Department of Exercise and Sport Science, University of North Carolina, Chapel Hill, North Carolina.
Institute for Health and Sport, Victoria University, Melbourne, Victoria, Australia.
J Appl Physiol (1985). 2020 Jul 1;129(1):5-16. doi: 10.1152/japplphysiol.00752.2019. Epub 2020 May 28.
Androgen deprivation therapy (ADT) decreases muscle mass, force, and physical activity levels, but it is unclear whether disuse atrophy and testosterone suppression are additive. Additionally, conflicting reports exist on load-mediated hypertrophy during ADT and if protein supplementation offsets these deficits. This study sought to determine the role of testosterone suppression and a high-protein diet on ) immobilization-induced atrophy and ) muscle regrowth during reloading. Eight-week-old male Fischer 344 rats underwent sham surgery (Sham), castration surgery (ORX), or ORX and a high-casein diet supplemented with branched-chain amino acids (BCAA) (ORX+CAS/AA) followed by 10 days of unilateral immobilization (IMM) and 0, 6, or 14 days of reloading. With IMM, body mass gains were 8% greater than ORX and ORX+CAS/AA that increased to 15% during reloading (both < 0.01). IMM reduced muscle mass by 11-34% (all < 0.01) and extensor digitorum longus and soleus (SOL) force by 21% and 49% (both < 0.01), respectively, with no group differences. During reloading, castration reduced gastrocnemius mass (12%) at 6 days and SOL mass (20%) and SOL force recovery (46%) at 14 days relative to Sham (all < 0.05). Specific force reduced castration deficits, indicating that muscle atrophy was a key contributor. IMM decreased SOL cross-sectional area by 30.3% ( < 0.001), with a trend for reduced regrowth in ORX and ORX+CAS/AA following reloading ( = 0.083). Castration did not exacerbate disuse atrophy but may impair recovery of muscle function, with no benefit from a CAS/AA diet during reloading. Examining functional outcomes in addition to muscle mass during dietary interventions provides novel insights into muscle regrowth during ADT. Low testosterone levels during skeletal muscle disuse did not worsen declines in muscle mass and function, although hypogonadism may attenuate recovery during subsequent reloading. Diets high in casein did not improve outcomes during immobilization or reloading. Practical strategies are needed that do not compromise caloric intake yet provide effective protein doses to augment these adverse effects.
雄激素剥夺疗法（ADT）会减少肌肉质量、力量和身体活动水平，但不清楚废用性萎缩和睾酮抑制是否具有累加作用。此外，关于 ADT 期间负荷介导的肥大以及蛋白质补充是否可以弥补这些缺陷，存在相互矛盾的报告。本研究旨在确定睾酮抑制和高蛋白饮食对 ) 固定诱导的萎缩和 ) 再加载期间的肌肉再生的作用。8 周龄雄性 Fischer 344 大鼠接受假手术（Sham）、去势手术（ORX）或 ORX 和富含支链氨基酸的高蛋白饮食（ORX+CAS/AA）治疗，随后进行 10 天的单侧固定（IMM）和 0、6 或 14 天的再加载。与 ORX 和 ORX+CAS/AA 相比，IMM 时体重增加了约 8%，而在再加载时增加了 15%（均 < 0.01）。IMM 使肌肉质量减少了 11-34%（均 < 0.01），使伸趾长肌和比目鱼肌（SOL）的力分别减少了 21%和 49%（均 < 0.01），但各组之间无差异。在再加载期间，与 Sham 相比，去势减少了腓肠肌质量（12%）在 6 天和 SOL 质量（20%）和 SOL 力恢复（~46%）在 14 天（均 < 0.05）。比力降低了去势的缺陷，表明肌肉萎缩是一个关键因素。IMM 使 SOL 横截面积减少了 30.3%（ < 0.001），再加载后 ORX 和 ORX+CAS/AA 出现减少的生长趋势（ = 0.083）。去势并没有加重废用性萎缩，但可能会损害肌肉功能的恢复，再加载期间富含 CAS/AA 的饮食没有带来益处。在饮食干预期间除了肌肉质量外，还检查功能结果，为 ADT 期间的肌肉再生提供了新的见解。在骨骼肌失用期间，低睾酮水平并没有使肌肉质量和功能下降更严重，尽管性腺功能减退可能会削弱随后再加载期间的恢复。高蛋白饮食并不能改善固定或再加载期间的结果。需要制定不影响热量摄入但又能提供有效蛋白质剂量以减轻这些不良影响的实用策略。
