乳酸菌诱导线粒体生物发生对绵羊肌纤维特性和肉品质的影响

Effects of lactobacillus induced mitochondrial biogenesis on muscle fiber properties and meat quality of sheep

为了研究乳酸菌对苏尼特羊肌纤维特性和肉品质的影响及其作用机理,选择12只、3月龄健康无病的纯种苏尼特羊,随机分为2组:对照组(基础日粮)和乳酸菌组(基础日粮、2 g/只(植物乳杆菌添加量为3×1010 cfu/g)),进行为期90 d的饲喂试验。屠宰后取其背最长肌,利用ATPase组织化学染色法和实时荧光定量技术对肌纤维特性、肌球蛋白重链(Myosin Heavy Chains,MyHCs)和线粒体生物发生相关基因的mRNA表达量进行测定,此外测定代谢酶活力、生长性能和肉品质,探究肌纤维特性存在差异的原因。结果表明:乳酸菌显著提高了肌肉排酸24 h的pH值(P<0.01),降低肉的黄度值(P<0.05)和蒸煮损失(P<0.01)。肌纤维分析结果显示乳酸菌显著提高了ⅡA型肌纤维的数量比例(P<0.01),降低了ⅡB型肌纤维的数量比例(P<0.01),同时MyHCⅠ(P<0.05)、MyHCⅡa(P<0.01)、MyHCⅡx(P<0.01)mRNA表达量均显著提高。乳酸菌显著提高了琥珀酸脱氢酶(Succinate Dehydrogenase,SDH)的酶活力(P<0.05),降低了乳酸脱氢酶(Lactic Dehydrogenase,LDH)的酶活力(P<0.05)。此外,乳酸菌显著提高了腺苷酸活化蛋白激酶α1(AMP-activated protein kinaseα1,AMPKα1)(P<0.01)、沉默信息调节因子1(Sirtuin1,SIRT1)(P<0.01)和细胞色素C氧化酶Ⅳ(Cytochrome c oxidase,COXⅣ)(P<0.05)mRNA表达量。综上所述,日粮添加乳酸菌可能通过提高AMPKα1、SIRT1和COXⅣmRNA表达量促进骨骼肌线粒体生物发生,增强肌肉的氧化代谢能力,促进苏尼特羊的肌纤维类型发生转化,进而改善肉品质,研究结果为改善绵羊的肉用品质提供参考。

The present study aimed to investigate the influence of dietary supplementation with lactobacillus on muscle fiber properties and meat quality in Sunit sheep.Totally 12 Sunit sheep aged 3 months with good body condition were selected,and then two groups were randomly divided.The control group was fed a basal diet(a typical corn-soybean diet)without any antibiotics,drugs,or growth promoters.Lactobacillus group was supplemented with lactobacillus plantarum at 3×1010 cfu/g based on the diet of the control group,where the feeding period lasted for 90 days.After slaughter,the longissimus dorsi muscle was taken for subsequent test.An ATPase histochemical staining and a real-time fluorescence quantitative technique were utilized to determine the muscle fiber properties,the mRNA expression of myosin heavy chains(MyHCs)and genes related to mitochondrial biogenesis.In addition,the activity of metabolic enzymes,growth performance,and meat quality were measured to explore the relationship between muscle fiber properties and meat quality.The results showed that the dietary supplementation with lactobacillus significantly increased the value of pH24(P<0.01),while reduced the value of b*(P<0.05)and cooking loss(P<0.01)of meat.There was no significant effect on the growth performance and other meat quality indicators(P>0.05).The analysis of muscle fiber showed that the dietary supplementation with the lactobacillus increased the number ratio of type IIA muscle fibers(P<0.01),but decreased the number ratio of type IIB muscle fibers(P<0.01),where there was no significant effect on the diameter and cross-sectional area of muscle fibers.At the same time,MyHCⅠ(P<0.05),MyHCⅡa(P<0.01),and MyHCⅡx(P<0.01)mRNA expression were significantly higher than those of the control group.The enzyme activity of Succinate Dehydrogenase(SDH)in the lactobacillus group was significantly higher than that in the control group(P<0.05),whereas,the enzyme activity of Lactic Dehydrogenase(LDH)became significantly lower(P<0.05).In addition,the dietary supplementation with the lactobacillus increased the mRNA expression of AMP-activated protein kinaseα1(AMPKα1)(P<0.01),Sirtuin1(SIRT1)(P<0.01),and Cytochrome c oxidaseⅣ(COXⅣ)(P<0.05)in the longissimus dorsi muscle of Sunit sheep.There was no significant difference(P>0.05)in the mRNA expression levels of AMP-activated protein kinaseα2(AMPKα2),Peroxisome proliferator-activated receptor gamma co-activator 1-alpha(PGC-1α),and Mitochondrial transcription factor A(TFAM)in the control group,particularly similar to that of lactobacillus group.Consequently,the lactobacillus increased the oxidative metabolism of muscle,thereby promoting the transformation of muscle fiber types to more oxidation type of longissimus dorsi muscle in Sunit sheep,indicating much better meat quality than before.In any way,the dietary supplementation with lactobacillus significantly promoted the generation of more oxidative muscle types,which can be associated with the AMPKα1-SIRT1-PGC-1αaxis and mitochondrial biogenesis.