Daly Anne, Pinto Alex, Evans Sharon, Geberhiwot Tarekegn, Jackson Richard, César Julio Rocha, Tang Jonathan C Y, MacDonald Anita
Birmingham Children's Hospital, NHS Trust, Steelhouse Lane, Birmingham B4 6NH, UK.
Queen Elizabeth Hospital, NHS Trust, Birmingham B15 2GW, UK.
Nutrients. 2025 Aug 19;17(16):2671. doi: 10.3390/nu17162671.
: The rate at which amino acids (AAs) are absorbed from casein glycomacropeptide (CGMP) when given as a protein substitute in phenylketonuria (PKU) is unknown. This three-way randomised, controlled, crossover study aimed to compare the AA absorption profile of phenylalanine (Phe)-free L-amino acids (L-AAs), low-Phe CGMP (CGMP) and casein in healthy adult subjects. : Area under the curve (AUC) was measured over 240 minutes after ingesting one dose of each protein source on three separate occasions, under the same test conditions. A total of 0.4 g/kg protein equivalent of each test product (L-AA, CGMP and casein) was given. Fasted blood samples were collected from healthy volunteers at 30, 60, 90, 120, 150, 180 and 240 minutes post-test. Insulin, blood urea nitrogen, glucose and total (TAAs), essential (EAAs), large neutral (LNAAs) and branch chain (BCAAs) amino acids were measured at each time point. : A total of 20 subjects (11 females), median age 43 y (range 23-49), with a median BMI 24.2 (20-30.5) were recruited. AUC was compared across groups. Statistically significant differences were noted for: AUC for TAAs and BCAAs between CGMP and L-AAs vs. casein [TAAs = 0.008 and = 0.03; BCAAs = <0.001 and = 0.002]. There were no AUC differences between L-AAs and CGMP. AUC was largest for L-AAs, then CGMP and finally casein. For LNAAs, EAAs, insulin, glucose and urea, there were no statistically significant differences. There was a consistent delivery of AAs for casein demonstrated by a sustained curve, but the absorption curves for L-AAs and CGMP were transient, rising rapidly and falling, with the exception of tyrosine with CGMP which showed a gradual increase over 240 minutes in contrast to L-AAs and casein. : Amino acids from CGMP and L-AAs were absorbed more rapidly than casein, inferring CGMP did not mimic casein, a slow-release protein source. The tyrosine concentration curve for CGMP suggests a beneficial effect on the Phe: tyrosine ratio. Kinetic labelled studies will help bring greater understanding on the utilisation of AAs particularly important for protein synthesis.
在苯丙酮尿症（PKU）中，当酪蛋白糖巨肽（CGMP）作为蛋白质替代物使用时，氨基酸（AAs）的吸收速率尚不清楚。这项三向随机、对照、交叉研究旨在比较健康成年受试者中无苯丙氨酸（Phe）的L-氨基酸（L-AAs）、低Phe的CGMP（CGMP）和酪蛋白的AA吸收情况。在相同测试条件下，于三个不同时间点分别摄入一剂每种蛋白质来源后，在240分钟内测量曲线下面积（AUC）。每种测试产品（L-AA、CGMP和酪蛋白）均给予0.4 g/kg蛋白质当量。在测试后30、60、90、120、150、180和240分钟从健康志愿者中采集空腹血样。在每个时间点测量胰岛素、血尿素氮、葡萄糖以及总（TAAs）、必需（EAAs）、大中性（LNAAs）和支链（BCAAs）氨基酸。共招募了20名受试者（11名女性），年龄中位数43岁（范围23 - 49岁），BMI中位数24.2（20 - 30.5）。对各实验组的AUC进行比较。结果发现CGMP和L-AAs与酪蛋白相比，TAAs和BCAAs的AUC存在统计学显著差异[TAAs = 0.008， = 0.03；BCAAs = <0.001， = 0.002]。L-AAs和CGMP之间的AUC无差异。L-AAs的AUC最大，其次是CGMP，最后是酪蛋白。对于LNAAs、EAAs、胰岛素、葡萄糖和尿素，无统计学显著差异。酪蛋白的AA释放呈持续曲线，表现出持续的释放，但L-AAs和CGMP的吸收曲线是短暂的，迅速上升然后下降，不过CGMP中的酪氨酸除外，其在240分钟内呈逐渐上升趋势，与L-AAs和酪蛋白不同。CGMP和L-AAs中的氨基酸比酪蛋白吸收更快，这表明CGMP无法模拟酪蛋白这种缓释蛋白质来源。CGMP的酪氨酸浓度曲线表明其对Phe:酪氨酸比值有有益影响。动力学标记研究将有助于更深入了解对蛋白质合成特别重要的氨基酸的利用情况。
