Effect of dietary alpha-linolenate/linoleate balance on endotoxin-induced hepatitis in mice

Mice were fed diets with three different ratios of alpha-linolenate (18:3n-3) to linoleate (18:2n-6), and the severity of hepatitis during endotoxic shock was compared. Dietary enrichment with alpha-linolenate increased the severity of hepatitis and the mortality induced by lipopolysaccharide (LPS) in combination with D-galactosamine (GalN). Differences in the dietary alpha-linolenate/linoleate balance were mainly reflected in the levels of arachidonate and eicosapenatenoate in liver phospholipids. Pretreatment of mice with indomethacin was found to also enhance the severity of GalN/LPS-hepatitis. This indicated that cyclooxygenase products of arachidonate may suppress the development of GalN/LPS-hepatitis. The enhancement by high alpha-linolenate diets was not observed when a lethal dose of LPS in the absence of GalN was given. Our results indicate that there are pathophysiological conditions of endotoxin-induced hepatitis under which cyclooxygenase products of arachidonate play protective roles.

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

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

Dietary alpha-linolenic acid is as effective as oleic acid and linoleic acid in lowering blood cholesterol in normolipidemic men

The effect of dietary oleic acid (OA), linoleic acid (LA), and linolenic acid (LNA) on plasma lipid metabolism was studied in eight normolipidemic men. A mixed-fat diet composed of conventional foods was fed during 6-d pre- and post-experimental periods. The same basic diet but with 75% of the fat (26% of total energy) provided by sunflower and olive; canola; soybean; and sunflower, olive, and flax oils was fed during four 18-d experimental periods. Mean plasma total cholesterol (-18%), low-density-lipoprotein-cholesterol, (-22%) and very-low-density-lipoprotein-cholesterol (-41%) concentrations were significantly (P less than 0.004) lower after the experimental diets than after the mixed-fat diet. Mean serum apolipoprotein B (-19%) and apolipoprotein A-I (-9%) concentrations were also significantly (P less than 0.0007) lower after the experimental diets. The experimental diets were equally effective in lowering total and lipoprotein cholesterol and apolipoprotein concentrations in plasma, indicating that dietary OA, LA, and LNA were equally hypocholesterolemic.

Dietary n-3 (omega-3) polyunsaturated fatty acid effects on animal tumorigenesis

Environmental variables influence the incidence and expression of disease. Dietary fat is one environmental variable that has been associated experimentally and epidemiologically with alterations in certain types of tumorigenesis. Recently, detailed biochemical analyses have shown that not all fatty acid families possess the same tumor-promoting potential. In general, diets containing high levels of the n-6 polyunsaturated fatty acids have routinely enhanced tumorigenesis in lipid sensitive carcinogen-induced and tumor transplant tumor models, whereas diets with equivalent levels of n-3 polyunsaturated fatty acids have diminished tumorigenesis. At present, there is no definitive biochemical mechanism that fully explains these observations, but several possibilities have been proposed. One of the most attractive of these hypotheses is that each polyunsaturated fatty acid family has an individual effect on eicosanoid metabolism which determines its tumor-promoting potential. Regardless of current uncertainties about mechanisms of action, however, results of numerous animal models affirm the importance of qualitative, as well as quantitative, dietary lipid differences on tumorigenesis. This knowledge strengthens the probability that further advances in our understanding of lipid-tumor interrelationships will have important preventive and therapeutic medical benefits.

Effect of dietary alpha-linolenic acid on endotoxin-induced production of tumor necrosis factor by peritoneal macrophages in horses

A study was conducted to determine whether dietary supplements with alpha-linolenic acid altered the ability of equine peritoneal macrophages to produce tumor necrosis factor (TNF) in response to endotoxin. Peritoneal macrophages were harvested from 6 healthy adult horses before and after the horses were fed a nutritionally balanced ration that contained 8% linseed oil as a source of alpha-linolenic acid. The macrophages were cultured in media containing no additives (control), endotoxin (0.5 to 50 ng/ml), or the calcium ionophore, A23187. Macrophage supernatants were collected after 6 and 24 hours' incubation and stored at -70 C. Tumor necrosis factor activity was estimated by a modified in vitro cytotoxicity bioassay, using the murine fibrosarcoma cell line, WEHI 164 clone 13. The TNF activity after 6 and 24 hours' incubation was greater in culture media of macrophages exposed to endotoxin than in media from control macrophages. For macrophages cultured in media that contained endotoxin, neither the concentration of endotoxin nor incubation time had any effect on TNF activity. Endotoxin-induced macrophage production of TNF, as determined by measurement of TNF activity, was significantly less after horses were fed the alpha-linolenic acid-rich ration for 8 weeks.

Influence of an omega-3 fatty acid-enriched ration on in vivo responses of horses to endotoxin

Because certain inflammatory processes are dependent on the fatty acid composition of the cellular membrane, dietary manipulations that replace omega-6 fatty acids with omega-3 fatty acids may modify inflammatory responses. We investigated the effect of supplemental dietary linseed oil, containing the omega-3 fatty acid, alpha-linolenic acid, on in vivo responses of horses to endotoxin. One group of horses (n = 6) was fed a control pelleted ration (0% linseed oil), and another group of horses (n = 6) was fed an 8% linseed oil pelleted ration. After 8 weeks of consuming these rations, all horses were given 0.03 micrograms of Escherichia coli 055:B5 endotoxin/kg of body weight, infused over 30 minutes. Horses were monitored over 24 hours. Compared with baseline values within each ration group, endotoxin infusion caused significant (P less than 0.05) increase in rectal temperature, heart rate, and plasma concentration of thromboxane B2, 6-keto-prostaglandin F1 alpha, and fibrinogen and significant (P less than 0.05) decrease in total WBC count. Compared with baseline values within each ration group, endotoxin infusion failed to cause significant changes in prothrombin, activated partial thromboplastin, thrombin, or whole blood recalcification times, serum concentration of fibrin degradation products, PCV, or plasma total protein concentration. Before and after endotoxin infusion, horses given the linseed oil ration had longer mean whole blood recalcification time and activated partial thromboplastin time than did horses fed the control ration.

The effect of three intravenous fat emulsions containing different concentrations of linoleic and alpha-linolenic acids on the plasma total fatty acid profile of neonates

We determined the fatty acid profile of total plasma lipids in infants who received one of three intravenous fat emulsions that differed primarily in their linoleic and alpha-linolenic acid content: (I) a safflower oil emulsion, (II) a 50:50 mixture of safflower and soybean oils, or (III) a soybean oil emulsion. After 2 weeks of fat therapy, oleic acid, expressed as a percentage of total plasma lipid fatty acids, decreased in all groups, but less so in group III (p less than 0.01). The linoleic acid percentage increased in all groups, but group I had the greatest increase (p less than 0.05). Group II patients had higher percentages of the linoleic acid metabolites, dihomo-gamma-linolenic acid (II greater than I, p less than 0.05; II greater than III, p less than 0.01) and arachidonic acid (II greater than III, p less than 0.05). Group II patients also had higher levels of alpha-linolenic acid (II greater than I, p less than 0.05) and its metabolite, eicosapentaenoic acid (II greater than I, p less than 0.05). Another alpha-linolenic acid metabolite, docosahexaenoic acid, however, increased in group III, remained stable in group II, and decreased in group I (III and II greater than I, p less than 0.05). We conclude that the content of linoleic acid and alpha-linolenic acid in intravenous fat emulsions results in statistically significant changes in the fatty acid profile of total plasma lipids in infants receiving total parenteral nutrition.

Effects of a high-linoleate and a high-alpha-linolenate diet on the learning ability of aged rats. Evidence against an autoxidation-related lipid peroxide theory of aging

This study examined the effect of dietary alpha-linolenate (18:3n-3)/linoleate (18:2n-6) balance on brain lipid compositions and brightness-discrimination learning ability in aged rats. An alpha-linolenate-rich diet with a peroxidizability index (PI) of 142 and a linoleate-rich diet with a PI value of 80 were used. Long-term feeding of these diets induced a significant difference in the n-3/n-6 ratios of highly unsaturated fatty acids in brain, but the PI values and the conjugated diene contents were similar between the two dietary groups. Rats fed the alpha-linolenate-rich diet had a longer mean survival time and an increased learning ability in senescence. These results contradict an autoxidation-related lipid peroxide theory of aging, and indicate that the aging process must also be considered in terms of n-3/n-6 balance of dietary fats.

Metabolic utilization of linoleate and alpha-linolenate in cultured Sertoli cells

1. The capacity of cultured Sertoli cells to synthesize long-chain polyunsatured fatty acids (PUFA) from the essential fatty acid (EFA) precursors 18:2 n-6 and 18:3 n-3 was tested, and the concentrations of each EFA required to obtain maximal incorporation into membrane lipids were determined. 2. The two EFA were added to the culture medium as free fatty acids complexed to albumin in a molar ratio of 12:1. 3. When the substrates were added individually, the maximal levels of biosynthesis were obtained with 0.7 micrograms/ml of 18:2 n-6 and 2 micrograms/ml of 18:3 n-3. 4. When the two EFA were added together, clear alterations in the behavior of the desaturases with regard to the n-6 and n-3 fatty acids were observed. 5. It was found that a concentration of 0.35 micrograms/ml of each EFA represented the "ideal" required level in order to ensure optimal incorporation of 22-carbon PUFA into the membrane lipids. 6. These results provide the first data on the definition of EFA requirements for Sertoli cells in culture.

Dietary alpha-linolenic acid and immunocompetence in humans

We examined the effect of dietary alpha-linolenic acid (ALA) on the indices of immunocompetence in 10 healthy free-living men (age 21-37 y) who consumed all meals at the Western Human Nutrition Research Center for 126 d. There was a stabilization period of 14 d at the start when all 10 subjects consumed basal diet (BD) and there were two intervention periods of 56 d each. Five of the subjects consumed the basal diet and the other five consumed flax-seed-oil diet (FD) during each intervention period. Feeding of FD suppressed the proliferation of peripheral blood mononuclear cells when they were cultured with phytohemagglutinin-P (P = 0.041) and concanavalin A (P = 0.054) and the delayed hypersensitivity response to seven recall antigens (NS). Concentrations of immunoglobulins in serum, C3, C4, salivary IgA, the numbers of helper cells, suppressor cells, and total T and B cells in the peripheral blood were not affected by the diets.

Effects of dietary oleic, linoleic and alpha-linolenic acids on blood pressure, serum lipids, lipoproteins and the formation of eicosanoid precursors in patients with mild essential hypertension

Forty-four male in-patients with mild essential hypertension were randomly allocated to three groups and put on diets supplemented with 60 ml/day of olive (n = 15), sunflowerseed (n = 15) or linseed oils (n = 14), respectively, for two weeks within a blind study. In the group receiving sunflowerseed oil an increase of linoleic acid in serum lipids could be observed, whereas arachidonic and eicosapentaenoic acids appeared unchanged in serum triglycerides and even significantly lower in cholesterol esters. The subjects ingesting the linseed oil-rich diet showed an increase of alpha-linolenic acid in serum lipids, whereas arachidonic and eicosapentaenoic acids remained unchanged in serum triglycerides. In cholesterol esters, however, arachidonic acid was significantly decreased and eicosapentaenoic acid appeared increased only to a low level of significance. In the group put on the olive oil-rich regimen only a significant fall of linoleic acid was obvious in serum triglycerides. The results might indicate a defective desaturation and elongation of linoleic and alpha-linolenic acids and, consequently, a slow formation of arachidonic and eicosapentaenoic acids in patients with mild essential hypertension, which should be considered in dietary studies. After the sunflowerseed oil-rich diet a significant decrease of total cholesterol, low density lipoprotein (LDL) cholesterol and the LDL/high density lipoprotein (HDL) cholesterol ratio was found. Systolic blood pressure during a psychophysiological stress test and urinary sodium excretion appeared significantly lower after the linoleic acid-rich diet. After the linseed oil-rich diet, in addition to total cholesterol, LDL cholesterol and the LDL/HDL cholesterol ratio, serum triglycerides and lecithin cholesterol acyl transferase (LCAT) activity were significantly depressed.(ABSTRACT TRUNCATED AT 250 WORDS)

n-3 fatty acids of marine origin lower systolic blood pressure and triglycerides but raise LDL cholesterol compared with n-3 and n-6 fatty acids from plants

We compared the cardiovascular risk-reduction potential of three major polyunsaturated fatty acids in a double-blind study. Thirty-three normotensive and mildly hypercholesterolemic men were randomly allocated to one of three diets supplemented with linoleic acid (14.3 g/d), alpha-linolenic acid (9.2 g/d), or eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) (3.4 g/d). Diets were matched to provide similar amounts of the major classes of fatty acids and cholesterol. Blood pressure and plasma lipids were measured for 6 wk after a 3-wk run-in period on the linoleic acid supplement. For the diet supplemented with EPA plus DHA compared with the linoleic acid diet systolic blood pressure fell 5.1 mm Hg (p = 0.01); plasma triglyceride and VLDL cholesterol fell by 39% (p = 0.001) and 49% (p = 0.01), respectively; and LDL cholesterol rose by 9% (p = 0.01). There were no significant changes with the diet supplemented with alpha-linolenic acid. The net effect on cardiovascular risk therefore is complex and the systolic blood pressure reduction was substantial.

n-3 fatty acids from vegetable oils

Principal food sources of the n-3 fatty acid alpha-linolenic acid are salad and cooking oil, salad dressing, shortening, margarine, and food-service fat and oil products made from canola oil or soybean oil. Using food production data provided by US trade associations and by Statistics Canada, I estimated the per capita availability of alpha-linolenic acid from vegetable-oil products in the United States to be approximately 1.2 g/d and in Canada, approximately 2 g/d. The higher alpha-linolenic acid availability in Canada is largely accounted for by widespread use of canola oil there. Considering also contributions to dietary alpha-linolenic acid of other foods such as nuts, dairy products, and vegetables, it would appear that total intake of alpha-linolenic acid in US and Canadian diets adequately exceeds the reported nutritional requirement. Emerging research has suggested possible health benefits associated with modest increases in dietary alpha-linolenic acid, including reduced blood-clotting tendency and reduced blood pressure.

Effect of dietary alpha-linolenate/linoleate balance on crescent type-anti-glomerular basement membrane nephritis in rats

Rats were fed diets with three different ratios of alpha-linolenate (18:3 n-3) and linoleate (18:2 n-6), and then crescentic-type anti-glomerular basement membrane (GBM) nephritis was induced. The urinary protein levels and the plasma urea nitrogen levels were significantly higher, and histological abnormalities of glomeruli were seen more frequently in the high-alpha-linolenate group than in the high-linoleate group. The differences in dietary alpha-linolenate/linoleate balances were reflected in the proportions of arachidonate and eicosapentaenoate in glomerular phospholipids. Our results indicate that dietary enrichment with alpha-linolenate causes unfavorable effects in this anti-GBM nephritis model.

Effects of dietary perilla oil, soybean oil and safflower oil on 7,12-dimethylbenz[a]anthracene (DMBA) and 1,2-dimethyl-hydrazine (DMH)-induced mammary gland and colon carcinogenesis in female SD rats

The effects of diet supplemented with perilla oil, which contains a large amount of n-3 alpha-linolenic acid, and n-6 linoleic acid rich soybean and safflower oil supplemented diets on 7,12-dimethylbenz[a]anthracene (DMBA)- and 1,2-dimethylhydrazine (DMH)-induced mammary gland and colon carcinogenesis were investigated in female SD rats. Groups of 23 or 24, 5 week old animals were first given three s.c. injections of 40 mg/kg body wt DMH followed by a single intragastric administration of 50 mg/kg body wt DMBA within 2 weeks of the commencement. Starting 1 week after the DMBA treatment, they were administered pellet diet containing 10% perilla oil, soybean oil or safflower oil for the succeeding 33 weeks. Histological examination revealed that the resultant numbers of mammary tumors per rat were significantly lower in rats given perilla oil diet (4.4 +/- 2.5) than in the soybean oil diet group (6.5 +/- 3.9). Furthermore, colon tumor incidence was significantly lower in animals receiving the perilla oil supplement (18.2%) than in those given safflower oil diet (47.4%), and the numbers of colon tumors per rat tended to be lowest in rats administered perilla oil. Also the incidence of nephroblastomas in rats receiving perilla oil diet (0%) was significantly lower than that for the soybean oil diet group (23.8%). The results thus indicate that the alpha-linolenic acid (n-3)-rich perilla oil diet inhibits development of mammary gland, colon and kidney tumors as compared to linoleic acid (n-6)-rich safflower or soybean oil diet.

Comparison of the inhibitory effect of polyunsaturated fatty acids on prostaglandin synthesis. II. Fibroblasts

In a previous publication we reported that PUFAs of the n-6 and n-3 series caused significant inhibition of synthesis of both PGE2 (28.4-92.8%) and PGF2 alpha (24.4-84.0%) in the oral squamous carcinoma cell line SCC-25. In this report we describe the inhibitory effect of the same acids on PG synthesis in normal human gingival fibroblasts under the same experimental conditions. It was found that a combination of EPA + DCHA (6:4), DCHA and ALA caused significant reduction in synthesis of PGE2 (10.1-87.8%) and PGF2 alpha (14.0-54.6%) at the four dose levels studied. The rank order of potency of acids in reduction of PG synthesis was: EPA + DCHA greater than DCHA greater than EPA greater than ALA greater than LA greater than DGLA greater than GLA. The data suggest that although PUFAs are effective inhibitors of PG synthesis by gingival fibroblasts and SCC-25, the fibroblast is less susceptible to the inhibitory effect of fatty acids.

n-3 fatty acid deficiency in man

A total of nine patients with n-3 fatty acid deficiency are described. They had been fed by gastric tube for 2.5-12 years, and had received 0.02-0.09% of calories as n-3 acids. The observed clinical symptoms of n-3 fatty acid deficiency were scaly and haemorrhagic dermatitis, haemorrhagic folliculitis of the scalp, growth retardation and impaired wound healing. All patients had extensive brain damage making it impossible to evaluate n-3 effects on cerebral functions. The patients were supplemented with cod liver and soya oil, alpha-linolenate followed by a purified fish oil, or with a mixture of linseed and cod liver oil. The results indicate that a dietary supply of 1.0-1.2% of alpha-linolenic acid is necessary to obtain a mid-normal lipid concentration of n-3 fatty acids, and suggest that the minimal dietary requirement is 0.2-0.3% of total calories. Long-chain n-3 fatty acids seem to be approximately twice as efficient as alpha-linolenic acid in maintaining normal n-3 fatty acid concentrations in plasma and red cell lipids.

The effects of dietary alpha-linolenic acid on the composition of nerve membranes, enzymatic activity, amplitude of electrophysiological parameters, resistance to poisons and performance of learning tasks in rats

Feeding rats diets containing oils that have a low alpha-linolenic acid [18:3(n-3)] content, such as sunflower oil, results in reduced amounts of docosahexaenoic acid [22:6(n-3)] in all brain cells and organelles compared to rats fed a diet containing soybean oil or rapeseed oil. During the period of cerebral development there is a linear relationship between the n-3 fatty acid content of the brain and that of food until alpha-linolenic acid represents approximately 200 mg/100 g food [0.4% of the total dietary energy for 18:3(n-3)]. Beyond that point brain levels reach a plateau. Similar values are also found for other organs. The level of 22:6(n-3) in membranes is little affected by the dietary quantity of linoleic acid [18:2(n-6)] if 18:3(n-3) represents approximately 0.4% of energy. In membranes from rats fed diets containing sunflower oil, Na+, K(+)-ATPase activity in nerve terminals was 60%, 5'-nucleotidase in whole brain homogenate was 80%, and 2',3'-cyclic nucleotide 3'-phosphodiesterase was 88% of that in membranes from rats fed diets containing soybean oil. A diet low in alpha-linolenic acid leads to anomalies in the electroretinogram, which partially disappear with age. It has little effect on motor activity, but it seriously affects learning tasks as measured with the shuttle box test. Rats fed a diet low in alpha-linolenic acid showed an earlier mortality in response to an intraperitoneal injection of a neurotoxin, triethyltin, than did rats fed a normal soybean oil diet.

Metabolism of gamma-linolenic acid in primary cultures of rat hepatocytes and in Hep G2 cells

Incorporation and metabolism of gamma-linolenic acid (GLA) in both rat hepatocytes and Hep G2 cells were compared to those of oleic (OA), linoleic (LA), alpha-linolenic (LLA), and dihomo-gamma-linolenic (DGLA) acids. The incorporation of GLA into both types of cells was higher than LLA and DGLA, but lower than OA and LA. It was efficiently converted into DGLA in both types of cells and increased the concentration of DGLA. LLA was converted to a small amount of C20:4 (n-3) only in Hep G2 cells. Incubation with LA, GLA, LLA, and DGLA did not increase the concentration of arachidonic acid (AA) in both types of cells. LA. GLA, LLA, and their metabolites were incorporated into phosphatidylcholine, but only GLA and its metabolite, DGLA, were also incorporated into phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol. The coexistence of GLA and LLA during their catabolism diminished the amounts of respective metabolite in Hep G2 cells. The presence of GLA inhibited completely the formation of C20:4(n-3) from LLA. The results indicate that GLA is more effective in raising the ratio of DGLA/AA. Also, polyunsaturated fatty acids of n-3 and n-6 series have competitively catabolized in both types of hepatocytes.

Interactions between the metabolism of n-3 and n-6 fatty acids

Dietary n-3 fatty acids modify the fatty acid composition of phospholipids of different cells and tissues from rats in diverse ways. Neutrophil and platelet phospholipids contain elevated amounts of 20:5n-3, but only relatively small changes occur in the levels of 22-carbon n-3 fatty acids. Conversely, dietary n-3 acids result primarily in an increase in 22-carbon n-3 acids in heart, liver and kidney phospholipids. Platelets metabolize exogenous n-6 and n-3 fatty acids into a variety of different autocoids. However, it appears that only arachidonate and 20:5n-3 are released from phospholipids upon agonist-induced stimulation of phospholipases. Neutrophils metabolize arachidonate and 20:5n-3 in similar ways, both relative to phospholipid biosynthesis and the subsequent release of these acids for metabolism into leukotrienes.

[Nature, origin and role of fatty acids of the nervous system: an essential fatty acid, an alpha-linolenic acid, changing the structure and the cerebral function]

Saturated and monounsaturated fatty acids are synthetized in cytosol, endoplasmic reticulum and mitochondria. Their mechanisms of synthesis and fate are different according to the organelle. For some of them, a nutritional origin is not excluded. Minimum dietary linoleic and alpha-linolenic acid to ensure normal brain structure and function are respectively 2.4% and 0.4% of the calories. Alpha-linolenic acid deficiency alters membrane composition and fluidity, changes the fluidizing effect of ethanol, reduces some enzymatic activities (ATP ase, 5' nucleotidase), diminishes the efficiency of the blood-brain barrier, affects electroretinogram, reduces learning capacities and makes the animals more fragile in the presence of neurotoxins. Very long polyunsaturated chains, which could be the essential fatty acids for the brain, must be considered at the level of nutrition, pharmacology and toxicology (alteration of structures and peroxidations).

Feeding pure docosahexaenoate or arachidonate decreases plasma triacylglycerol secretion in rats

Essential fatty acid (EFA)-deficient rats were fed highly purified methyl esters of docosahexaenoate (22:6n-3), arachidonate (20:4n-6), alpha-linolenate (18:3n-3) or oleate (18:1n-9) (100 mg/day, tube fed for 3-10 days), and their plasma triacylglycerol (TG) secretion rates were measured. Secretion rates of TG into plasma were reduced by tube-feeding 22:6n-3, 20:4n-6, 18:3n-3, but not 18:1n-9, to EFA-deficient rats. A significant reduction occurred after feeding 22:6n-3 for only three days. Feeding 22:6n-3 or 18:3n-3 to EFA-deficient rats for three days also reduced the activities of liver lipogenic enzymes and sharply increased the proportions of 22:6n-3 and 20:5n-3 in liver phospholipid fractions. Mechanisms by which these EFA may reduce lipogenesis are discussed.