Lipid transport mechanism in the fish. III. Plasma transport form and metabolism of dietary fatty alcohol and wax ester in carp.

To study the mechanism of non-glyceride lipids transport and metabolism in fish, the fate of dietary fatty alcohols and wax esters were investigated by force-feeding [1-14C] oleyl alcohol and [1-4C] oleyl pahmitate to carp. When [1-14C] oleyl alcohol was fed, the total radioactivities in plasma lipoproteins increased gradually, the maximum being around 28h. When [1-14C] oleyl palmitate was given, it was hydrolyzed largely in the intestinal lumen and the total radioactivities in plasma lipoproteins increased with the maximum being around 12h. In both cases, almost all the radioactivities were found in HDL fraction as the forms of mainly triglyceride (TG) and phosphatidylcholine (PC). After 72h of feeding, the radioactivities from [1-14C] oleyl alcohol and [1-14C] oleyl palmitate were found mostly in muscle, intestine, hepatopancreas and gill as mainly in the forms of TG or PC. Tn either cases, a little amount of radioactivity was detected in the class of wax ester or fatty alcohol in each tissue. The dietary fatty alcohol and alcohol moiety of wax ester were largely oxidized to the corresponding acids in the intestinal tissue, which then behaved as in the case of dietary acid, and some were reesterified to form wax esters. Then, most of them were transported as TG and PC with HDL in plasma. Finally, it is suggested that the fatty alcohol in various tissues of carp, which seems to be a substrate of acyl CoA: alcohol acyltransferase, is one of the most important key precursor to form wax esters. Moreover the circulating lecithin: alcohol acyltransferase (LAAT) in plasma also seems to relate to wax ester synthesis.