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Tilapia tolerate hypoxia; thus, they are an excellent model for the study of hypoxic adaptation. In this study, we determined the effect of acute hypoxia stress on the antioxidant capacity, metabolism, and gill/liver ultrastructure of male genetically improved farmed tilapia (GIFT, Oreochromis niloticus). Fish were kept under control (dissolved oxygen (DO): 6.5 mg/L) or hypoxic (DO: 1.0 mg/L) conditions for 72 h. After 2 h of hypoxia stress, antioxidant enzyme activities in the heart and gills decreased, while the malondialdehyde (MDA) content increased. In contrast, in the liver, antioxidant enzyme activities increased, and the MDA content decreased. From 4 to 24 h of hypoxia stress, the antioxidant enzyme activity increased in the heart but not in the liver and gills. Cytochrome oxidase activity was increased in the heart after 4 to 8 h of hypoxia stress, while that in the gills decreased during the later stages of hypoxia stress. Hypoxia stress resulted in increased Na+-K+-ATP activity in the heart, as well as hepatic vacuolization and gill lamella elongation. Under hypoxic conditions, male GIFT exhibit dynamic and complementary regulation of antioxidant systems and metabolism in the liver, gills, and heart, with coordinated responses to mitigate hypoxia-induced damage. [ABSTRACT FROM AUTHOR]

Simple Summary: Microorganisms are important components of biological communities in the aquaculture ecosystems, which play fundamental roles in regulating the water quality and maintaining the health of cultured animals. Microalgae addition as a common aquaculture practice has been reported to have positive effects on both the aquaculture environment and organisms. However, the ecological effects of microalgae addition on the aquaculture ecosystems from the perspective of microbial community ecology are still unclear. In the present study, we analyzed the characteristics of microbial communities in various microhabitats in tilapia aquaculture systems with different microalgae additions. It was found that microalgae addition exhibited greater impacts on the diversity, compositions, and co-occurrence patterns of the gill-associated bacterial communities than those of water and fish gut. The mucosal surface of the fish gill represented an important barrier essential for fish health. Microalgae addition altered the composition of gill-associated bacterial communities, which could be important for mucosal immunity and thereby influence fish health. These findings provided a new insight into the mechanisms underlying the impacts of microalgae addition on aquaculture. Microalgae has been widely used in aquaculture to improve both the water environment and fish growth; however, the current understanding of the effects of microalgae addition on the key players involved in regulating the water environment and fish health, such as microorganisms, remains limited. Here, a 50-day mesocosm experiment was set up to simulate the culture of Genetic Improvement of Farmed Tilapia (GIFT, Oreochromis niloticus) with an average weight of 14.18 ± 0.93 g and an average length of 82.77 ± 2.80 mm. Different amounts of Chlorella pyrenoidosa were added into these artificial systems to investigate dynamics of bacterial communities in aquaculture water, fish gill, and gut using amplicon-based high-throughput sequencing technology. Our results showed that Chlorella pyrenoidosa addition increased diversity and network complexity of gill-associated bacterial communities rather than those of the water and gut. Furthermore, more biomarkers in the gill-associated bacterial communities were detected in response to Chlorella pyrenoidosa addition than the water and fish gut samples. These findings highlighted the high sensitivity of gill-associated bacterial communities in response to the Chlorella pyrenoidosa addition, implying Chlorella pyrenoidosa addition could play important roles in regulating the fish mucosal immunity by altering the gill-associated microbiota. [ABSTRACT FROM AUTHOR]

Aquaculture feed containing olive oil (OO) instead of fish oil (FO) can cause oxidative stress and impair gonad development in fish. We determined the effect of dietary OO-induced oxidative stress on ovarian development, and explored whether vitamin E (VE) could mitigate negative effects. Female Nile tilapia (Oreochromis niloticus) were fed for 10 weeks with four diets: 5% OO + 70 mg/kg VE, 5% OO + 200 mg/kg VE, 5% FO + 70 mg/kg VE, or 5% FO + 200 mg/kg VE. Dietary OO reduced the specific growth rate and gonadosomatic index, inhibited superoxide dismutase and catalase, delayed ovarian development, decreased serum sex hormone levels, and reduced ovarian triglyceride and n-3 highly unsaturated fatty acid contents. The transcript levels of genes encoding sex hormone receptors (erα, fshr, lhr) and components of the lipid metabolism pathway (pparα, pparγ, hsl, accα, elovl6), the nrf2 signaling pathway (nrf2, keap1), and the nf-κb signaling pathway (nf-κb, tnfα, infγ, il1β) differed between the 70VE/OO and 70VE/FO groups. Supplementation with 200 mg/kg VE mitigated the adverse effects of OO by improving antioxidant capacity and alleviating inflammation and abnormal lipid metabolism. This may be because VE is an antioxidant and it can regulate the nrf2-nf-κb signaling pathway. [ABSTRACT FROM AUTHOR]

Genetically improved farmed tilapia (Oreochromis niloticus, GIFT) is prone to hepatic metabolic imbalances and fatty liver disease during intensive farming. Long non-coding RNAs (lncRNAs) perform essential roles in various biological processes, including lipid metabolism. However, the lncRNAs involved in hepatic lipid metabolism in tilapia have not yet been identified. In this study, Illumina sequencing and bioinformatic analyses were performed on the liver of juvenile male GIFT fed a high-fat diet (HFD, 18.5% lipid) or a normal-fat diet (NFD, 8% lipid) for 56 days. RNA-seq analyses revealed 299 differentially expressed (DE)-mRNAs and 284 DE-lncRNAs between these two groups. The transcript profiles of 14 candidates (seven DE-mRNA and seven DE-lncRNAs) were verified by qRT-PCR, and the results were consistent with the RNA-seq results. Furthermore, 65 cis target genes and 3610 trans target genes of DE-lncRNAs were predicted. Functional analyses suggested that multiple metabolic pathways are affected by a high fat intake, including the PPAR signaling, fatty acid degradation, and fatty acid metabolism pathways. A co-expression network analysis indicated that many lncRNAs interact with numerous genes involved in lipid metabolism, and that some genes are regulated by multiple lncRNAs. The expression patterns of three lncRNAs (MSTRG.14598.1, MSTRG.6725.3, and MSTRG.13364.2) and their potential target genes (faldh, slc25a48, and fabp7a) in the PPAR signaling pathway were investigated. Our study provides new information about lncRNAs associated with lipid metabolism in tilapia. [ABSTRACT FROM AUTHOR]

Anti-Müllerian hormone (amh), an important regulator of gonad development in male teleosts, regulates the development and differentiation of germ cells. We performed transcriptional knock-down of amh in Nile tilapia (Oreochromis niloticus) using antisense RNA technology, resulting in down-regulation in the expression of amh transcription and Amh protein in males. Compared with the control groups, the fish in treatment groups with down-regulated amh had increased weight and an extremely significant decrease in the gonadosomatic index. Hematoxylin–eosin staining revealed impaired testis development and significant reductions in numbers of sperm. Serum estradiol levels were significantly increased, and the levels of testosterone, luteinizing hormone, and follicle-stimulating hormone were significantly decreased. RNA-sequencing analysis of the fish in the down-regulated amh and control groups identified 12,048 differentially expressed genes, of which 1281 were up-regulated and 10,767 were down-regulated. Kyoto Encyclopedia of Genes and Genomes analysis revealed that differentially expressed genes related to growth and development were mainly enriched in the Cell cycle, Endocytosis, TGF-beta signaling pathway, Wnt signaling pathway, FoxO signaling pathway, Insulin signaling pathway, and MAPK signaling pathway. The RNA-sequencing data accuracy was verified by qRT-PCR analysis of the expression levels of selected differentially expressed genes. The abnormal TGF-beta signaling pathway may cause fish weight gain, testis dysplasia, and abnormal spermatogenesis: smad5, smad3a, tgfb2, tgfbr1b, gsdf, and amh were significantly down-regulated. These findings indicated that antisense RNA technology has strong application prospects and can specifically knock down amh in Nile tilapia, resulting in an abnormal TGF-beta signaling pathway, inhibiting testis development and inducing weight gain. [ABSTRACT FROM AUTHOR]

A 60-day feeding experiment was performed to evaluate the effect of dietary astaxanthin on gonad development, the antioxidant system, and its inherent mechanism in female Nile tilapia (Oreochromis niloticus). Fish were fed with diets containing astaxanthin at five levels [0 mg/kg (control), 50 mg/kg, 100 mg/kg, 150 mg/kg, and 200 mg/kg]. At the end of experiment, the group fed with 150 mg/kg astaxanthin showed significantly increased specific growth rate, feed utilization, viscerosomatic index, and hepatosomatic index compared with the control group (P < 0.05). Gonad development was stimulated in the groups fed with 100 mg/kg and 150 mg/kg astaxanthin, and their gonadosomatic index and egg diameter were significantly higher than those of the control group and the group fed with 200 mg/kg astaxanthin. The ovaries of females in the groups fed with 100 mg/kg and 150 mg/kg astaxanthin were fully developed, the eggs were gray-yellow and uniform in size, and a large number of oocytes developed to stages IV and V. The serum levels of 17 β-estradiol, follicle-stimulating hormone, and luteinizing hormone were significantly higher in the groups fed with 100 mg/kg and 150 mg/kg astaxanthin than in the group fed with 200 mg/kg astaxanthin. Compared with the control and the other groups, the group fed with 150 mg/kg astaxanthin showed significantly higher transcript levels of genes encoding hormone receptors and higher catalase activity in ovarian tissues, lower malondialdehyde content, decreased apoptosis (reduced granulosa cell apoptosis and lower transcript levels of bax and caspase-3), and reduced follicular atresia. Gene ontology analyses revealed that cell division and the cell cycle were enriched with differentially expressed genes in the group fed with 150 mg/kg astaxanthin, compared with the control group. We concluded that dietary astaxanthin at a concentration of 150 mg/kg activates follicle development by inhibiting expression of mapk1 (involved in MAPK signaling) and increasing the expression genes involved in oocyte meiosis (chp2, ppp3ca, map2k1, and smc1a1) and progesterone-mediated oocyte maturation (igf1, plk1, and cdk1). In conclusion, female Nile tilapia fed with 150 mg/kg astaxanthin showed increased growth, reduced oxidative stress in ovarian tissue, lower levels of cell apoptosis, and improved oocyte development. [ABSTRACT FROM AUTHOR]

High temperature affects egg quality and increases follicular atresia in teleosts. The present study aimed to explore the regulated mechanism of ovary syndrome of Nile tilapia (Oreochromis niloticus) exposed to heat stress. To this end, we conducted histological and biochemical analyses and integrated miRNA-target gene analyses. The histochemical analyses confirmed that heat stress promoted the apoptosis of granulosa cell and therefore resulted in increased follicular atresia in the ovary. Heat stress led to the differential expression of multiple miRNAs (miR-27e, -27b-3p, -33, -34a -133a-5p, and -301b-5p). In a luciferase activity assay, miR-33 bound to the 3′-untranslated region (UTR) of the TGFβ1I1 (transforming growth factor-β1-induced transcript 1) gene and inhibited its expression. A TGFβ1I1 gene signal was detected in the granulosa cells of Nile tilapia by immunohistochemical analysis. Up-regulation of the miR-33 of tilapia at 6 d and 12 d exposed to heat (34.5 °C ± 0.5 °C) had significant down-regulation of the TGFβ1I1 expression of the gene and protein in tilapia ovaries. An miRNA-target gene integrated analysis revealed that miR-33 and TGFβ1I1 function in an apoptosis-related signal pathway. The signal transduction of the vascular endothelial growth factor (VEGF) family members VEGFA and its receptor (KDR) in the heat-stressed group decreased significantly compared with the control group. Transcript-levels of the Bax and Caspase-3 as apoptotic promotors were activated and Bcl-2 and Caspase-8 as apoptotic inhibitors were suppressed in the heat-stressed tilapia. These results suggest that heat stress increases the expression of miR-33, which targets TGFβ1I1 and inhibits its expression, resulting in decreased levels of follicle-stimulating hormone and 17β-estradiol and increased apoptosis by suppressing VEGF signaling, eventually inducing follicular atresia. In conclusion, our results show that the miR-33/TGFβ1I1 axis of Nile tilapia is involved in the follicular development of broodstock, and can suppress VEGF signaling to accelerate follicular atresia. Our findings demonstrate the suppressive role of miR-33 during oocyte development in Nile tilapia. [ABSTRACT FROM AUTHOR]

Glycyrrhiza total flavones (GTF) have been confirmed to possess anti-oxidation and lipid-lowering effects, but whether they have a protective effect on fatty liver injury in tilapia (Oreochromis niloticus) is unknown. Thus, the aim of this study was to investigate the protective effects of GTF on liver injury induced by a high-fat diet (HFD) and its underlying mechanism in fish. A total of 180 tilapia were randomly divided into four experimental groups: normal control group (basic diet, 6% crude fat), HFD group (fed with HFD, 21% crude fat), and two GTF treatment groups (addition of 0.1 and 1.0 g/kg of GTF to the high-fat diet). After 90 days of feeding, blood and liver tissues were collected to measure biochemical parameters, mRNA levels, and protein expression to evaluate the liver protection of GTF. Compared with the HFD group, addition of GTF to the diet significantly reduced the indexes of liver enzyme activity and fat metabolism in serum. In liver, addition of GTF to the diet upregulated mRNA levels of the oxidative stress-related genes glutathione transferase alpha (GSTα) and NAD(P)H dehydrogenase (NQO1), and downregulated mRNA level of kelch-like epichlorohydrin-associated protein 1 (Keap1). GTF treatments also significantly reduced mitogen-activated protein kinase 8 (MAPK8) and caspase 3 (CAS-3) protein expression. Meanwhile, GTF treatments downregulated mRNA levels of toll-like receptor1 (TLR1), toll-like receptor5 (TLR5), interleukin 1 receptor-associated kinase (IRAK1), tumor necrosis factor receptor-related factor 6 (TRAF6), complement 3 (C3), heat shock protein 70 (HSP70), and immunoglobulin M (IgM). These results showed that GTF had a well protective effect against fatty liver injury caused by an HFD in tilapia. The beneficial effects of these flavones may be related to changes of nuclear factor-related factor 2 and TLR signaling pathways. [ABSTRACT FROM AUTHOR]

The response of synthetic substrates of sex steroid hormones—cholesterol (CHO), pregnenolone (PREG), and progesterone (PROG)—in the serum and testes of male tilapia (Oreochromis niloticus) to the environmental estrogen pesticide methomyl (0.2, 2, 20, and 200 μg·L−1) was evaluated using static-water contact toxicity tests. The results showed that low methomyl concentrations (0.2 and 2 μg·L−1) had no significant effects on the contents of CHO, PREG, and PROG in the serum and testes of male tilapia (p > 0.05). Consequently, the concentration of 2 μg·L−1 could be used as a preliminary reference threshold for the non-effective dose of methomyl in male tilapia. Exposure to high methomyl concentrations (20 and 200 μg·L−1) significantly inhibited the levels of CHO, PREG, and PROG in the serum and testes of male tilapia (p < 0.05) and showed a dose–response relationship. Sex steroid hormone synthesis substrate damage to male tilapia caused by less than 20 μg·L−1 methomyl was reversible, while the damage caused by equal to or greater than 200 μg·L−1 methomyl was irreversible when tilapia were transferred to methomyl-free water for 18 days. Thus, a concentration of 200 μg·L−1 could be used as a reference threshold for irreversible damage caused by methomyl in male tilapia. [ABSTRACT FROM AUTHOR]

Total flavones of Glycyrrhiza uralensis Fisch (GTF) are main components of Glycyrrhiza uralensis Fisch, which have anti-oxidation and lipid-lowering effects. However, its protective effects on the intestinal tissue of tilapia (Oreochromis niloticus) are unknown. The aims of the study were to evaluate the protective effects of GTF on the intestinal tissue of tilapia after high-fat diet (HFD) feeding. Tilapia (initial weight 30 ± 1 g) received diets containing four doses of GTF (0.05, 0.1, 0.5, and 1.0 g/kg diet) for 90 days. The intestinal tissues were collected to determine biochemical parameter, gene expression and protein level. The results showed that the HFD reduced antioxidant indexes and increased the fat level, lipid oxidation products in the intestinal tissue relative to the control. Adding GTF to the HFD resulted in an increase of antioxidant indexes, fat level and lipid oxidation products decreased after 60, 90 days. In the HFD group, mRNA level of fatty acid transport protein 1 (FATP1) was increased at 60 day and then decreased at 90 day. The mRNA levels of fatty acid binding protein 1 (FABP1) and sterol regulatory element binding protein 1c (SREBP 1c) were significantly increased at 60 or 90 day after HFD feeding. The mRNA levels of acetate coenzyme A carboxylase (ACCA) peroxisome proliferator-activated receptor γ (PPAR-γ) and PPAR-α were decreased significantly at 30, 60 and/or 90 days after HFD feeding. Western blotting results also showed that nuclear factor (NF)-κβ C-Rel (NF-κβ C-Rel) and mitogen-activated protein kinase 8 (MAPK8) protein expression in intestinal tissue increased after consumption of the HFD. However, adding GTF to the HFD reversed the changes of genes related to fatty acid synthesis and metabolism, and the level of NF-κβ c-Rel and MAPK8 at different degrees. Overall, these results indicated that GTF promoted decomposition and metabolism of fatty acids in intestinal tissue, alleviated oxidative stress damage caused by the HFD, and had certain protective effects on the intestinal tissue of tilapia. [ABSTRACT FROM AUTHOR]

The chronic effect of environmental methomyl on the antioxidant system in testis of Nile tilapia (Oreochromis niloticus) and its recovery pattern was investigated. Tilapia were exposed to sublethal concentrations of 0.2, 2, 20 and 200 μgL−1 methomyl for 30 days and thereafter moved to methomyl-free water for 18 days. Antioxidant levels in testis, including glutathione peroxidase, catalase, glutathione-S-transferase, glutathione reductase, superoxide dismutase, reduced glutathione, oxidized glutathione were measured every 6 days during the period of exposure, and at 18 days after being transferred to methomyl-free water. The results showed that lower methomyl concentration (0.2 μgL−1) had no effect on the above antioxidants, thus 0.2 μgL−1 could be seen as NOAEL for methomyl to tilapia. However, higher methomyl concentration of 2, 20 and 200 μgL−1 could significantly influence the above antioxidants. Glutathione peroxidase and oxidized glutathione increased significantly. On the contrary, reduced glutathione decreased significantly. Catalase, superoxide dismutase, glutathione reductase, glutathione-S-transferase increased at lower methomyl (2 and 20 μgL−1), but decreased at higher methomyl (200 μgL−1). The recovery test showed that oxidative damage caused by lower methomyl of 2 and 20 μgL−1 was reversible, and oxidative damage caused by higher methomyl of 200 μgL−1 was irreversible within 18 days of recovery period. [ABSTRACT FROM AUTHOR]

Background: Dissolved oxygen (DO) in the water is a vital abiotic factor in aquatic animal farming. A hypoxic environment affects the growth, metabolism, and immune system of fish. Glycolipid metabolism is a vital energy pathway under acute hypoxic stress, and it plays a significant role in the adaptation of fish to stressful environments. In this study, we used multi-omics integrative analyses to explore the mechanisms of hypoxia adaptation in Genetically Improved Farmed Tilapia (GIFT, Oreochromis niloticus). Results: The 96 h median lethal hypoxia (96 h-LH50) for GIFT was determined by linear interpolation. We established control (DO: 5.00 mg/L) groups (CG) and hypoxic stress (96 h-LH50: 0.55 mg/L) groups (HG) and extracted liver tissues for high-throughput transcriptome and metabolome sequencing. A total of 581 differentially expressed (DE) genes and 93 DE metabolites were detected between the CG and the HG. Combined analyses of the transcriptome and metabolome revealed that glycolysis/gluconeogenesis and the insulin signaling pathway were down-regulated, the pentose phosphate pathway was activated, and the biosynthesis of unsaturated fatty acids and fatty acid metabolism were up-regulated in GIFT under hypoxia stress. Conclusions: The results show that lipid metabolism became the primary pathway in GIFT under acute hypoxia stress. Our findings reveal the changes in metabolites and gene expression that occur under hypoxia stress, and shed light on the regulatory pathways that function under such conditions. Ultimately, this information will be useful to devise strategies to decrease the damage caused by hypoxia stress in farmed fish. [ABSTRACT FROM AUTHOR]

Hepatic steatosis commonly occurs in intensively farmed tilapia. This disease is harmful to fish growth and health, but knowledge of the metabolic changes in tilapia with fatty liver is limited. In the present study, we compared male genetically improved farmed tilapia (GIFT, Oreochromis niloticus) fed a high‐fat diet (HFD) with those fed a normal‐fat diet (NFD) for 8 weeks using LC–MS‐based hepatic metabolomic assays and traditional nutritional assessments. Juvenile GIFT fed a HFD accumulated more fat in the liver than did those fed a NFD. The metabolomic analyses revealed 36 differentially accumulated metabolites between the two groups, and these metabolites were involved in 25 signalling pathways. Our results indicate that development of fatty liver severely impairs hepatic lipid metabolism, leading to blockage of the TCA cycle and further disruptions to protein and carbohydrate metabolism in GIFT. These physiological changes may be related to the lower growth rate of GIFT fed a HFD. Overall, our results reveal the details of metabolic disorders in GIFT fed a HFD and enhance our knowledge of the mechanism of fatty liver formation in GIFT. [ABSTRACT FROM AUTHOR]

A 6‐week feeding trial was conducted to investigate the effects of dissolved oxygen (DO) levels on growth performance, physiological parameters and the immune response of juvenile GIFT fed with three different levels of dietary protein. Triplicate groups of fish (0.45 ± 0.01 g) were fed 30%, 40% and 50% protein diet at hypoxia (2.0 ± 0.3 mg/L) and normoxia (6 ± 0.4 mg/L). The fish were hand‐fed to apparent satiation twice a day (8:00 am and 16:00 pm). Fish growth, feed intake and feed conversion ratio were adversely affected by hypoxia. However, fish growth improved with the increasing dietary protein levels. Feed intake endured the individual and combined effects of DO and dietary protein levels. Somatic indices reduced significantly after hypoxia exposure, with the interaction effects observed on the viscerosomatic index. Red blood cells reduced with decreasing DO levels. Apart from glucose, the serum biochemical modules increased at hypoxia. Triglyceride was affected by the interaction of the factors of interest. Alanine aminotransferase, glucose and total protein contents were significantly changed by the experimental diets, wherein the excess and lower protein levels triggered the increased values of these parameters. Hypoxia diminished liver oxidation enzymes and serum complement component 3. Lipase and amylase were negatively affected by low DO. Experimental diets influenced the cytochrome C oxidase and lactate dehydrogenase in the muscle and gill; besides, cytochrome C oxidase in the gill was also altered by DO, whereas that in the muscle was affected by the interaction of DO and diets. These data show that hypoxia is detrimental to growth performance, feed utilization, liver and immunity. [ABSTRACT FROM AUTHOR]

miR-92a miRNAs are immune molecules that regulate apoptosis (programmed cell death) during the immune response. Apoptosis helps to maintain the dynamic balance in tissues of fish under hypoxia stress. The aim of this study was to explore the role and potential mechanisms of miR-92a in the liver of tilapia under hypoxia stress. We first confirmed that CaSR (encoding a calcium-sensing receptor) is a target gene of miR-92a in genetically improved farmed tilapia (GIFT) using luciferase reporter gene assays. In GIFT under hypoxia stress, miR-92a was up-regulated and CaSR was down-regulated in a time-dependent manner. Knocked-down CaSR expression led to inhibited expression of p53, TP53INP1, and caspase-3/8, reduced the proportion of apoptotic hepatocytes, and decreased the activity of calcium ions induced by hypoxia in hepatocytes. GIFT injected in the tail vein with an miR-92a agomir showed up-regulation of miR-92a and down-regulation of CaSR, p53, TP53INP1, and caspase-3/8 genes in the liver, resulting in lower serum aspartate aminotransferase and alanine aminotransferase activities under hypoxia stress. These findings suggest that stimulation of miR-92a interferes with hypoxia-induced apoptosis in hepatocytes of GIFT by targeting CaSR, thereby alleviating liver damage. These results provide new insights into the adaptation mechanisms of GIFT to hypoxia stress. [ABSTRACT FROM AUTHOR]

In fish under hypoxia stress, homeostasis can become imbalanced, leading to tissue and organ damage and decreased survival. Therefore, it is useful to explore the molecular and physiological regulation mechanisms that function in fish under hypoxia stress. The microRNA miR-34a is involved in fat and glycogen metabolism, and in apoptosis. In this study, we first verified that GLUT1 , the gene encoding glucose transporter 1, is a potential target gene of miR-34a in genetically improved farmed tilapia (GIFT, Oreochromis niloticus) by dual luciferase reporter assays. Then, we clarified the regulatory relationship between miR-34a and GLUT1 by qRT-PCR analyses. We analyzed the regulatory effects of knockdown or promotion of GLUT1 expression in vitro and in vivo in GIFT under hypoxia stress. The results confirm that GLUT1 is a target gene of miR-34a in GIFT. Down-regulation of miR-34a significantly promoted GLUT1 expression. Knockdown of GLUT1 reduced the glycogen content in GIFT liver cells, inhibited HIF-1a gene expression, up-regulated the expression of genes involved in P53 signaling pathways (P53 and CASPASE-3 genes), and accelerated hepatocyte apoptosis under hypoxia stress. Compared with the control group, the group injected in the tail vein with miR-34a antagomir showed up-regulated expression of GLUT1 in the liver, increased liver glycogen content at 96 h of hypoxia stress, down-regulated expression of P53 and CASPASE-3 , and decreased serum aspartate aminotransferase and alanine aminotransferase enzyme activities. Our results provide information about the molecular regulation mechanism of miRNAs and their target genes in fish during the response to hypoxia stress. [ABSTRACT FROM AUTHOR]

Streptococcosis, a bacterial disease for multiple fish species, especially tilapia, caused more disruption to the fish culture industry. However, the underlying mechanisms for the occurrence of streptococcosis remain unclear. The aim of this study was to study the effects of streptococcus on the liver of tilapia. In this study, tilapia were injected streptococcal solution (0.05 ml/10 g body weight) and collected blood and liver at 4, 8, 24, 48, 72, 96, 120 and 144 hr after injection. The results showed that the activities of glutamate oxalate transaminase (GOT), glutamate pyruvate transaminase (GPT), alkaline phosphatase (AKP) and superoxide dismutase (SOD) in the serum of tilapia exhibited irregular changes: increase at first, then decrease and increase again. The levels of total antioxidant capacity (T‐AOC), glutathione (GSH) and malondialdehyde (MDA) showed a decreasing tendency in serum after injection, except GSH at 4 hr. The activity of catalase (CAT) decreased in serum at 4, 24, 120 and 144 hr after injection of streptococcal solution, while the content TP enhanced in serum at 48, 72 and 120 hr after injection. Observations of pathological sections showed obvious damage to the liver tissue structure in response to streptococcal infection. Western blotting revealed an increase in ikkbeta (Ikkβ) protein with prolonged infection time and a decrease in NF‐kappa‐B inhibitor alpha (IkB‐α) and ikappab kinase alpha (Ikkα) proteins. The gene expression of cytochrome P4501A (CYP1A) was downregulated in liver at 24 and 48 after injection, while the mRNA levels of heat stress protein 70 (HSP70) and tumour necrosis factor alpha (TNF‐α) increased at 48 and/or 72 hr. Taken together, our findings confirmed that streptococcus can cause serious damage to the liver of tilapia. [ABSTRACT FROM AUTHOR]

Fish culture using an in‐pond raceway system (IPRS) is a new mode of freshwater aquaculture in China. This study was carried out to assess the effect of feeding rates on growth performance, serum parameters, digestive enzyme activity, and body composition of juvenile, genetically improved, farmed Nile Tilapia Oreochromis niloticus (GIFT) reared in an IPRS. Fish with an initial mean body weight of 6.25 g were fed twice daily at rates of 3, 4, or 5% body weight per day (BW/d) for 50 d. Results indicated that final fish body weight, weight gain, and specific growth rate of GIFT improved with increasing feeding rates from 3% to 5%. Growth of GIFT fed 5% BW/d was significantly higher than for those fed 3% BW/d; however, there was no significant difference from that of fish fed at 4% BW/d. Serum parameters and digestive enzyme activities were not affected by feeding rates. Lipid content in muscle and whole body increased with increasing feeding rates, and fish fed 5% BW/d had higher values compared with those fed 3% BW/d. Based on growth and physiological and biochemical variables, it could be concluded that a feeding level of 5% BW/d is suitable for juvenile GIFT fed twice daily reared in an IPRS. [ABSTRACT FROM AUTHOR]

High-density aquaculture and nutritional imbalances may promote fatty liver in genetically improved farmed tilapia (GIFT, Oreochromis niloticus), thus reducing the gains achieved by breeding. In this study, apple peel powder (APP) was used as a feed additive for GIFT. A control group (fed on a diet without APP) and five groups fed on diets supplemented with APP (at 0.05%, 0.1%, 0.2%, 0.4%, or 0.8% of the diet, by weight) were established to investigate the effects of APP on GIFT growth performance and physiological parameters, and on gene expression as determined by transcriptomic analysis. Dietary supplementation with APP at 0.2% promoted GIFT growth, reduced total cholesterol and triacylglycerol levels in the serum and liver, and decreased alanine aminotransferase and aspartate aminotransferase activities in the serum. Gene expression profiles in the liver were compared among the control, 0.2% APP, and 0.8% APP groups, and differentially expressed genes among these groups were identified. Annotation analyses using tools at the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases showed that the differentially expressed genes were mainly involved in the regulation of immunity and fat metabolism. The results showed that excessive supplementation with APP in the diet significantly inhibited the expression of insulin-like growth factor 2 and liver-type fatty acid-binding protein, and stimulated the expression of fatty acid desaturase 2, heat shock protein 90 beta family member 1, and nuclear factor kappa B. This resulted in disordered lipid metabolism and increased pro-inflammatory reactions, which in turn caused liver damage. Therefore, APP has good potential as an environmentally friendly feed additive for GIFT at levels of 0.1%–0.2% in the diet, but excessive amounts can have adverse effects. [ABSTRACT FROM AUTHOR]

Tilapia were exposed to sub-lethal concentrations of 0, 0.2, 2, 20 or 200 μg/L for 30 days, then transferred to methomyl-free water for 18 days. E2, T, 11-KTand VTG in serum were examined. There were no significant changes in all the parameters in serum of tilapia exposed to 0.2 μg/L and 2 μg/L methomyl compared to the control. However, 20 μg/L and 200 μg/L have the potential to disrupt the endocrine system of male tilapia, as shown by its ability to increase VTG and E2 and decrease T and 11-KT in serum. Thus it would appear the no observed adverse effect level for sexual steroid hormones of methomyl is lower than 2 μg/L. Recovery data showed that the effects produced by 20μg/L were reversible but not at 200μg/L. Furthermore, the sensitivity of above parameters to methomyl followed the order of VTG>E2>11-KT>T>GSI, suggesting VTG being the better biomarkers. [ABSTRACT FROM AUTHOR]

The present study was performed to investigate the effects of dietary lipid level on growth performance, antioxidant defense, and mRNA levels of digestive enzymes and immune genes in larval genetically improved farmed tilapia ( Oreochromis niloticus). The results show that larvae fed lipid levels of 4-11.5% had greater weight gain ( WG), feed efficiency, protein efficiency ratio and survival than larvae fed the other dietary lipid levels ( P < 0.05). No difference whole-body crude protein, ash or moisture contents were found between treatments ( P > 0.05) but lipid contents increased as dietary lipid level was increased. The 8% and 11.5% dietary lipid levels had stimulatory effects on trypsin mRNA level compared with those of larvae fed the 15% and 18.5% lipid diets. Intestinal and liver amylase mRNA levels decreased in larvae fed the 18.5% lipid diet, following the decrease in dietary starch. Analysis of the secondary curve equation for WG indicated that the optimal dietary lipid level in larval tilapia was 8.56%. In addition, the 4-11.5% lipid levels improved superoxide dismutase and glutathione peroxidase activities and increased mRNA levels of heat shock protein70, hepcidin antimicrobial peptide-1, and C-type lysozyme in the liver of larvae ( P < 0.05). A 192-h Streptococcus iniae challenge study was conducted after the 35-day feeding trial, and the results showed that post-challenge mortality of larvae fed the 11.5% lipid level was the lowest and enhanced the immune activities. [ABSTRACT FROM AUTHOR]

Tilapia juveniles are a very important life stage, and reliably assessing their growth performance is of prime importance in aquaculture production. The suitability of the RNA/ DNA as a bioindicator for growth evaluation in tilapia has not yet been reported. In this study, we examined suitability of RNA/ DNA ratio for assessing growth of tilapia juveniles and variation in the ratio under the concurrent influences of temperature and salinity using the central composite design and response surface methodology. Results showed that under our experimental conditions, the synergistic effects of temperature and salinity on the RNA/ DNA ratio were highly significant ( P < 0.01), and the ratio varied with the two factors in a nonlinear fashion; the temperature × salinity interaction was detected at 1% significance level, and had a negative effect on the RNA/ DNA ratio particularly at higher temperatures. Temperature was found to have a greater influence on RNA/ DNA ratios than salinity. A model of the relation between RNA/ DNA, temperature and salinity was developed, with an R2 greater than 98%. The linear relationships of absolute growth, cumulative growth and specific growth of tilapia juveniles to RNA/ DNA ratio all showed an R2 of greater than 95%. Our results indicate that the RNA/ DNA ratio was a responsive and accurate bioindicator for evaluating the growth performance of juvenile tilapia. These ratio-based models are neither temperature- nor salinity-dependent, and could be readily applicable to freshwater or brackish water aquaculture within temperature-salinity combinations ranging from 16 to 36°C and 0-16 ppt. [ABSTRACT FROM AUTHOR]

We evaluated the hypothesis that administering dietaryAloe verato sexually undifferentiated fry of genetically improved farmed Nile TilapiaOreochromis niloticusfor 30 d would affect their sex ratio. Five experimental treatments were designed, including a control and 100%A. verapowder incorporated into the feed at 0.5, 1.0, 2.0, and 4.0%. After 30 d of feeding, the experimental diets were replaced with a commercial diet, which was administered to the fish for another 42 d to attain the size at which sex determination was possible. Based on logistic regression analysis, an increase in theA. verainclusion level from 1.0% to 4.0% resulted in a significantly greater percentage of males compared to the control and the 0.5%A. verainclusion level, with the 4.0%A. veragroup presenting potent masculinization effects (67.62% male). However, the survival percentage among fish that received 4.0%A. verawas significantly lower than survival in the other groups. The present results indicate thatA. veraextracts have the potential to be used as sex-reversal agents in Nile Tilapia culture, but additional studies are necessary. Received December 30, 2015; accepted September 4, 2016 Published online December 6, 2016 [ABSTRACT FROM PUBLISHER]

Tilapia were exposed to sublethal methomyl concentrations of 0, 0.2, 2, 20 or 200 μg/L for 30 days, and then transferred to methomyl-free water for 18 days. The sexual steroid hormones 17β-estradiol (E2), testosterone (T), and 11-ketotestosterone (11-KT) in tilapia testes were examined at 0, 6, 12, 18, 24 and 30 days after methomyl exposure, and at 18 days after fish were transferred to methomyl-free water. There were no significant changes in the hormone parameters in testes of tilapia exposed to low concentration 0.2 and 2 μg/L methomyl compared with the controls. However, high concentration 20 and 200 μg/L methomyl had the potential to disrupt the endocrine system of male tilapia, as shown by an increase in E and a decrease in T and 11-KT in the testes. Thus, it would appear that the 2 μg/L methomyl might be considered the no-observed-adverse-effect level. Recovery data showed that the effects produced by the lower concentration of 20 μg/L were reversible but the effects were not reversible at the higher concentration of 200 μg/L. [ABSTRACT FROM AUTHOR]

The effects of high-carbohydrate diets on endocrine status and gene expression of hepatic metabolism enzymes in genetically improved farmed tilapia ( GIFT) juveniles ( Oreochromis niloticus) at different sampling times were investigated. Two isonitrogenous (28% crude protein) and isolipidic (5% crude lipid) diets were formulated to contain 40% gelatinized wheat starch ( WS) or glucose ( GLU). Diets were assigned to triplicate groups of 30 fish (initial weight: 51 g) for 42 days. At the end of the trial, there were no significant difference in growth between WS group and GLU group. Hepatosomatic and visceral index and liver glycogen in juveniles were not significantly influenced by high-carbohydrate diets on Day 42 ( P > 0.05). Plasma glucose was higher in the GLU group than the WS group from Day 7 onwards. Data on gene expression showed that G6 PD, but not GK and G6Pase, were affected by high-carbohydrate diet. The levels of G6 PD in the GLU group on Days 35 and 42 were significantly higher than those in the WS group. Serum IGF-I levels of both groups significantly decreased on Day 42, whereas serum insulin levels were unaltered by high-carbohydrate diet. The serum GH level decreased significantly in the GLU group compared with the WS group. Overall, our data suggest that high-glucose diets were efficiently used as an energy source by GIFT tilapia juveniles, and significantly affected liver lipogenic activity and serum GH levels. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of dietary protein level on growth performance and haemato-immunological parameters of juvenile genetically improved farm tilapia, Oreochromis niloticus, fed five iso-caloric diets of dietary protein levels 25-45 %, formulated using white fish, casein, gelatine, soybean, cottonseed and rapeseed meals as protein sources. The diets influenced the significant increase in final weight, condition factor and whole body lipid composition ( P < 0.05). Conversely, the 25 % protein diet resulted in a significantly ( P < 0.05) lower weight gain and higher feed conversion ratio than the 30-45 % protein diets. Protein efficiency ratio and protein retention efficiency of the fish significantly reduced as dietary protein level increased ( P < 0.05). Meanwhile, hepatosomatic index increased with dietary protein. Haemato-immunological parameters, white blood cell, red blood cell, immune globulin M, superoxide dismutase and lysozyme activity, were not significantly affected by the dietary protein levels ( P > 0.05). Quadratic regression model, y = −0.493 x + 41.03 x + 267.3, informed that 41.6 % dietary protein supported maximum growth of tilapia juvenile. Fish fed 35 % protein diet had a similar growth performance, but better protein utilization than the 40 % group. These results demonstrated possibility of reducing protein level in commercial feeds, thus lowering feed costs . [ABSTRACT FROM AUTHOR]

This study investigated the effect of feeding rates (2-10% of body weight), on the growth performance, feed utilization, and blood-chemistry indicators of nutritional status in juvenile GIFT strain tilapia, (Oreochromis niloticus) initial weight 72.73±0.15g. The 56 day trial conducted in cages tested five groups, with three replicates each. Fish were fed twice a day. Data were analyzed using one way ANOVA. Results showed that final body weight, food conversion rate (FCR), weight gain, specific growth rate (SGR), protein retention efficiency (PRE), protein efficiency ratio (PER), feed intake, and condition factor (CF) were significantly affected by the feeding rates (P<0.05). The broken line method of linear regression analysis, y=17638x-217.9, R2=0.945; y=280x+860.6, R2=1, indicated that maximum weight gain occurred at 6.21% feeding rate. Insulin growth factor-one (IGF-I) level, hepatosomatic index (HSI), white blood cell (Wbc), red blood cell (Rbc), hemoglobin (Hb), and hematocrit (Ht) parameters were not significantly affected by the feeding rates (P>0.05). Serum indicative parameters of liver-enzyme functions and food metabolism, including blood glucose (GLU), triglyceride (TG), total protein (TP) levels, aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) enzyme activities were assayed. Blood glucose level of the fish was significantly affected by the feeding rates (P<0.05). TG and TP levels; AST, ALT and ALP activities were not significantly affected by the feeding rates (P>0.05). Feed provided at a rate of 2%-10% of body weight may meet physiological wellbeing of GIFT strain tilapia, however growth performance and other endocrine functions (IGF-I) are affected by lower and higher feeding rates. Our findings could be very useful to tilapia farmers. [ABSTRACT FROM AUTHOR]

Hepatic antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) of Nile tilapia in response to pesticide methomyl and recovery pattern were researched by exposing tilapia to sub-lethal methomyl concentrations of 0, 0.2, 2, 20 and 200 μg/L for 30 days, and then transferred to methomyl-free water for 18 days. Hepatic SOD and CAT were measured at 10 min (day 0), 6, 12, 18, 24 and 30 days after starting the experiment and at 18 days after transferring to methomyl-free water. The results showed hepatic SOD and CAT activities in 2, 20 and 200 μg/L groups were affected significantly, however, that in 0.2 μg/L group didn't change significantly compared to control during 30-day exposure period. Thus it would appear the 0.2 μg/L methomyl might be considered the no observed adverse effect level. Recovery data showed that, for SOD, the effects produced by lower concentration of methomyl 2 μg/L were reversible but not at concentrations higher than 20 μg/L, however, for CAT, the effects produced by all the concentrations were reversible. [ABSTRACT FROM AUTHOR]

The chronic effect of methomyl on the antioxidant system in tilapia (Oreochromis niloticus) was investigated. Fish were exposed to sub-lethal concentrations of 0.2, 2, 20 and 200μgL−1 for 30 days, and then transferred to methomyl-free water for 18 days. Hepatic antioxidant parameters, including Glutathione-S-transferase (GST), Glutathione peroxidase (GPx), Glutathione reductase (GR), Reduced glutathione (GSH) and oxidized glutathione (GSSG), were measured at 10min (day 0), 6, 12, 18, 24 and 30 days after starting the experiment and at 18 days after transferring to methomyl-free water. There were no significant changes in enzymatic activity and content of antioxidants in liver of tilapia exposed to 0.2μgL−1 methomyl compared to controls. However, the results showed significant increases in activities of GST, GR, GPx and levels of GSSG accompanied by a decrease in GSH levels following methomyl exposure in tilapia to 2, 20 or 200μgL−1 over the 30-day exposure period and the highest induction rates in GST, GR, GPx and GSSG were 150.87%, 163.21%, 189.76%, and 179.56% of the control respectively, and the highest inhibition rate in GSH was 50.67% of the control, suggesting the presence of oxidative stress. Thus it would appear that the 0.2μgL−1 methomyl might be considered as the no observed adverse effect level (NOAEL). Recovery data showed that the effects produced by lower concentration of methomyl 20μgL−1 were reversible but not at the higher 200μgL−1 concentration. [Copyright &y& Elsevier]

Tilapia were exposed to sublethal methomyl concentrations of 0, 0.2, 2, 20, or 200 μg/L for 30 d, and then were transferred to methomyl-free water for 18 d. Renal antioxidant parameters, including catalase (CAT), superoxide dismutase (SOD), glutathioneS-transferase (GST), glutathione peroxidase (GPx) , glutathione reductase (GR), total glutathione (GSH), and reduced glutathione (GSSG), were examined in tilapia at d 0, 6, 12, 18, 24, and 30 after starting the experiment and at 18 d after transferring to methomyl-free water. There were no significant changes in enzymatic activity and content of antioxidants in kidney of tilapia exposed to 0.2 μg/L methomyl compared to controls. The results showed significant increases in SOD, CAT, GST, GR, GPx, and level of GSSG accompanied by a decrease in GSH levels following methomyl exposure in tilapia to 2, 20, or 200 μg/L over the 30-d exposure period, suggesting the presence of oxidative stress. Thus, it would appear the 0.2 μg/L methomyl might be considered the no-observed-adverse-effect level (NOAEL). Recovery data showed that the effects produced by lower concentration of methomyl at 20 μg/L were reversible but not at the higher 200 μg/L concentration. [ABSTRACT FROM AUTHOR]

Acanthopanax senticosus (APS) is a natural and officinal herb with an impressive range of health benefits for animal. An 8-week feeding trail with different APS levels (0, 0.5, 1, 2, 4, and 8‰) was conducted to evaluate the promotive effects of APS in GIFT. Results indicate that APS improved the growth performance, improved specific growth ratio (SGR) and feed efficiency ratio (FER), the optimum APS supplementation was estimated to 1.97‰ based on the regression analysis of SGR. Meanwhile, 2‰ and 4‰ APS improved the immune and antioxidant capacity in some extent evidenced by the plasma and hepatic biomarkers. With the analysis of transcriptome sequencing, 293 differentially expressed genes (DEGs) were identified, including 106 up-regulated and 187 down-regulated. According to the GO and KEGG enrichments, DEGs were mainly involved in lipid metabolism regulation, followed by amino acid metabolism, carbohydrate metabolism, immunity, and antioxidant response. Transcriptional expression of PPARs signaling and key genes retrieved from transcriptome database confirmed that lipid metabolism was the main active biological process in response to dietary APS administration. These results indicate optimum APS (2‰) could be used as a feed additive that improve the growth performance by regulating lipid metabolism. This may provide insights for Chinese herb additive application in aquaculture production. Unlabelled Image • Acanthopanax senticosus improves growth performance, antioxidant, and immune capacity. • RNA-seq reveals lipid metabolism is the most active biological process. • Acanthopanax senticosus could be used as a feed additive in GIFT production. [ABSTRACT FROM AUTHOR]

Chronic hypoxia in aquaculture impairs gonad growth and reduces the reproductive capacity of farmed fish. The aim of this study was to investigate how prolonged hypoxia affects gonad maturation, the degree of oxidative stress, and apoptosis in female Nile Tilapia. We conducted an 85-day experiment in which female Nile tilapia were cultured with dissolved oxygen (DO) levels of 6.0 ± 0.1, 4.0 ± 0.1, and 2.0 ± 0.1 mg/L, designated as the normal-DO group (NG), the low-DO group (LG), and the hypoxia-stressed group (HG), respectively. The results show that chronic hypoxia reduced the specific growth rate and gonadosomatic index of female Nile tilapia. The chronic hypoxia significantly affects the final body weight, weight gain rate, feed conversion ratio, hepatosomatic index and gonado somatic index, compared with the fish in the NG, those in the HG and LG had significantly lower values for all growth indicators (P < 0.05). The gonads of fish in the LG and HG did not reach maturity, whereas those of fish in the NG developed normally. This was related to their higher levels of follicle-stimulating hormone, luteinizing hormone, and estradiol, causing their oocytes to reach stages IV and V. In contrast, the majority of oocytes in fish in the LG were in stages II and III, and the presence of more atretic follicles in the ovary of fish in the HG indicated that their gonads were still immature. Compared with fish in the NG and LG, those in the HG showed increased malondialdehyde levels in ovarian tissues and decreased activities of superoxide dismutase and catalase. The transcript levels of genes related to the nrf2 signaling pathway (nrf2, keap1) and apoptosis (nfκb, bcl-2, caspase-3, caspase-8) in the ovary differed among the three groups. The nrf2-bcl2 pathways were also positively correlated with GSI. The pathogenic changes were linked to chronic hypoxia, according to the results of the PCA, and the negative consequences were more severe for the fish in the HG (DO 2.0 mg/L) than for those in the NG and LG. Together, our results show that apoptosis and the antioxidant system are dysregulated under chronic hypoxia stress, and this may be responsible for impaired gonad development in hypoxia-stressed female Nile tilapia. • Disruption of ovarian development in Nile tilapia under chronic hypoxia. • Chronic hypoxia altered serum hormones related to reproduction. • Chronic hypoxia causes oxidative damage and apoptosis in the ovary tissues. • nrf2 and nfκb signaling pathway may play a crucial role in the hypoxia-induced oocyte degeneration. [ABSTRACT FROM AUTHOR]

Elongation of very long-chain fatty acids protein 6 (ELOVL6) plays a pivotal role in the synthesis of endogenous fatty acids, influencing energy balance and metabolic diseases. The primary objective of this study was to discover the molecular attributes and regulatory roles of ELOVL6 in male Nile tilapia, Oreochromis niloticus. The full-length cDNA of elovl6 was cloned from male Nile tilapia, and was determined to be 2255-bp long, including a 5′-untranslated region of 193 bp, a 3′-untranslated region of 1252 bp, and an open reading frame of 810 bp encoding 269 amino acids. The putative protein had typical features of ELOVL proteins. The transcript levels of e lovl6 differed among various tissues and among fish fed with different dietary lipid sources. Knockdown of elovl6 in Nile tilapia using antisense RNA technology resulted in significant alterations in hepatic morphology, long-chain fatty acid synthesis, and fatty acid oxidation, and led to increased fat deposition in the liver and disrupted glucose/lipid metabolism. A comparative transcriptomic analysis (elovl6 knockdown vs. the negative control) identified 5877 differentially expressed genes with significant involvement in key signaling pathways including the peroxisome proliferator-activated receptor signaling pathway, fatty acid degradation, glycolysis/gluconeogenesis, and the insulin signaling pathway, all of which are crucial for lipid and glucose metabolism. qRT-PCR analyses verified the transcript levels of 13 differentially expressed genes within these pathways. Our findings indicate that elovl6 knockdown in male tilapia impedes oleic acid synthesis, culminating in aberrant nutrient metabolism. [Display omitted] • Nile tilapia elovl6 encodes a protein with typical characteristics of ELOVL proteins. • The highest transcript level of elovl6 was in the liver. • The transcript level of elovl6 was significantly influenced by dietary lipid sources. • elovl6 knockdown impedes oleic acid synthesis, culminating in aberrant glucose/lipid metabolism. [ABSTRACT FROM AUTHOR]

Temperature is one of the most important non-genetic sex differentiation factors for fish. The technique of high temperature-induced sex reversal is commonly used in Nile tilapia (Oreochromis niloticus) culture, although the molecular regulatory mechanisms involved in this process remain unclear. The brain is an essential organ for the regulation of neural signals involved in germ cell differentiation and gonad development. To investigate the regulatory roles of miRNAs-mRNAs in the conversion of female to male Nile tilapia gender under high-temperature stress, we compared RNA-Seq data from brain tissues between a control group (28 °C) and a high temperature-treated group (36 °C). The result showed that a total of 123,432,984 miRNA valid reads, 288,202,524 mRNA clean reads, 1128 miRNAs, and 32,918 mRNAs were obtained. Among them, there were 222 significant differentially expressed miRNAs (DE miRNAs) and 810 differentially expressed mRNAs (DE mRNAs) between the two groups. Eight DE miRNAs and eight DE mRNAs were randomly selected, and their expression patterns were validated by qRT-PCR. The miRNA-mRNA co-expression network demonstrated that 40 DE miRNAs targeted 136 protein-coding genes. Functional enrichment analysis demonstrated that these genes were involved in several gonadal differentiation pathways, including the oocyte meiosis signaling pathway, progesterone-mediated oocyte maturation signaling pathway, cell cycle signaling pathway and GnRH signaling pathway. Then, an interaction network was constructed for 8 miRNAs (mir-137-5p, let-7d, mir-1388-5p, mir-124-4-5p, mir-1306, mir-99, mir-130b and mir-21) and 10 mRNAs (smc1al , itpr2 , mapk1 , ints8 , cpeb1b , bub1 , fbxo5 , mmp14b , cdk1 and hrasb) involved in the oocyte meiosis signaling pathway. These findings provide novel information about the mechanisms underlying miRNA-mediated sex reversal in female Nile tilapia. • miRNA-mRNA network of brain in high-temperature-induced masculinization was built. • 8 miRNAs and 10 genes were involved in the oocyte meiosis signaling pathway. • High temperature-induced masculinization may be due to inhibition of oocyte division. [ABSTRACT FROM AUTHOR]

Fatty liver injury (or disease) is a common disease in farmed fish, but its pathogenic mechanism is not fully understood. Therefore the present study aims to investigate high-fat diet (HFD)-induced liver injury and explore the underlying mechanism in fish. The tilapia were fed on control diet and HFD for 90 days, and then the blood and liver tissues were collected to determine biochemical parameter, gene expression and protein level. The results showed that HFD feeding signally increased the levels of plasma aminotransferases and pro-inflammatory factors after 60 days. In liver and plasma, HFD feeding significantly suppressed antioxidant ability, but enhanced lipid peroxidation formation, protein oxidation and DNA damage after 60 or 90 days. Further, the Nrf2 pathway and antioxidative function-related genes were adversely changed in liver of HFD-fed tilapia after 60 and/or 90 days. Meanwhile, HFD treatment induced apoptosis via initiating mitochondrial pathway in liver after 90 days. Furthermore, after 90 days of feeding, the expression of genes or proteins related to JNK pathway and TLRs-Myd88-NF-κB pathway was clearly upregulated in HFD treatment. Similarly, the mRNA levels of inflammatory factors including tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), IL-6, IL-8 and IL-10 were also upregulated in liver of HFD-fed tilapia after 60 and/or 90 days. In conclusion, the current study suggested that HFD feeding impaired antioxidant defense system, induced apoptosis, enhanced inflammation and led to liver injury. The adverse influences of HFD in the liver might be due to the variation of Nrf2, JNK and TLRs-Myd88-NF-κB signaling pathways. • HFD feeding impairs Nrf2 pathway to weaken antioxidant defense system in liver of tilapia. • HFD feeding induces apoptosis via mitochondrial pathway. • HFD feeding activates JNK-NF-κB pathway and TLRs-MyD88-NF-κB pathway to mediate inflammatory response. [ABSTRACT FROM AUTHOR]

Radix Bupleuri extract (RBE) is one of the most popular oriental herbal medicines, which has anti-oxidative and anti-inflammatory properties. However, its protective effects and underlying molecular mechanisms on oxidative damage in tilapia are still unclear. The aims of the study were to explore the anti-oxidative, anti-inflammatory and hepatoprotective effects of RBE against oxidative damage, and to elucidate underlying molecular mechanisms in fish. Tilapia received diet containing three doses of RBE (0, 1 and 3 g/kg diet) for 60 days, and then were given an intraperitoneal injection of H 2 O 2 or saline. Before injection, RBE treatments improved growth performance and partial anti-oxidative capacity in tilapia. After oxidative damage, RBE pretreatments were able to signally reduce the higher serum aminotransferases, alkaline phosphatase (AKP) and liver necrosis. In serum and liver, the abnormal lipid peroxidation level and antioxidant status induced by H 2 O 2 injection were restored by RBE treatments. Furthermore, RBE treatments activated erythroid 2-related factor 2 (Nrf2) signaling pathway, which promoted the gene expression of heme oxygenase 1 (HO-1), NAD(P) H:quinone oxidoreductase 1 (NQO-1), glutathione-S-transferase (GST) and catalase (CAT). Meanwhile, RBE treatments reduced inflammatory response by inhibiting TLRs-MyD88-NF-κB signaling pathway, accompanied by the lower interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and IL-8 mRNA levels. In addition, RBE treatments upregulated complement (C3) gene expression and downregulated heat shock protein (HSP70) gene expression. In conclusion, the current study suggested that RBE pretreatments protected against H 2 O 2 -induced oxidative damage in tilapia. The beneficial activity of RBE may be due to the modulation of Nrf2/ARE and TLRs-Myd88-NF-κB signaling pathway. • RBE exerts anti-oxidative, anti-inflammatory and hepatoprotective effects against liver injury in fish. • RBE activities Nrf2 signaling pathway to improve antioxidant defense. • RBE inhibits TLRs-MyD88-NF-κB signaling pathway to ameliorate inflammatory response. [ABSTRACT FROM AUTHOR]

Vitamin E plays an important role in maintaining normal metabolism and physiological functions in animals. The health of fish fingerlings directly affects the rate of disease incidence in adult fish, and healthy fingerlings ultimately result in better breeding outcomes for cultured fish. To date, no previous studies have focused on the effects vitamin E deficiency on tilapia at the fingerling stage. In this study, we investigated the effects of dietary vitamin E on the growth, fat metabolism, antioxidant capacity, and inflammatory response of genetically improved farmed tilapia (GIFT, Oreochromis niloticus) fingerlings. Vitamin E at different concentrations (0, 20, 40, 80, 160, and 320 mg/kg) was added to the diet and GIFT were fed for 55 days. Then, the GIFT were intraperitoneally injected with Streptococcus iniae and tested for infection. Vitamin E deficiency decreased growth and increased the food conversion ratio of GIFT fingerlings. Vitamin E deficiency also reduced the white blood cell count, increased hematocrit and hemoglobin contents in the blood, increased serum aspartate aminotransferase and alanine aminotransferase activities, and increased liver stress (P < 0.05). Vitamin E deficiency inhibited fat metabolism, down-regulated the expression of genes encoding lipoprotein lipase and heart-type and liver-type fatty acid-binding proteins, and increased serum total protein and fat deposition. Vitamin E deficiency significantly decreased superoxide dismutase, glutathione peroxidase, and catalase activities, increased malondialdehyde content, and caused oxidative damage. Vitamin E deficiency also up-regulated the expression of genes encoding interleukin 1β and tumor necrosis factor α in the head kidney, and stimulated a pro-inflammatory response. Overall, vitamin E deficiency inhibited growth, impaired fat metabolism, and disrupted the inflammatory response of GIFT fingerlings, whereas vitamin E supplementation in the diet reversed these negative effects. The diets with high concentrations of vitamin E (160–320 mg/kg) led to vitamin E accumulation in the fish tissues and rapid activation of the inflammatory response and antioxidant capacity in GIFT fingerlings exposed to S. iniae. • Vitamin E deficiency decreased growth and increased the FCR of GIFT. • Vitamin E deficiency increased hematocrit/hemoglobin in blood. • Vitamin E deficiency decreased antioxidant capacity of liver of GIFT fingerlings. • Vitamin E deficiency reduced LPL, H-FABP , and L-FABP and induced fat deposition. • Vitamin E regulated signaling response of pro-inflammatory gene expression. [ABSTRACT FROM AUTHOR]

Abstract Resveratrol, a dietary polyphenol, has been shown to exert antioxidation, hepatoprotection, anti-inflammation and immunostimulation. However, the effects and underlying mechanism of resveratrol on liver injury in fish are still unclear. In the present study, we investigated the potential protective effects and mechanism of resveratrol on oxidative stress-induced liver damage in tilapia. Fish were fed diet containing four doses of resveratrol (0, 0.1, 0.3, and 0.6 g/kg diet) for 60 days, and then given an intraperitoneal injection of H 2 O 2 or saline. The results showed that administration of resveratrol significantly ameliorated H 2 O 2 -induced liver injury. In serum and liver, resveratrol treatment suppressed the oxidative stress, as evidenced by the decline of lipid peroxidation level and increase of antioxidant activity. Resveratrol also activated erythroid 2-related factor 2 (Nrf2) signaling pathway and enhanced the heme oxygenase 1 (HO-1), NAD(P) H:quinone oxidoreductase 1 (NQO-1), glutathione S-transferase (GST) mRNA levels. Meanwhile, resveratrol treatment repressed TLR2-Myd88-NF-κB signaling pathway to decrease the inflammatory response in H 2 O 2 -induced liver injury as evidenced by the lower interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and IL-8 mRNA levels and higher IL-10 mRNA level. Moreover, resveratrol treatment attenuated immunotoxicity in liver of H 2 O 2 -treated fish, accompanied by upregulation of hepcidin (HEP), complement 3 (C3) and lysozyme (LZM) mRNA levels. Overall results suggested that the protection of resveratrol on H 2 O 2 -induced liver injury, inflammation and immunotoxicity was due to its antioxidant property and its ability to modulate the Nrf2 and TLR2-Myd88-NF-κB signaling pathways. Graphical abstract Unlabelled Image Highlights • Resveratrol ameliorates H 2 O 2 -induced liver injury. • Resveratrol activates Nrf2 signaling pathway. • Resveratrol represses TLR2-Myd88-NF-κB signaling pathway. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are non-coding RNAs that function as post-transcriptional gene regulators and that play vital roles controlling lipid metabolism. miR-205 is an important miRNA related to adipogenesis and lipid metabolism. However, little is known about the potential role of miR-205-5p in genetically improved farmed tilapia (GIFT, Oreochromis niloticus ). In this study, we used miRanda software to search for potential miR-205-5p target genes and found a lipid-metabolism-related gene called acetyl-CoA carboxylase β ( ACACβ ). Quantitative real-time polymerase chain reaction data indicated that there may be a negative regulation relationship between miR-205-5p and ACACβ gene expression under HFD rearing. Using luciferase reporter assays, we verified the binding site of miR-205-5p in the 3′-untranslated region of the ACACβ mRNA. Furthermore, an in vivo functional analysis of miR-205-5p was performed by injecting GIFT juveniles with a miR-205-5p antagomir. Reduced levels of miR-205-5p in GIFT liver increased ACACβ mRNA expression 12 h post-injection. miR-205-5p suppression also increased fatty acid synthase and peroxisome proliferator-activated receptor-α mRNA levels 48 h and 120 h post-injection, respectively. Taken together, our results indicate that miR-205-5p negative regulates hepatic ACACβ mRNA expression, and may serve as an important regulator in controlling hepatic lipid metabolism in GIFT. [ABSTRACT FROM AUTHOR]

We investigated the effects of heat stress on genetically improved farmed tilapia, focusing on metabolic and immune responses. Differences in blood parameters, serum biochemistry, muscle fatty acid composition, and microRNA (miRNA) expression were analyzed in fish under heat stress. Fish were exposed to heat stress at 35 °C and sampled at 0, 6, 12, 24, and 48 h after exposure and compared with a control group maintained at 28 °C. The results showed that red and white blood cell counts, hemoglobin levels, and hematocrit values tended to increase ( P  < 0.05) and reached their maximum levels after 24 h, then declined. Acute heat stress enhanced serum glucose, total protein, and total cholesterol levels, and muscle fatty acid components were also altered. Serum alanine aminotransferase (ALT) activity was significantly increased after heat stress for 6 and 12 h. Polyunsaturated fatty acids levels were increased after heat stress for 12 and 24 h, whereas levels of monounsaturated fatty acids decreased in response to heat stress. Expression of hepatic miR-1 and miR-122 was significantly upregulated, and expression of miR-10c was significantly increased ( P  < 0.05) only after heat stress for 48 h. Acute heat stress altered metabolism closely related to the immune system and the liver of tilapia. These findings contribute to a theoretical framework for tilapia breeding at high temperatures. [ABSTRACT FROM AUTHOR]

The survival and growth of fish are significantly impacted by a hypoxic environment (low dissolved oxygen). In this study, we compared tissue structure, physiological changes, and mRNA/miRNA transcriptome, in gills of genetically improved farmed tilapia (GIFT, Oreochromis niloticus) between the hypoxic group (DO: 0.55 mg/L, HG) and the control group (DO: 5 mg/L, CG). The results showed that the gill filaments in the hypoxic group showed curling, engorgement, and apoptotic cells increased, and that exposure for 96 h resulted in a reduction in the antioxidant capacity. We constructed and sequenced miRNA and mRNA libraries from gill tissues of GIFT at 96 h of hypoxia stress. Between the HG and CG, a total of 14 differentially expressed (DE) miRNAs and 1557 DE genes were obtained. GO and KEGG enrichment showed that DE genes were mainly enriched in immune and metabolic pathways such as natural killer cell mediated cytotoxicity, steroid biosynthesis, primary immunodeficiency, and synthesis and degradation of ketone bodies. Based on the results of mRNA sequencing and screening for miRNA-mRNA pairs, we selected and verified six DE miRNAs and their probable target genes. The sequencing results were consistent with the qRT-PCR validation results. The result showed that under hypoxia stress, the innate immune response was up-regulated, and the adaptive immune response was down-regulated in the gill of GIFT. The synthesis of cholesterol in gill cells is reduced, which is conducive to the absorption of solvent oxygen. These findings offer fresh information about the processes of fish adaptation to hypoxic stress. • mRNA-miRNA sequencing analysis were used to explore the regulatory mechanism of gills in GIFT under hypoxic stress. • A total of 14 different expressed miRNA and 1557 different expressed mRNA were identified. • Hypoxic stress affects the immunomodulation mode of GIFT, and the innate immune response is activated. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) play vital roles in modulating diverse metabolic processes in the liver, including lipid metabolism. Genetically improved farmed tilapia (GIFT, Oreochromis niloticus ), an important aquaculture species in China, is susceptible to hepatic steatosis when reared in intensive culture systems. To investigate the miRNAs involved in GIFT lipid metabolism, two hepatic small RNA libraries from high-fat diet-fed and normal-fat diet-fed GIFT were constructed and sequenced using high-throughput sequencing technology. A total of 204 known and 56 novel miRNAs were identified by aligning the sequencing data with known Danio rerio miRNAs listed in miRBase 21.0. Six known miRNAs (miR-30a-5p, miR-34a, miR-145-5p, miR-29a, miR-205-5p, and miR-23a-3p) that were differentially expressed between the high-fat diet and normal-fat diet groups were validated by quantitative real-time PCR. Bioinformatics tools were used to predict the potential target genes of these differentially expressed miRNAs, and Gene Ontology enrichment analysis indicated that these miRNAs may play important roles in diet-induced hepatic steatosis in GIFT. Our results provide a foundation for further studies of the role of miRNAs in tilapia lipid homeostasis regulation, and may help to identify novel targets for therapeutic interventions to reduce the occurrence of fatty liver disease in farmed tilapia. [ABSTRACT FROM AUTHOR]

Dietary supplementation with rutin may have some pharmacological qualities including anti-inflammatory effects. Kupffer cell activation resulted in increased transcription of pro- and anti-inflammatory cytokines. The main purpose of this study was to investigate the pro- and anti-inflammatory activities in juvenile freshwater tilapia, Oreochromis niloticus , in response to 0.1 or 0.3 g/kg dietary supplementation of rutin. Results showed that hepatic IgM, anti-inflammatory-cytokines, and pro-inflammatory cytokines were significantly decreased in groups treated with high doses of rutin. Hepatic IgM and anti-inflammatory cytokines (IL-10 and IFN-γ) transcripts were significantly decreased, whereas the transcripts of the pro-inflammatory cytokines, TNFα and IL- 1 β were significantly decreased, whereas IL- 8 was significantly increased. The number of Kupffer cells in rutin-treated groups was significantly decreased, and scanning electron micrographs showed that rutin enriched the number of gut microvilli and secretion pits. With the phenomena of cell apoptosis occurred in the rutin groups, the present study demonstrated that optimum levels of rutin may be beneficial but excessive level may cause liver impairment, which may be absorbed by the gut and then transported to the liver. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are small, non-coding RNAs that regulate target gene expression by binding to the 3′-untranslated regions (3′-UTRs) of their target mRNAs. The miR-92 family is an important miRNA family, which was discovered to be related to regulation of tumor proliferation, apoptosis, invasion, and metastasis. Inhibition of miR-92d-3p was found previously in head kidney of genetically improved farmed tilapia (GIFT, Oreochromis niloticus ) exposed to Streptococcus iniae infection. In this study, we found that miR-92d-3p regulated complement C3 mRNA levels by binding to its 3′-UTR by 3′-UTR luciferase reporter assay, and reduced miR-92d-3p expression resulted in increased C3 mRNA levels. We detected a negative relationship between the expression levels of miR-92d-3p and C3 in GIFT injected with miRNA antagomir. We performed in vivo functional analysis by miR-92d-3p silencing. Inhibition of miR-92d-3p levels in GIFT head kidney caused a significant increase in C3 expression, which consequently increased the white blood cell counts and interleukin-1β, tumor necrosis factor-α, and interferon-γ mRNA levels, all of which may help to activate the inflammatory response in GIFT post-infection with S. iniae . Our findings indicate that miR-92d-3p regulated C3 levels by binding with the C3 mRNA 3′-UTR, and this interaction affected S. iniae infection induction and the immune response in GIFT. We concluded that miR-92d-3p plays an important role in modulating the inflammatory response in GIFT head kidney. Our findings may contribute to understanding the mechanisms of miRNA-mediated gene regulation in tilapia in response to S. iniae infection. [ABSTRACT FROM AUTHOR]