Dietary structured triacylglycerols containing docosahexaenoic acid given from birth affect visual and auditory performance and tissue fatty acid profiles of rats

Abstract

To examine whether it is possible to enhance the level of 22:6(n-3) in the central nervous system, newborn rats were fed dietary supplements containing oils with either specific or random triacylglycerol structure, but similar concentrations of polyunsaturated fatty acids. In the specific structured oil, 22:6(n-3) was located in the sn-2 position, whereas it was equally distributed among the three positions in the triacylglycerol molecule in the randomized oil. A reference group was fed rat milk before weaning and nonpurified diet after weaning. After 12 wk, the levels of 22:6(n-3) in brain and liver phospholipids were higher in the groups fed the experimental diets than in the reference group. The specific structured oil resulted in the highest level of 22:6(n-3) in the brain, whereas the level of 22:6(n-3) was highest in the liver of the group fed randomized oil, indicating differences in metabolism of fatty acids resulting from their position in the dietary triacylglycerol molecule. The higher levels of 22:6(n-3) were accompanied by significantly lower levels of the long-chain (n-6) polyunsaturated fatty acids compared with the reference group. The fatty acid profiles, including the level of 22:6(n-3), in the retina phospholipids were not affected by the three different diets apart from a lower level of 20:4(n-6) in rats fed the experimental diets, indicating a strong tendency to maintain a high level of 22:6(n-3) in the retina. The changes in the fatty acid profiles did not result in differences in learning ability, but caused changes in visual function, evidenced by higher latency of the b-wave and lower oscillatory potential, and in auditory brainstem response, evidenced by generally greater amplitude of wave Ia in the group fed specific structured oil.