Incorporation of fatty acids from dietary neutral lipid in eye, brain and muscle of postlarval turbot fed diets with different types of phosphatidylcholine

Previous results demonstrated the stimulating effect of soybean phosphatidy lcholine (PC) on the utilization of dietary neutral lipid in larval and pos tlarval fish. The present study further investigated the effect of the degr ee of saturation of dietary PC on the enhancement of dietary fatty acid inc orporation in lipids of turbot. Newly-weaned turbot were fed for 20 days on four isolipidic diets containing the same amount of highly unsaturated fat ty acids (HUFA), presented either as neutral lipid, i.e. fish oil ethyl est ers, or as polar lipid. Diet FO was a phospholipid-free control diet. Diets HPC, SPC and FPC were supplemented with 3% hydrogenated soybean PC, 3% nat ive soybean PC and 3% marine fish roe PC, respectively. The three PC-supplemented diets resulted in better growth and higher muscle triacylglycerol levels than the PC-free diet FO. The fish fatty acids were determined in 3 lipid das ses (neutral lipid, PC, phosphatidylethanolamine ) of 3 organs or tissues (eye, brain and muscle). Despite the identical amo unts of n-6 and n-3 fatty acids provided by the soybean oil and by the HUFA ethyl esters, the substitution of 3% hydrogenated coconut oil in diet FO b y 3% hydrogenated PC in diet HPC caused, averaged over the various tissues and lipid classes, a 7 to 12% higher incorporation of 18:2n-6, 20:4n-6, 20: 5n-3 and a 32% higher 22:6n-3 level in turbot lipid. Diet HPC appeared as e fficient as diet SPC for enhancing the incorporation of the n-3 HUFA from t he ethyl esters. Feeding diet FPC, in which the n-3 HUFA were provided thro ugh the marine PC source, resulted in slightly higher levels of these fatty acids in the fish than feeding the ethyl eater HUFA diets, even if supplem ented with PC. Present results confirm the positive effect of PC, either hy drogenated or native, on the utilization of fatty acids provided in the die t as neutral lipid. The slightly higher incorporation of HUFA, when esterif ied on dietary PC instead of neutral lipid, raises the question regarding t he form of intestinal absorption of PL in fish.