Rouaze-Romet M, Savu L, Vranckx R, Bleiberg-Daniel F, Le Moullac B, Gouache P, Nunez E A
U224 Inserm, Faculté de médecine Xavier Bichat, Paris, France.
Acta Endocrinol (Copenh). 1992 Nov;127(5):441-8. doi: 10.1530/acta.0.1270441.
Thyroxine-binding globulin, the highest affinity thyroid hormone binder of rat serum, was studied during 28 days of dietary protein restriction (6% protein vs 18% protein in isocaloric control diet) or energy restriction (60% intake of control diet). Studies were performed on male rats aged four weeks at the beginning of experiments: the animals had reached the ontogenic stage when the thyroxine-binding globulin had declined, after its high postnatal surge, to undetectable levels. Short-term administration (seven days) of one or the other restricted diet similarly induced resynthesis of the protein. Its serum concentrations reached 26-46% of those measured in eight-day pups (peak of the neonatal surge) and its liver mRNAs showed corresponding enhanced signals. Serum T4 binding activities were increased, although concomitantly transthyretin, second specific T4 carrier of the rat serum, decreased markedly (65-75% of controls) in response to the dietary restrictions. Longer-term diet administration (14 or 28 days) resulted in the further increase of the thyroxine-binding globulin in the protein-restricted rats, in contrast to its decline and eventual disappearance in the energy-restricted animals. Protein restriction was associated with increased total and free T3 serum concentrations, in contrast to energy restriction which little affected these parameters. These studies reveal rat thyroxine-binding globulin as a positive (increasing), highly sensitive reactant of malnutrition, able to discriminate between energy deficiency and composition dysequilibrium of diets. They suggest that up-regulation of its synthesis in the two dietary models involves differential mechanisms.
甲状腺素结合球蛋白是大鼠血清中对甲状腺激素亲和力最高的结合蛋白，在为期28天的饮食蛋白质限制（蛋白质含量为6%，而等热量对照饮食中为18%）或能量限制（摄入量为对照饮食的60%）期间进行了研究。实验开始时对四周龄雄性大鼠进行研究：这些动物已达到个体发育阶段，此时甲状腺素结合球蛋白在出生后急剧上升后已下降至无法检测的水平。短期（七天）给予其中一种限制饮食同样会诱导该蛋白的重新合成。其血清浓度达到八天大的幼崽（新生儿激增峰值）所测浓度的26 - 46%，其肝脏mRNA显示出相应增强的信号。血清T4结合活性增加，尽管与此同时，大鼠血清中第二种特异性T4载体甲状腺素转运蛋白因饮食限制而显著下降（为对照的65 - 75%）。长期饮食（14天或28天）导致蛋白质限制的大鼠中甲状腺素结合球蛋白进一步增加，而能量限制的动物中该蛋白则下降并最终消失。与能量限制对这些参数影响较小相反，蛋白质限制与血清总T3和游离T3浓度增加有关。这些研究表明大鼠甲状腺素结合球蛋白是营养不良的一种阳性（增加）、高度敏感的反应物质，能够区分能量缺乏和饮食成分失衡。它们表明在两种饮食模型中其合成的上调涉及不同的机制。
