Effect of Diet and Hormone on the Regulation of Body Protein Synthesis

蛋白质代谢受多种因素调节，包括激素和营养因素。作者表明，身体蛋白质的获得或损失可以很好地解释胰岛素样生长因子（IGFs）及其特异性结合蛋白（IGFBPs）的血浆浓度。特别地，IGFBP-1的血浆浓度在蛋白质缺乏或糖皮质激素分泌增强或胰岛素缺乏的情况下大大增加。这些血浆IGFBP-1浓度的增加与肝脏中IGFBP-1 mRNA含量的增加或IGFBP-1基因转录速率的增加相关。本研究分析了IGFBP-1基因表达增加的机制，在IGFBP-1基因5 ′上游区发现了一个氨基酸反应元件。此外，他还证明了特异性转录因子的结合对IGFBP-1基因转录率的提高具有重要意义。上述结果为解释饮食和激素因素影响的全身蛋白质代谢调节的分子机制提供了可能。

Protein metabolism is regulated by many factors including hormonal and nutritional factors. The author showed that body protein gain or loss is well explained by the plasma concentrations of insulin-like growth factors (IGFs) and their specific binding proteins called IGFBPs. Particularly, plasma concentration of IGFBP-1 increases greatly under protein deficiency or under enhanced glucocortocoid secretion or under insulin deficiency. These increases in plasma IGFBP-1 concentration is correlated to the increase in the content of IGFBP-1 mRNA in liver or the increase in the transcription rate of IGFBP-1 gene. In the present investigations, the mechanism of the increase in the IGFBP-1 gene has been analyzed.The author identified an amino acid-responsive element in the 5'upstream region of IGFBP-1 gene. Furthermore, he showed that the binding of specific transcription factors is important for the increase in the transcription rate of IGFBP-1 gene.The above results made it possible to explain the molecular mechanisms of the regulation of whole body protein metabolism as affected by dietary and hormonal factors.