背景:针对老年人的蛋白质建议是基于年轻人的氮平衡数据。使用指示剂氨基酸氧化方法的生理研究表明,它们需要比目前的建议多30-50%的蛋白质。我们在此介绍谷胱甘肽(GSH)作为老年人蛋白质充足性的生理估计。
目的:目的是在60岁以上的健康成年人中使用前体产品方法在重复测量设计中测量GSH动力学,以响应不同的蛋白质摄入量。
方法:研究了16名健康老年人(n=8名男性和n=8名女性;BMI≤30kg/m2)。每个人按随机顺序(0.66、0.8、0.9、1.1、1.3和1.5g·kg-1·d-1)接受6种蛋白质摄入量中的4种。在每个摄入水平,参与者接受了持续7小时的同位素输注研究,之后3天适应蛋白质的测试水平.第四天,GSH分数(FSR)和绝对合成(ASR)速率通过测量[U-13C2-15N]甘氨酸在同位素稳态下掺入GSH来定量。使用混合效应变化点回归模型来确定FSR和ASR中的断点。次要结果包括氧化应激标志物的血浆浓度,同型半胱氨酸,5-L-氧代脯氨酸(5-OP),和尿硫酸盐。使用联合线性混合效应模型和Tukey的事后检验分析次要结果对GSH动力学的影响。
结果:蛋白质摄入量为1.08g·kg-1·d-1(95%CI:0.83,1.32,Rm2=0.207,Rc2=0.671;P<0.001)使GSHFSR最大化。蛋白质摄入对红细胞GSH浓度没有影响,血浆同型半胱氨酸,氧化应激标志物或5-OP(P>0.05)。蛋白质摄入对尿硫酸盐排泄有积极影响(P<0.0001)。
结论:来自高质量蛋白质的1.08g·kg-1·d-1的蛋白质摄入量使≥60岁的成年人的GSH合成最大化。这支持了表明要求高于当前建议的数据。
背景:临床试验:NCT02971046。
BACKGROUND: Protein recommendations for older adults are based on nitrogen balance data from young adults. Physiological studies using the indicator amino acid oxidation method suggest they need 30% to 50% more protein than current recommendations. We herein present glutathione (GSH) as a physiological estimate of protein adequacy in older adults.
OBJECTIVE: The objective was to measure GSH kinetics in response to varying protein intakes in a repeated-measures design in healthy adults aged ≥60 y using the precursor-product method.
METHODS: Sixteen healthy older adults (n = 8 male and n = 8 female; body mass index ≤30 kg/m2) were studied. Each received 4 of 6 protein intakes in random order (0.66, 0.8, 0.9, 1.1, 1.3 and 1.5 g⋅kg-1⋅d-1). At each intake level, participants underwent isotope infusion studies of 7 h duration following a 3-d adaptation to the test level of protein. On the fourth day, GSH fractional (FSR) and absolute synthesis (ASR) rates were quantified by measuring the incorporation of U-[13C2-15N]glycine into GSH at isotopic steady state. A mixed-effect change-point regression model was used to determine a breakpoint in FSR and ASR. Secondary outcomes included plasma concentrations of oxidative stress markers, homocysteine, 5-L-oxoproline (5-OP), and urinary sulfate. The effect of secondary outcomes on GSH kinetics was analyzed using a joint linear mixed-effect model and Tukey\'s post hoc test.
RESULTS: A protein intake of 1.08 g⋅kg-1⋅d-1 (95% confidence interval [CI]: 0.83, 1.32; Rm2 = 0.207; Rc2 = 0.671; P < 0.001) maximized GSH FSR. There was no effect of protein intake on concentrations of erythrocyte GSH, plasma homocysteine, oxidative stress markers, or 5-OP (P > 0.05). Protein intake had a positive effect on urinary sulfate excretion (P < 0.0001).
CONCLUSIONS: A protein intake of 1.08 g⋅kg-1⋅d-1 from a high-quality protein maximized GSH synthesis in adults ≥60 y. This lends support to data suggesting a requirement higher than the current recommendation. This
study was registered at clinicaltrials.gov as NCT02971046.