Endotoxin-induced alterations in hepatic glucose-6-phosphatase activity and gene expression

The mechanisms responsible for the glycemic changes associated with endotoxic shock are not fully understood, but are known to involve the ability of the liver to produce glucose. The purpose of the present study was to determine whether endotoxin (LPS) influences the expression and activity of glucose-6-phosphatase (Glu-6-Pase) during the early hyperglycemic phase and the later hypoglycemic phase. Rats were injected with a relatively large dose of LPS (20 mg/kg) or saline (control), and sacrificed at 1 or 5 h post-injection. Both the plasma glucose concentration and glucose production were elevated 1 h post-LPS (2-fold) and both decreased at 5 h postinjection (50%). Compared to time-matched control values, hepatic glucose-6-phosphate and fructose-6-phosphate levels were significantly decreased at both 1 and 5 h. Hepatic Glu-6-Pase activity and mRNA levels were moderately increased, 1 h after injection of LPS. At 5 h, an 88% decrease in mRNA abundance for Glu-6-Pase was associated with a 30% decrease in activity of this enzyme. Plasma insulin concentrations were not different 1 h after LPS and were elevated 2-fold from control values at 5 h. Circulating levels of glucagon and corticosterone were elevated at both time points following LPS. Our data indicate that the LPS-induced hypoglycemia and reduction in hepatic glucose production were accompanied by a depression in Glu-6-Pase activity and gene expression.