Low doses of eicosapentaenoic acid, docosahexaenoic acid, and hypolipidemic eicosapentaenoic acid derivatives have no effect on lipid peroxidation in plasma

Docosahexaenoic Acid as Master Regulator of Cellular Antioxidant Defenses: A Systematic Review

Docosahexaenoic acid (DHA) is a polyunsaturated fatty acid that benefits the prevention of chronic diseases. Due to its high unsaturation, DHA is vulnerable to free radical oxidation, resulting in several unfavorable effects, including producing hazardous metabolites. However, in vitro and in vivo investigations suggest that the relationship between the chemical structure of DHA and its susceptibility to oxidation may not be as clear-cut as previously thought. Organisms have developed a balanced system of antioxidants to counteract the overproduction of oxidants, and the nuclear factor erythroid 2-related factor 2 (Nrf2) is the key transcription factor identified for transmitting the inducer signal to the antioxidant response element. Thus, DHA might preserve the cellular redox status promoting the transcriptional regulation of cellular antioxidants through Nrf2 activation. Here, we systematically summarize the research on the possible role of DHA in controlling cellular antioxidant enzymes. After the screening process, 43 records were selected and included in this review. Specifically, 29 studies related to the effects of DHA in cell cultures and 15 studies concerned the effects of consumption or treatment with DHA in animal. Despite DHA's promising and encouraging effects at modulating the cellular antioxidant response in vitro/in vivo, some differences observed among the reviewed studies may be accounted for by the different experimental conditions adopted, including the time of supplementation/treatment, DHA concentration, and cell culture/tissue model. Moreover, this review offers potential molecular explanations for how DHA controls cellular antioxidant defenses, including involvement of transcription factors and the redox signaling pathway.

DHA from microalgae Schizochytrium spp. (Thraustochytriaceae) modifies the inflammatory response and gonadal lipid profile in domestic cats

The present study aimed to evaluate the inflammatory response, oxidative status and fatty acid deposition in reproductive tissues of cats supplemented with the dried microalgae Schizochytrium spp. (Thraustochytriaceae) as a DHA source. Thirty-seven cats (males, n 21; females, n 16; 11·5 (sd 0·5) months of age) were divided by sex into five groups. Treatment diets contained algae biomass at 4·0, 8·0, 12·0 or 16·0 g/kg replacing poultry fat (n-6 source). Cats were fed the respective diet for 62 d and neutered on day 58. Blood samples were collected at the beginning of the experiment (day 1), before neutering (day 58) and 4 d after surgery (day 62) for analysis of inflammation and oxidative markers. Acute-phase protein levels were altered (P < 0·01) in the postoperative period, without any treatment effect (P > 0·05). PGE2 concentrations after surgery were reduced linearly (R2 0·8706; P = 0·002) with microalgal inclusion. Blood platelet count was reduced (P = 0·001) after the surgery regardless treatment, but it was higher in the DHA group compared with control (P < 0·001). The DHA deposition (testicles, R2 0·846; ovaries, R2 0·869) and the n-6:n-3 ratio (testicles, R2 0·859; ovaries, R2 0·955) in gonads had a pattern which fitted a quadratic model. DHA from Schizochytrium spp. modifies PGE2 response after the surgery in cats. The physiological roles of the DHA in the reproduction of cats were not investigated, but its gonadal deposition after supplementation was observed.

ω-3 fish oil fat emulsion preconditioning mitigates myocardial oxidative damage in rats through aldehydes stress

ω-3 fish oil fat emulsions contain a considerable quantity of unsaturated carbon-carbon double bonds, which undergo lipid peroxidation to yield low-dose aldehydes. These aldehydes may stimulate the production of antioxidant enzymes, thereby mitigating myocardial oxidative damage. This study aims to (1) verify the cardioprotective effect of ω-3 fish oil fat emulsion in vivo and in vitro, and (2) determine whether aldehyde stress is a protective mechanism. For modeling purposes, we pretreated rats with 2 ml/kg of a 10% ω-3 fish oil fat emulsion for 5 days in order to generate a sufficient aldehyde stress response to trigger the production of antioxidant enzymes, and we obtained similar response with H9C2 cells that were pretreated with a 0.5% ω-3 fish oil fat emulsion for 24 h. ω-3 fish oil fat emulsion pretreatment in vivo reduced the myocardial infarct size, decreased the incidence of arrhythmias, and promoted the recovery of cardiac function after myocardial ischemia/reperfusion injury. Once the expression of nuclear factor E2-related factor 2 (Nrf2) was silenced in H9C2 cells, aldehydes no longer produced enough antioxidant enzymes to reverse the oxidative damage caused by tert-butyl hydroperoxide (TBHP). Our results demonstrated that ω-3 fish oil fat emulsion enhanced the inhibition of oxidation and production of free radicals, and alleviated myocardial oxidative injury via activation of the Nrf2 signaling pathway.

Ω3-Polyunsaturated fatty acids prevent lipoperoxidation, modulate antioxidant enzymes, and reduce lipid content but do not alter glycogen metabolism in the livers of diabetic rats fed on a high fat thermolyzed diet

Ω3-Polyunsaturated fatty acids (Ω3-PUFAs) are known to act as hypolipidaemics, but the literature is unclear about the effects that Ω3-PUFAs have on oxidative stress in obese and diabetic patients. In this study, our aim was to investigate the effects of Ω3-PUFAs on oxidative stress, including antioxidant enzyme activity and hepatic lipid and glycogen metabolism in the livers of diabetic and non-diabetic rats fed on a high fat thermolyzed diet. Rats were divided into six groups: (1) the control group (C), (2) the control diabetic group (D), (3) the high fat thermolyzed diet group (HFTD), which were fed a diet that was enriched in fat that was heated for 60 min at 180°C, (4) the high fat thermolyzed diet diabetic group (D + HFTD), (5) the high fat thermolyzed diet + Ω3 polyunsaturated fatty acid group (HFTD + Ω3), and (6) the high fat thermolyzed diet + Ω3 polyunsaturated fatty acid diabetic group (D + HFTD + Ω3). The most important finding of this study was that Ω3-PUFAs are able to reduce triglycerides, non-esterified fatty acid, lipoperoxidation levels, advanced glycation end products, SOD/CAT enzymatic ratio, and CAT immunocontent and increase SOD2 levels in the livers of diabetic rats fed with a HFTD. However, Ω3-PUFAs did not alter the observed levels of protein damage, blood glucose, or glycogen metabolism in the liver. These findings suggest that Ω3-PUFAs may represent an important auxiliary adjuvant in combating some diseases like diabetes mellitus, insulin resistance, and non-alcoholic fatty liver disease.

The efficacy of omega-3 fatty acid supplementation on plasma homocysteine and malondialdehyde levels of type 2 diabetic patients

BACKGROUND AND AIMS

Cardiovascular diseases are the major cause of mortality among diabetic patients. The concentration of malondialdehyde (MDA) and homocysteine is believed to play a role in cardiovascular diseases. Omega-3 fatty acid supplementation could be effective in some diabetes complications and in the control of the glycemic index. However, it may increase lipid peroxidation. The objective of this study was to determine the effect of omega-3 fatty acids on the concentration of homocysteine and MDA in diabetic patients.

METHODS AND RESULTS

A randomized double-blind, placebo-controlled clinical trial was conducted on 81 patients with type 2 diabetes. The patients were randomly assigned to either the treatment or control groups. Each subject received three capsules of omega-3 fatty acids or a placebo every day for a period of 2months. The two groups were similar in terms of body mass index and food intake. At the beginning of the study and after 2months of supplementation their levels of HbA(1)c, homocysteine, MDA, C-reactive protein (CRP), total cholesterol, LDL-cholesterol and fasting blood sugar (FBS) were determined. Due to omega-3 fatty acid supplementation, homocysteine was changed significantly in both treatment and control groups up to -3.10mumol/L and 0.10mumol/L respectively, and HbA(1)c decreased by 0.75% in the treatment group and increased by 0.26% in the control group. However, the changes in fasting blood sugar (FBS), malondialdehyde (MDA), C-reactive protein (CRP), total cholesterol and LDL-cholesterol levels were not significant.

CONCLUSION

The consumption of omega-3 fatty acid supplements (3g/day) for 2months decreases the levels of homocysteine in diabetic patients with no change in FBS, MDA and CRP levels.

Tetradecylthioacetic acid attenuates dyslipidaemia in male patients with type 2 diabetes mellitus, possibly by dual PPAR-alpha/delta activation and increased mitochondrial fatty acid oxidation

AIM

We previously demonstrated that a modified fatty acid, tetradecylthioacetic acid (TTA), improves transport and utilization of lipids and increases mitochondrial fatty acid oxidation in animal and cell studies. We conducted an exploratory study of safety and effects of this novel drug in patients with type 2 diabetes mellitus and investigated the mechanism of action in human cell lines.

METHODS

Sixteen male patients with type 2 diabetes mellitus received 1 g TTA daily for 28 days in an open-labelled study, with measurement of parameters of lipid metabolism, glucose metabolism and safety (ClinicalTrials.gov NCT00605787). The mechanism of action was further investigated in a human liver cell line (HepG2) and in cultured human skeletal muscle cells (myotubes).

RESULTS

Mean LDL cholesterol level declined from 4.2 to 3.7 mmol/l (p < 0.001), accompanied by increased levels of the HDL apolipoproteins A1 and A2, and a decline in LDL/HDL ratio from 4.00 to 3.66 (p = 0.008). Total fatty acid levels declined, especially the fraction of the polyunsaturated n-3 fatty acids docosahexaenoic acid (-13%, p = 0.002) and eicosapentaenoic acid (-10%, p = 0.07). Glucose metabolism was not altered and the drug was well tolerated. In cultured liver cells, TTA acted as a pan-PPAR agonist with predominant PPAR-alpha and PPAR-delta activation at low TTA concentrations. In myotubes, TTA and a PPAR-delta agonist, but not the PPAR-alpha or PPAR-gamma agonists, increased the fatty acid oxidation.

CONCLUSIONS

We demonstrate for the first time that TTA attenuates dyslipidaemia in patients with type 2 diabetes mellitus. These effects may occur through mechanisms involving PPAR-alpha and PPAR-delta activation, resulting in increased mitochondrial fatty acid oxidation.

Effect of Docosahexaenoic Acid Ingestion on Temporal Change in Urinary Excretion of Mercapturic Acid in ODS Rats

We hypothesized a suppressive mechanism for docosahexaenoic acid (22:6n-3; DHA)-induced tissue lipid peroxidation in which the degradation products, especially aldehydic compounds, are conjugated with glutathione through catalysis by glutathione S-transferases, and then excreted into urine as mercapturic acids. In the present study, ascorbic acid-requiring ODS rats were fed a diet containing DHA (3.6% of total energy) for 31 days. Lipid peroxides including degradation products and their scavengers in the liver and kidney were determined, and the temporal change in the urinary excretion of mercapturic acids was also measured. The activity of aldehyde dehydrogenase, which catalyzes the oxidation and detoxification of aldehydes, tended to be higher in the liver of DHA-fed rats. The levels of lipid peroxides as measured by thiobarbituric acid-reactive substances and aldehydic compounds were higher and that of alpha-tocopherol was lower in the liver, and the pattern of temporal changes in the urinary excretion of mercapturic acids was also different between the n-6 linoleic acid and DHA-fed rats. Accordingly, we presume from these results that after dietary DHA-induced lipid peroxidation, a proportion of the lipid peroxidation-derived aldehydic degradation products is excreted into urine as mercapturic acids.

Thia fatty acids with the sulfur atom in even or odd positions have opposite effects on fatty acid catabolism

As tools for mechanistic studies on lipid metabolism, with the long-term goal of developing a drug for the treatment of lipid disorders, thia FA with the sulfur atom inserted at positions 3-9 from the carboxyl group were fed to male Wistar rats for 1 wk to determine their impact on key parameters in lipid metabolism and hepatic levels of thia FA metabolites. Thia FA with the sulfur atom in even positions decreased hepatic and cardiac mitochondrial beta-oxidation and profoundly increased hepatic and cardiac TAG levels. The plasma TAG level was unchanged and the hepatic acyl-CoA oxidase activity increased. In contrast, thia FA with the sulfur atom in odd positions, especially 3-thia FA, tended to increase hepatic and cardiac FA oxidation and acyl-CoA oxidase and carnitine palmitoyltransferase-II activities, and decreased the plasma TAG levels. The effects seem to be related to differences in the catabolic rate of the thia FA. Differences between the two groups of acids were also observed with respect to the regulation of genes involved in FA transport and catabolism. Feeding experiments with 3- and 4-thia FA in combination indicated that the 4-thia FA partly attenuated the effects of the 3-thia FA on mitochondrial FA oxidation and the hepatic TAG level. In summary, the position of the sulfur atom in the alkyl chain, especially whether it is placed in the even or odd position, is crucial for the biological effect of the thia FA.

Effects of ferrous sulphate and non-ionic iron-polymaltose complex on markers of oxidative tissue damage in patients with inflammatory bowel disease

BACKGROUND

Iron deficiency is a common complication of inflammatory bowel disease. Oral iron therapy may reinforce intestinal tissue injury by catalyzing production of reactive oxygen species.

AIM

To compare the effects of ferrous sulphate and non-ionic iron-polymaltose complex on markers of oxidative tissue damage and clinical disease activity in patients with inflammatory bowel disease.

METHODS

Forty-one patients with inflammatory bowel disease and iron deficiency were randomized to treatment with ferrous sulphate 100 mg twice a day or iron-polymaltose complex 200 mg once a day for 14 days.

RESULTS

Following ferrous sulphate, plasma malondialdehyde increased (P = 0.02), while urine 8-isoprostaglandin F(2alpha) and plasma antioxidants did not change significantly. Iron-polymaltose complex did not change plasma malondialdehyde, urine 8-isoprostaglandin F(2alpha) or plasma antioxidants. Comparing the two treatments, changes in plasma malondialdehyde tended to differ (P = 0.08), while urine 8-isoprostaglandin F(2alpha) and plasma antioxidants did not differ. Neither ferrous sulphate nor iron-polymaltose complex altered clinical disease activity indices.

CONCLUSIONS

Ferrous sulphate increased plasma malondialdehyde, a marker of lipid peroxidation. Comparing treatment with ferrous sulphate and iron-polymaltose complex, changes in plasma malondialdehyde tended to differ. Clinical disease activity was unchanged after both treatments.

Oral ferrous fumarate or intravenous iron sucrose for patients with inflammatory bowel disease

OBJECTIVE

Iron therapy may reinforce intestinal inflammation by catalysing production of reactive oxygen species. The effects of oral ferrous fumarate and intravenous iron sucrose on clinical disease activity and plasma redox status were investigated in patients with inflammatory bowel disease (IBD).

MATERIAL AND METHODS

Nineteen patients with iron deficiency anaemia and Crohn's disease (11) or ulcerative colitis (8) were included in a crossover study. The patients were randomly assigned to start treatment with ferrous fumarate (Neo-fer) 120 mg orally once daily or iron sucrose (Venofer) 200 mg intravenously 3 times during a period of 14 days. Clinical disease activity assessment and blood and faecal analysis were performed on days 1 and 15.

RESULTS

Following oral ferrous fumarate clinical disease activity (p=0.037), general well-being score (i.e. patients felt worse) (p=0.027) and abdominal pain score (p=0.027) increased, while no changes were seen following iron sucrose treatment. C-reactive protein (CRP) and faecal calprotectin were unchanged after both treatments. As compared with iron sucrose, ferrous fumarate increased Crohn's disease activity index (CDAI) scores of general well-being (p=0.049), whereas alterations in clinical disease activity (p=0.14) and abdominal pain score (p=0.20) did not differ. Ferrous fumarate did not significantly alter plasma malondialdehyde (MDA) or plasma antioxidants. Iron sucrose increased plasma MDA (p=0.004) and decreased plasma vitamin C (p=0.017) and betacarotene (p=0.008).

CONCLUSIONS

Oral ferrous fumarate, but not intravenous iron sucrose, increased clinical disease activity in IBD patients. Intravenous iron sucrose increased intravascular oxidative stress.

Low-dose oral ferrous fumarate aggravated intestinal inflammation in rats with DSS-induced colitis

BACKGROUND

Oral ferrous iron therapy may reinforce intestinal inflammation. One possible mechanism is by catalyzing the production of reactive oxygen species. We studied the effects of low-dose oral ferrous fumarate on intestinal inflammation and plasma redox status in dextran sulfate sodium (DSS)-induced colitis in rats.

METHODS

Forty male Wistar rats were divided into 5 groups: no intervention, sham gavage (distilled water), ferrous fumarate, DSS, and ferrous fumarate + DSS. Ferrous fumarate was dissolved in distilled water (0.60 mg Fe/kg per day) and administered by gavage on days 1 to 14. All rats were fed a standard diet. Colitis was induced by 5% DSS in drinking water on days 8 to 14. Rats were killed on day 16. Histologic colitis scores, fecal granulocyte marker protein, plasma malondialdehyde, plasma antioxidant vitamins, and plasma aminothiols were measured.

RESULTS

DSS significantly increased histologic colitis scores (P < 0.001) and fecal granulocyte marker protein (P < 0.01). Ferrous fumarate further increased histologic colitis scores (P < 0.01) in DSS-induced colitis. DSS + ferrous fumarate decreased plasma vitamin A compared with controls (P < 0.01). Otherwise, no changes were seen in plasma malondialdehyde, plasma antioxidant vitamins, or plasma aminothiols.

CONCLUSION

Low-dose oral ferrous iron enhanced intestinal inflammation in DSS-induced colitis in rats.

Ferrous fumarate deteriorated plasma antioxidant status in patients with Crohn disease

BACKGROUND

Iron deficiency anaemia is a frequent complication of Crohn disease. Treatment with ferrous iron (Fe2-) compounds is often unsatisfactory and is associated with gastrointestinal side effects. Theoretically, oral iron supplementation may even be harmful, because iron may reinforce intestinal inflammation by catalysing production of reactive oxygen species. We investigated the effect of ferrous iron on disease activity and plasma antioxidant status in patients with active Crohn disease.

METHODS

Ten patients with Crohn disease and iron deficiency and 10 healthy controls were given ferrous fumarate 120 mg for 7 days. The Crohn Disease Activity Index, gastrointestinal complaints and blood samples for antioxidant status, anaemia, inflammation and iron absorption were investigated on day 1 and day 8.

RESULTS

During 1 week of ferrous fumarate supplementation, the Crohn Disease Activity Index tended to increase (P = 0.071). Patients experienced aggravation of diarrhoea, abdominal pain and nausea. Plasma-reduced cysteine was lower (P = 0.038) in patients than it was in controls. One week of ferrous iron supplementation further decreased reduced cysteine (P < 0.001) and significantly decreased plasma-reduced glutathione (P = 0.004) in the patients. Serum iron increased significantly in patients after an oral iron load test (from 5.8 +/- 3.2 micromol/L to 30.9 +/- 13.1 micromol/L).

CONCLUSIONS

Treatment of iron deficiency with ferrous fumarate deteriorated plasma antioxidant status and increased specific clinical symptoms in patients with active Crohn disease. Plasma reduced cysteine may be a sensitive indicator for oxidative stress in the intestine.

Pro- and antioxidant activities of docosahexaenoic acid on human blood platelets

n - 3 polyunsaturated fatty acids may protect against vascular diseases, however, their high accumulation in membranes may increase lipid peroxidation and subsequently induce deleterious effects in patients suffering from oxidative stress. This led us to investigate in vitro the dose-dependent effect of docosahexaenoic acid (DHA) on the redox status of human platelets. We have compared the effect of different DHA concentrations (0.5, 5 and 50 micro mol L(-1)) corresponding to DHA/albumin ratios of 0.01, 0.1 and 1. At the highest concentration, DHA elicited a marked oxidative stress, as evidenced by high malondialdehyde and low vitamin E levels whereas the lowest DHA concentration significantly decreased the malondialdehyde formation, with no change in vitamin E. The proportion of DHA was only increased in plasmalogen phosphatidylethanolamine at low concentration to rise in all phosphatidyl-choline and -ethanolamine subclasses at high concentration. Thus, the results show a biphasic effect of DHA with antioxidant and prooxidant effects at low and high concentrations, respectively, with a possible relationship with the phospholipid subclass in which it accumulates.

Antiproliferative effects of a non-beta-oxidizable fatty acid, tetradecylthioacetic acid, in native human acute myelogenous leukemia blast cultures

The lipid metabolism is important in the regulation of cell proliferation. We have examined effects of a fatty acid analogue, tetradecylthioacetic acid (TTA), on the functional phenotype of native, human AML cells. TTA inhibited AML blast proliferation in the presence of single cytokines (GM-CSF and SCF: P > 0.05, 35 patients with detectable proliferation) and a combination of cytokines (P < 0.005, n = 21). This antiproliferative effect was generally stronger than for the normal fatty acid palmitic acid (PA). Both TTA and PA increased the secretion of tumor necrosis factor alpha (TNFalpha) (P < 0.05, 27 patients with detectable cytokine release), but only PA increased interleukein 1beta (IL-1beta) release (P < 0.005, n = 34). AML blast populations varied significantly in their levels and activities of metabolites and enzymes characterizing oxidative status and fatty acid metabolism, and there was no significant correlation between the intrinsic oxidative status and the effects of PA and TTA on blast proliferation. Although TTA reduced the proliferation of mitogen-stimulated normal T cells derived from healthy individuals (P < 0.05, n = 8), no adverse effects were seen on peripheral blood cell counts (reticulocytes, platelets, total white blood cells, differential leukocyte counts) for healthy volunteers receiving TTA (oral administration of 1000 mg/day for 7 consecutive days). Our results suggest that TTA can inhibit AML blast proliferation through pathways that are unrelated to autocrine cytokine secretion and intrinsic oxidative status.

Docosahexaenoic acid abundance in the brain: a biodevice to combat oxidative stress

Docosahexaenoic acid (DHA) (22:6) is a polyunsaturated fatty acid of the n - 3 series which is believed to be a molecular target for lipid peroxides (LPO) formation. Its ubiquitous nature in the nervous tissue renders it particularly vulnerable to oxidative stress, which is high in brain during normal activity because of high oxygen consumption and generation of reactive oxygen species (ROS). Under steady state conditions potentially harmful ROS and LPO are maintained at low levels due to a strong antioxidant defense mechanism, which involves several enzymes and low molecular weight reducing compounds. The present review emphasizes a paradox: a discrepancy between the expected high oxidability of the DHA molecule due to its high degree of unsaturation and certain experimental results which would indicate no change or even decreased lipid peroxidation when brain tissue is supplied or enriched with DHA. The following is a critical review of the experimental data relating DHA levels in the brain to lipid peroxidation and oxidative damage there. A neuroprotective role for DHA, possibly in association with the vinyl ether (VE) linkage of plasmalogens (pPLs) in combating free radicals is proposed.

Habitual fish intake is associated with decreased LDL susceptibility to ex vivo oxidation

A sample of 101 free-living individuals eating their habitual diets had fish consumptions ranging from less than one serving per week to over five servings per week. Statistically significant positive correlations were found between the amounts of EPA (20:5), DHA (22:6), and total n-3 PUFA ingested with the diet and their amounts in serum and in the phospholipid and cholesterol ester fractions of isolated LDL. No statistically significant correlations were observed between the intake and the serum or LDL amounts of any other FA [total n-6 PUFA, linoleic acid (18:2), arachidonic acid (20:4), monounsaturated FA, or saturated FA)]. The increase in serum n-3 PUFA did not affect the Trolox-equivalent antioxidant capacity of serum (1.18 +/- 0.1 7 mmol/L). When isolated LDL were subjected to Cu2+-induced ex vivo oxidation, a statistically significant but negative correlation was found between intake of n-3 PUFA and the rate of appearance of conjugated dienes as well as with the total amount of conjugated dienes. In contrast, intake of n-6 PUFA showed a significant and positive correlation with these two oxidation parameters. The observed results suggest that 22:6 but not 20:5 could have a possible protective effect, whereas perhaps 20:4 and 18:2 could have a prooxidant effect.

Inhibition of rat lipoprotein oxidation after tetradecylthioacetic acid feeding

We have previously shown that tetradecylthioacetic acid (TTA), a sulfur containing saturated fatty acid analogue, inhibits the oxidative modification of human low-density lipoprotein (LDL) in vitro. The oxidative modification of LDL is believed to be a crucial step in the progression of atherosclerosis. In the present study, we investigated the effect of TTA oral administration on the susceptibility of rat lipoprotein to undergo oxidative modification ex vivo. Lipoprotein resistance to copper-induced oxidation was highly improved after TTA administration to rats. Conjugated dienes produced after 150 min of lipoprotein oxidation were dramatically lowered in the TTA treated rats compared to controls. Malondialdehyde and lipid peroxides production by oxidation was highly limited. These effects were independent of any Vitamin E effects. More than 50% relative reduction in polyunsaturated fatty acids of the n-3 family, and more than 30% relative increase in 18:1n-9 fatty acid in the triacylglycerol (TAG)-rich lipoprotein were observed. TAG-rich lipoprotein lipids of TTA fed rats were decreased with more than 50% reduction in TAG. The data reported in this paper indicate a potent in vivo antioxidant capability of TTA that beside its hypolipidemic effect might be of importance in relation to the development of atherosclerosis.

Modulation of carbon tetrachloride-induced oxidative stress by dietary fat in rats(open star)

Oxidative stress is believed to be involved in the pathophysiology of a number of chronic diseases including atherosclerosis, diabetes, and cataracts and to accelerate the aging process. The aim of this study was to elucidate the role of various dietary fats in the in vivo modulation of CCl(4) induced oxidative stress using rat as a model. Rats were raised on diets enriched with saturated (Beef Tallow), n-9 (Sunola oil), n-6 (Safflower oil) or n-3 (Flaxseed oil) fatty acids and exposed to elevated oxidative stress by administration of CCl(4.) Plasma concentration of 8-iso-PGF(2alpha), antioxidant micronutrients and antioxidant enzymes were measured to examine changes to oxidative stress subsequent to the administration of CCl(4). The fatty acid profiles of plasma and RBC membranes reflected the fats fed in the different diets. CCl(4) administration had no significant effect on fatty acid composition of plasma or RBC lipids. Plasma 8-iso-PGF(2alpha) concentrations were elevated by CCl(4) administration regardless of the dietary fat fed. Within the induced oxidative groups the 8-iso-PGF(2alpha) concentrations were highest in Safflower oil followed by Sunola oil, Tallow and finally Flaxseed oil. Induction of oxidative stress by CCl(4) administration was associated with a significant reduction in Vitamin A content reaching a significantly lower concentration (P <0.05) in the Tallow and Flaxseed oil groups. Vitamin E concentrations were significantly lower (p = 0.01) in the Safflower oil and the Flaxseed oil than in the Tallow diet group following CCl(4) administration. Superoxide Dismutase (SOD) and Glutathione Peroxidase (GSHPx) activities were not affected by dietary fat manipulation. The results of this study indicate that dietary fat can modulate lipid peroxidation and antioxidant defenses when exposed to a pro-oxidant challenge.

Growth reduction in glioma cells after treatment with tetradecylthioacetic acid: changes in fatty acid metabolism and oxidative status

During aerobic metabolism, a small amount of partially reduced oxygen is produced, yielding reactive oxygen species (ROS). Peroxisomes and mitochondria are major contributors to cellular ROS production, which is normally balanced by consumption by antioxidants. The fatty acid analogue tetradecylthioacetic acid (TTA) promotes mitochondrial and peroxisomal proliferation, and may induce oxidative stress and change the growth potential of cancer cells. In the present study, we found that TTA reduced [(3)H]thymidine incorporation in the glioma cell lines BT4Cn (rat), D54Mg (human), and GaMg (human) in a dose- and time-dependent manner. The 50% inhibitory TTA doses were approximately 125 microM for BT4Cn and D54Mg cells and 40 microM for GaMg cells after 4 days. alpha-Tochopherol counteracted this inhibition in GaMg cells. TTA enhanced the oxidation of [1-(14)C]palmitic acid, which could be explained by stimulation of enzymes involved in peroxisomal (fatty acyl-CoA oxidase) and/or mitochondrial (carnitine palmitoyltransferase) fatty acid oxidation. The glutathione content and the activities of glutathione peroxidase, glutathione reductase, and glutathione S-transferase were differentially affected. Increased malondialdehyde (MDA) production was seen in TTA-treated GaMg and D54Mg cells, but not in BT4Cn cells, in vitro. In BT4Cn tumor tissue from TTA-treated rats, MDA was increased while the alpha-tocopherol content tended to decrease. TTA increased the level of cytosolic cytochrome c in BT4Cn cells, which suggests induction of apoptotic cascades. Although several mechanisms are likely to be involved in the TTA-mediated effects on growth, we propose that modulation of cellular redox conditions caused by changes in fatty acid metabolism may be of vital importance.

Enhanced level of n-3 fatty acid in membrane phospholipids induces lipid peroxidation in rats fed dietary docosahexaenoic acid oil

The effect of dietary docosahexaenoic acid (DHA, 22:6n-3) oil with different lipid types on lipid peroxidation was studied in rats. Each group of male Sprague-Dawley rats was pair fed 15% (w/w) of either DHA-triglycerides (DHA-TG), DHA-ethyl esters (DHA-EE) or DHA-phospholipids (DHA-PL) for up to 3 weeks. The palm oil (supplemented with 20% soybean oil) diet without DHA was fed as the control. Dietary DHA oils lowered plasma triglyceride concentrations in rats fed DHA-TG (by 30%), DHA-EE (by 45%) and DHA-PL (by 27%), compared to control. The incorporation of dietary DHA into plasma and liver phospholipids was more pronounced in the DHA-TG and DHA-EE group than in the DHA-PL group. However, DHA oil intake negatively influenced lipid peroxidation in both plasma and liver. Phospholipid peroxidation in plasma and liver was significantly higher than control in rats fed DHA-TG or DHA-EE, but not DHA-PL. These results are consistent with increased thiobarbituric acid reactive substances (TBARS) and decreased alpha-tocopherol levels in plasma and liver. In addition, liver microsomes from rats of each group were exposed to a mixture of chelated iron (Fe(3+)/ADP) and NADPH to determine the rate of peroxidative damage. During NADPH-dependent peroxidation of microsomes, the accumulation of phospholipid hydroperoxides, as well as TBARS, were elevated and alpha-tocopherol levels were significantly exhausted in DHA-TG and DHA-EE groups. During microsomal lipid peroxidation, there was a greater loss of n-3 fatty acids (mainly DHA) than of n-6 fatty acids, including arachidonic acid (20:4n-6). These results indicate that polyunsaturation of n-3 fatty acids is the most important target for lipid peroxidation. This suggests that the ingestion of large amounts of DHA oil enhances lipid peroxidation in the target membranes where greater amounts of n-3 fatty acids are incorporated, thereby increasing the peroxidizability and possibly accelerating the atherosclerotic process.

Susceptibility of LDL to oxidative modification in healthy volunteers supplemented with low doses of n-3 polyunsaturated fatty acids

The objective of the present study was to evaluate the oxidative susceptibility of LDL in human volunteers following supplementation with various low doses (<1 g/d) of n-3 polyunsaturated fatty acids (PUFA). Sixty-two healthy volunteers (thirty-seven males and twenty-five females, aged 19-63 years) were recruited to take part in a randomised placebo-controlled trial. Volunteers were required to take 0.9, 0.6 or 0.3 g n-3 PUFA as fish oil or placebo capsules daily for 16 weeks. Susceptibility of LDL to oxidative modification was assessed by measuring the production of conjugated dienes and thiobarbituric acid-reactive substances in LDL oxidised by Cu2+ (15 microM) or 2,2'-azobis(2-amidinopropane) dihydrochloride (1 mM) for 5 h. Plasma fatty acid and LDL-fatty acid composition, cholesterol levels and antioxidant concentrations were also measured. While post-treatment n-3 PUFA compositions of plasma and LDL reflected the capsule contents, no meaningful differences in antioxidant concentrations or cholesterol levels were observed between the groups. Supplementation with low doses of n-3 PUFA as fish oil did not influence the oxidative susceptibility of LDL. The results of the present study suggest that moderate dietary intakes of n-3 PUFA do not significantly influence the susceptibility of LDL to oxidative modification in vitro.

Effect of n-3 polyunsaturated fatty acid supplementation on lipid peroxidation of rat organs

The present study was undertaken in order to reexamine the effect of n-3 polyunsaturated fatty acid (PUFA)-rich diet supplementation on lipid peroxidation and vitamin E status of rat organs. Male Wistar rats were fed a diet containing safflower or fish oil at 50 g/kg diet and an equal amount of vitamin E at 59 mg/kg diet (1.18 g/kg oil; and 1.5 g/kg PUFA in safflower oil diet, and 4.3 g/kg PUFA in fish oil diet) for 6 wk. Fatty acid composition of total lipids of brain, liver, heart, and lung of rats fed fish oil was rich in n-3 PUFA, whereas that of each organ of rats fed safflower oil was rich in n-6 PUFA. The vitamin E levels in liver, stomach, and testis of the fish oil diet group were slightly lower than those of the safflower oil diet group, but the levels in brain, heart, lung, kidney, and spleen were not different between the two diet groups. The levels of phospholipid hydroperoxides were determined by the high-performance liquid chromatography-chemiluminescence method and the levels of thiobarbituric acid-reactive substances (TBARS) were determined at pH 3.5 in the presence of butylated hydroxytoluene with or without EDTA. Levels of phospholipid hydroperoxides and TBARS in the brain, liver, heart, lung, kidney, spleen, stomach and testis of the fish oil diet group were similar to those of the safflower oil diet group. The results indicate that high fish oil intake does not induce increased levels of phospholipid hydroperoxides and TBARS in rat organs.