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

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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.