MUSCLE HYPERTROPHY AND PROTEIN SYNTHESIS--EFFECT OF AGE

本项目的长期目标是阐明 与衰老相关的肌肉萎缩，并检查 干预可能会扭转这一进程。 近期目标是测试 以下假设：1.肌原纤维蛋白 在人类中，合成随着衰老而下降; 2.进步的抵抗 运动增加肌原纤维蛋白合成; 3.生长激素 治疗增加老年受试者中的肌原纤维蛋白合成; 4. 生长激素和抗阻运动具有相加或协同作用， 对强度和肌原纤维蛋白合成影响。 受试者将 未受过训练，但健康，男女老少（18-30岁） (over 60年）。 在进行任何干预之前，他们将接受以下测试： 动态肌肉力量、肌肉质量（无肉 饮食和选定肌肉的磁共振成像）、肌肉纤维大小 (both 1型和2型）在取自股四头肌（股四头肌）的组织中 股外侧肌中肌原纤维蛋白合成 （通过亮氨酸掺入肌原纤维的速率确定） 使用稳定同位素示踪剂的蛋白质）。 这些研究将重复进行 在以下干预之一的3个月期间之后：1.没有 干预或安慰剂注射（对照组）; 2.进步 力量训练（举重）; 3.人生长激素注射剂 （仅老年受试者）; 4.渐进式力量训练加生长激素 （仅限老年人）。 年龄较大的受试者将继续研究3 停止生长激素（或安慰剂）治疗后数月， 确定是否有任何长期利益的临时计划， 生长激素治疗 这些研究可能提供重要的新 有关老年人肌肉萎缩的机制及其 治疗或预防。

The long-term goal of this project is to elucidate the mechanism of the muscle atrophy associated with aging, and to examine the effects of interventions that may reverse this process. The immediate goal is to test the following hypotheses: 1. that the rate of myofibrillar protein synthesis declines with aging in humans; 2. that progressive resistance exercise increases myofibrillar protein synthesis; 3. that growth hormone- treatment increases myofibrillar protein synthesis in older subjects; 4. that growth hormone and resistance exercise have an additive or synergistic effect on strength nd myofibrillar protein synthesis. Subjects will be untrained, but health, men and women, both young (18-30 years) and old (over 60 years). Before any interventions, they will undergo tests of dynamic muscle strength, muscle mass (creatinine excretion on a meat-free diet and magnetic resonance imaging of selected muscles), muscle fiber size (both type 1 and type 2) in tissue taken from quadriceps muscle (vastus lateralis), and myofibrillar protein synthesis in vastus lateralis muscle (determined by the rate of incorporation of leucine into myofibrillar protein using a stable isotope tracer). These studies will be repeated after a 3 month period of one of the following interventions: 1. No intervention or placebo injections (control groups); 2. Progressive strength training (weight lifting); 3. Human growth hormone injections (older subjects only); 4. Progressive strength training plus growth hormone (older subjects only). Older subjects will continue to be studied for 3 months after stopping the growth hormone (or placebo) treatment to determine if there is any long-term benefit of a temporary program of growth hormone treatment. These studies may provide significant new information about the mechanism of muscle atrophy in the elderly, and its treatment or prevention.