Abstract
Dietary lipids provide energy for growth and development and provide fatty acids necessary for normal structure and biological function. However, oxidized lipids cause oxidative stress and intestinal damage. An 8-week feeding trial with fresh fish oil (FFO, control group), oxidized fish oil (OFO), and taurine-supplemented diets (OFOT, OFO + 0.2% of taurine) was conducted to evaluate the protective effect of taurine on oxidized fish-oil-induced liver oxidative stress and intestine impairment in juvenile Ictalurus punctatus. The results showed that (1) Growth performance was significantly lower in fish fed OFO than in those fed other diets, whereas the opposite occurred in the hepatosomatic index. (2) OFO-feeding significantly increased lipid deposition compared with the FFO group. The addition of taurine ameliorated the OFO-induced increase in lipid vacuolization in the liver, significantly upregulated lpl mRNA expression, and downregulated fas and srebp1 mRNA expression. (3) OFO-feeding significantly reduced oxidative damage of liver. Compared with the OFO group, the OFOT group remarkably upregulated antioxidant enzyme mRNA expression through the Nrf2-Keap1 signaling pathway based on the transcriptional expression. (4) OFO diets induced intestinal physical and immune barrier damage. Compared with the OFO group, OFOT diets remarkably downregulated il-1β, il-6, tnf-α, and il-8 mRNA expression and upregulated tgf-β mRNA expression through the NF-κB signaling pathway. Besides, the addition of taurine to OFO diets significantly upregulated zo-2 and zo-1 mRNA expression, and downregulated claudin-15 and claudin-12 mRNA expression. In conclusion, oxidized-fish-oil diets can cause negative physiological health effects in Ictalurus punctatus, while adding taurine can increase growth and antioxidant ability, reduce lipid deposition, and improve intestinal health.
Highlights
IntroductionIt is well known that, as one of the important nutrients of aquatic animals, dietary lipids provide energy for growth and development in fish, and provide the essential fatty-acid and fat-soluble vitamins that maintain normal structure and biological function [1]
Compared with the oxidized fish oil (OFO) group, hepatosomatic index (HSI) in the OFOT group significantly decreased (p < 0.05), and there was no significant difference from the Fresh fish oil (FFO) group (p > 0.05)
Studies have reported that tight junction proteins are closely related to the integrity of intestinal structure, and the upregulation of transmembrane protein-related genes can maintain the structural integrity of intestinal epithelial cells, while the upregulation of cytoplasmic protein-related genes can damage the structural integrity of intestinal epithelial cells [54,72]. This present study found that oxidized-fish-oil diets substantially downregulated intestinal zo-1 and zo-2 mRNA transcriptional levels of channel catfish, and upregulated claudin-12 and claudin-15 mRNA transcriptional levels, indicating that oxidized-fish-oil diets may increase the intestinal barrier structure damage caused by intercellular space by regulating tight junction protein genes
Summary
It is well known that, as one of the important nutrients of aquatic animals, dietary lipids provide energy for growth and development in fish, and provide the essential fatty-acid and fat-soluble vitamins that maintain normal structure and biological function [1]. The main lipid sources in aquatic feed are fish oil and soybean oil. Fish oil has a high content of unsaturated fatty acids (HUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and a good feeding attraction effect, so it is the best lipid source for aquatic animals [2,3]. EPA and DHA are oxidized during the storage and processing of fish 4.0/).
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