The Glucose-Insulin Control System

Christine Erikstrup Hallgreen, Thomas Vagn Korsgaard, Rene Normann Hansen, and Morten Colding-Jargensen 

Biosimulation in Drug Development. Edited by Martin Bertau, Erik Mosekilde, and Hans V. WesterhofF Copyright 2008 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-31699-1 

The storage option is important. Food intake is intermittent, with intervals of hours or even days. So in some periods the uptake from the intestine exceeds the organism s demands, and in other periods there is no uptake, so the organism must rely on its nutrient stores. Consequently there is traffic of nutrients and metabolites back and forth, and the regulation of this traffic is one of the major challenges of our metabolic control. 

The reality is that there are numerous glucose sensors in the body, and that they are interconnected both by hormones and by the nervous system. Similarly, the fate of the glucose is complex, and control of the intracellular movements may be even more important than control of the uptake. 

The control system may rather be regarded as a complex, self-organizing system that controls the detailed metabolic traffic, and where the movements of fatty acids play an integral role. 

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The present chapter has several aims. The first is to describe the glucose-insulin control system in a fashion that includes the most important physiological and biochemical processes governing the glucose metabolism. The second is to demonstrate how biosimulation models can be built and to show the quantitative arguments behind the setup of model equations. The third is to use these biosimulation models to reveal critical mechanisms in the glucose handling and to relate these mechanisms to experimental and clinical problems. 

As previously mentioned, the glucose-insulin control system is often regarded as a simple system to keep the plasma glucose concentration within narrow limits. In this context it has been compared to technical control systems and described by simple, often linear or linearized models. Section 6.2 of this chapter gives an outline of classic control and underlines some of the peculiarities of biological control systems. 

The analysis reveals that the glucose-insulin control system functions as a regulator of the flux of nutrients - not only glucose - between the different organs in a smooth, controlled manner. In this control, the nervous system has an important... 

The features of the hepato-portal system together with the previous mentioned integral control supports the concept that the glucose-insulin control system is not so much a control of plasma glucose concentration as a system that controls the nutrient fluxes after a meal. 

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