Abstract
The susceptibility of animals to pathogenic infection is significantly affected by nutritional status. The present study took yellow catfish (Pelteobagrus fulvidraco) as a model to test the hypothesis that the protective roles of glutamine during bacterial infection are largely related to its regulation on the immune and antioxidant system, apoptosis and autophagy. Dietary glutamine supplementation significantly improved fish growth performance and feed utilization. After a challenge with Flavobacterium columnare, glutamine supplementation promoted il-8 and il-1β expression via NF-κB signaling in the head kidney and spleen, but inhibited the over-inflammation in the gut and gills. Additionally, dietary glutamine inclusion also enhanced the systematic antioxidant capacity. Histological analysis showed the protective role of glutamine in gill structures. Further study indicated that glutamine alleviated apoptosis during bacterial infection, along with the reduced protein levels of caspase-3 and the reduced expression of apoptosis-related genes. Moreover, glutamine also showed an inhibitory role in autophagy which was due to the increased activation of the mTOR signaling pathway. Thus, our study for the first time illustrated the regulatory roles of glutamine in the fish immune and antioxidant system, and reported its inhibitory effects on fish apoptosis and autophagy during bacterial infection.
Highlights
The susceptibility of animals to pathogenic infection is significantly affected by nutritional status
Introduction with regard to jurisdictional claims in Unlike mammals, teleosts live in aquatic environments which are more conducive to bacterial growth [1,2], potential pathogens could enter the bodies of fish across their mucosal epithelial barriers including the gills, gastrointestinal system or skin lesions [3,4,5]
The programmed cell death including autophagy and apoptosis are related to an early evolution of defense against bacterial infection, for example, successful autophagic contributes to the clearance of the invading microbe and cell survival [12] while apoptosis helps to preserve the whole organism or the species from the spread of infection [13]
Summary
The susceptibility of animals to pathogenic infection is significantly affected by nutritional status. The present study took yellow catfish (Pelteobagrus fulvidraco) as a model to test the hypothesis that the protective roles of glutamine during bacterial infection are largely related to its regulation on the immune and antioxidant system, apoptosis and autophagy. Our study for the first time illustrated the regulatory roles of glutamine in the fish immune and antioxidant system, and reported its inhibitory effects on fish apoptosis and autophagy during bacterial infection. Reactive oxygen species (ROS) would be induced by bacterial infection, the over-production of O2− would cause oxidative damage to proteins, nucleic acids, and lipids [9]. Like other animals, develop a cellular antioxidant defenses system to function in multiple situations including ROS scavenging, oxidative stress published maps and institutional affiliations. The induction of apoptosis in epithelial or endothelial cells might break the epithelia/endothelial cell barrier and permit the bacteria to reach the sub-mucosa [18]
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