Regulation of glucose metabolism by altered pyruvate dehydrogenase activity. I. Potential site of insulin resistance in sepsis.

Regulation of the pyruvate dehydrogenase (PDH) complex has been demonstrated to be a key mechanism in the control of carbohydrate oxidation and conservation of glucose carbon. The effect of sterile inflammation and chronic sepsis (small and large abscess) on the activity of the PDH complex was examined in liver and skeletal muscle. Sepsis altered the proportion of PDH in the active, dephosphorylated form. In hepatic tissue, sterile inflammation leads to a 2.5-fold increase in the proportion of active PDH complex compared to fed control. The same increase in the proportion of active PDH complex was observed in rats with a small septic abscess. However, when the severity of septic episode was increased, the proportion of active PDH complex decreased relative to sterile inflammation or small septic abscess animals. A different pattern in the response to sterile inflammation and sepsis on the proportion of active PDH complex was observed in skeletal muscle compared to liver. In contrast to liver, sterile inflammation did not alter the proportion of active PDH in skeletal muscle. In addition, sepsis (either small or large septic abscess) resulted in a 3-fold decrease in the proportion of active PDH relative to fed control or sterile inflammatory animals. The decrease in the proportion of active PDH complex in sepsis was associated with a corresponding increase in the skeletal muscle acetyl-CoA/CoA ratio. The mechanism responsible for lowered PDH complex activity may have been due to increased PDH kinase activity, secondary to increased skeletal muscle acetyl-CoA/CoA ratios.