Abstract To assess the role of dietary creatine on myofibre characteristics and protein synthesis in muscle, we fed grass carp ( Ctenopharyngodon idellus , initial body weight: 88·47 ± 1·44 g) creatine-supplemented diets (1·84, 5·91, 8·48 and 15·44 g/kg diet) for 8 weeks. Creatine supplementation did not affect growth performance, but significantly increased creatine contents in muscle and liver. At 8·48 g/kg, creatine decreased the activities of alanine transaminase and aspartate aminotransferase in serum and improved hardness and chewiness of muscle due to shorter myofibre mean diameter, higher myofibre density and the frequencies of the diameters of classes I and III and collagen content, longer sarcomere length and upregulated mRNA levels of slow myosin heavy chains. Creatine supplementation upregulated the mRNA expressions of myogenic regulatory factors. The 8·48 g/kg creatine-supplemented diet significantly increased the contents of protein, total amino acids (AA), essential AA and free flavour AAs in muscle, the protein levels of insulin-like growth factor I, myogenic differentiation antigen and PPAR- γ coactlvator-1 α in muscle and stimulated the phosphorylation of target of rapamycin (TOR) pathway in muscle. In summary, 8·48 mg/kg creatine improved fish health and skeletal muscle growth and increased hardness and protein synthesis in muscle of grass carp by affecting myofibre characteristics and the TOR signalling pathway. A second-order regression model revealed that the optimal dietary creatine supplementation of grass carp ranges between 8·48 and 12·04 g/kg.
This research aimed to examine the effects of dietary rutin supplementation on growth, body composition, serum biochemical indexes, liver enzyme activities and antioxidant-related genes expression, intestinal morphology, and microbiota composition of juvenile yellow catfish (Pelteobagrus fulvidraco). Rutin was added to the basal diets at doses of 0 (control), 100 mg/kg, and 500 mg/kg. Each diet was fed randomly into three tanks, each tank containing 30 fish with an initial body mass of (10.27 ± 0.62) g. The feeding trial was conducted in an indoor recirculating aquiculture system at 28 °C for 56 days. According to the findings, the inclusion of 100 mg/kg rutin significantly improved the growth performance of yellow catfish and reduced the feed conversion ratio; however, the growth promotion effect was diminished when the diet was supplemented with 500 mg/kg of rutin. The inclusion of 500 mg/kg rutin in the diet significantly reduced the level of crude lipid and protein of the whole fish. Serum activities of alkaline phosphatase, albumin, and total protein were all significantly increased when fish were fed the diet supplemented with 500 mg/kg rutin, while serum glucose was significantly lower compared to the control group. Meanwhile, dietary rutin at a concentration of 500 mg/kg significantly induced the hepatic mRNA expressions of antioxidant-related genes (including Cu/Zn-SOD, Mn-SOD, CAT, GPx) and inflammatory-associated genes (including TNFα, IL-10, LYZ). Incorporating rutin at doses of 100 mg/kg and 500 mg/kg into the diets resulted in a notable increase in superoxide dismutase (SOD) activity, while simultaneously reducing malondiadehyde (MDA) content in the liver and intestine. Intestinal villus height, villus width, muscular thickness, and lumen diameter were significantly increased with the administration of 500 mg/kg of dietary rutin. Gut microbial diversity analysis indicated that supplementing diets with 100 mg/kg and 500 mg/kg rutin significantly enhanced the abundance of Cetobacterium while decreasing Plesiomonas richness. In conclusion, dietary rutin levels at 100 mg/kg could enhance the growth, antioxidant capability, and intestinal health of yellow catfish under present experimental conditions.
Ammonia is a key risk factor in intensive aquaculture systems. This experiment is aimed at investigating the influence of dietary protein levels on genetically improved farmed tilapia (GIFT, Oreochromis niloticus) under chronic ammonia stress. GIFT juveniles of g were exposed to high ammonia level at 0.88 mg/L and fed with six diets comprising graded protein levels at 22.64%, 27.26%, 31.04%, 35.63%, 38.47%, and 42.66% for 8 weeks. The fish in negative control was fed the diet with 31.04% protein in normal water (0.02 mg ammonia/L water). Our results showed that high ammonia exposure (0.88 mg/L) caused significant decrease in fish growth performance, hematological parameters, liver antioxidant enzymes (catalase and glutathione peroxidase), and gill Na+- and K+-dependent adenosine triphosphatase (Na+/K+-ATP) activity. When fish were under high ammonia exposure, the weight gain rate, special growth rate, feed efficiency, and survival rate elevated significantly with dietary protein supplementation increase to 35.63%, whereas protein efficiency ratio, hepatosomatic index, and viscerosomatic index showed a decreased tendency. Dietary protein administration significantly enhanced crude protein but reduced crude lipid contents in the whole fish. Fish fed diets with 35.63%-42.66% protein had higher red blood cell counts and hematocrit percentage than fish fed 22.64% protein diet. The values of serum biochemical indices (lactate dehydrogenase, aspartate aminotransferase, and alanine aminotransferase), hepatic antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase), and gill Na+/K+-ATP activity were all elevated with the increment of dietary protein. Moreover, histological analysis indicated that dietary protein administration could prevent the ammonia-induced damages in fish gill, kidney, and liver tissues. Based on weight gain rate as a response criterion, the optimal dietary protein requirement for GIFT juveniles under chronic ammonia stress was 37.9%.
This study was to evaluate the potential of a host-associated Bacillus velezensis as a probiotic for hybrid yellow catfish (Pelteobagrus fulvidraco ♀ × Pelteobagrus vachelli ♂). Diets (B0 to B5) containing 0, 0.90 × 108, 0.80 × 109, 0.85 × 1010, 0.90 × 1011, 0.83 × 1012 CFU/kg B. velezensis YFI-E109 were fed to the fish with initial weight (3.07 ± 0.08 g) in a recirculating aquaculture system for six weeks with three replicates, respectively. Probiotic effects were analyzed based on growth, body composition, liver and gut morphology, gut microbiome, and liver metabolome. Analysis of the bacterial genome has shown that the most abundant genes in B. velezensis YFI-E109 were distributed in carbohydrate and amino acid metabolism. Fish in groups B3 and B4 had better growth performance, and higher intestinal amylase (AMS) and lipase (LPS) activities compared with other groups (P < 0.05). Fish in groups B0 and B5 showed significant liver damage, while this status improved in group B3. The liver malondialdehyde (MDA) content in group B3 was lower than that in other groups (P < 0.05). The abundance of Mycoplasma, Ralstonia and Acinetobacter was significantly reduced in B3 and B5 compared to B0. The amino acid and carbohydrate metabolism pathways were enriched in group B3 compared with group B0. In conclusion, dietary B. velezensis YFI-E109 supplementation has the potential to improve growth, liver metabolism, and liver and gut health, and reshape the gut microbiome of hybrid yellow catfish. Excessive B. velezensis YFI-E109 reduced the prebiotic effects. The recommended dietary supplementation of B. velezensis YFI-E109 is 0.31 × 1010 to 0.77 × 1011 CFU/kg for hybrid yellow catfish according to the quadratic regression method by plotting specific growth rate (SGR), feed conversion ratio (FCR), MDA and activities of AMS against dietary B. velezensis YFI-E109 levels.
To investigate the effects of a high-carbohydrate (HC) diet on the growth, serum biochemistry, and DNA methylation and gene transcription profiles of muscle tissue of grass carp (Ctenopharyngodon idella), fish with initial body weight (27.87 ± 0.40) g were fed with a control diet (CON, containing 330 g kg−1 carbohydrate) and an HC diet (containing 490 g kg−1 carbohydrate) for 8 weeks. The results showed that the HC diet had side-effects on muscle growth and health, and caused excessive fat accumulation in the tissues of grass carp. A total of 3135 differentially methylated regions (DMRs) and 530 differentially expressed genes (DEGs) in muscle were screened by bisulfite sequencing and transcriptome sequencing analysis. Twenty-seven DMRs were negatively correlated with DEGs, and eleven DMRs were located in the promoters of DEGs. The methylation level of promoter regions of seven target genes decreased and their transcription levels increased, including FOX protein, diacylglycerol kinase (DGKZ), proto-myosin regulatory protein (tmod1), Notch2, DnaJ homolog (dnajc1), von Willebrand factor D and EGF domains (vwde), and zgc:77838. The methylation level of promoter regions of four target genes increased and their transcription levels decreased, including epidermal growth factor-like domain 6 (EGFL6), estrogen receptor alpha (Erα), cohesin subunit SA-1-like, and LOC795573. These eleven essential genes were mainly involved in GO terms containing cell differentiation, muscle contraction, lipid phosphorylation, PI3K/Akt signaling pathway, and Notch signaling pathway. This study provides a new research direction for the molecular mechanism of the HC diet on muscle growth of grass carp.
An eight-week growth experiment was conducted to investigate the growth performance and liver transcriptome response of juvenile top-mouth culter Erythroculter ilishaeformis fed with different dietary protein levels. Six isoenergetic diets supplemented with protein at a level of 25%, 30%, 35%, 40%, 45% and 50% were prepared. The fish (initial mean weight 6.27 ± 0.30 g, 35 fish per tank, n = 3) were fed the six test diets in a recirculating aquaculture system at 30 ± 2 °C. Our results showed that weight gain rate (WGR) increased from 161.88% to 247.20% with the increase of dietary protein level from 25% to 40%, and then kept nearly stabilized with further increases in dietary protein concentration. Feed conversion ratio (FCR) showed an opposite trend to WGR. Using WGR and FCR as the response criterion, the optimal protein requirement for maximum growth of this juvenile fish species was 41.14% and 43.75%, respectively. The liver transcriptome profiles using RNA-seq technology showed that a total of 189.13 million clean data was generated and 202,677 unigenes with 435,540 transcripts were assembled. Unigenes were then searched against four databases including Swiss-Prot, COG, KOG, and KEGG. Differentially expressed genes (DEGs) were considered as a threshold of the fold change (FC) ≥ 2 and a false discovery rate (FDR) ≤ 0.01 in a comparison. Trend analysis revealed that these DEGs were significantly clustered into five clusters. Several DEGs associated with growth (igf1 and ST), lipid metabolism (fasn and accα), glucose metabolism (pepck, pk, gk and g6pd), aspartate biosynthesis (AST), immune (MHC-II), were validated with qPCR analysis. Moreover, function analysis indicated that the DEGs were mainly involved in metabolism, immunity, antioxidation, and a variety of signal pathways. Taken together, our data provide a comprehensive understanding of the feed formulation and molecular mechanism underlying the effects of dietary protein on E. ilishaeformis.
Lead (Pb) is one of the major heavy metals that are toxic to vertebrates and usually considered as environmental pollutants. ABCC4/MRP4 is an organic anion transporter that mediates cellular efflux of a wide range of exogenous and endogenous compounds such as cyclic nucleotides and anti-cancer drugs; however, it remains unclear whether ABCC4 and its orthologs function in the detoxification and excretion of toxic lead. In this study, we found that the transcriptional and translational expression of zebrafish abcc4 was significantly induced under lead exposure in developing zebrafish embryos and adult tissues. Overexpression of zebrafish Abcc4 markedly decreased the cytotoxicity and accumulation of lead in pig renal proximal tubule cell line (LLC-PK1 cells). To further understand the functions of zebrafish Abcc4 in lead detoxification, the clustered regularly interspaced palindromic repeats (CRISPR)/Cas9 system was used to create an abcc4−/− mutant zebrafish line. In comparison with the wild-type (WT) zebrafish, the abcc4−/− mutants showed a higher death rate and lead accumulation upon exposure to lead. Furthermore, a stable abcc4-transgenic zebrafish line was successfully generated, which exerted stronger ability to detoxify and excrete lead than WT zebrafish. These findings indicate that zebrafish Abcc4 plays a crucial role in lead detoxification and cellular efflux and could be used as a potential biomarker to monitor lead contamination in a water environment.
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