Dirks Amie J, Leeuwenburgh Christiaan
Wingate University, School of Pharmacy, Wingate, NC 28174, USA.
J Nutr Biochem. 2006 Aug;17(8):501-8. doi: 10.1016/j.jnutbio.2005.11.002. Epub 2005 Dec 1.
Past the age of 50 years, aging individuals lose muscle mass at an approximate rate of 1-2% per year. This age-related muscle atrophy, termed sarcopenia, can have significant effects on individual health and quality of life and can also impact the socioeconomic status. Sarcopenia is due to both a decrease in the number of fibers and the atrophy of the remaining fibers. The mechanisms causing loss of fibers have not been clearly defined, but may likely involve apoptosis. Elevated levels of circulating tumor necrosis factor alpha (TNF-alpha) and adaptations in TNF-alpha signaling in aged skeletal muscle may be contributing factors for the activation of apoptosis. These adaptations may be fiber-type specific, which could explain the selective loss of type II fibers, vs. type I fibers, in the aging process. Caloric restriction, a proven antiaging intervention, is known to attenuate the loss of muscle mass and function with age. Furthermore, caloric restriction has been shown to attenuate the age-associated adaptations in TNF-alpha signaling in skeletal muscle, which may be a possible mechanism by which CR prevents apoptosis and the loss of muscle fibers with age. The potential role of TNF-alpha in the progression of sarcopenia will be discussed, as well as the effects of life-long caloric restriction on TNF-alpha signaling.
50岁以后，老年人肌肉质量以每年约1-2%的速度流失。这种与年龄相关的肌肉萎缩，即少肌症，会对个人健康和生活质量产生重大影响，也会影响社会经济地位。少肌症是由于纤维数量减少和剩余纤维萎缩所致。导致纤维丢失的机制尚未明确界定，但可能涉及细胞凋亡。循环肿瘤坏死因子α（TNF-α）水平升高以及老年骨骼肌中TNF-α信号通路的适应性变化可能是细胞凋亡激活的促成因素。这些适应性变化可能具有纤维类型特异性，这可以解释在衰老过程中II型纤维相对于I型纤维的选择性丢失。热量限制是一种经过验证的抗衰老干预措施，已知它可以减轻随着年龄增长而出现的肌肉质量和功能损失。此外，热量限制已被证明可以减弱骨骼肌中与年龄相关的TNF-α信号通路适应性变化，这可能是热量限制预防细胞凋亡和随着年龄增长肌肉纤维丢失的一种可能机制。将讨论TNF-α在少肌症进展中的潜在作用，以及终身热量限制对TNF-α信号通路的影响。
