6533b821fe1ef96bd127b69c

RESEARCH PRODUCT

Simulation of Metabolism for The Calculation of Enzyme Activities in Stress Metabolism

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Abstract Using data of indirect calorimetry, total energy turnover as well as the rate of combustion of carbohydrates, fat and amino acids can be calculated. For the evaluation, simple standard procedures (4) are used. These procedures presume, that several assumptions are satisfied, e.g. a complete degradation of the energy delivering substrates and undisturbed enzyme activities. To be able to interprete also measurements, which are performed in the post-traumatic state as well as for estimation of the extent and consequences of reduced enzyme activities, a new method for the simulation of metabolism was developed. Hie underlying model considers a reduced activity of key enzymes and a switch-over of accumulated intermediates to alternative pathways. The metabolic model is described by a non-linear system of equations, whose solution is determined by a modified Simplex algorithm. The simulation was used for the evaluation of indirect calorimetric measurements, which were carried out on traumatized patients, supported by total parenteral nutrition. The results of simulation of a 27 hour period of indirect calorimetry is shown exemplarily. A marked reduction of relative activity down to 20 % is detected for pyruvate dehydrogenase: Gluconeogenesis reaches up to 800 g/d, while glykogen utilization varies between 0 and i00 g/d. These and additional results show that the method described is suitable to record enzyme activities and substrate turnover in a non-invasive manner, and to get a general idea of the posttraumatic metabolism on the enzymatic level.