Ogawa Aki, Naruse Yuka, Shigemura Yasutaka, Kobayashi Yukiko, Suzuki Isao, Wada Sayori, Hayamizu Kohsuke, Kuwahata Masashi, Kido Yasuhiro
Division of Applied Life Science, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan.
J Nutr Sci Vitaminol (Tokyo). 2011;57(6):418-25. doi: 10.3177/jnsv.57.418.
Currently, protein requirements are generally determined based on nitrogen balance studies, but there are a variety of limitations associated with this method. The indicator amino acid oxidation (IAAO) method, with a theoretical base that differs widely from the nitrogen balance method, was developed as an alternative method for humans. The objective of the present study was to evaluate protein intakes for metabolic demands and protein quality, using protein itself, in rats employing the IAAO technique with L-[1-(13)C]phenylalanine. Male Wistar/ST rats (5-6 wk old) received a graded casein (4.3, 8.6, 12.9, 17.2, 21.5, 25.8%), or a wheat gluten (7.2, 10.8, 14.4, 18.0, 21.6, 25.2%) diet, along with L-[1-(13)C]phenylalanine. An isotopic plateau in breath was achieved 210 min after the start of the (13)C ingestion. The protein intakes for metabolic demands were calculated by applying a mixed-effect change-point regression model to breath (13)CO(2) data, which identified a breakpoint at minimal breath (13)CO(2) in response to graded protein intake. The protein intakes for metabolic demands determined by the IAAO method were 13.1 g/kg BW/d for casein and 18.1 g/kg BW/d for wheat gluten, showing a tendency similar to that determined by the nitrogen balance method. These results demonstrated that the IAAO method could be employed to evaluate not only the protein intakes for metabolic demands, but the dietary protein quality in freely living rats, suggesting that this method might be viable in a clinical setting.
目前，蛋白质需求量通常是基于氮平衡研究来确定的，但这种方法存在多种局限性。指示性氨基酸氧化（IAAO）法，其理论基础与氮平衡法有很大差异，是作为一种适用于人类的替代方法而开发的。本研究的目的是在大鼠中使用L-[1-(13)C]苯丙氨酸的IAAO技术，利用蛋白质本身来评估代谢需求的蛋白质摄入量和蛋白质质量。雄性Wistar/ST大鼠（5 - 6周龄）接受分级酪蛋白（4.3%、8.6%、12.9%、17.2%、21.5%、25.8%）或小麦麸质（7.2%、10.8%、14.4%、18.0%、21.6%、25.2%）饮食，同时给予L-[1-(13)C]苯丙氨酸。在摄入(13)C开始210分钟后，呼吸中达到同位素平台期。通过将混合效应变点回归模型应用于呼吸(13)CO₂数据来计算代谢需求的蛋白质摄入量，该模型在响应分级蛋白质摄入时在最低呼吸(13)CO₂处确定了一个断点。IAAO法确定的代谢需求蛋白质摄入量，酪蛋白为13.1 g/kg体重/天，小麦麸质为18.1 g/kg体重/天，显示出与氮平衡法确定的趋势相似。这些结果表明，IAAO法不仅可用于评估代谢需求的蛋白质摄入量，还可用于评估自由活动大鼠的膳食蛋白质质量，这表明该方法在临床环境中可能是可行的。
