Lipid peroxidation and antioxidant status in adults receiving lipid-based home parenteral nutrition

A one size vial does not fit all: An evaluation of the micronutrient status of adult patients receiving home parenteral nutrition (HPN)

BACKGROUND & AIMS

Patients with chronic intestinal failure require HPN. Previous studies have reported a high prevalence of micronutrient deficiencies. We examined the micronutrient status of our patients receiving.

METHODS

We measured vitamins A, E, D, B12, Folate, Zinc, Selenium and Copper. Patients were excluded if they had undergone surgery or amendments in IV or oral micronutrient provision in the past six months. Blood samples were excluded if C-reactive protein was >15 mg/L. Univariate and multivariate analyses were performed on concentrations below normal to determine if clinical or demographic categories were significant.

RESULTS

93 samples were included (33 males:60 females). Samples were excluded due to surgery (n = 8) amendment in micronutrient provision (n = 42) or if C-reactive protein >15 mg/L (n = 18). Vitamins A, D and E were below normal in 26%, 33% and 13% of patients respectively. Lower vitamin A was more likely in patients >50 years (P = 0.02) and lower vitamin E was more likely in men (P = 0.02). No patients had low vitamin B12 or folate whereas 29% and 9% had concentrations above the normal range respectively. Zinc and selenium were below normal in 19% and 13% respectively. Patients with surgical complications were more likely to have lower zinc (P = 0.007) and selenium (P = 0.04). Lower zinc was more likely in patients with a BMI of >25 kg/m2 (P = 0.01) and those who received Additrace® ≤3 day/week (P = 0.06).

DISCUSSION

Low and high concentrations were observed in our patients but clinical and demographic factors did not impact consistently on micronutrient concentrations highlighting the importance of ongoing monitoring and adequate supplementation as per ESPEN guidelines. Current micronutrient preparations may be inadequate for some patients with dependent on HPN. Our results indicate a need for a preparation with higher amounts of vitamin D.

Antioxidant balance in plasma of patients on home parenteral nutrition: A pilot study comparing three different lipid emulsions

BACKGROUND & AIMS

Parenteral nutrition (PN) can supply all essential nutrients to a patient with gastrointestinal insufficiency. However, the sensitivity to lipid peroxidation might increase in those receiving PN, especially home parenteral nutrition (HPN). This study aimed to investigate whether PN affects the antioxidant balance of plasma of HPN patients without comorbidities and whether this balance is influenced by comorbidities and according to the type of lipid emulsion included in the PN.

METHODS

Adult patients on HPN (n = 86) received one of three types of lipid emulsion (based on 1) soyabean oil, 2) olive and soyabean oil or 3) soyabean, coconut, olive and fish oil) in all-in-one mixtures; in addition healthy controls (n = 66) were studied as comparators. HPN patients were classified to the following subgroups: 1) patients without (n = 58) or with (n = 28) comorbidities 2) patients on Intralipid (G_INTRA, n = 53), ClinOleic (G_CLIN, n = 17) or SMOFlipid (G_SMOFn = 16). The activities of total glutathione peroxidase (GSH-Px), selenium dependent glutathione peroxidase (Se-GSHPx) and glutathione S-transferase (GST) in plasma were determined spectrophotometrically. The antioxidant potential of plasma was determined using oxygen radical absorbance capacity (ORAC). The lipid peroxidation marker malondialdehyde (MDA) was analyzed with high performance liquid chromatography.

RESULTS

MDA concentration was the highest in G_INTRA and the lowest in G_SMOF (p < 0.05). G_SMOF also had the highest activity of GSH-Px. No differences in Se-GSHPx, GST and ORAC were observed among G_INTRA, G_CLIN and G_SMOF. Comparing with healthy controls, significantly lower GST (p = 0.0293) and ORAC (p < 0.0001) were observed in the HPN patients. Among all measured parameters only the concentration of MDA was significantly higher in patients with comorbidities compared to those without them. Comorbidities did not influence MDA level in G_INTRA and G_SMOF being still the lowest in G_SMOF (p = 0.0033). In contrast, significantly higher MDA level was observed for G_CLIN in those with vs. without comorbidities (p = 0.0262).

CONCLUSIONS

Patients on HPN have lower antioxidant defenses than healthy controls. The type of lipid emulsion used in HPN affects lipid peroxidation (even after taking into account comorbidities which often involve oxidative stress) being the highest in G_INTRA and the lowest in G_SMOF. Thus, to minimize the risk of oxidative stress, SMOFlipid can be considered in patients in HPN especially for those with comorbidities. ClinOleic can be considered in HPN patients without comorbidities. The observation should be confirmed in larger studies.

Antioxidants in patients receiving total parenteral nutrition after gastrointestinal cancer surgery

Total parenteral nutrition (TPN) is essential for patients with postoperative impairing gastrointestinal function who are unable to receive and absorb oral/enteral feeding for at least 7 days. Oxidative stress plays a major role in the ethiopathogenesis of cancers. In this study, total antioxidant status (TAS), glutathione peroxidase (GPx), superoxide dismutase, malondialdehyde and ascorbic acid were studied in patients operated because of small intestine, colorectal or pancreatic cancer and subsequently receiving TPN in comparison with patients receiving standard nutrition after the operation. TAS level and GPx activity were decreased in patients with small intestine cancer but did not differ in patients with colorectal and pancreatic cancer before and after surgery. In all patient groups receiving TPN, superoxide dismutase activity after the surgery was kept at the same level as before. On the fifth day after the surgery, malondialdehyde concentration in each group was restored to the value observed before surgery. On the fifth day of TPN treatment, ascorbic acid concentration was increased in every group of patients. TPN applied during the postoperative period alleviates oxidative stress resulting from surgery. In the case of small intestine cancer, the addition of vitamins and antioxidants to the nutrition mixture seems to result in depletion of antioxidant enzymes' activities.

Serum vitamins in adult patients with short bowel syndrome receiving intermittent parenteral nutrition

BACKGROUND

Short bowel syndrome (SBS) occurs after massive intestinal resection, and parenteral nutrition (PN) therapy may be necessary even after a period of adaptation. The purpose of this study was to determine the vitamin status in adults with SBS receiving intermittent PN.

METHODS

The study was conducted on hospitalized adults with SBS who were receiving intermittent PN therapy (n = 8). Nine healthy volunteers, paired by age and sex, served as controls. Food ingestion, anthropometry, plasma folic acid, and vitamins B(12), C, A, D, E, and K were evaluated.

RESULTS

The levels of vitamins A, D, and B(12) in both groups were similar. SBS patients presented higher values of folic acid (21.3 ± 4.4 vs 14.4 ± 5.2, P = .01) and lower values of vitamin C (0.9 ± 0.4 vs 1.2 ± 0.3 mg/dL, P = .03), α-tocopherol (16.3 ± 3.4 vs 24.1 ± 2.7 µmol/L, P < .001), and phylloquinone (0.6 ± 0.2 vs 1.0 ± 0.5 nmol/L, P < .03). Eight-seven percent of patients had vitamin D deficiency, and all patients presented with serum vitamin E levels below reference values.

CONCLUSIONS

Despite all efforts to offer all the nutrients mentioned above, SBS patients had lower serum levels of vitamins C, E, and K, similar to those observed in patients on home PN. These findings suggest that the administered vitamins were not sufficient for the intermittent PN scheme and that individual adjustments are needed depending on the patient's vitamin status.

Lipid emulsions - Guidelines on Parenteral Nutrition, Chapter 6

The infusion of lipid emulsions allows a high energy supply, facilitates the prevention of high glucose infusion rates and is indispensable for the supply with essential fatty acids. The administration of lipid emulsions is recommended within ≤7 days after starting PN (parenteral nutrition) to avoid deficiency of essential fatty acids. Low-fat PN with a high glucose intake increases the risk of hyperglycaemia. In parenterally fed patients with a tendency to hyperglycaemia, an increase in the lipid-glucose ratio should be considered. In critically ill patients the glucose infusion should not exceed 50% of energy intake. The use of lipid emulsions with a low phospholipid/triglyceride ratio is recommended and should be provided with the usual PN to prevent depletion of essential fatty acids, lower the risk of hyperglycaemia, and prevent hepatic steatosis. Biologically active vitamin E (α-tocopherol) should continuously be administered along with lipid emulsions to reduce lipid peroxidation. Parenteral lipids should provide about 25–40% of the parenteral non-protein energy supply. In certain situations (i.e. critically ill, respiratory insufficiency) a lipid intake of up to 50 or 60% of non-protein energy may be reasonable. The recommended daily dose for parenteral lipids in adults is 0.7–1.3 g triglycerides/kg body weight. Serum triglyceride concentrations should be monitored regularly with dosage reduction at levels >400 mg/dl (>4.6 mmol/l) and interruption of lipid infusion at levels >1000 mg/dl (>11.4 mmol/l). There is little evidence at this time that the choice of different available lipid emulsions affects clinical endpoints.

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.

A randomized controlled trial on parenteral nutrition, oxidative stress, and chronic lung diseases in preterm infants

OBJECTIVES

To evaluate the effect of trace elements (TEs), when added to total parenteral nutrition (TPN) solutions, on peroxides load, and to test the hypothesis that protection of TPN from light can decrease peroxides load and is associated with improvement in oxidant-related clinical outcomes in preterm infants.

SUBJECTS AND METHODS

A total of 80 preterm infants were randomized to 1 of 4 groups (n=20 each): group 1 received a mixture of dextrose and amino acids; group 2 received a mixture of dextrose, amino acids, and lipid emulsion; group 3 received dextrose, amino acids, lipid emulsion, and multivitamins (MVP); and group 4 received dextrose, amino acids, lipid emulsion, MVP, and TEs. Each group was subdivided into photo-protected and photo-exposed subgroups (n=10 each). Using ferrous oxidation of xylenol orange technique, we measured the baseline level of excreted urinary peroxides before and 48 hours after starting TPN. We examined the association among light protection, urinary peroxides, and clinical outcomes of these infants.

RESULTS

Baseline urinary peroxides ranged between 5.5 and 24.8 micromol/L. A significant increase in urinary peroxides was observed in all groups after receiving TPN. The use of TEs did not affect peroxide production. In regression analysis, the addition of MVP (P<0.0001) and the exposure to light (P=0.02) were significantly associated with increased urinary peroxides. In the overall population, light exposure was associated with a significant increase in the incidence of chronic lung disease (adjusted OR 9.26, confidence interval 1.2-73; P=0.03) but had no effect on mortality, necrotizing enterocolitis, or sepsis.

CONCLUSIONS

TEs in TPN solutions have no effect on the production of urinary peroxides. Addition of MVP and exposure of TPN to light are the 2 major sources of peroxides in TPN. Protection from ambient light is associated with a decrease in chronic lung disease.

Prospective analysis of serum carotenoids, vitamin A, and tocopherols in adults with short bowel syndrome undergoing intestinal rehabilitation

OBJECTIVE

Carotenoids, vitamin A, and tocopherols serve important roles in many key body functions. However, availability of these compounds may be decreased in patients with short bowel syndrome (SBS) due to decreased oral intake of fruits and vegetables and/or decreased intestinal absorption. Little information is available on serum concentrations of carotenoids, vitamin A, and tocopherols during chronic parenteral nutrition (PN) or during PN weaning. The aim of this study was to prospectively examine serum concentrations of a wide variety of carotenoids, vitamin A, and tocopherols in patients with SBS undergoing an intensive 12-wk intestinal rehabilitation program.

METHODS

Twenty-one PN-dependent adult patients with SBS were enrolled in a 12-wk intestinal rehabilitation program, which included individualized dietary modification, multivitamin supplementation, and randomization to receive subcutaneous placebo (n = 9) or human growth hormone (0.1 mg . kg(-1) . d(-1); n = 12). PN weaning was initiated after week 4 and advanced as tolerated. Serum concentrations of carotenoids, vitamin A, and tocopherols were determined at baseline and at weeks 4 and 12.

RESULTS

A significant percentage of subjects exhibited low serum concentrations for carotenoids and alpha-tocopherol at study entry, and a few subjects had low concentrations of retinol (5%). Carotenoid and vitamin A valves did not improve over time, while alpha-tocopherol levels rose. Serum alpha-tocopherol concentration was negatively associated with PN lipid dose (r = -0.34, P < 0.008).

CONCLUSION

Patients with SBS are depleted in diet-derived carotenoids despite oral and intravenous multivitamin supplementation and dietary adjustment during intestinal rehabilitation and PN weaning. Reduction of PN lipid infusion may improve serum alpha-tocopherol concentrations.

Influence of different intravenous lipid emulsions on hepatobiliary dysfunction in a rabbit model

OBJECTIVES

Long-term total parenteral nutrition (TPN) in children is often complicated by the development of cholestasis, liver fibrosis, and liver failure. High doses of intravenous lipids may be involved in the pathogenesis of hepatobiliary dysfunction. The purpose of this study was to determine whether the use of 2 newly developed lipid emulsions could reduce liver damage.

MATERIALS AND METHODS

Three groups of prepubescent rabbits received TPN including a lipid emulsion either based on soybean oil, olive oil, or soybean oil with n-3 fatty acids added. Enterally fed animals served as controls. After 21 d the animals were killed. Serum samples were obtained at the beginning and end of the study period. Specimens were processed for histological evaluation using a specific score to assess the severity of liver damage.

RESULTS

Biochemical parameters did not predict the extent of liver damage. Hydropic degeneration as an indicator of toxic liver injury was the predominant histological alteration regardless of the type of lipids infused. The extent of fibrosis did not significantly differ among treatment groups except for animals infused with n-3 fatty acids exhibiting increased fibrotic transformation as compared with controls.

CONCLUSION

In our animal model, the use of a lipid emulsion with a reduced amount of polyunsaturated fatty acids was not superior to a lipid emulsion based on soybean oil. Long-term application of n-3 fatty acids was associated with more extensive fibrosis. Therefore, intravenous n-3 fatty acids containing lipid preparations (fish oil) should not be used in patients for long-term TPN.

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.

Parenteral nutrition-associated liver disease and the role for isolated intestine and intestine/liver transplantation

Parenteral nutrition-associated liver disease (PNALD) is the most devastating complication of long-term parenteral nutrition therapy. Because its progression is typically insidious and its long-term consequences are generally underappreciated, PNALD is often recognized too late, when liver injury is irreversible. When end-stage liver disease (ESLD) develops in these patients, most potential interventions are futile and transplantation of both an intestine and a liver becomes the only viable option, despite the relatively poor outcomes associated with this combined procedure. Although likely multifactorial in origin, the etiology of PNALD is poorly understood. Early clinical intervention with a combination of nutritional, medical, hormonal, and surgical therapies can be effective in preventing liver disease progression. If these interventions fail, intestinal transplantation should be performed expeditiously before development of ESLD mandates simultaneous inclusion of a liver graft as well.

Endothelial function and mechanical properties of the common carotid artery in children on parenteral nutrition

Intravenous administration of nutrition mixtures induces endothelial damage and arterial wall remodeling in animal models. To study endothelial function and common carotid artery mechanical properties in children receiving parenteral nutrition, we used noninvasive ultrasonic measurements in 18 children on parenteral nutrition and 18 controls. No difference appeared in the geometry of the common carotid artery (intima media thickness, systolic and diastolic diameters) between the patients on parenteral nutrition and the controls. The incremental elastic modulus was significantly higher in the patients on parenteral nutrition (1.8 +/- 0.4 versus 1.4 +/- 0.5 4 mm Hg x 10(3), p < 0.05) reflecting alteration of the elastic properties of the arterial wall independent of the vessel geometry. The flow-mediated dilatation of the brachial artery was significantly lower in the patients on parenteral nutrition (6 +/- 3 versus 8 +/- 3%, p < 0.05), whereas the dilatation after glyceryl trinitrate administration was similar (22 +/- 9 versus 25 +/- 9%). Children on parenteral nutrition exhibit endothelial dysfunction and altered stiffness of the common carotid artery. The noninvasive methods used in this study may prove useful for objectively determining the effects of various preventive methods.

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.

Oxidized omega-3 fatty acids in fish oil inhibit leukocyte-endothelial interactions through activation of PPAR alpha

Omega-3 fatty acids, which are abundant in fish oil, improve the prognosis of several chronic inflammatory diseases although the mechanism for such effects remains unclear. These fatty acids, such as eicosapentaenoic acid (EPA), are highly polyunsaturated and readily undergo oxidation. We show that oxidized, but not native unoxidized, EPA significantly inhibited human neutrophil and monocyte adhesion to endothelial cells in vitro by inhibiting endothelial adhesion receptor expression. In transcriptional coactivation assays, oxidized EPA potently activated the peroxisome proliferator-activated receptor alpha (PPAR alpha), a member of the nuclear receptor family. In vivo, oxidized, but not native, EPA markedly reduced leukocyte rolling and adhesion to venular endothelium of lipopolysaccharide (LPS)-treated mice. This occurred via a PPAR alpha-dependent mechanism because oxidized EPA had no such effect in LPS-treated PPAR alpha-deficient mice. Therefore, the beneficial effects of omega-3 fatty acids may be explained by a PPAR alpha-mediated anti-inflammatory effect of oxidized EPA.

Lack of effectiveness of short-term intravenous micronutrient nutrition in restoring plasma antioxidant status after surgery

BACKGROUND AND AIMS

Many patients recovering from surgery may be in a state of negative antioxidant balance. For those whose postoperative nutritional requirements are provided intravenously, this may not be adequate for antioxidant repletion. This study was undertaken to assess the total antioxidant status of these patients peri-operatively and prior to beginning intravenous nutrition (IVN), and to determine the adequacy of IVN, including daily micronutrients, in maintaining or restoring antioxidant status in the post-operative period.

METHODS

Plasma total antioxidant status (TAS) was measured in 30 patients who were fed by standard IVN following surgery. Additionally, the 'antioxidant gap' (AOG, a measure of the contribution of antioxidants other than albumin and urate) was calculated. Blood samples were taken on beginning IVN and daily for the duration of IVN, which lasted for up to 26 days.

RESULTS

Prior to IVN, 20 of the 30 patients had a plasma TAS below the reference range and 15 of these 20 remained deficient even after IVN of up to 19 days. A further 3 patients became deficient whilst on IVN. When the group of patients who were deficient was compared with the group who were not, it was found that this difference was predominantly due to a difference in the AOG, (518 (115) v 709 (68) micromol/L (mean (SD)), P<0.0001). The groups did not differ in terms of age, C-reactive protein level, duration of IVN or daily thiol intake/Kg body weight.

CONCLUSIONS

The difference in the gap antioxidants was thought to be due to their utilization in opposing the extra oxidative burden of surgery. Consideration of the antioxidant provision of standard IVN, principally the thiol-containing amino acids, ascorbate, alpha -tocopherol and trace elements suggests that this is insufficient to counter the sum of the pre-existing oxidative stress and the additional oxidative burden imposed by the surgery.

Phospholipid hydroperoxide glutathione peroxidase activity and vitamin E level in the liver microsomal membrane: effects of age and dietary alpha-linolenic acid deficiency

Age and diet-induced variations of phospholipid hydroperoxide glutathione peroxidase (PHGPx) activity and alpha-tocopherol concentration in the liver microsomal membrane were studied in male Wistar rats fed a semipurified diet either balanced in n-6 and n-3 polyunsaturated fatty acids (PUFA) (Control) or deprived of alpha-linolenic acid, i.e. n-3 PUFA (Deficient) over two generations. The animals were studied at the age of 6 months (adult) or 24 months (old). Both PHGPx activity and vitamin E level were significantly higher in 24-month old rats as compared to 6-month old rats. By contrast, the thiobarbituric acid reactive substances (TBARS) following stimulated in vitro peroxidation of membrane lipids were markedly lower (P < 0.01) with aging. The fatty acid composition of microsomal membrane phospholipids (PL) was also considerably modified by age. In particular, the levels of arachidonic acid and total n-6 PUFA were lower (P < 0.001) whereas n-3 PUFA levels were higher (P < 0.001) in most PL main classes. The alpha-linolenic acid deficiency markedly influenced these age-related changes. The higher PHGPx activity in the old rats as compared to the adult rats was only significant in those fed the control diet. In the 6-month old rats (but not in the 24-month old rats), the deficient diet led to a higher membrane vitamin E level and to lower TBARS production than the control diet. The results suggest that the nature of dietary PUFA may influence the age-related variations in this pair of membrane antioxidants and also in the fatty acid composition of microsomes.

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.

New developments in total parenteral nutrition for children

The field of parenteral nutrition continues to evolve along two major paths: prevention of complications and refining of nutritional needs. Parenteral nutrition-associated liver disease remains a vexing problem. No single factor is to blame; rather, it requires a number of "hits." In the infant, the liver disease primarily appears to be related to prematurity of bile flow and production, infection, lack of enteral feedings, and most recently appreciated, perhaps free radicals. We are able to meet the nutritional needs of our patients, but our knowledge of actual nutritional requirements remains incomplete. Future studies need to define better appropriate intakes and to rigorously test the utility of proposed nutrients such as glutamine.

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.

Growth factors and nutrients in the short bowel syndrome

Massive intestinal resection often results in long-term dependence on parenteral nutrition (TPN). In an effort to enhance bowel rehabilitation, the amino acid glutamine, growth hormone and a diet optimized to enhance absorption have been administered to >300 patients with the short bowel syndrome. Initially about 60% of the patients were weaned from TPN and an additional 30% had reduced TPN requirements. At long-term follow up (2 years) 40% of the group remained off TPN, 40% had reduced TPN requirements, and 20% had the same requirements. This report addresses issues such as the optimization of diet and provides a care map which should enhance the rehabilitation of patients with the short bowel syndrome.

Home artificial nutrition

Home artificial nutrition is a mature technology that has been with us for over a quarter of a century. Its use appears to be more widespread in the USA than in other western countries. Issues of outcome, ethics, and quality of life are increasingly important. Complications continue to be reported, some newly recognized and some that we must continually relearn.

Are metals dietary carcinogens?

Humans have been in contact with metals almost since the beginning of our existence. In fact, one cannot even think on human evolution without considering the great role played by metals in mankind's development. Metals are common moieties of molecules involved in a wide variety of biological processes, and hence are found in virtually all living organisms. Some metals are essential for human nutrition; others are found as contaminants in foodstuffs. One feature of the normal human diet which is frequently found is the simultaneous presence of both essential and toxic metals. Other factors important in the risk-evaluation analysis of metals are their pharmacokinetics, interactions among them and with other major components of the diet, and, especially, the great differences in the dietary habits of different populations and in the regional distribution of metals. In attempting to understand the role which dietary metals could play in human carcinogenesis, we found that the many factors involved and the lack of specific information made it difficult to reach firm conclusions on the hazards of dietary metals. We hope that this paper will raise the interest of genetic toxicologists in the subject and will consequently facilitate a risk analysis of the carcinogenic potential of dietary metals.

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.