MUSCLE HYPERTROPHY AND PROTEIN SYNTHESIS--EFFECT OF AGE

这个项目的长期目标是阐明 与衰老相关的肌肉萎缩，并检查 可能逆转这一进程的干预措施。目前的目标是测试 以下假设：1.肌原纤维蛋白的比率 人类的合成能力随着年龄的增长而下降；2.渐进性抵抗 运动增加了肌原纤维蛋白的合成；3.生长激素- 治疗增加了老年受试者肌原纤维蛋白的合成； 生长激素和抵抗力训练具有相加或协同作用 对肌力和肌原纤维蛋白合成的影响。主题将是 未受过训练，但身体健康，有男有女，既有年轻人(18-30岁)，也有老年人 (60岁以上)。在进行任何干预之前，他们将接受 动态肌力、肌体质量(无肉上肌酐排泄 饮食和选定肌肉的磁共振成像)、肌肉纤维大小 (1型和2型)取自股四头肌(股四头肌)的组织 和股外侧肌的肌原纤维蛋白合成 (由亮氨酸掺入肌原纤维的速率决定 使用稳定的同位素示踪剂的蛋白质)。这些研究将重复进行 在下列干预措施之一的3个月期间之后：1.否 干预或安慰剂注射(对照组)；2.进展 力量训练(举重)；3.人体生长激素注射 (仅限年龄较大的受试者)；4.渐进力量训练加生长激素 (仅限较老的对象)。较老的科目将继续学习3年。 停止生长激素(或安慰剂)治疗几个月后 确定临时计划是否有任何长期好处 生长激素治疗。这些研究可能会提供重要的新的 关于老年人肌肉萎缩机制的信息，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.