Dietary Coenzyme Q10 improves salinity adaptation in Nile tilapia (Oreochromis niloticus) through coordinated energy metabolism and redox homeostasis

Salinity stress imposes substantial energetic and oxidative challenges on fish, thereby limiting their survival and growth in saline aquaculture systems. This study evaluated the effects of dietary CoQ10 supplementation on growth performance, osmoregulation, intestinal function, and metabolic responses in Nile tilapia (initial body weight: 2.18 ± 0.10 g) under hyperosmotic conditions. A total of 500 fish were randomly distributed into 20 tanks (four replicates per treatment) and fed five diets containing 0, 5, 10, 20, and 40 mg/kg CoQ10 for 8 weeks under 20 psu salinity. The results showed that moderate CoQ10 supplementation significantly improved survival rate and weight gain, with an estimated optimal level of 13.03 mg/kg. CoQ10 also improved osmoregulatory responses under salinity stress, as reflected by improved serum ion homeostasis, altered expression of gill ion transport-related genes (cftr, nka, nhe1, and nkcc), and reduced gill cell apoptosis. In addition, intestinal physiological status was improved, as evidenced by enhanced digestive enzyme activities, reduced intestinal permeability markers, and modulation of intestinal barrier- and inflammation-related genes. Together, these findings suggest that CoQ10 effectively enhances physiological adaptation to salinity stress in Nile tilapia under hyperosmotic conditions. Mechanistically, CoQ10 promoted glucose utilization and tricarboxylic acid (TCA) cycle activity, enhanced fatty acid β-oxidation, increased ATP and acetyl-CoA production, and reduced lactate accumulation, indicating improved metabolic efficiency and energy supply capacity. Meanwhile, hepatic oxidative stress and histological damage were markedly alleviated, as evidenced by reduced MDA and ROS levels together with elevated GSH content, T-AOC, and SOD activity. Overall, these findings demonstrate that dietary CoQ10 improves salinity adaptation of Nile tilapia through coordinated regulation of energy metabolism and redox homeostasis, thereby enhancing intestinal physiological function and osmoregulatory capacity under hyperosmotic conditions.