Acute Endotoxin Tolerance Is Accompanied by Stimulated Glucose Use in Macrophage-Rich Tissues

A single injection of E. coli LPS at a dose of 10 mg/kg b.w. ("high dose") is lethal in Sprague Dawley rats. However, animals given a sublethal dose of LPS (0.5 mg/kg bw; "low dose") at time zero, followed by a second high dose injection at 48 h, display endotoxin tolerance with 100 % survival. The aim of the present study was to assess the relationship between this observed endotoxin tolerance and the endotoxin-induced glucose metabolic response in selected tissues and nonparenchymal hepatic cells. In each experimental group two injections, the first at time zero, the second at 48 h were given in vivo. Four experimental groups constituted these studies: A) saline followed by saline, B) low dose LPS followed by saline, C) saline followed by high dose LPS, and D) low dose LPS followed by high dose LPS. In vivo glucose use in tissues and cells was measured 3h after the last treatments employing the 2-deoxy-glucose tracer technique. Glucose use by liver, lung, spleen and intestine was not different between saline/saline (group A) and low dose LPS/saline injected (group B) animals. Saline/high dose LPS injection (group C) doubled glucose uptake, while the sequential LPS injections (group D) caused an additional, 2-3 fold increase in the glucose use by these tissues. Hepatic endothelial cells showed a similarly elevated glucose use in vivo in both group C and D. Kupffer cells from group D animals, however, displayed markedly elevated glucose use in vivo as compared to cells from group C. Our data indicate that high dose LPS in endotoxin tolerant animals is accompanied by a more markedly stimulated tissue glucose use than found following lethal LPS treatment alone. This increased peripheral glucose use may support cellular functions responsible for the protection of the host.