Motor unit changes seen with skeletal muscle sarcopenia in oldest old rats.
Sarcopenia leads to many changes in skeletal muscle that contribute to atrophy, force deficits, and subsequent frailty. The purpose of this study was to characterize motor unit remodeling related to sarcopenia seen in extreme old age. Whole extensor digitorum longus muscle and motor unit contractile properties were measured in 19 adult (11-13 months) and 12 oldest old (36-37 months) Brown-Norway rats. Compared with adults, oldest old rats had significantly fewer motor units per muscle, smaller muscle cross-sectional area, and lower muscle specific force. However, mean motor unit force generation was similar between the two groups due to an increase in innervation ratio by the oldest old rats. These findings suggest that even in extreme old age both fast- and slow-twitch motor units maintain the ability to undergo motor unit remodeling that offsets some effects of sarcopenia.
Section of Plastic Surgery, Department of Surgery and.
Theodore A
TA
Kung
Section of Plastic Surgery, Department of Surgery and cederna@med.umich.edu.
Paul S
PS
Cederna
The Institute of Gerontology, University of Michigan, University of Michigan Health System, Ann Arbor.
Jack H
JH
van der Meulen
Section of Plastic Surgery, Department of Surgery and.
Melanie G
MG
Urbanchek
Section of Plastic Surgery, Department of Surgery and.
William M
WM
Kuzon
The Institute of Gerontology, University of Michigan, University of Michigan Health System, Ann Arbor.
John A
JA
Faulkner
D000375:Aging; D000818:Animals; D004195:Disease Models, Animal; D018450:Disease Progression; D008297:Male; D009046:Motor Neurons / Q000473:pathology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation* / Q000503:physiopathology; D051381:Rats; D011914:Rats, Inbred BN; D055948:Sarcopenia / Q000473:pathology / Q000503:physiopathology*
Aging.; Innervation ratio; Motor unit; Sarcopenia