Protective effect of vitamin E on exercise-induced oxidative damage in young and older adults

The protective effect of vitamin E supplementation on exercise-induced oxidative damage was tested in 21 male volunteers. Nine young (22-29 yr) and 12 older (55-74 yr) sedentary male subjects participated in a double-blind protocol and received either 800 IU dl-alpha-tocopherol or a placebo daily. After 48 days, vitamin E supplementation significantly increased alpha-tocopherol in plasma and skeletal muscle. Subjects then performed a bout of eccentric exercise at 75% of their maximum heart rate by running down an inclined treadmill for 45 min. All vitamin E-supplemented subjects excreted less (P < 0.05) urinary thiobarbituric acid adducts after the exercise bout than placebo subjects at 12 days postexercise (35 and 18% above baseline in young and old supplemented groups, respectively, vs. 60 and 80% in young and old placebo groups, respectively). After exercise, the initial difference in alpha-tocopherol concentration of muscle between young placebo and vitamin E-supplemented groups was diminished and muscle lipid conjugated dienes tended to increase (P = 0.09) in placebo subjects. Placebo subjects had a significant decrease in major fatty acids of muscle biopsy taken immediately after exercise. When normalized for the hemoconcentration effects of exercise, the plasma concentration of vitamins E and C and uric acid showed no significant change. The alterations in fatty acid composition, vitamin E, and lipid conjugated dienes in muscle and in urinary lipid peroxides in controls after eccentric exercise are consistent with the concept that vitamin E provides protection against exercise-induced oxidative injury.

Excretion of malondialdehyde, formaldehyde, acetaldehyde and acetone in the urine of rats following acute and chronic administration of ethanol

Recent studies have shown that xenobiotics which induce oxidative stress result in an increased production and excretion of acetaldehyde (ACT), formaldehyde (FA), acetone (ACON) and malondialdehyde (MDA) in the urine of rats. We have therefore examined the effect of acute and chronic ethanol administration on the excretion of these four lipid metabolites in female Sprague-Dawley rats. Urine samples were collected over dry ice for 6 hr time periods. Aliquots of urine were derivatized with 2,4-dinitrophenylhydrazine HCl, and extracted with n-pentane. High pressure lipid chromatogrpahy (HPLC) was used to quantitate and the hydrazones of the four lipid metabolite products. Following a single, oral, acute dose of 5 g ethanol/kg, urinary excretion of ACT increased approximately 5.8-fold from 6 to 12 hr posttreatment, and decreased thereafter. FA excretion decreased by approximately 50% from 0 to 12 hr, returned to control values in the 18-24 hr urine samples, and was 1.3-fold greater than control values at 42-48 hr. ACON increased 3.1-fold over control values from 0 to 30 hr and remained elevated throughout the remaining 18 hr of the study. The excretion of MDA increased approximately 1.5-fold from 18 to 36 hr, then remained constant through the 48 hr time point. In a separate series of experiments, a chronic oral dose of 0.5 g ethanol/kg was administered to rats for 10 consecutive days and the urinary excretion of the lipid metabolites MDA, FA, ACT and ACON was examined for 11 days, beginning with the first day of ethanol administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary malondialdehyde concentration in preterm neonates: is there a relationship to disease entities of neonatal intensive care?

In a retrospective study, urinary malondialdehyde concentration in 45 preterm neonates (25-35 weeks' gestation) during their first month of life was measured by HPLC. Urine was collected on different days of life as a 3-h sample. The frequency of urine collection and measurement varied between one (n = 22) and seven times (n = 8) per child. The study group was divided into three categories according to birth weight: low-birth-weight infants (LBW) (n = 16), very low-birth-weight infants (VLBW) (n = 17) and extremely low-birth-weight infants (ELBW) (n = 12). Urinary malondialdehyde concentration was highest in the ELBW group: 1.15 (0.66, 2.12) mumol/l (median and quartiles) versus 0.58 (0.34, 1.18) mumol/l in the VLBW and 0.60 (0.40, 1.06) mumol/l in the LBW groups (ELBW versus VLBW, p < 0.005; ELBW versus LBW, p < 0.02). In oxygen-treated neonates, significantly higher malondialdehyde values were found compared to those without supplementary oxygen (0.89 (0.48, 1.74) versus 0.58 (0.32, 0.89) mumol/l; p < 0.005). Likewise, a higher malondialdehyde concentration was found in infants requiring mechanical ventilation (intermittent mandatory IMV or high frequency ventilation) compared to those breathing spontaneously (intermittent mandatory ventilation: 0.80 (0.42, 1.66); p > 0.05 and high frequency ventilation: 1.20 (0.83, 2.13); p < 0.001 versus 0.57 (0.33, 0.88) mumol/l). Malondialdehyde concentrations correlated significantly with FiO2 values of the individual patients (r = 0.22; p < 0.02). Comparing urinary malondialdehyde concentrations in infants with and without bronchopulmonary dysplasia, a significantly higher malondialdehyde concentration was found in the former group (0.96 (0.51, 2.07) versus 0.60 (0.32, 0.98) mumol/l; p < 0.005)).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of exercise on clearance of oxidant stress products and loosely bound iron

The significance of free radical chemistry within the exercise and post-exercise milieu is not yet well understood. It is yet to be determined whether adequate biochemical defense mechanisms exist to protect the organism from oxygen-centered radicals generated by exercise. Rats trained at 70% VO2peak for 6 wk were compared with controls after an exhaustive run. Post-exhaustion urinary malondialdehyde, gastrocnemius loosely bound iron, and susceptibility to oxidant stress were assessed. Exhaustive exercise resulted in a significant (P < 0.05) increase in urinary malondialdehyde, tissue loosely bound iron, and susceptibility to oxidative stress in both control and trained rats. The untrained group's tissue iron and susceptibility to oxidative stress were both significantly greater than trained rats. Electrical stimulation of perfused hindquarters of untrained and trained rats resulted in a significant increase of malondialdehyde into the perfusate. Trained rats cleared the malondialdehyde from the perfusate more rapidly than did the untrained.

A thermospray liquid chromatography/mass spectrometry method for analysis of human urine for the major malondialdehyde-guanine adduct

A method is described for detection and quantitation of the major malondialdehyde-guanine adduct (M1G) based on thermospray liquid chromatography/mass spectrometry. A stable isotope analog of M1G ([2H2]M1G) was used as an internal standard. Thermospray mass spectra of M1G and [2H2]M1G showed intense protonated molecular (MH+) ions that were suitable for use in quantitation of M1G. M1G was purified from human urine and reduced with NaBH4 to a dihydro derivative that was cleanly separated from the contaminants in the urine. The detection limit of reduced M1G by thermospray liquid chromatography/mass spectrometry in the selected ion monitoring mode was 250 fmol on column. Six human urine samples were analyzed, and the concentrations of M1G were below the limit of detection of the assay (500 fmol/mL).

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

Previous studies have shown that endrin induces an oxidative stress in rats as demonstrated by an increase in hepatic lipid peroxidation, a decrease in glutathione content and a decrease in the activity in selenium-dependent glutathione peroxidase. We have therefore examined the effects of orally administering 1.5, 3.0, 4.5 and 6.0 mg endrin/kg on the urinary excretion of the lipid metabolites formaldehyde, malondialdehyde, acetaldehyde and acetone. The simultaneous determination of these four lipid metabolites may be a useful biomarker for assessing exposure to xenobiotics which induce an oxidative stress and enhanced lipid peroxidation. Urine samples were collected up to 72 h post-treatment. The identities of the lipid metabolites were confirmed by gas chromatography-mass spectroscopy, while the 2,4-dinitrophenylhydrazine derivatives of these metabolic products were quantitated by high pressure liquid chromatography. Maximum increases in the excretion of the four lipid metabolites occurred at approx. 24 h post-treatment at all doses with no significant increases in excretion occurring thereafter. The maximum increases in excretion of malondialdehyde, formaldehyde, acetaldehyde and acetone were approx. 160%, 93%, 121% and 162%, respectively, relative to control values. Seventy-two hours after endrin administration, the liver weight/body weight and spleen weight/body weight ratios significantly increased while the thymus weight/body weight ratio markedly decreased. The results demonstrate that endrin induces dose- and time-dependent alterations in lipid metabolism with the enhanced excretion of specific metabolic products in the urine.

Dose-response relationships between dietary (n-3) fatty acids and plasma and tissue lipids, steroid excretion and urinary malondialdehyde in rats

For a 28-d experimental period, rats were fed a nonpurified, cereal-based diet containing 9.1% supplemental beef tallow or fish oil or one of the following beef tallow:fish oil blends: 95:5; 90:10; 80:20 and 50:50. All diets provided between 21.3 and 22.7 g linoleic acid/kg. Higher fish oil intake was paralleled by elevated incorporation of long-chain (n-3) fatty acids in plasma total lipid, mainly at the expense of arachidonic acid. Significant inverse relationships were found between plasma total (n-3) fatty acid concentration and plasma triglyceride, cholesterol or free fatty acid concentrations. Fish oil intake did not lead to a shift of triglycerides or cholesterol from the plasma to the tissues (liver, heart, kidneys). Reduced plasma cholesterol concentrations in the fish oil-fed rats could not be explained by higher fecal excretion of neutral sterols and bile acids. In vivo lipid peroxidation, assessed by urinary malondialdehyde excretion, was enhanced when diets containing greater than 1.8% fish oil were fed.

Lipoperoxides in sebum of substance users and controls

Sebum was collected from forehead skin in five compulsive heroin and/or cocaine (substance) users and in five controls over three consecutive periods, each lasting three hours. The participants were adult black and white men similar in age and smoking habits, who did not consume alcohol. Lipoperoxides were determined in sebum as malondialdehyde by high performance liquid chromatography. Two participants were excluded in the control group: in both, urinary lipoperoxides were elevated; in one, urine tested positive for delta-9 tetrahydrocannabinol (THC). All other participants had negative urine drug screening tests. Relative to the controls, all substance users had elevated concentrations of lipoperoxides in urine. Compared to the controls, the rate of sebum excretion in the last collecting period was higher in substance users, but sebum had significantly lower lipoperoxide concentration. It is assumed that compulsive drug use may influence lipoperoxidation of incipient sebum, possibly by altered tissue perfusion.

Excretion of formaldehyde, malondialdehyde, acetaldehyde and acetone in the urine of rats in response to 2,3,7,8-tetrachlorodibenzo-p-dioxin, paraquat, endrin and carbon tetrachloride

Formaldehyde (FA), acetaldehyde (ACT), malondialdehyde (MDA) and acetone (ACON) were simultaneously identified in urine, and their excretion quantitated in response to chemically induced oxidative stress. Urine samples of female Sprague-Dawley rats were collected over dry ice and derivatized with 2,4-dinitrophenylhydrazine. The hydrazones of the four lipid metabolic products were quantitated by high-performance liquid chromatography on a Waters 10-microns mu-Bondapak C18 column. The identities of FA, ACT, MDA and ACON in urine were confirmed by gas chromatography-mass spectrometry. An oxidative stress was induced by orally administering 100 micrograms/kg 2,3,7,8-tetrachlorodibenzo-p-dioxin, 75 mg/kg paraquat, 6 mg/kg endrin or 2.5 ml/kg carbon tetrachloride to rats. Urinary excretion of FA, ACT, MDA and ACON increased relative to control animals 24 h after treatment with all xenobiotics. The system has wide-spread applicability to the investigation of altered lipid metabolism in disease states and exposure to environmental pollutants.

Urinary response to in vivo lipid peroxidation induced by vitamin E deficiency

Experiments were carried out to measure the urinary excretion of free and conjugated malonaldehyde (MDA) and other thiobarbituric acid reactive substances (TBARS) in vitamin E deficient and vitamin E supplemented rats. From both dietary groups, six TBA positive fractions were isolated, in addition to that containing free MDA, by high-performance liquid chromatography (HPLC) on a TSK-GEL G-1000PW column. Three of the fractions isolated were found to be significantly increased in vitamin E deficiency. After acid hydrolysis, only one of the above compounds produced free MDA which indicated the presence of derivatized MDA. Only this fraction exhibited fluorescence at excitation 370 nm and emission 450 nm. The five other fractions formed 2,4-dinitrophenylhydrazones (2,4-DNPH), indicating the presence of carbonyl groups, but the derivatized MDA fraction did not. No significant differences were found in free MDA levels between the vitamin E deficient and the vitamin E supplemented groups.

[Daily dynamics of iron excretion with murine in experimental hepatosis]

Experimental hepatosis induced by intragastric administration of CCl4 was revealed to be accompanied by changes in temporal organization of lipid peroxidation, sideremia and iron excretion with urine. Even at early stages of organ lesions, the activation of free-radical lipid oxidation and rearrangement of sideruria circadian rhythm were found to result in a substantial and stable increase in mesor of the trace element excretion with urine in spite of a statistically significant decrease in water release.

Enhanced lipid peroxidation in rat gastric mucosa caused by NaCl

The effects of NaCl on lipid peroxidation levels in gastric mucosa and urine were investigated in male Wistar rats. The animals were fed NaCl-supplemented diet at concentrations of 4.0, 2.0, 1.0, 0.5, 0.25 and 0% (control) for 5 weeks. Further groups were maintained on the 4.0 or 0% NaCl diets and simultaneously administered 20 p.p.m. indomethacin dissolved in the drinking water. When the rats were killed, a dose-related increase of malondialdehyde (MDA) was found in both gastric mucosa and urine, the urinary MDA levels clearly correlating with those for stomach tissue. Cell proliferation of fundic mucosa was also significantly increased in rats fed 4.0 or 2.0% NaCl-supplemented diet. Indomethacin suppressed the 4% NaCl-associated MDA increase in both gastric mucosa and urine as well as the elevation in cell proliferation. The results clearly show that administration of NaCl, a gastric tumor promoter, is associated with enhanced lipid peroxidation in the gastric mucosa.

Malonaldehyde determination in tissues and biological fluids by ion-pairing high-performance liquid chromatography

A method for the analysis of malonaldehyde by ion pairing high-performance liquid chromatography is described. The method is direct; no thiobarbiturate chromogen formation is required, and sample preparation is simple. After deproteinization with 50% ethanol and removal of particulate by centrifugation samples were passed through a small silica amino column to remove contaminants. Diluted samples (20 microL) were injected onto an octadecylsilane column (25 cm x 4.6 mm ID, 5 micron) which is eluted with 30 mM sodium phosphate buffer, pH 6.5 containing 30% ethanol and 1 mM tetradecyltrimethylammonium bromide. Detection was accomplished by monitoring absorbance at 267 nm. The lower limit for reliable quantification was 5 pmol per injection. The method has been successfully applied to the quantification of malonaldehyde present in plasma, urine and tissues of rats kept under different dietary conditions as well as after in vivo treatment with CCl4 and iron-dextran. The method was also applied to the quantification of malonaldehyde during liver microsomal lipid peroxidation and was compared to the thiobarbituric acid test.

The possible role of lipid peroxidation in breast cancer risk

Breast cancer remains the commonest cause of death from cancer in women in most of the Western world. There is considerable evidence that breast cancer risk is influenced by environmental factors and can therefore potentially be modified. In this paper we describe evidence suggesting a relationship of lipid peroxidation to breast cancer risk, and propose that the method used to generate this information might usefully be applied to other disease states, and make some suggestions for further work. We have compared the urinary excretion of the mutagen malonaldehyde (MDA) in premenopausal women at different risks for breast cancer as determined by the appearance of the breast parenchyma on mammography. MDA was measured in 24-h urine samples from both groups and excretion in 30 women with mammographic dysplasia (high risk) was found to be approximately double that of 16 women without these radiological changes (p less than 0.02). These results suggest that mammographic dysplasia may be associated with lipid peroxidation. Further study of environmental factors associated with states that precede the development of breast and other cancers may lead to the identification of factors that can be modified and that may prevent the development of malignant disease.

Free malondialdehyde levels in the urine of rats intoxicated with paraquat

We examined the excretion of free malondialdehyde (MDA) in the urine of rats to which a herbicide, Gramoxone, had been orally administered. The herbicide was administered for 2 days at a dose of 60 mg paraquat/kg body weight/day. As a result, the concentration of free MDA decreased following the intake of Gramoxone. The total amount of free MDA increased temporarily, but then it decreased significantly to below normal values. Rats that died during this experimental period did not excrete any free MDA. In the surviving animals, the MDA concentration in serum and lung microsomes decreased, while that in liver microsomes increased slightly after intake of the poison. Although the cause of the decrease in the urinary free MDA level remains unclear, the marked changes may provide valuable information regarding a toxic mechanism of paraquat intake.

Oxygen consumption and oxidant stress in surviving nephrons

We investigated the effects of reduction of renal mass on rates of oxygen consumption, sodium transport, and indexes of oxidant stress in surviving nephrons. Rates of oxygen consumption in surviving nephrons were elevated by more than twofold compared with nephrons in intact kidneys in rats on standard protein intakes. Absolute rates of sodium reabsorption (TNa) in the surviving nephrons were increased with a lower ratio of TNa to oxygen consumption. To determine oxidant stress, we measured malondialdehyde (MDA) in the kidney and urine and the glutathione redox ratio in kidney tissue. MDA per nephron was increased in the subtotally nephrectomized model and was accompanied by increased absolute and fractional urinary excretion of MDA but not by an increase in kidney MDA per milligram protein. The glutathione redox ratios were similar. Since increased dietary protein intake worsens renal injury, we studied the effects of dietary protein manipulation (30 vs. 6%) on oxygen consumption, MDA levels, and the glutathione redox ratio. The kidneys of subtotally nephrectomized animals maintained on 30% protein diets exhibited increased rates of oxygen consumption. Increased dietary protein intake led to increased MDA per nephron, increased urinary excretion of MDA, and increased MDA per milligram protein in subtotally nephrectomized animals, and markedly increased the glutathione redox ratio. We conclude that, despite increased oxygen consumption, surviving nephrons compared with intact nephrons in rats on standard protein intake demonstrate no evidence of oxidant stress. Increased urinary clearance of MDA may provide a mechanism that prevents the buildup of lipid peroxidation. Subjecting the remnant nephron to increased protein increases oxygen consumption and imposes oxidant stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence of lipid peroxidation in premenopausal women with mammographic dysplasia

We have compared the urinary excretion of the mutagen malonaldehyde in premenopausal women at different risks for breast cancer as determined by the appearance of the breast parenchyma on mammography. Thirty women with extensive mammographic densities were compared with 16 controls without these radiological changes. Malonaldehyde was measured in 24-h urine samples from both groups and excretion in 30 women with mammographic dysplasia (high risk) was found to be approximately double that of 16 women without these radiological changes (P less than 0.02). These results suggest that mammographic dysplasia may be associated with lipid peroxidation and raise the possibility that mutagenic products generated by this process may influence breast cancer risk.

A modification of the thiobarbituric acid reaction

A simple modification of the thiobarbituric acid reaction, which removes nonspecific chromogenic reaction products, involves incubation at room temperature for 16-20 hr and a column chromatographic step. The chromogen-concentrating capacity of the latter step is useful for determination of low concentrations of thiobarbituric acid-reactive materials in biological preparations.

Increased urinary lipoperoxide levels in renal transplant patients

Using high performance liquid chromatographic methods, both plasma and urine lipoperoxide concentrations were measured, as malondialdehyde (MDA), in 30 stable renal transplant patients receiving daily cyclosporine and/or azathioprine therapy. Their MDA concentrations were compared with previously reported reliable reference values using the same liquid chromatographic methods. Although their plasma concentrations were within the reference range, their mean urine MDA values averaged 3.7 to 5.0 times the normal reference values (p less than 0.001). The primary cause of the increased urine MDA concentrations following renal transplantation in these patients is unknown; it could be due to (a) renal lipid peroxidation directly related to the cyclosporine/azathioprine therapy, (b) drug-induced or other nephrotoxicity by an alternative mechanism with secondary lipid peroxidation, (c) increased lipid peroxidation owing to an immunologic response to the kidney graft, or (d) a combination of these possibilities.

Identification of N-(2-propenal)ethanolamine as a urinary metabolite of malondialdehyde

N-(2-propenal)ethanolamine was isolated from rat and human urine using anion exchange, cation exchange, size exclusion and high performance liquid chromatography. Acid hydrolysis of the isolate yielded malondialdehyde (MDA) and ethanolamine (E) in a 1:1 molar ratio. A 1:1 E-MDA adduct was synthesized and found to be chromatographically inseparable from the urinary metabolite. Its NMR and UV spectra and lack of fluorescence were consistent with those of an enaminal formed by a Schiff's base reaction. The identification in urine of an adduct of MDA with ethanolamine, and the previous identification of an adduct with serine, constitutes direct evidence for the oxidative decomposition in vivo of polyunsaturated fatty acids present in the relevant phospholipids. The absence in urine of MDA adducts with other alpha-amino compounds (at least in comparable amounts) indicates that the ethanolamine and serine derivatives are formed in situ and not as a result of reactions with MDA generated in enzymatic processes.

Increased urinary lipoperoxides in drug abusers

Urine lipoperoxides were measured, as the malondialdehyde-thiobarbituric acid adduct, by "high performance" liquid chromatography in men who tested positive for any of the common "drugs of abuse." Urine malondialdehyde concentrations were within the reference range in those urines containing barbiturates and amphetamines. On the other hand, significant urine malondialdehyde elevations were associated with those testing positive for marijuana (p less than 0.005), cocaine, opiates, benzodiazepines, and in those urines containing multiple drugs (p less than 0.001). The mechanism of tissue damage by these drugs is not necessarily by lipid peroxidation, since their primary toxic effects might result in cellular injury by an alternative mechanism; the observed increased lipid peroxidation could be a secondary phenomenon following tissue injury.