THE LEVEL OF LINOLEIC-ACID IN NEURAL CARDIOLIPIN IS LINEARLY CORRELATED TO THE AMOUNT OF ESSENTIAL FATTY-ACIDS IN THE DIET OF THE WEANLING RAT

We have reported that an unidentified characteristic of the dietary fatty acid composition can greatly alter the percentage of linoleic acid (18:2n6) in the brain. Neural 18:2n6 is concentrated in cardiolipin (CL), which occurs almost entirely in mitochondria and is specifically bound by several enzymes. The purpose of the work reported here was to identify the dietary fat characteristic that is responsible for altering the 18:2n6 levels in neural CL and to establish the dose-response curve for the two variables. Weanling rats were fed for three weeks on diets designed to separate the neural effects of the amount of dietary saturated, monounsaturated, and essential fatty acids (EFA). The results revealed that the level of 18:2n6 in neural CL was very strongly correlated (r2 = 0.851; P < 0.0001) with the amount of EFA in the diet. This relationship was linear (slope = 0.793, y-intercept = 6.53%) over a wide range of dietary EFA levels (4-15% wt/wt of diet) with the level of 18:2n6 in CL varying by two-fold. Neural 18:2n6 levels were not affected by the ratio of dietary EFA (18:2n6/18:3n3) when the total amount of EFA was held constant. These results indicate that: 1) the amount of dietary EFA substantially alters the level of 18:2n6 in CL from the brain of the weanling rat in a relatively short time; and 2) this relationship is linear over a wide range of EFA levels that are well above the accepted EFA requirements for the rat and within levels that are typical of human diets.