Dietary protein modulates digestive enzyme activities and gene expression in red tilapia juveniles

Abstract

It is known that the level of dietary protein modulates the enzymatic activity of the digestive tract of fish; however, its effect at the molecular level on these enzymes and the hormones regulating appetite has not been well characterised. The objective of this study was to evaluate the effect of CP on the activity of proteases and the expression of genes related to the ingestion and protein digestion of juveniles of red tilapia (Oreochromis sp.), as well as the effects on performance, protein retention and body composition of tilapia. A total of 240 juveniles (29.32 ± 5.19 g) were used, distributed across 20 tanks of 100 l in a closed recirculation system. The fish were fed to apparent satiety for 42 days using four isoenergetic diets with different CP levels (24%, 30%, 36% and 42%). The results indicate that fish fed the 30% CP diet exhibited a higher growth performance compared to those on the 42% CP diet (P < 0.05). Feed intake in fish fed 24% and 30% CP diets was significantly higher than that in fish fed 36% and 42% CP diets (P < 0.05). A significant elevation of protein retention was observed in fish fed with 24% and 30% CP diets. Fish fed with 24% CP exhibited a significant increase in lipid deposition in the whole body. The diet with 42% CP was associated with the highest expression of pepsinogen and the lowest activity of acid protease (P < 0.05). The expression of hepatopancreatic trypsinogen increased as CP levels in the diet increased (P < 0.05) up to 36%, whereas trypsin activity showed a significant reduction with 42% CP (P < 0.05). The diet with 42% CP was associated with the lowest intestinal chymotrypsinogen expression and the lowest chymotrypsin activity (P < 0.05). α-amylase expression decreased with increasing (P < 0.05) CP levels up to 36%. No significant differences were observed in the expression of procarboxypeptidase, lipase or leptin among all the groups (P > 0.05). In addition, the diet with 42% CP resulted in a decrease (P < 0.05) in the expression of ghrelin and insulin and an increase (P < 0.05) in the expression of cholecystokinin and peptide yy. It is concluded that variation in dietary protein promoted changes in the metabolism of the red tilapia, which was reflected in proteolytic activity and expression of digestion and appetite-regulating genes.

Leptin signalling in teleost fish with emphasis in food intake regulation

“…On the contrary, no differences in plasma leptin levels were detected in gilthead sea bream (Ganga et al, 2005), rainbow trout (Ettore et al, 2012) and Murray cod (Ettore et al, 2012) in response to the substitution (complete or partial) of fish oil by vegetable oil in the diet. A similar lack of changes in response to diet composition was observed for the hepatic expression of lep in red tilapia fed diets with different protein content (Santos et al, 2020), in GIFT tilapia fed high plant-based diets (Zou et al, 2017), and in gilthead sea bream fed a high-carbohydrate, high-protein or high-fat diet (Babaei et al, 2017). Likewise, lep mRNA levels remained unaltered in the intestine of pacu when fed diets with a different soy protein concentration (Volkoff et al, 2017), and in the brain and gut of zebrafish fed a diet with high levels of plant protein (Kwasek et al, 2020).…”

Cellulase hydrolyzed Indigofera zolingeriana leaf utilization as a feed ingredient for gourami fingerling

“…Protease enzyme activity on control treatment and 15% doze also showed a higher result than 30% and 45% doze (P<0.05; Table 5). According to Santos et al (2020), declined protease enzyme activity is caused by some factors, such as protein ingredient source and high value of glucose/ monosaccharides in feed. Therefore, the amino acid transport in digestive tract is inhibited due to this condition.…”

Protein hydrolysates derived from aquaculture and marine byproducts through autolytic hydrolysis

“…The type of dietary proteins affected the gene expression of visceral enzymes and thus the activity of trypsin or other visceral peptidases to digest proteins, as shown in farmed Atlantic salmon (Lilleeng et al, 2007) and red tilapia (Santos et al, 2020). Therefore, for autolytic hydrolysis of BPs from farmed aquatics, culture systems and feed type (besides freshness and composition presented in Subsection 4.1) might influence the hydrolytic capacity of visceral proteases and the end-product properties.…”