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

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

Heart phospholipid content and fatty acid composition in the rat after feeding different lipid supplemented diets.

The heart phospholipid content and fatty acid composition were examined in adult rats after four weeks of feeding lipid-supplemented diets (20 g % w/w) containing sunflower oil-lard (1:1) mixture (SL group) or margarine (M group). Our results showed a decreased cardiolipin content and distribution in both experimental groups and an increased lysophosphatidylcholine and phosphatidylcholine content and distribution in the SL group with a tendency to lower phosphatidylcholine/phospatidylethanolamine ratio in both experimental groups. In the SL group, the content of saturated fatty acids was higher and that of monounsaturated fatty acids was lower than in the control group. The M group showed inverse results. The content of saturated fatty acids was lower and that of monounsaturated was higher than in the control group. Polyunsaturated n-6 fatty acids were decreased in both experimental groups and n-3 fatty acids were increased in the M group. Feeding lipid-supplemented diets reduced n-6/n-3 and 20:4/22:6 ratios in the M group. The polyunsaturated/saturated fatty acid ratio was lower in the SL and higher in indicating the M group than in the control group. Our results are in agreement with the other reports indicating that the heart is sensitive to diet-induced lipid alterations.     

Alteration of α-Tocopherol Content in the Developing and Aging Peripheral Nervous System: Persistence of High Correlations with Total and Specific (n-6) Polyunsaturated Fatty Acids

In contrast to brain, the sciatic nerve concentration of vitamin E in rats increased rapidly during the postnatal period (approximately fivefold between days 1 and 8), then decreased dramatically (about twofold between days 8 and 30), and further decreased slowly between days 30 and 60 and remained constant up to 2 years. Although the sciatic nerve concentration of vitamin E decreased by 58% between days 8 and 30, the concentration of vitamin E in serum presented a marked decrease (approximately 75%). The vitamin E concentrations varied in a similar pattern in whole sciatic nerve and in endoneurium and showed a very close correlation (r = 0.94). The age-related changes in fatty acid concentration of the endoneurial fraction of the sciatic nerve were characterized by a large increase in content of saturated and monounsaturated fatty acids up to 6 months (twofold for saturated and fourfold for monounsaturated fatty acids). Then, up to 24 months, the amount of these fatty acids decreased very slowly. The content of (n-6) polyunsaturated fatty acids (PUFAs) decreased rapidly up to 1 year and slowly afterward. In contrast, during development the amount of (n-3) PUFA was relatively stable and decreased during aging. A highly significant correlation between vitamin E and (n-6) PUFA [18:2(n-6), 20:4(n-6), and total (n-6)] was observed but not between (n-3) PUFA and vitamin E. It is suggested that there may be a relationship between vitamin E and (n-6) PUFA in the PNS membranes during development and aging.     

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

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

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

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

Changes in liver microsome lipids and plasma fatty acids induced by dietary orotate in the weanling rat.

1. Dietary orotate produced a decrease in total plasma fatty acids which was reflected in low values of saturated, monounsaturated and polyunsaturated fatty acids longer than 18 carbon atoms of the n-6 series. The relative content of saturated fatty acids in microsomes of animals fed orotate was also decreased. 2. Rat liver delta-9 desaturase activity was lower in the group fed orotate. However, delta-6 desaturase activity did not show significant differences between the groups. 3. Microsomal cholesterol content was lower in rats fed orotate than in controls but phospholipid phosphorus contents were similar. These results suggest a direct effect of dietary orotate on the key enzymes which regulates cholesterol liver metabolism.     

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.     

Dietary effects on brain fatty acid composition: the reversibility of n-3 fatty acid deficiency and turnover of docosahexaenoic acid in the brain, erythrocytes, and plasma of rhesus monkeys

Rhesus monkeys given pre- and postnatal diets deficient in n-3 essential fatty acids develop low levels of docosahexaenoic acid (22:6 n-3, DHA) in the cerebral cortex and retina and impaired visual function. This highly polyunsaturated fatty acid is an important component of retinal photoreceptors and brain synaptic membranes. To study the turnover of polyunsaturated fatty acids in the brain and the reversibility of n-3 fatty acid deficiency, we fed five deficient juvenile rhesus monkeys a fish oil diet rich in DHA and other n-3 fatty acids for up to 129 weeks. The results of serial biopsy samples of the cerebral cortex indicated that the changes of brain fatty acid composition began as early as 1 week after fish oil feeding and stabilized at 12 weeks. The DHA content of the phosphatidylethanolamine of the frontal cortex increased progressively from 3.9 +/- 1.2 to 28.4 +/- 1.7 percent of total fatty acids. The n-6 fatty acid, 22:5, abnormally high in the cerebral cortex of n-3 deficient monkeys, decreased reciprocally from 16.2 +/- 3.1 to 1.6 +/- 0.4%. The half-life (t 1/2) of DHA in brain phosphatidylethanolamine was estimated to be 21 days. The fatty acids of other phospholipids in the brain (phosphatidylcholine, -serine, and -inositol) showed similar changes. The DHA content of plasma and erythrocyte phospholipids also increased greatly, with estimated half-lives of 29 and 21 days, respectively. We conclude that monkey cerebral cortex with an abnormal fatty acid composition produced by dietary n-3 fatty acid deficiency has a remarkable capacity to change its fatty acid content after dietary fish oil, both to increase 22:6 n-3 and to decrease 22:5 n-6 fatty acids. The biochemical evidence of n-3 fatty acid deficiency was completely corrected. These data imply a greater lability of the fatty acids of the phospholipids of the cerebral cortex than has been hitherto appreciated.     

Effect of dietary fish oil (active EPA-30) on liver phospholipids in young and aged rats.

We explored the uses of fish oil (active EPA-30) as a source of eicosapentaenate (EPA; 20:5 n-3), to young and old rats. We treated three subgroups of rats each comprising 20 young or old rats, respectively. The first group was kept on the basal ration (lab-pellet) as control diet, the second group was fed semi-purified diets contained 5% pig-fat (n-3 fatty acids deficient diet). The third group was fed a modified diet in which 50% of pig-fat was replaced by active EPA-30. Livers of young rats fed pig-fat had a drastic decrease in the amount of phosphatidylethanolamine (PE) and omega-3 polyunsaturated fatty acids (EPA, 20:5 n-3 and docosahexaenoic, DHA, 22:6 n-3) and compensatory increase of phosphatidylcholine, saturated fatty acids and n-6 polyunsaturated fatty acids in the liver phospholipids. In contrast, the liver of young rats fed active EPA-30 had large amounts of PE and concomitant enrichment in polyunsaturated fatty acids. The liver of old rats, fed on active EPA-30 supplemented diet had lower amounts of PE and there were no significant changes in the phospholipid fatty acid composition.     

Plant-based diet, serum fatty acid profile, and free radicals in postmenopausal women: the diet and androgens (DIANA) randomized trial

High calorie and fat consumption and the production of free radicals are two major mechanistic pathways between diet and disease. In this study we evaluated the effect of a plant-based diet poor in animal fat and rich in (n-3) fatty acids on fatty acids of serum phospholipids and on the production of reactive oxygen metabolites (ROMs). One hundred and four healthy female postmenopausal volunteers were recruited and randomized to a dietary intervention or a control group. Dietary intervention included a program of food education and biweekly common meals for 18 weeks. When the intervention and control groups were compared, it was seen that dietary intervention resulted in a significant reduction of saturated fatty acids (-1.5%) and a significant increase in (n-3) fatty acids (+20.6%), in particular docosahexaenoic acid (+24.8%). We observed that arachidonic acid decreased (-7.7%), while (n-6) fatty acids did not, and the (n-3)/(n-6) polyunsaturated ratio increased significantly (+24.1%). As expected, ROMs decreased significantly in the intervention group (-6%). The results indicated that a plant-based diet can improve the serum fatty acid profile and decrease ROMs production. These results suggest that a plant-based diet may reduce the body's exposure to oxidative stress.     

Inverse modifications of heart and liver alpha-tocopherol status by various dietary n-6/n-3 polyunsaturated fatty acid ratios

The effect of dietary n-6/n-3 fatty acid ratio on alpha-tocopherol homeostasis was investigated in rats. Animals were fed diets containing fat (17% w/w) in which the n-6/n-3 ratio varied from 50 to 0.8. This was achieved by combining corn oil, fish oil, and lard. The polyunsaturated to saturated ratio and total alpha-tocopherol remained constant in all diets. Results showed that enrichment of n-3 polyunsaturated fatty acids in the diet, even at a low amount (3.9% w/w), resulted in a dramatic reduction of blood alpha-tocopherol concentration, which, in fact, is the result of a decrease in plasma lipids, since the alpha-tocopherol to total lipids ratio was not significantly altered. The most striking effect observed was a considerable alpha-tocopherol enrichment (x 4) of the heart as its membranes became enriched with n-3 polyunsaturated fatty acids. This process appeared even with a low amount of fish oil (3.9% w/w) added to the diet. Accordingly, a strong positive correlation was found between heart alpha-tocopherol and docosahexaenoic acid (r = 0.86) or docosahexaenoic acid plus eicosapentaenoic acid levels (r = 0.84). Conversely, the liver alpha-tocopherol level dropped dramatically when n-3 polyunsaturated fatty acids were gradually added to the diet. It is concluded that fish oil intake dramatically alters the alpha-tocopherol homeostasis in rats.     

EFFECTS OF DIFFERENT DIETARY LEVELS OF ESSENTIAL FATTY ACIDS ON THE FATTY ACID COMPOSITION OF ETHANOLAMINE PHOSPHOGLYCERIDES IN MYELIN AND SYNAPTOSOMAL PLASMA MEMBRANES

Abstract— Three dietary levels of essential fatty acids (EFA), 3 0, 0 75 and 0 07 calorie-% were fed to rats for two generations or more. Myelin was isolated at the ages of 18, 30, 45 and 120 days and synaptosomal plasma membranes at 18, 30 and 45 days. No difference was found in the lipid composition between the dietary groups in either subcellular fraction. The fatty acid patterns of ethanolamine phosphoglycerides (EPG) were analysed. In myelin the proportions of 18:1 and 20:1 increased with age, while those of 20:4 (n-6) and 22:6 (n-3) decreased, in synaptosomal plasma membranes the proportions of 20:4 (n-6) decreased with age, but 22:6 (n-3) increased and the sum of the polyunsaturated fatty acids was constant. At no age were significant differences found between the proportions of saturated and monounsaturated fatty acids, in either myelin or the synaptosomal plasma membrane fraction, when the different dietary groups were compared. In myelin from rats fed 007 calorie-% EFA the proportions of 20:4 (n-6) were slightly lower than in the two other groups, while those of 22 6 (n-3) were considerably lower. The synaptosomal plasma membranes fraction of rats fed O-07 calorie-% EFA had equal or slightly larger amounts of 20:4 (n-6) than in the two other groups, while 22:6 (n-3) was considerably smaller. In both subcellular fractions the decreased proportion of fatty acids of linoleic and linolenic acid series was compensated for by an increase in 20:3 (n-9) and 22:3 (n-9). The sum of these two fatty acids was equal in the EPG of myelin and synaptosomal plasma membranes at 18 days of age. At 30 and 45 days of age a lower value was found in the synaptosomal plasma membranes, while in the myelin fraction a slight decrease was found only at 120 days of age.     

不同类型脂肪酸对SD大鼠血清脂肪酸及胰岛素抵抗的影响

目的分析中链饱和脂肪酸（MC-SFA,MCF组）、长链饱和脂肪酸（LC-SFA,LCF组）、n-6多不饱和脂肪酸（n-6 PUFA,SUF组）和n-3多不饱和脂肪酸（n-3 PUFA,TUF组）四种脂肪酸对大鼠血清脂肪酸及胰岛素抵抗的影响。方法雄性SD大鼠40只随机分为5组,对照组给予普通日粮,高脂组给予脂肪热量比相同的高脂日粮。喂养10周,每18 d测定空腹血糖（GLU）、血清脂肪酸、血清胰岛素水平,根据胰岛素敏感性指数（ISI）=ln1/（FPG×FINS）评定大鼠的胰岛素敏感性。结果10周后,LCF组和SUF组大鼠体重显著高于对照组和其它高脂组;LCF组血清胰岛素显著高于对照组（P﹤0.05）;LCF组、TUF组ISI显著低于对照组（P﹤0.05）;各组间血糖无明显差异（P〉0.05）。SUF组、TUF组血清LC-SFA浓度显著低于LCF组（P﹤0.05）;TUF组血清（n-3 PUFA）显著高于对照组和其它高脂组（P﹤0.05）。结论不同类型脂肪酸的高脂饲料对SD大鼠的血清脂肪酸组成和含量有显著的影响,SD大鼠脂肪沉积及胰岛素抵抗程度随血清脂肪酸代谢作用的不同而变化。     

Fatty acid compositions of red blood cell phospholipids in children with autism

We compared the compositions of fatty acids including n-3, n-6 polyunsaturated fatty acids, trans- and cis-monounsaturated fatty acids, and saturated fatty acids in the red blood cell membranes of 40 children with autism (20 with early onset autism and 20 with developmental regression) and age-matched, 20 typically developing controls and 20 subjects with non-autistic developmental disabilities. The main findings include increased levels of eicosenoic acid (20:1n9) and erucic acid (22:1n9) in autistic subjects with developmental regression when compared with typically developing controls. In addition, an increase in 20:2n6 and a decrease in 16:1n7t were observed in children with clinical regression compared to those with early onset autism. Our results do not provide strong evidence for the hypothesis that abnormal fatty acid metabolism plays a role in the pathogenesis of autism spectrum disorder, although they suggest some metabolic or dietary abnormalities in the regressive form of autism.     

Effects on plasma lipoproteins of monounsaturated, saturated, and polyunsaturated fatty acids in the diet of African green monkeys

Work by other investigators has shown that an increase in dietary content of monounsaturated fatty acids can result in a decreased plasma low density lipoprotein (LDL) cholesterol concentration. This observation, combined with the epidemiologic evidence that monounsaturated fat-rich diets are associated with decreased rates of death from coronary heart disease, suggests that inclusion of increased amounts of mono-unsaturated fat in the diet may be beneficial. The present study was carried out in a primate model, the African green monkey, to evaluate the effects of dietary monounsaturated fat on plasma lipoprotein cholesterol endpoints. Two study periods were carried out in which the fatty acid compositions of the experimental diets were varied. All diets contained 35% of calories as fat. In the first experimental period, a mixture of fats was used to set the dietary fatty acid composition to be approximately 50-60% of the desired fatty acid, either saturated, monounsaturated, or polyunsaturated (n-6). In the second experimental period, pure fats were used (palm oil, oleic acid-rich safflower oil, and linoleic acid-rich safflower oil) to maximize the difference in fatty acid composition. The effects of the more exaggerated dietary fatty acid differences of period 2 were similar to those that have been reported in humans. For the group fed the diet enriched in monounsaturated fat compared to saturated fat, whole plasma and LDL cholesterol concentrations were significantly lower while high density lipoprotein (HDL) cholesterol concentrations were not affected. For the group fed the diet enriched in polyunsaturated fat compared to saturated fat, both LDL and HDL cholesterol concentrations were significantly lower than in the group fed saturated fat. LDL cholesterol concentrations were comparable in the monounsaturated and polyunsaturated fat groups and the percentage of cholesterol in LDL was lowest in the monounsaturated fat fed group. Trends were similar for the mixed fat diets, although no statistically significant differences in plasma lipoprotein endpoints could be attributed to monounsaturated fatty acids in this dietary comparison. Since effects on plasma lipoproteins similar to those seen in humans were identified in this primate model, relevant mechanisms for the effects of dietary fatty acids on lipoprotein endpoints related to coronary artery atherosclerosis, per se, can subsequently be examined.     

Myogenic differentiation and lipid-raft composition of L6 skeletal muscle cells are modulated by PUFAs

Lipid composition and fatty acid analysis of the major classes of membrane phospholipids were determined during myogenic differentiation of L6 skeletal muscle cells. The cholesterol to glycerophospholipids ratio decreased during differentiation, both in total (TM) and detergent-resistant membranes (DRM). Analyses of the membrane lipids showed that differentiation had a major impact on the molecular composition of glycerophospholipids. A significant decrease in the concentration of saturated fatty acids was detected in glycerophospholipid classes, and to a lesser extent in sphingolipids, while the concentration of 16:1n-7, 18:1n-7 and 18:1n-9 increased. At the same time, the concentration of long polyunsaturated fatty acid chains decreased in TM and DRM glycerophospholipids, resulting in a lower saturated to unsaturated fatty acid ratio in myotubes as compared to myoblasts. Interestingly, the observed n-3/n-6 ratio was lower in differentiated cell membranes. PUFA supplementation of L6 cells led to an increase in myogenic differentiation correlated to an incorporation of added PUFAs in TM and DRM glycerophospholipids. As expected after n-3 PUFA supplementation, the n-3/n-6 ratio was clearly increased in TM and, surprisingly, this was also the case in isolated DRM. n-3 and n-6 PUFAs significantly and time-dependently increased the phosphorylation of kinase p70S6K1 during myogenic differentiation, revealing the activation of the upstream kinase mTORC1, a major regulator of cell cycle and protein translation. In contrast, PUFAs did not affect the phosphorylation of the kinase Akt, another pivotal regulator of cell metabolism. These results suggest that PUFA supplementation modified the membrane lipid composition and affected the differentiation of L6 cells.     

Polyunsaturated and saturated fatty acids-rich diets and immune tissues. 1. Fresh weight, DNA content, percentage of lipids and rate of lipogenesis from 3H2O in thymus, spleen and mesenteric lymph nodes

It has been widely reported that polyunsaturated fatty acids-rich diets (PUFA n-6) cause immunodeficiency. In this study, fresh weight, DNA and lipid content and rate of lipogenesis from 3H2O of thymus, spleen, mesenteric lymph nodes and liver were assessed in rats fed polyunsaturated (UC) or saturated (SC) fatty acids-rich chows. The results obtained indicate that both types of fatty acids caused similar increment of lipid content in the immune tissues. The rate of lipogenesis was decreased only in the thymus of (UC) rats and liver of both experimental groups as compared to control rats. The results of fresh weight and DNA content was decreased only by (UC) diet.     

Saturated, but not n-6 polyunsaturated, fatty acids induce insulin resistance: role of intramuscular accumulation of lipid metabolites.

Consumption of a Western diet rich in saturated fats is associated with obesity and insulin resistance. In some insulin-resistant phenotypes this is associated with accumulation of skeletal muscle fatty acids. We examined the effects of diets high in saturated fatty acids (Sat) or n-6 polyunsaturated fatty acids (PUFA) on skeletal muscle fatty acid metabolite accumulation and whole-body insulin sensitivity. Male Sprague-Dawley rats were fed a chow diet (16% calories from fat, Con) or a diet high (53%) in Sat or PUFA for 8 wk. Insulin sensitivity was assessed by fasting plasma glucose and insulin and glucose tolerance via an oral glucose tolerance test. Muscle ceramide and diacylglycerol (DAG) levels and triacylglycerol (TAG) fatty acids were also measured. Both high-fat diets increased plasma free fatty acid levels by 30%. Compared with Con, Sat-fed rats were insulin resistant, whereas PUFA-treated rats showed improved insulin sensitivity. Sat caused a 125% increase in muscle DAG and a small increase in TAG. Although PUFA also resulted in a small increase in DAG, the excess fatty acids were primarily directed toward TAG storage (105% above Con). Ceramide content was unaffected by either high-fat diet. To examine the effects of fatty acids on cellular lipid storage and glucose uptake in vitro, rat L6 myotubes were incubated for 5 h with saturated and polyunsaturated fatty acids. After treatment of L6 myotubes with palmitate (C16:0), the ceramide and DAG content were increased by two- and fivefold, respectively, concomitant with reduced insulin-stimulated glucose uptake. In contrast, treatment of these cells with linoleate (C18:2) did not alter DAG, ceramide levels, and glucose uptake compared with controls (no added fatty acids). Both 16:0 and 18:2 treatments increased myotube TAG levels (C18:2 vs. C16:0, P < 0.05). These results indicate that increasing dietary Sat induces insulin resistance with concomitant increases in muscle DAG. Diets rich in n-6 PUFA appear to prevent insulin resistance by directing fat into TAG, rather than other lipid metabolites.     

Docosahexaenoic acid affects insulin deficiency- and insulin resistance-induced alterations in cardiac mitochondria

The effect of docosahexaenoic acid (DHA) intake on cardiac mitochondrial function was evaluated in permeabilized fibers in insulin deficiency and insulin resistance in rats. The insulin-deficient state was obtained by streptozotocin injection 2 mo before investigations. Insulin resistance was obtained by feeding a 62% fructose diet for 3 mo. DHA was incorporated in the diet to modify the fatty acid composition of cardiac membranes, including mitochondria. Insulin deficiency decreased mitochondrial creatine kinase (mi-CK) activity and mitochondrial sensitivity to ADP. DHA intake prevented these alterations. Moreover, the insulin-deficient state significantly decreased n-3 polyunsaturated fatty acids (PUFA) and slightly increased n-6 PUFA in both cardiac and mitochondrial membranes, inducing a significant increase in the n-6-to-n-3 ratio. DHA intake maintained high myocardial and mitochondrial DHA content. Insulin deficiency also decreased glutamate- and palmitoylcarnitine-supported mitochondrial respiration, but DHA intake did not prevent these effects. In contrast, insulin resistance did not affect mi-CK activity or sensitivity to ADP. However, insulin resistance influenced the myocardial fatty acid composition with decreased n-6 and n-3 PUFA contents and increased monounsaturated fatty acid content. Only slight alterations were observed in mitochondrial fatty acid composition, and they were corrected by DHA intake. Moreover, insulin resistance decreased the glutamate-supported respiration, and DHA intake did not influence this effect. In conclusion, the impairment of cardiac mitochondrial function was more pronounced in the insulin-deficient state than in insulin resistance. The modification of fatty acid composition of cardiac and mitochondrial membranes by DHA partially prevented the mitochondrial alterations induced in the two models.     

Role of dietary oleic acid from two different sources on fatty acid composition of erythrocyte membrane and blood pressure in healthy subjects

This study has been undertaken to determine the effect of a diet enriched with olive oil (OO) and high-oleic sunflower oil (HOSO) on fatty acid composition of erythrocyte membrane phospholipids and blood pressure in healthy women. OO and HOSO were used as natural sources of monounsaturated fatty acids (MUFAs) in a random-order sequence over two 4-week periods with a 4-week washout period between both MUFA diets. HOSO diet resulted in significant increases in oleic [(18:1n-9) 8.6%, P < 0.001], eicosenoic [(20:1n-9) 33.3%, P < 0.05], arachidonic [(20:4n-6) 6.2%, P < 0.05], and docosapentaenoic [(22:5n-6) 56.0%, P < 0.001] acids, whereas OO diet besides increased the content of stearic acid [(18:0) 13.6%, P < 0.01] and long-chain polyunsaturated fatty acids (PUFAs) of the n-3 family (22:5n-3 and 22:6n-3), when compared with the baseline [a diet high in saturated fatty acids (SFAs) and low in MUFAs]. In contrast, there was a significant decrease in linoleic acid [(18:2n-6) 21.8%, P < 0.001] for both MUFA diets. Consistent with these data, dietary intake of OO significantly raised total PUFAs (7.2%, P < 0.05), the n-3 fatty acids (22.2%, P < 0.01) and the PUFAs/SFAs ratio (9.3%, P < 0.01), as well as decreased the ratio of cholesterol to phospholipids (26,1%, P < 0.001) versus HOSO-based diet. Interestingly, dietary OO, but not HOSO, was able to significantly reduce the systolic (3%, P < 0.05) and diastolic (4%, P < 0.05) blood pressures. Although both vegetable oils provided a similar content of MUFAs (mainly oleic acid), our findings rather indicate that OO has important benefits to modulate the fatty acid composition of membranes and the mechanisms involved in the regulation of blood pressure in human.