Hyperglycemia enhances the cytokine production and oxidative responses to a low but not high dose of endotoxin in rats

Abstract

The aim of this study was to investigate whether hyperglycemia enhances the systemic inflammatory response and oxidative stress induced by endotoxin.Laboratory investigation.University medical school.Forty-one male Sprague-Dawley rats.A hyperglycemic condition was produced in rats by glucose clamp for 3 hrs. Immediately on stopping the glucose infusion, animals received different doses of endotoxin injection (0, 0.2, or 1 mg/kg), and then blood glucose concentration was monitored over the ensuing 2 hrs. At the end of 2 hrs, levels of tumor necrosis factor-alpha, interleukin-1beta, interleukin-6, corticosterone, and alpha-1 acid glycoprotein were determined in serum, and malondialdehyde and total glutathione content were determined in the liver.Over the 2-hr period, blood glucose concentrations returned to normal in initially hyperglycemic rats. However, the levels of cytokines, corticosterone, and alpha-1 acid glycoprotein were significantly higher in these animals compared with nonhyperglycemic controls, demonstrating an extended effect of prior hyperglycemia on markers of systemic inflammation. With low-dose (0.2 mg/kg) but not high-dose (1 mg/kg) endotoxin administration, hyperglycemic animals had significantly higher levels of cytokines compared with controls, indicating that prior hyperglycemia can enhance the systemic inflammatory response to a moderate endotoxin dose, but that the maximum effects of endotoxin on production of inflammatory cytokines are not altered by transient high glucose exposure.Systemic inflammation persists for a period following hyperglycemia, and this can enhance the systemic inflammatory response to a subsequent moderate stress.