INCORPORATION OF N-3 FATTY-ACIDS INTO PHOSPHOLIPIDS OF RAT-LIVER AND WHITE AND BROWN ADIPOSE TISSUES - A TIME-COURSE STUDY DURING FISH-OIL FEEDING

The aim of this study was to determine the time-course incorporation o f dietary n-3 polyunsaturated fatty acids into phospholipids of tissue s highly involved in lipid and energy metabolism: the liver and the wh ite (WAT) and brown (BAT) adipose tissues. Bats were fed a diet supple mented with 19% fish oil for up to 4 weeks. Minor changes in the relat ive proportions of tissue phospholipids were observed in the three tis sues. Fish-oil feeding induced rapid and large replacements of n-6 fat ty acids by n-3 fatty acids. In liver, the 22:6n-3 level increased pro gressively and reached a plateau after 3 (phosphatidylethanolamine and phosphatidylserine) or 7 days (phosphatidylcholine and phosphatidylin ositol). In contrast, the 20:5n-3 level transiently peaked in all live r phospholipids at days 1-3 before reaching a plateau after day 7. In WAT as in BAT the level of n-3 fatty acids increased progressively and reached in all phospholipids a plateau after day 7. As a general tren d, in each phospholipid class the 22:6n-3/20:5n-3 ratio was higher in liver than in the two adipose tissues. This study shows that each diet ary n-3 fatty acid is incorporated very rapidly into liver, WAT and BA T phospholipids but according to time courses and at levels that depen d simultaneously on the tissue and phospholipid class considered.