饲养方式对宰后苏尼特羊肉一磷酸腺苷激活的蛋白激酶活力及糖酵解的影响

Effect of Different Feeding Methods on AMP-Activated Protein Kinase Activity and Glycolysis of Postmortem Sunit Sheep

本研究测定了放牧和圈养条件下苏尼特羊宰后羊肉一磷酸腺苷激活的蛋白激酶(AMP-activated protein kinase,AMPK)活力、AMPK基因(PRKAA1、PRKAA2、PRKAG3)m RNA相对表达量和糖酵解指标,分析了AMPK活力与糖酵解指标之间的相关性,研究不同饲养方式对羊肉AMPK活力及糖酵解的影响。结果表明:放牧条件下苏尼特羊背最长肌的剪切力、亮度值以及黄度值均显著大于圈养条件(P<0.05);两种饲养方式的胴体初p H值(p H1)和静止排酸24 h后胴体最终pH值(pH24)差异不显著(P>0.05);圈养条件下苏尼特羊PRKAA1和PRKAG3基因的相对表达量显著大于放牧条件(P<0.05),PRKAA2基因相对表达量显著小于放牧条件(P<0.05);AMPK活力和己糖激酶活力均为圈养条件大于放牧条件,但差异不显著(P>0.05);圈养条件下乳酸含量显著大于放牧条件(P<0.05)。通过相关性分析可知:PRKAG3基因相对表达量与AMPK活力、己糖激酶活力以及乳酸含量均呈显著正相关(P<0.05),与剪切力呈显著负相关(P<0.05);PRKAA1基因相对表达量仅与乳酸含量呈显著正相关(P<0.05);PRKAA2基因相对表达量与AMPK活力以及糖酵解指标无显著相关性;AMPK活力和己糖激酶活力以及乳酸含量均呈显著正相关(P<0.05)。综上所述,PRKAA1和PRKAG3基因相对表达量高时,AMPK被激活,使己糖激酶活力增加,加速组织内的糖酵解,增加肌肉乳酸含量,降低p H值,进而影响肉的品质。

The effect of different feeding methods on AMP-activated protein kinase（AMPK） and glycolysis in longissimus dorsi muscle from Sunit sheep were investigated in this study. The results showed that longissimus dorsi muscle from grazing sheep exhibited significantly higher Warner-Bratzler shear force, L＊ and b＊ values when compared with pen-reared sheep（P〈0.05）. The p H1 and p H24 of longissimus dorsi were not significantly between different feeding methods（P〈0.05）. PRKAA1 and PRKAG3 gene expression in pen-fed sheep were significantly higher than in grazing sheep（P〈0.05）, but the opposite was found for PRKAA2 gene expression（P〈0.05）. AMPK and hexokinase activity under pen-fed conditions were higher but not statistically significantly than under grazing conditions（P〈0.05）. Lactic acid content under pen-fed conditions was significantly higher than under grazing conditions（P〈0.05）. Correlation analysis revealed that PRKAG3 gene expression positively regulated AMPK activation, hexokinase activity and lactic acid content（P〈0.05）, but had a significantly negative correlation with Warner-Bratzler shear force（P〈0.05）. PRKKA1 gene expression and lactic acid content were significantly positively correlated with each other（P〈0.05）, while PRKKA2 had no significant correlation with AMPK or glycolysis indicators. AMPK activity was significantly positively correlated with hexokinase activity and lactic acid content（P〈0.05）. From the above results, we concluded that high levels of PRKAA1 and PRKAG3 gene expression resulted in AMPK activation and consequently an increase in hexokinase activity, thereby accelerating the process of glycolysis, increasing lactic acid content, reducing p H and consequently affecting meat quality.