Wada Yasuaki, Seto Namiko, Komatsu Yosuke, Tsuda Muneya, Kitamura Yohei, Izumi Hirohisa, Shimizu Takashi, Takeda Yasuhiro
Wellness & Nutrition Science Institute, Morinaga Milk Industry Co. Ltd., Zama, Japan.
Front Nutr. 2019 Feb 15;6:12. doi: 10.3389/fnut.2019.00012. eCollection 2019.
We recently reported that plasma albumin redox state, which correlates with albumin synthesis rate, could be associated with the quality of dietary protein. Aiming to elucidate the association between them, plasma albumin redox state was investigated in rats fed various kinds of AIN-93G-based low protein diets. Plasma albumin redox state was shifted to a more oxidized state in rats fed 3% casein (CN) diet than those fed 3% whey protein or 3% wheat gluten diet, while supplementing 3% CN diet with cystine reversed it to a more reduced state, indicating that cystine would complement the shortage of cysteine in CN, thereby increasing albumin synthesis rate. Supplementation with glutathione, a cysteine-containing antioxidative tripeptide, normalized hepatic glutathione redox state modulated by ingestion of 3% CN diet, but it only reversed the oxidized shift of plasma albumin redox state to an extent similar to cystine alone or the constituting amino acid mixture of glutathione (i.e., glutamic acid, cystine, and glycine), indicating that glutathione would primarily serve as a source of cysteine rather than exert its antioxidative activity. Plasma albumin would thus be influenced by amino acid balance in dietary proteins, and it could be useful as a biomarker that contributes to prevention of protein under-nutriton, caused by not only insufficient protein intake but also ingestion of poor-quality protein.
我们最近报道，与白蛋白合成速率相关的血浆白蛋白氧化还原状态可能与膳食蛋白质的质量有关。为了阐明它们之间的关联，我们对喂食各种基于AIN-93G的低蛋白饮食的大鼠的血浆白蛋白氧化还原状态进行了研究。与喂食3%乳清蛋白或3%小麦麸质饮食的大鼠相比，喂食3%酪蛋白（CN）饮食的大鼠血浆白蛋白氧化还原状态转变为更氧化的状态，而在3%CN饮食中补充胱氨酸可将其逆转至更还原的状态，这表明胱氨酸可以补充CN中半胱氨酸的不足，从而提高白蛋白合成速率。补充谷胱甘肽（一种含半胱氨酸的抗氧化三肽）可使因摄入3%CN饮食而调节的肝脏谷胱甘肽氧化还原状态正常化，但它仅将血浆白蛋白氧化还原状态的氧化转变逆转到与单独使用胱氨酸或谷胱甘肽的组成氨基酸混合物（即谷氨酸、胱氨酸和甘氨酸）相似的程度，这表明谷胱甘肽主要作为半胱氨酸的来源，而不是发挥其抗氧化活性。因此，血浆白蛋白会受到膳食蛋白质中氨基酸平衡的影响，并且它可能作为一种生物标志物，有助于预防不仅由蛋白质摄入不足而且由摄入低质量蛋白质引起的蛋白质营养不良。
