Cold exposure increases slow-type myosin heavy chain 1(MyHC1) composition of soleus muscle in rats

摘要

The aim of this study was to examine the effects of cold exposure on rat skeletal muscle fiber type, according to myosinheavy chain (MyHC) isoform and metabolism-related factors. Male Wistar rats (7 weeks old) were housed individually at4 ± 2°C as a cold-exposed group or at room temperature (22 ± 2°C) as a control group for 4 weeks. We found that coldexposure significantly increased the slow-type MyHC1 content in the soleus muscle (a typical slow-type fiber), while theintermediate-type MyHC2A content was significantly decreased. In contrast to soleus, MyHC composition of extensordigitorum longus (EDL, a typical fast-type fiber) and gastrocnemius (a mix of slow-type and fast-type fibers) muscle did notchange from cold exposure. Cold exposure increased mRNA expression of mitochondrial uncoupling protein 3 (UCP3) inboth the soleus and EDL. Cold exposure also increased mRNA expression of myoglobin, peroxisome proliferator-activatedreceptor gamma coactivator 1α (PGC1α) and forkhead box O1 (FOXO1) in the soleus. Upregulation of UCP3 and PGC1αproteins were observed with Western blotting in the gastrocnemius. Thus, cold exposure increased metabolism-relatedfactors in all muscle types that were tested, but MyHC isoforms changed only in the soleus.