Regulation of Skeletal Muscle Protein Degradation and Synthesis by Oral Administration of Lysine in Rats
Regulation of Skeletal Muscle Protein Degradation and Synthesis by Oral Administration of Lysine in Rats
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DOI：
10.3177/jnsv.59.412
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发表时间：
2013-10-01
影响因子：
1.6
通讯作者：
Nagasawa, Takashi
中科院分区：
文献类型：
--
作者：
Sato, Tomonori;Ito, Yoshiaki;Nagasawa, Takashi
几种分解代谢疾病和卸载诱导肌肉质量消耗，这导致各种疾病和衰老的严重病理进展。已知亮氨酸通过刺激骨骼肌中的蛋白质合成和抑制蛋白质降解来减轻肌肉损失。本研究旨在探讨赖氨酸摄入对骨骼肌蛋白质降解和合成的影响。给予禁食大鼠22.8-570 mg赖氨酸/100 g体重，并在给予赖氨酸后0-6 h评估肌原纤维蛋白降解速率。在给予114 mg Lys/100 g体重和570 mg Lys/100 g体重后，通过从离体肌肉释放Me His来评价的肌原纤维蛋白降解速率被显著抑制。自噬-溶酶体途径的标志物LC 3-II在摄入Lys（114 mg/100 g体重）后趋于降低（p=0.05，0.08）。然而，泛素连接酶E3 atrogin-1 mRNA的表达和泛素化蛋白的水平并没有受到抑制赖氨酸摄入。赖氨酸摄入后，腓肠肌中mTOR、S6 K1和4 E-BP 1的磷酸化水平没有改变。这些结果表明，赖氨酸能够抑制肌原纤维蛋白降解至少部分通过自噬-溶酶体途径，而不是泛素-蛋白酶体途径，而赖氨酸可能无法刺激蛋白质合成在这个时间范围内。
Several catabolic diseases and unloading induce muscle mass wasting, which causes severe pathological progression in various diseases and aging. Leucine is known to attenuate muscle loss via stimulation of protein synthesis and suppression of protein degradation in skeletal muscle. The aim of this study was to investigate the effects of lysine intake on protein degradation and synthesis in skeletal muscle. Fasted rats were administered 22.8-570 mg Lys/100 g body weight and the rates of myofibrillar protein degradation were assessed for 0-6 h after Lys administration. The rates of myofibrillar protein degradation evaluated by Me His release from the isolated muscles were markedly suppressed after administration of 114 mg Lys/100 g body weight and of 570 mg Lys/100 g body weight. LC3-II, a marker of the autophagic-lysosomal pathway, tended to decrease (p=0.05, 0.08) after Lys intake (114 mg/100 g body weight). However, expression of ubiquitin ligase E3 atrogin-1 mRNA and levels of ubiquitinated proteins were not suppressed by Lys intake. Phosphorylation levels of mTOR, S6K1 and 4E-BP1 in the gastrocnemius muscle were not altered after Lys intake. These results suggest that Lys is able to suppress myofibrillar protein degradation at least partially through the autophagic-lysosomal pathway, not the ubiquitin-proteasomal pathway, whereas Lys might be unable to stimulate protein synthesis within this time frame.