Inhibition of rat microsomal lipid peroxidation by the oral administration of D002

The effect of D002, a defined mixture of higher primary alcohols purified from bee wax, on in vivo and in vitro lipid peroxidation was studied. The extent of lipid peroxidation was measured on the basis of the levels of thiobarbituric acid reactive substances (TBARS). When D002 (5-100 mg/kg body weight) was administered orally to rats for two weeks, a partial inhibition of the in vitro enzymatic and non-enzymatic lipid peroxidation was observed in liver and brain microsomes. Maximal protection (46%) occurred at a dose of 25 mg/kg. D002 behaved differently depending on both the presence of NADPH and the integrity of liver microsomes, which suggests that under conditions where microsomal metabolism was favored the protective effect of D002 was increased. D002 (25 mg/kg) also completely inhibited carbon tetrachloride- and toluene-induced in vivo lipid peroxidation in liver and brain. Also, D002 significantly lowered in a dose-dependent manner the basal level of TBARS in liver (19-40%) and brain (28-44%) microsomes. We conclude that the oral administration of D002 (5, 25 and 100 mg/kg) for two weeks protected rat liver and brain microsomes against microsomal lipid peroxidation in vitro and in vivo. Thus, D002 could be useful as a dietary natural antioxidant supplement. More studies are required before these data can be extrapolated to the recommendation for the use of D002 as a dietary antioxidant supplement for humans.

Oxidative stress in the latissimus dorsi muscle of diabetic rats

The purpose of the present study was to investigate the effects of experimental diabetes on the oxidant and antioxidant status of latissimus dorsi (LD) muscles of male Wistar rats (220 ± 5 g, N = 11). Short-term (5 days) diabetes was induced by a single injection of streptozotocin (STZ, 50 mg/kg, iv; glycemia >300 mg/dl). LD muscle of STZ-diabetic rats presented higher levels of thiobarbituric acid reactive substances (TBARS) and chemiluminescence (0.36 ± 0.02 nmol/mg protein and 14706 ± 1581 cps/mg protein) than LD muscle of normal rats (0.23 ± 0.04 nmol/mg protein and 7389 ± 1355 cps/mg protein). Diabetes induced a 92% increase in catalase and a 27% increase in glutathione S-transferase activities in LD muscle. Glutathione peroxidase activity was reduced (58%) in STZ-diabetic rats and superoxide dismutase activity was similar in LD muscle of both groups. A positive correlation was obtained between catalase activity and the oxidative stress of LD, as evaluated in terms of TBARS (r = 0.78) and by chemiluminescence (r = 0.89). Catalase activity also correlated inversely with glutathione peroxidase activity (r = 0.79). These data suggest that an increased oxidative stress in LD muscle of diabetic rats may be related to skeletal muscle myopathy.

Incorporation of dietary trans monounsaturated fatty acids into tissues of Walker 256 tumor-bearing rats

The correlation between dietary trans fatty acids and neoplasia was examined in the present study. Walker 256 tumor-bearing and control rats were fed a trans monounsaturated fatty acid (MUFA)-rich diet for 8 weeks and the incorporation of trans fatty acids by tumor tissue was examined. Also, the effect of tumor growth on trans fatty acid composition of plasma and liver, and the content of thiobarbituric acid-reactive substances (TBARS) was determined. Walker 256 tumor cells presented both trans and cis MUFAs given in the diet. The equivalent diet proportions were 0.66 for trans and 1.14 for cis. Taking into consideration the proportion of trans MUFAs in plasma (11.47%), the tumor incorporated these fatty acids in a more efficient manner (18.27%) than the liver (9.34%). Therefore, the dietary trans fatty acids present in the diet are actively incorporated by the tumor. Tumor growth itself caused marked changes in the proportion of polyunsaturated fatty acids in the plasma and liver but provoked only slight modifications in both trans and cis MUFAs. Tumor growth also reduced the unsaturation index in both plasma and liver, from 97.79 to 86.83 and from 77.51 to 69.64, respectively. This effect was partially related to an increase in the occurrence of the lipid oxidation/peroxidation process of TBARS content which was increased in both plasma (from 0.428 to 0.505) and liver (from 9.425 to 127.792) due to tumor growth.

Determination of serum aluminum, platelet aggregation and lipid peroxidation in hemodialyzed patients

Aluminum (Al3+) overload is frequently associated with lipid peroxidation and neurological disorders. Aluminum accumulation is also reported to be related to renal impairment, anemia and other clinical complications in hemodialysis patients. The aim of the present study was to determine the degree of lipid peroxidation, platelet aggregation and serum aluminum in patients receiving regular hemodialytic treatment. The level of plasma lipid peroxidation was evaluated on the basis of thiobarbituric acid reactive substances (TBARS). Mean platelet peroxidation in patients undergoing hemodialysis was significantly higher than in normal controls (2.7 ± 0.03 vs 1.8 ± 0.06 nmol/l, P<0.05). Platelet aggregation and serum aluminum levels were determined by a turbidimetric method and atomic absorption spectrophotometry, respectively. Serum aluminum was significantly higher in patients than in normal controls (44.5 ± 29 vs 10.8 ± 2.5 µg/l, P<0.05). Human blood platelets were stimulated with collagen (2.2 µg/ml), adenosine diphosphate (6 µM) and epinephrine (6 µM) and showed reduced function with the three agonists utilized. No correlation between aluminum levels and platelet aggregation or between aluminum and peroxidation was observed in hemodialyzed patients.

Lipid peroxidation and total radical-trapping potential of the lungs of rats submitted to chronic and sub-chronic stress

Exposure to stress induces a cluster of physiological and behavioral changes in an effort to maintain the homeostasis of the organism. Long-term exposure to stress, however, has detrimental effects on several cell functions such as the impairment of antioxidant defenses leading to oxidative damage. Oxidative stress is a central feature of many diseases. The lungs are particularly susceptible to lesions by free radicals and pulmonary antioxidant defenses are extensively distributed and include both enzymatic and non-enzymatic systems. The aim of the present study was to determine lipid peroxidation and total radical-trapping potential (TRAP) changes in lungs of rats submitted to different models of chronic stress. Adult male Wistar rats weighing 180-230 g were submitted to different stressors (variable stress, N = 7) or repeated restraint stress for 15 (N = 10) or 40 days (N = 6) and compared to control groups (N = 10 each). Lipid peroxidation levels were assessed by thiobarbituric acid reactive substances (TBARS), and TRAP was measured by the decrease in luminescence using the 2-2'-azo-bis(2-amidinopropane)-luminol system. Chronic variable stress induced a 51% increase in oxidative stress in lungs (control group: 0.037 ± 0.002; variable stress: 0.056 ± 0.007, P < 0.01). No difference in TBARS was observed after chronic restraint stress, but a significant 57% increase in TRAP was presented by the group repeatedly restrained for 15 days (control group: 2.48 ± 0.42; stressed: 3.65 ± 0.16, P < 0.05). We conclude that different stressors induce different effects on the oxidative status of the organism.

Effect of an aqueous extract of Scoparia dulcis on blood glucose, plasma insulin and some polyol pathway enzymes in experimental rat diabetes

The effects of an aqueous extract of the plant Scoparia dulcis (200 mg/kg) on the polyol pathway and lipid peroxidation were examined in the liver of streptozotocin adult diabetic male albino Wistar rats. The diabetic control rats (N = 6) presented a significant increase in blood glucose, sorbitol dehydrogenase, glycosylated hemoglobin and lipid peroxidation markers such as thiobarbituric acid reactive substances (TBARS) and hydroperoxides, and a significant decrease in plasma insulin and antioxidant enzymes such as glutathione peroxidase (GPx), glutathione-S-transferase (GST) and reduced glutathione (GSH) compared to normal rats (N = 6). Scoparia dulcis plant extract (SPEt, 200 mg kg-1 day-1) and glibenclamide (600 µg kg-1 day-1), a reference drug, were administered by gavage for 6 weeks to diabetic rats (N = 6 for each group) and significantly reduced blood glucose, sorbitol dehydrogenase, glycosylated hemoglobin, TBARS, and hydroperoxides, and significantly increased plasma insulin, GPx, GST and GSH activities in liver. The effect of the SPEt was compared with that of glibenclamide. The effect of the extract may have been due to the decreased influx of glucose into the polyol pathway leading to increased activities of antioxidant enzymes and plasma insulin and decreased activity of sorbitol dehydrogenase. These results indicate that the SPEt was effective in attenuating hyperglycemia in rats and their susceptibility to oxygen free radicals.

Protective effects of organoselenium compounds against methylmercury-induced oxidative stress in mouse brain mitochondrial-enriched fractions

We evaluated the potential neuroprotective effect of 1-100 µM of four organoselenium compounds: diphenyl diselenide, 3’3-ditri-fluoromethyldiphenyl diselenide, p-methoxy-diphenyl diselenide, and p-chloro-diphenyl diselenide, against methylmercury-induced mitochondrial dysfunction and oxidative stress in mitochondrial-enriched fractions from adult Swiss mouse brain. Methylmercury (10-100 µM) significantly decreased mitochondrial activity, assessed by MTT reduction assay, in a dose-dependent manner, which occurred in parallel with increased glutathione oxidation, hydroperoxide formation (xylenol orange assay) and lipid peroxidation end-products (thiobarbituric acid reactive substances, TBARS). The co-incubation with diphenyl diselenide (100 µM) completely prevented the disruption of mitochondrial activity as well as the increase in TBARS levels caused by methylmercury. The compound 3’3-ditrifluoromethyldiphenyl diselenide provided a partial but significant protection against methylmercury-induced mitochondrial dysfunction (45.4 ± 5.8% inhibition of the methylmercury effect). Diphenyl diselenide showed a higher thiol peroxidase activity compared to the other three compounds. Catalase blocked methylmercury-induced TBARS, pointing to hydrogen peroxide as a vector during methylmercury toxicity in this model. This result also suggests that thiol peroxidase activity of organoselenium compounds accounts for their protective actions against methylmercury-induced oxidative stress. Our results show that diphenyl diselenide and potentially other organoselenium compounds may represent important molecules in the search for an improved therapy against the deleterious effects of methylmercury as well as other mercury compounds.

Time-course effects of aerobic exercise training on cardiovascular and renal parameters in 2K1C renovascular hypertensive rats

Exercise training (Ex) has been recommended for its beneficial effects in hypertensive states. The present study evaluated the time-course effects of Ex without workload on mean arterial pressure (MAP), reflex bradycardia, cardiac and renal histology, and oxidative stress in two-kidney, one-clip (2K1C) hypertensive rats. Male Fischer rats (10 weeks old; 150–180 g) underwent surgery (2K1C or SHAM) and were subsequently divided into a sedentary (SED) group and Ex group (swimming 1 h/day, 5 days/week for 2, 4, 6, 8, or 10 weeks). Until week 4, Ex decreased MAP, increased reflex bradycardia, prevented concentric hypertrophy, reduced collagen deposition in the myocardium and kidneys, decreased the level of thiobarbituric acid-reactive substances (TBARS) in the left ventricle, and increased the catalase (CAT) activity in the left ventricle and both kidneys. From week 6 to week 10, however, MAP and reflex bradycardia in 2K1C Ex rats became similar to those in 2K1C SED rats. Ex effectively reduced heart rate and prevented collagen deposition in the heart and both kidneys up to week 10, and restored the level of TBARS in the left ventricle and clipped kidney and the CAT activity in both kidneys until week 8. Ex without workload for 10 weeks in 2K1C rats provided distinct beneficial effects. The early effects of Ex on cardiovascular function included reversing MAP and reflex bradycardia. The later effects of Ex included preventing structural alterations in the heart and kidney by decreasing oxidative stress and reducing injuries in these organs during hypertension.

Inflammatory cytokines and plasma redox status responses in hypertensive subjects after heat exposure

Hypertension is characterized by a pro-inflammatory status, including redox imbalance and increased levels of pro-inflammatory cytokines, which may be exacerbated after heat exposure. However, the effects of heat exposure, specifically in individuals with inflammatory chronic diseases such as hypertension, are complex and not well understood. This study compared the effects of heat exposure on plasma cytokine levels and redox status parameters in 8 hypertensive (H) and 8 normotensive (N) subjects (age: 46.5±1.3 and 45.6±1.4 years old, body mass index: 25.8±0.8 and 25.6±0.6 kg/m2, mean arterial pressure: 98.0±2.8 and 86.0±2.3 mmHg, respectively). They remained at rest in a sitting position for 10 min in a thermoneutral environment (22°C) followed by 30 min in a heated environmental chamber (38°C and 60% relative humidity). Blood samples were collected before and after heat exposure. Plasma cytokine levels were measured using sandwich ELISA kits. Plasma redox status was determined by thiobarbituric acid reactive substances (TBARS) levels and ferric reducing ability of plasma (FRAP). Hypertensive subjects showed higher plasma levels of IL-10 at baseline (P<0.05), although levels of this cytokine were similar between groups after heat exposure. Moreover, after heat exposure, hypertensive individuals showed higher plasma levels of soluble TNF receptor (sTNFR1) and lower TBARS (P<0.01) and FRAP (P<0.05) levels. Controlled hypertensive subjects, who use angiotensin-converting-enzyme inhibitor (ACE inhibitors), present an anti-inflammatory status and balanced redox status. Nevertheless, exposure to a heat stress condition seems to cause an imbalance in the redox status and an unregulated inflammatory response.

Effect of dietary supplementation with selenium-enriched yeast or sodium selenite on selenium tissue distribution and meat quality in beef cattle

The objective was to determine the concentration of total selenium (Se) and the proportion of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys) in post mortem tissues of beef cattle offered diets containing graded additions of selenized enriched yeast (SY) [Saccharomyces cerevisae CNCM I-3060]), or sodium selenite (SS). Oxidative stability and tissue glutathione peroxidase (GSH-Px) activity of edible muscle tissue were assessed 10 d post-mortem. Thirty two beef cattle were offered, for a period of 112 d, a total mixed ration which had either been supplemented with SY (0, 0.15 or 0.35 mg Se/kg DM) or SS (0.15 mg Se/kg DM). At enrollment (0 d) and at 28, 56, 84 and 112 d following enrollment, blood samples were taken for Se and Se species determination, as well as whole blood GSH-Px activity. At the end of the study beef cattle were euthanized and samples of heart, liver, kidney, and skeletal muscle (LM and psoas major) were retained for Se and Se species determination. Tissue GSH-Px activity and thiobarbituric acid reactive substances (TBARS) were determined in skeletal muscle tissue (LM only). The incorporation into the diet of ascending concentrations of Se as SY increased whole blood total Se and the proportion of total Se comprised as SeMet, as well as GSH-Px activity. There was also a dose dependant response to the graded addition of SY on total Se and proportion of total Se as SeMet in all tissues and GSH-Px activity in skeletal muscle tissue. Furthermore, total Se concentration of whole blood and tissues was greater in those animals offered SY when compared with those receiving a comparable dose of SS, indicating an improvement in Se availability and tissue Se retention. Likewise, GSH-Px activity in whole blood and LM was greater in those animals offered SY when compared with those receiving a comparable dose of SS. However, these increases in tissue total Se and GSH-Px activity appeared to have little or no effect in meat oxidative stability.

Effects of dietary supplementation with selenium enriched yeast or sodium selenite on selenium tissue distribution and meat quality in lambs

The objective was to determine the concentration of total selenium (Se) and the proportion of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys), as well as meat quality in terms of oxidative stability in post mortem tissues of lambs offered diets with an increasing dose rate of selenized enriched yeast (SY), or sodium selenite (SS). Fifty lambs were offered, for a period of 112 d, a total mixed ration which had either been supplemented with SY (0, 0.11, 0.21 or 0.31 mg/kg DM to give total Se contents of 0.19, 0.3, 0.4 and 0.5 mg Se/kg DM for treatments T1, T2, T3 and T4, respectively) or SS (0.11 mg/kg DM to give 0.3 mg Se/kg DM total Se [T5]). At enrolment and at 28, 56, 84 and 112 d following enrolment, blood samples were taken for Se and Se species determination, as well as glutathione peroxidase (GSH-Px) activity. At the end of the study lambs were euthanased and samples of heart, liver, kidney, and skeletal muscle were retained for Se and Se species determination. Tissue GSH-Px activity and thiobarbituric acid reactive substances (TBARS) were determined in Longissimus Thoracis. The incorporation into the diet of ascending concentrations of Se as SY increased whole blood total Se and the proportion of total Se comprised as SeMet, and erythrocyte GSH-Px activity. Comparable doses of SS supplementation did not result in significant differences between these parameters. With the exception of kidney tissue, all other tissues showed a dose dependant response to increasing concentrations of dietary SY, such that total Se and SeMet increased. Selenium content of Psoas Major was higher in animals fed SY when compared to a similar dose of SS, indicating improvements in Se availability and retention. There were no significant treatment effects on meat quality assessments GHS-Px and TBARS, reflecting the lack of difference in the proportion of total Se that was comprised as SeCys. However, oxidative stability improved marginally with ascending tissue Se content, providing an indication of a linear dose response whereby TBARS improved with ascending SY inclusion.

Mechanisms by which cysteine can inhibit or promote the oxidation of low density lipoprotein by copper

Oxidised low density lipoprotein (LDL) may play a role in atherogenesis. We have investigated some of the mechanisms by which the thiol cysteine and the disulphide cystine can influence the oxidation of LDL by copper ions. Cysteine or cystine (100 PM) inhibited the oxidation of native LDL by copper in a simple phosphate buffer. One of the mechanisms by which cysteine (or more likely its oxidation products in the presence of copper) and cystine inhibited LDL oxidation was by decreasing the binding of copper to LDL (97% inhibition). Cysteine, but not cystine, rapidly reduced Cu2+ to Cu+. This may help to explain the antioxidant effect of cysteine as it may limit the amount of Cu2+ that is available to convert alpha-tocopherol in LDL into the prooxidant alpha-tocopherol radical. Cysteine (but not cystine) had a prooxidant effect, however, toward partially oxidised LDL in the presence of a low copper concentration, which may have been due to the rapid breakdown of lipid hydroperoxides in partially oxidised LDL by Cu+ generated by cysteine. To prove that cysteine can cause the rapid breakdown of lipid hydroperoxides in LDL, we enriched LDL with lipid hydroperoxides using an azo initiator in the absence of copper. Cysteine, but not cystine, increased the rate of lipid hydroperoxide decomposition to thiobarbituric acid-reactive substances (TBARS) in the presence of copper. (C) 2003 Elsevier Ireland Ltd. All rights reserved.

Antioxidant properties of Teaw (Cratoxylum formosum Dyer) extract in soybean oil and emulsions

The antioxidant activity of an extract from Teaw (Cratoxylum formosum Dyer) leaves was studied in soybean oil and soybean oil-in-water emulsions. Samples containing the extract or reference antioxidants including chlorogenic acid, which comprises 60% of the Teaw extract, were stored at 60 degrees C and analyzed periodically for peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) to allow both hydroperoxides and hydroperoxide degradation products to be monitored. Chlorogenic acid and the Teaw extract were more effective than a-tocopherol in inhibiting lipid oxidation in bulk oil but were less effective in an oil-in-water emulsion in accordance with the polar paradox. The PV/TBARS ratio for oil samples containing chlorogenic acid was higher than for alpha-tocopherol and BHT because chlorogenic acid inhibits both hydroperoxide formation by radical scavenging and hydroperoxide decomposition by metal chelation. The importance of the metal-chelating activity in retarding hydroperoxide decomposition was confirmed by studying the decomposition of oil samples containing added ferric ions. The PV/TBARS ratio was higher for citric acid than for (x-tocopherol in the presence of added ferric chloride, but the order was reversed in samples lacking ferric chloride. Samples containing added chlorogenic acid gave the highest PV/TBARS ratios both in the presence and absence of ferric ions. The PV/TBARS ratios for the samples containing antioxidants fell rapidly to lower values in a soybean oil-in-water emulsion than in the soybean oil. This was due to increased hydroperoxide decomposition in the emulsion at the same PV. The Teaw extract contained 12% oil-soluble components, which contributed to a slightly higher oil-water partition coefficient than that of chlorogenic acid. The antioxidant activity of the aqueous phase of the Teaw extract was reduced more than that of chlorogenic acid by partitioning of the oil-soluble components into oil, which showed that the less-polar components contributed to the antioxidant activity of the Teaw extract in aqueous media.

Enhancing the oxidative stability of rice crackers by addition of the ethanolic extract of phytochemicals from Cratoxylum formosum Dyer

Craloxylum formosum Dyer is consumed throughout the year as food and medicine in Thailand. It contains large amounts of chlorogenic acid and quinic acid derivatives. The antioxidative activity of the extract was studied in refined soybean oil coating on rice crackers without any seasoning. They were stored in accelerated oxidation conditions at 40 degrees C, 80% relative humidity (RH) in the dark for 18 days. The oxidative state of each sample was monitored by analyzing of the peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) as well as by odor analysis by quantitative descriptive analysis (QDA). The C formosum extract was more effective than alpha-tocopherol due to metal ions present in the crackers, which resulted in alpha-tocopherol being less effective as an antioxidant. Sensory odor attributes of rice crackers were related more closely to TBARS than to PV values by linear regression analysis. The present study indicated that C. formosum extract was a promising source of a natural food antioxidant and was effective in inhibiting lipid oxidation in rice crackers.

Effects of dietary selenium supplementation on tissue selenium distribution and glutathione peroxidase activity in Chinese Ring Necked Pheasants

The objective of this study was to determine the concentration of total selenium (Se) and the proportions of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys) in the post mortem tissues of female pheasants (Phasianus Colchicus Torquator) offered diets containing graded additions of selenized enriched yeast (SY) or sodium selenite (SS). Thiobarbituric acid reactive substances (TBARS) and tissue glutathione peroxidase (GSH-Px) activity of breast (Pectoralis Major) were assessed at 0 and 5 d post-mortem. A total of 216 female pheasant chicks were enrolled onto the study. 24 birds were euthanased at the start of the study and samples of blood, breast muscle, leg muscle (Peroneus Longus and M. Gastrocnemius), heart, liver, kidney and gizzard collected for determination of total Se. Remaining birds were blocked by live weight and randomly allocated to one of four dietary treatments (n=48 birds/treatment) that either differed in Se source (SY vs. SS) or dose (Con [0.2 mg total Se/kg], SY-L and SS-L [0.3 mg/kg total Se as SY and SS, respectively], and SY-H [0.45 mg total Se/kg]). Following 42 and 91 days of treatment 24 birds/treatment were euthanased and samples of blood, breast muscle, leg muscle, heart, liver, kidney and gizzard retained for determination of total Se and the proportion of total Se comprised as SeMet or SeCys. Whole blood GSH-Px activity was determined at each time point. Tissue GSH-Px activity and TBARS were determined in breast tissue at the end of the study. There were positive responses (P<0.001) in both blood and tissues to the graded addition of SY to the diet but the same responses were not apparent in the blood and tissues of selenite supplemented birds receiving comparable doses. Although there were differences between tissue types in the distribution of SeMet and SeCys there were few differences between treatments. There were effects of treatment on erythrocyte GSH-Px activity (P = 0.012) with values being higher in treatments SY-H and SS-L when compared to the negative control and treatment SY-L. There were no effects of treatment on tissue GSH-Px activity which is reflected in the overall lack of any treatment effects on TBARS.