Augmented glucose use and pentose cycle activity in hepatic endothelial cells after in vivo endotoxemia

Glucose use and pentose cycle activity were determined in freshly isolated rat hepatic endothelial cells 3 hr after an intravenous injection of Escherichia coli lipopolysaccharide (0.1 mg/kg body weight), by use of (1‐¹⁴C)glucose, [6‐¹⁴C]glucose and [2‐H]glucose. Lipopolysaccharide treatment in vivo increased glucose use fivefold, whereas glucose oxidation in the pentose cycle was elevated from 0.2 to 1.5 nmol/hr/10⁷ cells. In vitro incubation of endothelial cells from saline‐ and lipopolysaccharide‐treated animals in the presence of phorbol 12‐myristate 13‐acetate (10⁻⁶ mol/L) increased pentose cycle activity twofold and eightfold, respectively. Phorbol 12‐myristate 13‐acetate caused only a 40% to 60% increase in glycolysis in both groups. Addition of t‐butyl hydroperoxide (0.5 mmol/L), a substrate for gluathione peroxidase, caused a 24‐fold and 16‐fold increase in the glucose flux through the pentose cycle in cells from saline‐ and lipopolysaccharide‐treated rats, respectively. Oxidation of glucose through the Krebs cycle was also increased several‐fold after t‐butyl hydroperoxide administration. Depletion of cellular glutathione by N‐ethylmaleimide (0.1 mmol/L) inhibited the phorbol 12‐myristate 13‐acetate–induced or t‐butyl hydroperoxide–induced increase in the pentose cycle activity with no marked effects on glycolysis. Diphenyleneiodonium (0.1 mmol/L), an inhibitor of superoxide and nitric oxide synthesis inhibited the phorbol 12‐myristate 13‐acetate–induced increased pentose cycle activity with no effects on the t‐butyl hydroperoxide–induced response. Endothelial cells from control animals treated with either 12‐myristate 13‐acetate or t‐butyl hydroperoxide in the presence of exogenous glucose 20 mmol/L showed a similar increase in glycolysis but less increase in the pentose cycle activity as found after lipopolysaccharide treatment in the presence of glucose 5 mmol/L. This finding suggests that glucose‐6‐phosphate dehydrogenase or pathways dependent on pentose cycle intermediates became up‐regulated after lipopolysaccharide administration. The lipopolysaccharide‐induced elevated glucose use, accompanied by an increased activity of the pentose cycle, may also represent a potentiated mechanism for eliminating hydrogen peroxide derived from intracellular sources or from activated Kupffer cells and sequestered neutrophils in the hepatic sinusoid. (HEPATOLOGY 1993;17:615–620.)