Yoshikawa Mayu, Morita Shunsuke, Sonoki Hirofumi, Iwamoto Hiroshi, Takeda Yasuhiro
Wellness & Nutritional Science Institute, Morinaga Milk Industry Co., Ltd.
J Nutr Sci Vitaminol (Tokyo). 2020;66(1):54-59. doi: 10.3177/jnsv.66.54.
The indicator amino acid oxidation (IAAO) method is a novel method for determining protein requirements. Recently, the protein requirement of healthy young men was reevaluated using this method, and the currently recommended protein requirement based on nitrogen balance study was found to be deficient. Similarly, with respect to experimental animals, the protein concentration used widely in the experimental diets was assumed to be deficient. However, only a few studies have tested the IAAO method in experimental animals. In particular, there are no studies on the protein requirement of adult rats measured using this method. Therefore, we applied the IAAO method to adult rats, to determine their casein protein requirement. Male Wistar/ST rats (15-18 wk old, housed in lighting (lights on from 23:00 to 11:00) conditions) were provided with the test diet including graded casein (5, 7, 9, 13, 17, 21 and 25%) every 2 h from 11:00 to 17:00. Tracer administration of C-phenylalanine was performed hourly from 14:00 to 17:00. Breath CO was measured every 30 min after the first tracer administration. There were significant differences between the CO concentration of the 5% and 17% casein groups at 17:00 and 18:00 (p<0.05). The mean casein protein requirement and recommended dietary allowance (RDA) were estimated to be 5.2 g/kg BW/d and 7.0 g/kg BW/d using the mixed-effect change point regression model, respectively. Our results indicated that the recommended casein value may be slightly deficient to satisfy the protein metabolic demand of some adult rats.
指示性氨基酸氧化（IAAO）法是一种测定蛋白质需求量的新方法。最近，使用该方法对健康年轻男性的蛋白质需求量进行了重新评估，结果发现基于氮平衡研究目前推荐的蛋白质需求量不足。同样，对于实验动物，实验日粮中广泛使用的蛋白质浓度也被认为不足。然而，只有少数研究在实验动物中测试了IAAO法。特别是，尚无使用该方法测量成年大鼠蛋白质需求量的研究。因此，我们将IAAO法应用于成年大鼠，以确定它们对酪蛋白的蛋白质需求量。雄性Wistar/ST大鼠（15 - 18周龄，饲养在光照条件下（23:00至11:00开灯）），从11:00至17:00每2小时提供一次含不同梯度酪蛋白（5%、7%、9%、13%、17%、21%和25%）的试验日粮。从14:00至17:00每小时进行一次C - 苯丙氨酸示踪剂给药。首次给药后每30分钟测量一次呼出的CO。在17:00和18:00时，5%和17%酪蛋白组的CO浓度存在显著差异（p<0.05）。使用混合效应变化点回归模型估计，酪蛋白的平均蛋白质需求量和推荐膳食摄入量（RDA）分别为5.2 g/kg体重/天和7.0 g/kg体重/天。我们的结果表明，推荐的酪蛋白值可能略低于满足一些成年大鼠蛋白质代谢需求的水平。
