Dietary Glutamine Inclusion Regulates Immune and Antioxidant System, as Well as Programmed Cell Death in Fish to Protect against Flavobacterium columnare Infection

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.

Effects of dietary glutamine supplementation on growth performance, intestinal digestive ability, antioxidant status and hepatic lipid accumulation in Xenocypris davidi (Bleeker,1871)

“…Jian) (Hu, et al, 2015;Liu, et al, 2015;Silva, et al, 2010). Glutamate has been demonstrated to reduce intestinal in ammation and protect intestinal epithelial cells from oxidative stress in studies on yellow cat sh (Jiao, et al, 2021) and Jian carp (Chen, et al, 2009). These ndings support the use of glutamine in aquatic animals to improve growth performance and intestinal structure.…”

Antioxidants in Animal Feed

“…Further, the work of Xu et al focused on docosahexaenoic acid (DHA), as a nutritional modulator, to alleviate palmitic-acid-induced inflammation of macrophages via the TLR22-MAPK-PPAR/Nrf2 pathway in large yellow croakers, thereby improving the utilization rate of palm oil in aquafeed [ 11 ]. Another study found that dietary glutamine could regulate immune and antioxidant capacity to protect against Flavobacterium columnare infection in yellow catfish [ 12 ]. The authors suggest their study firstly demonstrated the regulatory roles of glutamine in the fish immune and antioxidant system and reported its inhibitory effects on fish apoptosis and autophagy during pathogenic infection.…”