SO-fed Rats Research Articles

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.

Could dietary trans fatty acids induce movement disorders? Effects of exercise and its influence on Na +K +-ATPase and catalase activity in rat striatum

The influence of trans fatty acids (FA) on development of orofacial dyskinesia (OD) and locomotor activity was evaluated. Rats were fed with diets enriched with 20% soybean oil (SO; n − 6 FA), lard (L; saturated FA) or hydrogenated vegetable fat (HVF; trans FA) for 60 weeks. In the last 12 weeks each group was subdivided into sedentary and exercised (swimming). Brains of HVF and L-fed rats incorporated 0.33% and 0.20% of trans FA, respectively, while SO-fed group showed no incorporation of trans FA. HVF increased OD, while exercise exacerbated this in L and HVF-fed rats. HVF and L reduced locomotor activity, and exercise did not modify. Striatal catalase activity was reduced by L and HVF, but exercise increased its activity in the HVF-fed group. Na +K +-ATPase activity was not modified by dietary FA, however it was increased by exercise in striatum of SO and L-fed rats. We hypothesized that movement disorders elicited by HVF and less by L could be related to increased dopamine levels in striatum, which have been related to chronic trans FA intake. Exercise increased OD possibly by increase of brain dopamine levels, which generates pro-oxidant metabolites. Thus, a long-term intake of trans FA caused a small but significant brain incorporation of trans FA, which favored development of movement disorders. Exercise worsened behavioral outcomes of HVF and L-fed rats and increased Na +K +-ATPase activity of L and SO-fed rats, indicating its benefits. HVF blunted beneficial effects of exercise, indicating a critical role of trans FA in brain neurochemistry.

Exercise affects memory acquisition, anxiety-like symptoms and activity of membrane-bound enzyme in brain of rats fed with different dietary fats: impairments of trans fat

Here we evaluated the influence of physical exercise on behavior parameters and enzymatic status of rats supplemented with different dietary fatty acids (FA). Male Wistar rats fed diets enriched with soybean oil (SO), lard (L), or hydrogenated vegetable fat (HVF) for 48 weeks were submitted to swimming (30 min/d, five times per week) for 90 days. Dietary FA per se did not cause anxiety-like symptoms in the animals, but after physical exercise, SO group showed a better behavioral performance than L and the HVF groups in elevated plus maze (EPM). In Barnes maze, HVF group showed impaired memory acquisition as compared to L group, and exercise reversed this effect. SO-fed rats showed an improvement in memory acquisition after 1 day of training, whereas lard caused an improvement of memory only from day 4. HVF-fed rats showed no improvement of memory acquisition, but this effect was reversed by exercise in all training days. A lower activity of the Na(+)K(+)-ATPase in brain cortex of rats fed lard and HVF was observed, and this effect was maintained after exercise. Similarly, the HVF diet was related to lower activity of hippocampal Na(+)K(+)-ATPase, and exercise reduced activity of this enzyme in the SO and L groups. Our findings show influences of dietary FA on memory acquisition, whereas regular exercise improved this function and was beneficial on anxiety-like symptoms. As FA are present in neuronal membrane phospholipids and play a critical role in brain function, our results suggest that low incorporation of trans FA in neuronal membranes may act on cortical and hippocampal Na(+)K(+)-ATPase activity, but this change appears to be unrelated to the behavioral parameters primarily harmed by consumption of trans and less so by saturated FA, which were reversed by exercise.

Effects of dietary fatty acids and exercise on body-weight regulation and metabolism in rats.

To assess the interaction of high-fat diets (HF) made with different dietary fatty acids and exercise on body-weight regulation, adiposity, and metabolism. Male Wistar rats born to dams fed HF diets (40% w/w) made with either fish oil (FO), soybean oil (SO), or palm oil (PO) were fed diets similar to their dams and divided randomly into exercise (EX, swimming) or sedentary control (SD) groups when they were 9 weeks old. EX lasted for 6 weeks. Twenty-four hours after the last EX bout, fasted rats were killed by decapitation. Chemical analyses and body composition analysis were conducted. The results demonstrated that different fatty acids had different effects on body weight, composition, and metabolism. SO-fed rats gained the most weight and fat. EX reduced body weight of FO- and PO-fed rats, but SO-fed rats were still heavier and fatter than other rats. Data from SO- and PO-fed rats suggested that they are insulin resistant and that EX normalized this abnormality. Of the three HF diets used, FO produced the least adverse effects compared with PO and SO. Not only the quantity of dietary fat, but also the type of fat used, will produce different effects on body weight and metabolism. EX ameliorates the suggested insulin resistance induced in rats fed either highly saturated or n-6 polyunsaturated fatty acids. Long-chain n-3 polyunsaturated fatty acids, as found in fish oil, are more beneficial than n-6 polyunsaturated fatty acids when fed in high amounts to rats.

Vegetable Oils High in Phytosterols Make Erythrocytes Less Deformable and Shorten the Life Span of Stroke-Prone Spontaneously Hypertensive Rats

Previous studies have shown that canola oil (CA), compared with soybean oil (SO), shortens the life span of stroke-prone spontaneously hypertensive (SHRSP) rats, a widely used model for hemorrhagic stroke. SHRSP rats are highly sensitive to dietary cholesterol manipulations because a deficiency of membrane cholesterol makes their cell membranes weak and fragile. Phytosterols, abundant in CA but not in SO, can inhibit the absorption of cholesterol and also replace a part of cholesterol in cell membranes. This study was performed to determine whether the high concentration of phytosterols in CA might account for its life-shortening effect on SHRSP rats. Male, 35-d-old SHRSP rats (n = 28/group) were fed semipurified diets containing CA, SO, CA fortified with phytosterols (canola oil + phytosterols, CA + P), SO fortified with phytosterols (soybean oil + phytosterols, SO + P), corn oil (CO), olive oil (OO) or a fat blend that mimicked the fat composition of a representative Canadian diet (Canadian fat mimic, CFM; 10 g/100 g diet). These fats provided 97, 36, 207, 201, 114, 27 and 27 mg phytosterols/100 g diet, respectively. Ten rats from each group were killed after 30-32 d for blood and tissue analyses. The remaining rats (18/group) were used for determination of life span. The life span of SHRSP rats fed the high phytosterol oils (CA, CA + P, SO + P and CO) was significantly (P<0.05) shorter than that of CFM- and SO-fed rats. At 30-32 d, the groups fed the high phytosterol oils had greater levels of phytosterols and significantly (P<0.05) higher ratios of phytosterols/cholesterol in plasma, RBC, liver and kidney, and a significantly (P<0.05) lower RBC membrane deformabilty index than the groups fed oils low in phytosterols (SO, OO and CFM). The mean survival times were correlated with RBC deformability index (r(2) = 0.91, P = 0.0033) and cholesterol concentration (r(2) = 0.94, P = 0.0016), and inversely correlated with RBC phytosterol concentration (r(2) = 0.58, P = 0.0798) and phytosterols/cholesterol (r(2) = 0.65, P = 0.0579), except in the OO group. This study suggests that the high concentration of phytosterols in CA and the addition of phytosterols to other fats make the cell membrane more rigid, which might be a factor contributing to the shortened life span of SHRSP rats.

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.

Effects of docosahexaenoic and eicosapentaenoic acid on lipid metabolism, eicosanoid production, platelet aggregation and atherosclerosis in hypercholesterolemic rats.

Exogenously hypercholesterolemic (ExHC) rats were fed on an atherogenic diet supplemented with 1% each of either ethyl ester docosahexaenoic acid [EE-DHA, 22:6(n-3)], ethyl ester eicosapentaenoic acid [EE-EPA, 20:5(n-3)] or safflower oil (SO) for 6 months. The rats fed on the diets containing EE-EPA or EE-DHA, compared with those fed on SO, had lower serum cholesterol and triacylglycerol levels, less aggregation of platelets and slower progress of intimal thickening in the ascending aorta. Relative to the SO-fed rats, both of the (n-3) fatty acid-fed rats had a significantly reduced proportion of arachidonic acid in the platelet and aortic phospholipids, and lower production of thromboxane A2 by platelets and of prostacyclin by the aorta. These results suggest that EPA and DHA are similarly involved in preventing atherosclerosis development by reducing hypercholesterolemia and modifying the platelet functions.

Plasma lipids and liver histochemistry of rats fed sea-lion or corn oil with or without cholesterol supplementation

Sea-lion oil (SO) is used as a dietary supplement in the treatment of cardiovascular disease. The effects of SO on plasma lipid concentration and liver lipid histochemistry were compared with those of corn oil (CO). Male Sprague-Dawley rats were fed diets containing 15% (w/w) SO or CO with or without 1% cholesterol for 25 days. Compared with rats fed CO, SO-fed rats showed lower plasma cholesterol levels ( P < 0.001), high-density lipoproteins (HDL) ( P < 0.05), very-low-density lipoproteins ( P < 0.05), triglycerides ( P < 0.05) and total lipids ( P < 0.05). Rats fed SO and cholesterol had lower plasma concentrations of cholesterol ( P < 0.001) and HDL ( P < 0.05) than those of animals fed CO. Alterations in liver cytology were observed in rats fed SO, including a differential accumulation of lipids in the canalicular regions of hepatocytes and a high density of lipid vesicles in hepatic lobule triads. The results indicated that, compared with CO, SO reduces plasma lipid levels and causes histochemical changes associated with an increased excretion of lipids from the liver.

Formation of prostanoids and hydroxy fatty acids by stimulated peritoneal mast cells: Role of the dietary fat type in rat

To study the influence of membrane fatty acid composition on the formation of prostanoids and hydroxy fatty acids by rat peritoneal mast cells (MC), animals were fed three different types of fatty acids: mackerel oil (MO), abundant in n−3 fatty acids; sunflower seed oil (SO), rich in linoleic acid; and hydrogenated coconut oil (HCO), mainly containing saturated fatty acids. The presence of n−3 fatty acids in the diet resulted in the incorporation of 20:5( n− 3), 22:5( n−3) and 22:6( n − 3) in MC phospholipids. A decrease of arachidonic acid, 20:4( n−6), was observed in MC-phospholipids of the MO-fed animals. Furthermore, increasing the relative amounts of 18:2( n−6) in the diet (SO group) led to an increased incorporation of linoleic acid, 18:2( n−6) in MC phospholipids when compared to both other dietary groups. The changes in MC phospholipid fatty acid composition were (partly) reflected in the formation of prostanoids and hydroxy fatty acids upon stimulation with the calcium ionophore A23187. The decrease in arachidonic acid content in MC phospholipids of MO-fed rats resulted in a decreased formation of PGD 2 when compared to both other groups. Also, the increased amounts of 18:2( n−6) in MC phospholipids of SO-fed rats resulted in an increased formation of 9-and 13-HODE upon stimulation. The results show that modifications in the fatty acid composition of the diet influences MC membrane fatty acid composition which ultimately results in changes in prostanoid and hydroxy fatty acid synthesis by MC upon stimulation with the calcium ionophore A23187.

Comparative effects of ω-3 and ω-6 polyunsaturated fatty acids on protein metabolism in rats bearing the mammary adenocarcinoma

The comparative effects of diets containing 20% (wt/wt) of either fish oil (FO) or safflower oil (SO) on protein synthesis and catabolism were determined in rats bearing the 7,12-dimethylbenz(a)anthracene (DMBA) 13762 mammary adenocarcinoma in vivo using a 6-hour constant infusion of l-(1- 14C)-leucine. Tumor-bearing animals fed FO had significantly lower tumor growth rate (36 ± 0.5 v 53 ± 0.7%/d, P < .05), total tumor protein synthesis (Ts) (1.25 ± 0.1 v 1.85 ± 0.1 μmol/h, P < .05), and tumor protein concentration (12.0 ± 0.5 v 14.0 ± 0.7%/d, P < 0.01). Tumor fractional synthetic rate and total protein breakdown rate of the tumor were unaffected by FO feeding. Both tumor-bearing and saline-control animals fed FO had significantly ( P < .01) lower liver fractional synthetic rate and total protein breakdown rate, and higher liver total protein compared with SO-fed rats. Muscle protein kinetics were unaffected by either treatment or diet. Whole body protein kinetics were not affected by dietary treatment, but the presence of tumor significantly ( P < .001) reduced whole body flux, synthesis, breakdown, and oxidation. Chronic FO feeding for 7 weeks significantly ( P < .001) lowered ω-6 polyunsaturated fatty acids (ω-6 PUFAs) and significantly elevated ω-3 polyunsaturated fatty acids (ω-3 PUFAs) ( P < .001) in both plasma phospholipid and triglycerides. The present study indicates that dietary FO can modulate mammary tumor growth in a manner that reflects changes in protein metabolism in both host and tumor tissues.

Effect of Diets High in Carbohydrate, Soy Oil, Medium-Chain Triglycerides or Tripelargonin on Blood and Liver Lipid and Glucose Intermediates in Meal-Eating Rats

Medium-chain odd carbon fats have been reported to be ketogenic as have medium-chain triglycerides (MCT). Such an odd carbon fat, tripelargonin, was compared to MCT for its effect on ketogenic and glucogenic intermediates when fed as a part of a complete diet to meal-eating rats. Isonitrogenous diets containing, as 68% of the calories, soy oil (SO), MCT, tripelargonin (C9TG) were fed 2 hours twice a day. After 4 weeks, the C9TG rats during meals had blood and liver β-hydroxybutyrate levels approximately 300 and 125%, respectively, of the fasting levels and similar to the prandial SO-fed levels. These levels were significantly less than the 1,000 and 500% elevations observed in the MCT-fed rats. Prandial blood glucose and liver glycogen levels were similar in the C9TG and SO-fed rats; whereas, these intermediates appeared to remain at or drop below the fasting levels in the MCT-fed animals. Levels of plasma non-esterified fatty acids and liver glucose-6-phosphate in the MCT and C9TG were similar and different from the SO-fed values. These results point to the uniqueness of C9TG when compared to even-numbered triglycerides under these dietary conditions.tripelargonin MCT ketones glycogen