Long-chain polyunsaturated fatty acid metabolism in carnivorous marine teleosts: insight into the profile of endogenous biosynthesis in golden pompano Trachinotus ovatus

Abstract

Golden pompano Trachinotus ovatus is an important farmed carnivorous marine teleost. Although some enzymes for long-chain polyunsaturated fatty acids (LC-PUFA) biosynthesis have been identified, the ability of T. ovatus for endogenous biosynthesis is unknown. Here, we evaluated in vivo LC-PUFA synthesis in a 56-day culture experiment using six diets (D1-D6) formulated with linseed and soybean oils to produce dietary linolenic/linoleic acid (ALA/LA) ratios ranging from 0.14 to 2.20. The control diet (D0) used fish oil as lipid source. The results showed that, compared with the corresponding indeces of fish fed D0, the weight gain rate and specific growth rate, as well as the contents of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids in tissues (liver, muscle, brain and eye) of D1-D6 groups were significantly lower (P < 0.05). These data suggested that T. ovatus could not synthesize LC-PUFA from C18 PUFA or such ability was very low. However, tissue levels of 20:4n-3 in fish fed diets D1-D6 were higher than that of D0 fish (P < 0.05), and positively correlated with dietary ALA/LA ratio, while levels of EPA showed no difference among the D1-D6 groups. These results indicated that Δ5 desaturation, required for the conversion of 20:4n-3 to EPA, may be lacking or very low, suggesting incomplete LC-PUFA biosynthesis ability in T. ovatus.