Effects of Burn and Disuse with Resistance Exercise on Free Fatty Acids and Fibroblast Growth Factor‐21 in Rats

Severe burn and disuse cause metabolic alterations associated with systemic endocrine changes including extreme inflammation, insulin insensitivity, hypermetabolism and catabolism. Using our rodent model of burn and disuse with resistance exercise, we measured free fatty acid (FFA) and Fibroblast Growth Factor‐21 (FGF‐21) in plasma 14 days following injury. Male rats were randomized into four groups: Sham Ambulatory (SA), Burn Ambulatory (BA), Sham/Hindlimb unloaded (SH) and Burn/Hindlimb unloaded (BH), with daily resistance exercise (EX) or no exercise (NEX) (N=6/group). No differences in body mass were observed between groups at injury. At day 14, NEX‐SA and NEX‐BA body mass were significantly greater than EX‐SA and EX‐BA. There was no effect of exercise in the unloaded groups, however, BH rats were significantly smaller than all other groups. In our previous studies, plasma insulin concentration has been significantly reduced in BH as compared to SA, demonstrating insulin insensitivity in this model. There were no differences in liver mass when corrected for body mass at day 14. Irrespective of exercise FFA in BA, SH and BH were significantly decreased from SA with an additive effect of SA>BA=SH>BH. No significant differences in plasma FGF‐21 were observed, irrespective of exercise. Our rat model is able to demonstrate that burn injury, accompanied by long‐term disuse illustrates these may influence the metabolic changes offering clinical opportunities for early intervention resulting in positive long‐term outcomes. (US Army MRMC W81XWH‐13‐1‐0489)