Effects of long-term fish oil-enriched diet on the sphingolipid metabolism in brain of old rats.

An increase of the neutral sphingomyelinase (SMase) activity in the animal brain at old age is associated with a higher expression of the inflammatory marker, interleukin-1beta and a cognitive decline. Dietary n-3 polyunsaturated fatty acids (n-3 PUFA) are found to exhibit anti-inflammatory effects and normalize the age- or dementia-related cognitive function decline. In the paper we investigate the ceramide, sphingomyelin (SM) and phosphatidylserine (PS) levels in the hippocampus of 3-month-old-32-month-old rats as well as the correction of sphingolipid turnover in the brain of old rats by means of the dietetic fish oil and PS. To study the lipid turnover, the [(14)C]-labeled SM and palmitic acid were used. The [(14)C]ceramide level significantly increased while those of the [(14)C]SM, SM and PS levels decreased in the hippocampus of aged rats as compared with 3-month-old animals. Treatment of the rats with the fish oil or PS reduced the [(14)C]ceramide content and neutral SMase activity in the hippocampus of the 24-month-old animals with respect to control rats of the same age. These results suggest that dietary n-3 PUFA can prevent the age-dependent abnormalities of sphingolipid turnover via increased PS content in the hippocampus of old rats.