Alpha-ketoglutaric acid mitigates the detrimental effects of soy antigenic protein on the intestinal health and growth performance of Mirror carp Cyprinus carpio

The study investigated the alleviated effects of Alpha-ketoglutaric acid (AKG) on the intestinal health of mirror carp ( Cyprinus carpio Songpu) caused by soy antigenic protein. The diets were formulated from fishmeal (CON), 50% soybean meal (SBM), the mixture of glycinin and β-conglycinin (11 + 7S) and adding 1% AKG in the 11 + 7S (AKG). Carp (~ 4 g) in triplicate (30 fish per tank) was fed to apparent satiation thrice a day for six weeks. Compared with CON, SBM treatment resulted in significantly poor growth performance ( P < 0.05), whereas 11 + 7S and AKG treatments were not significantly different from CON ( P > 0.05). Gene expression of tumor necrosis factor (TNF-α) and interleukin-1 β (IL-1β) in proximal intestines (PI) and distal intestines (DI) were increased ( P < 0.05), and transforming growth factor (TGF-β) in PI and middle intestines (MI) was decreased ( P < 0.05) in both SBM and 11 + 7S. The caspase-3 in DI increased in SBM ( P < 0.05) and the caspase-3 and caspase-9 in DI increased in 11 + 7S ( P < 0.05); conversely, TGF-β in PI and MI was increased, TNF-α and IL-1β in the MI, caspase-3, and caspase-9 in DI was decreased in AKG ( P < 0.05). The TOR (target of rapamycin) in PI and MI, ACC in PI, MI and DI was decreased in SBM (P < 0.05), the AMPK in the PI and DI, TOR in PI, MI and DI, ACC in PI and DI, 4E-BP in DI was reduced in 11 + 7S ( P < 0.05). AMPK in the PI and DI, ACC in the PI and MI, TOR in PI, MI, and DI, 4E-BP in PI and DI was recovered by AKG supplementation ( P < 0.05). Lipids and lipid-like metabolism, organic acids and derivatives metabolism increased in AKG dietary treatment. In conclusion, AKG reduces the expression of intestinal inflammation and apoptosis pathway and changes glycerophospholipid metabolism and sphingolipid metabolism in the intestine of fish.