Diabetes

Pancreatic islets regulate blood glucose homeostasis. Although islet architecture is stable under homeostatic conditions, increased metabolic demand drives compensatory islet expansion. In mice, islets are organized as a {beta} cell core surrounded by a mantle of and {delta} cells. The formation of islet architecture during development requires expression of Roundabout receptors 1 and 2 (Robo1/2) in endocrine cells and of Slits 2 and 3 (Slit2/3) from islet-extrinsic sources. Furthermore, expression of Robo2 in endocrine cells is required to maintain islet architecture in the adult mouse. However, the cellular sources of Slit2/3 in the adult pancreas and their expression dynamics during islet expansion remain unknown. Here, we identify distinct stromal populations, including fibroblasts and pericytes, as well as neurons within intrapancreatic ganglia, as the sources of Slit2/3. We further show that Slit3 expression is increased in Ob/Ob mice, and that SLIT2 expression is elevated in stromal cell populations of humans with type 2 diabetes. The expression of neither Slit2 nor Slit3 was affected by deletion of Robo2 in {beta} cells. Together, these findings define the cellular origins of Slit2/3 and their expression dynamics in the adult pancreas, supporting a potential role for Slit signaling in the diabetic islet microenvironment.

PRV-101 is a multivalent formalin-inactivated Coxsackievirus B (CVB) vaccine developed to prevent CVB infections, which are associated with increased risk of islet autoimmunity. While PRV-101 induces robust neutralizing antibody responses, its T-cell immunogenicity is unknown. We analyzed peripheral blood mononuclear cells from 25 healthy adults receiving three high or low PRV-101 doses or placebo in a Phase I randomized, placebo-controlled trial. CVB-reactive CD8 T-cell responses were assessed using HLA Class I multimers, and CD4 and T follicular helper (Tfh) responses were measured by activation-induced marker assays following stimulation with a CVB peptide library. PRV-101 elicited minimal CVB-reactive CD8 T-cell responses but robust CD4 and Tfh responses, peaking at week 12 and persisting through week 32. Responses were observed in both seronegative and seropositive individuals, consistent with effective immune priming and boosting. Tfh frequencies correlated with neutralizing antibody titers. Female participants exhibited higher peak Tfh responses than males. We conclude that PRV-101 elicits a CVB-protective immune profile, dominated by Tfh responses supporting durable humoral immunity and devoid of potentially diabetogenic cytotoxic T-cell responses. This profile invites further investigations in vaccine trials for type 1 diabetes prevention.

Wolfram syndrome is a rare autosomal recessive disorder caused by pathogenic variants in the WFS1 gene, characterized by early-onset diabetes mellitus, optic atrophy, sensorineural hearing loss, arginine vasopressin deficiency, and progressive neurodegeneration. The condition selectively affects pancreatic {beta} cells and neurons via chronic endoplasmic reticulum (ER) stress, and no proven disease-modifying therapy currently exists. Diabetes mellitus is typically the first manifestation, presenting at a mean age of 6 years as an insulin-dependent phenotype with preserved C-peptide and negative diabetes-related autoantibodies. Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are well-established agents in the management of type 2 diabetes, augmenting glucose-dependent insulin secretion, suppressing glucagon, slowing gastric emptying, and promoting satiety. Preclinical evidence further suggests that GLP-1 RAs preserve {beta}-cell mass, attenuate ER stress, and confer neuroprotective effects, properties of particular therapeutic relevance to Wolfram syndrome. We conducted a retrospective cohort study of 84 participants with genetically confirmed Wolfram syndrome and insulin-dependent diabetes mellitus enrolled in the Washington University Wolfram Syndrome International Registry and Clinical Study. Clinical data were extracted from medical records; for participants concurrently enrolled in the Tracking Neurodegeneration in Early Wolfram Syndrome study, longitudinal data were obtained from that source as well. Thirty-five percent of eligible participants had received a GLP-1 RA at some point during follow-up. We characterize the prevalence of GLP-1 RA use, documented rationale for initiation, observed effects on glycemic control and visual outcomes, adverse effects, and reasons for discontinuation. No statistically significant changes in hemoglobin A1c (HbA1c) or body mass index (BMI) were observed. Visual acuity declined significantly at two years, consistent with expected disease progression. Gastrointestinal adverse effects were common and contributed to frequent discontinuation. These observational data provide important clinical context and a foundation for future prospective trials evaluating GLP-1 RAs as a potential disease-modifying strategy in Wolfram syndrome.

Metformin has been linked to mortality benefits in type 2 diabetes that may extend beyond glycemic control, but population-level evidence connecting these benefits to inflammation-related pathways remains limited. Using NHANES 2013-2018 data with mortality follow-up through 2019, we examined associations between metformin use and four inflammatory markers, including neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), serum albumin, and high-sensitivity C-reactive protein (hs-CRP), and evaluated their relevance to all-cause and cardiovascular mortality. Among 2,122 adults with self-reported diabetes (60% metformin users; 2,116 with valid mortality follow-up), survey-weighted linear regression adjusted for demographic, socioeconomic, and metabolic covariates showed metformin use was associated with lower NLR ({beta} = - 0.35; 95% CI -0.57, -0.14), lower MLR ({beta} = -0.04; 95% CI -0.06, -0.02), and higher serum albumin ({beta} = +0.11 g/dL; 95% CI 0.06, 0.16); the hs-CRP association was directionally consistent but not significant. Associations for NLR and MLR were essentially unchanged after BMI and HbA1c adjustment, remained robust in an active comparator analysis against sulfonylurea monotherapy, and were consistent across propensity score and overlap weighting sensitivity analyses. Survey-weighted Cox regression linked metformin to lower all-cause (HR 0.64; 95% CI 0.48, 0.86) and cardiovascular mortality (HR 0.49; 95% CI 0.26, 0.94). NLR was independently associated with all-cause mortality, with the highest tertile carrying nearly twice the hazard of the lowest, and inclusion of NLR or MLR modestly attenuated the metformin-mortality association. Metformin use is associated with a distinct cellular immune-inflammation profile in adults with type 2 diabetes, supporting further investigation of non-glycemic pathways relevant to its long-recognized clinical benefits.

Individuals with Down syndrome (trisomy of human chromosome 21) are at a significantly higher risk of developing type 2 diabetes (T2D) than the general population. Systemic metabolic defects in Down syndrome have been linked to gene expression dysregulation in peripheral tissues like the liver, muscle, brain, and adipose. However, the contribution of gene expression dysregulation in the islets of Langerhans to the increased risk of T2D in Down syndrome has not been explored. Here we show that trisomic Ts65Dn mice, a common Down syndrome mouse model, are glucose intolerant and display reduced {beta}-to- cell ratio compared to disomic controls. Using single cell RNA sequencing on islets from Ts65Dn mice we found genome-wide, cell type-specific, and sex-specific transcriptional dysregulation in trisomic islets compared to controls. The Down syndrome-associated transcriptional signature revealed important islet defects, both at the cell autonomous level and at the whole-islet level, increasing T2D susceptibility. Our results put forth innate islet defects as a central underlying cause of Down syndrome-related T2D, warranting additional studies.

Many genetic variants associated with increased type 1 diabetes (T1D) risk are located within the SKAP2 gene; however, the mechanisms by which these variants confer disease risk remain unclear. SKAP2 encodes an adapter protein that functions within the integrin signaling pathway and is found at the highest levels in myeloid leukocytes. We recently identified a de novo gain-of-function SKAP2 mutation in an individual with T1D, leading to hyperactive integrin signaling in myeloid cells. To dissect the mechanisms by which this mutation may lead to T1D, we generated a knock-in mouse line containing the orthologous p.G153R substitution in mouse SKAP2 on the diabetes-prone nonobese diabetic (NOD) genetic background. Both female and male SKAP2G153R/G153R mice developed accelerated T1D. The SKAP2G153R/G153R mice also exhibited a unique spectrum of autoantibodies, leading to immune-complex nephritis. Accelerated infiltration of pancreatic islets by myeloid cells, B lymphocytes, and activated T cells was observed in SKAP2G153R/G153R mice. Single-cell RNA sequencing demonstrated a type 1 IFN{gamma}-driven inflammatory program within the pancreatic islets of SKAP2G153R/G153R mice. Dendritic cells from SKAP2G153R/G153R mice demonstrated increased antigen-presenting capacity, characterized by enhanced adhesion to T cells during immune synapse formation. Macrophages and neutrophils from SKAP2G153R/G153R mice also showed increased integrin signaling responses, with neutrophils expressing high levels of activated {beta}2 integrins on the cell surface. When backcrossed onto the C57BL/6J genetic background, the SKAP2G153R/G153R mice developed spontaneous autoantibody formation and exhibited accelerated autoimmunity, including nephritis, in the pristane-induced model of autoimmune disease. These findings demonstrate that dysregulation of leukocyte integrin signaling, through alterations in SKAP2, may increase the genetic risk for autoimmunity and T1D.

Type 1 diabetes (T1D) is characterized by the autoimmune destruction of pancreatic beta cells. While most beta cells are lost, a subset of beta cells persists years and even decades after disease onset. Studying these surviving cells is challenging, and thus how they escape immune killing remains poorly understood. Here, we applied a gene regulatory network inference-based clustering approach on existing islet scRNAseq data from cadaveric donors with T1D, autoantibody positive donors at risk for T1D, and non-diabetic donors to analyze beta cells from patients with established T1D. This approach identified a novel beta cell subtype enriched in T1D donors defined by the activity of several transcription factors which have well-characterized roles in beta cell survival, most notably IRF1. We found increased expression of immunomodulatory genes (e.g. SOCS1/3, HLA-E) as well as decreased expression of autoantigens and secretory genes, suggesting dedifferentiation. We identified inflammatory cytokines as a driver of this phenotype by reanalyzing public data from primary human beta cells stimulated with inflammatory cytokines in vitro. We additionally find a similar transcriptional program active in a subset of alpha cells, consistent with cell-extrinsic inflammatory cytokine signaling in vivo. Overall, we propose that this population represents a resilient beta cell phenotype, and that the transcriptional program active in these cells may identify targets for T1D prevention and reversal.

Obesity affects one in three adults and is complicated by adipose inflammation, lipotoxicity and cell death. We previously identified RIPK1 as a genetic determinant of human obesity risk and adipose inflammation. Because RIPK1 is the apical kinase in the necroptosis pathway upstream of RIPK3 and the executioner protein MLKL, and emerging evidence links MLKL to lipid metabolism, MLKL has surfaced as a potential metabolic regulator. However, conflicting findings in Mlkl knockout mice fed a high fat diet have left its therapeutic relevance unresolved. MLKL has not been previously targeted through therapeutic knockdown in vivo in the context of diet-induced obesity. Here, we evaluated two independent MLKL antisense oligonucleotides (ASOs) in high fat diet (HFD)-fed C57BL/6J mice. In a 24-week progression model, MLKL ASO markedly reduced body weight, fat mass and hepatic steatosis compared with controls, while preserving lean mass. MLKL knockdown also lowered the respiratory exchange ratio, indicating a shift toward increased fat oxidation. In the intervention model, once obesity was established after 12 weeks of HFD feeding, both MLKL ASOs, and similarly, two independent RIPK1 ASOs, reversed weight gain and improved systemic glucose control. In vitro, MLKL-CRISPR/Cas9 knockout blocked 3T3-L1 adipogenesis, indicating a requirement for MLKL during adipocyte differentiation. However, in mature adipocytes, MLKL siRNA reduced palmitic acid-induced lipid accumulation, increased isoprenaline-stimulated lipolysis, and prevented TNF-mediated suppression of insulin-mediated AKT signalling and glucose uptake. Collectively, these findings demonstrate that partial MLKL suppression reprograms whole-body energy metabolism, enhances insulin sensitivity and limits diet-induced adiposity. MLKL, therefore, represents a promising and mechanistically novel therapeutic target for obesity and insulin resistance.

BackgroundThe glucagon-like peptide-1 receptor (GLP1R) is a key regulator of glucose metabolism and appetite and a major therapeutic target for type 2 diabetes (T2D) and obesity. Genetic studies have implicated the GLP1R locus in both body mass index (BMI) and T2D, but it remains unclear whether their underlying genetic associations are the same. MethodsWe analyzed 431,107 participants of genetically inferred European ancestry from the Million Veteran Program. Within {+/-} 500 kb of GLP1R, we performed locus-wide linear regression models for BMI and logistic regression models for T2D, adjusted for age, sex, and 10 principal components. We identified primary and secondary BMI sentinel variants using conditional analyses and evaluated their associations with T2D. Bayesian fine-mapping was used to construct credible sets of GLP1R locus for BMI and T2D. ResultsConditioning on the primary sentinel variant rs12213929 (upstream of GLP1R, {beta} = 0.11; 95% CI 0.09-0.14; p = 1.94x10-17), we identified a secondary variant (rs13216992, intron of GLP1R) independently associated with BMI ({beta} = 0.10; 95% CI 0.07-0.13; p = 7.88x10-14). The two sentinel variants showed low linkage disequilibrium (r2 = 0.03). A two-variant allelic burden score (0-4; sum of the rs12213929 G-allele count and rs13216992 C-allele count) showed that participants with 4 risk alleles had 0.47 kg/m2 higher BMI than those with 0 risk alleles (95% CI 0.39-0.55; p < 2x10-16). Both variants were associated with higher T2D risk, but with distinct patterns after BMI adjustment: the rs12213929-T2D association persisted after adjustment for BMI (OR = 1.02; 95% CI 1.01-1.03; p = 0.0004), whereas the rs13216992-T2D association was fully attenuated (OR = 1.00; 95% CI 0.99-1.01; p = 0.68). Fine-mapping identified a compact 95% BMI credible set of 17 variants and a broader 95% T2D credible set of 42 variants, with all BMI credible variants contained within the T2D set. ConclusionsThe GLP1R locus harbors at least two independent BMI-associated variants that exhibit heterogeneous relationships with T2D: rs12213929 influences T2D risk partly through BMI-independent pathways, whereas rs13216992 appears to act predominantly via adiposity. These findings refine the genetic architecture at this key therapeutic target gene and provide a foundation for functional and pharmacogenomic studies to determine whether GLP1R variation can inform precision prevention and treatment of obesity and T2D.

Exercise is a cornerstone therapy for diabetes because working skeletal muscles take up glucose at dramatically greater rates than postprandial insulin-stimulated glucose uptake and, notably, do so without a requirement for insulin. This remarkable ability of working muscles is preserved in diabetes, when muscles become resistant to insulin. However, the mechanism of insulin-independent glucose uptake by working muscles is not fully understood. Here we describe a previously unrecognized glucose uptake pathway in muscle, which we refer to as "mSGLT" based on shared properties with the Sodium Glucose Linked Transporter family. In contrast to the abundant GLUT4 transporter, mSGLT is not regulated by insulin, requires Na,K-ATPase-2 activity, and transports the hexose -methyl-D-glucoside (MDG), a glucose derivative that is handled by SGLTs but not GLUT4. The mSGLT pathway and GLUT transport pathways are independent and additive. In addition to exercise, mSGLT imports glucose under other conditions of adrenergic stimulation, which inhibits pancreatic insulin release and reduces the insulin sensitivity of muscle. SGLT2-specific antibodies recognize a protein in muscle of similar size to the kidney SGLT2; this protein localizes to the muscle t-tubules, together with Na,K-ATPase-2 and MAP17, the regulatory subunit of SGLT2. However, skeletal muscles do not express a full-length transcript of Slc5a2 (SGLT2), and SGLT2-specific inhibitors do not inhibit mSGLT with high affinity. The novel transporter may be a muscle variant of Slc5a2 that results from post-transcriptional or post-translational mechanisms. mSGLT and its regulation offer potential muscle-specific therapeutic targets for treating hyperglycemia and other conditions when insulin-stimulated glucose disposal into muscle is impaired.

Obesity is a chronic inflammatory disease associated with immune dysregulation. However, alterations in adaptive immune function remain unclear, particularly in the setting of childhood obesity and weight loss. We defined peripheral T cell dysregulation in a cross-sectional cohort of pediatric participants across weight categories and in a longitudinal cohort of adolescents with severe obesity undergoing bariatric surgery. We found increased expression of activation markers (including PD-1 and CD69) in non-naive CD8+ T cells whereas non-naive CD4+ T cells were skewed towards Tfh, Th17, and mixed Th2/Th17 populations. Consistent with a hyperactive state, T cells had enhanced capacity for inflammatory cytokine production (including IFN-{gamma} and TNF-), along with enrichment of gene sets associated with cytokine signaling, cell proliferation, and cell death. Notably, these phenotypic, functional, and transcriptional alterations were not fully resolved after bariatric surgery, despite clinically meaningful weight loss. Together, these findings demonstrate that pediatric obesity leads to dysregulation of adaptive immune function with incomplete normalization after weight loss. SUMMARYThe impact of pediatric obesity on immune cell function is not well understood. This study demonstrates that both CD4+ and CD8+ T cells are dysregulated in children living with obesity and further identifies that this dysregulated state persists following clinically significant weight loss.

Effector CD8+ T cells are key cellular drivers of type 1 diabetes (T1D) pathogenesis, yet questions remain regarding the molecular defects leading to altered cytotoxicity, their signature in peripheral tissues, and their receptor specificity. Thus, we analyzed human pancreatic lymph nodes (pLN) using mass cytometry and single cell RNA sequencing (scRNAseq) with combined proteomic and T cell receptor (TCR) profiling. Cytometric analysis revealed an enriched population of T stem-cell memory (TSCM)-like cells (CD8+CD45RA+CD27+CD28+CCR7+CXCR3+ T cells) in T1D pLNs. scRNAseq profiling indicated an elevated inflammatory cytokine gene signature (IFITM3, LTB) along with regulators of terminal differentiation (BCL6, BCL3), coupled with reduced expression of exhaustion-associated genes (DUSP2, NR4A2, TSC22D3) in CD8+ T cells in T1D pLN. Additionally, effector CD8+ T cells expressed features of progenitor exhausted cells (BCL2) in T1D pLN. Immune Response Enrichment Analysis (IREA) indicated IL-15 signaling as a significant driver of these phenotypes. Integrated TCR and transcriptomic analysis revealed a cluster of diverse naive-like CD8+ T cell clones in T1D pLN. When comparing pLN and pancreatic slice cellular isolates, we observed sharing of effector CD8+ T cells, with upregulation of terminal effector signatures detected within the pancreas relative to paired pLN samples. Multiplex imaging revealed differential localization of TCF1 and TOX expressing T cells in the pancreas, with TCF1+TOX+ cells located in closer proximity to the islets and displaying a mixture of activation and exhaustion-associated phenotypes. Thus, we provide multimodal cellular profiles enriched in T1D tissues for consideration in therapeutic targeting.

BackgroundObesity arises from a complex interplay of genetic and environmental factors, with alterations of transcriptional networks that integrate metabolic, immune, and regulatory pathways. Conventional measures such as body mass index (BMI) quantify body size but fail to capture the molecular heterogeneity underlying divergent metabolic outcomes. We therefore sought to construct a gene expression-based transcriptomic representation of obesity, using BMI as a practical training anchor, and to use this framework to delineate transcriptional programs associated with metabolically healthy and pathogenic obesity, with subsequent projection to mouse transcriptomic data for cross-species validation. MethodsTranscriptome data of human visceral adipose tissue (N= 1,298) were used to derive the transcriptomic BMI model, and genes contributing to the model were functionally annotated by gene set enrichment analysis. The human-trained model was subsequently applied to mouse selection lines (N = 18) with divergent obesity phenotypes. In the human cohort, post hoc stratification into metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO) groups was performed using a downstream classification framework incorporating observed BMI together with predicted BMI, to assess whether model-derived predicted BMI reflected obesity-related pathophysiologic status. ResultsModel-selected genes were involved in coordinated regulation of lipid metabolism, immune activation, and growth signaling, extending to mitochondrial and translational pathways. Cross-species analyses uncovered conserved metabolic polarization: DU6 mice exhibited lipid-anabolic and inflammatory remodeling, whereas DU6P mice displayed oxidative, mitochondrial, and GH-axis-enriched transcriptional states. In human cohorts, MHO individuals showed upregulation of mitochondrial energetics and protein synthesis, while MUO individuals were characterized by increased autophagy, lipid catabolism, and stress-adaptive signaling on the transcriptional level. Together, these findings define a conserved molecular continuum linking oxidative efficiency to metabolic health and inflammation to metabolic vulnerability. ConclusionsThis integrative transcriptomic framework bridges human and mouse adipose biology to uncover conserved mechanisms underlying obesity phenotypes. By contrasting mitochondrial and translational programs with inflammatory and catabolic pathways, it provides mechanistic insight into metabolic resilience and a foundation for precision approaches to obesity management.

Variants in the human PAX4 gene are associated with both monogenic and complex forms of diabetes, yet their pathogenic effects remain difficult to define in models that accurately mimic human islet architecture and neonatal metabolic transitions. Here, we created a porcine PAX4 loss-of-function model using CRISPR/Cas9 cytidine deaminase base editing to introduce a premature stop codon in the PAX4 coding sequence. PAX4 knockout piglets developed severe hyperglycemia within 24 hours of birth, followed by rapid postnatal clinical deterioration and uniform death by day 3. Biochemical analysis showed significant diabetic decompensation, including electrolyte imbalances, hyperosmolality, azotemia, dyslipidemia, and metabolic acidosis. Gross and histological examinations revealed notable pancreatic hypoplasia with preservation of exocrine tissue. Single-nucleus RNA sequencing and immunohistochemistry demonstrated an almost complete loss of insulin-and somatostatin-producing {beta}-and {delta}-cells, respectively, with relative preservation of glucagon-expressing -cells. Overall, these results establish PAX4 as a crucial factor in pancreatic endocrine development and postnatal glucose regulation in a large-animal model. This platform offers a human-relevant system for studying diabetes-associated PAX4 variants and for testing regenerative and gene-based therapies for insulin-deficient diabetes.

Background Glycated haemoglobin (HbA1c) underpins type 2 diabetes (T2D) and prediabetes management worldwide and reflects both glycaemia and erythrocyte biology. A missense variant in PIEZO1 (rs563555492T), carried by 1 in 12 South Asians, has been associated with a nonglycaemic reduction in HbA1c. We aimed to further characterise this association and evaluate its clinical consequences. Methods We undertook genetic and linked health data analyses across two cohorts: 19,898 (37.4% female) South Indians from the Madras Diabetes Research Foundation (MDRF) and 43,011 (54.4% female) British Bangladeshis and British Pakistanis in Genes & Health. In MDRF, we tested associations with glycaemic and erythrocytic traits using additive genetic models. In Genes & Health we modelled diagnosis of prediabetes, T2D, and diabetic eye disease using flexible parametric survival models. Ten-year absolute risks were estimated for a population aged 40-50 years. Findings PIEZO1 rs563555492T was associated with erythrocytic traits and lower HbA1c, but not with fasting glucose, postprandial glucose, or C-peptide. This variant reduced risk of prediabetes (HR 0.63, 95% CI 0.58-0.69) and T2D (0.85, 0.78-0.93) diagnosis, and increased risk of diabetic eye disease among individuals with T2D (1.20, 1.01-1.43). Modelling suggested approximately 1,019 missed prediabetes and 303 missed T2D diagnoses per 100,000 adults over 10 years. Interpretation An ancestry-enriched PIEZO1 variant is associated with lower HbA1c independent of glycaemia, reduced prediabetes and T2D diagnosis suggesting delayed detection, and increased complication risk. Reliance on HbA1c may systematically underestimate glycaemic risk in a substantial minority of South Asians. Funding The Wellcome Trust; NIHR

White adipose tissue and pancreatic islets play central roles in the regulation of metabolic homeostasis. Although ectopic lipid accumulation is established as a driver of impaired insulin secretion, the acute contribution of adipocyte lipolysis to islet function remains poorly documented. Here, we investigated a mouse model with inducible adipocyte-specific deletion of both adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL), which leads to defective adipocyte lipolysis. Despite preserved ex vivo islet function, these mice displayed a marked reduction in insulin secretion in response to stimulation of adipocyte {beta}3-adrenoceptors, as well as following glucose and arginine challenges. Mechanistically, we identified non-esterified fatty acids as critical mediators of lipolysis-driven insulin secretion, engaging pancreatic signaling of the free fatty acid receptors FFAR4 (a.k.a. GPR120) and FFAR1 (a.k.a. GPR40). The regulation of insulin secretion by adipocyte lipolysis was preserved in high-fat diet-induced obesity. These findings identify an underappreciated adipose-islet crosstalk that couples adipocyte lipolysis to insulin secretion and links lipid and glucose metabolism.

Background. Type 2 diabetes mellitus (T2D) is defined by progressive pancreatic {beta}-cell dysfunction whose molecular underpinnings remain incompletely understood. Single-cohort transcriptomic analyses of donor islets have yielded heterogeneous gene lists of limited cross-study reproducibility, constraining both mechanistic interpretation and biomarker development. Methods. We combined two complementary analytical strategies applied to four public human islet transcriptomic cohorts (GSE25724, GSE20966, GSE38642, and GSE164416; n = 7-57 donors per contrast). For the integrative arm, three microarray datasets and one bulk RNA-seq dataset were processed independently and unified through gene-level random-effects meta-analysis, hallmark pathway scoring (GSVA/MSigDB), and iterative module refinement, yielding a two-axis disease framework. For the diagnostic arm, a consensus multi-method machine learning pipeline, combining LASSO penalized logistic regression, Support Vector Machine Recursive Feature Elimination (SVM-RFE), and Random Forest importance scoring, was applied to 184 differentially expressed genes from the RNA-seq cohort, with all normalization steps performed within leave-one-out cross-validation (LOOCV) folds to prevent data leakage. Machine learning classification of the RNA-seq cohort was additionally subjected to external transportability testing in the independent bulk human islet RNA-seq cohort GSE50244 using an overlap-restricted reduced score and a threshold fixed in the discovery cohort. Results. Meta-analysis across all four cohorts identified 337 high-confidence T2D-associated genes (96.1% directional concordance in beta-cell-enriched tissue). These were distilled into two refined 14-gene modules: ImmuneStress (MICB, HLA-DRA, HLA-DPA1, IL1R2, and others) and BetaCellIdentitySecretion (RASGRP1, PPP1R1A, SLC2A2, and others), whose composite IsletDysfunctionScore provided the most stable cross-platform separation of non-diabetic from T2D islets (Hedges' g = 1.80, p = 9.83 x $10^-17$, $\text{I}^2$= 0%). Consistent with progressive disease, IsletDysfunctionScore increased monotonically from non-diabetic to impaired glucose tolerance to T2D. Separately, the machine learning pipeline derived a 10-gene diagnostic panel: GABRA2, SLC2A2, ARG2, DKK3, PRIMA1, TAFA4, HHATL, PARVG, RNU1-70P, and the novel lncRNA ENSG00000284653, that achieved perfect discrimination in LOOCV (AUC = 1.000, sensitivity = 1.000, specificity = 1.000, zero misclassifications across all 57 donors). A leakage-verification experiment confirmed that this performance reflected genuine biological signal: global quantile normalization prior to cross-validation collapsed AUC to 0.380. External testing showed that 8 of the 10 panel genes were measurable in GSE50244. The frozen 8-gene reduced score retained strong discrimination (external AUC = 0.907), with 6 of 8 genes preserving directional concordance, but the discovery-derived threshold did not transfer because the external score distribution was shifted upward and compressed, yielding complete sensitivity but zero specificity at the frozen cutoff Conclusions. Integrating pathway-level meta-analysis with machine learning classification, we present a coherent two-axis model: immune/stress activation and loss of beta-cell identity/secretory competence, together with a compact, biologically interpretable 10-gene diagnostic signature. Panel genes converge on GABA signaling, glucose transport, arginine metabolism, WNT pathway inhibition, and a novel lncRNA, providing both mechanistic hypotheses and high-priority targets for external validation. These findings offer a reproducible transcriptomic scaffold for future mechanistic, biomarker, and clinical translation studies of human islet dysfunction. They also support external transportability of the core biological signal, while indicating that absolute operating thresholds are cohort-dependent and would require recalibration before deployment in independent datasets.

The establishment of mixed hematopoietic chimerism is a promising way to induce immune tolerance for islet replacement therapy and to treat the underlying autoimmunity in Type 1 diabetes (T1D). Mixed chimerism not only promotes effective thymic negative selection of autoreactive cells but also restores regulatory T cell (Treg) function and peripheral tolerance. In the current study, we determined that a novel class of donor-derived CD8+CD44+CD122+ Tregs (d-CD8+CD122+ Tregs) plays a crucial role in controlling autoimmunity in non-obese diabetic (NOD) mice with induced mixed chimerism. Using adoptive T cell transfer experiments, we showed that d-CD8+CD122+ Tregs abrogate autoimmunity by selectively depleting the exogenously injected diabetogenic T cells in Recombination-Activating Gene deficient NOD mice. These d-CD8+CD122+ Tregs from NOD chimeras show upregulation of Helios, Programmed cell death protein 1, perforin, granzyme-B, CD39, Folate receptor 4, and downregulation of proinflammatory markers like Scart1 and Scart2. Using in vitro assays, we show that d-CD8+CD122+ Tregs respond specifically to a Complementarity-Determining Region-3 peptide sequence derived from T cell receptors of islet antigen-specific autoreactive T cells. Thus, mixed chimerism might be a method to revitalize CD8+CD122+ Tregs which are decreased in number and functionality in NOD mice. Similarly, we found that individuals with T1D have a deficiency in CD8+CD122+ Tregs, suggesting a potential loss of regulatory function accompanies disease onset. Revitalizing CD8+CD122+ Tregs may offer a new therapeutic strategy of restoring immune tolerance in autoimmune diabetes. One sentence summary Inducing mixed donor chimerism in NOD mice generates donor-derived CD8+CD122+ Tregs that suppress autoimmunity and restore immune tolerance by selectively eliminating autoreactive T cells.

Background: Genetic variants impacting red blood cell biology disrupt the relationship between glycaemia and glycated haemoglobin (HbA1c), with implications for diagnosis and management of type 2 diabetes (T2D). Thalassaemia trait is estimated to affect 350 million people globally, but its impact on T2D and related outcomes is not clear. Methods: We explored associations between thalassaemia trait, HbA1c, and T2D diagnosis and complications in 43,088 British Bangladeshi and Pakistani participants in the Genes & Health study with linked multisource England National Health Service (NHS) electronic health record data and whole exome sequencing. Findings: 2,490 participants (5.8%) were heterozygous carriers of ClinVar pathogenic / likely pathogenic thalassaemia variants, however 3 in 4 of these were not diagnosed with thalassaemia in their NHS health records. rs33950507, a common variant causal for HbE thalassaemia, was associated with increased HbA1c (beta=0.13, 95%CI:0.08-0.18, p=7.8x10-8), but not glucose levels (beta=0.01, 95%CI:-0.04-0.06, P=0.72). rs33950507 was associated with increased hazards of prediabetes (HR=1.38, 95%CI:1.26-1.52, p=2.2x10-6) and T2D (HR=1.11, 95%CI:1.01-1.22, p=0.03), and reduced hazards of diabetic eye disease (HR=0.74, 95%CI:0.56-0.96, p=0.02) and cerebrovascular disease (HR=0.44, 95%CI:0.20-0.94, p=0.03). Sensitivity analyses suggested mediation by overdiagnosis and overtreatment of T2D. Interpretation: Alternatives to HbA1c, and/or precision medicine approaches to defining and managing hyperglycaemia, are needed, particularly on a global scale. This may be particularly relevant to individuals from ancestral groups among whom erythrocytic traits are more common but often undiagnosed. Funding: Wellcome Trust, MRC, NIHR, Barts Charity, Genes & Health Industry Consortium

BackgroundVertical sleeve gastrectomy (VSG) improves glycaemic control in type 2 diabetes (T2D) through mechanisms that extend beyond weight loss. The interaction between glucocorticoid metabolism and inflammation in this context remains unclear. MethodsWe investigated the role of 11{beta}-hydroxysteroid dehydrogenase type 1 (11{beta}HSD1) in mediating the metabolic effects of VSG in humans and mice. Subcutaneous adipose tissue biopsies were collected before and 6 months after VSG. Parallel studies were conducted in lean and high-fat diet-fed mice undergoing VSG or sham surgery, alongside 11{beta}HSD1 knockout models. Glucose tolerance and expression of 11{beta}HSD1 and interleukin-6 (IL6) were assessed. Mechanistic interactions were examined in IL6-treated human hepatocytes. ResultsVSG reduced 11{beta}HSD1 and IL6 expression in human adipose tissue and improved insulin resistance. In lean mice, VSG improved glucose tolerance and downregulated both markers independently of weight loss. 11{beta}HSD1 knockout mice exhibited improved glucose tolerance despite increased adiposity, partially recapitulating the VSG phenotype. Both interventions reduced circulating and tissue IL6 levels. IL6 stimulation increased HSD11B1 expression in hepatocytes. Conclusions11{beta}HSD1 links glucocorticoid metabolism, inflammation, and glucose homeostasis following VSG. Targeting this pathway may offer a strategy to replicate key metabolic benefits of metabolic bariatric surgery.