Search

The aim of this study was to investigate the effects of dietary protein inclusion level on growth, protein absorption pathway and liver metabolism-related pathway in triploid crucian carp (Carassius carassius triploid). Six experimental diets with different protein levels (26%, 29%, 32%, 35%, 38%, 41%) were formulated. A total of 540 fish with an initial weight of 11.79 ± 0.09 g were randomly assigned to 18 cages and six treatments with three replicates of 30 fish each for 8 weeks feeding. The results showed that the specific growth rate (SGR) and feed efficiency (FE) of triploid crucian carp were highly positively correlated with protein content (p < 0.05). The broken-line regression analysis showed that the optimal dietary inclusion level was determined to be 39% considering SGR of triploid crucian carp. In addition, genes related to protein absorption were influenced by the protein inclusion level of dietary. The mRNA expressions of pept1, lat2, cdx2, jak2 and sp1 exhibited similar change tendency and promoted to highest expression at 41% groups, 32% followed. Furthermore, the expressions of hepatic metabolism genes tor, s6k1, igf1, ampd1 and adsl reached peak at 38% dietary protein inclusion level, while 4e-bp2 gene showed the highest expression levels at 41% dietary protein inclusion level. Finally, igf1 expression in liver and cdx2 in intestine showed high pearson coefficients with dietary protein level suggesting their expressions were significant positively regulated by dietary protein level. In conclusion, this study evidenced the influence of dietary protein level on growth, protein absorption pathway, TOR and IGF pathways of hepatic metabolism related in triploid crucian carp. 39% dietary protein inclusion level would be optimum level of triploid crucian carp dietary, which will lead to a better growth and high feed efficiency of triploid crucian carp.

A two-month growth experiment was conducted to investigate the effect of the total fish meal replacement by plant meal on growth performance, nutrient utilization and intestinal microbiota in an improved bream (BBTB) obtained by multistep breeding technologies. Three diets were formulated to replace 0 (FM), 65% (MM) and 100% (PM) of dietary fish meal protein by plant meal (soybean meal and rapeseed meal), respectively. The results showed that the fish meal and plant meal diets could significantly increase the weight gain rate (WGR), specific growth rate (SGR) and feed efficiency ratio (FER) of BBTB compared to their mixed diet. Besides, BBTB fed with PM could significantly decrease the liver lipid contents, but the fish fed with FM showed the more complete microscopic structure in the intestine. Nevertheless, there was no significant difference between FM and PM groups in trypsin activity. In additional, the fish fed with PM showed the higher expression levels in ACCα, PPARα, PPARγ, CPT1a, PepT1 and APN genes, which might affect its nutrient utilization. The results in intestinal microbiota showed that BBTB possessed the herbivorous fish characteristics of intestinal microbiota. These results indicated that BBTB possessed herbivorous characteristics. It is of great significance for the sustainable development of aquaculture.

The forkhead box O3 (foxo3) regulates the target genes expression involved in regulating cell cycle and biological metabolism. In the study, foxo3a and foxo3b of grass carp (Ctenopharyngodon idella) were cloned. The foxo3a cDNA have a complete open reading frame (ORF) spanning 1431 bp, which encodes a polypeptide of 476 amino acids. The foxo3b cDNA contains a complete ORF encompassing 1959 bp, encoding a protein consisting of 652 amino acid residues. The analysis of genetic codon preference and phylogenetic relationships revealed that the foxo3a and foxo3b genes in grass carp are closely related to the counterparts of Danio rerio and Megalobrama amblycephala. Tissue expression analysis showed that foxo3a expression reached the maximum in the brain while foxo3b expression in the muscle being the highest. Circadian expression pattern showed that, foxo3a expression presented a periodic upward trend from 3:00–9:00, 12:00–18:00 and 21:00–24:00, and the maximum level of foxo3b was detected at 9:00. Moreover, dietary regulation of foxo3a and foxo3b expression were performed in our research. In the feeding trial with different protein sources, the groups of fishmeal, rapeseed meal and soybean meal are in contrast to each other. Foxo3a expression was significantly higher in fish fed with rapeseed meal compared to those fed with soybean meal and fishmeal at 14th and 21st days of the experiment. Foxo3b expression was highest in the fishmeal group, followed by rapeseed meal, while it was lowest in soybean meal at 14th and 28th days. Analysis of the effect of dietary alanine-glutamine dipeptide on foxo3 expression in grass carp revealed that the expression of foxo3a gradually increased with increasing dietary Ala-Gln dipeptide concentration and reached its highest level at a concentration of 1.5%. Conversely, foxo3b expression significantly decreased when the dipeptide concentration reached 2%. The findings of this study may provide new insights into the molecular properties, spatiotemporal dynamics, and nutritional regulation of foxo3 in fish.

A 56-day feeding trial was conducted to evaluate the effect of different dietary protein sources on the growth performance, muscle flavor substances, and quality structure of Triploid Crucian Carp. Three isonitrogenous (32.00%), isolipidic (8.00%), and isoenergetic (18.00 MJ kg−1) practical diets were formulated. These diets consisted of fishmeal as the animal-derived protein source (AP), a combination of soybean meal and rapeseed meal as the plant-derived protein source (PP), and a mixture of fishmeal, soybean meal, and rapeseed meal as the mixed protein source (MP). Each diet was randomly assigned to triplicate tanks of fish and each tank was stocked with 25 fish (11.5 ± 0.4 g). The fish were fed until apparent satiation twice a day. The results showed a significant enhancement in the growth performance of Triploid Crucian Carp in the AP group compared with both the MP and PP groups (p < 0.05). Dietary plant derived protein can remarkably reduce the crude lipid content and increase the moisture content of the whole body and the dorsal muscle (p < 0.05). The antioxidant ability of fish in the PP group and MP group was better than that in the AP group (p < 0.05). Regarding free amino acids composition of muscle, the contents of glycine, methionine, and lysine were significantly enhanced in the AP group, while the histidine content was significantly increased in the PP group (p < 0.05). In terms of texture, dietary plant protein significantly improved the muscular hardness, gumminess, and chewiness. The activities of intestinal trypsin and alkaline phosphatase (ALP) of fish in the PP group were significantly higher than that in the AP group (p < 0.05). The expression levels of hepatopancreas TOR and IGF1 genes in the PP group were significantly higher than that in the MP group (p < 0.05). The present results indicate dietary fishmeal significantly improved the growth performance and muscular flavor glycine content, while dietary plant-based protein increased crude protein content, antioxidant ability, and muscular texture performance of Triploid Crucian Carp.

Inosine monophosphate (IMP) is the main flavoring substance in aquatic animal, and adenosine monophosphate deaminase1 (AMPD1) gene is a key gene in IMP formation. At present, the research on the mechanism of AMPD1 regulating IMP formation in aquatic animal is still blank. In this study, in order to study the mechanism of AMPD1 regulating IMP formation in fish, the full open reading frame (ORF) of AMPD1 which was 2160bp was obtained for the first time in triploid crucian carp (Carassius auratus). It encoded 719 amino acids with a molecular mass of 82.97 kDa, and the theoretical isoelectric point value was 6.31. The homology analysis showed that the homology of triploid crucian carp and diploid Carassius auratus was the highest, up to 99%. And the phylogenetic tree showed that triploid crucian carp was grouped with diploid Carassius auratus, Culter alburnus, and Danio rerio. And real-time fluorescence quantitative results showed that AMPD1 was expressed specifically in muscle of triploid crucian carp (p < 0.05). The results of detection the localization of AMPD1 in cells indicated that the AMPD1 was mainly localized in cytoplasm and cell membrane. Further, we examined the effects of glutamate which was the promotor of IMP formation on the expression of AMPD1 and the formation of IMP in vivo and in vitro experiments, the results showed that 3% glutamate and 2 mg/ml glutamate could significantly promote AMPD1 expression and IMP formation in triploid crucian carp muscle tissue and muscle cells (p < 0.05). Then we inhibited the expression of AMPD1 in vivo and in vitro experiments, we found the formation of IMP in muscle tissue and muscle cells of triploid crucian carp all were inhibited and they affected the gene expression of AMPK-mTOR signaling pathway. The all results showed that AMPD1 mediated glutamate through AMPK-mTOR signaling pathway to regulate the formation of fish IMP.

Mitogen-activated protein kinase kinase kinase 3 (MEKK3) is an evolutionarily conserved Ser/Thr protein kinase of the MEKK family that is essential for the host immune response to pathogen challenges in mammals. However, the immune function of MEKK3s in lower vertebrate species, especially in bony fish, remains largely unknown. In this study, a fish MEKK3 (designated CiMEKK3) gene was cloned and identified from grass carp (Ctenopharyngodon idella). The present CiMEKK3 cDNA encoded a 620 amino acid polypeptide containing a conserved S-TKc domain and a typical PB1 domain. Several potential immune-related transcription factor-binding sites, including activating protein 1 (AP-1), nuclear factor kappa B (NF-κB) and signal transducer and activator of downstream transcription 3 (STAT3), were observed in the 5’ upstream DNA sequence of CiMEKK3. A phylogenetic tree showed that CiMEKK3 exhibits a close evolutionary relationship with MEKK3s from Cyprinus carpio and Carassius auratus. Quantitative real-time PCR analysis revealed that CiMEKK3 transcripts were widely distributed in all selected tissues of healthy grass carp, with a relatively high levels observed in the gill, head kidney and intestine. Upon in vitro challenge with bacterial pathogens (Aeromonas hydrophila and Aeromonas veronii) and pathogen-associated molecular patterns (PAMPs) (lipopolysaccharide (LPS), peptidoglycan (PGN), L-Ala-γ-D-Glu-mDAP (Tri-DAP) and muramyl dipeptide (MDP)), the expression levels of CiMEKK3 in the intestinal cells of grass carp were shown to be significantly upregulated in a time-dependent manner. In vivo injection experiments revealed that CiMEKK3 transcripts were significantly induced by MDP challenge in the intestine; however, these effects could be inhibited by the nutritional dipeptides carnosine and Ala-Gln. Moreover, subcellular localization analysis and luciferase reporter assays indicated that CiMEKK3 could act as a cytoplasmic signal-transducing activator involved in the regulation of NF-κB and MAPK/AP-1 signaling cascades in HEK293T cells. Taken together, these findings strongly suggest that CiMEKK3 plays vital roles in the intestinal immune response to bacterial challenges, which will aid in understanding the pathogenesis of inflammatory bowel disease in bony fish.

An eight-week experiment was undertaken to examine the effect of dietary hydroxyproline (Hyp) supplementation on growth performance, collagen synthesis, muscle quality of an improved triploid crucian carp (Carassius auratus Triploid) (ITCC). Six isonitrogenous (340 g/kg diet), isolipidic (60 g/kg diet) and isocaloric (17.80 MJ/kg diet) diets were formulated containing a certain amount of Hyp: 0.09% (the control group), 0.39, 0.76, 1.14, 1.53 and 1.90%. Each diet was randomly assigned to three tanks and each group was fed two times daily until apparent satiation. The results showed that growth performance and feed utilization of ITCC were significantly improved with the dietary Hyp level was increased from 0.09 to 0.76%. Crude protein, threonine and arginine content in the dorsal muscle in 0.76% hydroxyproline group were significantly higher than those in basic diet group (p < 0.05). The muscle textural characteristics increased remarkably with the amount of Hyp in the diet rising from 0.09 to 1.53% (p < 0.05). Meanwhile, the contents of type I collagen (Col I) and Pyridinium crosslink (PYD) in the muscle of fish were significantly increased by dietary Hyp (p < 0.05). The muscle fiber diameter and density of the fish were significantly increased when fed with 0.76% Hyp (p < 0.05). Furthermore, dietary supplementation with an appropriate concentration of Hyp substantially increased the expression of genes involved in collagen synthesis (col1a1, col1a2, p4hα1, p4hβ, smad4, smad5, smad9, and tgf-β) and muscle growth (igf-1, tor, myod, myf5, and myhc) (p < 0.05). In conclusion, dietary supplementation of Hyp can enhance fish growth performance, collagen production, muscle textural characteristics and muscle growth of ITCC. According to the SGR broken-line analysis, the recommended supplementation level of Hyp was 0.74% in the diet for ITCC, corresponding to 2.2% of dietary protein.

Leptin receptor (LEPR) is a type of transmembrane receptor and a member of the class I cytokine receptor family that plays a decisive role in the physiological functions mediated by leptin. In this study, a fish LEPR gene (CiLEPR) was cloned from Ctenopharyngodon idella. The open reading frame (ORF) sequence of the CiLEPR gene included 3504 bp, which encoded 1078 amino acids that formed six functional domains, including five FN3 domains and a lep_receptor_Ig domain. Phylogenetic analysis showed that the CiLEPR amino acid sequence was closely related to that of LEPR from Hypophthalmichthys molitrix. The qRT-PCR results showed that the CiLEPR gene was widely expressed in all investigated tissues of C. idella and was relatively highly expressed in the gills. The results of the circadian rhythm experiment revealed that the intestinal expression of the CiLEPR gene changed regularly over time. In C. idella intestinal cell experiments, it was observed that recombinant leptin could upregulate the expression levels of CiLeptin, CiLEPR and CiPepT1 in the intestines of C. idella. The results of experiments in which fish were fed with various protein sources demonstrated that the mRNA expression levels of CiLeptin, CiLEPR and CiPepT1 in the fish meal group were higher than those in the soybean meal group at 28 d. The data indicated that C. idella fed diets with medium amounts of dietary protein (37%) expressed the highest mRNA levels of CiLeptin, CiLEPR and CiPepT1 after 4 weeks. These results provide a basis for further studies on the nutritional regulation and physiological functions of leptin receptors in fish.

Ghrelin can stimulate pituitary growth hormone (GH) release, and has a key role in the regulation of food intake and adiposity in vertebrates. At present, no relevant studies have reported the effects of Ghrelin on intestinal cell proliferation, protein absorption and metabolism. In this paper, firstly we established the intestinal epithelial cell lines of juvenile grass carp (Ctenopharyngodon idella) that can be passed stably and identified by the intestinal specific expression proteins E-cadherin and ZO-1. And we used this cell line as a model to investigate the effects of Ghrelin, Ala-Gln, Ala-Gln+Ghrelin on the proliferation of juvenile grass carp intestinal cells. We found that the use of Ghrelin, Ala-Gln and Ala-Gln+Ghrelin could promote the proliferation of intestinal cells of juvenile grass carp, but Ala-Gln+Ghrelin had the strongest promoting effect. Further, we investigated the effects of Ghrelin on the expression of cdx2, PepT1 and mTOR which are related to intestinal cell proliferation, protein absorption and metabolism of grass carp in vitro and in vivo experiments. And we studied the effects of different protein sources on the expression of Ghrelin, PepT1 and mTOR in grass carp at individual level. The results suggested that Ghrelin can promote grass carp intestinal cell proliferation, and affect the expression of genes which are related to intestinal peptide absorption and metabolism in juvenile grass carp.

Kidney-type glutaminase, encoded by the gls1 gene, plays a critical role in glutamate production and improvement of meat flavor. In this study, a gls1 gene encoding 595 amino acids was cloned from triploid crucian carp (Carassius auratus) (TCC) and showed a high similarity with the gls1 gene found in Cyprinus carpio, Sinocyclocheilus rhinocerous and Puntigrus tetrazona. Comparing the abundance of gls1 in different tissues, we found its expression level in the brain and liver were significantly higher than that in heart, gut, kidney, spleen and muscle. gls1 expression in the brain reached the highest value. In addition, the expression levels of gls1 also appeared different in diurnal variation, with the highest expression seen at 9:00, while it was low at 3:00, 6:00, 15:00 and 24:00. Furthermore, dietary regulation of gls1 expression was investigated in our study. In each feeding trial, each diet was randomly assigned to triplicate tanks. Fish were fed one of the tested diets up to satiation twice daily. The results showed that gls1 expression increased in 32% protein group and decreased in 35–41% protein group. The results of different protein source experiments showed that the expression of gls1 gene in the mixed protein group (the control group) was significantly higher than that in the fish meal and soybean meal groups. Glutamate treatment revealed that appropriate concentrations (0.10 mg/mL in vivo and 2.00% in vitro) of glutamate remarkably improved the expression of gls1. Besides, diets supplemented with 0.80–1.60% lysine-glutamate dipeptide exhibited a down regulatory impact on gls1 expression. In conclusion, this study demonstrated that the expression of gls1 in TCC was increased by 32% protein diet, mixed protein source diet and diet with 2.00% glutamate concentration, while decreased by 0.80–1.60% lysine-glutamate dipeptide. The findings of this study provide a reference for the regulation of gls1 and have a potential application in the optimization of dietary formula in aquaculture.

This study was conducted to evaluate the effect of acute ammonia stress on intestinal oxidative stress levels, histology, and activity of digestive enzymes and oligopeptide transporter 1 (PepT1) in grass carp. Three concentrations of ammonia nitrogen: 0 mg/L total ammonia nitrogen (TAN) (the control group), 1.7 mg/L TAN were used in the present study. Fish were sampled at 0 h, 12 h, 24 h, and 48 h after exposure to ammonia. The results showed that the activities of reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT) and the content of cortisol were all increased in fish exposed to the two concentrations of TAN. Compared with the control group, the activities of intestinal trypsin and chymotrypsin significantly increased in the 1.7 mg/L TAN group, while amylase activity was significantly suppressed in the 50 mg/L TAN group. After ammonia exposure, the expression of intestinal Nrf2 gene significantly increased in the 1.7 mg/L TAN group while the expression of Keap1 gene significantly increased in the 50 mg/L TAN group. Moreover, the expression of intestinal PepT1, Sp1 and CDX2 significantly increased after fish exposed to 1.7 mg/L TAN. The width of mid-intestine villi of fish from the 50 mg/L TAN group was significantly higher than fish from the other two groups. Meanwhile, the area density of PepT1 in the 50 mg/L TAN group was significantly smaller than that in the control and 1.7 mg/L TAN groups. The results suggested that ammonia stress induces intestinal oxidative stress, and 1.7 mg/L TAN increased the expressions of PepT1-related genes and the activities of the intestinal trypsin and chymotrypsin. This conclusion indicates that ammonia nitrogen stress affects the intestinal digestion and absorption performance of aquatic animals, and reducing ammonia nitrogen to a suitable level can improve the protein digestion ability of animals.

Liver Kinase B1 (LKB1) is a serine/threonine kinase that can regulate energy metabolism and skeletal muscle growth. In the present study, LKB1 cDNA of triploid crucian carp (Carassius auratus) was cloned. The cDNA contains a complete open reading frame (ORF), with a length of 1326 bp, encoding 442 amino acids. Phylogenetic tree analysis showed that the LKB1 amino acid sequence of the triploid crucian carp had a high sequence similarity and identity with carp (Cyprinus carpio). Tissue expression analysis revealed that LKB1 was widely expressed in various tissues. LKB1 expressions in the brain were highest, followed by kidney and muscle. In the short-term LKB1 activator and inhibitor injection experiment, when LKB1 was activated for 72 h, expressions of myogenic differentiation (MyoD), muscle regulatory factor (MRF4), myogenic factor (MyoG) and myostatin 1 (MSTN1) were markedly elevated and the content of inosine monophosphate (IMP) in muscle was significantly increased. When LKB1 was inhibited for 72 h, expressions of MyoD, MyoG, MRF4 and MSTN1 were markedly decreased. The long-term injection experiment of the LKB1 activator revealed that, when LKB1 was activated for 15 days, its muscle fibers were significantly larger and tighter than the control group. In texture profile analysis, it showed smaller hardness and adhesion, greater elasticity and chewiness. Contrastingly, when LKB1 was inhibited for 9 days, its muscle fibers were significantly smaller, while the gap between muscle fibers was significantly larger. Texture profile analysis showed that adhesion was significantly higher than the control group. A feeding trial on triploid crucian carp showed that with dietary lysine-glutamate dipeptide concentration increasing, the expression of the LKB1 gene gradually increased and was highest when dipeptide concentration was 1.6%. These findings may provide new insights into the effects of LKB1 on fish skeletal muscle growth and muscle quality, and will provide a potential application value in improvement of aquaculture feed formula.

The nutritional functions of tributyrin (TB) have been extensively studied, but questions remain regarding its influence on the growth of juvenile grass carp (Ctenopharyngodon idellus) and the regulation pathway to PepT1 in the intestine of grass carp. To answer the remaining questions, feeding trials, cell trials, and peritoneal injection trials were conducted in this study. The results showed that an appropriate level of TB (0.5 g/kg and 1.0 g/kg) supplementation in feed significantly promoted the growth performance of juvenile grass carp. The expressions of intestine genes (CDX2, SP1 and PepT1) related to oligopeptide transportation increased in the 0.5 g/kg TB group of feeding trials and both the 5 mM and 10 mM TB groups of the intestine cell trials, respectively. Subsequently, the injection trials of inhibitors CDX2 and SP1 demonstrated that the inhibition of CDX2 or SP1 decreased the mRNA expression of PepT1. Finally, the results of independent or combined treatments of TB and the inhibitors suggested that CDX2/SP1 mediated TB regulation on PepT1. These findings may help us to better understand the functions of TB on growth and PepT1 oligopeptide transportation, which could be modulated by dietary TB through the CDX2/SP1-PepT1 pathway in juvenile grass carp.

Glutamine synthetase (GS) is a key enzyme that catalyzes the synthesis of glutamine from glutamate, which plays a role in the promotion of muscle cell growth and in improving the flavor of meats. In this study, a GS gene encoding 371 amino acids was cloned from triploid crucian carp and showed the highest level of similarity with the GS gene found in Cyprinus carpio. Meanwhile, GS was differentially expressed in different tissues, and its day–night expression changes showed obvious oscillation. Additionally, the effects of glutamate and glutamine on GS expression in muscle cells were investigated in vitro and in vivo. We found that its expression was obviously increased due to high levels of glutamate (2 mg/mL) but decreased by glutamine in vitro. However, it was significantly promoted by glutamate and glutamine in vivo, with an optimal concentration of 2%. Furthermore, the use of lysine–glutamate dipeptides as feed additives also had a positive influence on GS expression (the optimal concentration is 0.8%). Finally, we explored the effects of different protein levels and sources on the expression of GS, and the results demonstrated that GS had the highest expression at the 35% protein level, but no significant differences were observed in the different protein sources between the fish meal diet (FM) and the mixed diet comprising soybean meal and rapeseed meal (SM). This study sheds new light on the regulation of GS in teleost fish and provides new perceptions and strategies for the formulation of high-quality feed for triploid crucian carp.

This study assessed the nutritional potential of supplementing the practical diets for gibel carp (Carassius auratus gibelio var. CAS V) with a blend of fermented plant meal. The fermented plant meal (FPM) comprised mixed fermentation of rapeseed meal (RM), sprayed corn husk (SCH), rice bran (RB), palm meal (PM) and soybean meal (SM) in the proportion of 30:25:25:15:5. Four experimental diets were including a basal diet (the control diet, Con) and three FPM diets (supplementing 3 g, 5 g and 8 g FPM per 100 g diet in the basal diet, FPM3, FPM5 and FPM8, respectively). Each diet was randomly allotted to triplicate fish tanks where each tank had 25 fish weighing 28.00 ± 0.02 g. Fish from each group were fed twice per day until apparent satiation for 60 days. From the results, gibel carp from the FPM5 group had significantly higher feed efficiency and specific growth rate despite having significantly lower feeding rate than the control group. Fish from FPM5 group had significantly higher hepatosomatic index and viscera somatic index than those from FPM3 group. Meanwhile, serum antioxidants (including aspartate aminotransferase, catalase, glutathione peroxidase, superoxide dismutase and malondialdehyde) and intestinal digestive enzymes (including chymotrypsin, trypsin and amylase) of fish increased proportionately to amount of FPM in the diet. Fish fed on FPM5 diet had significantly higher expression of TOR and IGF-1 in the liver than those fed on the control diet. Further, supplemented with 8% of FPM significantly increased the relative mRNA abundance of hepatopancreas GH and S6K1. These results reveal that moderate level of dietary FPM significantly enhanced growth performance, antioxidant capacity, digestive enzymes activities and the expression of TOR signaling pathway genes of juvenile gibel carp, and dietary supplementation of 5% FPM is recommended for the juveniles base on the performance of growth and antioxidant properties.

AlaSerCys Transporter 2 (ASCT2), encoded by the SLC1A5 gene, plays an important role in the absorption of glutamine. In this study, the full-length cDNA sequence of ASCT2 was cloned from triploid crucian carp. It encodes 539 amino acid residues and a stop codon. Phylogenetic analysis revealed that the sequences of the ASCT2 ORF region in cyprinid fishes shared high sequence homology. Comparing the abundance of ASCT2 in different tissues, we found its expression level in muscle was significantly higher than that in intestine (p < 0.05). In addition, the expression levels of ASCT2 also appeared different in diurnal variation. Then we found the addition of 2.5% glutamate in a feeding diet significantly increased the expression levels of ASCT2 in intestine and muscle (p < 0.05). However, in glutamine experiments, the muscle showed the highest expression level of ASCT2 when fish were fed the diet containing 3.0% glutamine (p < 0.05). In vitro, ASCT2 was sensitive to glutamine and its expression level appeared down-regulated when the addition of glutamine was added to 0.1 mg/mL. Finally, we found that the diet with 29% protein level significantly increased the expression level of ASCT2 in intestine (p < 0.05). Nevertheless, different protein sources (fish meal and soybean meal) had no significant effect on the expression levels of ASCT2 in intestine and muscle (p > 0.05). These results provided data for the study of ASCT2 in triploid crucian carp regulated by feeding nutrition, which had a potential application in improving feed formulation in aquaculture.