Homeostatic control of membrane fatty acid composition in the rat after dietary lipid treatment

Partial replacement of poly- with monounsaturated fatty acids and vitamin E supplementation in pig diets: effect on fatty acid composition of subcutaneous and intramuscular fat and on fat and lean firmness

The effect of partial replacement of poly- (PUFA) with monounsaturated (MUFA) fatty acids in pig diets on fatty acid composition of subcutaneous and intramuscular fat and on fat and lean firmness was studied. No effect of dietary fat was observed on total saturated fatty acid concentration in any of the backfat layers or intramuscular lipid fractions. No significant effect of dietary fat was observed for the MUFA concentration in the outer layer, but a marked effect was evident for the inner layer (P < 0·001). A linear effect of dietary MUFA was observed for MUFA (P < 0·001) and PUFA (P < 0·001) in polar lipids. No significant effect of dietary treatment was observed on total concentration of n-3 fatty acids in any lipid location but a marked effect was observed for total n-6 fatty acid concentration. The response of pig fatty acid n-6 concentration was different depending on the lipid location. The neutral lipid fraction showed significantly lower n-6/n-3 fatty acid ratio than the subcutaneous fat. Intramuscular polar lipids showed no significant response of n-6/n-3 ratio. A linear effect of dietary MUFA concentration was observed on the melting point on the inner backfat layer (MP = 34·4 (s.e. 2·51) + 0·15 (s.e. 0·07) ✕ dietary MUFA (g/kg dry matter) (R2 = 0·24, P < 0·05)), indicating that the partial substitution of dietary PUFA by MUFA produced a fat of higher consistency. No response of the melting point of the outer layer to dietary treatment was observed. A marked effect of dietary fat was shown for backfat hardness (P < 0·001), gumminess (P < 0·001) and chewiness (P < 0·001). No effect of dietary fat was observed on the rheological properties of longissimus lumborum muscle.

Influence of a hyperlipidic diet on the composition of the non-membrane lipid pool of red blood cells of male and female rats

Background and objectives. Red blood cells (RBC) are continuously exposed to oxidative agents, affecting their membrane lipid function. However, the amount of lipid in RBCs is higher than the lipids of the cell membrane, and includes triacylglycerols, which are no membrane components. We assumed that the extra lipids originated from lipoproteins attached to the cell surface, and we intended to analyse whether the size and composition of this lipid pool were affected by sex or diet. Experimental design. Adult male and female Wistar rats were fed control or cafeteria diets. Packed blood cells and plasma lipids were extracted and analysed for fatty acids by methylation and GC-MS, taking care of not extracting membrane lipids. Results. The absence of ω3-PUFA in RBC extracts (but not in plasma) suggest that the lipids extracted were essentially those in the postulated lipid surface pool and not those in cell membrane. In cells' extracts, there was a marked depletion of PUFA (and, in general, of insaturation). Fatty acid patterns were similar for all groups studied, with limited effects of sex and no effects of diet in RBC (but not in plasma) fatty acids. Presence of trans fatty acids was small but higher in RBC lipids, and could not be justified by dietary sources. Conclusions. The presence of a small layer of lipid on the RBC surface may limit oxidative damage to the cell outer structures, and help explain its role in the transport of lipophilic compounds. However, there may be other, so far uncovered, additional functions for this lipid pool.

Oxidative Stress and Dietary Fat Type in Relation to Periodontal Disease

Oxidative stress is one of the main factors studied to explain the pathophysiological mechanisms of inflammatory conditions, such as periodontitis. In this respect, nutrition may be of great importance. Actually, research on nutrients' effects on periodontal diseases has expanded to include those influencing the redox status, which correlates to the inflammatory process. Dietary fat or lipids are often blamed as the major source of excess energy. Consequently, when caloric intake exceeds energy expenditure, the resultant substrate-induced increase in citric acid cycle activity generates an excess of reactive oxygen species (ROS). In addition, dietary fatty acid intake influences in relative fatty acid composition of biological membranes determining its susceptibility to oxidative alterations. From this standpoint, here, we reviewed studies analyzing the dietary fat role in periodontal disease. Research data suggest that periodontal health could be achieved by main dietary strategies which include substitution of saturated fats with monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA), particularly n-3 PUFA. Maybe in the future, we should analyze the diet and provide some advice to periodontitis patients to improve treatment outcomes.

Antioxidants, redox signaling, and pathophysiology in schizophrenia: an integrative view

Schizophrenia (SZ) is a brain disorder that has been intensively studied for over a century; yet, its etiology and multifactorial pathophysiology remain a puzzle. However, significant advances have been made in identifying numerous abnormalities in key biochemical systems. One among these is the antioxidant defense system (AODS) and redox signaling. This review summarizes the findings to date in human studies. The evidence can be broadly clustered into three major themes: perturbations in AODS, relationships between AODS alterations and other systems (i.e., membrane structure, immune function, and neurotransmission), and clinical implications. These domains of AODS have been examined in samples from both the central nervous system and peripheral tissues. Findings in patients with SZ include decreased nonenzymatic antioxidants, increased lipid peroxides and nitric oxides, and homeostatic imbalance of purine catabolism. Reductions of plasma antioxidant capacity are seen in patients with chronic illness as well as early in the course of SZ. Notably, these data indicate that many AODS alterations are independent of treatment effects. Moreover, there is burgeoning evidence indicating a link among oxidative stress, membrane defects, immune dysfunction, and multineurotransmitter pathologies in SZ. Finally, the body of evidence reviewed herein provides a theoretical rationale for the development of novel treatment approaches.

Effect of feeding diets high in monounsaturated fatty acids and α-tocopheryl acetate to rabbits on resulting carcass fatty acid profile and lipid oxidation

The effects of olive (MONO) or sunflower (POLY) oil-enriched (30 g/kg) diets with either a basal (10 mg/kg food) or supplemented (200 mg/kg) level of a-tocopheryl acetate on some measures of production, fatty acid composition of animal tissues and susceptibility to oxidation of rabbit meat and membrane extracts have been studied. MONO diet produced higher levels of C18:1 in animal tissues. Animals that received POLY diet had a higher level of C18:2 in perirenal and neutral fraction of intramuscular fat and higher levels of C18:2, C20:4, C22:4 and C22:5 in phospholipid, reaching a higher overall unsaturation (P = 0·001). Muscle samples from rabbits given the POLY diet were more susceptible to lipid oxidation (P = 0·0001). Differences in membrane lipid oxidation, between groups followed a similar pattern to that of meat. Diets rich in C18:2 resulted in increases in concentration of pentanal (P < 0·001), hexanal (P = 0·0001) and total volatile aldehydes (P = 0·0001) in meat as monitored by headspace gas liquid chromatography. Dietary supplementation with α-tocopheryl acetate reduced the overall concentration of volatile aldehydes (P < 0·05), particularly hexanal (P < 0·05). Dietary administration of monounsaturated fatty acids not only reduces membrane and meat lipid oxidation but also modifies the relative proportion of volatile aldehydes generated upon heating, with a specific decrease in those generally related to rancidity and off-flavour of meats.

Attenuation of ciclosporin-induced nephrotoxicity by dietary supplementation of seal oil in Sprague-Dawley rats

Fish oil, rich in omega-3 (n-3) polyunsaturated fatty acids (PUFAs), has been reported to attenuate nephrotoxicity induced by ciclosporin (cyclosporine A). Harp seal oil is a rich source of n-3 PUFAs. This study investigated the ability of dietary seal oil to reduce nephrotoxicity caused by ciclosporin. Sprague-Dawley rats were maintained on a standard diet (with sunflower oil as lipid, SFO) or a diet enriched with seal oil (with 85% seal oil and 15% sunflower oil as lipid, SO) for four weeks before and four weeks after intravenous administration of ciclosporin (15 mg kg−1 daily). Kidney function was assessed by measuring blood urea nitrogen, creatinine clearance, urinary N-acetyl-1-β-d-glucosaminidase, 6-keto-prostaglandin F1α, thromboxane B2 and malondialdehyde. Systolic blood pressure (SBP) was monitored. Ciclosporin concentrations in blood were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The fatty acid compositions of the diets and erythrocyte membranes were analysed by gas chromatography (GC). The results showed that nephrotoxicity was induced by ciclosporin in rats maintained on both SO and SFO diets. However, rats fed on SO diet endured less toxicity than those on SFO diet. The n-3 and n-6 PUFAs in the erythrocyte membrane of rats maintained on SO diet were found to be 10.79% and 11.93%, while those in rats maintained on SFO diet were found to be 1.67% and 22.71%, respectively. In conclusion, dietary supplementation of seal oil was found to reduce ciclosporin-induced nephrotoxicity in rats.

Intracellular composition of fatty acid affects the processing and function of tyrosinase through the ubiquitin-proteasome pathway

Proteasomes are multicatalytic proteinase complexes within cells that selectively degrade ubiquitinated proteins. We have recently demonstrated that fatty acids, major components of cell membranes, are able to regulate the proteasomal degradation of tyrosinase, a critical enzyme required for melanin biosynthesis, in contrasting manners by relative increases or decreases in the ubiquitinated tyrosinase. In the present study, we show that altering the intracellular composition of fatty acids affects the post-Golgi degradation of tyrosinase. Incubation with linoleic acid (C18:2) dramatically changed the fatty acid composition of cultured B16 melanoma cells, i.e. the remarkable increase in polyunsaturated fatty acids such as linoleic acid and arachidonic acid (C20:4) was compensated by the decrease in monounsaturated fatty acids such as oleic acid (C18:1) and palmitoleic acid (C16:1), with little effect on the proportion of saturated to unsaturated fatty acid. When the composition of intracellular fatty acids was altered, tyrosinase was rapidly processed to the Golgi apparatus from the ER (endoplasmic reticulum) and the degradation of tyrosinase was increased after its maturation in the Golgi. Retention of tyrosinase in the ER was observed when cells were treated with linoleic acid in the presence of proteasome inhibitors, explaining why melanin synthesis was decreased in cells treated with linoleic acid and a proteasome inhibitor despite the abrogation of tyrosinase degradation. These results suggest that the intracellular composition of fatty acid affects the processing and function of tyrosinase in connection with the ubiquitin-proteasome pathway and suggest that this might be a common physiological approach to regulate protein degradation.

Cold acclimation or grapeseed oil feeding affects phospholipid composition and mitochondrial function in duckling skeletal muscle

The phospholipid fatty acid (FA) composition and functional properties of skeletal muscle and liver mitochondria were examined in cold-acclimated (CA, 4 degrees C) ducklings. Phospholipid FA of isolated muscle mitochondria from CA birds were longer and more unsaturated than those from thermoneutral (TN, 25 degrees C) reared ducklings. The rise in long-chain and polyunsaturated FA (PUFA, mainly 20:4n-6) was associated with a higher State 4 respiration rate and a lower respiratory control ratio (RCR). Hepatic mitochondria, by contrast, were much less affected by cold acclimation. The cold-induced changes in phospholipid FA profile and functional properties of muscle mitochondria were reproduced by giving TN ducklings a diet enriched in grapeseed oil (GO, rich in n-6 FA), suggesting a causal relationship between the membrane structure and mitochondrial functional parameters. However, hepatic mitochondria from ducklings fed the GO diet also showed an enrichment in long-chain PUFA but opposite changes in their biochemical characteristics (lower State 4, higher RCR). It is suggested that the differential modulation of mitochondrial functional properties by membrane lipid composition between skeletal muscle and liver may depend on muscle-specific factors possibly interacting with long-chain PUFA and affecting the proton leakiness of mitochondrial membranes.

Coconut oil induces short-term changes in lipid composition and enzyme activity of chick hepatic mitochondria

We studied the short-term effects of a 20% coconut oil supplementation to the chick diet on lipid composition of liver and hepatic mitochondria, and changes that occurred in mitochondrial-associated enzymes as a result of this diet. No significant differences were observed in the lipid contents of liver when young chicks were fed the experimental diet, whereas hepatic mitochondria rapidly changed in response to this diet. Total cholesterol significantly increased in mitochondria at 24 hours of coconut oil diet feeding and decreased when dietary treatment was prolonged for 5 to 14 days. Changes in total mitochondrial phospholipids showed an inverse profile. A significant decrease in phosphatidylethanolamine and an increase in sphingomyelin were found at 24 hours. The cholesterol/phospholipid molar ratio significantly and rapidly (24 hours) increased in mitochondria from treated animals. Cytochrome oxidase activity drastically increased after 24 hours of experimental diet feeding and lowered to the control values when dietary manipulation was prolonged for 5 to 14 days. ATPase activity showed an inverse profile. Changes in cytochrome oxidase activity were parallel to changes in the cholesterol/phospholipid molar ratio, whereas changes in ATPase activity showed an inverse correlation with changes in this molar ratio. To our knowledge, this is one of the first reports on the very rapid response (24 hours) of mitochondrial lipid composition and function to saturated fat feeding.

Effect of dietary (n-9), (n-6) and (n-3) fatty acids on membrane lipid composition and morphology of rat erythrocytes

Studies focused on the intake of different dietary fats have shown changes in membrane lipid composition and, as a result, alterations in membrane physical properties. These changes affect erythrocyte morphology, receptor activity and oxygen transport, among others. Here, we compare the effects of diets exclusively differing in the type of fat (olive oil rich in monounsaturates, sunflower oil rich in n-6 polyunsaturates and fish oil rich in n-3 polyunsaturates) on fatty acid composition of plasma and erythrocyte membranes and erythrocyte morphology under scanning electron microscopy in rats. Monounsaturates are highest in animals fed olive oil diets; as are linoleic and arachidonic acids in sunflower oil-fed animals and n-3 PUFAs in fish oil-fed animals. The lowest levels of arachidonic acid are found in fish oil-fed animals and so are n-3 PUFAs in sunflower oil-fed animals. Our results show that sunflower oil-fed animals present lower discocyte, the major cell shape related to tissue oxygen supply, and higher codocyte percentages than olive oil- and fish oil-fed groups. Echinocyte percentage is higher in fish oil-fed animals with respect to the other two groups. The collective data indicate that olive oil elevates monounsaturates and the number of discocytes, pointing out a possible beneficial aspect of this dietary fat.

Supplementation of coconut oil from different sources to the diet induces cellular damage and rapid changes in fatty acid composition of chick liver and hepatic mitochondria

Supplementation of 20% coconut oil from two commercial sources pharmaceutical ("Pharmacy") and cooking ("Pastry") use, to the chick diet for 14 days produced a clear damage to the hepatic mitochondria, accompanied by an accumulation of glycogen and lipid droplets in the hepatocyte cytoplasm. These effects may be accounted for the high proportion of fat supplemented to the diets (20%). Pharmacy coconut oil induced a high percentage of cellular death when administered for 14 days. Fatty acid profiles in liver and hepatic mitochondria rapidly changed (24 hr) after both coconut oils supplementation to the diet. The accumulation of shorter chain fatty acids (12:0 and 14:0) was always higher after Pharmacy than after Pastry diet feeding. This fact may contribute, at least in part, to the cellular damage mentioned above especially after Pharmacy diet feeding. Mitochondrial ratios of saturated/unsaturated and saturated/polyunsaturated fatty acids rapidly changed in parallel to these ratios in both diets. Most of the mitochondrial parameters measured tend to recuperate the control values when diets were supplied for 5-14 days. Nevertheless, the maintenance of the mentioned ratios after 14-days Pharmacy diet feeding at significantly higher levels than those observed in control, seems to suggest the lack of the homeostatic mechanism in these membranes and could be also related with the high percentage of cellular death observed after this dietary manipulation.

Dietary sunflower oil reduces plasma and liver triacylglycerols in fasting rats and is associated with decreased liver microsomal phosphatidate phosphohydrolase activity

Plasma and liver lipids were studied in male weanling rats fed diets containing moderate levels of fat (6% by weight) as sunflower oil (SF diet, rich in linoleic acid), salmon oil (SM diet, rich in long-chain n-3 fatty acids), or a blend of peanut and rapeseed oil (PR diet, rich in oleic acid). After nine weeks of feeding, the fasting plasma cholesterol concentrations were 49 and 24% lower in groups SM and SF, respectively, as compared to group PR. Both dietary salmon oil and sunflower oil lowered the triacylglycerol concentration of plasma and liver but, unexpectedly, the response was higher with sunflower oil. Indeed, in group SM the values were 15 and 30% lower in plasma and liver, whereas in group SF, they were 24 and 53% lower, respectively. As compared to group PR, liver triacylglycerols and microsomes contained 2.5- and 2.3-fold less oleic acid, respectively, in group SF, and they were 9.2- and 3.2-fold enriched in n-3 fatty acids, respectively, in group SM. The liver triacylglycerol concentrations were correlated with changes in the microsomal Mg(2+)-dependent phosphatidate phosphohydrolase activity (r = 0.47, P < 0.01). As oleic acid, unlike long-chain n-3 fatty acids, is considered to promote the triacylglycerol synthesis and secretion, our findings suggest that changes in the membrane fatty acid composition could affect the triacylglycerol content of liver and plasma. Moreover, the availability within the liver, of oleic acid, predominantly incorporated into triacylglycerols, might limit the triacylglycerol production in SF-fed rats.

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.

Effects of chronic ethanol exposure on cultured cerebellar granule cells

The aim of this study was to investigate the lipid content and composition of rat cerebellar granule cells grown in the presence of ethanol (40, 55, or 80 mM) during in vitro differentiation. Quantitative analyses showed no effects of 40 mM ethanol, whereas a significant increase of total cholesterol was observed at 55 mM. Cells exposed to the highest ethanol dose (80 mM) were characterized by a higher sialidase activity, and by the modification of the ganglioside pattern and phospholipid fatty acid composition. The observed modifications were accompanied by changes of membrane anisotropy fluorescence assessed by the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene.

Modulation of membrane fluidity and lipidic metabolism in transformed rat fibroblasts induced by the sesquiterpenic hormone farnesylacetone

Farnesylacetone is a natural terpene extracted from androgenic glands of the crustacean Carcinus maenas and is capable of inhibiting proliferation, notably in transformed mammalian cells. Flow cytometry with three lipophilic probes, diphenylhexatriene, trimethylammonium-diphenylhexatriene, and Nile red, has revealed modifications of the lipidic metabolism in transformed FR3T3-mTT4 rat fibroblasts treated by farnesylacetone, including changes in membrane fluidity. Farnesylacetone strongly increased the number of neutral lipidic droplets in the cytoplasm. Moreover, after prolonged terpene treatment, the membrane fraction of cells contained a substantial level of triglycerides. Farnesylacetone provoked an immediate but transitory increase in membrane fluidity of the cell membrane. The change in measured lipid fluidity appears to be due to these triglycerides rather than to the phospholipids.

Influence of heated and nonheated partially hydrogenated dietary fats on ileal chyme fat and fatty acid composition of ileal mucosa in pigs

In this study the effects of partially hydrogenated chemically processed fats (CPF) and non-CPF on the ileal chyme fat and the fatty acid (FA) profile of the ileal mucosa and the subcutaneous tissue were analyzed. Samples were collected via an ileocutaneous fistula. For three months pigs were fed a control meal or diets containing either non-CPF high on 16:0, non-CPF high on 18:2 n6, CPF with 50% trans-18:1 or 20% trans-18:1. The latter fat was used after heat treatment. With both CPF diets, the fat content in the ileal chyme was three times higher than with non-CPF. In contrast to subcutaneous tissue reflecting dietary composition, changes in FA profile of ileal mucosa were restricted. Each non-CPF resulted in an increase of the characteristic major dietary FA. Both CPF increased the mucosal trans-FA percentage from 0 to 12% on average, although dietary composition was different. This study suggests: (1) less effects of trans-FA on the regulation of intraluminal fat load compared to saturated and cis-polyunsaturated FA, and (2) higher mucosal incorporation of trans-FA with heated CPF. This may play a role in the development of epithelial lesions in the ileum, which are known following ingestion of these fats.

Ileal and colonic fatty acid profiles in patients with active Crohn's disease

In patients with active Crohn's disease and in a control group the fatty acid profiles in the whole lipid fraction of ileal and colonic mucosal biopsy specimens were determined by capillary gas chromatography. The biopsy specimens in Crohn's disease patients were taken from the inflamed terminal ileum as well as from the inflamed and macroscopically normal colon. Compared with controls the fatty acid distribution in the inflamed ileal mucosa was significantly characterised by (a) a decrease of 18:2 n6 and 18:3 n3 accompanied by a substantial increase of the highly polyunsaturated fatty acids 20:4 n6, 22:4 n6, and 22:6 n3 and (b) a higher unsaturation index of total fatty acids compared with controls. These changes were similar in the inflamed colon. Additionally, both the inflamed and the macroscopically normal colonic mucosa showed an increase of saturated (18:0) and a decrease of monounsaturated fatty acids (18:1 n9). Fatty acid profiles of ileum and colon showed side variations in controls, but not in the Crohn's disease group. These data suggest that in Crohn's disease changes in the distribution of polyunsaturated fatty acids seem to be the general feature of inflamed mucosa in small and large intestine. Results further suggest that colonic fatty acid metabolism in Crohn's disease is altered by degrees, showing changes in saturated and monounsaturated fatty acids as an additional, primary event.

[The effect of zinc depletion on the fat content and fatty acid composition of the liver and brain in forcibly fed rats]

In the present work the influence of zinc deficiency on fat content and fatty acid composition of liver and fatty acid composition of brain of rats with a high food intake was investigated. Using the force-feeding technique the rats were fed 14.5 g food daily at days 1 to 4, and then 11.6 g food for later days. After 7 days the zinc-deficient animals had a fatty liver which was characterized by an increase in fat content (68%) and dry matter (23%). The amounts of lauric acid, myristic acid, myristoleic acid, palmitic acid, palmitoleic acid, and oleic acid were also increased by 100 to 200% in the liver of zinc-deficient animals, whereas the amount of arachidonic acid was decreased by 29%. The amounts of phosphatidylcholine and phosphatidylethanolamine in the liver were not changed by zinc deficiency, but the fatty acid composition of these phospholipids was changed. The liver phospholipids of zinc-deficient animals had a decreased proportion of arachidonic acid, but an increased proportion of docosahexaenoic acid. In the zinc-deficient animals there also existed a positive correlation between the fat content in the liver and the ratio between linoleic and arachidonic acid in the liver and a negative correlation between the fat content in the liver and the amount of arachidonic acid in the liver. These correlations as well as the changes in liver fatty acid composition of zinc-deficient animals suggest that the fatty liver might be the result of a disturbed metabolism of linoleic acid. In contrast, zinc deficiency did not influence the fatty acid composition of brain. This means that brain is protected against the effects of short-term zinc deficiency.

Characteristics and specificity of the inhibition of liver glucose-6-phosphatase by arachidonic acid. Lesser inhibitability of the enzyme of diabetic rats

The effect of arachidonic acid (delta 4Ach) on liver glucose-6-phosphatase (Glc6Pase) has been studied in vitro using untreated and detergent-treated microsomes prepared from fed and 48-h-fasted normal rats and from streptozotocin-induced diabetic rats. Glc6Pase of both untreated and detergent-treated microsomes (60 micrograms protein/ml) is inhibited by delta 4Ach in a dose-dependent manner between 10-100 microM. The inhibition is very rapid and does not depend on preincubation of microsomes in the presence of delta 4Ach. It does depend on the concentration of microsomal membranes and on the concentration of glucose 6-phosphate: it is more pronounced at low Glc6P concentrations than at high. As a consequence, the enzyme displays sigmoidal kinetics in the presence of delta 4Ach. Hill coefficients (equal to 1 in the control experiments) of about 1.4 were determined in the presence of 50 microM delta 4Ach, indicating a clear positive cooperative dependency of the Glc6Pase upon its substrate in the presence of delta 4Ach. The delta 4Ach inhibition is fully reversible in the presence of bovine serum albumin. The inhibition does not depend on the metabolism of delta 4Ach through the prostaglandin synthase (cyclooxygenase) or arachidonate 12-lipoxygenase pathways since it is not affected by indomethacin and nordihydroguaiaretic acid. Several other unsaturated fatty acids are able to inhibit the enzyme within the same concentration range. In contrast, saturated fatty acids, the arachidonic acid methyl ester and numerous other lipid compounds containing esterified unsaturated fatty acids do not inhibit Glc6Pase within the same concentration range. The enzyme of fed rats was inhibited in the same manner as the enzyme of 48-h-fasted rats. However, Glc6Pase of untreated microsomes from diabetic rats was less inhibitable by delta 4Ach than the Glc6Pase of normal rats. This difference does not persist after solubilization of the membrane lipids by detergent treatment.

Increments of dietary linoleate raise liver arachidonate, but markedly reduce heart n-6 and n-3 fatty acids in the rat

Four diets containing 20% of energy (en%) as fat and with linoleic acid contents of 1.9, 3.1, 7.7 and 10.1 en%, respectively, were fed to one-month-old male rats for three months. The fatty acid profiles and the levels of the major n-6 and n-3 fatty acids in the lipids of plasma, liver, heart and kidney were measured. We found that with increasing concentrations of 18:2n-6 in the diet, linoleic acid rose in plasma and in all organs, but long-chain n-6 and n-3 fatty acids responded differently. In liver, arachidonic acid increased and n-3 fatty acids were not significantly affected; in heart, both arachidonic and docosahexaenoic acids were progressively reduced; and in kidney, there was no change of n-6 and n-3. The results indicate that incremental changes in dietary linoleate affect the levels of polyunsaturated fatty acids in liver and extrahepatic organs differently.

Cardiolipins and biomembrane function

Evidence is discussed for roles of cardiolipins in oxidative phosphorylation mechanisms that regulate State 4 respiration by returning ejected protons across and over bacterial and mitochondrial membrane phospholipids, and that regulate State 3 respiration through the relative contributions of proteins that transport protons, electrons and/or metabolites. The barrier properties of phospholipid bilayers support and regulate the slow proton leak that is the basis for State 4 respiration. Proton permeability is in the range 10(-3)-10(-4) cm s-1 in mitochondria and in protein-free membranes formed from extracted mitochondrial phospholipids or from stable synthetic phosphatidylcholines or phosphatidylethanolamines. The roles of cardiolipins in proton conductance in model phospholipid membrane systems need to be assessed in view of new findings by Hübner et al. [313]: saturated cardiolipins form bilayers whilst natural highly unsaturated cardiolipins form nonlamellar phases. Mitochondrial cardiolipins apparently participate in bilayers formed by phosphatidylcholines and phosphatidylethanolamines. It is not yet clear if cardiolipins themselves conduct protons back across the membrane according to their degree of fatty acyl saturation, and/or modulate proton conductance by phosphatidylcholines and phosphatidylethanolamines. Mitochondrial cardiolipins, especially those with high 18:2 acyl contents, strongly bind many carrier and enzyme proteins that are involved in oxidative phosphorylation, some of which contribute to regulation of State 3 respiration. The role of cardiolipins in biomembrane protein function has been examined by measuring retained phospholipids and phospholipid binding in purified proteins, and by reconstituting delipidated proteins. The reconstitution criterion for the significance of cardiolipin-protein interactions has been catalytical activity; proton-pumping and multiprotein interactions have yet to be correlated. Some proteins, e.g., cytochrome c oxidase are catalytically active when dimyristoylphosphatidylcholine replaces retained cardiolipins. Cardiolipin-protein interactions orient membrane proteins, matrix proteins, and on the outerface receptors, enzymes, and some leader peptides for import; activate enzymes or keep them inactive unless the inner membrane is disrupted; and modulate formation of nonbilayer HII-phases. The capacity of the proton-exchanging uncoupling protein to accelerate thermogenic respiration in brown adipose tissue mitochondria of cold-adapted animals is not apparently affected by the increased cardiolipin unsaturation; this protein seems to take over the protonophoric role of cardiolipins in other mitochondria. Many in vivo influences that affect proton leakage and carrier rates selectively alter cardiolipins in amount per mitochondrial phospholipids, in fatty acyl composition and perhaps in sidedness; other mitochondrial membrane phospholipids respond less or not at all.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of dietary supplementation with eicosapentaenoic acid on the phospholipid and fatty acid composition of erythrocytes of marmoset

Adult male marmoset monkeys were fed eicosapentaenoic acid (20:5n-3) as the ethyl ester in diets containing either 32% (reference diet, no added cholesterol) or 7% (atherogenic diet with 0.2% added cholesterol) linoleic acid (18:2n-6) for 30 wk. No changes were seen in the level of phosphatidylcholine (PC) or phosphatidylethanolamine (PE) but minor changes were observed in both the sphingomyelin (SPM) and phosphatidylinositol plus phosphatidylserine (PI+PS) fractions of erythrocyte lipids. The extent of total n-3 fatty acid incorporation into membrane lipids was higher in atherogenic diets (polyunsaturated/monounsaturated/saturated (P/M/S) ratio 0.2:0.6:1.0) than reference diets (P/M/S ratio 1:1:1) and this was true for both PE (33.4 +/- 1.0% vs 24.3 +/- 1.1%) and PC (9.3 +/- 0.5% vs 4.9 +/- 0.3%). Although suitable controls for cholesterol effects were not included in the study, earlier results obtained with marmosets lead us to believe such effects were probably small. Regardless of basic diet (atherogenic, reference), 20:5n-3 was preferentially incorporated into PE (10.8 +/- 0.2%, 6.0 +/- 0.02%) while smaller amounts were incorporated into PC (6.9 +/- 0.4%, 3.2 +/- 0.2%). The major n-3 polyunsaturated fatty acid found in PE in response to dietary 20:5n-3 was the elongation metabolite 22:5n-3 in both the atherogenic (17.7 +/- 0.7%) and reference (14.3 +/- 1.0%) dietary groups; 22:6n-3 levels were less affected by diet (4.7 +/- 0.3% and 3.9 +/- 0.2%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary manipulation with high marine fish oil intake of fatty acid composition and arachidonic acid metabolism in rat cerebral microvessels

Male weanling Wistar rats were maintained on one of two semisynthetic diets, differing only in the type of oil used: (i) 10% by weight marine fish oil (MFO group) containing 20% eicosapentaenoic acid (EPA) and 17% docosahexaenoic acid (DHA), or (ii) 10% by weight sunflower oil (SFO group). The control group was kept on standard diet for 4 weeks. Blood-free microvessels were isolated from brain cortex by a rapid micromethod, and their fatty acid composition was determined by gas chromatography. It was found that the proportion of n-3 fatty acids (including EPA and DHA) increased significantly in the microvessels of the MFO group, accompanied by a decrease of the n-6 fatty acid series. The changes in fatty acid composition of endothelial cells were not significant in the SFO group in comparison to the control. The amounts of lipoxygenase and cyclooxygenase metabolites were determined. Dietary fish oil decreased the percentage of total products of arachidonate by 50%, while the SFO diet had no effect on it. The amount of lipoxygenase products in the MFO group decreased significantly from 16931 +/- 3131 dpm to 6399 +/- 357 dpm/300 mg wet weight of brain. Significantly less PGF-1 alpha, PGF-2 alpha and 12-hydroxyheptadecatrienoic acid (HHT) were found in the capillaries of MFO treated animals, in comparison to the SFO group. The ratios of vasoconstrictor and vasodilator metabolites of arachidonate cascade were not modified by the diets. Our results suggest that fish oil diet reduces the arachidonate cascade in cerebral microvessels. This effect may explain for the efficiency of n-3 fatty acids in vascular diseases.

Characterization of the lipid and protein contents of myelin bodies isolated from the renal cortex of gentamicin-treated rats

Myelin bodies were isolated from the renal cortex of gentamicin-treated rats (100 mg/kg body weight, twice daily for 3 days, i.p.) employing an initial pelleting by differential centrifugation and subsequent flotation on a discontinuous sucrose gradient. These structures were found to contain almost twice as much protein as phospholipid and SDS-polyacrylamide gel electrophoresis revealed the presence of many different polypeptides. All the major phospholipids are present, although myelin bodies contain a considerably higher proportion of phosphatidylinositol, somewhat more phosphatidylcholine and considerably lower percentages of phosphatidylserine and sphingomyelin than do normal renal phospholipids. The fatty acids of myelin body phospholipids are highly saturated (67.3-87.9%) and a striking feature is the occurrence of relatively large amounts of 22:1, presumably erucic acid, especially in sphingomyelin. Myelin bodies contain small amounts of unesterified cholesterol, unesterified dolichol and coenzymes Q9 and Q10.

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.

The effect of a fish oil enriched diet on oxygen toxicity and lipid peroxidation in mice

Mice were fed a chow diet or diets enriched in fish oil, sunflower oil or beef tallow for 3 weeks. Fatty acid analysis was carried out in samples of plasma, brain and lungs from these animals and large changes were found in plasma and lungs with relatively small dietary-induced changes in brain tissue. Bleeding times were increased very significantly in the fish oil group, and slightly increased in the sunflower oil group. Endogenous lipid peroxidation (measured as thiobarbituric acid reactive substances) was unchanged in lung and brain, but lung tissue from fish oil fed mice produced more lipid peroxides in vitro during incubation at 37 degrees than those of other dietary groups. Mice fed the four different diets were exposed to hyperbaric oxygen at 618, 585 and 515 kPa and convulsive activity and lung damage was recorded. No dietary-induced alterations in susceptibility to oxygen toxicity were found.

Prostaglandin synthesis and fatty acid composition of phospholipids and triglycerides in skeletal muscle of chicks fed combinations of flaxseed oil and animal tallow

Chicks were fed isocaloric and isonitrogenous diets containing 6% (w/w) added fat consisting of various proportions of animal tallow and flaxseed oil (FSO). No differences among treatments were seen in growth rate, muscular deposition of protein and lipids nor in the muscle phospholipid (PL) and triglyceride (TG) contents. Prostaglandin (PG)E2 synthesis in isolated skeletal muscle was depressed significantly by feeding FSO or by treatment with naproxen (6-methoxy-alpha-methyl-2-napthaleneacetic acid), an inhibitor of PG synthesis. The changes associated with diet may be related to differences in the fatty acid composition of muscle lipids. Levels of saturated fatty acids in muscle PL and TG were relatively insensitive to dietary treatments. Monounsaturated fatty acid levels were significantly lower in the FSO-fed groups. FSO diets caused significant depression in muscle PL 20:4 omega 6 and almost completely inhibited 22:5 omega 6 incorporation. FSO diets decreased ratios of omega 6/omega 3 fatty acids and increased the unsaturation index of muscle PL. Muscles of chicks fed FSO showed increased levels of 18:3 omega 3, and of its derivatives 20:4 omega 3 and 22:5 omega 3. These results suggest that FSO inhibits PG synthesis and modifies the fatty acids of PL and TG of chick muscle. These changes may have implications for PG-dependent and/or membrane-dependent processes in muscle metabolism.

Lipid composition and peroxide levels of mucosal cells in the rat large intestine in relation to dietary fat

To examine whether dietary fat alters membrane lipid composition and peroxidation of polyunsaturated fatty acids in "non-proliferative" and "proliferative" cells in the large intestine, Sprague-Dawley rats were fed diets providing a polyunsaturated-to-saturated fatty acid ratio of 1.2 or 0.3 at a high or low level of fat intake for a 25-day period. Cell populations were isolated and the effect of dietary fat on membrane polyunsaturated fatty acid content and peroxide levels was determined. Neither fat level nor fatty acid composition of diet influenced total cholesterol, total phospholipids, and percentage of phospholipid classes in membrane phospholipids. Feeding the high fat and/or high polyunsaturated-to-saturated fatty acid ratio diet increased polyunsaturated fatty acid content of mucosal cell phospholipids. Increase in polyunsaturated fatty acid content was paralleled by a decrease in the monounsaturated fatty acid content of mucosal cell phospholipids. Membrane content of total saturated fatty acids was not significantly affected by diet. Variation in phospholipid fatty acid composition between "non-proliferative" and "proliferative" cells was observed. Lipid peroxide levels in mucosal cell lipid fractions were altered by dietary fat treatment. Animals fed high fat diets, compared to groups fed low fat diets, exhibited higher membrane peroxide levels when results are expressed as nmol/mg protein. Higher peroxide levels were observed in mucosal cells for rats fed high polyunsaturated-to-saturated fatty acid ratio diets when results were expressed per nmol of phospholipid. It is concluded that changes in fat level and fatty acid composition of the diet alters the mucosal cell membrane lipid composition in the rat large intestine and influences susceptibility of mucosal cell lipid to peroxidation. Further research is required to delineate which dietary factors--fat level, polyunsaturated-to-saturated fatty acid ratio, or both--have a primary influence on the degree of lipid peroxidation.

Fatty acid composition of serum lipids and erythrocyte membranes in type 2 (non-insulin-dependent) diabetic men

The fatty acid (FA) composition of serum lipids and erythrocytes was studied in 21 men with non-insulin-dependent diabetes mellitus (NIDDM) and in 14 normal subjects matched for age, sex, body weight, and dietary intake. Lower levels of linoleic acid and higher levels of highly unsaturated FA (daughter) of n-3 and n-6 family FA, reflected in a higher unsaturation index, were found in serum phospholipids (S-PL), in phospholipids of erythrocyte membranes (ery-PL), and in serum cholesterolesters (S-CHE). The unsaturation index of serum phospholipids significantly correlated with glycosylated hemoglobin A1c (P less than .05) and blood glucose levels after glucose load (P less than .001). The results suggest that elongation and desaturation of essential FA (linoleic acid in particular) are increased. The above changes may be associated with accelerated atherosclerosis in type 2 diabetics.

Changes in lipid composition and desaturase activities of duodenal mucosa induced by dietary fat

In the present work we have studied the effects of feeding either olive or sunflower oil on lipid composition and desaturase activities of duodenal mucosa microsomes. Duodenal microsomes prepared from dogs fed the sunflower oil diet showed higher percentages of saturated, of linoleic and of n - 3 polyunsaturated fatty acids as well as lower levels of oleic, dihomo-gamma-linolenic and arachidonic acids in phosphatidylcholine and phosphatidylethanolamine than those prepared from animals fed the olive oil diet. In sphingomyelin, the dietary supplementation did not produce significant differences between the two groups. The cholesterol/phospholipid molar ratio was higher in the sunflower oil group than in the olive oil group. The in vitro delta 9-desaturase activity was higher in microsomes from the olive oil dogs. The delta 6-desaturase activity was similar in microsomes from the two groups and lower than that found for delta 9-desaturase activity. Desaturase activities were higher in duodenal microsomes than those previously found for liver microsomes.

Effect of dietary fat on the lipid composition and utilization of short-chain fatty acids by rat colonocytes

The objective of the present studies was to examine the effect of dietary fat on the lipid composition of rat colonocytes and their utilization of short-chain fatty acids (SCFA). Rats were fed 14% beef fat, fish oil or safflower oil plus 2% corn oil in a semi-synthetic base diet for 4 wk. Colonocytes were isolated and their lipid composition was examined. Feeding beef fat and fish oil resulted in an increase in monounsaturated fatty acids and a reduction in omega-6 fatty acids. Feeding fish oil resulted in an enrichment with omega-3 fatty acids. There was no dietary influence on the amount of either cholesterol or phospholipids of colonocytes. Fish oil feeding resulted in significant increase in colonocyte free fatty acids (FFA) as compared to other diets. Dietary fat was found to have no effect on SCFA utilization by colonocytes. Colonocytes were found to utilize SCFA in the order of butyrate greater than or equal to acetate greater than or equal to propionate. The presence of acetate and propionate in the medium had no effect on the rate of butyrate utilization.

Black currant seed oil feeding and fatty acids in liver lipid classes of guinea pigs

Guinea pigs were fed one of three diets containing 10% black currant seed oil (a source of gamma-linolenic (18:3 n-6) and stearidonic (18:4 n-3) acids), walnut oil or lard for 40 days. The fatty acid composition of liver triglycerides, free fatty acids, cholesteryl esters, phosphatidylinositol, phosphatidylserine, cardiolipin, phosphatidylcholine and phosphatidylethanolamine were determined. Dietary n-3 fatty acids found esterified in liver lipids had been desaturated and elongated to longer chain analogues, notably docosapentaenoic acid (22:5 n-3) and docosahexaenoic acid (22:6 n-3). When the diet contained low amounts of n-6 fatty acids, proportionately more of the n-3 fatty acids were transformed. Significantly more eicosapentaenoic acid (EPA) (20:5 n-3) was incorporated into triglycerides, cholesteryl esters, phosphatidylcholine and phosphatidylethanolamine of the black currant seed oil group compared with the walnut oil group. Feeding black currant seed oil resulted in significant increases of dihomogamma-linolenic acid (20:3 n-6) in all liver lipid classes examined, whereas the levels of arachidonic acid (20:4 n-6) remained relatively stable. The ratio dihomo-gamma-linolenic acid/arachidonic acid was significantly (2.5-fold in PI to 17-fold in cholesteryl esters) higher in all lipid classes from the black currant seed oil fed group.

Changes in lipid composition of liver microsomes and fatty acyl-CoA desaturase activities induced by medium chain triglyceride feeding

Changes in fatty acid composition, microsomal delta 9- and delta 6-desaturase activities and liver contents of cholesterol and phospholipids were studied in rats fed medium chain triglyceride-supplemented diets. Weanling rats were divided into four groups and fed for three weeks a basal diet with different 10%-fat supplements: corn oil, medium chain triglyceride-corn oil, olive oil and medium chain triglyceride-olive oil. The highest relative content of saturated fatty acids corresponded to corn oil-fed animals. Both monounsaturated fatty acid content and delta 9-desaturase activity were higher in the animals fed olive oil diets than in corn oil-fed rats. The long chain polyunsaturated fatty acids of the n-3 series were increased in the olive oil and medium chain triglyceride-olive oil-fed groups probably due to the lower linoleic/alpha-linolenic ratios found in these two diets. The cholesterol/phospholipid molar ratio was unaffected by diet and the unsaturation index was only slightly changed in the four groups. Thus, some mechanism may be operative under these conditions to maintain the homeostasis of the membrane.

The development of pulmonary surfactant lipids in a neonatal marsupial and the rat

The composition of pulmonary surfactant during development was compared in a marsupial, the tammar wallaby, and the rat. For both species phospholipid fatty acid and neutral lipid fatty acid composition is similar, and phosphatidylcholine was the principal phospholipid at each age group. The relative amount of each phospholipid class significantly changed with time in both species but the extent of these changes did not vary between species. The neutral lipid component of surfactant varied significantly between the marsupial and eutherian, with higher levels of free cholesterol observed in the former. Overall the lipid composition of pulmonary surfactant in the developing wallaby is similar to that seen in eutherians with the exception being the level of free cholesterol.

Influences of biotin deficiency and dietary trans-fatty acids on tissue lipids in chickens

1. The combined effects of feeding hydrogenated fats and varying the levels of biotin and linoleate (18:2 omega 6) on polyunsaturated fatty acids were studied in the chicken. 2. Biotin deficiency signs were not exacerbated by feeding hydrogenated fats or by diets low in linoleate for 21 d. 3. Biotin deficiency resulted in proportionately higher levels of 18:2 omega 6 and gamma-linolenate (18:3 omega 6) in liver triglycerides, and lower levels of dihomo-gamma-linolenate (20:3 omega 6) in liver and heart phospholipids irrespective of the 18:2 omega 6 level in the diet. 4. Biotin deficiency did not alter arachidonate (20:4 omega 6) levels in tissue lipids at 21 d. 5. Feeding high levels of trans-18:1 isomers with adequate biotin led to reduced 20:3 omega 6 and 20:4 omega 6 levels in liver and heart phospholipids with compensatory increases in omega 3 fatty acids. 6. The trans-isomers of 18:1 were incorporated into several tissues of the chick. Incorporation was dependent on the levels fed. Very small amounts were incorporated into brain compared with other tissues when dietary trans-isomer levels were high, but were similar when dietary trans-isomer levels were low. The trans-18:1 isomers appear to be preferentially incorporated into phospholipids as opposed to triglycerides in heart and liver.

Age-related changes in respiration coupled to phosphorylation. I. Hepatic mitochondria

Age-related changes affecting mitochondrial adenine nucleotide metabolism may underlie age-related decreases in hepatic metabolic activities. Oxidative activity coupled with phosphorylation, the apparent Km and Vmax of the adenine nucleotide translocase (AdNT), the adenine nucleotide pool size and membrane lipid composition were determined for hepatic mitochondria from young (3 months), mature (12 months) and aged (24 months) Fischer 344 male rats which had been fed NIH-31 diet. The age-related decreases in state 3 respiration supported by NAD-linked substrates were 2-4-fold greater than that of an FAD-linked substrate. The 32% (P less than 0.05) decrease in the AdNT Vmax calculated for the aged rats was accompanied by a 17% decrease in the AdNT Km. The exchangeable pool of adenine nucleotides in mitochondria from aged rats was 72% (P less than 0.05) that in the young rats. While the age-related increase in the cholesterol/phospholipid-Pi ratio and changes in the phospholipid head group pattern were not significant, the overall change in the fatty acid pattern effected a 20% (P less than 0.05) decrease in the n-6/n-3 fatty acid ratio. These data suggest that the reduced Vmax of the AdNT is a consequence of a diminished pool of exchangeable adenine nucleotides. The lower AdNT velocity may reflect the effect of changes in the lipid environment of the membrane in which it is embedded. The major shifts in these parameters occurred during the second year of life.

Dietary fat in relation to fatty acid composition of red cells and adipose tissue in colorectal cancer

Fatty acids were determined in erthrocytes in 49 patients with colorectal cancer and compared with age and sex-matched controls. Marginally increased levels of stearic acid (P = 0.057) and oleic acid (P = 0.064) and decreased arachidonic acid (P = 0.043) occurred in cancer patients. There was no difference in the stearic to oleic acid ratio between the two groups. Dietary intake, assessed by dietary recall and adipose tissue analysis was also not different. In control subjects the polyunsaturated:saturated (P:S) fatty acid ratio correlated between diet and adipose tissue (P less than 0.01, at least). In contrast cancer patients showed different correlations; in particular dietary and erythrocyte P:S fatty acid ratios correlated (P less than 0.01). These findings may indicate disturbed fat metabolism in cancer patients. The erythrocyte stearic to oleic acid ratio is of no diagnostic value.

Dietary linoleic acid and the fatty acid profiles in rats fed partially hydrogenated marine oils

The influence of the linoleic acid levels of diets containing partially hydrogenated marine oils (HMO) rich in isomeric 16:1, 18:1, 20:1 and 22:1 fatty acids on the fatty acid profiles of lipids from rat liver, heart and adipose tissue was examined. Five groups of rats were fed diets containing 20 wt % fat--16% HMO + 4% vegetable oils. In these diets, the linoleic acid contents varied between 1.9% and 14.5% of the dietary fatty acids, whereas the contents of trans fatty acids were 33% in all groups. A sixth group was fed a partially hydrogenated soybean oil (HSOY) diet containing 8% linoleic acid plus 32% trans fatty acids, mainly 18:1, and a seventh group, 20% palm oil (PALM), with 10% linoleic acid and no trans fatty acids. As the level of linoleic acid in the HMO diets increased from 1.9% to 8.2%, the contents of (n-6) polyunsaturated fatty acids (PUFA) in the phospholipids increased correspondingly. At this dietary level of linoleic acid, a plateau in (n-6) PUFA was reached that was not affected by further increase in dietary 18:2 (n-6) up to 14.5%. Compared with the HSOY- or PALM-fed rats, the plateau values of 20:4(n-6) were considerably lower and the contents of 18:2(n-6) higher in liver phosphatidylcholines (PC) and heart PC. Heart phosphatidylethanolamines (PE) on the contrary, had elevated contents of 20:4(n-6), but decreased 22:5(n-6) compared with the PALM group.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of dietary butter enrichment on the fatty acid distribution of phospholipid fractions isolated from rat platelets and aortae

Rats were maintained for 2 weeks on a low-fat basal diet (5% energy) and a diet from which 50% of the energy was derived from butter. Lipids were extracted from aortae and platelets and the fatty acid profiles of individual phospholipids were examined. Similar responses to dietary butter enrichment occurred in PI, PS, PE and PC fractions from either tissue: 20:4(n - 6) and all other n - 6 series longer-chain polyunsaturated fatty acids except 20:3(n - 6) decreased in percentage; all n - 3 series polyunsaturated fatty acids increased, including 20:5(n - 3) and 22:6(n - 3); n - 9 series polyunsaturated fatty acids, derived from 18:1(n - 9), increased. Despite the considerable redistribution of polyunsaturated fatty acids, the percentages of total polyunsaturated fatty acids in each phospholipid were, in every case, independent of diet. None of the changes were localized in a particular phospholipid fraction. Quantitation of fatty acids using heptadecanoic acid as an internal standard revealed that the concentrations of 20:4(n - 6) in platelet and aortic PE and PC was higher than in PI fractions. Therefore, in terms of substrate amount, it appears that PC and PE as well as PI have the potential to provide endogenous 20:4(n - 6) for oxygenation to the prostanoids thromboxane A2 and prostacyclin I2.

Lipid composition of liver microsomes in rats fed a high monounsaturated fatty acid diet

The fatty acid and cholesterol contents of tissue membranes are the determinants of membrane stability and functionality. This study was designed to evaluate the influence of a high monounsaturated fatty acid diet on the fatty acid composition of rat liver microsomes and on their cholesterol and lipid phosphorus content. Weanling animals were fed for 5 weeks with high fat diets containing olive oil or corn oil. Saturated fatty acids were increased and oleic acid decreased in microsomal total phospholipids and in the three major phosphoglycerides, phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI), of rats fed corn oil as compared to the olive oil group. The percentage of linoleic acid was higher in the corn oil group, but only for total phospholipids and PC. Linoleic and alpha-linolenic metabolites were significantly increased in total phospholipids of olive oil-fed animals with respect to those fed corn oil. These changes were responsible for the low unsaturation index found in microsomal phospholipids of the corn oil group. The diet did not affect the microsome cholesterol or the lipid phosphorus content. These results show that, in olive oil-fed rats, the cholesterol content and the degree of unsaturation of liver microsomes was similar to that observed in weanling animals; this probably suggests an adequate maintenance of functionality of membranes in olive oil-fed animals.

Dietary fat ratios and liver plasma membrane lipid composition

Male Sprague-Dawley weanling rats were fed isocaloric diets consisting of 10% (by wt) fat. The six groups differed in the ratio of corn oil and butter fat present in the diets such that: 10C, 10% corn oil (C); 8C2B, 8% C/2% butter fat (B); 6C4B, 6% C/4% B; 4C6B, 4% C/6% B; 2C8B, 2% C/8% B; and 10B, 10% B. Liver plasma membranes were analyzed for fatty acid composition and cholesterol/phospholipid molar ratio. The 18:2n-6 content was constant in the 10C and 8C2B diets and then decreased linearly through the 2C8B diet. The 20:4n-6 and 18:1n-9 contents were constant except in the 10B diet, in which a significant decrease and increase, respectively, were observed. The cholesterol/phospholipid molar ratio increased between the 10C and 6C4B diets and subsequently (4C6B and 10B diets) remained constant. This data indicates that changes in n-6 fatty acid content in the liver plasma membrane are directly related to dietary intake only for 18:2n-6. Arachidonic acid content in the membrane is maintained at a constant level until the linoleic acid content of the diet is reduced to 0.5% of calories. It also indicates that the cholesterol content of the membrane becomes saturated and does not increase with increasing concentrations of saturated fat in the diet.

Compensatory mechanisms in erythrocyte lipids in patients with atherosclerosis

The quantitative composition of phospholipids and fatty acids of erythrocytes was investigated in patients with atherosclerosis. It was stated that the erythrocyte lipids of atherosclerotic patients contained smaller quantities of phosphatidylcholine and phosphatidylinositol, a significantly larger quantity of sphingomyelin, and higher sphingomyelin/phosphatidylcholine and cholesterol/phospholipid ratios. The existence of compensatory changes was stated, which was evident in the reduction of palmitic and stearic acids and the increase of linoleic and eicosatrienoic acids in erythrocyte phospholipids. These changes in fatty acid composition probably cause minimal changes in the membrane fluidity induced by an increased cholesterol/phospholipid and sphingomyelin/phosphatidylcholine ratios. This paper was the first evidence of occurrence of those changes in erythrocytes during spontaneous atherosclerosis in human.