Department of Geriatrics, The Center for Translational Research in Aging & Longevity, Donald W. Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, AR, USA; Department of Molecular Medicine, Lee Gil Ya Cancer and Diabetes Institute Gachon University School of Medicine, Incheon, Republic of Korea.
Department of Prescription & Rehabilitation of Exercise, Dankook University, Cheonan, Republic of Korea.
Clin Nutr. 2018 Dec;37(6 Pt A):2076-2083. doi: 10.1016/j.clnu.2017.09.025. Epub 2017 Oct 6.
BACKGROUND & AIMS: It has been demonstrated that the relative content and profile of essential amino acids (EAA) play a determining role for stimulation of muscle protein synthesis (MPS) following intake of pure EAA or protein alone.
To test if this also holds in the context of mixed meals at both whole body and muscle levels, twelve older subjects (57-74 yrs) received primed continuous infusion of L-[ring-H]phenylalanine and L-[ring-H]tyrosine over a 9-h experimental period to determine whole body protein kinetics and MPS in the fasted state and following consumption of egg-based (EGG) or cereal-based (CEREAL) isocaloric and isonitrogenous breakfast. A standardized lunch, primarily consisting of beef protein was also consumed by each group. Whole body protein kinetics [protein synthesis (PS), breakdown (PB), and net balance (NB)] were expressed as changes from basal fasted period.
We found that EGG breakfast resulted in a greater NB through a greater suppression of PB compared with the CEREAL breakfast. The greater NB during the post-breakfast period with the EGG was normalized following the standard lunch despite the sustained elevations in plasma EAA concentrations. However, the EGG breakfast stimulated both PS and PB compared with the CEREAL breakfast during the post-lunch period. MPS was not different between meals despite larges differences in the plasma EAA responses.
We conclude that in the context of mixed meals, quality of protein affects NB through changes in protein breakdown and affects protein turnover following subsequent meal intake.
已证实，必需氨基酸（EAA）的相对含量和分布在单独摄入 EAA 或蛋白质后刺激肌肉蛋白质合成（MPS）方面起着决定性作用。
为了检验这一原理在混合餐的情况下是否同样适用，我们对 12 名老年人（57-74 岁）进行了试验，在 9 小时的实验期间，通过连续输注 L-[ring-H]苯丙氨酸和 L-[ring-H]酪氨酸，对空腹状态和摄入鸡蛋（EGG）或谷物（CEREAL）早餐后的整体和肌肉水平的蛋白质动力学和 MPS 进行了检测。两组均摄入了以牛肉蛋白为主的标准化午餐。整体蛋白质动力学[蛋白质合成（PS）、分解（PB）和净平衡（NB）]以空腹基础期的变化表示。
我们发现，与谷物早餐相比，鸡蛋早餐可通过更大程度地抑制 PB 来增加 NB。尽管血浆 EAA 浓度持续升高，但标准午餐后，鸡蛋早餐在早餐后的恢复期中可使 NB 恢复正常。然而，与谷物早餐相比，鸡蛋早餐在午餐后的时期刺激了 PS 和 PB。尽管血浆 EAA 反应存在较大差异，但每餐之间的 MPS 并无差异。
我们得出结论，在混合餐的情况下，蛋白质的质量通过蛋白质分解的变化影响 NB，并影响随后摄入的餐后蛋白质周转率。
