Reduction in plasma cholesterol and increase in biliary cholesterol by a diet rich in n-3 fatty acids in the rat

Cholesterol and lipoprotein metabolism were investigated in a group of rats fed a fish oil-supplemented diet, a rich source of n-3 fatty acids. For comparison purposes, other groups of rats were fed either safflower oil (n-6 fatty acids) or coconut oil (saturated fatty acids). Diets were isocaloric and contained identical amounts of cholesterol. Rats fed fish oils for 2 weeks showed a 35% lower plasma cholesterol level than rats fed safflower oil, who in turn showed a 14% lower plasma cholesterol level than those fed coconut oil. The fall in plasma cholesterol level with fish oils was associated with significant falls in low density and high density lipoprotein cholesterol levels, but with no significant change in the ratio of low density to high density lipoprotein cholesterol. The fatty acid compositions of plasma, hepatic, and biliary lipids showed relative enrichment with n-3 fatty acids, reflecting the composition of the diet. The fish oil diet increased the basal secretion rate of cholesterol into bile, but the bile acid secretion rate remained unchanged. It is suggested that n-3 fatty acids reduce the plasma cholesterol level in rats by increasing the transfer of cholesterol into bile.     

Dietary oils mediate cortisol kinetics and the hepatic mRNA expression profile of stress-responsive genes in gilthead sea bream (Sparus aurata) exposed to crowding stress. Implications on energy homeostasis and stress susceptibility

Juveniles of gilthead sea bream were fed with plant protein-based diets with fish oil (FO diet) or vegetable oils (66VO diet) as dietary lipid sources. No differences in growth performance were found between both groups, and fish with an average body mass of 65–70 g were crowded (90–100 kg/m³) to assess the stress response within the 72 h after the onset of stressor. The rise in plasma cortisol and glucose levels was higher in stressed fish of group 66VO (66VO-S) than in FO group (FO-S), but the former stressed group regained more quickly the cortisol resting values of the corresponding non-stressed diet group. The cell–tissue repair response represented by derlin-1, 75 kDa glucose-regulated protein and 170 kDa glucose-regulated protein was triggered at a lower level in 66VO-S than in FO-S fish. This occurred in concert with a long-lasting up-regulation of glucocorticoid receptors, antioxidant enzymes, enzyme subunits of the mitochondrial respiratory chain, and enzymes involved in tissue fatty acid uptake and β-oxidation. This gene expression pattern allows a metabolic phenotype that is prone to “high power” mitochondria, which would support the replacement of fish oil with vegetable oils when theoretical requirements in essential fatty acids for normal growth are met by diet.     

The effect of dietary menhaden,olive, and coconut oil fed with three levels of vitamin E on plasma and liver lipids and plasma fatty acid composition in rats

The effect of dietary fats with varying degrees of unsaturation in the presence of different concentrations of vitamin E on tissue lipid levels was studied in rats. Rats were fed either menhaden oil, olive oil or coconut oil at 15% levels with either 0.1, 0.3 or 0.6 mg/g of vitamin E as alpha-tocopherol for four weeks. Rat serum and liver were analyzed for total cholesterol, HDL-cholesterol, triacylglycerol and phospholipids. In addition, fatty acid composition of serum lipids was also analyzed. Serum total cholesterol and triacylglycerol were significantly lower in rats fed menhaden oil than in those fed olive or coconut oil, while the HDL-cholesterol was significantly higher in serum of rats fed menhaden and olive oil than in those fed coconut oil. Levels of vitamin E in the diet had only a significant effect on serum cholesterol and liver phospholipids. The Pearson correlation coefficient showed a significant positive relationship between serum triacylglycerol and total cholesterol, and a negative correlation between triacylglycerol and HDL-cholesterol, and between total and HDL-cholesterol.In the liver, total cholesterol was significantly higher in rats fed coconut oil than in rats fed menhaden oil. Total liver phospholipids were lower in rats fed either coconut oil or olive oil compared to those fed menhaden oil, especially with higher levels of vitamin E intake. Higher levels of vitamin E in the diet appear to increase triacylglycerol and phospholipids in livers of rats fed menhaden oil. In the liver a significant negative correlation was observed between phospholipids and cholesterol. The type and degree of unsaturation (polyunsaturated fatty acids in menhaden oil, monounsaturated fatty acids in olive oil and saturated fatty acids in coconut oil) significantly affected plasma and tissue lipids.     

Effect of n-6 and n-3 dietary fatty acids on phospholipid composition of plasma, platelets and aorta in the rat

Female Wistar rats were fed with diets containing as dietary lipids 10% of hydrogenated coconut oil, grape-seed oil, olive oil, linseed oil and fish oil, respectively, for a period of 60 days. At the end of dietary treatment plasma, platelets and aorta phospholipids were extracted and fatty acid spectra determined. Plasma and platelet phospholipids showed the largest diet dependent changes. Anyway in aorta samples too, phospholipids showed marked increase in oleic (olive oil group) linoleic (grape-seed oil group) and alpha linoleic (linseed oil group) acids percentage. Conversely decreased amounts of arachidonic acid were detected in rats fed with diets containing linseed and fish oils. In these samples eicosapentenoic acid partly replaced arachidonic one.     

Effect of fish oil and coconut oil diet on the LDL receptor activity of rat liver plasma membranes

The influence of 4 weeks treatment with fish oil and coconut oil enriched diets on the chemical composition of rat liver plasma membranes and LDL and on the binding of LDL to liver membranes was investigated. Rats fed fish oil diet showed a total, LDL and HDL plasma cholesterol concentration lower than the values observed in rats fed coconut oil and to a lesser extent lower than those of rats fed standard laboratory diet. LDL of rats on fish oil diet had a relative percentage of cholesterol and phospholipid lower, while that of triacylglycerol was greater. Furthermore, fish oil feeding was associated with a greater concentration of n - 3 fatty acids and a lower arachidonic and linoleic acid content in LDL. Liver plasma membranes isolated from fish oil rats showed a higher percentage of n - 3 fatty acids, while only a trace amount of these fatty acids was found in control and coconut oil fed animals. In binding experiments performed with LDL and liver membranes from fish oil fed rats and control rats, binding affinity (Kd = 3.47 +/- 0.93 and 4.56 +/- 1.27, respectively) was significantly higher (P less than 0.05) as compared to that found using membranes and lipoprotein from coconut oil fed rats (Kd = 6.82 +/- 2.69). In cross-binding experiments performed with fish oil LDL and coconut oil liver plasma membranes or coconut oil LDL and fish oil liver plasma membranes, the LDL binding affinity was comparable and similar to that found in fish oil fed animals. No difference was found in the Bmax among all the groups of binding experiments. Our data seem to indicate that during fish oil diet the higher binding affinity of LDL to liver plasma membranes might be partly responsible of the hypocholesterolemic action of marine oil rich diet as compared to saturated diet. Furthermore, the modifications of binding affinity induced by changes of LDL and membrane source, suggest that lipoprotein and liver plasma membrane composition may be an important variable in binding studies.     

Effect of Fish Oil and Coconut Oil on Antioxidant Defence System and Lipid Peroxidation in Rat Liver

Diets high in fish oil containing polyunsaturated fatty acids of the n-3 family. have been suggested to decrease the risk of cardiovascular disease. However these lipids are highly susceptible to oxidative deterioration. In order to investigate the influence of n-3 fatty acids on oxidative status, the effect of feeding rats with fish oil or cocunut oil diets was studied by measuring different parameters related to an oxidative free radical challenge. Synthetic diets containing 15% (w/v) fish oil or coconut oil were used to feed growing rats for 4 weeks. As compared to control diet, the fish oil containing diet produced a significant decrease of cholesterol and triglyceride concentration in serum. however there was a significant increase in lipid peroxidation products. In addition, in fish oil fed animals, there was also a decrease in vitamin E and A concentration. Furthermore, the rate of lipid peroxidation in isolated microsomes was three fold higher in rats fed fish oil as compared to rats with coconut oil diet. No significant differences between the two experimental groups were observed in superoxide dismutase (SOD) and phospholipid hydroperoxide glutathione peroxidase (PHGPX) activities. However, there was a decrease in glutathione peroxidase (GPX) activity. These results suggest that fish oil feeding at an amount compatible with human diet, although decreasing plasma lipids, actually challenge the antioxidant defence system, thus increasing the susceptibility of tissues to free radical oxidative damage.     

Effect of Fish Oil and Coconut Oil on Antioxidant Defence System and Lipid Peroxidation in Rat Liver

Diets high in fish oil containing polyunsaturated fatty acids of the n-3 family. have been suggested to decrease the risk of cardiovascular disease. However these lipids are highly susceptible to oxidative deterioration. In order to investigate the influence of n-3 fatty acids on oxidative status, the effect of feeding rats with fish oil or cocunut oil diets was studied by measuring different parameters related to an oxidative free radical challenge. Synthetic diets containing 15% (w/v) fish oil or coconut oil were used to feed growing rats for 4 weeks. As compared to control diet, the fish oil containing diet produced a significant decrease of cholesterol and triglyceride concentration in serum. however there was a significant increase in lipid peroxidation products. In addition, in fish oil fed animals, there was also a decrease in vitamin E and A concentration. Furthermore, the rate of lipid peroxidation in isolated microsomes was three fold higher in rats fed fish oil as compared to rats with coconut oil diet. No significant differences between the two experimental groups were observed in superoxide dismutase (SOD) and phospholipid hydroperoxide glutathione peroxidase (PHGPX) activities. However, there was a decrease in glutathione peroxidase (GPX) activity. These results suggest that fish oil feeding at an amount compatible with human diet, although decreasing plasma lipids, actually challenge the antioxidant defence system, thus increasing the susceptibility of tissues to free radical oxidative damage.     

Aging-related oxidative stress depends on dietary lipid source in rat postmitotic tissues

We investigate mitochondrial-lipid peroxidation of mitotic (liver) and postmitotic (heart and skeletal muscle) tissues of rats fed lifelong on two different lipid sources: virgin olive oil (monounsaturated fatty acids) and sunflower oil (n–6 polyunsaturated fatty acids). Two groups of 80 rats each were fed over 24 months on a diet differing in the lipid source (virgin olive oil or sunflower oil). Twenty rats per group were killed at 6, 12, 18, and 24 months; liver, heart, and skeletal muscle mitochondria were isolated and the lipid profile, hydroperoxides, vitamin E, and ubiquinone as well as catalase activity measured. Lipid peroxidation was higher in postmitotic tissues, and sunflower oil led to a higher degree of polyunsaturation and peroxidation. The levels of -tocopherol adapted to oxidative stress and preferentially accumulated during aging in heart and skeletal muscle. In conclusion, the type of dietary fat should be considered in studies on aging, since oxidative stress is directly modulated by this factor. This study confirms that postmitotic tissues are more prone to oxidative stress during aging and proposes a hypothesis to explain this phenomenon.     

Biological significance of phosphorylation and myristoylation in the regulation of cardiac muscle proteins

The effect of different dietary fats on peritoneal macrophage plasma membrane fluidity, intracellular cyclic AMP (cAMP) production, GTP hydrolysis and TNF binding and TNF-induced IL1 and IL6 production was investigated. After a four week period, fluidity, as determined by both fluorescence recovery after photobleaching (FRAP) and anisotropy was lowest and highest in animals fed corn and fish oil respectively. After eight weeks feeding, lateral membrane movements were decreased substantially in fish, olive and coconut oil fed dietary groups, whereas an increase in the corn oil fed group was observed, no effect was observed in macrophages from the butter fed group. However, an increase in the packing was observed in macrophages from all dietary groups except in the olive oil fed group. GTPase values for the coconut oil and butter groups were higher than in any other dietary group. After receiving the diet for 8 weeks these differences between the groups were no longer apparent. Exposure of macrophages to TNF had no effect on the rate of GTP hydrolysis. A major enhancement of cAMP production became apparent between weeks 4 and 8 of dietary treatment. After 4 weeks on the diet, values were significantly higher from cells of animals fed corn and olive oils than from animals fed fish oil. After 8 weeks, while there was a general enhancement of production, further differences became apparent. Feeding corn and coconut oils resulted in the highest values and olive oil and chow in the lowest. It is proposed that fats rich in n-3 fatty acids (fish oils) alter membrane fluidity, decrease TNF binding affinity, GTPase activity and cAMP production which appears not to modify cytokine production after short term dietary supplementation. However, after long term feeding it appears that increases in the sensitivity of the TNF receptors plays a major role in modifying cytokine production. (Mol Cell Biochem 166: 135-143, 1997)     

Improved n-3 fatty acid status does not modulate insulin resistance in fa/fa Zucker rats

The objective was to examine the effect of polyunsaturated fatty acid type (plant vs fish oil-derived n-3, compared to n-6 fatty acids in the presence of constant proportions of saturated, monounsaturated and polyunsaturated fatty acids) on obesity, insulin resistance and tissue fatty acid composition in genetically obese rats. Six-week-old fa/fa and lean Zucker rats were fed with a 10% (w/w) mixed fat diet containing predominantly flax-seed, menhaden or safflower oils for 9 weeks. There was no effect of dietary lipid on obesity, oral glucose tolerance (except t=60 min insulin), pancreatic function or molecular markers related to insulin, glucose and lipid metabolism, despite increased n-3 fatty acids in muscle and adipose tissue. The menhaden oil diet reduced fasting serum free fatty acids in both fa/fa and lean rats. These data suggest that n-3 composition does not alter obesity and insulin resistance in the fa/fa Zucker rat model when dietary lipid classes are balanced.     

The prostaglandin outflow from perfused mesenteric vasculature of rats fed different fats

The effects of dietary n-6 polyunsaturated fatty acids and replacement with saturated fat or fish oil on the prostaglandin outflow from perfused mesenteric vasculature in rats were studied. Seventy-two weanling male rats were fed ad libitum a semi-synthetic diet supplemented with 10% by weight of oil, composed wholly of n-6 fatty acid-rich evening primrose oil, or replaced partly or completely (25, 50, 75 or 100%) by n-6 fatty acid-deficient fish oil or hydrogenated coconut oil for 8 weeks. The outflows of 6-keto-PGF1 alpha, thromboxane B2, and prostaglandin E from the perfused mesenteric vasculature were measured at 60 min-time point after starting the perfusion. In general, the release of prostanoids from the mesenteric vasculature was significantly reduced in rats fed a diet in which evening primrose oil was partly or completely replaced by either hydrogenated coconut or fish oil. This was probably due to the insufficient conversion of linoleic acid to arachidonic acid. The extent of reduction was greater in fish oil-fed than in hydrogenated coconut oil-fed rats, while the levels of arachidonic acid in aortic phospholipids were similar between these two groups. This result implies that the greater reduction of prostaglandin synthesis in rats fed fish oil was due to the inhibitory effect of eicosapentaenoic and docosahexaenoic acids in fish oil on the conversion of arachidonate to eicosanoids.     

The adaptive effects of dietary fish and safflower oil on lipid and lipoprotein metabolism in perfused rat liver

To elucidate the mechanisms underlying the plasma triacylglycerol-lowering effects of certain fish oils, livers from male rats fed either a standard commercial diet (controls) or diets supplemented with 15% (w/w) fish or safflower oils were perfused with undiluted rat blood. Rates of hepatic lipogenesis, measured by the incorporation of 3H2O into fatty acids, followed the order: control greater than safflower oil greater than fish oil. Secretion of newly synthesized fatty acids in very-low-density lipoproteins was also inhibited by the feeding of both oil-supplemented diets with the greater suppression being seen in livers from animals fed fish oil. The hepatic release of very-low-density lipoprotein triacylglycerol mass was also significantly depressed in animals fed the fish oil-supplemented diet but not in those fed safflower oil. Ketogenesis did not differ between livers from rats fed the control and safflower oil diets but was significantly raised in the fish oil group. Increased ketogenesis with fish oil was paralleled by a decrease in the sensitivity of carnitine palmitoyl transferase of isolated mitochondria to inhibition by malonyl-CoA. The inhibitory effect of malonyl-CoA in the safflower oil group was intermediate between that in the fish oil and control groups. Activities of glycerophosphate acyltransferase with either palmitoyl-CoA or oleyl-CoA were increased by feeding oil-supplemented diets. Activity with palmitoyl-CoA that was suppressible by N-ethylmaleimide was also considerably diminished in both groups. The results indicate that the lowering of plasma triacylglycerols by fish oil reflects: (a) diminished lipogenesis; (b) increased fatty acid oxidation possibly in peroxisomes; and (c) diminished secretion of triacylglycerols by the liver.     

Does membrane fatty acid composition modulate mitochondrial functions and their thermal sensitivities?

We investigated the effect of modifying fatty acid modification of heart mitochondrial membranes by dietary intervention on the functions and thermal sensitivity of electron transport system complexes embedded in the inner mitochondrial membrane. Four groups of rats were fed diets differing in their fat (coconut, olive or fish oil) and antioxidant (fish oil with or without probucol) contents. After 16 weeks of feeding, the coconut and olive oil groups had lower long-chain n-3 polyunsaturated fatty acids contents and a lower unsaturation index compared to both fish oil groups. These differences in fatty acid composition were not related to any differences in the mitochondrial respiration rate induced at Complexes I, II or IV, or to differences in their thermal sensitivity. The coconut oil group showed a lower mitochondrial affinity for pyruvate at 5 degrees C (k(mapp)=6.4+/-1.8) compared to any other groups (k(mapp)=3.8+/-0.5; 4.7+/-0.8; 3.6+/-1.1, for olive, fish oil and fish oil and probucol groups, respectively). At least in rat heart, our results do not support a major impact of the fatty acid composition of the mitochondrial membrane on the function of mitochondrial enzymatic complexes or on their temperature sensitivity.     

Regulation of glucose transport and transporter 4 (GLUT-4) in muscle and adipocytes of sucrose-fed rats: effects of N-3 poly- and monounsaturated fatty acids.

The goal of this study was to compare the short-term effects of dietary n-3 polyunsaturated (fish oil) and monounsaturated (olive oil) fatty acids on glucose transport, plasma glucose and lipid controls in a dietary insulin resistance model using sucrose-fed rats. The underlying cellular and molecular mechanisms were also determined in the muscle and adipose tissue. Male Sprague-Dawley rats (5 weeks old) were randomized for diets containing 57.5 % (w/w) sucrose and 14 % lipids as either fish oil (SF), olive oil (SO) or a mixture of standard oils (SC) for 3 weeks. A fourth control group (C) was fed a diet containing 57.5 % starch and 14 % standard oils. After three weeks on the diet, body weight was comparable in the four groups. The sucrose-fed rats were hyperglycemic and hyperinsulinemic in response to glucose load. The presence of fish oil in the sucrose diet prevented sucrose-induced hyperinsulinemia and hypertriglyceridemia, but had no effect on plasma glucose levels. Insulin-stimulated glucose transport in adipocytes increased after feeding with fish oil (p < 0.005). These modifications were associated with increased Glut-4 protein (p < 0.05) and mRNA levels in adipocytes. In the muscle, no effect was found on Glut-4 protein levels. Olive oil, however, could not bring about any improvement in plasma insulin, plasma lipids or Glut-4 protein levels. We therefore conclude that the presence of fish oil, in contrast to olive oil, prevents insulin resistance and hypertriglyceridemia in rats on a sucrose diet, and restores Glut-4 protein quantity in adipocytes but not in muscle at basal levels. Dietary regulation of Glut-4 proteins appears to be tissue specific and might depend on insulin stimulation and/or duration of dietary interventions.     

Olive oil preparation determines the atherosclerotic protection in apolipoprotein E knockout mice

Oils enriched in monounsaturated fatty acids do not seem to behave similarly in protecting against the development of atherosclerosis in animal models, which has been attributed to the presence of soluble phenolic compounds. To test the relevance of other components of oils in the prevention of atherosclerosis, two olive oils from the same cultivar devoid of soluble phenolic compounds were prepared using different procedures (pressure or centrifugation), characterized and fed to apolipoprotein E-deficient mice as 10% (w/w) of their diet. The 2 olive oils had similar levels of monounsaturated fatty acids and squalene, but they differed in their content of linoleic, phytosterols, tocopherols, triterpenes and waxes, which were particularly enriched in the test olive oil obtained by centrifugation. In mice that received a diet enriched in the olive oil derived through centrifugation, the progression of atherosclerosis was delayed compared to the mice that received standard olive oil. That effect was associated with decreases in plasma triglycerides, total and non-high-density lipoprotein cholesterol and isoprostane 8-iso-prostaglandin F(2alpha). Our results clearly indicate that the preparation of olive oil is crucial in determining its antiatherosclerotic effect, which extends beyond the presence of phenolic compounds. The test olive oil exerted its antiatherosclerotic effects by modifying plasma lipids and oxidative stress, and it might be a good candidate to replace other fats in functional foods.     

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.     

Consumption of soybean or olive oil at recommended concentrations increased the intestinal microbiota diversity and insulin sensitivity and prevented fatty liver compared to the effects of coconut oil

Diets rich in mono or polyunsaturated fats have been associated with a healthy phenotype, but there is controversial evidence about coconut oil (CO), which is rich in saturated medium-chain fatty acids. Therefore, the purpose of the present work was to study whether different types of oils rich in polyunsaturated (soybean oil, SO), monounsaturated (olive oil, OO), or saturated fatty acids (coconut oil, CO) can regulate the gut microbiota, insulin sensitivity, inflammation, mitochondrial function in wild type and PPARα KO mice. The group that received SO showed the highest microbial diversity, increase in Akkermansia muciniphila, high insulin sensitivity and low grade inflammation, The OO group showed similar insulin sensitivity and insulin signaling than SO, increase in Bifidobacterium, increase in fatty acid oxidation and low grade inflammation. The CO consumption led to the lowest bacterial diversity, a 9-fold increase in the LPS concentration leading to metabolic endotoxemia, hepatic steatosis, increased lipogenesis, highest LDL-cholesterol concentration and the lowest respiratory capacity and fatty acid oxidation in the mitochondria. The absence of PPARα decreased alpha diversity and increased LPS concentration particularly in the CO group, and increased insulin sensitivity in the groups fed SO or OO. These results indicate that consuming mono or polyunsaturated fatty acids produced health benefits at the recommended intake but a high concentration of oils (three times the recommended oil intake in rodents) significantly decreased the microbial alpha-diversity independent of the type of oil.     

Effect of sex and dietary fat intake on the fatty acid composition of phospholipids and triacylglycerol in rat heart

Variations in the fatty acid composition of lipids in the heart alter its function and susceptibility to ischaemic injury. We investigated the effect of sex and dietary fat intake on the fatty acid composition of phospholipids and triacylglycerol in rat heart. Rats were fed either 40 or 100 g/kg fat (9:1 lard:soybean oil) from weaning until day 105. There were significant interactive effects of sex and fat intake on the proportions of fatty acids in heart phospholipids, dependent on phospholipid classes. 20:4n-6, but not 22:6n-3, was higher in phospholipids in females than males fed a low, but not a high, fat diet. There was no effect of sex on the composition of triacylglycerol. These findings suggest that sex is an important factor in determining the incorporation of dietary fatty acids into cardiac lipids. This may have implications for sex differences in susceptibility to heart disease.     

Effect of age on the modification of rat plasma lipids by fish and soybean oil diets

The effects of sardine and soybean oils on plasma lipids have been studied in young and aged rats. Plasma cholesterol and bile acids of aged rats fed on a sardine oil diet decreased to a greater degree than those of young rats. Cholesterol, bile acids and phospholipids of the soybean oil diet group decreased only in aged rats. Increases in plasma eicosapentaenoic (sardine) and linoleic (soybean) acid levels of aged rats were observed to be greater than those of young rats. These results indicate that the age enhances the effects of fish and soybean oils on plasma lipids by suppressing their characteristic fatty acid metabolism.     

Oleuropein supplementation increases urinary noradrenaline and testicular testosterone levels and decreases plasma corticosterone level in rats fed high-protein diet

The effects of oleuropein, a phenolic compound in extra virgin olive oil, on protein metabolism were investigated by measuring testicular testosterone and plasma corticosterone levels in rats fed diets with different protein levels. In Experiment 1, rats were fed experimental diets with different protein levels (40, 25 and 10 g/100 g casein) with or without 0.1 g/100 g oleuropein. After 28 days of feeding, the testosterone level in the testis was significantly higher and the plasma corticosterone level was significantly lower in rats fed the 40% casein diet with oleuropein than in those fed the same diet without oleuropein. The urinary noradrenaline level, nitrogen balance and hepatic arginase activity were significantly higher in rats fed the 40% casein diet with oleuropein supplementation than in those fed the 40% casein diet without oleuropein supplementation. In Experiment 2, the effects of oleuropein aglycone (a major phenolic compound in extra virgin olive oil and the absorbed form of oleuropein ingested in the gastrointestinal tracts) on the secretion of luteinizing hormone (LH) from the pituitary gland, which regulates testosterone production in the testis, were investigated in anesthetized rats. Plasma LH level increased dose dependently after the administration of oleuropein aglycone (P<.001, r= 0.691). These findings suggest that dietary supplementation with 0.1 g/100 g oleuropein alters the levels of hormones associated with protein anabolism by increasing urinary noradrenaline and testicular testosterone levels and decreasing plasma corticosterone level in rats fed a high-protein diet.