GLP-1, Pancreatic β-Cells, and Insulin Secretion: What We Know and Where We Need to Go.

Abstract

GLP-1 receptor agonists have emerged as key pharmacological tools in the treatment of type 2 diabetes and obesity. While their anorexigenic effects are well characterized, the mechanisms by which GLP-1 modulates pancreatic β-cell function remain only partially understood. In this article, we argue that GLP-1 receptor agonists should be viewed as integrative regulators of β-cell function and explore the multifaceted actions of GLP-1 analogs on β-cell signaling. GLP-1 influences key secretagogues and intracellular mediators (calcium, glutamate, γ-aminobutyric acid, serotonin, and urocortin-3), with complex roles in insulin exocytosis. Additionally, we discuss the interplay between calcium and cAMP, and how GLP-1 modulates both pathways to coordinate insulin secretion. Emerging evidence suggests that GLP-1 analogs affect mitochondrial morphology and redox homeostasis. Considering the relatively low expression of classical antioxidant enzymes in β-cells, and their reliance on both glycolytic and mitochondrial metabolism to sustain insulin secretion, the influence of GLP-1 on mitochondrial dynamics and reactive oxygen species may play a central role in sustaining cell function and viability. Despite recent advances, critical gaps persist in the literature, particularly regarding organelle cross talk, intracellular calcium stores, and the modulation of vesicular content. Drawing on current evidence, we propose that three mechanistic dimensions (intracellular neurotransmitters, mitochondrial remodeling, and redox control) represent key areas where clarifying GLP-1 actions could most effectively advance the field. Further investigation into these mechanisms is essential for a comprehensive understanding of GLP-1 actions in β-cells. This knowledge may help refine current incretin-based therapies and identify novel molecular targets for the treatment of metabolic disorders.

Article highlights: GLP-1 and its analogs enhance insulin secretion, but the specific intracellular mechanisms in β-cells remain unclear. Key intracellular mediators including calcium, glutamate, γ-aminobutyric acid, serotonin, and urocortin-3 are modulated by GLP-1 signaling with variable and sometimes contradictory effects. GLP-1 may affect mitochondrial dynamics and redox balance in β-cells, both critical for function and survival. Gaps in knowledge remain regarding cross talk between classical secretagogues and GLP-1 pathways. Further investigation is needed to clarify how GLP-1 integrates metabolic, signaling, and organelle-based processes in insulin secretion.