A Whole-Body Model for Glycogen Regulation Reveals a Critical Role for Substrate Cycling in Maintaining Blood Glucose Homeostasis
Figure 7
Enzymes and substrate responses over a series of
ranging from
to
. A: System response time to glucose stimulus plotted against
in a glycogen depleted liver. Blue: system response time defined by the cross-over point of glycogen synthase a (GSa) and glycogen phosphorylase a (GPa). Black: system response time defined by the time when liver glycogen concentration exceeds 0.5 mM. Note that the difference in system response time is about 30 mins for the lowest and highest values of
selected here under both definitions. B: The co-activated percentage of GSa and GPa at the cross-over point as a function of
. Note that this percentage represents the maximum co-active percentage of both enzymes, hence it is an indicator of the level of substrate cycling in the system. The points inside the rectangles (
) and triangles (
) are the two values chosen in Figure 6.