141 Mild Burns Combined with Diet Induced Demyelination Does Not Affect Skeletal Muscle Function

Abstract Introduction Severe burns result in decreased skeletal muscle mass and function. Recent evidence suggests that massive burns disrupt the motor-neural system including motor neurons to partially explain skeletal muscle dysfunction in response to burns. However, impact of demyelination on burn induced skeletal muscle dysfunction has not been investigated. The purpose of this study was to determine the impact of exaggerated demyelination on skeletal muscle dysfunction after burn. Methods C57BL/6 (20-25g, male, n = 26) mice were separated into 6 groups (4–5 animals per group) by diet, burn injury and timepoint (burn or sham groups with two different diets measured at two different timepoints). Mice were fed with either cuprizone diet (0.2 %) to induce severe demyelination or regular diet (18 % protein) for 5 weeks prior to injury. Burns were administered by immersing the dorsal side of the animal into ~95 °C hot water for 10 seconds (~15 % body surface area, full thickness burn). In-situ gastrocnemius function was assessed by attaching the distal tendon of the muscle to a lever arm of a force transducer and stimulating the muscle via exposed sciatic nerve while the animal was under anesthesia. In-situ gastrocnemius muscle function was evaluated 3- and 7-days after burn. Results Food intake was 30 % higher in cuprizone diet group compared to the regular diet group (p=0.002). However, there was no significant difference in body weight among groups (p=0.071). No significant difference was found in gastrocnemius wet weight, peak twitch tension, time to reach peak twitch tension, peak twitch half relaxation time, force-frequency relationship, maximum tetanic force, and fatigue index among groups (burn effect, diet effect, time effect, and their interactions; NS). Conclusions Mild burns combined with demyelination by diet had no effect on skeletal muscle function on our timepoints, and 15 % TBSA burn size was not sufficient to induce skeletal muscle dysfunction. The impact of burn induced neural damage on muscle function and performance indicates further investigation.