Effects of dietary tryptophan levels on growth performance, whole body composition and gene expression levels related to glycometabolism for juvenile blunt snout bream,Megalobrama amblycephala

Abstract

To investigate the effects of dietary tryptophan on growth and glycometabolism in juvenile blunt snout bream, 450 fish (initial weight 23.33 ± 0.03 g) were fed six practical diets with graded levels of tryptophan (from 0.79 g/kg to 5.96 g/kg dry matter) for 8 weeks. Results showed that final weight, per cent weight gain (PWG), protein efficiency rate, feed intake and feed conversion ratio (FCR) were significantly improved by 2.80 g/kg diet. The maximum values of protein and ash were observed in 2.80 g/kg diet, while moisture was minimum. Lipid content of fish fed 3.95 g/kg diet was significantly higher than other diets. The highest plasma insulin‐like growth factor‐1 (IGF‐1) content was observed in 0.79 g/kg diet. In the liver, IGF‐1 mRNA levels were significantly downregulated by 2.80 g/kg dietary tryptophan, while glucokinase levels were by 3.95 g/kg, while glucose‐6‐phosphatase and phosphoenolpyruvate carboxykinase mRNA levels showed a converse trend compared with IGF‐1. Based on PWG and FCR, the optimal dietary tryptophan level was determined to be 1.99 g/kg (6.20 g/kg of dietary protein) and 1.96 g/kg (6.11 g/kg of dietary protein), respectively, using broken‐line regression analysis.

Dietary Tryptophan Supplementation Alters Fat and Glucose Metabolism in a Low-Birthweight Piglet Model

“…Further, the protein expression of SGLT1 in the jejunum and GLUT2 in the liver was decreased in the LBW-T0.4 group. Unlike our study, where we showed an increased mRNA abundance of GCK in LBW-T0.8, others have either failed to detect a change in the hepatic GCK mRNA expression in rats fed with diets supplemented with Trp [ 22 ] or showed a downregulation in the GCK expression in the liver with a higher dose of dietary Trp in blunt snout bream [ 69 ]. Differences in the amount of supplemented Trp and animal species used may contribute to the discrepancy in the findings.…”

Effects of Dietary Lysine Levels on Growth Performance and Glycolipid Metabolism via the AKT/FoxO1 Pathway in Juvenile Largemouth Bass, Micropterus salmoides

“…In addition, the mRNA levels of the gluconeogenesisrelated gene PEPCK were upregulated with high dietary lysine levels (4.09% dietary lysine level); its expression was higher in this group than in all other groups. Moreover, a high plasma GLU content was observed in the high lysine supplementation group, and this finding is similar to the findings of previous studies on the essential amino acids arginine [47] and tryptophan [48] in blunt snout bream (Megalobrama amblycephala). Our previous study indicated that gluconeogenesis could be stimulated by high lysine levels in grass carp [15].…”

Complete replacement of fish meal by plant protein ingredients with dietary essential amino acids supplementation for juvenile blunt snout bream ( Megalobrama amblycephala )

“…It has been introduced in many countries worldwide such as in Africa, North America and Eurasia (Habte‐Tsion et al, ). Accordingly, recent studies have been carried out to grasp the specific nutrient requirements on dietary carbohydrate (Zhou, Liu, Ge, Xie, & Xu, ), protein (Habte‐Tsion et al, ) and amino acids such as methionine (Liang et al, ), threonine (Habte‐Tsion, Ge, et al, ; Habte‐Tsion, Liu, et al, ), arginine (Ren et al, ) and tryptophan (Ji et al, ). However, few studies dealt with the issue of fish meal substitution by plant proteins in the diet of the target species such as rice protein concentrate, canola meal and cottonseed meal (Cai et al, ; Zhou, Habte‐Tsion, Ge, Liu, et al, ; Zhou, Habte‐Tsion, Ge, Xie, et al, ).…”