Exenatide substantially improves proinsulin conversion and cell survival that augment Ins2^+/Akita beta cell function

Area of Science:

• Endocrinology
• Molecular Biology
• Diabetes Research

Background:

• Proinsulin misfolding leads to beta-cell dysfunction and is implicated in diabetes.
• The Ins2^+/Akita mouse model exhibits a spontaneous mutation causing proinsulin misfolding and beta-cell defects.

Purpose of the Study:

• To investigate exenatide's effects on proinsulin conversion, beta-cell survival, and insulin secretion in Ins2^+/Akita beta-cells.
• To determine the mechanisms underlying exenatide's efficacy in this diabetes model.

Main Methods:

• Administration of exenatide (15 or 120 minutes) to Ins2^+/Akita beta-cells and Akita islets.
• Assessment of glucose-stimulated insulin secretion, proinsulin/insulin ratio, and beta-cell survival.
• Analysis of prohormone convertase levels (PC1/3, PC2) and dependence on calcium/cAMP.

Main Results:

• Exenatide significantly improved glucose-stimulated insulin secretion and the proinsulin/insulin ratio.
• Enhanced proinsulin conversion to insulin was observed, independent of PC1/3 and PC2 levels.
• Short-term exenatide treatment was calcium-independent, while longer treatment involved calcium and/or cAMP pathways.
• Exenatide improved beta-cell survival and glucose tolerance in Akita mice.

Conclusions:

• Exenatide effectively alleviates defective proinsulin conversion and improves beta-cell function in a genetic model of diabetes.
• Incretin mimetics represent a promising therapeutic strategy for addressing proinsulin misfolding-related diabetes complications.
• The findings highlight the potential of targeting protein folding defects in diabetes treatment.