Investigating how aquatic animals respond to hypoxia brought about by changes in environmental temperature may be of great significance to avoid oxidative injury and maintain the quality of farmed fish in the background of global warming. Here, we investigated the effects of hypoxia on oxidative injury and environment-sensing pathway in blood cells of Micropterus salmoides. The total blood cell count (TBCC) and Giemsa staining showed that hypoxia could lead to damage of blood cells. Flow cytometry analysis confirmed that the apoptosis rate, Ca2+ level, NO production and ROS of blood cells were significantly increased under hypoxia stress. Environment-sensing pathways, such as Nrf2 pathway showed that hypoxia resulted in significant up-regulation of hiF-1 alpha subunit (Hif-1α), nuclear factor erythroid 2-related factor 2 (Nrf2) and kelch-1ike ECH- associated protein l (Keap1) expression. Meanwhile, the expression of Hippo pathway-related genes such as MOB kinase activator 1 (MOB1), large tumor suppressor homolog 1/2 (Lats1/2), yes-associated protein/transcriptional co-activator with PDZ-binding motif (YAP/TAZ), protein phosphatase 2A (PP2A) were significantly increased in blood cells after hypoxia exposure. In addition, hypoxia stress also increased the expression of catalase (CAT) and glutathione peroxidase (GPx), but decreased the expression of superoxide dismutase (SOD). Consequently, our results suggested that hypoxia could induce oxidative injury and apoptosis via mediating environment-sensing pathway such as Nrf2/Hippo pathway in blood cells of M. salmoides.
Faba bean meal (FBM) was used to replace protein materials in different proportions, and its impacts on amino acid and fatty acid composition, flesh quality and expression of muscle quality-related genes in muscle of grass carp (Ctenopharyngodon idella) were evaluated. In the breeding process of crispy grass carp, the addition of FB is very high, which has adverse effects on the physiological function of grass carp. In order to determine the optimum addition amount of FB in crispy grass carp culture, five isonitrogenous (approximately 33.79% crude protein, CP) and isolipidic (approximately 3.43% crude lipid) diets containing different levels of FBM replacing protein materials 0% (CON), 70% (FBM70), 80% (FBM80), 90% (FBM90) and 100% (FBM100) were formulated and were randomly assigned to triplicate groups of fish for 100 days.The results showed that FBM supplement significantly enhanced the myofiber area and radius, content of collagen and CP in muscle. Moreover, compared with the CON group, the content of inosine 5′-monphosphate (IMP), total amino acid (TAA), total non-essential amino acid (TNAA) and the expression of collagen-related (collagen type 1 alpha 1 chain [col1a1] and collagen type 1 alpha 2 chain [col1a2]) and muscle quality-related genes (fibroblast growth factor 6a [fgf6aI] and fibroblast growth factor 6b [fgf6b]) was the highest in the FBM70 group and the lowest in the FBM100 group.In conclusion, the maximal proportion of dietary protein replacement with FBM was 70% based on the flesh quality of grass carp, which provided guidance for the cultivation of crisp grass carp. K E Y W O R D S faba bean, flesh quality, grass carp, muscle 1 | INTRODUC TI ON Grass carp (Ctenopharyngodon idellus) is the largest fish produced in artificial freshwater aquaculture in China, with an annual production of about 5.5 million tons in China (Xu et al., 2020). It is popular for providing low-cost, high-quality animal protein.However, in recent years, the growing production of aquaculture has not brought profits to farmers (Ma et al., 2020). Therefore, the
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