ABSTRACT
This chapter focuses on the glucose-insulin circuit. It is the hydrogen atom of hormone circuits – it provides principles that apply to many other systems. Mathematical models for this circuit, developed since the 1970s, have benefitted clinical practice. Glucose concentration in the blood is maintained within a tight range around 5 mM. Insulin sensitivity varies between people and over time because it is a physiological knob that allows the body to allocate glucose resources and determine which tissues get the glucose. The minimal model provides a glucose set point, and the observed rise and fall of glucose and insulin in response to a meal. In contrast, during infection and inflammation, insulin sensitivity drops – insulin resistance rises – due to inflammatory signals in the circulation. Beta cells secrete more insulin for a given level of glucose during the day than during the night. This can be modeled as a change in the parameter in the insulin-glucose model.
