Effect of season on the fatty acid composition and free amino acid content of the sardine Sardinops melanostictus

The purpose of this study was to clarify the seasonal variation of fatty acid composition and free amino acid content in the Japanese sardine (Sardinops melanostictus) from the sea of Hyuga-Nada, and the relationship between the fatty acid composition of this sardine and that of plankton in the area. The lipid content of sardines at the sea of Hyuga-Nada was low in February (1.8%) and high (7.2%) from July to September. The major fatty acids in the total lipids from sardine were myristic acid (14:0), palmitic acid (16:0), stearic acid (18:0), palmitoleic acid (16:1 n-7), oleic acid (18:1 n-9), eicosapentaenoic acid (20:5 n-3), and docosahexaenoic acid (22:6 n-3). The characteristics of the fatty acids isolated from sardines in July were similar to those from plankton in the same season. This reflects the deposition of plankton fatty acids in sardine depot fat. The season of high free histidine content in the ordinary meat corresponded with that of high lipid content. These results suggested that both the fatty acid composition of sardines and the high concentrations of certain amino acids in free form are influenced by the intake and seasonal variation of composition of plankton.     

Interactions of saturated, n-6 and n-3 polyunsaturated fatty acids to modulate arachidonic acid metabolism

Anti-thrombotic effects of omega-3 (n-3) fatty acids are believed to be due to their ability to reduce arachidonic acid levels. Therefore, weanling rats were fed n-3 acids in the form of linseed oil (18:3n-3) or fish oil (containing 20:5n-3 and 22:6n-3) in diets containing high levels of either saturated fatty acids (hydrogenated beef tallow) or high levels of linoleic acid (safflower oil) for 4 weeks. The effect of diet on the rate-limiting enzyme of arachidonic acid biosynthesis (delta 6-desaturase) and on the lipid composition of hepatic microsomal membrane was determined. Both linseed oil- or fish oil-containing diets inhibited conversion of linoleic acid to gamma-linolenic acid. Inhibition was greater with fish oil than with linseed oil, only when fed with saturated fat. delta 6-Desaturase activity was not affected when n-3 fatty acids were fed with high levels of n-6 fatty acids. Arachidonic acid content of serum lipids and hepatic microsomal phospholipids was lower when n-3 fatty acids were fed in combination with beef tallow but not when fed with safflower oil. Similarly, n-3 fatty acids (18:3n-3, 20:5n-3, 22:5n-3, and 22:6n-3) accumulated to a greater extent when n-3 fatty acids were fed with beef tallow than with safflower oil. These observations indicate that the efficacy of n-3 fatty acids in reducing arachidonic acid level is dependent on the linoleic acid to saturated fatty acid ratio of the diet consumed.     

Effect of n-3 and n-6 fatty acids on hepatic microsomal lipid metabolism: a time course study

The present study examines the time dependent effects of n-6 and n-3 polyunsaturated fatty acids on liver microsomal lipid metabolism in FVB mice fed a diet supplemented with a mixture of free fatty acids (mainly 18:3n-6 and 20:5n-3) at 25 mg/g diet. Significant changes in the fatty acid composition of total liver and microsomal lipids were observed after 7 days on the diets. Thereafter, some animals remained on the same diet while others were fed a diet supplemented with hydrogenated coconut oil (HCO). With the exception of 20:5n-3 which showed a slower recovery, establishment of the HCO pattern was rapid indicating that the diet-induced changes could be easily reversed. The unsaturation index, the cholesterol/phospholipid ratio and the microviscosity of the microsomal membranes were not affected by these dietary manipulations. Unsaturated fatty acid supplementation reduced the activity of ⁹ desaturase by 50%. Feeding the HCO diet to mice previously fed the EPA/GLA diet led to a progressive increase in ⁹ desaturase activity, reaching 80% of the day zero values after 14 days. The monoene content of hepatic total lipids reflected, in most cases, the changes in enzyme activity. This study shows that a low dose of a n-3 and n-6 free fatty acid mixture increases the quantities of members of the n-3 family, without loss of n-6 fatty acids in microsomal membranes and modifies the activity of ⁹ desaturase without altering the microsome physicochemical parameters.     

The opposing effects of n-3 and n-6 fatty acids

Polyunsaturated fatty acids (PUFAs) can be classified in n-3 fatty acids and n-6 fatty acids, and in westernized diet the predominant dietary PUFAs are n-6 fatty acids. Both types of fatty acids are precursors of signaling molecules with opposing effects, that modulate membrane microdomain composition, receptor signaling and gene expression. The predominant n-6 fatty acid is arachidonic acid, which is converted to prostaglandins, leukotrienes and other lipoxygenase or cyclooxygenase products. These products are important regulators of cellular functions with inflammatory, atherogenic and prothrombotic effects. Typical n-3 fatty acids are docosahexaenoic acid and eicosapentaenoic acid, which are competitive substrates for the enzymes and products of arachidonic acid metabolism. Docosahexaenoic acid- and eicosapentaenoic acid-derived eicosanoids antagonize the pro-inflammatory effects of n-6 fatty acids. n-3 and n-6 fatty acids are ligands/modulators for the nuclear receptors NFkappaB, PPAR and SREBP-1c, which control various genes of inflammatory signaling and lipid metabolism. n-3 Fatty acids down-regulate inflammatory genes and lipid synthesis, and stimulate fatty acid degradation. In addition, the n-3/n-6 PUFA content of cell and organelle membranes, as well as membrane microdomains strongly influences membrane function and numerous cellular processes such as cell death and survival.     

Food availability and reproduction affects lipid and fatty acid composition of the brown mussel, Perna perna, raised in suspension culture

We examined the influence of the reproductive cycle and environmental factors on variations of the condition index (CI), tissue dry mass, shell size, total lipid content, and relative percent of fatty acids in the mussel, Perna perna. Spat or juveniles were reared to commercial size (70 mm) in suspension culture in the Golfo de Cariaco, Venezuela between May and October 2004. The dry mass of soft tissues and shell, a visual assessment of gonadal status and the organism lipid profile were established every fortnight. In parallel, we measured the environmental conditions, following chlorophyll a, salinity, temperature and seston levels. After an initial decrease, the CI rose and remained high until August after which it decreased continuously until October. Total lipid values also decreased initially, after which they showed two periods of rapid recuperation and depletion, the first between May and August and the second between August and October. Similar tendencies were noted in the fatty acids, C18:3n-3, C18:4n-3 and C22:6n-3. Correlation analysis found no significant relationships between environmental parameters and the variations in total lipids. However, significant correlations were noted between fatty acids and specific environmental parameters. In particular, temperature was inversely correlated with C14:0, C16:1n-7, C18:0, C18:1n-9 and 20:5n-3. Chlorophyll a was positively correlated with C14:0, C16:1n-7, C18:1n-7, C18:4n-3 and 20:4n-6. On the other hand, gametogenesis had an effect on C14:0, C16:1n-7, C18:1n-9 and C18:1n-7, while spawned and gonadal regression states had an effect on fatty acid 20:4n-6. Temperature and chlorophyll a levels strongly influenced the proportion of mussels spawning, suggesting that their influence upon lipid composition may be secondary to their impact upon reproduction. Despite the thermal stability of this tropical system, the lipid composition of mussels changed markedly during the study, reflecting the central role of diet and reproductive investment upon lipid composition.     

Effects of cold water swimming on blood rheological properties and composition of fatty acids in erythrocyte membranes of untrained older rats

This is the first report on the effects of a single bout of swimming to exhaustion in cold water on rat erythrocyte deformability, aggregation and fatty acid composition in erythrocyte membranes. The results indicate that there was a significant decrease in body temperature of experimental rats swimming in water at 4 degrees C and 25 degrees C when compared to the control. Erythrocyte aggregation indices did not change after swimming in water at 4 degrees C whereas erythrocyte deformability increased at shear stress 1,13 [Pa] and 15,96 [Pa]. Physical effort performed in water at 4 degrees C when compared to the control group resulted in an increase in monounsaturated and polyunsaturated n-3 fatty acid content in erythrocyte membranes that influenced the increase in their fluidity and permeability even though that of polyunsaturated n-6 fatty acids decreased. Physical effort performed in 25 degrees C water resulted in an increase in saturated fatty acid content and a decrease in all polyunsaturated fatty acids and polyunsaturated n-6 fatty acids when compared to the control group. Swimming of untrained old rats in cold water affected rheological properties oferythrocytes in a negligible way while changes in the fatty acid composition of erythrocyte membranes were more pronounced.     

Fatty acids composition in erythrocyte membranes of athletes after one and after a series of whole body cryostimulation sessions

Whole body cryotherapy (WBC) is a treatment often used by athletes as part of biological renewal. Despite the large interest in this form therapy there is still a lack of information on the effects of WBC on the concentration of fatty acids in erythrocyte membranes. Our study aimed at comparing the fatty acids (FA) composition of erythrocyte membranes of athletes after one session and after a series of sessions of whole body cryostimulation. In our study small changes in the level of total cholesterol (decrease) were observed 24 h after a single session. After the twelfth session of whole body cryostimulation, the level of saturated fatty acids (SFA), mainly palmitic acid (C16:0) and n-3 fatty acid eicosapentaenoic (EPA, C20:5n-3) increased almost two-times fold in the red blood cell membranes. The level of n-6 polyunsaturated fatty acids (PUFA n-6), mainly gamma-linolenic acid (C18:3n-6) as well as trans fatty acids (elaidic acid) decreased in the erythrocyte membranes from men after a series of session in a cryochamber, when compared to the control sample. The n-3/n-6 FA ratio in the erythrocyte membranes was higher after twelfth session in a cryochamber in comparison to the control sample.The data obtained during our study will be important for further research regarding the biochemistry of lipids in men after sessions of whole body cryostimulation.     

Seasonal dynamics of fatty acid composition in female northern pike (Esox lucius L.)

Seasonal changes in the fatty acid composition of neutral and polar lipids were measured in the ovary, liver, white muscle, and adipopancreatic tissue of northern pike. The role of environmental and physiological factors underlying these changes was evaluated. From late summer (August–September) to winter (January–March), the weight percentage of n-3 polyunsaturated fatty acids (especially 22:6n3) declined significantly in the neutral lipids of all somatic tissues examined. However, large quantities of n-3 polyunsaturated fatty acids accumulated in the recrude cing ovaries during fall and the weight percentage of n-3 polyunsaturated fatty acids in ovary polar lipids also increased significantly. Additionally, the n-3 polyunsaturated fatty acid content of somatic polar lipids increased significantly during fall due to increases in the total polar lipid content of the somatic tissues. This suggests that during fall n-3 polyunsaturated fatty acid are diverted away from somatic neutral lipids and thereby conserved for use in ovary construction and for incorporation into tissue polar lipids. The percentage of n-3 polyunsaturated fatty acid in ovary neutral lipids also declined during fall and early winter, perhaps as an adaptation to conserve these fatty acids for storage in oocyte polar lipids and later incorporation into cellular membranes of the developing embryo. Reductions in the n-3 polyunsaturated fatty acids content of somatic and ovarian neutral lipids during fall were compensated for specifically by increases in the percentage of monounsaturated fatty acids rather than saturated fatty acids. This suggests that the ratio of saturated to unsaturated fatty acids in pike neutral lipid, is regulated physiologically, and hence may influence the physiological functioning of these lipids. During fall and early winter the percentage of saturated fatty acids declined significantly in the polar lipids of all tissues examined. This change was consistent with the known effects of cold acclimation on the fatty acid composition of cellular membranes. As the ovaries were recrudescing from September to January, liver polar lipids exhibited significant decreases in the percentage of total polyunsaturated fatty acids and n-3 polyunsaturated fatty acids and increases in monounsaturated fatty acids, and acquired a fatty acid composition very similar to that of ovary polar lipids. Therefore, seasonal changes in the percentage of polyunsaturated and monounsaturated fatty acids in liver polar lipids probably reflect the liver's role in vitellogenesis rather than the effects of temperature on membrane fatty acid composition. At all times of year, the fatty acid compositions of white muscle and adipopancreatic tissue neutral lipids were very similar, which may indicate a close metabolic relationship between these lipid compartments.Abbreviations AP adipopancreatic - BHT butylated hydroxytoluene - CI confidence interval - EFA essential fatty acids - MUFA monounsaturated fatty acids - NL neutral lipids - PL polar lipids - PUFA polyunsaturated fatty acids - SFA saturated fatty acids     

Changes in the Fatty Acid Composition of Hepatopancreas of the Mollusk Mytilus trossulus Fed on Microalgae

The influence of diet on the fatty acid composition of the hepatopancreas of Mytilus trossulus was studied. Three groups of mollusks were fed monocultures of the microalgae Phaeodactylum tricornutum, Chaetoceros muelleri (Bacillariophyceae), and Nannochloropsis sp. (Eustigmatophyceae) for 10 days. After 10 days, the proportion of polyunsaturated fatty acids, mainly eicosapentaenoic and docosahexaenoic, increased in the total lipids of the hepatopancreas in all mollusk groups. The content of saturated fatty acids in the mussel tissues decreased and was not dependent on the amount in the algal diet. Toward the end of the experiment, the fatty acid composition of the hepatopancreas of mussels was similar irrespective of the fatty acid composition of their food. The fatty acid analysis of M. trossulus feces suggests a selective assimilation by mussels of predominantly the n-3 polyunsaturated fatty acids. The role of fatty acid metabolism in M. trossulus is discussed.     

Ice-Encasement Injury to Microsomal Membranes Isolated from Winter Wheat Crowns : II. Changes in Membrane Lipids during Ice Encasement

The physical properties and chemical composition of microsomal membranes were examined during a 7 day period of ice encasement in crown tissue of winter wheat (Triticum aestivum L. cv Norstar). Membrane damage, detected as an increase in microviscosity and electrolyte leakage, began between 1 and 3 days of icing, and was associated with a reduction in the recovery of microsomal membranes from stressed tissue, an increase in the microsomal free fatty acid:total fatty acid ratio, and a decrease in the phospholipid:total fatty acid ratio. These trends were amplified between 3 and 7 days of ice encasement. Examination of the free and total fatty acid fractions showed there was a slight, but not statistically significant (P = 0.05) reduction in the degree of unsaturation of the total fatty acid fraction. The composition of the free and total fatty acid fractions were very similar during ice encasement. Furthermore, analysis of phospholipid classes revealed no significant change in the relative amounts of phosphatidylcholine, phosphatidylethanolamine, phosphatidic acid, or lysophospholipids in microsomal membranes during icing. Membrane injury during ice encasement apparently involves hydrolysis of the ester bond between glycerol and the acyl groups of the phospholipid resulting in loss of the phosphate-containing polar head group and a concomitant accumulation of free fatty acids in the bilayer.     

Phosphatidylethanolamine methyltransferase: evidence for influence of diet fat on selectivity of substrate for methylation in rat brain synaptic plasma membranes

Male weanling rats were fed diets containing 20% (w/w) fat differing in fatty acid composition for 24 days. Synaptic plasma membranes were isolated from the brain and the fatty acid composition of phosphatidylethanolamine and phosphatidylcholine was determined. In vitro assays of phosphatidylethanolamine methyl-transferase activity were performed on fresh membrane samples to assess effect of dietary fat on the rate of phosphatidylethanolamine methylation for phosphatidylcholine synthesis via the phosphatidylethanolamine methyltransferase pathway. Dietary level of n-6 and ratio of n-6 to n-3 fatty acids influenced membrane phospholipid fatty acid composition and activity of the lipid-dependent phosphatidylethanolamine methyltransferase pathway. Rats fed a diet rich in n-6 fatty acids produced a high ratio of n-6/n-3 fatty acids in synaptosomal membrane phosphatidylethanolamine, and elevated rates of methylation of phosphatidylethanolamine to phosphatidylcholine by phosphatidylethanolamine methyltransferases, suggesting that the pathway exhibits substrate selectivity for individual species of phosphatidylethanolamine containing long-chain homologues of dietary n-6 and n-3 fatty acids (20:4(n-6), 22:4(n-6), 22:5(n-6) and 22:6(n-3). It may be concluded that diet alters the membrane content of n-6, n-3 and monounsaturated fatty acids, and that change in phosphatidylethanolamine species available for methylation to phosphatidylcholine alters the rate of product synthesis in vivo by the phosphatidylethanolamine methyltransferase pathway.     

The calcium uptake of the rat heart sarcoplasmic reticulum is altered by dietary lipid

Summary Small amounts of dietary n-3 fatty acids can have dramatic physiological effects, including the reduction of plasma triglycerides and an elevation of cellular eicosapentanoic (EPA) and docosahexanoic acids (DHA) at the expense of arachidonic acid (AA). We investigated the effects of alterations in the fatty acid compositions of cardiac sarcoplasmic reticulum (CSR) produced by dietary manipulation on the calcium pump protein that is required for energy dependent calcium transport. CSR was isolated from rats fed menhaden oil, which is rich in n-3 fatty acids, and from control animals that were given corn oil. Relative to control membranes, those isolated from rats fed menhaden oil, had a lower content of saturated phospholipids, an increased DHA/AA ratio, and an increased ratio of n-3 to n-6 fatty acids. These changes were associated with a 30% decrease in oxalate-facilitated, ATP-dependent calcium uptake and concomitant decreased Ca-ATPase activity in the membranes from the animals fed menhaden oil. In contrast, there was no alteration in active pump sites as measured by phosphoenzyme formation. Thus, the CSR Ca-ATPase function can be altered by dietary interventions that change the composition, and possibly structure, of the phospholipid membranes thereby affecting enzyme turnover.     

Gamma-linolenic acid dietary supplementation can reverse the aging influence on rat liver microsome delta 6-desaturase activity.

We have recently demonstrated that in rats the process of delta 6-desaturation of linoleic and alpha-linolenic acids slows with aging. One method of counteracting the effect of slowed desaturation of linoleic acid would be to provide the 6-desaturated metabolite, gamma-linolenic acid (18:3(n-6) GLA) directly. We have here investigated the 6-desaturation of both linoleic and alpha-linolenic acids in liver microsomes of young and old rats given GLA in the form of evening primrose oil (EPO) (B diet) in comparison to animals given soy bean oil alone (A diet), monitoring also the fatty acid composition of liver microsomes and relating this to the microviscosity of the membranes. In young rats the different experimental diets did not produce any difference in delta 6-desaturase (D6D) activity on either substrate suggesting that, when D6D activity is at or near its peak, the variations in diet tested are unable to influence it. In the old animals the rate of 6-desaturation of linoleic and particularly of alpha-linolenic acid was significantly greater in the B diet fed animals than in the A diet fed. The effects of the diets on the fatty acid composition of liver microsomes were consistent with the findings with regard to 6-desaturation. Administration of GLA partially corrected the abnormalities of n-6 essential fatty acid (EFA) metabolism by raising the concentration of 20:4(n-6) and other 6-desaturated EFAs. Furthermore, the GLA rich diet also increased the levels of dihomo-gamma-linolenic acid and of 6-desaturated n-3 EFAs in the liver microsomes. The microviscosity of microsomal membranes as indicated by DPH polarization was correlated with the unsaturation index of the same membranes. There was a very strong correlation between the two. In both young and old rats the B diet reduced the microviscosity and increased the unsaturation index. However, the effect was much greater in the old animals.     

Effect of chronic alcohol consumption on rat brain microsome lipid composition, membrane fluidity and Na+-K+-ATPase activity

The present study reports differences in phospholipid classes, fatty acids of individual phospholipids, and changes in membrane fluidity and Na+-K+-ATPase activity in brain microsomes of rats maintained on an alcohol diet for 35 days compared to sex, age and weight-matched control rats maintained on a calorically-equivalent, non-alcohol diet. Although no difference in Na+-K+-ATPase activity was found in microsomes from alcohol vs control rats when measured in the absence of added alcohol, the presence of low concentrations of ethanol (less than 100 mM) stimulated, while high concentrations (greater than 100 mM) inhibited enzyme activity. The stimulation was differentially expressed in that the microsomal enzyme from alcohol rats was stimulated to a lesser extent than the enzyme from control rats. However, the inhibiting effect of high concentrations of alcohol was similar in microsomes from both alcohol and control rats. Also in membranes from alcohol rats, there was a lower quantity of phosphatidylethanolamine (PE) and higher quantities of phosphatidylserine (PS) and phosphatidylinositol (PI) compared to membranes from control rats. The major change in fatty acid composition was a reduction in the level of polyunsaturated fatty acids, which was particularly evident in PI and PS. The linoleic acid: arachidonic acid ratio (18:2/20:4) and the saturation:unsaturation ratio were also increased in PI and PS in membranes from alcohol animals. However, the ratio of n-6/n-3 fatty acids remained the same or was reduced in membranes from alcoholic animals. Although no difference in the inherent "fluidity" of membranes from alcohol vs control rats could be demonstrated by electron paramagnetic resonance, molecular tolerance to ethanol was demonstrated in the membranes from alcohol rats by the resistance to the disordering effects of added ethanol.     

Interactive effects of dietary (n-3) polyunsaturated fatty acids and chronic ethanol intoxication on synaptic membrane lipid composition and fluidity in rats.

The influence of dietary polyunsaturated fatty acids on fatty acid composition, cholesterol and phospholipid content as well as 'fluidity' (assessed by fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) probes) of brain synaptic plasma membranes (SPM) and their interactions with chronic ethanol effects were studied in rats fed for two generations with diets either devoid of (n-3) fatty acids (sunflower oil diet), rich in alpha-linolenic acid (soya oil diet) or in long chain (n-3) fatty acids (sunflower + cod liver oil diet). Results were compared with rats fed standard lab chow. Sunflower oil led to an increase in the (n-6)/(n-3) ratio in the membranes with an increase of the 'fluidity' at membrane apolar level; sunflower + cod liver oil decreased the (n-6)/(n-3) ratio without affecting membrane 'fluidity' while no difference was seen between the SPM of rats fed soya oil and standard diet. After 3 weeks alcohol intoxication in rat fed the standard diet: oleic alpha-linoleic acids and cholesterol levels were increased, arachidonic acid and the double bond index/saturated fatty acids were decreased and there was a decrease of 'fluidity' in the lipid core of the SPM. Soya oil almost totally abolished these usually observed changes in the SPM fatty acids composition but increased oleic acid and cholesterol without any change in fluidity. Sunflower oil led to the same general alterations of fatty acid as seen with standard diet but to a greater extent, with decrease of the 'fluidity" at the apolar level and in the region probed by TMA-DPH. When sunflower oil was supplemented with cod liver oil, oleic and alpha-linoleic acids were increased while the 'fluidity' of the apolar core of SPM was decreased. So, the small changes in fatty acid pattern seem able to modulate neural properties i.e. the responses to a neurotoxic like ethanol. A structurally specific role of PUFA is demonstrated by the pernicious effects of the alpha-linolenic acid deficient diet which are not totally prevented by the supply of long chain (n-3) PUFA.     

Alterations of Na,K-ATPase Isoenzymes in the Rat Diabetic Neuropathy: Protective Effect of Dietary Supplementation with n-3 Fatty Acids

Abstract: Diabetic neuropathy is a degenerative complication of diabetes accompanied by an alteration of nerve conduction velocity (NCV) and Na,K-ATPase activity. The present study in rats was designed first to measure diabetes-induced abnormalities in Na,K-ATPase activity, isoenzyme expression, fatty acid content in sciatic nerve membranes, and NCV and second to assess the preventive ability of a fish oil-rich diet (rich in n-3 fatty acids) on these abnormalities. Diabetes was induced by intravenous streptozotocin injection. Diabetic animals (D) and nondiabetic control animals (C) were fed the standard rat chow either without supplementation or supplemented with either fish oil (DM, CM) or olive oil (DO, CO) at a daily dose of 0.5 g/kg by gavage during 8 weeks. Analysis of the fatty acid composition of purified sciatic nerve membranes from diabetic animals showed a decreased incorporation of C16:1(n-7) fatty acids and arachidonic acids. Fish oil supplementation changed the fatty acid content of sciatic nerve membranes, decreasing C18:2(n-6) fatty acids and preventing the decreases of arachidonic acids and C18:1(n-9) fatty acids. Protein expression of Na,K-ATPase α subunits, Na,K-ATPase activity, and ouabain affinity were assayed in purified sciatic nerve membranes from CO, DO, and DM. Na,K-ATPase activity was significantly lower in sciatic nerve membranes of diabetic rats and significantly restored in diabetic animals that received fish oil supplementation. Diabetes induced a specific decrease of α1- and α3-isoform activity and protein expression in sciatic nerve membranes. Fish oil supplementation restored partial activity and expression to varying degrees depending on the isoenzyme. These effects were associated with a significant beneficial effect on NCV. This study indicates that fish oil has beneficial effects on diabetes-induced alterations in sciatic nerve Na,K-ATPase activity and function.     

Polyunsaturated fatty acid supplements modulate mast cell membrane microdomain composition

In the present study, the lipid raft composition of a canine mastocytoma cell line (C2) was analyzed. Lipid rafts were well separated from non-raft plasma membranes using a detergent-free isolation technique. To study the influence of n-3 and n-6 polyunsaturated fatty acids (PUFA) on raft fatty acid composition in comparison to non-raft cell membrane, C2 were supplemented with one of the following: α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, linoleic acid or arachidonic acid. Enrichment of the culture medium with a specific PUFA resulted in an increase in the content of this fatty acid both in rafts and non-raft membranes. Contents of cholesterol and protein were found not to be affected by the changes in the fatty acid profiles. In conclusion, our data provide strong evidence that PUFA modulate lipid composition and physiological properties of membrane micro domains of mast cells which in turn may have effects on mast cell function.     

Response of rat heart membranes and associated ion-transporting ATPases to dietary lipid

The effects of different dietary fat intake on the lipid composition and enzyme behaviour of sarcolemmal (Na+ + K+)ATPase and sarcoplasmic reticulum Ca2+-ATPase from rat heart were investigated. Rat diets were supplemented with either sunflower seed oil (unsatd./satd. 5.6) or sheep kidney fat (unsatd./satd. 0.8). Significant changes in the phospholipid fatty acid composition were observed in both membranes after 9 weeks dietary lipid treatment. For both membranes, the total saturated/unsaturated fatty acid levels were unaffected by the dietary lipid treatment, however the proportions of the major unsaturated fatty acids were altered. Animals fed the sunflower seed oil diet exhibited an increase in n-6 fatty acids, including linoleic (18:2(n-6] and arachidonic (20:4(n-6] while the sheep kidney fat dietary rats were higher in n-3 fatty acids, principally docosahexaenoic (22:6), with the net result being a higher n-6/n-3 ratio in the sunflower seed oil group compared to sheep kidney fat dietary animals. Fluorescence polarization indicated that the fluidity of sarcoplasmic reticular membrane was greater than that of sarcolemmal membrane, with a dietary lipid-induced decrease in fluidity being observed in the sarcoplasmic reticular membrane from sheep kidney fat dietary animals. Despite these significant changes in membrane composition and physical properties, neither the specific activity nor the temperature-activity relationship (Arrhenius profile) of the associated ATPases were altered. These results suggest that with regard to the parameters measured in this study, the two ion-transporting ATPases are not modulated by changes which occur in the membrane lipid composition as a result of the diet.     

n-3 and n-6 polyunsaturated fatty acids have different effects on acyl-CoA:cholesterol acyltransferase in J774 macrophages.

The effects of incubating J774 mouse macrophages with different fatty acids on cholesterol esterification were investigated. In cells incubated with n-3 polyunsaturated fatty acids, the rate of cholesterol esterification was significantly reduced compared with cells incubated with n-6 polyunsaturated fatty acids or with oleic acid. This change in cholesterol esterification appears to be the result of reductions in the activity of acyl-CoA:cholesterol acyltransferase (ACAT) in the endoplasmic reticulum of the macrophages incubated with the n-3 polyunsaturated fatty acids. No differences in microsomal cholesterol were observed among cells incubated with different fatty acids. However, cellular cholesterol levels were lower in cells incubated with n-3 polyunsaturated fatty acids. In microsomes from cells incubated with n-3 polyunsaturated fatty acids, both the Km and the Vmax of ACAT were lower than in microsomes from cells incubated with n-6 fatty acids or oleic acid. These findings may explain some of the reduction in atherosclerotic lesions that are observed with dietary fish oils that contain high levels of n-3 polyunsaturated fatty acids.     

Copper deficiency-induced changes in the fatty acid composition of mitochondrial and microsomal membranes of rat liver

The effects of copper deficiency on the fatty acid composition of mitochondrial and microsomal phospholipids in rat liver were studied. Copper deficiency was induced by a milk powder diet. To evaluate the effect of the milk diet on the fatty acid pattern of mitochondrial and microsomal phospholipids, one group of rats was fed Cusupplemented powdered milk. A decrease in the relative proportion of linoleic acid and an increase in the level of oleic and docosahexaenoic acids in membrane phospholipids were found in this group. However, no changes in the fatty acid pattern characteristic of essential fatty acid deficiency were observed. Dietary copper deficiency produced a significant decrease in the relative amounts of linoleic and arachidonic acids, as well as an increase in the docosahexaenoic acid content in both mitochondrial and microsomal membranes compared to the nondeficient controls. The disproportionate quantities of polyunsaturated fatty acids are discussed with a view to the disturbances of membrane function in copper deficiency.