Under metabolic stress in type 2 diabetes mellitus (T2DM), β cells accumulate damaged mitochondria, and proinflammatory macrophages infiltrate pancreatic islets. In several tissues, mitochondrial transfer between macrophages and parenchymal cells has been shown to alleviate inflammation and sustain cellular function reponse to stress. However, whether a similar process occurs between pancreatic β cells and macrophages remains unclear. Here, we identified a form of intercellular communication mediated by damaged mitochondrial-rich extracellular vesicles (mEVs) from β cells to macrophages within the inflammatory islets, promoted by Reg3g. Using time-lapse confocal microscopy, flow cytometry and split-GFP mitochondrial fusion assays, we demonstrated that stressed β cells release damaged mitochondria via mEVs, which were internalized by macrophages through a heparan sulfate (HS)-dependent mechanism and subsequently degraded through mitophagy. Under metabolic stress, β cells increased mEVs release, but macrophage uptake was impaired due to reduced HS biosynthesis. The protein Reg3g restored this process by binding macrophage exostosin-like glycosyltransferase 3 (EXTL3) receptors, promoting HS synthesis. Mechanically, increased HS enhanced mEVs uptake and strengthened the heparan sulfate proteoglycan (HSPG)-NF-κB interaction, sequestering NF-κB in the cytoplasm and suppressing purinergic receptor P2X7 (P2RX7) expression. P2RX7 downregulation subsequently promoted metabolic remodeling and an anti-inflammatory shift in macrophages. Collectively, our study identifies a Reg3g-orchestrated transcellular mitophagy pathway, wherein macrophages clear mEVs from β cells, promoting islet homeostasis. Targeting this axis may offer new therapeutic strategies for T2DM.
Copyright © 2025 The Author(s). Published by Elsevier B.V. All rights reserved.

The pancreas plays a central role in major human diseases, yet our understanding of its cellular diversity and plasticity remains incomplete. Here, we present a single-cell multiomics atlas of the human pancreas, profiling over four million cells and nuclei from 57 donors across fetal development, adult homeostasis, and type 2 diabetes (T2D). Integrating sc/snRNA-seq, snATAC-seq, VASA-seq, spatial transcriptomics (Xenium), and multiplexed proteomics (CODEX), we resolve gene expression, chromatin accessibility, and spatial organization at high resolution. We identify transcriptionally plastic centroacinar-like cells (pCACs) in adults with fetal-like features, delineate endocrine and exocrine lineage trajectories during development, and uncover HNF1A-defined beta cell epigenetic states. In T2D, we observe shifts in beta cell subtypes and altered regulatory programs. Glucose perturbation of healthy islets reveals cell-type-specific adaptation and stress responses. This atlas provides a foundational framework to understand pancreas biology and the role of cellular plasticity in regeneration and disease.

Metabolic stress elicits functional changes in pancreatic islets, contributing to the pathogenesis of type 2 diabetes. However, the molecular mechanisms underlying overnutrition stress in islet cells is not well understood. In our study, we subjected human islets to overnutrition with 25 mmol/L glucose and 0.5 mmol/L palmitic acid (glucolipotoxicity) or to a control culture condition with 5.1 mmol/L glucose. We used single-cell RNA sequencing to comprehensively characterize the gene expression changes between these two conditions in a cell type-specific manner. We found that among all islet endocrine cell types, α-cells were the most resilient to glucolipotoxicity, while β-cells were the most susceptible. We also observed a reduction in cell-cell interactions within islet endocrine cells under glucolipotoxicity, alongside alterations in gene regulatory networks linked to type 2 diabetes genetic risk. Finally, targeted drug screening underscored the critical role of histone H3K9 methyltransferases G9a (EHMT2) and GLP (EHMT1) in modulating the β-cell cellular response to overnutrition.
Glucolipotoxicity disrupts insulin secretion in human islets, yet its cell type-specific impacts and the molecular mechanisms driving these effects remain poorly understood. Single-cell RNA sequencing reveals β-cells as the most sensitive to glucolipotoxicity, with pronounced shifts in the gene regulatory network linked to cellular stress and lineage-specific transcription factors, while α-cells exhibit greater resilience. Cell-cell communications among islet endocrine cells are reduced under glucolipotoxicity. H3K9 methyltransferases G9a and GLP mediate glucolipotoxicity in β-cells. Our study provides a road map of how metabolic stress causally contributes to cellular dysfunction and diabetes pathogenesis.
© 2025 by the American Diabetes Association.

Long non-coding RNAs (lncRNAs) are emerging as crucial regulators of beta cell function. Here, we show that an lncRNA-transcribed antisense to Pax6, annotated as Pax6os1/PAX6-AS1, was upregulated by high glucose concentrations in human as well as murine beta cell lines and islets. Elevated expression was also observed in islets from mice on a high-fat diet and patients with type 2 diabetes. Silencing Pax6os1/PAX6-AS1 in MIN6 or EndoC-βH1 cells increased several beta cell signature genes' expression. Pax6os1/PAX6-AS1 was shown to bind to EIF3D, indicating a role in translation of specific mRNAs, as well as histones H3 and H4, suggesting a role in histone modifications. Important interspecies differences were found, with a stronger phenotype in humans. Only female Pax6os1 null mice fed a high-fat diet showed slightly enhanced glucose clearance. In contrast, silencing PAX6-AS1 in human islets enhanced glucose-stimulated insulin secretion and increased calcium dynamics, whereas overexpression of the lncRNA resulted in the opposite phenotype.
© 2024 The Authors.

Summary Incretin mimetic drugs are in widespread use for the treatment of type 2 diabetes and obesity and more recently have been prescribed for weight loss in otherwise healthy individuals. These drugs are all agonists of the glucagon-like peptide 1 receptor (GLP-1R) and function by supplementing effects produced by the endogenous hormone agonist glucagon-like peptide 1 (GLP-1). The therapeutic benefits of these medications, including improved glucose control and weight loss, require continued usage and wane with time. The molecular mechanisms underlying this loss of effect to incretin drugs remain unknown. Following activation by agonist and signaling to G protein, the GLP-1R engages arrestins and is endocytosed. Here we investigated the role of G protein-coupled receptor associated sorting protein 1 (GASP1), a critical regulator of the post-endocytic trafficking of GLP-1R, on tolerance to GLP-1R agonist drug. We found that tolerance to incretin drug was prevented at the cellular, tissue and whole animal level in mice with a selective disruption of the GASP1 protein in beta cells of the pancreatic islet. These studies implicate post-endocytic sorting of the GLP-1R in the loss of effectiveness of incretin therapeutics with prolonged use. These findings also suggest a novel strategy to prevent tolerance by biasing incretin drugs for G protein and away from arrestin engagement.