Inhibitory effect of tumor necrosis factor α on gluconeogenesis in perfused rat liver.

Tumor necrosis factor α (TNFα) is a cytokine involved in many metabolic responses in both normal and pathological states. Considering that the effects of TNFα on hepatic gluconeogenesis are inconclusive, we investigated the influence of this cytokine in gluconeogenesis from various glucose precursors. TNFα (10 μg/kg) was intravenously injected in rats; 6 h later, gluconeogenesis from alanine, lactate, glutamine, glycerol, and several related metabolic parameters were evaluated in situ perfused liver. TNFα reduced the hepatic glucose production (p < 0.001), increased the pyruvate production (p < 0.01), and had no effect on the lactate and urea production from alanine. TNFα also reduced the glucose production (p < 0.01), but had no effect on the pyruvate production from lactate. In addition, TNFα did not alter the hepatic glucose production from glutamine nor from glycerol. It can be concluded that the TNFα inhibited hepatic gluconeogenesis from alanine and lactate, which enter in gluconeogenic pathway before the pyruvate carboxylase step, but not from glutamine and glycerol, which enter in this pathway after the pyruvate carboxylase step, suggesting an important role of this metabolic step in the changes mediated by TNFα.