饲料中添加不同脂肪酸对大菱鲆幼鱼生长、脂代谢和非特异性免疫的影响

DIETARY SUPPLEMENTATION OF DIFFERENT FATTY ACIDS ON GROWTH,LIPID METABOLISM AND NON-SPECIFIC IMMUNITY OF TURBOT(SCOPHTHALMUS MAXIMUS L.)

为揭示不同链长和不饱和度的脂肪酸对水产动物生长、脂代谢和非特异性免疫的影响,研究挑选初始体重为(8.00±0.20) g的大菱鲆(Scophthalmus maximus L.)幼鱼作为实验对象,设置了添加不同链长和不饱和度脂肪酸的8种等氮等脂配合饲料:对照组(CON)、棕榈酸组(PA)、硬脂酸组(SA)、油酸组(OA)、亚油酸组(LA)、亚麻酸组(ALA)、花生四烯酸组(ARA)和二十二碳六烯酸/二十碳五烯酸组(DHA/EPA),在18℃的循环水养殖系统中进行为期8周的养殖实验。结果表明:随着饲料中添加脂肪酸链长和不饱和度的增加,大菱鲆幼鱼增重率(WGR)、特定生长率(SGR)和蛋白质效率(PER)均有增高的趋势, ARA组WGR和SGR最高, DHA/EPA组PER最高。饲料中添加不同脂肪酸对大菱鲆幼鱼鱼体的灰分和水分没有显著性影响(P>0.05),但鱼体的粗蛋白含量随着脂肪酸链长和不饱和度的增加而增加,粗脂肪含量随着脂肪酸链长和不饱和度的增加而降低。随着脂肪酸链长和不饱和度的增加,大菱鲆幼鱼血浆胆固醇(T-CHO)含量逐渐降低,而血浆甘油三酯(TG)含量在SA组最高,在DHA/EPA组最低;血浆低密度脂蛋白(LDL-C)含量随着添加脂肪酸链长和不饱和度的增加而降低,高密度脂蛋白(HDL-C)呈相反的趋势。进一步对大菱鲆肝脏脂代谢相关基因检测得出,饲料中添加不同脂肪酸可以通过调控脂代谢相关基因表达(FAS、PPARγ、SREBP1、PPARα和ACOX1)进而控制大菱鲆幼鱼鱼体的脂肪合成和分解。PA组的肝脏总抗氧化能力(T-AOC)最低,且显著低于其他各处理组(P<0.05)。DHA/EPA组的肝脏超氧化物歧化酶(SOD)和过氧化氢酶(CAT)含量最高,肝脏丙二醛(MDA)含量最低。进一步对肝脏免疫基因定量得出, PA、SA组显著提高了促炎因子(IL-1β、IL-8、MyD88、NF-κB p65、TLR2、TLR8、TLR9和TNF-α)的基因表达量,且显著降低了抗炎因子的表达量(TGF-β),而LA、ALA、ARA和DHA/EPA组则呈现出相反的趋势。研究结果表明,随着饲料中添加脂肪酸链长和不饱和度的增加,可以显著影响大菱鲆幼鱼的生长、脂代谢和非特异性免疫。

Due to the continued strain on global fish oil resources,the utilization of alternative fats such as vegetable oil in aquaculture feed has gradually increased.However,there are differences in the types and concentrations of fatty acids between vegetable oil and fish oil.In order to reveal the effects of fatty acids with different chain lengths and degrees of unsaturation on the growth,lipid metabolism,and non-specific immunity of aquatic animals,juvenile turbot(Scophthalmus maximus L.)with an initial body weight of(8.00+0.20)g were selected as the experimental subjects in this study.Eight isonitrogenous and isolipidic compound diets with different chain lengths and unsaturated levels of fatty acids were set up:control group(CON),palmitic acid group(PA),stearic acid group(SA),oleic acid group(OA),linoleic acid group(LA),linolenic acid group(ALA),arachidonic acid group(ARA),and docosahexaenoic acid/eicosapentaenoic acid group(DHA/EPA).The experiment was conducted in a recirculating aquaculture system at 18C for 8 weeks.The results showed that with an increase in dietary fatty acid chain length and unsaturated degree,the weight gain rate(WGR),specific growth rate(SGR),and protein efficiency ratio(PER)of juvenile turbot exhibited an increasing trend.Notably,the ARA group displayed the highest WGR and SGR,while the DHA/EPA group exhibited the highest PER.Dietary variations in fatty acids had no significant effects on the ash and water content of juvenile turbot(P>0.05).However,crude protein content increased with rising fatty acid chain length and unsaturation degree,whereas crude fat content decreased.Moreover,as fatty acid chain length and unsaturated degree increased,the plasma cholesterol(T-CHO)content of juvenile turbot gradually decreased,while the plasma triglyceride(TG)content was the highest in SA group and the lowest in DHA/EPA group.Plasma low density lipoprotein(LDL-C)content decreased with the increasing fatty acid chain length and unsaturation degree,whereas the high density lipoprotein(HDL-C)showed an opposite trend.Further analysis of lipid metabolism-related genes in turbot liver showed that dietary fatty acids could control lipid synthesis and decomposition by regulating the expression of lipid metabolism-related genes(FAS,PPARy,SREBPI,PPARa,and ACOXI).The total antioxidant capacity(T-AOC)of liver in PA group was the lowest,and was significantly lower than that in other treatment groups(P<0.05).The liver superoxide dismutase(SOD)and catalase(CAT)contents were the highest in DHA/EPA group,while the liver malondialdehyde(MDA)content was the lowest.Furthermore,gene expressions of pro-inflammatory factors(IL-1β,IL-8,MyD88,NF-kB p65,TLR2,TLR8,TLR9,and TNF-a)in PA and SA groups were significantly increased,whereas the expression of anti-inflammatory factor(TGF-β)was significantly decreased.Conversely,in LA,ALA,ARA,and DHA/EPA groups,the trend was reversed.These results suggest that dietary supplementation of fatty acids with longer chain lengths and higher unsaturated degree can significantly affect the growth,lipid metabolism and non-specific immunity of juvenile turbot.