At what point does phase 2 insulin secretion begin?

From the Guidelines

Phase 2 insulin secretion begins approximately 10 minutes after the initial insulin release, lasting around 60 to 120 minutes. This phase is characterized by a slower and more sustained insulin secretion compared to the first phase, which occurs within 3 to 5 minutes after glucose exposure 1. The second phase of insulin secretion is crucial for maintaining glucose homeostasis during extended periods of elevated blood glucose, such as after meals. Some key points about phase 2 insulin secretion include:

• It is a slower and more sustained insulin release compared to phase 1
• It depends on the synthesis of new insulin and mobilization of storage granules from the pancreatic beta cells
• It is crucial for maintaining glucose homeostasis during extended periods of elevated blood glucose
• The mechanism involves continued glucose metabolism within beta cells, maintaining elevated ATP levels that keep potassium channels closed, cell membranes depolarized, and calcium channels open, which triggers ongoing insulin exocytosis 1. In patients with type 2 diabetes, this glucose-mediated insulin secretion pulse is blunted to approximately 70% of normal, and first-phase insulin secretion is often lost 1.

From the Research

Phase 2 Insulin Secretion

• Phase 2 insulin secretion begins after the first phase, which is a brief spike lasting approximately 10 min 2
• The second phase reaches a plateau at 2-3 h 2
• The first phase of insulin release is almost invariably lost in patients with impaired glucose tolerance or in the early stages of type 2 diabetes, despite the enhancement of second-phase secretion 3
• Both animal and human studies support the critical physiologic role of the first-phase of insulin secretion in the maintenance of postmeal glucose homeostasis 3
• The deterioration of the first and second phases of insulin secretion is not synchronized 4
• Significant correlations were noted between the second phase of insulin secretion and the first phase of insulin secretion, as well as between the second phase of insulin secretion and log HOMA-beta 4