Individual fish-oil n-3 polyunsaturated fatty acid deposition and mobilization rates for adipose tissue of rats in a nutritional steady state.

The storage in and mobilization from rat adipose tissue of 20:5n-3, 22:6n-3, 22:5n-3, and 18:4n-3 fatty acids were investigated. After fish-oil feeding, substantial amounts of these fatty acids were stored in fat depots. However, the in vivo relative incorporation (% in triacylglycerols/% in diet) increased significantly in this order: 20:5n-3 (0.25) < 18:4n-3 (0.37) < 22:6n-3 (0.49) < 22:5n-3 (0.78). The in vitro relative mobilization (% in free fatty acids/% in triaclyglycerols) decreased significantly in this order: 20:5n-3 (2.88) > 18:4n-3 (1.51) > 22:6n-3 (1.08) > 22:5n-3 (0.91). Similar results were obtained from rats maintained on a low-fat control diet. Dietary essential n-3 polyunsaturated fatty acids are therefore selectively mobilized from fat stores, which could explain their selective storage. The preferential mobilization of eicosapentaenoic acid could contribute to its maintenance in the circulation after fish-oil feeding, but it probably limits its postintake long-term storage.