Chalvon-Demersay Tristan, Gaudichon Claire, Moro Joanna, Even Patrick C, Khodorova Nadezda, Piedcoq Julien, Viollet Benoit, Averous Julien, Maurin Anne-Catherine, Tomé Daniel, Foretz Marc, Fafournoux Pierre, Azzout-Marniche Dalila
Université Paris-Saclay, AgroParisTech, INRAE, UMR PNCA, Paris, France.
Institut Cochin, CNRS, INSERM, Université de Paris, 75014, Paris, France.
Eur J Nutr. 2023 Feb;62(1):407-417. doi: 10.1007/s00394-022-02983-z. Epub 2022 Sep 7.
Protein synthesis and proteolysis are known to be controlled through mammalian target of rapamycin, AMP-activated kinase (AMPK) and general control non-derepressible 2 (GCN2) pathways, depending on the nutritional condition. This study aimed at investigating the contribution of liver AMPK and GCN2 on the adaptation to high variations in protein intake.
To evaluate the answer of protein pathways to high- or low-protein diet, male wild-type mice and genetically modified mice from C57BL/6 background with liver-specific AMPK- or GCN2-knockout were fed from day 25 diets differing in their protein level as energy: LP (5%), NP (14%) and HP (54%). Two hours after a 1 g test meal, protein synthesis rate was measured after a C valine flooding dose. The gene expression of key enzymes involved in proteolysis and GNC2 signaling pathway were quantified.
The HP diet but not the LP diet was associated with a decrease in fractional synthesis rate by 29% in the liver compared to NP diet. The expression of mRNA encoding ubiquitin and Cathepsin D was not sensitive to the protein content. The deletion of AMPK or GCN2 in the liver did not affect nor protein synthesis rates and neither proteolysis markers in the liver or in the muscle, whatever the protein intake. In the postprandial state, protein level alters protein synthesis in the liver but not in the muscle.
Taken together, these results suggest that liver AMPK and GCN2 are not involved in this adaptation to high- and low-protein diet observed in the postprandial period.
已知蛋白质合成和蛋白水解受哺乳动物雷帕霉素靶蛋白、AMP 激活的蛋白激酶（AMPK）和一般控制非抑制性 2（GCN2）信号通路调控，具体取决于营养状况。本研究旨在探讨肝脏 AMPK 和 GCN2 在适应蛋白质摄入量大幅变化中的作用。
为评估蛋白质相关信号通路对高蛋白或低蛋白饮食的反应，从第 25 天起，给雄性野生型小鼠以及来自 C57BL/6 背景的肝脏特异性 AMPK 或 GCN2 基因敲除的转基因小鼠喂食蛋白质水平不同的日粮，日粮中的能量水平保持一致：低蛋白（LP，5%）、正常蛋白（NP，14%）和高蛋白（HP，54%）。在给予 1g 测试餐两小时后，静脉注射缬氨酸冲击剂量后测量蛋白质合成速率。对参与蛋白水解和 GNC2 信号通路的关键酶的基因表达进行定量分析。
与 NP 日粮相比，HP 日粮而非 LP 日粮会使肝脏中的蛋白质合成率降低 29%。编码泛素和组织蛋白酶 D 的 mRNA 表达对蛋白质含量不敏感。无论蛋白质摄入量如何，肝脏中 AMPK 或 GCN2 的缺失均不影响肝脏或肌肉中的蛋白质合成速率及蛋白水解标志物。在餐后状态下，蛋白质水平会改变肝脏中的蛋白质合成，但不会改变肌肉中的蛋白质合成。
综上所述，这些结果表明肝脏 AMPK 和 GCN2 不参与餐后观察到的对高蛋白和低蛋白饮食的这种适应性调节。
