Diabetes

The decline in first-phase insulin response (FPIR) during the presymptomatic period of type 1 diabetes (T1D) is well established. In-situ functional studies with pancreas tissue slices showed that {beta}-cell loss of glucose-responsiveness was independent of T-cell infiltration into islets in recent-onset T1D cases. However, the mechanisms driving {beta}-cell dysfunction before the onset of T1D remain unclear. In pancreas tissue from donors across the natural history of T1D, we utilized an in-situ, whole-islet phenotypical and transcriptomic approach to unravel novel targets in the glucose-stimulus coupled secretion pathway that are similarly impaired in T-cell infiltrated and non-infiltrated islets. Specifically, we observed that islets from autoantibody positive (single(s) or multiple(m) AAb+) donors exhibited activation of post-transcriptional gene regulation along with reduced protein translation, processing in the endoplasmic reticulum (ER), and ER stress. Disrupted mitochondrial metabolism and bioenergetics were prominent in islets from multiple AAb+ and T1D donors with disease durations [≤]7 years. In addition, T1D islets presented reduced mitochondrial protein import, quality control, and dynamics, together with downregulated genes in insulin secretory pathways. During infiltration, these pathways remain dysregulated while immune/inflammatory transcripts were increased. These studies identified novel mechanisms of {beta}-cell dysregulation before symptomatic onset and independent of T-cell infiltration in T1D pathogenesis.

Type 1 diabetes (T1D) is a complex autoimmune disease characterized by the destruction of insulin-producing pancreatic {beta} cells. Both genetic susceptibility and epigenetic dysregulation contribute to T1D risk. Recent studies have reported {beta}-cell dysfunction before disease onset, suggesting that {beta}-cell-intrinsic mechanisms contribute to pathogenesis. However, the mechanistic link between disease-associated variants and {beta}-cell dysfunction remains poorly understood. We hypothesized that a subset of T1D-associated variants directly influences cell type-specific candidate cis-regulatory elements (cCREs) by disrupting transcription factor (TF) binding and altering gene expression. To define cell type-specific cCREs in human islets, we integrated publicly available epigenomic datasets, including bulk histone modification profiles and single-cell multiomic data from human pancreatic islets. We combined these data with T1D genome-wide association study (GWAS) variants to identify disease-associated SNPs located within enhancer regions. Using multiomic datasets from PANC-DB, we characterized cell type-specific chromatin accessibility in nondiabetic and T1D islets and identified regulatory regions that may control gene expression in {beta} cells and other islet cell types. We then applied ChromBPNet, a deep learning model that predicts base-pair-resolution chromatin accessibility from scATAC-seq data, to evaluate how specific variants may alter local regulatory activity. In parallel, we used TF footprinting to nominate TFs likely to bind these variant-containing regions. These analyses identified several T1D-associated SNPs predicted to alter chromatin accessibility at candidate TF binding sites, suggesting mechanisms by which noncoding variants may contribute to {beta}-cell dysfunction and T1D susceptibility. Our findings link T1D-associated variants to cell type-specific enhancer activity and regulatory pathways and provide candidates for future mechanistic studies.

Type 2 diabetes is a complex metabolic disease with a strong genetic component, yet this genetic risk is driven by common variants in up to 600 loci with small effect sizes. Variants in the STEAP2 locus, encoding Six-transmembrane epithelial antigen of the prostate-2, are highly associated with altered glycemic traits and type 2 diabetes risk. To elucidate its function in pancreatic beta-cells, we utilized Crisp-Cas9 assisted homologous recombination to derive a conditional null allele for Steap2 (Steap2fl/fl) in mice and crossed this to the rat insulin promoter (Rip)-Cre transgene. Ablation of Steap2 induced glucose intolerance, blunted glucose-stimulated Ca2+ mobilization and stunted first phase glucose-simulated insulin secretion. In contrast, the incretin effect and second phase insulin secretion were not affected. Islet respirometry and transmission electron microscopy (TEM) identified disrupted cristate morphology and impaired glucose-stimulated oxygen consumption as causally responsible for the observed, impaired triggering pathway of insulin secretion. These findings suggest that at least part of the genetic risk for T2D conferred by Steap2 variants is likely due to its function in maintaining optimal mitochondrial respiration in pancreatic beta-cells.

The Mediator complex, a vital transcriptional coregulator in eukaryotes, partners with transcription factors to orchestrate gene transcription and in turn many developmental and physiological processes. Mediator subunit MED15 is required for the pre-natal development and post-natal maturation of pancreatic {beta}-cells in mice. However, whether MED15 plays a role in {beta}-cell function after initial development and throughout adulthood is unknown. To investigate the role of MED15 in {beta}-cells post-maturation, we induced a {beta}-cell specific Med15 knockout at six weeks age in male and female mice. This post-developmental Med15 ablation led to glucose intolerance and impaired insulin secretion. RNA-sequencing revealed downregulation of {beta}-cell maturation markers, indicating that MED15 is continuously required to maintain {beta}-cell functionality. Further, we implanted insulin pellets into Med15 knockout mice to lower blood glucose and used RNA-seq to validate that the transcriptional changes we observed are a direct consequence of Med15 loss and not an indirect effect of hyperglycemia arising in the knockout mice. In sum, our study shows that MED15 is continuously required after weaning to maintain functional {beta}-cell maturity.

Most polygenic scores (PS) for type 1 diabetes were developed using European (EUR) ancestry datasets, limiting performance in non-European (non-EUR) populations. We evaluated novel type 1 diabetes PS across diverse populations to assess whether newer models improve prediction in underrepresented populations. Seven type 1 diabetes PS (T1D GRS2, T1D GRS2', T1D GRSHLA, T1GRS, TA-PS, TA-PS (S), T1D MAPS) were evaluated in All of Us and Mass General Brigham Biobank. Predictive performance was assessed using the area under the receiver operating characteristic curve (AUC). T1D GRS2 and T1D MAPS showed the highest AUC in All of Us, while other scores demonstrated comparatively lower performance. These highest-performing scores were then evaluated in a meta-analysis across three additional biobanks (Genomic Health Initiative at Endeavor Health, Penn Medicine BioBank, Geisinger MyCode). Among 2,782 individuals with type 1 diabetes and 546,577 controls, T1D MAPS showed comparable performance to T1D GRS2 in EUR populations but significantly improved discrimination in non-EUR populations (meta-analysis {Delta}AUC=0.049, p=1.7x10-7). Overall, T1D MAPS improves prediction in non-EUR populations, highlighting the importance of multi-ancestry approaches for equitable genetic risk prediction. These findings could inform precision medicine in diverse populations.

Pregnancy requires maternal pancreatic {beta}-cells adaptations to increased insulin demand, yet the embryo-derived signals contributing to this response remain poorly defined. Here we identify preimplantation factor (PIF), an embryo-derived peptide present in maternal circulation from early gestation, as a regulator of {beta}-cell adaptation. In a murine model of gestational diabetes mellitus (GDM), circulating PIF levels were reduced during mid-gestation, indicating that this endogenous signal is altered under gestational metabolic dysfunction. Conversely, chronic exposure of non-pregnant female mice to synthetic PIF (sPIF) recapitulated key temporal features of gestational {beta}-cell adaptation, including early {beta}-cell proliferation, increased glucose-stimulated circulating C-peptide, expansion of {beta}-cell mass and sustained enhancement of ex vivo glucose-stimulated insulin secretion (GSIS). Mechanistically, sPIF activated rapid ERK-, AKT- and PKA-dependent signaling that converged on estrogen receptor alpha (ER) phosphorylation and nuclear translocation. Pharmacological inhibition and genetic silencing demonstrated that ER is required for full propagation of the functional and kinase responses. This kinase-ER axis was conserved in human islets, where sPIF enhanced insulin secretion in an ER-dependent manner. These findings identify PIF as an embryo-derived metabolic signal supporting maternal {beta}-cell compensation and suggest that reduced PIF availability may contribute to inadequate {beta}-cell adaptation in GDM.

SLAM-associated protein (SAP) is required for T follicular helper (Tfh)-B cell interactions that underlie germinal center formation, but it is unclear if SAP governs islet-reactive CD4+ T cell-B cell interactions and downstream pro-inflammatory CD8+ T cell destruction of islets in type 1 diabetes (T1D). To address this question, we utilized the VH125SD.NOD mouse model, whereby 1-3% of all B cells bind insulin. Germline SAP loss in this model led to reduced T1D incidence and impaired germinal center B cell formation, yet did not alter T follicular helper cell formation or phenotype. SAP loss reduced pro-inflammatory and activated insulin-autoreactive B-T interactions and limited anti-insulin B cell proliferation, activation, and upregulation of co-stimulatory molecules otherwise enhanced in the pancreas. Anti-insulin extrafollicular antibody and memory responses following immunization were preserved in VH125SD.SAP-/-.NOD mice, but activated atypical anti-insulin B cell responses were reduced. Ultimately, SAP loss led to reduced pro-inflammatory CD8+ T cell formation and islet-reactive progenitor exhausted CD8+ T cells in pancreata. These data highlight the essential role of SAP in mediating proinflammatory, anti-insulin B-T interactions to support T1D. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=161 SRC="FIGDIR/small/741363v1_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@1f5eb40org.highwire.dtl.DTLVardef@27f133org.highwire.dtl.DTLVardef@4c7047org.highwire.dtl.DTLVardef@5f612a_HPS_FORMAT_FIGEXP M_FIG C_FIG

{beta} cell expression of the immune checkpoint ligand PD-L1 (encoded by CD274) limits autoimmune {beta} cell destruction in type 1 diabetes (T1D). {beta} cell display PD-L1 not only at the cell surface but also secreted on extracellular vesicles (EVs), which bind PD-1 and restrain CD8+ T cell activation. {beta} cell IFN signaling is an early driver of T1D pathogenesis, yet the mechanisms linking IFN signaling to the fate of PD-L1 protein remain undefined. Here, we identify an IFN- and coxsackievirus-inducible alternatively spliced isoform of PD-L1, PD-L1{Delta}3, lacking cassette exon 3 and generated in human {beta} cells and islets in response to IFN signaling or viral infection. PD-L1{Delta}3 transcripts are elevated in islets from donors with single autoantibody positivity (AAB+) and T1D. Unlike full-length PD-L1, which localizes to the plasma membrane, PD-L1{Delta}3 is retained intracellularly and loses the capacity to bind PD-1. Functionally, PD-L1{Delta}3 fails to suppress CD8+ and CD4+ T cell proliferation, activation, and cytotoxic cytokine release, and is not efficiently sorted into EVs. Convergently, a germline CD274 splice-site variant (c.682+1G>A) found in siblings with neonatal T1D yields a protein with the same intracellular retention, reduced {beta} cell PD-1 binding, and reduced {beta} cell and circulating EV PD-L1. Together these findings define PD-L1{Delta}3 as an IFN-induced splice variant that diverts PD-L1 away from its immunoregulatory, EV-competent form, revealing a post-transcriptional axis that shapes {beta} cell immune communication.

Autoreactive B cells must escape immune tolerance mechanisms to drive autoimmune disease, potentially through alternative paths to memory and antibody-secreting cell formation. "Atypical" B cells represent one such alternative pathway and are expanded in several human autoimmune diseases. Atypical B cells display phenotypic heterogeneity, but how this connects with differences in transcriptional programming, isotype switching and somatic hypermutation is incompletely understood in type 1 diabetes (T1D). Screening efforts to detect T1D prior to clinical diabetes onset affords an opportunity to study B cells early in immunopathogenesis, in which they primarily function as antigen-presenting cells. Prior evidence points to atypical B cell populations as reservoirs for islet autoreactivity in human T1D. We therefore developed sorting strategies to enrich for atypical and other autoreactive-prone B cell populations from the peripheral blood of early-stage T1D individuals and performed single-cell RNA/BCR-sequencing. We identified four transcriptionally defined atypical B cell clusters, each showing differential upregulation of atypical B cell defining genes. Additional gene expression changes were noted in broadly transcriptionally similar, but phenotypically distinct atypical B cell populations, with differences noted in the average extent of isotype switching and somatic hypermutation. Some atypical B cell populations showed extensive clonal sharing with classical memory or plasmablast subsets, consistent with relationships amongst these subsets. B cells reactive against a key islet autoantigen, insulin, were enriched in select atypical B cell populations. These findings highlight specific atypical B cell populations and features with potential value as biomarkers of disease progression or response to immunotherapy in T1D, and potentially other autoimmune diseases.

PURPOSE: To assess the predictive performance of panel protein biomarkers as well as an established algorithm that considers repeat biomarker testing for risk prediction of PDAC among a prospective cohort of patients with New-onset diabetes. PATIENTS AND METHODS: A panel of protein biomarkers (CA19-9, CA125, CEA, LRG1, REG3A and TIMP1) were assayed in 6,516 serially collected pre-diagnostic plasma samples from 2,121 NOD patients from the Consortium of Chronic Pancreatitis Diabetes and Pancreatic Cancer (CPDPC)-initiated NOD study who completed the 3-year study follow-up period. The specimen set included 25 pre-diagnostic samples from the 12 PDAC cases diagnosed during study follow-up. We applied a single threshold (ST) method, which considers biomarker levels at a single time point, as well as a previously established parametrical empirical Bayes (PEB) algorithm, which considers prior biomarker measurements, with case calls made based on pre-specified cutoffs corresponding to 1% 1-year risk. Resultant biomarker data as well as case calls were provided to the EDRN Data Management and Coordinating Center as part of a Prospective-sample-collection-Retrospective-Blinded-Evaluation (ProBE)-compliant Phase 3 biomarker validation study. Area under the Receiver Operating Characteristic Curves (AUC), sensitivity, specificity, population-level positive predictive value (PPV), and negative predictive value (NPV) are reported. RESULTS: The 3-year incidence of PDAC in the NOD cohort was 0.57%. When considering PDAC vs non-cancer controls, respective AUCs of individual protein biomarkers ranged from 0.52-0.94, with CA19-9 achieving the highest overall performance of 0.94 (95% CI: 0.86-1.00). At the pre-defined 1% 1-year risk threshold, CA19-9 yielded sensitivity of 83.3% at 97.2% specificity. Additional markers CEA, CA125, and TIMP1 demonstrated sensitivity of 33.3%, 41.7%, and 8.3%, respectively. In a subset of patients, CA19-9 first tested positive at a median (interquartile range [IQR]) of 7 months (4 to 14 months) prior to clinical PDAC diagnosis. Of the two PDAC cases missed by CA19-9 using the ST method, one (diagnosed with stage III PDAC) was detected using the PEBCA19-9 algorithm. CONCLUSION: In the setting of adult new onset diabetes, CA19-9 is a readily available and promising biomarker that can be leveraged for earlier detection of an underlying pancreatic cancer. Additional protein biomarkers may improve sensitivity for earlier detection of PDAC among cases with low CA19-9.

Type 1 diabetes (T1D) is an autoimmune disease characterized by CD8 T cell-mediated destruction of pancreatic {beta} cells; however, the cellular interactions that organize immune activation within human islets remain poorly understood. Here, we integrated thirteen CD45 immune cell single-cell RNA sequencing datasets from human islets spanning non-diabetic donors, stage 3 T1D, and type 2 diabetes (T2D) to comprehensively define immune cell heterogeneity and decipher the intercellular communication networks that drive islet autoimmunity. We identified distinct macrophage states, including CD14 inflammatory macrophages, CD14/TREM2 macrophages, and quiescent-like macrophages, together with CD8 T cells and mast cells. Trajectory and communication analyses revealed CD14 macrophages as central immune hubs that coordinate antigen presentation, costimulatory signaling, and inflammatory chemokine production. Compared with non-diabetic and type 2 diabetic islets, T1D macrophages displayed a disease-specific inflammatory program characterized by enhanced TNF, IL18, CCL3, CCL4, CCL5, and ICOSLG expression, supporting CD8 T cell recruitment and activation. Spatial transcriptomic analysis of human T1D pancreas further demonstrated a {beta}-cell-macrophage-CD8 T cell inflammatory niche, where macrophage-derived CCL3/CCL4/CCL5 and CD8 T cell-expressed CCR5 suggest a chemokine-mediated mechanism of immune targeting. Together, these findings identify CD14 macrophages as key orchestrators of a feed-forward inflammatory circuit driving human islet autoimmunity.

Obesity-associated insulin resistance is driven in part by adipose tissue dysfunction and oxidative stress, yet the role of extracellular mechanisms in modulating insulin signaling remains poorly understood. Here, we show that extracellular Glutathione Peroxidase 3 (GPX3) enhances adipocyte insulin sensitivity and functionalities independent of its canonical peroxidase function. GPX3, a secreted selenoprotein highly expressed in white adipose tissue (WAT), is suppressed in obesity, but whether it actively regulates insulin sensitivity had not been established. We find that WAT GPX3 expression closely mirrors insulin receptor (InsR) expression across a broad range of metabolic parameters in humans and increases dynamically following weight loss. Prolonged therapeutic selenium supplementation in diet-induced obese mice selectively suppressed epididymal WAT oxidative damage, restored GPX3 and InsR expression, and enhanced insulin-stimulated AKT phosphorylation, improving oral glucose tolerance. Mechanistically, recombinant GPX3 extracellularly administered at physiological concentrations induced InsR expression across multiple adipocyte models, including pre-adipocytes, epididymal WAT explants, and adipocyte organoids, by promoting binding of the transcription factor Specificity Protein 1 (SP1) to the Insr promoter, while knockdown of GPX3 completely blocks SVF adipogenesis. These effects rely on the structural integrity, rather than selenocysteine-dependent activity. Thus, we identify a GPX3-SP1-InsR signaling axis in adipose tissue insulin sensitivity, suggesting GPX3 is a novel paracrine mediator of metabolic health and a potential therapeutic target to reinstate WAT insulin sensitivity in obesity and type 2 diabetes.

Dysregulated hormone secretion and erosion of endocrine cell identity are features of type 1 and type 2 diabetes, but the transcriptional programs maintaining adult human islet identity and function remain poorly defined. The large MAF transcription factor MAFB is expressed in human - and {beta}-cells, marks their most functionally mature subpopulations, and is downregulated in diabetes, but its role in adult human islets has not been tested directly. Using shRNA-mediated MAFB knockdown (KD) in whole and CD26+ -cell-enriched human pseudoislets, we found that whole pseudoislet MAFB KD impaired glucagon synthesis and secretion while only modestly reducing insulin content and cAMP-potentiated insulin release. Single-cell profiling detected no {beta}-cell transcriptional response beyond MAFB KD itself, consistent with buffering by the related {beta}-cell-enriched MAFA transcription factor. In contrast, -cell-restricted MAFB KD unmasked a cell-autonomous requirement for MAFB in stimulus-secretion coupling. MAFB deficiency also destabilized -cell identity, downregulating canonical -cell and neuroendocrine secretory genes while ectopically inducing mesenchymal and extracellular matrix remodeling programs. In addition, MAFB-dependent downregulation of electron transport chain genes was confined to a large -cell subcluster, manifesting as impaired islet-wide mitochondrial respiration within the broader -cell population. Together, these findings identify MAFB as an essential adult human -cell maintenance factor that links diabetes-associated downregulation to impaired glucagon secretion, -cell identity erosion, and mitochondrial dysfunction. RESEARCH IN CONTEXTO_LIWhat is already known about this subject? O_LIMAFB is expressed in adult human - and {beta}-cells, marks their most functionally mature subpopulations, and is downregulated in type 1 and type 2 diabetes C_LIO_LIIn human stem cell models, MAFB is essential for generating insulin-producing {beta}-like cells, whereas glucagon-producing -like cells are reduced but still formed C_LIO_LINeither model addresses adult human islets: rodent MafB becomes -cell restricted after birth, and stem cell models capture differentiation, not maintenance C_LI C_LIO_LIWhat is the key question? O_LIIs MAFB required to maintain identity and secretory function in adult human islet cells? C_LI C_LIO_LIWhat are the new findings? O_LIMAFB knockdown in primary human pseudoislets impaired glucagon synthesis and secretion but minimally affected {beta}-cells, consistent with buffering by MAFA C_LIO_LIKnockdown in CD26+ -cell-enriched pseudoislets revealed a cell-autonomous requirement for MAFB in stimulus-secretion coupling, and destabilized -cell identity by inducing mesenchymal and extracellular matrix programs C_LIO_LIMAFB loss downregulated electron transport chain genes in the largest -cell subcluster and reduced mitochondrial respiration C_LI C_LIO_LIHow might this impact on clinical practice in the foreseeable future? O_LIPreserving MAFB activity in adult human -cells may represent a strategy to limit -cell dysfunction in diabetes C_LI C_LI

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by T-cell mediated destruction of pancreatic islet {beta}-cells with genetic, environmental, and molecular triggers involved in disease pathogenesis. Patients with T1D have elevated serum levels of microRNA146a (miR146a). Polymorphisms in the miR146a gene that result in reduced expression of miR146a are associated with protection from T1D. We studied physiological regulators of miR146a expression and found that both hyperglycemia and elevated O-GlcNAcylation increased miR146a expression in T cells. Peripheral blood mononuclear cells (PBMCs) from T1D patients showed increased miR146a and O-GlcNAc transferase (OGT) expression, suggesting increased O-GlcNAcylation may promote miR146a expression in T1D patients. To determine the genetic and developmental role of miR146a in T1D, we generated miR146a-knockout (KO) non-obese diabetic (NOD) mice and found that absence of miR146a significantly protected NOD mice from spontaneous autoimmune diabetes. While we found no impact of miR146a knockout on general hematopoietic parameters and immune cell populations, remarkably, immune cell infiltration into the pancreas was significantly attenuated. Protection from autoimmune diabetes in miR146a-KO NOD mice was associated with increased regulatory T (Treg) cells in the spleen and pancreatic lymph node. Mechanistically, absence of miR146a increased NF-{kappa}B c-Rel expression in Treg cells and enhanced c-Rel binding at the Forkhead box protein P3 (FOXP3) promoter, which positively regulated Treg cell development and suppressor function, offering protection from T1D in miR146a-KO NOD mice. Our findings reveal miR146a as a key regulator of Treg cell-mediated immune tolerance through controlling NF-{kappa}B c-Rel-dependent FOXP3 expression and suggest targeting miR146a as a potential strategy to restore peripheral tolerance in T1D.

Aims/Hypothesis: Atypical forms of diabetes often provide diagnostic challenges and are suboptimally treated. We sought to determine whether type 1 and 2 diabetes polygenic scores (PS) would help improve classification of islet autoantibody-negative (IAb-) atypical diabetes cases. Methods: We implemented type 1 diabetes PS (T1D PS) and type 2 diabetes PS (T2D PS) in 309 IAb- individuals' genome sequencing from the Rare and Atypical Diabetes Network (RADIANT), the largest and most comprehensively phenotyped collection of unsolved and atypical diabetes cases. We performed regression analyses to assess associations between PS, clinical characteristics, and glycemic measures. Results: Both T1D and T2D PS were significantly higher in RADIANT than in ancestry-matched controls from UK Biobank. Both PS were associated with C-peptide measures throughout participant oral glucose tolerance tests (OGTT), although in opposite directions; T1D PS was associated with lower C-peptide measures, while T2D PS was associated with higher measures. Participants with T1D PS above a previously established optimal PS value for differentiating cases and controls (T1D PS GRS2>12.88) had 13-fold higher odds of both insulin deficiency on OGTT and use of both basal and bolus insulin therapy. Conclusions/Interpretation: Individuals in RADIANT with ambiguous diabetes subtypes displayed genetic enrichment for both type 1 and type 2 diabetes, despite ascertainment to remove standard type 1 and type 2 diabetes. T1D PS identified individuals with an unrecognized "type 1 diabetes-like" phenotype with insulin deficiency and need for intensive insulin in the absence of islet autoantibodies. PS may help identify individuals with atypical diabetes who will ultimately benefit from insulin therapy.

Insulin production is a cardinal feature of pancreatic {beta} cells. Studies in rodents show that {beta} cells can switch between low and high insulin gene activity states and that elevated insulin production makes {beta} cells more vulnerable to stresses associated with diabetes. In people, genetically elevated insulin production increases the risk of type 1 diabetes. Via effects on obesity, hyperinsulinemia contributes to the pathogenesis of type 2 diabetes. Here, we characterize {beta} cells in low and high INS gene activity states sorted from primary human islets transduced with INS-GFP adenovirus and differentiated INS-EGFP knock-in embryonic stem cells (SC{beta} cells). We profile {beta} cell function, protein synthesis, resilience to diabetes associated stress, single {beta} cell transcriptomes and their co-activity networks, and purified {beta} cell proteomes. We show that human {beta} cells transition between distinct states. High INS cells have elevated maturity marker mRNAs and proteins, increased protein translation, are larger, but also more susceptible to cell death when exposed to diabetes-relevant stresses. We also catalogue thousands of differences in proteins in high INS stem cell-derived {beta} cells compared directly with high INS primary {beta} cells. Our study improves our understanding of the delicate balance between insulin production and {beta} cell resilience and guides the engineering of better {beta} cells. Blurbtranscriptional, proteomic, and functional analyses of insulin gene expression states in human {beta} cells from donor islets and stem cells Key findingsO_LIWe identify high and low INS gene activity states in human insulin-producing cells from donor islets and embryonic stem cell differentiations. C_LIO_LIWe characterize the relationship between insulin production and fragility, demonstrating that increased insulin production comes at a cost of reduced resilience to multiple stresses. C_LIO_LIFunctional, transcriptomic, and proteomic analyses identify similarities and differences between how primary and stem cell-derived {beta} cells manage stress and insulin production. C_LIO_LIWe report a comprehensive side-by-side proteomic analysis of purified primary and stem cell- derived {beta} cells in the high INS state and identify differences in protein production and secretion machinery, providing a roadmap for making better {beta} cells. C_LI

Body mass index (BMI) alone may underestimate clinically relevant obesity because it does not capture central fat distribution. We compared obesity prevalence in Mexico using BMI-only criteria, adiposity-confirmed criteria, and the clinical obesity definition proposed by the Lancet Diabetes and Endocrinology Commission. We conducted a population-based, cross-sectional study of 13,160 adults aged 18 years or older who participated in the 2018-2019 Mexican National Health and Nutrition Survey (ENSANUT). Obesity prevalence was estimated through survey-weighted analyses that accounted for the complex sampling design. The weighted prevalence of obesity based on BMI was 34.5% (95% CI, 33.1-35.9), while 30.9% (95% CI, 29.6-32.2) met criteria for clinical obesity. One quarter of individuals with clinical obesity had a BMI under 30 kg/m2, a phenotype more common among older adults. Half of adults with a BMI under 30 kg/m2 showed elevated central adiposity. BMI alone underestimates clinically relevant obesity in Mexican adults. Adding waist-based measurements could improve the identification of individuals with excess fat and metabolic risk, both in clinical settings and population monitoring.

Aims/hypothesis Fasting plasma uridine concentrations are elevated in obese mice and in individuals with type 2 diabetes (T2D), suggesting that uridine may function as a metabolic signal that adjusts insulin secretion to changes in metabolic demand. Here, we tested this hypothesis by determining whether uridine potentiates glucose-stimulated insulin secretion (GSIS) in mouse and human islets and by identifying uridine phosphorylase 1 (UPP1), the principal enzyme responsible for systemic uridine catabolism, as a key mediator of this effect. Methods Whole-body Upp1 knockout (KO) and {beta}-cell-specific Upp1 knockout (KO{beta}) mice were used to determine the requirement for UPP1 in uridine-potentiated glucose-stimulated insulin secretion (GSIS) and glucose-stimulated MAPK activation. Leptin-deficient and diet-induced obese mouse models were used to assess the impact of obesity on uridine responsiveness. UPP1 protein abundance and subcellular localization were examined in islets from obese mice and human donors spanning a range of glycemic control. Integrated single-nucleus RNA sequencing and ATAC sequencing were performed on wild-type and Upp1 KO mouse islets to characterize {beta}-cell molecular remodeling associated with UPP1 deficiency and altered responses to uridine. Results Uridine potentiated GSIS in islets from chow-fed and high-fat diet-fed mice, but not in leptin-deficient obese mice. Uridine also potentiated GSIS in human islets, although this effect progressively declined with worsening glycemic control. In mouse islets, uridine potentiation was accompanied by transient activation of the MAPK pathway. Both uridine-potentiated GSIS and uridine-enhanced glucose-stimulated MAPK activation were abolished in islets from Upp1 KO and KO{beta} mice. The requirement for a transient MAPK signaling was further supported by pharmacological inhibition of MEK and constitutive activation of MEK1. Leptin-deficient islets exhibited impaired glucose-induced MAPK activation together with increased UPP1 protein expression. In human islets, UPP1 protein abundance positively correlated with donor HbA1c and displayed heterogeneous subcellular localization. Integrated single-nucleus multiomic analysis identified UPP1 as an important regulator of {beta}-cell identity, function, and transcriptional responses to uridine. Conclusions These findings establish UPP1 as a key regulator linking pyrimidine metabolism to {beta}-cell function and identify impaired uridine responsiveness as a potential contributor to and/or consequence of {beta}-cell dysfunction during the progression of T2D.

Acute glucose-stimulated beta-cell secretion is a key dimension of beta-cell function, but the hyperglycemic clamp used to assess it is technically demanding and resource-intensive, limiting its use at scale. We aimed to develop and validate the oral glucose tolerance test (OGTT) Early C-peptide (OEC) Index for estimating clamp-derived acute C-peptide response to glucose (ACPRg). We defined OEC as the 0-60-min incremental C-peptide area under the curve (AUC) normalized to the geometric mean of incremental and total glucose AUCs, with a fasting-glucose correction of 100/G0. OEC was evaluated in paired OGTT-clamp data from RISE Adult Medication (baseline n=257; internal validation) and BetaFat (baseline n=70; external validation). Predictive R^2 and Pearson r for log-ACPRg were assessed using participant-level 5-fold cross-validation in RISE and external validation without refitting in BetaFat, with the C-peptidogenic, insulinogenic, and CIR30 indices as comparators. In RISE Adult, cross-validated R^2 for OEC was 0.47, 0.61, and 0.54 at baseline, 12, and 15 months, respectively, with corresponding Pearson r of 0.69, 0.78, and 0.74; nested cross-validation showed only modest attenuation. Applied without refitting in BetaFat, OEC yielded R^2 of 0.55, 0.41, and 0.39 at baseline, 12, and 24 months, with corresponding r of 0.76, 0.70, and 0.64. OEC had higher predictive R^2 point estimates than all three comparators at every visit in both cohorts. OEC provides a simple, transparent OGTT-based estimate of acute beta-cell secretory capacity that retained predictive performance in BetaFat and may broaden access to physiological assessment of early beta-cell function.

Plasma proteomic scores for body mass index have been derived primarily in European populations, and it is unclear whether these scores are generalizable and useful in other ancestries. Here, we show that plasma proteomic BMI scores developed in participants of European, East Asian, South Asian and African ancestries from the UK Biobank (UKBB; N=50,621) and the South African Middle-Aged Soweto Cohort (MASC; N=948) are portable across ancestries, explain up to 48.7% of trait variance and significantly predict incident obesity. We identified eight protein biomarkers common across all scores, six of which showed causal associations with BMI in Mendelian randomization analyses and were associated with BMI across the Olink (UKBB, MASC) and SomaScan platforms (Qatar Biobank; N= 2410). Discrepancy analysis between the high predicted proteomic BMI and low measured BMI revealed metabolically unhealthy normal weight (MUNW) individuals, with higher visceral fat, elevated triglycerides, and low insulin sensitivity. Thus, plasma proteomic BMI scores may enhance the precision of cardiometabolic risk stratification across diverse populations