Aging causes loss of skeletal muscle mass and function, which is called sarcopenia. While sarcopenia impairs the quality of life of older adults and is a major factor in long-term hospitalization, its detailed pathogenic mechanism and preventive measures remain to be identified. Caloric restriction (CR) suppresses age-related physiological and pathological changes in many species and prolongs the average and healthy life expectancy. It has recently been reported that CR suppresses the onset of sarcopenia; however, few studies have analyzed the effects of long-term CR on age-related skeletal muscle atrophy. Thus, we investigated the aging and CR effects on soleus (SOL) muscles of 9-, 24-, and 29-month-old ad libitum-fed rats (9AL, 24AL, and 29AL, respectively) and of 29-month-old CR (29CR) rats. The total muscle cross sectional area (mCSA) of the entire SOL muscle significantly decreased in the 29AL rats, but not in the 24AL rats, compared with the 9AL rats. SOL muscle of the 29AL rats exhibited marked muscle fiber atrophy and increases in the number of muscle fibers with a central nucleus, in fibrosis, and in adipocyte infiltration. Additionally, although the decrease in the single muscle fiber cross-sectional area (fCSA) and the muscle fibers' number occurred in both slow-type and fast-type muscle fibers, the degree of atrophy was more remarkable in the fast-type fibers. However, CR suppressed the muscle fiber atrophy observed in the 29AL rats' SOL muscle by preserving the mCSA and the number of muscle fibers that declined with aging, and by decreasing the number of muscle fibers with a central nucleus, fibrosis and denervated muscle fibers. Overall, these results revealed that advanced aging separately reduces the number and fCSA of each muscle fiber type, but long-term CR can ameliorate this age-related sarcopenic muscle atrophy.

衰老会导致骨骼肌质量和功能的丧失，这被称为肌肉减少症。虽然肌肉减少症会损害老年人的生活质量并且是长期住院的主要因素，但其详细的发病机制和预防措施仍有待确定。热量限制 (CR) 抑制了许多物种与年龄相关的生理和病理变化，并延长了平均和健康的预期寿命。最近有报道称，CR 可抑制肌肉减少症的发作；然而，很少有研究分析长期 CR 对年龄相关骨骼肌萎缩的影响。因此，我们研究了 9、24 和 29 个月大的随意喂养的大鼠（分别为 9AL、24AL 和 29AL）和 29 个月大的比目鱼肌 (SOL) 肌肉的衰老和 CR 影响。 CR (29CR) 大鼠。与 9AL 大鼠相比，29AL 大鼠的整个 SOL 肌肉的总肌肉横截面积 (mCSA) 显着降低，但 24AL 大鼠没有。29AL 大鼠的 SOL 肌肉表现出明显的肌纤维萎缩和具有中央核的肌纤维数量增加、纤维化和脂肪细胞浸润。此外，尽管慢型和快型肌纤维的单根肌纤维横截面积（fCSA）和肌纤维数量均减少，但快速型肌纤维的萎缩程度更为显着。然而，CR 通过保留 mCSA 和随年龄增长而下降的肌纤维数量，以及通过减少具有中央核的肌纤维数量，抑制了在 29AL 大鼠 SOL 肌肉中观察到的肌纤维萎缩，纤维化和去神经支配的肌肉纤维。总体而言，这些结果表明，晚期衰老分别减少了每种肌纤维类型的数量和 fCSA，但长期 CR 可以改善这种与年龄相关的肌肉减少症肌肉萎缩。