Effect of starvation on lipid metabolism and stability of DHA content of lipids in horse mackerel (Trachurus japonicus) tissues.

For the purpose of characterizing the effect of starvation on 22:6n-3 (DHA) content in marine fish tissues, horse mackerel (Trachurus japonicus) were reared in a tank containing filtered, sterilized seawater under nonfeeding conditions for 107 d (survival rate of the fish was 96.51%). The crude total lipids (TL) of ordinary dorsal muscle, dorsal skin, and viscera of the starved individuals were separated into classes on silicic acid columns, and the constituents of the TL were quantified by gravimetric recovery from column chromatography. The TL, initially > 85% TAG in dorsal muscle, and even more in skin lipids, decreased dramatically within the first 44 d of starvation, and then decreased more gradually during the remainder of the test period, whereas the visceral TL decreased more slowly. The percentages of both saturated and monoenoic FA in the muscle TL also decreased somewhat, but those of DHA increased significantly in muscle during the test periods. Decreases in PE and PC initially were much smaller than TAG, but DHA levels remained high in both PE and PC. These findings indicate that all of the FA in the depot lipids of horse mackerel tissues are easily metabolized for energy production during starvation, but DHA in muscle lipids of the starved fish was maintained at a consistently high level, indicating that starvation did not affect DHA stability in phospholipids. The findings suggest that preservation of DHA in cell membrane lipid PE and PC is necessary for self-protection functions in starving fish.