FO-fed Rats Research Articles

Juvenile/Peripubertal Exposure to Omega-3 and Environmental Enrichment Differentially Affects CORT Secretion and Adulthood Stress Coping, Sociability, and CA3 Glucocorticoid Receptor Expression in Male and Female Rats.

In adult rats, omega-3 supplementation through fish oil (FO) and environmental enrichment (EE) have shown beneficial effects on cognition and stress regulation. This study assessed sex-specific effects of FO and EE during adolescence, a period critical for brain maturation, on adulthood coping mechanisms, sociability, and glucocorticoid regulation. An amount of 64 Wistar rats [n = 32/sex; postnatal day (PND) 23] were assigned to supplementation of control soybean oil (CSO) or menhaden fish oil (FO; 0.3 mL/100 g) from PND28 to 47 and exposed to EE or regular cage (RC) housing from PND28 to 58, with their blood corticosterone (CORT) levels being assessed weekly. As adults, exposure to repeated forced swim tests (FSTs; PND90-91) enabled analysis of coping responses, while socioemotional and memory responses were evaluated using the OFT, EPM, SIT, and Y maze tests (PND92-94). Immunohistochemistry determined hippocampal CA1/CA3 glucocorticoid receptor (GR) expression (PND95). CORT secretion gradually increased as the supplementation period elapsed in female rats, while changes were minimal in males. Coping strategies in the FST differed between sexes, particularly in FO-fed rats, where females and males, respectively, favoured floating and tail support to minimise energy consumption and maintain immobility. In the SIT, FO/EE promoted sociability in females, while a CSO diet favoured social recognition in males. Reduced CA3 GR-ir expression was found in FO/RC and CSO/EE rat groups, supporting stress resilience and memory consolidation. Our findings support environment and dietary conditions to exert a sex-specific impact on biobehavioural responses.

Dietary (n-3) Polyunsaturated Fatty Acids Improve Adipocyte Insulin Action and Glucose Metabolism in Insulin-Resistant Rats: Relation to Membrane Fatty Acids

To study the effects of dietary fish oil on insulin-stimulated glucose metabolism in adipocytes of insulin-resistant rats (rats fed 50% sucrose and 30% fat), eighteen 5-wk-old Sprague-Dawley rats were fed, for 6 wk, a diet containing 30% fat as either fish oil (FO) or a mixture of vegetable and animal oils [control oils (CO)]. A third reference group was fed a standard diet (62% corn starch and 13% fat). At the end of the 6-wk period, the two experimental groups had comparable plasma glucose concentrations that were higher than that found in the reference group. FO feeding corrected the hyperinsulinemia of the experimental rats (P < 0.05) to reach values in the reference group. Plasma triacylglycerol (P < 0.01) and cholesterol (P < 0.001) concentrations were also lower in rats fed FO than in those fed CO. The body weights of FO-fed rats were similar to that of CO-fed rats, but epididymal adipose tissue weight was lower (P < 0.01). Adipocytes of FO-fed rats, compared with those of CO-fed rats, had high insulin-stimulated glucose transport (P < 0.05), oxidation (P < 0.001) and incorporation into total lipids (P < 0.05). The incorporation of (n-3) polyunsaturated fatty acids in adipocyte membrane phospholipids was higher in FO-fed rats than in those fed CO (P < 0.0001). Insulin action was positively correlated with the fatty acid unsaturation index in membrane phospholipids. Thus dietary fish oil has beneficial effects on insulinemia, plasma lipids and insulin-stimulated glucose metabolism in insulin-resistant slightly diabetic rats.

Muscle fatigue resistance in the rat hindlimbin vivofrom low dietary intakes of tuna fish oil that selectively increase phospholipidn-3 docosahexaenoic acid according to muscle fibre type

Dietary fish oil (FO) modulates muscle O2 consumption and contractile function, predictive of effects on muscle fatigue. High doses unattainable through human diet and muscle stimulation parameters used engender uncertainty in their physiological relevance. We tested the hypothesis that nutritionally relevant FO doses can modulate membrane fatty acid composition and muscle fatigue. Male Sprague-Dawley rats were randomised to control (10% olive oil (OO) by weight) or low or moderate FO diet (LowFO and ModFO) (HiDHA tuna fish oil) for 15 weeks (LowFO: 0.3% FO, 9.7% OO, 0.25% energy as EPA+DHA; ModFO: 1.25% FO, 8.75% OO, 1.0% energy as EPA+DHA). Hindlimb muscle function was assessed under anaesthesia in vivo using repetitive 5 s burst sciatic nerve stimulation (0.05 ms, 7-12 V, 5 Hz, 10 s duty cycle, 300 s). There were no dietary differences in maximum developed muscle force. Repetitive peak developed force fell to 50% within 62 (SEM 10) s in controls and took longer to decline in FO-fed rats (LowFO 110 (SEM 15) s; ModFO 117 (sem 14) s) (P<0.05). Force within bursts was better sustained with FO and maximum rates of force development and relaxation declined more slowly. The FO-fed rats incorporated higher muscle phospholipid DHA-relative percentages than controls (P<0.001). Incorporation of DHA was greater in the fast-twitch gastrocnemius (Control 9.3 (SEM 0.8) %, LowFO 19.9 (SEM 0.4), ModFO 24.3 (SEM 1.0)) than in the slow-twitch soleus muscle (Control 5.1 (SEM 0.2), LowFO 14.3 (SEM 0.7), ModFO 18.0 (SEM 1.4)) (P<0.001), which was comparable with the myocardium, in line with muscle fibre characteristics. The LowFO and ModFO diets, emulating human dietary and therapeutic supplement intake, respectively, both elicited muscle membrane DHA enrichment and fatigue resistance, providing a foundation for translating these physiological effects to humans.

Effect of dietary eicosapentaenoic and docosahexaenoic acid on expression of rat liver genes controlling cholesterol homeostasis and on plasma cholesterol level

A hypothesis that eicosapentaenoic acid + docosahexaenoic acid (EPA+DHA) lower plasma cholesterol via increased expression of the Insig-1 gene with ensuing decrease of expression of genes coding for 3-hydroxy-3-methyl-glutaryl-CoA reductase (Hmgcr) and low density lipoprotein receptor (Ldlr) was tested in rats fed a diet with 3% of fish oil (FO). Expression of the Insig-1 gene in the liver of the FO-fed rats was 730% (P &amp;lt; 0.05) of the control. However, contrary to the hypothesis, expression of the Hmgcr gene and Ldlr gene was 165% and 210% of the control (P &amp;gt; 0.05). Nevertheless, FO in the diet decreased (P &amp;lt; 0.05) plasma cholesterol of rats by 10% (from 1.19 to 1.07 mmol/l); it was therefore concluded that the cholesterol-lowering effect of EPA+DHA is at least partly based on mechanisms other than tested in the present experiment. &amp;nbsp;

Effect of dietary Schizochytrium microalga oil and fish oil on plasma cholesterol level in rats.

The purpose of the study was to test the hypothesis that the dietary oils with different content of n-3 polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) affect plasma lipid level in rats in a different degree. The diets with 6% of fish oil (FO) and Schizochytrium microalga oil (SchO; EPA+DHA content in the diets 9.5+12.3 and 2.6+29.5% of the sum of total fatty acids, respectively) were used; the diet with 6% of safflower oil (high content of n-6 PUFA linoleic acid, 65.5%; EPA+DHA content 0.7+0.9%) was used as a control. The difference between FO and SchO was established only in the case of plasma triacylglycerol (TAG) level: plasma TAG of the FO-fed rats did not differ from the control rats (p>0.05), while SchO decreased (p<0.05) plasma TAG to 46% of the control. On the other hand, FO and SchO decreased (p<0.05) total plasma cholesterol (TC) in rats in the same extent, to 73% of the control. Regarding the underlying mechanisms for the TC decrease, both SchO and FO up-regulated hepatic Insig-1 gene (181 and 133% of the control; p<0.05), which tended (p=0.15 and p=0.19 respectively) to decrease the amount of hepatic nSREBP-2 protein (61 and 66% of the control). However, neither SchO nor FO influenced hepatic 3-hydroxy-3-methyl-glutaryl-CoA reductase gene expression (p>0.05); SchO (but not FO) increased (p<0.05) low-density lipoprotein receptor mRNA in the liver. It was concluded that the decrease of total plasma cholesterol might be caused by an increased cholesterol uptake from plasma into the cells (in the case of SchO), but also by other (in the present study not tested) mechanisms.

Mammary inflammation around parturition appeared to be attenuated by consumption of fish oil rich in n-3 polyunsaturated fatty acids

BackgroundMastitis endangers the health of domestic animals and humans, and may cause problems concerning food safety. It is documented that n-3 polyunsaturated fatty acids (PUFA) play significant roles in attenuating saturated fatty acids (SFA)-induced inflammation. This study was therefore conducted to determine whether mammary inflammation could be affected by consumption of diets rich in n-3 PUFA.MethodsForty-eight rats after mating began to receive diets supplemented with 5% fish oil (FO) or 7% soybean oil (SO). Blood and mammary tissue samples (n = 6) at day 0 and 14 of gestation and day 3 postpartum were collected 9 hours after intramammary infusion of saline or lipopolysaccharide (LPS) to determine free fatty acids (FFA) concentration and FA composition in plasma and inflammation mediators in mammary tissues.ResultsAt day 14 of gestation and day 3 postpartum, the FO-fed rats had lower plasma concentrations of C18:2n6, C20:4n6, total n-6 PUFA and SFA, and higher plasma concentrations of C20:5n3 and total n-3 PUFA than the SO-fed rats. Plasma C22:6n3 concentration was also higher in the FO-fed than in the SO-fed rats at day 3 postpartum. Compared with the SO-fed rats, the FO-fed rats had lower mammary mRNA abundance of xanthine oxidoreductase (XOR) and protein level of tumor necrosis factor (TNF)-α, but had higher mammary mRNA abundances of interleukin (IL)-10 and peroxisome proliferator-activated receptor (PPAR)-γ at day 14 of gestation. Following LPS infusion at day 3 postpartum, the SO-fed rats had increased plasma concentrations of FFA, C18:1n9, C18:3n3, C18:2n6 and total n-6 PUFA, higher mammary mRNA abundances of IL-1β, TNF-α and XOR but lower mammary mRNA abundance of IL-10 than the FO-fed rats.ConclusionsMammary inflammation around parturition appeared to be attenuated by consumption of a diet rich in n-3 PUFA, which was associated with up-regulated expression of IL-10 and PPAR-γ.

Beneficial effect of fish oil on bone mineral density and biomarkers of bone metabolism in rats

This study evaluated the effect of fish oil rich in n-3 fatty acids on bone characteristics in Sprague-Dawley rats. Wean - ling male rats were randomized to receive either a diet containing high fish oil (FO), fish oil blended with corn oil (FICO), or soy oil rich in n-6 fatty acids (SO) for 4 weeks. All diets provided 70 g/kg fat based on the AIN-93G diet. Growth and biomarkers of bone metabolism were analyzed, and femur bone characteristics were measured by dual-energy X-ray ab- sorptiometry. After the dietary treatment, no significant differences among the diet groups were observed for serum con - centrations of Ca, parathyroid hormone, calcitonin, or osteocalcin. Alkaline phosphatase activity was significantly great - er in FO-fed rats compared to that in the FICO and SO groups, whereas no difference in deoxypyridinoline values was observed, supporting the positive effect of a FO diet on bone formation. These results were accompanied by a significant increase in femur bone mineral density (BMD) in FO-fed rats. These findings suggest that providing fish oil rich in n-3 fatty acids correlates with higher alkaline phosphatase activity and BMD values, favoring bone formation in growing rats. (Korean J Nutr 2012; 45(2): 121 ~ 126)

Effects of fish oil and Tamoxifen on preneoplastic lesion development and biomarkers of oxidative stress in the early stages of N-methyl-N-nitrosourea-induced rat mammary carcinogenesis

Epidemiologic studies on the protective role of omega-3 fatty acids (n:3) on breast cancer prevention remain inconclusive but studies in preclinical models provide more positive outcome. However, the mechanisms accounting for the protective effect of n:3 are not defined. In the present study, conducted in the N-methyl-N-nitrosourea-induced rat mammary carcinogenesis model, we examined the effects of n:3 individually and in combination with the anti-estrogen Tamoxifen (Tam) on a comprehensive panel of systemic and preneoplastic mammary gland restricted biomarkers which may be critical in the progression to invasive cancer. We observed that fish oil (FO) rich diets significantly reduced Ki67 expression in hyperplastic lesions, while cleaved caspase-3 expression was not affected. Dietary FO and/or Tam did not have major effects on systemic oxidative stress biomarkers, based on oxidative damage to DNA measured as 8-hydroxy-2-deoxyguanosine (8-OH-dG) and lipid peroxidation assessed as thiobarbituric acid reactive substances (TBARS). Tissue levels of 8-isoprostane, on the other hand, were markedly reduced (p<0.0001) in FO-fed rats, possibly as a result of FO-induced depletion of arachidonic acid in the mammary gland. These results suggest that the protective effect of n:3 in this experimental system is not mediated by changes in the levels of oxidative stress but may result from suppression of arachidonic acid-specific pathways.

A krill oil supplemented diet reduces the activities of the mitochondrial tricarboxylate carrier and of the cytosolic lipogenic enzymes in rats

The mitochondrial tricarboxylate carrier supplies cytosol with the carbon units necessary for hepatic lipogenesis. The activities of cytosolic acetyl-CoA carboxylase and fatty acid synthetase are therefore strictly connected to the function of mitochondrial tricarboxylate carrier. Dietary polyunsaturated fatty acids (PUFA) are potent modulators of hepatic lipogenesis. In rats fed with a diet enriched with 2.5% krill oil (KO), a novel source of dietary n-3 PUFA, a time-dependent decrease in the activities of the mitochondrial tricarboxylate carrier and of the lipogenic enzymes was found. The KO induced inhibition of hepatic lipogenesis was more pronounced than that found in fish oil (FO)-fed rats, at least at short feeding times. The decrease in the activity of the mitochondrial tricarboxylate carrier caused by KO was due to a reduced expression of the protein. Furthermore, in the KO-fed animals a greater reduction in the levels of hepatic triglycerides and cholesterol was found in comparison to FO-fed rats.

Dietary Echium Oil Increases Tissue (n-3) Long-Chain Polyunsaturated Fatty Acids without Elevating Hepatic Lipid Concentrations in Premature Neonatal Rats ,

Echium oil (EO) contains notable quantities of both (n-6) and (n-3) PUFA and has not, to our knowledge, been studied in neonates. We compared growth, tissue PUFA concentrations, and liver lipid profiles in premature neonatal Sprague-Dawley rats that were fed an EO diet with those that were dam-fed (DF) or fed rat milk substitute (RMS) or a fish oil (FO) diet. EO or FO comprised 10% of dietary fat. Rats were delivered prematurely at d 21 of gestation by caesarean section and then DF or fed one of the diets for 6 d. Rats were killed and the fatty acid (FA) concentrations in brain, liver, ileum, and serum and liver lipid profiles were analyzed. All diet-fed rats had similar weight gain and tissue protein concentrations. Compared with DF rats, EO-fed rats had similar brain docosahexaenoic acid (DHA) levels, similar brain and liver arachidonic acid (ARA) levels, higher liver and ileal eicosapentaenoic acid (EPA) levels (P < 0.05), and similar ARA:(EPA+DHA) ratios in brain, liver, and serum. Compared with RMS-fed rats, EO-fed rats had lower liver triglyceride FA and cholesterol ester concentrations (P < 0.05), higher EPA and DHA levels in liver, ileum, and serum, a higher DHA level in brain, and lower tissue and serum ratios of total (n-6):(n-3) PUFA and ARA:(EPA + DHA) (P < 0.05). Compared with FO-fed rats, EO-fed rats had higher ARA levels in brain, liver, ileum, and serum. In conclusion, dietary EO increases tissue EPA and DHA without reducing ARA in brain and liver and without elevating hepatic lipid concentrations of premature neonatal rats.

Ratio of n6 to n-3 Fatty Acids in the Diet Affects Tumor Growth and Cachexia in Walker 256 Tumor-Bearing Rats

: In this study we investigate the impact of the dietary ratio of n-6 to n-3 fatty acids (FAs) from postweaning until adult age upon tumor growth, lipid peroxidation in tumor tissue, and metabolic indicators of cancer cachexia in Walker 256 tumor-bearing rats. Weanling male Wistar rats received a normal low-fat (40 g/kg diet) chow diet or high-fat diets (300 g/kg) that included fish oil (FO) or sunflower oil or blends of FO and sunflower oil to yield n-6 to n-3 FA ratios of approximately 6:1, 30:1, and 60:1 ad libitum. After 8 wk, half of each group was inoculated with 1 ml of 2 × 107 Walker 256 cells. At the 14th day after tumor inoculation, the animals were killed, and tumors and blood were removed. The different diets did not modify the blood parameters in the absence of tumor bearing, except the high-FO diet, which decreased serum cholesterol and triacylglycerol concentrations. Tumor weight in chow-fed rats was 19 g, and these rats displayed cancer cachexia, characterized by hypoglycemia, hyperlacticidemia, hypertriacylglycerolemia, loss of body weight, and food intake reduction. Tumor weight in FO-fed rats was 7.7 g, and these animals gained body weight (14.6 g) and maintained blood metabolic parameters similar to non-tumor-bearing animals. Tumor weight in rats fed the diet with an n-6 to n-3 FA ratio of 6:1 was similar to tumor-bearing, chow-fed rats, but they gained 2 g in the body weight and blood metabolic parameters were similar to those in non-tumor-bearing rats. However, a further increase in the n-6 FA content of the diet did not change the cachectic state associated with tumor bearing. In this experimental model, a dietary n-6 to n-3 FA ratio of 6:1 was able to increase food intake and body weight, restore the biochemical blood parameters of cachexia, and prevent the development of cancer cachexia.

Differential effects of coconut oil- and fish oil-enriched diets on tricarboxylate carrier in rat liver mitochondria

The mitochondrial tricarboxylate carrier (TCC) plays an important role in lipogenesis being TCC-responsible for the efflux from the mitochondria to the cytosol of acetyl-CoA, the primer for fatty acid synthesis. In this study, we investigated the effects of two high-fat diets with different fatty acid composition on the hepatic TCC activity. Rats were fed for 3 weeks on a basal diet supplemented with 15% of either coconut oil (CO), abundant in medium-chain saturated fatty acids, or fish oil (FO), rich in n-3 polyunsaturated fatty acids. Mitochondrial fatty acid composition was differently influenced by the dietary treatments, while no appreciable change in phospholipid composition and cholesterol level was observed. Compared with CO, the TCC activity was markedly decreased in liver mitochondria from FO-fed rats; kinetic analysis of the carrier revealed a decrease of the Vmax, with no change of the Km. No difference in the Arrhenius plot between the two groups was observed. Interestingly, the carrier protein level and the corresponding mRNA abundance decreased following FO treatment. These data indicate that FO administration markedly decreased the TCC activity as compared with CO. This effect is most likely due to a reduced gene expression of the carrier protein.

Dietary fish oil reduces oxidative DNA damage in rat colonocytes.

Prolonged generation of reactive oxygen species by inflammatory mediators can induce oxidative DNA damage (8-oxodG formation), potentially resulting in intestinal tumorigenesis. Fish oil (FO), compared to corn oil (CO), has been shown to downregulate inflammation and upregulate apoptosis targeted at damaged cells. We hypothesized FO could protect the intestine against 8-oxodG formation during dextran sodium sulfate- (DSS-) induced inflammation. We provided 60 rats with FO- or CO-supplemented diets for 2 weeks with or without 3% DSS in drinking water for 48 h. Half the treated rats received 48 additional h of untreated water before termination. Due to DSS treatment, the intestinal epithelium had higher levels of 8-oxodG (p =.04), induction of repair enzyme OGG1 mRNA (p =.02), and higher levels of apoptosis at the top of colonic crypts (p =.01) and in surface cells (p <.0001). FO-fed rats, compared to CO, had lower levels of 8-oxodG (p =.05) and increased apoptosis (p =.04) in the upper crypt region; however, FO had no significant effect on OGG1 mRNA. We conclude that FO protects intestinal cells against oxidative DNA damage in part via deletion mechanisms.

IRP1 Activity and Expression Are Increased in the Liver and the Spleen of Rats Fed Fish Oil–Rich Diets and Are Related to Oxidative Stress

Many clinical studies have indicated that diets rich in fish oil (FO) reduce the risk of cardiovascular disease and have anti-inflammatory and antithrombotic properties. Although the therapeutic effects of FO have been well described, their impact on iron metabolism remains unclear. The aim of this work was to study the activity and expression of IRP1 in the liver and the spleen of rats fed FO-rich diets with 0 (FO-0) or 100 (FO-1) mg/kg of all-rac-alpha-tocopherol acetate. We also measured nonheme iron, alpha-tocopherol and retinol concentrations, and superoxide (SOD) and catalase activity in these organs. Rats fed FO were compared to rats fed a corn oil (CO)-rich diet with 100 mg/kg all-rac-alpha-tocopherol acetate. The activity and expression of IRP1 in both the liver and the spleen of rats fed FO diets were greater than in those fed the CO diet. FO-fed rats also had lower nonheme iron concentrations in these organs. Hepatic alpha-tocopherol and retinol concentrations and SOD activity were lower in FO-0-fed rats compared to those fed the CO diet. In the spleen, alpha-tocopherol and retinal concentrations were not altered but SOD activity was lower in FO-0- fed rats, whereas catalase activity was greater than in rats fed CO. The results indicate that there is an increase in oxidative stress in the liver and in the spleen of rats fed FO diets. These changes, together with the reduction of nonheme iron concentrations in both FO-0- and FO-1-fed rats, may explain the increase in activity and expression of IRP1. Therefore, the ingestion of FO-rich diets should be monitored under close supervision.

Liver Lipid Composition and Antioxidant Enzyme Activities of Spontaneously Hypertensive Rats After Ingestion of Dietary Fats (Fish, Olive and High-Oleic Sunflower Oils)

Hypertension is associated with greater than normal lipoperoxidation and an imbalance in antioxidant status, suggesting that oxidative stress is important in the pathogenesis of this disease. Although many studies have examined the effect of antioxidants in the diet on hypertensión and other disorders, less attention has been given to the evaluation of the role of specific dietary lipids in modulating endogenous antioxidant enzyme status. Previously, we have described that liver antioxidant enzyme activities may be modulated by consumption of different oils in normotensive rats. The purpose of the present study was to examine the effects of feeding different lipidic diets (olive oil, OO, high-oleic-acid sunflower oil, HOSO, and fish oil, FO) on liver antioxidant enzyme activities of spontaneously hypertensive rats (SHR). Plasma and liver lipid composition was also studied. Total triacylglycerol concentration increases in plasma and liver of animals fed on the HOSO and OO diets and decreases in those fed on the FO diet, relative to rats fed the control diet. The animals fed on the oil-enriched diet show similar hepatic cholesterol and phospholipid contents, which are higher than the control group. Consumption of the FO diet results in a decrease in the total cholesterol and phospholipid concentration in plasma, compared with the high-oleic-acid diets. In liver, the FO group show higher levels of polyunsaturated fatty acids (PUFA) of the (n - 3) series, in relation to the animals fed on the diets enriched in oleic acid. Livers of FO-fed rats, compared with those of OO- and HOSO-fed rats showed: (i) significantly higher activities of catalase, glutathione peroxidase and Cu/Zn superoxide dismutase; (ii) no differences in the NADPH-cytochrome c reductase activity. The HOSO diet had a similar effect on liver antioxidant enzyme activities as the OO diet. In conclusion, it appears that changes in the liver fatty acid composition due mainly to n - 3 lipids may enhance the efficiency of the antioxidant defence system and may yield a benefit in the hypertension status. The two monounsaturated fatty acids oils studied (OO and HOSO), with the same high content of oleic acid, but different content of natural antioxidants, had similar effects on the antioxidant enzyme activities studied.

Effects of dietary polyunsaturated fatty acids and hepatic steatosis on the functioning of isolated working rat heart under normoxic conditions and during post-ischemic reperfusion.

The purpose of this study was to modify the amount of 22:4 n-6, 22:5 n-6 and 20:5 n-3 in cardiac phospholipids and to evaluate the influence of these changes on the functioning of working rat hearts and mitochondrial energy metabolism under normoxic conditions and during postischemic reperfusion. The animals were fed one of these four diets: (i) 10% sunflower seed oil (SSO); (ii) 10% SSO + 1% cholesterol; (iii) 5% fish oil (FO, EPAX 3000TG, Pronova) + 5% SSO; (iv) 5% FO + 5% SSO + 1% cholesterol. Feeding n-3 PUFA decreased n-6 PUFA and increased n-3 PUFA in plasma lipids. In the phospholipids of cardiac mitochondria, this dietary modification also induced a decrease in the n-6/n-3 PUFA ratio. Cholesterol feeding induced marked hepatic steatosis (HS) characterized by the whitish appearance of the liver. It also brought about marked changes in the fatty acid composition of plasma and mitochondrial phospholipids. These changes, characterized by the impairment of deltaS- and delta6-desaturases, were more obvious in the SSO-fed rats, probably because of the presence of the precursor of the n-6 family (linoleate) in the diet whereas the FO diet contained large amounts of eicosapentaenoic and docosahexaenoic acids. In the mitochondrial phospholipids of SSO-fed rats, the (22:4 n-6 + 22:5 n-6) to 18:2 n-6 ratio was decreased by HS, without modification of the proportion of 20:4 n-6. In the mitochondrial phospholipids of FO-fed rats, the amount of 20:5 n-3 tended to be higher (+56%). Cardiac functioning was modulated by the diets. Myocardial coronary flow was enhanced by HS in the SSO-fed rats, whereas it was decreased in the FO-fed animals. The rate constant k012 representing the activity of the adenylate kinase varied in the opposite direction, suggesting that decreased ADP concentrations could cause oxygen wasting through the opening of the permeability transition pore. The recovery of the pump function tended to be increased by n-3 PUFA feeding (+22%) and HS (+45%). However, the release of ascorbyl free radical during reperfusion was not significantly modified by the diets. Conversely, energy production was increased by ischemia/reperfusion in the SSO group, whereas it was not modified in the FO group. This supports greater ischemia/reperfusion-induced calcium accumulation in the SSO groups than in the FO groups. HS did not modify the mitochondrial energy metabolism during ischemia/reperfusion. Taken together, these data suggest that HS- and n-3 PUFA-induced decrease in 22:4 and 22:5 n-6 and increase in 20:5 n-3 favor the recovery of mechanical activity during post-ischemic reperfusion.

Effects of dietary fats (fish, olive and high-oleic-acid sunflower oils) on lipid composition and antioxidant enzymes in rat liver

The effects of two oleic-acid-rich diets (containing olive oil, OO, and high-oleic-acid sunflower oil, HOSO) on plasma and liver lipid composition detoxification enzyme activities, were compared with those of a fish-oil (FO) diet and a control diet. Compared with the control diet, plasma and hepatic total triacylglycerol concentrations were increased in the animals fed on the HOSO and OO diets and decreased in those fed on the FO diet. The animals fed on FO showed the highest level of cholesterol in the liver and had lower plasma cholesterol concentrations when compared with those fed on the two oleic-acid-rich diets. In comparison with the animals fed on the diets enriched in oleic acid, the FO group showed higher hepatic levels of polyunsaturated fatty acids of the n-3 series and lower levels of fatty acids of the n-6 series. Livers of FO-fed rats, compared with those of OO- and HOSO-fed rats showed: (1) significantly higher activities of catalase (EC 1.11.1.6) glutathione peroxidase (EC 1.11.1.9) and Cu/Zn superoxide dismutase (EC 1.15.1.1); (2) no differences in the NADPH-cytochrome c reductase (EC 1.6.99.3) activity. The HOSO diet had a similar effect on liver antioxidant enzyme activities as the OO diet. In conclusion, it appears that changes in the liver fatty acid composition due mainly to n-3 lipids may enhance the efficiency of the antioxidant defence system. The two monounsaturated fatty acids oils studied (OO and HOSO), with the same high content of oleic acid but different contents of natural antioxidants, had similar effects on the antioxidant enzyme activities measured.

Effects of dietary fatty acids on lipid metabolism in streptozotocin-induced diabetic rats

We measured the activity of liver Δ 9- and Δ 6-desaturases and examined plasma and liver microsome phospholipid fatty acid composition in control and diabetic rats fed a basal diet supplemented with 5% (by weight) olive oil (OO), sunflower oil (SO), or fish oil (FO), respectively. Plasma glucose, cholesterol, triacylglyceride, and phospholipid levels were also measured. An increase in plasma and liver microsome oleic acid and a decrease in arachidonic acid were found in diabetes. In the liver, docosahexaenoic acid levels were higher in diabetic versus control rats. Diabetes increased liver Δ 9-desaturase in OO-fed rats and did not modify Δ 6-desaturase activity in OO- or SO-fed rats. Both enzymatic activities were decreased in diabetic rats fed the FO diet. As a main conclusion, it appears that diet-induced alterations in membrane composition provide a mechanism for improving the diabetic condition in animals and overcoming the effect of insulin deficiency on desaturase activities. Plasma cholesterol was not modified either by diabetes or by diet. In diabetes, OO-fed rats showed the lowest levels of triglycerides. Plasma phospholipids were significantly higher in OO-fed versus FO-fed rats. These findings suggest that OO contributes to a better control of the hypertriglyceridemia accompanying diabetes as compared with the other two diets in this rat model.

Effects of Fish Oil Feeding Alone in Combination with Clofibric Acid on Serum Levels of Triacylglycerol and Cholesterol in Rats

Rats were fed diets prepared with soybean oil (SO), perilla oil (PO), or fish oil (FO) for 4 weeks, and some of the rats received daily s.c. injections (100mg/kg) of p-chlorophenoxyisobutyric acid (clofibric acid) for 1 week before being killed. The levels of serum triacylglycerol and cholesterol were conspicuously lower in FO-fed rats than in SO-fed rats. The administration of clofibric acid further decreased serum levels of triacylglycerol and cholesterol in SO-fed rats, but not in FO-fed rats. The decreased level of these serum lipids with FO-feeding alone were comparable to those observed in SO-fed rats which had received clofibric acid. The activity of peroxisomal β-oxidation in the liver of FO-fed rats was significantly higher (2.48 times) than that of SO-fed rats. The treatment of FO-fed rats with clofibric acid caused an additional increase in activity, as compared to the SO-fed control. The activity of peroxisomal β-oxidation in SO-fed rats treated with clofibric acid was 3.74 times that of the FO-fed control. In contrast to peroxisomal β-oxidation, the activities of catalase, glutathione (GSH) peroxidase towards hydrogen peroxide and GSH reductase were not increased by clofibric acid, regardless of the type of oil ingested. Moreover, the activities of GSH S-transferases towards 1-chloro-2, 4-dinitrobenzene (CDNB) and 1, 2-dichloro-4-nitrobenzene (DCNB) were both depressed to the same level by the administration of clofibric acid, regardless of the type of dietary oil, although FO-feeding significantly increased the activity of GSH S-transferase towards CDNB. PO comprises essentially the same effects on the parameters tested, to a lesser extent, compared with FO. Consequently, FO-feeding can reduce the dose of clofibric acid required to lower serum lipids, which concomitantly may prevent hepatocytes from oxidative stress that might be caused by an imbalance of hydrogen peroxide metabolism due to the increased activity of peroxisomal β-oxidation and to the decrease in the activities of detoxification by GSH S-transferase.

Characteristics of lipid and lymphocytes collected from the lymph of rats fed a low fat diet or high fat diets rich in N-6 or N-3 polyunsaturated fatty acids

Lymphatic fluid and lymphocytes were isolated from lymph collected by cannulation of the thoracic duct of rats which had been fed for six weeks on a low fat (LF) diet or on high fat diets with safflower oil (SO) or fish oil (FO) as the sources of fat. The fatty acid composition of lymphatic fluid was markedly influenced by that of the diet. There were significant linear correlations between the proportions of lauric, myristic, palmitic, palmitoleic, stearic, oleic and linoleic acids in the diet and in the lymphatic fluid. Eicosapentaenoic and docosahexaenoic acids appeared in the lymphatic fluid of rats fed the FO diet. The fatty acid composition of lymph lymphocytes was influenced by that of the diet fed, but the effects of diet were weaker than those upon lymphatic fluid. The principal effect was seen in cells from the FO-fed rats; these had a significantly lower proportion of arachidonic acid than cells from rats fed either of the other diets and they contained measurable proportionss of eicosapentaenoic and docosahexaenoic acids. The amount and type of fat fed did not affect the proportions of CD4-positive, CD8-positive, CD11b/c-positive or κ-light chain-positive lymph lymphocytes. Lymph lymphocytes from rats fed either the SO or FO diets proliferated less well than those from rats fed the LF diet.