Glucose is the most frequently used energy source during parenteral feeding. Gollowing trauma, glucose infusion above the endogenous production rate, is associated with an increase of blood glucose and insulin levels, thereby reducing the redistribution of substrates from peripheral to visceral organs which is a characteristic metabolic adaptation to altered requirements, resulting in only limited protein-sparing properties. Non-glucose carbohydrates like xylitol are metabolized primarily in the liver and there converted by insulin-independent pathways to glucose-6-phosphate, resulting in only modest increases of blood glucose and insulin levels during intravenous use. The tissue affected by insulin resistance after trauma is predominantly muscle, immobilization during such a state will inevitably induce an increased catabolism in this tissue. We do not believe that optimal nitrogen sparing can be achieved by means of manipulating muscle protein turnover. A rapid and substantial protein preservation can only be achieved in organ systems with a high daily protein turnover rate, such as the viscera. Xylitol does not attenuate the amino acid flux from peripheral to visceral organs, so that together with the undisturbed fat oxidation, nitrogen is spared by enhancing protein synthesis in the visceral organs. It is the goal of this proposal to show that glucose, given above the endogenous production rate of 80 kcal/kg BW/day in the rat results in limited protein sparing. By restricting glucose intake to 80 kcal/kg BW/day and by providing additional equal amount of calories as xylitol, the glucose related metabolic disadvantages can be avoided. Simultaneous xylitol infusion will lead to an increase in endogenous fat and carbohydrate utilization, and by providing the liver with a substrate it can metabolize significantly even after trauma, body protein preservation will be substantially improved. The value of such a regimen will be determined by dynamic and static measurements of protein, carbohydrate and fat metabolism.
