Tryptophan ameliorates soybean meal-induced enteritis via remission of oxidative stress, mitophagy hyperactivation, and apoptosis inhibition in hybrid yellow catfish gut ( Pelteobagrus fulvidraco ♀ x Pelteobagrus vachelli ♂)

In this study, the effects of Trp on the growth performance and intestinal health of hybrid yellow catfish suffering from soybean meal-induced enteritis (SBMIE) were investigated. A total of 600 individuals (initial body weight: 6.47 +/- 0.01 g) were randomly divided into 12 cages, each with a water volume of 0.9 m(3) and containing 50 individuals. Four different diets were used to feed hybrid yellow catfish: a fish meal-based diet (containing 40 % fishmeal, FM diet), a soybean meal-based diet (dietary replacement of 75 % FM with soybean meal, SBM diet), and two tryptophan-supplemented diets (soybean meal-based diet containing 0.5 % or 1.0 % of tryptophan, respectively, Trp1 diet and Trp2 diet), were used to feed hybrid yellow catfish. After 42 days of feeding, growth performance, oxidation and antioxidant indices, intestinal histomorphology, mitophagy and apoptosis were analyzed. The results revealed that the final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), feed conversion rate (FCR), viscerosomatic index (VSI), hepatosomatic index (HSI), and condition factor (CF) were unaffected by Trp (P > 0.05) compared with those of fish fed the SBM diet. The fish fed the SBM diet exhibited typical SBMIE, with significantly decreased T-AOC, T-SOD, CAT, and GSH-PX, and increased MDA, ROS, DAO and D-lactate (P < 0.05). The intestinal and mitochondrial morphologies were disrupted. Conversely, the decreased antioxidant capacity, increased oxidant stress and intestinal permeability were significantly reversed by dietary Trp, and the intestinal and mitochondrial structures were repaired (P < 0.05). Moreover, the protein and mRNA levels of ZO-1, Occludin, and Claudin-1, as well as the mRNA expression levels of tgf-beta, il-10, caspase 3, caspase 9, fis1, mff, drp1, mfn1, opa1, and nrf1, were significantly higher in the dietary Trp groups compared to the SBM group (P < 0.05). Additionally, the apoptotic signals in the hindgut were significantly greater in the dietary Trp groups than in the SBM group. (P < 0.05). The mRNA expression levels of tnf-alpha, il-1 beta, beclin1, lc3a, lc3b, parkin, pink1, bnip3, and fundc1, as well as the protein level of LC3B, were significantly decreased by dietary Trp (P < 0.05). In conclusion, these results suggest that Trp can be used as a feed additive to alleviate oxidative stress, ameliorate intestinal epithelial injury, and reduce hyperactivated mitophagy and apoptosis resistance in the intestinal epithelium of hybrid yellow catfish subjected to SBMIE.