Increased lipid peroxidation in kidney of vitamin B-6 deficient rats

Lipid peroxidation in kidney of rats fed with vitamin B-6 deficient diet for a period of 12 weeks was studied with pair-fed controls. The basal lipid peroxide level as well as the degree of susceptibility to lipid peroxidation in presence of promotors such as NADPH, ascorbate, t-butyl hydroperoxide, Fe2+, Cu2+ and oxalate, were increased in vitamin B-6 deficient kidney. The observed increased lipid peroxidation in vitamin B-6 deficient kidney was correlated with high levels of lipids, copper, iron, calcium and oxalate, low levels of antioxidants and antioxidant enzymes and increased levels of hydroperoxides and hydroxyl radicals.     

Effect of vitamin E on adjuvant arthritis in rats

Adjuvant arthritis was induced in rats fed a diet deficient in or supplemented with vitamin E, and its severity was scored according to the macroscopic findings of their legs, tails, and ears. The average score so obtained was higher in the vitamin E-deficient diet group than in the group of rats supplemented with vitamin E. Whereas the A/G ratio remained depressed in vitamin E-deficient rats, rats on a vitamin E-supplemented diet showed a fast recovery from A/G-ratio depression. The serum levels of beta-glucuronidase and acid phosphatase were elevated after administration of an adjuvant. The serum levels of these lysosomal enzymes showed a remarkable increase in rats fed a vitamin E-deficient diet, while the elevation in lysosomal enzyme levels in rats fed a vitamin E-supplemented diet was inhibited. The levels of thiobarbituric acid (TBA) reactants in the synovia were elevated at 2 weeks after exposure to the adjuvant and were decreased thereafter. In rats maintained on a diet supplemented with vitamin E, on the other hand, the increase in synovial level of TBA reactive substances was inhibited. These observations suggest that the aggravation of adjuvant arthritis may be associated with lipid peroxidation and that antioxidants, such as vitamin E, may be beneficial for arthritis.     

Effect of dietary vitamin E and Santoquin on regenerating rat liver

The influence of dietary vitamin E and Santoquin on lipid peroxidation and liver regeneration in partially-hepatectomized rats was studied. Rats were fed either a basal 10% tocopherol-stripped corn oil diet, the basal diet plus 40 mg dl-alpha-tocopheryl acetate/kg, or the basal diet plus 2 g Santoquin (6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline)/kg. After 6 weeks, rats fed the antioxidant-deficient diet produced more of the lipid peroxidation product, pentane, than did the rats fed antioxidants. Partial hepatectomy was performed after six and one-half weeks or ten weeks of feeding the diets. At 3 and 6 days after surgery, pentane production was significantly elevated over pre-surgery levels in rats fed the antioxidant-deficient or vitamin E-supplemented diets, but not in rats fed the Santoquin-supplemented diet. Six days after surgery, there were fewer thiobarbituric acid reactants in regenerating liver of Santoquin-fed rats than of vitamin-E fed rats or antioxidant-deficient rats. There was no increase in the 6-day level of thiobarbituric acid reactants over the 3-day level in livers of rats fed Santoquin, while there was an increase in livers of the antioxidant-deficient and vitamin E-supplemented rats. Liver sulfhydryl levels were higher at 3 and 6 days post surgery in the Santoquin-fed rats than in the antioxidant-deficient or vitamin E-supplemented rats. Plasma gamma-glutamyl-transpeptidase activity was not different among the groups of rats. Between the third and sixth day following surgery, liver regeneration was significantly stimulated in Santoquin-fed, but not vitamin E-fed rats. After 11 days, a stimulatory, but not statistically significant, effect of vitamin E was found. Although DNA content of liver was higher at 6 days than at 3 days post surgery, it was not different among the dietary groups, indicating that cell proliferation rather than hypertrophy had occurred. Partial hepatectomy could have altered the ability of the liver to metabolize pentane, thus explaining part of the increased production of pentane. However, the results obtained support the interpretation that elevated levels of dietary antioxidants can be beneficial in terms of reduced lipid peroxidation and increased rates of liver regeneration following liver surgery.     

Increased plasma lipidperoxidation in vitamin B-6 deficient rats

Lipidperoxidation in plasma of rats fed with vitamin B-6 deficient diet for a period of 12 weeks was studied with pair-fed controls. Plasma pyridoxal 5'-phosphate, alanine amino transferase and aspartate amino transferase, the markers of vitamin B-6 status, were significantly low in vitamin B-6 deficient rats. Plasma malondialdehyde level, conjugated dienes and lipofuscin like pigments were increased in vitamin B-6 deficiency. Increased levels of plasma lipids, calcium, iron and copper were observed in vitamin B-6 deficiency. Plasma susceptibility to lipidperoxidation was maximal in vitamin B-6 deficiency, upon stimulation by the promotors, Fe2+, Fe3+, Cu2+, ascorbate, t-butyl hydroperoxide and hydrogen peroxide.     

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.     

The effects of in vitro lipid peroxidation on the activity of rat liver microsomal glutathione S-transferase from rats supplemented or deficient in antioxidants

Glutathione S-transferases are a group of multifunctional isozymes that play a central role in the detoxification of hydrophobic xenobiotics with electrophilic centers (1). In this study we investigated the effects of in vitro lipid peroxidation on the activity of liver microsomal glutathione S-transferases from rats either supplemented or deficient in both vitamin E and selenium. Increased formation of malondialdehyde (MDA), a by-product of lipid peroxidation, was associated with a decreased activity of rat liver microsomal glutathione S-transferase. The inhibition of glutathione S-transferase occurred rapidly in microsomes from rats fed a diet deficient in both vitamin E and selenium (the B diet) but was delayed for 15 minutes in microsomes from rats fed the same diet but supplemented with these micro-nutrients (B+E+Se diet). Lipid peroxidation inhibits microsomal glutathione S-transferase and this inhibition is modulated by dietary antioxidants.     

Supplementation of vitamin E and selenium prevents hyperoxaluria in experimental urolithic rats

Renal injury is considered as one of the prerequisites for calcium oxalate retention. In order to determine the role of lipid peroxidation related effects for hyperoxaluria, we evaluated the alterations in lipid peroxidation, antioxidants and oxalate synthesizing enzymes in lithogenic rats with response to vitamin E + selenium treatment. In kidney of lithogenic rats, the level of lipid peroxidation and the activities of oxalate synthesizing enzymes were found to be increased whereas the levels/activities of non-enzymatic and enzymatic antioxidants were found to be decreased. The urinary excretion of both oxalate and calcium were significantly elevated. Supplementation of lithogenic rats with vitamin E + selenium decreased the levels of lipid peroxides and the activities of oxalate synthesizing enzymes like glycolic acid oxidase (GAO), lactate dehydrogenase (LDH), xanthine oxidase (XO) with a concomitant increase in the activities of enzymatic antioxidants like superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glucose-6-phosphate dehydrogenase (G6PDH) and increased levels of non-enzymatic antioxidants like ascorbic acid, alpha-tocopherol and reduced glutathione (GSH). The urinary excretion of oxalate and calcium were normalized. The antioxidants vitamin E + selenium thereby protected from hyperoxaluria.     

Effects of different dietary amounts of LCPUFA n3 and vitamin B6 on lipid composition and antioxidant defences in rat kidney

Our previous report demonstrated that, when vitamin deficiency is associated with high contents of long chain polyunsaturated fatty acids (LCPUFA) n3, lipid peroxidation susceptibility in rat heart and liver increases. In this paper, we evaluated the effect of the same dietary administration on lipid composition and antioxidant defenses of rat kidney. Results showed that vitamin B(6) deficiency, when associated with a fish oil diet, as compared to vegetable oil condition, increased relative kidney weight and decreased pyridoxal-5P contents. The different LCPUFA n3 dietary contents produced, on kidney phospholipids, effects interlaced with those of vitamin B(6) deficiency; in particular fish oil and vitamin B(6) deficient diet caused a significant decrease of arachidonic acid showing that the processes of elongation and desaturation of linoleic acid were slowed. Also, peroxidation susceptibility was higher, as demonstrated both by increased TBARS formation and glutathione peroxidase activity, and by decreased vitamin E contents and reduced glutathione/oxidized glutathione ratio.     

Renal parathyroid hormone-dependent adenylate cyclase activity after repletion of vitamin D-deficient rats with vitamin D-2

Rats fed a diet deficient in both vitamin D and Ca²⁺ exhibited a greater depression of the renal parathyroid hormone (PTH)-dependent adenylate cyclase than was observed in rats fed diets deficient in either vitamin D or calcium. Total serum Ca²⁺ was decreased from a control level of 11.2 mg/dl to 8.5 mg/dl in rats fed the diet deficient in calcium alone, and to 5.4 mg/dl in rats fed the diet deficient in vitamin D. Serum calcium was decreased further to 4.3 mg/dl in rats fed the diet deficient in both vitamin D and Ca²⁺. Serum immunoreactive PTH was significantly elevated over control levels when rats were fed the test diets; however, there were no significant differences between the elevated levels in the three experimental groups. Repletion of rats deficient in vitamin D only with a single oral dose of 3200 I.U. vitamin D-2 resulted in restoration of serum calcium to normal levels, a return of serum PTH to the control state, and an associated increase in PTH-dependent adenylate cyclase activity to the control level by 72 h. Repletion of rats deficient in both vitamin D and Ca²⁺ with the same dose of vitamin D-2 raised serum Ca²⁺ to 7.2 mg/dl by 72 h, but did not cause a reduction in circulating PTH, nor did it result in any significant improvement in the responsiveness of the membrane adenylate cyclase to PTH. These results suggest that elevated PTH is a factor in the down regulation of the PTH-dependent adenylate cyclase, but do not rule out a role for calcium as a regulatory factor.     

The role of antioxidant nutrients in preventing hyperbaric oxygen damage to the retina

Vitamin E and selenium play essential roles in preventing in vivo lipid peroxidation and free radical damage. Hyperbaric oxygen (HBO) treatment adversely affected the electroretinograms (ERGs) of rats fed a diet deficient in both vitamin E and selenium (the basal or B diet) or a diet deficient in vitamin E alone (B + Se diet). After 4 weeks of HBO treatment (3.0 ATA or 100% oxygen, 1.5 hours per day, 5 day/week) rats fed the B diet deficient in vitamin E and selenium for 6 weeks showed decreased (p less than 0.05) a-wave amplitudes, 85 +/- 9 microvolts (microV), n = 11, compared with a-waves recorded (150 +/- 10 microV, n = 21) for age matched rats fed an identical diet for 6 weeks but not treated with HBO. After 15 weeks of HBO treatment, rats fed the B + Se diet deficient in vitamin E alone showed decreased (p less than 0.01) a-wave (61 +/- 9 microV, n = 4) and b-wave (253 +/- 23 microV, n = 4) amplitudes compared with a-wave (115 +/- 7 microV, n = 4) and b-wave amplitudes (450 +/- 35 microV, n = 4) for age matched rats fed the same diet but not treated with HBO. Decreased a- or b-wave amplitudes provide evidence of retinal damage. Rats fed a diet supplemented with vitamin E and selenium or vitamin E alone showed no decreases in either a- or b-wave amplitudes after 15 weeks of HBO treatment.     

Effect of 3-methylindole on respiratory ethane production in selenium and vitamin E deficient rats

Lipid peroxidation has been proposed as a mechanism of 3-methylindole pneumotoxicity. In this report, lipid peroxidation was measured over 16 h in awake rats given 400 mg/kg i.p. 3-methylindole or its carrier, Cremophore EL. Rats were studied after 8 weeks of feeding a diet either adequate or deficient in vitamin E and selenium. Respiratory ethane production was used as the index of lipid peroxidation. 3-methylindole had no effect on lipid peroxidation for rats fed the adequate diet. For rats on the deficient diet, 3-methylindole suppressed lipid peroxidation by 50% of control. These results indicate that lipid peroxidation is not a mechanism of 3-methylindole pneumotoxicity and support the conclusion that 3-methylindole may act as an antioxidant.     

Effects of gallic acid on brain lipid peroxide and lipid metabolism in streptozotocin-induced diabetic Wistar rats

This study evaluated the protective effects of gallic acid on brain lipid peroxidation products, antioxidant system, and lipids in streptozotocin-induced type II diabetes mellitus. Streptozotocin-induced diabetic rats showed a significant increase in the levels of blood glucose, brain lipid peroxidation products, and lipids and a significant decrease in the activities of brain enzymic antioxidants. Oral treatment with gallic acid (10 mg and 20 mg/kg) for 21 days significantly decreased the levels of blood glucose, brain lipid peroxidation products, and lipids and significantly increased the activities of brain enzymic antioxidants in diabetic rats. Histopathology of brain confirmed the protective effects of gallic acid. Furthermore, in vitro study revealed the free radical scavenging action of gallic acid. Thus, our study shows the beneficial effects of gallic acid on brain metabolism in streptozotocin-induced type II diabetic rats. A diet containing gallic acid may be beneficial to type II diabetic patients.     

A diet high in cholesterol and deficient in vitamin E induces lipid peroxidation but does not enhance antioxidant enzyme expression in rat liver

Expression of antioxidant enzymes (AOE), an important mechanism in the protection against oxidative stress, could be modified by the redox status of the cells. The aim of this project was to evaluate the role of vitamin E deficiency in association with a high-cholesterol diet in the hepatic lipid peroxidation and the expression of AOE. Two groups of 6 male rats were fed with a high-cholesterol or a high-cholesterol vitamin E-deficient diet. All animals were sacrificed at 72 days of treatment. Liver lipid peroxidation index (Malondialdehyde; MDA) and hepatic AOE were evaluated. Total liver RNA was extracted, and the steady state messenger RNA (mRNA) levels of glutathion peroxydase, manganese superoxide dismutase, Cu/Zn superoxide dismutase and catalase were examined by northern blot. After 72 days on the diet, a significant increase in the lipid peroxidation index was observed in the vitamin E deficient group (MDA : 4.45 +/- 0.29 nmol/mg protein versus 3.65 +/- 0.1 nmol/mg protein in vitamin E normal group). Despite this oxidative stress, the activities and mRNA levels of liver AOE were not significantly different in the 2 groups. These preliminary results show that chronic vitamin E deficiency associated with high cholesterol diet is able to increase lipid peroxidation without modulation of AOE expression and activity in the liver. This suggests that beneficial effects of dietary vitamin E are due to a plasma antioxidant effect or a cell mediated action, rather than to a specific modulation of cellular enzymes.     

The effect of long-term selenium and vitamin E-enriched diet on the content of lipid peroxides and cholesterol in rats

The effect of long-term diets enriched with natural antioxidants was studied on Wistar rats with average initial body weight 150 g. After enrichment of the diet with selenium (0.1 ppm of sodium selenite per 100 g of diet), with vitamin E (6 mg of alpha-tocopherol per 100 g of diet) and selenium and vitamin E together the following results were obtained: diets enriched with selenium or vitamin E given for 12 months reduced the production of lipid peroxides in the liver and serum of the rats. On the other hand, addition of both antioxidants to the diet had no effect on lipid peroxide levels in the animals. Diet enrichment for 12 and 18 months with selenium or vitamin E had no effect on the levels of total cholesterol and HDL cholesterol. The obtained results suggest that selenium and alpha-tocopherol exert an inhibitory action on the processes of ageing in the experimental animal model.     

Effect of antioxidants (vitamin C,E and turmeric extract) on methimazole induced hypothyroidism in rats

The study was to investigate the protective effect of antioxidants against methimazole (MMI) induced hypothyroidism in rats. Male Wistar rats were fed MMI, MMI plus vitamin C, MMI plus vitamin E and MMI plus turmeric extract (TE) supplemented diet. At the end of the experiments, thyroid weights, thyroxine (T4), triiodothyronine (T3) and cholesterol levels were determined. It was observed that MMI treated rats showed increase in thyroid weights, very low levels of circulating T4, T3 and increased levels of total cholesterol as compared to controls (P< 0.001). However, rats which received Vit. C, Vit. E or TE along with MMI showed reduced weights (38-55% less) in thyroid glands (P < 0.01), less suppressed T4 and T3 levels (2-6% and 7-35% respectively) and less increase in total cholesterol levels (19-52%) which are statistically significant. The data suggest the positive effect of antioxidants on thyroid gland which could be due to direct involvement of antioxidants on thyroid gland.     

Triiodothyronine and vitamin A-deficiency in the rat

The total (TT3) and free serum triiodothyronine (fT3) and the distribution of a tracer dose of 125I-T3 were studied in rats on a vitamin A-deficient diet. After 6 weeks on the diet there was an increased serum T3 (TT3 and fT3). But after injection of 125I-T3 a smaller radioactivity was counted in kidney and liver of deficient animals, thus revealing a smaller transport of T3 into the target cells. So vitamin A-deficiency induces an original hormonal status responsible for the conflicting metabolic changes already described in deficient rats.     

The effect of long-term enrichment of diet with selenium, vitamin E and B15 on the activity of certain enzymes in rat brain

The aim of this study was tracing of changes in the activity of glutathione peroxidase (GSHPx), glutathione transferase (GSH S-Tr), aspartate aminotransferase (AspAT) and alanine aminotransferase (A1AT) in the brain as a result of diet enrichment with antioxidants: selenium (Se), vitamin E and vitamin B15 (pangamic acid). The experiment was carried out on Wistar rats with initial body weight 150 g. Following prolonged enrichment of diet with Se (0.1 ppm of sodium selenite), vitamin E (6 mg/100 g of diet) and vitamin B15 (2.5 mg/100 g of diet) the following results were obtained. The activity of GSHPx in brain microsomes was not changed after one year of vitamin E administration when it was measured against hydrogen hydroxide and against cumene hydrochloride; vitamin E administration increased the activity of GSH S-Tr in the cytoplasmic fraction of brain cells. Diet enrichment with selenium increased after 12 and 18 months the activity of GSHPx measured against both substrates, and GSH S-Tr activity increased considerably. Presence of vitamin B15 in diet reduced GSHPx activity after one-year or longer administration, after 18 months the activity of GSH S-Tr was reduced also. No changes were noted in the activity of AspAT and A1AT.     

Effect of retinol on the hemolysis and lipid peroxidation in vitamin E deficiency

A study on the effect of retinolin vitro on the hemolysis of vitamin E deficient rat red blood cells showed that retinol enhanced the lysis of the E deficient cells as compared to the lysis of normal cells. The lipid peroxidation present during hydrogen peroxide induced lysis of E deficient cells was however markedly inhibited in the presence of retinol without affecting the rate of lysis. In an actively peroxidising system of non-enzymatic lipid peroxidation of rat liver or brain homogenates and of brain lysosomes incubated with human erythrocytes, no lysis was obtained; incorporation of retinol in such systems resulted in lysis but no peroxidation. Hydrogen peroxide generating substances almost completely inhibited the lysis of normal human erythrocytes by retinol, but linoleic acid hydroperoxide and auto-oxidised liver or brain homogenates and ox-brain liposomes increased the lysis. It is concluded that vitamin E deficient erythrocyte hemolysis may be augmented by retinol, an anti-oxidant, having a lytic function without the peroxidation of stromal lipids