【作者】 左然涛；

【导师】 艾庆辉；

【作者基本信息】 中国海洋大学 ， 水产养殖， 2013， 博士

【摘要】 以我国重要海水肉食性养殖鱼类大黄鱼（Larmichthys crocea）为研究对象，在海水浮式网箱内进行摄食生长实验，以观测饲料中脂肪酸水平和组成对大黄鱼生长、脂肪酸组成、免疫力、抗病力及相关基因表达的影响，在此基础上探讨饲料脂肪酸调控大黄鱼免疫力和脂肪酸代谢的分子机制。本文的研究内容和主要研究结果如下：1.饲料中n-3HUFA对大黄鱼幼鱼生长、非特异性免疫、抗病力以及刺激隐核虫感染后免疫相关基因表达的影响以初始体重9.79±0.6g的大黄鱼（Larmichthys crocea）为研究对象，在海水浮式网箱（1.0×1.0×1.5m）内进行为期58d的摄食生长实验，以探讨饲料中n-3HUFA对大黄鱼幼鱼生长、非特异性免疫、TLR22和MyD88相对表达量及抗病力的影响。通过梯度添加DHA油、EPA油和软脂酸配制等氮等脂的六种饲料（粗蛋白41.3%，粗脂肪11.7%），使饲料中n-3HUFA的含量依次为：0.15、0.60、0.98、1.37、1.79和2.25%，并使DHA/EPA固定在2.0左右。实验期间，将六组饲料分别随机投喂三个网箱的实验鱼（60尾/箱），每天两次（05:00和17:00）投喂至表观饱食状态。实验结果表明，适中水平n-3HUFA（0.98%）组特定生长率（SGR）显著高于对照组（P<0.05），高水平n-3HUFA（1.37%、1.79%和2.25%）会对大黄鱼生长产生不利影响，但差异不显著（P>0.05）。头肾白细胞NBT阳性比例、血清超氧化物歧化酶（SOD）和溶菌酶活性随着饲料n-3HUFA水平升高具有先上升后下降的趋势，其中头肾白细胞NBT阳性比例和SOD在0.60%组具有最大值，而溶菌酶在1.37%组活性最高。各组间头肾白细胞的吞噬活性未见明显趋势及显著性差异（P>0.05）。海水刺激隐核虫感染3d后，各处理组肾脏TLR22mRNA相对表达量未见显著性差异（P>0.05），而当饲料中n-3HUFA含量从0.15%增加至0.98%时,MyD88相对表达量显著升高至2.06，之后随n-3HUFA水平进一步升高显著降低至1.36（P<0.05）；而感染海水刺激隐核虫13d后，各处理组肾脏MyD88mRNA相对表达量未见显著性差异（P>0.05），而当饲料中n-3HUFA含量从0.15%增加至0.60%时，肾脏TLR22的相对表达量显著升高至2.17；而当n-3HUFA含量从0.60%升高至2.25%时，肾脏TLR22的相对表达量显著降低至1.11（P<0.05）。肝脏TLR22和MyD88mRNA相对表达量在海水刺激隐核虫感染3d和13d随n-3HUFA水平升高均有先升高后下降的趋势，且表达量最高值出现在0.98-1.79%范围内。海水刺激隐核虫感染13d后各处理组累计死亡率具有与非特异性免疫和基因表达相似的趋势，其中0.60%n-3HUFA组累计死亡率最低，显著低于除0.98%组之外的各处理组。实验结果表明，0.60%和0.98%n-3HUFA组大黄鱼具有最佳免疫力和SGR，低水平和适中水平n-3HUFA具有较高非特异性免疫力、TLR22和MyD88mRNA相对表达量，说明n-3HUFA可能通过调控TLR22和MyD88mRNA相对表达量来影响大黄鱼SGR、免疫力及其抗病力。2.饲料中DHA/EPA对大黄鱼幼鱼生长、非特异性免疫、抗病力以及刺激隐核虫感染后免疫相关基因表达的影响以初始体重9.79±0.6g的大黄鱼（Larmichthys crocea）为研究对象，在海水浮式网箱（1.0×1.0×1.5m）内进行为期58d的摄食生长实验，以探讨饲料中DHA/EPA对大黄鱼幼鱼生长、非特异性免疫、TLR22和MyD88相对表达量及抗病力的影响。以鱼粉、豆粕为主要蛋白源，DHA油、EPA油、ARA油和软脂酸酯为主要脂肪源配制等氮等脂的五种饲料（粗蛋白41.3%，粗脂肪11.7%），使饲料中DHA/EPA依次为0.61、1.54、2.17、3.04和3.88，且DHA和EPA（n-3HUFA）总量固定在1.08%左右。实验期间，将五组饲料分别随机投喂三个网箱的实验鱼（60尾/箱），每天两次（05:00和17:00）投喂至表观饱食状态。结果表明，大黄鱼的特定生长率（SGR）随DHA/EPA增大具有先升高后下降的趋势，当DHA/EPA由0.61升高至2.17时，SGR由2.03%/d显著升至2.26%/d（P<0.05），当该比例进一步增大时，SGR有下降趋势，但差异不显著（P>0.05）。头肾白细胞NBT阳性比例和血清溶菌酶活性随着DHA/EPA升高具有先上升后下降的趋势，其中头肾白细胞NBT阳性比例和血清溶菌酶活性分别在2.17和3.04组具有最大值，且均显著高于对照组和比率为3.88组（P<0.05）。但头肾白细胞吞噬活性和血清SOD活性在各处理组间未见显著性差异（P>0.05）。海水刺激隐核虫感染3d后，各处理组肾脏MyD88mRNA相对表达量未见显著性差异；当饲料中DHA/EPA由0.61升高到2.17时，肾脏TLR22mRNA相对表达量由1.02显著升至2.47（P<0.05），之后随DHA/EPA的增大降至1.73（P>0.05）；肝脏MyD88相对表达量随着DHA/EPA的增大具有显著上升的趋势，且DHA/EPA为3.88时具有最高值，显著高于比率为0.61、1.54和2.17处理组（P<0.05）；当饲料中DHA/EPA由0.61升高到3.04时，肝脏TLR22mRNA相对表达量由1.00显著升至1.95（P<0.05），之后随DHA/EPA的增大降至1.51（P>0.05）。刺激隐核虫感染13d后，各处理组肾脏TLR22和MyD88mRNA相对表达量均未见显著性差异（P>0.05）；肝脏TLR22相对表达量随DHA/EPA升高由1.01显著降低至0.46（P<0.05）；当饲料中DHA/EPA由0.61升高到2.17时，肝脏MyD88mRNA相对表达量由1.00显著升至1.64（P<0.05），之后随DHA/EPA的增大降至1.16（P>0.05）。感染刺激隐核虫13d后大黄鱼累计死亡率随DHA/EPA增大具有先降低后下降的趋势，DHA/EPA为1.54、2.17和3.04时累计死亡率较低，显著低于对照组（P<0.05）。实验结果表明，DHA/EPA在2.17-3.04之间时，大黄鱼生长和整体免疫水平最佳，过高DHA/EPA会降低SGR、非特异性免疫及抗病力，这可能是通过影响TLR22和MyD88相对表达量来实现的。3.豆油为基础的饲料中添加共轭亚油酸对大黄鱼生长、非特异性免疫力、抗氧化能力、脂肪沉积和相关基因表达的影响以初始体重为7.56±0.60g的大黄鱼为研究对象，通过摄食生长实验并利用实时定量PCR技术来探讨饲料中共轭亚油酸对大黄鱼生长、非特异性免疫力、抗氧化能力、脂肪沉积和相关基因表达的影响。通过梯度添加CLA油，使得饲料中CLA含量依次为0（对照组）、0.42%、0.83%和1.70%饲料干物质。实验在海水浮式网箱进行，每天两次投喂，周期为70d。实验结果表明，大黄鱼增重率（WGR）和头肾巨噬细胞吞噬指数随着饲料中CLA的升高呈现先升高后下降的趋势，当饲料中CLA由0升高至0.42%时，WGR由499.30%显著升高至572.52%，之后随着饲料中CLA的进一步升高显著降至444.21%。吞噬指数在饲料CLA含量为0.42%时具有最高值（34.7%），显著高于对照组（17.9%）和最高CLA含量组（24.7%）。当饲料中CLA由0升高至0.83%时，头肾巨噬细胞呼吸爆发、肝脏过氧化氢酶（CAT）活力和肝脏总抗氧化力（T-AOC）显著升高，之后随着CLA的进一步升高显著下降。其中，呼吸爆发在0.83%时最高（0.50），显著高于对照组（0.34）和最高CLA组（0.42）。而肝脏丙二醛（MDA）随着饲料CLA的升高由3.30显著降至1.66nmol/mg protein（P<0.05）。鱼体和肌肉脂肪水平随着饲料中CLA含量的升高而升高（P<0.05）。肝脏和肾脏炎症相关的基因（环氧化酶-2和白细胞介素β）和肾脏脂肪酸氧化相关基因（肉碱脂酰转移酶Ⅰ和乙酰辅酶A氧化酶）的mRNA表达量会随着饲料中CLA含量的升高而显著降低。肝脏PPARα和乙酰辅酶A氧化酶的表达随着饲料中CLA由0.42%升高至1.70%而显著降低（P<0.05）。上述结果表明饲料中CLA能够显著影响大黄鱼的生长、非特异性免疫、抗氧化能力及炎性和脂肪酸氧化相关的基因表达，呈现出较为显著的抗炎、抗氧化效果。这有助于理解CLA在鱼类中的具体生理作用。4.饲料中亚麻酸/亚油酸对大黄鱼生长、非特异性免疫、抗氧化能力和相关基因表达的影响随着饲料工业的发展，鱼油短缺问题日益突出。研究表明，高摄入量的亚油酸（18:2n-6）会严重影响海水鱼类的生长和免疫性能的发挥。然而，目前仍不清楚亚油酸的这种不利影响是否能够通过适当提高ALA/LA的比例来消除。本实验以初始体重9.56±0.60g的大黄鱼（Larmichthys crocea）为研究对象，在海水浮式网箱（1.0×1.0×1.5m）内进行为期70d的摄食生长实验，以探讨饲料中亚麻酸和亚油酸比例（ALA/LA）对大黄鱼生长、非特异性免疫、抗氧化能力及炎性、脂肪酸氧化和合成相关基因表达的影响。对照组饲料含有30%的鱼粉和9%的鱼油，之后用不同植物油的混合物（亚麻油、葵花油和棕榈油）替代对照组中78%的鱼油，使饲料中ALA/LA的比例依次为：0.03、0.45、0.90和1.51。实验结果表明，与鱼油组相比，高摄入量的亚油酸显著降低了大黄鱼的增重率（WGR）和非特异性免疫力（吞噬指数、呼吸爆发和血清溶菌酶活力），然而这种不利影响随着饲料中ALA/LA的升高至0.45或0.90时得到完全消除。肝脏超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活力在比例为0.45时最高，显著高于最低或最高比例组。肝脏丙二醛（MDA）含量呈现与SOD和CAT活力相反的变化趋势，当比例为0.90时鱼体肝脏MDA含量最低，显著低于对照组。肝脏、肾脏和肌肉炎性相关基因（环氧化酶-2（COX-2），白细胞介素1β（IL-1β）和肿瘤坏子因子α（TNF-α））、脂肪酸氧化相关基因（过氧化物酶体增殖激活受体α（PPARα），肉碱脂酰转移酶（CPTⅠ）和脂酰CoA氧化酶（ACO））以及脂肪酸合成相关基因（脂肪酸合酶（FAS），苹果酸脱氢酶（ME）和6磷酸葡萄糖脱氢酶（6GPD））相对mRNA表达量显著高于对照组，但上述基因表达量在ALA/LA比例为0.45时显著降至与对照组相似的水平。上述结果表明饲料中ALA/LA能够显著影响大黄鱼生长、非特异性免疫、肝脏抗氧化能力以及炎性、脂肪酸氧化和合成相关基因表达，比例过高或过低均不利于其生长、免疫和脂肪酸代谢。ALA虽然不是大黄鱼的必需脂肪酸，但在抗炎和抗氧化方面却具有与n-3HUFA极为相似的特性。5.大黄鱼脂肪酸Δ6去饱和酶和延长酶5基因的克隆、表征和营养学调控通过同源克隆和RACE技术从大黄鱼中获得脂肪酸Δ6去饱和酶和延长酶5的cDNA全长。脂肪酸Δ6去饱和酶全长为2049bp，其中5′-UTR为107bp，3′-UTR为604bp，开放阅读框1338bp，编码445个氨基酸。脂肪酸延长酶5全长1551bp,包括120bp5′-UTR,546bp3′-UTR和885bp的开放阅读框。序列比对发现这两个基因分别属于脂肪酸Δ6去饱和酶和延长酶5家族。组织差异性表达结果显示该基因在肝脏和脑中表达量较高，而在胃、肠、心脏和脾脏中表达量较低。之后通过58d的摄食生长实验观测饲料中n-3HUFA（0.15,0.60,0.98,1.37,1.79和2.25%）及DHA/EPA（0.61,1.54,2.17,3.04和3.88）对肝脏脂肪酸Δ6去饱和酶和延长酶5mRNA表达量的影响.结果发现，脂肪酸Δ6去饱和酶和延长酶5随着饲料中n-3HUFA含量的升高而显著降低。与最高n-3HUFA组（2.25%n-3HUFA）相比，0.15%,0.60%and0.98%n-3HUFA处理组脂肪酸Δ6去饱和酶表达量分别升高了46倍、4.8倍和1.17倍。与最高n-3HUFA组（2.25%n-3HUFA）相比，0.15%,0.60%and0.98%n-3HUFA处理组延长酶5的表达量显著升高了1.77倍,1.41倍和1.41倍。肝脏脂肪酸Δ6去饱和酶表达量随着饲料中DHA/EPA的升高显著降低，肝脏延长酶5的表达量随着饲料中DHA/EPA的升高有增加的趋势，但各处理组间差异不显著（P>0.05）.更多还原

【Abstract】 This study was conducted to investigate the effects of dietay fatty acid ongrowth, fatty acid composition, nonspecific immnity, disease resistance and relatedgene expression in large yellow croaker (Larmichthys crocea). Based on thesestudies, it was aimed to investigate mechamisms involved in the regulation of dietaryfatty acid on immunity and fatty acid metabolism of large yellow croaker. The resultsand conclusions are summarized as follows:1. Effects of dietary n-3highly unsaturated fatty acids on growth, nonspecificimmunity, expression of some immune related genes and disease resistance oflarge yellow croaker (Larmichthys crocea)The study was conducted to investigate the effects of dietary n-3highlyunsaturated fatty acid (n-3HUFA) on growth, nonspecific immunity, gene expressionand disease resistance of juvenile large yellow croaker (Larmichthys crocea). Sixisoproteic and isolipidic diets were formulated with graded levels of n-3HUFAranging from0.15%to2.25%of the dry weight and the DHA/EPA was approximatelyfixed at2.0. Each diet was randomly allocated to triplicate groups of fish in floatingsea cages (1.0×1.0×1.5m), and each cage was stocked with60fish (initial averageweight9.79±0.6g). Fish were fed twice daily (05:00and17:00) to apparent satiationfor58days. Results showed that moderate n-3HUFA level (0.98%) significantlyenhanced growth compared with the control group (P<0.05), while higher n-3HUFAlevels (1.37%,1.79%and2.25%) had detrimental effects on the growth though nosignificance was found (P>0.05). Nitro blue tetrazolium (NBT) positive leucocytespercentage of head kidney and serum superoxide dismutase (SOD) activity increasedwith increasing n-3HUFA from0.15%to0.60%, and decreased with further increaseof n-3HUFA from0.60%to2.25%(P<0.05). Serum lysozyme activity increasedsignificantly as n-3HUFA increased from0.15%to1.37%, and then decreased withn-3HUFA from1.37%to2.25%(P>0.05). There were no significant differences in phagocytosis percentage (PP) of head kidney leucocytes among dietary treatments(P>0.05). The hepatic mRNA expression of Toll-like receptor22(TLR22) andMyeloid differentiation factor88(MyD88) was increased in fish fed the diets withlow or moderate levels, while in kidney this increment was only found at specificsampling time. The cumulative mortality rate after parasite infection test withIchthyophthirius marinus decreased with n-3HUFA increased from0.15%to0.60%(P<0.05), and significantly increased with n-3HUFA from0.60%to2.25%(P<0.05).Results of this study suggested that dietary n-3HUFA could significantly influencefish growth, nonspecific immune responses, immune related gene expression anddisease resistance of large yellow croaker and low n-3HUFA levels (0.60%and0.98%)may benefit the immunity and growth by upregulating the mRNA expression ofcertain immune related genes.2. Effects of dietary docosahexaenoic to eicosapentaenoic acid ratio (DHA/EPA)on growth, nonspecific immunity, expression of some immune related genes anddisease resistance of large yellow croaker (Larmichthys crocea) following naturalinfestation of parasites (Cryptocaryon irritans)The study was conducted to investigate the effects of dietary docosahexaenoic toeicosapentaenoic acid ratio (DHA/EPA) on growth, nonspecific immunity, immunerelated gene expression and disease resistance of juvenile large yellow croaker(Larmichthys crocea) following natural infestation of parasites (Cryptocaryonirritans). Five isoproteic and isolipidic diets were formulated with graded ratios ofDHA/EPA (0.61,1.54,2.17,3.04and3.88) and the total amount of n-3highlyunsaturated fatty acids (n-3HUFA) was approximately fixed at1.0%of the dry weight.Each diet was randomly allocated to triplicate groups of fish in floating sea cages(1.0×1.0×1.5m), and each cage was stocked with60fish (initial average weight9.8±0.6g). Fish were fed twice daily (05:00and17:00) to apparent satiation for58days. Results showed that specific growth rate (SGR) significantly increased from2.03%/d to2.26%/d (P<0.05) and then decreased with no significant differences(P>0.05). Serum lysozyme activity increased with increasing dietary DHA/EPA from0.61to3.04, and decreased with further increase of DHA/EPA from3.04to3.88(P<0.05). Nitro blue tetrazolium (NBT) positive leucocytes percentage of head kidneyshowed a similar changing trend with serum lysozyme activity with the highest value in the ratio of2.17, significantly higher than that in the control and ratio of3.88groups. Hepatic Toll-like receptor22(TLR22) and Myeloid differentiation factor88(MyD88) expression levels were significantly increased in fish fed higher DHA/EPA(3.04or3.88) at the early stage after natural infestation of parasites. At the later stageafter natural infestation of parasites, hepatic TLR22transcription was up-regulated infish fed moderate ratio of DHA/EPA (2.17). In kidney, the expression of TLR22wassignificantly up-regulated in fish fed moderate dietary DHA/EPA (2.17) at the earlystage after natural infestation of parasites. The13d cumulative mortality ratefollowing natural infestation of parasites decreased significantly with DHA/EPAincreased from0.61to3.04(P<0.05), and then increased with DHA/EPA from3.04to3.88(P>0.05). Results of this study suggested that fish fed moderate or higherDHA/EPA had higher growth, nonspecific immunity, immune related gene expressionand disease resistance following natural infestation of parasites and dietary DHA/EPAmay regulate fish immunity and disease resistance by altering the mRNA expressionlevels of TLR22and MyD88.3. Effects of conjugated linoleic acid (CLA) on growth, nonspecific immunity,antioxidant capacity, lipid deposition and related gene expression in juvenilelarge yellow croaker (Larmichthys crocea) fed soybean oil based dietsThe effects of conjugated linoleic acid (CLA) on growth performance,nonspecific immunity, antioxidant capacity, lipid deposition and related geneexpression were investigated in large yellow croaker, Larmichthys crocea. Fish (7.56(SEM0.60) g) were fed soybean oil based diets with graded levels of CLA (0,0.42,0.83,1.70%) for70days. Quantitative PCR was used to assess the effects of CLA ontranscription of inflammation and fatty acid oxidation related genes. Results showedthat growth in fish fed the diet with0.42%CLA was significantly higher. Also,phagocytic index and respiratory burst activity were significantly higher in treatmentsof0.42%and0.83%CLA, respectively. Hepatic total anti-oxidative capacity andcatalase activities increased significantly when CLA increased from0%to0.83%, andthen decreased with further increase of CLA. While hepatic maleic dialdehyde contentdecreased significantly as dietary CLA increased. Lipid concentration in whole bodyand muscle increased significantly with increasing dietary CLA. Transcription ofgenes related with inflammation (cyclooxygenase-2and IL-β) in liver and kidney and fatty acid oxidation (carnitine palmitoyl transferase Ⅰ and acyl CoA oxidase) inkidney decreased significantly as dietary CLA increased. PPARα and acyl CoAoxidase expression in liver decreased significantly as CLA increased from0.42%to1.70%. These results strongly suggested that dietary CLA could significantly affectgrowth performance, nonspecific immunity, antioxidant capacity, lipid deposition andtranscription of inflammation and fatty acid oxidation related genes of large yellowcroaker. This may contribute to understanding the mechanisms on the physiologicaleffects of dietary CLA in fish.4. Effects of dietary ratio of alfa-linolenic to linoleic acid (ALA/LA) on growth,nonspecific immunity, antioxidant capacity and related gene expression injuvenile large yellow croaker (Larmichthys crocea)Fish oil has seen a great shortage with the fast development of aquatic feedindustry. High inclusion of linoleic acid rich oils has deleterious effects on growth andhealth of marine fish species. However, it is still unclear whether these negativeeffects could be eliminated by enhancing dietary alfa-linolenic to linoleic acid ratio(ALA/LA). Thus, this study was conducted to investigate the effects of dietaryALA/LA on growth performance, nonspecific immunity, antioxidant capacity, lipiddeposition and related gene expression in juvenile large yellow croaker, Larmichthyscrocea. The control diet (FO) was formulated with30%fish meal and9%fish oil.Then, four other diets were formulated by replacing78%fish oil in the FO withvegetable oil to acquire graded ratios of ALA/LA (0.03,0.45,0.90and1.51), whichwere named R-0.03, R-0.45, R-0.90and R-1.51, respectively. Fish were fed twicedaily (05:00and17:00) for70days. Results showed that experimental fish hadsignificantly lower weight gain rate (WGR) and worse nonspecific immunity after78%fish oil was replaced by sunflower oil. However, the negative effects of LA onWGR and nonspecific immunity could be completely eliminated as dietary ALA/LAincreased to0.45and0.90, respectively. Anti-oxidative capacity in liver was increasedto some extent after78%fish oil was replaced by vegetable oil. Hepatic superoxidedismutase and catalase activities increased significantly when ALA/LA increasedfrom0.03to0.45, and then decreased with further increase of this ratio. While hepaticmaleic dialdehyde content first decreased with dietary ALA/LA increasing from0.03 to0.90, and then increased as this ratio increased to1.51(P>0.05). Transcription ofgenes related with inflammation (cyclooxygenase-2, IL-1β and TNF-α), fatty acidoxidation (carnitine palmitoyl transferase Ⅰ and acyl CoA oxidase), and fatty acidsynthesis (fatty acid synthase and malic enzyme) in liver and kidney was significantlyincreased in R-0.03, and then decreased to comparable levels in FO as dietaryALA/LA reached equal to or above0.45. These results strongly suggested that dietaryALA could exert some similar properties like n-3HUFA at least from the points ofinflammation, fatty acid oxidation and synthesis. This may contribute tounderstanding the mechanisms on the physiological effects of dietary ALA/LA in fish.5. Molecular cloning, characterization, and nutritional regulation of fatty acyl Δ6desaturase and elovl5elongase of large yellow croaker, Larmichthys croceaIn this study, the full-length cDNA of fatty acyl Δ6desaturase and elovl5elongase were first cloned from the large yellow croaker, Larmichthys crocea. Thefatty acyl Δ6desaturase was2049bp, with a107bp5′-UTR, a604bp3′-UTR, and anORF of1338that specified a protein of445amino acids. The fatty acyl elovl5elongase was1551bp, including a5′-terminal untranslated region (UTR) of120bp, a3′-terminal UTR of546bp and an open reading frame (ORF) of885bp encoding apolypeptide of294amino acid residues. Sequence comparison and phylogeneticanalysis showed that the two enzymes belong to the fatty acyl Δ6desaturase andelovl5elongase family, respectively. Tissue distribution analysis revealed that theLcElovl5expression level was higher in liver, brain and gill while lower in stomach,intestine, heart and spleen. Then two58d feeding experiments were conducted toinvestigate the effects of dietary n-3long chain polyunsaturated fatty acid (n-3HUFA)levels (0.15,0.60,0.98,1.37,1.79and2.25%) and docosahexaenoic toeicosapentaenoic acid ratio (DHA/EPA)(0.61,1.54,2.17,3.04and3.88) on thehepatic expression levels of LcElovl5in large yellow croaker juveniles. The resultsshowed that the transcriptional levels of LcElovl5decreased significantly with theincreasing dietary n-3LC-PUFA (P<0.05). The LcElvol5transcript levels wereup-regulated by1.77-fold,1.41-fold, and1.41-fold in the level of0.15%,0.60%and0.98%n-3LC-PUFA treatments compared with the control group (2.25%n-3LC-PUFA), respectively. The hepatic expression levels of LcElovl5transcriptshowed an increasing tendency in response to the increased dietary DHA/EPA though no significance was observed among dietary groups (P>0.05).更多还原