Mechanisms regulating skeletal muscle glucose metabolism in sepsis.

Carbohydrate dyshomeostasis is a characteristic feature of sepsis. Sepsis elevates glucose uptake and cellular lactate levels in muscle. The mechanisms responsible for these alterations are unknown. We examined the effects of a chronic, intra-abdominal septic abscess upon glucose uptake, the expression of the insulin receptor, glucose transporter proteins (Glut-1 and Glut-4) and mRNA, and the content of glycolytic intermediates in muscle from the hindlimb. Sepsis caused a 67% increase in glucose uptake compared with control. A differential expression of the Glut-1 and Glut-4 transporter proteins in skeletal muscle of septic rats was observed. Sepsis increased the expression of Glut-1 protein 1.7-fold. The increased Glut-1 protein correlated with a similar increase in the relative abundance of Glut-1 mRNA. In contrast, sepsis did not alter the amount of Glut-4 protein and mRNA or insulin receptor protein. The tissue content of glucose-6-phosphate was increased approximately twofold compared with control. The increase in the glucose-6-phosphate content was not associated with increased glycogen deposition in skeletal muscle of septic animals. Analysis of the glycolytic intermediates showed that only the lactate content of muscles from septic rats was significantly elevated in sepsis. The results are consistent with the hypothesis that sepsis enhances glucose uptake secondary to increased Glut-1 expression. Furthermore, once transported, glucose may be preferentially metabolized to lactate.

Analysis of physiological amino acids using dabsyl derivatization and reversed-phase liquid chromatography.

A method is described for the measurement of the specific radioactivity of primary amino acids in physiological samples. The amino acids were dabsylated followed by separation using high-performance liquid chromatography. We measured the concentration of amino acids from rat plasma or liver samples. Chromatographic analyses resolved phenylalanine from a mixture of amino acids in plasma within 30 min. An extended chromatographic gradient program completely separated all physiological amino acids within 75 min. This method is as sensitive as any current method of amino acid analysis and offers several advantages including (1) simple pre-column derivatization and (2) stability of derivatized samples.