Submitted to: Fish Physiology and Biochemistry Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2004
Publication Date: 12/1/2004
Citation: Welker, T.L., Congleton, J.L. 2004. Relationship between dietary lipid source, oxidative stress, and the physiological response to stress in sub-yearling chinook salmon (Oncorhynchus tshawytscha). Fish Physiology and Biochemistry. 29: 225-235. Interpretive Summary: Oxidative stress, produced as a consequence of normal cellular metabolism, can cause damage in biological systems and has been implicated in the pathogenesis of many diseases in humans and also in fish. Recent evidence indicates that the physiological response to stress leads to oxidative stress in mammals, and although there is ample evidence to support a relationship between oxidative stress and the stress response in mammals, the relationship has received little examination in fish. In addition, dietary lipids may affect the stress response by mediating prostaglandin hormone synthesis, which can influence stress hormone release. Therefore, the relationship between dietary lipid source, stress, and oxidative stress was examined in juvenile chinook salmon. Four different experimental diets were used: menhaden oil (elevated 20:5n-3 and 22:6n-3), soybean oil (elevated 18:2n-6), linseed oil (elevated 18:3n-3), and a mixture of 55% linseed oil and 45% soybean oil (approximately equal levels of 18:2n-6 and 18:3n-3). The results suggest a stress-oxidative stress-dietary lipid connection in fish, where stress increases oxidative stress and dietary n-6 fatty acids enhance (n-3 fatty acids suppress or do not enhance) the cortisol response to stress leading to an increase peroxidative damage to tissues. This is the first evidence of such a relationship in fish.
Technical Abstract: Relationships between dietary lipid source, stress, and oxidative stress were examined in juvenile chinook salmon (Oncorhynchus tshawytscha). Four different experimental diets were used: menhaden oil (MHO; elevated 20:5n-3 and 22:6n-3), soybean oil (SBO; elevated 18:2n-6), linseed oil (LSO; elevated 18:3n-3), and a mixture of 55% linseed oil and 45% soybean oil (MIX; approximately equal levels of 18:2n-6 and 18:3n-3). Juvenile salmon (initial body weight of 16.0 g) were fed experimental diets for 12 weeks (early March to early June). At the end of feeding, fish subjected to a low-water stressor for 96 h had greater liver and brain lipid peroxidation compared to unstressed controls; peroxidation was not influenced by diet. Diet and stress affected plasma cortisol levels. Stressed fish fed SBO had the greatest cortisol concentrations, followed by MIX, MHO, and LSO (mean concentrations for the SBO and LSO diets differed significantly). The cortisol response to stress may have been influenced by the ratio of prostaglandin 1- and 2-series to prostaglandin 3-series precursor fatty acids provided by the different diets. The results of this study suggest a connection between the physiological response to stress, dietary lipid quality, and oxidative stress. This is the first evidence of such a relationship in fish.