Lipid Composition and Fatty Acid Profiles of Myelin and Synaptosomal Membranes of Rat Brain in Response to the Consumption of Different Fats

Abstract

Experiments were performed to ascertain the effect of dietary fats like safflower, mustard, peanut, and coconut oil, which differ widely in the essential fatty acid components on the distribution patterns of specific lipids such as cholesterol, phospholipids, and cerebrosides and the fatty acid profile of the latter two lipid fractions obtained from myelin and synaptosomal membranes of three anatomical regions of the rat brain (cerebrum, cerebellum, and brain stem). Weanling male CFY rats received diets adequate in all essential nutrients but varied with respect to the nature of dietary fat. The fat was fed at the 20% level in the diet for 16 weeks. Myelin and synaptosomal membranes from cerebrum, cerebellum, and brain stem of these rat brains were prepared using discontinuous sucrose density gradient ultracentrifugation. Cholesterol to phospholipid molar ratio remained constant in the synaptosomal membranes in cerebrum and brainstem regions irrespective of the dietary fat treatment, except in the cerebellar region of coconut and mustard oil-fed animals, which showed significantly higher ratio. The cerebroside content of myelin membranes obtained from cerebra and cerebella of these animals were significantly lower compared with those of groundnut and safflower oil-fed rats. Fatty acid compositions of myelin and cerebroside fractions of these membranes were determined. Mustard oil feeding resulted in the enrichment of synaptosomal phospholipid fraction with docosahexaenoic (22:6 n-3) acid (DHA) in the cerebral and cerebellar regions. On the contrary, myelin phospholipid fractions of these regions of mustard oil-fed group were characterized by a lower degree of unsaturation. Lignoceric (24:0) and nervonic (24:1 n-9) acids, the marker fatty acids of myelin, were significantly lower in the brain regions of coconut and mustard oil-fed animals. Results indicate that the brain can adapt to essential fatty acid deficiency in response to coconut oil feeding by retaining high concentrations of polyunsaturated fatty acid in its membranes. On the other hand, dietary fats rich in linoleic (18:2 n-6) acid (safflower) or linolenic acid (18:3 n-3) (mustard oil) significantly elevated the polyunsaturated fatty acid content. In addition, they also altered the long chain fatty acids (like lignoceric and nervonic acids) of a stable membrane, like myelin.