Modeling phasic insulin release: immediate and time-dependent effects of glucose

Area of Science:

• Endocrinology
• Cellular Physiology
• Metabolic Regulation

Background:

• Insulin secretion is critical for glucose homeostasis.
• Existing research often overlooks the dynamic regulatory mechanisms of insulin release.
• The biphasic nature of insulin secretion requires further elucidation.

Purpose of the Study:

• To review and synthesize decades of research on insulin secretion physiology.
• To highlight the complex, dynamic regulation of insulin release, including time-dependent potentiation (TDP) and time-dependent inhibition (TDI).
• To propose a model integrating TDP and TDI in insulin response modulation.

Main Methods:

• Review of studies on insulin secretion in perifused islets and perfused pancreases from rats and humans.
• Analysis of insulin responses to glucose and non-nutrient secretagogues under varying stimulation durations.
• Comparison of acute insulin response and TDP in glucose-tolerant versus glucose-intolerant models.

Main Results:

• Insulin secretion exhibits a biphasic pattern: an initial rapid phase followed by a sustained second phase.
• Short glucose stimulation induces time-dependent inhibition (TDI), reducing subsequent secretion.
• Prolonged glucose stimulation leads to time-dependent potentiation (TDP), enhancing responsiveness.
• TDI is induced by both nutrient and non-nutrient secretagogues, while TDP requires prolonged nutrient exposure.
• TDP appears intact in glucose-intolerant states, unlike the acute insulin response.

Conclusions:

• Insulin secretion is regulated by a balance between opposing time-dependent processes: potentiation (TDP) and inhibition (TDI).
• These dynamic regulatory mechanisms are distinct from the acute secretory signaling pathways.
• Future research on insulin secretion mechanisms must account for TDP and TDI, especially in conditions like glucose intolerance.