410 Effects of the Combination of Daily Insulin plus Resistance Exercise During the Unloading and Reloading Phases Following Burn and Disuse in Rats on Body Mass, Food Intake and Fat Mass

Abstract

Treatment and recovery of patients with severe traumatic injuries is impacted by an increase in metabolism. After burn injury, the ability to resume normal activities is compromised due to inactivity associated with bed rest as well as the catabolic response. Following discharge, a major goal is the ability to execute a long-term recovery plan. Previously we found daily exercise combined with SQ insulin improved body mass loss during the unloading period. The purpose of this study was to determine immediately following burn and disuse injury how a combination of daily resistance exercise and daily insulin injections during the unloading phase followed by daily resistance exercise during the reloading phase affects body and fat mass and food intake. Male, Sprague-Dawley rats were used. Injury was induced by a 40% TBSA burn injury and hindlimb unloaded immediately following injury. Rats were weight-matched into either saline vehicle (VEH; N=12) or insulin (INS; 5U/kg; N=12) for 14 days with daily resistance exercise. Daily resistance exercise was completed prior and following injury by adding weight to the tail during repetitive ladder climbing (5 climbs, 2X/days). Following removal from unloading at 14 days, rats were re-distributed within the original VEH or INS to exercise (EX; N=6) or no exercise (NEX; N=6) for 14 days. Body mass and food intake was collected daily throughout the study. Fat mass was collected at the end of the study. No differences in body mass were observed between any groups at the time of injury or day 14. Daily insulin showed a decrease in mean food intake over the last 5 days of the unloading phase with no differences in body mass. During the reloading phase, a steady increase in body mass was shown in all groups, however, INS, irrespective of exercise had a greater body mass increase. In addition, mean food intake was significantly increased in the INS + EX group during the reloading phase. Fat mass was not different between any of the groups. During the unloading phase, daily exercise with insulin elicited a decrease in food intake, however, the decrease in food intake did not result in differences between treatment groups in either body mass or fat mass, possibly showing additional mechanisms are causing overall metabolic changes. Possible metabolic changes during the reloading phase, indicate improvements may be occuring following removal from disuse. Different underlying factors seem to be influencing the acute metabolic changes offering possible opportunities for combinations of early interventions resulting in positive long-term outcomes. An exercise program may improve metabolic health following discharge.