Differential activation of the calpain system involved in individualized adaptation of different fast-twitch muscles in hibernating Daurian ground squirrels

We examined the lateral gastrocnemius (LG), plantaris (PL), and extensor digitorum longus (EDL) muscles to determine whether differential activation of the calpain system is related to the degree of atrophy in these fast-twitch skeletal muscles during hibernation in Daurian ground squirrels ( ). Res...

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Bibliographic Details
Published in:Journal of applied physiology (1985) 2019-08, Vol.127 (2), p.328-341
Main Authors: Ma, Xiufeng, Chang, Hui, Wang, Zhe, Xu, Shenhui, Peng, Xin, Zhang, Jie, Yan, Xia, Lei, Tingyun, Wang, Huiping, Gao, Yunfang
Format: Article
Language:English
Subjects:
Activation
Arousal
Atrophy
Calcium homeostasis
Calcium ions
Calcium-binding protein
Calpain
Calpastatin
Degradation
Desmin
Ground squirrels
Hibernation
Homeostasis
Muscles
Skeletal muscle
Squirrels
Substrates
Summer
Troponin
Troponin T
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Summary:We examined the lateral gastrocnemius (LG), plantaris (PL), and extensor digitorum longus (EDL) muscles to determine whether differential activation of the calpain system is related to the degree of atrophy in these fast-twitch skeletal muscles during hibernation in Daurian ground squirrels ( ). Results from morphological indices showed various degrees of atrophy in the order LG > PL > EDL. Furthermore, all three muscles underwent fast-to-slow fiber-type conversion in hibernation. In regard to the calpain system in the LG muscle, cytosolic Ca increased significantly in hibernation, followed by recovery in posthibernation. Furthermore, calpastatin expression significantly decreased, and calpain 1 and 2 expression significantly increased, which may be responsible for the increased degradation of desmin during hibernation compared with that during summer activity. In the EDL muscle, Ca overload was observed during interbout arousal, and calpastatin showed an increase during hibernation and interbout arousal, which could explain the increased levels of troponin T during both periods compared with levels during summer activity. These findings suggest that cytosolic Ca overload and subsequent calpain 1 and 2 activation may be an important mechanism of LG muscle atrophy during hibernation. Cytosolic Ca homeostasis and high expression of calpain inhibitor calpastatin during hibernation may also be an important mechanism for the EDL muscle to maintain muscle mass. Thus, the differential activation of the calpain system and selective degradation of downstream substrates may be involved in muscle atrophy of different fast-twitch muscles during hibernation. We found that the extent of both muscle atrophy and calpain system activation differed in fast-twitch lateral gastrocnemius (LG), plantaris (PL), and extensor digitorum longus (EDL) skeletal muscles in hibernating Daurian ground squirrels, but similar hierarchies in the order of LG > PL > EDL. The differential activation of the calpain system and selective degradation of downstream substrates may be involved in muscle atrophy in different fast-twitch muscles during hibernation.
ISSN:8750-7587
1522-1601
DOI:10.1152/japplphysiol.00124.2019