Deutz N E, Bruins M J, Soeters P B
Department of Surgery, Maastricht University, P.O. Box 616, NL-6200 MD Maastricht, The Netherlands.
J Nutr. 1998 Dec;128(12):2435-45. doi: 10.1093/jn/128.12.2435.
For routine evaluation of the quality of dietary protein, amino acid scoring patterns were used. Evaluation of this pattern for soy and casein revealed that these proteins are of almost equal quality. However, in vivo studies showed a large difference. To study the biological effects of meals with casein and soy protein, the contributions of individual amino acids to net protein retention and amino acid kinetics in gut, liver and muscle in healthy pigs were investigated. Isonitrogenous enteral nutrition, infused at a rate of 10 mL. kg body wt-1. h-1 and consisting of maltodextrin (137 g/L) with added casein (53 g/L) or soy protein (68 g/L), was given to conscious, healthy female multicathetized pigs (20-22 kg, n = 12). A primed-constant infusion protocol with L-[ring-2,6-3H]phenylalanine, L-[3,4-3H]valine and [15N-15N]urea was used to measure amino acid and urea kinetics in gut, liver and muscle. Measurements were done postabsorptively and 2-6 h after initiation of the enteral nutrition. During the meal, appearance of amino acids into the portal vein and the uptake by the liver was lower with casein infusion. Muscle uptake did not differ. Gut protein synthesis tended to be lower with soy infusion (P = 0.1). Liver protein synthesis and degradation were higher with casein infusion (P < 0.05), while in muscle, soy infusion stimulated protein turnover (P < 0.05). In comparison to the postabsorptive condition, liver urea production was unchanged after casein infusion, while it was significantly increased after soy infusion. These results suggest that the quality of soy protein is inferior to that of casein protein.
为了对膳食蛋白质质量进行常规评估，采用了氨基酸评分模式。对大豆蛋白和酪蛋白的这种模式评估表明，这些蛋白质的质量几乎相等。然而，体内研究显示出很大差异。为了研究酪蛋白和大豆蛋白餐的生物学效应，研究了健康猪肠道、肝脏和肌肉中单个氨基酸对净蛋白质保留和氨基酸动力学的贡献。对清醒的、健康的、多导管插入的雌性猪（20 - 22千克，n = 12）给予等氮肠内营养，以10毫升·千克体重-1·小时-1的速率输注，其由含有添加酪蛋白（53克/升）或大豆蛋白（68克/升）的麦芽糊精（137克/升）组成。采用L-[环-2,6-3H]苯丙氨酸、L-[3,4-3H]缬氨酸和[15N-15N]尿素的首剂量-恒速输注方案来测量肠道、肝脏和肌肉中的氨基酸和尿素动力学。在吸收后以及肠内营养开始后2 - 6小时进行测量。进餐期间，输注酪蛋白时氨基酸进入门静脉的量和肝脏的摄取量较低。肌肉摄取没有差异。输注大豆蛋白时肠道蛋白质合成有降低的趋势（P = 0.1）。输注酪蛋白时肝脏蛋白质合成和降解较高（P < 0.05），而在肌肉中，输注大豆蛋白刺激蛋白质周转（P < 0.05）。与吸收后状态相比，输注酪蛋白后肝脏尿素生成未改变，而输注大豆蛋白后肝脏尿素生成显著增加。这些结果表明大豆蛋白的质量低于酪蛋白的质量。
