Optimizing Protein Intake in Older Americans with Mobility Limitations

描述(申请人提供)：蛋白质的推荐膳食摄入量(RDA)，成年男性和女性设定为0.8克/公斤/天，引起了争论，许多专家主张蛋白质摄入量大大超过RDA，以帮助维持老年人的肌肉合成代谢。目前尚不清楚，在目前摄入量低于RDA的美国老年人中，增加蛋白质摄入量是否会增加骨骼肌量、肌肉表现和身体功能。我们的第一个目标是确定与RDA(0.8 g7 kg-17天-1)相比，服用1.3 g7 kg-17天-1的蛋白质是否会在老年男性的瘦体重、最大自愿肌肉力量和力量以及自我报告和基于表现的身体功能测量方面产生更大的改善。我们的第二个目标是确定在服用睾丸素期间，服用1.3克蛋白质的老年男性在瘦身质量、最大自愿力量、自我报告和基于表现的身体功能指标方面的增长是否比服用优卡路里饮食的老年男性的RDA更大。我们将采用2×2析因设计进行随机、安慰剂对照、双盲试验。居住在社区，65岁或以上的男性，如果自报有活动受限，每天蛋白质摄入量为0.8g7 kg-17day-1，并且没有睾酮治疗的禁忌症，将被随机分配到四组中的一组：安慰剂注射+蛋白质0.8g7 kg-17day-1；安慰剂注射+蛋白质1.3g7 kg-17day-1；睾丸酮enanthate每周125 mg+蛋白质0.8g7 kg-17day-1；睾丸酮enanthate每周125 mg+蛋白质1.3g7 kg-17day-1。疗程为6个月。主要结果是通过双能X射线骨密度仪测量，从基线到6个月瘦体重的变化。次要结果包括腿部和胸部按压练习中的最大自愿力量、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、爬楼梯能力和负重)、疲劳、幸福感和情感平衡。安全措施包括估计肾小球滤过率、尿钙排泄、红细胞压积、PSA和前列腺检查。将使用几种策略--包装餐、份量控制、频繁增援以及通过使用食品合规性检查表进行遵从性检查--来提高对饮食处方的遵从性。仔细的受试者选择，纳入好的试验设计的属性，如随机化、分层和盲法，基于对效果大小和效力的考虑的适当的样本量，仔细的安全监测，以及一个多学科团队，应该最大限度地成功实现拟议目标的机会，这些目标具有重要的公共卫生和政策影响。 与公共健康相关：蛋白质的推荐膳食摄入量(RDA)引发了极大的争议。许多专家主张老年人的蛋白质摄入量比目前的RDA更高。我们将确定在改善瘦体重和身体功能方面，更高的蛋白质摄入量是否单独比RDA更安全和更有效，以及这种更高的蛋白质摄入量是否会增强行动能力受限的老年人对促进合成代谢治疗的合成反应。这一问题对美国老年人的公共健康和政策具有巨大的影响。

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. PUBLIC HEALTH RELEVANCE: The recommended dietary allowance (RDA) for protein has invited a great deal of controversy. Many experts advocate higher levels of protein intake for older individuals than the current RDA. We will determine whether higher protein intakes alone are safe and more effective than the RDA in improving lean body mass and physical function and whether this higher protein intake augments the anabolic response to function promoting anabolic therapy in older persons with mobility limitations. This issue has enormous public health and policy implications for older Americans.