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The effects of various dietary fish oil concentrations on lipid metabolism of rats were studied. Increased fish oil intake resulted in increased incorporation of long chain (n-3) fatty acids in plasma total lipid at the expense of arachidonic acid. The decreased plasma cholesterol level due to increased fish oil intake can not be explained by triglyceride or cholesterol shifts into tissues nor fecal excretion of neutral sterols and bile acids since the fish oil diet did not affect these variables. Urinary excretion of malondialdehyde, which assesses lipid peroxidation, was increased with fish oil diet concentrations of more than 1.8%.

A 10-week trial was conducted to determine the response of juvenile jade perch Scortum barcoo on the replacement of dietary fish oil ( FO) in a fishmeal free diet. Three iso-nitrogenous, isocaloric and isolipidic diets were formulated, each containing a different primary fat source: FO, linseed oil ( LO), and a mixture of Schizochytrium and LO. The substitution of FO with the mixture of Schizochytrium and LO did not cause a difference in growth. However, there was an 8% reduction in weight gain in fish fed dietary LO, indicating that juvenile jade perch do require a minimal concentration of dietary n-3 highly unsaturated fatty acids ( HUFA). Fish fed the Schizochytrium diet stored more efficient n-3 HUFA and in particular DHA in their flesh, and retained a higher fillet recovery compared to fish fed FO. In addition, we demonstrated that jade perch are able to produce both n-3 HUFA and n-6 HUFA when dietary PUFA are present. Fish fed the LO diet for 10 weeks contained the lowest amount of n-3 HUFA in fillets among dietary treatment groups. However, feeding these fish the Schizochytrium diet for an additional 4 weeks increased the n-3 HUFA content towards the same concentration of n-3 HUFA found in the flesh of fish fed FO, without affecting the sensory properties of the fillets. In contrary, feeding the Schizochytrium diet for a continuous period of 14 weeks lowered overall sensory property scores. [ABSTRACT FROM AUTHOR]

This study was designed to test the hypotheses that digestibility and post-absorption metabolism of fish oil are influenced by impaired lipolysis and by the stereospecific composition of its triacylglycerols. Male Wistar rats were fed nonpurified diets containing one of the following fat sources: 9% native fish oil (NFO), 9% autorandomized fish oil (RFO), 8.1% fish oil-derived free fatty acids (FO-FFA) plus 0.9% glycerol, or 9% soybean oil (SO) as a reference fat. In a 24-day balance study, apparent digestibility of total dietary fat averaged 93.1% in the SO, NFO and RFO groups, and 90.9% in the FO-FFA group. Randomization of fish oil had no effect on apparent digestibility of individual fatty acids. In rats fed FO-FFA, apparent absorption of saturated and monounsaturated fatty acids was lower when compared to the NFO and RFO groups. Feeding the FO-FFA diet tended to increase plasma triglyceride content. The hypocholesterolemic effect of polyunsaturated n−3 fatty acids was not influenced by the dietary source. Similar effects on fatty acid profiles of plasma and liver phospholipids were caused by the NFO, RFO and the FO-FFA diets. We conclude that once polyunsaturated n−3 fatty acids are absorbed, their effect on lipid metabolism is not determined by the dietary source. [ABSTRACT FROM AUTHOR]

A procedure has been developed to separate and quantitate phospholipids, including phosphatidylinositol and phosphatidylserine, from animal tissues by means of the Iatroscan TLC/FID technique. The method is based on the use of 0.01 M oxalic acid impregnated Chromarods-SII and stepwise resolution of the phospholipids in the presence of 1,2-dipalmitoyl- sn-glycero-3-phospho ( N,N-dimethylethanolamine) as internal standard. To remove the neutral lipids, the rods are initially developed in a nonpolar solvent mixture followed by partial scanning. Next, the rods are impregnated with oxalic acid, developed twice in CHCl/CHOH/CHCOOH/HCOOH/HO (80∶35∶2∶1∶3, v/v/v/v/v) and partially scanned for measuring lysophosphatidylcholine, sphingomyelin and phosphatidylcholine. The subsequent step involves double development in CHCl/CHOH/30% NHOH (60∶35∶0.9, v/v/v) to resolve cardiolipin, internal standard, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine and phosphatidic acid. For each phospholipid a linear calibration curve with a highly significant correlation coefficient was obtained. However, the calibration lines extrapolated to negative intercepts on the ordinate, indicating declining sensitivity at low phospholipid loads. [ABSTRACT FROM AUTHOR]