Burn injury impairs insulin-stimulated Akt/PKB activation in skeletal muscle.
The molecular bases underlying burn- or critical illness-induced insulin resistance still remain unclarified. Muscle protein catabolism is a ubiquitous feature of critical illness. Akt/PKB plays a central role in the metabolic actions of insulin and is a pivotal regulator of hypertrophy and atrophy of skeletal muscle. We therefore examined the effects of burn injury on insulin-stimulated Akt/PKB activation in skeletal muscle. Insulin-stimulated phosphorylation of Akt/PKB was significantly attenuated in burned compared with sham-burned rats. Insulin-stimulated Akt/PKB kinase activity, as judged by immune complex kinase assay and phosphorylation status of the endogenous substrate of Akt/PKB, glycogen synthase kinase-3beta (GSK-3beta), was significantly impaired in burned rats. Furthermore, insulin consistently failed to increase the phosphorylation of p70 S6 kinase, another downstream effector of Akt/PKB, in rats with burn injury, whereas phosphorylation of p70 S6 kinase was increased by insulin in controls. The protein expression of Akt/PKB, GSK-3beta, and p70 S6 kinase was unaltered by burn injury. However, insulin-stimulated activation of ERK, a signaling pathway parallel to Akt/PKB, was not affected by burn injury. These results demonstrate that burn injury impairs insulin-stimulated Akt/PKB activation in skeletal muscle and suggest that attenuated Akt/PKB activation may be involved in deranged metabolism and muscle wasting observed after burn injury.
Sugita
Hiroki
H
Department of Anesthesia and Critical Care, Massachusetts General Hospital, Boston, MA, USA.
Kaneki
Masao
M
Sugita
Michiko
M
Yasukawa
Takashi
T
Yasuhara
Shingo
S
Martyn
J A Jeevendra
JA
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002056:Burns / Q000378:metabolism / Q000503:physiopathology*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D015151:Immunoblotting; D007328:Insulin / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology; D007333:Insulin Resistance / Q000502:physiology; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism / Q000503:physiopathology*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D013912:Threonine / Q000378:metabolism
D001786:Blood Glucose; D007328:Insulin; D011518:Proto-Oncogene Proteins; D013912:Threonine; D012694:Serine; C494920:Akt1 protein, rat; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D038362:Glycogen Synthase Kinase 3