Ethanol Inhalation and Dietary N-6, N-3, and N-9 Fatty Acids in the Rat: Effect on Platelet and Aortic Fatty Acid Composition

The effects of 18-carbon n-6, n-3, and n-9 fatty acid diets and ethanol exposure on the fatty acyl composition of platelets and vascular tissue were examined. An experimental design was devised to control the dietary content of 18-carbon fatty acids. The levels of 18:3n6, 18:3n3 and 18:1n9 were varied by a formulation of dietary oils which contained similar proportions of 18:2n6. Male Sprague-Dawley rats were fed a purified diet containing 11% by weight of either borage oil (BOR) rich in 18:3n6, linseed/safflower oil (LSO) rich in 18:3n3, or sesame oil (SES) rich in 18:1n9 for 7 weeks and exposed to ethanol vapors by means of inhalation for the final 6 days of the dietary regimen. Moderate blood ethanol levels of 118 +/- 6.6 mg/dl were obtained. Total lipids were extracted from platelets and aortae, and the fatty acid distributions were analyzed by gas chromatography. BOR feeding resulted in increases in the proportion of n-6 fatty acids (18:3n6, 20:3n6, 20:4n6) in platelets and aorta. Animals fed the LSO diet had increased levels of n-3 fatty acids (18:3n3, 20:5n3, 22:6n3). The SES-based diet resulted in an increase in 18:1n9 in both aorta and platelets. Following ethanol exposure alone, the most marked change in the fatty acid profile was a decrease in 20:4n6 in the platelet. This effect was not observed in rats supplemented with BOR. No significant changes were observed in the aortic fatty acid content at this level of ethanol exposure. The results suggested that, in the rat, a diet enriched with BOR effectively prevented ethanol-induced alterations in platelet fatty acid composition.     

Placental transfer of essential fatty acids in humans: venous-arterial difference for docosahexaenoic acid in fetal umbilical erythrocytes.

Docosahexaenoic acid [22:6(n-3); 22:6(4,-7,10,13,16,19) (DHA)] is required in quantity by the developing nervous system of the fetus. This need could be met through synthesis of DHA from linolenic acid in the fetus or through placental transfer of DHA directly. To study the placental transfer of n-3 fatty acids, we obtained umbilical and maternal blood samples from 26 healthy women and infants at parturition and measured the fatty acid composition and content of both plasma and erythrocytes. A striking finding was a considerable venous-arterial difference for DHA in the umbilical erythrocytes as a proportion of total fatty acids and in absolute concentration. This difference of 2.2 micrograms per billion erythrocytes was 6 times larger than the difference in fetal plasma, when the plasma and erythrocyte concentrations were normalized to whole blood. Most other erythrocyte fatty acids showed a similar trend. In umbilical plasma, significant venous-arterial differences were found for 16:0, 16:1, 18:2, and total saturated fatty acids. There was a similar trend for most other plasma fatty acids. Compared with maternal blood, fetal plasma and erythrocytes had higher levels of 20:4 and DHA and lower levels of 18:2 and 18:3(n - 3) fatty acids as a proportion of total fatty acids. These results suggest that erythrocytes play a major role in the necessary transport of the essential fatty acid DHA into the fetus.     

Influence of different dietary fatty acid sources on erythrocyte lipids and plasma and liver essential fatty acids in hamsters fed ethanol

Hamsters fed ethanol were given three different dietary sources of essential fatty acids; safflower oil, evening primrose oil (both mainly n-6 fatty acids) or linseed oil (mainly n-3 fatty acids). After 7 weeks, plasma, erythrocyte and liver lipids and fatty acids were analyzed. Plasma and liver lipids were not significantly different in the ethanol-fed hamsters compared to the controls. Erythrocyte total phospholipid was increased only in the ethanol-fed groups given n-6 but not n-3 fatty acids. Some fatty acid changes induced by ethanol were predictable, e.g. lower 20:4 n-6 in hamsters fed n-6 fatty acids, but others were not predictable, e.g. higher 22:6 n-3 in all the ethanol-fed groups. The effect of ethanol on hamster lipids and fatty acid composition appears dependent on the predominant class of dietary fatty acids.     

Alterations in polyunsaturated fatty acid composition of cardiac membrane phospholipids and alpha 1 adrenoceptor mediated phosphatidylinositol turnover

STUDY OBJECTIVE - The aim of the study was to investigate the steps at which polyunsaturated fatty acids are involved in alpha 1 adrenoceptor mediated phosphatidylinositol turnover. DESIGN - Phosphatidylinositol turnover rates were investigated after preincubating neonatal rat ventricular myocytes with culture media enriched with linoleic acid (18:2n-6) or eicosapentaenoic acid (20:5n-3) to change the polyunsaturated fatty acid composition of their membrane phospholipids. EXPERIMENTAL MATERIAL - Cardiomyocytes were isolated from ventricles of 2-4 d old Wistar rats by trypsinization and were then cultured. Experiments were started 48 h after seeding, when there was a confluent monolayer of beating cardiomyocytes. MEASUREMENTS and RESULTS - In 18:2n-6 treated cells the 18:2n-6 content in the total phospholipid fraction rose from 45 to 68 nmol.mg-1 protein; in 20:5n-6 treated cells the 20:5n-3 content rose from 1.5 to 12.5 nmol.mg-1 protein, and the docosapentaenoic acid (22:5n-3) content rose from 5.1 to 14.7 nmol.mg-1 protein. The major n-3 fatty acid, 22:6n-3 (11.4 nmol.mg-1 protein), did not change after 20:5n-3 treatment. Although the phosphatidylinositol fraction showed changes paralleling those in the total phospholipids, none were significant. In this fraction the major n-3 fatty acid appeared to be 22:5n-3 (0.4 nmol.mg-1 protein). The fatty acid treated cells were prelabelled with [3H]-inositol to estimate the rate of phosphatidylinositol-4,5-bisphosphate turnover. There were no differences in the rate of [3H]-inositolphosphate formation between control, 18:2n-6 treated cells, and 20:5n-3 treated cells. Prolonged alpha 1 adrenergic stimulation of control and treated cells did not change the polyunsaturated fatty acid composition of the total phospholipid and phosphatidylinositol fractions. CONCLUSIONS - The alpha 1 adrenoceptor mediated phosphatidylinositol turnover rate is not affected by changes in polyunsaturated fatty acid composition of membrane phospholipids, neither does prolonged alpha 1 adrenergic stimulation lead to significant depletion of any specific or total polyunsaturated fatty acids in the phosphatidylinositol lipids.     

Hepatic metabolism of dietary alpha-linolenic acid in suckling rats, and its possible importance in polyunsaturated fatty acid uptake by the brain

The presence of large amounts of long chain-polyunsaturated fatty acids (PUFA) in the brain implies an exogenous intake of unsaturated fatty acids, either as essential fatty acids, or in the form of higher homologues resulting from hepatic metabolism. To determine the influence of the diet upon the potential availability of polyunsaturated fatty acids to the brain, four different diets were used with comparable amounts of 18:2 n-6, but variable amounts of 18:3 n-3 (0.2, 1, 2 and 9%). These diets were administered to female rats from the day of mating and during the periods of gestation and lactation. Fifteen days after birth suckling animals were killed and the fatty acid distribution was studied in the serum in two lipoprotein classes (VLDL-LDL and HDL). On the whole, an increase in dietary 18:3 n-3 resulted in an increase of polyunsaturated fatty acids of the n-3 series and a decrease in fatty acids of the n-6 series. The modification chiefly concerned the terminal fatty acids in each series (22:5 n-6 and 22:6 n-3). It is noteworthy that the influence of exogenous 18:3 n-3 upon the 20:4 n-6 content of lipoproteins was not significant below 2% of 18:3 n-3 intake, a level that we have previously shown to be both necessary and sufficient to satisfy the requirements of the brain for fatty acids of the n-3 series. In the liver, the intermediary metabolism ensures an important release of long-chain polyunsaturated fatty acids, which may help to satisfy the lipid requirements of the brain.     

Effect of dietary alpha-linolenic fatty acid derived from chia when fed as ground seed, whole seed and oil on lipid content and fatty acid composition of rat plasma

Coronary heart disease (CHD) is the most common cause of death in the Western world. In both the USA and the EU it accounts for over 600,000 deaths yearly. Early data showing the benefits n-3 fatty acids provide in preventing CHD disease were obtained using 20:5n-3 and 22:6n-3 fatty acids derived from fish. Recently, however, it has been shown that reduced risks of CHD and other cardiovascular diseases are found with 18:3n-3 fatty acid as well. To determine if 18:3n-3 fatty acids positively influence plasma composition, 32 male Wistar rats were fed ad libitum four isocaloric diets with the energy derived from corn oil (T(1)), whole chia seed (T(2)), ground chia seed (T(3)), or chia oil (T(4)) for 30 days. At the end of the feeding period the rats were sacrificed, and blood samples were analyzed to determine serum CHOL, HDL, LDL, TG content, hemogram, and fatty acid composition. Chia decreased serum TG content and increased HDL content. Only with the T(2) diet was TG significantly (p < 0.05) lower, and only with the T(3) diet was HDL significantly (p < 0.05) higher, than the control diet. Chia significantly (p < 0.05) increased the 18:3n-3, 20:5n-3 and 22:6n-3 plasma contents compared to the control diet, with no significant (p < 0.05) difference among chia diets detected. Significant (p < 0.05) improvement in n-6/n-3 fatty acid ratio was observed for all chia diets when compared to the control.     

Development of alcoholic fatty liver and fibrosis in rhesus monkeys fed a low n-3 fatty acid diet

BACKGROUND: The amount and type of dietary fat seem to be important factors that modulate the development of alcohol-induced liver steatosis and fibrosis. Various alcohol-feeding studies in animals have been used to model some of the symptoms that occur in liver disease in humans. METHODS: Rhesus monkeys (Macaca mulatta) were maintained on a diet that had a very low concentration of alpha-linolenic acid and were given free access to an artificially sweetened 7% ethanol solution. Control and ethanol-consuming animals were maintained on a diet in which the linoleate content was adequate (1.4% of energy); however, alpha-linoleate represented only 0.08% of energy. Liver specimens were obtained, and the fatty acid composition of the liver phospholipids, cholesterol esters, and triglycerides of the two groups were compared at 5 years and histopathology of tissue samples were compared at 3 and 5 years. RESULTS: The mean consumption of ethanol for this group over a 5-year period was 2.4 g.kg.day. As a consequence of the ethanol-dietary treatment, there were significantly lower concentrations of several polyunsaturated fatty acids in the liver phospholipids of the alcohol-treated group, including arachidonic acid and most of the n-3 fatty acids and particularly docosahexaenoic acid, when compared with dietary controls. Liver specimens from animals in the ethanol group at 5 years showed a marked degree of steatosis, both focal and diffuse cellular necrosis, and an increase in the development of fibrosis compared with specimens obtained at 3 years and with those from dietary controls, in which there was no evidence of fibrotic lesions. CONCLUSION: These findings suggest that the advancement of ethanol-induced liver disease in rhesus monkeys may be modulated by the amount and type of dietary essential fatty acids and that a marginal intake of n-3 fatty acids may be a permissive factor in the development of liver disease in primates.     

Retinal function in rats and guinea-pigs reared on diets low in essential fatty acids and supplemented with linoleic or linolenic acids

Rats were reared into a third generation on diets deficient in essential fatty acids supplemented with linoleic acid (18:2 n-6) or linolenic acid (18:3 n-3) with the object of depleting the retina of n-6 or n-3 fatty acids. In the rats fed 18:2 n-6 the percentage by weight of 22:6 n-3 in retinal fatty acids fell from 22.5 to 8.5% in first-generation animals but then remained unchanged in second and third generations. There was no difference in b-wave amplitudes of the electroretinogram between the rats fed 18:2 n-6 and those fed 18:3 n-3. In guinea-pigs fed purified diets low in 18:3 n-3 the percentage by weight of 22:6 n-3 in retinas fell from 8 to less than 0.5% by the third generation. However, there were no statistical differences in the b-wave amplitudes between these animals and those reared on a commercial diet. It is concluded that if n-3 fatty acids are involved in retinal function their role is too subtle to be detected by standard electroretinographic techniques.     

Effects of introducing linseed in livestock diet on blood fatty acid composition of consumers of animal products

Reducing the ratio between essential fatty acids: C18:2 n-6/C18:3 n-3 down to 5 is recommended by Nutritional Guidelines. We studied the fatty acid (FA) changes in consumers' plasma following changes in livestock diet. First, a zootechnical study introduced 5% of extruded linseed into the diet of livestock to replace other oleaginous ingredients, and on an iso-nutritional values basis. The products from linseed-fed animals contained more n-3 fatty acids (precursor alpha-linolenic and derivatives obtained by elongations and desaturations) than control animal products (issued from animals fed without linseed), and more conjugated linoleic acids (CLA). The n-6/n-3 ratio was reduced by 54% in butter, 60% in meat and 86% in eggs. Following this, a double-blind, randomised, cross-over clinical study involving 75 healthy volunteers compared plasma and erythrocyte FA profiles in consumers of animal products (from livestock fed the linseed diet or from livestock fed standard diet). It showed modifications in the FA composition of the experimental human regimen with more C18:3 n-3 (1.65 vs. 0.75 g/day), and more n-3 derivatives. The C18:2 n-6/C18:3 n-3 ratio decreased (7 vs. 15). In volunteers' plasma, C18:3 n-3 increased in the essay group (0.93 vs. 0.44% of the FA), so did n-3 derivatives and CLA. The n-6/n-3 ratio decreased from 14.3 to 10.2. In erythrocytes, C20:5 n-3 increased in the essay group (0.59 vs. 0.45%) and so did C22:6 n-3. The n-6/n-3 ratio decreased in parallel from 4.2 to 3.8. Without any changes in consumers' eating habits, foodstuffs from animals fed linseed diets induced significant modifications of human plasma and erythrocyte fatty acid composition (comparable to that noted under the 'Cretan' diet) and a sharp increase in CLA.     

Metabolism of long-chain polyunsaturated fatty acids in rat kidney cells

The metabolism of long-chain polyunsaturated fatty acids is characterized in tissues, such as liver and heart, especially from studies based on isolated cells incubated with radiolabelled fatty acid substrates. Differently, only little is known about the metabolism of fatty acids in the kidney. It is controversial whether the kidney possesses the ability to desaturate long-chain fatty acids or whether kidney cells are dependent on performed polyunsaturated fatty acids transported from the liver. In this study we used isolated rat kidney cells obtained by a perfusion technique. The cells were incubated with [1-(14)C]-labelled 18:3(n-3) or 20:3(n-6) fatty acids which were incorporated into complex lipids or desaturated/elongated. The lipids were separated by thin-layer chromatography and high-performance liquid chromatography. The present study shows that isolated kidney cells take up and esterify labelled long-chain polyunsaturated fatty acids in a time- and concentration-dependent manner. We have also demonstrated that isolated rat kidney cells only to a minor extent Delta6-desaturate labelled 18:3(n-3) to 18:4 (n-3). Conversely, the Delta 5-desaturation of 20:3(n-6) to 20:4(n-6) is far more active. It may thus be concluded that the kidney, at least in part, must obtain its C(20) and C(22) fatty acids from the circulation, while the active Delta5-desaturase suggests that preformed C(20) fatty acids can be converted to more unsaturated homologues in the kidney.     

Effect of the linolenic acid content of the mother's diet on the polyunsaturated fatty acid composition of subcellular fractions in brain development in the rat

In order to determine precisely the respective roles of linolenic acid and linoleic acid in the maternal diet on rat brain subcellular fractions during development, we used two diets with different percentages of linolenic acid (18:3 n-3). The animals were fed peanut oil (group A) or soybean oil (group B) during pregnancy and throughout lactation. Nature and amount of essential fatty acids had no incidence on saturated and monounsaturated fatty acid distributions in myelin, synaptosomal, mitochondrial and microsomal fractions. In adult rats, all subcellular fractions are marked by an increase of n-3 fatty acid and a decrease of n-6 fatty acid levels in group B compared to group A. In 15-day-old animals, on the contrary, only the synaptosomal fractions are significantly affected by the diet. Independent of diet, brain development is marked by a decrease of n-6 fatty acids in all subcellular fractions; on the other hand, the n-3 fatty acid level is increased in the synaptosomal and mitochondrial fractions, and decrease in the myelin and microsomal fractions. The sum of (n-3 + n-6) fatty acids remains constant in group B and in group A in all subcellular fractions. Finally, under our experimental conditions, we found no marked effect of diet composition upon linoleic acid conversion to arachidonic acid; only the delta 4-7-10-13-16-docosapentaenoic acid (22:5 n-6) level decreased in group B. delta 7-10-13-16-19-Docosapentaenoic acid (22:5 n-3) seemed to be a better substrate for delta 4 desaturase than delta 7-10-13-16-docosatetraenoic acid (22:4 n-6).     

Arachidonic and docosahexaenoic acids are biosynthesized from their 18-carbon precursors in human infants.

It is becoming clear that an adequate level of long-chain highly unsaturated fatty acids in the nervous system is required for optimal function and development; however, the ability of infants to biosynthesize long-chain fatty acids is unknown. This study explores the capacity of human infants to convert 18-carbon essential fatty acids to their elongated and desaturated forms, in vivo. A newly developed gas chromatography/negative chemical ionization/mass spectrometry method employing 2H-labeled essential fatty acids allowed assessment of this in vivo conversion with very high sensitivity and selectivity. Our results demonstrate that human infants have the capacity to convert dietary essential fatty acids administered enterally as 2H-labeled ethyl esters to their longer-chain derivatives, transport them to plasma, and incorporate them into membrane lipids. The in vivo conversion of linoleic acid (18:2n6) to arachidonic acid (20:4n6) is demonstrated in human beings. All elongases/desaturases necessary for the conversion of linolenic acid (18:3n3) to docosahexaenoic acid (22:6n3) are also active in the first week after birth. Although the absolute amounts of n-3 fatty acid metabolites accumulated in plasma are greater than those of the n-6 family, estimates of the endogenous pools of 18:2n6 and 18:3n3 indicate that n-6 fatty acid conversion rates are greater than those of the n-3 family. While these data clearly demonstrate the capability of infants to biosynthesize 22:6n3, a lipid that is required for optimal neural development, the amounts produced in vivo from 18:3n3 may be inadequate to support the 22:6n3 level observed in breast-fed infants.     

Effect of dietary elaidic versus vaccenic acid on blood and liver lipids in the hamster.

Male hamsters (30 per group) were fed five different semi-purified diets ad libitum. The diets, containing 30% of energy (en%) as fat, differed in their dietary fat composition (specified fatty acids exchanged at 10 en%) and were fed for 4 weeks. The five fatty acids compared in mixed triglycerides were elaidic acid (C18:1 9t), vaccenic acid (C18:1 11t), their cis-counterpart oleic acid (C18:1 9c), medium-chain fatty acids (MCFA; C8:0 and C10:0), and palmitic acid (C16:0). Compared with oleic acid, dietary MCFA and palmitic acid tended to increase blood cholesterol levels in the hamsters. The effect of elaidic and vaccenic acid on blood cholesterol did not differ from that of oleic acid. When elaidic acid and vaccenic acids were compared directly, the ratio of LDL/HDL-cholesterol in plasma was significantly higher in hamsters fed vaccenic acid than in those fed elaidic acid, and elaidic acid was incorporated at low levels, but more efficiently than vaccenic acid at the sn-2 position of platelet phospholipids. Biological consequences of this low incorporation are considered unlikely as levels of arachidonic acid (C20:4 n-6) and docosohexaenoic acid (C22:6 n-3) in the platelet phospholipids of all dietary groups did not differ. With respect to the effect on the LDL/HDL-cholesterol ratio, elaidic acid may be preferable to vaccenic acid. We conclude that this animal study does not provide evidence for the suggestion, based on epidemiological observations, that elaidic acid would be more detrimental to cardiovascular risk than vaccenic acid.     

Early growth restriction, membrane phospholipid fatty acid composition, and insulin sensitivity

An animal model of protein restriction during pregnancy and lactation with subsequent dietary fatty acid manipulation was used to investigate the association between poor early growth, defective unsaturated fatty acid handling, and later disease. Both control and early growth-restricted animals fed a diet rich in saturated fatty acids showed a doubling of the plasma insulin levels as well as a reduced degree of unsaturation in liver and skeletal muscle membrane phospholipids compared with animals fed diets rich in unsaturated fatty acids. The skeletal muscle of early growth-restricted animals weaned onto a saturated fat diet had reduced proportions of 22:6n-3 and increased proportions of 18:1n-9. This reduction in 22:6n-3 is similar to that observed in Pima Indians, a population with a high prevalence of type 2 diabetes.     

Incorporation, distribution, and metabolism of polyunsaturated fatty acids in the pineal gland of rainbow trout (Oncorhynchus mykiss) in vitro

The in vitro incorporation of 3H-radio-labeled arachidonic (20:4n-6) and docosahexaenoic (22:6n-3) acids by the photosensitive trout pineal gland was visualized using photon and electron microscopy. After 6 hr of incubation, 3H-20:4n-6 appeared distributed in photoreceptors, as well as in glial cells, whereas 3H-22:6n-3 was preferentially taken up by photoreceptors, mainly in the apical part (including the photoreceptive outer segment). Radioactivity was mainly seen over membranes of glia when the incorporation of 3H-20:4n-6 was followed by 12-18 hr of chase. We also report differences in the incorporation of 14C-radio-labeled linoleic (18:2n-6), linolenic (18:3n-3), eicosapentenoic (20:5n-3), 20:4n-6, and 22:6n-3 acids into the lipids in glands cultured under different lighting regimes. Phosphatidylcholine and triacylglycerols contained most of the radio-labeled polyunsaturated fatty acids (PUFA) incorporated. The proportion of incorporated 20:4n-6 recovered in phosphatidylinositol was always significantly higher than that found with the other PUFA. At least 10% of radioactivity from each incorporated substrate, except 22:6n-3, was recovered in elongation products. It is concluded that the pineal gland of the trout can assimilate exogenous PUFA into cellular lipids in vitro, in a manner consistent with our previous in vivo findings. In terms of lipid composition, the trout pineal gland resembles more the vertebrate retina than the rat pineal gland. This might be related to the loss of direct photosensitivity of the mammalian pineal. Together, the differences reported herein between 22:6n-3 and 20:4n-6 suggest the former plays an important role in the phototransduction process, whereas the latter might be more specifically involved in the production of phosphoinositide-derived second messengers.     

The antihypertensive effect of dietary supplementation with a 6-desaturated essential fatty acid concentrate as compared with sunflower seed oil.

There is increasing evidence that the type of fat in the diet may play a role in the control of blood pressure and development of hypertension. The purpose of the present study was to investigate the effect of a concentrated preparation of the 6-desaturated essential fatty acids gamma-linolenic acid (C18:3n-6), eicosapentaenoic acid (C20:5n-3) and docosahexaenoic acid (C22:6n-3) on individuals with raised BP. Eighteen volunteers from our College staff with elevated BP on several occasions but otherwise healthy, were divided into two groups following a two-week baseline period. One group received 4g sunflower seed oil daily and the other 4g of an oil preparation rich in C18:3n-6, C20:5n-3 and C22:6n-3 for six weeks. Major measurements included BP and fatty acids in phospholipids and cholesteryl esters. Dietary intakes and urinary fluid and electrolyte excretion were also monitored during baseline and intervention periods. The subjects' office diastolic BP showed a significantly greater effect of the concentrate over the sunflower seed oil, both overall (P = 0.03) and in interaction with time (P = 0.012). Fatty acids in plasma cholesteryl esters underwent mild alterations following the administration of the concentrate. There were no important changes in nutrient intakes or in sodium, potassium and fluid excretion during the trial period.     

Altered levels of n-6/n-3 fatty acids in rat heart and storage fat following variable dietary intake of linoleic acid

Fat-supplemented dies enriched with linoleic acid by the addition of 12% w/w sunflower seed oil or proportionally reduced in linoleic acid by addition of 12% mutton fat were fed to rats for 18 months before the fatty acid composition of perirenal storage fat and myocardial membranes (phospholipids) was determined. Although the fatty acid composition of perirenal fat generally reflected that of the diet, there was an inverse relationship between the consumption of n-6 and the deposition of n-9 fatty acids. In addition, enhanced deposition of oleic acid (18:1, n-9) appears to be related to the dietary intake of stearic acid (18:0). In contrast, in myocardial membranes the n-3 polyunsaturated fatty acids are found to be increased when the intake of n-6 polyunsaturated fatty acids is reduced. This is particularly evident for docosahexaenoic acid (22:6, n-3) which is significantly increased in phosphatidylcholine, phosphatidylethanolamine, and diphosphatidylglycerol fractions of myocardial membranes, when the mutton fat diet was fed. After feeding the sunflower seed oil diet, the increased consumption of linoleic acid produced only small changes in the 18:2, n-6 content of cardiac phosphatidylcholine and phosphatidylethanolamine. These major classes of membrane phospholipids also showed only small increases in 20:4, n-6. In diphosphatidylglycerol, increased 18:2, n-6 also followed increased dietary intake, but this was not accompanied by increased 20:4, n-6. These changes in myocardial phospholipid fatty acid composition are similar to those observed after short-term feeding reported previously and confirm that changes in dietary n-6/n-3 fatty acid intake affect the fatty acid composition of both myocardial membranes and storage fat. These changes persist for the duration of the feeding period.     

Familial aggregation of red blood cell membrane fatty acid composition: the Kibbutzim Family Study

The fatty acid composition of membranes plays an important role in health and diseases. Whether genetic factors play a role in interindividual variability in membrane fatty acid levels has received limited attention. Using variance decomposition methods, we estimated the heritability of red blood cell (RBC) membrane fatty acids in an unselected population sample of 80 families (205 male and 212 female subjects) living in kibbutz settlements in Israel. Fatty acid levels were measured by gas chromatography. We estimated that polygenes explained 40% to 70% of the sex- and age-adjusted interindividual variability in all RBC fatty acids: saturated, monounsaturated, and polyunsaturated. The heritability estimates remained very similar after further adjustment for smoking, alcohol consumption, physical activity, lipoproteins, body mass index, waist to hip ratio, education, and religiosity. In bivariate genetic analyses, we observed positive genetic correlations for the fatty acid pairs 20:4n6-22:6n3 and 20:5n3-22:6n3, and negative genetic correlations for the pairs 16:0-20:4n6, 16:0-22:6n3, 18:1n9-20:3n6, 18:2n6-20:4n6, 18:2n6-24:0, and 20:3n6-20:4n6, suggesting that shared effects of the same sets of loci account for 12% to 30% of the additive genetic variance in these pairs of fatty acids. This study suggests a considerable polygenic component for all RBC membrane fatty acids and provides evidence that shared genetic effects account for the additive genetic variance in various fatty acid pairs. Future studies are needed to map the genes underlying the interindividual variation in these inherited phenotypes.     

The role of n-3 polyunsaturated fatty acids in brain: modulation of rat brain gene expression by dietary n-3 fatty acids

Rats were fed either a high linolenic acid (perilla oil) or high eicosapentaenoic + docosahexaenoic acid (fish oil) diet (8%), and the fatty acid and molecular species composition of ethanolamine phosphoglycerides was determined. Gene expression pattern resulting from the feeding of n-3 fatty acids also was studied. Perilla oil feeding, in contrast to fish oil feeding, was not reflected in total fatty acid composition of ethanolamine phosphoglycerides. Levels of the alkenylacyl subclass of ethanolamine phosphoglycerides increased in response to feeding. Similarly, levels of diacyl phosphatidylethanolamine molecular species containing docosahexaenoic acid (18:0/22:6) were higher in perilla-fed or fish oil-fed rat brains whereas those in ethanolamine plasmalogens remained unchanged. Because plasmalogen levels in the brains of rats fed a n-3 fatty acid-enriched diet increased, it is plausible, however, that docosahexaenoic acid taken up from the food or formed from linolenic acid was deposited in this phospholipid subclass. Using cDNA microarrays, 55 genes were found to be overexpressed and 47 were suppressed relative to controls by both dietary regimens. The altered genes included those controlling synaptic plasticity, cytosceleton and membrane association, signal transduction, ion channel formation, energy metabolism, and regulatory proteins. This effect seems to be independent of the chain length of fatty acids, but the n-3 structure appears to be important. Because n-3 polyunsaturated fatty acids have been shown to play an important role in maintaining normal mental functions and docosahexaenoic acid-containing ethanolamine phosphoglyceride (18:0/22:6) molecular species accumulated in response to n-3 fatty acid feeding, a casual relationship between the two events can be surmised.     

Effects of dietary restriction on age-related changes in the phospholipid fatty acid composition of various rat tissues

BACKGROUND AND AIMS: Polyunsaturated fatty acids (PUFAs) are essential components of the cell lipid bilayer and are involved in membrane fluidity and normal functioning, but they are vulnerable to free radical attack. Given the role of oxidative stress in the aging process, age-related changes in phospholipid fatty acid (PLFA) composition in rat liver, kidney and heart were assessed in 3-, 12- and 24-month-old rats fed either ad libitum but only every other day, or daily but only 60% of the quantity normally consumed by age-matched controls. METHODS: Lipids were extracted and phospholipids (PLs) were separated using the solid phase extraction technique, then transesterified and assayed by gas-liquid chromatography. RESULTS: Saturated fatty acids (FAs) did not change significantly with age; mono- and bi-unsaturated FAs decreased in the liver and heart, and the ratio of the former to the latter increased in the liver, kidney and heart. PUFAs increased in the liver and heart. As regards individual FAs, 20:1(n-9) decreased in all organs, 14:1 and 18:1(n-7) increased in the kidney and heart, 18:1(n-9) increased in the kidney, 20:2(n-6), 18:2(n-6) and 22:5(n-3) decreased in the liver and heart, 20:3(n-6) decreased in the kidney and increased in the heart. The most abundant PUFAs, 20:4(n-6) and 22:6(n-3), either remained the same or increased with age. The N-9 family increased in the kidney, the N-7 family increased in the kidney and heart, the N-6 family decreased in all three organs, and the N-3 family increased in the liver and kidney. Dietary restriction (DR) significantly counteracted most of these changes, but changes in some FAs [20:2(n-6) in the heart] were magnified by DR and may not be age-related. CONCLUSIONS: Most age-related changes (that occurred in the rat liver, kidney and heart and were counteracted by the two different types of DR) may be involved in the mechanism of aging.