Insulin Control of Blood Glucose and GLUT4 Expression in the Skeletal Muscle of Septic Rats

Insulin resistance is common in septic patients. The level at which the serum glucose should be maintained using insulin infusions for optimal utilization by skeletal muscles is not yet established.

The objective of the present study was to compare glucose transporter 4 (GLUT4) mRNA and GLUT4 expression and glucose utilization at the recommended glucose levels of 6-8 mmol/L (110-140 mg/dL) and 8-10 mmol/L (140-180 mg/dL) in septic rats.

This was a prospective randomized study using 44 Sprague-Dawley rats (260-330 g). Rats were anaesthetized with gaseous diethyl ether. Catheters were implanted into the jugular vein and artery. Following a laparotomy, rats in the experimental group (n = 36) were rendered septic by standard caecal ligation and puncture (CLP) and intraperitoneal lipopolysaccharide (LPS) infusion (O111:[B4], 1 mg/kg). Control animals (n = 8) underwent laparotomy, but no caecal ligation or puncture and no LPS injection. Four experimental groups were studied: sham-operated control, sepsis treated with fluid maintenance only, sepsis treated with fluid and insulin infusion controlling blood glucose concentration at 6-8 mmol/L and sepsis treated with fluid and insulin infusion controlling blood glucose concentration at 8-10 mmol/L. Hyperinsulinaemic-euglycaemic clamp experiment was done before fluid maintenance and insulin treatment to calculate average glucose infusion rate.

All septic rats were markedly hyperglycaemic compared with sham-operated controls two hours after operation. Glucose infusion rate during hyperinsulinaemic-euglycaemic clamp experiment was slower in septic rats, suggesting that they were insulin resistant. At the 12th and 24th hour, skeletal muscle was taken to observe pathological change and analyse the GLUT4 mRNA and GLUT4 levels. There were more inflammatory cells, less GLUT4 mRNA and GLUT4 expression in the skeletal muscles of septic rats. Insulin increased the expression of GLUT4 mRNA and GLUT4 in the skeletal muscle of septic rats. Among all septic rats, the expression of GLUT4 mRNA and GLUT4 was more in the 8-10 mmol/L group.

Blood glucose concentration of 8-10 mmol/L results in more glucose utilization than 6-8 mmol/L in the skeletal muscle of septic rats during insulin therapy.