Effects of hypoxia stress on digestive enzyme activities, intestinal structure and the expression of tight junction proteins coding genes in juvenile cobia ( Rachycentron canadum )

Abstract

In this study, juvenile cobia fish (Rachycentron canadum) (body weight: 50.44 ± 2.78 g) were used as a study object to investigate the effects of hypoxia stress (dissolved oxygen: 3.15 ± 0.21 mg/L) on the activities of their digestive enzymes, intestinal morphology and relative expression of tight junction proteins coding genes. Under the experimental conditions, the juvenile cobia were given 28 days of hypoxia stress. The results showed that the activities of digestive enzymes in the intestines of the hypoxia stress group decreased. In addition, the amylase and lipase activities decreased significantly (p < 0.05), and the trypsin activity in the hypoxia stress group compared to that in the control group. The morphology and structure of the intestine also showed significant changes. Under the microscopic observation, the mucosal fold height and muscle thickness of the intestine showed a significant decrease (p < 0.05); also, the villi's width showed a significant decrease (p < 0.05) in the hypoxia stress group as compared to that in the control group. The observation under a transmission electron microscope showed that the microvilli of juvenile cobia in the hypoxia stress group were irregularly arranged, atrophied and fallen off compared to the control group. Furthermore, there were gaps in the tight junction. In addition, the boundary between cells was unclear. The relative expression of intestinal tight junction proteins coding genes was down-regulated to varying degrees. The mRNA expressions of ZO-1 and claudin-4 were significantly down-regulated (p < 0.05) and ZO-2 and occludin in the hypoxia stress group compared to those in the control group. These results indicated that hypoxia stress could inhibit the activities of intestinal digestive enzymes, damage intestinal morphology and decrease the expression of tight junction proteins coding genes in cobia. The present study provided a scientific foundation for evaluating the multifaceted impacts of hypoxia stress on fish species, such as cobia.

Transcriptome and 16S rRNA Analyses Reveal That Hypoxic Stress Affects the Antioxidant Capacity of Largemouth Bass (Micropterus salmoides), Resulting in Intestinal Tissue Damage and Structural Changes in Microflora

“…Previous studies have shown that oxidative stress can lead to excessive ROS production, damage to intestinal structure [41], cell apoptosis [42], and impaired function of the intestinal barrier [43]. Intestinal villus morphology and muscle thickness are important indices to measure the function of the intestinal barrier [13]. Previous studies have shown that hypoxia can significantly affect the morphology and thickness of the intestinal muscle layer [12,44].…”

“…Several studies have shown that hypoxic stress significantly affects the intestinal structure of fish. Dong et al found that intermittent hypoxia for 7 days led to the exfoliation of intestinal epithelial cells and a significant decrease in the length of intestinal villi [12]; Yang et al found that the height and width of intestinal villi and the thickness of the muscle layer decreased significantly after 28 days of hypoxic stress [13]. Hypoxia also affects the immune system of fish, and was shown to affect neutrophils and cause inflammation in the intestinal mucosa of Salmo salar [9] and increase oxidative stress and apoptosis-related factors in the intestine of Lateolabrax maculatus [14].…”

Effects of low-temperature stress on intestinal structure, enzyme activities and metabolomic analysis of juvenile golden pompano (Trachinotus ovatus)

“…Lipase adopts a colorimetric method, which is defined as the reaction of each gram of tissue protein with the substrate in this reaction system for 1 min at 37°C, and each consumption of 1 mmol of the substrate is an enzyme activity unit. Trypsin adopts the ultraviolet colorimetric method, which is defined as a unit of enzyme activity when the trypsin contained in each milligram of protein changes the absorbance by 0.003 per minute under the reaction of pH 8.0 and 37°C (Yang et al, 2021).…”

Effects of dietary Bacillus velezensis LSG2-5 on digestion, intestinal morphology, microflora, and related gene expression in Rhynchocypris lagowskii Dybowski

“…The tangible obstacle of the enteric canal comprises intestinal epithelial cells in its majority. and tight junctions between cells (Yang et al, 2021). Absorbing cells, goblet cells, and paint cells make up the majority of intestinal epithelial cells.…”

“…Research has revealed that Bacillus can promote intestinal mucosa development in animals (Ruiz Sella et al, 2021). The intestinal mucosa is essential to enable sh to process and assimilate nutrients and for intestinal microorganisms to adhere to it (Yang et al, 2021). Simultaneously, the muscular layer of the intestinal tract powers peristalsis and promotes the intestinal absorption of nutrients (He et al, 2022).…”