Minor lipid metabolic perturbations in the liver of Atlantic salmon (Salmo salar L.) caused by suboptimal dietary content of nutrients from fish oil

Fish Physiology and Biochemistry

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Authors

Sanden M, Liland NS, Sæle Ø, Rosenlund G, Du S, Torstensen BE, Stubhaug I, Ruyter B, Sissener NH

  • Atlantic salmon
  • Cholesterol
  • DHA
  • EPA
  • Lipid droplets
  • Phytosterols

The present study was conducted to evaluate the effects on Atlantic salmon hepatic lipid metabolism when fed diets with increasing substitution of fish oil (FO) with a vegetable oil (VO) blend. Four diets with VOs replacing 100, 90, 79 and 65 % of the FO were fed for 5 months. The levels of eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) in the experimental diets ranged from 1.3 to 7.4 % of fatty acids (FAs), while cholesterol levels ranged from 0.6 to 1.2 g kg-1. In hepatocytes added [1-14C] α-linolenic acid (ALA, 18:3n-3), more ALA was desaturated and elongated to EPA and DHA in cells from fish fed 100 % VO, while in fish fed 65 % VO, ALA was elongated to eicosatrienoic acid (ETE; 20:3n-3), indicating reduced Δ6 desaturation activity. Despite increased desaturation activity and activation of the transcription factor Sp1 in fish fed 100 % VO, liver phospholipids contained less EPA and DHA compared with the 65 % VO group. The cholesterol levels in the liver of the 100 % VO group exceeded the levels in fish fed the 65 % VO diet, showing an inverse relationship between cholesterol intake and liver cholesterol content. For the phytosterols, levels in liver were generally low. The area as a proxy of volume of lipid droplets was significantly higher in salmon fed 100 % VO compared with salmon fed 65 % VO. In conclusion, the current study suggests that suboptimal dietary levels of cholesterol in combination with low levels of EPA and DHA (1.3 % of FAs) can result in minor metabolic perturbations in the liver of Atlantic salmon.

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