Integrated response of growth performance, fatty acid composition, antioxidant responses and lipid metabolism to dietary phospholipids in hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) larvae

Abstract

Dietary phospholipids supplementation is essential for normal development of fish larvae due to their limited phospholipid biosynthetic ability. The present study was conducted to investigate the effects of dietary phospholipids on growth performance, fatty acid composition, antioxidant capacity and lipid metabolism of larval hybrid grouper. The larvae (40 day after hatching, 0.37 ± 0.01 g) were fed the diet with graded level of phospholipids (1.87, 3.61, 5.53, 7.25 and 9.69%) four times daily for 23 days. Results showed that the specific growth rate of grouper larvae was significantly improved with the increase of dietary phospholipids, and optimal dietary phospholipids was estimated to be 9.17%. Fatty acids composition of whole fish body and liver was highly reflective of dietary fatty acid profile. In addition, the increase of dietary phospholipids resulted in a significantly elevated hepatic crude lipid and triglyceride content in a dose-dependent manner. The analysis of gene expression revealed that increased dietary phospholipids did not produce any statistical effect on the expression of lipogenesis genes including LXRɑ, FAS and ACC, but significantly facilitated the expression of DGAT2, a rate-limiting enzyme involved in triglyceride synthesis. The expression of genes, CPT1, involved in β-oxidation was not significantly influenced as dietary phospholipids increased. However, phospholipids inclusion significantly reduced the expression of ATGL, an rate-limiting lipolytic enzyme. Additionally, the supplementation of dietary phospholipids significantly elevated the activity of antioxidant relate enzymes, CAT, SOD and T-AOC, but significantly decreased the MDA content, an end product of fatty acid peroxidation. In summary, dietary phospholipids supplementation was beneficial in improving growth performance and antioxidant capacity of grouper larvae, and meanwhile, promoted hepatic lipid deposition through regulating the synthesis and hydrolysis of triglyceride.