Brain Fatty Acid Composition Research Articles

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

1. 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. 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. 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. 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. 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. 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.

Variation in the fatty acid composition of juvenile chinook and coho salmon from Fraser river estuary determined by multivariate analysis; role of environment and genetic origin

Juvenile chinook and coho salmon were collected at five sites from the lower Fraser River and estuary for fatty acid analysis of brain, heart, gill-arch and muscle tissue during the winter and spring 1992. Using multivariate analysis, a novel statistical method for this type of data, we found that the fatty acid composition in various fish tissues differed. The brain fatty acid composition was least similar to the fatty acid profiles of the various food species, while the fatty acids extracted from gills showed a profile with more similarity to the food species. The rearing history (hatchery-reared vs. wild fish) influenced the fatty acid composition in the four tissues from both salmon species. The composition of fatty acids from the chinook brain tissue was influenced by developmental changes during the first year of life. In the chinook and coho smolts, species-specific differences were detected in brain and especially the heart tissue fatty acid profile. We suggest that the fatty acid composition from the heart tissue may be best suited to differentiate between juvenile chinook and coho, and it is believed that gill tissue is best to differentiate wild and hatchery fish.

Effects of organophosphorous compounds on fatty acid compositions and oxidative phosphorylation system in the brain of rats

Effects of organophosphorous compounds, O,O-dimethyl O-4-nitro-m-tolyl phosphorothioate (MEP), O-ethyl O-p-nitrophenyl phenylphosphonothioate (EPN) and O-(4-cyanophenyl) O-ethyl phenylphosphonothioate (CYP), on the fatty acid composition and the subsequent effects on the oxidative phosphorylation system in the brain of rats were studied. After 6 days exposure in pesticides, polyunsaturated fatty acids in brain free fatty acid fractions of CYP treated rats decreased, and the unsaturation index in them were lower than those in the control rats. The polyunsaturated/saturated ratio (P/S ratio) in brain total lipids of CYP treated rats was lower than that in the control. The fatty acid composition in the brain of EPN treated rats had the same inclination as that of CYP treated rats. In the P/S ratio and unsaturation index in serum no difference was observed between CYP treated rats and the control, therefore CYP could affect the fatty acid composition in the rat brain directly. Free fatty acid contents in the brain of EPN and CYP treated rats decreased after 6 days exposure. Activities of complex I of brains were significantly higher in the EPN and CYP exposed rats than in the control rats in spite of the fact that no difference of ATP productivity was observed between them. These results suggest that EPN and CYP may affect the free fatty acid content, especially the polyunsaturated fatty acid content and consequently the enzyme activities in the oxidative phosphorylation system in the brain. Those phenomena, however, were not observed after 28 days exposure in pesticide, therefore those effects may be a passing phenomenon in an acute stage.

Effects of dietary levels of 20:5n-3 and 22:6n-3 on tissue lipid composition in juvenile Atlantic salmon, Salmo salar , with emphasis on brain and eye

Four dietary groups of juvenile Atlantic salmon, Salmo salar L., each with three replicates, were fed diets with increasing levels of docosahexaenoic acid (22:6n‐3; DHA) and eicosapentaenoic acid (20:5n‐3; EPA). Fatty acid composition of brain and eye was determined at the start and approximately every 3 weeks during the experimental period, and fatty acid composition of liver and fillet was determined in fish from the final sampling. Lipid class composition of brain and eye, and fatty acid composition of these lipid classes was determined at the end of the experiment. There was no effect of increasing dietary DHA content on fatty acid composition, lipid class composition or DHA levels in the lipid classes in the juvenile Atlantic salmon brain. The increasing dietary EPA content, however, was reflected in both the total fatty acid composition and in the EPA content in neutral lipids, phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI). A minor effect of the increasing dietary DHA content was found in the lipid composition of the juvenile salmon eye. Both EPA and 18:2n‐6 levels in eye, however, clearly reflected the increasing and decreasing, respectively, dietary levels of these two fatty acids. The dietary EPA levels also affected the EPA levels in neutral lipids, PC, PE, PI and PS (phosphatidylserine) in the juvenile salmon eye. The results demonstrate that these dietary levels of DHA had no effect on brain lipid composition and only a minor effect on eye lipid composition. Furthermore, the dietary EPA levels significantly affected the lipid composition of both brain and eye. The fillet fatty acid composition reflected the dietary fatty acid composition, except for the DHA/EPA ratio, which was reversed in fillet compared with that in the diets. The liver fatty acid composition was also affected by the increasing dietary EPA and DHA levels.

During neuronal and glial cell development diet n−6 to n−3 fatty acid ratio alters the fatty acid composition of phosphatidylinositol and phosphatidylserine

Brain development was examined in the neonatal rat in response to feeding increased levels of 18:3 n−3, 20:4 n−6 or 22:6 n−3 at levels proposed for infant formula. Diets varying in n−6 to n−3 fatty acid ratio, with or without 20:4 n−6 and 22:6 n−3 alone or in combination, were fed to nursing dams at parturition and subsequently to weaned pups until six weeks of age. Neuronal and glial cells were isolated from the frontal, cerebellar and hippocampal brain regions of rat pups at birth, one, two, three and six weeks of age. Fatty acid analysis of inositol- and serine- phosphoglycerides indicated that small changes in dietary n−6 to n−3 fatty acid ratio significantly affect neuronal and glial cell membrane composition. Fatty acid composition of phosphatidylinositol and phosphatidylserine was distinct and exhibited change with age. Individual brain regions and cell types varied in amount and rate of 20:4 n−6 and 22:6 n−3 accretion. Alteration of brain fatty acid composition reflected the fatty acid composition of the diet fed. If analogous changes occur during human brain development, feeding infants 20:4 n−6 and 22:6 n−3 or a reduced 18:2 n−6 to 18:3 n−3 ratio may alter fatty acid profiles of brain cells.

Modifying the n-3 fatty acid content of the maternal diet to determine the requirements of the fetal and suckling rat.

During perinatal development, docosahexaenoic acid (22:6n-3) accumulates extensively in membrane phospholipids of the nervous system. To evaluate the n-3 fatty acid requirements of fetal and suckling rats, we investigated the accumulation of 22:6n-3 in the brain and liver of pup rats from birth to day 14 postpartum when their dams received increasing amounts of dietary 18:3n-3 (from 5 to 800 mg/100 g diet) during the pregnancy-lactation period. The fatty acid composition of brain and liver phospholipids of pups, as well as that of dam's milk, was determined. At birth, 22:6n-3 increased regularly to reach the highest level when the maternal diet contained 800 mg 18:3n-3/100 g. On days 7 and 14 postpartum, brain 22:6n-3 plateaued at a maternal dietary supply of 200 mg/100 g. Docosapentaenoic acid (22:5n-6) had the opposite temporal pattern. The unusually high concentration of eicosapentaenoic acid (20:5n-3) in liver and dam's milk observed at the highest 18:3n-3 intake suggests an excessive dietary supply of this fatty acid. All these data suggest that the n-3 fatty acid requirements of the pregnant rat are around 400 mg 18:3n-3 and those of the lactating rat at 200 mg (i.e., 0.9 and 0.45% of dietary energy, respectively). The values of 18:3n-3 and 22:6n-3 milk content which allowed brain 22:6n-3 to reach a plateau value in suckling pups were 1% of total fatty acids and 0.9% (colostrum) to 0.2% (mature milk), respectively. These levels are similar to those recommended for infant formulas.

Small Changes of Dietary (n-6) and (n-3)/Fatty Acid Content Ratio Alter Phosphatidylethanolamine and Phosphatidylcholine Fatty Acid Composition During Development of Neuronal and Glial Cells in Rats

It has been suggested that the fat composition of infant formula should provide arachidonic acid [20:4(n-6)] and docosahexaenoic acid [22:6(n-3)] or increased α-linolenic acid [18:3(n-3)] to optimize the (n-3) and (n-6) fatty acid content of brain during infant development. This experiment examined the effects of feeding increased levels of 18:3(n-3), 20:4(n-6) and 22:6(n-3) on brain development in neonatal rats. Diets varying in (n-6) and (n-3) fatty acid content with or without 20:4(n-6) or 22:6(n-3), at levels proposed for infant formula, were fed to nursing dams from parturition and subsequently to weaned pups until 6 wk of age. Neuronal and glial cells were isolated from the frontal region, cerebellum and hippocampus of the brain. Fatty acid analyses of ethanolamine- and choline-phosphoglycerides indicated that small changes in the dietary (n-6)/(n-3) ratio significantly altered neuronal and glial membrane fatty acid composition. Brain regions and cell types varied in amount and rate of 20:4(n-6) and 22:6(n-3) accretion. Fatty acid composition of individual phosphoglycerides was distinct and exhibited changes with age. Inclusion of both 20:4(n-6) and 22:6(n-3) in the diet resulted in alteration of brain fatty acid composition reflecting the fatty acid composition of the diet. If analogous developmental changes occur in human brain, then these results imply that addition of 20:4(n-6) and 22:6(n-3) or a reduced 18:2(n-6):18:3(n-3) ratio in infant formula may result in fatty acid profiles of neuronal and glial cells in formula-fed infants similar to those observed in breast-fed infants.

The effect of a formula supplemented with n-3 and n-6 long-chain polyunsaturated fatty acids on plasma phospholipid, liver microsomal, retinal, and brain fatty acid composition in neonatal piglets

We explore in this study the influence of dietary (n-6) and (n-3) long-chain polyunsaturated fatty acids (LC-PUFA) on tissues fatty acid composition in early life. Eight newborn piglets were fed sow milk for 20 days (group SM, n = 8); another sixteen newborn piglets were initially fed an adapted pig milk formula for 3 days and then assigned to receive for 17 days either the same adapted formula (group F, n = 8), or a formula supplemented with a phospholipid source of (n-6) and (n-3) LC-PUFA (group P, n = 8). Plasma phospholipid and liver microsomes 16:1(n-7) and 18:1(n-7) were increased in animals fed maternal milk compared with those fed formulas. Feeding the LC-PUFA formula produced significantly high plasma phospholipid and liver microsomal 22:6(n-3) than feeding the control formula. Similar plasma phospholipid and liver microsomal (n-6) and (n-3) LC-PUFA were found in animals fed SM and in those fed the control formula. The supplementation of LC-PUFA did not lead to any change in brain and retinal 20:4(n-6) and 22:6(n-3). No differences were found in brain and retinal 22:6(n-3) between animals fed the formula devoid of LC-PUFA and those fed sow milk. Retinal 22:4(n-6), 22:5(n-6) and 22:5(n-3) contents were significantly higher in maternal milk fed animals as compared with control formula fed animals. In brain, animals fed sow milk had higher (n-6) LC-PUFA than animals fed the supplemented formula. The results obtained in this study indicate that the supplementation of a phospholipid source of LC-PUFA influences plasma and liver microsomes 22:6(n-3). Under these experimental conditions, brain and retinal 22:6(n-3) were insensitive to the dietary supplementation.

Arachidonic Acid Offsets the Effects on Mouse Brain and Behavior of a Diet with a Low (n-6):(n-3) Ratio and Very High Levels of Docosahexaenoic Acid , ,

This study investigated the effects of varying dietary levels of very long-chain polyunsaturated fatty acids on growth, brain fatty acid composition and behavior in mice. Five groups of pregnant and lactating B6D2F1 mice were fed diets with either a very high (n-6):(n-3) ratio of 49 [(n-3) deficient)], a normal ratio of 4.0 or a low ratio of 0.32. The (n-6) fatty acids (FA) were provided either entirely as linoleic acid (LA) or as LA in combination with arachidonic acid (ARA), and the (n-6):(n-3) ratios were adjusted by partial replacement of the (n-6) FA with docosahexaenoic acid (DHA). Offspring were maintained on these diets after weaning. The diets with the low (n-6):(n-3) ratio had no effect on the birth weights of the pups, but after 15 d resulted in a significant 12% reduction in body weights. This effect persisted to adulthood and was apparent in both brain and body weights unless ARA was substituted partially for LA as the source of (n-6) FA. There were significant effects of diet on brain fatty acid composition. Increasing levels of DHA in the diet increased brain DHA and decreased ARA, and there was also retroconversion of DHA in EPA in the mice fed high levels of DHA. Addition of ARA to the diet increased brain ARA, and, at high levels only, decreased DHA. There were no effects of this wide variation in dietary (n-6):(n-3) ratio on the ability of the mice to learn the place of the hidden platform in the Morris water maze. However, in both the cued and the place learning, the mice fed the low (n-6):(n-3) diet swam more slowly, unless ARA substituted partially for LA as the source of (n-6) FA. There were no effects of diet on activity in the spatial open field. These findings show that the effects of a diet with a low (n-6):(n-3) ratio and (n-3) FA provided as DHA, can be overcome if LA is partially replaced by ARA as the source of (n-6) FA.

Fatty Acid Composition of Neural Tissues of Normally Pigmented and Unpigmented Juveniles of Japanese Flounder Using Rotifer and <i>Artemia</i> Enriched in n-3 HUFA

The lipid class and fatty acid composition of brain and eyes of unpigmented and normally pigment ed Japanese flounder (Paralichthys olivaceus), reared using live food, were analysed. The neural tissues of normally pigmented and unpigmented fish showed a similar lipid class composition. However nor mally pigmented individuals had a higher content of polyunsaturated fatty acids in the polar lipid frac tion, specially arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid. Considering the im portance of docosahexaenoic acid in the composition of neural tissues, as well as eicosapentaenoic, and arachidonic acids in eicosanoid production, a relationship among vision, neural transmission, and pig mentation is suggested.

Effect of dietary docosahexaenoic acid on brain composition and neural function in term infants.

There is a need to determine whether there is a dietary requirement for docosahexaenoic acid (DHA, 22:6n-3) by term infants to achieve their full developmental potential. Studies of brain fatty acid composition demonstrated that infants who were breast fed had greater levels of cerebral cortex DHA than did infants who were formula fed, suggesting that DHA in the cerebrum is dependent on a supply in the diet. Some physiological studies reported that electrophysiological and behavioral assessments of visual function were improved in breast-fed infants relative to those fed formula and that this was related to the length of breast feeding. While some randomized studies of DHA supplementation of infant formula to term infants demonstrated that the visual function of formula-fed infants could be improved to breast-fed levels by adding DHA to formula, others failed to demonstrate an effect. Variations in dietary treatments and methods of assessment make comparison of the studies difficult. Further work is necessary to rigorously establish if there are long-term benefits of dietary DHA to the term infant.

Is dietary docosahexaenoic acid essential for term infants?

There is a need to determine whether there is a dietary requirement for docosahexaenoic acid (DHA, 22:6 omega 3) by term infants to achieve their full developmental potential. Studies of brain fatty acid composition have demonstrated that infants who were breast fed have greater levels of cerebral cortex DHA than infants who were formula fed, suggesting that DHA in the cerebrum is dependent on a supply in the diet. Some physiological studies report that electrophysiological and behavioral assessments of visual function are improved in breast-fed infants relative to those fed formula, and that this is related to the level of DHA in their erythrocytes, whereas other studies demonstrate equivalent visual function between breast- and formula-fed infants. However, randomized studies of DHA supplementation of infant formula demonstrate that the visual function of formula-fed infants can be improved to breast-fed levels by adding DHA to formula. Further work is necessary to establish if there are long-term benefits of dietary DHA to the term infant.

The short-term effect of dietary fats on the brain fatty acid composition in rats.

The effects of dietary fats on brain fatty acid composition were studied in weanling rats. Three groups of rats were fed for six days a basal diet supplemented with a 10% (w/w) of fat as coconut, olive or sunflower oil. There were no differences in the saturated and monounsaturated fatty acid content among the different groups. The more abundant polyunsaturated fatty acids were arachidonic (20:4 n-6) and docosahexaenoic (22:6 n-3) acids. No effect of the diet on their amount in brain membranes has been found. We can conclude that the brain does not modify its fatty acid composition after a short-time administration of these lipids.

Fatty acid composition of brain, retina, and erythrocytes in breast- and formula-fed infants

Breast-fed infants score better on visual and developmental tests than do formula-fed infants and this has been related to higher concentrations of erythrocyte docosahexaenoic acid (DHA, 22:6 omega 3). This prompted an investigation into the relationship between brain, retina, and erythrocyte fatty acids and diet in infancy. Total lipids of erythrocytes, retina, and brain cortex from 35 term infants were analyzed by capillary gas chromatography. Breast-fed infants had a greater proportion of DHA in their erythrocytes and brain cortex relative to those fed formula (P < 0.005) but differences were not observed in retina. Cortex DHA increased in breast-fed (but not formula-fed) infants with age (r2 = 0.72, P < 0.01, n = 15), largely an effect of length of feeding (r2 = 0.62, P < 0.01, n = 35). There was an association between age at death and erythrocyte DHA with cortex DHA (r2 = 0.50, P < 0.01). In contrast, accretion of cortex arachidonic acid was dependent on age but not diet. The higher concentration of DHA in brains of breast-fed infants may explain the improved neurodevelopment reported in breast-fed compared with formula-fed infants.

Fatty acid composition in liver, serum and brain of rat inhalated with trichloroethylene

Temporal variations in chronic effects of inhalated 300 ppm trichloroethylene (TCE) on the fatty acid composition in rats were investigated to clarify influences of TCE on the fatty acid metabolism of serum, liver and brain, including synaptosome, myelin and mitochondria fractions on weeks 0, 4, 8, 12 after exposure and on week 4 after rehabilitation started following 12 weeks exposure. On week 4, rats exposed to TCE had significantly lighter body weight, lighter epididymal fat pads weight and heavier liver weight compared with controls. In liver and serum, increases in 16:0, 18:0, 18:1n-9, 20:2n-6, 20:3n-6 and 20:4n-6 and decreases in 18:2n-6, 18:3n-6, 18:3n-3, 20:5n-3, 22:5n-3 and 22:6n-3 were also observed. The differences between the exposure and the control groups in the fatty acid composition in liver and serum, except for 18:1n-9 and 18:2n-6, did not enhance from week 4 after TCE exposure. In brain, significant changes of fatty acid composition caused by TCE appeared as decreases in 18:2n-6 and 22:5n-3, and increases in 20:4n-6 and 22:4n-6 during the whole exposure period. Changes of fatty acid composition in brain occurred in the same manner as in serum and liver phospholipids, except that 18:1n-9 was elevated in mitochondria. Changes in brain were slighter and appeared later than those in liver and serum. TCE had a strong effect on the fatty acid composition of mitochondria in neural cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Fatty acid composition of brain and heart of rats fed various dietary oils

The present experiment was designed to comprehensively examine the effect of feeding several dietary oils differing in chain length and in position and number of double bonds of fatty acids on brain and heart fatty acid composition of rats. Therefore, 110 male Sprague-Dawley rats were initially fed a control diet with 10% coconut oil for 28 days; 10 groups of 10 rats each were then switched to semipurified test diets for another 20 days containing 5% or 10% olive oil, safflower oil, evening primrose oil, linseed oil or salmon oil for exchange of coconut oil. Dietary test oils did not have substantial effects on saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) in brain. The most striking changes provoked by dietary manipulation were observed on the n-6 and n-3 polyunsaturated fatty acids (PUFA). PUFA in rat brain were remarkable for its high levels of 20:4 n-6 and 22:6 n-3. n-6 PUFA, respectively 18:2 n-6 and 20:4 n-6 were slightly, but significantly elevated after feeding safflower and evening primrose oil; in contrast, linseed oil and salmon oil increased the proportion of long chain n-3 PUFA at the expense of n-6 PUFA in brain compared to the control group. The reduction in n-6 PUFA was mainly due to 22:5 n-6 and in the case of salmon oil diets also 20:4 n-6 and 22:4 n-6 were consistently lowered. In rat heart the amount of SFA was highest in control rats fed coconut oil. Both coconut oil and olive oil diets produced much higher levels of MUFA, especially 18:1 in the heart than did the other diets. As in brain, the most marked variations in heart were observed on n-6 and n-3 fatty acids. In contrast to brain lipids, rat heart was remarkable for its high proportions of 18:2 n-6 and 20:4 n-6. Both safflower oil and evening primrose oil markedly increased 18:2 n-6, 22:4 n-6 and 22:5 n-6 in rat hearts compared to the other diets. Conversely, the addition of linseed oil and salmon oil lowered 20:4 n-6, 22:4 n-6 and 22:5 n-6, whereas, salmon oil had a stronger effect on 20:4 n-6 than linseed oil. A rise in all cardiac n-3 PUFA was found, however, linseed oil mainly increased 18:3 n-3 and 22:5 n-3 and salmon oil mainly elevated 20:5 n-3 and 22:6 n-3. This inverse relationship between the n-6 and n-3 PUFA suggests a competition between these fatty acids for incorporation into brain and heart lipids.

Utilization of Uniformly Labeled 13C‐Polyunsaturated Fatty Acids in the Synthesis of Long‐Chain Fatty Acids and Cholesterol Accumulating in the Neonatal Rat Brain

Polyunsaturated fatty acids are needed for normal neonatal brain development, but the degree of conversion of the 18-carbon polyunsaturated fatty acid precursors consumed in the diet to their respective 20- and 22-carbon polyunsaturates accumulating in the brain is not well known. In the present study, in vivo 13C nuclear magnetic resonance spectroscopy was used to monitor noninvasively the brain uptake and metabolism of a mixture of uniformly 13C-enriched 16- and 18-carbon polyunsaturated fatty acid methyl esters injected intragastrically into neonatal rats. In vivo NMR spectra of the rat brain at postnatal days 10 and 17 had larger fatty acid signals than in uninjected controls, but changes in levels of individual fatty acids could not be distinguished. One day after injection of the U-13C-polyunsaturated fatty acid mixture, 13C enrichment (measured by isotope ratio mass spectrometry) was similar in brain phospholipids, free fatty acids, free cholesterol, and brain aqueous extract; 13C enrichment remained high in the phospholipids and cholesterol for 15 days. 13C enrichment was similar in the main fatty acids of the brain within 1 day of injection but 15 days later had declined in all except arachidonic acid while continuing to increase in docosahexaenoic acid. These changes in 13C enrichment in brain fatty acids paralleled the developmental changes in brain fatty acid composition. We conclude that, in the neonatal rat brain, dietary 16- and 18-carbon polyunsaturates are not only elongated and desaturated but are also utilized for de novo synthesis of long-chain saturated and monounsaturated fatty acids and cholesterol.

The effects of dietary fatty acid composition combined with environmental enrichment on brain and behavior in mice.

In this study we investigated the effects of dietary fatty acid (FA) composition combined with postweaning environmental enrichment on brain fatty acid composition and behavior in mice. There were three dietary conditions: a saturated fat group deficient in essential fatty acids, a group deficient in n-3 fatty acids only, and a control group containing both n-3 and n-6 fatty acids in a ratio of 0.27. Animals were fed these diets during pregnancy and lactation and after weaning. Brain fatty acid composition was determined on days 1, 9, 17 and 25 after birth and in adult animals at 3 months. At weaning two females from each litter were assigned randomly to either an enriched or standard environmental condition. After six weeks in these environments they were tested in the Morris water maze and open field. Adult percentages of 22:6n-3 were present in the brain within the first week after birth. These values were reduced by 50% in the n-3 deficient diet and by 80% in the saturated fat diet; adult animals on the saturated fat diet were also severely retarded in growth. Animals fed the saturated fat diet were initially slightly slower in locating the hidden platform in the Morris maze relative to the control group, but this was not apparent in the reversal learning phase; a cued learning task using a visible platform indicated that these effects did not appear to be related to differences in motor or motivational capacities. The n-3 deficient group did not differ from either the saturated fat group or the controls. All dietary groups showed beneficial effects of environmental enrichment in decreasing their latency to locate the hidden platform, and these effects appeared to be partially independent of the increased swimming speed of the enriched animals. Enriched animals in all groups showed less rearing activity in the open field and spent more time stationary; the animals fed saturated fat reared less and travelled shorter distances more slowly. In all cases the effects of diet and environment were additive, thereby providing little support for the hypothesis that dietary fatty acid composition would affect the animals' capacity to benefit from the functional effects of environmental enrichment.

Developmental sensitivity of the brain to dietary n-3 fatty acids.

The developing brain readily incorporates dietary fatty acids, while the adult brain is refractory to changes in fatty acid composition. In order to localize the time in development when this transition occurs, chicks were fed large amounts of n-3 fatty acids from fish oil beginning at 0, 1, 2, or 3 weeks of age. Control chicks were fed a soybean oil-based diet, as were the experimental chicks before introduction of the fish oil diet. Resistance to diet-induced increases in brain n-3 fatty acid levels began at 2 weeks of age, and was substantial at 3 weeks. Docosahexaenoic acid was particularly resistant to change as the brain matured, increasing by 38% when fish oil was fed from time of hatching, but only by 8% when fish oil feeding was delayed until 3 weeks of age. Dietary fish oil caused a compensatory decrease in brain n-6 fatty acids, and this decrease occurred even at later time points when the rise in brain n-3 fatty acids was much less prominent. The liver incorporated high levels of n-3 fatty acids at all ages, and compensated by decreasing monounsaturated fatty acids at early time points and n-6 fatty acids at later time points. These results show that resistance to changes in brain fatty acid composition is evident at a relatively early age, before brain development is complete.

Alteration of brain and liver microsomal polyunsaturated fatty acids following dietary vitamin E deficiency

The effects of dietary vitamin E deficiency on fatty acid composition of brain and liver microsomes were studied in rats fed a vitamin E-deficient diet for 9 weeks. In brain microsomes, vitamin E deficiency resulted in a significant decrease in palmitic acid and total saturated fatty acids. Cervonic acid was increased. In contrast, no marked changes were observed in the levels of (n-6) polyunsaturated fatty acid (PUFA). In liver microsomes, vitamin E deficiency resulted in significant alterations in fatty acid composition: higher amounts of stearic acid and total saturated fatty acids, lower amounts of mono-unsaturated fatty acids, linoleic and dihomo gamma linoleic acids. In contrast, arachidonic acid was not altered. The overall decrease in the amounts of (n-6) PUFA was compensated by an increase in the level of (n-3) PUFA. It is concluded that vitamin E may alter the enzymatic activities of chain elongation-desaturation and the relationship between vitamin E and PUFA in brain and liver microsomes.