Insulin reduces the multiple organ injury and dysfunction caused by coadministration of lipopolysaccharide and peptidoglycan independently of blood glucose: role of glycogen synthase kinase-3beta inhibition.
OBJECTIVE
Insulin reduces morbidity and mortality among critically ill patients, but the molecular mechanisms of its effect remain unknown. Insulin is a well-known inhibitor of glycogen synthase kinase-3, which may play an important role in systemic inflammation and shock. Here we investigate the role of blood glucose and glycogen synthase kinase-3beta inhibition in the protective effect of insulin on the organ injury/dysfunction associated with excessive systemic inflammation.


METHODS
Prospective, randomized study.


METHODS
University-based research laboratory.


METHODS
Eighty-five anesthetized Wistar rats.


METHODS
Rats received Escherichia coli lipopolysaccharide (1 mg/kg) and Staphylococcus aureus peptidoglycan (0.3 mg/kg) or vehicle intravenously. Insulin (1.4 units/kg intravenously) was administered in the absence or presence of continuous glucose administration (4.5 mg/kg/hr intravenously) either prophylactically or therapeutically. The potent and selective glycogen synthase kinase-3beta inhibitor TDZD-8 (1 mg/kg intravenously) or vehicle (10% dimethyl sulfoxide) was administered either prophylactically or therapeutically.


RESULTS
Coadministration of lipopolysaccharide and peptidoglycan resulted in increases in the serum levels of creatinine (indicator of renal dysfunction), alanine aminotransferase, and aspartate aminotransferase (indicators of liver injury) at 6 hrs. Insulin or TDZD-8 similarly attenuated the organ injury/dysfunction caused by lipopolysaccharide and peptidoglycan when given either prophylactically or therapeutically. Continuous glucose administration had no effect on blood glucose levels or organ injury/dysfunction at 6 hrs. Treatment with insulin or TDZD-8 reduced the plasma levels of the proinflammatory cytokine interleukin-1beta. In vitro, insulin or TDZD-8 caused similar reductions in the nuclear factor-kappaB p65 activity and similar increases in the phosphorylation of Ser9 of glycogen synthase kinase-3beta.


CONCLUSIONS
Therapy with insulin or the potent and selective glycogen synthase kinase-3beta inhibitor TDZD-8 reduced the organ injury/dysfunction caused by lipopolysaccharide and peptidoglycan in the rat. We propose that the inhibitory effect of insulin on the activity of glycogen synthase kinase-3beta contributes to the protective effect of insulin against the organ injury/dysfunction caused by excessive systemic inflammation independently of any effects on blood glucose.
Centre for Experimental Medicine, Nephrology and Critical Care Medicine, The William Harvey Research Institute, St. Bartholomew's and The Royal London School of Medicine and Dentistry, Charterhouse Square, London, UK.
Laura
L
Dugo
Marika
M
Collin
David A
DA
Allen
Oliver
O
Murch
Simon J
SJ
Foster
Muhammad M
MM
Yaqoob
Christoph
C
Thiemermann
D000704:Analysis of Variance; D000818:Animals; D001786:Blood Glucose / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002478:Cells, Cultured; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors*; D000071679:Glycogen Synthase Kinase 3 beta; D006339:Heart Rate / Q000187:drug effects; D007004:Hypoglycemic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D007249:Inflammation / Q000503:physiopathology; D007328:Insulin / Q000494:pharmacology* / Q000627:therapeutic use; D007375:Interleukin-1 / Q000097:blood; D008070:Lipopolysaccharides; D008297:Male; D010457:Peptidoglycan; D011446:Prospective Studies; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D018805:Sepsis / Q000503:physiopathology*; D018746:Systemic Inflammatory Response Syndrome / Q000503:physiopathology / Q000517:prevention & control; D013830:Thiadiazoles / Q000494:pharmacology; D051996:Transcription Factor RelA / Q000037:antagonists & inhibitors
C494356:4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione; D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D007375:Interleukin-1; D008070:Lipopolysaccharides; D010457:Peptidoglycan; D013830:Thiadiazoles; D051996:Transcription Factor RelA; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3