Omega-6 fatty acids and coronary artery disease: the pros and cons

Basal omega-3 fatty acid status affects fatty acid and oxylipin responses to high-dose n3-HUFA in healthy volunteers

A subject's baseline FA composition may influence the ability of dietary highly unsaturated omega-3 FAs (n3-HUFA) to change circulating profiles of esterified FAs and their oxygenated metabolites. This study evaluates the influence of basal n3-HUFA and n3-oxylipin status on the magnitude of response to n3-HUFA consumption. Blood was collected from fasting subjects (n = 30) before and after treatment (4 weeks; 11 ± 2 mg/kg/day n3-HUFA ethyl esters). Esterified FAs were quantified in erythrocytes, platelets, and plasma by GC-MS. Esterified oxylipins were quantified in plasma by LC-MS/MS. Treatment with n3-HUFAs increased n3-HUFAs and decreased n6-HUFAs in all reservoirs and increased plasma n3-oxylipins without significantly changing n6-oxylipin concentrations. As subject basal n3-HUFAs increased, treatment-associated changes decreased, and this behavior was reflected in the percentage of 20:5n3 + 22:6n3 in red blood cell membrane FAs (i.e., the omega-3 index). To maintain an omega-3 index of 8% and thus reduce cardiovascular disease risk, our analyses suggest a maintenance dose of 7 mg/kg/day n3-HUFA ethyl esters for a 70-kg individual. These results suggest that the basal n3 index may have clinical utility to establish efficacious therapeutic experimental feeding regimens and to evaluate the USDA Dietary Guidelines recommendations for n3-HUFA consumption.

Association of serum n-6 and n-3 polyunsaturated fatty acids with lipids in 3 populations of middle-aged men

BACKGROUND

The association of serum polyunsaturated fatty acids (PUFAs) with lipids in different populations is not known.

OBJECTIVE

Our aim was to examine the association of serum n-6 (omega-6) or n-3 (omega-3) PUFAs with triglycerides or HDL-cholesterol concentrations in 261 white, 285 Japanese, and 212 Japanese American men aged 40-49 y.

DESIGN

We used a population-based cross-sectional study. Of the original sample (n = 926), those taking lipid-lowering medications or who had diabetes (n = 168) were excluded. Serum fatty acids were analyzed by capillary gas-liquid chromatography. Multiple regression models as a function of tertile groups of each PUFA were used.

RESULTS

Serum n-6 PUFAs were significantly inversely associated with triglycerides across populations after adjustment for age, body mass index, pack-years of smoking, and ethanol consumption [beta = -0.39 (P < 0.001), -0.38 (P < 0.001), and -0.33 (P < 0.001) in whites, Japanese, and Japanese Americans, respectively]. Marine n-3 PUFAs were significantly inversely associated with triglycerides across populations [beta = -0.15 (P < 0.001), -0.22 (P < 0.001), and -0.13 (P < 0.001) in whites, Japanese, and Japanese Americans, respectively]. n-6 PUFAs were significantly positively associated with HDL cholesterol in whites (beta = 4.49, P < 0.001) and Japanese (beta = 3.73, P < 0.01). Marine n-3 PUFAs were significantly positively associated with HDL cholesterol in Japanese (beta = 2.15, P < 0.05), and eicosapentaenoic acid was significantly positively associated with HDL cholesterol in whites (beta = 2.68, P < 0.01).

CONCLUSION

Serum n-6 and n-3 PUFAs are inversely associated with triglycerides across populations.

Fish oil in combination with high or low intakes of linoleic acid lowers plasma triacylglycerols but does not affect other cardiovascular risk markers in healthy men

Both (n-3) long-chain PUFA (LCPUFA) and linoleic acid [LA, 18:2(n-6)] improve cardiovascular disease (CVD) risk factors, but a high-LA intake may weaken the effect of (n-3) LCPUFA. In a controlled, double-blind, 2 x 2-factorial 8-wk intervention, we investigated whether fish oil combined with a high- or low-LA intake affects overall CVD risk profile. Healthy men (n = 64) were randomized to 5 mL/d fish oil capsules (FO) [mean intake 3.1 g/d (n-3) LCPUFA] or olive oil capsules (control) and to oils and spreads with either a high (S/B) or a low (R/K) LA content, resulting in a 7.3 g/d higher LA intake in the S/B groups than in the R/K groups. Diet, (n-3) LCPUFA in peripheral blood mononuclear cells, blood pressure (BP), heart rate (HR), and plasma CVD risk markers were measured before and after the intervention. FO lowered fasting plasma triacylglycerol (TAG) (P < 0.001) by 51% and 19% in the FO+R/K-group and FO+S/B-group, respectively, which was also reflected in postprandial TAG measured after the intervention (P < 0.01). Although a fat x FO interaction was found for monocyte chemoattractant protein-1, neither the FO nor fat intervention affected fasting plasma cholesterol, glucose, insulin, fibrinogen, C-reactive protein, interleukin-6, vascular cell adhesion molecule-1, P-selectin, oxidized LDL, cluster of differentiation antigen 40 ligand (CD40L), adiponectin, or fasting or postprandial BP or HR after adjustment for body weight changes. In conclusion, neither fish oil supplementation nor the LA intake had immediate pronounced effects on the overall CVD risk profile in healthy men, but fish oil lowered plasma TAG in healthy subjects with initially low concentrations.

Induction of mitochondrial nitrative damage and cardiac dysfunction by chronic provision of dietary omega-6 polyunsaturated fatty acids

Increased awareness of obesity has led to a dietary shift toward "heart-friendly" vegetable oils containing omega-6 polyunsaturated fatty acid (omega-6 PUFA). In addition to its beneficial effects, omega-6 PUFA also exhibits proinflammatory and prooxidative properties. We hypothesized that chronic dietary omega-6 PUFA can induce free radical generation, predisposing the cardiac mitochondria to oxidative damage. Male Wistar rats were fed a diet supplemented with 20% w/w sunflower oil, rich in omega-6 PUFA (HP) or normal laboratory chow (LP) for 4 weeks. HP feeding augmented phospholipase A(2) activity and breakdown of cardiolipin, a mitochondrial phospholipid. HP hearts also demonstrated elevated inducible nitric oxide synthase expression, loss of Mn superoxide dismutase, and increased mitochondrial nitrotyrosine levels. In these hearts, oxidative damage to mitochondrial DNA (mDNA) was demonstrated by 8-hydroxyguanosine immunopositivity, overexpression of DNA repair enzymes, and a decrease in the mRNA expression of specific respiratory subunits encoded by the mDNA. Functionally, at higher workloads, HP hearts also demonstrated a greater decline in cardiac work than LP, suggesting a compromised mitochondrial reserve. Our study, for the first time, demonstrates that consumption of a high fat diet rich in omega-6 PUFA for only 4 weeks instigates mitochondrial nitrosative damage and causes cardiac dysfunction at high afterloads.

Nutritional Recommendations for Patients With Heart Failure

Promoting optimal nutritional intake may play an important role in the management of patients with heart failure. Unfortunately, no nutritional guidelines are currently available to assist clinicians in assuring adequate nutritional intake of these patients. The purposes of this article are to review currently available information on nutrition in heart failure and outline initial recommendations for micronutrient, protein, and omega-3 fatty intake. In addition, implications regarding the recent data showing improved health outcomes in obese patients are also addressed.