Total Hydroperoxides Research Articles

PWE-133 Vascular inflammation is associated with endothelial dysfunction and oxidative stress in patients with non-alcoholic fatty liver disease

Introduction Individuals with non-alcoholic fatty liver disease (NAFLD) have a significantly increased risk of cardiovascular (CV) disease independent of other cardiometabolic risk factors. We explored the relationship between endothelial function, oxidative stress, vascular inflammation and insulin resistance in patients with NAFLD. Method Patients with proven NAFLD but without cirrhosis were recruited into the study and the following parameters were assessed: Endothelial function – change in reflective index post salbutamol using digital plethysmography, urine albumin:creatinine ratio, plasma vascular cell adhesion molecule-1 (VCAM-1) and plasma cyclic guanosine monophosphate (cGMP) Oxidative stress – blood glutathione ratio (GSH:GSSG), plasma total anti-oxidant status and plasma lipid hydroperoxides Inflammation – highly-sensitive plasma CRP Insulin resistance – HOMA-IR Results We studied 42 patients: 31 males and 11 females. We found 79% had T2DM or impaired fasting glucose. Mean age was 58 ± 8 years, BMI 33.2 ± 5.5 kg/m 2 , BP 133/82 ± 12/7 mmHg, duration of NAFLD diagnosis 1.0 ± IQR 3.4 years, HbA1c 53 ± 13 mmol/mol, total cholesterol 4.43 ± 1.14 mmol/l, HDL 1.06 ± 0.32 mmol/l, LDLc 2.51 ± 1.02 mmol/l, and triglycerides 1.93 ± 0.85 mmol/l. There was moderate correlation between VCAM-1 and hsCRP (Spearman’s rho=0.392, p = 0 .01); moderate correlation between hsCRP and blood glutathione ratio (Spearman’s rho=0.325, p = 0.04) and moderate correlation between HOMA-IR and aspartate aminotransferase [AST] (Spearman’s rho=0.489, p = 0 .001). Conclusion Markers of both vascular (VCAM-1) and systemic low grade inflammation (hsCRP) were associated with evidence of endothelial dysfunction and oxidative stress, whilst insulin resistance was associated with AST in non-cirrhotic patients with NAFLD. VCAM-1 as a marker of endothelial activation may be a potential CV risk predictor in this group of patients. Disclosure of interest None Declared.

UV-B radiation induces biphasic burst of hydrogen peroxide in mesophyll Chlorella vulgaris

The fluctuations of hydrogen peroxide and total hydroperoxides were followed up at different time points in UV-B-irradiated cell suspension cultures of the green microalga Chlorella vulgaris. A biphasic burst of hydrogen peroxide was recorded, while cell viability was strongly reduced. This pattern is similar to the two wave oxidative burst in plants expressing hypersensitive response to pathogens and PCD and implies the occurrence of a PCD-like response in UV-B-exposed unicellular green algae.

Monitoring peroxides generation during model wine fermentation by FOX-1 assay

The quality of wine is mainly determined during the alcoholic fermentation that gradually transforms the grape juice into wine. Along this process the yeast goes through several stressful stages which can affect its fermentative ability and industrial performance, affecting wine quality. Based on their actual application on industrial winemaking, commercial Saccharomyces cerevisiae strains (EC1118, QA23, VIN7 and VL3) were used. They were inoculated in batch laboratory fermentations in a model wine solution for evaluating the production of reactive oxygen species (ROS) during the yeast’s alcoholic fermentation. For first time total hydroperoxides were determined by FOX-1 assay to follow ROS generation. The total hydroperoxides accumulated along the 10days of fermentation peaked up to 10.0μM in yeast EC1118, of which 1.3μM was hydrogen peroxide (H2O2). The FOX-1 based analytical approach herein presented is a valuable tool for the quantification of ROS oxidative damage during winemaking.

Estresse oxidativo sistêmico e folicular em mulheres inférteis com endometriose submetidas à injeção intracitoplasmática de espermatozoide

ObjectivesThe aim of the study was to compare eight oxidative stress (OS) markers in serum and follicular fluid (FF) of infertile women with and without endometriosis (E) undergoing controlled ovarian stimulation (COS) for intracytoplasmic sperm injection (ICSI). Material and methodsEight‐seven serum samples (43 with E and 44 without E ‐ with male or tubal factor) and 61 FF samples (29 with E and 32 without E) were collected in the day of oocyte retrieval. Total hydroperoxides (FOX1), malondialdehyde (MDA), advanced oxidation protein products (AOPP), glutathione (GSH), superoxide dismutase (SOD) and the total antioxidant capacity (TAC) were determined by spectrophotometry, vitamin E (Vit E) by high performance liquid chromatography, and 8‐hydroxy‐2’–deoxyguanosine (8OHdG) by ELISA. ResultsWe observed higher serum concentrations of GSH (220.32±43.2 nmol/g pt) and SOD (677.9±282.21 U/mL), lower serum concentrations of TAC (0.34±0.17 mEq Trolox/L), and higher follicular concentrations of 8OHdG (23.19±6.8ng/mL) and Vit E (13.0±5.33μmol/L) in infertile women with E compared to those without E (193.92±43.25 nmol/g pt, 563.04±169.82 U/mL, 0.46±0.15 mEq Trolox/L, 17.22±5.6ng/mL and 8.71±2.51μmol/L, respectively). ConclusionsWe evidenced the occurrence of systemic and follicular OS in infertile patients with E undergoing COS for ICSI. We suggest that the OS may be involved in the etiopathogenesis of infertility‐related disease

MnSOD overexpression reduces fibrosis and pro-apoptotic signaling in the aging mouse heart.

Contractility of the heart is impaired with advancing age via mechanical remodeling, as myocytes are lost through apoptosis and collagenous fibers accumulate. Exercise training confers protection against fibrosis and apoptosis in the aging heart, but the mechanisms remain poorly understood. We recently reported that exercise training elevates Mn isoform of superoxide dismutase (MnSOD) in the aging heart, concomitant with reduction in oxidative stress and fibrosis. Here, we tested the hypothesis that overexpression of MnSOD would be causal in protection against fibrosis and apoptosis in the aging heart. Hearts were extracted from young (8 months) wild-type, young mice overexpressing the Sod2 (MnSOD) gene, old (28 months) wild-type, and old transgenic mice. Left ventricle MnSOD protein levels were elevated in young mice overexpressing the Sod2 (MnSOD) gene and old transgenic mice. MnSODTg mice exhibited lower oxidative stress (total hydroperoxides, 4-hydroxynonenal, and 8-isoprostane) in the old group. Age-related cardiac remodeling and fibrosis was mitigated in MnSOD Tg mice with reductions in extramyocyte space (-65%), collagen-I, and transforming growth factor-β. Pro-apoptotic markers Bax (-38%) and caspase-3 cleavage (-41%) were reduced and apoptosis (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive nuclei, DNA laddering) was mitigated in MnSOD Tg hearts compared with old wild-type. We conclude that MnSOD elevation is indeed protective against oxidative stress, fibrosis, and apoptosis in the aging heart.

Oxidative Stress and Antioxidant Defences in the Tasar Silkworm Antheraea mylitta D: Challenged with Nosema Species

This study was designed to find out the effect of Nosema spore on oxidative damages and antioxidant defence in the midgut of tasar silkworm Antheraea mylitta. Higher level of lipid peroxidation (LPX) and total hydroperoxides indicate the resultant oxidative stress in the Nosema exposed specimen. Increased superoxide dismutase (SOD) suggests activation of physiological mechanism to scavenge the superoxide radical produced during Nosema infection. Higher activities of catalase and glutathione-S-tranferase on 18 th d indicate adaptive behaviour of the tissue against oxyradicals. The results suggest that Nosema infection is involved in altering the active oxygen metabolism by modulating LPX and reactive oxygen species (ROS), which is indicative of pebrine disease disorder.

Lipid and protein oxidation in newborn infants after lutein administration.

Objectives. To test the hypothesis that neonatal supplementation with lutein in the first hours of life reduces neonatal oxidative stress (OS) in the immediate postpartum period. Methods. A randomized controlled, double-blinded clinical trial was conducted among 150 newborns divided into control group, not supplemented (n = 47), and test group, supplemented with lutein on the first day postpartum (n = 103). Blood Samples were collected at birth from cord and at 48 hrs postpartum while routine neonatal metabolic screenings were taking place. Total hydroperoxide (TH), advanced oxidation protein products (AOPP), and biological antioxidant potential (BAP) were measured by spectrophotometry and data were analyzed by Wilcoxon rank sum test and by multivariate logistic regression analysis. Results. Before lutein supplementation, the mean blood concentrations of AOPP, TH, and BAP were 36.10 umol/L, 156.75 mmol/H2O2, and 2361.04 umol/L in the test group. After lutein supplementation, significantly higher BAP increment (0.17 ± 0.22 versus 0.06 versus ± 0.46) and lower TH increment (0.46 ± 0.54 versus 0.34 ± 0.52) were observed in the test group compared to controls. Conclusion. Neonatal supplementation with lutein in the first hours of life increases BAP and reduces TH in supplemented babies compared to those untreated. The generation of free radical-induced damage at birth is reduced by lutein. This trial is registered with ClinicalTrials.gov NCT02068807.

Natural surfactant combined with superoxide dismutase and catalase decreases oxidative lung injury in the preterm lamb

We performed a randomized study in preterm lambs to assess the hypothesis that treatment with a natural surfactant combined with superoxide dismutase (SOD) and catalase (CAT) might decrease pulmonary oxidative stress in an animal model of respiratory distress syndrome (RDS). Animals received 200 mg/kg of porcine natural surfactant or 200 mg/kg of natural surfactant combined with 2 mg/ml of SOD and 3,000 U/ml of CAT. Lung tissue oxidation was studied by measuring total hydroperoxide (TH), advanced oxidation protein products (AOPP), and non-protein bound iron (NPBI) in bronchial aspirate samples. In addition, the animal's lung mechanics were evaluated. TH, AOPP, and NPBI were lower in the groups treated with surfactant plus SOD and CAT than in the surfactant group, while lung mechanics did not vary. We concluded that natural surfactant combined with SOD and CAT is effective in reducing the oxidative lung stress in an animal model of RDS.

Resuscitation of Preterm Neonates With Limited Versus High Oxygen Strategy

To determine whether a limited oxygen strategy (LOX) versus a high oxygen strategy (HOX) during delivery room resuscitation decreases oxidative stress in preterm neonates. A randomized trial of neonates of 24 to 34 weeks' gestational age (GA) who received resuscitation was performed. LOX neonates received room air as the initial resuscitation gas, and fraction of inspired oxygen (Fio2) was adjusted by 10% every 30 seconds to achieve target preductal oxygen saturations (Spo2) as described by the 2010 Neonatal Resuscitation Program guidelines. HOX neonates received 100% O2 as initial resuscitation gas, and Fio2 was adjusted by 10% to keep preductal Spo2 at 85% to 94%. Total hydroperoxide (TH), biological antioxidant potential (BAP), and the oxidative balance ratio (BAP/TH) were analyzed in cord blood and the first hour of life. Secondary outcomes included delivery room interventions, respiratory support on NICU admission, and short-term morbidities. Forty-four LOX (GA: 30 ± 3 weeks; birth weight: 1678 ± 634 g) and 44 HOX (GA: 30 ± 3 weeks; birth weight: 1463 ± 606 g) neonates were included. LOX decreased integrated excess oxygen (∑Fio2 × time [min]) in the delivery room compared with HOX (401 ± 151 vs 662 ± 249; P < .01). At 1 hour of life, BAP/TH was 60% higher for LOX versus HOX neonates (13 [9-16] vs 8 [6-9]) µM/U.CARR, P < .01). LOX decreased ventilator days (3 [0-64] vs 8 [0-96]; P < .05) and reduced the incidence of bronchopulmonary dysplasia (7% vs 25%; P < .05). LOX is feasible and results in less oxygen exposure, lower oxidative stress, and decreased respiratory morbidities and thus is a reasonable alternative for resuscitation of preterm neonates in the delivery room.

Comparative study of total hydroperoxides and antioxidant defense system in the Indian tropical tasar silkworm, Antheraea mylitta, in diapausing and non-diapausing generations.

In the present study, the total hydroperoxides, catalase, glutathione-s-transferase, and ascorbic acid contents were determined in different developmental stages of the non-diapause and the diapause generation of the tropical tasar silkworm, Antheraea mylitta Drury (Lepidoptera: Saturniidae). The results showed stage-specific significantly higher levels of total hydroperoxides, catalase, and ascorbic acid contents in the non-diapause as compared to the diapause generation (p < 0.05). However, a significantly enhanced level of glutathione-S-transferase activity was observed in mature 5th instar larvae of the diapause generation (p < 0.05). In the case of pupae, significantly higher levels of total hydroperoxides, catalase, and glutathione-s-transferase activity were observed in the non-diapause generation (p < 0.05). These results could be the effect of intensive metabolic transformation that takes place in tissues of the non-diapause generation and causes increased production of reactive oxygen species, such as hydroperoxides. The results suggest that antioxidants play an important role in protecting cells against reactive oxygen species.

Investigation of Lipid Peroxidation Products and Antioxidant Enzyme Activities in End-Stage Renal Disease Patients

Background: Intravenous application of iron preparations which is a routine treatment of anemia in hemodialysis patients with end-stage renal disease can lead to iron overload in the body. Redox-active iron can catalyze the formation of hydroxyl radicals and initiation of lipid peroxidation, increase oxidative stress and speed up the development of complications in these patients. Objective: In this study, we determined the markers of lipid peroxidation, protein oxidation and antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase, glutathione S-transferase) in serum of patients with end-stage renal disease on hemodialysis, who had received repeated treatment of iron supplementation. Patients and Methods: The study included 29 patients undergoing regular hemodialysis treatment. These patients were divided into three groups according to the serum ferritin levels: group I (serum ferritin between 100 and 300 mg/L); group II (serum ferritin between 301 and 600 mg/L), and group III (serum ferritin above 601 mg/L). Results: The serum of patients with the highest concentration of serum ferritin and iron contained significantly higher level of lipid peroxidation products, total hydroperoxides and malondialdehyde and advanced oxidation protein products and the lowest concentration of sulfhydryl groups, reduced glutathione and total antioxidant capacity. Conclusion: Based on the obtained results, it can be concluded that iron supplementation in hemodialysis patients and consequently body iron overload of exacerbated oxidative stress have already been present in these patients.

Relationship between oxidant and antioxidant activity in hyperemesis gravidarum

Objective: To evaluate oxidant and antioxidant activity in patients with hyperemesis gravidarum (HG) by using serum total antioxidant activity (TAO), total free sulfhydryl (–SH), ceruloplasmin and lipid hydroperoxide (LOOH) levels.Materials and methods: In a cross-sectional trial, blood samples were collected from patients with HG (n = 25) and healthy pregnant women (n = 25) as control group. Serum TAO activities, –SH levels and LOOH levels and ceruloplasmin levels were measured.Results: Serum TAO activity was found to be significantly lower (p = 0.003) in patients with HG compared with controls. However, serum –SH levels, LOOH levels and ceruloplasmin levels did not change significantly in patients with HG compared to controls.Conclusion: Presence of oxidative stress in HG patients depends more on reduced antioxidant activities than increased oxidative stress.

Development of a chemiluminescent method for the evaluation of total hydroperoxide content of edible oils

One of the most important quality indices of edible oils is the total hydroperoxide content expressed as peroxide value (PV). Oils with high hydroperoxide content show a degree of oxidation and, hence, lower quality. For these reasons, the development of methods for the evaluation of this quality index of edible oils is required.The aim of the present work is to develop, a rapid, accurate, sensitive, simple and low cost chemiluminescence (CL) method for the determination of the total hydroperoxide content of different kinds of olive oils and other types of edible oils. The CL method proposed is based on the chemiluminescent reaction of alkaline luminol and the hydroperoxides of oil, catalyzed by Fe(III) using 1-propanol as the reaction solvent. Calibration curves of the CL intensity as a function of concentration of di-tert-butyl peroxide, used as an external peroxide standard, and of different types of edible oils were prepared. In all the cases the correlation coefficient (R) of the regression lines was satisfactory (R>0.996). The precision of the method expressed in terms of repeatability and reproducibility was also satisfactory, as repeatability in terms of mean %RSD was 4.8% and reproducibility in terms of mean %RSD was 8%. The method was applied for the evaluation of total hydroperoxide content of olive oils, corn oils, sunflower oils, sesame oils and soybean oils, within the concentration range of 0.1–9.0%v/v and the obtained results were compared with those of the official method for peroxide value. Finally, the different types of olive oils and seed oils have been classified according to their estimated total hydroperoxide content.

Effects of temperature on modulation of oxidative stress and antioxidant defenses in testes of tropical tasar silkworm Antheraea mylitta

High temperatures are known to cause physiological stress in organisms. This is often associated with enhanced generation of reactive oxygen species (ROS) leading to oxidative damage. The commercially important tropical tasar silkworm Antheraea mylitta has to endure high summer temperature before egg production on the onset of monsoon. In this study the status of pro-oxidants and antioxidants was studied in the testes of male pupae of tasar silkworm A. mylitta under thermal stress condition. Further, to find out the impact of temperature on physiological activity, oxygen consumption rate was measured. The result indicated higher level of thiobarbituric acid reactive substances (TBARS, as an index of lipid peroxidation) and total hydroperoxides in the male pupae exposed to high temperature (40±1°C). Similarly, it was found that increased levels of antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), ascorbic acid (ASA) and low molecular thiols (L-SH) in testes are more prominent in high temperature rather than in moderate temperature (35±1oC) suggesting the activation of physiological mechanism to scavenge the ROS produced during stress. Further more, the order of higher level of oxygen consumption rate was observed as high temperature (40±1°C) > moderate temperature (35±1°C) > control groups (28±1°C). Oxygen consumption rate was positively correlated with oxidative stress and antioxidant defence indices. We infer from these findings that the testes of A. mylitta pupae modulate testicular antioxidant responses to thermal stress.

Effects of astaxanthin on antioxidation in human aqueous humor

We evaluated the antioxidative effects of astaxanthin through the changes in superoxide scavenging activity, levels of hydrogen peroxide and total hydroperoxides in human aqueous humor. The study subjects were 35 patients who underwent bilateral cataract surgery on one side before and the other side after intake of astaxanthin (6 mg/day for 2 weeks). Their aqueous humor was taken during the surgery and subjected to measurements of the three parameters. After astaxanthin intake, the superoxide scavenging activity was significantly (p<0.05) elevated, while the level of total hydroperoxides was significantly (p<0.05) lowered. There was a significant negative correlation between the superoxide scavenging activity and the level of total hydroperoxides (r = −0.485, p<0.01), but no correlations between the hydrogen peroxide level and the other two parameters. Astaxanthin intake clearly enhanced the superoxide scavenging activity and suppressed the total hydroperoxides production in human aqueous humor, indicating the possibility that astaxanthin has suppressive effects on various oxidative stress-related diseases.

Determination of total plasma hydroperoxides using a diphenyl-1-pyrenylphosphine fluorescent probe

Plasma hydroperoxides (HPs) are widely accepted to be good indicators of oxidative stress. By means of the method proposed here, which uses diphenyl-1-pyrenylphosphine (DPPP) as a fluorescent probe, all types of plasma HP were determined. The limits of detection and quantification of the method were 0.08 and 0.25nmol of cumene hydroperoxide (CHP) equivalents in 40μl of plasma, respectively. The method is satisfactory in terms of precision (5.3% for 14.5μM CHP eq., n=8), and the recoveries were 91% and 92% after standard additions of 26 and 52μM CHP, respectively. The selectivity of the proposed method is higher than 96%. Moreover, optimization of the reaction conditions and the addition of ethylenediaminetetraacetic acid (EDTA) disodium salt and 2,6-di-tert-butyl-4-methylphenol (BHT) prevented the formation of HP artifacts during the analysis. Therefore, the proposed method is useful for simple and quantitative determination of total plasma HPs.

Thioredoxin-1 and oxidative stress status in pregnant women at early third trimester of pregnancy: relation to maternal and neonatal characteristics

This study examined the clinical and biological importance of thioredoxin-1, a redox-active defensive protein that controls multiple biological functions, in pregnant women. We measured serum concentrations of thioredoxin-1, total hydroperoxides, and redox potential in 60 pregnant women at the early third trimester: gestational age of 27–29 weeks. The thioredoxin-1 concentration (mean ± SD) was 90 ± 42 ng/ml. Total hydroperoxides was 471 ± 105 U.CARR (1 U.CARR = 0.08 mg/dl H2O2). Redox potential was 2142 ± 273 µmol/l. The total hydroperoxides: redox potential ratio (oxidative stress index) was 0.23 ± 0.08. Thioredoxin-1, total hydroperoxides, and oxidative stress index were higher and redox potential was lower than in blood of healthy adults. Total hydroperoxides and redox potential were mutually correlated significantly and negatively. Thioredoxin-1 correlated significantly and negatively and redox potential correlated significantly and positively with body weight and body mass index. Thioredoxin-1 and redox potential correlated significantly and positively with uric acid and albumin, respectively. Thioredoxin-1 and oxidative stress index correlated significantly and negatively and redox potential significantly and positively with neonatal birth weight. These results suggest that high concentrations of thioredoxin-1 are linked to high oxidative stress status in pregnant women and that neonatal birth weight is affected by the maternal oxidative condition during later pregnancy.

Endothelin receptor antagonist attenuates oxidative stress in a neonatal sepsis piglet model

Oxidative stress (oxidant-antioxidant imbalance) plays an important role in the pathophysiology of neonatal sepsis. This study evaluated whether an antisense peptide endothelin receptor antagonist, ETR-P1/fl, could attenuate oxidative stress in a neonatal sepsis model. A total of 18 3-d-old piglets were anesthetized and mechanically ventilated. Six piglets received cecal ligation and perforation (CLP group) for induction of sepsis. Six piglets also received continuous infusion (0.05 mg/kg/h) of ETR-P1/fl 30 min after CLP (ETR-P1/fl group). Six piglets received a sham operation. Serum total hydroperoxide (TH), biological antioxidant potentials (BAPs), oxidative stress index (OSI, calculated as TH/BAP), interleukin (IL)-6, serum glutamic oxaloacetic transaminase (GOT), and creatinine were measured before CLP and at 1, 3, and 6 h after CLP. CLP evoked a state of shock resulting in elevated TH, OSI, and IL-6 levels. ETR-P1/fl administration after CLP resulted in lower serum TH at 1 and 3 h after CLP, OSI at 1 and 3 h after CLP, IL-6 at 1 and 3 h after CLP, and GOT at 3 and 6 h after CLP as compared with the CLP group. ETR-P1/fl treatment significantly attenuated the elevation of serum oxidative stress markers (TH and OSI), IL-6, and GOT in a progressive neonatal sepsis CLP model.

Method for the simultaneous determination of free/protein malondialdehyde and lipid/protein hydroperoxides

A simple and sensitive method is presented for the simultaneous quantification (spectrophotometric and spectrofluorimetric) of the main lipid and protein peroxidation products after their initial fractionation: free malondialdehyde (FrMDA), protein-bound malondialdehyde (PrMDA), total hydroperoxides (LOOH), and protein hydroperoxides (PrOOH). FrMDA and PrMDA (released from proteins by alkaline hydrolysis) are measured after the reaction of MDA with thiobarbituric acid (TBA) under acidic conditions, by the specific fluorimetric quantification of the resulting MDA–(TBA)2 adduct chromophore. The measurement of LOOH and PrOOH is based on the reaction of Fe3+ (resulting from the reaction of LOOH and PrOOH with Fe2+) with xylenol orange (XO) and the photometric quantification of the resulting XO–Fe complex. The sensitivity of the assays for FrMDA/PrMDA and LOOH/PrOOH is 20 and 100pmol, respectively. The method was applied successfully on human plasma and can be used for the evaluation of oxidative stress in both basic and clinical research.

Lipofundin 20% induces hepatic lipid peroxidation in New Zealand white rabbits

ABSTRACTObjective. The aim of the present work was to evaluate the effects of Lipofundin 20% on lipid peroxidation markers in the liver of New Zealand white rabbits. Materials and methods. The animals were treated with an intravenous injection (2 ml/kg) of the lipid emulsion during 8 days through the marginal ear vein. At the end of the experiment some lipid peroxidation parameters and lipid profile were tested through spectrophotography. Results. Lipofundin was found to induce a significant (p&lt;0.05) increase of malondialdehyde, total hydroperoxides, and peroxidation potential. Also, high levels of total cholesterol, triglycerides, LDL - cholesterol and HDL-cholesterol were observed in treated animals compared with the control group (p&lt;0.05). Conclusions. Data proved that Lipofundin induces hepatic lipid peroxidation in rabbits, mainly through a mechanism which involves an induction of hyperlipidemia