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.

Type 2 diabetes (T2D) is a devastating chronic disease marked by pancreatic β cell dysfunction and insulin resistance, whose pathophysiology remains poorly understood. HNF1A, which encodes transcription factor hepatocyte nuclear factor-1 alpha, is the most commonly mutated gene in Mendelian diabetes. HNF1A also carries loss- or gain-of-function coding variants that respectively predispose to or protect against polygenic T2D. The mechanisms underlying HNF1A-deficient diabetes, however, are still unclear. We now demonstrate that diabetes arises from β cell-autonomous defects and identify direct β cell genomic targets of HNF1A. This uncovered a regulatory axis where HNF1A controls transcription of A1CF, which orchestrates an RNA splicing program encompassing genes that regulate β cell function. This HNF1A-A1CF transcription-splicing axis is suppressed in β cells from T2D individuals, while genetic variants reducing pancreatic islet A1CF are associated with increased glycemia and T2D susceptibility. Our findings, therefore, identify a linear hierarchy that coordinates β cell-specific transcription and splicing programs and link this pathway to T2D pathogenesis.
Copyright © 2025 The Authors. Published by Elsevier Inc. All rights reserved.

Activation of the IRE1/XBP1s signaling arm of the unfolded protein response (UPR) has emerged as a promising strategy to mitigate etiologically diverse diseases. Despite this promise, few compounds are available to selectively activate IRE1/XBP1s signaling to probe the biologic and therapeutic implications of this pathway in human disease. Recently, we identified the compound IXA4 as a highly selective activator of protective IRE1/XBP1s signaling. While IXA4 has proven useful for increasing IRE1/XBP1s signaling in cultured cells and mouse liver, the utility of this compound is restricted by its limited activity in other tissues. To broaden our ability to pharmacologically interrogate the impact of IRE1/XBP1s signaling in vivo, we sought to identify IRE1/XBP1s activators with greater tissue activity than IXA4. We reanalyzed 'hits' from the high throughput screen used to identify IXA4, selecting compounds from structural classes not previously pursued. We then performed global RNAseq to confirm that these compounds showed transcriptome-wide selectivity for IRE1/XBP1s activation. Functional profiling revealed compound IXA62 as a selective IRE1/XBP1s activator that reduced Aβ secretion from CHO7PA2 cells and enhanced glucose-stimulated insulin secretion from rat insulinoma cells, mimicking the effects of IXA4 in these assays. IXA62 robustly and selectively activated IRE1/XBP1s signaling in the liver of mice dosed compound intraperitoneally or orally. In treated mice, IXA62 showed broader tissue activity, relative to IXA4, inducing expression of IRE1/XBP1s target genes in additional tissues such as kidney and lung. Collectively, our results designate IXA62 as a selective IRE1/XBP1s signaling activating compound with enhanced tissue activity, which increases our ability to pharmacologically probe the biologic significance and potential therapeutic utility of enhancing adaptive IRE1/XBP1s signaling in vivo.