The differences in postprandial free amino acid concentrations and the gene expression of PepT1 and amino acid transporters after fishmeal partial replacement by meat and bone meal in juvenile turbot (Scophthalmus maximus L.)

Abstract

Meat and bone meal (MBM) is a high‐quality alternative protein source used to replace fishmeal (FM). However, the molecular mechanisms of over‐substituted FM by MBM resulted in growth reduction are still not clear. The objective of the study was to evaluate the effect of FM replacement by MBM on the concentration of postprandial free amino acid (FAA) and mRNA abundance of peptide and amino acid transporters in juvenile turbot (Scophthalmus maximus L.). Fish were fed with FM diet (60% FM), MBM diet (33% FM + 34.2% MBM) and MBM + AA diet (MBM diet with essential amino acid (EAA) added to match the AA profile of FM) for 30 days. Results showed that compared with the FM diet, MBM diet led to a reduction in FAA concentration peak values in plasma and muscle. MBM + AA diet significantly elevated the peak values of FAA concentrations to FM diet level in plasma, but not in muscle. Furthermore, compared with FM diet, MBM diet significantly increased gene expression of PepT1 and major amino acid transporters in intestine, whereas MBM diet greatly downregulated gene expression of T‐type amino acid transporter‐1, system ASC amino acid transporter‐2 and cationic amino acid transporter‐2 in muscle. Supplemented EAA did not ameliorate these different effects in intestine and muscle. Overall, this study provided a comprehensive explanation for the relationship between diet, FAA concentrations and AA transportations, which provides a molecular basis for further using MBM to replace FM in aquafeeds.

Dietary Lysine Regulates Body Growth Performance via the Nutrient-Sensing Signaling Pathways in Largemouth Bass (Micropterus salmoides)

“…It is noteworthy that the concentrations of free AA in plasma were easily influenced by nutritional state, developmental stage, and endocrine status (Bos et al, 2003;Wu, 2013). Our previous study in turbot revealed that crystalline AA addition could significantly increase the plasma free AA concentration (Song et al, 2017). Consistent with the turbot study, the present study showed that largemouth bass fed the LL diet for 8 weeks presented significantly lower concentration of total EAA, TAA, and individual AA than did fish fed the LS diet.…”

“…Furthermore, peptide and AA transporters, as the bridge connecting the internal and exterior cell milieu, are the AA sensing mechanisms that lie upstream of the TOR and AAR pathways (Castagna et al, 1997;Russell et al, 2003). In recent years, peptide and AA transporters have been considered as the first step for AA sensing and are increasingly thought to play a pivotal role in body nutrient sensing (Bröer, 2008;Song et al, 2017). In mammals, numerous reports have revealed the regulatory mechanism of dietary lysine levels on nutrient-sensing signaling pathways (Sato et al, 2015).…”

Fish protein hydrolysate affected amino acid absorption and related gene expressions of IGF‐1/AKT pathways in turbot ( Scophthalmus maximus )

“…Yamamoto, Unuma, and Akiyama () reported that the appearance of plasma‐free AA peak time in rainbow trout was delayed when fishmeal in feed had been replaced by plant protein sources, which was largely in agreement with other studies on turbot (Song et al, ; Xu, He, et al, ). According to the results of Song et al () and Xu, He, et al (), decreased postprandial influx of free AAs, particularly EAAs, may lead to reducing growth and feed utilization when turbot was fed a plant protein‐based diet.…”

“…Yamamoto, Unuma, and Akiyama () reported that the appearance of plasma‐free AA peak time in rainbow trout was delayed when fishmeal in feed had been replaced by plant protein sources, which was largely in agreement with other studies on turbot (Song et al, ; Xu, He, et al, ). According to the results of Song et al () and Xu, He, et al (), decreased postprandial influx of free AAs, particularly EAAs, may lead to reducing growth and feed utilization when turbot was fed a plant protein‐based diet. As a per‐digested protein, fish fed FPH diets showed faster and higher concentrations of plasma‐free AAs compared with fish fed intact protein diets containing raw fish or fishmeal (Espe, Lied, & Torrissen, ; Espe, Sveier, Høgøy, & Lied, ; Mach & Nortvedt, ).…”

dl-Methionine supplementation in a low-fishmeal diet affects the TOR/S6K pathway by stimulating ASCT2 amino acid transporter and insulin-like growth factor-I in the dorsal muscle of juvenile cobia (Rachycentron canadum)

“…However, little information about ASCT2 and B 0 AT1 is available for marine fish. Previous studies have provided the gene expression profiles and dietary regulation of these two transporters in turbot, Scophthalmus maximus L. (20,21) .…”