n-3高不饱和脂肪酸对黑鲷幼鱼生长及脂肪代谢的影响

Effects of dietary n-3 HUFA on growth performance and lipid metabolism in juvenile black sea bream,Sparus macrocephalus

研究了饲料中不同水平n-3 HUFA(0.79%,0.83%,0.85%,0.88%,0.92%,0.94%;DHA/EPA=2.8/1)对黑鲷幼鱼生长及脂肪代谢的影响。结果显示:(1)黑鲷幼鱼肝体指数(HSI)及腹脂率(IPF ratio)随饲料中n-3 HUFA含量的增加而减小,且于0.92%和0.94%组时显著低于其他各组;脂肪细胞直径呈减小趋势,其中0.94%组显著小于0.85%组;肌肉脂肪含量受n-3 HUFA的影响显著,于0.88%组时达到最低。各组全鱼水份和脂肪含量差异不显著(P>0.05)。肝脏、肌肉及腹腔脂肪组织饱和脂肪酸(∑SFA)和C16∶0含量均随饲料n-3HUFA水平增加呈下降趋势,而∑n-3 HUFA呈显著上升趋势。各组织中DHA/EPA不受饲料脂肪酸组成的影响。以增重率为参考指标,二次回归分析结果表明,黑鲷幼鱼[(8.08±0.09)g]获得最佳增重时对饲料中n-3 HUFA的需要量为0.87%DM;(2)黑鲷幼鱼肝脏脂肪酸合成酶(FAS)活性及基因表达水平均在n-3 HUFA>0.92%时有显著下降(P<0.05);腹腔脂肪激素敏感脂肪酶(HSL)活性及基因表达水平均随饲料中n-3 HUFA的添加呈升高趋势(P<0.05),且高含量n-3 HUFA(0.94%)可使HSL活性增加近一倍。结果表明,饲料中n-3HUFA通过同步调控脂肪合成与分解两个过程影响黑鲷幼鱼脂肪代谢。

Six diets containing graded levels （0.79,0.83,0.85,0.88,0.92 and 0.94% ） of n-3 highly unsaturated fatty acids （n-3 HUFA） with a constant DHA/EPA, were fed randomly to six groups （Diet 1 - 6） of fish with triplicate [ average weight, （8.08 ±0.09） g ; 20 fish/replicate ] to determine the effects of dietary n-3 HUFA on growth and lipid metabolism in juvenile black sea bream （Sparus macrocephalus ）. Results of the 8-week growth trial showed that ： （ 1 ） Hepotasomatic index （HSI） and intraperitoneal fat （IPF） ratio of juvenile black sea bream decreased with the increase of dietary n-3 HUFA and the values in Diet 5 and 6 were significantly lower than those in other four groups （ P 〈 0.05 ）. Adipocyte diameter in IPF was decreased by dietary n-3 HUFA and the significance occurred between Diet 3 and 6. Lipid content in muscle was significantly affected by dietary n-3 HUFA and reached the bottom in Diet 4. No significance was found in whole body proximate composition of juvenile black sea bream. Concerning the fatty acid composition, ∑ SFA and the main constituent, C16：0 were negatively correlated with dietary n-3 HUFA, while ∑ n-3 HUFA content was obviously increased among all the treatments. DHA to EPA ratios （DHA/ EPA） in liver, dorsal muscle and IPF were unchanged with the supplementation of dietary n-3 HUFA. Quadratic analysis based on weight gain rate （WGR） indicated that dietary n-3 HUFA requirement for black sea bream was 0.87 % DM. （2） Determination of fatty acid synthase （FAS） and hormone-sensitive lipase （HSL） activities showed that FAS activity kept constant in Diet 1 to 4, and then decreased significantly with further increment of dietary n-3 HUFA. HSL activity in IPF increased significantly with the elevation of dietary n-3 HUFA level and increased to almost two times in Diet 6 （0.94% n-3HUFA ）. Gene expression of FAS changed following the similar trend with FAS activity in liver; while expression of HSL in IPF was positively correlated with dietary n-3 HUFA level. In summary, we can deduce that n-3 HUFA regulation in lipid metabolism was realized by affecting the lipogenesis and lipolysis at the same time.