Optimizing Protein Intake in Older Americans with Mobility Limitations

描述（由申请人提供）：蛋白质的推荐膳食允许量（RDA）为成年男性和女性设定为0.8克/公斤/天，这引起了争论，许多专家主张蛋白质摄入量大大高于RDA，以帮助维持老年人的肌肉合成代谢。目前尚不清楚增加美国老年人的蛋白质摄入量是否会增加骨骼肌质量、肌肉表现和身体功能，他们目前的摄入量低于RDA。我们的第一个目标是确定与RDA （0.8 g7kg-17day-1）相比，1.3 g7kg-17day-1的蛋白质管理是否会导致老年男性瘦体重，最大随意肌力量和力量，以及自我报告和基于性能的身体功能测量的更大改善。我们的第二个目标是确定在睾酮给药期间，1.3 g蛋白质的老年男性在瘦体重、最大自主力量、自我报告和基于表现的身体功能测量方面的增加是否大于营养饮食的RDA。我们将进行一项随机、安慰剂对照、双盲、2 × 2因子设计的试验。居住在社区的65岁以上男性，自我报告活动受限，每日蛋白质摄入量< 0.8 g7kg-17day-1，无睾酮治疗禁忌症，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1.3g7kg-17day-1；睾酮酸125mg /周加蛋白0.8 g7kg-17day-1；睾酮125mg每周加1.3 g蛋白质7kg-17day-1。治疗时间为6个月。主要结果是通过双能x线吸收仪测量从基线到6个月的瘦体重变化。次要结果包括腿部和胸部按压练习中最大自主力量的变化、腿部力量、自我报告（SF-36的身体功能域）和基于性能的身体功能测量（6分钟步行距离和速度、爬楼梯能力和负重）、疲劳、健康和情感平衡。安全措施包括估计GFR、尿钙排泄、红细胞压积、PSA和前列腺检查。将采用几种策略——包装食品、控制份量、频繁强化以及使用食品合规清单进行合规检查——来加强对饮食处方的遵守。仔细选择受试者，结合良好试验设计的特点，如随机化、分层和盲法，在考虑效应大小和威力的基础上适当的样本量，细心的安全监测，以及一个多学科团队，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意义。

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.