Vascular Endothelial Growth Factor A (VEGFA) Regulates Hepatic Lipid and Glycogen Metabolism in Schizothorax prenanti

Vascular endothelial growth factor A (VEGFA) plays important roles in angiogenesis, inflammatory response as well as energy metabolism in mammals. However, its effect on glycolipid metabolism in fish has not been reported. In this study, we cloned and characterized the vegfa gene of Schizothorax prenanti (S. prenanti). vegfa expression was significantly higher in liver and muscle than that in other tissues. Then, the VEGFA recombinant protein was expressed in Escherichia coli and obtained after purification. VEGFA i.p. injection significantly increased the serum glucose and TG content compared with the control group. Moreover, VEGFA protein aggravated the glycogen and lipid deposition in the liver of S. prenanti. In addition, we found that VEGFA treatment increased hepatocyte glycogen and lipid droplet content and increased the levels of pAMPKα (T172). Furthermore, AMPKα inhibition attenuated the ability of VEGFA to induce TG and glycogen accumulation. These results demonstrate that VEGFA regulates hepatic lipid and glycogen metabolism through AMPKα in S. prenanti, which may contribute to a better understanding of VEGFA functions in the glycolipid metabolism of fish.

Molecular Cloning of Toll-like Receptor 2 and 4 (SpTLR2, 4) and Expression of TLR-Related Genes from Schizothorax prenanti after Poly (I:C) Stimulation

Toll-like receptor (TLR) signaling is conserved between fish and mammals, except for TLR4, which is absent in most fish. In the present study, we aimed to evaluate whether TLR4 is expressed in Schizothorax prenanti (SpTLR4). The SpTLR2 and SpTLR4 were cloned and identified, and their tissue distribution was examined. The cDNA encoding SpTLR4 and SpTLR2 complete coding sequences (CDS) were identified and cloned. Additionally, we examined the expression levels of seven SpTLRs (SpTLR2, 3, 4, 18, 22-1, 22-2, and 22-3), as well as SpMyD88 and SpIRF3 in the liver, head kidney, hindgut, and spleen of S. prenanti, after intraperitoneal injection of polyinosinic-polycytidylic acid (poly (I:C)). The SpTLR2 and SpTLR4 shared amino acid sequence identity of 42.15-96.21% and 36.21-93.58%, respectively, with sequences from other vertebrates. SpTLR2 and SpTLR4 were expressed in all S. prenanti tissues examined, particularly in immune-related tissues. Poly (I:C) significantly upregulated most of the genes evaluated in the four immune organs compared with the PBS-control (p < 0.05); expression of these different genes was tissue-specific. Our findings demonstrate that TLR2 and TLR4 are expressed in S. prenanti and that poly (I:C) affects the expression of nine TLR-related genes, which are potentially involved in S. prenanti antiviral immunity or mediating pathological processes with differential kinetics. This will contribute to a better understanding of the roles of these TLR-related genes in antiviral immunity.

UNC93B1 facilitates TLR18-mediated NF-κB signal activation in Schizothorax prenanti

Toll-like receptor 18 (TLR18), a non-mammalian TLR, has been believed to play an important role in anti-bacterial immunity of teleost fishes. UNC93B1 is a classical molecular chaperone that mediates TLRs transport from endoplasmic reticulum to the located membrane. However, TLR18-mediated signal transduction mechanism and the regulatory effect of UNC93B1 to TLR18 are still unclear in teleost fishes. In this study, the coding sequences of TLR18 and UNC93B1 were cloned from Schizothorax prenanti, named spTLR18 and spUNC93B1, respectively. The spTLR18 and spUNC93B1 are 2583 bp and 1878 bp in length, encode 860 and 625 amino acids, respectively. The spTLR18 widely expressed in various tissues with the highest expression level in liver. After stimulation of Aeromonas hydrophila, lipopolysaccharide (LPS) and Poly(I:C), the expression levels of spTLR18 were significantly increased in spleen and head kidney. The spTLR18 located in the cell membrane, while spUNC93B1 located in the cytoplasm. Luciferase and overexpression analysis showed that spTLR18 activated NF-κB and type I IFN signal pathways, and spTLR18-mediated NF-κB activation might depend on the adaptor molecule MyD88. Besides, spUNC93B1 positively regulates spTLR18-mediated NF-κB signal. Our study first uncovers TLR18-UNC93B1-mediated signal transduction mechanism, which contributes to the understanding of TLR signaling pathway in teleost fishes.

Cloning of Toll-like Receptor 3 Gene from Schizothorax prenanti (SpTLR3), and Expressions of Seven SpTLRs and SpMyD88 after Lipopolysaccharide Induction

Toll-like receptor 3 (SpTLR3) from Schizothorax prenanti (S. prenanti) was cloned and identified, and the tissue distribution of the SpTLR3 gene was examined in this study. Moreover, the relative mRNA expression levels of myeloid differentiation factor 88 gene (SpMyD88) and seven TLR genes (SpTLR2, SpTLR3, SpTLR4, SpTLR18, SpTLR22-1, SpTLR22-2 and SpTLR22-3) from S. prenanti after lipopolysaccharide (LPS) challenge were analyzed through quantitative real-time polymerase chain reaction (qRT-PCR). The full length of SpTLR3 gene is 3097 bp, and complete coding sequence (CDS) is 2715 bp, which encodes 904 amino acids. The SpTLR3 amino acid sequence shared 43.94−100% identity with TLR3 sequences from other vertebrates; SpTLR3 was expressed in all eight tissues examined; and the highest level appeared in the liver, which was significantly higher than in all other tissues (p < 0.05), followed by the levels in the heart and muscles. LPS significantly up-regulated all eight genes in the S. prenanti tissues at 12 or 24 h (p < 0.05). Compared with the PBS control group, no significant transcripts changes were found in SpTLR2 or SpTLR3 at 12 h after LPS induction, but they were significantly up-regulated at 24 h (p < 0.001). The most abundant transcripts were found in the head kidney SpTLR22 genes after 24 h LPS induction, with high to low levels, which were SpTLR22-1 (564-fold), SpTLR22-3 (508-fold) and SpTLR22-2 (351-fold). Among these eight genes, the expression level of SpTLR4 was the least up-regulated. Overall, SpTLR4 in the head kidney was involved in the antibacterial immune response earlier, and the level was increased at 12 h with extreme significance after LPS stimulation (p < 0.001), while the other seven genes were the most significantly up-regulated at 24 h post injection. Taken together, the results suggest that SpMyD88, SpTLR2, SpTLR3, SpTLR4, SpTLR18, SpTLR22-1, SpTLR22-2 and SpTLR22-3 participate in an innate immune response stimulated by LPS, and the response intensity of the genes was organ-specific, with differing kinetics. Our findings will contribute to a more complete understanding of the roles of these TLR genes in antibacterial immunity.

Schizothorax prenanti Heat Shock Protein 27 Gene: Cloning, Expression, and Comparison with Other Heat Shock Protein Genes after Poly (I:C) Induction

We identified and cloned cDNA encoding the heat shock protein (Hsp) 27 gene from Schizothorax prenanti (SpHsp27), and compared its expression with that of SpHsp60, SpHsp70, and SpHsp90 in the liver, head kidney, hindgut, and spleen of S. prenanti that were injected with polyinosinic-polycytidylic acid [Poly (I:C)]. The SpHsp27 partial cDNA (sequence length, 653 bp; estimated molecular mass, 5.31 kDa; theoretical isoelectric point, 5.09) contained an open reading frame of 636 bp and a gene encoding 211 amino acids. The SpHsp27 amino acid sequence shared 61.0−92.89% identity with Hsp27 sequences from other vertebrates and SpHsp27 was expressed in seven S. prenanti tissues. Poly (I:C) significantly upregulated most SpHsps genes in the tissues at 12 or 24 h (p < 0.05) compared with control fish that were injected with phosphate-buffered saline. However, the intensity of responses of the four SpHsps was organ-specifically increased. The expression of SpHsp27 was increased 163-fold in the head kidney and 26.6-fold SpHsp27 in the liver at 24 h after Poly (I:C) injection. In contrast, SpHsp60 was increased 0.97−1.46-fold in four tissues and SpHsp90 was increased 1.21- and 1.16-fold in the liver and spleen at 12 h after Poly (I:C) injection. Our findings indicated that Poly (I:C) induced SpHsp27, SpHsp60, SpHsp70, and SpHsp90 expression and these organ-specific SpHsps are potentially involved in S. prenanti antiviral immunity or mediate pathological process.

[Fishway design based on the swimming ability of two Schizothorax species in the Yalung River, China]

To investigate the swimming ability of two Schizothorax species in the Yalung River and provide basic parameters for the studies on fish behavior and the design of fish passage, we exa-mined the induced velocity, critical swimming speed, and burst swimming speed in Schizothorax dolichonema and Schizothorax prenanti with incremental velocity method and the durable swimming speed in S. dolichonema with fixed velocity method. The results showed that the induced velocity of both species increased first and then plateaued with the increases of body length, with the maximum values being lower than 0.2 m·s^-1. The critical swimming speed and burst swimming speed of S. dolichonema were (0.81±0.20) and (1.49±0.26) m·s^-1, respectively, while the relative critical swimming speed and the relative burst swimming speed were (4.90±1.73) and (9.77±1.72) BL·s^-1 (BL: body length), respectively. For S. prenanti, the critical swimming speed and burst swimming speed were (0.73±0.24) and (1.17±0.39) m·s^-1, respectively, while the relative critical swimming speed was (6.88±2.82) BL·s^-1, and the relative burst swimming speed was (11.75±2.77) BL·s^-1. The swimming duration of S. dolichonema was negatively correlated with the flow velocity of 0.7-1.5 m·s^-1, and the relationship between fatigue time (T) and flow velocity (V) was fitted into lgT=-2.52V+5.59. The relationship between expected fishway length (d) and the tolerable maximum average flow velocity (V_{f max}) was accordingly derived to be V_{f max}=-0.17lnd+1.74. Taken together, the fishway targeting S. dolichonema and S. prenanti was recommended to generate the in-channel velocity larger than 0.2 m·s^-1, while the velocity at the entrance and verticle slot should be 0.73-1.67 m·s^-1, and the main-flow velocity in rest pools should be 0.2-0.7 m·s^-1.

Effects of acclimation temperature regime on the thermal tolerance, growth performance and gene expression of a cold-water fish, Schizothorax prenanti

Acclimation temperature is crucial for the optimization of a condition in aquaculture; we experimentally investigated the effects of temperature acclimation on the thermal tolerance, growth performance and gene expression levels of heat shock proteins (hsp70), growth hormone (gh) and insulin-like growth factors (igf-1) in Schizothorax prenanti, a cold-water fish in the Yangtze River basin. Critical thermal maximum (CT_max), critical thermal minimum (CT_min), lethal thermal maximum (LT_max), lethal thermal minimum (LT_min), feeding intake (FI), feeding efficiency (FE), and specific growth rate (SGR) were assessed at three stable temperatures (17, 22 and 27 °C) and one variable temperature (22 ± 5 °C) for 28 d. Better growth performance was observed under variable treatment compared to stable treatments. However, fish under the 27 °C treatment exhibited much weaker growth performance than those in the 17 °C treatment. Fish under variation temperature treatment fed like those under 22 °C treatment; the fish exhibited similar SGR but a higher gh and hsp70 level under variation temperature treatment. This may be due in part to a trade-off energy expenditure to deal with the temperature fluctuation. Together, these findings suggest that juvenile Schizothorax prenanti are resilient to daily fluctuations within the temperature tested here.

Schizothorax prenanti swimming behavior in response to different flow patterns in vertical slot fishways with different slot positions

Fish swimming behavior is a critical parameter for the design of vertical slot fishways. Although Schizothorax prenanti is a significant reproductive potamodromous migratory fish species in the upper reaches of the rivers in Southwest China, its swimming behavior has not been extensively researched. Therefore, in this study, a comparative experiment was conducted in vertical slot fishways to analyze the behavior of Schizothorax prenanti in response to different flow patterns, with respect to different slot positions. The experimental model was designed with a length scale of 1:4, and a method for selecting the appropriate fish size in the scaled physical model was proposed. Based on these experiments, it was found that the typical upstream trajectories of Schizothorax prenanti are traceable to the sidewall of the pool, which are characterized by low velocity and turbulent kinetic energy (TKE). The hydraulic variables exhibited an asymmetric distribution within the vertical slot, and the fish were found to pass through the area with the lowest velocity and TKE. A flow pattern with a guide wall length-to-pool width ratio of P/B = 0.25, in which Schizothorax prenanti can immediately find the sidewall, is suitable for fish migration. Therefore, this is the recommended value for the construction of effective vertical-slot fishway structures.

Abamectin at environmentally-realistic concentrations cause oxidative stress and genotoxic damage in juvenile fish (Schizothorax prenanti)

Abamectin (ABM) has been extensively used in Chinese aquaculture systems for parasite control, but no information is available regarding its effects on the important freshwater commercial fish species Schizothorax prenanti. We performed an acute toxicity test to determine the effects of ABM on S. prenanti, and the 48- and 96-h median lethal concentration values were 33.32 and 15.98 μg/L, respectively. In a second test, animals were exposed to sublethal concentrations of ABM (0.5, 2 or 8 μg/L) for 8 days, and various cytological and biochemical parameters were measured. ABM caused DNA damage in hepatocytes, with significant increases in Olive Tail Moment values and 8-hydroxy-2'-deoxyguanosine levels. Hepatocytic apoptosis occurred following all treatments, and was accompanied by an increase in reactive oxygen species (ROS) generation and caspase activity in a dose- and time-dependent manner. In addition, there were significant decreases in glutathione peroxidase levels and superoxide dismutase and catalase activity and increases in malonaldehyde levels. ABM-induced hepatocytic apoptosis in S. prenanti was probably triggered by ROS generation following a cascade reaction of caspases in mitochondrial or death receptor pathways, which caused antioxidant inhibition, oxidative product accumulation, and DNA damage in the liver.

Expression patterns and oestradiol regulation of growth differentiation factor 9 in Schizothorax prenanti

Growth differentiation factor 9 (GDF9) plays pivotal roles in regulating follicular development in many mammalian species. In the present study, the full-length Schizothorax prenanti gdf9 cDNA sequence was isolated and characterized, and its expression pattern in developing gonads and in the gonads of exogenous oestradiol (E₂)-fed fish were analysed. The S. prenanti gdf9 cDNA sequence consisted of 1958 base pairs (bp), encoded a 413 amino acid, and showed high sequence similarity with Carassius gibelio and Cyprinus carpio. The quantitative real-time PCR analysis revealed that gdf9 was mainly expressed in the gonads, with particularly high expression in the cortical alveoli stage ovary and late-spermatogenic stage testis. Immunohistochemical signals for Gdf9 were mainly detected in chromatin nucleolar oocytes, spermatogonia and spermatocytes. Furthermore, the gonadal expression of gdf9 induced by exogenous E₂ was related to the feeding time and dose. Taken together, these findings were helpful to gain a better understanding of the role of Gdf9 in both folliculogenesis and spermatogenesis in S. prenanti.

Clone, identification and functional character of two toll-like receptor 5 molecules in Schizothorax prenanti

Mammal Toll-like receptor 5 (TLR5) can directly recognize bacterial flagellin, initiate the inflammatory signaling cascades and trigger body immune system to clear the "non-self" substances. In teleosts, TLR5 has presented more complexes not only in increasing the molecular types, but also in elevating the functional diversity. In this study, we identified two TLR5 family members in Schizothorax prenanti, named as spTLR5-1 and spTLR5-2. The complete coding sequence (CDS) of spTLR5-1 is 2622 bp, encoding 873 amino acids, while the complete CDS of spTLR5-2 is 2640 bp, encoding 879 amino acids. Phylogenetic analysis showed that spTLR5-1 and spTLR5-2 were clustered to the TLR5 of schizothorax richardsonii and Cyprinus carpio respectively. The 3D structure analysis exhibited that the α-helix, β-sheet, and the ligand binding site of spTLR5-1, spTLR5-2 and human TLR5 have large differences. The spTLR5-1 and spTLR5-2 had extensively expressed in various tissues, including the higher expression in liver, spleen and head kidney. Both the expression levels of spTLR5-1 and spTLR5-2 were significantly up-regulated after Aeromonas hydrophila (A. hydrophila) challenge. And, the downstream genes, such as AP-1, IKK-α, NF-kB, IL-1β, IL-8 and TNF-α, were also significantly up-regulated after A. hydrophila challenge. Apart from that, the luciferase reporter assay demonstrated that the co-transfection of spTLR5-1 or spTLR5-2 into HEK293T cells showed the significantly increased NF-kB luciferase activity after flagellin stimulation. In conclusion, our results reveal that both two molecular types of fish TLR5 may commonly mediate the recognition of flagellin and the activation of the downstream inflammatory signaling molecules.

GSK3β inhibition suppresses the hepatic lipid accumulation in Schizothorax prenanti

Glycogen synthase kinase-3β (GSK3β) is a serine/threonine kinase involved in the regulation of embryonic development, glycogen metabolism, protein synthesis, mitosis, and apoptosis. To understand the role of GSK3β in hepatic lipid accumulation of Schizothorax prenanti, we used lithium chloride (LiCl), a GSK3β inhibitor, to inhibit the expression and activity of GSK3β. LiCl increased levels of phosphorylation of GSK3β (Ser9) and decreased the protein level of GSK3β. Plasma TG, TC, and LDL-C levels were greatly decreased after LiCl treatment. Additionally, GSK3β inhibition significantly reduced the levels of hepatic triglyceride (TG) and decreased the expression of lipogenesis-related genes in liver. Interestingly, LiCl decreased levels of phosphorylation of STAT3 (Tyr705), and then inhibited the activity of STAT3. These results indicate that in vivo LiCl treatment, which inhibited GSK3β activity, effectively decreased hepatic lipid accumulation through STAT3 in Schizothorax prenanti.

Multiple subtypes of TLR22 molecule from Schizothorax prenanti present the functional diversity in ligand recognition and signal activation

Evolutionary development has increased the diversity of genotypes and the complexity of gene functions in fish. TLR22 has been identified as a teleost-specific gene, but its functions are tremendously different among different fish species. Whether the functional diversity relates to the difference of genotypes remains poorly understand. In this study, we cloned and identified three TLR22 molecules from Schizothorax prenanti (S. prenanti), named as spTLR22-1, spTLR22-2 and spTLR22-3. The full-length coding regions of spTLR22s are 2841 bp, 2805 bp and 2868 bp and coding 946 aa, 934 aa and 955 aa, respectively. All spTLR22s are composed of multiple leucine-rich repeat (LRR) domains, a transmembrane structure and a Toll/IL-1 receptor (TIR) region. The phylogenetic analysis showed that three spTLR22s were close to Cyprinus carpio TLR22-1, TLR22-2 and TLR22-3, respectively. Among the spTLR22s, they presented not close relationship but remained to belong to TLR22 subfamily. All spTLR22s were ubiquitously expressed in all tested tissues, but the expression levels of spTLR22s were dominant in immune-related tissues, such as gill and spleen. The expression levels of spTLR22-1 and spTLR22-3 were significantly increased after treatment with bacteria, LPS and Poly(I:C). However, spTLR22-2 seems like no response to these treatments. The luciferase reporter assay demonstrated that all spTLR22s could activate NF-κB signaling pathway, but only spTLR22-1 and spTLR22-2 could activate IFN-β signaling pathway. Interestingly, in the ligand recognition analysis, spTLR22-1 and spTLR22-3 but not spTLR22-2 had the recognized potential to Poly(I:C), and all spTLR22s could not recognize LPS. Both spTLR22-1 and spTLR22-3 significantly up-regulated the expression of anti-viral-related genes (Mx, IFN and ISG15) and down-regulated the expression of anti-inflammatory factor IL-10 after the overexpression in carp EPC cell line, but spTLR22-2 failed to impact the expression of these genes. Moreover, we found that all spTLR22s localized to the intracellular region. Taken together, our results reveal that spTLR22-1 and spTLR22-3 but not spTLR22-2 may be involved into the anti-viral immune response via IFN-β signaling pathway, and all spTLR22s can activate NF-κB signaling pathway but only spTLR22-1 and spTLR22-3 response to the stimulation of bacteria and LPS.

Effect of Dietary Acidolysis-Oxidized Konjac Glucomannan Supplementation on Serum Immune Parameters and Intestinal Immune-Related Gene Expression of Schizothorax prenanti

The present study was conducted to investigate the effects of dietary acidolysis-oxidized konjac glucomannan (A-OKGM) (0%, 0.4%, 0.8%, and 1.6%) supplementation on the immunity and expression of immune-related genes in Schizothorax prenanti. After feeding for eight weeks, the serum and guts were used for measurement of biochemical parameters, and immune-related gene expression in the gut were also analyzed by real-time quantitative polymerase chain reaction (RT-qPCR). C-reactive protein and IgM levels were significantly higher in the A-OKGM fed groups than in the control group, regardless of the dosage. The 0.4% and 1.6% A-OKGM groups showed significant up-regulation of tumor necrosis factor α (TNFα) in the anterior gut. The 0.8% and 1.6% A-OKGM groups also showed significantly enhanced TNFα expression in the mid- and distal guts. Interleukin-1β (IL-1β) expression in the anterior gut of fish fed with 0.4% and 1.6% A-OKGM diets was significantly enhanced. The 0.8% and 1.6% A-OKGM diets resulted in significantly increased the expression of IL-1β in the distal gut. Similarly, the interleukin-6 (IL-6) messenger RNA (mRNA) levels in the 0.4% and 1.6% diet groups were significantly higher in the anterior gut. The 0.8% and 1.6% A-OKGM diet groups showed significant induction of IL-6 gene expression in the distal gut. A-OKGM modified from KGM can act as an immunostimulant to enhance the immunity of S. prenanti.

Identification and characterization of microRNAs in the muscle of Schizothorax prenanti

MicroRNAs (miRNAs) regulate gene expression by fully or partially binding to complementary sequences and play important roles in skeletal muscle development. However, the roles of miRNAs in the skeletal muscle of Schizothorax prenanti remain unknown. In this study, we analyzed the miRNA profiling in the skeletal muscle of S. prenanti at 30 days post-hatching (dph), 1 year, and 3 years by high-throughput sequencing. Two hundred twenty-nine unique miRNA types aligned to 201 independent pre-miRNA loci according to sequence similarity and 28 novel miRNAs were obtained. The nucleotide bias analysis of identified miRNAs showed that the miRNAs in S. prenanti were highly conserved. Eight identified miRNAs validated using stem-loop qRT-PCR were differentially expressed in the process of skeletal muscle development of S. prenanti. This study provide not only an overall insight into the miRNA landscape in the skeletal muscle of S. prenanti but also a basis for further investigation of miRNA roles in skeletal muscle development of S. prenanti.

Transcriptome profiling of spleen provides insights into the antiviral mechanism in Schizothorax prenanti after poly (I: C) challenge

Schizothorax prenanti (S. prenanti) is an important economical cold-water fish species in southwestern China, but it is susceptible to various pathogens infection. In order to clearly elucidate the antiviral mechanism, in this study, we have analyzed the transcriptome of S. prenanti spleen after challenge with the virus mimic, poly (I:C) (pIC), using next generation sequencing technology (RNA-seq). A total of 313 differential expressed genes (DEGs) in spleen at 12 h were obtained after pIC treatment, including 268 significantly up-regulated unigenes (fold change > 2) and 45 significantly down-regulated unigenes (fold change > 2). Through the immune-related DEGs (IRDs) screening, 47 IRDs were used to establish heat map, which intuitively showed a significantly difference after pIC treatment. To validate the RNA-seq data and observe gene expression, the expression levels of 14 IRDs were detected by qPCR after pIC treatment at 0, 4, 8, 12, and 24 h. The results indicated that the qPCR data presented a positive line correlation with RNA-seq data, and the 14 IRDs were responsive to pIC stimulation except IL-1β. Thus, based on the RNA-seq and qPCR data, we inferred that MDA5- and Jak-mediated signaling pathways may involve in the antiviral signaling transduction, and induce type I IFNs and ISGs to block virus invasion, respectively. Unfortunately, TLR3 and TLR22, as receptors of virus dsRNA, were no significantly expressed in this study. Nonetheless, our study still provides useful mRNA sequences of antiviral immunity for further immunological research, and facilitates improving disease restriction in S. prenanti.

Molecular characterization and expression analysis of Hsp90 in Schizothorax prenanti

Aquatic animals suffer from various environmental stresses because the aquatic environment is a very complex system. To monitor the health status of fish, Hsp90 a potential early warning marker was determined in Schizothorax prenanti after infection with a bacterium. In this study, we cloned Hsp90 from S. prenanti for the first time. The full-length cDNA sequence of SpHsp90 was 2663 bp, contains an open reading frame of 2181 bp, and has a gene encoding 726 amino acids, an estimated molecular mass of 83.38 kDa, and a theoretical isoelectric point of 4.91. The SpHsp90 amino acid sequence has five conserved HSP90 family signatures and shares 87.0-95.5 % identity with other vertebrates. Phylogenetic analysis and structure comparison indicated that SpHsp90 should be a β isoform of the HSP90 family. SpHsp90 was ubiquitously expressed in all examined tissues, and the highest level of expression was in the kidney. After Streptococcus agalactiae infection, the level of SpHsp90 expression had significant changes (P < 0.05) in the hepatopancreas, spleen, kidney, and blood. The expression increased to the highest level at 6 h in the blood and at 24 h in the hepatopancreas, spleen, and kidney. The results suggested that the SpHsp90 gene could be induced by S. agalactiae in S. prenanti and that SpHsp90 may be involved in resistance to bacterial infection and provide an early warning information. The kidney is the most suitable for detecting SpHsp90 after bacterial infection.

Molecular characterization of melanin-concentrating hormone (MCH) in Schizothorax prenanti: cloning, tissue distribution and role in food intake regulation

Melanin-concentrating hormone (MCH) is a crucial neuropeptide involved in various biological functions in both mammals and fish. In this study, the full-length MCH cDNA was obtained from Schizothorax prenanti by rapid amplification of cDNA ends polymerase chain reaction. The full-length MCH cDNA contained 589 nucleotides including an open reading frame of 375 nucleotides encoding 256 amino acids. MCH mRNA was highly expressed in the brain by real-time quantitative PCR analysis. Within the brain, expression of MCH mRNA was preponderantly detected in the hypothalamus. In addition, the MCH mRNA expression in the S. prenanti hypothalamus of fed group was significantly decreased compared with the fasted group at 1 and 3 h post-feeding, respectively. Furthermore, the MCH gene expression presented significant increase in the hypothalamus of fasted group compared with the fed group during long-term fasting. After re-feeding, there was a dramatic decrease in MCH mRNA expression in the hypothalamus of S. prenanti. The results indicate that the expression of MCH is affected by feeding status. Taken together, our results suggest that MCH may be involved in food intake regulation in S. prenanti.

Appetite regulation in Schizothorax prenanti by three CART genes

In recent years, cocaine- and amphetamine-regulated transcript (CART) has received much attention as mediators of appetite regulation in mammals. However, the involvement of CART in the feeding behavior of teleosts has not been well understood. In this study, three distinct CARTs were cloned from the Schizothorax prenanti (S. prenanti). Real-time quantitative PCR were applied to characterize the tissue distribution and appetite regulatory effects of CARTs in S. prenanti. The S. prenanti CART-1, CART-2 and CART-3 full-length cDNA sequences were 597 bp, 694 bp and 749 bp in length, encoding the peptides of 125, 120 and 104 amino acid residues, respectively. All the S. prenanti CARTs consisted of three exons and two introns. Tissue distribution analysis showed that the high mRNA levels of S. prenanti CART-1 were observed in the telencephalon and eye, followed by the hypothalamus, myelencephalon, and mesencephalon. The S. prenanti CART-2 mRNA was mainly found in the mesencephalon, hypothalamus, telencephalon and myelencephalon. The S. prenanti CART-3 mRNA was widely distributed among the tissues, with the high levels in the hypothalamus and foregut. In the periprandial experiment, all three CARTs mRNA expressions in the hypothalamus were highly elevated after a meal, suggesting that CARTs are postprandial satiety signals. In the fasting experiment, all three CARTs mRNA expressions decreased after fasting and increased after refeeding, suggesting that CARTs might be involved in regulation of appetite in the S. prenanti.

Leptin and cholecystokinin in Schizothorax prenanti: molecular cloning, tissue expression, and mRNA expression responses to periprandial changes and fasting

In the present study, full-length cDNA sequences of leptin and cholecystokinin (CCK) were cloned from Schizothorax prenanti (S. prenanti), and applied real-time quantitative PCR to characterize the tissue distribution, and appetite regulatory effects of leptin and CCK in S. prenanti. The S. prenanti leptin and CCK full-length cDNA sequences were 1121 bp and 776 bp in length, encoding the peptide of 171 and 123 amino acid residues, respectively. Tissue distribution analysis showed that leptin mRNA was mainly expressed in the liver of S. prenanti. CCK was widely expressed, with the highest levels of expression in the hypothalamus, myelencephalon, telencephalon and foregut of S. prenanti. The CCK mRNA expression was highly elevated after feeding, whereas the leptin mRNA expression was not affected by single meal. These results suggested that CCK is a postprandial satiety signal in S. prenanti, but leptin might not be. In present study, leptin and CCK gene expression were both decreased after fasting and increased after refeeding, which suggested leptin and CCK might be involved in regulation of appetite in S. prenanti. This study provides an essential groundwork to further elucidate the appetite regulatory systems of leptin and CCK in S. prenanti as well as in other teleosts.

Effects of Oxidized Konjac glucomannan (OKGM) on growth and immune function of Schizothorax prenanti

Schizothorax prenanti is an important existemic commercial fish in River Yangtze. OKGM (Oxidized Konjac glucomannan) is a kind of polysaccharide oxidative degraded from KGM. Added 500, 1000, 2000, 4000, 8000 mg/kg OKGM into the diets of S. prenanti. After 60 days feeding trial, WGR (weight gain rate), SGR (specific growth rate), PER (protein efficiency ratio) of groups fed the diet with 8000 mg/kg OKGM was all significantly (P < 0.05) higher; FCR (feed conversion ratio) was significantly lower than the control group whose diet have no OKGM. Hepatopancreas index, spleen index of group 6 whose feed added 8000 mg/kg OKGM were significantly higher and gallbladder index was significantly lower than the control group. Erythrocyte number, leukocyte number of group 5, 6 whose feed added 4000, 8000 mg/kg OKGM were excellent significantly (P < 0.01) more than the control group. At the same time, Erythrocyte phagocytic rate, erythrocyte phagocytic index, neutrophilic granulocyte phagocytic rate, neutrophilic granulocyte phagocytic index of all the groups whose diet added OKGM were significantly higher than the control group. Content of IgM, C3 of group 4 whose feed added 2000 mg/kg OKGM were significantly more than the control group. As for activity of CAT, group 6 was significantly higher than the control group. When compared activity of SOD, group 6 was significantly higher than group 1, 2, 3. Accordingly, activity of GSH-Px of group 3, 4, 5, 6 were significantly higher than the control group. On the contrary, content of MDA, group 3, 4, 5, 6 whose feed added 1000-8000 mg/kg OKGM was excellent significantly lower than the control group. After injected Aeromonas hydrophila 21 days, only group 6 whose feed added 8000 mg/kg OKGM survived excellent significantly more than the control group. So we can draw a conclusion of that added OKGM in the diets of S. prenanti, not only promoted growth, but also improved immune function, and the best dose was 8000 mg/kg in this experiment.

Cloning, distribution and effects of fasting status of melanocortin 4 receptor (MC4R) in Schizothorax prenanti

Melanocortin 4 receptor (MC4R) has an important role in the regulation of energy homeostasis in both mammals and fish. In this study, MC4R was characterized in S. prenanti (Schizothorax prenanti) and designated as SpMC4R. SpMC4R cDNA is composed of 1004 nucleotides with a 978 nucleotide open reading frame encoding a protein of 326 amino acids. The SpMC4R contained predicted regions that were structural features of MCR subtypes of vertebrates. In addition, phylogenetic analyses suggested that S. prenanti MC4R was closely related to fish MC4Rs. The SpMC4R mRNA was detected in embryos at developmental stages. Further, its mRNA was detectable in unfertilized eggs. Using real-time RT-PCR, MC4R is widely expressed, with highest levels of expression in brain and ovary. An experiment was conducted to determine the expression profile of MC4R during short-term and long-term fasting of the brain. The expression level of MC4R in unfed fish was significantly increased at 6, 9 and 24h post-fasting (hpf) and 14days fasting than in fed fish, this suggests that MC4R is conserved peptide that might be involved in the regulation of food intake and other physiological function in S. prenanti.

Identification, tissue distribution and regulation of preproghrelin in the brain and gut of Schizothorax prenanti

Ghrelin is an important gastrointestinal hormone involved in the regulation of feeding in both mammals and fish. In this study, the preproghrelin cDNA sequence was cloning in the gut of Schizothorax prenanti (S. prenanti). The preproghrelin gene, encoding 103-amino acids, was strongly expressed in the gut and brain using real-time quantitative RT-PCR (qPCR). The S. prenanti preproghrelin was detected in embryonic developmental stages. Further, it was detectable in unfertilized eggs, suggesting that ghrelin could be classified as maternal mRNA. An experiment was conducted to determine the expression profile of ghrelin during post-feeding and fasting status of the brain and gut. The results revealed a significant postprandial decrease in ghrelin mRNA expression in the gut 6h post-feeding (hpf) and brain (1.5 and 9hpf) compared to an unfed control group, indicating that food intake and processing affect the regulation of expression of ghrelin in S. prenanti. The constructed recombinant plasmid pMD-19T-ghrelin was transformed to Escherichia coli BL21 and induced with IPTG, and the expressed product was identified by SDS-PAGE. The prokaryotic expression vector for ghrelin was constructed successfully, and fusion protein was expressed in E. coli BL21, which laid the foundation for the further study on the function of this protein and its mechanism. Overall, our results provide evidence for a highly conserved structure and biological actions of ghrelin in S. prenanti. Further studies are required to identify the tissue specific functions of ghrelin in S. prenanti.

Characterization, tissue distribution and regulation of agouti-related protein (AgRP) in a cyprinid fish (Schizothorax prenanti)

Agouti-related protein (AgRP) is an important neuropeptide involved in the regulation of feeding in both mammals and fish. In this study, we have cloned the full-length cDNA sequence for AgRP in a cyprinid fish (Schizothorax prenanti). The AgRP gene, encoding 126-amino acids, was strongly expressed in the brain. The AgRP gene was detected in embryos at developmental stages. Further, its mRNA was detectable in unfertilized eggs. An experiment was conducted to determine the expression profile of AgRP during short-term and long-term fasting of the hypothalamus. The expression level of AgRP in unfed fish was significantly increased at 3 and 4h post-fasting than in fed fish but did not affect AgRP mRNA expression after 14 days fasting. Overall, our results suggest that AgRP is a conserved peptide that might be involved in the regulation of short-term feeding and other physiological function in Schizothorax prenanti.