Effects of Hypoxia on Oxidative Damage and Glucose Metabolism in Rainbow Trout Muscle

This study aims to investigate hypoxia-induced oxidative damage in rainbow trout muscle and to explore the mechanism underlying the resulting alterations in the antioxidant defense system from the perspective of glucose metabolism. Rainbow trout were randomly assigned into six groups with nine fish each: the control group (CG) was transported for 3 h at a dissolved oxygen (DO) level of (7.5 ± 0.5) mg/L; the moderate hypoxia group (MHG) was transported for 3 h at a DO level of (5.5 ± 0.5) mg/L; the severe hypoxia group (SHG) was transported for 3 h at a DO level of (3.0 ± 0.5) mg/L; the three reoxygenated groups were transported for 3 h at a DO level of (3.0 ± 0.5) mg/L and then revived at a DO level of (7.5 ± 0.5) mg/L for 12 (R12), 24 (R24) and 48 h (R48), respectively. We measured reactive oxygen species (ROS) level, antioxidant enzyme activities, lipid metabolism related enzyme activities, glucose metabolism indexes, and related gene expressions in muscle tissues. The results showed that the levels of ROS and malondialdehyde (MDA) in the muscle of rainbow trout significantly increased in the SHG compared to the other groups (P < 0.05), and significantly decreased after 24 h of reoxygenation (P < 0.05). Catalase (CAT) activity was significantly higher in the MHG than in the CG (P < 0.05). Total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) activities were significantly lower in both MHG and SHG compared to the CG (P < 0.05). The MHG and SHG showed a significant decrease in muscle glycogen content as well as phosphofructokinase (PFK) and pyruvate kinase (PK) activities, and a significant increase in cortisol content and hexokinase (HK) activity compared to the CG (P < 0.05). The SHG had significantly higher lipase activity than the other groups and significantly higher lactic acid levels than the CG (P < 0.05). Lipoprteinlipase activity was significantly lower in the MHG than in the CG (P < 0.05). The mRNA relative expression of the HIF-1α, AMPK, SIRT1 and PFK genes in the hypoxia-inducible factor 1α (HIF-1α) signaling pathway was significantly upregulated following hypoxia treatment (P < 0.05) but significantly downregulated after reoxygenation for 24 h (P < 0.05). Hypoxia-induced oxidative damage in rainbow trout muscle, which is mitigated by the activation of glucose metabolism-related gene transcription in the HIF-1α signaling pathway.