Intervention of taurine on fatty acid profiles, oxidative injury and autophagy status in the muscle of rice field eel (Monopterus albus) fed oxidized fish oil

Abstract

Fish oil is the primary oil source in the aquatic feed, easily oxidized in feed production and storage. To avoid the potentially negative effects caused by oil oxidation and diversify the study of taurine in aquatic animals, the present study was carried out to investigate the effects of taurine on fatty acid composition, oxidative stress and autophagy status in the muscle of rice field eel (Monopterus albus) subjected to oxidized fish oil (OFO) feed. The feeding experiment was conducted for 8 weeks, and three isonitrogenous and isolipidemic experimental diets were set, namely CON (containing 2% fresh fish oil), OFO (containing 2% OFO), OFOT (containing 2% OFO and 0.2% taurine). A total of 450 eels with an initial weight of 30.06 ± 0.03 g were chosen and randomly distributed to 9 tanks for feeding. It could be found that the muscle moisture and crude protein contents significantly increased in the OFO group (P < 0.05). Dietary taurine significantly increased the muscle n3 PUFA content compared to the OFO group (P < 0.05), and the significantly increased n6 PUFA and total fatty acid contents could be observed in the OFO and OFOT group (P < 0.05). Moreover, dietary taurine significantly decreased myofiber density and muscle hardness by up-regulating the expression of MRF4, Myf5 and MyoD1 compared to the OFO group (P < 0.05), with a larger myofiber diameter due to the decreased connective tissue ratio. Furthermore, dietary taurine alleviated the disturbance of muscle redox endocytosis associated with oxidized fish oil by up-regulating Nrf2 to activate antioxidant enzymes and clear reactive oxygen species (ROS) and malondialdehyde (MDA) in the muscle. Autophagy levels induced by oxidized fish oil improved in the OFOT group, as evidenced by a decrease in protein expression of microtubule-associated protein 1 light chain 3 (LC3). In summary, muscle nutritional composition, redox status and autophagy levels were potentially cross-linked to muscle quality. Dietary taurine reshaped muscle fatty acid composition and effectively improved the extent of muscle oxidative stress and autophagy status induced by oxidized fish oil, leading to greater muscle quality.