Wada Yasuaki, Sato Yoshiyasu, Miyazaki Keisuke, Takeda Yasuhiro, Kuwahata Masashi
Nutritional Science Institute, Morinaga Milk Industry Co, Ltd, 5-1-83, Higashihara, Zama, Kanagawa-Pref, 252-8583, Japan.
Food Ingredients & Technology Institute, Morinaga Milk Industry Co, Ltd, 5-1-83, Higashihara, Zama, Kanagawa-Pref, 252-8583, Japan.
Nutr Res. 2017 Jan;37:46-57. doi: 10.1016/j.nutres.2016.12.003. Epub 2016 Dec 8.
The reduced/oxidized state of plasma albumin is influenced by many factors, including chronic diseases and strenuous training. Recently, the reduced/oxidized state has also been shown to be associated with dietary protein and energy intakes in rats. We hypothesized that dietary protein intake may modulate the reduced/oxidized state of plasma albumin by altering the rate of albumin synthesis and that the reduced/oxidized state could therefore serve as a novel marker of protein undernutrition. We tested this hypothesis by examining male growing rats placed on a low-protein or energy-restriction diet. In the 4-week experiment, animals fed a low-protein diet (3% casein), whose dietary intakes were lower than those fed control diet (20% casein), showed significant decreases in plasma albumin level and the ratio of the reduced form of albumin to total albumin. Animals given the same amount of control diet as the low-protein diet group (approximately 30% energy restriction) also showed the above decreases, albeit to much more limited extents. The ratio of reduced to total plasma albumin correlated significantly with plasma albumin fractional synthesis rate. When animals were maintained on the low-protein diet for as long as 12 weeks and then fed the control diet for 1 week, the decreased ratio of reduced to total plasma albumin, but not plasma albumin level, resolved rapidly. The reduced/oxidized state of plasma albumin would thus reflect dietary protein status via plasma albumin turnover including the fractional synthesis rate and could prove useful as a sensitive marker of protein undernutrition.
血浆白蛋白的还原/氧化状态受多种因素影响，包括慢性疾病和高强度训练。最近，还原/氧化状态也被证明与大鼠的膳食蛋白质和能量摄入有关。我们假设膳食蛋白质摄入可能通过改变白蛋白合成速率来调节血浆白蛋白的还原/氧化状态，因此还原/氧化状态可作为蛋白质营养不良的一种新标志物。我们通过研究处于低蛋白或能量限制饮食的雄性生长大鼠来验证这一假设。在为期4周的实验中，喂食低蛋白饮食（3%酪蛋白）的动物，其膳食摄入量低于喂食对照饮食（20%酪蛋白）的动物，血浆白蛋白水平以及白蛋白还原形式与总白蛋白的比率均显著降低。给予与低蛋白饮食组相同量对照饮食（约30%能量限制）的动物也出现了上述降低，尽管程度更为有限。血浆白蛋白还原形式与总血浆白蛋白的比率与血浆白蛋白分数合成率显著相关。当动物维持低蛋白饮食长达12周，然后喂食对照饮食1周时，血浆白蛋白还原形式与总血浆白蛋白降低的比率迅速恢复，但血浆白蛋白水平未恢复。因此，血浆白蛋白的还原/氧化状态将通过包括分数合成率在内的血浆白蛋白周转率反映膳食蛋白质状态，并可能被证明是蛋白质营养不良的一种敏感标志物。
