L-Arginine reduces lipid peroxidation in patients with diabetes mellitus

A current concept for the development of diabetic long-term complications is the involvement of oxidative stress, as, e.g., lipid peroxidation, in the diabetic state. Data published recently show also oxidative damage to DNA, which might be one factor for accelerated aging and diabetic microangiopathy. In our study we tested the hypothesis that L-arginine can reduce lipid peroxidation in patients with diabetes. We performed a blind placebo controlled study with crossing over two treatment periods for 3 months. Thirty patients with diabetes mellitus were randomly assigned to treatment group A (first treatment then placebo) and B (first placebo then treatment). Treatment consisted of two daily dosages of 1 g L-arginine free base. Lipid peroxidation as reflected by malondialdehyde was evaluated in urine using a standard HPLC assay. After 3 months of treatment there was a significant reduction in malondialdehyde levels in group A (p < .0032), whereas there was no difference compared to the baseline values after three months of placebo treatment in group B (p < .97). After crossing over, there was a significant reduction in malondialdehyde levels in group B (p < .0002). Group A showed a significant increase in malondialdehyde levels (p < .0063) returning to baseline values. L-Arginine treatment was able to reduce the lipid peroxidation product malondialdehyde. This provides evidence that treatment with L-arginine may counteract lipid peroxidation and thus reduce microangiopathic long-term complications in diabetes mellitus.

Vitamin E decreases urine lipid peroxidation products in young healthy human volunteers under normal conditions

An experimental study on the effects of supplementation with antioxidant vitamins on urine lipid peroxidation products was performed in 21 young healthy men. The subjects ingested placebo, 1 g of vitamin C, or 100 mg of vitamin E per day just after the midday meal during 30 days. Urine samples were obtained 0, 15 and 30 days after the beginning of the study. These samples were analyzed by spectrophotometry or fluorometry after reaction with thiobarbituric acid. Prescan fluorometric studies of the thiobarbituric acid reactive substances in both malondialdehyde standards and urine samples indicated 503 nm and 548 nm as optimum excitation and emission wavelengths. The fluorescence measurements proved to be superior both in terms of selectivity and capacity of detection of antioxidant effects in relation to spectrophotometry. Identical emission peaks were obtained with malondialdehyde standards and urine samples, showing the specificity of the fluorometric method. When measured by fluorometry, the urine of the subjects supplemented with vitamin E showed significantly and progressively smaller lipid peroxidation products as the time of supplementation increased, reaching a 27% decrease at the end of the longitudinal trial. The results indicate the usefulness of the fluorescent measurement of urine thiobarbituric acid reactive substances to easily and rapidly detect variations in whole body oxidative stress in humans. They also show the capacity of safe vitamin E dietary doses to decrease endogenous oxidative stress in healthy humans routinely performing their normal activities.

alpha-Tocopherol influences in vivo indices of lipid peroxidation in postmenopausal women given fish oil

Although diets containing fish have been shown to be therapeutically valuable, the vitamin E requirement when large quantities of (n-3) fatty acids are consumed is not known. Additionally, as estrogens may function as an antioxidant, the requirement may be modified in postmenopausal women using hormone replacement therapy (HRT). Consequently, the purpose of this study was to measure the impact of graduated doses of RRR-alpha-tocopheryl acetate (TA) on in vivo indices of lipid peroxidation in postmenopausal women with and without hormone replacement therapy when given a supplement of fish oil. Forty-eight postmenopausal women, half receiving (+HRT) and half not receiving (-HRT) hormone replacement therapy, participated in a four-period, double-blind crossover trial. Each period lasted 5 wk followed by a 4-wk washout interval. During each period, the subjects consumed a 15-g supplement of fish oil and either 0, 100, 200, or 400 mg TA/d in a balanced, single square dosing order. Plasma levels of (n-3) fatty acids were significantly higher after fish oil supplementation; alpha-tocopherol concentration of plasma was significantly higher at each level of supplementation compared with the level without supplementation. Urinary excretion of thiobarbituric acid reactive substances (TBARS) and malondialdehyde, measured as the thiobarbituric-malondialdehyde adduct (TRA-MDA adduct), and the plasma concentration of the adduct were significantly greater after the fish oil supplement. Although urinary TBARS decreased linearly as the dose of TA increases (P < or = 0.05), urinary and plasma concentrations of TBA-MDA adduct did not. This study suggests that the evaluation of highly unsaturated fatty acids as oxidative stressors requires several measures of assessment.

Urinary malondialdehyde and 8-hydroxydeoxyguanosine as potential markers of oxidative stress in industrial art glass workers

Previous epidemiological studies have indicated that industrial art glass workers have increased mortality risks for certain types of cancer and for cardio- and cerebrovascular disease. To test the hypothesis that increased oxidative stress might contribute to these increased mortality risks, the urinary levels of the lipid peroxidation product, malondialdehyde (MDA), and the oxidative DNA adduct, 8-hydroxydeoxyguanosine (8OHdG) were determined in 343 workers (230 men and 113 women) from the art glass industry in the southeast of Sweden. Of the study subjects, 199 (181 men and 18 women) were engaged in the process of glass production and were regarded as exposed, whereas the remainders performed clerical, warehouse and other service work and were regarded as unexposed. One hundred and sixteen were smokers (75 men and 41 women) and 215 were non-smokers (142 men and 73 women). The findings indicate that (a) exposure to industrial art glass work per se does not cause any major oxidative stress as measured by urinary levels of MDA and 8OHdG, (b) the effects from smoking per se are limited to increased lipid peroxidation among men, and (c) joint exposure to industrial art glass work and smoking may cause increased lipid peroxidation among men and increased DNA hydroxylation among both men and women. While these findings provide no evidence for increased oxidative stress due to industrial art glass work per se, the increased 8OHdG excretion, in workers who smoke may be associated with a higher risk of developing free radical-dependent degenerative diseases including cancer.

Serum and urine malondialdehyde levels in NIDDM patients with and without hyperlipidemia

Malondialdehyde (MDA), a marker of lipid peroxidation, was measured as thiobarbituric acid reactive substance (TBARS) in 78 noninsulin-dependent diabetic patients, 38 hyperlipidemic patients, and 28 healthy subjects. Diabetic patients were divided into groups and subgroups according to the existence of hyperlipidemia and other complications. Serum and urine MDA concentrations were significantly higher in diabetic and nondiabetic patient groups than in the control group. By contrast to urine MDA levels, serum MDA level was significantly higher in hyperlipidemic diabetics than that of normolipidemic diabetics. Serum MDA levels in the hyperlipidemic diabetic group and urine MDA levels in both diabetic groups were significantly higher than those in hyperlipidemic nondiabetic group. In both diabetic groups, the existence of complications didn't affect serum and urine MDA levels. No correlation existed between serum and urine MDA levels in both patient groups and control subjects. This study confirmed the existence of lipid peroxidation disorders in diabetic patients.

Urinary malondialdehyde-equivalents during ingestion of meat cooked at high or low temperatures

Excretion of malondialdehyde (MDA)-generating substances in the urine has been suggested as an indicator of in vivo lipid peroxidation. However, MDA in the urine also reflects the amount of lipid peroxidation products consumed in the diet. We determined MDA as the thiobarbituric acid (TBA)-MDA complex in urine of 19 healthy adults (10 male and 9 female) fed large quantities (3.6-4.1 g/kg body weight) of ground beef cooked at a low or a high temperature. Subjects ate a controlled diet with no alcohol or nutritional supplements. For 7 d they consumed ground beef cooked at 100 degrees C for 20 min (low-temperature meat) followed by 7 d with meat fried at 250 degrees C for 22 min (high-temperature meat). Prior to the study, subjects consumed their normal free choice diet with moderate amounts of meat. The concentration of MDA in urine at baseline was 2.1 +/- 0.3 mumol TBA-MDA equivalents/day (mean +/- SEM). After 7 d of low-temperature meat, urinary TBA-MDA equivalents increased to 23.1 +/- 1.4 mumol/d. Urinary TBA-MDA equivalents were consistently lower (6.9-8.0 mumol/d) 1, 2, 3, and 7 d after subjects changed to high-temperature meat. After 7 d of treatment, 97% of the MDA-equivalents in the meat was recovered in 24-h urine samples. The low temperature meat had 3-4 times more MDA than did the high-temperature meat. These data indicate that the amount of meat eaten and the cooking procedures used can dramatically alter urinary MDA. Dietary sources of MDA must be controlled if urinary MDA is to be used as an indicator of oxidative stress.

Relations between copper, zinc and selenium intakes and malondialdehyde excretion after major burns

Copper, zinc and selenium are involved in free radical scavenging. As trace element status is altered after major burns, related free radical scavenging may be decreased: consequently lipid peroxidation, reflected by increased urinary malondialdehyde excretion (MDA), is considerably increased. This preliminary study aimed to investigate the relationship between trace elements and MDA excretion. Sixteen patients aged 34 +/- 9 years (mean +/- s.d.) burned over 37 +/- 11 per cent of body surface, were studied prospectively. Trace element balance studies from days 1 to 7 and serum and urine concentrations on days 10, 15, 20 and 25 were measured. The first 11 patients (groups 1--SBU < 80, and 2--SBU > or = 80) were given standard supplements and the five next patients increased supplements (group 3, SBU > or = 80). The MDA excretion from days 1 to 3 was correlated with burn severity (r = 0.59). The correlations between serum trace element levels after day 3 and MDA were negative: Cu, r = -0.065; Zn, r = -0.52; Se, r = -0.53. In Group 3, MDA excretion after day 3 decreased with increasing cumulative Zn (r = -0.46) and Se intakes (r = -0.57). It can be concluded that the MDA decrease after day 3 was not clearly attributable to the trace element supplements, but the negative trend observed between Zn and Se supplements and decreased MDA excretion requires further studies.

Increased formation and degradation of malondialdehyde-modified proteins under conditions of peroxidative stress

The effect of increased in vivo lipid peroxidation on excretion of the main urinary metabolites of malondialdehyde (MDA) was investigated. peroxidative stress in the form of vitamin E deficiency or the administration of iron nitrilotriacetate or carbon tetrachloride was imposed on rats fed an MDA-free diet. Significant increases were observed in excretion of the lysine-MDA adduct epsilon-propenal lysine, its N-acetyl ester, and free MDA. Under the conditions imposed, the increments in excretion of the lysine adducts reflect increased peroxidative modification of tissue proteins in vivo. These adducts also were found to be the main forms of MDA excreted in human urine. Reacting 14C-bovine serum albumin (BSA) with MDA resulted in its accelerated proteolysis in vitro by soluble enzyme preparations derived from human erythrocytes and rat liver mitochondria. The increments observed were similar to those reported for the hydrolysis of BSA following its exposure to hydroxyl radicals. The results show that lipid peroxidation in vivo results in peroxidative damage to tissue proteins and indicate that such proteins are subject to an accelerated rate of proteolysis.

Plasma lipids, lipoproteins, and mammographic densities

There is strong evidence that the risk of breast cancer in populations is influenced by environmental factors. Plasma lipids and lipoproteins are known to be under environmental control and to have epidemiological and/or biological characteristics that suggest they may be relevant to breast cancer risk. The purpose of the study described here was to determine whether plasma lipids, lipoproteins, and the urinary excretion of the mutagen malondialdehyde (MDA) are associated with differences in breast cancer risk. We measured plasma lipids, lipoproteins, and urinary MDA in women without breast cancer but with different degrees of density of the breast parenchyma on mammography, a strong risk factor for breast cancer. Mammograms from 273 premenopausal women were digitized to high spatial resolution by a scanning densitometer, and images were analyzed to quantify the extent of density. The percentage of the breast occupied by mammographic densities was found, after controlling for the effects of age and the Quetelet index of obesity, to be significantly associated with plasma levels of high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglyceride, apoprotein B, and urinary excretion of MDA. A multivariate model comprised of the Quetelet index of obesity, alcohol consumption, apoprotein B, parity, daily MDA excretion, and the skinfold thickness sum accounted for 36% of the variation in breast density. These results suggest that differences in lipid metabolism are associated with differences in breast cancer risk as defined by mammographic densities. These findings are consistent with several other observations that show a relationship between plasma lipids, lipoproteins, and risk factors for breast cancer.

Plasma and urine malondialdehyde levels in non-insulin-dependent diabetic patients with and without microalbuminuria

Malondialdehyde, a marker of lipid peroxidation, was measured as thiobarbituric acid-reactive substance in 78 non-insulin-dependent diabetic patients and 28 healthy subjects. Patients were divided into groups and subgroups according to the presence of microalbuminuria and other complications. Plasma and urine malondialdehyde concentrations were significantly higher in patients with and without microalbuminuria than in controls. In contrast to urine malondialdehyde, plasma malondialdehyde levels were significantly higher in microalbuminuric diabetes than in the normolbuminuric diabetic group. There was no correlation between malondialdehyde concentration and glycemic control. This study confirmed the existence of lipid peroxidation disorders in diabetic patients.

Oxidative stress induced by chronic administration of sodium dichromate [Cr(VI)] to rats

Chromium occurs in the workplace primarily in the valence forms Cr(III) and Cr(VI). Recent studies have demonstrated that sodium dichromate [Cr(VI)] induces greater oxidative stress as compared with Cr(III), as indicated by the production of reactive oxygen species by peritoneal macrophages and hepatic mitochondria and microsomes, and enhanced excretion of urinary lipid metabolites and hepatic DNA-single strand breaks (SSB) following acute oral administration of Cr(III) and Cr(VI). We have therefore examined the chronic effects of sodium dichromate dihydrate [Cr(VI); 10 mg (33.56 mumol)/kg/day] on hepatic mitochondrial and microsomal lipid peroxidation, enhanced excretion of urinary lipid metabolites including malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT), acetone (ACON) and propionaldehyde (PROP), and hepatic DNA damage over a period of 90 days. The maximal increases in hepatic lipid peroxidation and DNA damage were observed at approximately 45 days of treatment. Maximum increases in the urinary excretion of MDA, FA, ACT, ACON and PROP were 3.2-, 2.6-, 4.1-, 3.3- and 2.1-fold, respectively, while a 5.2-fold increase in DNA-SSB was observed. The results clearly indicate that chronic sodium dichromate administration induces oxidative stress resulting in tissue damaging effects which may contribute to the toxicity and carcinogenicity of hexavalent chromium.

Chromium-induced excretion of urinary lipid metabolites, DNA damage, nitric oxide production, and generation of reactive oxygen species in Sprague-Dawley rats

Chromium and its salts induce cytotoxicity and mutagenesis, and vitamin E has been reported to attenuate chromate-induced cytotoxicity. These observations suggest that chromium produces reactive oxygen species which may mediate many of the untoward effects of chromium. We have therefore examined and compared the effects of Cr(III) (chromium chloride hexahydrate) and Cr(VI) (sodium dichromate) following single oral doses (0.50 LD50) on the production of reactive oxygen species by peritoneal macrophages, and hepatic mitochondria and microsomes in rats. The effects of Cr(III) and Cr(VI) on hepatic mitochondrial and microsomal lipid peroxidation and enhanced excretion of urinary lipid metabolites as well as the incidence of hepatic nuclear DNA damage and nitric oxide (NO) production were also examined. Increases in lipid peroxidation of 1.8- and 2.2-fold occurred in hepatic mitochondria and microsomes, respectively, 48 hr after the oral administration of 25 mg Cr(VI)/kg, while increases of 1.2- and 1.4-fold, respectively, were observed after 895 mg Cr(III)/kg. The urinary excretion of malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT) and acetone (ACON) were determined at 0-96 hr after Cr administration. Between 48 and 72 hr post-treatment, maximal excretion of the four urinary lipid metabolites was observed with increases of 1.5- to 5.4-fold in Cr(VI) treated rats. Peritoneal macrophages from Cr(VI) treated animals 48 hr after treatment resulted in 1.4- and 3.6-fold increases in chemiluminescence and iodonitrotetrazolium reduction, indicating enhanced production of superoxide anion, while macrophages from Cr(III) treated animals showed negligible increases. Increases in DNA single strand breaks of 1.7-fold and 1.5-fold were observed following administration of Cr(VI) and Cr(III), respectively, at 48 hr post-treatment. Enhanced production of NO by peritoneal exudate cells (primarily macrophages) was monitored following Cr(VI) administration at both 24 and 48 hr post-treatment with enhanced production of NO being observed at both timepoints. The results indicate that both Cr(VI) and Cr(III) induce an oxidative stress at equitoxic doses, while Cr(VI) induces greater oxidative stress in rats as compared with Cr(III) treated animals.

Increased glomerular and urinary malondialdehyde in puromycin aminonucleoside-induced proteinuria in rats

Puromycin aminonucleoside (PAN)-induced proteinuria in rats may be mediated by reactive oxygen metabolites (ROM), which are injurious to several cell components including membrane lipids. Increased malondialdehyde (MDA) production is indicative of lipid peroxidation. We examined if MDA content of glomeruli and its urinary excretion were increased in rats administered PAN. Of three groups of 8 Sprague-Dawley rats each, group 1 served a control, group 2 animals received a single intravenous injection of PAN (5 mg/100 g body weight) and group 3 animals PAN with intraperitoneal injections of dimethylthiourea (DMTU), a free radical scavenger of oxidants such as hydroxyl radicals, for 4 days. The rats were sacrificed on day 8 after PAN injection. Increasing proteinuria, starting on day 4, developed in animals in group 2 but not in the others. The glomerular MDA (nmol/mg protein) in group 2 animals was 2.93 +/- 1.91, significantly higher than 0.87 +/- 0.63 and 1.26 +/- 0.76 in groups 1 and 3, respectively. Urinary levels of MDA markedly increased in group 2 rats on day 3 and remained high thereafter, but no such increase occurred in the control animals and those administered PAN with DMTU; the latter was thus protective against PAN toxicity. Our observations support the view that ROM are involved in PAN-induced glomerular injury and that increased urinary MDA excretion can be a marker of ROM-mediated lipid peroxidation.

Adriamycin-induced hepatic and myocardial lipid peroxidation and DNA damage, and enhanced excretion of urinary lipid metabolites in rats

Adriamycin produces clinically useful responses in a variety of human cancers including lymphomas, leukemias, and solid tumors. However, the toxicity of adriamycin has limited its usefulness. Iron-catalyzed free radical reactions as the peroxidation of membrane lipids, inactivation of critical enzymes, and the inhibition of DNA, RNA and protein synthesis in heart, liver and kidney have been implicated in the toxicity of adriamycin. In order to further assess the role of oxidative stress in the toxicity of adriamycin, the effects of adriamycin were examined on the urinary excretion of lipid metabolites at 0, 6, 12, 24, 48 and 72 h post-treatment, and on myocardial and hepatic lipid peroxidation and nuclear DNA single strand breaks at 24 h post-treatment following single oral and intravenous (i.v.) doses of 10 mg/kg adriamycin. Urinary malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT) and acetone (ACON) excretion was significantly increased at all time points examined. Following the oral administration of adriamycin, maximum excretion of MDA, FA, ACT and ACON of 6.2-, 2.7-, 3.7- and 2.2-fold relative to control values, respectively, occurred 24 h after treatment. However, following the i.v. administration of adriamycin, greatest increases in excretion of MDA, FA and ACT reaching 6.9-, 3.3- and 6.3-fold relative to control values, respectively, were observed 6 h after treatment, while the greatest increase in ACON excretion of 4.2-fold relative to control values occurred 12 h post-treatment. Following oral and i.v. administration of adriamycin, significant increases were observed in myocardial and hepatic lipid peroxidation in mitochondrial and microsomal membranes, and myocardial and hepatic nuclei DNA single strand breaks 24 h after treatment. The results indicate that adriamycin administration induces myocardial and hepatic lipid peroxidation which may be responsible for enhanced excretion of urinary lipid metabolites as a result of membrane damage, and also induces enhanced DNA damage. These effects may be due to adriamycin-induced production of reactive oxygen species.

Identification of a deoxyguanosine-malondialdehyde adduct in rat and human urine

In an ongoing study, rat and human urine have been examined for the presence of malondialdehyde (MDA) derivatives as indicators of the nature of lipid peroxidative damage caused by this compound in vivo. MDA in urine was found to be present mainly in the form of two lysine adducts, one acetylated and the other unacetylated, reflecting in vivo reactions with tissue proteins. Two minor metabolites were identified as adducts with the phospholipid bases serine and ethanolamine and a third one as an adduct with the nucleic acid base guanine. The identification of an MDA adduct with deoxyguanosine (dG-MDA) among the products of hydrolysis of rat liver DNA suggested the possible occurrence of this compound in urine. In the present study dG-MDA was identified in rat and in human urine, and a high-performance liquid chromatographic method utilizing fluorescence detection was developed for its estimation. The method is sensitive to 1 pmol of dG-MDA and requires a minimum of 1 mL of rat urine or 5 mL of human urine. Its rate of excretion by five-week-old rats (28.54 +/- 2.28 nmol/kg/24 h) (mean +/- SEM) was higher than that for nine-week-old rats (6.29 +/- 1.02) and much higher than that for adult humans (0.40 +/- 0.05). The results indicate that, as reported for 8-hydroxy-deoxyguanosine, dG-MDA excretion is related to metabolic rate. Excretion of dG-MDA by the rat, like the excretion of total MDA, declines during growth on a body weight basis at a rate similar to the decrease in resting energy metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Excretion of malondialdehyde, formaldehyde, acetaldehyde, acetone and methyl ethyl ketone in the urine of rats given an acute dose of malondialdehyde

A high pressure liquid chromatographic system (HPLC) has recently been developed for the simultaneous detection of malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT) and acetone (ACON). We have examined the urinary excretion of these four lipid metabolites in the urine of rats following the acute oral administration of MDA (158 mg/kg body weight). During the first 12 h, increases in the urinary excretion of MDA and ACT of approximately 192- and 70-fold, respectively, were observed. The urinary excretion of both MDA and ACT decreased thereafter. An increase in FA excretion was observed only 12-24 h after MDA administration. A significant decrease in ACON relative to control values was observed 12-48 h after MDA treatment. Two new peaks were present in the HPLC chromatograms of urine samples 0-24 h after MDA administration. Both peaks were shown to be due to methyl ethyl ketone (MEK) which appears to be formed as a result of MDA metabolism. The results demonstrate that orally administered MDA is rapidly excreted in the urine, and alters the metabolism and excretion of other lipid metabolites.

Malondialdehyde measurement in urine

Malondialdehyde (MDA) is an end product of lipid peroxidation and is a frequently measured index of these processes. The thiobarbituric acid (TBA) test is commonly used to measured MDA, but its specificity is questionable due to the presence of interfering chromogens. Wade and van Rij described in 1988 a method which removes these chromogens by HPLC. However, the sensitivity and the resolution of this method was not adequate for measurements of MDA in urine. We have improved this method by replacing TBA with diethylthiobarbituric acid (DETBA). The less polar MDA-DETBA complexes were isolated on Bakerbond cartridges and quantified by HPLC without interference. MDA was detectable using a fluorescence or ultraviolet detector at picomole levels. This technique was applied to urine samples obtained from ten burns patients on different days following their hospitalization. Urinary MDA in burns patients was very high and reached 18.6 mumol/mmol creatinine in one patient compared with a mean value of 0.23 mumol/mmol creatinine in healthy controls. Maximum MDA levels were attained on the third day for the majority of patients and remained, on average, much higher than normal even after 20 days. Using this method, picomole quantities of MDA can be easily and specifically detected in urine samples. This method is useful for assessing an oxidative stress.

Antiperoxide activity of sodium metabisulfite. A double-edged sword

Sulfites are chemical substances that are used widely in the pharmaceutical industry to reduce or prevent oxidation. Sodium metabisulfite (Na2S2O5) is still present in several parenteral amino acid solutions. Since intravenous lipid emulsions are contaminated by hydroperoxides, we evaluated whether metabisulfite had an antioxidant activity against hydroperoxides. In vitro, Na2S2O5 inhibited the oxidant activity of H2O2, tert-butyl-, and cumene hydroperoxides. The antioxidant capacity of metabisulfite was supported in vivo by the lower (P < 0.01) excretion of malondialdehyde, a stable end product of lipid peroxidation, in babies receiving metabisulfite in their parenteral nutrition. However, for concentrations outside the range found in solutions for parenteral nutrition, the reduction of hydroperoxides by Na2S2O5 could transform this compound into an oxidant, like a sulfite radical. It is suggested that metabisulfite has antiperoxide properties that, under specific conditions, contribute to the generation of toxic oxidants.

Exercise-induced connective tissue turnover and lipid peroxidation in horses

Four unfit thoroughbred horses were exercised on a treadmill twice, 5 weeks apart. Exercise consisted of stepwise increments in treadmill speed up to a maximum of 12 m s-1 and then maintained at this speed until the horses were fatigued. Two of the horses were administered phenylbutazone (4.4 mg kg-1) intravenously immediately before the first exercise period and the other two horses immediately before the second exercise period. Clinical observation revealed stiffness of gait and palpable soreness over the lumbar-sacral region in the horses 24 h after the exercise concluded. Mean plasma aspartate aminotransferase and creatine kinase activities and urinary creatinine clearance did not change as a result of exercise. The mean urinary excretion and clearance of hydroxyproline significantly increased in the 24 h following exercise (P < 0.001). A concurrent increase in the urinary excretion of malondialdehyde also occurred (P < 0.001). Prior administration of phenylbutazone did not affect hydroxyproline or malondialdehyde excretion or clearance, nor did it appear to reduce the severity of soreness after exercise. The results indicate that lipid peroxidation and the excretion and clearance of hydroxyproline increase when unfit thoroughbreds are strenuously exercised on a treadmill.

Detection of paraquat-induced in vivo lipid peroxidation by gas chromatography/mass spectrometry and high-pressure liquid chromatography

The cyclic oxidation-reduction of paraquat results in the formation of oxygen free radicals, which are believed to mediate the toxic manifestations of this herbicide. Because of paraquat's profound effects on lipid peroxidation, the effect of oral administration of 75 mg paraquat/kg to rats has been examined on the urinary excretion of the lipid metabolites malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT), and acetone (ACON) over 48 hours post-treatment. The urinary metabolites were identified by gas chromatography/mass spectrometry and quantitated by high-pressure liquid chromatography. Time-dependent increases in the urinary excretion of the four metabolites were observed after paraquat administration. Over the 48 hours of the study, the paraquat-induced urinary excretion of MDA, FA, ACT, and ACON increased by approximately 218, 155, 331, and 995%, respectively, relative to control animals. The data were expressed in nmol/kg body weight/4.5 h. The results clearly demonstrate that paraquat increases the urinary excretion of four lipid metabolites, which may have widespread applicability as biomarkers of altered lipid metabolism in disease states and cases of exposure to environmental pollutants and xenobiotics that induce enhanced lipid peroxidation.

Carbon-tetrachloride-induced urinary excretion of formaldehyde, malondialdehyde, acetaldehyde and acetone in rats

Previous studies have demonstrated that the hepatotoxin carbon tetrachloride rapidly promotes lipid peroxidation and inhibits microsomal calcium sequestration, microsomal glucose-6-phosphatase activity and cytochrome P-450. Due to its profound effects on lipid peroxidation, we have examined the oral administration of 2.5 ml/kg carbon tetrachloride on the urinary excretion of the lipid metabolites formaldehyde, malondialdehyde, acetaldehyde and acetone. Urine samples were collected up to 48 h after treatment. The urinary metabolites were identified and quantitated by gas chromatography-mass spectrometry and high-pressure liquid chromatography. Time-dependent increases in the urinary excretion of the four metabolites were observed after carbon tetrachloride administration. At 48 h after treatment, the increases in the excretion of malondialdehyde, formaldehyde, acetaldehyde and acetone were approximately 55, 78, 57 and 268%, respectively, relative to control values. The data were expressed in nanomoles per kilogram body weight per 4.5 h. The results clearly demonstrate that carbon tetrachloride increases the urinary excretion of four lipid metabolites which may serve as noninvasive biomarkers of xenobiotic-induced lipid peroxidation.

Protective effects of antioxidants against endrin-induced hepatic lipid peroxidation, DNA damage, and excretion of urinary lipid metabolites

Oxidative stress is believed to play a pivotal role in endrin-induced hepatic and neurologic toxicity. Therefore, the effects of the antioxidants vitamin E succinate and ellagic acid have been examined on hepatic lipid peroxidation, DNA single-strand breaks (SSB), and the urinary excretion of lipid metabolites following an acute oral dose of 4.5 mg endrin/kg. Groups of rats were pretreated with 100 mg/kg vitamin E succinate for 3 d followed by 40 mg/kg on day 4, or 6.0 mg ellagic acid/kg for 3 d p.o. followed by 3.0 mg/kg on day 4 or the vehicle. Endrin was administered p.o. on day 4 2 hr after treatment with the antioxidant. All animals were killed 24 h after endrin administration. Vitamin E succinate pretreatment decreased the endrin-induced increase in hepatic mitochondrial and microsomal lipid peroxidation by approximately 60% and 40%, respectively. Ellagic acid pretreatment reduced the endrin-induced increased in mitochondrial and microsomal lipid peroxidation by approximately 76 and 79%, respectively. Both vitamin E succinate and ellagic acid alone produced small but nonsignificant decreases in hepatic mitochondrial and microsomal lipid peroxidation. A 3.3-fold increase in the incidence of hepatic nuclear DNA single-strand breaks was observed 24 h after endrin administration. Pretreatment of rats with vitamin E succinate, vitamin E, and ellagic acid decreased endrin-induced DNA-SSB by approximately 47%, 22%, and 21%, respectively. Pretreatment of rats with vitamin E succinate decreased the endrin-induced increase in the urinary excretion of malondialdehyde, acetaldehyde, formaldehyde, and acetone by approximately 68, 65, 70, and 55%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

The urinary excretion of thiobarbituric acid reactive substances and malondialdehyde by normal adult males after consuming a diet containing salmon

In this study we investigated the output of thiobarbituric acid reactive substances (TBARS) and malondialdehyde (MDA), as thiobarbituric acid (TBA)-MDA adduct, in the urine from subjects eating a diet in which the only source of n-3 long-chain, polyunsaturated fatty acids was fresh salmon. Nine healthy men, ages 30-65, were confined in the United States Department of Agriculture Western Human Nutrition Research Center, San Francisco, CA, for 100 d; food intake and exercise levels were controlled. All subjects were placed on a stabilization diet (StD) for 20 d, then six were fed the salmon diet for 40 d. The others remained on the StD. The groups switched diets for the last 40 d. Both diets were isocaloric (16% protein, 54% CHO and 30% fat by energy %). The salmon diet contained 7.5% of calories from n-6 fatty acids (FAs) and 2% from n-3 FAs, primarily eicosapentaenoic acid and docosahexaenoic acid in a 50:60 ratio, while the StD contained 7.5% from n-6 FAs and < 0.3% n-3 FAs (with presumably no significant amounts of C20 or C22 n-3 FAs). Twenty-four hour urinary output was collected, and 2% 3-d pool samples prepared for analysis of urinary TBARS and the TBA-MDA adduct. The total urinary output of each individual varied considerably, and on a daily basis the concentration of autoxidation products in an individual's urine varied also.(ABSTRACT TRUNCATED AT 250 WORDS)