Rat brain fatty acid composition: effect of dietary fat and age.

The polyunsaturated fatty acid composition of human brain changes, as well as progressively decreases, with age. To determine if whole brain rat lipid shows similar changes with age, rats born to mothers fed semi-synthetic diets were raised on the same diet as their mothers for varying periods prior to sacrifice. Whole brain lipid composition was determined for female offspring, fed diets containing 20% w (by weight) of either lard or safflower oil, from age 6 days to 730 days. The percentage of 20:4omega6 and 22:6omega6 decreased with age; as in man these changes were compensated for largely by increases in 18:1omega9. In contrast, 22:6omega3 rose gradually from 6 to 730 days of age. Varying the degree of unsaturation and/or the amount of dietary fat, with the exception of lard, did not influence the fatty acid composition of whole brain lipid or of the two major phospholipids, phosphatidyl ethanolamine (PE) and phosphatidyl choline (PC). Lard was found to contain trace amounts of 22:5omega3; this acid was avidly retained in the brain accompanied by corresponding decreases in 22:5omega6. The functional significance of the observed age-related brain lipid changes is unknown; it is likely that the lipid changes are in some way related to the deterioration of the central nervous system with time.