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

Abstract

The aim of this study was to examine the effects of cold exposure on rat skeletal muscle fiber type, according to myosin heavy chain (MyHC) isoform and metabolism-related factors. Male Wistar rats (7 weeks old) were housed individually at 4 ± 2°C as a cold-exposed group or at room temperature (22 ± 2°C) as a control group for 4 weeks. We found that cold exposure significantly increased the slow-type MyHC1 content in the soleus muscle (a typical slow-type fiber), while the intermediate-type MyHC2A content was significantly decreased. In contrast to soleus, MyHC composition of extensor digitorum longus (EDL, a typical fast-type fiber) and gastrocnemius (a mix of slow-type and fast-type fibers) muscle did not change from cold exposure. Cold exposure increased mRNA expression of mitochondrial uncoupling protein 3 (UCP3) in both the soleus and EDL. Cold exposure also increased mRNA expression of myoglobin, peroxisome proliferator-activated receptor gamma coactivator 1α (PGC1α) and forkhead box O1 (FOXO1) in the soleus. Upregulation of UCP3 and PGC1α proteins were observed with Western blotting in the gastrocnemius. Thus, cold exposure increased metabolism-related factors in all muscle types that were tested, but MyHC isoforms changed only in the soleus.

A One-Step Immunostaining Method to Visualize Rodent Muscle Fiber Type within a Single Specimen

“…Our SDS-PAGE analyses revealed that the soleus muscles (slow twitch fiber dominant muscle) from cold-exposed rats were composed primarily of MyHC1, while those from the control population expressed high levels of MyHC1 but also expressed MyHC2A (Fig 4B left, SDS-PAGE results from published data [24]). Likewise, the staining of cold-exposed and control soleus muscles clearly demonstrated that the cold-exposed tissues were composed entirely of MyHC1 fibers (Fig 4B right).…”

“…To examine whether our staining method could be applied to the evaluation of muscle fiber type transitions, we analyzed a panel of muscle samples obtained during two of our previous studies [23][24]. In these studies, we assessed alterations in muscle fiber types by SDS-PAGE analysis of muscle tissue homogenates.…”

“…(B) The cold exposure experiment: The electrophoretic image and the graph, published by Mizunoya et al . [24], in the panels at the left show that cold exposure increased the prevalence of slow-type MyHC1 fibers in the soleus muscles of rats. Consistent with these findings, our staining method clearly depicts the predominance of MyHC1 in cross-sections of soleus muscles from these same cold-exposed rats.…”

“…The muscle complexes of the gastrocnemius, plantaris, and soleus muscles were rapidly dissected from rats or mice after euthanasia by cervical dislocation under sevoflurane inhalation anesthesia. In addition, we used rat muscles obtained in previous studies for these experiments; the plantaris [23] and soleus [24] muscles obtained from 12-week-old male Wistar rats and stored at -80°C without any treatment, which were thawed and handled as fresh muscle samples. Meanwhile, longitudinal cryosections were also prepared from the plantaris muscles.…”

Standardized Boesenbergia pandurata Extract Stimulates Exercise Endurance Through Increasing Mitochondrial Biogenesis

“…27,28 The activation of PPARd in skeletal muscle of BPE-treated mice could strongly increase the amount of slow-twitch type muscle fiber, which leads to the improvement of exercise endurance by elevating mitochondrial number.…”