Oxidative stress has a major pathogenic role in diabetic retinopathy, and neuroretina dysfunction is recognized as an early and important problem. Soluble guanylate cyclase (sGC) has been implicated for its neuroprotective effects in the central nervous system, but its role in the retina remains unclear. Here we demonstrated expression of sGC subunits GUCY1A1 and GUCY1B1 in healthy human and rodent retina in vascular cells and neuronal elements including retinal ganglion cells, bipolar, and amacrine cells. We provided evidence using in vitro and in vivo studies that sGC function is impaired by oxidative stress-induced damage in retina. The sGC activator runcaciguat activated sGC in multiple retinal cell types and counteracted the inhibitory effect of damage induced by oxidative stress on the retina and retinal cells. In the rat retinal ischemia-reperfusion model, runcaciguat treatment improved neuroretinal and visual function as measured by electroretinography and optokinetic tracking and resulted in retinal morphologic improvement. In the STZ-induced diabetic rat model, runcaciguat significantly improved neuroretinal function and improved inner plexiform layer thickness. These studies suggest that sGC signaling is involved in neuroretinal function and vision and that diabetes negatively affects this pathway, supporting restoring sGC activation as a novel therapy for early DR.

Obesity-induced biological changes often persist after weight loss and are difficult to reverse, a phenomenon known as 'obesogenic memory'. This enduring effect is associated with metabolic inflammation, particularly in adipose tissue. In this study, we characterise a mouse model of obesogenic memory and evaluate the efficacy of the unimolecular conjugate GLP-1/Dexa, which selectively and safely delivers the anti-inflammatory drug dexamethasone to GLP-1 receptor (GLP-1R)-expressing cells. We document that this precision pharmacological approach outperforms treatment with GLP-1 or dexamethasone alone, significantly reducing body weight, food intake, adiposity and markers of adipose tissue inflammation in male mice with obesogenic memory. In addition, we identify the CCR2/CCL2 inflammatory pathway as an important mediator of glucose intolerance and adipose tissue inflammation associated with obesogenic memory. Our findings suggest that targeting inflammation via GLP-1R signalling may be a promising therapeutic strategy to alleviate obesogenic memory and improve the long-term clinical management of metabolic diseases.

Obesity is a growing global health threat, and inducing browning of white adipose tissue (WAT) to increase energy expenditure has become an attractive strategy for treating obesity and related metabolic complications. BRCA1-associated protein 1 (BAP1), a ubiquitin C-terminal hydrolase (UCH) domain-containing deubiquitinase (DUB) expressed broadly across tissues, has previously been shown to play an important role in liver carbohydrate and lipid metabolism. However, its role in the browning of inguinal white adipose tissue (iWAT) has not been studied. Our study initially found that BAP1 expression was downregulated in cold-induced mouse iWAT but upregulated in obese conditions. Furthermore, overexpression of BAP1 in the inguinal fat tissue suppressed iWAT browning and thermogenesis. Mechanistically, we found that BAP1 interacts with KDM1B and stabilizes it through deubiquitination. Subsequently, KDM1B demethylates H3K4me1/2 modifications in proximity to thermogenesis-related genes, thereby inhibiting the expression of genes essential for browning. In summary, our study shows that BAP1 negatively regulates iWAT browning via a mechanism mediated by KDM1B.

Wolfram Syndrome 1 (WS1) is a rare genetic disorder caused by WFS1 variants that disrupt Wolframin, an endoplasmic reticulum-associated protein essential for cellular stress responses, Ca2+ homeostasis, and autophagy. Here, we investigated how the c.316-1G>A and c.757A>T WFS1 mutations, which yield partially functional Wolframin, affect the molecular functions of β cells and explored the therapeutic potential of the Glucagon-like peptide 1 receptor (GLP-1R) agonist liraglutide. Pancreatic β cells obtained from patient-derived induced Pluripotent Stem Cells (iPSCs) carrying this WFS1 variant exhibited reduced insulin processing and impaired secretory granule maturation, as evidenced by proinsulin accumulation and decreased prohormone convertase PC1/3. Moreover, they exhibited dysregulated Ca2+ fluxes due to altered transcription of Ca2+-related genes, including CACNA1D, and significantly reduced SNAP25 levels, leading to uncoordinated oscillations and poor glucose responsiveness. Affected cells also showed increased autophagic flux and heightened susceptibility to inflammatory cytokine-induced apoptosis. Notably, liraglutide treatment rescued these defects by normalizing Ca2+ handling, enhancing insulin processing and secretion, and reducing apoptosis, likely through modulation of the unfolded protein response. These findings underscore the importance of defining mutation-specific dysfunctions in WS1 and support targeting the GLP-1/GLP-1R axis as a therapeutic strategy.

Gestational diabetes mellitus (GDM) is one of the most common medical complications of pregnancy. It is generally defined as glucose intolerance with onset or first recognition during pregnancy. The pathogenesis of GDM has long been attributed to inadequate pancreatic β-cell compensation for the physiological insulin resistance of pregnancy. This defect is thought to resolve after pregnancy but become manifest in later life as an increased risk of diabetes. Examination of mechanisms underlying GDM does not support this commonly held picture. In this Perspective we present evidence that, like diabetes outside of pregnancy, GDM has no single etiology. It results from multiple causes of a common physiological manifestation, inadequate β-cell function, which leads to a common clinical manifestation, elevated glucose levels. We provide evidence that GDM often represents detection of chronic and progressive β-cell dysfunction that is temporally, but not mechanistically related to pregnancy. We provide detailed characterization of the β-cell defect in one high-risk group, Hispanic Americans. Finally, we address some of the clinical and research implications of these findings.

By stimulating hepatic glucose production, glucagon (released by islet α-cells) restores normal blood glucose levels when they fall below the normal range. We used optogenetics in conjunction with electrophysiology, [Ca2+]i imaging and hormone release measurements to explore the intrinsic and paracrine regulation of glucagon secretion. Many α-cells were spontaneously active at 1mM glucose. However, up to ∼50% of the α- cells were electrically silent. KATP channel blockade, amino acids and somatostatin receptor (SSTR) antagonism restored electrical activity in such α-cells. Termination of optoactivation resulted in KATP channel-dependent (tolbutamide-sensitive) membrane repolarization in active α-cells but long-lasting membrane depolarization and action potential firing in silent α-cells. The latter effect was associated with an increased cytoplasmic ATP:ADP-ratio. Optoactivation or -inhibition of somatostatin-releasing δ- cells inhibits and stimulates electrical activity in adjacent (but not distal) α-cells. There is an inverse relationship between basal glucagon secretion (a measure of the fraction active α-cells) and the relative stimulatory effects of amino acids. We conclude that islet α-cells are functionally heterogenous and that their electrical excitability and glucagon release are determined by K+ channel activity due to variable mosaic of KATP and somatostatin-sensitive K+ channels reflecting metabolic state and proximity to δ-cells, respectively.

Glycated haemoglobin (HbA1c) has shown disagreements with other glycaemic indices; termed the glycation gap. The glycation gap can be influenced by non-glycaemic factors like protein deglycation, through the fructosamine 3 kinase (FN3K) enzyme. This cross-sectional study aimed to examine whether single nucleotide polymorphisms (SNPs) in the FN3K gene can explain the glycation gap. Amongst the 826 participants, 79.8% were female, 22.3% presented with DM and the median age was 53 years. The results suggest that genetic polymorphisms in the FN3K gene may influence the glycation gap in individuals with diabetes mellitus (DM). With the SNP rs1056534 analysis, the CC genotype was associated with a negative glycation gap (All, p<0.02), whilst the GG genotype was associated with positive glycation gap (All, p<0.03), in the adjusted models. Similarly, with the SNP rs2256339, the TT genotype was associated with a negative glycation gap (p<0.08), whereas the TA genotype was associated with a positive glycation gap (All, p<0.05), in the adjusted models. The studied genotypes are associated with protein glycation, contributing to differences in measures of glycaemic control. Future studies are needed to explore the clinical implications of these findings.

Intrahepatic islet transplantation is followed by islet loss due to instant blood-mediated inflammatory response (IBMIR), in which platelet activation plays a key role. The KEATSTF-fragment (KF7), a newly discovered platelet inhibitor that interferes with the formation of the 14-3-3z-c-Src-integrin-β3 complex, holds significant potential in inhibiting IBMIR without causing significant bleeding. This study introduces a novel surface modification technique using L-DOPA (3,4-Dihydroxy-L-phenylalanine) conjugated with KF7 to enhance the engraftment of transplanted islets in a syngeneic marginal mass model. KF7 loaded with L-DOPA(L-DOPA-KF7) formed a protective coating on the surface of islets without interfering with their viability and functionality. Islets coated with L-DOPA-KF7 restored normoglycemia in diabetic mice, and survival time was significantly longer compared to control group. Transplantation of L-DOPA-KF7 coated islets was associated with reduced blood clot formation and decreased infiltration of CD11b+ cells and platelets. In conclusion, composite L-DOPA-KF7 coating significantly prolongs the survival of transplanted islets by providing a robust IBMIR -isolation barrier, thereby enhancing the overall success of islet transplantation in preclinical models.

Pathological signaling via the receptor for advanced glycation end-products (RAGE) is critical in diabetic kidney disease (DKD) development, while RAGE deletion is reno-protective. Non-coding RNAs (ncRNAs), including microRNAs (miRs), also play key roles in DKD, including renal fibrosis. However, the involvement of ncRNAs in RAGE signaling remains unclear. This study investigated the regulation of ncRNAs by RAGE and assessed renal expression of ncRNAs, miRs, fibrotic/inflammatory markers in diabetic RAGE knockout (KO) and wild-type (WT) mice, as well as in mesangial cells (MCs) obtained from these mice. Diabetes induction in both RAGE-/- and WT mice exhibited elevated renal expression of miR-214 and its host ncRNA, Dnm3os. miR-214 and Dnm3os levels were remarkably higher in RAGE-/- MCs compared to WT MCs. Overexpression of miR-214 in WT MCs reduced fibrotic/inflammatory gene expression, while its inhibition increased these markers. Human DKD tissue demonstrated higher Dnm3os expression compared to controls. Notably, miR-214 targeted the RAGE signaling mediator diaphanous1 (DIAPH1), while Dnm3os had an opposing effect, enhancing fibrosis and inflammation. miR-214 administration in a DKD mouse model significantly reduced renal fibrosis. These findings propose a novel mechanism where miR-214 and Dnm3os act as negative and positive regulators of fibrosis via the RAGE-DIAPH1 axis.

Since little is known about the disposition index (DI) in autoantibody-positive individuals, we have assessed whether DI has a similar association between insulin secretion and resistance to the association observed in other populations. In TrialNet Pathway to Prevention (TNPTP; n=6620) and Diabetes Prevention Trial-Type 1 (DPT-1; n=704) study participants, two secretion-sensitivity pairs each representing a DI were analyzed cross-sectionally at baseline: AUC C-peptide/AUC glucose (AUC Ratio) and Matsuda Index (MI) from TNPTP OGTTs (oral DI), first-phase insulin response (FPIR) and 1/fasting insulin (1/FI) from DPT-1 from IVGTTs (DI). Participants were followed for progression to type 1 diabetes. Within the normal and diabetes glucose ranges, associations of AUC ratio with MI in TNPTP, and FPIR with 1/FI in DPT-1, had inverse curvilinear patterns with convexities to the origin. After logarithmic transformations to linearize the secretion and sensitivity measures, the inverse slope was steeper for the diabetes range (p<0.0001). In a Cox regression model including the AUC Ratio and MI as variables and another model including FPIR and 1/FI, the interaction terms of secretion x sensitivity (i.e., the DI/ODI), predicted stage 3 type 1 diabetes in both (p<0.0001). The DI remained significantly predictive (p<0.0001) when the DPT-1 risk score was added as a covariate in regression models. In autoantibody-positive populations, insulin secretion is inversely related to sensitivity in a quasi-hyperbolic relationship in normal and diabetes ranges of glucose. The DI can be represented by a statistical and physiologic interaction between secretion and sensitivity that is predictive of stage 3 type 1 diabetes.

Activation of GPR119 receptors, expressed on enteroendocrine and pancreatic islet cells, augments glucagon counterregulatory responses to hypoglycemia in pre-clinical models. We hypothesized that MBX-2982, a GPR119 agonist, would augment counterregulatory responses to experimental hypoglycemia in participants with type 1 diabetes. To assess this, we designed a phase 2a double-masked, cross-over trial in 18 participants (20-60 years) with type 1 diabetes. Participants were randomized to treatment with 600 mg MBX-2982 or placebo daily for 14 days with a two-week washout between treatments. Counterregulatory responses to hypoglycemia during a hyperinsulinemic-hypoglycemic clamp and hormonal responses during a mixed meal test (MMT) were measured. The maximum glucagon response, glucagon area under the curve (AUC) and incremental AUC were not significantly different during MBX-2982 vs placebo treatment. MBX-2982 did not alter epinephrine, norepinephrine, pancreatic polypeptide, free fatty acid, or endogenous glucose production responses to hypoglycemia compared to placebo. However, glucagon-like peptide-1 (GLP-1) response during the MMT was 17% higher with MBX-2982 compared to placebo treatment. In conclusion, GPR119 activation with MBX-2982 did not improve counterregulatory responses to hypoglycemia in people with type 1 diabetes. Increases in GLP-1 during the MMT are consistent with GPR119 target engagement and the expected pharmacodynamic response from L-cells.

G protein-coupled receptor 119 (GPR119) is predominantly expressed in pancreatic β-cells, enteroendocrine cells, and the liver. It is a novel therapeutic for dyslipidemia and type 2 diabetes. DA-1241, a GPR119 agonist, improves glucose tolerance by inhibiting gluconeogenesis and enhancing insulin secretion. It mitigates hepatic inflammation by inhibiting NFĸB signaling. However, the mechanism by which DA-1241 ameliorates nonalcoholic fatty liver disease (NAFLD) remains unknown. We hypothesized that DA-1241 improves liver steatosis by inducing autophagy in a TFEB-dependent manner. It induced autophagy and TFEB nuclear translocation, and decreased lipid content in liver cell lines. Lysotracker staining and DQ-Red BSA assay revealed it increased lysosomal activity. Furthermore, DA-1241 increased the colocalization of mRFP-LC3 and lipid droplets, which were completely abolished by GPR119 knockdown. DA-1241 treatment improved glucose tolerance and insulin sensitivity, and decreased liver enzymes activity and hepatic triglyceride levels, and the NAFLD activity score with increased number of autophagosomes and lysosomes in high-fat diet-fed mice. Despite DA-1241 treatment, lysosomal activity and subsequent lipid content reduction were not induced in tfeb knockout HeLa cells. DA-1241 treatment failed to produce favorable metabolic effects, including reduced hepatic triglyceride levels, in liver-specific Tfeb knockout mice. Thus, DA-1241 attenuates hepatic steatosis through TFEB-mediated autophagy induction.

Effective treatment strategies for diabetes-related pain are limited due to its complex pathogenesis, particularly brain mechanisms underlying this disease. The acid-sensing ion channel 1a (ASIC1a) emerges as a key player in the development and treatment of various types of pain. Here, we investigated the role of ASIC1a in diabetes-related pain and its molecular mechanisms in the anterior cingulate cortex (ACC). Our findings demonstrate that the up-regulation of ASIC1a expression drives enhanced activity of excitatory glutamatergic neurons in the ACC (ACCGlu), promoting the development of pain hypersensitivity in streptozotocin (STZ)-induced diabetic male mice. Pharmacological inhibition and genetic knockout of ASIC1a in ACCGlu neurons significantly reduced neuronal activity and alleviated mechanical and thermal pain sensitizations in STZ-induced diabetes. Furthermore, increased levels of TNF-α in the ACC up-regulated ASIC1a through triggering NF-κB pathways, which led to the development of diabetes-related pain. Notably, the clinically used medication, infliximab, exhibited therapeutic effects on diabetes-related pain via its influencing on TNF-α/NF-κB/ASIC1a pathway in STZ mice. Collectively, this study identifies ASIC1a as a potential therapeutic target for diabetes-related pain, and the neutralization of TNF-α leads to pain relief through the TNF-α/NF-κB/ASIC1a pathway in the ACC. These findings hold promise for the development of the new clinical therapeutic strategies for diabetes-related pain.

Glucagon stimulates hepatic glucose production, in part by promoting the uptake and catabolism of amino acids. Inhibition of liver glucagon receptor (GCGR) results in elevated plasma amino acids, which triggers the proliferation of pancreatic alpha-cells, forming a liver-alpha cell loop. This study aims to delineate hepatic signaling molecules downstream of GCGR which mediate the liver-alpha cell loop. We knocked down liver GCGR, its G-coupled protein GNAS, and two GNAS downstream effectors, PKA and EPAC2 (RAPGEF4). Mice with GCGR, GNAS, and PKA knockdown had similar suppression of hepatic amino acid catabolism genes, hyperaminoacidemia, and alpha cell hyperplasia, but EPAC2 knockdown did not. We then demonstrated that activating liver PKA was sufficient to reverse hyperaminoacidemia and alpha cell hyperplasia caused by GCGR blockade. These results suggest that liver GCGR signals through PKA to control amino acid metabolism, and that hepatic PKA plays a critical role in the liver-alpha cell loop.

Diabetic patients are at an increased risk of diabetic cardiomyopathy (DCM) and acute myocardial infarction (AMI). Protecting the heart against AMI is more challenging in DCM than non-diabetic hearts. We investigated whether intravenous atorvastatin administration during AMI exerts cardioprotection in DCM as seen in non-diabetic hearts. Sprague-Dawley rats were divided into streptozotocin-induced DCM and normoglycemic-control groups. Our model of DCM rats exhibited interstitial fibrosis and cardiac dysfunction at 5 weeks. At this time point, all animals underwent AMI-induction (coronary ligation for 45min), receiving intravenous atorvastatin or vehicle during ischemia. Animals were reperfused and sacrificed 24h later for myocardial infarct size analysis and cardiac tissue sampling. Echocardiography was performed. DCM vehicle rats had larger infarcts than normoglycemic vehicle-treated animals at comparable area-at-risk. Intravenous atorvastatin reduced infarct size and preserved systolic function in both groups. In comparison to vehicle animals, intravenous atorvastatin inhibited RhoA membrane translocation, induced AMPK phosphorylation, prevented apoptosis execution and improved cardiac remodelling in the infarcted heart of both groups whereas innate immune cell infiltration was further reduced in intravenous atorvastatin-treated DCM animals. The proven cardioprotective effectiveness of this intravenous statin formulation in the presence of DCM warrants its further development into a clinically therapeutic option.

HLA class I (HLA-I) molecules present intracellular antigenic peptides to CD8+ T lymphocytes during immune surveillance. In donors with type 1 diabetes, hyperexpression of HLA-I occurs in islets with residual insulin-producing β-cells as a hallmark of the disease. HLA-I hyperexpression is frequently detected beyond the islet boundary, forming a 'halo'. We hypothesized that this halo may reflect the diffusion of soluble forms of HLA-I (sHLA-I) from the islets to the surrounding pancreatic parenchyma. To verify this, we assessed the expression of total, cell surface and sHLA-I in β-cell lines and isolated human islets, following treatment with interferons (IFN)-α and IFN-γ. Consistent with the expression patterns of HLA-I in situ, both β-cell lines and cultured human islets dramatically upregulated total and surface HLA-I when exposed to IFNs. Concomitantly, sHLA-I release was significantly increased. HLA-I released within extracellular vesicles and cleaved forms of HLA-I did not significantly contribute to the sHLA-I pool. Rather, IFNs upregulated mRNA splice variants lacking the transmembrane domain. Our findings suggest that β-cells respond to IFNs by upregulating cellassociated and soluble forms of HLA-I. Soluble HLA-I may play a role in modulating islet inflammation during the autoimmune attack.

Recent evidence has shown that adipose tissue eventually develops fibrosis through complex cellular crosstalk. Although advances in single-cell transcriptomics have provided new insights into cell diversity during this process, little is known about the interactions among the distinct cell types. In this study, we employed single-cell analytical approaches to investigate cell-tocell communications between macrophages and fibroblasts in the adipose tissue of diet-induced obese mice. Spatial transcriptomics was used to understand local cellular interaction within crown-like structures (CLSs), a characteristic histological feature of adipose tissue in obesity driving inflammation and fibrosis. Macrophages and fibroblasts were divided into several subclusters that appeared to interact more intensely and complexly with the degree of obesity. Besides previously reported Lipid-associated macrophages (LAMs), we found a small subcluster expressing Macrophage-inducible C-type lectin (Mincle), specifically localizing to CLSs. Mincle signaling increased the expression of Oncostatin M (Osm), suppressing collagen gene expression in adipose tissue fibroblasts. Consistent with these findings, Osm-deficiency in immune cells enhanced obesity-induced adipose tissue fibrosis in vivo. Moreover, Osm expression was positively correlated with Mincle expression in human adipose tissue during obesity. Our results suggest that Osm secreted by Mincle-expressing macrophages is involved in dynamic adipose tissue remodeling in the proximity of CLSs.

This study compares novel type 1 diabetes-related autoantibody assays developed to improve upon the standard radiobinding assay (RBA). Samples from 1505 individuals, followed for 5 years or to clinical type 1 diabetes, originally tested by RBA were aliquoted and sent blindly to 5 laboratories (BDC, IDR, DRI, MSD, Enable) to be tested by electrochemiluminescence (ECL) assays, Luciferase Immuno Precipitation System (LIPS) assays, multiplex antibody detection by agglutination-PCR (ADAP) assays, and N-terminally truncated GAD65 or IA2β autoantibody RBAs (tGADA/IA2βA). Findings: The fraction of samples that were concordant for negative/positive interpretations across all assays were 79.7% (GADA), 65.2% (IA-2A), 36.2% (IAA), and 67.5% (ZnT8A). The assays with the highest Youden index for predicting the previous RBA results differed by autoantibody: 0.65 LIPS(IDR) for IAA, 0.91 ECL(BDC) for ZnT8A, 0.82 tGADA RBA(IDR) for GADA, 0.91 ECL(MSD and BDC) for IA-2A. The Youden index for predicting 5-year type 1 diabetes varied significantly across assays and was highest for LIPS(DRI) for all autoantibody combinations, with little variation in the respective maximum Youden index. The discordance between assays makes it problematic to interpret positivity when comparing results from different assays. Longitudinal autoantibody assessments should be tested with the same assay.