Tissue specific interactions of exercise, dietary fatty acids, and vitamin E in lipid peroxidation

Both physical exercise and ingestion of polyunsaturated fatty acids that play an essential role in free radical-mediated damages cause lipid peroxidation. The intake of specific fatty acids can modulate the membrane susceptibility to lipid peroxidation. Data confirmed that liver, skeletal muscle, and heart have different capabilities to adapt their membrane composition to dietary fatty acids, the heart being the most resistant to changes. Such specificity affects membrane hydroperoxide levels that depend on the type of dietary fats and the rate of fatty acid incorporation into the membrane. Sedentary rats fed a monounsaturated fatty acid-rich diet (virgin olive oil) showed a higher protection of their mitochondrial membranes against peroxidation than sedentary rats fed a polyunsaturated fatty acid-rich diet (sunflower oil). Rats subjected to training showed higher hydroperoxide contents than sedentary animals, and exhaustive effort enhanced the aforementioned results as well as in vitro peroxidation with a free radical inducer. This study suggests that peroxide levels first depend on tissue, then on diet and lastly on exercise, both in liver and muscle but not in heart. Finally, it appears that alpha-tocopherol is a less relevant protective agent against lipid peroxidation than monounsaturated fatty acids.     

Incorporation of n-3 fatty acids into plasma lipid fractions, and erythrocyte membranes and platelets during dietary supplementation with fish, fish oil, and docosahexaenoic acid-rich oil among healthy young men

The effects of n-3 fatty acid supplementation in the form of fresh fish, fish oil, and docosahexaenoic acid (DHA) oil on the fatty acid composition of plasma lipid fractions, and platelets and erythrocyte membranes of young healthy male students were examined. Altogether 59 subjects (aged 19-32 yr, body mass index 16.8-31.3 kg/m2) were randomized into the following diet groups: (i) control group; (ii) fish diet group eating fish meals five times per week [0.38 +/- 0.04 g elcosapentaenoic acid (EPA) and 0.67 +/- 0.09 g DHA per day]; (iii) DHA oil group taking algae-derived DHA oil capsules (1.68 g/d DHA in triglyceride form); and (iv) fish oil group (1.33 g EPA and 0.95 g DHA/d as free fatty acids) for 14 wk. The fatty acid composition of plasma lipids, platelets, and erythrocyte membranes was analyzed by gas chromatography. The subjects kept 4-d food records four times during the study to estimate the intake of nutrients. In the fish diet, in DHA oil, and in fish oil groups, the amounts of n-3 fatty acids increased and those of n-6 fatty acids decreased significantly in plasma lipid fractions and in platelets and erythrocyte membranes. A positive relationship was shown between the total n-3 polyunsaturated fatty acids (PUFA) and EPA and DHA intake and the increase in total n-3 PUFA and EPA and DHA in all lipid fractions analyzed. DHA was preferentially incorporated into phospholipid (PL) and triglyceride (TG) and there was very little uptake in cholesterol ester (CE), while EPA was preferentially incorporated into PL. and CE. The proportion of EPA in plasma lipids and platelets and erythrocyte membranes increased also by DHA supplementation, and the proportion of linoleic acid increased in platelets and erythrocyte membranes in the DHA oil group as well. These results suggest retroconversion of DHA to EPA and that DHA also interferes with linoleic acid metabolism.     

Comparative costs of family planning services and hospital-based maternity care in Turkey

The effect of dietary fats on the chemical composition and enzyme activities has been studied in intestinal brush border membranes (BBM) or rats. Animals were given commercial rat pellet diet (RP) or semisynthetic diet rich in either saturated [coconut oil (CCO))] or polyunsaturated [n-6, corn oil (CO) or n-3, fish oil (FO)] fat at the 10% level for 5 weeks. The membrane cholesterol/phospholipid ratio was augmented in CO- or RP-fed rats. There was an increase in level of saturated fatty acids in BBM from CCO- or FO-fed animals. n-3 polyunsaturated fatty acid content was raised in FO-fed rats, while the proportion of linoleic acid and arachidonic acid was enhanced in animals given a CO diet. Membrane fluidity was in the order of CCO < RP = CO < FO. The membrane hexose content was high (p < 0.05) in the CCO group. Hexosamines were elevated (p < 0.05) in CCO- or FO-fed rat brush borders. Membrane fucose was unaltered, while sialic acid content was elevated in CO- (p < 0.05) and FO- (p < 0.01) fed vs. CCO-fed rats. Lectin binding to brush borders corroborated these findings. The activities of alkaline phosphatase, sucrase and lactase were augmented (p < 0.001) in CCO-fed animals. Leucine-aminopeptidase and sucrase activities were depressed by FO feeding. The activities of PNP-beta-glycosidases were the highest in FO-fed rats. These results indicate that dietary fat quality markedly affects microvillus membrane lipid composition, glycosylation and enzyme functions in rat intestine.     

Plasmatic and membrane lipid alterations in erythrocytes from diabetic rats fed either n-6 or n-3 fatty acids

We examined the effect of dietary n-6 and n-3 fatty acids on the lipid composition and physical properties of erythrocyte membranes together with cholesterol and triglyceride plasmatic levels in normal and experimental diabetic rats. Plasmatic total cholesterol and triglyceride did not change in normal rats under the dietary regime, but both parameters decreased significantly in the diabetic animals after the consumption of either n-6 or n-3 fatty acids. Lipid analyses of erythrocyte membranes revealed a significant decrease in the total cholesterol together with an increase in the phospholipid amount in the diabetics compared to the normal rats. As a consequence, cholesterol/phospholipid ratio decreased in these groups of animals and markedly in those fed n-3 fatty acids. These changes would be responsible for the lower fluorescent polarization of DPH observed in the latter group. We conclude that equivalent and adequate amounts of dietary either n-6 or n-3 fatty acids produce plasmatic and red cell membrane lipid changes in diabetic rats that may improve the evolution of the disease.     

Dietary fish oil affects monoaminergic neurotransmission and behavior in rats

We studied the effects of a fish oil enriched diet on fatty acid composition of cerebral membranes and on several neurochemical and behavioral variables of monoaminergic function in rats. The frontal cortex, striatum, hippocampus and cerebellum were studied in rats fed fish oil (FPO, 50% salmon oil + 50% palm oil), which provided an (n-6)/(n-3) polyunsaturated fatty acid (PUFA) ratio of 0.14 versus 6. 19 in controls fed a diet containing a mixture of African peanut oil and rapeseed oil. In the FPO group compared to the control group, the major modifications in fatty acid composition of cerebral membranes included the following: higher levels in 22:6(n-3), lower levels in 20:4(n-6) and a significantly greater proportion of phosphatidylserine. Dopamine levels were 40% greater in the frontal cortex of rats fed FPO than from those fed the control diet. In this cerebral region there was also a reduction in monoamine oxidase B (MAO-B) activity and greater binding to dopamine D2 receptors. By contrast, a lower binding to dopamine D2 receptors (-7%) was observed in the striatum. Ambulatory activity was also reduced in FPO-fed rats, possibly related to observed changes in striatal dopaminergic receptors. This suggested that the level of (n-6) PUFA, which was considerably lower in the FPO diet than in the control diet, could act on locomotion through an effect on striatal dopaminergic function, whereas the high level of (n-3) PUFA could act on cortical dopaminergic function.     

Influence of dietary fats upon systolic blood pressure in the rat

Studies were performed to determine whether feeding diets with differing fatty acid content and composition had an influence on systolic blood pressure in the rat. Weanling male rats were fed standard laboratory chow (2.9% fat in total), or synthetic diets (10% fat in total) containing fish oil, butter, coconut oil or corn oil, for 5 weeks. Coconut oil and butter diets were rich in saturated fatty acids, whilst fish oil and corn oil were rich in the n-3 and n-6 unsaturated fatty acids respectively. Systolic blood pressure was measured using an indirect tail-cuff method at the end of the feeding period, and compared to a group of weanling rats. Feeding the different diets did not alter the growth of the rats, so all animals were of similar weights at the time of blood pressure determination. Control (chow fed) animals, at nine weeks of age, had higher systolic blood pressures than the weanling, baseline control group. Fish oil fed rats had similar pressures to the chow fed rats. Corn oil fed rats had significantly lower systolic pressures than the controls. The rats led the diets rich in saturated fatty acids (butter and coconut oil) had significantly higher blood pressures than all other groups. Systolic blood pressure was found to be significantly related to the dietary intakes of saturated and unsaturated fatty acids. The dietary intake of linoleic acid was significantly higher in corn oil fed rats than in other groups. Systolic blood pressure was inversely related to linoleic acid intake. Feeding a diet rich in saturated fatty acids significantly increases blood pressure in the rat. A high intake of n-6 fatty acids, and in particular linoleic acid, appears to have a hypotensive effect. Prenatal exposure of the rats to a maternal low protein diet, abolished the hypertensive effects of the coconut oil diet and the hypotensive effect of the corn oil diet upon young adult females. The intrauterine environment may, therefore, be an important determinant of the effects of these fatty acids on blood pressure in later life.     

Alteration in 5'-nucleotidase activities and composition of liver and brain microsomes of developing rats fed different dietary fats

Four groups of male weanling rats were fed during three months, diets different in the nature of fats and the activity of 5' nucleotidase and fatty acid composition of brain and liver microsomes were studied. Group A were fed a standard commercial diet, group B a fat free-diet and group C and D a fat free-diet, containing respectively 10% of peanut-rapeseed oil and 10% of salmon oil. In brain and liver microsomes, 5'-nucleotidase activity increased throughout the development for all diets (except for the fat-free diet). Slight differences were found in rats fed the peanut-rapeseed oil diet compared to controls estimated at the same time. However, in animals fed the fish-oil diet, 5' nucleotidase had the highest activity in both brain and liver microsomes. Marked changes occurred in the fatty acid patterns of brain and liver microsomes among the various groups. The greatest alterations were found in the liver microsomes. In brain and liver microsomal membranes the fat-free diet induced an increase in monounsaturated fatty acids, an synthesis of eicosatrienoic acid, and a decrease in (n-6) and (n-3) polyunsaturated fatty acids. Animals fed a peanut-rapeseed oil and control diet showed similar fatty acid patterns in liver and brain microsomes. However, when rats were fed a fish-oil diet, the liver microsomal membranes were highly enriched in eicosapentaenoic and docosahexaenoic acids, and simultaneously there was a decrease in arachidonic acid. These results suggest that manipulation of the lipid environment influences 5'-nucleotidase activity by the interaction of the enzyme with specific membrane lipids.     

Fish oils lower rat plasma and hepatic, but not immune cell alpha-tocopherol concentration

These studies were designed to measure the impact of different fish oil sources of dietary (n-3) polyunsaturated fatty acid on the alpha-tocopherol content of rat immune cells. In the first experiment, rats were fed diets containing either lard, corn oil, menhaden fish oil or cod liver oil. In the second study, sardine fish oil replaced corn oil. Dietary fat source did not significantly influence body weights or the yield of immune cells in either study. In both studies, plasma and liver alpha-tocopherol concentrations were significantly lower in (n-3) polyunsaturated fatty acid-fed rats than in rats fed lard. In the first study, immune cell alpha-tocopherol concentrations followed those observed in the plasma and liver. These concentrations closely paralleled the amount of RRR-alpha-tocopheryl acetate added to diets and not the total vitamin E present, which was the same for all treatment groups. However, in the second study, alpha-tocopherol concentration of immune cells was not significantly different among rats fed lard, menhaden fish oil, and sardine fish oil. In that study both the amount and form of vitamin E were carefully balanced across dietary treatment groups. In conclusion, despite having similar amounts of (n-3) polyunsaturated fatty acids, two out of three fish oils tested did not lower immune cell alpha-tocopherol concentration even in the face of significantly reduced plasma and liver alpha-tocopherol concentrations.     

The influence of dietary fatty acid composition on N-ethyl-N-nitrosourea-induced mammary tumour incidence in the rat and on the composition of inositol- and ethanolamine-phospholipids of normal and tumour mammary tissue

This study has investigated the influence of dietary fatty acid composition on mammary tumour incidence in N-ethyl-N-nitrosourea (ENU)-treated rats and has compared the susceptibility to dietary fatty acid modification of the membrane phospholipids phosphatidylinositol (PI) and phosphatidylethanolamine (PE) from normal and tumour tissue of rat mammary gland. The incidence of mammary tumours was significantly lower in fish oil--(29%), compared with olive oil--(75%; P < 0.04) but not maize oil--(63%; P < 0.1) fed animals. No differences in PI fatty acid composition were found in normal or tumour tissue between rats fed on maize oil, olive oil or fish oil in diets from weaning. When normal and tumour tissue PI fatty acids were compared, significantly higher amounts of stearic acid (18:0) were found in tumour than normal tissue in rats given olive oil (P < 0.05). A similar trend was found in animals fed on maize oil, although differences between normal and tumour tissue did not reach a level of statistical significance (P < 0.1). In mammary PE, maize oil-fed control animals had significantly higher levels of linoleic acid (18:2n-6) than either olive oil- or fish oil-fed animals (P < 0.05, both cases) and levels of arachidonic acid were also higher in maize oil- compared with fish oil-fed animals (P < 0.05). In tumour-bearing animals no differences in PE fatty acid composition were found between the three dietary groups. When normal and tumour tissue PE fatty acids were compared, significantly lower amounts of linoleic acid (18:2n-6; P < 0.01) and significantly greater amounts of arachidonic acid (20:4n-6; P < 0.05) were found in tumour than normal tissue of rats fed on maize oil. The present study shows that the fatty acid composition of PI from both normal and tumour tissue of the mammary gland is resistant to dietary fatty acid modification. The PE fraction is more susceptible to dietary modification and in this fraction there is evidence of increased conversion of linoleic acid to arachidonic acid in tumour compared with normal tissue. Lower tumour incidence rates in rats given fish oils may in part be due to alteration in prostanoid metabolism secondary to displacement of arachidonic acid by eicosapentaenoic acid, but PE rather than PI would appear to be the most likely locus for diet-induced alteration in prostanoid synthesis in this tissue. Effects of dietary fatty acids other than on the balance of n-6 and n-3 fatty acids, and on prostanoid metabolism, should also be considered. The significance of increased stearic acid content of PI in tumours of olive oil-fed animals and the possible influence of dietary fatty acids on the capacity for stearic acid accumulation requires further study.     

Isolation of the Pichia pastoris PYC1 gene encoding pyruvate carboxylase and identification of a suppressor of the pyc phenotype

It has been reported that both n-3 and n-6 octadecatrienoic acids can increase hepatic fatty acid oxidation activity. It remains unclear, however, whether different enzymes in fatty acid oxidation show a similar response to n-3 and n-6 octadecatrienoic acids. The activity of hepatic fatty acid oxidation enzymes in rats fed an oil mixture rich in alpha-linolenic acid (18:3n-3) and borage oil rich in gamma-linolenic acid (18:3n-6) was therefore compared to that in rats fed an oil mixture rich in linoleic acid (18:2n-6) and a saturated fat (palm oil) in this study. Linseed oil served as the source of 18:3n-3 for the oil mixture rich in this octadecatrienoic acid and contained 30.6% 18:3n-3 but not 18:3n-6. Borage oil contained 25.7% 18:3n-6 and 4.5% 18:3n-3. Groups of seven rats each were fed diets containing 15% various fats for 15 d. The oxidation rate of palmitoyl-CoA in the peroxisomes was higher in rats fed a fat mixture rich in 18:3n-3 (3.03 nmol/min/mg protein) and borage oil (2.89 nmol/min/mg protein) than in rats fed palm oil (2.08 nmol/min/mg protein) and a fat mixture rich in 18:2n-6 (2.15 nmol/min/mg protein). The mitochondrial palmitoyl-CoA oxidation rate was highest in rats fed a fat mixture rich in 18:3n-3 (1.93 nmol/min/mg protein), but no significant differences in this parameter were seen among the other groups (1.25-1.46 nmol/min/mg protein). Compared to palm oil and fat mixtures rich in 18:2n-6, a fat mixture rich in 18:3n-3 and borage oil significantly increased the hepatic activity of carnitine palmitoyltransferase and acyl-CoA oxidase. Compared to palm oil and a fat mixture rich in 18:2n-6, a fat mixture rich in 18:3n-3, but not fats rich in 18:3n-6, significantly decreased 3-hydroxyacyl-CoA dehydrogenase activity. Compared to palm oil and a fat mixture rich in 18:2n-6, borage oil profoundly decreased mitochondrial acyl-CoA dehydrogenase activity, but a fat mixture rich in 18:3n-3 increased it. 2,4-Dienoyl-CoA reductase activity was significantly lower in rats fed palm oil than in other groups. Compared to other fats, borage oil significantly increased delt3,delta2-enoyl-CoA isomerase activity. Activity was also significantly higher in rats fed 18:2n-6 oil than in those fed palm oil. It was confirmed that both dietary 18:3n-6 and 18:3n-3 increased fatty acid oxidation activity in the liver. These two dietary octadecatrienoic acids differ considerably, however, in how they affect individual fatty acid oxidation enzymes.     

Kinetics of the incorporation of dietary fatty acids into serum cholesteryl esters, erythrocyte membranes, and adipose tissue: an 18-month controlled study

Tissue levels of n-3 fatty acids reflect dietary intake, but quantitative data about rate of incorporation and levels as a function of intake are scarce. We fed 58 men 0, 3, 6, or 9 g/d of fish oil for 12 months and monitored fatty acids in serum cholesteryl esters, erythrocytes, and subcutaneous fat during and after supplementation. Eicosapentaenoic acid (EPA) in cholesteryl esters plateaued after 4-8 weeks; the incorporation half-life was 4.8 days. Steady-state levels increased by 3.9 +/- 0.3 mass % points (+/- SE) for each extra gram of EPA eaten per day. Incorporation of docosahexaenoic acid (DHA) was erratic; plateau values were 1.1 +/- 0.1 mass % higher for every g/d ingested. Incorporation of EPA into erythrocyte membranes showed a half-life of 28 days; a steady state was reached after 180 days. Each g/d increased levels by 2.1 +/- 0.1 mass %. C22:5n-3 levels increased markedly. Changes in DHA were erratic and smaller. EPA levels in adipose tissue rose also; the change after 6 months was 67% of that after 12 months in gluteal and 75% in abdominal fat. After 12 months each gram per day caused an 0.11 +/- 0.01 mass % rise in gluteal fat for EPA, 0.53 +/- 0.07 for C22:5n-3, and 0.14 +/- 0.03 for DHA. Thus, different (n-3) fatty acids were incorporated with different efficiencies, possibly because of interconversions or different affinities of the enzymatic pathways involved. EPA levels in cholesteryl esters reflect intake over the past week or two, erythrocytes over the past month or two, and adipose tissue over a period of years. These findings may help in assessing the intake of (n-3) fatty acids in epidemiological studies.     

Effects of dietary n-6 and n-3 lipids on antioxidant defense system in livers of exercised rats

OBJECTIVE: The present study was designed to investigate the effects of dietary n-6 and n-3 lipids and exercise on the activities of hepatic antioxidant enzymes and microsomal lipid composition and peroxidation in Fischer-344 male rats. METHODS: Weanling male Fischer-344 rats were fed ad libitum semipurified diets containing 10% corn oil (CO) or 10% fish oil (FO), with equal levels of antioxidants. After 2 months on the diets, weight-matched animals in each diet group were divided into sedentary (S) and exercised (Ex) groups, and the diets were continued. The animals in the exercise group were run on a treadmill 30 to 40 minutes to exhaustion 6 days/week for 2 months. At the end of 2 months, the rats were sacrificed and livers were collected; antioxidant enzymes were determined in the cytosol, fatty acid composition was analyzed in the microsomes, and vitamin E levels were analyzed in the sera. RESULTS: The rats in the FO-S group exhibited significantly higher liver cytosolic catalase activity, while their superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were significantly lower compared to the CO-S group. The GSH-Px activity was significantly higher in the FO-Ex group compared to FO-S group. The source of dietary lipids significantly influenced the fatty acid composition of the total lipids in the microsomes. Feeding the FO-based diet significantly increased 18:0 and n-3 fatty acids incorporation into the microsomes (18:3, 20:5, 22:5, and 22:6), whereas ingestion of CO resulted in a significant increase in 14:0, 14:1, 18:1, and n-6 fatty acids (18:2 and 20:4). The serum vitamin E levels were significantly higher in the CO groups, and exercise had no effect on vitamin E levels. Exercise significantly decreased the generation of thiobarbituric acid reactive substances (TBARS) by liver microsomes. Consumption of FO, which is highly susceptible to oxidation, did not show any significant changes in membrane lipid peroxidation. CONCLUSIONS: The present study suggests that feeding FO increases the activity of liver cytosolic catalase in FO-S rats and GSH-Px in FO-Ex rats. In addition, exercise significantly decreased the generation of TBARS by the liver microsomal lipids. Serum vitamin E levels were higher in the CO group and exercise did not alter vitamin E levels. This suggests that the amount of vitamin E included in the diets was possibly adequate to cope with the oxidative stress induced during exercise.     

Effect of diet on the rate of depletion of n-3 fatty acids in the retina of the guinea pig

This study has assessed the influence of maternal n-3 long chain polyunsaturated fatty acid supply and dietary manipulation after weaning on the retinal polyunsaturated fatty acid profile. Infant guinea pigs born of dams fed one of two commercial chow diets (differing in the amount of eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids) were raised in two separate experiments, and subsequently partitioned into two diet groups, one supplied with a high level of alpha-linolenic acid (canola oil supplemented), the other with a very low level of alpha-linolenic acid (safflower oil supplemented). Guinea pigs born of dams supplied with the longer chain n-3 fatty acids in the commercial pellets (experiment 2) showed higher levels of retinal docosahexaenoic acid at weaning compared with those born to dams fed chow containing only alpha-linolenic acid (experiment 1). The rate of depletion of retinal docosahexaenoic acid after weaning onto the safflower oil diet was described by a two-stage exponential decay, possibly reflecting systemic and local conservation mechanisms, in conditions of dietary n-3 fatty acid deprivation. The rate of docosahexaenoic acid depletion in the group with the lower retinal docosahexaenoic acid at weaning was more than double the rate of depletion in the group with the higher weaning docosahexaenoic acid value. The endpoint retinal docosahexaenoic acid level at 16 weeks post-weaning after dietary n-3 fatty acid depletion on the safflower oil diet in the group, which started with the lower retinal docosahexaenoic acid level, was approximately half that compared with the group from the dams fed long chain n-3 fatty acids (experiment 1, 5% (interpolated), experiment 2, 9%). These results suggest that an adequately supplied mother is capable of providing an infant with enough n-3 fatty acids to withstand a longer period of dietary deprivation imposed after weaning.     

Protein carbonyl content roughly reflects the unsaturation of lipids in muscle but not in other tissues of stroke-prone spontaneously hypertensive strain (SHRSP) rats fed different fats and oils

We examined in vivo the effect of dietary fats and oils with different peroxidizability on protein carbonyl content, the presumed index of free radical-mediated protein oxidation. For 15.6 months, SHRSP (stroke-prone spontaneously hypertensive strain) rats were fed a diet supplemented with lard, safflower oil, perilla oil or fish oil/soybean oil, the peroxidizability of which increases in this order. The peroxidizability of tissue lipids was positively correlated with the protein carbonyl content in skeletal muscle, but not in the brain, heart or liver. The protein carbonyl content in the lard group was higher in the brain and liver compared to the other dietary groups. These results contradict the concept that long-term feeding of easily autoxidizable fatty acids allows the accumulation of lipid peroxides to accelerate the development of the free radical diseases, and suggest that tissue protein carbonyl content is not a simple reflection of autoxidizability-related lipid peroxidation but is also influenced by other biochemical processes.     

How C-L services can comply with new HCFA guidelines

Ten healthy volunteers were given a daily supplement of 30 g olive oil for 6 weeks in order to evaluate how it would affect cell membrane composition and ultimately platelet function. Fasting blood and cheek cell samples were taken before commencing the study, after 21 and 42 days of supplementation and also at 30 days after finishing the supplement (washout). C18:1n-9 was significantly increased (p < 0.01) in platelet and cheek cell phospholipids. Erythrocytes were not good markers for C18:1n-9 intake and no significant change was found in this tissue. There was a small nonsignificant decrease in platelet phospholipid 20:4n-6 after the supplementation, in accordance with previously published results. C18:1n-9 did not persist in platelet membranes after the volunteers stopped consuming the olive oil supplement, but in erythrocytes a significant increase (p < 0.05) was found after the washout period. None of these changes in fatty acid composition in the different tissues were related to significant changes in serum cholesterol-related variables or in clotting factors or adenosine diphosphate-induced platelet aggregation.     

Changes in dietary fatty acids alter phospholipid fatty acid composition in selected regions of rat brain

1. Eighty rats were randomized into four groups receiving one of the following diets: rat chow containing (1) 6% soybean oil, (2) 6% primrose oil, (3) 6% fish oil, (4) a combination of 4.5% primrose and 1.5% fish oil. 2. Following two months of each regimen, the rats were sacrificed by microwave irradiation and the brain's fatty acid composition was analysed with gas chromatography for each of the following regions: frontal cortex, striatum, occipital cortex, hippocampus, hypothalamus, cerebellum and pituitary. 3. Linoleic acid was decreased by both primrose and fish oil supplementations. The fish oil substitution resulted in a significant elevation of 20:3n-6, a decrease of 22:4n-6 and a non-significant decrease of 20:4n-6, probably reflecting inhibition of delta-5-desaturation. At the same time the fish oil diet significantly elevated 22:5n-3 while 22:5n-6 was decreased. 4. The primrose oil diet lowered the n-3/n-6 ratio in all regions except in the cerebellum. In contrast, the fish oil diet elevated the n-3/n-6 ratio in all regions. 5. The results demonstrate that changes in dietary fat composition can alter the fatty acid composition of the adult rat brain and that these effects are region specific. 6. This is of interest since metabolites of essential fatty acids may be involved in physiological and pathological processes in the brain and it has been hypothesized that dietary intake of fats may influence the outcome of psychiatric disorders such as schizophrenia.     

Effects of ions on partitioning of serum albumin and lysozyme in aqueous two-phase systems containing ethylene oxide/propylene oxide co-polymers

To examine the influence of dietary polyunsaturated fatty acids (PUFA) on the lipid composition of the pineal organ and its production of prostaglandins, Atlantic salmon were fed diets containing either fish oils rich in long-chain n-3 polyunsaturated fatty acids, or plant oils with high levels of 18:2(n-6) (sunflower oil) or 18:3(n-3) (linseed oil) for 12 weeks. Lipid content and lipid class composition of the pineal organ were not greatly influenced by the type of oil fed to the fish: choline phosphoglycerides were always the predominant lipid class and the proportion of polar lipids exceeded that of neutral lipids. The pattern of PUFA present in total lipid and individual lipid classes was, however, related to that of the dietary oil. The major PUFA in pineal total lipid from all four dietary groups was 22:6(n-3) and the proportion of n-6 PUFA present was highest in lipid from salmon fed sunflower oil. Both PGE and PGF analogues of the 2- and 3-series were detected in pineal homogenates from all dietary groups with the former prostaglandin being the most abundant. The ratio of PGE2/PGE3 was greatest in fish fed sunflower oil and lowest in those fed linseed oil. The results provide further evidence that despite its anatomical location the pineal organ resembles non-neural tissues more than brain in terms of lipid composition and prostaglandin production.     

A comparison of immunohistochemical staining of human cultured mesothelial cells and ovarian tumour cells using epithelial and mesothelial cell markers

Atlantic salmon (Salmo salar) post-smolts were fed diets containing either Fosol (FO), a North Sea fish oil, sunflower oil (SO), linseed oil (LO) or Marinol K (MO), a southern hemisphere fish oil rich in 20:5(n-3) for 12 weeks. A macrophage-enriched leucocyte preparation was obtained from head kidney and the fatty acid compositions of the individual membrane phospholipids measured. In general phospholipids from SO- and LO-fed fish had increased 18:2(n-6), 20:2(n-6) and 20:3(n-6) compared to the fish oil treatments while LO-fed fish had lower 20:4(n-6) than any other dietary treatment. Fish fed LO also had increased 18:3(n-3), 18:4(n-3), 20:3(n-3) and 20:4(n-3). The 20:5(n-3) content of kidney macrophage-enriched leucocyte phospholipids was highest in MO-fed fish followed by FO- and LO-fed fish with the lowest level in fish fed SO. The overall effect on the ratio of eicosanoid precursors, 20:4/20:5, showed the highest value in SO-fed fish and the lowest in fish fed LO. Production of LTB5 by kidney macrophage-enriched leucocytes stimulated with A23187 was highest in MO-fed fish and lowest in those fed SO. Production of LTB4 was greatest in SO-fed fish and lowest in fish fed LO. Serum Ig levels were significantly affected by dietary treatment with highest values in fish fed FO and SO and lowest in fish fed MO and LO.     

Dietary (n-3) and (n-6) polyunsaturated fatty acids rapidly modify fatty acid composition and insulin effects in rat adipocytes

The influence of dietary (n-3) compared with (n-6) polyunsatured fatty acids (PUFA) on the lipid composition and metabolism of adipocytes was evaluated in rats over a period of 1 week. Isocaloric diets comprised 16.3 g/100 g protein, 53.8 g/100 g carbohydrate and 21.4 g/100 g lipids, the latter containing either (n-3) PUFA (32.4 mol/100 mol) or (n-6) PUFA (37.8 mol/100 mol) but having identical contents of saturated, monounsaturated and total unsaturated fatty acids and identical polyunsaturated to saturated fatty acid ratios and double bond indexes. Despite comparable food intake, significantly smaller body weight increments and adipocyte size were observed in rats of the (n-3) diet group after feeding for 1 wk. Rats fed the (n-3) diet also had significantly lower concentrations of serum triglycerides, cholesterol and insulin compared with those fed the (n-6) diet, although levels of serum glucose and free fatty acids did not differ in the two dietary groups. In the (n-6) diet group, the (n-6) and (n-3) PUFA contents of plasma triglycerides, free fatty acids and phospholipids were 30-60% higher and 60-80% lower, respectively, than in the (n-3) diet group, whereas adipocyte plasma membrane phospholipids showed a significantly higher unsaturated to saturated fatty acid ratio and greater fluidity. Glycerol release in response to noradrenaline was significantly higher in the adipocytes of rats fed the (n-3) diet, whereas the antilipolytic effect of insulin generally did not differ in the two groups. Finally, insulin stimulated the transport of glucose and its incorporation into fatty acids to a lesser extent in adipocytes of (n-3) diet fed rats compared with (n-6) diet fed rats. This reduction in the metabolic effects of insulin in rats fed a (n-3) diet for 1 wk could be related to smaller numbers and a lower binding capacity of the insulin receptors on adipocytes and/or to a lesser degree of phosphorylation of the 95 kDa beta subunit of the receptor. In conclusion, dietary intake for 1 wk of (n-3) rather than (n-6) PUFA is sufficient to induce significant differences in the lipid composition and metabolic responses to insulin of rat adipocytes.