Figure 5.

Signalling cascade of insulin secretion in the β-cells in response to glucose and GLP-1. Glucose triggers the cascade of events outlined in figure 1. GLP-1 potentiates the activity of glucose by inhibiting K⁺_ATP channels, facilitating the opening of VDCCs, and inhibiting membrane repolarization via K_v channels. GLP-1 also sensitizes IP₃ (IP₃R) and ryanodine (RYR) receptors to the effects of Ca²⁺, facilitating Ca²⁺-induced Ca²⁺ release (CICR). CICR promotes enhanced insulin secretion and enhanced ATP production, the latter of which facilitates a feed-forward loop to promote further rounds of depolarization and insulin secretion.