Pancreatic Islet Cell Crosstalk: Insight into α-/β-Cell Compensatory Mechanisms

Aim: To investigate the compensatory role of α-cell-derived paracrine signaling through glucagon and GLP-1 receptors in maintaining β-cell function when insulin secretion is compromised. Methods: A β-cell-specific Nox4 knockout mouse (Nox4βKO), which displays defective glucose-stimulated insulin secretion, was used to assess adaptive changes in pancreatic islets. We analyzed islet composition, hormone secretion dynamics, receptor expression profiles, and downstream signaling pathways. Methodologies included immunocytochemistry, flow cytometry, RNA sequencing, cAMP assays, and functional insulin/glucagon secretion assays using both isolated islets and pancreatic slices across different glucose levels and receptor-modulating conditions. Results: Prediabetic Nox4βKO islets showed increased α-cell numbers, expansion of bihormonal cells, and elevated production of glucagon and GLP-1. Receptor profiling revealed a shift in receptor usage: whereas GLP-1R dominated in wild-type islets, GCGR signaling gained prominence in Nox4βKO islets. This restructuring appears to reflect an adaptive response to emerging β-cell dysfunction. Functional assays demonstrated that insulin secretion in prediabetic islets became increasingly reliant on glucagon-driven activation of GLP-1R and cAMP-dependent pathways. Transcriptomic and signaling data confirmed enhanced expression of cAMP-related intermediates and calcium-handling components, indicating partial preservation of insulin secretory capacity despite underlying defects. Conclusion: α-cell remodeling and flexible engagement of glucagon and GLP-1 receptors act as key compensatory mechanisms that help maintain insulin secretion during early β-cell stress. The context-dependent reordering of intra-islet receptor dominance highlights a coordinated multicellular adaptation in prediabetes and suggests that targeting intra-islet endocrine crosstalk may help preserve β-cell function in prediabetes and early type 2 diabetes.