Meeting Abstract
Optimal organismal performance relies on the maintenance of muscle contractile properties. Just as humans weaken from prolonged bed rest, most animals lose muscle mass (atrophy) with significant disuse. However, some organisms have physiological solutions to mitigate the negative effects of being sedentary. Hibernating animals can go months at a time with little to no loss of muscle. Many mammals can marginally lower body temperature and activate physiological pathways during hibernation to not only limit muscle loss, but to prevent the common shift from slow to fast muscle fiber types. However, our knowledge on muscle atrophy resistance during hibernation is largely limited to endotherms, which necessarily maintain a high metabolic rate throughout hibernation. In order to understand the effects of metabolic rate and physiology on muscle atrophy and performance, we investigated a hibernating ectotherm, the lizard, Sceloporus occidentals. To better understand the role of metabolic rate on muscle atrophy, we denervated the sciatic nerve unilaterally and housed the lizards at 30 C for six weeks. At the end of this period, we quantified the morphological and contractile properties of the gastrocnemius muscles bilaterally, using the non-denervated side as a control. Denervated muscles were 15% lighter than control when controlling for body weight. Muscle atrophy is usually associated with a shift from slow to fast fiber types, but our data show a reduction in maximum shortening velocity of the atrophied muscles. These results suggest that ectothermic organisms maintained at high body temperatures are susceptible to muscle atrophy. By comparing these results to treatments at lower temperatures we aim to understand the effects of metabolic rate on the mechanism of muscle atrophy.
