Effect Of Dietary Docosahexaenoic Acid Research Articles

Dietary supplementation with docosahexaenoic acid, but not with eicosapentaenoic acid, reduces host resistance to fungal infection in mice.

The effect of dietary docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on host resistance to Paracoccidioides brasiliensis infection was investigated. Mice fed palm oil supplemented with DHA showed reduced antifungal activity in the spleen and liver, as compared with mice fed palm oil or soybean oil without supplementation with DHA. Mice fed DHA-supplemented soybean oil also showed reduced antifungal activity in the liver, but the extent of reduction was less profound. This reduction in antifungal activity was not observed with EPA-supplemented palm or EPA-supplemented soybean oil. These results suggest that two factors, DHA and palm oil in combination, are involved in reducing the host resistance. DHA-enriched palm oil was also responsible for an increase in DHA concentration and a marked decrease in arachidonic acid content in the spleen and liver. However, this group did not show elevated spleen and liver phospholipid hydroperoxide levels compared with the other groups, excluding the possibility that the reduction in antifungal activity observed with DHA-enriched palm oil is due to acceleration of in vivo lipid peroxidation. Greater infection-induced increases in spleen and serum interferon-gamma concentrations were observed in mice fed DHA-enriched palm oil compared with the other groups.

Effect of dietary DHA on DHA levels in retinal rod outer segments in young versus mature rats.

We compared the effect of direct supplementation with docosahexaenoic acid (DHA) on the fatty acid composition of the liver and the rod outer segment (ROS) membranes of the retina in young (five-week-old) and mature (one-year-old) rats. In young rats, a high content of DHA in the diet (9.7% of total energy) effectively increased the proportion of DHA in ROS membranes (41.8%), compared with the proportion observed in a linoleic acid (LA) diet group (control, 31.6%). The proportion of DHA was also significantly higher in the livers of young DHA-fed rats. These results show that direct supplementation with DHA is very effective in increasing DHA levels in the ROS membranes and livers of developing animals. In contrast, in mature rats there was no significant increase in the proportion of DHA in the ROS membranes, even after the highest dose (8.4% of total energy) of DHA, although the proportion of DHA was significantly higher in the livers of DHA-fed rats. The changes in fatty acid composition in the ROS membranes were different in young and mature rats fed high-DHA diets. Our findings indicate that mature rats maintain a constant level of DHA in the ROS membranes even after being directly supplemented with high doses of DHA.

Efecto de la suplementación de la dieta de la madre durante la lactancia con ácidos grasos omega 3 en la composición de los lípidos de la leche

Introduction : Docosahexaenoic acid (DHA) is an important component of membrane phospholipids in brain and retinal tissues. The capability of infants to form DHA may be inadequate to support their metabolic requirements. Indeed they are dependent on the maternal supply. Women with a customarily high consumption of marine foods show increased levels of DHA in their breast milk. In Chile there is a low consumption of marine foods. Objective : To determine whether DHA supplementation of lactating women with jurel increases the DHA content of breast milk. Breast feeding women were randomly assigned to a supplemented or control group. The supplemented group (n = 12) consumed 160 g of jurel twice a week for 2 weeks, the control group (n = 12) maintained their usual diet. The jurel ( Trachurus murphyi ) contained 621mg of DHA per 100 g edible portion. Results : DHA supplementation increased DHA intake from 64 mg per day to 335.9 mg/day. Basal line DHA levels in milk were 0.15 ± 0.05% of total fatty acids and increased significantly to 0.22 ± 0.10% (p < 0.05). There was no effect of dietary DHA on breast milk arachidonic acid levels. Conclusion : maternal DHA supplementation with jurel significantly elevated milk DHA content.

Dose-response effect of docosahexaenoic acid ethyl ester on maze behavior and brain fatty acid composition in adult mice.

The dose-response effect of dietary docosahexaenoic acid (DHA, 22:6 n-3) ethyl ester (EE) on maze-learning ability in mice was studied. Male Crj:CD-1 mice aged three months were fed a) a diet containing 5 g palm oil/100 g diet (control group); b) a diet containing 0.5 g DHA ethyl ester/100 g diet plus 4.5 g palm oil/100 g diet (DHA-EE 0.5% group); c) a diet containing 1 g DHA ethyl ester/100 g diet plus 4 g palm oil/100 g diet (DHA-EEE 1% group); d) a diet containing 2 g DHA ethyl ester/100 g diet plus 3 g palm oil/100 g diet (DHA-EE 2% group) for four months. Maze-learning ability was assessed three months after the start of the experiment. The time required to reach the maze exit and the number of times that a mouse strayed into blind alleys in the maze were measured in three trials, performed every four days. In trial 1, the DHA-EE 0.5%, 1% and 2% groups required less (p < 0.05) time to reach the maze exit, and the DHA-EE 2% group strayed (p < 0.05) into blind alleys fewer times than the control group. In trial 3 performed four days after the second trial, the DHA-EE 2% group needed less (p < 0.05) time to find the exit and spent a fewer (p < 0.05) number of times in blind alleys than did the control group. In the total lipids of plasma and brain of mice fed DHA, increasing intakes of DHA resulted in an increase in DHA levels, with a corresponding decrease in arachidonic acid (20:4 n-6). Improved maze-learning ability in mice fed DHA-EE 2% was associated with higher DHA levels in brain. Our resulted suggest that there are no linear dose-response effects of DHA on maze-learning ability, however, the intake of DHA-EE 2% diet improves learning ability in adult mice as demonstrated by maze performance.

The effect of dietary docosahexaenoic acid on schooling behaviour and brain development in larval yellowtail

The onset of schooling behaviour and brain growth in larval yellowtail Seriola quinqueradiata larvae fed on Artemia enriched with oleic acid (OA), eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) for 10 days was investigated. Larvae from the DHA groups schooled with parallel orientation while those of the EPA groups showed only aggregation. Larvae of the OA groups were dispersed. DHA and EPA groups showed significantly smaller nearest neighbour distance compared with OA groups, and DHA groups showed significantly smaller values of nearest neighbour angle compared with the other groups. The relative volume of the tectum opticus (TO) of the DHA group was significantly larger in two experiments and also the relative volume of the cerebellum (CE) of that group was significantly larger in one experiment. Dietary DHA is probably critically important for the development of the brain, particularly TO, during the larval stages, and that development of TO may be the key factor of the ontogeny of schooling behaviour.

The effect of dietary docosahexaenoic acid on schooling behaviour and brain development in larval yellowtail

The effect of dietary docosahexaenoic acid on schooling behaviour and brain development in larval yellowtail

Enhanced level of n-3 fatty acid in membrane phospholipids induces lipid peroxidation in rats fed dietary docosahexaenoic acid oil

The effect of dietary docosahexaenoic acid (DHA, 22:6n-3) oil with different lipid types on lipid peroxidation was studied in rats. Each group of male Sprague–Dawley rats was pair fed 15% (w/w) of either DHA-triglycerides (DHA-TG), DHA-ethyl esters (DHA-EE) or DHA-phospholipids (DHA-PL) for up to 3 weeks. The palm oil (supplemented with 20% soybean oil) diet without DHA was fed as the control. Dietary DHA oils lowered plasma triglyceride concentrations in rats fed DHA-TG (by 30%), DHA-EE (by 45%) and DHA-PL (by 27%), compared to control. The incorporation of dietary DHA into plasma and liver phospholipids was more pronounced in the DHA-TG and DHA-EE group than in the DHA-PL group. However, DHA oil intake negatively influenced lipid peroxidation in both plasma and liver. Phospholipid peroxidation in plasma and liver was significantly higher than control in rats fed DHA-TG or DHA-EE, but not DHA-PL. These results are consistent with increased thiobarbituric acid reactive substances (TBARS) and decreased α-tocopherol levels in plasma and liver. In addition, liver microsomes from rats of each group were exposed to a mixture of chelated iron (Fe 3+/ADP) and NADPH to determine the rate of peroxidative damage. During NADPH-dependent peroxidation of microsomes, the accumulation of phospholipid hydroperoxides, as well as TBARS, were elevated and α-tocopherol levels were significantly exhausted in DHA-TG and DHA-EE groups. During microsomal lipid peroxidation, there was a greater loss of n-3 fatty acids (mainly DHA) than of n-6 fatty acids, including arachidonic acid (20:4n-6). These results indicate that polyunsaturation of n-3 fatty acids is the most important target for lipid peroxidation. This suggests that the ingestion of large amounts of DHA oil enhances lipid peroxidation in the target membranes where greater amounts of n-3 fatty acids are incorporated, thereby increasing the peroxidizability and possibly accelerating the atherosclerotic process.

Effect of dietary docosahexaenoic acid and phosphatidylcholine on maze behavior and fatty acid composition of plasma and brain lipids in mice.

We investigated the effects of dietary docosahexaenoic acid (DHA, 22:6 n-3) and phosphatidylcholine (PC) on maze behavior and brain fatty acids in mice. Male Crj:CD-1 mice (3 wk old) were fed a diet containing 2% DHA and 3% palm oil (DHA group); 5% PC (PC group); 1% DHA, 2.5% PC and 1.5% palm oil (DHA + PC group); 5% palm oil (Palm oil control group) or MF laboratory chow (MF control group) for 7 mo. After this time maze-learning ability was assessed. The time required to reach the maze exit and the number of times that a mouse strayed into blind alleys in the maze were measured three times every four days. After the last learning test, all mice were sacrificed and plasma and brain were analyzed for fatty acid composition. The DHA and PC groups required less time to reach the maze exit and strayed less into blind alleys than the control group in the third trial. The difference between the DHA or PC groups and control mice was statistically significant (p < 0.05). In the total lipids of plasma and brain of mice fed DHA, there was a significant increase in DHA levels and a concomitant decrease in arachidonic acid (AA, 20:4 n-6). Similar changes in fatty acid composition were observed in brain phosphatidylcholine and phosphatidylethanolamine for this group of mice. However, this pattern of changes in brain fatty acids was not evident in the PC group. Our data suggest that maze-learning ability in mice is enhanced by intakes of DHA and PC. However, the mechanisms by which the DHA and PC diets improved learning ability appear to be different. A synergistic effect of DHA and PC on learning ability is not apparent in the DHA + PC group.

Preliminary study of the effect of dietary docosahexaenoic acid on the volumetric growth of the brain in larval yellowtail +

Preliminary study of the effect of dietary docosahexaenoic acid on the volumetric growth of the brain in larval yellowtail +

Intakes of Dietary Docosahexaenoic Acid Ethyl Ester and Egg Phosphatidylcholine Improve Maze-Learning Ability in Young and Old Mice

The effect of dietary docosahexaenoic acid (DHA) [22:6 (n-3)] ethyl ester (EE) and egg-phosphatidylcholine (PC) on maze-learning ability in young and old mice was studied. Male Crj:CD-1 mice aged either 3 wk or 14 mo were fed a diet containing 2 g DHA-EE/100 g diet plus 3 g palm oil/100 g diet (DHA-EE Group), 5 g egg-PC/100 g diet (egg-PC Group), 1 g DHA-EE/100 g diet plus 2.5 g egg-PC/100 g diet plus 1.5 g palm oil/100 g diet (DHA-EE + egg-PC Group) or 5 g palm oil/100 g diet (Control Group) for 5 mo. Maze-learning ability was assessed 4 mo after the start of the experiment. The time required to reach the maze exit and the number of times that a mouse strayed into blind alleys in the maze were measured in three trials every 4 d. In trial 2 of young mice, performed on d 4 after the first trial, the DHA-EE group required less (P < 0.05) time to reach the maze exit and DHA-EE and egg-PC groups strayed (P < 0.05) into blind alleys fewer times than the control group. In trial 2 of old mice, the DHA-EE, egg-PC and DHA-EE + egg-PC groups needed less (P < 0.05) time to find the exit and spent a fewer (P < 0.05) number of times in blind alleys than did the control group. The DHA-EE, DHA-EE + egg-PC and egg-PC groups strayed into blind alleys fewer times than the control group in trial 3 of old mice (P < 0.05). Our results suggest that the intake of DHA-EE and the egg-PC diet effectively enhances maze-learning ability and brain functions in old mice.

Dietary docosahexaenoic acid can alter the surface expression of CD4 and CD8 on T cells in peripheral blood.

The effect of dietary docosahexaenoic acid (DHA) on T cell states in peripheral blood was investigated. Weanling male C57Bl/6N mice were kept on one of three 10% fat diets containing various amounts of DHA and linoleic acid for 4 weeks. Changing the concentration of dietary DHA did not alter the proportion of T cells expressing CD4 or CD8. However, increasing the concentration of dietary DHA lowered the expression of CD4 and CD8 on the cell surface. The decreased expression of these surface molecules involved in T cell proliferation has serious implications in the role of DHA as an immunosuppressant.

A randomized controlled trial of early dietary supply of long‐chain polyunsaturated fatty acids and mental development in term infants

The effects of dietary docosahexaenoic acid (DHA) supply during infancy on later cognitive development of healthy term infants were evaluated in a randomized clinical trial of infant formula milk supplemented with 0.35% DHA or with 0.36% DHA and 0.72% arachidonic acid (AA), or control formula which provided no DHA or AA. Fifty‐six 18‐month‐old children (26 male, 30 female) who were enrolled in the trial within the first 5 days of life and fed the assigned diet to 17 weeks of age were tested using the Bayley Scales of Infant Development, 2nd edition (BSID‐II) (Bayley 1993) at the Retina Foundation of the Southwest, Dallas, TX. These children had also been assessed at 4 months and 12 months of age for blood fatty‐acid composition, sweep visual evoked potential (VEP) acuity, and forced‐choice preferential looking (FPL) acuity (Birch et al. 1998). Supplementation of infant formula with DHA+AA was associated with a mean increase of 7 points on the Mental Development Index (MDI) of the BSID‐II. Both the cognitive and motor subscales of the MDI showed a significant developmental age advantage for DHA‐ and DHA+AA‐supplemented groups over the control group. While a similar trend was found for the language subscale, it did not reach statistical significance. Neither the Psychomotor Development Index nor the Behavior Rating Scale of the BSID‐II showed significant differences among diet groups, consistent with a specific advantage of DHA supplementation on mental development. Significant correlations between plasma and RBC‐DHA at 4 months of age but not at 12 months of age and MDI at 18 months of age suggest that early dietary supply of DHA was a major dietary determinant of improved performance on the MDI.

Dietary docosahexaenoic acid suppresses inflammation and immunoresponses in contact hypersensitivity reaction in mice.

This study was designed to examine the immunomodulatory effects of dietary docosahexaenoic acid (DHA) in the absence of eicosapentaenoic acid (EPA). We investigated the effects of feeding dietary DHA ethyl ester (DHA-Et) (97% pure) at levels of 4.8 wt% of the total diet and of feeding EPA ethyl ester (EPA-Et) (99% pure) at 4.8 wt% on the inflammatory response in the challenge phase of the contact hypersensitivity reaction (CHR) in the ears of mice sensitized with 2,4-dinitro-1-fluorobenzene (DNFB). The effect of DHA-Et on T lymphocytes at the CHR site was examined using anti-CD4 antibodies. Furthermore, we examined the cytokines formed at the CHR site on the mRNA level. It was found that 24 h after the challenge, DHA-Et but not EPA-Et reduced the ear swelling. Infiltration of inflammatory cells, in particular, CD4-positive T lymphocytes, into the ears in the challenge phase of CHR was observed. DHA-Et reduced the infiltration of CD4-positive T lymphocytes into the ears. DHA-Et also decreased the expression of interferon-gamma, interleukin (IL)-6, IL-1beta, and IL-2 mRNA in ears. These observations suggest that DHA, but not EPA, may exert an antiinflammatory and immunosuppressive effect. The immunosuppressive effectiveness of fish oil may be attributed mainly to DHA.

Effect of dietary docosahexaenoic acid on desaturation and uptake in vivo of isotope-labeled oleic, linoleic, and linolenic acids by male subjects.

The effect of dietary docosahexaenoic acid (22:6n-3, DHA) on the metabolism of oleic, linoleic, and linolenic acids was investigated in male subjects (n = 6) confined to a metabolic unit and fed diets containing 6.5 or <0.1 g/d of DHA for 90 d. At the end of the diet period, the subjects were fed a mixture of deuterated triglycerides containing 18:1n-9[d6], 18:2n-6[d2], and 18:3n-3[d4]. Blood samples were drawn at 0, 2, 4, 6, 8, 12, 24, 48, and 72 h. Methyl esters of plasma total lipids, triglycerides, phospholipids, and cholesterol esters were analyzed by gas chromatography-mass spectrometry. Chylomicron triglyceride results show that the deuterated fatty acids were equally well absorbed and diet did not influence absorption. Compared to the low-DHA diet (LO-DHA), clearance of the labeled fatty acids from chylomicron triglycerides was modestly higher for subjects fed the high DHA diet (HI-DHA). DHA supplementation significantly reduced the concentrations of most n-6[d2] and n-3[d4] long-chain fatty acid (LCFA) metabolites in plasma lipids. Accumulation of 20:5n-3[d4] and 22:6n-3[d4] was depressed by 76 and 88%, respectively. Accumulations of 20:3n-6[d2] and 20:4n-6[d2] were both decreased by 72%. No effect of diet was observed on acyltransferase selectivity or on uptake and clearance of 18:1n-9[d6], 18:2n-6[d2], and 18:3n-3[d4]. The results indicate that accumulation of n-3 LCFA metabolites synthesized from 18:3n-3 in typical U.S. diets would be reduced from about 120 to 30 mg/d by supplementation with 6.5 g/d of DHA. Accumulation of n-6 LCFA metabolites synthesized from 18:2n-6 in U.S. diets is estimated to be reduced from about 800 to 180 mg/d. This decrease is two to three times the amount of n-6 LCFA in a typical U.S. diet. These results support the hypothesis that health benefits associated with DHA supplementation are the combined result of reduced accretion of n-6 LCFA metabolites and an increase in n-3 LCFA levels in tissue lipids.

Docosahexaenoic acid is an antihypertensive nutrient that affects aldosterone production in SHR.

The effects of dietary docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid, on blood pressure and some pressure-regulating systems were measured in young spontaneously hypertensive rats (SHR). Plasma aldosterone and corticosterone levels, adrenal aldosterone production in vitro, and characteristics of adrenal angiotensin receptors were measured after 6 weeks of diet. Renal cytochrome P450 (CYP) 4A gene expression and arachidonic acid metabolism by renal microsomes were also investigated. Plasma cholesterol, triglycerides, and high-density lipoprotein cholesterol were measured. Diets contained either corn/soybean oil alone (CSO), or oil enriched with DHA. After 6 weeks, rats fed DHA had systolic blood pressures averaging 34 mmHg less than controls (P < 0.001). Plasma aldosterone levels were 33% lower in the DHA-fed animals than in controls (22 +/- 3 vs. 33 +/- 3.7 ng/dl, P < 0.05). Plasma levels of corticosterone were 18% lower in animals fed DHA than in controls, but this difference was not statistically significant. Adrenal glomerulosa cells from DHA-fed rats produced less aldosterone in vitro in response to angiotensin II, ACTH, or potassium. The difference was less marked when aldosterone production was stimulated by supplying exogenous corticosterone, suggesting an effect of DHA on postreceptor steps in signal transduction or the early pathway of aldosteronogenesis. We found no significant differences in angiotensin receptor subtype, number, or affinity. Production of arachidonic epoxides by renal microsomes was 17% lower in DHA-fed animals than in controls (P < 0.05). Renal cortical mRNA levels of CYP4A genes and formation of 19- and 20-hydroxyeicosatetraenoic acid (HETE) did not differ between dietary groups. Plasma total cholesterol and high-density-lipoprotein (HDL) levels were significantly reduced in SHR fed the DHA supplement, but triglyceride levels were not significantly different. The effects of DHA on steroid and eicosanoid metabolism may be part of the mechanism by which this fatty acid prevents some of the hypertension in growing SHR.

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

It is known that n-3 polyunsaturated fatty acids (PUFA) such as docosahexaenoic acid (DHA) suppress immunity as compared with n-6 PUFA such as linoleic acid (LA), but the mechanism involved in this phenomenon is still unclear. The present study was designed to assess the effect of dietary DHA on the surface molecules involved in T cell proliferation. Weanling male C57BL/6 mice were divided into four dietary groups that were fed a 10% fat diet for 4 weeks varying in amounts of DHA and LA. As the dietary DHA concentration increased, the surface expression of CD4 and CD8 on splenic T cells decreased, while that of CD28 increased. The surface expression of CD3, however, was invariable in all dietary groups. DNA synthesis of splenic T cells, induced by CD3 crosslinkage with anti-CD3ϵ monoclonal antibody in the presence of CD28-mediated costimulation, increased as the DHA concentration was elevated. These observations suggest that diets rich in DHA exert some of their immunomodulatory effects by a downregulation of surface expression of CD4 and CD8 and by an upregulation of CD28-mediated costimulatory signal.

Dietary docosahexaenoic acid enhances ferric nitrilotriacetate-induced oxidative damage in mice but not when additional α-tocopherol is supplemented

Weaning mice were fed a diet supplemented with beef tallow (BT) or BT plus docosahexaenoic acid (DHA) containing 100 mg α-tocopherol/kg (α-Toc100) or 500 mg α-tocopherol/kg (α-Toc500) for 4 wk to modify membrane fatty acid unsaturation, and then were administered ferric nitrilotriacetate (Fe-NTA). The mortality caused by Fe-NTA was higher in the group fed the DHA (α-Toc100) diet than in the BT diet groups but the DHA (α-Toc500) diet suppressed this increase. Serum and kidney α-tocopherol contents were slightly influenced by the dietary fatty acids but not significantly. These results indicate that the increased unsaturation of tissue lipids enhances oxidative damage induced by Fe-NTA in mice fed DHA (α-Toc100) but not when additional α-tocopherol is supplemented. The apparent discrepancy between the observed enhancement by dietary DHA of oxidative damage and the beneficial effects of dietary DHA on the so-called free radical diseases is discussed in terms of strong bolus oxidative stress and moderate chronic oxidative stress.

Dietary docosahexaenoic acid reduces the thromboxane/prostacyclin synthetic ratio in humans

The effect of fish oils, rich in docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), on eicosanoid production in vivo has been extensively studied, but data on the effects of dietary DHA alone on the synthesis of thromboxane (TXA 2) and prostacyclin (PGI 2) in humans are lacking. We quantified the effect of an isocaloric shift in DHA intake from trace (low-DHA diet) to about 6% of total fatty acids (high-DHA diet), ca. 2 en%, on the excretion of 11-dehydrothromboxane B 2 (11-DTXB 2) and 2, 3-dinor-6-oxo-prostaglandin F 1α (PGI 2-M). In a longitudinal study, seven healthy men, living in a metabolic unit, were fed a 30% fat low-DHA diet for 30 days, then a high-DHA diet containing 6g/day of DHA for 90 days. A control group of four subjects remained on the low-DHA diet for the duration of the study (120 days). Three-day urine pools were collected at the end of each dietary period (around day 30 and day 120) and analyzed for eicosanoids by gas chromatography-electron capture negative ion-tandem mass spectrometry. Mean excretion of 11-DTXB 2 was 590 ± 256 ng/d (SD; n = 7) with the low-DHA diet, and 385 ± 148 ng/d ( n = 7) with the high-DHA diet, a 35% reduction ( p = 0.013, n = 11 including the control group, when log transformed data were used). Production of 11-DTXB 2 in the control group was unchanged. Mean excretion of PGI 2-M was 229 ± 73 ng/day (SD; n = 7) and 210 ± 102 ng/day with the low-DHA and the high DHA diet, respectively (a nonsignificant reduction). This study confirms that the synthesis of TXA 2 is more open to diet-induced modulation than the synthesis of PGI 2. The observed reduction of 11-DTXB 2 excretion may be associated with measurable effects on several physiologically significant cellular functions, such as platelet aggregation in vivo and inflammation in response to immune challenges.

Dose-Response Effect of Dietary Docosahexaenoic Acid on Fatty Acid Profiles of Serum and Tissue Lipids in Rats.

The dose-response effects of dietary docosahexaenoic acid (22:6n-3, DHA) on the fatty acid profiles of total lipids of rat serum and tissues were investigated. Rats were fed diets containing graded levels of purified DHA at 0, 1.0, 3.4, and 8.7% of total energy in the diets for 2 weeks. It was found that each tissue had its own peculiar composition of fatty acids which differed markedly from that of circulating serum lipid. This composition was basically influenced dose-dependently by the dietary lipids with graded levels of DHA, but to different degrees in different tissues. Those of brain were most resistant and of heart most susceptible to dietary DHA.

Is a dietary n-3 fatty acid supplement able to influence the cardiac effect of the psychological stress?

Epidemiological studies suggest that n-3 polyunsaturated fatty acids (PUFA) are involved in the prevention of cardiovascular disease. Stress is known to increase the incidence of CVD and the present study was realised to evaluate some physiological and biochemical effects of dietary docosahexaenoic acid (DHA) in male Wistar rats subjected to a psycho social stress. Rats were fed for 8 weeks a semi-purified diet containing 10% of either sunflower seed oil or the same oil supplemented with DHA. This food supply represented 50% of their daily requirement. The remaining 50% were supplied as 45 mg food pellets designed to induce stress in rats by an intermittent-feeding schedule process. The control group (n = 12) was fed the equivalent food ration as a single daily feeding. The physiological cardiovascular parameters were recorded by telemetry through a transmitter introduced in the abdomen. At the end of the experimentation, the heart and adrenals were withdrawn and the fatty acid composition and the catecholamine store were determined. Dietary DHA induced a pronounced alteration of the fatty acid profile of cardiac phospholipids (PL). The level of all the n-6 PUFAs was reduced while 22:6 n-3 was increased. The stress induced a significant increase in heart rate which was not observed in DHA-fed group. The time evolution of the systolic blood pressure was not affected by the stress and was roughly similar in the stressed rats of either dietary group. Conversely, the systolic blood pressure decreased in the unstressed rats fed DHA. Similar data were obtained for the diastolic blood pressure. The beneficial effect of DHA was also observed on cardiac contractility, since the dP/dt(max) increase was prevented in the DHA-fed rats. The stress-induced modifications were associated with an increase in cardiac noradrenaline level which was not observed in DHA-fed rats. The fatty acid composition of adrenals was significantly related to the fatty acid intake particularly the neutral lipid fraction (NL) which incorporated a large amount of DHA. Conversely, n-3 PUFAs were poorly incorporated in adrenal phospholipids. Moreover the NL/PL ratio was significantly increased in the DHA fed rats. The amount of adrenal catecholamines did not differ significantly between the groups. These results show that a supplementation of the diet with DHA induced cardiovascular alterations which could be detected in conscious animals within a few weeks. These alterations were elicited by a reduced heart rate and systolic and diastolic blood pressure.