Taste is crucial to meat quality, and free Glu is an important taste-active component in meat. Our recent study showed that the short-term feeding of a low-Lys diet increases the concentration of free Glu and other free amino acids in chicken muscle and improves its taste. Here, we investigated the mechanisms by which the feeding of a low-Lys diet increases free Glu in chicken muscle. Two groups (n = 10 per group) of 28-day-old female Ross strain broiler chickens were fed diets with a graded Lys content of 90% or 100% of the recommended Lys requirement (according to National Research Council [1994] guidelines) for 10 D. Free amino acid concentrations and the mRNA abundance of protein metabolism-related genes were measured in breast muscle, and breast muscle metabolome analysis was conducted. Free Glu in muscle was increased by 51.8% in the Lys 90% group compared with the Lys 100% group (P < 0.01). Free threonine, glutamine, glycine, valine, isoleucine, leucine, tyrosine, phenylalanine, histidine, and 3-methyl-histidine concentrations in breast muscle were also increased in the Lys 90% group (P < 0.05). Metabolome analysis also showed that free amino acids were increased in the Lys 90% group. The mRNA abundance of μ-calpain, caspase-3, and 20S proteasome C2 subunit were increased in the Lys 90% group (P < 0.05). Moreover, the free Glu concentration in muscle was correlated with mRNA abundance of μ-calpain (r = 0.74, P < 0.01), caspase 3 (r = 0.69, P < 0.01), 20S proteasome C2 subunit (r = 0.65, P < 0.01), and cathepsin B (r = 0.52, P < 0.05). Our study suggests that the feeding of a low-Lys diet to chickens increased the free Glu content of breast muscle by promoting protein degradation.

中文翻译：

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饮食中赖氨酸的减少通过鸡蛋白质代谢的变化而增加肌肉游离氨基酸。

味道对肉质至关重要，而游离谷氨酸是肉中重要的味觉活性成分。我们最近的研究表明，短期饲喂低Lys饮食会增加鸡肌肉中游离Glu和其他游离氨基酸的浓度，并改善其味道。在这里，我们研究了低赖氨酸饮食喂养增加鸡肌肉游离Glu的机制。向两组（每组n = 10）的28日龄雌性Ross品系肉鸡饲喂Lys的分级Lys含量为建议的Lys要求量的90％或100％（根据国家研究委员会[1994]指南）测定10D。在胸肌中测量游离氨基酸浓度和蛋白质代谢相关基因的mRNA丰度，并进行胸肌代谢组分析。肌肉中的游离Glu增加了51。Lys 90％组的8％高于Lys 100％组的（P <0.01）。Lys 90％组的胸肌游离苏氨酸，谷氨酰胺，甘氨酸，缬氨酸，异亮氨酸，亮氨酸，酪氨酸，苯丙氨酸，组氨酸和3-甲基组氨酸的浓度也增加了（P <0.05）。代谢组学分析还显示，Lys 90％组的游离氨基酸增加。Lys 90％组的μ-钙蛋白酶，caspase-3和20S蛋白酶体C2亚基的mRNA丰度增加（P <0.05）。此外，肌肉中的游离Glu浓度与μ-钙蛋白酶的mRNA丰度相关（r = 0.74，P <0.01），caspase 3（r = 0.69，P <0.01），20S蛋白酶体C2亚基（r = 0.65，P < 0.01）和组织蛋白酶B（r = 0.52，P <0.05）。