Supplementation of enzyme-treated soy protein saves dietary protein and promotes digestive and absorptive ability referring to TOR signaling in juvenile fish

Abstract

This study was conducted to evaluate the effect of enzyme-treated soy protein (ETSP) supplementation in the low-protein diet on growth performance, digestive and absorptive capacities, and related signaling molecules' gene expressions in juvenile Jian carp. The results showed that percent weight gain (PWG), specific growth rate (SGR), and feed intake (FI) were decreased by reducing dietary protein from 34 to 32% (P < 0.05). Supplying low-protein diet with optimal ETSP increased previously mentioned indices of juvenile Jian carp (P < 0.05), which also had no significant difference with the high-protein diet (34%CP) (P > 0.05). Compared with the low-protein diet, appropriate ETSP supplementation in the low-protein diet increased (P < 0.05) (1) the trypsin, lipase, and amylase activities in the hepatopancreas; (2) cholecystokinin concentration in the proximal intestine; (3) the γ-glutamyl transpeptidase (γ-GT), alkaline phosphatase (AKP), and Na + /K + -ATPase activities in all intestinal segments; and (4) the messenger RNA (mRNA) levels of trypsin, lipase, and amylase in hepatopancreas and γ-GT in the mid (MI) and distal (DI) intestine, alkaline phosphatase in MI, and Na + /K + -ATPase and target of rapamycin in all intestinal segments. At the same time, appropriate ETSP supplementation in the low-protein diet downregulated the mRNA levels of AKP in the DI and eIF4E-binding protein 2 in all intestinal segments (P < 0.05). In conclusion, adding 10 g ETSP/kg diet in the low-protein diet can restore the growth performance and digestive and absorptive abilities to the levels in group with 34% dietary protein. Supplementation of optimal ETSP in the low-protein diet enhanced the digestive and absorptive abilities and regulated the signaling molecules related to the TOR signaling pathway.

Effect of dietary enzyme‐treated soy protein on the immunity and antioxidant status in the intestine of juvenile Jian carp ( Cyprinus carpio var. Jian)

“…This study used the same growth trial as in our previous study, which observed that adding optimal level of ETSP to the low‐protein diet improved the growth of juvenile Jian carp (the final mean weight and SD of groups 1–7 are 86.67 ± 2.70 b , 82.22 ± 2.01 a , 86.81 ± 2.43 b , 89.69 ± 2.61 b , 87.58 ± 2.27 b , 86.53 ± 3.79 b , 85.39 ± 2.12 ab g respectively), and promoted digestive and absorptive ability referring to TOR signalling in juvenile fish, showing that 1% of ETSP (only provided 0.46% crude protein) can save 2% of dietary crude protein (Xiao et al, ). Our laboratory's previous study showed that the digestion and absorption function mainly rely on the intestinal health in aquatic animals, which has been found to be correlated with the intestinal immunity and structure (Zhao et al, ).…”

“…The intermediate product after enzyme hydrolysis was dried at 90°C for 12 hr. Proximate composition and peptide profile of ETSP were quoted from Xiao et al () providing in Table .…”

“…Weichhart et al () reported that promotion of mTOR decreased the TNF‐α production and increased the release of IL‐10 in human peripheral blood mononuclear cells (PBMCs). Our previous study found that ETSP improved TOR gene expression in the intestine of juvenile carp (Xiao et al, ). These data indicate that ETSP may be related to the intestinal immune response of fish, further studies are warranted to address these important questions.…”

“…Our previous study has indicated that adding ETSP to the low‐protein diet improved the growth performance and promoted the digestive and absorptive ability referring to TOR signalling in juvenile Jian carp ( Cyprinus carpio var. Jian), showing the effect of saving dietary protein (Xiao et al, ). Study found that the growth performance and the digestion and absorption ability mainly rely on the intestinal health in aquatic animals (Zhao et al, ).…”

“…This study was a part of a larger study that involved in the determination of the effects of ETSP on the digestive and absorptive ability in fish using the same growth trial as the previous study (Xiao et al, ). Our previous study has shown that adding ETSP to the low‐protein diet promoted the digestive and absorptive ability of fish, along with the improvement of growth performance and saving of dietary protein (Xiao et al, ).…”