Insulin effects on glucose tolerance, hypermetabolic response, and circadian-metabolic protein expression in a rat burn and disuse model.
Insulin controls hyperglycemia after severe burns, and its use opposes the hypermetabolic response. The underlying molecular mechanisms are poorly understood, and previous research in this area has been limited because of the inadequacy of animal models to mimic the physiological effects seen in humans with burns. Using a recently published rat model that combines both burn and disuse components, we compare the effects of insulin treatment vs. vehicle on glucose tolerance, hypermetabolic response, muscle loss, and circadian-metabolic protein expression after burns. Male Sprague-Dawley rats were assigned to three groups: cage controls (n = 6); vehicle-treated burn and hindlimb unloading (VBH; n = 11), and insulin-treated burn and hindlimb unloading (IBH; n = 9). With the exception of cage controls, rats underwent a 40% total body surface area burn with hindlimb unloading, then IBH rats received 12 days of subcutaneous insulin injections (5 units·kg(-1)·day(-1)), and VBH rats received an equivalent dose of vehicle. Glucose tolerance testing was performed on day 14, after which blood and tissues were collected for analysis. Body mass loss was attenuated by insulin treatment (VBH = 265 ± 17 g vs. IBH = 283 ± 14 g, P = 0.016), and glucose clearance capacity was increased. Soleus and gastrocnemius muscle loss was decreased in the IBH group. Insulin receptor substrate-1, AKT, FOXO-1, caspase-3, and PER1 phosphorylation was altered by injury and disuse, with levels restored by insulin treatment in almost all cases. Insulin treatment after burn and during disuse attenuated the hypermetabolic response, increased glucose clearance, and normalized circadian-metabolic protein expression patterns. Therapies aimed at targeting downstream effectors may provide the beneficial effects of insulin without hypoglycemic risk.
U.S. Army Institute of Surgical Research, Fort Sam Houston, Texas;
Heather F
HF
Pidcoke
University of Texas Health Science Center at Houston, Houston, Texas; and.
Lisa A
LA
Baer
U.S. Army Institute of Surgical Research, Fort Sam Houston, Texas;
Xiaowu
X
Wu
University of Texas Southwestern Medical Center, Dallas, Texas.
Steven E
SE
Wolf
U.S. Army Institute of Surgical Research, Fort Sam Houston, Texas;
James K
JK
Aden
University of Texas Health Science Center at Houston, Houston, Texas; and Charles.E.Wade@uth.tmc.edu.
Charles E
CE
Wade
D000818:Animals; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000187:drug effects* / Q000378:metabolism; D002056:Burns / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D053148:Caspase 3 / Q000378:metabolism; D002940:Circadian Rhythm; D056925:Circadian Rhythm Signaling Peptides and Proteins / Q000378:metabolism*; D004195:Disease Models, Animal; D004334:Drug Administration Schedule; D004734:Energy Metabolism / Q000187:drug effects*; D051858:Forkhead Transcription Factors / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000008:administration & dosage*; D007279:Injections, Subcutaneous; D007328:Insulin / Q000008:administration & dosage*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D009133:Muscular Atrophy / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000378:metabolism; D056950:Period Circadian Proteins / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D015431:Weight Loss / Q000187:drug effects; D000071161:Forkhead Box Protein O1
D015415:Biomarkers; D001786:Blood Glucose; D053148:Caspase 3; D056925:Circadian Rhythm Signaling Peptides and Proteins; D051858:Forkhead Transcription Factors; D007004:Hypoglycemic Agents; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D009419:Nerve Tissue Proteins; D056950:Period Circadian Proteins; D051057:Proto-Oncogene Proteins c-akt; C526296:Irs1 protein, rat; C539024:Per1 protein, rat; C074639:Foxo1 protein, rat; D000071161:Forkhead Box Protein O1; C505410:Casp3 protein, rat
burn and disuse; circadian rhythm; glucose tolerance; hypermetabolism; insulin