Effects of Nano-sustained Release Sodium Butyrate on Growth and Intestinal Cell Proliferation of Grass Carps

Taking grass carps with the initial weight of about 20g as the research object,the basic feeds of grass carps were added with0.0%,0.1%,0.3%,0.6%,0.8%,and 1% of nano-sustained release sodium butyrate to prepare 6 types of experimental feeds with equal nitrogen and energy.The effects of different concentrations of nano-sustained release sodium butyrate were surveyed on growth and intestinal cell proliferation of grass carps.The experiment was carried out in cages with 50 carps per cage,and each treatment was repeated 3 times for60 days.Experimental results indicated that the addition of nano-sustained release sodium butyrate significantly promoted the growth of grass carps and significantly increased the ratio of intestinal villus to crypt depth.When the addition of nano-sustained release sodium butyrate was0.6%,the weight increase rate,specific growth rate,fullness and intestinal villus height of grass carps were the highest,which was significantly higher than that of the control group(P < 0.05).The study results indicated that addition of appropriate amount of nano-sustained release sodium butyrate can promote the growth of grass carps through increasing the intestinal villus height,and the suitable addition dosage was0.6%.

Unveiling the emerging role of curcumin to alleviate ochratoxin A-induced muscle toxicity in grass carp(Ctenopharyngodon idella):in vitro and in vivo studies

Background Ochratoxin A(OTA),a globally abundant and extremely hazardous pollutant,is a significant source of contamination in aquafeeds and is responsible for severe food pollution.The developmental toxicity of OTA and the potential relieving strategy of natural products remain unclear.This study screened the substance curcumin(Cur),which had the best effect in alleviating OTA inhibition of myoblast proliferation,from 96 natural products and investigated its effect and mechanism in reducing OTA myotoxicity in vivo and in vitro.Methods A total of 720 healthy juvenile grass carp,with an initial average body weight of 11.06±0.05 g,were randomly assigned into 4 groups:the control group(without OTA and Cur),1.2 mg/kg OTA group,400 mg/kg Cur group,and 1.2 mg/kg OTA+400 mg/kg Cur group.Each treatment consisted of 3 replicates(180 fish)for 60 d.Results Firstly,we cultured,purified,and identified myoblasts using the tissue block culture method.Through preliminary screening and re-screening of 96 substances,we examined cell proliferation-related indicators such as cell viability and ultimately found that Cur had the best effect.Secondly,Cur could alleviate OTA-inhibited myoblast differentiation and myofibrillar development-related proteins(Myo G and MYHC)in vivo and in vitro and improve the growth performance of grass carp.Then,Cur could also promote the expression of OTA-inhibited protein synthesis-related proteins(S6K1 and TOR),which was related to the activation of the AKT/TOR signaling pathway.Finally,Cur could downregulate the expression of OTA-enhanced protein degradation-related genes(murf1,foxo3a,and ub),which was related to the inhibition of the Fox O3a signaling pathway.Conclusions In summary,our data demonstrated the effectiveness of Cur in alleviating OTA myotoxicity in vivo and in vitro.This study confirms the rapidity,feasibility,and effectiveness of establishing a natural product screening method targeting myoblasts to alleviate fungal toxin toxicity.

Dietary protein levels changed the hardness of muscle by acting on muscle fiber growth and the metabolism of collagen in sub-adult grass carp(Ctenopharyngodon idella)

Background:Nutrient regulation has been proven to be an effective way to improve the flesh quality in fish.As a necessary nutrient for fish growth,protein accounts for the highest proportion in the fish diet and is expensive.Although our team found that the effect of protein on the muscle hardness of grass carp was probably related to an increased collagen content,the mechanism for this effect has not been deeply explored.Moreover,few studies have explored the protein requirements of sub-adult grass crap(Ctenopharyngodon idella).Therefore,the effects of different dietary protein levels on the growth performance,nutritional value,muscle hardness,muscle fiber growth,collagen metabolism and related molecule expression in grass carp were investigated.Methods:A total of 450 healthy grass carp(721.16±1.98 g)were selected and assigned randomly to six experimen-tal groups with three replicates each(n=25/replicate),and were fed six diets with 15.91%,19.39%,22.10%,25.59%,28.53%and 31.42%protein for 60 d.Results:Appropriate levels of dietary protein increased the feed intake,percentage weight gain,specific growth rate,body composition,unsaturated fatty acid content in muscle,partial free amino acid content in muscle,and muscle hardness of grass carp.These protein levels also increased the muscle fiber density,the frequency of new muscle fibers,the contents of collagen and IGF-1,and the enzyme activities of prolyl 4-hydroxylases and lysyloxidase,and decreased the activity of matrix metalloproteinase-2.At the molecular level,the optimal dietary protein increased col-lagen type Iα1(Colα1),Colα2,PI3K,Akt,S6K1,La ribonucleoprotein domain family member 6a(LARP6a),TGF-β1,Smad2,Smad4,Smad3,tissue inhibitor of metalloproteinase-2,MyoD,Myf5,MyoG and MyHC relative mRNA levels.The levels of the myostatin-1 and myostatin-2 genes were downregulated,and the protein expression levels of p-Smad2,Smad2,Smad4,p-Akt,Akt,LARP6 and Smad3 were increased.Conclusions:The appropriate levels of dietary protein promoted the growth of sub-adult grass carp and improved muscle hardness by promoting the growth of muscle fibers,improving collagen synthesis and depressing collagen degradation.In addition,the dietary protein requirements of sub-adult grass carp were 26.21%and 24.85%according to the quadratic regression analysis of growth performance(SGR)and the muscle hardness(collagen content),respectively.

Implications of vitamin D for flesh quality of grass carp(Ctenopharyngodon idella):antioxidant ability,nutritional value,sensory quality,and myofiber characteristics

Background Muscle represents a unique and complex system with many components and comprises the major edible part of animals.Vitamin D is a critical nutrient for animals and is known to enhance calcium absorption and immune response.In recent years,dietary vitamin D supplementation in livestock has received increased attention due to biological responses including improving shear force in mammalian meat.However,the vitamin D acquisition and myofiber development processes in fish differ from those in mammals,and the effect of vitamin D on fish flesh quality is poorly understood.Here,the influence of dietary vitamin D on fillet quality,antioxidant ability,and myofiber development was examined in grass carp(Ctenopharyngodon idella).Methods A total of 540 healthy grass carp,with an initial average body weight of 257.24±0.63 g,were allotted in 6 experimental groups with 3 replicates each,and respectively fed corresponding diets with 15.2,364.3,782.5,1,167.9,1,573.8,and 1,980.1 IU/kg vitamin D for 70 d.Results Supplementation with 1,167.9 IU/kg vitamin D significantly improved nutritional value and sensory quality of fillets,enhancing crude protein,free amino acid,lipid,and collagen contents;maintaining an ideal pH;and reduc-ing lactate content,shear force,and cooking loss relative to respective values in the control(15.2 IU/kg)group.Average myofiber diameter and the frequency of myofibers>50μm in diameter increased under supplementation with 782.5–1,167.9 IU/kg vitamin D.Levels of oxidative damage biomarkers decreased,and the expression of antioxi-dant enzymes and nuclear factor erythroid 2-related factor 2 signaling molecules was upregulated in the 1,167.9 IU/kg vitamin D treatment compared to respective values in the control group.Furthermore,vitamin D supplementation activated cell differentiation by enhancing the expression of myogenic regulatory factors and myocyte enhancer factors compared to that in the control group.In addition,supplementation with 1,167.9 IU/kg vitamin D improved protein deposition associated with protein synthesis molecule(target of rapamycin)signaling and vitamin D receptor paralogs,along with inhibition of protein degradation(forkhead box protein 1)signaling.Conclusions Overall,the results demonstrated that vitamin D strengthened antioxidant ability and myofiber devel-opment,thereby enhancing nutritional value and sensory quality of fish flesh.These findings suggest that dietary vitamin D supplementation is conducive to the production of nutrient-rich,high quality aquaculture products.

Mannan oligosaccharides alleviate oxidative injury in the head kidney and spleen in grass carp(Ctenopharyngodon idella)via the Nrf2 signaling pathway after Aeromonas hydrophila infection

Background Mannan oligosaccharides(MOS)are recommended as aquaculture additives owing to their excellent antioxidant properties.In the present study,we examined the effects of dietary MOS on the head kidney and spleen of grass carp(Ctenopharyngodon idella)with Aeromonas hydrophila infection.Methods A total of 540 grass carp were used for the study.They were administered six gradient dosages of the MOS diet(0,200,400,600,800,and 1,000 mg/kg)for 60 d.Subsequently,we performed a 14-day Aeromonas hydrophila challenge experiment.The antioxidant capacity of the head kidney and spleen were examined using spectrophotometry,DNA fragmentation,qRT-PCR,and Western blotting.Results After infection with Aeromonas hydrophila,400-600 mg/kg MOS supplementation decreased the levels of reactive oxygen species,protein carbonyl,and malonaldehyde and increased the levels of anti-superoxide anion,antihydroxyl radical,and glutathione in the head kidney and spleen of grass carp.The activities of copper-zinc superoxide dismutase,manganese superoxide dismutase,catalase,glutathione S-transferase,glutathione reductase,and glutathione peroxidase were also enhanced by supplementation with 400-600 mg/kg MOS.Furthermore,the expression of most antioxidant enzymes and their corresponding genes increased significantly with supplementation of 200-800 mg/kg MOS.mRNA and protein levels of nuclear factor erythroid 2-related factor 2 also increased following supplementation with 400-600 mg/kg MOS.In addition,supplementation with 400-600 mg/kg MOS reduced excessive apoptosis by inhibiting the death receptor pathway and mitochondrial pathway processes.Conclusions Based on the quadratic regression analysis of the above biomarkers(reactive oxygen species,malondialdehyde,and protein carbonyl)of oxidative damage in the head kidney and spleen of on-growing grass carp,the recommended MOS supplementation is 575.21,557.58,531.86,597.35,570.16,and 553.80 mg/kg,respectively.Collectively,MOS supplementation could alleviate oxidative injury in the head kidney and spleen of grass carp infected with Aeromonas hydrophila.

Growth,digestive and absorptive capacity and antioxidant status in intestine and hepatopancreas of sub-adult grass carp Ctenopharyngodonidella fed graded levels of dietary threonine

Background： This study was carried out to investigate effects of threonine levels on growth, digestive and absorptive capacity and antioxidant status in intestine and hepatopancreas of sub-adult grass carp （ Ctenopharyngodonidella）. Results： Weight gain, specific growth rate, feed intake and feed efficiency were significantly improved by dietary threonine （P 〈 0.05）. Intestinal activities of trypsin, chymotrypsin, alpha-amylase, lipase, alkaline phosphatase, y-glutamyl transpeptidase and creatine kinase took the similar trends. Contents of malondialdehyde and protein carbonyl in intestine and hepatopancreas were significantly decreased by dietary optimal threonine supplementation （P 〈 0.05）. Anti-superoxide anion capacity, anti-hydroxyl radical capacity, glutathione content and activities of superoxide dismutase, catalase and glutathione-S-transferase in intestine and hepatopancreas were enhanced by dietary threonine （P 〈 0.05）. Conclusions： Dietary threonine could improve growth, enhance digestive and absorptive capacity and antioxidant status in intestine and hepatopancreas of sub-adult grass carp. The dietary threonine requirement of sub-adult grass carp （441.9-1,013.4 g） based on weight gain was 11.6 g/kg diet or 41.5 g/kg of dietary protein by quadratic regression analysis.

Construction and Characterization of Grass Carp (Ctenopharyngodon idellus) Fosmid Library

Grass carp （Ctenopharyngodon idellus） genomic fosmid library cotaining 129 014 clones was constructed and characterized from one diploid grass carp. The average insert size of the fosmid library was determined to be 35 kb by pulsed field gel electrophoresis, which is 4.1-fold coverage of the grass carp genome. To demonstrate the probability of picking the functional genes from the library, eleven functional genes were screened by three-dimensional PCR technique. The number of positive clones of these genes was from 1 to 6. So, this library may screen any useful genes from grass carp. This grass carp genome fosmid library will be integrated in the presently ongoing efforts to determine the sequence of the grass carp genome.

Renal failure and hepatitis following ingestion of raw grass carp gallbladder:A case report

BACKGROUND Fish gallbladder has long been used as a folk remedy in Asian countries.Multiple organ damage after ingestion of fish gallbladder resulting in near mortality has been known to us.Here,we describe a case of acute renal failure(ARF)and hepatitis due to grass carp gallbladder poisoning and review the literature.CASE SUMMARY A previously healthy,50-year-old woman was admitted to our hospital with a 2-d history of generalized abdominal pain and repeated vomiting following ingestion of two raw grass carp gallbladders in an attempt to alleviate her cough.She developed anuria on day 4 with markedly elevated serum creatinine,urea,bilirubin,alanine aminotransferase,and aspartate aminotransferase.Based on thorough evaluation of her history and prompt biochemical investigations,we diagnosed her with ARF and hepatitis secondary to fish gallbladder poisoning.Her renal biopsy revealed acute tubular necrosis,following which she underwent six sessions of conventional hemodialysis due to renal failure.Supportive treatment with gastric mucosal protectant and liver protectant was administered for targeted organ protection.The patient’s liver function gradually recovered,and serum creatinine was 164 mmol/L at discharge on day 24.Over a follow-up period of 2 wk,her renal function completely recovered.CONCLUSION Physicians should be mindful of toxic complications of raw grass carp gallbladder ingestion and we should promote awareness to reduce incidences of food poisoning.

Study on the Feeding Intensity of Grass Carp at Different Physiological Stages on Water Hyacinth ( Eichhornia crassipe )

[Objectives]This study was conducted to investigate the feeding intensity of different sizes of grass carp on water hyacinth.[Methods]Grass carp of 10 sizes,i.e.,50,100,150,200,250,300,350,400,450 and 500 g,were put in cages.Thirty grass carp were stocked in each cage,and only water hyacinth was fed.The grass carp were caught after 120 d,and the food intake and growth of the grass carp were analyzed.[Results]The body weight of all sizes of grass carp increased significantly,and the overall length of grass carp increased significantly.Compared with feeding feed,the body length and body weight in the experimental treatments were lower,and they were more slender;and the feed coefficient of small-sized grass carp was slightly larger than that of large-sized grass carp.When the stocking size was above 414.7 g,the net weight gain of grass carp increased rapidly,and the total food intake also increased.[Conclusions]This study provides a theoretical basis for achieving an ideal purification effect of water hyacinth on aquaculture water by maintaining the growth of grass carp and the biomass and coverage of water hyacinth within suitable ranges.

Production and characterization of monoclonal antibodies against grass carp CD4-1 and CD4-2

CD4 T helper cells are an important group of cells in the immune system of vertebrates and express CD4 receptor on the cell surface.In mammals,the CD4 receptor is encoded by a single copy gene,whilst in fish,two copies of cd4 genes,namely cd4-1 and cd4-2,are found.In this study,the ectodomains of grass carp(Ctenopharyngodon idella,Ci)CD4-1 and CD4-2 were expressed in the E.coli cells and used to generate monoclonal antibodies in mice.Western blotting,confocal microscopy and flow cytometry were performed to characterize the monoclonal antibodies.It has been shown that the CiCD4-1 and CiCD4-2 monoclonal antibodies had good specificity to react with the recombinant ectodomains of CiCD4-1 and CiCD4-2 expressed in the CHO-S cells and the native CD4 molecules of grass carp.The CiCD4-1 monoclonal antibody did not recognize CiCD4-2 and verse versa.In addition,the CD4-1 and CD4-2 monoclonal antibodies specifically recognized the CD4-1 and CD4-2 receptors expressed in the HEK293 cells and native molecules of fish cells.Further,the percentages of lymphocytes in immune tissues of healthy fish were analyzed by flow cytometry.It was found that 17.6%of lymphocytes were CD4-1^(+)cells and 22.5%were CD4-2^(+)in the head kidney.In the spleen,13.1%of lymphocytes were CD4-1^(+)and 18.6%were CD4-2^(+)while 7.3%of blood lymphocytes were CD4-1^(+)cells and 8.8%were CD4-2^(+)cells.The availability of the CD4-1 and CD4-2 monoclonal antibodies provides antibody-based tools for further elucidation of the functions of CD4 T cells in grass carp.

草鱼血液的研究

本文报道了212尾池养草鱼Ctenopharyngodon idellus的血液中红细胞数、自细胞数、血红蛋白值、红细胞脆性值、比积及比重值、血细胞沉降率、白细胞分类计数和各型血细胞体的大小等正常数值和上述常数值在雌雄个体上的差异,以及鱼体年龄和繁殖季节产卵前后的差异等,为草鱼血液的常数值提供了较为系统的资料。

阿维菌素·毒死蜱对草鱼的毒性效应研究(英文)

[ Objective] The study aimed to discuss the toxicity effect of abamectin and ehlorpyrifos on grass carp （ Ctenopharyngdon idllus ） and their interrela- tions. [ Method] Taking healthy and active grass carp as the object, the acute toxicity test of single pesticide and the combined toxicity test of two pesticides on grass carp were carried out. [ Result] The LC50 of abamectin and chlorpyrifes and the mixture of two pesticides against grass carp at 24, 48, 72 and 96 h were as follows： abamectin： 0.54, 0.49, 0. 17 and 0.10 rag/L; chlorpyrifes ： 0.29, 0.21, 0.12 and 0.05 rag/L; the mixture of two pesticides ： 1.22, 1.08, 0.99 and 0. 86 mg/L. The safe concentration （SC） of ahamectin, chlorpyrifos and the mixture of two pesticides were 0.010, 0.005 and 0.086 rag/L, respectively. The tox- icity of the pesticides in sequence was ablorpyrifos 〉 ahamectin 〉 the mixture of two pesticides. [ Conclusion ] Different concentrations of abamectin, chlorpyrifos and the mixture of two pesticides had remarkable effect on the growth of grass carp, the higher the concentration was, the greater the toxicity effect was. Ahamectin at low toxicity intensity had certain relief function on the toxicity of ehlorpyrifos.

Study of Embryonic and Postembryonic Development of the Hybrid(Ctenopharyngodon idellus ♀ ×Elopichthys bambusa♂)

[ Objective ] The purpose was to provide a reference for crossbreeding of grass carp. [ Method] We conducted hybridization between Ctenopharyngodon ideUus （ ♀ ） and Elopichthys bambusa ♂ ） by artificial methods. The process of embryo and postembryonic development were observed and recorded. [ Result ] The fertilization rate, hatching rate and survival rate of the hybrid F1 were （75.8 ± 6. 2）%, （41.9 ± 8.2）% and （9.3± 3.7）%, respectively. At the water temperature of 20.1 -21.6℃, the larvae was hatched for about 34 h and 25 rain after fertilization. The whole length of newly-hatched larvae of the hybrid Fl was （5.8 ± 0.12） mm. The larvae could feed rotifer and unicellular algae after 3 or 4 days hatching. Postembryonic development of the hybrid at the formation of scales, lasted for 65 days when the young was（74.0 ± 2.1 ） mm in whole length. [ Conclusion] The embryonic development of hybrid F1 was intermediate to their parents, the form of the hybrid F1 was similar to that of their female line of grass carp. The growth rate of larva was faster than that of grass carp and similar to that of their paternal fish.

Improving flesh quality of grass carp(Ctenopharyngodon idellus)by completely replacing dietary soybean meal with yellow mealworm(Tenebrio molitor)

In order to find viable alternative protein sources for aquaculture,we evaluated the effect of partial or complete replacement of dietary soybean meal with yellow mealworm(TM)on the flesh quality of grass carp.In this study,180 grass carp(511.85±0.25 g)were fed 3 experimental diets in which 0%(CN),30%(YM30)and 100%(YM100)dietary soybean meal was replaced by TM for 90 d.The results showed that growth performance,biological parameters and serum antioxidant capacity of grass carp were not affected by dietary TM(P>0.05).Both muscle and whole body crude protein were obviously promoted with the increase of dietary TM(P<0.05),and the concentration of heavy metal in muscle was not influenced(P>0.05),indicating that food safety was not influenced by TM.Dietary TM improved muscle textural characteristics by elevating adhesiveness,springiness and chewiness in YM100(P<0.05).In addition,the muscle tenderness was significantly increased by declining the shear force(P<0.05).The muscle fiber density in YM30&YM100 and length of dark bands and sarcomeres in YM100 were obviously increased(P<0.05).The expression of myf5,myog and myhc exhibited a significant upward trend with the increase of dietary TM(P<0.05),which promoted fiber density,length of sarcomere and texture of grass carp muscle.According to the results of metabolomics,the arachidonate(ARA)and eicosapentaenoic acid(EPA)were notably elevated in YM30 and YM100,which indicated that the improvement of flesh quality of grass carp may contribute to the dietary TM influence on muscle lipid metabolism,especially the polyunsaturated fatty acids.In conclusion,TM can completely replace dietary soybean meal and improve the nutritional value of grass carp.

Temperature-regulated typeⅡgrass carp reovirus establishes latent infection in Ctenopharyngodon idella brain

Grass carp reovirus(GCRV)causes extensive infection and death in grass carp and black carp fingerlings,with a highly seasonal prevalence.Previous studies suggested that GCRV can become latent after primary infection.In this study,we investigated type II GCRV(GCRV-II)latency in asymptomatic grass carp with GCRV infection or exposure history.We found that during latent infection,GCRV-II was detectable only in the brain of grass carp,unlike the multi-tissue distribution observed in natural infection.GCRV-II only caused damage to the brain during latent infection,while in natural infection,brain,heart,and eye tissues had relatively higher viral loads.We also discovered viral inclusion bodies in infected fish brains.Additionally,GCRV-II distribution in grass carp was notably affected by ambient temperature,with the virus targeting the brain only during low temperatures and multi-tissue distribution during high temperatures.This study provides insights into the mechanisms of GCRV-II latent infection and reactivation and contributes to the prevention and control of GCRV pandemics.

Electrophoretic Analysis of Isozymes and Proteins in F_1 Hybrids of Ctenopharyngodon idellus ♀ × Elopichthys bambusa ♂

[ Objective] This study aimed to investigate the biochemical and genetic characteristics of F1 hybrids of Ctenopharyngodon idellus ♀× Elopichthys bambusa ♂ - [ Method ] By using vertical polyacrylamide gel electrophoresis technology, three isozymes （LDH, EST, MDH） in nine tissues （heart, brain, eyes, liver, kidney, spleen, fin, muscle, plasma） of F1 hybrids of C. ideUus and parents were compared. [Result] Three isozymes in F1 hybrids of ♀× E. bambusa ♀ were analyzed; differences in isozyme and proteins between F1 hybrids idellus ♀× E. bambusa ♀ exhibited varying degrees of tissue-specificity; isozymes and proteins in F, hybrids were signiticandy different from the parents. [ Conclusion] These nine differences could be used as indicators to identify F1 hybrids and parents.

Native Aquatic Plant Establishment Efforts in a High-Herbivore, Central Texas Reservoir

Maintaining beneficial, native plant structure and diversity while reducing invasive, nuisance species dominance is an important management domain for natural resource managers. One such vegetation component in North American lakes and reservoirs is submerged aquatic vegetation—a valuable aquatic resource which serves as productive habitat for fish, aquatic macroinvertebrates, and other wildlife. Reservoirs in the southern parts of the United States have experienced varying aquatic plant dominance dynamics due to historical water resource management actions, including drawdowns and introduction of herbivorous fish for the purpose of controlling invasive aquatic vegetation. Some of these management options have also been detrimental to native submerged aquatic vegetation. This paper explores an adaptive management research effort by installing herbivore-protected, fenced-pen submerged aquatic vegetation sites in a high-herbivore reservoir to determine effectiveness of protecting habitat and serving as founder colony sources for propagule spread. Four experimental sites with three management treatments each were planted with American eelgrass. Each site utilized one un-fenced treatment and two treatments with varying mesh sizes for protective fencing-pens. Site integrity, species survival and spread, and grazing were documented. One additional site was installed and planted with other native submerged aquatic vegetation species for nominal species performance descriptions. No plants survived unprotected in the high-herbivore system and plants, in general, performed consistently better within the smaller mesh size. These test planting results were ultimately used to inform adaptive management decision making for plant installation and expansion designs for managing reservoirs invested with Hydrilla, considered one of the most serious invasive aquatic plants in the United States.

Assessment of Heavy Metal Pollution in the Water, Sediment and Fish during a Complete Breeding Cycle in the Pond of the Pearl River Delta, China

The paper aimed to investigate the concentration variations and evaluate the bioaccumulation as well as the health risk of Cr, Ni, Cu, Zn, As, Cd and Pb in the aquaculture pond ecosystem during a complete breeding cycle. The samples of water, sediment and aquatic organisms were collected from the pond of gull island in the Pearl River Delta, China. In the breeding cycle, the results revealed the metal concentration in the water increased, while the sediment metal concentration showed no significant difference. The heavy metal concentrations in the water were higher than the background values (December 2017) which related to the input of feeds. Sediment metal concentrations (Cr, Ni, Cu, Zn, As and Cd) in the sediment were higher than the background values of Guangdong Province, China, indicating these metal pollutions came from anthropogenic activities. While the concentration of Pb was comparable to the background value, implying that the Pb was mainly from the earth crust. In addition, various metals showed different affinity to fish organs (muscle, skin, bladder, gill, heart, kidney and liver). Zinc was abundant in skin, while As and Cd concentrations were highest in kidneys;Cu was accumulated highest in liver;Cr concentrations was highest in hearts;and Ni was mainly found in bladders, and the Pb was most commonly found in gills. The distribution of heavy metals in the tissues organs was in the sequence of: Zn > Cu > Cr > Ni > Pb > As > Cd. As the fish ages, the Cu and Zn concentration in tissue organs declined, while the Cr, Ni, As, Cd and Pb increased slightly. Estimations of health risks showed no evidence of potential threats to consumers.

DHA induces adipocyte lipolysis through endoplasmic reticulum stress and the cAMP/PKA signaling pathway in grass carp(Ctenopharyngodon idella)

Docosahexaenoic acid(DHA)is a biologically active fatty acid that reduces the accumulation of lipids.However,the molecular mechanism underlying this process,particularly in fish,is not well understood.Recent studies show that endoplasmic reticulum(ER)stress triggers the activation of the unfolded protein response,which has been revealed to play an essential role in lipid metabolism.In this study,we explored the effect of DHA on ER stress and investigated the potential molecular mechanisms underlying DHA-induced adipocyte lipolysis in grass carp(Ctenopharyngodon idella)both in vivo and in vitro.We found that DHA remarkably reduced the triglyceride content,increased the secretion of glycerol,pro-moted lipolysis in adipocytes and evoked ER stress,whereas inhibiting ER stress using 4-phenyl butyric acid(4-PBA)inhibited the effects of DHA(P<0.05).These results implied that ER stress potentially participates in DHA-induced adipocyte lipolysis.Additionally,STF-083010,a specific inositol-requiring enzyme 1a(IRE1a)-inhibitor,attenuated the effects of DHA on lipolysis,demonstrating that IRE1a and X-box binding protein 1 potentially participate in DHA-induced lipolysis.DHA also activated the cyclic adenosine monophosphate(cAMP)-dependent protein kinase A(PKA)pathway by increasing the level of cAMP and activating the PKA enzyme(P<0.05).Nevertheless,H89,a PKA inhibitor,weakened DHA-induced lipolysis by inhibiting the cAMP/PKA signaling pathway.Furthermore,inhibiting ER stress us-ing 4-PBA also inhibited lipolysis and alleviated DHA-induced activation of the cAMP/PKA signaling pathway,suggesting that ER stress may participate in DHA-induced lipolysis through the activation of the cAMP/PKA signaling pathway.Our data illustrate that DHA supplementation can be a promising nutritional strategy for ameliorating lipid accumulation in grass carp.The present study elucidated the molecular mechanism for DHA-induced lipolysis in grass carp adipocytes and emphasized the impor-tance of ER stress and the cAMP/PKA pathway in DHA-induced lipolysis.These results deepen our un-derstanding of ameliorating lipids deposition in freshwater fish by targeting DHA.

Selenium reduces hepatopancreas lipid accumulation of grass carp(Ctenopharyngodon idella)fed high-fat diet via lipophagy activation

It has been reported that selenium(Se)can reduce hepatopancreas lipid accumulation induced by highfat diet.However,its mechanism is still unknown.This study aims to investigate the specific mechanisms by which Se alleviates high-fat diet-induced lipid accumulation.Grass carp were fed control diet(4.8%lipid,Con),high-fat diet(8.8%lipid,HFD)or HFD supplemented with 0.3 mg/kg nano-Se(HSe0.3)for 10weeks.Growth performance,Se deposition,lipid accumulation,hepatic ultrastructure,and gene and protein expression levels associated with autophagy were examined.Furthermore,oleic acid(OA)was used to incubate the grass carp hepatocytes(L8824)for 24 h,and then the L8824 were incubated with sodium selenite in presence or absence of an autophagy inhibitor for 24 h.L8824 was analyzed for triglyceride concentration,immunofluorescence,and gene and protein expression levels associated with autophagy.We found that dietary nano-Se improved the growth of fish fed HFD and also decreased hepatosomatic index and intraperitoneal fat ratio of fish fed HFD(P<0.05).HFD significantly increased hepatopancreas lipid accumulation and decreased autophagic activity(P<0.05).Treatment of grass carp fed HFD with nano-Se decreased lipid accumulation and restored hepatic autophagy(P<0.05).In vitro,Se(100μM sodium selenite)obviously activated autophagy in L8824 incubated with OA,and consequently reduced the lipid accumulation induced by OA(P<0.05).Furthermore,using pharmacological inhibition(chloroquine)of the autophagy greatly diminished the beneficial effects of Se on alleviating OA-induced lipid accumulation and increased the co-localization of lipid droplets with autophagosome(P<0.05),which indicated that Se increased autophagic flux.In conclusion,these results suggest that Se alleviates HFD-induced hepatopancreas lipid accumulation by activating lipophagy.