Calorie restriction modulates beta cell IP₃R activity to regulate Ca²⁺ homeostasis and cell network connectivity

Area of Science:

• Endocrinology
• Cell Biology
• Metabolism

Background:

• Calorie restriction (CR) is known to promote beta cell longevity and regulate cellular processes.
• CR enhances beta cells' cAMP levels and mitochondrial ATP production.
• However, the impact of CR on beta cell calcium (Ca²⁺) homeostasis and insulin secretion remains unclear.

Purpose of the Study:

• To investigate how calorie restriction (CR) affects beta cell Ca²⁺ homeostasis.
• To understand the mechanisms linking CR, cAMP, and insulin release.

Main Methods:

• Utilized acute pancreatic tissue slices from ad-libitum (AL) and CR mice.
• Employed fast confocal imaging with a low-affinity Ca²⁺ indicator to record cytosolic Ca²⁺ gradients.
• Analyzed Ca²⁺ spiking events in individual beta cells upon glucose stimulation.

Main Results:

• CR beta cells exhibit fast, short-amplitude Ca²⁺ oscillations driven by elevated cAMP.
• These oscillations potentiate insulin release despite a less connected beta cell network.
• Faster IP₃R-driven Ca²⁺ oscillations, associated with higher cAMP, protect beta cells from ER Ca²⁺ depletion.

Conclusions:

• Calorie restriction (CR) promotes beta cell longevity and secretory function.
• CR enhances beta cell Ca²⁺ and cAMP homeostasis, improving overall beta cell function.
• CR protects beta cells by maintaining ER Ca²⁺ levels through cAMP-mediated mechanisms.