Brain neutral lipids and phospholipids are modified by long-term feeding of beef tallow vs. corn oil diets

Previous studies examining the response of brain lipids to dietary fat modification have not quantified neutral lipids such as diacylglycerols (DG) and triacylglycerols (TG). In this study we measured the concentrations of neutral lipids and phospholipids, and their fatty acid profiles, in the cerebra of rats fed defined diets containing either beef tallow (BT) or corn oil (CO) at 12% or 37% of energy. The diets were fed to rat pups beginning at 18 d of age and continued for 31 wk. The proportion of brain linoleic acid [18:2(n-6)] in TG from CO-fed rats was two- to fourfold greater than in BT-fed rats. Although 18:2(n-6) levels were higher in serum and brain TG of rats fed CO, differences in other TG fatty acid concentrations in serum were not reflected in the brain. Rats fed CO diets had higher concentrations of 18:2(n-6) in brain phospholipids as well as neutral lipids compared with rats fed BT diets, and the differences were greater in rats fed 37% rather than 12% of energy as fat. Differences in other polyunsaturated fatty acids associated with dietary fat composition were also found among the brain phospholipids. Most notably, the concentration of docosapentaenoic acid [22:5(n-6)] in brain phospholipids was highest in rats fed diets containing the lowest concentrations of alpha-linolenic acid [18:3(n-3)]. A concentration of 0.1 mg 18:3(n-3)/g diet appeared to be adequate to prevent elevation of 22:5(n-6) in brain phospholipids. These results demonstrate that consumption of a low fat diet (12% of energy) primarily comprised of saturated fats may potentiate an 18:3(n-3) deficiency in brain of rats.