Insulin resistance is a frequent manifestation of the metabolic response to injury, burn shock, or systemic infection. Evidence suggests that the insulin resistance may be due to a post-receptor defect in intracellular glucose metabolism especially in skeletal muscle. The post-receptor defect in glucose metabolism may be located in the steps involved in glucose uptake (transport and phosphorylation), glycogenolysis (phosphorylase), glycolysis (phosphofructokinase) or oxidation (pyruvate dehydrogenase). The proposed study will determine the rate of glucose flux through each of these steps in control, sterile inflammatory, and chronic septic animals. The chronic septic model will be produced by an intra-abdominal abscess in the rat using a biclonal (aerobic and anaerobic) bacteria infected sterile fecal pellet as a foreign body abscess nidus of. The tissue level of metabolites in the glycolytic pathway will be determined and potential sites of metabolic control will be determined. These studies will provide information as to intracellular site and biochemical mechanisms of insulin resistance. Oxidation of both glucose and lactate is regulated by the activity of the pyruvate dehydrogenase complex which exists in interconvertible phosphorylated (inactive) and dephosphorylated (active) forms. The activity of the pyruvate dehydrogenase (PDH) complex is decreased in skeletal muscle in sepsis. The significance of this decrease in regulating glucose oxidation during sepsis will be determined by defining the relationship between glucose flux through PDH complex and concentration of active complex. In contrast, in hepatic tissue, the activity of the pyruvate dehydrogenase was either increased or unchanged during sepsis suggesting that septic effects are tissue specific. The molecular mechanisms responsible for these changes in pyruvate dehydrogenase complex will be determined by measuring the acetyl CoA/CoA, NADH/NAD and ATP/ADP concentration ratios and mitochondrial Ca2+ in sterile inflammation and sepsis. In skeletal muscle, the level of acetyl CoA and the acetyl CoA/CoA are elevated in sepsis, and this may account for the decreased PDH activity by increasing PDH kinase activity in sepsis. An attempt to reverse the effects of sepsis on the activity of the pyruvate dehydrogenase complex will be determined by inhibiting the pyruvate dehydrogenase kinase with dichloroacetate. The proposal will provide evidence for the hypothesis that part of the insulin resistance is due to a defect in glucose metabolism. The metabolic step which is altered by sepsis will be determined and the extent to which the severity of the septic episode alters glucose metabolism will be determined.
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