寒冷环境对民猪骨骼肌肌纤维类型及相关基因表达的影响

Effects of cold environment on skeletal muscle fiber types and related gene expressions in Min pig

为了研究寒冷环境下民猪骨骼肌肌纤维类型及相关基因表达的变化,试验按照饲养温度和时间将18头体重约为95 kg的230日龄的健康民猪随机均分为3组,即常温组(舍内,15~25℃)、低温36 h组(试验结束前36 h置于舍外半敞式大棚内,-15~-25℃;之前置于舍内,15~25℃)和低温21 d组(舍外半敞式大棚内,-15~-25℃),每组6头。试验结束后,试验猪全部屠宰,取1 g左右背最长肌样品,采用qPCR技术分析寒冷环境下民猪骨骼肌四种肌纤维类型(MyHCⅠ、MyHCⅡa、MyHCⅡx和MyHCⅡb)、肌红蛋白(Mb)、过氧化物酶体增殖激活受体γ辅助激活因子α(PGC-1α)以及FoxO1的基因表达情况。结果表明:寒冷环境下36 h,试验民猪的MyHCⅠ、MyHCⅡa和Mb基因的mRNA相对表达量显著高于常温组(P<0.05),MyHCⅡx、MyHCⅡb和FoxO1基因的mRNA相对表达量与常温组差异不显著(P>0.05),PGC-1α基因的mRNA相对表达量极显著高于常温组(P<0.01);寒冷环境下21 d,MyHCⅠ和PGC-1α基因的mRNA相对表达量显著高于常温组(P<0.05),MyHCⅡb和FoxO1基因的mRNA相对表达量显著低于常温组(P<0.05),Mb基因的mRNA相对表达量极显著高于常温组(P<0.01),MyHCⅡa和MyHCⅡx基因的mRNA相对表达量与常温组差异不显著(P>0.05)。说明寒冷环境下民猪背最长肌中酵解型纤维含量减少,氧化型纤维含量增多,增强了肌肉的氧化代谢能力;同时诱导Mb和PGC-1α基因表达,抑制FoxO1基因表达,促进了肌纤维由酵解型向氧化型的转化。

To study the effects of cold environment on skeletal muscle fiber types and related gene expressions in Min pig,eighteen 230-days-old healthy Min pigs with body weights of approximately 95 kg were randomly divided into 3 groups according to feeding temperature and time,namely normal temperature group(15-25℃in the house),low temperature group for 36 h(-15--25℃in the semi-open greenhouse for 36 h before the end of the test;15-25℃in the house at other test time),and low temperature group for 21 d(-15-25℃in the semi-open greenhouse).There were six pigs in each group.At the end of the experiment,all the pigs were slaughtered.About 1 g back longest muscle samples were collected and used to analyze the gene expression changes of four muscle fiber types(MyHCⅠ,MyHCⅡa,MyHCⅡx and MyHCⅡb),myoglobin(Mb),peroxisome-proliferator-activated receptorγcoactivator-1α(PGC-1α),and FoxO1 in Min pig skeletal muscle in cold environment by real-time PCR technology.The results showed that the mRNA expressions of MyHC I,MyHCⅡa,and Mb genes of Min pigs in the cold environment for up to 36 h group were significantly higher than normal group(P<0.05),and the mRNA expressions of MyHCⅡx,MyHCⅡb and FoxO1 genes were not significantly different than normal group(P>0.05),the mRNA expression of PGC-1αgene was significantly higher than that in the normal temperature group(P<0.01).In cold environment for up to 21 d group,the mRNA expressions of MyHC I,PGC-1αgenes were significantly higher than that in normal group(P<0.05),on the contrary,the mRNA expressions of MyHCⅡb and FoxO1 genes were significantly lower(P<0.05),and the mRNA expressions of Mb gene was extremehy significantly different than normal group(P<0.01),and the mRNA expressions of MyHCⅡa and MyHCⅡx gens were not significatly different than normal group(P>0.05).The results indicated that the content of fermentable fiber in the longus dorsi muscle of Min pigs decreased under cold environment,while the content of oxidized fiber increased,and the oxidative metabolism of muscle was enhanced.Meanwhile,the expression of Mb and PGC-1 genes was induced,FoxO1 gene was inhibited,and the transformation of muscle fibers from the glycolytic type to the oxidative type was promoted.