Cytotoxic action of cis-unsaturated fatty acids on human cervical carcinoma (HeLa) cells in vitro

The effect of n-3 and n-6 fatty acids (FAs) on the growth of human cervical carcinoma (HeLa) cells was studied. Of all the FAs tested, docosahexaenoic acid (DHA, 22:6 n-3) and eicosapentaenoic acid (EPA, 20:5 n-3) were found to be the most potent in their cytotoxic action on HeLa cells and the potency of various fatty acids with regard to their cytotoxic action was as follows: DHA > EPA > dihomo-gamma-linolenic acid (DGLA) = gamma-linolenic acid (GLA) > linoleic acid (LA) > arachidonic acid (AA) > alpha-linolenic acid (ALA). The cycloxygenase inhibitor indomethacin, the lipoxygenase inhibitor nordihydroguaretic acid (NDGA), the antioxidants vitamin E, butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT), the superoxide anion quencher superoxide dismutase (SOD), the hydroxyl and hydrogen peroxide quenchers mannitol and catalase, respectively, and the calmodulin antagonists trifluoperazine (TFP) and chlorpromazine (CPZ) could all block the cytotoxic action of GLA, which was used as a representative cytotoxic FA, on HeLa cells. On the other hand, copper and iron salts and buthionine sulfoxamine, a glutathione (GSH) depletor, potentiated the cytotoxic action of suboptimal doses of GLA. GLA-induced radical generation and lipid peroxidation in HeLa cells could be blocked by indomethacin, NDGA and calmodulin antagonists. The cytotoxic action of cis-unsaturated fatty acids (c-UFAs) is not dependent on the alteration in the protein kinase C levels since no alteration in the diacylglycerol levels was observed. Hydroxy and hydroperoxy products of GLA were found to be toxic to HeLa cells, whereas prostaglandin (PG)E1, PGF2 alpha, and prostacyclin stimulated cell growth. From these results, it is evident that radicals are the modulators of the cytotoxic action of c-UFAs, that their formation is a calmodulin-dependent process, and that lipoxygenase products may mediate the tumoricidal action of FAs.     

Low levels of eicosapentaenoic and docosahexaenoic acids mimic the effects of fish oil upon rat lymphocytes

Fish oil is rich in the long chain n-3 polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA); typically these fatty acids constitute 20 to 25 g/100 g total fatty acids in fish oil. Feeding rodents diets rich in fish oil has been shown to decrease lymphocyte proliferation and natural killer cell activity. It is not known what level of EPA + DHA is required in the diet to exert these effects. This question was addressed in the current study. Weanling rats were fed on high fat (178 g/kg) diets which contained 4.4 g alpha-linolenic acid (control) or 4.4 g EPA + DHA (4.4 EPA + DHA) or 6.6 g EPA + DHA (6.6 EPA + DHA)/100 g total fatty acids. The n-6 to n-3 polyunsaturated fatty acid ratio was maintained at approximately 7. The fatty acid compositions of the serum and of spleen leukocytes were markedly influenced by that of the diet. Spleen lymphocyte proliferation in response to concanavalin A, spleen natural killer cell activity and PGE2 production by spleen leukocytes were reduced by feeding the EPA + DHA diets compared with feeding the control diet; the 4.4 and 6.6 EPA + DHA diets caused very similar reductions. The 4.4 EPA + DHA diet reduced popliteal lymph node weight following a localised graft versus host response; this response was not investigated in rats fed the 6.6 EPA + DHA diet. The reductions in lymphocyte functions and in the in vivo graft versus host response caused by the EPA + DHA diets were similar to those previously reported following the feeding of diets rich in fish oil. Thus, this study shows that diets containing relatively low levels of EPA + DHA (20 to 25% of the level found in fish oil) exert immunomodulatory effects. Furthermore, this study suggests that the maximal effect of EPA + DHA is exerted when these fatty acids constitute a level of less than or equal to 4.4 g/100 g total dietary fatty acids.     

Alpha-linolenic acid and marine long-chain n-3 fatty acids differ only slightly in their effects on hemostatic factors in healthy subjects

The effects of alpha-linolenic acid (ALA, 18:3n-3), eicosapentaenoic acid (EPA, 20:5n-3), and docosahexaenoic acid (DHA, 22:6n-3) on hemostatic factors were compared. Healthy subjects (29 women and 17 men aged 20-44 y) received either linseed oil (average ALA intake: 5.9 g/d) or fish oil plus sunflower oil (average EPA + DHA intake: 5.2 g/d) for 4 wk. The supplemented amount of fat was 1.19 mg/kJ (1 g/200 kcal) calculated energy expenditure. Stability of habitual diets was monitored. Blood samples were collected at baseline, at the end of the experimental period, and after a 12-wk follow-up period. Different changes in the study groups were seen only in serum cholesterol and triacylglycerols, platelet fatty acid composition, and ADP-induced platelet aggregation. The treatments did not differ in their effects on collagen-induced platelet aggregation and thromboxane production, aggregation to the thromboxane A2 mimic I-BOP, urinary excretion of 11-dehydro-thromboxane B2 and beta-thromboglobulin, bleeding time, plasma fibrinogen concentration, antithrombin III activity, factor VII coagulant activity, or activity of plasminogen activator inhibitor 1. The results indicate that supplemented ALA from vegetable oil and EPA and DHA from a marine source have largely parallel effects on hemostatic factors.     

CHARGE association: an update and review for the primary pediatrician

A diet including 2-3 portions of fatty fish per week, which corresponds to the intake of 1.25 g EPA (20:5n-3) + DHA (22:6n-3) per day, has been officially recommended on the basis of epidemiological findings showing a beneficial role of these n-3 long-chain PUFA in the prevention of cardiovascular and inflammatory diseases. The parent fatty acid ALA (18:3n-3), found in vegetable oils such as flaxseed or rapeseed oil, is used by the human organism partly as a source of energy, partly as a precursor of the metabolites, but the degree of conversion appears to be unreliable and restricted. More specifically, most studies in humans have shown that whereas a certain, though restricted, conversion of high doses of ALA to EPA occurs, conversion to DHA is severely restricted. The use of ALA labelled with radioisotopes suggested that with a background diet high in saturated fat conversion to long-chain metabolites is approximately 6% for EPA and 3.8% for DHA. With a diet rich in n-6 PUFA, conversion is reduced by 40 to 50%. It is thus reasonable to observe an n-6/n-3 PUFA ratio not exceeding 4-6. Restricted conversion to DHA may be critical since evidence has been increasing that this long-chain metabolite has an autonomous function, e.g. in the brain, retina and spermatozoa where it is the most prominent fatty acid. In neonates deficiency is associated with visual impairment, abnormalities in the electroretinogram and delayed cognitive development. In adults the potential role of DHA in neurological function still needs to be investigated in depth. Regarding cardiovascular risk factors DHA has been shown to reduce triglyceride concentrations. These findings indicate that future attention will have to focus on the adequate provision of DHA which can reliably be achieved only with the supply of the preformed long-chain metabolite.     

Differential accumulation and release of long-chain n-3 fatty acids from liver, muscle, and adipose tissue triacylglycerols

Eicosapentaenoic acid (EPA, 20:5n-3) is less efficiently accumulated in tissue triacylglycerols (TAGs) during fish oil feeding than docosahexaneoic acid (DHA, 22:6n-3) or docosapentaenoic acid (DPA, 22:5n-3), and EPA is preferentially released from the TAG of isolated adipocytes in vitro and adipose tissue in vivo during fasting compared with DHA or DPA. It is not known if this preferential release occurs in vivo under nonfasting conditions or if it is limited to adipose tissue. Accordingly, we have carried out experiments to study the turnover of EPA, DHA, and DPA in the TAG of adipose tissue, liver, and skeletal muscle. Weanling rats were fed diets containing fish oil for 6 weeks and then switched to diets containing only corn oil as the dietary fat for 8 weeks. The fatty acid composition and mass in epididymal fat pads, omental fat, liver, and soleus muscle TAGs were determined weekly for the first 10 weeks and at weeks 12 and 14. Subsequent to the change to the corn oil diet, EPA (20:5n-3), DPA (22:5n-3), and DHA (22:6n-3), which had accumulated during fish oil feeding, were lost from the tissue TAG pools of each tissue examined. After 8 weeks on the corn oil diet, less than 10% of the accumulated EPA, DPA, and DHA remained in the liver and muscle. The loss of EPA, DPA, and DHA from epididymal fat pad was slower. In each tissue, EPA was lost more rapidly than DPA or DHA. This selective loss of EPA relative to DHA or DPA may explain the previously reported underrepresentation of EPA compared with DHA or DPA in tissue TAG.     

Deficit in prepulse inhibition in mice caused by dietary n-3 fatty acid deficiency.

Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) may be biosynthesized from a precursor α-linolenic acid (LNA) or obtained preformed in the diet. Dams were fed four diets with different levels of the various n-3 fatty acids during pregnancy and lactation, and their offspring were weaned to the same diets: “n-3 Deficient,” containing (as % total fatty acids) 0.07% of LNA; “Low LNA” (0.4%); “High LNA” (4.8%); and a “DHA + EPA” diet, containing 0.4% of LNA, 2% DHA, and 2% EPA. Sensorimotor gating was measured by prepulse inhibition (PPI) of the acoustic startle response in C57Bl6 mice. The n-3 Deficient and Low LNA diets caused a substantial deficit in PPI compared to the DHA + EPA diet, whereas the High LNA diet induced a less pronounced, but significant reduction of PPI. These are the first data that demonstrate a deficit in sensorimotor gating in rodents caused by an inadequate amount of the n-3 fatty acids in the diet. Our results differentiate the effects of a High LNA diet from one with added EPA and DHA even though the difference in brain DHA content is only 12% between these dietary groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of dietary docosahexaenoic acid on surface molecules involved in T cell proliferation

It is known that n-3 polyunsaturated fatty acids (PUFA) such as docosahexaenoic acid (DHA) suppress immunity as compared with n-6 PUFA such as linoleic acid (LA), but the mechanism involved in this phenomenon is still unclear. The present study was designed to assess the effect of dietary DHA on the surface molecules involved in T cell proliferation. Weanling male C57BL/6 mice were divided into four dietary groups that were fed a 10% fat diet for 4 weeks varying in amounts of DHA and LA. As the dietary DHA concentration increased, the surface expression of CD4 and CD8 on splenic T cells decreased, while that of CD28 increased. The surface expression of CD3, however, was invariable in all dietary groups. DNA synthesis of splenic T cells, induced by CD3 crosslinkage with anti-CD3 epsilon monoclonal antibody in the presence of CD28-mediated costimulation, increased as the DHA concentration was elevated. These observations suggest that diets rich in DHA exert some of their immunomodulatory effects by a downregulation of surface expression of CD4 and CD8 and by an upregulation of CD28-mediated costimulatory signal.     

The effect of highly purified eicosapentaenoic and docosahexaenoic acids on monocyte phagocytosis in man

The n-3 fatty acids (FA) from marine sources are known to exert antiinflammatory effects on monocyte function. There is still controversy whether n-3 FA may increase the susceptibility to infections. The present study was designed to assess the effect of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on monocyte phagocytosis and respiratory burst activity. Fifty-eight healthy men were randomized to take a daily supplement of 3.8 g highly purified EPA (n = 20), 3.6 g DHA (n = 19), or corn oil (n = 19) for 7 wk. Mononuclear leukocytes were collected, isolated, and cryopreserved prior to and after dietary supplementation. Paired samples were analyzed in the presence of autologous serum in a crossover design. Monocyte phagocytosis and respiratory burst activity were measured by flow cytometry after ingestion of Escherichia coli. Monocytes retained their phagocytic ability and respiratory burst activity after supplementation. No reduction in internalization of bacteria was registered. Dietary n-3 FA and particularly EPA improved bacterial adherence to the monocyte surface. In the crossover experiments, there was an adverse effect of serum enriched with n-3 FA on bacterial adherence. We conclude that monocytes retain their phagocytic potential after supplementation with purified EPA and DHA.     

Incorporation of n-3 fatty acids into plasma lipid fractions, and erythrocyte membranes and platelets during dietary supplementation with fish, fish oil, and docosahexaenoic acid-rich oil among healthy young men

The effects of n-3 fatty acid supplementation in the form of fresh fish, fish oil, and docosahexaenoic acid (DHA) oil on the fatty acid composition of plasma lipid fractions, and platelets and erythrocyte membranes of young healthy male students were examined. Altogether 59 subjects (aged 19-32 yr, body mass index 16.8-31.3 kg/m2) were randomized into the following diet groups: (i) control group; (ii) fish diet group eating fish meals five times per week [0.38 +/- 0.04 g elcosapentaenoic acid (EPA) and 0.67 +/- 0.09 g DHA per day]; (iii) DHA oil group taking algae-derived DHA oil capsules (1.68 g/d DHA in triglyceride form); and (iv) fish oil group (1.33 g EPA and 0.95 g DHA/d as free fatty acids) for 14 wk. The fatty acid composition of plasma lipids, platelets, and erythrocyte membranes was analyzed by gas chromatography. The subjects kept 4-d food records four times during the study to estimate the intake of nutrients. In the fish diet, in DHA oil, and in fish oil groups, the amounts of n-3 fatty acids increased and those of n-6 fatty acids decreased significantly in plasma lipid fractions and in platelets and erythrocyte membranes. A positive relationship was shown between the total n-3 polyunsaturated fatty acids (PUFA) and EPA and DHA intake and the increase in total n-3 PUFA and EPA and DHA in all lipid fractions analyzed. DHA was preferentially incorporated into phospholipid (PL) and triglyceride (TG) and there was very little uptake in cholesterol ester (CE), while EPA was preferentially incorporated into PL. and CE. The proportion of EPA in plasma lipids and platelets and erythrocyte membranes increased also by DHA supplementation, and the proportion of linoleic acid increased in platelets and erythrocyte membranes in the DHA oil group as well. These results suggest retroconversion of DHA to EPA and that DHA also interferes with linoleic acid metabolism.     

Essential fatty acid metabolism in cardiomyocytes grown in media enriched with different N-6/N-3 fatty acid combinations

We have evaluated the effects of three different 18:3n-6, 20:5n-3 and 22:6n-3 fatty acid combinations on essential fatty acid (EFA) metabolism in rat cultured cardiomyocytes. The desaturating/elongating activities for linoleic (LA) and alpha-linolenic acid (ALA) were evaluated by radiolabeling the cells with 1-[14C]LA or 1-[14C]ALA and the fatty acid pattern of cardiomyocytes was assessed by gas chromatography. LA and ALA conversion to more unsaturated metabolites was reduced by increasing respectively n-3 and n-6 fatty acid concentration in the media. The all three combinations used reduced the saturated and increased the polyunsaturated fatty acid content of cardiomyocytes. The n-6/n-3 fatty acid ratio did not change compared to control cells in cardiomyocytes receiving the highest amount of 18:3n-6 and the lowest amounts of n-3 fatty acids. This combination may be suitable for modifying EFA desaturating/elongating activities without altering the physicochemical parameters which are related to the correct balance between n-6 and n-3 fatty acid content.     

Dietary modulation of phase 1 and phase 2 activities with benzo(a)pyrene and related compounds in the intestine but not the liver of the channel catfish, Ictalurus punctatus

EPA, DHA, C15SCH2COOH (n-3), C15SCH2COOH (n-6) and C18SCH2COOH (n-3) are extensively incorporated into phospholipids and triacylglycerol in rat hepatocytes after 24 h incubation with 80 microM fatty acid/derivative. Only traces of polyunsaturated 3-oxa fatty acids (C15OCH2COOH, C18OCH2COOH) were incorporated. C15-S-butyric acid (n-3) is a stronger inhibitor of delta6-desaturase in rat liver-microsomes than C15SCH2COOH (n-3), C15-S-propionic acid (n-3), EPA and DHA. It inhibits delta5-desaturase in a similar manner to EPA and DHA. Arachidonic acid and C15SCH2COOH, (n-6) are better substrates for PGH-synthase than EPA and C15SCH2COOH, (n-3), showing the inhibitory effect of the n-3 bond. The n-3 polyunsaturated fatty acids, including the sulfur-substituted fatty acid derivatives, are poor substrates for PGH-synthase. However, they inactivate the PGH-synthase activity at least as efficiently as arachidonic acid. C15SCH2COOH (n-3), C15S(CH2)2COOH (n-3) and C18SCH2COOH (n-3) induce peroxisomal beta-oxidation more than EPA and DHA.     

Effects of fish meal in beef cattle diets on growth performance, carcass characteristics, and fatty acid composition of longissimus muscle

We investigated the effects of fish meal (FM) in beef cattle diets on growth performance, carcass characteristics, and fatty acid (FA) composition of longissimus muscle in 63 yearling steers (335 +/- 23 kg). High-moisture corn and alfalfa silage diets were supplemented with either a corn gluten/blood meal mixture or FM at 10% of the diet. Fish meal contained (as-is basis) 5.87 g/kg eicosapentaenoic acid (EPA) and 9.84 g/kg docosahexaenoic acid (DHA). Seven strategies were developed to feed either a control diet (no FM) or diets containing 5 or 10% FM with FM fed for either 56, 112, or 168 d before slaughter. Average daily gain and feed efficiency were not affected (P > .10) by FM feeding but DMI decreased. Within FM diets, cattle fed 5% FM consumed more (P < .01) DM and gained more (P < .02) than cattle fed 10% FM. Carcass traits were not affected (P > .05) by feeding strategy except for fatter (P < .05) and lower (P < .06) yielding carcasses in cattle fed 5 vs 10% FM diets. Fish meal feeding increased (P < .01) concentrations of (n-3) FA, including EPA and DHA, and decreased (P < .05) concentrations of arachidonic acid. Increasing the amount of dietary FM further increased (P < .01) concentrations of EPA and DHA and decreased (P < .05) concentrations of (n-6) FA. We estimate that a 114-g steak from cattle fed 10% FM would supply 35 to 90% of the current average daily intake of EPA and DHA in North America. The results indicate that FM may have a role in niche marketing of beef provided that eating quality is not compromised.     

Omega-3 fatty acids and prevention of ventricular fibrillation

Interest in the potential cardiovascular benefits of omega-3 long chain polyunsaturated fatty acids has been largely focused on possible antiatherothrombotic effects. In addition, however, definitive antiarrhythmic effects of these dietary omega-3 fatty acids have been reported by Charnock & McLennan. Our studies commenced with the observation that two of these fatty acids, eicosapentaenoic (C20:5n-3, EPA) and docosahexaenoic acid (C22:6n-3, DHA) prevented contracture and fibrillation of isolated neonatal cardiac myocytes when exposed to toxic levels of ouabain (0.1 mM). This protection was associated with prevention of excessively high intracellular calcium concentrations in the myocyte. Further, it was shown that these fatty acids modulate calcium currents through L-type calcium channels and that the effect occurs within a few minutes of adding EPA or DHA to the medium perfusing the cultured cardiac myocytes. Infusing an emulsion of the omega-3 fatty acids intravenously just prior to compression of a coronary artery in a conscious, prepared dog will prevent the expected subsequent ischemia-induced ventricular fibrillation.     

Implantation of collagen IV/poly(2-hydroxyethyl methacrylate) hydrogels containing Schwann cells into the lesioned rat optic tract

Fifty-seven healthy volunteers matched for sex and age were subdivided in 3 groups and their usual Western diets were supplemented according to three different protocols: group 1, fish oil supplement (20 ml/day); group 2, soybean phosphatidylcholine (PC) (25 g/day) and group 3, no supplementation (control group). After 2 weeks several important modifications of neutrophil fatty acid composition were observed: fish oil induced a significant decrease of linoleic (LA) and arachidonic acid (AA) and a significant increase of eicosapentaenoic (EPA) and docosahexaenoic acid (DHA), while soy PC induced significant increases of LA, total polyunsaturated fatty acid (PUFA) and PUFA/SFA ratio. Neutrophil superoxide generation and adhesion were not modified by fish oil diet, on the contrary a slight but significant increase of O2.- production in response to fMLP was measured after soy PC diet. Our study confirms the possibility of changing neutrophil fatty acid composition in vivo by dietary means, but also suggests that the manipulation of cell functions, like superoxide anion generation and adhesion, is not easily and directly achieved by controlling membrane lipid environment.     

Effect of omega-3 fatty acids on the progression of metastases after the surgical excision of human breast cancer cell solid tumors growing in nude mice

We showed previously that a diet rich in linoleic acid (LA), an omega-6 fatty acid, stimulates the growth and metastasis of human breast cancer cells in athymic nude mice. In contrast, diets supplemented with eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA), omega-3 fatty acids, exert suppressive effects. We have now assessed EPA and DHA as adjuvant nutritional therapy in the nude mouse model and compared the responses when the intervention was commenced 1 week before ("neoadjuvant") or immediately after ("postoperative adjuvant") surgical excision of the primary tumor. Female nude mice received a high-fat, 8% LA diet beginning 7 days before 10(6) MDA-MB-435 human breast cancer cells were injected into a thoracic mammary fat pad. As the tumor surface areas approached 0. 7 cm2, the mice were assigned to either continue on the LA-rich diet or to commence one containing 8, 4, or 2% EPA or DHA. Seven days later, the mammary fat pad tumors were excised; the mice still consuming the 8% LA diet were then allocated sequentially to either continue this diet or commence one of the six postexcision omega-3 fatty acid dietary interventions. Eight weeks later, the mice were necropsied and evaluated for local recurrence and lung metastases. Although there were no differences in the incidence of local recurrence between groups, EPA and DHA both inhibited the development of lung metastases. When the dietary interventions were commenced 7 days before surgery, the severity of lung metastasis was reduced by the two omega-3 fatty acids in a dose-dependent manner; at all three levels, the suppressive effects were statistically significant (P < 0.05). Postexcision EPA treatment produced small, statistically insignificant effects, but lung involvement was reduced significantly by feeding DHA at the 2 and 4% levels (P < 0. 05). Overall, these results suggest that omega-3 fatty acids may have a place as adjuvant nutritional therapy in breast cancer and particularly as part of a neoadjuvant regimen.     

A survey of blood component use in a German university hospital

In view of the promising future for use of n-3 polyunsaturated fatty acids (PUFA) in the prevention of cancer and cardiovascular diseases, it is necessary to ensure that their consumption does not result in detrimental oxidative effects. The aim of the present work was to test a hypothesis that low doses of eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) do not induce harmful modifications of oxidative cell metabolism, as modifications of membrane fatty acid composition occur. Wistar rats received by gavage oleic acid, EPA, or DHA (360 mg/kg body weight/day) for a period of 1 or 4 wk. Fatty acid composition and alpha-tocopherol content were determined for plasma, red blood cell (RBC) membranes, and liver, kidney, lung, and heart microsomal membranes. Susceptibility to oxidative stress induced by tert-butylhydroperoxide was measured in RBC. EPA treatment increased EPA and docosapentaenoic acid (DPA) content in plasma and in all the membranes studied. DHA treatment mainly increased DHA content. Both treatments decreased arachidonic acid content and n-6/n-3 PUFA ratio in the membranes, without modifying the Unsaturation Index. No changes in tissue alpha-tocopherol content and in RBC susceptibility to oxidative stress were induced by either EPA or DHA treatment. The data suggest that EPA and DHA treatments can substantially modify membrane fatty acids, without increasing susceptibility to oxidative stress, when administered at low doses. This opens the possibility for use of low doses of n-3 PUFA for chemoprevention without risk of detrimental secondary effects.     

Genetic mechanisms for duplication and multiduplication of the human CYP2D6 gene and methods for detection of duplicated CYP2D6 genes

PURPOSE: To investigate the nature and reversibility of biochemical and functional changes in the retina encountered over a single generation of dietary n-3 polyunsaturated fatty acid deficiency in guinea pigs. METHODS: Dunkin-Hartley guinea pigs were fed for 16 weeks after weaning with diets supplemented with safflower seed oil (n-3 deficient) or canola oil (n-3 sufficient, control). A number of deficient animals were repleted at 6 weeks with canola oil for 5 or 10 weeks, or at 11 weeks for 5 weeks. Electroretinograms (0.8 and 4.3 log scot td x sec) were collected at 6, 11, and 16 weeks after weaning. Conventional waveforms (a- and b-waves), oscillatory potentials, and receptoral and postreceptoral subcomponents (PIII and PII, respectively) were evaluated. Cone pathway function was assessed with 30-Hz flicker at the brighter intensity. Retinal phospholipid fatty acids were measured by capillary gas-liquid chromatography. RESULTS: Electroretinographic amplitudes showed statistically significant losses in b- and a-waves after 6 and 16 weeks of dietary n-3 deficiency, respectively. The response amplitude to 30-Hz flicker was reduced 42% after 16 weeks. Retinal docosahexaenoic acid (DHA) levels of animals maintained on the safflower oil diet for 16 weeks were 42% of levels in age-matched control subjects. There were significant losses in maximum response amplitudes (R(mPIII) and R(mPII)), although the major effect was a reduction in sensitivity of the receptoral response. Complete functional recovery was observed only in animals repleted for 10 weeks. CONCLUSIONS: Functional deficits in PIII and PII of the electroretinogram were apparent in first-generation guinea pigs fed an n-3 deficient diet. These losses showed a correlation with age and retinal DHA level, although varying degrees of dependence on the DHA level were found. All functional deficits were reversed after 10 weeks of dietary n-3 repletion. The results suggest that DHA may serve several functional and structural roles in the retina and further emphasize the requirement for DHA in the normal development of vision.     

Phospholipid fatty acid composition affects enzymatic antioxidant defenses in cultured Swiss 3T3 fibroblasts

The aim of this work was to study the adaptation of enzymatic antioxidant cell defense to the nature of the membrane polyunsaturated fatty acids (PUFA). 3T3 Swiss fibroblasts were grown for 5 days in a medium supplemented with 50 microM linoleic acid (LA) or eicosapentaenoic acid (EPA) and compared to control cells (C). The phospholipid fatty acid content was evaluated: LA were enriched in n-6 PUFA (27.8%) in comparison to C (6.7%) or EPA (5.6%); EPA were enriched in n-3 PUFA (26.2%) in comparison to LA (4.4%) or C (4.6%). The fatty acid double bond index (DBI) increased from C to LA and EPA. The activities of the three key enzymatic antioxidant defenses, SOD, GPx and GST, increased with the degree of unsaturation of the phospholipid fatty acids. In the cells with fatty acids that are very sensitive to oxidative stress, the higher activities of SOD and GPx might act to limit the initiation of lipid peroxidation and the higher activities of GST and GPx to decrease the toxic effects of the various species produced from lipid degradation.     

Determination of DNA adducts of malonaldehyde in humans: effects of dietary fatty acid composition

The effects of dietary fatty acid composition on the endogenous formation of DNA adducts of malonaldehyde (MA), the major product of lipid peroxidation, were investigated in humans. A group of 59 healthy individuals of both sexes and different ages was initially fed a milk fat-based diet rich in saturated fatty acids for 14 days. Following this initial period, after which the group was considered homogeneous with respect to diet, 30 randomly chosen subjects were given a sunflower oil-based (rich in polyunsaturated fatty acids) (SO) diet and the remaining 29 individuals a low erucic acid rapeseed oil-based (rich in monounsaturated fatty acids) (RO) diet for 25 days. The fatty acid composition of plasma lipid fractions and the level of DNA adducts of MA in total white blood cells were then determined at the end of the SO and RO dietary periods. DNA adduct levels were measured by 32p-postlabelling using reversed-phase HPLC with on-line detection of radioactivity. Higher concentrations of polyunsaturated fatty acids in plasma triglycerides and higher levels of DNA adducts of MA were found in the subjects on the SO diet when compared with those in the RO dietary group. A large inter-individual variation in adduct levels was observed. The average adduct level in the SO diet group was 7.4 +/- 8.7 adducts/10(7) nucleotides (n = 23). This level was 3.6-fold higher than that found in individuals in the RO diet group (P < 0.001). Our results, in conjunction with the mutagenic and carcinogenic properties of MA, thus suggest the interaction of lipid peroxidation products such as MA with DNA as one plausible mechanism explaining the involvement of dietary fat in carcinogenesis.     

Effect of dietary alpha-linolenic acid and its ratio to linoleic acid on platelet and plasma fatty acids and thrombogenesis

The effect of dietary alpha-linolenic acid (18:3n-3) and its ratio to linoleic acid (18:2n-6) on platelet and plasma phospholipid (PL) fatty acid patterns and prostanoid production were studied in normolipidemic men. The study consisted of two 42-d phases. Each was divided into a 6-d pre-experimental period, during which a mixed fat diet was fed, and two-18 d experimental periods, during which a mixture of sunflower and olive oil [low 18:3n-3 content, high 18:2/18:3 ratio (LO-HI diet)], soybean oil (intermediate 18:3n-3 content, intermediate 18:2/18:3 ratio), canola oil (intermediate 18:3n-3 content, low 18:2/18:3 ratio) and a mixture of sunflower, olive and flax oil [high 18:3n-3 content, low 18:2/18:3 ratio (HI-LO diet)] provided 77% of the fat (26% of the energy) in the diet. The 18:3n-3 content and the 18:2/18:3 ratio of the experimental diets were: 0.8%, 27.4; 6.5%, 6.9; 6.6%, 3.0; and 13.4%, 2.7, respectively. There were appreciable differences in the fatty acid composition of platelet and plasma PLs. Nevertheless, 18:1n-9, 18:2n-6 and 18:3n-3 levels in PL reflected the fatty acid composition of the diets, although very little 18:3n-3 was incorporated into PL. Both the level of 18:3n-3 in the diet and the 18:2/18:3 ratio were important in influencing the levels of longer chain n-3 fatty acid, especially 20:5n-3, in platelet and plasma PL. Production of 6-keto-PGF1 alpha was significantly (P < 0.05) higher following the HI-LO diet than the LO-HI diet although dietary fat source had no effect on bleeding time or thromboxane B2 production.(ABSTRACT TRUNCATED AT 250 WORDS)