低温和摄食对虹鳟脂肪酸合成基因表达的影响

Influence of Low Temperature and Feeding on Expressions of Unsaturated Fatty Acid Biosynthesis Genes of Rainbow Trout(Oncorhynchus mykiss)

通过分析低温和摄食对虹鳟(Oncorhynchus mykiss)脂肪酸生物合成相关基因表达的影响,探究其低温适应机制,为虹鳟的成功越冬提供一定的理论依据。本实验设定了正常温度摄食组(NF)、正常温度不摄食组(NU)、低温摄食组(CF)和低温不摄食组(CU)4个实验处理,分别测定了虹鳟肝脏和肌肉在1、3、5、7和14d时硬脂酰辅酶A去饱和酶(Stearoyl-Coenzyme A desaturase,SCD)、Δ6-去饱和酶(Δ6fatty acid desaturase,Δ6Fad)和延长酶2(Elongation of very long chain fatty acids like 2,Elovel2)3个基因的相对表达水平。实验表明:摄食显著影响虹鳟肝脏对脂肪酸的生物合成,在营养供给充足的情况下,主要通过脱酰和重酰化作用(替代作用)来满足机体对单一不饱和脂肪酸(Monounsaturated fatty acid,MUFA)和多不饱和脂肪酸(Polyunsaturated fatty acid,PUFA)的需求;在营养供给不足时,可以通过相关脂肪酸生物合成通路合成MUFA和PUFA。虹鳟肌肉中有大量脂肪沉积,因而短时间的不摄食对其影响较小。当周围环境温度降低时,SCD、Δ6Fad和Elovel2三个基因的表达量均显著上升,表明虹鳟为了适应低温,生物膜磷脂脂肪酸中不饱和脂肪酸的比例上升,虹鳟肝脏和肌肉中MUFA和PUFA生物合成量增加。此外,虹鳟肝脏SCD mRNA的表达量在CF组较低,这可能是因为摄食可以在一定程度上补充MUFA。虹鳟在正常营养条件下,大约在5～7d可适应低温;在长时间的饥饿和低温胁迫下,虹鳟机体内的脂肪酸生物合成会受到影响。

This study was carried out to determine the relative mRNA abundances of stearoyl-coenzyme A desaturase(SCD)and Δ6 fatty acid desaturase(Δ6 Fad)genes,and very long chain fatty acids like 2(Elovel2)elongation gene in muscle and liver of rainbow trout at 1 d,3 d,5 d,7 d,and 14 d,respectively.Four treatments included normal temperature and feeding(NF),normal temperature and no feeding(NU),cold and feeding(CF),and cold and no feeding(CU).Results revealed that feeding influenced unsaturated fatty acid biosynthesis in liver of rainbow trout.The demand for MUFA and PUFA in liver were met either by deacylation and reacylation when food was sufficient or by relevant fatty acid biosynthesis when food was not sufficient.Rainbow trout has rich lipid deposits in its muscles,thus the effect of short-term non-feeding is negligible.When the ambient temperature decreased,the relative mRNA abundances of SCD,Δ6 Fad,and Elovel2 in both muscle and liver significantly increased,indicating that MUFA and PUFA increased by biosynthesis in order to adapt to low temperature.Moreover,the relative mRNA abundance of SCD in liver was low in CF.This may be caused by intaking food to supply the MUFA.Rainbow trout can adapt to low temperatures within 7 d under normal nutrient conditions.However,unsaturated fatty acid biosynthesis of this speices can be affected by long-term starvation and cold stress.