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Vol. 54, 2015
The research on the formation mechanism of extraordinary oxidative capacity of skeletal muscle in hibernating ground squirrels (Spermophilus dauricus)
Shanfeng Jiang1, Yunfang Gao1*, Yangmei Zhang1, Kun Liu1, Huiping Wang1 and Nandu Goswami2
1Key
Laboratory of Resource Biology and Biotechnology in Western China
(Northwest University), Ministry of Education, Xi’an 71069, China
2Institute of Physiology, Center of Physiological Medicine, Medical University Graz, Graz, Austria
Abstract
Background: Previous
studies indicate that hibernating animals, under conditions of torpor
for long periods, show an increased oxidative muscle fibers (type I)
ratio and a decreased glycolytic muscle fibers (type II) ratio in
skeletal muscle and accompanied by extraordinary oxidative ability.
This observation is completely contrasted with non-hibernators, which
show a shift of oxidative muscle fibers (type I) to glycolytic muscle
fibers (type II). Presently, the mechanisms by which these changes
occur remain unclear. To investigate the mechanism of high oxidative
capacity of the skeletal muscles in hibernating ground squirrels,
capillary density (CD), and capillary/fiber (C/F) were measured by
immunohistochemistry. mRNA expression levels of hypoxia-inducible
factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) were
determined using real-time quantitative PCR assay. Spectrophotometry
was applied to determine the activities of hexokinase (PK), pyruvate
kinase (HK), and cytochrome c oxidase (CcO).
Results: In
the soleus muscle (SOL), mRNA expression levels of HIF-1α and VEGF in
torpor became slightly lower but were not statistically significant;
they were, however, significantly higher in the arousal group. In
hibernating animals, no significant change occurred in CD but C/F
increased by 15 %. CcO showed the highest activity in torpor. There
were no significant differences in the activities of HK and PK between
the torpid animals and summer active animals in SOL. However, PK
activity increased by 34 % after hibernation.
Conclusions: Oxidative capacity may be ensured by an increase of capillary supply of skeletal muscle in hibernating animals.
Key words: Muscle disuse atrophy; Hibernation; C/F; HIF-1α; VEGF.
*Correspondence: E-mail: gaoyunf@nwu.edu.cn
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