长期饲喂不同蛋白质水平饲粮对猪脂肪代谢相关基因表达的影响

Effects of Long-Term Feeding Diets with Different Protein Levels on Gene Expressions Related to Lipid Metabolism of Pigs

本试验旨在研究长期饲喂不同蛋白质水平饲粮对猪脂肪代谢相关基因表达的影响。试验选用18头三元(杜×长×大)杂交28日龄断奶仔猪,随机分为3组,每组6个重复,每个重复1头。对照组[高粗蛋白质(HCP)组]采用符合NRC(2012)推荐营养需要的饲粮,试验组是根据NRC(2012)标准,在添加赖氨酸(Lys)、蛋氨酸(Met)、苏氨酸(Thr)、色氨酸(Try)4种必需氨基酸基础上,将饲粮蛋白质水平分别降低3%[中粗蛋白质(MCP)组]和6%[低粗蛋白质(LCP)组]。试验期125 d。结果表明:1)在肝脏中,与HCP组相比,LCP组显著降低脂肪酸合成相关基因乙酰辅酶A羧化酶(ACC)、脂肪酸合成酶(FAS)、苹果酸酶1(ME1)及锚蛋白1(ANK1)的基因表达量(P<0.05);同时显著提高脂肪酸转运相关基因过氧化物酶体增殖物激活受体γ(PPARγ)及脂肪酸结合蛋白(FABP)的基因表达量(P<0.05);而MCP组与HCP组相比,脂肪酸合成、转运相关基因表达量均无显著性差异(P>0.05);与HCP组相比,MCP及LCP组均显著降低脂肪酸氧化分解相关基因、过氧化物酶体增殖物激活受体α(PPARα)、肉毒碱棕榈酰转移酶(CPT)的基因表达量(P<0.05)。2)在背最长肌(LDM)中,MCP组中脂肪酸合成相关基因胆固醇调节元件结合蛋白(SREBP)、FAS、硬脂酰辅酶A去饱和酶(SCD)的基因表达量显著高于其他2组(P<0.05);ACC及FABP在LCP组的基因表达量显著低于其他2组(P<0.05);CPT基因表达量及LDM的肌内脂肪(IM F)含量在LCP及M CP组显著低于HCP组(P<0.05)。3)肝脏和LDM中,各组甘油三酯脂酶(ATG L)及二烯酰辅酶A还原酶(DECR)基因表达量均无显著性差异(P>0.05)。由此可见,在NRC(2012)基础上,适当的降低饲粮蛋白质水平(3%)可促进LDM中脂肪酸合成、转运相关基因的表达,但对肝脏中脂肪酸合成相关基因的表达无显著影响;适当的降低饲粮蛋白质水平(3%)可降低LDM及肝脏中脂肪酸氧化分解相关基因的表达,但并不增加LDM肌内脂肪含量。

This experiment was conducted to study the effects of long-term feeding diets with different protein levels on gene expressions related to lipid metabolism of pigs. Eighteen cross-bred （ DurocxLandracex York-shire ）piglets weaned 28 days of age were randomly assigned to 3 groups with 6 replicates per group and 1 pig-let per replicate. Piglets in control group [ （high crude protein, HCP） group] were fed a diet based on the Na-tional Research Council （NRC ） （2012） recommendation, those in experimental groups were fed diets with decreasing 3% [ （medium crude protein, MCP） group ] and 6 % crude protein levels [ （ low crude protein, LCP） group] , respectively, based on NRC （2012） , and supplemented with 4 essential amino acids, which were lysine, methionine, threonine and tryptophane. The experiment lasted for 125 days. The results showed as follows ; 1） in l iver, compared with HCP group, LCP group significantly decreased expressions of fatty acid synthesis genes including acetyl Co A carboxylase （ACC ） , fatty acid synthase , malicenzyme 1 （M El）and ankyrin 1 （ANKl） （P 〈0.05） , and significantly increased expressions of fatty acid transport genes like peroxisome proliferator-activated receptor gamma （PPARy） and fatty acid binding proteins （FABP） （P 〈 0.05）. However, there were no significant differences between MCP and HCP groups in hepatic expressions of fatty acid synthesis genes and fatty acid transport genes （P 〉0.05）. Compared with HCP group, there were sig-nificant increases in hepatic expressions of fatty acid oxygenolysis genes like peroxisome proliferator-activated receptor alfa （PPARa） and carnitine palmitoyltransferase （CPT） in MCP and LCP groups （P〈0.05）. 2） In the longissimus dorsis muscle （LDM ） , the expressions of fatty acid synthesis genes like sterol regulatory ele-ment binding protein （SREBP） , FAS and stearoyl CoA desaturase （SCD） showed significantly higher in MCP group than those in the other two groups （P 〈0.05） , but ACC and FABP displayed significantly lower expres-sions in LCP group than those in the other two groups （P 〈0.05）. The expression of CPT gene and intramuscu-lar fat （IMF ） content of LDM were significantly lower in LCP and MCP groups compared to HCP group （P〈 0.05）. 3） In liver and LDM , there were no significant differences in expressions of adipose triglyceride lipase （ATGL） and 2,4-dienoyl-CoA reductase （DECR） genes among three groups （P 〉0.05）. In conclusion, de-creasing dietary crude protein level （3 %） properly can promote expressions of fatty acid synthesis and transport genes, but has no significant effects on hepatic expressions of fatty acid synthesis genes ; decreasing dietary crude protein level （3 %） properly can decrease hepatic expressions of fatty acid oxygenolysis genes, but does not affect IMF content of LDM .