Evidence of retinal vascular inflammation accompanies diabetic retinopathy (DR) progression, and inflammatory cytokines TNFα and IL-1β are experimentally linked to several hallmark DR features, including retinal leukostasis. Cannabinoid receptor 2 (CB2) agonism has been shown to decrease inflammatory cytokine production and leukocyte recruitment and adhesion in nonocular inflammation models, suggesting CB2 agonism could have therapeutic potential in DR. We tested the efficacy of two CB2-selective agonists, HU-308 and CB65, to attenuate leukocyte adhesion to human retinal microvascular endothelial cells (hRMEC) in response to diabetes-relevant inflammatory stimuli and to the walls of retinal capillaries in murine models of DR. In vitro, HU-308 and CB65 significantly reduced TNFα-induced and IL-1β-induced gene expression of the adhesion molecules ICAM1, VCAM1, and SELE and protein expression of ICAM-1 and VCAM-1 in hRMEC. Additionally, HU-308 and CB65 inhibited TNFα-induced and IL-1β-induced leukocyte adhesion to hRMEC monolayers, aligning with their effects on adhesion protein levels. HU-308 and CB65 reduced TNFα-induced and IL-1β-induced nuclear factor κB translocation and activation, suggesting downstream mechanisms of CB2 receptor activation. In vivo, both intraocular and systemic HU-308 administration significantly decreased retinal leukostasis in cytokine-induced inflammation and streptozotocin-induced diabetes. Therefore, CB2 agonism demonstrates potential for mitigating leukostasis and its pathogenic consequences in DR.

Senescence is a β-cell stress response in type 1 diabetes (T1D), the origins of which are not understood. We wanted to determine the role of the T cell-mediated autoimmune process in β-cell senescence during T1D. In the nonobese diabetic mouse model, β-cell senescence largely depended on damage inflicted by autoreactive CD4+ and CD8+ T cells during the development of T1D. Chronic exposure to sublethal doses of proinflammatory cytokines associated with the diabetogenic process was sufficient to elicit stable senescence phenotypes in human islets in culture. Our findings suggest that autoreactive T cells trigger not only β-cell death but also β-cell senescence, potentially via cytokine-dependent mechanisms in T1D. This finding has implications for understanding the mechanisms of action and beneficial impacts of immunotherapy using CD3 antibodies in T1D.

Type 1 diabetes has detrimental effects in white matter in young children. We performed a longitudinal study using brain MRI (diffusion tensor imaging) and cognitive assessments in 4- to 9-year-old children, control participants without diabetes (n = 71) and with type 1 diabetes (n = 143), plus continuous glucose monitoring, to assess changes at four time points as children grow over 6-8 years. White matter myelination and fiber integrity were assessed using axial diffusivity, which was decreased in the diabetes versus control group, less so during puberty, and fractional anisotropy was reciprocally related to hyperglycemia. Data suggest continued negative impact of chronic hyperglycemia in the developing brain.

Administration of the gut hormone glucose-dependent insulinotropic polypeptide (GIP) increases splanchnic blood flow. We investigated the role of endogenous GIP in splanchnic blood flow regulation using a receptor antagonist in humans. Oral glucose ingestion increased blood flow in the superior mesenteric artery by ∼70%, and the increase was significantly lower during concurrent infusion of the GIP receptor antagonist. Thus, endogenous GIP contributed ∼22% of the postprandial increase in superior mesenteric artery blood flow. We have identified a novel physiological aspect of vascular biology related to the GIP receptor in humans. Treatments targeting the GIP receptors are likely to affect splanchnic blood flow.

Instant blood-mediated inflammatory reactions (IBMIRs) and low extracellular matrix (ECM) concentrations hinder islet implantation and survival in the spleen. Islets were encapsulated in hepatocytes and fibroblasts. The low expression of von Willebrand factor in hepatocytes enables them to form a protective coating with fibroblasts. This coating reduces IBMIRs and supports islet survival through ECM production by fibroblasts. The hepatocyte-fibroblast encapsulation significantly reduces islet mortality during the posttransplantation stress period, enabling rapid engraftment and vascularization in the spleen.

This study was conducted to assess splanchnic and leg glucagon metabolism in humans using stable glucagon isotopes. We wanted to evaluate whether splanchnic and leg glucagon metabolism differed between participants with no diabetes (ND) and those with type 1 diabetes (T1D) at glucagon concentrations spanning the physiological range. Whereas splanchnic glucagon extraction did not differ between participants with ND and those with T1D, leg glucagon extraction fell in those with ND but did not change in those with T1D as glucagon concentrations increased. Net splanchnic glucagon production did not change with exogenous glucagon infusion. Our study has implications for dual hormone closed loop control in T1D where glucagon is infused for prevention of hypoglycemia and for investigating the effects of emerging GLP-1, glucose-dependent insulinotropic polypeptide, and glucagon receptor agonists on endogenous glucagon secretion and clearance.

We aimed to develop a dual-targeted mRNA-based therapy to address both neural degeneration and vascular insufficiency in diabetic peripheral neuropathy. We identified NGFR100W as a mutation that enhances neuritogenic activity without pain sensitization and investigated its transcriptome to explore its ability to uncouple neuroprotective and nociceptive pathways. Combination therapy using lipid nanoparticles for codelivery of NGFR100W and VEGFA mRNA improved blood flow, increased microvessel formation, and preserved nerve function in a diabetic mouse model. This approach, which combines structure-based design and mRNA therapy, offers a novel strategy for decoupling protein functions and developing therapeutic molecules with specific functionalities.

The effects of acute atmospheric pressure changes on glucose metabolism in type 1 diabetes remain controversial and may have safety implications for pilots and travelers alike. What are the differences in glucose kinetics and hormones between ground and simulated flight environments? Glucose disposal and insulin concentration are increased in response to a meal during flight, without associated changes in endogenous glucose production or meal glucose appearance rates. Pressure-related changes in insulin pump performance and hypoxia may explain these findings. Because glucose concentrations were unaffected, there is no evidence that insulin pump therapy is a risk factor in flight.

Individuals with type 1 diabetes (T1D) have a markedly smaller pancreas, but the mechanism responsible for the reduction in size is unknown. How pancreas volume differs in individuals with specific forms of monogenic diabetes and how pancreas volume relates to the severity of insulin deficiency are unknown. Measured by MRI, individuals with permanent neonatal diabetes due to an INS gene mutation (INS-PND) or the HNF1B gene associated with maturity onset diabetes of the young had smaller pancreas than individuals without diabetes. Across all types of monogenic diabetes, individuals receiving insulin replacement therapy had smaller pancreas than individuals not using insulin. These results support the conclusion that insulin deficiency is a major factor contributing to changes in pancreas volume in T1D, INS-PND, and other forms of monogenic diabetes.

Glucokinase activators (GKA) are a long-sought therapeutic modality for the treatment of Type 2 Diabetes (T2D). However, all GKAs failed clinical trials, with the recent exception of dorzagliatin (Hua Medicine). A comprehensive approach using human islet perfusions, enzyme kinetics, x-ray crystallography, and modeling studies was applied to compare the effects of dorzagliatin with the failed GKA MK-0941 (Merck Pharmaceuticals), which is well-characterized both clinically and mechanistically. Dorzagliatin improves glucose stimulation of insulin secretion (GSIS) in a dose- and glucose-dependent manner, in contrast to MK-0941 which induces maximal insulin secretion at low doses and glucose concentrations. To understand these functional differences, the atomic resolution structure of the dorzagliatin-glucokinase (GK) complex was determined and compared with the GK/MK-0941 structure. MK-0941 binds to a pocket accessible in both open and closed conformations, has a strong interaction with Y214, mutation of which produces the most clinically severe activating mutation, and produces a high energy barrier for the open-to-close transition. In contrast, dorzagliatin only binds favorably to the closed form of glucokinase, interacting primarily with R63, and causing a low energy barrier for the open-to-close transition. This provides the molecular rationale for the clinical success of dorzagliatin which can guide the future development of next-generation allosteric activators of GK.

Pancreatic β-cell KATP channel closure underlies electrical excitability and insulin release, but loss or inhibition of KATP channels can lead to paradoxical crossover from hyperinsulinism plus hypoglycemia, to glucose-intolerance or diabetes. We report genotype-phenotype information on a set of patients clinically diagnosed with maturity onset diabetes of the young (MODY), and carrying coding variants in the KATP regulatory subunit gene ABCC8. In contrast to the naïve prediction that diabetes should be associated with KATP gain-of-function (GOF, as in KATP-dependent neonatal diabetes) each mutation caused mild to severe loss-of-function (LOF), through distinct molecular mechanisms, suggesting the affected individuals may have crossed over to glucose intolerance from KATP channel LOF-dependent congenital hyperinsulinism (CHI). Our data provide definitive support for a paradoxical form of MODY in association with KATP channel LOF, genetically and mechanistically distinct from a late diagnosis of diabetes resulting from KATP GOF. To avoid confusion and inappropriate treatment efforts, we argue that diabetes driven by KATP-GOF and KATP-LOF mutations should be officially recognized as distinct diseases.

Accurate measurement of GLUT4 translocation is crucial for understanding insulin resistance in skeletal muscle, a key factor in the development of metabolic diseases. However, current methods rely on overexpressed epitope-tagged GLUT4 constructs or indirect measurements, limiting their physiological relevance and applicability. To overcome these challenges, we developed an innovative high-sensitivity imaging-based method that enables the direct assessment of endogenous GLUT4 translocation in primary skeletal muscle fibers. This approach uses antibodies targeting exofacial epitopes on native GLUT4. Our method allows multiplexed analysis of multiple insulin-sensitive processes, including transferrin receptor trafficking and FOXO nuclear exclusion, alongside mitochondrial oxidative stress. This comprehensive approach provides a unique opportunity to simultaneously assess insulin action across different signaling branches within individual muscle fibers. We validated this method across multiple inbred mouse strains and models of insulin resistance, including chronic insulin exposure, palmitate treatment, and obesity induced by a high-fat diet. Notably, we identified a selective defect in GLUT4 trafficking in insulin-resistant muscle fibers, while other insulin-dependent processes remained intact. By offering a high-fidelity model that maintains physiological relevance, this novel approach represents a significant advancement in the study of skeletal muscle insulin resistance and provides a powerful tool for dissecting gene-environment interactions that underpin metabolic disease.

We tested genetic variants in GCK, GCKR, and PNPLA3 in a large sample of self-identified Mexican Americans from the BetaGene Study for association with type 2 diabetes-related phenotypes under the hypothesis that they may regulate metabolic balance across the liver and contribute to hepatic steatosis and insulin resistance. We further tested whether interactions with dietary fructose and total sugar contributes to the observed associations. GCK rs1799831 was not associated with any type 2 diabetes-related phenotypes either alone or with any interaction tested. We replicated previous associations reported for GCKR rs780094 and PNPLA3 rs738409. We also show the interaction between GCKR rs780094 and dietary fructose is associated with both glucose effectiveness and glucose effectiveness at zero insulin, measures reflective of hepatic glucose uptake. We further show the interaction between GCKR rs780094 and PNPLA3 rs738409 is associated with type 2 diabetes-related traits, including insulin sensitivity. We conclude variations in GCKR and PNPLA3 and their interactions with each other and dietary fructose are partial determinants of hepatic fat, likely due to alterations in relative contributions of different metabolic pathways in the liver. These findings point to both GCKR and PNPLA3 as important therapeutic targets to mitigate hepatic metabolic dysfunction.

Diabetes is a metabolic disorder associated with an increased risk of systemic vascular complications. Notably, diabetic retinopathy (DR) represents a major microvascular complication and a leading cause of blindness and vision impairment. Despite its clinical significance, the precise molecular mechanisms underlying vascular dysfunction and the associated metabolic disturbances in DR remain incompletely understood. In this study, we identified tsRNA-1797, a transfer RNA-derived small RNA, as a critical regulator of retinal vascular dysfunction. tsRNA-1797 expression was markedly upregulated under diabetic conditions. Functional studies demonstrated that silencing tsRNA-1797 ameliorated endothelial dysfunction in vitro and inhibited retinal vascular dysfunction in vivo. Mechanistically, tsRNA-1797 was found to disrupt purine metabolism by regulating adenosine production through CD73. The tsRNA-1797-CD73-adenosine axis emerged as a key mediator of retinal vascular dysfunction in DR. These findings establish tsRNA-1797 as a novel regulatory factor that links metabolic dysregulation to vascular dysfunction in DR, highlighting its potential as a promising therapeutic target for diabetes-induced vascular complications.

We aimed to identify distinct axes of obesity using advanced magnetic resonance imaging (MRI)-derived phenotypes. We used 24 MRI-derived fat distribution and muscle volume measures (UK Biobank; N = 33,122) to construct obesity axes through principal component analysis. Genome-wide association studies were performed for each axis to uncover genetic factors, followed by pathway enrichment, genetic correlation, and Mendelian randomization analyses to investigate disease associations. Four primary obesity axes were identified: 1) general obesity, reflecting higher fat accumulation in all regions (visceral, subcutaneous, and ectopic fat); 2) muscle dominant, indicating greater muscle volume; 3) peripheral fat, associated with higher subcutaneous fat in abdominal and thigh regions; and 4) lower-body fat, characterized by increased lower-body subcutaneous fat and reduced ectopic fat. Each axis was associated with distinct genetic loci and pathways. For instance, the lower-body fat axis was associated with RSPO3 and COBLL1, which are emerging as promising candidates for therapeutic targeting. Disease risks varied across axes; the general obesity axis was correlated with higher risks of metabolic and cardiovascular diseases, whereas the lower-body fat axis seemed to protect against type 2 diabetes and cardiovascular disease. This study highlights the heterogeneity of obesity through the identification of obesity axes and emphasizes the potential to extend beyond BMI in defining and treating obesity for obesity-related disease management.