Xylanase improves the intestinal barrier function of Nile tilapia(Oreochromis niloticus)fed with soybean(Glycine max)meal

Background Soybean(Glycine max)meal is one of the important protein sources for fish,but the non-starch polysaccharides(NSP)in soybean meal impair the intestinal barrier function.Here we aimed to investigate whether xylanase can alleviate the adverse effects on the gut barrier induced by soybean meal in Nile tilapia and to explore the possible mechanism.Results Nile tilapia(Oreochromis niloticus)(4.09±0.02 g)were fed with two diets including SM(soybean meal)and SMC(soybean meal+3,000 U/kg xylanase)for 8 weeks.We characterized the effects of xylanase on the gut barrier,and the transcriptome analysis was performed to investigate the underlying mechanism.Dietary xylanase improved intestinal morphology and decreased the concentration of lipopolysaccharide(LPS)in serum.The results of transcriptome and Western blotting showed that dietary xylanase up-regulated the expression level of mucin2(MUC2)which may be related to the inhibition of protein kinase RNA-like endoplasmic reticulum kinase(perk)/activating transcription factor 4(atf4)signaling pathways.Microbiome analysis showed that addition of xylanase in soybean meal altered the intestinal microbiota composition and increased the concentration of butyric acid in the gut.Notably,dietary sodium butyrate was supplemented into the soybean meal diet to feed Nile tilapia,and the data verified that sodium butyrate mirrored the beneficial effects of xylanase.Conclusions Collectively,supplementation of xylanase in soybean meal altered the intestinal microbiota composition and increased the content of butyric acid which can repress the perk/atf4 signaling pathway and increase the expression of muc2 to enhance the gut barrier function of Nile tilapia.The present study reveals the mechanism by which xylanase improves the intestinal barrier,and it also provides a theoretical basis for the application of xylanase in aquaculture.

Hypoxia tolerance in fish depends on catabolic preference between lipids and carbohydrates

Hypoxia is a common environmental stress factor in aquatic organisms,which varies among fish species.However,the mechanisms underlying the ability of fish species to tolerate hypoxia are not well known.Here,we showed that hypoxia response in different fish species was affected by lipid catabolism and preference for lipid or carbohydrate energy sources.Activation of biochemical lipid catabolism through peroxisome proliferator-activated receptor alpha(Pparα)or increasing mitochondrial fat oxidation in tilapia decreased tolerance to acute hypoxia by increasing oxygen consumption and oxidative damage and reducing carbohydrate catabolism as an energy source.Conversely,lipid catabolism inhibition by suppressing entry of lipids into mitochondria in tilapia or individually knocking out three key genes of lipid catabolism in zebrafish increased tolerance to acute hypoxia by decreasing oxygen consumption and oxidative damage and promoting carbohydrate catabolism.However,anaerobic glycolysis suppression eliminated lipid catabolism inhibition-promoted hypoxia tolerance in adipose triglyceride lipase(atgl)mutant zebrafish.Using 14 fish species with different trophic levels and taxonomic status,the fish preferentially using lipids for energy were more intolerant to acute hypoxia than those preferentially using carbohydrates.Our study shows that hypoxia tolerance in fish depends on catabolic preference for lipids or carbohydrates,which can be modified by regulating lipid catabolism.

甘肃不同产地黄管秦艽中无机元素的相关性和主成分分析

以甘肃不同产地黄管秦艽为材料,测定其无机元素含量,分析黄管秦艽中无机元素特征及评价药材质量。采用火焰原子吸收光谱法测定黄管秦艽中无机元素含量,并运用相关性分析和主成分分析对其含量进行分析和评价。结果表明不同产地黄管秦艽中无机元素Ca、K、Mg、Mo含量较高,部分无机元素之间存在相关性;经主成分分析得到3个主因子,3个主成分的累计方差贡献率为83.20%。从无机元素含量的主成分分析来看,产于卓尼县尼巴乡的黄管秦艽质量最优,本实验可为黄管秦艽的资源开发利用、质量控制以及安全评价提供参考依据。

基于遗传算法的无线传感器网络非均匀分簇路由协议

无线传感器网络能量消耗不均衡易造成网络中某一区域的传感器节点因能量过快消耗而死亡,被称为“热点”问题。为此,提出了一种基于遗传算法的无线传感器网络非均匀分簇路由协议(Unequal clustering routing protocol based on genetic algorithm,UCR-GA)。簇头选举阶段,综合考虑节点的剩余能量、密度和距离来构造适应度函数,并选择合适的节点作为簇头;数据传输阶段,簇头根据与基站的距离选择通信方式为单跳或者多跳,在综合考虑簇头剩余能量及其与基站的通信能耗的基础上,选择出合适的中继节点。对设计的协议在能量同构和能量异构的条件下分别进行仿真,结果表明,该协议能够有效均衡能量消耗,延长网络生命周期,并适用于异构网络。

硼烷缺电子多中心桥键的H-F力研究

Hellmann-Feynman静电力表现了分子中电荷分布及对各原子核的作用。H-F力的方向性可描述电子电荷的数量和位置,具有定量、形象和直观的特点,已在弯键的研究中显示出来。这一方法尚可用于多中心缺电子桥键的研究。1理论与方法按LCAO-MO理论对H-F力进行分解,除有重叠力、极化力和屏蔽力外.

雄激素受体缺乏抑制肝脏Vtg合成导致卵巢发育障碍

为研究雄激素受体(Androgen receptor,Ar)在卵巢发育中的作用机制,文章以雄性激素受体敲除的雌性斑马鱼(Danio rerio;ar^(–/–))为研究对象,利用ELISA和蛋白质免疫印迹等方法分析Ar对斑马鱼肝脏中卵黄蛋白原(Vitellogenin,Vtg)产生、母体营养通过Vtg运输、卵黄形成和卵巢成熟的影响。研究发现在ar^(–/–)雌性斑马鱼的肝脏中,Vtg的产生和雌激素受体的表达水平显著降低。在ar^(–/–)雌性斑马鱼中的卵巢质量、脂质含量和类胡萝卜素含量均显著下降,表明Ar的缺失可导致雌性斑马鱼通过Vtg转运到卵巢的脂质和类胡萝卜素等营养物质供应减少。此外,ar^(–/–)雌性斑马鱼中与卵巢发育相关的几个基因转录表达水平显著下调,这与卵巢发育异常存在相关性。研究结果表明,Ar的缺乏可通过对肝脏中的雌激素受体表达的影响,降低肝脏Vtg蛋白的合成,从而损害由Vtg向卵巢的营养物质运输和卵黄的正常形成,影响卵巢发育。研究阐明了雄激素信号通路与体内肝脏Vtg产生之间的联系。

气相色谱法测定黄瓜中丙溴磷农药残留量的测量不确定度评定

为评定检测方法NY/T 761-2008处理的黄瓜中丙溴磷农药残留检测结果的测量不确定度,找出对测量不确定度影响大的因素,规范实验操作,提高检测结果的准确性,本文通过外部加标,建立数学模型,从量器使用、标准工作液配制、重复性测量等各个分量进行评定。结果表明,丙溴磷残留量0.45 mg/kg,其扩展标准不确定度0.04 mg/kg,对测量不确定度有显著贡献的有三个方面:标准物质纯度的相对标准不确定度2%;使用6次移液器产生的相对标准不确定度2.661%;标准曲线拟合的相对标准不确定度1.615%。因此,在检测中,建议购买纯度在98.6%以上的标准溶液,做好贮存和期间核查;在配制标准工作液时,减少使用移液器的频次或使用更精密的量器且定期做好校准;按时做好测量仪器的检定和期间核查。

敲除 SOCS1a 基因对斑马鱼肝脏氧化应激的影响

为探讨SOCS1a基因敲除对斑马鱼肝脏氧化应激的影响,以SOCS1a敲除系为试验组,同胞野生型为对照组,分别采用高脂和普通饲料喂养成年斑马鱼6周后,对试验组和对照组斑马鱼的肝脏组织进行透射电镜(TEM)分析,肝脏中抗氧化酶活力测定及转录组分析。TEM结果显示:SOCS1a基因敲除的斑马鱼肝组织线粒体出现异常膨胀现象,线粒体脊密度明显减少,肝细胞中有明显的脂滴积累;抗氧化酶检测结果显示,在普通饲料饲养条件下,SOCS1a敲除组肝脏中超氧化物歧化酶(SOD)和谷胱甘肽还原酶(GR)活力分别低于野生型组27.813和3.879 U/mg(prot)。在高脂条件下,SOCS1a敲除组肝脏中SOD和GR活力分别低于野生型组14.015和3.865 U/mg(prot);转录组数据分析显示,敲除SOCS1a基因后,导致斑马鱼肝脏氧化应激相关信号通路显著上调。敲除斑马鱼SOCS1a基因对机体造成了一定的氧化损伤,发生氧化应激反应,而在高脂诱导下,氧化应激反应更为激烈。

Uridine alleviates high-carbohydrate diet-induced metabolic syndromes by activating sirt1/AMPK signaling pathway and promoting glycogen synthesis in Nile tilapia(Oreochromis niloticus)

Carbohydrates have a protein sparing effect,but long-term feeding of a high-carbohydrate diet(HCD)leads to metabolic disorders due to the limited utilization efficiency of carbohydrates in fish.How to mitigate the negative effects induced by HCD is crucial for the rapid development of aquaculture.Uridine is a pyrimidine nucleoside that plays a vital role in regulating lipid and glucose metabolism,but whether uridine can alleviate metabolic syndromes induced by HCD remains unknown.In this study,a total of480 Nile tilapia(Oreochromis niloticus)(average initial weight 5.02±0.03 g)were fed with 4 diets,including a control diet(CON),HCD,HCD+500 mg/kg uridine(HCUL)and HCD+5,000 mg/kg uridine(HCUH),for 8 weeks.The results showed that addition of uridine decreased hepatic lipid,serum glucose,triglyceride and cholesterol(P<0.05).Further analysis indicated that higher concentration of uridine activated the sirtuin1(sirt1)/adenosine 5-monophosphate-activated protein kinase(AMPK)signaling pathway to increase lipid catabolism and glycolysis while decreasing lipogenesis(P<0.05).Besides,uridine increased the activity of glycogen synthesis-related enzymes(P<0.05).This study suggested that uridine could alleviate HCD-induced metabolic syndrome by activating the sirt1/AMPK signaling pathway and promoting glycogen synthesis.This finding reveals the function of uridine in fish metabolism and facilitates the development of new additives in aquatic feeds.

Double-edged effect of sodium citrate in Nile tilapia(Oreochromis niloticus):Promoting lipid and protein deposition vs.causing hyperglycemia and insulin resistance

Citrate is an essential substrate for energy metabolism that plays critical roles in regulating glucose and lipid metabolic homeostasis.However,the action of citrate in regulating nutrient metabolism in fish remains poorly understood.Here,we investigated the effects of dietary sodium citrate on growth performance and systematic energy metabolism in juvenile Nile tilapia(Oreochromis niloticus).A total of 270Nile tilapia(2.81±0.01 g)were randomly divided into three groups(3 replicates per group,30 fish per replicate)and fed with control diet(35%protein and 6%lipid),2%and 4%sodium citrate diets,respectively,for 8 weeks.The results showed that sodium citrate exhibited no effect on growth performance(P>0.05).The whole-body crude protein,serum triglyceride and hepatic glycogen contents were significantly increased in the 4%sodium citrate group(P<0.05),but not in the 2%sodium citrate group(P>0.05).The 4%sodium citrate treatment significantly increased the serum glucose and insulin levels at the end of feeding trial and also in the glucose tolerance test(P<0.05).The 4%sodium citrate significantly enhanced the hepatic phosphofructokinase activity and inhibited the expression of pyruvate dehydrogenase kinase isozyme 2 and phosphor-pyruvate dehydrogenase E1 component subunit alpha proteins(P<0.05).Additionally,the 4%sodium citrate significantly increased hepatic triglyceride and acetyl-Co A levels,while the expressions of carnitine palmitoyl transferase 1a protein were significantly down-regulated by the 4%sodium citrate(P<0.05).Besides,the 4%sodium citrate induced crude protein deposition in muscle by activating m TOR signaling and inhibiting AMPK signaling(P<0.05).Furthermore,the 4%sodium citrate significantly suppressed serum aspartate aminotransferase and alanine aminotransferase activities,along with the lowered expression of pro-inflammatory genes,such as nfκb,tnfa and il8(P<0.05).Although the 4%sodium citrate significantly increased phosphor-nuclear factor-k B p65 protein expression(P<0.05),no significant tissue damage or inflammation occurred.Taken together,dietary supplementation of sodium citrate could exhibit a double-edged effect in Nile tilapia,with the positive aspect in promoting nutrient deposition and the negative aspect in causing hyperglycemia and insulin resistance.

High cholesterol intake remodels cholesterol turnover and energy homeostasis in Nile tilapia(Oreochromis niloticus)

The roles of dietary cholesterol in fish physiology are currently contradictory.The issue reflects the limited studies on the metabolic consequences of cholesterol intake in fish.The present study investigated the metabolic responses to high cholesterol intake in Nile tilapia(Oreochromis niloticus),which were fed with four cholesterol-contained diets(0.8,1.6,2.4 and 3.2%)and a control diet for eight weeks.All fish-fed cholesterol diets showed increased body weight,but accumulated cholesterol(the peak level was in the 1.6%cholesterol group).Then,we selected 1.6%cholesterol and control diets for further analysis.The high cholesterol diet impaired liver function and reduced mitochondria number in fish.Furthermore,high cholesterol intake triggered protective adaptation via(1)inhibiting endogenous cholesterol synthesis,(2)elevating the expression of genes related to cholesterol esterification and efflux,and(3)promoting chenodeoxycholic acid synthesis and efflux.Accordingly,high cholesterol intake reshaped the fish gut microbiome by increasing the abundance of Lactobacillus spp.and Mycobacterium spp.,both of which are involved in cholesterol and/or bile acids catabolism.Moreover,high cholesterol intake inhibited lipid catabolic activities through mitochondrialβ-oxidation,and lysosome-mediated lipophagy,and depressed insulin signaling sensitivity.Protein catabolism was elevated as a compulsory response to maintain energy homeostasis.Therefore,although high cholesterol intake promoted growth,it led to metabolic disorders in fish.For the first time,this study provides evidence for the systemic metabolic response to high cholesterol intake in fish.This knowledge contributes to an understanding of the metabolic syndromes caused by high cholesterol intake or deposition in fish.

介形纲(甲壳亚门)系统分类中核基因18S rDNA的应用研究

本研究采用贝叶斯法(Bayesian-inference,BI)、最大似然法(Maximum-likelihood,ML)和最大简约法(Maximumparsimony,MP),基于18SrDNA序列对介形纲4目12超科间以及其它相关泛甲壳动物(Pancrusacea)间的系统分类关系进行了分析,其目的是探讨单独的核基因18SrDNA序列研究介形纲各阶元分类时的稳定性,及分析介形纲两大主要类群内的系统分类关系。结果发现,应用单独的核基因18SrDNA序列对介形类进行研究时,所获的三种系统树的拓扑结构在介形纲的目、亚目和超科阶元均表现稳定,表明单独的核基因18SrDNA序列在该3个阶元的分类研究中可发挥重要作用。基于此,进一步对介形类内两主要类群的系统分类研究,结果支持Martin和Davis(2001)对介形纲中壮肢亚纲(又称丽足亚纲,Myodocopa)在目、亚目和超科阶元上的分类;但尾肢亚纲(又称速足亚纲,Podocopa)中各主要类群间的系统发育关系却与Martin和Davis(2001)的分类略有不同,其中Punciidae游离于尾肢亚纲主要类群尾肢目(又称速足目,Podocopida)之外,而该结果却与Liebau(2005)对Punciidae归类一致;此外尾肢目中5个主要类群的分类关系呈现[浪花介亚目Cytherocopina+[金星介亚目Cypridocopina+简肢亚目Platycopina(小花介科Cytherellidae)+[达尔文介亚目Darwinulocopina+巴氏介亚目Bairdiocopina]]]。

Lipophagy is essential for lipid metabolism in fish

Lipophagy is a form of autophagy in mammals.In this cellular process,lipid droplets(LDs)are degraded through the lysosomal degradative pathway[1].During lipophagy,LDs sequestrated in autophagosomes are delivered to lysosomes,which fuse to form autophagosomes and then develop into autophagolysosomes,leading to LDs degradation of[1].A number of studies have demonstrated that lipophagy play important roles in lipid

Inhibition of pyruvate dehydrogenase kinase improves carbohydrate utilization in Nile tilapia by regulating PDK2/4-PDHE1αaxis and insulin sensitivity

Pyruvate dehydrogenase kinases(PDKs)-pyruvate dehydrogenase E1αsubunit(PDHE1α)axis plays an important role in regulating glucose metabolism in mammals.However,the regulatory function of PDKsPDHE1α axis in the glucose metabolism of fish is not well known.This study determined whether PDKs inhibition could enhance PDHE1αactivity,and improve glucose catabolism in fish.Nile tilapia fingerlings(1.90±0.11 g)were randomly divided into 4 treatments in triplicate(30 fish each)and fed control diet without dichloroacetate(DCA)(38% protein,7% lipid and 45% corn starch)and the control diet supplemented with DCA,which inhibits PDKs through binding the allosteric sites,at 3.75(DCA3.75),7.50(DCA7.50)and 11.25 g/kg(DCA11.25),for 6 wk.The results showed that DCA3.75,DCA7.50 and DCA11.25significantly increased weight gain,carcass ratio and protein efficiency ratio(P<0.05)and reduced feed efficiency(P<0.05)of Nile tilapia.To investigate the effects of DCA on growth performance of Nile tilapia,we selected the lowest dose DCA3.75 for subsequent analysis.Nile tilapia fed on DCA3.75significantly reduced the mesenteric fat index,serum and liver triglyceride concentration and total lipid content in whole fish,and down-regulated the expressions of genes related to lipogenesis(P<0.05)compared to the control.The DCA3.75 treatment significantly improved glucose oxidative catabolism and glycogen synthesis in the liver,but significantly reduced the conversion of glucose to lipid(P<0.05).Furthermore,the DCA3.75 treatment significantly decreased the PDK2/4 gene and protein expressions(P<0.05),accordingly stimulated PDHE1αactivity by decreasing the phosphorylated PDHE1αprotein level.In addition,DCA3.75 treatment significantly increased the phosphorylated levels of key proteins involved in insulin signaling pathway and glycogen synthase kinase 3β(P<0.05).Taken together,the present study demonstrates that PDK2/4 inhibition by using DCA promotes glucose utilization in Nile tilapia by activating PDHE1αand improving insulin sensitivity.Our study helps to understand the regulatory mechanism of glucose metabolism for improving dietary carbohydrate utilization in farmed fish.