Effects of fish oil fatty acids on plasma lipids and lipoproteins and oxidant-antioxidant imbalance in healthy subjects

Improvement of cardiometabolic markers after fish oil intervention in young Mexican adults and the role of PPARα L162V and PPARγ2 P12A

Polyunsaturated fatty acids (PUFA) contained in fish oil (FO) are ligands for peroxisome proliferator-activated receptors (PPAR) that may induce changes in cardiometabolic markers. Variation in PPAR genes may influence the beneficial responses linked to FO supplementation in young adults. The study aimed to analyze the effect of FO supplementation on glucose metabolism, circulating lipids and inflammation according to PPARα L162V and PPARγ2 P12A genotypes in young Mexican adults. 191 young, non-smoking subjects between 18 and 40 years were included in a one-arm study. Participants were supplemented with 2.7 g/day of EPA+DHA, during six weeks. Dietary analysis, body composition measurements and indicators for glucose metabolism, circulating lipids, and markers for inflammation were analyzed before and after intervention. An overall decrease in triglycerides (TG) and an increase in HS-ω3 index were observed in all subjects [-4.1 mg/dL, (SD:±51.7), P=.02 and 2.6%, (SD:±1.2), P<.001 respectively]. Mean fasting insulin and glycated hemoglobin (HbA1c%) were significantly decreased in all subjects [-0.547mlU/L, (SD:±10.29), P=.034 and-0.07%, (SD:±0.3), P<.001 respectively], whereas there was no change in body composition, fasting glucose, adiponectin and inflammatory markers. Subjects carrying the minor alleles of PPARα L162V and PPARγ2 P12A had higher responses in reduction of TG and fasting insulin respectively. Interestingly, doses below 2.7 g/day (1.8 g/day) were sufficient to induce a significant reduction in fasting insulin and HbA1c% from baseline (P=.019 and P<.001). The observed responses in triglycerides and fasting insulin in the Mexican population give further evidence of the importance of FO supplementation in young people as an early step towards the prevention of cardiometabolic disease.

Cardioprotective effect of pentacyclic triterpene, lupeol and its ester on cyclophosphamide-induced oxidative stress

Cyclophosphamide (CP), an alkylating agent widely used in cancer chemotherapy, causes fatal cardiotoxicity. In the present study, lupeol, a pentacyclic triterpene, isolated from Crataeva nurvala stem bark and its ester, lupeol linoleate were investigated for their possible cardioprotective effects against CP-induced toxicity. Male albino rats of Wistar strain were injected with a single dose of CP (200 mg/kg body weight, ip). In CP-administered rats, activities of lactate dehydrogenase and creatine phosphokinase were elevated in serum with a concomitant decline in their activities in the cardiac tissue. Significant increases (P B < 0.001) in the levels of lipid peroxides and a decrease (P B < 0.001) in the levels of enzymic (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and glutathione-s-transferase) and nonenzymic (reduced glutathione, vitamin C and vitamin E) antioxidants in the heart were also observed. The cardioprotective effects of lupeol (50 mg/kg body weight for 10 days orally) and its ester, lupeol linoleate (50 mg/kg body weight for 10 days orally) were evident from the significant reversal of the above alterations induced by CP. These observations highlight the antioxidant property of triterpenes and their cytoprotective action against CPinduced cardiotoxicity.

Genetic evidence for role of carotenoids in age-related macular degeneration in the Carotenoids in Age-Related Eye Disease Study (CAREDS)

PURPOSE

We tested variants in genes related to lutein and zeaxanthin status for association with age-related macular degeneration (AMD) in the Carotenoids in Age-Related Eye Disease Study (CAREDS).

METHODS

Of 2005 CAREDS participants, 1663 were graded for AMD from fundus photography and genotyped for 424 single nucleotide polymorphisms (SNPs) from 24 candidate genes for carotenoid status. Of 337 AMD cases 91% had early or intermediate AMD. The SNPs were tested individually for association with AMD using logistic regression. A carotenoid-related genetic risk model was built using backward selection and compared to existing AMD risk factors using the area under the receiver operating characteristic curve (AUC).

RESULTS

A total of 24 variants from five genes (BCMO1, BCO2, NPCL1L1, ABCG8, and FADS2) not previously related to AMD and four genes related to AMD in previous studies (SCARB1, ABCA1, APOE, and ALDH3A2) were associated independently with AMD, after adjusting for age and ancestry. Variants in all genes (not always the identical SNPs) were associated with lutein and zeaxanthin in serum and/or macula, in this or other samples, except for BCO2 and FADS2. A genetic risk score including nine variants significantly (P = 0.002) discriminated between AMD cases and controls beyond age, smoking, CFH Y402H, and ARMS2 A69S. The odds ratio (95% confidence interval) for AMD among women in the highest versus lowest quintile for the risk score was 3.1 (2.0-4.9).

CONCLUSIONS

Variants in genes related to lutein and zeaxanthin status were associated with AMD in CAREDS, adding to the body of evidence supporting a protective role of lutein and zeaxanthin in risk of AMD.

Effects of lutein and docosahexaenoic Acid supplementation on macular pigment optical density in a randomized controlled trial

We studied the macular pigment ocular density (MPOD) in patients with early age macular degeneration (AMD) before and 1 year after nutritional supplementation with lutein and docosahexaenoic acid (DHA). Forty-four patients with AMD were randomly divided into two groups that received placebo (n = 21) or a nutritional supplement (n = 23, 12 mg of lutein and 280 mg of DHA daily). Heterochromatic flicker photometry was used to determine the MPOD. At baseline, the MPOD in AMD patients with placebo was 0.286 ± 0.017 meanwhile in AMD patients with supplementation it was 0.291 ± 0.016. One year later, the mean MPOD had increased by 0.059 in the placebo group and by 0.162 in patients receiving lutein and DHA. This difference between groups was significant (p < 0.05). Lutein and DHA supplementation is effective in increasing the MPOD and may aid in prevention of age related macular degeneration.

Stressing the heart of the matter: re-thinking the mechanisms underlying therapeutic effects of n-3 polyunsaturated fatty acids

Despite their clear therapeutic effects in coronary heart disease, use of n-3 polyunsaturated fatty acids (PUFAs) to treat other types of cardiovascular disease remains controversial, and serious obstacles exist in implementing them as a reliable and consistent drug therapy. The foremost of these is that a molecular mechanism and relevant dosages have not been firmly established in other forms of cardiovascular disease. In this brief review, we highlight the current state of knowledge regarding the mechanisms behind n-3 PUFA action in the cardiovascular system. We also propose the novel hypothesis that lipid peroxidation products derived from n-3 PUFAs may be driving much of their beneficial cardiovascular effects, particularly in the myocardium. We conclude by discussing evidence to support this hypothesis, and its possible clinical ramifications.

Influence of fish oil or folate supplementation on the time course of plasma redox markers during pregnancy

Maternal supplementation with long-chain PUFA, to improve infant neurological development, might cause additional increase of oxidative stress. Pregnant women aged 18-41 years were randomised into one of four supplementation groups. From week 22 on, they received supplements containing either modified fish oil (n 69), 5-methyl-tetrahydro-folate (n 65), both (n 64), or placebo (n 72). Plasma Trolox-equivalent antioxidative capacity (TEAC), concentrations of alpha-tocopherol, retinol, beta-carotene, free thiol groups, uric acid and thiobarbituric acid-reactive substances (TBARS) were determined at weeks 20 and 30 and at delivery. The studied antioxidants showed no significant differences between the four supplementation groups. At week 30 plasma TBARS levels were found to be significantly higher in the fish oil group (0.80 (sem 0.04) micromol/l) than in the folate (0.67 (sem 0.03) micromol/l; P = 0.024) and control (0.69 (sem 0.04) micromol/l; P = 0.01) groups. Concentrations of retinol and free thiol groups decreased during pregnancy, whereas uric acid increased and beta-carotene as well as TEAC showed only minor changes. Fish oil supplementation during the second half of pregnancy appears not to decrease antioxidant status. The increased TBARS levels at week 30 may indicate a period of increased oxidative stress in plasma at this time.

Fatty acid desaturase expression in human leucocytes correlates with plasma phospholipid fatty acid status

Associations between and changes in plasma phospholipid fatty acid (FA) concentrations and expression of delta 5 desaturase (D5D), delta 6 desaturase (D6D) and delta 9 desaturase (D9D) in leucocytes were investigated both before and during n-3 FA supplementation for 2 weeks in 20 healthy individuals. Participants were divided into two groups depending on fish intake: one fish meal or less per week and no marine FA supplement (Lowfish, n = 9) and more than one fish meal per week and/or daily oral marine FA supplement (Highfish, n = 11). Before starting supplementation (t = 0), concentrations of n-3 FAs were significantly lower in the Lowfish group compared to the Highfish group. During supplementation in both groups, n-3 FAs increased, whereas n-6 FAs decreased. D5D expression was significantly higher in Lowfish compared to Highfish at t = 0. No difference in D6D or D9D expression was observed. D5D expression was inversely correlated with EPA, DPA, DHA and total n-3 FA, and positively correlated with the ratio total n-6 FA/total n-3 FA at t = 0. Expression of D5D in the Lowfish group as well as D6D in both groups significantly decreased relative to the expression at t = 0 during the first day of supplement. PUFA concentration was generally predicted by its precursor FA and D5D or D6D expression. The correlations mentioned disappeared after 2 weeks of supplementation. This indicates that steady-state FA desaturase expression is associated with plasma phospholipid FA composition. Whether leucocyte desaturase expression may have potential as a marker of PUFA status merits further investigation.

The influence of supplemental lutein and docosahexaenoic acid on serum, lipoproteins, and macular pigmentation

BACKGROUND

Lutein and docosahexaenoic acid (DHA) may protect against age-related macular degeneration (AMD). Lutein is a component of macular pigment. DHA is in the retina.

OBJECTIVE

The objective of this 4-mo study was to determine the effects of lutein (12 mg/d) and DHA (800 mg/d) on their serum concentrations and macular pigment optical density (MPOD).

DESIGN

Forty-nine women (60-80 y) were randomly assigned to placebo, DHA, lutein, or lutein + DHA supplement. Serum was analyzed for lutein and DHA (0, 2, and 4 mo). MPOD was determined (0 and 4 mo) at 0.4, 1.5, 3, and 5 degrees temporal retinal eccentricities. Serum was analyzed for lipoproteins (4 mo).

RESULTS

There was no interaction between lutein and DHA supplementations for serum lutein and MPOD. The lutein supplementation x DHA supplementation x month interaction was significant for serum DHA response (P < 0.05). In the lutein group, serum lutein increased from baseline at 2 and 4 mo (P < 0.001), and MPOD increased at 3.0 degrees (P < 0.01). In the DHA group, serum DHA increased at 2 and 4 mo (P < 0.0001), and MPOD increased at 0.4 degrees (P < 0.05). In the lutein + DHA group, serum lutein and DHA increased at 2 and 4 mo (P < 0.01), and MPOD increased at 0.4, 1.5, and 3 degrees (P = 0.06, 0.08, and 0.09, respectively). Differences from placebo in lipoprotein subfractions were greatest for the lutein + DHA group (4 mo).

CONCLUSIONS

Lutein supplementation increased MPOD eccentrically. DHA resulted in central increases. These results may be due to changes in lipoproteins. Lutein and DHA may aid in prevention of age-related macular degeneration.

Bone turnover and nutritional status in Crohn's disease: relationship to circulating mononuclear cell function and response to fish oil and antioxidants

Crohn's disease is associated with osteoporosis, malnutrition and altered function of peripheral blood mononuclear cells (PBMC). The responses of circulating immune cells and extra-intestinal manifestations to increased inflammatory activity and to modulation by dietary supplementation are uncertain. The relationships between disease status, bone turnover and body mass and composition, PBMC function and fatty acid availability have been investigated in patients with Crohn's disease. The availability of n-3 and n-6 PUFA is altered in adult patients and interferon (IFN)-γ production by PBMC is lower. Increased inflammatory activity is associated with increased bone resorption in adult patients and decreased body mass in paediatric patients. In healthy male subjects there is a proportionate relationship between supplementary intake of EPA and DHA (0.3–2.0 g as fish oil/d) in combination with antioxidants (vitamins A, C and E and Se) and incorporation into plasma phospholipids and PBMC, and a non-linear relationship with PBMC synthesis of TNF-α, IL-6 and prostaglandin E2 (decrease) and IFN-γ (increase). In adults with Crohn's disease high-dose fish oil (2.7 g EPA+DHA/d) in combination with antioxidants (vitamins A, C and E and Se) increases the EPA and DHA content of PBMC and decreases the production of IFN-γ by PBMC, but is not associated with effects on bone turnover or nutritional status.

Suplementação de ácidos graxos ômega 3 em atletas de competição: impacto nos mediadores bioquímicos relacionados com o metabolismo lipídico

OBJETIVO: Avaliar o efeito da suplementação dos ácidos graxos ômega 3 em atletas de natação sobre indicadores bioquímicos. MÉTODOS: Nadadores de elite (n = 14) do sexo masculino foram avaliados em estudo randomizado, controlado por placebo pelo período de seis semanas (45 dias). O grupo placebo (GP) recebeu óleo mineral (n = 6) e o grupo suplementado (n = 8), óleo de peixe (GOP) contendo, no total, 950mg de ácido eicosapentaenóico e 500mg de ácido docosapentaenóico. Amostras de sangue foram coletadas imediatamente antes (T0), aos 15 (T15), aos 30 (T30) e aos 45 (T45) dias de suplementação para análise da composição dos ácidos graxos por cromatografia gasosa e para quantificação das lipoproteínas plasmáticas através de kits comerciais específicos. RESULTADOS: Os resultados revelaram um desajuste na dieta dos atletas considerando a ingestão g/kg de massa corporal dos macronutrientes. A análise do questionário de freqüência de consumo mostrou que os atletas não ingeriram regularmente fontes alimentares de ômega 3 e que o consumo de peixes, em 85% da amostra, era inferior ou igual a uma vez na semana. O perfil de ácidos graxos plasmáticos evidenciou aumento dos ácidos graxos poliinsaturados ômega 3 (P < 0,05) e redução do ácido araquidônico no grupo suplementado (P < 0,05). A suplementação com óleo de peixe ocasionou efeito hipocolesterolêmico, com redução nos teores sanguíneos de VLDL, LDL e colesterol total. Os valores de HDL não apresentaram diferenças significativas entre os grupos em nenhum momento estudado (P > 0,05). CONCLUSÃO: A suplementação de ácidos graxos N-3 em atletas nadadores altera os indicadores bioquímicos do metabolismo lipídico, influenciando na redução das lipoproteínas plasmáticas, ricas em colesterol e na prevenção de doenças cardiovasculares.

Supplementation with fruit and vegetable soups and beverages increases plasma carotenoid concentrations but does not alter markers of oxidative stress or cardiovascular risk factors

This study was aimed at determining whether an increase of 5 portions of fruits and vegetables in the form of soups and beverages has a beneficial effect on markers of oxidative stress and cardiovascular disease risk factors. The study was a single blind, randomized, controlled, crossover dietary intervention study. After a 2-wk run-in period with fish oil supplementation, which continued throughout the dietary intervention to increase oxidative stress, the volunteers consumed carotenoid-rich or control vegetable soups and beverages for 4 wk. After a 10-wk wash-out period, the volunteers repeated the above protocol, consuming the other intervention foods. Both test and control interventions significantly increased the % energy from carbohydrates and decreased dietary protein and vitamin B-12 intakes. Compared with the control treatment, consumption of the carotenoid-rich soups and beverages increased dietary carotenoids, vitamin C, alpha-tocopherol, potassium, and folate, and the plasma concentrations of alpha-carotene (362%), beta-carotene (250%) and lycopene (31%) (P < 0.01) and decreased the plasma homocysteine concentration by 8.8% (P < 0.01). The reduction in plasma homocysteine correlated weakly with the increase in dietary folate during the test intervention (r = -0.35, P = 0.04). The plasma antioxidant status and markers of oxidative stress were not affected by treatment. Consumption of fruit and vegetable soups and beverages makes a useful contribution to meeting dietary recommendations for fruit and vegetable consumption.

Influence of three rapeseed oil-rich diets, fortified with alpha-linolenic acid, eicosapentaenoic acid or docosahexaenoic acid on the composition and oxidizability of low-density lipoproteins: results of a controlled study in healthy volunteers

OBJECTIVE

To compare the individual effects of dietary alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) on low-density lipoprotein (LDL) fatty acid composition, ex vivo LDL oxidizability and tocopherol requirement.

DESIGN, SETTING AND SUBJECTS

A randomized strictly controlled dietary study with three dietary groups and a parallel design, consisting of two consecutive periods. Sixty-one healthy young volunteers, students at a nearby college, were included. Forty-eight subjects (13 males, 35 females) completed the study.

INTERVENTIONS

Subjects received a 2-week wash-in diet rich in monounsaturated fatty acids (21% energy) followed by experimental diets enriched with about 1% of energy of ALA, EPA or DHA for 3 weeks. The omega-3 (n-3) fatty acids were provided with special rapeseed oils and margarines. The wash-in diet and the experimental diets were identical, apart from the n-3 fatty acid composition and the tocopherol content, which was adjusted to the content of dienoic acid equivalents.

RESULTS

Ex vivo oxidative susceptibility of LDL was highest after the DHA diet, indicated by a decrease in lag time (-16%, P<0.001) and an increase in the maximum amount of conjugated dienes (+7%, P<0.001). The EPA diet decreased the lag time (-16%, P<0.001) and the propagation rate (-12%, P<0.01). Tocopherol concentrations in LDL decreased in the ALA group (-13.5%, P<0.05) and DHA group (-7.3%, P<0.05). Plasma contents of tocopherol equivalents significantly decreased in all three experimental groups (ALA group: -5.0%, EPA group: -5.7%, DHA group: -12.8%). The content of the three n-3 polyunsaturated fatty acid differently increased in the LDL: on the ALA diet, the ALA content increased by 89% (P<0.001), on the EPA diet the EPA content increased by 809% (P<0.001) and on the DHA diet, the DHA content increased by 200% (P<0.001). In addition, the EPA content also enhanced (without dietary intake) in the ALA group (+35%, P<0.01) and in the DHA group (+284%, P<0.001).

CONCLUSIONS

Dietary intake of ALA, EPA or DHA led to a significant enrichment of the respective fatty acid in the LDL particles, with dietary EPA preferentially incorporated. In the context of a monounsaturated fatty acid-rich diet, ALA enrichment did not enhance LDL oxidizability, whereas the effects of EPA and DHA on ex vivo LDL oxidation were inconsistent, possibly in part due to further changes in LDL fatty acid composition.

Fat supplementation, health, and endurance performance

Pre-exercise fat ingestion (i.e., long chain triacylglycerol ingestion 1 to 4 h before exercise), medium-chain triacylglycerols, fish oil, and conjugated linoleic acid have been suggested to alter metabolism to achieve weight loss, alter lipid profiles, or improve performance. However, studies have demonstrated that ingestion of meals with long-chain triacylglycerols before exercise has little or no effect on metabolism and does not alter subsequent exercise performance. Also, medium-chain triacylglycerol supplementation before or during exercise has not been shown to be ergogenic, although this could be related to the small amounts of medium-chain triacylglycerol that can be ingested before gastrointestinal discomfort occurs. Fish oil may improve red blood cell deformability, but these effects are likely to be small and do not seem to influence maximum oxygen delivery or exercise performance. Conjugated linoleic acid has been implicated in weight loss, but based on the results of human studies it must be concluded that the effects of conjugated linoleic acid on body weight loss are far less clear than those observed in animal studies. Most studies have not found any evidence for a beneficial effect of conjugated linoleic acid.

Lipid peroxidation and oxidant stress regulate hepatic apolipoprotein B degradation and VLDL production

How omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) lower plasma lipid levels is incompletely understood. We previously showed that marine omega-3 PUFAs (docosahexaenoic acid [DHA] and eicosapentaenoic acid) stimulate a novel pathway, post-ER presecretory proteolysis (PERPP), that degrades apolipoprotein B100 (ApoB100), thereby reducing lipoprotein secretion from liver cells. To identify signals stimulating PERPP, we examined known actions of omega-3 PUFA. In rat hepatoma or primary rodent hepatocytes incubated with omega-3 PUFA, cotreatment with the iron chelator desferrioxamine, an inhibitor of iron-dependent lipid peroxidation, or vitamin E, a lipid antioxidant, suppressed increases in thiobarbituric acid-reactive substances (TBARSs; a measure of lipid peroxidation products) and restored ApoB100 recovery and VLDL secretion. Moreover, omega-6 and nonmarine omega-3 PUFA, also prone to peroxidation, increased ApoB100 degradation via intracellular induction of TBARSs. Even without added fatty acids, degradation of ApoB100 in primary hepatocytes was blocked by desferrioxamine or antioxidant cotreatment. To extend these results in vivo, mice were infused with DHA, which increased hepatic TBARSs and reduced VLDL-ApoB100 secretion. These results establish a novel link between lipid peroxidation and oxidant stress with ApoB100 degradation via PERPP, and may be relevant to the hypolipidemic actions of dietary PUFAs, the basal regulation of ApoB100 secretion, and hyperlipidemias arising from ApoB100 overproduction.

Effects of enhanced consumption of fruit and vegetables on plasma antioxidant status and oxidative resistance of LDL in smokers supplemented with fish oil

OBJECTIVE

To determine whether consumption of five portions of fruit and vegetables per day reduces the enhancement of oxidative stress induced by consumption of fish oil.

SUBJECTS

A total of 18 free-living healthy smoking volunteers, aged 18-63 y, were recruited by posters and e-mail in The University of Reading, and by leaflets in local shops.

DESIGN

A prospective study.

SETTING

Hugh Sinclair Unit of Human Nutrition, School of Food Biosciences, The University of Reading, Whiteknights PO Box 226, Reading RG6 6AP, UK.

INTERVENTION

All subjects consumed a daily supplement of 4 x 1 g fish oil capsules for 9 weeks. After 3 weeks, they consumed an additional five portions of fruits and vegetables per day, and then they returned to their normal diet for the last 3 weeks of the study. Fasting blood samples were taken at the ends of weeks 0, 3, 6 and 9.

RESULTS

The plasma concentrations of ascorbic acid, lutein, beta-cryptoxanthin, alpha-carotene and beta-carotene all significantly increased when fruit and vegetable intake was enhanced (P<0.05). Plasma concentrations of alpha-tocopherol, retinol and uric acid did not change significantly during the period of increased fruit and vegetable consumption. Plasma oxidative stability, assessed by the oxygen radical absorbance capacity (ORAC) assay, also increased from weeks 3-6 (P<0.001) but not in association with increases in measured antioxidants. Lag phase before oxidation of low-density lipoprotein (LDL) significantly decreased in the first 3 weeks of the study, reflecting the incorporation of EPA and DHA into LDL (P<0.0001). Subsequent enhanced fruit and vegetable consumption significantly reduced the susceptibility of LDL to oxidation (P<0.005).

CONCLUSION

Fish oil reduced the oxidative stability of plasma and LDL, but the effects were partially offset by the increased consumption of fruit and vegetables.

Dietary supplementation with a natural carotenoid mixture decreases oxidative stress

OBJECTIVE

To determine whether dietary supplementation with a natural carotenoid mixture counteracts the enhancement of oxidative stress induced by consumption of fish oil.

DESIGN

A randomised double-blind crossover dietary intervention.

SETTING

Hugh Sinclair Unit of Human Nutrition, School of Food Biosciences, The University of Reading, Whiteknights PO Box 226, Reading RG6 6AP, UK.

SUBJECTS AND INTERVENTION

A total of 32 free-living healthy nonsmoking volunteers were recruited by posters and e-mails in The University of Reading. One volunteer withdrew during the study. The volunteers consumed a daily supplement comprising capsules containing fish oil (4 x 1 g) or fish oil (4 x 1 g) containing a natural carotenoid mixture (4 x 7.6 mg) for 3 weeks in a randomised crossover design separated by a 12 week washout phase. The carotenoid mixture provided a daily intake of beta-carotene (6.0 mg), alpha-carotene (1.4 mg), lycopene (4.5 mg), bixin (11.7 mg), lutein (4.4 mg) and paprika carotenoids (2.2 mg). Blood and urine samples were collected on days 0 and 21 of each dietary period.

RESULTS

The carotenoid mixture reduced the fall in ex vivo oxidative stability of low-density lipoprotein (LDL) induced by the fish oil (P=0.045) and it reduced the extent of DNA damage assessed by the concentration of 8-hydroxy-2'-deoxyguanosine in urine (P=0.005). There was no effect on the oxidative stability of plasma ex vivo assessed by the oxygen radical absorbance capacity test. beta-Carotene, alpha-carotene, lycopene and lutein were increased in the plasma of subjects consuming the carotenoid mixture. Plasma triglyceride levels were reduced significantly more than the reduction for the fish oil control (P=0.035), but total cholesterol, HDL and LDL levels were not significantly changed by the consumption of the carotenoid mixture.

CONCLUSIONS

Consumption of the natural carotenoid mixture lowered the increase in oxidative stress induced by the fish oil as assessed by ex vivo oxidative stability of LDL and DNA degradation product in urine. The carotenoid mixture also enhanced the plasma triglyceride-lowering effect of the fish oil.

SPONSORSHIP

: The study was supported by funding from the Greek Studentship Foundation and from Unilever Bestfoods plc. Carotenoids were contributed by Overseal Foods plc.

Hepatoprotective effect of the extract and isocytisoside from Aquilegia vulgaris

The hepatoprotective effect of the ethanol extract (AvEE) and the main fl avonoid compound 4'-methoxy-5,7-dihydroxy fl avone 6-C-beta-glucopyranoside (isocytisoside, ISOC) from the leaves and stems of Aquilegia vulgaris L. were studied using the CCl(4)-induced hepatotoxicity test. The acute toxicity test in mice showed that AvEE can be classi fi ed as nontoxic since a dose of 3000 mg/ kg did not cause mortality. The barbiturate-induced sleeping time prolonged by CCl(4) administration to mice was signi fi cantly reduced after AvEE treatment proving the protective effect of the extract on microsomal drug-metabolizing enzymes.AvEE and ISOC administered to rats 48 h, 24 h and 2 h before, and 6 h after CCl(4) intoxication caused a signi fi cant decrease in the CCl(4)-induced elevation of hepatic enzymes activity in serum, i.e. sorbitol dehydrogenase (SDH), glutamate oxaloacetate and glutamate pyruvate transaminases (GOT, GPT). Both substances induced CCl(4)-diminished erythrocyte superoxide dismutase (SOD) and reduced the activities of glutathione peroxidase (GPx) and glutathione reductase (GR) preliminarily enhanced by CCl(4). The hepatoprotective properties of AvEE and ISOC were con fi rmed by pathomorphological examination of the liver.

Influence of fish oil supplementation on in vivo and in vitro oxidation resistance of low-density lipoprotein in type 2 diabetes

OBJECTIVE

Fish oil supplement has been proposed as a non-pharmacological strategy to correct the atherogenic lipid profile associated with type 2 diabetes mellitus. However, fish oil may have deleterious effects on lipid peroxidation and glycemic control.

DESIGN

In this study, 44 type 2 diabetic patients were randomized to vitamin E standardized (53.6 mg/day) supplementation (capsules) with 4 g daily of either fish oil (n=23) or corn oil (n=21) for 8 weeks preceded by a 4 week run-in period of corn oil supplementation. LDL was isolated by density gradient ultracentrifugation and oxidized in vitro with Cu(2+). As a marker of in vivo oxidation malondialdehyde concentration in LDL (LDL-MDA) was measured.

RESULTS

Fish oil reduced both mean lag time (before, 57.8; after, 48.8 min, P<0.001) and mean propagation rate (before, 0.018 DeltaOD/min; after, 0.015 DeltaOD/min, P<0.001), whereas corn oil had no influence on lag time and propagation rate. The changes in lag time and propagation rate differed significantly between fish oil and corn oil treatment. LDL-MDA changes differed borderline significantly between groups (FO, 110.4 pmol/mg protein; CO, 6.7 pmol/mg protein; P=0.057). Fish oil supplementation had no influence on glycemic control as assessed from HbA(1c) and fasting blood glucose.

CONCLUSION

According to our findings, fish oil supplementation leads to increased in vivo oxidation and increased in vitro oxidation susceptibility of LDL particles. More studies are needed to clarify the clinical importance of this finding.

Plant- and marine-derived n-3 polyunsaturated fatty acids have differential effects on fasting and postprandial blood lipid concentrations and on the susceptibility of LDL to oxidative modification in moderately hyperlipidemic subjects

BACKGROUND

Dietary alpha-linolenic acid (ALA) can be converted to long-chain n-3 polyunsaturated fatty acids (PUFAs) in humans and may reproduce some of the beneficial effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on cardiovascular disease risk factors.

OBJECTIVE

This study aimed to compare the effects of increased dietary intakes of ALA and EPA+DHA on a range of atherogenic risk factors.

DESIGN

This was a placebo-controlled, parallel study involving 150 moderately hyperlipidemic subjects randomly assigned to 1 of 5 interventions: 0.8 or 1.7 g EPA+DHA/d, 4.5 or 9.5 g ALA/d, or an n-6 PUFA control for 6 mo. Fatty acids were incorporated into 25 g of fat spread and 3 capsules to be consumed daily.

RESULTS

The change in fasting or postprandial lipid, glucose, or insulin concentrations or in blood pressure was not significantly different after any of the n-3 PUFA interventions compared with the n-6 PUFA control. The mean (+/- SEM) change in fasting triacylglycerols after the 1.7-g/d EPA+DHA intervention (-7.7 +/- 4.99%) was significantly (P < 0.05) different from the change after the 9.5-g/d ALA intervention (10.9 +/- 4.5%). The ex vivo susceptibility of LDL to oxidation was higher after the 1.7-g/d EPA+DHA intervention than after the control and ALA interventions (P < 0.05). There was no significant change in plasma alpha-tocopherol concentrations or in whole plasma antioxidant status in any of the groups.

CONCLUSION

At estimated biologically equivalent intakes, dietary ALA and EPA+DHA have different physiologic effects.

Modulation of antioxidant defence system by dietary fat in rats intoxicated with o-toluidine

o-Toluidine was administered to rats in the diet for four weeks at levels approximately 40, 80 and 160 mg/kg b.w. per day. Two types of diet have been used, standard (4% fat) and high fat (14% fat). Activity of antioxidant enzymes, level of glutathione and thiobarbituric acid reactive substances were measured in liver. Glutathione peroxidase was significantly increased in all treated groups while glutathione S-transferase and glutathione reductase were elevated in rats fed high-fat diet. o-Toluidine slightly enhanced catalase activity regardless of the kind of diet. Superoxide dismutase was the only enzyme whose activity was lowered in almost all treated groups. Enzymatic and nonenzymatic microsomal lipid peroxidation was enhanced 2- to 3-fold in both diet groups. Reduced glutathione level in liver was 2.3- to 4.0-fold increased in all treated groups. Our findings indicate that free radical processes can be involved in the toxic effects of o-toluidine and dietary fat can modify the response of some antioxidant enzymes to this compound.

Rapid alterations of serum oxidant and antioxidant status with the intravenous administration of n-6 polyunsaturated fatty acids

In an attempt to achieve the safe intravenous administration of two n-6 polyunsaturated fatty acids (PUFAs), gamma-linolenic acid (GLA) and arachidonic acid (AA), and to study the subsequent changes on the total oxidant and antioxidant status, various steadily increasing doses of each acid were injected intravenously at different infusion times in 28 male rabbits. Blood samples were collected at 15-min time intervals by the hepatic veins and from the carotid artery; oxidant status was determined by the thiobarbiturate assay and total antioxidant status (TAS) was assessed by a colorimetric assay. Both n-6 PUFAs were administered with safety at a dose of 25 mg/kg within 10 min accompanied by an increase of malonodialdehyde concentrations in the hepatic veins and in the carotid artery 30-45 min, respectively, after the end of the infusion of GLA and/or AA. Similar changes did not occur in red cell membranes after the infusion of AA. TAS presented reciprocal changes to malonodialdehyde production; the main consumption of TAS was observed in all samples 30-60 min after the end of the infusion of n-6 PUFAs. The above-mentioned rapid alterations occurring in both serum oxidant and antioxidant status after GLA might have a future clinical therapeutic significance in conditions like cancer and disseminated infectious diseases.

A diet containing rapeseed oil-based fats does not increase lipid peroxidation in humans when compared to a diet rich in saturated fatty acids

OBJECTIVE

To compare the effects of a rapeseed oil-based diet containing an increased proportion of easily oxidised polyunsaturated fatty acids such as alpha-linolenic acid with a diet rich in saturated fatty acids on the degree of lipid peroxidation in the human body.

DESIGN

A randomised cross-over study.

SUBJECTS AND INTERVENTIONS

Nineteen healthy moderately hyperlipidemic subjects (six women and 13 men, age 50+/-8 y and body mass index (BMI) 24.5+/-2.6 kg/m(2)) were given a rapeseed oil-based diet (RO) and a control diet (SAT) rich in saturated fatty acids during two consecutive 4 week periods separated by a 4 week wash-out period. Biomarkers of lipid peroxidation and antioxidants were analysed in plasma and urine.

RESULTS

No significant differences in plasma or urinary levels of free 8-iso-prostaglandin F(2alpha), plasma total 8-iso-prostaglandin F(2alpha) plasma hydroperoxides or plasma malondialdehyde were observed between the RO and SAT diets (P=0.14-0.95). A higher concentration of serum gamma-tocopherol was detected after the RO diet compared to the SAT diet (P<0.001), whereas the serum alpha-tocopherol concentration and plasma antioxidative capacity did not differ between the two test diets. The total cholesterol, LDL cholesterol and LDL/HDL ratio were lower after the RO diet compared to the SAT diet (P<0.001), while HDL cholesterol and total triglyceride levels were similar after the two diets.

CONCLUSION

These results suggest that a rapeseed oil-based diet rich in alpha-linolenic acid does not seem to increase the degree of lipid peroxidation in plasma and urine compared to a diet rich in saturated fats. This is possibly due to a sufficient content of antioxidants in the rapeseed oil diet to increase circulating concentrations of antioxidants that may protect unsaturated fatty acids from oxidation.

SPONSORSHIP

Swedish Council for Forestry and Agricultural Research and Foundation for Geriatric Research.

n-3 Fatty acids and cardiovascular disease risk factors among the Inuit of Nunavik

BACKGROUND

Inuit traditionally consume large amounts of marine foods rich in n-3 fatty acids. Evidence exists that n-3 fatty acids have beneficial effects on key risk factors for cardiovascular disease.

OBJECTIVE

Our goal was to verify the relation between plasma phospholipid concentrations of the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and various cardiovascular disease risk factors among the Inuit of Nunavik, Canada.

DESIGN

The study population consisted of 426 Inuit aged 18-74 y who participated in a 1992 health survey. Data were obtained through home interviews and clinical visits. Plasma samples were analyzed for phospholipid fatty acid composition.

RESULTS

Expressed as the percentage of total fatty acids, geometric mean concentrations of EPA, DHA, and their combination in plasma phospholipids were 1.99%, 4.52%, and 6.83%, respectively. n-3 Fatty acids were positively associated with HDL-cholesterol concentrations and inversely associated with triacylglycerol concentrations and the ratio of total to HDL cholesterol. In contrast, concentrations of total cholesterol, LDL cholesterol, and plasma glucose increased as n-3 fatty acid concentrations increased. There were no significant associations between n-3 fatty acids and diastolic and systolic blood pressure and plasma insulin.

CONCLUSIONS

Consumption of marine products, the main source of EPA and DHA, appears to beneficially affect some cardiovascular disease risk factors. The traditional Inuit diet, which is rich in n-3 fatty acids, is probably responsible for the low mortality rate from ischemic heart disease in this population.

Effects of two low-dose oral contraceptives containing ethinylestradiol and either desogestrel or levonorgestrel on serum lipids and lipoproteins with particular regard to LDL size

This study was designed to determine the effects of two low-dose oral contraceptives, most frequently given in our area, monophasic desogestrel/ethinylestradiol (DG/EE) and triphasic levonorgestrel/ethinylestradiol (LNG/EE), on lipoprotein parameters, especially LDL particle size and HDL subclass distribution (determined by lipid-stained 2%-20% polyacrylamide gradient gel electrophoresis) in 37 healthy normolipidemic women aged 19 to 27 years. Lipid and lipoprotein parameters were measured before the start of treatment and in the third month of oral contraceptive use. Results reflected the estrogen-progestin balance. As compared with baseline values, with both formulations, plasma total cholesterol, phospholipids, and HDL3 cholesterol increased, and LDL-predominant peak size decreased, with a translation of LDL pattern A towards pattern I. With DG/EE, plasma triglycerides, apolipoproteins AI and B increased. With LNG/EE, LDL cholesterol increased, and HDL2 cholesterol decreased. All these modifications were moderate, within threshold limits. Estrogen-dominant monophasic DG/EE appears to be more favorable than progestin-dominant triphasic LNG/EE, since the reduction in LDL-predominant peak size is not associated with an increase in LDL cholesterol or with a decrease in HDL2 cholesterol.

Reactive oxygen species and acute modulation of albumin microvascular leakage in the microcirculation of diabetic rats in vivo

Endothelial cells have been reported to generate reactive oxygen species such as the superoxide anion, hydrogen peroxide, and the hydroxyl radical. The aim of this work was to evaluate the role of reactive oxygen species in diabetes-induced changes in vascular permeability. Intravital videomicroscopy was used to study albumin microvascular leakage in the cremaster muscle. The extravasation of a fluorescent macromolecular tracer (FITC-albumin) was measured for 1 h and, after computer-aided image analysis, was expressed as variations of normalized gray levels (arbitrary units). The extravasation of the macromolecular tracer was greater in diabetic rats (5.28 +/- 1.29 vs. 1.96 +/- 0.41 AU at 1 h in diabetic and control rats, respectively). Administration of superoxide dismutase (SOD), which dismutates.O(-)(2) to H(2)O(2), and of catalase which reacts with H(2)O(2) to form H(2)O and molecular oxygen failed to inhibit the increased extravasation of the macromolecular tracer when administered separately. However, a significant inhibition of diabetic increase in albumin extravasation was found when these 2 drugs were administered simultaneously, and in this case, the extravasation of the macromolecular tracer at 1 h was similar in diabetic rats (2.11 +/- 0.61 AU) and normoglycemic rats (1.43 +/- 0. 48 AU). No difference was found in adherent leukocytes or in the leukocyte rolling flux between diabetic and normoglycemic rats. We conclude that reactive oxygen species are responsible for an increase in microvascular permeability likely via leukocyte-independent mechanisms.

Distal proctocolitis and n-3 polyunsaturated fatty acids (n-3 PUFAs): the mucosal effect in situ

It has been postulated that patients with ulcerative colitis (UC) have altered reactivity of gut-associated lymphoid tissue. In such cases there is intense infiltration of the mucosa with immune competent cells and associated tissue damage. We have shown previously that the dietary supplementation with the n-3 polyunsaturated fatty acids (n-3 PUFAs), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) results in significant systemic immune suppression. The aim of this study, therefore, was to evaluate the in situ effect of n-3 PUFAs on distal proctocolitis. Each patient received either fish oil extract (EPA 3.2 g, DHA 2.4 g) (n = 9) or sunflower oil (n = 9) daily in a double blind manner for six months. Monthly assessment included: (1) disease activity using clinical, sigmoidoscopic, and histological scores and (2) immunohistochemical analysis (immunoglobulins, CD profiles) of rectal biopsy specimens (before and after six months supplementation) using monoclonal antibodies and quantitative computer-assisted video image analysis. Prior to receiving supplementation, patients with proctocolitis (n = 18) showed significantly higher numbers of cells expressing CD3 (pan T cells) and HLA-DR and IgM containing cells compared with non-colitic controls (n = 8). Six months supplementation with n-3 PUFAs resulted in significant reduction in the number of cells expressing CD3 and HLA and the percentage of cells containing IgM. There was no significant change in the CD20 nor the percentage of IgG or IgA containing cells in either group of patients with procto-colitis. In patients receiving n-3 PUFA supplementation, there was improvement in the disease activity and histological scores, compared with pretreatment evaluation. This study has demonstrated both evidence of suppression of in situ immune reactivity and concurrent reduction in disease activity in patients with proctocolitis receiving n-3 PUFA supplementation. This may have important implication for therapy in patients with ulcerative colitis.