Dietary saturated fat level alters the competition between alpha-linolenic and linoleic acid

Dietary natural products as emerging lipoprotein(a)-lowering agents

Elevated plasma lipoprotein(a) (Lp(a)) levels are associated with an increased risk of cardiovascular disease (CVD). Hitherto, niacin has been the drug of choice to reduce elevated Lp(a) levels in hyperlipidemic patients but its efficacy in reducing CVD outcomes has been seriously questioned by recent clinical trials. Additional drugs may reduce to some extent plasma Lp(a) levels but the lack of a specific therapeutic indication for Lp(a)-lowering limits profoundly reduce their use. An attractive therapeutic option is natural products. In several preclinical and clinical studies as well as meta-analyses, natural products, including l-carnitine, coenzyme Q ₁₀ , and xuezhikang were shown to significantly decrease Lp(a) levels in patients with Lp(a) hyperlipoproteinemia. Other natural products, such as pectin, Ginkgo biloba, flaxseed, red wine, resveratrol and curcuminoids can also reduce elevated Lp(a) concentrations but to a lesser degree. In conclusion, aforementioned natural products may represent promising therapeutic agents for Lp(a) lowering.

Improvement of the omega 3 index of healthy subjects does not alter the effects of dietary saturated fats or n-6PUFA on LDL profiles

BACKGROUND AND AIMS

Dietary fat composition is known to modulate circulating lipid and lipoprotein levels. Although supplementation with long chain omega-3 polyunsaturated fatty acids (LCn-3PUFA) has been shown to reduce plasma triglyceride levels, the effect of the interactions between LCn-3PUFA and the major dietary fats consumed has not been previously investigated.

METHODS

In a randomized controlled parallel design clinical intervention, we examined the effect of diets rich in either saturated fatty acids (SFA) or omega-6 polyunsaturated fatty acids (n-6PUFA) on plasma lipid levels and lipoprotein profiles (lipoprotein size, concentration and distribution in subclasses) in subjects with an adequate omega 3 index. Twenty six healthy subjects went through a four-week pre-supplementation period with LCn-3PUFA and were then randomized to diets rich in either n-6PUFA or SFA both supplemented with LCn-3PUFA.

RESULTS

The diet rich in n-6PUFA decreased low density lipoprotein (LDL) particle concentration (-8%, p=0.013) and LDL cholesterol (LDL-C) level (-8%, p=0.021), while the saturated fat rich diet did not affect LDL particle concentration or LDL-C levels significantly. Nevertheless, dietary saturated fatty acids increased LCn-3PUFA in plasma and tissue lipids compared with n-6PUFA, potentially reducing other cardiovascular risk factors such as inflammation and clotting tendency.

CONCLUSION

Improvement on the omega 3 index of healthy subjects did not alter the known effects of dietary saturated fats and n-6PUFA on LDL profiles.

Effects of dietary saturated and n-6 polyunsaturated fatty acids on the incorporation of long-chain n-3 polyunsaturated fatty acids into blood lipids

BACKGROUND/OBJECTIVES

Omega-3 polyunsaturated fatty acids (n-3PUFA) are better absorbed when they are combined with high-fat meals. However, the role of different dietary fats in modulating the incorporation of n-3PUFA in blood lipids in humans has not been previously explored. Omega-6 polyunsaturated fatty acids (n-6PUFA) are known to compete with n-3PUFA in the metabolic pathways and for the incorporation into phospholipids, whereas saturated fats (SFA) may enhance n-3PUFA incorporation into tissues.

SUBJECTS/METHODS

In a randomized parallel-design trial, we aimed to investigate the long-term effects of n-3PUFA supplementation in subjects consuming a diet enriched with either SFA or n-6PUFA on fatty acid incorporation into plasma and erythrocytes and on blood lipid profiles (total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides).

RESULTS

Dietary supplementation with n-3PUFA co-administered with SFA for 6 weeks resulted in a significant rise in total cholesterol (0.46±0.60 mmol/L; P=0.020) and LDL-C (0.48±0.48 mmol/L; P=0.011) in comparison with combination with n-6PUFA. The diet enriched with SFA also induced a greater increase in eicosapentaenoic acid (2.07±0.79 vs 1.15±0.53; P=0.004), a smaller decrease in docosapentaenoic acid (-0.12±0.23 vs -0.30±0.20; P=0.034) and a similar increase in docosahexaenoic acid (3.85±1.14 vs 3.10±1.07; P=0.128) percentage in plasma compared with the diet enriched with n-6PUFA. A similar effect was seen in erythrocytes. N-3PUFA supplementation resulted in similar changes in HDL-C and triglyceride levels.

CONCLUSIONS

The results suggest that dietary substitution of SFA with n-6PUFA, despite maintaining low levels of circulating cholesterol, hinders n-3PUFA incorporation into plasma and tissue lipids.

Adding nutritional value to meat and milk from pasture-fed livestock

Staple meat and milk provide excellent nutrition, but when traditional foods and ingredients are tailored to meet the particular nutritional or lifestyle demands of a population they become even more attractive and valuable. These foods can be considered as delivery systems for health-promoting nutrients. Nutritional improvement of meat and milk can be achieved several ways, preferably by making desirable changes on-farm to directly improve the food without subsequent manipulations. Scope for these changes is limited by animal homeostasis, but alternatives may be less desirable. Methods in vivo that suit typical pastoral farming practice and can complement the solving of animal health and production problems include: selection of traits or phenotypes; specialty diets; long-acting parenteral supplements; and modification of ruminal microflora. Successful techniques to increase the concentration of calcium, selenium, iodine and iron in milk or meat are described. Manipulations to change composition are only one part of bringing tailored foods to market. Commercial realisation of these new products needs the initiative and collaboration of scientists, veterinarians, growers and producers responding to market pull. The uptake of future biotechnologies to capture more value inside the farm gate will also be required if the pastoral industry in New Zealand is to sustain a global competitive advantage.

A dietary quality comparison of popular weight-loss plans

Popular weight-loss plans often have conflicting recommendations, which makes it difficult to determine the most healthful approach to weight loss. Our study compares the dietary quality of popular weight-loss plans. Dietary quality, measured by the Alternate Healthy Eating Index (AHEI), was calculated via sample menus provided in published media for the New Glucose Revolution, Weight Watchers, Atkins, South Beach, Zone, Ornish, and 2005 US Department of Agriculture Food Guide Pyramid (2005 Food Guide Pyramid) plans. The criterion for determining which weight-loss plans were the most popular was their status on the New York Times Bestseller list. Weight Watchers and the 2005 Food Guide Pyramid plan were included because they are the largest commercial weight-loss plan, and the current government recommendation, respectively. Analysis of variance was used to compare nutrient information among the weight-loss plans. The AHEI scores adjusted for energy content were also compared. Of a maximum possible score of 70, the AHEI scores for each weight-loss plan from the highest to the lowest plan were: Ornish (score 64.6), Weight Watchers high-carbohydrate (score 57.4), New Glucose Revolution (score 57.2), South Beach/Phase 2 (score 50.7), Zone (score 49.8), 2005 Food Guide Pyramid (score 48.7), Weight Watchers high-protein (score 47.3), Atkins/100-g carbohydrate (score 46), South Beach/Phase 3 (score 45.6), and Atkins/45-g carbohydrate (score 42.3). Dietary quality varied across popular weight-loss plans. Ornish, Weight Watchers high-carbohydrate, and New Glucose Revolution weight-loss plans have an increased capacity for cardiovascular disease prevention when assessed by the AHEI.

Dietary intervention increases n-3 long-chain polyunsaturated fatty acids in skeletal muscle membrane phospholipids of obese subjects. Implications for insulin sensitivity

OBJECTIVE

Cross-sectional studies suggest that the fatty acid (FA) composition of phospholipids in skeletal muscle cell membrane may modulate insulin sensitivity in humans. We examined the impact of a hypocaloric low-fat dietary intervention on membrane FA composition and insulin sensitivity. DESIGN Muscle membrane FA profiles were determined in muscle (vastus lateralis) biopsies from 21 obese subjects before and after 6 months of dietary restriction. Diet instructions emphasized low intake of FA of marine origin by recommending lean fish and prohibiting fatty fish and fish oil supplements. Insulin resistance was estimated by the homeostasis model assessment (HOMA-IR). RESULTS The mean weight loss was 5.1 kg (range -15.3 to +1.3 kg). BMI decreased from 36.5 to 34.9 kg/m(2) (P=0.003). Saturated FA (SFA) decreased 11% (P=0.0001). Polyunsaturated FA (PUFA)n-6 increased 4% (P =0.003). Long-chain PUFAn-3 increased 51% (P= 0.0001), mainly due to a 75% increase (P<0.0001) in docosahexaenoic acid. Changes in HOMA-IR correlated significantly with changes in long-chain PUFAn-3 (R=-0.57, P< 0.01), SFA (R=0.58, P<0.01) and waist circumference (R=0.46, P<0.05). A multivariate linear regression analysis that included changes in weight, fat mass, waist circumference, plasma lipids, PUFA, SFA and long-chain PUFAn-3 indicated that SFA and long-chain PUFAn-3 were independent predictors of HOMA-IR (R(2)=0.33, P<0.01).

CONCLUSIONS

A hypocaloric low-fat dietary intervention programme increased incorporation of long-chain PUFAn-3 and reduced SFA in skeletal muscle membrane phospholipids of obese subjects, a setting that may impact on insulin action.

Dietary PUFA and the metabolic syndrome in Indian Asians living in the UK

Indian Asians living in the UK have a 50% higher CHD mortality rate compared with the indigenous Caucasian population, which cannot be attributed to traditional risk factors. Instead, features of the metabolic syndrome, including raised plasma triacylglycerol, reduced HDL-cholesterol (HDL-C) and an increased proportion of small dense LDL particles, together with insulin resistance and central obesity, are prevalent among this population. The present review examines evidence to support the hypothesis that an imbalance in dietary PUFA intake, specifically a higher intake of n-6 PUFA in combination with the lower intake of the long-chain (LC) n-3 PUFA, plays an important role in the prevalence of the metabolic syndrome observed in Indian Asians. Data are presented to illustrate the impact of manipulation of the background n-6 PUFA intake (moderate or high n-6 PUFA) and the subsequent response to supplementation with LC n-3 PUFA on blood lipids and insulin action in a group of Indian Asian volunteers. The results demonstrate that supplementation with LC n-3 PUFA had no impact on insulin action in those subjects consuming either the moderate- or high-n-6 PUFA diet. In the postprandial phase reductions in plasma triacylglycerol concentrations were greater in those consuming the high-n-6 PUFA background diet subsequent to fish oil supplementation. The present study concludes that, contrary to the central hypothesis, the prevalence of metabolic abnormalities in Indian Asians compared with Caucasians may not be attributable to differences in intakes of n-6 and n-3 PUFA.

Flaxseed improves lipid profile without altering biomarkers of bone metabolism in postmenopausal women

The risk of cardiovascular disease and osteoporosis drastically increases at the onset of menopause. Phytoestrogens have been suggested to inhibit bone loss and protect the cardiovascular system, in part by improving lipid profiles. The purpose of the present study was to examine the effects of flaxseed, a rich source of the phytoestrogens called lignans, on lipid metabolism and biomarkers of bone turnover in postmenopausal women. Postmenopausal women who were not on hormone replacement therapy were assigned to one of two treatment groups in a double-blind randomized study. Women were asked to consume 40 g of either ground flaxseed or wheat-based comparative control regimen daily for 3 months. In addition, all subjects received 1,000 mg calcium and 400 IU vitamin D daily. Flaxseed supplementation lowered (P < 0.05) both serum total cholesterol and non-high-density lipoprotein cholesterol by 6%, whereas the comparative control regimen had no such effect. Flaxseed regimen reduced serum levels of both low-density- and high-density-lipoprotein cholesterol by 4.7% and triglyceride by 12.8%, albeit not statistically significant. Serum apolipoprotein A-1 and apolipoprotein B concentrations were significantly (P < 0.005) reduced by 6 and 7.5%, respectively, by the flaxseed regimen. Markers of bone formation and resorption were not affected by either of the treatments. The findings of this study indicate that flaxseed supplementation improves lipid profiles but has no effect on biomarkers of bone metabolism in postmenopausal women.

Types of dietary fat and risk of coronary heart disease: a critical review

During the past several decades, reduction in fat intake has been the main focus of national dietary recommendations to decrease risk of coronary heart disease (CHD). Several lines of evidence. however, have indicated that types of fat have a more important role in determining risk of CHD than total amount of fat in the diet. Metabolic studies have long established that the type of fat, but not total amount of fat, predicts serum cholesterol levels. In addition, results from epidemiologic studies and controlled clinical trials have indicated that replacing saturated fat with unsaturated fat is more effective in lowering risk of CHD than simply reducing total fat consumption. Moreover, prospective cohort studies and secondary prevention trials have provided strong evidence that an increasing intake of n-3 fatty acids from fish or plant sources substantially lowers risk of cardiovascular mortality. In this article, we review evidence from epidemiologic studies and dietary intervention trials addressing the relationship between dietary fat intake and risk of CHD, with a particular emphasis on different major types of fat, n-3 fatty acids and the optimal balance between n-3 and n-6 fatty acids. We also discuss the implications of the available evidence in the context of current dietary recommendations.

Dietary omega-3 and polyunsaturated fatty acids modify fatty acyl composition and insulin binding in skeletal-muscle sarcolemma

Feeding animals with diets high in saturated fat induces insulin resistance, and replacing saturated fat isocalorically with poly-unsaturated fat, especially long-chain omega-3 fatty acids, will prevent the development of insulin resistance in skeletal-muscle tissue. To investigate the mechanism, rats were fed on high-fat (20%, w/w) semipurified diets for 6 weeks. Diets containing ratios of polyunsaturated/saturated (P/S) fatty acid of 0.25 (low-P/S diet) and 1.0 (high-P/S diet) were used to study the effect of the level of saturated fat. To study the effects of omega-3 fatty acids, diets with a low-P/S ratio containing either 0 (low-omega-3 diet) or 3.3% (high-omega-3 diet) long-chain omega-3 fatty acids from fish oil were fed. Plasma membrane from skeletal muscle was purified. The content of fatty acids in sarcolemmal phospholipid was significantly related to the dietary composition. Insulin binding to intact sarcolemmal vesicles prepared from rats fed on diets high in omega-3 fatty acids increased 14-fold compared with animals fed on the low-omega-3 diet (P < 0.0001). Feeding rats on a diet with a high P/S ratio increased sarcolemmal insulin binding by 2.3-fold (P < 0.05). Increased insulin binding was due to increased receptor number at the low-affinity high-capacity binding site. Dietary effects on insulin binding were eliminated when studies were carried out on detergent-solubilized membranes, indicating the importance of the phospholipid fatty acyl composition for insulin binding. The results suggest that dietary omega-3 and polyunsaturated fatty acids increase insulin binding to sarcolemma by changing the fatty acyl composition of phospholipid surrounding the insulin receptor, and this might be the mechanism by which dietary fatty acids modify insulin action.

The effect of dietary fat level and quality on plasma lipoprotein lipids and plasma fatty acids in normocholesterolemic subjects

This study examined the effect on the plasma lipids and plasma phospholipid and cholesteryl ester fatty acids of changing froma typical western diet to a very low fat (VLF) vegetarian diet containing one egg/day. The effect of the addition of saturated, monounsaturated or polyunsaturated fat (PUFA) to the VLF diet was also examined. Three groups of 10 subjects (6 women, 4 men) were fed the VLF diet (10% energy as fat) for two weeks, and then in the next two weeks the dietary fat in each group was increased by 10% energy/week using butter, olive oil or safflower oil. The fat replaced dietary carbohydrate. The VLF diet reduced both the low density lipoprotein (LDL)- and high density lipoprotein (HDL)-cholesterol levels; addition of the monounsaturated fats and PUFA increased the HDL-cholesterol levels, whereas butter increased the cholesterol levels in both the LDL- and HDL-fractions. The VLF diet led to significant reductions in the proportion of linoleic acid (18:2 omega 6) and eicosapentaenoic acid (20:5 omega 3) and to increases in palmitoleic (16:1), eicosatrienoic (20:3 omega 6) and arachidonic acids (20:4 omega 6) in both phospholipids and cholesteryl esters. Addition of butter reversed the changes seen on the VLF diet, with the exception of 16:1, which remained elevated. Addition of olive oil resulted in a significant rise in the proportion of 18:1 and significant decreases in all omega 3 PUFA except 22:6 compared with the usual diet. The addition of safflower oil resulted in significant increases in 18:2 and 20:4 omega 6 and significant decreases in 18:1, 20:5 omega 3 and 22:5 omega 3. These results indicate that the reduction of saturated fat content of the diet (< 6% dietary energy), either by reducing the total fat content of the diet or by exchanging saturated fat with unsaturated fat, reduced the total plasma cholesterol levels by approximately 12% in normocholesterolemic subjects. Although the VLF vegetarian diet reduced both LDL- and HDL-cholesterol levels, the long-term effects of VLF diets are unlikely to be deleterious since populations which habitually consume these diets have low rates of coronary heart disease. The addition of safflower oil or olive oil to a VLF diet produced favorable changes in the lipoprotein lipid profile compared with the addition of butter. The VLF diets and diets rich in butter, olive oil or safflower oil had different effects on the 20 carbon eicosanoid precursor fatty acids in the plasma.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of a high fat diet on phospholipid class distribution and fatty acid composition in rat liver

1. Long term consumption (20 weeks) of a high fat diet (65% of the energy content as fat) rich in either saturated [30% (w/w) coconut oil] or unsaturated [30% (w/w) sunflower oil] fatty acids resulted in strikingly similar alterations in the phospholipid class distribution and fatty acid composition in the liver of male Wistar rats. 2. The effect of these two diets was compared to a control group maintained on a 2% fat diet (w/w) for the same time interval. 3. In spite of the difference in the PUFA/SFA (polyunsaturated fatty acid/saturated fatty acid) ratio between the two high fat diets (0.1, saturated fatty acid diet; 5.4, unsaturated fatty acid diet), both diets resulted in a similar PUFA/SFA ratio in liver phospholipids, a similar reduction in palmitic acid (16:0), oleic acid (18:1, n-9) and arachidonic acid (20:4, n-6) and an elevation in stearic acid (18:0), linoleic acid (18:2, n-6) and docosahexaenoic acid (22:6, n-3). 4. Further, changes in the phospholipid classes were also similarly affected by both high fat diets.

High alpha-linolenic acid flaxseed (Linum usitatissimum): some nutritional properties in humans

Although high alpha-linolenic acid flaxseed (Linum usitatissimum) is one of the richest dietary sources of alpha-linolenic acid and is also a good source of soluble fibre mucilage, it is relatively unstudied in human nutrition. Healthy female volunteers consumed 50 g ground, raw flaxseed/d for 4 weeks which provided 12-13% of energy intake (24-25 g/100 g total fat). Flaxseed raised alpha-linolenic acid and long-chain n-3 fatty acids in both plasma and erythrocyte lipids, as well as raising urinary thiocyanate excretion 2.2-fold. Flaxseed also lowered serum total cholesterol by 9% and low-density-lipoprotein-cholesterol by 18%. Changes in plasma alpha-linolenic acid were equivalent when 12 g alpha-linolenic acid/d was provided as raw flaxseed flour (50 g/d) or flaxseed oil (20 g/d) suggesting high bioavailability of alpha-linolenic acid from ground flaxseed. Test meals containing 50 g carbohydrate from flaxseed or 25 g flaxseed mucilage each significantly decreased postprandial blood glucose responses by 27%. Malondialdehyde levels in muffins containing 15 g flaxseed oil or flour/kg were similar to those in wheat-flour muffins. Cyanogenic glycosides (linamarin, linustatin, neolinustatin) were highest in extracted flaxseed mucilage but were not detected in baked muffins containing 150 g flaxseed/kg. We conclude that up to 50 g high-alpha-linolenic acid flaxseed/d is palatable, safe and may be nutritionally beneficial in humans by raising n-3 fatty acids in plasma and erythrocytes and by decreasing postprandial glucose responses.

Formula α-linolenic (18:3 (n−3)) and linoleic (18:2(n−6)) acid influence neonatal piglet liver and brain saturated fatty acids, as well as docosahexaenoic acid (22:6 (n−3))

Saturated fatty acids can be synthesized de novo and play a role in determining properties of structural membranes. The effect of dietary essential fatty acids, linoleic acid (18:2(n - 6)) and alpha-linolenic acid (18:3(n - 3)), on the saturated fatty acid content of membrane phospholipid has not previously been considered in newborn nutrition. The studies report the effect of low (1% fatty acids) or high (4%) formula 18:3(n - 3) with low (16%) or high (30-35%) formula 18:2(n - 6) on the saturated and unsaturated fatty acid composition of liver and brain structural lipid of piglets fed formula from birth for 15 days. A significant inverse relationship between the formula % 18:3(n - 3), but not 18:2(n - 6), and the liver phospholipid palmitic acid (16:0) was found. This may indicate a possible effect of dietary 18:3(n - 3) on de novo synthesis of 16:0 and requires further investigation. Monounsaturated fatty acids in both liver and brain were significantly lower in response to high 18:3(n - 3) and to high 18:2(n - 6) plus low 18:1(n - 9) in the formula. Liver phospholipid and brain total lipid % docosahexaenoic acid (22:6(n - 3)) were significantly higher when formula containing 4% rather than 1% 18:3(n - 3) was fed, suggesting that 1% 18:3(n - 3) may limit tissue (n - 3) fatty acid accretion. These results suggest that future studies of essential fatty acid requirements, specifically 18:3(n - 3), should consider possible influences on the saturated fatty acids which also play a functional role in tissue structural lipids.

Effects of dietary n-3 fatty acid-enriched chicken eggs on plasma and tissue cholesterol and fatty acid composition of rats

The purpose of this study was to examine the effects of feeding n-3 polyunsaturated fatty acid (PUFA)-enriched chicken eggs on plasma and liver cholesterol levels and fatty acid composition in rats. Eggs were collected from laying hens fed diets containing 10% flax seed (Hn-3), 12% sunflower seed (Hn-6), or wheat and soybean meal control (CON). Yolk powders were prepared and fed at the 15% level to weanling female Sprague-Dawley rats for 28 days. Consumption of n-3 PUFA-enriched yolks significantly reduced both plasma and liver total cholesterol. Liver total lipids and phospholipids of rats fed Hn-3 diet were enriched with linolenic, eicosapentaenoic, and docosahexaenoic acids with a concomitant reduction of arachidonic acid in liver phospholipids. The plasma cholesterol of rats fed yolk powders enriched with n-6 PUFA (mainly linoleic acid) was reduced to the same extent as in those fed the n-3 enriched, but the liver cholesterol was significantly increased, indicating differential effects of dietary n-3 and n-6 PUFA. The results demonstrated that the cholesterolemic and tissue lipid modulating properties of chicken eggs could be modified in a favorable way by altering the fatty acid composition of yolk lipids through manipulation of laying hen diets.

The effect of dietary supplementation with eicosapentaenoic acid on the phospholipid and fatty acid composition of erythrocytes of marmoset

Adult male marmoset monkeys were fed eicosapentaenoic acid (20:5n-3) as the ethyl ester in diets containing either 32% (reference diet, no added cholesterol) or 7% (atherogenic diet with 0.2% added cholesterol) linoleic acid (18:2n-6) for 30 wk. No changes were seen in the level of phosphatidylcholine (PC) or phosphatidylethanolamine (PE) but minor changes were observed in both the sphingomyelin (SPM) and phosphatidylinositol plus phosphatidylserine (PI+PS) fractions of erythrocyte lipids. The extent of total n-3 fatty acid incorporation into membrane lipids was higher in atherogenic diets (polyunsaturated/monounsaturated/saturated (P/M/S) ratio 0.2:0.6:1.0) than reference diets (P/M/S ratio 1:1:1) and this was true for both PE (33.4 +/- 1.0% vs 24.3 +/- 1.1%) and PC (9.3 +/- 0.5% vs 4.9 +/- 0.3%). Although suitable controls for cholesterol effects were not included in the study, earlier results obtained with marmosets lead us to believe such effects were probably small. Regardless of basic diet (atherogenic, reference), 20:5n-3 was preferentially incorporated into PE (10.8 +/- 0.2%, 6.0 +/- 0.02%) while smaller amounts were incorporated into PC (6.9 +/- 0.4%, 3.2 +/- 0.2%). The major n-3 polyunsaturated fatty acid found in PE in response to dietary 20:5n-3 was the elongation metabolite 22:5n-3 in both the atherogenic (17.7 +/- 0.7%) and reference (14.3 +/- 1.0%) dietary groups; 22:6n-3 levels were less affected by diet (4.7 +/- 0.3% and 3.9 +/- 0.2%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of a fish oil enriched diet on oxygen toxicity and lipid peroxidation in mice

Mice were fed a chow diet or diets enriched in fish oil, sunflower oil or beef tallow for 3 weeks. Fatty acid analysis was carried out in samples of plasma, brain and lungs from these animals and large changes were found in plasma and lungs with relatively small dietary-induced changes in brain tissue. Bleeding times were increased very significantly in the fish oil group, and slightly increased in the sunflower oil group. Endogenous lipid peroxidation (measured as thiobarbituric acid reactive substances) was unchanged in lung and brain, but lung tissue from fish oil fed mice produced more lipid peroxides in vitro during incubation at 37 degrees than those of other dietary groups. Mice fed the four different diets were exposed to hyperbaric oxygen at 618, 585 and 515 kPa and convulsive activity and lung damage was recorded. No dietary-induced alterations in susceptibility to oxygen toxicity were found.

Effects of dietary fats on prostanoid production and aortic and plasma fatty acid composition in rats

Male Sprague-Dawley rats were fed diets with 10%, 30%, or 50% of energy derived from fat for two weeks. The fats used were beef tallow, olive oil, peanut oil and butter. Aortic prostacyclin (PGI2) production, platelet aggregation and thromboxane A2 (TXA2) production and plasma and aortic phospholipid (PL) content were measured. Butter- and beef tallow-feeding reduced aortic PGI2 production and collagen-induced TXA2 production in a dose-dependent manner as the level of fat in the diet increased. Neither olive oil nor peanut oil had any effect on aortic PGI2 production or collagen-induced TXA2 production. Butter-feeding also resulted in a decrease in collagen-induced platelet aggregation; however, none of the other fats had any effect on collagen-induced platelet aggregation. The observed decreases in aortic PGI2 and collagen-induced TXA2 production were paralleled by similar decreases in aortic and plasma PL arachidonic acid content and an increase in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Only the most saturated fats, butter and beef tallow, had significant inhibitory effects on prostanoid production and platelet aggregation.