Insulin resistance in human sepsis: implications for the nutritional and metabolic care of the critically ill surgical patient

Loss of the anabolic effect of insulin (insulin resistance) is a key component of the adverse metabolic consequences of sepsis and may contribute to the apparent lack of efficacy of feeding regimens in critically ill patients. The mechanisms which underlie the development of insulin resistance in stress remain unclear. In this series of studies, the locus of insulin resistance in the septic patient was shown to lie within the metabolic pathways of glucose storage (glycogen synthesis) within skeletal muscle, was noted to be unrelated to the actions of hormone mediators such as leptin and was shown not to be associated with altered nutrient-induced thermogenesis during total parenteral nutrition (TPN). Clinically applicable maximal rates of glucose-based TPN for septic patients were calculated. A technique was also developed in which insulin resistance could be induced and studied in healthy volunteers. These studies demonstrated that insulin resistance develops within 7 h of an inflammatory stimulus and, as in clinical sepsis, is characterised by selective impairment of glucose storage. Finally, a series of related studies indicated that the magnitude and nature of the inflammatory response in vivo could be enhanced by exogenous insulin infusion, indicating links between the hormone systems involved in intermediary metabolism and the inflammatory response. These findings have significant implications for the optimal design of feeding regimens for critically ill patients.