Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCB225

Poster Communications

Skeletal muscle atrophy before hibernation and recovery after hibernation in a mammalian hibernator, Syrian hamster

Y. Yamaguchi1

1. Institute of Low Temperature Science, Hokkaido University, Sapporo, Hokkaido, Japan.

Hibernation (HIB) is a strategy to survive harsh winter with a little or no food in immobility state. Such immobility induces severe muscle atrophy, whereas mammalian hibernators can manage to maintain skeletal muscle mass during HIB. However, molecular mechanisms how mammalian hibernators preserve skeletal muscles during HIB remain to be elucidated. A mammalian hibernator, Syrian golden hamsters (Mesocricetus auratus), undergo hibernation when exposed to chronic short photoperiod and cold ambient temperature (SD-Cold; Light:Dark=8:16 hours at 4oC cold room) (Chayama et al. 2016). In this study, female hamsters raised in lond day photoperiod and warm ambient temperature (LD-warm; Light:Dark=16:8 hours at 23oC) were subjected to prolonged SD-Cold over 2 months or more to induce hibernation. The animals were anesthetized with inhalation of 4% isoflurane and then sacrificed by decapitation to collect tissues of interest. We found that mass of their skeletal muscles was significantly decreased by the onset of hibernation during the pre-HIB period, while its ratio to body mass was relatively preserved during HIB. Quantitative RT-PCR and immunostaining for fiber-type specific myosin heavy chains revealed that skeletal muscle fiber-composition was dramatically remodeled from fast-type to slow-type during HIB periods (n=5 or move per each group, p<0.01). The observed fiber-type changes began after over 2 months of SD-Cold before HIB. Along with these changes, proteasome components and atrophic markers MuRF1 and MAFbx were significantly up-regulated (n=5 or move per each group, p<0.01). Simultaneously, expression of myostatin, an inhibitor of myogenesis and muscle hypertrophy, was significantly reduced during HIB (n=5 or move per each group, p<0.01). Remarkably, these changes were cancelled in animals that spontaneously quit HIB even under SD-Cold condition. These results suggest that muscle-fiber type shift and suppression of myostatin may operate as a mechanism for preserving skeletal muscles during HIB in this species.

Where applicable, experiments conform with Society ethical requirements