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Summary: Inflammation-mediated crosstalk between neuroglial cells and endothelial cells (ECs) is a fundamental feature of many vascular diseases. Nevertheless, the landscape of inflammatory processes during diabetes-induced microvascular dysfunction remains elusive. Here, we applied single-cell RNA sequencing to elucidate the transcriptional landscape of diabetic retinopathy (DR). The transcriptome characteristics of microglia and ECs revealed two microglial subpopulations and three EC populations. Exploration of intercellular crosstalk between microglia and ECs showed that diabetes-induced interactions mainly participated in the inflammatory response and vessel development, with colony-stimulating factor 1 (CSF1) and CSF1 receptor (CSF1R) playing important roles in early cell differentiation. Clinically, we found that CSF1/CSF1R crosstalk dysregulation was associated with proliferative DR. Mechanistically, ECs secrete CSF1 and activate CSF1R endocytosis and the CSF1R phosphorylation-mediated MAPK signaling pathway, which elicits the differentiation of microglia and triggers the secretion of inflammatory factors, and subsequently foster angiogenesis by remodeling the inflammatory microenvironment through a positive feedback mechanism.

Summary: Type 1 diabetes (T1D) is a chronic condition caused by autoimmune destruction of the insulin-producing pancreatic β cells. While it is known that gene-environment interactions play a key role in triggering the autoimmune process leading to T1D, the pathogenic mechanism leading to the appearance of islet autoantibodies—biomarkers of autoimmunity—is poorly understood. Here we show that disruption of the complement system precedes the detection of islet autoantibodies and persists through disease onset. Our results suggest that children who exhibit islet autoimmunity and progress to clinical T1D have lower complement protein levels relative to those who do not progress within a similar time frame. Thus, the complement pathway, an understudied mechanistic and therapeutic target in T1D, merits increased attention for use as protein biomarkers of prediction and potentially prevention of T1D.

Summary: An altered gut microbiota is associated with type 1 diabetes (T1D), affecting the production of short-chain fatty acids (SCFA) and glucose homeostasis. We previously demonstrated that enhancing serum acetate and butyrate using a dietary supplement (HAMSAB) improved glycemia in non-obese diabetic (NOD) mice and patients with established T1D. The effects of SCFA on immune-infiltrated islet cells remain to be clarified. Here, we performed single-cell RNA sequencing on islet cells from NOD mice fed an HAMSAB or control diet. HAMSAB induced a regulatory gene expression profile in pancreas-infiltrated immune cells. Moreover, HAMSAB maintained the expression of β-cell functional genes and decreased cellular stress. HAMSAB-fed mice showed preserved pancreatic endocrine cell identity, evaluated by decreased numbers of poly-hormonal cells. Finally, SCFA increased insulin levels in human β-like cells and improved transplantation outcome in NOD/SCID mice. Our findings support the use of metabolite-based diet as attractive approach to improve glucose control in T1D.

Summary: Inhibitors of neprilysin improve glycemia in patients with heart failure and type 2 diabetes (T2D). The effect of weight loss by diet, surgery, or pharmacotherapy on neprilysin activity (NEPa) is unknown. We investigated circulating NEPa and neprilysin protein concentrations in obesity, T2D, metabolic dysfunction-associated steatotic liver disease (MASLD), and following bariatric surgery, or GLP-1-receptor-agonist therapy. NEPa, but not neprilysin protein, was enhanced in obesity, T2D, and MASLD. Notably, MASLD associated with NEPa independently of BMI and HbA1c. NEPa decreased after bariatric surgery with a concurrent increase in OGTT-stimulated GLP-1. Diet-induced weight loss did not affect NEPa, but individuals randomized to 52-week weight maintenance with liraglutide (1.2 mg/day) decreased NEPa, consistent with another study following 6-week liraglutide (3 mg/day). A 90-min GLP-1 infusion did not alter NEPa. Thus, MASLD may drive exaggerated NEPa, and lowered NEPa following bariatric surgery or liraglutide therapy may contribute to the reported improved cardiometabolic effects.

Summary: Tubulointerstitial abnormalities contribute to the progression of diabetic kidney disease (DKD). However, the underlying mechanism of the pathobiology of tubulointerstitial disease is largely unknown. Here, we showed that MYCT1 expression was downregulated in in vitro and in vivo DKD models. Adeno-associated virus (AAV)-Myct1 significantly attenuated renal dysfunction and tubulointerstitial fibrosis in diabetic db/db mice and downregulated Sp1 transcription and TGF-β1/SMAD3 pathway activation. In human proximal tubular epithelial cells, high glucose-induced high expression of SP1 and TGF-β1/SMAD3 pathway activation as well as overaccumulation of extracellular matrix (ECM) were abrogated by MYCT1 overexpression. Mechanistically, the binding of VDR to the MYCT1 promoter was predicted and confirmed using dual-luciferase reporter and ChIP analysis. VDR transcriptionally upregulates MYCT1. Our data reveal MYCT1 as a new and potential therapeutic target in treating DKD.

Summary: The strategies for eliminating excess reactive oxygen species (ROS) or suppressing inflammatory responses on the wound bed have proven effective for diabetic wound healing. In this work, a zinc-based nanoscale metal-organic framework (NMOF) functions as a carrier to deliver natural product berberine (BR) to form BR@Zn-BTB nanoparticles, which was, in turn, further encapsulated by hydrogel with ROS scavenging ability to yield a composite system of BR@Zn-BTB/Gel (denoted as BZ-Gel). The results show that BZ-Gel exhibited the controlled release of Zn2+ and BR in simulated physiological media to efficiently eliminated ROS and inhibited inflammation and resulted in a promising antibacterial effect. In vivo experiments further proved that BZ-Gel significantly inhibited the inflammatory response and enhanced collagen deposition, as well as to re-epithelialize the skin wound to ultimately promote wound healing in diabetic mice. Our results indicate that the ROS-responsive hydrogel coupled with BR@Zn-BTB synergistically promotes diabetic wound healing.

Summary: Loss of insulin-secreting β-cells in diabetes may be either due to apoptosis or dedifferentiation of β-cell mass. The ubiquitin-proteasome system comprising E3 ligase and deubiquitinases (DUBs) controls several aspects of β-cell functions. In this study, screening for key DUBs identified USP1 to be specifically involved in dedifferentiation process. Inhibition of USP1 either by genetic intervention or small-molecule inhibitor ML323 restored epithelial phenotype of β-cells, but not with inhibition of other DUBs. In absence of dedifferentiation cues, overexpression of USP1 was sufficient to induce dedifferentiation in β-cells; mechanistic insight showed USP1 to mediate its effect via modulating the expression of inhibitor of differentiation (ID) 2. In an in vivo streptozotocin (STZ)-induced dedifferentiation mouse model system, administering ML323 alleviated hyperglycemic state. Overall, this study identifies USP1 to be involved in dedifferentiation of β-cells and its inhibition may have a therapeutic application of reducing β-cell loss during diabetes.

Summary: While adiponectin (APN) was known to significantly abolish the diabetic endothelial inflammatory response, the specific mechanisms have yet to be elucidated. Aortic vascular tissues from mice fed normal and high-fat diets (HFD) were analyzed by transcriptome analysis. GO functional annotation showed that APN inhibited vascular endothelial inflammation in an APPL1-dependent manner. We confirmed that activation of the Wnt/β-catenin signaling plays a key role in APN-mediated anti-inflammation. Mechanistically, APN promoted APPL1/reptin complex formation and β-catenin nuclear translocation. Simultaneously, we identified APN promoted the expression of CD44 by activating TCF/LEF in an APPL1-mediated manner. Clinically, the serum levels of APN and CD44 were decreased in diabetes; the levels of these two proteins were positively correlated. Functionally, treatment with CD44 C-terminal polypeptides protected diabetes-induced vascular endothelial inflammation in vivo. Collectively, we provided a roadmap for APN-inhibited vascular inflammatory effects and CD44 might represent potential targets against the diabetic endothelial inflammatory effect.

Summary: Glucose stimulation induces the remodeling of microtubules, which potentiates insulin secretion in pancreatic β-cells. CAMSAP2 binds to microtubule minus ends to stabilize microtubules in several cultured clonal cells. Here, we report that the knockdown of CAMSAP2 in primary β-cells reduces total insulin content and attenuates GSIS without affecting the releasability of insulin vesicles. Surprisingly, CAMSAP2 knockdown does not change microtubule stability. Unlike in cultured insulinoma cells, CAMSAP2 in primary β-cells predominantly localizes to the Golgi apparatus instead of microtubule minus ends. This novel localization is specific to primary β- but not α-cells and is independent of microtubule binding. Consistent with its specific localization at the Golgi, CAMSAP2 promotes efficient Golgi-ER trafficking in primary β-cells. Moreover, primary β-cells and insulinoma cells likely express different CAMSAP2 isoforms. We propose that a novel CAMSAP2 isoform in primary β-cells has a non-canonical function, which promotes Golgi-ER trafficking to support efficient production of insulin and secretion.

Summary: ARID1A is a tumor suppressor gene mutated in 7–10% of pancreatic cancer patients. However, its function in pancreas development and endocrine regulation is unclear. We generated mice that lack Arid1a expression in the pancreas. Our results showed that deletion of the Arid1a gene in mice caused a reduction in islet numbers and insulin production, both of which are associated with diabetes mellitus (DM) phenotype. RNA sequencing of isolated islets confirmed DM gene signature and decrease of developmental lineage genes. We identified neurogenin3, a transcription factor that controls endocrine fate specification, is a direct target of Aird1a. Gene set enrichment analysis indicated the enhancement of histone deacetylase (HDAC) pathway after Arid1a depletion and a clinically approved HDAC inhibitor showed therapeutic benefit by suppressing disease onset. Our data suggest that Arid1a is required for the development of pancreatic islets by regulating Ngn3+-mediated transcriptional program and is important in maintaining endocrine function.

Summary: Growth differentiation factor 15 (GDF15) is a stress-induced secreted protein whose circulating levels are increased in the context of obesity. Recombinant GDF15 reduces body weight and improves glycemia in obese models, which is largely attributed to the central action of GDF15 to suppress feeding and reduce body weight. Despite these advances in knowledge, the tissue-specific sites of GDF15 production during obesity are unknown, and the effects of modulating circulating GDF15 levels on insulin sensitivity have not been evaluated directly. Here, we demonstrate that hepatocyte Gdf15 expression is sufficient for changes in circulating levels of GDF15 during obesity and that restoring Gdf15 expression specifically in hepatocytes of Gdf15 knockout mice results in marked improvements in hyperinsulinemia, hepatic insulin sensitivity, and to a lesser extent peripheral insulin sensitivity. These data support that liver hepatocytes are the primary source of circulating GDF15 in obesity.

Summary: Single-cell RNA sequencing has paved the way for delineating the pancreatic islet cell atlas and identifying hallmarks of diabetes. However, pathological alterations of type 2 diabetes (T2D) remain unclear. We isolated pancreatic islets from control and T2D mice for single-cell RNA sequencing (scRNA-seq) and retrieved multiple datasets from the open databases. The complete islet cell landscape and robust marker genes and transcription factors of each endocrine cell type were identified. GLRA1 was restricted to beta cells, and beta cells exhibited obvious heterogeneity. The beta subcluster in the T2D mice remarkably decreased the expression of Slc2a2, G6pc2, Mafa, Nkx6-1, Pdx1, and Ucn3 and had higher unfolded protein response (UPR) scores than in the control mice. Moreover, we developed a Web-based interactive tool, creating new opportunities for the data mining of pancreatic islet scRNA-seq datasets. In conclusion, our work provides a valuable resource for a deeper understanding of the pathological mechanism underlying diabetes.

Summary: Diabetic kidney disease (DKD) is the leading cause of end-stage renal diseases. DKD does not have efficacious treatment. The cGAS-STING pathway is activated in podocytes at the early stage of kidney dysfunction, which is associated with the activation of STING downstream effectors TBK1 and NF-κB but not IRF3. Lipotoxicity induces mitochondrial damage and mtDNA leakage to the cytosol through Bcl-2 associated X protein (BAX) in podocytes. BAX-mediated mtDNA cytosolic leakage can activate the cGAS-STING pathway in the absence of lipotoxicity and is sufficient to cause podocyte injury. Depletion of cytosolic mtDNA, genetic STING knockdown, or pharmacological inhibition of STING or TBK1 alleviates podocyte injury and improves renal functions in cultured podocytes or mouse models of diabetes and obesity. These results suggest that the mtDNA-cGAS-STING pathway promotes podocyte injury and is a potential therapeutic target for DKD or other obesity-related kidney diseases.

Summary: As a common complication of diabetes, the pathogenesis of diabetic peripheral neuropathy (DPN) is closely related to high glucose but has not been clarified. Exosomes can mediate crosstalk between Schwann cells (SC) and neurons in the peripheral nerve. Herein, we found that miR-21 in serum exosomes from DPN rats was decreased. SC proliferation was inhibited, cell apoptosis was increased, and the expression of miR-21 in cells and exosomes was downregulated when cultured in high glucose. Increasing miR-21 expression reversed these changes, while knockdown of miR-21 led to the opposite results. When co-cultured with exosomes derived from SC exposed to high glucose, neurite outgrowth was inhibited. On the contrary, neurite outgrowth was accelerated when incubated with exosomes rich in miR-21. We further demonstrated that the SC-derived exosomal miR-21 participates in neurite outgrowth probably through the AKT signaling pathway. Thus, SC-derived exosomal miR-21 contributes to high glucose regulation of neurite outgrowth.

Summary: Metabolic syndrome is associated with obesity, insulin resistance, and the risk of cancer. We tested whether oncogenic transcription factor c-JUN metabolically reprogrammed cells to induce obesity and cancer by reduction of glucose uptake, with promotion of the stemness phenotype leading to malignant transformation. Liquid alcohol, high-cholesterol, fat diet (HCFD), and isocaloric dextrin were fed to wild-type or experimental mice for 12 months to promote hepatocellular carcinoma (HCC). We demonstrated 40% of mice developed liver tumors after chronic HCFD feeding. Disruption of liver-specific c-Jun reduced tumor incidence 4-fold and improved insulin sensitivity. Overexpression of c-JUN downregulated RICTOR transcription, leading to inhibition of the mTORC2/AKT and glycolysis pathways. c-JUN inhibited GLUT1, 2, and 3 transactivation to suppress glucose uptake. Silencing of RICTOR or c-JUN overexpression promoted self-renewal ability. Taken together, c-JUN inhibited mTORC2 via RICTOR downregulation and inhibited glucose uptake via downregulation of glucose intake, leading to self-renewal and obesity.

Summary: Pancreatic islets respond to metabolic and inflammatory stress by producing hormones and other factors that induce adaptive cellular and systemic responses. Here we show that intracellular Ca2+ ([Ca2+]i) and ROS signals generated by high glucose and cytokine-induced ER stress activate calcineurin (CN)/NFATc2 and PI3K/AKT to maintain β-cell identity and function. This was attributed in part by direct induction of the endocrine differentiation gene RFX6 and suppression of several β-cell “disallowed” genes, including MCT1. CN/NFATc2 targeted p300 and HDAC1 to RFX6 and MCT1 promoters to induce and suppress gene transcription, respectively. In contrast, prolonged exposure to stress, hyperstimulated [Ca2+]i, or perturbation of CN/NFATc2 resulted in downregulation of RFX6 and induction of MCT1. These findings reveal that CN/NFATc2 and PI3K/AKT maintain β-cell function during acute stress, but β-cells dedifferentiate to a dysfunctional state upon loss or exhaustion of Ca2+/CN/NFATc2 signaling. They further demonstrate the utility of targeting CN/NFATc2 to restore β-cell function

Summary: KLF15 is a transcription factor that plays an important role in the activation of gluconeogenesis from amino acids as well as the suppression of lipogenesis from glucose. Here we identified the transcription start site of liver-specific KLF15 transcript and showed that FoxO1/3 transcriptionally regulates Klf15 gene expression by directly binding to the liver-specific Klf15 promoter. To achieve this, we performed a precise in vivo promoter analysis combined with the genome-wide transcription-factor-screening method “TFEL scan”, using our original Transcription Factor Expression Library (TFEL), which covers nearly all the transcription factors in the mouse genome. Hepatic Klf15 expression is significantly increased via FoxOs by attenuating insulin signaling. Furthermore, FoxOs elevate the expression levels of amino acid catabolic enzymes and suppress SREBP-1c via KLF15, resulting in accelerated amino acid breakdown and suppressed lipogenesis during fasting. Thus, the FoxO-KLF15 pathway contributes to switching the macronutrient flow in the liver under the control of insulin.

Summary: The rs58542926C >T (E167K) variant of the transmembrane 6 superfamily member 2 gene (TM6SF2) is associated with increased risks for nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes (T2D). Nevertheless, the role of the TM6SF2 rs58542926 variant in glucose metabolism is poorly understood. We performed a sex-stratified analysis of the association between the rs58542926C >T variant and T2D in multiple cohorts. The E167K variant was significantly associated with T2D, especially in males. Using an E167K knockin (KI) mouse model, we found that male but not the female KI mice exhibited impaired glucose tolerance. As an ER membrane protein, TM6SF2 was found to interact with inositol-requiring enzyme 1 α (IRE1α), a primary ER stress sensor. The male Tm6sf2 KI mice exhibited impaired IRE1α signaling in the liver. In conclusion, the E167K variant of TM6SF2 is associated with glucose intolerance primarily in males, both in humans and mice.

Summary: Pancreatic islets are essential for maintaining physiological blood glucose levels, and declining islet function is a hallmark of type 2 diabetes. We employ mass spectrometry-based proteomics to systematically analyze islets from 9 genetic or diet-induced mouse models representing a broad cross-section of metabolic health. Quantifying the islet proteome to a depth of >11,500 proteins, this study represents the most detailed analysis of mouse islet proteins to date. Our data highlight that the majority of islet proteins are expressed in all strains and diets, but more than half of the proteins vary in expression levels, principally due to genetics. Associating these varied protein expression levels on an individual animal basis with individual phenotypic measures reveals islet mitochondrial function as a major positive indicator of metabolic health regardless of strain. This compendium of strain-specific and dietary changes to mouse islet proteomes represents a comprehensive resource for basic and translational islet cell biology.

Summary: The capacity of the brain to elicit sustained remission of hyperglycemia in rodent models of type 2 diabetes following intracerebroventricular (icv) injection of fibroblast growth factor 1 (FGF1) is well established. Here, we show that following icv FGF1 injection, hypothalamic signaling by extracellular signal-regulated kinases 1 and 2 (ERK1/2), members of the mitogen-activated protein kinase (MAPK) family, is induced for at least 24 h. Further, we show that this prolonged response is required for the sustained antidiabetic action of FGF1 since it is abolished by sustained (but not acute) pharmacologic blockade of hypothalamic MAPK/ERK signaling. We also demonstrate that FGF1 R50E, a FGF1 mutant that activates FGF receptors but induces only transient hypothalamic MAPK/ERK signaling, fails to mimic the sustained glucose lowering induced by FGF1. These data identify sustained activation of hypothalamic MAPK/ERK signaling as playing an essential role in the mechanism underlying diabetes remission induced by icv FGF1 administration.

Summary: Skeletal muscle insulin resistance is a central defect in the pathogenesis of type 2 diabetes (T2D). Here, we analyzed skeletal muscle proteome in 148 vastus lateralis muscle biopsies obtained from men covering all glucose tolerance phenotypes: normal, impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and T2D. Skeletal muscle proteome was analyzed by a sequential window acquisition of all theoretical mass spectra (SWATH-MS) proteomics technique. Our data indicate a downregulation in several proteins involved in mitochondrial electron transport or respiratory chain complex assembly already in IFG and IGT muscles, with most profound decreases observed in T2D. Additional phosphoproteomic analysis reveals altered phosphorylation in several signaling pathways in IFG, IGT, and T2D muscles, including those regulating glucose metabolic processes, and the structure of muscle cells. These data reveal several alterations present in skeletal muscle already in prediabetes and highlight impaired mitochondrial energy metabolism in the trajectory from prediabetes into T2D.

Summary: Dihydroorotate dehydrogenase (DHODH) is essential for the de novo synthesis of pyrimidine ribonucleotides, and as such, its inhibitors have been long used to treat autoimmune diseases and are in clinical trials for cancer and viral infections. Interestingly, DHODH is located in the inner mitochondrial membrane and contributes to provide ubiquinol to the respiratory chain. Thus, DHODH provides the link between nucleotide metabolism and mitochondrial function. Here we show that pharmacological inhibition of DHODH reduces mitochondrial respiration, promotes glycolysis, and enhances GLUT4 translocation to the cytoplasmic membrane and that by activating tumor suppressor p53, increases the expression of GDF15, a cytokine that reduces appetite and prolongs lifespan. In addition, similar to the antidiabetic drug metformin, we observed that in db/db mice, DHODH inhibitors elevate levels of circulating GDF15 and reduce food intake. Further analysis using this model for obesity-induced diabetes revealed that DHODH inhibitors delay pancreatic β cell death and improve metabolic balance.

Summary: To investigate the molecular mechanisms underlying islet dysfunction and insulin resistance in diet-induced diabetes, we conducted temporal RNA sequencing of tissues responsible for insulin secretion (islets) and action (liver) every 4 weeks in mice on high-fat (HFD) or chow diet for 24 weeks, linking to longitudinal profile of metabolic characteristics. The diverse responses of α, β, and δ cells to glucose and palmitate indicated HFD-induced dynamic deterioration of islet function from dysregulation to failure. Insulin resistance developed with variable time course in different tissues. Weighted gene co-expression network analysis and Ingenuity Pathway Analysis implicated islets and liver jointly programmed β-cell compensatory adaption via cell proliferation at early phase and irreversible islet dysfunction by inappropriate immune response at later stage, and identified interconnected molecules including growth differentiation factor 15. Frequencies of T cell subpopulation showed an early decrement in Tregs followed by increases in Th1 and Th17 cells during progression to diabetes.

Summary: Type 2 diabetes incidence continues to increase rapidly. This disease is characterized by a breakdown in blood glucose homeostasis. The impairment of glycemic control is linked to the structure of glycogen, a highly branched glucose polymer. Liver glycogen, a major controller of blood sugar, comprises small β particles which can link together to form larger α particles. These degrade to glucose more slowly than β particles, enabling a controlled release of blood glucose. The α particles in diabetic mice are however easily broken down into β particles, which degrade more quickly. Because this may lead to higher blood glucose, understanding this diabetes-associated breakdown of α-particle molecular structure may help in the development of diabetes therapeutics. We review the extraction of liver glycogen, its molecular structure, and how this structure is affected by diabetes and then use this knowledge to make postulates to guide the development of strategies to help mitigate type 2 diabetes.

Metabolic diseases such as obesity and diabetes induce lipotoxic cardiomyopathy, which is characterized by myocardial lipid accumulation, dysfunction, hypertrophy, fibrosis and mitochondrial dysfunction. Here, we identify that mitochondrial glycerol 3-phosphate dehydrogenase (mGPDH) is a pivotal regulator of cardiac fatty acid metabolism and function in the setting of lipotoxic cardiomyopathy. Cardiomyocyte-specific deletion of mGPDH promotes high-fat diet induced cardiac dysfunction, pathological hypertrophy, myocardial fibrosis, and lipid accumulation. Mechanically, mGPDH deficiency inhibits the expression of desuccinylase SIRT5, and in turn, the hypersuccinylates majority of enzymes in the fatty acid oxidation (FAO) cycle and promotes the degradation of these enzymes. Moreover, manipulating SIRT5 abolishes the effects of mGPDH ablation or overexpression on cardiac function. Finally, restoration of mGPDH improves lipid accumulation and cardiomyopathy in both diet-induced and genetic obese mouse models. Thus, our study indicates that targeting mGPDH could be a promising strategy for lipotoxic cardiomyopathy in the context of obesity and diabetes., Competing Interests: The authors declare no competing interests., (© 2024 The Author(s).)

Summary: Myc has emerged as a pivotal transcription factor for four metabolic pathways: aerobic glycolysis, glutaminolysis, polyamine synthesis, and HIF-1α/mTOR. Each of these pathways accelerates the utilization of sugar. The BCG vaccine, a derivative of Mycobacteria-bovis, has been shown to trigger a long-term correction of blood sugar levels to near normal in type 1 diabetics (T1D). Here we reveal the underlying mechanisms behind this beneficial microbe-host interaction. We show that baseline glucose transport is deficient in T1D monocytes but is improved by BCG in vitro and in vivo. We then show, using RNAseq in monocytes and CD4 T cells, that BCG treatment over 56 weeks in humans is associated with upregulation of Myc and activation of nearly two dozen Myc-target genes underlying the four metabolic pathways. This is the first documentation of BCG induction of Myc and its association with systemic blood sugar control in a chronic disease like diabetes.

Inflammation-mediated crosstalk between neuroglial cells and endothelial cells (ECs) is a fundamental feature of many vascular diseases. Nevertheless, the landscape of inflammatory processes during diabetes-induced microvascular dysfunction remains elusive. Here, we applied single-cell RNA sequencing to elucidate the transcriptional landscape of diabetic retinopathy (DR). The transcriptome characteristics of microglia and ECs revealed two microglial subpopulations and three EC populations. Exploration of intercellular crosstalk between microglia and ECs showed that diabetes-induced interactions mainly participated in the inflammatory response and vessel development, with colony-stimulating factor 1 (CSF1) and CSF1 receptor (CSF1R) playing important roles in early cell differentiation. Clinically, we found that CSF1/CSF1R crosstalk dysregulation was associated with proliferative DR. Mechanistically, ECs secrete CSF1 and activate CSF1R endocytosis and the CSF1R phosphorylation-mediated MAPK signaling pathway, which elicits the differentiation of microglia and triggers the secretion of inflammatory factors, and subsequently foster angiogenesis by remodeling the inflammatory microenvironment through a positive feedback mechanism., Competing Interests: The authors declare no competing interests., (© 2024 The Authors.)

Clopidogrel has been shown to play a protective role against diabetic nephropathy. However, whether clopidogrel exerts a protective effect against diabetic cardiomyopathy (DCM) is unknown. Three-month-old male db/db mice were administered clopidogrel daily at doses of 5, 10, and 20 mg/kg by gavage for 5 months. Here, we showed that clopidogrel effectively attenuated diabetes-induced cardiac hypertrophy and cardiac dysfunction by inhibiting cardiac fibrosis, inflammatory responses, and oxidative stress damage in db/db mice. Diabetes-induced cardiac fibrosis was inhibited by clopidogrel treatment via blockade of the TGF-β1/Smad3/P2RY12 pathway and inhibition of macrophage infiltration in db/db mice. The protective effects of clopidogrel against oxidative damage were mediated by the induction of the Nrf2 signaling pathway. Taken together, our findings provide strong evidence that clopidogrel is a promising effective agent for the treatment of DCM by alleviating diabetes-induced cardiac hypertrophy and dysfunction. P2RY12 might be an effective target for the treatment of DCM., Competing Interests: The authors declare no competing interests., (© 2024 The Authors.)

Type 1 diabetes (T1D) is a chronic condition caused by autoimmune destruction of the insulin-producing pancreatic β cells. While it is known that gene-environment interactions play a key role in triggering the autoimmune process leading to T1D, the pathogenic mechanism leading to the appearance of islet autoantibodies-biomarkers of autoimmunity-is poorly understood. Here we show that disruption of the complement system precedes the detection of islet autoantibodies and persists through disease onset. Our results suggest that children who exhibit islet autoimmunity and progress to clinical T1D have lower complement protein levels relative to those who do not progress within a similar time frame. Thus, the complement pathway, an understudied mechanistic and therapeutic target in T1D, merits increased attention for use as protein biomarkers of prediction and potentially prevention of T1D., Competing Interests: The authors declare no competing interests., (© 2024 Battelle Memorial Institute, The Author(s).)

An altered gut microbiota is associated with type 1 diabetes (T1D), affecting the production of short-chain fatty acids (SCFA) and glucose homeostasis. We previously demonstrated that enhancing serum acetate and butyrate using a dietary supplement (HAMSAB) improved glycemia in non-obese diabetic (NOD) mice and patients with established T1D. The effects of SCFA on immune-infiltrated islet cells remain to be clarified. Here, we performed single-cell RNA sequencing on islet cells from NOD mice fed an HAMSAB or control diet. HAMSAB induced a regulatory gene expression profile in pancreas-infiltrated immune cells. Moreover, HAMSAB maintained the expression of β-cell functional genes and decreased cellular stress. HAMSAB-fed mice showed preserved pancreatic endocrine cell identity, evaluated by decreased numbers of poly-hormonal cells. Finally, SCFA increased insulin levels in human β-like cells and improved transplantation outcome in NOD/SCID mice. Our findings support the use of metabolite-based diet as attractive approach to improve glucose control in T1D., Competing Interests: E.M. is an inventor on a patent WO2018027274A1 submitted by Monash University that covers methods and compositions of metabolites for treatment and prevention of autoimmune disease related to this paper and stock ownership for ImmunoBiota Therapeutics Pty Ltd. E.N.G. declares that there are no other relationships or activities that might bias, or be perceived to bias, the present work., (© 2023 The Author(s).)

Inhibitors of neprilysin improve glycemia in patients with heart failure and type 2 diabetes (T2D). The effect of weight loss by diet, surgery, or pharmacotherapy on neprilysin activity (NEPa) is unknown. We investigated circulating NEPa and neprilysin protein concentrations in obesity, T2D, metabolic dysfunction-associated steatotic liver disease (MASLD), and following bariatric surgery, or GLP-1-receptor-agonist therapy. NEPa, but not neprilysin protein, was enhanced in obesity, T2D, and MASLD. Notably, MASLD associated with NEPa independently of BMI and HbA1c. NEPa decreased after bariatric surgery with a concurrent increase in OGTT-stimulated GLP-1. Diet-induced weight loss did not affect NEPa, but individuals randomized to 52-week weight maintenance with liraglutide (1.2 mg/day) decreased NEPa, consistent with another study following 6-week liraglutide (3 mg/day). A 90-min GLP-1 infusion did not alter NEPa. Thus, MASLD may drive exaggerated NEPa, and lowered NEPa following bariatric surgery or liraglutide therapy may contribute to the reported improved cardiometabolic effects., Competing Interests: The authors declare no competing interests., (© 2023 The Authors.)

Tubulointerstitial abnormalities contribute to the progression of diabetic kidney disease (DKD). However, the underlying mechanism of the pathobiology of tubulointerstitial disease is largely unknown. Here, we showed that MYCT1 expression was downregulated in in vitro and in vivo DKD models. Adeno-associated virus (AAV)-Myct1 significantly attenuated renal dysfunction and tubulointerstitial fibrosis in diabetic db/db mice and downregulated Sp1 transcription and TGF-β1/SMAD3 pathway activation. In human proximal tubular epithelial cells, high glucose-induced high expression of SP1 and TGF-β1/SMAD3 pathway activation as well as overaccumulation of extracellular matrix (ECM) were abrogated by MYCT1 overexpression. Mechanistically, the binding of VDR to the MYCT1 promoter was predicted and confirmed using dual-luciferase reporter and ChIP analysis. VDR transcriptionally upregulates MYCT1. Our data reveal MYCT1 as a new and potential therapeutic target in treating DKD., Competing Interests: The authors declare no competing interests., (© 2023 The Author(s).)

The strategies for eliminating excess reactive oxygen species (ROS) or suppressing inflammatory responses on the wound bed have proven effective for diabetic wound healing. In this work, a zinc-based nanoscale metal-organic framework (NMOF) functions as a carrier to deliver natural product berberine (BR) to form BR@Zn-BTB nanoparticles, which was, in turn, further encapsulated by hydrogel with ROS scavenging ability to yield a composite system of BR@Zn-BTB/Gel (denoted as BZ-Gel). The results show that BZ-Gel exhibited the controlled release of Zn 2+ and BR in simulated physiological media to efficiently eliminated ROS and inhibited inflammation and resulted in a promising antibacterial effect. In vivo experiments further proved that BZ-Gel significantly inhibited the inflammatory response and enhanced collagen deposition, as well as to re-epithelialize the skin wound to ultimately promote wound healing in diabetic mice. Our results indicate that the ROS-responsive hydrogel coupled with BR@Zn-BTB synergistically promotes diabetic wound healing., Competing Interests: The authors of this study declare that there is no conflict of interest., (© 2023.)

Loss of insulin-secreting β-cells in diabetes may be either due to apoptosis or dedifferentiation of β-cell mass. The ubiquitin-proteasome system comprising E3 ligase and deubiquitinases (DUBs) controls several aspects of β-cell functions. In this study, screening for key DUBs identified USP1 to be specifically involved in dedifferentiation process. Inhibition of USP1 either by genetic intervention or small-molecule inhibitor ML323 restored epithelial phenotype of β-cells, but not with inhibition of other DUBs. In absence of dedifferentiation cues, overexpression of USP1 was sufficient to induce dedifferentiation in β-cells; mechanistic insight showed USP1 to mediate its effect via modulating the expression of inhibitor of differentiation (ID) 2. In an in vivo streptozotocin (STZ)-induced dedifferentiation mouse model system, administering ML323 alleviated hyperglycemic state. Overall, this study identifies USP1 to be involved in dedifferentiation of β-cells and its inhibition may have a therapeutic application of reducing β-cell loss during diabetes., Competing Interests: The authors declare no competing. The authors of the above noted article, Anujith Kumar and Meenal Francis have filed certain aspects of this work for patenting., (© 2023 The Authors.)

While adiponectin (APN) was known to significantly abolish the diabetic endothelial inflammatory response, the specific mechanisms have yet to be elucidated. Aortic vascular tissues from mice fed normal and high-fat diets (HFD) were analyzed by transcriptome analysis. GO functional annotation showed that APN inhibited vascular endothelial inflammation in an APPL1-dependent manner. We confirmed that activation of the Wnt/β-catenin signaling plays a key role in APN-mediated anti-inflammation. Mechanistically, APN promoted APPL1/reptin complex formation and β-catenin nuclear translocation. Simultaneously, we identified APN promoted the expression of CD44 by activating TCF/LEF in an APPL1-mediated manner. Clinically, the serum levels of APN and CD44 were decreased in diabetes; the levels of these two proteins were positively correlated. Functionally, treatment with CD44 C-terminal polypeptides protected diabetes-induced vascular endothelial inflammation in vivo . Collectively, we provided a roadmap for APN-inhibited vascular inflammatory effects and CD44 might represent potential targets against the diabetic endothelial inflammatory effect., Competing Interests: We, the authors, have a patent related to this work (No. ZL 202110749325.X)., (© 2023 The Authors.)

Glucose stimulation induces the remodeling of microtubules, which potentiates insulin secretion in pancreatic β-cells. CAMSAP2 binds to microtubule minus ends to stabilize microtubules in several cultured clonal cells. Here, we report that the knockdown of CAMSAP2 in primary β-cells reduces total insulin content and attenuates GSIS without affecting the releasability of insulin vesicles. Surprisingly, CAMSAP2 knockdown does not change microtubule stability. Unlike in cultured insulinoma cells, CAMSAP2 in primary β-cells predominantly localizes to the Golgi apparatus instead of microtubule minus ends. This novel localization is specific to primary β- but not α-cells and is independent of microtubule binding. Consistent with its specific localization at the Golgi, CAMSAP2 promotes efficient Golgi-ER trafficking in primary β-cells. Moreover, primary β-cells and insulinoma cells likely express different CAMSAP2 isoforms. We propose that a novel CAMSAP2 isoform in primary β-cells has a non-canonical function, which promotes Golgi-ER trafficking to support efficient production of insulin and secretion., Competing Interests: The authors declare no conflicts of interest., (© 2023 The Authors.)

ARID1A is a tumor suppressor gene mutated in 7-10% of pancreatic cancer patients. However, its function in pancreas development and endocrine regulation is unclear. We generated mice that lack Arid1a expression in the pancreas. Our results showed that deletion of the Arid1a gene in mice caused a reduction in islet numbers and insulin production, both of which are associated with diabetes mellitus (DM) phenotype. RNA sequencing of isolated islets confirmed DM gene signature and decrease of developmental lineage genes. We identified neurogenin3, a transcription factor that controls endocrine fate specification, is a direct target of Aird1a. Gene set enrichment analysis indicated the enhancement of histone deacetylase (HDAC) pathway after Arid1a depletion and a clinically approved HDAC inhibitor showed therapeutic benefit by suppressing disease onset. Our data suggest that Arid1a is required for the development of pancreatic islets by regulating Ngn3 + -mediated transcriptional program and is important in maintaining endocrine function., Competing Interests: The authors declare no competing interests., (© 2022 The Author(s).)