Effects of dietary protein levels on activities of protease and expression of ingestion and protein digestion‐related genes in Nile tilapia juveniles

Abstract

While some studies have investigated the effects of dietary protein on the activities of protease in Nile tilapia, little information exists about these enzymes and hormones regulating appetite at the molecular level. Therefore, we investigated the performance, protease activities and expression of genes related to protein intake and digestion in juvenile tilapia fed with diets containing different levels of crude protein (CP): 25.14, 31.12, 36.60 and 42.05%. The fish were fed to apparent satiation three times a day for 65 days. The animal performance and the retention rates of protein and energy linearly decreased with an increase in dietary CP content. A positive quadratic effect of CP on pepsinogen was observed, although the acid protease activity was not affected. Trypsinogen and trypsin activity in the intestine presented similar patterns, showing a positive quadratic response to dietary protein levels. A linear increase in intestinal chymotrypsinogen expression was observed, but the activity of chymotrypsin showed a positive quadratic response. In addition, the expression of cholecystokinin (cck) and peptide yy (pyy) increased linearly with increasing CP. Dietary protein modulates the activity of alkaline proteases as well as the expression of these protease genes and hormones involved in appetite regulation. These changes can help expand our understanding of feed intake and digestion control, thereby improving feed formulations for this species.

Responses of the gastrointestinal microbiota to the protein metabolism of pond-cultured Japanese flounder (Paralichthys olivaceus)

“…Although these genes can regulate the synthesis of pepsinogen, trypsinogen, and chymotrypsinogen, the activations are also related to the specific environment in the gastrointestinal tract. Some studies have reported that protease activity is affected by both intrinsic and extrinsic factors, such as the physiological stage and health status of the organism, nutrient level of the feed, temperature, and exogenous protease (Liu et al, 2019;Choi et al, 2020;Hassani et al, 2020;Santos et al, 2020a;Santos et al, 2020b).. The feed, living environment, species, and physiological stage among the Japanese flounder used in this study have no differences.…”

“…Protein is one of the most important nutrients for organisms because it participates in essential physiological processes, such as the maintenance and repair of damaged tissues and the production of enzymes, hormones, and antibodies, through the anabolism and catabolism of protein during growth and reproduction (Tu et al, 2015;Santos et al, 2020a;Santos et al, 2020b). Proteases are enzymes that specifically break peptide bonds between amino acids during protein degradation.…”

“…Pepsinogen, a precursor of pepsin, belonging to the aspartic proteinase family, is activated in the acidic environment of the stomach and converted to the biologically active pepsin (Foltmann, 1981;Korbova and Kohout, 1981;Chi et al, 2013;Nazemroaya et al, 2020). Trypsinogen and chymotrypsinogen, the pancreatic serine proteases of teleosts, are activated to perform their biologically active function in the gut (Berger and Schechter, 1970;Psochiou et al, 2007;Santos et al, 2020a;Santos et al, 2020b). The synthesis of pepsinogen, trypsinogen, and chymotrypsinogen is regulated by the expression of the respective genes (pepsinogen, trypsinogen, and chymotrypsinogen).…”

The influence of napier grass biomass mixed feed on the biorefinery indicator for Nile tilapia production

“…The activity of protease will vary with the level of protein intake. In addition, dietary protein modulates the activity of alkaline proteases as well as the expression of these protease genes and hormones involved in appetite regulation [ 22 ]. The digestive enzyme pattern can reflect the feeding habit of fish which the quantity and composition of the diet can influence.…”