Safflower Oil Diet Group Research Articles

High Fat Diet Rich in Linoleic Acid Oil Increases Linoleate-Rich Cardiolipin Species in C57BL6/J Mice

ObjectivesDietary fat quality alters the fatty acid composition of phospholipids in cell membranes. The fatty acid composition of the inner mitochondrial membrane phospholipid cardiolipin (CL) impacts mitochondria function where linoleic acid (LA) -rich cardiolipin, e.g., tetralinoleoyl-cardiolipin (L4CL). This study compared the effects of a LA-rich diet and a saturated fat (SF)-rich diet on L4CL in the liver of mice. MethodsMale C57BL6/J mice (9 weeks, N = 24) randomized by body weight to a high fat diet (24% fat w/w) containing LA-rich safflower oil (SO) or SF-rich oil (LD) for 18 weeks. Food intake and body weight were measured every two days. Fasting blood glucose and body composition (Echo/MRI) were measured in the washout period and again 11 weeks later. Insulin tolerance test (ITT) measured insulin sensitivity on day 85, and mice were euthanized starting after day 100. Liver cardiolipin speciation was measured using HPLC/MS. A two-sample t-test at a 5% significance level was used to determine differences between diet groups. ResultsBody weight, cumulative food intake, adipose and lean tissues were not significantly different between diet groups at Day 130. Fasting glucose between diets was not significantly different at any timepoints throughout the study. Blood glucose during the ITT was significantly different between LA-rich and SF-rich diets for the last two time points, 90 minute and 120 minute. The SO diet increased hepatic L4CL (% of total CL) compared to the LD diet (P-value: < 0.01). ConclusionsHepatic CL fatty acid composition reflected dietary fat composition. Feeding of a high fat LA-rich diet increased hepatic L4CL species and hastened resolution of glucose levels in response to insulin in the SO diet group (vs. LD diet group). Funding SourcesSupported by Human Nutrition - Human Sciences, Carol S. Kennedy endowment, OADRC.

Protective effect of supplementation of fish oil with high n-3 polyunsaturated fatty acids against oxidative stress-induced DNA damage of rat liver in vivo.

The present study was undertaken to know the effect of supplementation of fish oil with high n-3 polyunsaturated fatty acids (PUFA) on oxidative stress-induced DNA damage of rat liver in vivo. Male Wistar rats were fed a diet containing fish oil or safflower oil with high n-6 PUFA at 50 g/kg of diet and an equal amount of vitamin E at 59 mg/kg of diet for 6 weeks. Livers of rats fed fish oil were rich in n-3 PUFA, whereas those of rats fed safflower oil were rich in n-6 PUFA. Ferric nitrilotriacetate was intraperitoneally injected to induce oxidative stress. The degree of lipid peroxidation of the liver was assessed by the levels of phospholipid hydroperoxides and thiobarbituric acid-reactive substances (TBARS), and the degree of oxidative DNA damage was assessed by comet type characterization in alkaline single-cell gel electrophoresis and 8-hydroxy-2'-deoxyguanosine levels. The levels of TBARS of the livers of the fish oil diet group increased to a greater extent than those of the safflower oil diet group, whereas the levels of the hydroperoxides of the livers of both diet groups increased to a similar extent. The vitamin E level of livers of the fish oil diet group was remarkably decreased. The degree of DNA damage of both diet groups was increased, but the increased level of the fish oil diet group was remarkably lower than that of the safflower oil diet group. The above results indicate that fish oil supplementation does not enhance but appears to protect against oxidative stress-induced DNA damage and suggest that lipid peroxidation does not enhance but lowers the DNA damage.

Effect of supplementation of n-3 polyunsaturated fatty acids on oxidative stress-induced DNA damage of rat hepatocytes.

The effect of supplementation of n-3 polyunsaturated fatty acids (PUFA) on oxidative stress-induced DNA damage of rat hepatocytes was examined. Male Wistar rats were fed a diet containing safflower oil (control n-6 PUFA diet) or fish oil (n-3 PUFA diet) in 50 g/kg of dried diet and an equal amount of vitamin E in 59 mg/kg of dried diet for 6 weeks. The liver of rats fed safflower oil was rich in n-6 PUFA, whereas that of rats fed fish oil was rich in n-3 PUFA. Isolated hepatocytes were treated in vitro with ADP/Fe (II) ion or hydrogen peroxide at 37 degrees C for 30 min to induce oxidative stress. The degree of lipid peroxidation was assessed by the levels of phospholipid hydroperoxides and thiobarbituric acid-reactive substances. The degree of oxidative DNA damage was assessed based on comet-type characterization in alkaline single-cell gel electrophoresis and 8-hydroxy-deoxyguanosine levels. In both ADP/Fe(II) ion and hydrogen peroxide oxidation, the degree of lipid peroxidation of hepatocytes increased in both diet groups, and the level of increase in the fish oil diet group was slightly higher than that in the safflower oil diet group. In ADP/Fe(II) ion oxidation, the degree of DNA damage increased in both diet groups, but there were no significant differences in the level of increase. In contrast, in hydrogen peroxide oxidation, the degree of DNA damage increased in both diet, and the increase in the fish oil diet group was significantly lower than that in the safflower oil diet group. It is unlikely that an n-3 PUFA-rich diet enhances oxidative stress-induced hepatocyte DNA damage as compared with the control n-6 PUFA-rich diet.

Effect of Feeding Plant Polyphenolics on Fatty Acid Composition, Vitamin E Level and Degree of Lipid Peroxidation in Rat Organs.

The present study was undertaken in order to evaluate the effect of feeding plant polyphenolics on fatty acid composition, the vitamin E level and degree of lipid peroxidation in rat organs. Male Wistar rats were fed a diet containing safflower or fish oil at 50g/kg diet and vitamin E at 59mg/kg diet in the absence and presence of plant polyphenolics at 7.5g/kg diet for 6 wk. Fatty acid composition of total lipids, vitamin E levels, the levels of phospholipid hydroperoxides and the levels of thiobarbituric acid-reactive substances (TBARS) in the TBA assay with butylated hydroxytoluene in each organ were measured. Feeding plant polyphenolics decreased the level of arachidonate content in the liver of rats fed safflower oil. Comsumption of vitamin E in heart, lung and testies was slightly prevented, but that in stomach was enchanced by feeding plant polyphenolics in both safflower and fish oil diet groups. Phospholipid hydroperoxide levels in brain and liver of rats fed both safflower and fish oil were lowered, whereas those in lung, kidney and spleen of rats fed both the oils were greatly increased by feeding plant polyphenolics. In determination of the hydroperoxides, the possibility that the values include artificial ones associated with sample handling cannot be excluded. TBARS levels in brain of the fish oil diet group and in liver of both tha safflower and fish oil diet groups were decreased, but those in heart, lung and kidney in both the safflower and fish oil diet groups and those in spleen in the safflower oil diet group were increased by feeding plant polyphenolics. It is likely that feeding plant polyphenolics had little effect in preventing lipid peroxidation in rat organs.

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.

Brain [β-adrenergic receptor binding in rats with obesity induced by a beef tallow diet

We have previously reported that compared with safflower oil diet, feeding a beef tallow diet leads to a greater accumulation of body fat by reducing sympathetic activities. The present study examined the effects of dietary fats consisting of different fatty acids on α 1- and β-adrenergic receptor binding in the hypothalamus and cerebral cortex. Male Sprague-Dawley rats were meal-fed isoenergetic diets based on safflower oil (rich in n-6 polyunsaturated fatty acids) or beef tallow (rich in saturated fatty acids) for 8 Weeks. Binding affinities of the β-adrenergic receptor in the hypothalamus and cortex were significantly lower in the beef tallow diet group, but those of the α 1-receptor did not differ between the two groups. The polyunsaturated to saturated fatty acid (P/S) ratio and fluidities of plasma membranes in the hypothalamus and cortex were lower in the beef tallow diet group than in the safflower oil diet group. These results suggest that the beef tallow diet decreases membrane fluidity by altering the fatty acid composition of plasma membranes in the hypothalamus and cerebral cortex of rat. Consequently, β-adrenergic receptor binding affinities in the brain were lower in rats fed the beef tallow diet than in rats fed the safflower oil diet. We recognized that there is possible link between the membrane fluidity and the changes in affinity of β-adrenoceptors in rat brain.

Lipoprotein Lipase in Peripheral Tissues in Rats with Insulin Resistance Induced by Beef Tallow Diet.

The modulation of lipoprotein lipase (LPL) activity and mass was examined in rats with insulin resistance induced by a beef tallow diet. Male sprague-Dawley rats were meal-fed an isoenergetic diet based on either beef tallow or safflower oil for an 8-week period. Insulin resistance brought about by long-term feeding of a beef tallow diet was confirmed by an oral glucose tolerance test. Plasma glucose and insulin levels were higher at almost all times of day in the rats fed the beef tallow diet than in those fed the safflower oil one. LPL activities of the skeletal and cardiac muscles and brown adipose tissue before and after a meal were lower in the beef tallow diet group than in the safflower oil diet group, however those of the perirenal and subcutaneous adipose tissues were not different between the two dietary groups. The amounts of LPL proteins in the soleus muscle and perirenal adipose tissue corresponded to the enzyme activities in these tissues. These results suggest that the effect of dietary saturated fat on LPL activity and mass are different in muscles and adipose tissues and that generalized peripheral insulin resistance, induced by feeding rats a beef tallow diet for a sufficient duration, is not followed by an impairment of the modulation of LPL activities and protein amount.

Effect of beef tallow diet on alpha 2-adrenergic receptor binding in rat brain regions.

We examined the effects of dietary fats consisting of different fatty acids on alpha 2-adrenergic receptor binding in the hypothalamus and cerebral cortex. Sprague-Dawley male rats were meal-fed isoenergetic diets based on safflower oil or beef tallow for 8 weeks. alpha 2-Adrenergic receptor bindings were determined with [3H]para-aminoclonidine. Binding affinities of alpha 2-adrenergic receptor in the hypothalamus and cortex were significantly higher in the beef tallow diet group. The values of the polyunsaturated/saturated fatty acid ratio and the fluidity of the plasma membrane in the hypothalamus and cortex were lower in the beef tallow diet group than in the safflower oil diet group. These results suggest that the beef tallow diet decreases membrane fluidity by altering the fatty acid composition in rat brain regions. Consequently, alpha 2-adrenergic receptor binding affinities in the brain regions are higher in rats fed the beef tallow diet than in rats fed the safflower oil diet.

Beef tallow diet decreases β-Adrenergic receptor binding and lipolytic activities in different adipose tissues of rat

The effects of dietary fats consisting of different fatty acids on lipolytic activity and body fat accumulation were studied in rats. Sprague-Dawley male rats were meal-fed an isoenergetic diet based on either beef tallow or safflower oil for 8 weeks. Lipolytic activities in epididymal and subcutaneous adipose tissues were lower in the beef tallow diet group than in the safflower oil diet group. Body fat accumulation was greater in rats fed the beef tallow diet versus the safflower oil diet. Norepinephrine (NE) turnover rates used as an index of sympathetic activities in adipose tissues were lower in the beef tallow diet group. β-Adrenergic receptor binding was determined with [ 3H]dihydroalprenolol. Binding affinities of β-receptors in adipose tissues were significantly lower in the beef tallow diet group. Membrane fluidities of adipose tissues were also lower in the beef tallow diet group. Membrane fluidities were correlated with the affinities of the β-receptor. We believe from these correlations that the decreases in β-receptor binding affinities are due to -the changes in membrane fluidities. The results of the present study suggest that intake of the beef tallow diet promotes body fat accumulation by reducing lipolytic activities resulting from lower β-receptor binding and sympathetic activity in adipose tissues.

Chemical Sympathectomy Increases Hepatic Acetyl-CoA Carboxylase Activity in Rats Fed a Safflower Oil Diet.

We previously reported that the feeding of the safflower oil diet results in lower acetyl-CoA carboxylase activity in the liver compared with the feeding of a beef tallow diet. We also suggested that sympathetic activity (norepinephrine turnover rate and α1-adrenergic receptor binding) in the liver was higher in the safflower oil diet group. In order to confirm the effect of dietary fats consisting of different fatty acids on the hepatic acetyl-CoA carboxylase activity related to sympathetic activity, we chemically sympathectomized rats by treating them with 6-hydroxydopamine. The sympathectomized rats and control rats were then meal-fed a safflower oil diet or a beef tallow diet for 8 weeks. Sympathectomy abolished the difference in acetyl-CoA carboxylase activity in the liver between the two dietary groups. The percentage of body fat was increased by sympathectomy, resulting in no difference between the safflower oil diet group and the beef tallow diet group. These results support the hypothesis that, the intake of a safflower oil diet decreases hepatic acetyl-CoA carboxylase activity by increasing the sympathetic activity.

Elevation of the Mitochondrial Oxidative Activity of Rat Liver by Long-Term Intake of a High-Fat Diet Based on Beef Tallow or Safflower Oil.

Using rats we examined the effects on liver mitochondrial functions of the long-term intake of a high-fat diet based on beef tallow or safflower oil. Forty-eight rats were divided into three dietary groups: a low-fat diet group and two high-fat ones (beef tallow and safflower oil). The low-fat diet provided 7, 73, and 20% of the total energy as fat, carbohydrate, and protein, respectively; and two high-fat diets, 45, 35, and 20% of energy, respectively. Rats were isoenergetically fed the appropriate diet for 4 months. The state-3 respiration of the mitochondria was significantly higher in the two high-fat diet groups than in the low-fat diet group, when both succinate and β-hydroxybutyrate were used as substrates for the respiration. However, there was no difference between the two high-fat diet groups. The groups were ranked in terms of cytochrome a content in their mitochondria as follows: low-fat diet group<beef tallow diet group<safflower oil diet group. The citrate synthase activity of the liver was also significantly higher in the two high-fat diet groups than in the low-fat one, but no difference was obtained between the two former. However, the mitochondrial DNA concentration in liver was not different among the three dietary groups. From these results, we conclude that long-term intake of high-fat diets increases the oxidative activity of liver mitochondria and that differences in the type of dietary fatty acids do not markedly alter mitochondrial functions.

Effects of Chemical Sympathectomy on Lipoprotein Lipase Activities in Peripheral Tissues of Rats Fed High Fat Diets Consisting of Different Fats.

We have previously reported that the feeding of a beef tallow diet gives lower lipoprotein lipase activities in the interscapuler brown adipose tissue, heart and soleus muscle compared with feeding of a safflower oil diet. We have also suggested that sympathetic activities (norepinephrine turnover rates and beta-adrenergic receptor bindings) in these peripheral tissues were lower in the beef tallow diet group. To confirm the effects of dietary fats on the lipoprotein lipase activities in these tissues related to sympathetic activities, rats were chemically sympathectomized by treatment with 6-hydroxydopamine. The sympathectomized rats and control rats were meal-fed with a beef tallow diet or a safflower oil diet for 8 weeks. Sympathectomy abolished the differences in lipoprotein lipase activities in the interscapuler brown adipose tissue, heart and soleus muscle between two dietary groups. The percentage of body fat was increased by sympathectomy, resulting in no difference between the beef tallow diet group and the safflower oil diet group. These results suggest that intake of the beef tallow diet decreased lipoprotein lipase activities by reducing the sympathetic activities.

Safflower Oil Diet Decreases Hepatic Acetyl CoA-Carboxylase Activity by Increasing .ALPHA.1-Adrenergic Stimulation in Rats.

Effects of dietary fats consisting of different fatty acids on the acetyl CoA-carboxylase activity in liver was studied in rats. Sprague-Dawley male rats were meal-fed an isoenergetic diet based on either beef tallow or safflower oil for 8 weeks. The acetyl CoA-carboxylase activity in liver was lower in the safflower oil diet group than in the beef tallow diet group. Body fat accumulation was less in rats fed the safflower oil diet, however, their norepinephrine turnover rate in liver was higher. α1-Adrenergic receptor binding was determined with [3H] prazosin. Binding affinity of α1-adrenergic receptor in liver was higher in the safflower oil diet group, presumably resulting from higher membrane fluidity in that group. These results suggest that the intake of the safflower oil diet promoted less body fat accumulation by reducing the acetyl CoA-carboxylase activity, which may be a result of higher sympathetic nervous system activity in the liver.

Beef tallow diet decreases lipoprotein lipase activities in brown adipose tissue, heart, and soleus muscle by reducing sympathetic activities in rats.

Effects of dietary fats consisting of different fatty acids on lipoprotein lipase activities in the interscapular brown adipose tissue, heart, and soleus muscle, and on body fat accumulation were studied in rats. Sprague-Dawley male rats were meal-fed an isoenergetic diet based on either beef tallow or safflower oil for 8 weeks. Lipoprotein lipase activities in the interscapular brown adipose tissue, heart, and soleus muscle before and after a meal were lower in the beef tallow diet group than in the safflower oil diet group. Body fat accumulation was greater in the beef tallow diet group than in the safflower oil diet group. The norepinephrine turnover rats in the interscapular brown adipose tissue, heart, and soleus muscle were lower in the beef tallow diet group. beta-Adrenergic receptor bindings were determined with [125I]iodocyanopindolol. Binding affinities of beta-adrenergic receptor in the interscapular brown adipose tissue, heart, and soleus muscle were lower in the beef tallow diet group probably resulted from lower membrane fluidities. These results suggest that intake of the beef tallow diet promotes body fat accumulation by reducing the lipoprotein lipase activities resulting from lower sympathetic activities in the brown adipose tissue, heart, and skeletal muscle.

Effects of dietary fatty acids on the activity of glucose transport in adipocytes

Lipid structure of plasma membrane plays an important role in regulating D-glucose transport in adipocytes. To investigate the effects of diet-induced alteration in cellular fatty acids on the activity of D-glucose transport in adipocytes, we fed rats iso-nutrient diets with high (20 energy% safflower oil) or low (2 energy% safflower oil plus 18 energy% beef tallow) safflower oil. After 31 days, adipocytes were isolated from epididymal fat pads using collagenase and incubated at 310°K (37°C) in KRB buffer containing 3% bovine serum albumin. Two-deoxyglucose transport into adipocytes was measured using an oil centrifugation method at 2, 5, and 10 minutes of incubation. The composition of fatty acids was analyzed in the fat pad and adipocyte incubation mixture by using gas chromatography. In the fat pad, fatty acids were composed of 61% linoleic, 18% each of palmitic and oleic, and 0.7% arachidonic acids in the high safflower oil group, and 56% oleic, 31% palmitic, 8% linoleic acids in the low safflower oil group. The compositions of dietary fatty acids were reflected directly in the composition of fatty acids in the fat pads and in the compositions of fatty acids released from isolated adipocytes. The high safflower oil diet significantly increased D-glucose transport in adipocytes compared with the low safflower oil diet group (8.66 vs. 6.31 nmol 2-deoxyglucose transport per 10 6 cells at 5-minute incubation). The results suggest that lipid composition in the tissue may have a regulatory effect on adipocyte glucose transport. Diet-induced high polyunsaturated fatty acids in the tissue facilitates carrier-mediated D-glucose transport in adipocytes.

Less Body Fat Accumulation in Rats Fed a Safflower Oil Diet Than in Rats Fed a Beef Tallow Diet

The effects on body fat accumulation of long-term feeding of high fat diets of differing fatty acid composition were studied in rats. The rats were meal-fed isoenergetic diets based on safflower oil or beef tallow for 4 mo. Each diet was freshly prepared every day throughout the experimental period. Oxygen consumption and carbon dioxide production for 6 h after meals were measured between the 50th and 54th d of the experimental period. Oxygen consumption for 3 h after meals was significantly greater in the safflower oil diet group than in the beef tallow diet group, indicating greater diet-induced thermogenesis in the former group. From the assessment of respiratory quotient, the fat oxidation rate was also higher in the former. After the experimental period (4 mo), body fat accumulation was significantly less in the rats fed safflower oil. This difference was, at least in part, ascribed to increased diet-induced thermogenesis and fat oxidation. Serum triacylglycerol level was markedly lower in the rats fed safflower oil than in those fed beef tallow. The lipoprotein lipase activities in heart and soleus muscle after meals appeared to be higher in the former than in the latter. These results suggest that the consumption of the safflower oil diet increased lipoprotein lipase activity in heart and skeletal muscle, resulting in the elevation of fat oxidation rate and the depression of serum triacylglycerol level.