Linseed oil injection into the yolk reserve strongly modulates lipid gene expression and fatty acid composition in juvenile Nile tilapia

Nutritional programming (NP) is an efficient tool for altering metabolic responses to specific nutrients. We aimed to investigate the effects of n-3 polyunsaturated fatty acid (PUFA)-based NP on lipid metabolic responses in Nile tilapia, an economically important freshwater fish species. To increase n-3 PUFA levels during early development, n-3 PUFA-based NP was conducted by injecting linseed oil into the yolk reserve, while the control group received a normal saline injection. Early injection of linseed oil altered the fatty acid profile of fish fry, suggesting the potential for n-3 PUFA stimulation in larvae. The long-term effects of the linseed oil injection were then assessed in juvenile fish. Early linseed oil injection improved feed efficiency throughout the juvenile stage (P < 0.05) and increased n-3 long chain-PUFA (LC-PUFA) levels in the liver and muscles (P < 0.05). Compared to fish injected with saline, those with a history of early linseed oil injection showed reduced hepatic fat content and an upregulation of the expression of several genes related to fatty acid oxidation in the liver (cpt1cb, acox1, pparα, and acadl) and muscles (acox1 and acadl; P < 0.05). Early linseed oil injection also modulated the expression of genes related to lipogenesis, fatty acid desaturation and elongation, hepatic cholesterol synthesis, fatty acid transportation, as well as interactions between carbohydrate and lipid metabolism, and eicosanoid synthesis. Moreover, the long-term impact of NP was determined when fish were challenged with a linseed oil-rich diet. In the context of the challenging diet, growth performance appeared to be similar between NaCl-injected and linseed oil-injected fish. The linseed injection history reduced the hepatic and muscular protein content, suggesting protein catabolism. With a linseed oil-rich diet challenge, linseed oil injection history led to an increase in n-3 LC-PUFA levels in the liver and muscle, as well as fatty acids and their related metabolism. Taken together, early nutritional stimuli were achieved by injecting linseed oil into the yolk reserve in Nile tilapia larvae, resulting in long-term effects on fatty acid composition, fatty acid oxidation, and LC-PUFA synthesis.