma concentrations of triacylglycerol decreased from base line in the fish-oil group (P < 0.05). The score on the Psoriasis Area and Severity Index, as evaluated by the physicians, did not change significantly during the trial in either group. This was also true of a total subjective score reported by the patients, but a selected area of skin in the corn-oil group showed a significant reduction in the clinical signs (P < 0.05). Scaling was reduced from base line in both groups (P < 0.01). The fish-oil group had less cellular infiltration (P < 0.01), and the corn-oil group had improvement in desquamation and redness (P < 0.05). There was no significant difference in clinical manifestations between the groups. Among the patients in the fish-oil group, an increase in the concentration of n-3 fatty acids in serum phospholipids was not accompanied by clinical improvement, whereas in the corn-oil group there was a significant correlation between clinical improvement and an increase in eicosapentaenoic acid and total n-3 fatty acids.

CONCLUSIONS

Dietary supplementation with very-long-chain n-3 fatty acids was no better than corn-oil supplementation in treating psoriasis. Clinical improvement was not correlated with an increase in the concentration of n-3 fatty acids in serum phospholipids among the patients in the fish-oil group, whereas there was a significant correlation between clinical improvement and an increase in eicosapentaenoic acid and total n-3 fatty acids in the corn-oil group.

Oral diet does not alter pulmonary pentane or ethane excretion in healthy subjects

Ethane and pentane are alkanes that are excreted through the lungs to a small degree in healthy subjects. These gasses are produced from the peroxidation of unsaturated fats which are found both in body tissues and in foods. These gasses are excreted in larger amounts by patients with increased production of reactive oxygen metabolites, including those with inflammation or ischemia. Thus, detection of these gasses in excessive quantities is considered evidence for lipid peroxidation. However, the effects of dietary factors on these measurements have not been defined. To define the effects of eating on the pulmonary excretion of these alkanes, 29 healthy subjects were fed a standardized liquid diet (1060 kcal, 12.9 g linoleic acid and 385 mg linolenic acid) after an overnight fast. Breath alkanes were measured at 0, 1, 3, and 6 hours. All subjects had normal vitamin E (1.11 + 0.26 mg/dl), retinol (64 +/- 14 micrograms/dl), beta carotene (27 +/- 21 micrograms/dl), lycopene (23 +/- 12 micrograms/dl) and zinc (81.9 +/- 13.5 micrograms/dl) levels. No statistically significant changes in either alkane were noted relative to the fasting level. We conclude that oral diet does not alter pulmonary ethane or pentane excretion in healthy subjects.

Monitoring of oxidative free radical damage in vivo: analytical aspects

Free radical damage is an important factor in many pathological and toxicological processes. During the last decade a wide range of methods has been developed to determine free radical damage in various biological fluids and at various stages of development. This review offers an overview of the state of the art of monitoring free radical damage in vivo, with special emphasis on the analytical aspects of non-invasive methods.

Antioxidant status (selenium, vitamins A and E) and aging

Antioxidant status can be evaluated by blood selenium, vitamins A and E. The level of selenium was determined in whole blood, erythrocytes and plasma of 170 French people (70-95 years old) healthy and with intercurrent illness, by using PIXE (proton-induced X-ray emission analysis). These results are discussed with other values from the literature. Plasma levels of vitamins A and E have been measured by HPLC. All data were compared with those obtained for younger subjects. Healthy elderly people residing in a geriatric home received selenium supplements during 1 month. The influence of this supplementation brought to light a deficiency for this trace element. The correlation of aging and nutritional requirements with immune function, heart and cancer death rate is presented and discussed.

Effects of high fat-, cholesterol-enriched diet on the antioxidant defence mechanisms in the rabbit heart

In 7 rabbits fed on hyperlipidic diet (0.5% cholesterol, 5% peanut oil and 5% lard) for 4 weeks, the ventricular myocardium was tested for antioxidant defences and thiobarbituric acid reactive substances. Seven age-matched rabbits served as controls. The hearts were previously subjected to 45 min Langendorff perfusion to study coronary flow, developed tension and resting tension; coronary effluent values of CPK activity, pH and UV absorbance at 250 nm (i.e., low molecular weight ATP catabolites) were also investigated. After 4 weeks of diet, a significant rise of plasma cholesterol (P < 0.0001) and triglycerides (P < 0.0001) was observed. Total superoxide dismutase, catalase and glutathione transferase activities underwent a significant increase (P < 0.05) in the hyperlipidemic animals. On the contrary, a depression of glutathione reductase (P < 0.01) and selenium-dependent glutathione peroxidase (P < 0.01) activities, associated with decreased levels of non proteic thiol compounds (P < 0.01), was assessed. The selenium-independent glutathione peroxidase activity was not detectable in both groups. Thiobarbituric acid reactive substances levels were significantly increased in the hyperlipidemic rabbit myocardium (P < 0.01). Even though heart hemodynamics, CPK release and perfusate pH did not differ in control and experimental animals, higher 250 nm absorbance values (P < 0.05) were detected in the myocardial effluent of hyperlipidemic rabbits. In conclusion, high fat-, cholesterol-enriched diet induces an imbalance in the rabbit heart antioxidant defences, some of which are increased, whereas others are depressed, eventually resulting in enhanced myocardial lipid peroxidation. These biochemical changes are associated with higher perfusate values of UV absorbance at 250 nm, but not with significant CPK leakage or myocardial hemodynamics derangement.

Recent progress in testing the longevity determinant and dysdifferentiation hypotheses of aging

An overview of the longevity determinant and dysdifferentiation hypotheses is presented, highlighting some of the major postulates and predictions. Results of recent experiments testing these hypotheses are discussed, including the search for specific longevity determinant genes and evidence that cancer and aging may have common causative mechanisms of action and control. Regulation of oxidative stress is considered a potential longevity determinant mechanism and methods and results testing this prediction are reviewed. Possibility of enhancing protective mechanisms against oxidative stress is discussed by way of intervention of central regulatory mechanisms of antioxidants using the cyclase-arachidonic acidcyclooxygenase (GAC model).

In vivo breath alkane as an index of lipid peroxidation

Interaction of active oxygen species with polyunsaturated fatty acids (PUFA) results in a series of reactions called lipid peroxidation. During the process of peroxidation of polyunsaturated fatty acids there is a scission of an alkane fragment extending from the methyl end of the fatty acid to the double bond. Thus, with a w-6 polyunsaturated fatty acid pentane is released, and with a w-3 polyunsaturated fatty acid ethane is released. These hydrocarbons are distributed in the body, partly metabolized, and excreted in the breath, making it possible to estimate the magnitude of in vivo lipid peroxidation by measuring pentane and ethane exhaled in breath. Advantages of this method are discussed as well as limitations and possible sources of error.