Wageningen University, Division of Human Nutrition, P.O. Box 8129, 6700 EV Wageningen, The Netherlands.
Radboud University, Donders Institute for Brain, Cognition and Behaviour, Centre for Cognitive Neuroimaging, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
Nutrients. 2017 Nov 23;9(12):1279. doi: 10.3390/nu9121279.
The effects of tyrosine on plasma response and cognition in aging are unknown. We assessed the dose-dependent response to tyrosine administration in older adults in both plasma tyrosine concentrations and working memory performance. In this double blind randomized cross-over trial 17 older adults (aged 60-75 years) received a single administration of 100, 150, or 200 mg/kg body weight of tyrosine. For comparison, 17 young adults (aged 18-35 years) received a dose of 150 mg/kg body weight of tyrosine. Tyrosine plasma concentrations were determined before and 90, 120, 150, 180, 210, and 240 min after tyrosine intake. Working memory was assessed using the N-back task at 90 min after tyrosine administration. Older adults showed a dose-dependent increase in plasma tyrosine concentrations ( < 0.001), and the plasma response was higher than for young adults with the same dose ( < 0.001). Load-dependent working memory performance decreased with higher doses of tyrosine ( = 0.048), especially in older adults with greater dose-dependent plasma tyrosine responses ( = 0.035). Our results show an age-related increase in plasma tyrosine response, which was associated with a dose-dependent decline in cognitive functioning in older adults.
酪氨酸对衰老时血浆反应和认知的影响尚不清楚。我们评估了在老年个体中给予酪氨酸后，随剂量增加引起的血浆酪氨酸浓度和工作记忆表现的变化。在这项双盲随机交叉试验中，17 名老年个体（年龄 60-75 岁）接受了 100、150 或 200mg/kg 体重的酪氨酸单次给药。为了进行比较，17 名年轻个体（年龄 18-35 岁）接受了 150mg/kg 体重的酪氨酸剂量。在给予酪氨酸前和 90、120、150、180、210 和 240 分钟时测定血浆酪氨酸浓度。在给予酪氨酸后 90 分钟时使用 N-回任务评估工作记忆。老年个体表现出随剂量增加的血浆酪氨酸浓度增加（<0.001），且与给予相同剂量的年轻个体相比，其血浆反应更高（<0.001）。与较低剂量的酪氨酸相比，较高剂量的酪氨酸导致依赖负荷的工作记忆表现下降（=0.048），特别是在具有更大剂量依赖性血浆酪氨酸反应的老年个体中（=0.035）。我们的结果显示，血浆酪氨酸反应随年龄增加而增加，这与老年个体认知功能的剂量依赖性下降有关。
