NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, the Netherlands.
Proc Nutr Soc. 2021 May;80(2):139-147. doi: 10.1017/S0029665120008009. Epub 2021 Jan 5.
All tissues are in a constant state of turnover, with a tightly controlled regulation of protein synthesis and breakdown rates. Due to the relative ease of sampling skeletal muscle tissue, basal muscle protein synthesis rates and the protein synthetic responses to various anabolic stimuli have been well defined in human subjects. In contrast, only limited data are available on tissue protein synthesis rates in other organs. Several organs such as the brain, liver and pancreas, show substantially higher (basal) protein synthesis rates when compared to skeletal muscle tissue. Such data suggest that these tissues may also possess a high level of plasticity. It remains to be determined whether protein synthesis rates in these tissues can be modulated by external stimuli. Whole-body protein synthesis rates are highly responsive to protein intake. As the contribution of muscle protein synthesis rates to whole-body protein synthesis rates is relatively small considering the large amount of muscle mass, this suggests that other organ tissues may also be responsive to (protein) feeding. Whole-body protein synthesis rates in the fasted or fed state can be quantified by measuring plasma amino acid kinetics, although this requires the production of intrinsically labelled protein. Protein intake requirements to maximise whole-body protein synthesis may also be determined by the indicator amino acid oxidation technique, but the technique does not allow the assessment of actual protein synthesis and breakdown rates. Both approaches have several other methodological and inferential limitations that will be discussed in detail in this paper.
所有组织都处于不断更新的状态，其蛋白质合成和分解速率受到严格控制。由于骨骼肌组织易于取样，因此人类骨骼肌基础蛋白合成率和对各种合成代谢刺激的蛋白合成反应已得到充分定义。相比之下，其他器官的组织蛋白合成率的数据则很有限。与骨骼肌组织相比，大脑、肝脏和胰腺等几个器官的基础蛋白合成率明显更高。这些数据表明，这些组织可能也具有较高的可塑性。尚不确定这些组织的蛋白合成率是否可以通过外部刺激来调节。全身蛋白质合成率对蛋白质摄入非常敏感。考虑到大量的肌肉质量，肌肉蛋白合成率对全身蛋白质合成率的贡献相对较小，这表明其他器官组织也可能对（蛋白质）喂养有反应。通过测量血浆氨基酸动力学可以定量测定禁食或进食状态下的全身蛋白质合成率，尽管这需要产生内源性标记的蛋白质。最大程度地提高全身蛋白质合成率的蛋白质摄入需求也可以通过指示氨基酸氧化技术来确定，但该技术无法评估实际的蛋白质合成和分解率。这两种方法都有其他一些方法学和推理上的限制，本文将详细讨论这些限制。
