Evaluation of Alpha-Ketoglutarate Supplementation on the Improvement of Intestinal Antioxidant Capacity and Immune Response in Songpu Mirror Carp (Cyprinus carpio) After Infection With Aeromonas hydrophila

Abstract

As an intermediate substance of the tricarboxylic acid cycle and a precursor substance of glutamic acid synthesis, the effect of alpha-ketoglutarate on growth and protein synthesis has been extensively studied. However, its prevention and treatment of pathogenic bacteria and its mechanism have not yet been noticed. To evaluate the effects of alpha-ketoglutarate on intestinal antioxidant capacity and immune response of Songpu mirror carp, a total of 360 fish with an average initial weight of 6.54 ± 0.08 g were fed diets containing alpha-ketoglutarate with 1% for 8 weeks. At the end of the feeding trial, the fish were challenged with Aeromonas hydrophila for 2 weeks. The results indicated that alpha-ketoglutarate supplementation significantly increased the survival rate of carp after infection with Aeromonas hydrophila (P < 0.05), and the contents of immune digestion enzymes including lysozyme, alkaline phosphatase and the concentration of complement C4 were markedly enhanced after alpha-ketoglutarate supplementation (P < 0.05). Also, appropriate alpha-ketoglutarate increased the activities of total antioxidant capacity and catalase and prevented the up-regulation in the mRNA expression levels of pro-inflammatory cytokines including tumor necrosis factor-α, interleukin-1β, interleukin-6, and interleukin-8 (P < 0.05). Furthermore, the mRNA expression levels of toll-like receptor 4 (TLR4), and nuclear factor kappa-B (NF-κB) were strikingly increased after infection with Aeromonas hydrophila (P < 0.05), while the TLR4 was strikingly decreased with alpha-ketoglutarate supplementation (P < 0.05). Moreover, the mRNA expression levels of tight junctions including claudin-1, claudin-3, claudin-7, claudin-11 and myosin light chain kinases (MLCK) were upregulated after alpha-ketoglutarate supplementation (P < 0.05). In summary, the appropriate alpha-ketoglutarate supplementation could increase survival rate, strengthen the intestinal enzyme immunosuppressive activities, antioxidant capacities and alleviate the intestinal inflammation, thereby promoting the intestinal immune responses and barrier functions of Songpu mirror carp via activating TLR4/MyD88/NF-κB and MLCK signaling pathways after infection with Aeromonas hydrophila.

Excessive Dietary Lipid Affecting Growth Performance, Feed Utilization, Lipid Deposition, and Hepatopancreas Lipometabolism of Large-Sized Common Carp (Cyprinus carpio)

“…Based on the strength of the second-order polynomial regression analysis of WGR and FCR, the requirement of dietary lipids for large-sized common carp with an IBW of 247.00 ± 16.67 g was estimated to be 59.5-70.4 g/kg. This requirement is 10-30 g/kg lower than that observed in common carp with an IBW of 5.51 ± 0.05 g (24), common carp with an IBW of 15 g (26), and common carp with an IBW of 36.12 ± 1.18 g (5). The above difference supports somehow the hypothesis that there is a more excellent nutritional requirement in the juvenile stage.…”

“…The common carp production in 2018 was 2,962,218 tons in China, which ranked at the fourth position out of a total of 25 species evaluated (23). However, to our knowledge, the available information on the dietary lipid requirement for common carp was limited to juvenile common carp with the body weights below 20 g and on growing common carp with the weights ranging from 20 to 100 g (24). Xu et al (24) obtained the results from the study on common carp [an initial body weight (IBW) of 5.51 ± 0.05 g] in which the optimum dietary lipid requirement of juvenile common carp was 8% at 16 • C and 11% at 23 • C in terms of immunity.…”

“…However, to our knowledge, the available information on the dietary lipid requirement for common carp was limited to juvenile common carp with the body weights below 20 g and on growing common carp with the weights ranging from 20 to 100 g (24). Xu et al (24) obtained the results from the study on common carp [an initial body weight (IBW) of 5.51 ± 0.05 g] in which the optimum dietary lipid requirement of juvenile common carp was 8% at 16 • C and 11% at 23 • C in terms of immunity. When the weight of common carp reached 15 g, a diet of them containing 80 g/kg lipids was optimal for growth performance and health status (25).…”

Low Protein Diets Supplemented With Alpha-Ketoglutarate Enhance the Growth Performance, Immune Response, and Intestinal Health in Common Carp (Cyprinus carpio)

“…A previous study has shown that AKG played a critical role in the intestinal immunity, and AKG could significantly increase the thickness of intestinal muscle layer and fold height and significantly enhance the activities of intestinal digestive enzymes ( 19 ). In addition, it has been confirmed that AKG alleviated the decline in intestinal function caused by the inflammatory response after Aeromonas hydrophila infection ( 20 ). However, the mechanism by which AKG regulates the immune function and structural integrity of the intestine health in an LP diet remains unclear in fish.…”

Novel Insight Into Nutritional Regulation in Enhancement of Immune Status and Mediation of Inflammation Dynamics Integrated Study In Vivo and In Vitro of Teleost Grass Carp (Ctenopharyngodon idella): Administration of Threonine

“…Considering that little evidence addressed the effect of Thr on immunocyte activation, it still needs further investigation. Once awakened by antigens in an immunologic process, innate immune factors produced by immunocytes, like LZ and C3 derived by macrophages, ACP released by leukocytes simultaneously executed the defense role by breaking down the foreign antigens in the immune organs of fish (86). In our study, compared with the Thr-insufficient-diet group, the optimal Thr level enhanced the enzyme activity of LZ and ACP, complement contents (C3 and C4), and gene expression of antimicrobial compounds hepcidin, LEAP-2A, LEAP-2B, and b-defensin1 in the HK and SP of juvenile grass carp after the challenge with A. hydrophila.…”