Glucose Oscillations Can Activate an Endogenous Oscillator in Pancreatic Islets
Fig 4
Glycolytic oscillations in the Dual Oscillator Model.
(A) Concurrent sawtooth F6P oscillations and FBP pulses produced by the glycolytic subsystem of the DOM. (B) Bifurcation diagram of the glycolytic subsystem. Sustained oscillations do not exist for low (Ge < Glow) or high (Ge > Gup) glucose, but can be triggered for an intermediate range (Glow < Ge < Gup). (C) Phase planes of the glycolytic subsystem within monostable (top) and bistable (bottom) glucose ranges. Initial states in the stable limit cycle (top and bottom, solid black curve) domain of attraction (top and bottom, white) trigger sustained oscillations. Initial states in the stable steady state (bottom, filled dot) domain of attraction (bottom, shaded gray) lead to transient, decaying oscillations. An unstable steady state (top, open dot) gains stability and gives rise to an unstable limit cycle (bottom, dashed curve) via a Hopf bifurcation as Ge increases past Gmid.