Showing papers on "Docosahexaenoic acid published in 1989"

The Effects of Dietary α-Linolenic Acid on the Composition of Nerve Membranes, Enzymatic Activity, Amplitude of Electrophysiological Parameters, Resistance to Poisons and Performance of Learning Tasks in Rats

Abstract: 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.

Membrane docosahexaenoate is supplied to the developing brain and retina by the liver.

Abstract: Docosahexaenoic acid [22:6 omega 3; 22:6(4, 7, 10, 13, 16, 19)] is concentrated in phospholipids of cellular membranes from brain and retina. Although linolenic acid [18:3 omega 3; 18:3(9, 12, 15)] is the major omega 3 fatty acid of mouse dams' milk, 22:6 is the prevalent omega 3 fatty acid in serum and tissues. Intraperitoneal injection of [1-14C]18:3 into 3-day-old mouse pups resulted in liver and serum lipid labeling that was initially high, followed by a rapid decline. In contrast, labeling of brain and retinal lipids were initially low and increased with time. Labeled 22:6 first appeared in liver 2 hr after injection and later in brain and retina. We suggest that 22:6 synthesized from 18:3 by the liver is secreted into the bloodstream in lipoproteins, taken up by brain and retina, and incorporated into cell membranes. We hypothesize that the 22:6 requirements of membranes (e.g., during synaptogenesis, photoreceptor membrane biogenesis, or repair after ischemic injury or neurodegenerative disorders) are met by a signal that is sent by the appropriate tissues to the liver to evoke the secretion of 22:6-containing lipoproteins.

Nutritional composition of fats in seafoods.

Abstract: Public interest in the health benefits of seafood lipids, or of fish oils, is a most unusual phenomenon because for once the recommendations of health authorities to "eat more fish" are in accord with newer and popular attitudes. Media exploitation of the more sensational health aspects is also generally in favor of more consumption of seafood. The public is however still confused by the multitude of species of fish and shellfish available, and in a quandary over whether fatty fish are risky in terms of calories or cholesterol, or of more benefit than lean fish in terms of omega-3 fatty acids. Most direct questions on how much omega-3 fatty acids are useful in the diet of an average individual may never be answerable until long term studies with humans are carried out. It does appear that marine fish can be broken down into four convenient categories: lean (including shellfish), low fat, medium fat and high fat; and in this review it is suggested that these could contribute, per 100 grams, respectively about 250, 750, 1000 and 2000 mg of total C20 + C22 omega-3 fatty acids. This intake can compare favorably with the alternative of commonly available fish oil capsules. Moreover this survey shows that at present the composite of total omega-3 fatty acids in fish and shellfish may contain roughly equal proportions of the functionally effective eicosapentaenoic acid, and of docosahexaenoic acid with its as yet unknown long-term biochemical effects, or be biased in favor of more of the latter. To assist the public, nutritionists, dietitians, and researchers this review discusses the distribution of fat in edible fish muscle, the classes of lipids encountered, and the major fatty acids of health interest. Included are limited numbers of analyses from parts of the world other than North America.

Summary of the NATO advanced research workshop on dietary omega 3 and omega 6 fatty acids: biological effects and nutritional essentiality.

Abstract: A number of human studies presented at the workshop indicate that the premature infant at birth is biochemically deficient in docosahexaenoic acid (DHA) in both the brain and liver phospholipids, and that DHA is essential for normal visual acuity. The amount of DHA necessary to maintain normal amounts of the liver and brain phospholipids postnatally is 11 mg/kg daily. Elderly patients on long-term gastric tube feedings and others on long-term intravenous fluids and on total parenteral nutrition are particularly prone to deficiencies of alpha-linolenic acid, eicosapentaenoic acid (EPA) and DHA. The amounts estimated to prevent deficiencies in the elderly are 800-1100 mg/d of alpha-linolenic acid and 300-400 mg/d of EPA and DHA combined. Preliminary data indicate that children with malnutrition and mucoviscidosis, women with toxemia, and elderly people have decreased amounts of DHA in plasma phospholipids. The omega 3 fatty acids lower triglycerides and, at high levels, lower cholesterol. The anti-aggregatory, anti-thrombotic and anti-inflammatory properties of omega 3 fatty acids have been confirmed, and a dose-response curve is emerging. Despite the increase in bleeding time, no clinical evidence of bleeding has been noted by the investigators in any of the studies. Clinical trials are necessary in order to precisely define the dose and mechanisms involved in defining the essentiality of omega 3 fatty acids in growth and development and their beneficial effects in coronary heart disease, hypertension, inflammation, arthritis, psoriasis, other autoimmune disorders, and cancer.

Supplementation with n-3 fatty acids from fish oil in chronic inflammatory bowel disease—a randomized, placebo-controlled, double-blind cross-over trial

Abstract: Thirty-nine patients with chronic inflammatory bowel disease were studied in a 7-month, double-blind, placebo controlled cross-over trial of dietary supplementation with fish oil, which provided about 3.2 g n-3 fatty acids per day. At control, biopsies from inflamed mucosa contained higher levels of arachidonic acid than uninvolved mucosa. Dietary n-3 fatty acids were well tolerated and incorporated into plasma and enteric mucosa phospholipids at the expense of n-6 fatty acids. The arachidonic acid-derived prostanoid generation was reduced by fish oil and the extension and severity of macroscopic bowel involvement was moderately improved. In patients with Crohn's disease, clinical activity was unchanged by fish-oil supplementation. In patients with ulcerative colitis, clinical disease activity fell during fish oil supplementation and thereafter; this was not significant however. Despite a moderate reduction in inflammatory lipid mediators by dietary n-3 fatty acids and limited morphological improvement in chronic inflammatory bowel disease, the clinical benefit seems to be confined to patients with ulcerative colitis.

Comparison between eicosapentaenoic and docosahexaenoic acids in terms of essential fatty acid efficacy in larval red seabream

Abstract: On compare l'efficacite de l'acide eicosapentaenoique et de l'acide docosahexaenoique en tant qu'acide gras essentiel pour les larves de la dorade en les alimentant avec des rotiferes et du methyloleate, ou de l'acide eicopentaenoique, ou docosahexaenoique ou des acides gras hautement insatures (n−3) et en etudiant la croissance, le taux de survie, la vitalite et la composition en acide gras (assimilation) des larves soumises a chacun de ces regimes alimentaires

A double-blind controlled trial of long chain n-3 polyunsaturated fatty acids in the treatment of multiple sclerosis.

Abstract: A trial of n-3 polyunsaturated fatty acids in the treatment of multiple sclerosis has been conducted over a 5 year period. Ambulant patients (312) with acute remitting disease were randomly allocated to treatment or placebo. Both groups were given dietary advice to increase the intake of n-6 polyunsaturated fatty acids and the treatment group in addition received capsules containing n-3 polyunsaturated fatty acids. Analysis of clinical outcome at the end of 2 years of treatment was made in terms of the duration, frequency and severity of relapses and the number of patients who had improved or remained unchanged. The results showed no significant difference at the usual 95% confidence limits but there was a trend in favour of the group treated with n-3 polyunsaturated fatty acids in all parameters examined.

Effects of eicosapentaenoic and docosahexaenoic acids on apoprotein B mRNA and secretion of very low density lipoprotein in HepG2 cells.

Abstract: Oleic acid (18:1n-9, OA), docosahexaenoic acid (22:6n-3, DHA), or eicosapentaenoic acid (20:5n-3, EPA) was added to HepG2 cells at a concentration of 1 mM in a 5:1 or 2:1 molar complex with bovine serum albumin (BSA), and this was incubated for 3 hours. The incorporation of 3H-glycerol into cellular and medium triglyceride (TG), and the mass of TG were measured. The effects of these fatty acids on the secretion of very low density lipoprotein (VLDL) apolipoprotein B (apo B) were estimated from the incorporation of 3H-leucine into the medium apo B in comparison to cells incubated with fatty acid-poor albumin. The secretion of human albumin by the cells was also estimated by immunochemical precipitation of the labeled albumin. In addition, the intracellular levels of apo B messenger ribonucleic acid (mRNA) were measured by the dot-blot hybridization technique. Relative to control cells incubated with BSA, OA (complexed to BSA at a 5:1 molar ratio) stimulated TG synthesis and secretion sevenfold. Compared to OA, EPA was 24% less effective for both processes, whereas DHA inhibited only the secretion of TG (-43%). The secretion of VLDL apo B was not affected by OA, but was decreased 31% by EPA and 54% by DHA. When the molar ratio of fatty acid complexed to albumin was changed to 2:1, similar results were obtained with respect to TG production. The levels of apo B mRNA relative to actin mRNA were not significantly altered by any of the fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dietary n-3 fatty acids on weight gain and liver polar lipid fatty acid composition of fingerling channel catfish.

Abstract: A 10-wk experiment was conducted to determine the effect of supplementing a 5% tristearin basal diet with linoleic acid [18:2(n-6)], linolenic acid [18:3(n-3)], an n-3 highly unsaturated fatty acid (n-3 HUFA) mixture, cod liver oil, corn oil or linseed oil on growth and fatty acid composition of the liver polar lipid fraction of fingerling channel catfish (Ictalurus punctatus). The lowest weight gain was observed in fish fed the basal diet. Weight gain was improved by certain levels of supplemental n-3 fatty acids. Fish fed a diet containing 2% 18:3(n-3) grew at the same rate as fish fed a diet containing 2.5% cod liver oil plus 2.5% corn oil. The best growth rate was observed in fish fed diets containing either 5% cod liver oil or 5% linseed oil. Growth rate was depressed by supplementation with 4% 18:3(n-3) or 1.25% n-3 HUFA mix. No improvement in growth rate was observed with dietary 18:2(n-6). Dietary linolenate was converted to docosahexaenoic acid [22:6(n-3)]. The ratio of 20:3(n-9) to 22:6(n-3) of the fish showing good growth was less than 0.4. The data obtained in this experiment indicate that n-3 fatty acids are essential for channel catfish and that the 18:3(n-3) or n-3 HUFA dietary requirement is 1.0-2.0% or 0.5-0.75%, respectively.

Dietary omega 3 fatty acids and endothelium-dependent relaxations in porcine coronary arteries

Abstract: Dietary supplementation with cod-liver oil significantly augments endothelium-dependent relaxations in porcine coronary arteries. The present study was designed to examine the effect of dietary administration of omega 3 polyunsaturated fatty acids (mainly eicosapentaenoic acid, the major component of fish oil) on endothelium-dependent relaxations in porcine coronary arteries. Male Yorkshire pigs were maintained 4 wk on a regular diet with or without supplementation with purified eicosapentaenoic acid (3.5 g/day) and docosahexaenoic acid (1.5 g/day). Endothelium-dependent relaxations were examined in vitro. In rings from the treated group, endothelium-dependent relaxations were augmented in response to bradykinin, serotonin, and ADP, but not to the calcium ionophore A23187. These augmentations were not altered by indomethacin but were significantly inhibited by methylene blue, an inhibitor of guanylate cyclase. In the treated group, endothelium-dependent relaxations to aggregating platelets also were significantly augmented; platelet-induced contractions of quiescent rings were inhibited more by the presence of the endothelium than in arteries from the control group. Bioassay experiments demonstrated that the release of endothelium-derived relaxing factor(s) by bradykinin and relaxations of the vascular smooth muscle to the factor(s) were greater in arteries from the treated group. These observations indicate that dietary omega 3 polyunsaturated fatty acids augment receptor-operated endothelium-dependent relaxations, partly due to the augmented release of endothelium-derived relaxing factor(s) and partly due to the augmented relaxation of the vascular smooth muscle to the factor(s).

Effect of redfish meal enriched diets on the taste and n‐3 pufa of 42‐day‐old broiler chickens

Abstract: Broiler chickens were fed diets supplemented with redfish meal at levels of 4,8 and 12 %. A control group was fed with an all-vegetable protein diet. After 42 days the birds were slaughtered and edible tissues (white, dark and skin) were analysed for lipid content and composition. The white and dark meats were tasted organoleptically for the possible presence of ‘fishy’ off-flavours. There was no change in the content or class composition of the lipids with diet or sex of the bird, but in meats an increase in fish meal in the diet caused an increase in the level of n-3 polyunsaturated fatty acids present, especially 20: 5n-3 eicosapentaenoic acid, 22: 5n-3 docosapentaenoic acid and 22: 6n-3 docosahexaenoic acid at the expense of n-6 fatty acids. The enrichment was most pronounced in white meat of both male and female birds and could make a contribution of n-3 polyunsaturated fatty acids to the human diet quantitatively similar to that of an equal portion of lean white fish. Taste panel results showed that there was no significant difference in flavour or taste among any of the samples. There was a tendency for the 12% dietary group birds to be the least preferred, but no panelist detected ‘fishy’ flavours or objected to the taste of the meat.

The Interrelated Effects of n-6/n-3 and Polyunsaturated/Saturated Ratios of Dietary Fats on the Regulation of Lipid Metabolism in Rats

Abstract: The effects of various n-6/n-3 (0.45-9.31) and polyunsaturated/saturated (P/S; 0.25-6.08) ratios of dietary fatty acids on various lipid parameters were studied in rats using a combination of palm oil, safflower oil, soybean oil and perilla oil. When the n-6/n-3 ratio was changed while maintaining a constant P/S ratio (1.2), the concentration of serum cholesterol tended to increase linearly with the increasing n-6/n-3 ratio, whereas liver cholesterol tended to decrease. Serum triglyceride level increased linearly up to a n-6/n-3 ratio of approximately 5, whereas liver triglyceride was not influenced. When the n-6/n-3 ratio was kept relatively constant (5.6-6.4), serum and liver cholesterol levels decreased up to a P/S ratio of approximately 2, whereas serum triglyceride tended to be low below this value. The ratio of arachidonate to linoleate in tissue phosphatidylcholine (PC) was also influenced by the n-6/n-3 and P/S ratios; it increased up to a n-6/n-3 ratio of approximately 4, whereas it decreased up to a P/S ratio of approximately 2. The percentage of eicosapentaenoic and docosahexaenoic acid (n-3) in tissue phosphatidylcholine was positively related to dietary n-3 fatty acid levels. Prostacyclin (PGI2) production by thoracic aorta reached a plateau at a n-6/n-3 ratio approximately 5, whereas it tended to decrease with an increasing P/S ratio. Platelet production of thromboxane A2 exhibited a parabola-like pattern with a peak value at a n-6/n-3 ratio of approximately 2, whereas it was independent of the P/S ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison between eicosapentaenoic and docosahexaenoic acids in terms of essential fatty acid efficiency in juvenile striped jack Pseudocaranx dentex

Abstract: A feeding experiment was conducted to compare the essential fatty acid (EFA) efficiency between eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for juvenile striped jack.The fish fed an EFA-deficient diet began to show a high mortality together with poor appetite and swimming activity around 10 days after feeding, although there was no marked external deficiency sign. The growth and feed efficiency were improved by addition of EPA and DHA to the diet. However, the supplementation of EPA alone was not effective in preventing high mortality or improving the growth rate of the fish. A replacement of one half of EPA with DHA effectively improved the growth and feed efficiency as well as reducing mortality. On the other hand, the growth and feed efficiency were highest in the fish fed the diet containing DHA and the mortality due to the EFA-deficiency was almost completely prevented by DHA alone. The fatty acid analyses of whole body lipids have shown that EPA is converted to 22:5n-3, but not to DHA, and that DHA is not retroconverted to 22:5n-3 and EPA.

Occurrence of geometrical isomers of eicosapentaenoic and docosahexaenoic acids in liver lipids of rats fed heated linseed oil.

Abstract: Monotrans geometrical isomers of 20∶5 n−3 and 22∶6 n−3 were detected in liver lipid of rats fed heated linseed oil. The isomers were identified as being 20∶5 δ5c, 8c, 11c, 14c, 17t and 22∶6 δ4c, 7c, 10c, 13c, 16c, 19t. These fatty acids were isolated as methyl esters by preparative high-performance liquid chromatography (HPLC) on reversed phase columns followed by silver nitrate thin layer chromatography (AgNO3-TLC). The structures were identified using partial hydrazine reduction, AgNO3-TLC of the resulting monoenes, oxidative ozonolysis of each monoene band, and gas-liquid chromatography (GLC) of the resulting dimethyl esters and monomethyl esters. Fourier-transform-infrared spectrometry confirmed thetrans geometry in isolated 20∶5 and 22∶6 isomers. The isomers of eicosapentaenoic and docosahexaenoic acids in liver lipids probably resulted from desaturation and elongation of 18∶3 δ9c, 12c, 15t, a geometrical isomer of linolenic acid present in the heated dietary oil.

Dietary [omega] 3 and [omega] 6 fatty acids : biological effects and nutritional essentiality

Abstract: Early studies on the biosynthesis of polyunsaturated fatty acids.- The food chain for n-6 and n-3 fatty acids with special reference to animal products.- Some aspects of omega-3 fatty acids from different foods.- Linoleic and linolenic acids intake.- Omega-3 fatty acids from vegetable oils.- Preparation of fish oil for dietary applications.- (N-3) and (N-6) fatty acid metabolism.- The effect of dietary fish oil supplementation and in vitro collagen stimulation on human platelet phospholipid fatty acid composition.- In vitro studies on docosahexaenoic acid in human platelets.- Alpha-linolenic acid and the metabolism of arachidonic acid.- Comparative uptake in rats and man of w3 and w6 fatty acids.- Dietary polyunsaturated fatty acids in relation to neural development in humans.- Sources of w3 fatty acids in artict diets and their effects on red cell and breast milk fatty acids in Canadian Inuit.- Polyunsaturated fatty acids and infant nutrition.- Polyunsaturated fatty acids of the n-3 serie and nervous system development.- Omega-3 fatty acids in the retina.- Polyunsaturated fatty acid metabolism in endothelial cells: relationship to eicosanoid formation.- Modification of arachidonic acid cascade by long-chain w-3 fatty acids.- N-6 and N-3 fatty acids in plasma and platelet lipids, and generation of inositol phosphates by stimulated platelets after dietary manipulations in the rabbit.- Dietary linolenic acid and tissue function in rodents.- The supply of omega-3 polyunsaturated fatty acids to photoreceptors and synapses.- Omega-3 and omega-6 fatty acids in serum lipids and their relationship to human disease.- Omega-3 fatty acids and lipoproteins.- Alpha-linolenic acid, platelet lipids and function.- Fish (oil) consumption and coronary heart disease.- Dietary polyunsaturates, vascular function and prostaglandins.- Polyunsaturated oils of marine and plant origins and their uses in clinical medicine.- Biochemical and bioclinical aspects of blackcurrant seed oil. w3-w6 balanced oil.- Quantitative determination of prostanoids by stable isotope dilution gas chromatography/mass spectrometry.- Linoleic acid and epidermal water barrier.- Different doses of fish-oil fatty acid ingestion in active rheumatoid arthritis: a prospective study of clinical and immunological parameters.- Dietary w-3 and w-6 fatty acids in cancer.- Marine mammals: animal models for studying the digestion and transport of dietary fats enriched in w-3 fatty acids. Positional analyses of milk fat triacylglycerol molecules.- Changes in the polyunsaturated fatty acid profiles in Zellweger syndrome suggesting a new enzymatic defect: delta-4 desaturase deficiency.- Selective incorporation of eicosapentaenoic acid in position 2 of plasma triglycerides after a dietary supply of 2 eicosapentaenoyl glyceride in man.- The effect of a fish oil preparation (EPAGIS) on serum lipids, apoproteins, circulating platelet aggregates and hemorheologic parameters in hyperlipidemic subjects.- Differential mobilization of essential fatty acids into the serum free fatty acid pool in response to glucose ingestion.- Flax as a source of alpha-linoleic acid.- Executive Summary.- General Recommendations on Dietary Fats for Human Consumption.- A double-blind controlled trial of oils containing long-chain-w3-polyunsaturated fatty acids in the treatment of multiple sclerosis.- Contributors.

Eicosapentaenoic acid and adult diseases in Japan: epidemiological and clinical aspects

Abstract: . Residents of a coastal fishing village in Japan consume larger amounts of fresh fish rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) than those in inland farming villages. A higher content of EPA and DHA in the plasma and reduced platelet aggregability was observed in the residents of the fishing village than in farmers. Incidence of thrombotic cardiovascular disorders was lower in the fishing area than in the farming area. Oral ingestion of highly purified EPA or DHA reduced platelet aggregability and improved serum lipid profile in healthy subjects and in hyperlipidaemic patients, though DHA seems to be much less potent. In clinical studies with highly purified EPA, improvement of clinical features was noted in patients with thrombotic cardiovascular disorders. It is also shown that EPA and DHA have an anti-inflammatory effect in man although EPA is far more active than DHA.

Specific susceptibility of docosahexaenoic acid and eicosapentaenoic acid to peroxidation in aqueous solution

Abstract: The peroxidation of different polyunsaturated fatty acids (PUFA) after photoirradiation in aqueous solution was evaluated by measuring fatty acid loss and malonaldehyde production in medium. The oxidation rates of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two highly unsaturated fatty acids of the n−3 series, were surprisingly lower (14 and 22%, respectively) than the oxidation rates of linoleic, α-linolenic, γ-linolenic, dihomo γ-linolenic, and arachidonic acids (62–90%). The quantities of malonaldehyde (MA) produced were assayed simultaneously by gas chromatography (GC) and high performance liquid chromatography (HPLC). MA production was found to be related to both the degree of unsaturation and the metabolic series of the fatty acid. The maximum value was observed with arachidonic acid (MA production from 2 mM arachidonic acid in aqueous solution was estimated at 44.9±6.0 μM by GC and 46.8 ±4.0 μM by HPLC). Eicosapentaenoic acid and docosahexaenoic acid produced lower MA quantities compared to arachidonic acid (MA production from 2 mM EPA and 2 mM DHA was estimated at 17.9±1.5 μM and 37.9±0.7 μM, respectively, by GC, and 26.3±4.9 μM and 37.3±4.2 μM, respectively, by HPLC). The MA yield, defined as the amount of MA (nmols) produced per 100 nanomoles of oxidized fatty acid, was used to express the susceptibility of individual PUFA to peroxidation. The MA yield correlated well with the degree of unsaturation, but was independent of carbon chain length and metabolic series. The study suggests that adequate assessment of lipid peroxidation cannot be achieved by measuring MA formation alone, but it also requires knowledge of the fatty acid composition of the system studied.

A low-fat diet supplemented with dietary fish oil (Max-EPA) results in improvement of psoriasis and in formation of leukotriene B5.

Abstract: Several studies have indicated that certain lipoxygenation products of arachidonic acid, particularly leukotriene B4 (LTB4), may be involved in psoriatic pathophysiology. One way of inhibiting the formation of LTB4 is to replace arachidonic acid in phospholipids with eicosapentaenoic acid. Eicosapentaenoic acid is converted into LTB5, which has a lower biologic activity than LTB4. In the present study psoriatic patients were put on a low-fat diet supplemented with dietary fish oil (Max-EPA 30 ml daily), a source of eicosapentaenoic acid, for 4 months. Twenty-six out of 30 patients with psoriasis vulgaris completed the study. Moderate or excellent improvement was observed in 58% of the patients, while mild improvement or no change was observed in 19% and 23%, respectively. The capacity of peripheral blood neutrophils to synthesize LTB4 and LTB5 in vitro was determined after stimulation with A23187. Before the study, negligible amounts of LTB5 were formed. After 1 month the average of LTB5/LTB4 ratio was 0.42. No further increase of the LTB5/LTB4 ratio was found. There existed no relationship between the clinical response and the LTB5/LTB4 ratio. The results of the present study suggest that dietary fish oil supplementation may be used in the therapy in psoriasis. However, studies defining the dose and the quality of fish oils are imperative.

Application of a specificity ofMucor miehei lipase to concentrate docosahexaenoic acid (DHA)

Abstract: Lipases catalyze the reesterification or hydrolysis of fats and oils and may show specificity towards certain fatty acids. An immobilized lipase from the fungusMucor miehei shows specificity towards docosahexaenoic acid (DHA) (DHA being a poor substrate), whether the DHA is used as a free fatty acid (FFA) as substrate in esterification with methanol, or fatty acid methyl ester (FAME) is used as a substrate for hydrolysis. The specificity of the lipase fromM. miehei may be applied to concentrate DHA originating from a marine oil in either the FAME or the FFA fraction, which can be separated.

n-3 fatty acids and cancer.

Abstract: Dietary fat has a positive correlation with cancers of the breast and colon and probably other types of cancer. In experimental tumour systems, linoleic acid (LA) has tumour-promoting effects that are mediated, in part, through eicosanoid production. The feeding of fish oil has resulted in decreased concentrations of LA and arachidonic (AA) and increased concentrations of n-3 eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Both n-3 fatty acids antagonize the production of eicosanoids from AA. Recent reports indicate that marine n-3 fatty acids inhibit the development and growth of several experimental tumours. The effect of n-3 fatty acids on 16-alpha-hydroxylation of oestradiol, a putative biomarker for risk of breast cancer, was studied in 25 women at enhanced risk. The control group of 25 high-risk women received vegetable oil. After 4 months, the level of oestradiol 16-alpha-hydroxylation was significantly reduced in women receiving fish oil, but no change was detected in the control group. Although the precise mechanism of action is unclear, these data suggest that use of marine n-3 fatty acids as chemopreventive agents in high-risk women requires further investigation.

Plasma fatty acid levels in patients with acquired immune deficiency syndrome and in controls.

Abstract: Polyunsaturated fatty acids (PUFAs) are known to modulate the immune system in vivo and to inactivate envelope viruses in vitro. Patients with AIDS had low total plasma lipid levels and low levels of a number of individual fatty acids. However, the C20 and C22 essential fatty acids of the n-3 series were selectively and highly significantly reduced. Normalization of these fatty acid levels in AIDS patients may be a worthwhile therapeutic aim.

Effect of fatty acid composition on insulin and IGF-I binding in retinoblastoma cells.

Abstract: Receptors for insulin and other hormones are often influenced by their environment, including fatty acid content and membrane fluidity. Y79 retinoblastoma cells enriched with arachidonic or docosahexaenoic acid show an increase in membrane fluidity determined by fluorescence polarization using the plasma membrane-specific probe, trimethylammonium-diphenylhexatriene. Unlike cells enriched with polyunsaturated fatty acids, cells cultured in media containing palmitic or oleic acid showed no changes in membrane fluidity or fatty acid composition. Cells enriched with docosahexaenoic acid show an increase in insulin binding at 15 degrees C that is due to an increase in the number of available insulin receptor sites on the plasma membrane. In contrast, insulin binding is not altered in cells enriched with arachidonic, palmitic or oleic acid. Furthermore, the binding of insulin-like growth factor-I (IGF-I) in Y79 cells is not changed by the fatty acid unsaturation of the cell membrane. Because docosahexaenoic acid is naturally present in high concentrations in the retina these studies suggest it may have a role in modulating insulin binding and function.

Guinea pig epidermis generates putative anti-inflammatory metabolites from fish oil polyunsaturated fatty acids.

Abstract: Clinical studies have indicated that dietary fish oil may have therapeutic value in the treatment of psoriasis, a hyperproliferative, inflammatory skin disorder characterized by elevated LTB4. To evolve a possible mechanism for these beneficial effects, we determined the metabolic fate of fish oil derived n-3 fatty acids in the skin. Specifically, we incubated guinea pig epidermal enzyme preparations with [3H]eicosapentaenoic acid (20∶5n−3) and [14C]docosahexaenoic acid (22∶6n−3). Analyses of the radiometabolites revealed the transformation of these n−3 fatty acids into n−6 lipoxygenase (arachidonate 15-lipoxygenase) products: 15-hydroxyeicosapentaenoic acid (15-HEPE) and 17-hydroxydocosahexaenoic acid (17-HDHE), respectively. Since 15-lipoxygenase products have been suggested as possible endogenous inhibitors of 5-lipoxygenase (an enzyme which catalyzes the formation of LTB4) we tested the ability of 15-HEPE and 17-HDHEin vitro to inhibit the activity of the 5-lipoxygenase. Incubations of these metabolites with enzyme preparations from rat basophilic leukemia (RBL-1) cells demonstrated that 15-HEPE (IC50=28 μM) and 17-HDHE (IC50=20 μM) are respectively potent inhibitors of RBL-I-5-lipoxygenase. The inhibitory potential of these fish oil metabolites provides a possible mechanism by which fish oil might act to decrease local cutaneous levels of LTB4, and thereby alleviate psoriatic symptoms.