The lipid metabolism of Atlantic halibut (Hippoglossus hippoglossus, L.) larvae determined by 14C in vivo incubations

Abstract

The in vivo ability of Atlantic halibut (Hippoglossus hippoglossus) larvae to incorporate, de-acylate and re-acylate [1-14C]fatty acids (FA) into lipid classes and to elongate and desaturate those substrates was elucidated. To this purpose, 30 days post-first-feeding (30 dpff) larvae were incubated in the presence of either free [1-14C]-FAs (18:2n-6, 18:3n-3, 20:4n-6, 20:5n-3 and 22:6n-3), [1-14C]18:1n-9 bound to mono- (MAG) and triacylglycerols (TAG), or [1-14C]20:4n-6 bound to phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Halibut larvae can efficiently incorporate dietary FAs through MAG, while FA incorporation when provided as free FAs and especially bound to TAG or phospholipids seems to be very low. These results suggest that lipid digestion might be a limiting factor in the FA absorption and incorporation by 30 dpff Atlantic halibut. The present study also shows that esterification into phospholipids is a strong metabolic fate for dietary long-chain polyunsaturated fatty acids (LC-PUFAs), and the capacity of 30 dpff Atlantic halibut larvae to metabolize dietary FAs through elongation/desaturation processes. Nonetheless, neither EPA nor DHA were detected from [1-14C]ALA, indicating a reduced capacity to biosynthesize these LC-PUFAs and the necessity for them to be adequately supplied through the diet for proper larval development.