나이들면 민첩성이 떨어지는 이유! 노인에게서 fast twitch fiber에 있는 위성세포가 특이적으로 줄어듬.

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아.. 그렇구나.. 

그래서 나이가 들면 민첩성이 떨어지는구나..

나이가 들면 피부를 제외한 모든 연부조직의 콜라겐 합성이 증가한다.

당연히 온몸의 조직은 굳어지는 방향으로 진행한다. 

골격근 성장과 수복을 담당하는 위성세포(satellite)

나이가 들면 빠른 움직임을 담당하는 type 2 근섬유의 위성세포가 특이적으로 줄어든다는 논문.

당연히 빠른 움직임 근육 재생이 느려지고 ...

대안은 뭘까? 

Satellite cell content is specifically reduced in type II skeletal muscle fiber in ter elderly.pdf

Satellite cell content is specifically reduced in type II skeletal muscle fibers in the elderly

Lex B. Verdijk,1 Rene´ Koopman,1,2 Gert Schaart,1 Kenneth Meijer,1

Hans H. C. M. Savelberg,1 and Luc J. C. van Loon1,2

Departments of 1Movement Sciences and 2Human Biology, Nutrition and Toxicology Research

Institute Maastricht (NUTRIM), Maastricht University, Maastricht, The Netherlands

Submitted 13 June 2006; accepted in final form 17 August 2006

Satellite cells (SC) are essential for skeletal muscle growth and repair. Because sarcopenia is associated

with type II muscle fiber atrophy, we hypothesized that SC content is specifically reduced in the type II fibers in the elderly. 

- 위성세포는 근육성장과 회복에 중요세포임. 근육감소는 type 2 근섬유 위축과 연관되기 때문에, 우리는 나이가 들면 type 2 위성세포가 줄어들 것으로 가설을 새움. 

A total of eight elderly (E; 76
1 yr) and eight young (Y; 20
1 yr) healthy males were selected. Muscle biopsies were collected from the vastus lateralis in both legs. ATPase staining and a pax7-antibody were used to determine fiber type-specific SC content (i.e., pax7-positive SC) on serial muscle cross sections. 

- 평균 76세와 21세 건강한 남성을 선택함. 양측 다리의 외측광근에서 생검을 시행함. 

In contrast to the type I fibers, the proportion and mean cross-sectional area of the type II fibers were substantially reduced in E vs. Y. The number of SC per type I fiber was similar in E and Y. However, the number of SC per type II fiber was substantially lower in E vs. Y (0.044
0.003 vs. 0.080
0.007; P  0.01). In addition, in the type II fibers, the number of SC relative to the total number of nuclei and the number of SC per fiber area were also significantly lower in E. 

This study is the first to show type II fiber atrophy in the elderly to be associated with a fiber type-specific decline in SC content. The latter is evident when SC content is expressed per fiber or per fiber area. The decline in SC content might be an important factor in the etiology of type II muscle fiber atrophy, which accompanies the loss of skeletal muscle with aging.

- 나이가 들면 type 2 위성세포가 줄어들고, type 2 근육 위축이 발생함. 

THE GRADUAL LOSS OF skeletal muscle mass with aging, or sarcopenia, represents a major factor determining the decline in functional capacity, mobility, and general health in the elderly.

Muscle mass represents a main determinant of muscle strength and has been strongly associated with performance in activities of daily living and the level of independence in the elderly (16, 36, 49). Much work has been devoted to describing the alterations in skeletal muscle that occur with aging. 

The most consistent findings have been the decline in the total number of muscle fibers and the specific atrophy of the type II fibers, both contributing to the loss of skeletal muscle mass (18, 28, 30). In accordance, type II muscle fiber atrophy and necrosis have been shown to result in a reduced (area) proportion of type II muscle fibers in skeletal muscle tissue in the elderly (15, 28, 29).

Although the exact mechanisms that cause sarcopenia remain to be elucidated, the hypothesis that satellite cells could play an important role in this age-related loss of skeletal muscle mass has recently gained much interest. 

Satellite cells (SC), or “muscle stem cells,” are the sole source for the generation of new myonuclei in vivo in skeletal muscle tissue(2, 34, 35). As such, SC seem to be essential for the repair and hypertrophy of skeletal muscle tissue. Normally, SC lie quiescent between the basal lamina and the plasma membrane of muscle fibers (32). On activation and subsequent proliferation, the majority of these SC differentiate to form new myonuclei that either fuse with existing fibers or generate new fibers, while a small proportion returns to quiescence (24, 50). Because SC are responsible for the maintenance of skeletal muscle mass, a decrease in the number of SC or in their ability to become activated and proliferate in response to anabolic stimuli is likely to result in impaired skeletal muscle structure and function (44). Although the latter has been speculated to occur in sarcopenia, studies investigating the effects of aging on skeletal muscle SC content in humans have been inconclusive.

Whereas some studies reported both a reduced number of SC per muscle fiber and a smaller proportion of SC relative to

the number of myonuclei in the elderly (22, 38), other studies have failed to observe such differences (15, 20, 40). Although

it has been reported that no differences exist in the number of SC between type I and II muscle fibers in young adults (23), it could be speculated that the specific type II muscle fiber atrophy with aging is associated with a fiber type-specific

reduction in SC content. Such a fiber type-specific reduction in SC content could represent an important factor in the etiology of sarcopenia and might explain the apparent discrepancy in the literature regarding the effects of aging on muscle fiber SC content.

In the present study, we assessed skeletal muscle fiber type-specific characteristics and fiber type-specific satellite cell

content in young and elderly men. Therefore, skeletal muscle biopsy samples were taken from the vastus lateralis in both the left and right legs of eight young (20
1 yr) and eight elderly (76
1 yr) lean males. Immunohistological staining of muscle cross sections was performed to assess muscle fiber type specific SC content and muscle fiber characteristics.

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Satellite cell content is specifically reduced in type II skeletal muscle fibers in the elderly