Insulin Intensive Treatment On Hyperproteolysis Of Skeletal Muscle In Burned Sepsis

Sepsis in severely burned patients is associated with high morbidity and mortality. It is well known that hypermetabolism and negative nitrogen balance invariably accompanies sepsis, and the process has been labeled as self-cannibalistic. Following the finding of the ubiquitin-proteasome pathway, one selected proteolysis pathway, the study of the mechanism of hyperproteolysis during sepsis has become one hot point in this field. Hyperproteolysis of skeletal muscle holding about forty percent dry weight of body has been known as the main cause for negative nitrogen balance during sepsis. However, the mechanism of hyperproteolysis in skeletal muscle during burn sepsis is still obscure, and up to now, there was no effectively treating method for it.OBJECTIVEProteolysis in skeletal muscle during burn sepsis has been labeled as self-cannibalistic, it can't be effectively corrected only through supplying protein and amino. Insulin is one of main anabolic hormones, as well as an important regulator for the balance of muscle nitrogen. Glucocorticoid and cytokines secreted higher during burn sepsis, which could impair the physiologic effects of insulin. But the relations between hyperproteolysis and insulin resistance during burn sepsis still need to be elucidated. On this background, the purpose of this study was to analysis the effects and the possible mechanisms of insulin intensive treatment on hyperproteolysis in skeletal muscle during burn sepsis.METHODS1. Animal Experiment(1) Thirty white rabbits were randomly divided into five groups, including scalding group(S group), scalding and insulin treating group(SI group ), scalding sepsis group(SS group), scalding sepsis and insulin treating group(SSI group), and control group. The rabbits of S group were suffered from 30% TBSA full thickness injury with boiling water, and those of SS group were injected with LPS (2mg/kg.bw) immediately after scalding injury. Insulin intensive treatment was performed with injection of insulin to keep the plasma glucose level in physiologic range (4.4- 6.1mmol/L) for SI group and SSI group. On post-injury twelve hours, the animals were killed and the samples were taken.(2) The plasma concentrations of cortisol, TNF-a and insulin were determined with radio-immunity.(3) The contents of 3-MH in skeletal muscle and urine were detected by highperformance liquid chromatography.(4) The gene and protein expressions of ubiquitin system in skeletal muscle were determined by Northern blot analysis, Western blot and immunopathology.2. Cell Culture Experiments(1) To establish stable methods for culturing skeletal muscle cells.(2) To label the myotube protein with L-[3,5-3H]-tyrosine.(3) The myotubes were cultured with medium containing dexamethasone or insulin, and the proteolytic rate, gene and protein expressions of ubiquitin system in myotubes were analyzed.RESULTS1. The animal experiment(1) The plasma concentrations of cotisol, TNF-a and blood glucose level were all significantly increased after scalding injury or sepsis, however there were no relative increase of the plasma concentrations of insulin, and the index of insulin resistance was markedly decreased.(2) The contents of 3-MH in skeletal muscle and urine were significantly increased after scalding injury or sepsis.(3) The gene expressions of Ub, E2-14k, C3a, C2 subunit, Cs subunit and the protein expressions of Ub, C2 subunit, Cs subunit were enhanced significantly after scalding injury or sepsis.(4) Insulin Intensive Treatment could effectively reduce the contents of 3-MH in skeletal muscle and urine, and it could also significantly inhibit the gene expressions of Ub, E2-14k, C3a, C2 subunit, Cs subunit and the protein expressions of Ub, C2 subunit, Cs subunit in skeletal muscle after scalding injury or sepsis.2. Cell culture experiment(1) Dexamethasone could enhance the gene expressions of Ub, E2-14k, C3a, C2 subunit, Cg subunit and the protein expressions of C2 subunit, Cs subunit in myotubes, which leads to high proteolytic rate.(2) Insulin could markedly inhibit the gene expressions of E2-14k, however change of the gene expressions of Ub, C3a, C2 subunit, Cs subunit and the protein expressions of C2 subunit, Cs subunit in myotubes were not observed.(3) Insulin could effectively inhibit the effects of dexamethasone on the gene, proein expressions of ubiquitin system and the proteolytic rate in myotubes.CONCLUSIONSIn our experiment, we report the effects and possible mechanisms of insulin intensive treatment on high proteolytic rate during severely burned sepsis for the first time in the world. The experiment results indicate that, ? The effects of glucocorticoid were enhanced and the effects of insulin were relative insufficiency during severely burned sepsis, and this...