[Effect of the linolenic acid content of the mother's diet on the polyunsaturated fatty acid composition of subcellular fractions in brain development in the rat]

Composition en acides gras des hémisphères cérébraux de rats spontanément hypertendus allaités par des femelles Wistar

Total lipid fatty acid composition was investigated in brain hemispheres of male Spontaneously Hypertensive Rats (SHR), compared with normotensive Wistar Kyoto rats (WKY) used as controls. Both strains were suckled by adoptive Wistar mothers, and then fed a standard diet after weaning. No difference was observed between the two hemispheres of WKY killed either at 10 or 30 days. In SHR killed at 10 days, the two hemispheres showed differences, SHR left hemispheres exhibiting greater fatty acid composition changes than those of WKY, phenomenon that toned down at 30 days. Hence, SHR pups showed a different total lipid fatty acid composition of their brain hemispheres when compared with their WKY controls, though the two strains received the same diet. Genetically programmed hypertension might be, directly or not, involved in these changes.

Effects of age and dietary essential fatty acids on desaturase activities and on fatty acid composition of liver microsomal phospholipids of adult rats

The combined effects of age and dietary n-6 and n-3 fatty acids were studied in 3-, 6- and 9-month-old rats. At each age, two groups were fed diets containing 5% (w/w) of vegetable oils rich in either 18:3n-6 (borage group) or 18:3n-6 plus 18:4n-3 (black currant group), for a period increasing with age. A control group was fed the essential fatty acids 18:2n-6 and 18:3n-3 only. For each group, delta 6, delta 5 and delta 9 desaturase activities were measured in liver microsomes, and fatty acid composition was determined in microsomal phospholipids. Desaturase activity varied as a function of age and dietary lipids. delta 6 Desaturation of 18:3n-3 was more sensitive to these factors while delta 6 desaturation of 18:2n-6 and delta 9 desaturation were more dependent on season than the other two. Desaturase activity was influenced more by the black currant than by the borage diet, especially at 6 and 9 months of age. A large proportion of arachidonic acid was maintained in the microsomes independent of the diet. Changes in the fatty acid composition did not strictly reflect the differences in desaturase activities. The effects of the two factors (age and diet) on the activities of the desaturases are complex, suggesting that the enzymes are susceptible to other factors as well.

Nutritional encephalomalacia in the chick: an exposure of the vulnerable period for cerebellar development and the possible need for both omega 6- and omega 3-fatty acids

1. Cockerels (1-d-old) received over a period of 4 weeks, a balanced diet containing either safflower oil (diet S) or linseed oil (diet L) as a source of polyunsaturated fatty acids (PUFA). Body-weight, and weights of cerebrum and cerebellum increased at similar rates in the two dietary groups. The total fatty acids (FA) of the cerebellum differed from the cerebral FA by their higher PUFA and oleic acid contents and their lower stearic acid level. During the 3rd week of life there was a spurt in accretion of PUFA in the cerebellum, but not in the cerebrum. At the end of the experimental period phosphatidylethanolamine was present at twice the concentration in the cerebellum, compared with the cerebrum. 2. Diets S and L resulted in extensive mutual replacement of omega 6- and omega 3-FA in brain, without any significant change in the total PUFA. Brain oleic acid concentration was higher in the diet-L group than in the diet-S group, but saturated FA were not affected by the dietary treatments. 3. These results may be relevant to basic brain biology and to chick nutritional encephalomalacia (NE). This disease, which specifically affects the cerebellum and is readily induced by diets supplying linoleic acid but deficient in vitamin E, usually reaches its highest incidence during the 3rd week of life and may thus be related to the cerebellar PUFA spurt that occurs at that time. The fact that NE was induced by linoleic acid, while alpha-linolenic acid exerted a protective action, points to an overproduction of arachidonic-derived eicosanoids as a factor in the etiology of the cerebellar lesion and possibly a structural change due to a loss of docosahexaenoic acid and gain of arachidonic acid in the chicks given diet S.

Recovery of altered fatty acid composition induced by a diet devoid of n-3 fatty acids in myelin, synaptosomes, mitochondria, and microsomes of developing rat brain

Rats were fed a semisynthetic diet containing either sunflower oil or soya oil. Half the litter fed with sunflower oil diet was changed to a soya oil diet when the pups were 15 days old (during active myelination). Fatty acid analysis was then performed on subcellular fractions of the animals fed (a) soya oil, (b) sunflower oil, and (c) soya oil replacing sunflower oil from the 15th day, to determine the speed of the recovery. All material from animals fed sunflower oil showed an important reduction in docosahexaenoic acid (22:6 n-3), compensated by an increase in docosapentaenoic acid (22:5 n-6), whereas arachidonic acid (20:4 n-6) was not affected. In all fractions examined, when sunflower oil was replaced by soya oil in 15-day-old pups the recovery started from the very first day but lasted more than 2 months (this recovery was determined by the increase of 22:6 n-3 up to the normal value and decrease of the 22:5 n-6). In addition a delay was found for myelin recovery, starting only from the 25th day.

Altered composition of polyunsaturated fatty acyl groups in phosphoglycerides of Down's syndrome fetal brain

We have observed recently that in vitro lipoperoxidation is enhanced in Down's syndrome brain homogenates of prenatal age. As this may relate to the composition of polyunsaturated acyl groups (PUFA) in phospholipids, we have examined the PUFA of ethanolamine and serine phosphoglycerides (EPG and SPG), which are particularly rich in PUFA, in the same series of cerebral cortex specimens of Down's syndrome and age-matched control fetuses. Although the total percentages of PUFA in the two phosphoglycerides were not altered, compared with controls the ratio of PUFA of the (n-3) series to those of the (n-6) series was very significantly elevated in Down's syndrome, from 0.32 to 0.55 in EPG and from 0.60 to 0.97 in SPG. In particular, docosahexaenoyl, 22:6(n-3), groups were uniformly increased in Down's syndrome compared with controls by 54% and 33% in EPG and SPG, respectively, while arachidonoyl, 20:4(n-6), groups were decreased by 16% and 30%, respectively. Similar changes occur during normal development, but the (n-3) to (n-6) ratio of PUFA in these phosphoglycerides of Down's syndrome at the fifth month of gestation resembled that of normal human cerebral grey matter at term. However, other developmental indices related to PUFA composition were not significantly affected. It seems therefore that in the developing Down's syndrome brain there may be a distortion of the normal transformations of essential fatty acids and of their incorporation into phosphoglycerides. The disproportion between docosahexaenoyl and arachidonoyl groups in membrane phosphoglycerides during prenatal development in Down's syndrome may also result in disturbances of the proper functioning, and the ontogenetic integration, of membrane enzymes and transport processes.