Type 1 diabetes (T1D) is an autoimmune disease characterized by β-cell destruction promoted by autoreactive T cells. Eukaryotic translation initiation factor 4E (eIF4E)–binding protein 1 (4E-BP1) and 4E-BP2 are translational repressors and downstream targets of mammalian target of rapamycin complex 1 (mTORC1). Activation of the 4E-BP2/eIF4E pathway by 4E-BP2 deletion promotes translation initiation, inducing β-cell expansion and proliferation and regulating adaptive immunity. However, the involvement of 4E-BP2 in T1D remains unexplored. This study aimed to determine the role of 4E-BP2/eIF4E signaling in T1D prevention. We used the NOD mouse model of T1D and generated mice with global 4E-BP2 deletion in the NOD background (Eif4ebp2−/−). We assessed T1D development, glucose homeostasis, pancreas morphometry, and immune responses in Eif4ebp2−/− and littermate control mice. We found that Eif4ebp2−/− male mice exhibited reduced diabetes incidence, which did not occur in female mice, as well as preserved β-cell mass, improved insulin secretion in vitro, and comparable insulitis. Characterization of T-cell compartments showed decreased splenic CD8+ cytotoxic T-cell proliferation and increased pancreatic regulatory T-cell infiltration in Eif4ebp2−/− mice, potentially resulting from increased proliferation and suppressive capacity. Adoptive transfer studies demonstrated that Eif4ebp2−/− male lymphocytes were less diabetogenic than those of controls. In conclusion, activation of 4E-BP2/eIF4E by 4E-BP2 deletion protected against T1D, supporting 4E-BP2 as a potential therapy target.

Obstructive sleep apnea (OSA) is a common condition strongly linked to increased cardiovascular risk and poor glycemic control. Little is known about OSA, cardiovascular risk, and glycemia in maturity-onset diabetes of the young (MODY), an inherited form of diabetes, which is different than both type 1 and type 2 diabetes. We assessed OSA, resting heart rate (RHR), an important prognostic marker of cardiovascular disease, and glycemic variability among the most common subtypes of MODY, glucokinase (GCK)-MODY, and transcription factor (TF)-related MODY (HNF1A, HNF4A, and HNF1B). Adults with GCK-MODY (n = 63) and TF-related MODY (n = 60) and control adults without diabetes (n = 65) were screened for OSA by home sleep test. Glycemic variability (continuous glucose monitoring) and RHR (wearable sleep-activity tracker) were concomitantly assessed for 2 weeks at home. Data from 188 individuals (2,853 recorded days) were analyzed. Individuals with TF-related MODY, compared with those with GCK-MODY or control individuals, had more OSA (48.3%, 27.0%, and 30.8%, respectively; P = 0.033), higher RHR (72.8 ± 10.8, 65.2 ± 7.9, and 67.3 ± 7.7 bpm, respectively; P < 0.001), and higher glycemic variability (coefficient of variation of glucose 31.6 ± 6.0%, 17.3 ± 4.5%, and 17.5 ± 4.0%, respectively; P < 0.001). Greater severity of OSA and higher RHR were associated with higher glycemic variability. These findings may have important clinical implications for cardiovascular risk assessment in MODY.

Type 1 diabetes is a progressive autoimmune disease characterized by the selective destruction of insulin-producing β-cells by CD8+ T cells. Although the mechanisms of antigen-specific β-cell killing are well established, the broader consequences of this targeted destruction on neighboring β-cells that escape direct T-cell receptor (TCR)-mediated attack remain poorly understood. Here, we developed a coculture model of HLA-A2-expressing human β-cells cultured as pseudoislets and CD8+ T cells specific for the INS15-24 epitope. Using this new in vitro model, we demonstrate that 1) β-cell death induced by CD8+ T cells strictly depends on TCR-HLA class I interactions and 2) neighboring β-cells that evade direct T-cell contact do not alter β-cell identity or glucose-stimulated insulin secretion. However, they exhibit increased expression of inflammatory markers, reduced insulin content, and impaired protein translation. The robust, versatile, and readily applicable model described here represents a strong basis to further address paracrine signaling that extend beyond direct cytotoxicity.

miRNAs are key regulators of metabolic homeostasis, yet their role in obesity-associated dysfunction remains incompletely understood. Here, we identify miR-432 as a driver of systemic metabolic dysregulation. Serum miRNA profiling revealed a positive correlation between miR-432 expression and obesity/type 2 diabetes mellitus. Functionally, adipose-specific miR-432 exacerbated high-fat diet-induced obesity and insulin resistance. Similarly, hepatic-specific miR-432 aggravated hepatic steatosis and systemic glucose dysregulation, while skeletal muscle-specific miR-432 disrupted glucose homeostasis without affecting body composition. Mechanistically, miR-432 disrupted insulin sensitivity by inhibiting the PIK3R3/AKT pathway and perturbed lipid homeostasis by suppressing the PIK3R3/PPAR-α axis. Notably, obesity-induced miR-432 upregulation was predominantly localized in adipocytes and driven by the CDK5/PPAR-γ axis. Furthermore, adipocyte-derived exosomal miR-432 was identified as a mediator of systemic metabolic dysfunction, facilitating intertissue cross talk in obesity. Collectively, our data demonstrate that miR-432 exacerbates obesity-induced dysregulation of glucose and lipid metabolism.

Diabetic cardiomyopathy (DbCM) is characterized by metabolic remodeling and energetic stress independent of coronary artery disease. Increased reliance on fatty acid and ketone body metabolism has been observed in DbCM, but the regulatory mechanisms linking altered substrate use to myocardial dysfunction remain poorly understood. In particular, lysine β-hydroxybutyrate (Kbhb), a ketone body-derived, posttranslational modification, has emerged as a potentially critical regulator but has not been fully investigated. We conducted a comprehensive multiomics study integrating metabolomics, transcriptomics, proteomics, and Kbhb-specific proteomics on myocardial tissues in a well-established mouse model of DbCM. Kbhb-modified proteins were systematically mapped and quantified, followed by motif, subcellular localization, and protein-protein interaction analyses. DbCM cardiac tissue exhibited coordinated upregulations of fatty acid β-oxidation, ketone metabolism, and tricarboxylic acid cycle activity at the transcriptomic, proteomic, and metabolomic levels. Kbhb profiling revealed extensive mitochondrial protein modification, with Atp5f1a-K239 identified as a key modification site strongly correlated with β-hydroxybutyrate and isocitric acid concentrations. This study identifies Kbhb as a potential metabolic-epigenetic modifier linking ketone body availability to the regulation of mitochondrial proteins in DbCM. Our findings provide novel insights into metabolic-epigenetic cross talk and identify potential therapeutic targets for interventions to restore mitochondrial function in alleviating diabetic heart disease.

Glucokinase (GK) catalyzes the key regulatory step in glucose-stimulated insulin secretion (GSIS). Correspondingly, hetero- and homozygous mutations in human GCK cause maturity-onset diabetes of the young (GCK-MODY) and permanent neonatal diabetes mellitus, respectively. To explore the possible utility of GK activators (GKAs) and of glucagon-like peptide 1 (GLP-1) receptor agonists in these diseases, we have developed a novel hypomorphic Gck allele in mice encoding an aberrantly spliced mRNA. In islets from homozygous knock-in (GckKI/KI) mice, GK immunoreactivity was reduced by >85%, and GSIS eliminated. Homozygous GckKI/KI mice displayed frank diabetes (fasting blood glucose >18 mmol/L; HbA1c ∼108 mmol/mol), ketosis, and nephropathy. Heterozygous GckKI/+ mice were glucose intolerant (HbA1c ∼37 mmol/mol). Abnormal glucose-stimulated Ca2+ dynamics in GckKI/+ islets were completely reversed by the GKA dorzagliatin, which was largely inactive in homozygous GckKI/KI mouse islets. The GLP-1 receptor agonist exendin-4 improved glucose tolerance in male GckKI/+ mice, an action potentiated by dorzagliatin. Sex-dependent additive effects of these agents were also observed on insulin secretion in vitro. Similar additive effects of the drugs were observed in obese hyperglycemic db/db mice. Combined treatment with GKA and incretin mimetics may thus be useful in GCK-MODY and in more common forms of type 2 diabetes.

Type 1 diabetes (T1D) is an autoimmune disease characterized by progressive stages culminating in T-cell-mediated destruction of the β-cells at the islets of Langerhans. The immune mechanisms that initiate T1D are not fully resolved but likely involve an interaction between proinflammatory antigen-presenting cells (APCs) and autoreactive T cells that initiate immune infiltration and activation. Previous studies have tested the use of tolerogenic APCs in adult female NOD mice to delay or prevent T1D with only slight to intermediate success. Moreover, immune infiltration begins as early as age 4 weeks; therefore, targeting autoreactive T cells with tolerogenic APCs in adult mice may not impact later stages of diabetes. Thus, we hypothesize that the transfer of tolerogenic APCs at the neonatal stage prior to priming and immune infiltration will result in effective protection from autoimmunity. Our studies demonstrate that immature APCs travel to the pancreatic draining lymph nodes, alter the cytokine milieu in young mice, divert autoreactive CD4+ T cells to anergy, and drastically decrease proliferation and function of cytotoxic lymphocytes in adult prediabetic mice, leading to a significant reduction in the incidence of T1D.

Activated neutrophils contribute to retinal endothelial cell (EC) death and capillary degeneration associated with early diabetic retinopathy (DR), a major vision-threatening complication of diabetes. However, the factors and mechanisms driving neutrophil activation and cytotoxicity in diabetes remain insufficiently understood. Here, we show that lysyl oxidase (LOX), a matrix cross-linking and stiffening enzyme that increases retinal EC susceptibility to activated neutrophils, simultaneously activates neutrophils in its soluble form. Specifically, treatment of diabetic mice with LOX inhibitor β-aminopropionitrile (BAPN) prevented the diabetes-induced increase in neutrophil activation (extracellular release of neutrophil elastase and superoxide) and cytotoxicity toward cocultured mouse retinal ECs. Mouse neutrophils and differentiated (neutrophil-like) human HL-60 cells treated with recombinant LOX alone exhibited significant activation and cytotoxicity. Mechanistically, this LOX-induced neutrophil activation was associated with biphasic F-actin remodeling, with the initial and rapid (∼10 min) F-actin depolymerization followed by a significant increase in F-actin polymerization and polarization. Preventing the initial F-actin depolymerization blocked LOX-induced neutrophil activation and cytotoxicity toward cocultured retinal ECs. Finally, this biphasic F-actin remodeling was found to be essential for LOX-induced membrane aggregation of azurophilic granule marker CD63 and NADPH organizer p47phox, which are associated with extracellular release of neutrophil elastase and superoxide, respectively. By revealing a previously unrecognized causal link between LOX and actin-dependent neutrophil activation in diabetes, these findings provide fresh mechanistic insights into the proinflammatory role of LOX in early DR that goes beyond its canonical matrix-stiffening effects.

Finding ways to increase β-cell mass is a key goal of diabetes research. During elevated insulin demand, β-cells turn on endoplasmic reticulum (ER) stress response pathways, and some β-cells enter the cell cycle. ER stress response protein activating transcription factor 6 (ATF6α) induces β-cell proliferation, but only in high glucose. The mechanism by which ATF6α increases proliferation, and the reasons for glucose dependence, remain unknown. Here we show that ATF6α activation in mouse and human islet cells increases expression of E2F1, a key cell cycle driver. E2F1 was required for ATF6α-induced proliferation in high glucose. However, E2F1 remained inactive in normal glucose, possibly because retinoblastoma (Rb), a direct E2F1 inhibitor, was in its dephosphorylated, active state. Indeed, inducing Rb phosphorylation by overexpressing cyclin-dependent kinase 4 (CDK4) allowed ATF6α to increase E2F1 activity and β-cell proliferation in normal glucose. E2F1 expression increased in an ATF6α-dependent manner during generalized ER stress by thapsigargin treatment. Importantly, in human β-cells, ATF6α failed to synergize with high glucose to induce proliferation, but the synergy was rescued by adding back CDK6. Taken together, this study establishes a new dual-input β-cell proliferation regulatory mechanism integrating ER load with current glycemic conditions via CDK4/6, in which Rb phosphorylation serves as a glucose sensor that permits ATF6α-driven proliferation.

Vascular dysfunction is considered a consequence of diabetes. However, in pancreatic islets, some hemodynamic changes occur before the onset of symptoms. The underlying mechanisms driving islet vascular abnormalities have not been fully characterized, but islet pericyte dysfunction seems to be an early event in the pathogenesis of type 1 diabetes in humans. It remains to be investigated, however, how abnormal pericyte physiology affects their ability to regulate islet blood flow and vascular permeability. To address this issue, we treated mice with multiple subdiabetogenic doses of the β-cell toxin streptozotocin (STZ; 50 mg/kg) and recorded islet vascular responses when animals developed glucose intolerance but were still not diabetic (average fed glycemia <200 mg/dL). At this stage, pericyte coverage of islet capillaries was abnormal, with capillaries either lacking pericytes or being covered by dysfunctional mural cells, which compromised islet vasomotor responses recorded ex vivo in living pancreas slices. These functional defects interfered with proper regulation of blood flow and compromised islet vascular integrity, because large fluorescent dextrans (500 kDa) could leak from peripheral islet vessels in the exteriorized pancreas of STZ-treated mice. Our study supports that the loss of functional pericyte coverage of islet capillaries is part of a pathogenic process occurring in islets before diabetes onset, associated with a loss of functional β-cell mass and inflammation.

Hyperglycemia (HG) is a well-established risk factor for secondary osteoporosis, primarily due to suppressed osteoblast activity. While gut microbiota (GM) dysbiosis has been implicated in various diseases, its role in HG-induced osteoporosis remains poorly understood. Here, we demonstrate that HG mice develop low-turnover osteoporosis accompanied by reduced GM diversity. Fecal microbiota transplantation (FMT) from HG mice (GMHG-FMT) induced osteoporosis in recipient mice, independent of blood glucose levels. A depletion of Bifidobacterium pseudolongum was associated with bone loss, whereas supplementation with either microbiota of normoglycemic mice or B. pseudolongum alleviated osteoporosis in HG mice. Both HG and GMHG-FMT recipient mice exhibited elevated serum interleukin-17A (IL-17A) levels, and anti-IL-17A antibody treatment mitigated osteoporosis in the GMHG-FMT model. Furthermore, decanoic acid levels were elevated in the feces of HG mice and the serum of GMHG-FMT recipients. Decanoic acid promoted the differentiation of naive CD4+ T cells into T helper17 cells, leading to increased IL-17A production. These findings reveal a microbiome dysbiosis-driven decanoic acid/IL-17A axis in HG-induced osteoporosis and highlight the therapeutic potential of microbiome-associated targets.

Maternal obesity is a known risk factor for metabolic dysfunction in offspring; however, its effect on metabolism during pregnancy in female offspring remains unclear. This study investigated how maternal obesity, induced by high-fat (HF) feeding in C57BL/6J mice, affects the metabolic adaptation to pregnancy in female offspring. Dams were fed an HF diet (60% fat) or chow for 3 months before and during pregnancy. Offspring of HF diet-fed dams (OF-HFD) exhibited reduced fetal growth, followed by rapid postnatal catch-up and increased adult adiposity, compared with offspring of chow-fed dams (OF-CD), despite having similar baseline glucose and insulin levels. During pregnancy, OF-HFD exhibited diminished increases in maternal body fat, blood triglycerides, and insulin concentrations, accompanied by glucose intolerance. In cultured islets, glucose-stimulated insulin secretion was markedly reduced in pregnant OF-HFD, despite unchanged β-cell mass or proliferation. Hepatic triglyceride secretion was decreased, whereas liver insulin signaling was enhanced, suggesting alterations in lipid and glucose metabolism. Feeding OF-HFD an HF diet before and during pregnancy further impaired fetal growth. These findings indicate that maternal obesity impairs the metabolic adaptation to pregnancy in female offspring, characterized by insulin insufficiency and disrupted lipid homeostasis. This may initiate a transgenerational cycle of metabolic dysfunction, potentially increasing the risk of gestational diabetes in subsequent generations. Our findings underscore the need for more research to explore these mechanisms in humans and develop strategies to reduce the long-term effects of maternal obesity.

Type 1 diabetes (T1D) is characterized by autoimmune destruction of insulin-producing β-cells. Recent evidence has implicated hybrid insulin peptides (HIPs) as targets of autoreactive CD4 T cells in human T1D patients and as critical autoantigens recognized by diabetogenic T cells in nonobese diabetic (NOD) mice. HIPs form within pancreatic islets through cross-linking reactions between proinsulin fragments and various β-cell peptides. In the NOD mouse model, highly pathogenic CD4 T cells specifically target HIPs generated through transpeptidation mediated by cathepsin D (CatD). These disease-relevant HIPs consistently incorporate a C-peptide fragment terminating in a critical leucine residue that binds to other β-cell peptides. In vitro experiments demonstrated that substituting isoleucine for this leucine residue in human C-peptide inhibited CatD-mediated HIP formation. To investigate the in vivo significance of this finding, we engineered NOD mice carrying a leucine-to-isoleucine mutation in the insulin 2 gene (NOD INS2I/I). Mass spectrometric analysis revealed significantly reduced HIP formation in islets from NOD INS2I/I mice. Significantly decreased activation of HIP-reactive T cells to islets from these mice was also observed. Furthermore, the NOD INS2I/I mice showed significantly delayed diabetes onset, with 43% remaining disease-free at 1 year compared with only 10% of wild-type NOD controls. These findings implicate HIPs as key mediators in T1D pathogenesis and demonstrate that targeted disruption of HIP formation significantly alters disease progression. Inhibiting CatD-mediated transpeptidation represents a promising therapeutic approach for preventing or delaying T1D onset in genetically susceptible individuals.

The control of muscle glucose uptake (MGU) is distributed across delivery, transport, and phosphorylation of glucose. These steps have been defined as control points of MGU in vivo due to the application of isotopic tracer techniques to transgenic mouse models. Using these techniques in a classic study published in Diabetes, Fueger et al. demonstrated that overexpression in skeletal muscle of hexokinase II (HKII), the enzyme responsible for intracellular glucose phosphorylation, enhanced MGU in insulin-sensitive but not in insulin-resistant mice. Conversely, HKII overexpression enhanced MGU in insulin-resistant mice in response to exercise. Since exercise reduces barriers of glucose delivery and transport, this suggested that these two processes contribute to the dysregulation of MGU in insulin-resistant states. These fundamental findings have spurred subsequent studies highlighting the contribution of glucose delivery and transport to the regulation of MGU in health and disease.