Intake of total omega-3 fatty acids,eicosapentaenoic acid and docosahexaenoic acid and risk of coronary heart disease in the Spanish EPIC cohort study

Background and aimsThe evidence about the benefits of omega-3 fatty acid intake on coronary heart disease (CHD) is not consistent. We thus aimed to assess the relation between dietary intake of total omega-3 fatty acids (from plant and marine foods) and marine polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on the risk of CHD in the Spanish cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC).Methods and resultsThe analysis included 41,091 men and women aged 20–69 years, recruited from 1992 to1996 and followed-up until December 2004. Omega-3 fatty acid intake was estimated from a validated dietary questionnaire. Only participants with definite incident CHD event were considered as cases. Cox regression models were used to assess the association between the intake of total omega-3 fatty acids, EPA or DHA and CHD. A total of 609 participants (79% men) had a definite CHD event. Mean intakes of total omega-3 fatty acids, EPA and DHA were very similar in the cases and in the cohort, both in men and women. In the multivariate adjusted model, omega-3 fatty acids, EPA and DHA were not related to incident CHD in either men or women. The hazard ratios (HR) for omega-3 were 1.23 in men (95% CI 0.94–15.9, p = 0.20); and 0.77 in women (95% CI 0.46–1.30, p = 0.76).ConclusionIn the Spanish EPIC cohort, with a relatively high intake of fish, no association was found between EPA, DHA and total omega-3 fatty acid intake and risk of CHD.     

Comparative effects of omega-3 and omega-6 polyunsaturated fatty acids on protein metabolism in rats bearing the mammary adenocarcinoma

The comparative effects of diets containing 20% (wt/wt) of either fish oil (FO) or safflower oil (SO) on protein synthesis and catabolism were determined in rats bearing the 7,12-dimethylbenz(a)anthracene (DMBA) 13762 mammary adenocarcinoma in vivo using a 6-hour constant infusion of L-(1-14C)-leucine. Tumor-bearing animals fed FO had significantly lower tumor growth rate (36 +/- 0.5 v 53 +/- 0.7%/d, P less than .05), total tumor protein synthesis (Ts) (1.25 +/- 0.1 v 1.85 +/- 0.1 mumol/h, P less than .05), and tumor protein concentration (12.0 +/- 0.5 v 14.0 +/- 0.7%/d, P less than 0.01). Tumor fractional synthetic rate and total protein breakdown rate of the tumor were unaffected by FO feeding. Both tumor-bearing and saline-control animals fed FO had significantly (P less than .01) lower liver fractional synthetic rate and total protein breakdown rate, and higher liver total protein compared with SO-fed rats. Muscle protein kinetics were unaffected by either treatment or diet. Whole body protein kinetics were not affected by dietary treatment, but the presence of tumor significantly (P less than .001) reduced whole body flux, synthesis, breakdown, and oxidation. Chronic FO feeding for 7 weeks significantly (P less than .001) lowered omega-6 polyunsaturated fatty acids (omega-6 PUFAs) and significantly elevated omega-3 polyunsaturated fatty acids (omega-3 PUFAs) (P less than .001) in both plasma phospholipid and triglycerides. The present study indicates that dietary FO can modulate mammary tumor growth in a manner that reflects changes in protein metabolism in both host and tumor tissues.     

Effects of dietary fat intake in sudden death: Reduction of death with omega-3 fatty acids

Sudden death is one of the most common modes of death in those who survive a myocardial infarction. A recent study of 11,324 patients showed a marked decrease in risk of sudden cardiac death as well as a reduction in all-cause mortality in the post-myocardial infarction group taking a highly purified form of omega-3 fatty acids, added to the use of other secondary prevention drugs, including à-blockers and lipid-lowering therapy. There is now amounting evidence indicating that the clinical benefits of highly purified omega-3 fatty acids may be attributed to their antiarrhythmogenic properties. Evidence for this mechanism of benefit is reviewed here.     

Fatty acid and enzymatic compositional changes in the pancreas of rats fed dietary n-3 and n-6 polyunsaturated fatty acids

The influence of n-3 and n-6 PUFA on the fatty acid composition and the enzyme content of zymogen granules of the normal exocrine pancreas was tested on rats. The animals were fed on different diets comprising 5% fish oil (FO), safflower oil (SFO), and evening primrose oil (EPO) used singly or in combination as dietary fats. The results were compared with those from animals fed 5% hydrogenated beef tallow (HBT). The fatty acid composition and digestive enzyme content were analyzed after a 6-wk feeding period. Differences in the pancreatic fatty acid profiles were related to the fatty acid composition of the ingested fats. Equivalent levels of n-3 fatty acids and 20:3n-6 were obtained with either EPO or FO fed singly or in combination. Similar results were observed with SFO/FO. Higher C20:3n-6/C20:4n-6 ratios were obtained with the oil mixtures. An increase in amylase levels, but a decrease in serine protease (Band 21 kdalton) levels, was associated with EPO. An elevation in procarboxypeptidase levels paralleled an increase in 18:0 levels, whereas the proportion of lipase (Band 49 kdalton) varied inversely with the proportion of C20:3n-6. The SFO/FO mixture elevated the proportions of protease II and proelastase. These results suggest that specific fatty acids influence the proportion of specific digestive enzymes in the zymogen granules.     

Dietary sesamin and docosahexaenoic and eicosapentaenoic acids synergistically increase the gene expression of enzymes involved in hepatic peroxisomal fatty acid oxidation in rats

The interaction of sesamin, one of the most abundant lignans in sesame seed, and highly purified docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA) in the form of ethyl ester in affecting hepatic fatty acid oxidation was examined in rats. In the first experiment, 3 groups of rats were fed with purified experimental diets free of n-3 fatty acid ethyl ester and containing 0%, 0.2%, and 0.4% sesamin (1:1 mixture of sesamin and episesamin), and 2 groups of animals were fed with a 2% DHA ethyl ester diet containing either 0% or 0.2% sesamin. In the second trial, 4 groups of rats were fed with either a 0% or a 2% EPA ethyl ester diet containing 0% or 0.2% sesamin. After 15 days of feeding, DHA and EPA ethyl esters added to a sesamin-free diet little affected the activity and messenger RNA (mRNA) levels of various enzymes involved in fatty acid oxidation. Sesamin increased the activity levels of various hepatic enzymes involved in fatty acid oxidation irrespective of the presence or absence of n-3 fatty acid ethyl ester in diets. However, the diet containing sesamin and DHA or EPA ethyl ester in combination increased many of these parameters synergistically. In particular, the peroxisomal palmitoyl-coenzyme A oxidation rate and acyl-coenzyme A oxidase activity level were much higher in rats fed with sesamin and DHA or EPA in combination than in animals fed with a diet free of n-3 fatty acid ethyl ester and containing sesamin. Analyses of mRNA levels revealed that a diet simultaneously containing sesamin and n-3 fatty acid ethyl ester increased the gene expression of various enzymes involved in peroxisomal fatty acid oxidation in a synergistic manner. However, the combination of sesamin and n-3 fatty acid ethyl esters was ineffective in causing a synergistic increase in mRNA levels of enzymes of mitochondrial fatty acid oxidation, microsomal cytochrome P-450 IV A1, and cytosolic liver-type fatty acid-binding protein. It was concluded that sesamin and DHA or EPA ethyl ester synergistically increased hepatic fatty acid oxidation primarily through up-regulation of the gene expression of peroxisomal fatty acid oxidation enzymes. The results essentially reproduced those observed in our previous study with a diet containing both fish oil and sesamin despite the fact that DHA and EPA ethyl esters were much less effective than fish oil in increasing hepatic fatty acid oxidation.     

Omega-6 and omega-3 polyunsaturated fatty acid levels are reduced in whole blood of Italian patients with a recent myocardial infarction: the AGE-IM study

Objective

The relationship between whole blood fatty acids and myocardial infarction (MI) risk has not been analyzed in detail, especially in Mediterranean countries. The AGE-IM (Acidi Grassi Essenziali e Infarto Miocardico) study was planned to examine the relationships between MI, whole blood fatty acids and the diet in an Italian cohort.

Methods

119 Patients with a recent MI and 103 control subjects were enrolled in the study. The whole blood fatty acid composition was determined; information on anthropometrics, biochemical parameters and blood pressure values were also obtained. Diet composition was assessed using a validated food frequency questionnaire from 86 cases and 72 controls.

Results

Total PUFA, omega-6 and omega-3 PUFA (as percentage of whole blood fatty acids) were significantly lower in MI patients than in matched controls, whereas saturated and monounsaturated fatty acids were higher in cases. MI infarction risk significantly and steadily decreased with increasing levels of total PUFA (OR: 0.14) and of total omega-6 and omega-3 (OR: 0.15 and 0.37, respectively). No correlation was identified between dietary fats and MI risk or between whole blood fatty acid levels and dietary nutrients and fats.

Conclusion

Percentage levels of total PUFA, total omega-3 PUFA and total omega-6 PUFA are lower in MI patients than in matched control subjects in the AGE-IM cohort. These data support a favorable association not only of whole blood percentage levels of total omega-3, but also of total omega-6, with cardiovascular risk.     

The effects of N-6 polyunsaturated fatty acid supplementation on the lipid composition and atherogenesis in mouse models of atherosclerosis

Despite numerous studies, the precise role of dietary n-6 polyunsaturated fatty acids in the pathogenesis of atherosclerosis remains controversial. It has been shown that feeding an n-6-enriched diet resulted in decreased atherosclerosis in African green monkeys and was associated with a reduction in LDL levels. However, other authors reported that n-6 supplementation increased the oxidative stress and the susceptibility of LDL to undergo in vitro oxidation, thus potentially enhancing atherosclerosis. The present study was designed to investigate the effect of dietary supplementation of n-6 polyunsaturated fats (safflower oil), as compared with a saturated fat-rich diet (Paigen), on the blood lipid profile and atherosclerosis in two mouse models. In the first experiment, female C57BL/6 mice (n=23–30 per group) were fed a cholate containing Paigen diet, a safflower oil-rich diet (with cholate), or normal chow for 15 weeks. No significant differences between the high fat diet groups were evident with respect to total cholesterol, LDL, HDL or triglyceride levels. The extent of aortic sinus fatty streaks did not differ significantly between the two groups. In the second experiment, LDL-receptor-deficient (LDL-RD) mice (n=20–30 per group) were randomized into similar dietary regimens. Mice consuming a safflower oil-enriched diet developed significantly less atherosclerosis, in comparison with Paigen diet-fed mice. A reduction in LDL levels, although not of a similar magnitude as the reduction in atherosclerosis, was evident in the safflower oil-fed mice when compared to the Paigen diet-fed littermates. In both mouse models of atherosclerosis, LDL isolated from the plasma of mice on the n-6 polyunsaturated diet was rendered slightly more susceptible to oxidation in vitro, as indicated by a shorter lag period for diene formation. Thus, the effects of n-6 fatty acids on the lipoprotein composition and other potential influences may have contributed to the anti-atherogenic effect in the LDL-RD mouse model.     

Modifying the n-6/n-3 polyunsaturated fatty acid ratio of a high–saturated fat challenge does not acutely attenuate postprandial changes in inflammatory markers in men with metabolic syndrome

Metabolic syndrome (MetS) features chronic inflammation and exaggerated postprandial triacylglyceride (TAG) responses. Fasting concentrations of interleukin-6 (IL-6) and C-reactive protein (CRP), key inflammatory mediators, decrease after sustained n-3 polyunsaturated fatty acid (PUFA) intake; however, the ability of n-3 PUFA to attenuate postprandial inflammatory responses is not well studied. Thus, we examined the acute effect of modifying the n-6/n-3 PUFA ratio of a high–saturated fatty acid (SFA) oral fat tolerance test (OFTT) on postprandial TAG and inflammatory responses in men with MetS. Men (n = 8, ≥45 years old) with MetS ingested 2 high-SFA OFTTs (1 g fat per kilogram body weight), with either a 20:1 (low n-3) or 2:1 (high n-3) n-6/n-3 PUFA ratio, and a water control in a randomized crossover design. Blood samples were collected for 8 hours after treatment to measure postprandial TAG, free fatty acids, IL-6, soluble IL-6 receptor, and CRP. Postprandial TAG increased at the same rate after ingestion of the low–n-3 and high–n-3 OFTTs; however, both OFTTs were significantly different from the water control. There were no differences in the rate at which IL-6 concentrations increased after ingestion of either of the OFTTs compared with water. Furthermore, neither time nor treatment affected circulating soluble IL-6 receptor or CRP concentrations. Thus, increasing the n-3 PUFA content of a high-SFA OFTT does not acutely change postprandial TAG or inflammatory responses in men with MetS.     

Identification of bifunctional delta12/omega3 fatty acid desaturases for improving the ratio of omega3 to omega6 fatty acids in microbes and plants

We report the identification of bifunctional Delta12/omega3 desaturases from Fusarium moniliforme, Fusarium graminearum, and Magnaporthe grisea. The bifunctional activity of these desaturases distinguishes them from all known Delta12 or omega3 fatty acid desaturases. The omega3 desaturase activity of these enzymes also shows a broad omega6 fatty acid substrate specificity by their ability to convert linoleic acid (LA), gamma-linolenic acid, di-homo-gamma-linolenic acid, and arachidonic acid to the omega3 fatty acids, alpha-linolenic acid (ALA), stearidonic acid, eicosatetraenoic acid, and eicosapentaenoic acid (EPA), respectively. Phylogenetic analysis suggests that omega3 desaturases arose by independent gene duplication events from a Delta12 desaturase ancestor. Expression of F. moniliforme Delta12/omega3 desaturase resulted in high ALA content in both Yarrowia lipolytica, an oleaginous yeast naturally deficient in omega3 desaturation, and soybean. In soybean, seed-specific expression resulted in 70.9 weight percent of total fatty acid (%TFA) ALA in a transformed seed compared with 10.9%TFA in a null segregant seed and 53.2%TFA in the current best source of ALA, linseed oil. The ALA/LA ratio in transformed seed was 22.3, a 110- and 7-fold improvement over the null segregant seed and linseed oil, respectively. Thus, these desaturases have potential for producing nutritionally desirable omega3 long-chain polyunsaturated fatty acids, such as EPA, with a significantly improved ratio of omega3/omega6 long-chain polyunsaturated fatty acids in both oilseeds and oleaginous microbes.     

Effects of polyunsaturated/saturated fatty acid ratio and antioxidant supplementation on hepatic TBARS and enzyme activities under the maintenance of dietary peroxidizability index value in young and adult rats

AIMS: To investigate the effects of the polyunsaturated/saturated fatty acid (P/S) ratio and antioxidant supplementation on hepatic lipid peroxidation and enzyme activities under the control of the dietary peroxidizability index (PI) value in young and adult rats. METHODS: We measured thiobarbituric acid-reactive substance (TBARS) concentration and enzyme activities in liver tissue. Female Sprague-Dawley rats aged 3 and 16 weeks were used. Dietary P/S ratios were 0.38 and 4.81 (LP and HP) when the PI value was 81.22. The diets were supplemented with vitamin E 1,000 mg/kg diet and selenium 2.5 mg/kg diet (LPS and HPS). RESULTS: The hepatic TBARS concentration was higher in LP and LPS than in HP and HPS. In reducing TBARS concentration, antioxidant supplementation was more effective in adult rats than in young rats. Glutathione peroxidase and glutathione-S-transferase activities were lower in young rats than in adult rats. CONCLUSION: We conclude that dietary fats and antioxidant supplementation play an important role in the change of hepatic TBARS concentration when the dietary PI value is maintained at the same level. However, with the exception of glutathione reductase, no effects of the P/S ratio and antioxidant supplementation on hepatic enzyme activities were detected. This may be due to the invisible effects of fixed PI value in diets.     

Rounding the corner on residual risk: Implications of REDUCE‐IT for omega‐3 polyunsaturated fatty acids treatment in secondary prevention of atherosclerotic cardiovascular disease

Patients with established atherosclerotic cardiovascular (CV) disease remain at increased risk of major adverse cardiovascular events even during optimal lipid‐lowering therapy. Recent studies using the methods of Mendelian randomization, as well as analyses of data from large statin trials, have concluded that elevated triglyceride (TG) levels contribute to that increased risk. Omega‐3 polyunsaturated fatty acids (omega‐3 PUFAs) from fish and shellfish (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) reduce TG levels when added to the diet in sufficient amounts, and they have favorable effects on several other markers of CV risk. However, trials of omega‐3 PUFAs have had inconsistent findings regarding CV risk reduction. Recently, the REDUCE‐IT (Reduction of Cardiovascular Events with EPA‐Intervention Trial) trial reported that treatment of such high‐risk patients with icosapent ethyl, a purified and stabilized ethyl ester of EPA, reduced the risk of the trial's primary CV endpoint by 25% (95% confidence intervals [CI], 32%‐17%; P < .001). To appreciate the clinical implications of this result, it is important to understand how the REDUCE‐IT trial differed from previous trials, especially with regard to patient enrollment criteria and treatment dosing. We discuss these design features relative to other trials. TG lowering can account for only part of the risk reduction seen with icosapent ethyl; we also consider other potential contributory mechanisms.     

Long-term saturated fat supplementation in the rat causes an increase in PGI2/TXB2 ratio of platelet and vessel wall compared to n-3 and n-6 dietary fatty acids

The effect of long-term manipulation of dietary lipid intake on platelet and vessel wall lipid composition and eicosanoid synthesis was investigated. Rats were fed a standard diet (REF diet) supplemented (12% w/w) with either sheep fat (SF), sunflower seed oil (SSO) or tuna fish oil (TFO) for a period of 15 months. Significant compositional changes both in the aorta and platelets were observed following dietary lipid treatment and differences between these tissues were particularly apparent with regard to the incorporation and conversion of n-3 fatty acids. For example, platelets displayed a selective accumulation of eicosapentaenoic acid (EPA, 20:5 n-3) over docosahexaenoic acid (DHA, 22:6, n-3), but in the aorta the proportion of DHA was considerably higher than that of EPA. In both tissues, compared to REF diet, n-3 dietary fatty acids replaced the n-6 unsaturates 20:4 and 22:4, but did not affect the proportion of linoleic acid. In contrast to aorta, the unsaturation index for platelet membrane varied significantly between dietary groups. The capacity of aorta and platelets to generate PGI2-like activity and thromboxane was unaltered by the SSO diet. However, changes were seen following SF and TFO supplementation. Rats fed the SF diet displayed a greater synthetic capacity whilst in animals maintained on TFO diet the synthesis of these two eicosanoids was considerably suppressed. The SF group displayed the highest value for PGI2/TXB2 ratio whereas TFO diet fed rats showed the lowest which may partly be due to synthesis of TXA3. The reduction in eicosanoids following the tuna fish oil supplementation can be explained on the basis of concurrent compositional changes.(ABSTRACT TRUNCATED AT 250 WORDS)