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 r ealised to evaluate some physiological and biochemical effects of diet ary docosahexaenoic acid (DHA) in male Wistar rats subjected to a psyc he social stress. Rats were fed for 8 weeks a semi-purified diet conta ining 10% of either sunflower seed oil or the same oil supplemented wi th DHA. This food supply represented 50% of their daily requirement. T he remaining 50% were supplied as 45 mg food pellets designed to induc e stress in rats by an intermittent-feeding schedule process. The cont rol group (n = 12) was fed the equivalent food ration as a single dail y feeding. The physiological cardiovascular parameters were recorded b y telemetry through a transmitter introduced in the abdomen. At the en d of the experimentation, the heart and adrenals were withdrawn and th e fatty acid composition and the catecholamine store were determined.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 redu ced while 22:6 n-3 was increased. The stress induced a significant inc rease in heart rate which was not observed in DHA-fed group. The time evolution of the systolic blood pressure was not affected by the stres s 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 press ure. The beneficial effect of DHA was also observed on cardiac contrac tility, since the dP/dt(max) increase was prevented mas in the DHA-fed rats. The stress-induced modifications were associated with an increa se in cardiac noradrenaline level which was not observed in DHA-fed ra ts. The fatty acid composition of adrenals was significantly related t o the fatty acid intake particularly the neutral lipid fraction (NL) w hich incorporated a large amount of DHA. Conversely, n-3 PUFAs were po orly incorporated in adrenal phospholipids. Moreover the NL/PL ratio w as 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 cardi ovascular alterations which could be detected in conscious animals wit hin a few weeks. These alterations were elicited by a reduced heart ra te and systolic and diastolic blood pressure.