Optimizing Protein Intake in Older Americans with Mobility Limitations

描述（由申请人提供）：成年男性和女性的蛋白质推荐膳食摄入量 (RDA) 为 0.8 克/公斤/天，这引起了争论，许多专家主张蛋白质摄入量远高于 RDA，以帮助维持老年人的肌肉合成代谢。目前尚不清楚美国老年人（目前的摄入量低于每日推荐摄入量）增加蛋白质摄入量是否会增加骨骼肌质量、肌肉性能和身体功能。我们的第一个目标是确定与 RDA（0.8 g7kg-17day-1）相比，服用 1.3 g7kg-17day-1 蛋白质是否会导致老年男性的去脂体重、最大随意肌力量和爆发力以及自我报告和基于表现的身体机能指标有更大的改善。我们的第二个目标是确定在服用睾酮期间，服用 1.3 克蛋白质的老年男性在去脂体重、最大自愿力量以及自我报告和基于表现的身体机能测量方面是否比采用每日每日摄入量（RDA）更大。我们将使用 2 X 2 析因设计进行随机、安慰剂对照、双盲试验。社区住宅、65 岁或以上的男性，自我报告行动能力受限、每日蛋白质摄入量 < 0.8 g7kg-17day-1 并且没有睾酮治疗禁忌症，将被随机分配到四组之一：安慰剂注射加蛋白质 0.8 g7kg-17day-1；安慰剂注射加蛋白质1.3g7kg-17day-1；庚酸睾酮 125 mg 每周加蛋白质 0.8 g7kg-17day-1；庚酸睾酮 125 mg 每周加 1.3 g 蛋白质7kg-17day-1。治疗持续时间为6个月。主要结果是通过双能 X 射线吸收测定法测量的去脂体重从基线到 6 个月的变化。次要结果包括腿部和胸部推举练习中最大自愿力量的变化、腿部力量、自我报告（SF-36 的身体功能领域）和基于表现的身体功能测量（6 分钟步行距离和速度、爬楼梯力量和负重）、疲劳、幸福感和情感平衡。安全措施包括估计 GFR、尿钙排泄、血细胞比容、PSA 和前列腺检查。多种策略——包装膳食、份量控制、频繁强化以及使用食品合规检查表进行合规性检查——将用于增强对饮食处方的依从性。仔细的受试者选择、纳入良好试验设计的属性（如随机化、分层和盲法）、基于效应大小和功效考虑的适当样本量、细心的安全性监测以及多学科团队，应最大限度地提高成功实现拟议目标的机会，这对公共卫生和政策具有重要影响。

DESCRIPTION (provided by applicant): The recommended dietary allowance (RDA) for protein, set at 0.8 grams/kg/day for adult men and women, has engendered debate and many experts advocate protein intakes substantially above the RDA to help maintain muscle anabolism in older individuals. It is not known whether increasing protein intake in older Americans, whose current intake is below the RDA, increases skeletal muscle mass, muscle performance and physical function. Our first aim is to determine whether administration of 1.3 g7kg-17day-1 of protein, compared to the RDA (0.8 g7kg-17day-1), will result in greater improvements in lean body mass, maximal voluntary muscle strength and power, and self-reported and performance-based measures of physical function in older men. Our second aim is to determine whether the gains in lean body mass, maximal voluntary strength and self-reported and performance-based measures of physical function during testosterone administration are greater with 1.3 g protein than with the RDA in older men on a eucaloric diet. We will conduct a randomized, placebo- controlled, double blind, and trial using a 2 X 2 factorial design. Community dwelling, men, 65 years or older, who have self-reported mobility limitation, a daily protein intake of < 0.8 g7kg-17day-1 and no contraindications for testosterone therapy, will be randomly assigned to one of four groups: placebo injections plus protein 0.8 g7kg- 17day-1; placebo injections plus protein 1.3g7kg-17day-1; testosterone enanthate 125 mg weekly plus protein 0.8 g7kg-17day-1; testosterone enanthate 125 mg weekly plus 1.3 g protein7kg-17day-1. Treatment duration will be 6 months. The primary outcome is change in lean body mass from baseline to 6 months, measured by dual energy X-ray absorptiometry. Secondary outcomes include change in maximal voluntary strength in leg and chest press exercises, leg power, self-reported (physical function domain of SF-36) and performance-based measures of physical function (6-min walking distance and speed, stair climbing power, and load carrying), fatigue, wellbeing, and affectivity balance. Safety measures include estimated GFR, urinary calcium excretion, hematocrit, PSA, and prostate examination. Several strategies - packaged meals, portion control, frequent reinforcements, and compliance checks by using food compliance checklists - will be used to enhance compliance with dietary prescription. Careful subject selection, incorporation of the attributes of good trial design such as randomization, stratification, and blinding, an appropriate sample size based on consideration of effect size and power, attentive safety monitoring, and a multidisciplinary team should maximize the chances of successful attainment of the proposed aims, which have important public health and policy implications.